Pressure accumulation system and operation method for pressure accumulation system

Abstract

To improve energy efficiency when liquefying a gas-phase working fluid and when vaporizing a liquid-phase working fluid.SOLUTION: A pressure accumulation system 100 comprises: a first pressure vessel 10 that stores a liquid and is filled with a gas-phase working fluid; a pump 20 that supplies a liquid to the first pressure vessel and through which a liquid discharged from the first pressure vessel passes; a motor generator 30 that can switch between a driving state for driving the pump 20 and a power generating state for generating power by power transmitted from the pump 20; a liquefaction facility 40 that liquefies a gas-phase working fluid introduced from the first pressure vessel 10 when the motor generator 30 operates in the driving state; a second pressure vessel 50 that stores a working fluid liquefied by the liquefaction facility 40; and a vaporization facility 60 that vaporizes a liquid-phase working fluid introduced from the second pressure vessel 50 and supplies the same to the first pressure vessel 10 when the motor generator 30 operates in the power generating state.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a pressure accumulation system and a method for operating a pressure accumulation system. [Background technology]

[0002] Conventionally, a night-time pressure storage device is known that uses overnight electricity to compress and cool air, store it in a pressure tank as liquefied air, and vaporize and expand the liquefied air stored in the pressure tank during the day to drive a generator and recover energy (see, for example, Patent Document 1). According to Patent Document 1, by liquefying air and storing it under pressure during the night, it is possible to use inexpensive electricity at night to level out the load on electricity usage between day and night. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-225018 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, room-temperature air is compressed in a short time by the compressor / expander, resulting in a high temperature of the compressed air. Therefore, the compressed air must be cooled to minus two hundred and several tens of degrees Celsius to be liquefied, which requires a great deal of energy for cooling. Furthermore, when the liquefied air is vaporized and expanded to operate the induction motor / induction generator connected to the compressor / expander, the vaporized air must be heated and expanded with high-temperature gas at 400°C to 450°C, which requires a great deal of energy for expansion.

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide a pressure storage system and an operating method for a pressure storage system that can efficiently compress the working fluid by liquefying the gas phase working fluid when the motor generator operates in a driving state, and can efficiently extract high-output energy by re-vaporizing the liquid phase working fluid when the motor generator operates in a power generating state. [Means for solving the problem]

[0006] In order to solve the above problems, the pressure accumulation system and the operating method of the pressure accumulation system of the present disclosure employ the following means. A pressure accumulation system according to one aspect of the present disclosure includes a first pressure vessel that stores liquid and is filled with a gaseous working fluid; a pump that supplies the liquid to the first pressure vessel and through which the liquid discharged from the first pressure vessel passes; a motor-generator that can switch between a driving state that drives the pump and a power generating state that generates electricity using power transmitted from the pump; a liquefaction facility that liquefies the gaseous working fluid guided from the first pressure vessel when the motor-generator operates in the driving state; a second pressure vessel that stores the working fluid liquefied by the liquefaction facility; and a vaporization facility that vaporizes the liquid-phase working fluid guided from the second pressure vessel and supplies it to the first pressure vessel when the motor-generator operates in the power generating state.

[0007] In a method for operating a pressure accumulation system according to one aspect of the present disclosure, the pressure accumulation system includes a first pressure vessel that stores a liquid and is filled with a gaseous working fluid, a pump that supplies the liquid to the first pressure vessel and through which the liquid discharged from the first pressure vessel passes, a motor-generator that is switchable between a driving state that drives the pump and a power generating state that generates electricity using power transmitted from the pump, and a second pressure vessel that stores the liquefied working fluid, and the method includes: a liquefaction step of liquefying the gaseous working fluid introduced from the first pressure vessel when the motor-generator operates in the driving state and supplying the liquefied working fluid to the second pressure vessel; and a vaporization step of vaporizing the liquid-phase working fluid introduced from the second pressure vessel when the motor-generator operates in the power generating state and supplying the liquid-phase working fluid to the first pressure vessel. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a pressure storage system and an operating method of a pressure storage system that can efficiently compress the working fluid by liquefying the gas phase working fluid when the motor generator operates in a driving state, and that can efficiently extract high-output energy by re-vaporizing the liquid phase working fluid when the motor generator operates in a power generating state. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram showing a pressure accumulation system according to a first embodiment of the present disclosure. [Figure 2] 4 is a flowchart showing a method for operating the pressure accumulation system according to the first embodiment of the present disclosure, illustrating the operation of liquefying a gas-phase working fluid by the liquefaction equipment. [Figure 3] 4 is a flowchart showing a method for operating the pressure accumulation system according to the first embodiment of the present disclosure, illustrating an operation of vaporizing a liquid-phase working fluid by the vaporization equipment. [Figure 4] FIG. 4 is a schematic configuration diagram showing a pressure accumulation system according to a second embodiment of the present disclosure. [Figure 5] FIG. 10 is a schematic configuration diagram showing a pressure accumulation system according to a third embodiment of the present disclosure. [Figure 6] FIG. 10 is a schematic configuration diagram showing a pressure accumulation system according to a fourth embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] [First embodiment] A pressure accumulation system 100 and an operating method for the pressure accumulation system 100 according to a first embodiment of the present disclosure will be described below with reference to the drawings. Fig. 1 is a schematic configuration diagram showing the pressure accumulation system 100 according to the first embodiment of the present disclosure. The pressure accumulation system 100 of this embodiment is a system that liquefies a gas-phase working fluid and vaporizes a liquid-phase working fluid.

[0011] As shown in FIG. 1, the pressure storage system 100 of this embodiment includes a first pressure vessel 10, a pump (which also serves as a water turbine) 20, a motor-generator 30, a liquefaction facility 40, a second pressure vessel 50, an evaporation facility 60, a supply / discharge unit 70, a pressure detection unit 80, and a control device 90.

