A systematic evaluation of sorption-based thermochemical energy storage for building applications: Material development, reactor design, and system integration

Sorption-based thermochemical energy storage (TCES) has attracted substantial attention due to its remarkable potential for long-term and high-capacity heat storage. The efficacy of a TCES system hinges on the seamless integration and coordinated operation of its components. For instance, the choice of thermochemical materials can exert a profound influence on the system's heat storage capacity and stability. Meanwhile, the design of the reactor, along with other critical system components, such as condensers and evaporators, can significantly affect the reaction kinetics of the sorption material, as well as the system’s achievable temperature lift and thermal power output. This review paper conducts a comprehensive evaluation of TCES technologies for building applications. It delves deep into three pivotal aspects: material development, reactor design, and system integration, with the aim of elucidating the synergistic relationships among these components. In the aspect of material development, it meticulously reviews the characteristics and system-scale performance of diverse sorption materials. These include physical adsorbents, mono-salt composites, mixed-salt composites, and encapsulated salts. Regarding reactor design, it explores the heat storage potential of various reactor configurations, such as packed bed, moving bed, fluidized bed, modular design, and those integrated with air channels or grain-coated heat exchangers. In terms of system integration, it investigates the effective ways in which TCES systems can be incorporated into building energy systems, such as solar heating systems, air conditioning units, and building envelopes. Through this systematic evaluation, the study endeavors to provide a detailed understanding of the current state-of-the-art and challenges in TCES for building applications, and moreover, to offer insights and directions for future research and development in this field to enhance the energy efficiency and sustainability of buildings. • A holistic perspective on TCES technologies, outlining strengths, limitations, and future directions. • Overview of low-temperature TCES, including its classifications, mechanisms, TRLs, and current challenges. • In-depth analysis of sorption materials. • Overview of non-packed-bed reactors, along with detailed guidelines on fluidized-bed-based TCES systems • Innovative approaches for TCES system integration within built environment.