Energy storage system utilizing low-grade heat source for heat storage and ice slurry for cold storage

Abstract

The invention discloses an energy storage system utilizing a low-grade heat source for heat storage and ice slurry for cold storage, which relates to the technical field of energy storage systems and comprises a heat pump heat storage assembly, a cold pump refrigeration ice slurry cold storage assembly and a steam turbine working assembly. According to the invention, grade improvement and energy storage of a low-grade heat source are realized by arranging a heat pump for heat storage, and grade improvement and energy storage of a low-grade cold source are realized by arranging a cold pump for ice slurry for cold storage; the high-temperature heat source and the low-temperature cold source drive the steam turbine to conduct grid-connected power generation through the carbon dioxide working medium under the working condition of large temperature difference, in the electricity consumption trough period at night, the electric energy drives the heat pump to obtain heat from the low-grade heat source and store heat energy in a phase change heat storage mode to achieve heat storage, and in the electricity consumption peak period at daytime, the heat energy is stored in a phase change heat storage mode. Heat stored by heat storage and cold stored by cold storage are utilized to drive a steam turbine through a carbon dioxide working medium for grid-connected power generation, and the purposes of storing energy at night and releasing energy in daytime for power generation are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage systems, and particularly to an energy storage system that utilizes low-grade heat sources for heat storage and ice slurry for cold storage. Background Art

[0002] With the development of technology, the global electricity demand has been continuously increasing. At the same time, this has brought about serious environmental deterioration problems. In the 1960s, the world began to realize environmental problems and gradually began to attach importance to and improve the current situation. One of the most important ways is to develop renewable resource substitution technologies (hydropower, wind energy, solar energy, biomass energy, tides) to replace fossil fuels (coal, oil, natural gas). In recent years, wind energy and solar energy in China have developed rapidly. However, both wind energy and solar energy have the characteristic of unstable power generation, resulting in large fluctuations in power generation on the power supply side. In addition, there are also large fluctuations in power consumption on the load side due to significant differences in electricity consumption between day and night on the load side, seriously affecting the stability of power grid operation. Therefore, it is particularly important to use energy storage technology for peak shaving and valley filling of grid energy.

[0003] Low-grade heat sources with a temperature greater than 40 degrees that are cheap, stable, and abundant are easily obtainable, such as waste heat from thermal power plants, geothermal hot springs, etc. (in this case, the cooling water from the condenser of a thermal power plant is used as the low-grade heat source as an example). Low-grade cold sources with a temperature lower than 20 degrees that are cheap and abundant are also easily obtainable, such as the natural environmental cold source with a night ambient temperature lower than 20 degrees in most parts of northern China, the large amount of cooling water that can be obtained through the operation of a cooling tower, and also some rivers, lakes, and groundwater in China, as well as seawater at a certain depth, etc., all meet the requirements of low-grade cold sources with a temperature lower than 20 degrees.

[0004] How to utilize these cheap and abundant low-grade heat sources and natural environmental cold sources for power generation is of great significance for realizing green and low-carbon development and energy conservation and emission reduction.

[0005] Therefore, it is necessary to invent an energy storage system that utilizes low-grade heat sources for heat storage and ice slurry for cold storage to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide an energy storage system that utilizes low-grade heat sources for heat storage and ice slurry for cold storage to solve the problems raised in the above background art.

[0007] To achieve the above purpose, the present invention provides the following technical solution: An energy storage system that utilizes low-grade heat sources for heat storage and ice slurry for cold storage, comprising:

[0008] A heat pump heat storage component, which is used to extract and store heat from the cooling water of a thermal power plant condenser. The heat pump heat storage component includes a circulation pump one, a heat exchanger one, a compressor one, a heat exchanger two, a throttle valve one, a circulation pump two 27, a phase change heat storage tank, a circulation pump three, a superheater, and an evaporator;

[0009] A loop is formed by pipes among the first circulation pump, the first heat exchanger, and the evaporator, and there is cooling water from a thermal power condenser in the loop. A loop is formed by pipes among the first heat exchanger, the first compressor, the second heat exchanger, and the first throttle valve, and there is carbon dioxide working medium gas in the loop. A loop is formed by pipes among the second heat exchanger, the second circulation pump 27, and the phase change heat storage pool, and there is hot water in the loop. A loop is formed by pipes among the phase change heat storage pool, the third circulation pump, and the superheater, and there is hot water in the loop;

