Underwater compressed air energy storage system coupled with thermal power generating unit and control method of underwater compressed air energy storage system

Abstract

The invention discloses an underwater compressed air energy storage system coupled with a thermal power generating unit and a control method of the underwater compressed air energy storage system, and belongs to the technical field of thermal energy storage. According to the underwater compressed air energy storage system coupled with the thermal power generating unit, the flexible underwater air storage cabin, the electric compressor, the expansion power generation device, the thermal power generating unit and the power grid are electrically connected through the control system; the gas storage state of the flexible underwater gas storage cabin and starting and stopping of the electric compressor and the expansion power generation device are controlled according to the operation working condition of the thermal power generating unit and the load condition of the power grid, the contradiction between power supply and demand is effectively relieved, and the flexibility and stability of a power system are improved; by arranging the flexible underwater gas storage cabin, the problem that gas storage pressure fluctuates due to the fact that ground gas storage is affected by external climate is stably avoided through the underwater environment, stable and efficient operation of the compressor and the expansion machine is guaranteed, the risk of the gas storage structure is reduced, and the reliability and efficiency of the energy storage system are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal energy storage, in particular to an underwater compressed air energy storage system coupled with a thermal power generating unit and a control method thereof. BACKGROUND

[0002] Traditional thermal power generating units, as the main power source of the power system, have long played a key role in ensuring the stability and reliability of power supply. They generate high-temperature and high-pressure steam by burning fossil fuels, drive the steam turbine to rotate, and then drive the generator to generate electricity. The technology is mature and the operation experience is rich. However, with the continuous growth of new energy power generation, traditional thermal power generating units are facing severe challenges in responding to the flexibility requirements of the power system. With the large-scale access of new energy power generation, due to its uncertainty, the peak-valley difference of the power system becomes more significant. At the same time, in order to maintain the real-time balance of the power system and ensure the quality of power supply, the demand for frequency modulation and peak shaving is greatly enhanced. In order to improve the response capability and operation efficiency of the power system, large-scale energy storage technology has emerged, and has gradually become one of the key means to solve the intermittency and volatility of new energy power generation. Large-scale energy storage technology can store excess power when power is surplus, and release stored energy when power is short, realize the time and space shift of power, and effectively alleviate the contradiction between power supply and demand.

[0003] At present, various large-scale energy storage technologies have been widely researched and applied. Among them, compressed air energy storage (CAES) as a large-scale energy storage form with great potential has attracted much attention. However, although compressed air energy storage technology has many advantages, existing compressed air energy storage systems mostly rely on ground air storage. Although this air storage method can meet the energy storage demand to some extent, it is easily affected by external environmental changes during actual air storage: the environmental parameters on the ground will fluctuate with the change of external climate conditions. This environmental change will directly affect the air pressure in the air storage room, resulting in unstable air storage pressure. On the one hand, the fluctuation of air storage pressure will affect the efficiency of the energy storage system. When the air storage pressure is unstable, the working state of the compressor and the expander will also fluctuate, which cannot always maintain the best efficiency point operation; on the other hand, the unstable air storage pressure may cause additional stress to the structure of the air storage room, which may cause fatigue damage to the air storage room under long-term operation, and even cause safety accidents such as leakage, threatening the safe and reliable operation of the energy storage system. SUMMARY

[0004] The purpose of the present application is to provide an underwater compressed air energy storage system coupled with a thermal power generating unit and a control method thereof, to overcome the problem that the existing compressed air energy storage system in the prior art relies on ground air storage, is easily affected by external environmental changes, causes unstable air storage pressure, and further causes the efficiency and reliability of the energy storage system to decrease.

[0005] The present application solves the above technical problems by the following technical solutions: The present application provides an underwater compressed air energy storage system coupled with a thermal power unit, comprising an electric compressor, a flexible underwater gas storage cabin, a gas pipeline, a first waste heat recovery heat exchanger, an expansion power generation device, a thermal power unit and a control system. The outlet of the electric compressor is connected to the inlet of the flexible underwater gas storage cabin through the gas pipeline, for delivering compressed air to the flexible underwater gas storage cabin for storage; the outlet of the flexible underwater gas storage cabin is connected to the high-pressure air inlet of the first waste heat recovery heat exchanger, the high-pressure air outlet of the first waste heat recovery heat exchanger is connected to the inlet of the multi-stage expansion power generation device, and the outlet of the multi-stage expansion power generation device is connected to the atmospheric environment; the high-temperature gas inlet of the first waste heat recovery heat exchanger is in communication with the boiler flue gas outlet of the thermal power unit, for recovering boiler waste heat; the control system is electrically connected to the flexible underwater gas storage cabin, the electric compressor, the expansion power generation device, the thermal power unit and the power grid, respectively, for controlling the gas storage state of the flexible underwater gas storage cabin and the start-stop of the electric compressor and the expansion power generation device according to the operating condition of the thermal power unit and the load condition of the power grid.

