Separated phase change battery thermal management system

Abstract

The invention provides a separated phase change battery thermal management system. Comprising a liquid-cooled battery pack, a three-way valve, a phase change regenerator, a refrigerating unit and a temperature sensor, the liquid-cooled battery pack comprises a plurality of single batteries arranged according to a row-column structure, and the temperature sensor collects the temperature value of the liquid-cooled battery pack in real time and transmits the temperature value of the liquid-cooled battery pack to the three-way valve; the three-way valve compares the temperature value of the liquid-cooled battery pack with a preset temperature threshold value, and when the temperature value of the liquid-cooled battery pack is larger than or equal to the preset temperature threshold value, the three-way valve is switched to an on state, so that the liquid-cooled battery pack is communicated with the phase change regenerator and the refrigerating unit to enter a cold release mode; cooling liquid is output by the refrigerating unit and then sequentially flows through the phase change regenerator and the liquid cooling plate, and heat exchange is carried out between the cooling liquid and the liquid cooling battery pack when the cooling liquid flows in the cooling liquid flow channel in the liquid cooling plate. The advantages of long-time low-power cold storage and short-time high-power cold release are achieved, and an efficient heat management solution capable of being engineered is provided for an energy storage power station and an electric automobile.

Description

Technical Field

[0001] This invention relates to the field of phase change battery technology, and more particularly to a separate phase change battery thermal management system. Background Technology

[0002] Lithium-ion batteries, with their high energy density, long cycle life, and fast charge / discharge capabilities, are widely used in energy storage, electric vehicles, and electronic products. However, their performance is still affected by various factors, with sensitivity to thermal effects being a major one. When the operating temperature of a lithium-ion battery is below 15°C or above 50°C, its electrochemical performance and lifespan decrease, and the risk of thermal runaway increases. A battery thermal management system can regulate the battery's temperature during operation, ensuring it operates within a safe and efficient temperature range, thereby optimizing battery performance, extending battery life, and improving battery safety. Therefore, an effective full-temperature-range thermal management system is crucial for ensuring the stable operation and long-term reliability of lithium-ion batteries in extreme environments.

[0003] Phase change materials (PCMs) can efficiently absorb or release energy during phase change processes while maintaining a constant temperature, exhibiting excellent temperature control. PCM-based thermal management systems not only offer advantages such as lightweight design, high energy efficiency, and low cost, but also do not consume additional energy, gradually becoming a "next-generation" battery thermal management technology. However, while PCM thermal management systems can slow down battery temperature drops at low temperatures by releasing heat through phase change, they cannot actively heat the battery and may even hinder the battery's own temperature rise. Currently, liquid cooling technology is the most widely used battery thermal management method, effectively controlling battery temperature under high heat load conditions. However, with the increase in capacity and power of liquid-cooled battery packs, liquid cooling systems require high-power chillers to cope with instantaneous heat dissipation demands. This not only increases system size and cost but also leads to inefficient operation of the chiller under most operating conditions, resulting in low overall energy utilization.

[0004] In terms of high-temperature cooling, phase change thermal management technology needs to work in conjunction with active cooling technologies such as liquid cooling to ensure the regeneration of latent heat of phase change. However, integrating too many phase change materials into liquid-cooled battery packs leads to increased weight, and the bulky refrigeration units of liquid cooling systems not only reduce the system's energy density but also cause a significant increase in energy consumption and cost. These problems severely restrict the application of phase change thermal management technology in engineered battery energy storage systems.

[0005] In recent years, to reduce the temperature rise and temperature difference of power batteries at high rates and high ambient temperatures, many solutions have directly integrated phase change materials (PCMs) into the battery pack. Typical approaches include coating or encapsulating PCMs on the outer surface of the cells, filling the spaces between module cells with porous metal / foam structures impregnated with PCM, or arranging gas-liquid phase change media in the cavities of the battery casing / cold plate. This utilizes the latent heat of the PCM to absorb heat during the phase change process and buffer temperature fluctuations, thereby improving the module's temperature uniformity and peak temperature. These solutions generally require adaptation and modification at the battery pack structure level, such as providing encapsulation cavities for the PCM, leakage suppression and electrical insulation designs, or introducing composite heat exchange fillers between modules. In engineering, this often increases assembly complexity and maintenance difficulty, and may affect the compatibility and replaceability of existing battery pack platforms (e.g., requiring disassembly for repair or complete pack replacement).

