Systems and methods for foam-based heat exchange during energy storage and recovery using compressed gas

Abstract

In various embodiments, foam is compressed to store energy and/or expanded to recover energy.

What is claimed is: 
     
         1 .- 434 . (canceled) 
     
     
         435 . A method of energy storage and recovery utilizing a power unit comprising a cylinder assembly for at least one of the compression of gas to store energy or the expansion of gas to recover energy, the method comprising:
 compressing gas in the power unit; and   at least one of prior to or during the compression, (i) withdrawing heat-transfer liquid from a first thermal well at a first temperature, and (ii) introducing the heat-transfer liquid into the gas to exchange heat therewith, the heat exchange bringing the heat-transfer liquid to a second temperature higher than the first temperature;   transferring the compressed gas to a compressed-gas store; and   transferring the heat-transfer liquid at the second temperature to at least one of the compressed-gas store or a second thermal well discrete from the first thermal well.   
     
     
         436 . The method of  claim 435 , further comprising:
 transferring compressed gas from the compressed-gas store to the power unit;   expanding the compressed gas in the power unit; and   at least one of prior to or during the expansion, (i) withdrawing heat-transfer liquid from at least one of the compressed-gas store or the second thermal well, and (ii) introducing the heat-transfer liquid into the gas to exchange heat therewith; and   transferring the heat-transfer liquid to the first thermal well.   
     
     
         437 . The method of  claim 436 , wherein expanding the compressed gas in the power unit comprises expanding the compressed gas in a first stage and a second stage each spanning a different pressure range. 
     
     
         438 . The method of  claim 437 , wherein (i) heat-transfer liquid is withdrawn from the compressed-gas store at least one of prior to or during expansion in the first stage and (ii) heat-transfer liquid is withdrawn from the second thermal well at least one of prior to or during expansion in the second stage. 
     
     
         439 . The method of  claim 436 , wherein the heat exchange between the gas and the heat-transfer liquid at least one of prior to or during the expansion renders the expansion substantially isothermal. 
     
     
         440 . The method of  claim 436 , wherein introducing the heat-transfer liquid into the gas at least one of prior to or during expansion comprises spraying the thermally conditioned heat-transfer liquid into the gas. 
     
     
         441 . The method of  claim 436 , wherein introducing the heat-transfer liquid into the gas forms a foam comprising the heat-transfer liquid and the gas. 
     
     
         442 . The method of  claim 441 , further comprising separating at least a portion of the foam into gas and heat-transfer liquid prior to transferring the heat-transfer liquid to the first thermal well. 
     
     
         443 . The method of  claim 435 , wherein compressing the gas in the power unit comprises compressing the gas in a first stage and a second stage each spanning a different pressure range. 
     
     
         444 . The method of  claim 443 , wherein (i) heat-transfer liquid is transferred to the compressed-gas store after or during compression in the first stage and (ii) heat-transfer liquid is transferred to the second thermal well after or during compression in the second stage. 
     
     
         445 . The method of  claim 435 , wherein the heat exchange between the gas and the heat-transfer liquid at least one of prior to or during compression renders the compression substantially isothermal. 
     
     
         446 . The method of  claim 435 , wherein introducing the heat-transfer liquid into the gas at least one of prior to or during compression comprises spraying the thermally conditioned heat-transfer liquid into the gas. 
     
     
         447 . The method of  claim 435 , wherein introducing the heat-transfer liquid into the gas at least one of prior to or during compression forms a foam comprising the heat-transfer liquid and the gas. 
     
     
         448 . The method of  claim 447 , further comprising separating at least a portion of the foam into gas and heat-transfer liquid before transferring the heat-transfer liquid at the second temperature to at least one of the compressed-gas store or a second thermal well discrete from the first thermal well. 
     
     
         449 . The method of  claim 435 , further comprising storing, in the second thermal well, waste thermal energy produced by the power unit. 
     
     
         450 . The method of  claim 435 , further comprising exchanging thermal energy between the surrounding environment and at least one of the first thermal well or the second thermal well. 
     
     
         451 . The method of  claim 450 , wherein thermal energy is exchanged with the surrounding environment while the power unit is neither compressing nor expanding.