The Influence Analysis of the Injection Concentration on the Energy Storage in Brackish Aquifers under the Model of Groundwater Flow, Heat Transferring and Solute Movement

This paper establishes a three-dimensional couple numerical model of groundwater flow, heat transferring and solute movement in advantage of the significant variation of groundwater density and viscosity coefficient in energy storage and recovery in brackish aquifer. The revised numerical model is applied to predict the evolution process of the groundwater flow and geo-temperature fields in one 2-dimensional axisymmetric conceptual model for the brackish aquifer energy storage and recovery process with various injection concentrations. The results show that: when the injection concentration decreases from 3000mg/L to 500mg/L during the summer operation period of energy storage and recovery system, the thermal effects radius increases for more than 6m because the coefficient of hydraulic conductivity K_ij will increase for 27%.The shrink ability of thermal effects radius is 1.5 times stronger under the condition that the injection concentration is 3000mg/L than that of 500mg/L when molecular diffusion will be the most important component of hydrodynamic dispersion during the intermittent recovery period.