Look Out, California: One of the Country’s Largest Solar Arrays is Taking Shape in… Illinois?

A 593-megawatt project has begun construction near Springfield and will power O’Hare Airport and Chicago government buildings.

Construction at the Double Black Diamond solar project in southeast Sangamon County on March 20, 2023 near Virden, Illinois. Photo Courtesy of Rich Saal/Swift Current Energy of Boston
Construction at the Double Black Diamond solar project in southeast Sangamon County on March 20, 2023 near Virden, Illinois. Photo Courtesy of Rich Saal/Swift Current Energy of Boston

Share this article

The largest solar arrays operating in the United States are located in the kinds of sunny states you would expect—five in California, four in Texas and one in Arizona.

But a project that began construction last month in Illinois is going to be about as large or larger than all of them.

The 593-megawatt Double Black Diamond Solar farm near Springfield is indicative of several trends in solar power, as projects grow ever larger and are built in places that get much less sun than the southwest.

The developer, Swift Current Energy of Boston, is building the project to meet demand from corporations and local governments aiming to meet clean energy goals.


We deliver climate news to your inbox like nobody else. Every day or once a week, our original stories and digest of the web’s top headlines deliver the full story, for free.

Among the buyers is the Chicago city government, which has said that the project will provide most of the electricity used by municipal properties, including some giant power users like O’Hare and Midway airports and two water purification plants. 

Chicago’s involvement with the project is tied to the city’s goal, adopted by former Mayor Rahm Emmanuel and affirmed by the current mayor, Lori Lightfoot, to use 100 percent renewable electricity in city buildings by 2025.

But the city doesn’t have a contract with the project itself. Instead, Chicago has a deal with Constellation Energy to supply the city with 100 percent renewable energy. The Baltimore-based company sells electricity and natural gas contracts in states—like Illinois—that allow customers to choose their supplier for those resources.

Double Black Diamond solar project

Constellation will obtain 70 percent of Chicago’s total from Double Black Diamond, once the project finishes construction in 2024. The rest could be renewable energy from anywhere, although city officials have said they would like to have much of it come from projects in the Chicago area.

“I am as excited as anybody to see shovels in the ground, so to speak, this spring,” said Jared Policicchio, Chicago’s deputy chief sustainability officer, about the solar project.

“We are hoping that we can demonstrate to other public agencies and, frankly, private organizations in the region, that you can cost effectively continue to spur the quick development of this critical industry,” he said.

The city’s electricity contract is helping to support the solar project while still paying electricity rates that are competitive, he said.

Double Black Diamond has customers in addition to Chicago. State Farm, the insurance company, and PPG, the paint manufacturer, have signed up to buy power from the project.

The largest operational U.S. solar project by capacity is Topaz Solar Farm in San Luis Obispo County on the Central Coast of California, with 586 megawatts, according to the Solar Energy Industries Association, which also provided the list of the top 10 projects I referred to at the beginning.

Installation at the Black Diamond solar project site. Photo Courtesy of Rich Saal/Swift Current Energy of Boston
Installation at the Black Diamond solar project site. Photo Courtesy of Rich Saal/Swift Current Energy of Boston

Double Black Diamond has slightly more capacity, with 593 megawatts, but it’s smaller than Topaz in acres. Double Black Diamond covers about 4,100 acres, while Topaz is about 4,700 acres. Let’s just say both of them are really big and they have about the same capacity. (I should also mention Copper Mountain Solar in Nevada, which has more than 800 megawatts, built over a decade in five phases; some observers say this is the largest operational project, while others count the phases as separate projects.)

The ever-increasing sizes of solar projects mean that several of the others in development are going to be larger than Topaz and Double Black Diamond. The research firm Wood Mackenzie says Double Black Diamond ranks at least eighth in capacity of projects that are in some phase of development but not yet operational.

Among the challenges wind and utility-scale solar projects in Illinois have faced is opposition from local residents who view the developments as ugly, and a lack of enough transmission lines to deliver the electricity.

Keep Environmental Journalism Alive

ICN provides award-winning climate coverage free of charge and advertising. We rely on donations from readers like you to keep going.

Donate Now

Double Black Diamond was able to navigate both challenges. It got approval in 2021 from the county government that hosts the project, despite testimony from some neighbors opposing it.

