PEMFC Power plant

TABLE 1. Weight and volume estimates for PEMFC power plants with hydrogen stored in 3 forms, compared with a diesel generator for powering a Warrior armoured vehicle. Fuel tank... 

The polymer membrane made of poly(styrenesulfonic acid) (PSSA) (Fig. 2) was used in the first PEMFC power plant built by General Electric in the midsixties for the Gemini space mission. The lifetime of these PMFCs was limited due to the degradation of the PSSA membrane under the impact of hydrogen peroxide radicals. 

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. 

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. 

Man-made contaminants come primarily from the combustion of hydrocarbons and the aforementioned impurities in the hydrocarbons that cause fuel-side contaminants. The combustion of hydrocarbons, such as coal in power plants or gasoline in cars, produces SO, and NO, emissions in the atmosphere. SO, and NO, are two important airborne contaminants that are the subject of many studies (Gould et al., 2009 Nagahara et al, 2008). Other man-made contaminants include road de-icers, such as MgCl2, which can have similar effects as sea salt, and the methanol in windshield wiper fluid. Man-made battlefield contaminants can lead to permanent performance losses in PEMFCs (Moore et al., 2000). Their sources include the combustion products of heavy fuels, explosive products, and chemical agents. 

At present, PEMFC batteries and power plants based on such batteries are produced on a commercial scale by a number of companies in many conntries. As a rule, the standard battery version of the 1990s is used in these batteries, although in certain cases different ways of eliminating water and regulating the water balance (water management) have been adopted. 

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). 

Plug Power (Latham, New York), founded in 1997, has delivered since 2000 emergency power plants on the basis of PEMFC batteries providing uninterruptible power supply for hospitals and other vitally important objects in cases of sudden loss of grid power (www.plugpower.com). 

At present, in addition to the United States, PEMFCs and power plants based on them have been developed in many other countries, including China, France, Germany, South Korea, and the United Kingdom. Most of the power plants delivered in 2006 (about 60%) were for power supply to portable equipment. A secondary use (about 26%) was as small stationary power plants for an uninterruptible power supply. 

A lower cost of production, both for the PEMFCs as such and for the entire power plant (Section 3.6.2), and the development of catalysts without platinum (Chapter 12) and of cheaper membranes (Chapter 13) associated with this lower cost... 

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.

In 2002, Schmidt et al. estimated the cost of the first PEMFCs as 20,000/kW (here and below, all prices are in U.S. dollars). Of this figure, 90% was for labor (the cells were hand-made), and only 10% was for materials. In mass production, for instance when making 1 million 50-kW power plants per year, labor cost could fall to 10/kW. In the opinion of Schmidt et al., it would be necessary to develop new membranes costing no more than 20/m, and to lower the platinum content of the electrodes to 0.25 mg/cm, in order to bring the cost of material down from 2000/kW to a desirable figure of 30/kW or at least to a temporarily acceptable value of 100 to 200/kW (also, platinum should be recovered and recycled). A very important and difficult problem is that of making cheaper corrosion-resistant metallic bipolar plates. All ancillary devices must also become much cheaper. 

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. 

The Japanese company Ebara Ballard, a subsidiary of the well-known Canadian company Ballard, is the most important maker of PEMFCs. They developed a 1-kW power plant for combined heat and power production. It is remarkable that this unit is designed to be operated for a period of 10 years, in accord with requirements set by the Japanese government. A similar unit also designed for an operating time of 10 years was developed by the Japanese company Fuji Electric. TTiese units cost 12,000 to 16,000 (Adamson, 2006). 

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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