Energy storage refrigeration system with breathing air storage tank and control method

Abstract

The present invention provides an energy storage refrigeration system with a breathing air tank and a control method, comprising a breathing air tank, a liquefaction component, a liquid storage container, and a refrigeration component, which are sequentially connected through a closed-loop pipeline. The breathing air tank includes an air membrane that separates the breathing air tank into an air cavity and a gaseous working medium cavity. The air cavity is connected to an air compression unit, and the gaseous working medium cavity is connected to the refrigeration component. The liquefaction component includes a compression unit and a cooling unit, and the compression unit is connected to the gaseous working medium cavity. The cooling unit is connected to the compression unit. The liquid storage container is used to store liquid working medium. The refrigeration component is connected to the liquid storage container and is used to vaporize the liquid working medium and reduce its temperature to cool external equipment requiring cooling. Using the working medium vaporization and cooling method to cool the external equipment requiring cooling reduces the energy loss caused by converting the working medium's potential energy into electrical energy and then performing the cooling process.

Description

Technical Field

[0001] The present invention relates to the field of carbon dioxide energy storage, and in particular to an energy storage refrigeration system with a breathing gas storage tank. Background Art

[0002] Vacuum freeze-drying technology is one of the most advanced food processing technologies currently available. However, vacuum freeze-drying equipment is a major energy consumer, requiring billions of kilowatts of electricity for production each year. This represents a significant cost for vacuum freezers and significantly increases the pressure on local power systems. Current compressed air energy storage technology stores waste electricity during off-peak periods as heat and potential energy, releasing it as electricity during peak periods, significantly reducing peak loads. Carbon dioxide energy storage (CES) technology is a new physical energy storage technology based on compressed air energy storage (CAES) and the Brayton power generation cycle. It can store energy for over 16 hours and release power at the gigawatt level. It offers advantages such as high energy storage density, long operating life, and compact system equipment, making it suitable for large-scale, long-term energy storage and promising development and application prospects.

[0003] In existing applications, a multi-stage compressor converts atmospheric-pressure gaseous CO2 into high-pressure liquid CO2 during periods of low electricity prices, converting electrical energy into the internal energy of CO2 for storage. During peak electricity demand, a multi-stage expander expands the high-pressure liquid CO2 into atmospheric-pressure gaseous CO2, which is then used to generate electricity, ultimately achieving both the storage and release of electrical energy. However, this system has two drawbacks: 1. The cost is substantial. This includes the multi-stage compressor, multi-stage expander, and atmospheric-pressure CO2 storage bladder, which contributes significantly to the cost of technology deployment; and 2. The energy conversion efficiency is low. The system converts electrical energy into internal energy via CO2, then outputs electrical energy when the internal energy is released. Ultimately, the electrical energy generates work and generates benefits. However, in scenarios requiring cooling energy, the system suffers from inefficiency due to the multiple energy conversions. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides an energy storage refrigeration system with a breathing gas storage tank and a control method, which has the characteristics of reducing costs and improving conversion efficiency.

[0005] The specific technical solution is as follows: it includes a breathing gas storage tank, a liquefaction component, a liquid storage container, and a refrigeration component connected in sequence through a closed-loop pipeline;

[0006] The breathing air storage tank includes an air membrane, which separates the breathing air storage tank into an air cavity and a gaseous working medium cavity. The air cavity is connected to an air compression unit and a generator respectively. The air compression unit is used to maintain a certain pressure in the breathing air storage tank. The generator is used to generate electricity when exhausting air. The gaseous working medium cavity is connected to a refrigeration component for storing the gaseous working medium exhausted by the refrigeration component.

[0007] The liquefaction component includes a compression unit and a cooling unit. The compression unit is connected to the gaseous working medium cavity and is used to pressurize the gaseous working medium. The cooling unit is connected to the compression unit and is used to cool the gaseous working medium pressurized by the compression unit to liquefy the gaseous working medium.

[0008] The liquid storage container is used to store liquid working medium;

[0009] The refrigeration component is connected to the liquid storage container and is used to gasify the liquid working medium and reduce its temperature to cool the external equipment that needs cooling.

