A coupled molten salt heat storage afterburning compressed air energy storage system and operation method

Abstract

The application discloses a coupled molten salt heat storage afterburning type compressed air energy storage system and an operation method thereof, which comprises an energy storage part and an energy release part, wherein the energy storage part comprises a double-well isothermal compression system and a gas storage system, the energy release part comprises a compressed air working system, a heat exchange system and a molten salt heat storage system, at a low electricity consumption valley, low-valley electricity is used to drive the double-well isothermal compression system to compress ambient air and store the ambient air in a salt cavern, at an electricity consumption peak period, a damper and a baffle are controlled to make the compressed air enter the energy release part to work, and the system works in four operation modes, corresponding to three kinds of electricity load demands, i.e., high, medium and low. The application combines high-temperature heat storage technology with molten salt as a heat storage medium, solves the problem of excessively high compressor outlet temperature in the adiabatic compression process, can achieve high electricity-electricity efficiency, improves the energy storage efficiency of the system, provides another solution for grid peak regulation, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to a compressed air energy storage system, specifically to a combustible compressed air energy storage system coupled with molten salt thermal storage and its operation method. Background Technology

[0002] Energy storage technology is crucial for building new power systems. Traditional energy storage technologies include pumped hydro storage, electrochemical energy storage, flywheel energy storage, and molten salt thermal energy storage. However, these technologies are subject to high development costs due to factors such as energy density, geographical location, and lifespan. Compressed air energy storage (CAES) is a highly promising large-scale, long-term energy storage technology. Current research on CAES largely focuses on non-combustion-type CAES systems, but these systems suffer from drawbacks such as difficulty in recovering compression heat, low electro-electric efficiency, and high construction costs. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to propose a combustible compressed air energy storage system and its operation method based on the first and second laws of thermodynamics and the principle of energy cascade utilization. By combining high-temperature thermal storage technology using molten salt as the thermal storage medium, the problem of excessively high compressor outlet temperature during adiabatic compression is solved, while also achieving high electro-electric efficiency, thus improving the system's energy storage efficiency. This provides another solution for grid peak shaving and has good prospects for industrial application.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A supplementary combustion compressed air energy storage system coupled with molten salt thermal storage, the system comprising an energy storage section and an energy release section, wherein the energy storage section consists of two subsystems: a dual-well isothermal compression system and an air storage system;

[0006] The dual-well isothermal compression system includes an air compressor 1, a first compression well 2, a second compression well 3, a water pump 4, and a water storage tank 5. The air inlet of the air compressor 1 is connected to the environment, the compressed air outlet of the air compressor 1 is connected to the compressed air inlet of the first compression well 2, the compressed air outlet of the first compression well 2 is connected to the compressed air inlet of the second compression well 3, the compressed air outlet of the second compression well 3 is connected to the inlet of the first damper 19, the cooling water return inlet of the water storage tank 5 is connected to the cooling water outlets of the first compression well 2 and the second compression well 3, the cooling water outlet of the water storage tank 5 is connected to the inlet of the water pump 4, and the outlet of the water pump 4 is connected to the cooling water inlets of the first compression well 2 and the second compression well 3.

[0007] The gas storage system includes a salt cavern 6 and a first air damper 19 and a second air damper 20 installed inside the salt cavern 6. The air inlet and outlet of the salt cavern 6 are respectively connected to the outlet of the first air damper 19 and the inlet of the second air damper 20.

[0008] The energy release section includes an air-flue gas heat exchanger 7, a low-temperature high-pressure air expander 8, a first generator 9, a combustion chamber 10, a high-temperature flue gas expander 11, a second generator 12, a flue gas-molten salt heat exchanger 13, a low-temperature molten salt storage tank 14, a high-temperature molten salt storage tank 15, an air-molten salt heat exchanger 16, a high-pressure air expander 17, a third generator 18, a third damper 21, a fourth damper 22, a first baffle 23, a second baffle 24, and a third baffle 25. The connection method of the energy release section is as follows: the first damper 19 and the second damper 20 inside the salt cavern 6 are used to control the entry and exit of compressed air into and out of the salt cavern 6. The outlet of the second damper 20 is connected to the inlet of the third damper 21 and the fourth damper 22, dividing the compressed air into two paths. One path, controlled by the third damper 21, has a combustion function. The outlet of the third damper 21 is connected to the low-temperature air inlet of the air-flue gas heat exchanger 7, and the low-temperature air outlet of the air-flue gas heat exchanger 7 is connected to the low-temperature air inlet. The inlet of the high-temperature and high-pressure air expander 8 is connected to the low-temperature and high-pressure air expander 8, which drives the first generator 9 to generate electricity. The outlet of the low-temperature and high-pressure air expander 8 is connected to the inlet of the combustion chamber 10. The outlet of the combustion chamber 10 is connected to the inlet of the high-temperature flue gas expander 11. The high-temperature flue gas expander 11 drives the second generator 12 to generate electricity. The outlet of the high-temperature flue gas expander 11 is connected to the inlet of the first baffle 23 and the second baffle 24. The outlet of the first baffle 23 is connected to the high-temperature flue gas inlet of the air-flue gas heat exchanger 7. The outlet of the second baffle 24 is connected to the flue gas inlet of the flue gas-molten salt heat exchanger 13. The molten salt inlet and outlet of the flue gas-molten salt heat exchanger 13 are connected to the outlet of the low-temperature molten salt storage tank 14 and the inlet of the high-temperature molten salt storage tank 15, respectively. The flue gas outlet of the flue gas-molten salt heat exchanger 13 is connected to the inlet of the third baffle 25. The outlet of the third baffle 25 and the first baffle 23 are both connected to the high-temperature flue gas inlet of the air-flue gas heat exchanger 7.

