Minnesota Revives 45-Year Geothermal Dream in New Housing

Forty-five years ago, scientists slept in trailers and woke every hour to check temperature gauges on an ambitious clean energy experiment beneath the University of Minnesota. They were testing whether water stored deep underground could heat buildings months later, and the results were promising enough that a 1991 federal report called it "the most cost-effective approach" to reducing energy use.

Now that dream is finally getting built. The Heights, a new development rising from a former golf course in St. Paul, will use underground water to heat and cool 850 homes and several industrial buildings with barely any greenhouse gas emissions.

Here's how it works: Electric heat pumps will draw groundwater from wells drilled 100 to 150 meters below the surface. While Minnesota air temperatures swing wildly from 30°C summers to -10°C winters, the aquifer stays a steady 10°C year-round. That stability means the heat pumps don't have to work as hard, making them dramatically more efficient.

The system gets even smarter. Excess heat from summer can be stored in the aquifer like a thermal battery, then retrieved in winter to warm homes. Cold from winter can be saved for air conditioning months later.

Marc Hoyer, now 82, worked on the original 1980s project and thought nobody cared about the technology anymore. When he heard about The Heights, he felt vindicated. "I figured nobody cared about it," he said from his home in Maryland.

The technology isn't actually new elsewhere. More than 3,000 similar systems operate worldwide, mostly in the Netherlands. But America largely abandoned the approach after those 1980s tests, even though the science worked.

The Ripple Effect

Yu-Feng Lin, director of the Illinois Water Resources Center, calls aquifer geothermal "the LED version of heating and cooling." Just like LED bulbs transformed lighting efficiency, this technology could revolutionize how we heat and cool buildings. The comparison fits: aquifer systems can cut emissions by up to 74% compared to conventional methods.

Minnesota is particularly well-suited for this approach because of its abundance of shallow underground aquifers. Rob Thornton of the International District Energy Association says "it kind of makes sense to utilize that local resource."

The $12 million system will be powered partly by solar panels, creating a nearly emissions-free heating and cooling network. And unlike wind and solar tax credits that are being phased out, federal incentives for geothermal projects remain largely intact under the Inflation Reduction Act.

Michael Ahern of Ever-Green Energy, the firm designing the system, stood in soft mud at the construction site in late June where rolling hills still hint at the old golf course. Soon those hills will hold wells tapping into decades-old clean energy dreams.

Sometimes the best innovations aren't new at all—they're the good ideas we finally decide to use.