Compressed air energy storage

northerner
northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
in Off Grid Solar & Battery Systems #1
It's possible to use water to compress air into tanks or a large vault in order to store excess energy produced from solar or wind power. The compressed air (stored energy) can then be used to pressurize water in order to run a generator and produce electrical power.

Normally, compressing air generates significant heat, and expanding it causes problems with severe cooling. This can be minimized by using water as the delivery mechanism for compressing or expanding the air, and by using higher volume/lower pressure air, and higher pressure/lower volume water. Of course, a larger tank would be necessary if storing air at lower pressures and the efficiency of the entire system would likely be lower than using batteries. The advantage is being able to store as much energy, as there is tank space, and long cycle life (other than system maintenance). Does this sound feasible?
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #2
    Re: Compressed air energy storage
    northerner wrote: »
    Does this sound feasible?

    The complications are the size of the tank needed, it's strength and the high losses for both charging and discharging. If I remember back of napkin calculations, it doesn't work out any cheaper than lead acid taken over 20 year life. Of course, it could last much longer than a lead acid batt...
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  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    #3
    Re: Compressed air energy storage
    stephendv wrote: »
    The complications are the size of the tank needed, it's strength and the high losses for both charging and discharging. If I remember back of napkin calculations, it doesn't work out any cheaper than lead acid taken over 20 year life. Of course, it could last much longer than a lead acid batt...

    Size of the tank in a lower pressure proposal would certainly be a concern. I don't think strength of the tank is an issue, as there are plenty of options with steel or fiber reinforced tanks out there. Round trip efficiency can be as high as 70% according to one company that has designed a compressed air system that also stores and recaptures heat.

    http://lightsailenergy.com/

    It may not be any cheaper to install than lead acid batteries, however, does have potential for a long cycle life with no degradation over time, and is easily scalable (at any time) with very large tanks. This would make it possible to store extra energy in sunnier periods, and use that excess during cloudy spells.
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #4
    Re: Compressed air energy storage

    And how much engergy is required for the water pump?
    While the tank may last a long time the pump will require maintainance and possibly replacement at some time.
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  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    #5
    Re: Compressed air energy storage
    john p wrote: »
    And how much engergy is required for the water pump?
    While the tank may last a long time the pump will require maintainance and possibly replacement at some time.


    Good point john! You'd have to factor in losses with the water pump vs higher thermal losses from using an air pump and the higher pressure air directly, with conventional compressed air storage systems. I know that pumped hydro storage is potentially very efficient, so thinking that it wouldn't be too significant a factor to utilize a water pump. And the pump would require some maintenance and eventual replacement, but also have the potential for a long trouble free lifespan.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #6
    Re: Compressed air energy storage

    Also, may be very noisy. Compared to lead-acid batteries anyway.
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  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    #7
    Re: Compressed air energy storage
    NorthGuy wrote: »
    Also, may be very noisy. Compared to lead-acid batteries anyway.

    That and the fact you'd want to enclose the tank, etc.. in a heated enclosure (or underground bunker), as extreme cold would also affect performance.
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