Electrical fuel cell stack power

The overall efficiency of a fuel processor/fiiel cell system is commonly defined as the ratio of the electrical fuel cell stack power output Ppuei ceU to the LHV of the fuel ... 

Both parameters, pressurized air and air stoichiometry are important for the development of the air system. An overall optimum needs to be found between increase of the fuel cell stack power and the electrical power consumption of the air system. This relation is important to optimize the influence of the auxiUaries, specially the air system, and the fuel cell system efficiency. 

Fuel Cells (UTC Fuel Cells). Worldwide, Fuji Electric Company and Mitsubishi Electric Company in Japan developed PAFC systems for residential and stationary power applications. The PAFC demonstration units have been developed for a wide variety of backup power and even transportation applications. In the 1990s Georgetown University helped operate a PAFC bus fueled by reformed methanol. The original stack was produced with a Fuji Electric fuel cell stack, and a second system was installed with an IFC 100-kWe PAFC stack, shown in Figure 7.15. This bus was operated successfully for a number of years and then sent to the University of Califomia-Davis. However, large relative system size and rapid development of the PEFC have since limited development of the PAFC to stationary power applications [37]. 

As of 2000, it also looks as though more and more electric utilities are becoming interested in fuel cell stacks as local microgenerators to top up power from large power stations, without the need for long-distance transmission of electricity and its attendant expense and power losses. 

A complete fuel cell system, even when operating on pure hydrogen, is quite complex because, like most engines, a fuel cell stack cannot produce power without functioning air, fuel, thermal, and electrical systems. Figure 3 illustrates the major elements of a complete system. It is important to understand that the sub-systems are not only critical from an operational standpoint, but also have a major effect on system economics since they account for the majority of the fuel cell system cost. 

Electrical management, or power conditioning, of fuel cell output is often essential because the fuel cell voltage is always dc and may not be at a suitable level. For stationai y applications, an inverter is needed for conversion to ac, while in cases where dc voltage is acceptable, a dc-dc converter maybe needed to adjust to the load voltage. In electric vehicles, for example, a combination of dc-dc conversion followed by inversion may be necessary to interface the fuel cell stack to a, 100 V ac motor. 

Although an FC produces electricity, an FC power system requires the integration of many components beyond the fuel cell stack itself, for the FC will produce only DC power and utilize only processed fuel. Various system components are incorporated into a power system to allow operation with conventional fuels, to tie into the AC power grid, and often,... 

Along with refueling vehicles, the system provides hydrogen into a fuel cell stack to produce electricity for buildings on the site, which are also warmed by the waste heat generated by the power unit. 

Hyundai introduced its new i-Blue Fuel Cell Electric Vehicle. The i-Blue platform incorporates Hyundai s third-generation fuel cell technology and is powered by a 100-kW electrical engine and fuel cell stack. It is fueled with compressed hydrogen at 700 bar stored in a 115 liter tank. The i-Blue is capable of running more than 600-km per refueling stop and has a maximum speed of 165-km/h. 

The power is created by batteries and other electricity sources. Batteries are energy storage devices, but tmlike batteries, fuel cells convert chemical energy to electricity. Fuel cell vehicles use electricity produced from an electrochemical reaction that takes place when hydrogen and oxygen are combined in the fuel cell stack. The production of electricity using fuel cells takes place without combustion or pollution and leaves only two byproducts, heat and water. Benefits include no emissions and fewer parts to be serviced and replaced. Electricity is also cheaper than gasoline. 

The core of the Ballard fuel cell consists of a membrane electrode assembly (MEA) that is placed between two flow-field plates. The flow-field plates direct H2 to the anode and Oz (from air) to the cathode. To obtain the desired amount of electric power, individual fuel cells are combined to form fuel cell stacks. Increasing the number of cells in a stack increases the voltage, and... 

How many things can you think of that use electricity There are big things, of course, like the refrigerator, television set, and computer in your house. Your house probably gets its electricity from a power plant that burns fossil fuels, but fuel cell stacks could also be used to produce this electricity. They... 

Figure 5.50. Electrical connection schematics of EIS measurement, a Grounded mode. (Reprinted from Journal of Power Sources, 161, Yuan XZ, Sun C, Wang H, Zhang J. AC impedance diagnosis of a 500 W PEM fuel cell stack part II individual cell impedance, 929-37, 2006, with permission from Elsevier.)...

The FCFTV uses the same drivetrain as the Prius but the fuel cell stack is inserted in place of the gasoline engine. As in the Prius, a secondary battery provides additional power. The combination of a secondary battery with a fuel cell stack is more easily achieved than combining a secondary battery with a gasoline engine since the output for both sources in the FCHV is direct current electricity. 

For instance, if there are high amp draws from motor start ups, etc., put a supercapacitor in parallel connection with a 12 volt rechargeable battery, and use this to supply those intermittent load needs adequately. To use a rechargeable battery alone, as mentioned, simply connect the output from the fuel cells to the battery and draw power from the battery. To use a supercapacitor and rechargeable battery, connect the battery and supercapacitor in parallel, connect the fuel cell output to these, and draw your power from the supercapacitor and battery connected leads. With these system additions you will need a diode so that reverse flow does not occur to the fuel cell stack, and fuse the circuit on both sides in case of shorts. A switch, either remote or direct, should be used to connect the power supply with any lines or equipment being powered. If you have AC power requirements you will need an inverter to convert DC to AC electricity. 

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