A review of the performance and application of molten salt-based phase change materials in sustainable thermal energy storage at medium and high temperatures

Growing energy demand and environmental pollution issues are placing greater demands on sustainable thermal energy storage. Research indicates that molten salt phase change materials (MSPCMs) represent a promising alternative for thermal energy storage (TES), effectively addressing the energy supply-demand imbalance. These salts typically have a range of excellent properties, such as high energy storage density, easy availability, and minimal environmental impact. Nevertheless, the widespread application of molten salts is considerably constrained in both industrial and commercial contexts due to their low thermal conductivity (TC) and leakage problems during phase transitions. Based on this, this paper provides a comprehensive examination of the synthesis and energy conversion characteristics of molten salt composite phase change materials (CPCMs), along with the integrated utilization of solid waste materials. Additionally, the potential applications of these phase change materials (PCMs) across various domains are thoroughly explored. The study also addresses the corrosion behavior of encapsulation materials induced by molten salt-based CPCMs. The findings indicate that the development of solid waste-derived and Shape-stabilized CPCMs (SSCPCMs) offers promising solutions to mitigate these challenges. Nevertheless, it is important to acknowledge that conventional energy conversion materials are predominantly organic, and research into molten salt CPCMs remains in its nascent stages, with current applications mainly limited to photothermal and magnetocaloric energy conversion. Furthermore, while coatings technology significantly enhances the corrosion resistance of carbon steel in molten nitrate environments, there remains an urgent need for further investigation into more effective corrosion protection strategies and materials. In conclusion, this review provides valuable insights into the prospective advancement of MSPCMs and underscores the necessity for continued research in this domain to fulfill the requirements of sustainable TES systems.