Silicon Nanowires for Solar Thermal Energy Harvesting: an Experimental Evaluation on the Trade-off Effects of the Spectral Optical Properties

TLDR

Silicon nanowires have great potential for renewable energy harvesting, but their benefit for solar thermal energy harvesting has not yet been clearly reported. The study aims to provide practical information and insight into the performance of silicon nanowires in solar thermal energy conversion systems. The authors measured spectral hemispherical reflectivity and transmissivity of black silicon nanowire arrays on silicon wafers and performed drying experiments and theoretical calculations to evaluate wavelength‑dependent scattering trade‑offs. Silicon nanowires exhibit lower visible reflectivity but higher infrared reflectivity than plain silicon, leading to a 17.8 % increase in solar thermal energy harvest and utilization.

Abstract

Silicon nanowire possesses great potential as the material for renewable energy harvesting and conversion. The significantly reduced spectral reflectivity of silicon nanowire to visible light makes it even more attractive in solar energy applications. However, the benefit of its use for solar thermal energy harvesting remains to be investigated and has so far not been clearly reported. The purpose of this study is to provide practical information and insight into the performance of silicon nanowires in solar thermal energy conversion systems. Spectral hemispherical reflectivity and transmissivity of the black silicon nanowire array on silicon wafer substrate were measured. It was observed that the reflectivity is lower in the visible range but higher in the infrared range compared to the plain silicon wafer. A drying experiment and a theoretical calculation were carried out to directly evaluate the effects of the trade-off between scattering properties at different wavelengths. It is clearly seen that silicon nanowires can improve the solar thermal energy harnessing. The results showed that a 17.8 % increase in the harvest and utilization of solar thermal energy could be achieved using a silicon nanowire array on silicon substrate as compared to that obtained with a plain silicon wafer.