A water vapor energy storage system coupling compressed air and flash evaporation and its control method

Abstract

The present invention discloses a water vapor energy storage system that couples compressed air with flash evaporation, and a control method thereof. The system comprises a first preheater, a second preheater, a compressor, a precooler, an aftercooler, a high-pressure air turbine, a heater, a low-pressure air turbine, a high-temperature molten salt tank, a medium-high-temperature molten salt tank, a hot water tank, a flash tank, a superheater, a high-pressure steam turbine, a first reheater, a second reheater, a low-pressure steam turbine, a condenser, a low-temperature water tank, a low-pressure pump, a medium-pressure pump, and a medium-temperature water tank, connected together by pipelines. The method includes controlling the system's energy storage process and the system's energy release process. The present invention has the advantages of a wide range of applications, environmental friendliness, a simple structure, and the ability to be deployed in a distributed manner.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage, and in particular relates to a water vapor energy storage system coupled with compressed air and flash evaporation and a control method thereof. Background Art

[0002] Energy storage systems are key to building new power systems and accommodating new energy sources. They can alleviate the mismatch between supply and demand across power generation, grid, and user networks, and effectively address the issue of wind and solar power curtailment. Conventional compressed air energy storage and pumped hydro storage, both of which are widely used, have drawbacks such as large storage vessel footprints and geographic constraints, hindering the miniaturization and distributed deployment of energy storage systems. Summary of the Invention

[0003] The present invention aims to provide a water vapor energy storage system that couples compressed air with flash evaporation, and its control method, to address one or more of the aforementioned technical problems. The energy storage system designed in this invention can improve unit operating stability, ensure system energy storage efficiency, and enhance energy utilization.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A water vapor energy storage system coupling compressed air with flash evaporation, comprising a first preheater, a second preheater, a compressor, a precooler, an aftercooler, a high-pressure air turbine, a heater, a low-pressure air turbine, a high-temperature molten salt tank, a medium-high-temperature molten salt tank, a hot water tank, a flash tank, a superheater, a high-pressure steam turbine, a first reheater, a second reheater, a low-pressure steam turbine, a condenser, a low-temperature water tank, a low-pressure pump, a medium-pressure pump, and a medium-temperature water tank;

[0006] Low-temperature waste heat is connected to the first inlet and the first outlet of the first preheater, and the low-temperature waste heat is connected to the first inlet and the first outlet of the heater, the air is connected to the second inlet of the first preheater, the second outlet of the first preheater is connected to the second inlet of the second preheater, the second outlet of the second preheater is connected to the compressor inlet, the compressor outlet is connected to the first inlet of the precooler, the first outlet of the precooler is connected to the first inlet of the aftercooler, the first outlet of the aftercooler is connected to the inlet of the high-pressure air turbine, the outlet of the high-pressure air turbine is connected to the second inlet of the heater, the second outlet of the heater is connected to the inlet of the low-pressure air turbine, and the outlet of the low-pressure air turbine is connected to the atmosphere;

[0007] The hot water tank outlet is connected to the flash tank inlet, the second outlet of the flash tank is connected to the first inlet of the first reheater, the first outlet of the first reheater is connected to the inlet of the medium-temperature water tank, and the outlet of the medium-temperature water tank is connected to the first inlet of the second preheater; the first outlet of the flash tank is connected to the second inlet of the superheater, the second outlet of the superheater is connected to the inlet of the high-pressure steam turbine, the outlet of the high-pressure steam turbine is connected to the second inlet of the first reheater, the second outlet of the first reheater is connected to the second inlet of the second reheater, the second outlet of the second reheater is connected to the inlet of the low-pressure steam turbine, the outlet of the low-pressure steam turbine is connected to the first inlet of the condenser, the first outlet of the condenser is connected to the inlet of the low-temperature water tank, the outlet of the low-temperature water tank is connected to the inlet of the low-pressure pump, the outlet of the low-pressure pump and the first outlet of the second preheater are commonly connected to the inlet of the high-pressure pump, the outlet of the high-pressure pump is connected to the second inlet of the aftercooler, and the second outlet of the aftercooler is connected to the inlet of the hot water tank;

[0008] The inlet of the high-temperature molten salt tank is connected to the second outlet of the precooler, and the outlet of the high-temperature molten salt tank is connected to the first inlet of the superheater and the first inlet of the second reheater; the inlet of the medium- and high-temperature molten salt tank is connected to the first outlet of the superheater and the first outlet of the second reheater, and the outlet of the medium- and high-temperature molten salt tank is connected to the second inlet of the precooler.

