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Parking Lot Power
Canopied parking lots fitted with solar panels could anchor vehicle charging stations and microgrids.
You slog under a hot sun across an unending asphalt parking on a simple quest to pick up a jug of milk at your local big-box store. Now, ask yourself: How much solar electricity could that huge lot generate?
The short answer is a lot, if the sun were captured by the large canopies that now sprawl across parking lots to protect shoppers from rain, snow, and heat.
Researchers at Western University in Ontario found that the average five-acre lot at a Walmart Supercenter in the United States held enough photovoltaic potential for about 100 electric vehicle charging stations.
“And if Wal-Mart went all in, their U.S. fleet could deploy over 11 gigawatts, which is, about 11 large power plants,” said Joshua Pearce, the John M. Thompson Chair in Information Technology and Innovation at Western University’s Thompson Centre for Engineering & Innovation, who led the study.

Micro scale imaging process techniques allowed researchers to determine potential power capacity of canopied parking lots.
To get there, the retailer could erect solar canopies across the parking lots at its 3,751 U.S. supercenters.
The canopies, after all, are little different than the house and building roofs that support photovoltaic solar arrays that capture sunlight and transform it into electricity. The move would be a win for electric car drivers, parking-lot owners, and area residents alike, Pearce said.
Parking-lot power could supply the charge for shopper’s electric vehicles. It could be harnessed into microgrids that have enough energy for the surrounding neighborhood, Pearce claimed. He’s also a professor of materials science, electrical, and computer engineering at Michigan Technical Univeristy, in Houghton, Mich.
“An obvious place to go for solar energy is parking lots covered with solar canopies. The covers protect your vehicle, they’re otherwise mostly wasted space,” Pearce said.

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The researchers have quantified just how much electricity a big-box-store-sized canopy could provide and how it could be put to use.
Pearce was familiar with using image-processing techniques for regional planning. For that use, planners study overhead images taken from satellites and drones to identify how land can be used. The technique is particularly helpful when planners need to cover large areas that can’t easily be mapped from the ground.
He and his team put the same image-processing technique to work on the micro scale to measure a roof and discover how many PV cells a typical canopy could support.
“When you know the roof area potential for PV, you can determine the potential installed power,” Pearce said. “And, with that, you can determine the amount of solar electricity that could be generated on the site for 20 years or more while the system is under warranty.”

Electric Vehicles and Microgrids

Were Walmart to solar-electrify its canopies, 90 percent of Americans who live within 15 miles of a store would have access to an EV charging station, he said.
Easily located charging stations will be crucial for EV adoption, especially as far fewer statins are sited in the Midwest and in sparsely populated areas than on either coast, said Gustavo Occhiuzzo, the chief executive officer of EVCS, which operates EV charging stations on the West Coast.
But it’s not only EV drivers who stand to benefit. So does the entire neighborhood that surrounds the store through local community-resilient microgrids. These could also be canopy powered, Pearce said.
A microgrid system could serve the electrical needs of 1,000 people, or about 350 residences, the researchers found in a study they ran at a Walmart Supercenter in Nova Scotia, Canada.

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The nonprofit U.S. Center for Climate and Energy Solutions defines a microgrid is a relatively small, controllable power system comprised of connected generators that are, in turn, connected to local load..
Microgrids can run on a variety of power sources—renewables, natural gas-fueled combustion turbines, or even emerging sources such as fuel cells. Grids powered by renewable energy would obviously be welcomed for environmental reasons, Pearce said.

Retailers could boost sales and profits with solar-powered canopies, he added. EV owners may prolong their shopping time—and make more purchase—while they wait for their car to charge. They might also be privy to in-store benefits offered only to those charging their vehicles, Pearce suggested.

Solar-powered canopies are beginning to pop up. Rutgers University built one of the largest solar parking facilities in the country at its Piscataway, N.J., campus, with a 32-acre footprint and an 8_MW output. 

Last fall, the Evansville Regional Airport in Indiana opened two solar-parking canopies. They cover 368 parking spaces and cost $6.5 million.  They’re projected to supply 1.3 MW of electricity and power 50 percent of the terminal building, said Nate Hahn, the airport’s executive director.

Yet, deployment of solar parking lots is still in its infancy, Pearce said, though he expects installations to pick up sharply in the next several years.
“We need more companies offering them as solutions. They’ll scale out with EV use, Pearce said. “I’m confident within the next few years it will no longer be a novelty and then, eventually, common. In the end the economics on distributed PV are just too good.
“Naked parking lots will become a thing of the past,” he said.

Jean Thilmany is a freelance writer in Saint Paul, Minn., who writes about engineering issues.

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