Fuel Cell Electric Vehicles (FCEVs) are emerging in the marketplace, with more than 500 patents for fuel cell technology and several FCEVs on display at the Washington Auto Show this week. The U.S. Department of Energy touts fuel cells as being an energy efficient source of power with virtually zero emissions. Fuel cells are one of the Energy Department’s alternative energy sources that will help reduce the nation’s dependency on foreign oil. Efforts by the Energy Department’s Fuel Cell Technology office have reduced the cost of fuel cells by 50% since 2006, which has helped make commercial FCEVs a reality.
Instead of being powered by gasoline or batteries, FCEVs employ simple technology to use hydrogen as an energy carrier to fuel their propulsion systems. Polymer exchange membranes (PEMs) are the most common fuel cells used in FCEVs. They contain positively charged cathodes, negatively charged anodes, and membranes between the anodes and cathodes. When a driver steps on the pedal, hydrogen flows from a tank into the anode of the fuel cell. Then the hydrogen reacts with the anode catalyst, losing electrons and converting into protons. The protons then pass through the fuel cell membrane and combine with oxygen from outside air to the cathode.
The Fuel Cell Technology Office breaks it down in further detail:
The membrane plays a unique role because it allows only protons to pass through it, not electrons (if it did, you would just have an electrical short). Instead, the electrons flow through an external circuit to power the FCEV and then recombine with the oxygen and protons at the anode to produce water. So the only emission from the tailpipe is water- no carbon emissions or other pollutants like nitrogen oxides, sulfur oxides, soot or particulates. Since a single fuel cell is flat, they can be easily stacked and combined together to produce higher voltages and greater amounts of electricity.