Fuel cell system of AUV "Urashima"

JAMSTEC (Japan Agency for Marine-Earth Science and Technology) and MHI (Mitsubishi Heavy Industries, Ltd.) have been developing the AUV (Autonomous Underwater Vehicle) "Urashima" since 1998. Long-distance cruising AUVs generally need an AIP (Air Independent Propulsion) power source characterized by high-energy density and high-energy efficiency. Fuel cells are the preferred AIP power source for small underwater vehicles and PEFC (Polymer Electrolyte Fuel Cell) have been adopted for "Urashima". It is understood that one of the main themes with fuel cell is storing the hydrogen, the metal hydride storage has been adopted for "Urashima" as a safer method of storing the hydrogen. In summer of 2002 the AUV "Urashima" successfully completed an autonomous 132.5 km long-distance cruise using large capacity lithium-ion rechargeable battery. In the meantime, a Closed Cycle PEFC (Polymer Electrolyte Fuel Cell) system with a metal hydride hydrogen storage system was developed as an alternative AIP power source in order to extend "Urashima"'s cruising range. The lithium-ion rechargeable battery was replaced by the Closed Cycle PEFC system and this system became the main power source of "Urashima" in winter of 2002. "Urashima", with its new power source (the Closed Cycle PEFC system) achieved the world's first and deepest fuel cell power source dive in summer of 2003 and completed an autonomous cruise of 220 km in spring of 2004. In sea trials, the fuel cell system with metal hydride hydrogen storage system worked adequately and underwater fuel cell operation was verified. There were no problem in supplying power to the vehicle and supplying hydrogen to fuel cell system. "Urashima" will carry out the AUV world record 300 km cruising at upcoming trial opportunity.