World Solar Challenge head to head: USA Challengers

The World Solar Challenge is an exciting race to find the best solar car in the world. That makes for serious competition between countries. But there are also some interesting contests within countries. The most obvious is between Nuon (3) and Twente (21), who came first and second in the Challenger class last time.

Within the USA, Michigan (2, Novum, above) has generally been the best, although Stanford (16, Sundae, below) has recently been close behind (see chart at top). This year, Michigan has “thought outside the box.” If their unusual design succeeds, they could win. If not, Stanford could take over as “Best in the West.” What will happen?

World Solar Challenge: Day 5

I was very happy to see the lead seven World Solar Challenge cars arrive in Adelaide today. The cars, with their approximate arrival times in Darwin time, were Nuon (team 3, Netherlands, 10:26), Twente (team 21, Netherlands, 10:35), Tokai (team 10, Japan, 11:20) – shown above – and Michigan (team 2, USA, 11:24), Punch (team 8, Belgium, 11:49), Stanford (team 16, USA, 13:54), and Kecskemét (team 23, Hungary, 15:34) – shown below. Add an hour to those times for Adelaide time, and another 20 minutes or so for them to get across the city from the timing point to Victoria Square.

Below is another race chart (as always, click to zoom). Data is taken from the official timing board for days 1 to 5 (but two obviously incorrect datapoints have been removed). In this chart, the distance is horizontal, and the vertical axis expresses time, specifically how many hours each car is behind a car driving at exactly 97.42 km/h (that’s the speed which would get a car into Adelaide at exactly closing time yesterday). Final positions on the vertical axis correspond to arrival times (but add an hour for Adelaide time, and another 20 minutes or so to get to Victoria Square). I have included Cruisers in this chart – note the compulsory overnight stop in Alice Springs for Cruiser cars.

I expect twelve cars to arrive during the course of Friday, including the top three Cruisers. The rules specify that “Solarcars must not proceed south of Port Augusta after 11:00 (Darwin time = 12:00 Adelaide time). Solarcars already running south of this point must trailer from this time.” It remains to be seen how many other cars will squeeze in under this limit to get into Adelaide on Saturday morning. In what I have started calling the B race, cars that have been trailered at some point will try to clock up as many solar kilometres as possible, given that limit, together with the closures of the Glendambo and Coober Pedy control stops at 11:20 and 14:00 tomorrow.

And here are the car positions this evening:

WSC: the areas of competition

In the World Solar Challenge, there are – as I see it – five key areas of competition. Winning the WSC requires doing well at all five.

Solar Cells

Solar cars run on solar energy, so the efficiency of the solar cells is critical. Going by what the teams report (in the histogram above) about 23% is typical (unfortunately, efficient solar cells are expensive). To get the best out of the solar cells, good MPPT electronics are also important.


Nuon Solar Team’s very aerodynamic Nuna8 (photo: Jan Willem de Venster)

At cruising speed, virtually all the solar energy goes into combating aerodynamic drag. The speed of the car at cruise is determined by the balance between electrical energy and drag. Reducing the drag coefficient is therefore an essential part of designing a fast car. Nuon Solar Team have been particularly good at this, partly because of input from aerospace engineering students at the Delft University of Technology. Computational Fluid Dynamics and wind-tunnel testing are two important techniques here.


The UNSW team perfecting their car (photo: UNSW Solar Racing Team)

Designing a fast car is not enough to win the World Solar Challenge, however. To travel 3,000 km along the less-than-perfect road from Darwin to Adelaide requires an extremely reliable car. Designing a car to survive the conditions means paying very careful attention to mechanical design.


University of Michigan running their practice race in 2015 (photo: University of Michigan Solar Car Team)

To develop a reliable car, extensive testing is important. To quote Rachel Abril from Stanford, “Test it. Test it again. Test it more.” However, testing is equally important in developing efficient race procedures, which is why teams like Michigan and Twente will run simulated practice races.

Race strategy

As part of managing the uncertainty about future sunshine, Solar Team Twente took a military meteorologist along for the 2013 WSC.

Finally, good race strategy is essential to doing well in the World Solar Challenge. This includes the psychological aspects of race strategy common to all forms of racing, together with choosing the optimum speed for the conditions (and also, in the Cruiser class, the optimum number of passengers). Managing the uncertainty about future sunshine is also critically important.

World Solar Challenge: Team 16

16  Stanford Solar Car Project (Arctan)

The team from Stanford University have competed in the World Solar Challenge several times, and came 4th in the Challenger class in 2013 (after Nuon, Tokai, and Twente). They recently produced an excellent documentary on their participation in that race:

This year, they are racing their new car, Arctan (below and top). The car is named in honour of a deceased team alumnus. Their website also has some interesting comments on their team structure and older vehicles. Good luck, team 16!

For up-to-date lists of all World Solar Challenge 2015 teams, see: