Groundwater, which lies in abundance beneath our feet, is retained in a geological formation called an aquifer made of materials such as sand and gravel. Compared with the outside air temperature, groundwater is warmer in the winter and cooler in the summer. Because of this difference in temperature, it is of high value as a heat/cold source, but this energy has been unused. In air conditioning systems known as aquifer thermal energy storage (ATES) systems, aquifers are used as if they were large heat/cold storage tanks. Using a centrifugal heat pump, waste heat produced during cooling operations and waste cold during heating operations are stored in aquifers. This enables the former to be effectively used for heating and the latter for cooling in different seasons. Mitsubishi Heavy Industries Thermal Systems, Ltd. developed a heating/cooling system that uses a high-efficiency centrifugal heat pump suitable for ATES systems and an energy management optimization control system.
