Stanford car racers enter North American Solar Challenge

By Latice Strickland

From July 17 to July 27, about 30 cars will soak up the sun in the world's longest solar car race, the North American Solar Challenge. The Stanford Solar Car team will be among the participants, racing 2,500 miles from Austin, Texas, to Calgary, Canada.

"By working with our partners—the [U.S. Department of Energy], industry and these young leaders of tomorrow—we are helping advance renewable energy technologies, a key to reducing our greenhouse gas emissions," says R. John Efford, minister of Natural Resources Canada, a federal government department specializing in the sustainable development and use of natural resources.

The Stanford entry, with almost 40 sponsors (for a full list, see http://www.stanford.edu/group/solarcar/index.shtml), took about $250,000 and a year and a half to complete. Departing from the team's previous "Burner" car series, the 2005 vehicle, which looks like a UFO with wheels, has been christened "Solstice," named after the summer solstice, which is the longest day of the year.

Stanford's seven-year track record of competing in the Department of Energy-sponsored race gave the team an advantage in designing its latest car. Efficiency was the key factor.

For maximum energy conversion, the racers decided to use solar cells from Sun Power, a manufacturer of efficient solar cells. They also switched from using either lead acid or nickel metal hydride batteries to one made of lithium, an ultra-light metal that stores more energy per pound.

In practice trials, the sleek racecar uses 1,250 watts—the amount of energy used to power a blow dryer—to go 45 mph on sunlight alone. With the battery pack, the vehicle can zoom to 70 mph. Why use a battery on a solar-powered car at all? Battery packs store energy for the car to use at a later time.

"In the race we start off with a full battery pack, then it charges off the solar cell," explains team leader Eerik Hantsoo. "So the battery pack just acts as a buffer."

A significant change from prior years' cars is the use of a frame made of steel instead of a carbon composite. The steel frame is heavier, which means it is less efficient in terms of weight, but more efficient in terms of manufacturing time. While the carbon composite frame took six months to produce, the steel frame was formed in a matter of days. The team compensated for the frame's weight with an aerodynamically designed shell.

The group of Stanford engineers and computer scientists went to Texas on July 7. During this time before the big race begins, they are subjecting Solstice to final prepping and "scrutineering," as the Solar Challenge website (http://www.americansolarchallenge.org/) calls it. The team also will have to complete another qualifying round. In this round, drivers are required to ride a minimum of 140 miles in one day.

Even though only four team members take turns driving Solstice, 11 other team members are in Texas for the race. But the nondriving participants won't sit back and watch the competition from the sidelines. From start to finish, they will be en route with the car executing a lengthy list of tasks. While trailing Solstice in a "chase van," the team members will monitor weather, temperatures, speed and voltages. They will relay this information to the driver by CB radio.

The team members, who already have driven hundreds of test miles, aren't worried about qualifying. In fact, the racing team seems downright confident. Says team member Addison Shelton, "It's going to be exciting, especially after we win."

Latice Strickland is a science-writing intern at Stanford News Service.

Editor Note:

Science-writing intern Latice Strickland wrote this release. Photos of the car are available at http://newsphotos.stanford.edu.

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