A geothermal solution was sought for the renovation of a complex with several holiday apartments in Clavadel near Davos in the canton of Graubünden. The property is located at 1,660 meters above sea level and is embedded in a mountainous landscape.
The original plan was to install several double-U boreholes with a 40-millimeter diameter and a depth of 200 meters each. However, the first boreholes already showed that an implementation of this size was not feasible due to artesian groundwater at depths of approximately 42 meters.
A quick response was needed. MR Erdwärme, in collaboration with separatus, was able to quickly and easily provide a practical alternative. By using the system, which specializes in short probes, the project was successfully adapted and implemented. Planning and implementation were switched to 40-meter-deep separatus geothermal probes.
To determine the required number of 40-meter-deep separatus geothermal probes for the project, a separatus probe with a backfill with a thermal conductivity of 2 W/(mK) was installed at the first borehole. A thermal response test (TRT) was conducted eight days after installation in July 2025.
In the first part of the test, an undisturbed average soil temperature of 9.8 degrees Celsius was measured. In the second part, the probe was operated with a specific heat dissipation power of 76 watts per meter. The thermal stress phase lasted 139 hours, exceeding the internationally recommended minimum requirements.
During the test, the average heat output was 3.8 kilowatts. The measured flow rate was 617 liters per hour. The effective thermal conductivity of the subsurface was determined to be 2 W/(mK), consistent with the locally known hydrogeological structure (moraine deposits). In addition, a subsurface water flow velocity of 2.1 × 10⁻⁶ meters per second was detected.
The geothermal system was dimensioned using the GHEtool design software. The soil parameters determined in the TRT served as the basis for the simulation.
The building has an annual heating requirement of 27,200 kilowatt-hours. Hot water demand is an additional 2,800 kilowatt-hours per year. An annual cooling requirement of 3,900 kilowatt-hours has been calculated for the summer months. A heat pump with a maximum heating output of 25 kilowatts is used.
Based on this information, a long-term simulation was conducted over a period of 50 years. This resulted in a minimum average fluid temperature of -1.31 degrees Celsius.
A total of 30 boreholes, each 40 meters deep, were distributed and implemented on the property.
The boreholes were drilled using casing with an outer diameter of 132 mm. Due to the geological conditions, continuous casing was required. The drill rod used had an outer diameter of 89 mm, and the hammer drill had a diameter of 108 mm.
Backfilling was carried out using a 25 mm injection pipe, which was inserted into the borehole together with the probe. The high-performance geothermal mortar K Zeo-Therm 2.0, with its high thermal conductivity, was used for maximum thermal transfer.
The connection work was carried out by Bruno Brunner AG. A separatus head with a 40-millimeter connection piece was welded onto each probe. Three probes were connected in series, forming a total of ten probe circuits, which were connected via two distribution shafts.
The distribution shafts were custom-made by Geser Erdwärme GmbH. A quadruple and a six-fold ECO 650 distribution shaft with A-35 covers, inline setters with 5 to 42 liters per minute, and D40 EWS connections were used.
This project impressively demonstrates how, with thoughtful planning, technical expertise, and innovative technology, a cost-effective and reliable geothermal solution can be realized under challenging geological conditions. Thanks to MR Erdwärme's many years of experience and solution-oriented approach, a feasible alternative was quickly found. Combined with the separatus system, which specializes in short drilling depths, an efficient geothermal solution was implemented. MR Erdwärme not only handled the operational implementation but also demonstrated high levels of expertise in project coordination and system integration.
The system meets all of the building's energy requirements and simultaneously demonstrates that geothermal systems can be implemented with reduced space requirements and shallower drilling depths without compromising efficiency or operational reliability.
This project is a compelling example of how modern geothermal energy can be planned and implemented sustainably in sensitive alpine regions through expertise, flexibility, and innovative system solutions. Despite challenging conditions, the client succeeded in implementing a functioning and sustainable geothermal system.
