EFFICIENT COLLECTION and STORAGE of SOLAR ENERGY By
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EFFICIENT COLLECTION AND STORAGE OF SOLAR ENERGY By Eng. ADEL ALY AHMED GHONEIM A thesis Submitted for the degree of Doctor Of Philosophy In Engineering Physics at the FACULTY OF ENGINEERING UNIVERSITY OF ALEXANDRIA 1989 ABSTRACT Since solar energy is available only during daylight hours of a certain periods of the year, a means of providing heat on a continuous bases from this intermittent source is required. This can be done by storing energy during daylight hours for later use. Energy storage provides a useful means of improving solar system performance. In this thesis, detailed theoretical models have been developed for both sensible and phase-change energy storage units. The present detailed models took all the assumptions made in earlier studies into account. The transient simulation program (TRNSYS) developed at Solar Energy Laboratory, University of Wisconsin-Madison was used to determine the performance of the solar heating systems. A comparison was made between the solar system performance obtained using the present detailed models and the corresponding performance obtained using the assumptions made in earlier studies for both air and water-based active solar heating systems. The effects of varying the melting temperature and latent heat of the phase-change materials on the performance of air-based solar active heating systems were also examined. These effects were studied for different locations and different heating season months. A sensible energy storage material called 'Abu-Siebera clay', which is found in Abu-Siebera, Egypt was investigated to test its performance as a sensible store medium. The thermal properties of this material were measured experimentally in the Faculty of Engineering, University of Alexandria. The transient probe method was used to measure the thermal properties of the material. The performance of solar heating systems with Abu-Siebera clay using the weather data of Alexandria, Egypt was compared to the corresponding performance obtained with pebble bed energy storage. Also, the effects of varying system parameters were examined. TRNSYS requires a high computer cost, and a lot of experience. An interesting alternative to the use of TRNSYS is the f-chart design method. The reliability of the f- chart design method in the Egyptian climate was investigated by comparing the performance of solar domestic hot water system (SDHW) obtained using f-chart design method and the corresponding performance obtained using TRNSYS. Lastly, the performance of phase-change materials (PCMs) as a collector-storage walls was investigated. A comparison was made between the performance of collector- storage walls using PCMs and the corresponding performance with the sensible store materials (masonry and water). Also, the effects of varying the thermal properties of PCMs on the performance of collector-storage walls were studied. oo ACKNOWLEDGEMENTS After completing this thesis and writing about all the sophisticated physical and engineering problems, it is a pleasure to write about the people who contributed to this work. People without their help, and guidance this thesis would not be completed. Professor J.A. Duffle, the previous director of the Solar Energy Laboratory at the University of Wisconsin-Madison, deserves much of the credit. He allowed me to use Solar Lab. facilities. His solar class introduced me to the Solar Energy field. He provided me during my weekly student-advisor meetings with many useful suggestions. His useful comments during the review of this thesis are deeply appreciated. Thank you, Jack, for showing that great interest in my research. I would like to extend a special 'thank you' to Professor S.A. Klein, my external advisor, for his helpful ideas, guidance, and never ending supply of suggestions during this work, a better advisor I could never hoped for. It is a pleasure to pursue research under his guidance. Thank you Sandy for always being there to check over my work and solve my problems. I have been fortunate to work and study under the supervision of these two great men, Jack and Sandy. My future will benefit from what they have taught me. I will be forever indebted to them. I am deeply grateful and thankful to my advisors in Egypt for their support, help, guidance, and continuous encouragement. Professor A.A. Ammar gave me the guidance to get started the research work. Professor A.M. Okaz always provided me with help iv and guidance. His advises, letters, phone calls during my stay in the United States are deeply appreciated. Useful suggestions and guidance of Professor M.M. Sorour are deeply acknowledged. Many thanks also to Professor W.A. Beckman, the new director of the Solar