Semitransparent Bifacial PV Windows with Integrated Blinds: Experimental and Modelling Results

The stricter requirements for the energy performance of buildings are creating a market for several building integrated photovoltaic (BIPV) technologies, including PV windows. Herein, we present an innovative multifunctional PV window concept designed to enhance energy generation while providing over-heating protection for better indoor thermal and visual comfort. This concept utilizes bifacial c-Si solar cell strips combined with Venetian blinds, all embedded in a unique insulating glazing unit. The bifacial technology increases the energy yield by using the blinds as reflectors, directing more irradiance to the cells' rear side. Twelve demonstrators were installed and monitored for a full year. Several measurement campaigns were conducted to assess the impact of different blind types and tilt angles on the total yield. It was found that the highest energy boosts occurs when the blinds are fully closed at a 75° angle with their convex side facing outwards. Blinds with the highest specular reflectance achieve a maximum performance increase of 25% on sunny days and a daily average increase of 13% compared to the case of no blinds. Simulations were conducted to better understand the complexity of the system and to assess the potential of this bifacial PV window concept.