Recent advances in multistage sorption thermal energy storage systems

Thermal energy storage (TES) systems are used to overcome daytime solar energy instability and fluctuation. Thermochemical TES systems are more promising than sensible and latent TES systems, particularly for solar energy applications with low and medium temperatures. The most recent literature reviews summarized the advancement of sorption energy storage systems (ESSs) in single-stage TES systems. However, multistage sorption ESSs have also attracted attention in recent years but have not been comprehensively reviewed. Thus, this article examined the energy storage density (ESD) and storage efficiency of multistage or cascaded sorption TES systems. The most recent sorption multistage TES prototypes were presented and compared on the basis of sorption material combination, ESD, and storage efficiency. Also, the most effective parameters for both single and multistage sorption ESSs were compared to highlight their advantages and disadvantages. Finally, challenges and future research directions for multistage sorption ESSs are summarized. On the basis of this review, limited numerical and experimental studies were implemented to determine the energy storage capabilities of multistage TESs.