More details about the flywheel 'kinetic energy recovery system'

Do your remember the hybrid system that stores braking energy not as electricity but in a rotating flywheel as kinetic energy? Well, the system is going to be mated to a special CVT transmission able to change 6-to-1 ratio within one revolution. That is, in 50 ms, the transmission can go to almost zero to full power.

The Kinetic Energy Recovery System (KERS), which is soon going to be tested with a Chevy V8 engine, becomes part of the transmission system of the car and it is light: for F1 applications, the variator and flywheel each weigh less than 5kg in a system with a total mass that does not exceed 25kg. This is both good for the upcoming Formula 1 hybrid racers and for regular car use, where it has a huge potential to help reduce CO2 emissions and pollutants.

The developers say that the device is twice as efficient as electric hybrids. And it's got an additional benefit: since the flywheel is vacuum sealed, the system is silent, except for the links to the transmission and bearings, which is something they're working on.

The flywheel is made from high-strength steel and composite material in which the maximum stresses are less than in the con-rod of a conventional internal combustion engine.

Flybrid, Torotrak and Xtrac promise to keep us updated on the evolution of this system, which you can check by clicking the Read link. Full press release after the jump.

[Source: Flybrid]

Xtrac and Flybrid to reveal technical details of flywheel 'kinetic energy recovery system' at global conference

* Motorsport experts to discuss mechanical alternative to hybrid electric vehicle technology for future road cars
* Fast-acting flywheel system offers up to twice the efficiency, half the mass and more rapid transfer of energy compared with current battery systems

Martin Halley, chief engineer with transmission technology specialist Xtrac and Jon Hilton, managing partner of Flybrid Systems, a new company taking a fresh look at hybrid vehicle technology, will describe the technical innovations behind their groundbreaking mechanical flywheel 'kinetic energy recovery system' (KERS) - which also incorporates advanced traction drive technology from Torotrak - at a forthcoming high-level motorsport industry conference.

"The Federation Internationale de l'Automobile (FIA) regulatory body, which governs motorsport, has recognised that motor racing provides a unique opportunity to demonstrate new technologies which could be relevant to the automotive mainstream," said Halley, whose presentation will provide an overview of new F1 regulations and the technology and materials required to develop the sophisticated transmission system required for a mechanical based KERS system.

"The new rules being drawn up for F1 will stimulate the development of new and exciting technologies, within a competitive environment, which may otherwise not have occurred. This means rapid product development is required right here and right now," commented Hilton, whose technical paper will discuss the recovery and storage of braking energy in a mechanical-based flywheel system.

Flybrid has already secured one unnamed F1 team as a customer and is confident others will follow given the benefits of a fast-acting flywheel system, which offers up to twice the efficiency, half the mass and more rapid transfer of energy compared with hybrid battery electrical systems. The company is also well on its way to bench testing a flywheel KERS system adapted for road car applications using a Chevrolet V8 engine.

Flybrid's brake regenerative system uses advanced gearbox technology provided by transmission specialists Torotrak and Xtrac. The system employs a small and sophisticated ancillary gearbox manufactured by Xtrac incorporating a continuously variable transmission (CVT) design licensed from Torotrak. Torotrak's patented traction drive technology is being developed for motorsport applications by Xtrac under an exclusive licensing agreement. Xtrac can sub-license the CVT 'variator' technology to Flybrid and other motorsport teams who may wish to design and build their own flywheel.

The role played by Flybrid, Torotrak and Xtrac in designing a mechanical KERS solution for F1 could be instrumental in developing this pioneering vehicle technology for more fuel efficient road cars without resorting to the expense and complexity of battery systems. Compared with hybrid electric vehicles, which use batteries for energy storage, a mechanical KERS system utilises flywheel technology as a highly efficient alternative to recover and store a moving vehicle's kinetic energy.

The combination of gearbox-variator and flywheel would form part of the driveline assembly. The kinetic energy is stored during a braking manoeuvre and is then released back into the driveline as the vehicle accelerates. Flybrid, Torotrak and Xtrac claim that compared to the alternative of battery systems, a mechanical KERS system can provide a more compact, lighter and environmentally-friendly solution.

