Soil to water heat pumps use soil energy as the primary heat source. The correct dimensioning of the probe field is particularly important for the efficient operation of the system, especially for systems with over 5 geothermal wells. The dimensioning starts with the T.R.T. (Thermal Response Test), so we use an integrated GeoGert 2.0 system. which provides us with information about the soil situation:
A test session lasts 72h, at the end we have a complete picture of the location:
- pressure test for the geothermal probe;
- flow test for the geothermal probe;
- Measure the undisturbed temperature of the soil;
- TRT test provides the thermal conductivity of the soil – the λ factor;
Geothermal probes field dimensions
Geothermal probes fields are divided into two categories according to the power required for the application to be cooled or heated: with a power of less than 30kW are considered small and over 30kW are considered high. For small installations in areas where measurements have already been made (and we already have data), the need for a response test is not absolutely necessary. Instead, for large systems over 30 kW, we need to perform these tests for a more efficient operation and to avoid over-dimensioning of the geothermal probes field. For the correct sizing of heat pumps and geothermal probes we follow the parameters:
- Local geology and hydrogeology – TRT geothermal response test.
- Required thermal energy to be provided (heating and cooling load)
- Temperature levels of heating and cooling distributions
- Number, position and length of possible geothermal probes
- Thermal exchanges under the edifice foundation if the wells are positioned under construction or not.
Estimating the value of thermal conductivity λ at a higher value than the real value leads to a subdimension of the heat exchanger to the ground, with the direct consequence of increasing the heat consumption of the heat pump (decreasing the COP) or even leaving it out of function. Underestimation of conductivity is also undesirable, oversize the geothermal drilling, significantly increasing the initial investment.
Thermal Response Test T.R.T. at the Magurele Institute for the sizing of a field of 1.000 geothermal probes
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