Geothermal thermosiphons present an innovative way of producing geothermal energy by means of a perpetual, closed-loop system. In this autonomous process, a cooling medium, that is a liquid with a low boiling point (e.g. propane or carbon dioxide), is vaporized through geothermal absorption, and subsequently condensed in a heat exchanger.
A geothermal thermosiphon consists of a long vertical pipe of 60 to 200 m. It can either be segmentally welded or spirally coiled - resulting in a smooth or corrugated pipe wall, respectively - and is tightly sealed at the bottom. At the upper end, the condensate from the heat exchanger is applied to the inside of the pipe through a pipe head.