In the town of Lendava we are building a district heating system with geothermal energy (geothermal energy source) based on the Law on mining (Zakon o rudarstvu Ur. List RS št. 56/59 and 46/04). Law on mining determines that the geothermal energy source is the source coming from earth's heat and it is possible to exploit it in a way so that after the heat is being taken away it can be returned back to the deposit. After the construction of the whole district heating system with geothermal energy, it will be the first one of its kind in Slovenia.
Figure 1: Principle of the district heating system
The production well Le-2g was initially drilled in the summer of 1994. The well is 1503 m deep and with the maximum pumping capacity of 90 m3/h (25 l/s) we get thermal water with a temperature of 66˚C at the mouth of the well.
The injection well Le-3g was drilled in the summer of 2007. The depth of the well is 1223 m and was deliberately constructed in a way so that the water is returned to the aquifer.
Both wells and all its users are interconnected with pre-isolated pipelines amounting to 2.000 meters of total length.
Figure 2: Scheme of the entire district heating system
The facilities foreseen for the connection to the district heating system are built in various periods and are mainly poorly isolated. Specific use of heat per year varies from 28 to 170 kWh/m2. For a more rational use of energy it would be necessary to renew most of the facilities.
In the existing facilities are placed heat conductor boilers running on classical fuels, which serve as a reserve for the operation in extremely low outside temperatures and defects in the thermal system.
In the first phase of the district heating construction we have connected users with a total of installed heat power of 5.650 kW and a total heating area of around 42.900 m2.
The users which are connected to the district heating system are mainly apartment buildings, business facilities (shops and offices) and educational institutions (school and gymnasium).
Heat consumption for all customers, including the annual level amounts to 5,000 MWh, which means about 1,500 tons CO2 less of greenhouse gases compared to the case where we would provide heat by burning 600,000 liters of light fuel oil.
The price of district heating with geothermal energy is formed so that it is tied to the price of gas, but less than the cost of energy which could be obtained from natural gas. Price of district heating with geothermal energy will grow more slowly than the growing price of natural gas. The current price of heat is extremely competitive and is about five cents per kilowatt-hour of heat.
In the second construction phase of the district heating system it is planned to connect new customers with a total installed thermal power of 3250 kW and heating surface of up to 20,000 m2.
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