A highly reversible distributed co2 carnot cell system and method of controlling the same

Abstract

The application discloses a highly reversible distributed CO2 Carnot battery system and a control method thereof, and comprises an energy storage working medium loop, an energy release working medium loop, a high-temperature heat storage medium loop and a low-temperature cold storage medium loop connected with a PID control unit; in the energy storage working medium loop, the compressor outlet is sequentially connected with the first heat exchanger, the regenerator, the expander, the second heat exchanger and the regenerator in communication with the compressor inlet; in the energy release working medium loop, the compressor outlet is sequentially connected with the regenerator, the first heat exchanger, the expander, the regenerator and the second heat exchanger in communication with the compressor inlet; the high-temperature heat storage medium loop is connected with the medium side of the first heat exchanger, and the low-temperature cold storage medium loop is connected with the medium side of the second heat exchanger. The application can significantly reduce the occupied space, improve the energy density of the system, realize the switching between the heat pump cycle and the Brayton cycle in the same system, and improve the working efficiency and stability of the distributed Carnot battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new energy storage technology, and particularly relates to a highly reversible distributed CO2 Carnot battery system and a control method thereof. BACKGROUND

[0002] The vigorous development of new energy industry provides sustainable energy supply and helps protect the ecological environment, but due to the characteristics of large output fluctuation of new energy and difficult source-load time domain matching, energy storage technology has become an indispensable important link in the new energy industry.

[0003] At present, the relatively mature energy storage methods in the world, such as pumped storage, compressed air energy storage, and photo-thermal molten salt, all have the disadvantage of large occupation area, which is difficult to adapt to the characteristics of wide distribution of new energy and small-scale dispersed utilization. Distributed energy storage technology with high energy density can better match the future city flexible power grid and energy grid facilities, and is an important future technology development route.

[0004] Distributed Carnot battery has many advantages such as high energy density heat storage, high heat storage temperature, large power density, no additional environmental pollution in operation process, good universality and distribution, and becomes an ideal choice for the new generation of energy storage methods. Compared with pumped storage, distributed Carnot battery has the advantage of not being limited by geographical conditions, and compared with compressed air energy storage, it has the advantages of no need for gas storage tank and small occupation area. Distributed Carnot battery can also integrate cold / heat / electricity multi-energy supply to realize multi-energy complementation of various resources and cascade utilization of heat energy, thereby improving the energy utilization rate. However, the heat pump cycle and Brayton cycle of the existing distributed Carnot battery need two different devices to exchange heat in different heat exchange devices, which increases the complexity of the equipment and pipelines and increases the initial investment. SUMMARY

[0005] The application aims to provide a highly reversible distributed CO2 Carnot battery system and a control method thereof, and solve the problem of complex equipment of the existing distributed Carnot battery.

[0006] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0007] A highly reversible distributed CO2 Carnot battery system comprises an energy storage working medium circuit, an energy release working medium circuit, a high-temperature heat storage medium circuit, a low-temperature cold storage medium circuit, and a PID control unit.

[0008] The outlet of the compressor is connected to the working medium inlet of the first heat exchanger, the working medium outlet of the first heat exchanger is connected to the compressed working medium inlet of the regenerator, the compressed working medium outlet of the regenerator is connected to the inlet of the expander, the outlet of the expander is connected to the working medium inlet of the second heat exchanger, the working medium outlet of the second heat exchanger is connected to the expanded working medium inlet of the regenerator, and the expanded working medium outlet of the regenerator is connected to the inlet of the compressor.

[0009] The outlet of the compressor is connected to the compressed working medium inlet of the regenerator, the compressed working medium outlet of the regenerator is connected to the working medium inlet of the first heat exchanger, the working medium outlet of the first heat exchanger is connected to the inlet of the expander, the outlet of the expander is connected to the expanded working medium inlet of the regenerator, the expanded working medium outlet of the regenerator is connected to the working medium inlet of the second heat exchanger, and the working medium outlet of the second heat exchanger is connected to the inlet of the compressor.

[0010] The high-temperature heat storage medium circuit is connected to the medium side of the first heat exchanger, the low-temperature cold storage medium circuit is connected to the medium side of the second heat exchanger, and the energy storage working medium circuit, the energy release working medium circuit, the high-temperature heat storage medium circuit and the low-temperature cold storage medium circuit are all connected to the PID control unit.

[0011] Further, the regenerator is provided with a compressed working medium pipeline and an expanded working medium pipeline, two ends of the compressed working medium pipeline are respectively connected to the compressed working medium inlet and the compressed working medium outlet, and two ends of the expanded working medium pipeline are respectively connected to the expanded working medium inlet and the expanded working medium outlet.

