The bit about the Antarctic water "bulb" mining and subsequent sewage dumping to fill the hollow reminded me of a bit of fiction:

https://en.wikipedia.org/wiki/Level_7_%28novel%29 - not mentioned in the wiki is the part where the underground reservoir for supplies has a moving partition, the other side of which is being filled with sewage.

Ah, cautionary tales ...

What if there's a leak in the salt mine?

I mean, a salt mine is just a large hole in the ground. What assurance do we have that it doesn't have any hairline cracks through which compressed air can escape?

And if the air does begin to escape and erode the surrounding rock, how do you prevent a massive explosion occurring at some point? Is the weight of the rock above the cavern enough to keep the air compressed at 1100 psi?

My favorite method of short-term energy storage at scale is to use excess energy during non-peak times to pump water uphill, back into a reservoir. The topology has to be right for it (and obviously it requires there to be plenty of excess water), but it's a simple method to smooth out peak demand.

It gets expensive, in direct and environmental costs, when you end up building additional small dams just for that.

Around here those costs were quietly palmed off on consumers, while the virtues of wind power were being sung.

Wikipedia has rather more information on this, including (in the History section) a bunch of examples of this at scale going back to the 70s

http://en.wikipedia.org/wiki/Compressed_air_energy_storage

Seems like if there is a salt mine they could make some sort of battery out of the salt.

If that were possible, couldn’t you do the same thing to the entire ocean?

This is pretty neat. I wonder how cost effective it is vs compressed fluid storage.

If by fluid you mean liquid, liquids don't compress.

Well, they do compress, just not enough to bother to store energy into them. (Sorry, I gotta nitpick the nitpickers.)