Colloidal Er₂O₃ nanofluids for enhanced thermal and exergy performance of flat plate solar collectors: Interfacial insights and energy sustainability implications

The increasing demand for sustainable and long-lasting energy sources has highlighted the limitations of conventional flat plate collectors (FPCs), particularly their reduced efficiency under low solar radiation and weak fluid heat transfer capabilities. The research aims at investigating how thermal and exergy performance of FPC can be optimized by incorporating Erbium (III) oxide (Er 2 O 3 ) nanofluids. The test of nanofluids in a split FPC system (outdoor absorber and indoor storage), 0.3 wt.%, 0.6 wt.% and 0.9 wt.% of nanofluid, dispersed by ultrasonication. At a solar radiation of less than 1200 W/m 2 , the nanofluid (0.9 wt.% nanofluid) had a maximum exit temperature of 84.1°C, which was considerably higher than that of water (70.9°C), 1136.7 W heat gain, 78.2 % thermal efficiency and 21.3 % exergy efficiency. It was projected that the annual energy production will be 1678.5 kWh with a CO 2 reduction potential of 20.7 tons. These findings confirm that Er 2 O 3 nanofluid is a valid additive to enhance the performance of FPC and aid in greener energy transformations. The paper indicates that the incorporation of nanotechnology into solar thermal systems presents a viable way of efficiency enhancement and mitigation of climate change.