Advances in Energy Research, Vol. 1: Selected Papers from ICAER 2017 (Springer Proceedings in Energy) [1st ed. 2020] 9811526656, 9789811526657

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Springer Proceedings in Energy

Suneet Singh Venkatasailanathan Ramadesigan   Editors

Advances in Energy Research, Vol. 1 Selected Papers from ICAER 2017

Springer Proceedings in Energy

The series Springer Proceedings in Energy covers a broad range of multidisciplinary subjects in those research fields closely related to present and future forms of energy as a resource for human societies. Typically based on material presented at conferences, workshops and similar scientific meetings, volumes published in this series will constitute comprehensive state-of-the-art references on energy-related science and technology studies. The subjects of these conferences will fall typically within these broad categories: – – – – – – –

Energy Efficiency Fossil Fuels Nuclear Energy Policy, Economics, Management & Transport Renewable and Green Energy Systems, Storage and Harvesting Materials for Energy

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Suneet Singh Venkatasailanathan Ramadesigan •

Editors

Advances in Energy Research, Vol. 1 Selected Papers from ICAER 2017

123

Editors Suneet Singh Department of Energy Science and Engineering Indian Institute of Technology Bombay Mumbai, Maharashtra, India

Venkatasailanathan Ramadesigan Department of Energy Science and Engineering Indian Institute of Technology Bombay Mumbai, Maharashtra, India

ISSN 2352-2534 ISSN 2352-2542 (electronic) Springer Proceedings in Energy ISBN 978-981-15-2665-7 ISBN 978-981-15-2666-4 (eBook) https://doi.org/10.1007/978-981-15-2666-4 © Springer Nature Singapore Pte Ltd. 2020 This work is subject to copyright. All rights are reserved 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, express 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

These proceedings contain selected papers presented in the 6th International Conference on Advances in Energy Research (ICAER 2017), which was held at IIT Bombay, Mumbai, India, from 12 to 14 December 2017. The biennial conference has been organised since 2007, for providing a common platform for the researchers in the field of energy and allied domains. The conference was inaugurated by the honourable Union Minister of Petroleum and Natural Gas and Skill Development and Entrepreneurship, Shri. Dharmendra Pradhan, and was presided over by Prof. Devang Khakkar, Director, IIT Bombay. The Department of Energy Science and Engineering (DESE) has been organising the biennial conference which serves an excellent forum to present new findings, exchange novel ideas, discuss new developments and finally reflect on the challenges that lie ahead in line with the vision of the department “To develop sustainable energy systems, solutions and workforce for the future”. DESE has developed several novel education programmes focussing on the application of science and engineering to problems in energy. Various aspects of energy research, including but not limited to renewable energy, energy storage, energy efficiency and modelling, energy policy and conventional energy, are covered in this conference. This conference throws light on various recent accomplishments by researchers worldwide in the areas of solar thermal, thermal storage, solar PV with new materials, novel batteries, biofuel-based transportation and rural energy needs, to name a few. More than 420 submissions were received, and a rigorous peer review process was followed for acceptance of the papers. About 150 papers were accepted for oral presentation, and around 110 papers were accepted in the poster category in the conference based on the reviews received. These proceedings are divided into two volumes. Volume 1 contains papers from topics related to solar photovoltaics, energy storage and conversion and energy efficiency and management. Volume 2 contains papers from topics related to renewable energy other than solar photovoltaics; IC engines, biofuels and other conventional energy; and power electronics and microgrids.

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We would like to take this opportunity to thank all the invited speakers, delegates, sponsors, the members of the organising and advisory committee and most importantly the students and the staff of DESE for their dedicated efforts in organising this conference. These papers represent the most recent research on the subject. The editors would like to thank all the authors and the anonymous referees for paying attention to the quality of the publications. We express our gratitude for the financial support and sponsorship from government agencies and industries— ONGC, SERB-DST, EESL, NCPRE-IITB, IMASE-IITB, Pine Instruments, BioLogic, Cummins, HHV and NPCIL. The awards were sponsored by the Royal Society of Chemistry (RSC) and Springer. The publication of the issue will surely amplify the conference outcome and generate a much larger discussion and scientific progress. The contents of these proceedings reveal the breadth of current activities in different themes related to energy. We hope they form a useful starting point for beginners as well as practitioners in this discipline. Mumbai, India December 2017

Suneet Singh Venkatasailanathan Ramadesigan (Organising Secretaries, ICAER 2017)

Contents

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Study of Soiling Effect on Inclined Photovoltaic Surfaces . . . . . . . . Sumon Dey, Veena Aishwarya and Bala Pesala

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Efficiency Enhancement of Betanin Dye-Sensitized Solar Cells Using Plasmon-Enhanced Silver Nanoparticles . . . . . . . S. Sreeja, S. Prabhakaran and Bala Pesala

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Improving the Short-Wavelength Spectral Response of Multi-crystalline Silicon Solar Cells by ZnS Downshifting Phosphor Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Amruta Pattnaik, Som Mondal, Monika Tomar, Vinay Gupta and B. Prasad

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SiO2 Grating-Based Photonic Structures as Ideal Narrowband Emitter for Solar Thermophotovoltaics Application . . . . . . . . . . . . M. V. N. Surendra Gupta, Ameen Elikkottil and Bala Pesala

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Reduction of Escape Cone Losses in Luminescent Solar Concentrators Using High-Contrast Gratings . . . . . . . . . . . . Ameen Elikkottil, Kiran Vaddi, K. S. Reddy and Bala Pesala

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Agri-Voltaic System for Crop Production and Electricity Generation from a Single Land Unit . . . . . . . . . . . . Priyabrata Santra, R. K. Singh, H. M. Meena, R. N. Kumawat, Dhananjay Mishra, D. Machiwal, Devi Dayal, D. Jain and O. P. Yadav

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Comparison of Different Photovoltaic Array Configurations Under Partial Shading Condition . . . . . . . . . . . . . . . . . . . . . . . . . . Vandana Jha and Uday Shankar Triar

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Effect of Thermal Stress over High-Efficiency Solar Photovoltaic Modules in real operating condition . . . . . . . . . . . . . . Rashmi Singh, Madhu Sharma, Rahul Rawat and Chandan Banerjee

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Contents

Enhancement of Visible Light Driven Photovoltaic Efficiency Upon Copper Incorporation to Silver Indium Sulfide Nanocrystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Jit Satra and Bibhutosh Adhikary

10 Improved Analytical Model for Electrical Efficiency of Semitransparent Photovoltaic (PV) Module . . . . . . . . . . . . . . . . Abhishek Tiwari, Rohit Tripathi and G. N. Tiwari

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11 Dielectric-Coated Metal-Integrated Lightweight Solar Panel . . . . . . 101 Prosenjit Bose, S. V. Narasimhamurthy, Ajith Shetty, Bhagwati Bharadwaj, Tapan Kumar Rout, A. N. Bhagat and Arul Shanmugasundram 12 Study on Spray-Deposited Cu2ZnSnS4 Thin Films: Deposition and Physical Properties . . . . . . . . . . . . . . . . . . . . . . . . . 115 Jitendra P. Sawant and Rohidas B. Kale 13 Cogeneration of Power and Desalination Using Concentrated Photovoltaic/Thermal Humidification and Dehumidification System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 B. Anand and T. Srinivas 14 Computational Fluid Dynamic (CFD) Analysis of Air-Based Photovoltaic Thermal System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 T. M. Sathe, A. S. Dhoble, Sandeep Joshi and Chidanand Mangrulkar 15 Synthesis of One-Dimensional Bismuth Sulfide Nanoparticle with Enhanced Photovoltaic Properties . . . . . . . . . . . . . . . . . . . . . . 151 Arpita Sarkar and Bibhutosh Adhikary 16 Effect of Forced Convection Cooling on Performance of Solar Photovoltaic Module in Rooftop Applications . . . . . . . . . . 159 Arunendra K. Tiwari, Rohit Kumar, Rohan R. Pande, Sanjay K. Sharma and Vilas R. Kalamkar 17 Influence of Deposition Temperature on the Si Richness in SiC-Based Thin Films for Optoelectronic Applications . . . . . . . . 173 S. Sam Baskar, Giri Goutham, Job Sandeep, Fabrice Gourbilleau and R. Pratibha Nalini 18 Optimization of TiO2 for Low-Temperature Dopant-Free Crystalline Silicon Solar Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 Swasti Bhatia, Irfan M. Khorakiwala, Kurias K. Markose, Neha Raorane, Pradeep R. Nair and Aldrin Antony

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19 Copper Oxide Phase Change During Pulsed Laser Deposition of SrTiO3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 Garima Aggarwal, Ashish K. Singh, Sandeep K. Maurya and K. R. Balasubramaniam 20 Thermo-Hydraulic Performance and Heat Storage of a Packed Bed Solar Energy Storage System Having Large-Sized Perforated Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . 199 Anshul Kunwar, Manoj Kumar and Sunil Chamoli 21 Spatial Distribution of Oxygen-Vacancy Pairs and Oxygen Movement in Yttria-Stabilized Zirconia . . . . . . . . . . . . . . . . . . . . . 209 Methary Jaipal and Abhijit Chatterjee 22 Approximate Analytical Model for Solidification Process in a Rectangular Phase-Change Material Storage with Internal Fins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 R. Kothari, S. Das, S. K. Sahu and S. I. Kundalwal 23 Photoelectrochemical Water Splitting Characteristics of Electrodeposited Cuprous Oxide with Protective Over Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 Priyanka Marathey, Biren Patel, Ranjan Pati, Indrajit Mukhopadhyay and Abhijit Ray 24 Effect of Solvent on Segregation Behavior in Pt-Ni Bimetallic Alloy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 Gargi Agrahari, Arindam Sarkar and Abhijit Chatterjee 25 Alkali Metal Ion Decorated Crown Ethers as an Enhancing Agent for Hydrogen Storage in the Metal–Organic Framework (MOF): Density Functional Theoretical Investigation . . . . . . . . . . . . . . . . . . 249 Anil Boda, Sk. Musharaf Ali, K. T. Shenoy and S. Mohan 26 Investigating Factors Affecting Mixing Patterns in Ternary Metal Alloy Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 Srikanth Divi and Abhijit Chatterjee 27 Estimation of Enthalpy of Formation of Metal Hydrides: Effect of Different Measurement Parameters . . . . . . . . . . . . . . . . . . 271 E. Anil Kumar, Dhananjay Mishra and Vinod Kumar Sharma 28 Electrochemical Synthesis of Interconnected Nanofiber Network of Polyaniline Electrode and Its Supercapacitive Properties . . . . . . 277 Snehal L. Kadam and Shrinivas B. Kulkarni 29 Reduced Order Model of Encapsulated PCMs-Based Thermal Energy Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 Mohit Jain, Appasaheb Raul and Sandip K. Saha

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30 Synthesis of Catalytically Active Pb from PbS for Electroreduction of CO2 to Formate in Alkaline Medium . . . . . . . . 297 Adhidesh S. Kumawat and Arindam Sarkar 31 Behavior of Nano-enhanced Phase Change Material in a Spherical Thermal Battery During Unrestricted Melting . . . . . 309 Vikram Soni and Arvind Kumar 32 An Experimental Study of a LTES with Compact Heat Exchanger Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321 Pavankumar Thippeswmay, Abhinav Bhaskar and Som Mondal 33 Modeling of Thermochemical Kinetics in Salt Hydrates for Thermal Energy Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331 Jagtej Singh Kharbanda, Sateesh Kumar Yadav, Vikram Soni and Arvind Kumar 34 Copper Oxide Synthesis on Cu Foam by Chemical Bath Deposition with Surfactant for Supercapacitor . . . . . . . . . . . . . . . . 345 Prasad E. Lokhande, Umesh S. Chavan, S. V. Deokar, Mukul Ingale and Himanshu Khadase 35 Numerical Analysis of Composite Phase Change Material in a Square Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 Santosh Chavan, Veershetty Gumtapure and D. Arumuga Perumal 36 High-Potential Cathode for Sodium-Ion Battery . . . . . . . . . . . . . . . 371 Ananta Sarkar, Pallavi Raj, Manas Ranjan Panda and Sagar Mitra 37 Investigation of NiO/CNF Coating on Glass Fiber Separator as Polysulfide Migration Inhibitors for High-Energy Lithium–Sulfur Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 P. Preetham, Amlan Roy, K. Anish Raj, Manas Ranjan Panda and Sagar Mitra 38 Performance Analysis of High Temperature Sensible Heat Solar Energy Storage System . . . . . . . . . . . . . . . . . . . . . . . . . 387 Geetanjali Raghav, Mohit Nagpal and Suresh Kumar 39 Influence of Geometric Configuration on Charging Characteristics of MmNi4.6Fe0.4 Based Hydrogen Storage Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397 Nithin Narmada Raju, Sayantan Jana and P. Muthukumar 40 Experimental Investigation on Micro-Scale Organic Rankine Cycle Using Scroll Compressor Converted Expander . . . . . . . . . . . 411 Bhavesh Patel, Nishith B. Desai, Surendra Singh Kachhwaha and Rahi Shah

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41 Some Investigations of External Shading Devices on Thermal and Daylighting Performance of a Building . . . . . . . . . . . . . . . . . . 421 Kishor Mane, Neeraj Agrawal and Abhijit Date 42 Computational Assessment of the Performance of an Air-Cooled Condenser Fan at Different Blade Pitch Angles and Speeds . . . . . . 429 Jay Sudani, Rutvesh Rathod, Harsimran Kassowal, Sunny Patel, Karan Panchal and Sodagudi Francis Xavier 43 Model for Assessment of Economics of Nuclear Power . . . . . . . . . . 439 Anil Antony and N. K. Maheshwari 44 Biomass Gasifier-Powered Adsorption Chiller for Atmospheric Water Harvesting: Prospects in Developing World . . . . . . . . . . . . . 451 Bathina Chaitanya, Ajay D. Thakur and Rishi Raj 45 Tuning the Solar Power Generation Curve by Optimal Design of Solar Tree Orientations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 461 Sumon Dey, Madan Kumar Lakshmanan and Bala Pesala 46 Development of Framework to Estimate Crop-wise, Region-wise Electricity Usage for Irrigation . . . . . . . . . . . . . . . . . . 471 Akanksha Doval and Priya Jadhav 47 Parametric Study of Ammonia-Activated Carbon Two-Bed Adsorption Refrigeration System . . . . . . . . . . . . . . . . . . . . . . . . . . 481 Ashok Verma, Satish and Prodyut R. Chakraborty 48 Solar PV for Irrigation in India: Developing a Framework for Determining Appropriate Pump Characteristics for a Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495 Namita Sawant and Priya Jadhav 49 How Do Supply-Side Constraints Affect the Rural Residential Feeder Parameters? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 505 Sneha Swami, Ganesh Hegde, Anand B. Rao and Satish B. Agnihotri 50 Building Energy Performance with Site-Based Airflow Characteristics in Naturally Ventilated Conditions in Low-Income Tenement Housing of Mumbai . . . . . . . . . . . . . . . . 519 Ronita Bardhan and Ramit Debnath 51 User Experience and Perception in First-Generation Green-Rated Office Buildings in India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531 Jeetika Malik and Ronita Bardhan 52 Electricity Planning for Bangladesh Under Various Scenarios . . . . 543 Dewan Mowdudur Rahman and Anand B. Rao

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53 Gap-Filling Techniques for Solar Radiation Data and Their Role in Solar Resource Assessment . . . . . . . . . . . . . . . . . . . . . . . . . 555 Dharmesh Kumar and B. Ravindra 54 A Model for Assessment of Economics of Renewable Hybrid Energy System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565 Anil Antony, Saikrishna Nadella and N. K. Maheshwari 55 Issues Pertaining to Energy Conservation in Railway Workshops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 Suresh D. Mane and N. Nagesha 56 Grid Management: Demand Forecasting in the Context of Increasing Renewables in the Grid . . . . . . . . . . . . . . . . . . . . . . . 589 Anasuya Gangopadhyay 57 A Simple Flowmeter for Fluids at High Temperature . . . . . . . . . . . 599 Pravin Gajbhiye, Nikhil Salunkhe, Shireesh Kedare and Manaswita Bose 58 Analysis of Energy Saving and Emission Reduction Potential Through the Energy Efficient Building Design of a Residential Building in a Warm Humid Climate . . . . . . . . . . . . . . . . . . . . . . . . 609 Sushibala Nambram, Arnab Jana and Krishnan Narayanan 59 Solar Water Heater: Efficient, Once-Through Heating Above 90 °C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 621 M. V. Rane and Tareke Tekia 60 Improved Performance of Mehsana Cookstove Through Minimal Design Modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 629 Munendra Singh Jha, Manaswita Bose and Shireesh Kedare 61 Techno-Economic Potential of Pre-combustion CO2 Capture in Bio-energy Pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 637 Harshit Agrawal and Anand B. Rao 62 Analysis of Heat Transfer and Entropy Generation During Natural Convection in a Cu–Water Nanofluid-Filled Porous Cavity for Different Thermal Boundary Conditions . . . . . . . . . . . . 649 D. Kashyap and A. K. Dass 63 Techno-Enviro-Economic Feasibility of CdTe and Micromorph-Based Thin-Film PV Systems . . . . . . . . . . . . . . . 663 Rahul Rawat, S. C. Kaushik, Tarun Singh and S. Manikandan 64 Study of Effects of Knurling on Heat Transfer of Rectangular Fins Through Forced Convection . . . . . . . . . . . . . . . . . . . . . . . . . . 675 Manoj S. Soni and Naga Veerendra Grandhi

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65 Intermediate Pyrolysis of Coconut Shells: Economics Related to Power Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 687 Kiran Kumar Dasari and Veershetty Gumtapure 66 Appliance Standards and Incremental Price of Efficiency . . . . . . . . 695 Manisha Jain, Anand B. Rao and Anand Patwardhan 67 Thermal Performance of Double-Pipe Concentric Heat Exchanger with Synthesized Zinc Oxide Nanofluid . . . . . . . . . . . . . 705 Surendra D. Barewar and Sandesh S. Chougule 68 Analyzing the Inequality Pathways of Domestic Electricity Consumption in India . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 715 Ganesh Hegde, Anand B. Rao and Satish B. Agnihotri 69 Experimental and Computational Evaluation of Pressure Drop and Heat Transfer Characteristics in Rectangular Channel with Helix Grooved Profile Pin Fins . . . . . . . . . . . . . . . . . 729 J. A. Siddiqui, Subhash Lahane, A. V. Gadekar and V. L. Lokawar 70 A Domestic Demand Model for India . . . . . . . . . . . . . . . . . . . . . . . 743 John Barton, Murray Thomson, Philip Sandwell and Alexander Mellor Author Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 755

About the Editors

Suneet Singh is a faculty at the Department of Energy Science and Engineering, Indian Institute of Technology Bombay (IITB), India. He received his MTech and PhD in Nuclear Engineering from the IIT Kanpur and the University of Illinois at Urbana-Champaign, USA, respectively. He completed his postdoctoral research at Idaho National Lab, USA. He has received the Bhaskara Advanced Solar Energy (BASE) Fellowship 2014 from the Indo-US Science & Technology Forum (IUSSTF). His research interests include stability analysis of nuclear reactors, advanced numerical methods for fluid flows and neutron diffusion, analytical solution of multilayer heat conduction problems, and solar thermal heat transfer. Venkatasailanathan Ramadesigan is a faculty at the Department of Energy Science and Engineering, Indian Institute of Technology Bombay (IITB), India. He received his MS in Chemical Engineering from the University of South Carolina USA, and PhD in Energy, Environmental, and Chemical Engineering from Washington University in Saint Louis, USA. His research interests include modelling and simulation of chemical and electrochemical processes, electrochemical large/ grid-scale energy storage systems, system integration, nonlinear parameter estimation, and system-level optimization and control, as well as numerical and applied mathematics.

