Hybrid energy storage system

Abstract

The disclosure provides a hybrid energy storage system, wherein the Brayton cycle unit comprises a first compressor, a first air-salt heat exchanger and an air-air heat exchanger forming a circulation loop, the cold side of the first air-salt heat exchanger is provided with a first inlet and a first outlet, the cold side of the air-air heat exchanger is provided with a second inlet and a second outlet, and the second inlet is used for air entering; the energy storage unit comprises a molten salt heat storage unit, the molten salt heat storage unit is connected with the first inlet and the first outlet to form a circulation loop; a Rankine cycle unit is connected with the molten salt heat storage unit to generate power by obtaining heat; and the processing unit comprises a first unit, the first unit comprises a compression section and an expansion section connected with the compression section, the compression section is connected with the second outlet, has a gas compression function, and is connected with the molten salt heat storage unit to deliver first temperature heat to the molten salt heat storage unit and second temperature compressed air smaller than the first temperature to the expansion section, and the expansion section has a gas expansion function to generate power.

Description

Technical Field

[0001] This disclosure relates to the field of energy storage technology, and in particular to a hybrid energy storage system. Background Technology

[0002] Carnot batteries can efficiently convert surplus electrical energy (such as during periods of low market electricity demand) into thermal energy for storage, and then convert the stored thermal energy back into electrical energy for transmission to the grid during peak electricity demand periods, thereby enhancing the operational stability and power supply reliability of the power system.

[0003] However, the current energy storage efficiency of Carnot batteries is limited and cannot meet the market's electricity needs. Summary of the Invention

[0004] This disclosure provides a hybrid energy storage system, the technical problem of which is to improve the energy storage efficiency of the Carnot battery in order to better meet the market's electricity needs.

[0005] To address the aforementioned technical problems, this disclosure provides a hybrid energy storage system, which may include: a Brayton cycle unit, an energy storage unit, a Rankine cycle unit, and a processing unit. The Brayton cycle unit may include: a first compressor forming a circulation loop, a first air-molten salt heat exchanger, and an air-to-air heat exchanger. The first air-molten salt heat exchanger has a first inlet and a first outlet on its cold side, and the air-to-air heat exchanger has a second inlet and a second outlet on its cold side, with the second inlet supplying air. The energy storage unit may include: a molten salt thermal storage unit, which is connected to the first inlet and the first outlet to form a circulation loop. The Rankine cycle unit is connected to the molten salt thermal storage unit to obtain heat and generate electricity. The processing unit may include: a first unit, which includes: a compression section and an expansion section connected thereto. The compression section is connected to the second outlet and has a gas compression function. It is also connected to the molten salt thermal storage unit to supply heat at a first temperature to the molten salt thermal storage unit and compressed air at a second temperature lower than the first temperature to the expansion section. The expansion section has a gas expansion function to generate electricity.

[0006] In some embodiments, the second outlet is configured to divide the air flowing out of the second outlet into a first branch and a second branch, wherein the unit volume of the first branch is greater than the unit volume of the second branch; the processing unit further includes a second unit, wherein the first unit is connected to the first branch, the second unit is connected to the second branch, and has a gas expansion function to generate electricity.

[0007] In some embodiments, the molten salt thermal storage unit includes: a high-temperature thermal storage tank, a medium-temperature thermal storage tank, and a low-temperature thermal storage tank; the Rankine cycle unit includes: a first molten salt-water heat exchanger; the inlet of the high-temperature thermal storage tank is connected to the first outlet, and the outlet is connected to the hot-side inlet of the first molten salt-water heat exchanger; the inlet of the medium-temperature thermal storage tank is connected to the hot-side outlet of the first molten salt-water heat exchanger, and the outlet is connected to the hot-side inlet of the expansion section; the inlet of the low-temperature thermal storage tank is connected to the cold-side outlet of the expansion section, and the outlet is connected to the first inlet of the first air-molten salt heat exchanger.

[0008] In some embodiments, the compression section includes: a first compression section and a second compression section; the first compression section includes: a first air-water heat exchanger, a second compressor, a second air-molten salt heat exchanger, and an air-liquid heat exchanger connected sequentially to the first branch; the second compression section includes: a third compressor, a third air-molten salt heat exchanger, and a second air-water heat exchanger connected sequentially to the first compression section; wherein, the cold-side outlet of the second air-molten salt heat exchanger and the cold-side outlet of the third air-molten salt heat exchanger are both connected to the inlet of the medium-temperature thermal storage tank, and the cold-side inlet of the second air-molten salt heat exchanger and the cold-side inlet of the third air-molten salt heat exchanger are both connected to the outlet of the low-temperature thermal storage tank.

[0009] In some embodiments, the energy storage unit further includes a high-pressure cryogenic gas storage tank and a throttling device, wherein the high-pressure cryogenic gas storage tank and the throttling device are located sequentially between the compression section and the expansion section, and the high-pressure cryogenic gas storage tank is used to store the high-pressure cryogenic gas of the compression section.

[0010] In some embodiments, the expansion section includes: a liquid-air heat exchanger, a first molten salt-air heat exchanger, a first expander, a second molten salt-air heat exchanger, and a second expander connected in sequence to the throttling device. The hot-side inlet of the first molten salt-air heat exchanger and the hot-side inlet of the second molten salt-air heat exchanger are both connected to the outlet of the medium-temperature thermal storage tank, and the hot-side outlet of the first molten salt-air heat exchanger and the hot-side outlet of the second molten salt-air heat exchanger are both connected to the inlet of the low-temperature thermal storage tank.

[0011] In some embodiments, the energy storage unit further includes: a first liquid heat storage tank and a second liquid heat storage tank; the inlet of the first liquid heat storage tank is connected to the cold-side outlet of the air-liquid heat exchanger, and the outlet is connected to the hot-side inlet of the liquid-air heat exchanger; the inlet of the second liquid heat storage tank is connected to the hot-side outlet of the liquid-air heat exchanger, and the outlet is connected to the cold-side inlet of the air-liquid heat exchanger; wherein the temperature inside the first liquid heat storage tank is greater than the temperature inside the second liquid heat storage tank.

