Sorption thermal energy storage: Advances and prospects from key materials towards system integration

The rapid advancement of renewable energy has placed heightened demands on long-duration energy storage and cross-regional energy redistribution. Sorption-based thermal energy storage technology achieves high-density, lossless conversion of thermal energy into chemical potential energy through reversible reactions between adsorbents and adsorbates (such as water vapour), effectively resolving temporal and spatial mismatches in energy supply and demand. This paper provides a systematic review of research progress in sorption-based thermal energy storage technology, covering material development, system design, and engineering applications. Regarding materials, traditional physical adsorbents (such as zeolites and silica gels) suffer from low energy density (approximately 200 kWh/m³), while chemical adsorbents (such as hydrated salts and metal chlorides) commonly exhibit poor thermal conductivity (<0.5 W/(m·K)), susceptibility to deliquescence, and weak cycling stability. The preparation of composite materials using porous matrices (e.g., expanded graphite, metal-organic frameworks) can effectively enhance thermal conductivity and cycling performance. Regarding systems, the structural characteristics and applicable scenarios of open versus closed thermal storage systems are compared, and the effectiveness of fixed-bed versus moving-bed configurations in enhancing heat and mass transfer is analyzed. Research demonstrates that sorption thermal storage technology shows applicability and economic benefits in typical application scenarios such as seasonal heating, industrial waste heat recovery, and combined cooling, heating, and combined cooling, heating and power (CCHP) systems. In summary, to overcome the current bottleneck, materials, systems and applications need to be optimized together, rather than isolated progress in any single field. The highlight of this review is to propose a comprehensive framework linking these areas, and to propose the combination of artificial intelligence and digital twins for life cycle control, thereby promoting the establishment of test standards and evaluation systems, and ultimately leading the sorption thermal energy storage technology to large-scale commercial applications.