Refrigerant direct cooling and heating management system and method of energy storage system

Abstract

The invention discloses a refrigerant direct cooling heat management system and method of an energy storage system, and relates to the technical field of heat management of energy storage systems. The system comprises a compressor, a four-way reversing valve, an outdoor heat exchanger, an electronic expansion valve and a battery direct cooling plate integrated on a battery module, and all the parts are communicated through pipelines to form a closed-loop primary loop refrigerant circulating system. According to the system, a traditional secondary liquid cooling loop is abandoned, and a refrigerant is subjected to direct phase-change heat exchange in a micro-channel of the direct cooling plate. The method comprises the steps of mode judgment, temperature difference priority control and temperature target control, and precise temperature control is achieved by dynamically adjusting the opening degree of the electronic expansion valve and the frequency of the compressor. The problems of low heat exchange efficiency, system complexity, leakage risk and the like of a traditional scheme are solved, the energy efficiency and the integration degree are remarkably improved, and the extreme temperature equalization effect that the temperature difference of the battery module is smaller than 3 DEG C is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage system thermal management, in particular to a refrigerant direct cooling thermal management system and method for an energy storage system, applied to an energy storage container or an energy storage unit. BACKGROUND

[0002] The statements in this section merely provide background information related to the present disclosure and can not constitute the prior art.

[0003] With the rapid expansion of electrochemical energy storage (especially lithium-ion battery energy storage), the thermal management of energy storage systems has become a core technology related to their safety, efficiency and service life. During the charging and discharging process of the energy storage system, the battery will generate a large amount of heat, and if it cannot be promptly and evenly removed, it will lead to excessive battery temperature and excessive temperature difference, thereby causing accelerated performance degradation, shortened service life, and even serious safety accidents such as thermal runaway. Currently, the mainstream thermal management solutions for energy storage systems in the industry are air cooling and liquid cooling, but both of these solutions have inherent defects and cannot meet the urgent needs of large-scale energy storage systems for high energy efficiency, high uniformity, high integration and high safety.

[0004] Prior art one: air cooling solution and its defects The air cooling solution uses a fan to drive air to flow through the surface of the battery and uses the convective action of the air to remove heat. Although this solution has a simple structure and low initial cost, its defects are particularly prominent in large-scale energy storage systems: 1. Low heat exchange efficiency and high energy consumption: The low specific heat capacity and poor thermal conductivity of air result in low heat exchange efficiency. To achieve the desired cooling effect, the air volume must be increased, which causes the fan to operate at high power for a long time, and its own energy consumption can account for a significant proportion of the total system energy consumption, severely reducing the overall energy efficiency (cycle efficiency) of the energy storage system. In high-temperature environments, the cooling capacity is dramatically reduced.

[0005] 2. Poor temperature uniformity: The air is continuously heated as it flows through the battery modules, resulting in a significant inlet and outlet temperature difference between the front and rear ends of the air duct, typically up to 8-15℃. The large temperature difference exacerbates the inconsistency between the batteries, forming a "bucket effect", accelerating the overall capacity decay of the battery pack, and causing safety hazards.

[0006] 3. Poor environmental adaptability: Its heat dissipation is completely dependent on external air, and in harsh environments such as dust, humidity, salt spray or high temperature, not only is the cooling effect difficult to guarantee, but also faults may be caused by dust blockage, condensation, corrosion, etc.

[0007] 4. High noise and low space utilization: The high-power fan operation produces considerable noise, and to ensure the smoothness of the air duct, the battery arrangement density is limited, reducing the unit volume energy density of the energy storage container.

[0008] Prior Art Two: Liquid Cooling Solution and Its Defects The liquid cooling solution uses a cooling liquid (such as a water-glycol solution) as a heat exchange medium, and exchanges heat with the battery through a liquid cooling plate. Compared with air cooling, its heat exchange capacity is significantly improved, but it still has the following fundamental problems: 1. Complex system with secondary heat exchange loss: The liquid cooling system is essentially a "secondary loop" system. First, the refrigerant circuit (primary loop) needs to prepare cold water in the "water chiller", then transfer the cold energy to the cooling liquid circuit (secondary loop), and finally flow to the battery by the cooling liquid. Both heat exchange processes have a temperature difference, causing significant irreversible energy loss, and the system energy efficiency ratio (COP) still has a large optimization space.

[0009] 2. There are risks related to cooling liquid: The entire secondary loop is filled with cooling liquid, which has a potential leakage risk. Cooling liquid leakage not only pollutes the environment, but also can cause short circuit and fire if it comes into contact with live parts. In addition, the cooling liquid may experience performance degradation, corrosion or microbial growth after long-term operation, requiring regular maintenance and replacement, increasing the operation and maintenance cost and complexity throughout the life cycle.