[0012] The first pressure vessel 10 is a vessel having a liquid region S1 for storing a liquid (e.g., water or seawater) and a gas region S2 filled with a gas-phase working fluid. The gas-phase working fluid is a gas such as carbon dioxide. The gas-phase working fluid used is preferably pure carbon dioxide. By using pure carbon dioxide, the liquefaction temperature of the working fluid can be near room temperature rather than an extremely low temperature, and the energy consumption required to liquefy the working fluid can be reduced.

[0013] The pump 20 is a device that supplies liquid from outside the system to the first pressure vessel 10 via the supply line L1 and the supply / discharge section 70 when the motor-generator 30, which will be described later, is in a driving state, and transmits power to the motor-generator 30 when liquid discharged from the first pressure vessel 10 passes through the pump 20 when it is in a power generating state. The pump 20 is connected to the motor-generator 30 so as to drive integrally with the motor-generator 30. When the pump 20 supplies liquid to the first pressure vessel 10, the regulating valve 21 is in an open state. When the liquid guided to the supply line L1 from the first pressure vessel 10 is discharged to the supply / discharge section 70, the regulating valve 21 is in an open state.

[0014] The motor generator 30 is a device that can switch between a driving state in which it drives the pump 20 and a power generating state in which it generates power using power transmitted from the pump 20. In the driving state, the motor generator 30 is supplied with power from a power generation facility 200 that uses renewable energy, such as a solar power generation facility. In the power generating state, the motor generator 30 supplies power to a load 300.

[0015] The liquefaction equipment 40 liquefies the gas-phase working fluid guided from the first pressure vessel 10 when the motor generator 30 operates in a driven state. The liquefaction equipment 40 includes a compressor 41, a heat exchanger (first heat exchanger) 42, a circulation pump (compressor) 43, a heat exchanger (third heat exchanger) 44, an expansion valve 45, and a cooling pump 46. Note that a cooling fan may be used instead of the cooling pump 46.

[0016] The compressor 41 is a device that compresses the gas phase working fluid that is guided via the supply line L2 from the first pressure vessel 10. The working fluid compressed by the compressor 41 is guided to the heat exchanger .

[0017] The heat exchanger 42 is a device that cools the working fluid compressed by the compressor 41 by heat exchange with a first heat exchange medium (e.g., a refrigerant) circulating through the circulation line L3. The first heat exchange medium circulates through the circulation line L3 by the power of the circulation pump 43. The first heat exchange medium expands as it passes through the expansion valve 45, becoming a low-temperature, low-pressure liquid, and cools the working fluid compressed by the compressor 41 in the heat exchanger 42.

[0018] The heat exchanger 44 is a device that cools the first heat exchange medium, which has been heated by heat exchange with the working fluid in the heat exchanger 42, by heat exchange with a second heat exchange medium (e.g., water or air) circulating through a supply line L4. The cooling pump 46 supplies the second heat exchange medium to the heat exchanger 44 via the supply line L4.

[0019] The second pressure vessel 50 is a vessel for storing the working fluid liquefied by the liquefaction facility 40. The working fluid in a liquid phase, which has been cooled by the first heat exchange medium while passing through the heat exchanger 42, is supplied to the second pressure vessel 50 via a supply line L2. The second pressure vessel 50 preferably has a double shell structure to suppress heat input from the outside. It is further preferable to provide a heat insulating material inside or outside the double shell structure.

[0020] The pressure accumulation system 100 of this embodiment can reduce the capacity of the second pressure vessel 50 by liquefying the working fluid to reduce its volume, thereby reducing the manufacturing cost of the second pressure vessel 50. Although power is required for the circulation pump 43 that circulates the first heat exchange medium to liquefy the working fluid, which increases operating costs, there is a significant economic effect in that the manufacturing cost of the second pressure vessel 50 can be reduced.

[0021] The vaporization equipment 60 is equipment that vaporizes the liquid-phase working fluid guided from the second pressure vessel 50 when the motor generator 30 operates in a power generating state and supplies the vaporized working fluid to the gas region S2 of the first pressure vessel 10. The vaporization equipment 60 has a heat exchanger (second heat exchanger) 61 and an adjustment valve 62 arranged in the supply line L5.

[0022] The heat exchanger 61 is a device that heats the liquid-phase working fluid guided from the second pressure vessel 50 via the supply line L5 by heat exchange with a heating medium (e.g., water or seawater) flowing through the supply line L6. When the motor generator 30 operates in a power generating state, a portion of the liquid guided from the first pressure vessel 10 to the supply / discharge section 70 via the supply line L1 is guided to the supply line L6 as the heating medium. When the vaporization equipment 60 vaporizes the working fluid, the adjustment valve 62 arranged on the supply line L5 and the adjustment valve 63 arranged on the supply line L6 are opened.

[0023] The supply / discharge unit 70 is a device that supplies liquid from outside the system to the first pressure vessel 10 via the supply line L1 when the motor generator 30 is in an operating state, and discharges the liquid guided from the first pressure vessel 10 via the supply line L1 to outside the system when the motor generator 30 is in an electric power generating state. The supply / discharge unit 70 is preferably provided with a screen (not shown) to prevent organisms, garbage, etc. from entering the supply line L1 from the outside.

[0024] The pressure detection unit 80 is a device that detects the pressure of the gas phase working fluid filled in the gas region S2 of the first pressure vessel 10, and transmits the detected pressure to the control device 90.

[0025] The control device 90 is a device that controls each part of the pressure storage system 100. When the power demand of the load 300 is smaller than the power generated by the power generation facility 200, the control device 90 detects that there is surplus power in the power generated by the power generation facility 200. Furthermore, when the power demand of the load 300 is greater than the power generated by the power generation facility 200, the control device 90 detects that the power generated by the power generation facility 200 is insufficient.

