Numerical evaluation of ground source heat pumps in a thawing permafrost region

Abstract

Permafrost degradation poses significant environmental and geological challenges in Arctic and subarctic regions, particularly in areas like Umiujaq, Canada. The warming climate leads to thawing permafrost, causing ground instability, disrupting hydrology, and impacting local built environment. This study evaluates the use of Ground Source Heat Pump (GSHP) operation for mitigating ground subsidence in a permafrost region using a two-dimensional Thermo-Hydro-Mechanical (THM) coupled finite element analysis considering the ground poro-elastic and poro-plastic responses. The research uses a single-well scenario to demonstrate the interactions among thermal, hydraulic, and mechanical processes. The impact of GSHP operation under different temperature management strategies, including a scenario with a constant GSHP temperature of −5 °C throughout the year is numerically investigated. Results indicate that GSHP operation exacerbates ground deformation near the borehole, particularly during winter months. However, maintaining GSHP operation throughout the entire year can mitigate extreme subsidence fluctuations, leading to a more stable subsurface environment. While GSHP systems provide effective thermal regulation, their operation can introduce mechanical stresses that potentially disturb the ground close to the borehole. Therefore, careful design, operation, and further research are essential to balance thermal benefits with ground stability in permafrost regions.