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Second chance for a district heating network in Geretstried, Bavaria?

Daldrup drilling rig on site in Geretsried, Germany (source: Daldrup & Söhne AG)
Alexander Richter 26 Jan 2019

Following the unsuccessfull drilling of two wells, Enex Power Germany, the developer of the Geretstried geothermal project is hopeful to revive the project for future district heating.

The geothermal project in Geretstried in Bavaria/ Germany might see a second chance. The project’s developer Enex Power Germany has submitted a new grant application to the Federal Ministry of Economics, so local publication Merkur in late December 2018.

“We hope that we get a positive reply in the middle of [this] year,” says Enex Managing Director. Robert Straubinger. It will then be possible to further investigate how geothermal energy can best be used on site in Gelting/ Geretstried. There is already a concrete idea.

“Stumble, fall, get up, fix yourself up and continue”, this is how Straubinger summarizes the almost ten years he has accompanied the geothermal project in Gelting for Enex as Managing Director. During this time, the 66-year-old had to take some setbacks. The worst scenario came true twice: drilling failed in 2013 and 2017. There was not enough hot water deep down in the earth. But the graduated physicist did not give up hope. “It could have been worse,” says Straubinger optimistically.

The Technical University (TU) Munich and the Leibniz Institute for Applied Geophysics (LIAG) are still busy analyzing the data obtained in 2017. The researchers scientifically accompanied and collected numerous rock samples during the drilling of the second well, a side-tracked well in underground fracture zones. The result: The rock under the project site is petrothermal. That means: tight, hot and dry. Almost all other geothermal sites in Bavaria are hydrothermal. There, of course, existing thermal water can be used to generate electricity and heat.

 How can that be? “The for developers interesting limestone layer was formed 140 million years ago. This was very similar throughout Bavaria, “explains Straubinger. Then there were changes. In the Munich area, the layer karstified, forming large-scale pores through which water can flow and be successfully extracted. “In our region, this layer was pushed very low by the later formation of the Alps.”

Enex had to drill very deep in Gelting/ Geretstried. The final depth was 6,036 meters, with the overall well length of more than 6,500 meters. There, Enex measured a record-breaking 169 centigrades. The much higher pressure and the heat, according to Straubinger, have allowed the pores to regrow and blocked the way for the water. This explanation fits into the picture: in Sauerlach, about 100 liters per second of thermal water can be pumped. For the geothermal project in Holzkirchen about 50 l/s. In Gelting it was not even 10 liters per second.

Despite the dryness Enex does not want to give up on the location in Gelting. The company hopes to use the heat in the rock similar to a similar project in Soultz-sous-Forêts in the Alsace region of France. There, water is injected into artificially enlarged cracks and fissures under high pressure. The water heats up and a production well pumps it back to the earth’s surface, where it is used to generate electricity.

“We would be the first to do something similar in Bavaria,” says Straubinger about the idea. However, the prerequisite is that the federal government re-subsidizes the project. The application is made. Now the Enex CEO hopes the ministry will approve the plan. “If we get a positive decision, we can continue in the middle of next year.”

The great dream of a 5 MW geothermla power plant, Enex has given up years ago. But Straubinger is sure: “For a district heating network for Geretsried it would be enough.”

Source: Merkur