Color rendering properties of semi-transparent thin-film PV modules

Performance characterization of semi-transparent photovoltaic (PV) modules usually includes data on electric power generation and visible light transmittance. However, when the modules are used as façade material, they also affect colors rendered in the indoor environment. It is important to quantify the color rendering property of these modules to ensure visual comfort of occupants. In this study, color rendering properties of semi-transparent building-integrated photovoltaic (STPV) modules were determined by evaluating the color rendering index (CRI) for the transmitted light. A mobile daylight measurement system was configured to allow measurement of the transmitted spectral power distribution (SPD) through the STPV in the laboratory and outdoors. The CRI of the STPV modules was measured for different incident angles of 0, 8 and 45° under laboratory conditions. Four modules of amorphous silicon show high CRI values above 90 for all angles of incidence. Two colored modules of micromorph silicon have CRI below 90 that could affect visual comfort. CRIs from the laboratory and outdoor measurements were compared for one of the amorphous silicon samples, with the sample installed in a building. Results obtained, CRI of 98 and 93, show that the sample renders colors well in laboratory conditions and achieves good color rendering outdoors as well.