Dead-volume management in compressed-gas energy storage and recovery systems
First Claim
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1. A method of increasing efficiency of an energy-recovery process performed in a first cylinder assembly and a second cylinder assembly in which gas is collectively expanded from an initial pressure to a final pressure, the method comprising:
- pre-compressing gas in the first cylinder assembly to approximately the initial pressure;
following the pre-compression, admitting compressed gas at the initial pressure into the first cylinder assembly, the pre-compression reducing coupling loss during the admission of compressed gas, wherein the admission of compressed gas comprises (i) withdrawing compressed gas from a storage reservoir, (ii) withdrawing heat-transfer fluid from the storage reservoir, (iii) mixing the compressed gas and the heat-transfer fluid within a mixing chamber, separate from the storage reservoir, to form a foam at the initial pressure, and (iv) admitting the foam into the first cylinder assembly;
substantially isothermally expanding the gas in the first cylinder assembly to a mid-pressure between the initial pressure and the final pressure by mingling, within the foam, substantially all of the gas with heat-transfer fluid in the first cylinder assembly, thereby maintaining substantially all of the gas at substantially the same temperature during expansion;
completing a partial expansion cycle by exhausting (i) only a portion of the expanded gas and (ii) at least a portion of the heat-transfer fluid out of the first cylinder assembly into a mid-pressure vessel at the mid-pressure;
mingling compressed gas and heat-transfer fluid within the mid-pressure vessel to form a mid-pressure foam at the mid-pressure;
admitting mid-pressure foam into a second cylinder assembly;
expanding the compressed gas of the mid-pressure foam within the second cylinder assembly to the final pressure;
exhausting gas at the final pressure from the second cylinder assembly; and
repeating the foregoing steps at least once, thereby performing at least one additional expansion cycle.
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Abstract
In various embodiments, coupling losses between a cylinder assembly and other components of a gas compression and/or expansion system are reduced or eliminated via valve-timing control.
721 Citations
18 Claims
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1. A method of increasing efficiency of an energy-recovery process performed in a first cylinder assembly and a second cylinder assembly in which gas is collectively expanded from an initial pressure to a final pressure, the method comprising:
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pre-compressing gas in the first cylinder assembly to approximately the initial pressure; following the pre-compression, admitting compressed gas at the initial pressure into the first cylinder assembly, the pre-compression reducing coupling loss during the admission of compressed gas, wherein the admission of compressed gas comprises (i) withdrawing compressed gas from a storage reservoir, (ii) withdrawing heat-transfer fluid from the storage reservoir, (iii) mixing the compressed gas and the heat-transfer fluid within a mixing chamber, separate from the storage reservoir, to form a foam at the initial pressure, and (iv) admitting the foam into the first cylinder assembly; substantially isothermally expanding the gas in the first cylinder assembly to a mid-pressure between the initial pressure and the final pressure by mingling, within the foam, substantially all of the gas with heat-transfer fluid in the first cylinder assembly, thereby maintaining substantially all of the gas at substantially the same temperature during expansion; completing a partial expansion cycle by exhausting (i) only a portion of the expanded gas and (ii) at least a portion of the heat-transfer fluid out of the first cylinder assembly into a mid-pressure vessel at the mid-pressure; mingling compressed gas and heat-transfer fluid within the mid-pressure vessel to form a mid-pressure foam at the mid-pressure; admitting mid-pressure foam into a second cylinder assembly; expanding the compressed gas of the mid-pressure foam within the second cylinder assembly to the final pressure; exhausting gas at the final pressure from the second cylinder assembly; and repeating the foregoing steps at least once, thereby performing at least one additional expansion cycle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification