Carbon dioxide energy storage system based on LNG cold energy utilization

Abstract

The present invention provides a carbon dioxide energy storage system based on the utilization of LNG cold energy, wherein the compression unit is used to compress liquid carbon dioxide into supercritical carbon dioxide, and provide cold energy for a cold exchange station under a first setting condition; the expansion unit is used to expand gaseous carbon dioxide into liquid carbon dioxide; the heat transfer medium supply unit is connected to the compression unit and the expansion unit respectively, and is used to provide a heat transfer medium for cooling the compression unit and a heat transfer medium for heating the expansion unit; the cold energy supply unit includes an LNG supply pipeline for providing LNG; the cold energy utilization unit receives the cold energy of LNG from the cold energy supply unit, and provides cold energy for the cold exchange station under a second setting condition, and provides cold energy under a third setting condition. Carbon dioxide energy storage is achieved by utilizing the cold energy of LNG, and the utilization of LNG in different time periods can be achieved under different setting conditions, thereby improving the utilization rate of LNG cold energy and achieving efficient utilization of LNG cold energy.

Description

Technical Field

[0001] The present invention relates to the technical field of cold energy utilization, and in particular to a carbon dioxide energy storage system based on LNG cold energy utilization. Background Art

[0002] With the large-scale application of new energy, the challenges faced by new energy power generation and grid connection are becoming increasingly prominent, and the importance of energy storage systems is increasing. Carbon dioxide energy storage technology is a compressed gas energy storage technology that has emerged in recent years. It has the advantages of high energy storage density, long life, and flexible system design. Among them, liquid carbon dioxide energy storage technology uses liquid phase to store carbon dioxide on both the high-pressure side and the low-pressure side of the system, with high energy storage density and strong operating stability.

[0003] LNG (liquefied natural gas) is a low-temperature (-162°C) liquid mixture made from low-pollution natural gas that has been deacidified and dehydrated and then frozen and liquefied through a low-temperature process. At LNG receiving stations, LNG needs to be gasified in a gasifier before use. It is estimated that the gasification process of each ton of LNG is equivalent to releasing 860MJ of cold energy (about 230kWh). How to efficiently recycle and utilize this large amount of cold energy is a problem. Summary of the invention

[0004] The purpose of the embodiment of the present invention is to provide a carbon dioxide energy storage system based on the utilization of LNG cold energy, so as to solve the problem of how to efficiently recycle and utilize LNG cold energy in the prior art.

[0005] The embodiment of the present invention adopts the following technical solution: a carbon dioxide energy storage system based on LNG cold energy utilization, comprising:

[0006] a first storage tank for storing liquid carbon dioxide;

[0007] a second storage tank for storing gaseous carbon dioxide;

[0008] a compression unit, which is connected to the first storage tank and the second storage tank respectively, and is used to compress the liquid carbon dioxide from the first storage tank into supercritical carbon dioxide after heating, provide cold energy for the cold exchange station under the first set condition, and transport the gaseous carbon dioxide to the second storage tank;

[0009] an expansion unit, which is connected to the first storage tank and the second storage tank respectively, and is used to expand the gaseous carbon dioxide from the second storage tank into liquid carbon dioxide after cooling, and transport the liquid carbon dioxide to the first storage tank;

[0010] a heat-conducting medium supply unit, which is connected to the compression unit and the expansion unit respectively, and is used to provide the compression unit with a heat-conducting medium for cooling and to provide the expansion unit with a heat-conducting medium for heating;

[0011] A cold energy providing unit, comprising an LNG supply pipeline for providing LNG;

[0012] The cold energy utilization unit is connected to the cold energy providing unit and the heat transfer medium supply unit respectively to receive the cold energy of the LNG from the cold energy providing unit and provide cold energy for the refrigeration station under the second setting condition and under the third setting condition.

[0013] In some embodiments, the cold energy utilization unit includes a refrigerant carbon dioxide pump, a cold exchange station heat exchanger, and an LNG heat exchanger;

[0014] The heat exchanger of the cold exchange station is connected to the compression unit so that the carbon dioxide from the compression unit is introduced into the cold fluid side thereof under the first set condition, and the carbon dioxide exchanges heat with the fluid on the hot fluid side of the heat exchanger of the cold exchange station, thereby providing cold energy for the cold exchange station, wherein the first set condition is that the cold exchange station has a cold energy demand within a first set time;

[0015] Under the second setting condition, LNG is passed into the cold fluid side of the LNG heat exchanger and exchanges heat with the fluid on the hot fluid side of the LNG heat exchanger, and the LNG flowing out of the LNG heat exchanger is passed into the expansion unit and output to the external transmission pipeline after providing cold energy to the expansion unit, wherein the second setting condition is that the cold exchange station has a cold energy demand within the second setting time;

[0016] The outlet of the refrigerant carbon dioxide pump is connected to the cold fluid side of the refrigeration station for heat exchange, and the hot fluid side of the LNG heat exchanger is connected to the inlet of the refrigerant carbon dioxide pump to form a circulation passage for the refrigerant carbon dioxide.

