Impacts, Barriers, and Future Prospective of Metal Hydride‐Based Thermochemical Energy Storage System for High‐Temperature Applications: A Comprehensive Review

This article summarizes various thermochemical energy storage (TCES) systems based on their thermochemical properties, operating temperature, and storage density. Metal hydride (MH)‐based TCES is a potential energy storage system due to its higher energy storage density (>100 kWh m −3 ), higher operating temperature (>500 °C), relatively better reaction kinetics, and minimal or no energy losses (theoretically). MHs operate at various temperature ranges, and based on temperature, they are classified as low‐temperature MH and high‐temperature MH. This article highlights potential metal alloys operating above 300 °C, with an energy storage density of more than 100 kWh m −3 , suitable for concentrated solar thermal power generation and industrial process heating applications. Magnesium (Mg) alloy‐based hydrides have shown good cyclic stability (up to 1500 cycles) at a temperature above 400 °C. The lower cost of material, higher energy storage capacity, better reversibility, and higher thermal stability of Mg‐based alloys have been explored in several small‐scale experimental investigations. The thermal energy storage (TES) efficiency of MH‐based TCES systems is reported ≈ 90%, which is significantly higher than sensible and latent TES systems. Challenges associated with MH‐based TES systems, such as heat transfer enhancement, cost reduction, and chemical and thermal stability, have been discussed in detail.