Aquifer Thermal Storage Could Cut Data Center Cooling Costs

Underground water systems offer cooling alternative

Data centers powering artificial intelligence applications could dramatically reduce their environmental footprint by tapping into naturally cool groundwater beneath them, according to research from the University of Illinois Urbana-Champaign.

Researchers at the Prairie Research Institute propose using aquifer thermal energy storage (ATES) systems to leverage the Earth's stable underground temperatures as a giant natural cooling mechanism. The approach addresses two pressing challenges: data centers currently dedicate 10 to 40 percent of their electricity consumption to cooling, and they consume enormous volumes of water through evaporative cooling methods.

How the system works

The concept operates on a straightforward principle. Cool water from underground aquifers flows through pipes into data centers, where it absorbs heat through heat exchangers. The warmed water then returns underground for storage and future use. During summer months, excess heat from cooling operations can be stored in the aquifer and retrieved in winter for heating purposes. Conversely, cold groundwater stored in winter becomes available for summer cooling.

"Instead of constantly trying to moderate the outdoor temperatures that swing from 90°F in summer to minus 10°F in winter, we can tap into the Earth's near-constant temperature," said Andrew Stumpf, one of the study's lead researchers. "You're no longer adjusting from 90°F to 70°F; you're adjusting from about 55°F to 70°F. That's a huge energy savings."

Why it matters

As AI adoption accelerates, the infrastructure supporting it faces mounting scrutiny over resource consumption. Aquifer thermal storage offers a path to decouple data center growth from proportional increases in electricity demand and freshwater use—particularly important as these facilities concentrate in regions with stressed water supplies. The technology exists and works; the barrier is primarily financial planning horizons that favor lower upfront costs over long-term operational savings.

Illinois as a testing ground

The research team identified three factors that make Illinois particularly well-suited for ATES implementation. The state experiences pronounced seasonal temperature swings that create ideal conditions for storing heat and cold underground. Abundant aquifers and groundwater resources enable efficient thermal exchange. And glacial deposits throughout central Illinois possess thermal properties that perform especially well when saturated with water.

Crucially, the systems need not rely on drinking water. Postdoctoral researcher Upasana Pandey noted that deeper saline aquifers—some saltier than seawater—contaminated groundwater, and water-filled abandoned mines all represent viable sources.

Economic and technical barriers

The primary obstacles are not technological. Geothermal and aquifer systems require higher initial investment but deliver lower operating costs across their 20- to 40-year operational lifespans. Many projects, however, are evaluated on five- to ten-year time horizons that favor conventional cooling infrastructure. The necessary drilling expertise already exists within the oil, gas, and water well industries.

"Data centers sit at the center of the water-energy nexus: If you try to reduce energy use, you often use more water, and if you reduce water use, you may need more energy," said Yu-Feng Lin, who led the study. "Our work looks for solutions that address both together."

The findings appear in the journal Groundwater and were first reported by the University of Illinois News Bureau. Previous research indicates the range of subsurface temperature changes associated with ATES systems should not raise environmental concerns.