I can see why Volvo doesn’t refer to their experimental Flywheel KERS (Kinetic Energy Recovery System) by the acronym FKERS (although it would make for hilarious interviews). But, all giggling aside, we’ve been hearing a lot of KERS lately. Ferrari has one in the LaFerrari. Porsche is putting one in their 918. Same with the Audi e-tron R18 Quattro. Hell, even Formula 1 cars use them. You can’t turn a corner without bumping into some carmaker working on a car with a Kinetic Energy Recovery System.
So, what makes Volvo’s Flywheel KERS so special? To begin with, Volvo has been playing around with flywheel propulsion since the 1980s when they tested it in a Volvo 260. However, due to limitations in materials, the whole system, while interesting, wasn’t really viable. The large steel flywheels from the 80s were too heavy and had limited rotational capacity.
Not so today. Thanks to carbon fiber, the Volvo system’s flywheel weighs a scant six kilos, has a diameter of 20 centimeters and spins in a vacuum to decrease losses of kinetic energy due to friction. Here’s how the new system works:
“The experimental 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 combustion engine that drives the front wheels is switched off as soon as braking begins. The energy in the flywheel can then be used to accelerate the vehicle when it is time to move off again or to power the vehicle once it reaches cruising speed.”
By harnessing the kinetic energy of the flywheel, Volvo claims a KERS-equipped car will achieve 25 percent better fuel economy. To test the whole shebang, Volvo bolted a KERS to an S60 test car. The S60 has a turbo four-cylinder internal combustion engine powering the front wheel and the KERS, which adds an additional 80 horse, powering the rear. With this setup, the S60 will jaunt from 0-62 mph in 5.5 seconds. A similar Volvo S60 powered by a traditional 3.0 liter T6 6-cylinder turbo engine put to the ground via all-wheel-drive take 6.6 seconds 0-62. The KERS is faster and gets 25 percent better fuel efficiency. Not bad. Not bad at all.
Like most hybrids, the greatest gains in fuel economy will come in urban areas and in periods of heavy braking and frequent stop/starts. Volvo estimates in ideal condition a KERS-equipped car could drive without using the internal combustion engine about 50 percent of the time when driving according to the New European Driving Cycle.
Kinetic Energy Recovery Systems have already made it onto the roads in the form of the Ferrari LaFerrari. But, if you’re like me, a supercar that costs over $1 million is slightly out of reach. Perhaps in the near future, a similar but more affordable system will sit comfortably in your driveway.