UNDERSEA TECHNOLOGY 53 



ENERGY CONVERSION 



The major candidates for deep ocean power applications are secondary 

 batteries, chemically fueled dynamic-machinery powerplants, fuel cells, 

 and nuclear powerplants. Analysis of specific weight versus mission time 

 curves shows clearly the time ranges that best fit the major candidate 

 systems. The curves are based on comparative parametric analyses of 

 several battery, chemical (fueled dynamic-machinery), fuel cell and 

 nuclear systems with an assumed 50 kw maximum sustained power out- 

 put. The curves give the weight for fuel and oxidant with associated 

 tankage. In considering the weights of the systems in air, no allocations 

 for material necessary to achieve neutral buoyancy were included, nor 

 were weights of any pressure capsules required, other than atmospheric 

 tankage for oxidant and fuels. These factors may alter the relative 

 attractiveness. 



Dynamic-machinery systems considered cover the range from high 

 power density turbomachinery systems fueled by cryogenically stored 

 hydrogen and oxygen to lithium hydride thermal energy storage with a 

 Stirling-cycle engine. The low machinery weights potentially achievable 

 with high-speed dynamic systems could provide superiority in specific 

 weight over other plants for fuel endurance times in the range of ten to 

 20 hours. 



Efficiency of fuel energy conversion becomes a dominating factor in 

 overall powerplant weight for chemically fueled systems when mission 

 times exceed ten hours. This fact is demonstrated in the lower specific 

 weights obtainable with fuel cell systems. Fuel cell systems represented 

 by the range of weight-to-energy data considered include hydrogen-oxygen 

 systems supplied by cryogenically stored reactants, alkali metal amalgam- 

 oxygen systems, and hydrazine-hydrogen peroxide fuel systems. They 

 also represent a range of systems designed for one-atmosphere operation, 

 which must be protected from deep ocean pressures in hardened pressure 

 cases, to those designed for operation at ambient sea pressures. 



Analysis of the data available indicates that fuel cell systems are par- 

 ticularly attractive for deep submergence vehicle power supplies with en- 

 durance requirements in the range of 20 to approximately 200 hours. 



Radioisotope power sources are needed as small power sources for long- 

 life acoustic beacons and various types of oceanographic instrumentation. 

 A program of test and evaluation in both laboratory and undersea environ- 

 ments of state-of-the-art radioisotope power sources is underway. 



