Présentations Colloques

    Oral Presentation
    Session 8.07: Hydrogeophysics: innovative non-invasive technologies for groundwater resources exploitation and management
    Lesparre Nolwenn
    A 4D ERT tool to characterize heat transfer and storage in aquifers
    Combining energy demand side management (DSM) and aquifer thermal energy storage (ATES) systems could lead to an improvement of seasonal performance factor (SPF) of such geothermal systems and to more flexibility. Before storing heat (efficiently converted from electricity) in aquifers, we must insure that a sufficient yield is possible with the help of predictive models of the subsurface.****The design and functioning of ATES systems have strong interconnections with the geology of the site which may be complex and heterogeneous, making predictions difficult. Today, most of models rely on local measurements made in wells. Due to budget constraints, it is impossible to collect a sufficient amount of data to capture aquifers heterogeneity. In this context, we developed a non-invasive and less expensive subsurface monitoring methodology to better characterize heat transfer and storage in the subsurface with the help of 4D electrical resistivity tomography (ERT), multiple hydrological measurements, and a short-term heat storage experiment conducted for the purpose in a confined alluvial aquifer. ****Results clearly show the ability of 4D ERT to delimit the thermal plume growth during injection, the diffusion and decrease of temperature during storage, and the decrease in size after heat recovery. Moreover, thanks to 4D ERT and hydrological measurements, we imaged semi-quantitatively the temperature distribution of the heat plume. By integrating these spatialized, permanent, and transient data in predictive models, we account for the local aquifer heterogeneity and therefore, improve the reliability of model predictions.****On the DSM side, energy balance shows that up to 70% of the stored energy can be easily recovered with an adapted strategy. By better designing storage recovery cycles with the help of reliable predictive models of the subsurface and by targeting specific aquifer characteristics, there is even a potentiality to reach better yields. This proves that short-term heat storage in alluvial aquifer during hours, days, or even a week is efficient enough to be used in the context of DSM and ATES systems.**


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