[0009] Another compressed air path is connected from the outlet of the fourth damper 22 to the low-temperature air inlet of the air-molten salt heat exchanger 16. The molten salt inlet and outlet of the air-molten salt heat exchanger 16 are connected to the outlet of the high-temperature molten salt storage tank 15 and the inlet of the low-temperature molten salt storage tank 14, respectively. The low-temperature air outlet of the air-molten salt heat exchanger 16 is connected to the inlet of the high-pressure air expander 17. The high-pressure air expander 17 drives the third generator 18 to generate electricity.

[0010] When energy is released, the second damper 20 at the outlet of the salt cavern 6 is energized, releasing the stored compressed air into the energy release section of the system to do work and generate electricity. At this time, the compressed air can be divided into two paths, which enter the three expanders to do work respectively. Depending on whether each expander does work and the amount of work done, the system can be divided into four operating modes.

[0011] 2. The operation method of a combustible compressed air energy storage system coupled with molten salt thermal storage as described in claim 1, characterized in that: during energy storage, a water pump 4 driven by off-peak electricity is used to pressurize cold water in the water storage tank 5 into the first compression well 2 and the second compression well 3 to cool the hot air compressed by the air compressor 1, and the cooled compressed air enters the salt cavern 6 for storage from the outlet of the second compression well 3.

[0012] During energy release, the second damper 20 opens, and the released compressed air is divided into two paths. One path passes through the third damper 21, the air-flue gas heat exchanger 7, the low-temperature high-pressure air expander 8, the combustion chamber 10, and the high-temperature flue gas expander 11 in sequence. The high-temperature flue gas at the outlet of the high-temperature flue gas expander T2 is further divided into two paths. One path passes through the first baffle 23 and directly enters the air-flue gas heat exchanger H1 before being discharged into the atmosphere. The other path passes through the second baffle 24, the flue gas-molten salt heat exchanger 13, and the third baffle 25 before entering the air-flue gas heat exchanger 7 and finally being discharged into the atmosphere. The other path of compressed air passes through the fourth damper 22 and the air-molten salt heat exchanger 16, enters the high-pressure air expander 17 to do work, and is then discharged into the atmosphere.

[0013] The operation method of the coupled molten salt thermal storage and combustion-type compressed air energy storage system is as follows: During off-peak electricity demand, room temperature water in the water storage tank 5 is pumped into the first compression well 2 and the second compression well 3 by the water pump 4. The room temperature water cools the compressed air in the first compression well 2 and the second compression well 3 by the air compressor 1. The compressed air passes through the two compression wells in sequence, so that its temperature is maintained in the range of 39℃-41℃ when it enters the salt cavern 6. The first damper 19 is energized to open and the second damper 20 is energized to close, so that the compressed air enters the salt cavern 6 and is stored at a constant temperature. The water in the two compression wells is continuously circulated due to the pressure of the water pump, so that it is kept at a constant temperature during the compression process.

[0014] When the system releases energy, there are four operating modes. The workflow of operating mode one is as follows: the compressed air passes through the third damper 21, and then passes through the air-flue gas heat exchanger 7, the low-temperature high-pressure air expander 8, the combustion chamber 10, the high-temperature flue gas expander 11, the first baffle 23, and the air-flue gas heat exchanger 7 in sequence before being discharged into the atmosphere. In this operating mode, the compressed air is supplemented and heated in the combustion chamber 10 before entering the high-temperature flue gas expander 11. After the low-temperature high-pressure air expander 8 and the high-temperature flue gas expander 11 reach their rated power, they drive the first generator 9 and the second generator 12 respectively. The exhaust gas from the high-temperature flue gas expander 11 is only used to heat the compressed air at the inlet of the low-temperature high-pressure air expander 8.

