Modelling hydrogen storage in metal hydrides

TL;DR

This paper presents a one-dimensional mathematical model for hydrogen loading in metal hydride tanks, capturing key physical processes and explaining temperature gradients through variable reaction kinetics.

Contribution

It introduces a reduced, decoupled model for hydrogen absorption in metal hydrides, incorporating spatially dependent reaction kinetics for better experimental alignment.

Findings

The model successfully describes hydrogen density, pressure, temperature, and metal transformation.

Decoupling of temperature and metal fraction simplifies analysis.

Variable reaction kinetics explain observed temperature gradients.

Abstract

We develop a one-dimensional mathematical model for the loading process of hydrogen in a metal hydride tank. The model describes the evolution of the density and pressure of the hydrogen gas, the temperature of the tank, the averaged velocity of the gas through the porous metal structure, and the transformed fraction of metal into a metal hydride. The non-dimensionalisation of the model indicates a possible reduction of the system of equations and also shows that the density and the transformed metal fraction may be decoupled from the temperature equation. The reduced model is solved numerically. Introducing a spatial dependence into the kinetic reaction constant allows to explain unexpected temperature gradients observed in experiments.