Geowatt Engineering

Heating and cooling with borehole heat exchangers

Borehole heat exchanger systems are the most common type of geothermal storage.

Borehole heat exchangers are the most efficient way to make thermal use of a large storage volume.

Heating and cooling with energy piles

Energy piles are generally used where borehole heat exchangers are not permitted.

Depending on the underground, larger buildings may have to be founded on piles. These piles can be equipped with heat exchangers to extract heat and cold from the ground.

Heating and cooling with horizontal register

Thermal component activation with relatively little power.

If no borehole heat exchangers may be built and no foundation piles are necessary, a floor slab can be equipped directly as a heat exchanger. However, the performance of such thermal component activation is limited.

Heating and cooling with groundwater systems

Near-surface aquifers are well suited for heat utilisation with heat pumps if they are sufficiently permeable.

As a rule, in such a system, the cooled water pumped from an extraction well must be returned to the aquifer in an infiltration system. During the planning phase, care must be taken to ensure that the infiltrated, cooled water has as little impact as possible on the extraction well.

Heating and cooling with forecourt heaters

Geothermal storage offers the possibility to keep critical areas such as house entrances, forecourts, steep driveways etc. free of snow in winter.

One possibility is to install heating coils under the pavement, which are connected to a geothermal storage tank. In this way, the pavement heat of the summer can be stored temporarily and thus the area can be kept free of snow and ice in winter. Energy is only required for the circulation pump.

Planning and quality assurance according to SIA 384/6

Geothermal systems must not only ensure a certain thermal output, but must also be able to extract the energy from the ground in a sustainable manner.

According to SIA standard 384/6, a borehole heat exchanger system must be planned for at least 50 years of operation. This requires a long-term view for all project phases. Comprehensive support for this is provided by SIA standard 384/6, which explains in detail the requirements in all phases of a borehole heat exchanger project.

Thermal Response Test (TRT)

Measurement of mean thermal conductivity / thermal borehole resistance

In order to calculate the thermal behaviour of borehole heat exchangers under heat input or extraction, the average thermal conductivity of the ground along the length of the borehole is required. For a first estimation, a value based on an assumed lithology can be used. According to SIA 384/6, such an estimated value must be provided with a safety margin.

For larger installations, however, it makes sense to determine the thermal conductivity of the soil by means of a thermal response test (TRT). During the first BHE of a field, a defined heat output is applied permanently for approx. 3 days and the temperature of the probe fluid is measured continuously. The development of the fluid temperature can then be used to determine the average thermal conductivity of the soil as well as the thermal borehole resistance (effect of the U-tube configuration and backfilling).

The data can be stored on GEOWATTCORE on a project-specific basis.

Enhanced Thermal Response Test (eTRT)

European Patent EP 1959213 Measurement of Thermal Conductivity Profile / Identification of Groundwater Flows

At sites with complex geological conditions, for example where there is a sudden increase in thermal conductivity during the transition from Quaternary to Tertiary or crystalline, we offer a patented method for the evaluation of Thermal Response Tests (TRT). The result of the so-called extended thermal response test (eTRT) is a depth-dependent profile of the vertical thermal conductivity. It can also be used to identify groundwater flow. With this method, continuous temperature-depth profiles must be measured before and after the TRT. The eTRT method is used for optimised planning of complex borehole heat exchanger fields, as the number and depth of borehole heat exchangers can be adapted to local conditions.

The data can be stored on GEOWATTCORE on a project-specific basis.

Ground temperature

Measurement of the ground temperature in borehole heat exchangers

The knowledge of the local ground temperature is, besides the thermal conductivity of the ground, an important parameter for a correct dimensioning of a borehole heat exchanger system. Usually, the measurement is carried out approx. 1 week after backfilling in the first borehole heat exchanger of a field. The prerequisite is that the geothermal probe in question is still freely accessible.

The data can be stored on GEOWATTCORE on a project-specific basis.