Surface Heat Transfer Influence Mechanism And Power Control Of Photovoltaic-thermoelectric Coupling System

Solar power generation technology has become an important part of global renewable energy development and is also widely used in agricultural production.The equipment used in agricultural production and facility agriculture has low power consumption,usually small solar power supply equipment.There is a problem of energy shortage in the area of facility agriculture.Improving the utilisation rate of solar energy is an effective way to solve the energy problem of agricultural production.Solar power supply for agricultural facilities can be controlled by solar tracking and Maximum Power Point Tracking(MPPT)to improve power generation.The photovoltaicthermoelectric coupling system can use the excess heat of the photoelectric conversion process to realise the cascade use of solar energy.The surface heat transfer of the system is usually ignored in research,which leads to a decrease in analysis accuracy.At present,the influence mechanism and influence range of surface heat transfer are not clear.The solar tracking characteristics of the photovoltaic-thermoelectric coupling system need to be explored.Combined with the tracking characteristics,the solar tracking control strategy of the system under complex weather conditions is investigated.At present,the engineering model in the MPPT control research of the photovoltaicthermoelectric coupling system cannot analyse the output characteristics of the concentrating system,and the model needs to be optimised.(1)Based on the principles of photovoltaic cell and thermoelectric cell power generation,the energy transfer model of the photovoltaic-thermoelectric coupling system was established,and the solar energy transfer process in the system was analyzed.According to the heat transfer calculation method of the photovoltaic-thermoelectric coupling system,the influence of interface contact thermal resistance and irradiance on different area ratio systems was analyzed considering the influence of system surface heat transfer.The interface thermal coupling characteristics of the photovoltaic-thermoelectric coupling system were studied,and the simulation results were verified by experiments.The simulation results showed that with the increase of area ratio,the system efficiency was improved,and the influence of contact thermal resistance on the hybrid power generation system was also increased.Therefore,the area ratio of the 1.00 system was analysed in the study of the surface heat transfer mechanism.(2)The model of the c-Si,CIGS and Ga As photovoltaic-thermoelectric coupling system was established.The influence of surface heat transfer on the heat flux,temperature and efficiency of the photovoltaic backplane under different cooling modes of non-concentrating and concentrating systems was analysed,and the influence range and mechanism of the surface heat transfer of the system were investigated.The simulation verified that the surface heat transfer effect of the nonconcentrating system was positively correlated with the ambient temperature and the photovoltaic temperature difference,and the surface heat transfer effect of the concentrating system was positively correlated with the concentration ratio and the reflection ratio of the photovoltaic cell.The maximum error of efficiency was 3.1269 % and the minimum error was-0.0268 %.The simulation model established in this paper can be used to analyse the characteristics of the photovoltaic-thermoelectric coupling system.The simulation model was used to participate in the power control research by considering the influence of the system surface heat transfer.(3)The solar hybrid tracking control of the photovoltaic-thermoelectric coupling system was carried out by Node-RED.The received irradiance of the non-concentrating and concentrating tracking system was measured,and the tracking characteristics of the systems under ideal cooling conditions were simulated and analyzed.The complex weather conditions were divided into highirradiance weather,low-irradiance weather and irradiance fluctuation weather.Set the highirradiance weather judgment threshold and the irradiance fluctuation threshold to control the tracking mode switching.It was found that the hybrid tracking system had the highest power under both non-concentrating and concentrating conditions,and the concentrating photovoltaicthermoelectric coupling system could effectively improve the power.The power of the sun-based motion trajectory tracking mode was increased by 5.08 %,the power of the photoelectric tracking mode was increased by 2.72 %,and the power of the hybrid tracking mode was increased by 2.75 %.The thermoelectric cell could improve the power stability of the system,and the photovoltaicthermoelectric coupling system was suitable for working under concentrated light conditions.(4)The optimization model of the photovoltaic-thermoelectric coupling system was established by using the relationship between the concentration ratio and temperature coefficient and the network connection formula.The output characteristics of the system with different connection modes under non-concentrating and concentrating conditions were analyzed.Two traditional MPPT algorithms and two intelligent MPPT algorithms were debugged,and the influence of temperature fluctuation on the MPPT control effect of the system was analyzed.The simulation showed that the conductance increment method of the non-concentrating system had the highest tracking performance and the fastest initial tracking speed.The fastest initial tracking algorithm of the concentrating system was also the conductance increment method.The MPPT control prototype of the photovoltaic-thermoelectric coupling system was designed using the conductance increment method to test the control effect under non-focusing and focusing conditions.Compared to the photovoltaic system,the average power of the non-concentrating system increased by 1.61%.The average power of the concentrating mode increased by 2.64%.In this study,the influence mechanism of surface heat transfer in the photovoltaicthermoelectric coupling system and the power control technology in the process of power generation were explored.It provides a theoretical reference for power control of photovoltaic-thermoelectric coupling systems.