The paper presents results of geothermal projects carried out in the last 23 years by the interdisciplinary research team at the AGH University of Science and Technology, in cooperation with numerous scientific institutions, published in the form of geothermal atlases in different parts of Poland. For many years, the Department of Fossil Fuels at the Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, has conducted the fundamental research and implementation work, aiming at the selection of optimum areas for utilization of geothermal waters and energy. Over the years, a methodology of estimation of geothermal resources with use of advanced techniques and numerical modeling has been developed. Recapitulation of the studies of the occurrence and utilization of geothermal waters and energy within geological units of the Polish Lowlands, Carpathians and Carpathian Foredeep has been reflected in seven Atlases. The Atlases represent a result of interdisciplinary, constructive cooperation of specialists from various, often remote fields of knowledge, fundamental and technological in nature, including: geologists, geophysicists, hydrogeologists, geochemists, drilling engineers, heat engineers, and many other specialists. The Atlases enable the selection of the most promising areas for utilization of geothermal waters and energy in Poland. The best geothermal conditions are predicted in the Polish Lowlands and Podhale region although in many areas of the Carpathians and the Carpathian Foredeep favorable geothermal conditions also occur.

Krakow has an extensive district heating network, which is approximately 900 km long. It is the second largest city in terms of the number of inhabitants in Poland, resulting in a high demand for energy—for both heating and cooling. The district heating of the city is based on coal. The paper presents the conception of using the available renewable sources to integrate them into the city’s heating system, increasing the flexibility of the system and its decentralization. An innovative solution of the use of hybrid, modular heat pumps with power dependent on the needs of customers in a given location and combining them with geothermal waters and photovoltaics is presented. The potential of deep geothermal waters is based on two reservoirs built of carbonate rocks, namely Devonian and Upper Jurassic, which mainly consist of dolomite and limestone. The theoretical potential of water intake equal to the nominal heating capacity of a geothermal installation is estimated at 3.3 and 2.0 MW, respectively. Shallow geothermal energy potential varies within the city, reflecting the complex geological structure of the city. Apart from typical borehole heat exchangers (BHEs), the shallower water levels may represent a significant potential source for both heating and cooling by means of water heat pumps. For the heating network, it has been proposed to use modular heat pumps with hybrid sources, which will allow for the flexible development of the network in places previously unavailable or unprofitable. In the case of balancing production and demand, a photovoltaic installation can be an effective and sufficient source of electricity that will cover the annual electricity demand generated by the heat pump installation, when it is used for both heating and cooling. The alternating demand of facilities for heating and cooling energy, caused by changes in the seasons, suggests potential for using seasonal cold and heat storage.

In the years 2010-2013, analysis of rocks that build the sedimentary covers in Poland was carried out from the point of view of energy utilization accumulated in hot dry rocks – used in Enhanced Geothermal Systems (EGS). As a result of a number of analytical studies, the area situated in the central part of Poland was selected as one of prospective areas for location of EGS in sedimentary rocks. This area encompasses a major part of the Mogilno-Łódź Trough, a part of the Kujawy Swell and a small fragment of the Fore-Sudetic Monocline. The most favourable conditions for development of EGS occur in deposits of the Lower Triassic in the Krośniewice-Kutno vicinity where they are buried to depths greater than 5000 m b.s.l., have thicknesses exceeding 1500 m and are characterized by porosity about 2.5% and permeability about 0.1 mD. In the selected area, thermal characterization of the formation was carried out for location of the EGS in sedimentary rocks. The temperature at the top of Lower Triassic reservoir is in the range 165-175°C. Characterization of petrophysical parameters constituted the basis for further modelling of EGS utilization in selected area.

Thermal waters in Poland occur in several different geothermal regions, but the best parameters for their effective utilisation are connected i.a. with the area of Polish Lowlands. One of the most prospective areas in the central part of Polish Lowlands for managing geothermal waters for various purposes is the area of Mogilno–Łódź Trough. There are currently 2 operating geothermal heating plants and several others in various stages of development. In this area, water with a temperature of 97.5 °C has been documented. The aim of this article is to determine and visualise the potential of geothermal waters of the central Poland (Mogilno–Łódź Trough) by providing the most important, potential geothermal water parameters. It is done by providing maps of potential temperature, mineralization, water outflow capacity, thermal power and physicochemical analysis (mineralization, waters type). The two most prospective geothermal reservoirs—Lower Jurassic and Lower Cretaceous—were analysed. The results of the studies indicate that this area is characterised by very favourable hydrogeological conditions. Geothermal energy utilisation should be connected with Lower Jurassic and Lower Cretaceous reservoirs, but it should be emphasised that a larger energy potential relates to waters from Lower Jurassic reservoir; however, they are characterised by high water mineralisation (up to 170 g/L). Waters of Lower Cretaceous reservoir are characterised by not only lower mineralisation (up to 100 g/L), but also lower temperature (max. 75 °C). The highest temperatures in the Lower Jurassic are recorded in the axial part of the Trough, where, locally, they exceed in the top of formation 100 °C. On the other hand, in edge Trough zones, water temperatures are 30–40 °C. The actual geothermal potential of the area is much higher than currently used. For example, potential discharge of wells is to over 400 m³/h in the Lower Cretaceous and up to over 500 m³/h in the Lower Jurassic.

Geological conditions of geothermal resources occurrence in Poland

Increasing the use of geothermal energy may be one of the tools bringing us closer to achieving the European Commission’s objective of reducing greenhouse gas emissions by 55% by 2030. Air quality improvement plays a strategic role in achieving sustainable energy development. Both European and national legislation in this field is particularly comprehensive and effective, establishing rules for monitoring and preventing air pollution in order to avoid adverse effects on human health and the environment. Unfortunately, the effective air pollution monitoring network currently in place in Poland, with 156 monitoring stations, mainly concerns agglomerations and cities with over 100,000 inhabitants. The lack of information on the state of pollution in smaller towns is a significant limitation in terms of research aimed at assessing the effects of corrective measures taken, such as the possible transformation of district heating systems based on RES, including the use of deep geothermal energy. This paper proposes some solutions which allow the effective estimation of air conditions in locations not covered by environmental monitoring, in the context of the potential to develop geothermal resources in the rich geothermal province of Central Poland.