Volvo Car Group has completed extensive testing of kinetic flywheel technology on public roads – and the results confirm that this is a light, cheap and very eco-efficient solution.
“The testing of this complete experimental system for kinetic energy recovery was carried out during 2012. The results show that this technology combined with a four-cylinder turbo engine has the potential to reduce fuel consumption by up to 25 per cent compared with a six-cylinder turbo engine at a comparable performance level,” says Derek Crabb, Vice President Powertrain Engineering at Volvo Car Group, “Giving the driver an extra 80 horsepower, it makes car with a four-cylinder engine accelerate like one with a six-cylinder unit.”
The experimental system, known as Flywheel KERS (Kinetic Energy Recovery System), is fitted to the rear axle. During retardation, the braking energy causes the flywheel to spin at up to 60,000 revs per minute. When the car starts moving off again, the flywheel’s rotation is transferred to the rear wheels via a specially designed transmission.
The stored energy was sufficient to power the car for short periods, meaning the engine could be switched off for as much as 50 percent of the time.
Compared to a conventional gasoline-electric hybrid, Volvo’s flywheel KERS is lighter, cheaper and easier to maintain.
The flywheel that Volvo Cars used in the experimental system is made of carbon fibre. It weighs about six kilograms and has a diameter of 20 centimetres. The carbon fibre wheel spins in a vacuum to minimise frictional losses.
“We are the first manufacturer that has applied flywheel technology to the rear axle of a car fitted with a combustion engine driving the front wheels. The next step after completing these successful tests is to evaluate how the technology can be implemented in our upcoming car models,” concludes Derek Crabb.