All-weather passive cold storage battery pack water cooling system and method

Abstract

The all-weather passive cold storage battery pack water cooling system comprises a battery pack and further comprises a first surface air cooler and a cold storage water tower used for heat insulation. A plurality of phase change energy storage water tanks which are vertically arranged are placed in the cold water storage tower, and the adjacent phase change energy storage water tanks are separated through heat insulation plates; the first surface air cooler is positioned above the cold water storage tower; and the battery pack is connected with a liquid cooling plate for cooling the battery pack. A gradient phase-change material cold storage technology and a water cooling system are combined to cool the battery pack, all-weather cold storage can be realized, the number of phase-change materials with various phase-change temperatures is configured according to the time of a phase-change temperature interval, the cold storage capacity of the whole cooling tower is slightly influenced by daily temperature change, and the cooling capacity of the whole cooling tower is greatly improved. Compared with a single-phase-change temperature material, the cold storage capacity is high, and the cooling efficiency is high; compared with the prior art, the system is more energy-saving and environment-friendly in the aspects of battery pack cooling and temperature control.

Description

Technical Field

[0001] The present invention relates to the technical field of battery packs, and in particular to a battery pack water cooling system and method for passively storing natural cold sources around the clock using multi-phase change temperature gradient phase change materials. Background Art

[0002] With the advancement of energy storage technology, energy storage systems, as an important part of improving grid efficiency and balancing electricity supply and demand, have been widely used in smart grids, and together with renewable energy systems such as photovoltaics and wind power, a more flexible and reliable energy network has been built. Currently, mainstream energy storage systems on the market mostly adopt container-type designs, and their core components are multiple battery packs placed in containers. However, during the operation of the battery packs, they release a lot of heat energy, so an efficient cooling system is needed to ensure the normal operation of the system. However, traditional cooling methods, such as air cooling or liquid cooling systems, have the following problems:

[0003] 1. Low cooling efficiency: The air cooling system relies on fans to dissipate heat, but because the fans are usually fixed in one position, the energy storage equipment close to the fans can get better cooling effect, while the cooling effect is poor at locations far away from the fans, which makes the entire energy storage system face the problem of uneven cooling;

[0004] 2. High energy consumption: Existing active cooling systems usually rely on mechanical equipment, which has high energy consumption and increases the operating cost of the system. In addition, the maintenance and failure rate of these devices are also high, affecting the stability and reliability of the system. Summary of the invention

[0005] The present invention is to solve the above problems and provides a battery pack water cooling system and method that configures multi-phase change temperature gradient phase change materials with different phase change temperature amounts according to the duration of different temperature segments throughout the day, thereby passively storing natural cold sources around the clock to achieve low energy consumption and efficient cooling of the battery pack.

[0006] To solve the above technical problems, the technical solution of the present invention is:

[0007] A battery pack water cooling system with all-weather passive cold storage includes a battery pack, a first surface cooler and a cold water tower for heat insulation; a plurality of vertically arranged phase change cold water tanks are placed in the cold water tower, and adjacent phase change cold water tanks are separated by insulation boards; the first surface cooler is located above the cold water tower; the plurality of vertically arranged phase change cold water tanks are filled with phase change material particles with different phase change critical point values, and according to the height of the phase change cold water tank, the higher the position of the phase change cold water tank, the greater the phase change critical point value of the phase change material particles filled therein, thereby forming a gradient; the phase change critical point value range of the phase change material particles is between 10°C and 50°C; the outer side of the phase change cold water tank is connected to a second surface cooler, and the position height of the second surface cooler is higher than the position height of the phase change cold water tank; the upper end of the phase change cold water tank is connected to the second surface cooler through a first liquid inlet pipe, and the phase change cold water tank The lower end is connected to the second surface cooler through the first liquid outlet pipe, so as to form a loop A; the loop A is filled with water, and loop A forms a circulating heat exchange with the air due to the characteristic of different densities caused by changes in the water's own temperature; the battery pack is connected to a liquid cooling plate for cooling itself; a plurality of the phase change cold storage water tanks are provided with heat exchange pipes, and the heat exchange pipes in two adjacent phase change cold storage water tanks are connected through pipes so as to communicate with each other; the liquid cooling plate is connected to the first surface cooler through a pipeline; the first surface cooler is connected to the heat exchange pipe of the phase change cold storage water tank located at the top through the second liquid inlet pipe; the heat exchange pipe of the phase change cold storage water tank located at the bottom is connected to the liquid cooling plate through the second liquid outlet pipe; the liquid cooling plate, the first surface cooler and the heat exchange pipes of the plurality of phase change cold storage water tanks form a loop B; the loop B is filled with refrigerant; a pump body for promoting the circulation of refrigerant in loop B is installed on the second liquid outlet pipe.

