Big Changes Coming to Formula E

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Open wheel racing has always been a monument to technological innovation, with many features eventually finding their way into consumer vehicles.

However, every now and again, the process is reversed. New technology begins in the commercial sphere and later makes its way into racing. This reversed process is the current situation with the new Formula E racing series, which is the first to use all-electric vehicles in full-on Grand-Prix racing. 

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Figure 1: The DS Virgin Racing Formula E car (source: DS Virgin Racing)

In its inaugural season in 2015, there were eleven races in major cities around the world - each race is referred to as an "ePrix" - and ten teams, including DS Virgin Racing, who partner with Arrow Electronics. To get the series off to a smooth start, all the teams used the same model vehicle, the Spark-Renault SRT-01E, and had no freedom to make changes. 

Starting in Season 2, big changes are underway in Formula E. It's becoming an open class, and the regulations are changing year-by-year to allow greater room for innovation. The goal is to spur new development in electric vehicle technology that will then make its way back into the commercial sector. 

This year, approved manufacturers can develop their own electric powertrains (motors, inverters and gearboxes), and the power allowed on race day has increased from 150kW to 170kW. Racing teams can change to a new powertrain, or stick with the updated season 1 powertrain. 

In future seasons, the regulations will open up even more, allowing manufacturers to change battery technology if they wish.

The Formula E Car

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Figure 2: The Formula E race car (source: MMDI )

As seen in figure 2, a Formula E car looks superficially very similar to cars used in Formula 1 and other traditional racing classes, but there are some important differences. 

The chassis (1) is by the French firm Spark Racing Technology, which built 42 identical cars for season 1. McLaren Applied Technology supplied the powertrain (2) and electronics for season 1 with system integration (3) by Renault, but season 2 will see new units from 8 different manufacturers; the motor, inverter, gearbox and cooling system can all change. 

The battery (4) is from Williams Advanced Engineering and produces 200kW maximum power. Italian firm Dallara builds the monocoque chassis (5), which meets the same FIA crash tests used to regulate Formula 1. In contrast to Formula 1, the Formula E car only has a single tire design (6), from Michelin, which must be used in both wet and dry conditions.

Overview of the Powertrain

The biggest difference between Formula E and other racing classes is, of course, in the powertrain. 

A 2015 Formula 1 car uses a 1.6-litre V6 with a single turbocharger that runs at up to 15,000 RPM, produces around 600bhp, and gets around 5 mpg. In contrast, the Formula E car uses a synchronous electric motor running at 17,000 RPM that outputs up to 270bhp; weighing in at a measly 26kg (57 lbs). 

With less than half the power, performance isn't quite up to Formula 1 standards, but Formula E cars can still reach 100 km/h (62 mph) in 3 seconds, and attain a maximum speed of 225 km/h (140 mph).

What does it take to make a race-worthy electric powertrain? Figure 3 shows an overview of the Formula E system used in Season 1. 

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Figure 3: the Formula E powertrain (source: Sporting Savvy)

The battery pack (1), from Williams Advanced Engineering, consists of more than 150 off-the-shelf Li-ion polymer cells within a carbon-fiber composite housing. The whole unit weighs 320kg (705 lbs), a significant fraction of the minimum allowed weight (car plus driver) of 896kg (1975 lbs); the design draws upon Williams' experience with the Formula 1 kinetic energy recovery system (KERS). 

The battery assembly forms a structural component of the vehicle, so it needs to withstand the high stresses and forces caused by the car's interaction with the road. Although the batteries are capable of 200kW maximum power, during a race they deliver their average power output for a maximum of 25 minutes, after which drivers change into a new car. In season 1, there was only one battery failure during 440 race starts. This impressive achievement earned Williams the Royal Automobile Club's prestigious Simms Medal. 

Heat generation is always a concern with power electronics, and thermal management is one of the biggest design challenges. The Formula E vehicles use a liquid cooling system (2).  The coolant flows through two radiators, one in each side pod. A system of hoses routes the non-conductive dielectric coolant through every part of the battery and electronics.
McLaren created the eMotor (3) and 800V inverter (5) for their P1 hybrid supercar and adapted it for Formula E use. Its 200kW (268 hp) maximum output is reserved for practice and qualifying; during a race, the regulations restrict the power to 133kW (178 hp). A limited number of “push-to-pass” power boosts add an extra 67kW (90 hp) when needed. The engine acts as a generator during braking, recharging the battery and helping to slow the vehicle. 

The Hewland gearbox (4) is bolted to the rear of the engine and provides five speeds plus reverse.

How does this stack up against the motor in a standard electric car? Very well - the Formula E motor delivers 200kW from a 26kg package, for a power density of 7.7kW/kg. In contrast, the motor in the all-electric Nissan Leaf weighs 58kg (128lbs), outputs 80kW (110 hp), for a figure of 1.4 kW/kg. 

This powertrain was required on all Season 1 cars, but for Season 2, DS Virgin Racing is using their Virgin DSV-1, a new powertrain developed by Citroen, owner of the DS brand, in conjunction with Spark Racing Technology. 

The Formula E Vision

The FIA, Formula E's controlling authority, envisions using motorsport to promote the electric car industry and spur technological development, and it has ambitious plans for the class over the next few seasons. 

In season 2 we've seen new developments in powertrain technology. In season 3, the regulations will still retain the same chassis but allow different batteries. A big change will come in season 5 with only one car allowed per race.

There are non-technical rule changes, too, some of them controversial. In an effort to boost awareness and engagement, Fan Boost, new for Season 2, gives a five-second, 40bhp boost to three drivers based on a vote of fans. Voting can take place both before the race and during the first six minutes; it's possible that this might extend to the whole race in future years. 

Formula E has a broader vision than just racing and electric vehicles – they also aim to be a "vehicle" for change. 

The Formula E web site contains a section on sustainability with areas devoted to environmental policy, tips on green living, the RE100 global initiative and more. They also have partners such as ONE DROP, which works to provide sustainable access to water in underdeveloped countries. 

These are worthy goals, and Arrow Electronics is proud to be associated with Formula E.  Look for us to continue using our expertise in automobile-related electronic components to support DS Virgin Racing in this exciting endeavor.

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