“‘The LED of heating’: cheap geothermal energy system makes US comeback”.
By: Robert Buluma
This story spotlights a groundbreaking project in Minnesota that's bringing back Aquifer thermal energy storage (ATES) nearly 45 years after pioneering U.S. experiments.
In the frigid winters of Minnesota, where temperatures can drop below -10°C (-14°F), keeping homes warm traditionally relies on fossil fuels or inefficient electric systems. But a new development called The Heights in St. Paul is changing that by tapping into the stable temperatures deep underground.
The Revival of a 1980s Idea
Back in the late 1970s and 1980s, the U.S. Department of Energy funded tests beneath the University of Minnesota's St. Paul campus. Researchers drilled wells to store hot water in aquifers over 100 meters (about 330 feet) deep during summer, then extracted it for winter heating. The concept, known as seasonal thermal energy storage, aimed to cut primary energy use significantly. A 1991 federal report called aquifers one of the most cost-effective options.
Despite promising results, the technology didn't take off widely in the U.S. due to various factors. Meanwhile, countries like the Netherlands built thousands of similar systems,over 3,000 worldwide by recent counts, mostly in Europe.
Now, just miles from those original test sites, The Heights is bringing it mainstream. This 112-acre (about 45-hectare) mixed-use redevelopment sits on the former Hillcrest Golf Course on St. Paul's Greater East Side. Led by the Saint Paul Port Authority, with engineering and operations from Ever-Green Energy (a District Energy St. Paul affiliate), the project transforms a brownfield site into a vibrant community.
How Aquifer Thermal Energy Storage Works at The Heights
The system draws groundwater from an aquifer 100–150 meters (roughly 330–500 feet) below ground, where temperatures stay around 10°C (50°F) year-round,far more stable than Minnesota's swinging air temperatures (30°C summers to sub-zero winters).
High-efficiency electric heat pumps, partly powered by on-site solar panels, exchange heat with this groundwater:
- In winter: Warm aquifer water helps heat buildings efficiently.
- In summer: Cool water provides air conditioning.
- Seasonally: Excess summer heat can "charge" the aquifer like a thermal battery for winter use, or winter cold can be stored for summer cooling.
This differs from conventional air-source heat pumps, which struggle in extreme weather as compressors work harder. Aquifer systems maintain high efficiency consistently. Compared to traditional methods, they can slash greenhouse gas emissions by up to 74%, per a 2024 study,akin to swapping incandescent bulbs for LEDs in lighting efficiency.
Experts like Yu-Feng Lin from the Illinois Water Resources Center call it “the LED version of heating and cooling.” It's not the high-temperature geothermal for electricity (think geysers or lava), but low-temperature ground-source tech ideal for direct building use.
The Heights features wells across the northern development area, connected via pipes and heat exchangers to serve around 850 homes (part of a planned 1,000 units) plus light-industrial buildings. It's one of the first large-scale ATES projects in the U.S. in decades, and reportedly the first commercial aquifer thermal energy storage system in the country.
Economic and Community Benefits
Construction costs for the core system (wells, exchangers, pipes) hit about $12 million (£8.9m), excluding building-level equipment. Federal tax credits from the Inflation Reduction Act cover roughly 50%. Earlier, Minnesota's Climate Innovation Finance Authority (MnCIFA) provided a $4.7 million loan,their first ever,for the project.
For residents, savings could be huge. St. Paul City Council member Cheniqua Johnson notes potential monthly bills dropping from $200–300 to under $100. In communities where utility shutoffs are common due to high costs, this means real affordability and energy security.
The project also creates jobs,aiming for 1,000 living-wage positions and includes parks, green spaces, and all-electric infrastructure for lower emissions.
Why Now? A Perfect Fit for Minnesota
Minnesota boasts abundant shallow aquifers, making ATES viable without deep, expensive drilling (unlike rock-based geothermal). Costs are comparable to other geothermal networks but with less invasive installation.
Industry voices like Rob Thornton of the International District Energy Association see it as smart use of local resources. With federal incentives intact for geothermal (despite cuts elsewhere), and growing climate goals, the timing aligns perfectly.
Retired scientist Marc Hoyer, who monitored the 1980s tests (even sleeping by wells for data), feels vindicated: “I figured nobody cared about it,” he said. Now, at 82, he's seeing the tech resurface.
Broader Implications for Geothermal in the U.S.
This isn't isolated. Networked geothermal and thermal energy systems gained traction in recent years, with states exploring policies for expansion. The Heights showcases how old ideas, updated with modern efficiency and renewables, can deliver cheap, low-carbon heating/cooling.
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As the U.S. pushes renewables, ATES offers a reliable, grid-friendly alternative especially in cold climates. It reduces peak loads, stores energy seasonally, and cuts reliance on volatile fossil fuels.
The Heights isn't just housing,it's a model for sustainable urban redevelopment. From a former golf course to a carbon-neutral hub, it proves innovative geothermal can make a comeback, one aquifer at a time.
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