Air-water vapor energy storage system coupled with thermal power plant and control method

Abstract

The invention belongs to the technical field of energy storage, and particularly relates to an air-water vapor energy storage system coupled with a thermal power plant and a control method. Comprising a precooler and a cooler which are connected in sequence, and further comprises a molten salt tank connected with the precooler, the water tank is connected with the cooler; the flash tank is connected with the water tank; the superheater is respectively connected with the molten salt tank and the flash tank; the boiler is provided with a superheating section and a reheating section, the superheating section is connected with the superheater and the steam turbine, the steam turbine is provided with a high-pressure cylinder and a low-pressure cylinder, the superheating section is connected with the high-pressure cylinder, and the high-pressure cylinder is connected with the reheating section; the generator is connected with the high-pressure cylinder and the low-pressure cylinder, and the generator is driven to generate electric energy after the high-pressure cylinder and the low-pressure cylinder do expansion work. The operation flexibility of a power plant system is improved, deep coupling with a thermal power plant is achieved, water is used as an energy storage medium, steam is generated through the flash evaporation technology, the steam is further overheated, and the power capability of the energy storage system is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage, and in particular relates to an air-steam energy storage system coupled to a thermal power plant and a control method thereof. Background Art

[0002] Thermal power generation is an indispensable part of my country's power generation sector. In a thermal power plant, the boiler converts the chemical energy in the fuel into thermal energy through combustion, heats the water into steam, and the steam enters the steam turbine to expand and do work. The rotation of the steam turbine drives the generator to generate electricity and generate electricity. With my country's energy transformation, thermal power plants need to perform deep peak regulation according to the load of the power grid. Thermal power plants face many safety issues due to low operating loads and frequent load changes. For example, the boiler is one of the core equipment in a thermal power plant, and its main function is to heat the water vapor with the heat energy generated by the full combustion of the fuel. During the deep peak regulation process, the flow rate of water fed to the boiler is reduced, which may lead to uneven local flow, overheating of the pipe wall and other problems, and increase the risk of pipe burst. For another core equipment in a thermal power plant, the steam turbine also faces problems such as increased risk of flutter of the last-stage blades, decreased stability of the shaft system and increased thermal stress. Applying energy storage technology to thermal power plants can effectively stabilize the load of thermal power plants and improve the safety of thermal power plant operations.

[0003] Energy storage technology refers to the technology of storing energy so that it can be released when needed. It plays an important role in the energy field, can improve the stability, reliability and efficiency of energy systems, and promote the large-scale application of renewable energy. Applying it to thermal power plants can not only improve the peak load regulation capacity and flexibility of thermal power plants, but also improve the safety and stability of thermal power plant operation.

[0004] In the prior art, such as application number 202410701333.0, a water vapor energy storage system coupling compressed air and flash evaporation and its control method are disclosed. The system includes 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 cooler, a low-temperature water tank, a low-pressure pump, a medium-pressure pump and a medium-temperature water tank connected together by pipelines. In the energy storage stage, the air heat pump system is used to generate high-quality heat, and the molten salt and high-pressure water are used to store compression heat respectively. In the energy release stage, the flash tank is used to generate medium-temperature and medium-pressure steam, which enters the steam Rankine cycle to do work after absorbing the heat of the molten salt. Redundant electricity is used to store heat during the off-peak period of electricity consumption, and heat is used to drive the turbine to generate electricity during the peak period of electricity consumption. At the same time, the energy release stage can be transformed on the basis of the existing thermal power plant to reduce the system cost.

[0005] However, the above energy storage system still cannot directly realize coupling with the traditional thermal power plant system and the energy source is single. Specifically, it cannot directly use the heat energy generated by the thermal power plant as the heat source of the device, and the heat generated by the compressed air is limited and cannot meet the higher power requirements. The heat source of the high-pressure steam turbine is only the heat generated after the air is compressed, and it is impossible to obtain heat energy from the boiler to heat the steam. Similarly, the heat source in the reheating process is only the heat generated by the compressed air, and it is impossible to directly obtain heat from other heat exchange sections of the boiler, and thus it cannot be coupled with the thermal power plant. In addition, the number of heat exchangers in the energy storage system is too large, reaching ten, and the required supporting connecting pipelines. The complexity makes it impossible to complete the installation and coupling between the existing power plant equipment. In summary, the above energy storage system has the problems that the water vapor parameters do not match the thermal power plant, there are too many heat exchange equipment, and the pipelines are complex and difficult to transform, and it is impossible to complete the installation and coupling between the existing power plant equipment. Summary of the invention

[0006] In order to solve the above problems, the present invention provides an air-steam energy storage system and control method coupled with a thermal power plant. The present invention increases the flexibility of the operation of the energy storage system and realizes deep coupling with the thermal power plant. Since the steam turbine can realize efficient and safe operation under the design conditions, the steam generated in the energy release process is heated to the circulating water steam parameters under the design working conditions of the steam turbine by a boiler, and the steam is reheated by the boiler to enter the low-pressure cylinder for further work. Water is used as the energy storage medium, and steam is generated by flash evaporation technology, and the steam is further superheated to improve the work capacity of the energy storage system. The heat in the boiler can be further used to further improve the steam parameters, thereby increasing the overall output of the system and realizing coupling with a traditional thermal power plant.

