High-speed flywheels are one promising system designers are pursuing to meet forthcoming Formula 1 energy recovery rules. Motor Sport looks at the options
By Gordon Cruickshank
As a PR challenge, making Formula 1 look green ranks with making John McCririck look stylish.
But from 2009 (unless the teams’ request for a delay is granted) F1 introduces novel technology designed to boost efficiency which should have road car applications too, thus saving fuel, F1’s image, and the planet.
It centres on recovering kinetic energy thrown away in braking. Slowing any car uses friction to turn that energy into heat – and currently we chuck the heat away into the atmosphere. A Kinetic Energy Recovery System (KERS) aims to capture redundant energy, store it, then feed it back into accelerating the car out of a corner.
There are several ways to do this: in braking, a hydraulic pump can compress gas in a tank, later released to expand and drive back through the pump. Or electrical: putting a resistance across an integral generator/motor will slow the car (electric brakes are common on coaches), and this energy can be creamed off, stored in a battery, and then used to spin up the motor again.
But the F1 application requires grabbing power during braking, which may be intense but only lasts one or two seconds a time – not much time to compress air or boost a battery, even using advanced cells. Batteries and compression tanks are heavy and affected by temperature, and the output drops off as the energy is used. In addition, batteries have limited charge/discharge rates, lose efficiency over repeated cycles, and include costly rare minerals hard to recycle cleanly.
There is a mechanical alternative – connect a flywheel to the transmission and spin it up during braking. After the corner you reconnect it to the wheels, and as it slows it releases energy for acceleration. This way there’s no change of energy state from rotational to electrical to chemical and back, and every change means an efficiency loss. But to have a braking effect you need to gear up, so the flywheel revs rise rapidly, and for acceleration similarly gear down, and the ratio change must be both large and rapid. This is where one KERS project appears to score.
Some F1 teams are developing their own KERS, but there are also commercial projects which will be for sale. Arguably the most promising is the British combine of Torotrak, Xtrac and Flybrid Systems. Xtrac, which builds F1 and Le Mans transmission systems, looks after the mechanical engineering, based on Torotrak’s compact CVT design, while new company Flybrid Systems, formed by two ex-Renault F1 engineers, has developed the flywheel end and is integrating the complete system.
This meant solving a core difficulty of flywheels. For the same energy you can make it large or you can make it spin fast.
High speed has major advantages: it keeps the unit compact and sidesteps precession forces – the twist reaction all flywheels exhibit when turned – which rise with diameter. Flybrid’s unit spins at up to 60,000rpm, but this equates to a rim speed of Mach 3.3. “If we left air in there,” says Flybrid’s Jon Hilton, “it would run at 400 deg C. We avoid that by running the flywheel in a very high vacuum.” Despite having a rotating shaft entering the chamber, Hilton says that their bearing seal will retain the vacuum for an entire race weekend, without pumps.
What about the effects of a 150mph crash? Would the flywheel fire out shrapnel at Mach 3? Not according to Hilton, who has conducted a 20g impact trial. The unit contains energy dissipation rings which slow any disintegration and keep the shards inside the housing.
With these hurdles overcome, we have to connect the flywheel to the car wheels. Enter Torotrak’s CVT. This remarkable device offers continuously variable gear ratios via rollers running within a doughnut-shaped space formed between two discs, one driven by the engine, the other forming the output. If you swivel the rollers one way you connect the maximum radius on the driving disc to the minimum on the driven disc – gearing up. Swivel the other – minimum to maximum – and you gear down. The Torotrak design uses triple rollers and two disc sets to handle the torque, but as they are a licensing company it was Xtrac’s task to engineer and manufacture a version small enough for F1.
The principle, says Torotrak’s Chris Brockbank, is not new but the difference is in modern materials and control. The steel rollers do not quite touch the disc face; they ride on a microscopic film of synthetic fluid which ‘shears’ to provide very high grip with effectively no wear. The ratio spread of 1:6 matches a normal gearbox, but with a lighting-fast change which can go from high to low in one revolution.
Flybrid’s package integrates the flywheel, the CVT, a clutch to disconnect the flywheel at low car speed, an epicyclic gearbox which steps up the CVT revs five times to match the flywheel’s speed regime, and the electronic control system. This could offer many different modes, from overtaking power burst to a fuel-saving mode for in-laps or safety car periods. Flybrid is working with one F1 team so far, but until the system appears in a car we won’t know whether it might be used on a light throttle or with foot flat, but it must be driver-controlled. However, it is unlikely to be used to boost top speeds: as engine revs are limited to 19,000 you would need to raise the gearing to compensate, which would compromise the car at other times.
