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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) 307

Posted by msmash from the closer-look dept.
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.
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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 More

Forget Better Batteries, Nothing That Exists Or is in Development Can Store Energy as Well, And as Cheaply, as Compressed Air

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  • I guess some places are air tight, but the rock where I live if full of holes and I could only imagine would leak profusely.

    • Re:Is it air tight (Score:4, Funny)

      by olsmeister ( 1488789 ) on Monday October 29, 2018 @12:24PM (#57555691)
      Hold my beer. I have a plan. [amazon.com]

      • The beauty of this is that you can also use the Heat as well as the Work.

        when compressing it will get hot, so use this for heating hot water. And when you release it things get cold. So chill your beer.

        • Would Carbon Dioxide make more sense? It turns to liquid around 800PSI, so the stored volume is greater and it doesn't require increasing the pressure to store more energy (just increase the volume).
          Finally, when you extract it you can make La Croix sparking soda's for an entire town's water supply at no cost.

    • Re: (Score:2)

      by lgw ( 121541 )

      And of course it's somewhat dangerous (a problem with most dense energy storage). At least stored underground it won't kill people if it fractures (if planned right). Seems like another "awesome where it works" plan, much like pumping water up hill is darn good if you have an abundance of water, and a hill.

      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). I know the biggest presses store po

      • And of course it's somewhat dangerous (a problem with most dense energy storage). At least stored underground it won't kill people if it fractures (if planned right). Seems like another "awesome where it works" plan, much like pumping water up hill is darn good if you have an abundance of water, and a hill.

        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). I know the biggest presses store power and operate at 4000+ PSI, but they're routinely checked for flaws (the US has 2 50,000 ton presses that make e.g. most large or military aircraft structural elements, one was down for several years when stress fractures were discovered).

        Like everything, it probably has it's niche and place in the world but isn't ideal for everything. Storing excess electrical energy? Maybe, although I thought that it was not very efficient.

        Cars? No, tried that several times over many decades, not safe, not efficient, not very good.

        There probably is some scenarios where it works though.

      • Re:Is it air tight (Score:5, Funny)

        by zieroh ( 307208 ) on Monday October 29, 2018 @01:15PM (#57556115)

        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.

        • Re: (Score:2)

          by lgw ( 121541 )

          It would be cool to find an energy storage solution that was great at the house level, not just at the industrial level. Sadly, this isn't that. Making use of caverns where the rock is strong enough is very cool, where you can do it, but is clearly something for power companies to do, not homeowners.

          • Thermal storage is practical for home heating. It's very common in electrically heated homes. The heaters run at night when electricity is cheaper, and heat up a big chunk of brickwork. Then in the day, air is circulated through the bricks. Only good for heating purposes though, and on a currency-per-Joule basis natural gas is usually a cheaper means for home heating, so you only see electric heating where gas is not available.

          • Re: (Score:3, Interesting)

            by Lab Rat Jason ( 2495638 )

            The answer lies in the phrase "economies of scale." There is almost NOTHING that you can do in your home, and have it be more efficient than the industrial version of the same. From baking bread to energy storage... industry has you beat. Solar power, wind power, battery storage, compressed air storage, geothermal... the list just keeps going... This is why as much as I love solar, I'll probably never have it on my house. The industry will find a way to do it better than I can, and I'm OK with that. He

        • I like the idea of deep water storage for places where that's convenient. I realize this probably isn't a huge issue considering the actual forces involved, but I'm not too fond on the idea of pumping water out of caves and then over-pressurizing them. Although if we get enough pressure then we might have the opportunity to set a new record. [businessinsider.com]

        • They only let you use that 20% off coupon for 1 item, no matter how much begging and pleading you do. Wait, maybe if each engineer had their own coupon...

        • Well, there goes my idea of a Beowulf cluster of compressed air tanks.