[0012] In some embodiments, the Brayton cycle unit further includes: a water-air heat exchanger, the inlet of which is used to introduce air, and the outlet of which is connected to a second inlet of the air-air heat exchanger; the energy storage unit further includes: a first hot water storage tank and a second hot water storage tank, the two inlets of the first hot water storage tank being connected to the cold-side outlet of the first air-water heat exchanger and the cold-side outlet of the second air-water heat exchanger respectively, and the outlet being connected to the hot-side inlet of the water-air heat exchanger; the two outlets of the second hot water storage tank being connected to the cold-side inlet of the first air-water heat exchanger and the cold-side inlet of the second air-water heat exchanger respectively, and the inlet being connected to the hot-side outlet of the water-air heat exchanger.

[0013] In some embodiments, the Rankine cycle unit includes: a boiler, a low-pressure cylinder, an intermediate-pressure cylinder, a high-pressure cylinder, a deaerator, a high-pressure heater, a second molten salt-water heat exchanger, and a generator. The inlet of the boiler is connected to the cold-side outlet of the first molten salt-water heat exchanger, and the outlets are respectively connected to the low-pressure cylinder and the intermediate-pressure cylinder. The outlet of the low-pressure cylinder is connected to the inlet of the boiler. The outlet of the intermediate-pressure cylinder is sequentially connected to the deaerator, the high-pressure heater, and the cold-side inlet of the first molten salt-water heat exchanger. The outlet of the deaerator is also sequentially connected to the cold-side inlet of the second molten salt-water heat exchanger and the cold-side inlet of the first molten salt-water heat exchanger. The hot-side outlet of the first molten salt-water heat exchanger is also connected to the second molten salt-water heat exchanger. The low-pressure cylinder, the intermediate-pressure cylinder, and the high-pressure cylinder are coaxially arranged and connected to the generator.

[0014] In some embodiments, the Rankine cycle unit further includes a condenser and a low-pressure heater, wherein the high-pressure cylinder, the condenser, the low-pressure heater and the deaerator are connected in sequence.

[0015] Through the above technical solution, the hybrid energy storage system provided in this disclosure includes a Brayton cycle unit, an energy storage unit, a Rankine cycle unit, and a processing unit. The Brayton cycle unit can compress air to generate high-temperature, high-pressure gas. The energy storage unit may include a molten salt thermal storage unit connected to the high-temperature position of the Brayton cycle unit, and the Rankine cycle unit is connected to the molten salt thermal storage unit. The processing unit includes a compression section connected to the low-temperature position of the Brayton cycle unit and an expansion section connected to the compression section. The compression section is also connected to the molten salt thermal storage unit to deliver high-temperature gas to the molten salt thermal storage unit and low-temperature compressed gas with a relatively lower temperature to the expansion section. Thus, the high temperature generated by the Brayton cycle unit and the high temperature generated by the compression section can be provided to the Rankine cycle unit for power generation, while the remaining low-temperature, high-pressure gas in the compression section can be expanded in the expansion section to generate electricity. In this way, through the coupling between the Brayton cycle unit, the energy storage unit, and the processing unit, more high-temperature gas can be provided to the Rankine cycle unit for power generation, and the remaining low-temperature, high-pressure gas in the compression section can also be used to generate electricity, thereby meeting the market's electricity needs.

[0016] The above description is only an overview of the technical solution of this disclosure. In order to better understand the technical means of this disclosure and to implement it in accordance with the contents of the specification, the preferred embodiments of this disclosure are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 Schematic diagram of the hybrid energy storage system provided in this disclosure Figure 1 ; Figure 2 Schematic diagram of the hybrid energy storage system provided in this disclosure Figure 2 .

[0019] Explanation of reference numerals in the attached figures: 100. Hybrid energy storage system; 10. Brayton cycle unit; 11. First compressor; 12. First air-molten salt heat exchanger; 121. First inlet; 122. First outlet; 13. Air-air heat exchanger; 131. Second inlet; 132. Second outlet; 1321. First branch; 1322. Second branch; 14. Water-air heat exchanger; 20. Energy storage unit; 21. Molten salt thermal storage unit; 211. High-temperature thermal storage tank; 212. Medium-temperature thermal storage tank; 213. Low-temperature thermal storage tank; 22. High-pressure low-temperature gas storage tank; 23. Throttling device; 24. First liquid thermal storage tank; 25. Second liquid thermal storage tank; 26. First hot water storage tank; 27. Second hot water storage tank; 30. Rankine cycle unit; 31. First molten salt-water heat exchanger; 32. Boiler; 33. Low-pressure cylinder; 3 4. Intermediate-pressure cylinder; 35. High-pressure cylinder; 36. Deaerator; 37. High-pressure heater; 38. Second molten salt-water heat exchanger; 39. Generator; 30A. Condenser; 30B. Low-pressure heater; 40. Processing unit; 41. First unit; 411. Compression section; 4111. First air-water heat exchanger; 4112. Second compressor; 4113. Second air-molten salt heat exchanger; 4114. Air-liquid heat exchanger; 4115. Third compressor; 4116. Third air-molten salt heat exchanger; 4117. Second air-water heat exchanger; 412. Expansion section; 4121. Liquid-air heat exchanger; 4122. First molten salt-air heat exchanger; 4123. First expander; 4124. Second molten salt-air heat exchanger; 4125. Second expander; 42. Second unit. Detailed Implementation

[0020] The embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings and examples. The detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of this disclosure by way of example, but should not be used to limit the scope of this disclosure. This disclosure can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0021] These embodiments are provided to make the disclosure thorough and complete, and to fully express the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as exemplary only and not as limiting.

[0022] It should be noted that, in the description of this disclosure, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationship, are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0023] Furthermore, the terms "first," "second," and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. "Vertical" is not strictly vertical, but within the permissible margin of error. "Parallel" is not strictly parallel, but within the permissible margin of error. Terms such as "including" or "contains" mean that the element preceding the word encompasses the element listed after the word, and do not exclude the possibility of encompassing other elements as well.

[0024] It should also be noted that, in the description of this disclosure, unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this disclosure depending on the specific circumstances. When a particular device is described as being located between a first device and a second device, an intermediary device may or may not be present between the particular device and the first or second device.

[0025] All terms used in this disclosure have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0026] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0027] Carnot batteries can efficiently convert surplus electrical energy (such as during periods of low market electricity demand) into thermal energy for storage, and then convert the stored thermal energy back into electrical energy for transmission to the grid during peak electricity demand periods, thereby enhancing the operational stability and power supply reliability of the power system.

[0028] However, the current energy storage efficiency of Carnot batteries is limited and cannot meet the market's electricity needs.

