An innovative, high-efficiency silver/silica nanocomposites for direct absorption concentrating solar thermal power

Using of nanofluids in the concentrating direct absorption solar collectors has the potential of reducing thermal losses because of the excessive temperature of the absorbing surface in the conventional solar collectors. However, increasing the concentration ratio of solar radiation must be followed by increasing the volume fraction of the nanoparticles, which, in turn, has the drawbacks of increasing the settlement and agglomeration rates of the nanoparticles. In this study, we have suggested using the plasmonic nanofluids for volumetric absorption in the concentrated solar power applications because of the less volume fraction of the plasmonic nanoparticles that are required to harvest the concentrated solar radiation. The interaction of concentrated solar radiation with different morphologies of silver nanoparticles coated by silica shell has been computationally studied. Then, the finite element method has been implemented to determine the photo-thermal conversion efficiency for silver nanosphere and nanoplates with a silica shell. Silver nanoparticles coated by silica exhibit a promising potential because of their distinct characteristics. The silica shell is transparent to the visible and near-infrared radiation bands; it also consolidates the intensity of the localized plasmon resonance and so the absorption characteristics, besides its protective role. A high-efficiency low concentration nanofluid has been designed using blended morphologies of Ag nanospheres and nanoprisms with silica-coating-based nanofluid for full-spectrum absorption characteristics. The suggested nanofluid exhibits a promising performance at a volume fraction of 0.0075 wt% where the volumetric solar collector efficiency exceeds 75% under the solar concentration ratio of 50.