Yes you did get a bit confused in your calcs. It would work fine. You are simply pumping up from a lower holding tank to a higher holding tank and generating power when you reverse the flow. Don't get lost in the details.
An energy provider would be ideal to finance it. Imagine you are doing what you dream of doing in the stock market, buying low and selling high. The energy provider would buy energy when there is excess and it's cheap then sell it back when there's a demand and it's worth more.
The government could also pay for it and run it as part of the grid as it currently spends billions to maintain that grid. It would be ideal closer to the source of the excess renewable energy and the end users for obvious reasons and that's where all those suitable locations would be so valuable.
