Fuel Cell
A fuel cell is a type of battery which converts chemical energy into electrical energy. Its invention goes back more than 150 years, yet its potential is just being realized in the space age.
Within a few weeks of Alessandro Volta's invention of his Voltaic pile in 1800, Englishmen William Nicholson (1753-1815) and Anthony Carlisle (1768-1840) used its electric current to decompose water into its two component parts, hydrogen and oxygen. This was the invention of electrolysis, and it paved the way for the fuel cell. Just as Michael Faraday discovered he could reverse Hans Christian Oersted's (1775-1851) discovery that electric current produces a magnetic field, William Grove (1811-1896) discovered in 1838 he could reverse electrolysis to produce an electric current, and the fuel cell was born. (Although thirty-six years earlier, Humphry Davy had described a fuel cell that used a carbon anode and aqueous nitric acid.)
As any chemist knows, combining hydrogen and oxygen can result in the production of prodigious amounts of energy. As early as 1903, Russian schoolteacher Konstantin Tsiolkovsky came up with a rocket design that was fueled by liquid hydrogen and liquid oxygen. Grove, in actual tests, used gaseous hydrogen and oxygen, which are less volatile than their liquid counterparts. He placed two platinum plates parallel to each other in a tank--these would be the electrodes of his "gas battery." Oxygen gas was introduced behind one plate and hydrogen behind the other. The space between the plates was filled with a liquid electrolyte (a conductor of ions). The platinum plates were porous enough to let the gas molecules penetrate, but not the liquid, so that this design prevented the two gasses from coming into direct contact with one another. As hydrogen gas mixed with the electrolyte, it produced a coating on the anode (positive electrode); oxygen gas made a coating on the cathode (negative electrode). When the electrodes were connected together, an electric current, albeit a small one, was generated. As the hydrogen and oxygen gasses were consumed, water was produced and the gasses had to be replenished.
Grove connected his fuel cells together in series to produce more power, but the fuel cell remained more of a curiosity for nearly a century. In 1932 English chemist Francis T. Bacon (1561-1626) resurrected the concept and made improvements to it. He used nickel electrodes, which were much less expensive than those of platinum, and pressurized the gas. In 1959 his "Bacon cell" was able to produce six kilowatts of power. While six kilowatts would not jeopardize the operation of conventional electric generating plants, it was a considerable improvement and rekindled interest.
Large corporations also became involved in the technology. General Electric built an experimental tractor using 1,008 fuel cells, and the Chrysler Corporation constructed a fuel-cell car with four electric motors, one for each wheel. The first practical use of the fuel cell was in powering satellites in orbit around the earth. Fuel cells were used to provide electrical power in the Gemini and Apollo spacecraft. On April 13, 1970, an oxygen tank aboard the Apollo 13 command module exploded causing two of the three fuel cells to fail. The loss of oxygen, electricity, and light very nearly resulted in disaster for the astronauts, who were en route to the moon at the time.
Fuel cells are extremely efficient and can theoretically convert 100% of their fuel into electricity; those aboard the Apollo spacecraft operated at 87% efficiency, much better (and cleaner) than the 40% to 50% efficiency of a conventional power plant and the 10% to 20% percent efficiency of an internal combustion engine. In 1984 a 4.8-megawatt plant was put into operation in Tokyo.
Cars powered by fuel-cells would easily outperform today's electric battery-powered cars, and several companies are working to develop such technology. In 1998, Ballard Power Systems Inc. of Vancouver, British Columbia, Canada produced a fuel cell about 2 mm (0.08 in) thick which, when stacked in series, powered a automobile 250 miles. A problem with such cars is the choice of fuel: pure hydrogen, methanol, or natural gas. Prototype cars often have large tanks replacing the rear seats, and can produce some carbon dioxide when, for example, the methanol is converted to hydrogen. Nonetheless, the future looks bright for fuel cells to eventually provide some of the power not supplied by conventional electric generating plants, and an efficient electric automobile may soon make its appearance.
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