Thermal-electrical Coupled Mechanism Investigation On Semi-transparent Photovoltaic Fa?ade Under Building Shaded Conditions

The photovoltaic(PV)buildings have great potential for development in green buildings due to their green ecological characteristics.In the context of national vigorous development of PV buildings,semi-transparent PV glazing fa?ade(STPVGF)system is widely used in actual projects as the main form of building integrated PV because of its advantages such as meeting the aesthetic needs of the building fa?ade,good light transmission and thus reducing the lighting load,stable performance and long service life.In the actual application process,due to the shading of building itself or the surrounding building group,making the STPVGF system is easy to work in the building shadow.Local shadow may cause power generation performance and thermal performance degradation of the STPVGF system,affecting the building energy consumption and building safety.The main purpose of this study is to study the performance of the STPVGF system under the effect of building shadow,and establish a theoretical model and numerical analysis method for analyzing the STPVG system under the influence of building shadows.This study can provide a theoretical basis for the optimization of the performance of the photovoltaic array under the influence of building shadow.The main research contents and results of this paper are as follows:Firstly,this paper establishes two types of mathematical models of building shading,namely,building self-shielding by building eave and building mutual shading by neighboring building,respectively,which simulates the real-time building shadow distribution within the STPVG system.Based on the building shadow model,this paper establishes an optical-electrical-thermal coupled model of the STPVGF system under the building shadow.This study built a full-scale experimental platform on the roof of an experimental building in Changsha,Hunan Province in the area of hot summer and cold winter zone.And verified various system models established in this paper from the perspective of experimental research.The simulated values of the sub-models are in good agreement with the experimental values,and the errors of each sub-model are analyzed with the experimental data of three consecutive days.The results show that the mean absolute error(MAE)of the transmitted radiation through the STPVGF system is 1.71W/m2;The MAE of the power at maximum power point is 1.01W;the MAE of the temperature of the transparent part and the PV cell part is 0.42°C and0.45°C,respectively.Then,the verified coupled model is used to simulate and analyze the characteristic output performance and temperature distribution of the STPVGF system under different building shadow projection types,and the overall energy performance analysis of the STPVGF system under different building eave width in Changsha area is compared throughout the year.The results show that the radiation through the STPVGF system entering the room,power generation and efficiency and total heat gain decrease with the increase of the eave width.When the eave width is 0.29 m,the Changsha area is affected by the building eave shadow from March to September.The transmission radiation loss rate in May is the largest at 3.86%,and the irradiation receiving loss rate is 2.68%;the largest power generation loss rate was 15.3% in April,and the irradiation receiving loss rate is only 1.32%;the largest indoor heat gain loss rate was 3.28% in August,and the radiation reception loss rate was 1.37%.Finally,the mathematical models of four different PV arrays(SP-V,SP-H,TCTV and TCT-H)under building shading are investigated,and the full-year power generation of different PV arrays is simulated and analyzed using this model.The results show that for a completely horizontal shadow,the power generated by the same direction TCT and SP is equal,and the power generated by the horizontal configuration is higher than that of the vertical configuration.For the completely vertical shadow,the power generation of the vertical TCT and SP are equal,and the vertical configuration power generation is higher than that of the horizontal configuration.In the annual power generation performance analysis of Changsha,it is found that PV arrays are affected by building shadows in January to February and October to December under the layout of the building complex described in this paper,where SPV PV array has the lowest power generation in all months and TCT-H PV arrays have the highest power generation and power generation efficiency among the four types of PV arrays considering building shadows.Among all months of the year,December has the largest irradiation loss rate of 19.03%,the maximum power generation loss rate is31.95% for the SP-V array,and the lowest power generation efficiency is 13.19% for the SP-V array.In this study,the coupled optical-electrical-thermal mechanism and experimental study of the STPVF system under building shadow are carried out,and the electrical numerical model of the STPVG array under the building shadow is established.These research are of great significance to the engineering application of the STPVGF system and can provide theoretical guidance for the system optimization and engineering application of the STPVG array system in building energy conservation.