Renewable Energy: Accelerating the Energy Transition (Energy Systems in Electrical Engineering) [1st ed. 2024] 9819961157, 9789819961153

Citation preview

Energy Systems in Electrical Engineering Series Editor Muhammad H. Rashid, Florida Polytechnic University, Lakeland, USA

Energy Systems in Electrical Engineering is a unique series that aims to capture advances in electrical energy technology as well as advances electronic devices and systems used to control and capture other sources of energy. Electric power generated from alternate energy sources is getting increasing attention and supports for new initiatives and developments in order to meet the increased energy demands around the world. The availability of computer–based advanced control techniques along with the advancement in the high-power processing capabilities is opening new doors of opportunity for the development, applications and management of energy and electric power. This series aims to serve as a conduit for dissemination of knowledge based on advances in theory, techniques, and applications in electric energy systems. The Series accepts research monographs, introductory and advanced textbooks, professional books, reference works, and select conference proceedings. Areas of interest include, electrical and electronic aspects, applications, and needs of the following key areas: • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

Biomass and Wastes Energy Carbon Management Costs and Marketing Diagnostics and Protections Distributed Energy Systems Distribution System Control and Communication Electric Vehicles and Tractions Applications Electromechanical Energy Conversion Energy Conversion Systems Energy Costs and Monitoring Energy Economics Energy Efficiency Energy and Environment Energy Management, and Monitoring Energy Policy Energy Security Energy Storage and Transportation Energy Sustainability Fuel Cells Geothermal Energy Hydrogen, Methanol and Ethanol Energy Hydropower and Technology Intelligent Control of Power and Energy Systems Nuclear Energy and Technology Ocean Energy Power and Energy Conversions and Processing Power Electronics and Power Systems Renewable Energy Technologies Simulation and Modeling for Energy Systems Superconducting for Energy Applications Tidal Energy Transport Energy

The books of this series are reviewed in a single blind peer review process by the main editor and/or the advisory board.

Rahul Goyal · Satyanarayan Patel · Abhishek Sharma Editors

Renewable Energy: Accelerating the Energy Transition

Editors Rahul Goyal Department of Mechanical Engineering Manipal University Jaipur Jaipur, India

Satyanarayan Patel Department of Mechanical Engineering Indian Institute of Technology Indore Madhya Pradesh, India

Abhishek Sharma Department of Mechanical Engineering B I T Sindri Dhanbad, Jharkhand, India

ISSN 2199-8582 ISSN 2199-8590 (electronic) Energy Systems in Electrical Engineering ISBN 978-981-99-6115-3 ISBN 978-981-99-6116-0 (eBook) https://doi.org/10.1007/978-981-99-6116-0 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore Paper in this product is recyclable.

Preface

According to the World Bank’s Development Indicators, energy plays a vital role in the growth of any modern society and country. Energy consumption per capita is strongly linked to wealth, health, nutrition, water, infrastructure, education, and life expectancy. The International Energy Agency (IEA) predicts that by 2040, there will be a 70% increase in global electricity demand, with India, China, Africa, the Middle East, and South-East Asia accounting for 24% of total energy consumption. On the other hand, petroleum fuels like petrol, diesel, coal, and natural gas, etc., are only available in limited quantities. Thus, we eventually run out of them over time if we continue to extract them. Therefore, it is time to look for other promising alternative energy sources due to the increase in population and limited fossil fuel sources. Renewable energy resources can be a potential substitute for fossil sources which will also help towards low carbon imprint. Selecting a particular type of renewable energy depends on the requirement and access to a specific energy source. The world is also seeking a sustainable indigenous technological solution to generate energy from different sources. This book reveals key challenges to ensuring the secure and sustainable production and use of energy resources and provides corresponding solutions. This book covers the advanced technologies applied in renewable energy generation, energy storage, an alternative to petroleum fuels, waste to energy, solar energy, and the impact of fossil fuel combustion on the environment, green buildings, and social sustainability. In turn, the book goes beyond theory and describes practical challenges and solutions associated with energy and sustainability. It will reference a broad spectrum of readers, including environmentalists, engineers, researchers, professionals, and students associated with this study area. It is unique to other available books because

v

vi

Preface

it covers various topics on a single platform. The present book is organized with sixteen chapters related to solar energy, biofuel production and utilization, batteries for electric vehicles, wind turbines, pyroelectric materials for energy harvesting, energy storage systems, and nanomaterial use in such systems and submitted by renowned authors. Jaipur, India Madhya Pradesh, India Dhanbad, India

Rahul Goyal Satyanarayan Patel Abhishek Sharma

About This Book

This book covers potential challenges related to conventional energy sources and provides possible solutions for sustainable production and renewable energy resource uses. It covers the advanced technologies applied in renewable energy generation, energy storage, an alternative to petroleum fuels, waste to energy, solar energy, and the impact of fossil fuel combustion on the environment, green buildings, and social sustainability. Further, the book also describes the practical challenges of renewable energy implementation and its associated solutions. This book particularly interests graduate students and academic or industrial researchers/professionals in renewable energy, sustainability, and mechanical and automobile engineering. It creates a strong base for establishing the role of renewable energy in energy transition for a sustainable, cleaner, and greener future. This book is unique to other available books because it covers various topics on a single platform. The important key features of the proposed book are given below. • It includes all principal forms of renewable energy transition presently being used. • The interdisciplinary methodology considers waste-to-energy technologies, economic and environmental. • It discusses the sustainable use of solar air heaters, dryers, and distillation for society. • It covers the alternative fuel’s cost and impact on engine performance and economy. Energy storage (Li batteries), capacitors, and energy harvesting via pyroelectric are also covered.

vii

Contents

Renewable Energy: Accelerating the Energy Transition . . . . . . . . . . . . . . . G. K. Chhaparwal and Rahul Goyal

1

Prospects of Renewable Energy Scenario in India . . . . . . . . . . . . . . . . . . . . Rahul Kumar, Nishikant Kishor Dhapekar, Rajesh Tiwari, Y. Anupam Rao, Renuka Shyam Narain, Anil Singh Yadav, and Abhishek Sharma

15

Solar Air Heater-Classifications and Performance Enhancement Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. K. Chhaparwal and Rahul Goyal

33

A Comprehensive Review of Recent Trends in Augmentation Heat Transfer Solar Air Heaters Using Arc-Shaped Ribs . . . . . . . . . . . . . . . . . . . Rajan Karir, Kunj Bihari Rana, and Piyush Kumar Jain

47

Performance Evaluation of Solar Air Heater Absorber Plate with Nanoparticles Coating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rahul Kumar, Sujit Kumar Verma, Amit Kumar Thakur, Abhishek Sharma, Tabish Alam, and Anil Singh Yadav CFD Investigation of Solar Air Heater Roughened with Transverse Discontinuous Trapezoidal Ribs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sarvapriya Singh, Mokshaa Sharma, Santanu Mitra, and Manish Kumar

73

93

Classification and Performance Enhancement of Solar Dryers . . . . . . . . . 111 Aditya Gaur, N. S. Thakur, and Satyanarayan Patel Solar Distillation and Water Heating Systems Integration with Photovoltaic Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 Rahul Dev, Yashwant Kashyap, Kirti Tewari, and Piyush Pal

ix

x

Contents

Recent Advancement in Biofuels Production and Its Environmental Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 Abhishek Sharma, Y. Anupam Rao, Piyush Tiwari, Nishikant Kishor Dhapekar, Jasmeet Kaur Sohal, Nishant Tiwari, and Rahul Kumar Fabrication of Nanocatalyst for Biodiesel Production Using Various Strategies from Different Feedstocks . . . . . . . . . . . . . . . . . . . . . . . . . 179 Vaishali Mittal, Jagdeep Nayak, and U. K. Ghosh Performance Investigation of Automotive Radiator Using Water-Al2 O3 and Ethylene Glycol Nanofluid Blends . . . . . . . . . . . . . . . . . . 197 Vednath P. Kalbande, Yogesh N. Nandanwar, Man Mohan, Shilpa Vinchurkar, Kishor Rambhad, Vijay Kalbande, Anil Singh Yadav, and Tabish Alam A Review on Fast Charging/Discharging Effect in Lithium-Ion Batteries for Electric Vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 Indra Kumar Lokhande, Nishant Tiwari, and Abhishek Sharma Li-ion Battery Energy Storage Management System for Solar PV . . . . . . 235 C. N. Chaitrashree, Yashwant Kashyap, and P. Vishnu Sidharthan Optimal Airfoil Selection and Aerodynamic Analysis of Small-Scale Horizontal Axis Wind Turbine Blade Profiles Using CFD . . . . . . . . . . . . . . 263 Ankush Jain, K. B. Rana, B. Tripathi, Rahul Jain, and B. L. Gupta Methods to Enhance the Pyroelectric Properties and Energy Harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 Nishchay Saurabh and Satyanarayan Patel Energy Storage Properties in Bulk Lead-Free Relaxor Ferroelectric Ceramics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 Nishchay Saurabh and Satyanarayan Patel

About the Editors

Dr. Rahul Goyal is presently working as a Professor in the Department of Mechanical Engineering at Manipal University Jaipur, India. He graduated in Mechanical Engineering from University of Rajasthan and completed his master’s from University College of Engineering, Kota in Thermal Engineering. He then pursued his PhD degree from MNIT, Jaipur. His major research interests include alternative fuels in an IC engine, Waste heat recovery technology, Thermal energy storage, Combustion, Renewable Energy etc. He has published more than 50 research publications in international peer-reviewed journals, reputed conferences, and book chapters. He also serves as reviewer in various reputable journals. He has to his credit Invited Talks & Keynote address and chaired/co-chaired sessions in various conferences. He is a regular reviewer of research articles for many high impact journals. He has supervised 3 Ph.D.s and currently 3 research scholars are under his supervision. He is a life member of ISTE, India. Dr. Satyanarayan Patel is currently working as a full-time assistant professor in mechanical engineering at Indian Institute of Technology (IIT) Indore, India. He supervises Ph.D., master and undergraduate students; and implements a research project funded by Science and Engineering Research Board (SERB) India. Previously, he worked as a prestigious Alexander Von Humboldt Post-doctoral Fellow in the Nonmetallic-Inorganic Materials Research Group, Technische Universität Darmstadt, Germany. His research focuses on bulk lead-free ceramics (piezoelectric and ferroelectric) for energy storage, conversion and caloric effects for solidstate refrigeration. He first demonstrated the elastocaloric and barocaloric effect in bulk ferroelectric ceramics using indirect measurements for solid-state refrigeration. He also explored an unforeseen component of the electric field-driven caloric effect termed inverse piezocaloric effect. Additionally, he performed work on the effect of compressive pre-stressed (mechanical confinement) for tuning ferroelectric/ pyroelectric/-piezoelectric properties for energy storage/conversion and other device applications. The current research is focused on pyroelectric energy harvesting and the flexocaloric effect in ferroelectric materials.

xi

xii

About the Editors

Dr. Abhishek Sharma has been working with B I T Sindri as Assistant Professor in the Department of Mechanical Engineering. He has total of 15 years of teaching and research experience in various reputed Indian universities. He is a graduate in Mechanical Engineering from Pt. Ravi Shankar Shukla University Raipur, did his Masters in Thermal Engineering from Maulana Azad National Institute of Technology Bhopal and his doctoral degree in Mechanical Engineering from National Institute of Technology Rourkela. In the last 10 years, he has been working in the field of waste to energy, alternative fuels for IC engines, renewable energy, air pollution etc. He was a Principal investigator for a research project focused on the conversion of waste plastic into liquid fuel, sponsored by Ministry of Human Resource Development, Government of India. He has to his credit around 80 research publications in international peer-reviewed journals, reputed conferences, and book chapters, which are readily available in Google Scholar and having more than 1750 citations with an h-index of 23. He has also been granted three Indian patent and registered two copyrights. Currently, 3 students are working under his guidance for their Ph.D. thesis. He has guided 10+ master’s students for their dissertation works.

Renewable Energy: Accelerating the Energy Transition G. K. Chhaparwal and Rahul Goyal

Abstract The world faces two major challenges; ever-growing energy demand and climate change. Renewable energy resources can meet both challenges; in this direction, leaders, investors, and researchers have shown great interest in this field in the last decade. Initially, wind energy gained momentum, but in the last 10 years, investors, scientists, and businessmen have favored solar energy-based resources. It is mainly due to its modularity, ease of installation, and safe working conditions, unlike wind turbines which can be installed only in certain areas. In solar energy, photovoltaic (PV) panels are the most used and researched application but nowadays, solar thermal energy-based applications have also gained momentum. Solar thermal energy-based appliances can reduce the burden on electricity consumption in specific applications like heating, cooling, and drying in residential, commercial buildings, agriculture, and industries. The major problem with these appliances is low thermal efficiency which needs various modifications to improve their designs and working conditions. Keywords Renewable energy · Global and national energy statistics · Solar energy · Wind energy · Air pollution

1 Introduction “The time will arrive when the industry of Europe will cease to find those natural resources so necessary for it. Petroleum springs and coal mines are not inexhaustible but are rapidly diminishing in many places. Will man, then, return to the power of water and wind? Or will he emigrate where the most powerful heat source sends its rays to all? History will show what will come.” The above statement was given in 1873 G. K. Chhaparwal Paanduv Applications Private Limited, Bareilly, Uttar Pradesh 243122, India R. Goyal (B) Department of Mechanical Engineering, Manipal University Jaipur, Jaipur 303007, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Goyal et al. (eds.), Renewable Energy: Accelerating the Energy Transition, Energy Systems in Electrical Engineering, https://doi.org/10.1007/978-981-99-6116-0_1

1

2

G. K. Chhaparwal and R. Goyal

by Professor Augustin Mouchot, who expressed the fear of the extinction of fossil fuels even in the 1870s. Although the recent developments in alternate resources have vanished the fear of the extinction of fossils, the aggravated ill effects of emissions of fossil fuels have revealed new challenges to humankind. Air pollution is a major threat or ill effects of fossil fuels. Air pollution due to fossil emissions costs us 3% of the global GDP and 5.1 million deaths yearly. Fossil fuels generate 35 billion tonnes of carbon dioxide annually, the primary cause of climate change and global warming by its greenhouse effect. Conversely, the world’s energy consumption has grown more than 2.5% since 2015. The Paris Agreement was signed in 2016 and which longterm target is to keep the global average temperature rise below 2 °C to minimize the effect of climate change. The world needs an urgent, significant, concerted transition from fossil to non-fossil fuels, balancing global development and climate change challenges to meet the Paris Agreement and SDG7 targets (REN21 2020). There are four major types of energy resources in the world: fossil fuels, nuclear energy, hydroelectric, and renewables. Whether hydroelectric is renewable is debatable due to its significant environmental baggage. Although India recently considered it in the renewables category so that it can enjoy the benefits of government policies on renewables. Fossil fuels amount to 85% (petroleum 34%, coal 27%, and natural gas 24%) of the primary energy consumption in the world as of 2018. While nuclear, hydroelectric, and renewables amount to 4.4, 6.8, and 4%, respectively. Investments and new installations in fossils, nuclear, and hydroelectric energy have declined but increased for renewable energy resources. The source of air pollution is of two major types: localized (power plants) and cooking and non-localized (transportation). It is relatively difficult to control the nonlocalized source of air pollution. Electricity and a clean source of cooking fuel (both are the source of localized air pollution) are required for economic development and improvement in the standard of living, respectively. A clean alternative for electricity and cooking fuel can prevent much air pollution. Around 40 countries have less than 50% electrification. In 1990, around 71% of the world’s population had access; this has increased to 89%, and still, 840 million people have not seen electricity in their houses. India recently achieved 100% electrification nationwide (a village is assumed to be electrified even if 10% of households have an electricity connection). However, even a decent hours supply, leave alone a 24 × 7 h supply, is still a big challenge. More than 2.6 billion people worldwide, with 670 million in India, do not have access to clean cooking fuel. In-house air pollution is a reason for around 5 million premature deaths annually worldwide. If India needs to grow economically and socially, it must work toward an environmentally friendly alternative for this large source of energy consumption. This chapter deals with the present detailed status of various energy sources in terms of potential, generation, consumption, per capita demand, etc. In addition to the world and India, five countries, Brazil, China, Russia, USA, Europe, and Africa, are considered for relative comparison as these geographical areas represent the maximum world population.

Renewable Energy: Accelerating the Energy Transition

3

2 Energy Consumption Statistics In 1965, if we exclude traditional biofuels like wood (a major energy source in Africa and the Asia Pacific), Europe, Eurasia, and North America collectively consumed 80% of the global energy consumption. In 2015, it changed to the Asia Pacific at 42%, North America, Europe, and Eurasia combined at 43%, Africa at 3%, Latin America at 5%, and the Middle East at 7% (Our World in Data 2020). There are two ways to represent energy consumption; a primary or direct method that tells energy statics in its raw form and a corrected or substitution method that accounts for the inefficiencies in fossil fuel conversions. Here, Figs. 1 and 2 show the primary energy consumption of the major energy source of the world and India, respectively, from 1965 to 2019. This dataset considers only commercially traded fuels, not traditional biofuels. Therefore, the consumption for Africa and developing Asia is low as these regions still depend on traditional fuels as a primary fuel source. The world has to transition from a fossil fuels-dominated economy to low-carbon alternatives to achieve various sustainable developments and environmental protection goals (IEA 2020a). It is difficult to achieve a low-carbon alternative in transportation (which accounts for more than 90% of petroleum consumption) due to its movable nature. However, it is possible to achieve this in the immovable or localized source of energy consumption like electricity generation. In the last decade (2010–2020), share of renewables in the electricity mix has increased by almost 10%, which has filled the gap created by the reduction in nuclear share by almost

Fig. 1 Global direct energy consumption. Adopted from https://ourworldindata.org/energy, accessed on April 18, 2023

4

G. K. Chhaparwal and R. Goyal

Fig. 2 National direct energy consumption. Adopted from https://ourworldindata.org/energy, accessed on April 18, 2023

the same amount. Similarly, natural gas and coal contributions to electricity have increased by 1% and 2%, respectively, balanced by reducing oil share by 2%. Thus overall picture, as shown in Figs. 3 and 4, is stable and not so motivating. It needs a further big push to achieve targets. Figure 5 shows the per capita energy consumption (which includes all forms of consumption like electricity, transport and heating) from 1965 to 2019 in kWh per year. The overall global per capita consumption has increased by 50%. However, the transitioning BRICS economies like China, India, and Brazil have increased by 300, 80, and 50% since 2000. For high-income nations like the USA and UK, their transitioning economy phase ended by the 1970s. In these nations, it was constant till 2000 and showed a decreasing trend of up to 30–40%, probably due to the increased use of efficient devices. However, global inequalities in per capita consumption still exist, as the average USA citizen consumes 10 times Indian, 5 times Brazilian, and 3 times Chinese nationals. Figure 6 shows the progress of various world regions regarding energy intensity from 1990 to 2015. It is the quantity of energy required to produce one unit of GDP growth and its unit is kWh per USD. Its value should be as low as possible to attain sustainable development. Various energy efficiency policies are drawn with the support of tax relief, market instruments, and public funding to achieve sustainable development goals (SDG7.3 targets) by 2030, which aims to double the global rate of increment in energy efficiency. In 1990, the global average was 2.1 kWh/$ which improved to 1.5 kWh/$ in 2014, almost a 30% reduction. According to International

Renewable Energy: Accelerating the Energy Transition

5

Fig. 3 Global share of renewable energy in electricity generation. Adopted from https://ourworldi ndata.org/energy, accessed on April 18, 2023

Fig. 4 National share of renewable energy in electricity generation. Adopted from https://ourwor ldindata.org/energy, accessed on April 18, 2023

6

G. K. Chhaparwal and R. Goyal

Fig. 5 Global per capita energy consumption. Adopted from https://ourworldindata.org/energy, accessed on April 18, 2023

Energy Agency (IEA) (2020b), in 2017 and 2018, there was just a 1.7 and 1.2% increment in global energy efficiency, which has further increased the target improvement rate to 2.9% annually to achieve SDG 7.3 targets. Although high-income economies have lower energy intensity values, developing Asia is improving fastest at an annual improvement rate of 3.3%.

3 Disadvantages of Fossil Fuels Over 95% of the population worldwide breathes low-quality air; 3.2 billion still use carbon-based sources (wood, dung, and crop residues) for household fuels. Nearly 1 in 8 death (5.1 million deaths annually worldwide: 1.7 million and 3.4 million from indoor and outdoor pollution, respectively) are by polluted air due to fossil fuel emission. Although WHO estimates deaths due to indoor pollution more than three times predicted by Institute of Health Metrics and Evaluation (IHME) due to large unreported cases in rural populations, accounting for a major part of indoor air pollution. India is the worst affected, with 2.1 million death per year. The deaths due to air pollution are continuously falling due to increasing access to clean energy for cooking fuel, which accounts for indoor pollution. However, there is less control over outdoor pollution. The low and middle economies with large populations are worst affected, as they have vital industrialization and construction in the growing

Renewable Energy: Accelerating the Energy Transition

7

Fig. 6 Global energy intensity level compared to the value in 2011. Adopted from https://ourwor ldindata.org/energy, accessed on April 18, 2023

phase with less strict rules and regulations for air quality control compared to wellestablished economies. This difference is up to a thousand folds. Carbon dioxide (9– 26%), methane (4–9%), and ozone (3–7%) are the major contributors to greenhouse gases after water vapor (36–85% with and without clouds). The industrial revolution in the 1750s increased the CO2 PPM level from 280 to 410 in 2020. Pharmaceutical industries emit CO2 more than automotive industries. Livestock and conventional rice cultivation account for a major source of methane emission that has a similar impact as aviation-CO2 emission. Greenhouse gases (GHG) are increasing the average earth’s temperature, and at the current rate, the earth will have a net temperature rise of 20 C by 2036. Since the Kyoto Protocol of 2005, China has become the largest CO2 emitter, India has the highest growth in emissions, while the USA and Europe have had a double-digit decline in emissions due to strong legislative changes. However, the cheaper shale gas boom in the USA has contributed to even double the renewables in the last decades. However, in terms of per capita CO2 emission, the USA is the largest contributor in the world, double China, but this number is declining in the USA and increasing in China. Global warming is a major harmful effect of increment in GHG emission, which further causes climate change and has the following ill effects: • Land surface temperature is increasing, expanding deserts, causing heatwaves, and wildfires more frequently than before. • The Arctic has the greatest temperature rise, causing the retreat of sea ice and glaciers and the melting of permafrost. • Atmospheric energy is increasing, causing frequent extreme weather and storms.

8

G. K. Chhaparwal and R. Goyal

• Ocean temperature is increasing, causing a decline in productivity and fish stock. • Heat stress is now becoming a significant threat to global health. • The ecosystem is changing in coral reefs, mountains, and the Arctic, causing the extinction or reallocation of many vulnerable species. • Even with the strictest measure, some losses, like sea-level rise and earth and ocean temperature, will be irreversible and irreparable. With renewable energy sources, the use of fossil fuels, which is a major source of GHG emissions, can be avoided. Renewable fills hardly 11.5% of the world’s total energy consumption and is growing slowly. However, its share in world total electricity consumption is more than 26%, growing fastest in history with 80% of total energy investment.

4 Renewable Energy Although previously discussed data of growth in the generation, consumption, new investments, and targets look promising for renewables, two essential things decide the selection of energy resources; cost per unit and safety. Fossil fuels have an undoubted loss to nature and human beings. However, Chornobyl and Fukushima’s nuclear accidents have created insecurity about nuclear energy as a future noncarbon alternative. Although data shows that it caused relatively negligible death, 4000 deaths in Chornobyl include only 31 direct deaths and 574 in Fukushima, which includes only 1 direct death compared to 5 million premature deaths caused by local pollution due to fossil fuel emissions. Large hydropower plants also cause irreparable damage to surrounding flora-fauna and human habitats. Hence, the ball comes in favor of mainly solar and wind. Other renewables, like biofuels, tidal energy, waste-to-energy, etc., contribute little to renewable energy consumption. The choice between solar and wind is primarily based on the region’s geographical position. The region lies between the tropic of Cancer and Capricorn and has solar as a major renewable energy source. However, the total coastlines in the world are 1.16 million km2 , which is suitable for wind energy. Hence, overall solar and wind share almost equal contributions to the renewable energy source. The world added 176 GW by the end of 2019, so the new renewable electricity capacity reached 2536.8 GW. Hydropower, wind, and solar were the largest sources at 1,310.2, 622.7, and 586.4 GW (installed PV 580.1 GW and CSP 6.27 GW), respectively.

Renewable Energy: Accelerating the Energy Transition

9

5 Solar Energy The global horizontal and normal irradiation potential is shown in Fig. 7. The renewable installed capacity of the world is 2536.8 GW as of December 2019, of which solar energy shares a total of 586.4 GW. Asia has the largest share at 330.1 GW, with China, Japan, India, and South Korea at 205.7, 61.8, 34.8, and 10.5 GW, respectively. The cumulative installation capacity of Europe, North America, Oceania, Australia, Eurasia, South America, Africa, the Middle East, Central America, and the Caribbean region reached 138.2, 68.2, 16.23, 15.9, 7.14, 6.46, 6.36, 5.14, and 2.1 GW, respectively. The USA (60.5 GW) and Germany (49.9 GW) share the largest share in the respective continents. The world and India have a vast potential for solar energy to harvest, as shown in Figs. 7 and 8. Solar energy is a relatively new concept but growing faster than any other renewable energy source worldwide. Solar energy showed its presence worldwide by 1982 with just a 1 MW power plant in Lugo, USA which increased in 2020 to the largest SPV power plant: Badhla Solar Park (2245 MW), Jodhpur, India. The second-largest Pavagada Solar Park, Tamkur (2050 MW), is also in India. The quest for solar energy in India gained momentum in November 2009 when Jawahar Lal National Solar Mission was launched. The installed solar capacity in 2010 was just 161 MW, which rose to 3.8 GW in 2015 and 46 GW in 2020. Now, we have a target of 113 GW till 2022. Figure 9 shows the global solar energy-based energy consumption. Although India has a target of 450 GW of energy from renewables, it is estimated to cross 500 GW, with more than 70% (more than 300 GW) shared by solar energy. Only 46% of private sector players in electricity generation, which is anticipated to increase in coming years, can boost the capacity beyond targets.

6 Renewable Energy Targets and Investments In 2006, biomass and liquid biofuels had a 36% share of the total investment in renewables. It dropped to just 4% in 2016, while the share of solar and wind energy has increased, especially in the last five years. It shows that investors see the future of renewables in these two major types of resources only. The worldwide annual investment in renewable energy resources is shown in Fig. 10. The world has a target of 826 GW of new non-hydro renewables by 2030, costing around 1 trillion dollars. In 2018 (160 GW) and 2019 (184 GW; 118 GW solar and 61 GW wind), a cost of 282.2 billion dollars was added to global power generation capacity (just 1% higher than in 2018, solar slipped 3% to $131.1 billion, and for wind climbed 6% to $138.2 billion due to the slow-down of the PV market in China). However, the all-in cost of solar and wind energy electricity continues to fall due to improvements in its technology, bidding, and economic scale. In 2019, electricity from new solar PV plants was 83% lower than a decade before. In 2019, the US and Europe invested $55.5 billion (28% up) and $54.6 billion (7% down from

10

G. K. Chhaparwal and R. Goyal

Fig. 7 Global horizontal and normal irradiation potential. Adopted from https://globalsolaratlas. info/map, accessed on April 18, 2023

last year). Developed countries committed $130 billion while developing countries (India and China slipped in 2019 while other developing nations committed 17% up with $59.5 billion) committed $152.2 billion. In 2019, 78% of the new generating capacity added globally was in non-hydro renewables (including small hydro), and investment committed was almost three times that in fossil fuel plants. The share of non-hydro renewables in global energy generation has increased from 5.9% in 2009 to 13.4% (1% up from 2018), which has prevented 2.1 gigatonnes of CO2 emission. In the last decade (2010–2019), 1213 GW of non-hydro renewable capacity has been added, with an investment of $2.7 trillion. Nevertheless, investment in terms of GDP percentage is an entirely different story. On average world spends less than 1% of the global GDP; China’s biggest investor in renewables spends only 0.9% of its GDP. The

Renewable Energy: Accelerating the Energy Transition

11

Fig. 8 National horizontal and normal irradiation potential in India. Adopted from https://global solaratlas.info/map, accessed on April 18, 2023

Fig. 9 Global solar energy-based energy consumption. Adopted from https://ourworldindata.org/ energy, accessed on April 18, 2023

12

G. K. Chhaparwal and R. Goyal

Fig. 10 Worldwide annual investment in renewable energy resources. Adopted from https://our worldindata.org/energy, accessed on April 18, 2023

USA’s second-biggest investor spends only 0.1% and India spends less than 0.5% of its GDP. However, India is planning to attract investors from worldwide and native to increase it to 10% of the current nation’s GDP (30 lac crores) by 2030. Overall, developing countries are doing much better than developed countries, possibly due to the already well-established power generation system in these developed countries. It is easy and economical to establish a new source of power generation for developing countries that do not have a well-established system. The Indian central government has a target of 450 GW of renewable energy by 2030 (revised 227 GW target for 2022) at the rate of 36 GW annual addition. The target 227 GW includes nearly 113 GW through solar power, 66 GW from wind power, 31 GW from floating solar and offshore wind power, 10 GW from biomass power, and 5 GW from small hydro. As of September 30, 2020, 36.17% (24% excluding large hydro) of India’s installed electricity generation capacity is from renewable sources (135 GW out of 373 GW). India has attracted investments of Rs 55,436 crore, Rs 40,459 crore, and Rs 62,603 crore ($ 8.4 billion) in 2017–2018, 2018–2019, and 2019–2020. India is the first nation to set up a ministry for non-conventional energy: the Ministry of New and Renewable Energy (MNRE)) (Ministry of Power (India) 2019). In the early 1980s, India has the Solar Energy Corporation of India (SECI) as PSU for developing solar energy industries and the National Institute for Wind Energy (NIWE), an autonomous R & D institution for wind energy-related research. Hydroelectricity is administered separately by the Ministry of Power, and initially, it was not included as an MNRE target. Renewable Energy Purchase Obligation mandates the power distribution companies (DISCOMs) to source a fixed percentage of power from

Renewable Energy: Accelerating the Energy Transition

13

renewables under solar and non-solar. In 2019, Government of India reclassified large hydropower plants in the renewable energy category to increase its sales.

7 Conclusions A detailed statistical review of energy production, consumption, investment, and potential in renewable energy resources shows that the world is moving toward accepting renewable energy. It will open doors to vast research opportunities in this domain. Solar energy is advantageous over wind energy and is visible regarding money pumped up in its scaling. Fortunately, India has had great availability of solar radiation throughout the years and coastal areas for harnessing wind energy. However, a strong determination is anticipated from global and national level governance to accelerate renewable energy goals to meet the target of saving the earth from catastrophic environmental disasters.

References IEA (2020a) World energy statistics and balances 2020 (database). IEA, Paris IEA (International Energy Agency) (2020b) World energy outlook. IEA, Paris Ministry of Power (India) (2019) State distribution utilities seventh annual integrated rating. Government of India, New Delhi Our World in Data (2020) https://ourworldindata.org/energy, https://github.com/owid/covid-19data/tree/master/public/data REN21 (2020) Renewables 2020 global status report, REN21, Paris. https://www.ren21.net/reports/ global-status-report/

Prospects of Renewable Energy Scenario in India Rahul Kumar, Nishikant Kishor Dhapekar, Rajesh Tiwari, Y. Anupam Rao, Renuka Shyam Narain, Anil Singh Yadav, and Abhishek Sharma

Abstract An exponential rise in the population, increases greenhouse gas (GHG) emissions through different human activities and has raised serious concern about climate change and global warming. This has also resulted in a sharp increase in the gap between the demand and supply of energy. It turns aggravated the need for the usage of non-exhaustible sources of energy. Fossil fuels usage is broadly considered unsustainable due to its limited availability and environmental pollution concerns. The energy requirement is rising continuously with rapid urbanization and industrialization. The developing countries mainly depend on conventional energy sources such as coal, petroleum, natural gas and many other exhaustible fuels. Scientists and researchers have been constantly encouraged to develop alternative energy sources to cater to the demands of the ever-increasing population. In this context, R. Kumar School of Mechanical Engineering, Lovely Professional University, Phagwara 144001, Punjab, India N. K. Dhapekar Department of Civil Engineering, MATS University, Raipur 493441, Chhattisgarh, India R. Tiwari Department of Management Studies, Graphic Era (Deemed to be University), Dehradun 248002, Uttarakhand, India Y. A. Rao Department of Mechanical Engineering, Oriental Institute of Science and Technology, Jabalpur 482003, Madhya Pradesh, India R. S. Narain School of Education, Indira Gandhi National Open University, Maidan Garhi, New Delhi 110068, Delhi, India A. S. Yadav Department of Mechanical Engineering, Bakhtiyarpur College of Engineering (Science, Technology and Technical Education Department, Govt. of Bihar), Bakhtiyarpur, Patna 803212, Bihar, India A. Sharma (B) Department of Mechanical Engineering, B I T Sindri, Dhanbad 828123, Jharkhand, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Goyal et al. (eds.), Renewable Energy: Accelerating the Energy Transition, Energy Systems in Electrical Engineering, https://doi.org/10.1007/978-981-99-6116-0_2

15

16

R. Kumar et al.

the different renewable energy sources, from biomass and waste-to-energy, can be a potential alternative to conventional energy sources. The chapter focuses about recent developments and prospects of renewable energy in India. Keywords Energy scenario · Fossil fuel · Global warming · Pollution · Renewable energy

1 Introduction Energy has various forms: heat, light, electrical, mechanical, wind, chemical, gravitational, magnetic and nuclear. It is an abstract scalar quantity that cannot be measured but is computed. The role of energy is not only limited to human activities but also to natural events. All life forms, such as plants, animals and other microorganisms, require energy for their respective tasks. Plants trap sunlight in order to obtain energy. Similarly, animals consume food to ensure that energy flow is not disrupted. Moreover, energy is vital for the survival of humans. Since the beginning of various civilizations, fire and fuels such as wood, charcoal, peat, straw and dried dung were extensively used to harness energy. The physical power of humans and animals was used to conduct daily activities such as hunting, agriculture, transportation and manufacturing. One of the major turns of events that occurred in the history of energy use was the harnessing of water and wind energy for electrification. With further development, the locomotive rail run on diesel became more common. World has been predominantly using coal as a fuel for electricity generation. The consumption of other fossil fuels, such as natural gas and petroleum, has increased tremendously in the last few decades. Later, scientists such as Michael Faraday, Nicolas Tesla, Thomas Edison, Frank Sprague, George Westinghouse and Alexander Graham Bell transformed the world toward electricity through scientific discoveries. Fossil fuels ran large power plants in the mid-twentieth century. The 1973 oil crisis originated when the Organization for Arab Petroleum Exporting Countries (OAPEC) announced an embargo on oil during the Arab-Israel conflict. The oil prices increased sharply, causing trouble for the countries importing oil, particularly the western world. This led to economic sluggishness in many countries and they had to face a recession in the next few years. This embargo was introduced to target the nations which supported Israel in the conflict. India has been one of the largest consumers of energy. In India, fossil fuel usage is increasing unprecedentedly due to industrialization, mechanization and an increase in population (Karthick et al. 2022). Hence, it becomes highly essential to switch toward renewable sources of energy. Renewable sources such as biomass, solar and wind energy seem to drive the Indian economy shortly. Renewable energy sources are derived from natural sources that can be constantly replenished or inexhaustible. Some of them are listed as follows:

Prospects of Renewable Energy Scenario in India

17

• Solar Energy–Sunlight is one of Earth’s most abundant energy sources. Studies suggest that the amount of solar energy received in only one hour on the Earth’s surface is more than the actual requirement of the total population in a whole year. • Wind Energy–Wind energy is one of the amplest and clean energy sources. The generators are driven with the help of turbines and produce electricity for the national power grid. • Hydro Energy–A controlled water flow can be created by building dams and reservoirs, generating electricity. • Tidal Energy–It uses daily tidal currents to drive turbine-run generators. • Geothermal Energy–The enormous heat beneath the Earth’s surface can harness to provide heat or generate electricity. • Biomass Energy–This process involves the conversion of agricultural, industrial and domestic waste into solid, liquid and gaseous fuels. This energy can be used to drive automobiles and generate electricity as well. Renewable energy has gained significant momentum in India in recent years as the country seeks to meet its growing energy demand while reducing its carbon footprint and addressing environmental concerns. India has set ambitious renewable energy targets and has implemented various policies and initiatives to promote developing and adopting renewable energy sources (Sparsh et al. 2022). Despite significant progress, there are challenges that India faces in the renewable energy sector, including land availability, grid integration, regulatory and policy uncertainties and financing constraints. However, India remains committed to expanding its renewable energy capacity and transitioning toward a more sustainable, low-carbon future. It takes millions of years to form fossil fuel available in some areas of the world. It is apparent that fossil fuels are exhaustible energy sources and will ultimately be depleted in the coming years (Sharma and Murugan 2013). Hence, it is necessary to identify alternative energy sources and use them extensively. The current chapter discusses the scope of renewable energy sources and consumption trends in the past few years and the need for innovative methods to develop these energy sources in India. The perspective of renewable energy, plan and policies toward the growth of the Indian government has also been covered in this chapter.

2 Overview of India’s Energy Sectors India is a country that has one of the most diversified energy sectors in the world. Conventional fuels such as coal, petroleum and natural gas have been abundant. The demand for renewable energy resources has increased in the last few decades. The government has introduced several subsidies and targets regarding the installation of these sources of energy (Madurai Elavarasan et al. 2020). As per the report published in 2023 (Charles Rajesh Kumar and Majid 2023), the installed renewable energy capacity in India is shown in Fig. 2.1. India has set an objective to decrease the

18

R. Kumar et al.

Fig. 2.1 Total installed renewable energy in India (as per January 2023 data from https://mnre.gov.in/the-min istry/physical-progress)

carbon dioxide (CO2 ) of the country’s under 45% and accomplish 50% combined electric power introduced by 2030 from renewables (Kumar et al. 2022). Detailed descriptions of different types of renewable energies are given below: • Solar Energy–This energy is considered one of India’s most profitable sources (Gupta et al. 2017). Solar projects require no fuel and there is almost no maintenance cost. However, many solar-powered countries have focused mainly on rooftop solar installations. On the other hand, India derives most of its solar power from huge plants installed on the ground, mainly in the deserted parts of Gujarat and Rajasthan. However, this may go for change as land prices increase and policy enables rooftop solar to get connected and make use of the grid. • Wind Energy–There has been a steady growth in wind power generation for about three decades. Researchers have estimated that India has a massive potential to generate wind energy, at about 302 GW at 100 m hub height and 695 GW at 120 m (Sitharthan et al. 2018). • Small Hydro–India has the world’s fifth largest hydropower generating capacity. The hydroelectric power generating potential in central India, mainly from the river basins of Godavari, Narmada and Mahanadi, has not been developed on a vast scale due to opposition from the tribal people. • Bioenergy–Biomass energy is one of the essential sources of energy generation, especially in India. The significant advantage of biomass is that it can be grown in or near water bodies such as seas or lakes, allowing the land to spread itself

Prospects of Renewable Energy Scenario in India

19

for food crops. It is abundant and its growth can be relatively more accessible in every part of the world.

