Numerical modeling of aquifer thermal energy storage system

The performance of the ATES (aquifer thermal energy storage) system primarily depends on the thermal interference between warm and cold thermal energy stored in an aquifer. Additionally the thermal interference is mainly affected by the borehole distance, the hydraulic conductivity, and the pumping/injection rate. Thermo-hydraulic modeling was performed to identify the thermal interference by three parameters and to estimate the system performance change by the thermal interference. Modeling results indicate that the thermal interference grows as the borehole distance decreases, as the hydraulic conductivity increases, and as the pumping/injection rate increases. The system performance analysis indicates that if η (the ratio of the length of the thermal front to the distance between two boreholes) is lower than unity, the system performance is not significantly affected, but if η is equal to unity, the system performance falls up to ∼22%. Long term modeling for a factory in Anseong was conducted to test the applicability of the ATES system. When the pumping/injection rate is 100 m3/day, system performances during the summer and winter after 3 years of operation are estimated to be ∼125 kW and ∼110 kW, respectively. Therefore, 100 m3/day of the pumping/injection rate satisfies the energy requirements (∼70 kW) for the factory.