Overall detail comparison for a building integrated concentrating photovoltaic/daylighting system

This paper aims to validate an efficient way to use the low-concentration ratio concentrator for the building integrated concentrating photovoltaic/daylighting system, which is able to collect maximum solar energy for the renewable electricity generation and provide the function of daylighting. A 2-D static concentrator has been designed by leaving the lower portion of the outer parabolas near the base area uncoated to form the "daylighting window", which is named as CPVD (indicating that the concentrator is for the concentrating photovoltaici/daylighting system), while the concentrator with the same structure but can only achieve the onefold function of the electricity generation is named as CPV. In order to address the interaction effects between the concentrating PV performance and daylighting performance, the overall detail comparison is made for the CPVD module and CPV module through the ray-tracing simulation and experimental characterization. It's found that CPVD and CPV have similar optical performance (indicated by concentrating PV performance, optical efficiency, opto-electric gain and flux distribution on the receiver etc.) at various incidence angles, which validates that setting the "daylighting window" have no native effects on the optical performance of the concentrator. At last, in order to quantify the beneficial harvest for the daylighting, the conducive lighting transmittance through the "daylighting window" under two different sky conditions: clear and overcast sky conditions are investigated through the outdoor experiments. The outdoor concentrating photovoltaic/daylighting experiment test rig is built and the transmittance of the CPVD is measured under two different sky conditions. Under the clear sky condition, the daily average transmittance of the CPVD is measured to be 8.73% which is pretty much consistent with the ray-tracing simulation results. Under the overcast sky condition, the transmittance value is lower, the daily average value of which is 7.11%. (C) 2019 Elsevier B.V. All rights reserved.