Fraunhofer Completes Drilling of Four 120-Meter Mine Geothermal Boreholes in Germany

en.Wedoany.com Reported - On October 30, the Fraunhofer Research Institution for Energy Infrastructures and Geothermal Systems (Fraunhofer IEG) announced the drilling results of the PUSH-IT underground thermal energy storage demonstration project in Bochum, Germany. All four boreholes have been completed, with the BO.REX mobile drilling rig successfully drilling at a depth of approximately 120 meters into roadways only a few meters wide within an abandoned flooded coal mine. The project has completed the verification of drilling into underground galleries, and the next phase will involve testing the mine's thermal storage performance.

The project used the BO.REX mobile drilling rig, which has a maximum lifting capacity of 40 tonnes, a mast height of over 12 meters, and a body width of 2.5 meters. The construction team combined geological data of the underground roadways, pre-planned borehole trajectories, and specially adjusted drill string counterweights to achieve directional positioning drilling into narrow underground galleries using conventional shallow geothermal drilling equipment.

Project leader Stefan Klein led the team in installing measurement sensors in the boreholes and using an autonomous underwater vehicle to inspect the underground mining galleries. The underwater imagery recorded water layers of varying turbidity and the rock walls on both sides of the galleries, verifying that all four boreholes entered the intended underground spaces. The research team will use the on-site measurement results to conduct subsequent thermal storage tests to determine the actual heat storage capacity achievable in the mine.

The Bochum demonstration project was jointly developed by the Fraunhofer Institute and Ruhr University Bochum, with the test site located at the Ruhr University Technology Center. The underground thermal storage target is the abandoned Mansfeld coal mine. According to the project plan, the four vertical boreholes will be used to establish mine water extraction and reinjection channels and to further verify the technical conditions for storing waste heat in underground mines.

The PUSH-IT project involves 18 European partner institutions researching three underground thermal energy storage technologies across six test sites. The project runs from January 2023 to December 2026, with a total budget of 17.9 million euros, of which the EU provides 3.8 million euros in funding to the Fraunhofer Institute. Subsequent testing at the Bochum site will also be used to assess investment conditions for surface facilities and the feasibility of using the mine thermal storage system for local buildings and data centers.