Compressed Air Energy Storage

Steven Lake
Steven Lake Solar Expert Posts: 402 ✭✭
in General Solar Power Topics #1
http://www.sustainableplant.com/2013/05/ins-and-outs-of-compressed-air-energy-storage/

It would seem that our local mad scientist wasn't all that crazy when he came up with a similar idea to this not long back. :) Basically take excess energy that's generated but not needed and store it as compressed air. And then when it's needed later on, release it into special air powered generators and reap the benefits. :)
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Compressed Air Energy Storage

    Anyone measured the efficiency of this?
    A lot of the energy going in to the compression will be turned into heat, which then radiates off as a loss. Release the compressed air ... more loss. Not that there aren't losses in any storage method.

    Somewhere on the forum is another thread or two about compressed air storage. Let's see ...

    http://forum.solar-electric.com/showthread.php?19692-Compressed-air-energy-storage&highlight=compressed

    http://forum.solar-electric.com/showthread.php?15932-compressed-air-generators&highlight=compressed

    And a mention here: http://forum.solar-electric.com/showthread.php?16002-Hello-All!-Introduction-and-a-question&highlight=compressed

    Of course pressurizing a liquid could also be used.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #3
    Re: Compressed Air Energy Storage

    Yes, to get decent efficiency compared to batteries requires sophisticated heat transfer and recovery equipment, which in turn does not work particularly well if you have no place to store the extra heat for the length of time that you need to store your energy in the pressurized gas. For some applications, like very short term stop and start delivery vehicles, storing the compressed gas in an insulated tank improves the overall efficiency quite a bit.
    SMA SB 3000, old BP panels.
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  • Mountain Don
    Mountain Don Solar Expert Posts: 494 ✭✭✭
    #4
    Re: Compressed Air Energy Storage

    Anyone with any amount of experience in using pneumatic tools like drills, grinders and similar rotary tools can attest to the high volumes of air these use. I would think this to be a major stumbling block in implementing pressurized air storage an an energy medium. I did some research into some air motors a few years ago. I ended up non being any more impressed than I was in the beginning.

    The 5 HP compressor in the workshop has a cooling system for the compressed air just like a refrigerator.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
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  • gww1
    gww1 Solar Expert Posts: 963 ✭✭
    #5
    Re: Compressed Air Energy Storage

    Some people are using exess pumping water to storage tanks/ponds as an opertunity load to be used during low sun wind times. Not effeciant but maby better then not using it at all.
    gww
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #6
    Re: Compressed Air Energy Storage
    Mountain Don wrote: »
    The 5 HP compressor in the workshop has a cooling system for the compressed air just like a refrigerator.
    Yup, and that makes the air easier to handle, but it wastes energy in the process.
    Now if only they could add a Stirling cycle heat engine to use that heat to pump more air..    . :)
    SMA SB 3000, old BP panels.
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  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    #7
    Re: Compressed Air Energy Storage

    I don't see it as a great system either, given all the heat issues you mention. *HOWEVER*, it does provide a good application as a green way to build up and store compressed air for use in your air tools if you use them a lot. We've got a farmer just north of me who actually does that. He uses so much air powered stuff that he's got a windmill for water, one for compressed air, and one for electricity. So I can see this having shop applications in the air tool department, and perhaps as an "overflow" system for solar or wind energy.

    I say that because I've always griped about the huge amounts of wasted energy I see coming off our systems where they start charging at sunup (solar) or when the winds kick up (wind turbine) and the batteries get to full power 2-3 hours in and the rest of the energy is dumped into dummy loads, utterly wasting it. Then when you need it later on a week, two weeks down the line because you exceeded capacity that day, or the sun/wind wasn't enough to fully charge the batteries, or charge them at all in some cases, you're having to waste gas topping off the batteries.

