An evaluation of ground-cooling systems in a saturated subarctic peatland

Abstract

The Canadian subarctic is one of the most rapidly warming regions on Earth. Permafrost thaw driven by climate change is linked to rapid landscape transition and is threatening northern infrastructure. Ground cooling systems are used in application-oriented projects largely pertaining to civil engineering operations and have been investigated in mineral-based soils with many successful outcomes. However, in near-saturated and peat-dominated environments they remain largely unexplored. The increasing rates of climate change and concomitant landscape evolution coupled with increasing economic activity in the North affirm the growing need for the advancement of ground cooling technologies in saturated peat-based soils. This study compared the performance of three ground cooling systems in saturated peat overlying thawing permafrost at the Scotty Creek Research Station in the Northwest Territories, Canada. The systems included a single-phase active thermosiphon combined with a snow reduction cone (advanced thermosiphon; ATS), a single-phase passive thermosiphon (simple thermosiphon; STS), and two stand-alone snow reduction cones. Performance was assessed based on subsurface temperature profiles (ranging 2017–2022), physical frost table measurements, and estimates of net annual and seasonal heat transfer. Each system displayed distinct ground cooling capabilities, successfully creating, and maintaining frozen ground. The ATS stood out with the highest net annual heat transfer rate, though it requires energy sources for actively circulating the coolant. The STS exhibited slightly lower effectiveness but demonstrated greater resilience to component failure. The snow reduction cone confirmed the significance of snow in ground insulation and augmented the performance of the thermosiphon system, enhancing its overall efficiency. It is anticipated that this study will foster the development of liquid-filled thermosyphons in the domain of cooling technologies, with a particular focus on their application in saturated peat and other similar environments. Moreover, these findings hold significant promise in offering valuable support for climate change adaptation strategies for local communities.