Energy storage system and method of controlling the same

Abstract

The application discloses an energy storage system and a control method thereof. The energy storage system comprises an energy storage circuit in which energy storage fluid flows and a first heat exchange circuit in which heat exchange fluid flows. The energy storage circuit is provided with a first energy conversion device, a second energy conversion device, a first shunt component, a first-stage pressure storage tank, a second-stage pressure storage tank and a third-stage pressure storage tank which are communicated. The energy storage system further comprises at least one heat exchange device. In the embodiment of the application, the high-pressure energy storage fluid in the third-stage pressure storage tank is divided into a first flow and a second flow through the first shunt component. The first flow is used to do work to supply power to a user power system. The second flow which does not do work is recovered through the second-stage pressure storage tank. The proportion of the first flow and the second flow is adjusted according to the demand of the user power system. The energy utilization efficiency in the energy storage system is improved.

Description

Technical Field

[0001] This application relates to the field of energy technology, specifically to an energy storage system and its control method. Background Technology

[0002] Because renewable energy generation is irregular and difficult to match with the peak and off-peak electricity demand of users' power systems, some energy storage systems exist to store excess renewable energy. These systems use fluids such as air and carbon dioxide as storage media, storing and releasing energy through changes in the pressure of the storage medium. However, compressed gas energy storage systems require adjusting the flow rate of the storage tank to regulate the amount of energy released when adapting to the peak and off-peak electricity demand of users' power systems. This leads to unstable output from the energy storage system, resulting in performance degradation and reduced lifespan of key components such as compressors and turbines, thus reducing the energy utilization efficiency and service life of the energy storage system. Summary of the Invention

[0003] The purpose of this application is to provide an energy storage system and its control method to address the shortcomings of the prior art, thereby at least solving the deficiencies of the prior art. This purpose is achieved through the following technical solutions.

[0004] This application provides an energy storage system, which includes an energy storage circuit through which an energy storage fluid flows and a first heat exchange circuit through which a heat exchange fluid flows.

[0005] The energy storage circuit is equipped with a first energy conversion device, a second energy conversion device, a first diversion component, a first-stage pressure tank, a second-stage pressure tank, and a third-stage pressure tank that are connected in series.

[0006] The energy storage fluid output from the first-stage pressure tank is pressurized by renewable energy and then flows to the second-stage pressure tank. The energy storage fluid output from the second-stage pressure tank is pressurized by renewable energy and then flows to the third-stage pressure tank.

[0007] The first diversion component is used to divert the energy storage fluid output from the third-stage pressure storage tank to obtain a first stream flowing to the first-stage pressure storage tank and a second stream flowing to the second-stage pressure storage tank, and to adjust the ratio of the first stream and the second stream according to the power demand of the user's power system.

[0008] The first energy conversion device is disposed on the path from the first diversion component to the first-stage pressure storage tank, and the first energy conversion device is connected to the second-stage pressure storage tank. The first energy conversion device is used to convert the pressure energy released by the first stream into energy to supply power to the user's power system.

[0009] The second energy conversion device is installed in the passage from the third-stage pressure storage tank to the first diversion component, and is used to convert the pressure energy released by the energy storage fluid output from the third-stage pressure storage tank into energy to supply power to the user's power system.

[0010] The energy storage system further includes at least one heat exchange device, each heat exchange device having two non-interconnected channels. The two channels of each heat exchange device are connected in series in the first heat exchange circuit and the energy storage circuit, respectively. Each heat exchange device is used to exchange heat with fluids flowing in different circuits in the two channels of the heat exchange device.

[0011] Optionally, the system also includes:

[0012] The fourth-stage pressure storage tank is where the energy storage fluid output from the third-stage pressure storage tank is pressurized by renewable energy and then flows to the fourth-stage pressure storage tank.

[0013] The second diversion component is used to divert the energy storage fluid output from the fourth-stage pressure storage tank to obtain a third stream flowing to the third-stage pressure storage tank and a fourth stream flowing to the second energy conversion device, and to adjust the ratio of the third stream and the fourth stream according to the power demand of the user's power system.

[0014] The third energy conversion device is installed in the passage from the fourth-stage pressure tank to the second diversion component, and is used to convert the pressure energy released by the energy storage fluid output from the fourth-stage pressure tank into energy to supply power to the user's power system.

[0015] Optionally, the first heat exchange circuit includes a heat collection device for collecting thermal energy; the at least one heat exchange device includes at least one heating device for heating the energy storage fluid using the thermal energy provided by the heat collection device, and the channels of each heating device connected in series in the energy storage circuit are arranged on the path flowing into any energy conversion device.

[0016] Optionally, the first heat exchange circuit may further include a buried heat storage device for recovering the heat energy.

[0017] Optionally, the heat collection device includes a solar heat collection device and / or a geothermal heat collection device.

[0018] Optionally, the energy storage system further includes a second heat exchange circuit, which includes a cold collection device for collecting cold energy; the at least one heat exchange device includes at least one cooling device for cooling the energy storage fluid using the cold energy provided by the cold collection device, and the channel of each cooling device connected in series in the energy storage circuit is arranged on the path flowing out from any energy conversion device.

[0019] Optionally, the energy storage circuit further includes:

[0020] Multiple regenerative devices are provided, each including two non-interconnected channels. Both channels in each regenerative device are connected in series in the energy storage circuit. The flow direction of one channel in each regenerative device is from the Nth-level pressure storage tank to the (N-1)th energy conversion device, and the flow direction of the other channel in each regenerative device is from the (N-1)th-level pressure storage tank to the (N-1)th energy conversion device, where N is a positive integer greater than 1.

[0021] Optionally, the renewable energy source is wind and solar power, and the energy storage system further includes:

[0022] Multiple wind and solar power hydraulic pumps are provided, each of which is installed on the output path of each pressure tank except for the highest pressure tank, for pressurizing the energy storage fluid based on wind and solar power.

[0023] Optionally, the energy storage system further includes:

[0024] Throttling valves are installed on the output passages of each storage tank, and each throttling valve is used to regulate the pressure of the energy storage fluid output from the corresponding storage tank.

[0025] This application also provides a control method for an energy storage system, which is applied to an energy storage system provided by any technical solution of this application. The method includes:

[0026] The ratio of the two current streams flowing out from each branch component is determined based on the electricity demand of the user's power system.

[0027] Each of the current splitting components is controlled to adjust according to the determined ratio.

