reneweconomy is becoming a useful lens for understanding how large battery storage is moving from a supporting role to a central grid asset. Neoen’s latest announcements point to two parallel moves: a 248MW/496MWh project in France and a 100MW/400MWh project in Japan, both scheduled for completion in 2028.
What Happens When the Biggest Battery Meets a High-Voltage Grid?
The French project is planned for Vernou-la-Celle-sur-Seine, about 90 kilometers southeast of Paris, where it will connect to RTE’s 400kV high voltage transmission network. Neoen says the system will be the largest BESS in France and the first linked to that network, though the interconnection only provides for 200MW of power.
That gap between energy capacity and power connection matters. It suggests the project is designed not just for bulk storage, but for targeted grid services. Neoen says the battery will provide frequency and voltage regulation, help relieve congestion in the Île-de-France area, and support a higher penetration of renewable energy. The context matters too: France currently has high ancillary service prices, which makes flexibility assets more commercially relevant.
What If Storage Becomes a Grid-Services Business?
Neoen’s move highlights a broader commercial pattern in which batteries are built not only to store electricity, but to monetize system needs. In this case, the French project includes a long-term service agreement with Nidec ASI, part of Nidec Corporation, which will supply the BESS units. Nidec ASI will also assemble the packs at its new production facility in La Fouillouse, near Saint-Étienne.
The project is also being paired with community measures: additional environmental studies, funding for local projects, and vouchers for local residents to help reduce energy bills. Those elements do not change the technical case, but they do show that large infrastructure now arrives with a wider social footprint than it did in earlier years.
At the same time, Neoen is nearing completion of the 92MW/183MWh Breizh Big Battery in Brittany, which is trialling grid-forming capabilities in partnership with RTE. Together, the two French projects suggest an ongoing shift from one-off storage assets toward a more integrated portfolio of grid support functions. In that sense, reneweconomy is not just about batteries increasing in size; it is about batteries becoming more strategically embedded in how power systems operate.
What Happens When French and Japanese Expansion Move Together?
Neoen’s Japanese entry is the second half of the story. The company plans to begin construction in the coming months on the 100MW/400MWh Ako Battery in the Kansai region, with operation also targeted for 2028. The project follows a notice to proceed and has a grid connection agreement with Kansai Electric Power Company.
The timing is notable: the French and Japan announcements were made during the French president’s state visit to Tokyo. Neoen says it already has a team on the ground in Tokyo and intends to take advantage of what it sees as an increasingly attractive Japanese energy storage market.
For now, the most important signal is not that these two projects are identical, but that they are synchronized. Neoen is building scale in France while entering Japan with a substantial first project. The company says the deal with Nidec marks the 12th battery it is building with the partner, and the two have more than 1GWh of capacity in their shared portfolio. That repeated partnership points to a maturing supply chain and a more repeatable storage model.
| Project | Location | Size | Timing | Key role |
|---|---|---|---|---|
| Vernou-la-Celle-sur-Seine BESS | France | 248MW/496MWh | Construction in summer 2026, operation in 2028 | Frequency, voltage regulation, congestion relief |
| Ako Battery | Japan | 100MW/400MWh | Construction in the coming months, operation in 2028 | Market entry and grid connection in Kansai |
Who Wins, Who Waits, and What Should Be Watched Next?
The clearest winners are likely to be grid operators and project developers that can deploy flexible assets where ancillary services are valuable. Nidec also stands to benefit from its role as supplier and long-term service provider, with manufacturing in France tied to the project pipeline.
France’s electricity network may gain from better congestion management and more flexibility around renewable integration. Local communities may benefit from the environmental studies, local project funding, and energy-bill vouchers tied to the French development. In Japan, the Ako project could give Neoen a foothold in a market it sees as increasingly attractive.
The biggest uncertainty is execution. Both projects are still ahead of construction, and the French battery’s 200MW connection cap means expectations should stay realistic about how much power can actually flow at once. Even so, the direction is clear: large batteries are becoming a standard part of how utilities, developers, and governments think about system resilience.
For readers tracking the next phase of the transition, the message is simple. Watch where storage is tied to transmission constraints, ancillary service demand, and repeatable partnerships. That is where the next wave of scale is most likely to emerge, and that is why reneweconomy matters now.
