I wonder if the excess energy could be used to do things like run carbon capture (although I've read that this is very much a pipe dream, that it'll take several magnitudes more carbon capture facilities to counter what we're currently producing).

In a very tiny Canary Island, their battery is many many tonnes of water pumped uphill when they have windpower: https://www.youtube.com/watch?v=RXhAj5BHdfM