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The territory of Bulgaria is rich in thermal water of temperature in the range of 20 C-100 C. Electricity generation from geothermal water is not currently available in the country. Direct thermal water use nowadays is mainly for balneology, space heating and air-conditioning, greenhouse heating, geothermal ground source heat pumps (GSHP), direct thermal water supply, and bottling of potable water and soft drinks. Several applications such as balneology and geothermal ground source heat pumps show more stable development in the current period, while geothermal energy used for heating of buildings and greenhouses has considerably decreased. The update information on hydrothermal fields is based on issued permits and concessions by the state since 2000 and concerns mainly state-owned hydrothermal fields. The current installed capacity amounts to about 85.8 MW (excl. GSHP). A progress has been recently made in the state policy promoting thermal water utilization. According to the latest amendments of the Water Act taxes for thermal water application are considerably reduced, and many state-owned reservoirs are made available for use by the municipalities. V C 2013 AIP Publishing LLC.

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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 ("Brigadir", "9.IX." and "Blagoev"). Their total volume of about 2.0 × 10 6 m 3 has been calculated considering the size of the stone drifts. The mine water temperature is measured to be about 16 • 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 The funding from the European Commission (CONCERTO II) for carrying out the survey is gratefully acknowledged. 565area 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.