Double-liquid-state energy storage system and method based on adjustable CO2 mixed working medium components

Abstract

The invention belongs to the technical field of energy storage, and particularly provides a double-liquid-state energy storage system and method based on adjustable CO2 mixed working medium components, and the system uses a mixture of CO2 and organic matter as an operation working medium for compression energy storage. The system uses the regenerator to realize gas-liquid conversion at a low-pressure end, so that a low-pressure working medium is stored in a liquid state, and uses the heat exchanger to realize gas-liquid conversion at a high-pressure end, so that a high-pressure working medium is stored in a liquid state. The working medium in the storage tank has gas and liquid phases at the same time, and the component proportions of the gaseous working medium and the liquid working medium are different, so that the component proportion of the mixed working medium in circulation can be adjusted by adjusting the flow proportion of gas and liquid, and the performance of the energy storage system is improved.

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] At present, the existing compressed energy storage technology mainly uses air or CO2 as the operating fluid. Compressed air energy storage is difficult to store in liquid form due to the physical properties of air, so a larger gas storage volume is required. As for compressed CO2 energy storage, since CO2 cannot be obtained directly from the air, storage tanks are required at both the high and low pressure ends. If CO2 is stored in gaseous form, a very large storage volume is required.

[0003] Although CO2 has the advantage of being easy to liquefy, if CO2 is stored in liquid form at both the high-pressure and low-pressure ends, it often requires reducing the round-trip efficiency of the system as a cost. At the same time, the critical temperature of CO2 is 31.0°C, the critical pressure is 7.38Mpa, the triple point temperature is -56.6°C, and the triple point pressure is 0.52MPa. This means that if compressed CO2 energy storage chooses liquid storage, the pressure of its high-pressure tank will not exceed 7.38MPa at most, and the pressure of the low-pressure tank will not be less than 0.52MPa at least. The pressure ratio of the liquid CO2 energy storage system is relatively low, which causes the amount of CO2 required at the same capacity to rise sharply. At the same time, during the energy storage and release process, the CO2 in the tank will undergo a gas-liquid phase change conversion process, which will cause a certain fluctuation in the temperature in the tank, which may cause dry ice to form in the low-pressure liquid tank, thereby blocking the pipeline and affecting the circulation of CO2. Therefore, for the liquid CO2 energy storage system, how to further improve the round-trip efficiency of the system and increase the high-low pressure ratio of the system is an urgent problem to be solved.

[0004] In this regard, 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] In order to solve the above technical problems, the present invention provides a dual-liquid energy storage system and method based on CO2 mixed working fluid with adjustable components. The system can store 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 flow ratio of gas and liquid can be adjusted to adjust the component ratio of the mixed working fluid in the cycle, thereby improving the performance of the energy storage system. The technical solution adopted by the present invention is: a dual-liquid energy storage system based on an adjustable CO2 mixed working fluid component, 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 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, the hot water pump supplies heat transfer medium to the first heater and the second heater, the water outlet of the first heater and the second heater is 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 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.

[0006] In a preferred embodiment, the working fluid circulating in the compressed energy storage circulation loop is a mixture of CO2 and organic matter.

[0007] In a preferred embodiment, the heat transfer medium circulating in the heat storage circuit is water or heat transfer oil.

[0008] In a preferred solution, the high-pressure liquid storage tanks are arranged 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.

[0009] In a preferred solution, the water outlet of the hot water tank is provided with an eighteenth stopcock.

[0010] In a preferred embodiment, the inlet and outlet of the heat-conducting medium of the second heater are respectively provided with a nineteenth stopcock and a twentieth stopcock, and the inlet and outlet of the heat-conducting medium of the first heater are respectively provided with a twenty-first stopcock and a twenty-second stopcock.

[0011] In the preferred scheme, 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 provided with a twenty-fifth stopcock and a twenty-sixth stopcock respectively, and the heat transfer medium inlet and outlet of the first cooler are provided with a twenty-seventh stopcock and a twenty-eighth stopcock respectively.

[0012] In the preferred scheme, it also includes a working fluid balance circuit, 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.

[0013] 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.

