Volvo says that tests on public roads showed its kinetic flywheel hybrid system can reduce a car's fuel consumption by as much as 25 percent. The system allows a car with a four-cylinder turbocharged engine to perform as well as one with a six-cylinder engine, yet use much less fuel. Based on these results, Volvo will now consider fitting the technology to a production car.
The Flywheel Kinetic Energy Recovery System uses a 13.2-pound, 7.9-inch carbon-fiber flywheel encased in a vacuum. A special transmission links the flywheel to the rear wheels so under braking, it spins up to 60,000 rpm. Then under acceleration, the flywheel connects to the rear wheels to provide up to 80 hp of extra power.
The flywheel's boost can reduce the Volvo test car's 0-to-60-mph time by at least one second, but by allowing the regular engine to turn off at a stop or under light acceleration, it can also improve fuel economy by 25 percent. Volvo says the system is so effective that in the European fuel-economy test cycle, the engine could be turned off almost 50 percent of the time.
Volvo experimented with flywheel hybrid technology as far back as the 1960s, but back then the system used steel flywheels that were heavy, expensive, and inefficient. The automaker claims its carbon-fiber unit would be much cheaper than a typical battery hybrid system.
If Volvo decides to put this technology into production, it could be attached to the four-cylinder VEA (Volvo Environmental Architecture) engines that will launch this fall. The Swedish company has publicly committed to selling cars primarily with four-cylinder engines to reduce fuel consumption. In fact, that commitment means Volvo won't pursue a large luxury car that might use a V-8 or V-12 engine.