Thermal transport of charging/discharging for hydrogen storage in a metal hydride reactor coupled with thermochemical heat storage materials

Abstract

Metal hydride is a promising alternative for hydrogen storage. A novel metal hydride reactor coupled with thermochemical heat storage material is proposed to reduce the energy loss. The hydrogen charging and discharging processes are numerically and analytically investigated in this paper. Hydrogen is stored in a compacted metal hydride disk, so the reaction characteristics under low permeability are studied. The dehydration kinetic equation has been re-established to determine the equilibrium temperature at a corresponding pressure. The reactor takes 139 min for the hydrogen charging process and takes 512.8 min for the hydrogen discharging process. The reaction characteristics are found to be affected by heat transfer and gas pressure at the permeability of 5.9×10-16m2. The analytical model is found to be only applicable to the prediction of reaction time with high permeability of hydrogen in metal hydride. The thermal management of thermochemical heat storage materials has been proven to be feasible. By increasing the hydration equilibrium temperature from 321.8 °C to 350 °C, the reaction time can be decreased to 43.1 %. By decreasing the dehydration equilibrium temperature from 300 °C to 270 °C, the reaction time can be decreased to 84.5 %. To enhance the heat transfer, meal foam is added to the thermochemical heat storage material. Adding metal foam can effectively shorten the reaction time, but will reduce the hydrogen production. A metal foam with a porosity of 0.96 will reduce the production of hydrogen by 3 %.