Computational Fluid Dynamics Simulation and Energy Consumption Analysis of Metal Hydride in Its Hydrogen Charging Process

Metal hydride is an alloy that reversibly reacts with hydrogen gas. Because it has low hydrogen storage pressure, it can contribute to the abatement of compression power in the hydrogen charging process. Despite this fact, owing to the exothermic reaction in its charging process, a longer hydrogen charging time is required. As a countermeasure to this problem, a cooling process for the metal hydride bed is necessary to enhance the reaction rate of the hydrogen charging process. Considering this background, in this study, an energy consumption comparison between metal hydride and compressed hydrogen (conventional) is conducted. In addition, a mathematical model of the hydrogen charging process is developed to estimate the effect of the metal hydride cooling process on the hydrogen charging time. The mathematical model is validated by comparison with experimental results and used to simulate different cooling conditions (outside temperature: 233, 253, 273, and 298 K). It was found that metal hydride could reduce the compression power compared to compressed hydrogen (maximum reduction of 7.57 kwh/kg-H2) and reduce the hydrogen charging time by removing reaction heat from the metal hydride tank (886 s at outside temperature 233 K, 1902 s at 273 K).