Integration of Groundwater Storage and Heat Pumps in Second-Generation District Heating Systems

District heating (DH) systems in Europe predominantly belong to the second and third generations, operating at temperatures often exceeding 100℃, which poses challenges for integrating renewable energy sources (RES). The feasibility of incorporating large-scale groundwater heat pumps into such systems was explored in this study, with a focus on adjusting the supply water temperature to thermal substations. This adjustment, achieved by lowering the temperature below design values in response to rising outdoor temperatures, facilitated the integration of RES and improved system efficiency. Additionally, groundwater or geothermal heat pumps enabled the effective utilisation of waste heat (WH) from industrial processes or excess heat from renewable sources, particularly during periods when the thermal demand of the DH system was insufficient to justify direct supply. This excess heat, once collected, can be stored in the ground and later retrieved for use during the heating season, contributing to the system’s overall sustainability. The integration of seasonal thermal storage further enhances the operational flexibility of DH systems by allowing for the balancing of supply and demand over extended periods. The findings underscore the technical viability and environmental benefits of such integration, providing a pathway for the modernisation of DH infrastructure and the advancement of energy transition goals