Liquified air.
Two points.
1. I don't think they are trying to hold it at high pressure. Sure, you compress the hell out of it when you liquify it, but then as long as you keep it cryogenically cool, it stays liquid at regular atmospheric pressure.
2. Need air conditioning? You got it! < }B^)
I'm all for new and useful ideas/inventions, but nearly all of these "alternative energy" scams are really getting boring, almost to the point of insulting the average person's intelligence!!!