A thermal power coupling compressed air energy storage system and energy storage and release method

Abstract

The application provides a thermal power coupling compressed air energy storage system and an energy storage and energy release method, which comprise a boiler, a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder, a high-pressure heater, a small steam turbine, an oxygen remover, a compressor, a low-pressure heater, a primary cooler, a secondary cooler, an energy storage tank, a waste heat exchanger, an air heater, an expander and a terminal heat exchanger; the system can cooperatively adjust the optimization method of the first-stage expander inlet air temperature, the system expansion ratio (or related pressure parameters) and the terminal waste heat recovery scheme, so as to effectively control the exhaust loss while improving the inlet temperature, and realize the comprehensive optimization of thermal economy and peak shaving performance.

Description

Technical Field

[0001] This invention relates to a compressed air energy storage system, specifically to a thermal power coupled compressed air energy storage system and a method for storing and releasing energy. Background Technology

[0002] Compressed air energy storage (CAES) technology is considered to have enormous development potential due to its long storage cycle, long service life, low maintenance costs, and environmental friendliness. More importantly, the unique energy time-shifting and bidirectional regulation capabilities of CAES systems provide a feasible path to fill the peak-shaving capacity gap of thermal power units.

[0003] During the energy storage phase, the CAES system absorbs the excess power generation capacity of the unit during low-load periods, further reducing the unit's electrical load below the boiler's stable combustion load. During the energy release phase, the CAES system releases electricity during peak electricity consumption periods, effectively reducing the unit's peak load. This operating mode significantly expands the unit's peak-shaving range without changing the boiler's minimum stable combustion load.

[0004] Existing CAES systems typically use electric motors to drive compressors during the energy storage phase. During periods of low electricity demand, they consume excess power from the grid to compress air to a high-pressure state and store it in the storage chamber. While this technology has been commercially applied, its inherent drawback is that the energy storage phase directly consumes grid power. This means that the CAES system is essentially a load on the grid rather than an extension of the peak-shaving capacity of thermal power units, and it does not directly address the peak-shaving bottleneck of the thermal power units themselves.

[0005] To overcome this limitation, a novel technical approach using steam extraction from a steam turbine to drive a CAES compressor has gained attention in recent years. This involves extracting a portion of the steam from the main turbine and storing the unit's surplus power generation and heating capacity in compressed air energy storage devices during periods of deep peak shaving. This scheme shifts the power source required by the CAES system during the energy storage phase from the grid to the thermal power unit itself. This allows the unit to store the output that would otherwise be reduced during low-load periods in the form of compressed air, achieving a technical path where the energy storage phase is independent of the grid and directly serves the peak shaving needs of the thermal power unit.

[0006] However, the aforementioned steam-driven scheme still has drawbacks. During the energy release phase, the expander inlet air temperature is limited by the finite heat of compression, thus restricting the improvement in power generation efficiency. In traditional adiabatic compressed air energy storage systems, the heat used to heat the expander inlet air comes solely from the heat of compression generated by the compressor during the energy storage phase. This heat source has limited quality and cannot adequately preheat the expander inlet air, resulting in insufficient work capacity of the compressed air during expansion and power generation. Meanwhile, the high-temperature feedwater system of thermal power units possesses ample high-grade heat sources, providing significant potential for the CAES system. The heat from the thermal power unit can be fully utilized to increase the expander inlet temperature, breaking the thermodynamic coupling limitation between energy storage and energy release.

[0007] The above problems cannot be solved simply by increasing the expander inlet temperature. From a thermodynamic perspective, the expander operation on the energy release side of the CAES system follows the thermodynamic laws of isentropic expansion (or actual expansion). For an ideal gas, the expander outlet temperature... With inlet temperature Expansion ratio The following relationship exists between them:

[0008] in This is the specific heat ratio of air. Under the condition of a constant expansion ratio, the inlet temperature... Increase, outlet temperature The temperature of the outlet air will inevitably rise simultaneously. The higher the outlet air temperature, the greater the energy carried when it is discharged into the atmosphere, resulting in significant energy loss. Although simply increasing the inlet air temperature of the expander thermodynamically helps to improve the work capacity per unit mass of air, it also increases the waste heat loss of the final stage exhaust and reduces the overall energy utilization rate of the system. Summary of the Invention

