A two-stage compression-expansion thermal energy storage power generation system

Abstract

A two-stage compression expansion heat storage power generation system, comprising a low-temperature heat storage power generation device, a first counterflow heat exchanger and a high-temperature heat storage power generation device; the low-temperature heat storage power generation device comprises a liquid storage tank, a low-temperature phase change heat storage device, a first compressor, a first expander, a first heat storage system, a liquid pump, a throttle valve, a first generator, a first circulating medium and connecting pipelines therebetween; the high-temperature heat storage power generation device comprises a low-temperature liquid storage device, a high-temperature liquid storage device, a high-temperature phase change heat storage device, a second heat storage system, a second expander, a second compressor, a second generator, a second circulating medium and connecting pipelines therebetween; the low-temperature heat storage power generation device and the high-temperature heat storage power generation device simultaneously perform heat storage and power generation modes. The two low-high-temperature heat storage power generation systems of the application complement each other by using freon and water vapor, and have the characteristics of non-toxicity, harmlessness, greenness, cleanness and high working efficiency.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and specifically relates to a two-stage compression expansion thermal energy storage power generation system. Background Technology

[0002] As green energy gradually replaces global electricity supply, large-scale energy storage will be needed worldwide, leading to the emergence of new technologies such as carbon dioxide energy storage, compressed air energy storage, and hydrogen energy storage. Among these new energy storage technologies, compressed air energy storage boasts large capacity, with single-unit capacities exceeding hundreds of megawatts, second only to pumped hydro storage. However, the compressed air used for storage is heated, resulting in energy loss during the conversion process and low energy utilization efficiency. It has not yet been commercialized and is heavily limited by geographical conditions. To address the technical and application bottlenecks of compressed air energy storage systems, carbon dioxide energy storage is proposed. Compared to air, carbon dioxide offers unique advantages as a medium; however, its cost is high, and the main equipment is still in the research stage, requiring extensive research and development to make it more feasible. The challenges of hydrogen energy storage include high hydrogen costs, high power plant construction costs, low energy conversion efficiency, low technological maturity, and a long process from hydrogen production to storage, transportation, and power generation. These factors pose significant challenges to the widespread application of hydrogen energy storage power generation.

[0003] Steam, as a high-heat-melting and low-cost heat storage and transfer medium, brings new opportunities to the field of energy storage and power generation when combined with heat pump technology. However, in the low-temperature section, steam is under negative pressure (below 100 degrees Celsius), resulting in low system heat transfer efficiency and high system requirements. To solve this problem, this invention adopts a multi-stage approach, using low-boiling-point organic media in the low-temperature section and steam in the high-temperature section, which not only reduces system costs but also improves power generation efficiency. Summary of the Invention

[0004] To find a low-cost, high-efficiency thermal energy storage power generation system, this invention provides a two-stage compression-expansion thermal energy storage power generation system. In the low-temperature stage, a low-boiling-point organic medium is used, while inexpensive high-temperature heat transfer media, such as steam, are employed at the high-temperature stage. The two stages are connected by a counter-current heat exchanger. The complementary interaction of the two circulating media enables a reversible cycle for thermal energy storage power generation. This system is low-cost and easily commercialized. The specific description is as follows:

[0005] A two-stage compression-expansion thermal energy storage power generation system includes a low-temperature thermal energy storage power generation device, a first counter-current heat exchanger, and a high-temperature thermal energy storage power generation device;

[0006] The cryogenic thermal power generation device includes a liquid storage tank, a cryogenic phase change thermal storage device, a first compressor, a first expander, a first thermal storage system, a liquid pump, a throttle valve, a first generator, a first circulating medium, and connecting pipes between them. The cryogenic phase change thermal storage device contains cryogenic phase change material, and heat transfer pipes are arranged around the cryogenic phase change material. The liquid storage tank is connected to the heat transfer pipes of the cryogenic phase change thermal storage device. The first compressor and the first expander are connected in parallel between the heat transfer pipes of the cryogenic phase change thermal storage device and the first circulating medium channel of the first counter-current heat exchanger. The other end of the first circulating medium channel of the first counter-current heat exchanger is connected to the first thermal storage system. The liquid pump and the throttle valve are connected in parallel between the first thermal storage system and the liquid storage tank.