[0015] The workflow of operating mode two is as follows: The compressed air passes through the third damper 21, and then sequentially passes through the air-flue gas heat exchanger 7, the low-temperature high-pressure air expander 8, the combustion chamber 10, the high-temperature flue gas expander 11, the second baffle 24, the flue gas-molten salt heat exchanger 13, the third baffle 25, and the air-flue gas heat exchanger 7 before being discharged into the atmosphere. In this operating mode, the compressed air is supplemented with combustion heating in the combustion chamber 10 before entering the high-temperature flue gas expander 11. The low-temperature high-pressure air expander 8 and the high-temperature flue gas expander 11 drive the first generator 9 and the second generator 12, respectively. The difference from the first operating mode is that in this operating mode, the high-temperature flue gas expander 11 reaches its rated power. The flue gas discharged from the high-temperature flue gas expander 11 needs to enter the flue gas-molten salt heat exchanger 13 to heat the low-temperature molten salt in the low-temperature storage tank 14. The resulting high-temperature molten salt is stored in the high-temperature molten salt storage tank 15 and then used to heat the compressed air at the inlet of the low-temperature high-pressure air expander 8. Therefore, the low-temperature high-pressure air expander 8 does not reach its rated power.

[0016] The workflow of operating mode three is as follows: A portion of the compressed air in the salt cavern 6 enters the air-molten salt heat exchanger 16 through the second damper 20 and the fourth damper 22. The high temperature of the air is increased by the high temperature molten salt stored in the high temperature molten salt storage tank 15. After the temperature is increased, the air enters the high pressure air expander 17. After the high pressure air expander 17 reaches the rated power, it drives the third generator 18 to do work and is finally discharged into the atmosphere.

[0017] The workflow of operating mode four is as follows: Compressed air is divided into two paths. One path passes through the third damper 21, air-flue gas heat exchanger 7, low-temperature high-pressure air expander 8, combustion chamber 10, high-temperature flue gas expander 11, first baffle 23, and air-flue gas heat exchanger 7 in sequence, and is discharged into the atmosphere. The other path passes through the fourth damper 22, air-molten salt heat exchanger 16, and high-pressure air expander 17 in sequence, and is finally discharged into the atmosphere. In this operating mode, the two paths of compressed air work simultaneously. The low-temperature high-pressure air expander 8, the high-temperature flue gas expander 11, and the high-pressure air expander 17 all reach their rated power, driving the first generator 9, the second generator 12, and the third generator 18 to do work, respectively.

[0018] Of the four operating modes of the system, operating mode four corresponds to high electrical load demand, operating modes one and two correspond to medium electrical load demand, and operating mode three corresponds to low electrical load demand. In operating mode two, some heat needs to be stored in molten salt, and the low-temperature high-pressure air expander 8 and the high-temperature flue gas expander 11 work simultaneously. In operating mode three, the high-pressure air expander 17 operates alone. In operating mode four, the low-temperature high-pressure air expander 8, the high-temperature flue gas expander 11, and the high-pressure air expander 17 all operate at rated power simultaneously.

[0019] The rated power of the low-temperature high-pressure air expander 8 is 7395kW, the rated power of the high-temperature flue gas expander 11 is 19300kW, and the rated power of the high-pressure air expander T317 is 4650kW. When the system operates in mode two, the output power of the low-temperature high-pressure air expander 8 is 5200kW. Therefore, among the four operating modes, mode four has the highest output power at 31345kW; mode two is the next highest at 26695kW; mode two is the next lowest at 24500kW; and mode three has the lowest output power at 4650kW.

[0020] The present invention has the following advantages:

[0021] This invention provides a supplementary combustion compressed air energy storage system coupled with molten salt thermal storage and its operation method. This system combines a novel energy storage method, using off-peak electricity to store compressed air and releasing energy to generate electricity during peak electricity demand. The four operating modes correspond to high, medium and low electricity demand, which is an effective supplement to existing energy storage systems and has high practical value.

[0022] 2. Because the system of the present invention has an air-flue gas heat exchanger 7 and a flue gas-molten salt heat exchanger 13, the temperature of the compressed air entering the low temperature high pressure air expander 8 is increased, thereby improving its power generation efficiency, while the energy utilization rate of the high temperature flue gas exhaust of the high temperature flue gas expander 11 is improved and the energy loss is reduced.

[0023] 3. Due to the presence of baffles 23 and 24 in the system of the present invention, the system can adjust its operating mode and change its output according to the power grid demand, thereby improving the system's flexibility.

