A dual-cycle solar thermal power generation system and method for compressed CO2 energy storage

Abstract

This application proposes a dual-cycle solar thermal power generation system and method for compressed CO₂ energy storage. This application includes a CO₂ dual-cycle power generation system, a compressed CO₂ energy storage system, and a concentrating solar heat collection system. The CO₂ dual-cycle power generation system includes a supercritical CO₂ Brayton cycle system and a transcritical CO₂ Brayton cycle system in which the CO₂ working fluid circulates, and the two are heat-exchanged and connected; the compressed CO₂ energy storage system is connected to the supercritical CO₂ Brayton cycle system and is used to input the CO₂ working fluid to the supercritical CO₂ Brayton cycle system or receive the CO₂ working fluid output by the supercritical CO₂ Brayton cycle system under different working conditions; the concentrating solar heat collection system uses solar energy to heat the CO₂ working fluid entering the supercritical CO₂ Brayton cycle system and the compressed CO₂ energy storage system. This application constitutes a dual cycle and an energy storage system with pure CO₂ as the working fluid, maximizing the energy utilization rate.

Description

Technical Field

[0001] This application relates to the technical field of solar power generation, and particularly relates to a dual-cycle solar thermal power generation system and method for compressed CO2 energy storage. Background Art

[0002] The large-scale development of solar thermal power generation technology is of great significance to the change of China's energy structure. Traditional solar thermal power generation systems mainly use the Rankine cycle for power generation, but the efficiency is relatively low. The supercritical carbon dioxide (S-CO2) Brayton cycle has a higher power generation efficiency, and its working fluid CO2 has the advantages of wide sources, not easily cracked at high temperatures, non-toxic, and harmless, and is widely used in fields such as solar power generation and nuclear power cooling. The high-temperature CO2 at the outlet of the turbine in the traditional supercritical CO2 Brayton cycle is still at a relatively high temperature after being cooled by the recuperator, and directly entering the cooler will cause heat waste, which limits the improvement of the power generation efficiency of the supercritical CO2 Brayton cycle. The transcritical CO2 cycle also uses CO2 as the working fluid, and the system operating temperature is much lower than that of the supercritical CO2 Brayton cycle, and can be used to recover the heat at the outlet of the turbine in the supercritical CO2 Brayton cycle.

[0003] Developing an efficient and economical energy storage system is crucial for the future development of solar energy. Currently, pumped hydro energy storage and compressed air are the most commonly used energy storage methods, and pumped hydro energy storage units account for 93% of the installed capacity of energy storage projects in China, but it has relatively high requirements for the selection of geographical locations. Compressed air energy storage technology has the advantages of high efficiency and flexible site selection. Since the critical pressure and temperature of CO2 are p c = 7.39 MPa and Tc = 31.1 °C respectively, compared with air, the critical temperature is lower, so CO2 is more likely to reach the critical state. Near the critical point, the density of CO2 is close to that of a liquid, and the temperature and pressure change greatly, which greatly reduces the power consumption of the compressor.

[0004] Considering the technical characteristics of compressed CO2 energy storage, supercritical CO2 Brayton cycle, and transcritical CO2 cycle comprehensively, if they are coupled, it will constitute a dual cycle and energy storage system with pure CO2 as the working fluid, which has higher power generation efficiency and good engineering application prospects. Summary of the Invention

[0005] This application aims to solve at least one of the technical problems in the related technologies to some extent. This application aims to provide a dual-cycle solar thermal power generation system and method for compressed CO2 energy storage to achieve efficient utilization of solar energy.

[0006] To achieve the above object, a dual-cycle solar thermal power generation system for compressed CO2 energy storage proposed in this application includes:

[0007] A CO2 dual-cycle power generation system, which includes a supercritical CO2 Brayton cycle system and a transcritical CO2 Brayton cycle system in which CO2 working fluid circulates; wherein the supercritical CO2 Brayton cycle system is heat-exchange connected to the transcritical CO2 Brayton cycle system;

[0008] A compressed CO2 energy storage system, which is connected to the supercritical CO2 Brayton cycle system and is used to input CO2 working fluid to the supercritical CO2 Brayton cycle system or receive the CO2 working fluid output by the supercritical CO2 Brayton cycle system under different working conditions; and

[0009] A concentrating solar collector system, which is respectively connected to the supercritical CO2 Brayton cycle system and the compressed CO2 energy storage system, and uses solar energy to heat the CO2 working fluid entering the supercritical CO2 Brayton cycle system and the compressed CO2 energy storage system.

