World Solar Challenge: The Designs

The World Solar Challenge Challenger class is seeing some nice-looking solar cars this year. The majority of cars (19 so far, or 66% – teams 2, 3, 4, 5, 8, 9, 10, 13, 14, 16, 17, 18, 21, 23, 25, 26, 46, 77, and 82) are some form of the increasingly standard flat wing with asymmetrical cockpit. Solar Team Twente’s Red One (photo above by Jérôme Wassenaar) is a good example. This design has aerodynamic advantages, since the driver sits behind one of the front wheels (often, the asymmetry extends to propulsion as well, with only a single wheel being powered). Such asymmetrical cars were introduced at WSC 2013 by a few teams, including Nuon and Tokai.

However, some teams this year (9 so far, or 31% – teams 7, 15, 22, 27, 30, 32, 36, 47, and 51), have either retained or built some form of symmetrical wing, like Nagoya Institute of Technology’s Horizon Z (below).

Finally, Cambridge University’s Evolution (team 12, below) reflects a quite different, and rather promising, approach.

Update: see also the in-depth analysis at mostdece.blogspot.com.

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World Solar Challenge: Drag Coefficients

The drag coefficient measures how aerodynamic a shape, such as the body of a car, is – and therefore how energy-efficient the car will be when driving at speed. Some example values are shown below, listed from low-drag to high-drag. A solar-powered Hummer is probably not on the cards any time soon.

Entries hoping to win the World Solar Challenge Challenger class should be aiming at drag coefficients around 0.1. In the Cruiser class, values under 0.2 would be appropriate. This year, the wide range of car shapes in the World Solar Challenge demonstrates that there are many ways of achieving these goals.


0.07 – Nuon’s Nuna 3 (photo: Hans-Peter van Velthoven)


0.14 – Bochum’s SolarWorld GT (photo: “SolarLabor”)


0.19 – General Motors EV1 (photo: Rick Rowen)


0.26 – BMW i8 (photo: “youkeys”)


0.30 – Saab 92 (photo: “Liftarn”)

VolkswagenBeetle-001_800px
0.48 – Volkswagen Beetle (photo: Robert Couse-Baker)


0.57 – Hummer H2 (photo: Thomas Doerfer)