Chemical Heat Battery Material Releases Energy on Demand

A new chemical composite could be used to store heat from the Sun during the day in a thermal battery, and release the heat when needed. A common approach to thermal storage is to use a phase change material (PCM), where input heat melts the material, and its phase change — from solid to liquid — stores energy. When the PCM is cooled back down below its melting point, it turns back into a solid, at which point the stored energy is released as heat. There are many examples of these materials, including waxes or fatty acids used for low-temperature applications, and molten salts used at high temperatures. But all current PCMs require a great deal of insulation, and they pass through that phase change temperature uncontrollably, losing their stored heat relatively rapidly.