[0010] In some embodiments, the supercritical CO2 Brayton cycle system includes a first cycle system and a recirculation path; in the first cycle system, according to the flow direction of the CO2 working fluid, it includes a main turbine, the hot side of a high-temperature gas heater, the hot side of a low-temperature gas heater, a first condenser, a main compressor, the cold side of the low-temperature gas heater, and the cold side of the high-temperature gas heater connected in sequence; in the recirculation path, a recirculation compressor is included, and the input end and the output end of the recirculation compressor are respectively connected to the output end of the hot side of the low-temperature gas heater and the output end of the cold side of the low-temperature gas heater.

[0011] In some embodiments, an intermediate heat exchanger is provided between the hot side of the low-temperature gas heater and the first condenser; wherein, the hot side of the low-temperature gas heater is connected to the hot side of the intermediate heat exchanger and is used to heat the CO2 working fluid circulating in the transcritical CO2 Brayton cycle system.

[0012] In some embodiments, according to the flow direction of the CO2 working fluid, the transcritical CO2 Brayton cycle system includes a booster pump, a second turbine, and a second condenser connected in sequence; the input end and the output end of the cold side of the intermediate heat exchanger are respectively connected to the booster pump and the second turbine.

[0013] In some embodiments, the input end and the output end of the concentrating solar collector system are respectively connected to the output end of the cold side of the low-temperature gas heater and the input end of the main turbine.

[0014] In some embodiments, the compressed CO2 energy storage system includes a third turbine, a second compressor, a high-pressure tank, a gas boiler, and a low-pressure tank arranged in sequence along the flow direction of the CO2 working fluid; wherein the output end of the gas boiler is connected to the input end of the main turbine; the output end of the first condenser is connected to the low-pressure tank; and the input end of the third turbine is connected to the output end of the concentrating solar collector system.

[0015] In some embodiments, a first valve is provided on the pipeline connecting the input end of the third turbine and the output end of the concentrating solar collector system.

[0016] In some embodiments, a second valve is provided on the pipeline connecting the output end of the first condenser and the input end of the low-pressure tank.

[0017] In some embodiments, the concentrating solar collector system includes a central absorption tower, an absorber, and solar reflectors; wherein the absorber is arranged on the central absorption tower; and a plurality of solar reflectors are arranged on the periphery of the central absorption tower to concentrate solar energy into the absorber to heat the CO2 working fluid.

[0018] In some embodiments, the present application proposes a dual-cycle solar thermal power generation method for compressed CO2 energy storage, which uses the dual-cycle solar thermal power generation system described in any of the above embodiments for power generation, including the following processes:

[0019] The CO2 working fluid heated by the concentrating solar collector system enters the supercritical CO2 Brayton cycle system and the compressed CO2 energy storage system respectively;

[0020] The CO2 working fluid entering the supercritical CO2 Brayton cycle system circulates in the first cycle system for power generation; wherein a part of the CO2 working fluid output from the hot side of the low-temperature gas heater is input to the cold-side output end of the low-temperature gas heater through a recirculation compressor through a recirculation path; at the same time, when the transcritical CO2 Brayton cycle system generates power, the remaining CO2 working fluid output from the hot side of the low-temperature gas heater exchanges heat with the CO2 working fluid circulating in the transcritical CO2 Brayton cycle system.

[0021] When the CO2 working fluid entering the compressed CO2 energy storage system is in the energy storage condition, the CO2 working fluid enters the third turbine to drive the second compressor to rotate, compresses the critical CO2 working fluid in the low-pressure tank, and stores it in the high-pressure tank; in the energy release condition, the high-pressure CO2 working fluid is output from the high-pressure tank, and after being heated by the gas boiler, enters the first cycle system.

