On a rainy spring day, a drill rig punched hundreds of feet into the earth, spilling muddy water out onto a dirt lot at the University of Louisville, where a new engineering school will soon stand.

Aric Andrew, managing the project for Luckett and Farley, trudged through the mud in a hard hat and hi-vis vest, raising his voice over the drill’s rumbling.

Beneath his feet, a construction crew was drilling 160 boreholes, he said, each one running hundreds of feet deep. The loop embraces the relatively constant temperatures found underground, typically between 50 and 60 degrees.

This steady warmth, tapped by a network of looping underground pipes and a ground-source heat pump at the surface, will ultimately manage 99% of the building’s heating needs and a majority of its cooling, reducing energy costs and emissions in the process.

In the summer, the system will pull heat from the building and move it underground. In the winter, it will pull heat from underground and move it into the building.

It’s a much more efficient process than conventional HVAC systems and even modern air-source heat pumps. Exchanging heat with Kentucky’s highly variable outdoor air temperatures takes more energy than exchanging with the temperatures underground, which stay closer to ideal indoor temperatures.

Many other major projects in town have looked to geothermal technology for the same reasons.

Last year, Louisville Muhammad Ali International Airport installed a $120 million system, building the largest geothermal wellfield of any airport in the country.

Jefferson County Public Schools has embraced the technology in half a dozen schools and counting.

Norton Commons has implemented geothermal across many of its homes, and has mandated it for the community’s developing north village.

Local firms are installing the systems in single-family homes across Louisville, too.

The popularity of geothermal heating and cooling systems — particularly in the last decade or so — comes amid generous federal tax credits, rising costs of fossil fuel-based utilities, and increased urgency among businesses and consumers to rein in greenhouse gas emissions.

Louisville has committed to achieving net zero greenhouse gas emissions across the community by 2040, a target set by resolution in 2022 with former Mayor Greg Fischer’s signature.

But it’s a lofty goal for a city currently relying almost solely on fossil fuels for its energy needs — a dependency that has “inflicted environmental injustices on its residents” and put public health at risk in marginalized communities, according to a recent report from Louisville Metro Government and the mayor’s Office of Sustainability.

Nearly half of the greenhouse gas emissions in Louisville and surrounding counties “are related to heating and cooling of residential and commercial buildings,” according to the report.

Louisville’s summers are also growing warmer amid climate change. As a consequence, residents will use more air conditioning, and more fossil fuels will be burned to keep those air conditioners running.

For the city to meet its net zero target, it must figure out how to heat and cool its buildings without heavy reliance on fossil fuels.

Geothermal heat pump systems, paired with energy efficiency improvements and renewables like rooftop solar, could be a key solution.

But despite technological advancements and a 30% federal tax credit, there’s still a key barrier to geothermal: Installing the systems, in some cases hundreds of feet underground, is expensive.

Louisville has worked to incentivize and streamline solar installation, among other sustainability measures.

So far, geothermal hasn’t gotten the same attention, with an absence of incentive programs from state and local governments, as well as LG&E and KU.

“We know it’s an important part of the solution but don’t have specific programs yet to promote it,” said Sumedha Rao, executive director of the mayor’s Office of Sustainability, adding, “It’s on our list.”

‘Is it really that good?’

Geothermal units are being built at Louisville's Norton Commons. A series of loops are used -- digging down around 350 feet -- for an alternative to traditional HVAC systems. The loops connect to geothermal heat pumps, which can reduce heating and cooling bills significantly.

On the outskirts of Norton Commons’ north village, there are still some dirt lots waiting for homes.

Pairs of black pipes jut out of piles of limestone on each lot, reaching up from hundreds of feet below ground. The underground loops will carry a water and antifreeze solution, joining with a ground-source heat pump once the home is built.

The property’s price tag will be higher by thousands of dollars — depending on the home’s heating and cooling load — compared to a home with a conventional system.

But the homeowner will see markedly lower utility bills, often recovering the difference in upfront cost within five or six years, according to spokespeople for Norton Commons, which sits on the eastern edge of Jefferson County.

From the outside, there’s no noise, and no visible equipment. Once underground, maintenance for the loop is almost unheard of, according to builders and industry experts.

Protected from the elements and with no moving parts, the underground loop is generally rated for a 50-year lifespan. The Department of Energy rates ground-source heat pumps for 20 years or more.

Mark Simpson owns a construction company and builds houses with geothermal at Norton Commons, where he’s also a resident.

