Driving 2,400 miles across the scorching Midwest in July without air conditioning is not pleasant, but it’s the only way to win a solar car race.

Eighteen collegiate teams will brave temperatures in the 90s and roads littered with road kill during the North American Solar Challenge, a 10-day road race from Texas to Alberta in cars powered only by the sun.

“It’s about 95 degrees and humid,” says Kathy Van Wormer, co-captain of the Oregon State University Solar Vehicle Team. “In the car it’s about 110. But what’s got us worried is the wind. The car is shaped like an airplane wing.”

No one involved in the race thinks we’ll all be driving solar cars one day, even if Automobiles Venturi is developing a solar-hybrid sports car. A vehicle with the practicality and comforts consumers demand would require more photovoltaic cells than it could carry. But experts say the Solar Challenge advances power management, vehicle efficiency and other technologies essential to getting electric and plug-in hybrids on the road.

Putting solar cells on cars isn’t as crazy as you might think. The National Renewable Energy Laboratory is experimenting with solar cells on a plug-in hybrid. Fisker Automotive plans to include them on its Karma plug-in hybrid, and solar cells reportedly will power the air conditioning on the next-generation Toyota Prius. “There is a role for solar cells in cars,” says NREL spokesman George Douglas. “There are uses for solar power beyond propelling a car across the country.”

The biennial Challenge highlights how far solar and battery technology has come since the first race in 1990. Back then, everyone used lead-acid batteries, and the cars topped out at 25 mph. This year, lithium is the norm, and some of the 2-horsepower cars can hit 75 mph — but the rules limit them to 65 for safety reasons.

“We’re only geared to do 45,” Van Wormer says. “We didn’t want to go much faster than that. It’s all about maximizing efficiency and managing power.”

The team spent three years and $50,000 building Rain Dancer. The three-wheeler has a titanium frame and a body of fiberglass and carbon fiber. It’s covered with 418 monocrystalline silicon cells that the team didn’t receive until June 20. “We’d been looking for cells for two years,” she says. “There’s a huge shortage of cells right now.”

That didn’t leave much time for testing the car, but Van Wormer — who’s financing the team’s trip with her credit card — says it’s performed well during this week’s qualifying. “If it stays intact, we’re set,” she says.

Oregon State is a newcomer to the race, but the University of Michigan Solar Car Team is one of four groups that have competed in all nine events. It rolled up in an 18-wheeler and four SUVs donated by General Motors. With a $2.4 million budget (donated by more than 300 sponsors) and a $500,000 car, it’s the Scuderia Ferrari of solar racing.

Like Ferrari, its carbon-fiber car is state-of-the-art. Dubbed Continuum, it weighs 485 pounds and is covered with about 2,500 aerospace-grade gallium arsenide solar cells that team race manager Jeff Ferman says “put out about as much power as your hair dryer.” A 5-kilowatt lithium-polymer battery keeps the hub-mounted motor moving when the clouds come out.

It isn’t clouds Ferman is worried about, but storms. The team ran into some hail during a test run last month, and solar cells aren’t designed to take that kind of abuse. “If you were to even push down on them with your thumb, they’ll crack, he says.

The motor in Continuum produces about as much power as an Amish buggy, but speed doesn’t win the race. Strategy does.

“You’ve got to take the weather into consideration,” says race official Cheryl Williams. “You’ve got to take traffic into consideration. Are there hills? Stop signs? What speed is most efficient for your cells? It’s called a challenge for a reason.”

Wired.com