[0010] 3. Slow response speed and limited temperature control precision: The cooling liquid has a large heat capacity, and the system has a large thermal inertia, which causes it to respond slowly to rapid changes in battery heat power. At the same time, since the cooling liquid itself has a temperature rise (usually 3-5°C) when flowing through the liquid cooling plate, it limits the further reduction of the internal temperature difference (ΔT) of the battery pack, making it difficult to achieve precise temperature control at the cell level.

[0011] 4. Additional power consumption and space occupation: The secondary loop needs to be equipped with a circulating water pump, a liquid storage tank, a water replenishment and filtration device, etc., which not only increases the additional power consumption point (water pump), but also occupies valuable internal space of the energy storage container, making it difficult to further improve the system integration.

[0012] In summary, the existing air cooling and liquid cooling solutions cannot achieve an optimal balance between energy efficiency, temperature uniformity, integration, safety, and maintenance convenience, restricting the development of energy storage systems in the direction of larger capacity, higher power, and longer life. Therefore, a new heat management technology path is urgently needed to fundamentally solve the above problems. SUMMARY

[0013] The purpose of the present application is: in view of the current mainstream energy storage thermal management scheme, the air cooling mode has low heat dissipation efficiency and poor temperature control uniformity, and the traditional liquid cooling mode has the problems of secondary heat exchange energy loss, cooling liquid leakage risk, slow system response and low integration, a refrigerant direct cooling thermal management system and method of energy storage system are provided, the traditional secondary liquid cooling circuit is abandoned, the air conditioner refrigerant circulation system is deeply integrated with the battery thermal management, the refrigerant is directly evaporated / condensed in the refrigerant plate embedded in the battery module, and direct and efficient heat exchange with the battery monomer is realized.

[0014] The technical scheme of the present application is as follows: A refrigerant direct cooling thermal management system of an energy storage system comprises: A compressor, a four-way reversing valve, an outdoor heat exchanger, an electronic expansion valve, a battery direct cooling plate and a gas-liquid separator; the compressor, the four-way reversing valve, the outdoor heat exchanger, the electronic expansion valve, the battery direct cooling plate and the gas-liquid separator are communicated through pipelines to constitute a closed one-loop refrigerant circulation system; The battery direct cooling plate is integrated in the battery module of the energy storage system, the inside of the battery direct cooling plate is provided with a flow channel for the circulation of refrigerant, and the refrigerant is configured to directly evaporate or condense in the flow channel to directly exchange heat with the battery module.

[0015] Further, the battery direct cooling plate is a flow channel plate with a parallel multi-branch microchannel structure inside, and the battery direct cooling plate is integrated as a structural support component in the bottom or side of the battery module; the outdoor heat exchanger is a finned tube heat exchanger, and one side of the outdoor heat exchanger is provided with a fan for providing forced convection.

[0016] Further, it further comprises a pressure sensor group and a temperature sensor group; the pressure sensor group comprises a high-pressure sensor arranged at the exhaust end of the compressor and a low-pressure sensor arranged at the suction end of the compressor; the temperature sensor group comprises a battery temperature sensor for detecting the temperature of the battery module and a system temperature sensor for detecting the ambient temperature and the coil temperature of the outdoor heat exchanger.

[0017] Further, the compressor is a variable frequency compressor configured to adjust the operating frequency according to the control instruction; the electronic expansion valve is a stepper motor driven valve configured to adjust the valve opening to control the refrigerant flow; the fan of the outdoor heat exchanger is a direct current brushless fan supporting stepless speed regulation.

[0018] Further, the four-way reversing valve is configured to change the flow direction of the refrigerant, so that the system operates in a refrigeration mode or a heating mode; In the cooling mode, the four-way reversing valve guides the refrigerant discharged by the compressor to flow through the outdoor heat exchanger as a condenser, the electronic expansion valve, the battery direct cooling plate as an evaporator, and finally return to the compressor through the gas-liquid separator. In the heating mode, the four-way reversing valve guides the refrigerant discharged by the compressor to flow through the battery direct cooling plate as a condenser, the electronic expansion valve, the outdoor heat exchanger as an evaporator, and finally return to the compressor through the gas-liquid separator.

[0019] The application further provides a refrigerant direct cooling thermal management method of an energy storage system, applied to the refrigerant direct cooling thermal management system of the energy storage system, and comprising the following steps: A mode judgment step: obtaining a temperature parameter of a battery module and an ambient temperature, and controlling the four-way reversing valve to switch the flow direction of the refrigerant according to the comparison result of the temperature parameter and a preset threshold value, so that the system enters a cooling mode or a heating mode; A temperature difference priority control step: monitoring the difference between the highest temperature and the lowest temperature in the battery module in real time, and preferentially adjusting the opening degree of the electronic expansion valve when the difference exceeds a preset temperature difference threshold value, so as to optimize the distribution of the refrigerant in the battery direct cooling plate; A temperature target control step: under the premise of satisfying the temperature difference priority control step, adjusting the operating frequency of the compressor according to the deviation of the temperature parameter of the battery module from a set target temperature.

