Absorption characteristics of nanoparticles with sharp edges for a direct-absorption solar collector

Abstract

Plasmonic nanofluids has been reported beneficial for enhancing absorption of the solar energy in a direct-absorption solar collector (DASC). In order to overcome the shortage of narrow absorption band associated with the localized surface plasmon, two strategies can be adopted. One is to blend nanoparticles with different absorption peaks, and the other is to develop nanoparticles capable of exhibiting multiple absorption peaks at different wavelengths. In this study, the latter strategy is explored systematically by investigating the absorption efficiency of metallic nanoparticles with sharp edges. The results show that the Ag nanoparticles with sharp edges can induce multiple absorption peaks due to both localized surface plasmon resonance and lightning rod effect. We also show that the sharper edges (i.e., with either smaller radius of curvature or smaller edge angle) can greatly enhance the lightning rod effect. In addition, the study of SiO2-core/Ag-shell suggests that the core/shell configuration is beneficial for further broadening the absorption band compared to the Ag nanoparticle. Further investigation shows that the solar-weighted absorption coefficient of a DASC using the four-edge nanoparticle is 35% and 20% point higher than the nanosphere and the nanorod respectively with a fixed volume fraction of 10−6.