[0022] Additional aspects and advantages of the present application will be given in part in the following description, will become apparent in part from the following description, or will be understood through the practice of the present application. Description of the Drawings

[0023] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description of embodiments in conjunction with the accompanying drawings, where:

[0024] Figure 1 is a schematic structural diagram of a dual-cycle solar thermal power generation system with compressed CO2 energy storage proposed in an embodiment of the present application;

[0025] Figure 2 is a schematic structural diagram of a dual-cycle solar thermal power generation system with compressed CO2 energy storage proposed in an embodiment of the present application;

[0026] Figure 3 is a flowchart of a method for dual-cycle solar thermal power generation with compressed CO2 energy storage proposed in an embodiment of the present application;

[0027] In the figure, 1, main turbine; 2, high-temperature gas heater; 3, low-temperature gas heater; 4, intermediate heat exchanger; 5, recirculation compressor; 6, first condenser; 7, main compressor; 8, low-pressure tank; 9, second compressor; 10, third turbine; 11, high-pressure tank; 12, gas boiler; 13, second turbine; 14, second condenser; 15, booster pump; 16, central absorption tower; 17, absorber; 18, heliostat; 19, first valve; 20, second valve. Detailed Embodiments

[0028] The embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary only for explaining the present application and should not be construed as limiting the present application. On the contrary, the embodiments of the present application include all changes, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0029] Refer to Figure 1To achieve the above object, a dual-cycle solar thermal power generation system for compressed CO2 energy storage proposed in this application includes a CO2 dual-cycle power generation system, a compressed CO2 energy storage system, and a concentrating solar collector system. The CO2 dual-cycle power generation system includes a supercritical CO2 Brayton cycle system and a transcritical CO2 Brayton cycle system in which a CO2 working fluid circulates; the supercritical CO2 Brayton cycle system and the transcritical CO2 Brayton cycle system are heat-exchanged and connected. In other words, the CO2 dual-cycle power generation system includes a supercritical CO2 Brayton cycle system and a transcritical CO2 Brayton cycle system, in both of which a CO2 working fluid circulates. Since the temperature at the turbine outlet in the supercritical CO2 Brayton cycle system is relatively high, to avoid waste of heat, the transcritical CO2 Brayton cycle system is used as the bottom cycle to recover the waste heat of the CO2 working fluid in the supercritical CO2 Brayton cycle system, and the supercritical CO2 Brayton cycle system and the transcritical CO2 Brayton cycle system are heat-exchanged and connected.

[0030] In this embodiment, the CO2 dual-cycle power generation system is coupled with the compressed CO2 energy storage system. Among them, the compressed CO2 energy storage system is connected to the supercritical CO2 Brayton cycle system and is used to input the CO2 working fluid into the supercritical CO2 Brayton cycle system under different working conditions to meet the power supply load of the CO2 dual-cycle power generation system; or, the compressed CO2 energy storage system receives the CO2 working fluid output from the supercritical CO2 Brayton cycle system and close to the critical point and stores it.

[0031] In this embodiment, the concentrating solar collector system is respectively connected to the supercritical CO2 Brayton cycle system and the compressed CO2 energy storage system, and it can use solar energy to heat the CO2 working fluid entering the supercritical CO2 Brayton cycle system and the compressed CO2 energy storage system. For example Figure 2 As shown, the concentrating solar collector system includes a central absorption tower 16, an absorber 17, and solar reflectors; the absorber 17 is arranged on the top of the central absorption tower 16; a plurality of solar reflectors are arranged on the periphery of the central absorption tower 16 to concentrate solar energy into the absorber 17 to heat the CO2 working fluid. The solar reflectors are heliostats 18, and solar energy can be concentrated into the top of the central absorption tower 16 through the heliostats 18 to generate high temperature, and then the absorber 17 is used to transfer the heat to the supercritical CO2 Brayton cycle system and the compressed CO2 energy storage system.

