St. Paul, Minnesota’s public schools are tapping geothermal to cut emissions and building costs 

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Geothermal heating and cooling is emerging as a go-to technology for St. Paul Public Schools as it seeks to renovate aging facilities in line with the district’s climate action plan.

Minnesota’s second-largest school district is also one of the city’s largest property owners, with 73 buildings containing more than 7.7 million square feet. Its climate action plan calls for reducing greenhouse gas emissions at least 45% by 2030.

New technology and federal incentives have helped convince district leaders that geothermal is among its best options for slashing emissions from school buildings. The energy efficient systems pump refrigerant through a closed loop circuit of pipes that moves heat between buildings and below ground reservoirs.  

Last year, the district completed a ground-source geothermal system while renovating the 1960s-era Johnson High School. This year, it’s installing a different type of system at two other schools that tap aquifers rather than the ground as a heating and cooling source.

The aquifer-based systems that will be used at Bruce Vento Elementary School and the nearly 100-year-old Hidden River Middle School were developed by a Twin Cities-based company called Darcy Solutions that specializes in water-based geothermal systems.

The company’s technology requires far fewer wells than conventional, ground-based systems, making them more practical for dense, urban neighborhoods. Darcy places heat exchangers directly into the wells, where they can capture heat from the constant, 52-degree groundwater.

Darcy’s system changed the school district’s thinking, said Tom Parent, the district’s executive director of operations and administration. The elementary school project required just five wells, compared to more than 150 ground source wells at Johnson High, which disrupted outdoor sports activities for two summers. 

“We see a lot of promise,” Parent said. “This is an incredible leap in technology.”

State and federal incentives

Geothermal and aquifer-based systems could be an essential strategy for reducing emissions, along with energy efficiency, LED lighting, electric buses and solar energy, Parent said. Because many St. Paul schools have small footprints, Darcy’s system could become a go-to HVAC solution.

Traditional ground-source geothermal would have been “impossible” at either school because of their small sites, according to the district’s indoor air quality coordinator Angela Vreeland. Darcy’s geothermal systems also take up less interior space than traditional, fossil fuel heating systems. 

In Minnesota, several trends are driving geothermal’s growth. Nearly all projects receiving state aid must follow the rigorous standards for energy efficiency. Matt Stringfellow, a manager with Kraus Anderson who works on geothermal installations, said that “any state-funded project pretty much requires that (geothermal) to meet their guidelines at this point.”

Another catalyst has been the Inflation Reduction Act. The law allows a commercial building owner installing geothermal to claim as much as a 30% tax credit. It will enable nonprofits to receive the equivalent amount in cash from the federal government.

Parent said the school district used federal money to pay for its first geothermal project and plans to submit paperwork to take advantage of the Inflation Reduction Act’s direct pay option for this year’s projects, too. While not the only driving force in selecting geothermal, it played a role, he said.

Geothermal ‘seems to be more and more the right answer’

Robert Ed, Darcy’s director of marketing strategy, said geothermal is one of the only solutions for electrifying large buildings in cold climates. “There are other energy efficient technologies, but in a northern climate, being able to use geothermal energy and not having to expend a lot of energy to provide thermal capacity is a big advantage,” he said.

The Netherlands, Denmark, Sweden, and Belgium have been the primary users of geothermal aquifers, but Darcy aims to change that. Ed said the startup has expanded to Wisconsin and will now begin adding more states that have the right groundwater characteristics to work with its technology. 

Parent said the Johnson project shows “just how viable (geothermal) can be under certain circumstances for our system. Now we’ve got two more projects underway with geoexchange systems; we’re learning how it can play a role in the continuous cycle of renewal in our buildings.”

Darcy advertises that its technology creates 70% fewer emissions and lower cooling costs than a traditional heating and cooling system. At Bruce Vento Elementary, named after a Minnesota congress member well-known for environmental advocacy, stakeholder engagement at the district level led to a desire to decrease energy intensity in buildings.

“Geothermal is the only way we are getting within spitting distance of what we want it to be able to do,” Parent said.

A Department of Energy analysis found retrofitting around 70% of buildings, combined with building envelope improvements, could bring a 13% reduction by 2050 in electricity demand.

Yet geothermal systems barely make a slice of the energy pie chart, producing less than 1% of the country’s energy capacity, according to the United States Department of Energy. The industry, however, is growing. Ground-source heat pump sales have grown by 3% annually, and the United States continues to be the international leader in geothermal energy.

The three schools will see significant savings over natural gas systems. Vreeland said the annual savings will be $143,000 at Hidden River Elementary and $200,000 at Bruce Vento. Both should pay for themselves in a decade. Johnson High’s savings will be $7 million over 30 years.

Darcy is also installing aquifer-based geothermal systems at two schools in Winona in southeastern Minnesota. It also recently installed a system at Rochester’s City Hall. 

Parent said geothermal may not be the answer to every HVAC renovation, but it shouldn’t’ be overlooked. 

“We don’t see a world in which geothermal energy is our only solution path forward because of the idiosyncrasies of our building, funding, and timing,” he said. “But it seems to be more and more the right answer.”

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