Low pressure, high capacity hydrogen storage: The adiabatic storage concept

Abstract

State of the art hydrogen storage is based on 700 bar pressure tanks. However, compression to such high pressures requires a significant amount of energy reducing the overall efficiency of the system. Hydrogen storage in metal hydrides with high capacities, such as MgH2, is a promising alternative. Nevertheless, it is challenging to provide and withdraw the required heat for the chemical reaction at temperatures of more than 200 °C. To overcome this drawback, a system was proposed integrating a thermochemical heat storage material, such as Mg(OH)2, which stores/releases the heat of reaction for the MgH2 hydrogenation/dehydrogenation. The two materials are in thermal contact to enable rapid heat transfer between them. Heat management with the environment is not necessary. Thus, the storage reactor can be operated adiabatically. The chosen materials are easily available and the system works at pressures less than 40 bar. Additionally, it exhibits a volumetric storage density twice as high as the 700 bar pressure tank. The basic operation principle of such a storage reactor has been published before. In this contribution, first experimental results of a storage reactor prototype will be shown.