European Solar Challenge: modelling strategy

The iLumen European Solar Challenge at Circuit Zolder in Belgium is still expected to go ahead on 18–20 September (see my list of teams here). Following up on my earlier post about the sun at Zolder, here is a simplistic model of a hypothetical car under plausible (partly sunny) weather conditions:

The blue lines show energy output (in kWh) at three different speeds. Notice that the car is stationary during two charging periods (under regulation 3.10.1, each Challenger-class car may make two recharge stops, of at least one hour each; the timing of these is an important strategy choice). The car speed is assumed to be constant. In other words, variation in speed as the car drives around the circuit is completely ignored (see the circuit map below by Will Pittenger). For this hypothetical car, 52 km/h is the maximum speed.

The orange lines show corresponding energy input, from initial battery charge, two recharges, and solar panels. The iLumen European Solar Challenge (iESC) is a 24-hour race, with just under 12 hours taking place in the dark (grey area on the chart). On past trends, during September, the sun at Zolder shines for about 6 hours a day, and there is rain on one day in two. Only a few kWh therefore comes from the sun at the iESC. The race is, in fact, mostly won on aerodynamics, the rolling resistance of tyres, regenerative braking, and driving skill. The iESC organisers can, therefore, allow a mixture of different solar panel sizes without any unfairness, because smaller cars with smaller panels also have lower aerodynamic drag. I look forward to seeing how the various teams cope with this challenging race.

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