[0006] Therefore, to achieve a phase change material solution for full-temperature-range thermal management of batteries, it is necessary to explore an efficient and rapid heating method that can quickly restore the battery's temperature and electrical energy under low-temperature conditions. Summary of the Invention

[0007] Embodiments of the present invention provide a separate phase change battery thermal management system to ensure the discharge efficiency and safety of the battery under low temperature conditions.

[0008] To achieve the above objectives, the present invention adopts the following technical solution.

[0009] A separate phase change battery thermal management system includes: a liquid-cooled battery pack, a three-way valve, a phase change cold storage device, a refrigeration unit, and a temperature sensor. The liquid-cooled battery pack, the three-way valve, the phase change cold storage device, and the refrigeration unit are connected in series. The temperature sensor is connected to the liquid-cooled battery pack and the three-way valve.

[0010] The liquid-cooled battery pack includes multiple battery cells arranged in a row and column structure. The liquid-cooled battery pack has a liquid cooling plate inside or at the bottom, and the liquid cooling plate has a cooling liquid flow channel inside.

[0011] The temperature sensor collects the temperature value of the liquid-cooled battery pack in real time and transmits the temperature value to the three-way valve. The three-way valve compares the temperature value of the liquid-cooled battery pack with a preset temperature threshold. When the temperature value of the liquid-cooled battery pack is greater than or equal to the set temperature threshold, the three-way valve switches to the on state, connecting the liquid-cooled battery pack with the phase change accumulator and the refrigeration unit. The system enters the cooling mode. The coolant is output from the refrigeration unit and flows sequentially through the phase change accumulator and the liquid cooling plate. When the coolant flows in the coolant channel in the liquid cooling plate, it exchanges heat with the liquid-cooled battery pack, absorbing the heat generated during battery operation. Subsequently, the coolant carrying the heat returns from the liquid-cooled battery pack to the refrigeration unit or the phase change accumulator for recooling, forming a closed loop.

[0012] Preferably, the system further includes a buffer tank connected to the liquid-cooled battery pack and the refrigeration unit, for storing the coolant transferred from the refrigeration unit. When the system is in cooling mode, the buffer tank transfers the cooled coolant to the liquid-cooled battery pack.

[0013] Preferably, the temperature sensor is installed at the coolant outlet inside the liquid-cooled battery pack or in the central area of ​​the battery module to monitor the maximum temperature and coolant temperature of the liquid-cooled battery pack in real time. Multiple temperature sensors are set according to the battery pack capacity and heat distribution characteristics and are respectively arranged at the battery pack inlet, outlet and different module positions to realize zoned monitoring of the temperature field.

[0014] Preferably, the three-way valve compares the temperature of the liquid-cooled battery pack with a preset temperature threshold. When the temperature of the liquid-cooled battery pack is lower than the set temperature threshold, the three-way valve switches to the off state, isolating the liquid-cooled battery pack from the phase change accumulator and the refrigeration unit. The system enters the cold storage mode, and the refrigeration unit is connected to the phase change accumulator. The low-temperature coolant output by the refrigeration unit flows into the heat exchange channel inside the phase change accumulator through the pipeline, and exchanges heat with the phase change material in the phase change accumulator, so that the temperature of the phase change material gradually decreases and changes from liquid to solid, thereby realizing the storage of cold energy.

[0015] Preferably, the phase change material in the phase change regenerator is a low-temperature phase change material with a melting point of 0-20°C. The low-temperature phase change material includes one or more of the following: undecane, dodecane, tridecane, n-octanol, n-nonanol, n-octanoic acid, n-nonanoic acid, RT15, ​​RT18, OP18, sodium sulfate decahydrate, calcium chloride hexahydrate, lithium chloride monohydrate, and sodium acetate trihydrate; or, the low-temperature phase change material is a composite phase change material with an organic / inorganic phase change material matrix and a thermal conductivity enhancer.

[0016] Preferably, the composite phase change material in the phase change regenerator comprises the following components by mass percentage: 50-90 wt% low-temperature phase change material and 10-50% expanded graphite.