[0007] The present invention solves the above technical problems through the following technical solutions.

[0008] In one aspect, the present invention provides an air-steam energy storage system coupled to a thermal power plant, comprising a precooler and a cooler connected in sequence, the precooler being connected to air, and further comprising:

[0009] The molten salt tank is connected to the precooler and is used to exchange heat with the air in the precooler to form high-temperature molten salt.

[0010] A water tank is connected to a cooler and is used to exchange heat with the air in the cooler to form high-temperature and high-pressure water.

[0011] Flash tank, which is connected to a water tank, is used to flash high-temperature and high-pressure water to produce saturated steam.

[0012] The superheater is connected to the molten salt tank and the flash tank respectively, and the saturated steam is heated by the high-temperature molten salt to form superheated steam and the first saturated water.

[0013] The boiler is provided with a superheating section and a reheating section, the superheating section is connected to the superheater and the steam turbine, the steam turbine is provided with a high-pressure cylinder and a low-pressure cylinder, the superheating section is connected to the high-pressure cylinder, the high-pressure cylinder is connected to the reheating section, the superheating section is used to heat the superheated steam and then transport it to the high-pressure cylinder for expansion work, and the first exhaust gas generated by the high-pressure cylinder is transported to the reheating section; the reheating section is connected to the low-pressure cylinder, the reheating section is used to heat the first exhaust gas to form superheated steam and transport it to the low-pressure cylinder for expansion work; the low-pressure cylinder is connected to the condenser, the condenser is connected to the water tank through a transport mechanism, the second exhaust gas generated by the low-pressure cylinder is transported to the condenser, the condenser is used to condense the second exhaust gas to form second saturated water, and after mixing the second saturated water with the first saturated water, transport it to the water tank through the transport mechanism.

[0014] The generator is connected to the high-pressure cylinder and the low-pressure cylinder. The generator generates electrical energy after the high-pressure cylinder and the low-pressure cylinder perform expansion work.

[0015] Furthermore, in the above-mentioned air-steam energy storage system coupled to a thermal power plant, a first inlet, a second inlet, a first outlet and a second outlet are provided on the precooler, the molten salt tank includes a low-temperature molten salt tank and a high-temperature molten salt tank, the first inlet is connected to the air, the first outlet is connected to the cooler, the second inlet is connected to the outlet of the low-temperature molten salt tank, and the second outlet is connected to the inlet of the high-temperature molten salt tank.

[0016] Furthermore, in the above-mentioned air-steam energy storage system of the coupled thermal power plant, a third inlet, a fourth inlet, a third outlet and a fourth outlet are provided on the superheater, the third inlet is connected to the flash tank, the third outlet is connected to the superheating section, the fourth inlet is connected to the outlet of the high-temperature molten salt tank, and the fourth outlet is connected to the inlet of the low-temperature molten salt tank.

[0017] Furthermore, in the above-mentioned air-steam energy storage system of the coupled thermal power plant, a second control valve is provided between the second inlet and the outlet of the low-temperature molten salt tank, and a third control valve is provided between the fourth inlet and the outlet of the high-temperature molten salt tank.

[0018] Furthermore, in the above-mentioned air-steam energy storage system coupled to the thermal power plant, the molten salt tank is connected to an electric heater, the electric heater is connected to the electric energy generated by the thermal power plant, the inlet of the electric heater is connected to the outlet of the low-temperature molten salt tank, and the outlet of the electric heater is connected to the inlet of the high-temperature molten salt tank.

[0019] Furthermore, in the above-mentioned air-steam energy storage system of the coupled thermal power plant, a fifth inlet, a sixth inlet, a fifth outlet and a sixth outlet are provided on the precooler, the water tank includes a high-temperature and high-pressure water tank and a low-temperature and high-pressure water tank, the fifth inlet is connected to the first outlet, the fifth outlet is connected to the air turbine, the sixth outlet is connected to the inlet of the high-temperature and high-pressure water tank, the sixth inlet is connected to the outlet of the low-temperature and high-pressure water tank, and a fourth control valve is also provided between the sixth inlet and the outlet of the low-temperature and high-pressure water tank.

[0020] Furthermore, in the above-mentioned air-steam energy storage system of the coupled thermal power plant, a seventh inlet, a seventh outlet and an eighth outlet are provided on the flash tank, the seventh inlet is connected to the outlet of the low-temperature and high-pressure water tank, the seventh outlet is connected to the outlet of the high-temperature and high-pressure water tank, and the eighth outlet is connected to the third inlet; the seventh outlet is connected to the inlet of the low-temperature and high-pressure water tank through a conveying mechanism, and the condenser is also connected to the seventh outlet; a fifth control valve is also provided between the seventh inlet and the outlet of the high-temperature and high-pressure water tank, and a sixth control valve is provided between the eighth outlet and the third inlet.