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Chapter 1

Study of Soiling Effect on Inclined Photovoltaic Surfaces Sumon Dey, Veena Aishwarya and Bala Pesala

Abstract The present work reports on the initial results of experiments conducted aiming to investigate the effects of soiling losses on tilted PV surfaces. Identical glass coupons have been exposed outdoors for eight weeks at different inclinations (0°–36°), and weekly hemispherical transmittance measurements and drop in shortcircuit current of solar cell placed under the glass are compared. The results show that the blue end of the spectrum is more affected by dust accumulation. Maximum losses as high as 6.86% and 7.66% in hemispherical transmittance and short-circuit current, respectively, have been recorded during the 8-week outdoor exposure for coupon with 0° tilt angle. Minimum loss occurred for the coupon kept at 36° tilt angle and was found to be 4.86% and 5.02% for hemispherical transmittance and short-circuit current, respectively. It is observed that transmittance drop is linearly correlated with that of tilt angle of a surface. As expected, more the tilt angle of a surface, less is the transmittance drop. Keywords Soiling · Tilted surface · Solar photovoltaics · Hemispherical transmittance · Short-circuit current

1.1 Introduction The solar photovoltaic (PV) market in Africa, Middle East, India, China, and USA is burgeoning because of the copious solar irradiance in these regions. However, PV installations in these places are severely affected by dirt accumulation on the module surface commonly referred to as “soiling.” Soiling causes reflection and absorption losses, thereby degrading the solar module performance. A recent S. Dey · B. Pesala (B) Academy of Scientific and Innovative Research, Ghaziabad 201002, India e-mail: [email protected] S. Dey CSIR-Structural Engineering Research Centre, Chennai 600113, India V. Aishwarya · B. Pesala CSIR-Central Electronics Engineering Research Institute, Chennai 600113, India © Springer Nature Singapore Pte Ltd. 2020 S. Singh and V. Ramadesigan (eds.), Advances in Energy Research, Vol. 1, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-15-2666-4_1

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review article on soiling provides an overview on the soiling issues [1]. Major solar installations are situated in places which are characterized by high air-borne particle environment, intense dust storms, and water availability concerns. These issues have raised concerns regarding soiling among the PV installers across the world. There have been numerous studies on the effect of soiling on solar PV performance. The reported annual loss for USA ranges from 0 to 6% depending on the geographic location. While for dusty environments found in countries such as Middle East, India, and China, the reported peak loss ranges are higher ranging from 20% to 50% [2, 3]. A number of research works have established the relation between cumulative dust accumulation, solar radiation, and energy loss [4]. These research works provide a knowledge base that helps us get an idea regarding the soiling trends at various locations. They also help system developers select appropriate sites and establish cleaning schedules. However, several of these studies are based on artificially deposited dust particles. Dust accumulation on the surface of PV panels depends on a number of factors which can be broadly categorized under three heads, namely environmental factors, dust type, and location and installation factors. Environmental factors include wind movement, wind direction, temperature, irradiation, air pollution level, air pressure, volcano, dust storm, snow, and humidity. Rain level and wind speed play significant roles on the cleaning rate depending on the tilt angle [5]. Dust type categories include the clay or carbon content of the soil. In a study conducted in 2014 on the effect of different pollutant types on solar PV systems, out of 15 different soil types’ studied, six of them (ash, calcium, limestone, soil, sand, and silica) were found to have significant effect on PV soiling [6]. The incident irradiance on PV cells and its operating temperature primarily dictate the power output of a module. In a dual-axis tracking system, when module surface and the incident light rays are perpendicular to each other, the power output will be the highest [7]. Location and installation factors could include proximity to sandy or industrial area, glass material of the solar panel surface, height, tilt angle and orientation of the panel, and latitude/longitude of the location. The dust effect is present at any angle, but the relative magnitude differs [8]. Interdependence of all the above-mentioned factors on each other makes the soiling process complicated and difficult to predict. The work presented here shows the preliminary results of an experiment aimed to investigate the effects of soiling on PV glass installed at different angles.

1.2 Description of Experimental Setup The test was conducted at Chennai, India, located at 13.08° N and 80.27° E. Sixteen identical BOROFLOAT® 33 glass coupons of size 4 cm × 5 cm and 2 mm thickness from Schott were used for the experimental purpose. The glasses were labeled as A, B, C, D and E which correspond to glasses installed at tilt angles 0°, 9°, 18°, 27°, and 36°, respectively. For the purpose of study, three glass coupons were installed under each label, i.e., at each tilt angle marked as A1, A2 and A3. All the coupons

1 Study of Soiling Effect …

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Fig. 1.1 Setup of experiment

were installed outdoors facing south, using supporting structures shown in Fig. 1.1. Another similar coupon labeled R was kept in a safe, dust-free container and used as reference to compare the spectrometer readings. Weekly hemispherical transmission measurements were taken on coupons 1, 2, and 3 of each label using Ocean Optics USB 2000+ spectrometer in the wavelength range from 400 to 1100 nm. Power output of a solar cell depends on the irradiance received on its surface, and the short-circuit current of solar cell is directly proportional to the incident irradiance. Hence, to measure the drop in output power due to soiling, a solar cell is placed under each soiled glass and the drop in short-circuit current (Isc ) was recorded. The measurement of Isc was done under Oriel Class AAA solar simulator. Coupon 1 was cleaned weekly, coupon 2 was cleaned every 4 weeks, and coupon 3 was never cleaned. A dry cleaning is performed by using a microfiber cleaning cloth. Daily weather data including solar irradiance, temperature, humidity, rainfall, and mean daily concentrations of particulate matter (PM2.5) have been recorded. The test is conducted for a period of two months.

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1.3 Results and Discussions 1.3.1 Impact of Soiling on Hemispherical Transmittance The study was commenced in May 2017. The average weekly drop in transmittance (T d ) of the coupons and the maximum drop are shown in Table 1.1. It can be seen clearly from the table that the drop in transmittance (T d ) decreases with an increase in tilt angle (β). The polynomial curve fitting to the data showed the linear relationship between transmittance drop (T d ) and tilt angle (β) of the surface. The curve fit equation, which has been shown below, has a low value of root mean squared error of 0.1 which shows goodness of fit. Figure 1.2 shows the fitted plot along with the higher and lower limits of transmittance loss (obtained by measuring at different locations on the surface) in one week. According to this study, for Chennai, an increase in transmittance of 0.3% can be expected for every 10° increase in tilt angle of the surface. The reason for this decrease in dust accumulation with increase in tilt angle could be due to the removal of higher weight dust particles from the tilted glass surface due to the effect of gravitational pull and wind. As a result when tilt angle increases, the amount of dust adhering to the surface decreases. Td = −0.034β + 2.426 Table 1.1 Coupons with average and maximum drop in 1 week

Fig. 1.2 Relation of transmittance drop with tilt angle of surface

(1.1)

Coupon

Tilt angle

Average weekly drop (%)

Maximum drop (%)

A

0°

−2.41

−3.00

B

9°

−2.22

−2.61

C

18°

−1.69

−2.41

D

27°

−1.52

−2.26

E

36°

−1.23

−1.97

1 Study of Soiling Effect …

5

During the period of study, a number of meteorological parameters such as temperature, humidity, rainfall intensity, particulate matter density (PM2.5), irradiance, and wind speed were recorded. The correlations of dust accumulation with each of the parameters were investigated. It is found that rainfall and PM2.5 intensity have a stronger correlation with the dust accumulation process. Figure 1.3 shows the drop in transmittance of coupon 3, which has never been cleaned manually, for various tilt angles. Figure 1.4 shows the trend in the rainfall and PM2.5 intensity over the experimental time period. It may be noticed that rate of decrease in transmittance is lower for higher values of tilt angle. The coupons are cleaned due to the rainfall after the fourth week. However, it is observed that the degree to which each of the coupon is cleaned varies and is maximum in the case of coupon E which is at a tilt angle of 36°. This is because the water easily flows down a tilted surface and carries the surface dust particles along with it, whereas for a horizontal surface, the water droplets accumulate on the surface of glass and create patches. Moreover, the first rain of 12 mm between week 4 and week 5 has not been able to clean the coupons completely. This may be due to the adhesion of the dust particles on the glass surface. The coupons have regained transmittance close to that of a clean coupon only after the consecutive heavy rains in the sixth week. Rate of transmittance drop is lower in the fifth week compared to weeks 1–4. This may be attributed to the low value of the PM2.5 during the week. Fig. 1.3 Trend of transmission drop in 8 weeks

Fig. 1.4 Rainfall and particulate matter (PM2.5) intensity during the period of study

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Fig. 1.5 Transmittance loss of coupons at different tilt angle when not cleaned for 4 weeks

Fig. 1.6 Comparison of transmission spectrum of the coupons with reference coupon

Figure 1.5 shows the trend in transmission losses the coupons exhibit for period of 4 weeks. Coupon A having 0° tilt angle shows the highest rate of transmittance drop. A maximum of 6.86% drop is encountered in coupon A (0° tilt) and 4.48% in coupon E (36° tilt) for period of 4 weeks. Figure 1.6 gives a comparison of transmission spectrum of reference coupon with that of the dusted coupons after 8 weeks of study. The reference coupon is preserved in a clean place without any kind of dust or soil particles in it. The figure shows the clear explanation that lesser the tilt, more the dust accumulation. Also, it may be noticed that the dust accumulation affects the blue part of the spectrum more than the rest of the spectrum due to higher Rayleigh scattering of lower wavelengths.

1.3.2 Impact of Soiling on Short-Circuit Current Figure 1.7 shows the loss in short-circuit current (Isc ) of a solar cell placed under the dusty coupons when they were not cleaned for 4 weeks. Measurements for all weeks exhibit the same trend, with maximum drop of 7.66% in 0° tilt and minimum drop of 5.02% in 36° tilt. The difference in the maximum and minimum drop was also

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7

Fig. 1.7 Decrease in short-circuit current (Isc ) at different tilt angle when not cleaned for 4 weeks

found to be increasing for each week. It can be inferred that drop in Isc is correlated with that of transmittance. But it may not always be linearly correlated due to the spatial non-uniformity of the soiling process.

1.4 Conclusion Soiling studies were done for various tilt angles, and the results clearly demonstrate that 0° inclination has more soling effect compared to 36° inclination. The coupons were not completely cleaned even after two consecutive heavy rainfalls. The adhesive dust accumulation requires manual cleaning to regain 100% transmissivity. The study showed that blue part of the spectrum is more affected by dust accumulation. Also, the drop in short-circuit current also followed the same pattern as that of hemispherical transmittance, with maximum of 7.66% drop in coupon A (0° tilt) and minimum of 5.02% drop in coupon E (36° tilt). Current studies are being continued to investigate the long-term soiling losses on tilted PV surfaces. These results would be extremely useful for solar power plant installers to understand the effect of soiling losses on PV module performance and to optimally choose the solar PV module cleaning schedules. Acknowledgements The authors would like to thank the Director General of CSIR, Director (CSIR-SERC), Director (CSIR-CEERI), Scientist-In-Charge (CSIR-CEERI) and Scientist-InCharge (CSIR-CSIO) for their kind support and encouragement throughout the research work. Part of the research work has been carried out with equipment of CSIR Innovation Complex. We would also like extend our heartfelt gratitude to all our colleagues from the AcSIR Renewable Energy program for all the support. Author Sumon Dey thanks Director, CSIR-SERC and CSIR-SRF fellowship for financial support.

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References 1. T. Sarver, A. Al-Qaraghuli, L.L. Kazmerski, A comprehensive review of the impact of dust on the use of solar energy: history, investigations, results, literature, and mitigation approaches. Renew. Sustain. Energy Rev. 22, 698–733 (2013) 2. S.C.S. Costa, A.S.A.C. Diniz, L.L. Kazmerski, Dust and soiling issues and impacts relating to solar energy systems: literature review update for 2012–2015. Renew. Sustain. Energy Rev. 63, 33–61 (2016) 3. L. Micheli et al., A unified global investigation on the spectral effects of soiling losses of PV glass substrates: preliminary results. 43rd IEEE Photovolt. Spec. Conf. 3–8 (2017) 4. A. Sayyah, M.N. Horenstein, M.K. Mazumder, Energy yield loss caused by dust deposition on photovoltaic panels. Sol. Energy 107, 576–604 (2014) 5. J. Cano, J.J. John, S. Tatapudi, G. Tamizhmani, Effect of tilt angle on soiling of photovoltaic modules. 2014 IEEE 40th Photovolt. Spec. Conf. PVSC 2014 3174–3176 (2014). https://doi. org/10.1109/pvsc.2014.6925610 6. M.R. Maghami et al., Power loss due to soiling on solar panel: a review. Renew. Sustain. Energy Rev. 59, 1307–1316 (2016) 7. N. Martín, J.M. Ruiz, Annual angular reflection losses in PV modules. Prog. Photovoltaics Res. Appl. 13, 75–84 (2005) 8. T. Negash, Experimental investigation of the effect of tilt angle on the dust photovoltaic module. Int. J. Energy Power Eng. 4, 227 (2015)

Chapter 2

Efficiency Enhancement of Betanin Dye-Sensitized Solar Cells Using Plasmon-Enhanced Silver Nanoparticles S. Sreeja, S. Prabhakaran and Bala Pesala

Abstract In this study, we investigate the use of silver (Ag) nanoparticles (NPs) to enhance the efficiency of betanin dye-sensitized solar cells (DSSCs) by plasmonic effect. Betanin is a natural pigment with an absorption band in the green region (from 450 to 600 nm peaking at 535 nm). If there is good energy match between the extinction bands of the metallic NPs and absorption bands of the dye, an enhancement in solar cell efficiency can be achieved by incorporating them with betanin in the solar cell. The extinction band of the metallic NPs depends upon its size, morphology and dielectric medium. In order to optimize the nanoparticle dimensions according to the absorption band of betanin, finite-difference time-domain (FDTD) simulations have been performed. The electric field profiles of the AgNPs were studied at ON and OFF resonant wavelengths. It was determined that the performance of DSSCs could be potentially enhanced by incorporating AgNPs of sizes ranging from 50 to 80 nm. An average efficiency of 0.581% is achieved for a betanin DSSC, while an increased efficiency of 0.683% is achieved for AgNP-incorporated betanin DSSCs. The 17.55% increase in efficiency is due to enhanced light harvesting by the AgNPs due to surface plasmon resonance (SPR) which resulted in an increased photocurrent density. Keywords Dye-sensitized solar cells (DSSCs) · Natural pigments · Surface plasmon resonance (SPR) · Metal nanoparticles · Finite-difference time-domain (FDTD) simulations

S. Sreeja · S. Prabhakaran · B. Pesala (B) Academy of Scientific and Innovative Research (AcSIR), Chennai, India e-mail: [email protected] S. Sreeja · B. Pesala CSIR-Central Electronics Engineering Research Institute (CSIR-CEERI), CSIR-Madras Complex, Chennai, India S. Prabhakaran CSIR-Central Scientific Instruments Organization (CSIR-CSIO), CSIR-Madras Complex, Chennai, India © Springer Nature Singapore Pte Ltd. 2020 S. Singh and V. Ramadesigan (eds.), Advances in Energy Research, Vol. 1, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-15-2666-4_2

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2.1 Introduction Dye-sensitized solar cells (DSSCs) have been receiving increasing attention in recent years due to their relatively high efficiency and low cost of component materials [1]. DSSCs conventionally use rare-metal-based toxic dyes; therefore, natural dyes are being explored by multiple research groups as alternative photosensitizers for DSSCs. These are comparatively advantageous in terms of their abundance, non-toxicity and reduced cost [2]. However, the efficiencies of natural dye solar cells are much lower than those that use synthetic dyes since their absorption bands are quite narrow [3, 4]. Several plant pigments, such as chlorophylls, anthocyanins and betalains, have been studied for their application in DSSCs [4, 5]. On comparing several natural dyes, betanin possesses better anchoring groups (carboxylic groups [–COOH]), which will enable strong binding to the TiO2 surface required for efficient electron injection. Betanin is extracted from beets, and its general chemical structure and absorption spectrum can be seen in Fig. 2.1a, b, respectively [6]. When electromagnetic radiation is incident on metal NPs in a dielectric medium, electrons inside the metal nanoparticle begin oscillating at their surface plasmon frequency, which results in an effective resonant behavior known as the surface plasmon resonance (SPR) [7]. This behavior can potentially enhance the absorption by the dye sensitized on the TiO2 surface if the absorption band of the dye matches the scattering band of the nanoparticles incorporated with it [8]. Gold, silver and copper nanoparticles show resonance in the visible or near-infrared region. Therefore, they are being explored for photovoltaic applications [9]. In this work, the dimensions of AgNPs required for its scattering band to match the absorption band of betanin were optimized through finite-difference time-domain (FDTD) simulations using Lumerical software. The study demonstrates that silver nanoparticles of sizes ranging from 50 to 80 nm can potentially be used in the betanin dye-sensitized solar cells to enhance its efficiency.

Fig. 2.1 a Chemical structure of betanin. b Absorption spectrum of betanin [6]

2 Efficiency Enhancement of Betanin …

11

The solar cells were fabricated, and their performance characteristics were measured. The results show an efficiency enhancement of 17.55% by incorporation of nanoparticles.

2.2 Methods 2.2.1 FDTD Simulations FDTD simulations using Lumerical software were performed to optimize the Ag nanoparticle dimensions. Ag parameters from Palik material database and a totalfield/scattered-field (TFSF) light source (with a wavelength range of 300–800 nm) were used to perform the 3D simulations. Water (refractive index = 1.33) was set as the surrounding environment. The mesh size of the simulation region was set as 0.5 nm, and perfectly matched layer (PML) boundary conditions were applied. The extinction, absorption and scattering plots were obtained for Ag nano-spheres of diameters of 20–100 nm, varied in steps of 10 nm.

2.2.2 Fabrication of the Solar Cells Preparation of the fluorine-doped tin oxide (FTO)-coated substrates (purchased from Solaronix, size = 15 mm × 15 mm × 2 mm; transmittance >83% and resistivity 1000

>1000

>1200

Pass (0.996 KV)

Pass (1.49 KV)

158 °C and 16 min

>1000

>1000

>1200

Pass (0.996 KV)

Failed (0.996 KV)

158 °C and 16 min

>1000

>1000

>1200

Pass (0.996 KV)

Failed (0.996 KV)

158 °C and 16 min

>1000

>1000

>1500

Pass (0.996 KV)

Failed (0.996 KV)

158 °C and 12 min

0

0

0

Failed (0.469 KV)

Failed (0.563 KV)

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11.3.3 Mounting Solution As these modules will be frameless modules there is a need of special mounting solution. The frame has been replaced by insulating tape sealed around the edges. This can also be clamped over the roof using clamping solution. Various options are being worked with the design team at Tata Elxsi, Bangalore, and IIT Mumbai. This product is now planned to be used as roofs of modular toilets and affordable units built by NEST-IN (Sub-brand of Tata Shaktee) (Fig. 11.16 and 11.17).

Fig. 11.16 Mounting solution for frameless modules

Fig. 11.17 Nest in toilet with solar roof

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11.3.4 Solar-Integrated Motor Vehicle The polymer coating can be used over other metals such as aluminum plate which can be used as a substrate for making solar panel for energizing vehicle. The main motive of the car is to harness and run solely on solar energy. Hence, it is very important that we have highly efficient and lightweight solar panels (Figs. 11.18, 11.19, and 11.20). Fig. 11.18 Solar panel in flexible design

Fig. 11.19 Initial analysis—to verify wind speed for the panel

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Fig. 11.20 Solar-driven motor vehicle

11.4 Conclusion Metal-integrated solar panel will be future technology look for the photovoltaic field due to advantage of lightweight and heat dissipation properties. This will also play major role in bringing down the cost of solar panels. More commodity products with this concept are on the verge of coming into the market such as solar bag and table. Acknowledgements The authors gratefully acknowledge the contribution of the Tata Steel Ltd. in their contribution on developing the dielectric coating.

