A closed-cycle fuel cell system jointly developed by Mitsubishi Heavy Industries, Ltd. (MHI) and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has become the world's first system of its kind to perform successfully in a test to supply power to observation equipment in actual use at sea.
With this success, this compact fuel cell system, which has cleared earlier technical hurdles through the adoption of a new gas circulation system and other innovations, is expected to supersede conventional storage batteries and fill a major role as an underwater power supply for operating seabed-installed observation instruments and marine research vessels over long periods of time.
The unit that passed the ocean field test is a solid-polymer type high-efficiency multi-less (HEML signifies Blower-less, humidifier-less and leak-less) fuel cell system. In testing, the fuel cell system equipped on JAMSTEC's "Deep Tow" marine research towing unit was submerged to a depth of 180 meters (m) to supply power simultaneously to two units of observation equipment. The test operation confirmed that power was supplied stably and that the equipment receiving power from the system continued to perform their observation duties without interruption.
Presently many different observation platforms are in use at sea, including deep-sea locations, whose equipment has become increasingly sophisticated and observation durations have lengthened, power requirements have grown to a level beyond the capacity of storage batteries having limited output capabilities. To supply the power needed, closed-cycle fuel cell systems have for some time been under development; but favorable results had not been obtained owing to issues such as the inability to achieve compact system size because of the need for gas circulation equipment and humidifiers to add dampness to the gas, compounded by the inability to prevent minuscule leaks of hydrogen gas.
The HEML fuel cell system newly developed by MHI and JAMSTEC has, through the adoption of a new structure in the gas circulation system, etc., resolved these various problems that until now impeded the creation of a viable system. Specifically, the structure uses valve operation to switch between the upstream and downstream sides of the fuel cell stack at fixed intervals – a configuration that has eliminated the need for a blower and humidifier, which together made large system size inevitable.
MHI and JAMSTEC's new system will proceed further toward the achievement of a fully practical closed-cycle fuel cell system offering output in the several kilowatt (kW) class.