Ideas to make electrification work in endurance racing

With the impending climate crisis, it’s more important than ever that we develop and deploy transportation technologies that minimize the impact of our daily transportation, including electric cars. Automakers have traditionally used motorsport as a venue for marketing their cars and their new technologies, and endurance racing has been one of the most road-relevant venues in the past. Electric cars, however, present a problem with that.

The problem

Endurance racing is, of course, one of the hardest tests of both car and driver… but it presents some unique challenges for electric vehicles, due to their charging requirements.

Modern top-class endurance racing, as practiced in the FIA World Endurance Championship, has a format based on three-driver crews (two-driver crews allowed for the shorter races). Refueling is done relatively quickly, and tires are routinely “triple-stinted” and “quadruple-stinted” – that is, only changed after three or four tanks of fuel. Drivers are typically changed at the same time as tires. All of this means that a typical pit stop is at most a minute with the car stationary, and a refueling-only pit stop is half that. With current technology, EVs take quite a lot longer than that to charge, and an EV sitting in the pits charging is an EV that’s losing the race.

Currently, most motorsport bodies that have an interest in electrification are focusing on short-range competition. Formula E comes to mind as the foremost example – relatively short races that take a bit over 45 minutes to complete, with one car (currently) completing the race on one charge of its battery. The cars are fairly slow as far as single-seater race cars go, to conserve energy, and the circuits are tight city circuits to bring competition closer together with these slow cars. This, however, doesn’t demonstrate endurance.

There are also EV-specific endurance races, like those in the Eco Grand Prix series, but this is not exactly a format that’s marketable, with only 22 kW charging. The winner of the most recent ecoGP race, a 24 hour race at Motorsport Arena Oschersleben in Germany, did an average of 49.84 km/h. Granted, this was a road car, not a purpose-built sports prototype, but this isn’t exactly exciting when compared to the 218.6 km/h of the most recent 24 Hours of Le Mans winner.

Possible solutions

There’s a bunch of ways to get an EV to be competitive against an ICE car in endurance racing, but some of them are more or less palatable than others. I’ll run through a few of them.

Relay races

In some amateur endurance racing series, it’s possible for teams to choose to run a relay race format of sorts. When a driver comes to the pits, their teammate leaves the pits in a different car, but under the same entry.

This format of changing cars at pit stops would work well for EVs. In fact, Formula E used a form of it – with the driver getting out of one car, and getting into a second car – in its first four seasons, as the spec battery in the first-generation Formula E car only had enough energy to complete half of the race distance.

However, this format was seen as laughable by many motorsports fans. And, honestly, it doesn’t look good if your goal is to market EVs – nobody in the real world is going to just jump into a second car instead of waiting for a charge on a road trip.

Handicapping

There’s a long history of handicapping in endurance racing, up to and including the 24 Hours of Le Mans, with things like the Index of Performance and Index of Thermal Efficiency, in which the “real” winner of the race wasn’t the car that traveled the furthest distance in 24 hours, but rather the one that did best compared to a formula of predicted performance.

It wouldn’t be beyond the pale to apply the same to allow an EV to win Le Mans…

…but it wouldn’t look good, either – there’s a reason why the ACO has moved away from that.

Battery swapping

Battery swapping could be very effective for getting an EV through a stint at Le Mans. No worries about charging time, the same car completes the whole race… but it’s not very road relevant. Let’s look at different scenarios in which an EV functions, to illustrate this.

The easiest thing for an EV to do is urban and suburban driving. Relatively short daily distances mean that overnight charging is extremely practical. The only caveat is charging availability for those who live in apartments – if they can’t charge at home or work, battery swapping and fast charging both become relevant in certain scenarios. Specifically, battery swapping works on light electric vehicles like Gogoro’s 50 cc-class and 125 cc-class electric scooters, where the batteries are light enough to be lifted out of the scooter and carried to a swap station.

