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• A high-performance hydrogen generator was developed using solid-state NaBH 4. • The satisfying performance of hydrogen supply was obtained for various flight conditions. • High purity of hydrogen of 99.64% was obtained for the entire conditions. • Performance for dynamic response to sudden hydrogen demand was evaluated. A solid NaBH 4 -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 NaBH 4 , 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 NaBH 4 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. [ABSTRACT FROM AUTHOR]

• High-density hydrogen generator was developed for unmanned aerial vehicles. • Solid-state NaBH 4 was used as a hydrogen source for high storage density. • Stable hydrogen generation was obtained for the entire operation time. • Restartability was evaluated to validate the possibility of commercialization. A hydrogen generator using solid-state sodium borohydride (NaBH 4) as a hydrogen source was proposed as part of a high-energy-density fuel-cell system for unmanned aerial vehicles. In this study, solid-state NaBH 4 was used in order to overcome problems of a hydrogen generator using catalytic hydrolysis of NaBH 4 aqueous solution such as low hydrogen yield and unstable hydrogen generation due to catalyst degradation. An agent solution, hydrochloric acid, was injected on to the NaBH 4 to generate hydrogen. In addition, all of the balance-of-plant systems and components were integrated to develop a lightweight, commercially-viable, high-density hydrogen generator. The developed hydrogen generator was evaluated in terms of stable hydrogen generation and restartability for the entire operation time in order to validate the possibility of commercialization. From the performance evaluation, the gravimetric and volumetric specific energy densities of the hydrogen generator were found to be 739.1 W hr/kg and 272.8 W hr/L, respectively. In addition, the hydrogen storage density was 5.1 wt%, which was 1.44 times higher in comparison of a typical hydrogen generator using NaBH 4 aqueous solution. [ABSTRACT FROM AUTHOR]