[0009] A further improvement of the present invention is that the flash tank can convert the medium-temperature, medium-pressure water that absorbs part of the compression heat of the air into medium-temperature, medium-pressure steam and medium-temperature, medium-pressure water respectively. The medium-temperature, medium-pressure steam enters the Rankine cycle to perform work, and the medium-temperature, medium-pressure water serves as a heat source to heat the circulating steam.

[0010] A further improvement of the present invention is that the temperature of the low-temperature waste heat is 35-80°C.

[0011] A further improvement of the present invention is that the low-temperature waste heat utilizes heat from solar panels or industrial waste heat.

[0012] A further improvement of the present invention is that the air is connected to the second inlet of the first preheater through a first control valve.

[0013] A further improvement of the present invention is that the outlet of the medium- and high-temperature molten salt tank is connected to the second inlet of the precooler through a second control valve.

[0014] A further improvement of the present invention is that the outlet of the medium-temperature water tank is connected to the first inlet of the second preheater through the third control valve, the outlet of the low-temperature water tank is connected to the inlet of the low-pressure pump through the fourth control valve, and the outlet of the hot water tank is connected to the inlet of the flash tank through the fifth control valve.

[0015] A further improvement of the present invention is that the outlet of the high-temperature molten salt tank is connected to the first inlet of the superheater and the first inlet of the second reheater through a sixth control valve.

[0016] A control method for a water vapor energy storage system coupled with compressed air and flash evaporation, wherein in an initial state, all six control valves are closed;

[0017] When the user is in the low electricity consumption period, the fifth control valve and the sixth control valve are closed, and the first control valve, the second control valve, the third control valve and the fourth control valve are opened, and the energy storage part of the coupled compressed air and flash vapor water storage system is operated; the normal temperature and normal pressure air enters the first preheater and the second preheater in turn, and is respectively heat-exchanged with the low temperature waste heat and the medium temperature and medium pressure water in the medium temperature water tank to medium temperature before entering the compressor; the high temperature and high pressure air after heating and pressurizing enters the precooler to exchange heat with the medium temperature and high pressure molten salt flowing out of the medium temperature and high pressure molten salt tank; the medium temperature and high pressure air enters the aftercooler to exchange heat with the low temperature and high pressure water After heat exchange, it enters the high-pressure air turbine to expand and perform work. The expanded low-temperature medium-pressure air enters the heater to absorb low-temperature waste heat and then enters the low-pressure air turbine to expand and perform work, offsetting part of the power consumption of the compressor and being discharged into the atmosphere; the medium and high-temperature molten salt absorbs heat in the precooler and then enters the high-temperature molten salt tank for storage. The low-temperature and low-pressure water flowing out of the low-temperature water tank is boosted by the low-pressure pump and enters the high-pressure pump together with the low-temperature and medium-pressure water at the outlet of the second preheater. The boosted low-temperature and high-pressure water enters the aftercooler to absorb heat to medium-temperature and high pressure and then enters the hot water tank for storage; the system energy storage process is completed at this point.

[0018] A further improvement of the present invention is that when the user is at the peak of electricity consumption, the first control valve, the second control valve, the third control valve and the fourth control valve are closed, and the fifth control valve and the sixth control valve are opened, and the energy release part of the coupled compressed air and flashed water vapor energy storage system is put into operation; the medium-temperature and high-pressure water in the hot water tank enters the flash tank for flash evaporation to produce medium-temperature and medium-pressure steam and water, and the medium-temperature and medium-pressure steam enters the superheater and exchanges heat with the high-temperature molten salt flowing out of the high-temperature molten salt tank, and then enters the high-pressure steam turbine to expand and perform work, and the expanded The steam enters the first reheater and the second reheater, exchanges heat with the medium-temperature and medium-pressure water at the outlet of the flash tank and the high-temperature molten salt flowing out of the high-temperature molten salt tank to increase its temperature, and then enters the low-pressure turbine to further expand and perform work. Finally, the steam expanded to low pressure is condensed into a saturated liquid through the condenser and then enters the low-temperature water tank for storage; the medium-pressure water that releases heat through the first reheater enters the medium-temperature water tank for storage, and the high-temperature molten salt releases heat in the superheater and the second reheater and then enters the medium- and high-temperature molten salt tank for storage; thus completing the system energy release process.

