How many MIT students does it take to build a solar-powered car? The MIT Solar Electric Vehicle Team (SEVT), an Edgerton Center-sponsored, student-run group, can do it in two years with just 15-20 students.
Currently, MIT SEVT is working on Valkyrie, a three-wheeled vehicle registered as a motorcycle. Valkyrie is a race car that seats one passenger, the driver, and can reach a maximum speed of about 80 mph. The total system can run on just 1.2 kW, about the same amount of energy as a hairdryer.
The team is preparing to race in the 2014 American Solar Challenge (from Austin, Texas to St. Paul, Minnesota) in July and the World Solar Challenge in Australia in 2015. These races are held every two years, so the SEVT builds a new car every two years in preparation. The team iterates on the previous design in order to make the new car. Having finished a year of design work, the team is now in the second year of the build phase.
Building a solar-powered car isn’t easy — it requires a lot of labor, as well as money. Julia C. Hsu ’14, captain of MIT SEVT, recalls her favorite team experience — working on a composite layup for the exterior shell of the car, which takes 72 hours straight and up to 15 people, over IAP one year. “It was so messy. We were up until 4 a.m. trying to find air bubbles in this one structure, and it took us two hours,” Hsu said. “In the end we were like, whatever, we don’t really care anymore. I definitely learned that sometimes things don’t go as planned. It’s OK though, you just have to let it go. It was a good team bonding experience.”
As for funding, the team must raise a quarter of a million dollars to build each car. Although the team consists of a diverse group of students from within the science and engineering majors, it lacks business students or a business and marketing subteam. The team finds sponsors and support from many external companies and departments at MIT. They even offer an “adopt a solar cell” sponsorship opportunity for the 391 solar cells powering Valkyrie, which is a popular and easy way to support the team. Hsu said, “Generally we build first and worry about money later, because we’re engineering-minded, but we try to be financially conscious.”
Once the car is ready, the testing begins. “We start out testing in a random parking lot, and then after that we get our car registered. And then we just drive out in Boston traffic. It’s really fun. You should see people’s faces when they see the car!” said Hsu. The team also does track testing at Seekonk Speedway, about an hour away from Boston.
Before competing in a race such as the American Solar Challenge, the car has to pass strict inspections to make sure it follows all the race regulations. This process, called scrutineering, usually disqualifies about half of the teams, so it’s no easy hurdle. Next, the teams compete in the Formula Sun Grand Prix (FSGP), a track qualifier race that determines the starting order of the cars. Finally, they compete in the cross-country American Solar Challenge race, which is six or seven days long, with set times for racing each day.
One person, usually someone who has been testing the car regularly, drives the solar car during the race, and the rest of the team rides in lead and chase cars. The same controls are used in the solar car as in a commercial car: steering wheel, mechanical brakes, lights, horn. According to Hsu, “The only difference is it might be a little more rickety!”
The teams are allowed to charge their battery packs at certain times, and there are set checkpoints in the course. The MIT team generally does very well in races. Hsu said, “In past years we’ve usually been top three in races. Last year wasn’t so hot, but we had other errors that won’t happen again. I feel confident about this year.”
During the last race MIT SEVT competed in, their car crashed into a speed limit pole. Hsu said, “The night after was the worst experience I’ve ever had; that moment of dread when we thought it would be really hard just to finish the race, instead of knowing that we could’ve done really well.” The team stayed up the entire following night trying to fix the car, and ended up successfully finishing the race. “It turned into a really good moment, because no one thought we would finish.”
Though MIT SEVT builds solar cars primarily for racing rather than commercial use, the work that the team does serves as a model for engineering innovation. Hsu said, “I personally think that the technology behind solar cells and batteries needs to be much more efficient before commercialization would happen, but I guess we’ll see. Technology has been changing a lot, and it would be really cool to see it happen.”