[0012] Further, in the energy storage working medium circuit, a first electromagnetic valve is arranged on the connecting pipeline between the outlet of the compressor and the working medium inlet of the first heat exchanger, a fourth electromagnetic valve is arranged on the connecting pipeline between the working medium outlet of the first heat exchanger and the compressed working medium inlet of the regenerator, a sixth electromagnetic valve is arranged on the connecting pipeline between the compressed working medium outlet of the regenerator and the inlet of the expander, a seventh electromagnetic valve is arranged on the connecting pipeline between the outlet of the expander and the working medium inlet of the second heat exchanger, a tenth electromagnetic valve is arranged on the connecting pipeline between the working medium outlet of the second heat exchanger and the expanded working medium inlet of the regenerator, and an eleventh electromagnetic valve is arranged on the connecting pipeline between the expanded working medium outlet of the regenerator and the inlet of the compressor.

[0013] Further, the second electromagnetic valve is arranged on a connecting pipeline between the outlet of the compressor and the compressed working medium inlet of the regenerator, the third electromagnetic valve is arranged on a connecting pipeline between the compressed working medium outlet of the regenerator and the working medium inlet of the first heat exchanger, the fifth electromagnetic valve is arranged on a connecting pipeline between the working medium outlet of the first heat exchanger and the inlet of the expander, the eighth electromagnetic valve is arranged on a connecting pipeline between the outlet of the expander and the expanded working medium inlet of the regenerator, the ninth electromagnetic valve is arranged on a connecting pipeline between the expanded working medium outlet of the regenerator and the working medium inlet of the second heat exchanger, and the twelfth electromagnetic valve is arranged on a connecting pipeline between the working medium outlet of the second heat exchanger and the inlet of the compressor.

[0014] Further, the sixteenth electromagnetic valve is arranged on a pipeline of the high-temperature medium outlet of the high-temperature thermal storage medium storage tank, the fifteenth electromagnetic valve is arranged on a pipeline of the low-temperature medium outlet of the high-temperature thermal storage medium storage tank, and the pipeline of the high-temperature medium outlet and the pipeline of the low-temperature medium outlet are connected to the medium inlet of the first heat exchanger through the first outlet pipeline.

[0015] Further, the thirteenth electromagnetic valve is arranged on a pipeline of the low-temperature medium inlet of the high-temperature thermal storage medium storage tank, the fourteenth electromagnetic valve is arranged on a pipeline of the high-temperature medium inlet of the high-temperature thermal storage medium storage tank, and the pipeline of the low-temperature medium inlet and the pipeline of the high-temperature medium inlet are connected to the medium outlet of the first heat exchanger through the first inlet pipeline, and the high-temperature pump is arranged on the first inlet pipeline.

[0016] Further, the twentieth electromagnetic valve is arranged on a pipeline of the low-temperature medium outlet of the low-temperature cold storage medium storage tank, the nineteenth electromagnetic valve is arranged on a pipeline of the high-temperature medium outlet of the low-temperature cold storage medium storage tank, and the pipeline of the low-temperature medium outlet and the pipeline of the high-temperature medium outlet are connected to the medium inlet of the second heat exchanger through the second outlet pipeline.

[0017] Further, the seventeenth electromagnetic valve is arranged on a pipeline of the high-temperature medium inlet of the low-temperature cold storage medium storage tank, the eighteenth electromagnetic valve is arranged on a pipeline of the low-temperature medium inlet of the low-temperature cold storage medium storage tank, and the high-temperature medium inlet and the low-temperature medium inlet are connected to the medium outlet of the second heat exchanger through the second inlet pipeline, and the low-temperature pump is arranged on the second inlet pipeline.

[0018] Further, the working medium in the energy storage working medium circuit and the energy release working medium circuit is CO2.

[0019] A control method of the highly reversible distributed CO2 Carnot cell system, comprising:

[0020] In the energy storage process, according to the current working condition parameters, the optimal exhaust temperature of the compressor outlet is selected, and according to the suction temperature and exhaust temperature of the expander, the outlet working medium temperature of the second heat exchanger and the suction pressure of the compressor, the optimal exhaust pressure of the expander is calculated;

[0021] In the energy release process, according to the current high-temperature heat storage medium loop and low-temperature cold storage medium loop temperature, the optimal suction temperature of the compressor in the Brayton cycle is calculated; then according to the current temperature parameters of each point in the Brayton cycle and the overall temperature interval, the optimal exhaust pressure of the compressor in the Brayton cycle is calculated; and then according to the pressure range and temperature interval of the current working condition, the optimal exhaust temperature for increasing the work capacity of the expander is calculated;

[0022] According to the calculated optimal working condition parameters, the error between the current working condition parameters and the optimal working condition parameters is obtained, and the control amount is obtained through the PID control unit to control each point to be in the optimal working condition;