[0007] The high-temperature thermal energy storage power generation device includes a cryogenic liquid storage tank, a high-temperature liquid storage tank, a high-temperature phase change thermal energy storage tank, a second thermal energy storage system, a second expander, a second compressor, a second generator, a second circulating medium, and connecting pipes between them. The high-temperature phase change thermal energy storage tank contains high-temperature phase change material, and heat transfer pipes are arranged around the high-temperature phase change material. The cryogenic liquid storage tank is connected to one end of the second circulating medium channel in the first counter-current heat exchanger. The second compressor and the second expander are connected in parallel between the other end of the second circulating medium channel of the first counter-current heat exchanger and the second thermal energy storage system. The other end of the second thermal energy storage system is connected to one end of the heat transfer pipe of the high-temperature phase change thermal energy storage tank, and the other end of the heat transfer pipe of the high-temperature phase change thermal energy storage tank is connected to the high-temperature liquid storage tank.

[0008] Furthermore, the first thermal storage system includes a second counter-current heat exchanger, a high-temperature thermal storage unit of the first thermal storage system, a low-temperature thermal storage unit of the first thermal storage system, a circulating pump of the first thermal storage system, a four-way valve of the first thermal storage system, and a first thermal storage medium; the high-temperature thermal storage unit of the first thermal storage system is directly connected to one end of the first thermal storage medium channel in the second counter-current heat exchanger, and the other end of the first thermal storage medium channel in the second counter-current heat exchanger is connected to the low-temperature thermal storage unit of the first thermal storage system via the four-way valve and the circulating pump of the first thermal storage system; one end of the first circulating medium channel in the second counter-current heat exchanger is connected to the first circulating medium channel in the first counter-current heat exchanger, and the other end is connected to the liquid pump and the throttle valve respectively.

[0009] Furthermore, the second thermal storage system includes a low-temperature thermal storage unit, a third counter-current heat exchanger, a high-temperature thermal storage unit, a circulating pump, and a four-way valve. The high-temperature thermal storage unit is directly connected to one end of the second thermal storage medium channel in the third counter-current heat exchanger. The other end of the second thermal storage medium channel in the third counter-current heat exchanger is connected to the low-temperature thermal storage unit via the four-way valve and the circulating pump. One end of the second circulating medium channel in the third counter-current heat exchanger is connected to the heat transfer pipe of the high-temperature phase change thermal storage unit. The other end of the second circulating medium channel in the third counter-current heat exchanger is connected to the second expander and the second compressor, respectively.

[0010] Furthermore, the high-temperature thermal energy storage power generation device also includes a circulating pump and a solenoid valve; the circulating pump and the solenoid valve are connected in parallel between the high-temperature liquid storage tank and the high-temperature phase change thermal energy storage tank.

[0011] Furthermore, the first expander is electrically connected to the first generator; the second expander is electrically connected to the second generator.

[0012] Furthermore, the circulation temperature of the first circulating medium is lower than that of the second circulating medium.

[0013] Compared with existing thermal energy storage power generation technologies, this invention employs a two-stage compression-expansion thermal energy storage power generation system. In the low-temperature stage, it utilizes a low-boiling-point organic medium, while in the high-temperature stage, it uses a clean, high-temperature heat transfer medium, represented by steam. The two stages are connected by a counter-current heat exchanger, allowing for the complementary use of the two circulating media. This also solves the negative pressure problem associated with using only steam as the heat transfer medium, achieving a reversible cycle for thermal energy storage power generation. Furthermore, water and sulfur or nitrates can be selected for the low-temperature and high-temperature phase change materials, respectively. While the cost is slightly higher than that of a pure steam thermal energy storage power generation system, the operating efficiency is significantly improved, and it is extremely easy to commercialize. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Appendix Figure 1 This is a schematic diagram of the first structure of the two-stage compression expansion thermal energy storage power generation system of the present invention.

[0016] Appendix Figure 2 It is attached Figure 1 A schematic diagram of the thermal storage working mode.

[0017] Appendix Figure 3 It is attached Figure 1 A schematic diagram of the power generation operation mode.

[0018] Appendix Figure 4 This is a schematic diagram of the second type of the dual-stage compression-expansion thermal energy storage power generation system of the present invention.