References 1. P. Bose, M. Narasimhan, A. Mahajan, T.K. Raut, A. Shanmugasundram, Light weight dielectric coated metal integrated solar module, Patent No. (1581/CHE/2015), Tata Power Solar Systems Ltd. and Tata Steel, 2015 2. F. Husser, T. K. Rout, S. Das, V. Naresh Rao, S. Maity, A. Sarkar, Patent Application Number 241/Kol/2013

Chapter 12

Study on Spray-Deposited Cu2 ZnSnS4 Thin Films: Deposition and Physical Properties Jitendra P. Sawant and Rohidas B. Kale

Abstract Cu2 ZnSnS4 thin films were deposited using spray pyrolysis deposition technique. The effect of deposition temperature and film thickness on various physical properties of Cu2 ZnSnS4 thin films was studied. The structural study using X-ray diffraction technique revealed that the crystallinity of films was improved on increasing substrate temperature and film thickness. Energy-dispersive X-ray spectroscopy analysis revealed near-stoichiometric film composition. The atomic force microscope images showed formation of smooth, compact and uniform Cu2 ZnSnS4 thin films over substrate surface. The X-ray photoelectron spectroscopy characterizations confirm the oxidation states of the elements in CZTS as 1+ , 2+ , 4+ and 2− for copper, zinc, tin and sulfur, respectively. Energy band gap was estimated to be 1.56 eV, indicating that Cu2 ZnSnS4 compound has absorbing properties favorable for applications for solar cell devices. Keywords Spray pyrolysis · X-ray diffraction · Nanomaterials

12.1 Introduction The interest in development of thin-film solar cells has been growing over the past decade. Recent advances in CdTe and CuIn1−x Gax Se2 (CIGS) thin-film solar cells have resulted in commercially viable photovoltaic modules [1–3]. Solar cell based on CdTe and CIGS technology is not amenable for large-scale production due to the large processing cost and availability issues of Te, In and Ga elements. Therefore, one major challenge to thin-film technology is to develop solar cells using non-toxic, low-cost deposition technique and earth-abundant material. Quaternary copper–zinc–tin–sulfide (Cu2 ZnSnS4 —CZTS) has emerged as a high potential photovoltaic material. The main advantages of CZTS material are that the constituent elements are non-toxic, low cost and earth abundant. The direct band gap of CZTS material is 1.5 eV, which is close to the optimum value of solar cell application. Optical absorption coefficient is ~104 cm−1 , which makes it suitable candidate to be used as a light absorber layer in thin-film solar cell. The CZTS J. P. Sawant (B) · R. B. Kale Department of Physics, The Institute of Science, Madam Cama Road, Mumbai 400032, India © Springer Nature Singapore Pte Ltd. 2020 S. Singh and V. Ramadesigan (eds.), Advances in Energy Research, Vol. 1, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-15-2666-4_12

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compound exists in kesterite and stannite phase with space group I¯4 and I¯42 m [4, 5]. Both having tetragonal structures, with cubic closely packed array of sulfur as anions, and cations positioning at one half of the tetrahedral voids, with a stacking similar to zincblende with lattice constant a = 5.46 Å and c = 10.93 Å [5]. Variety of methods has been utilized for fabrication of CZTS thin film that includes sputtering [6, 7], thermal and vacuum evaporation [8–10], ion beam sputtering [11], sputtering with sequential evaporation [12], electrodeposition [13], SILAR [14, 15], etc. The direct growth of CZTS thin films using simple and scalable technique would be highly desirable in order to reduce the fabrication costs. In this contest, spray pyrolysis deposition method could be suitable deposition methods of deposition of CZTS thin films. In the present work, we have reported on direct growth of CZTS layers on the glass substrate via spray pyrolysis. The effect of substrate temperature and film thickness on the structural, compositional, morphological and optical properties CZTS thin films was investigated. In most of the reports, CuCl2 , ZnCl2 and SnCl2 were used as anionic precursors and also N2 gas as a carrier gas. Herein, we have deposited CZTS thin films using CuSO4 , ZnSO4 and SnCl2 as an anionic precursor and [(NH2 )2 CS] as a sulfur source, and deposition was carried out at relatively lower substrate temperatures.

12.2 Experimental Section 12.2.1 Film Deposition and Characterization Technique The CZTS thin films were deposited by spray pyrolysis technique starting with an aqueous solution containing (0.02 M) CuSO4 .5H2 O, (0.02 M) ZnSO4 , (0.02 M) (SnCl2 ) and (0.4 M) (NH2 )2 CS. The aqueous solution of the above precursors was mixed in the ratio of Cu:Zn:Sn:S = 2:1:1:8. Few drops of concentrated HCl (30%) were added into it to lower the pH < 4 so as to avoid the precipitation of the reactant solution. Finally, the resultant solution was sprayed on a glass substrate in the air atmosphere at a rate of 7 ml/min. Vigil-Galán demonstrated that the films deposited in the air atmosphere showed improved crystallinity than the films deposited in N2 atmosphere [16]. Excess thiourea was used in order to compensate the sulfur loss that occurs when thin films were deposited by spray pyrolysis technique [17]. In order to find optimum temperature for depositing good quality CZTS thin films, deposition was carried by varying substrate temperature in the range of 250–400 °C by spraying 80 ml of solution on the glass substrate. To study the effect of film thickness, thin films were deposited at temperature of 400 °C by spraying 40, 60, 80 and 100 ml solution. The structural characterization of CZTS thin films was carried out by analyzing X-ray diffraction (XRD) patterns obtained in range 20° ≤ 2θ ≤ 80° with a scan rate of 2°/min using XRD system (XPERT-PROMPD) equipped with a CuKα source of λ = 1.5412 Å. The surface morphology and film composition of deposited thin films were studied by scanning electron microscope (SEM) model,

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JEOL-JSM-IT300 equipped with energy-dispersive X-ray spectroscopy (EDS). The three-dimensional (3D) surface topography was observed using atomic force microscope (AFM) of PicoScan. The optical properties were studied by measuring optical absorption at room temperature using Shimadzu UV-1800 spectrophotometer. The CZTS film thickness was measured using surface step profiler (DektakXT Profilometer). X-ray photoelectron spectroscopy (XPS) measurements were carried out on PHI 5000 VersaProbe II spectrometer.

12.3 Results and Discussions 12.3.1 Structural Characterization Figure 12.1a depicts XRD pattern of CZTS thin films deposited at different substrate temperatures. The film prepared at 250 °C is poorly crystalline, and no well-defined peaks were observed. The intensity of diffraction peaks increased gradually and the peak become narrower with increasing reaction temperatures, indicating the improvement in the crystallinity. The observed peaks could be indexed to (112), (220) and (312) planes, which are the characteristic peaks of standard kesterite structure of CZTS material (JCPDS File no. 26-0575). Figure 12.1b shows the XRD patterns of CZTS thin films of different thicknesses deposited at 400 °C substrate temperature. The XRD patterns clearly illustrate that the CZTS thin film deposited with lower thickness was poorly crystallized, and only (112) plane shows its appearance. However, there is doublet of peak that is appeared at smaller thickness, may be due to the presence of Cu3 ZnS3 phase. In Fig. 12.1b, all the samples exhibit weak peak at around 42°, may be due to the presence of Cu3 Sn phase. The new diffraction

Fig. 12.1 XRD patterns of spray-deposited CZTS thin film at a 250, 300, 350 and 400 °C substrate temperatures and b different thicknesses 0.44, 0.963 and 1.534 μm

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Table 12.1 Details of XRD analysis of spray-deposited CZTS thin film deposited at different substrate temperatures Substrate temperature (°C)

2θ (deg) (112)

FWHM (deg)

d spacing (nm)

Lattice parameters (nm)

D-S (nm)

Eg (eV)

a

c

D

400

28.54

0.34

0.312

0.542

1.084

24

1.55

350

28.54

0.38

0.315

0.541

1.082

21

1.50

300

28.54

0.42

0.313

0.542

1.084

19

1.48

250

28.54

0.52

0.312

0.542

1.084

16

1.48

Table 12.2 Details of XRD analysis of spray-deposited CZTS thin film of different thicknesses Film thickness (μm)

2θ (deg)

FWHM (deg)

d spacing (nm)

Lattice parameters (nm)

D-S (nm)

E g (eV)

a

c

D

0.44

28.60

0.6

0.312

0.54

1.08

13

1.44

0.698

28.56

0.55

0.316

0.53

1.07

15

1.5

1.541

28.56

0.45

0.315

0.54

1.08

18

1.56

peaks (220) and (312) show their appearance of enhancement in peak intensity with increasing thickness. The intensity of (112) plane is higher as compared to other diffracted peaks, confirming preferred orientation of grown films along the (112) plane. The average crystallite size of CZTS was calculated using Debye–Scherrer formula [18]. The lattice parameters were calculated and are summarized in Tables 12.1 and 12.2. The values are in well agreement with earlier report [19]. From Table 12.1, it is revealed that the particle size increased as the substrate temperature increased. There is no significant change in the average particle size that was observed as the thickness of the film increased (Table 12.2). It is worthwhile to note that the crystallite size of CZTS thin film was found to be increased with increasing deposition temperature. Katagiri et al. [20] studied the effect of thickness of CZTS absorber layer on the device parameter. Conversion efficiency of 1.46% was reported from 0.95 μm thin CZTS absorber layer, grown using e-beam evaporation method.

12.3.2 Morphological and Compositional Study Figure 12.2a–e depicts SEM images of three CZTS samples of different thicknesses deposited at 400 °C. For lower film thickness, surface of the film is observed to be smooth, compact and homogenous as shown in Fig. 12.2a, b. As film thickness increased, the particle agglomeration starts to take place and size of the grain is

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Fig. 12.2 SEM images of spray-deposited CZTS thin films of a 0.44 μm, b 0.698 μm and c 1.53 μm thicknesses

observed to be increased. Careful examination further revealed two-layer growth of CZTS over the substrate surface (Fig. 12.2c–f). The initially formed layer is seen to be covered with densely packed micron-sized interconnected spherical CZTS grains [21]. The morphological observations clearly reveal nanocrystalline nature at higher magnification. Valdes et al. have reported such a compact structure of CZTS thin films at the same range of substrate temperature [22]. The typical EDS pattern of CZTS thin film is shown in Fig. 12.3a. The strong peaks of Cu, Zn, Sn and S were clearly seen in the EDS spectrum. The compositional variation of Cu, Zn, Sn and S in the film with respect to three temperatures is shown

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Fig. 12.3 a EDS spectrum of CZTS thin film. b Histogram representing the composition of elements in CZTS thin film deposited at different temperatures

in Fig. 12.3b. From the figure, it is found that at lower temperature, all film showed the sulfur-rich composition. The CZTS films which grown at 400 °C temperature exhibit sulfur content close to stoichiometric value. The compositional analysis of as-deposited CZTS thin films is given in Table 12.3. Surface morphology of CZTS thin films was also observed using AFM technique. Figure 12.4a–c depicts the 3D AFM images of CZTS thin films of different thicknesses. Based on the 3D AFM micrographs, the average roughness of the CZTS films of 0.44, 0.693 and 1.534 μm thickness was found to be 10.42, 16.46 and 29.88 nm, respectively. It is revealed that the average roughness of CZTS thin films was found Table 12.3 Details of XRD analysis of spray-deposited CZTS thin film of different temperatures Temperature (°C)

Cu/(Zn + Sn)

Zn/Sn

52.10

0.97

0.836

51.35

0.93

0.81

49.29

0.92

0.88

Elemental composition (in at. %) Cu

Zn

Sn

S

300

25.11

11.80

14.10

350

26.33

12.64

15.68

400

28.18

14.30

16.25

Fig. 12.4 AFM image of spray-deposited CZTS thin film of a 0.44 μm, b 0.698 μm and c 1.53 μm thicknesses

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to be increased with increasing film thickness. AFM micrograph shows the clusters of size of the range of 100–200 nm. X-ray photoelectron spectroscopy analysis was carried out to investigate oxidation state of the constituent elements Cu, Zn, Sn and S present in the CZTS thin films. Figure 12.5a shows a Cu 2p core-level XPS spectrum of CZTS. There are two peaks located at 932.37 (2p3/2 ) and 952.37 eV (2p1/2 ). It is in good agreement with the standard separation (19.9 eV) of Cu(I) [23] indicating the formation of Cu(I) after reduction of Cu(II) of the starting material during the course of reaction [24]. Figure 12.5b shows well-resolved Zn doublet located at 1045.65 eV (2p3/2 ) and 1022.35 eV (2p1/2 ) with orbital splitting of 23.25 eV, which can be assigned to Zn (II) and consistent with standard splitting of 22.97 eV [25]. Figure 12.5c depicts peaks of Sn 3d with binding energies of 486.2 (2p5/2 ) and 494.8 eV (2p3/2 ) with an orbital splitting of 8.6 eV, which is in good accordance with the value of Sn (IV) [25]. Figure 12.5d shows S 2p peaks located at 161.93 (2p3/2 ) and 163.16 eV (2p1/2 ), which are consistent with the binding energy of S in the sulfide state in CZTS [26].

Fig. 12.5 High-resolution XPS analysis of four constituent elements a Cu 2p, b Zn 2p, c Sn 3d and d S 2p

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Fig. 12.6 (αhν)2 versus (hν) plot of spray-deposited CZTS thin film at a different substrate temperatures and b different film thicknesses

12.3.3 Optical Properties Inset of Fig. 12.6a shows the plot of optical absorbance (αt) with wavelength (λ) of CZTS thin films deposited at different temperature. It is seen that the optical absorption of CZTS increases with increasing in substrate temperature. The band gap of the CZTS films was determined by extrapolating the linear region of the (αhν)2 versus hν curve on energy axis (Fig. 12.6a). From plot, it is clear that the band gap was decreased from 1.55 to 1.48 eV as substrate temperature increased. Our estimated band gap values are in good agreement with values reported by Srinivasan et al. [27]. In the similar way, optical absorbance of CZTS thin films with different film thicknesses is shown in Fig. 12.6b. The estimated band gap values are 1.44, 1.5 and 1.56 eV, respectively, for 0.44, 0.693 and 1.534 μm film thickness which agreed with reported values [20]. Rajeshmon et al. [28] and Seboui et al. [29] reported that CZTS films prepared using copper chloride and zinc acetate, and stannous SnCl2 exhibits a direct band gap of 1.3 and 1.79 eV, respectively, and predicted that pure kesterite CZTS phase may have formed. Small change in band gap was observed with respect to optimized value of band gap 1.5 eV, and it may be because of the composition change of CZTS sample. Average absorption coefficient is found to be > 104 cm−1 . Our results are in well agreement with the earlier reporter [30–32] in which CuCl2 and ZnCl2 precursors were used as Cu and Zn ion source.

12.4 Conclusion Cu2 ZnSnS4 quaternary semiconductor thin films were successfully deposited via low-cost spray pyrolysis method. The effects of substrate temperature and film thickness on structural, morphological and optical properties were investigated. All film

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exhibited nanocrystalline nature and were grown with kesterite crystal structure. XRD, EDS, XPS, AFM and optical characterizations confirm the successful growth of CZTS thin films. XPS characterizations confirm desired valence state of elements of kesterite CZTS compound. The direct optical band gap of CZTS films deposited under optimized conditions was found to be 1.55 eV with an optical absorption coefficient of > 104 cm−1 suitable for its use as a light absorber layer in the solar cell. SEM study revealed compact and dense CZTS thin films grown on glass substrate. EDS analysis showed that at lower substrate temperature, films were found to be rich in sulfur content, but at optimized temperature (400 °C), sulfur was close to stoichiometry in as-grown CZTS films. The present work gives an insight that the sprayed CZTS thin films could be used as a light absorber layer in the CZTS-based solar cell. It is concluded that easy, low-cost, convenient and eco-friendly spray pyrolysis method can be used to deposit good quality quaternary CZTS thin films. Acknowledgements This research work is supported by the Department of Science and Technology, India, under DST-FIST (SR/FST/PSI-173/2012) program. Authors are thankful to Director, The Institute of Science, Mumbai, for encouragement and providing the necessary facilities. Authors are also thankful to INUP, as a part of the reported work (characterization) that was carried out at the IITBNF, IITB, under INUP which is sponsored by DeitY, MCIT, Government of India.

References 1. J. Scragg, P. Dale, L. Peter, G. Zoppi, I. Forbes, New routes to sustainable photovoltaics: evaluation of Cu2 ZnSnS4 as an alternative absorber material. Phys. Status Solidi (b) 245, 1772–1778 (2008) 2. C. Wadia, A. Alivisatos, D. Kammen, Materials availability expands the opportunity for largescale photovoltaics deployment. J. Environ. Sci. Technol. 43, 2072–2077 (2009) 3. P. Jackson, D. Hariskos, E. Lotter, S. Paetel, R. Wuerz, R. Menner, W. Wischmann, M. Powalla, New world record efficiency for Cu(In,Ga)Se2 thin-film solar cells beyond 20%. Prog. Photovolt. Res. Appl. 19, 894–897 (2011) 4. S. Hall, J. Szymanski, J. Stewart, Structurally similar but distinct minerals. Can. Mineral. 16, 131–137 (1978) 5. J. Paier, R. Asahi, A. Nagoya, G. Kresse, Cu2 ZnSnS4 as a potential photovoltaic material: a hybrid Hartree-Fock density functional theory study. Phys. Rev. B 79, 115–126 (2009) 6. K. Jimbo, R. Kimura, T. Kamimura, S. Yamada, W. Maw, H. Araki, Cu2 ZnSnS4 -type thin film solar cells using abundant materials. Thin Solid Films 515, 5997–5999 (2007) 7. H. Katagiri, K. Jimbo, S. Yamada, T. Kamimura, W. Maw, T. Fukano, Fabrication of Cu2 ZnSnS4 thin films by co-evaporation. Appl. Phys. Express 1, 041201 (2008) 8. T. Tanaka, D. Kawasaki, M. Nishio, Q. Guo, H. Ogawa, Fabrication of Cu2 ZnSnS4 thin films by co-evaporation. Phys. Status Solidi C 3, 2844–2847 (2006) 9. H. Katagiri, N. SasaGuchi, S. Hando, S. Hoshino, J. Ohashi, T. Yokota, Preparation and evaluation of Cu2 ZnSnS4 thin films by sulfurization of EB evaporated precursors. Sol. Energy Mater Sol. Cell 49, 407–414 (1997) 10. L. Shao, Y. Fu, J. Zhang, D. He, Electrical and optical properties of Cu2 ZnSnS4 thin films prepared for solar cell absorber. Chin. J. Semicond. 28, 337–340 (2007) 11. J. Zhang, L. Shao, Y. Fu, E. Xie, Cu2 ZnSnS4 thin films prepared by sulfurization of ion beam sputtered precursor and their electrical and optical properties. Rare Met. 25, 315–319 (2006)

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12. A. Weber, I. Kotschau, S. Schorr, H. Schock, Formation of Cu2 ZnSnS4 and Cu2 ZnSnS4 -CuInS2 thin films investigated by in-situ energy dispersive X-ray diffraction. Mater. Res. Soc. Symp. Proc. 1012, 201–208 (2007) 13. B. Ananthoju, F.J. Sonia, A. Kushwaha, D. Bahadur, N.V. Medhekar, M. Aslam, Improved structural and optical properties of Cu2 ZnSnS4 thin films via optimized potential in single bath electrodeposition. Acta 137, 154–163 (2014) 14. K. Patel, D. Shah, V. Kheraj, Influence of deposition parameters and annealing on Cu2 ZnSnS4 thin films grown by SILAR. J. Alloys Compd. 622, 942–947 (2015) 15. J. Henry, K. Mohanraja, G. Sivakumar, Electrical and optical properties of CZTS thin films prepared by SILAR method. J. Asian Ceram. Soc. 4, 81–84 (2016) 16. O. Vigil-Galán, M. Courel, M. Espindola-Rodriguez, V. Izquierdo-Roca, E. Saucedo, A. Fairbrother, Toward a high Cu2 ZnSnS4 solar cell efficiency processed by spray pyrolysis method. J. Renew. Sustain. Energy 5, 053137 (2013) 17. M. Espindola-Rodriguez, M. Placidi, O. Vigil-Galán, V. Izquierdo-Roca, X. Fontané, A. Fairbrother, E. Sylla, E. Saucedo, A. Pérez-Rodríguez, Compositional optimization of photovoltaic grade Cu2 ZnSnS4 films grown by pneumatic spray pyrolysis. Thin Solid Films 535, 67–72 (2013) 18. R. Kale, C. Lokhande, Influence of air annealing on the structural, optical and electrical properties of chemically deposited CdSe nano-crystallites. Appl. Surf. Sci. 223, 343–351 (2004) 19. W. Schafer, R. Nitsche, Tetrahedral quaternary chalcogenides of the type Cu2 ZnSnS4 (Se4 ). Mater. Res. Bull. 9, 645–654 (1974) 20. H. Katagiri, K. Saitoh, T. Washio, H. Shinohara, T. Kurumadani, S. Miyajima, Development of thin film solar cell based on Cu2 ZnSnS4 thin films. Sol. Energy Mater. Sol. Cells 65, 141–148 (2001) 21. R. Kale, S. Lu, Air annealing induced transformation of cubic CdSe microspheres into hexagonal nanorods and micro-pyramids. J. Alloys Comp. 640, 504–510 (2015) 22. M. Valdes, G. Santoro, M. Vazquez, Spray deposition of Cu2 ZnSnS4 thin films. J. Alloys Comp. 585, 776–782 (2014) 23. W.H. Zhou, M. Li, J. Guo, Y.L. Zhou, Z.L. Hou, J. Jiao, Z.J. Zhou, Z.L. Du, S.X. Wu, Synthesis of pure metastable wurtzite CZTS nanocrystals by facile one-pot method. J. Phys. Chem. C 116, 26507–26516 (2012) 24. P. Dai, X. Shen, N. Lin, Z. Feng, Z. Xu, J. Zhan, Band-gap tunable (Cu2 Sn)x/3 Zn1−x S nanoparticles for solar cells. Chem. Commun. 46, 5749–5751 (2010) 25. J. Liu, K. Choy, M. Placidi, J. López-García, E. Saucedo, D. Colombara, Fabrication and characterization of kesterite Cu2 ZnSnS4 thin films deposited by electrostatic spray assisted vapour deposition method. Phys. Status Solidi A 212, 135–139 (2015) 26. J. Shulin, S. Tongfei, Q. Xiaodong, J. Zhang, G. Xu, C. Chen, Z. Jiang, C. Ye, A route to phase controllable Cu2 ZnSn(S1−x Sex )4 nanocrystals with tunable energy bands. Sci. Rep. 3, 2733 (2013) 27. S. Thiruvenkadam, D. Jovina, A. Leo Rajesh, The influence of deposition temperature in the photovoltaic properties of spray deposited CZTS thin films. Sol. Energy 106, 166–170 (2014) 28. V. Rajeshmon, C. Kartha, K. Vijayakumar, C. Sanjeeviraja, T. Abe, Y. Kashiwaba, Role of precursor solution in controlling the opto-electronic properties of spray pyrolysed Cu2 ZnSnS4 thin films. Sol. Energy 85, 249–255 (2011) 29. Z. Seboui, Y. Cuminal, N. Kamoun-Turki, Physical properties of Cu2 ZnSnS4 thin films deposited by spray pyrolysis technique. J. Renew. Sustain. Energy 5, 023113 (2013) 30. S. Swami, N. Chaturvedi, A. Kumar, V. Dutta, Effect of deposition temperature on the structural and electrical properties of spray deposited kesterite (Cu2 ZnSnS4 ) films. Sol. Energy 122, 508–516 (2015) 31. M. Patel, I. Mukhopadhyay, A. Ray, Structural, optical and electrical properties of spraydeposited CZTS thin films under a non-equilibrium growth condition. J. Phys. D: Appl. Phys. 45, 445103 (2012) 32. K. Kumar, Y.B. Babu, G. Bhaskar, P. Sundara Raja, Effect of copper salt and thiourea concentrations on the formation of Cu2 ZnSnS4 thin films by spray pyrolysis. Phys. Status Solidi A 207, 149–156 (2010)

