Investigation of Efficient Heat Storage of Aquifer Thermal Energy Storage System by Numerical Simulation

Abstract

The air-conditioning systems with groundwater heat pumps using the Aquifer Thermal Energy Storage (ATES) are known to be energy efficient and are well developed in European countries. On the other hand, the number of systems is still few in Japan due to the lack of knowledge of optimum design for the system.

In this research, long-term heating and cooling tests were carried out in an ATES system installed in Japan Groundwater Development Co., Ltd., located in Yamagata City, northern part of Japan. During the tests, field data, i.e., the temperatures and flow rates of the pumped and injected water, performance of heat pump, etc., were recorded and these data were analyzed to demonstrate the high energy efficiency of the system.

Then, based on the geological and groundwater information at the test site, a 3D numerical model was developed using a groundwater and heat transport simulator. Using the numerical model, the long-term performance of the ATES system was predicted based on the climate conditions of Yamagata City. The simulation predicted the formation of the cold water zone in the aquifer, due to the imbalance of the extracted and disposed heat. On the other hand, performance of ATES system could be improved by introducing appropriate placement of wells.