A dual-liquid energy storage system and method based on adjustable CO2 mixed working fluid components

Abstract

The present invention belongs to the field of energy storage technology, and specifically provides a dual-liquid energy storage system and method based on an adjustable CO2 mixed working fluid component. The system uses a mixture of CO2 and organic matter as the operating working fluid for compressed energy storage. The system uses a cold accumulator to achieve gas-liquid conversion at the low-pressure end, so that the low-pressure working fluid is stored in a liquid state, and uses a heat exchanger to achieve gas-liquid conversion at the high-pressure end, so that the high-pressure working fluid is stored in a liquid state. Since the working fluid in the storage tank exists in both gas and liquid phases, and the component proportions of the gaseous working fluid and the liquid working fluid are different, the component proportion of the mixed working fluid in the cycle can be adjusted by adjusting the gas-liquid flow ratio, thereby improving the performance of the energy storage system.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage technology, and in particular, relates to a dual-liquid energy storage system and method based on adjustable CO2 mixed working fluid components. Background Art

[0002] Currently, existing compressed energy storage technologies primarily use air or CO2 as the working fluid. Compressed air energy storage, due to the physical properties of air, is difficult to store in liquid form, thus requiring a large gas storage volume. Compressed CO2 energy storage, on the other hand, requires storage tanks at both the high- and low-pressure ends, as CO2 cannot be directly obtained from air. Storing CO2 in gaseous form requires a very large storage volume.

[0003] Although CO2 has the advantage of being easily liquefied, storing it in liquid form at both the high-pressure and low-pressure ends often comes at the expense of reduced round-trip efficiency. Furthermore, CO2 has a critical temperature of 31.0°C, a critical pressure of 7.38 MPa, a triple point temperature of -56.6°C, and a triple point pressure of 0.52 MPa. This means that if compressed CO2 energy storage is stored in liquid form, the high-pressure tank pressure must not exceed 7.38 MPa, while the low-pressure tank pressure must be at least 0.52 MPa. The relatively low pressure of a liquid CO2 energy storage system causes a sharp increase in the amount of CO2 required for the same capacity. Furthermore, during the storage and release process, the CO2 within the tank undergoes a gas-liquid phase transition, causing temperature fluctuations within the tank. This can potentially lead to the formation of dry ice within the low-pressure liquid tank, potentially blocking the pipeline and affecting CO2 flow. Therefore, for liquid CO2 energy storage systems, further improving the system's round-trip efficiency and increasing the system's high-to-low pressure ratio are pressing issues.

[0004] To this end, the present invention mixes CO2 with organic matter to improve the physical properties of CO2, thereby effectively improving system performance and preventing low-pressure CO2 from freezing. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a dual-liquid energy storage system and method based on an adjustable CO2 mixed working fluid component. The system can store the working fluid in liquid form at both the low-pressure and high-pressure ends. The working fluid in the storage tank exists in both gas and liquid phases. The gas-liquid flow ratio can be adjusted to adjust the component ratio of the mixed working fluid in the circulation, thereby improving the performance of the energy storage system.

[0006] The technical solution adopted by the present invention is: a dual-liquid energy storage system based on adjustable CO2 mixed working medium components, including a compression energy storage circulation loop and a heat storage loop, the compression energy storage circulation loop includes a low-pressure liquid storage tank and a high-pressure liquid storage tank, the exhaust port at the top of the low-pressure liquid storage tank is provided with a first plug valve, the discharge port at the bottom of the low-pressure liquid storage tank is provided with a second plug valve, the outlet of the second plug valve is connected to the throttle valve, the third plug valve and the cold storage device in sequence through a pipeline, the air outlet of the cold storage device is provided with a fourth plug valve, the outlet of the first plug valve is connected to the outlet of the fourth plug valve through a pipeline, and then connected to the first compressor, the fifth plug valve, the first cooler, the sixth plug valve, the second compressor, the seventh plug valve and the second cooler in sequence through a pipeline, the liquid outlet of the second cooler is connected to the eighth plug valve and the high-pressure liquid storage tank in sequence through a pipeline, the exhaust port at the upper end of the high-pressure liquid storage tank is provided with an eleventh plug valve, and the discharge port at the lower end of the high-pressure liquid storage tank is provided with a tenth plug valve, The outlets of the tenth stopcock and the eleventh stopcock are merged through a pipeline and are connected to the twelfth stopcock, the first heater, the thirteenth stopcock, the first expander, the fourteenth stopcock, the second heater, the fifteenth stopcock, the second expander, and the sixteenth stopcock in sequence through the pipeline. The outlet of the sixteenth stopcock is connected to the cold accumulator through a pipeline. The low-pressure working medium is cooled and liquefied in the cold accumulator and then flows into the low-pressure liquid storage tank through the seventeenth stopcock; the heat storage circuit includes a hot water tank, the water outlet of the hot water tank is connected to the hot water pump through a pipeline, and the hot water pump supplies heat transfer medium to the first heater and the second heater. The water outlets of the first heater and the second heater are connected to the cold water tank through a pipeline. The heat transfer medium in the cold water tank is transported to the radiator through the cold water pump. The drain outlet of the radiator is connected to the water inlet of the first cooler and the second cooler respectively through a pipeline, and the heat transfer medium discharged from the first cooler and the second cooler is transported to the hot water tank through a pipeline.

