Carbon dioxide energy storage system with step reheating and method of controlling the same

Abstract

The present disclosure relates to the technical field of energy storage, and particularly relates to a carbon dioxide energy storage system with cascade heat supplement and a control method thereof. The carbon dioxide energy storage system comprises, in sequence, a gas storage, an energy storage assembly, a liquid storage tank and an energy release assembly, the energy storage assembly being configured to convert gaseous carbon dioxide into liquid carbon dioxide. The system further comprises a heat exchange assembly, the energy storage assembly and the energy release assembly being connected to the heat exchange assembly, the heat exchange assembly being configured to transfer energy in the energy storage assembly to the energy release assembly. The energy release assembly comprises, in sequence, an evaporator, a heat supplement heat exchanger, an energy release heat exchanger and a turbine, the heat supplement heat exchanger being configured to supplement heat for gaseous carbon dioxide flowing between the evaporator and the energy release heat exchanger. The above technical solution forms a cascade heating mode, so that the superheat degree of carbon dioxide working medium at the inlet of the energy release heat exchanger is effectively improved, the temperature difference between hot and cold fluids is significantly reduced, and the entropy production and the exergy loss in the heat exchange process are reduced.

Description

Technical Field

[0001] This disclosure relates to the field of energy storage technology, and more specifically, to a carbon dioxide energy storage system with cascaded heat replenishment and its control method. Background Technology

[0002] Currently, compressed carbon dioxide (CCCO) energy storage technology is developing rapidly and receiving increasing attention. A CCCO energy storage system consists of an energy storage phase and an energy release phase. In the energy storage phase, surplus electricity during off-peak hours drives a compressor to compress gaseous CO2. After cooling, the CO2 is stored in a liquid form in a storage tank, while the heat of compression is recovered and stored in a heat tank. In the energy release phase, the liquid CO2 is pressurized by a liquid pump and sent to an evaporator for vaporization. Then, after absorbing the stored heat of compression in an energy release heat exchanger, the CO2 is heated and enters a turbine for expansion to generate electricity.

[0003] However, in the energy release loop of existing compressed carbon dioxide energy storage systems, the CO2 working fluid at the evaporator outlet is in a low-temperature, low-superheat state. It enters the energy release heat exchanger to exchange heat with a high-temperature heat source. The excessive temperature difference between the hot and cold sides leads to irreversible heat transfer losses, reducing system efficiency. Simultaneously, the heating process of the working fluid from the evaporator outlet to the turbine inlet is completed by the energy release heat exchanger. Limited by the heat exchanger equipment, irreversible heat transfer losses are positively correlated with the heat exchange temperature difference. Excessive temperature difference results in significant energy losses, and the usable thermal energy of the high-temperature storage medium cannot be efficiently transferred to the carbon dioxide working fluid, thus restricting the system's power generation efficiency.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this disclosure is to overcome the shortcomings of the prior art and provide a carbon dioxide energy storage system with cascaded heat replenishment and its control method.

[0006] According to one aspect of this disclosure, a carbon dioxide energy storage system with cascaded heat replenishment includes a gas storage tank, an energy storage component, a liquid storage tank, and an energy release component connected sequentially along the flow path of the carbon dioxide working fluid to form a circulation loop. The gas storage tank is used to store gaseous carbon dioxide, the liquid storage tank is used to store liquid carbon dioxide, and the energy storage component is used to convert gaseous carbon dioxide into liquid carbon dioxide to store the energy generated in the conversion process. It also includes a heat exchange component. The energy storage component and the energy release component are both connected to the heat exchange component. The heat exchange component is used to transfer the energy in the energy storage component to the energy release component. The energy release component includes an evaporator, a supplementary heat exchanger, an energy release heat exchanger, and a turbine connected in sequence along the flow path of the carbon dioxide working fluid. The evaporator is used to evaporate liquid carbon dioxide into gaseous carbon dioxide, the energy release heat exchanger is used to heat the gaseous carbon dioxide, the turbine is used to use the heated gaseous carbon dioxide to do work, and the supplementary heat exchanger is used to supplement the heat of the gaseous carbon dioxide flowing between the evaporator and the energy release heat exchanger. The heat exchange component is used to provide the compression heat in the energy storage component to the energy release heat exchanger and the supplementary heat exchanger to heat the gaseous carbon dioxide.

[0007] In one embodiment, the heat exchange assembly includes a heat exchange medium, which absorbs the heat of compression, releases heat in the energy release heat exchanger, and then flows into the supplementary heat exchanger to release heat.

[0008] In one embodiment, the energy storage component includes a compressor, an energy storage heat exchanger, and a condenser connected sequentially along the flow path of the carbon dioxide working medium. The compressor is used to compress and heat the gaseous carbon dioxide. The energy storage heat exchanger is used to exchange heat between the compressed carbon dioxide and the heat exchange medium in the heat exchange component to cool the carbon dioxide. The condenser is used to condense the cooled carbon dioxide into a liquid state. After the heat exchange medium exchanges heat with the compressed carbon dioxide, it enters the energy release heat exchanger through the heat exchange component to heat the gaseous carbon dioxide. The heat exchange medium after exchanging heat with the energy release heat exchanger flows into the supplementary heat exchanger to heat the carbon dioxide flowing through the supplementary heat exchanger.

[0009] In one embodiment, the supplementary heat exchanger has a first heat source inlet connected to a first heat source inlet pipe, which is used to introduce the heat exchange medium in the heat exchange assembly into the supplementary heat exchanger.

[0010] In one embodiment, after the heat exchange medium releases heat in the energy release heat exchanger, it is introduced into the supplementary heat exchanger through the first heat source introduction pipeline to release heat, and then flows back to the heat exchange component.

[0011] In one embodiment, the carbon dioxide energy storage system further includes a superheat control module, which includes a flow regulator disposed on the first heat source inlet pipe and is used to regulate the flow rate of the heat exchange medium entering the supplementary heat exchanger so that the superheat of the carbon dioxide output by the supplementary heat exchanger reaches a preset superheat.

[0012] In one embodiment, the superheat control module further includes:

[0013] A temperature sensing element is installed on the carbon dioxide outlet pipe of the heat exchanger to detect the carbon dioxide temperature at the outlet of the heat exchanger. A pressure sensing element, installed on the carbon dioxide outlet pipe of the heat exchanger, is used to detect the carbon dioxide pressure at the outlet of the heat exchanger; and The control module is connected to the temperature sensor, pressure sensor, and flow regulator respectively, and is used to control the opening degree of the flow regulator based on the temperature signal fed back by the temperature sensor and the pressure signal fed back by the pressure sensor.

[0014] In one embodiment, the heat exchanger further has a second heat source inlet, which is connected to a second heat source inlet pipe, which is used to introduce the heat storage medium into the heat exchanger. The heat storage medium is either lubricating oil or carbon dioxide discharged from the turbine, or the heat storage medium includes lubricating oil and carbon dioxide discharged from the turbine. The lubricating oil and carbon dioxide discharged from the turbine are respectively equipped with corresponding second heat source inlet pipes and enter the heat exchanger through the corresponding second heat source inlet pipes. The heat carried by the lubricating oil comes from the mechanical friction loss during the operation of the compressor and / or turbine, and the carbon dioxide discharged from the turbine carries the heat remaining from the expansion and work done.

