Renewable Energy and Storage Devices for Sustainable Development: Select Proceedings of IWRESD 2021 (Springer Proceedings in Energy) 9811692793, 9789811692796

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Springer Proceedings in Energy

V. K. Jain Chandima Gomes Abhishek Verma   Editors

Renewable Energy and Storage Devices for Sustainable Development Select Proceedings of IWRESD 2021

Springer Proceedings in Energy

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V. K. Jain · Chandima Gomes · Abhishek Verma Editors

Renewable Energy and Storage Devices for Sustainable Development Select Proceedings of IWRESD 2021

Editors V. K. Jain Amity Institute for Advanced Research and Studies (Materials and Devices) Amity University Uttar Pradesh Noida, India

Chandima Gomes School of Electrical and Information Engineering University of the Witwatersrand Johannesburg, South Africa

Abhishek Verma Amity Institute of Renewable and Alternative Energy Amity Institute for Advanced Research and Studies (Materials and Devices) Amity University Uttar Pradesh Noida, India

ISSN 2352-2534 ISSN 2352-2542 (electronic) Springer Proceedings in Energy ISBN 978-981-16-9279-6 ISBN 978-981-16-9280-2 (eBook) https://doi.org/10.1007/978-981-16-9280-2 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Preface

The Sustainable Development Goal (SDG)-7 is a universal call for affordable, sustainable, and clean energy for all nations and to all humankind on Earth. The increase in pressure due to rise in population and demand for a better lifestyle have necessitated the need for greater use of energy. This has resulted in increased pressure for consumption of available resources, mostly the fossil fuels. However, the conventional sources of energy like oil, gas, coal, etc., will not be able to provide the desired levels of energy security to mankind in foreseeable future. Therefore, various renewable sources have been investigated to produce clean and sustainable energy. The potential of solar energy being enormous makes it a crucial component of renewable energy portfolio, which aims toward the development of a sustainable energy resource and also reduces global emissions of greenhouse gasses into the atmosphere. To understand and discuss various aspects of such important issue, Amity Institute for Advanced Research and Studies (Materials & Devices) and Amity Institute of Renewable and Alternative Energy jointly with the Centre for Science & Technology of the Non-Aligned and other Developing Countries (NAM S&T Centre) had organized “International Workshop on Renewable Energy and Storage Devices for Sustainable Development” from January 12 to 14, 2021, at Amity University, Noida. Researchers, scientists, technologists, government officials, policy makers, and representatives from industry and non-government organizations from various countries (including more than 30 representatives from 15 NAM countries), who are engaged in R&D, generation of power, promotion, and policy making on various renewable energy sectors, attended the workshop and exchanged their ideas and expertise. The purpose and objective of this meeting was to share the vast knowledge and latest investigations with the scientific and industrial community and how to include in the production level to get more efficient solar cells or systems. The academia and industry and the government working together in a well-coordinated manner may bring revolutionary changes over the globe. With this view in mind, a special session was also organized, in which scientists, industrialist, and representatives from the government agencies participated and presented their views in order to

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bring the ultimate solution in terms of energy security, clean, and affordable energy through renewable sources. The Book “Renewable Energy and Storage Devices for Sustainable Development” comprises of selected peer-reviewed scientific contributions from different veins of renewable energy generation, harvesting, and the related technologies. The contribution has been made by different researchers and eminent scientists, who presented their paper in IWRESD 2021. The chapters of the book include various latest and significant topics, i.e., solar photovoltaics, solar thermal, solar energy harvesting, hybrid systems, novel artifact-based solar PV integrated smart city solutions, agrivoltaics concept, on-grid and off-grid power plant, batteries, material’s synthesis and characterization, nano-materials/composites, energy-efficient devices, along with energy management. The book gives the holistic view on cuttingedge technologies and other significant aspects related to solar and alternative energy generation and harvesting. It includes the latest findings of eminent scientists in connection to the synthesis, optimization, and characterization of different materials related to efficient energy devices; investigation on thermo-physical properties nano-enhanced phase change materials for solar thermal energy storage applications; novel artifact-based solar PV integrated smart city solutions, agrivoltaics concept, degradation analysis on photovoltaic panels; fabrication and efficiency enhancement in solar cells; hybrid organic–inorganic solar cells; study on efficient daylighting devices; solar parabolic concentrators; fabrication and characterization of perovskite solar cells; renewable power plant; and apart from this, the book also includes the chapters having power plant case studies and energy management. These contributory papers were full of new scientific knowledge, thought provoking ideas, skills, brain storming discussions, and exchange of ideas. We are sure that all the recent results and findings reported here will be useful to the young researchers or scientists working in these areas and will serve as an important document for all those associated with solar and alternate energy research, development, and its use. We are highly grateful to all of them who have given their guidance and support. It was a great success due to all the support given by NAM S&T Centre. Although it is difficult to name all of our colleagues, but we would like to thank each one. The organizers wish to place on record our appreciation to Dr. Ashok K. Chauhan, Founder President, Amity Education Group, for his continuous guidance, support, and encouragement. We are also thankful to Dr. Atul Chauhan, Chancellor, AUUP, for providing us the full support to organize this workshop. We are thankful to Dr. Amitava Bandoupadhyay, Director General, NAM S&T Centre, for collaborating to organize this workshop. We would also like to thank Mr. M. Bandoupadhyay, Senior Advisor, NAM S&T Centre, and the entire team for providing full support in organizing the event. The organizers would also like to express gratitude to Prof. (Dr.) Balvinder Shukla, Vice Chancellor, AUUP. Our special thanks to team members for

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their cooperation as without their hard work and dedicated efforts, it was impossible to organize this workshop. Noida, India Johannesburg, South Africa Noida, India

Vinod Kumar Jain Chandima Gomes Abhishek Verma

Contents

Fine Line Printing for Solar Cells with Knotless Screens . . . . . . . . . . . . . . Shivangi Jha, Himadri Agrawal, B. K. Pant, Ajai Kumar, and Priyanka Kumari Chemical Bath Deposited CdS Along with Electrodeposited and Closed Space Sublimated CdTe for Solar Cell Fabrication . . . . . . . . . G. K. U. P. Gajanayake, A. A. I. Lakmal, D. S. M. De Silva, and B. S. Dassanayake Reducing Land Occupancy Using Solar PV Artefact: A Study . . . . . . . . . Maharshi Vyas, Sumit Chowdhury, Abhishek Verma, D. N. Singh, and V. K. Jain Recent Advances in Hybrid Organic–Inorganic Perovskite Solar Cells with Different Halides and Their Combinations . . . . . . . . . . . . . . . . . Jampana Gayathri, Dalip Singh Mehta, and Kanchan Saxena Design and Optimization of an Agrivoltaics System . . . . . . . . . . . . . . . . . . . Mohd Adil Faizi, Abhishek Verma, and V. K. Jain Implementation of the Family Size Biogas Plant to Achieve a Sustainable Lifestyle: Case Study a Farm in Village 37 . . . . . . . . . . . . . . Kifah A. Fayad Al-Imarah, Waleed M. Dawood, Ismaeel M. Abood, Mudher H. Mahmood, Taha M. Al-Muwali, Milad A. Aldhaher, and Thomas H. Culhane Humidity-Enabled Graphene Based Bilayer Device for Power Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Omita Nanda, A. M. Biradar, and Kanchan Saxena Long-Term Performance Analysis of Solar Collectors . . . . . . . . . . . . . . . . . Subhra Das and Subhayan Das

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21 31

37

51 57

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Contents

Mitigation of Soiling of Solar Panels by Applying Superydrophobic Aluminum Oxide Thin Film and Dry Cleaning by Electrodynamic Screen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Deepanjana Adak, Silajit Manna, Shoubhik De, Manish Kumar, Santanu Maity, and Raghunath Bhattacharyya

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Propagation of Microwaves in Magnetized Plasma and Air-Based Ternary Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N. Kumar, Mahima Singh, G. N. Pandey, and B. Suthar

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Photocatalytic Degradation of Chlorobenzene Using Easily Recoverable Fe3 O4 /OMS-2 Nanocomposite . . . . . . . . . . . . . . . . . . . . . . . . . . Monika Dubey, Navakanth Viay Challagulla, Monika Joshi, Ranjit Kumar, and Sandeep Kumar Srivastava Efficient Removal of Crystal Violet Dye Using Fly Ash-Supported Nanoscale Zerovalent Iron Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shubhangi Madan and Sangeeta Tiwari

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Increased Heat Transfer Characteristics of Molten Salt-Synthesized Titania Nanoparticles Embedded in Palmitic Acid . . . . . . . . . . . . . . . . . . . . 103 Shriya Iyer, Sharon Santhosh, Malvika Satish, and Asha Anish Madhavan Reduced Graphene Oxide-Based Metal Nanocomposites as Advanced Functional Electrode Material for Ni/Fe Rechargeable Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Harish Kumar, Rahul Sharma, and A. K. Shukla Influence of Variation of Excitation Wavelength on Optical Properties of Silicon Nanowires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 Vikas Kashyap, Neeru Chaudhary, Navdeep Goyal, and Kapil Saxena Invariance of Thermal Emissivity in Spray Coated ZrB2 Film . . . . . . . . . 129 Atasi Dan and Nagarajan Kirupakaran Gopinath Role of Semiconductors in Various Renewable Energy Systems . . . . . . . . 139 Neha Lyka Muttumthala and Apurv Yadav Design of Photovoltaic System for DC Pumping Unit . . . . . . . . . . . . . . . . . . 147 Apurv Yadav, Abhishek Verma, P. K. Bhatnagar, and V. K. Jain Glycerol Material’s Impact on Growth of Microalgae for Sustainable Renewable Energy Production . . . . . . . . . . . . . . . . . . . . . . . 155 Rupesh Kumar Basniwal, S. Shankara Narayanan, and V. K. Jain Study of Jaggery Derived Carbon Spheres for Supercapacitor Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 Swati Chaudhary and O. P. Sinha

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Optimum Concentration Ratio for Plastic Optical Fiber-Based Fresnel Lens Daylighting System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 Vikas Kumar, Karanvir Sharma, Devendra Singh Bisht, and Harry Garg Energy-Efficient Tunnel FET for Application as a Biosensor . . . . . . . . . . . 181 Manjula Vijh, Aekta Singh, and Sujata Pandey

About the Editors

V. K. Jain completed his Ph.D. in Solid State Physics from IIT Delhi in 1970. He joined Solid State Physics Laboratory in 1972 and worked as Director Grade Scientist until 2003. He was Head of the silicon devices and Micro Electro Mechanical Systems (MEMS) division and developed many new technologies. His research on electro-luminescence in porous silicon was the first international observation and was reported by Photonics Spectra, USA, and Electronics Asia. He has also developed the technology for space quality silicon solar cells. He is among those who have started the MEMS program in the country and also produced many devices. He was also associated with the National Programme on Smart Materials and MEMS technology from the beginning. He has published more than 200 papers in national and international journals, edited a few books, and has filed more than 50 patents (including 12 granted). His research interests include solar energy, thermal heat storage system, sensors, biosensors, water purification, etc. He has started two new institutes at Amity University—Amity Institute for Advanced Research and Studies (Materials and Devices) and Amity Institute of Renewable and Alternative—and working as Distinguished Scientist and Professor. Chandima Gomes is a Full Professor of High Voltage Engineering at the University of Witwatersrand, South Africa. He has about 25 years of teaching experience. His specialization areas include high-voltage engineering, lightning and thunderstorm physics, energies, environmental sciences, and electromagnetics. He has 18 research and 10 program grants, 128 journal publications, 17 chapters, and 200 conference proceedings papers to his credit. He is Senior Adviser to the National Lightning Safety Institution, USA, and was Chief Adviser to African Centers for Lightning and Electromagnetics based in Uganda. Being an engineering consultant for several companies in Asia and Africa, he has over 20 years of international experience in designing lightning protection systems and providing solutions for electromagnetic issues. Abhishek Verma did his Ph.D. in Electronic Science from Delhi University in 2009. He further joined the National University of Singapore, Singapore, as a postdoc in xiii

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About the Editors

solar cells technologies. Presently, he is working as Associate Professor at Amity University, Noida. His areas of interest are organic and inorganic 3rd-generation solar cells, solar thermal nano-enhanced phase change materials, nanotechnology, Agrivoltaics, clean energy generation, quantum dots, CNT, Graphene, Si NWs, optical (UV and IR) sensors, volatile/toxic gas sensors, LPG sensors, Si nanowire technology-based sensors and devices. He has organized the many prestigious International Conferences, as Secretary. He has filed over 20 patents (2 granted), published 5 books as an editor and published over 60 papers in refereed international journals and conferences.

Fine Line Printing for Solar Cells with Knotless Screens Shivangi Jha, Himadri Agrawal, B. K. Pant, Ajai Kumar, and Priyanka Kumari

1 Introduction The photovoltaic (PV) power is gradually emerging as a viable source of renewable energy. Silicon solar cells comprising mono-crystalline and multi-crystalline varieties constitute about 90% of world production. The trend would continue, and crystalline silicon PV technology is poised to dominate the PV industry for some decades to come. Screen printed solar cells currently dominate the commercial market because of low production cost and process simplicity. The grid lines printed on the front side of solar cells contribute to shadowing losses. One option is to reduce the finger width of the silver front contact in order to reduce the shadowing loss and hence increase the short circuit current density (J sc ). However, this may increase the finger contact and line resistances leading to decrease in cell efficiency. Therefore, fine line printing requires a smooth finger profile in combination with a higher aspect ratio of the finger. Worldwide many solar cell manufacturers are trying to achieve maximum aspect ratio through intensive R&D efforts. Summarizing the challenging steps in metallization of solar cells are to reduce finger width and improve aspect ratio while decreasing paste consumption per cell. In crystalline silicon (c-Si and mc-Si) solar cell manufacturing, the p-type wafers are diffused with phosphorous to form a thin n-layer (emitter) on the surface of the wafer, and thereby, a large area P–N junction is formed, which is required for separation of photo-carriers. The complete process steps for solar cell are given in Fig. 1. Metallization is the most important part of any solar cell structure. No matter how great a device’s structure design is to enhance photo-collection and charge carrier generation, it cannot solve the purpose without a complementing contacting scheme. S. Jha (B) · H. Agrawal · B. K. Pant · A. Kumar · P. Kumari BHEL ASSCP, Gwalpahari, Gurgaon, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_1

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Fig. 1 Complete process steps for solar cell fabrication

A simple screen printing process which is most effective, robust, and fast is used for metallization of front and back contacts of solar cell. Metallization strongly affects performance of solar cell due to its effect on short circuit current density (J sc ), open circuit voltage (V oc ), series resistance (Rs ), shunt resistance (Rsh ), and fill factor (F F ).

2 Experiment Conventional process steps as shown in Fig. 1 are followed for the fabrication of multi-crystalline Si solar cells. P-type, 156 mm square silicon wafers are used for fabrication of solar cells. Texturing of silicon wafers is carried out in an acid mixture. The textured wafers are diffused with phosphorus in an open-tube furnace using a conventional POCl3 diffusion source. The sheet resistance obtained are in the range of 80–85 /. The phosphor silicate glass (PSG) formed during diffusion process is removed using an inline single side etching tool. The ARC deposition is done by plasma-enhanced chemical vapor deposition (PECVD) method to achieve desired ARC thickness and R.I. After proper benchmarking of the processes up to ARC, wafers are grouped into two batches of considerable number. The back metallization screen printing (with aluminum paste) is carried out using high precision DEK printer (Eclipse model). For front metallization (using silver paste), batch 1 is printed using conventional screen and paste, whereas batch 2 is printed using knotless screen and compatible paste by a renowned manufacturer. Knotless screens are nothing but screens that have a 0-degree mesh angle in its open areas. The schematic diagram of both the screen is shown in Fig. 2. The conventional screen has a mesh angle between 22.5 and 30°, and there is always a knot in the open area as seen in Fig. 2, part (a). The difference with knotless

Fine Line Printing for Solar Cells with Knotless Screens

Part (a)

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Part (b)

Fig. 2 Schematic diagram of screens (Conventional vs Knotless)

is that there is no wire-wire knot in the open area of the knotless screen as seen in part (b). Hence, printing with knotless screen ensures better transfer of paste on the wafer through thinner fingers. This in turn has a considerable effect on active area for solar power generation. In addition, with conventional printing higher thicknesses to increase the cross-sectional area screen printing technique is not fully production worthy. Techniques like Print on print, double print, etc., needs to be done which is time consuming and requires more paste quantity. Further, alignment of two prints is also an issue sometimes when printer is not up to the mark. These problems are eliminated if printing is done using knotless screens and with better transfer of paste to the wafer -higher thickness of the finger is also achieved. Use of knotless screen does not require any major change in the printer side. Hence, it can be used in the conventional production line by just replacing the screens. Printing of both the batches is then followed by baking and co-firing of the contacts in a conveyer belt furnace. The furnace zone temperatures, belt speed, and squeegee pressure are optimized and adjusted to get the desired print quality and temperature profile as recommended by paste manufacturer. The final printed cells are characterized by light I-V measurement. The measurement set up has a provision to hold solar cell firmly on a gold-plated, temperature controlled vacuum chuck. It is equipped with a AAA class light source, and results are very accurate and repeatable. EQE measurements are carried out using a setup supplied by M/s Bentham.

3 Results The samples were analyzed optically and electrically. The scanning electron microscope (SEM) images were taken to see the continuity and metallization finger profile. The images are shown in Fig. 3. The width and height of the fingers for 3 samples were measured using Banbros Microscope. The results are given in Table 1.

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Fig. 3 SEM images at 50X, a and 5000X, b showing uniform fingers printed by knotless screen

Table 1 Analysis of aspect ratio of solar cells printed with knotless screens vis-a-vis conventional screens S. No

Knotless screen printed samples

Conventional screen printed samples

Avg. height (µm)

Avg. width (µm)

Aspect ratio

Avg. height (µm)

Avg. width (µm)

Aspect ratio

1

21.21

33.47

0.63

48.22

17.27

0.35

2

20.50

32.83

0.62

49.56

18.19

0.36

3

20.20

34.93

0.58

49.85

19.62

0.39

It can be seen from the data in Table 1 that for solar cells printed with conventional screen with 40 microns finger width, aspect ratio up to 0.39 has been achieved. On the contrary, solar cells printed with knotless screens with 30 micron finger opening, the width is controlled and difference between screen opening and actual print is reduced. The height achieved is as high as ~35 microns which is quite motivating. Aspect ratio of 0.63 has been achieved. Achieving the same property using conventional screen is near to impossible. Table 2 shows the average electrical properties of both the batches where batch 1 is solar cells printed with knotless screen and batch 2 is solar cells printed with conventional screens. Table 2 Comparison of electrical properties of solar cells printed with knotless screens vis-a-vis conventional screens

Parameters

Batch-1

Batch-2

Sheet resistance (/)

80–85

80–85

Cell V oc (mV)

632 mV

630 mV

Cell I sc (Amp)

9.18 A

9.05 A

Series resistance

(-cm2 )

1.27

1.29

Fill factor

78.8%

78.9%

Cell efficiency

18.81%

18.51%

Fine Line Printing for Solar Cells with Knotless Screens

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It is inferred from the cell performance data that solar cells printed with knotless screens show increase in Short circuit current. This increase is attributable to increase in active area due to narrowing of fingers. The fill factor of solar cells is comparable in both the batches. Knotless screen cells show reduction in series resistance due to high aspect ratio. High aspect ratio means more current carrying capacity as it increases overall cross section of the metallized fingers. Since there is lesser shadowing and due to reduction in series resistance, an increase in short circuit current by 0.13 A is seen, enabling more charge carriers to be generated and collected by metal lines. All these factors lead to an improvement in solar cell efficiency of knotless screen printed cells by 0.3% absolute, as compared to conventional screen printed cells.

4 Conclusion A number of experiments have been conducted on full size (156.75 mm × 156.75 mm) mc-Si wafers for studying the effect of printing using knotless screens in place of conventional screens. Through the results, it can be invariably seen that solar cells printed with knotless screens have better uniformity, continuity of fingers, and finer fingers. Aspect ratio for fingers is better than 0.5. Shadow area of the fingers is reduced from about 6 to 5% which results in gain of short circuit current and hence higher efficiency. Knotless screens eliminate the knots in open area, which enables minimization in interruptions with thinner finger openings. Durability of screen was found to be better. Acknowledgements Authors are grateful to the BHEL management and staff for providing constant support and encouragement during the course of this work and finally for permitting publication of the results of the study. We also acknowledge the Department of Science and technology (DST), Government of India, for their generous support in establishing the printing and firing facilities. Authors are also thankful to IIT Delhi for extending their help in establishing the finger profile of fine grid lines.

References 1. T. Dullweber, H. Hannebauer, U. Baumann, T. Falcon, K. Bothe, S. Steckemetz, R. Brendel, Fine-line printed 5 busbar PERC solar cells with conversion efficiencies beyond 21%, in 29th EU PV Solar Energy Conference, p. 621 (2014) 2. Taiyang News, Market survey Metallization pastes 2018 3. M. Aoki, K. Nakamura, T. Tachibana, I. Sumita, H. Hayashi, H. Asada, Y. Ohshita, 30µm fineline printing for solar cells, in 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC) (2013) 4. Y. Zhang, L. Zhang, L. Jiang, L. Song, C. Guo, V. Dua, H. Yang, E. Kim, C. Chen, Knotless screen printing for crystalline silicon solar cells, in 7th Workshop on Metallization Konstanz (2017)

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5. A. Ebong, M.Hilali, V. Upadhyaya, B. Rounsaville, I. Ebong, A. Rohatgi, High efficiency screen printed planner solar cells on single crystalline silicon materials, in Georgia Institute of Technology, 777 Atlantic Drive, Atlanta, GA, pp. 30332–0250 6. T. Falcon, Ultra fine line printing for solar cells (2011)

Chemical Bath Deposited CdS Along with Electrodeposited and Closed Space Sublimated CdTe for Solar Cell Fabrication G. K. U. P. Gajanayake, A. A. I. Lakmal, D. S. M. De Silva, and B. S. Dassanayake

1 Introduction Among the means of energy generation, photovoltaics can be regarded as the most attractive, ecofriendly and unfailing technology. Among the photovoltaic devices, the CdTe thin film devices are at the forefront and gradually emerging at commercial level. CdTe has been recognized as a remarkable material due to its optimal band gap of 1.45 eV which allows a film of 1–3 µm thickness to absorb more than 90% of lights energy [1]. The thin film CdS window material and CdTe absorber material are often deposited using methods such as chemical bath deposition (CBD), closed space sublimation (CSS), thermal evaporation (TE), screen printing and electrodeposition (ED) [1, 2]. Fabrication methods for CdS and CdTe layers have a significant effect on cell efficiency and cost of manufacture. Among these deposition techniques, the effective use of CBD for CdS and ED for CdTe thin film growth was reported recently [3]. This combination of growth techniques is quite inexpensive and needs attempts for further development. The reporting work discusses the CdS/CdTe solar cell performance by improvisation of CdS layer to act as a steady substrate in EDCdTe formation and compares the cell performance by pairing the CdS layer along with an electrodeposited and closed space sublimated-CdTe thin films.

G. K. U. P. Gajanayake · D. S. M. De Silva (B) Department of Chemistry, University of Kelaniya, Kelaniya, Sri Lanka e-mail: [email protected] A. A. I. Lakmal · B. S. Dassanayake Department of Physics, University of Peradeniya, Peradeniya, Sri Lanka © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_2

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2 Fabrication of CBD-CdS/ED-CdTe and CBD-CdS/CSS-CdTe Devices 2.1 Chemical Bath Deposition of CdS The chemical bath deposition is the simplest and well-suited method for large area CdS thin film fabrication that allows the material growth on both conducting and non-conductive substrates. The controlling factors of growth are the concentration of precursor ions, bath temperature and its pH and the rate of stirring during the deposition. Thin films of CdS were grown using Cd(CH3 COO)2 , CS(NH2 )2 as cadmium and sulfur precursors, respectively, while the pH of the bath was regulated with NH4 OH and NH4 (CH3 COO). Previously reported CBD bath conditions [4] were applied to produce one set of CdS*, while the another set of CdS was prepared as detailed in our recent publication [3]. Although the former CdS* was distressed in the highly acidic ED bath of CdTe, the CdS remained unaffected in the same. The CdS* and CdS samples were thermally annealed in air at 375 °C for 30 min, prior to the deposition of CdTe absorber layer. The film thickness of the both CBD-CdS was maintained around 80–85 nm.

2.2 Electrodeposition of CdTe Electrodeposition is a low-cost fabrication method for deposition of a wide variety of thin films which is based on reduction or deposition potential of counter ions in the electrolyte. Though there are many experimental factors to be considered in controlling the process, in situ observations make it more viable. The thin films of CdTe were electrodeposited [5] on air annealed glass/FTO/CBDCdS in a three electrode electrolytic bath. Subsequently, glass/FTO/CBD-CdS/EDCdTe samples were treated with CdCl2 prior to air annealing.

2.3 Closed Space Sublimation of CdTe The closed space sublimation technique is one of the fastest and simplest physical vapor deposition methods of thin film fabrication. During the deposition of CSSCdTe, evaporation grade CdTe powder was added to a graphite crucible, and the FTO/CdS substrates were kept on the crucible so that the source–substrate separation was maintained at 4 mm. Prior to the deposition of the CSS-CdTe absorber layer, the vacuum chamber was purged with Ar, and later, the Ar pressure was maintained at 7.9 Torr. Then, the substrate temperature and the source temperature were ramped up to 580 and 640 °C, respectively, and maintained for 25 min, allowing the

Chemical Bath Deposited CdS Along …

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Fig. 1 Schematics of the glass/FTO/CdS/CdTe device

solid CdTe material to be sublimated on a glass/FTO/CdS substrates. Thereafter, the glass/FTO/CBD-CdS/CSS-CdTe samples were mediated for NP etching followed by Cu/Au back contact formation by thermal evaporation. The structure of the glass/FTO/CBD-CdS/CdTe is illustrated in Fig. 1.

3 Experimental Elucidations 3.1 XRD Analysis The GIXRD was performed to identify the structural properties of the CdTe materials deposited by ED and CSS techniques. According to the reference pattern (PDF-00015-0770), the diffraction peaks ensured the formation of cubic CdTe lattice in both Ed-CdTe and CSS-CdTe with characteristic diffractions by (111), (220) and (311) planes (Fig. 2). The crystallite size (D) and the microstrain (ε) of both ED-CdTe and CSS-CdTe materials were estimated based on the most intense diffraction from (111) by using the Scherrer’s formula D = 0.9λ/β cos θ and ε = β4 tan θ, respectively, [1, 6] as shown in Table 1. The full width at half maximum (β) values was calculated using Lorentz fitting with the diffractograms. Consequently, the CdTe material grown by CSS technique demonstrated higher crystallite sizes and lower microstrain compared to those of ED-CdTe, suggesting higher crystallinity of the material grown by CSS.

G. K. U. P. Gajanayake et al.

Intensity (a.u.)

10 700 600 500 200 100 0 1200 1000 800 200

C (111)

CSS-CdTe C (220)

C (311)

C (400) C (331)

C (422) C (511)

ED-CdTe

0 300

FTO

200 100 0

20

30

40

50

60

70

80

Fig. 2 The GIXRD pattern of electrodeposited and closed space sublimated CdTe on glass/FTO

Table 1 Crystallite size and the microstrain of the ED-CdTe and CSS-CdTe materials

Sample

Crystallite size (nm)

Microstrain (10–3 )

ED-CdTe

35.7050

4.706

CSS-CdTe

37.0178

4.541

3.2 Performance of the Photovoltaic Cells The performance of the devices glass/FTO/CBD-CdS/ED-CdTe/Cu/Au, glass/FTO/CBD-CdS/CSS-CdTe/Cu/Au and glass/FTO/CBD-CdS*/CSSCdTe/Cu/Au was characterized under the illumination of 100 mW/cm2 . Among, the highest open circuit voltage (V oc ) was obtained for the device with CBDCdS/ED-CdTe (Fig. 3, Table 2). Remarkable short circuit current densities (J sc ) of 36.7 and 35.6 mA/cm2 were observed for CBD-CdS*/CSS-CdTe and CBDCdS/CSS-CdTe, respectively, which can be credited to the better crystallinity of the CSS-CdTe absorber layer. The efficiency of the CBD-CdS*/ED-CdTe was 7.8% while CBD-CdS/ED-CdTe device was 6.2% and CBD-CdS/CSS-CdTe was 8.7%. Further, the difference in performance of CBD-CdS*/CSS-CdTe and CBDCdS/CSS-CdTe can be resulted due to the structural changes observed in CdS and CdS*. As reported by Gajanayake et al. [3] the lattice of CBD-CdS was found to be mixed hexagonal/cubic (60:40%) structure, while that of CBD-CdS* was mostly hexagonal (70%). The performance of the blend CdS was reported to be shown better performance as reported elsewhere [7, 8].

Chemical Bath Deposited CdS Along …

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Fig. 3 J-V characteristics of CdS/CdTe solar cells with different CdS films and different CdTe deposition techniques

Table 2 Performance of the glass/FTO/CBD-CdS*/CSS-CdTe, glass/FTO/CBD-CdS/ED-CdTe and glass/FTO/CBD-CdS/CSS-CdTe solar cell devices CBD-CdS*/CSS-CdTe CBD-CdS/ED-CdTe CBD-CdS/CSS-CdTe Open circuit voltage (V oc ) (mV)

510

664

585

Short circuit current 36.7 density (J sc ) (mA/cm2 )

24.7

35.6

Fill factor (FF)

41.6

38.0

42.0

Efficiency (η)

7.8

6.2

8.7

4 Conclusions Thin films of identical CBD-CdS were used to fabricate glass/FTO/CBD-CdS/EDCdTe/Cu/Au and glass/FTO/CBD-CdS/CSS-CdTe/Cu/Au devices successfully, yielding efficiencies 6.2% and 8.7%, respectively, while the glass/FTO/CBDCdS*/CSS-CdTe/Cu/Au device fabricated using the conventional recipe of CBDCdS yielded 7.8%. Also, the CSS-CdTe was found to result better conversion efficiency when compared to ED-CdTe. Both the CSS-CdTe deposited devices yielded impressive J sc value in excess of 35 mA/cm2 . Acknowledgements This work was supported by the State Ministry of Skills Development, Vocational Education, Research and Innovations, Sri Lanka, under the Edu-Training program on Prototype Manufacturing of Solar Panels, the Innovation Research Grant of the University Grants Commission of Sri Lanka, Prof. Siva Sivananthan and Sivananthan Laboratories INC, USA.

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References 1. K.S. Rahman, M.N. Harif, H.N. Rosly, M.I.B. Kamaruzzaman, M. Akhtaruzzaman, M. Alghoul, H. Misran, N. Amin, Influence of deposition time in CdTe thin film properties grown by CloseSpaced Sublimation (CSS) for photovoltaic application. Results Phys. 14(102371) (2019) 2. N. Amin, K.S. Rahman, Close-spaced sublimation (CSS): a low-cost, high, in Modern Technologies for Creating the Thin-film Systems and Coatings, s.l (Intech Open, 2017), pp. 361–379 3. G.K.U.P. Gajanayake, D.S.M. De Silva, H.Y.R. Atapattu, Altering NH4OH concentration in producing chemical bath deposited CdS. Mater. Sci. Eng. B 265(114952) (2021) 4. D.H. Rose, F.S. Hasoon, R.G. Dhere, D.S. Albin, R.M. Ribelin, X.S. Li, Y. Mahathongdy, T.A. Gessert, P. Sheldon, Fabrication procedures and process sensitivities for CdS/CdTe solar cells. Prog. Photovoltaics Res. Appl. 7, 331–340 (1999) 5. H.Y.R. Atapattu, D.S.M. De Silva, K.A.S. Pathiratne. I.M. Darmadasa, An investigation into the effect of rate of stirring of bath electrolyte on the properties of electrodeposited CdTe thin film semiconductors. J. Mater. Sci. Mater. Electron, 6236–6244 (2018) 6. B.E. Warren, X-ray diffraction (Dover Publications Inc., New York, 1990) 7. Kaur, D.K. Pandya, K.L. Chopr, Growth kinetics and polymorphism of chemically deposited CdS films. Electrochem. Soc. 943–948 (1980) 8. H. Moualkia, S. Hariech, M.S. Aida, N. Attaf, E.L. Laifa, Growth and physical properties of CdS thin films prepared by chemical bath deposition. J. Phys. D Appl. Phys. 7 (2009) 9. B.E. McCandless, J. S. Sites, Cadmium telluride solar cells, in: Handbook of Photovoltaic Science and Engineering (John Wiley & Sons, 2003), pp. 617–662 10. Y.D. Gambury, G. Zangari, Theory and practice of metal electrodeposition (Springer, New York, 2011)

Reducing Land Occupancy Using Solar PV Artefact: A Study Maharshi Vyas, Sumit Chowdhury, Abhishek Verma, D. N. Singh, and V. K. Jain

Abbreviations CAPEX EV kWp LCOE PV RE SPV STC

Capital expenditures Electric vehicle Kilo-watt peak Levelized cost of energy Photovoltaic Renewable energy Solar photovoltaic Standard test conditions

1 Introduction The quest for green and sustainable energy sources has become one of the biggest challenges for our time, due to the swift exhaustion of conventional fossil fuels, climate change, global warming, and forever-growing energy demand [1]. The major application of solar energy is in solar PV. Due to rapidly increasing urbanization and M. Vyas · S. Chowdhury · A. Verma (B) · V. K. Jain Amity Institute of Renewable and Alternate Energy, Amity University Uttar Pradesh, Sector 125, Noida, UP 201313, India e-mail: [email protected] A. Verma · V. K. Jain Amity Institute for Advanced Research and Studies (Materials and Devices), Amity University Uttar Pradesh, Sector 125, Noida, UP 201313, India D. N. Singh Bergen Group, Gurgaon, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_3

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use of land, plain empty land area is very scarcely available for installation of solar PV plants and procurement of land for SPV projects both expensive and difficult in urban areas. In urban landscapes, building integrated SPV systems can be used, but their cost and operational efficiency are still not addressed. To promote solar energy among public and motivate them to switch to renewables, new type of structures which are aesthetically pleasing and require less land area for installation need to be used. In this paper, the authors have proposed a concept of solar artefact design to replace conventional-style ground-mounted SPV plants. The solar artefact structure has very less land area requirement, which can help address the issue of land scarcity for SPV installations.

2 Simulation Study In this simulation study, we have worked on a comparative study of conventionalstyle SPV plant installed on ground, with the solar artefact design. The study is based in Delhi NCR region of India. The main aim of this simulation study is to propose an effective, artistic, and novel solution for reducing the land area occupancy in SPV plants. A land area of 500 m2 is selected in Delhi NCR region, and a conventionalstyle SPV power plant is designed in Sketchup software as shown in Fig. 1. The conventional-style SPV plant is installed on ground with a clearance of 500 mm from ground level. The PV modules are placed at an angle of 20° and azimuth of 0°. PV modules are installed in a structure configuration of 2P9, i.e.

Fig. 1 Graphical layout design of conventional-style SPV power plant

Reducing Land Occupancy Using Solar PV Artefact: A Study

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Fig. 2 Inverter mounting arrangement in conventional-style SPV power plant

two rows and nine PV modules in each row in portrait orientation. The structure is supported on ground using pile foundations. Each structure uses two pile foundations on ground. The inverters are usually mounted on the structure at the backside of PV modules or on a separate inverter-stand near the PV modules (refer Fig. 2). Total six structures of 2P9 configuration have 108 PV modules, each with a rating of 380 Wp (at STC). Hence, total DC capacity of the plant is 41.04 kWp. One inverter of 33 kW rating is used in this system; hence, the total DC:AC ratio is 1.24:1. Here, the pitch between two rows is kept 8.5 m, in order to have the PV modules shadow-free from 08:00 am to 04:00 pm (as per shadow analysis done for 21st December, in Sketchup software). As a part of this simulation study, the authors have proposed a new solar PV artefact design. The SPV artefact model is named Banyan Tower model. This model is supported by one single support structure in the middle, as shown in Fig. 3. The SPV modules are installed at an angle of 20° and with three different azimuth angles. The branches are attached to the main support structure on three different sides, facing three directions. SPV modules are not installed at an azimuth of 180° (facing north direction) as the energy generation decreases when PV modules are facing north (refer Fig. 4). There are 36 PV modules installed, facing south, east, and west directions; hence, the total number of PV modules in this artefact is 108, leading to total DC capacity to 41.04 kWp (which is same as the DC capacity of conventional-style ground-mounted SPV power plant installed in 500 m2 area). The azimuth angles for each pair of 36 PV modules are 0°, 90°, and −90° (from true south). In the selected land area of 500 m2 , the land area occupied by the foundation of the support structure in Banyan Tower is 16 m2 . The ground clearance of

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Fig. 3 Graphical layout design of Banyan Tower (SPV artefact)

Fig. 4 Side view of graphical layout design of Banyan Tower (indicating no North facing panels)

the lowest edge of PV modules is 8 m, and the height of the Banyan Tower is approximately 10.5 m. The support structure of Banyan Tower can be made using steel or concrete (re-enforced with steel bars). As shown in Fig. 5, the inner branches have been installed with an outward slope, while the outer branches have been installed

Reducing Land Occupancy Using Solar PV Artefact: A Study

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Fig. 5 Arrangement of branches in Banyan Tower

with an inward facing slope, to avoid shadows falling on the PV modules. The main idea behind the design of this SPV artefact model is to generate same DC power as compared to conventional ground-mounted SPV plant while using minimum land area.

3 Results and Discussion The concept of Banyan Tower is proposed in order to achieve the target of generating same amount of DC power as generated by ground-mounted SPV plant while utilizing as minimum land area as possible. A comparison between conventional-style groundmounted SPV plant and Banyan Tower artefact can be seen in Table 1. Through the simulation study, we can conclude that the Banyan Tower generates 41.04 kWp power by utilizing 16 m2 area out of the total available land area of 500 m2 . Here, it is to be noted that only 16 m2 land area becomes unusable for any other purpose, whereas the remaining land area is available for other uses. Also, the ground clearance of the PV modules in Banyan Tree is also very high (8 m) as compared to conventional ground-mounted SPV plant structure. In case of conventional ground-mounted SPV plant, out of the available land area of 500 m2 , no land area is available for any other uses, as the ground clearance of PV modules is less (0.5 m) as compared to that in Banyan Tower. The higher ground clearance in Banyan Tower gives an additional advantage of higher air flow around the PV modules, which provides an additional cooling effect on the PV modules and

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Table 1 Comparison of Banyan Tower v/s conventional ground-mounted SPV plant S. No

Particulars

Ground-mounted plant

Banyan tower

1

Diagram

2

PV modules rating (Wp)

380

380

3

Inverter rating (kW)

33

33

4

No. of PV modules in each structure

18

108

5

Total no. of structures simulation

6

1

6

Total number of PV modules in entire plant

108

108

7

Total DC capacity (kWp)

41.04

41.04

8

Total AC capacity (kW)

33

33

9

Ground clearance (m)

0.5

8

10

Height of structure (m)

2.1

10.5

11

Total land area available (m2 )

500

500

12

Land area occupied by the plant (m2 )

500

16

13

Land area that is free for use in other purposes (m2 )

0

484

14

DC power generated per unit land area occupied (kWp/m2 )

0.08

2.56

15

Land area required per kWp (m2 /kWp)

12.18

0.39

resulting into lesser temperature losses as compared to conventional ground-mounted PV plant. As shown in Table 1, the Banyan Tower occupies only 3.2% of the land area occupied by conventional ground-mounted SPV plant, bringing the land area requirement per kWp to 0.39 m2 /kWp in case of Banyan Tower, as compared to 12.18 m2 /kWp in case of conventional ground-mounted SPV plant. For an example, in Delhi NCR region, as per the market rates prevalent in the year 2020, the land area procurement cost is |0.1400 per sq. ft., which is approximately |0.15,400 per m2 of land area [11]. In our simulation study, in case of conventional ground-mounted SPV plant, total 500 m2 land area is used, which costs around |0.77 lakh. In case of Banyan Tower, out of total land area of 500 m2 , only 16 m2 is used for installation of the SPV artefact, which amounts to |0.2.46 lakh. Here, the remaining land area of 484 m2 can be utilized for other purposes like farming, car parking, EV charging station, recreational park, cottage industry shops. Only the cost of 16 m2 area will be added in the CAPEX budget of installing Banyan Tower,

Reducing Land Occupancy Using Solar PV Artefact: A Study

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whereas the cost of entire 500 m2 land area will be added in the CAPEX budget of installing a conventional ground-mounted SPV power plant. Thus, Banyan Tower can be beneficial for saving the land area and the CAPEX cost incurred for procurement of land.