[0006] The present application further improves in that: it further comprises a second waste heat recovery heat exchanger, which is arranged between the stages of the multi-stage expansion power generation device, the high-temperature gas inlet of the second waste heat recovery heat exchanger is in communication with the boiler flue gas outlet of the thermal power unit, for recovering boiler waste heat; and the high-temperature gas outlet of the second waste heat recovery heat exchanger is connected to the atmospheric environment.

[0007] The present application further improves in that: it further comprises an anchoring device, by which the flexible underwater gas storage cabin is fixed at a predetermined water level.

[0008] The present application further improves in that: the predetermined water level is calculated according to the gas storage pressure of the flexible underwater gas storage cabin.

[0009] The present application further improves in that: the electric compressor adopts a multi-stage compression structure, for compressing air into high-pressure gas in stages, and the outlet of the last-stage compressor serves as the outlet of the electric compressor.

[0010] The present application further improves in that: an intercooler is arranged between adjacent compression structures.

[0011] The present application further improves in that: the expansion power generation device adopts a multi-stage expansion structure.

[0012] The present application further improves in that: the multi-stage expansion structure comprises a multi-stage turbine expander and a generator coaxially connected, for driving the generator to generate electricity through the expansion work of the multi-stage turbine expander.

[0013] The further improvement of the application is that the reheating heat exchanger is arranged between the stages of the multi-stage turbo-expander.

[0014] The application also provides a control method of the underwater compressed air energy storage system coupled with the thermal power generating unit, wherein the operation condition of the thermal power generating unit and the load condition of the power grid are obtained by the control system, when the load of the power grid drops to the bottom and the load of the thermal power generating unit decreases, the flexible underwater gas storage tank is used to store gas and the compressor is started to enter the energy storage stage; when the load of the power grid rises to the peak and the load of the thermal power generating unit increases, the flexible underwater gas storage tank is used to release gas and the expansion power generation device is started to enter the energy release stage. When the system enters the energy storage stage, the valley electricity is connected to the electric compressor through the control system, the air is compressed into high-temperature gas by the electric compressor and is transported to the flexible underwater gas storage tank through the gas pipeline to be stored at constant temperature and pressure. When the system enters the energy release stage, the high-temperature gas is released from the flexible underwater gas storage tank, the high-temperature gas is transported to the first waste heat recovery heat exchanger to be heated, the heated high-temperature gas is introduced into the expansion power generation device to be expanded to generate power, and the electric energy is transported to the thermal power generating unit through the control system.

[0015] Compared with the prior art, the positive progress effect of the application is that: The underwater compressed air energy storage system coupled with the thermal power generating unit provided by the application is electrically connected to the flexible underwater gas storage tank, the electric compressor, the expansion power generation device, the thermal power generating unit and the power grid through the control system, and the gas storage state of the flexible underwater gas storage tank and the start-stop of the electric compressor and the expansion power generation device are controlled according to the operation condition of the thermal power generating unit and the load condition of the power grid, so that the contradiction between power supply and demand is effectively alleviated, and the flexibility and stability of the power system are improved; the high-temperature gas inlet of the first waste heat recovery heat exchanger is communicated with the boiler flue gas outlet of the thermal power generating unit, and the high-pressure air inlet is connected with the outlet of the flexible underwater gas storage tank, so that the waste heat of the boiler flue gas of the thermal power generating unit can be recovered to heat the high-pressure air when the compressed air is released to generate power, the temperature of the air inlet of the expansion power generation device is improved, the air expansion work capacity is increased, the power generation efficiency of the entire energy storage system is improved, the energy cascade utilization is realized, and the energy utilization efficiency is improved; by arranging the flexible underwater gas storage tank, the problem of pressure fluctuation of ground gas storage caused by external climate is avoided by using the stable underwater environment, the stable and efficient operation of the compressor and the expander is ensured, the risk of gas storage structure is reduced, and the reliability and efficiency of the energy storage system are improved.