[0019] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0020] The water vapor energy storage system coupled with compressed air and flash evaporation utilizes an air heat pump system to generate high-quality heat during the storage phase, while molten salt and high-pressure water are used to store heat of compression. During the release phase, a flash tank generates medium-temperature, medium-pressure steam, which absorbs heat from the molten salt and then enters the steam Rankine cycle to perform work. This system utilizes redundant power to store heat during off-peak periods and uses that heat to drive turbines for power generation during peak periods. Furthermore, the release phase can be retrofitted to existing thermal power plants, reducing system costs.

[0021] Furthermore, the present invention sets a flash tank in the energy release stage, and uses the medium-high quality compression heat to generate medium-temperature and medium-pressure steam as the energy release working medium in a flash manner, avoiding the traditional steam Rankine cycle from generating working steam by absorbing a large amount of latent heat, thereby improving the energy conversion efficiency of the system.

[0022] Furthermore, the present invention utilizes low-temperature waste heat to preheat and reheat the air during the energy storage stage, thereby reducing the net power consumption of the system and improving system performance and energy utilization.

[0023] Furthermore, the present invention utilizes an air heat pump process to generate high-quality heat during the energy storage stage, thereby avoiding the arrangement of a high-pressure air storage tank and further reducing system costs.

[0024] In summary, the present invention uses molten salt and pressurized water to store the air compression heat of the air heat pump cycle. The stored medium and high temperature pressurized water generates steam in the flash tank, absorbs the heat of the high temperature molten salt, and enters the steam turbine to perform work. During the off-peak period of electricity consumption, redundant electricity is used to drive the air heat pump system to generate high-quality thermal energy. During the peak period of electricity consumption, the stored compression heat is used to generate high-temperature steam to drive the turbine to achieve power output. The energy release cycle can be modified using existing coal-fired power plants to reduce system costs; after the energy storage process is completed, the air is directly discharged into the atmosphere, avoiding the layout of air storage tanks and further reducing system costs; the energy storage process can use low-temperature waste heat to increase the air inlet temperature, reduce compression power consumption, and improve energy storage efficiency and energy utilization. The present invention has the advantages of a wide range of applications, green and environmental protection, simple structure, and distributed layout. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art; obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 Schematic diagram of a water vapor energy storage system coupling compressed air and flash evaporation provided by an embodiment of the present invention.

[0027] Description of reference numerals:

[0028] 1. First preheater; 2. Second preheater; 3. Compressor; 4. Precooler; 5. Aftercooler; 6. High-pressure air turbine; 7. Heater; 8. Low-pressure air turbine; 9. High-temperature molten salt tank; 10. Medium- and high-temperature molten salt tank; 11. Hot water tank; 12. Flash tank; 13. Superheater; 14. High-pressure steam turbine; 15. First reheater; 16. Second reheater; 17. Low-pressure steam turbine; 18. Condenser; 19. Low-temperature water tank; 20. Low-pressure pump; 21. Medium-pressure pump; 22. Medium-temperature water tank; 23. First control valve; 24. Second control valve; 25. Third control valve; 26. Fourth control valve; 27. Fifth control valve; 28. Sixth control valve. DETAILED DESCRIPTION

[0029] To make the purpose, technical effects, and technical solutions of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention. Based on the embodiments disclosed in the present invention, other embodiments obtained by ordinary technicians in this field without making any creative efforts should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0031] See also Figure 1 The present invention provides a water vapor energy storage system that couples compressed air with flash evaporation, comprising: a first preheater 1, a second preheater 2, a compressor 3, a precooler 4, an aftercooler 5, a high-pressure air turbine 6, a heater 7, a low-pressure air turbine 8, a high-temperature molten salt tank 9, a medium- and high-temperature molten salt tank 10, a hot water tank 11, a flash tank 12, a superheater 13, a high-pressure steam turbine 14, a first reheater 15, a second reheater 16, a low-pressure steam turbine 17, a condenser 18, a low-temperature water tank 19, a low-pressure pump 20, a medium-pressure pump 21, and a medium-temperature water tank 22. Furthermore, the system includes six control valves: a first control valve 23, a second control valve 24, a third control valve 25, a fourth control valve 26, a fifth control valve 27, and a sixth control valve 28.

