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Title (Primary) Gas-phase formation during thermal energy storage in near-surface aquifers: experimental and modelling results
Author Lüders, K.; Firmbach, L.; Ebert, M.; Dahmke, A.; Dietrich, P.; Köber, R.;
Journal Environmental Earth Sciences
Year 2016
Department MET;
Volume 75
Issue 21
Language englisch;
POF III (all) T53;
Keywords Thermal energy storage; Gas-phase formation; Time-lapse ER measurements; Aquifer hydraulics; ANGUS+
UFZ wide themes RU5;
Abstract Heating of groundwater by thermal energy storage (TES) poses a potential for the formation of a separate gas phase. Necessary boundary conditions, potential effects and monitoring feasibility of this process were not focused within previous studies. Since the formation of a gas phase could change groundwater flow conditions, hydrochemistry, porous media properties and thus efficiency of TES applications, improved understanding of the process is needed. The temperature of percolated sediment column tests was adjusted to 10, 25, 40 and 70 °C to quantify temperature-induced physical gas-phase formation and its effect on electrical resistance. Gas-phase formation, its accumulation and effects on hydraulic conductivity, heat conductivity and heat capacity were investigated using scenario calculations based on a closed-loop borehole TES system at 60 °C for different geochemical conditions. Experimentally quantified degassing ratios were within the expected range of thermodynamic calculations. The laboratory time-lapse electrical resistivity measurements proofed as a suitable tool to identify the onset and location of the gas-phase formation. Depending on the geochemical conditions, hydraulic conductivity in the area of the simulated heat storage site decreased between 60% and up to one order of magnitude in consequence of degassing within the scenario calculations. Heat conductivity and heat capacity decreased by maximally 3 and 16%, respectively. The results indicate that gas-phase formation as a result of aquifer heating can have pronounced effects especially on groundwater flow conditions and therefore should be considered particularly for nearly or fully gas-saturated groundwater and aquifers containing gas sources.
ID 18211
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Lüders, K., Firmbach, L., Ebert, M., Dahmke, A., Dietrich, P., Köber, R. (2016):
Gas-phase formation during thermal energy storage in near-surface aquifers: experimental and modelling results
Environ. Earth Sci. 75 (21), art. 1404