Vehicles auxiliary power supplies

It is the authors contention in this paper, that a cryogenic auxiliary power supply can be designed to provide power levels and operating times useful to aircraft, missiles and space vehicles. Further, that the state of the art" is such that these designs are imminent realities. The chief advantage claimed for such APU s is that they have inherent heat dissipation capabilities. 

Because both electricity and heat are desirable and useful products of SOFC operation, the best applications are those which use both, for example residential combined heat and power, auxiliary power supplies on vehicles, and stationary power generation from coal which needs heat for gasification. A residential SOFC system can use this heat to produce hot water, as currently achieved with simple heat exchangers. In a vehicle the heat can be used to keep the driver warm. A stationary power system can use the hot gas output from the SOFC to gasify coal, or to drive a heat engine such as a Stirling engine or a gas turbine motor. 

There is now a great interest in developing different kinds of fuel cells with several applications (in addition to the first and most developed application in space programs) depending on their nominal power stationary electric power plants (lOOkW-lOMW), power train sources (20-200kW) for the electrical vehicle (bus, truck and individual car), electricity and heat co-generation for buildings and houses (5-20 kW), auxiliary power units (1-100 kW) for different uses (automobiles, aircraft, space launchers, space stations, uninterruptible power supply, remote power, etc.) and portable electronic devices (1-100 W), for example, cell phones, computers, camcorders [2, 3]. 

The first practical use of fuel cells was to provide auxiliary power in space vehicles. What was the principal reason for this choice Considering fuel cells runningon H2 and air 02, supplied by the re-forming of CH4 or CH3OH, discuss the various fuel cell types and suggest what applications will be made of re-formed H. (Bockris)... 

At 1-10 W (watts), fuel cells could be used as battery replacements at 100 W to 1 kW, fuel cells could find military applications which require lightweight portable power sources for communications and weapon power at 1 - 10 kW, fuel cells could supply power to residential buildings and serve as auxiliary power units in vehicles and trucks. At higher power levels, the solid oxide fuel cell (SOFC) could be an effective approach for the distributed power generation and the cogeneration (i.e., combined heat and power). Above 1 MW, the SOFC could be integrated with a turbine power plant to improve the overall efficiency of power generation and reduce emissions. ... 

Flow cells are ideal for stors e systems in remote locations. Vanadium redox systems, for instance, deliver up to 500 kW for up to ten hours. Zinc-bromine systems have been produced for 50-kWh and 500-kWh systems to reinforce weak distribution networks or prevent power fluctuations. Hydrogen fuel cells can potentially do almost anything a battery can do provide backup power, perform power leveling, run handheld devices, and supply primary or auxiliary power to cars, trucks, buses, and boats. In many cases they are more efficient than petrochemical fuels. A hydrogen fuel cell in a vehicle that uses an electric motor, for example, can be 40 to 60 percent efficient, compared with the 35 percent peak efficiency of the internal combustion engine. 

For mobile applications, systems designed to move a vehicle need to be distinguished from the Auxiliary Po ver Unit (APU), which either creates extra energy for the vehicle (e.g., the air conditioning and refrigerator system of a truck) or works as a stand alone system for the electrical power supply. 

A typical schematic for a small SOFC system is given in Figure 1.9. The electrical power output for a mobile power application could be 100 We for communications up to 5 kWe to power a house or to supply air conditioning and auxiliary power in a vehicle. The heat output is less important for such devices because electrical efficiency is not the main performance criterion. 

A major application of SOFC systems is perceived at the 1-10 kW level to supply power to residential buildings and as auxiliary power units in vehicles and trucks. A number of projects are underway at present to show the feasibility... 

If the theater s interest in the auxiliary flame thrower could have been called mild, its concern for the main armament version was almost nonexistent. Army commanders indicated their reluctance to give up standard tanks for main armament flame throwers not only because of the reduced fire power but also because of the additional tanks needed to protect the vulnerable special weapon. And, as General Rowan pointed out, matters were all the worse because tanks and other armored vehicles remained in short supply. 

Of all the system characteristics of DMFC with regard to commercialization as a mobile device energy source, energy efficiency, energy density, power density, and cost have to be competitive with rechargeable batteries. These requirements are somewhat different from other types of fuel cells for residential or vehicle application, which can utilize auxiliary compartments more freely. These compartments include a balance of plant (BOP), such as a compressor or pump, for fuel and oxidant supply, humidifier, heat exchanger, and so on. These comparnnents have to be miniaturized effectively or eliminated. This means that the materials in the stack should themselves have the functions of BOP. 

---