Energy storage system and method

Abstract

An energy storage system has a pressure vessel exposed to an ambient temperature and containing a working fluid (CWF) condensable at the ambient temperature; a liquid reservoir in communication with one of the containers and containing a non-vaporizable liquid in the reservoir and the container; and means for delivering the liquid from the reservoir to the container. The condensable working fluid can be compressed within the container when in direct contact with the liquid, and can be stored in a liquid state after being compressed to the saturation pressure of the condensable working fluid. In the method, at least some of the liquids located in the container are propelled by a condensable working fluid toward the turbine to generate power. In one embodiment, a module comprises: a first pressure vessel having at least four ports; a second container at ambient temperature; and a flow control member operatively connected to the corresponding conduit to selectively control fluid flow.

Description

Technical Field

[0001] The present invention relates to the field of mechanical energy storage. More particularly, the present invention relates to energy storage systems and methods for energy storage systems from which compressed gas can be released for later use. Background Art

[0002] It is known that energy collected from various sustainable energy sources, such as wind energy, solar energy and wave energy, will be stored in the form of compressed gas. During the period of power demand, the compressed gas is discharged from the storage container and electricity can be generated. Alternatively, the stored compressed gas can be used in different industrial applications.

[0003] Many compressed air energy storage (CAES) systems are known in the prior art. Compressed air has traditionally been stored in large and expensive underground caverns or underwater elastic spheres. Although CAES devices have large power ratings and storage capacities, they also have some major disadvantages. First, air has a very large heat of compression, thereby experiencing about 85% heat loss when compressed. As the temperature of the compressed air increases, less compressed air can be stored. Second, as additional air is released, the pressure in the cavern where the compressed air is stored becomes slowly reduced, thereby negatively affecting the amount of electricity that can be generated by the turbine driven by the released compressed air.

[0004] Attempts have been made to reduce the heat of compression by isothermalizing the charge and exhaust air; however, the need to employ heat exchangers to facilitate isothermal compression unnecessarily increases the cost of storage facilities.

[0005] In other CAES systems, non-adiabatic air energy storage (D-CAES), adiabatic air energy storage (A-CAES) and liquid air energy storage (LAES) have been used. The air temperature of these prior art systems deviates significantly from the ambient temperature, and therefore these prior art systems also require the use of expensive heat exchangers and rotating equipment, namely compressors and gas turbines.

[0006] It is an object of the present invention to provide a compressed gas energy storage system having an increased energy density relative to prior art systems.

[0007] It is another object of the present invention to provide a compressed gas energy storage system having an increased system round trip efficiency relative to prior art systems.

[0008] It is another object of the present invention to provide a compressed gas energy storage system and method having reduced capital and operating costs relative to the prior art.

[0009] Other objects and advantages of the invention will become apparent as the description proceeds. Summary of the invention

[0010] A multiphase energy storage system comprises: a first pressure vessel having at least four ports, corresponding pipes being in fluid communication with each of the at least four ports; and a second pressure vessel configured with one or more ports, the second pressure vessel being set to a temperature no greater than ambient temperature and being in fluid communication with the first pressure vessel, wherein a condensable working fluid (CWF) that is condensable at ambient temperature can be introduced into the first pressure vessel through a first port of the at least four ports, and a liquid that is non-evaporable in the first pressure vessel and the second pressure vessel and can be introduced into the first pressure vessel through a second port of the at least four ports can be directly discharged into the first pressure vessel. The invention relates to a method for preparing a pressure vessel ...

[0011] In one aspect, the system further includes a gas source in fluid communication with the first pressure vessel and containing a CWF, the CWF being feedable from the gas source to the first pressure vessel.

[0012] In one aspect, the energy storage system further comprises at least one hydraulic turbine capable of being driven by the non-vaporizable liquid, wherein at least a portion of the non-vaporizable fluid located within the first pressure vessel can be propelled toward the at least one hydraulic turbine by the compressed CWF when the compressed CWF is released from the second pressure vessel.

[0013] In one aspect, the system further comprises: a liquid reservoir in fluid communication with the first pressure vessel and containing a non-evaporable liquid; and a device for delivering the non-evaporable liquid from the liquid reservoir to the first pressure vessel, wherein the non-evaporable liquid can be introduced into the first pressure vessel by the delivery device through a second port of the at least four ports.

[0014] It is understood that a "non-evaporable liquid" may be able to evaporate when subjected to other conditions. Under the conditions imposed by the multiphase energy storage system, and in particular by the first and second pressure vessels and optionally by the liquid reservoir, the liquid, also referred to as the "transfer liquid", is non-evaporable.

[0015] In one aspect, non-evaporable liquid exhausted from at least one hydraulic turbine can be contained in a liquid reservoir.

[0016] In one aspect, the CWF is substantially isothermally compressible and isothermally expandable during direct contact with the non-vaporizable liquid within the first pressure vessel.

[0017] In one aspect, the delivery device is at least one hydraulic pump for delivering the non-evaporable liquid from the liquid reservoir to the first pressure vessel.

[0018] In one aspect, the energy storage system further comprises at least one additional hydraulic pump for delivering the non-vaporizable liquid from the first pressure vessel to the liquid reservoir.

[0019] In one aspect, the CWF within the first pressure vessel is continuously and additionally compressed while additional non-vaporizable liquid is introduced into the first pressure vessel.

[0020] In one aspect, the energy storage system further includes a liquid-gas separator located between the first pressure vessel and the second pressure vessel to prevent the non-evaporable liquid from flowing to the second pressure vessel, and may also include a liquid-liquid separator located between the first pressure vessel and the second pressure vessel to prevent the non-evaporable liquid from flowing to the second pressure vessel.

[0021] In one aspect, the energy storage system further includes a liquid-liquid separator located between the first pressure vessel and the second pressure vessel to prevent the non-evaporable liquid from flowing to the second pressure vessel.

[0022] In one aspect, the energy storage system further comprises a third pressure vessel capable of being in fluid communication with the first pressure vessel, wherein, prior to performing one of a charging cycle or a discharging cycle, the third pressure vessel is completely filled with a first fluid selected from a CWF gas or a non-evaporable liquid, and the first pressure vessel is completely filled with a second fluid selected from a CWF gas or a non-evaporable liquid that is different from the first fluid, such that upon termination, the third pressure vessel is completely filled with the second fluid and the first pressure vessel is completely filled with the first fluid.

[0023] In one aspect, the first pressure vessel is also exposed to ambient temperature.

[0024] In one aspect, an energy storage system includes a first plurality of pressure vessels.

[0025] In one aspect, all of the first pressure vessels are in fluid communication with each other, or selected first pressure vessels are in fluid communication with each other.

[0026] In one aspect, the energy storage system includes a plurality of second pressure vessels.

[0027] In one aspect, all of the second pressure vessels are in fluid communication with each other, or selected second pressure vessels are in fluid communication with each other.

[0028] In one aspect, the gas retainer additionally contains a non-CWF that can be mixed with the CWF, and the non-CWF gas can be additionally compressed after liquefaction of the CWF.

[0029] In one aspect, the energy storage system further includes a flow control component operatively connected to each of the corresponding conduits to selectively control the flow of fluid through the conduits.

[0030] In one aspect, the second pressure vessel is exposed to ambient temperature or to a temperature below ambient temperature.

[0031] A method for generating power from stored energy, the method comprising the steps of: providing a first pressure vessel and a second pressure vessel, wherein the second pressure vessel is fluidically communicable with the first pressure vessel and is set to a temperature no greater than ambient temperature; compressing a condensable working fluid (CWF) capable of condensing at ambient temperature substantially isothermally within the first pressure vessel during direct contact with a non-evaporable liquid, and causing at least a portion of the compressed CWF to be transferred from the first pressure vessel to the second pressure vessel in response to interaction with the non-evaporable liquid; transferring an additional amount of the compressed CWF to the second pressure vessel so that all or a majority of the CWF within the second pressure vessel is compressed to a saturation pressure of the CWF and condensed to produce liquid CWF; propelling at least some of the non-evaporable liquid located in the first pressure vessel toward at least one hydraulic turbine by the compressed CWF discharged from the second pressure vessel; and rotatably driving the at least one hydraulic turbine by the propelled non-evaporable liquid to generate power, wherein the non-evaporable liquid is prevented from flowing to the second pressure vessel while at least a portion of the compressed CWF is transferred from the first pressure vessel to the second pressure vessel.