[0020] Further, in the cooling mode, the temperature target control step specifically comprises: dynamically calculating a target evaporation temperature according to the highest temperature of the battery module, the target evaporation temperature being negatively correlated with the highest temperature, that is, when the highest temperature rises, the target evaporation temperature is reduced; The method further comprises a superheat protection step: calculating the superheat degree of the refrigerant at the suction port of the compressor in real time, and reducing the opening degree of the electronic expansion valve when the superheat degree is lower than a preset safety threshold value, so as to prevent liquid refrigerant from entering the compressor.

[0021] Further, in the heating mode, the temperature target control step specifically comprises: adjusting the operating frequency of the compressor according to the deviation of the lowest temperature of the battery module from a preset heating target temperature; The method further comprises a defrosting control step: monitoring the coil temperature of the outdoor heat exchanger in real time, and controlling the four-way reversing valve to switch to the cooling mode for defrosting when the coil temperature is lower than a preset frosting threshold value and the duration exceeds a preset time length, until the coil temperature rises to a defrosting exit threshold value.

[0022] Further, a fan rotating speed control step is further included, which acquires a system exhaust pressure value or a middle part temperature value of the outdoor heat exchanger in real time, and dynamically adjusts a rotating speed of a fan arranged on the outdoor heat exchanger according to a deviation of the exhaust pressure value or the middle part temperature value from a preset target value, so as to maintain a condensing pressure of the system in a preset high-efficiency operation interval.

[0023] Further, a system safety protection step is further included, which includes at least one of the following logics: When it is detected that the exhaust pressure of the system or the exhaust temperature of the compressor exceeds a preset safety upper limit, a degradation protection strategy is executed, the operating frequency of the compressor is reduced, the opening degree of the electronic expansion valve is increased, and the rotating speed of the fan arranged on the outdoor heat exchanger is adjusted to a maximum value; When it is detected that the low pressure of the system is lower than a lower limit of a saturation pressure corresponding to a current evaporation temperature and lasts for a preset time length, a refrigerant leakage alarm is triggered; When it is detected that a difference between the highest temperature and the lowest temperature of the battery module exceeds a preset alarm threshold and lasts for a preset time length, a battery consistency alarm is triggered or a power reduction request is sent.

[0024] Compared with the existing technology, the present application has the following beneficial effects: The present application is different from the traditional liquid cooling "refrigerant-cooling liquid-battery" secondary heat exchange architecture, and creatively integrates the battery thermal management system and the air conditioner refrigerant circulation system to form a closed refrigerant direct phase change heat exchange loop. The system can not only efficiently dissipate heat for the battery in the refrigeration mode, but also can heat the battery at low temperature through the heat pump circulation in the heating mode, and realizes intelligent temperature control in all climates. The present application has the following beneficial effects: 1. Revolutionary energy efficiency improvement: canceling the secondary heat exchange loop and reducing the heat transfer links, the system COP (coefficient of performance) can be improved by 25%~40% compared with the traditional liquid cooling system, and the self-consumption power of the energy storage system is greatly reduced.

[0025] 2. Extreme temperature uniformity: using the phase change isothermal property and the microchannel design, the overall temperature difference of the battery pack can be stably controlled within 3℃, and the battery cycle life is effectively prolonged by more than 20%.

[0026] 3. High system integration and simplification: a large number of components such as cooling liquid, water pump, liquid storage tank, etc. are saved, the system volume and weight are reduced by about 30%, and the power density and reliability of the energy storage system are improved.

[0027] 4. Intelligent temperature control in all climates: integrating the heat pump function, the system can work efficiently in the environment temperature range of-25℃ to +50℃, realize rapid low-temperature heating and high-temperature heat dissipation of the battery, and guarantee the performance and safety of the energy storage system in all time domains and all regions.

[0028] 5. Significantly reduced maintenance costs: The system is a fully sealed design, eliminating the need to replace coolant and essentially achieving maintenance-free operation, thus reducing the operating costs throughout the entire life cycle. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in the embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0030] Fig. 1 This is a schematic diagram of the refrigerant circulation flow direction of the system in cooling mode provided in the embodiment of the present invention; Fig. 2 This is a schematic diagram of the refrigerant circulation flow in the heating mode of the system provided in this embodiment of the invention; Fig. 3 This is a schematic flowchart of the refrigerant direct cooling and heating management method for an energy storage system provided in an embodiment of the present invention.

[0031] Attached reference numerals: 1-Compressor; 2-Four-way reversing valve; 3-Outdoor heat exchanger; 4-Electronic expansion valve; 5-Battery direct cooling plate; 6-Gas-liquid separator; 7-Pressure sensor; 8-Temperature sensor; 9-Fan; 10-Battery compartment. Detailed Implementation

[0032] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0033] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0034] Example 1 This embodiment provides a refrigerant direct cooling and heating management system for an energy storage system, such as... Figs. 1-3 As shown, the system includes: compressor 1, four-way reversing valve 2, outdoor heat exchanger 3, electronic expansion valve 4, battery direct cooling plate 5, and gas-liquid separator 6.