[0010] The above-described technical solution enables a breathing air tank to include an air chamber and a gaseous working fluid chamber, maintaining a constant pressure within the tank. This significantly reduces the space occupied by a high-pressure breathing air tank compared to a normal-pressure breathing air tank. While the cost of air membranes is relatively high, the amount of air membranes used can be reduced when accommodating the same mass of working fluid. The combined use of a compression unit and a cooling unit reduces the pressure required for liquefaction of the working fluid, thereby reducing the energy loss of the high-power compression unit. By using the working fluid to vaporize and cool external equipment, the cooling system reduces the energy loss associated with the conversion of the working fluid's potential energy into electrical energy and subsequent refrigeration.

[0011] Preferably, the working fluid is carbon dioxide.

[0012] By using carbon dioxide as the working fluid, carbon dioxide is easier to obtain than other working fluids, has a higher energy storage density per unit volume than air, and its liquefaction conditions are easier to achieve than air, thereby reducing the investment cost of liquefaction equipment and energy loss during operation.

[0013] Preferably, a liquefaction buffer tank is installed between the liquefaction assembly and the liquid storage container, the cooling unit is connected to the middle of the liquefaction buffer tank through a pipeline, the bottom of the liquefaction buffer tank is connected to the liquid storage container through a pipeline, and the top of the liquefaction buffer tank is connected to the pipeline between the compression unit and the cooling unit through a pipeline.

[0014] The above technical solution improves the liquefaction effect of the liquefaction component.

[0015] Preferably, the energy storage refrigeration system with a breathing gas storage tank also includes a heat circulation system, which includes a hot water storage tank and a cold water storage tank. The cold water in the cold water storage tank is used to take away the heat in the cooling unit. The cold water is heated by the cooling unit and flows into the hot water storage tank. The hot water in the hot water storage tank is used to recover the coldness of the gaseous working medium discharged by the refrigeration component. The hot water is cooled by the gaseous working medium and flows into the cold water storage tank.

[0016] Through this technical solution, the cold water in the cold water storage tank can cool the condenser of the cooling unit, reducing the energy consumption when the cooling unit cools the compressed gaseous working fluid. The hot water in the hot water storage tank can heat the gaseous working fluid discharged from the refrigeration component, facilitating the conversion of the potential energy of the gaseous working fluid into electrical energy for recovery.

[0017] Preferably, the cooling unit is an R507A cascade system, which includes multiple coupled R507A cooling systems, each of which includes a compressor, a condenser, a pressure reducing valve and a liquid reservoir connected in sequence. The last R507A cooling system is used to cool the gaseous working medium compressed by the compression unit, and the cold water in the cold water storage tank flows through the condenser of the first R507A cooling system and then flows into the hot water storage tank.

[0018] Through the above technical solution, the R507A cascade system is adopted, which can facilitate the cooling temperature of the gaseous working medium to be lower.

[0019] The air cavity is connected to the generator.

[0020] Through the above technical solution, the expansion potential energy of the gaseous working medium can be converted into electrical energy for recovery.

[0021] A control method for an energy storage refrigeration system with a breathing air storage tank, which consumes electricity during a low electricity consumption period, further pressurizes the gaseous working medium in the breathing air storage tank through a compression unit, and then cools the pressurized gaseous working medium through a cooling unit to liquefy it and store it in a liquid storage container, while consuming cold water in a cold water storage tank, which is stored in a hot water storage tank after being heated, and at this time, an air compression unit compresses air into the breathing air storage tank to maintain the pressure in the breathing air storage tank; during a peak electricity consumption period, the liquid working medium in the liquid storage container is decompressed and vaporized, and the hot water in the hot water storage tank heats and expands the vaporized gaseous working medium, thereby increasing the volume of the gaseous working medium cavity in the breathing air storage tank, compressing the air cavity of the breathing air storage tank, and the air in the air cavity flows out of the air cavity to drive the motor to generate electricity; during the refrigeration process, the liquid working medium is decompressed and vaporized at the refrigeration component to cool the external equipment requiring cooling through the refrigeration component.