[0007] In a preferred embodiment, the working fluid circulating in the compressed energy storage cycle is a mixture of CO2 and organic matter.

[0008] In a preferred embodiment, the heat transfer medium circulating in the heat storage circuit is water or heat transfer oil.

[0009] In a preferred solution, the high-pressure liquid storage tanks are provided in multiple groups, and the liquid inlet of each group of high-pressure liquid storage tanks is provided with a ninth stopcock, and the outlet of the eighth stopcock is connected to the inlet of the ninth stopcock through a pipeline.

[0010] In a preferred solution, the water outlet of the hot water tank is provided with an eighteenth stopcock.

[0011] In a preferred solution, the inlet and outlet of the heat transfer medium of the second heater are respectively provided with a nineteenth stopcock and a twentieth stopcock, and the inlet and outlet of the heat transfer medium of the first heater are respectively provided with a twenty-first stopcock and a twenty-second stopcock.

[0012] In the preferred embodiment, the water outlet of the cold water tank is provided with a twenty-third stopcock, the water inlet of the radiator is provided with a twenty-fourth stopcock, the heat transfer medium inlet and outlet of the second cooler are respectively provided with a twenty-fifth stopcock and a twenty-sixth stopcock, and the heat transfer medium inlet and outlet of the first cooler are respectively provided with a twenty-seventh stopcock and a twenty-eighth stopcock.

[0013] In the preferred embodiment, a working fluid balance circuit is also included, which includes a twenty-ninth stopcock connected to the outlet of the second stopcock through a pipeline, the outlet of the twenty-ninth stopcock is connected to the inlet of the working fluid pump through a pipeline, the outlet of the working fluid pump is connected to the high-pressure liquid storage tank through a pipeline, the outlet of the high-pressure liquid storage tank is connected to the inlet of the regulating valve through a pipeline, and the outlet of the regulating valve is connected to the inlet of the seventeenth stopcock through a pipeline.

[0014] In a preferred solution, the cold storage device includes a vacuum interlayer outer wall and a multi-layer coil arranged in the vacuum interlayer outer wall, and the cold storage material is filled between the multi-layer coil and the vacuum interlayer outer wall.

[0015] The present invention also provides an operating method for a dual-liquid energy storage system based on an adjustable CO2 mixed working fluid component, including the following two operating modes:

[0016] Mode 1: Electrical energy is converted into hot water internal energy and pressure potential energy storage:

[0017] The mixed working medium in the low-pressure liquid storage tank exists in gas-liquid two-phases. The gaseous working medium flows out through the first plug valve, and the liquid working medium flows out through the second plug valve. The liquid working medium at the outlet of the second plug valve is reduced in pressure and temperature by the throttle valve, then passes through the third plug valve and absorbs heat and vaporizes in the cold accumulator, then passes through the fourth plug valve and mixes with the gaseous working medium at the outlet of the first plug valve. The mixed working medium is pressurized by the first compressor, then passes through the fifth plug valve and cools down in the first cooler, then flows through the first cooler and is pressurized again by the second compressor, then passes through the seventh plug valve and cools down and liquefies in the second cooler, and then enters the high-pressure liquid storage tank through the eighth plug valve and the ninth plug valve;

[0018] In the hot water storage circuit, the cold water in the cold water tank passes through the 23rd stopcock, the cold water pump, the 24th stopcock, and the radiator in sequence, and then is divided into two paths. One path flows through the 25th stopcock to cool the working medium in the second cooler, and then passes through the 26th stopcock to enter the hot water tank. The other path flows through the 27th stopcock, cools the working medium in the first cooler, and then passes through the 28th stopcock to enter the hot water tank.

[0019] In the working medium balance circuit, in order to adjust the amount of mixed working medium at the high and low pressure ends, part of the liquid working medium in the high pressure liquid storage tank enters the low pressure liquid storage tank after passing through the tenth stopcock valve, the regulating valve and the seventeenth stopcock valve;

[0020] Mode 2: The stored energy is released in the form of electrical energy:

[0021] The mixed working fluid in the high-pressure liquid storage tank exists in gas-liquid two-phase. The gaseous working fluid flows out through the eleventh stopcock, and the liquid working fluid flows out through the tenth stopcock. After the two fluids are mixed, they pass through the twelfth stopcock and are heated in the first heater, where the liquid working fluid is completely vaporized. Then, the mixed working fluid flows through the thirteenth stopcock and drives the first expander to generate work and electricity. After that, it passes through the fourteenth stopcock and is heated in the second heater. Then, it flows through the fifteenth stopcock and drives the second expander to generate work and electricity. After that, it flows through the sixteenth stopcock, releases heat and liquefies in the cold accumulator, and finally enters the low-pressure liquid storage tank through the seventeenth stopcock.

