Effect of the Changeable Organic Semi-Transparent Solar Cell Window on Building Energy Efficiency and User Comfort

Building-integrated photovoltaics (BIPV) are one of the most important sustainability technologies for building energy, and the semi-transparent solar cell is one of the most promising photovoltaic systems for building integration because it can generate electricity and is transparent with a range of beneficial optical properties. On the other hand, the utilization of semi-transparent solar cells for a building facade is limited, as the optimal transparency and power conversion efficiency (PCE %) of the solar cell vary according to the purpose of the space, facing orientation, and number of occupants. This study designed a changeable organic semi-transparent solar cell window (COSW), in which the transparency can be altered by adjusting its temperature and solvent vapor pressure. A simulation test with the proposed COSW was conducted to examine the effects of the proposed window on energy consumption, electricity production, and occupant comfort. The results show that the proposed window has a huge potential for energy conservation and occupant comfort. Compared to the double-glazed Low-E windows, the proposed window reduces the energy consumption by approximately 14.80 kW/m2 (53.29 MJ/m2), 11.51 kW/m2 (41.45 MJ/m2), and 15.02 kW/m2 (54.07 MJ/m2), for the south-facing, east-facing, and west-facing facades, respectively, and increases user satisfaction, particularly in spring and autumn.