Numerical simulation on the storage performance of a phase change materials based metal hydride hydrogen storage tank

In metal hydride (MH) hydrogen storage tanks, the integration of phase change materials (PCM) can store and release the reaction heat to promote the reaction process without an external heat source. In order to get a highperformance MH-PCM storage tank and understand the effect of mass ratio of PCM to MH on the storage performance, this research proposes a novel MH-PCM storage unit (PCM sandwiched between two layers of MH) stacked inside a cylindrical tank. A mathematical model is established to describe the heat and mass transfer in the process of hydrogen ab/desorption and heat storage/release. It is found that the PCM sandwiched structure has a larger heat transfer area than the surrounding structure, which improves the hydrogen absorption and desorption rate. For the MH-PCM unit, the mass ratio of PCM to MH affects the hydrogen ab/desorption rate. Varying the mass ratio of PCM to MH requires adjustments in the hydrogen absorption pressure for completely absorbing the hydrogen, which also impacts the amount of sensible and latent heat stored in the PCM. The results show that in order to fully absorb the hydrogen, the hydrogen absorption pressure must increase to compensate for reduced mass ratio of PCM to MH, and the ratio of sensible heat to latent heat storage increases.