PERFORMANCE EVALUATION OF HYBRID PHOTOVOLTAIC THERMAL (PVT) SYSTEMS:
A COMPARATIVE STUDY
by
RAJEEV KUMAR MISHRA Centre for Energy Studies
Submitted
in fulfillment of the requirements of the degree of Doctor of Philosophy
to the
Indian Institute of Technology Delhi JULY 2013
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Certificate
This is to certify that the thesis entitled “Performance Evaluation of Hybrid Photovoltaic Thermal (PVT) Systems: A Comparative Study”, being submitted by Rajeev Kumar Mishra to the Indian Institute of Technology Delhi, is worthy of consideration for the award of the degree of ‘Doctor of Philosophy’ and is a record of the original bona fide research work carried out by him under my guidance and supervision.
The results contained in the thesis have not been submitted in part or full, to any other University or Institute for the award of any degree or diploma.
(Dr. G. N. Tiwari) Professor
Centre for Energy Studies
Indian Institute of Technology Delhi Date: July 2013 Hauz Khas, New Delhi – 110 016, India
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Acknowledgements
I wish to express my deep sense of gratitude to my supervisor Dr. G. N. Tiwari, Professor, Centre for Energy Studies, for his excellent support and guidance throughout the work. I am heartily thankful to him for his wonderful co-operation, constant encouragement, proper guidance and fruitful academic discussions for carrying out my research work.
I owe many thanks and appreciation to Dr. Brian Norton, President, Dublin Institute Technology, Dublin, Ireland for his guidance and support during my stay at Dublin Institute Technology. A big thanks to Dr. Sanjay Agrawal, Reader, School of engineering and technology, IGNOU, Delhi for his invaluable input and advice throughout the research work. I am very thankful to my colleagues Dr. G. K. Singh, Mr. C. S. Rajoria, Mr. Shyam, Mr. Vihang Garg, Mr. Vivek Tomar, Mr. Madhusudan, Ms. Ankita Gaur and many others for their positive criticism and moral support during my research work. I am thankful to Mr. Lakhmi Chand, Junior Technical Superintendent for his support during the experiments.
I also express my gratitude to Prof. R. P. Sharma, Head, Centre for Energy Studies, Prof. T. S. Bhatti, Centre for Energy Studies and Prof. I. P. Singh, IDDC for providing moral support and encouragement for the present Ph.D. research work.
I am extremely thankful to my wife Mrs. Prem lata Mishra and my son, Utkarsh for their cooperation and patience in bearing with me during the research work.
Last but not the least, I express my deep heartfelt gratitude to my respected grandparent Smt. Indrawati Devi and Shri Aniroodh Mishra and my parent, Smt. Sharda Mishra and Shri S. B. Mishra for their blessings, which helped me to reach this target.
Date: July, 2013 (Rajeev Kumar Mishra)
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Abstract
In the present thesis, the analytical expression for temperature dependent electrical efficiency of an opaque and a semitransparent type PV modules have been developed and are experimentally validated for New Delhi, India climatic condition. A good agreement has been observed between theoretical and experimental results. The average electrical efficiency was increased by 2.29% from opaque PV module with water flowing over the PV module (case I) to opaque PV module with air flowing below the PV module through air duct and water flowing over the PV module (case III). The average electrical efficiency was increased by 4.17% from semitransparent PV module with water flowing over the PV module (case II) to semitransparent PV module with air flowing below the PV module through air duct and water flowing over the PV module (case IV).
Analysis of photovoltaic thermal (PVT) water collector has been carried out for constant collection temperature mode unlike constant flow rate mode. Two different configurations namely case A (collector partially covered by PV module) and case B (collector fully covered by PV module) have been considered. The characteristic equations for both the cases have been developed by using regression method. The annual overall thermal energy gain was decreased by 9.48 % in case B as compared to case A and exergy gain was increased by 39.16% in case B as compared to case A. It has also been observed that the energy payback time (EPBT) was lower for case A. Total carbon credit earned in both the cases has been evaluated.
Photovoltaic thermal (PVT) water collector have been analyzed with five different types of silicon and non-silicon based PV modules namely mono crystalline silicon (c-Si), poly crystalline silicon (p-Si), thin film of amorphous silicon (a-Si), Cadmium Telluride (CdTe) and Copper Indium Gallium Selenide (CIGS). The net annual electrical energy, an overall
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thermal energy and overall exergy outputs from the PVT water collector with different PV modules have been calculated for New Delhi (India) climatic condition. The sustainability assessment of the system, based on the sustainability index method has also been conducted. The maximum annual electrical and overall thermal energy of 880.73 kWh and 13968 kWh respectively was obtained for crystalline silicon (c-Si) PV module. The maximum and minimum value of annual overall exergy gain of 1621.89 kWh and 1098.25 kWh was obtained for c-Si and a-Si PV modules respectively. An attempt has been made to evaluate and compare the energy matrices of a PVT water collector with five different types of PV modules. Annual average overall exergy efficiency was maximum (14.72%) with c-Si and minimum (5.96%) with a-Si PV modules. The highest sustainability index of 1.17 has been obtained with c-Si PV module which means that the PVT water collector with c-Si PV module will be the most sustainable system.
