Performance analysis of direct absorption-based parabolic trough solar collector using hybrid nanofluids

Addition of a small amount of nanoparticles to the working fluids of a parabolic trough collector does not only enhance the heat transfer properties and thermal conductivity of basefluid but also improves the thermal efficiency of the system. The current investigation presents a comparative analysis of experimental performance of a conventional parabolic trough collector and direct absorption parabolic trough collector for capturing solar thermal energy. Two separate nanomaterials, Al2O3 (with high scattering properties) and CuO (with high absorption properties), were selected for the preparation of the hybrid nanofluids. A customized experimental setup was developed to evaluate their photothermal performance. The nanofluid samples in the concentration range of 0.01–0.5 wt% were investigated under a natural solar flux. Thermal efficiency of conventional parabolic trough collector was increased by 31% using hybrid nanofluid as compared to basefluid. The thermal efficiency enhancement of direct absorption parabolic trough collector was observed as 19% higher than that of conventional parabolic trough collector due to higher heat transfer rate, solar trapping and volumetric absorption. These binary nanofluids can be potential working fluids in various applications based on solar thermal energy.