3 Solar Energy Solar energy is sunlight converted into thermal or electrical energy with the help of various technology suited for different purposes (Agrawal et al. 2023; Shrivastava et al. 2022). There are three primary ways of harnessing solar energy, namely: (a) Photovoltaic cells directly convert the energy from sunlight into electrical energy. (b) Solar thermal technology—heat from the sun is effectively utilized to make hot water or steam. (c) Passive Solar Heating—simply allows the sunlight to heat the required object or area concerned. Solar power is one of the most consumed renewable energy sources in India. According to a survey held in 2019, five states, Rajasthan, Gujarat, Karnataka, Tamil Nadu and Telangana, contribute up to 51% of the total solar energy installations in India (Status 2021). The vital areas of application of solar energy are: • Telecom service providers have regarded solar power as one of the most reliable and efficient energy sources. It reduces the utilization of diesel in remote areas, where the grid connectivity is relatively low. • Previously, petroleum-generated power was used for oil drilling, an overpriced venture. Studies proved that there is an immense potential for solar-powered oil drilling, especially in tropical parts. However, it was later observed that the power output from solar power is relatively low, primarily due to space and weight constraints. • A DC motor coupled with the vapor compression refrigeration system can be operated using solar photovoltaic panels to produce cooling. Here, sunlight converts into electrical energy, making the refrigeration process possible. • Indian railways have encouraged the use of solar-powered signaling systems in a phased manner where there is a lack of conventional power sources or the power transmitted through the cables is cost-effective. • Photovoltaic water pumping systems contain photovoltaic (PV) cells that convert sunlight into electricity to power the electric pumps. This electrical energy can be supplied to DC motors or converted into alternating current by an inverter. • PV-integrated buildings replace traditional building materials in parts of the building envelope, such as roofs, skylights or facades. The significant advantage of these systems over the non-integrated ones is that the initial cost can be reduced by decreasing the amount spent on building materials and labor that would generally be a part of the construction of the building part that the Building Integrated Photovoltaics (BIPV) modules would replace.

20

R. Kumar et al.

3.1 Advantages of Solar Energy The sun has much potential as a clean and dependable way to power the world because it is Earth’s most abundant energy source. The key advantages of solar energy are: • The energy source is renewable and pollution free. • When people need large amounts of electricity in summer, it is the most suitable energy source and considerably reduces the electricity bill. • This energy is silent without noise and had negligible maintenance costs over the years. • It is one of the most stable energy sources. Almost zero transportation is required as often available everywhere. • Solar dryers, heaters and cookers are the few home appliances utilizing solar energy.

3.2 Technological Challenges of Usage of Solar Energy Solar energy is gaining popularity with technological advancements. Some of the challenges and drawbacks of sun energy-powered devices are as follows: • • • • • • • • •

The initial cost of solar plant installation is high. DC equipment is relatively expensive. The power output is comparatively low at night or on cloudy days. The battery is used to store electricity and is quite overpriced. Location sensitivity is one of the major challenges faced by solar power plants. Environmental pollutants can severely affect the working of solar panels. Its installation requires large areas of land. Solar panels vary a lot in terms of quality. Some resources that are needed for the production of solar power plants are relatively scarce. • In some instances, solar panels can also be regarded as hazardous waste.

3.3 Future Prospects of Solar Energy The amount of sunlight (irradiation) that falls on a solar panel’s surface is converted into electricity and is measured by its efficiency. Due to numerous technological advancements, the average panel conversion efficiency of modern-day solar panels has increased from 15% to well over 27% over the past few years. It indicates that most energy from sunlight gets wasted even if we consider ideal conditions. It is probably one of the major hurdles that must be taken care of to achieve exponential growth in the energy sector. Researchers predict that due to further technological developments, solar power will get cheaper and energy bills will get drastically reduced while using

Prospects of Renewable Energy Scenario in India

21

clean and green energy. Much research has been done on developing technological improvements for solar energy use. The employment opportunities created in this area will help the country’s economic growth.

4 Bioenergy Biomass is one of another India’s most abundantly available renewable energy sources. It is found that about one-third of the total primary energy use is still derived from biomass. About 70% of the population is still dependent on it. The Indian economy has always been agriculture driven. As a result, tons of plant and animal waste are generated annually. Wood logs, energy crops and the wastes from forests, yards, or farms are available in the form of biomass and can be used to produce energy (Sharma and Murugan 2015). The different available biomass sources in India are depicted in Fig. 2.2. The fuel that is eventually produced through different processes from biomass as a feedstock is known as biofuel (Powar et al. 2022). Biomass can be converted into liquid fuel and used for transportation (Taneja et al. 2021). They are equivalent to fossil-based fuels in terms of power output, such as gasoline, jet and diesel. These bioenergy techniques ensure that organic waste and biomass carbon can be reused as fuels for cars, trucks, jets and ships and reduce engine emissions (Sharma and Murugan 2022). Some of the significant advantages of biomass energy are as follows: • • • • • •

An inexhaustible source of energy. Almost no environmental impact. Potentially create a considerable number of employees in rural areas. The availability of biomass is universal. Reduces landfills. Relatively cheaper than other sources of energy.

The Government of India has worked hard to ensure biomass-derived energy usage in various sectors (Sharma and Murugan 2017). They have initiated several programs for biomass power generation, known as the biomass power and cogeneration program. The main objective of this program is to intensify the use of biomass materials such as straws, rice husk, cotton stalks, coconut shells, jute wastes and other organic wastes for grid power generation to meet the electricity demands of the country’s population. It is estimated that the current availability of biomass products in India is around 750 metric tonnes per year (Negi et al. 2023). Researchers have also found that India has a surplus of bioenergy availability, which indicates a promising statistic to boost biomass usage in various industries and power plants. The main sources of biomass are as follows: • Trees and plants shrubs, scrubs, bushes (coffee, tea, bamboo, palm). • Agricultural wastes: grass, cereal straw, sugarcane, cotton, tobacco, bananas and pulses.

22

R. Kumar et al.

Fig. 2.2 Available Biomass resource in India. Reproduced with permission from Anil Kumar et al. Renewable and Sustainable Energy Reviews, 45, 530–539, 2015. Copyright© 2015 Elsevier Ltd. (Kumar et al. 2015)

• Animal wastes: cattle slurry, poultry manure and yard waste. • Other wastes: food, kitchen, pulp and sludge can be used to generate more power.

4.1 Biomass Waste-to-Energy Biomass waste-to-energy refers to converting organic waste materials, such as agricultural residues, forestry residues, animal manure, food waste and other organic waste streams, into usable energy forms, such as electricity, heat or biofuels. This process involves utilizing the energy content of biomass waste, which would otherwise decompose and release greenhouse gases, and converting it into a valuable renewable energy source. Biomass can be converted into biofuels by three main conversion processes (Sharma and Murugan 2014; Sharma et al. 2021). • Thermochemical conversion–Pyrolysis, direct combustion, gasification and liquefaction.

Prospects of Renewable Energy Scenario in India

23

• Biochemical conversion–Anaerobic digestion, fermentation and enzymatic conversion. • Biotechnology and nanotechnology-based processes.

4.2 Applications of Biomass Energy Biomass energy, derived from organic materials such as agricultural residues, forestry residues, food waste and other organic waste streams, has a wide range of applications across various sectors. Biomass energy has diverse applications, including electricity generation, heat production, biofuels, cogeneration, rural electrification, waste management and environmental remediation (Kumar et al. 2021). The versatility and sustainability of biomass energy make it a valuable source of renewable energy with potential benefits for various sectors and applications. The potential applications of biomass as an energy source include: • Hot gas is derived from biomass used in boilers and steam engines for space heating, hot water and generating electricity. • The biomass gasification process produces fuel gas and synthetic gas for gas turbines and fuel cells. • Biomass is used to derive liquid fuel, such as ethanol and biodiesel, used in engines and boilers. The blending of 10% ethanol with petrol has been achieved. They can also be used for transportation purposes. National Policy on Biofuels (2018) program aims to blend 20% of ethanol in petrol by 2025/26 (Kumar and Rao 2022).

4.3 Policies Implemented for Biomass Utilization A roadmap has been designed by the Ministry of New and Renewable Energy to achieve the target of 24 × 7 electrification of every household by 2024 (Narnaware and Panwar 2022). It consists of steps such as. • Enhanced domestic ways to improve the current production of biodiesel and ethanol. • Extensively setting up second-generation bio-refineries. • Encourage the development of new feedstocks for biofuels. • Technology-driven equipment and techniques in order to boost biofuel production. • Easing the blending of biofuel with conventional fuels.

24

R. Kumar et al.

5 Wind Energy Wind energy is probably the fastest-growing renewable energy with a massive power capacity. Researchers have studied wind turbines’ aerodynamic and structural designs to increase the output of wind power plants. It mainly produces electricity with the help of rotating wind turbines. According to a survey conducted in 2021, the total wind energy generated in India is the fourth largest in the world. States such as Tamil Nadu, Gujarat and Maharashtra account for nearly 55% of the total wind energy output in the country. The potential wind map at 120 m above ground level is shown in Fig. 2.3. The Government of India has provided various fiscal and financial incentives through private sector investments to ensure significant growth in wind energy projects. The National Institute of Wind Energy, Chennai, has played a pivotal role in providing technical assistance to many private companies in setting up various wind energy generating plants. Even the government has waived the inter-state transmission charges and losses to liberate the transportation of such goods from any obstacles. Regarding different surveys and statistics, the wind energy sector has grown enormously in a few decades. It plays a crucial role in assuaging the challenges posed in today’s world, such as meeting the electricity demands, greenhouse gas emissions and fossil fuels depletion. It contributes about 64% of the total renewable energy capacity of the entire country. Wind speeds near the offshore areas are high. Hence, they yield more power as the wind power is directly proportional to the cube of wind speed. Studies suggest that wind speed increases with increasing altitude, so they are slower toward the Earth’s surface. However, the main issue with offshore wind projects is that they are relatively more expensive than on-field wind farms. The most predominantly used wind turbine designs are the horizontal axis wind turbines, which have a maximum theoretical efficiency of around 60%. They extract around 50% of the energy from the wind that passes through the rotor. Wind energy can significantly reduce the environmental hazards caused by the burning of fossil fuels. Research has been conducted regarding the Energy Return on Investment (EROI) on wind energy and almost 18–20:1. The Indian government has set up an ambitious 60 GW wind power target by 2022. Wind energy in India has been a forerunner in emerging technologies, supply chain management and workforce development. The industry and government’s collective efforts have ensured significant growth in this sector along with the integration of recent trends such as Artificial Intelligence (AI) and power casting.

5.1 Applications of Wind Energy Wind energy, which is generated by harnessing the power of wind through wind turbines, has a wide range of applications across various sectors. Some major wind

Prospects of Renewable Energy Scenario in India

25

Fig. 2.3 Wind potential map at 120 m above ground level. Reproduced from a report on “India’s Wind Potential Atlas at 120 m agl” by National Institute of Wind Energy, 2019, page 26. (https:// niwe.res.in/assets/Docu/India’s_Wind_Potential_Atlas_at_120m_agl.pdf) (Status 2021)

26

R. Kumar et al.

energy applications are off-grid power supply, water pumping, heating and cooling, desalination, hybrid systems and industrial applications. The versatility and sustainability of wind energy make it a valuable source of clean and renewable energy for various sectors and applications. The potential applications of wind energy are as follows • Industrial applications such as food processing and textile processing. • Wind-powered pumps play an essential role in desalinating water. They are even used to produce various inorganic chemicals, i.e., chlorine, bromine, etc. • Agricultural purposes such as irrigation. • Telecommunication sector. • Water pumps for supplying drinking water to every household. • Run small homes and commercial systems.

5.2 Economic Aspect of Wind Energy The ability of a renewable energy system to repay its initial investment and operating costs within a reasonable time frame is the primary focus of economic analysis. The lifetime cost of the wind energy system can be parted into (i) starting expenses for framework assembling and establishment, (ii) working and upkeep costs and (iii) decommission costs. The turbine (including rotor, tower and drivetrain), foundation, land rent, electrical equipment, connection to the grid, road construction and other infrastructure, transportation, installation labor and expertise and associated soft costs are typically included in the wind energy system’s initial upfront cost, which typically exceeds 75%. The investment, operational and maintenance cost of setting up a wind energy system is depicted in Fig. 2.4.

5.3 Challenges and Potential Solutions of Wind Energy Wind energy is one of the world’s fastest-growing sources due to its numerous benefits. Researchers are addressing technical and socioeconomic obstacles to expand wind energy’s capabilities and community benefits. The crucial observations on wind energy are: • One of the major challenges of wind energy is its unreliability. Wind speeds vary across different seasons, times and locations. Thus, they cannot be controlled. • Wind turbines produce lower power output as compared to that conventional sources of energy. More wind turbines are needed to generate sufficient power to meet the consumers’ demands. • They are highly inefficient. • Building wind power plants, along with their maintenance, are highly expensive.

Prospects of Renewable Energy Scenario in India

27

Fig. 2.4 Investment, operational and maintenance cost of setting up wind energy system. Reproduced with permission from John K. Kaldellis et al. Renewable Energy, 36(7), 1887–1901, 2011. Copyright© 2011 Elsevier Ltd. (Kaldellis and Zafirakis 2011)

• These projects require large lands and cause severe damage to the local wildlife. Estimates suggest that each wind turbine can kill at least 4 birds yearly. • These are mainly located in remote areas, which may increase transportation costs. • It also produces much noise in the surrounding areas. There are many ways to mitigate challenges are • Using forecasts and predicting, the severity of turbine failure can reduce maintenance costs to a certain extent.

28

R. Kumar et al.

• Control technologies can also be implemented to reduce the impact of load on wind turbines, which can also increase efficiency. • Different simulation techniques in wind turbine designs can ensure sufficient power output, considering parameters such as torque, power, blade loading and tip speed ratios.

6 Renewable Energy in India at Present Currently, renewable energy continues to be a rapidly growing sector in India. Here are some key updates on renewable energy in India: • Installed Renewable Energy Capacity: As of 2023, India’s total installed renewable energy capacity has reached around 167.7 GW, with solar and wind energy being the dominant sources. Solar energy constitutes the majority share with over 63 GW of installed capacity, followed by wind energy with over 41GW. • Renewable Energy Targets: India has revised its renewable energy targets, aiming to achieve 500 GW of renewable energy capacity by 2030, which includes 280 GW from solar energy, 140 GW from wind energy, and 50 GW from other sources such as biomass, small hydro and waste-to-energy. This demonstrates India’s commitment to further expanding its renewable energy capacity. • Renewable Energy Auctions: Competitive auctions remain a prominent mechanism for procuring renewable energy in India. Solar and wind energy auctions are regularly conducted at both central and state levels, resulting in record-low tariffs, making renewable energy increasingly cost-competitive. • Policy and Regulatory Framework: India has implemented various policy and regulatory measures to promote renewable energy, including the National Solar Mission, National Wind-Solar Hybrid Policy, National biofuel policy and Green Energy Corridors Project, etc. These policies provide incentives such as subsidies, tax breaks and waivers for renewable energy projects and aim to create an enabling environment for investment and growth in the sector. • Solar Energy: Solar energy remains a key focus area in India, with the government implementing initiatives such as the KUSUM (Kisan Urja Suraksha evam Utthaan Mahabhiyan) program to promote solar-powered irrigation, solar rooftop installations, and solar parks. India has also launched the PM-KUSUM scheme to provide financial support to farmers to install solar pumps, further driving solar energy adoption. • Wind Energy: Wind energy continues to be a significant renewable energy source in India. The country has implemented measures such as repowering old wind turbines, introducing competitive auctions, and developing wind-solar hybrid projects to promote wind energy. India has also launched the “One Sun One World One Grid” initiative to harness wind and solar resources nationwide.

Prospects of Renewable Energy Scenario in India

29

• Other Renewable Energy Sources: India also promotes other renewable energy sources, such as biomass, small hydro and waste-to-energy. The government has introduced policies and incentives to encourage investments in these sectors, including feed-in tariffs and grants for research and development. • Innovation and Technology: India is also focusing on innovation and technological advancement in the renewable energy sector, including research and development in advanced solar technologies, energy storage and smart grid solutions to improve the efficiency, reliability and affordability of renewable energy. • Investment and Financing: Renewable energy in India attracts significant investments from domestic and foreign sources. The government has implemented various financing mechanisms, such as green bonds, green corridors and viability gap funding, to mobilize investment in the sector. India has also established dedicated institutions, such as the Green Energy Corridor Fund and the Indian Renewable Energy Development Agency (IREDA), to support renewable energy projects financially. • Benefits of Renewable Energy: Renewable energy in India has numerous environmental, social and economic benefits. It helps reduce greenhouse gas emissions, improve air quality, enhance energy security, create jobs and promote sustainable development. Renewable energy also has the potential to provide electricity to remote and underserved areas, support rural electrification and contribute to India’s climate change mitigation and adaptation goals. • While India has made significant progress in the renewable energy sector, there are ongoing challenges, including grid integration, land acquisition, policy stability and financing issues.

7 Conclusions Renewable energy in India is a rapidly growing sector with a total installed capacity of around 167.7 GW, primarily dominated by solar and wind energy. India has set ambitious targets to achieve 500 GW of renewable energy capacity by 2030 and has implemented various policies, incentives and financing mechanisms to promote renewable energy investments. Solar energy, wind energy and other sources such as biomass, small hydro and waste-to-energy are being promoted, focusing on innovation and technology. Renewable energy in India has numerous environmental, social and economic benefits. However, challenges such as grid integration, land acquisition, policy stability and financing need to be addressed for sustained growth in the sector. The future outlook for renewable energy is optimistic, with expected continued growth, increasing targets, technology advancements, improved integration, transportation electrification, energy access, green jobs and economic growth. Transitioning to renewable energy is essential for mitigating climate change, reducing greenhouse gas emissions and achieving a sustainable and clean energy future.

30

R. Kumar et al.

References Sparsh S, Ramakrishna CS, Sahu R, Narain RS, Sohal JK, Sahu M, Sharma N, Kumar V, Sharma A (2022) Future prospects of biodiesel production from jatropha in India. Mater Today Proc 63:A22–A26 Sharma A, Murugan S (2013) Investigation on the behaviour of a DI diesel engine fueled with Jatropha Methyl Ester (JME) and Tyre Pyrolysis Oil (TPO) blends. Fuel 108:699–708. https:// doi.org/10.1016/j.fuel.2012.12.042 Madurai Elavarasan R, Selvamanohar L, Raju K, Rajan Vijayaraghavan R, Subburaj R, Nurunnabi M, Khan IA, Afridhis S, Hariharan A, Pugazhendhi R (2020) A holistic review of the present and future drivers of the renewable energy mix in Maharashtra, state of India. Sustainability 12(2020):6596 Charles Rajesh Kumar J and Majid MA (2023) Advances and development of wind–solar hybrid renewable energy technologies for energy transition and sustainable future in India. Energy Environ 0958305X231152481 Kumar A, Pal D, Kar SK, Mishra SK, Bansal R (2022) An overview of wind energy development and policy initiatives in India. Clean Technol Environ Policy 1–22 Gupta V, Sharma A, Gupta KS (2017) Numerical analysis of direct type greenhouse dryer, ASME 2017 Gas Turbine India Conf. GTINDIA 2:5–9. https://doi.org/10.1115/GTINDIA2017-4784 Sitharthan R, Swaminathan JN, Parthasarathy T (2018) Exploration of wind energy in India: A short review. In: 2018 national power engineering conference, IEEE, 2018. pp 1–5 Agrawal Y, Yugbodh K, Ayachit B, Tenguria N, Nigam PK, Gautam A, Sharma A, Alam T (2023) Experimental investigation on thermal efficiency augmentation of solar air heater using copper wire for discrete roughened absorber plate. Mater Today Proc Shrivastava V, Yadav AS, Sharma AK, Singh P, Alam T, Sharma A (2022) Performance comparison of solar air heater with extended surfaces and iron filling. Int J Veh Struct Syst 14:607–610 C. Status, Ministry of New and Renewable Energy, Government of India (2021) Report on India’s wind potential atlas at 120m agl. National Institute of Wind Energy, 2019, p 26. https://niwe. res.in/assets/Docu/India’s_Wind_Potential_Atlas_at_120m_agl.pdf Sharma A, Murugan S (2015) Potential for using a tyre pyrolysis oil-biodiesel blend in a diesel engine at different compression ratios. Energy Convers Manag 93:289–297. https://doi.org/10. 1016/j.enconman.2015.01.023 Powar RS, Yadav AS, Ramakrishna CS, Patel S, Mohan M, Sakharwade SG, Choubey M, Ansu AK, Sharma A (2022) Algae: a potential feedstock for third generation biofuel. Mater Today Proc 63:A27–A33 Taneja S, Singh P, Sharma A, Singh G (2021) Use of alcohols and biofuels as automotive engine fuel. In: Energy Systems and Nanotechnology. Springer, 161–183 Karthick M, Logesh K, Baskar S, Sharma A (2022) Performance and emission characteristics of single-cylinder diesel engine fueled with biodiesel derived from cashew nut shell. In: Advancement in materials, manufacturing and energy engineering, vol II. Springer, pp 521–529 Sharma A, Murugan S (2022) Combustion analysis of a diesel engine run on non-conventional fuel at different nozzle injection pressure. Innov Energy Power Therm Eng 109–118. Springer Kumar A, Kumar N, Baredar P, Shukla A (2015) A review on biomass energy resources, potential, conversion and policy in India. Renew Sustain Energy Rev 45:530–539 Sharma A, Murugan S (2017) Effect of blending waste tyre derived fuel on oxidation stability of biodiesel and performance and emission studies of a diesel engine. Appl Therm Eng 118:365– 374. https://doi.org/10.1016/j.applthermaleng.2017.03.008 Negi P, Singh Y, Yadav A, Chen W-H, Sharma A, Sisodia A (2023) Current scenario of renewable energy in India and its possibilities in the future. In: Biofuel Technologies for a Sustainable Future: India and Beyond 1 Sharma A, Murugan S (2014) Influence of fuel injection timing on the performance and emission characteristics of a diesel engine fueled with Jatropha methyl ester-tyre pyrolysis oil blend.

Prospects of Renewable Energy Scenario in India

31

Appl Mech Mater 592–594:1627–1631. https://doi.org/10.4028/www.scientific.net/AMM.592594.1627 Sharma A, Khatri D, Goyal R, Agrawal A, Mishra V, Hansdah D (2021) Environmentally friendly fuel obtained from pyrolysis of waste tyres. Energy Syst Nanotechnol Springer 185–204 Kumar SS, Rajan K, Mohanavel V, Ravichandran M, Rajendran P, Rashedi A, Sharma A, Khan SA, Afzal A (2021) Combustion, performance, and emission behaviors of biodiesel fueled diesel engine with the impact of alumina nanoparticle as an additive. Sustainability 13:12103 Kumar A, Rao AB (2022) A historical perspective on the biofuel policies in India. In: Greener scalable e-fuels decarbonization transport. pp 33–64 Narnaware SL, Panwar NL (2022) Biomass gasification for climate change mitigation and policy framework in India: a review. Bioresour Technol Rep 17:100892 Kaldellis JK, Zafirakis D (2011) The wind energy (r) evolution: a short review of a long history. Renew Energy 36:1887–1901

Solar Air Heater-Classifications and Performance Enhancement Techniques G. K. Chhaparwal and Rahul Goyal

Abstract Renewable energy-based energy resources and appliances have become the need of the hour in the global environmental challenges. Solar and wind energybased appliances are the most popular in this domain. However, solar energy-based appliances outweigh wind energy-based appliances due to ease of construction, installation, robustness, and scalability. World consumes a significant ratio of total world energy production for heating, ventilation, and drying purposes. The solar air heater can save an appreciable amount of power consumption in these applications. In this chapter, a detailed discussion on various types of solar air heaters and methods to improve their heat transfer is discussed in detail. Solar thermal energy-based appliances can reduce the burden on electricity consumption in certain applications like heating, cooling, and drying in residential, commercial buildings, agriculture, and industries. The major problem with these appliances is low thermal efficiency which various modifications can improve in their designs and working conditions. Keywords Solar energy-based appliances · Solar air heater · Heat transfer enhancement · Vortex generators · Artificial rib roughness · Fins · Baffles

1 Introduction Renewable energy’s major contribution is electricity generation because it can produce almost any kind of work. Most of the research in solar energy is based on solar PV channels. The solar harnessing appliance after the PV channel is Concentrated Solar Power (CSP), which amounts to only 10% of the total solar installed capacity of 586 GW worldwide. Specific small-scale devices to harness solar energy, such as solar air heaters (SAH), solar chimneys, solar lanterns, solar pumps, water G. K. Chhaparwal Paanduv Applications Private Limited, Bareilly 243122, Uttar Pradesh, India R. Goyal (B) Department of Mechanical Engineering, Manipal University Jaipur, Jaipur 303007, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Goyal et al. (eds.), Renewable Energy: Accelerating the Energy Transition, Energy Systems in Electrical Engineering, https://doi.org/10.1007/978-981-99-6116-0_3

33

34

G. K. Chhaparwal and R. Goyal

heaters, solar cookers, thermal energy storage and water treatment, can save the need for electricity for a particular application. It is generally said that saving electricity is the generation of electricity. Another important aspect of such devices is the high solar conversion (up to 90% or up to 500–600 peak thermal W/m2 ), low capitalcost, non-corrosive and non-reactive air as a working fluid, and eco-friendly, cheap construction material than PV channels. The present study focuses on non-electric or solar thermal technology-based devices—solar air heaters. It is a device that absorbs insolation to heat air, and heated air has various industrial, agricultural, commercial, and household applications. However, a large volume of air is required to handle it due to its low density, and its thermal properties are also poor compared to a solar water heater. The most popular applications are as follows (i) Space heating: Air is drawn from a building or outdoor environment and made to pass through SAH-duct, where it gets heated via convection and conduction from an absorber plate and then supplied to the building space via a fan. (ii) Process heat or drying: The heated air can be used for various types of drying operations like crop drying in agriculture, clothes drying in hotels and hospitals, food, species drying, packaging in food industries, etc. (iii) Night cooling: Long radiation wave from the warmer surface (here, it can be roof or metal in the case of SAH) causes heat loss to the colder sky via radiation cooling. In summer, the hot ambient air can flow over this relatively colder metal surface to cool the air (which will lose this heat to the sky), and cold air can be drawn into HVAC units to cool any system. (iv) Ventilation: In sunny winter, the SAH can heat relatively cold ambient air that can be drawn into HVAC units for direct room heating, preheating of air in the ventilation system, or creating suction by venting heated air out via a solar chimney.

2 Classification of SAH A solar air heater is classified into two major types; non-porous and porous SAH. This section discusses the further classification of these two major SAH types with suitable schematic diagrams.

2.1 Non-porous SAH A non-porous solar air heater does not have heat-absorbing parts and it is simply a smooth SAH-duct. Further, a non-porous SAH can be of different types based on the characteristics of airflow in the system as (a) above the absorber plate, (b) below the absorber plate and (c) on both sides of the absorber plate. Case (a) is not recommended because in this configuration, the absorber plate faces the sunlight with a glass cover plate, which causes high temperature than ambient air, hence higher top heat losses.

Solar Air Heater-Classifications and Performance Enhancement …

35

Fig. 1 Single-pass conventional non-porous SAH. Reproduced from Singh et al. (2022). Copyright © 2022 by the authors. Licensee MDPI, Basel, Switzerland (Singh et al. 2022)

2.2 Single-Pass Conventional Non-porous SAH Figure 1 shows the single-pass conventional non-porous solar air heater, designed as simply a wooden box, with one side facing sunlight as a metal absorber plate with a glass cover to trap isolation. Its maximum possible thermal efficiency is 60%, with constant material properties and heat transfer coefficient of air (Singh et al. 2022).

2.3 Double-Exposure SAH Figure 2 shows the double-exposed SAH, where two parallel blackened and glazed metallic absorber plates are exposed to the isolation. It also forms the duct passage, unlike single-exposed SAH, where another side is insulated and made of a wooden sheet. The SAH’s outlet air temperature and thermal efficiency will be higher in double-exposed SAH (Tiwari et al. 2016).

2.4 SAH with Airflow on Both Sides of the Absorber Plate In this type of SAH, there is an upper and lower air passage; air first flows over the absorber plate in the upper passage, and then it flows below the absorber plate in the

36

G. K. Chhaparwal and R. Goyal

Fig. 2 Double-exposure SAH. Reproduced with permission from Tiwari et al. (2016). https://doi.org/10. 1007/978-981-10-0807-8_9. Copyright © 2016, Springer Science Business Media Singapore (Tiwari et al. 2016)

Fig. 3 SAH with airflow on both sides of the absorber plates. Reproduced with permission from El-Sebaii et al. (2011), Copyright © 2010 Elsevier Ltd. (El-Sebaii et al. 2011)

lower passage see Fig. 3. The outlet air temperature and SAH’s thermal efficiency will be higher than conventional SAH. The upper air passage will have more heat loss and low air temperature than the lower passage. The upper and lower passages share a single absorber plate, and the remaining side is insulated (El-Sebaii et al. 2011).

2.5 Two-Pass SAH It also has two air passages, but the upper passage is either made by a glass cover and absorber plate or by two glass cover plates. In contrast, the lower passage comprises an absorber and insulated plate (Fig. 4). Double glass cover reduces top heat loss and increases performance by 10–15% compared to the conventional SAH (Ismail et al. 2022).

Solar Air Heater-Classifications and Performance Enhancement …

37

Fig. 4 Two-pass SAH with lava rock. Reproduced with permission from Ismail et al. (2022). Copyright © 2022 by the authors. Licensee MDPI, Basel, Switzerland (Ismail et al. 2022) Fig. 5 PVT two-pass SAH. Reproduced with permission from Singh and Agrawal (2015). Copyright © 2015 Elsevier Ltd. (Singh and Agrawal 2015)

2.6 PVT Two-Pass SAH In this type of SAH-duct, the passage is divided into two parts: a semitransparent PV module between the top glass cover and the blackened absorber plate. Both parts have uniform airflow see Fig. 5. The overall system has improved performance (Singh and Agrawal 2015).

2.7 Porous SAH In this type of SAH, heat is absorbed in depth via wire mesh, honeycomb, or overlapped glass plates. The pressure loss is usually higher than the conventional SAH. The depth of porous media should be optimized to have maximum heat transfer

38

G. K. Chhaparwal and R. Goyal

Fig. 6 Wire mesh SAH. Reproduced with permission from Prasad et al. (2009). Copyright © 2009 Elsevier Ltd. (Saxena and Goel 2013)

and minimum pressure loss. This type of SAH is suitable for high-temperature applications only.

2.8 Wire Mesh Here, wires are knitted in a cross-like structure to form porosity in the depth of the solar air heater, and wire size is optimized for the maximum performance of the SAH. A selective coating over the wire mesh’s top surface can reduce top losses, as the top surface acts as a black cavity for higher absorption (El-Sebaii et al. 2011). Three types of arrangements are possible, as shown in Fig. 6, which causes minimum top heat loss, as inlet air is always in contact with the SAH cover. A loosely packed mesh has in-depth absorption, while in a compactly packed mesh, only the top surface absorbs a maximum portion of the insolation. To make it cost-effective, aluminum, stainless steel, carbon steel, blackened fiberglass insulation, and dust filters can be used for making wire mesh (Saxena and Goel 2013).

2.9 Overlapped Glass-Plate SAH Figure 7 shows the overlapped glass-plate type SAH. Here, glass plates are set so that the overlapped part of the plate is blackened. In contrast, the rest of the part is kept transparent, which allows solar radiation to fall on the blackened part for its absorption. It is subsequently transferred to air flowing on either side of the glass plate. The top side is glass covered, the bottom side is insulated, and the whole system is assembled in a metal box. The overall arrangement has comparably low-pressure loss at higher thermal efficiency for moderate to high-temperature applications. However, the use of more glass plates increases its construction cost. The optimum glass thickness and spacing between the plates are 3 and 5–7 mm, respectively (Saini et al. 2018).

Solar Air Heater-Classifications and Performance Enhancement …

39

Fig. 7 Overlapped glass-plate SAH. Reproduced with permission from Saini et al. (2018). https:// doi.org/10.1007/978-981-10-7206-2_9. Copyright © 2018 Springer Nature Singapore Pte Ltd. (Saini et al. 2018)

2.10 Honeycomb Absorber in SAH In this type of SAH, transparent honeycomb structures of hexagonal or rectangular shape are used between the glass cover and absorber plate to reduce top heat losses, as shown in Fig. 8. A thin lacquer-coated reflecting wall and porous matrix between the honeycomb and absorber plate can reduce radiative and convective losses from the absorber plate, further increasing the SAH performance (Zhang et al. 2009). Fig. 8 Honeycomb absorber in SAH. Reproduced with permission from Zhang et al. (2009). Copyright © 2009 Springer Nature Singapore Pte Ltd. (Zhang et al. 2009)

40

G. K. Chhaparwal and R. Goyal

Fig. 9 Artificial roughness over the absorber plate of SAH. Reproduced with permission from Patil (2015). Copyright © 2009 Elsevier Ltd. (Patil 2015)

3 Thermal–Hydraulic Performance Enhancement Techniques 3.1 Artificial Roughness When relatively cold air flow over the absorber plate, it forms a viscous sub-layer within the turbulent boundary layer, which opposes the heat transfer. The artificial repeated rib roughness or ribs can be mounted up to the overlap layer to disturb the viscous sub-layer, as shown in Fig. 9. The viscous sub-layer first separates from the absorber plate over the head of the ribs to give away heat by mixing with the main airflow. Then it attaches again downstream with some fresh, relatively cold fluid to collect heat to give it away on subsequent separation. The ribs also cause a secondary flow along with their length, which can be made to mix with the primary fluid flow with the help of gaps, and further disturbance is possible with staggered ribs in front of these gaps. These ribs can have various cross sections (circular, square, rectangular, etc.) and orientations (transverse, inclined, V-shape, and arc shaped). Apart from this, ribs also act as fins since it increases a little heat transfer area, but the height of ribs is relatively minimal than fins (ribs usually have a height of 2–3 mm while fins can be 20–40 mm). It increases pumping power also; hence, various shape-sizeorientation-cross-section of ribs are studied to find the optimum configuration (Patil 2015).

3.2 Fins Fins are extended surfaces that mainly increase the contact and heated surface area, as shown in Fig. 10. Fins are larger than ribs; hence, these are generally mounted

Solar Air Heater-Classifications and Performance Enhancement …

41

Fig. 10 Fins over the absorber plate of SAH. Reproduced with permission from Pramanik et al. (2017). Copyright © 2009 Elsevier Ltd. (Pramanik et al. 2017)

over the sun-facing side of the absorber plate and covered by a glass plate. So, to obtain the optimum configuration of fins in terms of shape and size, the only criterion is to minimize shadow formation due to the large height of fins over the absorber plate, which reduces heat absorption (El-Sebaii et al. 2011). In the case of airflow, the orientation of ribs must be considered to keep pressure loss. Another possible arrangement with relatively less height is mounting over the air flow facing the side of the absorber plate. However, in this arrangement, the depth of the duct will be high, lowering the penetration of heat and reducing the velocity of the flow, further reducing the thermal efficiency of SAH (Pramanik et al. 2017).

3.3 Baffles Baffles, as shown in Fig. 11 also extended surfaces, but unlike fins attached to the absorber surface, these are mainly attached to the fins themselves. Baffles are mostly used with fins and increase heat transfer surface area (if made of similar material as fins) and create disturbance in the path of airflow to increase turbulence. It increases heat transfer from fins at the cost of increased pressure loss (Chii-Dong et al. 2012).

3.4 Longitudinal Vortex Generators (LVGs) Vortex generators can be of two types based on the position of the axis of the rotation; longitudinal or transverse to fluid flow, as shown in Fig. 12. In SAH, only longitudinal vortex generators (LVGs have swirl or vortex axis parallel to fluid flow) have been investigated as per the literature survey (Jacobi and Shah 1995). LVGs are of many types based on their shape-size orientation. The delta winglet, as shown in

42

G. K. Chhaparwal and R. Goyal

Fig. 11 Baffles in the SAH. Reproduced with permission from Chii-Dong et al. (2012). Copyright © 2012 Elsevier Ltd. (Chii-Dong et al. 2012)

Fig. 12, is the most studied LVG. It improves thermal–hydraulic performance via three mechanisms; (1) disruption or thinning of the boundary layer from downwash flow, (2) longitudinal swirling or vortex flow causing better mixing of cold and hot air in core fluid flow, and (3) flow destabilization due to velocity fluctuations generated by vortices downstream of LVGs. Other than the shape of LVGs, various geometrical parameters like angle of attack, height, and length are commonly investigated. It causes low to moderate pressure loss and is usually suitable for low-temperature applications. In the literature survey, the vortex mechanism has been studied by assuming it as a steady flow.

3.5 Jet Impingement The hydraulic and thermal boundary layer formation over the absorber plate is the leading cause of low heat transfer from it to the primary fluid flow. Previous techniques focused on thinning or disturbing these boundary layers using surface modifications (Yadav and Saini 2020). However, in jet impingement, the air flows as a jet from the holes provided on the absorber plate, which mixes with the primary airflow, creating rigorous mixing and turbulence in the overall flow, see Fig. 13. The pressure loss is moderate. It was first used to cool turbine blades and was later introduced in the solar air heater. Here, the parameters to be investigated are; jet to jet spacing, jet diameter ratio, the arrangement of jets (in-line, staggered, square, hexagonal, etc.), jet width, and jet height ratio.

Solar Air Heater-Classifications and Performance Enhancement …

43

Fig. 12 Longitudinal vortex generator in SAH. Reproduced with permission from Jacobi and Shah (1995). Copyright © 1995 Published by Elsevier Inc. (Jacobi and Shah 1995)

4 Conclusions This chapter details solar air heaters application, classification (non-porous and porous), and various thermal–hydraulic performance enhancement techniques like ribs, fins, baffles, vortex generators, and jet impingement briefly discussed. The various types of SAH and performance improvement techniques are also illustrated. A SAH also has high conversion efficiency due to low construction, operational, storage, and transmission costs. Over a long period of operation, it proves as the best option over using direct electricity. Various techniques have been developed to improve its performance, in which surface modification (ribs, fins, baffles, longitudinal vortex generators, etc.) is commonly used. An in-depth literature review suggests that transverse vortex generators (TVGs) are good at heat transfer enhancement with minimum pressure loss in a duct flow. However, this technique is never used in SAH-duct. After obtaining optimum geometrical dimensions of smooth SAH-duct, a numerical and experimental investigation is carried out using suspended circular cylinders as TVGs to see the effect of associated geometrical parameters like, blockage ratio, clearance ratio, and relative pitch on the thermal–hydraulic performance of SAH-duct.