[0016] Further, the second waste heat recovery heat exchanger is arranged between the stages of the multi-stage expansion power generation device, and the boiler flue gas waste heat is further recovered to heat the air between the stages; through the two-stage waste heat recovery, the air can be more fully expanded to work in the expansion power generation device, the power generation efficiency is greatly improved, the energy cascade efficient utilization is realized, and the energy comprehensive utilization rate is enhanced.

[0017] The application provides a control method of the underwater compressed air energy storage system coupled with a thermal power generating unit. When the thermal power generating unit generates excess power or the power grid is in a load trough period, the control system controls the electric compressor to start, compressed air is transported to the flexible underwater air storage cabin through the gas pipeline for storage, so that the conversion and storage of electric energy into air pressure energy are realized; when the thermal power generating unit generates insufficient power or the power grid is in a load peak period, the control system controls the flexible underwater air storage cabin to release compressed air, the compressed air absorbs the waste heat of the flue gas of the thermal power generating unit in turn through the first waste heat recovery heat exchanger, and then enters the multi-stage expansion power generation device to expand and generate power, so that the conversion of pressure energy into electric energy is realized and the electric energy is transmitted to the power grid, the contradiction between power supply and demand is effectively relieved, and the flexibility and stability of the power system are improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings are included to provide a further understanding of the application, and are incorporated in and constitute a part of this application. The schematic embodiments of the application and the descriptions thereof serve to explain the application, and do not constitute an improper limitation on the application.

[0019] Figure 1 It is a connection schematic diagram of the underwater compressed air energy storage system coupled with a thermal power generating unit.

[0020] 1-electric compressor; 2-flexible underwater air storage cabin; 3-gas pipeline; 41-first waste heat recovery heat exchanger; 42-second waste heat recovery heat exchanger; 5-expansion power generation device; 6-thermal power generating unit; 7-control system. DETAILED DESCRIPTION

[0021] In order to make the objects, technical solutions and advantages of the embodiments of the application clearer, the technical solutions in the embodiments of the application will be described below in connection with the drawings in the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, rather than all the embodiments. The components of the embodiments of the application described and shown in the drawings can be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of the application provided in the drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the application without creative labor are within the scope of protection of the application.

[0023] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0024] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0025] Furthermore, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be interpreted broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, which are intended to explain the present invention rather than to limit it.

[0027] An underwater compressed air energy storage system coupled to a thermal power unit 6, comprising an electric compressor 1, a flexible underwater air storage tank 2, a gas transmission pipeline 3, a first waste heat recovery heat exchanger 41, an expansion power generation device 5, the thermal power unit 6, and a control system 7; The outlet of the electric compressor 1 is connected to the inlet of the flexible underwater gas storage tank 2 through the gas transmission pipeline 3, and is used to compress the air and transport it to the flexible underwater gas storage tank 2 for storage; the outlet of the flexible underwater gas storage tank 2 is connected to the high-pressure air inlet of the first waste heat recovery heat exchanger 41, and the high-pressure air outlet of the first waste heat recovery heat exchanger 41 is connected to the inlet of the multi-stage expansion power generation device 5, and the outlet of the multi-stage expansion power generation device 5 is connected to the atmospheric environment; the high-temperature gas inlet of the first waste heat recovery heat exchanger 41 is connected to the boiler exhaust outlet of the thermal power unit 6, and is used to recover the waste heat of the boiler; the control system 7 is electrically connected to the flexible underwater gas storage tank 2, the electric compressor 1, the expansion power generation device 5, the thermal power unit 6 and the power grid, respectively, and is used to control the gas storage state of the flexible underwater gas storage tank 2 and the start and stop of the electric compressor 1 and the expansion power generation device 5 according to the operating conditions of the thermal power unit 6 and the load conditions of the power grid.