[0022] In the hot water storage circuit, the hot water in the hot water tank is divided into two paths after passing through the 18th stopcock and the hot water pump. One path flows through the 19th stopcock and is heated in the second heater before passing through the 20th stopcock and entering the cold water tank. The other path flows through the 21st stopcock and is heated in the first heater before passing through the 22nd stopcock and entering the cold water tank.

[0023] In the working fluid balance circuit, in order to adjust the amount of mixed working fluid at the high and low pressure ends, part of the liquid working fluid in the low-pressure liquid storage tank 1 flows through the twenty-ninth stopcock after passing through the second stopcock, is pressurized by the working fluid pump, and then passes through the ninth stopcock and enters the high-pressure liquid storage tank.

[0024] The present invention provides a dual-liquid energy storage system and method based on adjustable CO2 mixed working fluid components, which has the following beneficial effects:

[0025] 1. The critical temperature of the CO2 mixed working fluid is higher and it can be easily condensed near the ambient temperature. This will make the temperature of the high-pressure liquid storage tank relatively high and the gas-liquid density difference larger, which is conducive to reducing the volume of the liquid storage tank.

[0026] 2. At the same saturation temperature, the pressure of the CO2 mixed working fluid is lower, which will reduce the pressure of the low-pressure liquid storage tank, which is conducive to increasing the pressure ratio of the system. At the same time, the introduction of organic working fluid will effectively prevent the formation of dry ice in the CO2 low-pressure liquid tank.

[0027] 3. Since the evaporation characteristics of organic working fluids and CO2 are significantly different, the CO2 mixed working fluid has temperature glide characteristics at different phase change pressures, which will enable better temperature matching during the CO2 evaporation or condensation process and reduce heat exchange exergy loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below with reference to the accompanying drawings and examples:

[0029] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0030] Figure 2 It is a structural schematic diagram of the cold storage device of the present invention;

[0031] Figure 3 It is a structural diagram of a multi-layer coil;

[0032] Figure 4 is the relationship between the mass fraction of carbon dioxide in the mixed working fluid and temperature;

[0033] In the figure: low-pressure liquid storage tank 1, first plug valve 2, second plug valve 3, throttle valve 4, third plug valve 5, cold accumulator 6, fourth plug valve 7, first compressor 8, fifth plug valve 9, first cooler 10, sixth plug valve 11, second compressor 12, seventh plug valve 13, second cooler 14, eighth plug valve 15, ninth plug valve 16, high-pressure liquid storage tank 17, tenth plug valve 18, eleventh plug valve 19, twelfth plug valve 20, first heater 21, thirteenth plug valve 22, first expander 23, fourteenth plug valve 24, second heater 25, fifteenth plug valve 26 , second expander 27, sixteenth plug valve 28, seventeenth plug valve 29, hot water tank 30, eighteenth plug valve 31, hot water pump 32, nineteenth plug valve 33, twentieth plug valve 34, twenty-first plug valve 35, twenty-second plug valve 36, cold water tank 37, twenty-third plug valve 38, cold water pump 39, twenty-fourth plug valve 40, radiator 41, twenty-fifth plug valve 42, twenty-sixth plug valve 43, twenty-seventh plug valve 44, twenty-eighth plug valve 45, regulating valve 46, twenty-ninth plug valve 47, working fluid pump 48, interlayer outer wall 601, multi-layer coil 602. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0035] Combine Figures 1 to 4 The specific embodiments of the present invention are described in further detail.

[0036] Example 1:

[0037] In the existing technology, it is difficult to complete double-end liquid storage while maintaining a high round-trip efficiency, and the pressure ratio of the high and low pressure tanks is relatively small, resulting in a small energy storage power corresponding to the unit amount of CO2. In addition, the low-pressure liquid CO2 storage tank faces the risk of dry ice, which causes related problems such as blockage of the flow channel. The present invention provides a dual-liquid energy storage system based on adjustable CO2 mixed working fluid components, including a mixed working fluid energy storage cycle, a hot water storage circuit and a working fluid balance circuit, such as Figure 1 shown.

