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Sumitomo Corporation announced a 62MW/291MWh project in Fukushima and a 16MW/70MWh project in Nagasaki, with operations planned for 2029 and 2028. Greenvolt Power has brought two merchant battery projects totaling 4MW/8MWh online in Kyushu, showing how developers are pursuing different sizes and revenue models in Japan’s developing storage market.
Sumitomo Corporation has advanced two battery energy storage projects in Japan, including a 62MW/291MWh facility in Fukushima selected for a government capacity auction, while Greenvolt Power has brought two smaller merchant systems online in Kyushu. The developments illustrate a market spanning large projects with contracted revenue and smaller batteries exposed to electricity-market prices.
On October 1, Sumitomo said its subsidiary BS Holdings had begun construction on the Namie storage facility in Fukushima Prefecture. The project has 62MW of power output and 291MWh of storage capacity, and was selected in Japan’s Long Term Decarbonisation Power Source Auction, or LTDA. BS Holdings arranged project financing with MUFG Bank and expects the facility to begin commercial operations in 2029. Sumitomo said it had worked with Namie Town during development and that the battery is intended to support renewable-energy integration in the Tohoku region.
On October 28, Sumitomo reported preparatory work for Battery Station Ishiya, a 16MW/70MWh project in Nagasaki Prefecture. It is being developed by Denki no Eki, a joint venture between Sumitomo and Kyushu Railway Company, on the site of a former railway substation and nearby land. Commercial operation is scheduled for December 2028. Sumitomo did not disclose financing details for this project in the Japanese- or English-language releases cited by Energy-Storage.News.
Greenvolt Power, the utility-scale renewable-energy business of Portugal-based Greenvolt Group, has put its first two Japanese battery projects into operation, according to the report. The standalone systems are in Kyushu and together provide 4MW of output and 8MWh of capacity, a two-hour duration. They operate on a merchant basis, earning revenue by participating in electricity markets rather than relying on the LTDA contracts described for Sumitomo’s Namie project. The source material does not identify the two Greenvolt project sites or provide their individual commissioning dates.
Two Revenue Models, Different Scales
The announcements show how Japan’s storage market is attracting projects with different approaches to scale and revenue. LTDA-backed projects receive a fixed annual capacity payment for keeping power available, providing a revenue component that can support financing. Greenvolt’s smaller systems instead depend on market participation, leaving earnings more exposed to electricity-market conditions.
BloombergNEF Japan analyst Umer Sadiq told Energy-Storage.News that developers are pursuing three broad types of projects: LTDA-contracted batteries, subsidised merchant projects and unsubsidised merchant projects. He said smaller systems can let investors enter markets with limited exposure and gain experience, while larger contracted projects may be easier to finance. These are market observations and analysis, not a guarantee of returns for either project.
The difference also matters for grid access and investment decisions. Sadiq said smaller projects can face shorter waits for interconnection, while larger projects can offer different financing and revenue profiles. For readers tracking Japan’s energy transition, the deployments offer concrete examples of how storage may support renewable integration while also participating in electricity and balancing markets.
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Japan’s Layered Storage Market
The LTDA is a capacity-market mechanism that pays qualifying low-carbon asset owners a fixed annual fee for 20 years to keep capacity available, rather than paying directly for electricity delivered. The first auction round, administered by grid coordinator OCCTO, awarded 1.1GW across 32 battery projects in April 2024. In May 2026, according to the supplied report, a later round selected 1,251MW across 19 battery projects and limited eligibility to systems with at least six hours of duration. That round also introduced cybersecurity certification and a cap on the share of awarded capacity using cells from any one foreign country.
Sumitomo’s two developments differ in size, location and reported status. Namie is the larger, auction-selected project in Fukushima, while Ishiya is a smaller joint-venture development in Kyushu. The latter is Battery Station’s third Japanese project; its first two, in Kumamoto, were completed in 2024 and 2026 and are participating in the supply-demand balancing market, the source report says.
Greenvolt’s systems sit at the small end of the market described by Sadiq. He said dozens of 2MW/8MWh systems are being deployed as unsubsidised merchant projects, often with corporate financing. The report also cites BloombergNEF’s forecast of around 1.3GW of storage deployment in Japan during 2026, counting both front-of-the-meter and behind-the-meter projects. That is a forecast, not a confirmed final deployment total.
“The joint venture combines Kyushu Railway’s network and local business roots with Sumitomo Corporation’s expertise in energy storage.”
— Sumitomo Corporation, describing the Denki no Eki joint venture
Project Details Still Unreported
Several project-level details are not available in the cited announcements. Sumitomo did not disclose Battery Station Ishiya’s financing, its specific revenue arrangements or an expected operating schedule beyond the planned December 2028 start. The Greenvolt report gives the combined capacity and merchant model for its two systems, but not their individual locations, financing structures, earnings or operating dates.
Planned commercial-operation dates are forward-looking company expectations, not confirmation that the facilities will meet those schedules. The source material also does not provide details on the batteries’ market strategies or quantify how much renewable generation they will absorb. Sadiq’s market estimates and revenue observations are attributed analysis; they do not establish the future performance of these specific assets.
Construction and Market Participation
The next stated milestones are commercial operation at Ishiya in December 2028 and at Namie in 2029. Until then, construction and development progress will determine whether those schedules hold. Greenvolt’s two Kyushu projects are already operating, and their merchant revenues will depend on participation in Japan’s electricity markets; the source report does not specify their earnings or detailed trading arrangements.
Further updates from the companies may clarify Ishiya’s financing, the Greenvolt sites and operating performance, and the project timelines. Across the wider market, future auction outcomes, grid-connection capacity and market revenues will shape whether Japan’s battery pipeline continues to include both large contracted assets and smaller merchant systems.
Key Questions
What did Sumitomo announce in Japan?
Sumitomo reported construction beginning on a 62MW/291MWh project in Fukushima and preparatory work for a 16MW/70MWh project in Nagasaki. Their expected commercial-operation dates are 2029 and December 2028, respectively.
How do the Sumitomo and Greenvolt projects differ?
Namie was selected for Japan’s Long Term Decarbonisation Power Source Auction, which pays for available capacity. Greenvolt’s two smaller Kyushu systems operate on a merchant basis, earning revenue through electricity-market participation.
Are Greenvolt’s Japanese batteries operating?
Energy-Storage.News reports that Greenvolt Power has brought its first two Japanese battery projects into operation. Together they total 4MW of output and 8MWh of capacity. The source does not give individual commissioning dates.
When are Sumitomo’s projects expected to begin operating?
BS Holdings expects the Namie project to start commercial operations in 2029. Commercial operation at Battery Station Ishiya is scheduled for December 2028. These are announced target dates, not confirmed completion dates.
What details have not been disclosed?
Sumitomo has not disclosed financing details for Ishiya in the cited releases. The source material also does not identify Greenvolt’s two project sites or report their individual financial arrangements, revenues or commissioning dates.
Source: energy-storage.news