[0028] The control system 7 is electrically connected with the flexible underwater gas storage tank 2, the electric compressor 1, the expansion power generation device 5, the thermal power generating unit 6 and the power grid respectively, and controls the storage state of the flexible underwater gas storage tank 2 and the start-stop of the electric compressor 1 and the expansion power generation device 5 according to the operation condition of the thermal power generating unit 6 and the load condition of the power grid, so as to effectively relieve the contradiction between power supply and demand, improve the flexibility and stability of the power system; the high-temperature gas inlet of the first waste heat recovery heat exchanger 41 is communicated with the boiler flue gas outlet of the thermal power generating unit 6, and the high-pressure air inlet is connected with the outlet of the flexible underwater gas storage tank 2; when the compressed air is released for power generation, the waste heat of the boiler flue gas of the thermal power generating unit 6 can be recovered to heat the high-pressure air, so as to improve the temperature of the inlet air of the expansion power generation device 5, increase the air expansion work capacity, and thus improve the power generation efficiency of the whole energy storage system, realize the cascade utilization of energy, and improve the energy utilization efficiency; by arranging the flexible underwater gas storage tank 2, the problem of pressure fluctuation of ground gas storage caused by external climate is avoided by using the stable underwater environment, the stable and efficient operation of the compressor and the expander is ensured, the risk of gas storage structure is reduced, and the reliability and efficiency of the energy storage system are improved.

[0029] Specifically, the second waste heat recovery heat exchanger 42 is arranged between the stages of the multi-stage expansion power generation device 5, the high-temperature gas inlet of the second waste heat recovery heat exchanger 42 is communicated with the boiler flue gas outlet of the thermal power generating unit 6, and is used for recovering the boiler waste heat; and the high-temperature gas outlet of the second waste heat recovery heat exchanger 42 is connected with the atmospheric environment.

[0030] The second waste heat recovery heat exchanger 42 is arranged between the stages of the multi-stage expansion power generation device 5, further recovers the boiler flue gas waste heat, reheats the air between the stages, and sends the heated air into the next stage of the turbine expander; so that the air can be more fully expanded and work in the expansion power generation device 5, the power generation efficiency is greatly improved, the energy cascade efficient utilization is realized, and the energy comprehensive utilization rate is enhanced.

[0031] Specifically, the anchor device is arranged to fix the flexible underwater gas storage tank 2 at the predetermined water level.

[0032] The anchor device ensures the stability of the position of the flexible underwater gas storage tank 2 in water, reduces the shaking of the gas storage tank caused by water flow impact and water level fluctuation, ensures the tightness and reliability of the connection components such as the gas storage tank and the gas pipeline 3, reduces the system failure rate, and improves the overall stability and safety of the system.

[0033] Specifically, the predetermined water level is calculated according to the gas storage pressure of the flexible underwater gas storage tank 2.

[0034] The anchoring device fixes the flexible underwater gas storage tank 2 accurately according to the predetermined water level calculated according to the gas storage pressure of the flexible underwater gas storage tank 2. By calculating the predetermined water level based on the gas storage pressure and fixing the gas storage tank, it is ensured that the gas storage tank can be in a stable position under different gas storage states, which greatly improves the stability and safety of the system.

[0035] Specifically, the electric compressor 1 adopts a multi-stage compression structure for compressing air into high-pressure gas in stages. The outlet of the last-stage compressor serves as the outlet of the electric compressor 1.

[0036] Multi-stage compression can gradually compress air to a higher pressure. Compared with single-stage compression, higher-pressure compressed air can be obtained under the same energy consumption. Storing higher-pressure compressed air in the flexible underwater gas storage tank 2 means storing more energy. In the subsequent power generation process, high-pressure air can be more fully expanded in the multi-stage expansion power generation device 5 to release more electric energy. Therefore, the electric compressor 1 with a multi-stage compression structure effectively improves the energy storage density and efficiency of the system, enabling the system to store and release more energy in a limited gas storage space, and enhancing the system's ability to respond to changes in power demand.

[0037] Specifically, an intercooler is arranged between adjacent compression structures.

[0038] The intercooler can timely reduce the temperature of air after each stage of compression, so that the air entering the next-stage compressor is in a relatively low temperature state. In this way, the energy consumed by the compressor in compressing low-temperature air is reduced, the power consumption of the compression process is reduced, and the compression efficiency is improved.

[0039] Specifically, the expansion power generation device 5 adopts a multi-stage expansion structure.

[0040] The multi-stage expansion structure enables high-pressure air to be expanded in stages. Each stage of expansion is relatively gentle, and through accurate control of the expansion process at each stage, smooth adjustment of the power generation power can be achieved, making it better adapt to changes in the load of the power grid and improving the compatibility and stability of the system with the power grid.

[0041] Specifically, the multi-stage expansion structure includes a plurality of coaxially connected multi-stage turbine expanders and a generator, for driving the generator to generate electricity through the expansion work of the multi-stage turbine expanders.