[0009] To address the technical problems existing in the prior art, this invention proposes a thermal power coupled compressed air energy storage system and its storage... The system employs energy release methods to coordinate and adjust the inlet air temperature of the primary expander, the system expansion ratio (or related pressure parameters), and the optimization method of the terminal waste heat recovery scheme. This can effectively control exhaust losses while increasing the inlet temperature, achieving the best overall performance in terms of thermal economy and peak shaving.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention proposes a thermal power coupled compressed air energy storage system, comprising a boiler, a high-pressure cylinder, a medium-pressure cylinder, a low-pressure cylinder, a high-pressure heater, a small steam turbine, a deaerator, a compressor, a low-pressure heater, a primary cooler, a secondary cooler, an energy storage tank, a waste heat exchanger, an air heater, an expander, and a terminal heat exchanger. The boiler generates high-temperature and high-pressure main steam, which is sequentially delivered to the high-pressure cylinder, the intermediate-pressure cylinder, and the low-pressure cylinder, and receives high-temperature feedwater heated by the high-pressure heater; the low-pressure cylinder coaxially drives the generator of the thermal power unit to generate electricity. The high-pressure heater includes multiple high-pressure heaters connected in series. The high-pressure heater receives pressurized feedwater from the deaerator, heats it, and sends it to the boiler. The inlet of the high-pressure heater connected to the boiler receives return water from the primary cooler after absorbing heat and raising its temperature. The outlet is equipped with a third pumping point to extract high-temperature water during the energy release stage and send it to the air heater for preheating high-pressure air. The deaerator simultaneously receives condensate from the low-pressure heater, condensate from the secondary cooler after absorbing heat and heating up, and return water from the energy release system after releasing heat and cooling down; the deaerator feed pump outlet is provided with a first pumping point for supplying water to the primary cooler as a cold source. The low-pressure heater includes multiple low-pressure heaters connected in series. The low-pressure heater receives condensate from the condenser, heats it, and sends it to the deaerator. The inlet of the low-pressure heater connected to the condenser is provided with a second pumping point and a fourth pumping point. The second pumping point is used to extract condensate as a cold source for the secondary cooler, and the fourth pumping point is used to extract condensate as a cold source for the terminal heat exchanger to cool the outlet air. The condenser receives the exhaust steam from the low-pressure cylinder, and the condenser inlet is equipped with a steam return point to receive the steam discharged by the small steam turbine after it has done work in the energy storage stage; the intermediate-pressure cylinder extracts part of the steam through the steam return point during the energy storage stage as a steam source and delivers it to the small steam turbine; the compressor is driven by the small steam turbine. The compressor, primary cooler, and secondary cooler are connected in series and then connected to the energy storage tank. The energy storage tank is connected to the waste heat exchanger. The waste heat exchanger is connected to the air heater and expander connected in series. The final expander is connected to the terminal heat exchanger.

[0011] As a further technical solution, the compressor includes a multi-stage compressor connected in series.

[0012] As a further technical solution, the primary cooler includes multiple primary coolers connected in series.

[0013] As a further technical solution, the secondary cooler includes multiple secondary coolers connected in series.

[0014] As a further technical solution, the first-stage compressor, primary cooler, and secondary cooler are connected in series and then connected in series with the next-stage compressor, primary cooler, and secondary cooler to form a multi-stage structure.

[0015] As a further technical solution, the air heater includes multiple air heaters connected in series; the expander includes multiple stages, with the first-stage air heater and expander connected in series and then connected in series with the next-stage air heater and expander to form a multi-stage structure.

[0016] As a further technical solution, the compressor pressure ratio is calculated from the inlet pressure, outlet pressure, and pressure loss during the heat exchange process of the overall energy storage system.

[0017] As a further technical solution, the small steam turbine is connected in parallel with the low-pressure cylinder. To ensure that the small steam turbine can operate normally during the energy storage stage, its expansion ratio is set as the ratio of the back pressure to the inlet pressure of the low-pressure cylinder.

[0018] Secondly, the present invention also provides a method for energy storage in a thermal power coupled compressed air energy storage system. In the energy storage stage, the system extracts a portion of steam from the exhaust extraction point of the intermediate-pressure cylinder of the thermal power unit as a steam source. The steam enters the small steam turbine to expand and do work, coaxially driving the compressor to work. After the steam expands and does work, it flows into the condenser inlet extraction return point of the thermal power unit. In the primary cooler, feedwater from the first extraction point of the deaerator feedwater pump outlet is used for primary cooling. After absorbing heat, the feedwater is heated and returned to the inlet return point of the first high-pressure heater. Condensate from the second extraction point of the low-pressure heater connected to the condenser enters the secondary cooler. After absorbing heat, the condensate is heated and returned to the inlet return point of the deaerator.

[0019] Secondly, this invention also provides a method for releasing energy in a thermal power coupled compressed air energy storage system. In the energy release stage, the air from the waste heat exchanger exchanges heat with high-temperature water drawn from the third pumping point at the outlet of the high-pressure heater of the thermal power unit feedwater system through an air heater. The high-temperature feedwater after heat exchange enters the waste heat exchanger to reheat the low-temperature air released from the gas storage tank, realizing energy cascade utilization. Then, the low-temperature feedwater returns to the thermal power unit return water point according to the principle of similar temperature. The high-temperature air discharged from the outlet of the final stage expander enters the terminal heat exchanger and exchanges heat with the low-temperature condensate drawn from the fourth pumping point at the outlet of the thermal power unit condensate pump. After the heat exchange is completed, the temperature of the condensate rises and flows back into the return water point, while the low-temperature air is discharged into the atmosphere. The entire process realizes the recovery and utilization of low-grade energy.

[0020] The beneficial effects of this invention are as follows: 1. The energy storage stage achieves cascaded recovery and utilization of compression heat, significantly improving system efficiency. This invention introduces a primary cooler and a secondary cooler in the energy storage stage to recover the high-temperature heat energy generated during compression in a cascaded manner. The system utilizes feedwater from the deaerator feedwater pump outlet and condensate from the inlet of the fourth low-pressure heater as cold sources for primary and secondary cooling, respectively. The water, after absorbing heat and heating up, is returned to the inlet of the high-pressure heater connected to the boiler and the deaerator, respectively, and the compression heat is returned to the condensate pipeline of the thermal power unit for absorption. This achieves efficient cascaded utilization of compression heat, significantly reduces heat loss, and improves the overall thermal efficiency of the system.

[0021] 2. In the energy release stage, high-temperature feedwater from the thermal power unit is used to heat the air, overcoming the thermodynamic limitation of compression heat. This invention directly utilizes high-temperature feedwater drawn from the outlet of the high-pressure heater on the thermal power unit side to heat the high-pressure air released from the gas storage tank during the energy release stage. This transforms the air into high-pressure, high-temperature air before it enters the expander to generate electricity. This design effectively solves the shortcomings of traditional adiabatic compressed air energy storage systems, where the heat used to heat the expander inlet air comes solely from the compression heat during the energy storage stage, resulting in limited heat source quality. It increases the expander inlet air temperature, improves the expander's working capacity, and breaks the thermodynamic coupling limitation between the energy storage and energy release systems imposed by compression heat. This effectively increases the expander inlet temperature and power generation, thereby significantly improving the overall energy release efficiency of the system.

[0022] 3. By introducing a terminal heat exchanger and a waste heat exchanger, deep recovery of low-grade energy is achieved, solving the problem of increased outlet heat loss caused by raising the expander inlet temperature. This invention introduces a waste heat exchanger and a terminal heat exchanger on the energy release side. After preheating the air, high-temperature feedwater enters the waste heat exchanger to reheat the low-temperature air released from the gas storage chamber, achieving further cascaded energy utilization. Simultaneously, the high-temperature air discharged from the final-stage expander enters the terminal heat exchanger to exchange heat with the low-temperature condensate pumped from the condensate pump outlet of the thermal power unit, recovering exhaust waste heat. This method synergistically regulates the inlet air temperature and terminal waste heat recovery, effectively controlling the heat loss carried away by the exhaust gas when it is discharged into the atmosphere, achieving optimal overall thermal economy.

