vol 9, issue 7

Formula E to test the limits of electric transport

14 July 2014
By Chris Edwards
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Formula E car

The first series of Formula E will begin in September when the drivers take to the streets of Beijing

Formula E battery

At 200kg, the battery in a Formula E car weighs about a quarter of the total weight of the vehicle

Sam Bird, driver, Virgin Racing team

‘If you make a mistake in practice it’s really going to hamper your weekend ... ’ 

Ten cities around the world will play host to an experiment to use racing to push electric vehicle design as Formula E takes to the streets later this year.

In the spring of 2011 Jean Todt of Formula One’s organising body FIA said it was time for the organisation to look at a type of race that would showcase technologies designed to deal with the environmental problems of motor transport. In September of this year, the 11 teams with all-electric open-wheeled race cars will head to one of the most polluted cities on Earth – Beijing – to kick off the first series of Formula E.

Unlike the distinctly petrol-headed F1 series, the cars will not roar as they rev up their engines. Although nowhere near as quiet as a Prius running around back streets on its electric engine, and more in line with a petrol-driven car passing at 70mph, the cars are expected to emit no more than 80dbA of noise as they charge past the finish line at speeds up to 225km/h. It will be way down from the ear-splitting 140dBA of F1 vehicles.

In a ‘burnout’ demonstration on an LA street last year, most of the noise came from the tyres as they slid on the road. As it revved up to leave a rubber stain on the streets, the engine noise was more reminiscent of a washing machine’s spin cycle and that was only when the driver put his foot down.

At a launch event last year, racing driver Lucas di Grassi said he noticed the difference with electric vehicles compared to conventional petrol-driven racers immediately: “The first thing you notice is the absence of vibration and noise, not when the car is running but when still or at low speed. You can hear what the car is doing... what the suspension is doing.”

But di Grassi stressed that in many other ways, Formula E cars, which go into full trials over the summer, will behave similarly to their petrol-driven counterparts. “Overall, the driving techniques will be very similar. Drivers who are good in Formula 1 will be good in Formula E.”

Urban street racing

Because of its showcase potential and Formula E Holdings chief Alejandro Agag’s belief that the electric car belongs in urban areas, the races will not be on long, remote, purpose-built courses. Instead, each of the ten races will be along city streets – sealing off parts of central London, for example, next June. Because of the disruption to busy city centres, practice, qualification and racing will take place in one day.

“If you make a mistake in practice it’s really going to hamper your weekend. So it’s going to favour those drivers that make no mistakes and at the same time are able to be quick straight out of the box,” says Sam Bird, one of the drivers for the Virgin Racing team.

Spectators close to the pits will get a clear view of one of the key problems that plagues electric vehicles: range. The battery is not big enough to keep the car running for the full duration of a race let alone practice and qualifying as well. At 30kWh and a maximum weight of 200kg, the battery capacity is limited to about half that of the base Tesla Model S road car, which has a range of 335km under normal driving conditions. A Formula E race will last around an hour.

One solution would be to swap batteries in and out during a pit stop, using similar techniques to those developed by failed Israeli company Better Place for road vehicles. However, the organisers claim safety concerns make a swappable battery difficult to implement. It would probably also increase vehicle weight – the battery is already a significant contributor at about a quarter of the total weight of vehicle and driver. The battery itself is twice as heavy as the maximum amount of petrol that an F1 car can carry over the entire course of a race. Thanks to the battery, a Formula E car is around 20 per cent heavier than an F1 car.

If the battery were scaled up to cover an entire race, it could easily soak up at least a third of the total weight and slow the vehicle down even further. Because of this, Formula E has gone for an approach reminiscent of endurance races such as Le Mans. Formula E is, after all, about the endurance of the technology.

Roughly halfway through the race, drivers will pull into the pits, clamber out and run over to another, fully charged car. After around 30 seconds of safety checks – drivers will not be allowed to perform the fast starts that were common in Le Mans endurance racing – the driver can re-enter the race and, with luck, take the car to the finish line.

 

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Pit-stop charging

Because everything is completed in one day, cars will have to charge in the pits whenever possible to ensure they can make it through the entire event. In keeping with the technology showcase element of Formula E, the safety car will be recharged wirelessly using systems supplied by Qualcomm’s Halo division. Keen to promote the wireless charging technology through Formula E, Qualcomm’s venture finance operation has put money into the championship.

Halo uses inductive charging technology to allow a car to charge while sitting on a powered pad instead of having to be plugged into the mains supply. Qualcomm claims the technology can deliver up to 20kW – about a tenth of the maximum power that the engine can draw from the battery during the practice and qualifying sessions – so that a battery could in principle be charged from empty in around 90 minutes.

To begin with, teams will use conventional wired charging connections but Qualcomm says it will make the Halo charger available to teams in the second season.

Like F1, Formula E teams will base their cars to some extent on standardised components built by companies such as McLaren, Renault and Williams. However, the standardisation is more to do with cost than trying to create a more level playing field – teams have greater latitude in picking components than their F1 counterparts if they feel they have the technology and expertise to do so. But the FIA is keen to ensure that it can get off to a good, competitive start by providing teams with the core components needed to ensure one well-financed group does not walk away with the championship and to prove the concept of electric racing with a low number of variables. During the first season, teams will use a car designed by French firm Spark Racing Technology. Drayson Racing expects to move to its own car design in 2015.

The battery design has been put together by Williams, which is using a currently undisclosed battery chemistry, although the choices are largely between variants of nickel metal hydride or lithium-polymer – the latter presents greater safety issues in an environment where sparks could be flying. Explosive chemistries and high-energy densities tend to go hand in hand in battery technology, although some researchers believe there are less flammable options waiting to be discovered.

