Investigation of metal hydride hydrogen storage performance using phase change materials

Metal hydride storage system (MHSS) has been widely used mostly because of its large storage capacity and high degree of safety. The improvement of the heat transfer performance is one of possible techniques to enhance the overall MHSS performance. The well arrangement of the heat exchanger structure from a semi-cylindrical coil heat exchanger with central return tube (SCHE-CR) significantly reduces the hydrogen absorption duration. However, the modelling of the thermal behaviour for the SCHE-CR during desorption process is missing in the literature. Therefore, this study aims to develop a model for both hydrogen absorption and desorption processes and analyse the thermal performance during the cycle. Phase change material (PCM) is incorporated with the heat exchanger for further improvement of the MHSS performance. The storage is designed under three different PCM configurations, including PCM jacket, pool bed, and capsule. The numerical results report that the duration of the absorption-desorption cycle is reduced by over 50% when using SCHE-CR instead of a helical coil. The PCM configurations, especially the PCM capsule, increase the MHSS performance, especially during the absorption. The duration of one cycle is decreased by at least 39% when combining the SCHE-CR with PCM. The HTF temperature significantly affects the MHSS performance, especially during the desorption. Reduction in HTF temperature reduces the absorption duration by at least 15%, while increasing the HTF temperature reduces the desorption duration by at least 25%. The new MHSS configuration would be beneficial to enhance the heat exchange during the absorption-desorption cycle of industrial MHSS applications.