[0026] Furthermore, the control device 90 may receive a command from an electric power company (electric power transmission and distribution company) that adjusts the supply and demand of electric power, and may store energy by driving the motor generator 30, or may generate electricity by driving the motor generator 30. In this case, the control device 90 constantly transmits information such as the power (kW) stored in the pressure storage system 100, the amount of power (kWh), the generated power (kW), and the amount of generated power (kWh) to the electric power company.

[0027] Next, a method for operating the pressure accumulation system of this embodiment will be described with reference to the drawings. Fig. 2 is a flowchart showing a method for operating the pressure accumulation system 100 of this embodiment, illustrating the operation of liquefying a gas-phase working fluid by the liquefaction equipment 40. Each step shown in Fig. 2 is performed by the control device 90 executing a control program.

[0028] In step S101, the control device 90 determines whether or not surplus power is being generated based on information (electronic power supply and demand adjustment signal) from the power transmission and distribution system to which the power generation facility 200 and the load 300 belong, detects or receives information about this, and if the answer is YES, the process proceeds to step S102, and if the answer is NO, the process proceeds to step S108.

[0029] In step S102, because surplus power is being generated, the control device 90 operates the motor-generator 30 as an electric motor to drive the pump 20. The control device 90 switches the regulating valve 21 to an open state when driving the pump 20. Before driving the pump 20 in step S102, the first pressure vessel 10 is in a state in which both a liquid region S1 and a gas region S2 exist, or in which only the gas region S2 exists. Because the inside of the first pressure vessel 10 is constantly pressurized to a constant pressure by the gas pressure in the gas region S2, the pump 20 can pump water against this pressure, thereby storing a large amount of energy and also storing a large amount of surplus power. The amount of water that can be stored can be adjusted by adjusting the opening of the adjusting valve 21 and thereby changing the amount of water that the pump 20 sends out.

[0030] When the motor-generator 30 is operated as an electric motor by the surplus power to drive the pump 20, liquid is introduced from outside the system to the first pressure vessel 10 via the supply line L1. As the liquid is introduced into the first pressure vessel 10, the liquid level 11 in the liquid region S1 of the first pressure vessel 10 rises, the liquid region S1 gradually increases in size, and the gas region S2 gradually decreases in size. As the gas region S2 decreases in size, the pressure of the gas-phase working fluid present in the gas region S2 increases.

[0031] The compression of the gas phase working fluid due to the reduction in the gas region S2 is carried out over a relatively long period of time in accordance with the rise in the liquid level 11 (for example, 120 minutes or more. When the gas region S2 is compressed over a period of 120 minutes or more, the rate of decrease in the gas region S2 per minute is approximately 0.83% or less). Therefore, the gas region S2 is compressed slowly, and the thermal cycle is close to isothermal compression, so the gas phase working fluid can be compressed more efficiently than a compressor that compresses the gas region S2 in a short period of time (close to adiabatic compression in terms of the thermal cycle).

[0032] In step S103, the control device 90 determines whether the pressure of the gas-phase working fluid in the gas region S2 of the first pressure vessel 10 detected by the pressure detection unit 80 is equal to or greater than P1. If the result is YES, the process proceeds to step S104. If the result is NO, step S101 is executed again. For example, if 3 MPa is the reference pressure P1N, then P1 is 3.3 MPa, which is a 10% increase from this pressure. The liquefaction process in step S104 is operated at pressure P1. The optimum setting is adjusted through testing and trial operation.

[0033] In step S104, the control device 90 liquefies the gas-phase working fluid using the liquefaction equipment 40, and supplies the liquefied working fluid to the second pressure vessel 50. The liquefaction equipment 40 operates the compressor 41, the circulation pump 43, and the cooling pump 46 to compress the gas-phase working fluid guided from the gas region S2 via the supply line L2, cools and liquefies the compressed working fluid using the first heat exchange medium in the heat exchanger 42, and supplies the liquid-phase working fluid to the second pressure vessel 50.

[0034] In step S104, the control device 90 controls the rotation of the compressor 41 so that the pressure of the gas phase working fluid in the gas region S2 of the first pressure vessel 10 detected by the pressure detection unit 80 is maintained at P1, for example.

[0035] In step S105, the control device 90 detects the liquid level using the level gauge 85 of the first pressure vessel 10 and determines whether the liquid level is H1H or higher. If the answer is YES, the process proceeds to step S108; if the answer is NO, the process proceeds to step S106.

[0036] In step S106, the control device 90 detects the pressure using the pressure detection unit 80 of the first pressure vessel 10 and determines whether the pressure is P1H or higher (for example, whether the pressure has risen to 3.45 MPa, which is 15% higher than the reference pressure of 3 MPa).If the result is YES, the process proceeds to step S108; if the result is NO, the process proceeds to step S107.

[0037] In step S107, the control device 90 detects the liquid level in the second pressure vessel 50 output from the level gauge 50a and determines whether the liquid level is equal to or higher than H2. If the result is YES, the process proceeds to step S108, and if the result is NO, the process continues to execute step S101. H2 is set, for example, to the maximum height of the liquid-phase working fluid that can be stored in the second pressure vessel 50, or to a height slightly lower than the maximum value.

[0038] In step S108, the control device 90 controls the motor generator 30 to stop driving the pump 20 by the motor generator 30. When stopping the driving of the pump 20, the control device 90 switches the regulating valve 21 to the closed state.

[0039] In step S109, the liquefaction equipment 40 is stopped. The control device 90 stops the compressor 41, the circulation pump 43, and the cooling pump 46. However, the liquefaction equipment 40 is stopped when the pressure detected by the pressure detection unit 80 of the first pressure vessel 10 drops to the reference pressure P1N or a pressure close to that reference pressure (for example, if the reference pressure P1N is 3 MPa, the liquefaction equipment 40 is stopped when the pressure drops to the reference pressure P1 or to 3.05 MPa, which is close to P1).