Chapter 13

Cogeneration of Power and Desalination Using Concentrated Photovoltaic/Thermal Humidification and Dehumidification System B. Anand and T. Srinivas Abstract In the present work, a mathematical modeling of concentrated photovoltaic/thermal humidification and dehumidification (CPV/T-HDH) desalination plant has been modeled and presented to estimate the performance of the plant. A concentrating photovoltaic thermal is a type of photovoltaic technology which generates electricity and useful thermal energy form high-intensity sunlight focused by lenses and curved mirrors. The efficiency of PV panel drops with increase in cell temperature. In order to maintain the cell temperature at an optimum level, the excess heat or thermal energy was recovered by circulating water. The recovered heat energy was used in humidification and dehumidification desalination plant to generate distilled water from seawater. The performance of plant was analyzed for various solar radiation values (800 W/m2 , 900 W/m2 , and 1000 W/m2 ) in terms of cell temperature, PV efficiency, hot water temperature, electricity generation, distilled water production, gained output ratio (GOR), and energy utilization factor (EUF) of the plant. The coolant water flow rate in PV panel was varied from 300 kg/h to 400 kg/h at each solar radiation level. The work is aimed to make use of process integration to optimize the existing system performance. The highest overall efficiency of the CPV/T system is 88.40%. The optimum operating condition of the plant is 800 W/m2 and 300 kg/h. The plant EUF and GOR at optimum operating condition are 0.1593 and 3.01, respectively. Keywords Concentrated photovoltaic/thermal · Humidification–dehumidification · Desalination and power

B. Anand (B) CO2 Research and Green Technologies Centre, Vellore Institute of Technology, Vellore, India e-mail: [email protected] T. Srinivas Department of Mechanical Engineering, Dr. B.R. Ambedkar National Institute of Technology, Jalandhar, India e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2020 S. Singh and V. Ramadesigan (eds.), Advances in Energy Research, Vol. 1, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-15-2666-4_13

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13.1 Introduction Solar cell efficiency drops with rise in cell temperature and also depends on the intensity of solar radiation falling on it. The electrical conversion efficiency of commercially available photovoltaic cells is 10–20%, and the remaining energy is either reflected or heat loss to the environment. Solar energy conversion into power using PV panel is considered as one of the costliest methods and also requires more land area. A well-known and proven method to optimize energy conversion and utilization is process integration [1]. There are various configurations of hybrid PV/T collectors to improve overall energy conversion efficiency. The heat generated from PV/T collectors is suitable for low-temperature applications, and also area required for electricity generation is more than CPVT collectors [2]. A concentrating PV thermal system is a combination of concentrated photovoltaic (CPV) and photovoltaic thermal (PVT) systems which produces both electrical and thermal energy simultaneously with the use of optical concentration. Concentrated photovoltaic panels are operated at higher temperature than PV/T collectors. Some multi-junction solar cells which is used in CPVT system could be operated at very high temperature (>150 °C) and produces more electrical energy per unit area with efficiency around 30–40% [3]. Cooling of photovoltaic panels under high concentration is a major concern while designing CPVT system. For large concentration ratio (100–2000 suns), cell efficiency drops due to elevated temperature which requires active cooling [4]. Francesco et al. [5] explained a CPV/T-based tri-generation system for power, cooling, and hot water production. Lee et al. [6] presented a CPV/T-driven multi-effect membrane distillation cycle. In another study [7], the performance of CPV/T system integrated with LiBr single-effect absorption chiller was briefly described. Kirbus et al. [8] presented a parabolic dish-based miniature CPV/T system of 500 × concentration ratios. Based on heat transfer fluid outlet temperature, the system could be coupled with various processes. The literature review shows that CPV/T systems are not integrated with HDH desalination unit. The main aim of this work is to focus on the use of process integration to improve the existing one. The combined cycle is developed by integrating a CPVT system with a HDH desalination plant. The proposed system was designed to produce electrical energy as well as distilled water production. Sizing of the CPVT system was based on the guidelines given by [9].

13.2 Modeling and Analysis of CPV/T-HDH Plant The schematic diagram in Fig. 13.1 represents the proposed CPV/T-HDH power and desalination plant. The plant consists of a point focus parabolic concentrator and a triple-junction solar panel (PV/T) placed on the receiver of the concentrator. The ratio of concentration and aperture area of the point focus parabolic collector is 200 and 12 m2 . The PV/T panel was cooled by circulating water (1) through the pipes attached to the back of the PV/T panel. The hot saline water available at the exit of the

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Hot water

2

Hot humid air 5

7

CPV/T Dehumidifier

Humidifier

1 Pump

Air from Blower

4

De-humidified

3

6

Distilled Water

8

Circulating water

Fig. 13.1 CPV/T-HDH desalination plant

PV/T panel (2) flows toward the inlet of the humidifier. The dry air (3) at low specific humidity and low relative humidity enters the humidifier for humidification process which is supplied from the blower at atmospheric temperature. At the humidifier entrance, the temperature of saline water is greater than the dry air which improves the humidification process. After latent heat loss to the air, the water temperature decreases and the brine water (4) is collected in the water tank or it can be re-circulated to the process depends on the condition of the water. The hot humid air (5) leaves the humidifier at high relative humidity, and specific humidity enters the dehumidifier where the air gets dehumidified by circulating water (7). The fresh distilled water is collected at the bottom of the dehumidifier. Since the amount of hot water required for desalination is smaller than the hot water available from the CPV/T plant, the excess water is supplied for domestic hot water needs which is not considered in this work and part of it is also supplied as makeup water for the desalination plant. The current work is focused on to improve the efficiency of the existing system through process integration. The proposed system was developed and simulated in MATLAB environment. The temperature of the saline water leaves the PV/T panel which could be controlled by adjusting the flow rate. The effect of cooling water (1) flow rate on desalination, PV efficiency thermal efficiency, overall efficiency, GOR, and plant EUF was also analyzed to evaluate the performance of the plant (Table 13.1).

13.2.1 Assumptions • Intensity of solar radiation throughout the area of PV cell is same. • The nominal conversion efficiency of the PV cell is 32%. • Efficiency of humidifier is 50% [10].

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Table 13.1 Operational characteristics of the CPV/T-HDH power and desalination plant Description

Symbol

Unit

Value

Parabolic dish collector Location

Chennai, Tamil Nadu, India

Ambient temperature

Ta

oC

25

Aperture area

Aap

m2

12

Concentration ratio

C

–

200

Optical efficiency

ηopt

%

90

Inverter efficiency

ηinv

%

90

Wind speed

Vw

m/s

5

PV/T Panel Solar cell type

Triple-junction GaAs solar cell

Cooler material

Copper

Active module size

l ×b

m

Thermal conductivity of tube

kp

W/m K

0.25 × 0.20

Specific heat of saltwater

Cp

kj/kg K

3.9

Specific heat of circulating cooling water at dehumidifier

C pcw

kj/kg K

4.18

385

• Mass flow rate of humid air inlet to dehumidifier is 0.0047 kg/s. • Mass flow rate of hot water into humidifier is constant for all solar radiation levels. • Circulating water inlet temperature at dehumidifier is 25 °C. The CPV/T system was exposed to various solar radiation levels (800 W/m2 , 900 W/m2 , and 1000 W/m2 ), and the temperature of solar cell (T c ) varies with weather variables such as ambient temperature, solar radiation (I b ), and wind speed. Since active cooling was adopted in this work, the operating temperature of PV module can be expressed by the simple explicit equation (Eq. 13.1) [11]. The electrical efficiency of the solar cell is ηcell = 0.288 − 0.000558 × (Tc − 25)

(13.1)

Note that the net electrical energy produced by the PV module also depends on module efficiency (ηmod ), inverter efficiency, optical efficiency of dish concentrator, concentration ratio. For a given solar radiation, the total electrical energy generation is Qe =



  Ib .Aap .ηopt .ηpv − Q par ηinv

(13.2)

where Qpar is parasitical power consumption and ηpv is PV panel efficiency The total thermal energy available at the receiver is   Q th = Q incident (1 − (ηPV ))ηopt

(13.3)

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The simple energy balance of the receiver is given in Eq. (13.4) Q th = Q u + Q l

(13.4)

where Ql is the heat loss by convection, conduction, and radiation which occur on front and backside of the receiver. Note that thermal efficiency (ηth ) of the CPV/T system is the ratio of total thermal energy used to the total thermal energy available which is given by Eq. (13.5) ηth =

m w Cp (Two − Twi ) Ib Aap

(13.5)

The overall efficiency of the CPVT system is ηoverall = ηpv + ηth

(13.6)

The mass and energy balance of humidifier and de-humidifier is given by Eqs. (13.7) and (13.8) [12]. m air (h 3 − h 5 ) = m w h 2 − m br h 4

(13.7)

m air (h 6 − h 5 ) = m dw h dw − m cw Cpcw (T8 − T7 )

(13.8)

where mdw is distilled water flow rate, mcw is circulating water flow rate, and mbr is mass flow rate of brine The gained output ratio (GOR) can be calculated in terms of distilled water flow rate (mdw ) using Eq. (13.9). GOR =

m dw × 2504.9 Ib Aap

(13.9)

Finally, the performance of the combined CPVT-HDH power and desalination plant is evaluated in terms of energy utilization factor which is given in Eq. (13.10). EUFplant =

Q dw + Wout Aap Ib + Win

(13.10)

where Qdw is equivalent heat of vaporization of distilled water, W in is net power supply to the plant, and W out is net power output from the plant.

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13.3 Results and Discussions The results of the proposed plant performance analysis have been carried out in this section. The performance of CPVT-HDH plant was investigated under 800 W/m2 , 900 W/m2 , and 1000 W/m2 solar radiation level. The cooling water flow rate for each solar radiation level was varied from 300 kg/h to 400 kg/h to improve the efficiency of PV panel as well as to produce distilled water. Figure 13.2 shows the water outlet temperature as a function of coolant water flow rate for different solar radiation levels. Water outlet temperature drops as the mass flow rate increases from 300 kg/h to 400 kg/h. For 800 W/m2 , 900 W/m2 , and 100 W/m2 , the water outlet temperature was increased by 19.98 °C, 22.63 °C, and 25.32 °C. The maximum water outlet temperature of 55.32 °C was reached at 1000 W/m2 and 300 kg/h. Figure 13.3 shows the relationship between the distilled water production and mass flow rate for various solar radiation levels. At 800 W/m2 when the mass flow rate was increased from 300 kg/h to 400 kg/h, the distilled water production was reduced from 0.4158 L/h to 0.3377 L/h. The distilled water production was reduced by 0.079 L/h, 0.096 L/h, and 0.12 L/h under 800 W/m2 , 900 W/m2 , and 1000 W/m2 . This is due to the drop in water outlet temperature with increase in water flow rate. The highest drop in water outlet temperature (6.33 °C) at 1000 W/m2 results in highest drop in distilled water production. But the maximum distilled water production of

Fig. 13.2 Effects of mass flow rate of water on its outlet temperature at various solar radiation levels

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Fig. 13.3 Effects of flow rate of water on distilled water production and at various solar radiation levels

0.5149 L/h was reached at 1000 W/m2 and 300 kg/h. This is due to the highest water outlet temperature of 55.33 °C was reached at the same operating condition. Figures 13.4, 13.5, and 13.6 depict the effect of mass flow rate on electrical energy production at 800 W/m2 , 900 W/m2 , and 1000 W/m2 . Initially without cooling, the PV efficiency and total electrical energy production were less under all solar radiation levels. Increasing the flow rate increases the PV efficiency which leads to more electrical energy production. At the operating condition of 1000 W/m2 , 400 kg/h, the highest electrical power production (2.25 kW) was observed and lowest (1.80 kW) was observed at 800 W/m2 and 300 kg/h. Compared with uncooled panel, cooled panel maximized the electrical power production by 0.52 kW, 0.63 kW and 0.72 kW at 800 W/m2 , 900 W/m2 and 1000 W/m2 respectively. It is clear that at higher solar radiation level, the electrical power produced by the PV panel with cooling is significantly higher than that of the PV panel without cooling under the same solar radiation levels. Figure 13.7 shows the effect of mass flow rate on overall efficiency of the CPV/T system under 800 W/m2 , 900 W/m2 , and 1000 W/m2 . At all solar radiation levels, the electrical energy production was increased as a result of increased mass flow rate. This caused the electrical efficiency of the system to increase while increasing the mass flow rate from 300 kg/h to 400 kg/h under all solar radiation levels. But increasing solar radiation level resulted in reduced electrical efficiency. Even though more energy available while increasing the solar radiation, the electrical efficiency

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Fig. 13.4 Effects of mass flow rate of water on electrical power and improved production of electricity at 800 W/m2

Fig. 13.5 Effects of mass flow rate of water on electrical power and improved production of electricity at 900 W/m2

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Fig. 13.6 Effects of mass flow rate of water on electrical power and improved production of electricity at 1000 W/m2

Fig. 13.7 Effects of mass flow rate on overall efficiency of CPV/T system

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of the CPV/T system was reduced. This was due to the rise in cell temperature at higher solar radiation levels. The highest electrical efficiency of the plat (20%) was reached at 800 W/m2 and 400 kg/h. Unlike electrical efficiency, thermal efficiency of the system increases with increase in solar radiation levels. But there was no change in thermal efficiency while increasing the flow rate from 300 kg/h to 400 kg/h under all solar radiation levels. The highest thermal efficiency (68.59%) was reached at 1000 W/m2 . The overall efficiency of the system depends on both electrical and thermal efficiency of the system. But it highly depends on the thermal efficiency the system. Overall efficiency of the plant was increased while increasing the flow rate as well as solar radiation levels. The highest overall efficiency of the plant (88.40%) was reached at 1000 W/m2 and 400 kg/h. Figure 13.8 depicts the influence of mass flow rate of water in PV panel on gained output ratio of the desalination plant. GOR was gradually reduced as the mass flow rate was increased from 300 kg/h to 400 kg/h. GOR value directly depends on distilled water production rate and indirectly affected by coolant water temperature which could be varied by its mass flow rate. The higher the water outlet temperature, the better GOR value could be obtained. At each solar radiation levels, the maximum GOR was reached at 300 kg/h. Even though the highest water outlet temperature (55.32 °C) and distilled water production (0.52 L/h) was achieved at 1000 W/m2 and 300 kg/h, the GOR value was less when compared to 800 W/m2 and 300 kg/h. The highest GOR (3.012) was achieved at 800 W/m2 and 300 kg/h.

Fig. 13.8 Effects of mass flow rate on Gained Output Ratio

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Figure 13.9 shows the effect of mass flow rate on energy utilization factor (EUF) of the CPV/T-HDH desalination plant. Since the air inlet condition, water flow rates to the humidifier, and water circulation to the dehumidifier are fixed, the EUF of the plant directly and indirectly depends on many factors such as solar radiation levels, water flow rate, and outlet temperature of water from CPV/T (i.e., inlet to humidifier) system, desalination yield, and electrical energy production. Increasing flow rate reduces EUF of the plant as it reduces the water outlet temperature and desalination yield. Since increasing the flow rate from 300 kg/h to 400 kg/h increases electrical power generation, there was no impact on EUF of the plant. But increasing the solar radiation level had significant effects on EUF of the plant as it produces more electrical power at lower solar radiation levels. It is clear that EUF of the plant depends on distilled water production when it comes to increasing the flow rate from 300 kg/h to 400 kg/h. Meanwhile, the highest EUF of the plant was achieved at 800 W/m2 and 300 kg/h. The amount of hot water required for desalination was less when compared to the actual amount of hot water production from the CPV/T system. The highest EUF of the plant is actually less because the hot water available after makeup water supply to the desalination plant was not considered in the work. It is clear that for a fixed flow rate higher the solar radiation higher the EUF of the plant and for a fixed solar radiation lower the flow rate results in higher EUF of the plant.

Fig. 13.9 Effects of mass flow rate on EUF of the plant

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13.4 Conclusions A combined power and desalination plant using CPV/T-HDH system has been modeled and analyzed. The performance of the plant was studied by changing the flow rate from 300 kg/h to 400 kg/h. The solar radiation increased in steps of 800 W/m2 , 900 W/m2 , and 1000 W/m2 . The power output is increased with the increase in circulating water flow rate and found a maximum of 2.5 kW at 1000 W/m2 and 400 kg/h. Similarly, a maximum of 0.56 L/h of desalinated water is produced at 57.5 °C hot water temperature and with circulating water flow rate of 300 kg/h. The combined power and thermal output efficiency of the CPV/T system is 88.40% at 1000 W/m2 and 400 kg/h. The highest EUF of 0.1593 and GOR of 3.01 was achieved at optimum operating conditions of 800 W/m2 and 300 kg/h. Acknowledgements The authors acknowledge the project grant of the Council of Scientific and Industrial Research (CSIR), New Delhi, India (22(0627)/13/EMR-II).

