A driving force.

Paul B. MacCready has a knack for knowing the difference between the impossible and that which is merely extremely difficult. In the late 1980s, MacCready, founder and CEO of AeroVironment, a company that consults on pollution management and wind energy, figured that a battery-powered automobile could be practical , provided the entire machine was optimized for efficiency. It would have to be exceptionally lightweight and streamlined to a degree never before seen in commercial cars. MacCready's idea became General Motors' EV1, now marketed in southern California and Arizona by Saturn dealers. Meanwhile, fuel cells, which supplied electricity on the Gemini space capsules of the mid-1960s, are widely considered to be the ultimate in efficiency and deanliness. Unfortunately, as far as cars were concerned , they were considered pie in the sky. But unexpectedly fast developments this decade have brought fuel cells down to earth, and now Daimler-Benz, the maker of Mercedes, and Ballard Power Systems of Vancouver, Canada, have announced a $350 million-plus joint venture to market fuel cells as automobile engines. One Ballard fuel cell bus is plying the streets of Vancouver and six more will be ferrying Chicagoans and British Columbians later this year. Ford and Chrysler have also recently announced ambitious fuel cell programs. Other technologies vying to power cars of the future range from deaner gasoline and diesel engines, to miniature gas turbines , to internal combustion/electric hybrids, to incredibly efficient Stirling-technology external combustion engines. In addition, an estimated 385,744 alternative fueled vehides are currendy in use in the United States, according to Alternatives to Traditional Transportation Fuels 1995, a December 1996 publication of the Energy Information Administration. These indude 273,000 vehicles that run on liquid petroleum gases, 81,000 that run on compressed natural gas, 26,000 that run on 85% alcohol, and 3,900 electric vehi-des (EVs). In 1996, the United States' automobiles, minivans, and sport utility vehicles burned 15 quadrillion British thermal units (quads) of gasoline, two-thirds of the nation's petroleum consumption. Total U.S. energy use was near-~ _ ly 90 quads that year. Half of the United States' petroleum comes from abroad, and the cost of importing oil is $100,000 every minute, says Jason Mark, a transportation analyst with the Union of Concerned Scientists' Berkeley, California, office. Although the rest of the economy became more energy-efficient after the 1979 oil shock, says Mark, consumers have little incentive to demand more energy-efficient autos, as fuel accounts …