Systems and methods for efficient two-phase heat transfer in compressed-air energy storage systems

Abstract

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

1 . A method of recovering energy, the method comprising:
 transferring a first foam to a first cylinder assembly, the first foam having a first foam expansion ratio;   expanding the first foam in the first cylinder assembly, thereby recovering energy therefrom;   thereafter, transferring a second foam to a second cylinder assembly different from the first cylinder assembly, the second foam having a second foam expansion ratio larger than the first foam expansion ratio; and   expanding the second foam in the second cylinder assembly, thereby recovering energy therefrom.   
     
     
         2 . The method of  claim 1 , further comprising exhausting the expanded second foam from the second cylinder assembly. 
     
     
         3 . The method of  claim 2 , wherein at least a gaseous portion of the expanded second foam is exhausted to ambient atmosphere. 
     
     
         4 . The method of  claim 1 , wherein (i) after expanding the first foam, the expanded first foam is exhausted from the first cylinder assembly and (ii) the second foam comprises at least a portion of the expanded first foam. 
     
     
         5 . The method of  claim 4 , wherein the expanded first foam is exhausted into a foam vessel, and further comprising circulating heat-transfer liquid in the foam vessel to form the second foam. 
     
     
         6 . The method of  claim 1 , further comprising:
 after expanding the first foam, separating at least a portion of the expanded first foam into gaseous and liquid components; and   forming the second foam by introducing heat-transfer liquid into the gaseous component of the expanded first foam.   
     
     
         7 . The method of  claim 6 , wherein the at least a portion of the expanded first foam is separated via at least one of mechanical separation or application of ultrasound energy. 
     
     
         8 . The method of  claim 7 , wherein the at least a portion of the expanded first foam is separated via mechanical separation by at least one of a blade, a shear, a baffle, or a centrifuge. 
     
     
         9 . The method of  claim 6 , further comprising storing the liquid component of the expanded first foam. 
     
     
         10 . The method of  claim 1 , wherein a mass ratio of the first foam is approximately equal to a mass ratio of the second foam. 
     
     
         11 . The method of  claim 1 , further comprising altering at least one of an average cell size or a uniformity of cell size of the first foam before expanding the first foam. 
     
     
         12 . The method of  claim 1 , further comprising altering at least one of an average cell size or a uniformity of cell size of the second foam before expanding the second foam. 
     
     
         13 . The method of  claim 1 , wherein a foam mass ratio of the first foam is selected from the range of 1 to 4. 
     
     
         14 . The method of  claim 1 , wherein a foam mass ratio of the second foam is selected from the range of 1 to 4. 
     
     
         15 . The method of  claim 1 , wherein the first foam is expanded substantially isothermally and the second foam is expanded substantially isothermally. 
     
     
         16 . The method of  claim 1 , further comprising forming the first foam by mingling heat-transfer liquid and compressed gas. 
     
     
         17 . The method of  claim 16 , further comprising controlling a void fraction of the first foam by controlling a rate of transfer of heat-transfer liquid into the compressed gas. 
     
     
         18 . The method of  claim 17 , further comprising sensing at least one of a pressure or a temperature within the first cylinder assembly, wherein the rate of transfer is controlled in response thereto. 
     
     
         19 . The method of  claim 1 , wherein expanding the first foam and expanding the second foam both drive a crankshaft mechanically coupled to the first and second cylinder assemblies. 
     
     
         20 .- 451 . (canceled)