Compressed CO2
for alternative
energy storage
MESH 520 - 5.1
Shai Ehrmann
March 31, 2023
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Compressed air energy storage (CAES):
● Excess energy used to compress air
● Air compressed and stored in cavern, drained
reservoir, or other large container, typically
● Air heated and released through turbine to recover
energy
● “Battery” similar to pumped hydro storage
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Compressed air vs. compressed CO2
● CO2 has a higher critical temperature than the
typical air mixture
○ Can liquefy at room temperature at >67 bar
(>972 psi)
● CO2 in liquid state requires only ~0.2% the volume
of ambient gaseous CO2
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LAES<->CAES
● The novel energy storage system takes advantage of the relatively easy liquefaction of CO2, making it a
Liquid Air Energy System
● Energy is stored as a liquid, requiring less volume
● Heat from the compressor is stored or co-cycled to regasify CO2
○ Technically considered an adiabatic CAES(A-CAES/A-LAES) since it does not require external
heat for operation
● CO2 is released into a large gas chamber (i.e. closed loop)
● CAES -> LAES to “charge”; LAES->CAES to “discharge”
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Currently only trial by Energy Dome
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Considerations
● Can work together with carbon capture, instead of injecting
● Levelized Cost of Storage (LCOS) <$100 per MWh (comparable to Li-ion) and
projected to achieve $50-60/MWh
● Scalable, unlike cavern-based CAES
● Efficiency >75% with heat co-cycle
● 4 MWh/2 MW pilot plant complete, 200 MWh/20 MW plant in progress
● Long-term storage possible
● Still experimental technology
● High pressure system (70 bar+)
● Not market-available, cost unknown but likely high
● Storage capacity limited by bladder size
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References
Pacific Northwest National Laboratory. (2019). PNNL: Compressed Air Energy Storage. Caes.pnnl.gov. https://caes.pnnl.gov/
Hydrostor. (2022). Hydrostor Announces Key Milestones for its 500 MW Advanced Compressed Air Energy Storage System in Southern California – Hydrostor. Hydrostor.
https://www.hydrostor.ca/hydrostor-announces-key-milestones-for-its-500-mw-advanced-compressed-air-energy-storage-system-in-southern-california/
EqualOcean. (2022). Zhangjiakou grid connection of the first 100 MW advanced compressed air energy storage project. EqualOcean.
https://equalocean.com/briefing/20220107230110116
Crownhart, C. (2022). This company wants to use carbon dioxide to store renewable power on the grid. MIT Technology Review.
https://www.technologyreview.com/2022/05/03/1051644/carbon-dioxide-storage-energy-dome/
Energy Dome. (2023). Home. Energy Dome. https://energydome.com/
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