[0023] 4. The invention employs a turbine extraction steam-driven compressor, effectively expanding the deep peak-shaving range of thermal power units. During the energy storage phase, this invention uses exhaust steam from the intermediate-pressure cylinder of the thermal power unit to drive a small steam turbine, which in turn coaxially drives the compressor. This scheme transfers the power source required for the energy storage phase from the external power grid to the thermal power unit itself, avoiding the drawback of traditional systems directly consuming grid power and becoming a grid load. This operating mode, without changing the boiler's minimum stable combustion load, converts the unit's surplus power generation capacity during low-load periods into pressure and thermal energy storage, directly filling the peak-shaving capacity gap of the thermal power unit and greatly expanding the unit's deep peak-shaving range. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 This is a schematic diagram of the structure disclosed in some embodiments of the present invention; In the diagram: 1. Boiler, 2. High-pressure cylinder, 3. Medium-pressure cylinder, 4. Low-pressure cylinder. 5. High-pressure heater; 51. First high-pressure heater; 52. Second high-pressure heater; 53. Third high-pressure heater. 6. Deaerator 7. Low-pressure heater; 71. First low-pressure heater; 72. Second low-pressure heater; 73. Third low-pressure heater; 74. Fourth low-pressure heater. 8. Condenser 9. Small steam turbine, 10. Expander; 101. First-stage expander; 102. Second-stage expander; 103. Third-stage expander; 104. Fourth-stage expander. 11. Generator of thermal power unit, 12. Compressed air energy release system generator, 13. Air inlet, 14. Compressor; 141. First-stage compressor; 142. Second-stage compressor; 143. Third-stage compressor. 15. Primary cooler; 151. Primary cooler No. 1; 152. Primary cooler No. 2; 153. Primary cooler No. 3. 16. Secondary cooler; 161. Secondary cooler No. 1; 162. Secondary cooler No. 2; 163. Secondary cooler No. 3. 17. Gas storage tank; 18. Waste heat exchanger. 19. Air heater; 191. Air heater No. 1; 192. Air heater No. 2; 193. Air heater No. 3; 194. Air heater No. 4 20. Terminal heat exchanger; 21. Air outlet; 22. Pressure regulating valve. Detailed Implementation

[0026] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. For ease of description, the words "up," "down," "left," and "right" appearing in this invention only indicate that they are consistent with the up, down, left, and right directions of the accompanying drawings themselves, and do not limit the structure. They are merely for the purpose of facilitating the description of this invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0028] As described in the background section, existing technologies have shortcomings. To address the aforementioned technical problems, this invention proposes a thermal power coupled compressed air energy storage system. Figure 1 As shown, in Figure 1 Light red lines indicate the direction of water vapor flow; dark red lines indicate the direction of high-temperature cooling water flow after heat absorption; blue lines indicate the direction of low-temperature cooling water flow; yellow lines indicate the direction of air flow; additionally, the diagram marks the extraction points and return points, specifically including the first extraction point 31, the first return point 41, the second extraction point 32, the second return point 32, the third extraction point 33, the third return point 33, the fourth extraction point 34, and the fourth return point 34. The thermal power coupled compressed air energy storage system includes a boiler 1, a high-pressure cylinder 2, a medium-pressure cylinder 3, a low-pressure cylinder 4, a high-pressure heater 5, a deaerator 6, a low-pressure heater 7, a condenser 8, a small steam turbine 9, an expander 10, a thermal power unit generator 11, a compressed air energy release system generator 12, a compressor 14, a primary cooler 15, a secondary cooler 16, an air storage tank 17, a waste heat exchanger 18, an air heater 19, and a terminal heat exchanger 20. Boiler 1, as the core heat source equipment of the thermal power unit, is responsible for heating water into high-temperature and high-pressure steam to power a small steam turbine. During peak-shaving operation, boiler 1 has a minimum stable combustion load limit (usually not lower than 30% to 40% of the rated load), which determines the physical lower limit of the downward peak-shaving of traditional thermal power units. Boiler 1 delivers the generated high-temperature and high-pressure main steam to high-pressure cylinder 2 and receives high-temperature feedwater heated by high-pressure heater 5, which is responsible for heating it into high-temperature and high-pressure steam.

