Study on solar absorptance and thermal stability of solid particles materials used as TES at high temperature on different aging stages for CSP applications

Abstract

The use of solid particles as heat transferfluid (HTF) presents a great potential to overcome drawbacks addressedin commercial Concentrated Solar Power (CSP) plants. The solid particles thermal energy storage (TES) systemallows achieving both high thermal performance at high temperature and low cost from the material perspective.The conversion efficiency of CSP solid particles-based systems at high temperatures strongly depends on theoptical properties and thermophysical properties of materials used both as HTF and as storage medium. Thepresent study is aimed to provide more experimental data and evidences of the potential in using particulatesolids for CSP application. The solar absorptance and the specific heat capacity of silicon carbide (SiC), silicasand (SiO2), and hematite (Fe2O3) are studied after different aging times at 750 °C and 900 °C. The solar ab-sorptance slightly increases over the aging process except for the silica sand, which decreases its absorptance inthefirst 100 h, reaching a plateau. After the aging treatment, the specific heat capacity is increased for both SiCand silica sand. However, for the iron oxide the specific heat capacity is lower after aging. The black siliconcarbide SiC is proven to be the best option to be used up to 900 °C as it shows the highest solar absorptance(96%) and the highest heat storage capacity.