Also, the project had the benefit of being close to a relatively new transmission line that had capacity available, the Illinois Rivers project built by the utility Ameren.

Double Black Diamond also got a boost from clean energy policies, including the Chicago 2025 target and several state laws that encourage wind and solar development. A 2021 state law, the Climate and Equitable Jobs Act, is one of the reasons that the project is required to be built with workers making union wages and meet standards for diversity in hiring.

If there are going to be more projects of this magnitude in Illinois, another law is going to play a role: the federal Inflation Reduction Act. This climate and clean energy law from 2022 passed too recently to have much of an effect on Double Black Diamond, but it is likely to have a huge effect on the clean energy economy going forward.

I asked Eric Lammers, CEO of Swift Current Energy, what the IRA means for his company and industry.

“The IRA has caused investment in renewable energy to accelerate,” he said in an email. “At Swift Current, we’re particularly excited about provisions in the IRA that increase investment in clean energy manufacturing and in communities that have historically contributed to America’s energy independence.”

Other stories about the energy transition to take note of this week:

New US Tailpipe Emissions Standards Could Make or Break Biden’s Climate Legacy: New vehicle emissions rules proposed Wednesday by the Biden administration are a big deal, with the potential to severely cut into the climate harm done by cars and trucks, as my colleague Marianne Lavelle reports. To meet the rules, automakers and consumers are going to need to accelerate their shift to electric vehicles, and there are signs of momentum in that direction. But I can’t overstate the scale of the change that would need to happen, with two-thirds of the passenger cars needing to be EVs within a decade. And I’m not going to underestimate the challenges that are sure to arise in the form of opposition from some elected officials, automakers and fossil fuel companies.

The Real-World Costs of the Digital Race for Bitcoin: The New York Times identified 34 large-scale U.S. sites that produce the cryptocurrency Bitcoin, a process that uses up tremendous amounts of electricity and contributes to an increase in carbon emissions and utility bills for everyone around them. The findings go against an argument commonly made by cryptocurrency businesses that their industry is mostly tied to clean energy and does not strain the grid, as Gabriel J.X. Dance reports. This well-reported story annihilates the idea that Bitcoin is part of the clean energy economy.

Four in 10 Say Their Next Vehicle May Be Electric: A substantial share of the U.S. population is considering a switch to an EV, but it’s not yet a majority, as Tom Krisher, Matthew Daly and Hannah Fingerhut report for the Associated Press. About 4 in 10 U.S. adults said they were likely to switch, according to a poll by the AP and its partners. Only 8 percent said they or someone in their household owns or leases an EV. Maybe it’s a “glass half full” kind of thing, but I find these numbers encouraging about the prospects for EV demand, even though I realize others are citing the same poll to say interest in EVs is low.

New York Auto Show Has More than Three Dozen New EV Models, and Also Concerns About Charging: The Ram 1500 Rev and Hyundai Ioniq 6 are among the more than three dozen new EV models on display at the New York International Auto Show, a number that shows rapid progress in the auto industry’s shift to electricity. But the show has also provided a forum to discuss some of the challenges hindering EV adoption, including the lack of easy access to charging for many people, as Maria Gallucci reports for Canary Media. One expert in the story says the lack of adequate public charging is the No. 1 obstacle to EV adoption, and that’s confirmed by the poll I just mentioned, in which three quarters of respondents cited this concern as a reason to stick with gasoline.

California Denies Bid from Home Solar Company to Sell Power as a ‘Micro-Utility’: California regulators have rejected a plan from Sunnova, the rooftop solar company, to set up microgrids to serve newly built communities with solar and energy storage, as my colleague Emma Foehringer Merchant reports. The California Public Utilities Commission said its denial of the plan was due in part to a lack of specificity in Sunnova’s application. The dynamics in this case are familiar to anyone who follows California energy policy. The state is the national leader in rooftop solar, but its regulators and policymakers often make decisions friendly to utilities, the giant companies that in this case viewed Sunnova’s plan as a threat that would take away market share.

Inside Clean Energy is ICN’s weekly bulletin of news and analysis about the energy transition. Send news tips and questions to dan.gearino@insideclimatenews.org.