fuel cell

Cell converting chemical energy directly to electrical energy. It works on the same principle as a battery but is continually fed with fuel, usually hydrogen and oxygen. Fuel cells are silent and reliable (they have no moving parts) but expensive to produce. They are an example of a renewable energy source.

Hydrogen is passed over an electrode (usually nickel or platinum) containing a catalyst, which splits the hydrogen into electrons and protons. The electrons pass through an external circuit while the protons pass through a polymer electrolyte membrane to another electrode, over which oxygen is passed. Water is formed at this electrode (as a by-product) in a chemical reaction involving electrons, protons, and oxygen atoms. A current is generated between the electrodes. If the spare heat also produced is used for hot water and space heating, 80% efficiency in fuel is achieved.

Fuel cells can be used to power cars, replacing the internal combustion engine, and to produce electricity on spacecraft.