[0017] Preferably, in the cold storage mode, the temperature difference between the phase change material in the phase change cold storage device and the cooling fluid output by the refrigeration unit is 10-15°C; in the cold release mode, the temperature difference between the phase change material in the phase change cold storage device and the coolant in the liquid-cooled battery pack is 35-40°C.

[0018] Preferably, the cold storage capacity of the phase change cold storage device meets the heat absorption requirements of the battery during the set operating period, and the calculation formula is as follows:

[0019]

[0020] in, For the quality of phase change materials, For its latent heat, This refers to the cold storage capacity of the phase change cold storage device.

[0021] Preferably, the phase change cooler has a structure of slat type, tubular type, plate shell type or serpentine tube type.

[0022] Preferably, the individual battery cells in the liquid-cooled battery pack are separated by insulating thermally conductive pads, and the individual battery cells are connected in series and parallel to form a battery module through conductive connectors.

[0023] As can be seen from the technical solutions provided by the embodiments of the present invention above, a separate phase change battery thermal management system is proposed. This system introduces a phase change cold storage device into a traditional liquid cooling system, utilizing the latent heat storage and release characteristics of the phase change material to achieve cooling capacity regulation. This effectively reduces the peak power demand of the refrigeration unit, achieving a "peak shaving and valley filling" effect. By rationally designing the cold storage capacity, power, and phase change material characteristics, the present invention achieves the advantages of long-term low-power cold storage and short-term high-power cold release, while reducing the size and energy consumption of the refrigeration unit, improving the system's energy density and economy. This provides an engineerable and efficient thermal management solution for energy storage power stations and electric vehicles.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a structural diagram of a low-power, adjustable full-temperature-range phase change battery thermal management system provided in an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the cold storage process in Example 1 of the present invention;

[0028] Figure 3 This is a schematic diagram of the cooling process in Example 1 of the present invention;

[0029] Figure 4 This is a schematic diagram comparing the cooling power consumption of Embodiment 2 and Comparative Example 1.

[0030] Figure 5This is a schematic diagram comparing the cooling energy consumption and coefficient of performance of the system in Embodiment 2 of the present invention with those in Comparative Example 1. Detailed Implementation

[0031] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0032] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or couplings. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0033] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0034] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments. These embodiments do not constitute a limitation on the embodiments of the present invention.

[0035] Phase change energy storage (PCE) accumulators store and release cooling capacity by absorbing and releasing latent heat: when battery cooling demand is low, excess cooling capacity from the refrigeration unit is stored in the PCE; when cooling demand surges, the PCE releases cooling capacity to replenish the liquid cooling system, thereby reducing the peak load of the refrigeration unit. This "peak shaving and valley filling" mechanism not only reduces the maximum design power and operating energy consumption of the refrigeration unit, but also improves the average load rate of the refrigeration equipment, making the system operation more stable, efficient, and economical.

[0036] This invention addresses the contradiction between low-temperature preheating, high-temperature heat dissipation, and thermal management efficiency by optimizing the performance of phase change materials, designing the structure of liquid-cooled battery packs, precisely controlling electrical energy, and efficiently integrating the system. It constructs a full-temperature-range phase change thermal management solution that balances efficiency, economy, and reliability, providing technical support for improving the performance of lithium-ion batteries in extreme environments.

[0037] The structure of a low-power, adjustable full-temperature-range phase change battery thermal management system provided in this embodiment of the invention is as follows: Figure 1 As shown, it includes: a liquid-cooled battery pack 1, a three-way valve 2, a phase change accumulator 3, a refrigeration unit 4, a buffer tank 5, and a temperature sensor 6. The liquid-cooled battery pack 1, the three-way valve 2, the phase change accumulator 3, and the refrigeration unit 4 are connected in series. The buffer tank 5 is connected to the liquid-cooled battery pack 1 and the refrigeration unit 4. The temperature sensor 6 is connected to the liquid-cooled battery pack 1 and the three-way valve 2.

[0038] In this embodiment of the invention, the temperature sensor (6) is preferably installed at the coolant outlet inside the liquid-cooled battery pack (1) or in the central area of ​​the battery module to monitor the highest temperature of the battery pack and the coolant temperature in real time, thereby accurately reflecting the heat dissipation effect of the system. Depending on the battery pack capacity and thermal distribution characteristics, 2 to 6 temperature sensors can be set and arranged at the battery pack inlet, outlet and different module positions to achieve zoned monitoring and precise control of the temperature field.