4 Conclusion Due to rapid urbanization and increase in population, the scarcity of land area increases, thus resulting into inflation in land prices. While calculation of LCOE for SPV plant, land price also needs to be considered in the CAPEX budget, which drastically impacts the cost of installation of SPV plant. By use of Banyan Tree model, the land procurement price can be brought down by almost 97% (as compared to that in conventional ground-mounted SPV plant), while maintaining the same DC power generation in comparison with the latter. The DC power generated per unit land area occupied in conventional ground-mounted SPV plant is 0.08 kWp/m2 , while that in Banyan Tower is 2.56 kWp /m2 . As a part of future scope, more different designs of SPV tower and artefact can be designed and their energy generation and structural comparison can be done in comparison with the conventional ground-mounted SPV plant. Acknowledgements Authors are thankful to Dr. Ashok K. Chauhan, Founder President, Amity University, for his continuous encouragement and support. One of the authors, Mr. Maharshi Vyas would like to thank Mr. Anant Patil, Ph. D Scholar, Amity University, Gurugram, Haryana, and Mr. Sachitanand Singh, Aryabhatt Institute of Technology, Delhi, for assisting in designing the solar tree models in this research.

References 1. A.K. Shukla, K. Sudhakar, P. Baredar, Renewable energy resources in South Asian countries: challenges, policy and recommendations. Resour-Effic. Technol. (2017). https://doi.org/10. 1016/j.reffit.2016.12.003 2. C. Small, Wind and Waves, and the Sun: The Rise of Alternative Energy (Cavendish Square Publishing, LLC, 2017) 3. R. Lamb, Analysis of net-zero energy homes and net-zero energy communities in hot and humid climates from the builder”s perspective, The University of Florida (Doctoral dissertation) (2009), pp. 1–108 4. S. Dey, M.K. Lakshmanan, B. Pesala, Tuning the solar power generation curve by optimal design of solar tree, in Advances in Energy Research, vol. 1: Selected Papers from ICAER 2017 (2020), 461 p 5. S. Gupta, M. Gupta, The benefits and applications of solar tree with natural beauty of trees. Int. J. Electr. Electron. Eng. 29–34 (2015) 6. S. Gupta, Quantum solar tree- design and production for domestic applications and future trends. IJAR 3(3), 439–444 (2017)

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7. S.N. Maity, Development of solar power tree–an innovation that uses up very less land and yet generates much more energy from the sun rays by SPV method. J. Environ. Nanotechnol. 2, 59–69 (2013) 8. J. Kaldellis, M. Kapsali, K. Kavadias, Temperature and wind speed impact on the efficiency of PV installations. Experience obtained from outdoor measurements in Greece. Renew. Energy 66, 612–624 (2014). https://doi.org/10.1016/j.renene.2013.12.041 9. F. Hyder, K. Sudhakar, R. Mamat, Solar PV tree design: a review. Renew. Sustain. Energy Rev. 82, 1079–1096 (2018) 10. P. Pandiyan, S. Saravanan, N. Prabaharan, R. Tiwari, T. Chinnadurai, N.R. Babu, E. Hossain, Implementation of different MPPT techniques in solar PV tree under partial shading conditions. Sustainability 13(13), 7208 (2021) 11. Property Rates & Price Trends in Delhi—2020. Accessed 02 June 2021. https://www.makaan. com/lite/price-trends/proprty-rates-for-buy-in-delhi

Recent Advances in Hybrid Organic–Inorganic Perovskite Solar Cells with Different Halides and Their Combinations Jampana Gayathri, Dalip Singh Mehta, and Kanchan Saxena

1 Introduction Among the third-generation solar cells, PSCs are intensively studied solar cells in the last decade given to their capabilities to form high-quality crystalline structure by low temperature solution processing and cost-effective fabrication. Perovskite used as an absorber layer in solar cells has many advantages like excellent tunable optical properties [1]; efficient charge collection [2]; low exciton binding energy [3]; higher absorption coefficient [4]; and long carrier diffusion lengths [5] have achieved an efficiency of 24.8% [6]. Hybrid perovskite is a combination of organic materials, metals and halide (halogen group) used as a light absorber material. The general formula for organic– inorganic hybrid perovskite solar cell is ABX3 (as shown in Fig. 1), where A is organic cation usually methyl ammonium (MA) (CH3 NH3 )+ or formamidium (FA) ((CH(NH2 )2 + ), B refers to a metallic cation (Pb, Sn, etc.), and X is the halide anion, e.g., I− , Cl− , Br− , or mixed halides like I− –Br− , I− –Cl− , or I− –Cl− –Br− . Perovskite stands at third position in terms of efficiency according to best cell efficiencies maintained by National Renewable Energy Laboratories (NREL) [7]. In this review, we investigate different halide perovskite-based solar cells and their efficiency trends.

J. Gayathri · K. Saxena (B) Amity Institute of Renewable and Alternative Energy, Amity University, Uttar Pradesh Sector 125, Noida, UP 201313, India e-mail: [email protected] Amity Institute of Advanced Research and Studies (Materials and Devices), Amity University, Uttar Pradesh Sector 125, Noida, UP 201313, India D. S. Mehta Department of Physics, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_4

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Fig. 1 Perovskite crystal structure

2 Efficiency Trends for Different Halides Two different architectures, namely mesoporous [6, 8] and planar structures [9, 10], were employed for the fabrication of PSCs. The mesoporous structure consists of a layer of compact TiO2 (c–TiO2 ), mesoporous TiO2 (mp–TiO2 ), or mesoporous Al2 O3 (mp–Al2 O3 ) [6, 11]. Different perovskite materials have been used as an active layer such as methyl ammonium lead iodide (MAPbI3 ) [12], methyl ammonium lead bromide (MAPbBr3 ) [13], formamidium lead iodide (FAPbI3 ) [6], formamidium lead bromide (FAPbBr3 ) [9], or mixed perovskites like MAPbI3−x Clx [11], MAPbI3−x Brx [14], (FAPbI3 )1−x (MAPbBr3 )x [8], Csx (MA0.17 FA0.83 )(100−x) Pb(I0.83 Br0.17 )3 [15], etc. Hole transport layers such as poly [bis(4-phenyl) (2,4,6-trimethylphenyl)amine] (PTAA), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), (Spiro2,2 ,7,7 -Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9 -spirobifluorene OMeTAD), and (N2,N2 , N7,N7 -tetrakis(9,9-dimethyl-9H-fluoren-2-yl)N2,N2 ,N7,N7 —tetrakis(4-methoxyphenyl)-9,9 -spirobi[fluorene]-2,2 ,7,7 tetraamine) (DM) [8–15], have been used. Various electron transport layers (ETLs), e.g., fullerene (C60), (Poly[3-(4-carboxybutyl)thiophene-2,5-diyl) (P3CTN), [6]-phenyl-C61 -butyric acid methyl ester (PC61 BM), bathocuproine (BCP), etc., have been used in PSCs inverted structures [8–15].

2.1 Iodine Based Various architectures based on iodine halide have been employed in perovskite solar cells. MAPbI3 (CH3 NH3 PbI3 ) is most commonly used perovskite material for the fabrication of PSCs. Perovskite was used as an alternative to sensitizer in DSSC configuration. In 2009, Kojima et al. used CH3 NH3 PbI3 as an active material to absorb

Recent Advances in Hybrid Organic–Inorganic …

23

light deposited on nano-crystalline-TiO2 coated substrates and achieved PCE of 3.81% [16]. In 2011, Im et al. produced CH3 NH3 PbI3 quantum-dot sensitizer of size 2–3 nm as it was enough to cover nano-crystalline TiO2 pores and varied the concentrations of equimolar mixture of CH3 NH3 I and PbI2 , modified the TiO2 surface and tried different annealing temperatures and achieved a PCE for quantum dot sensitizer of 6.54% at 100 mWcm−2 [17]. To enhance the stability, Kim et al. in 2012 replaced liquid electrolyte with hole transport layer-spiro-MeOTAD and achieved a PCE of 9.74% with CH3 NH3 PbI3 [18]. They also successfully demonstrated charge carrier separation from light excited hybrid perovskite (CH3 NH3 PbI3 ) using femto second laser spectroscopy where holes are injected into p-type organic spiro-MeOTAD and electrons toward n-type inorganic TiO2 [18]. Etgar and co-workers fabricated hole conductor free perovskite solar cell and synthesized TiO2 nanosheets with dominant facets as the electron transport for the first time and showed the ambipolar nature of CH3 NH3 PbI3 which acts as light absorber as well as hole transporter, allowing the electron injection into the TiO2 layer and holes into the back contact Au [19]. They achieved a maximum PCE of 7.28% at 100 W/m2 and 5.5% at 1000 W/m2 [19]. Further, Malinkiewicz et al. have produced inverted thin-film solar cell based on metal oxide and scaffold free perovskite (CH3 NH3 PbI3 ) crystals utilizing organic n-type (PCBM) and p-type (PEDOT: PSS) layers as charge transport layers acting as hole and electron blocking layers, respectively, in a high vacuum chamber at room temperature and obtained a power conversion efficiency of 12% at 100 mW cm−2 [20]. To avoid large morphological variations due to uncontrolled precipitations, Burschka et al. [21] demonstrated sequential deposition of the perovskite (CH3 NH3 PbI3 ) for the first time by depositing PbI2 first on top of the nanoporous TiO2 and then transforming into perovskite by exposing it to CH3 NH3 I solution where the color of the composite TiO2 /PbI2 film changes from yellow to dark brown which indicates the formation of the perovskite and achieved a PCE of 14.4%. Over the years, the efficiency of iodide-based PSCs have been significantly improved by researchers using different approaches [22–25]. Jeong et al. [6] developed PSCs with Spiro-OMeTAD as HTM and developed two fluorinated isomeric analogs Spiro-mF and Spiro-oF. They achieved the best PCE of 24.8% for iodidebased halide PSC with configuration FTO/C-TiO2 -mp-TiO2 /FAPbI3 /Spiro-mF/Au [6].

2.2 Bromine Based It is well known that bromine-based PSCs has larger bandgap compared to iodinebased PSCs [26]. Moreover, they are moisture insensitive and thermally stable due to its closely packed cubic structure which avoids phase transition [26]. The first photovoltaic application of Br-based perovskite solar cell was reported by Kojima et al. in 2006 using CH3 NH3 PbBr3 (MAPbBr3 ) as absorber material which resulted into a nano-structured TiO2 perovskite-sensitized solar cell where TiO2 works as an ETL and they achieved power conversion efficiency (PCE) of 2.19% [13]. Later in

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2009, they developed perovskite layer CH3 NH3 PbBr3 and achieved a PCE of 3.13% using nano-crystalline TiO2 as ETL and Pt-coated FTO as counter electrode [16]. Over the years, the efficiency has been improved and Br-based halide perovskites became one of the most explored PSCs. Hanusch and co-workers in 2014 fabricated FAPbBr3 (having wide bandgap) perovskite absorber layer for the first time and showed that FAPbBr3 has longer diffusion length, higher charge collection, higher thermal stability as FA cation spaces the PbBr6 extra owing to its larger size compared to MAPbBr3 [27]. They have achieved a PCE of 6.5% for planar heterojunction PSC without the necessity of mesoporous scaffold [27]. The best efficiency for brominebased halide perovskite was reported in 2018 by Zhang et al. [9]. They fabricated FAPbBr3 by two-step deposition process with compact SnO2 as the ETL as it has advantages like high stability and efficiency compared to TiO2 . The intermolecular exchange process is tuned by adding different concentrations of urea to complement with Pb during the growth process of the perovskite layer and reported a PCE of 10.61% [9].

2.3 Iodine-Chlorine Mixed Halide An interesting deviation from simple iodine-based (MAPbI3 ) PSC is adding a small amount of Cl to this composition and making it a mixed phase perovskite (MAPbI3−x Clx ) which increased the bandgap, stability, decreased the recombination and helped in the charge transfer in the PSC [28]. In 2012, Lee and co-workers worked on meso-super structured solar cells (MSSC) using extremely thin layer of mixed halide perovskite (CH3 NH3 PbI2 Cl) adsorbed on electron transport layers mpTiO2 and mp-Al2 O3 and witnessed PCE up to 8% and 10.9%, respectively [11]. They analyzed that due to the band mismatching electrons could not jump in the conduction band of mp-Al2 O3 , so it just delivers a scaffold structure for better coverage. This was the first time when ambipolar characteristic of perovskite material was observed which acts as a light absorber and electron conductor [11]. In the following year 2013, Ball and coworkers reported a perovskite solar cell with planar architecture, where CH3 NH3 PbI3−x Clx perovskite absorber layer can act as absorber layer and charge carrier separation and transportation to their selective contacts [29]. A compact nonmesoporous TiO2 layer was used as hole-blocking layer to avoid losses due to poor interface. They observed a higher PCE of 12.3% [29]. Wojciechowski et al. developed CH3 NH3 PbI3−x Clx based low temperature processed (150ºC) MSSC using two metal oxide nanoparticles of highly crystalline anastase-TiO2 and inert Al2 O3 and have reported an efficiency of 15.9% [30]. In 2019, Wu et al. [10] showed the best efficiency till date for perovskite MAPbI3-x Clx based solar cell using P3CT-N and PC61 BM as charge carrying layers. They have doped different concentrations (0–5%) chloroformamidinium chloride (Cl-FACl) to the precursor solution of the perovskite as a competitor and stabilizer to regulate the formation and advance the optoelectronic properties. The devices with the Cl-FACl additive showed greater average lifetime of 110.1 ns compared with the control device without the additive of 90.3 ns. The

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device with Cl-FACl doping has exhibited a best PCE of 20.36% in the forward scan with V oc = 1.2 V, J sc = 22.10 mA/cm2 and F F = 0.81[10].

2.4 Iodine-Bromine Mixed Halide Bromine added to iodide-based perovskite compound tuned the optical properties producing increased overall efficiency and stability of the device. Jeon et al. [14] reported a solution processed PSC with dense and uniform perovskite layer MAPb(I1−x Brx )3 where the precursors are mixed with DMSO and γ-butyrolactone (GBL) followed by anti-solvent toluene to remove the excess DMSO. They used PTAA as the HTL and achieved a PCE of 16.2% compared to the mp-TiO2 HTL of PCE 15.9% [14]. Yi et al. [31] developed a mixed cation and halide-based perovskite. Cs added to FAPbI3 showed better absorption near IR and the stabilization of the perovskite phase. Br added to this composition Csx FA(1−x) PbI3 caused no change in the perovskite phase and showed a blue shift from 785 to 735 nm which was observed using UV–vis spectroscopy. They have achieved the best device with the composition of Cs0.2 FA0.8 PbI2.84 Br0.16 without any phase transitions at the inactive or yellow or δ phases at a rather low temperature yielding a power conversion efficiency of 17.35% with the best efficiency of 18.02% by replacing small fraction of bromide anions with iodide [31]. In another approach, Saliba et al. [15] have studied that adding Cs improved the MA/FA cation-based perovskite compound by suppressing the impurities resulting in defect-free PSCs. Therefore, for the first time, using triple cation mixed halide perovskite (Csx (MA0.17 FA0.83 )(100−x) Pb(I0.83 Br0.17 )3 ) as an absorber layer achieved a PCE of 21.1% and a record of 18% PCE after 250 h under full illumination at room temperature [15]. Further, Ergen and coworkers fabricated graded bandgap PSCs with steady state efficiency using absorber layers CH3 NH3 SnI3 and CH3 NH3 PbI3−x Brx with hexagonal-boron nitride (h-BN) layer sandwiched between to avoid cation mixing deposited on top of HTLgraphene aerogel (GA) which avoids moisture access and helps in crystallinity and morphology [32]. Both h-BN and GA enable this graded bandgap PSC achieving a PCE of 21.7% [32]. Jeon and co-workers [8] fabricated highly efficient and stable PSCs with (FAPbI3 )0.95 (MAPbBr3 )0.05 as the absorber layer and a fluorine-terminated HTL named DM with device configuration (FTO) substrate/blocking layer of compact TiO2 (c-TiO2 )/mp-TiO2 /(FAPbI3 )0.95 (MAPbBr3 )0.05 /HTL/Au. Different concentrations of Li-TFSI (Lithium bis (trifluoromethanesulfonyl) imide) and tBP additives were doped to the HTL by optimizing carefully. They achieved a best PCE with 10 μl dopant of 23.2% in reverse scan with J sc , V oc , and FF of 24.91(mA/cm2 ), 1.144 V, and 81.29%, respectively [8], which is the record breaking PCE for perovskite solar cells till date for mixed halide PSCs (Table 1).

1.14 1.11

I & Br mixed FTO/c–TiO2 –mp–TiO2 /(FAPbI3 )0.95 (MAPbBr3 )0.05 /DM with Li–TFSI/Au 24.9

I & Cl mixed

ITO/P3CT-N/MAPbI3-x Clx /PC61 BM/BCP(bathocuproine) /Ag

1.16

26.35 8.39

FTO/C–TiO2 –mp–TiO2 /FAPbI3 /Spiro-mF/Au

Bromide (Br) FTOglass/SnO2 /FAPbBr3 /Spiro-OMeTAD/Au 22.10

1.16

0.81 20.36

0.81 23.2

0.73 10.61

2020

Year

Wu et al. [10]

Jeon et al. [8]

2019

2018

Zhang et al. [9] 2018

Jeong et al. [6]

PCE (%) References 0.80 24.82

(mA/cm2 ) V oc (V) F F

Iodide (I)

Device parameters

Device architecture

Halide used

Table 1 Best efficiency achieved by different halide PSCs

26 J. Gayathri et al.

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3 Conclusion Iodine, chlorine, and bromine have similar properties but incorporated into perovskites MAPbCl3 and MAPbBr3 show higher band gaps of 3.11 and 2.22 eV compared to that of MAPbI3 1.5 eV [33]. The larger bandgap of the MAPbCl3 suggest that it may block both electron and hole extraction, and therefore, it is the least explored material in PSCs [34]. On the other hand, MAPbBr3 which is moisture and thermally stable have low efficiencies because Eg/q –V oc value is rather high 0.93 V compared to MAPbI3 with 0.45 V [26]. Coming to mixed halide perovskites, optical properties can be tuned by adding halogen bromide or chloride to iodide-based perovskite compound by reducing the lattice constants, and increasing the band gap by relocating the energy bands in band structure resulting in increased efficiency, stability, and overall performance of the device [35].

References 1. M.R. Filip, G.E. Eperon, H.J. Snaith, F. Giustino, “Steric engineering of metal-halide perovskites with tunable optical band gaps. Nat Comm. 5(1), 6757 (2014) 2. N.J. Jeon, J.H. Noh, W.S. Yang, Y.C. Kim, S. Ryu, J. Seo, S. Il Seok, Compositional engineering of perovskite materials for high-performance solar cells. Nat. 517(7535), 476–480 (2015) 3. N.-G. Park, Perovskite solar cells: an emerging photovoltaic technology. Mater. Today 18(2), 65–72 (2015) 4. Y. Yamada, T. Nakamura, M. Endo, A. Wakamiya, Y. Kanemitsu, Photocarrier recombination dynamics in perovskite CH3NH3PbI3 for solar cell applications. J. of the Am. Chem. Soc. 136, 11610–11613 (2014) 5. F. Zhang, B. Yang, Y. Li, W. Deng, R. He, Extra long electron–hole diffusion lengths in CH3 NH3 PbI3−x Clx perovskite single crystals. J. of Mat. Chem. C 5, 8431–8435 (2007) 6. M. Jeong, I.W. Choi, E.M. Go, Y. Cho, M. Kim, B. Lee, S. Jeong, Y. Jo, H.W. Choi, J. Lee, J.-H. Bae, S.K. Kwak, D.S. Kim, C. Yang, Stable perovskite solar cells with efficiency exceeding 24.8% and 0.3-V voltage loss. Science 369, 1615–1620 (2020) 7. Best research-cell efficiency chart (2018). National Renewable Energy Laboratory. https:// www.nrel.gov/pv/assets/images/efficiency-chart.png 8. N.J. Jeon, H. Na, E.H. Jung, T.-Y. Yang, Y.G. Lee, G. Kim, H.-W. Shin, S.I. Seok, J. Lee, J. Seo, A fluorene-terminated hole-transporting material for highly efficient and stable perovskite solar cells. Nat. Energy 3, 682–689 (2018) 9. Y. Zhang, Y. Liang, Y. Wang, F. Guo, L. Sun, D. Xu, Planar FAPbBr 3 solar cells with the power conversion efficiency above 10%. ACS Energy Lett. 3(8), 1808–1814 (2018) 10. Y. Wu, X. Li, S. Fu, L. Wan, J. Fang, Efficient methylammonium lead trihalide perovskite solar cells with chloroformamidinium chloride (Cl-FACl) as additive. J. Mater. Chem. A 14, 1–8 (2019) 11. M.M. Lee, J. Teuscher, T. Miyasaka, T.N. Murakami, H.J. Snaith, Efficient hybrid solar cells based on meso-superstructured organometal halide perovskites. Sci. 338, 643–647 (2012) 12. Z. Chen, B. Turedi, A.Y. Alsalloum, C. Yang, X. Zheng, I. Gereige, A. AlSaggaf, O.F. Mohammed, O.M. Bakr, Single-crystal MAPbI3 perovskite solar cells exceeding 21% power conversion efficiency. J. Am. Chem. Soc. 4, 1258–1259 (2019) 13. A. Kojima, K. Teshima, T. Miyasaka, Y. Shirai, Novel photoelectrochemical cell with mesoscopic electrodes sensitized by lead-halide compounds (2)” ECS Meeting Abstracts (2006)

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14. N.J. Jeon, J.H. Noh, Y.C. Kim, W.S. Yang, S. Ryu, S.I. Seok, Solvent engineering for highperformance inorganic–organic hybrid perovskite solar cells. Nat. Mat. 13(9), 897–903 (2014) 15. M. Saliba, T. Matsui, J. –Y. Seo, K. Domanski, J. –P. C. -Baena, M. K. Nazeeruddin, S. M. Zakeeruddin, W. Tress, A. Abate, A. Hagfeldt and M. Grätzel, Cesium-containing triple cation perovskite solar cells: improved stability, reproducibility and high efficiency. Ener. Environ. Sci. 9, 1989–1997 (2016) 16. A. Kojima, K. Teshima, Y. Shirai, T. Miyasaka, Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. J. Am. Chem. Soc. 131(17), 6050–6051 (2009) 17. J.-H. Im, C.-R. Lee, J.-W. Lee, S.-W. Park, N.-G. Park, 6.5% efficient perovskite quantum-dotsensitized solar cell. Nanoscale 3, 4088–4093 (2011) 18. H.-S. Kim, C.-R. Lee, J.-H. Im, K.-B. Lee, T. Moehl, A. Marchioro, S.-J. Moon, R.H. Baker, J.-H. Yum, J.E. Moser, M. Grätzel, N.-G. Park, Lead iodide perovskite sensitized all-solid-state submicron thin film mesoscopic solar cell with efficiency exceeding 9%. Sci. Rep.2(591), 1–7 (2012) 19. L. Etgar, P. Gao, Z. Xue, Q. Peng, A.K. Chandiran, B. Liu, Md.K. Nazeeruddin, M. Grätzel, Mesoscopic CH3 NH3 PbI3 /TiO2 heterojunction solar cells. J. Am. Chem. Soc. 134, 17396– 17399 (2012) 20. O. Malinkiewicz, A. Yella, Y.H. Lee, G.M. Espallargas, M. Graetzel, M.K. Nazeeruddin, H.J. Bolink, Perovskite solar cells employing organic charge-transport layers. Nat. Photo. 8, 128– 131 (2014) 21. J. Burschka, N. Pellet, S.-J. Moon, R.H. Baker, P. Gao, M.K. Nazeeruddin, M. Grätzel, Sequential deposition as a route to high-performance perovskite-sensitized solar cells. Nat. 499, 316–320 (2013) 22. H. Zhou, Q. Chen, G. Li, S. Luo, T.-B. Song, H.-S. Duan, Z. Hong, J. You, Y. Liu, Y. Yang, Interface engineering of highly efficient perovskite solar cells. Sci. 345(6196), 542–546 (2014) 23. N. Ahn, D.Y. Son, I.H. Jang, S.M. Kang, M. Choi, N.G. Park, Highly reproducible perovskite solar cells with average efficiency of 18.3% and best efficiency of 19.7% fabricated via Lewis base adduct of lead(ii) iodide. J. Am. Chem. Soc. 137(27), 8696–8699 (2015) 24. W.S. Yang, J.H. Noh, N.J. Jeon, Y.C. Kim, S. Ryu, J. Seo, S.I. Seok, High-performance photovoltaic perovskite layers fabricated through intramolecular exchange. Sci. 348, 1234–1237 (2015) 25. S.S. Shin, E.J. Yeom, W.S. Yang, S. Hur, M.G. Kim, J. Im, J. Seo, J.H. Noh, S.I. Seok, Colloidally prepared La-doped BaSnO3 electrodes for efficient, photostable perovskite solar cells. Sci. 356(6334), 167–171 (2017) 26. X. Zheng, B. Chen, M. Yang, C. Wu, B. Orler, R.B. Moore, K. Zhu, S. Priya, The controlling mechanism for potential loss in CH3NH3PbBr 3 hybrid solar cells. ACS Energy Lett. 1, 424– 430 (2016) 27. F.C. Hanusch, E. Wiesenmayer, E. Mankel, A. Binek, P. Angloher, C. Fraunhofer, N. Giesbrecht, J.M. Feckl, W. Jaegermann, D. Johrendt, T. Bein, P. Docampo, Efficient planar heterojunction perovskite solar cells based on formamidinium lead bromide. J Phy Chem Lett 5(16), 2791– 2795 (2014) 28. M. Caputo, N. Cefarin, A. Radivo, N. Demitri, L. Gigli, J.R. Plaisier, M. Panighel, G.D. Santo, S. Moretti, A. Giglia, Maurizio Polentarutti, F.D. Angelis, E. Mosconi, P. Umari, M. Tormen, A. Goldoni, Electronic structure of MAPbI3 and MAPbCl3 : importance of band alignment. Nat. 9, 15159 (2019) 29. J.M. Ball, M.M. Lee, A. Hey, H.J. Snaith, Low-temperature processed meso-superstructured to thin-film perovskite solar cells. Energy Environ. Sci. 6, 1739–1743 (2013) 30. K. Wojciechowski, M. Saliba, T. Leijtens, A. Abate, H.J. Snaith, Sub 150 °C processed mesosuperstructured perovskite solar cells with enhanced efficiency. Ener. Environ. Sci. 7, 1142– 1147 (2014) 31. C. Yi, J. Luo, S. Meloni, A. Boziki, N.A. Astani, C. Grätzel, S.M. Zakeeruddin, U. Röthlisberger, M. Grätzel, Entropic stabilization of mixed A-cation ABX3 metal halide perovskites for high performance perovskite solar cells. Energy Environ. Sci. 9(2), 656–662 (2016)

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32. O. Ergen, S.M. Gilbert, T. Pham, S.J. Turner, M.T.Z. Tan, M.A. Worsley, A. Zettl, Graded bandgap perovskite solar cells. Nat. Mat. 16(5), 522–525 (2016) 33. Y.Y. Pan, Y.H. Su, C.H. Hsu, L.W. Huang, C.C. Kaun, The electronic structure of organic– inorganic hybrid perovskite solar cell: a first-principles analysis. J. CommatSci. 117, 573–578 (2016) 34. S.R. Raga, M.C. Jung, M.V. Lee, M.R. Leyden, Y. Kato, Y. Qi, Influence of air annealing on high efficiency planar structure perovskite solar cells. Chem. Mater. 27(5), 1597–1603 (2015) 35. M.A. Mohebpour, M. Saffari, H.R. Soleimani, M.B. Tagani, High performance of mixed halide perovskite solar cells: role of halogen atom and plasmonic nanoparticles on the ideal current density of cell. Physica E 97, 282–289 (2018)

Design and Optimization of an Agrivoltaics System Mohd Adil Faizi, Abhishek Verma, and V. K. Jain

1 Introduction A pioneering idea of using the combined land for harvesting solar photovoltaic (PV) energy and agriculture means mounting solar PV system “overhead the crops at certain height” and “inter space between the solar modules for plant photosynthesis.” This concept will rise the land efficiency and solar PV performance increase due to ventilation for solar panels as process of evaporation, and likewise the crop yields upsurge by optimizing the solar PV design structure for suitable type of plants and crops. Since the technology has been came into reality, numerous research and pilot projects being executed globally, for example, developing countries like Germany, China, Japan, India, etc. Rare researches demonstrated that Agrivoltaics projects will increase the land efficiency nearly twofold as compared with conventional groundmounted Solar PV projects depending up on the different type of crop in a particular season [1, 2]. Worldwide scenario energy demands with clean renewable and sustainable energy, such as, with solar (PV) systems, large surface areas are essential due to the comparatively diffuse nature of solar energy and low efficiency of solar cells [1]. Approximately demand can be matched with aggressive building-integrated system (BIPV) and rooftop PV, but the others can be met with dual land-based PV farms. But use of more land for solar farms will decrease land resources for food production [3]. Such problems can be resolved by using the new concept of Agrivoltaics system; where dual use of land combined for agriculture and energy harvesting, simultaneously. It is a solution to the intense competition for the land resources between food M. A. Faizi · A. Verma (B) · V. K. Jain Amity Institute of Renewable and Alternative Energy, Amity University, Noida, UP, India e-mail: [email protected] A. Verma · V. K. Jain Amity Institute for Advanced Research and Studies (Materials and Devices), Amity University, Noida, UP, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_5

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and energy production [4, 5]. In this paper, a simulation-based analysis has been carried out with two different Agrivoltaics design models Agrivoltaics Model 1 and another Agrivoltaics Model 2. These models are analyzing the total shadow coverage area as per movement of module shadow throughout the day.

2 Experimental Details A simulation-based design has been set up with two different Agrivoltaics design models, Agrivoltaics Model 1 and Agrivoltaics Model 2 to analyze the total shadow effect on a ground surface. Specification of both the designs is 10 kW PV power plant of 320Wp each PV modules, and total number of panels are 33 installed in an area of 144 m2 for Agrivoltaics Model 1 and 216 m2 for Agrivoltaics Model 2. The orientation of a PV panel facing toward the true south is with a tilt angle of 30 degree, in Model 2, gaping between module is about 2.5 m and inter row spacing about 2.4 m, and pitch length is approximately 1.5 m (edge-to-edge). Each row contains nine number of panels in Model 1 and five panels in Agrivoltaics Model 2. These models are analyzed under the parameter of shadow coverage area (SCA) and shadow density level. The shadow area measured at every single hour starts from morning 8.00 AM to evening 5.00 PM, as according to the movement of Sun in the sky. The movement of shadow appears partially on the ground during morning and reaches peak at twelve noon, and afternoon shadow keeps dropping to the same. The entire simulation is supported through Google SketchUp Pro 18 and PVsyst version 7.0, both software helps in designing and analyzing the constructive part for the study. Shadow coverage area is an elementary and significant parameter for any analysis required in an Agrivoltaics, crops under PV module required proper sunlight and climatic factors for efficient growth.

3 Results and Discussions The observation of shadow effect in parameter, i.e., total shadow area coverage and shadow density level under Agrivoltaics system, was recorded at every 1 h of time interval from morning to evening (during peak of summer season). The area of the shadow recorded manually by outlining the shadow cast by each single PV module on the ground. The recorded data analyzed throughout the day and described in a graphical form (Figs. 1 and 2). Figure 3 shows amount of shadow (m2 ) covered the crop area at every interval of 1 h. This shadow reached to its maximum peak at 12.00 noon and minimum at 8.00 am and 5.00 pm. The total time traveled by the shadow is approximately 9.00 h from morning to evening till shadow remain in an Agrivoltaics field. The shadow density measures the number of PV module shadow cast on the ground at different time interval, at every single hour shadow density logarithmically increase

Design and Optimization of an Agrivoltaics System

33

Fig. 1 Isometric view of Agrivoltaics Model 1

Fig. 2 Isometric view of Agrivoltaics Model 2

and reaches at its maximum and again decreases. Likewise, shadow density in a form of coverage area at 9.00 am is about 22.17 m2 and at 4.00 pm is about 22.22. But at 12.00 noon, coverage area is about 47.63 m2 by cast of all PV modules mounted in PV system power plant. The maximum shadow coverage area (SCA) falls during twelve noon in both the Agrivoltaics models, shadow of each PV module cast on the ground surface since morning to evening. Due to the variation in sun hour angle, the shadow of each individual module appears on the ground logarithmically, depending upon the time (hrs.). It is observed that shadow having minimum coverage area and minimal density

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Fig. 3 Maximum and minimum shadow coverage area

level during morning and evening shown in Agrivoltaics Model 2 (Fig. 4). In Model 1 shadow cast under the PV module in a majority due to no gaping between modules

Fig. 4 Agrivoltaics Model 2 illustrate the maximum shadow density at 12.00 noon and partial shadow density level during morning 9.00 am and evening 4.00 pm

Design and Optimization of an Agrivoltaics System

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as compared with Model 2. Gaping between PV modules increase more amount of light fall on the crops as model with no gapping cast higher density shadow for longer duration, due to this crop remain under the shadow for longer period.

4 Conclusions The simulation-based prototype design is with two different models, Agrivoltaics Models 1 and Agrivoltaics Model 2. These models analyze the effect of shadow under shadow area coverage and shadow density. Both Agrivoltaics simulation-based prototypes are ideal for crop growth as per selection of the crops as per season. The simulation-based analysis shows that the average shadow coverage area (SCA) between two models, Model 1 is 30.87 m2 and Model 2 is 30.09 m2 . The maximum shadow area observed during twelve solar noon for both the models is dissimilar approximately 47.63 m2 in Agrivoltaics Model 1 and approximately 54.88 m2 Agrivoltaics Model 2; minimal shadow area keeps varying from model to model; during 9.00 am, Agrivoltaics Model 1 area is about 27.46 m2 and during 4.00 pm 5.82 m2 , where in Agrivoltaics Model 2, during morning 9.00 am area is 22.17 m2 and during 4.00 pm area is about 22.22 m2 . Shadow area during morning is nearly equivalent to shadow during evening. Both Agrivoltaics Model 1 and Agrivoltaics Model 2 are suitable for Agrivoltaics depending upon the selection of crop and plants under sciophytes (shade) crops and heliophytes (intensive insolation) crops. Due to no spacing between the module in Model 1, shadow is more compressed and appear dark. Therefore, it has been found that the maximum shadow area is 14.14% more in Agrivoltaics Model 1 as compared with Agrivoltaics Model 2. The shadow coverage area can be much improved with gap between module, inter row spacing, and more so the effect of shadow in an Agrivoltaics system (AVS) minimized at some level with the help of improved design and structures. Acknowledgements Authors are thankful to Dr. Ashok K. Chauhan, Founder President, Amity University, for his continuous encouragement and support.

References 1. A. Weselek, A. Ehmann, S. Zikeli, I. Lewandowski, S. Schindele, P. Högy, Agrophotovoltaic systems: applications, challenges, and opportunities-a review. Agron. Sustain. Dev. 39(4) (2019). https://doi.org/10.1007/s13593-019-0581-3 2. E. Wollenberg, S.J. Vermeulen, E. Girvetz, A.M. Loboguerrero, J. Ramirez-Villegas, Reducing risks to food security from climate change. Glob. Food Sec. 11, 34–43 (2016). https://doi.org/ 10.1016/j.gfs.2016.06.002 3. P.R. Malu, U.S. Sharma, J.M. Pearce, Agrivoltaics potential on grape farms in India. Sustain. Energy Technol. Assessments 23, 104–110 (2017). https://doi.org/10.1016/j.seta.2017.08.004

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4. R. Ferroukhi et al., Renewable energy benefits: measuring the economics. IRENA Int. Renew. Energy Agency 92 (2016) 5. U.R. Patel, P.M. Chauhan, Studies of climatic parameters under Agrivoltaics structure. 54(7), 139–145 (2009)

Implementation of the Family Size Biogas Plant to Achieve a Sustainable Lifestyle: Case Study a Farm in Village 37 Kifah A. Fayad Al-Imarah, Waleed M. Dawood, Ismaeel M. Abood, Mudher H. Mahmood, Taha M. Al-Muwali, Milad A. Aldhaher, and Thomas H. Culhane

1 Introduction The difficult security conditions and Iraq’s displacement crisis have led to the isolation of many villages and communities and deprived them of obtaining electricity and public services [1]. Therefore, it has become imperative to support these communities and improve the lifestyle of individuals by exploiting locally available resources. Creating jobs and adapting technology to treat organic waste to reach the integrated management of these wastes by introducing biogas production technology to generate sustainable energy and organic fertilizers [2]. The production of biogas from organic waste is concurrent with the United Nations Sustainable Development Goals (SDG), especially goal numbers 1 and 7, which require that this technology can help reduce socio-economic poverty by providing clean energy from renewable sources [3]. Anaerobic digestion is a microbiological process where microorganisms degrade the organic materials in the absence of oxygen to generate biogas and nutrient rich digestate [4]. The biodegradation of the complex organic matter undergoes four main steps, namely hydrolysis, acidogenesis, acetogenesis, and methanogenesis [5]. Raw biogas from anaerobic degradation is generally composed of methane (55–70%) and carbon dioxide (30–45%). Other gasses and contaminants present are nitrogen (0–15%), oxygen (0–3%), water (1–5%), hydrocarbons (0–200 mg m−3 ), hydrogen sulfide (0–10,000 ppmv), ammonia (0–100 ppmv), and siloxanes (0–41 mg silicon m−3 ) [6]. The energy value of biogas shows typical lower heating values (LHV) of K. A. F. Al-Imarah (B) · W. M. Dawood · I. M. Abood · M. H. Mahmood · T. M. Al-Muwali · M. A. Aldhaher Ministry of Science and Technology, Renewable Energy Directorate, Baghdad, Iraq e-mail: [email protected] T. H. Culhane Patel College of Global Sustainability, University of South Florida, Tampa, USA © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_6

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21–24 MJ/m3 or around 6 kWh/m3 [7]. Biogas (after cleaning for impurities) could be used as boiler fuel, power engines, in a dual fuel mix with petrol and diesel, and can aid in pumped irrigation systems [8]. Biogas system is a convenient technology in the rural economy in the developing countries where millions of household digesters are currently in operation [9]. Biogas access to renewable fuel sources for cooking and lighting as a fuel substitute for firewood, dung, agricultural residues, and fossil fuels [10]. Biogas systems also yield a digestate (effluent slurry) that has superior nutrient qualities over the usual fertilizer, cattle dung, as it is in the form of ammonia [11]. As well, recycling of organic waste would significantly reduce the amount of organic waste that needs handling and thus reduce costs at the disposal facilities and prolongs its life span. Also, reduce the environmental impact of the disposal site as the organics are responsible for the polluting leachate, methane, and odor problems [12]. Although biogas is better off as a rural energy resource in the world, factors were hindering its spread. Technically, problems have arisen due to the under-collection of organic materials, estimated typically at 30–40% of the required plant capacity [13]. For family size digesters, the design should ensure that gas production remains sufficient even during the most unfavorable season of the year due to low winter temperatures that inhibit methanogenesis [14]. Another factor that the biogas plants need maintenance skills, which should be available in every village, otherwise develops problems that lead to the non-functioning of the plant [15]. Rural areas generating a high fraction of organic waste. In our biogas project, the nature and characteristics of the available organic waste determine as anaerobic digestion (AD) treatment technology can be used because it can treat such waste. Moisture content and carbon–nitrogen ratio (C:N) for organic waste are sufficient to judge AD technology should be considered [16]. Therefore, this paper covers a construction option of the underground 10 m3 fixed dome digester, which is a wet digestion system operated in the continuous mode under mesophilic conditions [17]. We choice underground construction to save space and protect the digester from physical damage and temperature fluctuation [18]. Also experienced biogas technicians with specific technical skill in construction are available to ensure a gas-tight construction. The choice of 10 m3 digester depends on the location, family members, and the quality of organic wastes available every day [19]. Add to Chinese fixed dome digester is the most popular digester and most implemented due to its reliability, low maintenance, and long lifespan [20]. Our work plan, following the site selection of the plant, a project team is to study the details of the material required, the time frame of the implementation and operation, and maintenance. Parallelly, gas distribution to beneficiaries, use of effluent slurry to produce soil conditioning, and training of beneficiaries for the plant operation. In the coming pages are provided detailed descriptions of each step.

