Numerical simulation study of BIPV/T double-skin facade for various climate zones in Australia: Effects on indoor thermal comfort

Maintaining indoor thermal comfort is crucial for the health and productivity of building occupants. Building envelope plays a major role in influencing the impact of outdoor climate and controlling the indoor thermal conditions. In this paper, comparative analysis of indoor comfortable temperature for four different types of building-integrated photovoltaic/thermal (BIPV/T) building models in a range of climate zones in Australia was conducted using TRNSYS simulation tool. In terms of system operational mode, the four types of BIPV/T building facade systems include a building-integrated photovoltaic single-skin facade (SSF), non-ventilated BIPV/T double-skin facade (BIPV/T-DSF), naturally ventilated BIPV/T-DSF and fan-assisted BIPV/T-DSF. In addition to the operational modes of the facade systems, two types of semi-transparent PV glazing with different visible light transmittance (VLT) were respectively applied to the models as external window glazing. The numerical results showed that the naturally ventilated BIPV/T-DSF with lower VLT (27%) PV glazing maintained a relatively better indoor temperature for the hot climatic conditions compared to the other operational modes, while the non-ventilated BIPV/T-DSF with higher VLT PV glazing (37.5%) offered more comfortable indoor temperature (i.e. 20 to 26 degrees C for office hours) for the cold climates in Australia. On the other hand, the naturally ventilated BIPV/T-DSF could basically maintain comfortable indoor temperatures from 22 to 27 degrees C during office hours without mechanical systems for the peak summer times for cool temperate climates in Australia. Moreover, it was found that the thermal insulation effect of semi-transparent PV glazing hardly affected indoor operative temperature in the ventilated modes of the BIPV/T-DSF. According to the sensitivity analysis, the change of U-value of internal window of the DSF would significantly lead to the change of indoor thermal comfort in both ventilated operational modes, but very few changes for the non-ventilated DSF. The variation of cavity depth had distinct impact on the indoor thermal comfort for fan-assisted DSF but slightly affected that of other modes. In addition, the changes of opening ratio for the ventilating louvers and fan airflow rate of the DSF also had a degree of influence on indoor thermal comfort for naturally ventilated DSF and fan-assisted DSF respectively.