Volvo seems an unlikely carmaker to explore the use of kinetic-energy recovery flywheels in its pedestrian automobiles, but the traditionally safety-oriented company is indeed working to bring the Formula 1 tech to its cars. Volvo joins Porsche and its GT3 R hybrid racer in the utilization of a kinetic-energy recovery system (KERS) that uses the energy of a flywheel spun to high speed by recovered braking energy to aid a car’s engine during acceleration.
In Volvo’s system, the flywheel is mechanically coupled and decoupled from the rear axle using a continuously variable transmission. The CVT engages the flywheel as the car slows, spinning it to up to 60,000 rpm, then decouples the flywheel as the car comes to a halt, finally re-coupling the spinning flywheel to the rear wheels when the car accelerates from a stop. Volvo’s mechanical, motorless rear-axle-mounted setup is unique from Porsche’s approach to KERS, which relies on motor-generators to spin up the flywheel, recover its energy, and transfer that energy back to the car’s forward motion. (Read more about the system in the 911 GT3 R hybrid here.) Volvo claims that the flywheel’s accelerative boost not only aids fuel economy, but performance as well, with up to 80 additional horsepower available when the flywheel and engine join forces.
Because the flywheel doesn’t spin forever—the laws of physics cannot be beat, so it loses rotational inertia over time—the KERS system is most effective in stop-and-go driving, where each stop can spin the flywheel, which can then be used to get the car going again for a brief period of time. Volvo is aware of the situational limits of the KERS system, so it has worked to make the flywheel as efficient as possible. This means that the flywheel is made of carbon fiber, making it lighter—the 7.84-inch diameter flywheel weighs just 13 pounds—and increasing its rotational capacity. The flywheel spins in a vacuum to minimize friction losses. Volvo plans to begin testing its KERS setup in its cars in the second half of 2011, and is confident it can reduce fuel consumption by up to 20% while giving a four-cylinder engine the punch of a six. We just hope an F1-style, driver-operable “boost button” makes the cut, because a Volvo with a go-faster button would make us giddy at the incongruity of it all.Tags: hybrid, Volvo |