[0035] The compressor 1, the four-way reversing valve 2, the outdoor heat exchanger 3, the electronic expansion valve 4, the battery direct cooling plate 5 and the gas-liquid separator 6 are connected by pipelines to form a closed loop primary refrigerant circulation system. It should be noted that in the present embodiment, the pipelines are high-strength pressure-resistant pipelines to ensure the reliability of the system under long-term high-pressure operation.

[0036] In the present embodiment, the specific selection and parameters of each component are as follows: Compressor 1: A variable frequency scroll compressor is selected, with a nominal refrigerating capacity of about 4.0-4.5 kW (under standard air conditioning operating conditions). The compressor 1 is configured to adjust the operating frequency according to the control command, specifically, it supports frequency adjustment in the range of 30 Hz to 120 Hz.

[0037] Four-way reversing valve 2: A pilot-operated electromagnetic four-way reversing valve is used, with a coil voltage of DC 24 V, a nominal reversing capacity not less than the maximum discharge capacity of the selected compressor, and capable of withstanding the maximum working pressure of the system (usually ≥ 4.5 MPa). The valve body and internal slider are made of special alloy to ensure the sealing and durability under long-term refrigerant scouring, with a leakage rate lower than the industry standard.

[0038] Outdoor heat exchanger 3 (with the functions of condenser and evaporator): Finned tube heat exchanger, using internally threaded enhanced tubes and hydrophilic aluminum foil fins.

[0039] Electronic expansion valve 4: An electronic expansion valve driven by a double-rotor stepper motor, with a nominal valve port capacity matching the system refrigerating capacity, capable of high-resolution adjustment in the range of 0-500 steps (or more), and the minimum opening adjustment can cause a refrigerant flow change of less than 1%, to achieve millinewton-level accurate control of superheat or evaporation pressure.

[0040] Direct cooling plate 5 (core heat exchange component, with the functions of evaporator and condenser): AA6063-T5 aluminum alloy is used, and the internal multi-channel flow channel plate is made by vacuum brazing process. The flow channel is designed as a parallel multi-branch microchannel structure, and the fluid force is calculated to ensure that the refrigerant distribution uniformity of each branch is greater than 95%; in refrigeration mode, as an evaporator, the average heat transfer coefficient of its contact surface with the battery should be not less than 1000 W / (m 2 ·K) to ensure that the overall temperature difference of the battery pack is controlled within 3°C; the direct cooling plate needs to be integrated as a structural support component of the battery module, with a burst pressure of not less than 10 MPa and passing the air tightness test (helium leak rate less than 1 x 10 -6 Pa·m 3 / s); it should be noted that the layout of the microchannel flow channel is optimized to ensure the temperature uniformity of the contact surface with each battery monomer and the dual role as an evaporator / condenser.

[0041] Gas-liquid separator 6: Its volume is designed to be no less than the compressor's displacement of 1 minute, to ensure that it can effectively separate and store liquid refrigerant that may flow back under any operating conditions, and prevent compressor liquid slugging.

[0042] The battery direct cooling plate 5 is integrated into the battery module (battery box 10, using 1P52S string configuration) of the energy storage system; the battery direct cooling plate 5 has a flow channel for refrigerant to flow through, and the refrigerant is configured to directly evaporate or condense in the flow channel to directly exchange heat with the battery module.

[0043] Furthermore, the battery direct cooling plate 5 is a flow channel plate with an internal multi-branch microchannel structure, and the battery direct cooling plate 5 is integrated into the bottom or side of the battery module as a structural support component. Specifically, the battery direct cooling plate 5 is made of AA6063-T5 aluminum alloy and is manufactured into an internal multi-channel flow channel plate through vacuum brazing. The flow channel is designed as a parallel multi-branch microchannel structure, and through fluid dynamics verification, it is ensured that the refrigerant distribution uniformity of each branch is greater than 95%. In cooling mode, when acting as an evaporator, its average heat transfer coefficient at the contact surface with the battery is not less than 1000 W / (m²). 2 •K) to ensure the overall temperature difference of the battery pack is controlled within 3℃, as per design goals. Furthermore, this direct cooling plate must be integrated as a structural support component of the battery module, with a design burst pressure of no less than 10MPa, and must pass an airtightness test (helium leak rate less than 1×10). -6 Pa·m 3 / s).