    • Re:Is it air tight (Score:4, Informative)

      by NEDHead ( 1651195 ) on Monday October 29, 2018 @01:13PM (#57556095)

      Small nukes can create a large cavern with fused glass walls

    • Comment removed based on user account deletion

  • Comment removed (Score:5, Funny)

    by account_deleted ( 4530225 ) on Monday October 29, 2018 @12:22PM (#57555673)
    Comment removed based on user account deletion

  • Seems impractical at small scale (Score:5, Interesting)

    by Linsaran ( 728833 ) on Monday October 29, 2018 @12:25PM (#57555709) Homepage

    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.

    • But instead of blaming the dog, you can blame your cellphone.

    • Re:Seems impractical at small scale (Score:4, Interesting)

      by alvinrod ( 889928 ) on Monday October 29, 2018 @12:38PM (#57555819)
      It seems like this is being pushed for large scale storage operations and isn't something that anyone would try to miniaturize. If that's the case, it makes the most sense to locate the compressors near the generation site. If you can build the storage beneath your wind or solar farm, there aren't too many people around to complain about any noise.

      I'm sure there's some other catch though. I understand any type of large scale power storage is going to be expensive in general, so you might not see a lot of action here, but if there's easy money being left on the table, someone should have jumped by now. I'm guessing that there might be some wishful thinking buried in here that runs afoul of physics, much like all of those kickstarters for solar powered water bottles that are mathematically impossible.

  • I was curious (Score:5, Informative)

    by Jfetjunky ( 4359471 ) on Monday October 29, 2018 @12:25PM (#57555713)
    I was curious about the energy density of this proposed solution. I dug in the comments and found a reply from the author of the study. Kinda interesting.

    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!

    • you would be storing ~23MJ in each cubic meter of cavern

      Wow. So, to put that claim in perspective, there's a Wikipedia page listing energy densities of common storage media [wikipedia.org]. Having converted CAES from MJ/m^3 to MJ/L, here are some highlights for comparison:

      - Lithium Ion Battery: 0.9 - 2.63 MJ/L
      - Alkaline Battery: 1.3 MJ/L
      - Flywheel: 5.3 MJ/L
      - Gunpowder: 5.9-12.9 MJ/L
      - Gasoline: 34.2 MJ/L
      - Coal: 38 MJ/L
      - Carbohydrates: 43 MJ/L
      - Protein: 105.1 MJ/L
      - Tritium: 158 MJ/L
      - Deuterium: 15,822 MJ/L
      - CAES: 23,000 MJ/L
      - Plutonium 238: 43,277,631 MJ/L
      - Thorium (in a breeder)

      • It looks like you forgot to convert from m^3 to liters. Isn't the right number around 31 MJ/L? So about the same as gas, which is not bad.

        • I converted...the wrong way. Instead of dividing by 1000, I multiplied, so I'm off by six orders of magnitude. The correct number, as many of the other replies have already noted, is about 0.023 MJ/L.

  • Completely unsubstantiated headline. (Score:5, Insightful)

    by Anonymous Coward on Monday October 29, 2018 @12:29PM (#57555745)

    Forget Better Batteries, Nothing That Exists Or is in Development Can Store Energy as Well

    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.

    • Yeah there's a pattern of this. Yesterday it was "New Zealand Chooses Google Chromebooks Over Microsoft Windows 10 For Education", when the story, hidden behind an additional layer of unprofessional blogging, said no such thing. The problem is in the sources Slashdot promotes to represent the story. There are usually many versions of the same story submitted, so it's a shame inaccurate (and often sensationalist and blatantly biased) ones keep making it through.

    • From the article, paragraph 3:

      However nothing that exists or is in development can store energy as well, and as cheaply, as compressed air.

      Pretty straightforward comparison to everything else, which includes batteries and pumped hydro.

