Aztec Electric Car Wins Top Honors in 6-Day RaceBy Eva Moy
Walking along Massachusetts Avenue a few weeks ago, one may have seen an airfoil-shaped vehicle with a panel of solar cells on its roof, and moped and bicycle tires for wheels. Named Aztec, the car is the product of two years of hard work by the MIT Solar Electric Vehicle Club, and it won top honors in the 1993 American Tour de Sol which ended on May 29.
Aztec finished first in the Tour de Sol Commuter class, first in Argonne efficiency testing, second in distance travelled by a student vehicle, and fourth place overall.
Commuter vehicles such as Aztec are designed to recharge their batteries overnight, according to Kathleen Allen, the club's advisor. The Tour de Sol category limited vehicles to two riders, 500 to 7200 watt-hour batteries, and other physical constraints. Other commuter categories included vehicles with unlimited battery power, and vehicles of which five or more had been sold.
Tour de Sol racers and Continental class vehicles, on the other hand, have only one driver and use sunlight as the primary energy source, Allen said.
Aztec is primarily powered by nine Sears Die-Hard lead-acid batteries, with about 12 percent of the power supplied by the solar cells. It is basically an "electric car with solar assist," Allen explained.
"The key reason for our success was the car's efficiency," said team member Hao Chien '95. "Our car's range was even better than most of racers in the unlimited battery power category."
Aztec achieved the second best student mileage using only $750 of lead-acid batteries, while the first place car, built by Texas A&M (??) University, used about $20,000 of zinc bromine batteries, Allen said.
"The team was a bit disappointed to discover the batteries were on sale for about $430 after the race," team member Michael B. Wittig '96 added jokingly.
The course zig-zagged along the east coast from Boston to Burlington, VT, over the course of six days. The competition was designed to test speed, reliability, and range. All of the vehicles were expected to keep up with highway traffic, while staying within the legal speed limits. They also had to be able to negotiate both flat and hilly roads, Allen said.
Each day covered at least 60 miles -- the minimum distance that an average commuter would use between recharges. Teams earned credit for any extra mileage driven until the batteries completely expired.
Aztec travelled a total of 563 miles by the end of the fifth day. In comparison, Solectria's car, the Force GT, had unlimited battery power and travelled the farthest with a total of 710 miles.
"In a race like this, reliability is a key asset. Despite several glitches just before the race ... the car ran flawlessly for almost the entire event," Wittig said.
At 780 pounds and about 14 feet long, Aztec has a top speed of 50 miles per hour and a maximum distance of 135 miles at 40 miles per hour on a single charge, Allen said. Two years ago, people were struggling to travel 40 miles per day, she added.
In comparison, commercial cars such as those made by General Motors and Chrysler range from 50 to 100 miles per charge, according to Wittig.
Aztec includes a double-wishbone suspension, coil-over shock suspension, rack and pinion steering, and three hydraulic disk brakes. The body is made from carbon fiber with a honeycomb core. "Everything else, while exotic for a car, is not unusual for this type of vehicle," Allen said.
The total price tag: $26,000. Most of the vehicles in the commuter category cost about $15,000 to $40,000, according to Allen.
Most of the costs are supported by corporate sponsors. The club is very successful in soliciting donations of materials such as fiberglass, carbon fiber, chrome-moly tubing, and epoxy, Allen said. But monetary donations, mostly needed to buy batteries and solar cells, are harder to obtain.
The club will be working on their next vehicle, Galaxy II, over the summer and the next two years. Galaxy II will be a purely solar-powered car so that the club can compete in more races, such as the General Motors Sunrayce and Australian World Solar Challenge, according to team member Ivano Gregoratto '96.