[0042] The multi-stage turbine expanders are coaxially connected to a generator. High-pressure air passes through each turbine expander in turn to do work, and its rotary kinetic energy is directly transmitted to the generator through the same shaft to drive the generator to generate electricity. This reduces the energy transmission path and reduces the energy loss in the transmission process, so that more expansion work can be directly converted into electric energy, improving the energy conversion efficiency of the system.

[0043] Specifically, the inter-stage of the multi-stage turbo expander is provided with a reheating heat exchanger.

[0044] The reheating heat exchanger is arranged between the stages of the multi-stage turbo expander, the air discharged from the upper-stage turbo expander enters the reheating heat exchanger, exchanges heat with a heat source, and then enters the lower-stage turbo expander to continue expansion and work, so that the air can be heated before entering the lower-stage expansion, the temperature and internal energy of the air are increased, and in this way, the multi-stage turbo expander as a whole can output more mechanical energy to drive the generator to generate more electric energy, and the power generation efficiency of the system is effectively improved.

[0045] The application also provides a control method of the underwater compressed air energy storage system coupled with the thermal power generating unit 6, the operation condition of the unit and the load condition of the power grid are obtained by the control system 7, when the load of the power grid drops to the bottom and the load of the thermal power generating unit 6 decreases, the flexible underwater gas storage tank 2 stores air and the compressor is started, and the system enters the energy storage stage; when the load of the power grid rises to the peak and the load of the thermal power generating unit 6 increases, the flexible underwater gas storage tank 2 releases air and the expansion power generation device 5 is started, and the system enters the energy release stage. When the system enters the energy storage stage, the valley electricity is connected to the electric compressor 1 through the control system 7, the air is compressed into high-temperature gas by the electric compressor 1 and is transported to the flexible underwater gas storage tank 2 through the gas pipeline 3 for constant-temperature and constant-pressure storage. When the system enters the energy release stage, the high-temperature gas is released from the flexible underwater gas storage tank 2, the high-temperature gas is transported to the first waste heat recovery heat exchanger 41 for heating, the heated high-temperature gas is introduced into the expansion power generation device 5 for expansion and power generation, and the electric energy is transported to the thermal power generating unit 6 through the control system 7.

[0046] The control method of the underwater compressed air energy storage system coupled with the thermal power generating unit 6 provided by the application, when the thermal power generating unit 6 generates excess electricity or the power grid is in the load bottom period, the control system 7 controls the electric compressor 1 to start, the air is compressed and then transported to the flexible underwater gas storage tank 2 through the gas pipeline 3 for storage, realizing the conversion and storage of electric energy to air pressure energy; when the thermal power generating unit 6 generates insufficient electricity or the power grid is in the load peak period, the control system 7 controls the flexible underwater gas storage tank 2 to release compressed air, the compressed air absorbs the waste heat of the boiler flue gas of the thermal power generating unit 6 in turn through the first waste heat recovery heat exchanger 41, and then enters the multi-stage expansion power generation device 5 to expand and generate power, realizing the conversion of pressure energy to electric energy and transporting the electric energy to the power grid, effectively relieving the contradiction between power supply and demand, and improving the flexibility and stability of the power system.

[0047] Embodiment one See Figure 1The application discloses an underwater compressed air energy storage system coupled with a thermal power unit 6, which comprises an electric compressor 1, a flexible underwater gas storage cabin 2, a gas conveying pipeline 3, a first waste heat recovery heat exchanger 41, a second waste heat recovery heat exchanger 42, an expansion power generation device 5, the thermal power unit 6 and a control system 7. The outlet of the electric compressor 1 is connected with the inlet of the flexible underwater gas storage cabin 2 through the gas conveying pipeline 3, so as to convey the compressed air to the flexible underwater gas storage cabin 2 for storage; the outlet of the flexible underwater gas storage cabin 2 is connected with the high-pressure air inlet of the first waste heat recovery heat exchanger 41, the high-pressure air outlet of the first waste heat recovery heat exchanger 41 is connected with the expansion power generation device 5, the inter-stage of the expansion power generation device 5 is provided with the second waste heat recovery heat exchanger 42, and the outlet of the last-stage expansion power generation device 5 is directly connected with the atmospheric environment; the high-temperature gas inlets of the first waste heat recovery heat exchanger 41 and the second waste heat recovery heat exchanger 42 are communicated with the boiler flue gas of the thermal power unit 6, so as to recover the boiler waste heat; the high-temperature gas outlet of the second waste heat recovery heat exchanger 42 is connected with the atmospheric environment; the control system 7 is connected with the electric compressor 1, the expansion power generation device 5, the thermal power unit 6 and a power grid through power transmission lines, and controls the energy storage or release operation of the compressed air energy storage system and the power distribution (peak shaving or plant power) according to the operation condition of the thermal power unit 6 and the load condition of the power grid, so as to realize the collaborative control of the underwater compressed air energy storage system and the thermal power unit 6.