[0008] There are four phase change cold water storage tanks in total; the four phase change cold water storage tanks are filled with 45℃ phase change material particles, 35℃ phase change material particles, 25℃ phase change material particles and 15℃ phase change material particles from top to bottom; the phase change critical point value of the 45℃ phase change material particles is 45℃, the phase change critical point value of the 35℃ phase change material particles is 35℃, the phase change critical point value of the 25℃ phase change material particles is 25℃, and the phase change critical point value of the 15℃ phase change material particles is 15℃.

[0009] The content distribution ratio of the 45°C phase change material particles, the 35°C phase change material particles, the 25°C phase change material particles and the 15°C phase change material particles is 2:3:3:2.

[0010] An energy storage container is also installed outside the battery pack and the liquid cooling plate.

[0011] The heat exchange pipe is a coil.

[0012] Fins are installed on the outside of the heat exchange pipe.

[0013] A battery pack water cooling method with all-weather passive cold storage, using the above-mentioned battery pack water cooling system with all-weather passive cold storage, comprises the following steps:

[0014] S1, when the battery pack starts working, the pump body is turned on, and the refrigerant is controlled by the pump body to circulate in loop B to circulate heat for the battery pack;

[0015] S2, during the heat exchange cycle of the battery pack, the refrigerant first exchanges heat with the battery pack and its temperature rises, thereby cooling the battery pack. Then, the refrigerant with the increased temperature is sent to the first surface cooler to exchange heat with the air for cooling. Then, it exchanges heat with multiple phase change cold storage tanks for cooling and is then sent back to the liquid cooling plate for heat exchange cycle with the battery pack.

[0016] S3, during the operation of the phase change cold storage water tank, the refrigerant entering the phase change cold storage water tank exchanges heat with the phase change material particles and water in the phase change cold storage water tank, thereby reducing its own temperature. At this time, the temperature of the phase change material particles and the water both rises, and the water begins to float due to the decrease in density due to the increase in temperature, while the water in the second cooler decreases in temperature due to heat exchange with the outside air, so the water density in the second cooler increases and begins to sink. The density of the water in the phase change cold storage water tank decreases while the density of the water in the second cooler increases, resulting in a density difference between the two, so that the water between the phase change cold storage water tank and the second cooler begins to flow and exchange heat, thereby circulating;

[0017] S4, during the water circulation process, when the outside air temperature is lower than the phase change critical point of the phase change material particles in the phase change cold water storage tank, the water in the second surface cooler exchanges heat with the outside air to keep the water temperature dropping, thereby utilizing the density difference to flow into the phase change cold water storage tank and exchange heat with the internal phase change material particles, so that the phase change material particles all drop to the phase change critical point of the phase change material particles themselves, thereby storing cold energy and facilitating subsequent heat exchange for the refrigerant.

[0018] The battery pack is also equipped with a temperature sensor; in step S1, the pump body is turned on only when the temperature sensor detects that the temperature of the battery pack is greater than or equal to 35°C.

