Fluid-flow control in energy storage and recovery systems

Abstract

In various embodiments, compressed-gas energy storage and recovery systems feature one or more valves, which may be disposed within end caps of cylinder assemblies in which gas is expanded and/or compressed, for admitting fluid to and/or exhausting fluid from the cylinder assembly.

What is claimed is: 
     
         1 . A method of energy recovery utilizing a system comprising (a) a cylinder assembly having an interior compartment, (b) a first valve for admitting fluid into the interior compartment of the cylinder assembly, (c) a second valve for exhausting fluid from the interior compartment of the cylinder assembly, each of the first and second valves comprising a gated port and an outside port, and the first and second valves controlling fluid communication with the interior compartment via respective separate fluid paths, (d) a first actuation mechanism for actuating the first valve, (e) a second actuation mechanism for actuating the second valve, and (f) a control system electrically connected to and configured to control the first and second actuation mechanisms to actively actuate the first and second valves, the control system executing a stored control application, wherein (i) the first valve is configured to check open, in the absence of actuating control signals from the control system, at a first passive checking pressure, and (ii) the second valve is configured to check open, in the absence of actuating control signals from the control system, at a second passive checking pressure, the method comprising:
 (A) with the control system and in opposition to a first pressure differential acting on the first valve, opening the first valve via the first actuation mechanism to admit compressed gas at a first pressure into the interior compartment of the cylinder assembly, the second valve remaining closed thereduring;   (B) closing the first valve;   (C) thereafter, expanding gas within the interior compartment to a second pressure lower than the first pressure;   (D) with the control system and at a second pressure differential (i) acting on the second valve and (ii) less than the second passive checking pressure, opening the second valve via the second actuation mechanism to exhaust expanded gas at the second pressure from the interior compartment of the cylinder assembly, the first valve remaining closed thereduring; and   (E) closing the second valve, thereby completing an expansion cycle.   
     
     
         2 . The method of  claim 1 , further comprising:
 repeating steps (A)-(E) at least once, thereby completing at least one additional expansion cycle; and   during at least one said additional expansion cycle, altering a timing between steps (A) and (D) based on the second pressure differential in at least one previous expansion cycle.   
     
     
         3 . The method of  claim 1 , further comprising:
 with the control system and at a third pressure differential (i) acting on the second valve and (ii) less than the second passive checking pressure, opening the second valve via the second actuation mechanism to admit gas at approximately the second pressure into the interior compartment of the cylinder assembly, the first valve remaining closed thereduring;   closing the second valve;   compressing gas within the interior compartment to approximately the first pressure; and   with the control system and at a fourth pressure differential (i) acting on the first valve and (ii) less than the first passive checking pressure, opening the first valve via the first actuation mechanism to exhaust compressed gas from the interior compartment of the cylinder assembly, the second valve remaining closed thereduring.   
     
     
         4 . The method of  claim 1 , wherein (i) each of the first and second valves comprises a disc that selectively closes the gated port, (ii) the gated port of the first valve is disposed between the disc of the first valve and the interior compartment, and (iii) the disc of the second valve is disposed between the gated port of the second valve and the interior compartment. 
     
     
         5 . The method of  claim 1 , wherein compressed gas is admitted from a compressed-gas reservoir. 
     
     
         6 . The method of  claim 5 , wherein the compressed-gas reservoir comprises at least one pressure vessel. 
     
     
         7 . The method of  claim 5 , wherein the compressed-gas reservoir comprises a cavern. 
     
     
         8 . The method of  claim 1 , wherein compressed gas is admitted from a second cylinder assembly configured for expansion of gas from a third pressure higher than the first pressure to approximately the first pressure. 
     
     
         9 . The method of  claim 1 , wherein expanded gas is exhausted to a vent to atmosphere. 
     
     
         10 . The method of  claim 1 , wherein expanded gas is exhausted to a second cylinder assembly configured for expansion of gas from approximately the second pressure to a third pressure lower than the second pressure. 
     
     
         11 . The method of  claim 1 , wherein gas is expanded substantially isothermally. 
     
     
         12 . The method of  claim 1 , further comprising spraying heat-transfer liquid into the gas, heat being exchanged between the heat-transfer liquid and the gas during expansion. 
     
     
         13 . The method of  claim 1 , further comprising producing electricity from potential energy of the gas released during expansion. 
     