44

G. K. Chhaparwal and R. Goyal

(a)

(b) Fig. 13 Schematic of a Jet impingement and b Jet plate in SAH. Reproduced with permission from Yadav and Saini (2020). Copyright © 2020 International Solar Energy Society. Published by Elsevier Ltd. (Yadav and Saini 2020)

References Chii-Dong H, Hsuan C, Rei-Chi W, Chun-Sheng L (2012) Performance improvement of a doublepass solar air heater with fins and baffles under recycling operation. Appl Energy 100:155–163 El-Sebaii AA, Aboulenein S, Ramadan MRI, Shalaby SM (2011) Investigation of thermal performance of double-pass flat plate and V-corrugated plate solar air heaters. Proceed ICE-Energy 36:601–622 Ismail AF, Abd Hamid AS, Ibrahim A, Jarimi H, Sopian K (2022) Performance analysis of a double pass solar air thermal collector with porous media using lava rock. Energies 15:905. https://doi. org/10.3390/en15030905

Solar Air Heater-Classifications and Performance Enhancement …

45

Jacobi AM, Shah RK (1995) Heat transfer surface enhancement through the use of longitudinal vortices: a review of recent progress. Exp Therm Fluid Sci 11(3):295–309 Patil AK (2015) Heat transfer mechanism and energy efficiency of artificially roughened solar air heaters—a review. Renew Sustain Energy Rev 42:681–689 Pramanik RN, Sahoo SS, Swain R (2017) Mohapatra performance analysis of double pass solar air heater with bottom extended surface. Energy Procedia 109:331–337 Prasad SB, Saini JS, Singh KM (2009) Investigation of heat transfer and friction characteristics of packed bed solar air heater using wire mesh as packing material. Sol Energy 83(5):773–783 Saini P, Patil D, Powar S (2018) Review on integration of solar air heaters with thermal energy storage. In: Tyagi H, Agarwal A, Chakraborty P, Powar S (eds) Applications of solar energy. Energy, Environ, Sustain 163–186. https://doi.org/10.1007/978-981-10-7206-2_9 Saxena A, Goel V (2013) Solar air heaters with thermal heat storages. Chin J Eng (4). https://doi. org/10.1155/2013/190279 Singh S, Agrawal S (2015) Parameter identification of the glazed PVT system using Genetic Algorithm-Fuzzy System (GA-FS) approach and its comparative study. Energy Convers Manag 105:763–771 Singh VP, Jain S, Karn A, Kumar A, Dwivedi G, Meena CS, Dutt N, Ghosh A (2022) Recent development and advancements in solar air heaters: a detailed review. Sustainability 14(19):12149 Tiwari GN, Tiwari A, Shyam GN, Tiwari et al (2016) Solar flat-plate air collectors. In: Handbook of solar energy. Energy systems in electrical engineering. Springer, Singapore. Chapter 9, 369–416. https://doi.org/10.1007/978-981-10-0807-8_9 Yadav S, Saini RP (2020) Numerical investigation on the performance of a solar air heater using jet impingement with absorber plate. Sol Energy 208(15):236–248 Zhang Z, Zuo R, Li P, Su W (2009) Thermal performance of solar air collector with transparent honeycomb made of glass tube. Sci China Ser E Technol Sci 52(8):2323–2329

A Comprehensive Review of Recent Trends in Augmentation Heat Transfer Solar Air Heaters Using Arc-Shaped Ribs Rajan Karir, Kunj Bihari Rana, and Piyush Kumar Jain

Abstract The solar air heater is a simple means to use abundant available solar energy. Solar air heaters have low thermal efficiency because air is a heat transfer medium. The passive boundary layer must be broken by creating turbulence over the surface to improve heat transfer. To accomplish it, many methods were used, like creating surface roughness by putting ribs, fins, or dimples over the surface. Over the period, many types of ribs were used to create surface roughness and a parametric study of heat transfer from the surface was done. The present study reviews arc-shaped ribs for various configurations used by many researchers and analyzes the effect of flow parameters. Comparison based on investigation of heat transfer coefficient at different Reynold numbers considering parameters such as Nusselt number and friction factor was performed. Keywords Arc rib · Surface roughness · Solar air heater · Nusselt number · Friction factor

Nomenclature I Cp K e DH e/D (RH ) W

Solar radiation intensity (W/m2 ) Specific heat capacity of air (J/kg·K) Air thermal conductivity (W/m2 ·K) Rib height (m) Hydraulic diameter (m) Relative roughness height Solar air heater width (m)

R. Karir (B) · K. B. Rana Mechanical Engineering Department, Rajasthan Technical University, Kota 324010, India e-mail: [email protected] P. K. Jain Mechanical Engineering Department, Bansal Institute of Science and Technology, Bhopal 462021, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Goyal et al. (eds.), Renewable Energy: Accelerating the Energy Transition, Energy Systems in Electrical Engineering, https://doi.org/10.1007/978-981-99-6116-0_4

47

48

g p H P’ p/e (RP ) g/e h v mf Tout Tin Tam Tpm Δps Δpr fs fr f ρ Nu Nus Nur Re (p’/p) η W/w Pr ν

R. Karir et al.

Gap width (m) Rib pitch (m) Flow channel height (m) Staggered rib position Relative roughness pitch Relative gap width Heat transfer coefficient (W/m2 ·K) Velocity of air (m/s) Mass flow rate of air (kg/s) mf Temperature at collector outlet (°C) Temperature at collector inlet (°C) Average temperature of collector at inlet and outlet (°C) Surface collector plate temperature (°C) Smooth plate pressure drop (Pa) Rough plate pressure drop (Pa) Friction factor of smooth plate Friction factor of rib surface Friction factor Air density (kg/m3 ) Nusselt number Nusselt number of smooth plate Nusselt number of rib surface Reynolds number Relative staggered rib pitch Thermal collector efficiency Relative roughness width Prandtl number Kinematic viscosity of air (m2 /s)

1 Introduction The human population is increasing drastically, which is a burden on the available energy resources. Fossil fuels are available in limited amounts, leading to more and more dependency on renewable resources for sustainable development. The gap between energy demand and generation is continuously increasing. Thus, research is going on to trap the maximum available energy with higher efficiencies. Efforts are being made to reduce carbon emissions and disastrous environmental effects. The solution to this problem is to adopt renewable energy systems to convert the available energy into the required form. A simple energy conversion device that converts solar energy is a solar heater. This thermal energy can be used in the process industry. However, in solar air heaters, the working fluid is air which transfers convective heat

A Comprehensive Review of Recent Trends in Augmentation Heat …

49

for thermal applications. The heat capacity of air is small; therefore, various techniques to enhance heat transfer are used. The augmentation methodology for heat transfer, such as fins, artificial roughness, and vortex generators, enhances performance. The artificial roughness increases turbulence, which results in the breaking of the laminar sublayer and increases the convective heat transfer coefficient. Hence, heat transfer increases airflow resistance, resulting in more significant friction losses with increased power requirements. The solar air heater had three insulated surfaces, and the fourth surface absorber metal sheet was used for analysis where artificial roughness to enhance heat transfer was applied. The overall performance is improved using ribs of different geometry and arrangement. The present study reviews arcshaped ribs for various configurations used by different investigators, and the effect of different flow parameters was analyzed. At different Reynolds numbers (Re), a comparison of Nusselt number (Nu), heat transfer coefficient, and resistance in the form of friction factor ( f ) was performed.

2 Parameters Affecting Heat Transfer from the Surface Heat transfer from the surface depends upon various geometric parameters, and their analysis was done by different researchers to determine optimum heat transfer.

2.1 Effect of Rib Geometry The geometry of surface roughness plays a vital role in heat transfer, as it affects the flow pattern, separation, and reattachment. For solar air heaters, certain crucial parameters significantly affect the overall performance. Many researchers observed that the cross-section or geometry of the rib dramatically affects the flow pattern. Delayed flow separation occurs if the geometry is smooth and symmetrical, like a circular cross-section. However, early flow separation occurs in the sharp cornerlike cross-section, viz. triangular or square, and its reattachment results in greater augmentation in Nu. It is also observed that smoother section results in a smaller pressure drop and thus slight impact on f are obtained, as shown in Fig. 1.

2.2 Effect of Rib Height Rib height should be such that it can break the passive layer and create turbulence in the boundary layer, resulting in more heat transfer, whereas the pressure drop was kept minimum. Prasad and Saini (1988) examined flow separation and reattachment between the ribs and found that rib height (e = RH × D) significantly affects flow separation. It was noticed that reattachment results in more significant heat transfer

50

R. Karir et al.

(a)

(b)

(c) Fig. 1 Effect of various rib geometry: a square, b triangular, and c circular Reproduced with permission from I Singh et al. Renewable and sustainable energy reviews 92, 405–425, 2018. Copyright © 2018 Elsevier Ltd. (Singh and Singh 2018)

and maximum occurs at the point of reattachment. Greater rib height results in a more significant pressure drop; heat transfer decreases due to loss of reattachment between the ribs, as shown in Fig. 2. Previous researchers (Hans et al. 2009; Alam and Kim 2017; Singh and Singh 2018) analyzed the arc rib using e/D (0.0213–0.0422).

Fig. 2 Rib height effect Reproduced with permission from B.N. Prasad et al. Solar Energy 41(6), 555–560, 1988. Copyright © 1988 Elsevier Ltd. (Prasad and Saini, 1988)

A Comprehensive Review of Recent Trends in Augmentation Heat …

51

Fig. 3 Relative rib pitch effect Reproduced with permission from B. N. Prasad et al. Solar Energy 41(6), 555–560, 1988. Copyright © 1988 Elsevier Ltd. (Prasad and Saini 1988)

2.3 Effect of Rib Pitch The heat transfer depends upon the reattachment of flow. It is the relative pitch that has a significant effect on the reattachment point and location. Therefore, investigating relative pitch is an essential parameter when deciding the amount of heat transfer from the rough surface of a solar air heater. Figure 3 shows that less heat transfer occurs when RP is less than 8 without flow reattachment. For RP ≥ 8, reattachment results in an improvement in heat transfer. However, if RP = 10, maximum reattachment along the length results in an improvement of thermo-hydraulic performance is recommended (Hans et al. 2009; Alam and Kim 2017; Singh and Singh 2018).

2.4 Effect of Rib Inclination If an inclined surface is placed in the regular flow stream, secondary vortices are created, which move from the front to the trailing end. The secondary flow vortices merge with primary vortices; turbulence increases the heat transfer as primary boundary layer gets broken. The rib inclination results in formation of secondary flow vortices, and its effect on heat transfer is shown in Fig. 4 (Taslimand Kercher 1996; Hans et al. 2009; Alam and Kim 2017; Singh and Singh 2018).

52

R. Karir et al.

Fig. 4 Effect of rib inclination movement on secondary vortices Reproduced with permission from K. R. Aharwal et al. Renewable Energy 33(4), 585–596, 2008. Copyright © 2008 Elsevier Ltd. (Aharwal et al. 2008)

Fig. 5 Effect of a gap in continuous ribs. Reproduced with permission from K. R. Aharwal et al. Renewable Energy 33(4), 585–596, 2008. Copyright © 2008 Elsevier Ltd. (Aharwal et al. 2009)

2.5 Presence of Gap in Continuous Ribs The gap in the continuous rib also creates an extra zone of turbulence, increasing the heat transfer (Aharwal et al. 2008). This is because as air passes through the gap, it accelerates, reducing boundary layer formation, as depicted in Fig. 5. Various researchers obtained the gap-based increase in heat transfer (Aharwal et al. (2009), Singh et al. (2011) and Kumar et al. (2013). Further, Singh et al. (2011) observed that gap near trailing edge has a more significant effect than its presence near the leading edge.

3 Parametric Study of Arc Ribs Geometry Variation This chapter comprehensively reviews recent trends in artificial roughness techniques for performance enhancement, especially arc shape ribs. Scientists studied variations from single continuous arcs to multiple arcs with gap and staggered. The results were

A Comprehensive Review of Recent Trends in Augmentation Heat …

53

analyzed based on flow and roughness parameters. It shows a clear improvement in heat transfer of flat surfaces when an arc-shaped rib is used. Further, it was noticed that using arc-shaped ribs results in minimum pressure drop and less increase in required power. Concerning flat surfaces, if a transverse rib with an inclination angle is used, it improves heat transfer. Saini and Saini (2008) investigated that the greatest improvement of 25% in thermal efficiency was observed with an inclination angle of 60°, as shown in Fig. 6. In solar air heaters, when arc-shaped ribs are used instead of transverse ribs, secondary flow vortices are formed, which increases turbulence and heat transfer. Saini and Saini (2008) explored arc-shaped ribs keeping a constant value of relative pitch 10 by varying α in the 30° to 60° and relative height RH was altered between 0.0213 and 0.0422. Singh et al. (2014) observed that secondary flow vortices increase performance for multiple arc ribs, as shown in Fig. 7. Parameters RH (0.018 to 0.45), RP (4 to 16), α (30° to 75°), W/H (11), and W/w (1 to 7) were varied with Re 220–22,300. It was found that Nu and f became 5.07 and 3.71 times increased than a flat plate. Also, a maximum thermo-hydraulic performance of 3.4 was stated for the RH of 0.045 and RP of 8, keeping α = 60° and W/w = 5. Lanjewar et at. (2015) analyzed rib configuration with a double arc, as shown in Fig. 8. They considered two positions up and down. For Re 3600 to 18,000, the

Fig. 6 Arc-shaped ribs with circular sections Reproduced with permission from S.K. Saini et al. Solar Energy 82(12), 1118–1130, 2008. Copyright © 2008 Elsevier Ltd. (Saini and Saini 2008)

Fig. 7 Multiple arc-shaped ribs with circular sections. Reproduced with permission from A.P. Singh et al. Solar Energy 105, 479–493, 2014. Copyright © 2014 Elsevier Ltd. (Singh et al. 2014)

54

R. Karir et al.

thermo-hydraulic performance for double arc was investigated. The double arc with a down orientation performs better than the single arc in the operating range of analysis (Fig. 8). It was also stated that the performance of double arc up roughness was inferior to single arc roughness for most ranges of Re. Multiple arc-shaped ribs (Fig. 9) generate more turbulence in the gap region Pandey et al. (2016). When variation in W/w was analyzed, an overall increase of 4.64 and 2.71 times in Nu and f was observed at an optimum W/w = 3 (Fig. 9). The gap width and location were also varied, keeping other parameters fixed, W g = 1 and d/w = 0.65. It was found that Nu and f increase to the maximum extent of 4.96 and 5.86 times, respectively, concerning flat plates. Circular wire ‘S’ shape ribs were explored by Kumar et al. (2017). Different parameters were studied in various ranges, and their effect on augmentation on heat transfer was investigated. The relative roughness pitch p/e (4–16), height (e/ Dh ) 0.022–0.054, arc angle α (30–75°), width W/w (1–4), and Re (2400–20,000) (Fig. 10a, b) are used for analysis. Nu and f were plotted at α = 60° and relative roughness height (e/Dh = 0.043). The Nu increases with increasing Re and f decreases, but at relative width, Nu is maximum, whereas f increases with width. This is because of the formation of secondary flow, and with an increase in several curved surfaces, an adverse effect is observed due to the formation of the second layer. The maximum value of Nu and f is obtained at α of 60° and p/e of 8. It is concluded that S shape rib results in good enhancement in Nu with less increase in f . Hans et al. (2017) explored the roughness of discrete arc rib experimentally and determined solar air heater duct performance (Fig. 11). Rib roughness is considered as d/w (0.2–0.8), P/e (4–12), e/D (0.022–0.043), g/e (0.5–2.5), α (15°–75°), and Re (2000–16,000). Solar air heater performance enhancement for the flat surface in Nu of 2.63 and f of 2.44 time for d/W = 0.65, W g = 1, and α = 30 was observed. Gill et al. (2017) explored the effect of heat transfer from a surface roughened with a “broken arc rib combined with staggered rib piece” Fig. 12, also, the effect on friction factor was analyzed. Various flow parameters considered were arc angle, relative roughness pitch, relative staggered rib position, relative roughness height, relative gap size, and relative gap position of 30°, 10, 0.043, 0.4, 1.0, and 0.65. Re was varied from 2000 to 16,000, and relative staggered rib size was altered from 1 to 6. The Nu and f were 2.37 and 2.55 times over staggered arc ribs, respectively. Also, the highest thermo-hydraulic performance achieved was 1.94 in this arrangement.

Fig. 8 Up and down roughness configuration of double arc rib Reproduced with permission from A.M. Lanjewar et al. Renewable and Sustainable Energy Reviews 43, 1214–1223, 2015. Copyright © 2015 Elsevier Ltd. (Lanjewar et at. 2015)

A Comprehensive Review of Recent Trends in Augmentation Heat …

55

(a)

(b) Fig. 9 Surface plate of multiple arc ribs with a gap a line diagram and b 3D view Reproduced with permission from N.K. Pandey et al. Solar Energy 134, 314–326, 2016. Copyright © 2016 Elsevier Ltd. (Pandey et al. 2016)

(a)

(b) Fig. 10 S-shaped ribs with circular section a line diagram and b actual view. Reproduced with permission from K Kumar et al. Experimental Thermal and Fluid Science 82, 249–261, 2017. Copyright © 2017 Elsevier Ltd. (Kumar et al. 2017)

56

R. Karir et al.

(a)

(b) Fig. 11 Arc ribs with a gap a line diagram and b actual photograph. Reproduced with permission from V.S. Hans et al. Experimental Thermal and Fluid Science 80, 77–89, 2017. Copyright © 2017 Elsevier Ltd. (Hans et al. 2017)

Fig. 12 Various combinations of broken arc ribs with different relative staggered rib pieces. Reproduced with permission from R.S. Gill et al. Renewable Energy 104, 148–162, 2017. Copyright © 2017 Elsevier Ltd. (Gill et al. 2017)

Ambade and Lanjewar (2019) tried to enhance the performance of solar air heaters using arc ribs with gap and staggered elements (Fig. 13) by varying Re from 3000 to 15,000. Other performance parameters considered were the (g/e) 4, the number of gaps on half arc (Ng) 3, relative rib height (e/Dh ) 0.0433, and pitch (p/e) varied from

A Comprehensive Review of Recent Trends in Augmentation Heat …

57

(a)

(b) Fig. 13 a Arc ribs having a gap and staggered element and b variations in rib pitch for arc ribs having a gap and staggered element (Ambade and Lanjewar 2019)

6–14 in the step of two units. The (p’/p) 0.4, the ratio of staggered length to height rib (r/e) 4 and arc angle (α) 30° and (p’/p) were varied as 6–14. Roughened plates with arc geometry with symmetrical gaps and staggered elements for five relative rib pitch values were tested and compared with the best-staggered element arc rib. A maximum increase in Nu of 2.18 times was observed at a relative pitch of 10 due to optimum air reattachment and a 3.88 times increase in f to a flat plate. The optimum thermo-hydraulic parameter is 1.41 at (p’/p) values of 10. Due to a gap, maximum acceleration in flow occurs after reattachment. In the case of flow strikes, a staggered scattering occurs. The secondary layer creates extra turbulence, which enhances heat transfer; a large part of the flow and reattachment occurs after the staggered member, which enhances heat transfer (Fig. 14a, b and c). Ghritlahre et al. (2020) experimentally studied the continuous arc rib geometry with apex up and down (Fig. 15). Thermal performance was compared, and it concluded that the roughened surface with an apex up rib gives relatively greater heat transfer than an apex down rib roughened surface. Kumar et al. (2020) investigated the roughness of multiple arcs with gap and the effect of various parameters on average Nusselt number (Nuavg ), f, and thermohydraulic performance (Fig. 16). Gap Ng was varied from 1 to 5 and found that Nuavg increases with Ng 1 to 3, for α = 60°, g/e = 1.0, e/D = 0.045, W/w = 5, and p/e = 8, and then decreases with a rise in turbulence. Friction penalty was investigated and defined as an increase in f for roughed duct over the smooth duct. The highest fpenalty

58

R. Karir et al.

(a)

(b)

(c) Fig. 14 Flow pattern in arc ribs with a gap a flow over main rib and staggered element, b flow reattachment in between main rib and staggered element, and c formation of secondary flow eddies over main rib and staggered element (Ambade and Lanjewar 2019)

observed was 4.98 at Re = 5600. The best Nuavg augmentation observed was for g/e = 1.0, which is 5.6. The highest fpenalty observed was 4.98 for the proposed configuration of surface roughness with g/e = 1. Maximum thermal–hydraulic performance was 4.68% lower than obtained for discrete V-shaped ribs.

A Comprehensive Review of Recent Trends in Augmentation Heat …

59

(a)

(b) Fig. 15 Arc ribs surface with a apex down and b apex up Reproduced with permission from H.K. Ghritlahre et al. Solar Energy 199, 173–182, 2020. Copyright © 2020 Elsevier Ltd. (Ghritlahre et al. 2020) Fig. 16 Multi-arc ribs with a gap Reproduced with permission from A Kumar et al. Experimental Heat Transfer 35(3) 239–257, 2022. Copyright © 2020 Taylor & Francis (Kumar et al. 2020)

Sahu et al. (2021) experimentally studied continuous arc ribs with apex up and down configurations. The thermal performance and pressure drop were observed considering different roughness parameters, angle of attack (α) 45°–75°, (P/e) 8–15, (e/D) of 0.0454, and (W /H) = 11. Also, during the investigation, Re was varied in the range 2983–13,955 and mass flow rate (m) from 0.0100–0.0471 kg s−1 . It was concluded that maximum thermal efficiency was observed at (P/e) = 8 and (α) = 60°. For the defined mass flow rate range, thermal efficiency enhancement was observed and found at 55.8% for apex downstream and 71.6% for apex upstream, enhancement in thermal efficiency compared to simple flat plate solar air heater. The apex down arc roughness has a greater pressure drop than the apex up arc roughness.

60

R. Karir et al.

(a)

(b) Fig. 17 a Rough surface of S-shape ribs with a gap. Reproduced with permission from D Wang et al. Solar Energy 195, 89–101, 2020. Copyright © 2020 Elsevier Ltd. (Wang et al. 2020). b representation of geometric parameters on S-shape ribs with a gap. Reproduced with permission from Nidhul K et al., Renewable and Sustainable Energy Reviews. 142; 110,871, 2021, Copyright © 2020 Elsevier Ltd. (Nidhul et al. 2021)

In the study conducted by Wang et al. (2020) S-shaped rib with a gap, the presence of a gap reduces the flow resistance (Fig. 17). SAH performance with an S-shaped rib containing a gap compared to a flat plate was investigated. The implication of duct height, relative pitch RP, solar insolation, and W g were evaluated while keeping RH fixed. If solar height was kept constant, no significant impact of the solar insolation on thermal efficiency was observed. In contrast, with varied duct height, a significant influence on thermal efficiency was investigated. A maximum 48% rise in thermal efficiency, peak augmentation in heat transfer, and 5.42 and 5.87 times increase in Nu and f were reported.

A Comprehensive Review of Recent Trends in Augmentation Heat …

61

(a)

(b) Fig. 18 a Discrete arc rib roughened plate and b Variation in gap width to rib element height (g/ e) (Azad et al. 2021)

Azad et al. (2021) studied experimentally novel discrete geometry, as shown in Fig. 18a, b, considering various parameters relative height e/Dh = 0.045, W = 200 mm, p/e = 10, g/e = 2–5, Ng = 3, and α = 30°, while the Re varied from 3000– 14,000. The optimum value of Nu and f were observed 2.26 and 3.87 times than smooth surface, for g/e as 4 and Re of 14,000, respectively. The highest increment of thermo-hydraulic performance of 1.4–1.55 for g/e 4 in the Re range was observed. Kumar et al. (2021) explored the transfer of heat in SAH having a roughness of multi-arc pattern with a gap (Fig. 19) for P/e of 8, e/D of 0.045, θ /60 of 1, W/w of 5, Ng of 3, and wg /e of 1.0. The maximum Nu of 5.76 at and a frictional penalty of 6.05 were found at Re 23,000 concerning the smooth duct. Bhuvad et al. (2022) examined the performance of an absorber plate with discrete arc rib solar air heater apex up with already established optimum downstream flow ribs geometries, as shown in Fig. 20. The optimized flow parameters were kept, and augmentation in Nu of 2.92 times was observed at α of 30°. Optimum thermohydraulic performance of 2.014 was observed at Re of 10,000 and angle of attach α of 30°. Table 1 presents the parametric study of various parameters and their optimized values obtained for different variations of arc roughness.

62

R. Karir et al.

Fig. 19 Multi-arc rib with a gap. Reproduced with permission R Kumar et al. Heat Transfer, 35:4, 466–483, 2022 Copyright © 2022 Taylor & Francis (Kumar et al. 2022) Fig. 20 Discrete arc rib roughened plate having apex up. Reproduced with permission from S.S. Bhuvad et al. Renewable Energy 185, 403–415, 2022. Copyright © 2020 Taylor & Francis. (Bhuvad et al. 2022)

Type of roughness

Single arc rib

Multi-arc rib

Double arc rib

Multi-arc rib with gap

Literature

Saini and Saini (2008)

Singh et al. (2014)

Lanjewar et at. (2015)

Pandey et al. (2016) RP –4–16 RH –0.016 to 0.044 (α/90–0.25–0.8333 d/x–0.25–0.85 W/w–1–7 W/H–11 g/e–0.5–2.0 Re–2100–21,000

RP –10 RH –0.029 (α/90)–0.5 W/H–11 Re- 4000–14,000

RP –4–16 RH –0.018–0.045 (α/90)–0.3333–0.8333 W/w- 1–7 W/H- 11 Re–2200–22,300

RP –10 RH –0.0213–0.0422 (α/90)- 0.3333–0.6666 W/H- 12 Re- 2000–17,000

Roughness parameters

RP –8 RH –0.044 W/w–5 (α/90)–0.667 (d/x)–0.65 W/H–11 g/e–1.0 Re–21,000

RH –0.029 (α/90)–0.5 RP –10 W/H–11 Re–8000

RH –0.045 W/H–11 (α/90)–0.667 W/w–5 RP - 8 Re–22,300

(α/90)–0.3333 RH - 0.0422

Optimum values

Table 1 Summary of outcomes obtained by various researchers using arc rib roughened surface

(continued)

Nur /Nus –5.85 fr /fs –4.96 thermo-hydraulic performance (THP)–3.24

Nur /Nus –0.957–2.27 (for double arc down and for up no enhancement fr /fs –1.84–2.27 times more for arc down

Nur /Nus –5.07 fr /fs –3.71

Nur /Nus –3.8 fr /fs –1.75

Maximum enhancement

A Comprehensive Review of Recent Trends in Augmentation Heat … 63

RP –4–16 RH –0.022–0.054 (α/90)–0.33–0.8333 W/w–1–4 W/H–12 Re–2400–20,000

S-shaped rib

Discrete arc rib

Discrete arc rib

Hans et al. (2017)

Gill et al. (2017)

RP –4–12 RH –0.022 to 0.043 (α/90)–0.16–0.8333 d/w–0.20–0.80 g/e–0.5–2.5 W/H–12 Re–2000–16,000

RP –4–12 RH –0.022 to 0.043 (α/90)–0.16–0.8333 g/e–0.5–2.5 d/x–0.25–0.85 W/H–12 Re–2000–16,000

Roughness parameters

Type of roughness

Literature

Kumar et al. (2017)

Table 1 (continued)

W/H–12 RP –8 RH –0.043 (α/90)–0.33 d/w–0.65 g/e–1.0 Re–11,000–14,000

W/H–12 RP 10 RH –0.043 (α/90)–0.33 d/x–0.65 g/e–1.0 Re- 11,000–14,000

W/H–12 RP –8 RH –0.043 (α/90)–0.667 W/w–3 Re–21,000

Optimum values

Nur /Nus –2.37 fr /fs –2.55 THP–1.94

Nur /Nus –2.63 fr /fs –2.44

Nur /Nus –4.64 fr /fs –2.27 THP–3.34

(continued)

Maximum enhancement

64 R. Karir et al.

Ng–3 RP –10 RH –0.043 P’ /p–0.4 r/g–1,2,3,4,5,6 (α/90)–0.333 g/e–1.0 d/w–0.65 W/H–12 Re–2000–16,000

Discrete arc rib with staggered element

Discrete arc rib with staggered element

Apex up continuous rib

Ambade and Lanjewar (2019)

Ghritlahre et al. (2020)

mf –0.007–0.022 kg/s RP –10 RH –0.0395 (α/90)–0.667 g/e–4.0 W/H–12 Re–2000–16,000

Ng–3 RP –6,8,10,12,14 RH –0.0433 P’ /p–0.4 (α/90)–0.333 g/e–4.0 d/w–0.65 r/e–4.0 W/H–12 Re–2000–15,000

Roughness parameters

Type of roughness

Literature

Gill et al. (2017)

Table 1 (continued)

W/H–12 mf –0.022 kg/s RP –10 RH –0.0395 (α/90)–0.667 g/e– 4.0 Re–2000–16,000

W/H–12 Ng–3 RP –10 RH –0.0433 P’ /p–0.4 (α/90)–0.333 d/w–0.65 g/e–4.0 r/e–4.0 Re–15,000

W/H–12 RP –10 RH –0.043 Number of gaps–3 P’ /p–0.4 (α/90)–0.333 g/e–1.0 d/w–0.65 r/g–4 Re–2000–16,000

Optimum values

(continued)

Thermal efficiency for apex up 73.2%(max.) and apex down 69.4%

Nur /Nus –2.18 fr /fs –3.88

Nur /Nus –3.06 fr /fs –2.50 THP–2.27

Maximum enhancement

A Comprehensive Review of Recent Trends in Augmentation Heat … 65

W/w–5 RP - 8 RH - 0.044 Ng–1–5 (α/60)–1 g/e–0.5–2.0 Re–5600–16,500 Ambient temperature, Ta –19.5–40.0 °C RP –8, 10, 15 RH –0.0454 (α/90)–0.5–0.8333 W/H-11 Solar insolation, I 600–900 W m−2 Wind velocity, Vw –0.3–4.5 m s−1 mf –0.010–0.0471 kg/s Re 2983–13,955 RP –20–30 RH - 0.023 to 0.034 W/w–3–5 g/e–1–2 W/H–6.6–10 Re–2000–20,000 Solar radiation intensity 450–650 (W/m2 )

Multi-arc rib with gap

Different orientations of arc-shaped ribs

S-shaped ribs with gap

Sahu et al. (2021)

Wang et al. (2020)

Roughness parameters

Type of roughness

Literature

Azad et al. (2021)

Table 1 (continued)

W/H–10 RP –20 g/e–1.5 W/w–4 Solar radiation intensity 450–650 (W/m2 ) Re–19,258

RP –8 RH - 0.0454 (α/90)–0.667 mf - 0.010–0.0471 kg/s

W/w–5 RP - 8 RH - 0.044 Ng–1–5 (α/60)–1 g/e–1.0 Re–5600–16,500

Optimum values

Nur /Nus –5.42 fr /fs –5.87

(continued)

For apex up maximum thermal efficiency 71.6% and for apex down 55.8%

Nur /Nus –5.6 fr /fs - 4.98 thermo-hydraulic performance 3.46

Maximum enhancement

66 R. Karir et al.

Type of roughness

Discrete arc rib

Symmetrical gap multi-arc rib pattern

Apex up discrete rib

Literature

Azad et al. (2021)

Kumar et al. (2022)

Bhuvad et al. (2022)

Table 1 (continued)

(α/90)–0.333,0.5,0.667 RP –10 Ng –3 RH - 0.045 g/e–4 W/H–8 Re–3000–14,000

(α/60)–0.5–1.25 W/w–1–7 RP –4–16 Ng –1–4 RH –0.018 to 0.045 g/e–0.5–2.0 W/H–11 Re–2300–23,000

(α/90)–0.333 RP –10 Ng –3 RH –0.045 g/e–2–5 W/H–8 Re–3000–14,000

Roughness parameters

W/H–8 (α/90)–0.333 RP –10 Ng –3 RH – 0.045 g/e–4 Re–10,000

W/H–11 (α/60)–1.0 W/w–5 RP –8 Ng –3 RH –0.045 g/e–1.0 Re–23,000

W/H–8 (α/90)–0.333 RP –10 Ng –3 RH –0.045 g/e– 4 Re–14,000

Optimum values

Nur /Nus –2.92 fr /fs –3.04 THPP–2.014

Nur /Nus –5.76 fr /fs –6.05 Thermal efficiency- 79%

Nur /Nus –2.26 fr /fs –3.87 At Re 14,000 discrete rib has THP-1.68, whereas for V rib1.59

Maximum enhancement

A Comprehensive Review of Recent Trends in Augmentation Heat … 67

68

R. Karir et al.

4 Conclusion A review of artificial roughness on the surface concludes that roughness enhances heat transfer, but pressure drop increases power requirement. The variation of different geometrical and operating parameters can be concluded as follows: • For arc shape roughness, different variations were investigated by different scientists. It was observed that a single arc has a sort of inclined rib effect, resulting in the development of secondary flow vortices. It is mixed with the primary flow, creating eddies and making the flow turbulent, increasing the heat transfer. • Flow parameters like W/H, RH , RP , etc., affect the heat transfer. Also, multi-arc enhances heat transfer, but too many arcs have an adverse effect as it increases friction losses. • A gap or staggering increases the flow velocity, increasing the turbulence and resulting in greater heat transfer. • Later on, a staggered member was introduced in the roughness geometry. It was found that when flow passes through the gap, it accelerates and strikes at the staggered member; further turbulence results in reattachment in flow and heat transfer increases.

