Review of salt hydrates-based thermochemical adsorption thermal storage technologies

With the continuous progress of new energy technology, the demand for large-scale energy storage is becoming increasingly obvious. The traditional way of heat storage based on physical changes cannot fully meet the actual demand of energy storage, so higher energy storage density media were studied. Salt hydrate is a kind of inorganic material with high heat storage density, no pollution, low cost and safety, which has great application potential in the field of phase change heat storage and thermochemical heat storage. As thermochemical adsorption heat storage materials, salt hydrate and their systems have been widely studied in recent years, and a series of important achievements have been made. Based on the latest literature, this paper systematically analyzes the basic characteristics, heat storage mechanism and factors affecting hydration and dehydration of salt hydrate heat storage materials. It is found that the key to this technology lies in the optimization of the thermal conductivity, porosity and permeability of materials, the thickness, geometric parameters and corrosion of the adsorbed materials, and the selection and optimization of the system type. In this paper, the current research status of salt hydrate thermochemical adsorption heat storage technology is summarized, the critical problems are discussed, and constructive suggestions for future development are put forward. • The difference of mechanism between the two heat storage methods is analyzed. • Different porous materials have different effects on salt hydrate recombination. • The geometric size and adsorbent particle size affect the reactor's performance. • The advantages and disadvantages of open/closed systems are described.