Fuel cell power plant PEMFC

The PEMFC is nowadays the most advanced low-temperature fuel cell technology [19, 20], because it can be used in several applications (space programs, electric vehicles, stationary power plants, auxiliary power units, portable electronics). The progress made in one application is greatly beneficial to the others. 

Proton exchange membrane fuel cell (PEMFC) Proton conductive polymer membrane H2 O2 (in air) 60-90 Transportation vehicles, stationary power plants, cogeneration plants, portable power supplies... 

Apart from the large volume of research and design work for PEMFC and DMFC, many studies of improved high-temperature fuel cells, SOFC and MCFC, have been conducted since 1990. A marked rise in the number of power plants based on MCFC was seen between 2003 and 2005. The volume of work concerned with alkaline fuel cells has strongly declined as the late 1980s. As to PAFC, the literature of recent years has offered only a few indications of research in this area. 

PEMFC and alkaline fuel cells operate at temperatures below 100 °C, while all other types of fuel cells need higher temperatures for their electrolytes to become ion-conducting. The operating temperatures play a crucial role for the flexibility of a power plant. 

At this point we would like to leave the field of low temperature PEMFCs for an excursion to solid oxide fuel cells (SOFCs) and consider an example of an LCA for SOFC modules (with each module combining many stacks within a steel pressrrre vessel) that are rrrass-produced for central power production. It can be assumed that the length of the stack flow field can be related to not orrly the mass of stack materials (e.g. the amount of stainless steel or cerarrrics used) but also to the stack efficiency, which subsequently dictates in part the nurrrber of modules needed to achieve the desired power. Including corrsideration of the balance of plant, the length of the flow field also dictates the amonrrt of fuel available for combustion off the stacks (also related to the cherrristry of balance-of-plant emissions) and therefore the energy that might also be obtained by the overall... 

UTC Power (South Windsor, Connectient), a United Technologies Company, produces power units with PEMFCs for different mihtary and civil applications. In 2002, regular electric bus service using fuel cell batteries developed by this company was started. The Pure Cell model 200M Power Solution power plant delivers 200 k W of electric power and about 900 Btu/h (about 950 kJ/h) of thermal power (www.utcpower.com). 

Since the power supply for a variety of portable devices is one of the more important future applications of PEMFCs, great efforts are made at present to reduce the dimensions and weight and even to miniaturize both the fuel cell battery and all ancillary equipment needed for a power plant. This aspect is discussed in more detail in Chapter 17. 

Figures for the time of smooth operation of PEMFCs (and other fuel cells used in the same applications) are given variously as 2000 to 3000 hours for power plants in portable devices, as up to 3000 hours over a period of five to six years for power plants in electric cars, and as five to 10 years for stationary power plants. Much time will, of course, be required to collect statistical data for the potential lifetime of different types of fuel cells. Research efforts are therefore concentrated on finding reasons for the gradual decline of performance indicators and for premature failure of fuel cells. In recent years, many studies have been conducted in this area.

A detailed cost analysis for a PEMFC power plant of 5 kW was provided in 2006 by Kamarudin et al. According to their data, the total cost of such a plant will be about 1200, of which 500 is for the acmal fuel cell stack and 700 is for the ancillary equipment (pumps, heat exchangers, etc.). The cost of the fuel ceU stack is derived from the components as 55/kW for the membranes, 52/kW for the platinum, 128/kW for the electrodes, and 148/kW for the bipolar plates. 

Lan and Tao (2010) showed that a direct use of anunonia (without its preliminary cracking into hydrogen and nitrogen) as a fuel is possible in fuel cells with alkaline anion-exchange membranes. The direct nse of anunonia (which is far more convenient than hydrogen in transportation and handling) would considerably simplify and mitigate the use of PEMFC-Uke power plants in electrical vehicles and different portable devices. 

Attention must be called to the fact that in practically all work concerning the use of fuel cells for road transport vehicles, only fuel cells using hydrogen as a fuel were considered. There can be no doubt that hydrogen-oxygen fuel cells (and in particular those of the PEMFC type) at present have been developed to such a degree that in all their technical parameters, they are fit for power plants of electric cars. Tests of different types of electric cars with such power plants, which have already been performed for almost 10 years, will undoubtedly be... 

As to the use of fuel cell-based power plants in other transport means, we have repeatedly spoken in the present book about practical applications of such plants in manned spacecraft. The first examples were 1-kW PEMFC plants used in the 1960s in Gemini spacecraft, now outdated then three 1.5-kW AFC plants each used in Apollo-ty t spacecraft in the 1970s, and finally, three 12-kW AFC plants each in the Orbiter space shuttles used until the present. 

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