[0019] In the diagram: 1. Liquid storage tank; 2. Low-temperature phase change thermal storage device; 31. First expander; 32. Second expander; 41. First compressor; 42. Second compressor; 5. First counter-current heat exchanger; 6. Second counter-current heat exchanger; 7. High-temperature thermal storage device of the first thermal storage system; 8. Low-temperature thermal storage device of the first thermal storage system; 9. Circulation pump of the first thermal storage system; 10. Liquid pump; 11. Throttling valve; 121. First generator; 122. Second generator; 13. Low-temperature liquid storage device; 14. High-temperature liquid storage device; 15. High-temperature phase change thermal storage device; 16. Low-temperature thermal storage device of the second thermal storage system; 17. Third counter-current heat exchanger; 18. High-temperature thermal storage device of the second thermal storage system; 19. Circulation pump of the second thermal storage system; 201. First check valve; 202. Second check valve; 203. Third check valve; 204. Fourth check valve; 205. Fifth check valve; 206. Sixth check valve; 211. Four-way valve of the first thermal storage system; 212. Four-way valve of the second thermal storage system; 213. Four-way valve of the third thermal storage system; 22. Circulation pump; 23. Solenoid valve; 24. Fourth counter-current heat exchanger; 25. High-temperature thermal storage unit of the third thermal storage system; 26. Low-temperature thermal storage unit of the third thermal storage system; 27. Circulation pump of the third thermal storage system. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below.

[0021] Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. To facilitate understanding of the embodiments, various embodiments or implementation methods are provided below to illustrate the relevant devices, modules, and functions of this invention.

[0023] Implementation Method 1

[0024] As attached Figure 1 As shown, a two-stage compression-expansion thermal energy storage power generation system includes a low-temperature thermal energy storage power generation device, a first countercurrent heat exchanger 5, and a high-temperature thermal energy storage power generation device;

[0025] The cryogenic thermal power generation device includes a liquid storage tank 1, a cryogenic phase change thermal storage device 2, a first compressor 41, a first expander 31, a first thermal storage system, a liquid pump 10, a throttle valve 11, a first generator 121, a first circulating medium, and connecting pipes between them. The cryogenic phase change thermal storage device 2 contains cryogenic phase change material, and heat transfer pipes are arranged around the cryogenic phase change material. One end of the heat transfer pipes of the liquid storage tank 1 and the cryogenic phase change thermal storage device 2 is connected, and the other end of the heat transfer pipes of the cryogenic phase change thermal storage device 2 is connected to the medium inlet of the first compressor 41 and the medium outlet of the first expander 31, respectively. The medium inlet of the first expander 31 and the medium outlet of the first compressor 41 are both connected to the first circulating medium channel in the first counter-current heat exchanger 5. The first circulating medium channel in the first counter-current heat exchanger 5 is connected to the first thermal storage system. The liquid pump 10 and the throttle valve 11 are connected in parallel between the first thermal storage system and the liquid storage tank 1. The first expander 31 is electrically connected to the first generator 121.

[0026] The first thermal storage system includes a second counter-current heat exchanger 6, a high-temperature thermal storage unit 7, a low-temperature thermal storage unit 8, a circulating pump 9, a four-way valve 211, and a first thermal storage medium. The high-temperature thermal storage unit 7 is directly connected to one end of the first thermal storage medium channel in the second counter-current heat exchanger 6. The other end of the first thermal storage medium channel in the second counter-current heat exchanger 6 is connected to the low-temperature thermal storage unit 8 via the four-way valve 211 and the circulating pump 9. One end of the first circulating medium channel in the second counter-current heat exchanger 6 is connected to the first circulating medium channel in the first counter-current heat exchanger 5, and the other end is connected to the liquid pump 10 and the throttle valve 11, respectively.

[0027] When the first thermal storage system stores heat, under the action of the circulation pump 9 of the first thermal storage system, the first thermal storage medium in the low-temperature thermal storage tank 8 of the first thermal storage system enters the circulation pump 9 of the first thermal storage system through the four-way valve 211 of the first thermal storage system, and then is sent to the first thermal storage medium channel of the second counter-current heat exchanger 6 through the four-way valve 211 of the first thermal storage system again. The first thermal storage medium absorbs the heat of the first circulating medium in another channel of the second counter-current heat exchanger 6, and the temperature of the first thermal storage medium rises. The heated first thermal storage medium is finally sent directly to the high-temperature thermal storage tank 7 of the first thermal storage system for storage.