[0024] 4. Due to the presence of the flue gas-molten salt heat exchanger 13, the low-temperature molten salt storage tank 14, the high-temperature molten salt storage tank 15, and the air-molten salt heat exchanger 16 in this invention, the system can store a portion of the energy of the high-temperature flue gas through heat storage when the power grid demand is low. When the power grid demand is high, the low-temperature high-pressure air expander 8, the high-temperature flue gas expander 11, and the high-pressure air expander 17 can simultaneously reach full-load operation. It can also realize the variable operating condition operation of the high-pressure air expander 17 when the power grid demand is extremely low, which greatly improves the output regulation capability of the system.

[0025] 5. Due to the presence of dampers 21 and 22 in the system of the present invention, the system can achieve wide operating conditions by adjusting their opening degree, which greatly improves the system flexibility. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a supplementary combustion compressed air energy storage system coupled with molten salt thermal storage according to the present invention. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] Because actual electricity consumption at different times is difficult to predict, the application of large-scale energy storage technologies is urgently needed. Traditional energy storage technologies include pumped hydro storage, electrochemical energy storage, flywheel energy storage, and molten salt thermal energy storage. However, these technologies are affected by various factors such as energy storage density, geographical location, and service life. Therefore, new energy storage technologies need to be developed to fill the gap in total energy storage capacity. Compressed air energy storage systems offer advantages such as relatively high energy storage density, environmental friendliness, efficient and flexible operation, and low initial investment, making them a worthy area of ​​research. This invention, based on the first and second laws of thermodynamics and the principle of energy cascade utilization, proposes a supplementary combustion compressed air energy storage system coupled with molten salt thermal energy storage. Combined with high-temperature thermal storage technology using molten salt as the thermal storage medium, this system solves the problem of excessively high compressor outlet temperature during adiabatic compression and achieves high electro-electric efficiency, improving system energy storage efficiency and providing a solution for grid peak shaving. It has promising prospects for industrial applications.

[0029] During energy release, the second damper 20 opens, and the released compressed air is divided into two paths. One path passes through the third damper 21, the air-flue gas heat exchanger 7, the low-temperature high-pressure air expander 8, the combustion chamber 10, and the high-temperature flue gas expander 11 in sequence. The high-temperature flue gas at the outlet of the high-temperature flue gas expander 11 is further divided into two paths. One path passes through the first baffle 23 and directly enters the air-flue gas heat exchanger 7 before being discharged into the atmosphere. The other path passes through the second baffle 24, the flue gas-molten salt heat exchanger 13, and the third baffle 25 before entering the air-flue gas heat exchanger 7 and finally being discharged into the atmosphere. The other path of compressed air passes through the fourth damper 22 and the air-molten salt heat exchanger 16, enters the high-pressure air expander 17 to do work, and is then discharged into the atmosphere.

[0030] When releasing energy, the system operates in four modes: mode four corresponds to high electrical load demand, mode one and mode two correspond to medium electrical load demand, and mode three corresponds to low electrical load demand.

[0031] In simple terms, during energy release, the compressed air energy release system and the molten salt thermal storage system operate. The second damper 20 at the outlet of salt cavern 6 is energized, releasing the stored compressed air into the downstream system to generate electricity. There are four operating modes:

[0032] (1) Operating mode 1: In this operating mode, compressed air only does work in the low temperature high pressure air expander 8 and the high temperature flue gas expander 11. The flue gas discharged from the high temperature flue gas expander 11 is only used to heat the compressed air at the inlet of the low temperature high pressure air expander 8. At this time, both the low temperature high pressure air expander 8 and the high temperature flue gas expander 11 reach their rated power, and the high pressure air expander 17 does not run.

[0033] (2) Operating mode 2: In this operating mode, compressed air only does work in the low temperature high pressure air expander 8 and the high temperature flue gas expander 11. The difference from the first operating mode is that the flue gas discharged from the high temperature flue gas expander 11 needs to heat the low temperature molten salt in the low temperature molten salt storage tank 14 first, and then use it to heat the compressed air at the inlet of the low temperature high pressure air expander 8. At this time, the high temperature flue gas expander 11 reaches the rated power, the low temperature high pressure air expander 8 does not reach the rated power, and the high pressure air expander 17 does not run.

[0034] (3) Operation mode three: In this operation mode, the high-temperature molten salt stored in the high-temperature molten salt storage tank 15 in mode two is used to heat the compressed air at the inlet of the high-pressure air expander 17, so that the high-pressure air expander 17 operates at the rated power. At this time, the low-temperature high-pressure air expander 8 and the high-temperature flue gas expander 11 do not operate.