[0019] The technical effect that the present invention can achieve is: the present invention adopts a combination of all-weather cold storage technology of gradient phase change materials with different phase change temperatures and a water cooling system to cool the battery pack, and its cooling efficiency is high; and water promotes itself to circulate and exchange heat in the phase change cold storage water tank, the second surface cooler, the first liquid inlet pipe and the first liquid outlet pipe due to its own temperature change characteristics, thereby continuously cooling the refrigerant, which not only reduces the energy consumption of mechanical equipment, but also reduces the operating cost of the system; when the refrigerant does not need to be cooled by heat exchange through the phase change material particles and the external temperature is lower than the phase change critical point value of the phase change material particles, the phase change material particles can use the second surface cooler to reduce their own temperature to their own phase change critical point value to store cold energy, and provide more cold energy for subsequent heat exchange of the refrigerant, thereby improving energy utilization efficiency and rationally utilizing natural cold sources. Compared with the prior art, the present invention is more energy-saving and environmentally friendly in terms of battery pack cooling and temperature control. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0021] Figure 1 It is a structural schematic diagram of a battery pack water cooling system with all-weather passive cold storage according to the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0023] See also Figure 1 .

[0024] A battery pack water cooling system with all-weather passive cold storage includes a battery pack 2, a first surface cooler 7 and a cold water storage tower 10 for heat insulation; a plurality of vertically arranged phase change cold water storage tanks 9 are placed in the cold water storage tower 10, and adjacent phase change cold water storage tanks 9 are separated by a heat insulation board 12, and the first surface cooler 7 is located above the cold water storage tower 10; a plurality of vertically arranged phase change cold water storage tanks 9 are filled with phase change material particles with different phase change critical point values, and according to the height of the phase change cold water storage tank 9, the higher the position of the phase change cold water storage tank 9, the greater the phase change critical point value of the phase change material particles filled therein, thereby forming a gradient, and the phase change critical point value range of the phase change material particles is between 10°C and 50°C; specifically, the phase change storage There are four cold water tanks 9 in total, and the four phase change cold water storage tanks 9 are filled with 45℃ phase change material particles 11, 35℃ phase change material particles 13, 25℃ phase change material particles 15 and 15℃ phase change material particles 17 from top to bottom; the phase change critical point value of the 45℃ phase change material particles 11 is 45℃, the phase change critical point value of the 35℃ phase change material particles 13 is 35℃, the phase change critical point value of the 25℃ phase change material particles 15 is 25℃, and the phase change critical point value of the 15℃ phase change material particles 17 is 15℃; more specifically, the content distribution ratio of the 45℃ phase change material particles 11, the 35℃ phase change material particles 13, the 25℃ phase change material particles 15 and the 15℃ phase change material particles 17 is 2:3:3:2.

[0025] The outer side of the phase change cold water storage tank 9 is connected to a second surface cooler 23, and the position height of the second surface cooler 23 is higher than the position height of the phase change cold water storage tank 9; the upper end of the phase change cold water storage tank 9 is connected to the second surface cooler 23 through a first liquid inlet pipe 24, and the lower end of the phase change cold water storage tank 9 is connected to the second surface cooler 23 through a first liquid outlet pipe 25, thereby forming a loop A; loop A is filled with water, and loop A forms a circulating heat exchange with the air due to the different density characteristics of water due to its own temperature change; a liquid cooling plate 3 for cooling itself is connected to the battery pack 2; a heat exchange pipe 18 is provided in each of the four phase change cold water storage tanks 9, and the heat exchange pipes 18 in two adjacent phase change cold water storage tanks 9 are connected by a pipe 6 so as to Specifically, the heat exchange pipe 18 is a coil, and fins are installed on the outside of the heat exchange pipe 18; the liquid cooling plate 3 is connected to the first surface cooler 7 through the pipeline 4, the first surface cooler 7 is connected to the heat exchange pipe 18 of the phase change cold storage water tank 9 located at the top through the second liquid inlet pipe 8, and the heat exchange pipe 18 of the phase change cold storage water tank 9 located at the bottom is connected to the liquid cooling plate 3 through the second liquid outlet pipe 22; the liquid cooling plate 3, the first surface cooler 7 and the heat exchange pipes 18 of the four phase change cold storage water tanks 9 form a loop B, and the loop B is filled with refrigerant. The second liquid outlet pipe 22 is installed with a pump body 5 for promoting the circulation of the refrigerant in the loop B; specifically, an energy storage container 1 is also installed on the outside of the battery pack 2 and the liquid cooling plate 3.

