New battery storage system launched in Finistère

A new battery storage system with a capacity of 183 MWh and a power output of 92 MW has been inaugurated in Finistère, south of Morlaix, Brittany. Named Breizh Big Batterie (BBB), it is the largest stationary battery storage system in the region and is designed to help stabilize the electrical grid.

Region’s energy mix and renewable goals

The region currently imports nearly 70 percent of its electricity but is working to reduce this dependence by expanding renewable energy sources. About 80 percent of the region's electricity is generated from wind and solar power, supported by major projects like the Saint-Brieuc Bay wind farm and the Pennavel offshore wind project, which has a power capacity of 250 MW.

Expansion of battery storage projects

Neoen, the company behind the BBB, is also planning a second battery storage installation near Rennes. Construction is expected to begin in 2028, with the system becoming operational in 2029. This expansion reflects the growing importance of battery storage in supporting renewable energy integration.

Grid forming mode for improved stability

Beyond optimizing renewable energy production, the BBB is part of an experiment by the network manager RTE. Traditionally, French battery storage systems have operated in grid following mode, adjusting their frequency and voltage to match the grid. In case of a power disruption, these systems would disconnect and could not help stabilize the supply.

Grid forming mode benefits

RTE aims to update inverters in the BBB to switch its operating mode to grid forming. This would allow the battery to generate its own reference for voltage and frequency, providing synthetic inertia essential for grid stability. This change will enable the battery to respond instantly to frequency fluctuations and reduce their impact.