Effects of frame shadow on photovoltaic/thermal system integrated with building

Air layers exist between glass covers and cells in most building-integrated photovoltaic/thermal (BIPV/T) systems. This layer significantly reduces heat loss and improves the overall efficiency of BIPV/T systems. However, the frame border that supports the glass cover casts a shadow over the cells near the frame according to the building enclosures and the location of the sun, thereby affecting the photovoltaic performance. This study aims to determine the effects of frame shadows on BIPV/T systems and estimate the loss caused by these shadow. A mathematical model was proposed to simulate the photovoltaic performance of BIPV/T system. The influences caused by building enclosures, the setting orientation of BIPV/T system, solar altitude, and solar azimuth were analyzed using the model. The annual energy yield loss caused by the frame shadow was estimated, and a highly accurate approach was presented to evaluate the average annual performance of the BIPV/T system. The results show that the frame shadow reduces the efficiency to 3.2% (normal efficiency, 13.0%), and the annual loss caused by frame shadow is 53.6 kWh/m².