25.04.22 “Geothermal heat is permanently available” Interview with Professor Dr. Rolf Bracke • Reading time: 4 min.

Scroll to Read

Professor Rolf Bracke is the head of the Fraunhofer Research Institution for Energy Infrastructures and Geothermal Systems IEG. In this interview, he discusses the potential of deep geothermal energy as a source of heating in Germany.

Professor Rolf Bracke, why has the process of expanding climate-friendly deep geothermal energy been so slow?

It is a question of traditional regional energy policy. Over recent years, geothermal energy has been promoted primarily by municipalities in the Munich area that were prosperous enough to run research projects with subsidies from the federal government. Once it had been shown that the technology worked, Stadtwerke München, Munich’s municipal utilities company, began investing in geothermal energy for the purposes of the heating transition. In Germany’s other energy-intensive regions, such as the Rhine-Ruhr district, Hamburg, Berlin, Frankfurt, and Mannheim, there is a strong focus on traditional fossil fuels, including black and brown coal and natural gas. For many years, coal was burnt to produce both electricity and heating and district heating networks were set up. Later the natural gas infrastructure was added. Geothermal energy was not able to compete with the traditional fossil-fuel energy sector. It was not until the phase-out of coal that there was genuine pressure to provide heating from renewable sources. 

Geothermal energy appears to be an attractive way of quickly increasing the proportion of renewable energy used in the heating sector. But serious problems have occurred in some of the projects. What impact has that had on the image of geothermal heating?

I do not get the impression that German citizens are fundamentally skeptical about geothermal energy. Quite the contrary. It is true that there is opposition in some regions, in particular in the Upper Rhine Plain. And I do not want to downplay the huge damage caused by the borehole in Staufen, for example. In my opinion, practical mistakes were made in this project that could have been avoided. On the other hand, Staufen was a near-surface geothermal project and the other 440,000 near-surface geothermal boreholes where there were no problems have not made the headlines. The companies that drill deep geothermal boreholes work to extremely high standards and are otherwise employed by the oil and gas industry. I believe that people’s fears can be effectively allayed using the approach taken by Stadtwerke München, in other words, by providing people with transparent information at an early stage and involving them in the planning process.  

The pressure to find renewable heating sources has increased massively since the war in Ukraine started. What needs to be done immediately to speed up the industrial-scale exploitation of geothermal energy?

Investigations have been underway in Bavaria for 30 years into the geothermal potential of the substrata at a depth of 1000 meters and more. This has not yet been done in other regions. Explorations below the coal seams in the Ruhr district were stopped. In Lower Saxony, Schleswig-Holstein, and Brandenburg, underground exploration was carried out by the gas and oil industries, but only in rural areas where there is no need for industrial-scale heating. The potential of deep geothermal energy lies in the supply of municipal district heating to whole cities, individual districts, or industrial plants. The task now is to start exploration programs with the aim of finding thermal-water-bearing strata under large urban areas. 

How costly is it to drill deep boreholes?

A borehole at a depth of 1,000 to 4,000 meters, which is where the thermal-water-bearing strata are usually found, would cost five to ten million euros. Small and medium-sized companies are not prepared to make investments of this kind if there is no information available about the chances of success. This is why we need a federal program to carry out the basic exploration with the help of the geological services of the federal states. This will involve using geophysical methods to create three dimensional images of the underground strata. We also require a financial instrument to mitigate the risks of drilling deep boreholes. Appropriate solutions could include insurance or a revolving geothermal fund that would pay the investment costs and be supported by the companies that have been successful in finding a geothermal source. A financial instrument of this kind has been used with success for some years in East Africa and Latin America for deep geothermal projects involving the KfW, Germany’s state-owned investment and development bank. 

What would the cost be if geothermal energy were to make a significant contribution to meeting Germany’s heating needs?

Underground exploration in a region such as the Ruhr using seismic technology, which is a geophysical measurement method similar to echo sounding, would cost tens of millions of euros. This would then be followed by the process of drilling the deep boreholes. We estimate that up to 100 of these are needed for each gigawatt of installed power. The total costs, including exploration, drilling, and the power plant, are between 2 and 2.5 billion euros per gigawatt of heating output. To meet a quarter of Germany’s current heating needs, we would have to make investments of 140 billion euros in the period up to 2040. That may sound like a large amount of money, but, to put it in perspective, it corresponds to the cost of Germany’s energy imports every year. And geothermal heat is permanently available. I am certain that if we want to phase out fossil-fuel-based heating systems, deep geothermal energy has the potential to be an important alternative. 

Professor Rolf Bracke is the head of the Fraunhofer Research Institution for Energy Infrastructures and Geothermal Systems IEG. Together with Professor Ernst Huenges from the GFZ German Research Center for Geosciences, he has published a study entitled “Roadmap Tiefe Geothermie” (Roadmap for deep geothermal energy). It investigates the potential of deep geothermal energy to provide a supply of heating in Germany and recommends actions to be taken by the government, businesses, and research institutions. 


The contents of this website are created with the greatest possible care. However, Uniper SE accepts no responsibility for the accuracy, completeness and topicality of the content provided. Contributions identified by name reflect the opinion of the respective author and not always the opinion of Uniper SE.