The use of geothermal energy is one way of decarbonizing heat generation. This is why interest in geothermal energy is growing steadily among politicians, businesses and the public. The political tailwind for geothermal energy is currently stronger than ever before, as the Geothermal Energy Congress in Potsdam in October showed.
Karin Thelen, Bundesverband Geothermie e. V., emphasized that "with the Geothermal Acceleration Act (GeoWG), the German government has made a clear commitment to geothermal energy as a key technology in the heat transition. For example, the draft law stipulates the overriding public interest in the construction and operation of geothermal plants. This legal concept gives geothermal projects additional weight when weighing up protected interests and increases planning security for project developers."
Municipal heat planning and acceptance
Cornelia Steiner, Federal Institute for Geology, Geophysics, Climatology and Meteorology Austria, presented an interactive geothermal atlas for Vienna. This atlas shows possible restrictions and potentials for the use of groundwater heat and geothermal probes in Vienna. An individual potential assessment is also possible for geothermal probe systems. Based on the selected location and depth of the probes as well as the operating hours, an estimate is made of the available output and amount of energy.
In Bavaria, near-surface geothermal systems can be used almost everywhere, as Kai Zosseder, Technical University of Munich, pointed out. There are hardly any exclusion areas, especially for geothermal collectors. However, geothermal probes have a lower overall potential, which is essentially limited by the drilling depth restrictions that apply in Bavaria. Groundwater heat pumps are limited to areas where a near-surface aquifer is present and show significant but lower potential.
For the implementation of a geothermal project, not only the geological but also the sociological conditions must be met. To this end, local social acceptance will be surveyed by means of an interview study in order to record the perspectives, concerns and needs of the various stakeholders in the community. Robin Renoth, University of Applied Sciences Neu-Ulm, derived recommendations for action to support municipalities in the use of geothermal energy in municipal heat planning and the associated social acceptance.
Cornelia Wolf and Daniel Bendahan Bitton, University of Leipzig, examined the public discourse on near-surface and deep geothermal energy over the past ten years (2014-2024) in regional and national public and private media in Germany. The results make it possible to identify misunderstandings in media reporting and particularly polarizing aspects in the discussion about geothermal energy. From this, information needs and acceptance factors can be derived that should be addressed in future science communication.
Geological feasibility and operational planning
Carlos Andres Rivera Villarreyes, DHI WASY GmbH, presented the Geothermal Information System (GeotIS) for estimating the geothermal potential in Germany. GeotIS consists of information on the use of geothermal energy, an e-learning platform and a map application for exploring geothermal subsurface conditions on site. GeotIS is based on data from more than 30,000 wells, especially oil and gas wells, but also geothermal wells and others. Recently, GeotIS was expanded with a traffic light map system to show the potential of near-surface geothermal energy.
Niklas Kracht, Institute for Solar Energy Research Hameln, reported on a more sustainable operation of a geothermal probe system. When using geothermal probes, it should be noted that the heat flowing in from the surrounding soil does not usually compensate for the energy extracted from the geothermal probes. This means that the ground is often not to be regarded as an energy source in the true sense of the word, but rather as an energy store. As heat pumps are particularly efficient with a low temperature range (difference between the heating flow temperature and the source temperature), the temperature of the borehole heat exchangers is an important parameter. The thermal regeneration of the subsurface by means of solar thermal energy, waste heat and building cooling must be taken into account.
Success stories
The first heat supplies using hydrothermal geothermal energy in Aarhus, Denmark, are due to start in 2025, reducing CO2 emissions by 165,000 tons per year. The transfer of the results will be used for projects in Germany to achieve similar successes in sustainable heat supply and improve the urban carbon footprint, as Alexander Richter, Innargi A/S, Denmark, reported.
Since spring 2020, the Munich-based aircraft turbine manufacturer MTU Aero Engines AG has been looking into the possibilities of using deep geothermal energy as a future heat source for the heat supply of the plant in the north of Munich, which is currently powered by gas. Florian Garsche, Fraunhofer IEG, spoke about the construction work for the heat distribution center, which is scheduled to go into operation in mid-2025.
Calcite precipitation (scaling) leads to a considerable reduction in the efficiency of geothermal plants. The use of a biodegradable scaling inhibitor has proven to be an effective solution, reported Hilke Würdemann, Merseburg University of Applied Sciences.
Large heat pumps
Felix Loistl, Stadtwerke München, emphasized that in addition to deep geothermal energy, large heat pumps will play a significant role in heat generation. These are operated in conjunction with geothermal systems, with thermal water serving as a high-quality heat source and heat energy being efficiently provided for various applications.
A study investigated the potential for increasing the thermal output of existing geothermal heating plants by integrating large heat pumps. Florian Heberle, University of Bayreuth, calculated heat production costs of 68 euros per MWh for the basic scenario.
Sven Klute, Fraunhofer Institute for Environmental, Safety and Energy Technology, spoke about industrial process steam generation from deep geothermal energy with thermally driven heat pumps. At many industrial sites, production-related waste materials and biomass accumulate that remain unused or have to be disposed of. Thermally driven heat pumps are a promising alternative to electrically driven heat pumps, especially in such applications.
At the Geothermal Congress, promising results from research and practice were presented on how geothermal energy can make an important contribution to energy independence as part of the heating transition. The course must now be set to exploit the considerable potential of geothermal energy for a climate-neutral future for Germany.
