Volvo has been testing a flywheel-based hybrid propulsion system that it claims can improve the fuel economy of its cars by as much as twenty-five per cent. The system, inspired by Formula One-style Kinetic Energy Recovery Systems (KERS) could provide a viable alternative to battery-based hybrid systems.
Volvo’s setup, tested in an S60, uses a four-cylinder internal combustion engine to drive the front wheels of the car and a six kilogram, 20 centimetre carbon fibre flywheel that can drive the rear axle. During braking, the engine is switched off and the flywheel begins to gather kinetic energy as it spins at up to 60,000 revolutions per minute.
Once the driver is ready to pull away, the still spinning flywheel engages with the rear axle, helping the car to pull away from a standstill. The same forces can also be used to assist the car while it is cruising.
As well as providing a boost in economy, Volvo’s flywheel technology can improve performance. Like the KERS systems in current Formula One cars, the unit provides an additional 80 horsepower and can help the prototype S60 complete the 0-62mph sprint in 5.5 seconds — that’s over a second faster than an S60 running Volvo’s 3-litre T6 six-cylinder engine.
Volvo’s flywheel system should really come into its own during urban driving. Indeed, Volvo suggests the internal combustion engine could be shut down for about fifty per cent of the time on the New European Driving Cycle, providing a massive boost in fuel savings and a significant reduction in emissions.
Assuming the system is as effective in practise as it is in theory, it could make for a compelling alternative to hybrid cars that use batteries and electric motors.
Volvo flywheel KERS pictures and video