[0026] A battery pack water cooling method with all-weather passive cold storage, using the above-mentioned battery pack water cooling system with all-weather passive cold storage, comprises the following steps:

[0027] S1, when the battery pack 2 starts working, the pump body 5 is turned on, and the refrigerant is controlled by the pump body 5 to circulate in the loop B so as to circulate heat for the battery pack 2;

[0028] S2, during the heat exchange cycle of the battery pack 2, the refrigerant first exchanges heat with the battery pack 2 and its temperature rises, thereby cooling the battery pack 2. Then, the refrigerant with the increased temperature is sent to the first surface cooler 7 to exchange heat with the air for cooling. Then, it exchanges heat with the multiple phase change cold storage water tanks 9 for cooling and then is sent back to the liquid cooling plate 3 to circulate heat exchange with the battery pack 2.

[0029] S3, during the operation of the phase change cold storage water tank 9, the refrigerant entering the phase change cold storage water tank 9 exchanges heat with the phase change material particles and water in the phase change cold storage water tank 9, thereby reducing its own temperature. At this time, the temperature of the phase change material particles and the water both rises, and the water begins to float due to the decrease in density due to the increase in temperature, while the water located in the second surface cooler 23 decreases in temperature due to heat exchange with the outside air, so the water density in the second surface cooler 23 increases and begins to sink. The change in that the water density in the phase change cold storage water tank 9 decreases and the water density in the second surface cooler 23 increases causes a density difference between the two, so that the water between the phase change cold storage water tank 9 and the second surface cooler 23 begins to flow and exchange heat, thereby circulating;

[0030] S4, during the water circulation process, when the outside air temperature is lower than the phase change critical point value of the phase change material particles in the phase change cold water storage tank 9, the water in the second surface cooler 23 exchanges heat with the outside air to keep the water temperature dropping, thereby utilizing the density difference to flow into the phase change cold water storage tank 9 and exchange heat with the internal phase change material particles, so that the phase change material particles all drop to the phase change critical point value of the phase change material particles themselves, thereby storing cold energy and facilitating the subsequent heat exchange for the refrigerant.

[0031] Preferably, a temperature sensor is also installed on the battery pack 2; in step S1, the pump body 5 is turned on only when the temperature sensor detects that the temperature of the battery pack 2 is greater than or equal to 35°C.

[0032] The present invention introduces gradient phase change material all-weather cold storage technology, and uses phase change materials with different phase change temperatures to configure the dosage according to the duration of each temperature segment in a day, so that natural cold sources can be used to induce the phase change process of phase change materials to passively store cold energy at any time of the day. The cold storage capacity is larger than that of a single phase change material, and refrigeration and cold storage do not need to rely on mechanical equipment, thereby reducing the energy consumption of the system; and a combination of a phase change cold storage system and a water cooling system is used to cool the battery pack, and the cooling efficiency is high; specifically in the design of the cooling system, the energy storage system has a wide operating temperature range, and the battery pack can generally withstand a temperature range from -40°C to 60°C. Using this wide temperature control range, the system can effectively use natural cold sources such as the temperature difference between day and night to cool the battery, thereby significantly improving the power utilization efficiency (PUE).

[0033] The workflow is roughly explained as follows:

[0034] (1) Heat generation and detection: During the charging and discharging process of the battery pack 2, the battery pack 2 will generate a certain amount of heat. The system's built-in temperature sensor continuously monitors the temperature of the battery pack 2. When it is detected that the temperature of the battery pack 2 reaches a preset threshold (i.e., the temperature of the battery pack 2 is greater than or equal to 35°C), the liquid cooling circulation mechanism will be automatically started to adjust the battery temperature.

