Theoretical analysis and testing of nanofluids-based solar photovoltaic/thermal hybrid collector

Abstract

Solar energy can be harvested via thermal, photovoltaic, and photovoltaic/thermal (PV/T) hybrid technologies. PV/T systems are advantageous because they utilize more of the solar spectrum and achieve a higher combined efficiency. One approach to PV/T design is to keep the operating temperature of the PV low while achieving a high temperature for the thermal absorber. Various designs of PV/T hybrids (both flat plate and concentrated) have already been proposed which utilize air or water to remove the heat from PV cells in order to enhance the overall efficiency of PV/T hybrid collector. We propose that a nanofluid can be used instead, doubling as both the heat transfer medium and an optical filter, which allows for thermal isolation of the PV and thermal receiver. Thus, unwanted IR and UV light is filtered before it hits the PV cells, which allows for higher overall efficiencies. In this study, a new design of a PV/T hybrid collector was proposed and two nanofluid filters (based on gold and silver nanoparticles) were tested with a silicon (Si) PV cell. The corresponding stagnation temperatures of PV/T hybrid collector were measured and compared with a theoretical model. The experimental measurements validate the theoretical model, giving similar results over the range of parameters tested. The silver nanofluid design achieved the highest thermal, PV and overall efficiency and both nanofluid configurations out-performed an analogous surface absorber PV/T design under similar conditions. Overall, this study shows that nanofluids represent a feasible and viable multifunctional (optical filter and heat transfer) media in PV/T solar systems.