[0029] The inventors of this disclosure have discovered a hybrid energy storage system that can include a Brayton cycle unit, an energy storage unit, a Rankine cycle unit, and a processing unit. The Brayton cycle unit can compress air to generate high-temperature, high-pressure gas. The energy storage unit can include a molten salt thermal storage unit connected to the high-temperature position of the Brayton cycle unit, and the Rankine cycle unit is connected to the molten salt thermal storage unit. The processing unit includes a compression section connected to the low-temperature position of the Brayton cycle unit and an expansion section connected to the compression section. The compression section is also connected to the molten salt thermal storage unit to deliver high-temperature gas to the molten salt thermal storage unit and low-temperature compressed gas with a relatively lower temperature to the expansion section. Thus, the high temperature generated by the Brayton cycle unit and the high temperature generated by the compression section can be provided to the Rankine cycle unit for power generation, while the remaining low-temperature, high-pressure gas in the compression section can be expanded in the expansion section to generate electricity. In this way, through the coupling between the Brayton cycle unit, the energy storage unit, and the processing unit, more high-temperature gas can be provided to the Rankine cycle unit for power generation, and the remaining low-temperature, high-pressure gas in the compression section can also be used for power generation, thereby meeting the market's electricity needs.

[0030] In some embodiments, see Figure 1 As shown, the hybrid energy storage system 100 may include: a Brayton cycle unit 10, an energy storage unit 20, a Rankine cycle unit 30, and a processing unit 40. The Brayton cycle unit 10 may include: a first compressor 11 forming a circulation loop, a first air-molten salt heat exchanger 12, and an air-to-air heat exchanger 13. The cold side of the first air-molten salt heat exchanger 12 is provided with a first inlet 121 and a first outlet 122. The cold side of the air-to-air heat exchanger 13 is provided with a second inlet 131 and a second outlet 132, with the second inlet 131 supplying air. The energy storage unit 20 may include: a molten salt thermal storage unit 21, which stores... The heating unit 21 is connected to the first inlet 121 and the first outlet 122 to form a circulation loop; the Rankine circulation unit 30 is connected to the molten salt thermal storage unit 21 to obtain heat and generate electricity; the processing unit 40 may include: a first unit 41, the first unit 41 including: a compression section 411 and an expansion section 412 connected thereto, the compression section 411 is connected to the second outlet 132, has a gas compression function, and is connected to the molten salt thermal storage unit 21 to deliver heat at a first temperature to the molten salt thermal storage unit 21 and compressed air at a second temperature lower than the first temperature to the expansion section 412, the expansion section 412 has a gas expansion function to generate electricity.

[0031] The Brayton cycle unit 10 can be driven by surplus power from the power grid or renewable energy to generate high-temperature, high-pressure air. The outlet of the first compressor 11, the hot-side inlet of the first air-molten salt heat exchanger 12, the hot-side inlet of the air-to-air heat exchanger 13, and the inlet of the first compressor 11 are connected to form a circulation loop. When air flows into the first compressor 11 within the circulation loop, it can be compressed to form high-temperature, high-pressure air. The first air-molten salt heat exchanger 12 is located behind the first compressor 11 in the Brayton cycle unit 10 and can acquire heat at a first temperature within the circulation loop. The air-to-air heat exchanger 13 is located behind the first air-molten salt heat exchanger 12 in the Brayton cycle unit 10 and can acquire heat at a second temperature below the first temperature within the circulation loop. Air can enter through the second inlet 131 at the cold end of the air-to-air heat exchanger 13 to supply and replenish air into the Brayton cycle unit 10.

[0032] Energy storage unit 20 can store media such as high-temperature heat and low-temperature high-pressure gas. For example, the molten salt heat storage unit 21 of energy storage unit 20 is connected to the first outlet 122 of the cold end of the first air-molten salt heat exchanger 12 of Brayton cycle unit 10 so as to obtain and store heat at the first temperature.

[0033] The Rankine cycle unit 30 can use the heat stored in the molten salt thermal storage unit 21 to heat the organic working fluid inside, generate steam, and drive the generator set to generate electricity.

[0034] The processing unit 40 can further process the compressed air at the second temperature in the Brayton cycle unit 10 to generate more energy, such as thermal energy and electrical energy. The compression section 411 of the first unit 41 can compress the compressed air at the second temperature and generate high-temperature and high-pressure gas. The high-temperature heat is stored in the molten salt heat storage unit 21 to store thermal energy, while the remaining low-temperature and high-pressure gas can enter the expansion section 412 to expand and do work, generating electrical energy.

[0035] In this embodiment, the hybrid energy storage system 100 may include a Brayton cycle unit 10, an energy storage unit 20, a Rankine cycle unit 30, and a processing unit 40. The Brayton cycle unit 10 is used to compress air to generate high-temperature and high-pressure gas. The energy storage unit 20 includes a molten salt thermal storage unit 21, which is connected to the high-temperature section of the Brayton cycle unit 10. The Rankine cycle unit 30 is connected to the molten salt thermal storage unit 21. The processing unit 40 includes a compression section 411 and an expansion section 412. The compression section 411 is connected to the low-temperature section of the Brayton cycle unit 10 and to the molten salt thermal storage unit 21 to deliver high-temperature gas to the molten salt thermal storage unit 21, while delivering relatively low-temperature and high-pressure gas to the expansion section 412. Here, the high temperature generated by the Brayton cycle unit 10 and the high temperature generated by the compression section 411 can be supplied to the Rankine cycle unit 30 for power generation. The remaining low-temperature and high-pressure gas in the compression section 411 can expand and do work in the expansion section 412 to generate more electricity. In this way, through the coupling between the Brayton cycle unit 10, the energy storage unit 20, and the processing unit 40, the system can not only provide a more sufficient high-temperature heat source for the Rankine cycle unit 30, but also effectively utilize the low-temperature and high-pressure residual gas in the compression section 411 for power generation, thereby better meeting the market's electricity demand.

[0036] In some embodiments, see Figure 2 As shown, the second outlet 132 is configured to split the air flowing out of the second outlet 132 into a first branch 1321 and a second branch 1322. The unit volume of the first branch 1321 is greater than that of the second branch 1322. The processing unit 40 may also include a second unit 42, wherein the first unit 41 is connected to the first branch 1321 and the second unit 42 is connected to the second branch 1322, and has a gas expansion function to generate electricity.