[0023] According to the temperature of the high-temperature heat storage medium loop and the low-temperature cold storage medium loop, and the load demand of the external condition, the highly reversible distributed CO2 Carnot battery system is in the energy storage working condition or the energy release working condition.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] The present application provides a highly reversible distributed CO2 Carnot battery system, which is suitable for the characteristics of new energy distribution, and is beneficial to small-scale distributed utilization. In the energy storage working medium loop, the compressor outlet is sequentially connected with the first heat exchanger, the regenerator, the expander, the second heat exchanger and the regenerator, and the compressor inlet is connected in communication. In the energy release working medium loop, the compressor outlet is sequentially connected with the regenerator, the first heat exchanger, the expander, the regenerator and the second heat exchanger, and the compressor inlet is connected in communication. The high-temperature heat storage medium loop is connected to the medium side of the first heat exchanger, and the low-temperature cold storage medium loop is connected to the medium side of the second heat exchanger. The heat pump cycle in the energy storage process and the Brayton cycle in the energy release stage share a set of equipment, which improves the utilization rate of the equipment and the flexibility of the system. At the same time, the PID control unit puts forward a control logic design scheme suitable for the highly reversible distributed Carnot battery system, which can select the optimal working parameters in real time according to the optimized analysis and quickly adjust the operating parameters of each point in the system according to the well-adapted control logic when the system operating condition is determined, and quickly respond to the system operating condition switching to reach the optimal operating state. Compared with the traditional distributed Carnot battery system, the present application can significantly reduce the volume occupied by the distributed Carnot battery and improve the energy density of the system. In the same system, the present application can quickly respond to the system operating condition change, complete the switching of the heat pump cycle and the Brayton cycle, improve the working efficiency and stability of the distributed Carnot battery, reduce the cost and complexity of the system, and make important contributions to the energy storage field.

[0026] Further, in the energy storage working medium circuit and the energy release working medium circuit of the present application, CO2 is used as the working medium, CO2 has lower flammability and explosiveness, in the supercritical state, CO2 has excellent heat transfer and mass transfer performance, and can exhibit higher efficiency and safety in the energy storage and energy release processes. Meanwhile, CO2 is a naturally occurring gas, has a wide source and a relatively low price, its use will not cause additional pollution to the environment, and also reduces the operation cost of the system, so that the present application has more competitiveness in commercial application. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced below, and it should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0028] Figure 1 A schematic diagram of the highly reversible distributed CO2 Carnot battery system of the present application.

[0029] Figure 2 A pressure-enthalpy diagram of the highly reversible distributed CO2 Carnot battery system of the present application.

[0030] Figure 3 A flowchart of the control method of the highly reversible distributed CO2 Carnot battery system of the present application.

[0031] Wherein: 1-compressor, 2-first heat exchanger, 3-expander, 4-second heat exchanger, 5-heat regenerator, 6-high-temperature pump, 7-high-temperature heat storage medium storage tank, 8-low-temperature pump, 9-low-temperature cold storage medium storage tank, 10-first electromagnetic valve, 11-second electromagnetic valve, 12-third electromagnetic valve, 13-fourth electromagnetic valve, 14-fifth electromagnetic valve, 15-sixth electromagnetic valve, 16-seventh electromagnetic valve, 17-eighth electromagnetic valve, 18-ninth electromagnetic valve, 19-tenth electromagnetic valve, 20-eleventh electromagnetic valve, 21-twelfth electromagnetic valve, 22-thirteenth electromagnetic valve, 23-fourteenth electromagnetic valve, 24-fifteenth electromagnetic valve, 25-sixteenth electromagnetic valve, 26-seventeenth electromagnetic valve, 27-eighteenth electromagnetic valve, 28-nineteenth electromagnetic valve, 29-twentieth electromagnetic valve. DETAILED DESCRIPTION

[0032] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0034] It should be noted that: similar reference numbers and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0035] In the description of the embodiments of the present application, it should be noted that, if the orientation or position relationship indicated by the terms "upper", "lower", "horizontal", "inner" and the like is based on the orientation or position relationship shown in the drawings, or is the orientation or position relationship when the product of the present application is usually placed, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only used for differentiation in description, and cannot be understood as indicating or implying relative importance.

[0036] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0037] In the description of the embodiments of the present application, it should also be noted that, unless otherwise explicitly specified and limited, if the terms "arrangement", "installation", "connection", "connection" appear, they should be understood in a broad sense, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be mechanically connected, can be electrically connected; can be directly connected, can be indirectly connected through an intermediate medium, can be the communication inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0038] The present application will be described in further detail below with reference to the drawings:

[0039] Referring toFigure 1 The application provides a highly reversible distributed CO2 Carnot battery system, comprising an energy storage working medium circuit, an energy release working medium circuit, a high-temperature heat storage medium circuit, a low-temperature cold storage medium circuit and a PID control unit, wherein the energy storage working medium circuit, the energy release working medium circuit, the high-temperature heat storage medium circuit and the low-temperature cold storage medium circuit are connected with the PID control unit. The energy storage working medium circuit and the energy release working medium circuit are provided with a compressor 1, a first heat exchanger 2, an expander 3, a second heat exchanger 4 and a regenerator 5. The high-temperature heat storage medium circuit is provided with a high-temperature pump 6 and a high-temperature heat storage medium storage tank 7, and the low-temperature cold storage medium circuit is provided with a low-temperature pump 8 and a low-temperature cold storage medium storage tank 9.

