Comparative Experimental Assessment of Energy, Exergy, and Environmental Performance of Photovoltaic Thermal Systems Using Different Working Fluids

Abstract Photovoltaic/thermal (PV/T) systems offer a promising solution for simultaneous electricity and heat generation from solar energy. This study presents an experimental assessment of the thermo-economic and environmental performance of a PV/T hybrid system employing two different working fluids: pure water and an ethylene glycol–water (EG/H2O) mixture. The experiments were carried out under typical summer conditions in Algeria, with all systems constructed to identical specifications and evaluated side by side. The performance of the water-based PV/T (W-PV/T) and ethylene glycol-based PV/T (EG-PV/T) systems was benchmarked against a conventional standalone photovoltaic (SPV) module. Results revealed notable differences in system outputs. The W-PV/T system achieved the highest daily exergy output at 210.08 Wh, outperforming the EG-PV/T (198.85 Wh) and SPV (137.94 Wh) systems. Economically, the W-PV/T configuration exhibited an 8.25-year payback period and delivered the most substantial CO2 emissions reduction at 725.8 kg CO2-eq/m2, translating to an estimated carbon credit value of $32.34/m2. These findings underscore the superior performance of water as a heat transfer fluid compared to EG/H2O mixtures and natural convection, highlighting its potential for enhancing PV/T system efficiency in hot climates. The study offers valuable guidance for optimizing PV/T technology in regions with similar environmental conditions.