[0035] (2) Liquid circulation start: When the system detects that cooling needs to be started, the pump body 5 starts and drives the refrigerant to flow from the liquid cooling plate 3 to the first surface cooler 7 through the pipeline 4. In the first surface cooler 7, the high-temperature refrigerant exchanges heat with the ambient air and releases heat to the external environment, thereby reducing the temperature of the refrigerant. According to the temperature difference between day and night, the system is divided into two modes: night mode, the temperature is lower at night, and the first surface cooler 7 is sufficient to reduce the high-temperature refrigerant to a suitable temperature through heat exchange with the air, thereby cooling the battery pack 2; day mode, due to the increase in temperature during the day, the first surface cooler 7 alone cannot meet the cooling demand. At this time, the high-temperature refrigerant can also be cooled by the phase change cold storage tank 9.

[0036] (3) Phase change cold water storage tank 9: The refrigerant enters the phase change cold water storage tank 9 from the first surface cooler 7 through the second liquid inlet pipe 8. The four phase change cold water storage tanks 9 contain phase change materials with different phase change critical point values ​​(i.e., 45°C phase change material particles 11, 35°C phase change material particles 13, 25°C phase change material particles 15 and 15°C phase change material particles 17). These materials will undergo solid-liquid phase change after absorbing heat, further absorbing a large amount of heat, thereby helping to reduce the refrigerant temperature.

[0037] (4) Layered control and auxiliary heat exchange: A heat insulation plate 12 is provided inside the cold storage water tower 10 to separate the phase change material particles in different temperature zones, ensuring that they undergo phase change within their respective suitable temperature ranges, while allowing water to flow evenly in the phase change cold storage water tank 9 to improve heat exchange efficiency. The heat exchange pipe 18 provides more surface area for the refrigerant entering through the second liquid inlet pipe 8 to exchange heat with the phase change cold storage water tank 9, thereby enhancing the cooling effect. If necessary, fins can be installed on the outside of the heat exchange pipe 18 to increase the heat exchange area.

[0038] (5) Low-temperature liquid returns to the liquid cooling plate 3: After being cooled by the first surface cooler 7 and the phase change cold water storage tank 9, the low-temperature refrigerant returns to the liquid cooling plate 3 through the second liquid outlet pipe 22. In the liquid cooling plate 3, the low-temperature refrigerant absorbs heat from the battery pack 2 and enters the system again after completing a cooling cycle.

[0039] (6) Cold storage and release: The second surface cooler 23 is responsible for the cold storage and heat release tasks in the phase change cold storage water tank 9. It forms a closed loop with the phase change cold storage water tank 9 through the first liquid inlet pipe 24 and the first liquid outlet pipe 25, ensuring that the system can release the heat stored during the day into the air through the second surface cooler 23 at night. Because the temperature is lower at night, the outside air temperature at night is easily lower than the phase change critical point value of the phase change material particles. Therefore, the water in the second surface cooler 23 continuously decreases through heat exchange with the outside air, thereby utilizing the density difference to flow into the phase change cold storage water tank 9 and exchange heat with the phase change material particles filled in the four phase change cold storage water tanks 9, so that the phase change material particles all drop to the phase change critical point value of the phase change material particles themselves, thereby storing cold energy, thereby providing refrigerant for cooling during the day.

[0040] Through the above-mentioned circulation mechanism, the entire system maintains the battery pack 2 in an ideal operating temperature range, avoids safety hazards caused by overheating, and ensures the overall stability and reliability of the energy storage system; in addition, the system can also be equipped with an intelligent control system, which can dynamically adjust operating parameters according to real-time collected data to achieve optimal cooling efficiency and energy utilization.