[0032] Therefore, in this embodiment, a CO2 dual-cycle power generation system is coupled with a compressed CO2 energy storage system, which has a higher energy storage efficiency compared to traditional compressed air energy storage. Moreover, in this application, the critical state of CO2 is more easily achieved. Near the critical point, the density of CO2 is close to that of a liquid and varies greatly with temperature and pressure, significantly reducing the work consumption of the compressor in the compressed CO2 energy storage system and greatly improving the overall energy storage efficiency. In addition, the CO2 dual-cycle power generation system incorporates a supercritical CO2 Brayton cycle system and a transcritical CO2 Brayton cycle system. Compared with the Rankine cycle power generation system in the related art, it can effectively improve the cycle efficiency and reduce the equipment volume. Therefore, this application constitutes a dual-cycle and energy storage system with pure CO2 as the working fluid, giving full play to the advantages of the two systems and maximizing the energy utilization rate, with good social and economic benefits and excellent engineering application prospects.

[0033] In some embodiments, the supercritical CO2 Brayton cycle system includes a first cycle system and a recirculation path. In the first cycle system, according to the flow direction of the CO2 working fluid, it includes a main turbine 1, the hot side of a high-temperature gas heater 2, the hot side of a low-temperature gas heater 3, a first condenser 6, a main compressor 7, the cold side of the low-temperature gas heater 3, and the cold side of the high-temperature gas heater 2 connected in sequence. In the recirculation path, there is a recirculation compressor 5, and the input end and output end of the recirculation compressor 5 are respectively connected to the hot-side output end and the cold-side output end of the low-temperature gas heater 3.

[0034] The first cycle system includes a main turbine 1, a high-temperature gas heater 2, a low-temperature gas heater 3, a first condenser 6, and a main compressor 7. The CO2 working fluid flowing into the main turbine 1 sequentially passes through the main turbine 1, the hot side of the high-temperature gas heater 2, the hot side of the low-temperature gas heater 3, the first condenser 6, the main compressor 7, the cold side of the low-temperature gas heater 3, and the cold side of the high-temperature gas heater 2. The input end and output end of the concentrating solar heat collection system are respectively connected to the cold-side output end of the high-temperature gas heater 2 and the input end of the main turbine 1, that is, the CO2 working fluid output from the cold side of the high-temperature gas heater 2 returns to the main turbine 1 after being heated by the concentrating solar heat collection system.

[0035] In this embodiment, the supercritical CO2 Brayton cycle system is a split-flow recompression S-CO2 Brayton cycle, that is, it further includes a recirculation path connected to the first cycle system. The recirculation path includes a recirculation compressor 5, and the input end of the recirculation compressor 5 is connected to the hot-side output end of the low-temperature gas heater 3; the output end of the recirculation compressor 5 is connected to the cold-side output end of the low-temperature gas heater 3.

[0036] In the supercritical CO2 Brayton cycle system of this embodiment, the circulation method of the CO2 working fluid is as follows: After the CO2 working fluid flows through the absorber 17 and is heated and raised in temperature, it enters the main turbine 1 to do work, and then flows into the high-temperature gas heater 2 to release heat and then enters the low-temperature gas heater 3 for further heat exchange; the CO2 working fluid flowing out from the hot side of the low-temperature gas heater 3 is split, and the first part of the CO2 working fluid enters the first condenser 6 after heat exchange with the CO2 working fluid circulating in the transcritical CO2 Brayton cycle system. The CO2 working fluid coming out from the first condenser 6 enters the main compressor 7 to be pressurized and then enters the cold side of the low-temperature gas heater 3; the remaining second part of the CO2 working fluid flowing out from the hot side of the low-temperature gas heater 3 passes through the recirculation compressor 5, and the CO2 working fluid flowing out from the recirculation compressor 5 converges with the CO2 working fluid flowing out from the cold side of the low-temperature gas heater 3, and then enters the cold side of the high-temperature gas heater 2 to absorb heat and raise the temperature. The CO2 working fluid coming out from the cold side of the high-temperature gas heater 2 enters the concentrating solar heat collection system to further absorb heat, completing one cycle.

[0037] In some embodiments, an intermediate heat exchanger 4 is provided between the hot side of the low-temperature gas heater 3 and the first condenser 6; the hot side of the low-temperature gas heater 3 is connected to the hot side of the intermediate heat exchanger 4 for heating the CO2 working fluid circulating in the transcritical CO2 Brayton cycle system.

