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 transfer fluid (HTF) presents a great potential to overcome drawbacks addressed in commercial Concentrated Solar Power (CSP) plants. The solid particles thermal energy storage (TES) system allows 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 the optical properties and thermophysical properties of materials used both as HTF and as storage medium. The present study is aimed to provide more experimental data and evidences of the potential in using particulate solids for CSP application. The solar absorptance and the specific heat capacity of silicon carbide (SiC), silica sand (SiO2), and hematite (Fe2O3) are studied after different aging times at 750 °C and 900 °C. The solar absorptance slightly increases over the aging process except for the silica sand, which decreases its absorptance in the first 100 h, reaching a plateau. After the aging treatment, the specific heat capacity is increased for both SiC and silica sand. However, for the iron oxide the specific heat capacity is lower after aging. The black silicon carbide 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.