25.04.22 “Geothermal energy is becoming much more important” Interview with Helge-Uve Braun and Dr. Christian Pletl • Reading time: 4 min.

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Stadtwerke München (SWM), Munich’s municipal utilities company, is one of the pioneers in the field of geothermal energy use in Germany. In this interview, Helge-Uve Braun (Technical Director of SWM and President of the German Geothermal Association) and Dr. Christian Pletl (head of decentralized generation and regional renewable energies at SWM) discuss the current status and the future of geothermal energy.

Geothermal energy is hardly ever mentioned alongside solar and wind power as part of the public debate on renewable energy sources. Why is that?

Braun: As the energy transition progresses, the focus of public interest is moving from electricity to heating, in other words from sun and wind to geothermal energy. There is a lot of potential in this area, because more than 50 percent of Germany’s energy is used for heat production. This transformation process can only succeed if we exploit geothermal resources, which could cover around 25 percent of our demand for heating. For this reason, we are seeing a new interest in using geothermal energy, against the background of the gas crisis caused by the war in Ukraine and the current focus on the heating transition. It is currently becoming much more important as a reliable climate-friendly, domestically available energy source. 

Which background conditions need to be improved in order to speed up the expansion of geothermal energy production in Germany?

Firstly, the government must make clear its determination to expand geothermal energy use. This could form the basis for a geothermal expansion strategy that includes the following key points: acceleration of approval processes (heating, electricity, and use of materials), increase in education and training for specialist staff (training bonus), obtaining and providing geodata by means of exploration (new data) and AI (existing data), and making securities available to cover the eventuality that a project does not find hot water. In addition, we need to offer investment incentives, for example by subsidizing the investment and operating costs with a focus on converting existing district heating networks and building new ones. And finally, we need more intensive research development activities and the amendment of administrative law for the purposes of the heating transition to make connecting to a geothermal district heating network mandatory for the owners of nearby properties. 

What potential does geothermal energy offer in Germany? And how much of it has already been exploited?

Braun: A number of studies have been carried out by well-known research institutes and public bodies into the potential of geothermal energy in Germany. For deep and medium-depth geothermal energy, it amounts to between 118 and 300 terawatt hours per year. Near-surface geothermal energy combined with heat pumps can provide an additional 68 terawatt hours per year. 

As things currently stand, deep geothermal plants are producing around 1.4 terawatt hours per year and near-surface systems about 8 terawatt hours per year. 

What role could geothermal energy play in 2030?

Braun: We are expecting to see a dramatic increase in the use of geothermal energy by 2030, providing that the government brings about a rapid improvement in the background conditions. In this case, geothermal energy could play an important role in supplying heating for residential and non-residential buildings and low-temperature heat for industrial processes. Near-surface and deep geothermal plants can supply dispatchable heat at any time of the day and year. In some regions, cooling, electricity generation, and lithium extraction from the thermal water could also contribute to the energy transition. 

You yourselves work in this area. How long has Stadtwerke München been using geothermal energy?

Pletl: For almost 18 years, which means that our plant will soon “come of age.” It is in the Riem area of Munich, where a whole new district has been created following the closure of the old airport in the early 1990s. We wanted to find the most environmentally friendly method of providing heating there. We now have a total of six geothermal plants that generate around 16 megawatts of electricity and 86 megawatts of heating. They produce around ten percent of the district heating needed by the city of Munich. 

What plans do you have to expand geothermal energy even further in Munich?

Pletl: On the one hand, we want to convert our existing plants from electricity generation to heat production and, on the other, we are planning to build new facilities. Our aim is to add a total of around 300 megawatts of heat. By the early 2030s, we aim to provide up to 70 percent of the entire district heating for the city of Munich from carbon-neutral sources, including geothermal energy and the incineration of waste. 

How long can the geothermal plants supply Munich with heating?

Pletl: Measured on a human scale, the energy is inexhaustible. We have run a simulation for the district of Riem which shows that the temperature of the thermal water we are pumping out will increase over the next 300 years or more, because we will gradually be extracting water from deeper levels of the aquifer. In the 300 years or so after that, the temperature will slowly fall and we will return to the original level after around 700 years. In other words, many generations will benefit from this one borehole. Geothermal energy is definitely more than a mere transition technology. 

Can the Munich model be applied to the whole of Germany?

Pletl: Geothermal energy cannot be used everywhere, because an underground aquifer is needed. But the right conditions can be found near all the major German cities. Here in Munich the conditions were not considered to be particularly good 18 years ago. The North German Basin and the Upper Rhine Plain appear to be much more attractive areas for the use of geothermal energy. 

Do we have enough expertise and enough companies to expand geothermal energy on a large scale in Germany?

Pletl: There have been developments in this area in the past, because many companies from the oil and gas extraction sector have moved into the field. However, there could be problems with expanding geothermal energy on a large scale because of the shortage of drilling and planning capacity. That is likely to be one of the major challenges in the future. 


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