Highly reversible distributed CO2 Carnot cell system and control method thereof

Abstract

The invention discloses a highly reversible distributed CO2 Carnot battery system and a control method thereof. The highly reversible distributed CO2 Carnot battery system 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 which are connected with a PID (Proportion Integration Differentiation) control unit, in the energy storage working medium loop, an outlet of the compressor is communicated with an inlet of the compressor through the first heat exchanger, the heat regenerator, the expansion machine, the second heat exchanger and the heat regenerator in sequence; in the energy release working medium loop, an outlet of the compressor is communicated with an inlet of the compressor through a heat regenerator, a first heat exchanger, an expansion machine, a heat regenerator and a second heat exchanger in sequence; 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. According to the invention, the occupied space can be obviously reduced, the energy density of the system is improved, the working condition change of the system is quickly responded in the same system, the switching between the heat pump cycle and the Brayton cycle is completed, and the working efficiency and the stability of the distributed Carnot battery are improved.

Description

Technical Field

[0001] The present invention belongs to the field of novel energy storage technology, in particular to a highly reversible distributed CO 2 Carnot battery system and control method thereof. Background Art

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

[0003] At present, the more mature energy storage methods in the world, such as pumped storage, compressed air energy storage, solar thermal molten salt, etc., all have the disadvantage of occupying a large area, and it is difficult to adapt to the characteristics of wide distribution of new energy and small-scale decentralized utilization. High energy density distributed energy storage technology can better match the future urban flexible power grid and energy network facilities, and is an important future technology development route.

[0004] Distributed Carnot batteries have many advantages, such as high energy density heat storage, high heat storage temperature, high power density, no additional environmental pollution during operation, good versatility and distribution, and have become an ideal choice for the new generation of energy storage. Compared with pumped storage, distributed Carnot batteries have the advantage of not being restricted by geographical conditions, and compared with compressed air energy storage, they have the advantage of not requiring gas tanks and occupying a small area. Distributed Carnot batteries can also integrate cold / heat / electricity multi-energy supply, realize multi-energy complementarity of various resources and cascade utilization of thermal energy, and improve energy utilization. However, the heat pump cycle and Brayton cycle of existing distributed Carnot batteries require two different sets of equipment, which exchange heat in different heat exchange equipment respectively. The equipment and pipelines are complicated, which increases the initial investment in construction. Distributed Carnot batteries face practical problems such as working fluid selection, further improving energy density, further reducing volume, and adapting to good control logic. They still need to continue to study, optimize, and improve from the technical route. Summary of the invention

[0005] The object of the present invention is to provide a highly reversible distributed CO 2 The Carnot battery system and its control method solve the complex problems of existing distributed Carnot battery equipment.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A highly reversible distributed CO 2 The Carnot battery system includes an energy storage medium circuit, an energy release medium circuit, a high-temperature heat storage medium circuit, a low-temperature cold storage medium circuit and a PID control unit; In the energy storage working medium circuit, 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; In the energy-releasing working medium circuit, 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; 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 medium circuit, energy release medium circuit, high-temperature heat storage medium circuit and low-temperature cold storage medium circuit are all connected to the PID control unit.

[0007] Furthermore, the regenerator is provided with a compressed working fluid pipeline and an expanded working fluid pipeline, the two ends of the compressed working fluid pipeline are respectively connected to the compressed working fluid inlet and the compressed working fluid outlet, and the two ends of the expanded working fluid pipeline are respectively connected to the expanded working fluid inlet and the expanded working fluid outlet.

[0008] Furthermore, in the energy storage working fluid circuit, a first solenoid valve is provided on the connecting pipeline between the outlet of the compressor and the working fluid inlet of the first heat exchanger, a fourth solenoid valve is provided on the connecting pipeline between the working fluid outlet of the first heat exchanger and the compressed working fluid inlet of the regenerator, a sixth solenoid valve is provided on the connecting pipeline between the compressed working fluid outlet of the regenerator and the inlet of the expander, a seventh solenoid valve is provided on the connecting pipeline between the outlet of the expander and the working fluid inlet of the second heat exchanger, a tenth solenoid valve is provided on the connecting pipeline between the working fluid outlet of the second heat exchanger and the expanded working fluid inlet of the regenerator, and an eleventh solenoid valve is provided on the connecting pipeline between the expanded working fluid outlet of the regenerator and the inlet of the compressor.

[0009] Furthermore, in the energy-releasing working fluid circuit, a second solenoid valve is provided on the connecting pipeline between the outlet of the compressor and the inlet of the compressed working fluid of the regenerator, a third solenoid valve is provided on the connecting pipeline between the outlet of the compressed working fluid of the regenerator and the working fluid inlet of the first heat exchanger, a fifth solenoid valve is provided on the connecting pipeline between the outlet of the first heat exchanger and the inlet of the expander, an eighth solenoid valve is provided on the connecting pipeline between the outlet of the expander and the inlet of the expanded working fluid of the regenerator, a ninth solenoid valve is provided on the connecting pipeline between the outlet of the expanded working fluid of the regenerator and the working fluid inlet of the second heat exchanger, and a twelfth solenoid valve is provided on the connecting pipeline between the outlet of the second heat exchanger and the inlet of the compressor.

[0010] Furthermore, in the high-temperature heat storage medium circuit, a sixteenth solenoid valve is installed on the pipeline of the high-temperature medium outlet of the high-temperature heat storage medium storage tank, and a fifteenth solenoid valve is installed on the pipeline of the low-temperature medium outlet of the high-temperature heat storage medium storage tank, and the pipeline of the high-temperature medium outlet and the pipeline of the low-temperature medium outlet are both connected to the medium inlet of the first heat exchanger through the first outlet pipeline.

[0011] Furthermore, a thirteenth solenoid valve is installed on the pipeline of the low-temperature medium inlet of the high-temperature heat storage medium storage tank, and a fourteenth solenoid valve is installed on the pipeline of the high-temperature medium inlet of the high-temperature heat storage medium storage tank. The pipeline of the low-temperature medium inlet and the pipeline of the high-temperature medium inlet are both connected to the medium outlet of the first heat exchanger through the first inlet pipeline, and a high-temperature pump is installed on the first inlet pipeline.

[0012] Furthermore, in the low-temperature cold storage medium circuit, a twentieth solenoid valve is installed on the pipeline of the low-temperature medium outlet of the low-temperature cold storage medium storage tank, and a nineteenth solenoid valve is installed on the 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 both connected to the medium inlet of the second heat exchanger through the second outlet pipeline.

[0013] Furthermore, a seventeenth solenoid valve is installed on the pipeline of the high-temperature medium inlet of the low-temperature cold storage medium storage tank, and an eighteenth solenoid valve is installed on the pipeline of the low-temperature medium inlet of the low-temperature cold storage medium storage tank. The high-temperature medium inlet and the low-temperature medium inlet are both connected to the medium outlet of the second heat exchanger through a second inlet pipeline, and a low-temperature pump is installed on the second inlet pipeline.

[0014] Furthermore, the working fluid in the energy storage working fluid circuit and the energy release working fluid circuit is CO 2 .

