HIGH ENERGY DENSITY FUEL AND OXIDANT STORAGE FOR FUEL CELL SYSTEMS SUITABLE FOR UNDERSEA POWER SOURCES

AUTONOMOUS UNDERSEA VEHICLES (AUVS), SUBSEA ROBOTS, AND OTHER INSTRUMENTED AND REMOTELY OPERATED SYSTEMS FOR MARINE APPLICATIONS REQUIRE A POWER SOURCE WHICH IS AS EFFICIENT AS POSSIBLE TO GIVE LONG RANGE OR EXTENDED USE TIMES. THE OBVIOUS CHOICE IS AN ELECTROCHEMICAL UNIT OF FUEL CELL TYPE. CONVENTIONAL FUEL CELLS REQUIRE HYDROGEN FUEL, AND THEY NORMALLY USE MOLECULAR OXYGEN AS OXIDANT. ABOARD AN AUV, FOR INSTANCE, THESE MATERIALS WOULD BE EXPECTED TO BE CARRIED AS CRYOGENIC LIQUIDS, AS IN A SPACE-CRAFT. THIS PRESENTS SEVERAL PRACTICAL PROBLEMS, AMONG WHICH ARE THE DIFFICULTIES OF STORAGE, SAFETY AND HANDLING, AND BUOYANCY PROBLEMS ABOARD THE AUV AS THEY ARE CONSUMED. THE PROJECT EXAMINES ALTERNATIVE FUEL AND OXIDANT COMBINATIONS FOR USE IN AN ELECTROCHEMICAL FUEL CELL POWER SYSTEM. THE OBJECTIVE IS TO EXPLORE THE POSSIBILITY OF FUEL-OXIDANT COMBINATIONS WITH A SPECIFIC ENERGY (KWH/KG) WHICH IS AN IMPROVEMENT ON CRYOGENIC HYDROGEN AND OXYGEN, AND ALSO TO DETERMINE WHETHER SUCH COMBINATIONS HAVE ADVANTAGES IN REGARD TO THEIR PRACTICAL SPECIFIC VOLUME (IN KWH/1), INCLUDING ANY ADDITIONAL VOLUME ON BOARD WHICH MAY BE REQUIRED FOR DISPLACEMENT CORRECTIONS DURING PROPELLANT DEPLETION. COMBINATIONS ARE EXAMINED IN REGARD TO THEIR AVAILABILITY, SAFETY, AND STABILITY. A NUMBER OF POSSIBLE FUEL-OXIDANT COMBINATIONS WHICH MAY HAVE THE REQUISITE PROPERTIES ARE BEING EXPERIMENTALLY EVALUATED AND IDENTIFIED.