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The Sun Race Gets Real

After a radical rule change, can the defending champion Nuon Solar Team win a fourth straight World Solar Challenge?

4 min read

Every two years, some of the world’s brightest young technologists get together in Australia to race across the continent on sunbeams alone. This World Solar Challenge, as it is known, is one of the greatest technology-based competitions on Earth. And since entering their first car in 2001, teams from the Delft University of Technology, in the Netherlands, have never lost.

Can the Dutch team grab an unprecedented fourth straight victory in the 2007 race? Despite the team’s recent domination (the smallest margin of victory was 33 minutes), it’s not a sure thing. The reason is that this year, it’s going to be a whole new race. In the 2005 contest the team’s winning entry, Nuna3, averaged 103 kilometers per hour—pretty close to the 110 km/h official speed limit on many Australian highways. So for this year’s race, which begins on 21 October, race officials rewrote the rules to make the cars safer—and, probably, slower.

For the first time, the drivers will have to wear crash helmets and sit upright, under a protective roll cage. The solar collector panels on the cars will also be limited to 6 square meters.

Members of the Dutch team, known as the Nuon Solar Team after its main sponsor, one of the largest Dutch electric utilities, are embracing the recent rule changes with their characteristic combination of grit and swagger. ”The technical challenge is back,” says Oliver van der Meer, a team member who is working on the aerodynamics of the vehicle. ”So we can show our prowess again,” he adds with a grin.

This past May, with five months to go before the start of the 2007 race, a reporter from IEEE Spectrum dropped in on the team at its comfy and frenetic headquarters in a building on the Delft campus. The team allowed the reporter to see the sleek, injection-molded composite-material body of its new vehicle, Nuna4, which it had just created and which was sitting upside down on a workbench in a nearby garage.

They forbid any pictures of the new racer, which is to be officially unveiled on 26 June. But they took the reporter on a tour that included their Nuna3 racer, whose 29 hours, 11 minutes in 2005 was the best ever for the approximately 3000-km race, first run in 1987. (That year, a car from General Motors called Sunraycer won with an average speed of 67 km/h.)

”It’s really an engineering competition now, rather than just putting more efficient solar panels on a light car,” says van der Meer, who, that Dutch name notwithstanding, actually hails from Portland, Oregon. Because the driver now has to sit upright, the front cross-sectional area of the cars must be larger, and the aerodynamics challenge that much greater, he notes. To design the new car’s aerodynamics, he assisted Susan Luijten, an aerospace engineering major and big Formula 1 racing fan.

”Three months of CFD” (computational fluid dynamics), he says, to sum up the magnitude of their effort. ”And another month and a half in a wind tunnel, with two different models,” he adds. Is he happy with the results? ”Let me tell you, it’s some extremely threatening data,” he says, the grin reappearing.

The total drag area of Nuna4 is higher than that of Nuna3, van der Meer says. But that’s because the frontal surface area of Nuna4 is considerably larger. Nuna4’s coefficient of drag—which does not take into account surface area—is lower, he adds.

Not only will the Nuon team not disclose the drag coefficient of Nuna4, it won’t reveal what the coefficient was for Nuna3. But in general, the coefficient for some competitive racers of that year was around 0.07. The frontal area of a solar racer is typically about one square meter or less. Those values multiply to give a total drag area of about 0.07 square meter. For comparison, a typical passenger sedan would have a total drag area about ten times that size.

Remarkably, despite the additional safety features demanded by the new rules, the Nuna4 car will be lighter and stiffer than Nuna3, promises Hjalmar Van Raemdonck, who is the team’s structural designer. Nuna3’s weight was about 190 kilograms. Van Raemdonck credited the use of advanced structural design methods from the aerospace industry for Nuna4’s presumably ethereal lightness.

The team lunches together every day in its cramped office. Today, it’s ”Turkish pizzas”—a big pita rolled and stuffed with a mouth-searing pizza filling and salad. They swig from bottles of cola and kid each other about their weight—the drivers haven’t been chosen yet, and the final selection will depend as much on body weight as on steely nerves and lightning reflexes. On tables, shelves, and the floor, crates of energy drinks and Belgian beer, loaves of bread, and bags of apples share space with various exotic, ultrahigh-performance vehicle parts: ceramic bearings, lightweight steering racks, and aramid-fiber tires from Michelin with superlow rolling resistance (they cost 250 apiece). It’s easy to see why budgets for competitive cars are now creeping toward US $2 million. Not including beer.

”They think I’m a reckless driver,” van der Meer confides. ”No, you’re just too fat,” quips Tine Lavrysen, the team’s petite communications director, laughing. They’re both on the short list to be drivers.

Asked how the Nuon Solar Team has managed to so thoroughly dominate in the competition, Lavrysen thinks for a moment before responding. ”Every team starts new,” she says. There are 11 people on the Nuon Solar Team, and not one of them worked on Nuna3. The 11 were chosen by Nuna3’s team, who then had very little to do with Nuna4, other than offering occasional informal advice when asked to do so. ”Because we start new each time, there are more chances of drastically changing the design. We can be really innovative,” says Lavrysen, a Belgian who just earned her bachelor’s degree in industrial design engineering. Other teams are typically far larger than Nuon’s, with people coming and going and working on more than one vehicle during their college years.

While the secret of their success may be moot, their record isn’t. ”They have a great legacy,” acknowledges Brian Ignaut, the leader of the team from the University of Michigan, a perennial rival. ”They came out in 2001, and kind of blew everyone away,” he notes. ”And since then, they’ve evolved—their designs have gotten better, and their overall execution is really clean.”

And while it’s great to have that kind of reputation, it comes with a certain burden. ”We’re gonna have a big problem on our hands if we don’t win,” says van der Meer, bravado slipping momentarily. ”We’ll be shamed for the rest of our lives.” Then the grin comes back. He likes their chances.

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