Why not put Michigan solar farms on parking lots instead of farmland?

• Putting solar arrays on undeveloped land can be a lightning rod for controversy, so some see parking lots as an alternative
• Putting solar canopies above parking lots means less sprawl — and more shade for parked cars — but a far higher pricetag 
• A Michigan State University installation illustrates the tradeoffs

EAST LANSING — Not too long ago, scores of Michigan State University students began winter weekends by digging their cars out of snowdrifts at the school’s commuter lots, while breathing soot from a coal-fired power plant across the street.

Those days are over, thanks to 45 acres of solar-powered carports that now protect vehicles from the elements while producing clean energy that has helped MSU ditch coal in pursuit of a greener future. 

The carports won awards for showing that renewable energy doesn’t always have to gobble up lots of open space. But seven years later, campus officials aren’t eyeing more parking lots to expand their solar portfolio. 

Like many renewable energy developers, they’re looking to farmland. In MSU’s case, a field the university owns to the south of its East Lansing campus.

“It's significantly cheaper,” said Wolfgang Bauer, an MSU physics and astronomy professor and key architect of the university’s renewable-energy shift.

As Michiganders debate where, how, and whether to expand renewable energy in the state, critics of greenfield solar projects often cite the installation at MSU as evidence that electricity providers should seek out already-developed land instead.

Bauer is uncomfortable with that argument, which he calls “a false dichotomy.”

“We should be doing all of the above,” he said.

While efforts to build more solar arrays on rooftops, parking lots and vacant industrial sites are picking up steam, cost is just one of many reasons why greenfield solar farms remain far more common.

Michigan’s solar dilemma 

Amid increasingly dire warnings that fossil fuel use is dangerously warming Earth’s climate, utilities around the globe have been racing to swap coal and natural gas-fired power plants for renewable energy.

A law passed in 2023 gives Michigan’s energy providers a 2040 deadline to achieve 100% clean energy. Beyond the climate benefits, solar energy is increasingly cost-competitive with fossil fuels, without the toxic emissions that prematurely kill hundreds of Michiganders each year. 

The downside is that solar panels take up more space than fossil fuel power plants. 

State officials estimate it may take 209,000 acres worth of renewable energy to achieve clean energy goals. That’s half a percent of Michigan's land mass, and about a third of the acreage Michigan currently uses to grow corn for ethanol-based gasoline. 

But it’s still more than twice the size of the city of Detroit. And neighbors often object to putting solar farms on open land for fear it will spoil the view, affect property values, destroy cropland and wildlife habitat or hinder outdoor recreation.

Those tension points arose last month after the Michigan Department of Natural Resources announced it was considering leasing 420 acres of state land near Gaylord for a solar array, prompting Rep. Ken Borton, R-Gaylord, to accuse the department of attempting to “kill wildlife to further the radical green energy agenda.”

Putting more solar panels on developed land is one way around the conflict. And it’s often technically feasible.

Related:

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• Michigan’s controversial wind, solar energy law is in effect. What to know

In Connecticut, Yale University researchers found that parking lots have the potential to fulfill 37% of the state’s electricity needs. And a 2021 study found that equipping the nation’s thousands of Walmart parking lots with solar carports could generate 11.1 gigawatts of electricity — enough to power 8.3 million homes .

“There’s a massive opportunity there,” said Joshua Pearce, an electrical engineering professor at Western University in Ontario who coauthored the study. “Every Walmart could become a renewable energy system for the community.”

Easier said than done

The catch? Putting solar panels on parking lots, rooftops or other already-built out land requires more labor and materials, which makes costs significantly higher than a comparable ground-mounted system.

The aluminum beams that support MSU’s solar carports are more than 14 feet off the ground. To withstand the elements, they needed to be anchored 20 feet underground. As a result, the roughly $20 million project was more expensive than a similar ground-mounted project (yet still $10 million cheaper than relying on fossil fuels over the duration of the project).

Beyond those challenges, it’s simply cheaper to build on flat, cleared farmland where taxes are lower, especially if the plot is big enough to achieve economies of scale. It’s the same force that drives homebuilders to turn farm fields into subdivisions rather than redeveloping urban lots.

“The cost of legal and siting transactions, negotiating contracts and negotiating with landowners — all of those things cost the same amount, no matter how big your project is,” said Laura Sherman, president of the Michigan Energy Innovation Business Council. 

One example: Consumers Energy officials considered two sites — a landfill in Grand Rapids and an undeveloped property in Muskegon County — for a new solar array in West Michigan. 

On a per-megawatt basis, the landfill would have been three times more expensive, said David Hicks, the company’s vice president of renewables development. Those costs would have been borne by utility ratepayers in the form of higher monthly bills.

“We need to decarbonize,” Hicks said, “but we need to decarbonize in a cost-effective manner.”

And then there are the technical limitations. Parking lots or rooftops surrounded by tall buildings or trees might get too little sun. The local electricity distribution system may need upgrades before it can support more power. Or the property owner — say, a big-box store — may hesitate to invest in solar panels that take decades to pay off, when it’s not clear their business will survive that long.

Michigan’s energy regulations also pose a barrier.

Monopoly utilities — which are also some of Michigan’s biggest political donors — have long fought to limit customers’ ability to power their homes and businesses with solar panels while getting credits on their power bills for feeding excess power back into the grid. 

They argue utilities are required to credit solar owners too much for that power, resulting in a subsidy that raises monthly bills for ratepayers who can’t afford the upfront cost to install their own panels. Solar advocates dispute that argument.

State law requires utilities to credit customers for renewable energy given back to the grid until the sum of that energy reaches 10% of a utility’s average peak demand. Under those limits, Sherman said, “we won't be able to achieve the amount of energy we need from renewables simply by doing rooftops, because we'll hit the 10% cap before we get there.”

Michigan lawmakers have made other efforts to encourage renewable energy projects on developed land. For example, new statewide permitting standards passed in 2023 require developers to show they've looked into vacant industrial property and brownfields before seeking state approval for projects on undeveloped land. 

Some other governments have gone further. ​​France now requires solar canopies to be built above parking lots larger than about 16,000 square feet (about a third of an acre).

Since the law passed, Pearce said, “the cost of parking lot solar in France dropped way down.”

But America lacks the land constraints of such a small country, making it less likely that lawmakers here will see a need for such a policy.

A joint solution? 

Pearce, the solar parking researcher, sees another potential solution to Michigan’s solar siting debates: Get more people to embrace farmland projects by demonstrating how agriculture and power generation can coexist on the same land.

Studies have shown that so-called agrivoltaic arrays can actually increase crop yields by shading plants that would otherwise become stunted in the sun. 

“There are so many examples now in the US, and in Europe, and in Asia, and now even in Canada, of purposely putting solar on the farm in a way that you continue to farm it,” he said.

At MSU, Bauer and his colleagues hope to add an example to the mix. MSU is preparing to solicit bids from developers interested in building a 20-megawatt solar array on 100 acres of university-owned farmland, where he envisions sheep grazing beneath the panels.

“You could also have wildflower pollinator habitat, because that’s a critical need if you have farms,” he said. Beyond those benefits, “it’s significantly cheaper than putting it over a parking lot.”