[0037] The second outlet 132 can be equipped with a three-port connecting pipe. The first port can connect to the second outlet 132, the second port can form a first branch 1321, and the third port can form a second branch 1322. The diameter of the second port can be larger than that of the third port, so that the unit gas volume of the first branch 1321 is greater than that of the second branch 1322. For example, the ratio of the diameter of the second port to that of the third port is 9:1, so that the ratio of the unit gas volume of the first branch 1321 to that of the second branch 1322 is within the range of 9:1.

[0038] The second unit 42 is connected to the second branch 1322 (compared to the first branch 1321), which has a relatively small unit output air volume, and has an expansion function to utilize a portion of the compressed air in the low-temperature section of the Brayton cycle unit 10 for expansion and power generation. Thus, in addition to the Rankine cycle unit 30 and the expansion section 412 of the first unit 41, an additional branch capable of generating electricity can be provided, further improving the utilization efficiency of the hybrid energy storage system 100. Here, the second unit 42 may include an expander structure with an expansion function.

[0039] In some embodiments, see Figure 2 As shown, the molten salt thermal storage unit 21 may include: a high-temperature thermal storage tank 211, a medium-temperature thermal storage tank 212, and a low-temperature thermal storage tank 213; the Rankine cycle unit 30 may include: a first molten salt-water heat exchanger 31; the inlet of the high-temperature thermal storage tank 211 is connected to the first outlet 122, and the outlet is connected to the hot-side inlet of the first molten salt-water heat exchanger 31; the inlet of the medium-temperature thermal storage tank 212 is connected to the hot-side outlet of the first molten salt-water heat exchanger 31, and the outlet is connected to the hot-side inlet of the expansion section 412; the inlet of the low-temperature thermal storage tank 213 is connected to the cold-side outlet of the expansion section 412, and the outlet is connected to the first inlet 121 of the first air-molten salt heat exchanger 12.

[0040] The heat storage temperatures in the high-temperature heat storage tank 211, the medium-temperature heat storage tank 212, and the low-temperature heat storage tank 213 can decrease sequentially. The first air-molten salt heat exchanger 12, the high-temperature heat storage tank 211, and the first molten salt-water heat exchanger 31 of the Rankine cycle unit 30 are connected in sequence so that the high-temperature heat storage tank 211 can store heat at a first temperature in the first air-molten salt heat exchanger 12, while the first molten salt-water heat exchanger 31 can provide the heat in the high-temperature heat storage tank 211 to the Rankine cycle unit 30 to heat the organic working fluid inside the Rankine cycle unit 30, generate steam, and drive the generator set to generate electricity.

[0041] The inlet of the medium-temperature thermal storage tank 212 is connected to the hot-side outlet of the first molten salt-water heat exchanger 31, and the outlet is connected to the hot-side inlet of the expansion section 412. In this way, the waste heat after the Rankine cycle unit 30 generates electricity can be provided to the expansion section 412 to heat up the low-temperature high-pressure air provided by the compression section 411, thereby improving the power generation efficiency of the expansion section 412 and further improving the efficiency of the hybrid energy storage system 100.

[0042] The inlet of the low-temperature heat storage tank 213 is connected to the cold side outlet of the expansion section 412, and the outlet is connected to the first inlet 121 of the first air-molten salt heat exchanger 12, so that the molten salt heat storage unit 21 forms a molten salt circulation loop with the cooperation of the expansion section 412.

[0043] In this embodiment, the high-temperature thermal storage tank 211, the medium-temperature thermal storage tank 212, and the low-temperature thermal storage tank 213 of the molten salt thermal storage unit 21, together with the expansion section 412, form a molten salt circulation loop. At the same time, heat can be released at the corresponding positions of the Rankine cycle unit 30 and the expansion section 412, so as to realize the full generation of electricity by utilizing the different temperatures at different positions, thereby further improving the efficiency of the hybrid energy storage system 100.

[0044] In some embodiments, see Figure 2 As shown, the compression section 411 may include: a first compression section and a second compression section; the first compression section may include: a first air-water heat exchanger 4111, a second compressor 4112, a second air-molten salt heat exchanger 4113 and an air-liquid heat exchanger 4114 connected in sequence to the first branch 1321; the second compression section includes: a third compressor 4115, a third air-molten salt heat exchanger 4116 and a second air-water heat exchanger 4117 connected in sequence to the first compression section; wherein, the cold side outlet of the second air-molten salt heat exchanger 4113 and the cold side outlet of the third air-molten salt heat exchanger 4116 are both connected to the inlet of the medium-temperature heat storage tank 212, and the cold side inlet of the second air-molten salt heat exchanger 4113 and the cold side inlet of the third air-molten salt heat exchanger 4116 are both connected to the outlet of the low-temperature heat storage tank 213.

[0045] In other words, the first air-water heat exchanger 4111 is sequentially connected to the inlet of the second compressor 4112, the hot-side inlet of the second air-molten salt heat exchanger 4113, the hot-side inlet of the air-liquid heat exchanger 4114, the inlet of the third compressor 4115, the hot-side inlet of the third air-molten salt heat exchanger 4116, and the second air-water heat exchanger 4117. The second compressor 4112 in the compression section 411 can perform one compression, and the third compressor 4115 can perform two compressions. The heat generated after each compression can be provided to the intermediate-temperature heat storage tank 212 for storage through the corresponding heat exchanger after the compressor (such as the second air-molten salt heat exchanger 4113 after the second compressor 4112 and the third air-molten salt heat exchanger 4116 after the third compressor 4115). The heat is then provided to the expansion section 412 through the intermediate-temperature heat storage tank 212 to increase the gas temperature in the expansion section 412, thereby improving the expansion efficiency of the expansion section 412 and further improving the efficiency of the hybrid energy storage system 100.

[0046] Here, the second compressor 4112 and the third compressor 4115 can be set separately, or as follows: Figure 2 The coaxial arrangement shown can be driven by the same motor, which can reduce production costs and space occupation; in the air-liquid heat exchanger 4114, the liquid can be water or heat transfer oil.

[0047] In some embodiments, see Figure 2 As shown, the energy storage unit 20 may further include: a high-pressure cryogenic gas storage tank 22 and a throttling device 23. The high-pressure cryogenic gas storage tank 22 and the throttling device 23 are located sequentially between the compression section 411 and the expansion section 412. The high-pressure cryogenic gas storage tank 22 is used to store the high-pressure cryogenic gas in the compression section 411.

[0048] Among them, the high-pressure cryogenic gas storage tank 22 can store gas at a temperature of 30-50℃ and a pressure of 10MPa-15MPa; the throttling device 23 can be a throttling valve with a throttling setting of 3MPa-5MPa.

