Optimization of metal hydride material and evaluation of metal hydride tank for hydrogen-powered micromobility

This study derived the criterion for the hydrogen storage properties of metal hydride materials for hydrogenpowered micromobility applications. In addition, metal hydride tanks were fabricated by loading AB2-type metal hydride materials, and their hydrogen charging and discharging characteristics were evaluated. To simulate the operational conditions of metal hydride tanks supplying hydrogen to fuel cells in micromobility, the tanks were exposed to atmospheric conditions and released hydrogen at a discharging pressure of 2 bar without heat exchange. A metal hydride tank was fabricated by loading metal hydride material charged hydrogen at 30 bar, and its hydrogen discharging characteristics were evaluated at 1 NL/min flow rate. The temperature inside the tank dropped to -18 degrees C, causing unstable discharging hydrogen flow rate. The Van't Hoff equation analysis revealed that the desorption plateau pressure at -20 degrees C fell below the discharging pressure of 2 bar. From this analysis, the criterion of the metal hydride for micromobility applications was established as having the desorption pressure of more than 2 bar at -20 degrees C. A metal hydride tank with an outer diameter of 60.5 mm, a length of 350 mm, and an internal volume of 0.73 L was fabricated by loading a material that satisfies the criterion. The tank was charged by applying hydrogen gas of 60 bar, and 48.9 g of hydrogen was stored. When hydrogen was discharged at a pressure of 2 bar and a flow rate of 2 NL/min, the temperature inside the tank dropped to a minimum of -23 degrees C. Despite this temperature drop, the discharging pressure and flow rate were stably maintained for 208 min, during which 37.1 g of hydrogen was released. These results confirmed that the metal hydride tank, using metal hydride materials that satisfy the established criterion, can stably supply hydrogen in hydrogen-powered micromobility applications.