[0015] A highly reversible distributed CO 2 A control method for a Carnot battery system, comprising: During the energy storage process, the optimal exhaust temperature at the compressor outlet is selected according to the current operating parameters, and the optimal exhaust pressure of the expander is calculated according to the suction temperature and exhaust temperature of the expander, the outlet working medium temperature of the second heat exchanger and the compressor suction pressure; During the energy release process, the optimal suction temperature of the compressor in the Brayton cycle is calculated based on the current temperatures of the high-temperature heat storage medium circuit and the low-temperature cold storage medium circuit; then, the optimal exhaust pressure of the compressor in the Brayton cycle is calculated based on the temperature parameters of each point in the current Brayton cycle and the overall temperature range; and then, the optimal exhaust temperature for increasing the work capacity of the expander is calculated based on the pressure range and temperature range of the current working conditions; According to the calculated optimal operating parameters, the error between the current operating parameters of each point and the optimal operating parameters is obtained, and the control amount is obtained through the PID control unit to control each point to be in the optimal operating condition; According to the temperature of the high-temperature heat storage medium loop and the low-temperature cold storage medium loop, as well as the load requirements of external conditions, the highly reversible distributed CO 2 The Carnot battery system operates in an energy storage condition or an energy release condition.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a highly reversible distributed CO 2 The Carnot battery system, in view of the characteristics of wide distribution of new energy and small-scale decentralized utilization, connects the compressor outlet to the compressor inlet through the first heat exchanger, regenerator, expander, second heat exchanger, and regenerator in the energy storage working medium loop, connects the compressor outlet to the compressor inlet through the regenerator, the first heat exchanger, expander, regenerator, and the second heat exchanger in the energy release working medium loop, connects the high-temperature heat storage medium loop to the medium side of the first heat exchanger, and connects the low-temperature cold storage medium loop to the medium side of the second heat exchanger, so that the heat pump cycle of the energy storage process and the Brayton cycle of the energy release stage share a set of equipment to work, thereby improving the utilization rate of the equipment and the flexibility of the system. At the same time, a control logic design scheme suitable for a highly reversible distributed Carnot battery system is proposed through a PID control unit. When determining the operating conditions of the system, it can select the optimal working parameters in real time according to the well-adapted control logic and the optimization analysis, quickly adjust the operating parameters of each point in the system, and quickly respond to the switching of the system operating conditions to achieve the optimal operating state. Compared with the traditional distributed Carnot battery system, the present invention can significantly reduce the volume occupied by the distributed Carnot battery and improve the energy density of the system. It has achieved rapid response to changes in system operating conditions in the same system, completed the switching between the heat pump cycle and the Brayton cycle, improved the working efficiency and stability of distributed Carnot batteries, reduced the cost and complexity of the system, and made important contributions to the field of energy storage.

[0017] Furthermore, in the energy storage working fluid circuit and the energy release working fluid circuit of the present invention, CO 2 As a working fluid, CO 2 It has low flammability and explosiveness. In the supercritical state, CO 2 The heat and mass transfer performance is excellent, and it can show high efficiency and safety in the process of energy storage and release. At the same time, CO2, as a naturally occurring gas, has a wide source and is relatively cheap. Its use will not cause additional pollution to the environment, and it also reduces the operating cost of the system, making the present invention more competitive in commercial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 The highly reversible distributed CO 2 Schematic diagram of the Carnot battery system.

[0020] Figure 2 The highly reversible distributed CO 2 Pressure-enthalpy diagram of a Carnot cell system.

[0021] Figure 3 It is a schematic flow chart of the control method of the highly reversible distributed CO2 Carnot battery system of the present invention.

[0022] Among them: 1- compressor, 2- first heat exchanger, 3- expander, 4- second heat exchanger, 5- 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 solenoid valve, 11- second solenoid valve, 12- third solenoid valve, 13- fourth solenoid valve, 14- fifth solenoid valve, 15- sixth solenoid valve, 16- seventh solenoid valve, 17- eighth solenoid valve, 18- ninth solenoid valve, 19- tenth solenoid valve, 20- eleventh solenoid valve, 21- twelfth solenoid valve, 22- thirteenth solenoid valve, 23- fourteenth solenoid valve, 24- fifteenth solenoid valve, 25- sixteenth solenoid valve, 26- seventeenth solenoid valve, 27- eighteenth solenoid valve, 28- nineteenth solenoid valve, 29- twentieth solenoid valve. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0026] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0027] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0028] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings: See also Figure 1The present invention provides a highly reversible distributed CO 2 The Carnot battery system includes an energy storage medium circuit, an energy release medium circuit, a high temperature heat storage medium circuit, a low temperature cold storage medium circuit and a PID control unit. The energy storage medium circuit, the energy release 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. A compressor 1, a first heat exchanger 2, an expander 3, a second heat exchanger 4 and a regenerator 5 are provided in the energy storage medium circuit and the energy release medium circuit. A high temperature pump 6 and a high temperature heat storage medium storage tank 7 are provided in the high temperature heat storage medium circuit, and a low temperature pump 8 and a low temperature cold storage medium storage tank 9 are provided in the low temperature cold storage medium circuit.

