Gas-liquid phase change pressure carbon dioxide energy storage system and control method thereof

Abstract

The application discloses a gas-liquid phase variable compression carbon dioxide energy storage system, which comprises a gas storage unit, an energy storage unit, a liquid storage unit and an energy release unit which are connected in sequence in a closed loop, the energy release unit comprises a superheater, a high-pressure turbine, a reheater and a low-pressure turbine which are connected in sequence, a second evaporator is arranged in an exhaust cylinder of the low-pressure turbine, an input end of the second evaporator is connected to an outlet end of the liquid storage unit, and an output end of the second evaporator is connected to an inlet end of the reheater. The second evaporator is configured to: in the air load starting stage of the energy release unit, receiving liquid working medium from the liquid storage unit so that the liquid working medium is evaporated and gasified, thereby reducing the exhaust temperature of the low-pressure turbine, and inputting the gaseous working medium formed by the evaporation and gasification into the low-pressure turbine through the reheater to continue working, so that not only the risk of equipment damage caused by the excessively high exhaust temperature during turbine operation is reduced, but also the turbine exhaust heat is recovered, the total turbine intake is reduced, and the overall efficiency of the system unit is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to a gas-liquid phase change compressed carbon dioxide energy storage system and a control method thereof. BACKGROUND

[0002] At present, the energy storage technology based on carbon dioxide gas-liquid phase change cycle compresses and condenses the gaseous carbon dioxide at normal temperature and pressure in the gas storage unit into liquid carbon dioxide stored in the liquid storage unit by using excess power or clean energy during the off-peak period, and stores the heat energy generated during the compression process. During the peak period, the stored heat energy is used to heat the liquid carbon dioxide to gaseous carbon dioxide, and the gaseous carbon dioxide drives the turbine to drive the generator to generate electricity, and the gaseous carbon dioxide after work returns to the gas storage unit for recycling, which has the advantages of simple structure, flexible layout, high energy storage efficiency, etc. and gradually attracts widespread attention.

[0003] In the system design of the existing carbon dioxide energy storage technology, the energy storage mode and the energy release mode are intermittent operation, and the energy storage unit and the energy release unit need to complete at least one start and stop operation per day to match the day and night fluctuation of the power grid load. When the energy release unit starts, the turbine needs to go through the acceleration process from zero speed to rated speed, and when the speed reaches the rated value, it can be connected to the power grid and output power externally. During the acceleration process of the turbine, the turbine is in an empty load running state, and the turbine cannot do work externally in this state. Due to the mechanical characteristics of the turbine, the energy conversion efficiency is very low when the turbine is in an empty load running state, and a large amount of high-pressure carbon dioxide energy is not effectively utilized, resulting in the turbine exhaust temperature often exceeding the safety alarm value set by the system. Moreover, since the turbine needs to be started every day, frequent high-temperature exhaust will cause continuous damage to the metal stress of the turbine low-pressure cylinder bearing, the performance of the lubricating oil, and the material strength of the last-stage blade, and long-term operation will greatly shorten the service life of the equipment, increase the maintenance cost and operation risk of the energy storage system. SUMMARY

[0004] In view of the problems existing in the prior art, the present application provides a gas-liquid phase change compressed carbon dioxide energy storage system and a control method thereof to solve the problem of how to reduce the turbine exhaust temperature during the start-up phase of the energy release unit and effectively utilize the energy of high-pressure carbon dioxide.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] The first aspect of the present application provides a gas-liquid phase change compression carbon dioxide energy storage system, comprising a gas storage unit, an energy storage unit, a liquid storage unit and a energy release unit connected in sequence in a closed loop, wherein the energy release unit comprises a superheater, a high-pressure turbine, a reheater and a low-pressure turbine connected in sequence, a second evaporator is arranged in the exhaust cylinder of the low-pressure turbine, the input end of the second evaporator is connected to the outlet end of the liquid storage unit, and the output end of the second evaporator is connected to the inlet end of the reheater; wherein the second evaporator is configured to receive liquid working medium from the liquid storage unit in the idle start stage of the energy release unit to evaporate and gasify the liquid working medium so as to reduce the exhaust temperature of the low-pressure turbine, and input the gaseous working medium formed by evaporation and gasification into the low-pressure turbine through the reheater.

