Thermal coupling characteristics of photovoltaic-thermoelectric interface and efficiency of hybrid power generation

When photovoltaic power generation is in sufficient light, heat generated by solar radiation will hinder photoelectric conversion effect. Excessive temperature will also shorten the working life of the photovoltaic cell itself. The photovoltaic-thermoelectric hybrid power generation technology is to add thermoelectric cell to the photovoltaic cell backplane, using the heat that affects the conversion efficiency and working life of photovoltaic cell as heat source for thermoelectric power generation. Through thermoelectric cell converting waste heat of photovoltaic cell into electrical energy. In actual application of photovoltaic-thermoelectric system uses a combination of multiple thermoelectric cells and photovoltaic cells. Multiple thermoelectric cell wires need to be wired，thermoelectric cells also have dimensional errors. Therefore, the area of photovoltaic cell is usually larger than that of thermoelectric cell. Part of photovoltaic cell backplane conducts natural convection and natural radiation heat exchange with the outside world. The thermal coupling characteristics of photovoltaic-thermoelectric interface are more complicated, and the law of influence on the efficiency of hybrid power generation system needs to be explored. These research use finite element software to simulate interface thermal field distribution of photovoltaic-thermoelectric hybrid power generation system, verification by experiment, in the case of 4 types of thermoelectric cell and photovoltaic cell area ratios investigating the influence law of hybrid power generation system temperature and hybrid power generation efficiency. The results show that the area ratio of thermoelectric cell to photovoltaic cell affects the temperature of hybrid power generation system, and system cooling effect of the photovoltaic cell in the hybrid power generation system increases when the area ratio of thermoelectric cell to photovoltaic cell increases. Respectively, under the standard conditions system with area ratios of 0.25, 0.50, 0.75 and 1.00 reduces the temperature of photovoltaic cell by 11.02%, 13.34%, 13.80% and 23.12%. Increasing area ratio of thermoelectric cell to photovoltaic cell can improve the efficiency of hybrid power generation system. Reducing contact thermal resistance can improve efficiency of hybrid power generation system on the same area ratio. As interface contact thermal resistance increases, efficiency of the hybrid power generation system decreases. Under condition of low irradiance, efficiency of photovoltaic-thermoelectric hybrid power generation system with different area ratios tends to be close. Through finite element simulation analysis and test verification, using high thermal conductivity interface materials, the hybrid power generation system with area ratio of 1.00 has the highest power generation efficiency. Therefore, in the practical application of photovoltaic-thermoelectric hybrid power generation, on the premise of ensuring the quality of the thermoelectric cell wiring, increasing the area ratio of thermoelectric cell and photovoltaic cell as much as possible. As the area ratio of thermoelectric cell to photovoltaic cell increases, contact thermal resistance influence on hybrid power generation system increases. For improve the efficiency of hybrid power generation system, the system interface contact thermal resistance requires the use of high thermal conductivity interface materials to reduce contact thermal resistance. The experiment uses cell widely used in the market to study the influence law of hybrid power generation system temperature and hybrid power generation efficiency, providing a reference for the combined use of photovoltaic cell and thermoelectric cell.