Students, Transportation Services develop solar-powered displays for university bus shelters 

Two people standing on a sidewalk with a metro bus on the right and the Wisconsin Union building on the left
Two students use a Solar Pathfinder device to determine sun exposure at a bus stop on the UW–Madison campus.

Although it manages arrival times, bus stops, repairs, signage, parking lots, road closures, permits, citations, and special event parking—all the tedious necessary aspects of public transit— Transportation Services also creates experiences. It may seem unusual to consider standing at a bus stop an experience: waiting, pacing, thumbing one’s smartphone, looking for the next ride. But Dar Ward, the Commuter Solutions Manager at Transportation Services, works to improve the experience of taking public transit by “adding transit amenities,” which are “meant to encourage people to take transit” and “to discourage them from driving places.”

Recently, Ward was developing a project to install screens with real-time arrival information in campus bus shelters. The concept was about convenience—riders would not have to worry about when an infrequent bus would arrive, repeatedly check bus schedules, or shoulder onto a packed bus when another would come shortly. The problem with installing displays, though, was power: electrical wires would need to be extended from a nearby building, which would be difficult, expensive, and require many approvals. 

This conundrum led to the solar bus shelter project, a collaboration between Transportation Services and two student organizations: Helios, which focuses on solar-powered sustainability, and Enactus, a national organization that seeks to use entrepreneurship to benefit social causes. Tanner Wagner-Durr, the Project Manager for Enactus’s Sol Solutions committee, and Simon Brooks, the President of Helios, ran into one another at a sustainability event and agreed to collaborate on the solar-powered project. The organizations filed a joint submission to the Office of Sustainability’s Green Fund, which connected the organizations with experts on campus, answered questions, and awarded them a $1,400 grant to purchase equipment.

As a result of the study, which demonstrated the feasibility of the project, Transportation Services will start installing solar panels, screens, and lights on campus bus shelters in 2022, using $100,000 of funding allocated for sustainability projects by the UW–Madison Physical Plant.

Students lead research on curved solar panels

The students began their study by gathering qualitative data: surveying and photographing sites, listing stop IDs, and constructing a database to store information. Then they collected further data with their Green Fund-supported Solar Pathfinder—what their final report calls “a rather primitive-looking instrument” that allows sunlight to pass through a reflective dome onto a gridded sheet of paper underneath, which corresponds to latitude and longitude. As Wagner-Durr explained, the manual device can “show how much sunlight it will get throughout the day and throughout different parts of the year.”

They also had to address aesthetics. Transportation Services had just completed a 10-year renovation of campus bus shelters, and it wanted to use curved solar panels to match the shelter design. “We didn’t want to come back and somehow deface them, so one of the things we were interested in was using a flexible solar panel that could bend over the existing round roof and … look like part of the bus shelter,” Ward said. “Not only were we interested in solar power, which you can just buy off the shelf, but we wanted to see the feasibility of this particular kind of flexible panel.”

Mary Ebeling, the Commuter Solutions Coordinator at Transportation Services, had researched this question and found no studies that described how flexible solar panels compared to flat panels for energy production. 

“There are a couple of places around the country that have done something like this, but most of them have not done it exactly this way,” Ward said. “It’s a very traditional concept to take the pole that the bus stop sign is on and stick either a light or a real-time arrival display on that pole, with the solar panel on top of the pole. But this idea of putting it inside the bus shelter—there’s only a couple of places that have done that.”

The students, Ebeling said, “actually helped answer a question that the professional world didn’t have the answer to.” They used the National Renewable Energy Lab’s System Advisory Model to generate the comparative data, but they adjusted it because of sparse research about curved panels.

“With the lack of academic research and publications, the software was optimized for flat panels, so we had to work around that,” said Atilla Veyssal, the business lead of Helios. With the support of Arganthaël Berson, a professor of mechanical engineering at UW, they approximated the curve of the panels by splitting the model’s line into four shorter lines that would allow more data points.

The findings: curved panels generated more power than flat panels in the summer because they could collect more sunlight when the sun is at its highest. In December—what the students called “the worst-case scenario” because of shorter days and a greater need for electricity—flat panels captured more energy than curved panels. 

“The curved panels, in the worst-case scenario, are capturing less energy, but it’s not significantly less energy,” said Brooks. “Based on this, we are confident the system can be powered throughout the year.”

The students’ study concluded that 51 of 66 shelters could power a display and lights with an average of 2.08 curved panels. Thirty of those shelters would only need one panel to generate sufficient energy. The remaining 15 shelters would need three panels, as they’re mostly in the southeast part of campus, shaded by tall buildings and trees. The study also recommended motion-sensor lighting for conservation and batteries for an energy reserve.

“A living laboratory for sustainable transportation”

Once completed, the bus shelter project will allow Transportation Services to improve commuter experiences while lessening contributions to climate change.

“Because we have one of the lowest parking per employee ratios of any peer university in the country, we’re a living laboratory for pushing sustainable transportation,” Ebeling said. “We’re living the changes to our climate in real time, so these small individual changes people make when they choose to not drive or to get a park-and-ride permit and take the bus or bike part of the way, those small changes make a difference cumulatively. It’s satisfying knowing that we’re working on something small and immediately beneficial to our university and community but that also has broader benefits.”

The students who produced the report also considered these effects. Although they study mechanical engineering and material science and chemistry and finance and information systems and economics (all of them hold at least two majors), they shared a motivation to apply their expertise toward sustainable causes.

“As Gen Z,” Wagner-Durr said, “we’re going to be the ones that are dealing with the effects of climate change, so it’s on us to push for those societal changes and make as much of an impact as we can.”

The students’ motivations respond to nostalgia and loss. Recently, Veyssal noticed himself talking separately with his friends and sister about the lost seasons in Wisconsin. They spoke of how the seasons shifted, “especially in March and around Thanksgiving. We feel like Thanksgivings are much milder than before. There’s a lot less snow in the winter because it’s milder or too cold to snow.”

“Even though the solar bus stop isn’t necessarily … replacing any coal or natural gas use,” Veyssal concluded, “being able to see that you can still effectively power something that would be widely used is a good stepping stone for transitioning into bigger applications.”

By: Marek Makowski