They rode on rockets to the moon and proved they can generate enough electricity to power an automobile. But fuel cells are still years away from widespread use by the auto industry.
Standing in their path are high costs and the problems of a complex technology. Together, these forces ensure large numbers of fuel-cell-powered vehicles will not hit showrooms for a decade or more.
'There's a lot of serious work going into it, and there's a lot of potential there,' says Bernard Robertson, DaimlerChrysler's vice president for engineering technologies. 'It's just that the challenges are pretty formidable.'
A fuel cell uses sophisticated membranes to strip electrons from hydrogen atoms, creating a charge imbalance and electrical current. The cell recombines the hydrogen with oxygen to form water vapor.
DaimlerChrysler is trying to lead the industry in fuel cells by forming joint ventures with Ford Motor Co. and Ballard Power Systems Inc. of Vancouver, British Columbia, a supplier of fuel-cell stacks. The goal is to be the first to manufacture complete fuel-cell powertrains for sale on the world market.
The task is daunting. At DaimlerChrysler's fuel-cell development center near Stuttgart, Germany, 900 technical people are devoted exclusively to fuel-cell research.
Necar 4, the fourth generation of the center's New Electric Car series of fuel-cell concepts, was unveiled to reporters in Washington two weeks ago. The company plans to begin limited production of a salable fuel-cell vehicle in 2004.
Necar 4 is technically impressive because it crams the entire fuel cell system in a 6-inch-deep space under the floor. Still, however, it is a good example of the shortcomings of current fuel-cell technology.
DaimlerChrysler officials admit the vehicle is overweight by more than 600 pounds, and astronomically expensive. A mass produced fuel cell system would cost $30,000 using today's technology, says DaimlerChrysler, although Necar 4's hand-built unit is estimated to have cost $350,000.
Gasoline engines typically cost about $3,000.
Specialized hardware is what drives the fuel cell's costs. A big money pit is the row of electricity-conducting bipolar plates in the fuel cell stack. These plates, made from ultrahard carbon-graphite, have dozens of intricate channels that must be individually cut by computer-controlled machine tools. For maximum efficiency, the channels must be machined to the high tolerances usually reserved for jet engine turbines.
Even so, Necar 4's energy efficiency, or the amount of hydrogen in the tank converted to motion at the wheels, is still too low. At 36 percent, it is better than the 24 percent of a gasoline-powered Mercedes-Benz A class, but below the target of 40 percent.
Methanol, which is derived from natural gas, may be the better alternative. It is cheaper and easier to handle than hydrogen, but would not be as clean. Small amounts of carbon dioxide, a contributor to global warming, is emitted from the tailpipe. Smog-producing hydrocarbons, poisonous sulfur dioxide and oxides of nitrogen also come out.
Compared to DaimlerChrysler's most efficient diesel engines, the methanol fuel cell's emissions are low: about 18 percent, 11 percent, and 3 percent respectively of the diesel's output of hydrocarbons, sulfur dioxide and oxides of nitrogen.
To achieve this performance, however, the methanol fuel cell needs complex reformers and platinum-lined catalysts that separate out the hydrogen and convert the remaining carbon monoxide to carbon dioxide.
These reformers are pricey, accounting for up to 25 percent of the fuel-cell system's total cost. The fuel cell also needs time to warm the catalysts to operating temperatures, necessitating a bulky onboard battery pack to provide power in the interim. One way engineers attack the problem is with a 'direct methanol' fuel cell that requires no reformers.
In the current design - which Ferdinand Panik, DaimlerChrys-ler's fuel-cell research director, says is little more than a laboratory experiment - methanol is piped directly to the fuel cell. There it is separated into positively and negatively charged particles by the fuel cell's membrane.
The problem, says Panik, is that 'methanol is getting through the membrane, so the hydrocarbon emissions are still too high.'