[0032] As used herein, the term "preventing non-evaporable liquid from flowing to the second pressure vessel" includes the possibility that only a negligible volume of non-evaporable liquid is introduced into the second pressure vessel relative to the volume of liquid CWF in the second pressure vessel. Preventing the non-evaporable liquid from flowing to the second pressure vessel is performed by suitable equipment, such as a mist eliminator.

[0033] In one aspect, the CWF is substantially isothermally compressed by activating a unit of a mixing device in fluid communication with the first pressure vessel or the second pressure vessel and thereby eliminating temperature gradients within the CWF.

[0034] In one aspect, a unit of the mixing device is activated in response to a sensed condition indicative of liquefaction of the CWF.

[0035] In one aspect, at least some of the non-vaporizable liquid in the first pressure vessel is propelled toward at least one hydraulic turbine by the compressed CWF discharged from the second pressure vessel when the discharged compressed CWF is in a liquid state, a gaseous state, or in a multiphase state.

[0036] In one aspect, the step of transferring at least a portion of the compressed CWF from the first pressure vessel to the second pressure vessel is performed during a plurality of charging cycles.

[0037] In one aspect, the step of advancing at least some of the non-vaporizable liquid located in the first pressure vessel by the compressed CWF discharged from the second pressure vessel is performed during a plurality of discharge cycles.

[0038] In one aspect, the method further comprises the steps of providing a third pressure vessel capable of being fluidly connected to the first pressure vessel, wherein, before performing one of a filling cycle or a discharging cycle, the third pressure vessel is completely filled with a first fluid selected from CWF gas or a non-evaporable liquid, and the first pressure vessel is completely filled with a second fluid selected from CWF gas or a non-evaporable liquid that is different from the first fluid; and performing one of the filling cycle or the discharging cycle such that, upon termination, the third pressure vessel is completely filled with the second fluid and the first pressure vessel is completely filled with the first fluid.

[0039] In one aspect, the method further includes performing the other of a fill cycle or a drain cycle when the third pressure vessel is completely filled with the second fluid and the first pressure vessel is completely filled with the first fluid.

[0040] In one aspect, the compressed CWF discharged from the second pressure vessel is expanded substantially isothermally during direct contact with the non-evaporable liquid within the first pressure vessel.

[0041] A direct contact fluid transfer (DCFT) module comprises: a first pressure vessel having at least four ports, a corresponding conduit being in fluid communication with each of the at least four ports; a second pressure vessel exposed to ambient temperature, the second pressure vessel having one or more ports; and a flow control component operatively connected to each of the corresponding conduits to selectively control the flow of fluid through the conduits, wherein a condensable working fluid (CWF) capable of condensing at ambient temperature can be introduced into the first pressure vessel through a first port of the at least four ports, wherein a non-evaporable liquid can be introduced into the first pressure vessel through a second port of the at least four ports to cause the CWF to condense in contact with an ambient temperature. Substantially isothermal compression in direct contact with a vaporizable liquid, wherein, after a sufficient additional volume of non-vaporizable liquid is introduced into the first pressure vessel, at least a portion of the compressed CWF can be transferred from the first pressure vessel through one of the one or more ports to the second pressure vessel through a third port of the at least four ports while in direct contact with the non-vaporizable liquid, and at least a portion of the compressed CWF can be stored in a liquid state in the second pressure vessel after being compressed to the saturation pressure of the CWF and condensed, wherein at least some of the non-vaporizable liquid in the first pressure vessel can be propelled by the CWF through a fourth port of the at least four ports when the CWF is discharged from the second pressure vessel to discharge stored energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In the attached picture:

[0043] - Figure 1 is a schematic diagram of an embodiment of a multiphase energy storage system;

[0044] - Figure 2 is a schematic diagram of another embodiment of a multi-phase energy storage system;

[0045] - Figure 3 is a flow chart representing the various steps involved during execution of a cycle of a charging mode according to one embodiment;

[0046] - Figure 4 It is a method for delivering gas by suction driven flow;

[0047] - Figure 5 is a flow chart showing the various steps involved in the execution of the discharge mode according to one embodiment;

[0048] - Figure 6 is a schematic diagram of another embodiment of a multi-phase energy storage system;

[0049] - Figure 7 is used for Figure 1 An exemplary pressure-volume diagram for an energy storage system of;

[0050] - Figure 8 is used for Figure 1 An exemplary temperature-entropy diagram for an energy storage system of;

[0051] - Fig. 9 is a schematic diagram of another embodiment of a multiphase energy storage system shown during a charging state;

[0052] - Fig.10 is a schematic diagram of another embodiment of a multi-phase energy storage system illustrating operations performed during a charging cycle; and

[0053] - Fig.11 yes Fig.10 Schematic diagram of a multiphase energy storage system illustrating operations performed during a discharge cycle. DETAILED DESCRIPTION

[0054] In the multiphase compressed gas energy storage system of the present invention, the significant heat losses experienced by the working fluid of prior art systems are advantageously avoided by employing a condensable working fluid (CWF) that is normally gaseous but condenses at ambient temperature when fully compressed. In conjunction with the CWF, a liquid-based direct contact fluid transfer (DCFT) module is employed to ensure that the CWF will undergo phase changes substantially isothermally in both charging and discharging modes. The DCFT module is capable of operating in conjunction with a transfer liquid that is ensured to be maintained in a liquid state, and therefore is able to advantageously employ relatively inexpensive hydraulic equipment that engages the flowing transfer liquid to reduce system cost and improve system round trip efficiency (RTE).

[0055] As referred to herein, "direct contact" refers to a heat transfer process involving the exchange of heat between two fluids that are in physical contact with each other when the two fluids are at different temperatures. In addition, "substantially isothermal" - a state in which heat transfer occurs at a near constant temperature - is defined as less than or equal to 5% of the absolute temperature difference between the final temperature and the initial temperature for an adiabatic heat transfer process having the same initial thermodynamic state as a given heat transfer process. Any deviation from a purely isothermal heat transfer process is due to a lower heat transfer coefficient than required, a smaller heat transfer area than required, or a shorter time than the time required for heat transfer to occur.

[0056] Figure 1An embodiment of a multiphase energy storage system, generally designated 1, capable of operating in both a charging mode and a discharging mode is schematically illustrated. Two fluids interact in the system 1, the first fluid being a multiphase CWF fluid and the second fluid being a transfer liquid.

[0057] The multiphase energy storage system 1 includes a gas holder 2 exposed to ambient temperature, the gas holder 2 being used to hold low-pressure CWF gas close to atmospheric pressure. The gas holder 2 is an inexpensive large-volume container, such as a container defined by a low-strength membrane. In addition, the system 1 includes: one or more compression tanks 4, the one or more compression tanks 4 constituting at least a portion of the DCFT module, being fluidly connected to the gas holder 2; and one or more storage tanks 3, the one or more storage tanks 3 being exposed to ambient temperature and being fluidly connected to each compression tank 4, for storing high energy density liquid CWF at the end of the charging mode. The one or more compression tanks 4 may also be exposed to ambient temperature without limitation. The one or more storage tanks 3 and the one or more compression tanks 4 are preferably pressure vessels that can withstand relatively high pressure compressed CWF gas. The transfer liquid, such as hydraulic oil or water, may be exposed to air and temperature at atmospheric pressure while being held in the liquid reservoir 5 to ensure that the transfer liquid will remain in the liquid phase. A liquid reservoir 5 is in fluid communication with each compression tank 4 and is also in fluid communication with a hydraulic feed pump 7 and a hydraulic turbine 6 for utilizing the stored gas energy in a discharge mode. The transfer liquid is optionally immiscible with the CWF fluid.

[0058] like Figure 2 As shown, the cost for operating the multiphase energy storage system 1 can be reduced in the following manner: during the charging mode, the supply pump 7 and the return pump, if used, are powered using electrical energy generated from a renewable energy source 11, such as a photovoltaic power generation system or a wind farm, or from any other energy source, such as a power plant. The electricity generated by the renewable energy source 11 is usually supplied to the power grid 14. When the power demand is lower than the power generated by the renewable energy source, the excess power can be delivered to the pump to charge the system. Excess electricity generated by the renewable energy source 11 can be used to power the supply pump and the return pump. Similarly, electricity generated by a generator connected to the hydraulic turbine 6 can be supplied to the power grid 14. In certain conditions, the system can also be powered by other means familiar to those skilled in the art.