[0017] In some embodiments, the cold energy utilization unit further includes a circulating heat exchanger, a circulating pump, and a circulating expander;

[0018] The circulating heat exchanger has an intermediate medium inlet and an intermediate medium outlet, the inlet of the circulating pump is connected to the intermediate medium outlet of the circulating heat exchanger, and the outlet of the circulating pump is connected to the intermediate medium inlet of the circulating heat exchanger; LNG is introduced into the cold energy inlet of the circulating heat exchanger under the third setting condition, and LNG flows out from the cold energy outlet of the circulating heat exchanger after providing cold energy to the circulating heat exchanger, and is introduced into the expansion unit to provide cold energy to the expansion unit and then output to the external transmission pipeline, wherein the third setting condition is that the cold exchange station has no cold energy demand.

[0019] In some embodiments, the first set time is from sunset time to sunrise time, and the second set time is from sunrise time to sunset time.

[0020] In some embodiments, the compression unit comprises:

[0021] a carbon dioxide pump connected to the first storage tank and the heat exchanger of the cold exchange station and used to pump out the liquid carbon dioxide in the first storage tank and pump the liquid carbon dioxide in the first storage tank to the heat exchanger of the cold exchange station under the first set condition;

[0022] a carbon dioxide evaporator connected to the carbon dioxide pump and used to heat the liquid carbon dioxide pumped out by the carbon dioxide pump under the third set condition;

[0023] a compressor connected to the carbon dioxide evaporator and used to compress the carbon dioxide after the heating treatment by the carbon dioxide evaporator under the third set condition to obtain gaseous carbon dioxide with a set pressure;

[0024] A cooler is connected to the compressor and the second storage tank respectively, and is used to cool the gaseous carbon dioxide compressed by the compressor and transport the cooled gaseous carbon dioxide to the second storage tank.

[0025] In some embodiments, the compressors include at least two, the coolers include at least two, the compressors and the coolers are connected via a first connecting pipeline, and at least two compressors and at least two coolers are spaced apart on the first connecting pipeline.

[0026] In some embodiments, the expansion unit comprises:

[0027] a heater connected to the second storage tank and used to heat the gaseous carbon dioxide from the second storage tank;

[0028] an expander connected to the heater and used to expand the gaseous carbon dioxide heated by the heater;

[0029] A carbon dioxide condenser is connected to the expander and the first storage tank and is used for condensing the carbon dioxide expanded by the expander to obtain liquid carbon dioxide and transport the liquid carbon dioxide to the first storage tank.

[0030] In some embodiments, the heaters include at least two, the expanders include at least two, the heaters are connected to the expanders via a second connecting pipeline, and at least two of the heaters and at least two of the expanders are spaced apart on the second connecting pipeline.

[0031] In some embodiments, the heat transfer medium supply unit includes:

[0032] a third storage tank having a first heat transfer medium outlet and a first heat transfer medium inlet, wherein the first heat transfer medium outlet is connected to the cooler and provides the heat transfer medium for cooling the cooler; and the first heat transfer medium inlet is connected to the heater and is used to receive the heat transfer medium flowing out of the heater;

[0033] The fourth storage tank has a second heat transfer medium outlet and a second heat transfer medium inlet. The second heat transfer medium outlet is connected to the heater and provides the heater with heat transfer medium for heating. The second heat transfer medium inlet is connected to the cooler and is used to receive the heat transfer medium flowing out of the cooler.

[0034] In some embodiments, the carbon dioxide energy storage system includes two sets of heat transfer medium supply units, wherein the heat transfer medium flowing in one set of the heat transfer medium supply units is water, and the heat transfer medium in the other set of the heat transfer medium supply units is heat transfer oil.

[0035] The beneficial effects of the embodiments of the present invention are:

[0036] 1. By utilizing the LNG cold energy of the LNG receiving station, the system efficiency of the liquid carbon dioxide energy storage is greatly improved, and the utilization rate of LNG cold energy is improved. The cold energy utilization efficiency of the LNG receiving station is improved through the cascade utilization and time-sharing utilization of cold energy, and by providing LNG as an external cold source, low-pressure carbon dioxide is stored in liquid form, reducing the energy storage density of liquid carbon dioxide energy storage. By adopting a high-low-grade heat storage dual cycle, the overall efficiency of the liquid carbon dioxide energy storage system is effectively improved.

[0037] 2. The LNG cold energy is used in a time-sharing manner. The LNG cold energy is not used at night when the LNG flow rate is low, and the LNG cold energy is fully used during the day when the LNG flow rate is high. This is in line with the operating characteristics of the LNG receiving station and solves the time unevenness of the LNG cold energy supply. At the same time, the LNG cold energy is used in a cascade manner. LNG first releases high-grade cold energy through the refrigerant cycle of the cold exchange station or the Rankine cycle, and then releases low-grade cold energy by cooling the liquefied carbon dioxide, which improves the utilization rate of LNG cold energy and reduces the overall energy consumption. loss.

[0038] 3. Effectively utilize external cold sources to liquefy carbon dioxide, improve the energy storage density of the carbon dioxide energy storage system, and operate carbon dioxide as a refrigerant medium and energy storage medium to effectively integrate the system cycle efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0040] Figure 1 It is a structural schematic diagram of the carbon dioxide energy storage system based on LNG cold energy utilization of the present invention.

