OPTIMIZATION OF SOLAR THERMAL COLLECTOR SYSTEMS FOR THE TROPICS Mahbubul Muttakin B.Sc (Hons.), BUET A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF ENGINEERING DEPARTMENT OF MECHANICAL ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2013 Page i Acknowledgements ACKNOWLEDGEMENTS For the successful completion of the project, firstly, the author would like to express his gratitude toward Almighty Allah for his blessing and mercy. The author wishes to express his profound thanks and gratitude to his project supervisors Professor Ng Kim Choon and Professor Joachim Luther for giving an opportunity to work under their guidance, advice, and patience throughout the project. In particular, necessary suggestions and recommendations of project supervisors for the successful completion of this research work have been invaluable. The author extends his thanks to all the scientific and technical staffs, particularly Dr. Khin Zaw, Dr. Muhammad Arifeen Wahed, Mohammad Reza Safizadeh, Saw Nyi Nyi Latt and Saw Tun Nay Lin, for their kind support throughout this project. The author expresses his heartfelt thanks to all of his friends who have provided inspiration for the completion of project. Finally, the author extends his gratitude to his wife, parents and other family members for their patience and support throughout this work. The author would like to acknowledge the financial support for this project provided by the Solar Energy Research Institute of Singapore (SERIS). SERIS is sponsored by NUS and NRF through EDB. Page ii Table of contents TABLE OF CONTENTS Acknowledgements ............................................................................................................... ii Table of Contents ................................................................................................................. iii Summary ....................................................................................................................... vi List of Tables ..................................................................................................................... viii List of Figures ...................................................................................................................... ix Nomenclature ..................................................................................................................... xiv CHAPTER 1 INTRODUCTION ........................................................................................... 1 1.1 Background ............................................................................................................. 1 1.2 Literature review ..................................................................................................... 2 1.2.1 Solar thermal collectors.................................................................................... 3 1.2.2 Modeling, simulation and optimization .......................................................... 10 1.2.3 Meteorological condition of Singapore ........................................................... 13 1.3 Objectives ............................................................................................................. 15 1.4 Thesis organization ............................................................................................... 16 CHAPTER 2 SOLAR THERMAL SYSTEM ...................................................................... 17 2.1 Flat plate solar collector ........................................................................................ 17 2.2 Evacuated tube solar collector ............................................................................... 22 2.3 Hot water pipes ..................................................................................................... 26 Page iii Table of contents 2.4 Storage tank .......................................................................................................... 28 2.5 Economic analysis ................................................................................................ 31 CHAPTER 3 EVACUATED TUBE COLLECTOR SYSTEM ............................................ 36 3.1 Experimental setup ................................................................................................ 36 3.2 Simulation with TRNSYS ..................................................................................... 41 3.3 Results & discussion ............................................................................................. 46 3.3.1 Validation of the simulation model ................................................................ 46 3.3.2 Optimization of the system............................................................................. 53 CHAPTER 4 FLAT PLATE COLLECTOR SYSTEM ........................................................ 64 4.1 Experimental setup ................................................................................................ 64 4.2 Simulation with TRNSYS ..................................................................................... 68 4.3 Results & discussion ............................................................................................. 70 4.3.1 Validation of the simulation model ................................................................ 71 4.3.2 Optimization of the system............................................................................. 73 CHAPTER 5 DYNAMIC MODEL OF EVACUATED TUBE COLLECTOR .................... 80 5.1 Model description ................................................................................................. 80 5.2 Parameter identification and validation of the model ............................................. 84 5.3 Determination of efficiency ................................................................................... 87 5.4 Results .................................................................................................................. 88 Page iv Table of contents 5.4.1 Parameter identification ................................................................................. 88 5.4.2 Validation of the simulation model ................................................................ 90 5.4.3 Determination of efficiency parameters .......................................................... 95 CHAPTER 6 CONCLUSION.............................................................................................. 99 References .................................................................................................................... 101 Appendix A .................................................................................................................... 108 Appendix B .................................................................................................................... 110 Appendix C .................................................................................................................... 111 Appendix D .................................................................................................................... 113 Appendix E .................................................................................................................... 114 Page v Summary SUMMARY Using experimental data and the TRNSYS (a transient system simulation program) simulation environment the behavior of solar thermal system is studied under various conditions. One system consists of evacuated tube collectors having aperture area of 15 m2 and a storage tank of volume 0.315 m3. Firstly, the system is modeled with TRNSYS and several independent variables like ambient temperature, solar irradiance etc. are used as inputs. Outputs of the simulation (e.g. collector outlet temperature, tank temperature etc.) are then compared with the experimental results. After successful validation, the prepared model is utilized to determine the optimum operating conditions for the system to supply the regeneration heat required by a special air dehumidification unit installed at the laboratory of the Solar Energy Research Institute of Singapore (SERIS). Using the meteorological data of Singapore, provided by SERIS, the annual solar fraction of the system is calculated. An economic analysis based on Singapore’s electricity prices is presented and the scheme of payback period and life cycle savings is used to find out the optimum parameters of the system. The pump speeds of the solar collector installation are set within the prescribed limits set by the American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) and optimized in order to meet the energy demand. Finally, the annual average system efficiency Page vi Summary of the solar heat powered dehumidification system is calculated and found to be 26%; the system achieves an annual average solar fraction of 0.78. Furthermore, a stand-alone flat plate collector system is also studied under the meteorological condition of Singapore. The system comprises 1.87 m2 of collector area and a storage tank of 0.181 m3. A TRNSYS simulation model of the system is prepared and also validated with the experimental data. An economic analysis is also done for the flat plate collectors. The system is then optimized with the flat plate collectors to supply the heat, required for the regeneration process of the desiccant dehumidifier, on the basis of payback period and life cycle savings. Finally, a methodology is developed to test an evacuated tube collector and determine its various parameters in the user end. For this, a dynamic model