[0030] In the energy storage condition, the outlet of compressor 1 is connected to the inlet of compressor 1 through the first heat exchanger 2, the regenerator 5, the expander 3, the second heat exchanger 4, and the regenerator 5 in sequence to form an energy storage working medium circuit; in the energy release condition, the outlet of compressor 1 is connected to the inlet of compressor 1 through the regenerator 5, the first heat exchanger 2, the expander 3, the regenerator 5, and the second heat exchanger 4 in sequence to form an energy release working medium circuit. Among them, the first heat exchanger 2 and the second heat exchanger 4 are both divided into a working medium side and a medium side.

[0031] In the high-temperature heat storage medium circuit and the low-temperature cold storage medium circuit, the high-temperature heat storage medium tank 7 and the low-temperature cold storage medium 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 are respectively connected to different solenoid valves. In the high-temperature heat storage medium circuit, the high-temperature medium inlet and the high-temperature medium outlet are connected to the high-temperature pump 6 and the first heat exchanger 2 in sequence after being connected to the corresponding solenoid valve; the low-temperature medium inlet and the low-temperature medium outlet are connected to the first heat exchanger 2 via the corresponding solenoid valve. In the low-temperature cold storage medium circuit, the high-temperature medium outlet and the high-temperature medium inlet are connected to the corresponding solenoid valve, and are connected to the low-temperature pump 8 and the second heat exchanger 4 in sequence, and the low-temperature medium inlet and the low-temperature medium outlet are connected to the second heat exchanger 4 via the corresponding solenoid valve.

[0032] The regenerator 5 is divided into a compressed gas flow side and an expanded gas flow side. The regenerator 5 is divided into two working fluid flow pipelines, namely a compressed working fluid pipeline and an expanded working fluid pipeline. The two ends of the compressed working fluid pipeline are respectively connected to the compressed working fluid inlet and the compressed working fluid outlet, and the two ends of the expanded working fluid pipeline are respectively connected to the expanded working fluid inlet and the expanded working fluid outlet.

[0033] In the energy storage working fluid circuit, the outlet of the compressor 1 is connected to the working fluid inlet of the first heat exchanger 2 via the first solenoid valve 10, the working fluid outlet of the first heat exchanger 2 is connected to the compressed working fluid inlet of the regenerator 5 via the fourth solenoid valve 13, the compressed working fluid outlet of the regenerator 5 is connected to the inlet of the expander 3 via the sixth solenoid valve 15, the outlet of the expander 3 is connected to the working fluid inlet of the second heat exchanger 4 via the seventh solenoid valve 16, the working fluid outlet of the second heat exchanger 4 is connected to the expanded working fluid inlet of the regenerator 5 via the tenth solenoid valve 19, and the expanded working fluid outlet of the regenerator 5 is connected to the inlet of the compressor 1 via the eleventh solenoid valve 20, completing the energy storage working fluid circuit.

[0034] In the energy-releasing working fluid circuit, the outlet of the compressor 1 is connected to the compressed working fluid inlet of the regenerator 5 via the second solenoid valve 11, the compressed working fluid outlet of the regenerator 5 is connected to the working fluid inlet of the first heat exchanger 2 via the third solenoid valve 12, the working fluid outlet of the first heat exchanger 2 is connected to the inlet of the expander 3 via the fifth solenoid valve 14, the outlet of the expander 3 is connected to the expanded working fluid inlet of the regenerator 5 via the eighth solenoid valve 17, the expanded working fluid outlet of the regenerator 5 is connected to the working fluid inlet of the second heat exchanger 4 via the ninth solenoid valve 18, and the working fluid outlet of the second heat exchanger 4 is connected to the inlet of the compressor 1 via the twelfth solenoid valve 21, thus completing the energy-releasing working fluid circuit.