[0028] Based on the above embodiments, this application has at least the following beneficial effects or advantages:

[0029] The energy storage system includes an energy storage circuit through which energy storage fluid flows and a first heat exchange circuit through which heat exchange fluid flows. The energy storage circuit is equipped with a first energy conversion device, a second energy conversion device, a first diversion component, a first-stage pressure tank, a second-stage pressure tank, and a third-stage pressure tank, all connected in series. The energy storage fluid output from the first-stage pressure tank is pressurized by renewable energy and flows to the second-stage pressure tank. The energy storage fluid output from the second-stage pressure tank is pressurized by renewable energy and flows to the third-stage pressure tank. The first diversion component is used to divert the energy storage fluid output from the third-stage pressure tank, resulting in a first stream flowing to the first-stage pressure tank and a second stream flowing to the second-stage pressure tank. The ratio of the first stream to the second stream is adjusted according to the electricity demand of the user's power system. The first energy conversion device is installed in the path from the first diversion component to the first-stage pressure storage tank, and is connected to the second-stage pressure storage tank. The first energy conversion device is used to convert the pressure energy released by the first stream into energy to supply power to the user's power system. The second energy conversion device is installed in the path from the third-stage pressure storage tank to the first diversion component, and is used to convert the pressure energy released by the energy storage fluid output from the third-stage pressure storage tank into energy to supply power to the user's power system. The energy storage system also includes at least one heat exchange device. Each heat exchange device includes two unconnected channels. The two channels of each heat exchange device are connected in series in the first heat exchange loop and the energy storage loop, respectively. Each heat exchange device is used to exchange heat with the fluids flowing in different loops in the two channels of the heat exchange device.

[0030] In this embodiment, the high-pressure energy storage fluid in the third-stage pressure tank is divided into a first stream and a second stream by a first diversion component. The first stream is used to perform work to supply power to the user's power system, while the second stream, which does not perform work, is recovered by the second-stage pressure tank. The ratio of the first stream to the second stream is adjusted according to the user's power system requirements, thereby improving the energy utilization efficiency of the energy storage system.

[0031] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0032] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0033] Figure 1 This is a schematic diagram of the structure of an energy storage system according to an embodiment of this application. Figure 1 ;

[0034] Figure 2 This is a schematic diagram of the structure of an energy storage system according to an embodiment of this application. Figure 2 ;

[0035] Figure 3 This is a schematic diagram of the structure of a first heat exchange circuit in an energy storage system according to an embodiment of this application;

[0036] Figure 4 This is a schematic diagram of the structure of a second heat exchange loop in an energy storage system according to an embodiment of this application;

[0037] Figure 5 This is a schematic diagram of the structure of an energy storage system in mode one of the energy release phase according to an embodiment of this application;

[0038] Figure 6 This is a schematic diagram of the structure of an energy storage system in mode two of the energy release phase according to an embodiment of this application;

[0039] Figure 7 This is a schematic diagram of the structure of an energy storage system in mode three of the energy release phase according to an embodiment of this application;

[0040] Figure 8 This is a schematic diagram of the structure of an energy storage system in mode four of the energy release phase according to an embodiment of this application;

[0041] Figure 9 This is a schematic diagram of the structure of an energy storage system in mode five of the energy release phase according to an embodiment of this application;

[0042] Figure 10 This is a schematic diagram of the structure of an energy storage system in mode one of the energy storage stages according to an embodiment of this application;

[0043] Figure 11 This is a schematic diagram of the structure of an energy storage system in mode two of the energy storage stage according to an embodiment of this application;

[0044] Figure 12 This is a schematic diagram of the structure of an energy storage system in mode three of the energy storage stage according to an embodiment of this application.

[0045] The following is a list represented by some of the labels in the attached diagram:

[0046] 101. Third-stage pressure storage tank; 102. Throttling valve of the third-stage pressure storage tank; 103. Second-stage preheater; 104. Second-stage regenerator; 105. Second-stage heater; 106. Second energy conversion device; 107. First diversion assembly; 1071. First three-way valve; 1072. Second three-way valve; 108. First-stage reheater; 109. First energy conversion device; 110. First-stage regenerator; 111. First-stage cooler; 112. Cold storage unit; 113. First-stage pressure storage tank; 114. Throttling valve of the first-stage pressure storage tank; 115. First-stage heater; 116. First-stage hydraulic pump; 117. First-stage preheater; 118. Second-stage pressure storage tank; 119. First throttling valve of the second-stage pressure storage tank; 120. Second-stage... Cooler, 121. Second throttle valve of the second-stage pressure storage tank, 122. Buried pipe heat exchanger, 123. Second-stage hydraulic pump, 124. Solar collector unit, 125. Heat storage unit, 127. Third-stage hydraulic pump, 128. Fourth-stage pressure storage tank, 129. Throttling valve of the fourth-stage pressure storage tank, 130. Third-stage preheater, 131. Third-stage regenerator, 132. Third-stage heater, 133. Third energy conversion device, 134. Second diversion assembly, 1341. Third three-way valve, 1342. Fourth three-way valve, 135. Second-stage reheater, 136. Third-stage cooler, 137. Water tank, 138. First buried heat storage device, 139. Second buried heat storage device, 140. Third buried heat storage device, 141. External cold source. Detailed Implementation

[0047] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0048] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0049] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0050] This application provides an energy storage system, referring to... Figure 1 The energy storage system includes an energy storage loop through which an energy storage fluid flows and a first heat exchange loop through which a heat exchange fluid flows. The energy storage fluid flows along... Figure 1 The solid line with an arrow indicates the direction of flow. The energy storage fluid is a fluid that stores energy under pressure. It can be a liquid, a gas, or a medium in a critical or supercritical state. Optionally, the energy storage fluid can be carbon dioxide. Depending on the temperature and pressure, the carbon dioxide may be in different stages of liquid, gas, or supercritical state in different parts of the energy storage circuit.

[0051] The energy storage circuit is equipped with a first energy conversion device 109, a second energy conversion device 106, a first diversion component 107, a first-stage pressure storage tank 113, a second-stage pressure storage tank 118, and a third-stage pressure storage tank 101 that are connected to each other.

[0052] The energy storage fluid output from the first-stage pressure storage tank 113, after being pressurized by renewable energy, flows to the second-stage pressure storage tank 118. The energy storage fluid output from the second-stage pressure storage tank 118, after being pressurized by renewable energy, flows to the third-stage pressure storage tank 101. Optionally, the pressurization module can be a hydraulic pump, and the renewable energy source can be wind energy and / or solar energy. After the renewable energy is converted into electrical energy, it drives the hydraulic pump to pressurize the energy storage fluid. By using renewable energy to pressurize the energy storage fluid, renewable green energy can be converted into pressure energy, and the renewable energy can be stored by storing the pressure energy of the energy storage fluid, thereby improving the environmental protection effect of the energy storage system. It is understood that, in addition to the above three-stage pressure storage tanks, the energy storage system provided in this embodiment of the invention can also be equipped with more stages of pressure storage tanks, for example, referring to... Figure 2 The energy storage system may also include a fourth-stage pressure tank 128, wherein the energy storage fluid output from the third-stage pressure tank 101 is pressurized by renewable energy and then flows to the fourth-stage pressure tank 128.