References Aharwal KR, Gandhi BK, Saini JS (2008) Experimental investigation on heat-transfer enhancement due to a gap in an inclined continuous rib arrangement in a rectangular duct of solar air heater. Renew Energy 33(4):585–596 Aharwal KR, Gandhi BK, Saini JS (2009) Heat transfer and friction characteristics of solar air heater ducts having integral inclined discrete ribs on the absorber plate. Int J Heat Mass Transf 52(25–26):5970–5977 Ahn SW (2001) The effects of roughness types on friction factors and heat transfer in roughened rectangular duct. Int Commun Heat Mass Transfer 28(7):933–942 Alam T, Kim MH (2017) A critical review on artificial roughness provided in rectangular solar air heater duct. Renew Sustain Energy Rev 1(69):387–400 Ambade J, Lanjewar A (2019) Evaluation of roughened duct with similar wideness gap of arc with staggered link and comparison with similar rib roughness geometries. Int J Mech Produc Eng Res Dev 9(5):1015–1022 Araujo A (2020) Thermo-Hydraulic performance of solar air collector with artificial roughened absorbers: A comparative review of semi-empirical models. Energies 13(14):3536. https://doi. org/10.3390/en13143536 ASHRAE standard, method of testing to determine the thermal performance of solar collectors, American society of heating, refrigeration and air conditioning engineers, Atlanta, GA: US department of energy, 30329, 2003 Azad R, Bhuvad S, Lanjewar A (2021) Study of solar air heater with discrete arc ribs geometry: experimental and numerical approach. Int J Therm Sci 167:107013 Bharadwaj G, Kumar VR, Sharma A (2017) Heat transfer augmentation and flow characteristics in ribbed triangular duct solar air heater: An experimental analysis. Int J Green Energy 14(7):587– 598. https://doi.org/10.1080/15435075.2017.1307751

A Comprehensive Review of Recent Trends in Augmentation Heat …

69

Bhattacharyya S et al (2016) Experimental investigation on heat transfer enhancement by swirl generators in a solar air heater duct. Int J Heat Technol 34(2):191–196. https://doi.org/10.18280/ ijht Bhattacharyya S, Chattopadhyay H, Benim AC (2017a) Computational investigation of heat transfer enhancement by alternating inclined ribs in tubular heat exchanger. Prog Comput Fluid Dyn 17(6):390–396. https://doi.org/10.1504/PCFD.2017.088818 Bhattacharyya S, Chattopadhyay H, Benim AC (2017b) 3D CFD simulation on heat transfer enhancement in turbulent channel flow with twisted tape inserts. Prog Comput Fluid Dyn 17(3):193–197. https://doi.org/10.1504/PCFD.2017.084356 Bhattacharyya S, Chattopadhyay H, Haldar A (2018) Design of twisted tape turbulator at different entrance angle for heat transfer enhancement in a solar heater. Beni-Suef Univ J Basic Appl Sci 7(1):118–126. https://doi.org/10.1016/j.bjbas.2017.08.003 Bhattacharyya S, Benim AC, Chattopadhyay H, Banerjee A (2019a) Experimental and numerical analysis of forced convection in a twisted tube. J Therm Sci 23(Suppl. 4):1043–1052. https:// doi.org/10.2298/TSCI19S4043B Bhattacharyya S, Chattopadhyay H, Guin A, Benim AC (2019b) Investigation of inclined turbulators for heat transfer enhancement in a solar air heater. Heat Transfer Eng 40(17–18):1451–1460. https://doi.org/10.1080/01457632.2018.1474593 Bhattacharyya S, Bashir AI, Dey K, Sarkar R (2020) Effect of novel short-length wavy-tape turbulators on fluid flow and heat transfer: Experimental study. Exp Heat Transfer 33(4):335–354. https://doi.org/10.1080/08916152.2019.1639847 Bhattacharyya S (2018) Fluid flow and heat transfer in a heat exchanger channel with short-length twisted tape turbulator inserts, Iran. J Sci Technol Transac Mech Engi (online Published). https:// doi.org/10.1007/s40997-018-0251–0 Sushant Suresh Bhuvad, Rajnish Azad, Atul Lanjewar (2021) Study of solar air heater with discrete arc ribs geometry: Experimental and numerical approach. Int J Therm Sci 167, 107013 Sushant Suresh Bhuvad, Rajnish Azad, Atul Lanjewar (2022) Thermal performance analysis of apex-up discrete arc ribs solar air heater-an experimental study. Renewable Energy 185, pp 403–415 Elyyan MA, Tafti DK (2009) A novel split-dimple interrupted fin configuration for heat transfer augmentation. Int J Heat Mass Transf 52(5–6):1561–1572. https://doi.org/10.1016/j.ijheatmas stransfer.2008.07.046 Ghritlahre HK, Sahu PK, Chand S (2020) Thermal performance and heat transfer analysis of arc shaped roughened solar air heater – An experimental study. Solar Ener 199:173–182 Gill RS, Hans VS, Saini JS, Sukhmeet Singh (2016) Investigation on performance enhancement due to staggered piece in a broken arc rib roughened solar air heaterduct, Renew Energy Goel V, Guleria P, Kumar R (2017) Effect of apex angle variation on thermal and hydraulic performance of roughened triangular duct. Int Commun Heat Mass Transfer 86:239–244. https://doi. org/10.1016/j.icheatmasstransfer.2017.06.008 Gupta D, Solanki SC, Saini JS (1993) Heat and fluid flow in rectangular solar air heater ducts having transverse rib roughness on absorber plates. Sol Energy 51:31–37 Gupta D, Solanki SC, Saini JS (1997) Thermohydraulic performance of solar air heaters with roughened absorber plates. Sol Energy 61(1):33–42 Gupta D, Solanki SC, Saini JS (1991) Enhancement of heat transfer in rectangular solar air heater ducts having artificial roughness on absorber plates. In: 11th National Heat and Mass Transfer Conference, IIT Madras, India Han JC, Park JS, Lei CK (1985) Heat transfer enhancement in channels with turbulence promoters. Trans. ASME. J Eng Gas Turbine Power 107:628–635 Hans VS, Saini RP, Saini JS (2009) Performance of artificially roughened solar air heaters—A review. Renew Sustain Energy Rev 13(8):1854–1869 Hans VS, Gill RS, Singh S (2017) Heat transfer and friction factor correlations for a solar air heater duct roughened artificially with broken arc ribs. Exp Thermal Fluid Sci 1(80):77–89

70

R. Karir et al.

Hans VS, Gill RS, Singh S (2017) Heat transfer and friction factor correlations for a solar air heater duct roughened artificially with broken arc ribs. Exp Therm Fluid Sci 80:77–89. https://doi.org/ 10.1016/j.expthermflusci.2016.07.022 Istanto T, Danardono D, Yaningsih I, Wijayanta AT (2016) Experimental study of heat transfer enhancement in solar air heater with different angle of attack of V-down continuous ribs. In: AIP Conference Proceedings 1737(1), p 060002. AIP Publishing LLC Jain SK, Agarwal GD, Misra R (2019) Heat transfer augmentation using multiple gaps in arc-shaped ribs roughened solar air heater: An experimental study. Energy Sources (part a). https://doi.org/ 10.1080/15567036.2019.1607945) Jain SK, Agarwal GD, Misra R (2020) Experimental investigation of thermohydraulic performance of the solar air heater having arc-shaped ribs with multiple gaps. J Therm Sci Eng Appl 12(1):011014. https://doi.org/10.1115/1.4044427 Jin D, Zuo J, Quan S, Xu S, Gao H (2017) Thermohydraulic performance of solar air heater with staggered multiple V-shaped ribs on the absorber plate, Energy, 127, pp 68–77, 10.1016/j. energy.2017.03.101 Jourker AR, Saini JS, Gandhi BK (2006) Heat transfer and friction characteristics of solar air heater duct using rib-grooved artificial roughness. Sol Energy J 80:895–907 Karwa R (1998) Effect of duct depth on the thermo-hydraulic performance of a conventional solar air heater. In: Proceedings of National Solar Energy Convention-98, Roorkee, India, pp 45–52 Kays WM (2012) Convective heat and mass transfer. Tata McGraw-Hill Education Kumar A, Saini RP, Saini JS (2013) Development of correlations for Nusselt number and friction factor for solar air heater with roughened duct having multi v-shaped with gap rib as artificial roughness. Renewable Energy 1(58):151–163 Kumar K, Prajapati DR, Samir S (2017) Heat transfer and friction factor correlations development for solar air heater duct artificially roughened with ‘S’shape ribs. Exp Thermal Fluid Sci 1(82):249– 261 Kumar R, Kumar A, Goel V (2017) A parametric analysis of rectangular rib roughened triangular duct solar air heater using computational fluid dynamics. Sol Energy 157:1095–1107. https:// doi.org/10.1016/j.solener.2017.08.071 Kumar R, Goel V, Kumar M (2020) Effect of providing gap in multiple-arc rib-roughened solar air heater - Part 1. J Mech Sci Technol 34(6):2619–2625. https://doi.org/10.1007/s12206-0200535-3 Kumar R, Goel V, Suvanjan Bhattacharyya VV, Tyagi & Abdullah M. Abusorrah, (2022) Experimental investigation for heat and flow characteristics of solar air heater having symmetrical gaps in multiple-arc rib pattern as roughness elements. Exp Heat Transf 35(4):466–483. https:// doi.org/10.1080/08916152.2021.1905752 Kumar A, Layek A (2020) Evaluation of the performance analysis of an improved solar air heater with Winglet shaped ribs, Exp. Heat Transfer, 2020, https://doi.org/10.1080/08916152.2020. 1838670 Lanjewar AM, Bhagoria JL, Agrawal MK (2015) Review of development of artificial roughness in solar air heater and performance evaluation of different orientations for double arc rib roughness. Renew Sustain Energy Rev 1(43):1214–1223 Maithani R, Kumar A, Raghav G, Nagpal M, Kumar B (2020) Thermal analysis of jet impingement on hemispherical protrusion on heated surface, Exp. Heat Transfer, pp 1–16. 10.1080/ 08916152.2020.1808117 Maithani R, Saini JS (2016) Heat transfer and friction factor correlations for a solar air heater duct roughened artificially with V-ribs with symmetrical gaps. Exp Therm Fluid Sci 70:220–227. https://doi.org/10.1016/j.expthermflusci.2015.09.010 Momin AM, Saini JS, Solanki SC (2002) Heat transfer and friction in solar air heater duct with V-shaped rib roughness on absorber plate. Int J Heat Mass Transf 45(16):3383–3396 Nanjundappa M (2020) Optimum thermo-hydraulic performance of solar air heater provided with cubical roughness on the absorber surface. Exp Heat Transfer 33(4):374–387. https://doi.org/ 10.1080/08916152.2019.1652214

A Comprehensive Review of Recent Trends in Augmentation Heat …

71

Nidhul K, Yadav AK, Anish S, Kumar S (2021) Critical review of ribbed solar air heater and performance evaluation of various V-rib configuration. Renew Sustain Energy Rev 142:110871 Pandey NK, Bajpai VK (2016) Experimental investigation of heat transfer augmentation using multiple arcs with gap on absorber plate of solar air heater. Sol Energy 1(134):314–326 Patel SS, Lanjewar A (2019) Experimental and numerical investigation of solar air heater with novel V-rib geometry. J Storage Mater 21:750–764 Patil AK (2015) Heat transfer mechanism and energy efficiency of artificially roughened solar air heaters—A review. Renew Sustain Energy Rev 1(42):681–689 Perwez A, Shende S, Kumar R (2019) Heat transfer and friction factor characteristic of spherical and inclined teardrop dimple channel subjected to forced convection. Exp Heat Transfer 32(2):159– 178. https://doi.org/10.1080/08916152.2018.1485786 Prakash C, Saini RP (2019) Heat transfer and friction in rectangular solar air heater duct having spherical and inclined rib protrusions as roughness on absorber plate. Exp. Heat Transfer 32(5):469–487. https://doi.org/10.1080/08916152.2018.1543367 Prasad and Saini (1988) Effect of artificial roughness on heat transfer and friction factor in a solar air heater. Sol Energy. 41(6):555–60 Prasad K, Mullick SC (1983) Heat transfer characteristics of a solar air heater used for drying purposes. Appl Energy 13(2):83–93 Prasad BN, Saini JS (1991) Optimal thermohydraulic performance of artificially roughened solar air heaters. Sol Energy 47(2):91–96 Sahu MM, Bhagoria JL (2005) Augmentation of heat transfer coefficient by using 90 broken transverse ribs on absorber plate of solar air heater. Renew Energy 30(13):2057–2073 Sahu MK, Matheswaran MM, Bishnoi P (2021) Experimental study of thermal performance and pressure drop on a solar air heater with different orientations of arc-shape rib roughness. J Therm Anal Calorim 144:1417–1434. https://doi.org/10.1007/s10973-020-09569-z Sahu MK, Prasad RK (2016) Exergy based performance evaluation of solar air heater with arcshaped wire roughened absorber plate. Renew Energy 96:233–243. https://doi.org/10.1016/j. renene.2016.04.083 Saini SK, Saini RP (2008) Development of correlations for Nusselt number and friction factor for solar air heater with roughened duct having arc-shaped wire as artificial roughness. Sol Energy 82(12):1118–1130 Saravanakumar PT, Somasundaram D, Matheswaran MM (2019) Thermal and thermo-hydraulic analysis of arc-shaped rib roughened solar air heater integrated with fins and baffles. Sol Energy 180:360–371. https://doi.org/10.1016/j.solener.2019.01.036 Singh I, Singh S (2018) A review of artificial roughness geometries employed in solar air heaters. Renew Sustain Energy Rev 1(92):405–425 Singh AP, Varun S (2014a) Heat transfer and friction factor correlations for multiple arc shape roughness elements on the absorber plate used in solar air heaters. Exp Therm Fluid Sci 54:117– 126. https://doi.org/10.1016/j.expthermflusci.2014.02.004 Singh AP, Varun S (2014b) Effect of artificial roughness on heat transfer and friction characteristics having multiple arc shaped roughness element on the absorber plate. Sol Energy 105:479–493. https://doi.org/10.1016/j.solener.2014.04.007 Singh S, Chander S, Saini JS (2011) Heat transfer and friction factor correlations of solar air heater ducts artificially roughened with discrete V-down ribs. Energy 36(8):5053–5064 Singh S, Singh B, Hans VS, Gill RS (2015) CFD (computational fluid dynamics) investigation on Nusselt number and friction factor of solar air heater duct roughened with non-uniform cross-section transverse rib. Energy 1(84):509–517 Singh AP, Varun, Siddhartha (2014c) Heat transfer and friction factor correlations for multiple arc shape roughness elements on the absorber plate used in solar air heaters. Exp Therm Fluid Sci. 54:117–26 Singh AP, Varun, Siddhartha (2014d) Effect of artificial roughness on heat transfer and friction characteristics having multiple arc shaped roughness element on the absorber plate. Sol Energy. 105:479–93

72

R. Karir et al.

Soi A, Singh R, Bhushan B (2018) Heat transfer and friction characteristics of solar air heater duct having protruded roughness geometry on absorber plate. Exp. Heat Transfer 31(6):571–585. https://doi.org/10.1080/08916152.2018.1468832 Taslim ME, Li T, Kercher DM (1996) Experimental heat transfer and friction in channels roughened with angled, V-shaped, and discrete ribs on two opposite walls. J Turbomach. 118(CONF940626) Wang D, Liu J, Liu Y, Wang Y, Li B, Liu J (2020) Evaluation of the performance of an improved solar air heater with “S” shaped ribs with gap. Sol Energy 1(195):89–101 Xie Y, Shi D, Shen Z (2017) Experimental and numerical investigation of heat transfer and friction performance for turbine blade tip cap with combined pin-fin-dimple/protrusion structure. Int J Heat Mass Transf 104(104):1120–1134. https://doi.org/10.1016/j.ijheatmasstransfer.2016. 09.032 Yadav AS, Bhagoria JL (2013) Heat transfer and fluid flow analysis of solar air heater: A review of CFD approach. Renew Sustain Energy Rev 1(23):60–79 Yadav AS, Bhagoria JL (2013) A CFD (computational fluid dynamics) based heat transfer and fluid flow analysis of a solar air heater provided with circular transverse wire rib roughness on the absorber plate. Energy 15(55):1127–1142 Yadav AS, Bhagoria JL (2014) A CFD based thermo-hydraulic performance analysis of an artificially roughened solar air heater having equilateral triangular sectioned rib roughness on the absorber plate. Int J Heat Mass Transf 1(70):1016–1039 Yadav AS, Bhagoria JL (2014) A numerical investigation of square sectioned transverse rib roughened solar air heater. Int J Therm Sci 1(79):111–131

Performance Evaluation of Solar Air Heater Absorber Plate with Nanoparticles Coating Rahul Kumar, Sujit Kumar Verma, Amit Kumar Thakur, Abhishek Sharma, Tabish Alam, and Anil Singh Yadav

Abstract Nanoparticles have shown great potential in improving the performance of solar air heaters (SAH). The nanoparticles coating on the surface of the absorber plate improves thermal efficiency, heat transfer rate, and durability of SAH. The most common nanoparticles in SAHs are metal oxides, carbon, and metal. The current work focuses on enhancing SAH using nanomaterial coatings on the absorber plate. It is found that when graphene, copper oxide (CuO), and cerium dioxide (CeO2 ) nanoparticles are mixed into the black paint more heat is absorbed. The Reynolds number fluctuates depending on the mass flow rate and selective coating on the absorber plate. The experimental results show that graphene/CuO-black paint improves average thermal efficiency by 3.58%. Entropy generation is increased from 0.1557 to 0.8447 for black paint and lowest for black paint containing graphene/ CuO. Bejan’s number, around ~0.999, highlights the enhanced thermal performance of SAH. Keywords Absorber plate · Black paint · Entropy generation · Nanoparticles · Triangular solar air heater · Solar intensity R. Kumar (B) · A. K. Thakur School of Mechanical Engineering, Lovely Professional University, Phagwara 144001, Punjab, India e-mail: [email protected] S. K. Verma Department of Mechanical Engineering, GLA University, Mathura 281406, Uttar Pradesh, India A. Sharma Department of Mechanical Engineering, B I T Sindri, Dhanbad 828123, Jharkhand, India T. Alam Architecture, Planning and Energy Efficiency, CSIR-Central Building Research Institute, Roorkee 247667, Uttarakhand, India A. S. Yadav Department of Mechanical Engineering, Bakhtiyarpur College of Engineering (Science, Technology and Technical Education Department, Govt. of Bihar), Bakhtiyarpur, Patna 803212, Bihar, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Goyal et al. (eds.), Renewable Energy: Accelerating the Energy Transition, Energy Systems in Electrical Engineering, https://doi.org/10.1007/978-981-99-6116-0_5

73

74

R. Kumar et al.

Nomenclature L W N DH Cp air ηth ηex ηc σ m Ac Tp Tsur Ti Ts UL Ut Ue Qu εp , εg ka ha Sgen, Δt Sgen, Δp W1 mout p0 Sgen Sin x1 , x2 , x3 , and xn C I V E Fr F’ Be Ap Ae Pr Nu Ta

Length of triangular section Width of triangular section Number of glazing plate Hydraulic diameter of triangular section Coefficient of air at constant pressure Thermal efficiency Exergy efficiency Collector efficiency Steafan–Boltzman constant Mass flow rate of air Area of glazing plate Absorber plate temperature Surrounding temperature Air inlet temperature Sun temperature Overall heat coefficients Top loss coefficients Edge loss coefficients Inlet heat Emissivity of absorber plate and glass cover Thermal conductivity of back insulation Heat transfer coefficients of air Entropy at temperature diffrence Entropy at pressure difference Work at constant rate Mass flow rate at outlet Pressure at outlet Entropy generation Entropy at inlet Uncertainty parameters Solar constant value Solar intensity Velocity of air Efficiency factor Friction factor Heat removal factor Benjan number Area of absorber plates Area of edge surface Prandtl number Nusselt number Ambient temperature

Performance Evaluation of Solar Air Heater Absorber Plate …

To Re Ub Qu Hout min Ex,dest Pin So Hin Xb

75

Air outlet temperature Reynolds number Base loss coefficients Useful heat Enthalpy at outlet Mass flow rate at inlet Exergy destruction Pressure at inlet Entropy at outlet Enthalpy at inlet Back insulation thickness

Abbreviations AC CAS CFD SAH TEM TSAH XRD FPSC

Alternating current Chemical Abstracts Service Computational fluid dynamics Solar air heater Transmission electron microscopy Triangular solar air heater X-ray diffraction Flat plate solar collector

Greek Symbol α β μ τ ρo

Absorptivity Tilt angle Viscosity of air Transmitivity Density of air

1 Introduction Nanomaterial coatings refer to thin films of materials applied to a substrate using advanced manufacturing techniques such as chemical vapor deposition, atomic layer deposition, or spray pyrolysis (Khanlari et al. 2022). These coatings are composed of nanostructured materials, which have unique properties and can be designed to enhance the performance of a wide range of applications (Kumar and Kumar Verma

76

R. Kumar et al.

2022). Nanomaterial coatings offer several advantages over traditional coatings. These improve materials’ strength, durability, and wear resistance and enhance their optical, electrical, and thermal properties (Kumar and Verma 2021). For example, coatings made from carbon nanotubes enhance materials’ strength while reducing weight (Kumar et al. 2021). Similarly, nanomaterial coatings made from metal oxides improve materials’ resistance to corrosion and wear. Applications for nanomaterial coatings are diverse and include electronics, energy, aerospace, and biomedical fields to enhance the biocompatibility of medical implants (Xavier 2023; Singh et al. 2022; Bansal et al. 2022). The nanomaterial coatings are used to improve the efficiency of solar cells. The coatings can also enhance the wings’ aerodynamic properties, improve performance, and reduce drag and maintenance requirements (Abbasi et al. 2020). The application of nanomaterial coatings to aircraft wings is still an area of active research, and these coatings’ long-term performance and safety are still being evaluated (Musee et al. 2020). Nevertheless, the potential benefits of these coatings make them an exciting area of research for the aerospace industry. Notably, developing and applying nanomaterial coatings is a complex and evolving field, which is required to ensure that the coating is safe and effective. However, it is essential to note that the production and use of nanomaterial coatings also raise concerns about their vital effect on humans and environment. Hence, proper handling and disposal of these materials are necessary (Nguyen-Tri et al. 2019). Further, polymer-based coatings are used for flexibility and chemical resistance (Wang et al. 2023). Thermal coatings provide a range of benefits, including increased energy efficiency, reduced heat loss, and improved safety (El-Sebaii and Al-Snani 2010). It helps to extend the life of equipment by protecting it from the damaging due to high temperatures. Graphene nanomaterials are made up of small flakes or particles of graphene, typically ranging from a few nanometers to a few microns. Graphene nanomaterials have distinctive properties, such as excellent thermal conductivity, high electrical conductivity, and mechanical strength (Sethi et al. 2023). These properties make them attractive for diverse uses, including electronics, energy storage, biomedical devices, sensors, and water filtration. However, there are still challenges for large-scale production and cost-effective synthesis before use in various applications. An absorber coating is an essential component of a solar air heater (SAH), designed to absorb solar radiation and convert it into heat energy (Mishra et al. 2021). The absorber coating material has high absorptivities and low emissivities, such as black paint, selective coatings, or metal plates. The absorber coating aims to maximize the amount of solar radiation absorbed while minimizing the heat lost to the surrounding environment. Some commonly used absorber coatings for solar air heaters include: • Black paint: This is the simplest and cheapest absorber coating and works well for low-temperature applications. However, it has low thermal stability and can degrade over time. • Selective coatings: These coatings are designed to have a high absorptivity in the visible and near-infrared regions of the spectrum while having a low emissivity in the far-infrared region. This allows them to absorb more solar radiation while

Performance Evaluation of Solar Air Heater Absorber Plate …

77

minimizing heat loss. Examples of selective coatings include black chrome, black nickel, and black copper oxide. • Metal plates: These are often used in high-temperature applications because they have good thermal conductivity and can withstand high temperatures. However, they are expensive and heavy. The choice of absorber coating depends on the specific requirements of the SAH, including the temperature range, the amount of solar radiation available, and the desired efficiency (Yadav and Sharma 2022; Kumar et al. 2022a). A SAH is a renewable energy-based device that uses the sun’s energy to heat air and is used for space heating, ventilation, or drying. The basic principle behind a SAH is using a solar collector, typically made of a material with high thermal conductivity and solar radiation absorption, to capture the sun’s energy. The absorbed energy is transferred to air and circulated through the collector by natural convection or forced air flow using a fan. There are two main types of solar air heaters: glazed and unglazed. Glazed solar air heaters have a transparent cover, usually made of glass or plastic that allows solar radiation to enter the collector and traps heated air inside. Unglazed solar air heaters, on the other hand, have no cover and are typically made of a dark, heatabsorbing material that is exposed to the sun. However, the effectiveness of a solar air heater depends on various factors, including the location and orientation of the solar collector, the amount of solar radiation available, and the design and efficiency of the system. The current work investigates thermal efficiency, Bejan number, entropy generation, and exergy efficiency using graphene/copper oxide (CuO)/cerium dioxide (CeO2 ) nanoparticles with black paint. In this study, solar intensity, the mass flow rate of air, the ambient temperature of the fluid, and graphene/CuO/CeO2 nanoparticles with black paint coating on the absorber plate are variable parameter that gives the entropy generation, exergy efficiency, and evaluation the performance of triangular solar air heater (TSAH). On the other hand, the experimental results provide a better understanding of the graphene/CuO/CeO2 nanoparticles in black paint coating material for the absorber plate in the TSAH system.

2 Experimental Setup The experiment is carried out at solar research center of the Mechanical Engineering Department, GLA University, Mathura (India). Mathura is situated in an area with a high potential for solar intensity (Latitude and longitude coordinates are 27.49 and 77.67). The annual average solar intensity is ~4.55 kWh/m2 /day. Figure 5.1 shows a schematic diagram of TSAH, and the experimental setup is shown in Fig. 5.2.

78

R. Kumar et al.

Fig. 5.1 Schematic diagram of TSAH

The triangular section length, width, thickness, hydraulic diameter, and aspect ratio is 1 m, 0.6 m, 0.52 m; 0.35 m, and 1.15, respectively. The pipe length from input to output is constant. Thus, flow within triangle portion is assumed turbulent with no wall slide, and thermal characteristics remain constant throughout the test section. A blower draws air and pressure into the section’s intake at room temperature. K-type (Ni–Cr/Ni–Al) thermocouple measured the inlet and outlet temperature. The solarimeter measures solar radiation intensity on glazing plate at the same inclined plane. The micromanometer measured inlet and outlet pressure. A digital anemometer was used for air speed measurement. A control device is used at the output section to control the hot air output.

Performance Evaluation of Solar Air Heater Absorber Plate …

79

Fig. 5.2 Photograph of the experimental setup

The tests were performed on graphene and CuO/CeO2 nanoparticles coated absorber plates. Graphene accounts for 80% of the bulk of the hybrid nanomaterial, while CuO and CeO2 each make up 20%. Black paint containing nanoparticles was mixed using magnetic stirring. Black paint was initially doped with a fraction of graphene and CuO nanoparticles (Platonic Nanotech Private Limited, Jharkhand, India) to boost absorption and lower emissivity in the absorber plate. Graphene produced by chemical exfoliation is a black powder that is extremely fluffy and light.

3 Data Reduction 3.1 Thermal Efficiency and Exergy of TSAH The effectiveness of the solar heating system is crucial. The TSAH’s rate of useable heat (Qu ) can be written in terms of the system’s heat absorption and heat loss as (Kumar et al. 2022b) (5.1)

U L = Ut + Ub + Ue

(5.2)

⎞−1

⎛ ⎜ Ut = ⎝

Q u = Ac Fr [I(τ α) − U L (Tin − Ta )]

1⎟ ( )e + ⎠ C (T p −Ta) ha N

Tp

(N + f )

+





σ T p − Ta T p 2 + Ta 2 1 E p +0.00591N h a

+

2N + f −1+0.133∈ p ∈g



f = 1 + 0.089h a − 0.01166h a E p (1 + 0.07866N )

−N

(5.3)

(5.4)

80

R. Kumar et al.



100 e = 0.43 1 − Tp

(5.5)

C = 520[1 − (0.000051β 2 )] For 00 < β < 700

(5.6)

kb Xb Ae Ue = Ub Ac    ' −F U L A p mC ˙ pair FR = 1 − exp Ac UL mC ˙ pair Ub =

(5.7) (5.8)

(5.9)

The heat transferred from the surrounding air to the glass found by Verma et al. (2017), ha = 5.7 + 3.8V

(5.10)

m ˙ = ρo Ad V

(5.11)

ρo Vd μ

(5.12)

Cpair ka

(5.13)

Re =

Pr = m ˙ Nu =

3.66 + 0.0668(Dh /L)Re Pr 2

1 + 0.04[(Dh /L)Re Pr] 3

; Re ≤ 2800

(5.14)

Nusselt number correlation is used to determine the convective heat transfer as h= '

F =

Nu ka DH

(5.15)

h h + UL

(5.16)

The effectiveness of the triangle solar heating system is calculated as the output heat energy divided by the input heat energy (Yadav et al. 2022)   U L (To − Ti ) ηth = FR τ α − I The exergy efficiency of TASH is estimated by

(5.17)

Performance Evaluation of Solar Air Heater Absorber Plate …

mC ˙ pair

dT p dt

81

 + mC ˙ pair (To − Tin ) = ηc I Ac − Uc T p − Te Tc

   Ta m˙ in ϕin − m˙o ϕo = E˙ x,dest 1− Q˙ s − w˙ + Tsur

 Ta 1− ˙ o − h in ) − Ta (so − sin ) = E˙ x,dest Q˙ s − m(h Tsur Q˙ s = I (τ α) Ac ΔS = So − Sin = C pa ln

(5.18) (5.19) (5.20) (5.21)

Po To − RTa ln Tin Pin

(5.22)

To Po Ta ˙ I (τ α) Ac − mC ˙ pa (To − Tin ) + mC − m˙ RTa ln E x,dest = 1 − ˙ pa Ta ln Tsur Tin Pin (5.23) E˙ x,dest = Ta .Sgen ηex = 1 −

(5.24)

Ts E˙ x,dest (Ts − Ta ) Q˙ s

(5.25)

3.2 Analysis of Bejan Number The distorted exergy rate is the sum of the distorted exergy rate caused by the absorber plate’s temperature difference with the sun, the distorted energy rate caused by the triangular duct’s pressure drop, the distorted exergy rate caused by the air’s temperature difference with the absorber plate, and the distorted exergy rate caused by the air’s temperature difference with the absorber plate. The equations are described as (Farahat et al. 2009): E˙ d = E˙ d,ΔTs + E˙ d,ΔP + E˙ d,ΔTa

E˙ d,ΔP



1 1 − Tp Ts ( ) To ln T a Ta mΔP ˙ = ρ (To − Tin )

E˙ d,ΔTs = ηc I Ac Ta

(5.26)

(5.27)

(5.28)

82

R. Kumar et al.



To (To − Tin ) ˙ p Ta ln − E˙ d,ΔTa = mC Tin Tp



 Ta ˙ El = U L Ac T p − Ta 1 − Tp Be =

(5.29) (5.30)

S˙ gen,ΔT S˙ gen,ΔT + S˙ gen,Δp

(5.31)

W˙ l E˙ d E˙ l = (5.32) S˙ gen = Ta Ta



To 1 1 (To − Tin ) + mC ˙ p Ta ln − − S˙ gen,ΔT Ta = ηc I Ac Ta Tp Ts Tin Tp



 Ta (5.33) + U L Ac T p − Ta 1 − Tp

To (To − Tin ) ˙Sgen,Δp Ta = mC (5.34) ˙ p Ta ln − Tin Tp

3.3 Experimental Uncertainty Analysis Uncertainty analysis is essential for estimating the enhancement in experimental measurement and ensuring comprehensive, successful measurements of the experimental parameters. In this investigation, we classified the variables by how they were measured. Exergy efficiency, thermal efficiency, and entropy production are important in formative the first-type characteristics. Parameters of the second category include temperature, air mass flow rate, and sun radiation, all of which are measured. The instrument determines these values in a controlled environment. The uncertainty analysis is obtained as (Moffat 1988),  δηc =

n  ∂ηc

∂ xi

i=1

∂ηex = ηex 

∂ηc = ηc



∂I I

∂ Ts Ts

2

+

2

+

∂(Ts −Ta ) (Ts −Ta )

∂(Ti − Ta ) (Ti − Ta )

2

δxi

2 1/ 2 (5.35)

2 ˙ 2 1/ 2 ˙ ∂ E x,dest ∂ Qs + + E˙ x,dest Q˙ s

2

+

∂(τ α) (τ α)

2

+

∂U L UL

2

+

(5.36)

 ∂ FR 2 FR (5.37)

Performance Evaluation of Solar Air Heater Absorber Plate …

∂ Sgen = Sgen





1/2 ∂ E˙ x,dest ∂ Tα 2 + Tα E˙ x,dest

83

(5.38)

The error estimate for dependent parameters may be used to assess the uncertainty of the second kind of parameter using the following relation: 1/2  W = (x1 )2 + (x2 )2 + (x3 )2 + . . . . . . . . . . . . . . . . . . . . . . . . . . . . + (xn )2 (5.39)

4 Results and Discussion The efficiency and exergy of an absorber plate coated with varying amounts of graphene, CuO, and CeO2 nanoparticles were analyzed. The ASHRAE standards were followed for TSAH experiment measurement and analysis. Each set of experimental observations was spaced out by 10 min to keep steady-state conditions. There were five sets of observations used to reduce the error margin. Thermal efficiency, exergy efficiency, and entropy production characterize TSAH’s performance. The relationship between TSAH’s thermal efficiency and mass flow rate is shown in Fig. 5.3. Each absorber plate coating material’s absorption coefficient was calculated for a fixed solar intensity (I = 800 W/m2 ) and ambient temperature (Ta = 289 K). Maximum thermal efficiency was attained when the air mass flow rate was 0.01847 kg/s. Considering the highest mass flow rate, it is evident that the average thermal efficiency of the graphene/CuO-black paint is 4.91% greater than that of the 0.1% graphene-black paint. The experimental results showed that the thermal efficiency improves across the board when the air mass flow rate is increased. As a result, at larger mass flow rates, the absorber plate loses heat to the surrounding air when turbulence inside the test section increases. Hence, it improves thermal efficiency by decreasing heat loss to the environment. Figure 5.4 depicts the exergy efficiency of TSAH versus mass flow rate at various absorber plate coating for I = 800 W/m2 and Ta = 289 K under controlled conditions. Increases in both mass flow rate and exergy efficiency are inefficient. Exergy efficiency ranges from 69.62 to 72.36% depending on the amount of absorber coating used at m of 0.01847 kg/s. By comparing graphene/CeO2 black paint to graphene/ CuO-black paint, the exergy efficiency concurrently improves while simultaneously decreasing with increasing air mass flow rate. Loss of heat energy at a greater mass flow rate increases the rate of entropy formation, as shown by the exergy destruction equation. Since entropy formation reduces exergy, energy efficiency decreases as the mass flow rate increases. With a fixed I (800 W/m2 ) and Ta (289 K), Fig. 5.5 displays the relationship between entropy generation and mass flow rate. The least amount of entropy production increases thermal efficiency in a thermal system. The rate at which entropy is

84

Fig. 5.3 Thermal efficiency as a function of mass flow rate

Fig. 5.4 Exergy efficiency variation with mass flow rate

R. Kumar et al.

Performance Evaluation of Solar Air Heater Absorber Plate …

85

Fig. 5.5 Entropy generation fluctuation as a function of mass flow rate

created is proportional to the mass flow rate of the air. The heat transfer rate and pressure drop between the inlet and outlet sections are reflected in the entropy produced. Since the coating of the absorber plate with graphene and CuO nanoparticles into black paint increases the surface area of the absorber plate and the heat transfer rate, the entropy generation is inferior for graphene/CuO-black paint than for graphene/ CeO2 -black paint for the equal mass flow rate. A plot of entropy production as a function of solar intensity for a range of absorber plate coatings and a fixed m of 0.01099 kg/s is presented in Fig. 5.6. Entropy production is inversely proportional to sun intensity, temperature differential, and pressure drop between input and output of the system. The absorber plate heats up when the sun shines, causing a temperature difference in input/output with a pressure drop. As a result, the TSAH as a whole generates less entropy. Figure 5.7 displays the relationship between the Bejan number and the mass flow rate for various absorber plate coatings when I = 900 W/m2 and Ta = 292 K are constant. Bejan number explains exergy efficiency and entropy production rate phenomena more deeply. The air mass flow rate and the absorber plate’s graphene and copper oxide layer have a role. The Bejan number drops with increasing air mass flow rate. Heat is transferred from the absorber plate to the air. Combined entropy is generated due to the air movement within the TSAH and the temperature differential between absorber plate and air, as shown by Bejan number (Eq. 5.31). Permanent heat transfer becomes a significant factor at larger air mass flow rates, lowering Bejan number, because graphene/CuO-black paint has better thermal conductivity and convective heat transfer coefficients than graphene-black paint. The relationship between ambient temperature and thermal efficiency with mass flow rate for a range of absorber plate coatings and a fixed mass flow rate of m is

86

R. Kumar et al.

Fig. 5.6 Entropy generation fluctuation with solar intensity

Fig. 5.7 Bejan number variation versus mass flow rate at various absorber plate coating

Performance Evaluation of Solar Air Heater Absorber Plate …

87

Fig. 5.8 Variation of mass flow rate as a function of ambient temperature and efficiency

0.07294 kg/s is presented in Fig. 5.8. The ambient air temperature rises with the sun’s intensity, reducing thermal efficiency. As a result, the TSAH loses some of its thermal efficiency. There is no roughness on the absorber plate, so the air has less time to interact with the surface, resulting in a lower heat transfer rate. As a result, the air temperature and sun intensity at the point of entry are both raised, and thermal efficiency is reduced for every scenario. Nusselt number and air friction factor as a function of Reynolds number for a range of TSAH absorber plate coatings are plotted in Fig. 5.9. The Nusselt number and the friction factor increase with the Reynolds number. The heat transmission at a boundary layer close to the absorber plate is demonstrated using the Hausen equation of Nusselt number (Eq. 5.14). The main flow contact with the absorber plate is enhanced, and the heat transfer rate increases with an increase in Reynolds number. As a result, the Nusselt number might become quite sensitive to the Reynolds number. There is a negative relationship between the Reynolds number and the friction coefficient. When the Reynolds number increases, the friction factor drops. Because of friction, the boundary layer is broken, which decreases the separation loss in the flow. Figure 5.10 depicts the relationship between exit temperature and thermal efficiency with air velocity. When heat transmission from the absorber plate to the air decreases with increasing air velocity, the exit temperature drops while thermal efficiency rises.

88

R. Kumar et al.

Fig. 5.9 Nusselt number (Nu) and friction factor variation versus Reynolds number (Re)

Fig. 5.10 Thermal efficiency and output temperature variation with air velocity

The air temperature with TSAH duration is depicted graphically in Fig. 5.11. The air gets hotter as its temperature rises in proportion to the length of the triangle part. The absorber plate and the incoming cold air have a significant temperature differential at the intake. When the length of a solar air heater is increased, the

Performance Evaluation of Solar Air Heater Absorber Plate …

89

Fig. 5.11 Changes in air temperature versus TSAH length

temperature gradient decreases because more heat is transferred from the absorber plate to the air. Graphene/CuO-black paint caused the greatest rise in air temperature, whereas graphene/CeO2 -black paint on an absorber plate caused the least rise in temperature.

5 Conclusions and Future Scope The influence on TSAH’s thermal efficiency, exergy efficiency, entropy production, and Bejan number was tested experimentally in this study. Graphene/CuO-black paint was more exergy efficient than standard black paint. With a solar intensity of I = 800 W/m2 , graphene/CuO-black paint has an average exergy efficiency increase of 4.39% compared to graphene-black paint. The entropy generation varies from 0.1557 to 0.8447 W/K, with the highest value in graphene/CeO2 -black paint and the lowest in graphene/CuO-black paint. Because the Bejan number for graphene/ CuO-black paint was 0.999, the highest of any coating, TSAH system improves the coating’s performance, making it more effective at transforming solar energy into meaningful work. The Reynolds number and heat transfer coefficients increase with a direct proportion to the flow rate. For a given selective coating on the absorber plate and mass flow rate, the Reynolds number can range from 4500 to 22,700. This experimental study found that the thermal and exergetic performance of a solar air heating system can be significantly improved by selected coatings and

90

R. Kumar et al.

a redesigned system. There is room for improvement in design iterations, selective coating designs, hybrid phase change material implementation, and obstruction (insert) design to increase the working fluid temperature. The prospects of SAHs are encouraging due to the vast requirement for clean and sustainable energy sources. Here are some potential areas where further developments and trends in solar air heaters can be carried out: • Advancements in technology: There is ongoing research and development in materials science, nanotechnology, and manufacturing techniques that could lead to more efficient and cost-effective solar air heaters. For example, new types of selective coatings or composite materials could improve the performance of solar collectors. • Integration with building design: Architects and engineers are increasingly incorporating solar air heaters into building design to reduce energy consumption and carbon emissions. This trend will continue as building codes and regulations prioritize energy efficiency and sustainability. • Increased adoption in emerging economies: Solar air heaters could play a significant role in providing affordable and clean energy for heating and ventilation in developing countries, especially in areas where access to electricity or traditional heating methods is limited. • Innovative applications: Solar air heaters could be used for various applications beyond heating and ventilation, such as crop drying, water heating, or industrial processes. • Growth of the renewable energy sector: As the global demand for renewable energy continues to grow, solar air heaters will likely become an increasingly important component of the overall mix of renewable energy technologies. • Overall, the future of solar air heaters looks bright as they offer a clean, affordable, and sustainable energy source for heating and ventilation and can potentially improve the lives of people around the world.