Implementation of the Family Size Biogas …

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2 What Are the Objectives of the Biogas Project? After the village’s farmers listened to the biogas production program, the high priority aspects for them have included safety and health matters in the workplace, gas production efficiency, and keep soil fertility due to the use of the digestate. Consequently, the project aims to achieve energy self-sufficiency by promoting sustainable production of renewable energy from biogas obtained from a small anaerobic digestion unit of agricultural waste and animal manure available on the farm. One of the most important objectives of the project is the availability of biogas in rural areas to replace using liquefied petroleum gas (LPG) cyclinders. LPG is not always available due to long distances and retard transport links between distribution centers and households. A move to electric cooking is hinder by slow rates of electricity access in rural areas, the prioritization of electricity for uses such as pumped irrigation systems [21]. The other specific objectives of this biogas project during the action are to simplify and upgrade the technical and financial barriers to increase the use of biogas energy in promoting sustainable rural development in Iraq. Also, reducing the negative global and local environmental impacts associated with using fossil fuels and unmanaged agricultural and organic waste. To courage the widespread of renewable energy resources in Iraqi rural communities, the renewable energy directorate has established household biogas digesters as a tool in part to drive rural development. Also, the generous help and collaboration of purchasing 10 m3 Puxin biogas digester by Prof. Thomas Henry Culhane, the co-founder of solar cities and is a National Geographic Emerging Explorer, through his trip on April 2013, involved a “renewable energy and sustainability road show” sponsored by the US. Embassy in Baghdad city [22]. The first biogas system was implemented into the Fadak farm (in An-Najaf province) about 40 km from the Imam Ali Holy Shrine [23], while the second biogas system understudy in a small private farm in village 37 about 10 km south of Baghdad city.

3 Why Puxin Biogas Plant? Globally, estimated that more than 50 million micro-digesters (household size) are installed [24]. China leads the world in small scale domestic biogas technology [25]. The most common digester model under national China biogas programs is the fixed dome digester [19]. In Sichuan Province alone, close to five million domestic biogas plants have been constructed by 2010 [26]. The Puxin biogas digester is an innovation of the Shenzhen Puxin Science and Technology Co. Ltd. The Puxin digester, Chinese technology, is currently gaining popularity in Ghana since 2007 when it was first introduced [27]. Since then, the technology has become widespread and in rural families with a few cattle where animal manure is used as feedstock together with the addition of small amounts of agricultural waste [28].

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The Puxin biogas plant has three major parts. Concrete digester; a set of steel mold help to construct the digester of the plant. The neck and cover are also made of a steel frame and are essential for fixing the gasholder. Gasholder is made of reinforced glass fiber of 1.2 m3 capacity that is 100% air and watertight. The Puxin biogas plant has more advantages than the traditional fixed dome biogas plant [29] as below: • The steel mold is reusable, high mechanical strength, gas tightness, and long lifespan. • It is environmentally friendly, durable, and easy to repair. • Installed underground to maintain the stable internal temperature. • Any solid biodegradable materials can be used like grass and straw so that the farmer does not need to have a large number of cattle. • If used as a batch plant, there is the regular discharge of gas over a long time (5–6 months) and after materials inside the digester must be removed. • The slurry from the plant is wholly digested and consists of 90% water. The plant is a very fruitful producer of bio-fertilizer to replace chemical fertilizer.

4 Methodology and Construction of the Plant The methodology defines all the steps to follow when implementing the biogas unit as summarized below. 1

2

The first step covers all planning activities required before conducting a farm site assessment, such as the number of family members and the quality and quantity of waste generated. Step two explains how the manual can create a fixed dome plant with specific technical skills in construction to ensure a gas-tight construction.

Therefore, once we know the digester dimensions (size), we need to decide where to locate the digester. Therefore, to protect the digester from temperature changes and save space must be located underground. The methodology adopted for the construction biogas plant included many main steps discussed in the next pages. There are two main parts for the construction of this 10 m3 size Puxin type biodigester [30]. Part I begins with the preparation stage to the final concrete plaster application to meet gas tightness and long lifespan [31]. The break between Part I and Part II is to allow for the proper curing of the concrete, a period of no less than one week. Part II is the activity of inspection for any structural damages, bitumen, and polymer emulsion seal surfacing that must be done after the curing period to provide water and gas-seal layer [32]. Checking for water and gas tightness will be done before the actual loading of the digester. The other activities of Part II will be the construction of inlet and outlet (effluent) chambers, digester cover, gas piping systems, and finally loading.

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5 Part I: Construction of Puxin Biogas Digester and Gas Storage Tank Construction Materials: We thoroughly discussed construction procedures like the plant layout, materials, and tools needed with the farm owner and builder. The materials to be used for the construction of Puxin digester are of good quality, and the workers involved in construction are excellent. The required quality standards and specifications of these materials are described briefly in Table 1. Selection of Construction Site: The location of the 10 m3 biogas unit is a crucial factor in its success as well as to other environmental requirements. The selected site facilitate easy construction works for operation and maintenance activities. The minimum distance between a biogas unit and a water supply is about 30 m to avoid water contamination in cases of a leak. It is not far from the point of gas utilization (kitchen) to save gas piping cost, but at the same time close as possible to the source of raw materials [30]. Since the biogas unit wholly underground, the site should be at a sufficient distance from trees to avoid damage of digester from roots. The area to construct the plant should have an even surface and enough space for a compost pit as it is an integral part of the digester. The site is close to vegetable fields (Fig. 1) where the digestate slurry was used. Plant laying out and base construction: After site selection, layout the relative position of the inlet, digester, and effluent slurry basin or chamber. The digester pit and its size must be a bit larger than the required steel mold that makes it convenient for construction a pit with (diameter 4.0 m and depth 3.1 m). The excavation dig takes between two to three days. The soil is then compacted using an electric compactor. Isolate the foundation area from mud and water puddles, which may contaminate concrete when pouring it for the biodigester base. To assume the strength of the floor, and along with being concave in shape reinforced concrete base was built with a (thickness of 20 cm). It was made out of (F´c = 250 kg cm-2) concrete and reinforced with (6–6/4–4 ) electro-welded steel mesh. We apply antirust paint to protect the rebars and low-density polyethylene (LDPE) sheets to enable filtration of the base structure. Construction of Digester: The reusable steel molds to construct a 10 m3 digester present in (Fig. 2, left). It is composed of 93 steel molding boards and 19 workpieces and is applied to build the concrete digester of the Puxin biogas plant [33]. The inner digester diameter is 280 cm, outer 300 cm, depth 120 cm, while the inner neck diameter is 166 cm, outer 196cm, depth 110 cm. After assembled the inner steel mold, we painted the metal plates with black grease to make it easy to remove them once the cement cured. The goal is to build a strong matrix of material that will withstand years of use. Before setting up two sets of steel plates and pour cement between them, place 3/8 steel bars all around the perimeter, with 20 cm2 separation between inner and outer molds. The structure was built with F’c = 250 kg cm−2 concrete and reinforced with 6–6/ 4–4 electro-welded steel mesh. The final structure was built monolithically

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Table 1 Types and quantity requirements of 10 m3 biogas plant construction materials A. Building materials

Unit

Quantity

Bricks (60 × 120 × 240 mm)

piece

300

Concrete block (150 × 180 x 360 mm)

piece

30

Sand

cu. m

3.5

Gravel

cu. m

4

Cement

cu. m

1.5

6 mm (2 × 4.6 m) welded wire reinforcement sheet

sheet

6

Steel basement mold (3.5 × 3.5 m)

piece

1

Bitumen emulsion paint

liter

20

Acrylic emulsion paint

liter

20

B. Labor

Unit

Quantity

Building skilled labor

days

14

Building unskilled labor

days

30

C. Pipes and appliances

Unit

Quantity

Vert. mixer device

piece

1

Concrete vibrator

piece

1

Small compactor

piece

1

Inlet PVC pipe (150 mm, L1350 mm)

piece

1

Outlet PVC pipe ( 150 mm, L1250 mm)

piece

1

Dome gas pipe

piece

1

GI wire

meter

25

Socket

piece

5

Elbow

piece

8

Tee

piece

3

Union

piece

1

Nipple

piece

4

Main gas valve

piece

1

Water drain

piece

1

Rubber hose

piece

2

Gas stove

piece

1

Gas lamp

piece

2

Biogas pump

piece

1

Solar charger

piece

1

Desulfurization filter

piece

1

Teflon tape

roll

3

D. Tools

Unit

Quantity

Tape measure

piece

1 (continued)

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Table 1 (continued) Pencil or chalk

piece

Shovel

piece

6 3

Hammer

piece

2

Pipe wrench

piece

2

Chisel (for concrete)

piece

6

Sifter (G.I. screen)

piece

1

Regular masonry trough

piece

4

Plastering masonry trough

piece

4

Tubular spirit level

piece

1

Fig. 1 The location of biogas unit close to cowshed and stockyard

(Fig. 2, right). The welded wire reinforcement minimizes the chance of misplacement since only one type of mat used on a given section [30]. Casting concrete mixture is with the help of an electric vibrator. It rotated as much as 10,000 times a minute. The use of a vibrator is essential to ensure that the concrete does not bubble or form holes. At the same time, preparation of the entrance and exit holes for the input and output pipes. Inlet/outlet is carried out simultaneously with vault construction. Placement of inlet/outlet pipes should be at one-half the height of the wall. Also, an additional iron bar to reinforce the inlet/outlet pipe to the wall to ensure that the top ring beam will attach to the wall more strongly. Gas Storage Construction: When the round wall of the digester is complete, later the gas storage tank (neck) is constructed. It is a reinforced concrete structure. It is formed by on-site construction using a mold, which is composed of an inner and

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Fig. 2 (left) Full 10m3 inner mold assembled with a bottom neck ring, (right) cast reinforced concrete slab with inlet and outlet pipes and assembly top ring

an outer mold. Steel mold neck for 10m3 plant is composed of 26 steel molding boards and six workpieces. The inner neck diameter is 166 cm, outer 196 cm, and depth 110 cm. The importance is all reinforced concrete work should be carried out continuously to avoid any delays in the concrete work. Concrete (F´c = 250 kg cm−2 ) and reinforced with (6–6/ 4–4 ) electro-welded steel mesh used, and monolithically, concrete poured in the casting cavity formed by the inner and outer molds. To prevent the chance for cleavages/cracks that may lead to leaks in the digester mold, either water, gas leakages, or both the steel joints should be well made. The neck, vault, and other molds are allowed to deconstruct (remove) after at least 48 h of the finish of the casting.

6 Part II: Inlet and Effluent Chambers, Gasholder Construction, and Finishing Work Plastering and Backfilling the Digester: Remove the small inlet and outlet pipes (L50mm) and install the inlet and outlet pipes have a minimum diameter of 6 inches PVC pipe (L1860mm) for inlet hole and (L1660mm) for outlet hole which shall be used as structures for feeding and releasing the digestate. We should be careful when placing the new ones and laid at a deep angle and will move down. There may be a need to support and hold the pipes in place. After all of the main structural concrete work has been completed and the “curing” process of the concrete properly started, the part I construction is considered finished. The break between Part I and Part II is to allow for the proper curing of the concrete, a period of no less than one week in cold weather and open area. The last concrete

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Fig. 3 (left) Curing structural concrete work and bitumen coat and cover with a plastic sheet, (right) backfill the soil, and bury the whole digester unit

plaster layer, 1:12:1 mix (cement, sand, and water, respectively), of the dome area to where the bitumen to be applied is a rough finish. The main Part II activity of bitumen emulsion coat application must be done after this curing period so that “most” of the water has been allowed to be lost from the concrete during this process, leaving a dry surface, (Fig. 3, left). If the concrete surface is wet or moist to which the bitumen is to be applied, it will not adhere as well and will not be an effective gas-seal layer. In (Fig. 3, right), the other activity of part II is backfilling the excavation made with soil and burying the digester underground carefully. Effluent and Inlet Chambers Construction: To prepare the base of outlet or inlet chambers, the length and breadth of digging should be the inner dimension plus wall thickness plus the plaster layer. The outlet or displacement chamber with measurements 3.22 × 1.67 × 1.24 m and a volume of 5.31 m3 . After finished the excavation, lay concrete on the surface. The ratio of the mix should be 1:2:4 (cement: sand: aggregate). The walls have to be vertical and finished with a smooth layer of cement plaster (1 cement to 3 sand). After the completion of the outlet, constructed the inlet chamber with measurements 1.00 × 1.00 × 1.00 m and a volume of 1 m3 . The bottom of the inlet is 20 cm above the overflow level in the outlet wall. The waste can automatically flow into the digester through the inlet pipe and flow out from the digester through the outlet pipe by gravity. Water and Gas Leaking Test: Finally, after the curing period, the next activity of Part II is the water and gas-proof coat application for the whole biogas plant. On the clean surface of the digester, to make the digester gas tighten, it must be applied the plaster coats from first to last coats as the following [34]:

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Fig. 4 (left) Gasholder inside the digester neck, (right) casting gas storage cover

(a) (b) (c)

Cement and water wash (1part cement: 3 three parts). 10 mm layer (1 part cement: 2 parts sand) to make sure there is no small hole on the face. Acrylic emulsion paint.

Allow at least one day between plaster coats to performance of the biogas plant is dependent on the gas tightness of the dome. After three days of the completion of the digester, the digester filling with water up to the inlet and outlet pipes level to test for water tightness. Let it sit for 3–5 h until the digester walls are saturated with water and mark the water level. Let it sit overnight. A significant drop in water level indicates leaks that must treat with cement. Fill with water again and repeat the test for water tightness. For the gas leaking test, fix the gasholder in the neck (Fig. 4, left) and pump air into the gasholder until the gasholder is full of air. If there is no air bubble from the gasholder, the gasholder is good. If the gasholder is leaking, find out the leaks and seal them with resin glue inside the gasholder [35]. Gasholder (Gas Storage) The other main component of the biogas plant is the gasholder, as in (Fig. 4, left). The lower opening edge of the removable glass fiber reinforced gasholder coupling with the opening of the biogas digester by using the plugs and the brackets. The gasholder has a vent hole formed at the top side to release the pressure inside the biogas digester. Alternately, the Puxin biogas plant is provided with five steel molds (slabs) to prevent rainwater and debris from entering the unit and increase the temperature of the feedstock inside the digester as in (Fig. 4, right) [36]. The mold must be 8 cm thick with proper reinforcement (rebar) 3 cm from the bottom side. Installing rebar loop handles may be useful for the occasional handling of the slabs. Gas Piping System Components: The piping system generally consists of four components such as gas line, condensation trap, flame arrester, and pressure gage.

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Gas Line: There are two alternative types of materials used in the system: (a) (b)

GI pipe for using outside and in situations where ultra-violet rays or sunlight is of high intensity. Flex tube, which is a heavy-duty rubber hose with ply, is recommended in cases where turns/bends exist in the piping system and especially for indoor use.

When used flex tube outdoors, it protected from high sunlight exposure. Generally, 1/2 diameter pipes require 3/4 diameter rubber tubes for connections or elbows [37]. Condensation Trap: The biogas generated from the digester saturated with water vapor. This water vapor will condense on the walls of the pipeline. The condensate water will ultimately clog the pipe gas line. Therefore, removed regularly through a water drain installed to the pipe gas line. The drain should be vertically below the lowest point of the pipe gas line to flow by gravity to the trap [37]. Flame Arrester: It is a safety device in case of accidental backfire flame returning to the digester and which may cause an explosion. This device is simply a ball or roll of fine copper wire mesh inserted in the gas line. Do not place it too tightly as it may block the gas flow. The device is located close to the digester and near the point of gas use. Pressure Gage: It serves as an indicator of gas pressure to show the relative amount of gas in storage within the biogas plant and as a safety device to indicate the build-up of the excessive-high level of gas pressure within the biogas tank. Operation of the Biogas Plant: After the raw materials and the inoculums have been put into the biogas plant, add water into the biogas plant. For the Puxin biogas plant, water-filled till the water level over the top of the gasholder. When adding water into the biogas plant, the gas valve should be open for pushing out the air inside the gasholder [33]. The water added into the biogas plant can be domestic wastewater, river water, reservoir water; it also can be well water or tap water, but cannot be toxic wastewater. The temperature of the water should be above 20°C. In a cold climate, well water is a perfect choice. Follow that the biogas plant is sealed with water, usually in 10–20 days, the biogas plant will produce biogas. If the biogas cannot be light up, should release all the biogas in the gasholder and recollect the biogas and repeat this process until the biogas can be light up. Therefore, the daily maintenance of the biogas plant: 1

2 3

To keep a constant gas production, after about 30 days from the day when the biogas plant begins to produce biogas, should add raw fermentation materials into the biogas plant regularly. For a 10 m3 biogas plant to keep a 5m3 /day biogas production, 150 kg cow dung is needed daily. In the period of regular operation should increase the concentration of the feeding materials up to 8–10%.

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Removal of Effluent from Chamber: The feedstock is loading daily. The amount of slurry was under the requirement of the particular digester volume and its retention time. Less material loaded than what is required results in low gas production since the bacteria will be “starved;” likewise, the excess slurry will result in raw material wastage since the slurry unable to be fully digested [38]. The loading of new slurry materials displaced an equal volume of effluent to the outlet chamber. Otherwise, to prevent digester overloaded removed the effluent from the outlet chamber. One way to check the correct digester level is that at zero gas pressure, the slurry should be at the level of the outlet chamber floor [39].

7 Conclusions This paper has proved that anaerobic digestion through the Puxin biogas digester can convert animal manure from a high risk of environmental pollution material to economically efficient material for producing energy and soil fertilizer. Therefore, it has become clear that the digester was capable of interacting more intimately with rural life as cooking, lighting, soil fertility. Through implementing and constructing biogas digester, we achieved successful digester operation and gas distribution to beneficiaries, use of digestate slurry to produce compost, and training beneficiaries for the biogas unit operation. The capacity of the installed digester is 10 m3 . The results show that the gas production rate based on that each cubic meter of tested raw material was (0.5–1.0) m3 of gas per day and (45–90) kg digested residue as liquid fertilizer and soil conditioner. The results of the field evaluation indicated that the system’s daily production rate of biogas was about (0.4–0.5 m3 /m3 of the digester volume) depending on the concentration of raw materials added. The percentage of methane content in the raw biogas from the digester was 65% percent and after upgrade through hydrogen sulfide filter was 85%. The local single gas burner consumed (0.45 m3 /h), one lux lamp consumed (0.07 m3 /h) gas, while the average consumption of the electric generator was (1.42 m3 /h). The project is in a position to. • prepare biogas standards and regulations for 10m3 scale fixed dome biogas pilot plant in Iraq from the treatment of cow slurry and organic agricultural waste to produce cheap renewable energy and organic fertilizer. • provide pilot testing of other biogas or energy generation that would utilize other agriculture waste such as water hyacinth. • design appropriate actions to scale-up the installation of household and poultry biogas units. Acknowledgements We are deeply grateful to the renewable energy directorate and Sheikh Shafiq Ahmed, the farm owner of village 37. Also, we would like to acknowledge individuals who contributed their efforts to this project, especially, we are particularly indebted to the U.S.A embassy

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in Baghdad. We also wish to express our sincere gratitude to Prof. Thomas Henry Culhane for his advice and encouragement that contributed a great deal to our implementation of the biogas plant through his Website Solar Cities.

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21. IEA (International Energy Agency), Outlook for biogas and Prospects for organic growth. World Energy Outlook Special Report (2020) [online]. https://www.iea.org/reports/outlookfor-biogas-and-biomethane-prospects-for-organic-growth/an-introduction-to-biogas-and-bio methane. Accessed 15 Jan. 2021 22. T.H. Culhane, Iraq’s Green Zone Gets Greener with Biogas and Other Clean Energy Solutions (2013) [online]. Available from https://www.nationalgeographic.com/environment/great-ene rgy-challenge/2013/iraqs-green-zone-gets-greener-with-biogas-and-other-clean-energy-soluti ons/. Accessed 15 Jan. 2021 23. K. Al-Imarah, D.J. Biaee, T. Majed, I. Mohammed, 10 m3 scale Chinese anaerobic digestion pilot plant in Fadak farm. Special issue of the first scientific conference on sustainable and renewable energy to ensure a better environment (part 1). AL-Muhandis J. 153 (2016) 24. D. Newman, Global potential of biogas, in World Biogas Association: London, UK (2019) [online]. Available from https://www.worldbiogasassociation.org/wp-content/uploads/2019/ 07/WBA-globalreport-56ppa4_digital.pdf. Accessed 15 Jan. 2021 25. L. Zheng, J. Chen, M. Zhao, S. Cheng, L. Wang, H.P. Mang, Z. Li, What could China give to and take from other countries in terms of the development of the biogas industry? Sustainability 12(4), 1490 (2020) 26. T. Abbasi, S.M. Tauseef, S.A. Abbasi, A brief history of anaerobic digestion and “biogas”, in Biogas Energy (Springer, New York, 2012), pp. 11–23 27. E. Hanekamp, J.C. Ahiekpor, Climate Support Facility—WO46—Feasibility Study of Ghana Institutional Biogas Programme (2008). Available from https://partnersforinnovation.com/ wp-content/uploads/2019/05/Feasibility-study-of-Ghana-Institutional-Biogas-Programme. pdf. Accessed 15 Jan. 2021 28. J. Wei, G. Liang, J. Alex, T. Zhang, C. Ma, Research progress of energy utilization of agricultural waste in China: bibliometric analysis by citespace. Sustainability 12(3), 812 (2020) 29. A.O. Jegede, G. Zeeman, H. Bruning, A review of mixing, design and loading conditions in household anaerobic digesters. Crit. Rev. Environ. Sci. Technol. 49(22), 2117–2153 (2019) 30. C.H. Nakagawa, Q.L. Honquilada, Chinese biogas digester, A Potential Model for Small-Scale, Rural Applications. (A Manual for Construction and Operation). Reprint No. R-51 (1985) 31. M. Osei-Marfo, E. Awuah, N.K. de Vries, Biogas technology diffusion and shortfalls in the central and greater Accra regions of Ghana. Water Practice Technol. 13(4), 932–946 (2018) 32. VicRoads and GeoPave, Bituminous Sprayed Surfacing Manual- Technical Bulletin No 45 [online] (2004). Available from https://www.vicroads.vic.gov.au/business-and-industry/techni cal-publications/technical-publications-a-to-z. Accessed 15 Jan. 2021 33. Puxin Household Biogas Systems, Manual.Technical Proposal (TP) Shenzhen Puxin Technology Co. Ltd Technical Proposal (TP) [online] (2008). Available from https://vdocuments. mx/puxin-household-biogas-systems-manual.html. Accessed 15 Jan. 2021 34. D. Macharia, W.N. Musungu, Institutional Biogas plant Instiller Manual. IT Power Eastern Africa (2008). Available from https://wisions.net/files/uploads/IT%20Power_Installer%20B iogas%20Manual_SEPS_SC048.pdf. Accessed 15 Jan. 2021 35. Biogas Co. Puxin family size and medium sized biogas systems (2010) [online]. Available from http://www.build-a-biogas-plant.com/PDF/puxinfamily.pdf. Accessed 15 Jan. 2021 36. V.D. Sharma. A Dozen Innovative Renewable Energy Technologies. 1st edn. (Bhanimandal Chowk, Ekantakuna, Lalitpur, Nepal), 28 p (2011) 37. S. Sfez, S. De Meester, J. Dewulf, Co-digestion of rice straw and cow dung to supply cooking fuel and fertilizers in rural India: Impact on human health, resource flows and climate change. Sci. Total Environ. 609, 1600–1615 (2017) 38. F. Lutaaya, Quality and usage of biogas digesters in Uganda. Published thesis of Master of Science—Sustainable Energy Engineering. Makerere University (2013) 39. A.O. Jegede, G. Zeeman, H. Bruning, Development of an optimised Chinese dome digester enables smaller reactor volumes; pilot scale performance. Energies 12(11), 2213 (2019)

Humidity-Enabled Graphene Based Bilayer Device for Power Generation Omita Nanda, A. M. Biradar, and Kanchan Saxena

1 Introduction Depletion of fossil fuels and growing energy demands has inspired the researchers to explore the renewable energy areas such as solar, wind, hydrothermal, and tidal sources [1–4]. But the use of these technologies is limited due to dedicated site requirements, costly equipment, processing, and the unavoidable effects owing to environmental changes. Therefore, energy storage and harvesting devices that can harvest energy from temperature [5], humidity [6], force [7], pressure [8] are explored to address the above issues. In recent years, humidity-enabled power generation has gained considerable attention. These devices generate power from ambient humidity [9, 10]. Graphene is one of the potential materials that can be used for power generation [11, 12]. It is a 2D material with honey comb crystal lattice structure. Graphene is an expensive material but efforts are done to explore its inexpensive derivatives. Graphene oxide (GO) is an oxidized form of graphene. It is a single atomic layered material which is decorated with oxygen-containing groups. Graphene oxide can be synthesized from low-cost graphite using low-cost and high-yield chemical methods. It is hydrophilic in nature and can form stable aqueous colloids. GO can further be reduced to form reduced graphene oxide (rGO) by removal of oxygen-containing groups.

O. Nanda · K. Saxena (B) Amity Institute of Advanced Research and Studies (Materials and Devices), Amity University, Noida, India e-mail: [email protected] Amity Institute of Renewable and Alternative Energy, Amity University, Sector 125, Noida, UP, India A. M. Biradar CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_7

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Herein, we report a bilayer device based on GO/rGO which can generate voltage on exposure to humidity. The graphene oxide films were fabricated using doctor blade technique. These films were reduced to rGO films. The device generates voltage of 1.25 V when exposed to 80% relative humidity. Interestingly, it generated 0.4 V at ambient humidity conditions.

2 Experimental Details Graphene oxide was synthesized by Hummer’s method [13], which involves chemical reduction of exfoliated and intercalated graphite oxide. GO obtained was rinsed with distilled water to remove residual acid. The device was fabricated on pre-cleaned glass substrates. GO obtained from the above procedure was dispersed in distilled water to obtain 30 wt % of solution of GO. Reduced graphene oxide can be directly synthesized by treating GO with hydrazine hydrate. But rGO is hydrophobic in nature and tends to form agglomerates when dispersed in water. Due to this, thin films of rGO are non-uniform and have poor adhesion. Therefore, to fabricate the device, GO suspension was coated onto glass substrates by doctor blade method. The films were dried in oven for three hours at 80 ˚C. GO coated samples were treated with hydrazine hydrate vapours to reduce them to rGO films. Figure 1 depicts the step-by-step procedure for the reduc-

Fig. 1 Step by step procedure for the reduction GO film to rGO film

Humidity-Enabled Graphene Based Bilayer Device …

53

Fig. 2 Bilayer structure of rGO/GO-based device for power generation

tion of GO film to rGO film. GO coated film was brown in colour which changed to dark grey on exposure to hydrazine vapours. The sheet resistance of rGO film was of the order of 1k per square. A layer of GO was coated on rGO films by drop casting technique to obtain a bilayer device (as shown in Fig. 2). Aluminium electrodes were fabricated on the device using thermal vapour deposition technique. The device was exposed to humidity varying from 30 to 80% RH. Electrical measurements were carried out using Keithley electrometer (6514).

3 Results and Discussion GO and rGO obtained from the above procedure have been characterized by XRD and SEM analysis in our previous studies reported earlier [14]. XRD and SEM analysis confirmed the reduction of GO to rGO [14]. The colour change of GO film from brown to grey also gave the evidence of the reduction of GO to rGO film. Humidity response of the fabricated bilayer device was studied. The device was placed inside an indigenously constructed humidity chamber and connected to Keithley electrometer. The effect of humidity on the device was investigated by raising the humidity level to 80%. An increasing trend in the voltage up to 1.25 V was observed when the humidity was raised from 30 to 80% RH. Graph in Fig. 3 shows the humidity response of the device. Initially, 0.4 V was observed across the bilayer device at 30% humidity, which escalated to 1.25 V when humidity was raised to 80% as seen in Fig. 3. On further increasing humidity, the voltage across the device reached its maximum voltage of 1.25 V. In order to study the humid and de-humid cycles, the device was repeatedly exposed to humidity varying from 30 to 80% RH. Figure 4 depicts the voltage generation cycles of the device. Initially, 0.5 V was observed across the bilayer device at an ambient relative humidity of 35% whereas the voltage dropped to 0.4 V

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Fig. 3 Humidity response of bilayer device

Fig. 4 Voltage generation cycles for bilayer device

at 30% RH value. The current measured across the bilayer device was found to be very small of the order of few nanoamperes. When the GO is exposed to air enriched with water molecules, the absorption and hydration of hygroscopic GO lead to the free charge carriers (i.e. protons). This gives rise to concentration gradient of H+ ions between GO and conducting rGO layers [15]. Further, these H+ ions gradually penetrate towards the rGO layer due to concentration gradient and thus generates the potential and electron movement in the external circuit. The increase in humidity leads to more free charge carriers. At 80% of humidity, the device may reach its saturation voltage due to the maximum moisture holding capacity of GO. Hence, the device attains maximum voltage of 1.25 V.

Humidity-Enabled Graphene Based Bilayer Device …

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4 Conclusion A bilayer device comprising of GO and rGO layers with aluminium electrodes has been fabricated. It has been shown that a humidity dependent voltage is developed across the device. Voltage ranging from 0.4 to 1.25 V is generated across the device by varying the humidity from 30 to 80% RH. Therefore, the device is highly sensitive to humidity and can also be used for sensor applications. Further, studies are being carried out to enhance the current of the device. Acknowledgements The authors are thankful to Dr. Ashok K. Chauhan, Founder President, Amity University, and Dr. V. K. Jain, Distinguished Scientist and Professor, AIARS (M&D), Amity University, Noida for their encouragements in carrying out this work.

References 1. A. Modi, F. Bühler, J. G. Andreasen, F. Haglind, A review of solar energy based heat and power generation systems. Renew. Sustain. Energy Rev. 67, 1047–1064 (2017) 2. S.A. Vargas, G.R.T. Esteves, P.M. Maçaira, B.Q. Bastos, F.L. Cyrino Oliveira, R.C. Souza, Wind power generation: a review and a research agenda. J. Clean. Prod. 218, 850–870 (2019) 3. M. Yamamoto, R. Nakamura, K. Takai, Deep-sea hydrothermal fields as natural power plants. Chem. Electro. Chem. 5(16), 2162–2166 (2018) 4. M.S. Chowdhury, K.S. Rahman, V. Selvanathan, N. Nuthammachot, M. Suklueng, A. Mostafaeipour, A. Habib, M. Akhtaruzzaman, N. Amin, K. Techato, Current trends and prospects of tidal energy technology. Environ. Dev. Sustain. 23, 8179–8194 (2020) 5. Y.K. Ramadass, A.P. Chandrakasan, A battery-less thermoelectric energy harvesting interface circuit with 35 mV startup voltage. IEEE J. Solid-State Circ. 46(1), 333–341 (2011) 6. K. Saxena, O. Nanda, N. Gupta, A. Kumar, P. Kumar, V.K. Jain, Humidity dependent electrical response of bilayer device based on poly (3,4-ethylene dioxythiophene)-poly (styrene sulphonate) and single walled carbon nanotubes. Synth. Met. 197, 86–89 (2014) 7. S.W. Chen, X. Cao, N. Wang, L. Ma, H.R. Zhu, M. Willander, Y. Jie, Z.L. Wang, An ultrathin flexible single-electrode triboelectric-nanogenerator for mechanical energy harvesting and instantaneous force sensing. Adv. Energy Mater. 7(1), 1601255 (2017) 8. M. Deterre, E. Lefeuvre, E. Dufour-Gergam, An active piezoelectric energy extraction method for pressure energy harvesting. Smart Mater. Struct. 21(8), 085004 (2012) 9. X. Liu, H. Gao, J.E. Ward, X. Liu, B. Yin, T. Fu, J. Chen, D.R. Lovley, J. Yao, Power generation from ambient humidity using protein nanowires. Nature 578, 550–554 (2010) 10. T. Ding, K. Liu, J. Li, G. Xue, Q. Chen, L. Huang, B. Hu, J. Zhou, All-printed porous carbon film for electricity generation from evapouration-driven water flow. Adv. Funct. Mater. 27(22), 1700551 (2017) 11. F. Zhao, Y. Liang, H. Cheng, L. Jiang, L. Qu, Highly efficient moisture-enabled electricity generation from graphene oxide frameworks. Energy Environ. Sci. 9(3), 912–916 (2016) 12. H. Cheng, Y. Huang, F. Zhao, C. Yang, P. Zhang, L. Jiang, G. Shi, L. Qu, Spontaneous power source in ambient air of a well-directionally reduced graphene oxide bulk. Energy Environ. Sci. 11(10), 2839–2845 (2018) 13. F.T. Thema, M.J. Moloto, E.D. Dikio, N.N. Nyangiwe, L. Kotsedi, M. Maaza, M. Khenfouch, Synthesis and characterization of graphene thin films by chemical reduction of exfoliated and intercalated graphite oxide. J. Chem. 2013, 1 (2012)

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14. O. Nanda, J. Gayathri, A.M. Biradar, K. Saxena, Fabrication of reduced graphene oxide conductive thin films using doctor blade technique, in Recent Trends in Materials and Devices (2020), pp. 53–57 15. C. Shao, J. Gao, T. Xu, B. Ji, Y. Xiao, C. Gao, Y. Zhao, L. Qu, Wearable fiberform hygroelectric generator. Nano Energy 53, 698–705 (2018)

Long-Term Performance Analysis of Solar Collectors Subhra Das and Subhayan Das

1 Introduction Solar resource assessment in India reveals the fact that nearly 58% of the geographical area potentially represents the solar hotspots in the country with more than 5 kWh/m2 /day of annual average global insolation [1]. Estimating solar radiation at any location [2], determining position of sun [3], and the angle of incidence of solar radiation had been conducted by various researchers in the past. The Government of India had announced an ambitious target of installing 175 GW of renewable energy capacity by 2022 to reduce the use of fossil fuels and increase the capacity of renewables. India has a solar potential of 748 GW, and solar thermal can be considered as one of the options for meeting the heating load of the country. Collares-Pereira and Rabl [4] conducted a simple procedure for predicting longterm average performance of concentrating and non-concentrating solar collectors. They defined the long-term average useful energy delivered by a collector a based on collector temperature, optical efficiency, tracking mode, concentration, latitude, clearness index, etc. Klein et al. [5] defined f factor as the fraction of the total heating load that can be supplied by solar energy. The f chart method is used to estimate the long-term performance of solar heating systems. Utilizability analysis techniques enable us to measure the impact of critical radiation on long-term performance of solar collectors. It has been reported by researchers that specific design of evacuated tube collector with low optical efficiency and having low critical radiation results in greater utilization of solar radiation depending on the temperature of heat transfer fluid [6]. Flat plate collectors and evacuated collector S. Das (B) Solar Engineering Department, Amity University Haryana, Gurugram, India S. Das School of Computer Engineering, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_8

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systems are widely used in Poland for production of hot water in households, multifamily buildings, and public buildings. A comparison of the performance of the two type of system for large scale installation reveals the fact that evacuated tube collectors (ETCs) perform better in comparison with flat plate collector system in terms of productivity. ETCs show better performance during colder season and ensure uniform hot water production [7]. Annual thermal efficiency of flat plate collector system was found to be 46% and that of heat pipe evacuated tube collector systems was found to be 62% in Mediterranean climatic conditions [8]. Flat plate solar thermal collectors are useful for providing thermal energy for application having low operating temperatures like aquaculture system. Study showed that 98% solar fraction can be achieved by a 63 m2 collector area for providing hot water for aquaculture [9]. Solar thermal water heaters are cost-effective way of preheating water for livestock processing plants having payback period less than its expected service period [11]. The objective of the paper is to study the long-term performance analysis of flat plate collector and evacuated tube collector for a location in Leh (34.1526° N, 77.5771° E) and Gurgaon (28.4595° N, 77.0266° E). Monthly average utilizability for both FPC and ETC has been computed, and the f factor for these collectors has been computed for meeting hot water requirement for a family of five. A program has been developed in Python to simulate the performance of these collectors.

2 Utilizability The concept of utilizability was pioneered by Hottel and Whillier and later generalized by Liu and Jordan. Klein and Beckman derived the generalized design method for solar systems using flat plate collectors. Collares-Pereira and Rabl derived a simple method to estimate long-term performance of solar systems using both concentrating and non-concentrating collectors. Utilizability is defined as the fraction of incident solar radiation that can be utilized by an ideal collector having no optical losses and perfect heat removal circuit.

2.1 Flat Plate Collector The useful heat gain by a flat plate collector is expressed as Q u = Ac FR [Ht (τ α) − U L (Ti − Ta )]

(1)

where Ac is area of the collector, T i is inlet fluid temperature, H t is hourly incident solar radiation on tilted surface, (τ α) is transmissivity-absorptivity product, F R is heat removal factor, U L is overall heat removal factor, and T a is ambient temperature.

Long-Term Performance Analysis of Solar Collectors

59

Hourly radiation on tilted surface for the entire year is estimated using Klucher’s model which provides good estimation for partly overcast and clear skies. These are characterized by a rising intensity in the proximity of circumsolar sky and horizon region. Klucher introduced a function F = 1 − [I D /I H ]2 that determines the degree of cloud cover. Solar radiation on tilted surface is estimated using the following relation using Klucher’s model [2]:   1 + cos(β/2) (H H − H D ) cos θ + H D Ht = sin α 2     β 1 + Fcos2 θ sin3 (θz ) 1 + Fsin 3 2

(2)

The critical radiation H t,c level is defined as the minimum radiation required to maintain the collector absorber plate at inlet fluid temperature [5]: Ht,c =

FR U L (Ti − Ta ) FR (τ α)

(3)

The useful heat gain can be expressed in terms of critical radiation for FPC as [5]: +  Q u = Ac FR (τ α) Ht − Ht,c

(4)

where + superscript indicates that only positive values are to be considered. Let Ht be monthly average hourly radiation on tilted collector for a given hour of the day. The monthly average hourly utilizability ϕ. as the fraction of total radiation during the month of N days which is above critical level is defined as [5]:  + 1  Ht − Ht,c ϕ= . N days Ht

(5)

2.2 Evacuated Tube Collector The useful heat gain from single collector tube of an evacuated be collector can be expressed as [10]:



Q u = Ac FR Heff (τ α) − U L A L Ac (Ti − Ta ) .

(6)

where H eff is the effective solar radiation on the collector surface, Ac is absorber tube diameter time’s collector length, and AL is equal to π Ac [10]:

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  Heff = H H RT + R p ρ 2 −

1 cos ω

 .