[0035] In the high-temperature heat storage medium loop, a sixteenth solenoid valve 25 is installed on the pipeline of the high-temperature medium outlet of the high-temperature heat storage medium storage tank 7, a fifteenth solenoid valve 24 is installed 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 both connected to the medium inlet of the first heat exchanger 2 through the first outlet pipeline. A thirteenth solenoid valve 22 is installed on the pipeline of the low-temperature medium inlet of the high-temperature heat storage medium storage tank 7, a fourteenth solenoid valve 23 is installed 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 both connected to the medium outlet of the first heat exchanger 2 through the first inlet pipeline, and a high-temperature pump 6 is installed on the first inlet pipeline to complete the high-temperature heat storage medium loop.

[0036] In the low-temperature cold storage medium loop, a twentieth solenoid valve 29 is installed on the pipeline of the low-temperature medium outlet of the low-temperature cold storage medium storage tank 9, a nineteenth solenoid valve 28 is installed 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 both connected to the medium inlet of the second heat exchanger 4 through the second outlet pipeline. A seventeenth solenoid valve 26 is installed on the pipeline of the high-temperature medium inlet of the low-temperature cold storage medium storage tank 9, an eighteenth solenoid valve 27 is installed on the pipeline of the low-temperature medium inlet of the low-temperature cold storage medium storage tank 9, and the high-temperature medium inlet and the low-temperature medium inlet are both connected to the medium outlet of the second heat exchanger 4 through the second inlet pipeline, and a cryogenic pump 8 is installed on the second inlet pipeline to complete the low-temperature cold storage medium loop.

[0037] The working fluid in the energy storage working fluid circuit and the energy release working fluid circuit of the present invention is carbon dioxide, and the working fluid only passes through a set of equipment including a compressor 1, a first heat exchanger 2, an expander 3, a second heat exchanger 4 and a regenerator 5. The heat pump cycle in the system's energy storage condition or the Brayton cycle in the energy release condition share a set of the above equipment. In the two working modes, the different connection sequences of the regenerator 5 and the heat exchanger can effectively match the heat exchange requirements under different working conditions. Therefore, when the system switches the working mode, it can still maintain the approximate working temperature range of the high-temperature heat storage medium tank 7 and the low-temperature cold storage medium tank 9. In addition, the use of the regenerator 5 can effectively improve the working efficiency of the Brayton cycle.

[0038] like Figure 2 As shown, the highly reversible distributed CO 2 The pressure-enthalpy diagram of the Carnot battery system includes the Brayton cycle of abcda and the heat pump cycle of a'-b'-c'-d'-a'. The system working fluid is carbon dioxide, and the parameters at each point are the optimal working parameters calculated based on the system efficiency. When the system is in the energy storage condition, the system performs the heat pump cycle of a'-b'-c'-d'-a', at which time the working fluid after compressor 1 heats the heat storage medium to store heat; when the system is in the energy release condition, the system performs the Brayton cycle of abcda, at which time the working fluid after compressor 1 absorbs heat from the heat storage medium.

[0039] like Figure 3 As shown, the control method of the highly reversible distributed CO2 Carnot battery system of the present invention comprises: Based on the highly reversible distributed CO 2 The real-time operating parameters of the Carnot battery are used to calculate the optimal operating parameters and adapt the control logic to ensure that the system is always in the optimal operating condition. In the PID control unit, it is necessary to calculate the compressor 1 under different inlet and outlet pressures according to the parameters of each point under different operating conditions. During the energy storage process (that is, the system process switches to the heat pump working mode), firstly, according to the current operating parameters, the optimal exhaust temperature at the outlet of compressor 1 during energy storage is selected to enhance the heat storage capacity of the system, that is:

[0040] in, is the compressor suction temperature during energy storage, is the current temperature of the high-temperature heat storage medium tank.

[0041] Afterwards, the optimal exhaust pressure of the compressor 1 is calculated according to the temperature conditions of the current cycle, that is:

[0042] in, is the expansion machine suction temperature during energy storage, It is the suction pressure of the compressor during energy storage.

