Présentations Colloques

    Session 7.01: Groundwater and Energy Resources
    Barbero Diego
    Thermal use of aquifers- insights on propagation of temperature disturbance from numerical modeling
    Prediction of thermal impacts induced by the use of heat pumps coupled with groundwater (GWHP) has strategic role in order to avoid efficiency depletion within the system -or with adjacent plants- and to define subsequent interferences between downgradient concurrent uses of groundwater and thermal plumes developed by reinjection wells. The evolution of temperature plumes is strongly related to thermophysical properties of the aquifer, as well as designing paramaters of GWHP system. Numerical modelling is a valid tool for predicting the thermal disturbance propagation. The present study investigates the role of hydraulic and thermic parameters on the reinjection of thermally altered water connected to the operation of GWHP system through the use of a numerical heat transport model.**A theoretical flow and heat transport model is built by means of the coupled use of MODFLOW and MT3DMS codes. A homogeneous, unconfined and porous aquifer is considered with thermal and hydraulic properties comparable to coarse alluvial medium. A uniform initial groundwater temperature is set. The GWHP system is simulated by a doublet of pumping and injection well, designed on a seasonally variable thermal energy demand. In order to understand the most influencing factor on the development of thermal plumes, a diversification of scenarios is obtained by varying Darcy velocity, aquifer dispersivity and reinjection rates.**Long-term simulations show that pronounced differences in longitudinal extension of thermal plume occur as long as Darcy velocity rises. At the same time, dispersivity plays a major role in reducing the absolute temperature values and the lateral boundaries of thermal plume. In short-term simulations the temperature of reinjected water is tailored on a seasonally cycle and colder or warmer water is reinjected respectively for summer and winter. In this case, the expected groundwater temperature deviations become negligible few hundreds of meters downstream the reinjection well. These results allowed a better understanding of the influence of thermophysical properties on temperature perturbations produced by a GWHP system in a porous medium.**


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