Combined cycle power generation system based on compressed gas energy storage

Abstract

The application provides a combined cycle power generation system based on compressed gas energy storage, comprising: a Brayton cycle power generation unit; a compressed gas energy storage unit connected with a power output end of the Brayton cycle power generation unit; a cold energy supply unit for providing a low-temperature fluid fuel to cool a circulating working medium in a cooling stage of the Brayton cycle power generation unit, and the low-temperature fluid fuel is gasified after absorbing the heat energy of the circulating working medium in the cooling stage; and a waste heat utilization unit connected with the cold energy supply unit and the compressed gas energy storage unit, the waste heat utilization unit is used for receiving and burning the gasified low-temperature fluid fuel, and the waste heat after the low-temperature fluid fuel is burned is used for heating a circulating working medium in an energy releasing stage of the compressed gas energy storage unit. The application improves the work quality of the compressed gas energy storage unit, and realizes the utilization of cold energy.

Description

Technical Field

[0001] This invention relates to the field of power generation systems, specifically a combined cycle power generation system based on compressed gas energy storage. Background Technology

[0002] Developing renewable energy is a current social trend. However, renewable energy generation is highly volatile, inevitably leading to a high proportion of grid fluctuations that need to be absorbed by the power grid. Currently, existing frequency and voltage regulation equipment is insufficient to fully absorb the electricity generated by new energy sources, posing a serious challenge to grid security. Energy storage technology has become one of the key technologies for solving this problem and an effective way to improve the safety and reliability of the power system.

[0003] Currently, CO2 energy storage systems are attracting significant attention from researchers and are a novel energy storage system proposed in recent years following compressed air energy storage. During periods of low electricity demand, this system utilizes clean energy power, surplus electricity, and waste electricity unusable by end users to compress low-temperature, low-pressure CO2, storing it in a high-pressure tank. Simultaneously, the heat of compression is transferred to the storage medium. In short, it converts electrical energy, which is difficult to store directly, into easily stored heat and pressure potential energy. During periods of peak electricity demand, conventional power generation systems are insufficient to meet normal user needs. The carbon dioxide in the high-pressure storage tank is heated and expanded to perform work, replenishing the power supply and ensuring stable grid operation. This significantly improves the overall efficiency, security, and economy of the power grid's transmission and distribution side. Therefore, vigorous research into electricity storage technology is urgently needed.

[0004] Currently, due to the low energy storage efficiency and limited capacity of compressed CO2 energy storage systems, the electricity released from compressed CO2 storage alone is insufficient to promptly complete the grid's peak-shaving work during peak electricity demand periods. Furthermore, the limited storage capacity also prevents deep and long-term peak-shaving. With the high-proportion growth in renewable energy utilization, the grid's rotational inertia is continuously decreasing, resulting in insufficient frequency and voltage regulation capabilities, posing a serious challenge to grid security. Therefore, how to further improve system operating efficiency, increase energy storage capacity, and extend energy release time are urgent problems that need to be solved in this field. Summary of the Invention

[0005] To address the above problems, this invention provides a combined cycle power generation system based on compressed gas energy storage. By using the waste heat from the higher temperatures to heat the low-temperature, high-pressure working fluid during the energy release phase, and using the heat of compression generated by the working fluid during the energy storage phase to heat the low-temperature working fluid in the heating phase of the Brayton cycle power generation unit, this system achieves efficient energy utilization while improving the work quality of the working fluid in both the compressed gas energy storage unit and the Brayton cycle power generation unit. Furthermore, by efficiently utilizing the cold energy provided by the cold energy supply unit through the Brayton cycle power generation unit, cold energy waste is reduced.

[0006] This invention provides a combined cycle power generation system based on compressed gas energy storage, comprising:

[0007] Brayton cycle power generation unit;

[0008] The compressed gas energy storage unit is connected to the power output terminal of the Brayton cycle power generation unit;

[0009] The cold energy supply unit is used to provide cryogenic fluid fuel, which is used to cool the working fluid in the cooling stage of the Brayton cycle power generation unit. The cryogenic fluid fuel absorbs the heat energy of the working fluid in the cooling stage and then vaporizes.

[0010] The waste heat utilization unit connects the cold energy supply unit and the compressed gas energy storage unit. The waste heat utilization unit is used to receive and burn the gasified low-temperature fluid fuel. The waste heat after the low-temperature fluid fuel is burned is used to heat the circulating working fluid in the energy release stage in the compressed gas energy storage unit.

[0011] In conventional compressed gas energy storage units, the temperature of the compression heat during the energy storage stage is relatively low. During the energy release stage, relying solely on the compression heat is insufficient to raise the gas temperature to an optimal level, keeping the gas's work capacity within the high-pressure, low-temperature range. This results in poor work efficiency, thus limiting the overall efficiency of the CO2 compression system. Furthermore, cryogenic fluids release a significant amount of cold energy during vaporization. Current methods primarily utilize this cold energy for the condensation of gases (such as CO2). However, excessively low-temperature fluids can cause icing during gas condensation. Current techniques often involve heating the cryogenic fluid with air to a usable temperature before using its cold energy to liquefy the gas, leading to substantial waste of cold energy.

