29 May 2025

Sumitomo Electric Successfully Completes its First Vanadium Redox Flow Battery at a Community Microgrid in Kyushu, Japan —Toward the Realization of the "Zero Carbon City" Concept in Minamikyushu City—

Sumitomo Electric Industries, Ltd. is pleased to announce that its vanadium redox flow battery (hereinafter "RF battery*1”), together with its energy management system sEMSA^🄬,*2 has been adopted as the energy storage system for the "Kurokiyama Solar Power Plant," which was developed by Minamikyushu City, Kagoshima Prefecture.

A completion ceremony for the "Kurokiyama Solar Power Generation Installation Project" was held on April 22, 2025, after the construction work by Mitaden Co., Ltd. (Headquarters: Kagoshima City, Kagoshima Prefecture; President: Izumi Hirose), which was contracted to design and construct the project.

(Photo courtesy of Mitaden Co., Ltd.)

(Scene from the Completion Ceremony)

The Kurokiyama Solar Power Plant was developed to reduce the amount of commercial electricity used on a daily basis as part of Minamikyushu City's regional decarbonization project to become a "Zero Carbon City.” Electricity generated by the solar power plant will be supplied to 10 major facilities in the surrounding area via dedicated lines. Our RF battery (installed capacity of 1,125 kWh: 250 kW x 4.5 hours) will serve as the energy storage system at this power plant, storing excess power during the day and releasing it at night, thereby contributing to reduced power usage. In the event of an emergency, the RF battery will operate independently to ensure the continuity of critical power infrastructure by supplying electricity to major evacuation centers as a priority.

In selecting the energy storage system, our RF battery was selected due to its long lifespan and its low risks of both degradation from long-term operation and fire due to ignition. The RF battery is made of materials that do not contain hazardous substances, thus minimizing environmental impact. Furthermore, this is the first time that our RF battery has been adopted for a project eligible for a regional decarbonization promotion subsidy*3 under the jurisdiction of the Ministry of the Environment.

We will apply our safe and long-lasting RF batteries to further contribute to local decarbonization projects, utilize renewable energy, and reduce greenhouse gas emissions.

■Features of the RF Battery

	High Level of Safety (Extremely Low Fire Risk) The electrolyte is non-flammable, and all components use flame-retardant materials, meaning it is not classified as hazardous under fire safety regulations. No special permits for hazardous materials or on-site hazardous materials handlers are required.
	Long Life Due to the charge-discharge principle, there is no degradation of electrolyte or electrodes, and the number of charge-discharge cycles does not accelerate degradation. The system can be operated for long periods, regardless of the operating method.
	Eco-Friendly The electrolyte has been proven to be reusable, and up to 99% of system materials can be recycled through proper separation. (Participation in the Green Transformation [GX] League led by the Ministry of Economy, Trade and Industry; obtaining wide-area certification for industrial waste from the Ministry of the Environment)