The first geothermal power plant…

Dravske elektrarne Maribor, a company of the Slovenske elektrarne Holding Group, has been awarded a construction permit from the Lendava Management Unit to build a geothermal power plant at Pg-8 in entiba near Lendava, which will serve as a demonstration project for good practices and increased geothermal energy use.

The pilot research project in the settlement of Čentiba in the municipality of Lendava will exploit the geothermal potential of a dry, non-productive well about three thousand meters long which is as such the first in Slovenia. It is a completely closed system where the liquid coolant (ammonia) does not come into contact with the extremely hot rocks. The Pg-8 well is tubing (steel lined with steel), riveted and completely sealed. A two-pipe system about a thousand meters long will be inserted into this sealed well. The geothermal power plant in the Pg-8 well will consist of an underground part, ie. Gravity tube and top ie cooling system and engine room.

From a technical point of view, a gravity tube is a hole in which two parallel tubes of smaller and larger diameters are installed. The liquid refrigerant will be introduced from the surface through a smaller diameter tube, which will be directed downwards due to gravity and will evaporate slowly as the temperature increases due to gravity. The superheated refrigerant vapor is returned to the surface through a larger diameter tube, which is used to produce electricity using a plant similar to the organic Rankine cycle (ORC). The function of the cooling system is to dissipate the excess heat of the medium after the end of electricity production. The engine room will be in a container placed right next to the well.

mag. Damjan Simi, Director of DEM He said: “The special feature of the geothermal experimental device is the use of a geothermal heat pipe, which enables a closed cooling circuit and only one dry well is required to operate the power plant. The power plant will therefore operate without gas or other emissions. The advantage of the geothermal power plant is that the Completely closed, which prevents losses as well as loss of refrigerant. Special equipment and sealants adapted to contact with ammonia will be used for the planned intervention, ensuring maximum safety.

The next step in the project is to rehabilitate the Pg-8 well, install the geothermal gravity tube and test for leakage. This is followed by the installation of the above-ground portion of the geothermal power plant, well abundance testing and all equipment. Testing is scheduled to begin in July 2023, and after successful tests, the power plant will start operating in April 2024.

Alexandre Brunico, General Manager of DEM So he adds: “This pilot project is a niche market on a global scale. The concept of using geothermal energy in this way is patented and exclusive use of the patent is granted to the Drava power plants in Maribor. The pilot project will be the first application of this patent, which is the fruit of Slovenian knowledge. The implementation, which represents a new step for all project partners on the path of development and transition to a low carbon society, represents an added value for both the local community and the whole of Slovenia.We are particularly pleased to have combined the knowledge, experience and interest of the Slovenian companies Petrol Geo and Nafta Lendava with the planned support and participation of Lendava municipality”.

If there are positive results for the pilot project, the designed concept will be used in other abandoned wells in Slovenia and around the world. The project therefore represents an important milestone for the development of geothermal energy and a contribution to reducing pollution from abandoned wells around the world.

Dravske elektrarne Maribor, along with Petrol Geo, the College of Chemistry and Chemical Technology in Maribor and the Geological Survey of Slovenia, also applied for a “public tender for co-financing projects under the Climate Change Mitigation and Adaptation Program” last fall co-financed by the European Area Financial Mechanism and the Norwegian Financial Mechanism and Related Slovenian Participation, published by the Office of the Government of the Republic of Slovenia for Development Policy and Cohesion. In April, DEM received a decision on the amount of co-financing allocated to the project, amounting to more than 730 thousand euros, which is an additional indication that this is a promising project.

What is geothermal energy anyway? And why does this method of generating electricity have so much potential?

Renewable energy sources are at the fore in the sustainable discussions of global companies. In addition to wind, water and solar energy, geothermal energy is also increasingly in the spotlight.

In addition to a good ecological balance, the geothermal method of energy production is almost infinitely accessible and, unlike other energy sources, is not subject to daily or seasonal fluctuations in availability. Why talk about an unlimited supply of energy?

In Earth’s molten core, temperatures are similar to those on the surface of the Sun, about 6000°C. Heat is constantly restored by the decay of naturally occurring radioactive elements with a flow of about 30 TW, which is almost twice the value of the entire human energy consumption. Experts predict that this process will continue for billions of years.

The ARPA-E AltaRock Energy Project estimates that “only 0.1% of Earth’s heat content can cover the entirety of human energy needs in two million years.” All we need to do is get that heat. Getting heat or getting heat on the surface is a major engineering challenge. To this end, geothermal technology is divided into different categories.

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