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Magneti Marelli and Flybrid Systems Collaborate on “Flywheel Capacitor” for KERS

Italian motorsport electronics specialist Magneti Marelli and UK high-speed flywheel specialist Flybrid Systems are collaborating to develop a new energy storage solution for Kinetic Energy Recovery Systems (KERS). The new product is targeted to be a high-power electrical storage system for hybrid racing cars capable of deep depths of discharge with no performance degradation and a long service life.

The new product—named the Flywheel Capacitor—consists of a high-speed carbon fiber flywheel incorporating Flybrid technology connected to a high-speed electric motor generator using technology from Magneti Marelli, all managed by Magneti Marelli’s control electronics.

The device works by applying to the electric motor generator the recovered electrical energy captured from the vehicle during braking events. The energy is stored into the Flywheel Capacitor by speeding up the flywheel. During the acceleration events of the vehicle, the energy stored into the flywheel capacitor is returned to the vehicle by transforming the kinetic energy of the flywheel into electrical energy via the motor generator.

The Flywheel capacitor will not use chemical battery-based energy storage systems.

The first Flywheel Capacitor to be developed will have a specification of 60 kW power and 600 kJ total storage capacity but the specification can be readily adapted to any vehicle requirements. Both partners will draw upon extensive experience with their own KERS products to deliver a working prototype in the next few months.

The electric motor and flywheel will rotate at up to 60,000 RPM and the flywheel will sit inside an evacuated chamber that includes special containment features to ensure complete safety. A small electric pump will occasionally top up the vacuum so that no regular maintenance is required.

State of the art magnetic design of the motor generator and high efficiency electronics are expected to deliver round trip storage efficiencies approaching 80%. The device has a low cooling requirement and contains no flammable materials. The complete flywheel capacitor including the associated electronics is expected to weigh just 20 kg.

This is an exciting new development that will deliver a high end product capable of exploitation in F1 but also suitable for more widespread use in motorsport. As well as offering low running costs the flywheel capacitor is a green alternative to regularly replacing batteries.

—Jon Hilton, Flybrid Systems Managing Partner

The new flywheel capacitor product will be commercially available from both Magneti Marelli and Flybrid Systems. Both companies will continue to develop, manufacture and distribute their own existing KERS products—a battery-based system from Magneti Marelli and a flywheel-based system from Flybrid (earlier post).



It seems to me that a flywheel with substantial mass would act like a gyroscope. Could be good for keeping the car level during high speed banked cornering on the race track. Or could be bad.


Flywheel hybrids would be really handy for grid frequency control, and should be quite straight forward to retrofit existing vehicles.

Neil, in answer to your question the energy contained in a flywheel depends on the rotational speed squared so to get maxium energy storage you want minimal mass and high rotational speed, carbon fibre is about the only material strong enough to use in these applications.

A winning technology would be turning hemp into carbon fibre flywheels. Store the carbon, saving carbon


if it's spinning on a vertical axis, then there's no affect on turning.


"if it's spinning on a vertical axis, then there's no affect on turning."

If the car is going uphill then reaches a level section, it will have tendency to take off.
Or downhill then level - front end will plunge. In both cases handling can be seriously affected.

Austrian A1 ring (no longer on F1 calendar) had uphill section. Also Japanese (? Suzuka) is a two level circuit (with overpass), so it must have uphill/ downhill sections - it has been replaced in F1 with another Japanese venue. But KERS is not limited to F1, other racing series may introduce it soon.
Laguna Seca is not flat either.


neophyte question:
if you had both a vertically rotating and a horizontally rotating flywheel would they cancel out each other's gyro effect?


WOW! Look at that specific power! Incredible!

What would be great is having these on everyday cars with low displacement atkinson cycle engines and IVTs. If you wanted to drive like an ass, you could just drop it into a sports mode where your engine "charges" the KERS for overtaking manouvers.

Or, you could leave it in economy mode and get phenominal fuel economy.


This is excellent timing for F1.

It has just been announced that next year teams will be allowed to run KERS at 120 kW. That's a massive 160 bhp boost that would make teams without it completely uncompetitive.

At the moment, Renault and Ferrari are dependent on Magneti Marelli KERS equipment, so will be pleased to see there is a flywheel option from next year to compete with Williams who already have a flywheel system.

Incidentally, a 120 kW flywheel system would weight 40 kg, and a 120 kW battery 24 kg, but the flywheel could require less cooling (so better aerodynamics).


Mounting the flywheel assembly on gimabals should solve the gyroscopic problems.

It would be interesting to know if the flywheel is equipped with magnetic bearings.


The energy density of a good flywheel is in the range of 130 Watt hours per kg. Life cycles of one hundred thousand to ten million have been reported. Also they contain no toxic materials making them relatively benign to the environment.


"The energy density of a good flywheel is in the range of 130 Watt hours per kg."

Is that for everything in the system or just the flywheel?


Two flywheels rotating in opposite directions will generate some big forces between the wheels but they will be opposite and cancel.

Gimbals might be better but must have adequate range of motion and "swing" space.

Henry Gibson

The maximum energy density for any flywheel material is the strength divded by the density. Every material has a feet per second rating. Small diameter wheels can run at higher speed. A properly designed flywheel hybrid has most of the advantages of a battery hybrid. ..HG..

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