Measuring of thermal conductivities of soils and rocks to be used in the calculation of A geothermal installation

Abstract

The thermal conductivity of soils and rocks constitutes an important property for the design of geothermal energy foundations and borehole heat exchange systems. Therefore, it is interesting to find new alternatives to define this parameter involved in the calculation of very low enthalpy geothermal installations. This work presents the development of an experimental set-up for measurements of thermal conductivity of soils and rocks. The device was designed based on the principle of the Guarded Hot Plate method using as heat source a laboratory heater. The thermal conductivity of thirteen rocky and soil samples was experimentally measured. Results are finally compared with the most common thermal conductivity values for each material. In summary, the aim of the present research is suggesting a procedure to determine the thermal conductivity parameter by a simple and economic way. Thus, increases of the final price of these systems that techniques such as the "Thermal Response Test" (TRT) involvs, could be avoided. Calculations with software "Earth Energy Designer" (EED) highlighted the importance of knowing the thermal conductivity of the surrounding ground of these geothermal systems.