[0007] In one specific embodiment, the input end of the second evaporator is connected to the outlet end of the liquid storage unit through a first pipeline, the output end of the second evaporator is connected to the inlet end of the reheater through a second pipeline, and a gate valve and a throttling regulating valve are arranged on the first pipeline.

[0008] In one specific embodiment, the second evaporator is an expansion evaporator.

[0009] In one specific embodiment, the gas-liquid phase change compression carbon dioxide energy storage system further comprises a condenser connected between the energy storage unit and the liquid storage unit, and a first evaporator connected between the liquid storage unit and the energy release unit.

[0010] In one specific embodiment, the high-pressure turbine and the low-pressure turbine are coaxially connected through a rotating shaft assembly, a first generator is connected to the first end of the rotating shaft assembly, and a second generator is connected to the second end of the rotating shaft assembly; wherein the first generator is connected to a power grid, and the first generator is used to convert the mechanical energy of the rotating shaft assembly into electrical energy and transmit the electrical energy to the power grid in the stable operation stage of the energy release unit; wherein the second generator is a permanent magnet direct current generator and is connected to a battery assembly, and the second generator is used to convert the mechanical energy of the rotating shaft assembly into electrical energy and transmit the electrical energy to the battery assembly in the shutdown stage of the energy release unit, and to provide electromagnetic resistance to the rotating shaft assembly so as to shorten the shutdown time of the energy release unit.

[0011] In one specific embodiment, the second generator is connected with a power regulator, and the power regulator is used to adjust the output power of the second generator.

[0012] In one specific embodiment, the first generator is connected to the power grid through a first switch assembly, and the second generator is connected to the battery assembly through a second switch assembly.

[0013] In one specific implementation, the battery assembly is electrically connected to the auxiliary power equipment.

[0014] A second aspect of the present application provides a control method of the gas-liquid phase change compression carbon dioxide energy storage system as described above, the control method comprising:

[0015] When the energy releasing unit starts to run, the high-pressure turbine and the low-pressure turbine run at idle speed, at this time, the liquid working medium in the storage unit is transported to the second evaporator to evaporate and gasify, and the gaseous working medium formed by the evaporation and gasification is input to the low-pressure turbine through the reheater.

[0016] After the high-pressure turbine and the low-pressure turbine reach the rated speed, the high-pressure turbine and the low-pressure turbine run at load, at this time, the transportation of the liquid working medium in the storage unit to the second evaporator is stopped.

[0017] A third aspect of the present application provides another control method of the gas-liquid phase change compression carbon dioxide energy storage system as described above, the control method comprising:

[0018] When the energy releasing unit starts to run, the high-pressure turbine and the low-pressure turbine run at idle speed, at this time, the liquid working medium in the storage unit is transported to the second evaporator to evaporate and gasify, and the gaseous working medium formed by the evaporation and gasification is input to the low-pressure turbine through the reheater.

[0019] After the high-pressure turbine and the low-pressure turbine reach the rated speed, the first generator is started and connected to the power grid to generate electricity, the energy releasing unit enters a stable running stage, the high-pressure turbine and the low-pressure turbine run at load, at this time, the transportation of the liquid working medium in the storage unit to the second evaporator is stopped, and the first generator converts the mechanical energy of the rotating shaft assembly into electrical energy and transmits the electrical energy to the power grid.

[0020] When the energy releasing unit enters a shutdown running stage, the first generator is turned off and the second generator is turned on, the second generator converts the mechanical energy of the rotating shaft assembly into electrical energy and transmits the electrical energy to the battery assembly and provides electromagnetic resistance, reduces the idling time of the rotating shaft assembly and shortens the shutdown time of the energy releasing unit.