[0028] When the first thermal storage system releases heat, under the action of the circulation pump 9 of the first thermal storage system, the first thermal storage medium stored in the high-temperature thermal storage tank 7 of the first thermal storage system is sent into the first thermal storage medium channel of the second countercurrent heat exchanger 6. The first thermal storage medium exchanges heat with the first circulating medium in another channel of the second countercurrent heat exchanger 6, and the first thermal storage medium releases heat. The first thermal storage medium after releasing heat is stored in the low-temperature thermal storage tank 8 of the first thermal storage system through the four-way valve 211 of the first thermal storage system and the circulation pump 9 of the first thermal storage system.

[0029] The high-temperature thermal energy storage power generation device includes a cryogenic liquid storage tank 13, a high-temperature liquid storage tank 14, a high-temperature phase change thermal energy storage tank 15, a second thermal energy storage system, a second expander 32, a second compressor 42, a second generator 122, a second circulating medium, and connecting pipes between them. The high-temperature phase change thermal energy storage tank 15 contains high-temperature phase change material, and heat transfer pipes are arranged around the high-temperature phase change material. The cryogenic liquid storage tank 13 is connected to one end of the second circulating medium channel in the first counter-current heat exchanger 5. The other end of the second circulating medium channel in the first counter-current heat exchanger 5 is connected to the medium inlet of the second compressor 42 and the medium outlet of the second expander 32, respectively. The medium inlet of the second expander 32 and the medium outlet of the second compressor 42 are connected to one end of the second thermal energy storage system. The other end of the second thermal energy storage system is connected to one end of the heat transfer pipe of the high-temperature phase change thermal energy storage tank 15. The other end of the heat transfer pipe of the high-temperature phase change thermal energy storage tank 15 is connected to the high-temperature liquid storage tank 14. The second expander 32 is electrically connected to the second generator 122.

[0030] Please refer to Figure 2 As shown, the high-temperature thermal energy storage power generation device also includes a circulating pump 22 and a solenoid valve 23; the circulating pump 22 and the solenoid valve 23 are connected in parallel between the high-temperature liquid storage tank 14 and the high-temperature phase change thermal energy storage tank 15.

[0031] The second thermal storage system includes a low-temperature thermal storage unit 16, a third counter-current heat exchanger 17, a high-temperature thermal storage unit 18, a circulating pump 19, and a four-way valve 212. The high-temperature thermal storage unit 18 is directly connected to one end of the second thermal storage medium channel in the third counter-current heat exchanger 17. The other end of the second thermal storage medium channel in the third counter-current heat exchanger 17 is connected to the low-temperature thermal storage unit 16 via the four-way valve 212 and the circulating pump 19. One end of the second circulating medium channel in the third counter-current heat exchanger 17 is connected to the heat transfer pipe of the high-temperature phase change thermal storage unit 15. The other end of the second circulating medium channel in the third counter-current heat exchanger 17 is connected to the second expander 32 and the second compressor 42, respectively.

[0032] During the second heat storage system, under the action of the circulation pump 19, the second heat storage medium in the low-temperature heat storage tank 16 of the second heat storage system enters the circulation pump 19 of the second heat storage system through the four-way valve 212 of the second heat storage system, and then is sent to the second heat storage medium channel of the third counter-current heat exchanger 17 through the four-way valve 212 of the second heat storage system again. The second heat storage medium absorbs the heat of the second circulating medium in another channel of the third counter-current heat exchanger 17, and the temperature of the second heat storage medium rises. The heated second heat storage medium is finally sent directly to the high-temperature heat storage tank 18 of the second heat storage system for storage.

[0033] When the second thermal storage system releases heat, under the action of the circulation pump 19 of the second thermal storage system, the high-temperature second thermal storage medium stored in the high-temperature thermal storage tank 18 of the second thermal storage system is sent into the second thermal storage medium channel of the third counter-current heat exchanger 17. The second thermal storage medium exchanges heat with the second circulating medium in another channel of the third counter-current heat exchanger 17. The second thermal storage medium releases heat, and the released second thermal storage medium enters the low-temperature thermal storage tank 16 of the second thermal storage system through the four-way valve 212 of the second thermal storage system and the circulation pump 19 of the second thermal storage system.