[0022] The above technical solution allows the gaseous working fluid to be pressurized and cooled during periods of low electricity consumption, liquefying it and storing it in a liquid storage container. The liquid working fluid in the liquid storage container continuously vaporizes and absorbs heat to achieve refrigeration, allowing the refrigeration system's power-consuming processes to operate only during periods of low electricity consumption. Furthermore, during peak periods of electricity consumption, compressed air can be used to generate electricity for other electrical equipment.

[0023] Preferably, the pressure of the breathing air storage tank is 0.8-1.2 MPa, the pressure after compression by the compression unit is 2.5-2.6 MPa, and the cooling temperature of the cooling unit is -12°C.

[0024] This technical solution significantly reduces the volume of a 0.8-1.2MPa breathing air tank compared to a normal-pressure breathing air tank, to approximately 1 / 8-1 / 12 of the normal-pressure container. This also reduces the use of air membranes, lowering investment costs. The compressed pressure is controlled at 2.5-2.6MPa and the temperature is -12°C, requiring only a low-power compressor. This reduces energy consumption compared to existing technologies that compress to 7MPa.

[0025] The beneficial effects of the present invention are:

[0026] 1. Changing the atmospheric pressure carbon dioxide gas storage bag into a breathing gas storage tank with a certain pressure reduces the investment cost of the gas bag and the pressurization required for phase change, greatly reducing the investment cost of the initial equipment.

[0027] 2. The energy storage process compresses the working fluid and condenses it into liquid for storage. The energy release process directly vaporizes the liquid working fluid to obtain cold energy, which greatly improves the energy conversion efficiency.

[0028] 3. Adding an R507A cascade system avoids the harsh compression and liquefaction conditions of carbon dioxide exceeding 3 MPa. By replacing the heat transfer medium, the carbon dioxide liquefaction temperature is lowered. This achieves better heat exchange efficiency using the most economical equipment investment method. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0030] Figure 1 This is a structural diagram of Example 1;

[0031] 1. Gas storage tank, 11. Gas film, 12. Air cavity, 13. Gaseous carbon dioxide cavity, 14. First compressor, 15. Generator, 2. Liquefaction component, 21. Second compressor, 22. Third compressor, 23. Condenser, 24. Liquid storage tank, 25. Pressure reducing valve, 26. First heat exchanger, 3. Carbon dioxide liquefaction tank, 31. Liquefaction buffer tank, 4. Refrigeration component, 41. Low-temperature pressure reducing valve, 42. Second heat exchanger, 51. Hot water storage tank, 52. Cold water storage tank, 53. Cold water pump, 54. Hot water pump, 55. Third heat exchanger. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0034] Example 1

[0035] like Figure 1 As shown, an energy storage refrigeration system with a breathing gas storage tank includes a breathing gas storage tank, a liquefaction component 2, a liquid storage container 3 and a refrigeration component connected in sequence through a closed-loop pipeline. In this embodiment, the working fluid is carbon dioxide.

[0036] The breathing air storage tank uses 12,000m 3 A gas storage tank 1 is provided with an air membrane 11, which divides the gas storage tank 1 into an air chamber 12 and a gaseous carbon dioxide chamber 13. The air chamber 12 is connected to an air compression unit, which in this embodiment is a first compressor 14. The first compressor 14 compresses air and feeds it into the air chamber 12, maintaining the pressure of the gas storage tank 1 at 1 MPa. The air chamber 12 is connected to a generator 15. The gaseous carbon dioxide chamber 13 is connected to the liquefaction assembly 2 and the refrigeration assembly, respectively.

[0037] The liquefaction assembly 2 includes a compression unit and a cooling unit. The compression unit uses a second compressor 21, which is connected to the gaseous carbon dioxide chamber 13 and is used to pressurize the gaseous carbon dioxide to 2.5 MPa. The second compressor 21 is connected to the cooling unit. In this embodiment, the cooling unit uses an R507A cascade system. The R507A cascade system includes a third compressor 22, a condenser 23, a liquid reservoir 24, a pressure reducing valve 25, and a first heat exchanger 26, which are connected in sequence. The first heat exchanger 26 is installed on the pipeline between the second compressor 21 and the liquid reservoir 3. The R507A cascade system reduces the temperature of the gaseous carbon dioxide to -12° and liquefies the gaseous carbon dioxide.

