LPG Fuel Cell Power Plant:

The LPG fuel cell power plant presents many of the same problems as the liquid hydrocarbon systems discussed in the next section with two major exceptions; the fuel is available as a gas and it is a much more pure fuel. These two exceptions reduce the complexity of the system; however, the fuel is again not compatible with military logistics.

Liquid Hydrocarbon Fuel Cell Power Plants:

Because of the compatibility of the fuel, the greatest portion of the Department of Defense effort is devoted to these systems with the exception of the Air Force interest in hydrogen systems for space application and the Navy's interest in some special fuels. These hydrocarbon systems are being developed for general purpose power plants in the range of 500 watts to 15 KW. The hardware programs of significance are shown on FIGURE 11. These three programs are backed up by extensive basic research and exploratory development in catalysts, electrodes, cell structures, stack structures, ancillary components and breadboard systems.

The three primary problem areas in liquid hydrocarbon fuel cell power plant development are weight, cost and complexity. As FIGURE 11 shows, the weight is somewhere in the 100 pounds per KW range at this stage, but this is for a militarized portable power plant. It appears that this weight can be reduced to 50 pounds per KW for a portable power plant and 15 - 25 pounds per KW for a vehicular power plant, based on what is presently being accomplished on a laboratory scale. Continued research will reduce the weight even more.

The high initial cost can be related to catalyst cost, primarily because from other standpoints the systems should not be too different from other power sources; mass production techniques can be used, materials being utilized today should not affect the comparative costs, ancillary system components are approximately the same for any power source, etc. Progress has been made in catalyst cost both in reduction of noble metals and elimination of noble metals. In 1959 the catalyst cost was $6000 per KW; in 1966, less than $100 per KW appears practical and elimination of noble metals completely is a definite possibility.

System complexity was a major problem but the emergence of the acid and molten carbonate systems has simplified the power plant.

It has been stated that fuel cells do not have peak capability. This is strictly semantics, and is dependent upon how the power plant is rated. FIGURE 12 illustrates that the fuel cell power plant can be rated to any combination of volts and amperes on the VA curve. The utilization of this peak power capability in the design of a vehicular power plant depends upor the duty cycle of the particular mission.