[0039] The liquid-cooled battery pack 1 comprises multiple battery cells arranged in a row-and-column structure, which are connected in series and parallel to form a battery module. A liquid-cooled plate is installed inside or at the bottom of the liquid-cooled battery pack for efficient heat dissipation. The liquid-cooled plate can be laid flat at the bottom of the liquid-cooled battery pack or inserted between adjacent liquid-cooled battery packs. The liquid-cooled plate has internal coolant channels for forming a surface-contact or sandwich-type heat exchange structure with the battery cells. The coolant, output from the refrigeration unit 4, flows sequentially through the phase change accumulator 3 and the liquid-cooled plate. While flowing within the liquid-cooled plate, it exchanges heat with the liquid-cooled battery pack, absorbing the heat generated during battery operation. Subsequently, the coolant, carrying heat, returns from the liquid-cooled battery pack 1 to the refrigeration unit 4 or the phase change accumulator 3 for recooling, forming a closed loop. This achieves efficient temperature control of the liquid-cooled battery pack 1 and dynamic regulation of the system energy.

[0040] The three-way valve 2 is used to control the on / off state of the liquid cooling circuit based on the temperature of the liquid-cooled battery pack. The temperature sensor 6 collects the temperature value of the liquid-cooled battery pack 1 in real time and transmits this value to the three-way valve 2. The three-way valve 2 compares the liquid-cooled battery pack temperature value with a preset temperature threshold. When the liquid-cooled battery pack temperature value is greater than or equal to the preset temperature threshold, the three-way valve 2 automatically switches to the on state, connecting the liquid-cooled battery pack 1 with the phase change cold storage unit 3 and the refrigeration unit 4, and the system enters a cooling release mode for rapid cooling of the liquid-cooled battery pack. When the liquid-cooled battery pack temperature is lower than the preset temperature threshold, the three-way valve 2 switches to the off state, isolating the liquid-cooled battery pack 1 from the phase change cold storage unit 3 and the refrigeration unit 4, and the system enters a cold storage mode, where the refrigeration unit 4 stores cold for the phase change cold storage unit 3 at low power. The temperature threshold can be set according to the battery type and application scenario, preferably 55℃ (the upper limit of safe operating temperature for lithium-ion liquid-cooled battery packs), but can also be adjusted within the range of 40℃ to 60℃ according to different thermal management requirements.

[0041] Phase change accumulator 3 is used to pre-cool the coolant from the liquid-cooled battery pack 1. When the three-way valve 2 is closed and the system is in cooling mode, the high-temperature coolant in the liquid-cooled battery pack 1 flows out and into the phase change accumulator 3. The coolant exchanges heat with the phase change material in the phase change accumulator 3, lowering the coolant temperature and enabling long-term, low-power cooling storage of the liquid-cooled system. The cooled coolant is then transferred to the refrigeration unit 4.

[0042] Refrigeration unit 4 provides a cold source for the system, and its outlet is connected to the inlet of phase change accumulator 3. Refrigeration unit 4 indirectly regulates the temperature of the liquid-cooled battery pack 1 through phase change accumulator 3. During the cooling phase, refrigeration unit 4 and phase change accumulator 3 operate in series, with the coolant flowing sequentially through refrigeration unit 4 and phase change accumulator 3 before entering the liquid cooling plate inside the liquid-cooled battery pack 1, achieving rapid cooling of the liquid-cooled battery pack. During the storage phase, refrigeration unit 4 operates at low power, connected only to phase change accumulator 3, providing cold energy storage for the phase change material in phase change accumulator 3, achieving dynamic regulation and recycling of the cold energy. Through this coordinated operation, the system can achieve low-power cold storage during low-load periods and high-power cooling during high-heat-load periods, thus achieving energy-saving effects such as peak shaving and valley filling.

[0043] Buffer tank 5 is used to store the coolant transferred from the refrigeration unit 4, balancing the flow and pressure of the entire thermal management system and improving operational stability and safety. When the system is in cooling mode, buffer tank 5 transfers the cooled coolant to the liquid-cooled battery pack 1.

