Flywheels: Transitioning From F1 to Freeway
By John O'Dell April 1, 2008Part 2 of 2 Parts
Flybrid Systems' John Hilton and flywheel he says could replace hybrid battery.
By Bill Visnic, Contributor
Can a non-electric power booster developed for exotic Formula 1 racecars find a home on board the family sedan?
The British developers of an F1 kinetic energy recovery system – KERS -- that uses a flywheel instead of the typical hybrid's electric drive system say yes, with a qualification: The technology is more suited to a so-called mild hybrid application than to a full hybrid that requires power to be delivered over relatively lengthy periods.
John Hilton, managing partner of flywheel developer Flybrid Systems, says power delivery from his company's flywheel "is completely adjustable and can be delivered either in a short burst or over a longer period. This might even be driver selectable via a "sport mode" switch." Flybrid is supplying the flywheel for the Formula 1 KERS.
But with present technology the flywheel wouldn't be able to assist for long-duration events such as climbing a long mountain slope. That could come later, but for now "the conventional engine must be big enough to cover this requirement," Hilton said.
Mild, Not Wild
Specialists in Chrysler's powertrain and advanced vehicle engineering units who are familiar with flywheel technology agreed.
"Mild hybrid" is a more reasonable format, the Chrysler insiders say of a potential flywheel-hybrid road car. That's because flywheel designs have very limited energy-storage capability. The device can be brought to maximum speed very quickly, but as with a conventional battery, it won't store any more energy until some is removed.
This only works well in short, stop-and-go cycles, a Chrysler flywheel specialist said. Batteries can store much more energy for prolonged use.
Chrysler's experience with flywheels dates back to at least the early 1990s.
At the 1994 Detroit Auto Show , the company displayed an intriguing hybrid-powered endurance racer concept, the Chrysler Patriot, that used a flywheel to capture braking energy.
Chrysler envisioned a large, pizza-shaped flywheel for 1994 racecar concept.
Possibilities Plentiful
Martin Halley, chief engineer at Xtrac, the company that's integrating the F1 KERS package, says there are many options to consider in the transfer of the technology to future hybrid passenger cars.
"Would a flywheel mass storage system be applicable for [passenger-car] start-stop strategy or to power the auxiliaries" such as air-conditioning and radio? he asks.
"We believe both are potential applications of the technology, but subject to the size of the flywheel, compactness of the system and vehicle packaging issues," he says, answering his own question.
Energy storage requirements for stop-start application in a passenger car, for example, will be considerably less than that required in Formula 1 – so the 55-pound system required for an F1 car might translate into a 26-pound system packaged for road cars.
Although the technology is still maturing "it would be appropriate at this stage to consider it as an energy-saving system rather than a performance enhancing system" in passenger car applications, Halley says.
Full Hybrids Possible
Flybrid's Hilton maintains, however, that flywheel storage is intrinsically scalable, insinuating that full-hybrid applicability is not necessarily out of the question. Nor, he suggests, would cost be an issue.
"For a road-car application for a vehicle like a Toyota Prius, we estimate that the cost of our device would be around $2,000 per car – with a real opportunity to halve this number for bigger volumes."
That compares, he said, to what Flybird believes is a present cost to Toyota of $8,000 per car for the Prius' hybrid system.
"And although this price will fall with higher volumes, the quantity of rare metals required for the [Prius] battery means it will be difficult to ever make them for less than about $4,000," still twice the flywheel system's cost, Hilton said.
"The Flybrid device is made of steel and aluminum and the machining operations required are very conventional. The only slightly difficult part to make in high volume is the flywheel rim, which is composite, but fully automated machines for this process are being developed," he said.
Cost Still an Issue
That means the Flybrid design may be costly enough – at least right now – to make it difficult for the world outside of cost-is-no-object racing. But Chrysler's engineers say cost, if not too outrageous, can be reduced.
"All new technologies are very expensive, and it takes mass production to be feasible. There are proper applications for flywheel technology, and someday it may come to fruition," said one engineer. Right now, though, Chrysler’s focus for hybrid systems is electricity.
Battery technology is rapidly advancing – and once lithium-ion (battery) systems are prevalent, issues surrounding the cost, the weight, energy storage and packaging will be minimized, the Chrysler engineers maintain.
The KERS developers are understandably more upbeat about when we might see passenger-car hybrids using their technology.
CO2 Rules Could Help
They suggest sometime around 2012 as a likely target for production vehicles using flywheel-hybrid technology – a timeframe coinciding with proposed new European Union CO2-emissions rules.
"We are already in discussion with a number of OEM's regarding road-car applications," says Peter O'Neill, managing director of KERS transmission developer Torotrak.
Flybrid says the three companies hope to have running prototype of their system late this year or in 2009.
Timing notwithstanding, all three companies say they are convinced there will be flywheel-hybrid production cars. Formula 1 racing will help develop the technology – and deliver high-profile exposure.
"There are many instances in history where a new technology initially looks challenging to install in certain applications, only to find a few years later that it is smaller, lighter and better than anyone ever envisaged," Xtrac's Halley says.
"F1 will certainly help advance that process."
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