Abstract

Thermal energy storage (TES) occurs by changing the internal energy of materials in the form of sensible heat, latent heat, and thermo-chemical heat or a combination thereof. Latent heat storage (LHS) by phase change materials (PCMs) has many applications among these storage techniques. Despite the many advantages of LHS, the main problem of LHS systems using PCMs is their low thermal conductivity, which necessitates the combination of heat transfer enhancement techniques. Numerous diverse studies have utilized only one improvement method, while limited research has employed hybrid enhancement techniques. The typical improvement methods, such as adding nanomaterials, using fins, employing porous media, and micro/nano encapsulating the PCMs, can be combined in the TES system. A hybrid technique is when a combination of two or more enhancement methods is applied to a TES system. In addition, a new approach is introduced and then utilized in the hybrid enhancement method. An auxiliary fluid in direct contact with the PCM improves heat transfer in the melting and solidification processes. In this direction, this review discusses different enhancement strategies of melting and solidification rates in TES systems in recent years. The hybrid techniques introduced in this literature review show that the TES system performance has improved, further justifying the use of this method in future studies. Lastly, the challenges and future work direction are recommended, for exploring other hybrid enhancement methods for LHS systems.