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Fuel Cells
Fuel cells are electrochemical devices that convert the energy of a chemical reaction directly into electrical energy, similar to a battery. However, unlike a battery, a fuel cell does not wear out or require recharging, it runs as long as it is continuously supplied with the fuel (usually hydrogen) that is needed for operation. And because fuel cells have no moving parts, they require very little maintenance and have extended life spans, making them a quiet, safe and reliable form of energy.
Photo credit: http://fuelcellbus.georgetown.edu/gfx/tbb6.jpg
Fuel cells are also highly efficient, averaging two to three times higher efficiency rates than the internal combustion engine.1 When fuel cells run solely on hydrogen they are completely emissions free making fuel cells a promising clean alternative in the development of new vehicles, which currently account for one-third of the greenhouse gas emissions in the US annually. The picture is of a fuel cell powered bus.
A fuel cell consists of two electrodes and an electrolyte (see diagram below). The reaction starts when hydrogen enters the anode, the negatively charged electrode, while oxygen is supplied to the cathode, the positively charged electrode. Material in the anode causes the hydrogen to lose some of its electrons, which travel via an outside circuit towards the positively charged cathode. Using this outside circuit allows the electric current created to be collected. The hydrogen protons then pass through the electrolyte membrane to combine with negatively charged oxygen anions on the cathode side, creating the only other products from this reaction, pure H20 and heat.
One fuel cell unit produces just under 1 volt of electricity, but when stacked together (as shown below), fuel cells can be made to power a variety of applications both large and small. Currently, fuel cells are still quite expensive to produce, but with many automotive companies actively developing fuel cell powered vehicles, prices for manufacturing should drop as the applications become more mainstream.
For more information on fuel cells:
World Fuel Cell Council
US Dept. of Energy (EREN)
American Hydrogen Association
