Fuel Cells

Fuel Cells are devices that generate electricity through a process which produces water as a by-product. Fuel cells consist of basic components which include two electrodes described as anodes and cathodes as well as an electrolyte. Electrodes are conductors of electrical currents. An electrolyte is a liquid medium which conducts electricity. Ions in the electrolyte enable the generation of power in fuel cells as they physically separate oxygen and hydrogen. Hydrogen passes over one electrode (the anode) and oxygen over the other (the cathode). A catalyst splits the proton of a hydrogen atom from its electron. The protons subsequently pass through the electrolyte while the electrons from the anode form a direct current that leaves the fuel cell through an electrical circuit. The opposite charges are directed to the cathode where a reaction with oxygen takes place producing water.

The hydrogen supplied to fuel cells can be either in liquid or gaseous form. But it can also be extracted from more conventional fuel sources which include diesel fuel, gasoline, methanol and natural gas. Extracting hydrogen from hydrocarbon fuel sources is known as fuel reforming also sometimes dubbed fuel processing. The reforming can be either external or internal. The former takes place outside a fuel cell while the latter inside the fuel cell stack. A chemical plant or a refinery can be the external location where the processing occurs.

This site offers a comparison of fuel cell technologies.