[0049] In this embodiment, the low-temperature and high-pressure gas of the compression section 411 can be stored in the high-pressure cryogenic gas storage tank 22, and the throttling device 23 can be opened to achieve the purpose when it is necessary to expand and generate electricity through the expansion section 412.

[0050] In some embodiments, see Figure 2 As shown, the expansion section 412 may include: a liquid-air heat exchanger 4121, a first molten salt-air heat exchanger 4122, a first expander 4123, a second molten salt-air heat exchanger 4124, and a second expander 4125, which are sequentially connected to the throttling device 23. The hot-side inlet of the first molten salt-air heat exchanger 4122 and the hot-side inlet of the second molten salt-air heat exchanger 4124 are both connected to the outlet of the medium-temperature heat storage tank 212, and the hot-side outlet of the first molten salt-air heat exchanger 4122 and the hot-side outlet of the second molten salt-air heat exchanger 4124 are both connected to the inlet of the low-temperature heat storage tank 213.

[0051] In other words, the cold-side outlet of the liquid-air heat exchanger 4121 is sequentially connected to the cold-side outlet of the first molten salt-air heat exchanger 4122, the inlet of the first expander 4123, the cold-side outlet of the second molten salt-air heat exchanger 4124, and the inlet of the second expander 4125; wherein the first expander 4123 and the second expander 4125 can expand independently to generate electricity separately, or they can be configured as follows: Figure 2 The first expander 4123 and the second expander 4125 shown are coaxially arranged to cooperate in power generation. Here, the coaxial arrangement simplifies the transmission structure and reduces energy transfer losses.

[0052] In this embodiment, the compressed air can be heated in stages through the liquid-air heat exchanger 4121, the first molten salt-air heat exchanger 4122, and the second molten salt-air heat exchanger 4124. In particular, the hot sides of the first molten salt-air heat exchanger 4122 and the second molten salt-air heat exchanger 4124 are both connected to the medium-temperature heat storage tank 212, which can utilize the waste heat after the Rankine cycle unit 30 generates electricity to reheat the air before expansion and the air between stages. This "interstage reheat" design can significantly increase the average expansion temperature of the air in the first expander 4123 and the second expander 4125, avoiding the problem of reduced subsequent work capacity due to excessively rapid cooling during a single expansion, thereby greatly increasing the total work done by the expansion of a unit mass of compressed air, and increasing the overall power generation of the hybrid energy storage system 100. In addition, the hot-side outlets of the first molten salt-air heat exchanger 4122 and the second molten salt-air heat exchanger 4124 are both connected to the inlet of the low-temperature heat storage tank 213, so that the residual heat of the molten salt flowing out of the medium-temperature heat storage tank 212 after heating the air can be returned to the low-temperature heat storage tank 213 for storage, realizing the efficient recycling of the heat storage medium in the entire temperature range.

[0053] In some embodiments, see Figure 2 As shown, the energy storage unit 20 may further include: a first liquid heat storage tank 24 and a second liquid heat storage tank 25; the inlet of the first liquid heat storage tank 24 is connected to the cold side outlet of the air-liquid heat exchanger 4114, and the outlet is connected to the hot side inlet of the liquid-air heat exchanger 4121; the inlet of the second liquid heat storage tank 25 is connected to the hot side outlet of the liquid-air heat exchanger 4121, and the outlet is connected to the cold side inlet of the air-liquid heat exchanger 4114; wherein, the temperature inside the first liquid heat storage tank 24 is greater than the temperature inside the second liquid heat storage tank 25.

[0054] Here, the first liquid heat storage tank 24 can be a water heat storage tank or a heat transfer oil heat storage tank; the second liquid heat storage tank 25 can be a water heat storage tank or a heat transfer oil heat storage tank.

[0055] In this embodiment, by adding a first liquid heat storage tank 24 and a second liquid heat storage tank 25, an independent liquid medium heat storage circulation loop is constructed. Part of the compression heat is stored and transferred to the expansion section 412 for preheating high-pressure air. This significantly reduces the consumption of high-quality heat in the medium-temperature heat storage tank 212 during the expansion process and improves the system's thermal efficiency. At the same time, it can replace the molten salt heat storage unit 21 to reduce the demand of the expansion section 412 on the molten salt heat storage unit 21, thereby replacing high-grade molten salt heat energy with low-grade waste heat, effectively reducing the system's self-consumption rate, and achieving dual optimization of energy cascade utilization and economy.

[0056] In some embodiments, see Figure 2As shown, the Brayton cycle unit 10 may further include: a water-air heat exchanger 14, the inlet of which is used to introduce air, and the outlet of which is connected to the second inlet 131 of the air-air heat exchanger 13; the energy storage unit 20 may further include: a first hot water storage tank 26 and a second hot water storage tank 27, the two inlets of which are respectively connected to the cold side outlet of the first air-water heat exchanger 4111 and the cold side outlet of the second air-water heat exchanger 4117, and the outlet of which is connected to the hot side inlet of the water-air heat exchanger 14; the two outlets of the second hot water storage tank 27 are respectively connected to the cold side inlet of the first air-water heat exchanger 4111 and the cold side inlet of the second air-water heat exchanger 4117, and the inlet of which is connected to the hot side outlet of the water-air heat exchanger 14.

[0057] The first hot water storage tank 26 can be a high-temperature hot water storage tank, and the second hot water storage tank 27 can be a low-temperature hot water storage tank. That is, the material selection requirements for the first hot water storage tank 26 are higher than those for the second hot water storage tank 27, so as to be able to adapt to higher temperatures.

[0058] In this embodiment, an independent water-medium heat storage circulation loop is constructed by adding a water-air heat exchanger 14, a first hot water storage tank 26, and a second hot water storage tank 27. This loop can store the hot water generated by compressed air in the first hot water storage tank 26 and transport it to the water-air heat exchanger 14 at the inlet of the Brayton cycle unit 10 to preheat the ambient air entering the system. This increases the inlet base temperature of the Brayton cycle unit 10, reduces the power consumption of the first compressor 11, and directly improves the efficiency of the charging cycle. Moreover, this loop feeds waste heat back to the cold end of the Brayton cycle for reuse, realizing the reverse transfer and cross-cycle coupling of compression heat from the "discharge side" to the "charging side". This further reduces the overall energy consumption of the system. At the same time, the dual-tank design decouples heat generation and use in time, enhancing the flexibility and thermal integration capability of the system operation.