(7)

where H H is the total insolation on a horizontal surface, ω is the hour angle, ρ diffuse reflectance of back screen, and RT , Rp, and are given by [10]: 

1 − [sin(s − L) cos δ cos ω + cos(s − L) sin δ]2 RT = g(ω) cos δ cos L cos ω + sin δ sin L

0.5 (8)

where L is latitude of the place, s is tilt angle, and δ is declination angle. The shading factor g(ω) is expressed as a function of tube spacings d, absorber and cover tube outer diameter D4 and D6, respectively, and hour angle as [10]:  g(ω) =

d D4

1,

cos ω +

1 2

1−

D6 D4

|ω| ≤ |ω0 | |ω| > |ω0 |

(9)

and |ω0 | = cos −1 [(D4 + D6 )/2d]

(10)

The angle factor Rp for converting beam radiation on a horizontal surface to a south facing tilted surface at angle s is expressed as [10]: RP =

cos(L − s) cos δ cos ω + sin(L − s) sin δ cos L cos δ cos ω + sin L sin δ

(11)

And back reflected light parameter is given by ≡

D6  Fi T |ω=0 D4 i

(12)

F iT are the shape factors of the strips whose views of the tube are unobstructed by other tubes. The array efficiency based on active area of the collector is given by [10]: η=

Qu D4l FR [τ α Heff − πU L (Ti − Ta )] = ld Ht ld Ht

(13)

where l is collector tube length, s is collector tilt factor to horizontal, and H T is hourly insolation on the plane of the collector which is estimated using Klucher’s model. The critical radiation H t,c level for evacuated tube collector can be expressed as:

Long-Term Performance Analysis of Solar Collectors

Ht,c =

π FR U L (Ti − Ta ) FR (τ α)

61

(14)

Let Ht be monthly average hourly radiation on tilted collector for a given hour of the day. Using Eq. (14), the monthly average hourly utilizability ϕ as the fraction of total radiation during the month of N days which is above critical level for evacuated tube collector can be computed using the following relation:  + 1  Ht − Ht,c ϕ= N days Ht

(15)

3 Flowchart for Long Term Performance Analysis See Fig. 1.

4 Results and Discussions The performance of solar system depends on the availability of solar radiation in that site. Thus, hourly solar radiation data for Gurugram and Leh obtained from National Institute of Wind Energy has been studied to access the availability of solar radiation in these two locations. Hourly global solar radiation on horizontal surface (GHI) for 8760 hours for the year 2011 is shown in Fig. 2 for Gurugram. It is observed that during noon over the entire year, GHI is above 500 W/m2 , and a maximum GHI equal to 979 W/m2 is obtained in the month of April. During May, June, and July, solar radiation intensity is less because of aerosols and cloud cover. Out of 8760 hours for which data is recorded over the entire year, only 128 times GHI is found to be greater than 900 W/m2 and 1313 times it is found to be greater than 600 W/m2 . The average global solar irradiation at noon during January is 454 W/m2 , there is an increase in radiation from mid of February, and a maximum GHI of 1009 W/m2 is obtained in the month of May. Out of 8760 h for which data is recorded over the entire year 2011 in Leh, only 223 times GHI is found to be greater than 900 W/m2 and 1335 times it is found to be greater than 600 W/m2 . Figure 3 shows that Leh receives solar radiation above 600 W/m2 from mid of February except for a few days. A simulation package for Klucher model built on Python to calculate solar radiations on a tilted surface at a particular location for a whole year has been developed and has been made available for any researcher to use it (https://pypi.org/project/ KlucherModelSDas/1.0.1/). Computer program has been developed in Python to compute the monthly average hourly utilizability ϕ as the fraction of total radiation

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Fig. 1 Flowchart for computing utilizability

S. Das and S. Das

Long-Term Performance Analysis of Solar Collectors

63

1200

GHI [W/m2]

1000 800 600 400 200

1 338 675 1012 1349 1686 2023 2360 2697 3034 3371 3708 4045 4382 4719 5056 5393 5730 6067 6404 6741 7078 7415 7752 8089 8426

0

Time in hour for 1 year Fig. 2 Hourly global solar radiation data for Gurugram for the year 2011 1200

GHI [W/m2]

1000 800 600 400 200

1 382 763 1144 1525 1906 2287 2668 3049 3430 3811 4192 4573 4954 5335 5716 6097 6478 6859 7240 7621 8002 8383

0

Time in hour for 1 year Fig. 3 Hourly global solar radiation data for Leh for the year 2011

during the month of N days which is above critical level computed using Eq. (5) for FPC and using Eq. (15) for ETC. The monthly utilizability for Leh and Gurugram for a flat plate collector with F R U L = 3 W/m2 C, F R (ατ ) = 0.85 has been computed for the entire year. It has been observed that utilizability of FPC is higher in Gurugram from January to August than that of Leh but shows a decline September onward as shown in Fig. 4. The decline in

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Monthly Average Ulizability

0.60 0.50 0.40 0.30

Leh Gurgaon

0.20 0.10 0.00

0

2

4

6

8

10

12

14

Month Fig. 4 Monthly average utilizability for Leh and Gurugram for a flat plate collector with F R U L = 3 W/m2 C, F R (ατ ) = 0.85

30

0.50 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00

25 20 15 10 5

Monthly Avg Ta

Monthly Avg Ulizability

utilizability can be attributed to the environmental pollution and foggy days during this time of the year. The monthly utilizability for Leh for an evacuated tube collector with F R U L = 3 W/m2 C, F R (ατ ) = 0.85 has been computed for the entire year. It has been observed that utilizability of ETC has an increasing trend from January to September and has a decreasing trend thereafter as shown in Fig. 5. From September onward, it is observed that ambient temperature starts decreasing sharply which may be due to snowfall in these areas. The decline in utilizability may be attributed to reduced availability of solar radiation above critical level during this period of the year. The fractions of heating load that can be supplied by a flat plate collector having areas 2 m2 , 4 m2 , and 5 m2 have been computed for Leh at 34.1526° N latitude for a family of five. The collector is considered to be facing south at a tilt angle

φ Ta

0 0

2

4

6

8

10

12

14

Month

Fig. 5 Monthly average utilizability for Leh for a evacuated tube collector with F R U L = 3 W/m2 C, F R (ατ ) = 0.85

Long-Term Performance Analysis of Solar Collectors

65

30°. Collectors are double glazed FPC with F R U L = 3 W/m2 K and F R (τ α) = 0.85. Storage tank has a capacity of 100 l of stored water per sq. m of collector area. The desired hot water temperature for domestic use is taken to be 60 °C and cold water supply is at 11 °C. The f factor and fraction of heating load for each month is computed that can be meet by flat plate collector for the entire year and is given in Table 1. It is observed that a FPC of 3 m2 collector area can supply 43% of the annual demand whereas 55% of annual demand can be met by FPC with 4 m2 collector area.

5 Conclusions The long-term performance analysis of flat plate collector and evacuated tube collector system are conducted for two different geographical locations in India. As per Köppen climate classification, Leh has cold desert climate and Gurugram has dry winter humid subtropical climate bordering to hot semi-arid climate. Leh experiences long cold winters starting from October to March which leads to increasing its heating load. Winters are cold in Gurgaon which starts from November and are extreme during the month of December and January. Both the locations receive adequate solar radiations to fuel domestic solar water heating systems. The study shows that solar thermal water heating systems can deliver a part of the heating load in these locations. Flat plate collectors were found to have an average monthly utilizability of 0.41 for Leh and 0.45 for Gurugram. Evacuated tube collector systems have an average monthly utilizability of 0.35 for Leh. It is observed that ETC perform better during winter months. The f factor of the water heating system increases from March till November when the solar radiation and ambient temperature increases; it is observed that 55% of annual heating load of a family of five people can be met by the system using flat plate collector of area 4 m2 . It can be concluded that solar thermal water heating systems can meet the hot water requirement efficiently for both Leh and Gurugram.

2

5

10

13

20

24

24

24

21

14

9

3

1

2

3

4

5

6

7

8

9

10

11

12

34.58

45.15

34.43

32.66

18.73

16.73

18.63

19.89

15.29

18.16

13.78

17.26

Ht MJ/m2 -day

0.21 0.24

3.18E + 09 3.18E + 09

3.75E + 10

0.45

0.24

3.08E + 09

3.18E + 09

0.25

3.18E + 09

0.57

0.19

3.08E + 09

3.08E + 09

0.24

3.18E + 09

0.41

0.18

2.87E + 09

0.45

0.22

3.18E + 09

3.08E + 09

f

D, J

3.18E + 09

2 m2

Area

Fractions of heating load that can be supplied by a flat plate collector

Total

Monthly average Ta, C

n

0.30

1.14E + 10

1.42E + 09

1.75E + 09

1.42E + 09

1.26E + 09

7.60E + 08

6.77E + 08

7.31E + 08

8.04E + 08

5.86E + 08

7.57E + 08

5.05E + 08

7.10E + 08

fD, J

Table 1 Fractions of heating load that can be supplied by a flat plate collector having different areas

0.62

0.78

0.63

0.58

0.35

0.31

0.34

0.36

0.28

0.34

0.26

0.32

f

3 m2

0.43

1.62E + 10

1.98E + 09

2.40E + 09

1.99E + 09

1.78E + 09

1.10E + 09

9.83E + 08

1.06E + 09

1.16E + 09

8.53E + 08

1.09E + 09

7.37E + 08

1.03E + 09

fD, J

0.78

0.95

0.78

0.73

0.44

0.40

0.44

0.47

0.36

0.44

0.33

0.42

f

4 m2

0.55

2.04E + 10

2.47E + 09

2.92E + 09

2.48E + 09

2.23E + 09

1.42E + 09

1.27E + 09

1.36E + 09

1.49E + 09

1.10E + 09

1.41E + 09

9.55E + 08

1.32E + 09

fD, J

66 S. Das and S. Das

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67

References 1. T.V. Ramachandra, R. Jain, G. Krishnadas, Hotspots of solar potential in India. Renew. Sustain. Energy Rev. 15, 3178–3186 (2011) 2. S. Das, Short term forecasting of solar radiation and power output of 89.6 kWp solar PV power plant. Mater. Today: Proc. (2020). https://doi.org/10.1016/j.matpr.2020.08.449 3. A.M. Pal, S. Das, Analytical model for determining the Sun’s position at all time zones. Int. J. Energy Eng. 5(3), 58–65 (2015) 4. M. Collares-Pereira, A. Rabl, Simple procedure for predicting long-term average performance of non-concentrating and of concentrating solar collectors. Report prepared for solar heating and cooling Research and Development Branch, Argonne National Laboratory, Argonne, Illinois (1978) 5. S.A. Klein, W.A. Beckman, J.A. Duffie, A design procedure for solar heating systems. Sol. Energy 18, 113 (1976) 6. M. Zlateva, Assessment of annual performance of solar collectors by means of the utilizability method, in E3S Web of Conferences 207, p. 02007PEPM (2020) 7. P. Olczak, D. Matuszewska, J. Zabagło, The comparison of solar energy gaining effectiveness between flat plate collectors and evacuated tube collectors with heat pipe: case study. Energies 13, 1829 (2020). https://doi.org/10.3390/en13071829 8. A. Maraj, A. Londo, C. Firat, A. Gebremedhin, Comparison of the energy performance between flat-plate and heat pipe evacuated tube collectors for solar water heating systems under Mediterranean climate conditions. J. Sustain. Dev. Energy Water Environ. Syst. 7(1), 87–100 (2019) 9. D.M. Atia, F.H. Fahmy, N.M. Ahmed, H.T. Dorrah, Optimal sizing of a solar water heating system based on a genetic algorithm for an aquaculture system. Math. Comput. Model. 55, 1436–1449 (2012) 10. Analysis and experimental tests of a high-performance tubular collector. Prepared from documents furnished by Owens-Illinois, for US Department of Energy (1978) 11. Y.M. Liu, K.C. Chang, W.M. Lin, K.M. Chung, Solar thermal application for the livestock industry in Taiwan. Case Stud. Thermal Eng. 6, 251–257 (2015)

Mitigation of Soiling of Solar Panels by Applying Superydrophobic Aluminum Oxide Thin Film and Dry Cleaning by Electrodynamic Screen Deepanjana Adak, Silajit Manna, Shoubhik De, Manish Kumar, Santanu Maity, and Raghunath Bhattacharyya

1 Introduction The solar photovoltaic (PV) panels and the concentrated solar power (CSP) mirrors are two proven methods for harvesting the solar energy. Many of the industrial level solar PV or CSP plants are being set up in areas with high solar irradiance round the year. However, it has been seen very often that in such areas due to low precipitation and strong winds, dust and dirt particles get accumulated over the PV panels or CSP mirror surfaces, ultimately reducing the net output power, commonly known as the soiling effect. Soiling, caused by dust accumulation on the surfaces of the PV module/CSP mirrors, significantly reduces the transparency/reflectivity of the solar glass covers over time, thereby resulting in loss of net output power of PV modules as well as CSP plants radically. In most of the dry and lower rainfall areas, particularly in the parts of China, India, and MENA region, the net loss in the PV power output is ~26–40% [1]. Experiments have reported that over 9.2% efficiency loss occurs over the course of nine weeks in solar PV plants, placed in desert areas. In the desert areas of India, the I sc (short circuit current) drop is estimated to be 2–17% a year [2, 3]. To ensure steady generation of output power from solar energy driven systems, dust removal from the surfaces of such devices is very important. To achieve this, a sustainable and economic cleaning method is required. There are several conventional cleaning methods that are used in power plants driven by solar energy such as manual cleaning, robotic cleaning, hydraulic cleaning, pneumatic cleaning, passive cleaning. However, the major disadvantage involves intensive manual labor and extensive use of natural (water) or chemical resources. It can be realized that sustainable power output from solar-energy-driven technologies can be accomplished by functionalizing the glass material used in these systems by applying an anti-reflecting (AR), D. Adak (B) · S. Manna · S. De · M. Kumar · S. Maity · R. Bhattacharyya School of Advanced Materials, Green Energy and Sensor Systems, Indian Institute of Engineering Science and Technology, Shibpur, Howrah, West Bengal 711103, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_9

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self-cleaning (SC)/anti-soiling (AS) coating on the exposed surface. Also, in arid and semi-arid areas where water scarcity is acute, adoption of a dry cleaning like electrodynamic screen (EDS) becomes very relevant. Water-assisted SC/AS coating on top of solar glass covers broadly is classified as a (super) hydrophilic and (super) hydrophobic coating. When the water droplets fall on a superhydrophilic surface, they seep into the layer under the fouling on such extremely wettable surface and under proper inclination glides from the surface carrying away the dirt particle with it, thereby, removing it from the surface. A variety of photoactive material, particularly, wide band-gap transparent metal oxides such as TiO2 , ZnO, and SnO2 , is being used to achieve SC functionality via photo-induced superhydrophilicity [4]. Photo-induced superhydrophilic SC mechanism involves oxidative degradation of organic pollutants on the surface photoactive metal oxide film in the presence of sunlight. Also, inspired by “Lotus effect,” a great variety of artificial superhydrophobic SC surfaces has been developed. We have previously carried out an important research where TiO2 films were variously tailored to meet such requirement, most importantly by tailoring its porosity to reduce refractive index in case of hydrophilic coatings [5]. Dirt particles are picked up by water droplets due to the structured surface with dual-scale micro-/nano-hierarchical roughness created by the hydrophobic coating. Also, by virtue of low contact angle hysteresis (CAH)/sliding angle (SA), water droplet glides down from the surface carrying away the dirt particles along with it when tilted slightly [6]. Moreover, such nanostructured surface is often subject to various mechanical abrasion which limits the lifetime of such coatings drastically. In most of the published literature, a multifunctional SC and AR coatings are made up of surface modified porous silica coatings. However, such porous silica coatings are often not adequate for such outdoor applications due to mechanical fragility. Thus, in the present study, an attempt has been made to fabricate extremely robust, durable, optically transparent, superhydrophobic aluminum oxide-based coatings for solar panel cover glasses [7]. A typical EDS consist of a set of inter-digited transparent conducting electrodes, organized in different patterns, on a dielectric or glass substrate and embedded in a dielectric layer. This is then suitably integrated to the solar PV or CSP panels. EDS under the influence of low frequency single-phase (1-F), two-phase (2-F) or three-phase (3-F) high-voltage pulsed supply helps to remove the dust accumulated over the solar panel and CSP mirror surfaces, based on the phenomenon of dielectrophoresis [8]. It is the phenomenon in which a charged dust particle is acted by a net displacement force, whenever it is placed under non-uniform electric field. The overall removal of dust by EDS films basically follows the principle of electriccurtain [9]. Tatom et al. first proposed this principle back in 1967 [10]. Later on, it was clarified more extensively by Masuda et al. [11]. A group led by M. K. Mazumder in Boston University under a grant under USA “Sunshot” project has brought to a pre-commercial level [2, 3]. We present here a robust and mechanically durable alumina-based transparent self-cleaning coating. Also, essential details of our investigations involving a dry cleaning method based on electrodynamic screen (EDS) have been presented.

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2 Experimental Details Aluminum oxide sol was prepared by mixing Aluminum tri-sec-butoxide (Al(O-secBu)3 ), ethyl acetoacetate (EAcAc), and isopropyl alcohol (i-PrOH), and the mix was stirred at room temperature for 3 h. Catalytic amount of water (H2 O) was carefully added to the solution for hydrolysis. The molar ratio of composition mixed to obtain Al2 O3 sol is Al(O-sec-Bu)3 :i-PrOH:EAcAc:H2 O = 1:20:1:4. The as prepared sol are coated on a clean glass substrate by dip coating technique. The withdrawal speed was maintained at 100 mm/min; after dip coating, the substrates are annealed in air at 400 °C for 10 min. The coated glass coupons were finally immersed in hot water at 70 °C for 10, 20, 30, and 60 s for the formation of γ-AlOOH (boehmite) nanoflakelets. Finally, 1.0 vol% 1H, 1H, 2H, 2H-perfluoro-octyltrichlorosilane (PFOTS) in hexane was spray-coated on the γ-AlOOH nanoflakelets and heat treated at 115 °C for 15 min to attain the water repellent coating. For EDS, the electrode patterns were created by both sputtering and subsequent processing by photolithography and wet chemical etching. Screen printing of the electrodes is a straightforward technique. Single-phase EDS on 3-inch as well as 6-inch glass substrates was fabricated by magnetron sputtering (RF-MS) of ITO followed by wet chemical etching, as also by screen printing of silver electrode pattern by screen printing, respectively. The EDS was energized by a variable 2 kV DC pulsed supply with 15 Hz duty cycle of 10%. The morphology deposited films were examined by a field-emission scanning electron microscope (JSM7610F JEOL, Japan) and atomic force microscope (5100, Agilent Technologies, USA). The chemical composition of the deposited films was analyzed using FTIR (Perkin Elmer 100 spectrophotometer), and energy dispersive X-ray (EDX) of JEOL, Japan (model no.-JSM7610F) make. JASCO make UV–Vis spectrophotometry (model no. V-530) was used to evaluate the optical properties of the as deposited films. Water contact angles (WCAs) of coatings were measured, at room temperature, with goniometer (290 G1, Ramehart, USA). The mechanical durability was evaluated using pencil hardness tester (Elcometer 501 Pencil Hardness Tester). A 2 kV bipolar pulsed power supply (Neo-Teletronix Private Limited, Kolkata, West Bengal, India) was used to generate electric field. An environmental chamber for dust deposition was built in-house which consists of humidifier, artificial dust deposition mechanism, and wind speed control. An amorphous Si photosensor was built in-house consisting a layer of a-Si:H. Finally, an EDS patter made up of silver ink was printed on corning glass substrate using screen printing. The micrograph of dust deposition on EDS samples is recorded using optical microscope (B380, Optika).

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3 Results and Discussions 3.1 Surface and Optical Properties of Transparent Superhydrophobic Alumina Coatings The as prepared coatings exhibited excellent optical transmission, mechanical hardness, and long-term durability. The moderately wettable coatings are further functionalized with perfluoro-silane (PFOTS) to achieve non-wetting superhydrophobic SC/AS layer on glass substrate. Table 1 summarizes the optical, mechanical, surface roughness, and wetting behavior of coatings obtained by varying hot water immersion (HWI) time. The transmission curve (Fig. 1) reveals nearly 0.5–1.5% transmission gain on deposition of alumina sol followed by HWI treatment. In order to study morphology and surface topography of the coatings, FESEM and AFM images (Fig. 2) were recorded. It is clearly evident from both the AFM and FESEM images that HWI step led to increase in the roughness of the coating surface, resulting in desirable Table 1 Various optical and surface properties of coatings obtained by varying HWI time Sample name

Etching time (s)

Transmission gain (%)

Contact angle (°)

S1

0

0.43

54.3

1.51

H

S3

10

0.66

54.5

1.82

2H

S5

20

1.26

68.3

3.05

3H

S6

30

1.33

69.2

10.33

5H

S7

60

1.19

70.2

13.14

4H

Fig. 1 Transmittance spectra of alumina obtained on varying HWI time

RMS roughness

Pencil hardness

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Fig. 2 FESEM image a before HWI and b after HWI for 60 s; AFM image with RMS roughness c before HWI and d after HWI for 60 s

hierarchical nanoflakelet like structure necessary for water-repelling (hydrophobic) surface [12]. The FTIR spectra (Fig. 3a) of Al-hydroxide coated glass substrate before HWI test clearly indicate peak at around 1028 cm−1 , which can be assigned to Al-O bonds in aluminum hydroxide [13]. Again, after HWI, the resulting γ-AlOOH (boehmite) nanoflakelets exhibit two characteristic peaks centered at 588 cm−1 and 750 cm−1 , which can be assigned to the stretching vibrations of Al–O bond in boehmite [13]. The EDS spectra (Fig. 3b) indicate Al and O peak with Al/O = 0.241 which may be due to transformation of annealed γ-Al2 O3 to γ-AlOOH after HWI step.

Fig. 3 a FTIR spectra before and after HWI, b EDS spectra after HWI

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Fig. 4 Water contact angle (CA) a after HWI step, and subsequent b silane treatment of aluminacoated substrate

From Fig. 4a and b, it can be clearly seen that the contact angle obtained after HWI for 60 s is 78°, which further increases to 160° after spray coating the surface with perfluoro-silane. The superhydrophobic surface was obtained without compromising the optical transmission of coating. The mechanical hardness of the coating were assessed using pencil hardness tester. The study reveals 4H hardness after silane treatment making it suitable for outdoor applications.

3.2 EDS-Related Investigations: Simulation Results of Dust Removal Mechanism of EDS Film Whenever an uncharged particle drops on the EDS film, integrated to a solar PV or CSP panel, an electric charge is induced in it, depending upon the polarity of the nearest electrode. After induction of electric charge, the particle experiences Coulomb forces of repulsion and attraction by the electrodes of the same and opposite polarity, respectively. Besides this, the force due to dielectrophoresis also acts on it which induces motion in them. Finally, the combination of the vertical components of Coulomb force lifts the particle up from the panel surface by overcoming the forces due to adhesion and the gravitational forces and vertical component of the dielectrophoresis force. Now, once it is lifted, the tangential component of the Coulomb force along with that of the dielectrophoresis force ultimately pushes the particle to the next electrode of opposite polarity, which in the next supply cycle changes its polarity, and the whole process repeats again. In this way, the particle is driven along the panel surface depending up on the particle polarity. In Fig. 5, F c , F DEP , F g , F adh represents Coulomb force, dielectrophoresis force, gravitational force, adhesive force (Capillary force (F cap ), Van der Waals force (F vdw ), and image force (F img ), etc.), respectively. Depending upon the types of electric supply, EDS can be classified in three types, 1-F, 2-F, and 3-F. In the 1-F operation, a pulsed supply alternates between positive

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Fig. 5 Schematic depicting net forces acting on a dust particle

maximum and negative maximum at one EDS electrode terminal, while the other one is kept at ground potential. In 2-F operation, the pulsated supply at the two electrode terminals of the EDS alternatively changes its polarity between positive maximum and negative maximum. In 3-F operation, a three-phase pulsated positive supply is applied in sequence at the three terminals of specially designed electrode samples. Again, depending upon the modes of operation, EDS could be of two types, such as a movable EDS or static type of EDS [14]. For PV application in case of the movable type, there is no need of the high transparency as they are fitted upside down over the panel, whereas the static type requires to be suitably integrated on the panel, hence demanding enough transparency so as to ensure high transmission of sunlight to the panel. For a smaller particle or lighter particle, the particle motion follows the surfing pattern, whereas the comparatively larger particles are prone to hopping from one electrode to the other [15]. In our laboratory, a 1-F supply has been constructed, capable of creating 2 kV pulsed, 15 Hz signals to the EDS samples. To assess the process of dust removal, a scaled model of the single-phase EDS film has been designed in COMSOL Multiphysics software. In this simulation, a 2 kV supply is alternatively applied to simulate a single-phase operation, and the results have been analyzed. The analysis (Fig. 6) clearly depicts the orientation of electric field lines between the electrodes and the variation of them in two successive supply cycle; the simulation voltage has also been increased from 2 kV to 2.5 kV to study the effect of increased supply voltage on EDS operation. It was seen that the increase of a mere 500 V led to significant increase in the number of field lines, as depicted in Fig. 7a and b. It also helps to visualize how in a single-phase operation,

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Fig. 6 Electric field lines distribution in simulation result at two successive cycle

Fig. 7 Electric field lines around the EDS electrode at a 2 kV and b 2.5 kV

the successive reversal of electrode polarity resembles the formation of a standing wave which helps in finally removal of the dust particle. We have first fabricated some PCB based EDS samples, as it is comparatively easy to fabricate, and this way we arrived at the optimized electrode design of EDS. The design revealed electrode width to be 0.5 mm and distance between two consecutive electrodes 1.3 mm, for a single-phase operation of the EDS. The pre-removal and post-removal of the dust samples have been estimated both by a gravimetric method and an innovative optical method involving amorphous hydrogenated silicon (a-Si:H)-based image sensor. The maximum dust removal efficiency (DRE) was estimated to be 87%. Similar simulation has been performed over a scaled three-phase inter-digitated (IDG) electrode design, and the dust removal process has been analyzed. It is found that in case of a 3-F simulation, the successive polarity reversal of the IDG(s) over the supply cycle creates a traveling wave type pattern to remove dust particles [16]. Once the optimized design was obtained by creating EDS patterns on PCB, the same was transferred to glass substrates, first by depositing silver lines using a paste by screen printing. The photographs images of dust deposited before (Fig. 8a) and after (Fig. 8b) cleaning at 2 kV and 15 Hz have been shown to demonstrate efficient cleaning with

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Fig. 8 As fabricated 1-F EDS a before and b after dust removal

the as fabricated EDS. In Table 2, the result of dust removal upon four dust samples collected from different locations at IIEST, Shibpur, and one collected from a very distant location, Haridwar, in North India have been summarized. This clearly reflects the overall change in the mean particle size diameter, after energizing EDS, due to dust movement and readjustment and removal. The particle size distribution of the dust samples gets substantially changed, after being subjected to such high-voltage low-frequency supply cycle and further due to the subsequent electric polarization and influence of several other factors. This in a way also helps in the particle levitation and movement, as they, being lighter and smaller are easier to be levitated above the panel surface. Thus, the sample becomes easy to be dry cleaned, without using water, as visible from the photomicrograph (Fig. 9) of the EDS before and after dust removal. This can be further investigated by recording the variation of threshold voltage and the dust removal efficiency or DRE for different dust samples collected. Here, threshold voltage, (V th ) signifies the minimum voltage at which the dust particle starts to move. We reached this voltage after conducting several repetitive experiments and averaging the same. From Table 3, it can be observed that the V th of dust sample 1 is the lowest out of the four, signifying removing dust from sample 1 would require the least voltage, hence power, to activate the IDG(s) and start dust removal process. The dust removal efficiency (DRE) of the four samples is given in Table 3. From Table 3, it can be seen that the DRE for sample 2 is the highest. Therefore, combining Table 2 Dust characteristics before and after EDS activation Dust sample

Mean diameter (μm)

Minimum diameter (μm)

Maximum diameter (μm)

Before activation

After activation

Before activation

After activation

Before activation

After activation

Sample 1

10.26

18.03

4.71

5.75

30.97

48.35

Sample 2

11.06

16.45

3.34

5.25

24.76

41.14

Sample 3

6.12

16.08

2.12

3.01

17.32

37.56

Sample 4

8.01

20.31

4.44

6.92

14.36

54.37

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Fig. 9 Photomicrograph of dust deposited a before and b after cleaning at 2 kV and 15 Hz

Table 3 Threshold voltage (V th ) and dust removal efficiency (DRE) of four dust samples under study

Dust sample Threshold voltage (V) Dust removal efficiency (%) Sample 1

420

84.12

Sample 2

465

87.34

Sample 3

600

78.87

Sample 4

770

85.27

the results of V th and DRE obtained from Table 3, we can say that sample 2 is the easiest to clean out of the four samples, since its V th is the lower side, and its DRE is also the highest. Thus, the EDS design can be suitably chosen depending upon soiling conditions prevailing upon the particular location, location-specific EDS design. Then finally, such electrode patterns were fabricated on sputtered aluminumdoped zinc oxide (AZO) films on glass substrate, by using a YAG laser facility available at our collaborator, HHV Bangalore. This allows us an ability to fabricate EDS over large areas.

4 Conclusions Extremely robust, durable, optically transparent, superhydrophobic aluminum oxidebased coatings for solar panel cover glasses. The as prepared boehmite coatings on glass substrate showed excellent water repellency after spray coating 1% v/v fluoroalkyl solution (CA 160°) without affecting the transmission gain (1.26%) obtained by hot water immersion experiment and overall mechanical hardness of the coatings. Single-phase electrodynamic screen (EDS) for dust cleaning without using water has been modeled, mechanism of cleaning explained, and the fabrication details have been presented. Dust collected from different locations have been studied by

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spreading on EDS surfaces and response to cleaning have been quantified. EDS screen with 87% dust cleaning efficiency has been recorded. Acknowledgements We wish to acknowledge DST-SERI, through Grant No.: DST/TMD/SERI/HUB/2(G) for generous financial support. Director, IIEST, and coordinator DST-IIST Solar PV Hub Project at IIEST, and Prof. H. Saha are thanked for their support.

References 1. T. Sarver, A. Al-Qaraghuli, L.L. Kazmerski, Renew. Sustain. Energy Rev. 22, 698 (2013) 2. A. Sayyah, M.N. Horenstein, M.K. Mazumder, Sol. Energy 107, 576–604 (2014) 3. A. Sayyah, M.K. Mazumder, in IEEE 42nd Photovoltaic Specialist Conference (PVSC), 1 (2015) 4. L. Zhang, R. Dillert, D. Bahnemann, M. Vormoor, Energy Environ. Sci. 5, 7491 (2012) 5. D. Adak, S. Ghosh, P. Chakraborty, K.M.K. Srivatsa, A. Mondal, H. Saha, R. Mukherjee, R. Bhattacharyya, Sol. Energy Mater. Sol. Cells 188, 127 (2018) 6. D. Quéré, Rep. Prog. Phys. 68, 2495–2532 (2005) 7. S. Sutha, S. Suresh, B. Raj, K.R. Ravi, Sol. Energy Mater. Sol. Cells 165, 128 (2016) 8. L.A. Kaledin, F. Tepper, G.T. Kaledin, Int. J. Smart Nano Mater. 7(1), 1–21 (2016) 9. S. Nami, N. Khan, Y. Elgendi, J. Aziz, M. Nasr, O. Trescases, in IEEE 18th Workshop on Control and Modeling for Power Electronics (COMPEL), vol. 2017, pp. 1–7 (2017) 10. G. Liu, J.S. Marshall, J. Electrostat. 68, 289–298 (2010) 11. F.B. Tatom, V. Srepel, R.D. Johnson, Lunar dust degradation effects and removal/prevention concepts (Northrop/Huntsville), Technical Report, NASA-CR-93594, TR -792-7-207A (1967) 12. S.H. Joghee, K.M. Uthandi, N. Singh, S. Katti, P. Kumar, R.K. Renganayagalu, B. Pullithadathil, ACS Appl. Nano Mater. 3, 9899 (2020) 13. M.A. González-Gómez, S. Belderbos, S. Yañez-Vilar, Y. Piñeiro, F. Cleeren, G. Bormans, M.C. Deroose, W. Gsell, H.U. Uwe, J. Rivas, Nanomaterials 9, 1626 (2019) 14. S. Masuda, K. Fujibayashi, K. Ishida, H. Inaba, Electr. Eng. Japan 92, 43–52 (1972) 15. Q. Sun, N. Yang, X. Cai, G. Hu, Science China physics. Mech. Astron. 55, 1018–1025 (2012) 16. S. De, M. Kumar, S. Manna, S. Ghosh, K. Sinha, D. Adak, S. Maity, R. Bhattacharyya, Surf. Interfaces 25, 101222 (2021)

Propagation of Microwaves in Magnetized Plasma and Air-Based Ternary Structure N. Kumar, Mahima Singh, G. N. Pandey, and B. Suthar

1 Introduction The electromagnetic propagation studies though photonic crystals (PCs), usually artificial structures with periodically modulated dielectric constants, have been emerged as a prominent field of research [1]. PCs offer ability to control the propagation modes of light in similar way as nanostructures control electronic phenomena [2]. Hence, the electromagnetic spectra obtained from such structures are characterized by the visualizing allowed and forbidden photonic bands with analogy similar to the electronic band structure of periodic potentials. The change in the structural parameters causes effective change in the reflectance/transmittance spectra. Thus, PCs are a new class of artificial optical material with periodic dielectric modulation that can be used to control and manipulate photons effectively. The dependences of photonic bandgaps (PBGs) on the structural parameters such as thickness and refractive index have already been reported, which have led to demonstrations of a wide variety of PC-based optical devices having various potential applications in many areas, such as communications, computing, sensing, and optical switches [1, 3, 4]. Among the three types of PCs, a one-dimensional photonic crystal (1DPC) structure has been found to be with many interesting applications, viz.

N. Kumar · M. Singh Department of Physics, SLAS, Mody University of Science and Technology, Lakshmangarh, Sikar, Rajasthan 332311, India G. N. Pandey (B) Department of Applied Physics, Amity Institute of Applied Sciences, Amity University, Uttar Pradesh, Noida 201303, India e-mail: [email protected] B. Suthar Department of Physics, MLB Govt. College, Nokha, Bikaner, Rajasthan 334803, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_10

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optical mirrors, low-loss waveguides, filters, and optical switches [5–10]. In addition to dielectrics, various other materials are also used like plasma, chalcogenide, superconductor, and magnetized cold plasma [1, 5, 6, 8]. Plasma photonic crystals (PPCs) were introduced in 2004 by considering plasma as one of the layers [11]. A new type of plasma called cold atmospheric plasma (CAP) has temperature less than 104°. In the beginning of last decade, PBGs were investigated in magnetized cold plasma. A periodicity is generated in the magnetized plasma under influence of negative and positive values of the external magnetic field, and so as left-hand and right-hand polarizations occur, respectively [12, 13]. Kumar et al. reported the variation in photonic band structures (PBSs) as a function of angle of incidence, magnetic field strength, electron density, and thickness variations [1, 13]. Abadla et al. [14] suggested that ternary photonic crystals can offer superior performance over the binary ones. Nowadays, researchers are considering ternary structures with new chosen materials for novel and efficient kind of tuning of the PBGs [14–21]. In this paper, we theoretically make an analysis of a ternary PPC structure, made of magnetized cold plasma layers of RHP/LHP and air as the unit cell; and by varying the air thickness for normal incidence and further the external parameter, that is, angle of incidence; some insights are drawn. Here, we keep the strength of applied magnetic field, electron density, and collision frequency constant in both cases.

2 Theoretical Framework Figure 1 depicts the ternary periodic structure, whose unit cell is made with three layers, RHP and LHP of cold plasma and third layer is of air, in which the layer thicknesses are taken as d 1, d 2, and d 3 , respectively. The thickness of unit call is d 1 + d 2 + d 3 = d, which is known as the lattice constant. The refractive indices of RHP and LHP are n1, n2 and of third layer is n3 , respectively; and the number of unit cells is N. The ternary photonic crystal containing magnetized cold plasma layers and third layer of air is in the periodic form of (ABC)N , where A and B represent the RHP and LHP layers of cold plasma, respectively, and C is the third layer of air.

Fig. 1 A schematic diagram of ternary magnetized cold plasma and air-based RHP/LHP/air ternary structure

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By applying the transfer matrix method (TMM), the total matrix for periodic structure (ABC)N with the thickness of lattice d is expressed as [1].  M(d) =

M1,1 M1,2 M2,1 M2,2

 (1)

where M(d) = (M A M B M C )N ; M A , M B , and M C are the characteristic matrices for the layers A, B, and C, respectively. The characteristics matrix of A, B, and C materials at the incident angle θi is M A, M B , and M C , and for the jth layer given as  Mj =

− pi i sin α j cos α j −i p j sin α j cos α j

 (2)

ω n j d j cos θ j , c is the speed of light in vacuum, θ j is the ray angle c  √ ε inside j-layer, the refractive index of the material n j = μ j ε j , p j = μjj cos θ j , n 2 sin2 and cos θ j = 1 − 0 n 2 θi in which the refractive index of air is n0 = n3 ; and the

where α j =

j

wave incident angle at the surface is θi , which is from air of refractive index n0 . Thus, the transmittance of the ternary PPC of the form (ABC)N is given by

2



2 pi



 

 T = 

M1,1 + ps M1,2 pi + M2,1 + ps M2,2

(3)

ni, ns are refractive indices of incident and substrate media, respectively. The cold plasma layers are under external periodic magnetic field B(x), that is,  B(x) =

+B, 0 ≤ x ≤ d1 −B, d1 ≤ x ≤ d2

(4)

Here, the complex permittivity of magnetized cold plasma layers can be given by [1, 8]. εplasma (ω) = 1 −

ω2pe  ω2 1 − i ωγ ∓

ωl e ω



(5)

, where −ωle, is taken for In the above expression, gyro-frequency is ωle = eB m the magnetic field in + B offering RHP; and + ωle for the magnetic field in −B resulting in LHP, where γ is the effective collision frequency, and plasma frequency  2 ne with n represents the electron density, and electronic mass is is ωpe = mε0 denoted by m.

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3 Results and Discussion In this section, we determine the transmission spectra of the proposed ternary structure by choosing the fixed values of the collision frequency γ = 2 × 2π × 107 Hz, B = 1 T, electron density n = 8 × 1017 m−3 , and d 1 + d 2 = 30 mm with N = 15 in all cases. In this analysis, we have considered two cases, in which for case: I, we take normal incidence for the above parameters; and by increasing the air thickness, we observe the effect of increasing thickness of air layer on the PBGs in GHz (microwave) range. In case: II, we fix the air thickness at 15 mm and increase the incident angle and observe the variations in the PBGs. In our study, nearby 100% reflection or zero transmission is considered as PBG. Comparing the transmission spectra in case: I as shown in Fig. 2, for three values of the air thickness at normal incidence, it is noticed that there are two zero transmission regions, i.e., PBGs are obtained for air thickness 15 mm and 30 mm, while for air thickness 60 mm, more than three such bands are obtained, while the bands become narrow and a shifting in the band locations is also observed. Such characteristics can be useful in designing multiband reflectors. Further, we compare the transmission spectra in case: II, as shown in Fig. 3, for three values of incident angles, viz. θi = 30◦ , 60◦ , and 89◦ , taking air thickness 15 mm, and at normal incidence (0◦ ), whose transmission spectrum has already been shown in Fig. 2a. By comparison of the transmission spectra at different incident angles, we find that, as we increase the incident angle, the zero transmission band width increases, and at θi = 89◦ , multiple sharp peaks of transmission are obtained. The property of obtaining multiple sharp transmission peaks can offer novel idea in designing multichannel filter application.

Fig. 2 Plots of transmission spectra of ternary magnetized cold plasma and air-based ternary photonic crystal for different air layer thicknesses: a d3 = 15 mm, b d3 = 30 mm, c d3 = 60 mm; keeping magnetic field B = 1 T, electron density n = 8 × 1017 m−3 , and RHP/LHP thickness ratio d1 /d2 = 1

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Fig. 3 Plots of transmission spectra of ternary magnetized cold plasma and air-based ternary photonic crystal for different incident angles a θ = 30◦ , b θ = 60◦ , c θ = 89◦ ; keeping magnetic field B = 1 T, electron density n = 8 × 1017 m−3 , and RHP/LHP thickness ratio d1 /d2 /d3 = 1, and lattice constant d = 45 mm

4 Conclusion In this paper, the transmission spectra in the microwave region, for magnetized cold plasma and air-based ternary photonic crystal structure, are obtained. We observe the impact of thickness of air layer and angle of incidence, for fixed values of other parameters. An enhancement in photonic bandgap with low air thickness for normal incidence is noticed. On varying the incident angle with the air thickness fixed, there is enlargement in the reflection band, while we get a large number of transmission peaks for incident angle nearby 89°. These two parameters, that is, air thickness and incident angle, act as controlling factors for such features of the ternary periodic structure. These novel properties can be proved to be useful in designing microwave mirrors, multichannel filters, and optical switches. Acknowledgements The first two authors acknowledge a constant encouragement received from Prof. (Dr.) Uma Bhardwaj, Dean-SLAS, and President, Mody University of Science and Technology, India, in preparation of the manuscript.

