Fuel cells convert the chemical energy of fuels directly into electricity. The principle of the fuel cell was developed by William Grove in 1839. Already around 1900 scientists and engineers were predicting that fuel cells would be common for producing electricity and motive power within a few years. That was roughly 100 years ago. Contrast this with the roughly 2 years that it took Nikolaus Otto to bring his Otto cycle 4-stroke internal combustion engine from the invention stage to a commercial success.
HOW A FUEL CELL WORKS:
A fuel cell works similar to a battery. In a battery there are two electrodes which are separated by an electrolyte. At least one of the electrodes is generally made of a solid metal. This metal is converted to another chemical compound during the production of electricity in the battery. The energy that the battery can produce in one cycle is limited by the amount of this solid metal that can be converted. In the fuel cell the solid metal is replaced by an electrode that is not consumed and a fuel that continuously replenishes the fuel cell. This fuel reacts with an oxidant such as oxygen from the other electrode. A fuel cell can produce electricity as long as more fuel and oxidant is pumped through it.