There are a bunch of other technologies as well. Huge flywheels [1], which are supposed to be used for very responsive power needs (i.e. grid stabilisation), trains loaded with weights which get pulled up a mountain and released [2], redox-flow batteries and so on.
The zoning commission runs at the town/country level, so even if you don't have HOA busybodies you still need to get the permits. The law is usually worded such that if you're doing something abnormal you don't get a "there is no rule that says a dog can't play baseball" loophole, you instead have to bring it up before the county council and justify the project.
https://www.solarthermalworld.org/news/molten-salt-storage-3...
People talk about making "personal" molten salt units for the home, which seems a little terrifying.