Geothermal water and energy management in Polish district heating – directions for effective use in the Polish Lowlands

Abstract

The possibility of utilising the available potential of the main geothermal reservoirs in Poland, i.e., the Lower Jurassic and Lower Cretaceous, by using the existing infrastructure in the form of still-operating district heating networks is the subject of this work. The suggested solution, therefore, integrates the resource side with the infrastructure side. This approach should significantly accelerate the implementation of the proposed solutions, supporting the achievement of the ambitious objectives of Poland’s Energy Policy 2040. Geothermal resources in Poland are characterised by low enthalpy and low temperature. Their temperature is often too low for direct utilisation in systems relying solely on geothermal energy. Existing district heating networks require significantly higher heating medium temperatures during specific periods (when low ambient air temperature is observed). Using gas boilers as peak energy sources while employing geothermal energy as the base load for meeting annual heating demands appears to be an attractive and feasible technical option. Poland, alongside Denmark, Latvia, Finland, Estonia, and Lithuania, is among the countries with the highest density of district heating networks. These networks serve as invaluable infrastructure, reducing the costs associated with geothermal energy extraction. However, this infrastructure is under real threat from the trend towards decentralised energy systems. The liquidation of district heating networks would be irreversible, further exacerbated by the lack of access to clean and alternative energy carriers to replace fossil fuels. It has been demonstrated that in most analysed cases the combination of available geothermal resources and district heating infrastructure can successfully contribute to achieving the assumed goals of Poland's Energy Policy. In the best locations, the share of renewable energy exceeded 80%, with an average of around 50%. The total reduction of $CO_2$ emissions is estimated as 1.16 million tonnes yearly. The work draws attention to the slow but positive change in the electricity mix, in which the share of RES is growing. This trend is extremely beneficial for popularising heat pumps powered by electricity using geothermal resources as a low-temperature energy carrier.