Department Water Resources and Drinking Water

High-Temperature Borehole Thermal Energy Storage (HT-BTES) systems use the subsurface as a thermal battery. They allow storing the excess of energy captured during the summer months deep in the subsurface, which is then available again for extraction in the winter months. From its operation, significant cyclic temperature gradients are induced in the subsurface. In this project, members of different research groups at Eawag investigate the aquifer response to these cyclic temperature changes, with special focus on the hydrogeochemistry, the microbiology and microbial community composition, and the groundwater fauna. This is approached through an extensive field work campaign, consisting of both continuous on-site monitoring and additional periodic sampling and post-analysis on three measurement stations. These stations have been created around three observation boreholes drilled strategically upstream, in immediate vicinity, and downstream of the facility. Some of the obtained outputs include the groundwater chemical composition and the aquifer’s microbiome and environmental DNA. The outputs from this on-site monitoring will be employed for generating a numerical model, which will allow a close representation of the hydro-bio-geo-chemical processes in the aquifer. It will be employed for long-term prediction of the aquifer’s behavior to future operational conditions of the HT-BTES facility.