[0040] In the energy storage working condition, the outlet of the compressor 1 is connected in sequence with the first heat exchanger 2, the regenerator 5, the expander 3, the second heat exchanger 4 and the regenerator 5 and the inlet of the compressor 1 to form the energy storage working medium circuit; in the energy release working condition, the outlet of the compressor 1 is connected in sequence with the regenerator 5, the first heat exchanger 2, the expander 3, the regenerator 5, the second heat exchanger 4 and the inlet of the compressor 1 to form the energy release working medium circuit. The first heat exchanger 2 and the second heat exchanger 4 are both divided into a working medium side and a medium side.

[0041] In the high-temperature heat storage medium circuit and the low-temperature cold storage medium circuit, the high-temperature heat storage medium storage tank 7 and the low-temperature cold storage medium storage tank 9 are both provided with a high-temperature medium inlet, a high-temperature medium outlet, a low-temperature medium outlet and a low-temperature medium inlet, and each inlet and outlet is connected with a different electromagnetic valve. In the high-temperature heat storage medium circuit, the high-temperature medium inlet and the high-temperature medium outlet are connected with corresponding electromagnetic valves and then connected in sequence with the high-temperature pump 6 and the first heat exchanger 2; the low-temperature medium inlet and the low-temperature medium outlet are connected with the first heat exchanger 2 through corresponding electromagnetic valves. In the low-temperature cold storage medium circuit, the high-temperature medium outlet and the high-temperature medium inlet are connected with corresponding electromagnetic valves and then connected in sequence with the low-temperature pump 8 and the second heat exchanger 4, and the low-temperature medium inlet and the low-temperature medium outlet are connected with the second heat exchanger 4 through corresponding electromagnetic valves.

[0042] The regenerator 5 is divided into a compressed gas flow passage side and an expanded gas flow passage side, and the regenerator 5 is divided into two working medium flow pipelines, namely a compressed working medium pipeline and an expanded working medium pipeline. The two ends of the compressed working medium pipeline are connected with a compressed working medium inlet and a compressed working medium outlet, respectively, and the two ends of the expanded working medium pipeline are connected with an expanded working medium inlet and an expanded working medium outlet, respectively.

[0043] In the energy storage working medium circuit, the outlet of the compressor 1 is connected with the working medium inlet of the first heat exchanger 2 through the first electromagnetic valve 10, the working medium outlet of the first heat exchanger 2 is connected with the compressed working medium inlet of the regenerator 5 through the fourth electromagnetic valve 13, the compressed working medium outlet of the regenerator 5 is connected with the inlet of the expander 3 through the sixth electromagnetic valve 15, the outlet of the expander 3 is connected with the working medium inlet of the second heat exchanger 4 through the seventh electromagnetic valve 16, the working medium outlet of the second heat exchanger 4 is connected with the expanded working medium inlet of the regenerator 5 through the tenth electromagnetic valve 19, the expanded working medium outlet of the regenerator 5 is connected with the inlet of the compressor 1 through the eleventh electromagnetic valve 20, and the energy storage working medium circuit is completed.

[0044] In the energy release working medium circuit, the outlet of the compressor 1 is connected with the compressed working medium inlet of the regenerator 5 through the second electromagnetic valve 11, the compressed working medium outlet of the regenerator 5 is connected with the working medium inlet of the first heat exchanger 2 through the third electromagnetic valve 12, the working medium outlet of the first heat exchanger 2 is connected with the inlet of the expander 3 through the fifth electromagnetic valve 14, the outlet of the expander 3 is connected with the expanded working medium inlet of the regenerator 5 through the eighth electromagnetic valve 17, the expanded working medium outlet of the regenerator 5 is connected with the working medium inlet of the second heat exchanger 4 through the ninth electromagnetic valve 18, the working medium outlet of the second heat exchanger 4 is connected with the inlet of the compressor 1 through the twelfth electromagnetic valve 21, and the energy release working medium circuit is completed.

[0045] In the high-temperature heat storage medium circuit, the pipeline of the high-temperature medium outlet of the high-temperature heat storage medium storage tank 7 is provided with the sixteenth electromagnetic valve 25, the pipeline of the low-temperature medium outlet of the high-temperature heat storage medium storage tank 7 is provided with the fifteenth electromagnetic valve 24, and the pipelines of the high-temperature medium outlet and the low-temperature medium outlet are both connected with the medium inlet of the first heat exchanger 2 through the first outlet pipeline. The pipeline of the low-temperature medium inlet of the high-temperature heat storage medium storage tank 7 is provided with the thirteenth electromagnetic valve 22, the pipeline of the high-temperature medium inlet of the high-temperature heat storage medium storage tank 7 is provided with the fourteenth electromagnetic valve 23, and the pipelines of the low-temperature medium inlet and the high-temperature medium inlet are both connected with the medium outlet of the first heat exchanger 2 through the first inlet pipeline, and the first inlet pipeline is provided with the high-temperature pump 6, and the high-temperature heat storage medium circuit is completed.