[0041] Figure 2 It is a structural schematic diagram of the carbon dioxide energy storage system based on LNG cold energy utilization under the first setting condition when there is a demand for a cold exchange station.

[0042] Figure 3 It is a structural schematic diagram of the carbon dioxide energy storage system based on LNG cold energy utilization under the second setting condition when there is a demand for a cold exchange station.

[0043] Figure 4 It is a structural schematic diagram of the carbon dioxide energy storage system based on LNG cold energy utilization under the third setting condition when there is no need for a cold exchange station.

[0044] Reference numerals: 1, carbon dioxide pump; 2, carbon dioxide evaporator; 3, first compressor; 4, first cooler; 5, second compressor; 6, second cooler; 7, third compressor; 8, third cooler; 9, first heater; 10, first expander; 11, second heater; 12, second expander; 13, third heater; 14, third expander; 15, carbon dioxide condenser;

[0045] 21. Second storage tank; 22. First storage tank; 23. Third storage tank; 24. Fourth storage tank;

[0046] 31. Refrigerant carbon dioxide pump; 32. LNG heat exchanger; 33. Refrigeration station heat exchanger;

[0047] 41. Rankine cycle heat exchanger; 42. Rankine cycle pump; 43. Rankine cycle expander.

[0048] In the figure, the solid line represents the circulation pipeline of carbon dioxide, the dotted line represents the circulation pipeline of the intermediate medium (which may be a medium with a lower boiling point than carbon dioxide, such as Freon, ammonia, etc.), the dotted line represents the circulation pipeline of the heat transfer medium, and the short horizontal line represents the circulation pipeline of LNG. DETAILED DESCRIPTION

[0049] Various aspects and features of the present invention are described herein with reference to the accompanying drawings.

[0050] It should be understood that various modifications may be made to the embodiments of the present application. Therefore, the above description should not be considered as limiting, but only as an example of the embodiments. Other modifications within the scope and spirit of the present invention will occur to those skilled in the art.

[0051] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the general description of the invention given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.

[0052] These and other characteristics of the invention will become apparent from the following description of a preferred form of embodiment given as a non-limiting example, with reference to the accompanying drawings.

[0053] It should also be understood that, although the invention has been described with reference to certain specific examples, those skilled in the art will be able to determine that many other equivalent forms of the invention have the characteristics of the above-mentioned "Summary of the Invention" and are therefore within the scope of protection defined thereby.

[0054] The above and other aspects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

[0055] Specific embodiments of the present invention are described hereinafter with reference to the accompanying drawings; however, it should be understood that the embodiments claimed are merely examples of the present invention, which may be implemented in a variety of ways. Well-known and / or repeated functions and structures are not described in detail to avoid unnecessary or redundant details that obscure the present invention. Therefore, the specific structural and functional details claimed herein are not intended to be limiting, but merely serve as a basis and representative basis for the above "Summary of the Invention" to teach those skilled in the art to use the present invention in a variety of ways with substantially any suitable detailed structure.

[0056] This specification may use the phrases "in one embodiment," "in another embodiment," "in a further embodiment," or "in other embodiments," which may all refer to one or more of the same or different embodiments according to the present invention.

[0057] In order to solve the problems in the background technology, the present application provides a carbon dioxide energy storage system based on the utilization of LNG cold energy.

[0058] Combination Figure 1 The carbon dioxide energy storage system includes a first storage tank 22, a second storage tank 21, a compression unit, an expansion unit, a heat transfer medium supply unit, a cold energy supply unit and a cold energy utilization unit.

[0059] Among them, the first storage tank 22 is used to store liquid carbon dioxide; the second storage tank 21 is used to store gaseous carbon dioxide, and the gaseous carbon dioxide in the second storage tank 21 has a higher pressure. In the second storage tank 21, carbon dioxide is stored in a high-pressure supercritical state, and in the first storage tank 22, liquid carbon dioxide is stored in a low-pressure liquid state. At the same time, since the density of the supercritical state and liquid state of carbon dioxide is greater than that of the gaseous state, the carbon dioxide energy storage system has the advantage of high energy storage density. In addition, both the first storage tank 22 and the second storage tank 21 are provided with a preset value pressure regulating valve, and the pressure of the first storage tank 22 and the second storage tank 21 can be adjusted as needed.

[0060] The compression unit is connected to the first storage tank 22 and the second storage tank 21 respectively, and is used to compress the liquid carbon dioxide from the first storage tank 22 into supercritical carbon dioxide with a certain pressure after heating. During the compression process, the carbon dioxide absorbs energy and is converted from liquid carbon dioxide to gaseous carbon dioxide, thereby realizing energy storage. Under the first set condition, the carbon dioxide acts as refrigerant to provide cold energy for the cold exchange station, wherein the first set condition at least includes a time limit. The compressed gaseous carbon dioxide can be transported to the second storage tank 21 via a delivery pipeline for storage for subsequent use.

