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Forget Better Batteries, Nothing That Exists Or is in Development Can Store Energy as Well, And as Cheaply, as Compressed Air (theconversation.com)
An anonymous reader shares a report: The concept seems simple: you just suck in some air from the atmosphere, compress it using electrically-driven compressors and store the energy in the form of pressurised air. When you need that energy you just let the air out and pass it through a machine that takes the energy from the air and turns an electrical generator. Compressed air energy storage (or CAES), to give it its full name, can involve storing air in steel tanks or in much less expensive containments deep underwater. In some cases, high pressure air can be stored in caverns deep underground, either excavated directly out of hard rock or formed in large salt deposits by so-called "solution mining", where water is pumped in and salty water comes out. Such salt caverns are often used to store natural gas. Compressed air could easily deliver the required scale of storage, but it remains grossly undervalued by policymakers, funding bodies and the energy industry itself. This has stunted the development of the technology and means it is likely that much more expensive and less effective solutions will instead be adopted.
Look up Shingeki no Kyojin for more info on the amazing potential of compressed air. Don't believe me? Watch this.
Hold my beer. I have a plan.
This seems unlikely to replace batteries at the small scale. Even discounting the risks of puncture or leakage in mobile devices like cell phones or computers; the equipment necessary to compress air into containers can likely only be scaled down so far before it loses efficiency.
Plus every air compressor I've ever seen or worked with is pretty loud. Maybe there are ways to reduce the noise; but this ultimately seems like more of a large scale way to store energy produced via solar or wind power than a replacement for traditional batteries.
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There is no “minimum storage pressure” but the economics are poor for anything lower than 50bar. For CAES with tanks, the economics push you towards pressures of 200 - 250 bar. In caverns, the pressure you can use depends on the cavern depth. 120bar is not unusual. For a cavern with 120bar storage pressure that was allowed to swing down to (say) 70bar when “discharged”, you would be storing ~23MJ in each cubic meter of cavern. Thus for 1GWh (3.6 million MJ), you would need 156,000 cubic metres of cavern. That is actually a relatively small salt cavern! If it was a sphere, it would have radius of 33.4m. Surprising as it may seem, most salt caverns in existence are bigger than that!
This is not a quote I find anywhere in TFS, TFA, or in any of the articles linked from TFA.
There are a lot of ways to store wind and solar, all of which are somewhat underutilized. Pumped hydro (where water is pumped uphill) is an alternative, as are giant flywheels spinning in a vacuum with magnets on the rim. There are a lot of alternatives to batteries that are in active use.
NOWHERE, other than in the headline, is the claim made that compressed air is SUPERIOR to any of these other "alternative to batteries" technologies.
NOWHERE is there even a direct comparison made to batteries, other than a passing (and unsubstantiated) reference that "batteries work well for short term storage" with an implicit comparison that CAES is more suited to longer term storage.
Where the heck did this headline come from? Citation needed.
Saw a pie chart a day or 2 ago that shows natural gas and coal are about equal now in the US market. And since natural gas is now cheaper than coal to build and run, US use of coal will continue to diminish. That, BTW, is the absolutely best way to replace polluting sources, by replacing them with cheaper things that don't pollute. IOW, don't pass a law against something, pass a law that helps create cheaper but cleaner resources and no, that doesn't mean subsidize something, because that is just the people paying more for something through taxes. No, REALLY make it cheaper - make something that is intrinsically cheaper. That's now natural gas. Hopefully some smart guy will build the 90% efficient solar cell, and these guys will perfect their air compression technique and we'll get 100% clean power.
What's the best way to move from coal to natural gas outside the USA? By fracking the F out of the oceans of natural gas reserves that the USA has, and selling it to the furriners... Its a win-win - they get cheaper electricity and the world gets less CO2 and other nasty shit in the air. Trump just did that by harrassing Angela Merkle, the German prime minister, into canceling her country's gas pipeline to Russia, and instead building liquified natural gas seaports for import of LNG by ships from... the USA. We better get to fracking every square inch if we want to reduce pollution.
Having worked with a lot of air compressors over the years I was suspicious of this as an efficient way to convert energy into a storage medium. After a quick Google I found a blurb on a manufacturer's website that up to 90% of electricity used to run a compressor is converted into heat.
https://www.quincycompressor.com/the-benefits-of-efficient-air-compressors/
I'd imagine that large-scale compressors are more efficient, and there would be some heat capture employed to utilize the energy lost there, but can this really compete?