“The question I get is, ‘Is it really that good?’” he said. “And I can just say, ‘well, from personal experience, yes.’”

When Norton Commons first announced its mandate for geothermal in its new homes in the north village, it was builders who were most skeptical.

The technology made for more expensive homes to sell, and builders like Simpson didn’t want to build out entire neighborhoods with faulty heating and cooling technology.

Geothermal units are being built at Louisville's Norton Commons. A series of loops are used -- digging down around 350 feet -- for an alternative to traditional HVAC systems. The loops connect to geothermal heat pumps, which can reduce heating and cooling bills significantly.

Simpson said it didn’t take long to get comfortable with it.

“If it was an abysmal failure, and you’d already put it in, we’d be stuck with these houses,” he said. “But it’s been a huge success.”

Still, Norton Commons is not representative of the average Louisville community. It’s new, and it’s affluent — making geothermal more accessible.

Across the nation, reducing upfront costs of implementing the technology, including drilling, is “the No. 1 hurdle for the industry,” according to Bryant Jones, executive director of Geothermal Rising, a nonprofit trade association.

This is especially true in Louisville, where there’s a gap in incentives at the state and local levels.

But finding ways to implement geothermal more broadly across the city, and elsewhere in Kentucky, could help assuage some of the energy fears brewing in the state legislature.

In recent years, lawmakers have shouted from the rooftops about grid reliability, energy costs and fears of losing out on economic development for lack of power. Republicans, especially, have cited this concern in efforts to keep aging coal-fired power plants running.

Widespread implementation of geothermal, where applicable, could ease burden on the grid and bring down costs for consumers.

Mass deployment of geothermal heat pumps across the nation, paired with weatherization of homes, could reduce consumer electricity payments by “at least $300 billion through 2050,” according to a Department of Energy-funded analysis published last year.

In June, state lawmakers held a hearing with industrial energy consumers about their future needs.

Industry representatives had mixed input about the continued use of fossil fuels versus carbon-free sources, but found general consensus on some concerns — including reliability of the grid and rising transmission costs.

In the same national analysis, researchers found mass geothermal deployment could avoid “as much as 24,500 miles of new grid transmission lines by 2050 — enough to cross the continental United States eight times.”

Louisville’s favorable conditions for geothermal

A sign marks the entrance to the construction site at the University of Louisville's $90 million engineering building, which is slated to open in 2025. Workers are drilling 160 geothermal boreholes for natural heating and cooling that will make the building much more energy efficient. March 6, 2024

Omid Ghasemi Fare, a professor of geotechnical engineering at the University of Louisville, began researching geothermal more than a decade ago.

“I got interested in this research more because of the future,” he said. “This will help us to decarbonize.”

At the time, research into geothermal energy, particularly for heating and cooling applications, was understudied, he said. And today, industry advocates say it’s still misunderstood.

“Too often, I’m talking to a policymaker, or even someone in the media … and they think geothermal is relegated to Iceland and volcanoes,” Jones said. “And that is a myth, a misconception about geothermal.

“Geothermal is everywhere,” he said, “because the planet is hot. It’s naturally creating heat.”

That includes Kentucky, and experts said there are several factors making Louisville and the surrounding region favorable for accessing geothermal resources.

The Louisville area has soil with high thermal conductivity, helping heat flow in geothermal systems, Ghasemi Fare said.

The region’s balance of warm summers and cool winters also lends itself to geothermal, allowing heat to move back and forth with the seasons.

And limestone, plentiful in the area’s geology, is favorable to drillers, Simpson said.

But funding geothermal projects remains a challenge. Despite some momentum in scaling the industry, upfront costs have remained high compared to conventional heating and cooling systems.

Some stakeholders in Louisville are hoping new models of financing geothermal projects can help deploy the technology in more buildings in a bid to meet ambitious carbon reduction targets.

Financing geothermal technology

While some states offer incentives for geothermal heat pump systems, Kentucky does not.

And LG&E does not have a residential rebate or incentive program for geothermal, though businesses can include geothermal in applications for the utility’s case-by-case, custom business rebate, according to spokesperson Chris Whelan.

At the mayor’s Office of Sustainability, staff are considering ways to make local investments in geothermal heating and cooling more achievable.

The office already has a model for encouraging renewable and efficient energy use. The popular Solarize Louisville program, formerly Solar Over Louisville, helps the community access wholesale prices and reliable contractors for the installation of rooftop solar.