References 1. N. Kumar, B. Suthar (eds.), Advances in Photonic Crystals and Devices (CRC Press, Taylor & Francis, Boca Raton, USA 2019) 2. J.D. Joannopoulos, S.G. Johnson, J.N. Winn, R.D. Meade, Photonic Crystals: Molding the Flow of Light, 2nd edn. (Princeton University Press, NJ, USA, 2008) 3. A. Bhargava, B. Suthar, J. Ovonic Res. 5, 187 (2009) 4. Ankita, B. Suthar, A. Bhargava, Plasmonics 16, 59 (2021) 5. B. Suthar, A. Bhargava, SILICON 7, 433–435 (2015) 6. A. Aly, W. Sabra, J. Supercond, Novel Mag. 29, 1981 (2016) 7. C.J. Wu, J. Electromagnet, Wave Appl. 19, 1991–1996 (2005) 8. B. Suthar, Optik 126, 3429 (2015)

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9. M.G. Kong, G. Kroesen, G. Morfill, T. Nosenko, T. Shimizu, J.V. Dijk, J.L. Zimmermann, New J. Phys. 11, 115012 (2019) 10. N. Kumar, S.P. Ojha, Prog. Electromagn. Res. 80, 431–445 (2008) 11. H. Hojo, A. Mase, J. Plasma Fusion Res. 80, 89–90 (2004) 12. T.C. King, C.C. Yang, P.H. Hseih, T.W. Chang, C.J. Wu, Physica E 67, 7–11 (2015) 13. N. Kumar, S. Ray, J. Saraf, R. Janma, B. Suthar, G.N. Pandey, K.B. Thapa, in AIP Conference Proceedings, vol. 2220, p. 020177 (2020) 14. M.M. Abadla, N.A. Tabaza, W. Tabaza, N.R. Ramanujam, K.S.J. Wilson, D. Vigneswaran, S.A. Taya, Optik 185, 784–793 (2019) 15. F. Xue, S.B. Liu, H.F. Zhang, X.K. Kong, Y.D. Wen, L.L. Wang, S. Qian, Opt. Quant. Electron 49, 19 (2017) 16. D.M. El-Amassi, S.A. Taya, D. Vigneswaran, J. Theor. Appl. Phys. 12, 293–298 (2018) 17. G.N. Pandey, K.B. Thapa, S.P. Ojha, Optik 124, 3396–3401 (2013) 18. G.N. Pandey, S.P. Ojha, Optik 124, 3514–3519 (2013) 19. G.N. Pandey, N. Kumar, K.B. Thapa, S.P. Ojha, in AIP Conference Proceedings, vol. 1728, pp. 020310-1 (2016) 20. G.N. Pandey, J.P. Pandey, A.K. Mishra, S.P. Ojha, in AIP Conference Proceedings, vol. 1728, p. 020312-1 (2016) 21. A. Kumar, N. Kumar, G.N. Pandey, D. Singh, K.B. Thapa, J. Phys.: Condens. Matter 32, 325701 (2020)

Photocatalytic Degradation of Chlorobenzene Using Easily Recoverable Fe3 O4 /OMS-2 Nanocomposite Monika Dubey, Navakanth Viay Challagulla, Monika Joshi, Ranjit Kumar, and Sandeep Kumar Srivastava

1 Introduction Industrial chlorinated organic pollutants like chlorobenzene (CB) are shown to be carcinogenic, mutagenic and genotoxic for mankind [1]. CB are widely used as solvent by many industries, and often found in groundwater [2]. CB has poor biodegradability, so it is also known as a persistent chlorinated organic compound which has an adverse and hazardous effect to humans as well as to the environment [3]. There are several methods [2, 4–6] of degradation of CB from aqueous solution. As a photocatalyst, metal oxide nanocomposites including MnO2 and Fe3 O4 are well explored due to their low cost, non-toxic, stable, and robust nature [7, 8]. Manganese octahedral molecular sieves (OMS-2) have a good photocatalytic property with microporous tunnel structure [9]. Magnetite (Fe3 O4 ) has an excellent absorption, catalytic, and magnetic properties [10]. So, a nanocomposite of magnetite and OMS-2 can be a good option as photocatalyst, having excellent ability of UV and visible light absorption and an easy recovery through magnetic separation. In this study, OMS-2 was synthesized using reflux method and Fe3 O4 /OMS-2 nanocomposite was synthesized using ultrasound-induced co-precipitation method. Fe3 O4 /OMS-2 nanocomposite was applied as photocatalysts for the degradation of

M. Dubey · N. V. Challagulla · M. Joshi (B) Amity Institute of Nanotechnology, Amity University, Noida, Uttar Pradesh 201313, India e-mail: [email protected] R. Kumar Department of Chemistry, University of Petroleum and Energy Studies (UPES), Bidholi, Dehradun 248007, India S. K. Srivastava Department of Physics, Central Institute of Technology Kokrajhar Deemed-To-Be University, Kokrajhar 783370, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_11

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CB. CB was taken as a model of organic chlorinated compound for the photocatalytic removal. The kinetics of photocatalytic removal of CB applying Fe3 O4 /OMS-2 nanocomposite were evaluated by linear curve fitting. Excellent photocatalytic property and easy separation show that the synthesized nanocomposite is suitable material to degrade chlorinated organic compounds at industrial scale.

2 Materials and Methods 2.1 Materials All analytical grade chemicals were used in this work without any further purification. Potassium permanganate (KMnO4 ), nitric acid (HNO3 ), manganese chloride (MnCl2 ), ferric chloride (FeCl3 ), ferrous chloride (FeCl2 ), urea, sodium hydroxide (NaOH), and chlorobenzene (CB) were purchased from Sigma Aldrich.

2.2 Synthesis of Fe3 O4 /OMS-2nanocomposite The synthesis of OMS-2 has been carried out using reflux method [11]. A total of 17.5 mL of 2 M solution of MnCl2 was mixed with 1.5 mL of concentrated nitric acid. A total of 56 mL of 0.4 M KMnO4 solution was added dropwise under vigorous stirring. The resultant mixture was refluxed for 12 h at 80 °C. The product was washed, dried at 110 °C, and calcined at 350 °C. For the synthesis of nanocomposite, 0.1 M solution of FeCl3 was added to 0.4 M urea solution at 85 °C for 2 h. 0.2 M of FeCl2 was added to the above solution and stirred for 15 min. Finally, 0.3 M NaOH was added dropwise until the o pH value was reached to 9 and stirred further for 20 min. A total of 500 mg of synthesized OMS-2 was mixed to the above solution and pH was optimized to 11. The reaction mixture was ultrasonicated for 50 min. The product was washed multiple times, separated using a magnet, and dried at 100 °C.

2.3 Characterizations The crystalline phase structure of Fe3 O4 /OMS-2 was obtained via X-ray diffractometer (Bruker D2 Phaser with Cu-Kα radiation, a beam voltage of 40 kV, and a beam current of 30 mA). Scanning electron micrograph (SEM) of Fe3 O4 /OMS-2 was taken using ZEISS EVO18. Magnetic property was measured using vibrating sample magnetometer (VSM) PAR-150. UV–vis measurements were done in aqueous medium using UV–visible spectrophotometer UV-1800 (Shimadzu’s Co., UV-Probe 2.42).

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2.4 Testing of CB Photocatalytic Degradation The stock solution of CB of 500 ppm was prepared in ethanol and added deionized water. A 125 W Hg lamp of UV–visible range 200–600 nm was employed for irradiation. The pH of CB solution was adjusting using 1 M HNO3 and 1 M NaOH. For the catalytic adsorption, the reaction with Fe3 O4 /OMS-2 nanocomposite was carried out in dark first, and analysis was done using UV–vis spectroscopy. The total removal rate (R%) of CB was evaluated by: R% = (C − Ct )/C × 100%

(1)

where C (ppm) and C t (ppm) are the initial and at t time concentrations of CB, respectively.

3 Results and Discussion 3.1 Characterization of Synthesized Fe3 O4 /OMS-2 Nanocomposite The XRD pattern (Fig. 1a) of nanocomposite shows peaks of magnetite indices (220), (311), (400), (422), (511), (440), which are in well agreement of the inverse cubic spinal phase (JCPDS#85-1436) [12] and peaks of OMS-2 were indexed as (310), (211), (301), (411), (521) showed tetragonal OMS-2 phase (JCPDS#44-0141) [11]. XRD pattern of nanocomposite after five cycles of photodegradation of CB also had all peaks which suggests the stability of synthesized nanocomposite. Figure 1b depicts the UV–visible absorption spectra of OMS-2 and Fe3 O4 /OMS-2 nanocomposite. λmax for OMS-2 was 410 nm, and it was shifted at 330 nm for Fe3 O4 /OMS-2 nanocomposite. OMS-2 had absorption band ranging from 300 to 500 nm [9], while Fe3 O4 /OMS-2 nanocomposite showed a band ranged from 250 to 450 nm. The calculated band gap of OMS-2 and Fe3 O4 /OMS-2 nanocomposite was 1.9 eV and 1.7 eV, respectively. Figure 1c presents the SEM image of Fe3 O4 /OMS-2 nanocomposite which reveals that nanocomposite consists two phases: nanoparticles of magnetite and nanofibres of OMS-2; nanoparticles were formed as aggregates on nanofibres. Figure 1d shows the paramagnetic behavior of synthesized Fe3 O4 /OMS-2 nanocomposite. The saturation magnetization of Fe3 O4 /OMS-2 nanocomposite was evaluated as 40.02 emu/g, which is lesser than magnetization of Fe3 O4 (60.64 emu/g) at room temperature [13] because Fe3 O4 nanoparticles were aggregated on OMS-2. Fe3 O4 /OMS-2 nanocomposite has high magnetic strength and can be separated easily applying external magnetism as shown in the optical images of magnetic separation (inset of Fig. 1d).

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Fig. 1 a XRD patterns of Fe3 O4 /OMS-2 nanocomposite before and after recovery (* shows peak for magnetite), b band gap of OMS-2 (Red) band gap of Fe3 O4 /OMS-2 nanocomposite (Black) inset: UV–visible absorption, c SEM of Fe3 O4 /OMS-2 nanocomposite, d M-H graph using vibrating sample magnetometer, inset: magnetic separation of Fe3 O4 /OMS-2 nanocomposite

3.2 Photocatalytic Degradation of CB The potential of synthesized nanocomposite was employed for photocatalytical degradation of CB. For that, experiment was carried out by taking 100 mg/L amount of nanocomposite applied for 50 ppm, 100 ppm, and 200 ppm concentration of CB in aqueous solution, respectively, as shown in Fig. 2a. The reactions were carried out up to 120 min, at pH 9. The number of photocatalysts was creating the same quantity of OH− species, which play the most critical roles for the CB degradation [14]. A high concentration of CB required more time to get excellent reduction efficiency. So, for further experiments, acquired concentration of CB has been decided 100 ppm. Almost ~100% removal of 100 ppm CB was achieved within 60 min at pH 9 using 100 mg/L nanocomposite. The amount of catalysts is an important parameter in the determination of effect of photocatalytic reaction [15]. The photocatalyst amounts were varied as 50 mg/L, 100 mg/L, and 150 mg/L for 100 ppm CB solution for 60 min at pH 9 as shown in Fig. 2b. As Fe3 O4 /OMS-2 dosage increases, the oxidative reaction sites available for CB are also increased due to large surface area [16]. pH is the most important parameter which affects the oxidation reaction. Figure 2c showed effect of pH varying as 3, 5, 7, 9, and 11 on the CB removal using nanocomposite under UV–visible irradiation. Maximum photodegradation efficiency of CB was found at

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Fig. 2 Photodegradation of CB a varying concentration (catalysts amount: 100 mg/L, pH = 9) b varying amount of catalysts (reaction time: 60 min, initial CB concentration: 100 ppm, pH = 9) c varying pH (catalysts amount: 100 mg/L, reaction time: 60 min, initial CB concentration: 100 ppm), d regeneration cycle of catalyst (catalysts amount: 100 mg/L, reaction time: 60 min, initial CB concentration: 100 ppm, pH = 9)

pH 9. In photocatalytic process, degradation rate may increase on account of the generation of hydroxyl radicals (OH•) with an increase in pH, and this was assisted by a higher oxidation potential of OH• which supported to higher removal of CB. In the acidic medium, OH• were less effective. Hence, in basic medium, more OH• can directly react with CB [12]. For the recovery test, the magnetic Fe3 O4 /OMS-2 nanocomposite was separated using magnet and dried at 100 °C in oven after each reaction for appropriate time. Magnetic Fe3 O4 /OMS-2 nanocomposite was ready to use for next reaction just after magnetic separation and drying. The recovery lifetime of magnetic Fe3 O4 /OMS2 nanocomposite was very important for their experimental application. The regeneration usages of the magnetic Fe3 O4 /OMS-2 nanocomposite were confirmed by XRD pattern after reaction (Fig. 1a) and stability of photocatalysts for five cycles of degradation of CB as shown in Fig. 2d. Figure 3 shows UV–visible absorption of photocatalytic degradation of CB using magnetic Fe3 O4 /OMS-2 using photocatalysts amount 100 mg/L, initial CB concentration 100 ppm, at pH 9 within 60 min. The high optical density was obtained in the

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Fig. 3 UV–visible absorption spectra of CB photodegradation using Fe3 O4 /OMS-2 nanocomposite with λmax at 280 nm. Inset: first-order reaction kinetics with rate constant k = 0.032 min−1 and R2 = 0.99. (Catalysts amount: 100 mg/L, reaction time: 60 min, initial CB concentration: 100 ppm, pH = 9)

range of 260–300 nm with λmax at 280 nm in specta. For a degradation of CB using photocatalyst, the Lagergren’s pseudo first-order kinetic equation is dC/dt = −kC. Pseudo first-order equation: ln C/C0 = −kt,

(2)

where C (mg/L) is the concentration of CB at time t and k (min−1 ) is the apparent firstorder rate constant. If C = C o at time t, (t is any time after the start of photocatalytic degradation). The kinetic curves in inset of Fig. 3 showed pseudo first-order as confirmed by the linear transform of ln C/C o = −kt for k = 0.032 min−1 and R2 = 0.99.

4 Conclusions In conclusion, the synthesized magnetic Fe3 O4 /OMS-2 nanocomposite showed an excellent ability of photodegradation of CB under UV–visible light. The 100 mg/L Fe3 O4 /OMS-2 nanocomposite was investigated for ~100% photocatalytic removal of 100 ppm CB at pH 9 within 60 min. Magnetic Fe3 O4 /OMS-2 nanocomposite had easy

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and complete recovery through magnetic separation, and it need not to be calcined at higher temperature. The photocatalytic removal kinetic of CB using Fe3 O4 /OMS-2 nanocomposite was considered of first-order reaction by linear curve fitting. Hence, the facile synthesis process, outstanding photocatalytic activity, reusability, and easy separation method make the nanocomposite a potential material for the removal of CB from contaminated water at industrial scale also.

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

C. Santhosh, A. Malathi, E. Daneshvar, P. Kollu, A. Bhatnagar, Sci. Rep. 8, 1–15 (2018) S. Krishnamoorthy, J.A. Rivas, M.D. Amiridis, supported on TiO. J. Catal. 193, 264–272 (2000) E. Dobrzy´nska, M. Po´sniak, M. Szewczy´nska, 8347 (2010) B. Yang, Y. Zhang, S. Deng, G. Yu, Y. Lu, J. Wu, J. Xiao, G. Chen, X. Cheng, L. Shi, Chem. Eng. J. 234, 346–353 (2013) C. Hariharan, Appl. Catal. A Gen. 304, 55–61 (2006) T.K. Tseng, L. Wang, T. Ho, H. Chu, J. Hazard. Mater. 178, 1035–1040 (2010) F. Schurz, J.M. Bauchert, T. Merker, T. Schleid, H. Hasse, R. Gläser, Appl. Catal. A Gen. 355, 42–49 (2009) Y. Liu, M. Luo, Z. Wei, Q. Xin, P. Ying, C. Li 29, 61–67 (2001) R. Kumar, L.J. Garces, Y.C. Son, S.L. Suib, R.E. Malz, J. Catal. 236, 387–391 (2005) M. Khalil, M.I. Khalil, Artic. Arab. J. Chem. (2015) R. Kumar, S. Sithambaram, S.L. Suib, J. Catal. 262, 304–313 (2009) M. Dubey, N.V. Challagulla, S. Wadhwa, R. Kumar, Colloids Surf. A Physicochem. Eng. Asp. 609, 125720 (2021) M.E.E. Pesqueira, I. Martínez-Mera, M.E. Espinosa-Pesqueira, R. Pérez-Hernández, J. ArenasAlatorre, (2007) Z. Yang, J. Wei, H. Yang, L. Liu, H. Liang, Y. Yang, Eur. J. Inorg. Chem. 3354–3359 (2010) M. Dubey, S. Wadhwa, R. Kumar, Mater. Today Proc. 28, 70–73 (2020) M. Dubey, R. Kumar, S.K. Srivastav, M. Joshi, Optik 167309 (2021). ISSN 0030–4026

Efficient Removal of Crystal Violet Dye Using Fly Ash-Supported Nanoscale Zerovalent Iron Particles Shubhangi Madan and Sangeeta Tiwari

1 Introduction In recent times, various industries, namely textile, paper production, pharmaceutical, leather, cosmetic industry and plastic industry, have been making use of several kinds of synthetic dyes for diverse applications, leading to discharge of excessive synthetic organic chemicals to the environment [1, 2]. Crystal violet (CV), a cationic dye, possesses a complex structure and is very stable to heat and light which makes its degradation process very difficult [3, 4]. If exposed for a prolonged time, it is a major threat to human health [5, 6]. A lot of research work have been done in order to get rid of it, by chemical methods such as oxidative degradation, physical methods including adsorption, flocculation or nanofiltration and biological techniques which include aerobic and anaerobic degradation [7, 8]. Among these, adsorption is believed to be the most efficient approach for the removal of CV dye. Out of the numerous adsorbents used for dye removal, activated carbon is the most preferred one, owing to its high surface area and consequently higher adsorption capacity. Nevertheless, the major limitation in its use involves its high cost, thus making the development of an efficient and economical adsorbent, an essential need. Nanoscale zerovalent iron (nZVI) is considered as an effective adsorbent for organic contaminants due to its large specific surface area, environment-friendly nature and high reduction reactivity. It has been widely used for the treatment of contaminated water containing heavy metals [9], nitro compounds [10], chlorinated compounds, dyes and pesticides [11]. However, nZVI particles are prone to easy aggregation and rapid oxidation. The possible solution to this problem would be immobilization of nZVI on some porous support that facilitates its dispersion [12]. Fly ash (FA) is an industrial by-product, cheap, inert and non-toxic and thus proves S. Madan · S. Tiwari (B) Amity Institute of Applied Sciences, Amity University, Noida, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_12

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to be a favorable substrate for immobilization of nZVI. The adsorption property of FA in wastewater treatment has been reported earlier [13, 14], but it’s very low adsorption efficiency for a variety of contaminants makes its modification an essential requirement for ideal use. The aim of the present work is to design and develop a composite by surface modification of fly ash with nZVI and study its application for CV dye removal. Formation of a layer of nZVI on fly ash surface has been confirmed using SEM and EDAX studies. The adsorption efficiency of the synthesized material was investigated at varying contact time and initial concentrations of CV dye solution. Moreover, comparison of the activity of developed material with its pure counterpart, i.e., FA particles has been done.

2 Experimental 2.1 Synthesis of nZVI/FA Nanoscale zerovalent iron-coated fly ash particles were synthesized by first activating the fly ash particles with NaOH solution, followed by dispersion in ferric chloride solution. Drop-wise addition of sodium borohydride was done while continuously stirring the solution in order to reduce Fe3+ ions to Fe0 . The resultant product was filtered, washed and dried with subsequent use in dye adsorption studies.

2.2 Characterization Scanning electron microscope analysis was done to study the morphology and to characterize the surface of nZVI/FA particles, while the elemental composition was confirmed by EDAX equipped with SEM (Nova NanoSEM 450). BET analysis was performed in order to determine the specific surface area of the synthesized particles.

2.3 Crystal Violet Dye Removal Kinetic studies were performed using 50 mg of the prepared nZVI/FA particles with 100 ml solution of 20 mg L−1 CV dye, and the effect of time (10–180 min) on dye removal was examined by analyzing the concentration of the suspension taken after regular intervals. Similarly, isotherm studies were carried out when 50 mg of the adsorbent was added to 100 ml solutions of varying dye concentrations [1–50 mg L−1 ], and the mixture was made to stir for the optimized time period. The dye adsorption efficiency

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of the composite was established by centrifuging the resulting solution in order to collect the supernatant, which was then subjected to UV–Vis spectrophotometer to analyze the concentration of dye at its characteristic wavelength. (λmax = 585 nm). The percent CV dye adsorption was calculated using Eq. (1). PercentCV adsorption =

Ci − Ct × 100 Ci

Adsorption capacity = V (Ci − Ct )/m

(1) (2)

where Ci (mg L−1 ) is the initial dye concentration, Ct (mg L−1 ) is the concentration of dye solution at any time “t”, V is volume of solution in liters, and m is mass of adsorbent used in grams.

3 Results and Discussion 3.1 Characterization SEM images were taken for examining the surface of the composite and to validate the coating of nZVI on the surface of fly ash. Figure 1 represents the SEM images of fly ash and the composite, showing a layer of nZVI on FA particles. The fly ash particles are characterized by the smooth, spherical structures in Fig. 1a, while the presence of ZVI nanoparticles is responsible for the flaky covering on the smooth surface of fly ash in Fig. 1b. The results also demonstrate that nZVI particles are welldistributed on the fly ash surface, limiting nZVI agglomeration [15] and displaying uniform coating on the FA surface. Furthermore, EDAX investigations (Fig. 2) and elemental distribution table (Table

Fig. 1 SEM images of a fly ash and b prepared nZVI/FA composite

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Fig. 2 EDAX spectra of as-prepared nZVI/FA particles

Table 1 Elemental composition of nZVI/FA

Element

Weight %

Atomic %

SiK

18.54

14.28

OK

51.37

69.46

AlK

11.52

9.24

NaK

0.78

0.73

MgK

0.35

0.31

FeK

12.14

4.70

1) reveal the presence of iron in nZVI/FA particles, verifying its existence. The presence of ZVI in the composite is also confirmed by the Fe peaks (with 12.14 weight percent). The specific surface area of the composite could impact the availability of active sites in the adsorbent. As a result, FA and nZVI/FA particles were subjected to BET analysis, and the findings were compared. The alteration of fly ash with nZVI raises its surface area (from 4.785 to 13.879 m2 /g) and pore volume (from 0.015 to 0.067) as shown in the data (Table 2), which promotes improved CV dye adsorption. Table 2 Surface area and pore volume of FA and nZVI/FA as obtained by BET analysis

Material FA nZVI@FA

Surface area (m2 /g)

Pore volume (cm3 /g)

4.785

0.015

13.879

0.067

Efficient Removal of Crystal Violet Dye Using Fly Ash-Supported … 100

80

% CV Removal

Fig. 3 Effect of variation of time with the percent CV adsorption [concentration of dye = 20 mg L−1 , volume of solution = 100 mL, adsorbent dose = 0.5 g L−1 , contact time = 10–180 min]

99

nZVI/FA

60

FA 40

20

0 0

50

100

150

200

Time( min)

3.2 Effect of Contact Time The percent CV dye removal was measured as a function of time by immersing 50 mg of nZVI/FA composite in 100 mL CV dye solution (concentration = 20 mg L−1 ), followed by continuous stirring for 180 min. The results (Fig. 3) indicate an increase in the dye removal rate with increasing time. For nZVI/FA, a rapid increase in the percentage adsorption of CV was observed till 75 min, after which it attains equilibrium. This increase in the adsorption percentage could be due to the increase in the time of interaction between the adsorbent particles and the dye. Hence, nZVI/FA was able to remove 95% of CV dye in 75 min, after which there was no significant effect of increasing time, whereas similar studies conducted with fly ash show only 30% dye removal in 120 min. The high dye removal capacity in the composite could be accredited to the formation of nZVI layer on the surface of fly ash, resulting in amplified surface area from 4.785 m2 /g in FA to 13.87 m2 /g in nZVI/FA particles (Table 2).

3.3 Effect of CV Dye Concentration Concentration variation study was carried out to analyze the effect of initial concentration of CV dye on the adsorption capacity of adsorbent. For this, 50 mg of the adsorbent was added to each of the 100 ml dye solution with varying concentration of 1–50 mg L−1 . The results displayed in Fig. 4 suggest that the adsorption capacity increases with increase in the concentration of dye solution, till a specific concentration, after which it ceases to increase and thereby reaches a state of equilibrium. One of the reason for this trend is that the active sites of the material get saturated after adsorption of a certain amount of dye (attaching itself to the material).

100 35 30 25

qe (mg/g)

Fig. 4 Adsorption capacity as a function of initial concentration of CV dye [concentration of solution = 1–50 mg L−1 , volume of solution = 100 mL, adsorbent dose = 0.5 g L−1 ]

S. Madan and S. Tiwari

nZVI/FA

20

FA

15 10 5 0 0

5

10

15

20

25

30

35

40

Ce (mg/L)

The increase in initial concentration increases the driving force of dye from the bulk solution to the surface of adsorbent, consequently increasing the adsorption of dye onto the nZVI/FA composite. The removal of CV by nZVI/FA involves two processes, namely adsorption by the composite followed by reduction by nZVI, whereas adsorption was the only phenomena for removal of CV by FA particles, leading to an increase in the uptake of dye by the synthesized composite. Therefore, for a 50 mg L−1 solution of CV dye, the maximum adsorption capacity (qmax ) of nZVI/FA was determined to be 30.26 mg g−1 [obtained in 75 min], which was significantly greater than that of bare FA particles (qmax = 10 mg g−1 ) in 120 min. Therefore, the results clearly point toward the effectiveness of the proposed material in CV dye removal.

3.4 Removal Mechanism of CV by nZVI/FA Composite Particles The removal of CV dye by nZVI/FA could be attributed to the possible n-π interactions among the surface hydroxyl groups of the nZVI/FA composite and the benzene rings present in dye. Another mechanism for adsorption of CV dye by the nVZI/FA composite involves the possible reduction of the molecules of dye by the oxidation of Fe0 to Fe2+ and/or Fe3+ , along with electron transfer to H+ on the surface of adsorbent, subsequently developing atomic hydrogen. This results in the formation of discolored products and hence dye decolorization [16].

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4 Conclusion In conclusion, nZVI functionalized fly ash particles have been specifically designed to increase the adsorption capacity of fly ash in an effective manner. It was observed that nZVI/FA was capable of removing 50 ppm of the dye within 75 min, attaining a maximum adsorption capacity of 30.256 mg/g. This is in contrast to the results obtained for pure fly ash particles, which remove only 30% of the dye in 120 min. Thus, the modification of FA with nZVI enhances the surface area of fly ash and reduces the aggregation of nZVI (taking micron-sized FA as support), thereby increasing the rate of adsorption and providing quick removal of organic contaminant (CV dye) from water. Moreover, the utilization of a waste product, i.e., fly ash in the treatment of CV dye contaminated water makes it an economical choice for practical applications.

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

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Increased Heat Transfer Characteristics of Molten Salt-Synthesized Titania Nanoparticles Embedded in Palmitic Acid Shriya Iyer, Sharon Santhosh, Malvika Satish, and Asha Anish Madhavan

1 Introduction In order to move towards long-term sustainable growth, energy storage and conservation play crucial roles in improving energy grid efficiency and eliminating the imbalance between supply and demand. Effective means of energy storage directly translates to saving fuel and making the energy generating system more economical and efficient by minimizing loss of energy [1]. Broad portfolio of thermal energystorage (TES) systems, in particular, phase change materials (PCMs) as solutions to energy storage expertly supports these transformations. Being able to control the nature of release of energy not only helps us use it efficiently but also reduces unnecessary loss, this power is granted by PCMs. PCMs are substances with a high heat of fusion, which on melting and solidifying at certain temperatures are capable of storing or releasing large amounts of energy [2, 3]. The material can undergo phase reversal multiple times. The repeatability of the switching allows PCMs to store thermal energy. They may be classified in the following major categories depending upon their composition: organic, inorganic and eutectic [4]. These materials exhibit three types of phase transitions: solid–solid, solid–liquid and liquid–gas [5]. Of late, solid–liquid PCMs have gained popularity because they exhibit little volume change and are of compact form [6]. PCMs have the ability to store large quantities of heat in small volumes. With the reduction in volume of storage, size of the system reduces and so does the cost associated with it. Hence, with the competence to absorb great quantities of energy, uniform energy storage and small range of temperature required for use, PCMs offer cost-effective solutions to thermal energy storage [7].

S. Iyer · S. Santhosh · M. Satish · A. A. Madhavan (B) Department of Engineering, Amity University Dubai, Dubai, UAE e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_13

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Palmitic acid (PA) is an organic fatty acid with a melting point of 62.9 °C and high latent heat of fusion of around 200 kJ/kg [7]. PA in solid state displays a thermal conductivity of 0.22 and 0.16 W/mK in the liquid state [8]. Poor thermal conductivities lead to poor storage capacities for thermal energy-storage applications. Hence, additives like nanoparticles have been developed to improve its performance. Apart from improving the thermal conductivity, nano-dispersion has also shown to improve thermo-physical properties such as latent heat of fusion, density, viscosity and phase change temperature to list a few [9]. Nanoparticles such as ZnO, TiO2 , MoS2 , SiO2 , Fe2 O3 and CuO have found to improve the thermal phase change properties of PCMs [10–15]. Nanostructures display remarkable chemical, electrical, optical and magnetic properties that their bulk counterparts cannot demonstrate [16– 18]. However, there exists a direct relation between thermal conductivity and thermal energy storage, where titanium dioxide nanoparticles show ideal qualities. R. K. Sharma et al. developed a nano-enhanced organic phase change material using palmitic acid–TiO2 composite. They were able to obtain the best thermal conductivity at 5% [19]. S. M. Iqbal et al. studied titanium dioxide (TiO2 ) nanoparticles in depth explaining its thermal properties based on parameters such as heat transfer, stability and conductance of heat [20]. TiO2 was found to have long-term stability, a high dispersive quality with thermal conductance values in the range 4– 11.8 W/mK and non-toxic nature. In the study conducted by Harikrishnan et al., a significant enhancement in thermal conductivity by incorporating TiO2 nanoparticles in stearic acid owing to its high thermal conductance value was reported [21]. R. K. Sharma et al. further carried out TiO2 nanofluid incorporation in liquid PA reported 80% enhancement in thermal conductivity [19]. However, when making a nanofluid, the dispersion ability, aggregation and sedimentation were impeding the final functioning of the component. For this reason, in our study, TiO2 nanoparticles (nanotitania) were synthesized by one-step molten salt method, and novel nano-PCM composite of TiO2— palmitic acid was developed to explore the thermal conductive behavior and chemical stability. Subsequently, after optimization, the nano-PCM composite with 2 wt% concentration of TiO2 showcased the maximum heat transfer rate enhancement. This indicated an enhancement in the thermal conductivity of pristine PA and improved its suitability for various heat-storage applications.

2 Experimental Details All chemicals were used without further purification. In this study, TiO2 nanoparticles were synthesized by the molten salt technique using TiOSO4 ×H2 SO4 , LiNO3 and LiCl [22]. Based on the weight percentages of TiO2 added, the samples were designated as TPA-0.5, TPA-1, TPA-1.5, TPA-2 and TPA-2.5, respectively, where T and PA represent TiO2 and palmitic acid, whereas the numbers represent the weight percentage of TiO2 added to the palmitic acid, respectively. Particle size was confirmed by transmission electron microscopy (TEM), and it was also used to image the TiO2 nanoparticles; additionally, adsorption spectrum was obtained

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using the UV-Vis spectrometer. Further phase characterization was performed by Xray diffraction analysis (XRD). Dynamic light scattering technique was performed to estimate the particle size. Experiment was aided using a digital hot water bath, Thermos Pro TP-17 dual probe digital thermometer, digital weighing scale and basic laboratory equipment. Fourier transform infrared (FTIR) spectroscopy was used to study the uniform dispersion and chemical stability of the nano-PCM composite.

3 Results and Discussion Molten salt synthesis was carried out, as it is known as a reliable, easy and timeefficient way of fabricating nanoparticles of lower particle sizes. The XRD pattern shown in Figure 1a confirmed the formation of anatase phase of TiO2 . Diffraction peaks (2θ) at 25.8°, 38.02°, 48.18°, 54.08°, 63.80°, 68.80° and 75.36° corresponding to (101), (004), (200), (105), (204) and (215), respectively, perfectly aligned with the anatase TiO2 X-ray diffraction pattern in JCPDS-21-1272 and other literature reviews [23–26]. Transmission electron microscopy (TEM) was used to image the as-synthesized TiO2 nanoparticle as they were capable of providing high resolution image by transmitting a beam of electrons through the sample. The analysis confirmed the formation of spherically shaped TiO2 nanoparticle with an average diameter of ~20 nm, Fig. 1b. This was further confirmed by dynamic light scattering technique. UV–Visible spectroscopy analysis resulted in λmax value of 235 nm, a characteristic peak of TiO2 nanoparticles. Charging and discharging analysis had been undertaken to investigate the thermal properties of TiO2 –PA nano-PCM composite by integrating as-synthesized TiO2 (T) into PA; subsequently, heat transfer rates and thermal conductivity were compared

Fig.1 a XRD pattern of TiO2 nanoparticles b TEM analysis of TiO2 nanoparticles

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to the pristine PA. The melting curves were plotted for pure PA and nano-PCM composites with TiO2 wt% in the range of 0.5% to 2.5 wt%, represented in Fig. 2a. These nano-PCM composites started at an initial average ambient temperature of 23 °C. The temperatures were increased beyond their phase change temperatures and were heated up to an average temperature of 80 °C. It was analyzed that the melting rate for TPA-2 increased to 23.13%, which was the highest value. This indicated that the least amount of time taken for the occurrence of complete heat

Fig. 2 a Melting curve of PA with various TiO2 wt%. b Cooling curve of PA with various TiO2 wt%

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transfer was observed at 2 wt% of TiO2 . The melting rates of the different weight concentrations were 2.97%, 9.61%, 10.18%, 23.13% and 8.13% for TPA-0.5, TPA1, TPA-1.5, TPA-2 and TPA-2.5 as compared to pure PA. Similarly, the cooling curves were plotted for pure PA and nano-PCM composites with TiO2 wt% in the range of 0.5% to 2.5 wt%. From an initial temperature of 80 °C, they were analyzed until temperatures were equivalent to ambient temperature of 25 °C. The analysis showed 14.34%, 30.40%, 20.77%, 33.61%, 29.55% for TPA-0.5, TPA-1, TPA-1.5, TPA-2 and TPA-2.5 as compared to pure PA, refer Fig. 2b. The highest value was observed at 2 wt% suggesting the heat transfer rate was the highest at that weight percent. A regular gradation was observed in both heating and solidification rate. The non-uniformity in the heating/cooling rates could be associated with the anomaly in the experimental setup. When compared to other studies reported earlier, in this present study, a significant increase in charging and discharging rates was observed by embedding 2 wt% of TiO2 nanoparticle. The enhanced heating and cooling rates were due to the good incorporation of nanoparticles at the optimized proportion TPA-2 which resulted in the better thermal conductivity. Further, the optimized doping of nanoparticles with high surface area into PA resulted in the decrease of phase change transition temperatures. Moreover, to the best of our knowledge, most of the studies conducted previously by eminent researchers have been in the form of nanofluid-based PCM. However, the result obtained in this study was solid–solid nano-PCM embedment which makes it easier on the application front, and the thermal properties could be tailored to meet the requirement by modifying the concentration of TiO2 nanoparticles. The possible mechanism to explain the enhancement of thermal conductivity of PA with the embedment of TiO2 nanoparticles was allied to three main factors: Brownian motion of nanoparticles, aggregation of nanoparticles and formation of a monolayer. In the present research, incorporating our as-synthesized nanoparticles in various weight proportion had enabled us to study this closely when the nanoparticles were embedded into the phase change material due to the decrease in the size to nano-regime initiated Brownian motion, consequently leading to increased particle interactions. During the melt cycle studies, it was observed that the heat transfer rates attained their peak value at 2 wt% (TPA-2) after which there was a decline in the heat transfer rate. It could be hypothesized, as temperature increased, it without a doubt altered the viscosity; this resulted in increased interaction of the fluid medium with the nanoparticle surface producing an ordered layer of liquid molecules on it. At this point, the transmission of heat energy to the bulk by phonons would be rapid increasing the heat transfer rate and thermal conductance, eventually lowering the time required to reach the melting point as compared to pristine counterpart that is devoid of nano-additives. With the increase in concentration of nano-additives, possibility of agglomeration and sedimentation was major impeding factors to the enhancement of thermal conductivity. Similar was the case for cooling cycle where TPA-2 showed best results compared to other concentrations. Therefore, above studies confirm that an increase in thermal properties was observed at a lower concentration of nano-additive making it more economically viable on application front.

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Fig. 3 FTIR analysis of TiO2 (A), pure PA (B) and PA + TiO2 (C)

Fourier transform infrared spectrum confirmed the effective and uniform dispersion of TiO2 in PA, Fig. 3. In addition, similar spectrum was observed even after repeated heating and cooling cycles which confirmed the absence of any chemical reaction between PA and TiO2 . The peaks observed at 483 cm−1 were due to the vibrations from the Ti–O band stretching, and the peaks falling in the range 400– 800 cm−1 were due to the presence of the band vibrations of Ti–O when considering the pure TiO2 nanoparticle graph [A]. When considering the pure PA graph [B], the peaks at 2848 cm−1 and 2916 cm−1 were formed due to the symmetric stretching vibration of the single-bond CH3 and single-bond CH2 groups in PA. The singlebond OH present in PA due to in-plane and out-plane bending had resulted in the formation of the peaks at 1304 cm−1 and 943 cm−1 . The peaks at 734 cm−1 and 1642 cm−1 were due to the characteristic single-bond O–H bending of the hydroxyl group. The graph of PA + TiO2 [C] showed the presence of all the individual characteristic peak of both the compounds thus proving efficient embedment and uniform distribution of the nanoparticles in the phase change material. Similar peaks were observed on analysis after repetitive thermal cycles showcasing chemical stability of the phase change material and the nano-additive. The appearance of both individual peaks from TiO2 nanoparticle and pristine palmitic acid in the FTIR spectrum of our novel nano-PCM composite indicated no interaction took place between TiO2 nanoparticle and PA, and thus, they did not alter the properties of one another.

4 Conclusions Palmitic acid having a melting point of 62–63 °C makes it a suitable candidates for PCM applications, and the incorporation of molten salt synthesized TiO2 nanoparticle is a novel approach to enhance the thermal properties of fatty acid. It was

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observed that thermal conductivity increased with the increase in TiO2 concentration as compared to pure PA. Results showed by embedding thermally conductive TiO2 nanoparticles into PA, heat transfer rates for cooling cycle and heating cycle were found to reach the highest values of 33.61% and 23.13%, respectively, when 2 wt% of TiO2 nanoparticles were embedded, which also suggested that it is the least amount of time taken to transfer heat as compared to pristine palmitic acid. Hence, it can be concluded that the inclusion of metal oxide nano-additives can result in better thermal conductivity and storage.

