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Cheaper Energy From Caverns of Compressed Air
Posted by
samzenpus
on Wed Jul 02, 2008 10:18 PM
from the fine-until-the-earth-burps dept.
from the fine-until-the-earth-burps dept.
An anonymous reader writes "By using the Earth's vast underground caverns to store compressed air generated by wind farms at night, several U.S. municipalities will be 'going green' by using that stored energy to generate daytime electricity on the cheap. Engineers at a National Lab think compressed air stored in underground caverns could cut in half the cost of electricity."
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Submission: Cheaper energy from caverns of compressed air? by Anonymous Coward
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vast? (Score:5, Funny)
I don't believe it... (Score:2, Funny)
I think those guys are full of vast hot air.
Re:vast? (Score:5, Funny)
Parent
Re: (Score:2)
Re:vast? (Score:5, Funny)
I suggest a vacuum cleaner for the task. (ducks)
Parent
Re:vast? (Score:5, Funny)
And this is why I have applied for a job at NASA. Think of all the vacuum we could mine from space!!! (Space is also very big but we'll make sure we get mines near to earth, to reduce our transport costs and make it cost effective)
We'll make a fortune selling vacuum to store in caves and then once we've sold to local authorities and energy companies we can sell to homeowners "A Vacuum for Every Yard" and then as the market becomes educated we can crack the enterprise and SMB market with "A Vacuum on every Desktop".
P.S.
I first got the inspiration for this awesome business opportunity idea from the documentary movie "Spaceballs".
Parent
Re: (Score:2)
Hmmm.. Instead of working on a space elevator, maybe we could build a vacuum pipeline so the rocket fuel doesn't contaminate the vacuum. We would have to be careful with them though, they would basically be long tubes and if we had a series of them, then teenage geeks will be wanting to surf pron with them.
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Untapped reserves (Score:5, Funny)
Production ... used up all the easily available vacuum on earth (mined from the air which contained precious little vacuum! - bringing it down from space is not cost-effective!)
Oh, come off it. There are still plenty of untapped vacuum sources around.
There's about of cubic foot of the stuff in any PHB cranium, you just need to open the thing and tap it! Granted, you'd need quite a bit of source PHB, but that's easy enough to come by -- and it's renewable.
Parent
Re: (Score:3, Funny)
You're right that the transportation costs are low, but the mining costs are prohibitive. Those PHB skulls are so dense, so they chew up the drill bits like there's no tomorrow.
I believe that they are more effective as the power source for air turbines. Harnessing all that hot air that they produce to spin a turbine should generate countless megawatts. And it might justify some of the meetings that I've had to go to.
- doug
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How Efficient is It? (Score:4, Insightful)
How far are the turbines from the caves? What happens if the wind that should be generating electricity for the compressors takes the day off and chooses to make an unfashionably late arrival? How much of a boost do the turbines get from the compressed air?
I'd think with enough losses along the way (steps up/down in voltage at transformers to transmit the power to the compressors, mechanical inefficiencies of the compressors, dependence of the turbines' optimum performance on this assistance) the project, while novel, could take a while to pay for itself. I'm not suggesting that bleeding-edge science should be economically feasible - that should come after the science is established - but that efficiency should be priority number one so that the technology can become competitive with other ways to store potential energy.
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Re:How Efficient is It? (Score:4, Insightful)
The current method as I understand it for large scale energy storage is water. Specifically http://en.wikipedia.org/wiki/Pumped_storage [wikipedia.org]
Compressed air probably less efficient but potentially cheaper to implement.
Parent
Re:How Efficient is It? (Score:4, Insightful)
I think they're mainly suggesting that it would be more efficient than storing the same energy in ordinary chemical batteries, which is the current method for storing energy from natural sources for times of higher demand (or lower production, in the case of solar). Presumably their calculations are based on minimizing the inefficiencies for both batteries and compressed air.