[0053] For example, the device for pressurizing the energy storage fluid in this energy storage system could be a wind and solar power hydraulic pump, with each pump installed on the output path of each pressure tank except the highest-pressure tank, for pressurizing the energy storage fluid based on wind and solar power. (Reference) Figure 1 The energy storage system may include a first-stage hydraulic pump 116 and a second-stage hydraulic pump 123. (Reference) Figure 2 The energy storage system may also include a third-stage hydraulic pump 127.

[0054] The pressures of the third-stage pressure storage tank 101, the second-stage pressure storage tank 118, and the first-stage pressure storage tank 113 decrease sequentially, corresponding to a high-pressure storage tank, a medium-pressure storage tank, and a low-pressure storage tank, respectively. The specific pressure values ​​of each storage tank can be designed according to actual conditions, and this embodiment does not impose any limitations on this. By using renewable energy to provide pressure to the energy storage fluid output from the low-pressure and medium-pressure storage tanks, renewable energy can be converted into pressure energy of the energy storage fluid, which can then be stored. When there is a power demand in the user's power system, the pressure energy can be converted into electrical energy.

[0055] Alternatively, the conversion process can involve first converting pressure energy into mechanical energy, and then converting the mechanical energy into electrical energy. For example, the pressure energy of the energy storage fluid can be converted into mechanical energy by a pneumatic turbine, and then into electrical energy by a generator.

[0056] The first energy conversion device 109 is disposed in the passage from the first diversion component 107 to the first-stage pressure storage tank 113, and is connected to the second-stage pressure storage tank 118. The first energy conversion device 109 is used to convert the pressure energy released by the first stream into energy to supply power to the user's power system. The first energy conversion device 109 can be a turbine device, used to convert the pressure energy of the energy storage fluid into mechanical energy, which can then be used to do work and convert it into electrical energy to supply power to the user's power system. For example, the turbine device can be a steam turbine, an expander, etc.

[0057] The first diversion component 107 is used to divert the energy storage fluid output from the third-stage pressure storage tank 101, resulting in a first stream flowing to the first-stage pressure storage tank 113 and a second stream flowing to the second-stage pressure storage tank 118. The ratio of the first and second streams is adjusted according to the electricity demand of the user's power system. The first stream performs work to supply power to the user's power system through the first energy conversion device 109, while the second stream, which does not perform work, is recovered through the second-stage pressure storage tank 118. This reduces energy waste from collected renewable energy and improves the energy utilization efficiency of the energy storage system by recovering unused pressure energy into the second-stage pressure storage tank 118. Furthermore, this embodiment does not require adjustment of the flow rate at the outlet of the third-stage pressure storage tank 101, allowing the output of the third-stage pressure storage tank 101 to remain stable. Energy storage fluid is delivered externally at a constant flow rate, and the first diversion component 107 adjusts the ratio of the first and second streams according to the peak and valley conditions of the user's power system. (Reference) Figure 1 The first diversion component 107 may include a first three-way valve 1071 and a second three-way valve 1072.

[0058] The second energy conversion device 106 is installed in the flow path from the third-stage pressure storage tank 101 to the first diversion assembly 107, and is used to convert the pressure energy released by the energy storage fluid output from the third-stage pressure storage tank 101 into energy to supply power to the user's power system. By installing two energy conversion devices at the outlet of the third-stage pressure storage tank 101 and the outlet of the first stream of the first diversion assembly 107, the pressure energy of the energy storage fluid can be fully converted, effectively improving the energy release and the pressure energy conversion efficiency.

[0059] The energy storage system also includes at least one heat exchange device. Each heat exchange device includes two channels that are not connected to each other. The two channels of each heat exchange device are connected in series in a first heat exchange loop and an energy storage loop, respectively. The channel connected in series in the first heat exchange loop carries heat exchange fluid, and the channel connected in series in the energy storage loop carries energy storage fluid. Each heat exchange device is used to exchange heat with the fluids in the different loops flowing in the two channels of the heat exchange device.

[0060] It is understood that, in the case where the energy storage system provided in this embodiment of the invention further includes a fourth-stage pressure tank, it also includes the following components: a second diversion assembly 134, used to divert the energy storage fluid output from the fourth-stage pressure tank 128 to obtain a third stream flowing to the third-stage pressure tank 101 and a fourth stream flowing to the second energy conversion device 106, and to adjust the ratio of the third stream and the fourth stream according to the power demand of the user's power system. (Reference) Figure 2 The second diversion assembly 134 may include a third three-way valve 1341 and a fourth three-way valve 1342.

[0061] The third energy conversion device 133 is installed in the passage from the fourth-stage pressure tank 128 to the second diversion component 134, and is used to convert the pressure energy released by the energy storage fluid output from the fourth-stage pressure tank 128 into energy to supply power to the user's power system.

[0062] Similarly, embodiments of the present invention can also include more levels of pressure storage tanks, which cannot all be listed here. By adding multiple levels of pressure storage tanks, more detailed differences can be created for the storage, utilization, and recovery of energy, thereby significantly improving energy efficiency.

[0063] Optionally, the energy storage system also includes throttle valves installed on the output paths of each storage tank. Each throttle valve is used to regulate the pressure of the energy storage fluid output from the corresponding storage tank, as shown in the reference diagram. Figure 1 and Figure 2 Throttling valves for various levels of pressure storage tanks. Throttling valves are used to stabilize the pressure of the energy storage fluid output from each pressure storage tank, thereby improving the pressure stability of the energy storage fluid output from the pressure storage tank and enhancing the pressure balance capability of the entire energy storage loop. (Reference) Figure 3 It also includes the throttle valve 129 for the fourth-stage pressure storage tank.

[0064] Optionally, the energy storage loop may further include: multiple regenerative devices, each regenerative device including two non-interconnected channels, both channels of each regenerative device being connected in series in the energy storage loop, one channel of each regenerative device flowing from the Nth-stage pressure tank to the (N-1)th energy conversion device, and the other channel of each regenerative device flowing from the (N-1)th-stage pressure tank to the (N-1)th energy conversion device, where N is a positive integer greater than 1. (Reference) Figure 1 Multiple regenerative devices include a first-stage regenerator 110 and a second-stage regenerator 104. (Reference) Figure 2 Multiple regeneration devices may also include a third-stage regenerator 131.