[0044] Cold storage process: The refrigeration unit 4 is controlled to operate continuously at low power for 2-6 hours to provide cooling energy for the phase change material in the phase change accumulator 3. Specifically, the low-temperature coolant output from the refrigeration unit 4 flows through pipelines into the heat exchange channel inside the phase change accumulator 3, where it exchanges heat with the phase change material, causing the temperature of the phase change material to gradually decrease and change from a liquid to a solid state, thereby achieving cold energy storage. During the cold storage period, the liquid-cooled battery pack 1 is disconnected from the liquid-cooled circuit by the three-way valve 2, and does not participate in heat exchange, allowing the refrigeration unit 4 to operate continuously under stable low-power conditions, reducing instantaneous load.

[0045] Cooling process: Control the three-way valve 2 to reconnect the liquid-cooled battery pack 1 to the liquid-cooling circuit, so that the phase change accumulator and the refrigeration unit can operate in series to cool the liquid-cooled battery pack 1 for 0.5 to 1.5 hours; when the liquid-cooled battery pack 1 is discharging, the refrigeration unit 4 can be shut down, and the cooling capacity can be released by relying solely on the phase change accumulator, or the output power of the refrigeration unit 4 can be significantly reduced to reduce the instantaneous peak load and improve the cooling efficiency by 1% to 10%.

[0046] In the technical solution of this invention, the capacity and power range of the phase change cold storage device 3 are set so that the phase change cold storage device 3 can absorb the heat generated by the battery during the 0-5C charging and discharging process of the liquid-cooled battery pack. 5C discharge refers to the battery discharging at 5 times the rated power to achieve partial or complete cooling. The capacity and power range of the phase change cold storage device (3) should be determined comprehensively based on multiple parameters such as the heat generation characteristics of the battery pack, the allowable temperature rise (or the maximum / target temperature), the phase change enthalpy and phase change temperature of the selected phase change material, the geometry and heat transfer performance of the heat exchanger, the flow rate of the liquid cooling circuit, and the charging and cooling time that the refrigerator (4) can be allocated. The cold storage capacity of the phase change cold storage device meets the heat absorption requirements of the battery during the set working period, and its calculation can be approximately determined by the formula:

[0047]

[0048] in, For the quality of phase change materials, For its latent heat, This refers to the cold storage capacity of the phase change cold storage device.

[0049] The power range is set based on the difference between the peak heat release of the battery and the cooling capacity that the refrigerator can provide, so that the cold storage can store enough energy in the low-power cold storage stage and release the cooling capacity quickly in the high-power cold release stage, thereby achieving a dynamic balance of the system's cooling capacity output.

[0050] When the liquid-cooled battery pack is not in operation, it can store cold for a long time at a low power of 10-50kW, providing thermal management capabilities for subsequent working cycles.

[0051] In the technical solution of this invention, the phase change material in the phase change cold storage device 3 is a low-temperature phase change material with a melting point of 0 to 20°C, including one or more of undecane, dodecane, tridecane, n-octanol, n-nonanol, n-octanoic acid, n-nonanoic acid, RT15, ​​RT18, OP18, sodium sulfate decahydrate, calcium chloride hexahydrate, lithium chloride monohydrate, sodium acetate trihydrate, etc., or a composite phase change material with an organic / inorganic phase change material matrix and a thermal conductivity enhancer, so as to improve the heat exchange efficiency and cold storage capacity.

[0052] In the technical solution of the present invention, the mass percentage of the composite phase change material in the phase change accumulator 3 is 50~90wt% low temperature phase change material and 10~50% expanded graphite.

[0053] In this technical solution, the selected phase change material creates a small temperature difference of approximately 10–15°C between itself and the cooling fluid output by the refrigeration unit during the cold storage stage. This allows the refrigeration unit to operate for extended periods under low power and stable conditions, achieving slow cold storage and stable energy storage. During the cooling release stage, the temperature difference between the phase change material within the phase change accumulator and the cooling fluid of the liquid-cooled battery pack can reach 35–40°C, significantly improving the instantaneous heat transfer driving force and thus enabling high-power cooling release. Through the differentiated design of the temperature difference between the cold storage and cooling release stages, dynamic control of the system's cooling output power is achieved, resulting in low power consumption during the cold storage stage and high efficiency during the cooling release stage, ensuring the energy efficiency and responsiveness of the thermal management system.

[0054] In the technical solution of this invention, by coordinating the operation of the phase change accumulator and the liquid cooling system, the rated cooling power of the refrigeration unit is reduced by 30% to 80% compared with the liquid cooling system without the phase change accumulator, which significantly reduces the system's operating energy consumption and the size of the refrigeration unit.