[0021] The gas-liquid phase change compressed carbon dioxide energy storage system and the control method thereof provided by the embodiment of the present application, by arranging a second evaporator in the exhaust cylinder of the low-pressure turbine of the energy releasing unit, the input end of the second evaporator is connected to the outlet end of the liquid storage unit and the output end is connected to the inlet end of the reheater. In the air load starting stage of the energy releasing unit, the second evaporator receives the liquid working medium from the liquid storage unit so that the liquid working medium evaporates and gasifies to reduce the exhaust temperature of the low-pressure turbine, and the gaseous working medium formed by the evaporation and gasification is input into the low-pressure turbine after being heated by the reheater to continue to do work, thereby not only reducing the risk of equipment damage caused by the too high exhaust temperature during turbine operation, but also recovering the turbine exhaust heat, reducing the total turbine intake, and improving the overall efficiency of the system unit. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a structural schematic diagram of the gas-liquid phase change compressed carbon dioxide energy storage system in the embodiment 1 of the present application;

[0023] Figure 2 is a structural schematic diagram of the gas-liquid phase change compressed carbon dioxide energy storage system in the embodiment 2 of the present application. DETAILED DESCRIPTION

[0024] In order to make the objects, technical solutions and advantages of the present application clearer, the specific embodiments of the present application will be described in detail below with reference to the drawings. The examples of these preferred embodiments are illustrated in the drawings. The embodiments of the present application shown in the drawings and described according to the drawings are only exemplary, and the present application is not limited to these embodiments.

[0025] It should be noted that the same or similar reference numerals in the drawings of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore, the terms describing the positional relationships in the drawings cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore, the terms describing the positional relationships in the drawings are only used for exemplary description, and cannot be understood as limiting the present patent, and for those skilled in the art, the specific meanings of the above terms can be understood according to the specific circumstances.

[0026] Here, it should also be noted that, in order to avoid obscuring the present application due to unnecessary details, only the structures and / or processing steps closely related to the scheme according to the present application are shown in the drawings, and other details not closely related to the present application are omitted.

[0027] Embodiment 1

[0028] The present embodiment first provides a gas-liquid phase change compressed carbon dioxide energy storage system, as shown inFigure 1 As shown in the figure, the gas-liquid phase change pressure carbon dioxide energy storage system mainly includes a gas storage unit 10, an energy storage unit 20, a liquid storage unit 30 and an energy release unit 40 connected in sequence. Among them, the gas storage unit 10 is used to store gaseous carbon dioxide at normal pressure, and the liquid storage unit 30 is used to store liquid carbon dioxide. The gaseous carbon dioxide flowing out of the gas storage unit 10 is converted into liquid carbon dioxide at a preset energy storage pressure through the energy storage unit 20, flows into the liquid storage unit 30, and in this process, the energy storage is completed. The liquid carbon dioxide output from the liquid storage unit 30 is converted into gaseous carbon dioxide at normal pressure through the energy release unit 40 to release energy, and flows into the gas storage unit 10, in this process, the energy release and application are completed. Generally, the gaseous carbon dioxide is compressed and liquefied into liquid carbon dioxide by the energy storage unit 20 during the low electricity consumption period or by using wind and light abandoned electricity, and stored in the liquid storage unit 30, and the energy conversion compression energy and heat energy are stored; during the electricity consumption peak period, the liquid carbon dioxide is gasified and expanded to do work by the energy release unit 40, and the stored energy is released and converted into electric energy for use.

[0029] As a specific case, in the embodiment, as shown in the figure, Figure 1 The energy storage unit 20 mainly includes a compressor 21 and an energy storage heat exchanger 22 connected between the gas storage unit 10 and the liquid storage unit 30. Further, a condenser 50 is arranged on the connecting pipeline between the energy storage unit 20 and the liquid storage unit 30. The gaseous carbon dioxide in the gas storage unit 10 is compressed by the compressor 21, then cooled by the energy storage heat exchanger 22, and then liquefied by the condenser 50 to form liquid carbon dioxide stored in the liquid storage unit 30.