[0010] The cold pump refrigerating ice slurry cold storage assembly is used to obtain colder cooling capacity from a low-temperature environment by using electric energy and store the cooling capacity with ice slurry as the storage medium. The cold pump refrigerating ice slurry cold storage assembly includes an evaporator, a superheater, a first valve, a first steam turbine, a first condenser, a third valve, a liquid storage tank, a pressurizing pump, a second throttle valve, a second condenser, a cooling tower, a phase change heat storage pool, and a second compressor;

[0011] A loop is formed by pipes among the liquid storage tank, the pressurizing pump, the evaporator, the superheater, the first valve, the first steam turbine, the first condenser, and the third valve, and there is steam turbine working medium gas stored inside the liquid storage tank in the loop. A loop is formed by pipes among the second compressor, the first condenser, the third valve, the second throttle valve, and the second condenser, and there is carbon dioxide working medium gas in the loop. A loop is formed by pipes between the first condenser and the cooling tower, and there is low-freezing-point water in the loop. A loop is formed by pipes among the fourth circulation pump, the phase change heat storage pool, and the cooling tower, and there is low-freezing-point water in the loop;

[0012] The steam turbine working assembly generates electricity through the heat source of the heat pump heat storage assembly and the cold source of the cold pump refrigerating ice slurry cold storage assembly. The steam turbine working assembly includes a second steam turbine, a second valve, a fourth valve, and a fifth valve. A loop is formed by pipes among the superheater, the second valve, the second steam turbine, the fifth valve, the second condenser, the fourth valve, the liquid storage tank, the pressurizing pump, and the evaporator, and there is carbon dioxide working medium gas from the liquid storage tank in the loop.

[0013] Preferably, the loop formed by pipes among the first circulation pump, the first heat exchanger, and the evaporator is used to exchange the heat of the cooling water in the thermal power condenser into the system;

[0014] The loop formed by the first heat exchanger, the first compressor, the second heat exchanger, and the first throttle valve is used to exchange the heat of the cooling water in the thermal power condenser into the carbon dioxide working medium gas and increase its pressure and temperature;

[0015] The loop formed by the second heat exchanger, the second circulation pump 27, and the phase change heat storage pool is used to exchange the heat in the carbon dioxide working medium gas with increased pressure and temperature into the hot water in the phase change heat storage pool to store heat.

[0016] Preferably, the loop formed by the phase change heat storage pool, the circulation pump three and the superheater is used to exchange the heat of the hot water in the phase change heat storage pool to the steam turbine working medium gas.

[0017] Preferably, the steam turbine working medium gas is carbon dioxide gas, and the loop formed by the liquid storage tank, the pressurizing pump, the evaporator, the superheater, the valve one, the steam turbine one, the condenser one and the valve three is used to drive the steam turbine one to rotate for power generation.

[0018] Preferably, the loop formed by the compressor two, the condenser one, the valve three, the throttle valve two and the condenser two is used for refrigeration and cold storage;

[0019] The loop formed by the condenser one and the cooling tower is used to exchange heat between the carbon dioxide working medium gas and the low freezing point water from the cooling tower to liquefy the carbon dioxide working medium gas;

[0020] A loop is formed by a pipeline between the phase change cold storage pool, the circulation pump five and the condenser two, and there is low freezing point water in the loop. The loop formed by the phase change cold storage pool, the circulation pump five and the condenser two is used to exchange heat between the liquefied carbon dioxide working medium and the low freezing point water in the phase change cold storage pool to partially condense the low freezing point water into ice and store it in the phase change cold storage pool.

[0021] Preferably, the loop formed by the superheater, the valve two, the steam turbine two, the valve five, the condenser two, the valve four, the liquid storage tank, the pressurizing pump and the evaporator is used to pressurize the carbon dioxide working medium gas and transport it to the steam turbine two to drive the steam turbine two to rotate for power generation.

[0022] Preferably, the power generation of the steam turbine one is used to drive the compressor two.

[0023] Preferably, the power generation of the steam turbine two is used to be incorporated into the power grid.

[0024] Preferably, the working process of the system includes a heat pump heat storage process, a slurry ice cold storage process and a steam turbine working process. The three processes can operate independently. The heat pump heat storage component operates during the period when the power supply at night is sufficient to realize the heat pump heat storage process. The cold pump refrigeration slurry ice cold storage component operates during other periods when grid-connected power generation is not carried out to realize the cold pump refrigeration slurry ice cold storage process. The steam turbine working component operates during the period when the power supply is insufficient during the day to realize the steam turbine working process.