[0021] Furthermore, in the air-steam energy storage system of the above-mentioned coupled thermal power plant, the first inlet is connected to an air compressor, and an electric motor is also provided on the air compressor. The air compressor is connected to the atmosphere through a first control valve, and the air compressor is also connected to an air turbine, and the turbine coaxially drives the generator.

[0022] On the other hand, the present invention provides a control method for the above-mentioned air-steam energy storage system coupled to a thermal power plant, comprising the following steps:

[0023] In the initial state, the first control valve, the second control valve, the third control valve, the fourth control valve, the fifth control valve and the sixth control valve are closed.

[0024] When the user is in the low electricity consumption period, the energy storage part of the air-steam energy storage system coupled to the thermal power plant operates at normal temperature and pressure. At this time, the third control valve, the fifth control valve and the sixth control valve are closed, and the first control valve, the second control valve and the fourth control valve are opened. The air in the atmosphere enters the air compressor for pressurization to obtain high-temperature and high-pressure air. The high-temperature and high-pressure air enters the precooler and exchanges heat with the low-temperature molten salt flowing out of the low-temperature molten salt storage tank through the second control valve. The molten salt after absorbing heat forms high-temperature molten salt and enters the high-temperature molten salt storage tank for storage. The air after releasing heat enters the cooler and exchanges heat with the water flowing out of the low-temperature and high-pressure water tank through the fourth control valve. The water after absorbing heat forms high-temperature and high-pressure water and enters the high-temperature and high-pressure water tank for storage. The air after releasing heat enters the air turbine, expands and does work, and is discharged into the atmosphere, completing the system energy storage process.

[0025] When the user is at the peak of electricity consumption, the first control valve, the second control valve and the fourth control valve are closed, and the third control valve, the fifth control valve and the sixth control valve are opened. The water in the high-temperature and high-pressure water tank enters the flash tank for flash evaporation to generate saturated steam. The saturated steam enters the superheater through the sixth control valve. After the saturated steam enters the superheater, it is heat exchanged with the high-temperature molten salt to obtain superheated steam. The molten salt after heat release enters the low-temperature molten salt storage tank for storage; the superheated steam enters the superheating section to heat the superheated steam and then transported to the high-pressure cylinder for expansion work. The first exhaust gas generated in the process of the high-pressure cylinder doing the expansion work is transported to the reheating section. The reheating section heats the first exhaust gas to form superheated steam and transports it to the low-pressure cylinder for expansion work. The high-pressure cylinder and the low-pressure cylinder coaxially drive the generator to rotate to generate electricity. The second exhaust gas generated in the process of the low-pressure cylinder doing the expansion work passes through the condenser to generate second saturated water, and after mixing with the first saturated water generated by flash evaporation, it is transported to the low-temperature and high-pressure water tank through the conveying mechanism for storage, completing the system energy release process.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The air-steam energy storage system coupled to a thermal power plant provided by the present invention, the electric energy required by the motor is directly derived from the electric energy generated by the thermal power plant, the molten salt in the molten salt tank is heat exchanged with the air in the precooler to form high-temperature molten salt, the water in the water tank is heat exchanged with the air in the cooler to form high-temperature and high-pressure water, the generated electric energy is stored, and by introducing a boiler and a steam turbine, during the energy release process, the saturated steam generated by the high-temperature and high-pressure water is heated by the flash tank, and the saturated steam is heated by the warm molten salt to form superheated steam, which is transported to the high-pressure cylinder for expansion work, the reheating section is used to heat the first exhaust gas to form superheated steam and transport it to the low-pressure cylinder for expansion work, and the generated second exhaust gas is transported to the condenser, the second exhaust gas is condensed to form second saturated water, and the second saturated water is mixed with the first saturated water and then transported to the water tank through a conveying mechanism, the steam turbine drives the generator to generate electric energy, the present invention uses water as an energy storage medium, uses flash evaporation technology to generate steam, and further superheats the steam to improve the working capacity of the energy storage system. The heat in the boiler can be further utilized to further improve the steam parameters, thereby increasing the overall output of the system and achieving coupling with traditional thermal power plants.

[0028] (2) The present invention utilizes electric heating to improve the speed of electricity storage. When peak load regulation is required, electric heating can be used to quickly absorb the electricity generated by the thermal power plant, store this energy in molten salt, and utilize it in the energy release process, thereby slowing down the load reduction rate of the thermal power unit, reducing damage to the thermal power plant equipment, and improving the safety of power plant operation.