[0061] The expansion unit is connected to the first storage tank 22 and the second storage tank 21 respectively, and is used to expand the gaseous carbon dioxide from the second storage tank 21 and then cool it into liquid carbon dioxide. During the expansion process, the carbon dioxide releases energy and is converted from gaseous carbon dioxide to liquid carbon dioxide, thereby completing the release of energy. The released energy can be used for power generation, but is not limited to it. The liquid carbon dioxide obtained after expansion can be transported to the first storage tank 22 via a delivery pipeline for storage for subsequent use. The carbon dioxide circulates between the first storage tank 22, the compression unit, the second storage tank 21 and the expansion unit, thereby completing energy absorption and energy release.

[0062] The heat transfer medium supply unit is connected to the compression unit and the expansion unit respectively, and is used to provide the heat transfer medium for cooling when the compression unit compresses carbon dioxide and to provide the heat transfer medium for heating when the expansion unit expands carbon dioxide.

[0063] The cold energy providing unit includes an LNG supply pipeline, which can be connected to an LNG receiving station to provide LNG to the carbon dioxide energy storage system, thereby providing cold energy to the carbon dioxide energy storage system.

[0064] Carbon dioxide can be used as an energy storage medium or a refrigerant medium as needed. Carbon dioxide is a non-toxic, non-flammable, high-density fluid with a suitable critical point (critical temperature Tc = 31.1 ° C, critical pressure Pc = 7.38 MPa), and has good fluidity and transmission characteristics. When carbon dioxide is used as a refrigerant medium, it has a low viscosity and good fluidity. At the same time, it has a high heat transfer coefficient and good heat transfer characteristics. Its boiling point is relatively low compared to traditional cold storage refrigerants such as Freon and ammonia. It is suitable as a refrigerant medium to transfer cold energy, and it is relatively safe and relatively environmentally friendly. When carbon dioxide is used as an energy storage medium, due to its high critical temperature, it is easy to reach a supercritical state, and its heat transfer characteristics will also increase. At the same time, the phase transition can be achieved at room temperature in a high-pressure state, and the cold source temperature required for liquefaction in a low-pressure state is relatively high and easy to obtain.

[0065] The cold energy utilization unit is connected to the cold energy providing unit and the heat transfer medium supply unit respectively to receive the cold energy of the LNG from the cold energy providing unit, and provide cold energy to the cold exchange station under the second setting condition and under the third setting condition. The second setting condition at least includes a time limit. The cold exchange station sometimes has a demand for cold energy and sometimes has no demand for cold energy. The carbon dioxide energy storage system can provide cold energy to the cold exchange station when the cold exchange station has a demand for cold energy.

[0066] The embodiment of the present application provides LNG as an external cold source for the carbon dioxide energy storage system, utilizes the cold energy of LNG to realize carbon dioxide energy storage, and can realize the time-divided utilization of LNG under different setting conditions, thereby improving the utilization rate of LNG cold energy and realizing the efficient utilization of LNG cold energy. The cold energy provided by LNG enables low-pressure carbon dioxide to be stored in liquid form, reduces the energy storage density of liquid carbon dioxide energy storage, and greatly improves the system efficiency of liquid carbon dioxide energy storage.

[0067] In one embodiment of the present application, the cold energy utilization unit includes a refrigerant carbon dioxide pump 31 , a cold exchange station heat exchanger 33 and an LNG heat exchanger 32 .

[0068] The heat exchanger 33 of the cooling station is connected to the compression unit, combined with Figure 2 and Figure 3Specifically, the cold fluid side of the heat exchanger 33 of the cold exchange station is connected to the compression unit, so that the cold fluid side of the heat exchanger 33 of the cold exchange station is fed with carbon dioxide from the compression unit under the first set condition. Carbon dioxide is used as a refrigerant of the cold energy source, and exchanges heat with the fluid on the hot fluid side of the heat exchanger 33 of the cold exchange station, thereby providing cold energy for the cold exchange station. Among them, the first set condition is that the cold exchange station has a cold energy demand within the first set time; specifically, the first set time is from sunset time to sunrise time, that is, night time. Since the LNG export volume is usually higher during the day and lower at night, the carbon dioxide energy storage system uses more LNG cold energy during the day and less LNG cold energy at night. Therefore, at night, LNG cold energy can be used without using it, and the cold energy required by the cold exchange station is provided by the liquid carbon dioxide in the first storage tank 22 through the heat exchanger 33 of the cold exchange station. After providing cold energy to the cold exchange station, the refrigerant carbon dioxide flows back to the compression unit again, and enters the second storage tank 21 after being compressed by the compression unit. The refrigerant for absorbing the cold energy of carbon dioxide in the heat exchanger 33 of the cold exchange station can be a refrigerant in the refrigeration cycle, such as freon, ammonia and other media with a lower boiling point than carbon dioxide, or an organic refrigerant or an inorganic refrigerant such as ethylene glycol aqueous solution or calcium chloride aqueous solution. The refrigerant is mainly determined by the user of the cold exchange station, and the user of the cold exchange station can be freeze-dried fruits and vegetables, cold storage, data center, etc.

