This study investigates the performance of an aquifer thermal energy storage system (ATES) that is coupled with the cooling tower of a seasonally-running thermal plant. The ATES supplies cool water and stores heated water for the cooling tower during the runtimes of the thermal plant. Moreover, it supplies warm water for bathing or irrigation during downtimes of the thermal plant. The performance of ATES is evaluated numerically for a full year, and well placement is optimized. Findings indicate that the ATES system could be optimized by locating the cool water supply well upstream of the storage well. In the optimized ATES, the outflow temperature from the cool water supply well can be maintained below 15 degrees C, which satisfies the temperature requirement for the cooling tower. The injection of heated water (with temperature of 70 degrees C) at 8400 m(3)/d for six months leads to over 140,000 m(3) of warm water (with temperature >= 40 degrees C) stored in the aquifer. This warm water can supply at least 12,000 m(3)/d of warm water for six months. The recovery efficiency is estimated at 60.9%, and the energy loss is attributed to rainfall infiltration, thermal diffusion into underlying low-permeability layer and advection downstream. (C) 2016 Elsevier Ltd. All rights reserved.