Experimental evaluation of SiO₂–MWCNT/water hybrid nanofluids for sustainable cooling of photovoltaic/thermal systems

This study experimentally investigates the performance of a 0.5 m² photovoltaic/thermal module cooled with a novel SiO₂–MWCNT/water hybrid nanofluid under outdoor climatic conditions in Hungary. The research addresses key limitations of conventional cooling methods, particularly the low thermal conductivity of water and the limited use of exergy and sustainability analyses in existing PV/T studies. The methodology involved developing a PV/T system equipped with serpentine copper tubes, fins, forced convection, and a heat recovery unit. The performance of the hybrid nanofluid-cooled module was experimentally compared with water-cooled and uncooled reference modules under identical operating conditions. Results showed that the hybrid nanofluid reduced PV cell temperature by approximately 13 °C, improving electrical efficiency by 11%, compared with 10 °C and 6% improvements for water cooling. Thermal and exergy efficiencies reached nearly 90% and 67%, respectively, demonstrating enhanced energy utilisation and reduced thermodynamic losses. The life cycle assessment indicated low environmental impacts, with a global warming potential of 25.6 g CO₂ kWh⁻¹ based on the combined electrical and thermal energy output. The study demonstrates that SiO₂–MWCNT hybrid nanofluids offer a practical, efficient, and sustainable solution to improve the performance of next-generation PV/T systems.