[0038] The compression energy storage cycle loop includes a low-pressure liquid storage tank 1 and a high-pressure liquid storage tank 17, and a mixture of CO2 and organic matter is used as the working medium of the compression energy storage cycle. The exhaust port on the top of the low-pressure liquid storage tank 1 is provided with a first plug valve 2, and the discharge port at the bottom of the low-pressure liquid storage tank 1 is provided with a second plug valve 3. The outlet of the second plug valve 3 is connected to the throttle valve 4, the third plug valve 5 and the cold accumulator 6 in sequence through a pipeline. The air outlet of the cold accumulator 6 is provided with a fourth plug valve 7. The outlet of the first plug valve 2 is connected to the outlet of the fourth plug valve 7 through a pipeline, and then connected to the first compressor 8, the fifth plug valve 9, the first cooler 10, the sixth plug valve 11, the second compressor 12, the seventh plug valve 13 and the second cooler 14 in sequence through a pipeline. The outlet of the second cooler 14 The liquid port is connected to the eighth stopcock 15 and the high-pressure liquid storage tank 17 in sequence through a pipeline. The exhaust port at the upper end of the high-pressure liquid storage tank 17 is provided with an eleventh stopcock 19, and the discharge port at the lower end of the high-pressure liquid storage tank 17 is provided with a tenth stopcock 18. The outlets of the tenth stopcock 18 and the eleventh stopcock 19 are merged through a pipeline and then connected to the twelfth stopcock 20, the first heater 21, the thirteenth stopcock 22, the first expander 23, the fourteenth stopcock 24, the second heater 25, the fifteenth stopcock 26, the second expander 27, and the sixteenth stopcock 28 in sequence through a pipeline. The outlet of the sixteenth stopcock 28 is connected to the cold accumulator 6 through a pipeline. The low-pressure working medium is cooled and liquefied in the cold accumulator 6 and then flows into the low-pressure liquid storage tank 1 through the seventeenth stopcock 29.

[0039] Preferably, the high-pressure liquid storage tanks 17 are provided in multiple groups, and the liquid inlet of each group of high-pressure liquid storage tanks 17 is provided with a ninth stopcock 16, and the outlet of the eighth stopcock 15 is connected to the inlet of the ninth stopcock 16 via a pipeline. Each group of high-pressure liquid storage tanks 17 is controlled separately by providing the ninth stopcock 16.

[0040] The heat storage circuit includes a hot water tank 30. The heat transfer medium circulating in the heat storage circuit is water or thermal oil. In this embodiment, the heat transfer medium is water. The water outlet of the hot water tank 30 is connected to a hot water pump 32 via a pipeline. The hot water pump 32 supplies the heat transfer medium to the first heater 21 and the second heater 25. The water outlet of the hot water tank 30 is provided with an eighteenth stopcock 31 to control the discharge of the heat transfer medium from the hot water tank 30. The water outlets of the first heater 21 and the second heater 25 are connected to a cold water tank 37 via a pipeline. The heat transfer medium in the cold water tank 37 is transported to the radiator 41 via a cold water pump 39. The drain port of the radiator 41 is connected to the water inlets of the first cooler 10 and the second cooler 14 via pipelines. The heat transfer medium discharged from the first cooler 10 and the second cooler 14 is transported to the hot water tank 30 via pipelines.

[0041] Preferably, the inlet and outlet of the heat transfer medium of the second heater 25 are respectively provided with a nineteenth stopcock 33 and a twentieth stopcock 34, and the inlet and outlet of the heat transfer medium of the first heater 21 are respectively provided with a twenty-first stopcock 35 and a twenty-second stopcock 36. By controlling the opening and closing of the nineteenth stopcock 33, the twentieth stopcock 34, the twenty-first stopcock 35, and the twenty-second stopcock 36 according to actual conditions, the second heater 25 and the first heater 21 can be controlled to operate simultaneously or independently.

[0042] Preferably, a twenty-third stopcock 38 is provided at the water outlet of the cold water tank 37 to control the discharge of the heat transfer medium in the cold water tank 37 , and a twenty-fourth stopcock 40 is provided at the water inlet of the radiator 41 .

[0043] A twenty-fifth plug valve 42 and a twenty-sixth plug valve 43 are respectively provided at the heat transfer medium inlet and outlet of the second cooler 14 , and a twenty-seventh plug valve 44 and a twenty-eighth plug valve 45 are respectively provided at the heat transfer medium inlet and outlet of the first cooler 10 .

[0044] According to actual conditions, by controlling the opening and closing of the twenty-fifth stopcock 42, the twenty-sixth stopcock 43, the twenty-seventh stopcock 44, and the twenty-eighth stopcock 45, the first cooler 10 and the second cooler 14 can be controlled to work simultaneously or separately.

[0045] The working fluid balance circuit includes a twenty-ninth stopcock 47 connected to the outlet of the second stopcock 3 through a pipeline, the outlet of the twenty-ninth stopcock 47 is connected to the inlet of the working fluid pump 48 through a pipeline, the outlet of the working fluid pump 48 is connected to the high-pressure liquid storage tank 17 through a pipeline, the outlet of the tenth stopcock 18 provided at the discharge port of the high-pressure liquid storage tank 17 is connected to the inlet of the regulating valve 46 through a pipeline, and the outlet of the regulating valve 46 is connected to the inlet of the seventeenth stopcock 29 through a pipeline.

