Efficient heat dissipation method and system for battery energy storage system

Abstract

The invention belongs to the technical field of battery heat dissipation, and discloses an efficient heat dissipation method and system for a battery energy storage system, and the method comprises the steps: determining a critical heat flux density which needs to be reached according to a temperature deviation value between the real-time temperature of a single cell and the optimal operation temperature; determining the target supply pressure of the liquid working medium according to the critical heat flux required to be reached, the function relationship between the critical heat flux and the temperature deviation value, and the function relationship between the supply pressure of the liquid working medium and the critical heat flux; a liquid working medium with target supply pressure is conveyed into the thin liquid film auxiliary phase change heat dissipation device, and the liquid working medium absorbs heat on the surfaces of all the single battery cells. The thin liquid film auxiliary phase change heat dissipation device is applied to heat dissipation of the battery energy storage system for the first time, efficient and accurate temperature control of the battery energy storage system is achieved, the accurate heat dissipation effect is achieved, and compared with a traditional heat dissipation scheme, the thin liquid film auxiliary phase change heat dissipation device has the advantages of being high in heat dissipation efficiency, low in energy consumption, small in occupied space, capable of improving the operation economical efficiency of an energy storage power station and the like.

Description

Technical Field

[0001] This invention belongs to the field of battery heat dissipation technology, and specifically relates to a high-efficiency heat dissipation method and system for battery energy storage systems. Background Technology

[0002] Energy storage battery containers are mainly composed of tens of thousands or even hundreds of thousands of individual battery cells connected in series and parallel. During operation, they generate a lot of heat. If this heat is not dissipated in time, it can easily lead to safety accidents such as fires and explosions in the battery energy storage system.

[0003] To address the above problems, traditional solutions involve installing industrial air conditioners (air-cooled) or liquid-cooled systems for heat exchange. However, these systems have low critical heat flux densities (CHF) during heat exchange (≤800W / cm³). 2 This results in the heat generated during battery (module) operation not being dissipated in a timely manner, and air-cooled and liquid-cooled systems have disadvantages such as high power consumption, affecting the economic efficiency of power plants. Summary of the Invention

[0004] To address the above problems, this invention provides a high-efficiency heat dissipation method and system for battery energy storage systems, employing the following technical solution:

[0005] A method for efficient heat dissipation in a battery energy storage system includes the following steps:

[0006] The real-time temperature of each individual cell in the battery energy storage system is obtained, and the critical heat flux density that the thin liquid film assisted phase change heat dissipation device needs to achieve is determined based on the temperature deviation between the real-time temperature of the individual cell and the optimal operating temperature.

[0007] Based on the critical heat flux density required for the thin-film assisted phase change heat dissipation device, the functional relationship between the critical heat flux density and the temperature deviation value, and the functional relationship between the supply pressure of the liquid working fluid and the critical heat flux density, the target supply pressure of the liquid working fluid for the thin-film assisted phase change heat dissipation device is determined.

[0008] A liquid working medium at the target supply pressure is delivered into the thin liquid film-assisted phase change heat dissipation device. The liquid working medium absorbs the heat from the surface of all individual cells in the battery energy storage system and turns into a gaseous state.

[0009] Furthermore, the functional relationship between the critical heat flux density and the temperature deviation is as follows:

[0010]

[0011] In the formula, CHF 临界热流密度 Where is the critical heat flux density, m is the mass flow rate of the liquid working fluid, h is the latent heat of the liquid working fluid, and C is the critical heat flux density. pΔT represents the specific heat capacity of the liquid working fluid; A represents the heat transfer area of ​​the thin liquid film-assisted phase change heat dissipation device; and ΔT represents the temperature deviation between the real-time temperature and the optimal operating temperature of a single battery cell.

