| Abstract |
Thermal water in the Slovenian part of the Mura-Zala basin, which appertains to the SW part of the Pannonian basin, is produced from low enthalpy geothermal system set in the Neogene sediments as well as from basement aquifers in the Pre-Neogene metamorphic and carbonate rocks. The water discharges from 26 geothermal wells managed by 14 users. Their density is especially high in the central Pomurje area between towns Murska Sobota and Moravske Toplice. Utilization schemes depend on water temperature mostly but the scaling potential and gas content also play an important role. The highest wellhead temperatures reach 72 °C in Benedikt and Moravske Toplice, however, temperatures between 50 and 60 °C are gained most often. The use is more diverse than a decade ago but the individual space heating, sanitary water heating and bathing with balneology still prevail as direct utilization schemes. Both, the installed capacity and the used geothermal energy show an increasing trend in the period 1995-2010, including geothermal ground-source heat pumps. The increase is pronounced especially after 2005 when new users in Lendava, Benedikt and Dobrovnik started to exploit geothermal heat for greenhouse and district heating. As higher abstraction rates are needed for this type of use the total annual thermal water abstraction increased noticeably in the last years and amounted to 3.29 million m3 in 2011. The available geothermal energy is not efficiently used as relatively low capacity factor of app. 25% is calculated. But it is positive that the majority of thermal health resorts apply cascade use of water and space and sanitary water heating is applied first, followed by bathing and balneology. Terme 3000 health and spa resort in Moravske Toplice is by far the biggest geothermal energy user in the area (98.3 TJ in 2010), but a good practice is identified as some of their thermal waste water is provided to another user for greenhouse heating. Greenhouse heating systems in Dobrovnik and Tešanovci operate in colder season of the year, similar to district heating systems in Benedikt, Murska Sobota and Lendava. The latter installation has also a pavement de-icing done. In Lendava, a reinjection well operates since 2009, and together with the abstraction one they form the only operating geothermal doublet in Slovenia. Another potential geothermal doublet is situated in Renkovci but it was still in a testing phase in 2012, while the third pair has just been drilled in Murska Sobota in the spring of 2013. Various direct use applications indicate that diverse utilization of thermal water already exist in this region and many experience on different exploitation systems has been gained therewith. However, it is estimated that the current thermal water extraction already surpasses the natural capacity of this geothermal system, which raises the need for appropriate measures to improve its hydrological conditions. As new exploitation is possible at five localities, where three wells are planned for thermal resorts and two for space or greenhouse heating, it is very important to establish threshold values of the existent state of the aquifers as well as to improve the efficiency of current use. These parameters should be controlled by an appropriate monitoring system. Together with more reinjection wells and more efficient utilization of the produced thermal water, further and even more diverse utilization systems can be developed and applied. |