[0065] The heat recovery device can recover the heat of the energy storage fluid flowing out of each energy conversion device and use this heat energy to heat the energy storage fluid flowing into the energy conversion device, thereby making full use of the thermal energy of the energy storage fluid and improving the thermal energy utilization efficiency.

[0066] Optionally, the first heat exchange loop may include a heat collection device for collecting heat energy, such as solar energy or geothermal energy. At least one heat exchange device includes at least one heating device for heating the energy storage fluid using the heat energy provided by the heat collection device, and the channels of each heating device connected in series in the energy storage loop are arranged in the path flowing into any energy conversion device. Optionally, refer to... Figure 1 The heating device in the first heat exchange circuit may include a first-stage heater 115 and a second-stage heater 105. Optionally, the heat collection device includes a solar heat collection device and / or a geothermal heat collection device. Figure 1 The solar collector is a solar collector unit 124. The solar collector unit 124 converts solar energy into thermal energy for the heat exchange fluid. Using the green energy collected by the solar collector unit 124 to heat the energy storage fluid can improve the environmental performance of the energy storage system. (Reference) Figure 2 For the added fourth-stage pressure storage tank 128, the heating device in the first heat exchange circuit may also include a third-stage heater 132.

[0067] Further, refer to Figure 1 The heating device in the first heat exchange loop may further include a first-stage preheater 117 and a second-stage preheater 103. Taking the second-stage preheater 103 as an example, its function is illustrated: the second-stage preheater 103 can increase the temperature of the energy storage fluid output from the third-stage pressure storage tank 101, which facilitates the conversion of the liquid energy storage fluid output from the third-stage pressure storage tank 101 into a supercritical or gaseous energy storage fluid. This allows subsequent energy conversion devices to utilize the pressure energy of the energy storage fluid to perform work, thus improving the energy conversion efficiency of the energy conversion devices. (Reference) Figure 2For the added fourth-stage pressure storage tank 128, the heating device in the first heat exchange circuit may also include a third-stage preheater 130.

[0068] Optionally, at least one heating device may further include a reheating device. (Reference) Figure 1 The reheating device includes a first-stage reheater 108, disposed in the passage flowing into the first energy conversion device 109, to heat the energy storage fluid flowing into the first energy conversion device 109. (Reference) Figure 2 The reheating device may further include a second-stage reheater 135, disposed in the passage flowing into the second energy conversion device 106, to heat the energy storage fluid flowing into the second energy conversion device 106. The reheating device can improve the energy conversion efficiency of the energy conversion device.

[0069] Optionally, the first heat exchange circuit also includes a buried heat storage device for recovering heat energy and storing excess heat energy in the first heat exchange circuit.

[0070] Optionally, the energy storage system may further include a second heat exchange loop, which is disconnected from the first heat exchange loop. The heat exchange fluid in the second heat exchange loop serves as a cold source for cooling the energy storage fluid in the energy storage loop. The second heat exchange loop includes a cold energy collection device for collecting cold energy; the cold energy collection device can collect cold energy, for example, the cold energy of air, water, or liquefied natural gas from a building. At least one heat exchange device includes at least one cooling device that uses the cold energy provided by the cold energy collection device to cool the energy storage fluid. The channels of each cooling device connected in series in the energy storage loop are arranged on the path flowing out from any energy conversion device. (Reference) Figure 1 The cooling system includes a first-stage cooler 111 and a second-stage cooler 120, as shown in the reference. Figure 2 The cooling device may also include a third-stage cooler 136. The cold energy collected by the cooling device can be used to cool the energy storage fluid as it passes through the cooling device before being recovered in the energy storage loop, thereby compressing the volume of the energy storage fluid, increasing its pressure, and improving the efficiency of the energy storage fluid in storing pressure energy. Taking the second-stage cooler 120 as an example, the effect of the cooler in cooling the energy storage fluid helps to convert gaseous or supercritical energy storage fluid back to a liquid state, thereby improving the energy storage efficiency of the second-stage pressure tank 118.

[0071] The temperature of the energy storage fluid flowing through the first heat exchange circuit can be adjusted, enabling control over the switching between different states of the energy storage fluid, such as gas, liquid, and supercritical. By specifying the location of the heat exchange device in the energy storage circuit, the temperature of the energy storage fluid can be regulated, thereby improving the efficiency of energy release and storage.

[0072] refer to Figure 3 This is an embodiment of the present invention. Figure 2 This embodiment provides a specific implementation of a first heat exchange circuit in an energy storage system. The first heat exchange circuit is... Figure 3 The loop shown by the dashed line has the heat exchange fluid flowing along... Figure 3 The flow is indicated by the dashed line with an arrow. The first heat exchange loop is equivalent to the circulation of the heat storage unit 125. The first heat exchange loop includes, as shown in the image. Figure 3 The system comprises three circuits. The first heat exchange circuit includes multiple buried heat storage devices: a first buried heat storage device 138, a second buried heat storage device 139, and a third buried heat storage device 140. The three circuits are described below:

[0073] refer to Figure 3 The first loop includes: after the heat storage unit 125 collects heat from the solar collector unit 124, it releases a working medium (water, oil, or other) to the third-stage heater 132 as a heat source. After the working medium undergoes a first cooling, optionally, excess heat can be stored in the first buried heat storage device 138, where the working medium undergoes a second cooling. Then, it passes through the second-stage heater 105, serving as the heat source for the second-stage heater 105, where the working medium undergoes a third cooling. Optionally, excess heat is stored in the first buried heat storage device 138, where the working medium undergoes a fourth cooling. Subsequently, it passes through the first-stage heater 115, serving as the heat source for the first-stage heater, and finally, the remaining heat is stored in the soil through the first buried heat storage device 138, and finally returns to the solar collector unit 124 for heating. In this loop, the buried heat storage device is in the heat storage process.

[0074] refer to Figure 3 The second loop includes: the working medium in a storage tank (specifically, water tank 137) for storing the working medium (i.e., heat exchange fluid, which can be water or other fluids). After entering the second buried heat storage device 139, the working medium is heated for the first time, enters the third-stage preheater 130 as a heat source, and is cooled for the first time. Then it enters the second buried heat storage device 139, where it is heated for the second time; then it enters the second-stage preheater 103 as a heat source, where it is cooled for the second time; then it enters the second buried heat storage device 139 again, where it is heated for the third time; finally, it enters the first-stage preheater as a heat source, where it is cooled for the third time, and finally returns to the water tank 137. This buried heat storage device is in a heat release process.