[0012] Furthermore, the functional relationship between the supply pressure of the liquid working fluid and the critical heat flux density is as follows:

[0013]

[0014] In the formula, e is the liquid flow constant, CHF 临界热流密度 C is the critical heat flux density, h is the latent heat of the liquid working fluid; p η is the specific heat capacity of the liquid working fluid; A is the heat transfer area of ​​the thin liquid film assisted phase change heat dissipation device; η is the viscosity of the liquid working fluid; ρ is the density of the liquid working fluid; d and L are the pore size and length of the hydrophobic film in the thin liquid film assisted phase change heat dissipation device, respectively; and ΔT is the temperature deviation between the real-time temperature and the optimal operating temperature of the single cell.

[0015] Furthermore, it also includes the following steps:

[0016] Obtain the actual supply pressure of the liquid working fluid in the thin liquid film assisted phase change heat dissipation device, and adjust the actual supply pressure of the liquid working fluid to the target supply pressure.

[0017] Furthermore, the actual supply pressure of the liquid working fluid is equal to the difference between the liquid phase pressure and the gas phase pressure in the liquid supply tank.

[0018] The present invention also provides a high-efficiency heat dissipation system for a battery energy storage system, including a thin liquid film-assisted phase change heat dissipation device, a battery management system, and a liquid supply pump; the thin liquid film-assisted phase change heat dissipation device is in contact with the surface of each individual cell in the battery energy storage system;

[0019] The battery management system is used to acquire the real-time temperature of each individual cell in the battery energy storage system, and to determine the critical heat flux density that the thin liquid film assisted phase change heat dissipation device needs to achieve based on the temperature deviation between the real-time temperature of the individual cell and the optimal operating temperature.

[0020] The battery management system is also used to determine the target supply pressure of the liquid working fluid of the thin liquid film assisted phase change heat dissipation device based on the critical heat flux density that the thin liquid film assisted phase change heat dissipation device needs to achieve, the functional relationship between the critical heat flux density and the temperature deviation value, and the functional relationship between the supply pressure of the liquid working fluid and the critical heat flux density.

[0021] The liquid supply pump is used to deliver a liquid working medium at the target supply pressure into the thin liquid film assisted phase change heat dissipation device. The liquid working medium absorbs the heat from the surface of all individual cells in the battery energy storage system and turns into a gaseous state.

[0022] Furthermore, the thin liquid film-assisted phase change heat dissipation device includes a liquid supply tank, a hydrophobic film, and a vapor collection chamber;

[0023] The liquid supply tank has an inlet and an outlet on each side. The bottom of the liquid supply tank is in contact with the surface of the individual battery cell. The top of the liquid supply tank has an opening. The hydrophobic film is disposed on the top of the liquid supply tank. The steam collection chamber is covered above the hydrophobic film. Both sides of the steam collection chamber are connected to steam pipes.

[0024] Furthermore, it also includes a liquid supply pressure controller, wherein the outlet of the liquid supply pump is connected to the inlet of the liquid supply tank, and the liquid supply pressure controller is disposed between the outlet of the liquid supply pump and the inlet of the liquid supply tank.

[0025] Furthermore, the heat dissipation system also includes a first pressure sensor and a second pressure sensor;

[0026] The first pressure sensor is located at the bottom of the liquid supply tank and is communicatively connected to the battery management system. The first pressure sensor is used to send the acquired liquid phase pressure in the liquid supply tank to the battery management system. The second pressure sensor is located at the top of the liquid supply tank and is communicatively connected to the battery management system. The second pressure sensor is used to send the acquired gas phase pressure in the liquid supply tank to the battery management system.

[0027] Furthermore, the battery management system is also used to obtain the actual supply pressure of the liquid working fluid in the thin liquid film assisted phase change heat dissipation device, and adjust the actual supply pressure of the liquid working fluid to the target supply pressure through the liquid supply pressure controller.

[0028] The beneficial effects of this invention are:

[0029] This invention, for the first time based on the principle of thin-film boiling technology, proposes a thin-film assisted phase change heat dissipation device for the heat dissipation of battery energy storage systems, achieving efficient and precise temperature control and thus providing accurate heat dissipation. Compared with traditional battery energy storage heat dissipation solutions (air cooling, liquid cooling), this invention has advantages such as high heat dissipation efficiency, low energy consumption, small footprint, and improved economic efficiency of energy storage power stations.