[0059] Figure 6Another embodiment of a multiphase energy storage system, generally designated 21, is illustrated. System 21 is similar to system 1 and is constructed with additional means such that each of the various components, such as gas discharge conduit 23, mixing device 24, liquid-gas separator 26, and heat exchanger 28, constitute another embodiment providing advantageous features. With respect to energy storage system 21, liquid reservoir 25 is not exposed to ambient air but is fluidly connected to gas holder 2 via gas discharge conduit 23, thereby allowing any gas that has been degassed from the transfer liquid after having been absorbed in the transfer liquid during either the charging mode or the discharge mode to flow back to the gas holder via a closed conduit loop arrangement. The transfer liquid remains non-evaporable at a given thermodynamic state in the charging mode and the discharge mode, whereby the pressure of the transfer liquid is significantly above the saturation pressure of the transfer liquid within the controlled temperature range.

[0060] Fig. 9 Another embodiment of a multiphase energy storage system generally designated 71 is illustrated. The cost-effective system 71 includes a single compression tank 74 exposed to atmospheric temperatures within which the CWF is retained and is able to condense while being in direct contact with a non-evaporable transfer liquid without the need for a storage tank. A liquid reservoir 5 adapted to receive the transfer liquid is exposed to atmospheric air and pressure and is in fluid communication with a liquid feed conduit to which a hydraulic pump 7 is operatively connected and a turbine inlet conduit to which a hydraulic turbine 6 is operatively connected. The system 71 may also interface with a renewable energy source 11 and a grid 14, as described with respect to FIG. Figure 2 as described.

[0061] if Figure 1 System 1 or Fig. 9 If the current gas mass retained in the system 71 is less than the minimum required for effective operation of generating power from the stored gas energy, a supplemental gas tank (not shown) may be used to inject a supplemental amount of gas into the compression tank or gas retainer.

[0062] Charging mode

[0063] Initially, refer to Fig. 9 In the multiphase energy storage system 71, the transfer liquid is retained in the liquid reservoir 5, the low-pressure CWF is retained in the compression tank 74 and all valves are closed. After the liquid feed valve is opened and the supply pump 7 is enabled, the transfer liquid is delivered to the compression tank 74. The introduced transfer liquid reduces the available volume that the CWF can occupy in the compression tank 74, causing the CWF to be compressed. As additional transfer liquid is introduced, the CWF becomes increasingly compressed until the pressure of the CWF increases above its saturation pressure and condenses. Due to direct contact with the transfer liquid, the CWF is essentially isothermally compressed. After the charging mode is completed, the liquid feed valve is closed and the supply pump is deactivated.

[0064] In reference Figure 1 System 1 and Figure 6 In the pre-filled state of the system 21, the CWF is retained in the gas retainer 2 in the gas phase at atmospheric pressure or a pressure slightly higher than atmospheric pressure, the transfer liquid is retained in the liquid reservoir 5, and one or more storage tanks 3 are pre-compressed with gas, and one or more compression tanks 4 are filled with atmospheric gas or filled with transfer liquid.

[0065] If one or more compression tanks 4 are filled with transfer liquid, the steps for Figure 4 The described procedure is to cause the transfer of liquid to the liquid reservoir 5 while the gas flows from the gas holder 2 to the one or more compression tanks 4.

[0066] When there is a sufficient volume of gas in one or more compression tanks 4, the isolation valve 3B at at least one port of each storage tank 3 is opened to provide a combined internal volume shared by each compression tank 3 and the storage tank 4 via the terminal conduit 3A extending between the compression tank 4 and the storage tank 3. The gaseous CWF flows from each compression tank 4 through the terminal conduit 3A and is received in the storage tank 3 after flowing through the isolation valve 3B without being discharged from the storage tank 3. If there is more than one storage tank 3, the gaseous CWF flows to the storage tanks through the corresponding isolation valves 3B and ports in parallel, but not all isolation valves 3B can be opened at the same time.

[0067] After the first portion of the CWF gas is introduced into the one or more tanks 3 and 4, the liquid feed valve 1B, which is operatively connected to a region of a liquid feed conduit 1A extending from the liquid reservoir 5 to the one or more compression tanks 4, which is located downstream of a feed pump 7, is opened, and the feed pump 7 is also operatively connected to the liquid feed conduit 1A. The hydraulic feed pump 7 is enabled and caused to deliver the transfer liquid from the reservoir 5 to the one or more compression tanks 4.

[0068] The transfer liquid introduced into the one or more compression tanks 4 reduces the combined volume of the tanks 3 and 4 occupied by the CFW gas. Therefore, the CFW gas can be compressed in the interior of the compression tank 4. As more transfer liquid is introduced into the one or more compression tanks 4, the combined volume of the tanks 3 and 4 occupied by the CFW gas decreases, and the CFW in both gas tanks 3 and 4 is additionally compressed. During compression, the CWF gas is directly contacted and cooled by the transfer liquid to reduce the heat of compression, so that the CWF gas can undergo compression at a substantially constant temperature. Eventually, the one or more compression tanks 4 are completely occupied by the transfer liquid, and the CWF gas previously in the one or more compression tanks 4 is displaced into the one or more storage tanks 3, thereby causing the CFW gas in the one or more storage tanks 3 to be further compressed. Once the CWF received in the one or more storage tanks 3 is compressed to at least the saturation pressure, the CWF will liquefy. All valves are then closed to complete the cycle of the charging mode.

[0069] If the pressure of the CWF received in one or more storage tanks 3 is less than the saturation pressure, additional cycles of the charging mode can be performed. During each additional cycle, another gas portion is supplied to the compression tank 4 to increase the pressure of the stored CWF fluid.

[0070] Figure 3 The combination according to one embodiment is shown Figure 1 System 1 and Figure 6 The system 21 illustrates the various steps involved in the execution of a charging mode cycle.

[0071] To start an additional cycle of the filling mode, or alternatively to start the first cycle of the filling mode, when the one or more compression tanks 4 are filled with the transfer liquid in step 29, the return valve 5B is opened in step 31 to allow the transfer liquid to be transferred from the one or more compression tanks 4 back to the liquid reservoir 5, and the return valve 5B is operatively connected to another conduit 5A, i.e., the return conduit, extending from the liquid reservoir 5 to the one or more compression tanks 4. At the same time, the gas feed valve 4B is immediately opened to allow the gas portion to flow from the gas holder 2 to the one or more compression tanks 4.

[0072] Once the transfer liquid has been returned to the reservoir 5, all valves are closed. Then, each isolation valve 3B is opened in step 36. The supply pump 7 is then enabled in step 37 to supply the transfer liquid to the one or more compression tanks 4, so that the CWF gas that has been fed from the gas holder to the one or more compression tanks 4 in the current cycle will be compressed in step 39, and then the compressed CWF gas will be displaced by the transfer liquid to the one or more storage tanks 3 in step 41. In step 43, the introduction of additional CWF gas to the one or more storage tanks 3 will increase the pressure of the stored CWF gas. Finally, after one or more cycles, in step 45, the pressure of the ambient temperature CWF admitted in the one or more storage tanks 3 increases to the saturation pressure and then liquefies.

[0073] If, in step 35 , one or more compressed tanks 4 are to be filled with gas, the charging mode cycle continues to step 36 .

[0074] In another embodiment, in step 33, gas is fed to one or more compression tanks via a gas feed valve, and steps 37 and 39 are performed to compress the feed gas in the one or more compression tanks, while the isolation valve at the inlet port of each storage tank is closed to increase the pressure accumulated in the compression tank. Then after the isolation valve is opened, the compressed fluid is displaced from the transfer liquid to the storage tank. The displaced fluid may be in a gaseous state or a two-phase, liquid-vapor state, thereby undergoing a first stage of compression in the compression tank and a second stage of compression in the storage tank until fully liquefied.

