EFFICIENT COLLECTION AND STORAGE OF SOLAR ENERGY By Eng. ADEL ALY AHMED ...

232 Pages·2012·13.31 MB·English

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.
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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. 1 Detailed Air-Based System TRNSYS Deck 172
B.2 Detailed Water-Based System TRNSYS Deck 181
Appendix C Fortran Code" Collector-Storage Wall Using Phase-Change
Materials 189
References 201
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