geothermal energy in Complex Geology at Bartholomew
A continuous geothermal project from the separatus partner network
For a holiday home on Bartholomäberg im Montafon (AT), a ground-source heat pump system with six separatus borehole heat exchangers is realised. The sophisticated geology with a groundwater floor required careful planning and an adapted drilling sequence.
The project shows how cooperation within the separatus partner network works. separatus took over thermal simulation and design / system sizing. Our drilling partner Plankel carried out the drilling work and installation of the borehole heat exchangers. Geser Erdwärme takes over the hydraulic connection.
This creates a continuous solution from planning to finished development.
Initial position
The holiday home is located on the Bartholomäberg in Montafon at about 734 metres above sea level. The shallow geothermal energy will be used for the heat supply of the building. In an initial planning, 6 borehole heat exchangers with a depth of 53 metres were roughly calculated.
separatus for short probe depths
The separatus system is particularly suitable for geothermal projects with short drilling depths. Vor and return are integrated in the compact Splitpipe pipe. This results in favorable hydraulic conditions, which can be decisive for efficient heat transfer in the case of short probes.
The distribution of the required total drilling length over several short drilling holes offers an important advantage in demanding geology. Particularly deep and technically riskier drilling sections can be avoided. At the same time, the probe field can be precisely adapted to local conditions.
thermal simulation by separatus
Geothermal probes should be carefully adapted to the building’s energy demand, climatic conditions, subsoil characteristics and hydraulic conditions.
In the course of detailed planning, the separatus planning team carried out a thermal simulation of the geothermal system and checked the project-specific boundary conditions. It was found that the initially scheduled flat-rate specific withdrawal benefit for this location was rather optimistic. Due to the climatic conditions at this altitude in Montafon and the local geology, the recommendation was to increase the probe length in order to optimise the plant efficiency in the long term. The plant was finally designed with 6 borehole heat exchangers of 60 metres each. The total probe length is thus 360 metres.
The thermal simulations also showed that higher brine temperatures can be expected for this project with the separatus system than with a conventional double U-tube BHE. The main reason for this is the flow conditions: In the case of double-U probes, a predominantly laminar flow would have been assumed due to the project-specific volume flows, which impairs the heat transfer in the probe tube. Under the same boundary conditions, the separatus system achieves more favorable hydraulic conditions and thus more efficient heat transfer.
With six uniformly dimensioned borehole heat exchangers, a clear drilling field is produced. The selected configuration combines a limited drilling depth with the required thermal performance.
Sophisticated geology with groundwater
The geological conditions placed particular demands on the execution. In the underground is a groundwater floor. The drilling process was adapted to the different geological areas.
First, a tubing with 160 millimeter diameter was introduced in the flush drilling process. The piping secures the upper borehole region and enables a controlled continuation of the drilling work. Subsequently, the pipeline was converted to the down-the-hole (DTH) hammer drilling. With a drilling diameter of 132 millimeters, the drilling was continued to a depth of 60 metres.
The combination of the two drilling methods enabled a subsurface-adapted and controlled execution.
Drilling and probe installation by planks
The drilling and installation of the separatus borehole heat exchangers were carried out by our experienced drilling partner Plankel.
Implementation included:
- 6 drillings, each 60 metres deep
- Total 360 metres borehole heat exchangers
- Installation of a 160 millimeter piping in the flush drilling process
- connecting bore with a 132 millimeter inlochhammer
- Installation of separatus borehole heat exchangers
- borehole grouting of drill holes with Fischer GeoSolid
Especially in complex geological conditions, experience, a suitable machine park and the right combination of drilling methods are crucial. Plankel brought these competencies to the project and implemented the planned solution professionally on the construction site.
Hydraulic connection by Geser Erdwärme
After the installation of the borehole heat exchangers, Geser Erdwärme takes over the hydraulic connection of the plant.
The individual probes are connected to the distribution system and integrated into the overall system. Careful hydraulic design is important so that all probes are uniformly flowed through and can reliably provide the planned power.
Due to the early coordination between planning, drilling and connection, the interfaces between the participating companies are clearly defined.
Three specialized partners for a joint solution
The project at Bartholomäberg shows the benefits of a coordinated partner network.
Each company takes over the area in which it has the appropriate experience. This creates a consistent solution for the client. The individual project phases are not considered in isolation, but technically coordinated.
This is important for challenging projects. Good simulation alone is not enough if the planned solution does not fit the available drilling technology. Likewise, the hydraulic connection must be matched to the design / system sizing and the actual drill field configuration.
The separatus partner network combines these competencies.
Overview of project data
- Object: Holiday home
- Region: Bartholomäberg in Montafon
- Probe system: separatus borehole heat exchangers
- Number of bores: 6
- probe depth: 60 metres
- Total probe length: 360 metres
- Hammer drilling diameter: 132 mm
- Piping: 160 mm
- Geological specificity: Groundwater floor
- Design and simulation: separatus
- Drilling and probe installation: plank
- Hydraulic connection: Geser Erdwärme
Conclusion
The project shows that geothermal energy can be reliably implemented even in short probe depths and challenging geological conditions. Crucial is a solution in which the thermal design / system sizing, drilling technology and hydraulic connection are coordinated.
With six separatus borehole heat exchangers à 60 metres, a compact ground-source heat pump system with a total probe length of 360 metres is created. The adapted drilling sequence with fluid-assisted rotary drilling, piping and subsequent hammer drilling takes into account the special conditions of the substrate.
At the same time, the reference shows the strength of the separatus partner network. From simulation to drilling to hydraulic connection, specialized companies bring their expertise to a common solution.
