Comparison of energy performance between PV double skin facades and PV insulating glass units

Building-integrated photovoltaic (BIPV) windows provide the benefits of generating electricity, reducing building cooling and heating energy consumption, and efficiently utilizing daylight simultaneously. In this paper, the overall energy performance of a PV double skin façade (PV-DSF) and a PV insulating glass unit (PV-IGU) is studied through comparative experiments on a test rig in Hong Kong. The PV-DSF means ventilated PV-DSF by default, if not special mentioned. It is found that the average solar heat gain coefficients (SHGCs) of the PV-DSF and the PV-IGU are 0.152 and 0.238, while the U-values are 2.535 W/m2 K and 2.281 W/m2 K. The results indicate that the PV-DSF has better performance than PV-IGU in reducing solar heat gains, while it has worse performance regarding thermal insulation. With a lower PV module temperature, the energy conversion efficiency of PV-DSF is 1.8% better than PV-IGU. Simulation models for the PV-DSF and the PV-IGU are developed and validated against experimental data. Using the validated models, the overall energy performances of PV-DSF and PV-IGU in five different climates of China are investigated. The results show that the average energy saving potential of the PV-DSF and the PV-IGU are 28.4% and 30%, respectively, compared to the commonly used insulating glass window in five different climates. On average, the performance of PV-IGU was 2% better performance than the ventilated PV-DSF in the five representative cities. However, if an appropriate ventilation control scheme was adopted, PV-DSF can have a much better performance than the PV-IGU. The models developed in this study can be used for selecting suitable PV windows in the design process, and the results achieved can be used as a guideline for utilizing PV windows in different climates.