[0029] (3) The water used in the energy storage of the present invention is the main working fluid in existing thermal power plants. The relevant technology is mature and easy to implement, safe and environmentally friendly. The working fluid in the energy storage is liquid water, which further reduces the volume of the energy storage system and greatly reduces the footprint of the device; the air used in the energy storage process is directly introduced from the atmosphere and finally discharged into the atmosphere. There is no need to set up a large-scale gas storage device, which greatly reduces the volume of the energy storage system, so that the energy storage system in the present invention can be coupled to thermal power units of different installed capacities and models.

[0030] (4) The present invention can utilize the opening of the control valve to adjust the steam ratio between the superheater and the boiler, thereby achieving the purpose of flexibly adjusting the steam parameters and further adjusting the energy release power of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the structure of the air-steam energy storage system coupled to a thermal power plant according to the present invention.

[0032] Illustration Description:

[0033] 1. Precooler, 2. Cooler, 3. Flash tank, 4. Superheater, 5. Boiler, 51. Superheat section, 52. Reheat section, 6. Steam turbine, 61. High-pressure cylinder, 62. Low-pressure cylinder, 7. Condenser, 8. Generator, 9. Low-temperature molten salt tank, 10. High-temperature molten salt tank, 11. Electric heater, 12. High-temperature and high-pressure water tank, 13. Low-temperature and high-pressure water tank, 14. Air compressor, 15. Electric motor, 16. Air turbine, 17. First control valve, 18. Second control valve, 19. Third control valve, 20. Fourth control valve, 21. Fifth control valve, 22. Sixth control valve. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Certain words are used in the present invention to refer to specific components. Those skilled in the art should understand that technicians will use different nouns to refer to the same component. The present invention does not distinguish between components by the difference in nouns, but by the difference in the functions of the components. As mentioned throughout the specification and claims, "including" is an open term and should be understood as "including but not limited to".

[0036] The invention is further described below through specific examples.

[0037] Example

[0038] The present invention provides an air-water vapor energy storage system coupled with a thermal power plant, comprising a precooler 1 and a cooler 2 connected in sequence, wherein the precooler 1 is connected to the air, and further comprising: a molten salt tank, which is connected to the precooler 1 and is used to perform heat exchange on the air in the precooler 1 to form high-temperature molten salt. A water tank, which is connected to the cooler 2 and is used to perform heat exchange on the air in the cooler 2 to form high-temperature and high-pressure water. A flash tank 3, which is connected to the water tank and is used to flash the high-temperature and high-pressure water to generate saturated steam and first saturated water. A superheater 4, which is respectively connected to the molten salt tank and the flash tank 3, and heats the saturated steam with the high-temperature molten salt to form superheated steam. The boiler 5 is provided with a superheating section 51 and a reheating section 52. The superheating section 51 is connected to the superheater 4 and the steam turbine 6. The steam turbine 6 is provided with a high-pressure cylinder 61 and a low-pressure cylinder 62. The superheating section 51 is connected to the high-pressure cylinder 61, and the high-pressure cylinder 61 is connected to the reheating section 52. The superheating section 51 is used to heat the superheated steam and then transport it to the high-pressure cylinder 61 for expansion work. The first exhaust gas generated by the high-pressure cylinder 61 is transported to the reheating section 52; the reheating section 52 is connected to the low-pressure cylinder 62, and the reheating section 52 is used to heat the first exhaust gas to form superheated steam and transport it to the low-pressure cylinder 62 for expansion work; the low-pressure cylinder 62 is connected to the condenser 7, and the condenser 7 is connected to the water tank. The second exhaust gas generated by the low-pressure cylinder 62 is transported to the condenser 7. The condenser 7 is used to condense the second exhaust gas to form second saturated water, and after mixing the second saturated water with the first saturated water, transport it to the water tank through the transport mechanism. The generator 8 is connected to the high-pressure cylinder 61 and the low-pressure cylinder 62 . The generator 8 generates electrical energy after the high-pressure cylinder 61 and the low-pressure cylinder 62 perform expansion work.

[0039] It should be noted that the boiler 5, steam turbine 6, generator 8, and condenser 7 mentioned in the present invention are all main operating components in the thermal power plant. The present invention can be modified on the existing basis of the thermal power plant to realize the coupling of the thermal power plant and the energy storage system, overcome the problems of water vapor parameters not matching the thermal power plant, too many heat exchange equipment, and complex pipeline transformation difficulties, and introduce electric heating and boiler 5 heating methods to increase the flexibility of the power plant system operation, achieve deep coupling with the thermal power plant, and add the energy storage system to the boiler to increase the output power. The use of electric heating improves the speed of power storage. When there is a need for peak regulation, electric heating can be used quickly to consume the electric energy generated by the thermal power plant, and this part of the energy is stored in the molten salt and used in the energy release process. In addition, the load reduction rate of the thermal power unit is delayed, the damage to the thermal power plant equipment is reduced, and the safety of the power plant operation is improved. Since the steam turbine 6 can achieve efficient and safe operation under the design conditions, the present invention uses a boiler 5 to heat the steam generated during the energy release process to the water vapor parameters under the design conditions of the steam turbine 6, and uses the boiler 5 to reheat and enter the low-pressure cylinder 62 for further work.

