Heat transfer augmentation in single and multiple (cascade) phase change materials based thermal energy storage: Research progress, challenges, and recommendations

Abstract

Latent heat storage technology is one of the prominent technologies for the efficient utilization and conservation of intermittent solar energy. It provides a reliable storage solution for various energy systems. The major shortcomings of latent thermal energy storage are the PCM's low thermal conductivity, which results in poor heat transfer in the storage. Many researchers across the world made substantial efforts to improve the melting/solidification process of the PCMs and the design of the latent heat storage systems. The researchers have suggested various techniques, such as fins, heat pipes, nanofluids, encapsulation, multiple (cascade) PCMs, and low-density porous materials in latent heat storage that can intensify the performance of the latent heat storage. In this article, these heat transfer augmentation techniques are discussed, and the current trend of research in this area has been underlined. The use of cascade latent heat storage (CLHS) is one of the potential techniques to improve the thermal performance of the latent heat storage systems, which provides a better charging/discharging rate, uniform melting/solidification, and better energy/exergy performance. In this article, attempts are made to fulfill the need for the consolidated compilation of the available studies on multi-PCM storage systems. A comprehensive review of cascade latent heat storage technology in diverse aspects is performed. The various design approaches and performance evaluation methods of CLHS are discussed in detail. The in-depth discussion on the qualitative and quantitative performance of the CLHS has been included. Moreover, a thorough discussion on the available numerical and experimental studies on multi-PCM systems and the process of optimized designing of storage having multiple PCMs have been included. This work also discusses combined techniques for performance augmentation in CLHS and its various design aspects. Although investigators made multidimensional efforts to improve the performance of CLHS, several research challenges still need to be tackled in order to make this technology more effective. This paper highlights the path for future research on the cascade PCM systems.