[0030] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A schematic diagram of a high-efficiency heat dissipation system for a battery energy storage system according to an embodiment of the present invention is shown;

[0033] Figure 2 A schematic diagram of the installation of a thin liquid film-assisted phase change heat dissipation device and a single battery cell according to an embodiment of the present invention is shown.

[0034] Figure 3 A schematic diagram of a thin liquid film-assisted phase change heat dissipation device according to an embodiment of the present invention is shown;

[0035] Figure 4 A schematic diagram of a high-efficiency heat dissipation system for a battery energy storage system according to an embodiment of the present invention is shown.

[0036] In the diagram: 1. Battery energy storage system; 2. Single battery cell; 3. Thin liquid film assisted phase change heat dissipation device; 4. Liquid supply tank; 5. Hydrophobic film; 6. Steam collection chamber; 7. Steam pipe; 8. Liquid supply pump; 9. Liquid supply pressure controller; 10. First pressure sensor; 11. Second pressure sensor; 12. First plexiglass plate; 13. Second plexiglass plate; 14. Screw. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] It should be noted that the terms "first," "second," etc., used in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," "longitudinal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings.

[0039] This invention provides a high-efficiency heat dissipation method and system for battery energy storage systems. Utilizing thin-film boiling technology, the critical heat flux density (CHF) during heat exchange can reach up to 2000 W / cm² under a 60°C heat source environment. 2 It can quickly dissipate the heat generated by the battery (module) during operation and has the advantages of high efficiency and low energy consumption.

[0040] The principle of thin-film boiling technology is that the critical heat flux (CHF) at the liquid vapor surface during boiling heat exchange is proportional to the flow pressure difference of the water, and the critical heat flux (CHF) can reach up to 1000 W / cm². 2 If the water is further pressurized in a stepwise manner, similar to the shifting process of an automatic transmission (AT) with a finite gear ratio, the critical heat flux density (CHF) at the liquid-vapor surface can reach 1500 W / cm². 2 If the pressurization method of the water supply is increased from one side to both sides, and the step size of the pressure increase is reduced while the heating power of the heat source is increased, the critical heat flux density (CHF) at the liquid-vapor surface continues to increase in a circuitous manner. When the pressure is varied with even smaller step sizes and higher frequencies, in the extreme case of continuous and synchronous changes in the supply pressure and heating power, the corresponding thin-film boiling process is similar to the gear shifting process of a continuously variable transmission (CVT). In this case, the CHF at the liquid-vapor surface can reach a maximum of 2000 W / cm². 2 Furthermore, the critical heat flux density (CHF) for boiling of this thin liquid film can be achieved at a heat source of 60°C, which perfectly meets the heat dissipation requirements of the battery (module).

[0041] First, the structure of battery energy storage system 1 will be explained, such as... Figure 1 As shown, the battery energy storage system 1 includes multiple battery packs connected in series, each battery pack includes multiple cells connected in parallel, each cell string includes several individual cells connected in series, and each individual cell includes a single cell 2.

[0042] like Figure 1 and Figure 2 As shown, a high-efficiency heat dissipation system for a battery energy storage system 1 includes a thin-film assisted phase change heat dissipation device 3, a battery management system (BMS), and a liquid supply pump 8. The thin-film assisted phase change heat dissipation device 3 is in contact with the surface of each individual battery cell 2. The thin-film assisted phase change heat dissipation device 3 is used to absorb the heat from the surface of all individual battery cells 2, thereby causing a phase change in the internal liquid working medium, achieving the purpose of heat dissipation for the battery energy storage system 1. For example, the liquid working medium can be water or other fluids with heat dissipation properties, such as ethylene glycol.

