Optimal design of inhomogeneous semi-transparent photovoltaic windows based on daylight performance and visual characters

Abstract

This study aims to optimize the solar cell strip width (CSW) and cell coverage ratio (CCR) of inhomogeneous semi-transparent photovoltaic (IH-STPV) windows to balance the daylight performance and visual characters. The IH-STPV windows with identical CSWs and CCRs but with vertical cell (V-cell) strip layout and horizontal cell (H-cell) strip layout were investigated through comparative experiments and a subjective survey. A visual angle model was first developed to optimize the CSW to mitigate the impact of cell strips on visual characters. By using the experimentally validated daylighting model, the annual daylighting simulation in various daylight climate regions was performed based on the optimized CSW. Finally, the optimal CCRs corresponding to specific CSWs were recommended. The experimental results indicated that the daylight glare risk of the V-cell window was lower than that of the H-cell window, but the difference became less significant when the viewpoint distance increased. Besides, the subjective survey results revealed that the visual discomfort caused by the solar cell strips could be alleviated by extending the viewpoint distance, and the visual characters of the H-cell window were better. The simulation results showed that cities at higher latitudes tended to require a higher CCR due to the low solar altitude angle which causes the higher frequency to see the sun in the view field of the window.