COMPUTER MODELING OF SOLAR THERMAL SYSTEM WITH UNDERGROUND STORAGE TANK FOR SPACE HEATING A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Renewable and Clean Energy Engineering By MOHAMMAD YOUSEF MOUSA NASER B.SC., The University of Jordan, Jordan, 2018 2021 Wright State University WRIGHT STATE UNIVERSITY GRADUATE SCHOOL April 27, 2021 I HEREBY RECOMMEND THAT THE THESIS PREPARED UNDER MY SUPERVISION BY Mohammad Yousef Mousa Naser ENTITLED Computer Modeling of Solar Thermal System with Underground Storage Tank for Space Heating BE ACCEPTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Master of Science in Renewable and Clean Energy Engineering. __________________________________ James Menart, Ph.D. Thesis Director __________________________________ Raghavan Srinivasan, Ph.D., P.E. Chair, Mechanical and Materials Engineering Department Committee on Final Examination ________________________________ James Menart, Ph.D. ________________________________ Nathan Klingbeil, Ph.D. ________________________________ Zifeng Yang, Ph.D. ________________________________ Barry Milligan, Ph.D. Vice Provost for Academic Affairs Dean of the Graduate School Abstract Naser, Mohammad Yousef Mousa. M.S.R.C.E.E. Department of Mechanical and Materials Engineering, Wright State University, 2021. Computer Modeling of Solar Thermal System with Underground Storage Tank for Space Heating Space heating is required in almost every dwelling across the country for different periods of time. The thermal energy needed to meet a heating demand can be supplied using different conventional and/or renewable technologies. Solar energy is one example of a renewable resource that can be used for supplying heating needs. It can be utilized either by using photovoltaic panels to generate electricity, that in turn can be used to operate heaters, or by using solar thermal panels. Solar thermal panels obtain higher operating efficiencies than photovoltaic panels, but solar energy for heating purposes suffers from a mismatch between supply and demand. This problem can be solved by employing large tanks that serve as seasonal thermal energy storage units. This work focuses on assessing the performance of solar thermal panels in supplying the space heating needs of a single-family dwelling in two different cities in the United States. These panels are coupled to a cylindrical tank buried in the ground for seasonal and daily energy storage, and a heat exchanger to transfer heat to the home. Storage tank size, collector area, and the working fluid mass flow rate are investigated to determine adequate values for these parameters to enhance the overall system performance. In addition, the simulation timestep for the program and the spatial grid sizes used in the CFD (computational fluid dynamics simulation) model of the storage unit have been examined to determine values of each to keep the simulation time reasonable without substantial loss in accuracy. These results are obtained by mathematically modeling the system components, the solar thermal panels, the heat exchanger, and the storage tank; then programming this mathematical model in MATLAB. Parts of the developed computer code were obtained from previous work and have been modified to suit the purpose of this project. Flat plate solar panels have been chosen for use as the solar collectors. An unmixed, crossflow heat exchanger is considered for transferring the thermal energy from the glycol-water mixture in the collectors to the air in the house. The storage unit CFD simulation is composed of the tank, insulation, and ground surrounding the tank and is based on the SIMPLE algorithm developed by Patankar. iii Contents CHAPTER 1. INTRODUCTION .............................................................................................................. 1 1.1. OBJECTIVES ................................................................................................................................... 1 1.2. STATUS OF RENEWABLE ENERGY ................................................................................................. 2 1.3. SOLAR HEATING SYSTEMS ............................................................................................................ 5 1.4. THESIS OUTLINE ............................................................................................................................ 7 CHAPTER 2. LITERATURE SURVEY ................................................................................................... 8 2.1. SOLAR THERMAL SYSTEMS CLASSIFICATIONS .............................................................................. 8 2.2. HISTORICAL OVERVIEW .............................................................................................................. 10 2.2.1. First Attempts ......................................................................................................................... 10 2.2.2. Seventies ................................................................................................................................. 10 2.2.3. Eighties and Nighties ............................................................................................................. 11 2.2.4. First Decade of the Twenty-First Century ............................................................................. 12 2.2.5. Second Decade of the Twenty-First Century ......................................................................... 13 2.3. CONTROL METHODOLIGIES AND RELATED WORK ...................................................................... 13 CHAPTER 3. MATHEMATICAL MODEL AND SOLUTION TECHNIQUE ................................. 16 3.1. SYSTEM DESCRIPTION ................................................................................................................. 17 3.2. SOLAR RESOURCE ....................................................................................................................... 19 3.3. SOLAR COLLECTORS ................................................................................................................... 21 3.4. HEAT EXCHANGER ...................................................................................................................... 24 3.5. STORAGE TANK ........................................................................................................................... 27 3.5.1. Flow Equations ...................................................................................................................... 27 3.5.2. Geometry ................................................................................................................................ 31 3.5.3. Nonuniform Grids .................................................................................................................. 34 3.5.4. Turbulence Model .................................................................................................................. 34 3.5.5. Performance Parameters ....................................................................................................... 36 3.6. SYSTEM OPERATION .................................................................................................................... 38 3.6.1. Coupling the Components ...................................................................................................... 38 3.6.2. System Control ....................................................................................................................... 40 CHAPTER 4. RESULTS AND DISCUSSION ....................................................................................... 44 4.1. GRID SURVEY .............................................................................................................................. 44 4.2. TIMESTEP SURVEY ...................................................................................................................... 46 4.3. COMPARISON STUDY ................................................................................................................... 49 4.4. INITIAL DESIGN ........................................................................................................................... 51 4.4.1. Mercury, Nevada.................................................................................................................... 52 4.4.2. Dayton, OH ............................................................................................................................ 70 4.5. FLOW RATE STUDY...................................................................................................................... 72 4.6. COLLECTOR AREA AND STORAGE VOLUME STUDY..................................................................... 74 4.7. ARRAY CONNECTION .................................................................................................................. 75 4.8. ENHANCED DESIGN FOR MERCURY, NEVADA ............................................................................. 77 CHAPTER 5. SUMMARY AND FUTURE WORK .............................................................................. 80 4.9. SUMMARY ................................................................................................................................... 80 4.10. RECOMMENDATIONS ................................................................................................................... 83 iv REFERENCES .........................................................................................................................................