Review on form-stable inorganic hydrated salt phase change materials: Preparation, characterization and effect on the thermophysical properties

Thermal energy storage based on inorganic hydrated salt phase change materials (PCMs) has attracted considerable attention due to the apparent advantages of high energy storage density, non-toxic, cost effective, etc. It is expected to improve the utilization efficiency of renewable energy and mitigate the energy crisis. Nevertheless, there are still some limitations including phase segregation, supercooling, low thermal conductivity and leakage, etc. For these reasons, stabilizing of PCMs is being developed as promising technique to overcome the obstacles. Although many works have been reported concerning the preparation of form-stable hydrated salt PCMs, to date, these stabilizing techniques and their effect on the thermophysical properties of hydrated salt PCMs have never been systematically summarized. Hence, we are committed to review the works about stabilizing techniques for hydrated salt PCMs, present the analysis around the influence of stabilizing method on the thermophysical properties of form-stable hydrated salt PCMs. Three major types of stabilizing hydrated salt PCMs are found: adsorption and impregnation into the porous materials, core-shell encapsulation methods and organic threedimensional network structures. Furthermore, the thermophysical properties such as phase change temperature, latent heat, thermal conductivity, supercooling and phase segregation as well as thermal cycling reliability are deeply discussed as well. In addition, the application areas of form-stable hydrated salt PCMs are presented from detailed investigations. Based on our best knowledge, this is the first profound review of stabilizing techniques for hydrated salt PCMs, and researcher will gain significant insight into the field for preparation and application of form-stable hydrated salt PCMs.