Geothermal & Borehole Thermal Power Storage Can Reliably Warmth Buildings in Excessive Chilly — NREL Modeling Outcomes

Final Up to date on: eleventh July 2025, 12:53 am

New Research Demonstrates Environment friendly Efficiency—Even on Frozen Alaska Soils

New power storage analysis from NREL, a U.S. Division of Power nationwide laboratory, has demonstrated a solution to retailer and reuse warmth underground to satisfy the heating calls for of chilly areas like Alaska.

Printed on June 17 within the journal Power & Buildings, the feasibility research examined a 20-year interval during which borehole thermal power storage (BTES)—a system that shops heating or cooling power underground—may reliably provide heating to 2 U.S. Division of Protection buildings in Fairbanks, Alaska.

By constructing power utilization and system efficiency modeling, researchers present how waste warmth from a close-by coal plant could possibly be captured throughout summer time months, saved underground, after which drawn on within the winter to heat the buildings through geothermal warmth pumps (GHPs).

The evaluation was led by Hyunjun Oh, a geothermal analysis engineer in NREL’s thermal power science and applied sciences analysis group, in collaboration with researchers Conor Dennehy, Saqib Javed, and Robbin Garber-Slaght at NREL’s Alaska Campus. NREL’s Utilized Analysis for Communities in Excessive Environments program is a nonprofit, industry-based initiative devoted to advancing excessive power effectivity, constructing science, and socioeconomic analysis for communities in Alaska and the broader Circumpolar North. The challenge was additionally in partnership with the U.S. Military Corps of Engineers’ Chilly Areas Analysis and Engineering Laboratory.

BTES depends on a community of slender holes drilled vertically underground, referred to as boreholes, which act as a chargeable battery for warmth. Throughout hotter months, waste warmth may be pumped into the boreholes, the place it’s insulated by surrounding soil and rock till it’s wanted. Within the winter, circulating pumps transfer a water-antifreeze answer by way of the boreholes to select up saved warmth and ship it to the constructing’s geothermal warmth pump. Reasonably than extracting warmth from chilly out of doors air, the warmth pump makes use of this hotter fluid to effectively switch warmth into the constructing’s heating, air flow, and air-con system.

NREL researchers modeled the heating and cooling calls for of the cold-climate buildings utilizing EnergyPlus software program and located that the annual heating demand was 5.6 occasions larger than the cooling demand—an imbalance typical of climates like Alaska’s, the place winters are lengthy and chilly and summers are quick and gentle.

To satisfy this heating load, the staff predesigned a system of 40 boreholes at a depth of 91 meters situated about 100 meters away from the buildings, in alignment with regulatory tips and close by land availability. They then modeled the 20-year efficiency of the BTES system, working simulations for 2 eventualities: one during which the bottom subsurface was preheated for 5 years utilizing a sizzling water injection earlier than supplying warmth to the buildings and one with out preheating.

In each eventualities, wells on the middle of the borehole discipline produced about one-third extra thermal power than these on the outer edges, seemingly as a result of the outer wells misplaced warmth to the encompassing floor. This discovering presents perception into how borehole fields may be higher designed and insulated for extra balanced power distribution.

Moreover, techniques that underwent preheating earlier than common use confirmed even higher efficiency, with larger underground temperatures and larger thermal power manufacturing in the course of the first eight years of operation in comparison with techniques with out preheating.

Altogether, the outcomes level towards BTES as a dependable heating answer in chilly climates, serving to communities seize waste warmth and use power extra effectively.

Oh mentioned that, whereas there have been in depth case research validating GHP efficiency in chilly areas of Europe, this is without doubt one of the first to indicate the potential of GHPs linked to BTES in america.

“This paper demonstrates that even chilly subsurface situations—like these in Alaska, the place 50% to 90% of the bottom has permafrost—can be utilized for heating,” Oh mentioned. “A geothermal warmth pump system can provide larger effectivity if we think about seasonal or storage-system-integrated operations.”

The research additionally confirmed that the native subsurface in Fairbanks is effectively suited for different kinds of geothermal techniques, too. The analysis staff used thermal response checks and former literature to estimate the geothermal gradient—the speed at which temperature will increase with depth—at about 27.9 levels Celsius per kilometer.

This gradient permits usable warmth to be accessed at comparatively shallow depths underground, making it a candidate for direct use or a future distributed power system, Oh mentioned.

As this research was supposed to evaluate the practicality of BTES and GHP at a particular location in Fairbanks, the staff recommends complete future analyses that transcend the eventualities described right here to raised tailor power techniques to native situations and obtainable waste warmth sources.

The research, “Techno-Financial Feasibility of Borehole Thermal Power Storage System linked to Geothermal Warmth Pumps for Seasonal Heating Load of Two Buildings in Fairbanks, Alaska,” was funded by the U.S. Division of Power Geothermal Applied sciences Workplace and the united statesDepartment of Protection Environmental Safety Know-how Certification Program.

Article from NREL. By Hannah Halusker.