[0046] In the low-temperature cold storage medium circuit, the pipeline of the low-temperature medium outlet of the low-temperature cold storage medium storage tank 9 is provided with the twentieth electromagnetic valve 29, the pipeline of the high-temperature medium outlet of the low-temperature cold storage medium storage tank 9 is provided with the nineteenth electromagnetic valve 28, and the pipelines of the low-temperature medium outlet and the high-temperature medium outlet are both connected with the medium inlet of the second heat exchanger 4 through the second outlet pipeline. The pipeline of the high-temperature medium inlet of the low-temperature cold storage medium storage tank 9 is provided with the seventeenth electromagnetic valve 26, the pipeline of the low-temperature medium inlet of the low-temperature cold storage medium storage tank 9 is provided with the eighteenth electromagnetic valve 27, and the high-temperature medium inlet and the low-temperature medium inlet are both connected with the medium outlet of the second heat exchanger 4 through the second inlet pipeline, and the second inlet pipeline is provided with the low-temperature pump 8, and the low-temperature cold storage medium circuit is completed.

[0047] The working medium in the energy storage working medium circuit and the energy release working medium circuit of the application is carbon dioxide, and the working medium only passes through a set of devices including a compressor 1, a first heat exchanger 2, an expander 3, a second heat exchanger 4 and a regenerator 5. The system is in a heat pump cycle in an energy storage mode or in a Brayton cycle in an energy release mode, and both share the above-mentioned devices. In the two working modes, different regenerators 5 and heat exchanger connection sequences can effectively match the heat exchange requirements in different modes. Therefore, when the system switches the working mode, the high-temperature heat storage medium storage tank 7 and the low-temperature cold storage medium storage tank 9 can still maintain the general working temperature range. Moreover, the use of the regenerator 5 can effectively improve the working efficiency of the Brayton cycle.

[0048] As shown in Figure 2 FIG. 1, it is a pressure-enthalpy diagram of the highly reversible distributed CO2 Carnot cell system of the application, including a Brayton cycle of a-b-c-d-a and a heat pump cycle of a'-b'-c'-d'-a'. The system working medium is carbon dioxide, and each point parameter is the optimal working parameter obtained according to system efficiency calculation. When the system is in an energy storage mode, the system performs the heat pump cycle of a'-b'-c'-d'-a', and at this time, the working medium after the compressor 1 heats the heat storage medium storage; when the system is in an energy release mode, the system performs the Brayton cycle of a-b-c-d-a, and at this time, the working medium after the compressor 1 absorbs heat from the heat storage medium.

[0049] As shown in Figure 3 FIG. 2, it is a control method of the highly reversible distributed CO2 Carnot cell system of the application, including:

[0050] According to the real-time working condition parameters of the highly reversible distributed CO2 Carnot cell, the optimal working parameters are calculated, and the well-adapted control logic ensures that the system always works in the optimal working condition. In the PID control unit, the compressor 1 under different inlet and outlet pressures needs to be calculated according to the point parameters under different working conditions. In the energy storage process (i.e., the system flow is switched to the heat pump working mode), first, according to the current working condition parameters, the optimal exhaust temperature of the compressor 1 outlet during energy storage is selected to enhance the heat storage capacity of the system, i.e.,

[0051]

[0052] Among them, is the suction temperature of the compressor during energy storage, is the current temperature of the high-temperature heat storage medium storage tank.

[0053] Then, according to the temperature conditions of the current cycle, the optimal exhaust pressure of the compressor 1 is calculated, i.e.,

[0054]

[0055] Among them, for the expander suction temperature when storing energy, for the compressor suction pressure when storing energy.

[0056] In the heat pump cycle, the expander 3 calculates the optimal discharge pressure of the expander 3 when storing energy according to the expander suction temperature, the expander discharge temperature, the second heat exchanger outlet working medium temperature and the compressor suction pressure, that is:

[0057]

[0058] wherein, is the working medium temperature after passing through the second heat exchanger.

[0059] In the energy release process (i.e. the system flow is switched to the heat engine working mode), the optimal compressor suction temperature in the Brayton cycle is calculated according to the current high-temperature heat storage medium tank 7 and the low-temperature cold storage medium tank 9 temperature, that is:

[0060]

[0061] wherein, is the temperature of the low-temperature cold storage medium tank.

[0062] Then, according to the current temperature parameters of each point in the Brayton cycle and the overall temperature range, the optimal discharge pressure of the compressor 1 in the Brayton cycle is calculated, that is:

[0063]

[0064] wherein, is the expander suction temperature when releasing energy, is the expander suction temperature when releasing energy.

[0065] According to the pressure range and temperature range of the current working condition, the optimal discharge temperature of the expander 3 to increase the work capacity of the expander 3 is calculated, that is:

[0066]

[0067] wherein, is the expander suction temperature when releasing energy.