[0075] refer to Figure 3 The third loop includes: after the heat storage unit 125 collects heat from the solar collector unit 124, it releases a working medium (water, oil, or other) which passes through the second-stage reheater 135 and the first-stage reheater 108 as a heat source; optionally, it then enters the third buried heat storage device 140 to store excess heat in the soil, and finally returns to the solar collector unit 124 for heating. This buried heat storage device in the loop is in the heat storage process.

[0076] It should be noted that: after the first buried heat storage device 138 has stored heat for a certain period of time or is close to saturation, or after the second buried heat storage device 139 has released heat for a certain period of time or is close to saturation, the first buried heat storage device 138 and the second buried heat storage device 139 need to be exchanged. That is, the first buried heat storage device 138 is connected to loop two, the second buried heat storage device 139 is connected to loop one, and the third buried heat storage device 140 can be used as a backup heat source to provide heat to loop one or other components that need heat, such as heat pumps.

[0077] refer to Figure 4 This is the second heat exchange loop in this embodiment of the invention. The heat exchange fluid flows in the direction of the dashed arrow. The second heat exchange loop can be a cold source loop. The cold storage unit 112 releases the working medium (i.e., the heat exchange fluid), which passes through the first-stage cooler 111, the second-stage cooler 120, and the third-stage cooler 136 successively, serving as a cold source for cooling the energy storage fluid. After the working medium is heated, it can be cooled by an external cold source 141 and then stored in the cold storage unit 112.

[0078] The following is for reference. Figure 1 The technical solution for the application of the energy storage system provided in this embodiment in a specific application scenario is described in detail.

[0079] With increasing industrialization and rapid economic development, global energy demand is surging, leading to excessive emissions of the greenhouse gas carbon dioxide. To address the environmental problems caused by excessive carbon dioxide emissions, the global energy structure is shifting towards cleaner energy sources. However, renewable energy sources such as wind and solar power are intermittent, meaning that excess electricity they generate may go unused. Furthermore, due to the inherent characteristics of renewable energy and the mismatch between renewable energy generation and user power systems, the curtailment rate of green electricity is high, with only a portion of renewable energy generation reaching end-users. Therefore, the application of energy storage technology is an effective solution to these problems.

[0080] Currently, several mature energy storage technologies have been put into commercial application, such as pumped hydro storage and compressed gas storage. Pumped hydro storage has higher energy storage efficiency than compressed gas storage, but its application is limited by geographical constraints. Compressed gas storage currently includes two types: compressed air storage and compressed carbon dioxide storage. Both generally suffer from low energy density. However, carbon dioxide's excellent thermophysical properties and relatively suitable critical point make it easier to achieve supercritical or liquid storage than air. Therefore, compressed energy storage systems using carbon dioxide as the working fluid have higher energy density than systems using air. Current research on liquid carbon dioxide energy storage systems mainly focuses on designing better system cycles and evaluating system performance from economic and thermodynamic perspectives. Few studies address the coupling of liquid carbon dioxide energy storage with renewable energy sources and the energy storage and release regulation issues of liquid carbon dioxide energy storage systems.

[0081] This embodiment provides an energy storage system utilizing liquid carbon dioxide. The system includes a liquid carbon dioxide energy storage and release unit, a solar thermal collector unit 124, a heat storage unit 125, a soil-source heat storage unit 125, and a cold storage unit 112. Aiming to optimize the energy storage system's circulation, the system provides a new peak-shaving strategy for user power systems by adding an intermediate-stage pressure tank. Furthermore, it achieves multi-stage compression and expansion of liquid carbon dioxide. The use of a photoelectric hydraulic pump in the energy storage system reduces heat transfer losses during vaporization when the liquid carbon dioxide energy storage system releases energy. Simultaneously, the solar thermal collector unit 124, heat storage unit 125, cold storage unit 112, and soil-source heat storage unit 125 provide corresponding thermal energy (including both heat and cold energy) to the liquid carbon dioxide energy storage and release unit, achieving the purpose of heat and cold storage. Through the cascade utilization of thermal energy, the thermal energy utilization efficiency of the energy storage system is improved.

[0082] The following is about Figure 1 The operation and control methods of the energy storage system, including the three-stage pressure storage tank, are explained. During the energy release phase, including... Figures 5-9 The five operating modes shown, in the energy storage phase, include Figures 10-12 The three working modes are shown.

[0083] refer to Figure 5 Energy release phase mode one:

[0084] The third-stage pressure storage tank 101 releases liquid energy storage medium, which passes through the second-stage preheater 103, the second-stage regenerator 104, and the second-stage heater 105 in sequence via pipelines. After being heated and vaporized to a gaseous or supercritical state, it then enters the steam turbine (equivalent to the second energy conversion device 106) to do work, and then enters the second-stage regenerator 104 and the second-stage cooler 120 to be cooled into a liquid state before entering the second-stage pressure storage tank 118.

[0085] refer to Figure 6 Energy release phase mode two:

[0086] The energy storage medium released from the third-stage pressure storage tank 101 passes through pipelines sequentially through the second-stage preheater 103, the second-stage regenerator 104, and the second-stage heater 105, where it is vaporized to a gaseous or supercritical state. After performing work in the turbine, it enters the diversion valve (first three-way valve 1071). One stream from the diversion valve passes through the second-stage regenerator 104 and the second-stage cooler 120, where it is cooled to a liquid state before entering the second-stage pressure storage tank 118 for storage. The other stream from the diversion valve is heated by the first-stage reheater 108 and then enters the expander (equivalent to the first energy conversion device 109). After performing work, it is liquefied by the second-stage cooler 120 before entering the first-stage pressure storage tank 113 for storage. The ratio of the flow to the second-stage pressure storage tank 118 to the first-stage pressure storage tank 113 is adjusted according to the user's electricity demand.

[0087] refer to Figure 7 Energy release phase mode three:

[0088] The energy storage medium released from the third-stage pressure tank 101 passes through the pipeline sequentially through the second-stage preheater 103, the second-stage regenerator 104, and the second-stage heater 105 to vaporize into a gaseous or supercritical state, enters the steam turbine to do work, is then heated in the first-stage reheater 108 and enters the expander to do work, and then passes through the second-stage regenerator 104 and the first-stage cooler 111 to cool into a liquid state before entering the first-stage pressure tank 113.

