Abstract

Fuel cells are devices that convert the chemical energy of a fuel directly into electrical energy and heat. This article begins by describing the operating principles of fuel cells, their construction, and the main problems currently limiting their commercial success. The thermodynamics of fuel cell systems is discussed, and also the effect of parameters such as pressure and temperature on cell voltage. Their use in conjunction with gas turbines is also addressed, and it is shown that this is a particularly advantageious way of operating. An overview of the main sources of losses in fuel cells is given.

Several different types of fuel cell are explained. This article divides them into six categories: the proton exchange membrane fuel cell (PEMFC), the direct methanol fuel cell (PEMFC), the alkaline fuel cell (AFC), the phosphoric acid fuel cell (PAFC), the molten carbonate fuel cell (MCFC), and finally the solid oxide fuel cell (SOFC). In all cases except one it is the electrolyte that distinguishes the different types. The special features, advantages, disadvantages, operating temperature, electrode and electrolyte construction, typical applications and fuels used are described for each of these six types of fuel cell.