[0059] In some embodiments, see Figure 2As shown, the Rankine cycle unit 30 includes: a boiler 32, a low-pressure cylinder 33, a medium-pressure cylinder 34, a high-pressure cylinder 35, a deaerator 36, a high-pressure heater 37, a second molten salt-water heat exchanger 38, and a generator 39. The inlet of the boiler 32 is connected to the cold-side outlet of the first molten salt-water heat exchanger 31, and the outlet is connected to the low-pressure cylinder 33 and the medium-pressure cylinder 34 respectively. The outlet of the low-pressure cylinder 33 is connected to the inlet of the boiler 32. The outlet of the medium-pressure cylinder 34 is connected in sequence to the deaerator 36, the high-pressure heater 37, and the cold-side inlet of the first molten salt-water heat exchanger 31. The outlet of the deaerator 36 is also connected in sequence to the cold-side inlet of the second molten salt-water heat exchanger 38 and the cold-side inlet of the first molten salt-water heat exchanger 31. The hot-side outlet of the first molten salt-water heat exchanger 31 is also connected to the second molten salt-water heat exchanger 38. The low-pressure cylinder 33, the medium-pressure cylinder 34, and the high-pressure cylinder 35 are coaxially arranged and connected to the generator 39.

[0060] The rotation of the low-pressure cylinder 33, intermediate-pressure cylinder 34, and high-pressure cylinder 35 causes the generator 39 to generate electricity. The low-pressure cylinder 33, intermediate-pressure cylinder 34, and high-pressure cylinder 35 can operate as follows: Figure 2 The coaxial arrangement shown simplifies the transmission mechanism and reduces energy conversion losses.

[0061] In this embodiment, the heat released by the high-temperature heat storage tank 211 first heats the working medium in the first molten salt-water heat exchanger 31. The cooled molten salt then enters the second molten salt-water heat exchanger 38 to preheat the working medium at the outlet of the deaerator 36. This achieves two-stage heat release and temperature matching utilization of the molten salt, significantly improving the heat release efficiency of the heat storage medium. Meanwhile, the exhaust steam from the intermediate-pressure cylinder 34 is split into two paths after passing through the deaerator 36. One path returns to the first molten salt-water heat exchanger 31 via the high-pressure heater 37, and the other path absorbs heat in the second molten salt-water heat exchanger 38 and also returns to the first molten salt-water heat exchanger 31. This forms a complex regenerative system with multi-stage regenerative steam extraction and molten salt preheating in parallel coupling, effectively increasing the initial temperature of the working medium before entering the boiler 32 and reducing the heat load of the boiler 32. In this way, the power generation efficiency and thermal economy of the Rankine cycle unit 30 are greatly improved.

[0062] In some embodiments, see Figure 2 As shown, the Rankine cycle unit 30 may also include: a condenser 30A and a low-pressure heater 30B, with the high-pressure cylinder 35, condenser 30A, low-pressure heater 30B and deaerator 36 connected in sequence.

[0063] In other words, the outlet of the high-pressure cylinder 35 is connected in sequence to the hot side inlet of the condenser 30A, the inlet of the low-pressure heater 30B, and the inlet of the deaerator 36.

[0064] In this embodiment, a steam-water regeneration system for the Rankine cycle unit 30 is achieved by adding a condenser 30A and a low-pressure heater 30B. The exhaust steam from the high-pressure cylinder 35, after performing work, enters the condenser 30A and condenses into liquid water. After initial heating by the low-pressure heater 30B, it enters the deaerator 36, significantly reducing cold source loss and increasing the initial temperature of the working fluid before entering the subsequent high-pressure heater 37 and the second molten salt-water heat exchanger 38. This further reduces the heat load on the first molten salt-water heat exchanger 31 and the second molten salt-water heat exchanger 38. At the same time, the condenser 30A ensures stable condensation of the exhaust steam, providing a reliable phase change driving force for the circulation of the working fluid and enhancing the stability and adaptability of the unit operation under varying conditions.

[0065] See one example. Figure 2 As shown, the hybrid energy storage system 100 may include: The Brayton cycle unit 10 includes: a first compressor 11, a first air-molten salt heat exchanger 12, an air-air heat exchanger 13, and a water-air heat exchanger 14; The energy storage unit 20 includes: a molten salt thermal storage unit 21, a high-pressure low-temperature gas storage tank 22, a throttling device 23, a first liquid thermal storage tank 24, a second liquid thermal storage tank 25, a first hot water storage tank 26, and a second hot water storage tank 27. The molten salt thermal storage unit 21 includes: a high-temperature thermal storage tank 211, a medium-temperature thermal storage tank 212, and a low-temperature thermal storage tank 213. The Rankine cycle unit 30 includes: a first molten salt-water heat exchanger 31, a boiler 32, a low-pressure cylinder 33, a medium-pressure cylinder 34, a high-pressure cylinder 35, a deaerator 36, a high-pressure heater 37, a second molten salt-water heat exchanger 38, a generator 39, a condenser 30A, and a low-pressure heater 30B. Processing unit 40 includes: a first unit 41 and a second unit 42. The first unit 41 is connected to a first branch 1321, and the second unit 42 is connected to a second branch 1322. The first unit 41 includes: a compression section 411 and an expansion section 412. The compression section 411 includes: a first compression section and a second compression section. The first compression section includes: a first air-water heat exchanger 4111, a second compressor 4112, a second air-molten salt heat exchanger 4113, and an air-liquid heat exchanger, which are connected in sequence to the first branch 1321. Heater 4114, the second compression section includes: a third compressor 4115, a third air-molten salt heat exchanger 4116, and a second air-water heat exchanger 4117 connected in sequence to the first compression section; expansion section 412 may include: a liquid-air heat exchanger 4121, a first molten salt-air heat exchanger 4122, a first expander 4123, a second molten salt-air heat exchanger 4124, and a second expander 4125 connected in sequence to the throttling device 23; the second unit 42 has a gas expansion function to generate electricity; The first compressor 11, the first air-molten salt heat exchanger 12, and the air-to-air heat exchanger 13 form a circulation loop. The cold side of the first air-molten salt heat exchanger 12 is provided with a first inlet 121 and a first outlet 122. The cold side of the air-to-air heat exchanger 13 is provided with a second inlet 131 and a second outlet 132. The inlet of the water-to-air heat exchanger 14 is used to enter air. The outlet of the water-to-air heat exchanger 14 is connected to the second inlet 131 of the air-to-air heat exchanger 13. The second outlet 132 is configured to split the air flowing out of the second outlet 132 into a first branch 1321 and a second branch 1322. The unit air volume of the first branch 1321 is greater than the unit air volume of the second branch 1322.

