The invention relates generally to a hydraulic actuator and, more particularly, to a hydraulic actuator operable in a number of actuation states that is greater than the number of valves associated with the actuator piping assembly.
A compressed air energy storage (CAES) system is a type of system for storing energy in the form of compressed gas (e.g., air). CAES systems may be used to store energy in the form of compressed air when electricity demand is low, typically during the night, and then to release the energy when demand is high, typically during the day. A CAES system may be operated by a hydraulic actuator, which drives a piston to compress gas in a pressure vessel chamber. Existing hydraulic actuators, however, are often structurally complex and require large valves and piping due to the high fluid flow rates required for operation. Further, such actuators suffer from the problems associated with tidal volume and the compression and decompression of large hydraulic chamber volumes in effecting actuation. What is needed then, is a hydraulic actuator usable in a CAES system that overcomes the deficiencies of existing actuators.
Various embodiments of a hydraulic actuator and methods for operating the same are described. In one aspect, a hydraulic actuator adapted to be coupled to a piston of a CAES system includes a housing forming three aligned bores and a shaft disposed in the housing for reciprocating movement. The shaft includes three or more pistons disposed in the three bores, thereby dividing the three bores into a plurality of pressure chambers. Further, the shaft is moveable relative to the housing by pressurizing at least one of the pressure chambers with hydraulic fluid.
In one embodiment, the housing includes a plurality of cylinders forming the bores, and corresponding dividers disposed between the cylinders. There can be two or more dividers, which can form a fluidic seal with the shaft. The pistons and the dividers can form six or more pressure chambers.
In another embodiment, the shaft further includes a rod, and the pistons are attached to the rod and/or forged on the rod. The rod can have a varying outer diameter, at least two of the bores can have different inner diameters, and/or at least two of the pistons can have different outer diameters.
In a further implementation, the actuator includes a plurality of fluidic valves fluidically coupled to the pressure chambers. The valves can be adapted to be independently operable to pressurize a combination of the pressure chambers to control direction of movement and force of the shaft. There can be four or more valves to pressurize selectively six pressure chambers.
In yet another embodiment, the shaft is adapted to be coupled at at least one of a proximal end and a distal end thereof to the CAES piston disposed in a separate housing. The shaft can be adapted to be coupled at the proximal end to a first CAES piston disposed in a first separate housing and at the distal end to a second CAES piston disposed in a second separate housing.
In another aspect, a method for operating a hydraulic actuator includes providing a hydraulic actuator having a housing forming three aligned bores and a shaft disposed in the housing for reciprocating movement. The shaft includes three or more pistons disposed in the three bores, thereby dividing the three bores into a plurality of pressure chambers. The shaft is moved relative to the housing by pressurizing at least one of the pressure chambers with hydraulic fluid.
In one embodiment, the housing includes a plurality of cylinders forming the bores, and corresponding dividers disposed between the cylinders. There can be two or more dividers, which can form a fluidic seal with the shaft. The pistons and the dividers can form six or more pressure chambers.
In another embodiment, the actuator includes a plurality of fluidic valves fluidically coupled to the pressure chambers. At least one of the valves can be operated to pressurize a combination of the pressure chambers to control direction of movement and force of the shaft. There can be four or more valves to pressurize selectively six pressure chambers.
In yet another embodiment, the shaft is coupled at at least one of a proximal end and a distal end thereof to a piston of a CAES system disposed in a separate housing. The shaft can be coupled at the proximal end to a first piston of a CAES system disposed in a first separate housing and at the distal end to a second piston of a CAES system disposed in a second separate housing.
Other aspects and advantages of the invention will become apparent from the following drawings, detailed description, and claims, all of which illustrate the principles of the invention, by way of example only.
A more complete appreciation of the invention and many attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description, when considered in connection with the accompanying drawings. In the drawings, like reference characters generally refer to the same parts throughout the different views. Further, the drawings are not necessarily to scale, with emphasis instead generally being placed upon illustrating the principles of the invention.
Described herein in various embodiments is a hydraulic actuator suitable for use in a compressed air energy storage (CAES) system, such as those described in U.S. Patent Application No. 61/792,880, filed Mar. 15, 2013, and entitled “Horizontal Actuation Compressed Air Energy Storage System” (the “Horizontal CAES application”), the entirety of which is incorporated by reference herein. The present actuator may also be incorporated in CAES systems such as those described in U.S. patent application Ser. No. 13/347,144, filed Jan. 10, 2012, and entitled “Compressor and/or Expander Device”; U.S. Pat. No. 8,522,538, issued Sep. 3, 2013, and entitled “Systems and Methods for Compressing and/or Expanding a Gas Utilizing a Bi-directional Piston and Hydraulic Actuator”; and U.S. Pat. No. 8,161,741, issued Apr. 24, 2012, and entitled “System and Methods for Optimizing Efficiency of a Hydraulically Actuated System,” the entireties of which are hereby incorporated by reference herein. Further, the present invention may be used in hydraulic, pneumatic, or other systems that would benefit from an actuator providing varying actuation forces in multiple directions.