Torotrak's patented technology is a vital element in a mechanical system as it provides a continuously variable connection between the flywheel and the vehicle driveline. Xtrac's exclusive licence and development of the system for motorsport applications allows it to design, manufacture, assemble and distribute complete variator systems and discrete components to F1 and other motorsport customers.

For F1 applications, the variator and flywheel each weigh less than 5kg in a system with a total mass not exceeding 25kg. This relatively low mass is a major advantage both for race and road cars. The high level of mechanical efficiency combined with the variator's ability to change ratio very rapidly helps to optimise flywheel performance. The transmission system selects the appropriate ratio depending on the torque demand and can change its 6-to-1 ratio within one revolution.

"Performance calculations show we can go from zero to full power in 50ms," says Hilton. "This is faster than the driver can apply the brake pedal."

Flybrid, Torotrak and Xtrac all see the potential for wider application beyond motorsport – initially on high-performance road cars – both as an aid to performance and as a means of developing vehicles with reduced fuel consumption and CO2 levels. Applied to road cars the system supports the current motor industry trend for smaller powertrains; a lightweight kinetic energy recovery system providing a means of boosting acceleration and overall performance and economy independently of the vehicle's internal combustion engine.

An ancillary flywheel is particularly suited to stop-start driving situations when real-world fuel economy is often at its worst. In these conditions, the variator can assist the launch of a vehicle which has slowed down or come to a standstill. In heavily congested traffic, where a car is frequently stopped and restarted, the system can help alleviate the heavy fuel consumption and emissions of greenhouse gasses normally associated with these conditions. However, unlike hybrid electric vehicles, a mechanical KERS system continues to provide the benefits of kinetic energy recovery throughout the speed range, and its benefits are maintained on the open road.

"This is a major plus point for a mechanically-based kinetic energy recovery system," says Halley, "in which the variator can also handle energy flows a lot faster than an electric vehicle."

"On a directly comparable basis, a flywheel system offers up to twice the efficiency of a kinetic energy recovery system that stores its energy in a battery," adds Hilton. "The overall in-out efficiency of a mechanical drivetrain feeding energy into a flywheel and back out to the vehicle again via an ancillary transmission system is approximately 65-70 per cent compared with 35-45 per cent for a hybrid battery-electric system. Fundamentally, this is because a purely mechanical system doesn't have to convert the kinetic energy into electrical and chemical energy as with a battery system."

"What this means is that with a flywheel each time the brakes are applied at least 65 per cent of the energy is available to re-accelerate the vehicle," explains Hilton, "whereas the best that can be achieved with existing battery technology is 45 per cent."

Flybrid has filed various technical patents to tackle the key engineering issues of safety and noise. The flywheel is made from high-strength steel and composite material and has been designed with a high factor of safety in which the maximum stresses are significantly less than in the con-rod of a conventional internal combustion engine.

"The flywheel also runs in a vacuum which is a natural barrier to noise," says Hilton. "For optimum refinement in a road car the engineering effort would be focussed on the transmission system and bearings - which provides the only noise path - it's exactly the same test and development process in other words as for a normal powertrain."

Halley and Hilton will join other influential figures from the automotive and motorsport industries attending the Global Motorsports Congress being held in Cologne on 5-6 November 2007 - where the hot topic of conversation is expected to be the future eco-friendliness of motorsport and the 'green revolution' in F1 envisaged by FIA president Max Mosley. This leading global industry event takes place the same week and in the same location as the Professional MotorSport World Expo, where Xtrac will be exhibiting a wide range of transmission systems alongside other leading motorsport manufacturers.

Later this year Chris Brockbank business development manager Torotrak will present a paper describing the sophisticated variator traction drive technology, which is a key part of the mechanical KERS system, at the CTi Transmission Symposium on 4/5 Dec 2007 in Berlin.

Adrian Moore, technical director, Xtrac, will similarly present a technical paper describing the technology behind the KERS system at the World Motorsport Symposium, which takes place on 29/30 November at Oxford Brooks University's brand new engineering centre. He joins other senior engineers who will be bringing their particular expertise to bear on subjects that are of special relevance to the growing demand that motorsport technologies should be of more relevance to the road car of tomorrow.

Moore will also discuss the mechanical KERS system with mainstream automotive engineers and technical experts attending the Global Powertrain Congress being held in Vaals in the Netherlands in June 2008.

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