[0038] Among them, the intermediate heat exchanger 4 with heat exchange function in this embodiment has the same structure as the high-temperature gas heater 2 and the low-temperature gas heater 3, that is, it all includes a hot side and a cold side that do not communicate with each other, and the media on the hot side and the cold side can conduct heat exchange. This is a conventional setting in this field and will not be elaborated. In the supercritical CO2 Brayton cycle system, since the temperature at the turbine outlet is relatively high, to avoid heat waste, a transcritical CO2 Brayton cycle system is used as the bottom cycle to recover the waste heat of the CO2 working fluid in the supercritical CO2 Brayton cycle system. An intermediate heat exchanger 4 can be provided between the hot side of the low-temperature gas heater 3 and the first condenser 6, that is, the hot side of the low-temperature gas heater 3 is connected to the hot side of the intermediate heat exchanger 4, and the CO2 working fluid circulating in the transcritical CO2 Brayton cycle system is passed through the cold side of the intermediate heat exchanger 4 for heat exchange. As Figure 1 and Figure 2 shown, the CO2 working fluid flowing out from the hot side of the low-temperature gas heater 3 is split, and the first part of the CO2 working fluid enters the first condenser 6 through heat exchange with the CO2 working fluid circulating in the intermediate heat exchanger 4 and the transcritical CO2 Brayton cycle system.

[0039] In some embodiments, according to the flow direction of the CO2 working fluid, the transcritical CO2 Brayton cycle system includes a booster pump 15, a second turbine 13 and a second condenser 14 connected in sequence; the cold side input end and output end of the intermediate heat exchanger 4 are respectively connected to the booster pump 15 and the second turbine 13.

[0040] Among them, the transcritical CO2 Brayton cycle system is used as the bottom cycle to recover the waste heat of the CO2 working medium in the supercritical CO2 Brayton cycle system. According to the flow direction of the CO2 working medium, it includes a booster pump 15, a second turbine 13, and a second condenser 14 connected in sequence. The cold-side input end of the intermediate heat exchanger 4 is connected to the output end of the booster pump 15, and the cold-side output end of the intermediate heat exchanger 4 is connected to the input end of the second turbine 13. That is, the high-pressure and low-temperature CO2 flowing out of the booster pump 15 enters the cold side of the intermediate heat exchanger 4 and is heated by the high-temperature CO2 working medium fluid of the supercritical CO2 cycle system, and then enters the second turbine 13 to expand and do work. After the work is completed, the CO2 working medium enters the second condenser 14, is cooled to the liquid state by cooling water, and finally enters the booster pump 15 to be pressurized to complete one cycle.

[0041] In some embodiments, the compressed CO2 energy storage system includes a third turbine 10, a second compressor 9, a high-pressure tank 11, a gas boiler 12, and a low-pressure tank 8 arranged in sequence according to the flow direction of the CO2 working medium; the output end of the gas boiler 12 is connected to the input end of the main turbine 1; the output end of the first condenser 6 is connected to the low-pressure tank 8; the input end of the third turbine 10 is connected to the output end of the concentrating solar collector system.

[0042] The compressed CO2 energy storage system includes a third turbine 10, a second compressor 9, a high-pressure tank 11, a gas boiler 12, and a low-pressure tank 8 arranged in sequence according to the flow direction of the CO2 working medium. In this embodiment, the third turbine 10 and the second compressor 9 rotate coaxially; and the input end of the third turbine 10 is connected to the output end of the concentrating solar collector system, and a first valve 19 is provided on the connecting pipeline between the two. In addition, the output end of the first condenser 6 is respectively connected to the main compressor 7 and the low-pressure tank 8, and a second valve 20 is provided on the connecting pipeline between the output end of the first condenser 6 and the input end of the low-pressure tank 8. In other words, the CO2 working medium at the output end of the first condenser 6 is also divided into two parts. One part enters the main compressor 7 to be pressurized, absorbs heat in the low-temperature gas heater 3, and then mixes with the CO2 working medium at the outlet of the recirculation compressor 5; the other part enters the low-pressure tank 8 in the compressed CO2 energy storage system for energy storage after the second valve 20 is opened.

