Luders, K., Firmbach, L., Ebert, Markus, Dahmke, Andreas, Dietrich, P. and Kober, R. (2016) Gas-phase formation during thermal energy storage in near-surface aquifers: experimental and modelling results. Environmental Earth Sciences, 75 (21). DOI 10.1007/s12665-016-6181-5.

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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 degrees 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 degrees 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.

Document Type:	Article
Additional Information:	Times Cited: 0 Lueders, Klas Firmbach, Linda Ebert, Markus Dahmke, Andreas Dietrich, Peter Koeber, Ralf
Keywords:	Thermal energy storage Gas-phase formation Time-lapse ER measurements Aquifer hydraulics ANGUS+
Research affiliation:	Kiel University OceanRep > The Future Ocean - Cluster of Excellence
Refereed:	Yes
Open Access Journal?:	No
Publisher:	American Medical Association
Projects:	Future Ocean
Date Deposited:	01 Mar 2017 08:34
Last Modified:	23 Sep 2019 22:20
URI:	https://oceanrep.geomar.de/id/eprint/36196

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