Lab., for allowing use of Solar Lab. facilities. His questions during my seminar were helpful in understanding many important points in my research. Great help given by TRNSYS engineers Jim Kummer and Ruth Urban in solving TRNSYS problems is greatly acknowledged. The cooperation and friendship of all graduate students in the Solar Lab. are greatly appreciated. An added thanks to James Braun for his useful suggestions. Thanks to all the people in the Solar Lab. They made my stay here memorable and enjoyable. I am also deeply grateful to Moustafa Azab for his friendship, support and help during my stay in the United States. Moustafa, you have the amazing habit of often doing favors before they were even asked. I am deeply grateful to all my colleagues in Laboratory of Physics at the Faculty of Engineering, University of Alexandria for their love, help, and friendship. They provided me by whatever I needed from my home department during my stay in the United States. My wife and daughter deserve much of the credit- my wife for her understanding, patience, and selfless support, my daughter 'Menat Alaa' for always welcoming me home at the end of the day. Their moral support made the ups and downs more up and less down. Without their moral support the entire stay here in the United States would not have been possible. Finally, but most important I would like to extend endless thanks and love to my wonderful parents. They have supported my college career with much prayers and love. The monthly letters from my father let me know what is going on in my home country. It was always a good feeling to know that things back home are going well. TABLE OF CONTENTS Abstract 11 Acknowledgements iv List of Figures xi List of Tables xv Nomenclature xvi Chapter 1 Thermal Energy Storage 1 1.1 Introduction 1 1.2 Sensible Heat Storage 1 1.3 Latent Heat Storage 2 1.3.1 Candidate Phase-Change Material 3 1.3.2 Phase-Change Materials Selection 3 1.3.2.1 Paraffins 4 1.3.2.2 Salt Hydrates 5 1.4 Chemical Energy Storage 6 1.5 Solar Heating Systems 7 1.5.1 Active Solar Heating Systems 7 1.5.2 Passive Solar Heating Systems 7 1.5.2.1 Direct Gain 8 1.5.2.2 Colector-Storage Wall 8 vi 1.5.2.3 Attached Sunspace 9 1.5.3 Hybrid Solar Heating Systems 9 1.6 Analysis of Solar Heating Systems 10 1.7 Literature Review 12 1.7.1 Active Solar Heating Systems 12 1.7.2 Passive Solar Heating Systems 14 1.8 Objectives 16 1.9 Organization 17 Chapter 2 Transient Simulation Program (TRNSYS) 18 2.1 Introduction 18 2.2 Utility Subroutines 20 2.2.1 Data Reader (TYPE 9) 21 2.2.2 Time Dependent Forcing Function (TYPE 14) 21 2.2.3 Solar Radiation Processor (TYPE 16) 21 2.2.4 Quantity Integrator (TYPE 24) 22 2.2.5 Psychrometrics (TYPE 33) 22 2.2.6 Weather Data Generator (TYPE 54) 23 2.3 Information Flow Diagram 23 2.4 TRNSYS Deck 27 2.5 Simulation Output 28 Chapter 3 Comparison of Theoretical Models of Phase-Change Heat Storage for Air and Water-Based Solar Heating Systems 29 3.1 Configuration of the Storage Unit 29 vii 3.2 Theoretical Model 30 3.2.1 Heat Transfer Coefficient Calculation 33 3.2.2 Solution Method 35 3.2.3 Model Stability and Accuracy 41 3.2.4 Incorporation into TRNSYS 42 3.3 Systems Description and Control Strategy 42 3.3.1 Air-Based System 43 3.3.2 Water-Based System 46 3.4 Results and Discussion 49 3.4.1 Air-Based System 50 3.4.2 Water-Based System 55 Chapter 4 The Effect of Phase-Change Material Properties on the Performance of Solar Air-Based Heating Systems 64 4.1 Introduction 64 4.2 System Configuration and Control Strategy 65 4.3 Analysis 68 4.4 Results and Discussion 69 Chapter 5 Comparison of Theoretical Models of Sensible Heat Storage for Air and Water-Based Solar Heating Systems 81 5.1 Introduction 81 5.2 Grain Size Distribution 81 vii 5.3 Thermal Properties Measurements 82 5.3.1 Sample Preparation 84 5.3.2 Apparatus 84 5.3.2.1 Thermal Probe 84 5.3.2.2 Thermal Property Analyzer 84 5.3.2.3 Printer 86 5.3.3 Measurements Procedure 86 5.3.4 Probe Calibration 87 5.4 Analysis 88 5.5 Results and Discussion 91 5.5.1 Air-Based System 91 5.5.2 Water-Based System 95 Chapter 6 Investigation of Solar Domestic Hot Water System Performance in Alexandria, Egypt 110 6.1 Introduction 110 6.2 System Description and Control Strategy 111 6.3 Analysis 116 6.4 Results and Discussion 118 Chapter 7 Analysis of Collector-Storage Building Walls Using Phase-Change Materials 128 7.1 Introduction 128 7.2 Analysis 129 7.3 Results and Discussion 146 ix Chapter 8 Conclusions and Recommendations for Future Work 162 8.1 Conclusions 162 8.1.1 Active Solar Heating Systems 162 8.1.1.1 Sensible Heat Storage 162 8.1.1.2 Latent Heat Storage 164 8.1.2 Passive Solar Heating System 165 8.2 Recommendations for Future Work 166 Appendix A TRNSYS Component Description 168 Appendix B TRNSYS Control Decks 171 B.