CAES systems may be used for energy storage and generation, as shown in
The conversion subsystem 112 converts the input electrical power from the wind turbines or other sources into compressed gas, which can be expanded by the conversion subsystem 112 at a later time period to access the energy previously stored. The conversion subsystem 112 may include an interconnected (in series or parallel) motor/generator, hydraulic pump/motor, hydraulic actuator and compressor/expander to assist in the energy conversion process. At a subsequent time, for example, when there is a relatively high demand for power on the power grid, or when power prices are high, compressed gas may be communicated from the storage subsystem 122 and expanded through a compressor/expander device in the conversion subsystem 112, Expansion of the compressed gas drives a generator to produce electric power for delivery to the power grid 124. In some embodiments, multiple conversion systems may operate in parallel to allow the CAES system to convert larger amounts of energy over fixed periods of time.
One or more working pistons of a CAES system may be driven by or drive one or more of the hydraulic actuators described herein. The loads applied to the working piston(s) can be varied during a given cycle of the CAES system. For example, in a hydraulic actuator, by applying hydraulic fluid pressure to different hydraulic pistons and/or different surfaces of the piston(s) within the hydraulic actuator(s), the ratio of the net working surface area of the hydraulic actuator to the working surface area of a working piston acting on the gas and/or liquid in a working chamber of the CAES system can be varied and, therefore, the ratio of the hydraulic fluid pressure to the gas and/or fluid pressure in the working chamber of the CAES system can be varied during a given cycle or stroke of the system. In addition, the number of working pistons, working chambers and actuators can be varied, as well as the number of piston area ratio changes within a given cycle.
The hydraulic actuator may be coupled to a hydraulic pump having operating ranges that can vary as a function of, for example, flow rate and pressure, among other parameters. Systems and methods of operating the hydraulic pumps/motors to allow them to function at an optimal efficiency throughout the stroke or cycle of the gas compression and/or expansion system are described in U.S. Pat. No. 8,161,741, issued Apr. 24, 2012, and entitled “Systems and Methods for Optimizing Efficiency of a Hydraulically Actuated System,” the entirety of which is hereby incorporated by reference herein.
The structure of the hydraulic actuator described herein provides a number of advantages over existing devices. For example, the uncomplicated design results in a high confidence level that simulated power levels will be achieved. In some embodiments, only four two-way, low power consumption, hydraulic valves are required to provide six gears (as discussed below). Further, the valves and piping may be of relatively small size, compared to those of actuators used in existing CAES systems, due to relatively low fluid volumetric flow rates. Increased efficiency results from the low flow velocities, as well as the reduced compression and decompression of large chamber volumes during gear progression. Moreover, in some embodiments, tidal volume and the problems associated therewith are reduced or avoided, because the actuator incorporates a closed-loop hydraulic circuit enabled by the flow of hydraulic fluid among the chambers of the actuator housing. The force produced by the actuator may also be split between two end connections at opposite ends of the actuator.
Referring now to
The valves 270a-270d are disposed on spools 272a, 272c that are coupled to the cylinders 210a-210c of the hydraulic actuator 200. Positioning the valves 270a-270d at the cylinders 210a-210c, rather than on one or more manifolds 274a, 274b, provides for simpler construction techniques. Because the valve connections 270a-270d are disposed on a greater number of components of lower mass (rather than a single component of higher mass), there is less risk in material quality and manufacturing error. Further, the valves 270a-270d and piping assembly 276a-276d can be mounted to the cylinders 210a-210c at a manufacturing facility, rather than assembled in the field, providing better quality control and a cleaner assembly environment.
The valving configuration can include one or more types of valves of any suitable construction. In one embodiment, a commercially available two-way valve can be used, such as a 100 mm elbow plug or poppet valve having a fast actuation time (less than 50 ms) and a low pressure drop, considering the 90-degree flow angle. Using flow coefficient values and measured test data, this particular valve is calculated to have a pressure drop of 0.26 bar at a flow rate of 6000 L/m.
As used herein the term “piston” is not limited to pistons of circular cross-section, but can include pistons with across-section of a triangular, rectangular, or other multi-sided shape or of a non-circular contoured shape (e.g., oval). In some embodiments, some or all of the pistons 230a-230c have different outer diameters. In other embodiments, the rod of the shaft 250 has a varying outer diameter. In further embodiments, some or all of the bores 220a-220c have varying inner diameters. Variations in the diameters of the actuator components may result in different net forces produced by the actuator 200 as the various chambers are pressurized, due to the net area being pressurized. The interior and/or exterior walls of the cylinders 210a-210c may conform to the shape of the pistons 230a-230c, and/or may include sealing elements to maintain a seal between the pistons 230a-230c and the interior walls of the cylinders 210a-210c. The pistons 230a-230c may be constructed of any suitable material.