[0015] In one embodiment, the heat exchanger includes any one or more of a coiled tube heat exchanger, a plate heat exchanger, a plate-and-shell heat exchanger, or a shell-and-tube heat exchanger.

[0016] In one embodiment, the carbon dioxide energy storage system further includes an air heat exchanger for drawing ambient air to the outer wall of the evaporator's outlet pipe, so that the ambient air and the carbon dioxide working fluid in the outlet pipe can exchange heat through the pipe wall.

[0017] In one embodiment, the supplementary heat exchanger is used to ensure that the superheat ΔT of the carbon dioxide working fluid at the outlet of the supplementary heat exchanger meets the condition: 5℃≤ΔT≤120℃.

[0018] In one embodiment, the heat exchange assembly includes: A hot tank is installed between the energy storage component and the energy release heat exchanger along the flow path of the heat exchange medium. The hot tank is used to store the heat exchange medium heated by the energy storage component and to supply the heated heat exchange medium to the energy release heat exchanger and the supplementary heat exchanger. The cold tank is located between the energy release heat exchanger and the energy storage component along the flow path of the heat exchange medium. It is used to store the heat exchange medium after it has been cooled by the energy release heat exchanger and the supplementary heat exchanger, and to supply the cooled heat exchange medium to the energy storage component.

[0019] According to another aspect of this disclosure, a control method for a carbon dioxide energy storage system with cascaded heat replenishment, employing any of the aforementioned carbon dioxide energy storage systems, includes: During the energy storage phase, gaseous carbon dioxide is controlled to be converted into liquid by the energy storage components and then stored in the liquid storage tank; During the energy release stage, the liquid carbon dioxide is controlled to vaporize in the evaporator. After being heated by the supplementary heat exchanger, the vaporized carbon dioxide enters the energy release heat exchanger for further heating. The heated carbon dioxide then enters the turbine to perform work, and the carbon dioxide working fluid after performing work returns to the gas storage tank.

[0020] In one embodiment, the control method further includes: The carbon dioxide temperature at the outlet of the supplementary heat exchanger is detected by the temperature measuring device, and the carbon dioxide pressure at the outlet of the supplementary heat exchanger is detected by the pressure measuring device. The real-time superheat of the carbon dioxide working fluid at the outlet of the supplementary heat exchanger is calculated based on temperature and pressure. Compare real-time superheat with preset superheat; The opening of the flow regulator is controlled based on the comparison results to regulate the flow rate of the heat exchange medium entering the supplementary heat exchanger.

[0021] In the aforementioned carbon dioxide energy storage system, liquid carbon dioxide, after flowing out of the storage tank, first enters the evaporator to complete phase change vaporization and achieve low-temperature temperature rise. It then enters the supplementary heat exchanger to absorb heat and increase superheat, and finally enters the energy release heat exchanger for high-temperature deep heating. This forms a three-stage cascade heating method: the evaporator is responsible for phase change temperature rise, the supplementary heat exchanger for primary temperature rise, and the energy release heat exchanger for secondary high-temperature temperature rise. This three-stage cascade heating method decomposes the large temperature difference heat exchange between the low-temperature, low-superheat working fluid at the evaporator outlet and the high-temperature heat source in the energy release heat exchanger into multiple stages of small temperature difference heat exchange. This effectively increases the superheat of the carbon dioxide working fluid at the inlet of the energy release heat exchanger, significantly reduces the temperature difference between the hot and cold fluids, and consequently reduces entropy production and heat loss during the heat exchange process. Meanwhile, the addition of a supplementary heat exchanger divides the entire heating process, which was originally handled solely by the energy release heat exchanger, into two stages. The energy release heat exchanger only needs to perform deep heating on top of the supplemented medium-temperature working fluid, reducing the heating burden, lowering the operating pressure of the energy release heat exchanger, and improving heat exchange efficiency. Finally, the gaseous carbon dioxide, heated in both stages by the supplementary and energy release heat exchangers, enters the turbine at a higher enthalpy value to expand and perform work, increasing the power generation capacity for the same working fluid flow rate and thus improving the system's cycle efficiency.

[0022] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0024] Figure 1 This is a schematic diagram of a carbon dioxide energy storage system with cascaded heat replenishment according to an embodiment of the present disclosure.

[0025] Explanation of reference numerals in the attached figures: 10. Gas storage facility; 20. Energy storage components; 21. Compressor; 22. Energy storage heat exchanger; 23. Condenser; 30. Liquid storage tank; 40. Energy release assembly; 41. Evaporator; 42. Compensation heat exchanger; 421. First heat source inlet pipe; 422. First heat source outlet pipe; 43. Energy release heat exchanger; 44. Turbine; 45. Liquid pump; 50. Heat exchanger assembly; 51. Hot tank; 52. Cold tank; 60. Flow regulating components. Detailed Implementation

[0026] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore detailed descriptions of them will be omitted. Furthermore, the drawings are merely illustrative of this disclosure and are not necessarily drawn to scale.

[0027] Although relative terms such as "up" and "down" are used in this specification to describe the relative relationship of one component of an icon to another, these terms are used only for convenience, such as according to the orientation of the examples shown in the accompanying drawings. It is understood that if the device of the icon is flipped upside down, the component described as "up" will become the component described as "down." When a structure is "up" of another structure, it may mean that the structure is integrally formed on the other structure, or that the structure is "directly" mounted on the other structure, or that the structure is "indirectly" mounted on the other structure through another structure.

[0028] The terms “a,” “one,” “the,” “the,” and “at least one” are used to indicate the presence of one or more elements / components / etc.; the terms “including” and “having” are used to indicate an open-ended inclusion and to mean that there may be other elements / components / etc. in addition to the listed elements / components / etc.; the terms “first,” “second,” and “third,” etc., are used only as markers and are not a limitation on the number of objects.

[0029] See Figure 1This application provides a carbon dioxide energy storage system with cascaded heat replenishment, comprising a gas storage tank 10, an energy storage component 20, a liquid storage tank 30, and an energy release component 40 connected sequentially along the flow path of the carbon dioxide working fluid to form a circulation loop. The gas storage tank 10 is used to store gaseous carbon dioxide, the liquid storage tank 30 is used to store liquid carbon dioxide, and the energy storage component 20 is used to convert gaseous carbon dioxide into liquid carbon dioxide to store the energy generated in the conversion process.

[0030] The carbon dioxide energy storage system with cascaded heat replenishment also includes a heat exchange component 50. The energy storage component 20 and the energy release component 40 are both connected to the heat exchange component 50. The heat exchange component 50 is used to transfer the energy in the energy storage component 20 to the energy release component 40.

[0031] The energy release assembly 40 includes an evaporator 41, a supplementary heat exchanger 42, an energy release heat exchanger 43, and a turbine 44 connected in sequence along the flow path of the carbon dioxide working fluid. The evaporator 41 is used to evaporate liquid carbon dioxide into gaseous carbon dioxide, the energy release heat exchanger 43 is used to heat the gaseous carbon dioxide, the turbine 44 is used to do work using the heated gaseous carbon dioxide, and the supplementary heat exchanger 42 is used to supplement the heat of the gaseous carbon dioxide flowing between the evaporator 41 and the energy release heat exchanger 43.

