Large-scale integration of low-grade sources into DH networks through geothermal seasonal storage and heat pumps

InteGradeDH aims to contribute to the identification of the best strategies to support existing DH (district heating) networks in achieving the transition from fossil fuels to more sustainable, independent, and local sources.

This will require the large-scale installation of renewable energy sources (RES) and/or waste heat (WH). Such transition necessitates significant investment and faces a challenge of low heat demand in summer and insufficient heat supply in winter. Seasonal thermal storages are considered to balance these seasonal fluctuations by storing summer excess heat for winter use.

For these reasons, the project focuses on medium-deep geothermal boreholes, which can serve both as energy sources and storage solutions, alongside the utilization of low-temperature waste heat (WH) combined with heat pump (HP) substations to enable heat recovery within existing DH systems. By adapting and enhancing available models for system simulation, the project aims to assess technical performance and efficiency of the waste heat recovery solutions and integrate these insights into a comprehensive techno-economic model.

The methodology of the project is demonstrated through two case studies of waste heat utilization, one in Göttingen (Germany) and another in Bolzano (Italy), both of which represent cases with significant potential for broader application.

Several challenges are addressed by the project, including:

• Developing a simplified model for medium-deep geothermal systems that balances rapid usability and reliability against the time-consuming numerical models, allowing for simulating multiple scenarios and conducting parametric analyses crucial for both techno-economic estimates and planning.
• Optimizing operational temperatures and configuring HP placements. Solutions will involve finding optimal connections between WH sources, HPs, and the DH network, balancing direct and indirect heat recovery.
• Enhancing flexibility and business and pricing models to handle substation operation, temperature reduction strategies, and new risks associated with the transition to waste heat recovery solutions.

The two-year project involves three research institutions: EURAC (Italy), HAWK (Germany), and IVL (Sweden). The results of the project may be of interest to stakeholders across the DH value chain, including applied researchers, utility company managers, city planners, engineers, and investors.