“Clearly to do that we have to run the flywheel in a vacuum, or the air friction that we would get on the outside of the flywheel would cause very high energy loss,” says Greenwood. “It would also heat up the composite to the point at which it would disintegrate.”
To maintain the vacuum the flywheel is in a sealed chamber, and a magnetic coupling is used.
“We take all of the drive out with a set of magnets which sit on the outside of the flywheel casing, and because of the clever way that we have arranged the magnets you get a gear ratio between the two,” he says.
“That means that although everything is rotating very fast inside the vacuum chamber, everything outside is rotating at relatively normal speeds.”
That reduces any drag and air resistance. And because the flywheel is rotating so fast, the engineers do not need very much torque to get a very high power from it, which reduces the strain on the magnetic coupling.
One of the first mass uses of fly wheels might be the “Flybus” – not, as the name would suggest, an airport shuttle - but a bus fitted with a flywheel. Buses have a long history of using flywheels stretching back to the 1940s when Swiss firm Oerlikon introduced the Gyrobus. But early designs needed fixed charging points at bus stops and junctions to give the flywheel a boost. But, like with cars, the ability to recover energy from the braking process means they are now more viable. And because their routes are by design stop-start, energy recovery could improve fuel consumption.
“It’s a technology which lends itself very well to working at very high power, but not needing to store energy for a very long time,” says Greenwood.
It is a sector that Williams also has its eye on with its GyroDrive technology. It claims that a flywheel – either retrofitted or built in to a new bus – could save up to 30% of fuel, along with associated CO2. The firm also envisages the system being used to power onboard lights and electrical systems.
And once it has proven itself to be safe, reliable, cheap, and effective, the technology may then begin to trickle down into other use. Experts currently believe it is about five years until flywheel technology being incorporated into passenger cars. When it is, it could offer an improvement in fuel consumption of 12-15%, for about half the price of a conventional hybrid, not to mention the performance gains that are so attractive to motorsports teams.
From racetracks to roads, it seems everyone could benefit from reinventing the wheel.