[0040] In some specific embodiments, the precooler 1 is provided with a first inlet, a second inlet, a first outlet and a second outlet, the molten salt tank includes a low-temperature molten salt tank 9 and a high-temperature molten salt tank 10, the first inlet is connected to the air, the first outlet is connected to the cooler 2, the second inlet is connected to the outlet of the low-temperature molten salt tank 9, and the second outlet is connected to the inlet of the high-temperature molten salt tank 10. The air in the atmosphere is pressurized by air compression to form high-temperature and high-pressure air, and then enters the precooler 1 through the first inlet, and heat exchanges with the low-temperature molten salt in the low-temperature molten salt tank 9 through the second inlet. The low-temperature molten salt after absorbing heat forms high-temperature molten salt, and the high-temperature molten salt enters the high-temperature molten salt storage tank through the second outlet for storage, and heat exchanges at high temperature and high pressure form heat-released air, and the heat-released air enters the cooler 2 through the first outlet.

[0041] In some specific embodiments, the superheater 4 is provided with a third inlet, a fourth inlet, a third outlet and a fourth outlet, the third inlet is connected to the flash tank 3, the third outlet is connected to the superheating section 51, the fourth inlet is connected to the outlet of the high-temperature molten salt tank 10, and the fourth outlet is connected to the inlet of the low-temperature molten salt tank 9. When the high-temperature molten salt in the high-temperature molten salt storage tank enters the superheater 4 through the fourth inlet, the saturated steam generated by the flash tank 3 enters the superheater 4 through the third inlet. The high-temperature molten salt performs heat exchange on the saturated steam to form superheated steam, and the superheated steam enters the superheating section 51 through the third outlet, and the high-temperature molten salt performs heat exchange on the saturated steam to form low-temperature molten salt, which enters the low-temperature molten salt tank 9 through the fourth outlet for storage.

[0042] In some specific embodiments, a second control valve 18 is provided between the second inlet and the outlet of the low-temperature molten salt tank 9, and a third control valve 19 is provided between the fourth inlet and the outlet of the high-temperature molten salt tank 10. The opening of the second control valve 18 can be used to adjust the flow of the low-temperature molten salt in the low-temperature molten salt tank 9, thereby controlling the degree of heat exchange and heat absorption of the low-temperature molten salt to form high-temperature molten salt, thereby controlling the temperature parameters of the high-temperature molten salt; the opening of the third control valve 19 controls the flow of the high-temperature molten salt in the high-temperature molten salt tank 10, thereby controlling the degree of heat exchange of the high-temperature molten salt with the saturated steam, thereby controlling the temperature parameters of the saturated steam.

[0043] In some specific embodiments, the molten salt tank is connected to an electric heater 11, the electric heater 11 is connected to the electric energy generated by the thermal power plant, the inlet of the electric heater 11 is connected to the outlet of the low-temperature molten salt tank 9, and the outlet of the electric heater 11 is connected to the inlet of the high-temperature molten salt tank 10. When there is a need for peak load regulation, the excess electric energy generated by the thermal power plant is input into the electric heater 11, and the heat generated by the electric heater 11 heats the low-temperature molten salt in the low-temperature molten salt tank 9.

[0044] In some specific embodiments, the precooler 1 is provided with a fifth inlet, a sixth inlet, a fifth outlet and a sixth outlet, the water tank includes a high-temperature high-pressure water tank 12 and a low-temperature high-pressure water tank 13, the fifth inlet is connected to the first outlet, the fifth outlet is connected to the air turbine 16, the sixth outlet is connected to the inlet of the high-temperature high-pressure water tank 12, the sixth inlet is connected to the outlet of the low-temperature high-pressure water tank 13, and a fourth control valve 20 is also provided between the sixth inlet and the outlet of the low-temperature high-pressure water tank 13. The air after heat release enters the cooler 2 through the first outlet and the fifth inlet in sequence, the low-temperature high-pressure water in the low-temperature high-pressure water tank 13 enters the cooler 2 through the sixth inlet, the low-temperature high-pressure water is heat exchanged with the air after heat release, and forms high-temperature high-pressure water, which enters the high-temperature high-pressure water tank 12 through the sixth outlet for storage, and the air after heat release enters the air turbine 16 for expansion and work and is discharged into the atmosphere; the opening of the fourth control valve 20 controls the flow of low-temperature high-pressure water in the low-temperature high-pressure water tank 13, thereby controlling the degree of heat exchange and the temperature of the high-temperature high-pressure water.

