Development of a portable hydrogen generator with differential pressure-driven control

A portable hydrogen generator with a high hydrogen storage capacity was developed in this work. The hydrogen gas was produced by introducing a stoichiometric amount of water to a mixture of solid sodium borohydride and boric acid powders. A simple and reliable control method, differential pressure-driven control, was applied to the hydrogen generator to generate a Hydrogen-On-Demand system. The key parameters related to the hydrogen generator design, including the discharge coefficient of the water flow control valve, hydrogen gas buffer volume and hydrogen consumption rate, were analyzed using a dynamic model built within the Matlab–Simulink software. The simulation results indicated that a suitable discharge coefficient must be defined to ensure the stable operation of the hydrogen generator. Furthermore, decreasing the gas buffer size and increasing the hydrogen consumption rate narrows the feasible range of the discharge coefficient. A prototype of such a hydrogen generator was built that could operate stably at both constant and variable hydrogen output conditions until more than 85% of the hydrogen stored in the chemicals was released. A gravimetric hydrogen storage capacity of 3.88 wt.% was achieved.