Volvo’s engineers reinvent the wheel
A NEW spin — if you’ll pardon the pun — has been put on fuel-saving energy recovery systems by Volvo.
Similar in principle to the kinetic energy recovery system (KERS) used in Formula 1, the Volvo set-up uses a flywheel instead of a battery to briefly store kinetic energy before redeploying it to the rear wheels, leaving the front wheels to be conventionally powered.
The Chinese-owned Swedish marque recently completed testing of the kinetic flywheel on public roads, and its results suggest the system will be financially viable provide and an ‘‘ecoefficient solution’’.
Volvo powertrain engineering vice-president Derek Crabb says the system gives an extra 80 horsepower and makes a car with a four-cylinder engine accelerate like one with a sixcylinder unit.
‘‘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,’’ he says.
The experimental flywheel KERS works within a vacuum and is fitted to the rear axle and — using braking energy — spins at up to 60,000rpm under braking; when the car accelerates, the flywheel’s rotation (and quick torque build-up) is transferred to the rear wheels via a system-specific transmission.
The front-drive combustion drivetrain shuts down as soon as brakes are applied, leaving the flywheel’s energy to accelerate or propel the vehicle once it s cruising again.
The system appears to be similar to a petrol-electric hybrid in the way that it can run with the internal combustion engine yet doesn’t require a heavy battery to store the energy or an electric motor to re-deploy it.
Porsche has also engaged in kinetic flywheel development as part of its hybrid drive-train programs, and Mazda recently introduced the i-Eloop system that uses a capacitor (lighter and more efficient than conventional battery systems) to store energy to run ancillary systems in the Mazda6.
‘‘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,’’ he says.
The flywheel technology test car, an S60, accelerates from 0 to 100km/h in 5.5 seconds — quicker than even the most powerful turbocharged six-cylinder Volvo model.
Volvo says it has been de- veloping flywheel systems as far back as the 1980s on the Volvo 260 sedan but that flywheels made of steel were large and too heavy, whereas the new experimental system is made of 200mm in diameter, is made from carbon fibre and weighs about 6kg.
‘‘We are the first manu- facturer 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,’’ he says.
Volvo powertrain engineering vice-president Derek Crabb demonstrates the car maker’s new kinetic energy system