Hydrogen: A long wait
Pros Low or virtually no harmful emissions.
Cons Fuel-supply problems, expensive fuel-cell technology, onboard fuel storage, range, cold-temperature driveability.
At first glance, hydrogen-powered electric cars using fuel cells seem like the ideal solution to pollution woes and dependence on imported oil. They don't use combustion but rather an electro-chemical reaction whose only major byproduct is water. Fuel cells have been used for years to power spacecraft, and hydrogen is the most abundant element in the universe.
Many automakers are testing working prototypes, including the DaimlerChrysler F-Cell, Ford Focus FCV, General Motors HydroGen3, Honda FCX, Hyundai Santa Fe FCEV, Toyota FCHV, and Volkswagen HyMotion.
And the federal government has committed hundreds of millions of dollars to do research on fuel cells and hydrogen issues. But daunting technical and infrastructure challenges make it unlikely that fuel-cell cars will get beyond the prototype stage for decades to come.
General Motors is committed to selling hydrogen fuel cell cars commercially by 2010. But don't expect that you'll be able to put one in your driveway that soon. Most alternative fuel vehicles are tested in fleets for years.
Of several fuel-cell designs, the one favored for vehicles—because of its compactness and high energy-to-weight ratio—is the PEM (proton exchange membrane) system. When hydrogen gas is applied to one side of the sheet-plastic cell, it combines with atmospheric oxygen and produces electricity and water—something like the reverse of electrolysis.
Manufacturing costs are now about a hundred times that of an equivalent gasoline car, however, and reliability and life-span issues are still unknown. Honda's little FCX city car is the first fuel-cell vehicle able to start at subzero temperatures, but a Honda spokesman told us they didn't expect to produce a mass-market fuel-cell vehicle for at least 20 years.
More pressing is the problem of where to get the hydrogen and how to get it to the vehicle. While hydrogen is abundant, it's almost always bound up in minerals, hydrocarbons, or water. The cheapest way to obtain hydrogen gas is by extracting it from natural gas. But if one of the goals of moving to hydrogen cars is to get away from fossil fuels, then taking hydrogen from natural gas is self-defeating.
An alternative is taking electricity from a nonpolluting source like solar, wind, or hydro power and using it to split water into its hydrogen and oxygen components. The problem here is that it takes more electricity to make the hydrogen than the hydrogen can generate in a fuel cell. Even if hydrogen fuel is relatively expensive, it could be the best alternative for making pollution-free vehicles.
Another problem is that hydrogen gas carries very little energy per cubic foot. So automakers are developing different ways of storing sufficient amounts of it in a car. One method is to compress hydrogen to very high pressures (5,000 to 10,000 psi). Another is to compress it into liquid form at temperatures near absolute zero (minus 459 degrees F), but that process consumes a lot of energy. Some automakers are developing ways to store hydrogen in a solid form, but this is heavy and expensive.
Building a hydrogen distribution network also faces a major chicken-and-egg problem. Without the ability to refill them, people won't buy the cars, and without masses of cars to service, businesses won't spend the billions of dollars it would take to build the infrastructure.
California is constructing a small network of hydrogen filling stations, which will increase the range of the tiny fleet of fuel-cell cars undergoing tests there. Those stations have electric-powered reformers that electrolyze water to make hydrogen on-site. Similar initiatives have been proposed in Canada.
A simpler solution is to burn hydrogen in a regular internal combustion engine, as BMW has demonstrated with a hydrogen-powered 7 Series sedan.
A hydrogen-burning engine creates no carbon dioxide (CO2), is relatively inexpensive to produce, and doesn't need the ultra-pure hydrogen a fuel cell demands. On the other hand, it still requires a hydrogen-fueling system and needs a catalytic converter to reduce NOx emissions.