      The scholarly article [psu.edu] that is the primary reference does not directly compare Wind/CAES to Wind/Battery, but the long-term costs per GW for a CAES plant vs a battery farm are very likely in favor of CAES due to the extremely low cost of storage. The GW storage of a large salt

  • When you compress air, the temperature goes up. This heat then dissipates into the environment. That is undoubtedly some of the energy used to compress the air, so you've lost some efficiency there.

    • When you release compressed air, it cools the environment. It's the nature of it, and air conditioning.

  • You know, the stuff most people directly use every day?

  • Energy and Safety. (Score:3)

    by jellomizer ( 103300 ) on Monday October 29, 2018 @12:34PM (#57555787)

    Compressed Air Energy has one major drawback. If there is a problem it could cause an explosion. And unlike from chemical energy storage such explosions cannot be monitored and cutoff as quickly.
    I once had a tanker truck drive by me, and at the same time, the tanker had buckled inwards a dent (probably from pressure differences from changing altitude) I needed to stop my car and inspect it, because that little buckle felt like something had hit my car from that pressure wave.

    There is a lot of danger in compressed air.

    This can be mitigated with proper maintenance and monitoring. But this is the same with nuclear energy, Companies don't want to do it, because it costs money that cuts into its profits, and governments don't want to do it, because the Tax payers need to pay for it.

    • Re: (Score:2)

      by Puls4r ( 724907 )
      It has a lot more drawbacks than that. Compressing air is incredibly inefficient. Incredibly. The starting point for their entire premise is garbage.

  • nothing that exists or is in development can store energy as well, and as cheaply, as compressed air

    The curious might ask for some references that prove this point.

  • Energy is banked as potential energy by moving massive chunks of concrete up an incline via rail. Later on, the chunks are coasted back down the incline, reintroducing the energy into the electrical grid. >80% efficiency!

  • Not sure about the thermodynamic efficiency difference of producing high pressure air vs. liquid air, but in terms of volume efficiency, liquid air may be a better choice. There are a lot of applications of gasses that have been turned to liquids and allowed to escape at atmospheric pressure. The escaping gas might be hooked up to a small generator to make electricity that could power some devices for charging batteries or other uses.
  • .. then see which direction it shoots off in when you let it all out simultaneously.

    Or just build the world's largest whistle.

  • Headline is dubious at best (Score:3)

    by Nethemas the Great ( 909900 ) on Monday October 29, 2018 @12:42PM (#57555861)
    All you have to do is observe the heat cast off by such a process from compressor to storage to know this to be a dubious claim. The greater the storage pressure, the worse the efficiency becomes. Never mind the challenges, expense, and hazards involved in implementing and maintaining pressure bottles. If you're free to concern yourself solely with energy density, as in this case with HPA then, you might as well bring nuclear fission--the gold standard for energy density--back on the table.

  • ...but what we really, really, really need is storage for vehicle propulsion. Still a battery, or maybe a supercapacitor, is required.

  • Ask you need is one leaky hose or device to screw up whatever efficiency the might be. Ever use air hoses in a shop? And people aren't going to absorb the costs of super close tolerance machining on every part to get around this. The practicalities of this make it stupid. Critical thinking is required.

  • How about gravity/weight energy storage? No need for airtight containers, the only danger is at the bottom of the tunnel/shaft, etc. Probably at least on par with the energy storage and cost of compressed air, maybe even better.

  • Efficiency of conversion? Probably not so good. (Score:5, Interesting)

    by Luminary Crush ( 109477 ) on Monday October 29, 2018 @12:57PM (#57555949)
    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/ [quincycompressor.com]

    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?

    • it can be a little better than that, where compressed air is 15% efficient. in other words 85% of energy is wasted. those of us who work in industrial engineering know that fact. it's a lousy energy storage system, to thing some "greenie" would advocate it is hilarious.

  • not as great as it sounds (Score:5, Interesting)

    by schematix ( 533634 ) on Monday October 29, 2018 @12:58PM (#57555961) Homepage
    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.

