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"Fuel cells are significantly more energy efficient than combustion-based power generation technologies. A conventional combustion-based power plant typically generates electricity at efficiencies of 33 to 35 percent, while fuel cell plants can generate electricity at efficiencies of up to 60 percent. When fuel cells are used to generate electricity and heat (co-generation), they can reach efficiencies of up to 85 percent." - U.S. Department of Energy
A fuel cell is a galvanic energy conversion device that changes chemical energy to electricity and heat.

The most used type of fuel cell is the Proton Exchange Membrane Fuel Cell (PEMFC). It generally consists of four parts: an anode, cathode, catalyst, and electrolyte.
  • anode: the negative electrode of the fuel cell where hydrogen gas is oxidized to produce hydrogen cations. It also conducts the freed electrons so they can be used in the electric circuit to generate usable electricity
  • cathode: the positive electrode of the fuel cell where oxygen gas from the atmosphere is reduced and combines with the hydrogen cations and electrons to form water (steam) and heat
  • catalyst: the material coated on carbon paper or cloth that lines the electrodes and facilitates the separation of hydrogen and oxygen gases. Powdered platinum, a noble metal, is widely used for this purpose.
  • electrolyte: the proton exchange membrane between the anode and cathode through which the positively charged hydrogen ions can travel. It also prevents electrons from entering, forcing them to go through the electrical circuit.
However, the reaction in this single cell only provides around 0.7 volts. For sufficient power to be generated, many cells must be combined to form a fuel cell stack. Furthermore, if increased current is needed, the surface area of each cell must be increased. A stack roughly the size of a small luggage will produce enough electricity to power a car.

You will need Macromedia Flash Player installed on your computer (download here) to view the following animation.


An animation demonstrating how fuel cells function.
Courtesy of HowStuffWorks.com
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More problems arise when obtaining the fuel necessary to run the cell. Hydrogen, although it is the most abundant element in the universe, is difficult to store. For enough hydrogen to power the cell that refueling is not frequently required, it must be condensed to a liquid, requiring infeasibly lower temperatures and high pressures. The most logical alternative is to generate hydrogen gas as needed by reforming hydrocarbons like methanol and ethanol.

The device that can perform this process is called a "fuel processor" or simply a "reformer." Via a complex process involving another catalyzed reaction, the carbons and hydrogens split, forming hydrogen gas and carbon dioxide. The hydrogen is used in the fuel cell while the carbon dioxide is released as pollution. Although carbon dioxide is produced during the process, the amount is less than that generated from the combustion of gasoline and natural gas in contemporary machines.

Incorporating a fuel processor to work in conjunction with a fuel cell does not take much work and the following system results:
  1. the fuel processor pumps fuel into the system and converts it to hydrogen gas
  2. the hydrogen splits in the fuel cell, producing electrons and current
  3. an electric controller supplies the current to a motor, generating torque
Such fuel cell systems could be applied to many areas--transportation, housing, etc.--and their implementation in everyday life is just on the horizon.
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