Thermal Performance of an Aquifer while Charging-Discharging Thermal Energy

With the progress of human civilization, demand for energy and power is rising rapidly. As the fossil fuel reserve on the planet is reducing and will be exhausted in not so far future, use of renewable energy and energy conservation is becoming utmost important. Storing excess or waste thermal energy in aquifers is a favorable option in terms of feasibility and economy which is being used for last few decades. Storing seasonal thermal energy or waste heat from other sources in groundwater by injecting it into subsurface and extracting in time of need is the principle of an aquifer thermal storage (ATES) system. This technique of energy conservation leads to energy savings, reduction of dependency on fossil fuels and thus reduction in greenhouse gas emission. This study presents a numerical model of an ATES system to store thermal energy and evaluates its performance.
A thermo-hydrogeological numerical model for a confined ATES system is presented in this study [1]. The numerical simulations have been performed by the software code DuMux [2]. The model takes into account heat transport processes of advection, conduction and heat loss to confining rock media, regional groundwater flow in the aquifer, geothermal gradient and anisotropy in the aquifer. Thermal interference in the system when the thermal-front reaches the production well affects the system performance and hence should be avoided. This study predicts the transient temperature distribution in the aquifer for different flow and geological conditions. This may be effectively used in designing an efficient ATES project by ensuring safety from thermal-breakthrough while catering to the energy demand. Based on the model results a safe well spacing is proposed. The thermal energy discharged by the system is estimated.The present numerical model is also found to approximate the results of an experimental field study quite well.