The Trans-Alaska Pipeline System (TAPS) transports crude oil at temperatures up to 145°F (63°C) over 800 miles of arctic landscape. If this heat were allowed to transfer into the underlying soil, it would thaw the delicate permafrost layer, turning solid ground into fluid mud and causing the pipeline to sag and rupture. To prevent this ecological disaster, engineers mounted over 120,000 Vertical Support Members (VSMs) equipped with sealed heat pipes called thermosyphons.
These thermosyphons require zero electricity or moving parts, operating purely on passive thermodynamics. Inside each hollow metal stilt is liquid ammonia. During the long arctic winter, ground heat at the base of the stilt vaporizes the liquid ammonia.
The warm gas rises to the top of the stilt above ground, where aluminum radiator fins expose it to cold ambient air. The ammonia gas cools, condenses back into liquid, and trickles down the interior walls back to the base, effectively carrying ground heat upward and releasing it into the atmosphere. This process keeps the soil permanently frozen below zero degrees Celsius.
In the summer, when the air is warmer than the ground, the cycle naturally stops, preventing hot air from transferring down into the earth.