     
         14 . The method of  claim 1 , wherein:
 the second valve comprises a disc for sealing the gated port of the second valve and, mechanically coupled to the disc, a stem within the second valve; and   the second actuation mechanism comprises two hydraulic chambers separated by a boundary mechanism, the boundary mechanism being mechanically coupled to the stem.   
     
     
         15 . The method of  claim 1 , wherein the second actuation mechanism is configured to (i) apply a first actuation force during the expansion cycle, and (ii) during a subsequent expansion cycle, apply a second actuation force only when the first actuation force is insufficient to open the second valve, the second actuation force being larger than the first actuation force. 
     
     
         16 . The method of  claim 15 , wherein the second actuation mechanism comprises a hydraulic mechanism selectively connectable to (i) a first source of fluid at a pressure sufficient to provide an actuation force greater than the first actuation force and less than the second actuation force and (ii) a second source of fluid at a pressure greater than the pressure of the first source of fluid and sufficient to provide an actuation force greater than the second actuation force. 
     
     
         17 . The method of  claim 16 , wherein the second actuation mechanism comprises:
 two chambers separated by a boundary mechanism, and   a mechanism for selectively connecting (i) one of the chambers to the first source of fluid and the second source of fluid and (ii) the other chamber to a body of fluid at a pressure less than the pressure of the first source of fluid.   
     
     
         18 . The method of  claim 16 , wherein the second actuation mechanism comprises:
 a first unit comprising (i) two chambers separated by a boundary mechanism and (ii) a mechanism for selectively connecting one of the chambers to the first source of fluid and the other chamber to a body of fluid at a pressure less than the pressure of the first fluid; and   a second unit comprising (i) two chambers separated by a boundary mechanism and (ii) a mechanism for selectively connecting (a) one of the chambers to the second source of fluid and the other chamber to a body of fluid at a pressure less than the pressure of the first fluid or (b) both chambers to a body of fluid at a pressure less than the pressure of the first fluid.   
     
     
         19 . The method of  claim 18 , further comprising a stem that extends through the first unit and the second unit and that is mechanically coupled to the boundary mechanisms of the first unit and the second unit. 
     
     
         20 . The method of  claim 15 , wherein the second actuation force is larger than the first actuation force by at least a factor of 10. 
     
     
         21 . The method of  claim 1 , wherein the second actuation mechanism is configured to (i) apply a first actuation force during the expansion cycle, and (ii) opening the second valve when a pressure within the interior compartment exceeds a threshold pressure, thereby relieving an overpressure within the cylinder assembly. 
     
     
         22 . The method of  claim 21 , wherein the second actuation mechanism comprises a hydraulic mechanism selectively connectable to (i) a first source of fluid at a pressure sufficient to provide the first actuation force, (ii) a second source of fluid at a pressure less than the pressure of the first source of fluid, and (iii) a sequence valve connectable to the second source of fluid. 
     
     
         23 . The method of  claim 22 , wherein the second actuation mechanism comprises:
 two chambers separated by a boundary mechanism, and   a mechanism for selectively connecting one of the chambers to the first source of fluid and one of the chambers to the second source of fluid, the sequence valve being connected to both chambers in parallel to the first and second sources of fluid.   
     
     
         24 . The method of  claim 22 , wherein the sequence valve is configured to divert fluid to the second source of fluid when the pressure within the interior compartment exceeds the threshold pressure, thereby opening the valve. 
     
     
         25 . The method of  claim 1 , wherein (i) the cylinder assembly comprises an end cap and (ii) the first and second valves are integrated within the end cap. 
     
     
         26 . The method of  claim 25 , wherein the cylinder assembly comprises, integrated within the end cap and separate from the first and second valves, a mechanism for exhausting fluid from the interior compartment (i) when a pressure within the interior compartment exceeds a threshold pressure and (ii) without actuating the first and second valves. 
     
     
         27 . The method of  claim 26 , wherein:
 compressed gas is admitted at the first pressure from a source of compressed gas; and   the threshold pressure exceeds the first pressure by a pressure differential.   
     
     
         28 . The method of  claim 27 , wherein the mechanism comprises a check valve disposed within a conduit between the source of compressed gas and the interior compartment, a cracking pressure of the check valve being approximately equal to the pressure differential.