ATESref - Aquifer Thermal Energy Storage and Reinjection using the example of Fürstenfeld, Austria

Seasonal Underground Thermal Energy Storage (UTES) offers a promising solution to balance future energy supply and demand. Specifically, Aquifer Thermal Energy Storage (ATES) systems facilitate the seasonal storage of energy, providing up to 10–100 MW of thermal output that can be utilized during periods of high energy demand (Dinkelman & Van Bergen, 2022). These systems store surplus heat from sources such as geothermal or power-to-heat systems, particularly from fluctuating renewable energy during summer. The extracted water is heated, reinjected into the ground via an injection well for storage and later retrieved through a production well during colder seasons. Despite the widespread adoption of ATES systems across Europe—especially in the Netherlands—Austria currently lacks any operational ATES plants.

The “ATESref” project presented here aims at evaluating the geological, technical, and economic feasibility of seasonal heat storage in the medium-to-deep subsurface of the Fürstenfeld area in the Styrian Basin (Austria). Geological studies and reprocessing of existing seismic profiles are used to estimate the depth, thickness, and spatial distribution of potential storage formations in coarse grained Neogene sediments, such as the Sarmatian-aged Carinthian gravel (approximately 650 m below ground level) and the Badenian Sandschaler Zone (approximately 1,600 m below ground level). Existing boreholes provide well logging data for deriving hydraulic parameters, which are incorporated into a numerical model. Subsequently this model helps to simulate plant operations, predict thermal effects on the subsurface, assesse impacts on third-party water rights, and estimate the potential of storable thermal energy.

The numerical model will then be refined into a storage simulation model, ensuring parameter accuracy and plausibility. This model will address questions about integrating the storage system efficiently into the existing district heating network. System simulations will evaluate the yields and loads for the Fürstenfeld case study, aiming to optimize renewable energy usage and incorporate existing excess heat sources.

Given that most storage horizons lie within the basin fill, reinjection of thermal water into the clastic sedimentary aquifers is a critical factor. Austria currently lacks deep geothermal applications in both unconsolidated and consolidated clastic sediments. A previous attempt to operate a doublet system in Badenian sediments failed due to abrupt collapse of the reinjection process. Findings from the completed “Reinjection” project point to technical causes behind this failure. Building on these insights, the “ATESref” project will develop a concept to reactivate this system for the use-case in Fürstenfeld, paving the way to achieve reinjection.

 

References:
Dinkelman Dorien & Van Bergen Frank: Evaluation of the country-wide potential for High-Temperature Aquifer Thermal Energy Storage (HT-ATES) in the Netherlands, European Geothermal Congress, Berlin, 2022