[0035] (4) Operating mode 4: In this operating mode, compressed air simultaneously enters the low-temperature high-pressure air expander 8, the high-temperature flue gas expander 11 and the high-pressure air expander 17 to do work. The flue gas discharged from the high-temperature flue gas expander 11 is only used to heat the compressed air at the inlet of the low-temperature high-pressure air expander 8. The molten salt heat storage part releases heat to heat the compressed air at the inlet of the high-pressure air expander 17. At this time, the low-temperature high-pressure air expander 8, the high-temperature flue gas expander 11 and the high-pressure air expander 17 reach their rated power.

[0036] During energy release, the system operates in four modes. When the system is running in mode one, the calculation steps are as follows: First, input the parameters such as the temperature and pressure of the compressed air in the salt cavern and the temperature of the flue gas discharged into the atmosphere. Then, arbitrarily give the compressed air temperature at the outlet of the air-flue gas heat exchanger 7 to obtain a definite excess air coefficient value and the high-temperature flue gas temperature at the inlet of the air-flue gas heat exchanger 7. Then, according to the conservation of heat exchanger heat transfer, a new compressed air temperature value at the outlet of the air-flue gas heat exchanger 7 can be obtained. By judging whether the two values ​​are equal, if they are not equal, a new compressed air temperature value at the outlet of the air-flue gas heat exchanger 7 will be obtained and the iteration will continue. Otherwise, input the obtained excess air coefficient value to obtain the maximum output under this operating condition.

[0037] When the system operates under mode two conditions, the system calculation process is as follows: First, input the known parameters and, through prior calculations, obtain the ideal inlet temperature of the high-pressure air expander 17 as 507℃, pressure as 12MPa, the ideal outlet temperature as 25℃, and pressure as 1MPa, as well as the heat Q1 required to heat the compressed air in the salt cavern to 507℃; then, given a compressed air flow rate at the inlet of the air-flue gas heat exchanger 7 and a compressed air temperature at the outlet, an excess air coefficient can be obtained, making the flue gas temperature at the inlet of the high-temperature flue gas expander 11 1400℃. Combining this with the Q1 value, the flue gas parameters at the inlet of the air-flue gas heat exchanger 7 can be obtained according to the conservation of heat exchange; finally, compare the obtained compressed air temperature at the outlet of the air-flue gas heat exchanger 7 with the given value. If they are equal, the system parameters can be output; if they are not equal, the iteration continues until they are equal.

[0038] The calculation methods for operating modes two and four are the same, but the operating procedures differ. Operating mode two requires storing some heat in molten salt, with the low-temperature high-pressure air expander 8 and the high-temperature flue gas expander 11 operating simultaneously. Operating mode three involves the high-pressure air expander 17 operating alone. Operating mode four involves the simultaneous operation of the low-temperature high-pressure air expander 8, the high-temperature flue gas expander 11, and the high-pressure air expander 17. The high-pressure air expander 17 reaches its rated power under both operating modes three and four, therefore the required heat is the same. It is only necessary to calculate the heat required when operating in one mode. Therefore, the calculation method will only be introduced using operating mode two as an example. Under this operating condition, some of the compressed air inside the salt cavern flows sequentially through the second damper 20 and the third damper 21 into the downstream equipment to perform work. The flue gas flowing out of the high-temperature flue gas expander 11 first enters the flue gas-molten salt heat exchanger 13 to heat the low-temperature molten salt in the low-temperature molten salt storage tank 14, and then enters the air-flue gas heat exchanger 7 to heat the compressed air at the inlet of the low-temperature high-pressure air expander 8. The heated low-temperature molten salt is stored in the high-temperature molten salt storage tank after its temperature rise, and is used to heat the remaining compressed air in the salt cavern that enters the high-pressure air expander 17 to perform work in another period. At this time, there should be a unique compressed air flow distribution coefficient and an excess air coefficient 'a', which simultaneously meets the temperature requirements of the compressed air entering the low-temperature high-pressure air expander 8 and the high-pressure air expander 17, and allows the high-temperature flue gas expander 11 and the high-pressure air expander 17 to reach their rated power. Based on the above analysis, the calculation process is as follows: First, input the known parameters and, through previous calculations, obtain the ideal inlet temperature of the high-pressure air expander 17 as 507℃, pressure as 12MPa, the ideal outlet temperature as 25℃, and pressure as 1MPa, as well as the heat Q1 required to heat the compressed air in the salt cavern to 507℃; then, given a compressed air flow rate at the inlet of the air-flue gas heat exchanger 7 and a compressed air temperature at the outlet, an excess air coefficient a can be obtained, making the flue gas temperature at the inlet of the high-temperature flue gas expander 11 1400℃. Combining this with the Q1 value, the flue gas parameters at the inlet of the air-flue gas heat exchanger 7 can be obtained according to the conservation of heat exchange; finally, compare the obtained compressed air temperature at the outlet of the air-flue gas heat exchanger 7 with the given value. If they are equal, the system parameters can be output; if they are not equal, the iteration continues until they are equal.