Pumped storage systems - essentially hydroelectric systems with a top reservoir, a bottom reservoir, and a system of pumps to move water back up to the top reservoir at times of excess generating capacity - are used in the UK at Dinorwig [fhc.co.uk] and at Ffestiniog [fhc.co.uk], and in the US at Luddington, Michigan [consumersenergy.com] (and probably in other places I don't know about). This is a reasonably simple, reasonably efficient system of storing energy at time of surplus production and releasing it at times of peak demand.
Parent
Re: (Score:3, Informative)
What happens if the wind that should be generating electricity for the compressors takes the day off and chooses to make an unfashionably late arrival?
You draw power from the grid, which you'll still be connected to.
Re:How Efficient is It? (Score:5, Informative)
How Efficient is It?
If you just throw away the heat generated during the compression, which I think is what is done in current large installations, I have read that you can get about 50% efficiency. The fact that natural gas is used in conjunction with the compressed air to regenerate the stored power confuses the issue, which leads to much higher efficiencies sometimes being claimed.
Here they are proposing to capture the compression heat and use it (with an "adiabatic generator"), which should help the efficiency. I'm a bit surprised the energy savings are worth enough to cover the capital costs of tapping such a low grade heat source, especially since this is also excess energy that will also need to be stored for later.
Parent
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Here they are proposing to capture the compression heat and use it (with an "adiabatic generator"), which should help the efficiency. I'm a bit surprised the energy savings are worth enough to cover the capital costs of tapping such a low grade heat source, especially since this is also excess energy that will also need to be stored for later.
As I understand it, they plan to store the heat energy separately, and as heat. I suppose it would be like a big thermos. When they release the compressed air they heat it with this stored heat before it goes to the engine.
Heating very dense air is more effective at increasing pressure than heating less dense air. The fact that the air is very dense allows them to take advantage of this "low grade heat." It's all ideal gas law stuff. [wikipedia.org] It's also why turbochargers are more effective when they have inte [wikipedia.org]
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Re: (Score:3, Interesting)
you have a lot of questions but here is the point.
at night time the wind dies down to the point where wind turbines generate 0 power. the whole point is that they can compress air in existing underground caves, near municipal wind farms, to run them after dark.
I'm worried about long term side effects, 1200 PSI is a lot of potential energy, and cave systems, even an airtight system as this must be, are underground and usually there are things above it, in this case, prime iowa farmland. if the cave blows a
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1200 PSI is a lot of potential energy.
Assuming the cavern has 1000 feet of granite (a medium density rock) above it, the amount of force exerted downward by the rock is also about 1200 PSI. 1000 feet is maybe a little high for natural formations, but an old mine could certainly work well. There are plenty of those, probably not many in Iowa though.
Re:How Efficient is It? (Score:4, Insightful)
Not very. The point however is to even out the load and fill the peaks, it's just another form of pump storage I suppose for places where you can't just conveniently pump water uphill. Despite the nuke lobby cry that it is all about base load the real problems are the peaks. With base load generation you have a whole lot of power being generated at night that isn't being used by anything and what is being used is lighting which mucks up the power factor. Running great big motors (like pumps) at night or resistance heating is what is usually done.
To sum up - a lot of energy is wasted but you get to fill the peaks without needing base load generation capacity equal to peak load requirements.
Sometimes wasting the energy is not a big deal. The ideal centuries old application for a windmill is to move enough water into a tank over the course of a week or two for use over the next week or two. With a long enough timeframe in the design it really doesn't matter if you have a few windless days or for solar a sudden cold snap. Compressed air however is a very inefficient way to store energy.
Parent
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You can say that about any energy storage mechanism, from capacitors to compressed air to iron-pine-cones-on-a-chain.
I think we can safely presume that the engineers involved in this project took such issues under consideration and didn't choose to use Playschool's My First Wind Turbine.
I'm not suggesting that bleeding-edge science should be economically feasible
This doesn't really count as "bleeding edge"... I don't know if the world has ever seen an
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[decompress air] when you release preassurized gas through an air regulator, the gas temperature will drop down, this is how refrigerators work. [...] The temperature would be so low that you have high equipment costs for the turbines, or simply damaged turbines.