[0046] In the mixed working fluid energy storage cycle, the gaseous mixed working fluid in the low-pressure liquid storage tank 1 flows out through the first plug valve 2, while the liquid mixed working fluid passes through the second plug valve 3, the throttle valve 4, and the third plug valve 5 in sequence, and then enters the cold accumulator 6 to be heated and vaporized, and then mixes with the gaseous working fluid at the outlet of the first plug valve 2 at the outlet of the fourth plug valve 7. The mixed gaseous working fluid enters the first compressor 8 for pressurization, then passes through the fifth plug valve 9 and is cooled by the first cooler 10, then passes through the sixth plug valve 11, is pressurized by the second compressor 12, then passes through the seventh plug valve 13 and is cooled in the second cooler 14, and finally passes through the eighth plug valve 15 and the ninth plug valve 16 in sequence, and is stored in the high-pressure liquid storage tank 17. The mixed working fluid in the high-pressure liquid storage tank 17 flows out in two paths: the liquid working fluid flows out through the tenth stopcock 18, and the gaseous working fluid flows out through the eleventh stopcock 19. Both flow through the twelfth stopcock 20 and are heated by the first heater 21, completely converting the liquid working fluid into a gaseous state. The mixed working fluid then passes through the thirteenth stopcock 22, driving the first expander 23 to produce work. It then passes through the fourteenth stopcock 24 and is heated in the second heater 25. It then passes through the fifteenth stopcock 26 and drives the second expander 27 to produce work. The low-pressure working fluid at the outlet of the second expander 27 flows through the sixteenth stopcock 28, where it is cooled and liquefied in the cold accumulator 6. It then flows through the seventeenth stopcock 29 and is stored in the low-pressure liquid storage tank 1.

[0047] In the hot water storage circuit, the hot water in the hot water tank 30 flows through the 18th stopcock 31 and the hot water pump 32 and is split into two paths. One path flows through the 19th stopcock 33, where it is heated in the second heater 25, before passing through the 20th stopcock 34 and entering the cold water tank 37. The other path flows through the 21st stopcock 35, where it is heated in the first heater 21, before passing through the 22nd stopcock 36 and entering the cold water tank 37. The cold water in the cold water tank 37 flows through the 23rd stopcock 38, the cold water pump 39, the 24th stopcock 40, and the radiator 41, before being split into two paths. One path flows through the 25th stopcock 42, where it is cooled in the second cooler 14, before passing through the 26th stopcock 43 and entering the hot water tank 30. The other path flows through the 27th stopcock 44, where it is cooled in the first cooler 10, before passing through the 28th stopcock 45 and entering the hot water tank 30.

[0048] In the working fluid balance circuit, the liquid working fluid in the high-pressure liquid storage tank 17 passes through the tenth stopcock 18, then flows through the regulating valve 46 and the seventeenth stopcock 29 into the low-pressure liquid storage tank 1. The liquid working fluid in the low-pressure liquid storage tank 1 passes through the second stopcock 3, then flows through the twenty-ninth stopcock 47, where it is pressurized by the working fluid pump 48, and then passes through the ninth stopcock 16 and enters the high-pressure liquid storage tank 17.

[0049] During energy storage, the mixed refrigerant in the low-pressure tank 1 is pressurized by the compressor, cooled in the cooler, and ultimately stored in the high-pressure tank 17. During energy release, the mixed refrigerant in the high-pressure tank 17 is first heated in the heater, then drives the expander turbine to generate power, releasing energy. Furthermore, a cold accumulator 6 is used on the low-pressure side to ensure that the refrigerant is stored in a liquid state, while a heat exchanger on the high-pressure side converts the gas into liquid, also storing the refrigerant in a liquid state.

[0050] Under the quasi-static state of gas-liquid phase equilibrium, taking the mixed working fluid of organic matter R32 and CO2 as an example, the gas-liquid components and the total components satisfy the following Figure 4 The equilibrium relationship shown in Figure 1 indicates that the operating components of the energy storage and release process can be adjusted by varying the gas-liquid mixing ratio, which is beneficial for further improving the performance of the energy storage system. In order to adjust the mixed working quality at the high and low pressure ends, a working fluid balance loop was constructed.

