Brittany: 92 MW battery tested to stabilize the grid

South of Morlaix, in Finistère, the Breizh Big Batterie, nicknamed BBB, has just been inaugurated. With 92 MW of power and 183 MWh of capacity, it is the largest stationary storage battery in Brittany. It was installed by Neoen, which is already working on a second facility near Rennes.

The region imports nearly 70% of its electricity, but produces 80% of what it consumes thanks to wind and solar power. These sources are variable by nature: the wind drops, the sun sets. To balance production and consumption, electricity must therefore be stored when there is a surplus. Large projects are underway, such as the Saint-Brieuc Bay wind farm or Pennavel, a 250 MW park due to be built off Belle-Île.

The real challenge of the BBB cannot be measured in megawatts alone. Until now, the inverters of French batteries, the devices that convert the battery's current for the grid, operated in “grid-following” mode: they tracked the frequency and voltage already present on the grid. In the event of an anomaly or outage, they simply disconnected, without being able to help restore power.

RTE wants to change that. Through a software update of these inverters, with no hardware modification at all, the battery would switch to “grid-forming” mode: it would generate its own voltage and frequency reference. It would thus provide a form of synthetic inertia, essential to grid stability, and could react instantly to frequency variations to curb them. For now, this is an experimental project: the sources say neither when the switch will take effect nor what results it has produced.

What does this change, and for whom? For the Breton and national grid, it promises a battery that no longer merely follows the grid but can help keep it stable. Neoen's second facility, near Rennes, is due to be built starting in 2028, with commissioning in 2029. It will show whether this mode can become the norm for future batteries, rather than the exception of a single site.