[0048] The control system 7 communicates with the plant-level monitoring system of the thermal power unit 6, and can automatically control the start and stop of the compressor and the expander according to the load condition of the power grid. In the control strategy, when the power grid load is detected to drop to the bottom and the thermal power unit 6 is connected with the reduced load, the control system 7 starts the compressor to store energy and charge air: directly uses the compressor to compress air into the flexible underwater gas storage cabin 2, the gas conveying pipeline 3 between the outlet of the compressor and the inlet of the flexible underwater gas storage cabin 2 is made of a strong heat exchange material, accelerates heat exchange, directly uses water to cool the compressed air, does not set a heat exchanger, can reduce the construction cost, the compressed air is gradually cooled in the process of flowing from the outlet of the compressor to the inlet of the flexible underwater gas storage cabin 2 through the gas conveying pipeline 3, continues to be cooled in the flexible underwater gas storage cabin 2, and is cooled until the temperature is the same as the water temperature; when the power grid load climbs to the peak and needs additional power, the control system 7 dispatches the gas storage cabin to release air and starts the expansion power generation unit to generate power, is used for plant power and improves the output of the system, realizes joint peak shaving: uses the flue gas waste heat in the boiler of the thermal power unit 6 to heat the compressed air at the outlet of the flexible underwater gas storage cabin 2 and the compressed air between the stages of the expander, improves the temperature of the compressed air entering the expander and the output power in the energy release process; the power output in the energy release process is used for peak shaving and part of the plant power (condensate pump, deaerator), the control system 7 is used for accepting the power grid information, and the proportion of the power generated in the energy release process used for peak shaving and plant power is dispatched.

[0049] The flexible underwater gas storage cabin 2 can be arranged in a deep water area (such as offshore sea area or deep water lake) far from the thermal power unit 6 according to geographical conditions, and is connected with the thermal power unit 6 through a long distance pressure pipeline. The flexible underwater gas storage cabin 2 is fixed by anchoring at a predetermined water depth, so as to realize constant pressure gas storage by using the hydrostatic pressure at the water depth. Even if the air storage changes, the pressure fluctuation in the cabin is small, and the expander can always operate at a pressure close to the design pressure.

[0050] The first waste heat recovery heat exchanger 41 is used for recovering the waste heat of the exhaust gas of the thermal power unit 6, and is used for heating the compressed air at the inlet of the expansion power generation device 5, so as to improve the output power. The flexible underwater gas storage cabin 2 is made of flexible material, and is fixed at a predetermined water level by anchoring according to the required gas storage pressure and the corresponding water depth. The electric compressor 1 comprises a plurality of electric motors and a plurality of stages of compressors. Each electric motor drives one stage of compressors, and is used for compressing the air to a high pressure state in stages. The outlet of the last stage of compressors is connected with the inlet of the flexible underwater gas storage cabin 2 through the gas pipeline 3. The expansion power generation device 5 comprises a plurality of stages of turbine expanders and a plurality of stages of generators, which are coaxially arranged. The last stage of turbine expanders is connected with the generator, and the generator generates electricity by the expansion work of the turbine expanders. The control system 7 analyzes and monitors the load signal of the thermal power unit 6, the load signal of the underwater compressed air energy storage system, the power grid on-grid signal and the power consumption signal of the thermal power unit 6, and connects the valley electricity to the electric compressor 1 when the power consumption of the power grid is low, so as to control the electric compressor 1 to store energy by compression. The expansion power generation device 5 is controlled to generate electricity by releasing energy when the power consumption of the power grid is high, so as to realize peak regulation of the power grid and partial plant power consumption. The electric compressor 1 preferably adopts a multi-stage compression structure, and an intercooler is arranged after each stage of compression, so as to improve the compression efficiency. The expander adopts a multi-stage expansion structure, and a reheating heat exchanger can be arranged between the stages, so as to improve the expansion power output.