[0044] Furthermore, the outdoor heat exchanger 3 is a finned tube heat exchanger, and a fan 9 for providing forced convection is provided on one side of the outdoor heat exchanger 3. In this embodiment, the outdoor heat exchanger 3 functions as both a condenser and an evaporator, employing internally threaded reinforced tubes and hydrophilic aluminum foil fins. The fan 9 is a continuously variable DC brushless (EC) fan that can provide an airflow of approximately 1000~1800 CFM (approximately 1700~3000 m³ / h) and maintain a static pressure of 50~150 Pa under the heat exchanger's design air resistance, ensuring that the airflow can penetrate the entire heat exchanger fins evenly and powerfully. The fan supports stepless speed regulation using PWM (pulse width modulation) signals or 0~10V voltage signals, with a speed regulation range of 30%~100% of the rated speed.

[0045] Furthermore, it also includes: a pressure sensor group and a temperature sensor group; the pressure sensor group includes a high-pressure sensor disposed at the discharge end of the compressor and a low-pressure sensor disposed at the suction end of the compressor; the temperature sensor group includes a battery temperature sensor for detecting the temperature of the battery module, and a system temperature sensor for detecting the ambient temperature and the temperature of the outdoor heat exchanger coil. Specifically, the high-pressure sensor 7 has a range of 0~5.0MPa, and the low-pressure sensor has a range of 0~2.5MPa. The temperature sensor 8 uses a PT1000 platinum resistance thermometer or an NTC thermistor with equivalent accuracy (±0.3℃). These sensors are distributed at key nodes to provide accurate data input for the control system.

[0046] Furthermore, the electronic expansion valve 4 is a stepper motor driven valve, configured to adjust the valve opening to control the refrigerant flow rate. In this embodiment, the electronic expansion valve 4 is driven by a dual-rotor stepper motor, the nominal valve port capacity is matched with the system cooling capacity, and it can be adjusted with high resolution within an opening range of 0 to 500 steps (or more). The minimum opening adjustment can result in a refrigerant flow rate change of less than 1%, thereby achieving millinewton-level precise control of superheat or evaporation pressure.

[0047] Furthermore, the four-way reversing valve 2 is configured to change the direction of refrigerant flow so that the system operates in cooling mode or heating mode; In the cooling mode, the four-way reversing valve 2 guides the refrigerant out of the compressor 1, which then flows sequentially through the outdoor heat exchanger 3 (serving as a condenser), the electronic expansion valve 4, and the battery direct cooling plate 5 (serving as an evaporator), finally returning to the compressor 1 via the gas-liquid separator 6. The specific working principle is as follows: When the energy storage system begins normal charging and discharging, and the battery temperature exceeds a set threshold (e.g., above 32°C), the thermal management system of this invention issues a command, the four-way reversing valve 2 switches, and the system starts the cooling mode. In this mode, the core function of the system is to extract heat from the high-temperature environment of the battery compartment 10 and efficiently transfer it to the outdoor heat exchanger 3 (which acts as a condenser at this time) for heat dissipation. The specific workflow is as follows: Compression and pressurization: The low-temperature, low-pressure superheated refrigerant gas is drawn into and compressed by compressor 1, transforming into a high-temperature, high-pressure superheated gas, with the pressure rising to 2.5~3.5MPa and the temperature rising to 80~100℃.

[0048] Condensation and heat release: High-temperature and high-pressure gas flows through the four-way reversing valve 2 and enters the outdoor heat exchanger 3 (which acts as a condenser at this time). Under the forced convection of the fan 9, the refrigerant releases sensible and latent heat to the ambient air, undergoing three stages: hot section cooling, two-phase section isothermal condensation, and subcooled section cooling. Finally, it becomes a medium-temperature and high-pressure subcooled liquid, with its temperature dropping to 10~15℃ higher than the ambient temperature, and achieving a subcooling degree of ≥5℃.

[0049] Throttling expansion: The subcooled liquid flows through the electronic expansion valve 4 for adiabatic throttling. During this process, its pressure and temperature drop sharply, with the pressure dropping to 0.5~1.0MPa and the temperature dropping to the target evaporation temperature, such as 5~15℃, thus becoming a low-temperature, low-pressure gas-liquid two-phase mixture.

[0050] Evaporation and heat absorption: The gas-liquid two-phase mixture enters the battery direct cooling plate 5. The refrigerant flows within the precision microchannels of the direct cooling plate 5, directly undergoing isothermal phase change heat exchange with the battery casing, absorbing the heat generated by the battery and completely evaporating into a low-temperature, low-pressure superheated gas. This process directly and efficiently transfers battery heat to the refrigerant, achieving rapid and uniform cooling of the battery.

[0051] Return and circulation: The superheated gas passes through the four-way reversing valve 2, flows through the gas-liquid separator 6 to ensure dryness, and then returns to the suction port of the compressor 1 to complete one refrigeration cycle.

[0052] In this embodiment, it should be noted that when the energy storage system is in a low-temperature environment (such as when the battery temperature is below 15°C) and needs to be started, charged, or kept warm, the system issues a command to energize the four-way reversing valve 2 switching coil, changing the refrigerant flow direction, and the system switches from cooling mode to heat pump heating mode. In this mode, the core function of the system is to extract heat from the low-temperature environment and efficiently transport it to the direct cooling plate 5 (which acts as a condenser at this time) to heat the battery compartment 10.