[0075] exist Figure 4 In another embodiment shown, if, for example, the pressure difference between the gas holder and the compression tank is relatively low, a portion of the gas is sucked from the gas holder by suction. This suction driven flow is possible when filling one or more compression tanks with the transfer liquid in step 31. In step 44, while the gas feed valve is opened, a return pump is activated, which is operatively connected to a return conduit extending between the one or more compression tanks and the reservoir. In step 48, the transfer liquid flows through the return conduit in the direction of the reservoir to generate suction, which sucks the gas from the gas holder to one or more compression tanks.

[0076] At a given pressure, the volume of CWF fluid that can be stored when in a liquid state is significantly less than when provided in a gaseous state, and therefore, the ability of systems 1, 21, and 71 to store CWF in a liquid state significantly increases the energy density, i.e., the potential stored energy per volume, of the working fluid relative to prior art practices of storing the working fluid in a gaseous state. The energy density that can be achieved by the CWF can also be advantageously increased due to the substantially isothermal compression and expansion, which results in reduced heat losses. The capital cost of the small volume storage tank 3 is significantly less than the large volume storage tank required to store the compressed gas in a gaseous state.

[0077] like Figure 6 As shown in system 21 of FIG. 1 , the energy density of the fluid stored in one or more storage tanks 3 may be additionally increased when the gas holder 2 contains an additional low pressure gas that is non-CWF but can be mixed with the CWF, such as air or a non-condensable gas (NCG). The mixture is compressed in step 39 and transferred to the one or more storage tanks in step 41. After the CWF is liquefied in step 45, the non-CWF gas can be additionally compressed, such as in response to the introduction of an additional volume of transfer liquid into the compression tank 4, to further increase the energy density of the stored fluid. It will be appreciated that non-CWF can also be mixed with the CWF to increase the energy density of the stored compressed fluid in system 1 and system 71.

[0078] The high energy density of the CWF received in the one or more storage tanks 3 is advantageous because more energy can be released from the stored CWF in the discharge mode.

[0079] Reference Figure 6 In the multiphase energy storage system 21 according to another embodiment schematically illustrated in FIG, the energy density of the CWF transferred to the storage tank 3 can be further increased by preventing the transfer liquid from flowing into each storage tank so that more CWF can occupy the interior of the storage tank and be condensed. By deploying a liquid-gas separator 26 or a liquid-liquid separator at the inlet of the storage tank port, the transfer liquid can be prevented from flowing into the storage tank when the CWF is also condensed in the compression tank. The liquid-gas separator 26 can be, for example, a separator that forces the transfer liquid to fall into the liquid-gas separator under the influence of gravity and return to the compression tank 4. The liquid-gas separator 26 can also be implemented by a buffer tank located above the height of each compression tank 4. The liquid-gas separator 26 or the liquid-liquid separator can be operably connected to a pipeline 27, which extends from a dedicated outlet provided with the corresponding compression tank 4 to a terminal pipeline 3A, and the compression tank 4 is fluidly connected to the terminal pipeline 3A.

[0080] Although there is no direct contact between the transfer liquid and the CFW fluid within the one or more storage tanks 3 when systems 1 and 21 employ liquid-gas separators 26, the CFW can be isothermally compressed due to the cooling effect provided by the ambient temperature air or ground surrounding the one or more storage tanks 3. Additionally, when the CFW is slowly compressed, for example, over a period of several hours, the heat of compression can be reduced or completely eliminated.

[0081] Alternatively or additionally, as in Figure 6 Multiphase energy storage system 21 and Fig. 9 As schematically illustrated in the multiphase energy storage system 71 of FIG. , isothermal compression can be ensured with the aid of a mixing device. When the CWF begins to liquefy, such as when a two-phase, liquid-vapor state is reached, unit 24B of the mixing device set to be in fluid communication with the corresponding storage tank 3 can be enabled. By providing a fluid having a substantially uniform temperature and heat transfer coefficient and also absorbing any released compression heat, the liquid and vapor portions of the CWF will be able to mix together to eliminate temperature gradients within the stored CWF. Unit 24B can be enabled in response to an associated sensor detecting a predetermined pressure within the corresponding storage tank 3 or detecting the presence of a liquid. Similarly, unit 24A of the mixing device, which may be the same as or different from unit 24B, can be set to be in fluid communication with the corresponding compression tank 4.

[0082] The mixing device may take various forms. A mixing device such as an agitator may be rotatably mounted with the corresponding tank. The agitator provides uniformity in temperature, heat transfer coefficient and composition to the stored fluid to mix any particles that may have precipitated from the compressed liquefied solution.

[0083] The mixing device may also be disposed outside the corresponding tank. In one embodiment, the mixing device is configured with a set of pipes and nozzles, whereby a portion of the fluid at one area of ​​the tank is discharged through one of the pipes, such as a pipe combined with a pump, and injected into another area of ​​the tank through one or more nozzles. This arrangement may also facilitate the circulation of the transfer liquid between two or more compression tanks 4 that may be connected to each other, or from one or more compression tanks 4 to one or more storage tanks 3 that may also be connected to each other.

[0084] In addition, a heat exchanger 28A set in heat exchange relationship with one or more compression tanks 4 or a heat exchanger 28B set in heat exchange relationship with one or more storage tanks 3 can be provided to help achieve constant temperature compression. Each of the heat exchangers can be shell and tube type, fin tube type, plate heat exchanger type, air cooling type or any other heat exchanger type known to those skilled in the art. The pipe through which the cooling medium flows can be shared with the pipe associated with the mixing device when in use, such as when one or more valves are selectively opened and / or closed to allow flow to the heat exchanger or the unit of the mixing device. More than one heat exchanger can be used, and each heat exchanger can be of the same type or of a different type.

[0085] Emission pattern

[0086] The condensed CWF can remain stored for a long period of time while undergoing a charging state until the discharge mode is activated. The discharge mode is usually activated during peak demand or when energy availability is short, because the energy stored in the multiphase energy storage system can be discharged and generate electricity to be supplied to the grid whenever needed.

[0087] During the discharge mode, the transfer liquid is propelled by the high pressure liquid CWF toward the hydraulic turbine to generate electricity. By using the transfer liquid to cause compression of the CWF during the charge mode and propelled by the CWF during the discharge mode, a hydraulic turbine can be advantageously employed to generate power, as compared to the gas turbine used in the prior art compressed gas storage system. Advantages of using a hydraulic turbine over using a gas turbine include higher efficiency, lower speed, easier maintainability, and lower operating costs.

[0088] These advantages are also associated with the use of hydraulic pumps in the multiphase energy storage system, rather than compressors for introducing compressed gas as in prior art compressed gas storage systems.

[0089] Now refer to Fig. 9 In the multiphase energy storage system 71, the CWF liquid and the high pressure transfer liquid are retained in the compression tank 74 in preparation for the subsequent activation of the discharge mode. Since the CWF fluid has been compressed to a CWF fluid saturation pressure that is significantly greater than its pressure during the pre-charge state, and the transfer liquid is retained in the same closed compression tank 74 as the CWF liquid, the CWF liquid exerts a force on the transfer liquid that pressurizes the transfer liquid to a saturation pressure that is the same as the saturation pressure of the CWF liquid. The pressurized transfer liquid in the compression tank 74 is at a pressure that is significantly higher than the atmospheric pressure to which the transfer liquid retained in the liquid reservoir 5 is exposed.

[0090] When the turbine injection valve is opened to start the discharge mode, due to the high pressure difference between the high pressure transmission liquid in the compression tank 74 and the low pressure transmission liquid in the liquid reservoir 5, the high pressure transmission liquid is forced to be discharged from the compression tank 74 with a sufficiently high kinetic energy to drive the hydraulic turbine in a rotatable manner and generate power. In response to the discharge of the high pressure transmission liquid from the compression tank 74, the additional volume in the compression tank 74 that is not occupied by the transmission liquid is available for use by the CWF, so the CWF can expand and achieve a two-phase, i.e., vapor-liquid state. It is worth noting that due to the constant pressure expansion of the multi-phase CWF, the pressure of the CWF and the pressure of the transmission liquid pressurized thereby remain unchanged, thereby allowing the power output to continue for a period of time. Once the CWF reaches the gaseous state, the pressure of the high pressure transmission liquid will decrease. However, the pressure of the propulsed transmission liquid is high enough before it drops below the turbine-specific threshold to drive the hydraulic turbine 6 in a rotatable manner and generate electricity. At the end of the discharge mode, the turbine injection valve is closed and the liquid feed valve is opened.