References 1. D.W. Wu, R.Z. Wang, Combined cooling, heating and power: a review. Prog. Energy Combust. Sci. 32, 459–495 (2006). https://doi.org/10.1016/j.pecs.2006.02.001 2. B. Singh, M.Y. Othman, A review on photovoltaic thermal collectors. J. Renew. Sustain. Energy 1, 062702 (2009). https://doi.org/10.1063/1.3266963 3. A.M. Rodriguez, P.P. Horley, J.G. Hernandez, Y.V. Vorobiev, P.N. Gorley, Photovoltaic solar cells performance at elevated temperatures. Sol. Energy 78, 243–250 (2004). https://doi.org/ 10.1016/j.solener.2004.05.016 4. A. Royne, C. Dey, D.R. Mills, Cooling of photovoltaic cells under concentrated illumination: a critical review. Sol. Energy Mater. Sol. Cells 86, 451–483 (2005). https://doi.org/10.1016/j. solmat.2004.09.003 5. F. Calise, D.A. Massimo, A. Palombo, L. Vanoli, Dynamic simulation of a novel hightemperature solar trigeneration system based on concentrating photovoltaic/thermal collectors. Energy 61, 72–86 (2013). https://doi.org/10.1016/j.energy.2012.10.008 6. C.L. Ong, W. Escher, S. Paredes, A.S.G. Khalil, B. Michel, A novel concept of energy reuse from high concentration photovoltaic thermal (HCPVT) system for desalination. Desalination 295, 70–81 (2012). https://doi.org/10.1016/j.desal.2012.04.005 7. G. Mittelman, A. Kribus, A. Dayan, Solar cooling with concentrating photovoltaic/thermal (CPVT) systems. Energy Convers. Manag. 48, 2481–2490 (2007). https://doi.org/10.1016/j. enconman.2007.04.004 8. A. Kribus, D. Kaftori, G. Mittelman, A. Hirshfeld, Y. Flitsanov, A. Dayan, A miniature concentrating photovoltaic and thermal system. Energy Convers. Manag. 47, 3582–3590 (2006). https://doi.org/10.1016/j.enconman.2006.01.013 9. C. Renno, F. Petito, Design and modeling of a concentrating photovoltaic thermal (CPV/T) system for a domestic application. Energy Build. 62, 392–402 (2013). https://doi.org/10.1016/ j.enbuild.2013.02.040 10. C. Chiranjeevi, T. Srinivas, Combined two stage desalination and cooling plant. Desalination 345, 56–63 (2014). https://doi.org/10.1016/j.desal.2014.04.023

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11. E. Skoplaki, J.A. Palyvos, Operating temperature of photovoltaic modules: a survey of pertinent correlations. Renewable Energy 34, 23–29 (2009). https://doi.org/10.1016/j.renene.2008. 04.009 12. B. Anand, T. Srinivas, Performance evaluation of photovoltaic/thermal–HDH desalination system. Appl. Solar Energy 53(3), 243–249 (2017). https://doi.org/10.3103/S0003701X17030045

Chapter 14

Computational Fluid Dynamic (CFD) Analysis of Air-Based Photovoltaic Thermal System T. M. Sathe, A. S. Dhoble, Sandeep Joshi and Chidanand Mangrulkar

Abstract This paper presents CFD study of air-based photovoltaic thermal (PVT) system with forced circulation of air. A PVT system is a combination of photovoltaic and solar thermal system that simultaneously generates electricity and produces lowgrade heat. Till now, huge research work has been carried out for the performance enhancement of PVT systems, though very few PVT systems are commercially available. The high overall cost of the PVT system, unavailability of long-term performance data, unawareness about the benefits of the PVT systems to the customers and production of low-grade heat are some of the important factors responsible for less availability of PVT systems in the commercial market. In this study, CFD analysis of PVT system has been carried out for its thermal performance enhancement using radiation model available in commercial software ANSYS Fluent. The temperature distribution at the PV surface and thermal efficiencies of PVT systems are compared with the experimental results available in the literature and found to be in good agreement. Keywords Air-based photovoltaic thermal (PVT) systems · CFD · Forced convection

14.1 Introduction The supply of electricity and thermal energy needs to be increased due to its everincreasing demand from various sectors like industries, commercial and residential apartments, schools, colleges, hospitals and so on. Till now, conventional energy sources like coal, natural gas and oil have been used widely for the generation of electricity and production of thermal energy; but, these are on the verge of extinction now and need to be replaced. Solar energy is found out to be the most viable renewable T. M. Sathe (B) · A. S. Dhoble · C. Mangrulkar Department of Mechanical Engineering, Visvesvaraya National Institute of Technology, Nagpur, Maharashtra, India e-mail: [email protected] S. Joshi Shri Ramdeobaba College of Engineering and Management, Nagpur, Maharashtra, India © Springer Nature Singapore Pte Ltd. 2020 S. Singh and V. Ramadesigan (eds.), Advances in Energy Research, Vol. 1, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-15-2666-4_14

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energy source as a replacement for the conventional energy resources. Photovoltaic (PV) panel is generally used for the generation of electricity, and PV-based power plants can be replaced with coal-fired power plants. Coal-fired power plants are also responsible for air pollution and cause high mortality rate for human beings. Prehoda and Pearce [1] studied effect of air pollution due to coal-fired power plants on the American’s life and found that the replacement of coal-fired power plants with PVpowered power generation system can save life of 51,999 Americans in a year. The initial investment cost of PV power plant is the biggest issue but due to tremendous research work going on improving design of PV systems and various government policies, the overall investment cost of the PV systems is getting down and attracting various investors for the installation of PV-based power plant. Solar energy has also been utilized very efficiently for the production of thermal energy with solar thermal systems. Solar thermal systems are very efficient and mature techniques now and very easily available in market with reasonable prices. Photovoltaic efficiency is generally measured at AM1.5, 25 °C temperature and with 1000 W/m2 of incoming radiations. Temperature has negative effect on the efficiency of PV panel; every 1 °C increase in surface temperature of PV above 25 °C causes approximately 0.45% decrease in its electrical efficiency. ηPV = ηPV @STC × (1 − β [T cell − 25 °C]) …… [2] Thus, PV temperature management is the important challenge that needs to be resolved, especially for the country like India where most of the time in a year, the ambient temperature is around 35 °C and sometimes it crosses 45 °C also. Photovoltaic thermal (PVT) systems come out as an efficient possible solution. In PVT systems, cooling fluid is passed through the PV surface, and fluid extracts heat, decreases PV surface temperature and enhances PV performance; at the same time, the hot fluid coming from the system can be used for the required thermal applications. Thus, PVT systems can be used very effectively in an application with simultaneous demand of heat and electricity like in industries, agriculture processes, space heating and so on. Huge experimental and analytical research work has been carried out by various researchers for the performance enhancement of PVT systems [3–6]. The availability of the literature on numerical analysis of PVT system using commercial software is very limited, though it can be very useful for the quick and low-cost analysis of PVT system instead of doing experiment in actual conditions. Hailu et al. [7] developed CFD model for building integrated PVT system using COMSOL Multiphysics finite element analysis software. The performance of system was investigated and found that the CFD model can be very useful for the prediction of temperature profile at various locations of PVT systems at a different airflow velocity. Liao et al. [8] carried out numerical and experimental investigation of building integrated PVT systems and developed relations for convective heat transfer coefficients. Numerical analysis was carried out using two-dimensional k-ε model, and temperature measured in experimentations was used as a boundary condition. Getu et al. [9] analyzed two amorphous photovoltaic panels. Experimentations were carried out using indoor solar simulator from different flow rates of air. Temperature distribution on PV surface, air channel and insulation was analyzed. A two-dimensional CFD model was developed and

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compared the results with the experimental data. It was found that the k-ε model in CFD was in agreement with the experimental results for predicting air channel and insulation temperature while k-ω model was predicting PV surface temperature correctly. Naewngerndee et al. [10] studied effect of air channel configurations and flow rate on the performance of photovoltaic thermal systems. Numbers of photovoltaic thermal modules were also changed, and optimum configuration for the system was identified. PVT systems will be one of the most sustainable renewable energy technologies in the near future as researchers are working on introducing more economic PVT system in commercial market. Experimental analysis of PVT system in actual operating conditions is the only source of getting exact output results; but in recent times, use of simulation software like TRNSYS, ANSYS, COMSOL, etc., has been increased widely. Simulation software with precise input parameters can give output results of thermal and electrical parameters of PVT systems with considerable accuracy; thus, there will be enormous reduction in time required and cost of actual field experimentation. Design parameters of PVT systems like tube diameter, collector area, length of tube, flow rate of fluid and so on can be optimized very effectively using simulation software. Three-dimensional numerical analysis of photovoltaic thermal system was performed by Nahar et al. [11] using finite element method-based COMSOL Multiphysics software. They analyzed the performance of PVT system with and without using absorber plate and found that the performance of PVT system was almost same in both the cases. Outdoor experimentation was carried out for the designed PVT system; they observed 4.4% difference in maximum overall efficiency in numerical and experimental results. Khelifa et al. [12] theoretically and experimentally studied the performance of hybrid PVT system. Sheet- and tube-type thermal extraction system was employed on the backside of PV panel. ANSYS software was used for the performance prediction of PV panel using sheet and tube heat extraction system, and they found 15–20% reduction in surface temperature of PV panel. ANSYS Fluent has been used widely to study the effect of changing thermal geometry on the performance of PV systems. Baloch et al. [13] analyzed the performance of converging channel heat exchanger for PV cooling. Numerical modeling had been carried out using ANSYS Fluent and compared with the experimental results. Electrical modeling was carried out for seven parameters, and equations were solved using MATLAB and EES; 35.5% increase in power output and 36.1% increase in conversion efficiency were observed as compared to uncooled PV system. In this study, air-based photovoltaic thermal system is analyzed using CFD approach. PV surface temperature, outlet air temperature and thermal efficiencies are calculated and compared with the experimental results.

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Fig. 14.1 Experimental setup [14]

14.2 System Description 14.2.1 Experimental Setup The air-based PVT system used in this CFD study is as given by Kasaeian et al. in their experimental work as shown in Fig. 14.1 [14]. Two monocrystalline PV panels with dimensions 1053 mm × 553 mm were used made by Aria Solar Company, Iran. Absorber plate made of steel was attached just below the PV panel to absorb heat from the PV surface. Air channels were prepared using 4-mm-thick Plexiglas, and Plexiglas holders were used for varying air channel depth. The experimentations were carried out with a different channel depth and flow rate of air.

14.2.2 Geometrical Modeling and Meshing Three-dimensional geometrical model of experimental setup is prepared in ANSYS ICEM commercial software, with the same dimensions used in the experimentations as shown in Fig. 14.2. Various dimensions of computational domain are shown in Table 14.1. It can be observed from the dimensions that the length and width of the glass layer, PV panel and absorber plate are taken as same in computational domain while in case

Fig. 14.2 Computational domain

14 Computational Fluid Dynamic (CFD) … Table 14.1 Dimensions of the computational domain of PVT system

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Layers

Dimensions (mm)

Glass layer

2000 × 500 × 3

PV panel

2000 × 500 × 0.5

Absorber plate

2000 × 500 × 3

Air duct

2000 × 5000 × 50 (100 and 150)

Fig. 14.3 Structured mesh

of experimental setup, PV panel and absorber plate have somewhat less dimensions than the duct size. Duct size in the experimental work varied with 5 cm, 10 cm and 15 cm; however, in this study only 5 cm duct size is modeled, compared and analyzed. Aluminum oxide paste was also used to attach absorber plate with the PV panel in the experimental work, while in computational domain, aluminum paste is not considered as the thermal resistance offered by aluminum paste is very less. Structural meshing of computational domain has been carried out using ANSYS ICEM. A total number of elements used for the analysis are 1815030 as shown in Fig. 14.3.

14.3 CFD Analysis Numerical computations were carried out using the commercial CFD software ANSYS Fluent 14.5, which has been widely accepted for general flow and heat transfer studies. Numerical modeling and methods used in the software are well known. Nevertheless, several important points of the numerical computation are briefly introduced in this section.

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14.3.1 Governing Equations The heat transfer in air-cooled PVT systems involves air as a fluid medium and multiple solid domains. The solid domain consists of different solid material layers (glass layer, PV, absorber plate). In this analysis, shear stress transport (SST) k-ω model is used for the analysis. Discrete transfer radiation model (DTRM) with solar ray tracing is also applied on the computation domain. The governing equations involved in the analysis are solved using commercial solver ANSYS Fluent 14.5. The governing equation involved [15] in the analysis is as follows: Continuity equation ∂u ∂v ∂w + + =0 ∂x ∂y ∂z

(14.1)

Momentum equation    ∂u j ∂u i ∂ ∂p ∂ 2 ∂u l ∂    μ − Bi − ρu i u j + + − δi j (ρu i u) = ∂x i ∂ xi ∂ xi ∂x j ∂ xi 3 ∂ xl ∂x i (14.2) where Reynolds stresses can be computed as below using the Boussinesq hypothesis       ∂u j ∂u i 2 ∂u k   − δi j ρk + μτ + −ρ u i u j = μτ ∂x j ∂ xi 3 ∂ xk

(14.3)

Transport equations for the shear stress transport (SST) k-ω model   ∂ ∂k ∂ ∂ Γk + G k − Yk (ρku i ) = (ρk) + ∂t ∂ xi ∂x j ∂ xi    ∂ ∂ω ∂ ∂  Γω + G ω − Yω + Dω ρωu j = (ρω) + ∂t ∂x j ∂x j ∂x j

(14.4) (14.5)

The energy equation in fluid flow   ∂ ∂T ∂ ∂ keff (ρeu i ) = − ( pu i ) + ∂ xi ∂ xi ∂ xi ∂ xi   ∂ ∂T ∂ ∂ keff . (ρeu i ) = − ( pu i ) + ∂ xi ∂ xi ∂ xi ∂ xi Where, e=h−

V2 p + = Specific internal energy ρ 2

(14.6) (14.7)

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The energy equation for the solid regions like absorber plate and other wall regions is given by  2  ∂h ∂ T + Sh ρ =k ∂t ∂n 2

(14.8)

The DTRM equations The equation for the change of radiant intensity dI, along a path dS, can be written as dI aσ T 4 + aI = dS π

(14.9)

where a is the gas absorption coefficient; T is the gas local temperature; I is the intensity; σ is the Stefan–Boltzmann constant.

14.3.2 Boundary Conditions The boundary conditions imposed on the computational domain in ANSYS Fluent are shown in Table 14.2. The solar insolation was invoked by making use of the solar load model feature available in the ANSYS Fluent software which calculates the solar insolation as well as the coordinates of the sun’s position for a given time, date and location. The Table 14.2 Boundary conditions Sr. no.

Boundary surface

Boundary condition

1.

At duct inlet

Velocity inlet varying from 2 to 5 m/s

2.

At duct outlet

Pressure outlet condition with specified pressure value of 101325 Pa

3.

Top surface of glass layer

Solar radiation heat flux applied through solar load model. A longitude of 35°41’46”N and 51°25’23”E and GMT of +4.30 are used in the solar load model to define the global position of Tehran, Iran; where experimentation has been carried out during September 2010

4.

Air–solid interface

No-slip and impermeable wall condition

5.

External atmospheric air domain

Atmospheric pressure of 101325 Pa is imposed

6.

Plane of symmetry for the computation domain

Planer symmetry condition

7.

All external boundaries of the computational domain

Adiabatic condition

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Air

Density (kg/m3 ) 1.225

Specific heat (J/kg·K)

Thermal conductivity (W/m·K)

1006.43

0.0242

Plexiglas

1180

1466

0.17

PV solar cell

2329

713

Steel absorber plate

8030

502.48

148 16.27

resulting solar load is applied as heat sources in the energy equation using solar raytracing approach. The solar load model feature is available in the software only for three-dimensional analysis. The material properties used in the analysis are shown in Table 14.3.

14.3.3 Numerical Analysis Setup Pressure-based, steady-state solver is selected without considering any gravity effects on the fluid flow. The pressure velocity coupling has been carried out using SIMPLE scheme. Gradient is discretized using least square cell-based method. Pressure discretization has been carried out using standard method. Second-order upwind scheme is used for energy and momentum; however, first-order upwind scheme is used of turbulent kinetic energy and specific dissipation rate. The convergence of the solution is considered when the residuals in the computation domain fall below 10-6 for energy and 10-5 for momentum and continuity equations. Besides the residuals, surface monitors for the temperature of air at duct outlet and absorber plate temperature are also used to confirm the convergence of the solution.

14.4 Results CFD analysis of air-based PVT system has been carried out on the PVT model, as experimentally investigated by [16]. The experimentations were performed in Tehran, Iran; thus, radiation heat flux is imposed on the top glass layer using the locations of Tehran, Iran. Outlet air temperature and PV surface temperature are examined as shown in Fig. 14.4. PV surface temperature distribution during CFD analysis is also analyzed as shown in Fig. 14.5. Temperature distribution on the PV surface is quite uneven; as temperature of air is quite low at the inlet, PV surface is at low temperature but as air proceeds further, it takes heat from the absorber plate; thus, PV surface temperature is quite high at the later stage.

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Fig. 14.4 Temperature of PVT system at different locations with respect to time

Fig. 14.5 Temperature distribution on the PV surface

Prediction of air outlet temperature and PV surface temperature. Air outlet temperature of PVT system is predicted using SST k-ω model. The inlet air temperature is considered to be 308 K as available during experimentations. It is found that the temperature of outside air with CFD analysis and that during experimentations is found to be in good agreement as shown in Fig. 14.6. PV surface temperature is analyzed with respect to solar radiations available throughout the day selected for the analysis. PV surface temperatures are also found to be in good agreement with the experimental result as shown in Fig. 14.7.

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Fig. 14.6 Outlet air temperature

Fig. 14.7 PV surface temperature

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14.5 Conclusions CFD analysis of air-based PVT system has been carried out using discrete transfer radiation model and with solar ray tracing. It was found that the PV surface temperature of the PVT system and the outlet air temperature are in good agreement with the experimental results. Thus, it can be concluded that the CFD tool has lots of possibilities to optimize performance parameters of PVT systems. It can also be possible for CFD tool to predict performance of PVT system at any locations on the earth, as solar ray tracing takes care of locations and radiations at that particular location. Thermal efficiency of PVT system mainly depends on the system configurations and temperatures at the inlet and the outlet. Thus, thermal efficiency and convective heat transfer coefficient can also be predicted with the CFD analysis. Thus, it can be concluded that CFD analysis is the future of designing commercially viable PVT system; it is either air-based or water-based PVT systems.

References 1. E.W. Prehoda, J.M. Pearce, Potential lives saved by replacing coal with solar photovoltaic electricity production in the U.S. Renew. Sustain. Energy Rev. 80, 710–715 (2017) 2. G.N. Tiwari, R.K. Mishra, S.C. Solanki, Photovoltaic modules and their applications: a review on thermal modelling. Appl. Energy 88(7), 2287–2304 (2011) 3. M. Hasanuzzaman, A.B.M.A. Malek, M.M. Islam, A.K. Pandey, N.A. Rahim, Global advancement of cooling technologies for PV systems: a review. Sol. Energy 137, 25–45 (2016) 4. S. Sargunanathan, A. Elango, S.T. Mohideen, Performance enhancement of solar photovoltaic cells using effective cooling methods: a review. Renew. Sustain. Energy Rev. 64, 382–393 (2016) 5. R. Kumar, M.A. Rosen, A critical review of photovoltaic–thermal solar collectors for air heating. Appl. Energy 88(11), 3603–3614 (2011) 6. R. Daghigh, M.H. Ruslan, K. Sopian, Advances in liquid based photovoltaic/thermal (PV/T) collectors. Renew. Sustain. Energy Rev. 15(8), 4156–4170 (2011) 7. D. Roeleveld, G. Hailu, A.S. Fung, D. Naylor, T. Yang, A.K. Athienitis, Validation of computational fluid dynamics (CFD) model of a building integrated photovoltaic/thermal (BIPV/T) system. Energy Procedia 78, 1901–1906 (2015) 8. L. Liao, A.K. Athienitis, L. Candanedo, K.-W. Park, Y. Poissant, M. Collins, Numerical and experimental study of heat transfer in a BIPV-thermal system. J. Sol. Energy Eng. 129(November 2007), 423 (2007) 9. H. Getu, T. Yang, A.K. Athienitis, A. Fung, Computational fluid dynamics (CFD) Analysis of air based building integrated photovoltaic thermal (BIPV/T) systems for efficient performance. IBPSA conference proceedings (2014) 10. R. Naewngerndee, E. Hattha, K. Chumpolrat, T. Sangkapes, J. Phongsitong, S. Jaikla, Solar energy materials & solar cells finite element method for computational fluid dynamics to design photovoltaic thermal (PV/T) system configuration. Sol. Energy Mater. Sol. Cells 95(1), 390–393 (2011) 11. A. Nahar, M. Hasanuzzaman, N.A. Rahim, Numerical and experimental investigation on the performance of a photovoltaic thermal collector with parallel plate flow channel under different operating conditions in Malaysia. Sol. Energy 144, 517–528 (2017) 12. A. Khelifa, K. Touafek, H. Ben Moussa, I. Tabet, Modeling and detailed study of hybrid photovoltaic thermal (PV/T) solar collector. Sol. Energy, 135, 169–176 (2016)

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13. A.A.B. Baloch, H.M.S. Bahaidarah, P. Gandhidasan, F.A. Al-sulaiman, Experimental and numerical performance analysis of a converging channel heat exchanger for PV cooling. Energy Convers. Manag. 103, 14–27 (2015) 14. A. Kasaeian, Y. Khanjari, S. Golzari, O. Mahian, S. Wongwises, Effects of forced convection on the performance of a photovoltaic thermal system: An experimental study. Exp. Therm. Fluid Sci. (2017) 15. S.K. Ranganathan, N. Elumalai, P.P. Natarajan, Numerical model and experimental validation of the heat transfer in air cooled solar photovoltaic panel. Therm. Sci. 20, 1071–1081 (2016) 16. Y. Khanjari, F. Pourfayaz, A.B. Kasaeian, Numerical investigation on using of nanofluid in a water-cooled photovoltaic thermal system. Energy Convers. Manag. 122, 263–278 (2016)

Chapter 15

Synthesis of One-Dimensional Bismuth Sulfide Nanoparticle with Enhanced Photovoltaic Properties Arpita Sarkar and Bibhutosh Adhikary

Abstract Bismuth sulfide is a promising n-type semiconductor for solar energy conversion. In this work, we have successfully synthesized bismuth sulfide nanoparticles (Bi2 S3 NPs)] from [Bi(ACDA)3 ] complex. The as-synthesized particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis spectroscopy. The prepared material exhibits a high absorbance coefficient, a low bandgap, and good disparity. Thus, prepared Bi2 S3 material provides a new candidate for the fabrication of environmentally friendly and low-cost inorganic hybrid solar cells. Keywords Bi2 S3 NPs · One-dimensional nanoparticles · Enhanced photovoltaic performance

15.1 Introduction Bismuth sulfide is a material with ultimate electric and optical properties for several optoelectronic, thermoelectric as well as solar cell applications [1]. Bismuth sulfide (Bi2 S3 ) has important electronic and intrinsic physical properties [2, 3]. Furthermore, bismuth sulfide nanoparticles have a large absorption coefficient [4]. Moreover, toxicity of Bi2 S3 NPs is less than other optoelectronic materials based on Hg, Cd, or Pb metal, and the material can be prepared by simple cost-effective method [5]. All these properties of bismuth sulfide nanomaterial are very attractive for photovoltaic conversion. In this respect, thin-film-based Bi2 S3 solar cell devices have been studied from last few years. But these kinds of photovoltaic devices have a relatively low efficiency. On the other hand semiconductors nanostructured materials have shown enormously promising perspectives in solar cell applications due to their low-cost, unique properties, scalable potential, and solution-process ability. Recently, research on the synthesis and applications of one-dimensional Bi2 S3 nanomaterials has been focused as it does enhance thermal, electric, and optoelectronic properties [6]. Numerous A. Sarkar · B. Adhikary (B) Department of Chemistry, IIEST, Shibpur, Howrah, India e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2020 S. Singh and V. Ramadesigan (eds.), Advances in Energy Research, Vol. 1, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-15-2666-4_15

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techniques have been reported for the synthesis of Bi2 S3 nanoparticles; hydrothermal and solvothermal decomposition, chemical vapor deposition, crystallization of amorphous colloids, microwave irradiation, bimolecular-assisted approaches, and sonochemical methods [7, 8]. These processes depend on decomposition of a mixture of the bismuth and sulfur-containing reactive components or isolation of defined bismuth complexes incorporating S-based ligands as single-source precursors. The S-based ligands are usually drawn from thiocarbamates, thiocarboxylates, thiosemicarbazides, thiolates, thiophosphates, xanthates, thiourea, thioacetamide, cysteine, glutathione, etc. In this work, we have reported a new synthesis method for preparation of one-dimensional bismuth sulfide nanoparticle from [Bi(ACDA)3 ] complex. The as-prepared material shows significant enhanced photovoltaic performances.