[0053] In the heating mode, the four-way reversing valve 2 guides the refrigerant out of the compressor 1, which then flows sequentially through the battery direct cooling plate 5 (serving as a condenser), the electronic expansion valve 4, and the outdoor heat exchanger 3 (serving as an evaporator), finally returning to the compressor 1 via the gas-liquid separator 6. The specific working principle is as follows: When the energy storage system is in a low-temperature environment (such as when the battery temperature is below 15°C) and needs to be started, charged, or kept warm, the four-way reversing valve 2 switches, and the system enters the heat pump heating mode: Compression and Heat Dissipation: Low-temperature, low-pressure superheated refrigerant gas (approximately 0.6 MPa and 5°C) is drawn into compressor 1 and compressed, transforming into high-temperature, high-pressure superheated gas. The pressure rises to 2.5~3.5 MPa, and the temperature rapidly increases to 80~100°C. This high-temperature, high-pressure gas is switched by the four-way reversing valve 2, no longer flowing to the outdoor heat exchanger 3, but directly into the battery direct cooling plate 5. At this point, the role of the battery direct cooling plate 5 changes from evaporator to condenser (or heat releaser).

[0054] Condensation and heat release: High-temperature, high-pressure refrigerant vapor flows within the microchannels of the battery direct cooling plate 5 (which acts as a condenser), directly releasing heat to the low-temperature battery core. This process includes the following three stages: a. Superheated section cooling: High-temperature steam at approximately 90°C first releases sensible heat, and the temperature drops to the saturated condensation temperature under the current pressure, which is set at 45°C.

[0055] b. Two-phase isothermal condensation (main heat release stage): Under a constant pressure of approximately 2.2 MPa and a constant temperature of approximately 45°C, the refrigerant releases a large amount of latent heat of condensation to the battery, gradually changing from a gaseous state to a liquid state. This is the most crucial and efficient stage for heating the battery.

[0056] c. Subcooling section: The liquid refrigerant continues to release a small amount of sensible heat, and the temperature drops slightly to 40°C, achieving a certain degree of subcooling.

[0057] During this process, the refrigerant changes from a high-temperature, high-pressure superheated gas to a medium-temperature, high-pressure subcooled liquid. The heat energy it carries is absorbed by the battery, causing the battery temperature to rise rapidly and evenly.

[0058] Throttling Expansion: The medium-temperature (40℃) and high-pressure (2.2MPa) subcooled liquid flowing from the battery direct cooling plate 5 undergoes adiabatic throttling through the electronic expansion valve 4. Its pressure drops to 0.6MPa, and its temperature drops to approximately -5℃, the saturation temperature corresponding to this pressure, transforming it into a low-temperature, low-pressure gas-liquid two-phase mixture, capable of absorbing heat from even lower temperature environments.

[0059] Evaporation and heat absorption: The gas-liquid two-phase mixture enters the external heat exchanger 3. At this point, the external heat exchanger changes its role from condenser to evaporator. Under the action of fan 9, the low-temperature refrigerant absorbs heat from the ambient air, evaporates isothermally at approximately -5°C in the microchannel, and completely transforms into a low-temperature, low-pressure superheated gas, with the temperature rising back to approximately 0~5°C. This process completes the key step of "transferring" free heat from the environment.

[0060] Return and circulation: The low-temperature and low-pressure superheated gas is guided by the four-way reversing valve 2, enters the gas-liquid separator 6 to ensure dryness, and finally returns to the compressor suction port to complete the heating cycle.

[0061] The refrigerant direct cooling and heating management control strategy of the energy storage system aims to ensure that the battery pack operates within the optimal operating window of 15°C to 32°C by precisely coordinating the control of each actuator, and to control the maximum temperature difference between cells within 3°C, so as to maximize the performance, safety and life of the battery system.

[0062] This invention also proposes a refrigerant direct cooling and heating management method for an energy storage system, applied to the aforementioned refrigerant direct cooling and heating management system, comprising the following steps: Mode determination steps: Obtain the temperature parameters of the battery module and the ambient temperature. Based on the comparison result of the temperature parameters with a preset threshold, control the four-way reversing valve to switch the refrigerant flow direction, so that the system enters either cooling mode or heating mode. The specific decision logic is as follows: Key parameters are read from the BMS and sensors: maximum battery temperature (T_max), minimum battery temperature (T_min), average battery temperature (T_avg), battery temperature difference (△T=T_max-T_min), ambient temperature (T_amb), evaporator outlet superheat (SH_evap), system high pressure (P_high), and system low pressure (P_low).

[0063] If (T_avg ≤ 17℃ or T_min ≤ 15℃), then the target mode is determined to be the heating mode; Otherwise, if (T_avg ≥ 28℃ or T_max ≥ 32℃), the target mode is determined to be cooling mode; Otherwise, it is determined to be in standby mode.