[0032] Specifically, the outlet of the liquid storage tank 30 is connected to the carbon dioxide inlet of the evaporator 41. Liquid carbon dioxide from the storage tank 30 undergoes phase change and vaporization inside the evaporator 41, forming a low-temperature, low-superheat gaseous working fluid. The carbon dioxide outlet of the evaporator 41 is connected to the carbon dioxide inlet of the supplementary heat exchanger 42. The low-temperature, low-superheat gaseous working fluid enters the supplementary heat exchanger 42, which provides supplementary heat to the carbon dioxide working fluid flowing through it, initially raising its temperature to form a medium-temperature carbon dioxide working fluid. The carbon dioxide outlet of the supplementary heat exchanger 42 is connected to the carbon dioxide inlet of the energy release heat exchanger 43. The medium-temperature carbon dioxide working fluid, after supplementary heating, enters the energy release heat exchanger 43, which further heats it to form high-temperature, high-pressure gaseous carbon dioxide. The carbon dioxide outlet of the energy release heat exchanger 43 is connected to the carbon dioxide inlet of the turbine 44. The heated high-temperature, high-pressure gaseous carbon dioxide enters the turbine 44, expands, and generates electricity.

[0033] The heat exchange assembly 50 is used to provide the heat of compression in the energy storage assembly 20 to the heat release heat exchanger 43 and the supplementary heat exchanger 42 to heat the gaseous carbon dioxide.

[0034] The operating time of the energy storage component 20 is determined by the electricity demand, which corresponds to the power generation of the energy release component 40. In other words, the operating time of the energy storage component 20 is determined by the power generation of the energy release component 40. The compression heat generated during the operation of the energy storage component 20 can simultaneously meet the heat source requirements of the energy release heat exchanger 43 and the supplementary heat exchanger 42. During the energy release phase, part of the compression heat stored in the heat exchange component 50 is supplied to the energy release heat exchanger 43 for high-temperature deep heating of the supplementary carbon dioxide working fluid, and another part is supplied to the supplementary heat exchanger 42 for preheating the low-temperature, low-superheat carbon dioxide working fluid at the outlet of the evaporator 41.

[0035] In the above embodiments, the energy release component 40 includes an evaporator 41, a supplementary heat exchanger 42, an energy release heat exchanger 43, and a turbine 44 connected sequentially along the flow path of the carbon dioxide working fluid. After flowing out of the storage tank 30, the liquid carbon dioxide first enters the evaporator 41 to complete phase change vaporization and achieve low-temperature temperature rise. Then it enters the supplementary heat exchanger 42 to absorb heat and increase superheat. Finally, it enters the energy release heat exchanger 43 for high-temperature deep heating. This forms a three-stage stepped heating method in which the evaporator 41 is responsible for phase change temperature rise, the supplementary heat exchanger 42 is responsible for supplementary heat initial temperature rise, and the energy release heat exchanger 43 is responsible for high-temperature secondary temperature rise. This three-stage stepped heating method decomposes the large temperature difference heat exchange between the low-temperature, low-superheat working fluid at the outlet of the evaporator 41 and the high-temperature heat source of the energy release heat exchanger 43 into multiple small temperature difference heat exchanges. This effectively increases the superheat of the carbon dioxide working fluid at the inlet of the energy release heat exchanger 43, significantly reduces the temperature difference between the hot and cold fluids, and consequently reduces entropy production and heat loss during the heat exchange process. Meanwhile, the addition of the supplementary heat exchanger 42 divides the entire heating process, which was originally handled solely by the energy release heat exchanger 43, into two stages. The energy release heat exchanger 43 only needs to perform deep heating on the basis of the supplemented medium-temperature working fluid, reducing the heating burden, decreasing the working pressure of the energy release heat exchanger 43, and improving the heat exchange efficiency. Finally, the gaseous carbon dioxide, heated in both stages by the supplementary heat exchanger 42 and the energy release heat exchanger 43, enters the turbine 44 at a higher enthalpy value to expand and do work. This increases the power generation capacity under the same working fluid flow rate, thereby improving the system cycle efficiency. The heat source for the supplementary heat exchanger 42 comes from the residual heat carried by the heat exchange medium after the energy release heat exchanger 43 releases heat. No additional external heat source is required to obtain supplementary heat, improving heat utilization, heat exchange efficiency, and overall system cycle efficiency.

[0036] In the above embodiments, the inventors' experiments showed that the three-stage heating method reduced system heat loss by 61%, increased system circulation efficiency to over 70%, and achieved a compression heat recovery utilization rate of over 97%.

[0037] See Figure 1In one embodiment, the energy storage component 20 includes a compressor 21, an energy storage heat exchanger 22, and a condenser 23 connected in sequence along the flow path of the carbon dioxide working medium. The compressor 21 is used to compress and heat up the gaseous carbon dioxide, the energy storage heat exchanger 22 is used to exchange heat between the compressed carbon dioxide and the heat exchange medium in the heat exchange component 50 to cool the carbon dioxide, and the condenser 23 is used to condense the cooled carbon dioxide into a liquid state.

[0038] Specifically, the carbon dioxide outlet of the gas storage tank 10 is connected to the carbon dioxide inlet of the compressor 21. At room temperature and pressure, gaseous carbon dioxide flowing from the gas storage tank 10 enters the compressor 21 and is compressed to form high-temperature, high-pressure gaseous carbon dioxide. The carbon dioxide outlet of the compressor 21 is connected to the carbon dioxide inlet of the energy storage heat exchanger 22. The high-temperature, high-pressure gaseous carbon dioxide enters the energy storage heat exchanger 22 and exchanges heat with the heat exchange medium in the heat exchange component 50. After transferring heat to the heat exchange medium, it is stored by the heat exchange component 50 and cooled to medium-temperature, high-pressure gaseous carbon dioxide. The carbon dioxide outlet of the energy storage heat exchanger 22 is connected to the carbon dioxide inlet of the condenser 23. The cooled medium-temperature, high-pressure gaseous carbon dioxide enters the condenser 23 and is further cooled to liquid carbon dioxide. The carbon dioxide outlet of the condenser 23 is connected to the inlet of the liquid storage tank 30, and the liquid carbon dioxide flows into the liquid storage tank 30 for storage.

[0039] In the above embodiment, gaseous carbon dioxide flowing out of the gas storage tank 10 is compressed and heated by the compressor 21 before entering the energy storage heat exchanger 22. The energy storage heat exchanger 22 transfers the heat carried by the carbon dioxide to the heat exchange medium in the heat exchange component 50, where it is stored. The carbon dioxide itself is cooled and then condensed into a liquid state by the condenser 23 and stored in the liquid storage tank 30. During this process, the heat of compression generated by the compressor 21 is recovered by the energy storage heat exchanger 22 and stored in the heat exchange component 50. After storing the heat of compression recovered during the energy storage stage, the heat exchange component 50 provides heat to the energy release component 40 during the energy release stage.

[0040] See Figure 1 In one embodiment, the energy release component 40 further includes a liquid pump 45, with the liquid storage tank 30 and the evaporator 41 respectively connected to the liquid pump 45. The liquid pump 45 is used to pressurize the liquid carbon dioxide from the liquid storage tank 30 and deliver it to the evaporator 41.

[0041] Specifically, the outlet of the liquid storage tank 30 is connected to the inlet of the liquid pump 45, and the outlet of the liquid pump 45 is connected to the carbon dioxide inlet of the evaporator 41.