[0066] The inlet of the high-temperature heat storage tank 211 is connected to the first outlet 122, and the outlet is connected to the hot side inlet of the first molten salt-water heat exchanger 31; the inlet of the medium-temperature heat storage tank 212 is connected to the hot side outlet of the first molten salt-water heat exchanger 31, and the outlet is connected to the hot side inlet of the expansion section 412; the inlet of the low-temperature heat storage tank 213 is connected to the cold side outlet of the expansion section 412, and the outlet is connected to the first inlet 121 of the first air-molten salt heat exchanger 12.

[0067] The cold-side outlets of the second air-molten salt heat exchanger 4113 and the third air-molten salt heat exchanger 4116 are both connected to the inlet of the medium-temperature thermal storage tank 212, and the cold-side inlets of the second air-molten salt heat exchanger 4113 and the third air-molten salt heat exchanger 4116 are both connected to the outlet of the low-temperature thermal storage tank 213. The hot-side inlets of the first molten salt-air heat exchanger 4122 and the second molten salt-air heat exchanger 4124 are both connected to the outlet of the medium-temperature thermal storage tank 212, and the hot-side outlets of the first molten salt-air heat exchanger 4122 and the second molten salt-air heat exchanger 4124 are both connected to the inlet of the low-temperature thermal storage tank 213.

[0068] The high-pressure cryogenic gas storage tank 22 and the throttling device 23 are located sequentially between the compression section 411 and the expansion section 412. The high-pressure cryogenic gas storage tank 22 is used to store the high-pressure cryogenic gas in the compression section 411. The inlet of the first liquid heat storage tank 24 is connected to the cold side outlet of the air-liquid heat exchanger 4114, and the outlet is connected to the hot side inlet of the liquid-air heat exchanger 4121. The inlet of the second liquid heat storage tank 25 is connected to the hot side outlet of the liquid-air heat exchanger 4121, and the outlet is connected to the cold side inlet of the air-liquid heat exchanger 4114. The temperature inside the liquid heat storage tank 24 is higher than the temperature inside the second liquid heat storage tank 25; the two inlets of the first hot water storage tank 26 are respectively connected to the cold side outlet of the first air-water heat exchanger 4111 and the cold side outlet of the second air-water heat exchanger 4117, and the outlet is connected to the hot side inlet of the water-air heat exchanger 14; the two outlets of the second hot water storage tank 27 are respectively connected to the cold side inlet of the first air-water heat exchanger 4111 and the cold side inlet of the second air-water heat exchanger 4117, and the inlet is connected to the hot side outlet of the water-air heat exchanger 14.

[0069] The inlet of boiler 32 is connected to the cold-side outlet of the first molten salt-water heat exchanger 31, and the outlet is connected to the low-pressure cylinder 33 and the intermediate-pressure cylinder 34 respectively. The outlet of the low-pressure cylinder 33 is connected to the inlet of boiler 32. The outlet of the intermediate-pressure cylinder 34 is connected in sequence to the deaerator 36, the high-pressure heater 37 and the cold-side inlet of the first molten salt-water heat exchanger 31. The outlet of the deaerator 36 is also connected in sequence to the cold-side inlet of the second molten salt-water heat exchanger 38 and the cold-side inlet of the first molten salt-water heat exchanger 31. The hot-side outlet of the first molten salt-water heat exchanger 31 is also connected to the second molten salt-water heat exchanger 38. The low-pressure cylinder 33, the intermediate-pressure cylinder 34 and the high-pressure cylinder 35 are coaxially arranged and connected to the generator 39. The high-pressure cylinder 35, the condenser 30A, the low-pressure heater 30B and the deaerator 36 are connected in sequence.

[0070] Among them, the first compressor 11, the second compressor 4112 and the third compressor 4115 can be centrifugal compressors, and the isentropic efficiency can be selected from 75% to 85%. The expansion structure of the first expander 4123, the second expander 4125 and the second unit 42 can be a turbine-type expander, and the isentropic efficiency can be selected from 80% to 90%. The liquid-liquid heat exchangers mentioned above can all be shell-and-tube heat exchangers, the gas-liquid heat exchangers can all be shell-and-tube heat exchangers, and the gas-gas heat exchangers can all be printed circuit board heat exchangers.

[0071] Table 1: Parameters of each node in the hybrid energy storage system

[0072] Table 2: Energy storage, energy release, and round-trip efficiency parameters of hybrid energy storage systems

[0073] In this example, during periods of low grid electricity demand, the compression components (such as the first compressor 11, the second compressor 4112, and the third compressor 4115) of both the Brayton cycle unit 10 and the processing unit 40 operate. The Brayton cycle unit 10 stores high-temperature heat in a high-temperature heat storage tank 211 and diverts low-temperature heat to the compression section 411 and the second unit 42. The high-temperature heat generated by the compression section 411 is stored in the medium-temperature heat storage tank 212, and the medium- and low-temperature heat is stored in the first liquid heat storage tank 24. The low-temperature high-pressure gas after heat exchange is stored in the high-pressure low-temperature gas storage tank 22. The second unit 42 can directly expand to generate electricity when needed. During periods of high grid electricity demand, the generator 39 and the expansion section 412 (such as the first expander 4123 and the second expander 4125) operate to generate electricity. In this way, during off-peak electricity supply periods, excess electricity from new energy sources can be efficiently converted into heat and mechanical energy for storage, with diverse storage methods and rational utilization of different energy storage media. During peak electricity demand periods, the stored energy can be quickly used for power generation through the expansion structure, effectively alleviating the power supply pressure during peak hours, enhancing the power system's ability to cope with load fluctuations caused by renewable energy grid integration, and ensuring the stability and reliability of power supply. Moreover, through different waste heat utilization and energy storage methods, the energy storage efficiency of the hybrid energy storage system 100 is improved (as shown in the table above, 65.19%), reducing the dependence on and consumption of traditional energy sources during power generation.

[0074] The embodiments of this disclosure have now been described in detail. To avoid obscuring the concept of this disclosure, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0075] While specific embodiments of this disclosure have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this disclosure. In particular, as long as there is no structural conflict, the technical features mentioned in the various embodiments can be combined in any manner.