[0055] In the technical solution of the present invention, the phase change cold storage 4 can be selected as a slat type, a tube type, a plate shell type or a serpentine tube type, or a combination of the above structures, to adapt to different installation space and heat exchange efficiency requirements.

[0056] In the technical solution of the present invention, the separate phase change battery thermal management system reduces the rated cooling capacity of the refrigeration unit by introducing a phase change cold storage device, thereby reducing the overall volume and operation and maintenance cost of the refrigeration unit 4 and significantly reducing the noise of refrigeration operation.

[0057] Comparative Example 1

[0058] The phase change regenerator is not present in the system; the entire system relies solely on a liquid cooling system for cooling. The refrigeration unit is an 8HP chiller to meet its cooling requirements. This chiller has a volume of 1.69 m³ and a weight of 320 kg.

[0059] The liquid-cooled battery pack comprises 120 square batteries, and the rated power of the liquid-cooled battery pack is 20kWh.

[0060] Example 1

[0061] The composite phase change material in the phase change energy storage device is composed of 60% RT18 phase change material and 40 wt% expanded graphite. The liquid-cooled battery pack contains 56 cells. The individual cells in the liquid-cooled battery pack are separated by insulating thermally conductive pads, and the ends of the individual cells are connected by copper sheets to form a series conductive path.

[0062] Figure 2 A schematic diagram of the cold storage process in Example 1 is shown. During the cold storage process, the liquid-cooled battery pack is disconnected from the circuit by controlling the three-way valve 2, and the refrigeration unit runs continuously at low power for about 4 hours to provide cooling capacity to the phase change cold storage device. During this period, the phase change material in the phase change cold storage device gradually solidifies, thereby achieving the storage of cooling capacity.

[0063] Figure 3 A schematic diagram of the cooling process in Example 1 is shown. During the cooling process, the liquid-cooled battery pack is connected to the circuit by adjusting the three-way valve 2. The phase change accumulator and the refrigeration unit operate in series to provide cooling for the battery. During this process, the phase change material in the phase change accumulator melts and releases cooling energy, lasting for about 1 hour. This meets the temperature control requirements of the battery under 3C discharge rate, ensuring that the battery remains within its optimal operating temperature range throughout the entire discharge process.

[0064] Example 2

[0065] The composite phase change material in the phase change regenerator is composed of 70% phase change material OP12 and 30wt% expanded graphite.

[0066] The liquid-cooled battery pack is a 20kWh battery module, which contains 120 square batteries and has a rated power of 20kWh.

[0067] Based on the operating mode of battery energy storage systems used for power peak shaving in Guangdong during the summer, the cooling performance of a split phase change battery thermal management system was evaluated under actual conditions, including the system's temperature control performance and cost. The battery energy storage system discharges during periods of high power load and charges during periods of low power load. The system's chiller provides cooling during the discharge and charging of the liquid-cooled battery pack, but not during other times. Under the condition that the temperature of the liquid-cooled battery pack does not exceed 30 ℃ and the latent heat of the phase change accumulator is completely recovered after each cycle, the maximum power, daily power consumption, and operating cost of the phase change thermal management system were tested.

[0068] Figure 4This is a schematic diagram comparing the cooling power consumption of the system in Example 2 and Comparative Example 1.

[0069] Figure 5 This is a schematic diagram comparing the cooling energy consumption and coefficient of performance of the systems in Example 2 and Comparative Example 1.

