| Title | Nationwide subsurface thermal-conductivity mapping for the assessment of the shallow geothermal potential in Germany |
|---|---|
| Authors | Tom Schintgen |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | WärmeGut project, geothermal information system, shallow geothermal potential, rock thermal conductivity, borehole heat exchanger |
| Abstract | Assessing the geothermal potential of shallow geothermal technologies, such as borehole heat exchangers (BHEs), is a primary objective of the WärmeGut project and requires both a nationwide estimate of mean subsurface thermal conductivities for different BHE lengths and a reasonably accurate shallow-subsurface temperature model. Maps of the shallow geothermal energy potential will be made accessible to the users via the public geothermal information system GeotIS. It includes a tool that estimates the potential share of local heat demand that could be covered by standardized BHEs, based on the heat demand density of different building classes and the available space for drilling. The main challenge of subsurface characterization is related to the lithological heterogeneity. However, at a nationwide scale, geological overview maps provide an adequate approximation of the geology at shallow depth. At a local scale, surface information can be combined or complemented with geological profiles and lithological information from boreholes. For thermal conductivity (TC) mapping, we generally assume that the subsurface is water saturated, which has a significant influence on the TC especially of porous or fractured rock. The TC mapping approach should also take into account the statistical spread of TC values representative of different lithotypes, which allows illustrating the heterogeneity and thus uncertainty of TC estimation. Communicating the statistical spread of values and the data origin is particularly important when using values from different sources such as the German guideline VDI 4640, various databases, literature or even laboratory measurements of specific geological formations. |