[0012] According to this technical solution, cryogenic fluid fuel cools the working fluid in the cooling stage of the Brayton cycle power generation unit, which not only overcomes the problem of wasted cold energy, but also allows the cold energy supply unit to cool the working fluid at the outlet of the second expander to a lower temperature, lowering the lower limit of its work capacity and increasing the work capacity of the Brayton cycle power generation unit, thereby improving power generation efficiency. The Brayton cycle power generation unit can generate electricity in a cycle to replenish the electricity required for the operation of the compressed gas energy storage unit, solving the problem of insufficient power generation and difficulty in maintaining high output for extended periods during peak electricity demand. The cryogenic fluid fuel, after heat exchange with the Brayton cycle unit, absorbs heat, gasifies, and then burns. The waste heat from combustion is used to heat the circulating working fluid in the compressed gas energy storage unit during the energy release stage, increasing the temperature and work quality of the working fluid in the compressed gas energy storage unit, and extending the energy release time. This is beneficial for meeting the needs of long-term and deep peak shaving, and can also increase peak load capacity. It has significant advantages due to its lower investment and operating costs. Compared to the more widely used compressed gas energy storage units, this application introduces the gas circulating working fluid into a heating device for reheating before expansion, so that its temperature reaches a higher work quality. By using waste heat to exchange heat in the first heat exchanger, it is beneficial to improve the utilization rate of waste heat.

[0013] In an optional technical solution of the present invention, the compressed gas energy storage unit includes:

[0014] High-pressure storage tank;

[0015] The first heat exchanger has its high-temperature medium inlet connected to the outlet of the waste heat recovery unit, and its low-temperature medium inlet connected to the outlet of the high-pressure storage tank.

[0016] The first expander is connected to the high-temperature medium outlet of the first heat exchanger.

[0017] The low-pressure storage tank is connected to the outlet of the first expander;

[0018] The first compressor is connected to the outlet of the low-pressure storage tank;

[0019] The second heat exchanger has a high-temperature medium inlet connected to the outlet of the first compressor, and a low-temperature medium outlet connected to the inlet of the high-pressure storage tank.

[0020] The outlet of the cryogenic storage tank is connected to the cryogenic medium inlet of the second heat exchanger.

[0021] The high-temperature storage tank is connected to the high-temperature medium outlet of the second heat exchanger;

[0022] The third heat exchanger has a high-temperature medium inlet connected to the outlet of the high-temperature storage tank and a low-temperature medium outlet connected to the inlet of the low-temperature storage tank. The compressed gas energy storage unit generates compression heat during the energy storage stage, which is used to heat the circulating working fluid in the heating stage of the Brayton cycle power generation unit.

[0023] According to this technical solution, the working fluid from the high-pressure storage tank outlet enters the first heat exchanger, where it is heated. The heated working fluid then enters the first expander, performs work, and finally enters the low-pressure storage tank, thus releasing the gas's energy. The working fluid from the low-pressure storage tank outlet is compressed by the first compressor, generating heat of compression. This heat is then exchanged in the second heat exchanger before returning to the high-pressure storage tank, achieving energy storage. The working fluid from the low-temperature storage tank outlet enters the second heat exchanger, where it is heated (absorbing the heat of compression from the working fluid in the second heat exchanger) and enters the high-temperature storage tank, storing the heat of compression. The working fluid from the high-temperature storage tank outlet enters the third heat exchanger, cools down, and then returns to the low-temperature storage tank for storage, completing the utilization of the heat of compression. This compressed gas energy storage unit can achieve both energy storage and release, as well as the storage and utilization of heat of compression, offering high flexibility. The heat of compression generated during the energy storage phase of the compressed gas energy storage unit is used to heat the working fluid in the Brayton cycle power generation unit, increasing the upper limit of the work done by the Brayton cycle power generation unit and improving its work capacity, thereby increasing power generation efficiency.

[0024] In an optional technical solution of the present invention, the Brayton cycle power generation unit includes:

[0025] Second compressor;

[0026] The preheater's inlet is connected to the outlet of the second compressor, and the preheater's outlet is connected to the low-temperature medium inlet of the third heat exchanger.

[0027] The inlet of the second expander is connected to the high-temperature medium outlet of the third heat exchanger;

[0028] The fourth heat exchanger has a high-temperature medium inlet connected to the outlet of the second expander, a low-temperature medium outlet connected to the inlet of the second compressor, a low-temperature medium inlet connected to the cold energy utilization unit, and a high-temperature medium outlet connected to the waste heat utilization unit.

[0029] According to this technical solution, the working fluid from the outlet of the second compressor enters a preheater, which can appropriately preheat the working fluid flowing in the Brayton cycle power generation unit. The preheated working fluid then enters a third heat exchanger where it exchanges heat with the compression heat from the high-temperature storage tank to increase its temperature. The heated working fluid then enters a second expander to expand and perform work. After performing work, the working fluid enters a fourth heat exchanger where it exchanges heat with the cold energy from the cold energy utilization unit to decrease its temperature. By utilizing the compression heat from the compressed gas energy storage unit and the cold energy from the cryogenic fluid fuel to heat or cool the working fluid flowing in the Brayton cycle, the utilization rate of compression heat and cold energy is improved. The cryogenic fluid fuel after heat exchange enters a waste heat utilization unit for combustion power generation.

[0030] In an optional technical solution of the present invention, the Brayton cycle power generation unit includes:

[0031] Second compressor;

[0032] The fifth heat exchanger has its low-temperature medium inlet connected to the outlet of the second compressor, and its high-temperature medium outlet connected to the low-temperature medium inlet of the third heat exchanger.

[0033] The inlet of the second expander is connected to the high-temperature medium outlet of the third heat exchanger;

[0034] The fourth heat exchanger has a high-temperature medium inlet connected to the outlet of the second expander, a low-temperature medium outlet connected to the inlet of the second compressor, a low-temperature medium inlet connected to the cold energy utilization unit, and a high-temperature medium outlet connected to the waste heat utilization unit.

[0035] Combined cycle power generation systems also include:

[0036] The water separation device has its inlet connected to the low-temperature medium outlet of the first heat exchanger and its outlet connected to the high-temperature medium inlet of the fifth heat exchanger.

[0037] The gas separation device is connected to the low-temperature medium outlet of the fifth heat exchanger.

