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GET-05 Geothermal utilization - direct use, electrical production, heat pumps, industry and leisure
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The Lund geothermal heat pump plant. From a national point of view a unique
district heating facility with regards to size and energy source
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Leif Bjelm, Lund University (Sweden)
Per-Gunnar Alm, Lund University (Sweden)
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Sweden has for many years installed hundreds of thousands of ground-source and groundwater heat pumps running as single house units around the country. The density of units in Sweden has world-leading dimensions. The Lund plant differs from all other heat pump installations in Sweden because of the size and character of the energy source. The Lund geothermal heat pump plant was connected to the district heating net late 1984 but its actual start of heat production took place during early 1985. Two heat pump units have a capability of around 45 MWth and the yearly energy production is around 230 GWh which today equals around 25% of the district heating demand in the university city of Lund. The heat is extracted from a low temperature aquifer situated at a depth of around 700 m. The aquifer is a part of a stratified and unconsolidated sandstone formation belonging to Campan of Upper Cretaceous. About 100 to 150 m of the aquifer thickness is used for production and re-injection. Nine wells were drilled and all have a gravel packed wire wrapped screen completion. Four of the wells are for production and the rest for re-injection. From the production wells submersible pumps deliver about 550 l/s of a 6% TDS brine with a temperature today of 16-20°C. In 1985 the temperature was 22-24°C but 23 years of production and re-injection has cooled down the aquifer to some extent. The distance between production and re-injection wells is from 1300 m to about 2500 m. A thermal cooling impact was possible to see about six years ago, very much in conjunction with the thermo-hydraulic numeric simulations carried out at the start of the project. The availability of the heat pumps has been very high, > 95% , and according to the operator the cost for the plant has been paid back many years ago. Total cost 1986 was around 11 M and the system has reduced emissions and the use of fossil fuel in Lund drastically.
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