References Abbasi S, Peerzada MH, Nizamuddin S, Mubarak NM (2020) Functionalized nanomaterials for the aerospace, vehicle, and sports industries. Handb Funct Nanomater Ind Appl, Elsevier, pp 795–825 Bansal K, Kumar R, Mishra SK, Kumar P, Sharma A (2022) Validation and CFD modeling of solar still with nanoparticle coating on absorber plate. Mater Today Proc El-Sebaii AA, Al-Snani H (2010) Effect of selective coating on thermal performance of flat plate solar air heaters. Energy 35:1820–1828 Farahat S, Sarhaddi F, Ajam H (2009) Exergetic optimization of flat plate solar collectors. Renew Energy 34:1169–1174 Khanlari A, Tuncer AD, Sözen A, Aytaç ˙I, Çiftçi E, Variyenli H˙I (2022) Energy and exergy analysis of a vertical solar air heater with nano-enhanced absorber coating and perforated baffles. Renew Energy 187:586–602

Performance Evaluation of Solar Air Heater Absorber Plate …

91

Kumar R, Kumar Verma S (2022) Performance estimation of triangular solar air heater roughened absorber surface: an experimental and simulation modeling. Sustain Energy Technol Assess 52:102208. https://doi.org/10.1016/J.SETA.2022.102208 Kumar SK Verma (2021) Review based on the absorber plate coating for solar air heater applications. IOP Conf Ser Mater Sci Eng IOP Publishing, p 12053 Kumar R, Verma SK, Singh M (2021) Experimental investigation of nanomaterial doped in black paint coating on absorber for energy conversion applications. Mater Today Proc 44:961–967 Kumar S, Das RK, Kulkarni K (2022a) Comparative study of solar air heater (SAH) roughened with transverse ribs of NACA 0020 in forward and reverse direction. Case Stud Therm Eng 34:102015 Kumar R, Verma SK, Mishra SK, Sharma A, Yadav AS, Sharma N (2022b) Performance Enhancement of solar air heater using graphene/cerium oxide and graphene-black paint coating on roughened absorber plate. Int J Veh Struct Syst 14:273–279 Mishra SK, Kumar R, Joshi R, Kumar H, Saxena N (2021) Experimental investigation, exergy analysis, and CFD simulation of solar air heater roughened with artificial V-shaped Ribs on absorber surface artificial roughness on absorber plate, pp 235–252. https://doi.org/10.1007/ 978-981-16-0235-1_20 Moffat RJ (1988) Describing the uncertainties in experimental results. Exp Therm Fluid Sci 1:3–17 Musee N, Leareng S, Kebaabetswe L, Tubatsi G, Mahaye N, Thwala M (2020) Implications of surface coatings on engineered nanomaterials for environmental systems: status quo, challenges, and perspectives. Handb Funct Nanomater Ind Appl 399–416 Nguyen-Tri P, Tran HN, Plamondon CO, Tuduri L, Vo D-VN, Nanda S, Mishra A, Chao H-P, Bajpai AK (2019) Recent progress in the preparation, properties and applications of superhydrophobic nano-based coatings and surfaces: a review. Prog Org Coatings 132:235–256 Sethi M, Tripathi RK, Bhardwaj P, Kumar M, Thakur G, Kumari A, Hasan M, Verma M (2023) Review of the impact of nanomaterial on the thermal efficiency of an evacuated tube solar air heater. Mater Today Proc Singh SK, Verma SK, Kumar R, Sharma A, Singh R, Tiwari N (2022) Experimental analysis of latent heat thermal energy storage system using encapsulated multiple phase-change materials. Proc Inst Mech Eng Part E J Process Mech Eng 09544089221110983 Verma SK, Tiwari AK, Chauhan DS (2017) Experimental evaluation of flat plate solar collector using nanofluids. Energy Convers Manag 134:103–115 Wang Y, Wang C, You Y, Cheng W, Dong M, Zhu Z, Liu J, Wang L, Zhang X, Wang Y (2023) Analysis on thermal stress of optimized functionally graded coatings during thermal shock based on finite element simulation. Mater Today Commun 35:105699 Xavier JR (2023) Multifunctional nanocomposite coatings for superior anticorrosive, flame retardant and mechanical properties in aerospace components. Surf Interf 102832 Yadav AS, Sharma A (2022) Experimental investigation on heat transfer enhancement of artificially roughened solar air heater. Heat Transf Eng 1–14 Yadav AS, Alam T, Gupta G, Saxena R, Gupta NK, Allamraju KV, Kumar R, Sharma N, Sharma A, Pandey U (2022) A numerical investigation of an artificially roughened solar air heater. Energies 15:8045

CFD Investigation of Solar Air Heater Roughened with Transverse Discontinuous Trapezoidal Ribs Sarvapriya Singh, Mokshaa Sharma, Santanu Mitra, and Manish Kumar

Abstract A three-dimensional Computational Fluid Dynamics (CFD) analysis was conducted to examine the thermal and hydraulic characteristics of a solar air heater featuring transverse ribs for surface roughness. These transverse ribs possess a trapezoidal cross-section and are positioned in a non-continuous manner. The study also includes an investigation into transverse continuous ribs with similar cross-sections. A comparative analysis was carried out, comparing discontinuous ribs to continuous ribs to gain insights into fluid flow characteristics. The research explores gap width (g) and discontinuous width (w) sizes across a range of Reynolds numbers spanning from 5000 to 24,000, with variations in gap and discontinuous width sizes between 7.5–12.5 mm and 20–50 mm, respectively. To ensure the accuracy of the numerical investigation, validation was conducted on both smooth and roughened ducts to select the appropriate turbulence model. The RNG k-ε turbulence model with enhanced wall treatment was selected. The study further delves into the reasons why the solar air heater exhibits superior performance when equipped with discontinuous ribs as opposed to continuous ribs. Consequently, the preference for discontinuous ribs arises from their ability to significantly reduce pressure drop penalties, making them a favorable choice over continuous ribs. Keywords Computational Fluid Dynamics · Nusselt number · Trapezoidal ribs · Discontinuous ribs · Thermo-hydraulic performance factor

S. Singh · M. Sharma · S. Mitra Department of Mechanical Engineering, Shiv Nadar Institute of Eminence (Deemed to be University), Tehsil Dadri, UP 201314, India M. Kumar (B) Department of Mechanical Engineering, Malaviya National Institute of Technology Jaipur, Jaipur, Rajasthan 302017, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Goyal et al. (eds.), Renewable Energy: Accelerating the Energy Transition, Energy Systems in Electrical Engineering, https://doi.org/10.1007/978-981-99-6116-0_6

93

94

S. Singh et al.

1 Introduction Energy efficiency has been widely regarded as how efficient and optimized use of sustainable resources can enhance the diurnal applications of everyday resources. Efficiently utilizing thermal energy from solar rays has been at the forefront of this avenue. Research in this aspect has yielded solar air heaters (SAH), which have direct applications in space heating for commercial and residential applications. Therefore, instilling the ribs on the wetted surface of the absorber plate is widespread practice regarded as a passive technique to improve the efficiency of SAH (Suman et al. 2015). Adding ribs to the absorber plate promotes adequate heat transfer enhancing the heat transfer through the plate. The ribs generate turbulence, which extends the convective heat transfer, although supplementing to frictional losses, which entail higher pumping power. Thus, to circumvent significant pumping power needs, methods to establish turbulence in the viscous sublayer only close to the surface of the absorber plate are the principal focus. Hence, discontinuous ribs are installed on the absorber plate roughened with a trapezoidal cross-section having a height most likely equal to the viscous sublayer thickness to keep pressure drop minimum across the test section (Verma and Prasad 2000). Instilling the ribs underneath an absorber plate surface is a popular way of disturbing the viscous sublayer region. Disturbance in viscous sublayer region creates turbulence at the absorber plate interface, which results in more heat transfer. Since the cylindrical ribs are easy to fabricate and simple in design, the earliest investigation was started by installing the transverse cylindrical ribs in tiny wires. Prasad and Mullick (1983) incorporated the small protrusion wires on the wetted absorber plate surface. The protruding wires improved the heat transfer to the flowing fluid. The plate efficiency was improved by 14 % at Re = 40,000. However, the maximum improvement in the plate efficiency was observed at a lower Reynolds number. Prasad and Saini (1988) also protruded the small diameter wires as artificial roughness to roughen the rectangular duct. The effects of roughness height and longitudinal pitch were investigated to observe the impact on thermo-hydraulic performance. The correlations for Nusselt number and friction factor were developed in terms of relative roughness height (e/Dh ), relative roughness pitch (P/e), and Reynolds number (Re). Hence, it was concluded from the investigation that the geometric parameter’s dimensions are crucial for the optimum thermo-hydraulic performance of a roughened SAH. Gupta et al. (1993) also instilled the cylindrical transverse wires on the wetted surface of the absorber plate. The effect of the aspect ratio (W/H) of rectangular cross-section on heat transfer and fluid flow characteristics in transitionally rough flow region is investigated along with different values of e/Dh and Re for a fixed value of P/e = 10. They observed that the rectangular duct’s aspect ratio plays a minimum role in heat transfer enhancement. The reported correlations were observed to be conformal with the experimental values. Verma and Prasad (2000) investigated with small diameter wires to achieve the optimum thermo-hydraulic performance. They observed that the rib roughness height should not exceed the viscous sublayer thickness to get the optimal performance of SAHs. Apart from the transverse cylindrical ribs, other

CFD Investigation of Solar Air Heater Roughened with Transverse …

95

configurations of artificial ribs are also investigated, such as repeated chamfered ribs (Karwa et al. 1999), transverse wedge-shaped (Bhagoria et al. 2002), and transverse rectangular ribs (Cavallero and Tanda 2002; Karwa 2003). The heat transfer rate was observed to be augmented with these configurations of the ribs, but the obstruction also rises significantly, resulting in more pressure drop. To circumvent the problem of pressure drop rise, the discontinuous ribs have started investigating. Discontinuous ribs have different cross-sectional ribs, such as interrupted transverse rectangular ribs (Cavallero and Tanda 2002), V-discrete (Karwa 2003), and transverse and V-shaped broken ribs (Tanda 2004) which are investigated experimentally. It was observed from the investigation of discontinuous ribs that the friction factor values had decreased immensely. Furthermore, the circulated fluid particles can move freely through the path provided in the discontinuous ribs. In addition, more studies have been carried out with discontinuous ribs having different configurations to get the advantage of less friction factor. Aharwal et al. (2008) arranged square cross-sectional split ribs with gaps inclined to the flowing fluid for conducting an experimental investigation. They observed that the opening in the inclined ribs enhances the heat transfer rate while reducing friction factor values. Similarly, discrete V-down ribs (Singh et al. 2011), multiple V-shaped with gaps (Kumar et al. 2013), broken arc ribs with a staggering piece (Gill et al. 2017a), broken arc ribs (Hans et al. 2017), V-shaped ribs with the symmetrical opening (Maithani and Saini 2016), transverse multiple broken ribs (Singh et al. 2019), broken arc ribs (Gill et al. 2017b), novel broken V-shaped ribs (Singh Patel and Lanjewar 2019), broken arc shape, and V-shaped (Srivastava et al. 2020) were investigated by researchers. The above succinct literature review suggests that most investigations are conducted experimentally, and only very few are investigated numerically (Gill et al. 2017a, b; Srivastava et al. 2020; Singh et al. 2019). Therefore, it is a dire need to perform a numerical analysis with a lot more configurations of ribs. The reasons behind an augmentation of heat transfer rate in discontinuous ribs conducted experimentally are only speculations. However, detailed information could be gained with the numerical investigation of a roughened SAH. Hence, this article presents the numerical investigation performed with discontinuous ribs having trapezoidal cross-sections to get the maximum THPF supported by the insight details.

2 CFD Investigation The numerical investigation is conducted in commercial software named ANSYS Fluent research R21. The study mainly aims to get insight into fluid flow characteristics of roughened SAH with discontinuous ribs.

96

S. Singh et al.

Fig. 1 The schematic of computational fluid domain used for CFD investigation

2.1 Geometry The computational fluid domain used for the numerical investigation is presented in Fig. 1. The aspect ratio of a rectangular duct is considered to be twelve. The computational fluid domain is made in the ICEM CFD package. The test section consists of a collector plate which has a length (L 2 ) of 1000 mm. Trapezoidal ribs are fixed on the underside surface of a collector plate. The ribs are instilled perpendicular to the absorber plate. The gap in the discontinuous trapezoidal ribs is denoted by the letter ‘g’. The width of the discontinuous ribs is represented by the letter ‘w’. The discontinuous ribs are arranged in line beneath the absorber plate. A constant heat flux of 1000 W/m2 is supplied on the top surface of the collector plate. The geometric details of roughened duct are provided in Table 1.

Fig. 2 Fluid domain discretization with different grid resolutions

CFD Investigation of Solar Air Heater Roughened with Transverse …

97

Table 1 Geometric dimensions of a duct used for CFD simulation Parameters

Values

Duct width (W )

300 mm

Aspect ratio (W/H)

12

Hydraulic diameter (Dh )

46.154 mm

Rib height (e)

2 mm

Relative roughness pitch (P/e)

8

Discontinuous rib width (w)

20–50 mm

Gap width (g)

7.5–12

2.2 Discretization of Domain The computational fluid domain is divided into small volumes for the CFD analysis. The governing equations are solved at the centroid of these discretized volumes. The discretization is done with such fine meshes are ensured near the walls where the viscous sublayer region is predominant. The first layer thickness is calculated based on y+ ~1. The fluid domain division with different grid resolutions is illustrated in Fig 2.

2.3 Solver Setting The numerical analysis of the current domain is carried out with a pressure-based solver in double precision. The absolute velocity component solves the steady-state 3D governing equations in ANSYS Fluent research R21. The periodic boundary conditions are used to get the numerical results, and the procedure to activate the periodic boundary conditions may be referred from this article (Singh et al. 2022). The thermo-physical property values are given in Table 2 for the absorber plate and the flowing fluid at Pr = 0.71 (Singh et al. 2021). The air is assumed incompressible as little change is observed in density at the mean fluid temperature throughout the analysis. The numerical analysis is done for Re ranges from 5000 to 24,000. The mass flow rate corresponding to these Re values is calculated from 0.0151 to 0.072 kg/s. These values are provided at the periodic inlet wall. The outlet is permanently deleted after the execution of the TUI command and behaves as the shadow of the inlet. A SIMPLE scheme is selected to solve the pressure–velocity coupling (Patankar 1980). Other components are solved with a second-order upwind scheme. Absolute criteria for convergence check are 10–5 , 10–6 , and 10–8 for mass, velocities, and energy, respectively.

98

S. Singh et al.

Table 2 Thermo-physical properties of an absorber plate and working fluid Properties

Aluminum

Air

Density (ρ)

2719 kg/m3

1.165 kg/m3

Dynamic viscosity (μ)

–

1.8566 × 10–5 N/m2 -s

Specific heat (Cp )

871 J/kg-K

1006.96 J/kg-K

Thermal conductivity (k)

202.4 W/m–K

0.0264 W/m–K

2.4 Governing Equations The following governing equations are used to solve the discretized fluid domain in 3D. Conservation of mass equation: ∂ (ρu i ) = 0 ∂ xi

(1)

Momentum equation: ∂ (ρu i u j ) ∂ xi    ∂u j ∂u i ∂ ∂ 2 ∂u l ∂p μ + + + − δi j (−ρu  l u  j ) =− ∂x j ∂x j ∂x j ∂ xi 3 ∂ xl ∂x j

(2)

where the Reynolds stresses are calculated using the Boussinesq hypothesis as,  −ρu 

l

u

j

= μt

∂u j ∂u i + ∂x j ∂ xi



  2 ∂u k − δi j ρk + μt + 3 ∂ xk

(3)

where μt = ρCμ k2 /ε is the turbulent viscosity, k is turbulent kinetic energy, and ε is the turbulent dissipation rate. Energy equation: ∂ ∂T ∂ ∂ ( pu i ) + (ke f f ) (ρeu i ) = − ∂ xi ∂ xi ∂ xi ∂ xi where e = h −

p ρ

+

V2 2

is specific internal energy.

(4)

CFD Investigation of Solar Air Heater Roughened with Transverse …

99

Fig. 3 Roughen duct validation for Nu against Re

2.5 Turbulence Model Selection Since there is no universal turbulence model that can solve all the problems in the field of science and engineering, therefore, validation is conducted for a roughen duct with transverse cylindrical ribs attached beneath the absorber plate. The correlations are developed by Gupta et al. (1993) regarding W/H, e/Dh , and Reynolds number for a fixed value of P/e = 10. The cylindrical ribs having e = 1.25 mm at P/e = 10 are chosen to validate the Nu and f . Figure 3 represents the roughen duct validation for the Nu as a function of Reynolds number for W/H = 10. The experimental values are plotted with the error provided in the article. The numerical values are found conformal to the experimental values within the range. RNG k-ε turbulence model with enhanced wall treatment is used to get the numerical values from CFD analysis. Likewise, Fig. 4 shows the f values validation against the Reynolds number ranging from 3000–18,000. It is observed from Fig. 4 that the f value is deviating far at Re = 3000. It is happening because the flow in the duct at Re = 3000 is still in the transition zone, and it would be challenging to get the exact value with the turbulence model used for the analysis. Again, the validation of friction factor values shows that the results match the experimental values.

2.6 Grid Sensitivity Analysis Since the numerical results are believed to be the function of grid resolutions. Thus, it is an important exercise to conduct the grid sensitivity test before proceeding toward the results extraction. Figure 5 illustrates the grid sensitivity analysis for different grid resolutions. The number of grids are ranged from 490,931 to 2,120,244. The

100

S. Singh et al.

Fig. 4 Roughen duct validation for f against Re

finer meshes are ensured near the walls where the viscous sublayer region is supposed to be predominant. Figure 5 shows the Nu and f values variation on increasing the number of nodes. It is observed that the values are changing on increasing the grid resolutions. Less than 1 % change in two consecutive values is the criterion for selecting the number of nodes for the numerical analysis. The change in the Nu and f values are observed to be less than 1 % after the third grid resolution with two consecutive grid resolutions. Hence, the grid size equal to 1,685,600 is selected for further analyses in the present study. The first cell thickness value calculated based on y + ~1 in the grid sensitivity analysis is further used to discretize the fluid domain with discontinuous ribs. As the fluid domain area is increased with the discontinuous ribs compared to the fluid domain with continuous ribs, the number of nodes increases slightly more than the 1,685,600.

3 Procedure to Calculate Thermal Performance The mass flow rate at inlet is defined by, m˙ = ρ Ac v

(5)

The velocity at inlet is calculated by, Re =

ρv Dh μ

The hydraulic diameter defined at inlet is,

(6)

CFD Investigation of Solar Air Heater Roughened with Transverse …

101

Fig. 5 Grid sensitivity test

Dh =

4 Ac Pwetted

(7)

The overall heat absorbed by the flowing fluid between inlet and outlet is calculated by, Q u = mc ˙ p (To − Ti )

(8)

The convective heat transfer near the collector plate is defined by, Q c = h A p (Tw − Tm )

(9)

Hence,  h=

h Ad A A

(10)

h Dh kair

(11)

The Nusselt number is calculated by, Nu =

The friction factor in a duct is calculated by, f =

)Dh ( P l 2ρv 2

(12)

102

S. Singh et al.

The THPF is defined by,

N ur N us



T H PF = 1 3

(13)

fr fs

4 Results and Discussion Parametric optimization of the discontinuous ribs with trapezoidal cross-section attached beneath the absorber plate surface is carried out for the optimal values’ gap width (g) and discontinuous width size (w). The optimum values are decided for maximum THPF as this factor incorporates both the desired parameters of the current study.

4.1 Parametric Optimization of Discontinuous Ribs It is concluded from the experimental study conducted with discontinuous ribs that the gap width size (g) and discontinuous width size (w) play a significant role in augmenting the thermal performance of a roughened SAH. Figure 6 represents the variation of Nu against Re for different sizes of the discontinuous ribs. The discontinuous rib results are compared with the smooth and roughened duct having continuous ribs. The discontinuous rib results are represented as g × w mm. It is found from Fig. 6 that the Nu values are increasing on increasing the Re values. The Re is varied from 5000 to 24,000. The discontinuous rib values are first seen to be less than the continuous rib values till Re = 18,000. However, discontinuous rib values surpass the continuous rib value afterward for the combination of the 10 × 40 mm and 10 × 50 mm. This happened because the heat transfer area decreased with the discontinuous ribs compared to the continuous ribs. However, the high-stream fluid particles compensate for this at a higher Reynolds number. Hence, it is concluded from the Nu variation against Re that a discontinuous rib with a combination of 10 × 40 mm and 10 × 50 mm is optimal for the highest Nusselt number values. The temperature contours are extracted from CFD analysis to understand the reason behind augmentation of Nu values. Figure 7 represents the temperature contours at the collector plate for the continuous and optimized combination of the discontinuous rib. It is observed from the temperature contours that temperature hotspots were forming in front of the continuous ribs because of the obstruction produced in the fluid domain. This obstruction eases down with the help of the gaps provided in the discontinuous ribs where the circulated fluid is passing freely with high streams through the gap and mixing with the less momentum fluid particles.

CFD Investigation of Solar Air Heater Roughened with Transverse …

103

Fig. 6 Variation in Nu values as a function of Re

Lower temperature values are observed in the gaps at the absorber plate means more heat is transfered to the fluid flow domain. Fig. 7 Temperature contours at the absorber plate

104

S. Singh et al.

It is said that the gaps provided in the discontinuous ribs are helping in augmenting the heat transfer from the collector plate. Thus, the temperate hotspots are distributed with the gaps provided in the discontinuous ribs compared to the continuous rib. In addition, the velocity contours are plotted for a continuous and optimized set of the discontinuous rib to better understand the fluid flow characteristic. Figure 8 illustrates the velocity contours at 1 mm below the absorber plate. It is seen from the velocity contour for a continuous rib that the fluid particles have zero momentum on both sides of the rib as they interact with the fixed continuous rib. This implies that the fluid particles near the absorber plate are stuck on both sides of the rib, reducing the heat transfer from the collector plate. Figure 9 represents the variation of f values against Re for continuous and discontinuous ribs. Therefore, it is necessary to disturb these stuck particles from the vicinity of the absorber plate. It has been carried out by providing the gap in the discontinuous ribs resulting in a turbulence increase. The fluid particles in the discontinuous ribs easily pass through the gaps and induce a high stream of fluid particles from the gaps. These high-stream fluid particles mix with the circulated fluid particles and enhance the momentum of the fluid particle. The f values diminish on increasing Re for smooth, continuous, and discontinuous ribs. This is owing to the reduction in the viscous sublayer thickness with an increase in the Re. Further, f values for discontinuous ribs are observed to be less in comparison with continuous ribs. This happened Fig. 8 Velocity contours at 1 mm below the absorber plate

CFD Investigation of Solar Air Heater Roughened with Transverse …

105

Fig. 9 Variation in friction factor values as a function of Re

due to the space provided in the discontinuous ribs for freely flowing the fluid with less obstruction. Moreover, f values are diminishing more with the large gap width. Since the THPF factor incorporated the Nu gain and the f loss, it is exciting to see the effect of the discontinuity in calculating this factor. In order to sum up the gains observed with the discontinuous ribs, THPF is calculated for all the combinations of discontinuous ribs and compared with the continuous ribs and smooth duct. Fig. 10 represents the changes in THPF values against Re. Figure 10 depicts that the THPF values are decreasing with an increase in Re for all investigated combinations of ribs. The THPF values are found to be maximum at Re = 5000 for continuous and discontinuous ribs. Nevertheless, the THPF values with discontinuous ribs surpass the continuous rib THPF after Re = 5000. This is Fig. 10 Variation in THPF values as a function of Re

106

S. Singh et al.

happening owing to an increase in fluid particles’ momentum on increasing the Re values passing through the gaps. This leads to more turbulence near the collector plate and transfers more heat from the collector plate to the flowing fluid. It is concluded from Fig. 10 that the discontinuous ribs with a combination of 10 × 40 mm and 10 × 50 mm are found to be the optimal case for maximum THPF except Re = 5000. In order to understand more about the reason for higher THPF values with the discontinuous ribs, Figs. 11 and 12 represent the turbulent kinetic energy and turbulent intensity contours drawn at the mid-plane normal to the absorber plate. The high intensity in both contours is observed near the absorber plate. Instilling the discontinuous ribs near the absorber plate distributes the intensity to the core of the fluid flow. This is the reason for enhancing the heat transfer from the collector plate to the flowing fluid resulting in an increased local convective heat transfer coefficient. It is further found that the peak of the turbulent kinetic energy and turbulent intensity starts developing near the sharp surface of the discontinuous ribs. It means the fluid flow turbulence is generated continuously from the discontinuous ribs surface. Hence,

Fig. 11 Turbulent kinetic energy contours at mid-plane perpendicular to the absorber plate

CFD Investigation of Solar Air Heater Roughened with Transverse …

107

Fig. 12 Turbulent intensity contours at mid-plane perpendicular to the collector plate

it is concluded that more turbulence is observed in discontinuous ribs compared to continuous ribs.

5 Conclusions CFD results are represented in this article by instilling the discontinuous ribs compared to the continuous ribs with similar trapezoidal cross-section. The simulations are performed in commercial software named ANSYS fluent R21. The gap width size (g) and discontinuous width (w) are investigated with a wide range of values as a function of Re. The Re is varied from 5000–24,000. Based on the investigation, some conclusions may be drawn:

108

S. Singh et al.

1. Installation of the discontinuous ribs is more effective than the continuous ribs of similar cross-section after Re = 5000. 2. It is found that the Nu values increase on increasing the Re, whereas the f values decrease on increasing the Re. 3. The re-circulated fluid particles on both sides of the continuous ribs are observed to be dispersed with discontinuous ribs near the absorber plate, augmenting THPF. 4. The maximum Nu values are found for discontinuous ribs with combinations of 10 × 40 mm and 10 × 50 mm. 5. The maximum THPF values are found at Re = 5000 for all cases of discontinuous ribs.

References Aharwal KR, Gandhi BK, Saini JS (2008) Experimental investigation on heat-transfer enhancement due to a gap in an inclined continuous rib arrangement in a rectangular duct of solar air heater. Renew Energy 33:585–596. https://doi.org/10.1016/j.renene.2007.03.023 Bhagoria JL, Saini JS, Solanki SC (2002) Heat transfer coefficient and friction factor correlations for rectangular solar air heater duct having a transverse wedge-shaped rib roughness on the absorber plate. Renew Energy 25:341–369. https://doi.org/10.1016/S0960-1481(01)00057-X Cavallero D, Tanda G (2002) An experimental investigation of forced convection heat transfer in channels with rib turbulators by means of liquid crystal thermography. Exp Therm Fluid Sci 26:115–121. https://doi.org/10.1016/S0894-1777(02)00117-6 Gill RS, Hans VS, Saini JS, Singh S (2017a) Investigation on performance enhancement due to staggered piece in a broken arc rib roughened solar air heater duct. Renew Energy 104:148–162. https://doi.org/10.1016/j.renene.2016.12.002 Gill RS, Hans VS, Singh S (2017b) Investigations on thermo-hydraulic performance of broken arc rib in a rectangular duct of solar air heater. Int Commun Heat Mass Transfer 88:20–27. https:// doi.org/10.1016/j.icheatmasstransfer.2017.07.024 Gupta D, Solanki SC, Saini JS (1993) Heat and fluid flow in rectangular solar air heater ducts having transverse rib roughness on absorber plates. Sol Energy 51:31–37. https://doi.org/10. 1016/0038-092X(93)90039-Q Hans VS, Gill RS, Singh S (2017) Heat transfer and friction factor correlations for a solar air heater duct roughened artificially with broken arc ribs. Exp Therm Fluid Sci 80:77–89. https://doi.org/ 10.1016/j.expthermflusci.2016.07.022 Karwa R (2003) Experimental studies of augmented heat transfer and friction in asymmetrically heated rectangular ducts with ribs on the heated wall in a transverse, inclined, v-continuous and v-discrete pattern. Int Commun Heat Mass Transfer 30:241–250. https://doi.org/10.1016/ S0735-1933(03)00035-6 Karwa R, Solanki SC, Saini JS (1999) Heat transfer coefficient and friction factor correlations for the transitional flow regime in rib-roughened rectangular ducts. Int J Heat Mass Transf 42:1597–1615. https://doi.org/10.1016/S0017-9310(98)00252-X Kumar A, Saini RP, Saini JS (2013) Development of correlations for Nusselt number and friction factor for solar air heater with roughened duct having multi v-shaped with gap rib as artificial roughness. Renew Energy 58:151–163. https://doi.org/10.1016/j.renene.2013.03.013 Maithani R, Saini JS (2016) Heat transfer and friction factor correlations for a solar air heater duct roughened artificially with V-ribs with symmetrical gaps. Exp Therm Fluid Sci 70:220–227. https://doi.org/10.1016/j.expthermflusci.2015.09.010

CFD Investigation of Solar Air Heater Roughened with Transverse …

109

Patankar SV (1980) Patankar Numerical Heat Transferand Fluid Flow Prasad K, Mullick SC (1983) Heat transfer characteristics of a solar air heater used for drying purposes. Appl Energy 13:83–93. https://doi.org/10.1016/0306-2619(83)90001-6 Prasad BN, Saini JS (1988) Effect of artificial roughness on heat transfer and friction factor in a solar air heater. Sol Energy 41:555–560 Singh S, Chander S, Saini JS (2011) Heat transfer and friction factor correlations of solar air heater ducts artificially roughened with discrete V-down ribs. Energy 36:5053–5064. https://doi.org/ 10.1016/j.energy.2011.05.052 Singh I, Vardhan S, Singh S, Singh A (2019) Experimental and CFD analysis of solar air heater duct roughened with multiple broken transverse ribs: a comparative study. Sol Energy 188:519–532. https://doi.org/10.1016/j.solener.2019.06.022 Singh S, Suman S, Mitra S, Kumar M (2022) ANN model for prediction of thermo-hydraulic performance of a solar air heater with vertical cylindrical ribs. Energy Rep 8:585–592. https:// doi.org/10.1016/j.egyr.2022.10.263 Singh S, Mitra S, Kumar M, Suman S (2021) Thermal performance evaluation of a solar air heater with rotating turbulators. Sustain Energy Techn Assess 48. https://doi.org/10.1016/j.seta.2021. 101647 Singh Patel S, Lanjewar A (2019) Experimental and numerical investigation of solar air heater with novel V-rib geometry. J Energy Storage 21:750–764. https://doi.org/10.1016/j.est.2019.01.016 Srivastava A, Chhaparwal GK, Sharma RK (2020) Numerical and experimental investigation of different rib roughness in a solar air heater. Thermal Sci Eng Prog 19. https://doi.org/10.1016/ j.tsep.2020.100576 Suman S, Khan MK, Pathak M (2015) Performance enhancement of solar collectors - a review. Renew Sustain Energy Rev 49:192–210. https://doi.org/10.1016/j.rser.2015.04.087 Tanda G (2004) Heat transfer in rectangular channels with transverse and V-shaped broken ribs. Int J Heat Mass Transf 47:229–243. https://doi.org/10.1016/S0017-9310(03)00414-9 Verma SK, Prasad BN (2000) Investigation for the optimal thermohydraulic performance of artificially roughened solar air heaters. Renew Energy 20:19–36. https://doi.org/10.1016/S0960-148 1(99)00081-6

Classification and Performance Enhancement of Solar Dryers Aditya Gaur, N. S. Thakur, and Satyanarayan Patel

Abstract Solar energy is one of the most feasible energy reservoirs with colossal potential. Photo-thermal and photoelectric conversions are paramount for transforming solar energy into a usable form. Solar dryers provide the best drying results in this direction by maintaining dry goods’ quality, color, and flavor. A solar dryer can be classified into natural circulation (passive solar dryers) and active solar dryers. Additional design modification leads to three more types of solar dryers such as integral, dispersed, and mixed-mode. Several factors help to improve solar dryer performance, such as geometrical parameters, operating conditions, and moisture removal rate. This chapter focuses on classifying solar dryers and performance parameters to enhance the effectiveness of the intended drying process. Finally, an in-depth examination of dryer design for indirect free convection and induced convection solar dryer system is provided. Keywords Solar energy · Solar dryer · Classification of solar dryer

1 Introduction Population growth is one of the biggest problems in the world. As the population grows, so does the consumption of food. This requirement is fulfilled by producing a large amount of food regularly or stored after some processing. Though, continuous food production and longtime storage are not possible. However, after drying the food for some time, it can be stored for a long time. Drying has defined a process to reduce moisture to safe limits. Sun drying is an ancient method used everywhere to preserve plants efficiently, food, and goods using solar energy (Bradford et al. 2020). Agricultural product drying leads to the fact that microscopic organisms counteract A. Gaur · S. Patel (B) Department of Mechanical Engineering, Indian Institute of Technology Indore, Khandwa Road Simrol, Indore, Madhya Pradesh 453552, India e-mail: [email protected] N. S. Thakur National Institute of Technology Hamirpur, Hamirpur, Himachal Pradesh 177005, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Goyal et al. (eds.), Renewable Energy: Accelerating the Energy Transition, Energy Systems in Electrical Engineering, https://doi.org/10.1007/978-981-99-6116-0_7

111

112

A. Gaur et al.

various activities. Crops can be stored long after drying without deterioration (Bewley et al. 2013). Dried crops have various benefits, such as improved product quality, longer safe shelf life, and lower post-harvest costs (Kiaya 2014). Crops or goods are laid on a mat or ground for sunny days while drying in the open or naturally. As a result of exposure to direct sunshine, dirt, pest infestation, and animal loss, plants can get contaminated. Researchers have used numerous drying methods in this direction, including spray, mechanical, electric, and solar drying (Brenndorfer, et al. 1985). These drying methods are used globally to dry agricultural and non-agricultural goods/items. Solar dryers provide the best drying results while consuming the least amount of fossil fuel with maintaining the quality, color, and flavor of dry goods. These dryers provide a product of superior quality while using less energy, less time, and less space (Sharma et al. 2009). Fruits, vegetables, and other crops can be reliably preserved using solar drying systems, which are also reasonably priced and favorable to the environment (Mustayen et al. 2014). The food and other products are dried on a flat surface by heating them with solar radiation (Sharma et al. 2009; Rocha et al. 2011; Green and Schwarz 2001; Bourdoux et al. 2016). A longer time is required to preserve/dry food and goods when solar radiation is used. Hence, various energy sources (biomass energy, burning wood, or dried leaves) were used for drying. In order to guarantee that there is an adequate supply of nutritious food for the general population, effective and economical drying technologies are required. Developing countries utilize high-temperature dryers because they have proven to be commercially feasible. Solar drying alone or along with other drying techniques can also be used. The first traditional drying industries emerged in the late 1800s (Bourdoux et al. 2016). Even though the drying industry was growing, farmers continued to put out necessary food and other products to dry on the ground. Additionally, it was done since solar energy is unlimited and uncontrolled; therefore, using it did not cost anything (Esper and Mühlbauer 1998). There is a dearth of trustworthy information about effective sun dryers in many areas where technologies for processing food, such as indirect drying are necessary (Bourdoux et al. 2016). One of the finest options for lowering the cause of product spoilage in drying and maintaining good quality products during manufacturing is controlling airflow in indirectly forced convection drying (Green and Schwarz 2001). Weather, collector assembly, insulation thickness, wind speed, collector dimensions, and absorber plate material are some variables that affect solar dryer performance. This chapter focuses on the basics of the solar dryer, its classification upgrading the design, and necessary parameters in order to enhance the effectiveness of the intended drying process. The principle of solar dryers is that heat from a source is transmitted to the product and moisture is removed from the product’s surface and transmitted to the surroundings. Figure 7.1a depicts the principle of the solar dryer, where it can be seen that cold air from the ambient enters the dryer and its temperature increases due to the solar insolation received via glazing. As a result, it removes the dry product’s moisture and moves out of the dryer from the exhaust vent. The oldest method is open sun drying, as shown in Fig. 7.1b, where products are exposed under direct exposure. This method has the disadvantage of high and

Classification and Performance Enhancement of Solar Dryers

113

Fig. 7.1 a Principle of the solar dryer. Reproduced with permission from Hage et al. Energy. 157, 815–829, 2018. Copyright© 2018 Elsevier Science Ltd. (Hage et al. 2018) b Open sun drying and c Shade drying. Reproduced with permission from Ndukwu et al. African J. Sci. Technol. Innov.13(2), 247–260, 2021. Copyright© 2020 African Journal of Science, Technology, Innovation, and Development (Ndukwu et al. 2021)

uncontrollable temperatures, which degrade product quality (Phadke et al. 2015). In the case of large quantity products that must be dried, shade drying is used, as presented in Fig. 7.1c. It uses the same principle: cold air enters from one side and gets heated due to solar insolation, which passes over the products; it removes the moisture from the products’ surface and moves out of the dryer. This method also has the disadvantage of products being kept open where dust and other weather and animal interference degrade the property of the product (Kumar and Singh 2020). The country’s most popular food preservation method is sun-drying crops due to the yearround high levels of sunshine irradiation (Esper and Mühlbauer 1998). Traditional drying techniques have many downsides, such as drying crops on rooftops or in concrete fields while exposed to the sun and wind. Factors such as dust pollution, insect infestation, enzymatic reactions, and microbial contamination contribute to lower food quality. Additionally, crops must be protected against animal assaults. It is employed in crop drying and space heating processes that call for temperatures lower than 80 °C. Adopting alternative renewable energy sources has grown more crucial due to rising fossil fuel prices and depletion. Several designs of solar dryers have been tested in a range of settings. The two main types of convection in solar drying are natural and forced convection. In contrast to forced convection solar dryers, which use fans or blowers aided by solar-powered batteries, free convection solar dryers use the

114

A. Gaur et al.

airflow created by buoyancy. In order to guarantee a sufficient supply of wholesome and clean food for the general public, drying technologies must be efficient and costeffective. High-temperature dryers are used in developing nations because they are known to be economically viable. Several solar dryer works are discussed in the next section. Additionally, this chapter examines how to design a dryer for an indirect type of free and induced convection solar dryer system based on moisture removal and heat transfer coefficients.

1.1 Classification of Solar Dryer Solar dryers may be classified into three groups based on air movement, mode of heat transfer, and drying chamber, as shown in Fig. 7.2. Additionally, based on the method of air movement, it is further classified into active solar dryers (or forced convection dryers) and passive solar dryers (natural convection dryers). However, solar dryers can be categorized in several ways. The two most helpful categories are heat transfer in wet solids and handling of wet materials and their physical qualities. The first classification technique shows differences in the dryer design and operations. In contrast, another method helps choose a set of dryers for primary evaluation in a specific drying problem. Two divisions of solar dryers are active solar drying systems, also recognized as hybrid dryers, and passive solar dryers. Active solar drying systems are also

Fig. 7.2 Classification of the solar dryer. Reproduced with permission from Hage et al. Energy. 157, 815–829, 2018. Copyright© 2018 Elsevier Science Ltd. (Hage et al. 2018)

Classification and Performance Enhancement of Solar Dryers

115

Fig. 7.3 Different designs of solar dryers. Reproduced with permission from Ekechukwu et al., Energy Convers. Manage. 40(6), 615–655, 1999. Copyright© 1998 Elsevier Science Ltd. (Ekechukwu and Norton 1999)

called forced convection dryers, and passive solar drying systems are called natural convection dryers. The active and passive solar dryers fall into three categories which depend on the design and use of solar insolation (integral, distributed, and mixed mode), as shown in Fig. 7.3.

1.2 Active Type of Solar Drying Systems Active solar drying systems consist of induced machinery (fans or blowers) to move hot air from the collection assembly to the drying cabinet, as shown in Fig. 7.3. Thus, the general term induced convection dryers describe all active solar dryers. These dryers are often employed in large-scale industries for drying processes where they work in tandem with fossil fuels to improve drying control by minimizing the impact of variations in solar intensity on drying temperature. Figure 7.3 depicted various active solar dryers as direct, indirect, and hybrid.

116

1.2.1

A. Gaur et al.

Indirect Type of Active Solar Drying Systems

A drying cabinet and collection assembly are in an indirect active drying system, as shown in Fig. 7.4. A solar air collector, a chamber for drying, an inlet and exhaust for air circulation, and ducting are typically its four primary components. Because of the independent air heating component, higher temperatures can be achieved easily by controlling the airflow rate. However, an appropriate temperature and airflow rate must be estimated to have an affordable design because collector efficiency decreases at higher temperatures. Besides, most solar collector assembly is made of metal and appropriately painted, and black plastic is employed as an option that is also economical. The fan placement also impacts the performance of an indirect-type active solar dryer. The fan’s job in the drying cabinet is to keep the flow rate appropriate so that the water content of the wet material is uniformly reduced, while the collector’s objective is to gather heat while minimizing heat losses. A study on the drying of Mulberry in an indirect type of active solar dryer for energy analysis and exergy losses was performed (Akbulut and Durmu¸s 2010). As the drying rate increases, the energy utilization ratio and exergy losses decrease (Akbulut and Durmu¸s 2010).

Fig. 7.4 Indirect type of solar drying. Reproduced with permission from Bhardwaj et al., Sustain. Energy Technol. Assess. 45, 101,119, 2021. Copyright© 2021 Elsevier Science Ltd. (Bhardwaj et al. 2021)

Classification and Performance Enhancement of Solar Dryers

1.2.2

117

Direct Type of Active Solar Energy Drying Systems

The direct-type active solar dryers have a built-in solar energy harvesting system. In this drying system, sunlight penetrates the glazing and heats the drying chamber, as presented in Fig. 7.5. There is no inlet for ambient air entry, but an exit hole is provided for the warm air to move out of the chamber and remove moisture. The three categories of direct types of active solar dryers that can be recognized are the absorption type of solar dryer, the storage type of solar dryer, and greenhouse solar dryers.

