Analysis of the thermal conductivity of the substrate
Since 2022, the topic of "heating without gas and oil" has become increasingly important, particularly due to the amendment of the Building Energy Act (GEG) 2023 and the Ukraine war. While air-to-water heat pumps are often discussed, geothermal energy is a particularly efficient and sustainable alternative.
As part of a pilot project, Nexiga determined the thermal conductivity of the subsurface of a specific federal state for each address (in W/m-K). This data provided valuable information on the efficient use of geothermal probes.
Efficient heat without gas and oil
Geothermal probes - Efficient, but with possible restrictions
Geothermal probes are one of the most effective methods for utilizing near-surface geothermal energy. They extract heat from depths of 40 to 150 meters and supply heat pumps with energy. However, they require deep drilling, which is associated with higher initial costs and is subject to notification or approval in many regions - especially in areas with sensitive water legislation. It is therefore essential to check the local regulations before planning.
Geothermal collectors
In addition to geothermal probes, there are also geothermal collectors that are laid horizontally at a depth of 1-2 meters. However, they require a larger area and are primarily suitable for unsealed plots. In densely built-up areas, deep drilling is often the only practicable solution.
Floor properties and thermal conductivity
Ein zentraler Faktor für die Effizienz einer Erdwärmeanlage ist die Wärmeleitfähigkeit des Bodens (W/m·K). Je nach Gesteinsart variiert sie erheblich – von schlecht leitendem Torf (< 1,0 W/m·K) bis hin zu hervorragend leitendem Granit (> 3,0 W/m·K).
Geothermal energy is divided into three categories:
- Near-surface geothermal energy (up to 400 meters)
- Medium-depth geothermal energy (400 - 1,500 meters)
- Deep geothermal energy (from 1,500 meters)
For private households and medium-sized companies, near-surface geothermal energy is particularly relevant, as deeper drilling is usually uneconomical.
- As part of a pilot project, Nexiga has provided data for a well-founded site assessment for the planning preparation of geothermal projects. As an expert in spatial data, Nexiga offers customized solutions for the energy sector - even for complex challenges.
Solution for a complex topic
As part of a pilot project, Nexiga has determined the thermal conductivity of the subsurface in Lower Saxony for each address (in W/m-K). The comprehensive analysis is based on data from over 11,000 boreholes and enables a precise assessment of geothermal suitability. In addition, detailed information is available on all water protection areas, so that both the efficiency potential of geothermal probes and the legal framework conditions for deep drilling can be examined on an address-specific basis.
This database provides a reliable basis for the planning and approval of geothermal plants.
All the data used comes from openly accessible sources(open data). Nexiga has specifically processed, combined and analyzed them in order to provide a comprehensive, building-specific information basis for geothermal energy use.
In Lower Saxony, around 56% of buildings are subject to restrictions on deep drilling. Permission is granted by the respective municipal water authority.
Most common reasons for restriction:
- Sulphate rock weathering, especially in the southern half of the country
- Drinking water and medicinal spring protection areas with specific requirements
- Specially protected drinking water conservation areas in which drilling for less than 1% of addresses is generally not permitted
Answering key questions
- Is deep drilling permitted at an address?
- How suitable is the ground at a location for the use of geothermal energy?
This information can be used to make well-founded decisions on the planning and implementation of geothermal probes.
Map example Lower Saxony
Irrespective of the legal requirements, 60% of the soils in Lower Saxony are good or very good for geothermal energy in terms of thermal conductivity. However, there are strong regional differences, even within individual municipalities. This is particularly evident in the example of the city of Oldenburg:
The map shows the restricted areas for drilling in Oldenburg on the one hand and the thermal conductivity of the ground at a depth of 100 meters on the other - a decisive factor for the efficiency of geothermal probes.