[0034] The first expander branch 31 is equipped with a first check valve 201, and the first compressor branch 41 is equipped with a second check valve 202.

[0035] The above-mentioned pump branch is equipped with a third check valve 203; the throttle valve 11 branch is equipped with a fourth check valve 204.

[0036] The second expander branch 32 is equipped with a fifth check valve 205, and the second compressor branch 42 is equipped with a sixth check valve 206.

[0037] The present invention provides a two-stage compression expansion thermal energy storage power generation system with two operating modes: thermal energy storage mode and power generation mode.

[0038] In thermal storage mode: Please refer to Figure 2As shown, the low-temperature thermal power generation device and the high-temperature thermal power generation device simultaneously enter the thermal storage working mode. In the low-temperature thermal power generation device, under the action of the first compressor 41, the first circulating medium in the storage tank 1 is sent into the heat transfer pipe of the low-temperature phase change thermal storage device 2. The first circulating medium undergoes isothermal heat exchange with the low-temperature phase change material in the low-temperature phase change thermal storage device 2. The first circulating medium absorbs heat from the low-temperature phase change material and becomes gaseous. The gaseous first circulating vapor medium enters the first compressor 41 and is compressed into a high-temperature, high-pressure superheated gaseous first circulating medium. This high-temperature, high-pressure superheated gaseous first circulating medium enters the first circulating medium channel of the first counter-current heat exchanger 5. Simultaneously, in the high-temperature thermal power generation device, the second circulating medium in the low-temperature storage tank 13, under the action of the second compressor 42, enters the second circulating medium channel of the first counter-current heat exchanger 5 and interacts with the high-temperature, high-pressure superheated gaseous gas in the first circulating medium channel of the first counter-current heat exchanger 5. The first circulating medium undergoes reverse heat exchange, releasing heat while the second circulating medium absorbs heat and vaporizes. The high-temperature, high-pressure first circulating medium after heat release is sent to the first circulating medium channel of the second counter-current heat exchanger 6. Simultaneously, under the action of the circulating pump 9 of the first heat storage system, the first heat storage medium in the low-temperature heat storage tank 8 of the first heat storage system is sent to the first heat storage medium channel of the second counter-current heat exchanger 6. Thus, the first circulating medium and the first heat storage medium undergo reverse heat exchange in the second counter-current heat exchanger 6. The first heat storage medium absorbs heat from the first circulating medium in another channel of the second counter-current heat exchanger 6, causing the temperature of the first heat storage medium to rise. The heated first heat storage medium is then directly sent to the high-temperature heat storage tank 7 of the first heat storage system for storage. The first circulating medium releases heat, and after heat release, the first circulating medium is throttled by the throttling valve 11 to become a low-temperature liquid first circulating medium, which is then sent to the storage tank 1 for the next cycle.In the high-temperature thermal energy storage power generation device, the gaseous second circulating medium exiting from the second circulating medium channel of the first counter-current heat exchanger 5 directly enters the first compressor 41 and is compressed into a high-temperature, high-pressure superheated gaseous second circulating medium. This high-temperature, high-pressure superheated gaseous second circulating medium then enters the third counter-current heat exchanger 17. Simultaneously, under the action of the circulation pump 19 of the second thermal energy storage system, the second thermal energy storage medium in the low-temperature thermal energy storage tank 16 of the second thermal energy storage system is sent to the second thermal energy storage medium channel of the third counter-current heat exchanger 17 via the four-way valve 212 of the second thermal energy storage system and the circulation pump 19 of the second thermal energy storage system. The second circulating medium and the second thermal energy storage medium undergo counter-current heat exchange in the third counter-current heat exchanger 17. The medium absorbs heat from the second circulating medium, causing its temperature to rise. The heated second circulating medium is then directly sent to the high-temperature thermal storage tank 18 of the second thermal storage system for storage. After releasing some heat in the third counter-current heat exchanger 17, the second circulating medium enters the heat transfer pipe of the high-temperature phase change thermal storage tank 15, where it undergoes isothermal heat exchange with the high-temperature phase change material. The high-temperature phase change material absorbs heat from the second circulating medium and undergoes a phase change, storing its latent heat in the high-temperature phase change thermal storage tank 15. Simultaneously, the second circulating medium releases heat and transforms into a liquid form, entering the high-temperature thermal storage tank 14 for use during power generation. This completes the thermal storage operation mode.

