But the pumps and turbines are based on how much power it can process, not how much it can store. Most storage systems have a big downside in that the J that y

But the pumps and turbines are based on how much power it can process, not how much it can store. Most storage systems have a big downside in that the J that you use once a year costs just as much to store as the one you use every day. This perhaps permits putting a lot of air down there as reserve for when the sun doesn't shine for days on end. Lithium is non-viable for dealing with long periods of darkness (big storm on top of your collectors.) To ensure the lights stay on in the worst case you need weeks worth of storage.