[0051] Example 2:

[0052] An operating method of a dual-liquid energy storage system based on an adjustable CO2 mixed working fluid component includes the following two operating modes:

[0053] Mode 1: Electric energy is converted into hot water internal energy and pressure potential energy for storage: During the energy storage process, electric energy drives the compressor to pressurize the mixed working fluid at the low-pressure end. The working fluid is then cooled by the cooler and stored in the high-pressure tank. The specific working process is as follows:

[0054] The mixed working medium in the low-pressure liquid storage tank 1 exists in gas-liquid two-phase. The gaseous working medium flows out through the first plug valve 2, and the liquid working medium flows out through the second plug valve 3. The liquid working medium at the outlet of the second plug valve 3 is reduced in pressure and temperature through the throttle valve 4, then passes through the third plug valve 5 and absorbs heat and vaporizes in the cold accumulator 6, then passes through the fourth plug valve 7 and mixes with the gaseous working medium at the outlet of the first plug valve 2. The mixed working medium is pressurized by the first compressor 8, then passes through the fifth plug valve 9 and is cooled in the first cooler 10, then flows through the first cooler 10 and is pressurized again by the second compressor 12, then passes through the seventh plug valve 13 and is cooled and liquefied in the second cooler 14, and then enters the high-pressure liquid storage tank 17 through the eighth plug valve 15 and the ninth plug valve 16.

[0055] In the hot water storage circuit, the cold water in the cold water tank 37 passes through the twenty-third stopcock 38, the cold water pump 39, the twenty-fourth stopcock 40, and the radiator 41 in sequence and is divided into two paths. One path flows through the twenty-fifth stopcock 42 to cool the working medium in the second cooler 14, and then enters the hot water tank 30 through the twenty-sixth stopcock 43. The other path flows through the twenty-seventh stopcock 44, cools the working medium in the first cooler 10, and then enters the hot water tank 30 through the twenty-eighth stopcock 45.

[0056] In the working medium balance circuit, in order to adjust the amount of mixed working medium at the high and low pressure ends, part of the liquid working medium in the high pressure liquid storage tank 17 enters the low pressure liquid storage tank 1 after passing through the tenth stopcock 18, the regulating valve 46 and the seventeenth stopcock 29;

[0057] Mode 2: The stored energy is released in the form of electrical energy: During the energy release process, the mixed working fluid at the high-pressure end is heated by the heater, then drives the turbine to generate power, and then stores it in the low-pressure tank. The specific working process is as follows:

[0058] The mixed working medium in the high-pressure liquid storage tank 17 exists in gas-liquid two-phase. The gaseous working medium flows out through the eleventh stopcock 19, and the liquid working medium flows out through the tenth stopcock 18. After the two fluids are mixed, they pass through the twelfth stopcock 20 and are then heated in the first heater 21, where the liquid working medium is vaporized. Then, the mixed working medium flows through the thirteenth stopcock 22 and drives the first expander 23 to generate work, then passes through the fourteenth stopcock 24 and is heated in the second heater 25, then flows through the fifteenth stopcock 26 and drives the second expander 27 to generate work, then flows through the sixteenth stopcock 28, releases heat and liquefies in the cold accumulator 6, and finally enters the low-pressure liquid storage tank 1 through the seventeenth stopcock 29.

[0059] In the hot water storage circuit, the hot water in the hot water tank 30 is divided into two paths after passing through the eighteenth stopcock 31 and the hot water pump 32. One path flows through the nineteenth stopcock 33 and then heats the working fluid in the second heater 25, and then enters the cold water tank 37 through the twentieth stopcock 34. The other path flows through the twenty-first stopcock 35 and then heats the working fluid in the first heater 21, and then enters the cold water tank 37 through the twenty-second stopcock 36.

[0060] In the working fluid balance circuit, in order to adjust the amount of mixed working fluid at the high and low pressure ends, part of the liquid working fluid in the low-pressure liquid storage tank 1 flows through the twenty-ninth stopcock valve 47 after passing through the second stopcock valve 3, is pressurized by the working fluid pump 48, and then passes through the ninth stopcock valve 16 and enters the high-pressure liquid storage tank 17.

[0061] Example 3:

[0062] Different from Example 1, Figures 2 and 3 As shown, the cold storage device 6 comprises a vacuum-interlayer outer wall 601 and a multi-layer coil 602 disposed within the vacuum-interlayer outer wall 601. The vacuum-interlayer outer wall 601 is a double-layer cylindrical structure, with the interlayer vacuumed to enhance thermal insulation. A cold storage material is filled between the multi-layer coil 602 and the vacuum-interlayer outer wall 601. The cold storage material can be made of pebbles or ceramic tiles, providing the cold required for liquid storage at the low-pressure end.

[0063] During energy storage, the liquid working fluid in the low-pressure liquid storage tank 1 passes through the third stopcock 5 and flows through the multi-layer coil 602 in the cold storage device 6, exchanges heat with the cold storage material, absorbs heat and vaporizes, and stores cold energy at the same time; during energy release, the gaseous working fluid discharged from the sixteenth stopcock 28 flows through the multi-layer coil 602, exchanges heat with the cold storage material, and is discharged from the cold storage device 6 after liquefaction, and the heat is stored in the cold storage material.

