State of the art on the high-temperature thermochemical energy storage systems

Thermal energy storage can provide cost-effective benefits for different commercial fields because it allows heat recycling for use, such as in concentrated solar power plants or metallurgical and steel plants. Compared to traditional sensible and latent energy storage, thermochemical energy storage (TCES) offers a greater possibility for stable and efficient energy generation owing to high energy storage densities, long-term storage without heat loss, etc. The aim of this review was to provide a comprehensive insight into the current state of the art of research on several typical TCES systems at high operation temperatures (673–1273 K). These systems include hydride, metal oxide and organic systems. Each system is discussed in regard to two aspects: cycle life and heat storage performance. A concrete analysis of the current research and development provided in this review exposes that the main challenges of the aforementioned TCES systems rely on robust cycling stability of materials, reliable energy charging and discharging reactors, and a high-efficiency system for widespread commercialization. To bring the TCES system to market, more intensive studies about enhancement of cycle life from micro perspective, charging-discharging behavior in the reactors and development of system integration are still required.