[0043] In the heat pump cycle, the expander 3 calculates the optimal exhaust pressure of the expander 3 during energy storage according to the expander suction temperature, the expander exhaust temperature, the working medium temperature at the outlet of the second heat exchanger and the compressor suction pressure, that is:

[0044] in, is the working medium temperature after passing through the second heat exchanger.

[0045] During the energy release process (i.e. the system process is switched to the heat engine working mode), the optimal compressor suction temperature in the Brayton cycle is calculated according to the current temperatures of the high-temperature heat storage medium tank 7 and the low-temperature cold storage medium tank 9, that is:

[0046] in, It is the temperature of the low-temperature cold storage medium tank.

[0047] Afterwards, according to the temperature parameters of each point in the current Brayton cycle and the overall temperature range, the optimal exhaust pressure of the compressor 1 in the Brayton cycle is calculated, that is:

[0048] in, is the compressor exhaust temperature during energy release, It is the suction temperature of the expander during energy release.

[0049] According to the pressure range and temperature range of the current working conditions, the optimal exhaust temperature is calculated to increase the working capacity of the expander 3, that is:

[0050] in, It is the suction pressure of the compressor during energy release.

[0051] Afterwards, according to the optimal operating parameters calculated above, the error between the current operating parameters at each point and the optimal operating parameters is obtained: , as the input signal to the PID control unit, according to the following formula:

[0052] in, is the error amount, is the proportionality constant, is the integration constant, is the differential constant, It is the control quantity output by the PID system.

[0053] According to the control quantity output by the PID system , each point in the control system is in the optimal working condition. Among them, the values ​​are , , .

[0054] The PID control unit controls the opening and closing of corresponding valves in different circuits in the system according to the temperatures of the high-temperature heat storage medium tank 7 and the low-temperature cold storage medium tank 9, as well as the load requirements of external conditions, so that the system works in an energy storage condition or an energy release condition.

[0055] When the system should be switched to the energy storage condition, the fifteenth solenoid valve 24 on the low-temperature medium outlet pipeline of the high-temperature heat storage medium storage tank 7 and the fourteenth solenoid valve 23 on the high-temperature medium inlet pipeline are switched to open, and the sixteenth solenoid valve 25 on the high-temperature medium outlet pipeline and the thirteenth solenoid 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 fluid releases heat to the heat storage medium; the nineteenth solenoid valve 28 on the high-temperature medium outlet pipeline and the eighteenth solenoid valve 27 on the low-temperature medium inlet pipeline of the low-temperature cold storage medium storage tank 9 are switched to open, and the twentieth solenoid valve 29 on the low-temperature medium outlet pipeline and the seventeenth solenoid 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 fluid absorbs heat from the cold storage medium. Then, the valves in the circuit are switched on and off, the first solenoid valve 10, the fourth solenoid valve 13, the sixth solenoid valve 15, the seventh solenoid valve 16, the tenth solenoid valve 19, and the eleventh solenoid valve 20 are opened, and the second solenoid valve 11, the third solenoid valve 12, the fifth solenoid valve 14, the eighth solenoid valve 17, the ninth solenoid valve 18, and the twelfth solenoid valve 21 are closed, and the working medium circulation circuit is switched to the energy storage working medium circuit that 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 in sequence, and the heat flow direction of the first heat exchanger 2 is switched to the compressed working medium releasing heat to the heat storage medium, and the heat flow direction in the second heat exchanger 4 is the expanded working medium absorbing heat from the cold storage medium. Then, the optimal value of the current operating condition parameter is calculated according to the PID control unit, and the operating condition parameters of the compressor 1 and the expander 3 are calculated and adjusted according to the PID control unit to reach the optimal value. During the cycle, the temperature in the high-temperature heat storage medium tank 7 is measured in real time and output as an output signal to the system state switching module to determine whether the current temperature of the high-temperature heat storage medium tank 7 has reached a temperature value that satisfies the Brayton cycle operation.