[0039] In power generation mode: Please refer to... Figure 3As shown, the low-temperature thermal energy storage power generation device and the high-temperature thermal energy storage power generation device simultaneously enter the power generation mode. The low-temperature thermal energy storage power generation device uses a liquid pump 10 to extract the low-temperature liquid first circulating medium from the storage tank 1, pressurizes it, and sends it into the first circulating medium channel of the second counter-current heat exchanger 6. Simultaneously, the circulating pump 9 of the first thermal energy storage system extracts the high-temperature first thermal energy storage medium stored in the high-temperature thermal energy storage tank 7 of the first thermal energy storage system and sends it into the first thermal energy storage medium channel of the second counter-current heat exchanger 6. The first thermal energy storage medium and the first circulating medium undergo counter-current heat exchange; the first thermal energy storage medium releases heat, and the first circulating medium absorbs heat. The released first thermal energy storage medium is then stored in the first thermal energy storage system via the four-way valve 211 and the circulating pump 9, respectively. In the low-temperature heat storage tank 8 of the thermal system, the first circulating medium after absorbing heat for the first time enters the first circulating medium channel of the first counter-current heat exchanger 5. At the same time, the second circulating medium after performing work also enters the second circulating medium channel of the first counter-current heat exchanger 5. The first and second circulating media flow in opposite directions in the first counter-current heat exchanger 5. The first circulating medium absorbs heat from the second circulating medium and becomes a high-temperature, high-pressure first circulating medium. The high-temperature, high-pressure first circulating medium directly enters the first expander 31 to perform work. The first expander 31 converts thermal energy into mechanical energy to drive the first generator 121 to generate electricity, ultimately realizing the conversion of thermal energy into electrical energy output. The first circulating medium after performing work is discharged through the first expander 31 and enters the low-temperature phase. The thermal storage device 2 exchanges heat with the low-temperature phase change material. The low-temperature phase change material absorbs heat from the first circulating medium, undergoes a phase change, and is stored in the low-temperature phase change thermal storage device 2 as latent heat. After releasing heat, the first circulating medium becomes a low-temperature liquid first circulating medium and finally enters the storage tank 1, thus completing the power generation process of the low-temperature thermal storage power generation device. In the high-temperature thermal storage power generation device, under the action of the circulating pump 22, the high-temperature and high-pressure liquid second circulating medium in the high-temperature storage tank 14 directly enters the heat transfer pipe of the high-temperature phase change thermal storage device 15, absorbs heat from the high-temperature phase change material in the high-temperature phase change thermal storage device 15, and becomes a high-temperature and high-pressure vapor second circulating medium. The high-temperature and high-pressure vapor second circulating medium enters the second circulating medium in the third countercurrent heat exchanger 17. In the annular medium channel, under the action of the circulation pump 19 of the second thermal storage system, the high-temperature second thermal storage medium stored in the high-temperature thermal storage tank 18 of the second thermal storage system is sent into the second thermal storage medium channel of the third countercurrent heat exchanger 17. The second thermal storage medium exchanges heat with the high-temperature second circulating medium. The second thermal storage medium releases heat. The released second thermal storage medium enters the low-temperature thermal storage tank 16 of the second thermal storage system through the four-way valve 212 of the second thermal storage system and the circulation pump 19 of the second thermal storage system. The second circulating medium absorbs heat and raises its temperature again. Then it directly enters the second expander 32 to do work. The second expander 32 converts thermal energy into mechanical energy to drive the second motor 122 to generate electricity, and finally realizes the conversion of thermal energy into electrical energy output.After performing work, the second circulating medium is discharged through the second expander 32 and enters the second circulating medium channel of the first counter-current heat exchanger 5. The first and second circulating media flow in opposite directions in the first counter-current heat exchanger 5. The second circulating medium releases heat and liquefies, finally entering the low-temperature storage tank 13. This completes one power generation process of the high-temperature thermal energy storage power generation device.

[0040] In the aforementioned low-temperature thermal energy storage power generation device, the first circulating medium is a low-temperature circulating medium, which can be a low-boiling-point organic medium, with Freon being the optimal choice for the first circulating medium, and its operating temperature is below 110℃. In the low-temperature phase change thermal energy storage device 2, the phase change material is a low-temperature solid-liquid phase change material, with inexpensive water being the optimal choice. In the thermal energy storage mode, the low-temperature phase change material undergoes isothermal heat release, changing from a liquid to a solid state; in the power generation mode, the low-temperature phase change material undergoes isothermal heat absorption, changing from a solid to a liquid state. Liquid water is preferentially selected as the first thermal energy storage medium in the first thermal energy storage system.