[0030] As a specific case, in the embodiment, as shown in the figure, Figure 1 The energy release unit 40 mainly includes a superheater 41, a high-pressure turbine 42, a reheater 43 and a low-pressure turbine 44 connected between the liquid storage unit 30 and the gas storage unit 10. Further, a first evaporator 60 is arranged on the connecting pipeline between the liquid storage unit 30 and the energy release unit 40. The liquid carbon dioxide in the liquid storage unit 30 is heated and evaporated by the first evaporator 60, then input into the superheater 41 to increase the temperature, and then input into the high-pressure turbine 42 to expand and do work to release energy. The carbon dioxide gas discharged from the high-pressure turbine 42 is heated again by the reheater 43, then input into the low-pressure turbine 44 to expand and do work to release energy, and finally forms gaseous carbon dioxide at normal pressure stored in the gas storage unit 10.

[0031] Among them, as shown in the figure, Figure 1As shown, in the energy releasing unit 40, the high-pressure turbine 42 and the low-pressure turbine 44 are coaxially connected through a rotating shaft assembly (including a rotor and a connecting shaft and the like) 45, a first end of the rotating shaft assembly 45 is connected with a first generator 1, and the first generator 1 is connected to a power grid 2, specifically connected to the power grid 2 through a first switch assembly 3. The first generator 1 is used to convert the mechanical energy of the rotating shaft assembly 45 into electrical energy and transmit the electrical energy to the power grid 2 in the stable operation stage of the energy releasing unit 40. Preferably, the first generator 1 is an alternating current generator.

[0032] In the prior art, in the energy releasing stage, when the energy releasing unit starts to operate, the turbine is in an empty load operation state and cannot do work externally, and a large amount of energy of high-pressure carbon dioxide is not effectively utilized. In addition, since the turbine needs to be started every day, frequent high-temperature exhaust gas will continuously damage the bearing metal stress, lubricating oil performance, and material strength of the last-stage blade of the low-pressure turbine, and long-term operation will greatly shorten the service life of the equipment, increase the maintenance cost and operation risk of the energy storage system.

[0033] To solve the above problems, in the gas-liquid phase change compression carbon dioxide energy storage system provided by the embodiment, referring to Figure 1 , the second evaporator 100 is arranged in the exhaust cylinder of the low-pressure turbine 44, an input end of the second evaporator 100 is connected to an outlet end of the liquid storage unit 30, and an output end of the second evaporator 100 is connected to an inlet end of the reheater 43. The second evaporator 100 is configured to receive liquid working medium from the liquid storage unit 30 in the empty load starting stage of the energy releasing unit 40, so that the liquid working medium is evaporated and gasified to reduce the exhaust temperature of the low-pressure turbine 44, and the gaseous working medium formed by evaporation and gasification is input to the low-pressure turbine through the reheater 43. As a preferred scheme, the second evaporator 100 is selected as an expansion evaporator.

[0034] Based on the gas-liquid phase change compression carbon dioxide energy storage system provided by the embodiment, in the empty load starting stage of the energy releasing unit 40, the second evaporator 100 receives liquid working medium from the liquid storage unit 30, the liquid working medium is evaporated and gasified in the second evaporator 100 to absorb heat, thereby reducing the exhaust temperature of the low-pressure turbine 44. Thus, not only the risk of equipment damage caused by too high exhaust temperature during turbine operation is reduced, but also the turbine exhaust heat is recovered. Further, the gaseous working medium formed by evaporation and gasification is heated by the reheater 43 and then input to the low-pressure turbine 44 for continuous work, thereby reducing the total intake amount of the energy releasing unit 40 and improving the overall efficiency of the system unit.