[0089] refer to Figure 8 Energy release phase mode four:

[0090] The energy storage medium released from the third-stage pressure storage tank 101 is vaporized to a gaseous or supercritical state through pipelines, passing sequentially through the second-stage preheater 103, the second-stage regenerator 104, and the second-stage heater 105, and then enters the steam turbine to perform work. At the same time, the energy storage medium released from the second-stage pressure storage tank 118 is vaporized to a gaseous or supercritical state through pipelines, passing sequentially through the first-stage preheater 117, the first-stage regenerator 110, and the first-stage heater 115, and then enters the diversion valve. After mixing with the energy storage medium released from the third-stage pressure storage tank 101 in the diversion valve, it is heated by the first-stage reheater 108 and then enters the expander to perform work. The stream from the expander outlet passes sequentially through the second-stage regenerator 104, the first-stage regenerator 110, and the first-stage cooler 111, and is cooled to a liquid state before entering the first-stage pressure storage tank 113 for storage.

[0091] refer to Figure 9 Energy release phase mode five:

[0092] The energy storage medium released from the second-stage pressure storage tank 118 passes through the first-stage preheater 117, the first-stage regenerator 110, and the first-stage heater 115 in sequence via pipelines to vaporize into a gaseous or supercritical state. After being heated by the first-stage reheater 108, it enters the expander to do work. The stream from the expander outlet passes through the first-stage regenerator 110 and the first-stage cooler 111 in sequence, and is cooled into a liquid state before entering the first-stage pressure storage tank 113 for storage.

[0093] refer to Figure 10 Energy storage stage mode 1: After the energy storage medium is released from the first-stage pressure storage tank 113 and passes through the throttle valve 114 of the first-stage pressure storage tank 113, it enters the first-stage hydraulic pump 116. The first-stage hydraulic pump 116 is driven by excess wind and solar power to pressurize the energy storage medium and then enter the second-stage pressure storage tank 118 for storage.

[0094] refer to Figure 11 Energy storage stage mode 2: The energy storage medium released from the second-stage pressure storage tank 118 enters the second-stage hydraulic pump 123 after passing through the throttle valve of the second-stage pressure storage tank 118. The excess wind and solar power drive the second-stage hydraulic pump 123 to pressurize the energy storage medium and then enter the third-stage pressure storage tank 101 for storage.

[0095] refer to Figure 12 Energy storage stage mode 3: The energy storage medium released from the first-stage pressure storage tank 113 enters the first-stage hydraulic pump 116 after passing through the throttle valve 114 of the first-stage pressure storage tank 113. The first-stage hydraulic pump 116 is driven by excess wind and solar power to pressurize the energy storage medium. After being pressurized by the second-stage hydraulic pump 123, it enters the third-stage pressure storage tank 101 for storage.

[0096] Furthermore, on Figure 1 The structure and working principle of the energy storage system shown are explained in detail:

[0097] refer to Figure 1 The aforementioned liquid carbon dioxide energy storage and release unit includes: a third-stage pressure storage tank 101, a throttle valve 102 of the third-stage pressure storage tank 101, a second energy conversion device 106 (specifically, a steam turbine), a first diversion component 107 (specifically, a three-way valve), a first energy conversion device 109 (specifically, an expander), a first-stage pressure storage tank 113, a throttle valve 114 of the first-stage pressure storage tank 113, a first-stage hydraulic pump 116, a second-stage pressure storage tank 118, a first throttle valve 119 of the second-stage pressure storage tank 118, a second throttle valve 121 of the second-stage pressure storage tank 118, and a second-stage hydraulic pump 123.

[0098] The energy storage system also includes a high-pressure carbon dioxide vaporization heating unit, specifically comprising a second-stage preheater 103 and a third-stage heater 132. The energy storage system also includes a medium-pressure carbon dioxide vaporization heating unit, specifically comprising a first-stage preheater 117 and a second-stage heater 105.

[0099] Figure 1 The specific connection relationships of the components in the energy storage system shown are as follows:

[0100] The outlet of the third-stage pressure storage tank 101 is connected via pipelines sequentially through the high-pressure storage tank throttle valve, the low-temperature side of the second-stage preheater 103, the low-temperature side of the second-stage regenerator 104, the low-temperature side of the third-stage heater 132, the second energy conversion device 106, and the first diversion assembly 107. One stream from the first diversion assembly 107 is connected via pipelines sequentially through the high-temperature side of the second-stage regenerator 104 and the high-temperature side of the second-stage cooler 120 to the inlet of the second-stage pressure storage tank 118. The outlet of the second-stage pressure storage tank 118 is connected via pipelines sequentially through the first throttle valve 119 of the second-stage pressure storage tank 118, the low-temperature side of the first-stage preheater 117, the low-temperature side of the first-stage regenerator 110, and the low-temperature side of the second-stage heater 105 to mix with the other stream from the first diversion assembly 107. After mixing, the stream flows sequentially through pipelines to the low-temperature side of the reheater, the first energy conversion device 109, the high-temperature side of the first-stage regenerator 110, and the high-temperature side of the first-stage cooler 111, connecting to the inlet of the first-stage pressure storage tank 113. The outlet of the first-stage pressure storage tank 113 is connected sequentially through pipelines to the throttle valve 114 of the first-stage pressure storage tank 113 and the first-stage hydraulic pump 116, connecting to the other inlet of the second-stage pressure storage tank 118. The other outlet of the second-stage pressure storage tank 118 is connected sequentially through pipelines to the second throttle valve 121 of the second-stage pressure storage tank 118 and the second-stage hydraulic pump 123, connecting to the inlet of the third-stage pressure storage tank 101. By adding a second-stage pressure storage tank 118 between the third-stage pressure storage tank 101 and the first-stage pressure storage tank 113, the energy storage and release can be regulated through the flow distribution of the first diversion component 107. Optionally, the third-stage pressure storage tank 101 can reach the minimum rated pressure during each energy release.

[0101] The energy storage system also includes a shallow geothermal utilization unit, specifically comprising: a buried pipe heat exchanger 122, wherein the buried pipe heat exchanger 122 is composed of multiple buried pipes connected in series. The outlet of the cold storage unit 112 is connected to the first-stage cooler 111 via a pipeline. The outlet of the solar collector unit 124 is connected to the heat storage unit 125 via a pipeline. One stream from the outlet of the heat storage unit 125 is connected to the inlet of the solar collector unit 124 via a pipeline, passing sequentially through the high-temperature side of the third-stage heater 132, the high-temperature side of the second-stage preheater 103, the buried pipe heat exchanger 122, the low-temperature side of the second-stage cooler 120, the high-temperature side of the second-stage heater 105, and the high-temperature side of the first-stage preheater 117. The other stream from the outlet of the heat storage unit 125 is connected to the inlet of the solar collector unit 124 via a pipeline, passing through the high-temperature side of the reheater. The solar thermal collector 124 collects solar heat and stores it in the heat storage unit 125. After releasing heat to the third-stage carbon dioxide vaporization heating unit, it is connected to the buried pipe heat exchanger 122. The heat exchange medium at the outlet of the solar thermal collector 124 enters the heat storage unit 125. The heat exchange medium at the outlet of the heat storage unit 125 passes through pipelines sequentially through the high-temperature side of the third-stage heater 132, the high-temperature side of the second-stage preheater 103, the buried pipe heat exchanger 122, the second-stage cooler 120, the second-stage heater 105, and the first-stage preheater 117, and is connected to the solar thermal collector 124 to form a loop. The heat exchange medium at the outlet of the heat storage unit 125 passes through pipelines through a reheater and is connected to the solar thermal collector 124 to form a second loop.