[0068] Then, according to the optimal working condition parameters calculated above, the error between the current working condition parameters and the optimal working condition parameters is obtained as an input signal input to the PID control unit, according to the following formula:

[0069]

[0070] wherein, is the error amount, is the proportional constant, is an integral constant, is a differential constant, is a control quantity output by the PID system.

[0071] According to the control quantity output by the PID system , each point in the control system is in an optimal working condition. Wherein, the values are respectively , , .

[0072] The PID control unit controls the opening and closing of the corresponding valves in different circuits in the system according to the temperatures of the high-temperature heat storage medium storage tank 7 and the low-temperature cold storage medium storage tank 9, and the load demand of external conditions, so that the system is in an energy storage working condition or an energy release working condition.

[0073] When the system should be switched to the energy storage working condition, the fifteenth electromagnetic valve 24 on the low-temperature medium outlet pipeline of the high-temperature heat storage medium storage tank 7 and the fourteenth electromagnetic valve 23 on the high-temperature medium inlet pipeline are switched to be opened, the sixteenth electromagnetic valve 25 on the high-temperature medium outlet pipeline and the thirteenth electromagnetic valve 22 on the low-temperature medium inlet pipeline are controlled to be closed, so that the heat flow direction in the first heat exchanger 2 is that the compressed working medium releases heat to the heat storage medium; the nineteenth electromagnetic valve 28 on the high-temperature medium outlet pipeline of the low-temperature cold storage medium storage tank 9 and the eighteenth electromagnetic valve 27 on the low-temperature medium inlet pipeline are switched to be opened, the twentieth electromagnetic valve 29 on the low-temperature medium outlet pipeline and the seventeenth electromagnetic valve 26 on the high-temperature medium inlet pipeline are controlled to be closed, so that the heat flow direction in the second heat exchanger 4 is that the expanded working medium absorbs heat from the cold storage medium. Then the opening and closing of the valves in the circuit are switched, the first electromagnetic valve 10, the fourth electromagnetic valve 13, the sixth electromagnetic valve 15, the seventh electromagnetic valve 16, the tenth electromagnetic valve 19, and the eleventh electromagnetic valve 20 are opened, and the second electromagnetic valve 11, the third electromagnetic valve 12, the fifth electromagnetic valve 14, the eighth electromagnetic valve 17, the ninth electromagnetic valve 18, and the twelfth electromagnetic valve 21 are closed, so that the working medium circulation loop is switched to the energy storage working medium loop which sequentially flows through the compressor 1, the first heat exchanger 2, the regenerator 5, the expander 3, the second heat exchanger 4, the regenerator 5, and the compressor 1, and the heat flow direction of the first heat exchanger 2 is that the compressed working medium releases heat to the heat storage medium, and the heat flow direction in the second heat exchanger 4 is that the expanded working medium absorbs heat from the cold storage medium. Then the PID control unit calculates the optimal values of the current working condition parameters, and adjusts the working condition parameters of the compressor 1 and the expander 3 to the optimal values respectively according to the PID control unit. In the process of circulation, the temperature in the high-temperature heat storage medium storage tank 7 is measured in real time and output as an output signal to the system state switching module, which is used to determine whether the temperature of the current high-temperature heat storage medium storage tank 7 has reached the temperature value that meets the operation of the Brayton cycle.

[0074] When the system should switch to the energy release working condition, the sixteenth electromagnetic valve 25 on the high-temperature medium outlet pipeline of the high-temperature heat storage medium storage tank 7 and the thirteenth electromagnetic valve 22 on the low-temperature medium inlet pipeline are opened, the fifteenth electromagnetic valve 24 on the low-temperature medium outlet pipeline and the fourteenth electromagnetic valve 23 on the high-temperature medium inlet pipeline are controlled to be closed, so that the heat flow direction in the first heat exchanger 2 is that the compressed working medium absorbs heat from the heat storage medium; the twentieth electromagnetic valve 29 on the low-temperature medium outlet pipeline of the low-temperature cold storage medium storage tank 9 and the seventeenth electromagnetic valve 26 on the high-temperature medium inlet pipeline are opened, the nineteenth electromagnetic valve 28 on the high-temperature medium outlet pipeline and the eighteenth electromagnetic valve 27 on the low-temperature medium inlet pipeline are controlled to be closed, so that the heat flow direction in the second heat exchanger 4 is that the expanded working medium releases heat to the cold storage medium. Then the opening and closing of the valves in the circuit are switched, the second electromagnetic valve 11, the third electromagnetic valve 12, the fifth electromagnetic valve 14, the eighth electromagnetic valve 17, the ninth electromagnetic valve 18 and the twelfth electromagnetic valve 21 are opened, and the first electromagnetic valve 10, the fourth electromagnetic valve 13, the sixth electromagnetic valve 15, the seventh electromagnetic valve 16, the tenth electromagnetic valve 19 and the eleventh electromagnetic valve 20 are closed, so that the working medium circulation circuit is switched to the energy release working condition, that is, the working medium flows through the compressor 1, the regenerator 5, the first heat exchanger 2, the expander 3, the regenerator 5, the second heat exchanger 4 and the compressor 1 in turn, and the heat flow direction of the first heat exchanger 2 is that the compressed working medium absorbs heat from the heat storage medium, and the heat flow direction of the second heat exchanger 4 is that the expanded working medium releases heat to the cold storage medium. Then the PID control unit calculates the optimal values of the current working condition parameters, and adjusts the working condition parameters of the compressor 1 and the expander 3 to the optimal values respectively according to the PID control unit.

