Ground Temperature Monitoring for a Coaxial Geothermal Heat Exchangers Field: Practical Aspects and Main Issues From the First Year of Measurements

Abstract

Ground temperature at shallow depths (< 50 m) is not stable, nor in space, neither in time, and its behaviour is the result of the superimposition of eff ects of heat pulses of diff erent origin: solar, geothermal and anthropic. The correct assessment of ground temperature is a crucial point when designing a shallow geothermal energy system. In geothermal closed loop projects using short borehole heat exchangers, the ground temperature has more variability and aff ects the rate of heat extraction/injection. Monitoring of the ground temperature can therefore be useful in ground source heat pump projects to correctly understand the behaviour of a shallow geothermal reservoir subjected to heat extraction/injection. This paper illustrates the practical aspects and main issues occurred in the installation, testing and working phases of a monitoring system realised to record ground temperature in a geothermal application. The case study is a fi eld of eight coaxial borehole heat exchangers, 30 m long, connected to a novel prototype of dual source (air and ground) heat pump.

Advantages of IoT-Based Geotechnical Monitoring Systems Integrating Automatic Procedures for Data Acquisition and Elaboration

“…It is worth mentioning that MEMS have a 360° measuring range, while electrolytic cells feature a full-scale value of ±25°. Additionally, the structure of MUMS-based arrays permits the exploitation of different sensor typologies in the same array, such as piezometers to detect water level variations [ 24 ] or high-accuracy thermometers to have a detailed description of the underground temperature at different depths [ 25 ]. Finally, IoNH allows the acquisition and elaboration of monitoring data sampled by traditional instrumentation featuring an analog output signal (e.g., extensometers, crack meters, load cells, etc.…”

Sequential coupled numerical simulations of an air/ground-source heat pump: Validation of the model and results of yearly simulations

“…Besides the eight CB-HEs, three Observation Boreholes (OBs) have been installed to monitor the ground temperature. Further details of the geology and hydrogeology of the area, the monitoring strategy and the system layout can be found in Tinti et al [19].…”

“…Finally, it has been used as a benchmark for evaluating the performance of other modelling tools (Nam and Ooka [37]). Specifically to the FEFLOW® model of the CB-HE field installed in the Tribano area, the validation was performed comparing the simulated temperature changes in the ground nodes with the measured values from the monitoring points in the three observation boreholes, which can be found in [19]. The details of the model realized in FEFLOW® can be found in [34].…”

Assessing the Impact of a Shallow Geothermal System Operation through Multi-Layer Temperature Monitoring in a Mediterranean Climate

“…Evaluating spatial soil temperature distribution during the geothermal system operation is of major importance in analysing SGE performance as well as its sustainability, e.g., [18,22]. The authors in their study [23] reported the thermal effect of the Borehole Heat Exchangers (BHE) on the ground temperature by monitoring a borehole located 1 m away from one BHE. This study highlighted the importance of long-term and multiyear monitoring to evaluate the effect of system operation on the entire ground impacted by the presence of BHEs.…”