Insights into the reliability of different thermal conductivity measurement techniques: a thermo-geological study in Mære (Norway)

Abstract

Thermal response tests (TRTs) are used to measure the effective thermal conductivity in boreholes. The results serve as a basis for the dimensioning of commercial ground-source heat pump installations with closed loop systems. The study evaluated the reliability of TRTs performed in winter by comparing two TRTs carried out under very different winter weather conditions. A third TRT elucidated the influence of convection in wells with a higher heat input. Rock cores were analysed for quartz content and these results and the laboratory-measured thermal conductivity data were compared with the TRT results. This highlighted the importance of the distribution and orientation of minerals in the rock, and that a high quartz content does not necessarily give high thermal conductivity values. It is concluded that winter TRTs give useful results if additional temperature loggers are installed in anticipated fracture zones to detect groundwater flow and to survey the effect of infiltrating water.

Effect of sedimentary facies and geological properties on thermal conductivity of Pleistocene volcanic sediments in Tokyo, central Japan

“…Each property can be obtained if the other two are known, as two of the three properties are independent parameters. The thermal properties of sediments/rocks are basic physical properties and are important for engineering problems [e.g., heat exchange performance of GSHP (Liebel et al 2012;Saito et al 2014)], but also for scientific investigations of heat circulation and heat flux in the earth's crust (Sass et al 1971;Pribnow and Sass 1995;Vosteen and Schellschmidt 2003;Goto and Matsubayashi 2009;Lin et al 2011Lin et al , 2014.…”

“…To cite cases in Europe, a GSHP with dynamic thermal energy storage was installed in hard rock (mica gneiss, Silurian sediments and Ordovician sediments) in Norway (Liebel et al 2012), a borehole thermal energy store was installed in fractured Triassic sedimentary rock with fractures in Germany (Mielke et al 2014) and a GSHP system was installed in a chalk layer in London, UK (Busby et al 2009;Arthur et al 2010). The main lithology in which GSHP systems are installed is fractured sedimentary rocks in Europe, which are countries in the process of introducing GSHP systems.…”