[0075] In the conventional distributed Carnot cell system, different equipment of heat pump cycle and Brayton cycle are needed respectively, and the switching of the heat pump cycle and the Brayton cycle is realized in the same system by adapting the control logic to control the parameters at each point according to the above control strategy, so that the system can quickly respond to the change of the system working condition, and the requirement of further reducing the occupied space of the distributed Carnot cell can be met.

[0076] In the present application, the thermodynamic parameters are calculated by the heat pump cycle model and the Brayton cycle model. In addition to the system model design idea, the complete calculation work can be finally completed by cooperating with the sub-model of the parts, and the sub-models of the parts include the compressor model, the heat exchanger model, the expander model, the regenerator model, the high-temperature heat storage medium storage tank model, the low-temperature cold storage medium storage tank model and the electromagnetic valve model.

[0077] The application provides a highly reversible distributed CO2 Carnot cell system, which realizes a heat pump cycle for energy storage and a Brayton cycle for energy release through the same set of equipment, compared with a traditional distributed Carnot cell, further reduces the occupied volume, improves the energy density, and is better adapted to the characteristics of new energy suitable for scattered utilization. An innovative control logic design scheme suitable for the highly reversible distributed Carnot cell system is provided, which can quickly adjust the operating parameters of each part of the system according to the control logic when the operating condition of the system is determined, quickly responds to the switching of the operating condition of the system, reaches an optimal operating state, and makes an important contribution to the energy storage field.

[0078] The above is only the preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A highly reversible distributed CO2 Carnot cell system, characterized by, The energy storage working medium circuit, the energy release working medium circuit, the high-temperature heat storage medium circuit, the low-temperature cold storage medium circuit and the PID control unit are connected. In the energy storage working medium circuit, the outlet of the compressor (1) is connected to the working medium inlet of the first heat exchanger (2), the working medium outlet of the first heat exchanger (2) is connected to the compressed working medium inlet of the regenerator (5), the compressed working medium outlet of the regenerator (5) is connected to the inlet of the expander (3), the outlet of the expander (3) is connected to the working medium inlet of the second heat exchanger (4), the working medium outlet of the second heat exchanger (4) is connected to the expanded working medium inlet of the regenerator (5), and the expanded working medium outlet of the regenerator (5) is connected to the inlet of the compressor (1). In the energy release working medium circuit, the outlet of the compressor (1) is connected to the compressed working medium inlet of the regenerator (5), the compressed working medium outlet of the regenerator (5) is connected to the working medium inlet of the first heat exchanger (2), the working medium outlet of the first heat exchanger (2) is connected to the inlet of the expander (3), the outlet of the expander (3) is connected to the expanded working medium inlet of the regenerator (5), the expanded working medium outlet of the regenerator (5) is connected to the working medium inlet of the second heat exchanger (4), and the working medium outlet of the second heat exchanger (4) is connected to the inlet of the compressor (1). The high-temperature heat storage medium circuit is connected to the medium side of the first heat exchanger (2), the low-temperature cold storage medium circuit is connected to the medium side of the second heat exchanger (4), and the energy storage working medium circuit, the energy release working medium circuit, the high-temperature heat storage medium circuit and the low-temperature cold storage medium circuit are all connected to the PID control unit.

2. A highly reversible distributed CO2 Carnot cell system according to claim 1, wherein, The regenerator (5) is provided with a compressed working medium pipeline and an expanded working medium pipeline, the two ends of the compressed working medium pipeline are respectively connected to the compressed working medium inlet and the compressed working medium outlet, and the two ends of the expanded working medium pipeline are respectively connected to the expanded working medium inlet and the expanded working medium outlet.

3. A highly reversible distributed CO2 Carnot cell system according to claim 1, wherein, In the energy storage working medium circuit, a first electromagnetic valve (10) is arranged on the connecting pipeline between the outlet of the compressor (1) and the working medium inlet of the first heat exchanger (2), a fourth electromagnetic valve (13) is arranged on the connecting pipeline between the working medium outlet of the first heat exchanger (2) and the compressed working medium inlet of the regenerator (5), a sixth electromagnetic valve (15) is arranged on the connecting pipeline between the compressed working medium outlet of the regenerator (5) and the inlet of the expander (3), a seventh electromagnetic valve (16) is arranged on the connecting pipeline between the outlet of the expander (3) and the working medium inlet of the second heat exchanger (4), a tenth electromagnetic valve (19) is arranged on the connecting pipeline between the working medium outlet of the second heat exchanger (4) and the expanded working medium inlet of the regenerator (5), and an eleventh electromagnetic valve (20) is arranged on the connecting pipeline between the expanded working medium outlet of the regenerator (5) and the inlet of the compressor (1).

