Experimental study on a concentrating solar photovoltaic/thermal system using different fluid spectral beam filters

Spectral splitting photovoltaic/thermal technology is the leading field in the area of extremely efficient utilization of solar energy. Due to its complexity, experimental research on spectral splitting photovoltaic/thermal devices is relatively limited, mainly focusing on the laboratory scale energy efficiency test or calculation process verification. These studies do not provide intuitionistic guidance for the actual operation of engineering systems. In this paper, a fluid filter-based compound parabolic concentrator solar photovoltaic/thermal system with engineering application dimensions is designed and experimentally studied under actual outdoor environments. Different fluid filters are prepared and used to regulate the spectral splitting characteristics of the proposed system, including the deionized water, silver/water nanofluids and silver-cobalt sulfate/water nanofluids. When the environmental parameters are relatively stable, the method of adjusting the composition of the fluid filter is used to obtain the dynamic operating characteristics of the system. The results show that silver nanoparticles and cobalt sulfate can improve the spectral absorptivity of the deionized water. Compared with the deionized water, when the silver/water nanofluids is used as the fluid filter, the thermal efficiency of the system increases, the electric efficiency and overall exergy efficiency of the system both decrease, and the three efficiencies are 56.0%, 8.5% and 19.6%, while for the silver-cobalt sulfate/water nanofluids, the efficiencies are 58.0% 8.0% and 20.0%. Moreover, the results reveal that for the photovoltaic/thermal system with a low solar concentration ratio, by enhancing the absorptivity of the fluid filter, the fill factor of the photovoltaic module can increase, but the output electric power will decrease. When the silver-cobalt sulfate/water nanofluids is used, the fill factor and maximum output power of the proposed system are 0.633 and 69.2 W. For a unit consisting of four sets of the proposed photovoltaic/thermal systems, the emission reductions of CO2, NOx, SO2 and dust for the whole lifetime are approximately 7794.19 kg, 181.48 kg, 191.95 kg and 111.68 kg, respectively.