[0032] The low-temperature waste heat is connected to the first inlet and the first outlet of the first preheater 1, and the low-temperature waste heat is connected to the first inlet and the first outlet of the heater 7. The air is connected to the second inlet of the first preheater 1 through the first control valve 23. The second outlet of the first preheater 1 is connected to the second inlet of the second preheater 2. The second outlet of the second preheater 2 is connected to the inlet of the compressor 3. The outlet of the compressor 3 is connected to the first inlet of the precooler 4. The first outlet of the precooler 4 is connected to the first inlet of the aftercooler 5. The first outlet of the aftercooler 5 is connected to the inlet of the high-pressure air turbine 6. The outlet of the high-pressure air turbine 6 is connected to the second inlet of the heater 7. The second outlet of the heater 7 is connected to the inlet of the low-pressure air turbine 8. The outlet of the low-pressure air turbine 8 is connected to the atmosphere, completing the compression and expansion process of the air in the energy storage stage.

[0033] The outlet of the medium- and high-temperature molten salt tank 10 is connected to the second inlet of the precooler 4 via the second control valve 24, which in turn is connected to the inlet of the high-temperature molten salt tank 9. The outlet of the low-temperature water tank 19 is connected to the inlet of the low-pressure pump 20 via the fourth control valve 26, and the outlet of the medium-temperature water tank 22 is connected to the first inlet of the second preheater 2 via the third control valve 25. The first outlet of the second preheater 2 and the outlet of the low-pressure pump 20 are both connected to the inlet of the high-pressure pump 21. The outlet of the high-pressure pump 21 is connected to the second inlet of the aftercooler 5, which in turn is connected to the inlet of the hot water tank 11, completing the hierarchical storage of the compressed air heat. These components together constitute the energy storage process.

[0034] The outlet of the hot water tank 11 is connected to the inlet of the flash tank 12 through the fifth control valve 27. The first outlet of the flash tank 12 is connected to the second inlet of the superheater 13. The second outlet of the superheater 13 is connected to the inlet of the high-pressure steam turbine 14. The outlet of the high-pressure steam turbine 14 is connected to the second inlet of the first reheater 15. The second outlet of the first reheater 15 is connected to the second inlet of the second reheater 16. The second outlet of the second reheater 16 is connected to the inlet of the low-pressure steam turbine 17. The outlet of the low-pressure steam turbine 17 is connected to the first inlet of the condenser 18. The first outlet of the condenser 18 is connected to the inlet of the low-temperature water tank 19; the second outlet of the flash tank is connected to the first inlet of the first reheater 15, and the first outlet of the first reheater 15 is connected to the inlet of the medium-temperature water tank 22, completing the flash evaporation of high-temperature and high-pressure water, the expansion of high-temperature and medium-pressure steam, and the storage of medium-temperature and medium-pressure water and low-temperature and low-pressure water in the energy release stage.

[0035] The outlet of the high-temperature molten salt tank 9 is connected to the first inlet of the superheater 13 and the first inlet of the second reheater 16 via the sixth control valve 28. The first outlet of the superheater 13 and the first outlet of the second reheater 16 are then connected to the inlet of the medium- and high-temperature molten salt tank 10, completing the utilization of high-quality compression heat. These components together constitute the energy release process.

[0036] The temperature of low-temperature waste heat is 35-80℃. Low-temperature waste heat utilizes the heat of solar panels or industrial waste heat to achieve the first preheating and reheating of air in the energy storage process, thereby improving system performance and further improving energy utilization.