[0042] In the above embodiment, a liquid pump 45 is installed between the storage tank 30 and the evaporator 41. After flowing out of the storage tank 30, the liquid carbon dioxide is first pressurized by the liquid pump 45 and then enters the evaporator 41 under high pressure. The pressurization effect of the liquid pump 45 ensures that the liquid carbon dioxide can overcome the resistance of the pipeline and equipment and be smoothly delivered to the evaporator 41. At the same time, after being pressurized, the liquid carbon dioxide enters the evaporator 41 and maintains a high pressure during the phase change and vaporization process in the evaporator 41. This helps to ensure that the working fluid enters the subsequent heat exchanger 42 and energy release heat exchanger 43 under high pressure, thereby providing a high-pressure working fluid for the turbine 44 to ensure the smooth progress of the expansion and work process, and ensuring the work capacity of the turbine 44.

[0043] In one embodiment, the heat exchange assembly 50 includes a heat exchange medium, which absorbs the heat of compression and releases it in the energy release heat exchanger 43 before flowing into the supplementary heat exchanger 42 to release heat.

[0044] In existing technologies, the heat sources for different heat exchangers generally come from different heat sources, or the heat source is split and supplied to different heat exchangers.

[0045] In this embodiment, the heat exchange medium flows sequentially through the energy release heat exchanger 43 and the supplementary heat exchanger 42, releasing heat at different temperature levels in stages. Simultaneously, the flow direction of the carbon dioxide working fluid is opposite to that of the heat exchange medium. The carbon dioxide first enters the supplementary heat exchanger 42 from the evaporator 41 to absorb heat, and then enters the energy release heat exchanger 43 to further absorb heat, gradually increasing its temperature. Meanwhile, the heat exchange medium first releases higher-grade heat in the energy release heat exchanger 43, and then releases lower-grade heat in the supplementary heat exchanger 42, gradually decreasing its temperature. The heat exchange medium and the carbon dioxide working fluid flow in opposite directions. Unlike conventional designs where the heat source and working fluid flow in the same direction or are configured independently, this scheme uses the same heat exchange medium to sequentially supply both heat exchangers. Combined with the reverse flow of carbon dioxide, this keeps the temperature difference between the hot and cold fluids small across the entire temperature range, reducing irreversible losses, improving heat exchange efficiency, and increasing heat utilization.

[0046] In actual operation, the heat exchange medium can be circulated first, and heat is released through the energy release heat exchanger 43 and the supplementary heat exchanger 42. After the two heat exchangers reach the temperature that meets the heating conditions, carbon dioxide is then introduced into the supplementary heat exchanger 42 and the energy release heat exchanger 43 for heating, so as to ensure the stability of the working fluid parameters in the initial stage of system startup.

[0047] In one embodiment, after the heat exchange medium exchanges heat with the compressed carbon dioxide, it enters the energy release heat exchanger 43 through the heat exchange assembly 50 to heat the gaseous carbon dioxide. The heat exchange medium after exchanging heat with the energy release heat exchanger 43 flows into the supplementary heat exchanger 42 to heat the carbon dioxide flowing through the supplementary heat exchanger 42.

[0048] In the above embodiments, during the energy release phase, the heat exchange medium enters the energy release heat exchanger 43 via the heat exchange component 50 to release heat, which is used to heat gaseous carbon dioxide. After releasing heat, the heat exchange medium flows into the supplementary heat exchanger 42 to continue releasing heat, which is used to heat the carbon dioxide flowing through the supplementary heat exchanger 42. During the energy storage phase, the compression heat generated by the compressor 21 is recovered by the energy storage heat exchanger 22 and stored in the heat exchange component 50. During the energy release phase, the same heat exchange medium flows sequentially through the energy release heat exchanger 43 and the supplementary heat exchanger 42 to release heat, and the compression heat is released step by step at different temperature levels. Throughout the process, the heat exchange medium recovers the compression heat in the energy storage phase and supplies it to the energy release heat exchanger 43 and the supplementary heat exchanger 42 sequentially in the energy release phase, realizing primary storage and two-stage release of compression heat. The energy release heat exchanger 43 only needs to perform deep heating on the basis of the supplemented medium-temperature carbon dioxide, reducing the heating burden and improving the heat exchange efficiency.

[0049] See Figure 1 In one embodiment, the supplementary heat exchanger 42 has a first heat source inlet connected to a first heat source inlet pipe 421, which is used to introduce the heat exchange medium into the supplementary heat exchanger 42.

[0050] In the above embodiment, through the first heat source introduction pipe 421, the heat exchange medium forms a flow channel between the energy release heat exchanger 43 and the supplementary heat exchanger 42, allowing the same heat exchange medium to release heat by flowing through the energy release heat exchanger 43 and the supplementary heat exchanger 42 sequentially, thus achieving the cascade utilization of heat. The heat exchange medium that would normally be returned to the heat exchange assembly 50 after releasing heat in the energy release heat exchanger 43 is instead introduced into the supplementary heat exchanger 42 through the first heat source introduction pipe 421, avoiding the waste of low-grade waste heat. The supplementary heat exchanger 42 can obtain supplementary heat without an independent external heat source.

[0051] See Figure 1 In one embodiment, after the heat exchange medium releases heat in the energy release heat exchanger 43, it is introduced into the supplementary heat exchanger 42 by the first heat source introduction pipe 421 to release heat, and then flows back to the heat exchange assembly 50.

[0052] Specifically, the heat exchange medium outlet of the energy-releasing heat exchanger 43 is connected to the first heat source inlet of the supplementary heat exchanger 42 via the first heat source inlet pipe 421, and the heat source outlet of the supplementary heat exchanger 42 is connected to the return port of the heat exchange assembly 50. After the heat exchange medium releases heat in the energy-releasing heat exchanger 43, it enters the supplementary heat exchanger 42 via the first heat source inlet pipe 421 to continue releasing heat, and the heat exchange medium after releasing heat flows back to the heat exchange assembly 50.

[0053] In the above embodiment, after the heat exchange medium releases heat in the energy release heat exchanger 43, it is directly introduced into the supplementary heat exchanger 42 by the first heat source inlet pipe 421 to continue releasing heat, and then flows back to the heat exchange assembly 50. The first heat source inlet pipe 421 ensures that the heat exchange medium enters the supplementary heat exchanger 42 immediately after releasing heat in the energy release heat exchanger 43, so the supplementary heat exchanger 42 can obtain supplementary heat without an independent external heat source.

[0054] See Figure 1 In one embodiment, the heat exchange assembly 50 includes a hot tank 51 and a cold tank 52. The hot tank 51 is disposed between the energy storage assembly and the energy release heat exchanger 43 along the flow path of the heat exchange medium. The hot tank 51 is used to store the heat exchange medium heated by the energy storage assembly and to supply the heated heat exchange medium to the energy release heat exchanger 43 and the supplementary heat exchanger 42. The cold tank 52 is disposed between the energy release heat exchanger 43 and the energy storage assembly 20 along the flow path of the heat exchange medium. It is used to store the heat exchange medium cooled by the supplementary heat exchanger 42 and the energy release heat exchanger 43 and to supply the cooled heat exchange medium to the energy storage heat exchanger 22.