    • I thought compression was an extremely wasteful process? did they find ways that involved less losses? I'm only guessing expansion works better because steam power is quite good.

      What about exploring tanks that leverage deep water pressure to cut down costs?

      • Yah they did have a solution. I know a little more than i'm going to post ,but NDA yadda yaddda. The info below could be determined from public press releases they made. Don't think of it as a traditional air compressor. Think of it more along the lines of they mixed air, along with a secret ingredient, and compressed that. The secret ingredient(s) changed the thermodynamics of the process to where the temperature of the resulting compressed gas was no more than the temperature going in. In other words, t

  • CAES can only be cost-effective when built on top of an existing disused mine in the appropriate type of rock. We still need better batteries for all the places where you might need electricity and don't have a convenient abandoned mine to convert. Mobile applications come to mind.

  • You know, those were I need a steel bottle and noisy generator to use compressed air as energy source? No? So maybe do _not_ forget about new battery tech?

  • ... the obvious, existing, efficient, works today, energy storage. Pump water up-hill. Release it downhill. Low tech. Massive storage amounts with a big enough reservoir. In use at multiple sites in California, often just to make money on power arbitrage (ie, San Louis dam, reservoir, and fore-bay).

  • What's the energy efficiency of an air compressor? What's the efficiency of the generator the compressed air drives later? What massive volume of space do you need as an air tank to make this even remotely practical? What pressure is necessary to make it practical, and how safe is it in reality to store massive amounts of compressed air at that pressure? Sounds incredibly lossy to me.

  • This isn't anything new, and not any kind of scientific analysis. This is a wishful thinking opinion piece on a technology that has yet to be proven economically viable.

    So, how many silly ideas are we going to have to shoot down before we come to a realization that we already have a solution with decades of proving itself economically viable, reliable, incredibly safe, and effectively unlimited? That would be nuclear power by the way.

    These air storage facilities would be incredibly large infrastructure pr

  • Seems all energy storage methods have pros and cons and this one seems to not be superior across the board from the replies I’m seeing. I remember seeing years ago compressed air as an energy storage type for cars. What I’m thinking though is it seems this method would make a really great adjunct storage solution where you need cooling. You have to add heat back in to get the efficiency back up, seems server farms could make great use of the added cooling. Maybe electric cars in warmer climb

  • Every time you compress air, it is heated. The heat is lost energy. Every time you release air pressure, the air is cooled. More lost energy. No mention by the author, no analysis of the amount of lost energy. Bullshit article.

  • Bags under lakes (Score:5, Interesting)

    by FeelGood314 ( 2516288 ) on Monday October 29, 2018 @02:15PM (#57556529)
    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?

    • Re:Bags under lakes (Score:5, Informative)

      by CanadianMacFan ( 1900244 ) on Monday October 29, 2018 @02:43PM (#57556685)

      Here's a review [euanmearns.com] of the project you are thinking of and another way of doing underwater compressed air storage. I was looking for this project to post before I came across your message. There's a diagram showing how the system in Toronto works. Unfortunately there's no detailed numbers on how efficient or competitive it is.

      They are storing the heat captured during compressing to heat up the air when they decompress the air.

  • Every set includes the empty set, so technically there is a linked article and it is sucks---like the vacuum it is.

    Also, the OP spouts hot air, like the empty claims asserted.

  • High Compression Air Powered Vehicles - accident....*boof* pressure tank integrity failure and all the occupants along with those in neighboring vehicles are instantly frozen to death as solid icecorpsicles.

  • If its not adiabatic the efficiency is only 25% (Score:3)

    by n2hightech ( 1170183 ) on Monday October 29, 2018 @03:47PM (#57557107)
    This assumes an adiabatic process. That means that you cannot loose any heat form the compressed air. So the storage tank would have to be insulated in a vacuum Dewar not practical or very expensive. A system that stores compressed air in a non adiabatic way, just about all the systems in existence, are only about 25% efficient. This really sucks compared to batteries.

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