[0038] According to this technical solution, in the Brayton cycle power generation unit, the working fluid from the outlet of the second compressor enters the fifth heat exchanger, where it exchanges heat with the waste heat from the outlet of the water separator, thus increasing its temperature. It then enters the third heat exchanger, where it exchanges heat with the working fluid from the outlet of the high-temperature storage tank, further increasing its temperature. Finally, it enters the second expander to perform work. The working fluid from the outlet of the second expander enters the fourth heat exchanger, where it exchanges heat with the cold energy of the low-temperature fluid fuel, thus decreasing its temperature and returning to the compressor. The working fluid from the outlet of the second compressor, after being heated by the fifth heat exchanger, enters the third heat exchanger for further heat exchange, increasing the temperature of the working fluid in the heating stage of the Brayton cycle power generation unit and improving its work-performing capacity.

[0039] In the waste heat utilization unit, the low-temperature fluid fuel, after heat exchange in the fourth heat exchanger, is gasified and enters the combustion chamber for combustion. The waste heat generated by combustion is stored in a thermal energy storage tank. The thermal energy stored in the thermal energy storage tank then enters the first heat exchanger to exchange heat with the working fluid at the outlet of the high-pressure storage tank, increasing the temperature of the working fluid at the outlet of the high-pressure storage tank. This improves the work quality of the working fluid in the energy release phase of the compressed gas energy storage unit. The working fluid with a certain amount of thermal energy from the low-temperature medium outlet of the first heat exchanger, after a portion of water is separated in the water separation device, enters the fifth heat exchanger to exchange heat with the working fluid at the outlet of the second compressor. After this heat exchange, the temperature decreases and the working fluid condenses into a liquid, facilitating the capture of the working fluid.

[0040] In an optional technical solution of the present invention, the cold energy supply unit includes a cold energy storage tank and a first booster pump connected in series, and the outlet of the first booster pump is connected to the low temperature medium inlet of the fourth heat exchanger.

[0041] According to this technical solution, by providing cold energy from the cold energy supply unit to the Brayton cycle power generation unit, the utilization of cold energy is realized, and the temperature of the working fluid in the Brayton cycle power generation unit is reduced, thus lowering the lower limit of work done and improving the power generation efficiency of the Brayton cycle power generation unit.

[0042] In an optional technical solution of the present invention, a flow divider is also included, with its inlet connected to the high-temperature medium outlet of the fourth heat exchanger, and one of the outlets of the flow divider connected to the waste heat utilization unit.

[0043] According to this technical solution, the cryogenic fluid fuel is vaporized after heat exchange in the fourth heat exchanger. The vaporized cryogenic fluid fuel is then discharged from the high-temperature medium outlet of the fourth heat exchanger and enters a distributor for diversion, which can realize diversified utilization of the cryogenic fluid fuel. For example, part of the cryogenic fluid fuel can be used for combustion power generation, and part can be supplied to users. Technicians can change the use of the cryogenic fluid fuel according to actual needs.

[0044] In an optional technical solution of the present invention, the waste heat utilization unit includes:

[0045] Air compressor; combustion chamber, the inlet of which is connected to the outlet of the cold energy supply unit and the outlet of the air compressor;

[0046] The third expander has its inlet connected to the outlet of the combustion chamber, and generates electricity by expanding.

[0047] The thermal energy storage tank is used to store the waste heat after the combustion of low-temperature fluid fuel. The inlet of the thermal energy storage tank is connected to the outlet of the third expander, and the outlet of the thermal energy storage tank is connected to the high-temperature medium inlet of the first heat exchanger.

[0048] According to the technical solution, the cryogenic fluid fuel exchanges heat with the working fluid of the Brayton cycle power generation unit in the fourth heat exchanger, then heats up and vaporizes before entering the combustion chamber for combustion. The heat generated by combustion can be used for expansion and power generation in the third expander. The waste heat of the working fluid after power generation is stored in the thermal energy storage tank and used to heat the working fluid in the energy release stage in the compressed gas energy storage unit, thereby increasing the temperature of the working fluid in the energy release stage and extending the energy release time.

[0049] In an optional technical solution of the present invention, an organic Rankine cycle is further included, the organic Rankine cycle comprising:

[0050] Second booster pump;

[0051] The sixth heat exchanger has a high-temperature medium inlet connected to the outlet of the first expander, a low-temperature medium outlet connected to the inlet of the low-pressure storage tank, and a low-temperature medium inlet connected to the outlet of the second booster pump.

[0052] The fourth expander has its inlet connected to the high-temperature medium outlet of the sixth heat exchanger;

[0053] The seventh heat exchanger has its high-temperature medium inlet connected to the outlet of the fourth expander, its low-temperature medium outlet connected to the inlet of the second booster pump, and its low-temperature medium inlet connected to the outlet of the gas separation device.

[0054] According to this technical solution, the working fluid at the outlet of the second booster pump in the organic Rankine cycle loop exchanges heat with the waste heat from the exhaust gas at the outlet of the first expander in the compressed gas energy storage unit at the sixth heat exchanger. This increases the temperature of the working fluid in the organic Rankine cycle loop, raises the upper limit of its work-capacity, improves system efficiency, and fully utilizes the waste heat after the compressed gas energy storage unit expands and performs work, thus improving waste heat utilization. Furthermore, this waste heat utilization lowers the temperature of the working fluid after the first expander performs work during the energy release stage, facilitating the storage of the liquid working fluid. The working fluid at the outlet of the fourth expander enters the seventh heat exchanger and exchanges heat with the low-temperature working fluid at the outlet of the gas separator, improving the utilization rate of cold energy and lowering the lower limit of the working fluid's work-capacity in the organic Rankine cycle loop, thereby improving the work quality and efficiency of the organic Rankine cycle loop.