[0064] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The scope of protection of the present invention should be the technical solutions described in the claims, including equivalent replacement solutions of the technical features in the technical solutions described in the claims. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made on the basis of the above description. It is not necessary and impossible to list all the implementation methods here. That is, equivalent replacement improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A dual-liquid energy storage system based on adjustable CO2 mixed working fluid components, characterized in that: The invention comprises a compression energy storage circulation loop and a heat storage loop, wherein the compression energy storage circulation loop comprises a low-pressure liquid storage tank (1) and a high-pressure liquid storage tank (17), wherein the exhaust port at the top of the low-pressure liquid storage tank (1) is provided with a first plug valve (2), and the discharge port at the bottom of the low-pressure liquid storage tank (1) is provided with a second plug valve (3), the outlet of the second plug valve (3) is connected to a throttle valve (4), a third plug valve (5) and a cold storage device (6) in sequence through a pipeline, and the outlet of the cold storage device (6) is provided with a fourth plug valve (7), and the outlet of the first plug valve (2) is connected to the outlet of the fourth plug valve (7) through a pipeline and then connected to the outlet of the first pressure storage tank (1) and the outlet of the fourth plug valve (7) in sequence through a pipeline. The compressor (8), the fifth plug valve (9), the first cooler (10), the sixth plug valve (11), the second compressor (12), the seventh plug valve (13) and the second cooler (14) are connected. The liquid outlet of the second cooler (14) is connected to the eighth plug valve (15) and the high-pressure liquid storage tank (17) in sequence through a pipeline. The exhaust port of the upper end of the high-pressure liquid storage tank (17) is provided with an eleventh plug valve (19). The discharge port of the lower end of the high-pressure liquid storage tank (17) is provided with a tenth plug valve (18). The outlets of the tenth plug valve (18) and the eleventh plug valve (19) are connected in sequence through a pipeline. The heat storage circuit is connected to the twelfth stopcock (20), the first heater (21), the thirteenth stopcock (22), the first expander (23), the fourteenth stopcock (24), the second heater (25), the fifteenth stopcock (26), the second expander (27), and the sixteenth stopcock (28). The outlet of the sixteenth stopcock (28) is connected to the cold storage device (6) through a pipeline. The low-pressure working medium is cooled and liquefied in the cold storage device (6) and then flows into the low-pressure liquid storage tank (1) through the seventeenth stopcock (29). The heat storage circuit includes a hot water tank (30). The water outlet of the hot water tank (30) is connected to the hot water pump through a pipeline. (32), the hot water pump (32) supplies heat transfer medium to the first heater (21) and the second heater (25), the water outlets of the first heater (21) and the second heater (25) are connected to the cold water tank (37) through pipelines, the heat transfer medium in the cold water tank (37) is transported to the radiator (41) through the cold water pump (39), the drain outlet of the radiator (41) is connected to the water inlet of the first cooler (10) and the second cooler (14) through pipelines, and the heat transfer medium discharged from the first cooler (10) and the second cooler (14) is transported to the hot water tank (30) through the pipeline.

2. A dual-liquid energy storage system based on adjustable CO2 mixed working fluid components according to claim 1, characterized in that: The working fluid circulating in the compressed energy storage cycle is a mixture of CO2 and organic matter.

3. A dual-liquid energy storage system based on adjustable CO2 mixed working fluid components according to claim 1, characterized in that: The heat transfer medium circulating in the heat storage circuit is water or heat transfer oil.

4. A dual-liquid energy storage system based on adjustable CO2 mixed working fluid components according to claim 1, characterized in that: The high-pressure liquid storage tanks (17) are provided in multiple groups, and the liquid inlet of each group of high-pressure liquid storage tanks (17) is provided with a ninth stopcock (16), and the outlet of the eighth stopcock (15) is connected to the inlet of the ninth stopcock (16) through a pipeline.

5. A dual-liquid energy storage system based on adjustable CO2 mixed working fluid components according to claim 1, characterized in that: The water outlet of the hot water tank (30) is provided with an eighteenth stopcock (31).

6. A dual-liquid energy storage system based on adjustable CO2 mixed working fluid components according to claim 1, characterized in that: The inlet and outlet of the heat-conducting medium of the second heater (25) are respectively provided with a nineteenth stopcock (33) and a twentieth stopcock (34), and the inlet and outlet of the heat-conducting medium of the first heater (21) are respectively provided with a twenty-first stopcock (35) and a twenty-second stopcock (36).

7. A dual-liquid energy storage system based on adjustable CO2 mixed working fluid components according to claim 1, characterized in that: The water outlet of the cold water tank (37) is provided with a twenty-third stopcock (38), the water inlet of the radiator (41) is provided with a twenty-fourth stopcock (40), the heat transfer medium inlet and outlet of the second cooler (14) are provided with a twenty-fifth stopcock (42) and a twenty-sixth stopcock (43), respectively, and the heat transfer medium inlet and outlet of the first cooler (10) are provided with a twenty-seventh stopcock (44) and a twenty-eighth stopcock (45), respectively.

