Overall energy assessment of semi-transparent photovoltaic insulated glass units for building integration under different climate conditions

Semi-transparent photovoltaic (STPV) windows, which can not only generate electricity in situ, but also effectively reduce solar heat gain while utilizing natural daylight, have gained increasing popularity due to their energy and environmental benefits. However, the poor thermal insulation performance of single-glazed STPV windows has restricted their application in cold climate regions. PV insulated glass unit (IGU) is an alternative for STPV window applications. This paper presents a comprehensive assessment on overall energy performance of PV-IGUs with different PV glazing transmittance and rear glasses in comparison with conventional IGUs in five different climate zones in China. The results show that PV-IGUs can achieve energy savings in all the representative cities. The largest energy savings are observed in Kunming where heating and cooling demands are low but annual solar radiation level is high. In cold climate regions like Harbin, the PV-IGU with higher transmittance and rear low-e glass consumes less net source energy in comparison with that with lower transmittance and rear clear glass. Although the lighting energy demand of PV-IGU is larger than conventional IGU, the daylight quality of the room with PV-IGU is better due to the higher useful daylight illuminance (UDI) and lower daylight glare probability (DGP).