By Hamish Johnston

UPDATE: The race was won by the Michigan solar car (pictured above), which travelled from Dallas to Calgary in a little under 52 hours. The final results can be found here.

This morning 15 solar-powered cars will leave Medicine Hat, Alberta in a final dash to Calgary, a distance of about 300 km. If the fastest vehicle could maintain its top speed all the way, it could get there in less than two hours.

Unfortunately, the cars competing in the 2008 North American Solar Challenge must obey the speed limit — which I’m guessing on that stretch of the Trans Canada Highway is 110 km/h, much slower that the 160 km/h that some solar cars have been known to reach.

The race began on July 13 in Plano, Texas (near Dallas) and the cars travelled due north for about 2100 km before crossing the Canadian border just south of Winnipeg. Then it was a left turn for the remaining 1400 km to Calgary.

As of yesterday, the leading car was from the University of Michigan, which travelled from Plano to Medicine Hat in 47 hours of driving time. That’s an average speed of nearly 75 km/h (about 45 mph).

Not bad when you consider that the winner of the first such long distance race — held in Australia in 1982 — averaged just 23 km/h.

The race looks wide open this morning because the fastest five cars arrived in Medicine Hat separated by about 13 minutes. The other four challengers with a chance are Principia College in Illinois, Germany’s FH Bochum, the University of Waterloo in Ontario, and the University of Minnesota.

The weather forecast for southern Alberta calls for sunny skies…so the race could be over sooner rather than later.

There is (of course) lots of interesting physics related to solar cells and you can read all about it in this feature article (Bright outlook for solar cells) in Physics World.