[0025] The technical effects and advantages of the present invention:

[0026] 1. The present invention realizes the upgrading of the grade and energy storage of low-grade heat sources by setting up heat pump heat storage, forming a high-temperature heat source with a higher temperature. It realizes the upgrading of the grade and energy storage of low-grade cold sources by setting up a cold pump ice slurry cold storage, forming a low-temperature cold source with a lower temperature. During the peak electricity consumption period in the daytime, the high-temperature heat source and the low-temperature cold source drive a steam turbine through a carbon dioxide working medium under the condition of a large temperature difference to generate grid-connected electricity. During the period when grid-connected power generation is not carried out, the low-grade heat source and the low-grade cold source drive a steam turbine through a carbon dioxide working medium under the condition of a small temperature difference to generate off-grid electricity. The generated electricity is used to drive the cold pump to realize ice slurry cold storage. During the valley period of electricity consumption at night, electric energy drives the heat pump to obtain heat from the low-grade heat source and store the thermal energy in the form of phase change heat storage to realize heat storage. During the peak electricity consumption period in the daytime, the stored heat and the stored cold of the cold storage are used to drive a steam turbine through a carbon dioxide working medium to generate grid-connected electricity, achieving the purpose of storing energy at night and releasing energy for power generation during the day;

[0027] 2. The present invention uses carbon dioxide gas as the working medium for the refrigeration cycle and the power generation cycle. The critical temperature of carbon dioxide is 31 degrees, and the temperature of the cooling water from the thermal power condenser is about 40 degrees. Using this cooling water at about 40 degrees as the heat source of the evaporator, the liquid working medium is vaporized into a supercritical gas, greatly saving the heat consumption required for steam turbine power generation. The energy of the heat pump heat storage is only used for the superheat of the working medium, so the thermal utilization rate is relatively high;

[0028] 3. When grid-connected power generation is not carried out, the low-grade heat source and the natural environment cold source drive a steam turbine one through a carbon dioxide working medium under the condition of a small temperature difference to generate off-grid electricity. The generated electricity is used to drive the compressor two for refrigeration and cold storage. The heat source end of the small temperature difference power generation cycle is the cooling water at about 40 degrees from the thermal power condenser, and the cold end is the cooling water of the cooling tower or other cold water sources with a temperature lower than 20 degrees. The power generation and power consumption realize an off-grid internal cycle within the system, which can ensure the effective utilization of electric energy and save the power consumption of the refrigeration link from the external power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of an energy storage system that utilizes low-grade heat source heat storage and ice slurry cold storage according to an embodiment of the present invention.

[0030] In the figure: 1. First circulation pump; 2. First heat exchanger; 3. First compressor; 4. Second heat exchanger; 5. First throttle valve; 6. Phase change heat storage pool; 7. Superheater; 8. First valve; 9. First steam turbine; 10. Second steam turbine; 11. Second valve; 12. Evaporator; 13. Pressurizing pump; 14. Liquid storage tank; 15. Third valve; 16. First condenser; 17. Second compressor; 18. Second condenser; 19. Second throttle valve; 20. Fourth valve; 21. Fifth valve; 22. Fifth circulation pump; 23. Phase change cold storage pool; 24. Fourth circulation pump; 25. Cooling tower; 26. Third circulation pump; 27. Second circulation pump 27. Specific embodiments

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] Embodiment 1

[0033] The present invention provides an energy storage system for heat storage using low-grade heat sources and ice slurry cold storage as Figure 1 shown, including:

[0034] A heat pump heat storage component for extracting and storing heat from the cooling water of a thermal power condenser. The heat pump heat storage component includes a first circulation pump 1, a first heat exchanger 2, a first compressor 3, a second heat exchanger 4, a first throttle valve 5, a second circulation pump 27, a phase change heat storage pool 6, a third circulation pump 26, a superheater 7, and an evaporator 12;

[0035] A circuit is formed between the first circulation pump 1, the first heat exchanger 2, and the evaporator 12 through pipelines. There is cooling water from the thermal power condenser in the circuit, and the circuit is used to exchange the heat of the cooling water in the thermal power condenser into the system;

[0036] A circuit formed between the first circulation pump 1, the first heat exchanger 2, and the evaporator 12 through pipelines, and a circuit is formed between the first heat exchanger 2, the first compressor 3, the second heat exchanger 4, and the first throttle valve 5 through pipelines. There is carbon dioxide working medium gas in the circuit, and the circuit formed by the first heat exchanger 2, the first compressor 3, the second heat exchanger 4, and the first throttle valve 5 is used to exchange the heat of the cooling water in the thermal power condenser into the carbon dioxide working medium gas and increase its pressure and temperature;