[0091] Due to the simplicity of the system 71, the transfer liquid can circulate back and forth between the liquid reservoir 5 and the compression tank 74 in a piston-like manner during alternating filling and discharge modes, respectively, to generate additional power.

[0092] In reference Figure 1 System 1 and Figure 6 In the pre-discharge state of the system 21, all valves are closed, and the CWF fluid retained in the one or more storage tanks 3 is in the liquid phase after having been exposed to the ambient temperature of the storage tanks and compressed to a relatively high pressure. If a non-CWF gas is mixed with the CWF fluid, the non-CWF gas compressed to a higher pressure than that of the CWF liquid is also retained in the one or more storage tanks 3.

[0093] Figure 5 The various steps involved in the execution of the exhaust mode according to one embodiment are illustrated.

[0094] In the first step 51 of the discharge mode, if after the final cycle of the filling mode, none of the compression tanks 4 currently contains transfer liquid, the return valve 5B is immediately opened, thereby allowing the transfer liquid received in the relatively high hydraulic head reservoir 5 to flow through the return conduit 5B and fill one or more compression tanks. Alternatively, the liquid feed valve 1B can be immediately opened, and the supply pump 7 can be operated to feed the required volume of transfer liquid to one or more compression tanks 4. If there is a sufficient volume of transfer liquid in one or more compression tanks 4, this step can be omitted. Each of the compression tanks can be equipped with a sensor, such as a capacitive level sensor or a float switch, to determine whether a predetermined level of transfer liquid is present, and each of the compression tanks may also be equipped with a pressure sensor. The return valve 1B or the return valve 5B is then closed to prevent the transfer liquid from flowing back.

[0095] In step 53, the turbine injection valve 2B and at least one storage tank isolation valve 3B are opened. In step 55, the high-pressure compressed fluid, including at least the CWF liquid, will therefore be released from the storage tank 3 via the terminal pipe 3A and expand to a small extent due to exposure to the lower pressure in the compression tank 4, and the corresponding opened isolation valve 3B is in fluid communication with the terminal pipe 3A. In step 57, the released CWF liquid is forced to contact the transfer liquid in each compression tank 4, and due to the pressure difference between the CWF liquid and the transfer liquid in the liquid reservoir, the released CWF liquid causes the transfer liquid to be propelled through the turbine inlet pipe 2A, to which the turbine injection valve 2B is operatively connected. The transfer liquid can be propelled as long as the pressure difference between the following two is greater than a predetermined threshold: the transfer liquid propelled by the CWF at the same pressure as the CWF; and the transfer liquid in the liquid reservoir 5 downstream of the hydraulic turbine 6. In step 59, the CWF liquid is able to evaporate and achieve a two-phase liquid-vapor state while expanding at constant pressure due to the larger volume occupied by the CWF liquid inside the combination of tanks 3 and 4 in response to the displacement of the transfer liquid. The pressure of the multiphase CWF fluid and the pressure of the CWF when it is in a completely gaseous phase are high enough to continue to push the transfer liquid through the turbine inlet pipe 2A. Due to the direct contact between the CWF gas and the transfer liquid, the temperature change of the CWF gas is reduced, thereby allowing the CWF gas to expand substantially at constant temperature. This expansion process continues while the transfer liquid is increasingly pushed and the CWF fluid that has reached a completely gaseous state occupies an increasing volume. In step 61, the transfer liquid pushed through the turbine inlet pipe 2A thus drives the hydraulic turbine 6 in a rotatable manner to generate power. In step 63, the transfer liquid leaving the hydraulic turbine 6 flows to the reservoir 5 to increase the liquid level in the liquid reservoir. In step 65, when the volume of the transfer liquid remaining in one or more compression tanks is less than the volume that can be pushed, all valves are closed to complete the cycle of the discharge mode. Thereafter, in step 67 , the gas feed valve 4B is opened, thereby allowing the gas remaining in the one or more compression tanks to flow back to the gas holder 2 through the gas feed pipe 4A due to the pressure difference between the one or more compression tanks 4 and the gas holder 2 .

[0096] Thus, the use of a phase-changing CWF fluid during the discharge mode does not reduce the amount of power that can be extracted, but rather the multiphase CWF fluid participates in continuing to propel the transfer fluid toward the hydraulic turbine to generate an additional amount of power. In addition to the advantages provided by the condensing fluid, an advantage of this power extraction capability is that it can also allow the volume of the compression tank and storage tank to be reduced.

[0097] If the pressure of the fluid including at least CWF remaining in the one or more storage tanks 3 is sufficiently greater than atmospheric pressure to facilitate the propulsion of the transfer liquid, one or more cycles involving the above steps may be repeated in the discharge mode. That is, if the one or more compression tanks 4 have been sufficiently emptied, step 51 is performed to refill the one or more compression tanks 4 with the transfer liquid from the reservoir 5, and then in step 57, the refilled transfer liquid is propelled by the fluid released from the one or more storage tanks. In step 69, additional cycles may be repeated until the pressure of the gas within the one or more storage tanks 3 is reduced to a pressure below the propulsionable pressure at which the transfer liquid can be propelled.

[0098] The sequence of the various steps of both the filling mode and the discharging mode can be controlled manually when manipulating the various flow control devices, or alternatively automatically in response to operation of the controller. Each step can be performed in response to a timed action or a sensed action commanded by the controller. By intervention of the controller, the filling step and the discharging step can be synchronized to provide a continuous discharging operation.

[0099] By adopting a large volume gas holder 2 and by performing multiple filling cycles and discharge cycles, the volume of one or more compression tanks 4 can be advantageously reduced to reduce costs. Depending on the gas energy storage requirements, system 1 and system 21 can be expanded or reduced by changing the number or size of one or more tanks. When system 1 or system 21 includes multiple storage tanks 3 and multiple compression tanks 4, each storage tank in the storage tank and each compression tank in the compression tank can be connected to each other. For a more efficient transfer operation, two different tanks can be combined to perform different steps simultaneously. For example, the transfer liquid can flow to the first compression tank 4 at the beginning of another discharge cycle, while in different discharge steps, the transfer liquid is propelled in the second compression tank by expanding the CWF so as to drive the hydraulic turbine in a rotatable manner.

[0100] Figure 7 and Figure 8 Various exemplary thermodynamic states of a CWF fluid are illustrated. In state F, CWF gas is introduced into a compression tank at a relatively low pressure, such as from a gas holder, and the pressure of the CWF gas steadily increases to the saturation pressure of the CWF in state G in response to the introduction of a transfer liquid into the compression tank. The CWF undergoes a phase change in state G to present a two-phase fluid and is then condensed at constant pressure until it is fully liquefied to occupy a minimum volume in state H. Through direct contact with the transfer liquid and the influence of the surrounding environment, the CWF is isothermally compressed from state F to state H throughout the charging mode. These states are reversed when the CWF fluid is isothermally expanded from state H to state F throughout the discharge mode.

[0101] Despite Figure 1 , Figure 6 and Fig. 9 Only a single hydraulic turbine 6 is shown, but it will be appreciated that more than one hydraulic turbine may be employed. When the sensor detects that the pressure of the CWF propelling the transfer fluid is sufficiently high, more than one hydraulic turbine stage may be used to generate an additional amount of power. A different turbine type may be used for each stage to maximize efficiency with respect to the designed operating conditions of a particular stage, such as a predetermined range of pressure drop, a specific speed or head. Alternatively, a plurality of turbines in parallel may be employed. A controller receiving the pressure reading detected by the sensor is able to command a flow control component, such as a valve at the outlet of the first stage turbine, to cause the transfer fluid leaving the first stage turbine to be delivered to the inlet of the second stage turbine and to rotatably drive the second stage turbine.

[0102] It will be appreciated that multiple feed pumps may be used in parallel or in series.

[0103] As described above, it is possible to alternately perform multiple charging cycles and discharging cycles with respect to the energy storage system, the charging cycles being repeatable if the CWF pressure is less than the saturation pressure, and the discharging cycles being repeatable if the pressure of the propulsion fluid including at least the CWF is sufficiently greater than atmospheric pressure to facilitate propulsion of the transfer liquid.