[0038] The liquid storage container is a carbon dioxide liquefaction tank 3, which is used to store liquid carbon dioxide. A liquefaction buffer tank 31 is installed between the carbon dioxide liquefaction tank 3 and the R507A cascade system. The R507A cascade system is connected to the middle of the liquefaction buffer tank 31 via a pipeline. The bottom of the liquefaction buffer tank 31 is connected to the liquid storage container 3 via a pipeline, and the top of the liquefaction buffer tank 31 is connected to the pipeline between the second compressor 21 and the first heat exchanger 26 via a pipeline.

[0039] The refrigeration assembly 4 includes a low-temperature pressure reducing valve 41 and a second heat exchanger 42. The second heat exchanger 42 is connected to an external device requiring cooling to cool the external device requiring cooling.

[0040] The heat circulation system includes a hot water tank 51 and a cold water tank 52. The cold water in the cold water tank 51 is used to cool the gaseous carbon dioxide pressurized by the second compressor 21. The cold water is heated by the gaseous carbon dioxide and then flows into the hot water tank 52. Specifically, the cold water in the cold water tank 51 flows through the condenser 23 via a cold water pump 53 to cool the R507A cascade system. The hot water in the hot water tank 52 is used to heat the gaseous carbon dioxide discharged from the second heat exchanger 42. The hot water is cooled by the gaseous carbon dioxide and then flows into the cold water tank 51. Specifically, the hot water in the hot water tank 52 flows through the third heat exchanger 55 via a hot water pump 54 to heat the gaseous carbon dioxide discharged from the second heat exchanger 42. The third heat exchanger 55 is installed on the pipeline between the second heat exchanger 42 and the gas storage tank 1.

[0041] Energy storage process: During periods of low electricity consumption, the low-pressure gaseous CO2 in the gaseous CO2 chamber 13 is compressed by the second compressor 21 to form high-pressure CO2. This high-pressure CO2 then passes through the liquefier of the R507A cascade system to form liquid CO2, which is then stored in the CO2 liquefier tank 3, completing the energy storage process. The heat energy generated by the compressor in the R507A cascade system is then exchanged with the cold water in the cold water storage tank 52 through the R507A condenser, generating hot water that is stored in the hot water storage tank 51.

[0042] Energy Release Process: During peak electricity consumption, the liquid carbon dioxide in the liquid storage container 3 passes through the cryogenic pressure reducing valve 41, transforming from a liquid to a low-pressure gaseous carbon dioxide, releasing a large amount of cold energy. The high-quality cold energy is captured by the cold supply second heat exchanger 42 and used for refrigeration in the freeze-drying process. Simultaneously, the unextracted waste cold energy is used in the third heat exchanger 55 to cool the water in the hot water storage tank 51 to low-temperature water, which is then stored in the cold water storage tank 52. The gaseous carbon dioxide eventually returns to the gaseous carbon dioxide chamber 13, completing the energy release process.

[0043] During the energy release process, the gaseous carbon dioxide in the gaseous carbon dioxide chamber 13 will continue to increase. At the same time, the air in the tank will be gradually discharged. When the air is discharged, a generator is connected to the release end to generate electricity and realize the reuse of waste gas.

