Three big jobs at the American Solar Challenge: charging the batteries, maintaining the chassis and tracking the sun. Larger photo. Photo by Team PrISUm.
AMES, Iowa – Thursday morning was full of sunshine and speed limits for Hyperion, Iowa State University’s solar race car.
But when afternoon clouds moved over Wisconsin, Team PrISUm had to slow its car for a few hours.
Even so, the students of Iowa State’s solar car team strengthened their hold on second place in the American Solar Challenge, an eight-day, 1,650-mile race for student-designed and student-built solar race cars. On day six of the challenge, Hyperion rolled into the Verona, Wis., checkpoint about an hour behind first-place Michigan and about an hour ahead of third-place Principia College.
As the team reported on twitter (@Team_PrISUm), “This afternoon has been very overcast. This has slowed Hyperion significantly.”
And why is that? How can Hyperion race with Michigan all morning under sunny skies, but has to drop back when the clouds roll in?
Well, said Evan Stumpges, the team’s project director and a May graduate in mechanical engineering, Michigan chose a different kind of battery for its car. The Michigan batteries have a higher energy density and hold more power for the cloudy days.
Hyperion’s batteries don’t hold as much power, but they can operate at higher temperatures.
“That’s the trade off,” Stumpges said.
It has been a good trade, given this year’s scorching sun over most of the race. Many teams have struggled with overheated battery packs. But Hyperion loves the heat.
“Overall, our batteries have definitely been an advantage,” Stumpges said. “But it’s something we have to continue to evaluate as we move forward.”
First things first, though. The team’s next goal is to make good time to Friday’s stage stop in La Crosse, Wis. Then on Saturday, it’s a sprint to the finish line at the Minnesota State Capitol in Saint Paul.
As he looked at the forecast Thursday evening, Stumpges felt good about the team’s prospects of returning to the speed limit: “It’s supposed to be sunny tomorrow.”