    I've actually considered this as an idea for our house and possible at least one of the family farms as a way to store excess energy where I hit my maximum required input to charge my bank. So rather than waste the energy I just put it into storage, or "bank" it, at which point if I lost some of it to heat, so what? It's excess energy. The critical time is when you're charging as you need max performance for that. But when you're banking extra that's beyond the capacity or needs for charging of the bank, then a bit of waste can be tolerated as it's all extra. My goal is just to try and minimize waste and later take some of that excess and use it when my main system isn't able to give me enough to get by. Also, the large bank of compressed air is a nice bonus too given all the air tools we have. :)
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  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    #8
    Re: Compressed Air Energy Storage

    PS, sorry for the late reply. It's harvest season and we've been getting our butts kicked on the farm with all kinds of work. We only just got our beans out day before yesterday, so we're way behind on our work. Plus we're putting up buildings, so that doesn't give me much web time anymore. ^_^;;
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    #9
    Re: Compressed Air Energy Storage

    Since half the power used to compressed air is lost as heat, compressing air for energy storage isn't a great option.
    It is a better option than a dump load.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #10
    Re: Compressed Air Energy Storage

    The french car maker Peugeot-Citroen is experimenting with a Hybrid air car: http://www.autoexpress.co.uk/car-reviews/87713/peugeot-2008-hybrid-air-prototype-review
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  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    #11
    Re: Compressed Air Energy Storage
    oil pan 4 wrote: »
    Since half the power used to compressed air is lost as heat, compressing air for energy storage isn't a great option.
    It is a better option than a dump load.
    Yeah, that was my idea. It's better than wasting the energy on a dump load. Even if the energy loss is 50%, I'm still saving 50% of my overage for a later time, which to me is more practical and ultimately cheaper than upsizing my battery bank.
    stephendv wrote: »
    The french car maker Peugeot-Citroen is experimenting with a Hybrid air car: http://www.autoexpress.co.uk/car-reviews/87713/peugeot-2008-hybrid-air-prototype-review
    Yeah, been following that. I'm hoping that they get that sorted out soon because once their design is final I can coopt their engine and tank pressurization idea for my needs. I admit that I probably wouldn't need the compressor side of it as I can redneck something on my own to meet my needs. But the air motor would be a big boon for me as far as taking the compressed air and turning it into extra energy when needed. The only question I'd have is whether I should make it a manual switch, or automatic. IE, if the bank drops below 50% due to unusually high usage or low solar/wind input over an extended period the air motor kicks in to pick up the slack on the battery charging side of things.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #12
    Re: Compressed Air Energy Storage
    oil pan 4 wrote: »
    Since half the power used to compressed air is lost as heat, compressing air for energy storage isn't a great option.
    It is a better option than a dump load.
    Half the power is lost unless you use an insulated tank and do not have to hold air very long. The heat input will come back out again when you expand the gas into your motor(s).
    SMA SB 3000, old BP panels.
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  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    #13
    Re: Compressed Air Energy Storage

    The compressors head is going to get hot and lose most of the heat.
    You can try to save the heat, but I think you are better off just cooling it off, separating out the water and cramming as much air into the tank at ambient temperature as possible.
    It sounded like the OP wanted to hold the air for hours if not days.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #14
    Re: Compressed Air Energy Storage
    oil pan 4 wrote: »
    The compressors head is going to get hot and lose most of the heat.
    How true.
    At a craft fair last weekend a guy was selling piston type fire starters. Metal piston with o-ring in a metal cylinder, both with wood handles. A very small recess in the piston to hold some wisps of charred cotton.
    One quick push and the temperature of the char gets up to ~700 degrees and produces a nice glow match that you can pull back out and use.
    SMA SB 3000, old BP panels.
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  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    #15
    Re: Compressed Air Energy Storage

    Yeah, if I was to use the idea it'd be stored for days and possible weeks or months, or however long it would be until I needed it. Give that it's green compressed air I'd probably use any air stored as part of my overage for our power tools and the rest as extra energy to make up for when the inputs aren't enough to keep the bank charged, like this time of year for example. Our inputs for the past week have been utterly horrible due to all the clouds and snow. The banks have been staying charged, but we're quickly heading into a period where I have to start playing the grinch with all of our power usage. Again, I don't have anything like this yet, but I'm considering it as it'd be a huge help. The only problem would be coming up with enough capacity to store all the volume I'd hope to capture.
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