[0040] The pressure inside the first pressure vessel 10 fluctuates due to the ambient temperature even when the pump 20 is not operating (when the gas temperature in the gas region S2 rises due to fluctuations in the ambient temperature, the gas expands and the pressure increases. Conversely, when the ambient temperature drops, the gas contracts and the pressure decreases). When the pressure in the first pressure vessel 10 increases due to the ambient temperature, this is detected by the pressure detection unit 80, and the control device 90 operates the liquefaction equipment 40. Through the above process, the surplus electricity generated by the power generation equipment 200 can be used to liquefy the gaseous working fluid in the first pressure vessel 10 using the liquefaction equipment 40 and store the liquefied gas in the second pressure vessel 50.

[0041] Next, the operation of vaporizing the liquid-phase working fluid in the second pressure vessel 50 by the vaporization equipment 60 will be described with reference to Fig. 3. Fig. 3 is a flowchart showing the operation method of the pressure accumulation system 100 according to the first embodiment of the present disclosure, and shows the operation of vaporizing the liquid-phase working fluid by the vaporization equipment 60. Each step shown in Fig. 3 is performed by the control device 90 executing a control program.

[0042] In step S201, the control device 90 determines whether there is a demand for electricity based on information (electronic power supply and demand adjustment signal) from the power transmission and distribution system to which the power generation facility 200 and the load 300 belong, detects or receives information, and if the answer is YES, the process proceeds to step S202, and if the answer is NO, the process proceeds to step S205.

[0043] In step S202, the control device 90 supplies the liquid (e.g., water or seawater) stored in the first pressure vessel 10 to the pump 20 (which also functions as a water turbine), and generates electricity by driving the motor-generator 30, which is operating in a power-generating state, with the pump 20. The control device 90 adjusts the opening of the regulating valve 21 so that the motor-generator 30 generates the desired amount of electricity.

[0044] In step S203, the control device 90 controls the vaporization equipment 60 to vaporize the liquid-phase working fluid stored in the second pressure vessel 50. The control device 90 controls, for example, the aperture of the regulating valve 62 so that the pressure of the gas-phase working fluid in the gas region S2 of the first pressure vessel 10 detected by the pressure detection unit 80 is maintained at P1.

[0045] In step S204, the control device 90 determines whether the height of the liquid level in the liquid region S1 of the first pressure vessel 10 detected by the level gauge 85 is equal to or greater than H1. If the result is YES, step S201 is executed again, and if the result is NO, the process proceeds to step S205. H1 is set, for example, to the minimum height of the liquid that can be stored in the first pressure vessel 10, or to a height slightly higher than the minimum value.

[0046] In step S205, the control device 90 stops the vaporization equipment 60 because the liquid level in the first pressure vessel 10 is below H1 and the liquid in the first pressure vessel 10 cannot be further reduced. The control device 90 closes the regulating valves 62 and 63.

[0047] In step S206, the control device 90 controls the supply of liquid from the first pressure vessel 10 to the pump 20 to be stopped. The control device 90 closes the regulating valve 21 to prevent the motor generator 30 from generating electricity, and ends the processing of this flowchart. Through the above process, the pump 20 is rotated by the liquid stored in the first pressure vessel 10 using the pressure of the gas phase working fluid obtained by vaporizing the liquid phase working fluid stored in the second pressure vessel 50, and electricity can be generated by the motor-generator 30 connected to the pump 20.

[0048] The pressure accumulation system 100 of this embodiment described above provides the following actions and effects. According to the pressure storage system 100 of this embodiment, when the motor-generator 30 is driven by surplus power or the like, the pump 20 connected to the motor-generator 30 is driven to supply liquid to the first pressure vessel 10. As the amount of liquid stored in the first pressure vessel 10 increases, the gas-phase working fluid is pressurized, reducing the volume of the working fluid. As the liquid level in the first pressure vessel 10 rises, the gas-phase working fluid is gradually pressurized over a relatively long period of time. Therefore, in terms of the thermal cycle, it is close to isothermal compression, and the gas-phase working fluid can be compressed with higher energy efficiency than a compressor that compresses in a short time. The compressed gas can be liquefied by further compressing and cooling using surplus power, allowing energy storage in a small-capacity pressure vessel.

[0049] Furthermore, according to the pressure accumulation system 100 of this embodiment, when the motor generator 30 operates in a power generating state, supplying the liquid stored in the first pressure vessel 10 to the pump 20 causes the motor generator 30 connected to the pump 20 to rotate and generate electricity. When the amount of liquid stored in the first pressure vessel 10 decreases, the gas-phase working fluid vaporized by the vaporization equipment 60 is supplied to the first pressure vessel 10, and the pressure of the gas-phase working fluid in the gas region S2 of the first pressure vessel 10 is maintained constant.

[0050] Therefore, regardless of the liquid level in the pressure vessel, the pump 20 (which acts as a water turbine) can be driven at a constant pressure, making it possible to supply a constant amount of electricity (allowing for operation in the same way as existing pumped-storage power generation). Also, in a heat engine, which obtains power generation power by heating and expanding gas such as air, it is not possible to generate electricity with high efficiency unless the pressure and temperature are increased, but in this embodiment, energy recovery can be performed using a water turbine, which is used in hydroelectric power generation, so energy recovery (= power generation using energy derived from stored surplus renewable electricity) can be performed with the same high efficiency as a water turbine even at room temperature.

[0051] In this way, according to the pressure storage system 100 of this embodiment, when the motor-generator 30 operates in a driving state, the gas-phase working fluid is liquefied, thereby efficiently compressing the working fluid, and when the motor-generator 30 operates in a power-generating state, the liquid-phase working fluid is re-vaporized, thereby efficiently extracting high-output energy.

