Probably this one: https://www.zenobe.com/news-and-events/blackhillock-battery-...

Very much aimed at storing surplus from a couple of wind farms in the Moray Firth.

Presumably we'll see a lot more of these given the scale of some of the new windfarms...

That one claims to Europe's biggest, this one is claiming to be the UKs biggest which I guess means an even larger one went live in Europe somewhere in between.