Geothermal & Borehole Thermal Energy Storage Can Reliably Heat Buildings in Extreme Cold — NREL Modeling Results - CleanTechnica

A recent study by the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) demonstrates that borehole thermal energy storage (BTES) combined with geothermal heat pumps (GHPs) can reliably heat buildings in extreme cold climates such as Alaska. The research, published in June 2025, modeled a 20-year period in which waste heat from a nearby coal plant was captured during summer, stored underground in boreholes, and then used in winter to heat two Department of Defense buildings in Fairbanks. The BTES system uses a network of vertical boreholes filled with a water-antifreeze solution to store and transfer heat, allowing the geothermal heat pumps to efficiently warm buildings without relying on cold outdoor air. Using EnergyPlus software, researchers found that heating demand in these cold-climate buildings was 5.6 times higher than cooling demand, a typical pattern for regions with long, harsh winters and mild summers. The study modeled two scenarios: one with a five-year prehe