“We went into Day 8 knowing it was going to be a blackhole of clouds,” 2016 Head Strategist Alan Li says. Solar car Aurum starts Day 8 off by driving at a set speed of 25 miles per hour, and the team knows that number is unlikely to go up on this rainy day.
Day 8 is the first time the University of Michigan sees any other solar car on the road—and they all want to pass Aurum. One by one, competitors pass Michigan’s caravan—Dunwoody, Principia, Iowa State, UC Berkeley’s CalSol, Appalachian State—running more aggressive strategies in the hopes that they can win Stage Four.
“We don’t budge,” Alan notes.
Aurum continues driving at a slow 25 mph. Michigan will stick with its set speed regardless of what the other teams do, regardless of how many cars pass Aurum. UM Solar sticks to the resolution it made last night: the other teams can do whatever they want, Michigan will run its best strategy, will run its own race.
As Aurum continues its steady trek towards the finish line, it passes Principia by the side of the road. Principia’s solar car has undervolted; its battery has reached 0%. And since there’s no sun, the car can’t charge. It can’t drive. Principia is now forced to trailer its car to the finish line.
Then, Aurum passes Iowa State. CalSol. Toronto. “It was like a graveyard,” Alan describes. Almost every team who didn’t trailer to the Stage Three Finish now sits on the side of the road, undervolted.
Sticking to its 25 mph gait, Aurum nears the timing finish line, and from half a mile away, Michigan can see it on the left. On the right, so close to the timing finish line, sits Dunwoody, undervolted.
Aurum at last crosses the timing finish line—but it’s not over yet. Aurum still has to make the uphill crawl to the ceremonial finish line at Wind Cave National Park in Hot Springs, South Dakota. Since it’s a hilly trip to Wind Cave, Michigan brings Aurum’s speed down a notch to 15 mph.
“Hills are the worst at a low state of charge because going uphill draws more power. When you draw more power, voltage drops. When voltage drops, the battery is more likely to go below the minimum,” Alan illustrates.
The team is nervous; there are many large hills between Aurum and its goal. Every time Aurum goes up a hill, its power numbers go up and the car’s state of charges dips dangerously low, bringing Aurum close to undervolting, and everyone in the Chase car holds their breath. Every time Aurum goes downhill, those power numbers go down again as its driver holds the regenerative brake, which essentially takes the kinetic energy of the wheels moving forward as the car slows down and converts that back into energy that can be stored in the battery. If it weren’t so rainy, the risk of undervolting would not be so high. But with virtually no access to the sun, if Aurum were to undervolt now, it wouldn’t be able to start up again.
“At the start, Michael Toennies asked me, ‘How many hills before we get to Wind Cave?’ I said, ‘Two or three.’” Alan recalls. He gave Michael the number he remembered from previous route surveys. “But there were actually like ten.”
Even Aurum’s slow speed gives reason for worry. Aurum doesn’t have windshield wipers; in place of those, UM Solar uses Rain-X, a hydrophobic coating that aids with visibility in the rain. The faster the car goes, the more effective Rain-X is, the faster the water slides off the windshield. But at a sluggish 15 mph, visibility is tough, and Engineering Director Clayton Dailey has a hard time seeing as he drives the solar car through heavy rain.
Earlier in the day, 2016 Business Director Sarah Zoellick broke away from the race route to arrive at the ceremonial finish line ahead of time. 2016 Operations Director Jonathan Cha and Operations Division member Jesse Velleu in the Scout vehicle joined Sarah, and now they wait together for Aurum and the rest of the team’s caravan. Communication is limited because there is no cell service, so the three of them don’t know how Aurum is doing. Based on recent reports, they think that Michigan is still on the road, but they know nothing for sure. As time drags on, other teams’ Weather and Scout vehicles pull in and share tidbits of news: “We undervolted” and “We had to trailer” and “I don’t know what’s going on.” Jon, Jesse, and Sarah wonder if the same fate has befallen Aurum. Did Aurum undervolt? Did Michigan have to trailer, too?
In the gray rain, they watch other teams pull in. They are still waiting in this uncertainty when at last they see it: a maize vehicle in the gray.
Everyone jumps out of their caravan vehicles and rallies around Aurum as it nears the finish line, running alongside it.
“It was pouring, we were all soaked, but we were really excited,” Sarah describes. “It was such a relief. There was a feeling of ‘We actually did this.’”
Aurum crosses the finish line surrounded by Michigan’s race crew, and everyone cheers and hugs and high-fives. The team breaks into a chorus of the University’s Victors Song, then celebrates some more.
And Michigan has much to celebrate: the University of Michigan Solar Car Team has won its ninth overall American Solar Challenge title. The team won with a whopping 11-hour lead on the second place team, breaking the previous record that Michigan itself had set of 10 hours and 19 minutes. Michigan was also the only team in the ASC to finish the race without trailering, the only team to finish the race on solar power alone.
“That’s what I’m most proud of,” Crew Chief Perry Benson says. “That we were the only team to successfully do that. We were able to plan ahead of time to get it done.”
Michigan has much to celebrate, “But it’s a bittersweet feeling,” Jon says. Jon, like the rest of the team, looks to the future. Now that the American Solar Challenge is over, UM Solar will decommission its winning car, Aurum. Come Fall, the team will recruit new members. This new team will work hard, training and designing and testing and fundraising and building the team’s next solar car with a singular goal in mind: to win the 2017 World Solar Challenge.
Longtime team advisor Chito Garcia turns to Jon at the finish line and tells him, “Congratulations. Now, the World Solar Challenge. The real work begins.”