[0039] The system has four operating modes, each corresponding to a different output condition. The rated output of each mode reflects the flexibility of the system's output power adjustment. In the first operating mode, the high-pressure air expander 17 is not operating, the molten salt thermal storage system does not store heat, and both the low-temperature high-pressure air expander 8 and the high-temperature flue gas expander 11 reach their rated power. In the second operating mode, the high-pressure air expander 17 is not operating, but the molten salt thermal storage system stores some heat. The low-temperature high-pressure air expander 8 does not reach its rated power, while the high-temperature flue gas expander 11 reaches its rated power. In the third operating mode, the heat stored in the molten salt thermal storage system is used to heat the compressed air at the inlet of the high-pressure air expander 17. At this time, the high-pressure air expander 17 operates at its rated power. In the fourth operating mode, the heat output from the molten salt thermal storage system heats the compressed air at the inlet of the high-pressure air expander 17, and the flue gas exiting the high-temperature flue gas expander 11 only heats the compressed air at the inlet of the low-temperature high-pressure air expander 8. The low-temperature high-pressure air expander 8, the high-temperature flue gas expander 11, and the high-pressure air expander 17 all operate at their rated power.

[0040] Based on the system's energy and material balance design calculations, the rated power of the cryogenic high-pressure air expander 8 is 7395kW, the rated power of the high-temperature flue gas expander 11 is 19300kW, and the rated power of the high-pressure air expander T3 is 4650kW. When the system operates in mode two, the output power of the cryogenic high-pressure air expander 8 is 5200kW. Therefore, among the four operating modes, mode four has the highest output power at 31345kW; mode two is the next highest at 26695kW; mode two is the next lowest at 24500kW; and mode three has the lowest output power at 4650kW.

[0041] When the system operates in all four modes, the excess air coefficient in the combustion chamber is 1.57, corresponding to a natural gas flow rate of 0.71 kg / s. The compressed air flow rate with the supplementary combustion line (entering the low-temperature high-pressure air expander 8 and the high-temperature flue gas expander 11 to perform work) is 18 kg / s, while the compressed air flow rate without the supplementary combustion line (entering the high-pressure air expander 17 to perform work) is 9.2 kg / s. When the thermal storage system operates under operating modes two and three, the flow rate of molten salt during both heat storage and heat release is 9.86 kg / s.

