Mines students design winning solar installation for commercial office complex in DOE Solar District Cup

A team of Colorado School of Mines students took second place in their division in the inaugural U.S. Department of Energy Solar District Cup.

Led by the DOE’s National Renewable Energy Laboratory (NREL), the collegiate design competition challenged multidisciplinary student teams from across the U.S. to design and model optimized energy systems for multi-building districts, ranging from college campuses to office complexes.

The Mines team, which participated in the competition as part of Capstone Design, was the runner-up in the cup’s Crystal Parks division, a commercial office development with ground-floor retail in five buildings in National Landing, an urban neighborhood of Arlington, Virginia, south of Washington, DC.

“The building’s owner was looking to do some sort of solar system on the roofs of their buildings, but they were also interested in a larger project that could be built off-site where they could purchase solar energy,” said Luke Kroh, who graduated in May with a bachelor’s degree in civil engineering with an emphasis in structural engineering. “That’s about all they gave us to go on.”

Under the competition’s rules, teams were not allowed to contact the property owner or local electric utilities. What they did get access to, though, was a suite of state-of-the-art modeling software from NREL and Aurora Solar, a San Francisco-based solar energy startup.

The Mines team proposed two solutions—rooftop photovoltaic systems for all five buildings, ranging from 160 to 290 kilowatts on each rooftop, and an off-site photovoltaic system at a decommissioned landfill 23 miles west of Arlington, which could offset 100 percent of the district’s energy usage when combined with the five rooftop systems.

“It felt like a very real project,” Kroh said. “One of the programs, REOPT from NREL, was a battery modeling system—you put in how much solar you’re going to have on the building and your expected usage, and then it spits out a battery size and a strategy for how you might discharge the battery.”

From that information, the team ended up ruling out a battery system entirely, said Cara Fragomeni, who graduated in May with a bachelor’s degree in civil engineering and will return to Mines in August to start a PhD.

“Battery systems allow customers to charge up when electricity is cheap and discharge when it’s expensive,” Fragomeni said. “But energy is so cheap in Virginia that there were only a few days that were really expensive. We couldn't really offer them a battery system that would meet their needs.”

Advising the team was Tim Ohno, associate professor of physics and faculty advisor for the Mines Solar Decathlon that won the 2019 competition in Africa. Ohno gave the team a lot of helpful advice on what judges would likely be looking for, Kroh said.

“We really focused on the client. We had 15 minutes to make a presentation, and we focused on how our design was going to meet the needs of the client and not all the technical details,” Kroh said. “The client was there, and they were interested in the bottom line and how these systems were going to help them meet the local energy goals or get them LEED platinum or just reduce their electricity bill. That really helped us.”

Rounding out the team were Cami De Voto Noonan (engineering physics), Nathan Collins (electrical engineering) and Paul Slade (mechanical engineering).

And while travel restrictions caused by the coronavirus pandemic nixed the final’s in-person judging and networking opportunities in Atlanta, the experience was still a valuable one. Thirty-five finalist teams from 32 institutions presented designs and financial models for systems that integrated solar, storage, demand response and other distributed technologies.

“It was a good introduction to renewable energy and the general considerations for companies that want to be more sustainable,” Fragomeni said. “The other schools had economists and electrical engineers on their teams. We had civil and environmental engineers and a physics student—it was very exciting to have two mechanical and electrical engineering students on our team for the second semester.”

Kroh was even able to channel the experience into a job offer in the solar industry. (He decided instead to return to Mines this fall to finish his master’s degree in civil engineering.)

“Before the Solar District Cup, I was interested in solar power but didn’t have much experience in it,” Kroh said. “I learned there’s actually a lot of civil engineering in solar. There’s a lot of structural engineering. For the large off-site system we proposed, there was a lot of geotechnical engineering, because you have to mount the panels on the ground. It surprised me. The electrical aspect is one part of solar, but there are a lot of different aspects to the industry.”