[0044] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. An energy storage refrigeration system with a breathing air storage tank, characterized by: It includes a breathing gas storage tank, a liquefied component, a liquid storage container, and a refrigeration component which are sequentially connected through a closed loop of pipelines; The breathing air storage tank includes an air membrane, which separates the breathing air storage tank into an air cavity and a gaseous working medium cavity. The air cavity is connected to an air compression unit and a generator respectively. The air compression unit is used to maintain a certain pressure in the breathing air storage tank. The generator is used to generate electricity when exhausting air. The gaseous working medium cavity is connected to a refrigeration component for storing the gaseous working medium exhausted by the refrigeration component. The liquefaction assembly includes a first compression unit and a cooling unit, wherein the first compression unit is connected to the gaseous working medium chamber and is used to pressurize the gaseous working medium, and the cooling unit is connected to the first compression unit and is used to cool the gaseous working medium pressurized by the first compression unit to liquefy the gaseous working medium; The liquid storage container is used to store liquid working medium; The refrigeration component is connected to the liquid storage container and is used to gasify the liquid working medium and reduce its temperature to cool the external equipment requiring cooling; The system also includes a heat circulation system, which includes a hot water storage tank and a cold water storage tank. The cold water in the cold water storage tank is used to remove heat from the cooling unit. The cold water is heated by the cooling unit and flows into the hot water storage tank. The hot water in the hot water storage tank is used to recover the cold energy of the gaseous working medium discharged by the refrigeration component. The hot water is cooled by the gaseous working medium and flows into the cold water storage tank. During the period of low electricity consumption, electricity is consumed, and the gaseous working medium in the breathing air storage tank is further pressurized by the first compression unit, and then the pressurized gaseous working medium is cooled by the cooling unit to liquefy it and store it in the liquid storage container. At this time, the cold water in the cold water storage tank is consumed, and the cold water is stored in the hot water storage tank after being heated. At this time, the air compression unit compresses air into the breathing air storage tank to maintain the pressure in the breathing air storage tank; during the period of peak electricity consumption, the liquid working medium in the liquid storage container is decompressed and vaporized, and the hot water in the hot water storage tank heats the vaporized gaseous working medium to expand, so that the volume of the gaseous working medium cavity in the breathing air storage tank becomes larger, compressing the air cavity of the breathing air storage tank, and the air in the air cavity flows out of the air cavity to drive the motor to do work and generate electricity.

2. The energy storage refrigeration system with a breathing air storage tank according to claim 1, characterized in that: The working fluid is carbon dioxide.

3. The energy storage refrigeration system with a breathing air storage tank according to claim 1, characterized in that: A liquefaction buffer tank is installed between the liquefaction assembly and the liquid storage container. The cooling unit is connected to the middle of the liquefaction buffer tank through a pipeline. The bottom of the liquefaction buffer tank is connected to the liquid storage container through a pipeline. The top of the liquefaction buffer tank is connected to the pipeline between the first compression unit and the cooling unit through a pipeline.

4. The energy storage refrigeration system with a breathing air storage tank according to claim 1, characterized in that: The cooling unit is an R507A cascade system, which includes multiple coupled R507A cooling systems. The R507A cooling system includes a compressor, a condenser, a pressure reducing valve and a liquid reservoir connected in sequence. The last R507A cooling system is used to cool the gaseous working medium compressed by the first compression unit. The cold water in the cold water storage tank flows through the condenser of the first R507A cooling system and then flows into the hot water storage tank.

5. A control method for an energy storage refrigeration system with a breathing air storage tank according to any one of claims 1 to 4, characterized in that: During the off-peak period of electricity consumption, electricity is consumed to further pressurize the gaseous working medium in the breathing air storage tank through the first compression unit, and then the pressurized gaseous working medium is cooled by the cooling unit to liquefy it and store it in the liquid storage container. At this time, the cold water in the cold water storage tank is consumed, and the cold water is stored in the hot water storage tank after being heated. At this time, the air compression unit compresses air into the breathing air storage tank to maintain the pressure in the breathing air storage tank; During peak hours of electricity consumption, the liquid working medium in the liquid storage container is decompressed and vaporized. The hot water in the hot water storage tank heats and expands the vaporized gaseous working medium, which increases the volume of the gaseous working medium cavity in the breathing gas storage tank, compresses the air cavity of the breathing gas storage tank, and the air in the air cavity flows out of the air cavity to drive the motor to generate power. During the refrigeration process, the liquid working medium is decompressed and gasified in the refrigeration component to cool the external equipment that needs to be cooled.

6. The control method of the energy storage refrigeration system with a breathing air storage tank according to claim 5, characterized in that: The pressure of the breathing air storage tank is 0.8-1.2 MPa, the pressure after compression by the first compression unit is 2.5-2.6 MPa, and the cooling temperature of the cooling unit is -12°C.

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