The high efficiency multi-less (HEML) fuel cell — A high energy source for underwater vehicles, buoys, and stations

Recently autonomous underwater plat forms are expected as efficient ocean research platforms which are equipped with physical and chemical sensors, acoustical sensors, and electro-magnetic sensors to obtain the earth information for earth environment researches, ocean resources explorations and so on. Increasing survey range of the platforms makes an increase of the consumption energy. Deep sea seismic system and active electromagnetic sensor have ability of deep sea-bottom surveys also consume much energy. Lithium ion battery is a better large energy source but it is not good choice for long endurance (over 1 week) movable platforms and for high power sensors (over 1kW) because the battery size is proportional to consumption energy. A compact fuel cell system is a better solution for such applications because its generator size is determined by its output power and its fuel tank size is only proportional to consumption energy. Since 2007 we have developed a new concept underwater fuel cell system for scientific survey and ocean resource explorations in entire oceans. This system configuration is drastically changed from conventional fuel cell systems which must have gas circulation blowers and humidifiers. The HEML fuel cell system is replaced blowers by valves. Humidifiers are discarded by improving materials and recipe of the MEA which a main parts of the HEML fuel cell. We thus achieved reducing size, consumption energy saving and obtaining high reliability of the new fuel cell system. In 2009 the desktop system marked operating efficiency of over 60 % and long operation of 1000 hours. In October 2010, we completed building the prototype of the fuel cell system. In January 2011 it achieved non-stop electric power generation for 600 hours. In March a sea-trial of the prototype which is installed on a deep tow was carried out. We succeeded in generating electricity in the sea trial.