[0043] Exemplarily, in the energy storage condition of the compressed CO2 energy storage system of this embodiment, the heat storage time is from 8:00 to 16:00, and the heat storage duration is 8 hours; in the heat storage condition, the CO2 working fluid first flows through the absorber 17 of the concentrating solar collector system to absorb heat, generating high-temperature and high-pressure carbon dioxide. Part of it enters the main turbine 1 to generate electricity to meet the electricity demand of the normal load, and the other part enters the third turbine 10 to drive the second compressor 9 to compress the CO2 in the critical state. The high-pressure CO2 working fluid compressed by the compressor enters the high-pressure tank 11 for storage. In the energy release condition of the compressed CO2 energy storage system, the heat release time is from 0:00 to 8:00 and from 16:00 to 24:00, and the heat release duration is 16 hours. Among them, the high-pressure CO2 working fluid stored in the high-pressure tank 11 flows out of the high-pressure tank 11, enters the gas boiler 12 for heating, and then enters the main turbine 1 of the S-CO2 Brayton cycle to do work to meet the electricity demand of users. The CO2 working fluid flowing out of the main turbine 1 reheats the CO2 working fluid circulating in the transcritical CO2 cycle system, and then enters the first condenser 6 to be cooled to near the critical point. The uncompressed CO2 flowing out of the first condenser 6 is stored in the low-pressure tank 8 to complete the cycle period.

[0044] In some embodiments, the present application proposes a dual-cycle solar thermal power generation method for compressed CO2 energy storage, as Figure 3 shown, using the dual-cycle solar thermal power generation system in any of the above embodiments for power generation, including the following processes:

[0045] S1: The CO2 working fluid heated by the concentrating solar collector system enters the supercritical CO2 Brayton cycle system and the compressed CO2 energy storage system respectively;

[0046] S2: The CO2 working fluid entering the supercritical CO2 Brayton cycle system circulates in the first cycle system for power generation; among them, a part of the CO2 working fluid output from the hot side of the low-temperature gas heater 3 is input to the cold-side output end of the low-temperature gas heater 3 through the recirculation compressor 5 through the recirculation path; at the same time, when the transcritical CO2 Brayton cycle system generates electricity, the remaining CO2 working fluid output from the hot side of the low-temperature gas heater 3 exchanges heat with the CO2 working fluid circulating in the transcritical CO2 Brayton cycle system;

[0047] S3: When the CO2 working fluid entering the compressed CO2 energy storage system is in the energy storage condition, the CO2 working fluid enters the third turbine 10 to drive the second compressor 9 to rotate, compresses the critical CO2 working fluid in the low-pressure tank 8 and stores it in the high-pressure tank 11; in the energy release condition, the high-pressure CO2 working fluid is output from the high-pressure tank 11, and after being heated by the gas boiler 12, it enters the first cycle system.

[0048] Among them, in the energy storage condition of the compressed CO2 energy storage system, the CO2 working medium first flows through the absorber 17 of the concentrating solar collector system to absorb heat, generating high-temperature and high-pressure CO2. Part of it enters the main turbine 1 to generate electricity to meet the power consumption demand of the normal load, and the other part enters the third turbine 10 to drive the second compressor 9 to compress the CO2 in the critical state. The high-pressure CO2 working medium compressed by the compressor enters the high-pressure tank 11 for storage. After the CO2 working medium that enters the main turbine 1 to generate electricity does work, it flows into the high-temperature gas heater 2 to release heat and then enters the low-temperature gas heater 3 for further heat exchange; the CO2 working medium flowing out from the hot side of the low-temperature gas heater 3 is split. The first part of the CO2 working medium enters the first condenser 6 after heat exchange with the CO2 working medium circulating in the transcritical CO2 Brayton cycle system. The CO2 working medium coming out of the first condenser 6 enters the main compressor 7 to boost the pressure and then enters the cold side of the low-temperature gas heater 3; the remaining second part of the CO2 working medium flowing out from the hot side of the low-temperature gas heater 3 passes through the recirculation compressor 5. The CO2 working medium flowing out from the recirculation compressor 5 converges with the first part of the CO2 working medium flowing out from the cold side of the low-temperature gas heater 3 and enters the cold side of the high-temperature gas heater 2 to absorb heat and increase the temperature. The CO2 working medium coming out of the cold side of the high-temperature gas heater 2 enters the concentrating solar collector system to further absorb heat and complete one cycle.