Only the KERS charge/release rate is limited, not the total storage, and the specified 60kw rate equates to an 80bhp surge for a maximum of 6.7 seconds per lap. When not ‘charging up’ the CVT adjusts ratios so the car does not ‘feel’ the flywheel. But, says Hilton, for a small increase in flywheel mass you can have a large increase in storage, another edge over batteries when the flow limit doubles in 2011. Meantime it makes a neat 24kg package, which according to Hilton is far more compact than the hydraulic/gas idea, and only half the weight of a battery system with close to double the wheel-to-wheel efficiency. “And,” he adds, “in F1 terms we’re cheap as chips. Initial costs are similar, but our unit will only need servicing every four races, like a gearbox. We estimate a season’s running costs of $2 million, whereas the electric guys are going to have to throw away their batteries every race and I can’t see that being less than $50m.”
Images released so far show a KERS unit on top of the gearbox, but according to Hilton designers, worried about keeping the centre of gravity low, want to place it on the crankshaft nose, in the fuel cell behind the driver. This highlights one advantage of an electric system – packaging. Batteries can be stowed around the car to benefit weight distribution, with generator/motors connected to any point in the transmission. When recovery/delivery is allowed on all four wheels from 2013 the balance may shift again – literally – as a mechanical system would require a second unit across the front axle. Of course, the over-gearbox option has the advantage of being removable, so avoiding the need for a unique KERS chassis. McLaren is only one team said to be building two different chassis for ’09.
Meanwhile, critics of KERS suggest minimal fuel savings, or even that a car without the weight of KERS (which is not compulsory for ’09) could be just as quick. McLaren-Mercedes, Renault and Ferrari have all expressed doubts about benefits versus development costs; BMW and Honda welcome it and its potential benefit for road cars, a feeling echoed by Brockbank. “You have to credit Max Mosley for arousing mainstream interest. I’m having conversations with car and bus people which wouldn’t have happened without KERS. It’s the FIA which is pushing this technology into road cars.”
Hilton says the Flybrid system could handle much higher energy figures, offering significant economies for road cars – the green spin-off Mosley is after. But while Torotrak, Xtrac and Flybrid can give convincing reasons why they have gone the flywheel route, some teams are pursuing other methods with equal commitment. Racing powertrain company Zytek is rumoured to be going electric, possibly with super-capacitors (a lightweight, short-term charge storage device) while Williams recently bought into a firm developing an electric flywheel, said to run at up to 100,000rpm. An integrated motor/flywheel would be powered up by a generator mounted wherever convenient on the transmission; for energy recovery the flywheel unit becomes a generator firing power back to a motor. This offers the packaging advantages of electrics but sidesteps the battery drawbacks. Honda, the only team yet to have run a KERS car, appears to favour this route. “That would be my second option,” says Hilton. “One energy change, but a lot of packaging flexibility.”
It’s hard to predict which KERS option will grab a lead through 2009, but whether or not Max succeeds in making F1 look green, there’s one certain result. This is the first time in years that we have seen ‘blue sky’ design ideas in Formula 1.
How the FIA banned KERS 10 years ago
In 1998 as McLaren’s ace designer, Adrian Newey helped to develop an energy recovery system. But initial support from the FIA soon turned to rejection
By Andrew Benson
Max Mosley is introducing energy recovery systems into Formula 1 from 2009 in an attempt to protect the sport from the inevitable criticisms that will come its way as climate change worsens and pressure inexorably increases on the world’s oil supplies.
It is a wise and responsible approach. Yet the history of energy recovery and storage in F1 is not quite as straightforward as that. In fact, F1 cars would have been using energy recovery systems for the past decade, had the FIA, with Mosley as the governing body’s president, not prevented it from happening.
In 1998, McLaren-Mercedes was developing a system designed to perform the same function as KERS. But after initially approving it, the FIA changed its mind and banned it.
The system was the brainchild of McLaren technical director Adrian Newey and his long-time friend Mario Illien, his counterpart at Mercedes engine builder Ilmor.
“Mario’s a very good all-round engineer,” Newey explains. “He has a broad interest in engineering matters, not simply motor racing, and has always been keen on energy conservation, which he demonstrated in the Ilmor factory, [with] little things like using the heat from the [engine] dynamometer water to heat the factory in the winter.
“He doesn’t like wastage. He likes to be efficient. We discussed that energy storage is used commercially in various areas, and we started to think, ‘this is something that could apply to F1.’”
That year’s McLaren, the MP4-13, was one of history’s great Grand Prix cars, and part of its advantage was in its light weight – as much as 40kg under the minimum limit. Newey and Illien started to think about how they could use the ballast needed to bring the car up to weight to gain performance – their answer was an energy recovery system.