[0069] Under the second setting condition, LNG is introduced into the cold fluid side of the LNG heat exchanger 32 and heat exchanged with the fluid on the hot fluid side of the LNG heat exchanger 32, wherein the LNG for providing cold energy is introduced into the cold fluid side of the LNG heat exchanger 32, and carbon dioxide flows through the hot fluid side of the LNG heat exchanger 32. Carbon dioxide on the hot fluid side of the LNG heat exchanger 32 absorbs the cold energy of LNG under the second setting condition and is transported to the heat exchanger 33 of the cold exchange station through the refrigerant carbon dioxide pump 31 to provide cold energy for the cold exchange station. Among them, the second setting condition is that the cold exchange station has a cold energy demand within the second setting time, and the second setting time is from sunrise time to sunset time, that is, daytime time. As mentioned above, since the LNG external transmission volume is usually higher during the day and lower at night, the system uses more LNG cold energy during the day and less LNG cold energy at night. The LNG cold energy is fully utilized during the day and not utilized at night, which is in line with the actual operation of the LNG receiving station, thereby realizing the time-divided utilization of LNG and improving the utilization rate of LNG cold energy. In case of insufficient LNG cooling capacity, an open cycle of carbon dioxide can be used as an emergency measure to supplement the cooling capacity of the refrigeration station. Carbon dioxide is directly provided by a liquid carbon dioxide tank, which is directly emptied after the cooling capacity is supplied, and then the carbon dioxide is supplemented to the liquid carbon dioxide tank. Corresponding to the first setting condition and the second setting condition, the source of the refrigerant entering the heat exchanger 33 of the refrigeration station can be controlled by adjusting the switch valve set on the corresponding transmission pipeline.

[0070] The LNG flowing out of the cold fluid side of the LNG heat exchanger 32 is passed into the expansion unit and provided with cold energy for the expansion unit before being output to the external transmission pipeline. That is, during the day, a part of the LNG cold energy provides cold energy to the cold exchange station, and then cools and liquefies the gaseous carbon dioxide at the outlet of the expansion unit, thus realizing the utilization of the LNG cold energy again.

[0071] The outlet of the refrigerant carbon dioxide pump 31 is connected to the cold fluid side of the heat exchanger 33 of the cold exchange station, and the hot fluid side of the LNG heat exchanger 32 is connected to the inlet of the refrigerant carbon dioxide pump 31 to form a closed circulation passage of the refrigerant carbon dioxide, and the closed passage only works during the period from sunrise to sunset. Liquid carbon dioxide enters the heat exchanger 33 of the cold exchange station after being pressurized by the carbon dioxide pump 1, and then returns to become gaseous carbon dioxide after being gasified by the refrigerant, and then enters the hot fluid side of the LNG heat exchanger 32, and is cooled by LNG to become liquid carbon dioxide for reciprocating circulation. That is, after carbon dioxide flows through the hot fluid side of the LNG heat exchanger 32 and absorbs the cold energy of LNG, it is transported to the cold fluid side of the heat exchanger 33 of the cold exchange station through the refrigerant carbon dioxide pump 31, and as a refrigerant, it provides cold energy to the cold exchange station through the heat exchanger 33 of the cold exchange station and then enters the hot fluid side of the LNG heat exchanger 32 to form a circulation passage of the refrigerant carbon dioxide, so that carbon dioxide can be used as a refrigerant in a reciprocating manner.

[0072] In one embodiment of the present application, the cold energy utilization unit further includes a circulating heat exchanger, a circulating pump and a circulating expander. The circulating heat exchanger is a Rankine cycle heat exchanger 41, the circulating pump is a Rankine cycle pump 42, and the circulating expander is a Rankine cycle expander 43.

[0073] The Rankine cycle heat exchanger 41 has an intermediate medium inlet and an intermediate medium outlet. The inlet of the Rankine cycle pump 42 is connected to the intermediate medium outlet of the Rankine cycle heat exchanger 41, and the outlet of the Rankine cycle pump 42 is connected to the intermediate medium inlet of the Rankine cycle heat exchanger 41. Figure 4 , the cold energy inlet of the Rankine cycle heat exchanger 41 is fed with LNG under the third setting condition, and the LNG provides cold energy to the Rankine cycle heat exchanger 41 and then flows out from the cold energy outlet of the Rankine cycle heat exchanger 41, and is fed into the expansion unit to provide cold energy to the expansion unit and then output to the external transmission pipeline. Among them, the third setting condition is that there is no cold energy demand for the cold exchange station. That is, when there is no cold energy demand for the cold exchange station, the Rankine cycle heat exchanger 41, the Rankine cycle pump 42 and the Rankine cycle expander 43 use the cold energy of LNG to generate electricity. High-grade cold energy is used for Rankine cycle, and low-grade cold energy is used for liquefaction of carbon dioxide. Among them, high-grade cold energy refers to cold energy with a lower temperature range, such as cold energy below -50°C, and low-grade cold energy refers to cold energy with a higher temperature range, such as cold energy above -50°C. When liquid carbon dioxide does not provide cooling for the cold exchange station, the heat of the evaporator in the expansion unit can be provided by the heat transfer medium (circulating cooling water) in the heat transfer medium supply unit.