[0037] A control method for a water vapor energy storage system coupled with compressed air and flash evaporation according to an embodiment of the present invention specifically includes the following steps:

[0038] In the initial state, all six control valves are closed;

[0039] When the user is in the low electricity consumption period, the fifth control valve 27 and the sixth control valve 28 are closed, and the first control valve 23, the second control valve 24, the third control valve 25 and the fourth control valve 26 are opened to couple the compressed air with the flashed water vapor energy storage system to work; the normal temperature and normal pressure air enters the first preheater 1 and the second preheater 2 in turn, and exchanges heat with the low temperature waste heat and the medium temperature and medium pressure water in the medium temperature water tank 22 to medium temperature before entering the compressor 3; the high temperature and high pressure air after heating and pressurizing enters the precooler 4 to exchange heat with the medium temperature and high pressure molten salt flowing out of the medium temperature and high pressure molten salt tank 10; the medium temperature and high pressure air enters the aftercooler 5 and exchanges heat with the low temperature waste heat and the medium temperature and medium pressure water in the medium temperature water tank 22 to medium temperature; After heat exchange, the high-pressure water enters the high-pressure air turbine 6 to expand and perform work. The expanded low-temperature medium-pressure air enters the heater 7 to absorb low-temperature waste heat and then enters the low-pressure air turbine 8 to expand and perform work, offsetting part of the power consumption of the compressor 3 and being discharged into the atmosphere. The medium- and high-temperature molten salt absorbs heat in the precooler 4 and then enters the high-temperature molten salt tank 9 for storage. The low-temperature low-pressure water flowing out of the low-temperature water tank 19 is boosted by the low-pressure pump 20 and enters the high-pressure pump 21 together with the low-temperature medium-pressure water at the outlet of the second preheater 2. The boosted low-temperature high-pressure water enters the aftercooler 5 to absorb heat to medium-temperature and high pressure and then enters the hot water tank 11 for storage. This completes the system energy storage process.

[0040] When the user is in the peak of electricity consumption, close the first control valve 23, the second control valve 24, the third control valve 25, and the fourth control valve 26, open the fifth control valve 27 and the sixth control valve 28, and couple the compressed air and the flashed water vapor energy storage system to work; the medium-temperature and high-pressure water in the hot water tank 11 enters the flash tank 11 for flash evaporation to produce medium-temperature and medium-pressure steam and water, and the medium-temperature and medium-pressure steam enters the superheater 13 and exchanges heat with the high-temperature molten salt flowing out of the high-temperature molten salt tank 9, and then enters the high-pressure steam turbine 14 to expand and do work, and the expanded steam enters the first In the reheater 15 and the second reheater 16, the medium-temperature and medium-pressure water at the outlet of the flash tank 12 and the high-temperature molten salt flowing out of the high-temperature molten salt tank 9 are respectively exchanged for heat and heated, and then enter the low-pressure turbine 17 for further expansion and work. Finally, the steam expanded to a low pressure is condensed into a saturated liquid through the condenser 18 and then enters the low-temperature water tank 19 for storage; the medium-pressure water that releases heat through the first reheater 15 enters the medium-temperature water tank 22 for storage, and the high-temperature molten salt releases heat in the superheater 13 and the second reheater 16 and then enters the medium- and high-temperature molten salt tank for storage; the system energy release process is completed at this point.

[0041] Preferably, the air is heated by introducing low-temperature waste heat into the first preheater 1 and the heater 7, thereby increasing the inlet temperature of the compressor 3 and the low-pressure air turbine 8, thereby reducing the net power consumption of the energy storage process system and improving the overall performance of the system.

[0042] Optionally, heat from solar photovoltaic cells or waste heat from industrial production can be selected as low-temperature waste heat.

[0043] The control method of the present invention can achieve: using redundant power to store heat during low electricity consumption periods, and using heat to drive turbines to generate electricity during peak electricity consumption periods, thereby having high energy storage efficiency.

