Reiche Zeche Freiberg

Silver has been prospected in Freiberg going back to the twelfth century. During its active years, this mining town delivered 80% of the silver in Saxony. Today, however, the reserves are close to completely mined. Left behind are the town’s mining traditions along with many kilometres of underground mining tunnels, shafts, and adits. With its mine, the “Reiche Zeche”, Freiberg University of Mining and Technology is the only university in Germany in possession of a fully intact mine for teaching and research purposes.

During the controlled decommissioning and flooding of the tunnels after mining concluded, nature reclaimed parts of the mine. Shafts and tunnels which once led miners through the mine are now filled with water. While part of this water is due to precipitation that has seeped down from the surface, the other part is from deep-lying groundwater. Water from tunnels deep within the mine can rise through the mine’s shafts, as has occurred in the main shaft of the Reiche Zeche, the „Himmelfahrt Fundgrube“, for example. Here, geothermal energy is transported with the water from a depth of 750 m to only 228 m below the surface, yielding water temperatures of approximately 19°C year-round. The water then flows into a cooler underground drainage tunnel, the Rothschönberger adit. The university’s geothermal energy system at the Reiche Zeche makes use of this energy for heating and cooling purposes [1,2].

 

Geothermal mine water system Reiche Zeche Freiberg (Graphic: Freiberg University of Mining and Technology)

In Winter, the 19°C mine water is pumped to two underground heat exchangers, which are connected with an intermediate heating loop. This heating loop transfers the heat to the surface, where the warm water stream is divided. The temperature of one fraction is increased to 60°C using heat-pump technology, while the other fraction is used for cooling of the computer labs and server rooms. In summer, the cooling system switches to pumping the cooler 14°C water from the Rothschönberger adit above ground. Thus, the water cools several laboratories, server rooms and offices energy efficiently. With the two installed heat pumps, a heating load of 175 kW can be achieved. By using the cool water from the Rothschönberger adit directly, the cooling load can reach 100 kW [1,2].

Summer Operation (Cooling Mode)

  • Pumping of water from the Roth­schön­berger adit primarily for the cooling
  • Discharge of the mine water, which has been warmed-up by absorbing heat in the cooling loop, back into the Roth­schön­berger adit with enough distance from the suction point
  • Direct cooling of laboratories, server rooms, and offices

Winter Operation (Heating Mode)

  • Use of water from the Reiche Zeche mine shaft primarily for heating
  • Heat pumps increase the temperature of the water for heating and warm water supply
  • Cooling is also required for laboratories and server rooms in winter
  • Support of cooling by recycling the cooled water from the heating loop

Literatur

[1] Schrön M., Dubiel J. (2016): Evaluierung einer Geothermieanlage zur Nutzung von Grubenwasser für Heizung und Kühlung auf dem Gebiet der Reichen Zeche, Projektarbeit, Technische Universität Bergakademie Freiberg
[2] Grötzsch S, Kleutges J.(2011): Geothermieanlagen zur Grubenwassernutzung für Heizung und Kühlung "Reiche Zeche" & "Schloss Freudenstein", Projektarbeit, Technische Universität Bergakademie Freiberg