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Aquifer thermal energy storage (ATES) is comparatively rarely used in Germany, in contrast to neighboring countries such as the Netherlands. This also applies to lower temperature ranges of less than 50 °C, which are mostly technically easier to handle than high-temperature storage. Since there is a lack of demonstration plants nationally, the goal of our BMBF-funded joint project “DemoSpeicher” (Development and Monitoring of Seasonal Heat and Cold Storage for the Demonstration of Aquifer Storage) is to implement and scientifically accompany a near-surface low-temperature aquifer storage system (NT-ATES). Within the scope of the project, the entire construction cycle of an NT-ATES is to be covered, which ranges from design and planning to grid integration and commissioning to thermal energy supply. An urban site in Germanys capital Berlin-Mitte was selected for the implementation of the demonstration plant, which is to be converted to climate-friendly heating and cooling concepts at an existing construction site. In addition to the necessary preliminary site investigations for the technical-economic feasibility, questions regarding legal approval requirements will also be presented.For this reason, a extensive monitoring program is planned, which provides the metrological supervision of the thermal-hydraulic underground processes. Another focus of the project will be possible changes in groundwater chemistry and temperature-sensitive groundwater ecology as a result of thermal loading. Monitoring of energy flows is also planned in order to estimate the thermal energy exchange between the aquifer reservoir and the building's systems engineering. This will include a heating and cooling demand analysis, as well as an assessment of potential synergistic use effects with other technologies that could be used, for example, for thermal loading of aquifer storage. All results will be presented in a coupled thermal-hydraulic modeling of the planned thermal energy storage. The project and the first results of the implementation of an ATES in a densely populated urban area will be presented and discussed in this presentation.

Recent deep boreholes Γ1 (205 m) and AIG 10 (1001 m), performed in the Aigion area, bring new information on syn-rift deposits. MIS1/Holocene (11.8–4.3 ka BP) and Upper Pleistocene are identified in the upper part of the boreholes. Below Holocene deposits, the borehole AIG 10 crossed successively a detrital system with fine intercalations and a thick development of clay. No specific dating was possible on this lower formation, so the age of the local basal syn-rift deposits is discussed. To cite this article: F. Lemeille et al., C. R. Geoscience 336 (2004).

In the frame of the EU Project Corinth Rift Laboratory (CRL), the AIG10 borehole was successfully drilled from July until September 2002 through the Aigion normal fault in the harbour of Aigion, northern Peloponnesus, Greece. The scientific objective focuses on the investigation of fault mechanics and the relationship with fluid flow and geochemistry, fluid pressure, stress- and strain fields and earthquakes. Recognition of stratification encountered in the AIG10 borehole is based on an online analysis of well cuttings (0–708.8 m and 787.4–1001 m), core descriptions (708.8–787.4 m), monitoring of drilling parameters, as well as a preliminary geophysical well-log interpretation (0–1001 m). Geologically, the area is part of the Olonos–Pindos tectonic nappe, which is overthrusted on the Tripolitza unit during the Alpine orogeny. The litho-log of the AIG10 borehole comprises at first syn-rift deposits (graben fill). At 496 m, the Olonos–Pindos tectonic unit was encountered, however, not as expected in the platy limestones, but in the Olonos–Pindos radiolarite. The borehole has crossed at least one thrust-fault zone and a major normal fault zone at 760 m. This normal fault zone separates well-fractured platy, micritic limestone in the hangingwall from highly fractured radiolarite in the footwall, both of the Olonos–Pindos tectonic unit. The observed succession of multiple imbrication is an indicator of Alpine tectonic activity, whereas normal faulting is of the Miocene–Quaternary extension of the Gulf of Corinth, confirming our expectations gained from geologic-tectonic fieldwork. To cite this article: D. Rettenmaier et al., C. R. Geoscience 336 (2004).

The AIG10 borehole provided direct access to hydraulic conditions. The first results of two open-hole pumping tests and one artesian production test are presented. From the first pumping test in the conglomerates, a hydraulic conductivity of 10−5– 10 −4 m s −1 was derived and it was suggested that there is a closed hydraulic system bounded by the Aigion Fault zone and other faults farther north. A second pumping test, in the Olonos–Pindos limestones, showed artesian flow (water pressure of 0.5 MPa and flow of 1.9×10 −4 m 3 s −1 ). The transmissivity is about 4×10 −6 m 2 s −1 . Below the fault zone, pressure and flux increased, suggesting karstic water-flow conditions. Water-pressure difference of more than 0.5 MPa between the hangingwall and the footwall provides evidence that the Aigion Fault zone acts as an impervious zone. An artesian production test for the interval 708–1001 m showed a fluid pressure of >1 MPa and natural flow of 1.5×10 −2 m 3 s −1 . A transmissivity of 2– 3 ×10 −4 m 2 s −1 was determined. A preliminary conceptual hydrogeological model, containing flow parameters and flow paths, is developed, based on data from AIG10 and other wells and springs. To cite this article: V. Giurgea et al., C. R. Geoscience 336 (2004).