Performance evaluation of solid NaBH4-based hydrogen generator for fuel-cell-powered unmanned autonomous systems

Abstract

A solid NaBH4-based hydrogen generator was developed as a hydrogen source for fuel-cell-powered unmanned autonomous systems (UAS). Although many studies have been conducted to extract hydrogen from solid NaBH4, performance evaluation required for commercialization are still insufficient so that a new structure of the hydrogen generator is required to meet the performance requirement. For this purpose, in this study, a new reactor was made of a magnesium alloy with perfluoroalkoxy coating to improve its thermal conductivity and chemical resistance. In addition, a porous partition was installed inside the reactor to separate the hydrogen buffer volume from the reaction zone where NaBH4 granules was filled. Next, The operational characteristics of the developed hydrogen generator were evaluated in high- and low-temperature environments, inclined pitch and roll angles, unpredictable power cut-off situations, and sudden hydrogen demand, including the idle, rated, and maximum power modes. A start-up of the hydrogen generator was possible without additional heating and insulation at −15 °C and the hydrogen generation was stable after start-up for all pitch (±30°) and roll (±45°) angles, whereas the CoG shifted forward by 26% of the total length as the agent solution was consumed. In addition, the hydrogen supply immediately recovered within 30 s after an unpredictable power cut-off. Hydrogen purity was 99.64% on average and impurities originated from the water vapor. Finally, the dynamic response to the sudden hydrogen demand and precise controllability of the hydrogen supply rate were tested according to the simulated hydrogen consumption profile for practical use in fuel cells. In conclusion, the developed hydrogen generator satisfied the requirements for commercialization.