Performance evaluation of a novel concentric metal hydride reactor assisted with phase change material

Hydrogen storage is a promising technique that could handle the challenges of intermittent renewable production on the electric grid. Metal Hydride (MH) is a promising hydrogen storage technique owing to its safety, availability, and high volumetric storage density. However, MH requires an efficient heat management system. Therefore, this paper proposes a multi-layer cylindrical reactor where layers of MH and phase change material (PCM) are alternatively arranged. A numerical model is developed utilizing COMSOL Multiphysics software and is validated to predict the performance of the proposed reactor at various design parameters. As PCM thermal conductivity changes from 0.2 to 3 W/m.K, absorption time, based on 90 % absorption, reduces from 3555 s to 675 s (similar to 5.33 times reduction). Compared to a reference case, four layers system reduces absorption time by 78 %. Lithium nitrate trihydrate as PCM material exhibits the best performance, allowing four layers to greatly reduce reactor volume with a slight absorption time delay. The analysis introduces two novel parameters expressing the absorption rate per system mass and volume. From the intensive analysis, the specific capacity rate (SCR) of the proposed reactor is 1.51 g(H2)/min/kg(sys), while the volumetric capacity rate (VCR) of the proposed reactor is 3016 g(H2)/min/m(sys)(3). SCR and VCR are 3.4 and 3.12 times higher than the corresponding values in literature.

Automated summary

This paper proposes a multi-layer cylindrical reactor with metal hydride (MH) and phase change material (PCM) alternately arranged to solve the heat management problem of MH. Through numerical modeling and validation, it is found that the reactor using lithium nitrate trihydrate as PCM material has the best performance, reducing reactor volume while slightly delaying absorption time. The specific capacity rate (SCR) and volumetric capacity rate (VCR) of the proposed reactor are 3.4 and 3.12 times higher than the corresponding values in literature.