4. A highly reversible distributed CO2 Carnot cell system according to claim 1, wherein, The second solenoid valve (11) is arranged on the connecting pipeline between the outlet of the compressor (1) and the compressed working medium inlet of the regenerator (5), the third solenoid valve (12) is arranged on the connecting pipeline between the compressed working medium outlet of the regenerator (5) and the working medium inlet of the first heat exchanger (2), the fifth solenoid valve (14) is arranged on the connecting pipeline between the working medium outlet of the first heat exchanger (2) and the inlet of the expander (3), the eighth solenoid valve (17) is arranged on the connecting pipeline between the outlet of the expander (3) and the expanded working medium inlet of the regenerator (5), the ninth solenoid valve (18) is arranged on the connecting pipeline between the expanded working medium outlet of the regenerator (5) and the working medium inlet of the second heat exchanger (4), and the twelfth solenoid valve (21) is arranged on the connecting pipeline between the working medium outlet of the second heat exchanger (4) and the inlet of the compressor (1).

5. A highly reversible distributed CO2 Carnot cell system according to claim 1, wherein, The sixteenth solenoid valve (25) is arranged on the pipeline of the high-temperature medium outlet of the high-temperature heat storage medium storage tank (7), the fifteenth solenoid valve (24) is arranged on the pipeline of the low-temperature medium outlet of the high-temperature heat storage medium storage tank (7), and the pipeline of the high-temperature medium outlet and the pipeline of the low-temperature medium outlet are connected to the medium inlet of the first heat exchanger (2) through the first outlet pipeline.

6. A highly reversible distributed CO2 Carnot cell system according to claim 5, wherein, The thirteenth solenoid valve (22) is arranged on the pipeline of the low-temperature medium inlet of the high-temperature heat storage medium storage tank (7), the fourteenth solenoid valve (23) is arranged on the pipeline of the high-temperature medium inlet of the high-temperature heat storage medium storage tank (7), the pipeline of the low-temperature medium inlet and the pipeline of the high-temperature medium inlet are connected to the medium outlet of the first heat exchanger (2) through the first inlet pipeline, and the high-temperature pump (6) is arranged on the first inlet pipeline.

7. A highly reversible distributed CO2 Carnot cell system according to claim 1, wherein, The twentieth solenoid valve (29) is arranged on the pipeline of the low-temperature medium outlet of the low-temperature cold storage medium storage tank (9), the nineteenth solenoid valve (28) is arranged on the pipeline of the high-temperature medium outlet of the low-temperature cold storage medium storage tank (9), and the pipeline of the low-temperature medium outlet and the pipeline of the high-temperature medium outlet are connected to the medium inlet of the second heat exchanger (4) through the second outlet pipeline.

8. A highly reversible distributed CO2 Carnot cell system according to claim 7, wherein, The seventeenth solenoid valve (26) is arranged on the pipeline of the high-temperature medium inlet of the low-temperature cold storage medium storage tank (9), the eighteenth solenoid valve (27) is arranged on the pipeline of the low-temperature medium inlet of the low-temperature cold storage medium storage tank (9), the high-temperature medium inlet and the low-temperature medium inlet are connected to the medium outlet of the second heat exchanger (4) through the second inlet pipeline, and the low-temperature pump (8) is arranged on the second inlet pipeline.

9. A highly reversible distributed CO2 Carnot cell system according to claim 1, wherein, The working medium in the energy storage working medium circuit and the energy release working medium circuit is CO2.

10. A method of controlling the highly reversible distributed CO2 Carnot cell system of any one of claims 1 to 9, characterized in that, The method comprises the following steps: In the energy storage process, the optimal exhaust temperature of the compressor (1) outlet is selected according to the current working condition parameters, the optimal exhaust pressure of the expander (3) is calculated according to the suction temperature and the exhaust temperature of the expander (3), the outlet working medium temperature of the second heat exchanger (4) and the suction pressure of the compressor (1); In the energy release process, according to the current high temperature heat storage medium loop and low temperature cold storage medium loop temperature, the optimal suction temperature of the compressor (3) in the Brayton cycle is calculated; then according to the current temperature parameters of each point in the Brayton cycle and the overall temperature interval, the optimal exhaust pressure of the compressor (1) in the Brayton cycle is calculated; According to the pressure range and temperature interval of the current working condition, the optimal exhaust temperature of the increased expander (3) to do the work is calculated; According to the calculated optimal working condition parameters, the error between the current working condition parameters and the optimal working condition parameters is obtained, and the control amount is obtained through the PID control unit to control each point to be in the optimal working condition; According to the temperature of the high temperature heat storage medium loop and the low temperature cold storage medium loop, and the load demand of the external condition, the highly reversible distributed CO2 Carnot battery system is in the energy storage working condition or the energy release working condition.

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