Surely there's a simple way to put this cooling to work: given that the cooling happens during daytime hours, you could build a series of Ben & Jerry's factories alongside these air storage facilities. And at night you could cook breakfast for all B&J's workers using the heat generated while filling the caverns.
HAL.
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Nononono! Even better idea! Cook TV dinners at night, freeze then during the day. This would be soooooooooooo efficient -- all that energy that would have otherwise have been used by cookers and freezers gives way to an incidental side-effect of the storage process.
Please forward my Nobel Prize c/o my employers.
HAL.
Not really new news? (Score:5, Informative)
This has been done on large scales by a couple of power plants in the past.
http://en.wikipedia.org/wiki/Compressed_air_energy_storage [wikipedia.org]
Kubla Khan (Score:5, Funny)
a stately pleasure dome decree
where Aleph, the sacred river ran
down to caverns measureless to man...
from memory, apologies to Coleridge
Those words were famously written after an opium-induced hallucination, as was this plan
Re: (Score:2)
Not bad, but it differs slightly from my memory:
through caverns measureless to man
down to a sunless sea
Flatulence (Score:5, Funny)
Maybe not such a good idea (Score:2)
I can just imagine some poor hiker being blasted into the sky walking or climbing over one of these pressurized caverns, just because the engineers had missed a hole somewhere inside the main cavern.
It'd be ideal if they could spray some kind of airtight lining along the walls, but that wouldn't be too eco-friendly, would it?
Ecofriendly? (Score:2, Insightful)
So, is it that only benefit here, cheaper energy costs, comes about because they're buying the
You FOOLS!!! (Score:2)
You've deflated the Earth!!!
How long will it last? (Score:2)
Re: (Score:2, Funny)
You mean cave-outs.
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Dual-Use for long-distance air-conditioning? (Score:2)
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Hmmm (Score:4, Funny)
Why not just put carbon dioxide down there, and burn more coal?
I get it now (Score:2)
And what about the ecosystems... (Score:2)
..that thrive in these caverns? Who knows what kind of impact it would have on the earth as a whole if we eliminate dozens/hundreds of subterranian life forms with this plan.
This could possibly be the most short-sighted plan yet.
Re: (Score:2, Insightful)
Also, you need a pressure difference to extract energy, just a high pressure is not good enough (similar to th
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Re: (Score:3, Informative)
Easy:
1/ Lift musical instrument high into the air.
2/ Let go.
3/ Voila - energy from gravity!
Re: (Score:3, Insightful)
If the poster meant using the pressure in the ocean to *store* energy (for instance, compress air down there) to then convert back to electrical (or whatever), that's possible but it would be even harder than storing huge amounts of pressurized air in up here since you still have to build a container and ensure it's integrity (which is why the cave idea is interesting).
However, I was assuming the poster wanted to use the pressure to induce some kind of perpetual
Re:Why air? (Score:4, Funny)
Easy:
1/ Lift musical instrument high into the air.
2/ Let go.
3/ Viola - energy from gravity!
Corrected.
Parent
Re: (Score:2)
Lots of places already use gravity as a form of energy storage.
During the night at some hydro plants, where energy demand is low but supply is relatively consistent, they use the excess energy to pump water to a reservoir at the top of a hill.
Then, during the day, they let that water flow down the hill and spin a turbine.
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You seem to be confusing energy generation with energy storage. Collected energy (say, your beloved solar energy) would be used to compress air, which would be stored. When more energy is needed than is instantaneously available, that compressed air would be utilized.
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Yes, but coal, gas, oil and nuclear power plants all must continue to run overnight. Most of these use steam turbines and reheating partially cooled water is a lot less efficient than keeping it on the boil. Starting a turbine up from static takes a lot more energy than keeping it moving. It also takes in the order of weeks to stop or start a nuclear reactor.
Even before the big push for renewables were overgenerating significantly at night. The low cost of night-time electricity gave rise to fire-brick stor