Geothermal energy indispensable for a heat transition

Joint roadmap by Helmholtz Centres and Fraunhofer institutes identifies fields of action for sustainable heat supply.


Half of municipal heating has to come from climate-neutral sources by 2030. Deep geothermal energy can make a major contribution to this goal of the German government, because it supplies local energy consistently and independently of weather conditions and occupies little space in built-up areas. A joint roadmap by institutions of the Helmholtz Association and the Fraunhofer Society shows that deep geothermal energy has a large market potential in Germany, opening up expansion targets of more than a quarter of Germany's annual heat demand (over 300 TWh). The paper makes recommendations for action to achieve this goal, e.g., it says there is a need for clear expansion targets, large-scale, geological exploration, investment in key technologies and the development of a skilled workforce.

“Without geothermal energy, decarbonization of the heating sector in Germany will not be possible. The natural underground heat potentials for this are available in most urban areas. The sustainable expansion of geothermal energy is an investment in the cities of our future,” says Prof. Ingo Sass, head of the ‘Geoenergy’ section at Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences. “The research institutions of the Helmholtz Association are making a significant contribution to the success of the transformation with their strategically oriented programs and their unique research infrastructures, such as the future underground research laboratory GeoLaB,” Sass continued.

“To be able to achieve the expansion target of more than 300 terawatt hours, we need technology development,” said Prof. Thomas Kohl of the Karlsruhe Institute of Technology (KIT), coordinator of GeoLaB, a joint initiative of KIT, GFZ, and the Helmholtz Centre for Environmental Research (UFZ). “The application and development of state-of-the-art monitoring and analysis tools at GeoLaB will provide the insights that are of great importance for a safe and ecologically sustainable use of geothermal energy and other subsurface resources. Very important in this context is also the transparent interaction with the public and decision-makers,” Kohl explains.

According to Sass, underground research laboratories such as GeoLab have a central importance, “because they shed light on the fundamental physical-chemical-biological understanding of sites with similar geological properties.” Ingo Sass adds, “we translate our research results into applied, industrial and demonstration projects, showing society the safe and large-scale applicability of geothermal energy provision.”

“The UFZ contributions focus in particular on the digitization process and geothermal system analyses,” says co-author Prof. Olaf Kolditz, who heads the Department of Environmental Informatics at the UFZ. “Among other things, we are pursuing concepts of ‘digital twins’ and virtualization to digitally replicate natural and technical systems (real-labs) as realistically as possible. This allows geothermal systems to be technically optimized, their efficient integration into the overall energy system to be simulated, and environmental impacts to be estimated over the long term,” Kolditz continued.

Together with Helmholtz colleagues from the Helmholtz Centre for Environmental Research (UFZ) and the Karlsruhe Institute of Technology (KIT) as well as from the Fraunhofer Society, the GFZ took part in developing the roadmap. GFZ researcher Ernst Huenges, co-editor alongside Rolf Bracke from the Fraunhofer Institute for Energy Infrastructures and Geothermal Energy (IEG), says: “Achieving climate neutrality in the heating market is a huge challenge and requires a whole bundle of measures. Market players such as energy suppliers, industrial companies, the housing industry, the financial sector, politics, administration, educators and municipalities need new tools for this complex implementation task.”

The strategy paper is intended to provide all stakeholders with the necessary information on the geothermal heat supply, the versatility of the heat market and the technological realization of the heat transition. The aim is to provide recommendations for action in order to implement the potential of geothermal energy in terms of climate-neutral heat supply.