15.2 Experimental 15.2.1 Chemicals and Materials Triethylenetetramine (TETA), bismuth nitrate [Bi(NO3 )3 ·5H2 O], methanol, etc., were purchased from Sigma-Aldrich. Ammonia, cyclopentanone, and carbon disulfide (CS2 ) were obtained from Spectrochem Pvt. Ltd., India. Milli-Q Millipore™ water, acetonitrile, methanol, and diethyl ether were used as received.

15.2.2 Synthesis Following the previously reported method, the ligand, HACDA (2aminocyclopentene-1-dithiocarboxylic acid), has been synthesized [9]. The [Bi(ACDA)3 ] complex was synthesized by the reaction of 2-aminocyclopentene-1 dithiocarboxylic acid (HACDA) with [Bi(NO3 )3 ·5H2 O] according to the previously prescribed method [10].

15.2.3 Preparation of Bi2 S3 NPs At first, TETA (8 ml) was added to [Bi(ACDA)3 ] (0.5 g) complex, and then, the mixture was heated to 100 °C for several minutes under vacuum to remove oxygen and moisture. After that, the temperature was raised to 210 °C and kept for 2 h. Next, the deposited black nanoparticles were obtained by centrifugation, washed with methanol, and finally dried in air.

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15.2.4 Physical Measurements Absorption spectra were recorded on a JASCO V-530 UV-vis spectrophotometer. Transmission electron microscopy (TEM) images were recorded on a JEOL-JEM 200CX transmission electron microscope, using an accelerating voltage of 200 kV. Philips PW 1140 parallel beam X-ray diffractometer was used to measure powder Xray diffraction pattern (XRD) (λ = 1.540598 Å). I–V measurements and impedance were carried out on m-AUTOLAB III/FRA2 electrochemical workstation.

15.2.5 Photoelectrochemical Measurements The device for photoelectrochemical measurements was fabricated by previously reported drop-cast method. At first, water–acetone–isopropanol solution was used to wash an ITO-coated glass slide. Then, the conducting side of the ITO-coated glass slide was drop coated with sample nanoparticles. The film was then dried in air and annealed at 210 °C for 1 h to use it as a working electrode. Linear sweep voltammetry was used to measure the photovoltaic characteristics and photocurrent responses at a scan rate of 0.05 V s−1 within a potential range of 1.0 to 1.0 V and using a 300 W Xe lamp. Chronoamperometry was used to investigate the photosensitivity of the materials by measuring the current in the dark and under illumination of light on–off mode at a steady voltage vs. Ag/AgCl (0 V vs. RHE) at intervals of 30 s. Electrochemical impedance spectroscopy (EIS) was carried out in the frequency range 0.1 Hz to 10.0 kHz using similar electrode setup.

15.3 Results and Discussion 15.3.1 Characterization of Bi2 S3 NPs The purity and composition of Bi2 S3 NPs were examined by powder X-ray diffractometry. The diffraction pattern of the crystalline product (Fig. 15.1) matches with the pure primitive orthorhombic phase of the Bi2 S3 NPs (JCPDS No. 170320). The comparative broad feature of the peaks (FWHM) specifies the presence of smaller crystallites. Average crystal diameter for Bi2 S3 NPs was calculated using the Debye– Scherrer equation [D = 0.9λ/(βcosθ), where β is the value of full-width at half maximum, D is the crystallite diameter, λ is the wave length of X-ray (λ = 1.540598 Å), and θ is Bragg’s angle] and is found to be 22.3 nm. Transmission electron microscopy (TEM) was used to investigate the morphology and size of the synthesized nanoparticles. Figure 15.2a displays that the Bi2 S3 nanoparticles are composed of rod-like nanostructures with edge lengths ranging

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Fig. 15.1 Powder XRD pattern for Bi2 S3 nanoparticles

(a)

(b)

(0.286 nm)

Fig. 15.2 a TEM image. b HRTEM image of the as-synthesized Bi2 S3 NPs

from ~ 60 to 200 nm and average diameter ~ 15–25 nm. High-quality clear lattice fringes were observed from the HRTEM image (Fig. 15.2b), indicating the good crystalline nature of Bi2 S3 NPs. Furthermore, the HRTEM images revealed that the inter-planar spacing is about ~ 0.2856 nm and nanoparticles were grown preferentially along the (211) direction.

15.3.2 Optical Properties The UV-vis absorption spectra of the synthesized Bi2 S3 NPs and the corresponding plots are shown in Fig. 15.3. The result was obtained by dispersing the sample in

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Fig. 15.3 a UV-vis spectra and b corresponding Tauc’s plot of Bi2 S3 NPs

methanol. The as-obtained absorption spectrum displays a sharp rise of the absorption bands in the high-energy region, and the bandgap energy (Eg) of the prepared material was calculated using Tauc’s relation [(αhυ)2 vs hυ] (Fig. 15.3b) and is found to be 1.32 eV.

15.3.3 Impedance Spectroscopy To investigate the electron transfer ability of the synthesized materials, the electrochemical impedance spectroscopy (EIS) was performed. Figure 15.4 shows the typical Nyquist plots of blank GCE and Bi2 S3 NPs. In each case, a characteristic semicircle has been obtained which indicates a single charge transfer process taking Fig. 15.4 Nyquist plots of bare GCE and Bi2 S3 NPs

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Fig. 15.5 a Current density (J) vs voltage plots and b time vs current density plots during consecutive off and on cycle of light for Bi2 S3 NPs

Table 15.1 Parameters of photovoltaic devices based on different nanoparticles Active material for the device

V OC (V)

J SC (mA/cm2 )

Fill factor (FF)

Power conversion efficiency (%)

One-dimensional Bi2 S3 NPs

0.186

0.73

0.64

1.27

place between the working material and the electrolyte. From Fig. 15.4, it is clear that Bi2 S3 NPs showed lower charge transfer resistance (Rct) implying the faster electron transfer rate than bare GCE, indicating its higher electron transfer ability. Furthermore, the photovoltaic characteristics and the temporal photocurrent response property are shown in Fig. 15.5a. The photocurrent measurements were evaluated using linear sweep voltammetry and chronoamperometric measurements under chopped light illumination. From Fig. 15.5a, it can be shown that the current density under light and the photocurrent gain are significantly high. Moreover, to investigate the photo stability of the material, current density versus time measurements were carried out during successive on and off cycles of light at intervals of 50 s at a constant potential (Fig. 15.5b). The study reveals that the synthesized material has steady increase in current density with time over a period of 250 s. The optimized photovoltaic parameters for synthesized device are given in Table 15.1.

15.4 Conclusion In conclusion, one-dimensional Bi2 S3 NPs have been successfully synthesized from [Bi(ACDA)3 ] complex. The optical property of as-synthesized nanoparticles clearly shows that it can be efficiently applicable in manufacturing a promising photovoltaic

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device. The Nyquist plot also clears the improved charge transport ability of the prepared material. The photocurrent efficiency of Bi2 S3 NPs materials has been investigated, and significant enhancement of photocurrent efficiency was observed. Acknowledgements A.S. is thankful to UGC (BSR), India, for her JRF [F. No.F.7223/2009(BSR)], and also Department of Chemistry, IIEST, Shibpur, for providing instrumental facilities.

References 1. J.L.T. Chen, V. Nalla, G. Kannaiyan, V. Mamidala, W. Ji, J.J. Vittal, Synthesis and nonlinear optical switching of Bi2 S3 nanorods and enhancement in the NLO response of Bi2 S3 @Au nanorod-composites. New J. Chem. 38, 985–991 (2014) 2. G. Xiao, Q. Dong, Y. Wang, Y. Sui, J. Ning, Z. Liu, W. Tian, B. Liu, G. Zou, B. Zou, One-step solution synthesis of bismuth sulfide (Bi2 S3 ) with various hierarchical architectures and their photoresponse properties. RSC Adv. 2, 234–239 (2012) 3. J. Black, E.M. Conwell, L. Seigle, C.W. Spencer, Electrical and optical properties of some vi−b Mv−b semiconductors. J. Phys. Chem. Solids 2, 240–251 (1957) 2 N3 4. R.J. Jyoti, S.K. Srivastava, Low temperature micelle-template assisted growth of Bi2 S3 nanotubes. Nanotechnology 16, 2415–2419 (2005) 5. C. Ye, G. Meng, Z. Jiang, Y. Wang, G. Wang, L. Zhang, Rational Growth of Bi2 S3 Nanotubes from Quasi-two-dimensional Precursors. J. Am. Chem. Soc. 124, 15180–15181(2002) 6. Q. Wang, X. Wang, W. Lou, J. Hao, Ionothermal synthesis of bismuth sulfide nanostructures and their electrochemical hydrogen storage behavior. New J. Chem. 34, 1930–1935 (2010) 7. G. Nie, X. Lu, J. Lei, L. Yang, C. Wang, Facile and controlled synthesis of bismuth sulfide nanorods-reduced graphene oxide composites with enhanced supercapacitor performance. Electrochim. Acta 154, 24–30 (2015) 8. J. Ma, Z. Liu, J. Lian, X. Duan, T. Kim, P. Peng, X. Liu, Q. Chen, G. Yao, W. Zheng, Ionic liquidsassisted synthesis and electrochemical properties of Bi2 S3 nanostructures. CrystEngComm, 13, 3072–3078, (2011) 9. K. Nag, D.S. Joardar, Metal complexes of sulphur-nitrogen chelating Agents. I. 2-aminocyclopentene-l-dithiocarboxylic acid complexes of Ni(II), Pd(II) and Pt(II). Inorg. Chim. Acta, 14, 133–141 (1975) 10. A.K. Dutta, S.K. Maji, K. Mitra, A. Sarkar, N. Saha, A.B. Ghosh, B. Adhikary, Single source precursor approach to the synthesis of Bi2 S3 nanoparticles: a new amperometric hydrogen peroxide biosensor. Sen. Actuators B 192, 578–585 (2014)

Chapter 16

Effect of Forced Convection Cooling on Performance of Solar Photovoltaic Module in Rooftop Applications Arunendra K. Tiwari, Rohit Kumar, Rohan R. Pande, Sanjay K. Sharma and Vilas R. Kalamkar Abstract Photovoltaic (PV) module converts only a fraction of the incident irradiation to electricity, and the remaining is mainly absorbed into the cells raising the cell temperature as a consequence the efficiency of the cell drops. A PV-thermal (PV-T) system has been designed, fabricated, and investigated experimentally in the present work. To actively cool the PV module, a parallel array of channel with inlet and outlet manifold was built for uniform airflow distribution and connected to the back of the module. The experiments have been carried out with and without active cooling. The forced convective fan cooling provided with two types of cooling arrangement and each arrangement consists of two PV modules. In one arrangement below one panel, air channel provided which is made of conducting material and another panel is reference panel without cooling arrangement. Similarly in second case non-conducting material provided in the place of conducting material and other is same as a reference panel. The purpose of the present study is to improve the design of photovoltaic installations placed in roof applications by comparing the electrical efficiency of the PV module with and without cooling arrangement by varying the air channel duct material. This will ensure low operating temperatures which will reverse the effects produced on efficiency by high temperature. The electrical performance has also been investigated. Keywords Photovoltaic · PV-thermal system · Operating temperature · Active cooling · Efficiency

16.1 Introduction Nowadays, fossil fuel is the main source of the world’s energy around (75%), and demand is steadily rising. Exhaustive exploitation of these resources is imposing a real threat to the environment, which is apparent through global warming, greenhouse effect, and acidification of the water cycle. To overcome this challenge, governments are trying to regulate the guidelines for the adoption of best practices by utilities A. K. Tiwari (B) · R. Kumar · R. R. Pande · S. K. Sharma · V. R. Kalamkar Visvesvaraya National Institute of Technology, Nagpur, Maharashtra, India e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2020 S. Singh and V. Ramadesigan (eds.), Advances in Energy Research, Vol. 1, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-15-2666-4_16

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in terms of the smart grid and renewable energy resources (RES). RES have huge potential to meet the present world energy requirement. The energy received from the sun is one of the promising options; the earth receives 174,000 terawatts (tw) of solar irradiance (insolation) at the outer atmosphere. Approximately 30% are reflected back to space and the rest is absorbed by the clouds, landmasses, and oceans. Solar energy is one of the most important renewable energy sources since it is a clean, unlimited, and environmentally friendly energy. PV cell is one of the most popular solar energy sources. The PV module power output depends on its operating temperature. The module operating temperature can be 20–30 °C higher than the atmosphere. It depends on the various parameters such as solar radiation and wind speed. The higher cell temperature increases the short-circuit current (I sc ) and decreases the open-circuit voltage (V oc ), but the decrease in V oc is more prominent than the increase in I sc . Therefore, the PV cell and module output power and efficiency decrease with an increase in its operating temperature [1]. The increase in I sc with temperature is due to the decrement in the bandgap of Si, and voltage decreases with temperature due to the increase in the carrier recombination. The effect of temperature on the PV cell performance has been studied by many researchers. Cell efficiency depends upon the standard temperature condition of the panel. Cell receives the energy in the form of irradiation, converts some part of the irradiation into electricity and remaining energy converts into heat results into increase in cell temperature. Cell may experience in the form of efficiency loss (short term) and damage of the panel due to thermal stress (long term). So, to decrease the impact of the temperature on the performance of PV Cell, cooling arrangement can be used to take heat out of the cell. There are many cooling techniques available for the photovoltaic module. Air and water cooling methods are both commonly used to cool the solar cell [2–4]. Heat pipe cooling method is also a promising cooling technology [5–7]. Meneses-Rodriguez et al. [8] presented a study on the PV cell performance at the higher temperature. They proved that the V oc and fill factor decreases with the increase in temperature and concluded the main reason for the efficiency loss. Radziemska [9] presented that the decrease in the output power (0.65%/K) and of the conversion efficiency (0.08%/K) of the PV cell with the increase in temperature, which is actually much higher than the theoretical value of −0.4%/°C. Skoplaki and Palyvos [10] presented the effect of operating temperature of commercial grade silicon solar modules on its electrical performance. Bahaidarah et al. [11] reviewed the cooling of PV panel and concluded the critical issue in the design and operation of concentrated PV (CPV) technology. High cell temperature and non-uniform temperature distribution result in efficiency loss or permanent structural damage because of thermal stresses. PV module only converts a small fraction, around 15% of the incident solar irradiation to electricity, and the remainder is converted mainly into waste heat in the cells which raise the module temperature; hence, the efficiency drops. Therefore, decreasing the temperature can boost the efficiency of the module. The cooling of PV module is a problem of great practical significance. This project is based on the experimental analysis of forced convection cooling and analysis of photovoltaic module.

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In this paper, forced convection cooling is used for the two arrangements. One is forced convection cooling method by providing air channel which is made by conducting material (cast iron) at the beneath of the solar panel to simulate the rooftop application of PV panel on roof made of cast iron sheets. In another arrangements, air channel is made by using non-conducting material (hard board material K = 0.15 W/mK) to simulate the performance of panel on rooftop (asbestos cement sheets K = 0.144 W/mK) applications.

16.2 Experimental Setup The experimental setup is placed on the roof of the VNIT, Nagpur (latitude 21.1500° N; longitude 79.0900° E; altitude 310 m above mean sea level). Nagpur has tropical savannah climate with dry conditions prevailing for most of the year with average ambient temperature 20 °C (January) 32 °C (June) [12]. Nagpur receives daily annual average global solar irradiation of 4–7 kWh/m2 /day, on a tilted PV surface [13, 14] and is shown in Fig. 16.1a, b. Experimentation has been performed on the polycrystalline silicon solar module (Akshaya Solar, Model ASP-24200). The objective of this work is to find out the effect of cooling the panel on the performance of module. The results have been compared with non-cooled PV module. Cooling system is provided at the beneath of the one PV panel, and other is left without any cooling arrangement. Forced convective cooling arrangement is provided by using fan. The experiments have been performed in two cases. In case one, the arrangement of the air channel is provided at the beneath of the solar PV module, which is made by using the conducting material (cast iron sheet). In second case, the air channel arrangement is made by using non-conducting material (insulating material: hard board material) is used. Six DC Fans have been used for blowing the air through the channel. DC fan run by the output of the solar panel only, and fan speed is controlled by the fan regulator. For the current fan setup, fan regulator components are purchased and assembled in the college laboratory only. Since commercially fan regulator was not available. Four thermal sensor (Model—PT 100 RTD) is used for the measurement of temperatures. One thermal sensor is attached at the upper surface of the PV panel, and another is at the back surface of the photovoltaic panel, where the cooling arrangement is provided. Remaining two thermal sensors are provided at the reference panel at a similar position. Voltage and current transducer (MECO, Model—DTI) was used for the measurement of voltage and current. All devices have been connected to 16-channel Unilog data logger as shown in Fig. 16.2. Anemometer is used for the measurement of the fan air velocity as well as ambient temperature. Two rheostats (R. B. Electronics, double tube rheostat) are used in this experiment, which is used to vary the load. So that graph of V-I characteristics curve has been plotted to obtain the maximum power.

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2

Average solar radiation (kWh/m /day)

162 8

(a) 2

Monthly Average solar radiation (kWh/m /day)

7 6 5 4 3 2 1 0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Month

(b)

Fig. 16.1 a Monthly average irradiance of Nagpur site. b Evolution of solar radiation during a sunny day (Site: Nagpur)

16.3 Methodology This study is to analyze the forced convection cooling effects on the PV module performance in terms of efficiency and maximum power output in rooftop applications. In order to evaluate the air channel material which is best suitable on photovoltaic performance by forced convective fan, cooling experiment was conducted. The experimental study was carried out with two identical polycrystalline silicon PV modules. One of the PV modules was equipped with an air channel made up of cast iron material as shown in Fig. 16.3 which is placed at the back of the solar PV panel, while the other was not. Temperatures of PV module were measured by thermal sensor which is placed at the upper and lower portion of both modules. In one module, simply

16 Effect of Forced Convection Cooling on Performance …

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Fig. 16.2 Experimental setup block diagram

Fig. 16.3 Experimental setup air channel with DC fan

natural convection occurs which is left without cooling arrangement is known as reference PV Module, while other is known as air-cooled PV module. Air channel width is 16 cm, and the velocity of the air is constant 2 m/s. Experiment is conducted in the month of April 2016 from 10 a.m. to 3 p.m. for 5 h duration. All the variables temperature of the panels, voltage, current, and solar radiations are recorded in data logger. The power output and the efficiency of the panels are calculated using the following equations. Power generated, P = V∗I

(16.1)

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Efficiency of the panel, η=

V∗I G∗A

(16.2)

16.4 Results and Discussion The experiment has been performed in two cases. In first case, air channel is made at the beneath of the PV panel with the help of conducting material (cast iron), and in second case, air channel is made by placing the non-conducting material (insulating material: hard board material). The result is compared between the PV panel on which cooling system is provided and second panel without cooling arrangement. The results obtained for two cases have also been compared. The results of experimental are discussed in the following chapters.