[0052] Second Embodiment Next, a pressure storage system 100A according to a second embodiment of the present disclosure will be described with reference to the drawings. This embodiment is a modified example of the first embodiment, and is similar to the first embodiment except where specifically described below, and therefore further description will be omitted. Figure 4 is a schematic diagram showing the configuration of a pressure storage system 100A according to the second embodiment of the present disclosure.

[0053] The pressure accumulation system 100 of the first embodiment uses a part of the liquid guided from the first pressure vessel 10 to the supply / discharge section 70 as a heat source for vaporizing the liquid-phase working fluid. In contrast, the pressure accumulation system 100A of the present embodiment uses another heat source in addition to a part of the liquid guided from the first pressure vessel 10 to the supply / discharge section 70 as a heat source for vaporizing the liquid-phase working fluid.

[0054] 4, the liquefaction equipment 40 of this embodiment includes a circulation pump 47, a circulation pump 48, a high-temperature tank 49a, and a low-temperature tank 49b, which are each arranged in the circulation line L7. The circulation pumps 47 and 48 circulate a second heat exchange medium (e.g., water) in the circulation line L7.

[0055] The heat exchanger 44 cools the first heat exchange medium heated by the working fluid in the heat exchanger 42 by heat exchange with the second heat exchange medium circulating through the circulation line L7. The second heat exchange medium heated in the heat exchanger 44 is guided to the high-temperature tank 49a. The second heat exchange medium guided to the high-temperature tank 49a is guided to the heat exchanger 61 as a heat source for vaporizing the liquid-phase working fluid. The second heat exchange medium cooled by the liquid-phase working fluid in the heat exchanger 61 is guided again to the heat exchanger 44 via the low-temperature tank 49b.

[0056] The heat exchanger 61 heats the liquid-phase working fluid introduced from the second pressure vessel 50 via the supply line L5 by heat exchange with the second heat exchange medium circulating in the circulation line L7. Thus, in the pressure accumulation system 100A of this embodiment, the heating medium used by the heat exchanger 61 to heat the working fluid (the fluid coming out of the second pressure vessel 50) is the second heat exchange medium heated by the first heat exchange medium in the heat exchanger 44.

[0057] According to the pressure storage system 100A of this embodiment, the first heat exchange medium heated by the working fluid in the heat exchanger 42 and the second heat exchange medium are heat exchanged in the heat exchanger 44, and the second heat exchange medium can be used as a heating medium for heating the liquid phase working fluid in the heat exchanger 61. By using the first heat exchange medium heated by the working fluid in the heat exchanger 42 as a heat source for heating the liquid phase working fluid, it can be effectively used to heat parts that freeze in the low temperature liquid phase working fluid, and energy efficiency can be improved.

[0058] Third Embodiment Next, a pressure accumulation system 100B according to a third embodiment of the present disclosure will be described with reference to the drawings. This embodiment is a modified example of the second embodiment, and is similar to the second embodiment except where specifically described below, and therefore further description will be omitted. Figure 5 is a schematic diagram showing the configuration of a pressure accumulation system 100B according to the third embodiment of the present disclosure.

[0059] In the pressure accumulation system 100A of the second embodiment, the first heat exchange medium heated by the working fluid in the heat exchanger 42 is heat exchanged with the second heat exchange medium in the heat exchanger 44, and the second heat exchange medium is used as a heat source for vaporizing the liquid-phase working fluid in the heat exchanger 61. In contrast, in the pressure accumulation system 100B of the present embodiment, the second heat exchange medium is heat exchanged with the third heat exchange medium in the heat exchanger 142, and the liquid-phase third heat exchange medium is used as a heat source for vaporizing the third heat exchange medium.

[0060] 5, the liquefaction equipment 40 of this embodiment includes a circulation pump 141, a heat exchanger (fourth heat exchanger) 142, a turbine 143, and a generator 144, which are all arranged in the circulation line L8. The circulation pump 141 circulates a third heat exchange medium (for example, an organic fluid having a boiling point lower than that of water, such as isopentane, butane, or propane) in the circulation line L8.

[0061] The heat exchanger 142 is a device that heats the third heat exchange medium by heat exchange with the second heat exchange medium that has been heated by the first heat exchange medium in the heat exchanger 44. The third heat exchange medium circulating through the circulation line L8 is heated by the second heat exchange medium in the heat exchanger 142 and evaporated, and is supplied to the turbine 143.

[0062] The turbine 143 is a device driven by a third heat exchange medium heated by heat exchange with the second heat exchange medium. The gaseous third heat exchange medium supplied to the turbine 143 drives the turbine 143 to rotate a generator 144 connected to the turbine 143. The generator 144 generates electricity when rotated by the power from the turbine 143.

[0063] The heat exchanger 61 vaporizes the liquid-phase working fluid guided from the second pressure vessel 50 via the supply line L5 by heat exchange with the third heat exchange medium circulating in the circulation line L8. The third heat exchange medium (=condenser) that is liquefied (=condensed) by heat exchange with the liquid-phase working fluid sent from the second pressure vessel 50 passes through the heat exchanger 61 and is then guided to the heat exchanger 142 by the circulation pump 141. Thus, in the pressure storage system 100B of this embodiment, the heat source that the heat exchanger 61 uses to vaporize the working fluid is the third heat exchange medium that has been heated by the second heat exchange medium in the heat exchanger 142 and has driven the turbine.

[0064] According to the pressure storage system 100B of this embodiment, the first heat exchange medium heated by the working fluid in the heat exchanger 42 and the second heat exchange medium are heat exchanged in the heat exchanger 44, the second heat exchange medium heated by the first heat exchange medium in the heat exchanger 44 and the third heat exchange medium are heat exchanged in the heat exchanger 142 and heated, the heated third heat exchange medium drives the turbine 143, electricity is generated in the generator 144, the third heat exchange medium leaving the turbine 143 is condensed in the heat exchanger 61, and at the same time the working fluid is vaporized from the liquid phase.