[0037] A loop is formed by pipes among the second heat exchanger 4, the second circulation pump 27 and the phase change heat storage tank 6, and there is hot water in the loop. The loop formed by the second heat exchanger 4, the second circulation pump 27 and the phase change heat storage tank 6 is used to exchange the heat in the carbon dioxide working medium gas with increased pressure and temperature to the hot water in the phase change heat storage tank 6 to store heat;

[0038] A loop is formed by pipes among the phase change heat storage tank 6, the third circulation pump 26 and the superheater 7, and there is hot water in the loop. The loop formed by the phase change heat storage tank 6, the third circulation pump 26 and the superheater 7 is used to exchange the heat of the hot water in the phase change heat storage tank 6 to the steam turbine working medium gas;

[0039] The cold pump refrigerates the ice slurry cold storage component, which is used to obtain colder cold energy from the natural environment by using electric energy and store the cold energy with ice slurry as the storage carrier. The cold pump refrigerates the ice slurry cold storage component includes an evaporator 12, a superheater 7, a first valve 8, a first steam turbine 9, a first condenser 16, a third valve 15, a liquid storage tank 14, a pressurizing pump 13, a second throttle valve 19, a second condenser 18, a cooling tower 25, a phase change heat storage tank 23 and a second compressor 17;

[0040] A loop is formed by pipes among the liquid storage tank 14, the pressurizing pump 13, the evaporator 12, the superheater 7, the first valve 8, the first steam turbine 9, the first condenser 16 and the third valve 15, and there is the steam turbine working medium gas stored inside the liquid storage tank 14 in the loop. The steam turbine working medium gas is carbon dioxide gas. The loop formed by the liquid storage tank 14, the pressurizing pump 13, the evaporator 12, the superheater 7, the first valve 8, the first steam turbine 9, the first condenser 16 and the third valve 15 is used to drive the first steam turbine 9 to rotate for power generation, and the power generation of the first steam turbine 9 is used to drive the second compressor 17;

[0041] A loop is formed by pipes among the second compressor 17, the first condenser 16, the third valve 15, the second throttle valve 19 and the second condenser 18, and there is carbon dioxide working medium gas in the loop. The loop formed by the second compressor 17, the first condenser 16, the third valve 15, the second throttle valve 19 and the second condenser 18 is used for cold pump refrigeration;

[0042] A loop is formed by pipes between the first condenser 16 and the cooling tower 25, and there is cooling water in the loop. The loop formed by the first condenser 16 and the cooling tower 25 is used to exchange heat between the carbon dioxide working medium gas discharged from the second compressor 17 and the cooling water from the cooling tower 25 to liquefy the carbon dioxide working medium gas;

[0043] A loop is formed by pipes among the fourth circulation pump 24, the phase change cold storage pool 23 and the cooling tower 25, and there is cooling water in the loop. A loop is formed by pipes among the phase change cold storage pool 23, the fifth circulation pump 22 and the second condenser 18, and there is low-freezing-point water in the loop. The loop composed of the phase change cold storage pool 23, the fifth circulation pump 22 and the second condenser 18 is used to conduct heat exchange between the liquefied carbon dioxide working medium gas and the low-freezing-point water in the phase change cold storage pool 23, so that part of the low-freezing-point water condenses into ice and enters the phase change cold storage pool 23 for storage. In this process, the liquefied carbon dioxide vaporizes and absorbs heat in the second condenser 18, and the temperature drops sharply. The second condenser 18 acts as an evaporator in this process.

[0044] The low-freezing-point water stored in the phase change cold storage pool 23 is an aqueous calcium chloride solution. The aqueous calcium chloride solution has a relatively low freezing point, and it can be converted into more ice slurry when absorbing cold, so as to increase the cold storage capacity. The cooling water in the cooling tower 25 also adopts an aqueous calcium chloride solution with a certain concentration. Its freezing temperature is relatively low, which can avoid the cooling water freezing during the operation of the cooling tower 25 and affecting the circulation. Moreover, the cooling water in the cooling tower 25 can be replenished regularly.

[0045] The steam turbine working component generates electricity through the heat source of the heat pump heat storage component and the cold source of the cold pump refrigerating ice slurry cold storage component. The steam turbine working component includes the second steam turbine 10, the fifth valve 21, the second condenser 18, the fourth valve 20, the liquid storage tank 14, the pressurizing pump 13, the evaporator 12, the superheater 7 and the second valve 11. A loop is formed by pipes among the superheater 7, the second valve 11, the second steam turbine 10, the fifth valve 21, the second condenser 18, the fourth valve 20, the liquid storage tank 14, the pressurizing pump 13 and the evaporator 12, and there is carbon dioxide working medium gas from the liquid storage tank 14 in the loop. The liquid storage tank 14, the pressurizing pump 13, the evaporator 12 and the superheater 7 are used to pressurize the liquid carbon dioxide working medium, vaporize it in the evaporator 12, and superheat it in the superheater 7 to form high-temperature and high-pressure carbon dioxide gas and transport it to the second steam turbine 10 to drive the second steam turbine 10 to rotate for power generation. The power generated by the second steam turbine 10 is used to be incorporated into the power grid. The fifth valve 21, the second condenser 18 and the fourth valve 20 are used to cool and liquefy the carbon dioxide working medium gas discharged from the second steam turbine 10.