[0102] The working principle and specific operation process of the energy storage system provided in this embodiment are as follows:

[0103] During the energy storage phase, only the liquid carbon dioxide energy storage and release system unit, which includes multi-stage pressure storage tanks, is operational. This is divided into two operating conditions: a sufficient photovoltaic (PV) supply condition and a insufficient PV supply condition.

[0104] When the photoelectric sensor is fully operational, the outlet of the first-stage pressure storage tank 113 provides low-temperature, low-pressure liquid carbon dioxide. After passing through the throttle valve 114 of the first-stage pressure storage tank 113 to a stable pressure, it enters the first-stage hydraulic pump 116. Driven by the photoelectric sensor, the first-stage hydraulic pump 116 pressurizes the liquid carbon dioxide to a low-temperature, medium-pressure state and then it enters the second-stage pressure storage tank 118 until the first-stage pressure storage tank 113 reaches its rated minimum pressure. Simultaneously, the outlet of the second-stage pressure storage tank 118 provides low-temperature, medium-pressure liquid carbon dioxide. After passing through the second throttle valve 121 of the second-stage pressure storage tank 118 to a stable pressure, it enters the second-stage hydraulic pump 123. Driven by the photoelectric sensor, the second-stage hydraulic pump 123 pressurizes the liquid carbon dioxide to a low-temperature, high-pressure state and then it enters the third-stage pressure storage tank 101 until the second-stage pressure storage tank 118 reaches its minimum rated pressure, while the third-stage pressure storage tank 101 reaches its maximum rated pressure.

[0105] When the photoelectric power is insufficient, the operating procedure is the same as when the photoelectric power is sufficient. The difference is that when the photoelectric power is insufficient, the first-stage hydraulic pump 116 is put into operation first, and the second-stage hydraulic pump 123 stops working. After ensuring that the second-stage pressure storage tank 118 reaches the maximum rated pressure, the first-stage hydraulic pump 116 and the second-stage hydraulic pump 123 work simultaneously.

[0106] During the energy release phase, the working cycle of the liquid carbon dioxide energy storage and release system unit, which includes multi-stage pressure storage tanks, is as follows: The third-stage pressure storage tank 101 provides high-pressure, low-temperature liquid carbon dioxide. After passing through the throttling valve of the high-pressure storage tank to a stable pressure, it absorbs heat from the heat transfer medium of the heat storage unit 125 on the low-temperature side of the second-stage preheater 103. Then, it recovers waste heat from the outlet of the second energy conversion device 106 on the low-temperature side of the second-stage regenerator 104. Finally, it passes through the third-stage heater 132 and is heated to a high-temperature supercritical state by the heat transfer medium of the heat storage unit 125. It then enters the second energy conversion device 106 to generate electricity. The medium-temperature, medium-pressure carbon dioxide gas at the outlet of the second energy conversion device 106 enters the first diversion assembly 107 and is divided into two streams. The second stream passes through the high-temperature side of the second-stage regenerator 104 via pipelines, then enters the high-temperature side of the second-stage cooler 120, and finally enters the second-stage pressure storage tank 118. The second stream, along with low-temperature, medium-pressure liquid carbon dioxide supplied by the second-stage pressure storage tank 118, is sequentially heated to medium-temperature, medium-pressure gaseous carbon dioxide via the low-temperature side of the first-stage preheater 117, the low-temperature side of the first-stage regenerator 110, and the low-temperature side of the second-stage heater 105 before being added to the first stream. The first stream, after being heated in the reheater, enters the first energy conversion device 109 to perform work. The flow rates of both streams are controlled by the user's electrical load; when the electrical load is high, more flow goes to the reheater. When the electrical load is low, more flow goes to the high-temperature side of the second-stage regenerator 104. The low-pressure carbon dioxide from the outlet of the first energy conversion device 109 then sequentially enters the high-temperature side of the first-stage regenerator 110 and the high-temperature side of the first-stage cooler 111 before entering the first-stage pressure storage tank 113, thus ending the energy release process.

[0107] After the solar collector unit 124 heats the heat transfer medium to a certain temperature, it is stored in the heat storage unit 125. During the energy release phase, the heat storage unit 125 releases the heat transfer medium. One stream flows through the pipeline into the high-temperature side of the third-stage heater 132, the high-temperature side of the second-stage preheater 103, the buried pipe heat exchanger 122, the second-stage cooler 120, the second-stage heater 105, and the first-stage preheater 117, and finally returns to the solar collector unit 124 to form a circulation loop one. The other stream enters the high-temperature side of the reheater and finally returns to the solar collector unit 124 to form a circulation loop two.

[0108] This embodiment proposes an energy storage system that can couple geothermal, solar thermal, wind and solar power, and utilize multi-stage liquid carbon dioxide pressure storage tanks for peak shaving. This energy storage system has the following characteristics:

[0109] 1. By using multiple storage tanks to regulate the storage and release power of the liquid carbon dioxide energy storage system, this method can make peak shaving more flexible, while keeping the output flow of the storage tanks stable, ensuring the thermodynamic performance of components such as compressors and turbines, and reducing the risk of equipment fatigue and damage.

[0110] 2. During energy release, the heat generated during liquefaction in the storage tank is recovered using a regenerator to improve energy efficiency;

[0111] 3. Multi-stage expansion with intermediate heating effectively increases energy release;

[0112] 4. Innovatively, the compressed energy storage system is coupled with wind, solar, solar thermal, and geothermal energy, which improves the utilization rate of renewable energy while reducing the heat exchange temperature difference and realizing the cascade utilization of energy.