[0045] In some specific embodiments, the flash tank 3 is provided with a seventh inlet, a seventh outlet and an eighth outlet, the seventh inlet is connected to the outlet of the low-temperature and high-pressure water tank 13, the seventh outlet is connected to the inlet of the high-temperature and high-pressure water tank 12, and the eighth outlet is connected to the third inlet; the seventh outlet is connected to the inlet of the low-temperature and high-pressure water tank 13 through a conveying mechanism, and the condenser 7 is also connected to the seventh outlet; a fifth control valve 21 is also provided between the seventh inlet and the outlet of the high-temperature and high-pressure water tank 12, and a sixth control valve 22 is provided between the eighth outlet and the third inlet. The high-temperature and high-pressure water in the high-temperature and high-pressure water tank 12 enters the flash tank 3 through the seventh inlet. The flash tank 3 flashes the high-temperature and high-pressure water to generate saturated steam. The generated saturated steam enters the third inlet and enters the superheater 4. The formed low-temperature and high-pressure water enters the low-temperature and high-pressure water tank 13 through the seventh outlet for storage, and the water generated by the condenser 7 is also transported to the low-temperature and high-pressure water tank 13 through the conveying mechanism. The conveying mechanism is a conveying pump. The purpose of the conveying pump is that the pressure will be lower than the initial pressure after a cycle. Because flash evaporation is a pressure drop process, the pressure is pumped to the original value at the beginning of a new cycle. The opening of the fifth control valve 21 adjusts the flow rate of high-temperature and high-pressure water to change the flow rate entering the flash tank 3, thereby adjusting the output power of the energy storage system; the opening of the sixth control valve 22 adjusts the flow rate of saturated steam entering the superheater 4, thereby adjusting the temperature of the superheated steam.

[0046] In some specific embodiments, the first inlet is connected to an air compressor 14, and the air compressor 14 is also provided with a motor 15. The air compressor 14 is connected to the atmosphere through a first control valve 17, and the air compressor 14 is also connected to an air turbine 16, and the steam turbine 6 coaxially drives the generator 8. The air compressor 14 is coaxially driven by the motor 15, and the air compressor 14 and the air turbine 16 are coaxially driven. When the air turbine 16 is running, it can provide shaft work to the air compressor 14 to reduce the operating power of the motor 15. The steam turbine 6 coaxially drives the generator 8 to do work.

[0047] The control method of the air-steam energy storage system coupled to the thermal power plant comprises the following steps:

[0048] In the initial state, the first control valve 17 , the second control valve 18 , the third control valve 19 , the fourth control valve 20 , the fifth control valve 21 , and the sixth control valve 22 are closed.

[0049] When the user is in the low electricity consumption valley, the energy storage part of the air-steam energy storage system coupled to the thermal power plant operates at normal temperature and pressure. At this time, the third control valve 19, the fifth control valve 21 and the sixth control valve 22 are closed, and the first control valve 17, the second control valve 18 and the fourth control valve 20 are opened. The air in the atmosphere enters the air compressor for pressurization to obtain high-temperature and high-pressure air. The high-temperature and high-pressure air enters the precooler 1 and performs heat exchange with the low-temperature molten salt flowing out of the low-temperature molten salt storage tank through the second control valve 18. The molten salt after absorbing heat forms high-temperature molten salt and enters the high-temperature molten salt storage tank for storage. The air after releasing heat enters the cooler 2 and performs heat exchange with the water flowing out of the low-temperature and high-pressure water tank 13 through the fourth control valve 20. The water after absorbing heat forms high-temperature and high-pressure water and enters the high-temperature and high-pressure water tank 12 for storage. The air after releasing heat enters the air turbine 16 to expand and do work and is discharged into the atmosphere, completing the system energy storage process.

[0050] When the user is at the peak of electricity consumption, the first control valve 17, the second control valve 18 and the fourth control valve 20 are closed, and the third control valve 19, the fifth control valve 21 and the sixth control valve 22 are opened. The water in the high-temperature and high-pressure water tank 12 enters the flash tank 3 for flash evaporation to generate saturated steam and first saturated water. The generated saturated steam enters the superheater 4 through the sixth control valve 22. After the saturated steam enters the superheater 4, it is heat exchanged with the high-temperature molten salt to obtain superheated steam. The molten salt after heat release enters the low-temperature molten salt storage tank for storage; the superheated steam enters the superheating section 51 The superheated steam is heated and then transported to the high-pressure cylinder 61 to perform expansion work. The first exhaust gas generated in the process of the expansion work of the high-pressure cylinder 61 is transported to the reheating section 52. The reheating section 52 heats the first exhaust gas to form superheated steam and transports it to the low-pressure cylinder 62 to perform expansion work. The high-pressure cylinder 61 and the low-pressure cylinder 62 coaxially drive the generator 8 to rotate to generate electricity. The second exhaust gas generated in the process of the expansion work of the low-pressure cylinder 62 passes through the condenser 7 to generate second saturated water, and after being mixed with the first saturated water generated by flash evaporation, it is transported to the low-temperature high-pressure water tank 13 for storage through the delivery pump, completing the system energy release process.

