A new MgH2 tank concept using a phase-change material to store the heat of reaction

The formation of magnesium hydride under hydrogen pressure is highly exothermic. The enthalpy of reaction represents 31% of the lower heating value (LHV) of the absorbed hydrogen. A new concept of MgH2 tank was developed to store the heat of reaction by using a phase-change material (PCM). The heat of desorption is mainly provided by the latent heat of solidification of the PCM. A metallic alloy based on Mg-Zn eutectic was selected as PCM in order to enhance the thermal exchange with the MgH2 compacts. A pilot tank of about 7000 NL of hydrogen was designed and tested under various experimental conditions. Desorption was achieved in 3 h and the daily storage efficiency was around 70%.