[0029] High-pressure cylinder 2 is the first-stage power-generating component of the steam turbine. It uses the expansion of the highest-pressure steam sent from the boiler to drive the generator 11 of the thermal power unit to rotate. Connection relationship: The inlet is connected to the main steam pipeline of boiler 1. Part of the exhaust steam is returned to the boiler reheater for heating, and then enters the intermediate-pressure cylinder 3. The other part is extracted steam and enters the high-pressure heater 5 for feedwater heating.

[0030] The intermediate-pressure cylinder 3 receives reheat steam and continues to expand to do work, driving the generator 11 of the thermal power unit to rotate; Connection relationship: The inlet is connected to the boiler reheat steam; Part of the exhaust steam enters the low-pressure cylinder 4 to continue to do work, and the other part is extracted through the "extraction point" in the energy storage stage as a steam source and sent to the small steam turbine 9; The low-pressure cylinder 4 is the final stage power-generating component of the steam turbine. It utilizes the lower-pressure steam discharged from the intermediate-pressure cylinder to continue expanding and performing work, and coaxially drives the generator of the thermal power unit to generate electricity. Connections: the inlet receives the exhaust steam from the intermediate-pressure cylinder 3; the exhaust steam directly enters the condenser 8; the low-pressure cylinder 4 and the small steam turbine 9 are connected in parallel. Simultaneously, the low-pressure cylinder 4 has multi-stage extraction steam pipelines connected to each stage of the low-pressure heater 7, and the extracted steam is used for condensate heating.

[0031] The high-pressure heater 5 includes a first high-pressure heater 51, a second high-pressure heater 52, and a third high-pressure heater 53. The high-pressure heater 5 utilizes high-pressure extracted steam from the small steam turbine 9 to heat the feedwater before it enters the boiler, improving the system's thermal efficiency. Connection: The water side receives pressurized feedwater from the deaerator 6, heats it, and then sends it to the boiler. In coupling with the energy storage system: The inlet of the first high-pressure heater 51 receives return water (return point 31) from the primary cooler 15 after heat absorption and temperature increase. The outlet of the first high-pressure heater 51 is equipped with a "third pumping point 33," which extracts high-temperature water during the energy release phase and sends it to the air heater 19 for preheating high-pressure air.

[0032] The main function of deaerator 6 is to remove oxygen and other non-condensable gases from condensate, prevent equipment corrosion, and also act as a mixing heater to raise the water temperature. Connections: It receives condensate from low-pressure heater 7. Simultaneously, the inlet of deaerator 6 receives condensate from secondary cooler 16 after heat absorption and heating (second return point 32), and receives return water from energy release system after heat release and cooling (third return point 33). The deaerator feed pump outlet is equipped with a "first pumping point 31" to supply water to primary cooler 15 as a cold source.

[0033] The low-pressure heater 7 includes a first low-pressure heater 71, a second low-pressure heater 72, a third low-pressure heater 73, and a fourth low-pressure heater 74 connected in series. Its main function is to heat the low-temperature condensate from the condenser 8 using the steam extracted from the low-pressure cylinder 4. Connection: It receives the condensate from the condenser 8, heats it, and sends it to the deaerator 6. The fourth low-pressure heater 74 has a "second pumping point 32" at its inlet for extracting condensate as a cold source for the secondary cooler 16, and a "fourth pumping point 34" for extracting condensate as a cold source for the terminal heat exchanger 20 to cool the outlet air.

[0034] The function of condenser 8 is to cool and condense the exhaust steam from the turbine into water, creating a vacuum to maintain the turbine's high efficiency and achieving water circulation. It receives the exhaust steam from the low-pressure cylinder 4. The condenser inlet also has a "steam return point" to receive the steam discharged from the small turbine 9 after it has performed work during the energy storage stage.