[0056] When the system should be switched to the energy release condition, the sixteenth solenoid valve 25 on the high-temperature medium outlet pipeline of the high-temperature heat storage medium storage tank 7 and the thirteenth solenoid valve 22 on the low-temperature medium inlet pipeline are switched to open, and the fifteenth solenoid valve 24 on the low-temperature medium outlet pipeline and the fourteenth solenoid 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 fluid absorbs heat from the heat storage medium; the twentieth solenoid valve 29 on the low-temperature medium outlet pipeline and the seventeenth solenoid valve 26 on the high-temperature medium inlet pipeline of the low-temperature cold storage medium storage tank 9 are switched to open, and the nineteenth solenoid valve 28 on the high-temperature medium outlet pipeline and the eighteenth solenoid 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 fluid releases heat to the cold storage medium. Then, the valves in the circuit are switched on and off, the second solenoid valve 11, the third solenoid valve 12, the fifth solenoid valve 14, the eighth solenoid valve 17, the ninth solenoid valve 18, and the twelfth solenoid valve 21 are opened, and the first solenoid valve 10, the fourth solenoid valve 13, the sixth solenoid valve 15, the seventh solenoid valve 16, the tenth solenoid valve 19, and the eleventh solenoid valve 20 are closed, and the working medium circulation circuit is switched to the energy release working medium circuit that 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 sequence, and the heat flow direction of the first heat exchanger 2 is switched to the compressed working medium absorbing heat from the heat storage medium, and the heat flow direction in the second heat exchanger 4 is the expanded working medium releasing heat to the cold storage medium. Then, the optimal value of the current operating condition parameter is calculated according to the PID control unit, and the operating condition parameters of the compressor 1 and the expander 3 are calculated and adjusted according to the PID control unit to reach the optimal value.

[0057] The present invention adapts the control logic to control the parameters of each point in the conventional distributed Carnot battery system, which requires the use of different devices for heat pump cycles and Brayton cycles respectively. According to the above control strategy, it can be achieved in the same system that the system can quickly respond to changes in system operating conditions and complete the switching between heat pump cycles and Brayton cycles, which can meet the requirement of distributed Carnot batteries to further reduce the occupied space.

[0058] In the present invention, various thermodynamic parameters are calculated by heat pump cycle model and Brayton cycle model. In addition to the system model design ideas, it is also necessary to cooperate with the sub-item models of the parts to finally complete the complete calculation work. The sub-item models of each part include compressor model, heat exchanger model, expander model, regenerator model, high-temperature heat storage medium tank model, low-temperature cold storage medium tank model and solenoid valve model.

[0059] The present invention proposes a highly reversible distributed CO 2The Carnot battery system uses the same set of equipment to achieve the heat pump cycle for energy storage and the Brayton cycle for energy release. Compared with the traditional distributed Carnot battery, it further reduces the occupied volume, improves the energy density, and better adapts to the characteristics of new energy suitable for decentralized utilization. An innovative control logic design scheme suitable for highly reversible distributed Carnot battery systems is proposed. When determining the system operating conditions, it can quickly adjust the operating parameters of various parts of the system according to the control logic, and quickly respond to the system condition switching to achieve the optimal operating state, making important contributions to the field of energy storage.

[0060] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A highly reversible distributed CO2 Carnot battery system, characterized in that: It includes an energy storage medium circuit, an energy release medium circuit, a high-temperature heat storage medium circuit, a low-temperature cold storage medium circuit and a PID control unit; 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-releasing 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 medium circuit, the energy release medium circuit, the high-temperature heat storage medium circuit and the low-temperature cold storage medium circuit are all connected to a PID control unit.