[0055] Specifically, the heat exchange medium outlet of the energy storage heat exchanger 22 is connected to the inlet of the hot tank 51, the outlet of the hot tank 51 is connected to the heat exchange medium inlet of the energy release heat exchanger 43, the heat exchange medium outlet of the energy release heat exchanger 43 is connected to the first heat source inlet of the supplementary heat exchanger 42 through the first heat source introduction pipe 421, the first heat source outlet of the supplementary heat exchanger 42 is connected to the inlet of the cold tank 52 through the first heat source outlet pipe 422, and the outlet of the cold tank 52 is connected to the heat exchange medium inlet of the energy storage heat exchanger 22, forming a complete circulation path for the heat exchange medium.

[0056] During the energy storage phase, high-temperature and high-pressure gaseous carbon dioxide in the energy storage heat exchanger 22 exchanges heat with the heat exchange medium. After absorbing heat, the temperature of the heat exchange medium rises, and the heated heat exchange medium flows from the energy storage heat exchanger 22 into the heat tank 51 for storage.

[0057] During the energy release phase, the high-temperature heat exchange medium stored in the hot tank 51 flows into the energy release heat exchanger 43, where it exchanges heat with the flowing carbon dioxide working fluid. The medium transfers higher-grade heat to the carbon dioxide working fluid, reducing its own temperature. The cooled heat exchange medium then flows from the energy release heat exchanger 43 through the first heat source inlet pipe 421 into the first heat source inlet of the supplementary heat exchanger 42. In the supplementary heat exchanger 42, it continues to release heat to preheat the low-temperature, low-superheat carbon dioxide working fluid at the outlet of the evaporator 41, further reducing its own temperature. The heat exchange medium, after releasing heat in the supplementary heat exchanger 42, flows into the cold tank 52 for storage. In the next energy storage phase, it flows from the cold tank 52 to the energy storage heat exchanger 22 to reabsorb the heat of carbon dioxide compression.

[0058] In the above embodiment, the hot tank 51 stores the compressed heat recovered during the energy storage stage for use in the energy release stage, while the cold tank 52 stores the heat exchange medium after heat release, which is then returned to the energy storage heat exchanger 22 to absorb heat again during the energy storage stage. The heat exchange medium flows sequentially through the energy release heat exchanger 43 and the supplementary heat exchanger 42 to release heat, and the same amount of compressed heat is utilized step by step at different temperature levels. The first heat source inlet pipe 421 serves as the connection channel between the energy release heat exchanger 43 and the supplementary heat exchanger 42, allowing the heat exchange medium to directly enter the supplementary heat exchanger 42 to continue releasing heat after releasing heat in the energy release heat exchanger 43. The supplementary heat exchanger 42 can obtain supplementary heat without an independent external heat source.

[0059] In one embodiment, the supplementary heat exchanger 42 has a second heat source inlet connected to a second heat source inlet pipe, which is used to introduce the heat storage medium into the supplementary heat exchanger 42.

[0060] The heat storage medium is either lubricating oil or carbon dioxide discharged from turbine 44, or the heat storage medium includes both lubricating oil and carbon dioxide discharged from turbine 44. The lubricating oil and the carbon dioxide discharged from turbine 44 are each equipped with corresponding second heat source inlet pipes, and enter the supplementary heat exchanger 42 through their respective second heat source inlet pipes. The heat carried by the lubricating oil originates from the mechanical friction losses during the operation of compressor 21 and / or turbine 44, while the carbon dioxide discharged from turbine 44 carries the heat remaining from the expansion and work done.

[0061] Specifically, when the heat storage medium is a lubricating oil, the lubricating oil outlet of the compressor 21 and / or turbine 44 is connected to the second heat source inlet of the supplementary heat exchanger 42 through the second heat source inlet pipe. After the lubricating oil flows out of the compressor 21 and / or turbine 44, it is introduced into the supplementary heat exchanger 42 through the second heat source inlet pipe. After releasing heat and cooling down in the supplementary heat exchanger 42, it flows back to the lubricating oil inlet of the compressor 21 and / or turbine 44 through the second heat source outlet pipe, forming a lubricating oil circulation loop.

[0062] When the heat storage medium is carbon dioxide discharged from turbine 44, the carbon dioxide outlet of turbine 44 is connected to the second heat source inlet of the supplementary heat exchanger 42 through the second heat source inlet pipe. The carbon dioxide discharged from turbine 44 is introduced into the supplementary heat exchanger 42 through the second heat source inlet pipe. After releasing heat and cooling down in the supplementary heat exchanger 42, it is discharged through the second heat source outlet pipe and flows back to the gas storage tank 10.

[0063] If the heat storage medium includes lubricating oil and carbon dioxide discharged from turbine 44, the lubricating oil and the carbon dioxide discharged from turbine 44 are respectively equipped with corresponding second heat source inlet pipes and second heat source outlet pipes. The lubricating oil and the carbon dioxide discharged from turbine 44 enter the supplementary heat exchanger 42 through their respective second heat source inlet pipes, and then flow out through their respective second heat source outlet pipes.

[0064] Furthermore, the supplementary heat exchanger 42 can be a multi-channel heat exchanger, which has independent channels for different heat source media (such as the aforementioned heat exchange medium, lubricating oil, and carbon dioxide discharged from the turbine 44) to flow through. Each heat source medium exchanges heat with the carbon dioxide working fluid in its respective channel. There can also be multiple supplementary heat exchangers 42, each corresponding to a different heat source medium (such as the aforementioned heat exchange medium, lubricating oil, and carbon dioxide discharged from the turbine 44). Multiple supplementary heat exchangers 42 are arranged in series along the flow path of the carbon dioxide working fluid, and the carbon dioxide working fluid flows through each supplementary heat exchanger 42 in sequence, absorbing heat step by step.

[0065] In one embodiment, the supplementary heat exchanger 42 includes any one or more of a coiled tube heat exchanger, a plate heat exchanger, a plate-and-shell heat exchanger, or a shell-and-tube heat exchanger.

[0066] Specifically, the specific structural form of the supplementary heat exchanger 42 is selected based on the system operating parameters and heat source conditions. Wound-tube heat exchangers are suitable for high-pressure conditions, offering a large heat exchange area and compact structure; plate heat exchangers have high heat transfer coefficients and small footprint; shell-and-tube heat exchangers combine the high efficiency of plate heat exchangers with the high-pressure resistance of shell-and-tube heat exchangers, making them suitable for high-temperature and high-pressure conditions; shell-and-tube heat exchangers have simple structure, reliable operation, and wide applicability. The supplementary heat exchanger 42 can be any one of the above or a combination of multiple heat exchanger types. For example, multiple different types of supplementary heat exchangers can be configured in a large energy storage system to adapt to different types of heat source media (such as the aforementioned heat exchange media and heat storage media) and heat source temperature ranges.

[0067] In the above embodiments, the heat exchanger 42 can be any one or more of the following: a coiled tube heat exchanger, a plate heat exchanger, a plate-shell heat exchanger, or a shell-and-tube heat exchanger. The actual selection can be flexibly determined according to the system pressure level, the type of heat source medium, the layout space, and cost requirements.

[0068] In one embodiment, the carbon dioxide energy storage system further includes an air heat exchanger for drawing ambient air to the outer wall of the outlet pipe of the evaporator 41 so that the ambient air and the carbon dioxide working fluid in the outlet pipe can exchange heat through the pipe wall.

[0069] Specifically, when ambient air flows through the outer wall of the outlet pipe, it exchanges heat with the carbon dioxide working fluid flowing inside the pipe through the pipe wall, transferring heat to the carbon dioxide working fluid and raising the temperature of the working fluid.