[0051] In summary, the present invention provides an air-steam energy storage system and control method coupled to a thermal power plant, which can store and release energy according to the grid load and actual user requirements, and store and release electric energy for users. Specific advantages include:

[0052] First, during the energy storage process, the electric energy required by the motor comes directly from the electricity generated by the thermal power plant. Storing the generated electricity reduces the electric energy input to the power grid and achieves deep peak regulation.

[0053] Second, the air used in the energy storage process is directly introduced from the atmosphere and finally discharged into the atmosphere. There is no need to set up a large-scale gas storage device, which greatly reduces the volume of the energy storage system. The energy storage system of the present invention can be coupled to thermal power units of different installed capacities and models.

[0054] Third, in the process of releasing energy, water is used as the energy storage medium, flash evaporation technology is used to generate steam, and the steam is further superheated to improve the work capacity of the energy storage system. The heat in the boiler can be further used to further improve the steam parameters, thereby increasing the overall output of the system, and achieving coupling with traditional thermal power plants.

[0055] Fourth, the water used in the energy storage system is the main working fluid in existing thermal power plants. The relevant technology is mature, easy to implement, safe and environmentally friendly. The working fluid in the energy storage is liquid water, which further reduces the volume of the energy storage system and greatly reduces the footprint of the device.

[0056] Fifth, the opening of the sixth control valve can be used to adjust the steam flow entering the superheater and the boiler, so as to flexibly adjust the steam parameters and further adjust the energy release power of the energy storage system.

[0057] Sixth, during the energy storage process of the energy storage system, since the air temperature at the air turbine outlet is low, it can be used as a cold source to provide cooling for users.

[0058] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0059] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An air-steam energy storage system coupled to a thermal power plant, comprising a precooler (1) and a cooler (2) connected in sequence, wherein the precooler (1) is connected to air, and is characterized in that: Also includes: A molten salt tank, the molten salt tank is connected to the precooler (1) and is used to perform heat exchange on the air in the precooler (1) to form high-temperature molten salt; A water tank connected to the cooler (2) and used for exchanging heat with the air in the cooler (2) to form high-temperature and high-pressure water; A flash tank (3), the flash tank (3) is connected to the water tank and is used to flash the high-temperature and high-pressure water to generate saturated steam and first saturated water; A superheater (4), the superheater (4) is connected to the molten salt tank and the flash tank (3) respectively, and heats the saturated steam with high-temperature molten salt to form superheated steam; The boiler (5) is provided with a superheating section (51) and a reheating section (52); the superheating section (51) is connected to the superheater (4) and the steam turbine (6); the steam turbine (6) is provided with a high-pressure cylinder (61) and a low-pressure cylinder (62); the superheating section (51) is connected to the high-pressure cylinder (61); the high-pressure cylinder (61) is connected to the reheating section (52); the superheating section (51) is used to heat the superheated steam and then transport it to the high-pressure cylinder (61) to perform expansion work; the first exhaust gas generated by the high-pressure cylinder (61) is transported to the reheating section (52); The reheat section (52) is connected to the low-pressure cylinder (62), and the reheat section (52) is used to heat the first exhaust gas to form superheated steam and transport it to the low-pressure cylinder (62) to perform expansion work; the low-pressure cylinder (62) is connected to the condenser (7), and the condenser (7) is connected to the water tank through a transport mechanism. The second exhaust gas generated by the low-pressure cylinder (62) is transported to the condenser (7), and the condenser (7) is used to condense the second exhaust gas to form second saturated water, and after mixing the second saturated water with the first saturated water, transport it to the water tank through the transport mechanism; The generator (8) is connected to the high-pressure cylinder (61) and the low-pressure cylinder (62). The generator (8) generates electrical energy by performing expansion work on the high-pressure cylinder (61) and the low-pressure cylinder (62).

2. The air-steam energy storage system coupled to a thermal power plant according to claim 1, characterized in that: The precooler (1) is provided with a first inlet, a second inlet, a first outlet and a second outlet, the molten salt tank comprises a low-temperature molten salt tank (9) and a high-temperature molten salt tank (10), the first inlet is connected to air, the first outlet is connected to the cooler (2), the second inlet is connected to the outlet of the low-temperature molten salt tank (9), and the second outlet is connected to the inlet of the high-temperature molten salt tank (10).

3. The air-steam energy storage system coupled to a thermal power plant according to claim 2, characterized in that: The superheater (4) is provided with a third inlet, a fourth inlet, a third outlet and a fourth outlet, the third inlet is connected to the flash tank (3), the third outlet is connected to the superheating section (51), the fourth inlet is connected to the outlet of the high-temperature molten salt tank (10), and the fourth outlet is connected to the inlet of the low-temperature molten salt tank (9).

4. The air-steam energy storage system coupled to a thermal power plant according to claim 3, characterized in that: A second control valve (18) is provided between the second inlet and the outlet of the low-temperature molten salt tank (9), and a third control valve (19) is provided between the fourth inlet and the outlet of the high-temperature molten salt tank (10).