References 1. A. Sharma, V.V. Tyagi, C.R. Chen, D. Buddhi, Review on thermal energy storage with phase change materials and applications. Renew. Sustain. Energy Rev. 13(2), 318–345 (2009) 2. S. Sundararajan, A.B. Samui, P.S. Kulkarni, Crosslinked polymer networks of poly (ethylene glycol)(PEG) and hydroxyl terminated poly (dimethyl siloxane)(HTPDMS) as polymeric phase change material for thermal energy storage. Sol. Energy 181, 187–194 (2019) 3. A.K. Ansu, R.K. Sharma, V.V. Tyagi, D. Tripathi, Prediction of thermal properties and reliability testing of binary eutectic mixture of polyethylene glycol 2000 and 10000 as phase change materials. Chem. Sel. 5(31), 9745–9757 (2020) 4. D. Juarez, R. Balart, S. Ferrandiz, M.A. Peydro, Classification of phase change materials and his behaviour in SEBS/PCM blends, in Manufacturing Engineering Society International Conference (2013) 5. D.C. Hyun, N.S. Levinson, U. Jeong, Y. Xia, Emerging applications of phase-change materials (PCMs): Teaching an old dog new tricks. Angew. Chem. Int. Ed. 53(15), 3780–3795 (2014) 6. X. Huang, G. Alva, Y. Jia, G. Fang, Morphological characterization and applications of phase change materials in thermal energy storage: A review. Renew. Sustain. Energy Rev. 72, 128–145 (2017) 7. D. Zhou, C.Y. Zhao, Y. Tian, Review on thermal energy storage with phase change materials (PCMs) in building applications. Appl. Energy 92, 593–605 (2012) 8. X. Li, H. Li, L. Zhang, Z. Liu, Phase change energy storage material suitable for solar heating system. in IOP Conference Series: Materials Science and Engineering, vol. 301, No. 1 (IOP Publishing, 2018), p. 012044 9. J. Wang, H. Xie, Z. Xin, Y. Li, L. Chen, Enhancing thermal conductivity of palmitic acid based phase change materials with carbon nanotubes as fillers. Sol. Energy 84(2), 339–344 (2010) 10. J. Wang, H. Xie, Z. Guo, L. Guan, Y. Li, Improved thermal properties of paraffin wax by the addition of TiO2 nanoparticles. Appl. Therm. Eng. 73(2), 1541–1547 (2014) 11. S. Santhosh, A.A. Madhavan, A review on the structure, properties and characterization of 2D molybdenum disulfide, in 2019 Advances in Science and Engineering Technology International Conferences (ASET) (IEEE, 2019), pp. 1–5 12. J. Wang, H. Xie, Y. Li, Thermal properties of phase change composites containing ferric oxide nanoparticles. J. Nanosci. Nanotechnol. 15(4), 3276–3279 (2015) 13. M. Satish, S. Santhosh, A. Yadav, S. Kalluri, A.A. Madhavan, Optimization and thermal analysis of Fe2 O3 nanoparticles embedded myristic acid-lauric acid phase change material. J. Electron. Mater. 1–7 (2020) 14. Y. Wang, X. Gao, P. Chen, Z. Huang, T. Xu, Y. Fang, Z. Zhang, Preparation and thermal performance of paraffin/Nano-SiO2 nanocomposite for passive thermal protection of electronic devices. Appl. Therm. Eng. 96, 699–707 (2016) 15. L. Cao, F. Tang, G. Fang, Preparation and characteristics of microencapsulated palmitic acid with TiO2 shell as shape-stabilized thermal energy storage materials. Sol. Energy Mater. Sol. Cells 123, 183–188 (2014)

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16. S.G. Ranjbar, G. Roudini, F. Barahuie, Fabrication and characterization of phase change material-SiO2 nanocomposite for thermal energy storage in buildings. J. Energy Storage 27, 101168 (2020) 17. M. Nidhin, R. Indumathy, K.J. Sreeram, B.U. Nair, Synthesis of iron oxide nanoparticles of narrow size distribution on polysaccharide templates. Bull. Mater. Sci. 31(1), 93–96 (2008) 18. I. Sharma, P. Kumar, S.K. Tripathi, Physical and optical properties of bulk and thin films of a–Ge–Sb–Te lone-pair semiconductors. Phase Transitions 90(7), 653–671 (2017) 19. I. Sharma, S. Sunder, Analysis of glass forming ability using percolation concept and tunability of physical parameters of a-Ge12Se76-xAs12Bix glassy semiconductors. Mater. Sci.-Pol. 36(2), 242–254 (2018) 20. R.K. Sharma, P. Ganesan, V.V. Tyagi, H.S.C. Metselaar, S.C. Sandaran, Thermal properties and heat storage analysis of palmitic acid-TiO2 composite as nano-enhanced organic phase change material (NEOPCM). Appl. Therm. Eng. 99, 1254–1262 (2016) 21. S.M. Iqbal, M. Arulprakasajothi, N.D. Raja, S.J. Bosko, M.B. Teja, Investigation on the thermal behaviour of titanium dioxide nanofluid. Mater. Today: Proc. 5(9), 20608–20613 (2018) 22. S. Harikrishnan, S. Magesh, S. Kalaiselvam, Preparation and thermal energy storage behaviour of stearic acid–TiO2 nanofluids as a phase change material for solar heating systems. Thermochim. Acta 565, 137–145 (2013) 23. A.A. Madhavan, R. Ranjusha, K.C. Daya, T.A. Arun, P. Praveen, K.P. Sanosh, K.R.V. Subramanian, S.K.V. Nair, A.S. Nair, A. Balakrishnan, Molten salt synthesized TiO2 -graphene composites for dye sensitized solar cells applications. Sci. Adv. Mater. 6(4), 828–834 (2014) 24. X. Wei, G. Zhu, J. Fang, J. Chen, Synthesis, characterization, and photocatalysis of welldispersible phase-pure anatase TiO2 nanoparticles. Int. J. Photoenergy 2013, 1–6 (2013) 25. T. Xiong, L. Zheng, K.W. Shah, Nano-enhanced phase change materials (NePCMs): A review of numerical simulations. Appl. Therm. Eng. 115492 (2020) 26. P. Pankaew, E. Hoonnivathana, S. Sujinnapram, K. Thamaphat, P. Limsuwan, K. Naemchanthara, Characterization of apatite from human teeth via XRD, FT-IR and TGA techniques. Adv. Mater. Res. 506, 90–93 (2012)

Reduced Graphene Oxide-Based Metal Nanocomposites as Advanced Functional Electrode Material for Ni/Fe Rechargeable Batteries Harish Kumar, Rahul Sharma, and A. K. Shukla

1 Introduction Presently, many renewable and non-renewable sources of energy satisfy the world’s energy needs; however, the abundance of non-renewable sources of energy, notably coal and oil, is progressively decreasing driven by the rising use of electrical and electronic devices, automotive as well as, most notably, the developing population demographic. There is a need for a sustainable, convenient, and renewable power storage system due to rapidly growing advancements in civilization and rising environmental impacts. Challenges have been out to build innovative energy storage systems with high energy efficiency and power capacity [1–6]. Thanks to their low cost, environmentally friendly behavior, and good output rate, batteries and capacitors have proven themselves as superior energy-storage devices [7–9]. But, the energy-storage system relying on batteries and hybrid capacitors for chemical reactions limits charging discharge power, life cycle, reversibility, and resource recyclability [10, 11]. As promising power sources, supercapacitors demonstrate excellent promise in combating this issue since “they make use of the energy-storage capabilities of rechargeable batteries and the high power output having potential applications in small functional portable electronic devices, electric cars, uninterrupted power supplies in computers and energy storage in solar cells” [11–15]. Foo’s et al. synthesized V2 O5 -rGO elastic and exceptionally scalable electrodes that can reach a power density of up to 625 Wkg−1 at 0.5 Ag−1 in the flat state, “an energy density of 1.22 W h kg−1 . The maximum achievable energy density was H. Kumar (B) · R. Sharma Department of Chemistry, School of Basic Sciences, Central University of Haryana, Mohindergarh 123 031, India e-mail: [email protected] A. K. Shukla Solid-State Structural Chemistry Unit, IISc, Bangalore, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_14

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13.3 Wh kg−1 , and the power density declined to 12.5 W kg−1 . The unit is capable of having a high energy density of 13.6 Wh kg−1 . These findings demonstrate that it is capable of fulfilling the specifications of commercial applications such as power tags for radiofrequency that need power from 1 to 100 µW” [16]. Fe2 O3 /rGO with a capacity of 1081 Fg−1 at 2 Ag−1 with retention of 75% power after one thousand cycles was synthesized by Gao et al. [17]. Zhao et al. introduced Fe3 O4 to boost conductivity and use graphene to avoid Fe3 O4 nanoparticles (NPs) from agglomerating and to implement improvements in the volume of NPs where it is possible to obtain a capacity of 337.5 mF cm−2 at 20 mA cm−2 and a power loss of just 2.3% between the 600th and 2000th cycles [18]. A hollow spheres assembly was designed by a simple one-step hydrothermal synthesis process of Mn-doped Fe2 O3 nanoparticles coated with rGO layers. At 1 A g−1 , manganese-doped Fe2 O3 /rGO NCs acted as the supercapacitor’s anode electrode material, displaying excellent electrochemical efficiency with a prominent 285 mAh g−1 basic capacitance, high rate capacity, and outstanding conductivity. In comparison, splendid cycling is 1 A g−1 [19]. A new approach was given for the feasible way to synthesize metal oxide/GO composite electrodes for condensers [20]. Substantially, rapid electrode kinetics and lengthy lifespan are responsible for the enhanced pseudocapacitive contribution. The lithium-ion capacitor offers appreciable energy densities of 147 Wh kg−1 and 76 Wh kg−1 at 300 and 13 kW kg−1 together with high cycle life [21]. In the lithium-ion battery application, Nb2 O5 /rGO NCs, the preliminary capacity, at 0.02 Ag−1 was 603 mAh/g, and the capacity sustained after 100 cycles was 335 mAhg−1 . This increased electrochemical performance was due to the unusual complementary architecture of predominantly Nb2 O5 NPs aided to produce composite material by strongly conductive rGO nanosheets, creating an adequate 2D transport channel through the (001) T-Nb2 O5 crystal planes. Recently designed composites based on T-Nb2 O5 indicate a feasible path for anode electrode generation in a lithium-ion battery [22]. The rGO-based CoV2 O4 (CVO) electrode displays a high 150 mAh g−1 discharge potential and shows 81.6% capacity at 200 mA g−1 after 1000 cycles. In addition, at 200 mAh g−1 , the CVO electrode shows 73.5% retention after 1000 cycles. At a density of 3200 mAh g−1 , the discharge power was reported to be 43 mAh g−1 [23]. “MoS2 /rGO/S cathodes exhibit a high reversible capacity of 1100 mA h g−1 at 0.2 °C, an outstanding cycling stability with a low capacity fading rate of 0.15% after 300 cycles at 1 °C and an excellent rate performance up to 620 mA h g−1 at 2 °C [24]. B. Lan et al. used FeVO4 , nH2 O@rGO composite to evaluate zinc ion storage capability as a cathode for the first time in 2 M Zn(TFSI)2 electrolyte. Benefiting from the large lattice spacing, dual electrochemical activity, and fast electron transfer, the composite delivers excellent rate performance and long life cycle (the capacity retained ~100 mAh g−1 at 1.0 A g−1 after 1000 cycle). In addition, the electrochemical performance of graphene-modified FeVO4 , nH2 O is superior to other precursors for comparison” [25].

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From the literature survey, it was observed that no researchers have reported the Fe2 O3 /CuO/rGO nanocomposites-based anode and Ni(OH)2 cathode material-based high-performance Ni/Fe rechargeable battery with high charge-storing capacity. For the first time, we have reported Fe2 O3 /CuO/rGO nanocomposites-based anode material for Ni/Fe alkaline rechargeable batteries with high charge-storing capacity.

2 Methods and Material Iron (III) oxide and graphite powder were procured from Sigma-Aldrich, CuO, and Ni (II) hydroxide were procured from Merck Scientific Pvt. Ltd. Double-distilled water was used for making the solution.

2.1 Synthesis of Graphene Oxide Graphene oxide was synthesized by the modified Hummers method. The 2 g graphite powder was selected as a precursor. Concentrated H2 SO4 , KMnO4, and H2 O2 solutions were used for oxidizing and reducing graphite powder, respectively.

2.2 Synthesis of Metal Nanoparticles Iron (III) oxide and Ni (II) hydroxide nanoparticles were synthesized from the modified sol–gel method. Sol A consists of metal salt solution, and Sol B consists of hydrogel in an alcoholic solution. Sol A was added drop-wise with continuous stirring in Sol B at 60–70 °C. The resultant was washed, filtered, and dried.

2.3 Synthesis of Fe2 O3 /CuO/rGO Nanocomposites by Ex-Situ Method Fe2 O3 /CuO/rGO nanocomposites were synthesized by the ex situ method. The Fe2 O3 , CuO nanoparticles were mixed with rGO powder. The resulting mixture was heat-treated, stirred, and a homogenous admixture was prepared by ex situ method at 70 °C. The characterization of Fe2 O3 /CuO/rGO nanocomposites was carried out by FTIR, XRD, and SEM techniques. The electrochemical characterization of Fe2 O3 /CuO/rGO nanocomposites as anode material was carried out by PGSTAT 302 N model electrochemical workstation. Figure 1 shows FTIR absorption spectra of

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Fig. 1 FTIR absorption spectra of Fe2 O3 /CuO/rGO nanocomposites as anode material of Ni/Fe rechargeable batteries

Fe2 O3 /CuO/rGO nanocomposites as the anode electrode material of Ni/Fe rechargeable batteries. Figure 2 shows the X-ray diffraction pattern of Fe2 O3 /CuO/rGO nanocomposites as the anode electrode material of Ni/Fe rechargeable batteries. Figure 3 shows SEM images at different magnification (1000X to 10000X) of Fe2 O3 /CuO/rGO nanocomposites as the anode electrode material of Ni/Fe rechargeable batteries. Figure 4 shows the Nyquist plot of Fe2 O3 /CuO/rGO nanocomposites as the anode electrode material of Ni/Fe rechargeable batteries. Figure 5 shows the

Fig. 2 X-ray diffraction pattern of Fe2 O3 /CuO/rGO nanocomposites as anode material for Ni/Fe rechargeable battery

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Fig. 3 SEM images of Fe2 O3 /CuO/rGO nanocomposite anode electrode material of Ni/Fe rechargeable battery. SEM image at X1000 magnification (a) and At X2500 magnification (b). SEM image at X5000 magnification (c) and At X10,000 magnification (d)

capacity of Fe2 O3 /CuO/rGO nanocomposite as anode material of Ni/Fe rechargeable battery as a function of charge/discharge cycle.

3 Results and Discussion The electrochemical performance of any rechargeable battery depends upon three important characteristics, i.e., nature of anode material, nature of cathode material, and nature of electrolyte. We have tried to increase the efficiency of Ni/Fe rechargeable batteries by modifying anode electrode material by use of Fe2 O3 , CuO, and rGO nanocomposites. Ni(OH)2 was used as cathode material, and aqueous KOH solution was used as electrolyte. Absorption spectra of anode electrode material show a broad peak at 3564 cm−1 due to the presence of moisture as an impurity (Fig. 1). The peak at 2850 cm−1 was due to C-H symmetric stretching vibration. A peak at 1621 cm−1 was due to C-H bending vibration. Two peaks in the fingerprint region at 833 cm−1 and

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Fig. 4 Nyquist plot of Fe2 O3 /CuO/rGO nanocomposites as anode material of Ni/Fe rechargeable battery

Fig. 5 Charge-storing capacity of Fe2 O3 /CuO/rGO nanocomposite as anode material of Ni/Fe rechargeable battery as a function of charge/discharge cycle

660 cm−1 correspond to Cu–O and Fe–O vibrations, respectively. X-ray diffraction pattern of rGO nanocomposite anode electrode shows the characteristic peak of rGO at 18 (Fig. 2). The other peak at 30.5° and multiple in the range 42–46° correspond to CuO. A characteristic sharp peak of Fe–O appears at 35.5° .

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SEM technique was used to study the shape and size of the anode before charge– discharge cycles. Figure 3a to d show SEM images of Fe2 O3 /CuO/rGO electrode material synthesized by the ex situ method (JEOL JSM5600LV make). The pores with a diameter of 100 nm were observed on the surface of the 10–20 µm anode material. XRD and SEM results show that the Fe2 O3 and CuO are uniformly mixed. The porous nature of electrode material was observed in high-resolution SEM images which were due to the presence of fibrous rGO in the nanocomposite. Nyquist plots were obtained at an open circuit potential (OCP) (AC impulse 5 mV peak to peak). The OCP was found to be −930 mV versus Ag/AgCl reference electrode (frequency starting from 100 to 5000 kHz) (Fig. 4). Figure 4 shows Nyquist plots for a Fe2 O3 /CuO/rGO anode in 5 M aqueous KOH. Initially, before starting impedance measurement, the anode was kept at constant OCP for 360 s. The hyperbolic shape of the Nyquist plot with frequency suggests the porous nature of the anode electrode which was due to adsorption of rGO on the Fe2 O3 electrode. Fe2 O3 /CuO/rGO nanocomposite anode was fabricated by the ex situ method. Reduced graphene oxide/Fe2 O3 /CuO nanocomposite and reduced graphene Fe2 O3 /CuO nanocomposite electrode material were prepared by modified Hummers method, improved sol–gel method, and ex situ synthesis methods, respectively. The synthesized nanocomposites were characterized by FTIR, SEM, and X-ray diffraction techniques. Solution resistance was found to be 51 mohm for Fe2 O3 /CuO/rGO electrode. The Ni/Fe rechargeable batteries and Fe2 O3 /CuO/rGO NCs show a capacity of 350 mAh/g, with a high charge–discharge cycle number and high retention of capacity even after 80 cycles (Fig. 5). The charge-storing capacity after 80 continuous charge–discharge cycle was 260 mAh/g. The result shows that the Fe2 O3 /CuO/rGO nanocomposite anode fabricated by the ex situ technique was highly efficient. The high performance of Fe2 O3 /CuO/rGO nanocomposite as anode material in Ni/Fe rechargeable battery was due to very stable, robust nanocomposites of Fe2 O3 /CuO/rGO in aqueous KOH solution as electrolyte. Further, the porous nature of rGO helps in holding Fe2 O3 and CuO nanoparticles tightly in the cavities of rGO making it a very robust material which makes it a very suitable anode material for the rechargeable alkaline battery. Fe2 O3 provides mechanical strength to the electrode, whereas CuO increases the electrical conductivity of the anode, and rGO provides a suitable surface for electrochemical reactions and also increases the electrical conductivity of the anode electrode so that there is a smooth transition of electrons between the anode and cathode.

4 Conclusions Fe2 O3 /CuO/rGO nanocomposite anode electrode material was synthesized by modified Hummers method, improved sol–gel method, ex situ method for chargeable Ni/Fe battery. Fe2 O3 /CuO/rGO nanocomposite anode was synthesized by facile three different methods. The synthetic route represents large-scale industrial production

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of Fe2 O3 /CuO/rGO nanocomposite. The synthesized nanocomposite was characterized by FTIR, scanning electron microscopy, and X-ray diffraction techniques. The internal resistance of the Ni/Fe battery was found to be 51 mohm. The Ni/Fe battery shows charge–discharge cycle capacities of 350 mAh/g with a high charge–discharge cycle and residual capacity of 260 mAh/g after 80 cycles. The result shows that the Fe2 O3 /CuO/rGO nanocomposite anode synthesized by facile three-step methods significantly improves the charge-storing capacity of conventional Ni/Fe alkaline rechargeable batteries.

References 1. F. Bonaccorso et al., Graphene, related two-dimensional crystals, and hybrid systems for energy conversion and storage. Science 347(6217) (2015). https://doi.org/10.1126/science.1246501 2. Y. Gogotsi, P. Simon, True performance metrics in electrochemical energy storage. Science 334(6058) (2011). https://doi.org/10.1126/science.1213003 3. H. Kumar et al., Recent advancement made in the field of reduced graphene oxide-based nanocomposites used in the energy storage devices: A review. J. Energy Storage 33, 102032 (2021). https://doi.org/10.1016/j.est.2020.102032 4. M.R. Lukatskaya, B. Dunn, Y. Gogotsi, Multidimensional materials and device architectures for future hybrid energy storage. Nat. Commun. 7(1) (2016). https://doi.org/10.1038/ncomms 12647 5. P. Simon, Y. Gogotsi, B. Dunn, Where do batteries end and supercapacitors begin? Science 343(6176) (2014). https://doi.org/10.1126/science.1249625 6. X. Xiao et al., Scalable salt-templated synthesis of two-dimensional transition metal oxides. Nat. Commun. 7(1) (2016). https://doi.org/10.1038/ncomms11296 7. C. de las Casas, W. Li, A review of the application of carbon nanotubes for lithium-ion battery anode material. J. Power Sources208 (2012). https://doi.org/10.1016/j.jpowsour.2012.02.013 8. H.B. Wu et al., Nanostructured metal oxide-based materials as advanced anodes for lithium-ion batteries. Nanoscale 4(8). https://doi.org/10.1039/c2nr11966h 9. Y. Zhang et al., Progress of electrochemical capacitor electrode materials: A review. Int. J. Hydrogen Energy 34(11) (2009). https://doi.org/10.1016/j.ijhydene.2009.04.005 10. L. Su, Y. Jing, Z. Zhou (2011). Li-ion battery materials with core-shell nanostructures. Nanoscale 3(10). https://doi.org/10.1039/c1nr10550g 11. J.P. Zheng, J. Huang, T.R. Jow, The limitations of energy density for electrochemical capacitors. J. Electrochem. Soc. 144(6) (1997). https://doi.org/10.1149/1.1837738 12. H. Chen et al., Progress in electrical energy storage system: A critical review. Prog. Nat. Sci. 19(3) (2009). https://doi.org/10.1016/j.pnsc.2008.07.014 13. S. Z. Iro, A brief review on electrode materials for supercapacitor. Int. J. Electrochem. Sci. (2016). https://doi.org/10.20964/2016.12.50 14. P. Sharma, T.S. Bhatti, A review on electrochemical double-layer capacitors. Energy Convers. Manage. 51(12) (2010). https://doi.org/10.1016/j.enconman.2010.06.031 15. M. Winter, R.J. Brodd, What are batteries, fuel cells, and supercapacitors? Chem. Rev. 104(10) (2004). https://doi.org/10.1021/cr020730k 16. C.Y. Foo et al., Flexible and highly scalable V2 O5 -rGO electrodes in an organic electrolyte for supercapacitor devices. Adv. Energy Mater. 4(12) (2014). https://doi.org/10.1002/aenm.201 400236 17. Y. Gao et al., One-step solvothermal synthesis of quasi-hexagonal Fe2 O3 nanoplates/graphene composite as high-performance electrode material for supercapacitor. Electrochim. Acta, 191 (2016). https://doi.org/10.1016/j.electacta.2016.01.072

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Influence of Variation of Excitation Wavelength on Optical Properties of Silicon Nanowires Vikas Kashyap, Neeru Chaudhary, Navdeep Goyal, and Kapil Saxena

1 Introduction The demand of energy in living-beings is continuously increasing. The recorded data of the global market energy usage will rise by 44% over the period from 2006 to 2030 (from 15.8 TW in 2006 to 22.7 TW in 2030) [1, 2]. In India, due to policy uncertainties and the impact of import duties on solar cells, installations had been expected to grow again and surpass 14 GW in 2020 [3]. Less prices and a large pipeline of projects were expected to spur the return to growth. But corona pandemic (caused by COVID 19) totally affected the system. Now, this is the time to make the things economically attractive and efficient. Therefore, the production and promotion of renewable energy sources are very essential for the technological and industrial applications. Sunlight reaches the surface of the earth at a level of ~120,000 TW [4, 5]. The utilization of these huge source of renewable energy (i.e by solar cells ) on the large scale should be done and for fullfilling that we need a economical based production of solar cell and that is the demand of present time. The major drawback for the production of solar-based system is heavy production cost and their low efficiency [6, 7]. There are various nano-structured material which can be utilized for fabrication of solar cells; however, Si/Si-based nano-structured materials prove itself as a most suitable materials which shows amazing optoelectronic properties as well as its technological availability [1]. Si is possibly the only substance that satisfies easy affordability with relatively high performance (more than 10%) [8]. It offers strong absorption of radiation with non-toxic nature. Si is permanently available as V. Kashyap · N. Chaudhary · N. Goyal Department of Physics, Panjab University, Chandigarh 160014, India K. Saxena (B) Department of Applied Sciences, Kamla Nehru Institute of Technology, Sultanpur, Uttar Pradesh 228118, India e-mail: [email protected]; [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_15

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it is the abundant part of the Earth’s crust (25.7%), without any protective layer, is stable and resistive to most acids, and is eco-friendly with its nontoxic nature [9]. Si currently plays a vital role in the demand for solar cells or in microelectronic industry. Si has long been established as the material of choice for the microelectronics industry. Recent developments, especially those enabled by nano-scale engineering of the electronic and photonic properties, are starting to change the picture, and some Si nanostructures now approach or even exceed the performance of equivalent direct-band gap materials. Focusing on application areas, namely photovoltaic (PV), we recently progress in Si-NWs as key examples of functional nanostructures [10, 11]. There are many challenges that need to be overcome to make Si a truly highperforming photonic material. It is globally required to develop cost-effective PV devices, absorbing solar energy-based systems, and breaking the existing limitation is the main target to explore. Light emission in Si nanostructures was first demonstrated with porous Si in the 1990s [12]. With the time, the research focused on the energy structure in a nano-configuration is influenced directly by the size of the nanowire because of quantum confinement effect [13–15]. As the surface-to-volume ratio (aspect ratio) increases with reduction of size, the local arrangement of atoms located on the surface plays an important role. Quantum confinement effect and surface effects have a profound impact on the band structure of the material and modify energy as well as momentum dependence. Equally, the energy bands may become discretized to such an extent that the “band” concept ceases to apply and a molecular approach becomes more appropriate. The energy structure of Si-NWs has been thoroughly investigated experimentally, looking both at individual structures and at ensembles. The orthogonalized path of absorption of light to the charging carriers collection is the major benefit of Si-NWs in the fabrication of solar devices. The electrons produced by the photon can only make the journey very short in a radial direction (less than the diameter of the NW). In this article, we have analyzed the room temperature excitation wavelength dependent PL. Excitation wavelength dependent PL from Si-NWs has attracted attention because of its surprising luminescent behavior and applications in various energy conversion devices. Although the origin and characteristics of PL bands of nanostructures is not fully understood, it is generally recognized that excitation wavelength dependent PL phenomenon is due to the size distribution of nanostructures, but here we have carried out it for same sample which reveals that PL bands are also due to defects present in the nanostructures. The work reveals a general framework for understanding the effect of excitation wave length on PL observed by Si-NWs. For this study, Si-NWs samples have been fabricated by metal-induced chemical etching (MICE) method [15–17]. Surface morphology had been analyzed through FESEM along with size estimation through the image J software. Here, we have also explored the quality of sample prepared by MICE method through the PL signal observed due to structure and various defects present along with the Si-NWs in the sample. Analysis of PL has been carried out to optimize the optical properties of Si-NWs samples. PL spectroscopy is used here to estimates energy band gap of Si-NWs.

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2 Methodology MICE has too much simpler processing than electrochemical etching, vapor liquid solid [18–20] and reactive ion etching [21]. MICE is a solution processed refined, high-performance technique. MICE requires two successive stages, nucleation of metal nanoparticles, and anisotropic etching in a solution containing HF and oxidizing agents (here, we are using hydrogen peroxide). MICE can produce SiNWs on a wafer scale with dimensions varying from tens to hundreds of nanometers. MICE is composed of two stages: (a) Deposition of metal nano-particles (b) metal catalyzed etching. The creation of Si nanostructures depends on anisotropic properties of MICE even though metals should be noble enough to prevent rapid dissolution in HF solution, and metal catalysts have been used. Ag were found to be the ideal catalysts for Si-NWs synthesis without formation of extra porous layer [22]. Si-NWs samples have been synthesized by MICE technique. All reactions were carried out at room temperature by using commercially available (by Sigma-Aldrich and Merck), AgNO3 , HF (48%), H2 O2 (30%), HNO3 , and deionized water. Deposition of silver (Ag) nanoparticles process was performed by immersing the cleaned n-type Si wafer (100) in a mixture of AgNO3 (5 mM) and HF (0.55 M) for 60 s at room temperature. Sample was prepared by immerging Ag deposited Si wafers in an aqueous solution of H2 O2 (4.6 M) and HF (0.5 M) through etching process for fixed etching time of 50 min., respectively. Then, sample was rinsed in deionized water and after that treated with solution of HNO3 to eliminate the Ag-NPs on the sample. After every step, the samples should be left to dry after dipping in deionized water. Microstructural and band gap analysis of Si-NWs was carried out by FESEM (HITACHI SU8010) and PL spectroscopy (Shimadzu Spectrofluorophotometer (RF 5301 PC), respectively.

3 Results and Discussion Figure 1 shows FESEM image of Si-NWs grown on cleaned n-type Si wafer (100) of resistivity of 1–10 -cm by MICE technique for etching time 50 minutes. It is clear from Fig. 1 that Si-NWs present in sample like quasi-ordered arrays along the [100] crystallographic orientation. The growth of Si-NWs is controlled by the redox reaction initiated by Ag nanoparticles which can be understood by well-established mechanism [23]. The top part of Si-NWs, is fused together to form the flat topped structure which is shown in Fig. 1. It is important to note that density of Si-NWs has been dependent on density of Ag nanoparticles grown on the Si wafer which lead to remarkable changes of the structural properties of Si-NWs monitored by FESEM. Si-NWs become so involved optically, electrically, and chemically than bulk silicon due to the effect of shrinking the dimensions which leads to increase the aspect ratio. The length of Si-NWs is roughly dependent on etching time up to a threshold etching time [13]. Figure 2 reveals that the rough estimation of average length and diameter

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N-50

Fig. 1 FESEM image of Si-NWs grown on cleaned n-type Si wafer (100) of resistivity of 1–10 cm by MICE technique for etching time 50 minutes

Fig. 2 Histogram for a diameter (size) and b length estimation of Si-NWs grown on cleaned n-type Si wafer (100) of resistivity of 1–10 -cm by MICE technique for etching time 50 min through Image J software

(size) of the Si-NWs was around by approximate 0.5 µm and 30 nm by using the Image J software. Figure 3a–c shows the wavelength dependent PL spectra of Si-NWs sample for etching time 50 min for different excitation wavelength 520 nm, 430 nm, and 330 nm, respectively. Figure 3 clearly reveals that when the Si-NWs sample was excited at various wavelengths, several PL bands are found for a particular excitation wavelength. Figure 3a shows that for excitation wavelength 520 nm, only one PL band around 775 nm was found. Figure 3b and c reveals that as excitation wavelength decreased to 330 nm, other PL bands (around 562, 591, 600, and 678 nm) are also appeared along with PL band around 775 nm. This can be attributed to the fact that

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Fig. 3 PL spectra of Si-NWs grown on cleaned n-type Si wafer (100) of resistivity of 1–10 -cm by MICE technique for etching time 50 min using excitation wavelength (a) 520 nm, (b) 430 nm and (c) 330 nm

as the excitation wavelength decreases, penetration of excitation radiation increases in the sample which leads to interaction of radiation with the various defects in the sample which results appearance of the excitation wavelength dependent PL bands in the PL spectra. The PL band position and broadening leads to size distribution of Si-NWs in the sample but should not be dependent on excitation wave length. PL spectroscopy can be used as a tool to tailoring the quality of sample of Si-NWs through analyzing the dispersive behavior of PL bands. This observation has been attributed to the presence of various defects forms along with the Si-NWs during etching process. This fact is well understood by taking into account that dispersive behavior of PL bands for samples. There is an interplay between variation in energy band gap and quantum confinement effect due to uncertainty principle. We had already observed that a sizedependent shift in visible PL emission at room temperature from Si-NWs is often treated as a confirmation of presence of quantum confinement effect [24]. Figure 3 reveals that PL band observed around 775 nm is at similar position with varying excitation wavelength; thus, it was due to band to band transition from the Si-NWs sample which confirms the enhancement of energy band gap of Si-NWs approximates equal to 1.59 eV as compared to the bulk Si due to quantum confinement effect.

4 Conclusion Concerning its low cost, easy method, and high controllability, MICE is chosen to fabricate Si-NWs. The analysis of the structure and optical properties of Si-NWs prepared by MICE of c-Si in hydrofluoric acid solutions open scope of new possibilities for flipping the optoelectronic properties of Si-based nano-systems. Rough estimation of average length and diameter (size) of the Si-NWs was around by approximate 0.5 µm and 30 nm by using the Image J software. We reported the excitation

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wavelength dependent PL behavior of a Si-NWs network. The PL bands, around 562, 591, 600, and 678 nm, are defect-induced transition and appear due to interaction of incident radiation and various defects for various excitation wavelength. PL band observed around 775 nm is at similar position with varying excitation wavelength and observed due to band–band transition from the Si-NWs sample which confirms the enhancement of energy band gap of Si-NWs which is found to be 1.59 eV as compared to the bulk Si. This study may also serve as an important landmark for developing a new form of conversion system for solar energy. Acknowledgements One of the authors (Vikas Kashyap) acknowledges financial support as SRF (Senior Research Fellowship) from University Grant Commission (UGC) India.

References 1. B. Liang, Y. Liu, Y. Xu, Silicon-based materials as high capacity anodes for next generation lithium ion batteries. J. Power Sources. 267, 469–490 (2014). https://doi.org/10.1016/j.jpo wsour.2014.05.096 2. C. Battaglia, A. Cuevas, S. De Wolf, High-efficiency crystalline silicon solar cells: Status and perspectives. Energy Environ. Sci. 9, 1552–1576 (2016). https://doi.org/10.1039/c5ee03380b 3. G. Li, H.S. Kwok, Silicon nanowire solar cells. Adv. Silicon Sol. Cells 269–298 (2018). https:// doi.org/10.1007/978-3-319-69703-1_10 4. G. Editors, D. Nocera, D. Guldi, Renewable Energy issue. Chem. Soc. Rev. 38, 165–84 (2009). https://doi.org/10.1039/b800582f 5. V.Y. Yerokhov, I.I. Melnyk, Porous silicon in solar cell structures: A review of achievements and modern directions of further use. Renew. Sustain. Energy Rev. 3, 291–322 (1999). https:// doi.org/10.1016/S1364-0321(99)00005-2 6. W. Tress, Organic solar cells—Chapter 3 (2014). https://doi.org/10.1002/adma.19910030303 7. J. Zhu, C.M. Hsu, Z. Yu, S. Fan, Y. Cui, Nanodome solar cells with efficient light management and self-cleaning. Nano Lett. 10, 1979–1984 (2010). https://doi.org/10.1021/nl9034237 8. K.A. Salman, K. Omar, Z. Hassan, The effect of etching time of porous silicon on solar cell performance. Superlattices Microstruct. 50, 647–658 (2011). https://doi.org/10.1016/j.spmi. 2011.09.006 9. K.A. Gonchar, V.Y. Kitaeva, G.A. Zharik, A.A. Eliseev, L.A. Osminkina, Structural and optical properties of silicon nanowire arrays fabricated by metal assisted chemical etching with ammonium fluoride. Front. Chem. 7, 1–7 (2019). https://doi.org/10.3389/fchem.2018. 00653 10. K.Q. Peng, S.T. Lee, Silicon nanowires for photovoltaic solar energy conversion. Adv. Mater. 23, 198–215 (2011). https://doi.org/10.1002/adma.201002410 11. A. Zhang, G. Zheng, C. Lieber, Nanowires : building blocks for nanoscience and nanotechnology (2016). https://doi.org/10.1007/978-3-319-41981-7 12. A.G. Cullis, L.T. Canham, Visible light emission due to quantum size effects in porous silicon. Nature 353, 335 (1991) 13. S.K. Saxena, G. Sahu, V. Kumar, P.K. Sahoo, P.R. Sagdeo, R. Kumar, Effect of silicon resistivity on its porosification using metal induced chemical etching: Morphology and photoluminescence studies. Mater. Res. Express. 2, 36501 (2015). https://doi.org/10.1088/2053-1591/2/3/ 036501 14. A.H. Chiou, J.F. Lin, C.K. Su, C.Y. Hsu, W.F. Wu, C.P. Chou, An analysis on synthesizing largearea silicon nanowire arrays by electroless metal deposition. Proc. IEEE Conf. Nanotechnol. 187–192 (2011). https://doi.org/10.1109/NANO.2011.6144523

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Invariance of Thermal Emissivity in Spray Coated ZrB2 Film Atasi Dan and Nagarajan Kirupakaran Gopinath

1 Introduction The emissivity of material determines the amount of thermal radiation from an object with respect to a blackbody at the same temperature [1]. A perfect blackbody exhibits an emittance (ε) of 1, while any real object possesses ε < 1. The measurement of emissivity is important because it gives an idea about the material’s thermal behavior. In particular, high emissivity is required in an application, wherein the requirement is to increase the heat radiation from the surface. High emissive films are useful in various applications, especially for thermal protection systems, solar heat absorbers, electrical insulation, thermo-photovoltaic infrared heaters, etc. [2, 3]. Particularly, exploring the films that emit infrared radiation in the wavelength range of 8–14 µm can contribute to maintaining the passive thermal heat transfer, as this spectral range is associated with the peak of blackbody spectrum in the temperature range of 300–400 K. Till date, different thin film deposition methods are utilized to deposit highly emissive thin/thick films on metallic substrates. However, simple and cost-effective ways like wet chemical process derived spray/dip coating are attractive as such processes can be used to deposit films on the substrate of any arbitrary shape. Massively-scalable spray coating techniques are desirable when translating academic research to real-world applications involving large area coating. Also, the ability to tailor the wet-chemistry processing route enables optimization of process parameters to achieve desired property combinations. Many high emissive coatings have been reported in the literature. For example, Shao et al. developed WSi2 -Si-glass hybrid coating on zirconia substrate for thermal protection system using dip coating and reported emissivity of 0.92 [4]. Similarly, A. Dan (B) Materials Research Centre, Indian Institute of Science, Bangalore 560 012, India N. K. Gopinath Centre of Excellence in Hypersonics, Indian Institute of Science, Bangalore 560 012, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_16

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Wang et al. used a slurry coating procedure to prepare a porous MoSi2 –SiO2 – SiOC layer on mullite, with a high spectral emissivity of 0.90 [5]. In another work, Mahadik et al. deposited SiO2 /Al2 O3 on stainless steel (SS) using spray coating, which exhibited a high emittance of 0.92–0.94 [6]. Some carbides and borides-based ultra-high temperature ceramics (UHTCs), like HfC, ZrC, TaC, TiB2 , HfB2, and TaB2 have received wide recognition for their good optical selectivity, high thermal conductivity, and desired emittance [7, 8]. Among the potential UHTCs, ZrB2 is a transition metal boride with a high melting point and modulus of elasticity, excellent thermal conductivity, exceptional hardness, and good wear resistance. ZrB2 is one of the super-hard materials whose outstanding capability has been proved in cutting tools, resistant armor, etc. Studies on the thermal emissivity of ZrB2 are still being pursued by researchers [9–11]. Rare-earth modified ZrB2 coatings have been synthesized by Tan et al. for the hypersonic aerospace application using plasma spray coating, which showed hemispherical emissivity of 0.93 [9]. Li et al. reported emissivity of 0.93 for 100 µm thick spray coated ZrB2 -SiC/acrylic [11]. Recently, ZrB2 -SiC-based multiphase ceramics for hypersonic applications has been developed and qualified [12, 13]. Considering various remarkable properties and continuing thermal characterization of ZrB2 , this work investigates thermal radiative properties of ZrB2 film prepared by slurry coating technique.

2 Materials and Method 2.1 Coating Preparation Wet-chemistry route-based slurry coating technique has been used to prepare ZrB2 coatings on stainless steel. This processing technique is cost-effective and enables easy scale-up for large area coating on complex geometries. Initially, the substrate is polished to mirror finish and degreased in ethanol and placed in a desiccator under vacuum to avoid environmental interaction. The coating slurry is prepared using ethanol as solvent, ZrB2 as coating material, and 3-glycidyloxypropyltrimethoxysilane (GPTS) as adhesion enhancer in the ratio of 49%, 45%, and 6% by weight, respectively. This composition enables homogenous slurry without agglomeration or sedimentation and required viscosity for spraying. Commercially procured high purity (>99%) ZrB2 powder (D50 ~ 5 µm) (Nanoshel, USA) is added to ethanol while stirring in a magnetic stirrer to avoid lumps. After stirring for about 1 h, the GPTS solution is carefully added to the slurry in a dropwise manner. Stirring is carried out for 2 h to enable proper mixing. Following this, a few drops of HNO3 (99%) are added to allow for the carboxylation, and the resulting slurry is stirred for 2 h. The slurry is loaded in a conventional paint spray gun operated at an air pressure of 6 bar. Substrates are cleaned once again in ethanol and placed in the spraying setup. The standoff distance of 0.15 m is maintained between the sample and the spray gun

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to enable proper interaction of the atomized spray with the substrate. The coating is performed by manual spraying, wherein multiple samples are coated by ZrB2 slurry in a single pass. The coated samples are dried in ambient atmospheric conditions and are free of shrinkage cracks for the optimized ratio of slurry ingredients. Multiple passes are performed sequentially without atmospheric drying of the previous layer for carrying out multi-layer coating. A maximum of 7 passes is performed for the present study. The coated specimens are treated in a hot air oven at 100 °C for 1 h in air atmosphere to remove the solvent. In addition to the coating, the ZrB2 pellet with a diameter of φ12.7 mm and thickness of ~3 mm is prepared by uniaxial cold pressing of the powder to study the bulk characteristics.

