Experimental study of using both ethylene glycol and phase change material as coolant in photovoltaic thermal systems (PVT) from energy, exergy and entropy generation viewpoints

In this paper, an experimental study of using both ethylene glycol and phase change material as coolant in photovoltaic thermal systems (PVT) from energy, exergy and entropy generation viewpoints is presented. Three different systems are used and compared with each other. The considered systems are: conventional photovoltaic (PV) module, photovoltaic system integrated with phase change material (PV/PCM), and photovoltaic thermal system integrated with phase change material (PVT/PCM). The working fluids used in the PVT/PCM system are pure water, mixture of water and ethylene glycol (EG/water) with a mass fraction of 50 wt%., and pure ethylene glycol. The experiments are performed on selected days in August at the Ferdowsi University of Mashhad, Mashhad, Iran. The results show that the PV/PCM system enhances the electrical exergy of the system by 4.22% compared to that of the PV unit. Furthermore, for the PVT/PCM system, adding ethylene glycol to water reduces the thermal energy efficiency of the system, while enhances the thermal exergy efficiency. Moreover, the reduction of the entropy generation in the PV/PCM, PVT/PCM (water), PVT/PCM (EG 50%), PVT/PCM (EG 100%) systems in comparison with PV unit is 0.58%, 2.42%, 2.51% and 2.84%, respectively.