What format will Formula E races use?

 

The high-drag, winged, open wheeled, Formula E car, with its inherent inefficiencies, is capable of going fast, but not capable of going far. This means the organizers are struggling to find a race format that they think will appeal to fans.

 

How bad is the problem? A quick back of the envelope estimate gives us some idea. The battery pack they are able to fit in the chassis can deliver 28 kWhs. With only rear wheel regenerative braking, the driver will be lucky to get an additional 10% capacity which gives the team 30.8 kWh to work with.

 

As a model, Formula 1 cars on the Monaco street course are at full throttle 45% of the time, part throttle 43%, no throttle (braking) 12% of the time. If we say part throttle equals half throttle, we can then say that they run the equivalent of 66.5% of the time at full throttle [(45%*1)+(43%*1/2)+(12%*0) = 66.5%]. A Formula 1 car has much more horsepower but also has much more grip, so we can use this as a rough template for a Formula E's behavior.

 

The Formula E has a 200 kW motor. From the Monaco course model of the previous paragraph, Formula E power usage should be around 132.8 kWs (66.5% of 200 kWs). Under these conditions, the car can race for around 14 minutes (30.8kWh pack divided by 132.8 kW times 60 minutes).

 

Keeping in mind that the teams need to leave a cushion to make sure the car does not run out of power on the track, actual run times will be less.

So that gives us an idea of the magnitude of the challenge that the Formula E organizers face. What format can they use to provide a full day event around cars that can only race for less than 15 minutes?

 

An early band-aid was to cut motor power from the originally specified 200 kWs to 133 kWs (except for limited use of a 'Push to Pass' button). This brought race times up to almost 21 minutes [30.8kWh pack divided by 88.4kW (66.5% of 133 kWs) times 60 minutes].

 

They combined this with the decision that drivers would use two cars during the race, switching to the second car during a pit stop.

This was still short of their one hour race length goal, so the organizers proposed quickly recharging the first car and requiring a second pit stop for the driver to switch back to the recharged car. As was pointed out in "Technical flaws that could kill Formula E", the extra pit stop idea will not happen due to a myriad of problems.

 

The most recent Summary of Formula E Championship Regulations approved by the World Motor Sports Council at the April 11, 2014, FIA meeting requires only a single pit stop to switch cars. A number of other new rules, particularly the requirement that the battery pack last the full season, make any fast recharging strategy unlikely.

 

The latest rules specify that there will be one practice session and four qualifying sessions, but do not state clearly that there will be only one race. There have been discussions of having two main races. If each race is around 45 minutes and the cars can recharge in an hour and a half between sessions, the whole day's event can be completed in eight and a half hours.

 

Alternatively, the race organizers might stay with a single race and set the race distance to further than the cars can be expected to go at the 133 kW power level. This would force teams to run various power limiting, motor 'mapping' programs to stretch their energy allotments. This will increase the importance of drafting and alternative strategies (see "Improving the Show").

 

The challenge to this format is making driver strategy visible and accessible to the fans. Formula 1 has live real time data on fuel and power use but, at least in the US broadcasts, have yet to find a way to present the evolving story implicit in those numbers.

 

There is also the exciting but more radical approach to a race format that is detailed in "Saving Formula E".

The Formula E organizers have created a difficult challenge with their chosen formula car design. We hope they will be able to find a race format that works within its limits.

 
 
 
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