[0064] If the target mode is inconsistent with the current mode, control the four-way directional valve 2 to switch to the target mode.

[0065] Temperature difference priority control step: Real-time monitoring of the temperature difference between the highest and lowest temperatures within the battery module. When the difference exceeds a preset temperature difference threshold, the opening of the electronic expansion valve is adjusted first to optimize the distribution of refrigerant within the battery direct cooling plate. Specifically, if ΔT > 3℃ is detected, the temperature difference control logic is activated. Electronic expansion valve 4 opening adjustment amount = PID_calculation (△T, set point = 2℃, output range ±50 steps); Meanwhile, in order to maintain uniform temperature, the compressor load is appropriately reduced, and the compressor 1 frequency adjustment is set to -5Hz.

[0066] This strategy utilizes phase change isothermal characteristics and microchannel design to keep the overall temperature difference of the battery pack stable within 3°C, effectively extending the battery cycle life by more than 20%.

[0067] Temperature target control steps: Under the premise of satisfying the temperature difference priority control steps, the operating frequency of the compressor is adjusted according to the deviation between the temperature parameters of the battery module and the set target temperature.

[0068] Furthermore, in the cooling mode, the temperature target control step specifically includes: The target evaporation temperature is dynamically calculated based on the highest temperature of the battery module. The target evaporation temperature is negatively correlated with the highest temperature; that is, when the highest temperature increases, the target evaporation temperature decreases. The specific calculation formula is: Target evaporation temperature T_evap_target = 25 - min(10, (T_max - 25) * 2).

[0069] Compressor 1 target frequency = PID_calculation (input = T_max, setpoint = 32℃, output range [30, 120]Hz).

[0070] The method further includes an overheat protection step: real-time calculation of the refrigerant superheat (SH_evap) at the compressor suction port; when the superheat is lower than a preset safety threshold, reduction of the opening of the electronic expansion valve to prevent liquid refrigerant from entering the compressor. The specific control logic is as follows: Set the target superheat SH_target = 7℃.

[0071] If (SH_evap < 5℃), then the superheat is judged to be too low, and there is a risk of liquid slugging. The opening of the electronic expansion valve 4 is reduced by 10 steps. Otherwise, if (SH_evap > 12℃), the opening of the electronic expansion valve 4 will be increased by 15 steps to improve heat exchange efficiency; Otherwise, perform fine adjustment: T_evap_actual = saturation temperature obtained by looking up the table based on P_low and refrigerant type, expansion valve 4 fine adjustment amount = PID_calculation(T_evap_actual, set point = T_evap_target, output range ±5 steps).

[0072] Furthermore, in the heating mode, the temperature target control step specifically includes: The operating frequency of the compressor is adjusted based on the deviation between the lowest temperature of the battery module and the preset heating target temperature. In specific implementation: Target condensation temperature T_cond_target = 40 + min(10, (18 - T_avg) * 2); Compressor 1 target frequency = PID_calculation(T_min, setpoint=18℃, output range[30, 100]Hz); Simultaneously control the target superheat SH_target_heating = max(5, 8 - (T_amb / 10)), and adjust the opening of expansion valve 4 through PID; expansion valve 4 opening = PID_calculation(SH_evap, setpoint = SH_target_heating, output range corresponding to valve opening).

[0073] The method further includes a defrost control step: real-time monitoring of the coil temperature of the outdoor heat exchanger; when the coil temperature is lower than a preset frosting threshold and the duration exceeds a preset time, controlling the four-way reversing valve to switch to cooling mode for defrosting, until the coil temperature rises back to the defrost exit threshold. The specific defrost logic is as follows: Read the outdoor heat exchanger coil temperature (T_outdoor_coil).

[0074] If (T_outdoor_coil < 2℃ and running time > 10 minutes), and further detects (T_outdoor_coil < -3℃ for more than 5 minutes), then initiate a forced defrost cycle, switch four-way valve 2 to cooling mode (using hot air for defrosting), until the temperature rises.

[0075] Furthermore, it also includes a fan speed control step: acquiring the system's exhaust pressure value or the mid-temperature value of the outdoor heat exchanger in real time; dynamically adjusting the fan speed configured on the outdoor heat exchanger based on the deviation between the exhaust pressure value or the mid-temperature value and a preset target value, so as to maintain the system's condensing pressure within a preset high-efficiency operating range. In specific implementation: In cooling mode, the target air outlet temperature of outdoor heat exchanger 3 (as a condenser) is T_cond_air_out_target = T_amb + 12℃.

[0076] Fan 9 PWM signal = PID_Calculation(Actual condenser mid-section temperature, Setpoint = T_cond_air_out_target, Output range [30%, 100%]).

[0077] In heating mode, fan speed 9 = PID_calculation(P_low, setpoint = optimal low pressure value corresponding to ambient temperature, output range [40%, 100%]).

