Utilization of Geothermal Waters for Space Heating in Bulgaria

Abstract

The Republic of Bulgaria is rich in geothermal waters. The temperatures are in the range of (20oC - 100oC). For about 25 % of the total discovered flow rate the temperature is between 40oC and 50oC and only for 3.6% - the temperature is higher than 80oC (Petrov et al.1998)

Geothermal waters have been used since ancient times. At first they were utilized for healing, bathing, swimming pools and hypocausts (a type of Roman floor heating system). The systematic application of geothermal energy in Bulgaria has began with heating of separate buildings using direct schemes only. As a result of their exploitation scaling and corrosion occurred. The first more contemporary geothermal heating and air-conditioning installations in Bulgaria were constructed after 1980. Schemes with plate heat exchangers and heat pumps have been used. All systems built so far have been designed for space heating of separate buildings or small recreation spa centers. There are no district heating systems built in Bulgaria due to the insufficient capacity of the reservoirs or number of consumers.

The total installed capacity of the geothermal systems (towards June 1999) is 95.35 MWt. The largest installed capacities (up to 15 MWt) of geothermal systems for space heating and airconditioning of buildings were realized in Northeast Bulgaria along the Black Sea coast. In Southern Bulgaria the number of geothermal stations is much greater, but all of them are of smaller installed capacity ranging from 0.200 to 1 MWt. Most of the realized schemes for space heating are composed of imported equipment, such as plate heat exchangers, heat pumps, submersible pumps, circulation pumps and control systems from world leading companies. The feasibility analysis of the existing geothermal systems has shown good results with regard to the primary capital investment per unit of installed capacity as well as per prime cost of the produced energy. The basic difficulties in the geothermal energy utilization for space heating and airconditioning are due to the lack of investments.