[0070] In the above embodiments, the air heat exchanger uses ambient air as a heat source. Heat exchange occurs between the air and the carbon dioxide working fluid within the outlet pipe of the evaporator 41, allowing the working fluid to be preheated before entering the energy-releasing heat exchanger 43. Ambient air acquisition is cost-effective, and there is no need for a separate heat source introduction pipeline and a heat storage medium circulation system, thus reducing system costs and operating energy consumption.

[0071] See Figure 1 In one embodiment, the carbon dioxide energy storage system further includes a superheat control module, which includes a flow regulator 60. The flow regulator 60 is disposed on the first heat source inlet pipe 421 and is used to regulate the flow rate of the heat exchange medium entering the supplementary heat exchanger 42 so that the superheat of the carbon dioxide output by the supplementary heat exchanger 42 reaches the preset superheat.

[0072] Optionally, the flow regulating element 60 is a flow regulating valve.

[0073] In the above embodiment, the flow regulator 60 adjusts the flow rate of the heat exchange medium entering the supplementary heat exchanger 42, so that the actual superheat of the carbon dioxide at the outlet of the supplementary heat exchanger 42 is maintained near the preset superheat. When the actual superheat deviates from the preset value, the flow regulator 60 changes its opening to adjust the flow rate of the heat exchange medium, thereby changing the amount of heat supplied to the supplementary heat exchanger 42, so that the superheat returns to near the preset value. When the system load changes, the flow regulator 60 can respond promptly according to the change in superheat, so as to stabilize the working fluid state at the outlet of the supplementary heat exchanger 42 and ensure that the parameters of the carbon dioxide entering the energy release heat exchanger 43 meet the requirements.

[0074] See Figure 1 In one embodiment, the superheat control module further includes a temperature sensor, a pressure sensor, and a control module. The temperature sensor is installed on the carbon dioxide outlet pipe of the supplementary heat exchanger 42 and is used to detect the carbon dioxide temperature at the outlet of the supplementary heat exchanger 42. The pressure sensor is installed on the carbon dioxide outlet pipe of the supplementary heat exchanger 42 and is used to detect the carbon dioxide pressure at the outlet of the supplementary heat exchanger 42. The control module is signal-connected to the temperature sensor, the pressure sensor, and the flow regulator 60, respectively, and is used to control the opening degree of the flow regulator 60 based on the temperature signal fed back by the temperature sensor and the pressure signal fed back by the pressure sensor.

[0075] Specifically, the temperature measuring element is a temperature sensor, which is installed on the pipeline between the carbon dioxide outlet of the supplementary heat exchanger 42 and the carbon dioxide inlet of the energy release heat exchanger 43. It is used to detect the temperature of the carbon dioxide working fluid flowing out after being heated by the supplementary heat exchanger 42 in real time, and transmit the detected temperature signal to the control module.

[0076] The pressure detection element is a pressure sensor, which is also installed on the pipeline between the carbon dioxide outlet of the supplementary heat exchanger 42 and the carbon dioxide inlet of the energy release heat exchanger 43. It is used to detect the carbon dioxide pressure at the outlet of the supplementary heat exchanger 42 in real time and transmit the detected pressure signal to the control module.

[0077] The control module can be a PLC controller, microprocessor, etc. The control module has a preset superheat for the carbon dioxide at the outlet of the supplementary heat exchanger 42. After receiving the actual temperature signal from the temperature sensor and the actual pressure signal from the pressure sensor, the control module calculates the saturation temperature at the current pressure based on the actual pressure, then calculates the actual superheat based on the actual temperature and the saturation temperature. The actual superheat is compared with the preset superheat, and based on the comparison result, a control command is sent to the flow regulator 60 to adjust the opening degree of the flow regulator 60.

[0078] When the actual superheat is lower than the preset superheat, the control module controls the flow regulator 60 to open wider, increasing the flow rate of the heat exchange medium entering the supplementary heat exchanger 42 and increasing the amount of heat supplied. When the actual superheat is higher than the preset superheat, the control module controls the flow regulator 60 to close narrower, decreasing the flow rate of the heat exchange medium entering the supplementary heat exchanger 42 and reducing the amount of heat supplied. When the actual superheat is equal to the preset superheat, the control module controls the flow regulator 60 to maintain its current opening. Through the above control process, the carbon dioxide superheat at the outlet of the supplementary heat exchanger 42 is maintained near the preset superheat.

[0079] In the above embodiments, the temperature measuring element, pressure measuring element, flow regulating element 60, and control module cooperate to form a regulating loop. The control module dynamically adjusts the flow rate of the heat exchange medium according to the deviation between the actual superheat at the outlet of the supplementary heat exchanger 42 and the preset superheat, thereby maintaining the carbon dioxide superheat at the outlet of the supplementary heat exchanger 42 near the preset superheat. When the system load changes, the control module can adjust the flow rate of the heat exchange medium in a timely manner according to the real-time monitored superheat deviation, so that the superheat of the working fluid at the outlet of the supplementary heat exchanger 42 responds quickly and recovers to the preset value, ensuring the stability of the working fluid entering the energy release heat exchanger 43 and turbine 44, and adapting to the variable load energy release conditions of the system.

[0080] In one embodiment, the flow regulating element 60 is disposed on the first heat source inlet pipe 421, and the second heat source inlet pipe is in a normally open state.

[0081] If there is only one second heat source inlet pipe, the heat supply of the first heat source inlet pipe 421 is greater than the heat supply of the second heat source inlet pipe; if there are multiple second heat source inlet pipes, the heat supply of the first heat source inlet pipe 421 is greater than the sum of the heat supply of all the second heat source inlet pipes.

[0082] In the above embodiment, the flow regulator 60 is installed on the first heat source inlet pipe 421, while the second heat source inlet pipe is always open. The first heat source inlet pipe 421 serves as the main heat source channel, and the flow rate of the main heat source entering the supplementary heat exchanger 42 is controlled by the flow regulator 60, thereby regulating the supplementary heat capacity. The second heat source inlet pipe does not have a flow regulator and remains connected at all times. This ensures that the total heat supply meets the supplementary heat demand, and the supplementary heat capacity control can be achieved by adjusting only the flow regulator 60 on the first heat source inlet pipe 421. The control logic is simple, the response speed is fast, and the control complexity caused by setting regulating valves on multiple pipes is avoided.

[0083] In one embodiment, the heat supply of the first heat source inlet pipe 421 is greater than the heat supply of the second heat source inlet pipe.

[0084] In the above embodiment, the heat supply of the first heat source inlet pipe 421 is greater than that of the second heat source inlet pipe. The first heat source inlet pipe 421, as the main heat source channel, has the largest heat supply. A flow regulator 60 is installed on it, and adjusting the main heat source flow rate can significantly affect the total supplementary heat, resulting in high regulation efficiency. The second heat source inlet pipe has a smaller heat supply, and keeping it constantly open will not cause excessive fluctuations in the total supplementary heat. The division of labor between the two heat source inlet pipes is clear, the control logic is simple, and the system operates stably.

[0085] In one embodiment, the supplementary heat exchanger 42 is used to ensure that the superheat ΔT of the carbon dioxide working fluid at the outlet of the supplementary heat exchanger 42 meets the condition: 5℃≤ΔT≤120℃.

