Research on metal hydrides revived for next-generation solutions to renewable energy storage

Metal hydrides appears poised to be the next generation of storage at concentrated solar power plants. Made from inexpensive, readily available materials such as magnesium, calcium, and titanium, these materials are 10 to 30 times more energy dense than molten salt, though some of that theoretical thermal storage capacity will be lost when engineering a storage system. These materials reversibly absorb and desorb hydrogen gas from their crystalline matrix. Energy is stored in the chemical bonds that change as a metal hydride releases hydrogen gas to become just a metal. The composition of the metal hydride influences the temperature and pressure at which the hydrogen absorption and desorption is reversible, with high-temperature, low-pressure materials favored for CSP storage. Once a metal hydride has been identified as a storage material, it is important to optimize the thermal conductivity of the material so that heat enters and leaves the material as quickly as possible.