[0049] In the energy release condition of the compressed CO2 energy storage system, the high-pressure CO2 working medium stored in the high-pressure tank 11 flows out from the high-pressure tank 11, enters the gas boiler 12 for heating, and then enters the main turbine 1 of the S-CO2 Brayton cycle to do work to meet the power consumption demand of users. The CO2 working medium flowing out from the main turbine 1 reheats the CO2 working medium circulating in the transcritical CO2 cycle system, and then enters the first condenser 6 to be cooled to near the critical point. The uncompressed CO2 flowing out from the first condenser 6 is stored in the low-pressure tank 8 to complete the cycle period.

[0050] Select the summer solstice as the research object. On the summer solstice, assume the input solar energy is 2142 MW·h and the input fuel is 1256 MW·h. In the compressed energy storage system, the temperature and pressure of the CO2 working fluid in the low-pressure tank 8 are near the critical point, with its pressure set at 8.14 MPa and temperature at 35°C. After being compressed and boosted by the second compressor 9, the pressure of the CO2 working fluid in the low-pressure tank 8 reaches 31.81 MPa and the temperature is 92.78°C, and it is stored in the high-pressure tank 11. The CO2 working fluid in the high-pressure tank 11 is heated by the combustion boiler, and the temperature reaches 620°C. Ignoring the pressure drop loss in the combustion boiler, the inlet temperature and pressure of the main turbine are 31.81 MPa and 620°C. The isentropic efficiency of the main turbine 1 is 0.93. The efficiencies of the high-temperature gas heater 2 and the low-temperature gas heater 3 are the same at 0.86. The CO2 working fluid flowing out of the main turbine 1 is shunted after a series of heat exchanges. Part of it flows into the intermediate heat exchanger 4 for heat exchange and then enters the first condenser 6, where the CO2 working fluid is cooled to the critical temperature and pressure. Part of it flows into the main compressor 7, with its inlet temperature at 35°C and isentropic efficiency at 0.9. Another part flows into the low-pressure tank 8, with a temperature of 35°C. The two fluid streams converge before the high-temperature gas heater 2 to complete a cycle. It is calculated that on the summer solstice, the system output work is 889 MW·h and the daily average efficiency is 26.17%. Compared with the existing molten salt energy storage system, the efficiency on the summer solstice is increased by 0.31%.

[0051] The situation on the winter solstice is similar to that on the summer solstice. Since the solar energy is less than that on the summer solstice, the heat storage time is shorter, the heat release time is longer, and the optical field efficiency is lower. It is calculated that the input solar energy on the winter solstice is 1239 MW·h and the input fuel is 628 MW·h, and other operating parameters remain unchanged. It is calculated that the system output work is 441 MW·h and the daily average efficiency is 23.61%. Compared with the existing molten salt energy storage system, the efficiency on the winter solstice is increased by 0.97%.

[0052] It should be noted that in the description of the present application, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present application, unless otherwise specified, the meaning of "a plurality" is two or more than two.

[0053] Any process or method description shown in the flowchart or described in other ways herein can be understood as representing a module, segment, or part of code including one or more executable instructions for implementing a specific logical function or process. The scope of the preferred embodiments of the present application includes additional implementations, where the functions can be executed in a way that is not shown or discussed, including in a substantially simultaneous manner or in the reverse order according to the involved functions, which should be understood by those skilled in the technical field to which the embodiments of the present application belong.

[0054] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any at least one embodiment or example.