[0043] like Figure 3As shown, the thin-film assisted phase change heat dissipation device 3 includes a liquid supply tank 4, a hydrophobic film 5, a steam collection chamber 6, and steam pipes 7. The liquid supply tank 4 has an inlet and an outlet on its two sides, respectively. The bottom of the liquid supply tank 4 is in contact with the surface of the individual battery cell 2, and the top of the liquid supply tank 4 has an opening. The hydrophobic film 5 is disposed on top of the liquid supply tank 4 and is composed of nanoporous structures. The steam collection chamber 6 is positioned above the hydrophobic film 5, and both sides of the steam collection chamber 6 are connected to the steam pipes 7, through which the gaseous working fluid is transported outwards.

[0044] The battery management system is used to obtain the real-time temperature of each individual cell 2, and to determine the critical heat flux density that the thin liquid film assisted phase change heat dissipation device 3 needs to achieve based on the temperature deviation between the real-time temperature of the individual cell 2 and the optimal operating temperature.

[0045] The battery management system is also used to determine the target supply pressure of the liquid working medium of the thin liquid film assisted phase change heat dissipation device 3 based on the critical heat flux density that the thin liquid film assisted phase change heat dissipation device 3 needs to achieve, the functional relationship between the critical heat flux density and the temperature deviation value, and the functional relationship between the supply pressure of the liquid working medium and the critical heat flux density.

[0046] The outlet of the liquid supply pump 8 is connected to the inlet of the liquid supply tank 4. For example, the cooling system also includes a liquid supply pressure controller 9, which is located between the outlet of the liquid supply pump 8 and the inlet of the liquid supply tank 4.

[0047] like Figure 3 As shown, for example, the heat dissipation system also includes a first pressure sensor 10 and a second pressure sensor 11. The first pressure sensor 10 is disposed at the bottom of the liquid supply tank 4 and is communicatively connected to the battery management system. The first pressure sensor 10 is used to send the acquired liquid phase pressure in the liquid supply tank 4 to the battery management system. The second pressure sensor 11 is disposed at the top of the liquid supply tank 4 and is communicatively connected to the battery management system. The second pressure sensor 11 is used to send the acquired gas phase pressure in the liquid supply tank 4 to the battery management system.

[0048] For example, the first pressure sensor 10 and the second pressure sensor 11 can be PT124B-230 series pressure sensors or PT510 series pressure sensors.

[0049] The battery management system is also used to obtain the actual supply pressure of the liquid working fluid in the thin-film assisted phase change heat dissipation device 3, and adjust the actual supply pressure of the liquid working fluid to the target supply pressure through the liquid supply pressure controller 9. The actual supply pressure of the liquid working fluid is equal to the difference between the liquid phase pressure and the gas phase pressure in the liquid supply tank 4.

[0050] The liquid supply pump 8 delivers liquid working fluid into the liquid supply tank 4 through the inlet of the liquid supply tank 4. The pressure of the liquid working fluid is adjusted by the liquid supply pressure controller 9. After absorbing the heat of the individual battery cell 2, the liquid working fluid becomes gaseous. The gaseous working fluid passes through the opening at the top of the liquid supply tank 4 and the hydrophobic membrane 5 in sequence, and then enters the steam collection chamber 6. After the gaseous working fluid inside the steam collection chamber 6 is stabilized, it is transported out through the steam pipe 7.

[0051] like Figure 3 As shown, for example, the liquid supply box 4 has an inverted T-shaped cross-section. The liquid supply box 4 includes a lower cavity and an upper cavity. Both the lower cavity and the upper cavity are square. The length of the lower cavity is equal to the length of the upper cavity. The height of the lower cavity is less than the height of the upper cavity. The width of the lower cavity is greater than the width of the upper cavity. The bottom of the lower cavity is in contact with the surface of the single cell 2. The top of the upper cavity has an opening.

[0052] The liquid supply tank 4 has an inverted T-shaped cross-section, which is wider at the bottom and narrower at the top. This increases the contact area with the individual battery cell 2 and is beneficial for the collection of gaseous working fluid.