[0035] Function of small steam turbine 9: As the prime mover of the compressed air energy storage system in the "energy storage stage," it converts the thermal energy of the thermal power unit into mechanical energy, directly driving the compressor. Connections: The inlet connects to the "extraction point" on the exhaust pipe of intermediate-pressure cylinder 3; the outlet exhaust flows into the "extraction return point" at the inlet of condenser 8. It coaxially connects to and drives the first, second, and third stage compressors on the mechanical shaft. Overall soft drink circulation process: First, the high-temperature, high-pressure steam generated by the boiler enters the high-pressure cylinder to expand and perform work. The steam then enters the intermediate-pressure cylinder for further expansion. The steam exiting the intermediate-pressure cylinder flows in two directions: the main steam flows into the low-pressure cylinder to complete the final stage of work and drive the generator of the thermal power unit; while in the energy storage stage, the system extracts some steam from the extraction point of the intermediate-pressure cylinder exhaust and introduces it into a small turbine for expansion and work. This turbine serves as the prime mover, directly driving the multi-stage compressor coaxially. The exhaust steam from the small turbine eventually flows into the extraction return point at the condenser inlet. Simultaneously, the steam exiting the low-pressure cylinder also enters the condenser and is cooled and condensed into water. This condensate then flows sequentially through multiple low-pressure heaters for preliminary heating, then enters the deaerator to remove oxygen and further mix and heat up. The feedwater, pressurized by the deaerator, finally flows through multiple high-pressure heaters for high-temperature heating and is ultimately sent back to the boiler for reheating into steam, completing the main cycle on the thermal power side.

[0036] The specific work process is as follows: During the energy storage phase, the system extracts a portion of steam from the exhaust point of the intermediate-pressure cylinder 3 of the thermal power unit as a steam source. The steam enters the small steam turbine 9 to expand and do work, coaxially driving the first-stage compressor 141, the second-stage compressor 142, and the third-stage compressor 143 to work. After expanding and doing work, the steam flows into the inlet exhaust return point of the condenser 8 of the thermal power unit.

[0037] The small steam turbine 9 is connected in parallel with the low-pressure cylinder 4. To ensure that the small steam turbine 9 can operate normally during the energy storage stage, its expansion ratio is set as the ratio of the back pressure to the inlet pressure of the low-pressure cylinder 4.

[0038] Air enters through air inlet 13, and after three stages of compression by compressor 14, the pressure increases from 0.1 MPa to 10.1 MPa before entering the air storage tank 17. The compressor pressure ratio is calculated based on the overall energy storage system inlet and outlet pressures, as well as the pressure loss during the heat exchange process. Considering the pressure drop loss on the interstage heat exchanger side, the outlet air pressure of the third-stage compressor 143 is set to 10.1 MPa.

[0039] The compressed high-temperature, high-pressure air is cooled in each stage of the heat exchanger. First, in the primary cooler 15, it is cooled by feedwater from the first pumping point 31 at the outlet of the deaerator 6 of the thermal power unit. The feedwater absorbs heat and is heated, then returns to the inlet return point 31 of the first high-pressure heater 51. After primary cooling, the air enters the secondary cooler 16, where it is cooled by condensate from the second pumping point 32 at the inlet of the fourth low-pressure heater 74. The condensate absorbs heat and is heated, then returns to the inlet return point 32 of the deaerator 6. By designing a cascade heat exchanger, the cascade utilization of the heat of compression is realized.

[0040] Specifically, the primary cooler 15 includes a first primary cooler 151, a second primary cooler 152, and a third primary cooler 152; the secondary cooler 16 includes a first secondary cooler 161, a second secondary cooler 162, and a third secondary cooler 163. After the air enters through air inlet 13, it is first compressed by the first-stage compressor 141 and then cooled by the first primary cooler 151; then it enters the first secondary cooler 161 for further cooling; then it is compressed by the second-stage compressor 142 and then cooled by the second primary cooler 152; then it enters the second secondary cooler 162 for further cooling; then it is compressed by the third-stage compressor 143 and then cooled by the third primary cooler 153; then it enters the third secondary cooler 163 for further cooling. During the energy release phase, in order to ensure constant pressure operation during the energy release phase, a pressure stabilizing valve 22 is installed at the outlet of the gas storage tank 17 so that the outlet pressure of the gas storage tank 17 is stabilized at 7 MPa after passing through the pressure stabilizing valve 22. The traditional energy release side model is optimized by introducing a waste heat exchanger 18 and a terminal heat exchanger 20. During the CAES energy release stage, the high-pressure air stored in the gas storage tank 17 is released. The air exchanges heat with high-temperature water drawn from the third pumping point 33 at the outlet of the first high-pressure heater of the thermal power unit feedwater system 51 through the air heater 19. After the air is preheated, it drives the expander 10 to do work, and the pressure potential energy is converted into electrical energy. The high-temperature feedwater after heat exchange enters the waste heat exchanger 18 to reheat the low-temperature air released from the gas storage chamber, realizing the cascade utilization of energy. Then, the low-temperature feedwater returns to the third return point 33 of the thermal power unit according to the principle of similar temperature (that is, the feedwater after heat exchange should return to the position in the thermal power unit with a similar temperature). The high-temperature air discharged from the outlet of the fourth expander 104 enters the terminal heat exchanger 20 to exchange heat with the low-temperature condensate drawn from the third pumping point 33 at the outlet of the thermal power unit condensate pump. After the heat exchange is completed, the condensate temperature rises and flows back into the fourth return water point 34. Low-temperature air is discharged into the atmosphere, and the whole process realizes the recovery and utilization of low-grade energy.