[0070] This study compares the cooling power and COP (Coefficient of Performance) of an independent liquid cooling system and a separate phase change thermal management system. The independent liquid cooling system has a maximum cooling power of 19.26 kW during battery discharge, but only 3.25 kW during charging. This significant imbalance in cooling power between discharge and charging necessitates a larger chiller unit and higher costs. The independent liquid cooling system requires an 8HP chiller to meet its cooling needs. This chiller has a volume of 1.69 m³ and weighs 320 kg. With the "peak shaving and valley filling" effect of the phase change regenerator, the maximum cooling power of the separate phase change thermal management system is reduced to 9.94 kW, and a 5HP chiller can meet the system's cooling requirements. Compared to the independent liquid cooling system, the maximum cooling power of this system is reduced by 48.4%, and the chiller's volume and weight are reduced by 0.91 m³ and 179 kg, respectively. The combined volume of the phase change energy storage unit and the refrigeration unit is still 5.3% smaller than that of the refrigeration unit in an independent liquid cooling system. During discharge, considering the difference in refrigeration unit energy efficiency between day and night, the cooling energy consumption of the split phase change thermal management system is reduced by 9.16 kWh compared to the independent liquid cooling system. The phase change energy storage unit releases cold energy during battery discharge and stores cold energy during battery charging; therefore, the cooling power of the system during charging is higher than that of the independent liquid cooling system. The cooling power of the split phase change thermal management system during charging is 7.2 kW, which is 3.95 kW higher than that of the independent liquid cooling system. Therefore, the cooling energy consumption of this system during charging is 8.53 kWh higher. In Guangdong, the industrial and commercial electricity price during peak daytime hours is 1.3 yuan / kWh, and the industrial and commercial electricity price during off-peak nighttime hours is 0.34 yuan / kWh. Considering the difference in peak and off-peak electricity prices, the cooling electricity cost of the split phase change thermal management system for one charge-discharge cycle is 41% lower than that of the independent liquid cooling system.

[0071] The above results demonstrate that the phase change energy storage device balances the cooling power of the battery cooling system between the discharge and charging processes, achieving peak shaving and valley filling of cooling power. The maximum power of liquid cooling is reduced by 48.4%, and the volume and weight of the water chiller are reduced by more than 50%. Furthermore, considering the difference in ambient temperature between peak and low load periods for the battery system, the COP of the split phase change thermal management system is improved by 9.24%, the cooling energy consumption per charge-discharge cycle is reduced by 7.4%, and electricity costs are reduced by 41%.

[0072] In summary, this invention introduces a phase change accumulator into the liquid cooling system, utilizing the latent heat storage and release characteristics of the phase change accumulator to regulate the cooling capacity, thereby achieving peak load shifting and valley filling, and effectively reducing the peak power demand of the refrigeration unit.

[0073] The phase change material has a small temperature difference with the cold storage fluid, enabling long-term cold storage with low power, while the phase change material has a large temperature difference with the cooling fluid of the liquid-cooled battery pack, enabling instantaneous high-power cooling, thereby improving the cold capacity regulation capability and cooling efficiency.

[0074] The selected phase change material and composite design can absorb heat during the 0-5C charge and discharge process of the liquid-cooled battery pack, achieving partial or complete cooling; when the liquid-cooled battery pack is not working, it can store cold for a long time through low-power cooling, providing thermal management capabilities for subsequent working cycles.

[0075] The power and size of the refrigeration unit can be reduced, the overall energy consumption of the system is significantly reduced, and the weight and cost of the system are reduced. While ensuring heat dissipation performance, the volume of the liquid-cooled battery pack can remain basically unchanged.

[0076] The combined cold storage and liquid cooling design balances efficient cooling with energy saving and economy, making it suitable for various application scenarios such as energy storage power stations and electric vehicles, and has good engineering and promotion value.

[0077] The technical approach of this invention emphasizes a "separate" design: the phase change material does not directly contact the battery, but instead forms an independent phase change cold storage unit (containing internal heat exchange pipes / channels), which is connected to the liquid cooling circuit in series / parallel via a standard interface, and switches between modes such as "complete cold storage - complete cold release - proportional distribution / bypass" as needed through valves. This structure avoids structural modifications to the battery pack itself, facilitating platform integration and subsequent maintenance. Furthermore, through engineered matching of cold storage capacity and heat exchange power, the available cooling capacity during the cold release phase at least covers the difference between the battery's peak heat generation and the output of the derating chiller unit. If necessary, the cold storage unit can passively provide short-term high-power cooling capacity when the chiller unit is off, achieving the system objectives of peak shaving and derating selection.

