Beyond batteries: new technologies power the car of the future.

Every year, 30,000 people die in the U.S. from airborne toxins released by automobiles. Also largely because of the car, 100 million Americans live in areas with dangerous ground-level ozone concentrations. It's plain that, with a million cars a month adding to the 200 million already here, the fossil-fueled automobile is choking us to death. Is there an alternative?

Although battery-powered electric cars seem to be finally about to find their place on the world's roads (see Consumer News this issue), they may prove to be an interim technology in the race to replace the internal-combustion engine with something cleaner. Though it's the battery cars that are road-ready now, fuel cells, hybrids and flywheels offer a tantalizing vision of a more practical, low-emission transportation future. Each of these alternatives has distinct advantages and drawbacks.

* FLYWHEELS. Since flywheels were used by potters millennia ago, their application in automobiles today could seem quaint. They're nothing more than perfectly balanced and rapidly turning discs, which store energy and then release it as they turn. In fact, as proposed by California-based U.S. Flywheel Systems, this spinning disc is a high-tech, carbon-fiber marvel capable of turning (in a vacuum) at an incredible 100,000 revolutions per minute (rpm). When harnessed to a generator, flywheels (also known as "electromechanical batteries") provide steady and reliable power, along with delivering big surges for quick acceleration. Unlike electric car batteries, flywheels contain no corrosive or toxic materials.

There are hurdles to be overcome before flywheels can be practical in automobiles. Because they turn so fast, a flywheel freed from its housing is a dangerous projectile. Rosen Motors, a California-based company whose principals include Benjamin Rosen, chairman of Compaq Computers, is probably the closest to a public demonstration of a safe, drivable hybrid flywheel car. Based on a Mercedes E320 sedan, the Rosen hybrid generates electricity through a low-emission gas turbine engine (running on unleaded fuel), and stores one kilowatt-hour of energy in its flywheel. Deborah Castleman, Rosen vice president, predicts that the company will have its system ready by February 1998, and that it expects to deliver gas mileage about double that of its host vehicle (about 60 miles per gallon in the case of the Mercedes E320). "We think battery-powered electrics will serve at best a niche market," Castleman says. "We're concentrating on a real replacement for the current generation of automobiles."

* HYBRID CARS. Although Amory Lovins of the Rocky Mountain Institute (RMI) is an environmental visionary, he's decidedly bearish on electric cars, calling them "a future technology whose time has passed." Instead, RMI advocates what Lovins calls the "hyper" car, a small, ultra-lightweight vehicle with a carbon fiber shell and a hybrid drivetrain incorporating both electric motors at the four wheels and a small internal-combustion engine driving a generator. The resulting car would not be zero-polluting, but it would be incredibly fuel efficient (up to 400 miles per gallon). With a range of at least 300 miles, it would also overcome one of the EV's biggest drawbacks. No one has yet produced even a prototype of a hyper car, but hybrids of various types are being widely tested, even raced on events like the Tour de Sol. And Toyota will soon be selling a hybrid sedan, incorporating a 1.5-liter gas engine and nickel metal-hydride batteries, to environmentally-conscious customers in Japan. "There is tons of interest in the hyper car out there," says Auden Schendler, outreach research associate at RMI. "The problem is the estimated $40 million it would cost to build a prototype."

* FUEL CELLS. The fuel cell, in which hydrogen and oxygen are combined in a chemical reaction to produce electricity (and, the only byproduct, steam), offers a highly promising clean car technology (as well as a source of uninterrupted power for electric utilities). The main problem: reducing the bulk and cost of the compressed hydrogen storage tanks, and ensuring their safety. One of the best things about fuel cells, though, is that they're flexible, able to run happily on a tank of methanol or methane (reformulated into hydrogen before it enters the fuel cell). Ballard Power Systems, based in British Columbia, is the leader in applying fuel cells (already a fixture in spacecraft) to the passenger car. Ballard's clients include Volvo, Volkswagen, Mercedes-Benz, General Motors and Honda. Fred Heller, a Mercedes spokesman, says the company (a part owner of Ballard) hopes to demonstrate a completely integrated fuel cell system in its tiny "A" class car in about 18 months. "We think it's completely feasible," Heller says. The car, which would produce a small amount of carbon-based emissions, should have a 300-mile range - comparable to today's gas cars. CONTACT: Ballard Power Systems, 9000 Glenlyon Parkway, Burnaby, British Columbia, Canada/[phone]; Rocky Mountain Institute, 1739 Snowmass Creek Road, Old Snowmass, CO 81654-9199/[phone]; Rosen Motors, 6430 Independence Avenue, Woodland Hills, CA 91367/[phone].