[0051] The control system 7 communicates with the plant-level monitoring system of the thermal power unit 6, and can automatically control the start and stop of the compressor and the expander according to the load of the power grid. When the load of the power grid is detected to be reduced to the valley and the load of the thermal power unit 6 is reduced, the control system 7 starts the compressor to store energy and charge air. When the load of the power grid is increased to the peak and additional power is required, the control system 7 schedules the air release of the gas storage cabin and starts the expansion power generation unit to generate electricity, so as to realize joint peak regulation of the plant power consumption and improve the output of the system.

[0052] The energy storage stage: when the power consumption of the power grid is low, the control system 7 connects the valley electricity to the electric compressor 1, so as to start the electric compressor 1 to compress the air and inject the air into the flexible underwater gas storage cabin 2 through the gas pipeline 3 for constant temperature and constant pressure storage. The energy release stage: when the power consumption of the power grid is high, the flexible underwater gas storage cabin 2 releases the compressed air, and the air is heated in the first waste heat recovery heat exchanger 41 and then enters the expansion power generation device 5 to expand and do work to generate electricity. Part of the electricity is used for the thermal power unit 6, so as to improve the overall output power of the system. Coordination control: By monitoring the grid load and the operating state of the thermal power unit 6 through the control system 7, the start and stop of the electric compressor 1 and the expansion power generation device 5 are automatically controlled, realizing the coordinated operation of the compressed air energy storage system and the thermal power unit 6.

[0053] The system compresses air to a high-pressure state by the electric compressor 1, and stores the high-pressure air in the flexible underwater gas storage cabin 2 by taking advantage of the natural pressure of the underwater environment, thereby effectively capturing and storing excess electric energy during the power valley period. During the power peak period, the gas storage cabin releases high-pressure air, which is preheated by the first waste heat recovery heat exchanger 41 to increase the air temperature, and then sent to the multi-stage expansion power generation device 5 for expansion work, finally converted into electric energy output, effectively relieving the peak load pressure of the power grid and improving the peak shaving capacity and operation flexibility of the thermal power unit 6. The core of this technical solution is to realize the isobaric storage of air in the underwater environment. Compared with land gas storage, the underwater gas storage cabin can better maintain pressure stability and avoid energy loss caused by gas storage. In addition, the integration of waste heat recovery with the thermal power unit 6 not only improves the overall thermal efficiency of the compressed air energy storage system, but also reduces the fuel consumption of the thermal power unit 6, achieving the effect of energy saving and emission reduction. The control system 7 as a key component can accurately capture the operating state of the thermal power unit 6 and the change of the grid load, automatically adjust the charging and discharging operation of the energy storage system, ensure the efficient coordination of energy storage and power generation, and improve the operation economy and stability of the entire power system. By skillfully combining the underwater compressed air energy storage and the operating characteristics of the thermal power unit 6, the efficiency and reliability of the energy storage system are improved, and the optimal scheduling of clean energy and the effective improvement of thermal flexibility are realized, providing strong support for building a more flexible and sustainable power supply system.

[0054] Finally, it should be noted that the above-mentioned embodiments are only one or more specific forms of the technical solution of the present application, and their purpose is to clearly explain the concept, principle and application mode of the present application through specific examples, and are not intended to limit the protection scope of the present application to these specific embodiments. In fact, the true value of the present application lies in its proposed technical ideas and innovative points, not its forms or implementation methods.

[0055] For those skilled in the art, after reading and understanding the technical solutions of the present application, they have the ability to make various forms of changes, modifications or equivalent replacements to the specific embodiments of the application based on their own professional knowledge and skills. These changes may include but are not limited to adjusting the value range of technical parameters, optimizing the algorithm process to improve efficiency, replacing part of the technical components to achieve better compatibility or reduce cost, etc. As long as the technical solutions after these changes still maintain the technical features required by the original invention, that is, still can realize the core function and effect of the present application, these changes should be considered as falling within the protection scope of the claims of the present application.

[0056] In addition, with the continuous progress and development of technology, new technical means and methods are emerging, which also provides a broad space for further improvement and perfection of the present application. Therefore, the protection scope of the present application should also include those reasonable foreseeable improvements and extensions based on the existing technology, as long as these improvements and extensions do not deviate from the basic principles and core ideas of the present application, they should be considered as the equivalents of the present application, and also be protected by the patent right.