8. A dual-liquid energy storage system based on adjustable CO2 mixed working fluid components according to claim 1, characterized in that: The invention also includes a working fluid balance circuit, wherein the working fluid balance circuit includes a twenty-ninth plug valve (47) connected to the outlet of the second plug valve (3) through a pipeline, the outlet of the twenty-ninth plug valve (47) is connected to the inlet of the working fluid pump (48) through a pipeline, the outlet of the working fluid pump (48) is connected to the high-pressure liquid storage tank (17) through a pipeline, the outlet of the tenth plug valve (18) provided at the discharge port of the high-pressure liquid storage tank (17) is connected to the inlet of the regulating valve (46) through a pipeline, and the outlet of the regulating valve (46) is connected to the inlet of the seventeenth plug valve (29) through a pipeline.

9. A dual-liquid energy storage system based on adjustable CO2 mixed working fluid components according to claim 1, characterized in that: The cold storage device (6) comprises a vacuum interlayer outer wall (601) and a multi-layer coil (602) arranged inside the vacuum interlayer outer wall (601), and a cold storage material is filled between the multi-layer coil (602) and the vacuum interlayer outer wall (601).

10. The method for operating a dual-liquid energy storage system based on adjustable CO2 mixed working fluid components according to any one of claims 1 to 9, characterized in that: There are two operating modes: Mode 1: Electrical energy is converted into hot water internal energy and pressure potential energy storage: The mixed working medium in the low-pressure liquid storage tank (1) exists in gas-liquid two-phases. The gaseous working medium flows out through the first plug valve (2), and the liquid working medium flows out through the second plug valve (3). The liquid working medium at the outlet of the second plug valve (3) is depressurized and cooled through the throttle valve (4), then passes through the third plug valve (5) and absorbs heat and vaporizes in the cold storage device (6), then passes through the fourth plug valve (7) and mixes with the gaseous working medium at the outlet of the first plug valve (2). The mixed working medium is pressurized by the first compressor (8), then passes through the fifth plug valve (9) and cools down in the first cooler (10), then flows through the first cooler (10) and is pressurized again by the second compressor (12), then passes through the seventh plug valve (13), cools down and liquefies in the second cooler (14), and then passes through the eighth plug valve (15) and the ninth plug valve (16) to enter the high-pressure liquid storage tank (17); In the hot water storage circuit, the cold water in the cold water tank (37) passes through the twenty-third plug valve (38), the cold water pump (39), the twenty-fourth plug valve (40), and the radiator (41) in sequence and is then divided into two paths. One path flows through the twenty-fifth plug valve (42) to cool the working medium in the second cooler (14), and then passes through the twenty-sixth plug valve (43) to enter the hot water tank (30). The other path flows through the twenty-seventh plug valve (44), cools the working medium in the first cooler (10), and then passes through the twenty-eighth plug valve (45) to enter the hot water tank (30). In the working medium balance circuit, in order to adjust the amount of mixed working medium at the high and low pressure ends, part of the liquid working medium in the high pressure liquid storage tank (17) passes through the tenth stopcock (18) and then enters the low pressure liquid storage tank (1) through the regulating valve (46) and the seventeenth stopcock (29); Mode 2: The stored energy is released in the form of electrical energy: The mixed working medium in the high-pressure liquid storage tank (17) exists in gas-liquid two-phase. The gaseous working medium flows out through the eleventh plug valve (19), and the liquid working medium flows out through the tenth plug valve (18). After the two fluids are mixed, they pass through the twelfth plug valve (20), and are then heated in the first heater (21). The liquid working medium is vaporized here. Then, the mixed working medium flows through the thirteenth plug valve (22) and drives the first expander (23) to generate power. Then, it passes through the fourteenth plug valve (24) and is heated in the second heater (25). Then, it flows through the fifteenth plug valve (26) and drives the second expander (27) to generate power. Then, it flows through the sixteenth plug valve (28), releases heat and liquefies in the cold storage device (6), and finally enters the low-pressure liquid storage tank (1) through the seventeenth plug valve (29). In the hot water storage circuit, the hot water in the hot water tank (30) is divided into two paths after passing through the eighteenth stopcock (31) and the hot water pump (32). One path flows through the nineteenth stopcock (33) and then heats the working medium in the second heater (25). The working medium then enters the cold water tank (37) through the twentieth stopcock (34). The other path flows through the twenty-first stopcock (35) and then heats the working medium in the first heater (21). The working medium then enters the cold water tank (37) through the twenty-second stopcock (36). In the working medium balance circuit, in order to adjust the amount of mixed working medium at the high and low pressure ends, part of the liquid working medium in the low-pressure liquid storage tank 1 flows through the 29th plug valve (47) after passing through the second plug valve (3), is pressurized by the working medium pump (48), and then passes through the 9th plug valve (16) and enters the high-pressure liquid storage tank (17).

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