[0035] In a specific scheme, as Figure 1As shown, the input end of the second evaporator 100 is connected to the outlet end of the liquid storage unit 30 through a first pipeline 200, the output end of the second evaporator 100 is connected to the inlet end of the reheater 43 through a second pipeline 300, and a gate valve 400 and a throttling regulating valve 500 are arranged on the first pipeline 200. By controlling the gate valve 400 and the throttling regulating valve 500, the flow of liquid working medium input into the second evaporator 100 is regulated. Specifically, when the high-pressure turbine 42 and the low-pressure turbine 44 are started at no load, as the turbine speed increases, the exhaust temperature of the exhaust cylinder of the low-pressure turbine 44 gradually increases, at this time, the gate valve 400 and the throttling regulating valve 500 are opened, and the high-pressure liquid carbon dioxide is throttled and regulated to enter the second evaporator 100 for expansion and heat absorption, the exhaust temperature of the exhaust cylinder of the low-pressure turbine 44 decreases, the high-pressure liquid carbon dioxide evaporates into high-pressure carbon dioxide gas in the second evaporator 100, the high-pressure carbon dioxide gas enters the reheater 43 for further heating and then enters the low-pressure turbine 44 for work, thereby recovering heat, and the total flow of turbine (high-pressure turbine 42 and low-pressure turbine 44) inlet gas decreases. When the turbine reaches the rated speed, it is synchronized with the power grid successfully, and outputs electric energy to the outside. When the turbine runs at load, the exhaust temperature of the exhaust cylinder of the low-pressure turbine 44 decreases, at this time, the gate valve 400 and the throttling regulating valve 500 are closed, and the turbine runs stably at load.

[0036] Based on the gas-liquid phase change compression carbon dioxide energy storage system as described above, the embodiment also provides a control method of the gas-liquid phase change compression carbon dioxide energy storage system, the control method of the gas-liquid phase change compression carbon dioxide energy storage system includes an energy storage stage and an energy release stage. In the energy release stage, the operation process of the energy release unit 40 includes the following steps:

[0037] S11, when the energy release unit 40 starts to run, the high-pressure turbine 42 and the low-pressure turbine 44 run at no load to increase the speed, at this time, the liquid working medium in the liquid storage unit 30 is transported to the second evaporator 100 for evaporation and gasification, and the gaseous working medium formed by evaporation and gasification is input into the low-pressure turbine 44 through the reheater 43.

[0038] In the above process, the liquid working medium evaporates and gasifies in the second evaporator 100, absorbs the heat of the exhaust cylinder of the low-pressure turbine 44, thereby reducing the temperature of the gaseous working medium in the exhaust cylinder of the low-pressure turbine 44, i.e. reducing the exhaust temperature of the low-pressure turbine 44, effectively reducing the risk of equipment damage caused by excessively high exhaust temperature during turbine operation. On the other hand, the gaseous working medium formed by evaporation and gasification is heated by the reheater 43 and then input into the low-pressure turbine 44 for further work, realizing the recycling of exhaust heat, reducing the total flow of turbine front-end required inlet gas, and improving the overall efficiency of the system unit.

[0039] S12, after the high-pressure turbine 42 and the low-pressure turbine 44 reach the rated speed, the first generator 1 is started and connected to the power grid 2 to generate electricity, and the high-pressure turbine 42 and the low-pressure turbine 44 are in load operation, at this time, the liquid working medium in the storage unit 30 is stopped from being delivered to the second evaporator 100, and the first generator 1 converts the mechanical energy of the rotating shaft assembly 45 into electrical energy and delivers it to the power grid 2.

[0040] Specifically, after the high-pressure turbine 42 and the low-pressure turbine 44 reach the rated speed, the first generator 1 is started and connected to the power grid 2 to generate electricity, and the high-pressure turbine 42 and the low-pressure turbine 44 are in load operation, the exhaust temperature of the low-pressure turbine 44 gradually decreases, and there is no need to cool it by the second evaporator 100, therefore, at this time, the gate valve 400 and the throttling regulating valve 500 are closed, and the liquid working medium in the storage unit 30 is stopped from being delivered to the second evaporator 100.