[0055] In an optional technical solution of the present invention, the circulating working fluid in the organic Rankine cycle loop is propane, butane, or ethylene.

[0056] According to this technical solution, the aforementioned working fluids are all common working fluids in the organic Rankine cycle, and the materials are readily available, which helps to reduce power generation costs.

[0057] In an optional technical solution of the present invention, the cryogenic fluid fuel is a cryogenic fluid fuel with a temperature below -150°C.

[0058] According to this technical solution, low-temperature fluid fuels below -150°C have a better cooling effect, and the gasified fluid fuels after heat exchange do not require preheating when combustion, thus realizing the rational utilization of cold energy. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the structure in the first embodiment of the present invention.

[0060] Figure 2 This is a schematic diagram of the structure in the second embodiment of the present invention.

[0061] Figure 3 This is a schematic diagram of the structure in the third embodiment of the present invention.

[0062] Figure label:

[0063] Compressed gas energy storage unit 1; high-pressure storage tank 11; first heat exchanger 12; first expander 13; low-pressure storage tank 14; first compressor 15; second heat exchanger 16; low-temperature storage tank 17; high-temperature storage tank 18; third heat exchanger 19; Brayton cycle power generation unit 2; second compressor 21; second expander 22; fourth heat exchanger 23; preheater 24; fifth heat exchanger 25; cold energy supply unit 3; second booster pump 31; waste heat utilization unit 4; combustion chamber 41; third expander 42; thermal energy storage tank 43; air compressor 44; distributor 5; water separator 61; gas separator 62; second booster pump 71; sixth heat exchanger 72; fourth expander 73; seventh heat exchanger 74. Detailed Implementation

[0064] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] like Figure 1 As shown, the first embodiment of the present invention provides a combined cycle power generation system based on compressed gas energy storage, including: a compressed gas energy storage unit 1, a Brayton cycle power generation unit 2, a cold energy supply unit 3, and a waste heat utilization unit 4.

[0066] Compressed gas energy storage unit 1 is connected to the power output terminal of Brayton cycle power generation unit 2. During the energy storage phase, compressed gas energy storage unit 1 generates compression heat, which is used to heat the circulating working fluid in the heating phase of Brayton cycle power generation unit 2. Specifically, compressed gas energy storage unit 1 includes a first loop consisting of a high-pressure storage tank 11, a first heat exchanger 12, a first expander 13, a low-pressure storage tank 14, a first compressor 15, and a second heat exchanger 16 connected in sequence to form a closed-loop cycle; and a second loop consisting of a low-temperature storage tank 17, a second heat exchanger 16, a high-temperature storage tank 18, and a third heat exchanger 19 connected in sequence to form a closed-loop cycle. In the first loop, the working fluid from the outlet of high-pressure storage tank 11 enters the first heat exchanger 12 for heat exchange and is heated. The heated working fluid then enters the first expander 13 to perform work before entering the low-pressure storage tank 14, thus realizing the release of gas energy, i.e., the energy release phase. The working fluid at the outlet of low-pressure storage tank 14 is compressed by the first compressor 15, generating heat of compression. This heat is then exchanged in the second heat exchanger 16 before returning to the high-pressure storage tank 11, thus achieving gas energy storage, i.e., the energy storage stage. In the second loop, the working fluid at the outlet of low-temperature storage tank 17 enters the second heat exchanger 16, where it is heated (absorbing the heat of compression of the working fluid in the second heat exchanger 16) and then enters the high-temperature storage tank 18 for storage, achieving heat of compression storage. The working fluid at the outlet of high-temperature storage tank 18 enters the third heat exchanger 19, cools down, and then returns to the low-temperature storage tank 17 for storage, completing the utilization of heat of compression. The compressed gas energy storage unit 1 of this application can realize the storage and release of gas energy, as well as the storage and utilization of heat of compression, offering high flexibility. In this embodiment, the working fluid circulating in the compressed gas energy storage unit 1 is CO2. It should be noted that in this embodiment, each heat exchanger includes a first flow channel and a second flow channel for mutual heat exchange. The first flow channel has a low-temperature medium inlet and a high-temperature medium outlet at both ends, and the second flow channel has a high-temperature medium inlet and a low-temperature medium outlet at both ends. The working fluid enters from the low-temperature medium inlet and flows out from the high-temperature medium outlet with an increased temperature. The working fluid enters from the high-temperature medium inlet and flows out from the low-temperature medium outlet with a decreased temperature.

[0067] The Brayton cycle power generation unit 2 includes a second compressor 21, a third heat exchanger 19, a second expander 22, and a fourth heat exchanger 23 connected in sequence to form a closed cycle. In some embodiments, a preheater 24 is provided between the third heat exchanger 19 and the second compressor 21. The working fluid from the outlet of the second compressor 21 enters the preheater 24, which can appropriately preheat the working fluid flowing in the Brayton cycle power generation unit. The preheated working fluid enters the third heat exchanger 19 and exchanges heat with the compression heat from the high-temperature storage tank 18 to increase its temperature. The heated working fluid enters the second expander 22 to expand and do work. After doing work, the working fluid enters the fourth heat exchanger 23 to exchange heat with the cold energy from the cold energy utilization unit to decrease its temperature. By utilizing the compression heat of the compressed gas energy storage unit 1 and the cold energy of the cryogenic fluid fuel to heat or cool the working fluid flowing in the Brayton cycle, the utilization rate of compression heat and cold energy is improved. The cryogenic fluid fuel after heat exchange enters the waste heat utilization unit 4 and can be used for combustion power generation. It should be noted that, in this embodiment, the heating stage refers to the stage from when the working fluid is discharged from the outlet of the second compressor 21 to when it enters the second expander 22, and the cooling stage refers to the stage from when the working fluid is discharged from the outlet of the second expander 22 to when it enters the second compressor 21. In this embodiment, the working fluid in the Brayton cycle power generation unit 2 cycle is defined as the first cycle working fluid, which is one or more combinations of helium (He), nitrogen (N2), or argon (Ar).

