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Comment by ncmncm | Hacker News Reader

Undersea storage of compressed air, as an alternative to batteries, needs no technological advances. Just air pumps, pipes, and bags.

Heat lost to the water (maybe half of the energy input to compressed air) could be reclaimed as the pressure is released, with simple heat exchangers.

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How much time have you spent underwater? Such schemes are totally unrealistic maintenance nightmares due to corrosion, encrustation, storms, and difficulty of site access.

It is a major challenge to have functioning mechanical equipment in a salty, high-pressure aquatic environment.

Came to say this. I always want to hear the maintenance story on wave power systems but the never seem to release it as well.

They’ve already got wind turbines and offshore oil rigs. The compressed air as stored energy under the sea idea uses Kevlar bladders anchored to the sea floor with a hose or pipe going to the surface. It’s not really that far fetched.

Huh?

No it's not. It's a solved problem.

Has been at least since way back when I was at Halliburton.

In fact, they're almost the same pumps, mechanically speaking.

> Heat lost to the water (maybe half of the energy input to compressed air) could be reclaimed as the pressure is released, with simple heat exchangers.

Heat lost to the water is lost. If you want to try to avoid that you need to save that heat energy after the compression stage.

I see that you have not thought this through. Yes, some of the heat will not be recoverable, but controlled expansion of highly pressurized air creates a large temperature drop that would readily absorb heat from the ambient water.

Why would you store it at sea instead of storing it just onshore?

The density of water is so much higher than that of air (if you are comparing subsea potential energy storage with compressed air storage onshore). And there is a lot of unused space at the bottom of the sea.

I dont think there's any unused space at the bottom of the ocean, we keep the ocean down there. If you fill that space with air bladders you'll have just raised the sea level by whatever amount of space you inflate the bags with.

Sure, it's not a solution that will scale. As is wind energy: if we cover all the oceans with it, it will influence our climate and probably slow down the rotation of the earth, etc. The point is that a relatively small such storage plant can already store a huge amount of energy - enough to help balance a lot of offshore wind.

Very funny.

You are aware, are you not, that there is 3x as much sea floor as land?

And raising the sea level would take more air than has ever been breathed by the entire taxon of primates. You would never store more air than needed for a day or two of power generation.

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