Trucking is something that is seen as extremely hard for an EV, but as long as you can get enough battery in there at a reasonable weight, the charging requirements aren’t a problem, thanks to driving time regulations. Tesla claims 500 miles range fully loaded on their longer-range Semi, and claims a (fairly typical for EVs) 80% charge in 30 minutes. In the US, driving time regulations allow 11 hours of driving in a 14 hour period (with 10 hours of rest required to start a new 14 hour period), and 8 hours of driving without at least a 30 minute break. The numbers work out such that the mandatory 30 minute break after 7 or 8 hours of driving gets you more than enough charge to do the remainder of your driving for the day, before a slow overnight charge – you could even set a charge limit on that overnight charge to 80% to limit degradation, stop after 6 hours instead, and still be perfectly fine. So, battery swapping – while potentially trivial with trailer-mounted batteries – is unnecessary here.

So, that leaves long distance road trips. Driving time regulations don’t apply here, and breaks can be as long or as short as desired. However, battery swapping was tried for this, and failed in the market (both with Better Place and with Tesla) – DC fast charging was fast enough, especially as the normal breaks that a road tripper makes are long enough to get a significant charge. Personally, I end up having my own limits on drive time that mean that owning an EV would only affect where I stop for meals, not when I stop or how long I stop, on road trips.

All of this means that fast charging is a much more marketable technology for EVs, and the cost of safe battery swapping tech is wasted.

Driver limitations

Ever since 1990, all entrants at the 24 Hours of Le Mans have had three drivers on the crew, but before then, two drivers were allowed, and at one point were the norm. In 1952, Pierre Levegh nearly won the race as a single driver (although a co-driver was entered, Levegh refused to allow his co-driver to take over due to a problem with the car), before an engine failure in the final hour led to a failure to finish the race.

Limiting the number of drivers, especially in combination with limitations on driver time – mirroring the situation in trucking – could make an EV more feasible for endurance racing, as it would force everyone to spend time stationary in the pits. This would mirror real-life long-distance driving better… but endurance racing has historically been a test of both man and machine, and this would reduce the test of man. I think it’s a non-starter.

Energy limitations

A more recent trend in endurance racing is limiting the energy available to a car. It’s seen as a more fair way to get the effect of the Index of Thermal Efficiency, while producing the win on track, rather than through a formula calculated after the race.

As far as I’m aware, an energy limitation formula first appeared in endurance racing in the Group C era, where a limit on total fuel used in the race applied – 600 liters at 1000 km races, 2600 liters at the 24 Hours of Le Mans. Subsequently, the 2014 LMP1 regulations returned to energy limitation to encourage development of vehicle efficiency, with a per-lap fuel allowance (measured by monitoring fuel flow over a three-lap rolling average, so it can be exceeded one lap, but then a slow lap must be done to make up for it).

Today, the focus on energy efficiency in road cars is to minimize emissions of carbon dioxide and other greenhouse gases. So, a formula could be created in which cars are limited to a certain amount of GHG emissions per kilometer, in terms of “well to wheels” – that is, all emissions involved in generating the energy used by the car, as well as the car’s own emissions – CO2 equivalents. Note that this could be easily converted to the existing energy restriction format – a liter of a certain type of fuel will always have the same well to wheels CO2 equivalent emissions when burned, so ICE vehicles could simply have a fuel allowance per lap set to be equivalent to the GHG target. (This is made easier by the fact that most series use spec fuels.) Similarly, electric vehicles can be given a constant well to wheels CO2 equivalent emission factor per kilowatt-hour for a given grid region – and I would vary that based on averages for the local electricity grid at the track, even if the race’s power demands require generators or similar – and can be given a per-lap kWh allowance.

In practice, except in the dirtiest grid regions, this would have the effect of slowing the ICE cars first, as they’d immediately be limited by their CO2 emissions. EVs in an endurance racing scenario would be limited instead by charging speed, and would therefore not be slowed down by this formula at first. The effect would, eventually, be to create a “tortoise and hare” situation – the ICE tortoises would go slowly, but would pit quickly, whereas the EV hares would go quickly, but pit slowly.

This is a race narrative that we’ve seen in the past: a slower, more reliable team spending less time in the pits than a faster, less reliable team, creating drama over the entire 24 hours of the race. It doesn’t tend to create the closest on-track action, but it still creates a compelling story. It still allows the first car across the line to win, unlike formats like the Index of Thermal Efficiency. It encourages technological development. And, it’s an adjustable target, allowing the organizers to set the target based on what creates the closest competition.


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