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Spring is officially here - so how do solar panels work across seasons?

A solar garden, operated by Consumers Energy, in Cadillac runs at its maximum output on a sunny March day.
Teresa Homsi
A solar garden, operated by Consumers Energy, in Cadillac runs at its maximum output on a sunny March day.

Solar is one of the fastest growing forms of energy. In 2023, it accounted for over 50% of new electric generation, according to a recent report from the Solar Energy Industries Association.

There are more than 70 solar projects on the docket in Michigan, and new state laws are paving the way for more renewable energy development.

But critics often question how solar works in a region marked by winters with shorter daylight hours, cloudy skies and snow cover. Solar operators say day-to-day variation of sunshine balances out, and a diverse energy profile can meet the state's power needs.

The state legislature passed a landmark package meant to help reach carbon neutrality and achieve the state's climate goals.

One bill — that passed and now requires Michigan utilities to fully run on clean energy by 2040 — drew comments during 2023 committtee hearings that questioned the wisdom of investing in solar.

"Reliability and affordability is going to explode in my neck of the woods," said Rep. David Prestin, from the Upper Peninsula.

"We all know that when the sun doesn't shine, solar is not generating electricity," said Melville Nickerson the nuclear electric company NRG.

"We're going to build a lot of solar in a state that's not known for its sunshine," said Jason Hayes, from the Mackinac Center for Public Policy.

But given the concern around energy reliability, how does solar actually work in a region that experiences all four seasons?

On a sunny, chilly day in Cadillac, a solar garden operated by Consumers Energy hums along.

Jeff Davis, a solar manager with the company, said the current conditions are ideal, and the garden can power around a hundred homes.

"We're putting out full production today," Davis said. "Plus, we'll pull off that production and charge our batteries with it."

It's no secret that solar panels need sunlight to generate power, but they actually operate more efficiently in colder temperatures.

Davis said this is due to the semiconductor in solar panels, which absorbs light energy from the sun and transfers it to electron particles in the solar cells.

As the excited electrons move through a circuit, they generate electric energy in the process. But temperatures above approximately 85F or 30C can disrupt this flow.

"As that semiconductor inside the solar panel heats up, it gets less effective," Davis said.

On the flipside, snow can cover panels up, blocking the sun's rays. A pile of brooms leaning on a fence by the garden holds the answer.

"The brooms are for snow ... and if we clean the bottom 6-12 inches, it's enough for the sun to get to the panel," Davis said. "And then at that point, it'll heat up and allow the snow to melt off the panels."

Teresa Homsi
Brooms lean against a fence at a Cadillac solar site. On snowy days, they're used to clear a portion of the solar panels to let sunlight reach the cells.

According to Consumers' data, the energy output for the Cadillac site bounces around through the year. Its lowest recorded point was in April of 2022, and since the site went online four years ago, its average output hovers around 11,000 megawatt-hours (MWh).

For reference, a single MWh can meet a home's electric needs for just over a month.

Jessica Woycehoski, the director of electric implementation with Consumers Energy, said output can range from 8-18,000 MWh within a single month.

Woycehoski said even if energy output drops in the winter — or really any time of year with cloudy days — a diverse energy profile and extra solar panels make up the difference.

"When the sun is out and it's getting its highest production of energy, it's lining up with the same peak demand," Woycehoski said. "And since it's free, I don't have to pay for fuel other than just the variability of if the sun is available or not."

The garden in Cadillac is one of the company's four solar facilities, but Woycehoski said there are more projects on the horizon.

Editor's note: In the interest of transparency, we note that Consumers Energy is a financial supporter of WCMU.

Teresa Homsi is an environmental reporter and Report for America Corps Member based in northern Michigan for WCMU. She covers rural environmental issues, focused on contamination, conservation, and climate change.
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