22 May 2002
In June 1998, Qingdao Institute of Architecture and Engineering built an experimental installation using a closed U-shaped loop system made of plastic pipe that was buried in the earth vertically. In summer indoor heat is extracted from room and transferred into the earth through liquid by the heat pump unit. In winter, the earth will be the heat resource of the heat pump to provide heat for the room.
Purposes of this experiment are to get knowledge concerning heat released into the earth or extracted from it annually, as well as experience of design and management. A U-shaped loop of plastic pipe inserted in a borehole with a depth of 53m is used to extract energy from the earth. Three secondary boreholes of a depth of 13m were drilled near the main borehole, which are spaced out by 0.8m apart. A large number of thermocouples were buried in the four holes to measure the earth temperature.
This paper will illustrate the experimental installation in detail and present the results of long term measurement. Finally, the primary conclusions will be introduced.