Appropriate selection of long endurance materials is critical to the cost effective use of fuel cell technology for near-term commercial and defense applications. To effectively transition this technology from laboratory prototype to fielded system, the durability of all fuel cell subsystems must be addressed. Material selection based upon a thorough understanding of system performance requirements, operational environments, and user interfaces not only provides high reliability and enhanced safety, but also lowers life cycle costs.
This paper discusses the development of an Aluminum Fuel Cell Power System (FCPS) for the Advanced Research Projects Agency (ARPA) Unmanned Underwater Vehicle (UUV) program, focusing on the operational endurance testing that was conducted to evaluate candidate materials for cell stack, electrolyte, and coolant subsystems.
The FCPS is a 15 kW closed aluminum-oxygen fuel cell system that provides up to 1.1 MWh energy. Loral has completed small-scale bench tests and is currently fabricating a full-scale system to be demonstrated in 1995. Requirements that strongly influenced material selection included: chemical compatibility - 4M KOH electrolyte pumped at 50°C, with dissolved aluminum and hydrargillite; system operational objectives - time between refueling and maintenance ranging from daily startup / shutdown to three weeks continuous; ARPA program objectives - commercial components, rapid prototyping, low life cycle costs.
A materials / component endurance test program was established and conducted early in the design phase of the FCPS program. To date, Loral has completed over 3000 operational test hours, with nearly 8000 hours of accumulated exposure to KOH. Results of these tests have been incorporated into the FCPS detailed design, and are expected to significantly enhance the performance of the fielded system. This program is sponsored by ARPA Maritime Systems Technology Office under NASA contract NAS3-26715.