Overall outdoor experiments on daylighting performance of a self-regulating photovoltaic/daylighting system in different seasons

Compared with the PV electricity generation alone system, the hybrid photovoltaic/daylighting system is more efficient and more economical for the building application. In this paper, a novel self-regulating concentrating photovoltaic/daylighting system is proposed. Because the concentrator is made of the transparent material, the daylighting function can be efficiently incorporated without decreasing its optical efficiency. The transmittance characteristic of the concentrating photovoltaic/daylighting system is a vital parameter that is related to the electrical and daylighting performance of it, which also has a significant impact on the building’s energy consumption behavior. To address this issue, the experimental investigation of this new system towards the visible light transmittance in different seasons and under different weather conditions is presented for the first time. The transmittance evaluation method based on the integrating box is adopted for the experimental test. The experiments are conducted on four different days that are corresponding to different seasons and different weather conditions. The conversion factor of the integrating box is first experimentally calibrated. The internal illuminance on four walls of the integrating box and the external illuminance are obtained, based on results of which, the transmittance of the concentrating photovoltaic/daylighting system is determined. It's found through experimental results that under the sunny weather condition in the summer, autumn, and winter seasons, the daily average tested transmittance of the concentrating photovoltaic/daylighting system is 8.57%, 6.78%, and 7.43% respectively. The experimental results under the overcast weather condition indicate that the transmittance of the concentrating photovoltaic/daylighting system for the diffuse solar irradiance is 7.22%.