Absorption Type of Dryers Direct-type absorption dryers, as the name implies, are designs for direct active drying in which the products immediately absorb solar energy. Practical examples of large-scale commercialized forced convection absorption dryers include transparent roof solar brans, solar kilns for drying timber, and small-scale induced convection dryers with supplementary heating (Visavale and Principles 2012).

Fig. 7.5 Direct solar drying for dehydrating operation. Reproduced with permission from Bhardwaj et al., Sustain. Energy Technol. Assess. 45, 101,119, 2021. Copyright© 2021 Elsevier Science Ltd. (Bhardwaj et al. 2021)

118

A. Gaur et al.

Storage Type of Solar Dryer Solar dryers depend on the meteorological conditions of the area where they are used. Some crops and food require several consecutive days to dry out their moisture and during sunset hours or bad weather conditions. The improper drying of such crops harms their quality. Thus, thermal storage has been introduced (Bal et al. 2010). Thermal storage is included with solar drying systems; the drying rate can be increased as it is charged during peak hours of sunshine and stored energy can heat the flowing air during sunset hours (Kant et al. 2016).

Greenhouse Solar Dryers Greenhouse solar dryer under the active mode classification operates under two energy sources: a flow of air and incident solar irradiation. It is used for drying products which are in large quantities. A greenhouse dryer prototype was designed to dry 300 kg of chilly, and the results were satisfactory concerning drying of chilly and economic (Kaewkiew et al. 2012).

1.2.3

Hybrid Type of Active Solar Energy Drying System

In hybrid solar dryers, the advantages of solar energy are combined with those of a conventional or backup energy source. They can be used alone or in tandem with any energy source (Shaikh and Kolekar 2015). These dryers come from medium to large and work at 50% to 60% of their capacity to account for temperature variations brought on by climatic uncertainty.

1.3 Passive Solar Drying Systems In a passive solar dryer, air temperature increases and circulates spontaneously due to buoyancy force, wind pressure, or a combination of both (Shaikh and Kolekar 2015). The typical cabinet and greenhouse dryer operate in passive mode. Passive crop drying is still common in tropical and subtropical regions, such as Africa and Asia, or tiny agricultural villages. In particular, these are easy to install at isolated places, affordable to build with locally available materials, and simple to operate (Udomkun et al. 2020). Bananas, mangoes, potatoes, and other similar fruits and vegetables can all be dried in small batches using passive dryers. The passive solar drying systems are further classified into indirect, direct, and hybrid, as shown in Fig. 7.3 and explained further.

Classification and Performance Enhancement of Solar Dryers

1.3.1

119

Indirect-Type Passive Solar Energy Drying Systems

These types of dryers employ natural air convection to dry goods. The trays are typically positioned upright, with some space between succeeding trays to improve the dryer’s functionality. The barrier to air movement caused by this arrangement of the trays is due to the “chimney effect” (Mohana et al. 2020). The effect of the chimney improves airflow upward due to the difference in densities between the air in the cabinet and the atmosphere.

1.3.2

Direct Type of Passive Solar Energy Drying Systems

In these solar dryers, crops are exposed to direct sunlight, promoting the color ripening desired in grape kinds, dates, coffee, and developing the full flavor in edible products. The three most prevalent types of dryers in this category are cabinet, greenhouse, and hybrid (Lingayat et al. 2020).

Solar Cabinet Dryers The passive form of solar cabinet dryers is typically a straightforward, inexpensive device with various applications. They are typically made with a drying surface and a proper capacity, and among other things, they are appropriate for drying agricultural products, herbs and spices (Balasuadhakar et al. 2016). The black interior absorbs the heat used to dry the crops after it passes through the glass cover. Under the influence of buoyant forces, heated air exits through the exit hole, creating suction in the inlet for fresh air and preserving the vital airflow. The passive solar cabinet type of dryer is less costly and easy to construct using materials readily available locally (Chua and Chou 2003). Nevertheless, its main drawbacks are insufficient moisture removal and a high-temperature range (70–100 °C), causing the product overheats. The difference in cabinet type of passive direct and passive indirect dryers can be seen clearly in Fig. 7.6a–d. The products are kept directly under the sunlight over the cabinet cover in passive direct type. In the later type, the products are kept inside the cabinet dryer’s drying chamber, which is not exposed to direct sunlight. Several studies have been done on cabinet type of dryers for various products like spearmint, Moroccan eucalyptus globulus, Colocynth gourd, and the effect of temperature, humidity, and tray position on the drying kinetics was investigated (Ayadi et al. 2015; Kouhila et al. 2002; Benhamou et al. 2014).

Natural Circulation Greenhouse Dryers These are also called tent dryers and are essentially modified greenhouse types of dryers (Kumar et al. 2017). Greenhouse dryers are categorized into passive or active modes, as shown in Fig. 7.7, where a chimney or ventilator is present in the passive

120

A. Gaur et al.

Fig. 7.6 Cabinet solar dryer design a passive direct solar dryer, b active direct solar dryer, c passive indirect solar dryer and d active indirect solar dryer. Reproduced with permission from Ndukwu et al. African J. Sci. Technol. Innov. 13(2), 247–260, 2021. Copyright© 2020 African Journal of Science, Technology, Innovation and Development (Ndukwu et al. 2021)

mode for air circulation. It is classified based on airflow, covering the material, structure, and north wall. An exhaust fan is present in active mode for moving heated air out of the dryer. They have vents that are the proper size and placement for managed airflow (Román-Roldán et al. 2021). They stand out to the substantial glass overlay that the transparent polyethylene sheet provides (Patil and Gawande 2016). A passive solar greenhouse dryer’s tilting glass roof exposes the product to direct solar radiation. The internal dryer is painted black for enhanced solar absorption, and an escape vent is located in the ridge cap above the roof. A schematic view of a passive greenhouse solar dryer with and without a covered floor is shown in Fig. 7.8a, b, where the DC fan is run using solar cell modules. High moisture level crops are dried using this setup, and a greenhouse dryer with a covered floor gives better results with elevated temperature and humidity reduction (Singh et al. 2018).

Classification and Performance Enhancement of Solar Dryers

121

Fig. 7.7 Classification of greenhouse solar dryer. Reproduced with permission from Singh et al. Renew. Sustain. Energy Rev. 82. 3250–3262, 2018. Copyright© 2017 Elsevier Science Ltd. (Singh et al. 2018)

Fig. 7.8 Greenhouse dryer a without covered floor and b with a covered floor. Reproduced with permission from Singh et al. Renew. Sustain. Energy Rev. 82. 3250–3262, 2018. Copyright© 2017 Elsevier Science Ltd. (Singh et al. 2018)

Hybrid-Type Passive Solar Energy Drying Systems A hybrid passive solar energy dryer has the identical initial design as the direct and indirect models (i.e., a combination of a solar collector, a separate cabinet for drying, and an exhaust exit vent), as well as glass walls resembling those in the direct dryers so that sunlight directly hits the product (Visavale and Principles 2012).

122

A. Gaur et al.

1.4 Additional Classification The active and passive solar dryer types are further classified into three varieties based on their design.

1.4.1

Direct Type of Dryers

Direct solar drying is the conventional technique for drying things. A density difference causes air movement, and the crop is quickly exposed to sunlight. The cropcarrying framework needs to be covered with transparent material for this purpose. The crop and the area around it take in the solar energy that enters through the glazing (Kumar et al. 2016). Direct crop absorption of solar energy is the most effective method of converting it into usable heat for drying. The final dried quality of many crops is enhanced by direct solar light. The biggest drawback of this drier kind is that temperatures are hard to regulate because the crop immediately absorbs solar energy.

1.4.2

Indirect Type of Dryers

Indirect solar drying is significantly more efficient than direct solar drying (Jangde et al. 2021). In this type of solar dryer, the air is heated by heat trapped in a solar collector assembly, which can be either concentrating or flat plate. The hot air is forced toward the products’ storage area, where convection could cause the products’ water content to evaporate. By avoiding direct sunlight, this technique lessens the adverse effects of direct solar drying. The drying rate is much better than that of a direct solar dryer. The advantages of the indirect type of solar drying are as follows: i. It is simple to govern the product’s final state. ii. Product losses due to natural disasters get reduced. iii. A direct sun dryer requires less floor surface area for the same amount of material. 1.4.3

Mix Mode Type of Dryers

The cabinet used for drying and solar air collector is divided among this model as an indirect dryer. In contrast to the indirect mode, the dryer provides additional drying by utilizing direct solar energy that enters via the glass walls and roof (Fudholi et al. 2010). A vent for exhaust is constructed at the back upper end of the cabinet to facilitate and control the convection circulation of air through the dryer. Ugwu et al. (2015) studied a mixed-mode solar dryer used with a pebble bed in the collector for storing energy, as shown in Fig. 7.9a. The highest temperature recorded inside the drying chamber was around 61.7 °C and the moisture level was reduced to 53.37%. Another experiment was on a mixed-mode solar dryer with recovery heating is done,

Classification and Performance Enhancement of Solar Dryers

123

as shown in Fig. 7.9b. Yassen and Al-Kayiem (2016) enhanced the performance of the solar dryer by recovery heating, which is used to store heat from plants’ flue gas, then supply it to the dryer during low insolation periods and after sunset. Figure 7.9c shows the schematic diagram of the forced convection mixed mode type of solar dryer in which the product to be dried simultaneously gets its moisture removed by direct sun insolation and from the heated air circulated using the blower. The design of the forced mixed-mode solar dryer and forced convection indirect solar dryer (Fig. 7.9d) is almost the same except for the drying chamber in case the mixed mode is not covered and sun insolation falls directly through the glazing on the product. In the case of forced convection indirect solar dryer, the drying chamber is covered, i.e., opaque, and does not allow the insolation to fall on the product being dried directly.

Fig. 7.9 Mixed-mode solar dryer a with pebble bed absorber and b with recovery heating. Reproduced with permission from Balasuadhakar et al. Mater. Today: Proc. 46. 4165–4168, 2021. Copyright© 2020 Elsevier Science Ltd (Balasuadhakar 2021) c forced convection mixed-mode solar dryer and d forced convection indirect type of solar dryer. Reproduced with permission from S Singh et al. Renew. Sustain. Energy Rev. 1(1/2). 6–13, 2012. Copyright© 2012, Infonomics Society (Singh and Kumar 2012)

124

A. Gaur et al.

1.5 Performance Enhancement of Solar Dryer There are different parameters on which a solar dryer’s performance depends. The different parameters like geometry, tilt angle, the addition of reflectors, concentrator, and thermal storage show an effect on the performance of the solar dryer. To enhance the efficiency of solar dryers, following parameters are studied.

1.6 Geometrical Parameters Different geometrical aspects like the angle of tilt, collector surface area, number of glazing surfaces, and roughness of absorber plate directly affect the performance of solar dryers. The angle of tilt (β): Flat plate collectors are often fixed at a single position and do not track or follow the sun’s path. So to receive a considerable amount of solar insolation, the absorber plate should be positioned appropriately (Kalogirou 2004). Thus, β is a crucial factor in improving solar dryer performance. Morse and Czarnecki’s research streamlined the issue by supposing that extraterrestrial illumination was falling on the collector. By first integrating the expression for the flux on a tilted surface over the length of the day and then adding up over the number of days in the year, they could determine the annual insolation per unit area (Iqbal 2012). They plotted their findings as relative insolation with latitude (φ). The findings indicated that the tilt would maximize the annual insolation by β = 0.9φ

(7.1)

Glazing surface: The glazing surface is the transparent glass cover placed parallel to the absorber plate at a distance to absorb sunlight. The solar insolation to be received by the collector is to be in the control amount; thus, it is neither in surplus nor in deficit. It is decided by the number of glazing required. The optimum number of glazing is based on the latitude of the place, as the different altitudes have different average solar radiation throughout the year (Agbo and Okoroigwe 2007). Collector surface area: Another important designing parameter in solar dryers is the collector surface area which is decided based on the amount of moisture to be removed from the substance and how much energy is required to remove that moisture (Brenndorfer et al. 1985). It significantly reduces drying time, which ultimately helps increase the solar dryer’s efficiency. The roughness of the absorber plate: The heat transfer between the absorber plate and flowing air, either in natural or in forced flow, plays a vital role in the drying of products effectively and quickly (Tyagi et al. 2012). Suppose there is enough turbulence and no stagnation; less adequate time is required to transfer heat from the absorber plate to flowing air. Hence, to increase the stagnation time, the surface of the

Classification and Performance Enhancement of Solar Dryers

125

absorber plate is roughened by creating artificial roughness geometries in different ways, like V-shaped ribs and chamfered grooves.

1.7 Addition of Reflectors and Concentrators Several reflectors and concentrators are added in the appropriate orientation to maximize the concentration of solar insolation falling on the glazing surface in latitudes where less average solar insolation is received throughout the year (Kalogirou 2004). Ringeisen et al. (2014) explained in their study the addition of a concave concentrator and its effect on the performance of the solar dryer. The drying rate increases with an increase in the average air temperature. Maiti et al. (2011) studied that adding reflectors enhance the collector efficiency from 40% to 58.5%, reducing the drying time. Several solar concentrators are used depending on geometrical and latitude conditions, like parabolic, petal-shaped dish, and multi-dish concentrators (Ssemwanga et al. 2020).

1.8 Air Circulation Mode There are mainly two types of air circulation modes in a solar dryer. One is the natural circulation mode in which air travels from the inlet to the collector and finally to the drying chamber by buoyancy due to density difference. Another air circulation method is forced circulation, in which air is forced from the inlet using solar-powered fans or blowers, depending on the rate of flow required. Slama and Combarnous (2011) studied the indirect type of solar dryer assisted with an electric fan for forced air circulation. It was found that the quality of drying can be controlled. Baffles in solar collector assembly also helped increase the dryer efficiency in case of a low flow rate (Romdhane 2007).

1.9 Use of Thermal Storage Lalit M. Bal et al. focus on increasing the solar dryer’s performance in addition to thermal storage (Bal et al. 2011). Thermal storage is an energy source that supplies heat to the air during sunset hours and reduces product drying time. Many techniques can be used to add thermal storage to the solar dryer. One way is to place solid paraffin wax below the absorber plate with proper insulation (Bal et al. 2010). During sunshine hours, it absorbs the excess solar energy to melt and then releases it during sunset hours to flowing air which gets heated up and flows to the drying chamber. Sopian et al. (2007) studied the double-pass solar collector in a solar dryer installed with the storage system. A porous storage medium was installed in the collector’s lower

126

A. Gaur et al.

part, which helped to maintain a high and stable temperature during non-favorable conditions. The moisture ratio was reduced from 63 to 15% in 7 h. Several studies and experiments have been done on different types of dryers in various conditions. Pangavhane et al. (2002) designed and fabricated a free convection solar dryer in which the average temperature recorded was about 50 °C to 55 °C, considered the best drying temperature for grapes. A study on forced convection solar dryers for drying potato slices found that moisture from the surface of slices was reduced from 85 to 14% in 4 h (Vijayan and Arjunan 2015). The drying of mangoes in an indirect forced convection solar dryer was investigated with the effect of temperature variation on drying kinetics. There was almost constant temperature throughout the dryer, and only a 1.3 °C difference was recorded for a bright day and 1.5 °C for a cloudy day at four different parts of the drying cabinet. The efficiency was found in the range of 30.9 to 33.8%, which indicated that this type of dryer outperformed previous industrial dryers (Wang et al. 2018). Sivakumar et al. (2020) investigated a mixed-mode solar dryer for drying maize. It consists of three parts drying trays, a collector assembly, and a blower. It was compared with standard models for a constant air flow rate and it found that the drying rate decreased by 6%. In another study on bananas drying, a comparison was made between open sun drying and indirect drying. It was found that drying for open sun drying was faster than indirect drying, but only for the initial stage. The drying rate for indirect drying increases as the air temperature inside the drying chamber increases compared to the ambient air temperature (Lingayat et al. 2017). A comparison was made based on drying time, moisture removal, and product quality; indirect drying is advantageous compared to the open sun and direct drying (Vijayan et al. 2017).

2 Experimental Analysis The experimental setup was developed using calculations for base insulation thickness and collector area drying. The drying performance using this data was investigated, and readings of the parameters were taken periodically to test the system. The basic design is considered using (i) minuscule service, (ii) moisture absorbing capacity, (iii) moisture removal rate, (iv) airflow rate, and (v) total heat loss from the side, top, and bottom of the collector. The dryer’s parts are (i) solar collector assembly, (ii) chamber for drying, (iii) exit vent for air, and (iv) PV solar panel attached to CPU fan used in induced convection setup. The indirect type of solar dryer for free convection consists of a solar collector assembly, a cabinet for drying with two trays, and an air exit vent in the drying cabinet. However, a trapezoidal duct has been added to the collector intake for the forced convection design, along with a CPU fan powered by a solar PV panel.

Classification and Performance Enhancement of Solar Dryers

127

2.1 Design Parameters Several parameters have been considered while designing both natural and forced convection indirect types of solar dryers. Angle of tilt (β): The optimum tilt to maximize the amount of solar radiation received is given by Eq. 7.1. But in the case of winter, when the demand for energy is more for removing the same amount of moisture as compared to summer, then φ = φ + 10◦

(7.2)

Moisture to be removed (M r ): The amount of moisture required to remove from any given product was the primary factor when constructing the solar dryer. Mr =

M(m i − m f ) (100 − m f )

(7.3)

Here, M is the mass of the product being dried, m i is the initial moisture content, and m f is the final moisture content for a specific product. Energy required for removing moisture (E): After deciding the amount of moisture to be removed, the energy required for removing that moisture is given by E = Mr × h f g

(7.4)

h f g = 4186(597 − 0.56T pr oduct )

(7.5)

Here, Tproduct is the temperature of the product in ambient conditions. Area of Collector (Ac ): The collector is one of the most crucial components of a solar dryer. Its efficiency must be calculated according to the number of glass covers. The transmissivity diminishes with an increase in coverings (glazing). As a result, one glass cover is used, assuming the collector’s efficiency (ηc ) is 50%, as determined by earlier tests (Papade and Boda 2014). Ac =

E I × ηc

(7.6)

Here, I is solar irradiation in W/m2 . Rate of drying (Dr ): The drying rate is the time to evaporate a specified amount of moisture from a product. Therefore, when constructing a solar dryer, it is vital to understand the amount of air mass needed for the regulated drying of any substance. Previous research has shown that the typical drying duration is 10 h (Amer et al. 2010). Dr =

Mr t

(7.7)

128

A. Gaur et al.

Mass of air needed for drying (M a ): After determining the necessary drying rate, determine the mass flow of air needed for drying at a controlled rate so that hightemperature air has enough time to dry the edible goods or materials. Ma =

Dr Δω × 3600

(7.8)

Here, Δω is the change in relative humidity. Rate of airflow (V af ): The mass flow rate’s ratio to air density is defined as the mass flow rate and is used to determine the airflow rate. Va f =

Ma ρa

(7.9)

Here, ρa is the density of the product being dried. Area of opening for airflow (Av ): The area of opening for the inlet of ambient air is given by Av =

Va f Vw

(7.10)

Here, Vw is the velocity of the air. The schematic diagram for the solar dryer system with indirect natural convection is shown in Fig. 7.10a. The raw material loaded over the wire mesh in the collector absorbs heat transmitted to it, resulting in uniform drying. The air inside the collector heats up owing to solar insolation. Figure 7.10b depicts a force convection solar drying system’s schematic diagram. The collector collects the solar insolation, which heats the air blown through a CPU fan powered by solar PV panels. This heated air is sent to the drying area, which is transferred to the raw material on the wire mesh to ensure uniform drying. There is various drying kinetics that estimates the efficiency of the solar dryer. The drying kinetics includes moisture ratio and moisture content (MC). The water level in a material is determined by its MC. Several methods are used to determine moisture content, such as weight loss and initial moisture content, which is determined by heating the substance in an oven for 24 h. The following equation determines the MC of the product: MC =

Mi − M f M if

(7.11)

where M i and M f are moisture content at the beginning and end, respectively. The moisture ratio (MR) is defined as the proportion of the current moisture level to the starting moisture level, MR =

MC t MC i

(7.12)

Classification and Performance Enhancement of Solar Dryers

129

Fig. 7.10 Systematic representation of a indirect type of natural convection solar dryer and b indirect type of forced convection solar dryer

2.2 Experimental Procedure First, a natural convection configuration was examined, and once that setup was complete, an experiment was conducted using a forced convection setup. Before the test with the material was conducted, the dryer was evaluated without a load. The load drying room had an average temperature of about 50 °C. Key factors affecting moisture migration from a substance inside to its surface include the substance’s temperature, moisture content, physical characteristics, internal structure, and composition. The relationship between the difference in moisture level over time and the moisture decreases across the particle from interior to surface. In other words, drying speed slows down as moisture content rises but speeds up as particle size decreases. As a result, the material needs to be well cleaned before slicing with a manual slicing machine to hasten it to dry.

130 Table 7.1 Properties of banana sample

A. Gaur et al.

Characteristics

Mean value

Shape

Cylindrical

Average thickness

4–5 mm

Mean weight

6–8 gm

Mean density

1.11 gm/cm3

Initial moisture level

73%

Final moisture level

12%

Both a forced convection indirect type of solar dryer and a natural convection indirect type of solar dryer were used in the current testing. In February 2022, the National Institute of Technology in Hamirpur (H.P.), India, hosted solar drying experiments. All of the experiments ran from 9:00 a.m. until 4:30 p.m. All the equipment was run for at least 30 min before the experiment to ensure steady drying conditions. The raw component was a banana cut into 4–5-mm-thick slices. Two different sets of samples were produced. One set was evenly distributed in the open air on each setup, and the other was placed on wire mesh within the drying chamber. The ambient temperature, the air’s inlet, outlet, and absorber plate temperatures inside the solar collector, the drying chamber’s temperature, the aluminum sheet’s inlet and outlet temperatures, the speed of the wind, and the amount of solar insolation at a 37.512 tilt were measured at 30-min intervals. Up until there was no longer any moisture loss, the drying process was continued. Banana characteristics used for an experiment are given in Table 7.1. The design parameters for the indirect type of solar dryer are given in Table 7.2 Solar collector assembly: Solar collector is a typical device that traps the energy from solar insolation falling on it. It uses that entrapped energy in space heating Table 7.2 Design values for the indirect type of solar dryer Design parameter

Symbol

Angle of tilt

β

37.512°

Moisture to be removed

Mr

2.079 kg

Insolation on collector surface area

I

16,200 kJ/m2

Value

Energy required for reducing moisture level

E

5107.784 kJ

Collector area

Ac

0.63 m2

Width of Collector

Wc

0.6 m

Length of Collector

Lc

1.05 m

Drying rate

Dr

0.2079 kg/hr

Mass of air needed for drying

Ma

0.051 kg/sec

Airflow rate

Vaf

0.0456 m3 /sec

Area of opening for airflow

Av

0.024 m2

Base insulation thickness

tb

0.02 m

Classification and Performance Enhancement of Solar Dryers Table 7.3 Collector assembly parts

Part of assembly Material

131

Function

Absorber plate

Mild steel

Glazing

Perspex glass Transmit light

Space heating

Collector side

Mild steel

Reduce leakage and heat loss

Fan (Blower)

Fiber blades

Forcing ambient air

through forced or natural convection. For the efficiency of the solar collector, different designs are altered for surface roughness to increase the stagnation time of entrapped heat. The solar collector assembly parts are given in Table 7.3.

3 Results and Discussions 3.1 Distribution of Temperature in Solar Dryer Figure 7.11a, b depict the natural and forced convection solar dryer’s interior temperature distribution. The temperatures of the two trays, the absorber plate, the collector outlet, and the entering air were measured. Heat supplied: A system of induced convection produces more heat than a system of free convection. The amount of heat supplied depends on the air mass flux; in an induced convection configuration with CPU fans, the higher the mass flux, the more heat is supplied. The minimum heat produced was 53.2 and 361.8 W, and the average heat produced was estimated to be 158.87 and 961.46 W for free and induced convection, respectively. The maximum heat natural and forced convection produced were 234.165 and 1479.36 W, respectively. Therefore, it can be said that forced convection performed better than free convection. Moisture content: Due to the higher initial water level on the surface, the moisture decreases gradually over the first 2 h of drying. The same pattern was seen on the experiment’s initial day for both the free and forced convection indirect types of solar dryer setups in Fig. 7.11c. After 2 h, it rapidly dropped until it reached the lowest value. Because higher air speeds carry more water levels than in natural convection setup, the product dried in a forced convection setup lost more water in a given drying time than the free convection setup. The initial moisture content for both sets was 73%, while the final moisture contents for forced convection and natural convection setup were 18.78% and 23.09%, respectively, after drying. Induced convection configuration has outperformed free convection setup regarding moisture level reduction. Drying rate: The results of the drying rates calculation for the free convection setup and the induced indirect type of solar dryer are depicted in Fig. 7.11d. As shown in Fig. 7.11d, the curve starts steep on the first day but then improves as drying progresses, peaking at 1.29 kg/hr for forced convection setup and 0.84 kg/

132

A. Gaur et al.

Fig. 7.11 Variation of temperature with time in a indirect type of natural convection solar dryer, b indirect type of forced convection solar dryer, c variation of moisture content with time, and d variation of drying rate

hr for natural convection setup at midday. It then started to fall quickly and eventually reached its lowest point. This suggests excessive water content on the sample’s surface was easily reduced during the initial phase. As time progressed, the rate of removal of moisture content slowed down. It was found that drying took longer than expected on day two. It takes a long time to extract the moisture from the delicate internal pores of the sample slices because the moisture has already got lowered from the surface layer on the first day. As a result, the drying process took longer on day two. A comparison of the collector performance for the indirect type of forced and indirect free convection setups has been calculated and depicted in Fig. 7.12a. The collector efficiencies for induced and natural convection indirect solar dryers are 26.66% and 47.69%, respectively. The dryer efficiency (ηd ) is calculated by ηd = QQoi , where Qo is the energy output from the dryer and Qi is the total energy supplied to the dryer. The comparative evaluation of the dryer performance for both free and induced convection setups has been determined, as shown in Fig. 7.12b. The dryer efficiency increases from 17.44% (natural convection) to 26.34% (force convection). The results indicated that force convection has higher collector and dryer efficiency than natural convection.

Classification and Performance Enhancement of Solar Dryers

133

Fig. 7.12 Performance comparison for indirect type of natural convection and forced convection a collector efficiency and b dryer efficiency

4 Conclusions and Future Scope Classification of dryers was done mainly based on the method of movement of air, mode of heat transferred, and different classes of drying chambers. The two main types were active and passive dryers, which included different classes of dryers according to the requirement, like indirect and direct. Also, some were classified based on their design and quantity to be dried, like storage type of solar dryer and greenhouse solar dryer, respectively. The studies were conducted to compare the performance and drying parameters of two types of indirect sun dryers: free convection and induced convection. Forced convection was facilitated by installing a trapezoidal duct, a CPU fan, and PV panels. The indirect forced and natural convection solar dryer is compared in the experimental analysis by drying banana slices. A different set of observations for solar irradiation with time for consecutive days were recorded along with the temperature at different parts of the solar dryer. The key conclusions from the test results are as follows: • The maximum temperatures measured on the collector outlet for the free and induced convection ITSD setups were 63.2 °C and 73.2 °C, with mean temperatures of 58.25 °C and 50.43 °C, respectively. • The moisture level of the samples was decreased for the indirect type of forced convection solar dryer from 73% to 18.76% and for natural convection solar dryer from 73% to 23.09%. • Free and induced convection’s average heat output was calculated to be 158.87 and 961.46 W, respectively; meanwhile, their corresponding minimum recordings were 53.2 and 361.8 W. Maximum heat was produced by natural and forced convection, respectively, at 234.165 and 1479.36 W.

134

A. Gaur et al.

• The mean drying rate for the forced convection indirect type of solar dryer was found to be 0.32 kg/hr, compared to 0.22 kg/hr for the natural convection indirect type of solar dryer. • It was estimated that the typical collector efficiencies for induced convection ITSD and natural convection indirect solar dryers were 26.66% and 47.69%, respectively. • The anticipated average dryer efficiencies for forced and natural convection ITSD were 17.44% and 26.34%, respectively. According to this study, forced convection ITSD outperformed free convection ITSD in every parameter examined for drying banana samples. Farmers and enterprises must use it on a large scale, so this study must be conducted on a large scale. Additionally, it must be explored alongside computational research to get better outcomes on a mass scale. Different modeling techniques should be applied for simulation in different conditions to enhance solar dryers’ performance. It helps optimize different parameters while designing the solar dryer and would help reduce the cost and time. The essential part of solar dyer is collector assembly. It should be modified using different designs of absorber plates and different surface roughness to improve the collector’s efficiency, ultimately improving the solar dryer’s performance. Different types of phase change materials should be used during the addition of thermal storage to check the chemical compatibility with the product being dried. A more cost-effective design should be tested alongside it in order to improve commercialization. The surface of the absorber plate should be modified in different ways to enhance the heat transfer between the air and absorber surface. The use of fuzzy networks and machine learning could be applied to various crops and edible products. So that optimization of different parameters could be done according to the product being dried and the meteorological conditions present. In order to enhance the heat transfer and the drying rate, different types of nanofluids could be used and there is much scope in this research area of the solar dryer.

References Agbo S, Okoroigwe E (2007) Analysis of thermal losses in the flat-plate collector of a thermosyphon solar water heater. Res J Phys 1(1):35–41 Akbulut A, Durmu¸s A (2010) Energy and exergy analyses of thin layer drying of mulberry in a forced solar dryer. Energy 35(4):1754–1763 Amer B, Hossain M, Gottschalk K (2010) Design and performance evaluation of a new hybrid solar dryer for banana. Energy Convers Manag 51(4):813–820 Ayadi M, Zouari I, Bellagi A (2015) Simulation and performance of a solar drying unit with storage for aromatic and medicinal plants. Int J Food Eng 11(5):597–607 Bal LM, Satya S, Naik S (2010) Solar dryer with thermal energy storage systems for drying agricultural food products: a review. Renew Sustain Energy Rev 14(8):2298–2314 Bal LM et al (2011) Review of solar dryers with latent heat storage systems for agricultural products. Renew Sustain Energy Rev 15(1):876–880

Classification and Performance Enhancement of Solar Dryers

135

Balasuadhakar A (2021) A review of construction, material and performance in mixed mode passive solar dryers. Mater Today: Proc 46:4165–4168 Balasuadhakar A et al (2016) A review on passive solar dryers for agricultural products. Int J Innov Res Sci & Technol 3(01/013):64–70 Benhamou A, Fazouane F, Benyoucef B (2014) Simulation of solar dryer performances with forced convection experimentally proved. Phys Procedia 55:96–105 Bewley JD et al (2013) Longevity, storage, and deterioration. Seeds. Springer, pp 341–376 Bhardwaj A et al (2021) Energy and exergy analyses of drying medicinal herb in a novel forced convection solar dryer integrated with SHSM and PCM. Sustain Energy Technol Assess 45:101119 Bourdoux S et al (2016) Performance of drying technologies to ensure microbial safety of dried fruits and vegetables. Compr Rev Food Sci Food Saf 15(6):1056–1066 Bradford KJ et al (2020) The dry chain: reducing post-harvest losses and improving food safety in humid climates. Food Industry Wastes. Elsevier, pp 375–389 Brenndorfer B, et al (1985) Solar dryers: their role in post-harvest processing. Commonwealth Secretariat Chua K, Chou S (2003) Low-cost drying methods for developing countries. Trends Food Sci Technol 14(12):519–528 Ekechukwu OV, Norton B (1999) Review of solar-energy drying systems II: an overview of solar drying technology. Energy Convers Manag 40(6):615–655 El Hage H et al (2018) An investigation on solar drying: a review with economic and environmental assessment. Energy 157:815–829 Esper A, Mühlbauer W (1998) Solar drying-an effective means of food preservation. Renew Energy 15(1–4):95–100 Fudholi A et al (2010) Review of solar dryers for agricultural and marine products. Renew Sustain Energy Rev 14(1):1–30 Green MG, Schwarz D (2001) Solar drying technology for food preservation. GTZ publication Eschborn, Germany Iqbal M (2012) An introduction to solar radiation. Elsevier Jangde PK, Singh A, Arjunan TV (2021) Efficient solar drying techniques: a review. Environ Sci Poll Res 2021:1–14 Kaewkiew J, Nabnean S, Janjai S (2012) Experimental investigation of the performance of a largescale greenhouse type solar dryer for drying chilli in Thailand. Procedia Engineering 32:433–439 Kalogirou SA (2004) Solar thermal collectors and applications. Prog Energy Combust Sci 30(3):231–295 Kant K et al (2016) Thermal energy storage based solar drying systems: a review. Innov Food Sci Emerg Technol 34:86–99 Kiaya V (2014) Post-harvest losses and strategies to reduce them. Technical Paper on post-harvest losses, action contre la faim (ACF), vol 25. p 1–25 Kouhila M et al (2002) Experimental study of sorption isotherms and drying kinetics of Moroccan Eucalyptus globulus. Drying Technol 20(10):2027–2039 Kumar P, Singh D (2020) Advanced technologies and performance investigations of solar dryers: a review. Renew Energy Focus 35:148–158 Kumar M, Sansaniwal SK, Khatak P (2016) Progress in solar dryers for drying various commodities. Renew Sustain Energy Rev 55:346–360 Kumar A et al (2017) Advancement in greenhouse drying system. Solar drying technology. Springer, pp 177–196 Lingayat A, Chandramohan V, Raju V (2017) Design, development and performance of indirect type solar dryer for banana drying. Energy Procedia 109:409–416 Lingayat AB et al (2020) A review on indirect type solar dryers for agricultural crops–Dryer setup, its performance, energy storage and important highlights. Appl Energy 258:114005

136

A. Gaur et al.

Maiti S et al (2011) Performance evaluation of a small scale indirect solar dryer with static reflectors during non-summer months in the Saurashtra region of western India. Sol Energy 85(11):2686– 2696 Mohana Y et al (2020) Solar dryers for food applications: concepts, designs, and recent advances. Sol Energy 208:321–344 Mustayen A, Mekhilef S, Saidur R (2014) Performance study of different solar dryers: a review. Renew Sustain Energy Rev 34:463–470 Ndukwu MC, Simo-Tagne M, Bennamoun L (2021) Solar drying research of medicinal and aromatic plants: an African experience with assessment of the economic and environmental impact. Afr J Sci Technol Innov Dev 13(2):247–260 Pangavhane DR, Sawhney R, Sarsavadia P (2002) Design, development and performance testing of a new natural convection solar dryer. Energy 27(6):579–590 Papade C, Boda M (2014) Design and development of indirect type solar dryer with energy storing material. Int J Innov Res Adv Eng 1(12):109–114 Patil R, Gawande R (2016) A review on solar tunnel greenhouse drying system. Renew Sustain Energy Rev 56:196–214 Phadke PC, Walke PV, Kriplani VM (2015) A review on indirect solar dryers. ARPN J Eng Appl Sci 10(8):3360–3371 Ringeisen B, Barrett DM, Stroeve P (2014) Concentrated solar drying of tomatoes. Energy Sustain Dev 19:47–55 Rocha R et al (2011) Influence of drying process on the quality of medicinal plants: a review. J Med Plants Res 5(33):7076–7084 Román-Roldán N et al (2021) A new air recirculation system for homogeneous solar drying: computational fluid dynamics approach. Renew Energy 179:1727–1741 Romdhane BS (2007) The air solar collectors: comparative study, introduction of baffles to favor the heat transfer. Sol Energy 81(1):139–149 Shaikh MT, Kolekar MA (2015) Review of hybrid solar dryers. Int J Innov Eng Res Technol 2(8):1–7 Sharma A, Chen C, Lan NV (2009) Solar-energy drying systems: a review. Renew Sustain Energy Rev 13(6–7):1185–1210 Singh S, Kumar S (2012) Comparative thermal performance study of indirect and mixed-mode solar dryers. Int J Sustain Energy Dev 1(1/2):6–13 Singh P, Shrivastava V, Kumar A (2018) Recent developments in greenhouse solar drying: a review. Renew Sustain Energy Rev 82:3250–3262 Sivakumar S et al (2020) Effect of nano cupric oxide coating on the forced convection performance of a mixed-mode flat plate solar dryer. Renew Energy 155:1165–1172 Slama RB, Combarnous M (2011) Study of orange peels dryings kinetics and development of a solar dryer by forced convection. Sol Energy 85(3):570–578 Sopian K et al (2007) Double-pass solar collectors with porous media suitable for higher-temperature solar-assisted drying systems. J Energy Eng 133(1):13–18 Ssemwanga M, Makule E, Kayondo S (2020) Performance analysis of an improved solar dryer integrated with multiple metallic solar concentrators for drying fruits. Sol Energy 204:419–428 Tyagi V et al (2012) Review on solar air heating system with and without thermal energy storage system. Renew Sustain Energy Rev 16(4):2289–2303 Udomkun P et al (2020) Review of solar dryers for agricultural products in Asia and Africa: an innovation landscape approach. J Environ Manage 268:110730 Ugwu S et al (2015) Design, construction, and evaluation of a mixed mode solar kiln with blackpainted pebble bed for timber seasoning in a tropical setting. Renew Sustain Energy Rev 41:1404–1412 Vijayan S, Arjunan T (2015) Performance study of an indirect forced convection solar dryer for potato. Int J Appl Eng Res 10(50):454–458 Vijayan S, Arjunan T, Kumar A (2017) Fundamental concepts of drying. Solar drying technology. Springer, pp 3–38

Classification and Performance Enhancement of Solar Dryers

137

Visavale G (2012) Principles, classification and selection of solar dryers. In: Hii CL, Ong SP, Jangam SV, Mujumdar AS (eds) Solar drying: fundamentals, applications and innovations. Singapore, p 1–50 Wang W et al (2018) Thermal performance of indirect forced convection solar dryer and kinetics analysis of mango. Appl Therm Eng 134:310–321 Yassen TA, Al-Kayiem HH (2016) Experimental investigation and evaluation of hybrid solar/ thermal dryer combined with supplementary recovery dryer. Sol Energy 134:284–293

Solar Distillation and Water Heating Systems Integration with Photovoltaic Technology Rahul Dev, Yashwant Kashyap, Kirti Tewari, and Piyush Pal

Abstract Solar energy is a renewable source with three major applications: photovoltaics (PV), thermal, and daylight. A photovoltaic cell has a conversion efficiency of around 16–35%, depending upon its fabrication technology. Hence, it is observed that ~65–84% of incident solar radiation is lost as thermal energy to the surroundings. At the same time, solar thermal has vast applications, e.g., solar water heating, solar greenhouse drying, solar greenhouse crop cultivation, solar distillation, solar aquaculture, etc. Solar thermal applications have a thermal efficiency of around 20– 45% depending upon fabrication materials, design, operating, and weather conditions. Integrating photovoltaic and thermal applications proved advantageous over their application with better overall efficiency. Over the years, many researchers have developed various concepts integrating these technologies to get more output, cost, and land use benefits. This chapter elaborates on different ‘PV-integrated solar distillation systems’ and ‘PV-integrated solar water heating systems’ with working principles and performances.

