Gear Up for a Four-Day Race, Fueled by the Sun
Solar-powered cars test new technology, increase public awareness in 'Sunrayce'
Boston, Mass. — With its annual Memorial Day auto race, Indianapolis is used to high-performance cars. Today the city is the starting point for an assortment of less conventional high-tech racers, bound for Golden, Colo.
The event is Sunrayce '95, a competition among 40 solar-powered cars designed by students from colleges, universities, and vocational schools in the United States, Canada, and Mexico. In this four-day contest, lightness, strength, efficiency, and aerodynamics replace brute horsepower as keys to winning.
The purpose of the race is twofold, according to race director Richard King, who also works in the US Department of Energy's photovoltaic research program. "We want to increase public awareness of photovoltaic technology," he says, referring to the solar cells the cars use to convert sunlight into electricity. And, he adds, the now-biennial event is designed to stimulate science and engineering education.
The rules are simple: Sunlight is the only allowable external energy source; only lead-acid batteries and off-the shelf solar cells designed for terrestrial use may be used; battery weight is limited to 308 pounds; and the cars must have safety features such as seat belts, turn indicators, brake lights, and a rear-view mirror.
The requirements for solar cells and batteries, in particular, help level the playing field and prevent the contest from becoming a fund-raising race. "You can easily spend $500,000 for solar cells and $30,000 for batteries if you use space-grade devices," Mr. King says. "I saw students break down and cry when their $100,000 photovoltaic array didn't work. Besides, we're interested in putting this stuff on your house and in your car, not in space."
Faced with tight restrictions on the energy source, students try to make the most they can out of lightweight composite materials, aerodynamic designs, and custom electronic controls.
Steve Garrison specializes in electronic controls. He heads the electronics-design team for the car entered by the University of Massachusetts at Lowell, one of 30 seeded teams. He points to the school's 1993 entry to describe to a visitor the changes being incorporated into the new car. During this visit, about 10 days prior to the race, the car is in several places at the same time: The frame is out being welded, courtesy of the local welders' union apprentice program; parts of the Kevlar laminate body are being "cooked" in an oven at a New Hampshire fabricator. (In term-paper fashion, all of the subassemblies didn't begin to come together until the day the team was to leave for Indianapolis.)
When Mr. Garrison transferred from the state of Washington, he "brought a couple of technical secrets with me," he says. Among them: using solar cells with a textured pattern etched into them. The raised portion of the patterns help collect sunlight coming in at odd angles and they also act as tiny cooling fins. "The cooler the cells are, the more power you get," he explains.
The students also designed custom "trackers" to wring maximum efficiency from arrays of solar cells. Terrestrial-grade solar cells convert up to 15 percent of the sunlight they receive into electricity. But a group of cells runs only as efficiently as the least efficient cell in the grid. The trackers gauge each cell's efficiency and electronically link it with cells operating at similar levels. This matchmaking ability becomes vital when the cells heat up with use, losing efficiency, says William Dye, an engineering supervisor with EDS Advanced Technology in Warren, Mich. EDS cosponsors the race, along with its parent company, General Motors, the DOE, and other corporate and government groups.
Mr. Dye, who first provided technical help to teams as a volunteer during the first American Sunrayce in 1990, has been helping teams refine the aerodynamics of their entries electronically. Most entries are designed on computers, he says. Teams put their designs on a floppy disks and send them to EDS. Dye runs the designs through software that simulates a variety of hypothetical race course conditions, giving graphical readouts of lift, drag, pressure, and friction. This "virtual wind tunnel" also allows students to analyze aerodynamic conditions underneath their cars, which they can't do with a conventional wind tunnel, he says.
Being this closely involved in car design and modification, Dye has noted significant changes in the way many entries are dealing with age-old automotive problems. "The biggest changes this year are in the motor and drive train. Some entries are mounting their electric motors right in the wheel hub, eliminating the need for a linkage," he notes. The result: Up to 99 percent of a motor's energy is transferred directly to the wheel. Other teams, he says, are using electronic controls as transmissions to automatically change a motor's torque as the car climbs hills.
Yet for all the high-tech wizardry - from the use of composite materials to telemetry monitoring a car's condition to global-positioning satellites to help track the contestants' progress - the educational aspect of the competition remains key.
"Not enough kids are going into engineering," says GM spokesman Tim Fritz. "In southeastern Michigan alone, employers are unable to fill 6,000 high-wage technical jobs because they can't find qualified candidates. I've seen estimates that the United States may face a shortage of 400,000 engineers by the year 2010."
For some, the issue is no less than the future of US competitiveness. "Who will be competitive in the world economy? The countries with the skilled workforce," says Sam Mil'shtein, director of UMass Lowell's Advanced Electronics Technology Center. "I get an idea, and I say to myself, it won't work because of the second law of thermodynamics. These kids don't think in those terms. That's why they're so creative. Pay attention to their education, and they'll perform miracles."