German Unterhaching, located on the outskirts of Munich, is the most important reference point on the map of Europe for Polish investors. While Iceland or Italy use easily accessible volcanic steam, Unterhaching draws energy from deep aquifers of the Molasse Basin – a geological structure very similar to those occurring in Poland (e.g., in the Szczecin or Łódź trough). The success of this project proved that deep geothermal in sedimentary rocks is viable and safe.
The project started with an ambitious plan for electricity production in the Kalina cycle, but over time operators made a strategic decision to switch almost exclusively to heat production. It turned out that direct use of hot water (approx. 122°C - 130°C) in the district heating network is much more energy-efficient and economical than conversion to electricity at these parameters. Today the installation powers thousands of households, schools, pools, and industrial facilities, serving as a model for the entire Bavaria region.
Basic project data:
Wells in Unterhaching reach a depth of over 3.3 kilometers, penetrating Jurassic limestone layers (Malm). The key to high efficiency (flow rate of 150 l/s) was precisely hitting tectonic fault zones, which naturally increase rock permeability. Water is extracted through one hole, releases heat in the exchanger station, and cooled returns through the second hole to the ground (doublet system), which is standard in modern environmental engineering.
This investment, realized by local government, became a catalyst for geothermal development throughout southern Germany. It showed that with appropriate geological reconnaissance, parameters can be obtained that allow for complete abandonment of fossil fuels in medium-sized city heating systems. This is the technology and scale (both depth and power) that Geotermia Stargard, among others, is striving for.