[0078] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0079] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for apparatus or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The apparatus and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0080] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A separate phase change battery thermal management system, characterized in that, include: The system includes a liquid-cooled battery pack, a three-way valve, a phase change cold storage device, a refrigeration unit, and a temperature sensor. The liquid-cooled battery pack, the three-way valve, the phase change cold storage device, and the refrigeration unit are connected in series. The temperature sensor is connected to the liquid-cooled battery pack and the three-way valve. The liquid-cooled battery pack includes multiple battery cells arranged in a row and column structure. The liquid-cooled battery pack has a liquid cooling plate inside or at the bottom, and the liquid cooling plate has a cooling liquid flow channel inside. The temperature sensor collects the temperature value of the liquid-cooled battery pack in real time and transmits the temperature value to the three-way valve. The three-way valve compares the temperature value of the liquid-cooled battery pack with a preset temperature threshold. When the temperature value of the liquid-cooled battery pack is greater than or equal to the set temperature threshold, the three-way valve switches to the on state, connecting the liquid-cooled battery pack with the phase change accumulator and the refrigeration unit. The system enters the cooling mode. The coolant is output from the refrigeration unit and flows sequentially through the phase change accumulator and the liquid cooling plate. When the coolant flows in the coolant channel in the liquid cooling plate, it exchanges heat with the liquid-cooled battery pack, absorbing the heat generated during battery operation. Subsequently, the coolant carrying the heat returns from the liquid-cooled battery pack to the refrigeration unit or the phase change accumulator for recooling, forming a closed loop.

2. The system according to claim 1, characterized in that, The system also includes a buffer tank connected to the liquid-cooled battery pack and the refrigeration unit, which stores the coolant transferred from the refrigeration unit. When the system is in cooling mode, the buffer tank transfers the cooled coolant to the liquid-cooled battery pack.

3. The system according to claim 1, characterized in that, The temperature sensor is installed at the coolant outlet inside the liquid-cooled battery pack or in the central area of ​​the battery module to monitor the maximum temperature and coolant temperature of the liquid-cooled battery pack in real time. Multiple temperature sensors are set according to the battery pack capacity and heat distribution characteristics and are respectively arranged at the battery pack inlet, outlet and different module positions to realize zoned monitoring of the temperature field.

4. The system according to claim 1, characterized in that, The three-way valve compares the temperature of the liquid-cooled battery pack with a preset temperature threshold. When the temperature of the liquid-cooled battery pack is lower than the set temperature threshold, the three-way valve switches to the off state, isolating the liquid-cooled battery pack from the phase change accumulator and the refrigeration unit. The system enters the cold storage mode, and the refrigeration unit is connected to the phase change accumulator. The low-temperature coolant output by the refrigeration unit flows into the heat exchange channel inside the phase change accumulator through the pipeline, and exchanges heat with the phase change material in the phase change accumulator, so that the temperature of the phase change material gradually decreases and changes from liquid to solid, thereby realizing the storage of cold energy.

5. The system according to claim 1, characterized in that, The phase change material in the phase change cold storage device is a low-temperature phase change material with a melting point of 0-20℃. The low-temperature phase change material includes one or more of the following: undecane, dodecane, tridecane, n-octanol, n-nonanol, n-octanoic acid, n-nonanoic acid, RT15, ​​RT18, OP18, sodium sulfate decahydrate, calcium chloride hexahydrate, lithium chloride monohydrate, sodium acetate trihydrate, etc.; or, the low-temperature phase change material is a composite phase change material with an organic / inorganic phase change material matrix and a thermal conductivity enhancer added.

6. The system according to claim 1, characterized in that, The composite phase change material in the phase change regenerator comprises the following components by mass percentage: 50-90 wt% low-temperature phase change material and 10-50% expanded graphite.

7. The system according to claim 1, characterized in that, In the cold storage mode, the temperature difference between the phase change material in the phase change cold storage unit and the cooling fluid output by the refrigeration unit is 10-15℃; in the cold release mode, the temperature difference between the phase change material in the phase change cold storage unit and the coolant in the liquid-cooled battery pack is 35-40℃.

8. The system according to claim 1, characterized in that, The phase change cold storage capacity of the cold storage device meets the heat absorption requirements of the battery during the set working period, and the calculation formula is as follows: ； in, For the quality of phase change materials, For its latent heat, This refers to the cold storage capacity of the phase change cold storage device.

9. The system according to claim 1, characterized in that, The phase change cold storage device can be in the form of a slat type, a tubular type, a plate-shell type, or a serpentine tube type.

10. The system according to claim 1, characterized in that, The individual battery cells in the liquid-cooled battery pack are separated by insulating thermally conductive pads, and the individual battery cells are connected in series and parallel to form a battery module through conductive connectors.

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