Researchers at the National Laboratory of the Rockies have demonstrated that underground thermal energy storage (UTES) can provide year-round cooling for server environments. This method utilizes subsurface reservoirs to capture cold air, potentially reducing the massive water and electricity demands of modern computing.
The $20 million annual savings for 1-gigawatt sites
Implementing cold UTES could reduce annual energy costs for data facilities by as much as 70%, according to the National Laboratory of the Rockies. For a massive 1-gigawatt site, this efficiency translates to an estimated $20 million in yearly savings. This reduction does more than just improve a company's bottom line; it also alleviates significant pressure on local grid capacities.
By lowering the electrical cooling load, facilities can redirect more of their available power toward actual computational tasks. This shift allows for greater compute power without requiring an immediate, massive expansion of the local electrical infrastructure, providing a more sustainable way to scale digital operations.
Replacing traditional chillers with subsurface boreholes
Current data center cooling methods typically rely on blowing cold air over components or circulating water through pipes, processes that consume vast amounts of electricity and water. As reported by the National Laboratory of the Rockies, cold UTES offers a fundamentally different approach by capturing thermal energy from cold ambient air during winter months or cool nights. This energy is then stored in subsurface reservoirs or boreholes until it is needed to manage cooling loads.
This method allows building owners to reduce capital expenditures by limiting their need to purchase and maintain large, energy-intensive chiller equipment.. By utilizing the earth itself as a thermal battery, the reliance on mechanical cooling during peak heat periods is significantly diminished.
Managing TWh-scale storage from diurnal to seasonal cycles
The potential scale of these underground systems is immense, with the study noting that storage capacities can reach the Terawatt-hour (TWh) level. These systems are versatile enough to handle various timescales, ranging from diurnal (daily) cycles to much longer seasonal storage durations. This flexibility is crucial for data centers that face fluctuating temperature demands throughout the year.
Because the storage is subsurface, it provides a stable environment that can mitigate the impact of extreme weather events on server temperatures. This stability is a key component of the comprehensive analysis provided by the researchers, which utilized both facility-level and grid-level modeling to determine the long-term value of the technology.
The roadmap for multi-lab collaboration after the Golden, Colorado workshop
While the findings were presented to over 100 participants—including researchers, developers, and industry partners—at the South Table Mountain Campus in Golden, Colorado, the practical application of this technology is still in its early staages. The workshop, held from June 30 to July 1, 2026, helped direct future research, which will now include collaboration with other national laboratories and industry stakeholders.
Despite the promising cost-competitiveness of the solution, several questions remain regarding the logistics of large-scale implementation. It is currently unverified how existing data centers with expansive IT infrastructure will manage the transition to UTES,or how the geological requirements of boreholes will limit deployment to specific geographic regions. the project team has noted that while the potential is high, the work is far from over.
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