Numerical study of a metal hydride hydrogen storage system equipped with phase change material

Phase change materials (PCM) are effective thermal energy storage media and can replace conventional heat transfer fluids (HTF) in metal hydride (MH) hydrogen storage systems, where heat transfer management is a key factor in the rate of hydrogen absorption and desorption. In this study, a transient computational fluid dynamics (CFD) model is developed to describe the heat and mass transfer associated with the hydrogen absorption and desorption in an MH hydrogen storage tank equipped with the PCM layer. For demonstration, this MH-PCM hydrogen storage tank includes lanthanum nickel (LaNi 5 ) as MH and lithium nitrate trihydrate (LiNO 3 -3H 2 O) as PCM. Hydrogen absorption and desorption performances of different tank designs are evaluated. The integration of embedded copper fins and MH and the PCM is numerically analysed and proposed the optimal design to enhance the heat transfer performance. Further design optimization, including MH-PCM and MH-Fin-PCM sandwich disks, are compared to analyze the effects of increased heat transfer surface area. The simulation results indicate that the tank with 10 MH-Fin-PCM sandwich disks improves hydrogen absorption and desorption rates by 94.9 % and 92.9 %, respectively, compared to the base design. Lastly, a total 14.4 h of 68 continuous hydrogen absorption and desorption cycles are performed with the tank of 10 MH-Fin-PCM sandwich disks at the ambient temperature between 14 °C and 35 °C, under the assumption of a 50 mm thickness polyurethane layer. The proposed design configuration and numerical verification demonstrate the potential application scenario of MH-PCM tanks as an independent system.