R. Dev (B) Department of Mechanical Engineering, Motilal Nehru National Institute of Technology Allahabad, Prayagraj, Uttar Pradesh 211004, India e-mail: [email protected] Y. Kashyap Department of Electrical and Electronics Engineering, National Institute of Technology Karnataka, Surathkal, Karnataka 575025, India e-mail: [email protected] K. Tewari Department of Mechanical Engineering, National Institute of Technology Sikkim, Ravangla, South Sikkim 737139, India e-mail: [email protected] P. Pal Department of Mechanical Engineering, Goel Institute of Technology and Management, Lucknow, Dr. A.P.J. Abdul Kalam Technical University, Lucknow, Uttar Pradesh 226031, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Goyal et al. (eds.), Renewable Energy: Accelerating the Energy Transition, Energy Systems in Electrical Engineering, https://doi.org/10.1007/978-981-99-6116-0_8

139

140

R. Dev et al.

Keywords Solar energy · Photovoltaic · Solar thermal · Conversion efficiency · Thermal efficiency · Photovoltaic-thermal solar energy systems

1 Introduction Solar energy, a renewable energy source, has three major applications: photovoltaics (PV), thermal, and daylight. The conversion efficiency of photovoltaic cells is low, ~16–35%, depending upon their fabrication technology, due to which ~65–84% incident solar radiation is lost as thermal energy to the surrounding after absorption (Tiwari and Tiwari 2016; Tiwari and Mishra 2012). On the other hand, various researchers have developed different solar thermal technologies for water heating, cooking, and solar still, as given in Table 1. It also indicates whether the technology and its product are sellable or not to earn the maximum profit with the research scenario in the solar technology field. They integrate photovoltaic and thermal applications, resulting in photovoltaic-thermal (PV-T) technologies with electrical power and thermal benefits (Tiwari and Mishra 2012; Tiwari and Sahota 2017). Out of various solar technologies, some solar technologies such as photovoltaics, solar water heating, solar distillation, and concepts of passive solar houses became very popular and are widely used (Tiwari and Tiwari 2016; Tiwari and Sahota 2017). Water is essential for life in all the natural habitats on Earth. Water is a prime source for all essential activities like drinking, cooking, and personal hygiene (GDWQ 2011). Due to the desultory and continuous use of water in various activities like agriculture (including irrigation, livestock, and aquaculture), construction works (buildings, highways, and dams), industries, electricity generation, etc., water resources are severely under pressure in most of the regions of the globe (Tiwari and Tiwari 2016; Tiwari and Sahota 2017; GDWQ 2011). Moreover, illegal deforestation and desertification; increased human population; widespread drying of rivers, aquifers, lakes, and wetlands; and unsustained anthropogenic human activities also negatively affected the ecosystem and environment. Water and weather patterns are also changing due to climate change, resulting in shortages and droughts in some regions and floods in others (Tiwari and Mishra 2012; GDWQ 2011). All the above-said factors leading toward a ‘water scarcity’ subsequently alarm us to work toward efficient conservation of water resources worldwide. In the wake of the above severe problem, a distillation technique using a renewable energy source (solar energy), i.e., solar distillation, can provide safe and potable water to fulfill at least the basic need for freshwater according to WHO guidelines (Tiwari and Tiwari 2016; Tiwari and Mishra 2012).

1.1 Water Availability on the Earth The glaciers in the poles and the alpine regions contain three-fourths of the world’s freshwater, and the remaining one-fourth is found more frequently (by a factor of

Solar Distillation and Water Heating Systems Integration …

141

Table 1 Solar energy technologies, their products, earnings, and research scenario (Tiwari and Mishra 2012; Tiwari and Sahota 2017) Solar technology

System’s name

Product

Earning scenario (Both can be sold or not)

Research scenario

Solar water heating (SWH)

Solar water heater

Hot water

No, only SWH tech. can be sold. Whereas its use saves conventional energy as well as money

Solar greenhouse crop cultivation

Solar greenhouse

Crop

Yes

Solar greenhouse drying

Solar greenhouse

Dried food

Yes and saves conventional energy as well as money

Solar desalination Solar still

Distilled water

Yes and saves conventional energy as well as money

Solar cooking

Solar cooker

Cooked food

Yes and saves conventional energy as well as money

Solar air heating (SAH)

Solar air heater

Hot air

No, only SAH tech. can be sold. Whereas its use saves conventional energy as well as money

Solar-based organic Rankine cycle (ORC)

ORC power plant

Electricity

Yes and saves conventional energy as well as money

Solar passive house (SPH) (heating/cooling, ventilation, daylight)

Solar passive House house

No, only SPH tech. can be sold. Whereas its use saves conventional energy as well as money

• Technology development (i) Process (ii) Efficiency • Replacement of material for improved performance (i) Mechanical properties (ii) Optical properties (iii) Thermal properties (iv) Economic aspects • Developing new technology for the same product or new products • Integration of solar technologies • Hybrid solar technology

Solar swimming pool (SP)

Solar greenhouse

Hot water

No, SP tech. can be sold. Whereas its use saves conventional energy as well as money

Solar aquaculture Solar pond

Fish

Yes

Solar thermal energy storage (STES)

Heat exchanger

Hot air/ water

No, only STES tech. and saves conventional energy as well as money

Solar photovoltaic

Photovoltaic module

Electricity

Yes and saves conventional energy as well as money

142

R. Dev et al.

Table 2 Water availability in the different types of water resources available on the Earth (Zheng 2017; El-Dessouky and Ettouney 2002) Water storage location

Percentage of total water

Volume ×106 (km3 )

Atmosphere

0.001

0.129

Glacier

1.02

240.64

Surface water

0.021

3.0

Rivers

0.0002

0.021

Lakes

0.013

1.764

Moors

0.0008

0.115

Underground soil

0.0012

0.165

Poles

0.70

105.3

Lithosphere

0.75

234.0

Oceans

97.5

1380

about 37) in groundwater than in surface water. Less than 0.36% of the freshwater in rivers, lakes, and groundwater is suitable for direct human use (Zheng 2017), and the planet’s entire water supply only makes up 0.014% of drinkable water (Ibrahim et al. 2017). The location and storage proportions of different water resources on the Earth’s surface are given in Table 2.

1.2 Characterization of Water As given in Table 2, though seawater is abundant, it cannot be directly used because of its high salinity. The salinity or salt quantity in various water sources can be determined by total dissolved solids content, generally calculated in parts per million (ppm, i.e., mg/l) (Ela 2007; Kucera 2014; Belessiotis et al. 2016; Dev 2012). The classification of various water resources as a function of salinity is represented in Table 3. Brackish water after the treatment can be a preferable resource for obtaining potable water. The distillation process can treat that highly saline water to less salty water at a cheaper cost (Kucera 2014; Belessiotis et al. 2016). However, due to the thermal characteristics of the source (salty) water, distillation (or desalination) effectiveness varies. Abdenacer and Nafila (2007) also claimed that distilling the brackish water (which contains less salt) uses less energy than distilling seawater.

Solar Distillation and Water Heating Systems Integration …

143

Table 3 Water classification as per the amount of total dissolved solids (Ela 2007; Kucera 2014; Belessiotis et al. 2016; Dev 2012; World Health Organization 2017) Total dissolved solids (TDS) (ppm)

Source water Drinking (potable)

watera

Classification

98% in just 30 min (Veljkovi´c et al. 2012). Mahamuni and Adewuyi noted that the ultrasonic wave’s frequency impacts the reaction rate and biodiesel production. The production of biodiesel is only a little affected by high-frequency ultrasound between 581 and 1300 Hz, but the yield is increased by increasing the ultrasonic energy from 46 to 143W (Mahamuni and Adewuyi 2009).

Fabrication of Nanocatalyst for Biodiesel Production Using Various …

187

The dilution technique blends vegetable oil with regular diesel or a solvent to dilute it. The blending ratio can be indicated as B10, B20, B30, B40, B50, etc. This process lowers the oil’s viscosity, minimizing the need for diesel fuel (Ambat et al. 2018; Akta¸s et al. 2020). A stirrer device is used in microwave technology to mix the reactants by giving energy directly to the reactants (oil, alcohol, catalyst) (Ambat et al. 2018; Motasemi and Ani 2012). Microwave-assisted technology is suitable for making biodiesel more affordable and commercially viable (Sherbiny et al. 2010). Microwave energy speeds up the chemical process and suggests a quick and simple method for producing biodiesel. According to Koech et al., MW-assisted technology is a loftier heating method since it speeds up separation and decreases reaction time. Traditional heating can take up to 8 h to complete to just 7 min (Koech et al. 2020). Moreover, high-quality biodiesel can be prepared using microwaveassisted technology. Additionally, compared to a two-step process employing conventional heating, biodiesel’s yield and production rate increased by 1.3 and 6 times, respectively, by microwave irradiation (Cheng et al. 2013). Reactive distillation is grounded on a multifunctional reactor, where distillation and chemical reactions occur in the same piece of machinery. By combining the chemical reaction and thermodynamic separation into one process, the reactive distillation method enhances the traditional distillation method (Ambat et al. 2018). There are two types of reactive distillation: catalytic and non-catalytic. According to research by (Boon-anuwat et al. 2015), reactive distillation using homogeneous and heterogeneous catalysts has advantages over the traditional TF process (Boonanuwat 2015). Comparatively, homogeneous catalyzed (NaOH) reactive distillation increases the biodiesel yield and eliminates the need for product separation and refinement compared to a conventional method that necessitates additional methanol in the feed. Similarly, heterogeneously catalyzed reactive distillation with magnesium methoxide offers significant advantages such as lower energy consumption, fewer unit operations, with a 98wt.% biodiesel yield and glycerol as a byproduct, using just 153 kWh/t of energy (Boon-anuwat 2015). Using a decanter, flash evaporator, and distillation column allows the procedure to produce a product free of impurities. (Baskar and Aiswarya 2016). In order to reduce the need for a catalyst and speed up the TF reaction, the supercritical method, also known as the Saka method, was created in 2001 (Lee and Saka 2010). Several oil extraction, esterification, or TF steps can use supercritical technology (Aransiola et al. 2014). Ambat et al. discovered that a material is said to be in a supercritical fluid state when its temperature and pressure are above the critical temperature or pressure and it can no longer condense (Ambat et al. 2018). Triglyceride may dissolve well in methanol due to the high miscibility of oil and alcohol under the supercritical condition, forming a single phase. Mass transfer substantially influences the reaction between oil and alcohol (Lee and Saka 2010). According to Farobie, producing biodiesel using supercritical technology has many advantages, including a rapid reaction rate, a short residence time, the lack of a catalyst requirement, the ability to use a variety of feedstocks, and easier separation and purification(Farobie and Matsumura 2017). However, supercritical CO2 offers a processing temperature that satisfies the ideal conditions for lipase and is an ideal replacement

188

V. Mittal et al.

for organic solvents for triglycerides (Aransiola et al. 2014). A significant barrier to this process could be the large energy required to reach supercritical conditions, which includes higher costs on an economic and technical level (Ambat et al. 2018; Farobie and Matsumura 2017). In situ TF turns oil seeds into biodiesel without intermediate steps by reacting methanol with a catalyst (Baskar and Aiswarya 2016). Reactive TF, also known as in situ TF, eliminates the pricey solvent extraction phase by allowing simultaneous oil extraction and TF conversion into biodiesel without needing prior oil extraction (Koech et al. 2020). According to Erturul Karatay et al.’s research, this procedure yields the highest levels of lipid accumulation with the highest content of C16 and C18 fatty acids, at 52% and 96.3%, respectively (Ertu˘grul Karatay et al. 2019). Thermal cracking is a pricey technique that results in low-purity biodiesel due to residue contamination and high equipment expenditures. On the other hand, pyrolysis is an environmentally favorable process, and the fuel it produces has a low viscosity, a high cetane number, and a small amount of sulfur (Ambat et al. 2018). Baskar and Aiswarya say biodiesel is thermally degraded from vegetable oils or fats through pyrolysis or thermal cracking beneath its boiling point without oxygen (Bano et al. 2020). The 350 °C and 500 °C temperatures produce the most liquids; no further separating or purifying is necessary (Jahirul et al. 2012). The micro-emulsion method is stable from a thermodynamic perspective. One or more amphiphiles and two immiscible liquids are used in the micro-emulsion technique to create colloidal dispersions of 1–150 nm of isotropic fluid, and short-chain alcohols like methanol, ethanol, or 1-butanol are used to lessen the high viscosity of vegetable oils or fats (Bano et al. 2020). High-viscosity oils can be employed with the straightforward micro-emulsion technique. According to Akta¸s, Demr, and Uçar’s analysis, the fuels produced by this technique have lower heat values since alcohol is present in them. The advantages and disadvantages of various non-catalytic techniques for biodiesel production are summarized in Table 3.

5 Optimization Parameters for Enhancing Biodiesel Production The methanol-to-oil molar ratio, reaction temperature, process duration, and catalyst content are the most critical operating factors in biodiesel production. The Artificial Neural Networks (ANN), Taguchi approach employing MINITAB software, Genetic Algorithms (GN), Design of Experiments, Fuzzy Logic, and Response Surface Methodology (RSM) were some of the software analysis of nonlinear techniques used to optimize the reaction parameters. These mathematical models can efficiently optimize multiple reaction parameters simultaneously. The vital benefit of optimization is that it yields essential statistics in fewer experimental runs (Bojan et al. 2011). The RSM is utilized to establish a functional association between several input factors and the response of interest, that is, FAME yield. The TF process is

Fabrication of Nanocatalyst for Biodiesel Production Using Various …

189

Table 3 Advantages and disadvantages of non-catalytic techniques Techniques

Advantages

Ultrasound-assisted transesterification

Reduces reaction time and production cost, less energy consumption

Disadvantages

Dilution

Simple

Incomplete combustion

microwave technology

High reaction rate, easy and simple, high yield and purity of biodiesel

Catalyst removal is required, not suitable for solid feedstocks

Reactive distillation

Simpler, easier separation, free Consume more energy, and from contaminants, applied for process conversion depends on feedstocks with high FFA content catalyst efficiency

Supercritical method

High reaction rate. Less residence Higher technical cost, corrosion, time, applicable to all feedstocks, and salt deposition consume more doesn’t require a catalyst, higher energy production efficiency

In situ transesterification

Inexpensive as it eliminates solvent extraction, highest lipid accumulation

Pyrolysis

Simple, pollution-free, no need for separation and purification

Expensive, low-purity of biodiesel, requires high temperatures

Micro-emulsion

Modest and suitable for usage with high-viscosity oil

Incomplete combustion, poor stability, and volatility

often carried out at a temperature (50–60 °C) below the alcohol boiling point since reaction temperature affects biodiesel production significantly. The ideal temperature is preferred for increased conversion since a rise in temperature speeds up the reaction and, as a result, reduces the reaction time (Eevera et al. 2009). Mandeep Kaur et al. used the nanocatalyst 1.75Li-CaO and carried out the TF reaction of karanja and jatropha oil at room temperature (35 °C). However, it took longer than expected to complete, taking 6 and 7 h for karanja and jatropha oils, respectively. Therefore, the time decreases from 6 to 1 h for karanja oil and from 7 to 2 h for jatropha oil when the reaction temperature is raised from 35 °C to 65 °C (Mofijur et al. 2021). A crucial component that has a considerable impact on the output of biodiesel synthesis is the molar ratio of alcohol to oil. Because the molar ratio varies depending on the catalyst and kind of oil, more alcohol is needed to proceed when there is a high fatty acid content. According to Bano et al. (2020), a higher MO ratio causes a greater conversion of esters over a shorter period (Bano et al. 2020; Atadashi et al. 2011). However, at the same time, it increases the complication of the separation and purification processes (Bano et al. 2020; Atadashi et al. 2011), which not only raises the cost of the procedure but also hurts the production of biodiesel. Therefore, the ideal MO ratio is needed to improve biofuel generation. The maximum FAME yield of 98.1% was obtained when the molar ratio of MO was continuously increased to 15:1, but increasing the MO molar ratio further to 18:1 lowers in FAME yield, according

190

V. Mittal et al.

to Gardy et al.‘s analysis of the effect of MO ratio (6:1 to 18:1) by using solid acid nanocatalyst TiO2 /PrSO3 H (Gardy et al. 2017). Conversely, a high catalyst weight can lead to agglomeration, which limits mass transfer by reducing the communication of active sites and influences the reaction rate while assisting in the production of soap and hydrolysis (Bano et al. 2020). The iron (II) doped ZnO nanocatalyst loading was increased by G. Baskar et al., from 2wt.% to 14wt.%, and the FAME yield improved correspondingly from 4 to 90% (Baskar and Soumiya 2016). However, the conversion somewhat decreased as the catalyst concentration was raised beyond 14 wt.% because the slurry thickened and emulsified (Baskar and Soumiya 2016). The nature of the catalyst will determine how long the reaction takes, but nanocatalysts often convert substances in a shorter amount of time (1–2 h). The conversion of fatty acids increases as reaction time increases. However, further surges in reaction time can degrade the yield and accelerate glycerol generation (Bano et al. 2020; Eevera et al. 2009; Vinoth Arul Raj et al. 2019) altered the reaction period from 2 to 6 h using Mn-ZnO capped with PEG while producing biodiesel from microalgae. After 4 h of transesterification reaction, a maximum yield of 87.5% of biodiesel was obtained. However, as the reaction time increased over 4 h, biodiesel production declined either because triglycerides were converted to other chemicals rather than esters or because transesterification is reversible (Vinoth Arul Raj et al. 2019).

6 Significance of Nanocatalyst in the Transesterification Process The transesterification process uses a variety of catalysts, including homogeneous, heterogeneous, and enzymatic catalysts. Including a catalyst speeds up the reaction, ultimately boosting biodiesel production. While heterogeneous catalysts require more energy, longer reaction times, and higher temperatures, homogeneous catalysts use less energy overall but entail more catalysts and require more washing and purifying phases. Additionally, it has restrictions on diffusion and has the potential to leak active catalyst sites, contaminating the finished product. Thus, numerous researchers from around the globe have perceived the utilization of nanocatalysts in the generation of various types of biodiesel. Using nanocatalysts accelerates the rate of reactions, combines the advantages of homogeneous and heterogeneous catalysts, and eliminates their corresponding drawbacks (Mittal et al. 2022). The most crucial properties of nanocatalysts, such as their enormous surface area, illuminate several issues with the TF for biodiesel generation. The number of nanocatalysts has been employed with the TF reaction to produce biodiesel. Transforming triglycerides into fatty acid methyl esters using a catalyst and methanol is known as transesterification. The experimental setup of the transesterification reaction is shown in Fig. 4. The calcium methoxide nanocatalyst was synthesized by Teo et al. using hydrothermal synthesis. They produced the maximum FAME yield of 99.0% from

Fabrication of Nanocatalyst for Biodiesel Production Using Various …

191

Fig. 4 Experimental setup of transesterification reaction. Reprint with permission from Elias, S. et al. Applied Sciences, 10(9), 3153, 2020. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. (Elias et al. 2020)

the algae Nannochloropsis sp. with over 3 wt.% of Ca(OCH3 )2 catalyst loading and a reaction period of 3 h at 80 °C (Teo et al. 2016). The nanocatalyst Cs/Al/Fe3 O4 was prepared by Feyzi et al. using a novel synthesis technique, and it demonstrated the maximum catalytic activity at 58 °C for 120 min with a molar ratio of 14:1 and catalyst loading Cs/Al = 2.5/1 and a biodiesel yield of 94.8% under optimum conditions (Feyzi et al. 2013). Using the response surface methodology-genetic algorithm (RSM-GA) method, K. Jawaharraj et al. 2017 increased the biomass, lipid, and biodiesel productivities. They also achieved the highest conversion of 36.583 mg FAME/g from Synechocystis sp. NN TF using TiO2 as a heterogeneous nanocatalyst linked whole cell TF technique (Jawaharraj et al. 2017). Balkis Hazmi et al. utilized a nanomagnetic bifunctional catalyst (RHC/K2 O-20%/Ni-5%). They attained a maximum biodiesel production of 98.2% with 4 wt.% of catalyst loading, a 12:1 methanol to UCO molar ratio at 65 °C, and 2 h of reaction time (Hazmi et al. 2021).

7 Conclusions Biodiesel production significantly reduces the need for energy produced from fossilderived products. Biodiesel from different feedstocks, including edible oils, poses certain financial and dietary constraints. In contrast, non-edible oils and some types of microalgae provide improved projections for the transesterification process. Although nanocatalysts have many benefits in synthesizing biodiesel over standard catalysts, including better catalytic activity, higher yields, and regenerability, the research in this area is relatively sparse. The unique characteristics of the metal oxides-based nanocatalysts include a high surface area to volume ratio, varied shape, high activity, and selectivity of the catalyst. Enhancing specific surface area, pore

192

V. Mittal et al.

size, and average pore diameter has been dramatically helped by nanomagnetic and mixed metal oxide-based nanocatalysts. This chapter debates different biodiesel production methods, concluding that transesterification is the most efficient process. Process optimization, especially response surface methodology, is an appropriate technique for optimizing operational parameters to escalate the yield of methyl esters. In order to resolve current issues designing effective, economical, and environmentally friendly catalysts is essential. Hence, it recommends a precise framework with clear objectives, doable initiatives, and a thorough policy structure to promote the successful and long-term development of a catalyst with such properties for effective transesterification.

References Akta¸s ES, Dem˙Ir Ö, Uçar D (2020) A Review of the Biodiesel Sources and Production Methods 5:1–10 Ambat I, Srivastava V, Sillanpää M (2018) Recent advancement in biodiesel production methodologies using various feedstock: A review. Renew Sustain Energy Rev 90:356–369. https://doi. org/10.1016/j.rser.2018.03.069 Aransiola EF, Ojumu TV, Oyekola OO, Madzimbamuto TF, Ikhu-Omoregbe DIO (2014) A review of current technology for biodiesel production: State of the art. Biomass Bioenerg 61:276–297. https://doi.org/10.1016/j.biombioe.2013.11.014 Atadashi IM, Aroua MK, Aziz AA (2011) Biodiesel separation and purification: A review. Renew Energy 36:437–443. https://doi.org/10.1016/j.renene.2010.07.019 Bano S, Sha A, Sultana S, Sabir S, Khan MZ (2020) Fabrication and optimization of nanocatalyst for biodiesel production : An overview, 8. https://doi.org/10.3389/fenrg.2020.579014. Baskar G, Aiswarya R (2016) Trends in catalytic production of biodiesel from various feedstocks. Renew Sustain Energy Rev 57:496–504. https://doi.org/10.1016/j.rser.2015.12.101 Baskar G, Soumiya S (2016) Production of biodiesel from castor oil using iron (II) doped zinc oxide nanocatalyst. Renewable Energy 98:101–107. https://doi.org/10.1016/j.renene.2016.02.068 Binod P, Gnansounou E, Sindhu R, Pandey A (2019) Enzymes for second generation biofuels: Recent developments and future perspectives. Bioresour Technol Rep 5:317–325. https://doi. org/10.1016/j.biteb.2018.06.005 Binod P, Gnansounou E, Sindhu R, Pandey A (2019) Enzymes for second generation biofuels: Recent developments and future perspectives. Bioresour Technol Rep 5:317–25. https://doi.org/ 10.1016/j.biteb.2018.06.005 Bojan SG, Chelladurai S, Durairaj SK (2011) Response surface methodology for optimization of biodiesel production from high FFA Jatropha curcas oil. Int J Green Energy 8:607–617. https:// doi.org/10.1080/15435075.2011.600373 Boon-anuwat N nan, Kiatkittipong W, Aiouache F, Assabumrungrat S (2015) Process design of continuous biodiesel production by reactive distillation: Comparison between homogeneous and heterogeneous catalysts. Chem Eng Process-Process Intensif, 92:33–44. https://doi.org/10. 1016/j.cep.2015.03.025 Borges LD, Moura NN, Costa AA, Braga PRS, Dias JA, Dias SCL, et al. (2013) Applied catalysis a : general investigation of biodiesel production by HUSY and Ce/HUSY zeolites : Influence of structural and acidity parameters. Appl Catal A, Gen, 450:114–9. https://doi.org/10.1016/j.apc ata.2012.10.009 Carmona-Cabello M, Sáez-Bastante J, Pinzi S, Dorado MP (2019) Optimization of solid food waste oil biodiesel by ultrasound-assisted transesterification. Fuel 255:115817. https://doi.org/ 10.1016/j.fuel.2019.115817

Fabrication of Nanocatalyst for Biodiesel Production Using Various …

193

Chelladurai K, Rajamanickam M (2014) Environmentally benign neem biodiesel synthesis using Nano-Zn-Mg-Al hydrotalcite as solid base catalysts 2014 Chen J, Li J, Dong W, Zhang X, Tyagi RD, Drogui P et al (2018) The potential of microalgae in biodiesel production. Renew Sustain Energy Rev 90:336–346. https://doi.org/10.1016/j.rser. 2018.03.073 Cheng J, Yu T, Li T, Zhou J, Cen K (2013) Using wet microalgae for direct biodiesel production via microwave irradiation. Biores Technol 131:531–535. https://doi.org/10.1016/j.biortech.2013. 01.045 Correa DF, Beyer HL, Possingham HP, Thomas-Hall SR, Schenk PM (2017) Biodiversity impacts of bioenergy production: Microalgae vs. first generation biofuels. Renew Sustain Energy Rev 74:1131–46. https://doi.org/10.1016/j.rser.2017.02.068 Doshi A, Pascoe S, Coglan L, Rainey TJ (2016) Economic and policy issues in the production of algae-based biofuels: A review. Renew Sustain Energy Rev 64:329–337. https://doi.org/10. 1016/j.rser.2016.06.027 Eevera T, Rajendran K, Saradha S (2009) Biodiesel production process optimization and characterization to assess the suitability of the product for varied environmental conditions. Renew Energy, 34:762–5. https://doi.org/10.1016/j.renene.2008.04.006 El Sherbiny SA, Refaat AA, El Sheltawy ST (2010) Production of biodiesel using the microwave technique. J Adv Res 1:309–314. https://doi.org/10.1016/j.jare.2010.07.003 Elias S, Rabiu AM, Okeleye BI, Okudoh V, Oyekola O (2020) Bifunctional heterogeneous catalyst for biodiesel production from waste vegetable oil. Appl Sci 10(9):3153. https://doi.org/10.3390/ app10093153 Elshahed MS (2010) Microbiological aspects of biofuel production: Current status and future directions. J Adv Res 1:103–111. https://doi.org/10.1016/j.jare.2010.03.001 Ertu˘grul Karatay S, Demiray E, Dönmez G (2019) Efficient approaches to convert Coniochaeta hoffmannii lipids into biodiesel by in-situ transesterification. Bioresour Technol, 285. https:// doi.org/10.1016/j.biortech.2019.121321 Faried M, Samer M, Abdelsalam E, Yousef RS, Attia YA, Ali AS (2017) Biodiesel production from microalgae: Processes, technologies and recent advancements. Renew Sustain Energy Rev 79:893–913. https://doi.org/10.1016/j.rser.2017.05.199 Farobie O, Matsumura Y (2017) State of the art of biodiesel production under supercritical conditions. Prog Energy Combust Sci 63:173–203. https://doi.org/10.1016/j.pecs.2017.08.001 Feyzi M, Khajavi G (2014) Investigation of biodiesel production using modified strontium nanocatalysts supported on the ZSM-5 zeolite. Ind Crops Prod 58:298–304. https://doi.org/10.1016/j. indcrop.2014.04.014 Feyzi M, Hassankhani A, Rafiee HR (2013) Preparation and characterization of Cs/Al/Fe3O4 nanocatalysts for biodiesel production. Energy Convers Manag 71:62–68. https://doi.org/10. 1016/j.enconman.2013.03.022 Galadima A, Muraza O (2014) Biodiesel production from algae by using heterogeneous catalysts: A critical review. Energy 78:72–83. https://doi.org/10.1016/j.energy.2014.06.018 Gardy J, Hassanpour A, Lai X, Ahmed MH, Rehan M (2017) Biodiesel production from used cooking oil using a novel surface functionalised TiO2 nanocatalyst. Appl Catal B 207:297–310. https://doi.org/10.1016/j.apcatb.2017.01.080 Gaurav N, Sivasankari S, Kiran GS, Ninawe A, Selvin J (2017) Utilization of bioresources for sustainable biofuels: A Review. Renew Sustain Energy Rev 73:205–214. https://doi.org/10. 1016/j.rser.2017.01.070 Georgogianni KG, Katsoulidis AK, Pomonis PJ, Manos G, Kontominas MG (2009) Transesterification of rapeseed oil for the production of biodiesel using homogeneous and heterogeneous catalysis. Fuel Process Technol 90:1016–1022. https://doi.org/10.1016/j.fuproc.2009.03.002 Hassan MH, Kalam MA (2013) An overview of biofuel as a renewable energy source: Development and challenges. Procedia Eng 56:39–53. https://doi.org/10.1016/j.proeng.2013.03.087

194

V. Mittal et al.

Hazmi B, Rashid U, Ibrahim ML, Nehdi IA, Azam M, Al-Resayes SI (2021) Synthesis and characterization of bifunctional magnetic nanocatalyst from rice husk for production of biodiesel. Environ Technol Innov 21:101296. https://doi.org/10.1016/j.eti.2020.101296 Ho WWS, Ng HK, Gan S (2016) Advances in ultrasound-assisted transesterification for biodiesel production. Appl Therm Eng 100:553–563. https://doi.org/10.1016/j.applthermaleng.2016. 02.058 Hosseini SA (2022) Nanocatalysts for biodiesel production. Arab J Chem 15:104152. https://doi. org/10.1016/j.arabjc.2022.104152 Hu S, Guan Y, Wang Y, Han H (2011) Nanomagnetic catalyst KF/CaO-Fe3O4 for biodiesel production. Appl Energy 88:2685–2690. https://doi.org/10.1016/j.apenergy.2011.02.012 Ibrahim NA, Rashid U, Hazmi B, Moser BR, Alharthi FA, Rokhum SL, et al. (2022) Biodiesel production from waste cooking oil using magnetic bifunctional calcium and iron oxide nanocatalysts derived from empty fruit bunch. Fuel 317:123525. https://doi.org/10.1016/j.fuel.2022. 123525. Ingle AP, Chandel AK, Philippini R, Martiniano SE, Silv S (2020) SS symmetry advances in nanocatalysts mediated biodiesel production : A Critical Appraisal, 1–21 Jahirul MI, Rasul MG, Chowdhury AA, Ashwath N (2012) Biofuels production through biomass pyrolysis- A technological review. Energies 5:4952–5001. https://doi.org/10.3390/en5124952 Jawaharraj K, Karpagam R, Ashokkumar B, Kathiresan S, Moorthy IMG, Arumugam M, et al. (2017) Improved biomass and lipid production in Synechocystis sp. NN using industrial wastes and nanocatalyst coupled transesterification for biodiesel production. Bioresour Technol 242:128–32. https://doi.org/10.1016/j.biortech.2017.03.067 Jume BH, Gabris MA, Rashidi Nodeh H, Rezania S, Cho J (2020) Biodiesel production from waste cooking oil using a novel heterogeneous catalyst based on graphene oxide doped metal oxide nanoparticles. Renew Energy 162:2182–9. https://doi.org/10.1016/j.renene.2020.10.046 Koech AK, Kumar A, Siagi ZO (2020) In situ transesterification of spirulina microalgae to produce biodiesel using microwave irradiation. J Energy 2020:1–10. https://doi.org/10.1155/2020/881 6296 Lee JS, Saka S (2010) Biodiesel production by heterogeneous catalysts and supercritical technologies. Biores Technol 101:7191–7200. https://doi.org/10.1016/j.biortech.2010.04.071 Mahamuni NN, Adewuyi YG (2009) Optimization of the synthesis of biodiesel via UltrasoundEnhanced Base-Catalyzed transesterification of soybean oil using a multifrequency ultrasonic reactor. Energy Fuels 23:2757–2766. https://doi.org/10.1021/ef900047j Mittal V, Ghosh UK (2022) Materials today : Proceedings Comparative analysis of two different nanocatalysts for producing biodiesel from microalgae. Mater Today: Proc. https://doi.org/10. 1016/j.matpr.2022.03.652 Mittal V, Namita K, Uttam T, Ghosh K (2022) A comprehensive review on biodiesel production from microalgae through nanocatalytic transesterification process : lifecycle assessment and methodologies. International Nano Letters. https://doi.org/10.1007/s40089-022-00372-2 Mittal V (2022) Potential of microalgae for phytoremediation of various wastewaters for nutrient removal and biodiesel production through nanocatalytic transesterification 1–15. https://doi.org/ 10.1002/apj.2847 Mofijur M, Sk Yasir Arafat Siddiki, Md Bengir Ahmed Shuvho F, Djavanroodi, IM Rizwanul Fattah, Hwai Chyuan Ong, Chowdhury MA, Mahlia TMI (2021) Effect of nanocatalysts on the transesterification reaction of first, second and third generation biodiesel sources-A mini-review. Chemosphere, 270: 128642. https://doi.org/10.1016/j.chemosphere.2020.128642 Motasemi F, Ani FN (2012) A review on microwave-assisted production of biodiesel. Renew Sustain Energy Rev 16:4719–4733. https://doi.org/10.1016/j.rser.2012.03.069 Nanocatalyst C A review on thermal conversion of plant oil (Edible and Inedible ) into green fuel using n.d.:1–25 Nayebzadeh H, Haghighi M, Saghatoleslami N, Tabasizadeh M, Yousefi S (2018) Fabrication of carbonated alumina doped by calcium oxide via microwave combustion method used as

Fabrication of Nanocatalyst for Biodiesel Production Using Various …

195

nanocatalyst in biodiesel production: Influence of carbon source type. Energy Convers Manag 171:566–575. https://doi.org/10.1016/j.enconman.2018.05.081 Shankar AA, Pentapati PR, Prasad RK (2017) Biodiesel synthesis from cottonseed oil using homogeneous alkali catalyst and using heterogeneous multi walled carbon nanotubes : Characterization and blending studies. Egypt J Pet 26:125–133. https://doi.org/10.1016/j.ejpe.2016.04.001 Sharma A, Murugan S (2022) Combustion analysis of a diesel engine run on non-conventional fuel at different nozzle injection pressure BT—Innovations in energy, power and thermal engineering. In: Palanisamy M, Natarajan SK, Jayaraj S, Sivalingam M, editors, Singapore: Springer Singapore, pp 109–18 Sharma A, Murugan S (2017) Durability analysis of a single cylinder DI diesel engine operating with a non-petroleum fuel. Fuel 191:393–402. https://doi.org/10.1016/j.fuel.2016.11.086. Sun J, Xiong X, Wang M, Du H, Li J, Zhou D et al (2019) Microalgae biodiesel production in China: A preliminary economic analysis. Renew Sustain Energy Rev 104:296–306. https://doi. org/10.1016/j.rser.2019.01.021 Talapatra N, Gautam R, Mittal V, Ghosh UK (2021) A comparative study of the growth of microalgae-bacteria symbiotic consortium with the axenic culture of microalgae in dairy wastewater through extraction and quantification of chlorophyll. Materials Today: Proceedings. https:// doi.org/10.1016/j.matpr.2021.06.227 Tariq M, Ali S, Khalid N (2012) Activity of homogeneous and heterogeneous catalysts, spectroscopic and chromatographic characterization of biodiesel: A review. Renew Sustain Energy Rev 16:6303–6316. https://doi.org/10.1016/j.rser.2012.07.005 Teo SH, Islam A, Taufiq-Yap YH (2016) Algae derived biodiesel using nanocatalytic transesterification process. Chem Eng Res Des 111:362–370. https://doi.org/10.1016/j.cherd.2016. 04.012 Veljkovi´c VB, Avramovi´c JM, Stamenkovi´c OS (2012) Biodiesel production by ultrasound-assisted transesterification: State of the art and the perspectives. Renew Sustain Energy Rev 16:1193– 1209. https://doi.org/10.1016/j.rser.2011.11.022 Vinoth Arul Raj J, Bharathiraja B, Vijayakumar B, Arokiyaraj S, Iyyappan J, Praveen Kumar R (2019) Biodiesel production from microalgae Nannochloropsis oculata using heterogeneous Poly Ethylene Glycol (PEG) encapsulated ZnOMn2+ nanocatalyst. Bioresour Technol 282:348– 52. https://doi.org/10.1016/j.biortech.2019.03.030 Zuliani A, Ivars F, Luque R (2018) Advances in nanocatalyst design for biofuel production. Chem Cat Chem 10:1968–1981. https://doi.org/10.1002/cctc.201701712

Performance Investigation of Automotive Radiator Using Water-Al2 O3 and Ethylene Glycol Nanofluid Blends Vednath P. Kalbande, Yogesh N. Nandanwar, Man Mohan, Shilpa Vinchurkar, Kishor Rambhad, Vijay Kalbande, Anil Singh Yadav, and Tabish Alam

Abstract This study aims to improve the heat transfer performance of radiators in automobiles using water-based Al2 O3 and ethylene glycol (EG) nanofluid. Three water-based nanofluids with different concentrations of Al2 O3 and EG were evaluated and compared with base water. The three selected concentrations of EG were 30%, 50% in water (by volume) without Al2 O3 and 50% EG + 0.1% Al2 O3 in water. The experiments evaluated the superiority of water-based Al2 O3 and EG nanofluid mixture over the base fluid. Additionally, experimentation was performed to optimize the distance between fan and radiator. It is found that the air-side thermal resistance is more prevalent in the vehicle radiator. A thorough examination of the air-side heat transfer coefficient is necessary to enhance the current fan and radiator designs and positioning. The analysis of the radiator’s heat transfer performance for automotive V. P. Kalbande (B) · Y. N. Nandanwar · S. Vinchurkar Department of Mechanical Engineering, G. H. Raisoni College of Engineering, Nagpur 440016, Maharashtra, India e-mail: [email protected] M. Mohan Department of Mechanical Engineering, Rungta College of Engineering and Technology, Bhilai 490024, Chhattisgarh, India K. Rambhad Department of Mechanical Engineering, St. John College of Engineering and Management, Palghar 401404, Maharashtra, India V. Kalbande Department of Mechanical Engineering, Nagpur Institute of Technology, Nagpur 441501, Maharashtra, India A. S. Yadav Department of Mechanical Engineering, Bakhtiyarpur College of Engineering (Science, Technology and Technical Education Department, Govt. of Bihar), Bakhtiyarpur, Patna 803212, Bihar, India T. Alam Architecture, Planning and Energy Efficiency, CSIR-Central Building Research Institute, Roorkee 247667, Uttarakhand, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Goyal et al. (eds.), Renewable Energy: Accelerating the Energy Transition, Energy Systems in Electrical Engineering, https://doi.org/10.1007/978-981-99-6116-0_11

197

198

V. P. Kalbande et al.

applications demonstrates how variations in the distance between the fan and radiator impact the choice of coolant and air movement through the core. Keywords Automotive radiator · Fan radiator distance · Heat transfer · Nanofluid · Ethylene glycol

1 Introduction In automobiles, a compact heat exchanger known as a radiator is used for efficient cooling and is essential for internal combustion (IC) engines. When the engine runs, the water absorbs heat from the cylinder walls and rejects it into the surrounding air through the radiator. As a consequence, radiators are used to regulate the operating temperatures of IC engines. A comprehensive set of numerical parametric is studied on car radiators by Oliet et al. (2007). The exhaust gas removed in an IC engine may operate at a minimum normal temperature of at least 800 °C. The first focus of parametric investigations was on the effects of the chosen coolant liquid and working conditions on the heat transfer characteristics. In addition to the significance of coolant flow on radiator performance, the effects of louver angle and fin spacing have been studied using a mathematical model. Taler (2004) developed a generic mathematical method for selecting the connections for energy transfer in cross-flow heat exchangers with longitudinal fins. A model for the average heat transfer coefficients, in terms of the Reynolds number (Re) and Prandtl number (Pr), was formulated by choosing the functional form of the Nusselt number (Nu) [N u = f (Re, Pr )]. It could be used to determine the heat transfer characteristics of various heat exchangers. Kays and London (1984) conducted one of the important studies on extended surface heat transmission and disseminated the key reliable and comprehensive test data on louvered surfaces for compact radiators. The fluctuations in the velocity, temperature, and pressure in the air and coolant flow direction were evaluated by Sridhara et al. (2005). It was observed that the coolant experienced a pressure drop of 52.3 Pa and a temperature drop of 6 K. Due to induced convection, the air temperature rises by 9.5 K, absorbing heat. Some researchers studied thermal storage performance using Al2 O3 as the nanoparticles for insertion of the base fluid (Kalbande et al. 2019, 2021a, b, 2022) and carried out a study using a flat plate collector for an oil-based thermal storage system (Kalbande and Walke 2019). The heat transfer and fluid flow study of a patterned roll-bonded aluminum radiator were explored by Witry et al. (2003) using a CFD model. Investigations were made into the tube and shell sides’ water and airflow patterns, respectively. The resulting values of the overall heat transfer coefficients vary from 75 to 560 W/m2 K. A new automotive radiator that uses nanofluid was developed by Fell et al. (2007). This hybrid vehicle has several cooling systems for IC engines, batteries, and electric motors. As the radiator operated at an inlet fluid temperature of 80 °C, the flow rate varied by 15, 30, 45, and 60 l/h corresponding temperature differences of 19, 16, 9, and 6 °C were observed. Chen et al. (2001) performed experiments on a tube-and-fin

Performance Investigation of Automotive Radiator Using Water-Al2 O3 …

199

radiator to examine the heat transfer properties. For experimental optimization, the radiator used in the car was mounted in a wind tunnel test rig. The author developed regression equations for the coolant pressure drop, air pressure drop, and heat dissipation rate. Most researchers employed water as a coolant in the automobile radiator. Compared to typical fluids in automotive radiators, blends of ethylene glycol and water with dispersed nanoparticles are a better option for the heat transfer agent. This study employed Al2 O3 /water + EG nanofluid as the heat transfer fluid to investigate the radiator’s heat transfer capabilities. Furthermore, the effect of the distance between fan and radiator on the radiator’s performance was investigated. The objectives of the current research work are (i) to optimize the fan–radiator distance, (ii) to investigate radiator performance using different concentrations of Al2 O3 /water and EG nanofluid, and (iii) to optimize coolant and air mass flow rates.

