Another possible solution

https://www.greentechmedia.com/articles/read/germany-thermal-storage-into-coal-plants?

"The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt or DLR) is investigating whether Germany’s coal plants could be reused as energy storage assets.

The research body, which has a track record in concentrated solar power (CSP) development, is planning a pilot that will involve ripping out the boiler from an old coal plant and replacing it with a molten salt thermal storage tank that will be heated using excess renewable energy.

If the concept works, then advocates say it could help safeguard coal generation jobs while giving Germany tens of gigawatts of storage capacity for renewable energy load-shifting on the German grid. Furthermore, a single pilot could be enough to prove the commercial viability of the concept, since the technology, described as a Carnot battery, is based on commercially available industrial components and standard engineering practices."