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

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

4. A highly reversible distributed CO2 Carnot battery system according to claim 1, characterized in that: In the energy-releasing working medium circuit, a second solenoid valve (11) is provided on the connecting pipeline between the outlet of the compressor (1) and the inlet of the compressed working medium of the regenerator (5), a third solenoid valve (12) is provided on the connecting pipeline between the outlet of the compressed working medium of the regenerator (5) and the inlet of the working medium of the first heat exchanger (2), a fifth solenoid valve (14) is provided on the connecting pipeline between the outlet of the first heat exchanger (2) and the inlet of the expander (3), an eighth solenoid valve (17) is provided on the connecting pipeline between the outlet of the expander (3) and the inlet of the expanded working medium of the regenerator (5), a ninth solenoid valve (18) is provided on the connecting pipeline between the outlet of the expanded working medium of the regenerator (5) and the inlet of the working medium of the second heat exchanger (4), and a twelfth solenoid valve (21) is provided on the connecting pipeline between the outlet of the second heat exchanger (4) and the inlet of the compressor (1).

5. A highly reversible distributed CO2 Carnot battery system according to claim 1, characterized in that: In the high-temperature heat storage medium circuit, a sixteenth solenoid valve (25) is installed on the pipeline of the high-temperature medium outlet of the high-temperature heat storage medium storage tank (7), and a fifteenth solenoid valve (24) is installed 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 both connected to the medium inlet of the first heat exchanger (2) through the first outlet pipeline.

6. A highly reversible distributed CO2 Carnot battery system according to claim 5, characterized in that: A thirteenth solenoid valve (22) is installed on the pipeline of the low-temperature medium inlet of the high-temperature heat storage medium storage tank (7), and a fourteenth solenoid valve (23) is installed 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 both connected to the medium outlet of the first heat exchanger (2) through a first inlet pipeline, and a high-temperature pump (6) is installed on the first inlet pipeline.

7. A highly reversible distributed CO2 Carnot battery system according to claim 1, characterized in that: In the low-temperature cold storage medium circuit, a twentieth solenoid valve (29) is installed on the pipeline of the low-temperature medium outlet of the low-temperature cold storage medium storage tank (9), and a nineteenth solenoid valve (28) is installed on the pipeline of the high-temperature medium outlet of the low-temperature cold storage medium storage tank (9). The pipeline of the low-temperature medium outlet and the pipeline of the high-temperature medium outlet are both connected to the medium inlet of the second heat exchanger (4) via a second outlet pipeline.

8. A highly reversible distributed CO2 Carnot battery system according to claim 7, characterized in that: A seventeenth solenoid valve (26) is installed on the pipeline of the high-temperature medium inlet of the low-temperature cold storage medium storage tank (9), and an eighteenth solenoid valve (27) is installed 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 both connected to the medium outlet of the second heat exchanger (4) via a second inlet pipeline, and a low-temperature pump (8) is installed on the second inlet pipeline.

9. A highly reversible distributed CO2 Carnot battery system according to claim 1, characterized in that: The working fluid in the energy storage working fluid circuit and the energy release working fluid circuit is CO2.

10. A control method for a highly reversible distributed CO2 Carnot battery system according to any one of claims 1 to 9, characterized in that: include: During the energy storage process, the optimal exhaust temperature at the outlet of the compressor (1) is selected according to the current operating parameters, and the optimal exhaust pressure of the expander (3) is calculated according to the suction temperature and 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); During the energy release process, the optimal suction temperature of the compressor (3) in the Brayton cycle is calculated according to the current temperatures of the high-temperature heat storage medium circuit and the low-temperature cold storage medium circuit; then, the optimal exhaust pressure of the compressor (3) in the Brayton cycle is calculated according to the temperature parameters of each point in the current Brayton cycle and the overall temperature range; Then, based on the pressure range and temperature range of the current working conditions, the optimal exhaust temperature for increasing the working capacity of the expander (3) is calculated; According to the calculated optimal operating parameters, the error between the current operating parameters of each point and the optimal operating parameters is obtained, and the control amount is obtained through the PID control unit to control each point to be in the optimal operating condition; According to the temperature of the high-temperature heat storage medium loop and the low-temperature cold storage medium loop, as well as the load requirements of external conditions, the highly reversible distributed CO2 Carnot battery system is operated in an energy storage condition or an energy release condition.

Images