Optimization Of Solar Thermoelectric Power Generation System

Solar thermoelectric power generation is another way to convert solar radiation directly into electricity besides photovoltaic technology, and has become new hot spot solar energy utilization in recent years. In this thesis, detailed theoretical analysis and experimental studies were conducted to optimize the solar thermoelectric power generation system.Firstly, description on the basic principles of different thermoelectric effects and their interrelationships were presented. Designing and prototype manufacturing of different components like; solar heat receivers having different surface profiles, water cooling chamber for the heat sink, and also theoretical designing and optimization of air cooled fin type heat sink were done. Based on diffused focal points (DFP) method, designing of Fresnel concentrator with high irradiance uniformity, and numerical simulations based on Monte-Carlo ray-tracing method were performed. The simulation results show that DFP method can significantly improve the uniformity of solar irradiance distribution over the solar heat receiver compare with the traditional method.Secondly, comparison of the outputs of the thermoelectric power generation system which has uniform temperature distribution with that without uniform temperature distribution over the heat receiver were conducted. In the simulation and experimental activities, electric current output, power output, open circuit voltage and the efficiency of the system for the two cases were conducted. The experimental and simulation results show that maintaining the temperature distribution uniform all over the top surface of the heat receiver of the thermoelectric power generation system delivers better outputs.Next to that, a complete mathematical model was developed to show the influence of Thomson heating and thermal contact resistances on solar driven thermoelectric power generation system. The analytical equations were derived for the hot junction and cold junction temperatures, the heat flow rates at the hot and cold junctions, the power output, the maximum power output, the system efficiency, system optimum efficiency, voltage output and the electric current output. The application of the model to a practical example in engineering indicates that neglecting the Thomson heating effect and thermal contact resistances at the interfaces between components highly influences the outputs of solar driven thermoelectric power generation system.Finally, experiments were conducted to investigate the effects of solar heat receiver’s top surface profile on the system optimization. From the experimental results, it is confirmed that the system outputs are better when we used a solar heat receiver having flat top surface. Besides the experimental work, numerical analysis were done to analyze the influence of lengths, thicknesses and cross-sectional areas of the thermoelectric elements, external load connected to the system, matching load, and figure of merit on the optimization of solar thermoelectric power generation system were analyzed. The maximum power output and maximum solar thermoelectric system efficiency are at matching load which is at Ro=Re and also, these maximum outputs mainly depend on the Th values. In addition to this, we found that the double stage type solar thermoelectric power generation system delivered better outputs than the single stage type.