[0014] The present invention also provides an operating method of a dual-liquid energy storage system based on an adjustable CO2 mixed working fluid component, including the following 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 exists in gas-liquid two-phases, the gaseous working medium flows out through the first plug valve, the liquid working medium flows out through the second plug valve, the liquid working medium at the outlet of the second plug valve is depressurized and cooled by the throttle valve, then passes through the third plug valve and absorbs heat and vaporizes in the cold storage device, 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; In the hot water storage circuit, the cold water in the cold water tank passes through the twenty-third plug valve, the cold water pump, the twenty-fourth plug valve, and the radiator in sequence and is divided into two paths. One path flows through the twenty-fifth plug valve to cool the working medium in the second cooler and then passes through the twenty-sixth plug valve to enter the hot water tank. The other path flows through the twenty-seventh plug valve to cool the working medium in the first cooler and then passes through the twenty-eighth plug valve to enter the hot water tank. 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 through the regulating valve and the seventeenth plug valve after passing through the tenth plug valve; Mode 2: The stored energy is released in the form of electrical energy: The mixed working medium in the high-pressure liquid storage tank exists in gas-liquid two-phases. The gaseous working medium flows out through the eleventh plug valve, and the liquid working medium flows out through the tenth plug valve. After the two fluids are mixed, they pass through the twelfth plug valve, and then are heated in the first heater, where the liquid working medium is gasified. Then, the mixed working medium flows through the thirteenth plug valve and drives the first expander to generate power, then passes through the fourteenth plug valve and is heated in the second heater, then flows through the fifteenth plug valve and drives the second expander to generate power, then flows through the sixteenth plug valve, releases heat and liquefies in the cold storage device, and finally enters the low-pressure liquid storage tank through the seventeenth plug valve; 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 heats the working medium in the second heater, and then passes through the 20th stopcock to enter the cold water tank. The other path flows through the 21st stopcock and heats the working medium in the first heater, and then passes through the 22nd stopcock to enter the cold water tank. 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.

[0015] 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: 1. The critical temperature of the CO2 mixed working fluid is higher and can be easily condensed near the ambient temperature, which 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.

[0016] 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 avoid the formation of dry ice in the CO2 low-pressure liquid tank.

[0017] 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 make the CO2 evaporation or condensation process have better temperature matching and reduce heat exchange exergy loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a structural schematic diagram of the cold storage device of the present invention; Figure 3 It is a schematic diagram of the structure of a multi-layer coil; Figure 4is the relationship between the mass fraction of carbon dioxide in the mixed working fluid and the temperature; 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 storage device 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 , the second expander 27, the sixteenth plug valve 28, the seventeenth plug valve 29, the hot water tank 30, the eighteenth plug valve 31, the hot water pump 32, the nineteenth plug valve 33, the twentieth plug valve 34, the twenty-first plug valve 35, the twenty-second plug valve 36, the cold water tank 37, the twenty-third plug valve 38, the cold water pump 39, the twenty-fourth plug valve 40, the radiator 41, the twenty-fifth plug valve 42, the twenty-sixth plug valve 43, the twenty-seventh plug valve 44, the twenty-eighth plug valve 45, the regulating valve 46, the twenty-ninth plug valve 47, the working fluid pump 48, the interlayer outer wall 601, and the multi-layer coil 602. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is 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 used to limit the present invention.

[0020] Combination Figure 1~Figure 4 The specific embodiments of the present invention are described in further detail.

[0021] Embodiment 1: In the prior art, it is difficult to complete double-end liquid storage while maintaining a high round-trip efficiency, and the pressure ratio of the high-pressure and low-pressure tanks is relatively small, resulting in a small energy storage power corresponding to a 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 relevant 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.

[0022] 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 fluid 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 storage device 6 in sequence through a pipeline. The air outlet of the cold storage device 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 are 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. After the low-pressure working medium is cooled and liquefied in the cold accumulator 6, it flows into the low-pressure liquid storage tank 1 through the seventeenth stopcock 29.

[0023] 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 through a pipeline. Each group of high-pressure liquid storage tanks 17 is controlled separately by providing the ninth stopcock 16.

[0024] The heat storage circuit includes a hot water tank 30, and the heat transfer medium circulating in the heat storage circuit is water or heat transfer oil. In this embodiment, the heat transfer medium is water. The water outlet of the hot water tank 30 is connected to the hot water pump 32 through a pipeline, and 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 the cold water tank 37 through a pipeline. The heat transfer medium in the cold water tank 37 is transported to the radiator 41 through the cold water pump 39. The drain port of the radiator 41 is connected to the water inlet of the first cooler 10 and the second cooler 14 through a pipeline, 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 a pipeline.

[0025] Preferably, the inlet and outlet of the heat transfer medium of the second heater 25 are respectively provided with a nineteenth plug valve 33 and a twentieth plug valve 34, and the inlet and outlet of the heat transfer medium of the first heater 21 are respectively provided with a twenty-first plug valve 35 and a twenty-second plug valve 36. According to actual conditions, by controlling the opening and closing of the nineteenth plug valve 33, the twentieth plug valve 34, the twenty-first plug valve 35 and the twenty-second plug valve 36, the second heater 25 and the first heater 21 can be controlled to work simultaneously or separately.

[0026] 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 of the cold water tank 37 , and a twenty-fourth stopcock 40 is provided at the water inlet of the radiator 41 .

