Optimised integration of thermal aquifer storage in district heating systems

The research project "Optimised Integration of Thermal Aquifer Storage in District Heating Systems" (OptInAquiFer) focuses on researching the contribution of aquifer storage for large district heating networks in the course of the upcoming decarbonisation and transformation. Through the integral consideration of geological, technical, energy economics and licensing aspects, the possibilities and limits of aquifer storage for district heating are examined.

The project, which is funded by the German Federal Ministry of Education and Research (BMBF), will run until mid-2025 and is carried out by a consortium of Hamburg Institut Research (consortium leader), Oeko-Institut and Friedrich-Alexander University Erlangen-Nuremberg. Geothermie Neubrandenburg GmbH is supplementing the project team as a subcontractor. In the course of the project, three district heating network operators are also involved as practical partners and a practical advisory board accompanies the work with external expertise.

The project is divided into three sub-projects:

1. Geological framework conditions for underground thermal storage.

The aim of this sub-project is to investigate the geological conditions for thermal storage in the geothermal provinces of the South German Molasse Basin, the Upper Rhine Rift and the North German Basin. The considered depth ranges below the horizons used for drinking water production and approx. 1,500 m. Geological subsurface models form the basis for a simulation of the loading and unloading behaviour of a model reservoir at the selected model sites. The work is initially based on regional geological data and publications, which are detailed at the model sites by local data (borehole data and possibly subsurface models). The results of the simulations are incorporated into the design, modelling, simulation and evaluation of thermal underground storage facilities.

2 Optimised storage integration into heating grids

In this sub-project, the design, modelling, simulation and evaluation of ATES (Aquifer Thermal Energy Storage) systems are used to determine application-related fields of use for concrete district heating networks. The findings from the holistic approach are compiled in cooperation with all research partners. In addition, recommendations are developed on how applicants and approval authorities can make the approval process as efficient as possible and easier to plan.

3. Optimised use of aquifer storage in existing heating networks.

The core of this sub-project is the analysis of the suitability and benefits of aquifer storage for large urban heating networks. In addition to achievable emission reductions and improvements regarding the integration and utilisation of renewable heat and unavoidable waste heat, operating and heat generation costs are calculated and evaluated using a dispatch model for heat generation and storage facilities in district heating systems developed at Oeko-Institut. Ultimately, the aim is to achieve the best possible use in terms of total costs and CO ₂ savings at the heating network level by integrating aquifer storage.

In a final step, relevant parameters for the successful and efficient design and integration of ATES systems in district heating networks are derived from the detailed investigations of specific locations. The potential of ATES systems in district heating systems and potential areas supplied with district heating in Germany is estimated.

The project is funded by the Federal Ministry of Education and Research (BMBF) under the funding code 03G0918B in the programme "Geoforschung für Nachhaltigkeit" (GEO:N) , thematic priority "Thermal Energy Storage in Aquifers".