Energy efficiency in a building complex through seasonal storage of thermal energy in a confined aquifer

Confined aquifers are formations surrounded by impermeable layers called cap rocks and bed rocks. These aquifers are suitable for the seasonal storage of thermal energy. A confined aquifer was designed to meet the cooling and heating energy needs of a residential building complex located in Tehran, Iran. The annual cooling and heating energy needs of the buildings were estimated to be 8.7 TJ and 1.9 TJ, respectively. Two different alternatives were analyzed for an aquifer thermal energy storage (ATES) system. These alternatives were: 1) using ATES for cooling alone, and 2) coupling ATES with a heat pump for both cooling and heating. The thermal annual energy recovery factor and the annual coefficient of performance (COP) of the system were determined. A COP of 10 was obtained when ATES was employed for cooling alone. When ATES was employed for cooling and heating (using a heat pump), a COP of 17 was obtained for the cooling mode, and 5 for the heating mode.