[0041] The aforementioned expander 10 includes a first-stage expander 101, a second-stage expander 102, a third-stage expander 103, and a fourth-stage expander 104; the first-stage expander 101, the second-stage expander 102, the third-stage expander 103, and the fourth-stage expander 104 are connected to the generator 12 of the compressed air energy release system. The aforementioned air heater 19 includes air heater 191, air heater 192, air heater 193, and air heater 194. The high-pressure air stored in the gas storage tank 17 passes through the waste heat exchanger 18, then enters the first air heater 191, then the first-stage expander 101, then the second air heater 192, then the second-stage expander 102, then the third air heater 193, then the third-stage expander 103, then the fourth air heater 194, and finally the fourth-stage expander 104. The high-temperature air discharged from the outlet of the fourth expander 104 enters the terminal heat exchanger 20, where it exchanges heat with the low-temperature condensate pumped from the third pumping point 33 at the outlet of the thermal power unit's condensate pump. In the energy storage phase, the system uses a small steam turbine to generate electricity, which drives a compressor to compress air, converting electrical energy into pressure energy and heat energy. The pressurized high-pressure air is stored in the gas storage chamber, while the heat generated by compression is absorbed by the condensate at the outlet of the condensate pump of the thermal power unit and then returned to the condensate pipeline. In the energy release phase, the system uses feedwater from the thermal power unit side to heat the high-pressure air released from the gas storage chamber, making it high-pressure, high-temperature air before it enters the expander to generate electricity. The cooled feedwater returns to the condensate pipeline. The entire process realizes energy conversion and transfer, ultimately achieving peak power regulation and supply.

[0042] This system solves the problem of low efficiency in the energy release stage of traditional compressed air energy storage systems due to the influence of compression heat, increases the power generation of the expander, and realizes the cascade utilization of energy, thereby improving system efficiency.

[0043] Finally, it should be noted that relational terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A thermal power coupled compressed air energy storage system, characterized in that, This includes boilers, high-pressure cylinders, medium-pressure cylinders, low-pressure cylinders, high-pressure heaters, small steam turbines, deaerators, compressors, low-pressure heaters, primary coolers, secondary coolers, energy storage tanks, waste heat exchangers, air heaters, expanders, and terminal heat exchangers. The boiler generates high-temperature and high-pressure main steam, which is sequentially delivered to the high-pressure cylinder, the intermediate-pressure cylinder, and the low-pressure cylinder, and receives high-temperature feedwater heated by the high-pressure heater; the low-pressure cylinder coaxially drives the generator of the thermal power unit to generate electricity. The high-pressure heater includes multiple high-pressure heaters connected in series. The high-pressure heater receives pressurized feedwater from the deaerator, heats it, and sends it to the boiler. The inlet of the high-pressure heater connected to the boiler receives return water that has been heated by absorbing heat from the primary cooler. The outlet is equipped with a third pumping point, which extracts high-temperature water during the energy release stage and enters the air heater to preheat the high-pressure air. The deaerator simultaneously receives condensate from the low-pressure heater, condensate from the secondary cooler after absorbing heat and heating up, and return water from the energy release system after releasing heat and cooling down; the deaerator feed pump outlet is provided with a first pumping point for supplying water to the primary cooler as a cold source. The low-pressure heater includes multiple low-pressure heaters connected in series. The low-pressure heater receives condensate from the condenser, heats it, and sends it to the deaerator. The inlet of the low-pressure heater connected to the condenser is provided with a second pumping point and a fourth pumping point. The second pumping point is used to extract condensate as a cold source for the secondary cooler, and the fourth pumping point is used to extract condensate as a cold source for the terminal heat exchanger to cool the outlet air. The condenser receives the exhaust steam from the low-pressure cylinder, and the condenser inlet is equipped with a steam return point to receive the steam discharged by the small steam turbine after it has done work in the energy storage stage; the intermediate-pressure cylinder extracts part of the steam through the steam return point during the energy storage stage as a steam source and delivers it to the small steam turbine; the compressor is driven by the small steam turbine. The compressor, primary cooler, and secondary cooler are connected in series and then connected to the energy storage tank. The energy storage tank is connected to the waste heat exchanger. The waste heat exchanger is connected to the air heater and expander connected in series. The final expander is connected to the terminal heat exchanger.

