Numerical modeling for transient temperature distribution in an aquifer thermal energy storage system

The production and conservation of renewable and sustainable energy is under research focus for quite some time. Aquifer thermal energy storage (ATES) has thus become a popular technology for long term storage of excess thermal energy. The aquifers provide a large volume for storage of thermal energy with low cost of implementation and maintenance and with almost no adverse environmental effects. Using low temperature geothermal resources in an aquifer by circulation of groundwater (Sanner [1], Rafferty [2]) i.e. storing the excess thermal energy in water by injecting it into an aquifer and extracting in time of demand is the main principle of the ATES system. Direct use of groundwater with relatively high volumetric heat capacity makes ATES system more efficient (Kim et al. [3]) than other heat storage systems. The efficiency of such a system depends entirely on the capacity of the aquifer to retain heat and hence modeling the heat transport and transient temperature distribution in the aquifer is very essential to design the injection-production well scheme. The present study is concerned about developing a three-dimensional coupled thermo- hydrogeological numerical model for such an ATES system consisted of a confined porous aquifer underlain and overlain by impermeable rock media where hot water is injected into the porous medium through an injection well. The transient temperature distribution in the porous aquifer is modeled here using a software code Dumux (Flemisch et al. [4]). The heat transport modes considered are the advection, conduction and the heat loss to the confining rock media. Influence of some parameters namely the injection rate, the thermal conductivity and the porosity of the porous media, on the transient heat transport phenomenon is judged later by observing the variation of result by varying the values of the parameters. A simplified version of the model has been validated using an analytical model developed by the authors here. The results show that injection rate and the thermal conductivity has high influence on the transient heat transport phenomenon.