[0113] Analysis of the above technical solutions and their characteristics shows that the energy storage system of this embodiment has at least the following beneficial technical effects: combining wind, solar, solar thermal, and shallow geothermal energy with liquid carbon dioxide energy storage system, reducing heat exchange losses through heat cascade utilization, improving the utilization rate of renewable energy, realizing the joint utilization of wind, solar, solar thermal, geothermal and energy storage, and proposing a new peak-shaving strategy for liquid carbon dioxide energy storage system by adding an intermediate pressure storage tank. This peak-shaving strategy can more flexibly control the pressure of the carbon dioxide storage tank.

[0114] The energy storage system provided in this embodiment can execute peak-shaving strategies based on the peak and valley conditions of the user's electricity system, regulating energy storage and release to reduce energy waste. Furthermore, the system's energy conversion efficiency is improved through a regenerative device, multi-stage expansion, and pre-expansion heating. While absorbing photovoltaic energy into pressure energy, the system also provides the necessary heat through the storage and utilization of solar and geothermal energy, reducing heat exchange temperature differences and improving heat utilization.

[0115] This application also provides a control method for an energy storage system. This method can be applied to control the energy storage system provided by any of the technical solutions in the above-described embodiments of this application. The method specifically includes the following steps:

[0116] Step 1: Determine the ratio of the two current streams flowing out from each branch component based on the user's power demand.

[0117] Step 2: Control each of the current splitting components to adjust according to the determined ratio.

[0118] This method can be applied to electronic devices, such as computers and processors. After execution, the electronic device outputs control signals to each shunt component to control each shunt component to adjust the shunt ratio.

[0119] For the parts of the control method for the energy storage system provided in this embodiment that are not described in detail, please refer to the relevant description of the energy storage system provided in the embodiment of this application, which will not be repeated here.

[0120] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0121] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0122] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

[0123] In this application specification and embodiments, any solutions involving the processing of personal information will be processed only under the premise of legality (such as obtaining the consent of the personal information subject, or being necessary for the performance of a contract), and will only be processed within the scope stipulated or agreed upon. A user's refusal to process personal information beyond that required for basic functions will not affect the user's use of basic functions.

Claims

1. An energy storage system, characterized in that, The energy storage system includes an energy storage circuit through which an energy storage fluid flows and a first heat exchange circuit through which a heat exchange fluid flows. The energy storage circuit is equipped with a first energy conversion device, a second energy conversion device, a first diversion component, a first-stage pressure tank, a second-stage pressure tank, and a third-stage pressure tank that are connected in series. The energy storage fluid output from the first-stage pressure tank is pressurized by renewable energy and then flows to the second-stage pressure tank. The energy storage fluid output from the second-stage pressure tank is pressurized by renewable energy and then flows to the third-stage pressure tank. The first diversion component is used to divert the energy storage fluid output from the third-stage pressure storage tank to obtain a first stream flowing to the first-stage pressure storage tank and a second stream flowing to the second-stage pressure storage tank, and to adjust the ratio of the first stream and the second stream according to the power demand of the user's power system. The first energy conversion device is disposed on the path from the first diversion component to the first-stage pressure storage tank, and the first energy conversion device is connected to the second-stage pressure storage tank. The first energy conversion device is used to convert the pressure energy released by the first stream into energy to supply power to the user's power system. The second energy conversion device is installed in the passage from the third-stage pressure storage tank to the first diversion component, and is used to convert the pressure energy released by the energy storage fluid output from the third-stage pressure storage tank into energy to supply power to the user's power system. The energy storage system further includes at least one heat exchange device, each heat exchange device having two non-interconnected channels. The two channels of each heat exchange device are connected in series in the first heat exchange circuit and the energy storage circuit, respectively. Each heat exchange device is used to exchange heat with fluids flowing in different circuits in the two channels of the heat exchange device.

2. The energy storage system according to claim 1, characterized in that, Also includes: The fourth-stage pressure storage tank is where the energy storage fluid output from the third-stage pressure storage tank is pressurized by renewable energy and then flows to the fourth-stage pressure storage tank. The second diversion component is used to divert the energy storage fluid output from the fourth-stage pressure storage tank to obtain a third stream flowing to the third-stage pressure storage tank and a fourth stream flowing to the second energy conversion device, and to adjust the ratio of the third stream and the fourth stream according to the power demand of the user's power system. The third energy conversion device is installed in the passage from the fourth-stage pressure tank to the second diversion component, and is used to convert the pressure energy released by the energy storage fluid output from the fourth-stage pressure tank into energy to supply power to the user's power system.

3. The energy storage system according to claim 1, characterized in that, The first heat exchange circuit includes a heat collection device for collecting heat energy; the at least one heat exchange device includes at least one heating device for heating the energy storage fluid using the heat energy provided by the heat collection device, and the channels of each heating device connected in series in the energy storage circuit are arranged on the path flowing into any energy conversion device.

4. The energy storage system according to claim 3, characterized in that, The first heat exchange circuit also includes a buried heat storage device for recovering the heat energy.

5. The energy storage system according to claim 3, characterized in that, The heat collection device includes a solar heat collection device and / or a geothermal heat collection device.

6. The energy storage system according to claim 1, characterized in that, The energy storage system further includes a second heat exchange circuit, which includes a cold collection device for collecting cold energy; the at least one heat exchange device includes at least one cooling device for cooling the energy storage fluid using the cold energy provided by the cold collection device, and the channels of each cooling device connected in series in the energy storage circuit are arranged on the path flowing out from any energy conversion device.

7. The energy storage system according to claim 1, characterized in that, The energy storage circuit also includes: Multiple regenerative devices are provided, each including two non-interconnected channels. Both channels in each regenerative device are connected in series in the energy storage circuit. The flow direction of one channel in each regenerative device is from the Nth-level pressure storage tank to the (N-1)th energy conversion device, and the flow direction of the other channel in each regenerative device is from the (N-1)th-level pressure storage tank to the (N-1)th energy conversion device, where N is a positive integer greater than 1.

8. The energy storage system according to claim 1, characterized in that, The renewable energy source is wind and solar power, and the energy storage system further includes: Multiple wind and solar power hydraulic pumps are provided, each of which is installed on the output path of each pressure tank except for the highest pressure tank, for pressurizing the energy storage fluid based on wind and solar power.

9. The energy storage system according to claim 1, characterized in that, The energy storage system also includes: Throttling valves are installed on the output passages of each storage tank, and each throttling valve is used to regulate the pressure of the energy storage fluid output from the corresponding storage tank.

10. A control method for an energy storage system, characterized in that, The method is applied to the energy storage system according to any one of claims 1-9, and the method includes: The ratio of the two current streams flowing out from each branch component is determined based on the electricity demand of the user's power system. Each of the current splitting components is controlled to adjust according to the determined ratio.

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