[0041] The following is an example of the calculation process:

[0042] In order to realize the technical solution of the present invention, the calculation process of several main devices is given to illustrate the solution. The following parameters are temporarily set to help better understand the following calculation process:

[0043] The total heat generated by battery pack 2 is Q = 10kW

[0044] Specific heat capacity of refrigerant c = 9.2 kJ / (kg·K)

[0045] Density of refrigerant ρ = 1000 kg / m 3

[0046] Enthalpy value of phase change material particles h = 200 kJ / kg

[0047] (1) Calculation of refrigerant parameters: The amount of heat that needs to be removed per hour by the system is Q (kJ / h), the specific heat capacity of the refrigerant is c (kJ / kg·K), the mass flow rate of the refrigerant is m (kg / h), and the temperature rise of the refrigerant is ΔT (K), then:

[0048] Q=m×c×ΔT

[0049] The liquid cooling plate needs to take away 10kw of heat per hour, which is 36000kJ / h. The specific heat capacity of the refrigerant c is 9.2kJ / kg·K. The temperature rise of the refrigerant is 10℃, so the flow rate of the refrigerant is m=36000 / 9.2 / 10=391kg / h. The density of the refrigerant ρ=1000kg / m 3 , the volume flow rate is 0.391m 3 / h. The water pump (ie, pump body 5) can be selected according to the parameters.

[0050] (2) Design of the liquid cooling plate 3: The area A of the liquid cooling plate 3 can be calculated using the following formula:

[0051]

[0052] Where: Q is the heat load;

[0053] U is the heat transfer coefficient;

[0054] ΔT is the mean temperature difference.

[0055] The heat that the liquid cooling plate 3 needs to take away per hour is Q 10kw, the refrigerant temperature rise is 10℃, and the heat transfer coefficient of the liquid cooling plate 3 is 1000W / (m 2 ·K), liquid cooling plate 3 area A = 10000 / 10 / 1000 = 1m 2 .

[0056] (3) Selection of phase change material particles: Select a variety of PCM materials with different phase change critical point values; for example, select four PCM materials with phase change temperatures of 15°C, 25°C, 35°C, and 45°C (the upper limit of the phase change critical point value is the highest temperature during the day in summer, and the lower limit of the phase change critical point value is the lowest temperature at night in summer); this can form a gradient thermal management environment to ensure that the corresponding PCM materials play a role in the entire temperature range.

[0057] (4) Design of phase change cold water storage tank 9: According to the phase change temperature and latent heat of the phase change material particles, the theoretical heat storage capacity of each temperature node is calculated. The formula is:

[0058] Q=m×h

[0059] The heat of battery pack 2 is 10kw, the latent heat of phase change material particles is 200kJ / kg, and the required cooling capacity of phase change material particles for 12 hours during the day is 120kW, i.e. 432000kJ. The required mass of phase change material is m=432000 / 200=2160kg; the density of phase change material particles is 800kg / m 3 , and at the same time increase the remainder by 20%, the volume of the phase change material particles is 3.24m 3 The volume of the phase change material particles changes when the solid-liquid phase changes. The phase change cold water storage tank 9 reserves 30% of the surplus and is filled with water at the same time. It is divided into four phase change cold water storage tanks 9 according to four different phase change temperature points. The final volume of each phase change cold water storage tank is 0.842m 3 、1.264m 3 、1.264m 3 、0.842m 3 The phase change cold storage water tank 9 is provided with an external insulation layer, which is an outer color plate + 150mm polyurethane high-efficiency insulation.

[0060] (5) Heat exchanger design: Determine the required heat exchange area based on cooling requirements. Consider both nighttime and daytime modes and calculate the required heat exchange area for each mode. The formula is:

[0061]

[0062] Calculation of the first surface cooler 7: In the night mode, 10kW of heat needs to be dissipated, the ambient temperature is 20℃, the refrigerant temperature difference is 10℃, the heat exchange temperature difference is 10℃, and the first surface cooler 7 is calculated based on the heat transfer coefficient of 10W / (m 2 ·K), the required heat exchange area is A = 10000 / 10 / 10 = 100m 2 .

