EFFICIENCY GAIN OF THE SOLAR TROUGH RECEIVER USING DIFFERENT OPTICALLY ACTIVE LAYERS Khaled Shehata Baiuomy Mohamad Supervised by: Professor Philippe Ferrer University of Witwatersrand Johannesburg, 24th October 2019 A dissertation submitted for the fulfillment of the requirements of the degree of Doctor of Philosophy to the Faculty of Science, University of Witwatersrand i Declaration I declare that this thesis is my own, unaided work. It is being submitted for the Degree of Doctor of Philosophy at the University of the Witwatersrand, Johannesburg. It has not been submitted before for any degree or examination at any other University. Student: Khaled Shehata Baiuomy Mohamad Supervisor: Professor Philippe Ferrer ii Dedication To my family. iii Presentations arising from this study Paper Presentation, “Thermal performance analysis of novel alternative designs for parabolic trough solar collector,” 64th Annual Conference of the South African Institute of Physics (July 2019). (Granted an award for the best Ph.D. oral presentation in Applied Physics division) Paper Presentation, “Experimental and numerical study of a cavity and hot mirror receiver of the parabolic trough collector,” 63rd Annual Conference of the South African Institute of Physics (June 2018). Invited presentation, “Parabolic trough Efficiency gain through the use of a cavity absorber with a hot mirror,” Material and Energy research group, workshop, (November 2017). Invited Presentation, “Experimental and Numerical Heat Transfer Analysis of Cavity absorber and The Application of Different Optically Active Layer for Parabolic Solar Trough Concentrator,” Physics school, Wits University, (October 2017). Paper Presentation, “Experimental and Numerical Heat Transfer Analysis of Cavity absorber and The Application of Different Optically Active Layer for Parabolic Solar Trough Concentrator,” 62nd Annual Conference of the South African Institute of Physics (July 2017). (Granted an award for the best Ph.D. oral presentation in Applied Physics division) iv Publications and patents arising from this study Patent Khaled Mohamad, Philippe Ferrer, “Thermal radiation loss reduction in a parabolic trough receiver by the application of a cavity mirror and a hot mirror coating” International Patent Application No. PCT/IB2019/053531 “ [1]. Papers Mohamad K and Ferrer P. Parabolic trough efficiency gain through the use of a cavity absorber with a hot mirror Appl. Energy 238 1250–1257. 2019 [Published][2]. Mohamad K and Ferrer P. Computational comparison of a novel cavity absorber for parabolic trough solar concentrators. Proc. 62th Annu. Conf. South Afr. Inst. Phys. SAIP2017 [Published][3]. Mohamad K and Ferrer. Experimental and Numerical Measurement of the thermal performance for parabolic trough solar concentrators. Proc. 63th Annu. Conf. South Afr. Inst. Phys. SAIP2018 [Published][4]. Kaluba V.S, Mohamad K, and Ferrer P. Experimental and simulated Performance of Heat Mirror Coatings in a Parabolic Trough Receiver. Applied Energy Journal. 2019 [Submitted] [5]. Mohamad K and Ferrer P. Cavity receiver designs for parabolic trough collector. Renewable & sustainable energy Journal. 2019 [Forthcoming] [6]. Mohamad K and Ferrer P. IR Reflection mechanism inside the annulus between two concentric cylindrical tubes . Renewable & sustainable energy Journal. 2019 [Forthcoming][7] Mohamad K and Ferrer P. Guide for the properties of the materials required for the parabolic trough collector receiver. Applied Energy Journal. 2019 [Forthcoming]. Mohamad K and Ferrer P. Experimental and numerical study analysis of the thermal performance of novel alternative designs for parabolic trough solar collector. Renewable & sustainable energy Journal. 2019 [Forthcoming]. v Abstract The Parabolic Trough Collector (PTC) technology is the most widely used Concentrated Solar Power (CSP) technology. This is due to its maturity, promising cost-effective investments and the possibility to be hybridized with fossil fuels or other renewable power plants. Furthermore, it ensures the best land use among CSP technologies. The PTC receiver unit is the central component of the solar collecting plant, which is designed to absorb a large amount of the concentrated solar irradiation and minimize the thermal and optical losses. The research of finding an optimum design of the receiver unit that provides higher thermal and optical efficiency than the alternatives is a very active area of research in this field. The receiver unit with high efficiency will help to maximize electricity production and to reduce the cost of thermal storage due to a decrease in the requirements of the storage quantity. In addition, it will achieve optimum plant temperature within a shorter length, thus reducing the needed receiver unit length. The alternative optimized PTC receiver in this work is a novel design of a mirrored cavity receiver with a hot mirror application. The design incorporates different optically active layers in conjunction with a cavity absorber. The cavity geometry and a hot mirror coating at the aperture enable heightened retention of thermal radiation in the receiver. The design was analyzed numerically and studied experimentally. Novel aspects of the background theory for the design were presented and implemented in a simulation code. Three experimental setups, including the cavity receiver unit, were introduced. The experimental results were compared to our model and simulation results. It was seen that the correspondence between the experiments and simulation results was encouragingly close, and we proceeded to investigate simulations of the performance regarding the receiver design. The simulation results for receiver temperature profiles, heat transfer fluid temperature, and efficiencies were shown. It was seen that our proposed design had advantages in terms of thermal behavior over conventional designs in that it could exceed the heat transfer fluid temperature and the efficiency of existing alternatives. vi Acknowledgments The work accomplished in this thesis could not have been any easier without the support of many people and organizations. Firstly, I would to deeply thank my supervisor, Professor Philippe Ferrer, for his enduring patience, trust, and encouragement. Your guidance and insight made executing this study more bearable. “You always lifted me up”. To John, Vincent and all who helped me in the Mechanical workshop at physics school. To my friends I met during the course of our study, I appreciate the companionship and sharing moments of difficulties. You all could rise to the occasion whenever called upon. Lastly, I would like to thank the following entities for their kind support: MERG (Materials for Energy Research Group) and MITP (Mandelstam Institute for Theoretical Research), at the University of the Witwatersrand. vii TABLE OF CONTENTS Declaration .......................................................................................................... ii Dedication .......................................................................................................... iii Presentations arising from this study ............................................................... iv Publications and patents arising from this study ............................................. v Abstract ........................................................................................................... vi Acknowledgments ............................................................................................ vii List of figures ...................................................................................................... xi List of tables ...................................................................................................... xiv Chapter 1 : Introduction .................................................................................... 1 1.1 Introduction .......................................................................................................... 1 1.2 Concentrated Solar Power (CSP) ......................................................................... 1 1.3 Parabolic Trough Collector (PTC) technology .................................................... 3 1.3.1 PTC components, materials, and physical aspects. ......................................................... 4 1.4 Problem statement ................................................................................................ 8 1.5 Objective and research justification ..................................................................... 8 1.5.1 Specific objectives .......................................................................................................... 9 1.5.2 Some of the research questions ....................................................................................... 9 1.6 Research organization ........................................................................................ 10 Chapter 2 : Literature review ......................................................................... 11 2.1 Introduction ........................................................................................................ 11 2.2 Thermal radiation ............................................................................................... 11 2.3 Solar radiation .................................................................................................... 12 2.3.1 Sun Geometry ..............................................................................................................