| Title | Ground temperature recovery time after BHE insertion |
|---|---|
| Authors | Montero, Urchueguía, Martos, Badenes |
| Year | 2013 |
| Conference | European Geothermal Conference |
| Keywords | Thermal Response Test, Ground Temperature, Ground Coupled Heat Pump. |
| Abstract | Thermal response tests to characterise ground thermal properties are an almost standard procedure for the design of large size ground coupled heat pump air conditioning systems. The purpose of this test is the measurement at site of three main parameters used for the design of a ground coupled heat pump system: ground thermal conductivity, borehole thermal resistance and undisturbed ground temperature. The test is usually performed a few days after borehole insertion. This contribution presents the experimental measurements of ground temperature recovery time after borehole heat exchanger insertion and its implications in the estimation of ground coupled heat pump design parameters. A 40 meters borehole heat exchanger with two independent U-pipes has been monitored after borehole insertion. Ground temperatures as a function of depth have been regularly measured. This contribution presents the evolution of the temperature profile from the date of U-pipe insertion until six months after. Main conclusion of this contribution is that the ground temperature profile achieves a stable profile at a time around five months after borehole insertion. This time scale is quite relevant for interpreting data extracted from a standard thermal response test performed, usually, a few days after borehole heat exchanger insertion. Ground temperature is biased by the heating effect produced by the drilling procedure, and the heating effect produced by the concrete setting. Then, ground thermal properties estimated by performing a TRT just a few days after borehole insertion may not be describing actual ground properties. |