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 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.
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.
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.