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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.
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.
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
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.