[0063] Calculation of four second coolers 23: Since the enthalpy values ​​of the four phase change material particles are basically the same, the heat exchange area of ​​the second cooler 23 is the same; the four second coolers 23 need to store the cooling capacity of 144kW required for cooling the battery pack 2 during the day in the phase change cold storage water tank 9 within 12 hours, and the heat load is also 12kW; at the same time, since the phase change material particles store cold and absorb latent heat, the temperature change of the phase change material particles is small, the refrigerant temperature difference in the phase change cold storage water tank 9 is set to 5°C, and the second cooler 23 is set to a heat transfer coefficient of 10W / (m 2 ·K), the total heat exchange area required is A = 12000 / 5 / 10 = 240m 2； The heat exchange area of ​​each second surface cooler 23 is 48m 2 、72m 2 、72m 2 、48m 2 .

[0064] (6) Calculation of heat exchange area of ​​heat exchange pipe 18: The heat exchange area A of heat exchange pipe 18 can be calculated using the following formula:

[0065]

[0066] Where: Q is the heat load;

[0067] U is the heat transfer coefficient;

[0068] ΔT is the mean temperature difference.

[0069] The heat exchange pipe 18 in the phase change cold storage water tank 9 needs to provide the liquid cooling plate 3 with a heat Q of 10kw per hour, the temperature rise of the cooling liquid is 10°C, the heat exchange pipe 18 is made of copper pipe, and the heat transfer coefficient is 100W / (m 2 K), heat exchange area of ​​heat exchange pipe 18 A = 10000 / 10 / 100 = 10m 2 .

Claims

1. A battery pack water cooling system with all-weather passive cold storage, comprising a battery pack (2), characterized in that: The invention also comprises a first surface cooler (7) and a cold water storage tower (10) for heat insulation; a plurality of vertically arranged phase change cold water storage tanks (9) are placed in the cold water storage tower (10), and adjacent phase change cold water storage tanks (9) are separated by a heat insulation board (12); the first surface cooler (7) is located above the cold water storage tower (10); the plurality of vertically arranged phase change cold water storage tanks (9) are filled with phase change material particles with different phase change critical point values, and according to the height of the phase change cold water storage tank (9), the higher the position of the phase change cold water storage tank (9), the higher the phase change cold water storage tank (9) is filled with phase change material particles with different phase change critical point values. The phase change critical point value of the phase change material particles filled is larger, thereby forming a gradient; the phase change critical point value range of the phase change material particles is between 10°C and 50°C; the outer side of the phase change cold storage water tank (9) is connected to a second surface cooler (23), and the position height of the second surface cooler (23) is higher than the position height of the phase change cold storage water tank (9); the upper end of the phase change cold storage water tank (9) is connected to the second surface cooler (23) through a first liquid inlet pipe (24), and the lower end of the phase change cold storage water tank (9) is connected to the second surface cooler (23) through a first liquid outlet pipe (25). The phase change cold storage water tanks (9) are connected to form a loop A; the loop A is filled with water, and the loop A forms a circulating heat exchange with the air due to the characteristics of the water's own temperature change and different density; the battery pack (2) is connected to a liquid cooling plate (3) for cooling itself; a plurality of phase change cold storage water tanks (9) are all provided with heat exchange pipes (18), and the heat exchange pipes (18) in two adjacent phase change cold storage water tanks (9) are connected through a pipe (6) so as to communicate with each other; the liquid cooling plate (3) is connected to a first surface cooler (7) through a pipeline (4); the first surface cooler (7) ) is connected to the heat exchange pipe (18) of the phase change cold storage water tank (9) located at the top through a second liquid inlet pipe (8); the heat exchange pipe (18) of the phase change cold storage water tank (9) located at the bottom is connected to the liquid cooling plate (3) through a second liquid outlet pipe (22); the liquid cooling plate (3), the first surface cooler (7) and the heat exchange pipes (18) of the plurality of phase change cold storage water tanks (9) form a loop B; the loop B is filled with refrigerant; and a pump body (5) is installed on the second liquid outlet pipe (22) for promoting the circulation of refrigerant in loop B.