2 Materials and Experimental Setup A car radiator is selected for an experiment. A radiator of size 337 mm (length) × 308 mm (height) is used for the experiment. The detailed specifications of a radiator are given in Table 1. Figures 1 and 2 show photographs and a schematic of a radiator. The following assumptions are considered: (i) heat gain from the engine’s coolant is equal to heat rejection by coolant in radiator and (ii) radiator temperature should not exceed 90 °C. The experimental setup shown in Fig. 3 was used for the investigation. The system includes a radiator, a coolant tank, a fan, and a pump connected using insulated copper tubes, as depicted in Fig. 3. A pump circulates coolant through the loop of radiator and coolant tank. Instead of a real IC engine, heater coils were used to heat coolant in tank. Force air flow by fan over the radiator coils removes heat from the radiator. A flowmeter was installed between the pump and radiator to measure the mass Table 1 Specifications of radiator model Parameter

Specification

Parameter

Specification

Radiator type

Cross-flow forced air-cooled radiator

Tube length (L tube )

310 mm

In hose barb (inlet)

25 mm

Total no. of tube (N tube )

36

Out hose barb (outlet)

25 mm

Fin length (L fin )

332 mm

Core length (L)

337 mm

Fin width (W fin )

26 mm

Core height (H)

308 mm

Fin thickness (t fin )

0.2 mm

Inner diameter of tube (Di)

6 mm

Total no. of fin (N fin )

225

Outer diameter of tube (Do)

8 mm

Material

Aluminum

Air gap between two fins

1.5 mm

200

V. P. Kalbande et al.

Fig. 1 Photograph of the car radiator model used for experimental analysis

Fig. 2 Schematic of the radiator model

flow rate of coolant. A flow control valve was installed between the pump and the flowmeter to adjust the coolant flow rate. Utilizing calibrated K-type thermocouples, the temperatures of the intake and outflow of both air and coolant were determined.

Performance Investigation of Automotive Radiator Using Water-Al2 O3 …

201

Fig. 3 Schematic diagram of the experimental setup

3 Methodology and Performance Investigation The selected coolant Al2 O3 /water + EG nanofluid mixture was filled in a coolant tank and then heated till it reached ~90 °C. The radiator fan is switched “ON” and a pump circulates heated coolant through the radiator. From the exit end of the radiator, cold coolant enters back in the coolant tank, again heated and recirculated to the radiator. The experiment was conducted at various coolant mass flow rates, measured using flowmeters ranging from 2.5 to 15 l/min. The inlet and outlet coolant temperatures (T ci and T co , respectively) across the radiator and air’s inlet and outlet temperatures (T ai and T ao , respectively) were also recorded. The coolant mixture varied as 0% EG + water, 30% EG + water, 50% EG + water, Al2 O3 /50% EG + water for analysis. The performance investigation carried out on the subject setup by varying four different parameters and the same is summarized below: 1. Variation of coolant flow rate: The heat transfer characteristics were studied at different coolant flow rates keeping all other parameters fixed (coolant composition, fan speed, and fan–radiator distance). 2. Variation of air flow rate: The heat transfer characteristics were studied at different air flow rates by varying the fan speed keeping all other parameters fixed. 3. Variation of the distance between the fan and radiator: The heat transfer characteristics were studied by varying the distance between fan and the radiator keeping all other parameters fixed. 4. Variation of coolant composition: The heat transfer characteristics were studied with different blends of Al2 O3 and EG, keeping all other parameters fixed. 5. The coolant inlet temperature was set at around 75–80 °C.

202

V. P. Kalbande et al.

The following model has been developed for analytical analysis of radiator in consideration. The mass air flow rate (m air ) through radiator core is evaluated by Holman (2002) m air = ρair × Vair × A f

(1)

where ρair is the density of air (kg/m3 ), Vair is the velocity of air (m/s), and A f is the face area of radiator (m2 ). However, the heat transfer rate (Q) is estimated by equating heat loss by coolant and heat gain by air is expressed as Q = m clt × C pclt × (Tci − Tco )

(2)

Q = m air × C pair × (Tao − Tai )

(3)

where m is the mass flow rate of coolant (kg/s), C p is isobaric specific heat (kJ/kg K), Tci and Tco are coolant inlet and outlet temperatures, respectively (°C), Tai and Tao are air inlet and outlet temperatures, respectively (°C), and suffixes clt and air indicates coolant and air, respectively. If one of the fluids experiences a temperature shift equal to the largest possible temperature difference, the radiator’s maximum value of actual heat transfer may be reached. A radiator’s overall heat transfer coefficient mainly consists of Kothandaraman (2004) coolant-side convection, air-side convection, and tube wall conduction. The overall heat transfer coefficient (U o ) is calculated by 1 1 Aair = + +R Uo h air h clt .Atube

(4)

where h air and h clt are the convective heat transfer coefficients on air side and coolant side, respectively (W/m K), Aair and Atube are the surface areas of the tube on air side and coolant side (m2 ), respectively, and R is metal resistance (°C/W), assumed to be negligible. Thus the final equation becomes 1 1 Aair = + Uo h air h clt .Atube

(5)

The flow situation occurs mainly in a turbulent region. Dittus and Boelter have developed an accurate expression for fully developed pipe flow in turbulent regions for the estimation of Nusselt number (Kothandaraman 2004) N u = 0.023 × (Reclt )0.8 ×(Pr clt )0.3

(6)

where the Prandtl number is calculated by Pr clt =

μclt × C pclt K clt

(7)

Performance Investigation of Automotive Radiator Using Water-Al2 O3 …

203

where μ is dynamic viscosity (N s/m2 ), k is thermal conductivity (W/m K) suffix clt indicates coolant. Moreover, the Reynolds number for coolant flow through radiator is estimated by Reclt =

ρclt × Vclt × Dh μclt

(8)

where Dh is the hydraulic diameter (m). The coolant-side heat transfer coefficient is obtained by h clt =

N u × K clt Dh

(9)

Applying a similar heat transfer equation to the external flow can evaluate the air-side heat transfer coefficient.

4 Results and Discussions Table 2 displayed the experimental results of the overall heat transfer coefficient on the air side when the distance between the fan and radiator was changed. The selected distances between fan and radiator were 1, 4, and 7 cm. The coolant flow and air velocity were kept constant. According to the findings, a fan–radiator distance of 1 cm results in the maximum overall heat transfer coefficient. Hence, the distance between fan and radiator is kept fixed at 1 cm for all subsequent experimentations. On the other hand, for different coolant concentrations viz. 0% EG + water, 30% EG + water, 50% EG + water, 50% EG + 0.1% Al2 O3 + water, the air side overall heat transfer coefficient was evaluated, keeping coolant and air flow rates constant. Table 3 shows that the heat transfer coefficient is at its highest value for coolant concentrations of 50% EG + 0.1% Al2 O3 + water. Figure 4 illustrates the difference in coolant temperature as a function of coolant flow rate and air velocity. The coolant used is base fluid (water). The coolant temperature difference is maximum at low coolant velocities but at higher air velocities. At lower coolant velocities, coolant gets more time for heat rejection to surrounding air; hence, more temperature drop is possible. However, it requires a greater flow rate of cold fluid (air). Table 2 Results for the distance between fan and radiator Fan–radiator distance (cm)

Coolant flow rate (l/ min)

The velocity of air (m/s)

Air Δt (°C)

U o (W/m2 °C)

1

18

6

10

80

4

18

6

14

60

7

18

6

20

45

204

V. P. Kalbande et al.

Table 3 Results for using various blends of Al2 O3 + EG + water as a coolant Coolant

Coolant flow rate (l/min)

Velocity of air (m/ s)

Coolant Δt (°C)

U o (W/m2 °C)

0% EG + water

18

6

15

20

30% EG + water

18

6

11

30

50% EG + water

18

6

10

45

50% EG + 0.1% Al2 O3 + water

18

6

9

80

16 14

5.0

12 4.0

ΔT (°C)

10 8

3.0

6

2.0

4

ΔT°C

2

V m/s

Velocity of air (m/s)

6.0

1.0 0.0

0 2

3

4

5 6 7 8 9 10 11 Flow rate of coolant (lit/min)

12

13

14

15

16

Fig. 4 Coolant temperature difference with variation in coolant and airflow rates

Figure 5 illustrates the difference in coolant temperature changes with various fanto-radiator distances. The most remarkable difference in coolant temperature between the radiator’s input and outflow is 1 cm. The temperature difference decreases for an increase in fan–radiator distance. The coolant used is water. Fig. 5 Coolant temperature difference concerning the fan’s and radiator’s distance

14 13

ΔT (°C)

12 11 10 9 8 7 6 0

1

2 3 4 5 6 7 Distance between fan and radiator (cm)

8

Performance Investigation of Automotive Radiator Using Water-Al2 O3 …

205

496

hclt (W/m2.K)

494 492 490 488 486 484 0

1

2 3 4 5 6 Distance between fan and radiator (cm)

7

8

Fig. 6 Heat transfer coefficient and coolant flow rate to the distance between fan and radiator

Figure 6 shows the trend for the convective heat transfer coefficient on the coolant side with various fan–radiator distance values for water as coolant. The convective heat transfer coefficient is maximum at 1 cm fan–radiator distance and drops with an increase in fan–radiator distance, similar to the coolant temperature differential. The overall heat transfer coefficient at the outer diameter is evaluated at different fan–radiator distances by varying the fan speed. The overall heat transfer coefficient is maximum at a distance of 1 cm between a fan and a radiator, as opposed to other distances of 4 and 7 cm, in a way analogous to that of coolant (here water is used) temperature differential and convective heat transfer coefficient. At all fan speeds ranging from 1500 to 3500 rpm. Similarly, Fig. 7 demonstrates that the overall heat transfer coefficient increases when fan speed increases. Figure 8 shows the coolant-side heat transfer coefficient for various ethylene glycol concentrations in water at various coolant flow rates. It was shown that the heat transfer coefficient decreases with an increase in the coolant flow rate for all blends. Additionally, it was discovered that the coolant combination consisting of Al2 O3 /50% EG + water nanofluid followed by water, 30%EG + water, and 50%EG + water. Hence, the performance of mixture Al2 O3 /50%EG in water is superior over base fluid (water). Similarly, Fig. 9 illustrates EG concentration effects on overall heat transfer coefficient. With increased EG content in water, the overall heat transfer coefficient falls. However, 50% EG in water and a suspension of 0.1% by weight Al2 O3 results in higher values of overall heat transfer coefficient.

206

V. P. Kalbande et al.

80 70

Uo (W/m 2 .K)

60 50 40 30

at 1 cm

20

at 4 cm

10

at 7 cm

0 1000

1500

2000

2500

3000

3500

4000

Fan rpm Fig. 7 Overall heat transfer coefficient at various distances between fan and radiator

600

hclt (W/m2.K)

500 400 300 200 Water 30% EG in water 50% EG in water 50% EG+ 0.1%Al₂O₃+water

100 0 2

3

4

5 6 7 Coolant flow rate (lit/min)

8

9

10

Fig. 8 Heat transfer coefficient of coolant for coolant flow rate

5 Conclusions Experimental research determined how coolant temperature differences were affected by coolant flow rate, air velocity, and the distance between radiator and fan. The impact of fan–radiator distance on convective heat transfer coefficient and coolant temperature difference is also estimated. The findings are as follows:

Performance Investigation of Automotive Radiator Using Water-Al2 O3 …

207

60

U0 (W/m 2.K)

50 40 30 20 10 0 0

10

20 30 Al2O3 / % Ethylene glycol in water

40

50

Fig. 9 Overall heat transfer coefficient vs. mixture concentration when flow rate is 9 l/min

• • • •

The coolant temperature differential diminishes as the coolant flow rate rises. The difference in coolant temperature rises as air velocity rises. The heat transfer rate reduces as the distance between the fan and radiator grows. For a distance of 1 cm, a higher overall heat transfer rate is obtained.

Experimental evaluation was also done on the impacts of different water and ethylene glycol mixtures on temperature differential and heat transfer coefficient. The estimated findings indicate that the outcomes were as anticipated, and conclusions are as follows: • The overall heat transfer coefficient falls as the coolant proportion of EG rises. However, the heat transfer coefficient is greater with 50% EG in water and 1% by weight Al2 O3 suspension. • For Al2 O3 /water + EG nanofluid, a better total heat transfer coefficient is obtained. • Lower coolant flow rates can result in improved heat transfer rates. The heat transfer characteristics of the radiator using water-based Al2 O3 + EG nanofluid and the effect of radiator–fan distance are analyzed. Though some improvement was observed, there is vast scope to improve the performance of automobile radiators using different combinations of water-based hybrid nanofluids such as CuO, TiO2 , Ag, etc. nanoparticles.

References Chen JA, Wang DF, Zheng LZ (2001) Experimental study of operating performance of a tube-and-fin radiator for vehicles. Proc Inst Mech Eng Part D J Automob Eng 215:911–918 Fell B, Janowiak S, Kazanis A, Martinez J (2007) High efficiency radiator design for advanced coolant Holman JP (2002) Heat transfer-Si units-Sie. Tata McGraw-Hill Education

208

V. P. Kalbande et al.

Kalbande VP, Walke PV (2019) Oil-and aluminum-based thermal storage system using flat plate solar collector. In: Smart technologies for energy, environment and sustainable development. Springer, Singapore, pp 553–562 Kalbande VP, Walke PV, Shelke R (2019) Aluminum-based thermal storage system with solar collector using nanofluid. Energy Storage 1:1–7. https://doi.org/10.1002/est2.99 Kalbande VP, Walke PV, Rambhad K (2021a) Performance of oil-based thermal storage system with parabolic trough solar collector using Al2 O3 and soybean oil nanofluid. Int J Energy Res 45:15338–15359. https://doi.org/10.1002/er.6808 Kalbande VP, Walke PV, Rambhad K, Nandanwar Y, Mohan M (2021b) Performance evaluation of energy storage system coupled with flat plate solar collector using hybrid nanofluid of CuO+Al2 O3 /water. J Phys Conf Ser 1913:12067. https://doi.org/10.1088/1742-6596/1913/1/ 012067 Kalbande VP, Walke PV, Untawale S, Mohan M (2022) Performance evaluation of novel heat pipeassisted thermal storage system with parabolic trough solar collector using nanofluid. Energy Technol. https://doi.org/10.1002/ente.202200118 Kays WM, London AL (1984) Compact heat exchangers Kothandaraman CP (2004) Heat and mass transfer data book. New Age International Oliet C, Oliva A, Castro J, Pérez-Segarra CD (2007) Parametric studies on automotive radiators. Appl Therm Eng 27:2033–2043. https://doi.org/10.1016/j.applthermaleng.2006.12.006 Sridhara SN, Shankapal SR, Babu V (2005) CFD analysis of fluid flow and heat transfer in a single tube-fin arrangement of an automotive radiator Taler D (2004) Determination of heat transfer correlations for plate-fin-and-tube heat exchangers. Heat Mass Transf 40:809–822. https://doi.org/10.1007/s00231-003-0466-4 Witry A, Al-Hajeri MH, Bondok AA (2003) CFD analysis of fluid flow and heat transfer in patterned roll-bonded aluminum plate radiators. In: Third international conference CFD minerals and process industries CSIRO, Melbourne, Aust., 2003, pp 11–12

A Review on Fast Charging/Discharging Effect in Lithium-Ion Batteries for Electric Vehicles Indra Kumar Lokhande, Nishant Tiwari, and Abhishek Sharma

Abstract Electric vehicles (EVs) fast charging and discharging of lithium-ion (Liion) batteries have become a significant concern. Reducing charging times and increasing vehicle range are desirable for better battery performance and lifespan. One of the main challenges associated with fast charging and discharging is the degradation of the battery’s electrodes, resulting in decreased battery capacity and increased internal resistance. Rapid charge/discharge rates can also cause high heat generation, leading to thermal runaway and damage to the battery’s electrolyte and electrodes. This review provides an underlying issue related to fast charging and discharging and explores their impact on the battery’s performance and lifespan. Furthermore, effective battery thermal management systems are essential to optimize the battery’s charging/discharging rates, monitor its temperature, and prevent overcharging/over-discharging. The insights provided by the review will be valuable for identifying and addressing the challenges associated with the fast charging/ discharging of Li-ion batteries for modern EVs. Keywords Electric vehicles (EVs) · Lithium-ion (Li-ion) batteries · BTMS · Battery charging/discharging

1 Introduction Electric Vehicles (EVs) are gaining popularity due to their zero emissions and highenergy utilization, aligning with strengthened environmental pollution regulations. Lithium-ion (Li-ion) batteries (rechargeable/nonrechargeable) are the recommended power source for EVs due to their high-power density and long-lasting life (Vertiz I. K. Lokhande · N. Tiwari (B) School of Mechanical Engineering, Vellore Institute of Technology, Vellore 632014, Tamil Nadu, India e-mail: [email protected] A. Sharma Department of Mechanical Engineering, B I T Sindri, Dhanbad 828123, Jharkhand, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024 R. Goyal et al. (eds.), Renewable Energy: Accelerating the Energy Transition, Energy Systems in Electrical Engineering, https://doi.org/10.1007/978-981-99-6116-0_12

209

210

I. K. Lokhande et al.

et al. 2014). However, fast charging capabilities require a high current supply, negatively affecting battery performance, life cycle, and safety due to temperature rise and uneven thermal distribution (Hannan et al. 2017; Wang et al. 2022). Safety is a primary concern, with frequent reports of battery fires in EVs. In EVs, battery cells are connected in series and parallel combinations to generate the required power with heat during charging/discharging. Thus, it is essential to maintain a temperature range of 25–40 °C and extract the additional heat generated within the battery. Researchers have suggested that high Depth of Discharging (DOD) and charging promote the formation of a Solid Electrolyte Interface (SEI) (Samba et al. 2014; Behi et al. 2020; Chen et al. 2020). This results in the rise of the battery electrode surface’s internal impedance and capacity fading. The SEI layer developed during high-rate charging and high DOD generates excess heat resulting in the cracking, loss of active material inside the Li-ion battery and thermal runaway (Lee et al. 2003; Vetter et al. 2005; Belov and Yang 2008; Wu et al. 2015; In Ho 2019). The Li-ion has to move from cathode to anode through electrolyte via a separator and perform intercalation while charging due to a faradic side reaction. Li-ion is reduced to metallic lithium, forming a layer instead of intercalating and deposited on an anode known as lithium dendritic growth. It further results in an internal short circuit giving rise to rapid heating of the cell, electrolyte drying and dissolution of positive electrode (Fear et al. 2020; Konz et al. 2020; Rangarajan et al. 2020; Bohinsky et al. 2021). Similarly, several researchers have reviewed the limitations and challenges of using Li-ion batteries at higher current charging/discharging (Bazinski and Wang 2016; Panchal et al. 2017; Liu et al. 2022). They concluded that electrolytes (Katzer and Danzer 2021), capacity fading (Choi and Aurbach 2016), Li-ion deposition (Katzer and Danzer 2021), aging, and heat generation (Choudhari et al. 2020) are the main affecting parameters for the poor performance of Li-ion batteries. In addition to the risk of internal short circuits, high-current charging and discharging of lithium-ion batteries also pose a safety hazard (Zhou et al. 2022). When a battery is charged or discharged at a high rate, it generates more heat, which causes the battery to overheat and potentially catch fire. To prevent these risks, a Battery Management System (BMS) is essential for the estimation of voltage, current, temperature, and State Of Charge (SOC) for Li-ion batteries used in EVs (Hannan et al. 2017). The above discussion reveals that excessive heat generation is the main factor affecting the battery life cycle. Thus, the heat generation mechanism was reviewed by Choudhari et al. (2020), as shown in Fig. 1 to understand its effect better. They found that the reversible heat generation rate is higher when the charging is performed at a lower current rate. In contrast, irreversible heat generation dominates at higher current rates because it is a function of the square of the current. The increase in cycles and operating temperature capacity also fade battery pack deterioration. The number of channels required and the flow rate of coolant in BTMS also dominate the thermal performance. Xu et al. (2020) analyzed that the core and outer surface temperature is too high. Thus, the temperature difference must be lower to prevent thermal runaway conditions. A numerical simulation is done to evaluate (i) where

A Review on Fast Charging/Discharging Effect in Lithium-Ion Batteries …

211

Fig. 1 Impact of high current supply on Li-ion battery. Reprint with permission from D. Choudhari et al. Journal of Energy Storage, 32, 101,729, 2020. Copyright© 2020 Elsevier Ltd. (Choudhari et al. 2020)

the rate of increase in temperature is slow and (ii) where the temperature is triggering and causing a risk of thermal runaway growth. Makuza et al. (2021) discuss the methods used to recycle the active cathode material from the battery, such as the thermal pretreatment method, hydrometallurgy, and extractive pyrometallurgical option. Recycling is another issue for the Li-ion battery as the Li-ion market is growing and an inevitable amount of batteries will be disposed of. The traditional recycling method such as pyrometallurgy, hydrometallurgy, and a combination of these processes are used. However, the recycling process has become more complex due to advancements in Li-ion batteries. Recent research focuses on cobalt recovery because of its volatile price. The current recycling process of Li-ion requires high capital investment and the efficiency of Li-ion extraction is also less.

2 Causes of Heat Generation Within Li-Ion Battery Li-ion batteries generate heat due to various factors, including capacity fading, lithium deposition, electrolyte decomposition, cathode and anode degradation, excess heat generation, and thermal runaway (Fleckenstein et al. 2011; Zhang 2011; McCleary et al. 2013). The details of these factors are discussed next. i. Capacity fading An optimized high current charging/discharging protocol aims to reduce the charging time/supply high power for a short duration when required, with high efficiency, safety, and minimal detrimental effect on the battery life cycle. It has been observed that after a high current charging/discharging process, the battery’s capacity is lost compared to the earlier one (Mussa et al. 2017). Heat generation is the primary cause

212

I. K. Lokhande et al.

of capacity fading as it gives rise to the degradation of the cathode, anode, electrolyte, separator, and electrode and its ability (Vetter et al. 2005; Choudhari et al. 2020). ii. Lithium deposition It has been observed that during fast charging, a faradic side reaction occurs and Li-ion on the negative electrode (anode) is deposited. During this reaction, Li-ion intercalation does not occur; instead, it deposits on the surface of graphite particles with a lower reversibility rate than intercalation (Katzer and Danzer 2021). iii. Electrolyte decomposition A liquid electrolyte is lithium hexa-flurophosphate; when operating at higher temperatures, this lithium hexa-flurophosphate breaks into lithium fluoride and phosphorus pentafluoride. Due to the limitation of liquid electrolytes nowadays, solid electrolytes are used in Li-ion batteries. The solid electrolyte interface layer also decomposes when operating at the temperature range between 90 and 120 °C, which gives rise in temperature and releases heat (Choudhari et al. 2020). iv. Cathode and anode degradation The development of surface film on the cathode electrode is the main reason for the electrode failure. It reduces the reaction rate for both Li-ion intercalation and de-intercalation. Because of the surface film on the cathode, the structural phase transition from hexagonal to cubic or spline takes place. It is found that when the temperature increases from 25 °C to 55 °C, the degradation percentage is 1.21% and 4.85% for a lower and higher number of cycles, respectively. The degradation of the anode is due to the SEI; when SEI is not entirely permeable to lithium ions, the other carbon particle will intercalate with the graphite anode instead of lithium ions. The degradation percentage of anode is 0.82% and 3.29% when the temperature rises from 25 °C to 55 °C for a lower and higher number of cycles, respectively (Tomaszewska et al. 2019; Choudhari et al. 2020). v. Excess heat generation and thermal runaway In the case of very fast overcharged or discharged, the dendrite is formed in the battery’s anode, penetrating the separator and giving rise to an internal short circuit. If an internal short circuit spreads over a large area, the battery’s energy is released rapidly as heat and can end with an explosion (Liu et al. 2022). Thus, if the temperature exceeds the critical point, a reaction occurs between the electrolyte and electrode, which advances rapid reaction and liberates a large amount of heat energy, giving rise to an explosion (Huang et al. 2018a). Veth et al. (2014) investigated a linear equivalence between the surface temperature of the cell and the discharging C-rate. Waldmann et al. (2016) found that an increase in the C-rate while discharging gives rise to the maximum temperature on the cell’s surface and the jelly roll. It is also observed that a higher temperature rise is found inside the jelly roll when lowering the numbering of the current collecting tab because of ohmic resistance and limited heat transfer to the cable. Cell aging is also highly affected at higher temperatures.

A Review on Fast Charging/Discharging Effect in Lithium-Ion Batteries …

213

Hence, knowing a battery pack’s operating range and cell design parameters is essential. Liu et al. (2022) studied thermal runaway behavior in a 18650 Li-ion battery. They observed that it could take place in two phases. In the first phase, there is a continuous explosion reaction; in the second phase, there is a combustion and an explosion reaction which is more aggressive than the first. Hence, from a safety point of view, reducing the cell’s maximum temperature and temperature difference is vital to prevent thermal runaway and extract the excess heat generated within the battery. The Li-ions are transported from cathode to anode and vice versa during charging/ discharging. In contrast, electrons flow from an external circuit from one electrode to another. The transport, oxidation and reduction process occurs continuously, which generates heat affecting the performance and degrading battery life (Xiao and Choe 2013). Bandhauer et al. (2011) propose that the primary cause of heat generation within the batteries are (i) activation (interfacial kinetics), (ii) concentration (species transport), and (iii) ohmic (Joule heating). The internal heat generation inside the battery can be classified as reversible heat related to intercalation and de-intercalation represented by entropy. However, irreversible heat is related to polarization and ohmic heat through electrochemical reactions and internal heat resistance (Du et al. 2017). The heat generation can also be evaluated in terms of enthalpy heating (diffusion of Li-ion) and heat of mixing (ion concentration) (Xiao and Choe 2013). Schuster et al. (2015) calculate the reversible heat through entropy coefficient (dE o /dt) and irreversible heat generation calculated from potentiometric and current interruption techniques. When a discharging rate is low reversible heat dominates the heat generation, whereas irreversible heat plays a dominant role at a high discharge rate. However, with the advancement in electronics equipment, it is also used for high-power requirements, which require a higher current at a higher rate. Here, irreversible heat generation dominates (Du et al. 2017). Overcharge and high current charging/discharging are the most common thermal abuse conditions responsible for heat generation due to side reactions at an elevated cell temperature. The total heat generated (Qsum ) is the addition of reversible heat (Q rev ), irreversible heat (Q irrev ), and heat of side reaction (Q side reaction ) generated inside the battery (Huang et al. 2018a). Q sum = Q rev + Q irrev + Q side reaction

(1)

The heat generation rate within the battery depends upon several factors, such as SOC, temperature, state of health (SOH) and applied C-rate. Measuring heat generation within a battery is complex since it differs from multiple variable operations (Diaz et al. 2022). Reversible heat generation can be expressed as: Q rev = As × jloc × T

∂Uocv S = IT nF ∂T

(2)

where As is specific surface area (m −1 ), jloc is local current density (A m −2 ), T is the absolute temperature (K), S is the absolute temperature (K), F is Faraday’s constant, I is current (A) and Uocv is Open circuit voltage (Du et al. 2017). The

214

I. K. Lokhande et al.

irreversible heat generation may be losses due to the difference in open circuit voltage and operating potential, including ohmic, kinetic and mass transport over-potential. Ohmic heat generation can be classified as (1) heat generated from the resistance offered by active solid-state material, (2) heat generated by ion transportation, and (3) heat generated at the current collector (Xiao and Choe 2013; Du et al. 2017). The irreversible heat plays a significant role in high current charging/discharging (Du et al. 2017) qirr = q p + qohmic = I (Uocv − Vt )

(3)

Measuring the heat generated on high current discharge, heat generation at high current and degradation of a Li-ion battery is vital to extract the heat generated within the battery. It is essential to design a battery thermal management system (BTMS) to extract the heat and maintain the pack’s temperature between 25 and 40 °C. The above-discussed issues reduce battery performance and safety risks, such as fire or explosion. Manufacturers employ various techniques to mitigate these issues, such as optimizing the battery’s chemical composition and design, implementing temperature monitoring and control systems, and using advanced materials and coatings to enhance battery safety.

3 Battery Thermal Management System The operating temperature range is critical for efficient and safe performance for EV and hybrid EVs. In order to maintain the operating temperature or extract the heat generated inside, a BTMS is required, which can monitor battery voltage, SOC, and thermal energy generation. BTMS can be classified as active, passive, and hybrid systems, as shown in Fig. 2.

3.1 Active Cooled BTMS When external power is required to operate the system for maintaining the temperature is known as active cooled BTMS. A fan, blower or pump is used as an external source for cooling/heating the battery pack as it operates under the limited temperature range from −10 to 40 °C. Active cooling includes air-based, liquid-based and thermoelectric-based BTMS, as presented in Fig. 3. (i) Air-based BTMS: When air is used to cool/heat the battery with the help of a fan, blower or pump for providing motion to the air, known as air-based BTMS. There may be sufficient airflow produced by fans or blowers on either inlets or outputs to disperse heat more evenly or to convey excessive heat. It has a low operating cost, low maintenance cost, and simple design. The air cooling of a battery can be performed in

A Review on Fast Charging/Discharging Effect in Lithium-Ion Batteries …

215

Fig. 2 Classification of BTMS for high current charging/discharging of Li-ion battery

(a)

(b)

Fig. 3 Active BTMS a air-cooled BTMS and b liquid-cooled BTMS

three different ways: (1) Only outside air is used as a cooling medium circulated with the help of a fan/blower at high velocity, (2) precooled air is used (T amb ) or moved by use of a heat exchanger, and (3) battery cooling with cabin pre-conditioned air and battery cooling with an extra evaporator to precisely cool the battery (Mali et al. 2021; Mitra et al. 2022). Rao et al. (2011) did numerical modeling on a thermal

216

I. K. Lokhande et al.

evaluation of a module of three cylindrical commercial 38120 high-powered cells placed in rectangular plexiglass of 16 cm × 14 cm × 5 cm. The thermal performance of the cell is tested at 25 °C inlet ambient air under different constant current rates from 1C to 5C at 0.5 m/s cooling air and a heat transfer coefficient of 35 W/m2 K. Bao et al. (2019) have done an experimental study on the thermal behavior of a 18650 cylindrical, 32 Li-ion cell battery pack for fast charging at various C-rate (1C–5C) with air velocities at 0.6–4 m/s, respectively. Yang et al. (2020) have done experimental and numerical modeling introducing a radiator with a bionic surface structure to enhance air cooling performance at a 3C discharge rate. The BTMS is tested on a 18650 Li-ion battery module with axial air cooling with an inlet air velocity higher than 0.8 m/s. Air-based cooling has the advantage of being naturally available in abundant simplicity. If forced circulation is considered, it enhances the performance of BTMS. However, it has a limitation of low-thermal conductivity and unbalanced thermal distribution and is inefficient for working above 3C. (ii) Liquid-based BTMS: Air-cooled BTMS cannot dissipate heat completely and provide uniform temperature distribution due to lower thermal conductivity, whereas liquid has higher thermal conductivity and high heat capacity. Sometimes dielectric fluid is also used as a coolant to extract heat, which has a better cooling rate and is compact compared to the setup of air-based BTMS. The dielectric heat transfer fluid should possess properties like high thermal conductivity, low viscosity, low density, and chemically stable so that it does not react with the surface of the battery. Coolant can be taken as fluid, either liquid or air and it has been found that liquid with higher viscosity cause more pressure drop and requires more pumping power (Mitra et al. 2022). The use of oils and water for direct contact liquid is limited due to low thermal conductivity. Adding nano-particles with higher thermal conductivity can improve the thermal conductivity of fluid for utilization in BTMS (Beheshti et al. 2014). Lan et al. (2016) innovative BTMS design has flat aluminum tubes/mini-channel for the liquid flow, extracting heat around the prismatic cell. Results show that maximum temperature difference can be maintained within a limiting range with low-power consumption. Jiaqiang et al. (2018) did an experimental study to enhance the operational performance of BTMS under a different set of parameters with an orthogonal design. The impact of multi variables such as channel width, height, pipe length, and coolant flow rate is with minimum time and cost. Finally, it concluded that liquid cooling has a better cooling rate than air and fluid properties can improve to enhance the heat transfer rate. Wang et al. (2020) did a numerical and experimental study on a practical modular liquid-cooled system to investigate the coolant flow rate and cooling mode. A 18650 cylindrical Li-ion battery pack discharges at 3C rate with an ambient temperature of 30 °C and a coolant mass flow rate of 80 ml/min is used for the experiment. Liquid-based BTMS has several advantages of maintaining the operating temperature range and thermal distribution but has a limitation of leakage, corrosion and toxicity. Hence, while designing the BTMS, it is also necessary to consider the harmful effect. (iii) Thermo-electric-based BTMS: A thermoelectric cooler is used to extract heat from the battery pack known as thermo-electric-based BTMS. A thermoelectric

A Review on Fast Charging/Discharging Effect in Lithium-Ion Batteries …

217

cooler is an electronic semiconductor device that works on the Peltier effect and consists of n-type and p-type thermoelectric (TE) legs connected electrically in series and thermally in parallel. A thermoelectric cooler has several advantages, such as a noiseless, static device, longer operational life, reliable operation, less maintenance and free from internal chemical reactions. The battery’s temperature was regulated using a thermoelectric and liquid cooling system, mainly when the temperature was too high. The thermoelectric cooler chips, arranged on the battery’s surface correctly, transmitted heat from the battery to the water cooling system (Zhang et al. 2018). Alaoui (2013) performed an experimental study using a thermoelectric cooler module in a BTMS to investigate the thermal performance of BTMS. The 60 Ah Li-ion pouch prismatic cell has been utilized with a 48-series connection required to drive the EV. The test is conducted for 1C and 3C discharge rates at an ambient temperature of 24 °C and tested for the worst condition at −20 °C ambient temperature. Also, it tested the battery at 24 °C, where the battery surface reached a maximum temperature of 48 °C using a thermoelectric cooler. The summary of the various active BTMS is given in Table 1. On comparing the different methodologies and cell structures used by the researchers, it has been found that active cooling can maintain the operating temperature of the battery within an efficient operating and safe temperature range of 35–50 °C. Although forced air cooling is safe up to 3C, increasing the C-rate of charging/discharging crosses the safe operating limit and increases the chance of thermal runaway. Whereas in the case of liquid cooling, the operating temperature Table 1 Summary of active BTMS Author

Cell type

Methodology

C-rate

Operating condition

Maximum temperature

Chakib Prismatic Alouni (2013)

Thermoelectric

3C

T f = 24 °C

48 °C (Alaoui 2013)

Zhuqian Zhang (2011)

Cylindrical

Forced air cooling

5C

T f = 25 °C, velocity 0.4 m/s

60 °C (Zhang et al. 2011)

Chuanjin Lan (2016)

Cylindrical

Liquid cooling

2C

T l = 27 °C, flow rate = 21 L/min

34.57 °C (Lan et al. 2016)

Jiaqiang E. (2018)

Prismatic

Liquid cooling

5C

T f = 25 °C

39 °C (Jiaqiang et al. 2018)

Yubai Li (2019)

Prismatic

Liquid cooling

3C

T f 1 = 27 °C, T f 2 37 °C & 52 °C (Li et al. 2019) = 42 °C

Yun Bao (2019)

Cylindrical

Forced air cooling

5C

T f 1 = 20 °C, velocity = 4 m/s

48.3 °C (Bao et al. 2019)

Wen Yang (2020)

Cylindrical

Forced air cooling

3C

T f = 23 °C, velocity =