PEMFC Plants

In the field of much larger units, Ballard has conducted trials on 250 kW PEMFC plants to evaluate their suitability and performance as distributed power generators for commercial use. An installation at Mingolsheim in Germany logged 6000 h of operation at 75% efficiency with utilization of waste heat. Stacks manufactured by Ballard are also being used to power electric buses see Section 7.5, Chapter 7. 

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 The first examples were 1-kW PEMFC plants used in the 1960s in Gemini spacecraft, now outdated then three 1.5-kW AFC plants each used in Apollo-ty t spacecraft in the 1970s, and finally, three 12-kW AFC plants each in the Orbiter space shuttles used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. 

Figure 8.6 Process flow diagram for a Ballard 250-kW PEMFC plant. (Reproduced by kind permission of Alstom Ballard GmbH.)...

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. 

In the US, the plan for 2010 is to develop and demonstrate technology to supply purified hydrogen for PEMFC from biomass at US 2.60/kg at the plant gate (projected to a commercial scale 75,000 kg/day). The objective is to be competitive with gasoline by 2015. There is also a Hydrogen Production from Biomass program" funded at US 1.2 million, which includes pyrolysis, gasification and fermentation. 

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 Daimlar Benz [2] has made the hydrogen bus named NEBUS whose output power is 250 kW. The PEMC costs about US 250 per W, which the same level as that of nuclear plants. We may expect a rapid spread of PEMFC, which is applied not only to the vehicles but also to the on-site generating systems including the domestic uses, in the near future. However, a special notice is stressed about the strong environmental pollution which may be caused by the wasted matters of used PEM, of which pH-value is very small (high acidity). 

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. 

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. 

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. 

Brunetti A, Barbieri G and Drioli E (2008), A PEMFC and H2 membrane purification integrated plant , Chem Eng Process, 47,1081-1089. 

The low-temperature fuel cells (PEMFC and PAFC) require pure hydrogen, as carbon monoxide is a poison to the platinum anode. A PSA unit as used in large-scale hydrogen plants (Figure 2.4) carmot be used at the small scale in question, and the final purifrcation is made either by methanation (as used in ammonia plants, Section 2.5) or by preferential partial oxidation (PROX) of carbon monoxide to carbon dioxide over a... 

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