Sorption thermal energy storage: Concept, process, applications and perspectives

Abstract

Sorption thermal energy storage is a promising technology for effectively utilizing renewable energy, industrial waste heat and off-peak electricity owing to its remarkable advantages of a high energy storage density and achievable long-term energy preservation with negligible heat loss. It is the latest thermal energy storage technology in recent decades and remains in the laboratory investigation stage. The objective of this review is to summarize the state of the art of sorption thermal energy storage technology, note the unresolved technology bottlenecks, and give investigation perspectives for commercial large-scale applications. First, the characteristics of sorption materials, including physical adsorbents, chemical sorbents, liquid absorbents and composite sorbents, are summarized and evaluated. Then, the basic open and closed sorption cycles and other ongoing improved working cycles are described and compared. Next, advanced reactor designs of open sorption, solid adsorption and liquid absorption systems are summarized, such as honeycomb-shaped reactors and heat exchangers with extended surface areas. Finally, the operation performances of typical open and closed prototypes are reviewed and analysed in terms of input issues, output performance and performance parameters. Based on the research achievements, the future challenges of sorption thermal energy sorption technology include improving the heat and mass transfer of reactors, discovering or synthesizing cheap novel porous materials, providing synthesis guidelines for obtaining composite sorbents with desired characteristics, uncovering the mechanisms for the different change trends of the output temperature in the discharging process and establishing evaluation criteria for the operation performance.