[0065] [Fourth embodiment] Next, a pressure accumulation system 100C according to a fourth embodiment of the present disclosure will be described with reference to the drawings. This embodiment is a modified example of the first embodiment, and is similar to the first embodiment except where specifically described below, and therefore further description will be omitted. Fig. 6 is a schematic diagram showing the configuration of a pressure accumulation system 100C according to the fourth embodiment of the present disclosure.

[0066] The first pressure vessel 10 of the pressure accumulation system 100 of the first embodiment was designed to bring the liquid in the liquid region S1 and the gas-phase working fluid in the gas region S2 into direct contact with each other. In contrast, the first pressure vessel 10C of the present embodiment isolates the liquid in the liquid region S1 from the gas-phase working fluid in the gas region S2 so that they do not come into direct contact with each other. By isolating the liquid region S1 and the gas region S2, it is possible to suppress the effects (e.g., deterioration in equipment performance and reliability) caused by the gas-phase working fluid dissolving into the liquid and reducing the pressure in the gas region S2. It is also possible to prevent the surrounding environment from being affected when the liquid in which the gas-phase working fluid has dissolved is discharged.

[0067] 6, the first pressure vessel 10C of this embodiment has multiple accumulators 12. Each accumulator 12 has an expandable bladder 12a filled with a gas-phase working fluid. As the liquid region S1 expands, the bladder 12a contracts, changing from the state shown by the solid line in FIG. 6 to the state shown by the dotted line.

[0068] The pressure accumulation system 100C includes multiple supply lines L9a, L9b, L9c, L9d, L9e, and L9f that supply gas-phase working fluid from multiple accumulators 12 to a liquefaction facility 40, multiple on-off valves 13 arranged on each supply line, and a mist separator 14. When a bladder 12a of an accumulator 12 is damaged and it is no longer possible to isolate the liquid in the liquid region S1 and the gas-phase working fluid in the gas region S2 from direct contact with each other, the control device 90 closes the on-off valve 13 corresponding to the damaged bladder 12a. The pressure accumulation system 100C can detect that the bladder 12a has been damaged at the location where the liquid region S1 has changed, for example, by detecting a sudden change in the liquid region S1.

[0069] The mist separator 14 is a device that removes liquid or liquid mist that has been mixed with the gas-phase working fluid after the bladder 12a is damaged and before the on-off valve 13 is closed, and supplies only the gas-phase working fluid to the compressor 41.

[0070] According to the pressure accumulation system 100C of this embodiment, by isolating the liquid region S1 and the gas region S2 of the first pressure vessel 10 by the accumulator 12, it is possible to prevent the gas-phase working fluid from dissolving into liquid and causing a pressure drop in the gas region S2. Furthermore, if the accumulator 12 is damaged, by closing the on-off valve 13, it is possible to prevent the liquid from being introduced into the liquefaction equipment 40 together with the gas-phase working fluid.

[0071] Other Embodiments In the above embodiments, when the pressure accumulation systems 100, 100A, 100B, 100C are installed on floating facilities such as offshore facilities, there is a possibility that the liquid in the liquid region S1 of the first pressure vessel 10 will be shaken by ocean waves, causing the liquid surface to become choppy. Therefore, multiple baffle plates (not shown) extending vertically may be installed inside the first pressure vessel 10 so as to divide the liquid region S1 of the first pressure vessel 10 into multiple sections.

[0072] The pressure accumulation system and the method of operating the pressure accumulation system described in each of the above-described embodiments can be understood, for example, as follows. A pressure accumulation system according to a first aspect of the present disclosure includes a first pressure vessel (10) that stores liquid and is filled with a gaseous working fluid, a pump (20) that supplies the liquid to the first pressure vessel and through which the liquid discharged from the first pressure vessel passes, a motor-generator (30) that can switch between a drive state in which it drives the pump and a power generation state in which it generates electricity using power transmitted from the pump, a liquefaction facility (40) that liquefies the gaseous working fluid introduced from the first pressure vessel when the motor-generator operates in the drive state, a second pressure vessel (50) that stores the working fluid liquefied by the liquefaction facility, and a vaporization facility (60) that vaporizes the liquid-phase working fluid introduced from the second pressure vessel and supplies it to the first pressure vessel when the motor-generator operates in the power generation state.

[0073] According to the pressure accumulation system according to the first aspect of the present disclosure, when the motor-generator is driven by surplus electricity or the like, the pump is driven and liquid is supplied to the first pressure vessel. As the amount of liquid stored in the first pressure vessel increases, the gas phase working fluid is pressurized, and the volume of the gas working fluid decreases. As the liquid level in the first pressure vessel rises, the gas phase working fluid is gradually pressurized over a relatively long period of time. Therefore, in terms of the thermal cycle, it is close to isothermal compression, and the gas phase working fluid can be compressed with higher energy efficiency than a compressor that compresses in a short period of time.

[0074] Furthermore, according to the pressure storage system according to the first aspect of the present disclosure, when the motor-generator is operating in a power generating state, supplying the liquid stored in the first pressure vessel to the pump rotates the motor-generator to generate electricity. When the amount of liquid stored in the first pressure vessel decreases, the vaporizer supplies the gas-phase working fluid to the first pressure vessel, maintaining a constant pressure fluctuation of the gas-phase working fluid in the first pressure vessel. Therefore, regardless of the liquid level in the pressure vessel, the pump 20 (which functions as a water turbine) can be driven at a constant pressure, and a constant power supply can be achieved (operation is possible in the same way as existing pumped-storage power generation).

[0075] Furthermore, in heat engines that generate power by heating and expanding gases such as air, electricity cannot be generated efficiently unless the pressure and temperature are increased. However, in this embodiment, energy recovery can be performed using a water turbine, which is used in hydroelectric power generation, so energy recovery (= power generation using energy derived from stored surplus renewable electricity) can be performed with the same high efficiency as a water turbine even at room temperature.

