EARTH HEAT PIPE WORKING WITH CARBON DIOXIDE STATUS OF DEVELOPMENT
After the fundamental investigations on an earth heat pipe working with carbon dioxide have been dealt with already at the last IEA Heat Pump Conference in Las Vegas, the further development of the patented novel system up to market introduction will be described. Preliminary measurements in comparison to a conventional brine earth probe have been performed and evaluated showing the energetic advantage of the CO2 heat pipe system because of the better heat transfer properties of the fluid carbon dioxide and the pump less working principle of a vertical thermosyphon as compared to a brine earth probe. A dozen heat pumps with such CO2 earth heat pipes have been installed at one family houses until 2007 and worked now since 2005 already up to three heating seasons successfully. It is expected that this novel earth heat probe system will gain a certain market share in the field of geothermal heat pumps because of the not ground water affecting working fluid CO2 favourable in water protection areas and because of the energetic advantages of the working principle with this fluid.