Inorganic salt based shape-stabilized composite phase change materials for medium and high temperature thermal energy storage: Ingredients selection, fabrication, microstructural characteristics and development, and applications

Inorganic salts are promising and effective candidates used as phase change materials (PCMs) for medium and high temperature thermal energy storage applications, owning to their suitable melting temperature range, favourable energy storage density and high thermal stability. However, limited by the two main challenges of low thermal conductivity and chemical incompatibility, the large-scale utilization of inorganic salts has been significantly restricted at both industrial and commercial scales. Recent researchers have indicated that the development of shape-stabilized composite phase change materials (CPCMs) could provide an effective solution to overcome these challenges. Such CPCMs are consisted of an inorganic salt for energy storage, a skeleton structure material (SSM) for shape stabilization and a thermal conductivity enhancement additive (TCEA) for heat transfer enhancement, and has shown to achieve an excellent combination of thermophysical and mechanical properties. In this review, the key research progresses on such salt based composites have been reviewed via summarizing the ingredients selection, module fabrication, microstructural characteristics and development, as well as applications in medium and high temperature thermal energy storage fields. The relationships between the material properties and microstructural formation mechanism are comprehensively reviewed and discussed by comparing different fabrication approaches with the aims to provide the reader an in-depth understanding on the design and fabricating considerations of these composites. Finally, the future research efforts and challenges of such salt based composites are also summarized and prospected through emphasizing on the significance of development of new fabrication technologies that are cost-effective and high-efficiency for practical applications.