I'm guessing that available fresh water is something of a limiting factor here as well.

We have abundant salt water of course. I imagine that generator turbines don't love salt water very much.

it is the most efficient in terms of energy transfer. I think it is lacking in terms of actual storage capacity. the upfront costs are also extreme.

ideally, every green energy farm would have a gravity well storage system nearby (like pumped storage) for the purposes of keeping discharge steady. Energy would be transferred into and out of this system pretty quickly, and stored in a more cost/size efficient storage option that could act as the true "battery" on dark days / longer periods of energy production downtime

A good example is the large scale hydropower project in Switzerland where they added 900MW capacity to the grid for storage. They do have a good geography for that.

https://www.reuters.com/business/sustainable-business/switze...

I wonder how difficult this would be to implement for consumers/smaller deployments. Could someone dig an underground pool sized hole for a tank of hot water that can be converted back to electricity?