5. The air-steam energy storage system coupled to a thermal power plant according to claim 4, characterized in that: The molten salt tank is connected to an electric heater (11), the electric heater (11) is connected to the electric energy generated by the thermal power plant, the inlet of the electric heater (11) is connected to the outlet of the low-temperature molten salt tank (9), and the outlet of the electric heater (11) is connected to the inlet of the high-temperature molten salt tank (10).

6. The air-steam energy storage system coupled to a thermal power plant according to claim 5, characterized in that: The precooler (1) is provided with a fifth inlet, a sixth inlet, a fifth outlet and a sixth outlet. The water tank includes a high-temperature and high-pressure water tank (12) and a low-temperature and high-pressure water tank (13). The fifth inlet is connected to the first outlet, the fifth outlet is connected to the air turbine (16), the sixth outlet is connected to the inlet of the high-temperature and high-pressure water tank (12), the sixth inlet is connected to the outlet of the low-temperature and high-pressure water tank (13), and a fourth control valve (20) is provided between the sixth inlet and the outlet of the low-temperature and high-pressure water tank (13).

7. The air-steam energy storage system coupled to a thermal power plant according to claim 6, characterized in that: The flash tank (3) is provided with a seventh inlet, a seventh outlet and an eighth outlet, the seventh inlet is connected to the outlet of the low-temperature high-pressure water tank (13), the seventh outlet is connected to the outlet of the high-temperature high-pressure water tank (12), and the eighth outlet is connected to the third inlet; The seventh outlet is connected to the inlet of the low-temperature and high-pressure water tank (13) via a conveying mechanism, and the condenser (7) is also connected to the seventh outlet; a fifth control valve (21) is also provided between the seventh inlet and the outlet of the high-temperature and high-pressure water tank (12), and a sixth control valve (22) is provided between the eighth outlet and the third inlet.

8. The air-steam energy storage system coupled to a thermal power plant according to claim 7, characterized in that: The first inlet is connected to an air compressor (14), and the air compressor (14) is also provided with an electric motor (15). The air compressor (14) is connected to the atmosphere through a first control valve (17). The air compressor (14) is also connected to an air turbine (16), and the steam turbine (6) coaxially drives a generator (8).

9. A control method for an air-steam energy storage system coupled to a thermal power plant according to claim 8, characterized in that: The following steps are involved: In the initial state, the first control valve (17), the second control valve (18), the third control valve (19), the fourth control valve (20), the fifth control valve (21) and the sixth control valve (22) are closed; When the user is in the low electricity consumption valley, the energy storage part of the air-steam energy storage system coupled to the thermal power plant starts working. At this time, the third control valve (19), the fifth control valve (21) and the sixth control valve (22) are closed, and the first control valve (17), the second control valve (18) and the fourth control valve (20) are opened. The air in the atmosphere enters the air compressor to be pressurized to obtain high-temperature and high-pressure air. The high-temperature and high-pressure air enters the precooler (1) to perform heat exchange with the low-temperature molten salt flowing out of the low-temperature molten salt storage tank through the second control valve (18). The molten salt after absorbing heat forms high-temperature molten salt and enters the high-temperature molten salt storage tank for storage. The air after releasing heat enters the cooler (2) to perform heat exchange with the water flowing out of the low-temperature and high-pressure water tank (13) through the fourth control valve (20). The water after absorbing heat forms high-temperature and high-pressure water and enters the high-temperature and high-pressure water tank (12) for storage. The air after releasing heat enters the air turbine (16) to expand and do work and then is discharged into the atmosphere, completing the system energy storage process. When the user is at the peak of electricity consumption, the first control valve (17), the second control valve (18) and the fourth control valve (20) are closed, and the third control valve (19), the fifth control valve (21) and the sixth control valve (22) are opened. The water in the high-temperature and high-pressure water tank (12) enters the flash tank (3) for flash evaporation to generate saturated steam and first saturated water. The generated saturated steam enters the superheater (4) through the sixth control valve (22). After the saturated steam enters the superheater (4), it is heat exchanged with the high-temperature molten salt to obtain superheated steam. The molten salt after heat release enters the low-temperature molten salt storage tank for storage; the superheated steam enters the superheating section (51). After the superheated steam is heated, it is transported to the high-pressure cylinder (61) to perform expansion work. The first exhaust gas generated in the process of the high-pressure cylinder (61) performing expansion work is transported to the reheating section (52). The reheating section (52) heats the first exhaust gas to form superheated steam, which is transported to the low-pressure cylinder (62) to perform expansion work. The high-pressure cylinder (61) and the low-pressure cylinder (62) coaxially drive the generator (8) to rotate to generate electric energy. The second exhaust gas generated in the process of the low-pressure cylinder (62) performing expansion work passes through the condenser (7) to generate second saturated water, which is mixed with the first saturated water generated by flash evaporation and then transported to the low-temperature high-pressure water tank (13) for storage through the transport mechanism, thereby completing the energy release process of the system.

Images