[0068] The cold energy supply unit 3 provides cryogenic fluid fuel, which is used to cool the working fluid in the cooling phase of the Brayton cycle power generation unit 2. The cryogenic fluid fuel absorbs the heat energy of the working fluid in the cooling phase and then vaporizes. The cold energy supply unit 3 includes a connected cryogenic storage tank (not shown in the figure) and a first booster pump 31. The outlet of the first booster pump 31 is connected to the cryogenic medium inlet of the fourth heat exchanger 23. In this embodiment, the cryogenic fluid fuel provided by the cold energy supply unit 3 is below -150°C. Cryogenic fluid fuel below -150°C has a better cooling effect and lowers the temperature of the working fluid in the Brayton cycle power generation unit 2, reducing the lower limit of work done and improving the power generation efficiency of the Brayton cycle power generation unit 2. Furthermore, the vaporized fluid fuel after heat exchange does not require reheating during combustion, achieving rational utilization of cold energy. Specifically, the LNG cold energy (0.1 MPa, -162℃) has a heat exchange temperature difference of about 20K between the LNG cold energy and the Brayton cycle unit 2, which greatly reduces the serious waste of LNG cold energy utilization. In addition, the heat exchange between the circulating medium in the heating stage of the Brayton cycle unit 2 and the compression heat of the compressed gas energy storage unit 1 also solves the problem of the compression heat of about 180℃ generated in the process of compressing the gas, improving the work quality of the first cycle working medium and the work efficiency of the Brayton cycle.

[0069] Furthermore, it also includes a distributor 5, whose inlet is connected to the high-temperature medium outlet of the fourth heat exchanger 23, and whose outlet is connected to the waste heat utilization unit 4 and the user side. After entering the fourth heat exchanger 23, the cryogenic fluid fuel is heated and vaporized. The vaporized cryogenic fluid fuel is discharged from the high-temperature medium outlet of the fourth heat exchanger 23 and then enters the distributor 5 for diversion, enabling diversified utilization of the cryogenic fluid fuel. For example, a portion of the cryogenic fluid fuel can be used for combustion power generation, and another portion can be supplied to users. Technicians can change the use of the cryogenic fluid fuel according to actual needs.

[0070] Waste heat utilization unit 4 connects cold energy supply unit 3 and compressed gas energy storage unit 1. Waste heat utilization unit 4 is used to receive and burn the gasified cryogenic fluid fuel. The waste heat generated by the combustion of the cryogenic fluid fuel is used to heat the circulating working fluid in the energy release stage in the compressed gas energy storage unit. Specifically, waste heat utilization unit 4 includes an air compressor 44, a combustion chamber 41, a third expander 42, and a thermal energy storage tank 43 connected in sequence. Air compressor 44 is used to supply oxygen required for combustion to combustion chamber 41. The inlet of combustion chamber 41 is connected to the outlet of cold energy supply unit 3 and the outlet of air compressor 44, and the outlet of thermal energy storage tank 43 is connected to the high-temperature medium inlet of first heat exchanger 12. In the cold energy supply unit 3, the low-temperature fluid fuel is vaporized after heat exchange in the fourth heat exchanger 23. The vaporized low-temperature fluid fuel enters the combustion chamber 41 and is burned under the action of air supplied by the air compressor 44. The heat energy generated by combustion is used to drive the third expander 42 to expand and generate electricity. The waste heat after the low-temperature fluid fuel has done work is stored in the thermal energy storage tank 43. The heat energy stored in the thermal energy storage tank 43 enters the first heat exchanger 12 and exchanges heat with the circulating working fluid at the outlet of the high-pressure storage tank 11, thereby increasing the temperature of the circulating working fluid at the outlet of the high-pressure storage tank 11 and improving the working capacity and quality of the circulating working fluid. In some embodiments, the power output terminal of the third expander 42 can also be connected to the compressed gas energy storage unit 1 to provide the electrical energy required by the compressed gas energy storage unit 1 during the energy storage and release stages. In this embodiment, the waste heat comes from the exhaust heat of the third expander 42 after it has done work and generated electricity but has not been fully utilized. In some embodiments, the waste heat can also be other types of waste heat generated after the combustion of the low-temperature fluid fuel, and this embodiment does not limit this.

[0071] In conventional compressed gas energy storage units, the temperature of the compression heat during the energy storage stage is relatively low. During the energy release stage, relying solely on the compression heat is insufficient to raise the gas temperature to an optimal level, keeping the gas's work capacity within the high-pressure, low-temperature range. This results in poor work efficiency, thus limiting the overall efficiency of the CO2 compression system. Furthermore, cryogenic fluids release a significant amount of cold energy during vaporization. Current methods primarily utilize this cold energy for the condensation of gases (such as CO2). However, excessively low-temperature fluids can cause icing during gas condensation. Current techniques often involve heating the cryogenic fluid with air to a usable temperature before using its cold energy to liquefy the gas, leading to substantial waste of cold energy.

