been developed primarily to provide power sources for limited shallow-depth 

 ocean applications for vehicle propulsion. The use of fuel oil results in a 

 waste product, carbon dioxide, which must either be pumped overboard or 

 compressed and stored as a liquid. This problem can be avoided by using 

 hydrogen as fuel. 



Hydrogen is one of the most desirable fuels because of its high energy 

 content with oxygen and the easily handled waste product (water). Other 

 fuels are available either as sources of hydrogen or as monopropellants; 

 however, these systems do not compare with a hydrogen-oxygen system in 

 terms of weight, volume, cost, safety, handling, and waste product disposal. 



The use of hydrogen and oxygen as reactants allows the use of a 

 mechanical conversion system, such as a turbine-generator, or direct con- 

 version in a fuel cell. Of these conversion systems, the fuel cell is more 

 efficient, especially at low power levels. Fuel costs range from a low of about 

 $0.25/kw-hr for the fuel cell and $0.50/kw-hr for the turbine system. 



Some unique problems are encountered in the storage of hydrogen 

 and oxygen within a submersible hull. Cryogenic and high-pressure methods 

 are available for storing these reactants. High-pressure gas storage is only 

 practical when two separate pressure hulls are used, with hull penetrations 

 made to the power source hull. Cryogenic liquids may be stored in a common 

 or separate pressure hull. 



Cryogenic and high-pressure storage of hydrogen and oxygen 

 reactants, storage configuration, and methods of transfer to point of usage 

 were analyzed and evaluated for various power plant concepts included in 

 the study program. Cryogenic storage within a common power plant 

 pressure hull was considered the most suitable method since it is the lightest 

 and requires the least volume. The gaseous transfer method could be 

 accomplished by using an external heat exchanger to vaporize the liquid. 

 The power plant's waste heat or seawater would provide the heat source with 

 a backup electrical heater to assure gas delivery in the event liquid flow 

 could not be obtained by the main heat exchanger. 



Difficulties and problems associated with the storage and transfer of 

 liquified gases are numerous. Spherical containers are most efficient for the 

 cryogenic storage of gases, but in pressure hulls such containers cause con- 

 siderable loss in usable volume. On the other hand, form-fit containers weigh 

 more than spherical containers. However, the reduction in size of the pressure 

 hull by the use of form-fit containers results in an acceptable trade-off. 

 Another problem encountered with liquified gas is the increase of pressure 

 due to heat leakage during the holdtime between fueling and power plant 

 operation. Methods which require further study in solving this problem 

 include providing a supply of subcooled liquid to the storage container, using 



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