2.2 Coating Characterization The film structure was characterized by X-ray diffraction (PANalytical, Netherlands) at room temperature using Cu-Kα as a radiation source (λ = 1.54 Å) operated at a constant voltage of 40 kV and a constant current of 40 mA with a scan rate and step size of 1º/min and 0.02, respectively. A field emission scanning electron microscope (FESEM) (Ultra 55, Carl Zeiss, Germany) operated at 20 keV was utilized to examine the surface morphology of the ZrB2 starting powder, pellet, and deposited films. Also, the thicknesses of the films were estimated from cross-sectional FESEM images. The surface roughness of films was measured by atomic force microscopy (AFM) (Bruker, Germany).

2.3 Radiation Property Evaluation The optical properties of the ZrB2 coating were experimentally measured, and the results were analyzed using the established theoretical framework. According to Kirchhoff’s law, at thermal equilibrium, the value of absorptance α(λ) at a particular wavelength is equal to the value of emittance, ε(λ) [14]. The absorptance value can, thus, be estimated from the diffuse reflectance data using the following relation (Eq. 1): α(λ) = 1 − R(λ) − T (λ)

(1)

where R(λ) and T (λ) represent the reflectance and transmittance at wavelength λ, respectively. In the present case, stainless steel was used as a substrate. Considering negligible transmittance, i.e., T (λ) = 0 for stainless steel [15, 16], R(λ) and α(λ) can be related as shown in Eq. (2): α(λ) = 1 − R(λ)

(2)

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The absorptance and emittance of the samples were measured by solar spectrum reflectometer and emissometer (M/s. Devices and Services). In addition to that, reflectance spectra of the samples were recorded using a Fourier-transform infrared (FTIR) spectrometer (PerkinElmer). The total normal emissivity at room temperature can be calculated by integrating spectral reflectance in the spectral region of 2.5–25 µm wavelength and is expressed as (Eq. 3), [17], ε(T ) =

∫25 2.5 [1 − R(λ, θ = 0)]i b (λ)dλ ∫25 2.5 i b (λ)dλ

(3)

where θ is the incident angle, i b (λ, T ) is the spectral intensity of a blackbody at temperature T which can be represented by the following equation (Eq. 4). i b (λ) =

λ5

C1   exp(C2 /λT ) − 1

(4)

3 Results and Discussion 3.1 Phase Assemblage Figure 1 shows the phase assemblage of ZrB2 powder, pellet, and deposited coatings for 3 and 7 passes investigated using XRD. The peaks have been indexed with

Fig. 1 X-ray diffraction pattern recorded on ZrB2 in a powder form; b pellet form; c 3 pass coating; and d 7 pass coating

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corresponding miller indices (hkl). The three strongest X-ray peaks, located at 2θ ≈ 41.6°, 32.6°, and 25.2°, correspond to the (hkl) values of (101), (100), and (001) planes of hexagonal-ZrB2 (a = b = 0.317 nm and c = 0.353 nm with space group P6/mmm). There are also other peaks located at 51.7°, 58.2°, 62.5°, 64.4°, 68.3°, and 74.1°, which are associated with (002), (110), (102), (111), (200), and (201) planes. The resemblance of XRD patterns between powder, pellet, and thin films for 3 and 7 passes can be observed for all cases in Fig. 1a–d. The absence of any measurable peak shift in the coating with respect to XRD peaks of powder and pellets indicates no residual strain in the coating. In addition, the presence of a highly crystallized and structurally ordered phase of ZrB2 is depicted by the sharp nature of the peaks. The diffractogram shows no oxide and other impurities after film preparation. The substrate peaks can appear either due to the film with less thickness or porous structure and weak zones of the coating, allowing X-ray to interact with the substrate. The absence of any peak of stainless steel substrate in the XRD pattern of the coatings deposited using 3 and 7 passes confirms the deposition of a thick and dense layer on the substrate, which is further ascertained using scanning electron microscopy. These thick coatings could effectively prevent the transmission of incident radiation and enhance the absorption, resulting in high emissive characteristics.

3.2 Coating Morphology Figure 2 represents FESEM images of ZrB2 powder, pellet, and coatings. The ZrB2 powder shows irregular and random shape morphology, without hard agglomerates, as shown in Fig. 2a. The average particle size is measured to be ~5 µm by assuming a circular fit (using ImageJ software). In the case of cold-pressed ZrB2 , Fig. 2b shows the presence of faceted features on the surface. This can be reasoned to the high pressure applied during uniaxial cold compaction, leading to possible defects/dislocations. FESEM images of two coatings in Fig. 2c and d represent that the surface finish is smooth without aberrations. No crack or delamination was observed after deposition, indicating good adhesion of the coating with the substrate. The presence of pores on the coating surface usually has a significant effect on the film’s radiative property. On the other hand, the formation of pores causes rapid erosion of the coating during processing as well as in service. However, for the present ZrB2 layer, no pore was formed on the coating surface, indicating the durability of the surface. The cross-sectional morphologies of the coatings are shown in Fig. 3. The thicknesses of the coatings are in the range of 60–280 µm. It can be observed that the higher the number of passes, the higher is the coating thickness. The thickness increases from 61 to 279 µm when the number of passes increase from 3 to 7. Considering the slurry’s solid content is constant (45 wt.%), the more slurry sprayed to the substrate, the thicker the coating is. Hence, the coating thickness increases with the number of passes of the slurry spray process. Roughly, the coating thickness increases by 50% with each pass under the specified experimental conditions. However, the minor

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Fig. 2 Surface morphology of (a) ZrB2 raw powder; (b) Cold pressed ZrB2 pellet; (c) 4 pass coating; and (d) 6 pass coating

Fig. 3 Scanning electron micrographs of ZrB2 coated stainless steel, showing the variation of coating thickness with multiple passes: a 3 pass; b 5 pass; and c 7 pass

deviations in the thickness are due to manual control of the spraying process. It can also be seen from the cross-section morphology that there are no defects throughout the thickness of the coating layer. This indicates good quality of the coating and the ability of the slurry spray technique to achieve this. The absence of any pits or cavities makes the coating compact. Moreover, the distinct multi-layer coating morphology is not seen, as the subsequent layers were sprayed in “wet” conditions without drying.

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3.3 Surface Roughness Surface roughness influences the radiative properties of the film. When an electromagnetic wave interacts with a smooth surface, the maximum portion of incident radiation is reflected, and the surface absorbs very little part of the incoming light. The relationship between surface roughness and reflectance can be represented by the following equation (Eq. 5):     4π σ 2 Rr = Rp exp − λ

(5)

Rr and Rp are the reflections from rough and plane surfaces, respectively, and σ is the sample’s surface roughness. This equation represents that a rough surface with multiple reflections from various randomly oriented faces exhibits low reflectivity, leading to the film’s high absorptance. According to Kirchhoff’s law, a higher absorptance of a film indicates higher emittance. So, it is indicative that a film with high surface roughness should possess high emissivity. Figure 4 represents the atomic force microscopy images of the ZrB2 coating deposited using 3 and 7 passes, on an area of 20 µm × 20 µm. It is evident that both coatings have microscopic roughness, and the arithmetic average of the roughness profile (Ra ) is ~ 40 nm. The processing approach can explain the reason for the similarity in roughness for different passes. As multi-layer coatings are repeated in similar fashion under wet conditions, it is plausible that the splats formed during the deposition of the spray droplets/ligaments mend together. Also, the thickness variations are in the range of 60–280 µm, leading to similar drying of coating at least at the surface, thereby resulting in near-identical Ra , even for multiple passes.

Fig. 4 Atomic force microscope image of (a) 3 pass and (b) 7 pass coating

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3.4 Thermal Emittance The emittance values of stainless steel (SS) substrate and ZrB2 coating were obtained to identify the role of radiative coating in improving the bare substrate’s performance. Polished SS has an emittance of 0.12–0.13. Incorporation of ZrB2 layer on SS increased the emittance significantly to 0.79–0.81. The infrared properties of the film depend on the composition of the film. GPTS used to deposit the film works as an adhesion promoter and possesses a high emissive nature contributing to enhancing the emittance. The emittance was greatly improved after the deposition of ZrB2 . To acquire knowledge on the thermal properties of the ZrB2 , emittance values were measured for the coatings deposited by increasing the number of passes. It is observed that as the thickness of the coating is increased, the emittance values nearly remained constant, i.e., 0.80±0.01. This finding indicates that improvement of emissivity by increasing the number of passes is, therefore, limited. In particular, for weight-saving applications such as aerospace vehicles, such results are essential, which give insights into the minimal thickness for required emittance. However, these design considerations must be looked at in combination with other functional requirements of the material for the intended application. The spectral emissive behavior of the coatings in the wavelength range of 2.5– 22 µm is shown in Fig. 5. As shown, the spectral reflectivity curves represent low reflective nature throughout the infrared range, implicating the film’s high emissivity. The coatings deposited by applying 3 and 7 passes have similar reflectance spectra with a reflectance ranging from 19–29% in 2.5–18 µm. However, two peaks appear around 19 and 21 µm with relatively high reflectance for both the coatings. The area above the reflection curve indicates the ZrB2 film’s absorptance and is, therefore, responsible for emissive properties. The insignificant difference in reflectance spectra for the coatings deposited using different passes also supports the fact that the number of passes may not influence the emissive nature of ZrB2 coating. Fig. 5 Reflectance spectra in FTIR range, for coating deposition by 3 and 7 passes, prepared via spray deposition process

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3.5 Invariance of Thermal Emittance It is reported that an increase in the number of cavities could enhance thermal emissivity by trapping electromagnetic waves and producing multiple reflections [18]. The present film’s compactness was not affected by multiple passes indicating the absence of the cavities, which is evident from the cross-sectional images of the film (Fig. 3). It has been observed that different deposition conditions influence the size and number of pores in a film, which effectively changes emissive properties [19]. It is believed that in the present case, the number of passes has a negligible effect on the size and distribution of cavities of the film, possibly due to multiple coating passes carried out in the wet condition. Hence, the emittance remained constant with an increase in the number of passes. Also, similar values of the surface roughness for both the coatings may explain the reason behind similar emissivity. The increase in the number of passes does not increase the emittance, which can be attributed to the irregular dispersion of ZrB2 particles for all the cases. The reason behind the high emissive nature of ZrB2 can also be explained by the resonance of lattice and molecular vibration beyond 4–5 µm, which causes a high absorption [20].

4 Conclusions A spray coating method of a chemical slurry prepared using ZrB2 with 3glycidyloxypropyl-trimethoxysilane resulted in a dense, pore-free coating possessing high emissivity (ε = 0.79–0.81). Phase analysis confirmed the absence of impurity in the film, whereas microscopic analysis showed that the number of passes of the spray coating method could not modify the surface topography of the film significantly. Due to the intrinsic property of ZrB2 , the emissive behavior recorded in the infrared range was invariant with an increase in coating thickness (60–280 µm). It is believed that the deposition process of ZrB2 coating developed in this study may open up new possibilities in the field of radiative films for thermal management applications. Acknowledgements The authors thank Mr. Srinivas, CSIR-NAL for FTIR measurements. Research at CSIR-NAL is partially supported by the Department of Science and Technology (DST), New Delhi (U-1-144). AD acknowledges DST for providing INSPIRE scholarship, and NKG acknowledges the support from the Center of Excellence in Hypersonics.

References 1. L. del Campo, M.D. De Sousa, A. Blin, B. Rousseau, E. Véron, M. Balat-Pichelin et al., Hightemperature radiative properties of an Yttria-Stabilized Hafnia Ceramic. J. Am. Ceram. Soc. 94, 1859–1864 (2011)

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2. A. Dan, H.C. Barshilia, K. Chattopadhyay, B. Basu, Solar energy absorption mediated by surface plasma polaritons in spectrally selective dielectric-metal-dielectric coatings: a critical review. Renew. Sustain. Energy Rev. 79, 1050–1077 (2017) 3. X. He, Y. Li, L. Wang, Y. Sun, S. Zhang, High emissivity coatings for high temperature application: Progress and prospect. Thin Solid Films 517, 5120–5129 (2009) 4. G. Shao, X. Wu, S. Cui, J. Jiao, X. Shen, Design, formation, and property of high emissivity WSi2 -Si-glass hybrid coating on fibrous ZrO2 ceramic for reusable thermal protection system. Sol. Energy Mater. Sol. Cells 172, 301–313 (2017) 5. Y. Wang, D. Su, H. Ji, X. Li, Z. Zhao, H. Tang, Gradient structure high emissivity MoSi2 -SiO2 SiOC coating for thermal protective application. J. Alloy. Compd. 703, 437–447 (2017) 6. D. Mahadik, S. Gujjar, G.M. Gouda, H.C. Barshilia, Double layer SiO2 /Al2 O3 high emissivity coatings on stainless steel substrates using simple spray deposition system. Appl. Surf. Sci. 299, 6–11 (2014) 7. S.S. Hwang, A.L. Vasiliev, N.P. Padture, Improved processing and oxidation-resistance of ZrB2 ultra-high temperature ceramics containing SiC nanodispersoids. Mater. Sci. Eng. A 464, 216–224 (2007) 8. A. Dan, K. Chattopadhyay, H.C. Barshilia, B. Basu, Shifting of the absorption edge in TiB2 /TiB (N)/Si3 N4 solar selective coating for enhanced photothermal conversion. Sol. Energy 173, 192–200 (2018) 9. W. Tan, C.A. Petorak, R.W. Trice, Rare-earth modified zirconium diboride high emissivity coatings for hypersonic applications. J. Eur. Ceram. Soc. 34(1), 1–11 (2014) 10. M. Zhang, G. Yang, L. Zhang, Y. Zhang, J. Yin, X. Ma, J. Wen, L. Dai, H. Chen, L. Zhang, L. Yin, Application of ZrB2 thin film as a low emissivity film at high temperature. Appl. Surf. Sci. 527, 146763 (2020) 11. Y. Li, X. Yang, W. Wang, Y. Chen, J. Li, Reaction behavior, microstructure, and radiative properties of in situ ZrB2 -SiC ceramic composites from a Si-Zr-B4 C system. J. Mater. Eng. Perform. 1, 1–8 (2020) 12. A. Purwar, R. Mukherjee, K. Ravikumar, S. Ariharan, N.K. Gopinath, B. Basu, Development of ZrB2 –SiC–Ti by multi stage spark plasma sintering at 1600 °C. J. Ceram. Soc. Jpn. 124, 393–402 (2016) 13. N.K. Gopinath, G. Jagadeesh, B. Basu, Shock wave-material interaction in ZrB2 –SiC based ultra high temperature ceramics for hypersonic applications. J. Am. Ceram. Soc. 102, 6925– 6938 (2019) 14. C.G. Granqvist, Solar energy materials. Adv. Mater. 15, 1789–1803 (2003) 15. X. Wang, H. Li, X. Yu, X. Shi, J. Liu, High-performance solution-processed plasmonic Ni nanochain-Al2 O3 selective solar thermal absorbers. Appl. Phys. Lett. 101(20), 203109 (2012) 16. T Soga, Nanostructured Materials for Solar Energy Conversion. (Elsevier, 2006) 17. A. Dan, A. Soum-Glaude, A. Carling-Plaza, C.K. Ho, K. Chattopadhyay, H.C. Barshilia, B. Basu, Temperature-and angle-dependent emissivity and thermal shock resistance of the W/WAlN/WAl2 ON/Al O3-based spectrally selective absorber. ACS Appl. Energy Mater. 2(8) 5557–5567 (2019) 18. G. Song, S. He, F. He, Y. Yao, J. Li, M. Li, X. He, Effect of doping graphene oxide on the structure and properties of SiO2 based high emissivity coatings. J. Appl. Polym. Sci. 137(23), 48794 (2020) 19. D.L. Domtau, J. Simiyu, E.O. Ayieta, G.M. Asiimwe, J.M. Mwabora, Influence of pore size on the optical and electrical properties of screen printed thin films. Adv. Mater. Sci. Eng. (2016) 20. A. Agrawal, A. Singh, S. Yazdi, A. Singh, G.K. Ong, K. Bustillo, R.W. Johns, E. Ringe, D.J. Milliron, Resonant coupling between molecular vibrations and localized surface plasmon resonance of faceted metal oxide nanocrystals. Nano Lett. 17(4), 2611–2620 (2017)

Role of Semiconductors in Various Renewable Energy Systems Neha Lyka Muttumthala and Apurv Yadav

1 Introduction Technological advancements in renewable energy are essential to deal with the global energy crisis and increasing demands, as well as the detrimental effects and depletion of non-renewable fossil fuels. Out of all sources of renewable energy—wind, solar, geothermal, biomass, hydrothermal—solar energy is, currently, the most abundant of all renewable resources; 1.6 × 1011 MW of power reaches the earth’s surface from the year [1], which is 1000 more times than all fossil fuels combined [1, 2]. Working toward sustainable development from the perspective of energy would take major technological changes involving energy demand, efficiency, and the phasing out of non-renewable sources—reserves of which are expected to be depleted in the next 30 years or less [3]. Current trends of fossil fuel usage, however, are resulting in critical environmental conditions worldwide [4]; this urges the switch to renewable energy sources. Radiation incident on earth’s surface, if harnessed correctly, is more than sufficient for present and expected energy requirements, despite being a diffused source of light. The utilization of solar energy has surged by over 20% in the past decade despite high installation costs and geographic limitations—and will continue to rise, as it becomes more and more economically viable [4]. Semiconductor materials are instrumental in the harnessing of this energy, as it is most efficient in absorbing electromagnetic radiation in the visible spectrum. Silicon, being the second most abundant element in the lithosphere, is primarily used [5]. This paper explores the applications of the same in renewable solar energy systems in particular. N. L. Muttumthala (B) · A. Yadav Amity University Dubai, Dubai, United Arab Emirates e-mail: [email protected] A. Yadav Amity Institute of Renewable and Alternate Energy, Noida, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_17

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2 Types of Renewable Energy Conversion A.

Conversion to Electrical Energy

Solar or PV arrays are capable of generating thousands of kilowatts of electric power. Presently, individual PV cells have an efficiency of about 15–20%. In individual photovoltaic cells, about 2 watts of energy are produced. The efficiency of PV arrays as a whole, however, just falls short—this accounts for inevitable faults in the system [6]. To maximize efficiency, PV technology accompanied with solar trackers may be used to identify the optimal location for their installment, but this is only economically justifiable if employed in large-scale energy generation plants [7]. (1) (2)

(3)

On a small scale: artificial lighting is sufficient to power calculators or watches. On a large scale: PV arrays are capable of powering industries, commercial buildings, as well as in homes as a source of power—either as a complete replacement of their regular power supply or simply augment it. As they do not have any moving parts, PV panels and arrays are ideal in (a) (b)

B.

Space applications: Only within the solar system as any external factors come into play; weight, efficiency, surface area, etc. Remote/ inaccessible regions: Conventional sources are expensive or difficult to maintain.

Conversion to Thermal Energy

Solar energy can be concentrated to be utilized as a heat source by a variety of methods—flat-plate collectors, for example, are often used for solar heating applications [8]. The plates must, however, cover large surface areas of about 40 m2 to satisfy the energy needs of a single individual [9]. When energy generation plants utilize these techniques, this heat energy may be converted to electrical energy that is sufficient for thousands of people. Apart from flat-plate collectors, solar ponds containing saltwater are often used in industrial products, i.e., chemical, food, textile, etc., or heating systems in greenhouses, swimming pools, and livestock buildings. On a smaller scale, sunlight can be harnessed passively; • Solar cookers—both portable and self-sufficient. • Heat absorbent paint and dyes—replacement for building heating. • Heat absorbent plates—replacement for water heating.

3 Photovoltaic Cells A.

Construction

For a majority of PV cells used, silicon is used in its fabrication, ranging from non-crystalline, amorphous (α-Si) silicon to varying crystalline (multi- and monocrystalline) forms which are used in high-efficiency solar cells. Its oxides are also used

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Fig. 1 Structure of a solar cell

as an anti-reflection material. The other semiconductor materials most commonly used are either elemental, i.e., silicon, gallium; or alloys involving semiconductors, i.e., gallium arsenide (GaAs), indium phosphide (InP), and copper indium selenide [10]. Silicon technology dominates in energy generation via PV devices (Fig. 1). B.

Working

The source of radiation is the sun’s light or photons, which strike the “absorber layer” of a PV cell, which is a junction involving a semiconductor, such as silicon. This striking of photons causes: • Formation of electron–hole pairs (excitons), • The electrons to be excited to higher energy states, and • The electrons flow through the external circuit and in turn, produce a direct (DC) current. The latter step can only take place in presence of an electric voltage, which is in-built; dissimilar semiconducting materials are placed next to one another causing the generation of a small voltage—otherwise, the motion these electrons take on is randomized and disorganized.

4 Types of Photovoltaic Cells A.

Thin-Film Photovoltaics

The primary advantage of thin-film PV cells is the cost factor. It also has the smallest ecological impact. The cell’s efficiency, however, would be the point of compromise.

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Here, a thin film of the active material is placed (by printing, coating, or vacuumdeposition) on a variety of substrates such as glass, this makes these cells much heavier than conventional PVs [11]. (1) (2) (3)

Amorphous silicon (α-Si): most redundant due to lesser efficiency and tendency to degrade on light exposure, but utilizes the least silicon and is least toxic. Cadmium telluride (CdTe): most used after silicon, cheap to manufacture, however, its commercial applications are limited due to cadmium’s toxicity. Copper indium gallium diselenide (CIGS): has the highest efficiency (~20%), but the manufacture of this lab-standard efficiency is difficult due to the number of elements.

The latter two are most promising and are close competitors (efficiency-wise) with conventional crystalline silicon PVs, which account for over 55% of the PV market. Their most attractive trait is their direct bandgap (which permits minimal material usage), low-temperature co-efficient, and ability to be integrated into buildings (BIPV). Both thin-film and classic crystalline silicon PVs are often used on rooftops to either replace or augment conventional electricity supply. However, in terms of how efficient, long-lasting, and reliable they are, more consumer trustworthiness needs to be put in for thin-film PVs to be put to use in BIPVs. B.

Organic PV (OPV)

Organic PV cells are currently only half as effective and have shorter operating lifetimes in comparison with crystalline silicon cells [12]. However, the advantages they possess over these conventional PVs are. • The ability for specific characteristics—such as bandgap, and transparency—to be tweaked, by tailor-fitting the organic, carbon-containing, compounds in them. • A large number of applications due to being able to be fabricated over materials like flexible plastic. • An economic advantage—particularly when manufactured in large quantities. C.

Concentration Photovoltaic cells (CPV)

As the intensity of radiation incidents on the earth is relatively low (as it is diffused), PV arrays must cover vast areas to harness moderate amounts of energy, making the price to output ratio less desirable (initially). Concentration PV cell power plants employ precisely aligned p [13]. Parabolic mirrors and lenses to concentrate light incident on a vast area onto a receiver– intensifying it by over a 100-fold—and are often accompanied by expensive solar tracking technology, making CPVs heavily capital intensive but high-efficiency. The heat generated by this process can reach up to 2,000 °C, which can then be used to generate current electricity via steam turbines. D.

Multijunction Photovoltaic cells

Conventional PV cells are capable of absorbing electromagnetic radiation of specific wavelengths within the visible region equivalent to its bandgap, leaving the rest of the solar spectrum unabsorbed. The number of junctions corresponds to the number

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Fig. 2 Multijunction solar cell

of band gaps [14]. Each bandgap absorbs regions of the spectrum that are unabsorbed by the other band gaps in the other junction layers, allowing a wide region of the spectrum to be absorbed (Fig. 2). Every PV cell with more than one junction (and hence band gap) falls under the category of a multijunction solar cell. The main types are i. ii.

Tandem solar cells: possess two junctions/band gaps. Multijunction III-V solar cells: group III and V (or 13 and 15) of the periodic table materials are used.

Multijunction PV cells are able of reaching tremendously high efficiencies (over 45%). The cost to efficiency ratio is desirable where it, as well as difficult to produce, is justifiable, i.e., research and space and military applications.

5 Emerging PV Technologies A.

Thermophotovoltaics

A new subset of photovoltaic which is currently developing uses heat or infrared (IR) radiation to generate electricity. This overcomes the disadvantage of conventional PVs of not being able to generate electricity during times of low light [15] (Fig. 3).

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Fig. 3 Mechanism of thermophotovoltaics

It does, however, require fuels (i.e., natural gas) for heat generation –but the use of conventional diesel generators is omitted, and semiconductors are used for higher efficiency fuel-to-electricity conversion. Additional advantages to this system are its reliability, minimal pollution, and quiet operation. B.

Perovskites in solar cells

Perovskite materials, named after a certain crystal structure, are utilized in thin-film technology. Developments in increasing their efficiency have been the fastest among all PV materials—over 20% since first reported in 2009. Their efficiencies have also developed faster than any other PV and are close approaching that of α-Si PV cells, they are also relatively easy to recreate [16]. Further research, however, needs to be put into its stability (must be durable for a minimum of 20 years) to be commercially manufactured. Once that is achieved, they must be able to be produced in large volumes, preferably at lower costs. C.

Quantum dots (QD)

The advantage QD solar cells possess is primarily its tweak-able bandgap; the region of the electromagnetic spectrum of light absorbed can be maximized. This makes them ideal in multijunction PV cells with say, perovskite materials. They are also quite easy to fabricate; they can be done at room temperature, using substrates and varying semiconductor nanocrystals [17]. This, however, complicates it from an

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electrical perspective; on their own, the efficiency of QD solar cells is not too desirable. Currently, stability, efficiency, and ability to mass-produce are current areas of weakness.

6 Conclusion The depletion of non-renewable resources and simultaneous detriment and irreversible damage caused by the process makes the need to shift to renewable resources sooner. Solar energy is in abundance and its poses zero threat to the environment, making its exploitation ethical. Silicon and semiconductor materials alike are key components in harnessing this energy—via photovoltaic systems—to convert it to numerous usable forms. PV cells are numerous and each has characteristic traits making them available for a wide range of novel applications. PV technology is nowhere near the end of its lifetime, we are only beginning to explore the potential of this vast, multifaceted, and versatile field. More research, consumer trust, and capital need to be invested to be able to make the harnessing of this inexhaustible resource more accessible and economically to every part of the world.

References 1. B. Parida, S. Iniyan, R. Goic, A review of solar photovoltaic technologies. Renew. Sustain. Energy Rev. 15(3), 1625–1636 (2011) 2. S.R. Bull, Renewable energy today and tomorrow. Proc. IEEE 89(8), 1216–1226 (2001) 3. R.F. Aguilera, R G. Eggert, G.L. CC, J. E. Tilton, Depletion and the future availability of petroleum resources. Energy J. 30(1) (2009) 4. Solar energy, https://www.britannica.com/science/solar-energy/Electricity-generation. Last accessed 22 Dec 2020 5. Solar energy, https://www.britannica.com/technology/solar-cell. Last accessed 22 Dec 2020 6. T. Saga, Advances in crystalline silicon solar cell technology for industrial mass production. npg Asia Mater. 2(3), 96–102 (2010) 7. G.K. Singh, Solar power generation by PV (photovoltaic) technology: A review. Energy 53, 1–13 (2013) 8. L.A. Chidambaram, A.S. Ramana, G. Kamaraj, R. Velraj, Review of solar cooling methods and thermal storage options. Renew. Sustain. Energy Rev. 15(6), 3220–3228 (2011) 9. T. Beikircher, M. Möckl, P. Osgyan, G. Streib, Advanced solar flat plate collectors with full area absorber, front side film and rear side vacuum super insulation. Sol. Energy Mater. Sol. Cells 141, 398–406 (2015) 10. M.A. Green, Solar cells: operating principles, technology, and system applications. Englewood Cliffs (1982) 11. H.W. Schock, Thin film photovoltaics. Appl. Surf. Sci. 92, 606–616 (1996) 12. B. Kippelen, J.L. Brédas, Organic photovoltaics. Energy Environ. Sci. 2(3), 251–261 (2009) 13. A.L. López, V.M. Andreev (Eds.),Concentrator Photovoltaics, vol. 130. (Springer, Berlinm, 2007) 14. D. Wilt, M. Stan, High efficiency multijunction photovoltaic development. Ind. Eng. Chem. Res. 51(37), 11931–11940 (2012)

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15. D. Chubb, Fundamentals of Thermophotovoltaic Energy Conversion (Elsevier, 2007) 16. M.A. Green, A. Ho-Baillie, H.J. Snaith, The emergence of perovskite solar cells. Nat. Photonics 8(7), 506–514 (2014) 17. A.J. Nozik, Quantum dot solar cells. Physica E 14(1–2), 115–120 (2002)

Design of Photovoltaic System for DC Pumping Unit Apurv Yadav, Abhishek Verma, P. K. Bhatnagar, and V. K. Jain

1 Introduction In today’s era, energy reserve capacity is a necessity for the economic advancement of a nation [1]. Hence, energy demand is perpetually increasing throughout the globe [2]. Conventional sources of energy, mainly fossil fuels are not sufficient to level up to this surge in energy demand [3]. In addition to this, they are a major contributor to pollutants in the environment. Environmental regulation agencies in association with many governments are formulating policies to regulate pollution emerging from energy generation [4]. Systematic implementation of renewable energy systems can help in reducing pollution and increasing the energy supply. These systems integrated with energy storage can also increase the dependency of these systems [5]. Therefore, more research is now focused on increasing the efficiency of renewable energy systems. Conventional fuels are being blended with biofuels [6]. The efficiency of solar-based energy storage systems is being enhanced [7, 8]. Wind energy systems are being modified using artificial intelligence [9]. Performance of various energy systems is being improved using phase change materials. Among all the renewable energy sources, solar energy has considerable potential. The reason for this is that solar photovoltaic (PV) is the most economical form A. Yadav (B) Solar and Alternate Energy, Department of Engineering, Amity University Dubai, Dubai, UAE e-mail: [email protected] A. Yadav · A. Verma · V. K. Jain Amity Institute of Renewable and Alternate Energy, Amity University, Noida, India A. Verma · V. K. Jain Amity Institute of Advanced Research and Studies (Materials & Devices), Amity University, Noida, India P. K. Bhatnagar Department of Electronic Science, University of Delhi, New Delhi, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_18

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of renewable energy generation technology. However, PV installation needs proper design and simulation before the fieldwork can be initiated [10, 11]. Designing a solar PV plant depends on various factors such as geographical latitude, climatic conditions, average daily incident sunlight, tilt angle, azimuth angle [12]. These factors drastically affect the overall output produced by a solar system. Helioscope is online software that simplifies the process of PV plant designing and provides an almost accurate energy generation report [13]. Design and modifications can be done based upon the actual space of the location, weather conditions and geographical factors. The effect on energy generation with the modification in design can be analyzed within few minutes. The software also generates a CAD editable single line diagram for the photovoltaic plant. In this study, a photovoltaic system is designed on Helioscope for a DC pumping unit at the renewable energy laboratory of Amity University Dubai.

2 Location The location is situated in the Nad Al Sheba region of Dubai, United Arab Emirates. The location is 82.28 m above mean sea level on the latitude and the longitude of 24’99° and 55’31°, respectively. The Google satellite image of the location is shown in Fig. 1. Fig. 1 Google satellite image of Amity University Dubai

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3 Designing of a PV System The energy required for the 1-hour operation of the pump is obtained from the SEnergy Chiller system from Emircom installed at Amity University Dubai Laboratory. The energy requirement obtained was 2.8 kW. According to the location data and structure of the facility, grid-connected solar power plant was found suitable. Monocrystalline solar panels from Canadian Solar, model CS6P-210P, are selected for the design. The panel has rated maximum power of 210 Wp and voltage and current values at maximum power were 29 V and 7.25 A, respectively. The opencircuit voltage and short circuit current of the panel are 36.4 V and 7.89 A, respectively. The panel has a temperature coefficient of power of −0.45%/°C. The panel weighs 20 kg and dimensions of 1638 mm × 982 mm × 40 mm. The maximum system voltage is 600 V and a series fuse rating of 15 A. At the panel tilt angle of 15°, azimuth angle of 39° in landscape orientation and intra-row spacing of 1.6 ft, the minimum loss is predicted by Helioscope. This design accommodated a total of 15 modules on the university roof as shown in Fig. 2. The performance ratio (PR) of a plant for a period of time is calculated by the following formula: PR =

Energy Measured (kWh)    kWh  Irradiance on panel m2 × Area of panels m2 × module efficiency

A 3 kW rating inverter from ABB model PVI-3.0-OUTD-S-US-ZA is selected for DC to AC conversion. Generic AC distribution box, DC distribution box, earthing systems, lightning arrestors and cables were selected. A single line diagram for the PV plant is presented in Fig. 3. Fig. 2 Arrangement of solar modules on the laboratory roof

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Fig. 3 Single line diagram for the photovoltaic system

4 Results and Discussion The shading heat map of the PV plant is shown in Fig. 4 and the monthly solar access and AC energy generation is provided in Table 1. It shows that at least 98.9% irradiance is available throughout the year. The monthly energy production data is presented in Fig. 5 and the losses on account of various factors are presented in Fig. 6. The performance ratio of the designed plant is 78.40% which is well above the minimum allowed value of 70%. It is a measure for the performance of a PV system taking into account environmental factors (temperature, irradiation, climate changes, etc.) Annual irradiance from the sun to the irradiance received at the modules are presented in Table 2. The annual energy received and energy generation chart on account of the losses is presented in Table 3a

Fig. 4 Shading heat map of the PV panels

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Table 1 Monthly solar access Months

Solar access (%)

AC power (kWh)

Soiling (%)

January

99.1

242.6

2

February

98.9

274.2

2

March

98.9

378.8

2

April

99

448.3

2

May

98.9

531.9

2

June

98.9

518.6

2

July

98.9

489.9

2

August

99

477

2

September

99.2

397.4

2

October

99.2

340.8

2

November

99.1

258.8

2

December

99

215.1

2

Fig. 5 Monthly energy generation from the PV system

5 Conclusion An on-grid photovoltaic plant of 3 kW has been designed on Helioscope. The plant is designed to fulfill the load requirements of the DC pumping unit of the renewable energy laboratory at Amity University Dubai. The designed plant is generating approximate annual energy of 5.45 MWh out of which, due to various losses, approximately 4.57 MWh is can be supplied to the system. After the required energy consumption by the chilling unit, the rest can be supplied to the grid. The plant shows an average performance ratio of 78.4% which is a good value in determining the feasibility of operation of the plant. More design modifications can be done through Helioscope and the effect on the performance of the plant can be simulated.

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Fig. 6 Sources of losses in the PV plant

Table 2 Monthly irradiance

Table 3 Annual energy

Irradiance (kWh/m2 ) Description

Output

Annual global horizontal irradiance

2009.2

POA irradiance

1851.2

% loss −7.9

Shaded irradiance

1832.5

−1.0

Irradiance after reflection

1762.6

−3.8

Irradiance after soiling

1727.4

−2.0

Total collector irradiance

1727.2

0.0

Energy (kWh) Description

Output

DC nameplate

5447.2

% loss

Output at iradiance levels

5415.3

−0.6

Output at cell temperature derate

4896.7

−9.6

Output after mismatch

4803.5

−1.9

Optimal DC output

4794.7

−0.2

Constrained DC output

4794.6

0.0

Inverter output

4596.4

−4.1

Energy to grid

4573.4

−0.5

References 1. Renewables 2019 Global Status Report, (2019). wedocs.uep.org/handle/20.500.11822/28496. Last accessed /2 May 2020

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2. H. Karunathilake, K. M. Nahiduzzaman, T. Prabatha, K. Hewage, R. Sadiq, S. Alam, P. Shaw, The nexus of climate change and increasing demand for energy: a policy deliberation from the Canadian context. Dyn. Energy. Environ. Econ. 263–294 (2020) 3. F. Johnsson, J. Kjärstad, J. Rootzén, The threat to climate change mitigation posed by the abundance of fossil fuels. Clim. Policy 19(2), 258–274 (2019) 4. I. Solorio, H. Jörgens, Contested energy transition? Europeanization and authority turns in EU renewable energy policy. J. Eur. Integr. 42(1), 77–93 (2020) 5. K. Wang, S. Chen, L. Liu, T. Zhu, Z. Gan, Enhancement of renewable energy penetration through energy storage technologies in a CHP-based energy system for Chongming, China. Energy 162, 988–1002 (2018) 6. A. Yadav, M.K. Shivhare, V.K. Vashishtha, H. Yadav, Nanofuels: an advancement in biodiesel applications, in Recent Advances in Mechanical Engineering (Springer, Singapore, 2021), pp. 509–514 7. C. Prieto, L.F. Cabeza, Thermal energy storage (TES) with phase change materials (PCM) in solar power plants (CSP). Concept and plant performance. Appl. Energy254, 113646 (2019) 8. H. Huang, Y. Xiao, J. Lin, T. Zhou, Y. Liu, Q. Zhao, Improvement of the efficiency of solar thermal energy storage systems by cascading a PCM unit with a water tank. J. Cleaner Prod. 245, 118864 9. X. Zhao, C. Wang, J. Su, J. Wang, Research and application based on the swarm intelligence algorithm and artificial intelligence for wind farm decision system. Renew. Energy 134, 681– 697 (2019) 10. S. Sindhu, Assessment, simulation and analysis of PV power generation for educational buildings of a rural women’s university in India: a case study. Int J. Energy Technol. Policy 17(1), 61–85 (2021) 11. A. Allouhi, M.S. Buker, H. El-houari, A. Boharb, M.B. Amine, T. Kousksou, A. Jamil, PV water pumping systems for domestic uses in remote areas: Sizing process, simulation and economic evaluation. Renew. Energy 132, 798–812 (2019) 12. A.A. Babatunde, S. Abbasoglu, M. Senol, Analysis of the impact of dust, tilt angle and orientation on performance of PV plants. Renew. Sustain. Energy Rev. 90, 1017–1026 (2018) 13. S. Goel, R. Sharma, Analysis of measured and simulated performance of a grid-connected PV system in eastern India. Environ. Dev. Sustain. 1–26

Glycerol Material’s Impact on Growth of Microalgae for Sustainable Renewable Energy Production Rupesh Kumar Basniwal, S. Shankara Narayanan, and V. K. Jain

1 Introduction Conventional fossil fuels such as coal are vanishing from the market at a fast rate. The demand for a reliable renewable fuel source has been increasing in the last two decades due to the high price of oil products. This demand will continuously rise unless we search for a new alternative source of energy. The monopoly of the oil-producing countries and the limited stocks of conventional fossil fuels will be increasing the price of petroleum product. That will ultimately affect the growth of the country. This has motivated the world’s eminent scientists and technocrats in search of economical, renewable and environmental-friendly fuel. As matching, properties with conventional petroleum fuel plant-derived biofuels are also good alternative source of energy. In plant-derived biofuel, algae are becoming the most prominent energy source because of their extraordinary characteristics. They are considered as the safer, non-competitive and rapidly growing organism among other existing plant organisms. Scientists explained that they grow on waste materials without much care and are away from the fuel versus food debate [1, 2]. Moreover, they are sustainable and much more in quantity as compared to conventional plants and crops. Algae had a different percentage of lipid in their cell structure which changes from species to species [3, 4]. As compared to conventional crops like soybeans and palm, some algae have a much higher lipid content [5, 6]. Another capability R. K. Basniwal (B) · V. K. Jain Amity Institute for Advanced Research and Studies (Materials and Devices), Amity University Utter Pradesh, Noida, Uttar Pradesh 201303, India e-mail: [email protected] S. Shankara Narayanan Material Research Laboratory, Department of Physics, School of Basic Sciences and Research, Sharda University, Greater Noida, Uttar Pradesh 201310, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_19

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of algae is that they can remove toxic elements from wastewater in a very diligent manner. Remediating role in wastewater treatment and higher lipid content makes them a suitable candidate for large-scale cultivation and biofuel production [6, 7]. Conventional fossil fuels contain sulphur and nitrogen elements, which are majorly responsible for environmental pollution. We can overcome this pollution problem by using algal biofuel because they do not contain nitrogen and sulphur. The same thing was reported by Haas et al. in the year 2001 that algal biodiesel can reduce emissions of total hydrocarbons, particulates and carbon monoxide up to 55%, 53% and 48%, respectively, as compared to conventional petro-diesel [8]. Rapid biodegradability, safer and environmentally friendly nature of algal biodiesel makes them a suitable choice for the current renewable energy-based industry. The most extensive research into the development of renewable biofuels from algae was performed by the National Renewable Energy Laboratory (NREL) from 1978 to 1996 [9]. The advantage of using algae is that they can be grown in a controlled manner in a photobioreactor, and their genetic engineering makes them a suitable and economical source of renewable fuel [10]. Higher growth and oil content, survivability on wastewater, emitting less sulphur and nitrogen pollutants during combustion of the fuel are some of the supporting factors for the large-scale production of algal strain, which ultimately turn into a source of renewable energy (biodiesel). After large-scale culturing of the algae, it requires some chemical or mechanical steps to extract oil from it. The extracted oil cannot be used directly in an automobile engine because of its higher viscosity. The viscosity of the algal oil can be reduced through a process known as transesterification reaction. Glycerol, a by-product of this reaction, is produced along with biodiesel. Generally, glycerol is discarded after separating biodiesel from the reaction mixtures. If we can reutilize this glycerol for the growth of the algae process for biodiesel production, it will be more economical and sustainable. In the current study, we have analysed the impact of glycerol material on the growth of algal species known as Chlorella sp.