[0055] Although the embodiments of this application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limitations to this application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A dual-cycle solar thermal power generation system for compressed CO2 energy storage, characterized in that, including a CO2 dual-cycle power generation system, which includes a supercritical CO2 Brayton cycle system and a transcritical CO2 Brayton cycle system in which a CO2 working fluid circulates; wherein the supercritical CO2 Brayton cycle system and the transcritical CO2 Brayton cycle system are heat exchange connected; the supercritical CO2 Brayton cycle system includes a first cycle system and a recirculation path; wherein in the first cycle system, according to the flow direction of the CO2 working fluid, it includes a main turbine, a hot side of a high-temperature gas heater, a hot side of a low-temperature gas heater, a first condenser, a main compressor, a cold side of the low-temperature gas heater, and a cold side of the high-temperature gas heater connected in sequence; wherein in the recirculation path, there is a recirculation compressor, and the input end of the recirculation compressor is connected to the output end of the hot side of the low-temperature gas heater; the output end of the recirculation compressor is connected to the output end of the cold side of the low-temperature gas heater; an intermediate heat exchanger is arranged between the hot side of the low-temperature gas heater and the first condenser; wherein the hot side of the low-temperature gas heater is connected to the hot side of the intermediate heat exchanger for heating the CO2 working fluid circulating in the transcritical CO2 Brayton cycle system; in the transcritical CO2 Brayton cycle system, according to the flow direction of the CO2 working fluid, it includes a booster pump, a second turbine, and a second condenser connected in sequence; wherein the cold side input end of the intermediate heat exchanger is connected to the booster pump, and the cold side output end of the intermediate heat exchanger is connected to the second turbine; a compressed CO2 energy storage system, which is connected to the supercritical CO2 Brayton cycle system and is used to input CO2 working fluid to the supercritical CO2 Brayton cycle system or receive the CO2 working fluid output by the supercritical CO2 Brayton cycle system under different working conditions; the compressed CO2 energy storage system includes a third turbine, a second compressor, a high-pressure tank, a gas-fired boiler, and a low-pressure tank arranged in sequence according to the flow direction of the CO2 working fluid; wherein the output end of the gas-fired boiler is connected to the input end of the main turbine; the output end of the first condenser is connected to the low-pressure tank; the input end of the third turbine is connected to the output end of the concentrating solar collector system; the CO2 working fluid in the low-pressure tank is compressed and boosted by the second compressor and then stored in the high-pressure tank; and the concentrating solar collector system, which is respectively connected to the supercritical CO2 Brayton cycle system and the compressed CO2 energy storage system, and uses solar energy to heat the CO2 working fluid entering the supercritical CO2 Brayton cycle system and the compressed CO2 energy storage system; the input end of the concentrating solar collector system is connected to the output end of the cold side of the high-temperature gas heater; the output end of the concentrating solar collector system is connected to the input end of the main turbine.

2. The double-cycle solar thermal power generation system according to claim 1, wherein A first valve is arranged on the pipeline connecting the input end of the third turbine and the output end of the concentrating solar collector system.

3. The double-cycle solar thermal power generation system according to claim 1, wherein A second valve is arranged on the pipeline connecting the output end of the first condenser and the input end of the low-pressure tank.

4. The double-cycle solar thermal power generation system according to claim 3, wherein The concentrating and heat-collecting system includes a central absorption tower, an absorber, and solar reflectors; wherein the absorber is arranged on the central absorption tower; the solar reflectors are multiple and arranged on the periphery of the central absorption tower to concentrate solar energy into the absorber to heat the CO2 working medium.

5. A dual-cycle solar thermal power generation method for compressed CO2 energy storage, characterized in that, Using the dual-cycle solar thermal power generation system according to any one of claims 1-4 for power generation, comprises the following processes: The CO2 working medium heated by the concentrating and heat-collecting system respectively enters the supercritical CO2 Brayton cycle system and the compressed CO2 energy storage system; The CO2 working medium entering the supercritical CO2 Brayton cycle system circulates in the first cycle system for power generation; wherein a part of the CO2 working medium output from the hot side of the low-temperature gas heater is input to the cold-side output end of the low-temperature gas heater through a recirculation compressor through a recirculation path; meanwhile, when the transcritical CO2 Brayton cycle system generates power, the remaining CO2 working medium output from the hot side of the low-temperature gas heater exchanges heat with the CO2 working medium circulating in the transcritical CO2 Brayton cycle system; When the CO2 working medium entering the compressed CO2 energy storage system is in the energy storage condition, the CO2 working medium enters the third turbine to drive the second compressor to rotate, and the critical CO2 working medium in the low-pressure tank is compressed and stored in the high-pressure tank; in the energy release condition, the high-pressure CO2 working medium is output from the high-pressure tank and enters the first cycle system after being heated by a gas-fired boiler.

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