Claims

1. A supplementary combustion compressed air energy storage system coupled with molten salt thermal storage, characterized in that: The system includes an energy storage section and an energy release section, wherein the energy storage section consists of two subsystems: a dual-well isothermal compression system and a gas storage system. The dual-well isothermal compression system includes an air compressor (1), a first compression well (2), a second compression well (3), a water pump (4), and a water storage tank (5). The air inlet of the air compressor (1) is connected to the environment, the compressed air outlet of the air compressor (1) is connected to the compressed air inlet of the first compression well (2), the compressed air outlet of the first compression well (2) is connected to the compressed air inlet of the second compression well (3), the compressed air outlet of the second compression well (3) is connected to the inlet of the first damper (19), the cooling water return inlet of the water storage tank (5) is connected to the cooling water outlet of the first compression well (2) and the second compression well (3), the cooling water outlet of the water storage tank (5) is connected to the inlet of the water pump (4), and the outlet of the water pump (4) is connected to the cooling water inlet of the first compression well (2) and the second compression well (3). The gas storage system includes a salt cavern (6) and a first air door (19) and a second air door (20) installed in the salt cavern (6). The air inlet and outlet of the salt cavern (6) are connected to the outlet of the first air door (19) and the inlet of the second air door (20), respectively. The energy release section includes an air-flue gas heat exchanger (7), a low-temperature high-pressure air expander (8), a first generator (9), a combustion chamber (10), a high-temperature flue gas expander (11), a second generator (12), a flue gas-molten salt heat exchanger (13), a low-temperature molten salt storage tank (14), a high-temperature molten salt storage tank (15), an air-molten salt heat exchanger (16), a high-pressure air expander (17), a third generator (18), a third damper (21), a fourth damper (22), a first baffle (23), and a second baffle (24). 24) and the third baffle (25); the energy release section is connected as follows: the first damper (19) and the second damper (20) in the salt cave (6) are used to control the compressed air entering and exiting the salt cave (6), the outlet of the second damper (20) is connected to the inlet of the third damper (21) and the fourth damper (22), dividing the compressed air into two paths, one controlled by the third damper (21) with supplementary combustion, the outlet of the third damper (21) is connected to the low-temperature air inlet of the air-flue gas heat exchanger (7), the low-temperature air inlet of the air-flue gas heat exchanger (7) The outlet is connected to the inlet of the low-temperature high-pressure air expander (8), which drives the first generator (9) to generate electricity. The outlet of the low-temperature high-pressure air expander (8) is connected to the inlet of the combustion chamber (10), and the outlet of the combustion chamber (10) is connected to the inlet of the high-temperature flue gas expander (11). The high-temperature flue gas expander (11) drives the second generator (12) to generate electricity. The outlet of the high-temperature flue gas expander (11) is connected to the inlet of the first baffle (23) and the inlet of the second baffle (24). The outlet of the first baffle (23) is connected to the inlet of the second baffle (24). The outlet of the second baffle (24) is connected to the high-temperature flue gas inlet of the air-flue gas heat exchanger (7), the outlet of the second baffle (24) is connected to the flue gas inlet of the flue gas-molten salt heat exchanger (13), the molten salt inlet and outlet of the flue gas-molten salt heat exchanger (13) are connected to the outlet of the low-temperature molten salt storage tank (14) and the inlet of the high-temperature molten salt storage tank (15) respectively, the flue gas outlet of the flue gas-molten salt heat exchanger (13) is connected to the inlet of the third baffle (25), and the outlet of the third baffle (25) and the first baffle (23) are both connected to the high-temperature flue gas inlet of the air-flue gas heat exchanger (7); Another compressed air is connected from the outlet of the fourth damper (22) to the low-temperature air inlet of the air-molten salt heat exchanger (16). The molten salt inlet and outlet of the air-molten salt heat exchanger (16) are connected to the outlet of the high-temperature molten salt storage tank (15) and the inlet of the low-temperature molten salt storage tank (14), respectively. The low-temperature air outlet of the air-molten salt heat exchanger (16) is connected to the inlet of the high-pressure air expander (17). The high-pressure air expander (17) drives the third generator (18) to generate electricity. When energy is released, the second damper (20) at the outlet of the salt cavern (6) is energized, releasing the stored compressed air into the energy release part of the system to do work and generate electricity. At this time, the compressed air can be divided into two paths, which enter the three expanders to do work respectively. Depending on whether each expander does work and the amount of work done, the system can be divided into four operating modes.

2. The operation method of a supplementary combustion compressed air energy storage system coupled with molten salt thermal storage as described in claim 1, characterized in that: During energy storage, the water pump (4) driven by off-peak electricity is used to press the cold water in the water storage tank (5) into the first compression well (2) and the second compression well (3) to cool the hot air compressed by the air compressor (1). The cooled compressed air enters the salt cavern (6) for storage through the outlet of the second compression well (3). When energy is released, the second damper (20) opens, and the released compressed air is divided into two paths. One path passes through the third damper (21), the air-flue gas heat exchanger (7), the low-temperature high-pressure air expander (8), the combustion chamber (10), and the high-temperature flue gas expander (11) in sequence. The high-temperature flue gas at the outlet of the high-temperature flue gas expander T2 is divided into two paths. One path passes through the first baffle (23) and directly enters the air-flue gas heat exchanger H1 before being discharged into the atmosphere. The other path passes through the second baffle (24), the flue gas-molten salt heat exchanger (13), and the third baffle (25) before entering the air-flue gas heat exchanger (7) and finally being discharged into the atmosphere. The other path of compressed air passes through the fourth damper (22) and the air-molten salt heat exchanger (16) before entering the high-pressure air expander (17) to do work and then being discharged into the atmosphere.

3. The operation method of a supplementary combustion compressed air energy storage system coupled with molten salt thermal storage as described in claim 2, characterized in that: The energy storage process is as follows: During off-peak hours, room temperature water in the water tank (5) is pumped into the first compression well (2) and the second compression well (3) by the water pump (4). The room temperature water cools the compressed air in the first compression well (2) and the second compression well (3) by the air compressor (1). The compressed air passes through the two compression wells in sequence, so that its temperature is maintained in the range of 39℃-41℃ when it enters the salt cavern (6). The first damper (19) is energized and opened, and the second damper (20) is energized and closed, so that the compressed air enters the salt cavern (6) and is kept at a constant temperature. The water in the two compression wells circulates continuously due to the pressure of the water pump, so that it remains at a constant temperature during the compression process.

