In-situ measurement of borehole thermal properties in Melbourne

• In-situ thermal response of borehole heat exchangers in Melbourne were analysed.
• Slope determination, two variable parameter fitting and the GPM model were applied.
• Three thermal conductivity values obtained were applied in TRNSYS simulations.
• The GPM model provides better agreement with measured temperatures from boreholes.

The ability to quantify the ground thermal properties of a site is important for the appropriate sizing of ground heat exchangers. This paper presents the results of in-situ measurements of the thermal properties of two 40 m deep borehole thermal storage systems in Melbourne. The measurements from the tests were analysed using three methods: conventional slope determination, two variable parameter fitting technique and using Geothermal Properties Measurement (GPM) model. The values of effective thermal conductivities obtained from the three methods were applied in 12 TRNSYS simulations. The value from the GPM model was found to give relatively less error when the measured and simulated outlet temperatures were compared.