Aquifer Geothermal Energy Gains Momentum in the U.S.

It has been close to five decades since the initial experiments with underground thermal storage conducted by the U.S. Department of Energy at the University of Minnesota, and there is a growing momentum towards making geothermal energy more affordable and sustainable. The initial project, which began in the 1970s, sought to store the excess heat produced during the summer months in deep aquifers so as to reduce dependence on conventional sources of energy and lower emissions of greenhouse gases. Currently, a large-scale aquifer thermal energy system (ATES) is being constructed less than ten miles away from where the initial experiments were conducted.

The Heights Development and Its Innovative System

The initiative is a component of The Heights, a mixed-use development that is currently turning a former golf course in the Greater East Side of Saint Paul into a thriving neighborhood with 850 residential units and several light industrial buildings. The Heights’ novel cooling and heating system will harness the groundwater stored in aquifers that lie 100 to 150 meters below ground level. Groundwater extraction wells will be distributed throughout the northern part of the 45-hectare land area, and the water will be treated using high-efficiency electric heat pumps.

Groundwater as a Thermal Battery

The groundwater in this aquifer will serve as a thermal battery, much like in the previous experiments and other systems around the world, most of which are in the Netherlands, where more than 3,000 systems are already in place. In winter, warm water will be extracted to heat buildings efficiently. In summer, cold water will be used to cool buildings, and excess heat will be stored in the aquifer for future use. According to Michael Ahern, senior vice president for system development at Ever-Green Energy, the company behind the project, this system has the potential to greatly decrease the use of conventional heating and cooling systems, which are energy-intensive and produce high levels of greenhouse gas emissions.

Historical Context and Early Research

This initiative represents one of the first large-scale U.S. projects of its kind since the 1980s, when federal field tests laid the groundwork for understanding aquifer thermal energy storage. The early research involved meticulous monitoring, with scientists like Marc Hoyer, then with the Minnesota Geological Survey, working around the clock to record temperature and pressure data at test sites. Hoyer, now 82 and living in Maryland, expressed enthusiasm about the renewed interest in this technology. “I figured nobody cared about it,” he said, reflecting on the early days of the project. Now, he sees the technology’s potential to play a key role in America’s sustainable energy future.

Environmental Benefits and Emission Reductions

One of the most compelling advantages of aquifer thermal energy storage (ATES) is its ability to dramatically cut greenhouse gas emissions—up to 74%, according to a 2024 study—making it comparable in impact to switching from incandescent lighting to LEDs, often called the “LED of heating and cooling.” Yu-Feng Lin, director of the Illinois Water Resources Center, describes this technology as “the LED version of heating and cooling,” emphasizing its efficiency and environmental benefits.

In contrast to traditional geothermal power plants that use hot rock or steam resources to produce electricity, aquifer geothermal power plants are much simpler and more economical. Aquifer geothermal power plants operate on shallow, water-saturated underground strata that are naturally abundant in Minnesota. These strata are both sources and sinks of thermal energy.

Economic Outlook and Support

The economics of aquifer geothermal are favorable, especially with federal support. The system planned for The Heights will cost approximately £8.9 million ($12 million) to build, covering wells, heat exchangers, and piping infrastructure. The costs of heat pumps and building-specific equipment are additional, but federal tax credits—secured through the Inflation Reduction Act—are expected to cover roughly half of the total expenditure. This financial support makes the project more accessible and attractive, particularly for community-focused developments aiming to reduce energy bills and carbon footprints.

Cheniqua Johnson, a Saint Paul city council member and treasurer of the Saint Paul Port Authority, highlights the economic impact: “It’s the difference between paying a $200 to $300 per-month bill, and less than $100.” Many residents in her district have faced utility shutoffs due to high energy costs, and she views geothermal as a way to provide more affordable, reliable heating.

Future of Sustainable Infrastructure

The project also features a geothermal system managed by Darcy Solutions, a local start-up company, that will provide heating and cooling for a new Xcel Energy service center in the area. Kristine Williams, the chief development officer of the Saint Paul Port Authority, believes that this is a look into the future of industrial and community infrastructure, embracing sustainable and local energy solutions.

Reviving a Promising Technology

As the new system at The Heights is now under construction, it symbolizes the revival of a technology that was previously believed to be a niche market but is now recognized for its ability to make a significant difference in the reduction of carbon emissions and energy expenses. With continued innovation, aquifer thermal energy systems could be the key to a sustainable energy future for America, proving that sometimes it is the simplest ideas that make the biggest difference.