[0041] In the high-temperature thermal energy storage power generation device described above, the second circulating medium is a high-temperature circulating medium, with steam being the optimal choice, and its circulating operating temperature is between 110℃ and 300℃. The phase change material in the high-temperature phase change thermal energy storage device 15 is a high-temperature solid-liquid phase change material, with nitrates being the optimal choice, such as sodium nitrate, potassium nitrate, sodium nitrite, potassium nitrite, or binary salts of nitrates. In the thermal energy storage mode, the high-temperature phase change material undergoes isothermal heat absorption, changing from a solid to a liquid state; in the power generation mode, the high-temperature phase change material undergoes isothermal heat release, changing from a liquid to a solid state. Molten salt is preferentially selected as the second thermal energy storage medium in the second thermal energy storage system.

[0042] Implementation Method 2

[0043] Please refer to Figure 4 As shown, compared with Example 1 Figure 1In comparison, the low-temperature thermal energy storage power generation device of the dual-stage compression expansion thermal energy storage power generation system of the present invention further includes a third thermal energy storage system; the third thermal energy storage system includes a fourth counter-current heat exchanger 24, a high-temperature thermal energy storage unit 25 of the third thermal energy storage system, a low-temperature thermal energy storage unit 26 of the third thermal energy storage system, a circulation pump 27 of the third thermal energy storage system, a four-way valve 213 of the third thermal energy storage system, a third thermal energy storage medium, and connecting pipes between them; the high-temperature thermal energy storage unit 25 of the third thermal energy storage system is directly connected to one end of the third thermal energy storage medium channel in the fourth counter-current heat exchanger 24, and the other end of the fourth thermal energy storage medium channel in the fourth counter-current heat exchanger 24 is connected to the low-temperature thermal energy storage unit 26 of the third thermal energy storage system via the four-way valve 213 of the third thermal energy storage system and the circulation pump 27 of the third thermal energy storage system; one end of the first circulation medium channel in the fourth counter-current heat exchanger 24 is connected to the first circulation medium channel in the first counter-current heat exchanger 5, and the other end is connected to the outlet of the first compressor 41 and the inlet of the first expander 31, respectively.

[0044] During the heat storage process of the third heat storage system described above, under the action of the circulation pump 27 of the third heat storage system, the third heat storage medium in the low-temperature heat storage tank 26 of the third heat storage system enters the circulation pump 27 of the third heat storage system through the four-way valve 213 of the third heat storage system, and then is sent to the third heat storage medium channel of the fourth counter-current heat exchanger 24 through the four-way valve 214 of the third heat storage system again. The third heat storage medium absorbs the heat of the superheated saturated first circulation medium in another channel of the fourth counter-current heat exchanger 24, and the temperature of the third heat storage medium rises. The heated third heat storage medium is finally sent directly to the high-temperature heat storage tank 25 of the third heat storage system for storage.

[0045] When the third thermal storage system releases heat, under the action of the circulation pump 27 of the third thermal storage system, the third thermal storage medium stored in the high-temperature thermal storage tank 25 of the third thermal storage system is sent into the third thermal storage medium channel of the fourth counter-current heat exchanger 24. The third thermal storage medium exchanges heat with the high-temperature and high-pressure first circulating medium in another channel of the fourth counter-current heat exchanger 24, and the third thermal storage medium releases heat. The released third thermal storage medium is stored in the low-temperature thermal storage tank 26 of the third thermal storage system through the four-way valve 213 of the third thermal storage system and the circulation pump 27 of the third thermal storage system. At the same time, the high-temperature and high-pressure first circulating medium coming out of the first circulating medium channel of the fourth counter-current heat exchanger 24 absorbs the third thermal storage medium and becomes a superheated high-temperature and high-pressure first circulating medium, which is sent into the first expander 31 to do work. Figure 4 The installation and operation principles of the other components shown are the same as in Example 1.

