Building on brownfields: A first-in-the-U.S. storage project lands on a coal site

A utility-led project shows the promise — and challenges — of developing climatetech projects on used sites.

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A view of a coal-fired power plant through a fence

Photo credit: Natalie Behring / Getty Images

A view of a coal-fired power plant through a fence

Photo credit: Natalie Behring / Getty Images

Today, the Columbia Energy Center in Pardeeville, Wisconsin, looks much like any coal plant: smokestacks billowing into the air and nondescript buildings, all surrounded by chain-link fencing. 

But in a matter of years, a huge, oblong dome is expected to be plopped onto 12 acres of the site. Inside, the dome will house a pioneering long-duration energy storage technology, the first of its kind planned in the U.S.

The Midwestern utility Alliant Energy owns the property, and will be one of the first to install this type of storage project, which is designed by an Italian company called Energy Dome and relies on compressed carbon dioxide. Once completed, the 20-megawatt project will have the capacity to power about 20,000 homes. If it's successful, the utility is interested in adding even more domes, potentially up to a dozen, after the site’s life as a coal facility ends in 2026.

Reusing sites like these for clean energy projects is not a new concept — indeed, industry observers have been encouraging the placement of renewable projects on brownfields for over a decade — but their use for long-duration storage projects, especially by the same utility that already owns the property, is a relatively new variation on the theme. Alliant’s reasons for building the project on the site of its own coal plant embody some of the advantages of the practice, which remains niche even after years of enthusiasm from state and federal government. 

There are indications that building on brownfields could become more common, however, especially as fossil fuel plants continue to retire and the benefits — including all-important access to transmission — are increasingly attractive. Illinois has recently provided funding to transform five old coal sites into solar facilities, and Alliant itself has built a solar project on an old coal ash landfill. In Wyoming, Bill Gates-backed TerraPower is developing a nuclear project near the location of an old coal plant.

Building clean energy and climate tech projects on brownfields is “happening a lot more, I think, than anybody really realizes,” said Gail Mosey, a senior researcher in land reuse at the National Renewable Energy Lab. “In many cases, it's the best reuse of land.”

Today, though, these cases of transformation still represent a tiny sliver of the country’s total brownfields sites, which now number more than 450,000. Only about 500 renewable energy projects have been built on those sites, according to data from the Environmental Protection Agency. 

It remains an open question when, and if, climatetech developers will fully embrace building on these sites, but there is certainly a potential synergy between the large number of them and the significant capacity that needs to be added to the grid, especially storage capacity. A grid built for net-zero emissions will need between 225 and 460 gigawatts of long-duration energy storage by 2050 alone, according to a recent Department of Energy report.

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Building on brownfields can be easier for a developer for a number of reasons, said experts like Mosey. Perhaps highest on that list is the potential to avoid long interconnection lines, a notorious project killer. In 2023, the U.S. interconnection backlog exceeded 2 terawatts, a figure likely to intimidate any developer. Many previous site uses, like manufacturing or electricity production using fossil fuels, required a connection that can be reused. In Wisconsin, that’s a key consideration for Alliant. 

“One of our objectives is to try to retain the interconnect capacity opportunities that we have at those retiring plants,” said Mike Bremel, the company’s director of engineering and customer solutions. 

Though Alliant’s coal plant is slated for decommissioning in the same year that the dome is projected to be constructed, there’s incremental capacity left on the grid that the utility can tap into. Finding a new location for the storage project would have required Alliant to put it at the end of a long queue. (MISO has more than 120 Wisconsin projects currently in line).

Cheap land is also good for clean energy projects, because that cost gets factored into the overall levelized cost of electricity. Certain sites may need remediation, but previously used land can be cheaper than greenfields, said Soji Adelaja, a professor of land policy at Michigan State University. Cleaning up those sites could also help a project move forward in the regulatory process, by creating societal benefits that decision makers may recognize. 