2. The all-weather passive cold storage battery water cooling system according to claim 1, characterized in that: There are four phase-change cold water storage tanks (9) in total; the four phase-change cold water storage tanks (9) are filled with 45°C phase-change material particles (11), 35°C phase-change material particles (13), 25°C phase-change material particles (15) and 15°C phase-change material particles (17) in order from top to bottom; the phase-change critical point value of the 45°C phase-change material particles (11) is 45°C, the phase-change critical point value of the 35°C phase-change material particles (13) is 35°C, the phase-change critical point value of the 25°C phase-change material particles (15) is 25°C, and the phase-change critical point value of the 15°C phase-change material particles (17) is 15°C.

3. The all-weather passive cold storage battery water cooling system according to claim 2, characterized in that: The content distribution ratio of the 45°C phase change material particles (11), the 35°C phase change material particles (13), the 25°C phase change material particles (15) and the 15°C phase change material particles (17) is 2:3:3:

2.

4. The all-weather passive cold storage battery water cooling system according to claim 1, characterized in that: An energy storage container (1) is also installed outside the battery pack (2) and the liquid cooling plate (3).

5. The all-weather passive cold storage battery water cooling system according to claim 1, characterized in that: The heat exchange pipe (18) is a coil.

6. The all-weather passive cold storage battery water cooling system according to claim 1 or 5, characterized in that: Fins are installed on the outside of the heat exchange pipe (18).

7. A battery pack water cooling method with all-weather passive cold storage, characterized in that: The battery pack water cooling system with all-weather passive cold storage according to any one of claims 1 to 6 comprises the following steps: S1, when the battery pack (2) starts to work, the pump body (5) is turned on, and the refrigerant is controlled by the pump body (5) to circulate in the loop B so as to circulate heat for the battery pack (2); S2, during the cycle heat exchange process of the battery pack (2), the refrigerant first exchanges heat with the battery pack (2) and its temperature rises, thereby cooling the battery pack (2). The refrigerant with the increased temperature is then sent to the first surface cooler (7) to exchange heat with the air for cooling. It is then cooled by exchanging heat with a plurality of phase change cold water storage tanks (9) and then sent back to the liquid cooling plate (3) for cycle heat exchange with the battery pack (2); S3, during the operation of the phase change cold storage water tank (9), the refrigerant entering the phase change cold storage water tank (9) exchanges heat with the phase change material particles and water in the phase change cold storage water tank (9), thereby reducing its own temperature. At this time, the temperature of the phase change material particles and the water both rises, and the density of the water decreases due to the increase in temperature, so it begins to float. The water in the second surface cooler (23) decreases in temperature due to heat exchange with the outside air, so the density of the water in the second surface cooler (23) increases and begins to sink. The density of the water in the phase change cold storage water tank (9) decreases and the density of the water in the second surface cooler (23) increases, so that a density difference occurs between the two, so that the water between the phase change cold storage water tank (9) and the second surface cooler (23) begins to flow and exchange heat, thereby circulating; S4, during the water circulation process, when the outside air temperature is lower than the phase change critical point value of the phase change material particles in the phase change cold water storage tank (9), the water in the second surface cooler (23) continuously decreases in temperature by exchanging heat with the outside air, thereby utilizing the density difference to flow into the phase change cold water storage tank (9) and perform heat exchange with the phase change material particles inside, so that the phase change material particles all decrease to the phase change critical point value of the phase change material particles themselves, thereby storing cold energy and facilitating subsequent heat exchange with the refrigerant.

8. The all-weather passive cold storage battery water cooling method according to claim 7, characterized in that: The battery pack (2) is also equipped with a temperature sensor; in step S1, the pump body (5) is turned on only when the temperature sensor detects that the temperature of the battery pack (2) is greater than or equal to 35°C.

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