All-electric vehicles, meanwhile, use no gasoline engine and thus produce zero emissions, but concerns over battery life persist. Thus far, all-electric solutions have been largely relegated to niche applications. Glaser noted that the U.S Postal Service has adopted all-electric powertrains for some delivery vehicles.
Stumbling blocks also stand in the way of the various fuel alternatives to gas and diesel fuel. They include the availability of fuel cells and the establishment of an infrastructure to refuel and service alternatively powered vehicles.
One fuel source drawing interest is hydrogen. The fuel can be produced by stripping molecules from hydrocarbons, according to the Northeast Sustainable Energy Association, but it is expensive and is considered less efficient than storing energy in batteries or ultracapacitors.
Wall said the DOE is conducting re- search on advanced combustion engines that run on hydrogen. "The issues are, can you store enough hydrogen, and can you manufacture hydrogen and get it into distribution points?"
Ford has developed what it calls the first drivable fuel-cell hybrid electric plug-in vehicle. The Ford Edge crossover with HySeries Drive combines an on-board hydrogen fuel-cell generator with lithium-ion batteries. The vehicle is designed to drive the first 25 miles each day on stored electricity alone, after which the fuel cell kicks in to keep the battery pack charged. An 110/220-Vac charger on board can refresh the battery pack when a standard home outlet is available. With the HySeries Drive, the Ford Edge reportedly delivers 41 mpg with zero emissions. Ford is also testing a fleet of 30 hydrogen-powered Focus fuel-cell vehicles.
Ethanol is likewise being promoted as an alternative to conventional gasoline for internal-combustion engines. While gasoline commonly has a small percentage of ethanol, ethanol formulations comprising 85 percent ethanol and 15 percent gasoline are also available.
According to the DOE's Wall, of the roughly 170,000 gas stations in the United States, 600 supply 85 ethanol--a small percentage of the total, but still far larger than at the decade's start.
To leverage ethanol's availability, automakers are developing "flexible fuel" vehicles that run on either ethanol or gasoline. GM equips its flexible-fuel-eligible vehicles with a yellow gas cap. n
Spencer Chin
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