District heating in Lendava
In northeastern Slovenia three towns have district heating networks, that are operational between late autumn and early spring: Benedikt, Murska Sobota and Lendava. As a part of this network town of Lendava drilled a pair of geothermal wells which represent the only functioning reinjection well in Slovenia. That well is of great importance for the maintenance of the edaquate water levels of the local aquifer (1).
It is stated in the Local energy concept of the Municipality of Lendava, that share of renewable energy sources rose between years 2001 and 2011. That is also due to introduction of new renewable energy source – geothermal energy production share in municipality in 2011 was 14,37 % (2). 614 housing units are connected to the district heating network in Lendava which presents about 13 % of all housing units. These housing units consume about 5 MWh of energy per year (3). Apartments in these housing units are heated from 4 heating stations that, between years 2008 and 2011, replaced old boiler rooms. Basic energy product used is geothermal water, supplied by Nafta Geoterm. Geothermal water has temperature of 65 °C at the wellhead. This water has enough energy to heat buildings as long as outside temperatures are above 0 °C. When temperatures drop below freezing point, water is additional heated up with natural gas. This is done in suppliers boiler room which also serves as a reserve in case of any malfunctions on the well. However reliability of geothermal water supply is extremely high. Since boiler rooms were transformed into heating stations in 2008 there were no disruptions in supply (4).
»District heating network operates on the following principle: thermal water from the production well gives its heat away through heat exchanges and then returns cold to the well. Production well Le-2g was drilled in the summer of 1994. It is 1503 m deep and at maximum pumping power it pumps 90 m3/h (25 liters/second) of water with the heat 66 ˚C at the wellhead. Injection well Le-3g was drilled in the summer of 2007 and is 1223 m deep. It was drilled with the purpose of returning the water back into the aquifer. Both wells and consumers are interconnected with pre-insulated pipelines in total length of 2.000 meters« (5).
With the introduction of geothermal district heating system CO2 emissions in the municipality were reduced for 1600 tons. In last few years approximately 1,2 million € was invested into energy-related building refurbishment, which also contributed to lower energy consumption and heating expenses – all neighborhoods are energy efficient (3).
In 2014 city council approved baselines for future use of geothermal energy in the municipality. It has also adopted an action plan for establishment of price setting systems for so called “standard rate consumers” based on the Regulation of the Government of the Republic of Slovenia. Price of heating will be among the lowest in Slovenia and the operator will have to commit to spread the use of geothermal energy for economic purposes (3). Geothermal energy could also be used for spa tourism and agriculture. A project of heating glasshouses is also being implemented in the local community Lendava (2).