[0104] Fig.10 and Fig.11 Another embodiment of a multiphase energy storage system is illustrated, generally designated 91. System 91 is a closed system comprising two or more DCFT modules, each of which can be in fluid communication with a gas holder, one or more storage tanks, a hydraulic turbine, and at least one other DCFT module. By providing two or more DCFT modules, a charging cycle or a discharging cycle can advantageously be repeatedly performed with minimal waiting time between subsequent cycles.

[0105] The multiphase energy storage system 91 includes a gas holder 92 exposed to ambient temperature, which is shown as containing low-pressure CWF gas close to atmospheric pressure and another low-pressure non-CWF gas, such as air or NCG, but the gas holder 92 can contain only CWF. In addition, the system 91 includes: two or more DCFT modules, such as DCFT modules 93a and 93b; one or more storage tanks, such as three storage tanks 94a to 94c, which are exposed to ambient temperature for storing high energy density CWF, especially liquid CWF or a mixture of liquid CWF and NCG at the end of the charging mode; at least one hydraulic turbine 96; a low-pressure liquid reservoir 98 for receiving liquid discharged from the hydraulic turbine 96; and pumps 108 and 109. The DCFT modules 93a and 93b, which can be respectively referred to as "first module" and "second module", are preferably pressure vessels that can withstand relatively high pressure compressed CWF gas. The fluid held by gas holder 92 and able to flow within the energy storage system may also be referred to as a “CWF-based fluid.” A schematically illustrated controller 107 in data communication with at least pumps 108 and 109 and valves synchronizes the flow of the transfer liquid and the flow of the CWF-based fluid.

[0106] Fig.10 The operation of the system 91 during the filling mode is illustrated. In the pre-filled state, all valves are closed. In addition, the first DCFT module 93a is filled with a non-evaporable transfer liquid, and the second DCFT module 93b and the storage tanks 94a to 94c are filled with CWF or a mixture of CWF and non-CWF gas, which is kept in the gas phase and at a predetermined pre-compression pressure before being compressed by the transfer liquid. The first DCFT module 93a, the second DCFT module 93b and the storage tanks 94a to 94c can be pre-filled by known means, such as with a pump and valve or by any other suitable means.

[0107] A pressure control device 103B connected to the second DCFT module 93b, which can communicate with the controller, ensures that the interior of the second module reaches a predetermined pre-compression pressure. The pressure control device 103B can be implemented by means of devices well known to those skilled in the art, such as a pressure gauge and a pressure regulator, and the pressure control device 103B can optionally also include a thermostatic compressor for rapidly increasing the gas pressure inside the second module while minimizing the heat of compression. A similar pressure control device 103A can be connected to the first DCFT module 93a.

[0108] To start the first charging cycle, the first module liquid discharge valve 101A, the second module liquid inlet valve 102B, the liquid feed valve 114, the first module gas inlet valve 111A, the second module gas inlet valve 111B, and the second module gas transfer valve 117B are opened. When the second module gas inlet valve 111B is opened and in fluid communication with the gas holder 92, the pressure of the gas in the gas holder is also maintained at a predetermined pre-compression pressure. The first pump 108 is then enabled, and the transfer liquid is delivered from the first module 93a to the second module 93b, thereby flowing in the direction of arrow A through the conduit 121 extending from the first port of the first module, flowing through the conduit 123 to which the first pump 108 and the liquid feed valve 114 are operatively connected, and flowing in the direction of arrow B through the conduit 124 extending from the end of the conduit 123 to the second port of the second module 93b.

[0109] The transfer liquid introduced into the second module 93b reduces the volume occupied by the retained gas. Therefore, the retained gas can be compressed inside the second module 93b. During compression, the retained gas is directly contacted and cooled by the transfer liquid to reduce the compression heat, so that the retained gas can undergo substantially constant temperature compression. When the second module 93b is filled with the transfer liquid, the compressed CWF-based gas is caused to shift and flow through the sixth port of the second module 93b, thereby flowing through the pipeline 127 in the direction of arrow C, and flowing through the pipeline 128 and the corresponding pipeline 129 in the direction of arrow D to reach the first port of one or more storage tanks 94a to 94c. The compressed gas transferred from the second module 93b causes the CWF-based gas stored in each storage tank in one or more storage tanks 94a to 94c to be additionally compressed.

[0110] When isolation valve 116B operatively connected to conduit 136 and isolation valve 118B operatively connected to conduit 138 are open, substantially isothermal compression of the CWF-based fluid may be ensured by circulating the cooling transfer liquid at the bottom of the second module 93b in a closed loop through the fourth and fifth ports of the second module and through conduits 136 to 138 by means of the second pump 109. The degree of cooling provided by the circulating transfer liquid may be increased by means of the heat exchanger 104 in heat exchange relationship with conduit 137. Alternatively or additionally, a mixing device or nozzle in use can help ensure substantially isothermal compression when isolation valves 116B and 118B are open.

[0111] In response to the pumped discharge of the transfer liquid from the first module 93a, a portion of the CWF-based gas retained by the gas retainer 92 flows to the first module 93a in the direction of arrows E and F via conduits 131 to 133 and the third port of the first module, thereby maintaining the non-liquid volume within the first module at a pre-compression pressure in preparation for a subsequent filling cycle.

[0112] The first filling cycle is terminated when the second module 93b is completely filled with the transfer liquid, the first module 93a is filled with the CWF-based gas at the pre-compression pressure, and the one or more storage tanks 94a to 94c are completely filled with the CWF-based gas, i.e., no other fluid is received in the one or more storage tanks, and the CWF-based gas is at a pressure higher than the pre-compression initial pressure after being compressed by the CWF-based gas transferred from the second module 93b to the storage tank. Then all valves are closed.

[0113] To start the second filling cycle, the second module liquid discharge valve 101B, the first module liquid inlet valve 102A, the liquid feed valve 114, the first module gas inlet valve 111A, the second module gas inlet valve 111B, and the first module gas transfer valve 117B are opened. The first pump 108 is then enabled, and the transfer liquid is delivered from the second module 93b to the first module 93a, thereby flowing in the direction of arrow G through the conduit 141 extending from the first port of the second module, flowing through the conduit 123, and flowing in the direction of arrow H through the conduit 144 extending from the end of the conduit 123 to the second port of the first module 93a. The same process performed in the first filling cycle is repeated in the second filling cycle. Therefore, when the first module 93a is filled with the transfer liquid, the compressed gas is caused to displace and flow through the sixth port of the first module 93a, flow through the conduit 147 in the direction of arrow I, and flow through the conduit 128 and the corresponding conduit 129 in the direction of arrow D to reach one or more storage tanks 94a to 94c. The compressed gas transferred from the first module 93a causes the CWF-based gas stored in each of the one or more storage tanks 94a to 94c to be additionally compressed.

[0114] The second filling cycle is terminated when the first module 93a is completely filled with the transfer liquid, the second module 93b is filled with the CWF-based gas at the pre-compression pressure, and the one or more storage tanks 94a to 94c are completely filled with the CWF-based fluid which is at a higher pressure than the pressure reached at the end of the first filling cycle after having been compressed by the CWF-based gas transferred from the first module 93a to the storage tanks. All valves are then closed.

[0115] The charging cycle can be repeated as well, provided that in each subsequent charging cycle, the first module and the second module are alternately filled with the transfer liquid and the CWF-based gas at the pre-compression pressure, respectively. By transferring the transfer liquid back and forth between the first module and the second module during each subsequent charging cycle and replenishing the volume of the module from which the transfer liquid is discharged with the CWF-based gas from the gas holder, the two modules are immediately ready for use in the subsequent charging cycle at the end of the previous charging cycle. The charging process will continue until the CWF-based fluid in the one or more storage tanks 94a to 94c will be condensed and changed from gas to liquid. The liquid CWF-based fluid is stored in the one or more storage tanks 94a to 94c until it is needed to be discharged.

[0116] During any of the charging cycles, if desired, the stored CWF-based fluid can undergo a cooling operation, a heating operation, or a mixing operation in conjunction with a suitable device 122 when the isolation valve 119 operatively connected to the conduit 126 is opened, and the conduit 126 is in fluid communication with the second port and the third port of each of the parallel storage tanks 94a to 94c to facilitate circulation of the stored CWF-based fluid through a closed loop. Alternatively, the conduit 126 is adapted to convey a cooling medium, such as water, which can flow within a cooling coil disposed within one or more storage tanks.