McLaren Electronics Systems is no stranger to providing standardised components to racing teams. The company already produces the electronic control units (ECUs) that every F1 car now needs to have. The FIA chose to standardise on a single engine-controlling computer to reduce the software burden on teams. Now, individual teams only have access to parameters that they can use to trade off performance variables, although the FIA and McLaren are looking at ways in which the ECUs might support customised tasks so that teams can innovate further.

In Formula E, McLaren’s role expands to the ‘engine’ – the motor-generator unit (MGU). Cars can have one or two MGUs. At just over 25kg each they are so much lighter than a battery that using two is an option. However, teams are restricted on where they can fit them: they can only connect them to the rear axle. As a synchronous motor design, the MGU is capable of much higher torque and control than a petrol motor and also helps with braking when the motor shifts to being a part-time electric generator. The synchronous motors are controlled electronically – magnets on the stator help force the rotor to move under processor control. This allows for a much higher degree of acceleration and, conversely, braking.

Racegoers can expect to see a fair amount of wheel spin, especially as drivers are not allowed the luxury of traction control. But a quiet form of racing could need a bit of screeching to get going when the rubber doesn’t quite hit the road firmly enough.

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Competing incentives

F1 has already demonstrated that the technology developed in racing can spin off into road vehicles. The FIA has limited the amount of fuel cars can use during a race and made the engine specifications much closer to those of a road car.

Some technology spinoffs remain speciality products. McLaren’s carbon-fibre moulding technique to make lighter F1 racers has made it into road cars – but only as far as models such as the hyperexpensive MP4-12C. The chassis makes the road car lighter than a VW Golf – but with a price tag that makes the technology unlikely to cross over to mass production soon.

Having been a sponsor of McLaren’s F1 team, chipmaker Freescale sees more benefits than its logo speeding past TV cameras. “In motor sport there is a consistent level of innovation going on,” says Steve Wainwright, vice president of European sales and marketing at Freescale. “The other thing is system knowledge: do we understand the applications for our products as clearly as we can. Racing provides that.”

Technologies do not always translate well. The kinetic energy recovery system (KERS) used to claw back energy that is lost during braking and through the exhaust has road car manufacturers split. Mercedes has claimed that technologies such as flywheels do not work well in passenger cars. Volvo has taken a different tack by experimenting heavily with flywheel technology. But it has some way to go before it goes into production cars.

Larger vehicles have been able to use KERS – some London buses now use the technology developed by Williams, which has developed the battery for the first season of Formula E.

Other technologies being developed for Formula E may be less than suitable for road vehicles. If you only have to make 50 batteries a year for a race series, engineers have far more freedom over viable battery chemistries.

Professor Gerbrand Ceder of the Massachusetts Institute of Technology is trying to find new materials to replace those currently used in batteries. The only way to stop high-density batteries bursting into flames is to move to non-combustible electrolytes. The problem is finding one that works well as an electrolyte.

“Is this possible?” Prof Ceder asked. “We thought the answer was no. But researchers in Japan proved us wrong.”

The material was a mixture of lithium – already widely used in laptop and cellphone batteries – germanium, phosphorus and sulphur. “This is a solid in which the ions go as fast as through a liquid. This is an amazing material,” says Prof Ceder.

But there is a catch. Total production of germanium is around 30 tonnes a year. That is enough to satisfy the needs of the semiconductor industry and Formula E. But this will not sustain a worldwide electric vehicle industry. “Thirty tonnes is just two trucks,” says Prof Ceder.

A battery that works well in a low-run exercise like Formula E can use such exotic chemistries, but battery designers are looking for other options.

The question is whether teams in Formula E, when they get the choice of battery technology will move to the more exploitable option or the one that wins.

On the road charging

The architecture of the electric vehicles for Formula E is conceptually simple but involves a number of subtle tradeoffs to optimise efficiency. For much of the time, a battery feeds a synchronous motor, which uses permanent magnets to help move the rotor rather than the electromagnets typically used in the AC motors of washing machines.

As well as providing a high degree of torque, especially at low speeds, the synchronous motor can work in reverse – generating current from its own momentum. This lets the car recover energy easily, as the driver lifts their foot off the accelerator, that can be transferred back to the battery. Managing this process can be complex. The electronic control unit (ECU) needs to interpret commands from the accelerator pedal as requests for torque and determine when to switch from motor to generator control.

A problem for the battery is the stress of rapid charge and discharge cycles. It may make more sense to put a buffer of supercapacitors – electrochemical capacitors with an ability to store higher levels of charge temporarily – between the battery and motor. In principle, it is possible to replace the battery with supercapacitors entirely. However, they lag behind today’s batteries in terms of energy density and they leak current far more readily. They also present a serious safety hazard. It takes time for a battery to discharge through a short. A supercapacitor can discharge itself in a matter of seconds or less if a circuit fails.

Charging systems such as Qualcomm’s Halo, which is gradually being phased into the fabric of Formula E, could prove instrumental in changing the architecture of the electric vehicle towards the supercapacitor. Yoichi Hori, researcher at the University of Tokyo, believes future road vehicles will dispense with batteries altogether and receive power from the road as they move along, citing the relatively high efficiency of transfer. Magnetic resonance techniques have shown an efficiency of 95 per cent over a distance of 1m.

Without a battery, the lighter vehicles will store their energy temporarily in supercapacitors, sustaining them until the next delivery of charge. Researchers are looking at ways to detect electric vehicles as they move along so that coils buried under the road surface only activate when they are needed. The massive cost of energising the roads in rural areas compared to urban may mean electric vehicles adopt a hybrid design where the battery is still needed – to sustain the car long enough to find the next buried coil.

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