Compressed air powered water pressure

Thread is reopened...

timMoore said:

If you want to use compressed air and water there are a few energy storage options.

Compressing air always involves heating it up and that thermal energy is of the same order as the stored mechanical energy. For good efficiency, it would be necessary to insulate the stored high pressure air which would limit the time period it could be used for. Also, very high temperatures would be involved.

Whoops - I already made this point two years ago. well spotted, Mods!