[0074] In one embodiment of the present application, the compression unit includes a carbon dioxide pump 1, a carbon dioxide evaporator 2, a compressor and a cooler.

[0075] The carbon dioxide pump 1 is connected to the first storage tank 22 and the heat exchanger 33 of the cold exchange station, and is used to pump out the liquid carbon dioxide in the first storage tank 22, and pump the liquid carbon dioxide in the first storage tank 22 to the heat exchanger 33 of the cold exchange station under the first set condition; specifically, in combination with Figure 2 Under the first setting condition, the carbon dioxide pump 1 pumps the liquid carbon dioxide in the first storage tank 22 to the cold fluid side of the heat exchanger 33 of the cold exchange station; Figure 4 , under the third setting condition, the liquid carbon dioxide in the first storage tank 22 is pumped out to the cold fluid side of the carbon dioxide evaporator 2, and heat is exchanged with the fluid flowing through the hot fluid side of the carbon dioxide evaporator 2. The heat source of the carbon dioxide evaporator 2, that is, the fluid flowing through the hot fluid side of the carbon dioxide evaporator 2 can be heat transfer oil or hot water. The carbon dioxide evaporator 2 is used to heat the liquid carbon dioxide pumped out by the carbon dioxide pump 1 under the third setting condition.

[0076] The compressor is connected to the carbon dioxide evaporator 2 and is used to compress the carbon dioxide heated by the carbon dioxide evaporator 2 under the third setting condition to obtain gaseous carbon dioxide with a set pressure. The compressor is also connected to the cold exchange station heat exchanger 33 and is used to compress the carbon dioxide flowing out of the cold fluid side of the cold exchange station heat exchanger 33 under the first setting condition to convert the liquid carbon dioxide into gaseous state.

[0077] The cooler is connected to the compressor and the second storage tank 21 respectively. Specifically, the hot fluid side of the cooler is introduced with carbon dioxide compressed by the compressor, and the cold fluid side of the cooler is introduced with a heat transfer medium for cooling from a heat transfer medium supply unit. The heat transfer medium is used to cool the gaseous carbon dioxide flowing through the cold fluid side of the cooler, and the cooled gaseous carbon dioxide is transported to the second storage tank 21 for storage.

[0078] In one embodiment of the present application, there are at least two compressors and at least two coolers, the compressors and the coolers are connected via a first connecting pipeline, and at least two compressors and at least two coolers are spaced apart on the first connecting pipeline. Figures 1 to 4The compression unit of the embodiment of the present application includes three compressors and three coolers, the three compressors are respectively a first compressor 3, a second compressor 5 and a third compressor 7, and the three coolers are respectively a first cooler 4, a second cooler 6 and a third cooler 8. When the compression unit compresses the carbon dioxide, the following compression and cooling method can be adopted: the carbon dioxide enters the first cooler 4 for cooling after being compressed by the first compressor 3, and then enters the second compressor 5 for compression and then enters the second cooler 6 for cooling, and finally enters the third compressor 7 for compression and then enters the third cooler 8 for cooling. The use of multi-stage compressors and coolers for inter-stage compression and cooling can improve the energy efficiency of the carbon dioxide energy storage system. The isentropic efficiency of the compression unit can be set to not less than 85%, and the compression unit evenly distributes the inlet and outlet pressures of each compressor according to the pressure ratio.

[0079] In one embodiment of the present application, the expansion unit includes a heater, an expander and a carbon dioxide condenser 15 .

[0080] The heater is connected to the second storage tank 21 and is used to heat the gaseous carbon dioxide from the second storage tank 21. Specifically, the gaseous carbon dioxide from the second storage tank 21 is introduced into the cold fluid side of the heater, and the hot fluid side of the second storage tank 21 is introduced into the heat transfer medium for heating provided by the heat transfer medium supply unit.

[0081] The expander is connected to the heater and is used to expand the gaseous carbon dioxide heated by the heater. Energy is released during the expansion of the carbon dioxide. The released energy can be used for, but is not limited to, power generation.

[0082] The carbon dioxide condenser 15 is connected to the expander and the first storage tank 22 respectively, and is used to condense the carbon dioxide expanded by the expander to obtain liquid carbon dioxide and transport the liquid carbon dioxide to the first storage tank 22 for storage.

[0083] Carbon dioxide is circulated among the first storage tank 22, the compression unit, the second storage tank 21 and the expansion unit. During the circulation of carbon dioxide, the cold energy of LNG can be utilized, and energy is stored when passing through the compression unit and released when passing through the expansion unit, thereby effectively realizing the efficient utilization of LNG cold energy.

