Once again this year, the GFZ Helmholtz Centre for Geosciences was represented at the GEOTHERM expo & congress with an information stand in the trade exhibition and contributions to the congress programme. Europe’s largest geothermal energy trade fair took place in Offenburg from 26 to 27 February 2026 and, with 302 specialist exhibitors from Germany and abroad, demonstrated the growing momentum in the industry.

The annual event covers a wide range of topics relating to deep, medium-depth and near-surface geothermal energy, as well as underground heat and cold storage. GeoTHERM has become the central meeting place for the European geothermal industry, bringing together business, research and politics.

The GFZ, represented by staff from Sections 4.3 “Geoenergy” and 4.2 “Geomechanics and Scientific Drilling”, appeared for the second time this year as an official partner of GeoTHERM and presented its research on “Geothermal Systems and Energy Storage”. Numerous visitors to the GFZ stand learned about the GFZ’s research work and areas of expertise in geothermal energy. As every year, the stand was also a meeting place for exchanging ideas with project partners from ongoing national and European research projects and developing new project ideas.

This year, the GFZ presentation focused on

• the European project TRANSGEO on the geothermal reuse of decommissioned boreholes with the demonstration site in Groß Schönebeck in northern Brandenburg.
• the Helmholtz-funded GeoLaB project, a planned geothermal laboratory in a research mine yet to be built.
• the EU-funded CRM-Geothermal project for the extraction of critical raw materials such as lithium from geothermal fluids.

TRANSGEO: Reuse of decommissioned boreholes…

TRANSGEO is investigating how decommissioned boreholes and facilities from gas and oil production can be reused for geothermal applications. This is a topic of great interest to the industry, as drilling is the largest cost factor in geothermal projects. The conversion or reuse of existing boreholes can significantly reduce initial investment costs. In addition, the exploration risk is significantly lower than for new drilling, as the files on old boreholes provide information about the geological conditions. In addition to the borehole itself, existing infrastructure can often be used. Reuse also avoids new interventions in the landscape and thus reduces the carbon footprint.

TRANSGEO is co-financed by the European Commission in the Interreg CENTRAL EUROPE programme and brings together eleven partners from five countries. The project is coordinated by Prof. Dr Hannes Hofmann, who heads the Helmholtz Young Investigators Group “Advanced Reservoir Engineering Concepts (ARES)” in Section 4.3 “Geoenergy” at the GFZ.

…with the Groß Schönebeck demonstration site

In this context, the GFZ research platform in Groß Schönebeck also serves as a demonstration site for the TRANSGEO project, which was presented by Hannes Hofmann in his poster contribution ‘Reuse of deep boreholes as deep geothermal probes: Demonstration at the Groß Schönebeck research platform’.

In order to further develop the technology for petrothermal systems and to research strategies for reusing existing boreholes, investigations have been ongoing at the site since 2025 in cooperation with the Danish company Greentherma with the aim of converting the existing Gt GrSk 4/05 A borehole into a deep geothermal probe. A test lasting several months, planned for May 2026, will evaluate the efficiency of the insulation, the stability of the vacuum, and the thermal performance and production temperature of the deep geothermal probe under various flow conditions – in particular under the influence of thermally conductive salt layers.

“The Groß Schönebeck site thus illustrates the transition from hydrocarbon to geothermal use and demonstrates the potential for reusing decommissioned oil, gas and geothermal wells. At the same time, it serves as a test field for advanced coaxial borehole heat exchanger technologies, thereby contributing to the development of sustainable geothermal utilisation concepts in sedimentary basins such as the North German Basin,” explains project manager Hannes Hofmann.

GeoLaB – Geothermal Laboratory in the Mine

The GeoLaB research infrastructure planned in the crystalline bedrock, a joint project of the Helmholtz Association's “Energy” and “Earth and Environment” research fields, also met with broad interest. Through interdisciplinary and cross-process research on a real scale in an underground laboratory, scientists from the three Helmholtz Centres GFZ, KIT (Karlsruhe Institute of Technology) and UFZ (Helmholtz Centre for Environmental Research) will develop technologies for the sustainable exploitation of the geothermal potential of the crystalline bedrock for the energy transition, for which partners and service providers from industry are also needed.

Information was provided on the comprehensive preliminary exploration measures carried out in the Odenwald, southern Germany, over the last two years, which included two seismic campaigns led by the GFZ and two exploratory boreholes. The results of the preliminary exploration form the basis for the decision on the suitability of the Tromm region for the planned underground geothermal laboratory, which in turn forms the basis for cooperation on further site planning and development.

The GFZ part of the project is managed by Prof. Dr.-Ing. Ingo Sass, head of GFZ Section 4.3 “Geoenergy”.

CRM-Geothermal – Critical raw materials from geothermal fluids: origin, extraction, demonstration

Dr Katrin Kieling, project manager in GFZ Section 4.3 “Geoenergy”, presented the CRM-Geothermal project as part of the accompanying conference programme. A separate project conference was also held in the run-up to GEOTHERM, at which interim results were reported.

The extraction of lithium and other critical raw materials (CRM), such as helium, strontium or rare earth elements from deep fluids is currently being investigated in many geothermal areas worldwide. The occurrence of CRMs and their extraction technologies are very location-specific, and the economic feasibility of co-extraction of heat and CRMs has hardly been proven to date.

In general, geological conditions determine the composition of geothermal fluids, while the efficiency of extraction technologies depends on the brine composition and the conditions of the plants.

The EU-funded CRM-Geothermal project takes a holistic approach to the assessment and extraction of critical raw materials from geothermal fluids in Europe and East Africa. 

The following objectives are being pursued:

(I) To assess the overall potential, a database is being set up and the collected fluid data visualised in a fluid atlas.

(II) The origin and mobilisation of CRMs will be investigated for different geological settings (e.g. in crystalline, fractured rock or in deep sedimentary basins where highly saline waters circulate through porous formations) in order to make predictions about the occurrence and sustainability of extraction during fluid circulation.

(III) Innovative extraction technologies are being developed for some CRMs such as lithium, strontium and helium for different fluid types.

(IV) Furthermore, economic, social and environmental aspects of the processes are being taken into account.

(V) Finally, the feasibility of CRM co-extraction is to be demonstrated at one site (Cornwall).

The project is funded by the EU as part of the Horizon Europe research and innovation programme and coordinated by Dr Katrin Kieling and Prof. Dr Simona Regenspurg, working group leader in GFZ Section 4.3 “Geoenergy”. Numerous European partner institutions are involved.