Claims

1. A hybrid energy storage system, characterized in that, include: The Brayton cycle unit includes: a first compressor forming a circulation loop, a first air-molten salt heat exchanger, and an air-to-air heat exchanger. The first air-molten salt heat exchanger has a first inlet and a first outlet on its cold side, and the air-to-air heat exchanger has a second inlet and a second outlet on its cold side. The second inlet is for air to enter. The energy storage unit includes: a molten salt thermal storage unit, wherein the molten salt thermal storage unit is connected to the first inlet and the first outlet to form a circulation loop; A Rankine cycle unit is connected to the molten salt thermal storage unit to obtain heat and generate electricity; The processing unit includes: a first unit, the first unit including: a compression section and an expansion section connected thereto, the compression section being connected to a second outlet and having a gas compression function, and being connected to the molten salt thermal storage unit to deliver heat at a first temperature to the molten salt thermal storage unit and compressed air at a second temperature lower than the first temperature to the expansion section, the expansion section having a gas expansion function to generate electricity.

2. The hybrid energy storage system according to claim 1, characterized in that, The second outlet is configured to divide the air flowing out of the second outlet into a first branch and a second branch, wherein the unit volume of the first branch is greater than the unit volume of the second branch. The processing unit further includes a second unit, wherein the first unit is connected to the first branch, the second unit is connected to the second branch, and has a gas expansion function to generate electricity.

3. The hybrid energy storage system according to claim 2, characterized in that, The molten salt thermal storage unit includes: a high-temperature thermal storage tank, a medium-temperature thermal storage tank, and a low-temperature thermal storage tank; The Rankine cycle unit includes: a first molten salt-water heat exchanger; The inlet of the high-temperature heat storage tank is connected to the first outlet, and the outlet is connected to the hot-side inlet of the first molten salt-water heat exchanger. The inlet of the medium-temperature thermal storage tank is connected to the hot-side outlet of the first molten salt-water heat exchanger, and the outlet is connected to the hot-side inlet of the expansion section. The inlet of the cryogenic heat storage tank is connected to the cold side outlet of the expansion section, and the outlet is connected to the first inlet of the first air-molten salt heat exchanger.

4. The hybrid energy storage system according to claim 3, characterized in that, The compression section includes: a first compression section and a second compression section; The first compression section includes: a first air-water heat exchanger, a second compressor, a second air-molten salt heat exchanger, and an air-liquid heat exchanger, which are sequentially connected to the first branch. The second compression section includes: a third compressor, a third air-molten salt heat exchanger, and a second air-water heat exchanger, which are connected in sequence to the first compression section; The cold-side outlets of the second and third air-molten salt heat exchangers are both connected to the inlet of the medium-temperature thermal storage tank, and the cold-side inlets of the second and third air-molten salt heat exchangers are both connected to the outlet of the low-temperature thermal storage tank.

5. The hybrid energy storage system according to claim 4, characterized in that, The energy storage unit further includes a high-pressure cryogenic gas storage tank and a throttling device, wherein the high-pressure cryogenic gas storage tank and the throttling device are located sequentially between the compression section and the expansion section, and the high-pressure cryogenic gas storage tank is used to store the high-pressure cryogenic gas in the compression section.

6. The hybrid energy storage system according to claim 5, characterized in that, The expansion section includes: a liquid-air heat exchanger, a first molten salt-air heat exchanger, a first expander, a second molten salt-air heat exchanger, and a second expander, which are sequentially connected to the throttling device. The hot-side inlet of the first molten salt-air heat exchanger and the hot-side inlet of the second molten salt-air heat exchanger are both connected to the outlet of the medium-temperature thermal storage tank, and the hot-side outlet of the first molten salt-air heat exchanger and the hot-side outlet of the second molten salt-air heat exchanger are both connected to the inlet of the low-temperature thermal storage tank.

7. The hybrid energy storage system according to claim 6, characterized in that, The energy storage unit further includes: a first liquid thermal storage tank and a second liquid thermal storage tank; The inlet of the first liquid heat storage tank is connected to the cold side outlet of the air-liquid heat exchanger, and the outlet is connected to the hot side inlet of the liquid-air heat exchanger. The inlet of the second liquid heat storage tank is connected to the hot-side outlet of the liquid-air heat exchanger, and the outlet is connected to the cold-side inlet of the air-liquid heat exchanger. The temperature inside the first liquid thermal storage tank is greater than the temperature inside the second liquid thermal storage tank.

8. The hybrid energy storage system according to claim 7, characterized in that, The Brayton cycle unit further includes: a water-air heat exchanger, the inlet of which is used to introduce air, and the outlet of which is connected to the second inlet of the air-air heat exchanger; The energy storage unit further includes: a first hot water storage tank and a second hot water storage tank. The two inlets of the first hot water storage tank are respectively connected to the cold side outlet of the first air-water heat exchanger and the cold side outlet of the second air-water heat exchanger, and the outlet is connected to the hot side inlet of the water-air heat exchanger. The two outlets of the second hot water storage tank are respectively connected to the cold side inlet of the first air-water heat exchanger and the cold side inlet of the second air-water heat exchanger, and the inlet is connected to the hot side outlet of the water-air heat exchanger.

9. The hybrid energy storage system according to claim 3, characterized in that, The Rankine cycle unit includes a boiler, a low-pressure cylinder, an intermediate-pressure cylinder, a high-pressure cylinder, a deaerator, a high-pressure heater, a second molten salt-water heat exchanger, and a generator. The inlet of the boiler is connected to the cold-side outlet of the first molten salt-water heat exchanger, and the outlets are respectively connected to the low-pressure cylinder and the intermediate-pressure cylinder. The outlet of the low-pressure cylinder is connected to the inlet of the boiler. The outlet of the intermediate-pressure cylinder is sequentially connected to the deaerator, the high-pressure heater, and the cold-side inlet of the first molten salt-water heat exchanger. The outlet of the deaerator is also sequentially connected to the cold-side inlet of the second molten salt-water heat exchanger and the cold-side inlet of the first molten salt-water heat exchanger. The hot-side outlet of the first molten salt-water heat exchanger is also connected to the second molten salt-water heat exchanger. The low-pressure cylinder, the intermediate-pressure cylinder, and the high-pressure cylinder are coaxially arranged and connected to the generator.

10. The hybrid energy storage system according to claim 9, characterized in that, The Rankine cycle unit further includes a condenser and a low-pressure heater, with the high-pressure cylinder, the condenser, the low-pressure heater, and the deaerator connected in sequence.

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