THE ABANDONED UNDERGROUND CHERNO MORE COAL MINE (SE BULGARIA) - A SOURCE OF LOW GRADE GEOTHERMAL ENERGY

Flooded abandoned coal mines are a potential source of geothermal energy, which could be used for heating and cooling of energy efficient buildings. Cherno More Coal Mine is located in SE Bulgaria and has been closed for more than 20 years. It represents a large human-induced subsurface reservoir which consists of three interconnected coalfields (Brigade, 9.IX. and Blagoev). Their total volume of about 2.0 x 10(6) m(3) has been calculated considering the size of the stone drifts. The mine water temperature is measured to be about 16 degrees C in the only accessible vertical shaft (9.IX. coalfield). This is the first study of an abandoned coal mine in Bulgaria aiming at assessing its low-valued energy potential and evaluating the opportunity for heating and cooling buildings. The geological and hydrogeological characteristics of Cherno More Mine have been analyzed by using existing archive data and conducting additional chemical analysis of water samples and temperature measurements in the mine. The obtained data were used to develop a regional groundwater model of the area and a local hydrothermal model for a thermally-insulated furniture factory located in the vicinity of the vertical shaft. The simulated temperature distribution in the mine during exploitation showed no impact on the production temperature by reinjected water under defined steady state conditions, which created a reliable basis for mine water energy use.