[0076] In this way, according to the pressure storage system according to the first aspect of the present disclosure, when the motor-generator operates in a driving state, the gas phase working fluid is liquefied, thereby efficiently compressing the working fluid, and when the motor-generator operates in a power generating state, the liquid phase working fluid is re-vaporized, thereby efficiently extracting high-output energy.

[0077] The pressure accumulation system according to a second aspect of the present disclosure is the same as the first aspect, and further includes the following configuration: the liquefaction facility includes a compressor (41) that compresses the working fluid in a gas phase guided from the first pressure vessel, and a first heat exchanger (42) that cools the working fluid compressed by the compressor by heat exchange with a first heat exchange medium. According to the pressure storage system of the second aspect of the present disclosure, the gas phase working fluid guided from the first pressure vessel is compressed by the compressor, the compressed working fluid is cooled by heat exchange with the first heat exchange medium in the first heat exchanger, and then the temperature is lowered by reducing the pressure in the expansion valve 45, thereby liquefying the gas phase working fluid.

[0078] The pressure accumulation system according to a third aspect of the present disclosure is the second aspect, and further includes the following configuration: The vaporization facility includes a second heat exchanger (61) that heats the working fluid in a liquid phase introduced from the second pressure vessel by heat exchange with a heating medium. According to the pressure storage system according to the third aspect of the present disclosure, the liquid-phase working fluid guided from the second pressure vessel can be vaporized by heating the liquid-phase working fluid through heat exchange with a heating medium in the second heat exchanger.

[0079] The pressure storage system according to a fourth aspect of the present disclosure is the third aspect, further including the following configuration: That is, the liquefaction facility has a third heat exchanger (44) that cools the first heat exchange medium heated by the working fluid in the first heat exchanger through heat exchange with a second heat exchange medium, and the heating medium that heats the working fluid in the second heat exchanger is the second heat exchange medium heated by the first heat exchange medium in the third heat exchanger.

[0080] According to the pressure storage system according to the fourth aspect of the present disclosure, the first heat exchange medium heated by the working fluid in the first heat exchanger is heat exchanged with the second heat exchange medium in the third heat exchanger, and the second heat exchange medium can be used as a heating medium for heating the liquid-phase working fluid in the second heat exchanger. By using the second heat exchange medium heated by the first heat exchange medium in the third heat exchanger as a heat source for heating the liquid-phase working fluid, it is possible to improve the energy efficiency when vaporizing the liquid-phase working fluid.

[0081] The pressure storage system according to a fifth aspect of the present disclosure is the third aspect, further including the following configuration: That is, the liquefaction facility includes a third heat exchanger (44) that heats a second heat exchange medium by heat exchange with the first heat exchange medium heated by the working fluid in the first heat exchanger, a fourth heat exchanger (142) that heats a third heat exchange medium by heat exchange with the second heat exchange medium heated by the first heat exchange medium in the third heat exchanger, and a turbine (143) driven by the third heat exchange medium heated by heat exchange with the second heat exchange medium, and the heating medium that heats the working fluid in the second heat exchanger is the third heat exchange medium that has passed through the turbine.

[0082] According to the pressure storage system of the fifth aspect of the present disclosure, the first heat exchange medium heated by the working fluid in the first heat exchanger is heat exchanged with the second heat exchange medium in the third heat exchanger, and the second heat exchange medium heated by the first heat exchange medium in the third heat exchanger is heat exchanged with the third heat exchange medium in the fourth heat exchanger, and the liquid phase can be used as a cooling medium to cool and condense the working fluid of the third heat exchange medium in the second heat exchanger, and drive the turbine (143) and the generator (144) to generate electricity, thereby improving energy efficiency. Furthermore, the third heat exchange medium heated by the second heat exchange medium in the fourth heat exchanger is used as a heat source to heat the liquid phase working fluid, thereby improving energy efficiency when vaporizing the liquid phase working fluid.

[0083] A pressure accumulation system according to a sixth aspect of the present disclosure is the pressure accumulation system of any one of the first to fifth aspects, further comprising the following configuration: the first pressure vessel has a plurality of accumulators (12) filled with the working fluid in a gas phase, a plurality of supply lines (L9a-L9f) for supplying the working fluid from the plurality of accumulators to the liquefaction facility, and a plurality of on-off valves (13) arranged in the plurality of supply lines, respectively.

[0084] According to the pressure accumulation system of the sixth aspect of the present disclosure, by isolating the liquid region and the gas region of the first pressure vessel by the accumulator, it is possible to prevent the gas phase working fluid from dissolving into liquid and causing a pressure drop in the gas region. Furthermore, if the accumulator is damaged, by closing the on-off valve, it is possible to prevent the liquid from being introduced into the liquefaction facility together with the gas phase working fluid.

[0085] In a method for operating a pressure accumulation system according to a seventh aspect of the present disclosure, the pressure accumulation system includes a first pressure vessel that stores liquid and is filled with a gaseous working fluid, a pump that supplies the liquid to the first pressure vessel and through which the liquid discharged from the first pressure vessel passes, a motor-generator that is switchable between a driving state that drives the pump and a power generating state that generates electricity using power transmitted from the pump, and a second pressure vessel that stores the liquefied working fluid, and includes: a liquefaction step of liquefying the gaseous working fluid introduced from the first pressure vessel when the motor-generator operates in the driving state and supplying the liquefied working fluid to the second pressure vessel; and a vaporization step of vaporizing the liquid-phase working fluid introduced from the second pressure vessel when the motor-generator operates in the power generating state and supplying the liquid to the first pressure vessel.