Claims

1. A two-stage compression expansion heat storage power generation system, characterized by, The low-temperature heat storage power generation device, the first counterflow heat exchanger and the high-temperature heat storage power generation device are connected by pipelines. The low-temperature heat storage power generation device comprises a liquid storage tank, a low-temperature phase change heat storage device, a first compressor, a first expander, a first heat storage system, a liquid pump, a throttle valve, a first generator, a first circulating medium and pipelines connecting them; the low-temperature phase change heat storage device is filled with a low-temperature phase change material, and a heat transfer pipeline is arranged around the low-temperature phase change material; the liquid storage tank is in communication with the heat transfer pipeline of the low-temperature phase change heat storage device, and the first compressor and the first expander are connected in parallel between the heat transfer pipeline of the low-temperature phase change heat storage device and a first circulating medium channel of the first counterflow heat exchanger; the first circulating medium channel of the first counterflow heat exchanger is in communication with the first heat storage system at the other end; the liquid pump and the throttle valve are connected in parallel between the first heat storage system and the liquid storage tank. The high-temperature heat storage power generation device comprises a low-temperature liquid storage device, a high-temperature liquid storage device, a high-temperature phase change heat storage device, a second heat storage system, a second expander, a second compressor, a second generator, a second circulating medium and pipelines connecting them; the high-temperature phase change heat storage device is filled with a high-temperature phase change material, and a heat transfer pipeline is arranged around the high-temperature phase change material; the low-temperature liquid storage device is in communication with one end of a second circulating medium channel in the first counterflow heat exchanger, the second compressor and the second expander are connected in parallel between the other end of the second circulating medium channel in the first counterflow heat exchanger and the second heat storage system, and the other end of the second heat storage system is in communication with one end of the heat transfer pipeline of the high-temperature phase change heat storage device, and the other end of the heat transfer pipeline of the high-temperature phase change heat storage device is in communication with the high-temperature liquid storage device.

2. The two-stage compression and expansion heat storage power generation system according to claim 1, wherein The first heat storage system comprises a second counterflow heat exchanger, a high-temperature heat storage device of the first heat storage system, a low-temperature heat storage device of the first heat storage system, a circulating pump of the first heat storage system, a four-way valve of the first heat storage system and a first heat storage medium; the high-temperature heat storage device of the first heat storage system is directly in communication with one end of a first heat storage medium channel in the second counterflow heat exchanger, the other end of the first heat storage medium channel in the second counterflow heat exchanger is connected with the low-temperature heat storage device of the first heat storage system through the four-way valve of the first heat storage system and the circulating pump of the first heat storage system. One end of a first circulating medium channel in the second counterflow heat exchanger is in communication with a first circulating medium channel in the first counterflow heat exchanger, and the other end of the first circulating medium channel in the second counterflow heat exchanger is in communication with the liquid pump and the throttle valve respectively.

3. The dual-stage compression-expansion heat storage power generation system of claim 1, wherein, The second heat storage system comprises a low-temperature heat storage device of the second heat storage system, a third counterflow heat exchanger, a high-temperature heat storage device of the second heat storage system, a circulating pump of the second heat storage system and a four-way valve of the second heat storage system; the high-temperature heat storage device of the second heat storage system is directly in communication with one end of a second heat storage medium channel in the third counterflow heat exchanger, the other end of the second heat storage medium channel in the third counterflow heat exchanger is connected with the low-temperature heat storage device of the second heat storage system through the four-way valve of the second heat storage system and the circulating pump of the second heat storage system; one end of a second circulating medium channel in the third counterflow heat exchanger is in communication with the heat transfer pipeline of the high-temperature phase change heat storage device; the other end of the second circulating medium channel in the third counterflow heat exchanger is in communication with the second expander and the second compressor respectively.

4. The dual-stage compression-expansion heat storage power generation system of claim 1, wherein, The high-temperature heat storage power generation device further comprises a circulating pump and a solenoid valve; the circulating pump and the solenoid valve are connected in parallel between the high-temperature storage reservoir and the high-temperature phase change heat storage device.

5. The dual-stage compression-expansion heat storage power generation system of claim 1, wherein, The first expander is electrically connected with a first generator; the second expander is electrically connected with a second generator.

6. The binary cycle compression expansion heat storage power generation system of claim 1, wherein, The circulating temperature of the first circulating medium is less than the circulating temperature of the second circulating medium.

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