en.Wedoany.com Reported - Japanese renewable energy developer Green Growth has commenced commercial operations of a battery energy storage system (BESS) co-located with the Kagashiya high-voltage solar power plant in Hita City, Oita Prefecture.
This project is the first to enter commercial operation under Green Growth's end-to-end battery co-location model, first announced in July 2025. The company had previously set a target operational date of January 2026. Green Growth stated that commercial operations officially began after completing permits, grid connection procedures, and trial runs.
Under the current arrangement, Kagashiya retains ownership of the solar assets, while Green Growth is responsible for business planning, project implementation, and ongoing operations and aggregation. Green Growth noted that this separation of ownership and management enables companies without in-house energy expertise to extract greater value from their assets.
The project aims to address Japan's transition from the feed-in tariff (FIT) mechanism to the feed-in premium (FIP) mechanism. Green Growth pointed out that renewable energy operators face challenges including increasing curtailment and greater wholesale market volatility, particularly within Kyushu Electric Power Company's service area. The company stated that Japan's curtailment priority rules are expected to be revised from fiscal year 2026, granting FIP generation priority over FIT generation—a change that will strengthen the rationale for converting FIT to FIP and pairing with battery storage.
According to Green Growth, the battery system has an output of 1,500 kW and a capacity of 4,515 kWh. The system will charge during daytime hours when electricity prices are low and curtailment is likely, and discharge during high-price periods, using an aggregation platform operated by Shizen Connect for dispatch.
Green Growth said it will serve as the aggregator for the project, handling power generation and price forecasting, trading on the Japan Electric Power Exchange (JEPX) wholesale market, and submitting relevant plans to the Organization for Cross-regional Coordination of Transmission Operators, Japan (OCCTO). The company plans to expand its FIT-to-FIP conversion and battery co-location business, particularly in areas with frequent curtailment, and is already preparing other projects.
This project comes as Japan gradually reduces feed-in tariff support for large-scale solar installations. The Japanese government has stated that competitive subsidy auctions for large-scale solar will end after fiscal year 2026, while continuing FIT support for smaller systems. As the first batch of FIT projects approaches the end of their guaranteed rate periods, some solar owners have turned to refinancing and other strategies to adapt to Japan's post-FIT market environment.
