22 May 2008

THERMAL RESPONSE TEST, A ROUTINE METHOD TO DETERMINE THERMAL GROUND PROPERTIES FOR GSHP DESIGN


To design borehole heat exchangers (BHE) for Ground Source Heat Pumps
(GSHP) or Underground Thermal Energy Storage (UTES), the knowledge of underground
thermal properties is paramount. In particular for larger plants (commercial GSHP or UTES),
the thermal conductivity should be measured on site. A useful tool to do so is a thermal
response test, carried out on a borehole heat exchanger in a pilot borehole (later to be part of
the borehole field). For a thermal response test, basically a defined heat load is injected into
the BHE, and the resulting temperature changes of the circulating fluid are measured. The
paper includes a short description of the basic concept and the theory behind the thermal
response test, reviews shortly the world-wide uptake and experience of this technology, and
gives the main emphasis on the experience in routine operation of the test, and on the economic
reasons for testing.