[0084] In one embodiment of the present application, the heaters include at least two, the expanders include at least two, the heaters and the expanders are connected via a second connecting pipeline, and the at least two heaters and the at least two expanders are spaced apart on the second connecting pipeline. Figures 1 to 4In the embodiment of the present application, the heater and the expander each include three, the three heaters are respectively the first heater 9, the second heater 11 and the third heater 13, and the three expanders are respectively the first expander 10, the second expander 12 and the third expander 14. The gaseous carbon dioxide from the second storage tank 21 enters the cold fluid side of the first heater 9, and after being heated by the heat-conducting medium from the heat-conducting medium supply unit, the carbon dioxide is introduced into the first expander 10 to expand and release energy, and then is heated again by the cold fluid side of the second heater 11 and introduced into the second expander 12 to expand again and release energy, and finally is heated by the cold fluid side of the third heater 13 and introduced into the third expander 14 to expand again and release energy. Similar to the compression unit, the use of a multi-stage expander for inter-stage expansion and heating can improve the energy efficiency of the carbon dioxide energy storage system. The isentropic efficiency of the expansion unit can be set to not less than 85%, and the expansion unit evenly distributes the inlet and outlet pressures of each expander according to the pressure ratio.

[0085] In one embodiment of the present application, the heat transfer medium supply unit includes a third storage tank 23 and a fourth storage tank 24. The third storage tank 23 has a first heat transfer medium outlet and a first heat transfer medium inlet, the first heat transfer medium outlet is connected to the cooler, and provides the cooler with a heat transfer medium for cooling. The first heat transfer medium inlet is connected to the heater, and is used to receive the heat transfer medium flowing out of the heater. The fourth storage tank 24 has a second heat transfer medium outlet and a second heat transfer medium inlet, the second heat transfer medium outlet is connected to the heater, and provides the heater with a heat transfer medium for heating. The second heat transfer medium inlet is connected to the cooler, and is used to receive the heat transfer medium flowing out of the cooler. The heat transfer medium can be hot water or heat transfer oil, and the heat transfer medium circulates between the third storage tank 23, the compression unit, the fourth storage tank 24, and the expansion unit through a delivery pipeline.

[0086] In one embodiment of the present application, the carbon dioxide energy storage system includes two sets of heat transfer medium supply units, wherein the heat transfer medium circulating in one set of heat transfer medium supply units is water, and the heat transfer medium in the other set of heat transfer medium supply units is heat transfer oil. In the two sets of heat transfer medium supply units, heat transfer oil absorbs high-grade heat, and water absorbs low-grade heat, that is, heat transfer oil is suitable for high-quality heat sources, that is, when the temperature is higher, and water is suitable for low-quality heat sources, that is, when the temperature is lower. When the factory conditions cannot use dangerous media, hot water can also be used as the heat transfer medium, which is suitable for carbon dioxide energy storage systems with low-quality heat sources. The system efficiency is slightly lower but the safety is higher. Heat transfer oil and water can also be used in combination. For example, the compression unit uses heat transfer oil to extract heat and uses water circulation for cooling; the expansion unit uses hot water circulation for heating and uses heat transfer oil for warming. By using heat transfer oil and hot water as high- and low-quality heat storage media for heat storage circulation, the heat storage cycle can be effectively improved. efficiency, thereby improving the overall efficiency of the carbon dioxide energy storage system.

[0087] In the embodiment of the present application, the cooler and the heat exchanger can adopt a shell and tube heat exchanger or a PCHE (microchannel heat exchanger). The shell and tube heat exchanger has the advantage of easy disassembly and maintenance, and the PCHE has the advantage of high heat exchange effect and compact structure.

[0088] A number of embodiments of the present invention have been described in detail above, but the present invention is not limited to these specific embodiments. Those skilled in the art can make various variations and modifications to the embodiments based on the concept of the present invention, and these variations and modifications should all fall within the scope of protection claimed by the present invention.

