Raised Arrays

Carport Solar: Combining Parking and Clean Energy Production Pays Off

Insights from four existing structures in Minnesota

Stacking Benefits

 

A sprawling community solar installation on the top floor of the A Ramp in downtown Minneapolis offers the most recent example of a Minnesota project combining solar panels and parking.

On a rooftop with views of Target Field and Target Center, Cooperative Energy Futures built a 1.3-megawatt solar garden subscribed mainly by low-income residents and the Minnesota Department of Transportation. The solar carport allows parking to continue underneath the arrays as they capture energy from the sun.

The A Ramp is among a handful of projects where public entities have built solar carports. The agencies and developers who installed them say solar carports cost more than traditional solar projects but pay off with other dividends that can make the investment worth it.

 

A good use of space and protection from the elements

It’s not exactly a growing trend, although the University of Minnesota plans to build a second solar carport at its Saint Paul campus after the success of an initial project on the West Bank campus. Whether more carports will emerge depends on the economics of solar, the sustainability goals of potential clients and the availability of parking lots and ramps that could support projects.

West Bank UMN

UMN Law School Solar Carport

We get lots of use for the same piece of land, which in an urban environment like Minneapolis and Saint Paul is at a premium. There is a lot of pressure to get the most out of every square foot and acre we’ve got.

Shane Stennes, UMN Sustainability Director

Employees like solar carports because they block the elements, offering the same benefits as a covered garage. “They make perfect sense,” said Jay McCleary, a former Red Wing city official who oversaw the construction of three solar carports several years ago. “If it’s raining, you’re dry. If it’s snowing, you don’t have to brush off your car. If it’s 95 degrees, your car isn’t hot when you get into it.”

The Challenges of Winter

But what about snow? People involved in managing solar carports say snow eventually melts or slides off into traffic lanes for easy removal by plows. They let nature take its course, wasting no staff time on brushing snow off panels. The dark colors of solar panels work to melt snow and ice off them, usually in at most a few days.

The university’s first solar carport—built and managed by Ameresco—opened at law school in 2018 and covers around 100 spaces of an existing parking lot, said Stennes. The continuous rows of solar panels for the 537 kilowatt (kW) project are slightly tipped at an angle, allowing snow to slide down one side into a traffic lane.

The university knew the solar canopy would make snow plowing more complicated, he added, but bobcats and pickup-mounted plows manage it almost as well as larger vehicles, he said.

Before adding two carports to municipal buildings, Red Wing rebuilt an aging surface parking lot. The city redesigned the surface lot to direct snow accumulation on panels to fall into landscaped areas filled with hearty plants rather than on the sidewalks leading to two public buildings, McCleary said.

Red Wing Public Works

Red Wing Public Works Solar Carport

Employees quickly began parking under the panels to protect their vehicles against snow and sun, a move that freed up spots closer to the two public buildings the parking lot serves.

Jay McCleary, a former Red Wing city official

If a parking garage is tall enough wind often blows hard enough to keep snow off panels and cars, said John J. Neville, Ameresco’s Midwest regional director. The company built two of the state’s largest solar carports on top of parking garages at Minneapolis-St. Paul International Airport. “The wind is strong up there and the snow doesn’t collect all that much on the panels,” he said.

None of the officials who developed solar carports reported issues with drivers bumping into the support system. They point out the raised structure is no different than pillars drivers must maneuver around in parking garages. Outside of a car occasionally dinging one the support poles vehicles have not damaged any projects, they said.

Solar Carports Add Cost

The cheapest solar installation method is mounting panels on infrastructure attached to the ground, followed by those placed on rooftops, said Neville. The most expensive approach remains solar carports, though he believes they eventually pay for themselves and have an attractive dual use. 

Cooperative Energy Futures’ general manager Timothy DenHerder-Thomas said the A Ramp, part of the ABC Ramps complex, cost around a third more than a typical roof-top or greenfield solar project. The university paid a third more for the law school project, Stennes said, or about an extra $1 per watt in cost.

Is the additional cost worth it? The advantage for the university is that it has little land for solar, and not all rooftops can handle panels, Stennes said. Having solar arrays where people can see them helps bolster the university’s credentials as a place serious about reducing its carbon impact, he added.

“The university has sustainability goals and carbon reduction goals and these projects help us achieve those goals,” he said.

Sometimes the cost is worth it when no other alternatives exist. Red Wing discovered the historic designation of city hall killed a plan to add solar to it. The community development building’s roof was too weak to support panels. A pole shed-style structure at Red Wing’s public works facility would not survive strong winds, nor would any panels atop it. “The only alternative was carports,” said McCleary.

Airport

MSP Airport Solar Carports

If the decision to build solar carports rests on their financial viability, then civic institutions have to be careful. Solar carports are cost-effective when bundled into rooftop and ground-mounted solar along with efficiency projects such as LED lighting retrofits, Neville said.

The university project, he noted, reduced costs by adding more solar to the roofs of the law school, six other campus buildings and a nearby field. At the international airport energy savings from LED lighting upgrades at six parking ramps mostly paid for the cost and installation of solar, he said.

For community solar developers such as DenHerder-Thomas, the falling reimbursement rates paid to community solar subscribers leave him little encouragement to build more of them. 

“There are not a lot of incentives” for solar carports, he said. “The primary value is nonfinancial—it's their visibility, the high profile nature of everyone being able to see it…maybe someday that will change as the cost of solar continues to come down.”

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