[0044] In summary, the present invention provides a water vapor energy storage system coupled with compressed air and flash evaporation and a control method thereof, which can realize energy storage and release according to the user's electricity demand, thereby reducing the user's electricity cost. Specific advantages include: (1) The present invention sets a flash tank in the energy release stage, and uses medium-high-quality compression heat to generate medium-temperature and medium-pressure steam as the energy release working medium in the form of flash evaporation, thereby avoiding the traditional steam Rankine cycle that absorbs a large amount of latent heat to generate working steam, thereby improving the system energy conversion efficiency; (2) The energy release stage of the present invention can be modified on the basis of an existing thermal power plant, thereby reducing the system cost; (3) The present invention uses molten salt and water as heat storage media respectively in the energy storage stage, thereby realizing the cascade storage and utilization of compression heat, thereby improving the system energy utilization efficiency; (4) The present invention uses low-temperature waste heat to preheat and reheat the air in the energy storage stage, thereby reducing the net power consumption of the system and improving the system performance and energy utilization rate; (5) The present invention uses the air heat pump process to generate high-quality heat in the energy storage stage, thereby avoiding the arrangement of high-pressure air storage tanks, thereby further reducing the system cost.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art may still modify or make equivalent substitutions to the specific implementations of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A water vapor energy storage system coupling compressed air and flash evaporation, characterized in that: Including the first preheater, the second preheater, the compressor, the precooler, the aftercooler, the high-pressure air turbine, the heater, the low-pressure air turbine, the high-temperature molten salt tank, the medium- and high-temperature molten salt tank, the hot water tank, the flash tank, the superheater, the high-pressure steam turbine, the first reheater, the second reheater, the low-pressure steam turbine, the condenser, the low-temperature water tank, the low-pressure pump, the medium-pressure pump and the medium-temperature water tank; Low-temperature waste heat is connected to the first inlet and the first outlet of the first preheater, and the low-temperature waste heat is connected to the first inlet and the first outlet of the heater, the air is connected to the second inlet of the first preheater, the second outlet of the first preheater is connected to the second inlet of the second preheater, the second outlet of the second preheater is connected to the compressor inlet, the compressor outlet is connected to the first inlet of the precooler, the first outlet of the precooler is connected to the first inlet of the aftercooler, the first outlet of the aftercooler is connected to the inlet of the high-pressure air turbine, the outlet of the high-pressure air turbine is connected to the second inlet of the heater, the second outlet of the heater is connected to the inlet of the low-pressure air turbine, and the outlet of the low-pressure air turbine is connected to the atmosphere; The hot water tank outlet is connected to the flash tank inlet, the second outlet of the flash tank is connected to the first inlet of the first reheater, the first outlet of the first reheater is connected to the inlet of the medium-temperature water tank, and the outlet of the medium-temperature water tank is connected to the first inlet of the second preheater; the first outlet of the flash tank is connected to the second inlet of the superheater, the second outlet of the superheater is connected to the inlet of the high-pressure steam turbine, the outlet of the high-pressure steam turbine is connected to the second inlet of the first reheater, the second outlet of the first reheater is connected to the second inlet of the second reheater, the second outlet of the second reheater is connected to the inlet of the low-pressure steam turbine, the outlet of the low-pressure steam turbine is connected to the first inlet of the condenser, the first outlet of the condenser is connected to the inlet of the low-temperature water tank, the outlet of the low-temperature water tank is connected to the inlet of the low-pressure pump, the outlet of the low-pressure pump and the first outlet of the second preheater are commonly connected to the inlet of the high-pressure pump, the outlet of the high-pressure pump is connected to the second inlet of the aftercooler, and the second outlet of the aftercooler is connected to the inlet of the hot water tank; The inlet of the high-temperature molten salt tank is connected to the second outlet of the precooler, and the outlet of the high-temperature molten salt tank is connected to the first inlet of the superheater and the first inlet of the second reheater; the inlet of the medium- and high-temperature molten salt tank is connected to the first outlet of the superheater and the first outlet of the second reheater, and the outlet of the medium- and high-temperature molten salt tank is connected to the second inlet of the precooler.

2. A water vapor energy storage system coupling compressed air and flash evaporation according to claim 1, characterized in that: The flash tank can convert the medium-temperature, medium-pressure water that absorbs part of the compression heat of the air into medium-temperature, medium-pressure steam and medium-temperature, medium-pressure water respectively. The medium-temperature, medium-pressure steam enters the Rankine cycle to perform work, and the medium-temperature, medium-pressure water serves as a heat source to heat the circulating steam.