[0041] S13, when the energy releasing unit 40 enters the shutdown operation stage, the first generator 1 is closed, and the rotating shaft assembly 45 gradually slows down until it finally stops.

[0042] Specifically, when the energy releasing condition ends, the first generator 1 is closed, the high-pressure turbine 42 and the low-pressure turbine 44 are stopped and the inlet valve is closed, the high-pressure turbine 42 and the low-pressure turbine 44 enter the idle state, and the rotating shaft assembly 45 gradually slows down until it finally stops.

[0043] Embodiment 2

[0044] The gas-liquid phase change carbon dioxide energy storage system provided in Embodiment 1 has the following problems in step S13 of the operation process of the energy releasing unit 40, in the shutdown operation stage of the energy releasing unit 40, the high-pressure turbine 42 and the low-pressure turbine 44 enter the idle state, and the rotating shaft assembly 45 needs to gradually slow down from high speed to zero speed until it is completely stopped by relying on the frictional resistance of the gas and the bearing, this stage has the following problems: (1) complete waste of rotor kinetic energy: a large amount of rotational kinetic energy contained in the rotor during the idle process is only converted into heat energy and dissipated by friction, without any recycling and utilization, resulting in energy waste; (2) increased consumption of auxiliary power: due to the limited frictional resistance, the rotor idle time is usually long, and the auxiliary system (such as the cooling water system, the shaft seal system, the oil pump, the cooling fan system, etc.) needs to be continuously operated until the rotor is completely stopped, resulting in additional consumption of auxiliary power during the idle period, which reduces the operation economy of the energy storage system.

[0045] To solve the above problems, the gas-liquid phase change compression carbon dioxide energy storage system provided in Embodiment 2 is further improved on the basis of the gas-liquid phase change compression carbon dioxide energy storage system provided in Embodiment 1. Only the different parts of the gas-liquid phase change compression carbon dioxide energy storage system of the present embodiment from Embodiment 1 will be described in detail below, and the same parts will not be described again.

[0046] Referring to Figure 2 The gas-liquid phase change compression carbon dioxide energy storage system provided in the present embodiment, in the energy releasing unit 40, the second end of the rotating shaft assembly 45 is connected with a second generator 4, the second generator 4 is a permanent magnet direct current generator and is connected to a battery assembly 5, specifically through a second switch assembly 6 to the battery assembly 5. The second generator 4 is used to convert the mechanical energy of the rotating shaft assembly 45 into electrical energy and transmit it to the battery assembly 5 during the shutdown stage of the energy releasing unit 40, and to provide electromagnetic resistance to the rotating shaft assembly 45 to shorten the shutdown time of the energy releasing unit 40.

[0047] Specifically, when the energy releasing working condition ends and the first generator 1 for grid-connected power generation is reduced to the minimum load, the outlet switch of the second generator 4 is closed, the high-pressure turbine 42 and the low-pressure turbine 44 are stopped and enter the idle state, the second generator 4 generates electricity and transmits it to the battery assembly 5. Because the turbine rotor is subjected to the electromagnetic resistance of the permanent magnet direct current generator (second generator 4) when outputting electrical energy, the turbine rotor will stop soon, the turbine rotor idle energy is recovered, the turbine shutdown time is shortened, and the auxiliary system is correspondingly stopped running in advance, reducing the plant power consumption. The electrical energy stored in the battery assembly 5 can be used for plant lighting and other direct current power supply systems, and continues to charge during the next energy releasing working condition.

[0048] Based on the gas-liquid phase change compression carbon dioxide energy storage system provided in the present embodiment, during the shutdown stage of the energy releasing unit 40: on the one hand, the second generator 4 recovers the rotational kinetic energy of the rotating shaft assembly 45 to generate electricity and store it in the battery assembly 5, thereby reducing energy waste; on the other hand, the second generator 4 can provide electromagnetic resistance to the rotating shaft assembly 45 while generating electricity, so that the rotating shaft assembly 45 stops rotating faster and the shutdown time of the energy releasing unit 40 is shortened, and the auxiliary system (such as the cooling water system, the shaft seal system, the oil pump, the cooling fan system, etc.) can also be stopped running in advance to reduce the plant power consumption, thereby improving the comprehensive economic benefit of the energy storage system operation.

