Baumann L., Kuschka E., Seifert T. (2000) Lagerstätten des Erzgebirges. ENKE im Georg Thieme Verlag, Stuttgart
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Geothermal use of Mine Water in Saxony
Mining has played a critical role in shaping the regional and historical development of Saxony. The start of mining activities can be dated as far back as 1168, when silver was discovered in Christiansdorf, which is now part of the old town of Freiberg. Further discoverie of silver ores in the Ore Mountain region led to the founding of other mining towns such as Schneeberg, Annaberg, Marienberg, and Johanngeorgenstadt. This period of continuous growth was interrupted during the Thirty-Years' War (1618-1648), as many towns and mining facilities were destroyed. A renewed increase in mining activities occurred first in the 18th century. In addition to the mining of silver and tin, there was an increase in copper, lead, bismuth, cobalt, and nickel at this time. After the second world war, ore mining in Saxony was concentrated on the extraction of lead, zinc, and tin. Of particular historical significance was the mining of uranium by the Wismut AG (later SAG/SDAG Wismut) during the GDR until the reunification of Germany. Various existing ore-deposits were explored searching for possible Uranium. By far, the largest amount was extracted from the open-pit mine of Schlema-Alberoda. Other important deposits included Zobes, Bergen, Johanngeorgenstadt, and Pöhla, as well as the uranium-rich bituminous coal deposit in Revier Freital/Gittersee. Up until 1989, approximately 12.4% of the total Uranium mined worldwide came from East-German mines .
Furthermore, the first surface deposits of coal were discovered in Zwickau going back to the 10th century . Reserves of hard (bituminous) coal were primarily concentrated in deposits in Zwickau (220M metric tons extracted), Lugau/Oelsnitz (140M metric tons), and Freital/Gittersee (50M metric tons) . The end of uranium-rich coal mining in Grubenfeld Gittersee in 1989 was accompanied by the end of hard coal mining in Saxony. Despite this, the mining of brown coal (lignite) was still of interest at the time and continues in Saxony today. With both the Middle-German and Lausitzer brown coal districts, two large mining areas are contained partially within Saxony, where three open-pit mines are still in operation as of 2018 (Nochten, Reichwalde, and Vereinigtes Schleehain).
Approximately 12.2 billion metric tons of geological resources are recorded for the total Lausitzer brown coal district and 10 billion metric tons for the Middle-German brown coal district. Of this, 3.7 and 2.1 billion metric tons, respectively, are considered economically feasible (as of 2006) . Additionally, the mining of spars, rocks, and soils play an important role in Saxonian history and the region’s development today.
Geothermal Energy from Mine Water in Saxony
As a result of this mining, a large number of man-made underground cavities can be found within Saxony, often filled with large quantities of water. The potential use of this mine water for supplying geothermal energy was recognized in previous studies, resulting in the installation of geothermal systems in various mining regions in Saxony. The systems differ greatly from one another due to the various existing conditions in the mines. An overview of these geothermal systems, as well as the important mining regions in Saxony, are given in the figure below:
 Baumann L., Kuschka E., Seifert T. (2000) Lagerstätten des Erzgebirges. ENKE im Georg Thieme Verlag, Stuttgart