ZnO-Au composite hierarchical particles dispersed oil-based nanofluids for direct absorption solar collectors

Direct absorption solar collector (DASC) is a promising technology for solar energy harvesting . Recently, nanofluids have shown great potential for DASC applications due to their tunable optical absorption properties . An advanced composite combining plasmonic gold nanoparticles (Au NPs) and hedgehog-like hierarchically structured ZnO particles (HPs) was prepared and used in DASCs. The nanofluid prepared with 1.0   mg   mL −1 HP-Au exhibited excellent stability and broadband optical absorption properties, and reached an equilibrium temperature of ~125   °C within 1   h of solar heating at an irradiation power of 10   kW   m −2 . A new photothermal conversion efficiency model was established to evaluate the solar harvesting performance of the HP-Au/oil nanofluid by simultaneously considering the effect of the working fluid temperature on the heating and cooling efficiencies. Compared to the base fluid, the HP-Au/oil nanofluid exhibits a 240% enhancement in photothermal conversion efficiency. The HP-Au/oil nanofluid shows great potential as a working fluid in direct absorption solar collectors.