[0049] Among them, such as Figure 2As shown, the second generator 4 is connected with a power regulator 7 for regulating the output power of the second generator 4. The battery assembly 5 is electrically connected to a plant power device 8, and the electric energy stored in the battery assembly 5 can be used as plant power, for example, a lighting device.

[0050] Based on the gas-liquid phase change compression carbon dioxide energy storage system provided in the embodiment, the embodiment further provides a control method of the gas-liquid phase change compression carbon dioxide energy storage system, and the control method of the gas-liquid phase change compression carbon dioxide energy storage system includes an energy storage stage and an energy release stage. In the energy release stage, the operation process of the energy release unit 40 includes the following steps:

[0051] S21, when the energy release unit 40 starts to operate, the high-pressure turbine 42 and the low-pressure turbine 44 are operated at an idle speed, at this time, the liquid working medium in the liquid storage unit 30 is transported to the second evaporator 100 to evaporate and gasify, and the gaseous working medium formed by evaporation and gasification is input to the low-pressure turbine 44 through the reheater 43. That is, step S21 is the same as step S11 in the embodiment 1.

[0052] S22, after the high-pressure turbine 42 and the low-pressure turbine 44 reach the rated speed, the first generator 1 is started and connected to the power grid to generate power, the energy release unit 40 enters a stable operation stage, the high-pressure turbine 42 and the low-pressure turbine 44 are operated under load, at this time, the transportation of the liquid working medium in the liquid storage unit 30 to the second evaporator 100 is stopped, and the first generator 1 converts the mechanical energy of the rotating shaft assembly 45 into electric energy and transmits the electric energy to the power grid 2. That is, step S22 is the same as step S12 in the embodiment 1.

[0053] S23, when the energy release unit 40 enters a shutdown operation stage, the first generator 1 is turned off and the second generator 4 is turned on, the second generator 4 converts the mechanical energy of the rotating shaft assembly 45 into electric energy and transmits the electric energy to the battery assembly 5 and provides electromagnetic resistance, reduces the idling time of the rotating shaft assembly 45 and shortens the shutdown time of the energy release unit 40.

[0054] Specifically, when the energy releasing condition ends, the first generator 1 is closed, the high-pressure turbine 42 and the low-pressure turbine 44 are tripped and closed, the high-pressure turbine 42 and the low-pressure turbine 44 enter the idling state, at this time, the second generator 4 is started and the second switch assembly 6 is closed, the second generator 4 is connected to the battery assembly 5, the output power of the second generator 4 is adjusted through the power regulator 7, and the second generator 4 converts the mechanical energy of the rotating shaft assembly 45 into electric energy and transmits the electric energy to the battery assembly 5. Thus, in the shutdown operation stage of the energy releasing unit 40, the second generator 4 can recover the rotational kinetic energy of the rotating shaft assembly 45 to generate electricity and reduce energy waste; further, while generating electricity, the second generator 4 can also provide electromagnetic resistance to the rotating shaft assembly 45 to shorten the shutdown time of the energy releasing unit 40.

[0055] The above is only a specific embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which should be considered as the protection scope of the present application.