[0117] Fig.11 The operation of the system 91 during the discharge mode is illustrated. In the pre-discharge state, all valves are closed. In addition, one module is completely filled with the transfer liquid and the other module is completely filled with the CWF-based gas at the pre-compression pressure. With respect to the following exemplary first discharge cycle, the first module 93a is completely filled with the transfer liquid and the second module 93b is completely filled with the CWF-based gas at the pre-compression pressure.

[0118] To start the first discharge cycle, the first module liquid discharge valve 101A, the first module gas transfer valve 117A and the turbine injection valve 151 are opened. A predetermined amount of CWF-based fluid is released from one or more storage tanks 94a to 94c, thereby flowing through pipes 129, 128 and 147 in directions J and K until it is introduced into the interior of the first module 93a. The predetermined amount of CWF-based fluid can be controlled by opening the first module gas transfer valve 117A for a predetermined duration or immediately in response to a sensed value. The released CWF-based fluid forcibly contacts the transfer liquid in the first module 93a, so that the transfer liquid will be pressurized to the same pressure as the pressure of the released CWF-based fluid. Due to the pressure difference between the turbine inlet and the turbine outlet, the transfer liquid is propelled toward the hydraulic turbine 96 in directions L and M through pipes 121, 148 and 153, the pressure of the turbine inlet is substantially equal to the pressure of the pressurized transfer liquid, and the turbine outlet is exposed to the low-pressure liquid reservoir 98. A conduit 153 to which the turbine injection valve 151 is operatively connected extends from the junction between the conduits 141 and 148 to the reservoir 98. The transfer liquid drives the hydraulic turbine 96 to generate electricity that can be supplied to the grid. The reservoir 98 receives the transfer liquid discharged from the hydraulic turbine 96, and the reservoir 98 may be in fluid communication with the gas holder 92 via the interconnecting conduit 143 and thus not exposed to the environment, or alternatively in fluid communication with the ambient air.

[0119] In response to the discharge of the high pressure transfer liquid from the first module 93a, the additional volume of the first module 93a not occupied by the transfer liquid can be used for the CWF-based fluid, so that the CWF-based fluid can expand and achieve a two-phase, i.e., vapor-liquid state or a completely gas phase. Due to the direct contact between the CWF-based fluid and the transfer liquid, the temperature change of the CWF-based fluid is reduced, thereby allowing the CWF-based fluid to expand substantially isothermally.

[0120] When the isolation valve 116A operatively connected to the pipeline 135 and the isolation valve 118A operatively connected to the pipeline 139 are opened, the heat transfer liquid located at the bottom of the first module 93a is circulated in a closed loop through the fourth port and the fifth port of the first module and through the pipelines 135, 137 and 139 by means of the second pump 109, and a substantially isothermal expansion of the CWF-based fluid in the first module 93a can be ensured, and the CWF-based fluid undergoes a cooling process during the substantially isothermal expansion. Alternatively or additionally, when the isolation valves 116A and 118A are opened, a mixing device or nozzle in use can help ensure the substantially isothermal expansion.

[0121] While the high pressure transfer liquid is being discharged from the first module 93a, the second module liquid inlet valve 102B, the second module gas outlet valve 113B and the return valve 156 are opened. Thus, while the transfer liquid flows into the reservoir 98, the received transfer liquid is delivered to the second module 93b by the first pump 108 for another discharge cycle, thereby flowing in directions N and O through the return conduit 158 ​​and conduits 123 and 124. In response, the CWF-based gas is displaced from the seventh port of the second module 93b through conduits 131 and 149 to the gas holder 92 in directions P and Q. The first discharge cycle is terminated when the first module 93a is completely filled with the CWF-based gas at a predetermined low pressure and the second module 93b is completely filled with the transfer liquid at near atmospheric pressure. All valves are then closed.

[0122] To start the second discharge cycle, the second module liquid discharge valve 101B and the turbine injection valve 151 are opened. When the second module gas transfer valve 117B is opened immediately during a predetermined duration or until a sensed value is detected, a predetermined amount of CWF-based fluid is released from one or more storage tanks 94a to 94c, thereby flowing through pipes 129, 128, 127 in directions J and R until introduced into the interior of the second module 93b. Once the predetermined amount of CWF-based fluid is introduced into the second module 93b, the valve 117B is closed. Therefore, the transfer liquid within the second module 93b is propelled by the released CWF-based fluid in directions S and M through pipes 141 and 153 toward the hydraulic turbine 96 to generate electricity that can be supplied to the grid.

[0123] The same process performed in the first discharge cycle is repeated in the second discharge cycle, but the same process is repeated for another module. Therefore, while the first module liquid inlet valve 102A, the first module gas outlet valve 113A and the return valve 156 are open, the transfer liquid that has flowed into the reservoir 98 is returned by the first pump 108 to the first module 93a for another discharge cycle, thereby flowing through the return pipe 158 and pipes 123 and 159 in directions N and T. In response, the CWF-based gas-delivered transfer liquid is displaced from the seventh port of the first module 93a in directions U, P and Q through pipes 131, 149 and 161 to the gas holder 92. The second discharge cycle ends when the second module 93b is completely filled with the CWF-based gas at a predetermined low pressure and the first module 93a is completely filled with the transfer liquid at a pressure close to atmospheric pressure. All valves are then closed.

[0124] The discharge cycle can be repeated as well, provided that in each subsequent discharge cycle, the first module and the second module are alternately filled with the transfer liquid and the CWF-based gas at a predetermined low pressure, respectively. By transferring the transfer liquid back and forth between the first module and the second module during each subsequent discharge cycle, and receiving the CWF-based gas from one or more storage tanks in the module discharging the transfer liquid, the two modules are immediately ready for use in the subsequent discharge cycle at the termination of the previous discharge cycle. The discharge process will continue until the pressure of the CWF-based fluid in the one or more storage tanks 94a to 94c is reduced to the predetermined pre-compression pressure.

[0125] As can be appreciated from the foregoing description, the system of the present invention is able to achieve reduced costs of mechanical energy storage and improved system-wide round-trip efficiency relative to prior art practices by using conventional hydraulic equipment, namely, using a hydraulic pump during the charging mode and a hydraulic turbine during the discharge mode. Cost reduction is also possible because the working fluid used in the system of the present invention is advantageously able to undergo substantially isothermal compression, thereby avoiding the need for additional thermal energy storage to absorb the heat of compression that is typically required in the prior art.

[0126] Although some embodiments of the present invention have been described by way of illustration, it will be apparent that the present invention may be implemented with numerous modifications, variations and adaptations, as well as the use of numerous equivalents or alternative methods within the purview of those skilled in the art, without departing from the scope of the claims.

Claims

1. A multiphase energy storage system comprising: a) a first pressure vessel having at least four ports, a corresponding conduit being in fluid communication with each of the at least four ports; as well as b) a second pressure vessel configured with one or more ports, the second pressure vessel set to a temperature no greater than ambient temperature, and the second pressure vessel capable of fluid communication with the first pressure vessel, wherein a condensable working fluid (CWF) capable of condensing at ambient temperature can be introduced into the first pressure vessel through a first port of the at least four ports, and the condensable working fluid can be compressed within the first pressure vessel when in direct contact with a liquid in the first pressure vessel and the second pressure vessel that is non-evaporable and can be introduced into the first pressure vessel through a second port of the at least four ports, wherein, after a sufficient volume of the condensable working fluid or the non-evaporable liquid is introduced into the first pressure vessel, at least a portion of the compressed condensable working fluid can be transferred from the first pressure vessel through a third port of the at least four ports through one of the one or more ports to the second pressure vessel when in direct contact with the non-evaporable liquid, so that all or most of the condensable working fluid in the second pressure vessel can be stored in the second pressure vessel in a liquid state after being compressed to the saturation pressure of the condensable working fluid and condensed, wherein at least some of the non-evaporable liquid in the first pressure vessel can be propelled by the compressed condensable working fluid discharged from the second pressure vessel through a fourth port of the at least four ports to discharge stored energy.

2. The energy storage system according to claim 1, further comprising: c) a gas source in fluid communication with the first pressure vessel and containing the condensable working fluid, the condensable working fluid being capable of being fed from the gas source to the first pressure vessel.