[0027] 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 .

[0028] 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.

[0029] 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 arranged 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.

[0030] In the mixed working medium energy storage cycle, the gaseous mixed working medium in the low-pressure liquid storage tank 1 flows out through the first plug valve 2, while the liquid mixed working medium passes through the second plug valve 3, the throttle valve 4, and the third plug valve 5 in sequence, and then enters the cold storage tank 6 to heat up and gasify, and then mixes with the gaseous working medium at the outlet of the first plug valve 2 at the outlet of the fourth plug valve 7. The mixed gaseous working medium 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 medium in the high-pressure liquid storage tank 17 flows out in two ways, wherein the liquid working medium flows out through the tenth plug valve 18 and the gaseous working medium flows out through the eleventh plug valve 19, and both pass through the twelfth plug valve 20 and are heated by the first heater 21, where the liquid working medium is completely converted into gaseous state. Then, the mixed working medium passes through the thirteenth plug valve 22 and drives the first expander 23 to do work, then passes through the fourteenth plug valve 24 and heats up in the second heater 25, then passes through the fifteenth plug valve 26 and drives the second expander 27 to do work. The low-pressure working medium at the outlet of the second expander 27 flows through the sixteenth plug valve 28 and is cooled and liquefied in the cold storage device 6, then flows through the seventeenth plug valve 29 and is stored in the low-pressure liquid storage tank 1.

[0031] In the hot water storage circuit, the hot water in the hot water tank 30 is divided into two paths after passing through the 18th stopcock 31 and the hot water pump 32. One path flows through the 19th stopcock 33 and heats the working medium in the second heater 25, and then enters the cold water tank 37 through the 20th stopcock 34. The other path flows through the 21st stopcock 35 and heats the working medium in the first heater 21, and then enters the cold water tank 37 through the 22nd stopcock 36. The cold water in the cold water tank 37 passes through the 23rd stopcock 38, the cold water pump 39, the 24th stopcock 40, and the radiator 41 in sequence and is divided into two paths. One path flows through the 25th stopcock 42 to cool the working medium in the second cooler 14, and then enters the hot water tank 30 through the 26th stopcock 43, and the other path flows through the 27th stopcock 44 to cool the working medium in the first cooler 10, and then enters the hot water tank 30 through the 28th stopcock 45.

[0032] In the working medium balance circuit, the liquid working medium in the high-pressure liquid storage tank 17 passes through the tenth plug valve 18 and then enters the low-pressure liquid storage tank 1 through the regulating valve 46 and the seventeenth plug valve 29. The liquid working medium in the low-pressure liquid storage tank 1 passes through the second plug valve 3 and then flows through the twenty-ninth plug valve 47 to be pressurized by the working medium pump 48, and then passes through the ninth plug valve 16 and enters the high-pressure liquid storage tank 17.

[0033] During the energy storage process, the mixed working fluid in the low-pressure liquid storage tank 1 is pressurized by the compressor, cooled in the cooler, and finally stored in the high-pressure liquid storage tank 17. During the energy release process, the mixed working fluid in the high-pressure liquid storage tank 17 is first heated in the heater, and then drives the expansion machine turbine to generate power to achieve energy release. In addition, at the low-pressure end, the cold storage device 6 is used to ensure that the working fluid can be stored in a liquid state, while the high-pressure end can complete the gas-liquid conversion by the heat exchanger, and the working fluid is also stored in a liquid state.

[0034] 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 component and the total component satisfy the following Figure 4 The balance relationship shown in Figure 1 means that the operating components of the energy storage and release process can be adjusted by different gas-liquid mixing ratios, which is beneficial to further improve 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 is constructed.

[0035] Embodiment 2: 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: Mode 1: Electric energy is converted into hot water internal energy and pressure potential energy storage: During the energy storage process, electric energy drives the compressor to pressurize the mixed working fluid at the low-pressure end, and then the working fluid is cooled by the cooler and stored in the high-pressure tank. The specific working process is as follows: 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 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 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.

[0036] 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 fluid 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 fluid in the first cooler 10, and then enters the hot water tank 30 through the twenty-eighth stopcock 45.

[0037] 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 through the regulating valve 46 and the seventeenth plug valve 29 after passing through the tenth plug valve 18; 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, and then drives the turbine to generate electricity, which is then stored in the low-pressure tank. The specific working process is as follows: 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 then are heated in the first heater 21, where the liquid working medium is vaporized. Then, the mixed working medium flows through the thirteenth plug valve 22 and drives the first expander 23 to do work and generate electricity, then passes through the fourteenth plug valve 24 and is heated in the second heater 25, then flows through the fifteenth plug valve 26 and drives the second expander 27 to do work and generate electricity, then flows through the sixteenth plug valve 28, releases heat and liquefies in the cold accumulator 6, and finally enters the low-pressure liquid storage tank 1 through the seventeenth plug valve 29.

