22 Nov 2021

Artificial Ground Freezing Using Solar-Powered Thermosyphons

Abstract: Thermosyphons are an artificial ground-freezing technique that has been used to stabilize permafrost since the 1960s. The largest engineered structure that uses thermosyphons to maintain frozen ground is the Trans Alaska Pipeline, and it has over 124,000 thermosyphons along its approximately 1300 km route. In passive mode, thermosyphons extract heat from the soil and transfer it to the environment when the air temperature is colder than the ground temperature. This passive technology can promote ground cooling during cold winter months. To address the growing need for maintaining frozen ground as air temperatures increase, we investigated a solar-powered refrigeration unit that could operate a thermosyphon (nonpassive) during temperatures above freezing. Our tests showed that energy generated from the solar array can operate the refrigeration unit and activate the hybrid thermosyphon to artificially cool the soil when air temperatures are above freezing. This technology can be used to expand the application of thermosyphon technology to freeze ground or maintain permafrost, particularly in locations with limited access to line power.

20 Aug 2020

PUBLICATION NOTICE: Concept for Artificial Freezing of Sea Ice at Winter Quarters Bay, Antarctica

ABSTRACT:  McMurdo Station serves as a major research and logistics hub for the United States Antarctic Program (USAP). Adjacent to the Station is Winter Quarters Bay (WQB), where vessels dock to unload cargo and fuel. The ice pier at McMurdo is essential for this annual vessel resupply but represents a failure potential, occasionally breaking up during or immediately after vessel operations. This study aimed to determine the feasibility of using thermopiles, a passive cooling technology, to artificially freeze seawater to “grow” the existing WQB bottomfast-ice edge so that ships can dock directly against it. Finite element simulations using modeling-parameter assumptions indicate that each row of thermopiles can grow a frozen wall to a depth of 9 m in about a month if installed on 1 July with an initial sea-ice thickness of 1 m and a thermopile spacing of 1.5 m. For our simulation scenarios, we approximate that it would take 255 to 820 days to complete a 40 m by 140 m wedge of bottomfast ice. The estimated cost ranges from about $600,000 to $1,600,000. These results serve as a preliminary feasibility study of successfully using thermopiles for generating a direct docking bottomfast-ice wharf at McMurdo.