4. The supplementary combustion compressed air energy storage system and its operation method coupled with molten salt thermal storage as described in claim 2, characterized in that: When the system releases energy, it is divided into four operating modes. The working process of operating mode one is as follows: the compressed air passes through the third damper (21), and then passes through the air-flue gas heat exchanger (7), the low temperature high pressure air expander (8), the combustion chamber (10), the high temperature flue gas expander (11), the first baffle (23), and the air-flue gas heat exchanger (7) in sequence, and is discharged into the atmosphere. In this operating mode, the compressed air is heated by combustion in the combustion chamber (10) before entering the high temperature flue gas expander (11). After the low temperature high pressure air expander (8) and the high temperature flue gas expander (11) reach the rated power, they drive the first generator (9) and the second generator (12) respectively. The exhaust of the high temperature flue gas expander (11) is only used to heat the compressed air at the inlet of the low temperature high pressure air expander (8). The workflow of operating mode two is as follows: The compressed air passes through the third damper (21), and then sequentially passes through the air-flue gas heat exchanger (7), the low-temperature high-pressure air expander (8), the combustion chamber (10), the high-temperature flue gas expander (11), the second baffle (24), the flue gas-molten salt heat exchanger (13), the third baffle (25), and the air-flue gas heat exchanger (7) before being discharged into the atmosphere; in this operating mode, the compressed air is supplemented with combustion and heated in the combustion chamber (10) before entering the high-temperature flue gas expander (11), and the low-temperature high-pressure air expander (8) and the high-temperature flue gas expander (11) are heated by combustion. 1) Drive the first generator (9) and the second generator (12) respectively; Compared with the first operating mode, the difference is that in this operating mode, the high temperature flue gas expander (11) reaches the rated power, and the flue gas discharged from the high temperature flue gas expander (11) needs to enter the flue gas-molten salt heat exchanger (13) to heat the low temperature molten salt in the low temperature storage tank (14). The obtained high temperature molten salt is stored in the high temperature molten salt storage tank (15) and then used to heat the compressed air at the inlet of the low temperature high pressure air expander (8). Therefore, the low temperature high pressure air expander (8) does not reach the rated power; The workflow of the three operating modes is as follows: A portion of the compressed air in the salt cavern (6) enters the air-molten salt heat exchanger (16) through the second air door (20) and the fourth air door (22), and uses the high temperature molten salt stored in the high temperature molten salt tank (15) to raise its temperature. After the temperature rises, it enters the high pressure air expander (17), and after the high pressure air expander (17) reaches the rated power, it drives the third generator (18) to do work, and finally discharges into the atmosphere; The working process of operating mode four is as follows: compressed air is divided into two paths. One path passes through the third damper (21), air-flue gas heat exchanger (7), low temperature high pressure air expander (8), combustion chamber (10), high temperature flue gas expander (11), first baffle (23), and air-flue gas heat exchanger (7) in sequence, and is discharged into the atmosphere. The other path passes through the fourth damper (22), air-molten salt heat exchanger (16), and high pressure air expander (17) in sequence, and is finally discharged into the atmosphere. In this operating mode, the two paths of compressed air work simultaneously. The low temperature high pressure air expander (8), high temperature flue gas expander (11), and high pressure air expander (17) all reach their rated power, driving the first generator (9), the second generator (12), and the third generator (18) to do work, respectively.

5. The operation method of a supplementary combustion compressed air energy storage system coupled with molten salt thermal storage as described in claim 4, characterized in that: Of the four operating modes of the system, operating mode four corresponds to high power load demand, operating mode one and operating mode two correspond to medium power load demand, and operating mode three corresponds to low power load demand. In operating mode two, some heat needs to be stored in molten salt, and the low temperature high pressure air expander (8) and the high temperature flue gas expander (11) work at the same time. In operating mode three, the high pressure air expander (17) operates alone. In operating mode four, the low temperature high pressure air expander (8), the high temperature flue gas expander (11), and the high pressure air expander (17) all operate at rated power at the same time.

6. The operation method of a supplementary combustion compressed air energy storage system coupled with molten salt thermal storage as described in claim 5, characterized in that: The rated power of the low-temperature high-pressure air expander (8) is 7395kW, the rated power of the high-temperature flue gas expander (11) is 19300kW, and the rated power of the high-pressure air expander T3 (17) is 4650kW. When the system is operating in mode two, the output power of the low-temperature high-pressure air expander (8) is 5200kW. Therefore, among the four operating modes, the output power corresponding to operating mode four is the largest, at 31345kW; the second largest is operating mode two, at 26695kW; the second largest is operating mode two, at 24500kW; and the smallest is operating mode three, at 4650kW.

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