The stability, optical properties and solar-thermal conversion performance of SiC-MWCNTs hybrid nanofluids for the direct absorption solar collector (DASC) application

Hybrid nanofluids have an advanced application prospect in the community of heat transfer fluids and particularly for the direct absorption solar collectors (DASCs). Therefore, stable ethylene glycol-based SiC-MWCNTs nanofluids with mass fractions ranging from 0.01% to 1% were prepared in this study. Combined with the unique properties of these two nanomaterials, the studied hybrid nanofluids displayed excellent stability, optical properties and photothermal conversion properties. The purpose of this paper is to simultaneously achieve the enhanced stability and high solar-thermal conversion efficiency of hybrid nanofluids used for DASC applications. The stability of hybrid nanofluids was confirmed. In addition, the hybrid nanofluids displayed an excellent solar irradiation absorption capacity in both visible and near-infrared regions (200–1100 nm). The fact proved that the hybrid nanofluid was effective working fluid in DASCs, where 0.5 wt% SiC-MWCNTs nanofluids could absorb 99.9% solar energy at only 1 cm path length. In addition, the solar-thermal conversion efficiency of hybrid nanofluids increased with the mass concentration. The maximum value of solar-thermal conversion efficiency was found to be 97.3% on 1 wt% SiC-MWCNTs nanofluid at 10 min, which was 48.6% higher than that of pure EG. The application potentials of SiC-MWCNTs hybrid nanofluids in low-temperature DASCs system were presented. •Homogeneous and stable EG-based SiC-MWCNTs hybrid nanofluids were prepared.•Excellent solar irradiation absorption capacity in both visible and near-infrared regions.•A 97.3% solar-thermal conversion efficiency was found on 1 wt% SiC-MWCNTs nanofluid.•0.5–1 wt% nanofluids are most suitable concentration range for DASCs applications.