Claims

1. A gas-liquid phase change compressed carbon dioxide energy storage system, comprising a gas storage unit, an energy storage unit, a liquid storage unit, and an energy release unit connected in a closed loop in sequence, characterized in that, The energy release unit includes a superheater, a high-pressure turbine, a reheater, and a low-pressure turbine connected in sequence. A second evaporator is installed in the exhaust cylinder of the low-pressure turbine. The input end of the second evaporator is connected to the outlet end of the liquid storage unit through a first pipe. The output end of the second evaporator is connected to the inlet end of the reheater through a second pipe. A gate valve and a throttling regulating valve are installed on the first pipe. The second evaporator is configured to receive liquid working fluid from the liquid storage unit during the no-load start-up phase of the energy release unit, thereby reducing the exhaust temperature of the low-pressure turbine by evaporating and vaporizing the liquid working fluid, and input the gaseous working fluid formed by evaporation and vaporization to the low-pressure turbine through the reheater. The high-pressure turbine and the low-pressure turbine are coaxially connected by a rotating shaft assembly. A first generator is connected to the first end of the rotating shaft assembly, and a second generator is connected to the second end of the rotating shaft assembly. The first generator is connected to the power grid and is used to convert the mechanical energy of the rotating shaft assembly into electrical energy and transmit it to the power grid during the stable operation phase of the energy release unit. The second generator is a permanent magnet DC generator connected to the battery pack. The second generator is used to convert the mechanical energy of the rotating shaft assembly into electrical energy and deliver it to the battery pack during the shutdown phase of the energy release unit, and to provide electromagnetic resistance to the rotating shaft assembly to shorten the shutdown time of the energy release unit.

2. The gas-liquid phase change compressed carbon dioxide energy storage system according to claim 1, characterized in that, The second evaporator is an expanded capacity evaporator.

3. The gas-liquid phase change compressed carbon dioxide energy storage system according to claim 1, characterized in that, The gas-liquid phase change compressed carbon dioxide energy storage system further includes a condenser connected between the energy storage unit and the liquid storage unit, and a first evaporator connected between the liquid storage unit and the energy release unit.

4. The gas-liquid phase change compressed carbon dioxide energy storage system according to claim 1, characterized in that, The second generator is connected to a power regulator, which is used to regulate the output power of the second generator.

5. The gas-liquid phase change compressed carbon dioxide energy storage system according to claim 1, characterized in that, The first generator is connected to the power grid via a first switching assembly, and the second generator is connected to the battery assembly via a second switching assembly.

6. The gas-liquid phase change compressed carbon dioxide energy storage system according to claim 1, characterized in that, The battery assembly is electrically connected to the plant's electrical equipment.

7. A control method for a gas-liquid phase change compressed carbon dioxide energy storage system as described in any one of claims 1-6, characterized in that, The control method includes: When the energy release unit starts running, the high-pressure turbine and the low-pressure turbine start up and accelerate under no-load conditions. At this time, the liquid working fluid in the liquid storage unit is transported to the second evaporator for evaporation and vaporization, and the gaseous working fluid formed by evaporation and vaporization is input to the low-pressure turbine through the reheater. After the high-pressure turbine and the low-pressure turbine reach their rated speeds, the high-pressure turbine and the low-pressure turbine operate under load, at which point the delivery of the liquid working fluid from the storage unit to the second evaporator is stopped.

8. A control method for a gas-liquid phase change compressed carbon dioxide energy storage system as described in any one of claims 1-6, characterized in that, The control method includes: When the energy release unit starts to run, the high-pressure turbine and the low-pressure turbine run under no-load to accelerate. At this time, the liquid working fluid in the liquid storage unit is transported to the second evaporator for evaporation and vaporization, and the gaseous working fluid formed by evaporation and vaporization is input to the low-pressure turbine through the reheater. After the high-pressure turbine and the low-pressure turbine reach their rated speed, the first generator is started and connected to the grid to generate electricity. The energy release unit enters a stable operation phase. The high-pressure turbine and the low-pressure turbine operate under load. At this time, the liquid working fluid in the liquid storage unit is stopped from being transported to the second evaporator. The first generator converts the mechanical energy of the rotating shaft assembly into electrical energy and transmits it to the power grid. When the energy release unit enters the shutdown operation phase, the first generator is turned off and the second generator is turned on. The second generator converts the mechanical energy of the rotating shaft assembly into electrical energy and delivers it to the battery assembly, providing electromagnetic resistance, reducing the coasting time of the rotating shaft assembly, and thus shortening the shutdown time of the energy release unit.

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