F1’s KERS technology could soon be found under the hood or our every day vehicles, creating a different kind of hybrid. Volvo Car Group and engineering company Flybrid Automotive have been conducting tests of lightweight Flybrid flywheel KERS technology. The end goal is to boost performance while cutting fuel consumption and emissions.
Both companies said the four-year partnership, using real-world driving data from tests on public roads and test tracks in both Sweden and the UK, has shown that the flywheel-based hybrid technology can deliver an 80 horsepower performance boost, as well as fuel savings of up to 25 percent.
The research forms part of Volvo’s continued Drive-E Powertrain research and development program. Just like its recently launched D4 engines, which combine 181 horsepower performance with CO2 emissions of 99g/km, Volvo said the Flybrid KERS tests deliver similarly impressive results and confirm that it is a lightweight, financially viable and very efficient solution.
The system is the first full-scale trial of a rear-axle mounted flywheel system in a front-wheel-drive passenger car and is the result of a partnership between Flybrid, Volvo and the Swedish government.
“This car is a great demonstration of how close to market this technology could be, and how class-leading fuel efficiency can be combined with real performance and driver enjoyment,” said Flybrid Automotive founder Jon Hilton, now Commercial Director of Torotrak plc following Flybrid’s acquisition by the Group in 2014.
The Flybrid KERS (Kinetic Energy Recovery System) being tested is installed on the rear axle of an S60 powered by a 254 horsepower five-cylinder T5 gasoline engine. Under braking, kinetic energy is transferred from the wheels to the KERS, and is used to spin a 6 kilograms carbon fiber flywheel at up to 60,000 revs per minute.
When the car starts moving again, energy stored in the spinning flywheel is transferred back to the rear wheels via a specially designed transmission, and can either boost power or reduce the load on the engine.
Using a stop-start system, 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.
“The flywheel’s stored energy is sufficient to power the car for short periods,” said Derek Crabb, Vice President Powertrain Engineering at Volvo Car Group. “This has a major impact on fuel consumption. Our calculations indicate that it will be possible to turn off the combustion engine about half the time when driving according to the official New European Driving Cycle.”
Volvo added since the flywheel is activated by braking, and the duration of the energy storage – that is to say the length of time the flywheel spins – is limited, the technology is at its most effective during driving featuring repeated deceleration and acceleration cycles. In other words, the fuel savings will be greatest when driving in busy urban traffic and during active driving.
If the energy in the flywheel is combined with the combustion engine’s full capacity, it will give the car an extra 80 horsepower. Partners said the experimental car, a Volvo S60 T5, accelerates from 0 to 62 mph 1.5 seconds quicker than the standard vehicle. The KERS drive to the rear wheels also offers the experimental car part-time four wheel drive to add extra traction and stability under acceleration.
According to Volvo, flywheel propulsion assistance was tested in a Volvo 260 back in the 1980s, and flywheels made of steel have been evaluated by various manufacturers in recent times. However this is not a viable option since a unit made of steel is large and heavy and has rather limited rotational capacity.
Flybrid explained the flywheel that Volvo Cars used in the experimental system is made with the combination of a steel hub and carbon fiber outer. It weighs about six kilograms and has a diameter of 20 centimeters. The carbon fiber wheel spins in a vacuum to minimize frictional losses.
“We are at Volvo Cars the first manufacturer that has applied flywheel technology to the rear axle of a car 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,” said Crabb.
