Characterization of Al 2 O 3 , TiO 2 , hybrid Al 2 O 3 -TiO 2 and graphene oxide nanofluids and their performance evaluations in photovoltaic thermal system

Advanced nanofluid with high stability is essential to meet the demands of the current industry and solar thermal systems. In industrial application, graphene oxide (GO) nanofluid formulated with ethylene glycol (EG)/water (W) is usually well-known for good stability along with high thermal conductivity. In this research, GO nanofluid is characterized for exploring its thermal, optical and suspension stability under certain conditions and then utilized as working fluid in photovoltaic thermal (PV/T) system for measuring its performance compared to those of water and Al 2 O 3 , TiO 2 and hybrid Al 2 O 3 -TiO 2 -based nanofluids. The thermal conductivity, thermal stability, morphology and optical absorbance are characterized by using thermal analyzer, TGA, SEM and UV–vis analysis, respectively. The results revealed that the thermal conductivity of GO/EG:W nanofluid was increased by 9.5% at 40 °C compared to water. It also showed good stability with a zeta potential of 30.3 mV. The numerical implantation of GO/EG:W nanofluid performed by COMSOL Multiphysics software presented significant improvement compared to Al 2 O 3 /EG:W, TiO 2 /EG:W and TiO 2 -Al 2 O 3 /EG:W nanofluids with a concentration of 0.01 mass% to 0.1 mass%. The measured electrical and thermal efficiencies of the PV/T system were 13.5% and 76%, respectively, using GO/EG:W with 0.07 kg s −1 mass flow rate and 0.01 mass% concentration. The stated findings identified GO/EG:W nanofluid as more effective in enhancing PV/T system’s performance than other tested working fluids.