16.4.1 Case 1: Air Channel Made of Conducting Material In this case, cooling system has been provided at the back of the solar PV module. Cooling system consists of air channel which made up of conducting material (cast iron sheet) to simulate the rooftop application of PV panel on roof made of cast iron sheets. Backside, lower portion of the solar PV module six DC fans are placed for cooling system. Two thermal sensors are placed at the upper and lower surface of the PV module. One solar module is used as a reference panel for the comparison without any cooling arrangement. Change in PV module temperature follows the radiation changes. It also depends on environment and wind velocity. In this experiment forced convective fan cooling have been used by providing an air channel, at the beneath of the PV panel. Temperature comparison is done between reference panel, air-cooled panel, and ambient. Figure 16.4 shows the variation in temperature along with the time. Temperature difference between the reference and air-cooled panel is minimum at the starting time (morning hours) of the experimentation. Temperature of the module increases along with the radiation. Temperature difference also increases along with the time. Maximum temperature difference of 8 °C is achieved at 2 p.m. and minimum of 0.3 °C at 10 a.m. The reason for lower difference in temperature during morning hours is less heat accumulated inside the module. During noon hours, some part of the heat conducted from the conducting material that heat naturally convected from lower surface of the cast iron sheet. So that heat transfer increases due to air cooling, and temperature difference also increases. The temperature of modules increases till 2 p.m. and then starts decreasing due to reduction in solar radiations.

165

15:00

14:40

14:20

14:00

13:40

13:20

13:00

12:40

12:20

12:00

11:40

11:20

11:00

10:40

10:20

65 60 55 50 45 40 35 30 25 10:00

Temperature in 0c

16 Effect of Forced Convection Cooling on Performance …

Time Reference Module

Air Cooled Module

Ambient Temperature

Fig. 16.4 Graph for temperature vs. time

The power and energy variations of modules are shown in Figs. 16.5 and 16.6. It is shown in Fig. 16.5 that initially the power output is less. Maximum and minimum difference in power output is 10 W and 2 W. The reason for lower power in morning is that panel is not able to produce power in the morning time, but as time increases sun radiation also increases along with power output. Changes in temperature primarily follow changes in irradiance. As time increases and at around 12 p.m. due to fluctuation in radiation and there is a period of low wind speed causing the heating of the modules so ultimately power output reduces. Again with an increase in radiation value, power output increases. Forced convection cooling by making air channel with the help of conducting material is able to cool PV module. The module temperature is 6–8 °C less than conventional reference photovoltaic module as shown in Table 16.1. High module temperature decreased the module efficiency, which is shown in Fig. 16.6. The differences in efficiency of both modules are 0.45–1.32% during 13:00 to 14:00 p.m. and 12:00 to 13:00 p.m., respectively, as shown in Table 6.7.

Power in watt

140 120 100 80 60 40 20 0

10:00

11:00

12:00

13:00

14:00

15:00

Time Reference PV Module

Fig. 16.5 Graph for power vs. time

Air Cooled PV Module

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Efficiency in %

16 14 12 10 8 6 4 2 0

10:00

11:00

12:00

13:00

14:00

15:00

Time Reference PV Module

Air Cooled PV Module

Fig. 16.6 Graph for efficiency vs. time

So forced convected cooled module with the air channel made of cast iron is able to improve 4–8.6% percentage efficiency during same duration.

16.4.2 Case 2: Air Channel Made of Non-conducting Material In this case, the air channel which is attached at the beneath of PV module is made of non-conducting material (hard board). The thermal conductivity of hard board material is same as the thermal conductivity of asbestos cement sheet, which is used for rooftop. That is why to check the performance of module when installed on asbestos cement sheet and to find the effect of forced convection cooling on such installation the experiments have been performed. Operating temperatures reduce significantly in comparison with a conventional reference module which is measured simultaneously with forced convective fan cooling method on which air channel is made at the beneath of the solar PV module with the help of non-conducting. In forced convective fan cooling with cast iron base roof along with the natural convection below the cast iron base, temperature difference is higher than paper material base air channel. Difference in temperature is more in this case around 1– 6 °C between both the reference PV module and air-cooled PV module as shown in Fig. 16.7. In the morning (starting time of the experiment), heat accumulation inside the air channel is less, so temperature difference is more compared with first case. As the increase in time and radiation difference in temperature increases, it is less compared to the first case in the same atmospheric conditions. Forced convective fan cooling method in case of air channel made of nonconducting material base roof is not much effective than the air channel made of conducting material. With the increase in radiation value, power output increases

T r (°C)

51

57

57

59.5

62.5

Time

11 a.m.

12 a.m.

1 p.m.

2 p.m.

3 p.m.

Table 16.1 Calculated values

54.4

54.2

53

52

50.6

T PVC (°C)

84.55

96.225

112.55

114.07

116.64

Pr (W)

90.1748

100.1466

122.2848

121.663

121.8328

PPVC (W)

40

39.1

37.1

35.8

32.8

T a (°C)

1.1

0.8

1.1

1.2

0.2

V a (m/s)

12.2

11.195

15.28

13.93

16

ηr (%)

13.01

11.65

16.6

14.855

16.712

ηPVC (%)

6.65

4.064

8.63

6.64

4.45

%η

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Temperature in 0c

70 60 50 40 30 20 10 10:00 10:10 10:20 10:30 10:40 10:50 11:00 11:10 11:20 11:30 11:40 11:50 12:00 12:10 12:20 12:30 12:40 12:50 13:00 13:10 13:20 13:30 13:40 13:50 14:00 14:10 14:20 14:30 14:40 14:50 15:00

0

Time

Reference Module Temperature ( C)

Air cooled Module Temperature ( C)

Ambient Temperature ( C)

Fig. 16.7 Temperatures vs. time

considerably. Due to this, temperature of PV panel also increases. Temperature difference between both arrangements of forced convective fan cooling method by making air channel with the help of non-conducting material is around 3–6 °C. Power output is more as compared with reference PV module. In forced convective fan cooling method by placing hard board material base roof on the air channel, efficiency pattern is the same as that the other arrangement in which air channel is made by the help of the cast iron base roof. In the cast iron base roof, as the radiation increases, power output increases with decrease in temperature. The temperature difference obtained between reference PV module and air-cooled PV module is 2–4 °C. Low temperature is obtained in the conducting material cast iron-based roof. The main reason behind this is cast iron which is the conducting material, and it conducted the heat from the body as well as convected from the lower portion of the air channel. So the heat accumulation in the cast iron base material is less compared to the hard board base material. Hard board material is the nonconducting, so it is not conducted heat from the paper material. The heat inside the air channel is not convected from the lower portion of the channel. So as the temperature increases, power output and efficiency both decrease in case of air channel made of hard board material (Figs. 16.8 and 16.9 and Table 16.2).

16.4.3 Comparison The case 1 comprises forced convective cooling by making air channel with the help of conducting material (cast iron sheet), and similarly, case 2 comprises forced convective cooling by making air channel with the help of non-conducting material (hard board). After the completion of experiment based upon the various results, the comparison has been done in terms of temperature as shown in Fig. 16.10. In the morning (at the low radiation level), both arrangements have the near about same temperature difference. From 10:00 a.m. to 12:00 p.m., temperature difference is very

15:00

169

14:00

13:00

12:00

11:00

140 120 100 80 60 40 20 0

10:00

Power in watt

16 Effect of Forced Convection Cooling on Performance …

Time Air Cooled PV Module

Reference PV Module

15:00

14:00

13:00

12:00

11:00

14 12 10 8 6 4 2 0 10:00

Efficiency

Fig. 16.8 Graph for power vs. time

Time Refrence PV Module

Air Cooled PV Module

Fig. 16.9 Graph for efficiency vs. time

fluctuating due to irradiation as well as the air velocity in the environment but after 12:00 pm as the velocity is high, so that heat removal from the PV module increases through the cast iron material due to natural convection as well. It helps in the increase in the temperature difference. It also affects the power as well as efficiency output. The lower temperature difference is −2 °C as well as higher temperature difference is 6 °C.

16.5 Conclusion The efficiency of PV module depends on the panel temperature; it decreases with the increase in panel temperature. The results of work show that the temperature of the panel can be reduced with forced convection cooling. The temperature of the PV module is also dependent on the ambient temperature. The module surface temperature significantly affects the open-circuit voltage than the short-circuit current. The conclusions drawn from the two mentioned cases are listed below.

T r (°C)

51

56.5

63.5

62.5

61

Time

11 a.m.

12 a.m.

1 p.m.

2 p.m.

3 p.m.

Table 16.2 Calculated values

T PVC (°C)

57.05

58.05

58.5

53.1

49.35

Pr (w)

80.3

98.938

112.7282

107.223

109.8162

PPVC (w)

86.8734

100.224

116.319

113.13

119.267

T a (°C)

40

38.8

34.9

32.3

31.3

V a (m/s)

0.9

0.7

1.3

0.4

0.9

ηr (%)

10.45

8.962

11.72

9.712

11.529

ηPVC (%)

11.31

9.078

12.09

10.248

12.521

%η

8.177

1.296

3.217

5.519

8.604

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∆T in 0c

10 8 6 4 2 10:00 10:10 10:20 10:30 10:40 10:50 11:00 11:10 11:20 11:30 11:40 11:50 12:00 12:10 12:20 12:30 12:40 12:50 13:00 13:10 13:20 13:30 13:40 13:50 14:00 14:10 14:20 14:30 14:40 14:50 15:00

0

Time Air Channel with Paper Material

Air Channel with Cast Iron

Fig. 16.10 Temperature difference vs. time

Forced convective fan cooling by making an air channel with the help of cast iron 1. The temperature difference between the air-cooled PV module and reference panel varies from 2 to 8 °C. 2. Experimental result shows that the increase in efficiency is 0.455–1.32%. 3. Percentage increase in efficiency is 4–8.63%. Forced convective air cooling by making air channel with the help of non-conducting material (hard board) 1. The temperature difference between the air-cooled PV module and reference panel is 1.3–6 °C. 2. Experimental results show that the increase in efficiency is 0.12–0.99%. 3. Percentage increase in efficiency is 1.29–8.62%. Forced convective cooling method with the cast iron made air channel gives satisfactory result compared to the other forced air cooling in which non-conductive paper material made air channel. It gives a good temperature difference than the second method. So uniformity in temperature is obtained throughout the panel. It helps in reduction in thermal stress as well as also becomes evident in power as well as efficiency enhancement.

References 1. J.J. Wysocki, Paul Rappaport, Effect of temperature on Photovoltaic solar energy conversion. J. Appl. Phys. 31(3), 1–9 (1960) 2. Z.J. Weng, H.H. Yang, Primary analysis on cooling technology of solar cells under concentrated illumination. Energy Technol. 29(1), 16–18 (2008) 3. K. Araki, H. Uozumi, M. Yamaguchi, A simple passive cooling structure and its heat analysis for 500 × concentrator PV module. 29th IEEE PVSC, New Orleans, May 2002, pp. 1568–1571 4. M. Brogren, B. Karlsson, Low-concentrating-water cooled PV-thermal hybrid systems for high latitudes. 29th IEEE PVSC, New Orleans, May 2002, pp. 1733–1736 5. M.A. Farahat, Improvement the thermal electric performance of a photovoltaic cells by cooling and concentration techniques. 39th UPEC International, Bristol, Vol. 2, 2004, pp. 623–628

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6. A. Akbarzadeh, T. Wadowski, Heat pipe-based cooling systems for photovoltaic cells under concentrated solar radiation. Appl. Therm. Eng. 116(1), 81–87 (1996) 7. W.G. Anderson, P.M. Dussinger, D.B. Sarraf, S. Tamanna, Heat pipe cooling of concentrating photovoltaic cells. 33rd IEEE Photovoltaic Specialists Conference, San Diego, May 2008, pp. 1–6 8. D. Meneses-Rodriguez et al., Photovoltaic solar cells performance at elevated temperatures. Sol. Energy 78, 243–250 (2005) 9. E. Radziemska, Effect of temperature on the power drop in crystalline silicon solar cells. Renew. Energy 28, 1–12 (2003) 10. E. Skoplaki, J.A. Palyvos, On the temperature dependence of photovoltaic module electrical performance: A review of efficiency/power correlations. Sol. Energy 83, 614–624 (2009) 11. M.S.H. Bahaidarah, A.B. Baloch, P. Gandhidasan, Uniform cooling of photovoltaic panels: A review. Renew. Sustain. Energy Rev. 57, 1540–1544 (2016) 12. A.K. Tiwari, V.R. Kalamkar, Performance investigations of solar water pumping system using helical pump under the outdoor condition of Nagpur, India. Renew. Energy 97, 737–745 (2016) 13. A.K. Tiwari, V.R. Kalamkar, Imran Arif, in Effect of pumping head on solar water pumping system. Proceedings of the India International Science Festival—Young Scientists’ Meet (Dec 4–8, 2015) 14. A.K. Tiwari, V.R. Kalamkar, Effects of total head and solar radiation on the performance of solar water pumping system. Renew. Energy 118, 919–927 (2018)

Chapter 17

Influence of Deposition Temperature on the Si Richness in SiC-Based Thin Films for Optoelectronic Applications S. Sam Baskar, Giri Goutham, Job Sandeep, Fabrice Gourbilleau and R. Pratibha Nalini Abstract Silicon nanoclusters/nanocrystals (Si-NC) embedded in silicon carbide (SiC) host matrix is a promising alternative to high bandgap dielectric matrices for solar cell application. However, the formation of Si-NC is a challenge since silicon carbide nanoclusters (SiC-NC) are formed with greater ease in the SiC host matrix. In this context, this work focuses on analyzing the influence of process parameters (deposition and annealing temperature) to synthesize the silicon-rich SiC film (aSix Cy ) for favoring Si-NC formation in the host matrix. In this paper, the Si-NC in a-Six Cy is obtained by co-sputtering of SiC and Si targets at different deposition temperatures (T d ) such as room temperatures 200 °C, 350 °C, and 500 °C. It is annealed at various temperatures and ambience such as vacuum (VA) and conventional thermal annealing (CTA). The structural and optical properties are investigated using spectroscopic ellipsometry, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and photoluminescence spectroscopy (PL). The refractive index varies between 3.3 and 3.7 which indicates the Si richness in the film. In FTIR absorption spectra and Raman spectra, change in intensity and position of Si-related vibrations varies depending on the excess Si incorporation. PL spectra show emission in the range of 412–440 nm that varies with different annealing and confirms the possibility of the Si-NC formation in the film. Keywords Co-sputtering · Silicon nanoclusters · Silicon carbide · Photoluminescence · Vacuum annealing

S. S. Baskar School of Electronics, VIT Chennai, Chennai, India G. Goutham · J. Sandeep · R. Pratibha Nalini (B) School of Mechanical and Building Sciences, VIT Chennai, Chennai, India e-mail: [email protected] F. Gourbilleau CIMAP CNRS/CEA/ENSICAEN/Normandie Université, 6 Bd Maréchal Juin, 14050 Caen Cedex 4, France © Springer Nature Singapore Pte Ltd. 2020 S. Singh and V. Ramadesigan (eds.), Advances in Energy Research, Vol. 1, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-15-2666-4_17

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17.1 Introduction Silicon nanocluster/nanocrystal (Si-NC) thin films have attracted huge attention due to their potential optoelectronic properties ever since the discovery of light emission from porous silicon [1]. The excellent optoelectronic properties of the SiC-based thin films make it suitable for various applications such as thin-film transistors, microelectronics, and alternative passivation layer material for solar cells [2–6]. Si nanoclusters (Si-NC) embedded in this type of matrices exhibit size-dependent tunable optical gap and tunable emission due to quantum confinement effect. The Si-NC formation in the sub-stoichiometric a-Six Cy occurs through phase separation and crystallization during the high-temperature post-processing annealing. However, the formation of crystallized Si-NC in a-Six Cy matrix is a huge challenge due to the formation of SiC-NC [7]. Also, the higher annealing temperatures (above 1000 °C) favor the formation of SiC-NC instead of Si-NC in a-Six Cy . Therefore, several synthesis methods and approaches such as single and multi-layers of SiC-based films are attempted by various researchers [7–13]. The results obtained so far suggest the need for further optimization of process parameter to favor the Si-NC formation. Increasing the absorption range, and/or having more than one energy level in the material, enhances the efficiency of optoelectronic devices though it is challenging [14]. The optical studies such as photoluminescence (PL) and spectroscopic ellipsometry yield some useful information of the material for use in device applications. Though a considerable number of studies are available on the emission and absorption characteristics of Si-NC in SiC-based matrix, most of them concern hydrogenated matrix [15, 16]. In this regard, this paper aims at carrying out investigation on unhydrogenated a-Six Cy films deposited by magnetron co-sputtering of the Si and SiC targets. The influence of deposition temperature (T d ) and the post-fabrication annealing treatment on the Si richness and thus in turn on the material’s optical characteristics are analyzed using spectroscopic ellipsometry and photoluminescence spectroscopy. The results thus obtained are important for future device incorporations, especially, for optoelectronic applications.

17.2 Materials and Methods Si-rich SiC films (a-Six Cy ) are deposited on a p-type 250-μm-thick (100) c-Si substrate using RF magnetron co-sputtering of silicon carbide (SiC) and silicon (Si) targets in the presence of argon (Ar) plasma. The base and working pressure are maintained at 8.0 × 10−7 Torr and 2.0 × 10−3 Torr, respectively. The input power density to SiC and Si targets is maintained at 6.7 W/cm2 and 3.1 W/cm2 , respectively. The deposition is carried out at different temperatures such as room temperatures (RTs) 200 °C, 350 °C, and 500 °C. Subsequently, the films are annealed at ultra-high

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vacuum (1 × 10−7 mbar) using e-beam vacuum annealing setup (VA) at 1000 °C for 60 min and conventional thermal annealing (CTA) at 1350 °C in Ar for 30 min. The refractive index (n1.95 eV ), absorption co-efficient (α), and thickness (t) of the films are investigated by spectroscopic ellipsometry using a HORIBA Jobin Yvon ellipsometer (UVISEL). The measurements are taken between 200 and 800 nm, fitted using the DeltaPsi software. The structural properties of the films are analyzed using Thermo Nicolet (Nexus model 670) Fourier transform infrared (FTIR) spectrometer. Raman spectra can be recorded from 50 to 4000 cm−1 of Raman shift, using microRaman system from Jobin Yvon Horibra LabRAM-HR visible. The bandgap of the films is investigated by using FL3-221 series of HORIBA Jobin Yvon photoluminescence spectroscopy. The excitation wavelength is fixed at 375 nm, and the emission spectra are recorded between 200 and 800 nm.

17.3 Results and Discussions 17.3.1 Spectroscopic Ellipsometry The thickness, refractive index (n1.95 eV ), and absorption co-efficient (α) of the films are extracted using spectroscopic ellipsometry (SE) [17–19]. The film thickness is in the range of 100–110 nm. Figure 17.1 shows the refractive index (n1.95 eV ) and deposition rate (r d ) of the films as a measure of T d . Both increase with T d . The

Fig. 17.1 Refractive index and deposition rate at various deposition temperatures (T d )

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film deposited at room temperature shows the n1.95 eV value of 1.6. With increase in T d, it varies from 3.3 to 3.7. Higher than the ideal values of SiC (2.5–2.6) confirms the transition from carbon rich or porous silicon carbide to Si-rich silicon carbide [20, 21]. At T d of 500 °C, decrease in n1.95 eV value is observed, due to saturation in Si incorporation [22] or due to the unintentional oxidation of the Si atoms. The possibility of unintentional oxidation is supported by the model used for extracting the n1.95 eV value and FTIR results. However, the refractive index (n1.95 eV ) and absorption co-efficient (1.7 × 105 cm−1 ) obtained render the film to be promising for optoelectronic applications.

