On Optimisation of Operating Conditions for Maximum Hydrogen Storage in Metal Hydrides

The climate crisis continues to grow as an existential threat. Establishing reliable energy resources that are renewable and zero-carbon emitting is a critical endeavour. Hydrogen has emerged as one such critical resource due to its high gravimetric energy density and near-abundant availability. However, it suffers from low volumetric energy density and is incredibly challenging to store and transport. The metal hydride, a solid-state storage method, provides a viable solution to the current limitations. Storage is achieved through the chemical absorption of hydrogen into a porous metal alloy�s sublattice. But its challenging thermodynamic functionality leaves a gap between the ideal storage capacity that current industry requires and the limited capacity that reusable metal hydrides currently provide. This work used mathematical modelling to determine optimal operating conditions for a metal hydride in order to maximise hydrogen storage capacity. Computational fluid dynamics is used to simulate the coupled heat and mass transfer that occurs during the absorption process into the metal alloy. The finite volume method is used to discretise governing equations, and the alternating direction implicit method is used for numerical solutions as it proved the most stable platform to conduct analyses. An initial investigation into numerical grid sizing is conducted to determine the optimal node allocation. The impact of the hydride bed thickness and supply pressure are varied and optimised. The alloy MmNi4.6Al0.4 is used in the investigation.