Models for the experiment design of a combined ATES and remediation pilot plant in an urban environment

In the KONATES project a pilot-scale Aquifer Thermal Energy Storage (ATES) system at the scientific park in Leipzig, Germany has been built, where the shallow quaternary aquifer is contaminated with chlorinated hydrocarbons. To demonstrate the integration of thermal energy storage and groundwater remediation, a surface remediation system works alongside the ATES facility.

Especially when ATES systems are located in an urban environment, regulatory limits are present on temperature increases at property boundaries, typically restricting them to a few Kelvin, while the injection temperatures range between 70 °C and 80 °C. This requires careful planning of injection and extraction cycles and flow rates to fulfill these regulations.

Complicated by dense infrastructure and the need for numerous monitoring wells to observe hydraulic, thermal, geochemical, and microbiological changes, the pilot-scale ATES operation requires a three-dimensional numerical model to simulate hydraulic flow and heat transport in the aquifer. This model predicts heat transport in the subsurface based on varying injection timeframes and flow rates.

Considering regulatory constraints and high groundwater velocities, the model recommends an operational strategy of two 10-day injection cycles each followed by 10-day extraction periods at a pumping rate of 0.6 m³/h and an injection temperature of 70 °C. The first batch of monitoring data shows that the numerical model predictions were successful in predicting the groundwater temperatures for the experiment. Meanwhile, it is also found that the aquifer is more heterogeneous than previously assumed. Implementing those behaviors in the model is an ongoing task to optimize the next experiment runs.

This work highlights the value of coupled hydro-thermal models in designing ATES systems to meet regulatory and site-specific challenges in urban environments.