Agreement signed to install the largest capacity rock thermal energy management facility in Japan - Contributing to realization of carbon-neutral society through effective use of renewable energy and heat

Toshiba Energy Systems & Solutions Corporation ("Toshiba ESS"), Chubu Electric Power Co., Inc. ("Chubu Electric Power"), and Okazaki City in Aichi Prefecture ("Okazaki City") today signed an agreement (the "Agreement") to install Japan's largest (Note1) plant using rock thermal energy storage and energy management technology with a thermal capacity of several tens of megawatt-hours (the "Rock Thermal Storage EM Facility"). The initiatives to be implemented based on the Agreement have been adopted by the Ministry of the Environment for its FY2024 Regional Co-creation and Cross-sectoral Carbon Neutral Technology Research and Development Program.

Based on the Agreement, the three parties will conduct a study and verification (the "Feasibility Study") from today until the end of FY2026, based on actual data on electricity and heat demand in Okazaki City, for the introduction of the facilities, including consideration of the optimal heat capacity and installation location of the Rock Thermal Storage EM Facility.
Based on the results of the Feasibility Study, Toshiba ESS and Chubu Electric Power plan to fabricate the equipment sequentially starting in 2027. The heat capacity of the equipment is expected to be several tens of megawatt-hours, which is the expected capacity when rock thermal storage is implemented in society.

Okazaki City is considering installing the Rock Thermal Storage EM Facility by FY2029 and supplying heat and electricity derived from the facility to residences, public facilities, and businesses in Okazaki City under the Ministry of the Environment's Decarbonization Leading Area Project. In addition, the city is considering coordinating the supply and demand of electricity using the Rock Thermal Storage EM Facility in cooperation with new power companies in the region to contribute to further utilization of renewable energy sources such as solar power generation ("renewable energy").

The generation and consumption of electricity occur simultaneously, so the two must always be matched, and if this balance is lost, a blackout will occur in the worst situation. In order to prevent blackouts, the output of natural variable power sources (solar and wind power) may be suppressed based on the priority dispatch rules (Note2) established by the national government and the Organization for Cross-regional Coordination of Transmission Operators, JAPAN. In recent years, the expansion of the introduction of renewable energy sources, primarily natural variable power sources, has led to a widening gap between electricity supply and demand during periods such as spring and autumn, when electricity consumption is low, and the output suppression of natural variable power sources has increased, which has become an issue.
In order to solve this issue, attention has been given to a technology that achieves stable energy supply and efficient energy use by storing excess electricity as thermal energy in thermal storage materials such as rock, molten salt, and concrete, and providing heat or generating electricity as needed ("thermal energy storage technology"). In particular, the rock thermal storage technology on which this Feasibility Study will be conducted is expected to be highly superior in terms of environmental friendliness, economic efficiency, and equipment reliability.

Toshiba ESS and Chubu Electric Power have focused on rock thermal storage technology, which is expected to be highly superior as a thermal energy storage technology, and have conducted joint research. In 2022, the two companies developed a test facility for a rock thermal storage system with a heat capacity of approximately 500 kilowatt-hours and conducted a full-scale technical development and demonstration test within the Yokohama Complex of Toshiba Corporation. In addition, in November 2024, a four-way agreement was signed including Shin Tokai Paper Co., Ltd. and Shimada City, Shizuoka Prefecture, to conduct a technology demonstration test in FY2026 at the Shin Tokai Paper Shimada Mill using the Rock Thermal Storage EM Facility with a thermal capacity of approximately 10MWh.

Through the efforts based on the Agreement, the three parties aim to contribute to the realization of a carbon-neutral society through the effective use of renewable energy and heat, and will accelerate efforts toward the practical application of rock thermal storage technology.

(Note1) This is the first plan in Japan to install tens of megawatt-hour-class facilities using rock thermal storage technology (as of March 2025, according to the three parties).

(Note2) Rules that specify the conditions and order of output control for power sources in operation, etc., in response to fluctuations in consumption and other factors, in order to achieve a balance between power generation and consumption.

Role of each party