In 2021, the Grohnde nuclear power plant in Lower Saxony on the Weser River was shut down. Now, immediately next to it, the Emmerthal energy cluster is growing with three very large battery storage systems, ground-mounted photovoltaic systems, and a new substation for several 380-kilovolt high-voltage lines.
Molten salt can also be used for heat storage. I’m not sure what the advantages are of molten salt vs water vs sand and what is most realistic.
I don’t think any of those alternatives are used in large scale.
As a side note, some ski resorts are saving snow during the summer to be able to open earlier in the season.