[0046] In summary, in the embodiment of the present invention, during the low electricity consumption period at night, electric energy drives the heat pump to obtain heat from a low-grade heat source and store the higher-temperature heat in the form of phase change heat storage as the heat source, and uses the lower-temperature cold energy obtained from the natural environment and stored by the refrigeration device as the cold source. The heat source and the cold source drive the steam turbine through the carbon dioxide working medium during the high electricity consumption period during the day for grid-connected power generation, achieving the purpose of storing energy at night and releasing energy for power generation during the day.

[0047] By using carbon dioxide gas as the working fluid for the refrigeration cycle and the power generation cycle, the critical temperature of carbon dioxide is 31 degrees Celsius, and the temperature of the cooling water from the thermal power condenser is about 40 degrees Celsius. Using this cooling water at about 40 degrees Celsius as the heat source for the evaporator 12, the liquid working fluid is vaporized into a supercritical gas, greatly saving the heat consumption required for steam turbine power generation. The energy for heat pump thermal energy storage is only used for the superheating of the working fluid, so the thermal utilization rate is relatively high.

[0048] Using a low-grade heat source and a natural environment cold source, under the condition of a small temperature difference, a steam turbine is driven by carbon dioxide working fluid for off-grid power generation. This electricity is used to drive the compressor II 17 for refrigeration. Since the heat source end of the off-grid power generation cycle is the cooling water at about 40 degrees Celsius from the thermal power condenser, and the cold source end is the cooling water of the cooling tower 25 or other cold water sources with a temperature below 20 degrees Celsius, power generation and power consumption achieve an off-grid internal cycle within the system, eliminating the power consumption of the refrigeration link from the external power grid. Therefore, the system conversion efficiency is relatively high;

[0049] In the embodiment of the present invention, the working process of the system includes a heat pump thermal energy storage process, a cold pump refrigeration ice slurry thermal energy storage process, and a steam turbine working process. The three processes can operate independently. The heat pump thermal energy storage component operates during the period when the power supply is sufficient at night, and the cold pump refrigeration ice slurry thermal energy storage component operates during the period when grid-connected power generation is not carried out, respectively used to realize the heat pump thermal energy storage process and the ice slurry thermal energy storage process. The steam turbine working component operates during the period when the power supply is insufficient during the day, used to realize the steam turbine working process;

[0050] During the heat pump thermal energy storage process, the working process of the heat pump thermal energy storage component is as follows:

[0051] The compressor I 3 compresses the carbon dioxide working fluid gas from the heat exchanger I 2, causing the pressure and temperature of the carbon dioxide working fluid gas to increase. The high-pressure and high-temperature carbon dioxide working fluid gas passes through the heat exchanger II 4 and exchanges heat with the hot water in the phase change thermal energy storage tank 6 through the heat exchanger II 4. After the heat exchange, the temperature of the carbon dioxide working fluid gas decreases, and then it undergoes throttling expansion through the throttle valve I 5, resulting in a decrease in temperature and pressure. The low-temperature and low-pressure carbon dioxide working fluid gas passes through the circulation pump I 1 and enters the heat exchanger I 2, where it exchanges heat with the cooling water from the thermal power condenser, and then enters the compressor I 3 for circulation. During this process, the heat in the cooling water from the thermal power condenser is exchanged with the hot water in the phase change thermal energy storage tank 6 through the carbon dioxide working fluid gas to realize the recovery and storage of thermal energy. The temperature of the cooling water from the thermal power condenser is about 40 degrees Celsius. This cooling water at about 40 degrees Celsius provides a good heat source for heat pump thermal energy storage. This heat source is stable and abundant, creating conditions for the heat pump to store thermal energy with higher efficiency;

[0052] During the off-peak period of night-time power consumption, the excess electric energy of the power grid drives a heat pump to heat the cooling water of the thermal power condenser to obtain heat medium water. The heat medium water is injected into the phase change heat storage pool 6 through the second circulation pump 27. The phase change heat storage pool 6 stores the hot water, and the hot water exchanges heat with the medium and low temperature solid phase change heat storage material in the phase change heat storage pool 6 to achieve heat energy storage;

