Structural Optimization And Thermoelectric Performance Of Air-cooled PV/T Modules

With the global attention to environmental issues such as climate warming,people pay more attention to the development of renewable energy.As a clean energy with a long history and abundant reserves,the efficient utilization of solar energy has been a hot issue in academic research.Because of the low energy density of solar energy,the use of solar energy will generally occupy a large amount of land,so combining solar energy with buildings and using distributed solar energy system to produce electricity and heat energy is a promising way of solar energy utilization.Photovoltaic/thermal(PV/T)technology is a combination of solar power generation and solar heat collector technology.While solar energy is converted into electricity,the cooling medium in the collector module takes away the heat of the battery and utilizes it.At the same time,it generates two benefits:high-quality electricity and low-quality heat.At present,most of the research results about PV/T system in the world are about improving the comprehensive utilization efficiency of solar energy,and the power generation efficiency is generally not high.According to the different refrigerants,the PV/T module can be divided into air-cooled PV/T module and water-cooled PV/T module.In order to improve the power generation efficiency,comprehensive utilization efficiency and heat transfer performance of air-cooled PV/T module,the structure optimization and thermoelectric performance of air-cooled PV/T module with fins were studied.The main work is as follows:(1)A solar cell power generation model and an air-cooled PV/T module heat transfer model were established,and a structural optimization scheme for improving heat transfer performance by transverse fins was given.According to the electronics theory of solar cells,the engineering mathematical model of single crystal silicon solar cells was established,and the simulation model of silicon solar cells was established by using MATLAB/Simulink module.The influence of different light intensity and temperature on the power generation performance was analyzed.The simulation results showed that the output power of solar cells was proportional to the intensity of light and inversely proportional to the temperature of solar cells.The heat transfer model of air-cooled PV/T module was constructed,and the heat flow diagram of the air-cooled PV/T module was obtained.The conclusion is that the optimization of heat transfer between radiator and air is the key to improve the overall heat transfer performance of air-cooled PV/T module,and the heat transfer performance of the module can be improved by transverse fins.(2)The heat transfer performance of air-cooled PV/T modules with different structural parameters was analyzed by numerical simulation.The physical model and mathematical model of PV/T module with transverse fins were established.The influence of the angle of fins and the holes of fins on the heat transfer performance of PV/T module was analyzed.When the fin has no holes,the heat transfer capacity of the PV/T module increases first and then decreases with the increase of the fin angle.The heat transfer performance of the PV/T module is the best,when the fin angle is 90°.Fin holes can significantly improve the heat transfer performance of the module.When the angle of the fin is 150°,the heat transfer performance is the best,and the temperature on PV backplane decreases by 4.6℃.Regardless of whether the fins have holes or not,the pressure drop at the inlet and outlet increases first and then decreases with the increase of the fin angle.The effects of fin length,fin angle and hole diameter on the heat transfer performance of PV/T module were analyzed by orthogonal test method.The optimum structure of air-cooled PV/T module was obtained.The length of rib plate was 50mm,the angle of rib plate was 150°,and the diameter of hole is 10mm.Among these three factors,the angle of fin is the most important one,followed by the diameter of hole and the length of fin.(3)The optimized air-cooled PV/T module was fabricated,and a comparative experimental system was set up to research its thermoelectric performance.By adding air chunnel to PV backplane to simulate the working condition of the PV plate placed on the roof of the building,it was found that compared with the free PV plate,the PV plate placed on the roof of the building has higher temperature and worse power generation performance,so it is necessary to take heat transfer measures for the PV plate placed on the roof of the building.When the air velocity was 1.5m/s,the air-cooled PV/T module was tested all-day.The test results show that,compared with the PV plate without heat transfer measures,the PV backplane temperature of the PV/T module is significantly lower and the power generation performance is significantly improved.Around noon,the temperature of the PV backplane decreases by about 10℃,the power generation power is increased by about 4.5%,and the power generation efficiency is increased by about 0.8%.The comparison proves that the PV/T module has better heat transfer performance.The change of photothermal photoelectric performance of PV/T module under different air flow rates was analyzed.Within the experimental flow range,the photothermal photoelectric efficiency increased with the increase of air flow rate,and the relationship was approximately linear.Under test conditions,the maximum instantaneous electrical efficiency,instantaneous thermal efficiency and comprehensive efficiency of PV/T module are 13.30%,23.78%and 55.0%respectively.Through theoretical analysis,numerical simulation and experimental research,it is found that the air-cooled PV/T module with transverse fins has good heat transfer performance,it can effectively improve the power generation efficiency and comprehensive utilization efficiency of the module,and this research has theoretical guiding significance and engineering application value for the further research of air-cooled PV/T system.