How solar is that solar car?

Above (click to zoom) is a chart showing WLTP-standard solar-only driving ranges for the three solar cars from my last post (battery ranges not shown here):

  • Solar Team Eindhoven’s Stella Era, winner of the BWSC Cruiser class
  • Lightyear One, a commercial solar car from the Netherlands
  • The Sion electric vehicle from Sono Motors

These solar-only driving ranges are marked on a smoothed distribution of electric vehicle driving patterns reported in this paper (distance driven per vehicle-day on days when the vehicle was driven).

The sleek Stella Era has a solar-only range more than 4 times the mean 70 km driven. On more than 99% of trips, Stella Era can operate solar-only, and, on average, its solar panel produces substantial excess electricity which can be donated to other vehicles.

Lightyear One has a solar-only range less than the mean 70 km, but is still able to operate solar-only on 57% of trips.

The less expensive Sion is able to operate solar-only on 19% of trips, and has a useful solar boost to its battery the rest of the time.

4 thoughts on “How solar is that solar car?

  1. A nice follow up to your previous piece Tony.
    Of course, one crucial piece of data is missing from the source paper – the time that elapses between individual trips in each day. If we were able to factor in the re-charging that would occur on a typical working day(ie whilst the car is parked) then the percentages would be significantly improved for both the Lightyear and Sono vehicles.

  2. If I understand the previous post (where these numbers are taken from) correctly, this is the bonus range added by solar during the time the car is traveling on battery power. As such, calling it “solar only range” is deceptive, as it suggest the car can travel on solar power only.

    Instead, this should be called something like “solar boost” and should be expressed as a percentage of the vehicle’s battery range. That way, the number would be an actual measure of the effectiveness of the solar power system of the vehicle. Expressing the value in miles means that you can improve the value by adding more batteries to the vehicle, which makes it a useless value for measuring how good a solar car the vehicle is.

    Expressing it as a percentage would effectively mean: what proportion of the time the vehicle spends in the sun can it be driven. A value of 100% would mean the vehicle can drive in the sun without its battery depleting.

    • Well, you still need a battery, obviously, but if you stay within the “solar only range,” then on an average day there would be no net battery drain, and you wouldn’t have to recharge. So “solar only range” is a fair term.

      The point of this chart is that, for the average user, Stella Era could operate without recharging just about every day (a few very long trips excepted); Lightyear One could do so on over half the days; the Sion on about 1 day in 5.

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