Exergoeconomic and enviroeconomic analyses of two different types of photovoltaic (PV) modules namely semitransparent and opaque have been performed. On the basis of exergoeconomic analysis it was found that the semitransparent PV module gives better performance in terms of energy saving. Environmental cost reduction is found to be 128.7
₹ /year and 125.95 ₹ /year for semitransparent and opaque PV modules, respectively.
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Table of contents
Certificate
Acknowledgements Abstract
List of figures List of tables Nomenclature
CHAPTER – I General introduction 1.1 Introduction
1.1.1 Solar thermal technology 1.1.2 Solar photovoltaic technology
1.1.3 Photovoltaic thermal (PVT) technology 1.2 Classification of photovoltaic thermal (PVT) system 1.3 Background
1.3.1 Solar cell and PV module
1.3.2 Different generations of PV technology 1.3.3 Solar cell parameters
1.3.3.1 Current-voltage (I-V) Characteristics 1.3.3.2 Short circuit current (Isc)
1.3.3.3 Open circuit voltage (Voc) 1.3.3.4 Fill factor (FF)
1.3.3.5 Efficiency of a solar cell (η)
1.3.3.6 Temperature dependent electrical efficiency 1.3.3.7 Packing factor (β) of a PV module
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1 1 2 2 3 3 3 6 7 7 8 8 9 9 10 11
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1.4 History and literature review of photovoltaic thermal (PVT) system 1.5 Basic energy balance equations
1.5.1 Semitransparent PV module 1.5.2 Opaque PV module
1.5.3 Overall thermal and exergy efficiency 1.6 Basic element of heat transfer
1.6.1 Top loss coefficient
1.6.2 Overall bottom loss coefficient 1.7 Objectives
1.8 Weather conditions
1.9 Organization of the chapters
CHAPTER – II Analytical expressions for temperature dependent electrical efficiency of photovoltaic thermal (PVT) modules
2.1 Introduction
2.2 Electrical efficiency of PV module
2.2.1 Opaque and semitransparent PV module without air duct 2.2.2 Opaque and semitransparent PV module with air duct 2.3 Effect of water flow on the electrical efficiency of PV module
2.3.1 Thermal analysis of PV module
2.3.1.1 Opaque PV module with water flowing over the PV module (case I)
2.3.1.2 Semitransparent PV module with water flowing over the PV module (case II)
2.3.1.3 Opaque PV module with air duct below tedlar and water flowing over the PV module (case III)
11 16 16 16 17 18 18 19 20 20 21
23 25 25 26 28 28 30
31
33
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2.3.1.4 Semitransparent PV module with air duct below module and water flowing over the PV module (case IV)
2.4 Results and discussion 2.5 Summary
CHAPTER – III Analysis of photovoltaic thermal (PVT) systems with different configurations: An experimental validation
3.1 Introduction
3.2 Experimental set-up and observations 3.3 Experimental electrical efficiency 3.4 Statistical analysis
3.5 Results and discussion 3.6 Summary
CHAPTER – IV Energy matrices and life cycle cost analysis of
photovoltaic thermal (PVT) water collector under constant collection temperature mode
4.1 Introduction
4.2 Working principle of photovoltaic thermal (PVT) water collector 4.3 Thermal analysis
4.3.1 Flat plate collector (FPC) 4.3.2 PVT water collectors 4.3.3 Useful thermal energy gain 4.3.4 Instantaneous thermal efficiency 4.3.5 Electrical energy gain
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39 41
43 44 49 49 50 53
54 56 57 58 58 60 60 60
viii 4.3.6 Overall thermal energy gain 4.3.7 Overall exergy gain
4.4 Methodology
4.5 Characteristic equations
4.6 Carbon credit earned by PVT water collectors 4.6.1 Overall thermal energy basis
4.6.2 Overall exergy basis
4.7 Energy matrices and life cycle cost analysis 4.7.1 Embodied energy consumption 4.7.2 Energy matrices
4.7.2.1 Energy payback time (EPBT) 4.7.2.2 Energy production factor (EPF)
4.7.2.3 Life cycle conversion efficiency (LCCE) 4.7.3 Annualized uniform cost (unacoct)
4.8 Results and discussion
4.9 Numerical accuracy assessment 4.10 Summary
CHAPTER – V Energy, exergy analyses and sustainability assessment of photovoltaic thermal (PVT) water collector with various PV technologies
5.1 Introduction 5.2 System description
5.3 Energy and exergy analysis 5.3.1 Thermal energy 5.3.2 Electrical energy
61 61 61 62 64 64 65 66 66 66 66 69 69 69 71 78 80
81 83 84 84 85
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5.4 Sustainability assessment 5.5 Energy matrices
5.6 Results and discussion 5.7 Summary
CHAPTER – VI Exergoeconomic and enviroeconomic analyses of photovoltaic modules
6.1 Introduction 6.2 Thermal modeling 6.3 Net present value
6.4 Exergoeconomic and enviroeconomic analyses 6.4.1 Exergoeconomic analysis
6.4.2 Enviroeconomic analysis 6.5 Results and discussion
6.6 Summary
CHAPTER – VII Conclusions and recommendations 7.1 Conclusions
7.2 Recommendations References
Appendix – I Appendix – II List of publications
Brief bio-data of the author
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