MHI Thermal Systems Begins Field Test of Surplus Energy Storage System

Mitsubishi Heavy Industries Thermal Systems, Ltd. (MHI Thermal Systems) has launched a field test of its jointly developed “Surplus Renewable Energy Absorption and Release System,” using Aquifer Thermal Energy Storage (ATES) technology. Conducted with partners including Osaka Metropolitan University, the project aims to address the effective utilization of surplus renewable energy.

The initiative, selected by Japan’s Ministry of the Environment in 2023 under the "Regional Co-creation and Cross-sectoral Carbon Neutral Technology Research Development Program," began cold storage operations in April 2025 at the Osaka City Maishima Sports Center for Persons with Disabilities (AMITY MAISHIMA). Starting July 1, the project enters a new phase using the stored cold water directly for air conditioning.

The system is designed to absorb surplus power—especially during spring and autumn when solar and wind energy production can exceed demand—by storing thermal energy underground. It is reportedly the first time an ATES system has incorporated a surplus energy absorption and release system, enabling both short-cycle and seasonal thermal storage through multi-layered underground water storage.

MHI Thermal Systems is overseeing the operation of the ATES system and centrifugal chillers, as well as designing and constructing a control system that adapts in real time to fluctuations in electricity market prices and surplus power availability. The system automatically adjusts between storage and discharge modes based on groundwater temperature and surplus energy conditions, aiming to reduce power consumption and enhance the use of renewable energy.

ATES systems use deep underground aquifers and gravel to store heat, allowing seasonal reuse—for example, cold stored in winter can be used for summer cooling. MHI Thermal Systems’ ATES system has previously received the Energy Conservation Center, Japan Chairman's Award in 2021 and the HPTCJ Promotion Award in 2022.