[0038] 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 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 heats the working fluid in the first heater 21, and then enters the cold water tank 37 through the twenty-second stopcock 36.

[0039] 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.

[0040] Embodiment 3: Different from Example 1, Figure 2~3 As shown, the cold storage device 6 includes a vacuum interlayer outer wall 601 and a multi-layer coil 602 arranged in the vacuum interlayer outer wall 601. The vacuum interlayer outer wall 601 is a double-layer cylindrical structure, and the interlayer is evacuated to enhance the thermal insulation performance. The multi-layer coil 602 and the vacuum interlayer outer wall 601 are filled with cold storage materials. The cold storage materials can be selected from pebbles or ceramic sheets, etc., to provide the cold required for liquid storage at the low-pressure end.

[0041] When storing energy, the liquid working fluid in the low-pressure liquid storage tank 1 passes through the third stopcock 5, 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; when releasing energy, 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 being liquefied, and the heat is stored in the cold storage material.

[0042] The above-mentioned embodiments are only preferred technical solutions of the present invention and should not be regarded as limitations of the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded 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 protection scope 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 an exhaust port at the top of the low-pressure liquid storage tank (1) is provided with a first plug valve (2), and a discharge port at the bottom of the low-pressure liquid storage tank (1) is provided with a second plug valve (3), wherein an 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, wherein an outlet of the cold storage device (6) is provided with a fourth plug valve (7), wherein an outlet of the first plug valve (2) is connected to an outlet of the fourth plug valve (7) through a pipeline, and then connected to an outlet of the first pressure storage tank (1) in sequence through a pipeline. The compressor (8), the fifth stopcock (9), the first cooler (10), the sixth stopcock (11), the second compressor (12), the seventh stopcock (13) and the second cooler (14) are connected; the liquid outlet of the second cooler (14) 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); 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 connected in sequence through a pipeline after being merged. The heat storage circuit is connected to a twelfth stopcock (20), a first heater (21), a thirteenth stopcock (22), a first expander (23), a fourteenth stopcock (24), a second heater (25), a fifteenth stopcock (26), a second expander (27), and a sixteenth stopcock (28); the outlet of the sixteenth stopcock (28) is connected to a cold storage device (6) via a pipeline; the low-pressure working fluid is cooled and liquefied in the cold storage device (6) and then flows into the low-pressure liquid storage tank (1) via a 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 a hot water pump via 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 circulation loop 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 loop 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: An eighteenth stopcock (31) is provided at the water outlet of the hot water tank (30).

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 device also comprises a working fluid balance circuit, wherein the working fluid balance circuit comprises a twenty-ninth plug valve (47) connected to the outlet of the second plug valve (3) via a pipeline, the outlet of the twenty-ninth plug valve (47) is connected to the inlet of a working fluid pump (48) via a pipeline, the outlet of the working fluid pump (48) is connected to a high-pressure liquid storage tank (17) via a pipeline, the outlet of a tenth plug valve (18) provided at the discharge port of the high-pressure liquid storage tank (17) is connected to the inlet of a regulating valve (46) via a pipeline, and the outlet of the regulating valve (46) is connected to the inlet of a seventeenth plug valve (29) via 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 operating method of 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 through the first compressor (8), then passes through the fifth plug valve (9) and cools 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 cools and liquefies in the second cooler (14), and then passes through the eighth plug valve (15) and the ninth plug valve (16) and enters 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 stopcock (38), the cold water pump (39), the twenty-fourth stopcock (40), and the radiator (41) in sequence and is then 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 passes through the twenty-sixth stopcock (43) to enter the hot water tank (30). The other path flows through the twenty-seventh stopcock (44), cools the working medium in the first cooler (10), and then passes through the twenty-eighth stopcock (45) to enter the hot water tank (30). In the working fluid balance circuit, in order to adjust the amount of the mixed working fluid at the high and low pressure ends, part of the liquid working fluid in the high pressure liquid storage tank (17) passes through the tenth stopcock (18) and then enters the low pressure liquid storage tank (1) via 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-phases. 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), where the liquid working medium is vaporized. Then, the mixed working medium flows through the thirteenth plug valve (22) and drives the first expander (23) to generate power, then passes through the fourteenth plug valve (24) and is heated in the second heater (25), then flows through the fifteenth plug valve (26) and drives the second expander (27) to generate power, then 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), and then passes through the twentieth stopcock (34) to enter the cold water tank (37). The other path flows through the twenty-first stopcock (35) and then heats the working medium in the first heater (21), and then passes through the twenty-second stopcock (36) to enter the cold water tank (37). 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 (47) after passing through the second stopcock (3), 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).

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