[0053] During the ice slurry cold storage process, the working process of the ice slurry cold storage component is as follows:

[0054] The liquid carbon dioxide in the liquid storage tank 14 is pressurized under the action of the pressurizing pump 13 and enters the evaporator 12. The liquid carbon dioxide in the evaporator 12 absorbs the heat energy from the cooling water of the thermal power condenser, causing the liquid carbon dioxide to gasify into a high-pressure carbon dioxide gas in a supercritical state. The high-pressure carbon dioxide gas passes through the superheater 7 (in this process, the third circulation pump 26 does not work and the high-pressure carbon dioxide gas is not superheated) and the first valve 8 and enters the first steam turbine 9 to generate electricity. After working, the temperature and pressure of the high-pressure carbon dioxide decrease. The low-temperature and low-pressure carbon dioxide gas enters the first condenser 16, where the carbon dioxide gas exchanges heat with the cooling water from the cooling tower 25 in a countercurrent manner and liquefies. The liquefied carbon dioxide flows through the third valve 15 and then enters the liquid storage tank 14 to complete the low-temperature difference power generation cycle. During this process, the first steam turbine 9 generates electricity and drives the second compressor 17 to work;

[0055] When the second compressor 17 works, the second compressor 17 compresses the carbon dioxide working medium gas. The compressed carbon dioxide working medium gas is mixed with the carbon dioxide working medium gas discharged from the first steam turbine 9 and then enters the first condenser 16. The mixed carbon dioxide working medium gas exchanges heat with the cooling water from the cooling tower 25 in a countercurrent manner and liquefies in the first condenser 16. The liquefied carbon dioxide passes through the third valve 15, and a part of it enters the liquid storage tank 14, and the other part enters the second condenser 18 through the second throttle valve 19. In the second condenser 18 (at this time, the second condenser 18 acts as an evaporator), the throttled and depressurized liquid carbon dioxide working medium gasifies into a low-temperature and low-pressure carbon dioxide gas. During the gasification process, the temperature of the working medium drops sharply. At this time, the low-freezing-point water in the phase change cold storage pool 23 enters the second condenser 18 under the action of the fifth circulation pump 22. The low-freezing-point water exchanges heat with the low-temperature carbon dioxide working medium gas in a countercurrent manner in the second condenser 18, causing part of the low-freezing-point water to condense into ice. The low-freezing-point water that has condensed into ice enters the phase change cold storage pool 23 under the action of the fifth circulation pump 22. As the second compressor 17 continuously works, the proportion of ice in the phase change cold storage pool 23 increases. At this time, the phase change cold storage pool 23 completes cold storage with ice slurry as the carrier;

[0056] During the steam turbine working process, the working process of the steam turbine working component is as follows:

[0057] The liquid carbon dioxide in the liquid storage tank 14 is pressurized by the booster pump 13 and enters the evaporator 12. The high-pressure liquid carbon dioxide exchanges heat with the cooling water from the thermal power condenser in the evaporator 12, so that the liquid carbon dioxide is vaporized into supercritical high-pressure carbon dioxide gas. The high-pressure carbon dioxide gas enters the superheater 7. At this time, the hot water in the phase change heat storage tank 6 enters the superheater 7 under the drive of the circulation pump three 26. At this time, the hot water and the high-pressure carbon dioxide gas perform countercurrent heat exchange, so that the high-pressure carbon dioxide gas is converted into supercritical high-pressure carbon dioxide gas with a higher temperature. The high-temperature supercritical high-pressure carbon dioxide gas enters the steam turbine two 10 through the valve two 11, and drives the steam turbine two 10 to work and generate electricity. During this process, the valve one 8 is in a closed state, and the steam turbine one 9 does not work;

[0058] After the high-pressure carbon dioxide gas has been operated by steam turbine No. 2 10, its temperature and pressure are reduced, and the low-temperature and low-pressure carbon dioxide working fluid gas enters condenser No. 2 18 through valve No. 5 21, and exchanges heat with the ice slurry and ice water in the phase change cold storage tank 23 through condenser No. 2 18, so that the low-temperature and low-pressure carbon dioxide gas is liquefied. The liquefied carbon dioxide enters the liquid storage tank 14 through valve No. 4 20, and then circulates under the drive of the booster pump 13. This process can complete the operation and power generation of steam turbine No. 2 10. Steam turbine No. 2 10 serves as the main steam turbine of the system, and the electricity it generates is directly connected to the power grid.