[0053] like Figure 3 As shown, for example, the thin liquid film assisted phase change heat dissipation device 3 also includes a fixing member. Fixing members are provided on both sides of the upper cavity. The bottom of the fixing member contacts the top of the lower cavity, and the top of the fixing member contacts the hydrophobic film 5 and the steam collection chamber 6. The fixing member is used to provide support for the hydrophobic film 5 and the steam collection chamber 6.

[0054] For example, the fastener includes a first plexiglass plate 12 and a second plexiglass plate 13 stacked together, and a screw 14 that fixes the second plexiglass plate 13 to the first plexiglass plate 12.

[0055] Based on the above-mentioned high-efficiency heat dissipation system of battery energy storage system 1, such as Figure 4 As shown, the present invention also provides a high-efficiency heat dissipation method for a battery energy storage system 1, comprising the following steps:

[0056] S1. The battery management system acquires the real-time temperature of each individual cell 2, and determines the critical heat flux density that the thin liquid film assisted phase change heat dissipation device 3 needs to achieve based on the temperature deviation between the real-time temperature of the individual cell 2 and the optimal operating temperature, as follows:

[0057] The optimal operating temperature of individual cell 2 is a known parameter, typically 25℃. The battery management system acquires the real-time temperature of each individual cell 2 in the battery energy storage system 1. Then, the real-time temperature of each individual cell 2 is compared with the temperature corresponding to the cell's optimal operating state to obtain the temperature deviation value ΔT = T. 电芯实际 -T 电芯运行最佳Then, the battery management system automatically analyzes and obtains the rate of change parameter of the temperature deviation value ΔT for each individual cell 2. Furthermore, the temperature deviation value ΔT for each individual cell 2 was analyzed. To conduct analysis and judgment.

[0058] S2. The battery management system determines the target supply pressure of the liquid working medium of the thin liquid film assisted phase change heat dissipation device 3 based on the critical heat flux density that the thin liquid film assisted phase change heat dissipation device 3 needs to achieve, the functional relationship between the critical heat flux density and the temperature deviation value, and the functional relationship between the supply pressure of the liquid working medium and the critical heat flux density.

[0059] The battery management system, based on the ΔT parameter obtained from data analysis, then uses CHF... 临界热流密度 =f(ΔT) and ΔP=f(CHF) 临界热流密度 The functional correspondence of CHF is used to further obtain parameters such as the critical heat flux density required for the thin liquid film-assisted phase change heat dissipation device 3 to dissipate heat for the single cell 2, and the supply pressure P of the liquid working fluid in the thin liquid film-assisted phase change heat dissipation device 3. Among them, CHF 临界热流密度 =f(ΔT) and ΔP=f(CHF) 临界热流密度 The functional relationships, such as those between the battery and the management system, are input into the battery management system based on the relevant mathematical model.

[0060] For example, the functional relationship between the critical heat flux density and the temperature deviation is as follows:

[0061]

[0062] In the formula, CHF 临界热流密度 Where is the critical heat flux density, m is the mass flow rate of the liquid working fluid (unit: kg / s); h is the latent heat of the liquid working fluid (unit: J / kg); C p A is the specific heat capacity of the liquid working fluid (unit: J / (kg·℃)); A is the heat transfer area of ​​the thin liquid film assisted phase change heat dissipation device 3 (unit: m²). 2 The heat transfer area is the sum of the contact areas between the liquid supply tank 4 and all the individual cells 2 in the battery energy storage system 1.

[0063] For example, the functional relationship between the supply pressure of the liquid working fluid and the critical heat flux density is as follows:

[0064]

[0065] In the formula, e is the liquid flow constant, for example, it can be 128; η is the viscosity of the liquid working medium (unit: Pa·s); ρ is the density of the liquid working medium (unit: kg / m³). 3 ); d and L are the pore diameter and length (unit: m) of the hydrophobic film 5 in the thin liquid film assisted phase change heat dissipation device 3, respectively.

