Analysis of hydrogen storage in metal hydride tanks introducing an induced phase transformation

Hydrogen absorption in a metal hydride tank is generally studied based on a heat and mass transfer analysis. The originality of this investigation is that the phase transformation from a solid (α phase) to hydride (β phase) solution is included in the hydrogen absorption mechanism. Toward this end, a modelling of the equilibrium pressure, composition (absorbed or desorbed hydrogen atoms per metal atoms), and isothermal curves of a LaNi5 alloy is performed. Moreover, a kinetic model is developed taking into account the steps of hydrogen absorption and desorption (i.e., physisorption, chemisorption, surface penetration, nucleation and growth of the hydride phase and diffusion).Simulations are then performed to show the impact of external conditions (hydrogen gas pressure and temperature) and parameter values (wall heat transfer, conductivities of gas and solid, viscosity, porosity, etc.) on refilling time. The physical nature of the phase transformation associated to the hydrogen storage remains an open problem.