Dual enhancement of solar organic Rankine cycle performance using SnO₂/R141b and Co₃O₄/R141b nano-refrigerants and MWCNT+SiC/water hybrid nanofluid

Considering the increasing demand for converting sustainable energy, advanced thermal systems have played a vital role in electricity generation. This study presents energy and exergy analyses of a small-scale solar organic Rankine cycle (SORC) system enhanced through a dual-stage strategy: a hybrid nanofluid (MWCNT + SiC/water) is used in the evacuated tube solar collector (ETSC), while SnO₂/R141b and Co₃O₄/R141b nano-refrigerants are applied in the ORC loop. Experimental results show that the hybrid nanofluid significantly improved the thermal performance of the ETSC, achieving a maximum thermal efficiency of 44.83% at 1.0 vol% and 3 lpm. The enhanced heat input from the ETSC contributed to higher cycle efficiencies. The ORC achieved its highest energy and exergy efficiencies—16.76% and 6.64%, respectively with SnO₂/R141b at 1.0 vol%. Compared to Co₃O₄/R141b, SnO₂/R141b exhibited superior thermal conductivity and energy output quality. Therefore, this study makes a major contribution to nano-refrigerants in small-scale SORCs, opening new technological avenues for next-generation sustainable, efficient power generation technology. This work discusses some critical gaps related to nano-refrigerant applications and indicates a pathway toward guaranteeing clean energy futures.