Challenges and opportunities for the multi-use of geothermal resources in urban areas

Decarbonising district heating systems poses a significant challenge in Central and Eastern Europe, as high-temperature networks predominantly rely on coal-fired power stations. State policy has expanded the number of sites, facilitating the exploration and development of geothermal energy resources while prioritising subsidies for drilling new wells in regions with intermediate geological exploration. A rise in new activity pertaining to the exploration and development of geothermal resources has been observed. One of such locations is Konin in central Poland. However, exploring geothermal resources in urban environments is hindered by limited data availability, dense infrastructure, and legal constraints. Access may also be restricted and constrained by open spaces and road accessibility. Conventional geothermal evaluations in Polish cases predominantly rely on well-drilling data, geophysical surveys, and thermal-gradient measurements. In addition, most geothermal systems utilise saline geothermal fluids as the energy carrier. Regrettably, most geothermal systems face several technological challenges associated with the disposal of saline geothermal fluids. In the presented work, the limitations of available data are analysed, and the necessity of advanced exploration methods, such as seismic surveys, is highlighted for the Konin site as a case study. To facilitate the development of the geothermal system, seismic surveys tailored to the urban area's specific characteristics have been planned. The surveys are being carried out as part of the URGENT project, which aims to provide sustainable and affordable solutions for urban seismic exploration of geothermal resources. Alternative methods of obtaining geothermal energy are also indicated in this case, thereby limiting problems related to high water mineralisation and enabling closed-loop systems, evaluated as part of the HOCLOOP project. In this configuration, the system can also be used for underground surplus energy storage, enabling wider use of underground structures. The results highlight the essential importance of data integrity and completeness in reducing investment risks and enhancing geothermal resource utilisation. They point to the importance of a comprehensive approach to the use of geothermal resources in urban areas. The application of such a solution enables a rational transition from coal-based heating systems to low-emission systems and multi-use of the subsurface structures.