3. The water vapor energy storage system coupling compressed air and flash evaporation according to claim 1, characterized in that: The temperature of low-temperature waste heat is 35-80°C.

4. The water vapor energy storage system coupling compressed air and flash evaporation according to claim 1, characterized in that: Low-temperature waste heat utilizes solar panel heat or industrial waste heat.

5. The water vapor energy storage system coupling compressed air and flash evaporation according to claim 1, characterized in that: The air is connected to the second inlet of the first preheater through the first control valve.

6. The water vapor energy storage system coupling compressed air and flash evaporation according to claim 5, characterized in that: The outlet of the medium and high temperature molten salt tank is connected to the second inlet of the precooler through a second control valve.

7. The water vapor energy storage system coupling compressed air and flash evaporation according to claim 6, characterized in that: The outlet of the medium-temperature water tank is connected to the first inlet of the second preheater through the third control valve, the outlet of the low-temperature water tank is connected to the inlet of the low-pressure pump through the fourth control valve, and the outlet of the hot water tank is connected to the inlet of the flash tank through the fifth control valve.

8. The water vapor energy storage system coupling compressed air and flash evaporation according to claim 7, characterized in that: The high-temperature molten salt tank outlet is connected to the first inlet of the superheater and the first inlet of the second reheater through the sixth control valve.

9. The control method of the water vapor energy storage system coupled with compressed air and flash evaporation according to claim 8, characterized in that: In the initial state, all six control valves are closed; When the user is in the low electricity consumption period, the fifth control valve and the sixth control valve are closed, and the first control valve, the second control valve, the third control valve and the fourth control valve are opened, and the energy storage part of the coupled compressed air and flash vapor water storage system is operated; the normal temperature and normal pressure air enters the first preheater and the second preheater in turn, and is respectively heat-exchanged with the low temperature waste heat and the medium temperature and medium pressure water in the medium temperature water tank to medium temperature before entering the compressor; the high temperature and high pressure air after heating and pressurizing enters the precooler to exchange heat with the medium temperature and high pressure molten salt flowing out of the medium temperature and high pressure molten salt tank; the medium temperature and high pressure air enters the aftercooler to exchange heat with the low temperature and high pressure water After heat exchange, it enters the high-pressure air turbine to expand and perform work. The expanded low-temperature medium-pressure air enters the heater to absorb low-temperature waste heat and then enters the low-pressure air turbine to expand and perform work, offsetting part of the power consumption of the compressor and being discharged into the atmosphere; the medium and high-temperature molten salt absorbs heat in the precooler and then enters the high-temperature molten salt tank for storage. The low-temperature and low-pressure water flowing out of the low-temperature water tank is boosted by the low-pressure pump and enters the high-pressure pump together with the low-temperature and medium-pressure water at the outlet of the second preheater. The boosted low-temperature and high-pressure water enters the aftercooler to absorb heat to medium-temperature and high pressure and then enters the hot water tank for storage; the system energy storage process is completed at this point.

10. The control method of a water vapor energy storage system coupled with compressed air and flash evaporation according to claim 9, characterized in that: During peak electricity consumption, the first, second, third, and fourth control valves are closed, and the fifth and sixth control valves are opened, allowing the energy release portion of the coupled compressed air and flash vapor water storage system to operate. The medium-temperature, high-pressure water in the hot water tank enters the flash tank for flash evaporation, generating medium-temperature, medium-pressure steam and water. The medium-temperature, medium-pressure steam enters the superheater, exchanges heat with the high-temperature molten salt flowing out of the high-temperature molten salt tank, and then enters the high-pressure steam turbine to expand and perform work. The expanded steam enters the first and second reheaters, where it exchanges heat with the medium-temperature, medium-pressure water at the flash tank outlet and the high-temperature molten salt flowing out of the high-temperature molten salt tank, respectively, to increase its temperature. It then enters the low-pressure steam turbine to further expand and perform work. Finally, the steam, expanded to a low pressure, is condensed into a saturated liquid in the condenser and then stored in the low-temperature water tank. The medium-pressure water, which releases heat in the first reheater, is stored in the medium-temperature water tank. The high-temperature molten salt, after releasing heat in the superheater and second reheaters, is stored in the medium-temperature molten salt tank. This completes the system's energy release process.

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