[0086] Specifically, the superheat ΔT refers to the difference between the actual temperature of the carbon dioxide working fluid at the outlet of the supplementary heat exchanger 42 and the saturation temperature of the carbon dioxide under pressure at the outlet of the supplementary heat exchanger 42.

[0087] In the above embodiment, the superheat ΔT of the carbon dioxide working fluid at the outlet of the supplementary heat exchanger 42 is controlled within the range of 5°C to 120°C. By setting a lower limit of 5°C, the carbon dioxide working fluid entering the energy release heat exchanger 43 is ensured to be in a single-phase gaseous state, avoiding the influence of two-phase flow on flow stability and heat exchange effect. At the same time, the working fluid already has a certain superheat before entering the energy release heat exchanger 43, reducing the temperature difference between the hot and cold fluids in the energy release heat exchanger 43 and correspondingly reducing irreversible losses. By setting an upper limit of 120°C, excessive supplementary heating is prevented from causing the working fluid temperature to be too high, thereby increasing the heat load and thermal stress of the energy release heat exchanger 43. It also avoids energy waste caused by excessive heat input, ensuring that the energy release heat exchanger 43 still has sufficient high-temperature heating space in the subsequent process. The above superheat range is adapted to the three-stage heating division of the evaporator 41, the supplementary heat exchanger 42, and the energy release heat exchanger 43, and the heating task of each heat exchange unit is clearly defined in the temperature range.

[0088] This application also provides a control method for a carbon dioxide energy storage system with cascaded heat replenishment, using any of the carbon dioxide energy storage systems described in the above embodiments, including the following steps: During the energy storage phase, gaseous carbon dioxide is controlled to be converted into liquid by the energy storage component 20 and then stored in the liquid storage tank 30.

[0089] During the energy release stage, the liquid carbon dioxide is controlled to vaporize through the evaporator 41. After being reheated by the heat exchanger 42, the vaporized carbon dioxide enters the energy release heat exchanger 43 for heating. The heated carbon dioxide then enters the turbine 44 to perform work. The working fluid after performing work returns to the gas storage tank 10.

[0090] Specifically, the method can be executed by a control module, which is connected to the signals of each device in the energy storage component 20 and the energy release component 40, and is used to control the start-up, shutdown and operating parameters of each device.

[0091] During the energy storage phase, gaseous carbon dioxide in the gas storage tank 10 enters the compressor 21 and is compressed by the compressor 21 to form high-temperature and high-pressure gaseous carbon dioxide. The high-temperature and high-pressure gaseous carbon dioxide enters the energy storage heat exchanger 22 and exchanges heat with the heat exchange medium in the energy storage heat exchanger 22, transferring heat to the heat exchange medium and storing it in the heat exchange component 50. After cooling, the gaseous carbon dioxide enters the condenser 23 and is further cooled by the condenser 23, changing into liquid carbon dioxide. The liquid carbon dioxide is stored in the liquid storage tank 30.

[0092] During the energy release stage, the liquid carbon dioxide in the storage tank 30 is pressurized by the liquid pump 45 and enters the evaporator 41. Inside the evaporator 41, it undergoes phase change vaporization under heat, forming a low-temperature, low-superheat gaseous working fluid. This low-temperature, low-superheat gaseous working fluid flows out of the evaporator 41 and into the supplementary heat exchanger 42. The supplementary heat exchanger 42 utilizes low-grade waste heat to provide supplementary heating to the flowing carbon dioxide working fluid, initially raising its temperature to form a medium-temperature carbon dioxide working fluid. The medium-temperature carbon dioxide working fluid flows out of the supplementary heat exchanger 42 and into the energy release heat exchanger 43. The energy release heat exchanger 43 uses high-temperature compression waste heat to further heat the carbon dioxide working fluid, forming high-temperature, high-pressure gaseous carbon dioxide. The high-temperature, high-pressure gaseous carbon dioxide flows out of the energy release heat exchanger 43 and into the turbine 44. Inside the turbine 44, it expands and performs work to generate electricity. The low-pressure gaseous carbon dioxide after performing work is discharged from the turbine 44 and returned to the gas storage tank 10.

[0093] In the above embodiment, after liquid carbon dioxide flows out of the storage tank 30, it first enters the evaporator 41 to complete phase change vaporization and achieve low-temperature temperature rise. Then, it enters the supplementary heat exchanger 42 to absorb heat and increase superheat. Finally, it enters the energy release heat exchanger 43 for high-temperature deep heating. This forms a three-stage stepped heating method: the evaporator 41 is responsible for phase change temperature rise, the supplementary heat exchanger 42 is responsible for supplementary primary temperature rise, and the energy release heat exchanger 43 is responsible for high-temperature secondary temperature rise. This three-stage stepped heating method decomposes the large temperature difference heat exchange between the low-temperature, low-superheat working fluid at the outlet of the evaporator 41 and the high-temperature heat source of the energy release heat exchanger 43 into multiple stages of small temperature difference heat exchange. This effectively increases the superheat of the carbon dioxide working fluid at the inlet of the energy release heat exchanger 43, significantly reduces the temperature difference between the hot and cold fluids, and consequently reduces entropy production and heat loss during the heat exchange process. Meanwhile, the addition of the supplementary heat exchanger 42 divides the entire heating process, which was originally handled solely by the energy release heat exchanger 43, into two stages. The energy release heat exchanger 43 only needs to perform deep heating on the basis of the supplemented medium-temperature working fluid, reducing the heating burden, decreasing the operating pressure of the energy release heat exchanger 43, and improving the heat exchange efficiency. Finally, the gaseous carbon dioxide, heated in both stages by the supplementary heat exchanger 42 and the energy release heat exchanger 43, enters the turbine 44 at a higher enthalpy value to expand and do work. This increases the power generation capacity under the same working fluid flow rate, thereby improving the system cycle efficiency.

[0094] In one embodiment, the control method further includes the following steps: acquiring the carbon dioxide temperature at the outlet of the supplementary heat exchanger 42 detected by the temperature measuring element, and the carbon dioxide pressure at the outlet of the supplementary heat exchanger 42 detected by the pressure measuring element; calculating the real-time superheat of the carbon dioxide working medium at the outlet of the supplementary heat exchanger 42 based on the temperature and pressure; comparing the real-time superheat with the preset superheat; and controlling the opening of the flow regulating element 60 based on the comparison result to regulate the flow rate of the heat exchange medium entering the supplementary heat exchanger 42.

[0095] Specifically, this method is executed by the control module.

[0096] In the above embodiments, the control module dynamically adjusts the flow rate of the heat exchange medium based on the deviation between the actual superheat at the outlet of the supplementary heat exchanger 42 and the preset superheat, thereby maintaining the carbon dioxide superheat at the outlet of the supplementary heat exchanger 42 near the preset superheat. When the system load changes, the control module can adjust the flow rate of the heat exchange medium in a timely manner according to the real-time monitored superheat deviation, so that the superheat of the working fluid at the outlet of the supplementary heat exchanger 42 responds quickly and recovers to the preset value, ensuring the stability of the working fluid entering the energy release heat exchanger 43 and the turbine 44, and adapting to the variable load energy release conditions of the system.