[0059] Embodiment 2

[0060] This embodiment is a supplement to the first embodiment. Considering that the method for obtaining low-temperature cooling water in the first embodiment is mainly to generate and store it through the operation of the cooling tower 25, and the ambient temperature is lower at night, and the grid load is smaller during the night trough, the amount of low-temperature cooling water generated is larger, and the cooling tower 25 has limited storage capacity for cooling water. The low-temperature cooling water generated under favorable conditions at night cannot be completely stored. In order to maximize the use of favorable conditions at night, it is necessary to build an additional cooling water reservoir for storage. The cost of building a cooling water reservoir is relatively high, which is inconsistent with the green and energy-saving requirements of this technical solution. To solve this problem, rivers, lakes and reservoirs with lower water temperatures can be selected directly as cooling water, so there is no need to build a cooling water reservoir to solve the problem that the large amount of low-temperature cooling water generated under favorable conditions at night cannot be stored.

[0061] Embodiment 3

[0062] This embodiment is a supplement to the first embodiment. Considering that in the first embodiment, the ambient temperature is lower than the set temperature of the phase change cold storage tank 23;

[0063] In this case, the cooling tower 25 directly uses the low-temperature cold energy in the ambient temperature to store cold in the phase change cold storage pool 23, and directly supports the operation of the condenser 16 through the low-freezing-point water. During this process, the loop formed by the pipeline between the second compressor 17, the first condenser 16, the third valve 15, the second throttle valve 19 and the second condenser 18 does not participate in the work. The cooling tower 25 stores cold through the ambient cold energy;

[0064] In this case, the excess cold energy drives the first steam turbine 9 to do work through the carbon dioxide working medium. At this time, the electricity generated by the first steam turbine 9 is directly incorporated into the power grid;

[0065] When this state occurs at night, the grid pressure is small. The electricity generated by the first steam turbine 9 can be directly used to drive the heat pump to improve the heat storage efficiency of the heat pump, and heat storage and energy storage are carried out through the heat pump heat storage component to achieve the maximum storage and utilization of energy.

[0066] Embodiment 4

[0067] As a supplement to Embodiment 1, in this embodiment, considering that in Embodiment 1, the ambient temperature is too high. For example, when the ambient temperature is close to or even exceeds 40 °C and the system does not use rivers, lakes and other water bodies for a large amount of cooling water supplement, at this time, the carbon dioxide working medium gas cannot drive the first steam turbine 9 to do work due to the too low temperature difference. At this time, the system cannot perform refrigeration and cold storage, and the system stops running in this state. It is necessary to wait for the ambient temperature to decrease or supplement cooling water to lower the system temperature. To avoid this situation, the system can be built in an area with a lower ambient temperature or near rivers, lakes and other water bodies, so as to utilize the ambient temperature for energy storage and power generation and use natural cooling water to cool the system.

[0068] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An energy storage system utilizing low-grade heat source for heat storage and ice slurry for cold storage, characterized in that: include: A heat pump heat storage component, which is used to extract and store heat from the cooling water of the thermal power condenser, and the heat pump heat storage component includes a circulation pump 1, a heat exchanger 1, a compressor 1, a heat exchanger 2, a throttle valve 1, a circulation pump 27, a phase change heat storage tank, a circulation pump 3, a superheater and an evaporator; A loop is formed between the circulating pump 1, the heat exchanger 1 and the evaporator through a pipeline, and the loop contains cooling water from the thermal power condenser; a loop is formed between the heat exchanger 1, the compressor 1, the heat exchanger 2 and the throttle valve 1 through a pipeline, and the loop contains carbon dioxide working medium gas; a loop is formed between the heat exchanger 2, the circulating pump 27 and the phase change heat storage tank through a pipeline, and the loop contains hot water; a loop is formed between the phase change heat storage tank, the circulating pump 3 and the superheater through a pipeline, and the loop contains hot water; A cold pump refrigeration ice slurry cold storage component is used to obtain cold energy from a low-temperature environment using electric energy to obtain cold energy at a lower temperature and store cold energy using ice slurry as a storage medium. The cold pump refrigeration ice slurry cold storage component includes an evaporator, a superheater, a valve 1, a steam turbine 1, a condenser 1, a valve 3, a liquid storage tank, a booster pump, a throttle valve 2, a condenser 2, a cooling tower, a phase change cold storage tank and a compressor 2; A loop is formed between the liquid storage tank, the booster pump, the evaporator, the superheater, the valve 1, the turbine 1, the condenser 1 and the valve 3 through a pipeline, and the loop contains the turbine working fluid gas stored in the liquid storage tank; a loop is formed between the compressor 2, the condenser 1, the valve 3, the throttle valve 2 and the condenser 2 through a pipeline, and the loop contains carbon dioxide working fluid gas; a loop is formed between the condenser 1 and the cooling tower through a pipeline, and the loop contains low freezing point water; a loop is formed between the circulating pump 4, the phase change cold storage tank and the cooling tower through a pipeline, and the loop contains low freezing point water; A steam turbine working component generates electricity through the heat source of the heat pump heat storage component and the cold source of the cold pump refrigeration ice slurry cold storage component. The steam turbine working component includes steam turbine 2, valve 2, valve 4 and valve 5. A loop is formed between the superheater, valve 2, steam turbine 2, valve 5, condenser 2, valve 4, liquid storage tank, booster pump and evaporator through pipelines, and the loop contains carbon dioxide working fluid gas from the liquid storage tank.

