Fuel Cell
Fuel Cell, a device that converts the chemical energy of a fuel directly into electrical energy. In contrast to a steam-powered generator system, the fuel cell does not first convert chemical energy into mechanical energy. Fuel cells, like electric cells (batteries), have no moving parts. Unlike electric cells, fuel cells use outside materials in producing an electric current. Fuel cells are very efficient in converting the chemical energy of a fuel into electrical energy. However, for most applications they are too expensive to compete with conventional methods of producing electricity. Their main use is on spacecraft and to provide power at remote locations on earth.
A fuel cell uses a fuel, usually hydrogen, and an oxidizer, usually oxygen (or air), to produce direct-current power. A typical fuel cell contains two electrodes, in the form of metallic screens, separated by a material saturated with an electrolyte, such as potassium hydroxide. Hydrogen is supplied to one screen, oxygen to the other. Chemical reactions between the electrolyte and each of the gases creates a voltage between the electrodes. Water is formed as a by-product of the reactions. The fuel cells used on American space shuttles weigh about 200 pounds (90 kg) and can produce up to 12,000 watts of power at 27.5 volts. Each space shuttle carries three cells.
The first research on fuel cells began in the mid-1800's, but promising models did not appear until the early 1960's. The first practical application of fuel cells was as the main power supply in Gemini spacecraft.