The roadmap identifies five recommendations for action to expand geothermal energy for the heating market in Germany:

  1. Clear expansion targets: Parliaments and local councils should formulate clear expansion targets and flank them with appropriate legislation and statutes ranging from the Federal Mining Act to municipal land use planning.
  2. Risk compensation for companies and municipalities: Small and medium-sized companies such as municipal utilities are active in the heating market and can only bear economic risks such as the exploration of deep geothermal energy to a limited extent. Therefore, there is a need for financial instruments for inter-municipal risk compensation. In addition, the states should set up a comprehensive geoscientific exploration program to reduce the discovery risk for municipalities and companies.
  3. Invest in key technologies: To turn a few dozen deep geothermal plants in Germany into thousands, investment in key technologies is needed to achieve large industrial scale. The key technologies are drilling methods, reservoir management, borehole water pumps, high-temperature heat pumps, large-scale heat storage, trans-municipal interconnected heat grids, and cross-sectoral system integration.
  4. Education and training of skilled workers: The growing geothermal industry creates regional jobs in technology development, planning and production as well as in construction and operation of the plants. One can assume about 5 to 10 full-time jobs per megawatt (MW) of installed capacity. In order to train thousands of specialists, academic education and supplementary curricula to the existing courses of the chambers of trade, industry and commerce are needed.
  5. Dialog with citizens: The solution to social challenges requires social acceptance. Municipal stakeholders therefore need more than just business management and plant engineering strategies. It is necessary to use citizen energy models, municipal communication strategies and transparent projects to bring all local stakeholders along on the path to regional heat transformation.

The heat sector accounts for 56 percent of the national energy demand. Only 15 percent of heat is renewable. The roadmap now presented discusses the contribution of geothermal energy to the heat transition. The focus is on hydrothermal reservoirs, i.e. thermal water-bearing rocks at depths between 400 meters and 5,000 meters. Geothermal waters can be produced at temperatures between 15 and 180 degrees Celsius from such deep wells. They are available regardless of the season and time of day and can be used in particular for local and district heating and even for low-temperature processes in industry. The technology is mature and has been used for decades in many European cities, such as Paris and Munich.

According to the roadmap's estimates, hydrothermal geothermal energy – combined with large-scale heat pumps – as a heat source for district heating networks could cover around a quarter of Germany's total heat demand, theoretically around 300 terawatt hours of annual work with 70 gigawatts of installed capacity. By comparison, in 2020, 42 plants nationwide supplied 359 megawatts of installed thermal capacity and 45 megawatts of electrical capacity.


«GEOTHERMIE-ROADMAP FÜR DEUTSCHLAND Handlungsempfehlungen für Politik, Wirtschaft und Wissenschaft für eine erfolgreiche Wärmewende»PDF Download 7,1 MB (German only)

List of authors and editorial board

Editorial Board
Rolf Bracke, Fraunhofer-Einrichtung für Energieinfrastrukturen und Geothermie (IEG)
Ernst Huenges, Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum GFZ

Daniel Acksel, Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum (GFZ)
Florian Amann, Fraunhofer IEG
Judith Bremer, Karlsruher Institut für Technologie (KIT)
David Bruhn, Fraunhofer IEG
Marcus Budt, Fraunhofer-Institut für Umwelt-, Sicherheits- und Energietechnik (UMSICHT)
Gregor Bussmann, Fraunhofer IEG
Uwe-Jens Görke, Helmholtz-Zentrum für Umweltforschung (UFZ)
Gunnar Grün, Fraunhofer-Institut für Bauphysik (IBP)
Florian Hahn, Fraunhofer IEG
Anja Hanßke, Fraunhofer IEG
Thomas Kohl, Karlsruher Institut für Technologie (KIT)
Olaf Kolditz, Helmholtz-Zentrum für Umweltforschung (UFZ)
Simona Regenspurg, Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum GFZ
Thomas Reinsch, Fraunhofer IEG
Karsten Rink, Helmholtz-Zentrum für Umweltforschung (UFZ)
Ingo Sass, Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum (GFZ)
Eva Schill, Karlsruher Institut für Technologie (KIT)
Clemens Schneider, Fraunhofer IEG
Haibing Shao, Helmholtz-Zentrum für Umweltforschung (UFZ)
Dimitra Teza, Fraunhofer IEG
Leo Thien, Fraunhofer IEG
Matthias Utri, Fraunhofer IEG
Harald Will, Fraunhofer-Institut für Bauphysik (IBP)

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