The beginning of 2022 was a time of major changes in the perception of energy availability and security in European countries. The aggression of Russia against Ukraine destabilizing the European energy economy, combined with the withdrawal from fossil fuels which has been going on for a dozen years, has strengthened activities to introduce new energy technologies based on renewable energy sources. One of the most promising and stable sources of renewable energy is geothermal energy, in particular enhanced geothermal systems (EGS) in hot dry rocks (HDR). These deposits occur at a great depth in almost every place on Earth, but due to their low permeability, they require hydraulic fracturing, which results in high investment costs. This technology has been developed for several decades. The current situation in Europe seems to confirm that its rapid development to a level that guarantees stable and profitable operation is crucial. This is of particular importance in the case of former member states of the economic zone of the Council for Mutual Economic Assistance, which until recently were heavily dependent on Russian energy. This review, based on the latest available data, covers potential HDR prospective areas in the countries of the south-eastern Baltic basin, including Lithuania, Latvia, Estonia and Poland. It is specific to this region that the original heat flux density is lower as a result of the paleoclimatic effect associated with the youngest ice age; however, thermal conditions do not deviate too much compared to western Europe, especially Rhine Graben, and significantly exceed the conditions of Finland, where an EGS project is currently being operated. In Lithuania, the most prospective area is the ZNI intrusion (south of Klaipeda), characterized by a geothermal gradient of up to 40 °C/1000 m. In addition, the Precambrian batholith south of Liepāja (Latvia) and the Rapakivi granites in the north and center of Estonia are promising EGS sites. Poland has relatively the most explored EGS potential, in both volcanic, crystalline and sedimentary rocks, especially in the area of the Szczecin Trough, Gorzów Block, Moglino-Łódź Trough and Karkonosze Mountains. Unfortunately, local tectonic conditions, in particular the development of faults and natural fracture zones that affect the directions of fracture propagation during hydraulic fracturing, have not been sufficiently recognized, which is one of the main barriers to the expansion of EGS pilot projects in these countries. These issues present challenges for the researchers, especially in terms of petrophysical analyses of rocks in target zones and local stress conditions, which have a key impact on fracturing operations and profitability of the systems. Despite high investment costs on the one hand and a significant slowdown in the global economy in 2022 on the other, it remains hopeful that the authorities of individual countries will decide to accelerate research work, leading to the implementation of pilot projects of EGS installations, and that this technology will be further improved to ensure a stable clean energy supply.

Zatwierdzona 2 lutego 2021 r. Polityka energetyczna Polski do 2040 r. (PEP2040) zakłada duży wzrost udziału energii pochodzącej z OZE we wszystkich sektorach gospodarki. Zgodnie z prognozą w 2030 r. udział OZE w końcowym zużyciu energii brutto powinien wynieść co najmniej 23%. Projekt PEP2040 zakłada rozwój energetyki wiatrowej i fotowoltaicznej, co wpłynie na wzrost zainstalowanej mocy elektrowni wiatrowych do około 8–11 GW oraz fotowoltaicznych do około 10–16 GW. Zgodnie z danymi publikowanymi przez Rynek Elektryczny sumaryczna moc zainstalowanych OZE w Polsce na koniec sierpnia 2022 r. osiągnęła 20,9 GW. Należy podkreślić, że sumaryczna moc zainstalowana w całej polskiej energetyce (OZE i konwencjonalna) w sierpniu 2022 r. wynosiła 59 GW. Spośród elektrowni OZE największy udział miała fotowoltaika (11 GW), co stanowiło 19,2% ogółu zainstalowanych mocy. Natomiast sumaryczna moc elektrowni wiatrowych wynosiła 7,7 GW (13,3%). W publikacji podkreślono również, że w 2022 r. moc zainstalowanej fotowoltaiki wzrosła w porównaniu z rokiem 2021 o 84%, a elektrowni wiatrowych – o 12,7%. Powodem szybkiego rozwoju OZE jest duży wzrost ceny konwencjonalnych nośników energii (paliwa kopalne), który wpłynął na wzrost ceny energii elektrycznej. W czerwcu 2022 r. cena kontraktów na dostawy energii elektrycznej wynosiła około 884,68 PLN/MWh. Dla porównania cena referencyjna energii elektrycznej produkowanej w elektrowniach wiatrowych, na podstawie wyników aukcji przeprowadzonej przez Prezesa Urzędu Regulacji Energetyki z grudnia 2021 r., wyniosła 250 PLN/MWh. Niestety produkcja prądu przez elektrownię wiatrową zależy od siły wiatru i cechuje się bardzo dużą zmiennością, często zmienia się z godziny na godzinę. Przykładowo w nocy elektrownie mogą pracować z mocą ponad 5 GW, a po południu wykorzystanie ich mocy będzie poniżej 1 GW. W związku z tym, że produkcja energii z OZE jest wysoce niestabilna, to jej nadwyżki powinny zostać zmagazynowane. Głównym celem publikacji jest określenie ilości wodoru, jaka może zostać wyprodukowana z nadwyżek energii pochodzących z elektrowni wiatrowej.

