The future of energy production may have had its beginnings in 1802, when Sir Humphry Davy passed an electric current through water, causing it to decompose into hydrogen and oxygen. He postulated that electric attraction held the two elements together.
By 1839, a Welsh judge, Sir William R. Grove, had invented the first hydrogen fuel cell - a development that languished for the next 100 years. In experiments leading up to his invention, Grove showed that hydrogen and oxygen could be combined to produce water and an electric current. He wrote that the current "could be felt by five persons joining hands, and which when taken by a single person was painful."
 | | | How They Work, Made Simple A fuel cell is similar to a battery and runs a controlled chemical reaction, sometimes called a cold fire. It has a positive terminal and a negative terminal, at which intermediate chemical reactions occur. The full chemical reaction is completed when an intermediate product diffuses from one side of a cell to the other and an electric current flows through an external wire connected between the terminals. Hydrogen flows past the anode, or negative terminal. A chemical reaction there extracts electrons from the hydrogen and leaves positive hydrogen ions, or cations. On the other side of the fuel cell, oxygen flows past the cathode, or positive terminal, where a reaction causes the oxygen molecules become negatively charged oxygen ions. As a result of this process, electrons are drawn from the negative anode (where they were extracted from hydrogen) to supply the reaction with oxygen at the positive cathode. There are now positive hydrogen ions on one side of the fuel cell and negative oxygen ions on the other side. The two sides are separated by a membrane that only allows hydrogen ions, or protons, to cross. Because they're positive, they're drawn to the negative side, where they combine with oxygen to produce water. This is the same type of reaction as the one that occurred with a great deal of force when the hydrogen of the Hindenburg zeppelin met the oxygen of the atmosphere. But it's controlled so that very little heat is produced and the energy given off can be channeled through a wire to drive electric machines. |
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Hydrogen, which is highly reactive, is usually found combined with other elements. Hydrogen extraction and management have been relatively expensive processes, and until now, no market has emerged to drive the development of the technology. But an unlikely combination of highly mobile computing and mass transportation may finally be creating that market.
Users of wearable computers need power - a source of portable, lightweight power that will last long enough to be useful. They need to drive their CPUs, their monitors and other peripherals, and all of that sucks the juice out of a rechargeable battery within a couple of hours.
In the transportation industry, prototype buses are in service in cities as disparate as Chicago and Reykjavik, Iceland. And German automaker DaimlerChrysler AG has introduced its hydrogen-powered Necar 4, which has a top speed of 90 miles per hour and a 280-mile tank capacity.
Beyond the Mainstream
These unusual niche markets may be heading toward a future powered by hydrogen fuel cells more quickly than the mainstream is.
Xybernaut Corp., one of the main makers of wearable computers, has introduced hydrogen fuel cells manufactured by DCH Technology Inc. in Valencia, Calif., to power its Mobile Assistant IV.
"Fuel cells can potentially prove [to be] an unlimited supply of portable power and may be the perfect solution to the currently limited life for batteries used for portable electronics," says Edward G. Newman, president and CEO of Fairfax, Va.-based Xybernaut. The company anticipates that a hydrogen fuel cell could keep a Mobile Assistant IV running for 12 to 24 hours, he says.
This particular fuel cell was developed in cooperation with the Electronic and Electrochemical Materials and Devices Group at Los Alamos National Laboratory in New Mexico. Its design is cylindrical, about the size of a standard 9-volt battery, including the hydrogen supply. The hydrogen canister is at the center of the cylinder and provides the gas to stacked, disclike fuel cells.
Oxygen, which is the other fuel required for the cell, comes from the ambient atmosphere outside the cylinder; this design also facilitates the small amount of cooling that's required. The output of the cell is a little bit of heat, water (which evaporates as it's produced) and an electric current.
Fuel cells are similar to batteries, except they require an external source of fuel, rather than an internal store of chemical energy. At an efficiency of about 40%, they're much more efficient than internal combustion engines, which operate at about 13% to 25% efficiency. (About 75% to 87% of the gas burned in an internal combustion engine in a car is not available for making the car move.)
In addition to the problem of extracting hydrogen, there are two other roadblocks to hydrogen becoming a common energy source.
One is distribution: Hydrogen canisters aren't on the rack next to the lithium batteries at the local pharmacy.
Conrad Electronic AG, a German electronics retailer, sells a hydrogen fuel cell for notebook computers that's produced by another German firm, the Fraunhofer Institute for Solar Energy Systems. Empty hydrogen fuel reservoirs, which are removable parts of the cell's flat design, may be exchanged at Conrad Electronic outlets for full reservoirs.
The combination of the fuel cell and reservoir offers longer life than the best lithium batteries. Also, there are no polluting, dead batteries to be disposed of.
The hope of hydrogen fuel cell developers is that as hydrogen energy becomes a larger part of the general economy, obtaining full hydrogen reservoirs will be as easy as purchasing conventional batteries.
The Hindenburg Dilemma
The second problem hydrogen fuel cells must overcome can be summed up in two words: the Hindenburg. When the zeppelin exploded in 1937 while docking at Lakehurst, N.J., killing 36, the public perception of hydrogen technologies was seriously damaged.
Not many mobile- or wearable-computer users would like to think of themselves as walking Hindenburgs. Hydrogen is very explosive at a concentration as low as 4% and can be ignited by a mere static spark.
On the other hand, hydrogen is 14 times lighter than air and dissipates very quickly. Even with the Hindenburg disaster, it's thought that the 7 million cubic feet of hydrogen in the zeppelin burned off in less than one minute and caused no fatalities. Diesel fuel, also carried by the airship, was responsible for the deaths and continued fires after the original explosion.
Retired NASA scientist Addison Bain has suggested that a mixture of materials in the Hindenburg's cover produced a compound that first caught fire from electrostatic discharges in the atmosphere. As long as the hydrogen reservoirs are designed safely, the gas is safe as a fuel, says Bain.
And NASA evidently feels that the technology is safe. All of the Gemini, Apollo and space shuttle missions have used hydrogen fuels to generate electricity and produce water.
Ironically, it may be the bastions of internal combustion technology and vehicle manufacturers that drive the development of hydrogen energy technology that will benefit portable electronics. In an effort to develop more efficient and cleaner-running automobiles, manufacturers have begun to turn to hydrogen. Most of the major automakers have hydrogen research groups. In the future, hydrogen technology could give new meaning to the phrase "gas station."
Matlis is a freelance writer in Newton, Mass.