Underwater Compressed Air Energy Storage (UW-CAES)
Here’s an idea that shows the enormous range of thinking outside the box of which clean energy inventors are capable. Use off-peak energy to compress air into a submerged bag. My reaction: Can this be done? Sure. Can it be done cost-effectively? Not in a million years.
Frequent commenter and senior energy analyst Glenn Doty should be along here any minute. I’m sure he’ll agree, given his position on even the best-case scenarios for CAES.
Hi Craig,
Yes you are right… this is a bizarre and foolish idea.
The idea was first presented to me several years ago. The supposed gain here relies on the lack of turbulence found in the deep – so a bag could theoretically be fairly thin and still hold a great deal of pressure (pressure equilibrium and all that)…
What the people pushing the idea apparently hadn’t thought about was that most gasses are lighter than water (certainly any non-condensable gas of reasonable cost), and these gasses would have a tendency to float… So if you fill the bag half full of sand to anchor it, then put several thousand m3 of air into it… there’s going to be thousands of tons of lift force pulling up against the bottom of the bag – which will be anchored…
The result – torn bag. Or the bag has to be made to be resistant against thousands of tons of shear, which means you can no longer use a thin, cheap bag to store high pressure gasses…
Oops.
We’ll both agree that we can chalk this up as another really bad idea.
😉
I would think you could engineer around that, by inserting the bag into a concrete structure like a pizza oven, but whatever. Bad idea.
I don’t want to sound sanctimonious, but I think a guy who bills himself as a “science journalist” (like the author of the article) has a responsibility to refuse to promote unworkable concepts.
Craig,
We certainly agree on the journalist’s responsibility to write more credible pieces…
But the idea of engineering around the buoyancy of the gas simply results in more costs. When this (dumb) idea first hit the scene, the selling point was it was supposed to be cheap. You just have to unroll a long, sausage-shaped plastic bag along the ocean floor… half fill it with sand, and presto! (??), you have a cheap, very high pressure compressed air storage reservoir… If you have to build a concrete bunker on the floor of 300 m water, that would cost more than using a high-strength bag….
There’s no workaround that can make this economically feasible… It’s just a dumb idea.
*shrug*
Absolutely; that pizza oven idea won’t be cheap….