Physicochemical properties of ettringite/meta-ettringite for thermal energy storage: Review

Abstract The cost of materials is one of main obstacles for the development of thermochemical energy storage. Compared with traditional inorganic salt hydrates, a mineral named ettringite can easily overcome this limit thanks to its large resource from cementitious materials. Meanwhile, possession of high energy density (about 500 kWh/m 3 ), low corrosiveness, non-toxicity and low working temperature (~ 60 °C) around or below common heat resource (solar energy, industrial waste heat, urbane heat system, and even combination with grid) makes ettringite very competitive to be used in an integrated thermal energy storage system. In this paper, the analysis on the available data for structure, preparation of material, thermal conversion, reaction enthalpies, carbonation durability, and ionic substitution of ettringite has been established. Moreover, potential research directions and solutions to improve thermal performance of ettringite-based materials are proposed.