Silver nanofluids based broadband solar absorber through tuning nanosilver geometries

This work explores the strategy for increasing the efficiency of solar thermal energy capture by the utilisation of a blended mixture of plasmonic silver nanofluids in a direct absorption solar collector. For the first time, a broadband absorber based on combining three silver-based nanofluids, each with a tailored plasmonic response covering a different wavelength range, was designed and synthesised. The potential efficiency of this broadband absorber was estimated from the UV-Vis-IR spectra and from direct measurement of the temperature rise obtained in static tests in a solar simulator. The results from the two methods were comparable. The broadband absorber was shown to increase the efficiency of capture compared to the component nanofluids and compared to water. The temperature rise in the solar simulator for the broadband mixture was more than four times that of water and the photo-thermal conversion efficiency was approximately 85%, demonstrating the promise of this mixture for enhancing solar energy capture. However, this work also illustrates the potential issues with utilising silver for solar applications, namely the change in morphology and UV-Vis-IR spectra with light exposure. A suitable stabilisation or coating strategy would hence be required to use this developed broadband absorber in solar energy applications.