2 Materials and Methods Organism and growth conditions Culture of green alga Chlorella sp. was obtained from Indian Agricultural Research Institute (IARI), New Delhi, India. The cultures were grown in a standard BG-11 medium in Erlenmeyer flasks at 3–4 Klux intensity of fluorescent white light for 16 h/8 h alternate cycles of light and dark in a photo-incubator at 30 °C. The cultures were manually hand-shaken 3–4 times daily to avoid the problem of culture sticking onto the bottom of the flask. Before starting the experiments, all the glasswares were sterilized at 121 °C temperature and 15 lb/inch2 pressure. No additional supply of CO2 was provided for the culture growth. They were grown under the naturally present CO2 in the environment. Each experiment was carried out in triplicates for result precision and for reducing the error in scientific data. Exponential phase cells were used for inoculum. Control algal

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culture flask containing only medium and inoculum showed autotrophic growth. Other experimental flasks with the medium and algal culture having additional glycerol material (as a carbon source) with different concentrations showed mixotrophic growth. Algal growth in the presence of glycerol To study the growth under mixotrophic conditions, glycerol was added into the experimental medium (except the control flask) as a carbon source at concentrations of 1%, 2% and 3%. Cell growth analysis For observing algal cell growth at different time intervals, a small amount of culture was taken from the sample culture flask, and their growth was monitored through microscope and spectrophotometer by taking their optical density (OD) measurement at 660 nm. Initial culture’s OD was measured to be 0.1 through the spectrophotometer. After attaining good proliferation and optimum growth, algal cell culture was subjected to centrifugation at 10,000 rpm for 10 min to collect the biomass in the form of a pellet. The pellet was then cleaned with distilled water twice to remove contaminants and salts. These centrifuged cultures were further dried at 105 °C for dry weight. Dry weight can be expressed in the form of gram per litre, i.e. g/l. Biomass concentration and biomass productivity were calculated according to the following formula: Biomass concentration (g/m3 ) = mass of culture/volume and biomass productivity (g/m3 .d) = mass of the culture/volume x days.

3 Results and Discussion In comparison with the autotrophic culture, mixotrophic culture has two energy sources: organic carbon source and light. Initially, scientists believed that the catabolism of organic substrate and photosynthesis is independent of each other [11]. However, recent studies showed that photosynthesis capability reduced in the presence of an organic component in the medium [12]. Instead, the presence of organic compounds enhanced respiration rate significantly in mixotrophic culture for assimilation of carbon source to produce energy and is, therefore, less dependent on light [13]. The present study reveals that microalgal strain Chlorella sp. can grow mixotrophically in the presence of glycerol carbon source and exhibit various effects on its cell growth. Figure 1 and Fig. 2 show mixotrophic growth of algae in the presence of different concentrations of glycerol material, and Fig. 3 reveals an algal growth curve in presence of glycerol (control and 1%). In the curve, the lag phase is the adaption phase, in which culture try to adapt themselves to the new environment, so the growth rate is very slow at this stage. Log phase indicates a higher growth rate of the culture due to the availability of lots of nutrients in the medium. Continuous consumption of nutrients from the growth medium by organism results in depletion of nutrients after

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Fig. 1 Growth of algae at different concentrations of glycerol (from left to right) 0% (i.e. control), 1%, 2% and 3%

Fig. 2 Comparison of Algal growth between control (left) and 1% glycerol (right)

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0.8 0.7

Absorbance (OD)

0.6 0.5 0.4

Control

0.3

1% Glycerol

0.2 0.1 0 1

2

3

4

5

6

7

8

Time (Days)

Fig. 3 Growth of algae in the presence of glycerol in the control experiment and at 1% glycerol concentration

some days. At this stage, growth nutrient becomes a limiting factor for the algal cell growth, and this results in arresting cell growth. This stage is known as the stationary phase. The stationary phase comes just after the log phase; at this stage, almost no change or limited change in optical density can be seen for the culture. It means algal growth is arrested in this phase due to the limited supply of nutrients. Mixotrophic cultures show better growth as compared to autotrophic control as shown in Figs. 1, 2 and 3. Best growth was observed in a 1% glycerol containing culture flask (Figs. 2 and 3). Maximum biomass production of 0.185 g was achieved with a 1% glycerol concentration. The addition of glycerol material enhanced the algal growth by 3.49 times as compared to control. At higher concentration (more than 2%), that material showed toxicity due to disturbance of the internal cell metabolism environment. Therefore, ≤ 1% volume fraction of carbon sources as glycerol is more effective instead of their higher concentration. As per Hongyan et al., the algae cannot grow when the glycerol addition is higher than 1%. [14]. This is in parity with the result of Liang et al. [15]. They reported that 1% glucose (carbon source) supports the growth of Chlorella vulgaris algae, and higher concentrations were inhibitory for them. According to Orosa et al., carbon source such as sodium acetate concentration > 2.5% was toxic for organism culture growth [16]. In that study, they added sodium acetate as a carbon supplement instead of glycerol material for the organism growth. In contrast, the present work shows an effective way to manage surplus glycerol by-product which generally produces in transesterification reactions of the biodiesel production process. That makes the biodiesel production process more economical and sustainable [17]. Other scientists have reported the work for Chlorella prtothecoides algal species, and they increased biomass 1.6 and 1.28 times with the addition of glycerol and acetate, respectively [18].

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4 Conclusions The current study is related to glycerol material’s impact on the growth of algae, i.e. Chlorella sp. This investigation provides an effective approach for the mixotrophic growth of Chlorella sp. to enhance the growth and biomass. The culture grown in the presence of organic glycerol material showed a higher growth rate. That paves the path for the competent, effective, economical and sustainable biodiesel production process. Before going to commercial production of algal biomass, knowing the optimum concentration of glycerol material is the necessity of the process. In future, the utilization of glycerol material for algal growth enhancement and biodiesel production will be preferable due to the green and renewable process. Thus, the process helps in waste management, and their economical and sustainable approach makes them a perfect choice for future generation for the biodiesel production process. Acknowledgements The authors wish to express gratitude to the Founder President of Amity University, Dr Ashok K. Chauhan, and Sharda University for their encouragement and support.

References 1. V. Patil, K.Q. Tran, H.R. Giselrød, Towards sustainable production of biofuels from microalgae. Int. J. Mol. Sci. 9(7), 1188–1195 (2008) 2. G.W. Roberts, M.O.P. Fortier, B.S. Sturm, S.M. Stagg-Williams, Promising pathway for algal biofuels through wastewater cultivation and hydrothermal conversion. Energy Fuels 27(2), 857–867 (2013) 3. Y. Chisti, Biodiesel from microalgae. Biotechnol. Adv. 25(3), 294–306 (2007) 4. Y. Chisti, Constraints to commercialization of algal fuels. J. Biotechnol. 167(3), 201–214 (2013) 5. M.K. Lam, K.T. Lee, Renewable and sustainable bioenergies production from palm oil mill effluent (POME): win-win strategies toward better environmental protection. Biotechnol. Adv. 29(1), 124–141 (2011) 6. D.C. Kligerman, E.J. Bouwer, Prospects for biodiesel production from algae-based wastewater treatment in Brazil: a review. Renew. Sustain. Energy Rev. 52, 1834–1846 (2015) 7. J.K. Pittman, A.P. Dean, O. Osundeko, The potential of sustainable algal biofuel production using wastewater resources. Bioresour. Technol. 102(1), 17–25 (2011) 8. M.J. Haas, K.M. Wagner, T.L. Alleman, R.L. McCormick, Engine performance of biodiesel fuel prepared from soybean soapstock: a high-quality renewable fuel produced from a waste. Feedstock Energy Fuels 15(5), 1207–1212 (2001) 9. J. Sheehan, T. Dunahay, J. Benemann, P. Roessler, A look back at the U.S. department of energy’s aquatic species programme biodiesel from algae. Nat. Renew. Energy Lab. NREL/TP580-24190 (1998) 10. C.Y. Chen, K.L. Yeh, R. Aisyah, D.J. Lee, J.S. Chang, Cultivation, photobioreactor design and harvesting of microalgae for biodiesel production: a critical review. Bioresour. Technol. 102(1), 71–81 (2011) 11. T. Ogawa, S. Aiba, Bioenergetic analysis of mixotrophic growth in Chlorella Vulgaris and Scendesmus acutus. Biotechnol. Bioeng. 23(5), 1121–1132 (1981)

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12. C. Yang, Q. Hua, K. Shimizu, Energetics and carbon metabolism during growth of microalgal cells under phototrophic, mixotrophic and cyclic light-autotrophic/dark heterotrophic growth condition. Biochem. Eng. J. 6(2), 87–91 (2000) 13. X.J. Liu, S.S. Duan, A.F. Li, N. Xu, Z.P. Cai, Z.X. Hu, Effect of organic carbon sources on growth, photosynthesis and respiration of Phaeodactylum tricornutum. J. Appl. Phyco. 21(2), 239–246 (2009) 14. R. Hongyan, T. Jinhua, M.A. Min, Z. Renchuan, Q. Lu, A. Erik, C. Paul, R. Roger, Cultivation of Chlorella Vulgaris in a pilot-scale photobioreactor using real central wastewater with waste glycerol for improving microalgae biomass production and wastewater nutrients removal. Bioresour. Technol. 245, 1130–1138 (2017) 15. Y. Liang, N. Sarkany, Y. Cui, Biomass and lipid productivities of Chlorella vulgaris under autotrophic, heterotrophic and mixotrophic growth conditions. Biotechnol. Lett. 31(7), 1043– 1049 (2009) 16. M. Orosa, D. Franqueira, A. Cid, J. Ablade, Analysis and enhancement of astaxanthin accumulation in Haematococcus Pluvialis. Bioresour. Technol. 96(3), 373–378 (2005) 17. Z. Chi, D. Pyle, Z. Wen, C. Frear, S. Chen, A laboratory study of producing docosahexaenoic acid from biodiesel waste glycerol microalgal fermentation. Process Biochem. 42(11), 1537– 1545 (2007) 18. Y.H. Chen, T. Walker, Biomass and lipid production of heterotrophic microalgae Chlorella protothecoids by using biodiesel derived crude glycerol. Biotechnol. lett. 33(10), 1973–1983 (2011)

Study of Jaggery Derived Carbon Spheres for Supercapacitor Applications Swati Chaudhary and O. P. Sinha

1 Introduction Over the past few years, supercapacitor technology has been emerged as the power solution to the increasing energy requirements among all the energy storage devices. This can be attributed to its high capacitive and charging-discharging ability. In addition, supercapacitors have been also considered as the potent solution where high power bursts are required for shorter duration. Further, the properties of the electrode materials affect the electrochemical performance of the supercapacitors to a greater extent, therefore due care must be taken while selecting the electrode material [1–3]. Supercapacitors have some demerits also like other energy storage systems, for instance, its high fabrication cost [4, 5]. To overcome this demerit, researchers have focussed on natural occurring electrode materials. In this regard, we have also reported synthesis of ternary doped layered graphene nanosheets from kitchen waste, i.e., onion peel [6]. Further, the present research work has been proposed in which jaggery powder derived carbon spheres have been synthesized and their electrochemical properties were studied for supercapacitor applications.

S. Chaudhary (B) · O. P. Sinha Amity Institute of Nanotechnology, Amity University, Sector-125, Noida, Uttar Pradesh 201303, India Present Address: S. Chaudhary Applied Sciences and Humanities Department, Lloyd Institute of Engineering and Technology, Knowledge Park-2, Greater Noida, Uttar Pradesh 201306, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_20

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2 Experimental Carbon spheres were synthesized using conventional hydrothermal method. Initially, 1 g of jaggery powder was stirred in 100 mL distilled water. The homogeneous obtained solution was then transferred to Teflon-lined autoclave and heated at 180 °C for 10 h such that hydrothermal reaction will take place in due time. The resultant solution was then cooled down and centrifuged to obtain the carbon spheres in dark brown powder form.

3 Results and Discussion The synthesized carbon spheres were studied via different analytical and electrochemical techniques such as X-ray diffraction (XRD) studies, scanning electron microscopy (SEM), cyclic voltammetry (CV) and galvanostatic charge discharge (GCD) studies. The electrochemical studies were performed on Biologics SP-150 electrochemical potentiostat.

3.1 X-ray Diffraction (XRD) The powder XRD studies were done to study the crystalline properties of synthesized carbon spheres as shown in Fig. 1a. A single broad peak obtained at 2Θ = 25.4° indicated the resemblance to the XRD pattern of rGO. The appearance of the obtained peak can be ascribed to the amorphous character of synthesized carbon spheres [7–10].

3.2 Scanning Electron Microscopy (SEM) The SEM studies have been also performed to study the morphological properties of synthesized carbon spheres. The SEM images depicted that microspheres have been formed with diameter approximately 3–3.5 µm (from Fig. 1b and c). Moreover, the size distribution appears to be uniform. While figure inferred the agglomeration of microspheres as shown in Fig. 1d [11–14].

3.3 Cyclic Voltammetry (CV) The cyclic voltammetric studies have been also performed for synthesized carbon spheres to study their redox tendency as shown in Fig. 2a and b. Initially, studies were done with three different concentrations of H2 SO4 electrolyte (i.e., 0.1 M, 1 M

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Fig. 1 a X-ray diffraction pattern of carbon spheres b, c, d SEM images of carbon spheres at different magnification

and 2 M). The obtained cyclic voltammogram clearly depicted that with increase in electrolyte concentration, corresponding current response also increases. This can be ascribed to faster generation of active ions at higher concentration [15, 16]. Further, CV studies were examined at five different scan rates (i.e., 5, 10, 20, 30 and 50 mV/s) with the highest electrolyte concentration, i.e., 2 M H2 SO4 . It was observed that as the scan rate increases, the current response also increases which clearly depicted the occurrence of Ohm’s law which states that when the potential difference applied between the two points increases, the corresponding generating current also increase [17, 18].

3.4 Galvanostatic Charge Discharge (GCD) Like CV studies, GCD studies were also initially performed with three different electrolytic concentrations as shown in Fig. 2c and d. Similar results have been obtained such that with increase in electrolyte concentration, the discharging time also increases. In addition, GCD studies have been also performed at three different current densities with 2 M H2 SO4 electrolytic solution. The obtained pattern depicted that with increase in current density, the discharging time decreases as high value of current density means faster charging–discharging or vice-versa [19–21].

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Fig. 2 a CV curves of carbon spheres at three different electrolyte concentrations, b CV curves of carbon spheres at five different scan rates, c GCD curves of carbon spheres at three different electrolyte concentrations, d GCD curves of carbon spheres at three different current densities

The specific capacitance for prepared carbon spheres were calculated according to the Formula 1. C = I dt/md V

(1)

where C=Capacitance (F/g); I = current density (A); m = mass of active material (g); dV = discharging voltage; dt = discharging time. The capacitance obtained with 2M H2 SO4 electrolytic solution is 540 F/g at 1 A/g current density.

4 Conclusion Carbon spheres were successfully synthesized using natural source, i.e., jaggery via hydrothermal treatment. Further, both the XRD and SEM results confirmed the same. In addition, the redox property and high capacitance value (540 F/g) obtained also adds to the effect. Thus, these synthesized carbon spheres may be successfully utilized in future energy storage applications.

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Acknowledgements The authors acknowledge the support of Amity University, Noida, Uttar Pradesh for carrying out all the characterization techniques.

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22.

M. Vangari, T. Pryor, L. Jiang, 139, 72 (2013) Z.S. Iro, C. Subramani, S.S. Dash, Int. J. Electrochem. Sci. 11, 10628 (2016) D.S. Su, R. Schlögl, Chemsuschem 3, 136 (2010) L.L. Zhang, X.S. Zhao, Chem. Soc. Rev. 38, 2520 (2009) A. Borenstein, O. Hanna, R. Attias, S. Luski, T. Brousse, D. Aurbach, J. Mater. Chem. A 5, 12653 (2017) S. Chaudhary, R. Mohan, O.P. Sinha, Appl. Phys. A Mater. Sci. Process. 126, 3 (2020) Y.L. Chen, Z.A. Hu, Y.Q. Chang, H.W. Wang, Z.Y. Zhang, Y.Y. Yang, H.Y. Wu, J. Phys. Chem. C 115, 2563 (2011) J. Xu, X. Fan, Q. Xia, Z. Shao, B. Pei, Z. Yang, Z. Chen, W. Zhang, J. Alloy. Compd. 685, 949 (2016) D.P. Dubal, N.R. Chodankar, G.S. Gund, R. Holze, C.D. Lokhande, P. Gomez-Romero, Energ. Technol. 3, 168 (2015) S. Chaudhary, L.S. James, A.B.V. Kiran Kumar, C.V.V. Ramana, D.K. Mishra, S. Thomas, D. Kim, J. Inorg. Organomet. Polym. Mater. 29, 2282 (2019) D. Kuntal, S. Chaudhary, A.B.V. Kiran Kumar, R. Megha, C.V.V. Ramana, Y.T. Ravi Kiran, S. Thomas, D. Kim, J. Mater. Sci.: Mater. Electron. 30, 15544 (2019) S. Chaudhary, D. Kuntal, K.K. Althurthi Bharani Venkata, R.C. Veera Venkata, N. Goli, S. Thomas, ChemistrySelect 4, 8719 (2019) M. Sharma, M. Joshi, S. Nigam, S. Shree, D.K. Avasthi, R. Adelung, S.K. Srivastava, Y. Kumar Mishra, Chem. Eng. J. 358, 540 (2019) S. Abdolhosseinzadeh, H. Asgharzadeh, H.S. Kim, Nature Publishing Group 1 (2015) A. Ambrosi, C.K. Chua, A. Bonanni, M. Pumera, (2014) J. Huang, J. Wang, C. Wang, H. Zhang, C. Lu, J. Wang, Chem. Mater. 27, 2107 (2015) J.S. Wei, H. Ding, P. Zhang, Y.F. Song, J. Chen, Y.G. Wang, H.M. Xiong, Small 12, 5927 (2016) S. Chaudhary, A.B.V. Kiran Kumar, N.D. Sharma, M. Gupta, Int. J. Energy Res. (2019) A. Kumar, S. Billa, S. Chaudhary, A.B.V. Kiran Kumar, C.V.V. Ramana, D. Kim, Inorg. Chem. Commun. 97, 191 (2018) F. Bonaccorso, L. Colombo, G. Yu, M. Stoller, V. Tozzini, A.C. Ferrari, R.S. Ruoff, V. Pellegrini, Science 347 (2015) T. Chen, L. Dai, Mater. Today 16, 272 (2013) S. Chaudhary, R. Mohan, O.P. Sinha, Adv. Nat. Sci. Nanosci. Nanotechnol. 12, 015011 (2021)

Optimum Concentration Ratio for Plastic Optical Fiber-Based Fresnel Lens Daylighting System Vikas Kumar, Karanvir Sharma, Devendra Singh Bisht, and Harry Garg

1 Introduction In twenty-first century, power consumption in the buildings is increasing at an alarming rate, and a significant amount of this electricity is used for the illumination needs. Artificial lighting and HVAC account for almost 40–50% of the total electricity consumption [1]. A trend of utilizing renewable resources for electricity generation is observed in the past decade, instead of the conventional non-renewable resources of energy like coal, natural gas. India is at the forefront in developing large solar power plants capable of generating huge sums of electricity from sunlight. The generated electricity is transported to the major cities and used for illumination purposes and other needs. This conversion of sunlight into electricity depends on various factors like the efficiency of solar panel, intensity of sunlight, position of the sun, weather, and some losses occur during transportation of this electric power from the power plant to the city. There is a suitable alternative to this artificial lighting known as daylighting. Daylighting is a method used for the illumination of a dark space using natural sunlight. The devices used for achieving this are known as daylighting systems. These systems are primarily categorized on the basis of the tracking method: active daylighting system and passive daylighting system. In the case of active daylighting system, the sunlight is collected using collectors like Fresnel lens, compound parabolic concentrator (CPC). Fresnel lens is used in most of the active daylighting systems like Himawari, Parans, Echy [2, 3]. The Fresnel lens is an arrangement of concentric prisms capable of focusing incident light on a target plane. Fresnel lens is generally made up of polymethyl methacrylate (PMMA)

V. Kumar (B) · K. Sharma · D. S. Bisht · H. Garg CSIR-Central Scientific Instrument Organization, Sector 30 C, Chandigarh 160030, India V. Kumar · D. S. Bisht · H. Garg Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_21

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and polycarbonates (PC) making them lightweight and compact alternative to the traditional glass concentrating lens. The sunlight concentrated by the Fresnel lens is transported deep inside the building using optical fiber cables. There are two types of optical fiber cables: silica optical fiber (SOF) and plastic optical fiber (POF) [4, 5]. SOF is more efficient compared to POF because of its lower attenuation rate, but SOF is expensive and less flexible compared to POF. POF has a large acceptance angle compared to SOF because of the higher refractive index value of core and cladding material. For an optimized daylighting system, POF cable is a suitable choice providing a balance of performance and cost without a significant reduction in overall efficiency. But, there is an inherent problem associated with the POF cable that it cannot sustain high temperatures and tend to deform after reaching 70 °C [6]. The research paper shed light on the concept of the concentration ratio of Fresnel lens-based daylighting system, effect of concentration ratio on the POF cable, and alternative option for POF cable.

2 Designing of Experimental Setup The concentration ratio plays a vital role in the daylighting systems utilizing POF for daylight transportation. The performance of POF decreases drastically while operating at high temperatures. The concentration ratio can be calculated using below equation. Concentration ratio (C.R.) =

π × D2 Effective area of solar collector D2 = 4π = 2 2 Optical fiber cross − sectional area × d d 4

Another important factor considered during the designing of the Fresnel lens is f -number. The f -number is the ratio of Fresnel lens focal length to the diameter of the Fresnel lens as shown in equation below [7]. f − number =

f Focal lenght of Fresnel lens = Diameter of Frenel lens D

Traditionally, it has been found that the slow focusing lens yields better results for the daylighting application, as the incident angle subtended by the sunlight after passing from the Fresnel lens is smaller than the acceptance angle of the optical fiber cable. The f -number selected for the experimentation is 1.5 which is capable of delivering more than 88% focused light on the target area [7]. The 2D view of the experimental setup is shown in Fig. 1. The angle subtended by the Fresnel lens is calculated by using trigonometric formula. tan θ =

0.5d 0.5d = = 0.33 f 1.5d

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Fig. 1 2D view of the experimental setup showing condition for TIR in plastic optical fiber

Incident angle on target area, θ = tan−1 (0.33) = 18.43◦ The acceptance angle of optical fiber cable is calculated by numerical aperture which depends on the refractive index of the core and cladding of the optical fiber cable [8]. NA = sin α =



n 21 − n 22 =

 (1.4955)2 − (1.46)2 = 0.3239139546

Half acceptance angle, α = 18.90◦ The angle subtended by the incident angle is smaller than the acceptance angle of the optical fiber cable. The incident sunlight will be transmitted through the POF cable because of TIR phenomenon. These angles are very critical for the overall efficiency of the system ensuring that all the refracted sunlight from the Fresnel lens will be transmitted through the POF.

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Table 1 Diameter of Fresnel lens as per the concentration ratio S. No.

Concentration ratio (C.R.)

Diameter of optical fiber cable (d)

Diameter of Fresnel lens (D)

1 2

50

6

42.426

100

6

60

3

150

6

73.484

4

200

6

84.862

5

250

6

94.868

6

300

6

103.923

7

350

6

112.249

In order to calculate the heat generation on the optical fiber inlet, a set of parameters is formed in which the optical fiber cable dimension is kept constant with a core diameter of 6 mm, and the diameter of the Fresnel lens is increased with respect to the concentration ratio as shown in Table 1. Fresnel lenses design and analysis on the basis of the set of parameters are conducted and discussed in simulation analysis section.

3 Simulation Analysis The modeled setup is designed and analyzed in TracePro. TracePro software is used in the design and analysis of the optical and illumination systems. There are some parameters that are kept constant in all the Fresnel lenses irrespective of their size, and all the lenses are 2 mm thick and have constant pitch configuration. The lenses are point-focusing lens, in order to focus the sunlight on the entry section of the optical fiber inlet. The optical fiber is moved toward the Fresnel lens to analyze the distribution of sunlight over the entire surface of the optical fiber inlet [9]. Figure 2 shows the 2D schematic of the simulation process and the layout of the same in the TracePro interface. This methodology has been opted in all the models, and the simulation was carried out. About 100,000 rays are projected normal to the Fresnel lens flat surface. The sun’s properties assigned to the source file are shown in Fig. 3. The simulated sun in the software assigns different weightage to different wavelengths of the solar spectrum which conform to the intensity distribution observed on the earth’s surface. There rays are of different wavelengths ranging from 380 to 3000 nm covering the entire visible region and near-infrared region of the solar spectrum. Solar emulator tool is used for the simulating the sun’s spectrum as different weightage value is given to the different wavelengths as per the solar spectrum. The intensity of the light varies over the entire solar spectrum as shown in Fig. 4. The Chandigarh location with coordinates of E76.7794, N30.7333 is chosen for the simulation in the solar emulator. Simulation is performed for clear sky condition to project maximum output figures.

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Fresnel Lens

Refracted Sunligh

Optical Fiber Inlet Distance moved for area focus

(a)

Source

Fresnel Lens

Plastic Optical Fiber Inlet

(b) Fig. 2 a 2D schematic of the simulation process; b Layout of the setup in TracePro interface

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Fig. 3 Snapshot of sun’s properties assigned to the source file in TracePro

Fig. 4 Spectral irradiance intensity of sun’s different wavelength light at outside atmosphere and at sea level [10]

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The Fresnel lens is designed by selecting the parameters like ring width, thickness, outer radius, material, foci in the software geometry. Similarly, the optical fiber cable is modeled as a cylinder geometry with diameter equal to 6 mm. The irradiance maps are observed on the optical fiber cable inlet showing the distribution of the rays on the entire surface after passing through the Fresnel lens. The irradiance maps are plotted for a photometric and radiometric conditions for all the different cases of concentration ratios. Different irradiance maps plotted for the different C.R. are illustrated in Table 2. The efficiency of designed Fresnel lenses is more than 90% when simulated for the visible spectrum light, but most of the concentrated sunlight is falling on the central area instead of the entire area of the optical fiber inlet. When optical fiber is moved closer to the Fresnel lens, a significant drop in the intensity of the sunlight in the center is observed, and the collected sunlight is distributed over a relatively large area at fiber inlet. For all the configurations considered during numerical analysis, it was made sure that minimum of 80% of visible part of incident sunlight falls on the fiber inlet. Simultaneously, the overall reduction of the IR light is observed which is a major contributor to the heat on the optical fiber inlet.

4 Discussion The study of the concentration ratio is conducted by designing and simulating the setup of Fresnel lenses for different level of concentration ratio. It is observed that as the C.R. increases above 100, the flux uniformity achieved at the fiber inlet by reducing the distance between the Fresnel lens and optical fiber inlet is not yielding satisfactory results. The majority of the concentrated light from the Fresnel lens is falling on the center of the optical fiber inlet. This is because of the high level of concentrated infrared light which will damage the optical fiber inlet. The relationship between the concentration ratio, photometric output, and radiometric output is plotted in Figs. 3 and 4. The relationship between the C.R. and the visible spectrum light (photometric) is a linear relationship, whereas the relationship between the C.R. and the overall sunlight from 380 to 3000 nm (radiometric) is linear up to 300 C.R. after which a sharp increase in the output is observed. This is due to the high concentration of the IR region light falling on the optical fiber inlet. This can be countered by using a hot mirror that is capable of eliminating the IR rays from the system which allows the visible light to pass through it. But, this arrangement is feasible up to certain temperature limit (or CR) only as during very high temperature conditions, the IR filter is not capable enough to restrict the attainment of temperature above 70° at fiber inlet (Figs. 5 and 6). The systems that are designed using less than 100 concentration ratios can be used without IR filters and will be a cost-effective solution in case of huts or lowcost structures. Integrating it with the low-cost solar panels and LED’s will make the system a complete solution for entire day irrespective of cloudy conditions or night hours.

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Table 2 Irradiance maps plotted on optical fiber inlet for different C.R C.R

Photometric

Radiometric

50

100

150

200

(continued)

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Table 2 (continued) C.R

Photometric

Radiometric

250

300

350

5 Conclusion The research study conducted for different levels of concentration ratio is to establish a relationship between the concentration ratio and the output of the Fresnel lens. The following conclusions are drawn after the design and simulation of the different scenarios. • The C.R. plays a crucial role when the plastic optical fiber is used for the daylight transmission purpose.

178 Fig. 5 C.R. versus photometric output (in lumens)

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Photometeric (in lumens)

800 700 600 500 400 300 200 100 0

0

100

200

300

400

300

400

ConcentraƟon raƟo (C.R.)

Fig. 6 C.R. versus radiometric output (in W/m2 )

Radiometeric (W/m2)

6 5 4 3 2 1 0 0

100

200

ConcentraƟon raƟo (C.R.)

• Large Fresnel lenses coupled with plastic optical fiber with C.R. of more than 100 need an IR protection system, which may be a hot mirror capable of reflecting the IR spectrum rays away from the system. This is because the non-uniform distribution of concentrated light on the optical fiber inlet is observed for the Fresnel lens-based daylighting system with C.R. above 100. • There is a sharp increase in the radiometric output post 300 C.R., whereas the photometric output follows the linear relationship. • Applying the configured parameters (i.e., CR ratio less than 100) to the daylighting system with the low-cost solar panels and LED’s will make the system a complete solution for illumination needs irrespective of cloudy conditions or night hours. Acknowledgements Authors are thankful to Director CSIO for their support and encouragement.

References 1. E. Loren, E. Abraham, AIA, IDSA et al., Building systems and IAQ—sustainable design, vol. 240, pp. 703–988 (2012)

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2. M.S. Mayhoub, Fifty years of building core sunlighting systems—eight lessons learned. Sol. Energy 184, 440–453 (2019). https://doi.org/10.1016/j.solener.2019.03.097 3. T.T. Pham, N.H. Vu, S. Shin, Daylighting system based on novel design of linear Fresnel lens. Buildings 7(4) (2017). https://doi.org/10.3390/buildings7040092 4. I. Ullah, S. Shin, Highly concentrated optical fiber-based daylighting systems for multi-floor office buildings. Energy Build. 72, 246–261 (2014). https://doi.org/10.1016/j.enbuild.2013. 12.031 5. I. Ullah, S. Shin, Development of optical fiber-based daylighting system with uniform illumination. J. Opt. Soc. Korea 16(3), 247–255 (2012). https://doi.org/10.3807/JOSK.2012.16. 3.247 6. J. Song, Y. Zhu, K. Tong, Y. Yang, M.A. Reyes-Belmonte, A note on the optic characteristics of daylighting system via PMMA fibers. Sol. Energy 136, 32–34 (2016). https://doi.org/10. 1016/j.solener.2016.06.071 7. A. Davis, F. Kühnlenz, Optical design using Fresnel lenses: basic principles and some practical examples. Opt. Photonik 2(4), 52–55 (2007). https://doi.org/10.1002/opph.201190287 8. G. Keiser, Optical fiber communications, in Wiley Encyclopedia of Telecommunications (John Wiley & Sons, Inc., Hoboken, NJ, USA, 2003) 9. D.T. Nelson, D.L. Evans, R.K. Bansal, Linear Fresnel lens concentrators. Sol. Energy 17(5), 285–289 (1975). https://doi.org/10.1016/0038-092X(75)90045-6 10. I. Fondriest Environmental, Solar radiation and photo-synthetically active radiation. [Online]. Available: https://www.fondriest.com/environmental-measurements/parameters/weather/pho tosynthetically-active-radiation/. Accessed 16 Nov 2020

Energy-Efficient Tunnel FET for Application as a Biosensor Manjula Vijh, Aekta Singh, and Sujata Pandey

1 Introduction Tunnel field effect transistors are gaining immense popularity in the domain of semiconductor devices. These devices have the potential to outperform conventional MOSFETs owing to various advantages like smaller subthreshold swing (below 60 mV/dec), low leakage currents, and resistance against various short channel effects [1–3]. Due to the merits like higher sensitivity, low power dissipation, and label-free detection of biospecies, tunnel FETs have also been explored for their use in biosensing applications. With the advancements in biomedical sciences, it has become very crucial to detect the disease-causing biomolecules for its timely diagnosis. Because of the gating effect of the biochemical species on the gate oxide, various properties of the device get modulated, such as drain current, conductance, and threshold voltage. Bergveld in 1970 gave the first demonstration of ionsensitive FET (ISFET)-based biosensor, in which the electrical properties change when charged biomolecules exist in an aqueous solution filled between the gate and oxide region [4]. However, the major demerit of ISFET biosensor was that it was incapable of detecting neutral biomolecules. To surmount this restriction, various device structures of MOSFETs were investigated for the detection of biospecies. With the latest progressions in designing TFETs, biosensors based on tunnel FETs are gaining recognition as they exhibit much higher sensitivity as compared to conventional FET biosensors [5, 6]. However, the major limitation with silicon-based tunnel FETs is that they yield lower ON-state current. Hence, alternate materials are explored to improve the characteristics of the device. One alternative is to use III-V compound semiconductors because of their lower band gap than silicon. However, using such materials throughout the device can also raise the OFF current in the device. Since M. Vijh (B) · A. Singh · S. Pandey Amity University Uttar Pradesh, Noida, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022 V. K. Jain et al. (eds.), Renewable Energy and Storage Devices for Sustainable Development, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-16-9280-2_22

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the ON-state current mainly depends upon the property of the semiconductor at the source and channel interface, there should be a low band gap material present at the source and channel interface and a high band gap material elsewhere in the device. Hence, heterojunction tunnel FETs can exhibit better device characteristics than homojunction tunnel FETs. There are various sensitivity metrics through which the sensitivity of a biosensor can be observed. One of them is the variation in threshold voltage that occurs because of biospecies when the device is working in the ON state. This change is examined by considering the presence and absence of biomolecules [7]. This work presents the design and simulation of a III-V cylindrical gate heterojunction tunnel FET biosensor and its performance analysis by observing a change in its transconductance-to-current ratio (gm /I ds ) as the sensitivity metric [8]. Silvaco ATLAS 2D device simulator is used to design and simulate the biosensor.

2 Device Structure The device structure of the gate all around heterojunction tunnel FET biosensor designed using III-V material is shown in Fig. 1. A GaSb-InAs broken gap heterojunction is used in the simulation. The tunnel FET biosensor designed in this work is nanogap embedded tunnel FET, where a nanogap region is created between the gate oxide and the gate metal. This nanogap consists of air with dielectric constant ‘k’ equal to 1. For the device to work as a biosensor, the biomolecules are assumed to be imprisoned in this nanogap. To suffice this, a material whose dielectric constant ‘k’ is more than 1 is introduced in the nanogap. These biomolecules are called neutral biomolecules, as they do not possess any charge. Some examples of neutral biochemical species are protein, biotin, streptavidin, and APTES. Uncovering neutral biospecies is termed as label-free detection. In the current work, the analysis is done by modifying the dielectric constant of the biomolecule present in the nanogap region

Fig. 1 Device structure of GaSb-InAs cylindrical gate tunnel FET biosensor

Energy-Efficient Tunnel FET for Application as a Biosensor Table 1 Design parameters for the structure shown in Fig. 1

183

Design parameters

Value

Channel length

22 nm

Radius

5 nm

Nanogap thickness

4 nm

Oxide thickness

2 nm

Source doping

1E20/cm3

Drain doping

1E19/cm3

Gate oxide

HfO2

with ‘k’ having the values: 1, 3, 5, and 7. The effective dielectric constant gets altered by the presence of these biomolecules which brings a variation in the effective capacitance and that in turn exhibits a modification in the electrical properties of the device. The effect of charged biomolecules is simulated by incorporating varying concentrations of negative and positive fixed oxide charges at the interface of semiconductor and oxide. The structure is simulated using SRH recombination model, CONMOB, BGN, and Kane’s tunneling model of the TCAD simulator [9]. The parameters used in the device are defined in Table 1.

3 Results and Discussion A very important parameter for a biosensor is its sensitivity which can be calculated as the comparative shift in the characteristics of the biosensor when biospecies get accumulated in the nanocavity. A modification in threshold voltage is one of the most commonly used sensitivity metrics for TFET biosensor. In this work, the transconductance-to-current ratio has been used to carry out the sensitivity analysis of the device. The corresponding absolute values of transconductance-to-current ratio (gm /I ds ) with respect to drain current for three different biomolecules having dielectric constant k = 3, 5, and 7 in comparison with k = 1 are depicted in Fig. 2, 3, and 4, respectively. The biomolecules are taken as neutral in this case. With the accumulation of biochemical species in the sensing region, the effective dielectric constant in the region increases and that results in the improvement of gm /I ds. The higher gm /I ds values indicate the modification in the current–voltage characteristics of the device in comparison with the case where no biomolecules are present. Also, this increase in the gm /I ds signifies a change in the subthreshold swing of the device when the biospecies are existing in the nanocavity. The transconductance-to-current ratio varies with the variation in the current level. This is one of the characteristics of TFETs where the bending of bands is governed by the gate voltage, and it enables the level of tunneling thereby leading to a change in the gm /I ds value. The width of the energy barrier is modulated by the presence of biospecies which directs the carrier

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Fig. 2 Transconductance-to-current ratio with drain current for biomolecule with k = 3

Fig. 3 Transconductance-to-current ratio with drain current for biomolecule with k = 5

tunneling, and therefore, the SS decreases (or gm /I ds increases) for k = 7 [10–13]. The shift in the value of gm /I ds is more in contrast to an unfilled nanogap region. Figure 5 shows the corresponding absolute values of transconductance-to-current ratio (gm /I ds ) with respect to gate voltage for neutral and charged biomolecules. The peak transconductance values do not show much of a variation; however, a lateral shift in the characteristics is observed. Comparable results are observed for all the three biomolecules. This shows the pertinency of the sensing measure for biochemicals that possess charge [8].

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Fig. 4 Transconductance-to-current ratio with drain current for biomolecule with k = 5

Fig. 5 Transconductance-to-current ratio with gate voltage for neutral and charged biomolecules

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4 Conclusion A gate all around III-V tunnel FET biosensor is designed and simulated for biosensing applications and label-free detection. Biomolecules with varying dielectric constants are used in the analysis, and the effect of positively/negatively charged species is also considered. It is assumed that the biomolecules exist at the sensing location and are spotted by witnessing the shift in device’s electrical characteristics. An analysis of transconductance-to-current ratio as a sensing metric is presented for different biomolecules. An improvement in peak (gm /I ds ) value signifies the accumulation of biospecies in the nanogap cavity as it indicates a change in the subthreshold swing in the device. The device is found to be sensitive to the presence of biomolecules.

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