MIT’s Solar Electric Vehicle Team will be headed to Austin, Texas, in mid-July for the American Solar Challenge with their latest incarnation, “Valkyrie.”
“It’s a race car, so there is only enough room for one person to sit in it to drive,” says freshman Michelle Chao of Houston, Texas, who will be one of the drivers on the road trip from Austin to St. Paul, Minn.
“There is a lead car that makes sure we are going the correct route and there is a chase car behind,” Chao says. “We also have a truck and trailer.” The rest of the team members are available for pit stops and maintenance.
The solar team is supported by the Edgerton Center at MIT and this year the Materials Processing Center is contributing $3,000 to the effort.
The team unveiled Valkyrie, a three-wheeled vehicle featuring an aluminum-carbon-fiber composite chassis, after Commencement on Friday, June 6.
“This year we’re trying a new design where it’s a monocoque, so instead of having a steel chassis, we have carbon fiber for the chassis,” Chao says.
“We have the lower body and the upper body complete, so all of the body work is done,” says MIT junior Rose Abramson, an electrical science and engineering major from Orinda, Calif., and electrical lead for the team. “We’re currently in the process of encapsulating solar cells, and putting those on."
The team is taking “raw” monocrystalline silicon solar cells from SunPower and making their own protective sheathing for the cells.
“They’re very brittle when you buy them bare; they’re just a thin slice of silicon with active parts on top,” Abramson explains, “and so you have to put them inside of glass or plastic to protect them. What we do is we use different plastic sheets and layer them on top of the cells and then put them in the laminator. That makes this really nice, bendable solar cell that we can put on top of our car. The actual encapsulation process was designed by an undergrad and he worked as part of his UROP figuring out the correct sequence of baking the cells and different layers, like what material was the best. Right now, we’re in the middle of doing that same process again, and we’ve had a little bit of trouble with one of the covers or the backsheets. We got a little bit too thick of one so some of the cells are cracking so we’re in the middle of trying to get thinner material and then continue encapsulating. The thinner it is, the more flexible it is and the more it can conform to the car’s shape which is better for the aerodynamics.”
Some electrical work and mechanical work, such as the roll bar, were in progress during May. “Our goal is to be done at the beginning of June so we can go test driving,” Abramson explains. “It’s always good to have a long time to test drive to shake down all the problems.”
“I think success on the race is largely determined by how reliable your car is,” Chao adds, “so testing is really important.”
“That makes it a good experience for engineering too, because you learn what actually is practical in the real world,” Abramson says. “I just think it’s a really good project in general because when I came I didn’t have any experience with soldering or with engineering or anything like that and working on the car, you gain the confidence because you are learning all these applicable skills.”
The team is hoping for better luck this year than in 2012, when the car spun out in the rain, hit a pole, and suffered a penalty for being hauled by trailer for repairs.
“Even though we were able to keep racing and still finished, that penalty took us out of the running. So we’re really hoping that this next one will get us back on top,” Abramson says. “Everybody’s working really hard to get it done.” It is Abramson’s third year with the team.
Besides Chao, other drivers are Priya Kikani '17, Joshua Sloane '17, Trang Dang '15, and Dillon McConnon '15. The team will first compete in a qualifying race, the Formula Sun Grand Prix, at the Circuit of the Americas in Austin July 17-19.
Because they are using carbon-fiber composite instead of steel for the chassis, the team has done additional testing with Instron instruments of its mechanical strength, as well as materials and quality testing. Currently without a faculty advisor, the team is assisted by James W. Bales, assistant director of the Edgerton Center, technical instructor Pat McAtamney, who manages the shop in Building N51, and Michael J. Tarkanian, a lecturer in the Department of Materials Science and Engineering who runs the Forge and Foundry program.
The team also does Finite Element Analysis on all of the parts for the mechanical systems. “Essentially you put a mesh over the shape that you want to build and the software will run simulations and say this will break at this force or has this much strain on it,” Abramson says. “The practical limit times five is what we design for. The race regulations also have very stringent guidelines about all the forces that the car has to have and all the safety features. For the electrical system, we have hard switches between all of our high voltage components that we can make sure that the driver is completely isolated and the car is completely off if need be. There are emergency off switches; there is monitoring in our battery pack to make sure voltages and temperatures are within the correct range. We also have several converters that essentially hook up the solar panels to the battery and those have safety features in them as well.”
“The whole driver cockpit is designed so that the driver is very safe,” she adds. “It even takes into account the seat back, so the most comfortable position for the driver as well.”
Since the American Solar Challenge is held every other year, the MIT team focuses on design during the off year and construction during race years.
Valkyrie is the 12th solar car since the MIT team began in 1985. The team hopes to participate next year in the 2015 World Solar Challenge in Australia, Chao says. There are 15 to 20 active team members.
It costs about $200,000 to $250,000 to build a solar car from scratch and participate in the American Solar Challenge. The team is supported by various MIT and industry sponsors, such as Cabot, Infinesse, 3M, and Ford. The team uses SolidWorks design software through MIT with add-ons such as HSM Works and Altium for electrical layout.