“Why don’t we do Geothermal Under Louisville?” asked Margaret Stewart, an advocate with the Renewable Energy Alliance of Louisville.

Rao, head of the Office of Sustainability, agreed there are lessons to be taken from the solar program and applied to other energy projects, including geothermal.

“People are curious about these technologies. They don’t know too much about them,” she said. “They don’t know where exactly to find a contractor, and what to look for to make sure that the pricing is right, the contractor is trustworthy and what the ROI is going to be.”

Other energy financing tools, including the U.S. Environmental Protection Agency’s Greenhouse Gas Reduction Fund and Louisville’s Energy Project Assessment District program, could also potentially offer support to geothermal projects, Rao added.

Sam Avery, a former solar installer and renewable energy advocate, called on the state to devise an incentive program for geothermal, “just to kind of get over the hump of the initial expense.”

He added geothermal heating and cooling to his farmhouse in Hart County, but he knows the systems aren’t the right fit for every building.

Land is needed for the underground loop to go in, and it can be difficult to install in some existing buildings, depending on their energy efficiency and weatherization.

“When I built my house here, I had no idea I was going to put in geothermal. And I was able to make it work,” Avery said. “Some buildings, it’s not going to work. For other buildings, it will.”

The stakes of decarbonizing Louisville

Jacob Brown, senior project manager with Whittenberg Construction, watches as workers drill one of 160 geothermal boreholes at the University of Louisville's $90 million engineering building, which is slated to open in 2025. March 6, 2024

The University of Louisville wants its new engineering building to be net zero. It also wants to set an example of sustainable ingenuity for the students who will soon walk the halls.

“We’re not just a business,” said Justin Mog, assistant to the provost for sustainability initiatives. “We’re here to change minds.”

Mog is hoping to build out the university’s sustainability office, as the campus works toward emission reductions. The university has reduced its total greenhouse gas emissions by more than half since 2008, and maintains a goal of climate neutrality by 2050, though Mog is aiming higher.

Not far from campus, Louisville’s airport is also betting big on geothermal technology. A $120 million project has produced the largest geothermal wellfield of any U.S. airport.

New geothermal heat pump equipment is shown at Louisville Muhammad Ali International Airport in this provided photo. The technology is expected to drastically reduce the airport's energy use and maintenance costs.

The investment is expected to bring a 45% reduction in energy costs and about a $400,000 per year reduction in maintenance costs, according to Brian Sinnwell, chief operating officer.

The savings could cover the higher upfront cost in a little more than a decade. Sinnwell said his team is still collecting data, but has been pleased with the system’s performance, including over this past winter.

The project will be paired with rooftop solar, among other sustainability efforts, as the airport undertakes a $400 million modernization.

But for community-wide decarbonization, Louisville will need to figure out how to democratize technologies afforded by the city’s largest institutions, including geothermal.

A large geothermal wellfield is drilled at Louisville Muhammad Ali International Airport in this provided photo. Upon construction in 2023, the wellfield became the largest of its kind at any U.S. airport, and is expected to reduce energy and maintenance costs for the facility.

In some cases, retrofitting geothermal systems for existing structures will prove cost-prohibitive, Simpson said.

Communities elsewhere are looking for solutions. Advocates in Chicago’s south side are hoping to install geothermal wells in alleys — where there aren’t underground utilities already in the way — to access more efficient, climate-friendly heating and cooling, according to reporting from Grist.

Louisville, too, has plenty of original neighborhoods with alleys weaving between them. But understanding the feasibility of scaling up geothermal use in Louisville’s original neighborhoods will likely require case-by-case assessments of existing buildings by experts.

Expert consultations consider a building’s weatherization and the necessary space for installing the underground loop, which in some cases means making room for a drill rig or other large equipment.

While policymakers and local leaders seek to chart a path for community-wide decarbonization, Louisville is getting hotter, and experts predict devastating consequences for public health.

“One of the biggest health threats facing Louisville residents is the increasing incidence, severity, and longevity of heat waves,” according to a 2020 climate vulnerability assessment conducted for Louisville Metro Government.

And by midcentury, Louisville can expect 48 days of temperatures over 100 degrees each year, compared to five days per year historically, according to a 2019 study cited in the assessment.

“This is something we all have to do eventually,” Avery said. “We all have to stop using fossil fuel for everything: for transportation, for electricity, for heating and cooling. It’s just not going to be there.”

Connor Giffin is an environmental reporter for The Courier Journal. Reach him directly at cgiffin@gannett.com or on X@byconnorgiffin.