Insights on mechanical and morphological metal hydride powder characteristics during hydrogen interaction and stress mitigation strategies for hydrogen storage vessels

Interstitial metal hydride alloys exhibit significant volume changes between the hydrogenated and dehydrogenated states during cycling, resulting in macroscopic stresses in powder beds that must be considered in tank design. Interactions are complex, and these stresses are primarily influenced by the local particle size distribution (PSD) and packing density. This study examines radial expansion forces in vertical storage containers using AB 2 - type hydride alloys and synchrotron-radiation micro-computed tomography (SRμCT). Up to 50 cycles, progressive particle decrepitation occurs, with densification in the lower layers reaching a 91% packing density. This results in local pressures of up to 605 bar in the hydrogenated state. A new empirical equation links packing density to exponentially increasing stress. Experiments have shown that optimized PSDs can reduce stress by up to 45% and increase storage capacity by 87% within the same tank volume.