• In collaboration with Osaka Metropolitan University and other partners, development is focused on new energy absorption and release system responding to challenges surrounding use of renewable energy
• MHI Thermal Systems is responsible for designing and constructing a new control system that efficiency utilizes surplus the energy, contributing to effective use through high-efficiency cold storage

Image courtesy of Osaka Metropolitan University

TOKYO, July 1, 2025 - (JCN Newswire) - Mitsubishi Heavy Industries Thermal Systems, Ltd. (MHI Thermal Systems), a part of Mitsubishi Heavy Industries (MHI) Group, has begun field test of a jointly developed "Surplus Renewable Energy Absorption and Release System" utilizing the Aquifer Thermal Energy Storage (ATES) system. The test is being carried out jointly with partners including Osaka Metropolitan University, which serves as project representative(1).

The project, titled "Development of Technology for Absorbing Surplus Renewable Energy in ATES systems," was selected by the Japan's Ministry of the Environment in 2023 as a "Regional Co-creation and Cross-sectoral Carbon Neutral Technology Research Development Program(2). In April 2025, cold-storage operation utilizing surplus energy began at the Osaka City Maishima Sports Center for Persons with Disabilities (AMITY MAISHIMA). From July 1, the project will transition to a new field test phase in which the stored cold water will be used directly for air-conditioning.

Today, renewable energy sources such as solar and wind power are being adopted toward realizing a decarbonized society. However, the amount of power generated is unstable due to their dependence on weather conditions. As a result, surplus energy often arises during transitional cooler seasons such as spring and autumn in Japan, when demand for air cooling/heating is low. To effectively utilize such surplus energy, infrastructural improvements are required-such as large-scale battery systems or extensive land use-both of which can result in significant additional costs. Against this backdrop, the joint project currently underway has focused on development of a surplus renewable energy absorption and release system that leverages the seasonal thermal storage function of the ATES system.

In this joint development, a surplus renewable energy absorption and release system is to be adopted in an ATES system for the first time worldwide. The system offers short-cycle thermal storage and discharge functionality, enabling flexible switching between cold and heat storage. It also incorporates a multi-layered seasonal storage function that allows lower-temperature chilled water to be stored within existing underground cold-water masses.

In conjunction with this project, MHI Thermal Systems is responsible for operating the ATES system and heat-pump type centrifugal chillers, as well as for designing and constructing a control system that efficiently utilizes surplus energy. The newly developed control system features a mode that automatically switches to the optimal operation depending on the surplus energy availability and underground water temperature. Furthermore, owing to the incorporation of a function that optimizes cold storage operation in real time based on fluctuations in electricity market prices and the volume of surplus power. This enables energy-saving operation that reduces electricity consumption during cooling while ensuring effective use of renewable energy.

An ATES system uses gravel and groundwater stored in aquifers deep underground as an enormous heat storage tank, allowing for the effective use of energy by enabling the circulation of heat across seasons, such as using the cold waste heat from winter heating for summer cooling, and the warm waste heat from summer cooling for winter heating. MHI Thermal Systems' ATES system received the "Energy Conservation Center, Japan Chairman's Award" in the "Best Practice Category" at the 2021 Energy Conservation Grand Prize,(3) and the "HPTCJ Promotion Award" at the 2022 "Demand Side Management Awards"(4).

MHI Group has made a declaration to achieve carbon neutrality by 2040, and is working to reduce CO2 emissions from its own plants and other production-related facilities, as well as reduce the CO2 emissions at customer facilities that use MHI Group products. As a part of MHI Group, MHI Thermal Systems supplies a large number of centrifugal chillers for general air conditioning, factory air conditioning, and district heating and cooling, boasting the top market share in Japan in this field. Going forward, MHI Thermal Systems will continue to respond to customer needs, and by delivering centrifugal chillers and thermal solution products with a low environmental load, contribute to the realization of a carbon neutral world.

(1) For further information, refer to the following press release issued by Osaka Metropolitan University:https://www.omu.ac.jp/info/research_news/entry-18319.html(Japanese)
(2) The project is part of the Ministry's "Carbon Neutral Technology Research and Development Program." For detailed information, refer to the following:  https://www.env.go.jp/earth/ondanka/cpttv_funds/pdf/pamph_e2023.pdf (page4)
(3) For further information regarding receipt of this award sponsored by the Energy Conservation Center, Japan(ECCJ), see the following press release:https://www.mhi.com/news/211222.html
(4) For further information regarding receipt of this award sponsored by the Heat Pump & Thermal Storage Technology Center of Japan (HPTCJ), see the following press release:https://www.mhi.com/news/22060301.html

About MHI Group

Mitsubishi Heavy Industries (MHI) Group is one of the world’s leading industrial groups, spanning energy, smart infrastructure, industrial machinery, aerospace and defense. MHI Group combines cutting-edge technology with deep experience to deliver innovative, integrated solutions that help to realize a carbon neutral world, improve the quality of life and ensure a safer world. For more information, please visit www.mhi.com or follow our insights and stories on spectra.mhi.com

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