Experimental Study of Plate CPC Solar Thermoelectric Power Generation
|School||South China University of Technology|
|Keywords||thermoelectric generation heat transfer characteristics performance optimization solar energy utilization compound parabolic concentrator|
With the high-speed development of industrialization, global environmental deterioration and energy have become increasingly prominent. Development and utilization of new energy and actively seeking new energy-saving technology are effective means of dealing with the energy crisis and environmental stress. Thermoelectric generation technology is friendly to the environment. Particularly it has no limit to temperature so the unique advantage makes more and more people see its potentiality in the Low-grade heat recovery field. The solar energy, as a novel green and renewable energy, is abundant, economic and non-pollution.Solar thermoelectric generation is a type of electricity generating technology, which could convert the solar power to electricity power. It has the advantages of high reliability, non-pollution and peaceful operations with immovable parts. It is a green and environmentally friendly technology and has a distinct advantage in the use of solar energy. Solar photovoltaic and solar thermal power have been discussed for a long time. But the research on solar thermoelectric generation is few. It is necessary to conduct a much deeper study on it. Based on the thermoelectric theory and solving the low solar energy density, the electricity generating and heat transfer performance are investigated by the means of theoretical analysis, mathematical modeling and experimental testing in this paper. The main research work and conclusions include the following:(1) The performance parameters and their calculation formulas were given based on the solar thermal energy analysis model. The working performance of thermoelectric generator is analyzed on the base of Temperature, contact effect and internal resistance. This relationship provides a foundation for optimizing output power and conversion efficiency.(2) A set of thermoelectric power generation device performance testing platform was built. Profound study was done through experiments on the output characteristics of single thermal power device and the effects of different cooling methods on the cold side. The results showed that the open circuit voltage increased with the temperature difference of the cold side and hot side. At different load resistance RL, the output power was first increased and then decreased with the RL increase. When the maximum output power was obtained, the matched load resistance value is greater than the internal resistance. When the heat source heat flux is constant, compared with the air natural convection, forced air cooling and water cooling can significantly reduce the cold side thermal resistance or temperature. And the output power can be increased by 30 % to 50 %. The larger heating power is, the more obvious this improvement is. (3) The characteristics of a thermoelectric generation system with series-parallel connection of thermoelectric components are investigated. The effects of the total number of thermoelectric components are discussed. The results show that, with the increasing of parallel component count, the maximum output power increase, but the output voltage decrease. For four components, when the load resistance is less than 11Ω, the output voltage of Two-two series and then parallel is the greatest. When the load resistance is greater than 11Ω, the output voltage of the four series is the greatest. When the load resistance is at between 2Ωand 11Ω, the output power of Two-two series and then parallel is the greatest. When the load resistance is 4Ωand temperature is 35℃, the output power is up to 0.45 W. When the load resistance is greater than 11Ω, the output power of four series is the greatest. When the load is 20Ωand temperature difference is 35℃, the output power is up to 0.42 W. This research would be an important reference to design.(4) The Compound Parabolic Concentrator (CPC) was designed based on the optical principle. The solar collecting performance and power output performance were experimental investigated. The results showed that the collector has a certain collector effect; the maximum collector temperature is 92℃. The open circuit voltage of the device increased with the temperature difference of the cold side and hot side. When the temperature difference was 50℃, and the cooling water flow was 340 L/h, we can obtain the maximum output power of 7.1 W and the total open-circuit voltage of 55.3 V with the load resistor of 75.6Ω.(5) The insulation of the collector can improve the collector effect, In the CPC entrance covered with a layer 0.6 mm thick polyethylene film which has good transmittance, not only can protect the CPC reflector foil, can also reduce the CPC slot convection heat loss.The regularity for change of output power、open circuit voltage of the thermoelectric generation system has been studied with the working conditions like different load resistance、temperature difference and so on with the experimental approach in this paper. The research of multi-component thermoelectric generator can provide a useful conclusion for achieving high power output. The Experimental Study of plate CPC solar thermoelectric power generation has enriched the research content about thermoelectric generation on solar energy recovering.