As an engineer, David Eisenhaure appreciates the quick acceleration of his Yamaha XF-650 motorcycle, which he rides every day to his office at SatCon Technology in Cambridge, Massachusetts. What really gets the 49-year-old president and chief executive officer excited, though, is the idea of driving a battery-powered car that performs just as well. Conventional lead-acid batteries, however, use slow-acting chemical reactions, which means they cannot deliver power quickly enough for fast acceleration.
The idea might have gone nowhere, except that François Castaing, vice president for vehicle engineering at Chrysler, had the same thought. Castaing and Eisenhaure put their heads together and found a solution in a familiar electromechanical energy storage device known as the flywheel. Although it has been around for centuries, the humble flywheel turns out to be far better than batteries at storing energy and releasing it fast. No one has come up with a battery technology that can compete, Eisenhaure says. For cars, that means more pep on the highway.
Chrysler commissioned SatCon to make a flywheel for a racing car, toughened it up to withstand vibration from the road, and came up with the Patriot, a hybrid car that uses both a combustion engine and a flywheel to conserve on gasoline. When the Patriot hits the road, it will funnel the energy typically lost in braking to the flywheel--as the car decelerates, the flywheel picks up the lost momentum--and then release that energy when a burst of acceleration is needed. The virtually frictionless flywheel, sealed in a vacuum and riding on custom-designed bearings, gives back 90 percent of the energy put into it. Before each race, technicians in the pit will rev the flywheel to 60,000 revolutions per minute, enough energy for the car to accelerate when the flag is dropped. Having a flywheel also means that the combustion engine can run at a constant rate, further increasing energy savings.
The goal is to ready the car for the Le Mans this summer or, failing that, the Daytona 500 next February. With 500 horsepower and weighing 1,700 pounds, the Patriot should deliver three times more punch per pound than Eisenhaure’s motorcycle. Castaing believes that hybrids are likely to be mass-produced early next century.