2. The energy storage system utilizing low-grade heat source for heat storage and ice slurry for cold storage according to claim 1, characterized in that: The loop formed by the pipeline between the circulating pump 1, the heat exchanger 1 and the evaporator is used to exchange the heat of the cooling water in the thermal power condenser to the system; The circuit formed by the heat exchanger 1, the compressor 1, the heat exchanger 2 and the throttle valve 1 is used to exchange the heat of the cooling water in the thermal power condenser into the carbon dioxide working medium gas and increase its pressure and temperature; The loop formed by the second heat exchanger, the second circulating pump 27 and the phase change heat storage tank is used to exchange the heat in the carbon dioxide working fluid gas with increased pressure and temperature into the hot water in the phase change heat storage tank to store heat.

3. The energy storage system utilizing low-grade heat source for heat storage and ice slurry for cold storage according to claim 2, characterized in that: The loop formed by the phase change heat storage tank, the circulating pump 3 and the superheater is used to exchange the heat of the hot water in the phase change heat storage tank to the working fluid gas of the steam turbine.

4. The energy storage system utilizing low-grade heat source for heat storage and ice slurry for cold storage according to claim 1, characterized in that: The working gas of the steam turbine is carbon dioxide gas. The loop formed by the liquid storage tank, the booster pump, the evaporator, the superheater, the valve one, the steam turbine one, the condenser one and the valve three is used to drive the steam turbine one to rotate to generate electricity.

5. The energy storage system utilizing low-grade heat source for heat storage and ice slurry for cold storage according to claim 4, characterized in that: The circuit formed by the compressor 2, the condenser 1, the valve 3, the throttle valve 2 and the condenser 2 is used for refrigeration and cold storage; The loop formed by the condenser 1 and the cooling tower is used to perform heat exchange between the carbon dioxide working medium gas and the low freezing point water from the cooling tower to liquefy the carbon dioxide working medium gas; A loop is formed between the phase change cold storage tank, the circulating pump five and the condenser two through a pipeline, and there is low freezing point water in the loop. The loop composed of the phase change cold storage tank, the circulating pump five and the condenser two is used to heat exchange the liquefied carbon dioxide working medium with the low freezing point water in the phase change cold storage tank so that part of the low freezing point water condenses into ice and enters the phase change cold storage tank for storage.

6. The energy storage system utilizing low-grade heat source for heat storage and ice slurry for cold storage according to claim 1, characterized in that: The loop formed by the superheater, valve 2, steam turbine 2, valve 5, condenser 2, valve 4, liquid storage tank, booster pump and evaporator is used to pressurize the carbon dioxide working fluid gas and transport it to steam turbine 2 to drive steam turbine 2 to rotate and generate electricity.

7. The energy storage system utilizing low-grade heat source for heat storage and ice slurry for cold storage according to claim 4, characterized in that: The steam turbine 1 generates electricity for driving the compressor 2.

8. The energy storage system utilizing low-grade heat source for heat storage and ice slurry for cold storage according to claim 6, characterized in that: The steam turbine 2 generates electricity for connection to the power grid.

9. The energy storage system utilizing low-grade heat source for heat storage and ice slurry for cold storage according to claim 1, characterized in that: The working process of the system includes a heat pump heat storage process, an ice slurry cold storage process and a steam turbine working process, and the three processes can be operated independently. The heat pump heat storage component operates during the night time period when the power supply is sufficient to realize the heat pump heat storage process. The cold pump refrigeration ice slurry cold storage component operates during other time periods when there is no grid-connected power generation to realize the cold pump refrigeration ice slurry cold storage process. The steam turbine working component operates during the day time period when the power supply is insufficient to realize the steam turbine working process.

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