3E (efficiency entropy, and exergy) analysis of a flat plate solar collector with a nanofluid based on reduced graphene oxide

Colloidal nanofluids have recently emerged as a promising solution for enhancing the efficiency of solar thermal systems. Recent research underscores the superior thermal properties of reduced graphene oxide (rGO)-based nanofluids as working fluids in flat plate solar collectors (FPSCs). This study evaluated nanofluids with varying rGO concentrations (0.05–0.25 vol.%) for their thermal and exergy performance. Key thermophysical properties, including thermal conductivity (TC), density, viscosity, and specific heat, were meticulously characterized. Results demonstrated that the incorporation of rGO significantly improved thermal efficiency compared to deionized (DI) water. Notably, rGO addition reduced system irreversibility by 8–29%, thereby enhancing entropy management within FPSCs. Furthermore, exergy efficiency improved by 3–12% with increasing rGO concentration. The heat removal factor exhibited a notable increase of 0.7–5.48%, accompanied by a 0.2–5.5% reduction in the overall heat loss coefficient. These improvements collectively underscore the potential of rGO-based nanofluids to revolutionize thermal management and operational efficiency in FPSCs, contributing to more sustainable and energy-efficient solar thermal systems.