[0086] According to the operating method of a pressure accumulation system according to a seventh aspect of the present disclosure, when the motor-generator is driven by surplus power or the like, the pump is driven and liquid is supplied to the first pressure vessel. As the amount of liquid stored in the first pressure vessel increases, the gas-phase working fluid is pressurized, reducing the volume of the working fluid. As the liquid level in the first pressure vessel rises, the gas-phase working fluid is gradually pressurized over a relatively long period of time. Therefore, in terms of the thermal cycle, it is close to isothermal compression, and the gas-phase working fluid can be compressed with higher energy efficiency than a compressor that compresses in a short period of time.

[0087] Furthermore, according to a method for operating a pressure storage system according to a seventh aspect of the present disclosure, when the motor-generator is operating in a power generating state, supplying the liquid stored in the first pressure vessel to the pump rotates the motor-generator to generate electricity. When the amount of liquid stored in the first pressure vessel decreases, the vaporized working fluid is supplied to the first pressure vessel, and the pressure of the gas-phase working fluid in the first pressure vessel is maintained without fluctuation. This allows the hydraulic turbine to be driven at a constant pressure, obtaining a constant generator output, enabling operation similar to that of a pumped-storage power plant, and generating generator output with the same high efficiency (approximately 85% at the rated operating point) as a hydraulic turbine. Furthermore, by liquefying the working fluid, the pressure vessel storing the pressurized working fluid can be made more compact.

[0088] As described above, the operating method of the pressure storage system according to the seventh aspect of the present disclosure can improve the energy efficiency when compressing the gas-phase working fluid when the motor generator is operating in a driving state, and the power generation efficiency when the motor generator is operating in a power generating state. Furthermore, the system can be operated in the same manner as existing pumped storage power plants, contributing to adjusting the balance between power supply and demand. [Explanation of symbols]

[0089] 10,10C First pressure vessel 11 Liquid level 12 Accumulator 12a Vlada 13 On-off valve 14 Mist separator 20 Pump 21 Regulating valve 30 Motor generator 40 Liquefaction equipment 41 Compressor 42 Heat exchanger 43 Circulation Pump 44 Heat exchanger 45 Expansion valve 46 Cooling pump 47,48 Circulation pump 49a High temperature tank 49b Cryogenic Tank 50 Second Pressure Vessel 50a,85 level meter 60 Vaporization Equipment 61 Heat exchanger 62,63 Regulating valve 70 Emission part 80 Pressure detection unit 90 Control device 100, 100A, 100B, 100C Pressure storage system 141 Circulation Pump 142 Heat exchanger 143 Turbine 144 Generator 200 Power generation facilities 300 load L1,L2,L4,L5,L6,L9a,L9b,L9c,L9d,L9e,L9f supply line L3, L7, L8 circulation lines S1 liquid area S2 Gas Region

Claims

1. a first pressure vessel for storing a liquid and filled with a gaseous working fluid; a pump through which the liquid is supplied to the first pressure vessel and discharged from the first pressure vessel; a motor generator that is switchable between a driving state for driving the pump and a power generating state for generating power using power transmitted from the pump; a liquefaction facility that liquefies the gaseous working fluid guided from the first pressure vessel when the motor-generator operates in the driving state; a second pressure vessel for storing the working fluid liquefied by the liquefaction facility; a vaporization facility that vaporizes the liquid-phase working fluid guided from the second pressure vessel when the motor generator operates in the power generating state and supplies the vaporized working fluid to the first pressure vessel.

2. The liquefaction facility comprises: a compressor that compresses the working fluid in a gas phase guided from the first pressure vessel; The pressure accumulation system according to claim 1 , further comprising: a first heat exchanger that cools the working fluid compressed by the compressor by heat exchange with a first heat exchange medium.

3. The pressure accumulation system according to claim 2 , wherein the vaporization facility has a second heat exchanger that heats the liquid-phase working fluid guided from the second pressure vessel by heat exchange with a heating medium.

4. the liquefaction facility has a third heat exchanger that cools the first heat exchange medium heated by the working fluid in the first heat exchanger by heat exchange with a second heat exchange medium, The pressure storage system according to claim 3 , wherein the heating medium that heats the working fluid in the second heat exchanger is the second heat exchange medium that has been heated by the first heat exchange medium in the third heat exchanger.

5. The liquefaction facility comprises: a third heat exchanger that heats a second heat exchange medium by heat exchange with the first heat exchange medium heated by the working fluid in the first heat exchanger; a fourth heat exchanger that heats a third heat exchange medium by heat exchange with the second heat exchange medium heated by the first heat exchange medium in the third heat exchanger; a turbine driven by the third heat exchange medium heated by heat exchange with the second heat exchange medium, The pressure accumulation system according to claim 3 , wherein the heating medium that heats the working fluid in the second heat exchanger is the third heat exchange medium that has passed through the turbine.

6. the first pressure vessel has a plurality of accumulators filled with the working fluid in a gas phase; a plurality of supply lines for supplying the working fluid from the plurality of accumulators to the liquefaction facility; The pressure accumulation system according to claim 1 , further comprising: a plurality of on-off valves arranged in the plurality of supply lines, respectively.

7. A method for operating a pressure accumulation system, comprising: The pressure accumulation system includes: a first pressure vessel for storing a liquid and filled with a gaseous working fluid; a pump through which the liquid is supplied to the first pressure vessel and discharged from the first pressure vessel; a motor generator that is switchable between a driving state for driving the pump and a power generating state for generating power using power transmitted from the pump; a second pressure vessel for storing the liquefied working fluid; a liquefaction step of liquefying the working fluid in a gas phase introduced from the first pressure vessel when the motor-generator operates in the driving state and supplying the liquefied working fluid to the second pressure vessel; a vaporization step of vaporizing the liquid-phase working fluid guided from the second pressure vessel when the motor-generator operates in the power generating state and supplying the liquid-phase working fluid to the first pressure vessel.

Images