They explored the various possibilities – a system based on batteries, which will probably be the most commonly used one in 2009, a flywheel, and hydraulics – and settled on hydraulics, even though, as Newey admits, it is “technically the least favourable”.
“We already had what’s known as a squish-plate pump, which is borrowed out of aircraft hydraulic pumps,” Newey says. “Basically it’s a very efficient, variable-displacement, variable-demand hydraulic pump. We were using that to power the hydraulics on the car, which at the time was reasonably advanced because lots of people were simply using gear pumps which were much more wasteful.
“So Mario had the idea, why don’t we go for a much higher output squish-plate pump and use that as a way of absorbing power from the rear axle under braking and being the motor in effect of putting the power back in under acceleration?”
High-pressure cylinders would have been placed alongside the engine as the energy store, and they would either be driven by the pump or drive it depending on whether the car was braking or accelerating.
Although McLaren recognised the system’s flaws compared to the alternatives, hydraulics was the approach they felt would give the most performance for the least development time. They could link it up relatively easily with technology already on the car, and the pump’s big benefit, Newey says, was “good response time” – one of the potential problems of a flywheel, which, like the battery system, would have taken much longer to develop.
The system, they calculated, would have given them a lap time gain in the region of 0.2sec – about half that being talked about with KERS for next year. “But we had a slightly different set of criteria,” Newey says, “in that we didn’t have any rules to work to, but we did have a tight budget and timescale. So we felt a guaranteed 0.2sec reasonably quickly was a much better route than a theoretical 0.4 two years away.”
Work started on the project, but then, Newey says, “very early on we recognised that we needed clarification on whether it was legal or not”.
The problem was the wording of the regulations, which said that propulsion had to come solely from a three-litre, four-stroke internal combustion engine.
“Of course,” Newey says, “the propulsion is initially being made by that, you’re simply re-harnessing it, and then reapplying it. But clearly there was going to be a debate on its legality, so we approached the FIA and they came back and said, no, it’s good, it’s exactly what we want, and yes, it’s legal as far as we’re concerned.”
Newey says that not only was the FIA aware of its potential benefits in terms of public relations for the wider sport, it had discussed these with McLaren.
“[The system was approved] in terms of new technology,” he says. “Even back then, green was starting to become an issue. It wasn’t quite as much in the forefront of the political agenda as it is now, but people were still talking about it, and this was something that was going to make a car more energy efficient.
“As far as we were concerned, we had the green light, regulation-wise, and then as we started to progress, suddenly we got a clarification saying, no, we’ve reconsidered and it’s not legal.”
Newey would not comment on what he thought had happened, but at the time the speculation was that – as had happened with a number of other systems over that period – Ferrari had got wind of it and lobbied against it, fearing they were going to be put at a competitive disadvantage.
Charlie Whiting, the FIA’s technical delegate at the time, says now that not only can he not remember what happened, or even much about the project, he cannot find a record of the clarification in question. But a glance in the record books confirms the banning of the system, and Whiting does admit a rule was added for 1999 to explicitly outlaw energy recovery systems.
Even now, Newey finds it difficult to hide his frustration – it was not the first nor the last time a team he was working for had a new technology outlawed in this way. In this case, though, that feeling is heightened by what he feels was a missed opportunity for F1 as a whole.
Japanese manufacturers had just started putting hybrid systems on their road cars, and this, Newey feels, would have speeded up their adoption.
“As a direct piece of technology, no [it wouldn’t], in as much as you wouldn’t choose hydraulics as the route for energy storage in road cars. But philosophically, yes. I’ve had a feeling for a long time that very rarely now, if ever, does a piece of F1 technology directly transfer on to a road car. But F1 does popularise general technologies.
“When F1 was using turbo-charged engines there were more turbo-charged sports cars around. Nowadays, every self-respecting boy racer wants flipper gear changes on his steering wheel. He also wants fake carbon-fibre trim. There is no doubt F1 technology in general does create showroom demand.”
Equally, once energy storage had been adopted in F1 by one team, there would have been a rush by the others to catch up. And inevitably that would have led to more efficient systems – such as battery-based technology. Despite his frustration, Newey welcomes the introduction of energy storage into F1.
“Quite rightly, Max – and I’ve had discussions with him about this – feels that potentially F1 could easily be criticised in this green age as being a wasteful and extravagant arena. So trying to show an awareness of that with a regulation designed to encourage the development of fuel-efficient cars is good for F1. It protects itself from that [allegation] by doing so.”
Is Mosley aware of the irony that the FIA banned something that would have seen F1 set the agenda with this technology, providing an even more powerful defence against its detractors?
“You’ll have to ask him that one.”
Has it come up?
“I haven’t raised it, no. I want to keep my pass.”