[0072] In this embodiment, the cryogenic fluid fuel cools the working fluid in the cooling stage of the Brayton cycle power generation unit 2, which not only reduces the problem of cold energy waste, but also the cold energy supply unit 3 cools the working fluid at the outlet of the second expander 22 to a lower temperature, lowering the lower limit of its work capacity. The compression heat generated by the compressed gas energy storage unit 1 in the energy storage stage is used to heat the circulating working fluid of the Brayton cycle power generation unit 2, raising the upper limit of the work capacity of the Brayton cycle power generation unit 2, improving its work capacity, and thus improving power generation efficiency. The Brayton cycle power generation unit 2 can generate electricity in a cycle to replenish the electricity required for the operation of the compressed gas energy storage unit 1, solving the problem of insufficient power generation and difficulty in maintaining high output for a long time during peak electricity demand periods.

[0073] After heat exchange with the Brayton cycle unit 2, the low-temperature fluid fuel absorbs heat and vaporizes before combustion. The waste heat from combustion is used to heat the working fluid in the compressed gas energy storage unit 1 during the energy release phase. This improves the temperature, work quality, and work capacity of the working fluid in the compressed gas energy storage unit 1, and extends the energy release time. This is beneficial for meeting the needs of long-term and deep peak shaving, and also increases peak load capacity. It has significant advantages due to its lower investment and operating costs. Compared to the more widely used compressed gas energy storage units, which introduce the gas circulating working fluid into a heating device for reheating before expansion to achieve a higher work quality, this application improves the utilization rate of waste heat by using waste heat to exchange heat in the first heat exchanger 12.

[0074] Specifically, during peak electricity consumption periods, CO2 in the high-pressure storage tank 11 flows through the first heat exchanger 12 to recover the waste heat of the exhaust gas (referring to the waste heat of the exhaust gas after expansion by the first expander 13) before entering the first expander 13 to expand and do work. The expansion process adopts a multi-stage expansion and inter-stage reheating expansion method. After expansion, the low-temperature and low-pressure CO2 is stored in the low-pressure storage tank 14, which facilitates the reuse of the circulating working fluid CO2 during off-peak electricity consumption periods.

[0075] During off-peak electricity demand, the remaining electricity in the grid drives the first compressor 15 to compress low-pressure CO2. The compression process is carried out in a multi-stage compression and interstage cooling manner. The CO2 compressed to the rated pressure is stored in the high-pressure storage tank 11, which is convenient for release and expansion to generate electricity during peak electricity demand. The compression heat generated during the compression process is stored in the high-temperature storage tank 18 through the third heat exchanger 19.

[0076] During peak electricity demand periods or when producing natural gas, the Brayton cycle power generation unit 2 operates. The heat energy stored in the high-temperature storage tank 18 is transferred to the first circulating working fluid via the third heat exchanger 19. The high-temperature, high-pressure first circulating working fluid flows through the second expander 22 to expand and perform work. After performing work, the low-temperature, low-pressure first circulating working fluid is further heated by the fourth heat exchanger 23. The cooled first circulating working fluid is finally pressurized by the second compressor 21. Given the difficulty of cold storage, the pressurized first circulating working fluid can first be preheated by the preheater 24, then heated by the third heat exchanger 19, and finally pressurized and heated first circulating working fluid enters the second expander 22 for cyclic expansion and work. After heat exchange by the third heat exchanger 19, the cooled working fluid flows to the low-temperature storage tank 17 for storage.

[0077] <Second Implementation Method>

[0078] like Figure 2 As shown, the second embodiment of the present invention provides a combined power generation system based on compressed gas energy storage. The difference from the first embodiment is that the Brayton cycle power generation unit 2 includes a second compressor 21, a fifth heat exchanger 25, a third heat exchanger 19, a second expander 22, and a fourth heat exchanger 23 connected sequentially to form a closed cycle. The combined cycle power generation system also includes:

[0079] Water separation device 61, the inlet of water separation device 61 is connected to the low temperature medium outlet of the first heat exchanger 12, and the outlet of water separator is connected to the high temperature medium inlet of the fifth heat exchanger 25.

[0080] The gas separation device 62 is connected to the low-temperature medium outlet of the fifth heat exchanger 25.

[0081] In the Brayton cycle power generation unit, the working fluid from the outlet of the second compressor 21 enters the fifth heat exchanger 25, where it exchanges heat with the waste heat from the outlet of the water separator 61, thus increasing its temperature. It then enters the third heat exchanger 19, where it exchanges heat with the working fluid from the outlet of the high-temperature storage tank 18, further increasing its temperature. Finally, it enters the second expander 22 to perform work. The working fluid from the outlet of the second expander 22 enters the fourth heat exchanger 23, where it exchanges heat with the cold energy of the low-temperature fluid fuel, thus decreasing its temperature and returning to the compressor. The working fluid from the outlet of the second compressor 21, after being heated by the fifth heat exchanger 25, enters the third heat exchanger 19 for further heat exchange, increasing the temperature of the working fluid in the Brayton cycle power generation unit 2 during the heating phase and improving its work-performing capacity.

[0082] In the waste heat utilization unit 4, the low-temperature fluid fuel, after heat exchange in the fourth heat exchanger 23, is gasified and enters the combustion chamber 41 for combustion. The waste heat generated by combustion is stored in the thermal energy storage tank 43. The thermal energy stored in the thermal energy storage tank 43 enters the first heat exchanger 12 to exchange heat with the working fluid at the outlet of the high-pressure storage tank 11, increasing the temperature of the working fluid at the outlet of the high-pressure storage tank 11, thereby improving the work quality of the working fluid in the energy release stage of the compressed gas energy storage unit 1. The working fluid with a certain amount of thermal energy from the low-temperature medium outlet of the first heat exchanger 12 enters the water separation device 61 to separate a portion of the water. The separated circulating working fluid enters the fifth heat exchanger 25 to exchange heat with the working fluid at the outlet of the second compressor 21, and its temperature decreases, condensing into a liquid, which facilitates the capture of the working fluid.