A paleokarst system developed in the Upper Jurassic–Lower Cretaceous carbonate complex has been recognized in the Carpathian Foreland area. Well logs testing and core data as well as an acoustic imager, a microresistivity scanner and six-arm dipmeter images were used to identify and analyze the character of the paleokarst features. A detailed interpretation of microresistivity and acoustic image logs allowed for the identification of different types of karst forms, such as caverns; multidirectional fractures, including fractures widened by dissolution; and the type of sediments filling them. The analysis of the seismic survey was conducted by linking the paleokarst characteristic features recognized in the seismic image to the karst intervals determined from borehole data. The set of seismic attributes calculated from the analyzed 3D seismic data, including the RMS amplitude, instantaneous frequency, consistent dip, variance, sweetness and relative acoustic impedance, helped to delineate the zones of the paleokarst distribution. Within the interpreted paleokarst surface developed in the carbonate formations in the study area, there are sinkholes, limestone pavements and valleys. Furthermore, in the northwestern part of the analyzed area, the development of paleokarst forms is related to the presence of a relatively deep branch of a paleovalley formed in the Paleogene, as well as to numerous discontinuities developed in carbonate formations. The development of this type of larger karst form was probably controlled primarily by tectonic faults. The research conducted by the authors of this paper showed the widespread presence of paleokarst features in Upper Jurassic–Lower Cretaceous carbonate formations in the study area. A good spatial identification of the paleokarst surface can be important in a regional context, since the highest part of the profile of carbonate formations is the most important reservoir for geothermal or hydrocarbon resources in this region.

The European Union’s climate policy promotes waste incineration as an alternative to landfilling. However, the continuous nature of waste generation, combined with seasonal variability in energy demand, leads to a mismatch between heat production and consumption in waste-to-energy systems. Seasonal Borehole Thermal Energy Storage (BTES) systems are one option for mitigating this mismatch. The aim of this study was to develop a theoretical geological model of a BTES-type storage system located in the Carpathian Foredeep and to simulate its multi-year operation using the FEFLOW numerical modeling software. The model represents an initial assessment of system performance under assumed geological and operational conditions and has not yet been validated against field measurements. Two operating scenarios were analyzed. In the 1st scenario, both heat injection and heat extraction from the storage system occurred through Borehole Heat Exchangers (BHEs) located in the center of the storage system. In the 2nd scenario, heat extraction is initiated through heat exchangers located in the outermost zone of the BTES field. The analysis focused on the temperature of the circulating working fluid in the U-tubes and on variations in heat transfer rate during injection and extraction cycles. The energy performance of the system was evaluated for both configurations. The results showed that the reversed-flow operating strategy provided a higher thermal energy recovery ratio and more favorable long-term thermal performance than the center-to-center flow configuration, indicating the potential feasibility of BTES operation under the assumed Carpathian Foredeep conditions.