Claims

1. An underwater compressed air energy storage system coupled with a thermal power unit, characterized in that: It includes an electric compressor (1), a flexible underwater gas storage tank (2), a gas transmission pipeline (3), a first waste heat recovery heat exchanger (41), an expansion power generation device (5), a thermal power generation unit (6), and a control system (7); The outlet of the electric compressor (1) is connected to the inlet of the flexible underwater gas storage tank (2) through the gas transmission pipeline (3), and is used to compress the air and transport it to the flexible underwater gas storage tank (2) for storage; the outlet of the flexible underwater gas storage tank (2) is connected to the high-pressure air inlet of the first waste heat recovery heat exchanger (41), the high-pressure air outlet of the first waste heat recovery heat exchanger (41) is connected to the inlet of the multi-stage expansion power generation device (5), and the outlet of the multi-stage expansion power generation device (5) is connected to the atmospheric environment; the high-temperature gas inlet of the first waste heat recovery heat exchanger (41) is connected to the boiler exhaust outlet of the thermal power generation unit (6), and is used to recover the waste heat of the boiler; the control system (7) is electrically connected to the flexible underwater gas storage tank (2), the electric compressor (1), the expansion power generation device (5), the thermal power generation unit (6) and the power grid, and is used to control the gas storage state of the flexible underwater gas storage tank (2) and the start and stop of the electric compressor (1) and the expansion power generation device (5) according to the operating conditions of the thermal power generation unit (6) and the load conditions of the power grid.

2. The underwater compressed air energy storage system coupled with a thermal power unit according to claim 1, characterized in that: The invention also includes a second waste heat recovery heat exchanger (42), which is arranged between the stages of the multi-stage expansion power generation device (5), and the high-temperature gas inlet of the second waste heat recovery heat exchanger (42) is connected to the boiler exhaust outlet of the thermal power unit (6) for recovering boiler waste heat; the high-temperature gas outlet of the second waste heat recovery heat exchanger (42) is connected to the atmospheric environment.

3. The underwater compressed air energy storage system coupled with a thermal power unit according to claim 1, characterized in that: It also includes an anchoring device, through which the flexible underwater gas storage tank (2) is fixed at a predetermined water level.

4. The underwater compressed air energy storage system coupled with a thermal power unit according to claim 3, characterized in that: The predetermined water level is calculated based on the gas storage pressure of the flexible underwater gas storage tank (2).

5. The underwater compressed air energy storage system coupled with a thermal power unit according to claim 1, characterized in that: The electric compressor (1) adopts a multi-stage compression structure for compressing air into high-pressure gas in stages, with the outlet of the final-stage compressor serving as the outlet of the electric compressor (1).

6. The underwater compressed air energy storage system coupled with a thermal power unit according to claim 1, characterized in that: An intercooler is provided between adjacent compression structures.

7. The underwater compressed air energy storage system coupled with a thermal power unit according to claim 1, characterized in that: The expansion power generation device (5) adopts a multi-stage expansion structure.

8. The underwater compressed air energy storage system coupled with a thermal power unit according to claim 5, characterized in that: The multi-stage expansion structure includes a coaxially connected multi-stage turbine expander and a generator, which is used to drive the generator to generate electricity through the expansion work of the multi-stage turbine expander.

9. The underwater compressed air energy storage system coupled with a thermal power unit according to claim 6, characterized in that: A reheat heat exchanger is provided between the stages of the multi-stage turbine expander.

10. The control method of the underwater compressed air energy storage system coupled with a thermal power unit according to any one of claims 1 to 7, characterized in that: The operating conditions of the generator set and the load of the power grid are obtained through the control system (7). When the load of the power grid drops to a low point and the load of the thermal power unit (6) decreases, the flexible underwater gas storage tank (2) is caused to store gas and the compressor is started, entering the energy storage stage; when the load of the power grid rises to a peak and the load of the thermal power unit (6) increases, the flexible underwater gas storage tank (2) is caused to release gas and the expansion power generation device (5) is started, entering the energy release stage; When the system enters the energy storage stage, the valley electricity is connected to the electric compressor (1) through the control system (7), and the electric compressor (1) compresses the air into high-temperature gas and transmits it to the flexible underwater gas storage tank (2) through the gas pipeline (3) for constant temperature and pressure storage; When the system enters the energy release phase, high-temperature gas is released through the flexible underwater gas storage tank (2), and the high-temperature gas is transported to the first waste heat recovery heat exchanger (41) for heating. The heated high-temperature gas is passed into the expansion power generation device (5) for expansion and power generation, and the electric energy is transported to the thermal power generation unit (6) through the control system (7).

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