[0083] On the other hand, the high-temperature exhaust gas discharged from the waste heat utilization unit 4 exchanges heat with the compressed gas energy storage unit 1 through the first heat exchanger 12. The low-temperature exhaust gas will enter the water separation device 61 to separate the water generated during combustion and circulation. Then it flows through the fifth heat exchanger 25, which recovers and utilizes the remaining heat energy in the exhaust gas and makes better use of the cold energy in the Brayton cycle system, further improving the efficiency of cold energy utilization and exhaust gas waste heat utilization. Finally, the liquid CO2 is collected by the gas separation device 62, which can not only provide users with pure CO2, but also achieve zero carbon emissions from the circulation system.

[0084] Since the temperature of the first circulating working medium after pressurization is close to the saturation point of low-pressure CO2, by adjusting the pressure ratio and flow rate of the second compressor 21, the temperature of the traditional cryogenic cooling medium in the circulating loop can be effectively avoided from being too low, which could cause the CO2 circulating working medium to cool below the triple point and thus freeze, thereby improving the reliability of the system operation.

[0085] Furthermore, the pressurized first circulating working fluid, acting as a cooling medium, can condense the CO2 circulating working fluid in the exhaust gas at a lower pressure. The liquid CO2 can be directly captured by the gas separation device 62 without the need for a compression device or to reduce the outlet temperature of the combustion chamber 41 and the back pressure of the third expander 42. Therefore, it can greatly save the system's power consumption, significantly save subsequent power consumption, and at the same time, replenish the absorbed exhaust gas waste heat to the Brayton cycle power generation unit 2, significantly improving the system's cycle efficiency and realizing the rational utilization of energy.

[0086] <Third Implementation Method>

[0087] like Figure 3 As shown, the third embodiment of the present invention provides a combined power generation system based on compressed gas energy storage, which differs from the second embodiment in that it further includes:

[0088] A second booster pump 71, a sixth heat exchanger 72, a fourth expander 73, and a seventh heat exchanger 74 are sequentially connected to form an Organic Rankine Cycle (ORC) loop. The low-temperature medium inlet of the sixth heat exchanger 72 is connected to the outlet of the second booster pump 71; the high-temperature medium outlet of the sixth heat exchanger 72 is connected to the inlet of the fourth expander 73; the high-temperature medium inlet of the sixth heat exchanger 72 is connected to the outlet of the first expander 13; and the low-temperature medium outlet of the sixth heat exchanger 72 is connected to the inlet of the low-pressure storage tank 14. The low-temperature medium inlet of the seventh heat exchanger 74 is connected to the outlet of the gas separator 62; and the low-temperature medium outlet of the seventh heat exchanger 74 is connected to the inlet of the second booster pump 71. In this embodiment, the working fluid flowing in the Organic Rankine Cycle loop is defined as the second circulating working fluid. Besides propane and butane, the second circulating working fluid also includes other common ORC working fluids such as ethylene.

[0089] In the ORC cycle system loop, the second booster pump 71 pressurizes the liquid second circulating working fluid. The pressurized second circulating working fluid flows through the sixth heat exchanger 72 and exchanges heat with the low-pressure, low-temperature CO2 at the outlet of the first expander 13 in the energy release stage. The cooled CO2 is stored in the low-temperature storage tank 17. The heated and vaporized second circulating working fluid flows through the fourth expander 73 to expand and do work. The outlet of the fourth expander 73 is connected to the high-temperature medium inlet of the seventh heat exchanger 74. The low-temperature medium inlet of the seventh heat exchanger 74 is connected to the outlet of the gas separation device 62. One branch of the gas separation device 62... The circuit collects liquid CO2, which can also replenish the working fluid leaking from the compressed gas energy storage unit 1, achieving zero carbon emissions from the circulation system. Another branch connected to the outlet of the gas separation device 62 is connected to the low-temperature medium inlet of the seventh heat exchanger 74 to provide cooling energy to the seventh heat exchanger 74. The gaseous second circulating working fluid after expansion and work is condensed in the seventh heat exchanger 74. The outlet of the seventh heat exchanger 74 is connected to the inlet of the second booster pump 71. The condensed liquid second circulating working fluid is pressurized by the second booster pump 71 to provide power for the ORC cycle.

[0090] In this embodiment, a sixth heat exchanger 72 is added at the outlet of the first expander 13 to further reduce the temperature of the gas after expansion and work during the energy release stage. This not only solves the problem of storing high-temperature gas, but also allows this heat energy to be used for work in the organic Rankine cycle, further improving the system's cycle efficiency. Furthermore, the seventh heat exchanger 74 absorbs the cold energy of the gas at the outlet of the gas separator 62, improving the utilization efficiency of cold energy in the cycle system and enhancing the work quality of the second circulating working fluid, thus further improving the power generation efficiency of the organic Rankine cycle system.

[0091] Furthermore, the first compressor 15 and / or the second compressor 21 can be single-stage or multi-stage compression, with interstage cooling for multi-stage compression. One or more of the first to fourth expanders (13, 22, 42, 73) can be single-stage or multi-stage expansion, with interstage heating for multi-stage expansion; specifically, the first to fourth expanders (13, 22, 42, 73) are turbines, which generate electricity. One or more of the first to seventh heat exchangers (12, 16, 19, 25, 72, 74) can be single-stage or multi-stage heat exchange. Technicians can select the number of compression, expansion, and heat exchange stages according to actual needs; this embodiment does not limit this selection.

[0092] Those skilled in the art will understand that specific technical features in various embodiments can be adaptively split or combined. Such splitting or combining of specific technical features will not cause the technical solution to deviate from the principles of the present invention; therefore, the technical solutions after splitting or combining will all fall within the protection scope of the present invention.