3. The energy storage system of claim 1 , further comprising at least one hydraulic turbine capable of being driven by the non-evaporable liquid, wherein: At least a portion of the non-vaporizable liquid within the first pressure vessel is capable of being propelled toward the at least one hydraulic turbine by the compressed condensable working fluid when the compressed condensable working fluid is released from the second pressure vessel.

4. The energy storage system according to claim 3, further comprising: a liquid reservoir in fluid communication with the first pressure vessel and containing the non-vaporizable liquid; and means for transferring the non-evaporable liquid from the liquid reservoir to the first pressure vessel, The non-evaporable liquid can be introduced into the first pressure container by the delivery device through the second port among the at least four ports.

5. The energy storage system according to claim 4, wherein: The non-evaporable liquid exhausted from the at least one hydraulic turbine can be received in the liquid reservoir.

6. The energy storage system according to claim 1, wherein: The condensable working fluid is substantially isothermally compressible and isothermally expandable during direct contact with the non-evaporable liquid within the first pressure vessel.

7. The energy storage system according to claim 4, wherein: The delivery device is at least one hydraulic pump for delivering the non-evaporable liquid from the liquid reservoir to the first pressure vessel.

8. The energy storage system of claim 7, further comprising at least one additional hydraulic pump for transferring the non-evaporable liquid from the first pressure vessel to the liquid reservoir.

9. The energy storage system according to claim 1, wherein: The condensable working fluid within the first pressure vessel is continuously and additionally compressed while additional non-vaporizable liquid is introduced into the first pressure vessel.

10. The energy storage system of claim 1, further comprising a liquid-gas separator located between the first pressure vessel and the second pressure vessel to prevent the non-vaporizable liquid from flowing to the second pressure vessel.

11. The energy storage system of claim 10, further comprising a liquid-liquid separator located between the first pressure vessel and the second pressure vessel to prevent the non-vaporizable liquid from flowing to the second pressure vessel.

12. The energy storage system of claim 1, further comprising a liquid-liquid separator located between the first pressure vessel and the second pressure vessel to prevent the non-vaporizable liquid from flowing to the second pressure vessel.

13. The energy storage system of claim 1 , further comprising: A third pressure vessel capable of being in fluid communication with the first pressure vessel, wherein, prior to performing one of a charge cycle or a discharge cycle, the third pressure vessel is completely filled with a first fluid selected from the group consisting of a condensable working fluid gas or the non-evaporable liquid, and the first pressure vessel is completely filled with a second fluid selected from the group consisting of a condensable working fluid gas or the non-evaporable liquid that is different from the first fluid, such that upon termination, the third pressure vessel is completely filled with the second fluid and the first pressure vessel is completely filled with the first fluid.

14. The energy storage system according to claim 1, wherein: The first pressure vessel is also exposed to ambient temperature.

15. The energy storage system of claim 1, comprising a plurality of said first pressure vessels.

16. The energy storage system according to claim 15, wherein: All of the first pressure vessels are in fluid communication with each other, or selected first pressure vessels are in fluid communication with each other.

17. The energy storage system of claim 1, comprising a plurality of said second pressure vessels.

18. The energy storage system according to claim 17, wherein: All of the second pressure vessels are in fluid communication with each other, or selected second pressure vessels are in fluid communication with each other.

19. The energy storage system according to claim 2, wherein: The gas retainer additionally contains a non-condensable working fluid that is miscible with the condensable working fluid, the non-condensable working fluid gas being additionally compressible after liquefaction of the condensable working fluid.

20. The energy storage system of claim 1, further comprising a flow control component operatively connected to each of the corresponding conduits to selectively control the flow of fluid through the conduits.

21. The energy storage system of claim 1, wherein: The second pressure vessel is exposed to ambient temperature or to a temperature below ambient temperature.

22. A method for generating power from stored energy, the method comprising the steps of: a) providing a first pressure vessel and a second pressure vessel, wherein the second pressure vessel is fluidly connectable to the first pressure vessel and is set to a temperature no greater than ambient temperature; b) compressing a condensable working fluid (CWF) capable of condensing at ambient temperature substantially isothermally within the first pressure vessel while in direct contact with a non-evaporable liquid, and causing at least a portion of the compressed condensable working fluid to transfer from the first pressure vessel to the second pressure vessel in response to interaction with the non-evaporable liquid; c) transferring an additional amount of the compressed condensable working fluid to the second pressure vessel so that all or a majority of the condensable working fluid in the second pressure vessel is compressed to the saturation pressure of the condensable working fluid and condensed to produce a liquid condensable working fluid; d) propelling at least some of the non-evaporable liquid located in the first pressure vessel toward at least one hydraulic turbine by the compressed condensable working fluid discharged from the second pressure vessel; and e) said at least one hydraulic turbine is rotatably driven by said propelled non-evaporable liquid to generate power, wherein the non-evaporable liquid is prevented from flowing to the second pressure vessel while the at least a portion of the compressed condensable working fluid is transferred from the first pressure vessel to the second pressure vessel.

23. The method according to claim 22, wherein: The condensable working fluid is substantially isothermally compressed by activating a unit of a mixing device in fluid communication with the first pressure vessel or the second pressure vessel and thereby eliminating temperature gradients within the condensable working fluid.

24. The method according to claim 23, wherein: A unit of the mixing device is activated in response to a sensed condition indicative of liquefaction of the condensable working fluid.

25. The method according to claim 22, wherein: When the discharged compressed condensable working fluid is in a liquid state, a gaseous state or in a multi-phase state, at least some of the non-evaporable liquid in the first pressure vessel is propelled toward the at least one hydraulic turbine by the compressed condensable working fluid discharged from the second pressure vessel.

26. The method of claim 22, wherein: Transferring at least a portion of the compressed condensable working fluid from the first pressure vessel to the second pressure vessel is performed during a plurality of charge cycles.

27. The method according to claim 26, wherein: The step of advancing at least some of the non-evaporable liquid located in the first pressure vessel by the compressed condensable working fluid discharged from the second pressure vessel is performed during a plurality of discharge cycles.

28. The method according to claim 27, further comprising the steps of: i. providing a third pressure vessel capable of being in fluid communication with the first pressure vessel, wherein, before performing one of a filling cycle or a draining cycle, the third pressure vessel is completely filled with a first fluid selected from a condensable working fluid gas or the non-evaporable liquid, and the first pressure vessel is completely filled with a second fluid selected from a condensable working fluid gas or the non-evaporable liquid that is different from the first fluid; and ii. performing said one of a fill cycle or a drain cycle such that upon termination, the third pressure vessel is completely filled with the second fluid and the first pressure vessel is completely filled with the first fluid.

29. The method of claim 28, further comprising performing the other of a charge cycle or a drain cycle when the third pressure vessel is completely filled with the second fluid and the first pressure vessel is completely filled with the first fluid.

30. The method of claim 28, wherein: The compressed condensable working fluid discharged from the second pressure vessel expands substantially isothermally during direct contact with the non-evaporable liquid within the first pressure vessel.

31. A direct contact fluid transfer (DCFT) module comprising: a) a first pressure vessel having at least four ports, a corresponding conduit being in fluid communication with each of the at least four ports; b) a second pressure vessel, the second pressure vessel being set to a temperature no greater than ambient temperature, the second pressure vessel having one or more ports; as well as c) a flow control component operatively connected to each of the corresponding conduits to selectively control the flow of fluid through the conduits, wherein a condensable working fluid (CWF) capable of condensing at ambient temperature can be introduced into the first pressure vessel through a first port of the at least four ports, wherein a non-evaporable liquid is capable of being introduced into the first pressure vessel through a second port of the at least four ports to cause substantially isothermal compression of the condensable working fluid when in direct contact with the non-evaporable liquid, wherein, after a sufficient additional volume of the non-evaporable liquid is introduced into the first pressure vessel, at least a portion of the compressed condensable working fluid can be transferred from the first pressure vessel through a third port of the at least four ports through one of the one or more ports to the second pressure vessel while in direct contact with the non-evaporable liquid, and the at least a portion of the compressed condensable working fluid can be stored in a liquid state in the second pressure vessel after being compressed to the saturation pressure of the condensable working fluid and condensed, wherein at least some of the non-evaporable liquid in the first pressure vessel can be propelled by the compressed condensable working fluid discharged from the second pressure vessel through a fourth port of the at least four ports to discharge stored energy.

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