Sone Yoshitsugu

Proton exchange membrane fuel cells (PEMFCs), which generate electrical energy as long as they are supplied with fuels and oxidants, have been receiving signifi cant attentions so that they offer higher specifi c energy densities than existing battery technologies in high-energy applications. We had been developing a 100 W-class fuel cell system that keeps electrolyte membrane well-hydrated without external humidification and can operates stably even under low pressure condition. The system aiming for super-pressure balloons had been tested emulating stratospheric conditions. Based on the previous works, the demonstration fl ight using the large balloon equipping the fuel cell system was launched to verify its performance in a practical high-altitude environment.

The fuel cell for space applications has special system requirements, such as operational conditions and designs due to its isolated low gravitational and closed environment, which is much different from that for terrestrial use. Polymer electrolyte fuel cell (PEFC) system for space applications has been studying in our group and several subsystems and operating methods were developed. We manufactured the 18-cell stack and assembled fuel cell system for space utilizations. It showed stable performance for 1,100 hours under various operational conditions. These results could realize the simple and practical PEFC system for space application. A small and light-weight PEFC system with these subsystems has also been developed and several properties were assessed.