Integration of thermal energy storage unit in a metal hydride hydrogen storage tank
Abstract In metal hydride hydrogen storage tank, a thermal energy storage unit can be efficiently integrated as it is economical by replacing the use of an external heat source. Hence, a Metal Hydride (MH) bed integrating a Phase Change Material (PCM) as latent heat storage system is appropriately selected and investigated in this study. Heat and mass transfer analysis is made to understand the influence of the bed geometry on the relationship between hydrogen absorption (or desorption) efficiency and heat storage processes. A mathematical model is developed and is used to simulate a few 3D novel configurations of MH PCM system (with spherical shells, hexagonal tubes and cylindrical tubes as phase change heat exchangers) For each of these cases, Mg2Ni alloy is used as a hydride bed and the sodium nitrate (NaNO3) is selected as the heat storage medium (PCM) Also, the effect of aluminum foam for enhancing the heat transfer is analyzed. Moreover, a sensitivity analysis is made on various operating parameters and material properties. Besides showing a thermal coupling between the MH bed and the PCM medium, the computational results indicate a considerable improvement of the thermal efficiency of metal hydride hydrogen storage tank, especially with cylindrical phase change heat exchanger which indicated 58% improvement in filling time over the basic configuration.