17.3.2 Fourier Transform Infrared Spectroscopy Figure 17.2 shows the FTIR spectra of as-grown (AG) films deposited at 200 °C, 350 °C, and 500 °C. The broad peak centered around 740–750 cm−1 is attributed to the stretching vibration of SiC (s) [21–24]. A shift in peak position is evident with the increase in T d . Upon annealing, peak shift toward higher wave numbers 770 cm−1 is noticed. It is attributed to temperature-assisted phase separation of SiC in the matrix [25]. Generally, the peak at 616–625 cm is attributed to Si–H bending mode or considered as Si–Si mode [21]. In our case, an interesting correlation between the peak at 620 cm−1 and n1.95 eV value is noticed. The sample deposited at T d of 350 °C (i.e., C2493 AG) has the n1.95 eV value of 3.7, due to enhanced Si incorporation in the film. It shows higher intensity at 620 cm−1 , which can be correlated with the

Fig. 17.2 FTIR absorbance spectra of a-Six Cy deposited at different T d

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excess Si incorporation. The additional peaks around 800 cm−1 , 877 cm−1 , and 1112 cm−1 are attributed to Si–O- and Si–O–Si-related bonds. It could be due to the bonding of Si with oxygen either unintentionally incorporated within the film or the interfacial/surface oxidation. Therefore, the Si–O bonds are indicative of oxygen presence in the FTIR spectra.

17.3.3 Raman Spectroscopy Figure 17.3 shows Raman spectra of the a-Six Cy films deposited at different T d . The as-grown sample has a broad peak around 470 cm−1 . It is attributed to the stretching vibration of Si–Si bonds of the amorphous silicon (a-Si) network [26], which confirms the amorphous nature of the as-grown film. Upon vacuum annealing, intense peak at around ~511 cm−1 and ~520 cm−1 is noticed, due to the contribution of Si-NCs [27] and crystalline silicon, respectively. Interestingly, a frequency downshift is also noticed in the spectra of annealed sample, due to small-grained nanostructures [27]. Generally, the peak shift to lower energy caused by a ~3 nm Si-NC size [28]. The Si-NC size estimated from this measurement is in reasonable agreement with the Si-NC size determined from PL observations. Other peaks observed at ~900 cm−1 and 972 cm−1 are due to amorphous SiC and crystalline SiC, respectively. The band at ~935 cm−1 may be due to changes in bonding states, from amorphous to nanocrystalline, during annealing [28].

Fig. 17.3 Raman spectra of a-Six Cy deposited at different T d

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17.3.4 Photoluminescence Spectroscopy The PL spectra of the film deposited T d of 200 °C, 350 °C, and 500 °C, respectively, are shown in Fig. 17.4a–c. The spectra of as-grown samples have two distinct peaks in the blue region, centered at 416 and 436 nm, attributed to the quantum confinement or possible nanocluster formation in SiC matrix [29]. The broadness in the spectra indicates the possible presence of multiple luminescent centers [30]. The lower intensity of the as-grown films is attributed to the amorphous nature of the film with unpassivated defect states that provide non-radiative pathways for photoemission. Upon VA, an increase in the intensity and blue shift in the peak positions is noticed due to the possible crystallization or surface passivation and the self-aggregation of Si-NC. When CTA annealed at 1350 °C in Ar, significant reduction in the intensity and red shift in PL peak position are noticed. The quenching of PL could be due to the formation of large Si-NC and a decreasing number of Si-NC caused by the Ostwald ripening phenomena [31]. This effect is more pronounced on the sample deposited at higher temperatures (T d of 350 °C and 500 °C). The higher T d could have favored the formation of Si seeds for nucleation even while deposition, which grows further upon annealing. It is also noticed that in all the samples, VA shows the highest emission intensity, and all the spectra (at different T d and annealing) show a similar shape of the spectra with two prominent peaks centering around 412 and 440 nm. These correspond to an energy gap around 2.9 and 2.8 eV, respectively. The shifts in the peak position as well as their enhancement in intensity from as-grown to VA indicate that the emission of the two pronounced peaks is related to luminescent center from Si-NC and is not defect related. Thus, the evolution of PL with annealing temperature can be correlated with structural change in the film. Using the empirical relation between PL emission peak position (sub band energy) and the Si-NC size reported by, E = 1.56 + 2.4/D 2 where D is the size of the Si-NC; it is noted that there may be Si-NC with different sizes (i.e., around 1.2 and 1.4 nm) predominantly present, contributing to the emission. The Stokes shift is evaluated for these two prominent bands as a measure of luminescence energy and absorption energy since the Stokes shift is lesser than 1 eV, and the nature of Si-NC formed is amorphous [31].

17.4 Conclusions The a-Six Cy films are deposited by co-sputtering Si and SiC targets. The structural and optical characteristics of the films (a-Six Cy ) are systematically investigated. The increase in T d is instrumental for increasing the Si incorporation in the film. The higher T d favors Si seed for nucleation that increases the n1.95 eV and structural

17 Influence of Deposition Temperature on the Si Richness … Fig. 17.4 a–c PL spectra of the film deposited T d of (a) 200 °C, (b) 350 °C, and (c) 500 °C

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transformation during post-fabrication process. Choosing the annealing treatment is crucial as it leads to agglomeration and Ostwald ripening. The PL indicates the two major peaks corresponding to band energy 2.9 and 2.8 eV, which could be due to the presence of amorphous cluster around 1.2–1.4 nm. The CTA at 1350 °C has quenched the PL emission, therefore annealing around 1000 °C is suggested, which could favor the Si-NC formation. The results obtained are useful for the photovoltaic or optoelectronic applications. Acknowledgements The authors thank Dr. V. Ganesan at UGC-DAE CSR, Indore, for providing vacuum annealing facilities. The authors gratefully acknowledge Dr. M.S. Ramachandra Rao, Materials Science Research Center, IIT Madras, for providing PL spectroscopic measurement facility.

References 1. L.T. Canham, Silicon quantum wire array fabrication by electrochemical dissolution of wafers. Appl. Phys. Lett. 57, 1046–1048 (1990) 2. J.P. Conde, V. Chu, M.F. da Silva, A. Kling, Z. Dai, J.C. Soares, S. Arekat, A. Fedorov, M.N. Berberan-Santos, F. Giorgis, C.F. Pirri, Optoelectronic and structural properties of amorphous silicon–carbon alloys deposited by low-power electron-cyclotron resonance Plasma-enhanced chemical-vapor deposition. J. Appl. Phys. 85(6), 3327–3338 (1999) 3. L. Gou, C. Qi, J. Ran, C. Zheng, SiC film deposition by DC magnetron sputtering. Thin Solid Films 345, 42–44 (1999) 4. A.K. Costa, S.S. Camargo Jr., C.A. Achete, R. Carius, Characterization of ultra-hard silicon carbide coatings deposited by RF magnetron sputtering. Thin Solid Films 377–378, 243–248 (2000) 5. M. Mukherjee, Silicon carbide based transit time devices: the new frontier in high-power THz electronics, in Properties and Applications of Silicon Carbide, ed. Prof. R. Gerhardt (InTech, Vienna, 2011) 6. J. Huran, A. Valoviˇc, P. Boháˇcek, V.N. Shvetsov, A.P. Kobzev, S.B. Borzakov, A. Kleinov, M. Sekáˇcová, J. Arbet, V. Sasinková, The effect of neutron irradiation on the properties of SiC and SiC(N) layer prepared by plasma enhanced chemical vapor deposition. Appl. Surf. Sci. 269, 88–91 (2013) 7. F. Maury, J.M. Agullo, Chemical vapor co-deposition of C and SiC at moderate temperature for the synthesis of compositionally modulated Six C1−x ceramic layers. Surf. Coat. Technol. 76–77, 119–124 (1995) 8. C. Iliescu, D.P. Poenar, PECVD amorphous silicon carbide (α-SiC) layers for MEMS applications, in Physics and Technology of Silicon Carbide Devices Solution (InTech, Vienna, 2013) 9. M. Ouadfel, C. Yaddaden, S. Merazga, A. Cheriet, L. Talb, S. Kaci, H. Menari, New devices Si-rich and C-rich a-Si1−x Cx thin films gas sensors based. J. Alloy. Compd. 579, 365–371 (2013) 10. N. Ledermann, J. Baborowski, P. Muralt, N. Xantaopolus, Sputtered silicon carbide thin films as protective coating for MEMS applications. Surf. Coat. Technol. 125, 246–250 (2000) 11. S. Baskar, R. Pratibha Nalini, Synthesis and characterization of silicon nanocrystals in SiC matrix using sputtering and PECVD techniques. Mater. Today Proc. 3(6), 2121–2131 (2016) 12. R. Gradmann, P. Loeper, M. Künle, M. Rothfelder, S. Janz, M. Hermle, S. Glunz, Si and SiC nanocrystals in an amorphous SiC matrix: formation and electrical properties. Phys. Status Solid C 8(3), 831–834 (2011)

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13. A. Mellor, A. Luque, I. Tobías, A. Martí, The influence of quantum dot size on the sub-bandgap intraband photocurrent in intermediate band solar cells. Appl. Phys. Lett. 101, 133909 (2012) 14. T.H. Wang, Q. Wang, E. Iwaniczko, M.R. Page, D.H. Levi, Y. Yan, C.W. Teplin, Y. Xu, X.Z. Wu, H.M. Branz, Proceedings of the 19th European Photovoltaic Solar Energy Conference 129 (2004) 15. G. Wen, J. Fan, X. Li, Y. Liu, The influence of local SiC bonding density on the photoluminescence of Si-QDs upon thermal annealing the hydrogenated amorphous Si-rich silicon carbide thin films. J. Non-Cryst. Solids 463, 50–55 (2017) 16. Y. Peng, J. Zhou, X. Zheng, B. Zhao, X. Tan, Structure and photoluminescence properties of silicon oxycarbide thin films deposited by the RF reactive sputtering. J. Mod. Phys. B 25(22), 2983–2990 (2011) 17. J. Fan, H. Li, J. Wang, M. Xiao, Fabrication and photoluminescence of SiC quantum dots stemming from 3C, 6H, and 4H polytypes of bulk SiC. Appl. Phys. Lett. 101, 131906 (2012) 18. G. Scardera, T. Puzzer, I. Perez-Wurfl, G. Conibeer, The effects of annealing temperature on the photoluminescence from silicon nitride multilayer structures. J. Cryst. Growth 310, 3680–3684 (2008) 19. F. Demichelis, F. Giorgis, C.F. Pirri, E. Tresso, G. Amato, U. Coscia, Density of gap states in a-SiC:H films by means of photoconductive and photo thermal spectroscopies. Phys. B 205, 169–174 (1995) 20. S. Janz, G.P. Willeke, E. Scheer, Amorphous Silicon Carbide for Photovoltaic Applications (Konstanzer Online-Publikations-System, Freiburg im Breisgau, 2006) 21. S. Kerdiles, A. Berthelot, F. Gourbilleau, R. Rizk, Low temperature deposition of monocrystalline silicon carbide thin films. Appl. Phys. Lett. 76(17), 2373–2375 (2006) 22. T. Rajagopalan, X. Wang, B. Lahlouh, C. Ramkumar, Low temperature deposition of monocrystalline silicon carbide films by plasma enhanced chemical vapor deposition and their structural and optical characterization. J. Appl. Phys. 94(8), 5252–5260 (2003) 23. K. Surana, H. Lepage, J.M. Lebrun, B. Doisneau, D. Bellet, L. Vandroux, G. Le Carval, M. Baudrit, P. Thony, P. Mur, Film-thickness-dependent conduction in ordered Si quantum dot arrays. Nanotechnology 23(10), 105401 (2012) 24. H.S. Medeiros et al., Six Cy thin films deposited at low temperature by DC dual magnetron sputtering: effect of power supplied to Si and C cathode targets on film physicochemical properties. Mater. Sci. Forum 717–720, 197–201 (2012) 25. M. Marinov, N. Zotov, Model investigation of the Raman spectra of amorphous silicon. Phys. Rev. B 55, 2938–2944 (1997) 26. H. Büscher, C. Falter, W. Ludwig, K. Zhang, Raman shifts in Si nanocrystals. Appl. Phys. Lett. 69, 200–202 (1996) 27. G. Faraci, S. Gibilisco, P. Russo, A.R. Pennisi, S. La Rosa, Modified Raman confinement model for Si nanocrystals. Phys. Rev. B 73(1–4), 033307 (2006) 28. L. Pavesi, R. Turan, Silicon Nanocrystals: Fundamentals, Synthesis and Applications (Wiley, Weinheim, 2010), p. 226 29. G. Bellocchi, G. Franzò, S. Boninelli, M. Miritello, T. Cesca, F. Iaco, F. Priolo, Structural and luminescence properties of undoped and Eu-doped SiOC thin films. IOP Conf. Ser.: Mater. Sci. Eng. 56, 012009 (2014) 30. D.J. Lockwood, P. Hawrylak, P.D. Wang, C.M. Sotomayor Torres, A. Pinczuk, B.S. Dennis, Shell structure and electronic excitations of quantum dots in a magnetic field probed by inelastic light scattering. Phys. Rev. Lett. 77, 354–357 (1996) 31. G. Allan, C. Delerue, M. Lannoo, Nature of luminescent surface states of semiconductor nano crystallites. Phys. Rev. Lett. 76, 296 (1996)

Chapter 18

Optimization of TiO2 for Low-Temperature Dopant-Free Crystalline Silicon Solar Cells Swasti Bhatia, Irfan M. Khorakiwala, Kurias K. Markose, Neha Raorane, Pradeep R. Nair and Aldrin Antony Abstract This study explores the deposition and post-deposition treatment of TiO2 films in the context of using those films as electron selecting layers in diffusionfree solar cells. The passivation provided by TiO2 films is known to improve after annealing. Therefore, the effect of annealing on electrical performance of the films is analyzed in this study. The study reveals that annealing may lead to a formation of thin interfacial silicon oxide which may impede the transport of electrons to the desired contact. It is also noted that annealing does not contribute significantly to lowering of reverse saturation current, and the ideality factor values also remain the same. Interestingly, while annealing improves the lifetime, the same is not reflected in electrical behavior of diodes. A plausible explanation of this behavior is given on the basis of numerical modeling of the fabricated device. Finally using the asdeposited TiO2 film as electron collecting contact and MoO3 as a hole quencher, solar cells are fabricated with an efficiency of 5.52%. Keywords TiO2 · Passivation · Heterojunction solar cell · Carrier selective contacts · Electron transport layer

18.1 Introduction Heterojunction solar cells that use transition metal oxides have attracted a lot of attention due to their low thermal budget that translates to low cost of fabrication. S. Bhatia · I. M. Khorakiwala · P. R. Nair Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai, India K. K. Markose Department of Physics, Cochin University of Science and Technology, Kochi, India N. Raorane Centre of Excellence in Nanoelectronics (CEN), Mumbai, India A. Antony (B) Department of Energy Science and Engineering, Indian Institute of Technology Bombay, Mumbai, India e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2020 S. Singh and V. Ramadesigan (eds.), Advances in Energy Research, Vol. 1, Springer Proceedings in Energy, https://doi.org/10.1007/978-981-15-2666-4_18

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S. Bhatia et al. Sample (°C)

J 0 (nA/cm2 )

Thermal 100

28.5

Thermal 250

7690

In terms of efficiency, heterojunction with intrinsic thin layer (HIT) solar cell has been the best performing one in terms of efficiency with the current record being held by Kaneka solar with their 26.7% solar cell [1]. However, heterojunction with intrinsic thin layer (HIT) silicon solar cells are limited by the parasitic absorption in the intrinsic and doped amorphous layers at the top surface of the solar cell. If the function of the doped intrinsic layer can be accomplished by a layer that is transparent to the UV and visible range (especially short wavelength) radiation, then the problem of front-side parasitic absorption could be eliminated. This can be achieved by carrier selective films that extract only one type of carrier, block the other and are also transparent in the visible region. If the selective film can passivate the silicon surface, then it could also replace the passivating intrinsic layer too. Interestingly, a few transition metal oxides align with silicon such that they allow selective passage of only one type of carrier through them. Recent studies have shown that by appropriate deposition conditions and post-deposition treatments, these special transition metal oxides can passivate the silicon surface reasonably well [2]. In this report, we investigate one such oxide, titanium dioxide which has already been reported to be electron selective and also reasonably passivating in the context of crystalline silicon. The deposition conditions for TiO2 via atomic layer deposition (ALD) have already been investigated. The summary of the finding is given in Table 18.1. Here, we study the effect of annealing on electrical properties of film apart from interface passivation. Solar cell is fabricated with the TiO2 film as an electron selective rear contact and MoO3 as a hole quenching front contact.

18.2 Experimental Details TiO2 films of 8 nm were deposited on RCA cleaned boron-doped CZ wafers via ALD at 100 °C. The as-deposited films were annealed in a forming gas (5% hydrogen + 95% nitrogen) environment at 300 °C for 45 min. Annealing treatment was followed by evaporation of 350 nm aluminum dots using shadow mask over TiO2 film. Finally, back contact with the p-type wafer was made by evaporating chromium and gold stack. For solar cell fabrication, after the deposition of TiO2 on p-type wafer, 6 nm MoO3 was evaporated on the other side. This was followed by deposition of 70 nm indium-doped tin oxide (ITO) over MoO3 , and finally contact metals were evaporated. The rear surface TiO2 film was contacted by 600 nm aluminum, and silver grid was deposited on top ITO as the front contact. No annealing treatment was done for the solar cells at any stage. For lifetime measurement using quasi-steady-state

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photoconductance decay (QSSPC) [3], 8 nm films were deposited on both sides of a RCA cleaned float zone (FZ) silicon wafer. The films were annealed in order to check for passivation enhancement with post-annealing.

18.3 Results It has been reported previously that for the purpose of using TiO2 as an electron selective layer in solar cells, it should preferably be deposited at low temperatures (Table 18.1). It has also been reported that the passivation offered by TiO2 can be enhanced by annealing treatment at temperatures between 200 and 350 °C [4]. Diodes (Fig. 18.1a) formed on annealed TiO2 films as described in the experimental section show slightly decreased reverse bias currents and significantly decreased forward bias current (Fig. 18.1b). One reason behind the same could be the formation of an interfacial SiO2 at the silicon surface. The presence of Si–O–Ti bonds at the surface has been reported [5] on annealing and even on exposure to air for long duration. Therefore, it is likely that an annealing at 300 °C leads to the formation of SiO2 at the interface. If this were to be true, annealed TiO2 films could affect the short-circuit current and also could increase the series resistance. Additionally, if the traps are indeed reduced significantly, the effects of hole accumulation region under forward bias conditions could be observed in the C-V characteristics. However, the C-V under forward bias conditions shows negligible change (Fig. 18.2b) and hence does

Fig. 18.1 a Structure of the fabricated diode. b IV characteristics of the diodes with differently processed TiO2 films

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Fig. 18.2 a IV characteristics. b C-V characteristics. c Mott–Schottky plots of two samples with annealed TiO2 films

not imply any significant reduction in the interface trap state density. Further, the V bi increase, as extracted from reverse bias capacitance (Fig. 18.2c), indicates an increased band bending in silicon. Hence, the C-V analysis reveals that annealing does not reduce trap density by a sufficient amount. It is possible that either the passivation enhancement that is observed in QSSPC result is partially field effect or it does not reduce trap density enough to block the holes entirely. In either case, the annealing is not fulfilling the purpose of reducing trap density at the interface. Additionally, formation of silicon oxide is also suspected. These results indicate limited utility of annealing of TiO2 films, and we conclude that it may not be the best method for lifetime enhancement. The next section discusses the reasons for the insignificant effect of enhanced carrier lifetime on the reverse saturation current.

18.4 Discussions The simulation of the diode structure as shown in Fig. 18.1a was done. Current– voltage and capacitance–voltage (C-V) characteristics were obtained, and reverse saturation current, ideality factor and built-in potential were calculated. Uniform trap density was introduced at the silicon–TiO2 interface throughout the silicon band gap. The dielectric constant of TiO2 was taken as 40 and the mobility as 0.1 m2 /(V-s). The density of traps and the doping inside TiO2 film varied. The reverse saturation current density (Fig. 18.3a) and ideality factor (Fig. 18.3b) show an interesting trend on the trap density. When the TiO2 films are highly doped, change in trap density at the interface is not reflected in the ideality factor and reverse saturation current. It is observed that ideality factor starts showing signature of SRH recombination at a very high density of traps for highly doped films (in low bias region). It is expected since the overall current for highly doped films is mostly constituted over the barrier current at the Si-TiO2 interface. The recombination generation current in the depletion region with ideality factor 2 can be observed only when the trap density

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Fig. 18.3 Simulated effect of changing TiO2 doping on reverse saturation current and ideality factor as a function of traps and doping of TiO2 film

Table 18.2 Effect of annealing on lifetime (from QSSPC), ideality factor and reverse saturation current (from diode’s current–voltage characteristics) and built-in potential (from diode’s capacitance–voltage characteristics) Sample

SRV (cm/s)

J 0 (nA/cm2 )

Ideality factor (diode)

Built-in potential V bi (V )

As deposited

>1000

28.5

1.2

0.54

Annealed