Check this out

https://spectrum.ieee.org/mix-mountains-and-gravity-for-longterm-energy-storage

There's another company doing something similar by building a tower and using barrels filled with garbage as the weights. Just using the excess solar energy to lift the buckets up high then let gravity return the energy. It doesn't matter if these methods are inefficient because the source of them is free solar power.

Edit: found a different company doing the same thing lol

https://www.azocleantech.com/article.aspx?ArticleID=1097