The pistons 230a-230c may be forged to the rod of the shaft 250, and/or attached to the rod using, e.g., various clamping mechanisms. For example, referring to
Use of the diamond ring 420 clamping structure results in forces on the rod 415 and piston 410 generally along the load paths shown in
FIGS. 7 and 8A-8F, in combination with
In one implementation, actuator 200 can operate in direction 610 in three different gears. Gear 1 (C) (shown in
Starting from gear 1 (C), gear 2 (AC)(shown in
Starting from gear 2 (AC), gear 3 (ACE) (shown in
In one embodiment, when the hydraulic actuator 200 reaches the end of a stroke, in order to reverse direction, manifold 274a is changed from a high pressure line to a low pressure line and, conversely, manifold 274b is changed from a low pressure line to a high pressure line. This changeover can be achieved with, for example, a swash-plate-style pump, by taking the swash plate over center, or by using any other pump type with a simple shuttle valve or combination of larger two-way valves. Direction reversal is a common function of a closed loop hydraulic transmission. During the direction reversal all of the valves change state; that is, valves 270a and 270c are set to a closed state and valves 270b and 270d are set to an open state.
When actuating in direction 620, actuator 200 may also operate in three different gears. In reverse gear 1 (ABDEF) (shown in
Starting from reverse gear 1 (ABDEF) (shown in
Starting from reverse gear 2 (BDEF) (shown in
Upon reaching the end of the reverse stroke, manifold 274a is switched back to a high pressure line, and manifold 274b is switched back to a low pressure line. The changeover can be achieved by, for example, taking a swash plate over center, During this reversal all of the valves change state; that is, valves 270a and 270c are set to a closed state and valves 270b and 270d are set to an open state.
As discussed above, embodiments of the hydraulic actuator described herein can be coupled at one or both ends to a piston in a separate housing, such as a working piston in a CAES system, Such a CAES system can utilize a plurality of hydraulic actuators, with each actuator coupled to at least one of a low-pressure and a high-pressure vessel arrangement to compress or expand a working gas, typically air.
As shown in
The horizontal center mount of the hydraulic actuator 940 has a number of advantages over other configurations, particularly with respect to use of the actuator 940 in a horizontally-actuated CAES system, such as that described in the Horizontal CAES application.
In particular, the close proximity of the pressure chambers of the actuator 940 reduces the required length of pipes for the valving assembly and allows for a centralized valve manifold. Force is transmitted from and to both ends of the actuator shaft, thereby simplifying the end connections and, given the degree of freedom at each end connection, the alignment of process vessels to the hydraulic cylinders may be less precise. Further, assembly of the actuator 940 is simplified, and the actuator 940 may be shipped as a single unit to a worksite. The horizontal configuration also allows for servicing and component replacement without complete disassembly of the unit.
Certain embodiments of the present invention are described above. It is, however, expressly noted that the present invention is not limited to those embodiments, but rather the intention is that additions and modifications to what is expressly described herein are also included within the scope of the invention. For example, the cylinders, chambers, pistons, valves, and other components of the actuators described herein may be different in size, shape, configuration and number from the embodiments described and illustrated herein. Further, the components of the actuator need not have uniform properties; for example, the inner and/or outer diameters of pistons, piston rods, and/or cylinders may vary among individual components, resulting, e.g., in different piston surface areas upon which pressurized fluid can act, and thereby resulting in more, fewer, or different possible gears or actuation forces. Other arrangements of the piping, manifolds, and valves are possible as well. It is to be appreciated that the teachings in this application can be applied to various other actuator embodiments to provide a greater number of actuator gears than valves. Further the principles of the invention can be applied to pneumatic actuators and other actuators that use liquids, aerosols, gases or other compressible or incompressible fluids for operation.
Moreover, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations, even if such combinations or permutations are not made express herein, without departing from the spirit and scope of the invention. In fact, variations, modifications, and other implementations of what is described herein will occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention. As such, the invention is not to be defined only by the preceding illustrative description, but rather by the claims, and all equivalents.
This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/792,872, filed Mar. 15, 2013, and entitled “Hydraulic Actuator for a Compressed Air Energy Storage System,” and U.S. Provisional Patent Application No. 61/792,880, filed Mar. 15, 2013, and entitled “Horizontal Actuation Compressed Air Energy Storage System,” the entireties of which are hereby incorporated by reference herein.
Number | Date | Country | |
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61792872 | Mar 2013 | US | |
61792880 | Mar 2013 | US |