A review for Ca(OH)2/CaO thermochemical energy storage systems

Thermochemical energy storage is an essential component of thermal energy storage, which solves the intermittent and long-term energy storage problems of certain renewable energy sources. The appropriate decomposition temperature, high heat storage capacity of the CaO/Ca(OH)2 system makes it one of the successful thermochemical energy storage materials. To better predict reaction process of the thermochemical heat storage process, and lay a foundation for the application design and control of the thermochemical heat storage, we summarized and analyzed the research on the physical and chemical properties of the materials by scholars in recent years. These studies include the structure changes as the reaction occurs, the specific heat capacity and the energy density under different conditions and chemical reaction directions, reaction enthalpy and the reaction kinetics during dehydration/hydration. However, some inherent problem (e.g. low thermal conductivity, agglomeration and influence of carbon dioxide during the reaction) limit the performance of this material. By adding other materials to calcium hydroxide to prepare composite materials, researchers can solve these problems to a certain extent. Therefore, this paper reviews the research status of such composite materials from the perspective of the types of added materials. Finally, to better apply the CaO/Ca(OH)2 thermal storage system to actual production, the performance of this material in different types of reaction beds is summarized. •The physical and chemical properties of calcium hydroxide/calcium oxide are summarized.•Problems in the reaction system are outlined and methods of improvement are summarized.•The performance of the reaction in different reactors is summarized.