Survey of Energy Resources 2007
Geothermal Country Notes
Different assessments put the number of hydrothermal sources in Bulgaria at between 136 and 154, with about 50 of them having a total of 469 MWt of proven potential for extraction of geothermal energy. The majority of the waters have been found to be low-temperature at intervals of 20-90oC. Only about 4% of the total capacity has been found to have water hotter than 90oC. The theoretical potential of Bulgaria's geothermal energy amounts to 13 856 TJ/yr with the technical potential put at 10 964 TJ/yr.
There are in the region of 100 MWt geothermal systems installed in the country, representing some 23% of the currently discovered thermal potential (440 MWt). Together with the as-yet undeveloped resources, the total capacity of thermal waters could reach from 5 100 l/s to 6 400 l/s. The energy that could be obtained when the temperature is reduced to 15oC is estimated at about 751 MWt.
Currently, geothermal heat is used entirely for direct purposes: a situation that has persisted since the Romans installed under-floor heating in their hypocausts. Today, individual space heating has the majority share at some 50 MWt, with air conditioning (10 MWt), greenhouse heating (17 MWt), bathing and swimming (26 MWt) and other uses - aquaculture, and the extraction of chemical derivatives (7 MWt) - as the remaining shares. A small plant, located on the northern Black Sea coast, has been installed for the production of iodine paste and the extraction of methane.
Since 1999 there has been significant development of ground-source heat pumps (GSHP) utilising the low-grade geothermal heat.
As part of the Bulgarian effort to reduce greenhouse gas emissions, the Government has received a grant (under the Japan Climate Change Initiative Grants Program and administered by the International Bank for Reconstruction and Development), to support the development of geothermal energy projects. Phase I covered the collection of technical data, the detailed analyses of financial and economic aspects of implementation and site case studies. Phase II beginning at end-2005 is covering the detailed planning of eight identified projects and also the study of the further use of GSHP.