[0093] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0094] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A combined cycle power generation system based on compressed gas energy storage, characterized in that, include: Brayton cycle power generation unit; A compressed gas energy storage unit is connected to the power output terminal of the Brayton cycle power generation unit; A cold energy supply unit is used to provide cryogenic fluid fuel, which is used to cool the working fluid in the cooling phase of the Brayton cycle power generation unit. The cryogenic fluid fuel absorbs the heat energy of the working fluid in the cooling phase and then vaporizes. The waste heat utilization unit connects the cold energy supply unit and the compressed gas energy storage unit. The waste heat utilization unit is used to receive and burn the gasified low-temperature fluid fuel. The waste heat generated by the combustion of the low-temperature fluid fuel is used to heat the circulating working fluid in the energy release stage in the compressed gas energy storage unit. The compressed gas energy storage unit includes: High-pressure storage tank; The first heat exchanger has a high-temperature medium inlet connected to the outlet of the waste heat utilization unit, and a low-temperature medium inlet connected to the outlet of the high-pressure storage tank. The first expander is connected to the high-temperature medium outlet of the first heat exchanger. A low-pressure storage tank is connected to the outlet of the first expander; The first compressor is connected to the outlet of the low-pressure storage tank; The second heat exchanger has a high-temperature medium inlet connected to the outlet of the first compressor, and a low-temperature medium outlet connected to the inlet of the high-pressure storage tank. The outlet of the cryogenic storage tank is connected to the cryogenic medium inlet of the second heat exchanger. A high-temperature storage tank is connected to the high-temperature medium outlet of the second heat exchanger; The third heat exchanger has a high-temperature medium inlet connected to the outlet of the high-temperature storage tank, and a low-temperature medium outlet connected to the inlet of the low-temperature storage tank. The compressed gas energy storage unit generates compression heat during the energy storage phase, and the compression heat is used to heat the circulating working fluid in the heating phase of the Brayton cycle power generation unit.

2. The combined cycle power generation system based on compressed gas energy storage according to claim 1, characterized in that, The Brayton cycle power generation unit includes: Second compressor; The preheater has its inlet connected to the outlet of the second compressor, and its outlet is connected to the low-temperature medium inlet of the third heat exchanger. The inlet of the second expander is connected to the high-temperature medium outlet of the third heat exchanger; The fourth heat exchanger has a high-temperature medium inlet connected to the outlet of the second expander, a low-temperature medium outlet connected to the inlet of the second compressor, a low-temperature medium inlet connected to the cold energy supply unit, and a high-temperature medium outlet connected to the waste heat utilization unit.

3. The combined cycle power generation system based on compressed gas energy storage according to claim 1, characterized in that, The Brayton cycle power generation unit includes: Second compressor; The fifth heat exchanger has a low-temperature medium inlet connected to the outlet of the second compressor, and a high-temperature medium outlet connected to the low-temperature medium inlet of the third heat exchanger. The inlet of the second expander is connected to the high-temperature medium outlet of the third heat exchanger; The fourth heat exchanger has a high-temperature medium inlet connected to the outlet of the second expander, a low-temperature medium outlet connected to the inlet of the second compressor, a low-temperature medium inlet connected to the cold energy supply unit, and a high-temperature medium outlet connected to the waste heat utilization unit. The combined cycle power generation system also includes: A water separation device, wherein the inlet of the water separation device is connected to the low-temperature medium outlet of the first heat exchanger, and the outlet of the water separation device is connected to the high-temperature medium inlet of the fifth heat exchanger; The gas separation device is connected to the low-temperature medium outlet of the fifth heat exchanger.

4. The combined cycle power generation system based on compressed gas energy storage according to claim 3, characterized in that, The cold energy supply unit includes a cold energy storage tank and a first booster pump connected in series. The outlet of the first booster pump is connected to the low-temperature medium inlet of the fourth heat exchanger.

5. The combined cycle power generation system based on compressed gas energy storage according to claim 4, characterized in that, It also includes a distributor, the inlet of which is connected to the high-temperature medium outlet of the fourth heat exchanger, and one of the outlets of the distributor is connected to the waste heat utilization unit.

6. The combined cycle power generation system based on compressed gas energy storage according to claim 5, characterized in that, The waste heat utilization unit includes: Air compressor; The combustion chamber has its inlet connected to the outlet of the cold energy supply unit and the outlet of the air compressor; The third expander has its inlet connected to the outlet of the combustion chamber, and generates electricity by expanding. A thermal energy storage tank is used to store the waste heat after the combustion of the cryogenic fluid fuel. The inlet of the thermal energy storage tank is connected to the outlet of the third expander, and the outlet of the thermal energy storage tank is connected to the high-temperature medium inlet of the first heat exchanger.

7. The combined cycle power generation system based on compressed gas energy storage according to claim 6, characterized in that, It also includes an organic Rankine cycle, which comprises: Second booster pump; The sixth heat exchanger has a high-temperature medium inlet connected to the outlet of the first expander, a low-temperature medium outlet connected to the inlet of the low-pressure storage tank, and a low-temperature medium inlet connected to the outlet of the second booster pump. The fourth expander has its inlet connected to the high-temperature medium outlet of the sixth heat exchanger; The seventh heat exchanger has a high-temperature medium inlet connected to the outlet of the fourth expander, a low-temperature medium outlet connected to the inlet of the second booster pump, and a low-temperature medium inlet connected to the outlet of the gas separation device.

8. The combined cycle power generation system based on compressed gas energy storage according to claim 7, characterized in that, The circulating working fluid in the organic Rankine cycle is propane, butane, or ethylene.

9. The combined cycle power generation system based on compressed gas energy storage according to any one of claims 1 to 8, characterized in that, The cryogenic fluid fuel is a cryogenic fluid fuel with a temperature below -150°C.

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