2. The thermal-electric coupled compressed air energy storage system as described in claim 1, characterized in that, The compressor mentioned includes a multi-stage compressor connected in series.

3. The thermal power coupled compressed air energy storage system as described in claim 2, characterized in that, The primary cooler comprises multiple primary coolers connected in series.

4. The thermal power coupled compressed air energy storage system as described in claim 3, characterized in that, The secondary cooler comprises multiple secondary coolers connected in series.

5. The thermal-electric coupled compressed air energy storage system as described in claim 4, characterized in that, The primary compressor, primary cooler, and secondary cooler are connected in series and then connected in series with the next stage compressor, primary cooler, and secondary cooler to form a multi-stage structure.

6. The thermal-electric coupled compressed air energy storage system as described in claim 1, characterized in that, The air heater includes multiple air heaters connected in series; the expander includes multiple stages, with the first-stage air heater and expander connected in series, and then connected in series with the next-stage air heater and expander to form a multi-stage structure.

7. The thermal-electric coupled compressed air energy storage system as described in claim 1, characterized in that, The compressor pressure ratio is calculated from the inlet pressure, outlet pressure, and pressure loss during the heat exchange process of the overall energy storage system.

8. The thermal-electric coupled compressed air energy storage system as described in claim 1, characterized in that, The small steam turbine is connected in parallel with the low-pressure cylinder. To ensure that the small steam turbine can operate normally during the energy storage stage, its expansion ratio is set as the ratio of the back pressure to the inlet pressure of the low-pressure cylinder.

9. The method for energy storage using a thermal power coupled compressed air energy storage system as described in claim 1, characterized in that, During the energy storage phase, the system extracts a portion of steam from the exhaust point of the intermediate-pressure cylinder of the thermal power unit as a steam source. The steam enters the small steam turbine to expand and do work, coaxially driving the compressor. After expanding and doing work, the steam flows into the condenser inlet exhaust return point of the thermal power unit. In the primary cooler, feedwater from the first pumping point at the deaerator feedwater pump outlet is used for primary cooling. After absorbing heat, the feedwater is heated and returned to the inlet return point of the first high-pressure heater. Condensate from the second pumping point at the inlet of the low-pressure heater connected to the condenser enters the secondary cooler. After absorbing heat, the condensate is heated and returned to the inlet return point of the deaerator.

10. The method for releasing energy from a thermal power coupled compressed air energy storage system as described in claim 1, characterized in that, During the energy release phase, the air exiting the waste heat exchanger exchanges heat with high-temperature water drawn from the third pumping point at the outlet of the high-pressure heater of the thermal power unit's feedwater system through an air heater. The high-temperature feedwater after heat exchange enters the waste heat exchanger to reheat the low-temperature air released from the gas storage tank, achieving energy cascade utilization. Then, the low-temperature feedwater returns to the thermal power unit's return water point according to the principle of similar temperature. The high-temperature air discharged from the outlet of the final stage expander enters the terminal heat exchanger and exchanges heat with low-temperature condensate drawn from the fourth pumping point at the outlet of the thermal power unit's condensate pump. After the heat exchange is completed, the temperature of the condensate rises and it flows back into the return water point, while the low-temperature air is discharged into the atmosphere. The entire process achieves the recovery and utilization of low-grade energy.

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