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Underground oil shale mining has been performed for 90 years in the middle-north part of Baltic oil shale deposit in Estonian deposit. After the mine closure mine workings are filled with water. Underground oil shale mining creates underground water pools called technogenic water bodies. Estonian oil shale deposit comprises ten closed mines that are fully or partly filled with water. Eight mines in the central part of the deposit: Ahtme, Kohtla, Kukruse, Käva, Sompa, Tammiku, mine No. 2 and mine No. 4 form one water body. Ubja mine and Kiviõli mines are located in the western part of the deposit, away from other mines.
The main aim of this paper is to analyze the feasibility of using minewater as heat source for heat pumps and to find suitable places to set up such systems. It would be useful to use this mine water like heat source for heat pumps to produce heat.
For defining underground space, properties and classification of used mining technologies have to be created and evaluated for defining hydro geological parameters. Classification helps defining space that is available for water in abandoned mines. 3D model was built with geometrical data from mine plans, mine closing acts and borehole data and from land survey data. The main tools chosen for spatial modelling were spreadsheets and MS Access databases for systemising and querying data, MapInfo for georeferencing, Vertical Mapper for interpolating and grid calculations and Modflow for pumping simulation. With help of interpolated grids, surface elevations, layer thicknesses and required properties were calculated.
Using minewater in heat pumps, the best possible technical solution is:
1) pumping the water through drillhole onto the ground surface
2) water goes to heat exchanger unit
3) minewater temperature will be lowered in heat pump heat exchanger about 1...4 degrees,
4) after that minewater is directed back to the mine.
If we use underground water pools water then the recommendation temperature reduction must be more then one degrees, it depends how large heat exchanger is economical. When temperature is lowered less, we have to use large volumes of minewater.