[0097] It should be noted that although the steps of the control method in this disclosure are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0098] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. A carbon dioxide energy storage system with cascaded heat replenishment, characterized in that, The system includes a gas storage tank, an energy storage component, a liquid storage tank, and an energy release component connected sequentially along the flow path of the carbon dioxide working medium to form a circulation loop. The gas storage tank is used to store gaseous carbon dioxide, the liquid storage tank is used to store liquid carbon dioxide, and the energy storage component is used to convert the gaseous carbon dioxide into the liquid carbon dioxide to store the energy generated in the conversion process. It also includes a heat exchange component, wherein the energy storage component and the energy release component are both connected to the heat exchange component, and the heat exchange component is used to transfer the energy in the energy storage component to the energy release component; The energy release assembly includes an evaporator, a supplementary heat exchanger, an energy release heat exchanger, and a turbine connected sequentially along the flow path of the carbon dioxide working fluid. The evaporator is used to evaporate liquid carbon dioxide into gaseous carbon dioxide. The energy release heat exchanger is used to heat the gaseous carbon dioxide. The turbine is used to perform work using the heated gaseous carbon dioxide. The supplementary heat exchanger is used to supplement the heat of the gaseous carbon dioxide flowing between the evaporator and the energy release heat exchanger. The heat exchange assembly is used to provide the compression heat in the energy storage assembly to the energy release heat exchanger and the supplementary heat exchanger to heat the gaseous carbon dioxide.

2. The carbon dioxide energy storage system according to claim 1, characterized in that, The heat exchange assembly includes a heat exchange medium, which absorbs the heat of compression and releases it in the energy release heat exchanger before flowing into the supplementary heat exchanger to release heat.

3. The carbon dioxide energy storage system according to claim 1 or 2, characterized in that, The energy storage assembly includes a compressor, an energy storage heat exchanger, and a condenser connected sequentially along the flow path of the carbon dioxide working medium. The compressor is used to compress and heat gaseous carbon dioxide. The energy storage heat exchanger is used to exchange heat between the compressed carbon dioxide and the heat exchange medium in the heat exchange assembly to cool the carbon dioxide. The condenser is used to condense the cooled carbon dioxide into a liquid state. After exchanging heat with the compressed carbon dioxide, the heat exchange medium enters the energy release heat exchanger through the heat exchange assembly to heat the gaseous carbon dioxide. The heat exchange medium after exchanging heat with the energy release heat exchanger flows into the supplementary heat exchanger to heat the carbon dioxide flowing through the supplementary heat exchanger.

4. The carbon dioxide energy storage system according to claim 1 or 2, characterized in that, The heat exchanger has a first heat source inlet, which is connected to a first heat source inlet pipe. The first heat source inlet pipe is used to introduce the heat exchange medium in the heat exchange assembly into the heat exchanger.

5. The carbon dioxide energy storage system according to claim 4, characterized in that, After the heat exchange medium releases heat in the energy release heat exchanger, it is introduced into the supplementary heat exchanger through the first heat source inlet pipe to release heat, and then flows back to the heat exchange component.

6. The carbon dioxide energy storage system according to claim 5, characterized in that, It also includes a superheat control module, which includes a flow regulator. The flow regulator is installed on the first heat source inlet pipe and is used to adjust the flow rate of the heat exchange medium entering the supplementary heat exchanger so that the superheat of the carbon dioxide output by the supplementary heat exchanger reaches a preset superheat.

7. The carbon dioxide energy storage system according to claim 6, characterized in that, The superheat control module also includes: A temperature measuring element is installed on the carbon dioxide outlet pipe of the heat exchanger to detect the carbon dioxide temperature at the outlet of the heat exchanger. A pressure detection device is installed on the carbon dioxide outlet pipe of the heat exchanger to detect the carbon dioxide pressure at the outlet of the heat exchanger. as well as The control module is connected to the temperature measuring element, the pressure measuring element, and the flow regulating element respectively, and is used to control the opening degree of the flow regulating element according to the temperature signal fed back by the temperature measuring element and the pressure signal fed back by the pressure measuring element.

8. The carbon dioxide energy storage system according to claim 4, characterized in that, The heat exchanger also has a second heat source inlet, which is connected to a second heat source inlet pipe. The second heat source inlet pipe is used to introduce the heat storage medium into the heat exchanger. The heat storage medium is either lubricating oil or carbon dioxide discharged from a turbine, or the heat storage medium includes lubricating oil and carbon dioxide discharged from a turbine. The lubricating oil and the carbon dioxide discharged from the turbine are respectively equipped with corresponding second heat source inlet pipes and enter the heat exchanger through the corresponding second heat source inlet pipes. The heat carried by the lubricating oil originates from the mechanical friction loss during the operation of the compressor and / or turbine, and the carbon dioxide discharged by the turbine carries the residual heat from the expansion and work done.

9. The carbon dioxide energy storage system according to claim 4, characterized in that, The heat exchanger includes any one or more of the following: coiled tube heat exchanger, plate heat exchanger, plate-shell heat exchanger, or shell-and-tube heat exchanger.

10. The carbon dioxide energy storage system according to claim 4, characterized in that, It also includes an air heat exchanger, which is used to lead ambient air to the outer wall of the outlet pipe of the evaporator so that the ambient air and the carbon dioxide working fluid in the outlet pipe can exchange heat through the pipe wall.

11. The carbon dioxide energy storage system according to any one of claims 1-2 and 5-10, characterized in that, The supplementary heat exchanger is used to ensure that the superheat ΔT of the carbon dioxide working fluid at the outlet of the supplementary heat exchanger meets the condition: 5℃≤ΔT≤120℃.

12. The carbon dioxide energy storage system according to any one of claims 1-2 and 5-10, characterized in that, The heat exchange assembly includes: A hot tank is disposed between the energy storage component and the energy release heat exchanger along the flow path of the heat exchange medium. The hot tank is used to store the heat exchange medium heated by the energy storage component and to provide the heated heat exchange medium to the energy release heat exchanger and the heat exchanger. A cold tank is disposed between the energy release heat exchanger and the energy storage component along the flow path of the heat exchange medium. It is used to store the heat exchange medium after it has been cooled by the energy release heat exchanger and the supplementary heat exchanger, and to provide the cooled heat exchange medium to the energy storage component.

13. A control method for a carbon dioxide energy storage system with cascaded heat replenishment, employing the carbon dioxide energy storage system according to any one of claims 1-12, characterized in that, include: During the energy storage phase, gaseous carbon dioxide is controlled to be converted into liquid by the energy storage components and then stored in the liquid storage tank; During the energy release stage, the liquid carbon dioxide is controlled to vaporize in the evaporator. After being heated by the supplementary heat exchanger, the vaporized carbon dioxide enters the energy release heat exchanger for further heating. The heated carbon dioxide then enters the turbine to perform work, and the carbon dioxide working fluid after performing work returns to the gas storage tank.

14. The control method according to claim 13, characterized in that, Also includes: The carbon dioxide temperature at the outlet of the supplementary heat exchanger is obtained by the temperature measuring device, and the carbon dioxide pressure at the outlet of the supplementary heat exchanger is obtained by the pressure measuring device. Calculate the real-time superheat of the carbon dioxide working fluid at the outlet of the supplementary heat exchanger based on the temperature and pressure. Compare the real-time superheat with the preset superheat; The opening degree of the flow regulator is controlled based on the comparison results to regulate the flow rate of the heat exchange medium entering the supplementary heat exchanger.

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