[0066] S3. A liquid working medium with a target supply pressure is delivered into the thin liquid film assisted phase change heat dissipation device 3. The liquid working medium absorbs the heat on the surface of each individual cell 2 in the battery energy storage system 1 and turns into a gaseous state, thereby dissipating heat for the battery energy storage system 1.

[0067] To achieve precise control of the liquid working fluid supply pressure ΔP in the thin-film assisted phase change heat dissipation device 3, it is necessary to monitor the liquid phase pressure P in the liquid supply tank 4 in real time. L and gas phase pressure P V The actual value.

[0068] S4. The battery management system is also used to obtain the actual supply pressure of the liquid working fluid in the thin liquid film assisted phase change heat dissipation device 3, and adjust the actual supply pressure of the liquid working fluid to the target supply pressure through the liquid supply pressure controller 9, as follows:

[0069] The first pressure sensor 10 will acquire the liquid phase pressure P in the liquid supply tank 4. L The data is sent to the battery management system, and the second pressure sensor 11 is used to transmit the acquired gas phase pressure P in the liquid supply tank 4. V Send to the battery management system.

[0070] The battery management system will P L and P V Perform a difference analysis on the actual value, i.e., ΔP 实际 =P L -P V According to ΔP 实际 The size of the battery management system is controlled by the liquid supply pressure controller 9(P) to regulate the pressure of the liquid working fluid in the liquid supply tank 4. L and P V The value is then continuously reduced by negative feedback control. 实际 The difference between the value and ΔP ultimately reaches the supply pressure ΔP of the liquid working fluid. 实际 The goal is consistent with ΔP, thereby achieving precise control of the critical heat flux density.

[0071] It should be noted that the battery management system command control liquid supply pressure controller 9(P) borrows the control principle of the host computer and slave computer, and can be realized through real-time control by PLC.

[0072] This invention can be applied to energy storage battery systems such as sodium-ion batteries, flow batteries, and lead-carbon batteries.

[0073] This invention is the first to propose a thin-film assisted phase change heat dissipation device 3 based on the principle of thin-film boiling technology, which is applied to the heat dissipation of battery energy storage system 1, providing a novel heat dissipation solution for battery energy storage system 1.

[0074] This invention utilizes a battery management system to control the heat dissipation of a thin-film-assisted phase change heat dissipation device 3, achieving efficient and precise temperature control of the battery energy storage system 1, and thus achieving precise heat dissipation for the battery (module). Compared with traditional battery energy storage heat dissipation solutions (air cooling, liquid cooling), this invention has advantages such as high heat dissipation efficiency, low energy consumption, small footprint, and improved economic efficiency of energy storage power stations.

[0075] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for efficient heat dissipation of a battery energy storage system, characterized in that, The method comprises the following steps: acquiring the real-time temperature of each single battery cell in the battery energy storage system, and determining the critical heat flux density required by the thin liquid film assisted phase change heat dissipation device according to the temperature deviation value of the real-time temperature of the single battery cell and the optimal operating temperature; determining the target supply pressure of the liquid working medium of the thin liquid film assisted phase change heat dissipation device according to the critical heat flux density required by the thin liquid film assisted phase change heat dissipation device, the functional relationship between the critical heat flux density and the temperature deviation value, and the functional relationship between the supply pressure of the liquid working medium and the critical heat flux density; delivering the liquid working medium with the target supply pressure into the thin liquid film assisted phase change heat dissipation device, and the liquid working medium absorbs the heat on the surface of all single battery cells in the battery energy storage system to become gaseous.

2. The method of claim 1, wherein, The functional relationship between the critical heat flux density and the temperature deviation value is as follows: In the formula, CHF 临界热流密度 is the critical heat flux density, m is the mass flow rate of the liquid working medium; h is the latent heat of the liquid working medium; C p is the specific heat capacity of the liquid working medium; A is the heat transfer area of the thin liquid film assisted phase change heat dissipation device, and ΔT is the temperature deviation value of the real-time temperature of the single cell and the optimal operating temperature.