Claims

1. A carbon dioxide energy storage system based on LNG cold energy utilization, characterized in that: include: a first storage tank for storing liquid carbon dioxide; a second storage tank for storing gaseous carbon dioxide; a compression unit, which is connected to the first storage tank and the second storage tank respectively, and is used to compress the liquid carbon dioxide from the first storage tank into supercritical carbon dioxide after heating, provide cold energy for the cold exchange station under the first set condition, and transport the gaseous carbon dioxide to the second storage tank; an expansion unit, which is connected to the first storage tank and the second storage tank respectively, and is used to expand the gaseous carbon dioxide from the second storage tank and cool it into liquid carbon dioxide, and then transport the liquid carbon dioxide to the first storage tank; during the expansion of carbon dioxide, carbon dioxide releases energy and is converted from gaseous carbon dioxide to liquid carbon dioxide, thereby completing the release of energy; the released energy is used for power generation; a heat-conducting medium supply unit, which is connected to the compression unit and the expansion unit respectively, and is used to provide the compression unit with a heat-conducting medium for cooling and to provide the expansion unit with a heat-conducting medium for heating; A cold energy providing unit, comprising an LNG supply pipeline for providing LNG; a cold energy utilization unit, which is connected to the cold energy providing unit and the heat transfer medium supply unit respectively, to receive cold energy of the LNG from the cold energy providing unit, and to provide cold energy for the refrigeration station under the second setting condition, and to provide cold energy under the third setting condition; The cold energy utilization unit includes a refrigerant carbon dioxide pump, a cold exchange station heat exchanger and an LNG heat exchanger; The heat exchanger of the cold exchange station is connected to the compression unit so that the carbon dioxide from the compression unit is introduced into the cold fluid side thereof under the first setting condition, and the carbon dioxide exchanges heat with the fluid on the hot fluid side of the heat exchanger of the cold exchange station, thereby providing cold energy for the cold exchange station, wherein the first setting condition is that the cold exchange station has a cold energy demand within a first setting time, and the first setting time is from sunset time to sunrise time; Under the second setting condition, LNG is introduced into the cold fluid side of the LNG heat exchanger and exchanges heat with the fluid on the hot fluid side of the LNG heat exchanger. The LNG flowing out of the LNG heat exchanger is introduced into the expansion unit and output to the external transmission pipeline after providing cold energy to the expansion unit. The second setting condition is that the cold exchange station has a cold energy demand within the second setting time, and the second setting time is from sunrise time to sunset time, so as to utilize the cold energy in a time-sharing manner. The cold energy utilization unit also includes a circulating heat exchanger, a circulating pump and a circulating expander; LNG first passes through the cold medium circulation of the cold exchange station or the circulating heat exchanger, the circulating pump and the circulating expander to perform Rankine cycle to release high-grade cold energy, and then cools the liquefied carbon dioxide to release low-grade cold energy, so as to perform cascade utilization of cold energy; the circulating heat exchanger has an intermediate medium inlet and an intermediate medium outlet, the inlet of the circulating pump is connected to the intermediate medium outlet of the circulating heat exchanger, and the outlet of the circulating pump is connected to the intermediate medium inlet of the circulating heat exchanger; the cold energy inlet of the circulating heat exchanger is introduced with LNG under the third setting condition, and the LNG flows out from the cold energy outlet of the circulating heat exchanger after providing cold energy to the circulating heat exchanger, and is introduced into the expansion unit to provide cold energy to the expansion unit and then output to the external transmission pipeline, wherein the third setting condition is that the cold exchange station has no cold energy demand; The outlet of the refrigerant carbon dioxide pump is connected to the cold fluid side of the refrigeration station for heat exchange, and the hot fluid side of the LNG heat exchanger is connected to the inlet of the refrigerant carbon dioxide pump to form a circulation passage for the refrigerant carbon dioxide.

2. The carbon dioxide energy storage system based on LNG cold energy utilization according to claim 1 is characterized in that: The compression unit comprises: a carbon dioxide pump connected to the first storage tank and the heat exchanger of the cold exchange station and used to pump out the liquid carbon dioxide in the first storage tank and pump the liquid carbon dioxide in the first storage tank to the heat exchanger of the cold exchange station under the first set condition; a carbon dioxide evaporator connected to the carbon dioxide pump and used to heat the liquid carbon dioxide pumped out by the carbon dioxide pump under the third set condition; a compressor connected to the carbon dioxide evaporator and used to compress the carbon dioxide after the heating treatment by the carbon dioxide evaporator under the third set condition to obtain gaseous carbon dioxide with a set pressure; A cooler is connected to the compressor and the second storage tank respectively, and is used to cool the gaseous carbon dioxide compressed by the compressor and transport the cooled gaseous carbon dioxide to the second storage tank.

3. The carbon dioxide energy storage system based on LNG cold energy utilization according to claim 2 is characterized in that: The compressors include at least two, the coolers include at least two, the compressors are connected to the coolers via a first connecting pipeline, and at least two compressors and at least two coolers are spaced apart on the first connecting pipeline.

4. The carbon dioxide energy storage system based on LNG cold energy utilization according to claim 2 is characterized in that: The expansion unit comprises: a heater connected to the second storage tank and used to heat the gaseous carbon dioxide from the second storage tank; an expander connected to the heater and used to expand the gaseous carbon dioxide heated by the heater; A carbon dioxide condenser is connected to the expander and the first storage tank and is used for condensing the carbon dioxide expanded by the expander to obtain liquid carbon dioxide and transport the liquid carbon dioxide to the first storage tank.

5. The carbon dioxide energy storage system based on LNG cold energy utilization according to claim 4 is characterized in that: The heaters include at least two, the expanders include at least two, the heaters are connected to the expanders via a second connecting pipeline, and at least two of the heaters and at least two of the expanders are spaced apart on the second connecting pipeline.

6. The carbon dioxide energy storage system based on LNG cold energy utilization according to claim 4 is characterized in that: The heat transfer medium supply unit comprises: a third storage tank having a first heat transfer medium outlet and a first heat transfer medium inlet, wherein the first heat transfer medium outlet is connected to the cooler and provides the heat transfer medium for cooling the cooler; and the first heat transfer medium inlet is connected to the heater and is used to receive the heat transfer medium flowing out of the heater; The fourth storage tank has a second heat transfer medium outlet and a second heat transfer medium inlet. The second heat transfer medium outlet is connected to the heater and provides the heater with heat transfer medium for heating. The second heat transfer medium inlet is connected to the cooler and is used to receive the heat transfer medium flowing out of the cooler.

7. The carbon dioxide energy storage system based on LNG cold energy utilization according to claim 1 is characterized in that: The carbon dioxide energy storage system includes two sets of heat transfer medium supply units, wherein the heat transfer medium flowing in one set of the heat transfer medium supply units is water, and the heat transfer medium in the other set of the heat transfer medium supply units is heat transfer oil.

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