An investigation of the electrical and thermal performances of the photovoltaic wall with different air gap thicknesses and modes in winter

The purpose of this paper is to investigate the optimal air gap thickness of PV wall in different modes (unclosed, partially-enclosed, enclosed). Based on the heat transfer models and evaluation indexes of PV wall, the electrical and thermal performances are analyzed with experimental method and COMSOL software. The experimental results show that 100 mm thickness can be selected as the optimum size for air gap. The computed results show that PV wall with a 50 mm thickness fully enclosed air gap is the best, with a daily total energy savings of 328.06 Wh/m2, but it is not obvious compared with 100 mm. Therefore, the optimal scheme in winter is to use the 50∼100 mm thickness fully enclosed air gap. The exterior surface temperature of 50 mm and 100 mm enclosed air gap are significantly higher than the bare wall. They can increase equivalent thermal resistances by 0.41 and 0.51 m2·K/W, respectively. Furthermore, the reasons for the total energy savings decreasing with the increase enclosed air gap thickness are discussed. The results of this research can provide some guidance for the application of PV walls in similar climate regions and promote the development of building integrated photovoltaics.