Evaluation of mono and hybrid nano-fluids on energy and exergy parameters of a photovoltaic-thermal system equipped with an eccentric parabolic trough concentrator

Abstract

Considering the problems caused by the use of non-renewable energy, such as climate change, air pollution and environmental destruction, it is necessary to utilize alternative and renewable sources of energy, e.g., solar power, to meet the energy requirements. This study analyzed the electrical, thermal, and total (overall) efficiencies of a photovoltaic-thermal system equipped with a parabolic trough concentrator and an eccentric receiver (ECPVT). The experiments were conducted at three fluid flow rates of 2, 4, and 6 l/m with three nano-fluids (i.e., Al2O3, ZnO, and hybrid Al2O3-ZnO). The weight percentages of the nano-fluids were considered at 0.01 and 0.05, whereas the hybrid nano-fluids had the Al2O3 0.01-ZnO 0.05 and Al2O3 0.05-ZnO 0.01 compositions. According to the findings, the use of hybrid nano-fluids compared with the mono nano-fluids and the pure water in the ECPVT system improved the filling coefficient. Moreover, the filling coefficient was directly related to the increase in the fluid flow in all test conditions (i.e., use of pure water as well as mono and hybrid nano-fluids). The maximum electrical and thermal efficiencies were obtained at 14.8 % and 85.34 % when a hybrid nano-fluid was utilized at a flow rate of 6 l/m. As opposed to the pure water, the total efficiency increased by employing the Al2O3 nano-fluid up to 18.55 %, the ZnO nano-fluid up to 11.29 %, and the hybrid nano-fluid up to 23.39 %. Similarly, the findings revealed that the use of the Al2O3 nano-fluid affected different efficiencies more than ZnO. Compared with the pure water, the exergy efficiency increased by 2.05 %, 2.63 %, and 4.24 % when the mono ZnO 0.05, Al2O3 0.05, and hybrid Al2O3 0.05 + ZnO 0.01 nanoparticles were utilized.