“The fact of the matter is, we just don't have enough money to clean up all the sites across the country,” said Adelaja. “By going from some of the more toxic and environmentally-degrading uses of land to some of the more promising and green and renewable uses of land, that’s just a major, major, major gain for society.”

Governments and community members may be eager for an abandoned site to be put to new use, said Mosey. In fact, renewables projects on undeveloped land have at times faced pushback from environmental groups and community groups, who say it would be better to build on already disturbed sites. 

In certain circumstances, redevelopment can even mean financial incentives. The EPA, for instance, provides a variety of grants for development on brownfields and has created a map specifically focused on brownfields that could be redeveloped for renewable energy, though currently it only estimates potential for wind, solar, geothermal, and biomass projects, but not storage. 

Alliant received a Department of Energy demonstration grant to build its long-duration energy storage project. The Inflation Reduction Act also includes tax credits for projects in “energy communities,” which include areas with brownfields or closed coal mines.

With all this upside, it may seem odd that more of those projects haven’t been completed. There are more than 3,600 solar projects larger than 1 megawatt across the U.S., according to a U.S. Geological Survey database; EPA data suggests only 465 of those are on brownfields. 

But there are also hurdles when picking a used site. Community engagement, for instance, can present a challenge for building on brownfields, because projects still require local consultation and buy-in. 

One of our objectives is to try to retain the interconnect capacity opportunities that we have at those retiring plants.
Mike Bremel, Alliant Energy's director of engineering and customer solutions

In the case of Alliant’s energy dome, the storage project will replace a facility that’s polluted the surrounding area since the 1970s. Though the new installation shouldn’t emit anything if it works properly, it isn’t entirely without risk. It uses carbon dioxide, essentially storing it in a big balloon inside the dome and switching it between liquid and gas forms to store and release energy. Carbon dioxide is dangerous if released at significant volumes — it displaces oxygen, which can cause vehicles to stop working and people to asphyxiate. 

The energy dome isn’t far from nearby towns. So for safety, the design includes sensors inside and outside of the dome. Alliant said they’ve consulted with the local community on the project.

The potential to provide some new jobs and buy equipment for the project from within the state, along with the project’s first-in-the-U.S. status, helped build local interest, according to Oliver Schmitz, an associate dean of research innovation and engineering professor at the University of Wisconsin, Madison. Schmitz worked with Alliant on its DOE proposal and helped found a university initiative focused on community-led energy transition projects.

“I think as a lighthouse project, it really plays a role in forming an innovation ecosystem,” Schmitz said. “It’s a real landmark.”

Alliant’s existing control of the site also provided another advantage to make construction simpler. Very old sites can also have a lot of history, numerous past users, and an opaque chain of ownership that may be difficult to navigate in order for a new company to purchase or clean up the land. 

Seeking out a site takes on new complexity when not looking for an open tract of land out in the desert or amid farms. 

And the cleanup of certain industrial sites can be costly and add engineering complexity. At the Columbia coal plant, Alliant is installing the energy dome on a part of the property that was largely untouched and only requires minimal grading. But other areas of the property contain coal ash ponds that can take years to settle. If the utility decides to add more domes later, they’ll have to ensure that the land is stable. 

“Obviously that's just going to increase your engineering and potential changes in your design,” said Bremel. 

Because each used site is different, companies often can’t just roll in and drop solar panels or a novel LDES technology. A brownfields project needs to take into account the site’s overall condition and size, which can potentially limit the configuration of a project as well as its scope.

More difficult engineering can add more cost and complicate the economies of scale that are so important in the early days of a technology’s development. But certain clean energy projects can leave land relatively undisturbed. The dome, for instance, is basically just placed on top of a site. 

Mosey says adding value, rather than taking it from an untouched piece of property, is always a worthwhile endeavor. And today, there’s plenty of sites to choose from.

“The earth has already been turned on those sites, and in many cases there's just not another viable reuse,” said Mosey. “It is technically probably easier to buy a pristine piece of land and build your house on that land than it is to buy an old house and renovate it.” 

But, she added, there are "a lot of reasons” that the proverbial old house should, at times, win out. 

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