I worked on a project doing exactly this about 5 years ago. The company, called SustainX, i believe is gone and disbanded. There are probably others too. They basically took a giant marine diesel engine and modified it become an air compressor in storage mode, and an expander in retrieval mode. They had solved some of the technical challenges of doing it in a thermodyanically efficient way. Something about isothermal and adiabatic. I forget the details but they have some elaborate mechanism for *both* the compression and expansion of the gas to extract a lot more usable energy. The big problem was storage. They used a giant tank array for their test system. They really wanted to deploy it globally but it turns out there's only a few locations in the entire word that have suitable geology for underground storage. So since tanks were relatively expensive and the geology wasn't prevalent, the company didn't sell anything and folded. Cool idea and very technically savvy company though.
Scott
Huh? We're talking about energy storage, not machine shop tools.
When considering safety, it's always good to look to people who have being doing it safely for decades, and see what's involved. The big presses have to store energy at very high PSI in order to operate. Their inspection procedures are non-trivial. Not very practical if you don't have the right kind of rock to use for storing vast quantities of energy.
Socialism: a lie told by totalitarians and believed by fools.
I'd be nervous, though, about any storage in steel containers as that goes very bad when it goes (a few hundred PSI is one thing, but a few thousand PSI is another).
Shoot. There goes my plan to create a vast energy storage system based on 100,000 Harbor Freight 10-gallon air compressors strung together with hoses and extension cords. I'll have to use my 20% off coupon for something else.
I guess this idea will never get off the ground, since there aren't any engineers capable of figuring out a better solution.
People who say "sheeple" have about as much sophistication as an AOL user, and in fact are probably actually AOL users.
You're talking about a liquid under pressure. Pressurize liquids store very little energy, because they are largely uncompressable.
You might find it informative to read about the biggest presses. The 1500 HP motors don't make nearly enough power to operate the press directly: they accumulate the energy in pressure accumulator bottles until there's enough in storage to operate the press once. it's a "hydro-pneumatic" system.
It's the only example I can think of where energy is routinely stored and discharged at thousands of PSI, and safely. Scuba tanks store air at a reasonable fraction of that pressure, but they aren't used for power (so limited fill/discharge rate) and they do blow up from time to time.
Socialism: a lie told by totalitarians and believed by fools.
Air is free and renewable, and doesn't need to be transported from where it is pumped from the ground over thousands of miles, and it doesn't need to be refined.
Other than the infrastructure, there is little resource cost, since it's not (yet) a commodity.
Now, does this make the article right? I'm not qualified to say that. But this guy is a professor of Dynamics, and is far more qualified than me.
In terms of storage of energy, and what you have to do to get there, it sounds like nobody is saying it's cheaper/more energy dense than gasoline, they're saying you can generate it and store it cheaply, and tie it in with other sources to smooth out the power generation and consumption.
By the time you're talking about tech with a long-life, over time it seems entirely reasonable the incremental cost at the end of that life is pretty damned small once you have it up and running.
You also get the added benefit you can fill your compressed air with pretty much any energy source, and save that power for later. Link a couple of sources together, and the usual whining about "but what about when it's dark outside" goes away.
Someone proposed putting a large bag of air under lake Ontario and filling that. I can't find the study. Best places are either next to a large city (Toronto), nuclear plant (Pickering or Darlington) or wind generation. The sealed bag meant they could use clean, low humidity air. Not sure how they solved the heat problem (compressing the air makes it hot, if you lose the heat then you lose a high percentage of your energy. Ontario doesn't have the political competence to make this viable though. Maybe it would work on the US East coast?
I was curious about efficiency myself, and google and this page (http://energystorage.org/compressed-air-energy-storage-caes) suggests that straightforward energy storage as compressed air is about 42% efficient, increasing to 55% efficient if you can use the waste heat.
If you can store the heat separately to make the process adiabatic, then the efficiency climbs to ~70% - but then you've got the additional cost and complexity of trying to store energy as heat, which is arguably a much more challenging task.
For comparison a Li-ion battery is about 99% efficient, and pumped water is generally in the 60%-80% range, with some claims approaching 90%.
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No, it definitely isn't. A process that sheds heat when done quickly, will still shed heat when done slowly. You might be thinking isothermal (constant temperature), in which case doing it slowly enough is one way to accomplish the goal. There's a lot of confusion between the two, but they're completely different concepts.
Adiabatic basically means "inside a well-insulated container" - it doesn't care how much the temperature changes, so long as no heat enters or leaves. In the case of compressed air storage, it sounds like the normal adiabatic process is to siphon off the heat generated by compression, store it separately in a medium that can store the same amount of heat with a much smaller temperature change and/or volume than the air, and then use it to re-heat the air as the pressure is released.
The Carnot cycle, basis of the internal combustion engine, actually contains two isothermal stages, in which pressure and volume change inversely (PV=constant) as heat is added and removed, and two reversible adiabatic stages where the gas changes temperature while expanding or contracting, without any external thermal transfer.
--- Most topics have many sides worth arguing, allow me to take one opposite you.