Dead-volume management in compressed-gas energy storage and recovery systems

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.

What is claimed is: 
     
         1 . An energy storage and recovery system comprising:
 a cylinder assembly for at least one of expanding gas to recover energy or compressing gas to store energy;   a high-side component, selectively fluidly connected to the cylinder assembly, for at least one of (i) supplying gas to the cylinder assembly for expansion therein or (ii) accepting gas from the cylinder assembly after compression therein;   a low-side component, selectively fluidly connected to the cylinder assembly, for at least one of (i) supplying gas to the cylinder assembly for compression therein or (ii) accepting gas from the cylinder assembly after expansion therein; and   a control system for operating the cylinder assembly to perform at least one of (i) a pre-compression of gas therewithin prior to admission therein of gas for expansion, thereby reducing coupling loss between the cylinder assembly and the high-side component, or (ii) a pre-expansion of gas therewithin prior to admission therein of gas for compression, thereby reducing coupling loss between the cylinder assembly and the low-side component.   
     
     
         2 . The system of  claim 1 , further comprising a sensor for sensing at least one of a temperature, a pressure, or a position of a boundary mechanism within the cylinder assembly to generate control information, the control system being responsive to the control information. 
     
     
         3 . The system of  claim 2 , wherein the control system is configured to operate the cylinder assembly, during at least one of (i) pre-compression of gas therewithin or (ii) expansion of gas therewithin, based at least in part on control information generated during at least one of (i) a previous gas expansion within the cylinder assembly or (ii) a previous pre-compression of gas within the cylinder assembly. 
     
     
         4 . The system of  claim 2 , wherein the control system is configured to operate the cylinder assembly, during at least one of (i) pre-expansion of gas therewithin or (ii) compression of gas therewithin, based at least in part on control information generated during at least one of (i) a previous gas compression within the cylinder assembly or (ii) a previous pre-expansion of gas within the cylinder assembly. 
     
     
         5 . The system of  claim 1 , wherein the high-side component comprises a compressed-gas storage reservoir. 
     
     
         6 . The system of  claim 1 , wherein the high-side component comprises a second cylinder assembly for at least one of compressing gas or expanding gas within a pressure range higher than a pressure range of operation of the cylinder assembly. 
     
     
         7 . The system of  claim 1 , further comprising a second cylinder assembly for at least one of compressing gas or expanding gas within a pressure range higher than a pressure range of operation of the cylinder assembly, wherein the high-side component comprises a mid-pressure vessel for containing gas at a pressure within both of or between pressure ranges of operation of the cylinder assembly and the second cylinder assembly. 
     
     
         8 . The system of  claim 1 , wherein the low-side component comprises a vent to atmosphere. 
     
     
         9 . The system of  claim 1 , wherein the low-side component comprises a second cylinder assembly for at least one of compressing gas or expanding gas within a pressure range lower than a pressure range of operation of the cylinder assembly. 
     
     
         10 . The system of  claim 1 , further comprising a second cylinder assembly for at least one of compressing gas or expanding gas within a pressure range lower than a pressure range of operation of the cylinder assembly, wherein the low-side component comprises a mid-pressure vessel for containing gas at a pressure within both of or between pressure ranges of operation of the cylinder assembly and the second cylinder assembly. 
     
     
         11 . The system of  claim 1 , further comprising a load mechanically coupled to the cylinder assembly and at least one of (i) driven by the cylinder assembly during gas expansion or (ii) driving the cylinder assembly during gas compression. 
     
     
         12 . The system of  claim 11 , wherein the load comprises at least one of a mechanical crankshaft or a hydraulic pump/motor. 
     
     
         13 . The system of  claim 1 , further comprising a heat-transfer subsystem for thermally conditioning gas during at least one of compression or expansion thereof. 
     
     
         14 . The system of  claim 13 , wherein the heat-transfer subsystem comprises a mechanism for introducing heat-transfer fluid into the gas. 
     
     
         15 . The system of  claim 14 , wherein the mechanism comprises at least one of a spray head or a spray rod. 
     
     
         16 . The system of  claim 13 , wherein the heat-transfer subsystem comprises a heat exchanger for thermally conditioning at least one of gas from the cylinder assembly or heat-transfer fluid. 
     
     
         17 . The system of  claim 13 , wherein the heat-transfer subsystem comprises at least one of (i) a mixing chamber for forming foam from gas and heat-transfer fluid or (ii) a screen for altering at least one of average bubble size or bubble-size variance of foam comprising gas and heat-transfer fluid.