As artificial intelligence (AI) continues to grow, so does the number of data centers needed to power it.
These facilities run around the clock and generate huge amounts of heat, making cooling one of their biggest challenges.
Now, researchers say a natural solution hidden underground could help reduce both electricity use and water consumption.
Scientists at the University of Illinois Urbana-Champaign have proposed using underground aquifers as giant natural “thermal batteries” to cool AI data centers.
Their study, published in the journal Groundwater, suggests that this technology could make cooling more efficient while reducing environmental impacts.
Data centers require enormous amounts of electricity. Depending on their design, between 10% and 40% of that electricity is used simply to keep servers from overheating.
Many cooling systems also consume large amounts of water, often by allowing water to evaporate, which permanently removes it from local water supplies.
The researchers believe an underground system called Aquifer Thermal Energy Storage (ATES) could offer a better solution.
An aquifer is an underground layer of rock or soil that holds groundwater. In an ATES system, cool groundwater is pumped from the aquifer into a heat exchanger inside the data center.
The water absorbs heat from the computer equipment without mixing directly with it. Once warmed, the water is returned underground, where the heat is stored for future use.
The system works throughout the year. During summer, extra heat collected from the data center is stored underground. In winter, that stored heat can be used to warm buildings. At the same time, cold groundwater collected during winter can be stored for cooling the following summer.
One major advantage is that underground temperatures remain much more stable than outdoor air temperatures. In places like Illinois, where summers are hot and winters are freezing, the ground a short distance below the surface stays close to 13°C (55°F) year-round.
Cooling equipment therefore starts with much cooler water than the outside air during summer, reducing the amount of energy needed to reach the ideal operating temperature.
The researchers say Illinois is especially well suited for this technology. The state has abundant groundwater, clear seasonal temperature changes, and underground rock and soil layers that transfer heat efficiently.
Another benefit is that the system does not require clean drinking water. It could use deep underground salty water, contaminated groundwater, or even water stored in abandoned mines, helping protect valuable freshwater supplies.
According to the research team, the biggest challenge is not the technology itself but the cost. Installing geothermal systems requires a larger investment at the beginning. However, once operating, they cost much less to run and can provide savings for decades. Because many businesses focus on short-term costs instead of long-term benefits, these systems are often overlooked.
The researchers also note that the drilling skills needed already exist in industries such as oil, gas, and water well construction.
As AI data centers continue to expand around the world, finding cleaner ways to cool them will become increasingly important.
Using underground aquifers as natural thermal batteries could offer a practical way to reduce electricity use, conserve water, and make the growing digital economy more environmentally sustainable.
