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Compressed air has significant fundamental limits to efficiency much higher than those for electrochemical storage technologies.  I think the gravity storage Thomas linked to a while back is more promising (if completely unproven).
by njh on Wed Jan 25th, 2012 at 12:42:36 PM EST
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True as that may be, I wonder whether compressed air isn't what's called for in much of the industrial sector. A lot of machinery already works off compressed air or hydraulic pressure, but used a relatively small vessel to create the "power supply."  

The easiest example of this being something like a nail gun that runs off tubing linked to a compressor that's small enough to be carted around by hand.  It takes maybe 5-10 minutes to load, and then tops itself off when depleted, which generally takes only a few minutes of continous use.

Where you have existing, natural features that could be used to store large amounts of compressed air you could conceibly use them as a massive version of the compressor that you can cart around by hand. And with smart grid technology, you can use this to push down peak electric loads.

What I'd be most interested to know is if there's a way to apply the same principle to fluids.  Greater density would seem to apply the same power storage in a much smaller area.

And I'll give my consent to any government that does not deny a man a living wage-Billy Bragg

by ManfromMiddletown (manfrommiddletown at lycos dot com) on Wed Jan 25th, 2012 at 12:59:41 PM EST
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Compressed air does have a relatively high mechanical power storage, but it's not so great for efficiency.  Hydraulic pressure can be stored - it's called hydroelectricity (but is really hydrogravitational storage).  You can't store liquids 'under pressure' because they are essentially incompressible and hence you can't do any useful work on them.  There are large scale compressed air storage systems: http://en.wikipedia.org/wiki/Compressed_air_energy_storage

All existing large scale systems get < 50% round trip efficiency IIRC.

by njh on Sat Jan 28th, 2012 at 01:44:41 PM EST
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