Fuel-cell systems

Article By:

Samuelsen, Scott National Fuel Cell Research Center, University of California, Irvine, California.

Last reviewed:2004

DOI:https://doi.org/10.1036/1097-8542.YB040180

Like traditional power generation systems, fuel cells extract the chemical energy bound in fuel and, in combination with air as an oxidant, transform it into electricity. Traditional systems, however, use combustion and mechanical devices to achieve the energy transformation. Combustion releases the fuel chemical energy as thermal energy (Fig. 1). The hot gases produced move pistons (as in automobiles) or turbine wheels (as in stationary gas turbines) which rotate the shafts of electrical generators. The mechanical pistons and turbines give rise to friction, which affects the overall conversion efficiency of fuel chemical energy to electricity. Efficiencies of 18% (automobiles) to 35% (electrical production) are common. The majority of the fuel chemical energy (82% for automobiles, 65% for electrical production) is dissipated as heat. Combustion also gives rise to the formation and emission of criteria pollutants, species that have been shown to degrade air quality, such as carbon monoxide (CO), partially oxidized hydrocarbons (HC), and oxides of nitrogen (NOx).

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