3. The battery energy storage system high efficiency heat dissipation method of claim 1, wherein, The functional relationship between the supply pressure of the liquid working medium and the critical heat flux density is as follows: where e is a liquid flow constant, CHF 临界热流密度 is the critical heat flux density, h is the latent heat of the liquid working medium; C p is the specific heat capacity of the liquid working medium; A is the heat transfer area of the thin liquid film assisted phase change heat dissipation device, η is the viscosity of the liquid working medium; ρ is the density of the liquid working medium; d and L are the pore diameter and length of the hydrophobic film in the thin liquid film assisted phase change heat dissipation device, respectively, and ΔT is the temperature deviation value of the real-time temperature of the single cell and the optimal operating temperature.

4. The method of claim 1-3, wherein, The method further comprises the following steps: acquiring the actual supply pressure of the liquid working medium of the thin liquid film assisted phase change heat dissipation device, and adjusting the actual supply pressure of the liquid working medium to the target supply pressure.

5. The battery energy storage system high efficiency heat dissipation method of claim 4, wherein, The actual supply pressure of the liquid working medium is equal to the difference between the liquid phase pressure and the gas phase pressure in the liquid supply tank.

6. A high efficiency heat dissipation system for a battery energy storage system, comprising: The heat dissipation system comprises a thin liquid film assisted phase change heat dissipation device, a battery management system and a liquid supply pump; the thin liquid film assisted phase change heat dissipation device is in contact with the surface of each single battery cell in the battery energy storage system; The battery management system is configured to acquire the real-time temperature of each single battery cell in the battery energy storage system, and determine the critical heat flux density required by the thin liquid film assisted phase change heat dissipation device according to the temperature deviation value of the real-time temperature of the single battery cell and the optimal operating temperature. The battery management system is further configured to determine the target supply pressure of the liquid working medium of the thin liquid film assisted phase change heat dissipation device according to the critical heat flux density required by the thin liquid film assisted phase change heat dissipation device, the functional relationship between the critical heat flux density and the temperature deviation value, and the functional relationship between the supply pressure of the liquid working medium and the critical heat flux density. The liquid supply pump is configured to deliver the liquid working medium with the target supply pressure into the thin liquid film assisted phase change heat dissipation device, and the liquid working medium absorbs the heat on the surface of all single battery cells in the battery energy storage system to become gaseous.

7. The battery energy storage system high efficiency thermal management system of claim 6, wherein, The thin liquid film assisted phase change heat dissipation device comprises a liquid supply tank, a hydrophobic film and a vapor collection bin. The liquid supply tank is provided with an inlet and an outlet on two sides thereof, the bottom of the liquid supply tank is in contact with the surface of the single battery cell, the top of the liquid supply tank is provided with an opening, the hydrophobic film is arranged on the top of the liquid supply tank, the vapor collection bin is arranged above the hydrophobic film, and the two sides of the vapor collection bin are in communication with a vapor pipeline.

8. The battery energy storage system high efficiency thermal management system of claim 7, wherein, The heat dissipation system further comprises a liquid supply pressure controller, the outlet of the liquid supply pump is in communication with the inlet of the liquid supply tank, and the liquid supply pressure controller is arranged between the outlet of the liquid supply pump and the inlet of the liquid supply tank.

9. The battery energy storage system high efficiency thermal management system of claim 7 or 8, wherein, The heat dissipation system further comprises a first pressure sensor and a second pressure sensor. The first pressure sensor is arranged at the bottom of the liquid supply tank, is in communication connection with the battery management system, and is configured to send the acquired liquid-phase pressure in the liquid supply tank to the battery management system; and the second pressure sensor is arranged at the top of the liquid supply tank, is in communication connection with the battery management system, and is configured to send the acquired gas-phase pressure in the liquid supply tank to the battery management system.

10. The battery energy storage system high efficiency thermal management system of claim 8, wherein, The battery management system is further configured to acquire an actual supply pressure of the liquid working medium of the thin liquid film assisted phase change heat dissipation device, and adjust the actual supply pressure of the liquid working medium to a target supply pressure through the liquid supply pressure controller.

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