[0078] Furthermore, it also includes system security protection steps, which include at least one of the following logics: When the system's exhaust pressure or the compressor's exhaust temperature exceeds a preset safety limit, a degradation protection strategy is implemented. This involves reducing the compressor's operating frequency, increasing the opening of the electronic expansion valve, and adjusting the fan speed on the outdoor heat exchanger to its maximum value. Specifically, if P_high > 3.8MPa or the compressor 1 exhaust temperature > 105℃, degradation or protection is implemented, reducing the compressor 1 frequency by 20%, opening the expansion valve 4, and setting the fan 9 to full speed.

[0079] A refrigerant leak alarm is triggered when the system's low pressure is detected to be below the lower limit of the saturation pressure corresponding to the current evaporation temperature for a preset duration. Specifically, if P_low < the saturation pressure corresponding to the evaporation temperature -10℃ for 10 seconds, a low-pressure alarm is triggered, prompting a check for refrigerant leakage.

[0080] When the difference between the highest and lowest temperatures of the battery module exceeds a preset alarm threshold and persists for a preset duration, a battery consistency alarm is triggered or a power reduction request is sent. Specifically, if ΔT > 6℃ for more than 2 minutes, a temperature difference alarm is triggered, requesting the BMS to check battery consistency or reduce charging / discharging power.

[0081] In this embodiment, a system control strategy is also proposed, which is as follows: Obtain the highest temperature (T_max), lowest temperature (T_min), and average temperature (T_avg) of the energy storage battery. The difference (ΔT) between the highest temperature (T_max) and the lowest temperature (T_min) is taken as the first control target, and the highest temperature (T_max) or the average temperature (T_avg) is taken as the second control target. When ΔT is greater than the first threshold, the opening of the electronic expansion valve is adjusted first to optimize the refrigerant distribution through each channel of the battery direct cooling plate; at the same time, the operating frequency of the compressor is adjusted according to the deviation between the second control target and the corresponding set value. In cooling mode, the target evaporation temperature is dynamically calculated based on T_max, and the target evaporation temperature decreases as T_max increases; and the superheat at the evaporator outlet is monitored in real time. When the superheat is lower than the safety threshold, the opening of the electronic expansion valve is reduced to prevent liquid refrigerant from entering the compressor.

[0082] For fan 5, the system control strategy is as follows: dynamically adjust the fan speed according to the system high pressure or the temperature in the middle of the condenser, so as to keep the system condensing pressure within the preset high-efficiency range.

[0083] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

[0084] This background section is provided to generally present the context of the invention. The work of the currently named inventors, the work to the extent described in this background section, and aspects of this section that did not constitute prior art at the time of application are neither expressly nor impliedly acknowledged as prior art to the invention.

Claims

1. A refrigerant direct cooling and heating management system for an energy storage system, characterized in that, include: The compressor, four-way reversing valve, outdoor heat exchanger, electronic expansion valve, battery direct cooling plate, and gas-liquid separator are connected by pipelines to form a closed-loop primary refrigerant circulation system. The battery direct cooling plate is integrated into the battery module of the energy storage system. The battery direct cooling plate has a flow channel for refrigerant to flow through. The refrigerant is configured to directly evaporate or condense in the flow channel to directly exchange heat with the battery module.

2. The refrigerant direct cooling and heating management system for an energy storage system according to claim 1, characterized in that, The battery direct cooling plate is a flow channel plate with a parallel multi-branch microchannel structure inside. The battery direct cooling plate is integrated into the bottom or side of the battery module as a structural support component. The outdoor heat exchanger is a finned tube heat exchanger, and a fan for providing forced convection is provided on one side of the outdoor heat exchanger.

3. The refrigerant direct cooling and heating management system for an energy storage system according to claim 1, characterized in that, Also includes: A pressure sensor group and a temperature sensor group; the pressure sensor group includes a high-pressure sensor disposed at the discharge end of the compressor and a low-pressure sensor disposed at the suction end of the compressor; the temperature sensor group includes a battery temperature sensor for detecting the temperature of the battery module, and a system temperature sensor for detecting the ambient temperature and the temperature of the outdoor heat exchanger coil.

4. The refrigerant direct cooling and heating management system for an energy storage system according to claim 1, characterized in that, The compressor is a variable frequency compressor, configured to adjust the operating frequency according to control commands; the electronic expansion valve is a stepper motor driven valve, configured to adjust the valve opening to control the refrigerant flow; the fan configured for the outdoor heat exchanger is a DC brushless fan that supports stepless speed regulation.

5. The refrigerant direct cooling and heating management system for an energy storage system according to claim 1, characterized in that, The four-way reversing valve is configured to change the direction of refrigerant flow so that the system operates in cooling mode or heating mode. In the cooling mode, the four-way reversing valve guides the refrigerant to be discharged from the compressor, and flows sequentially through the outdoor heat exchanger (which serves as a condenser), the electronic expansion valve, the battery direct cooling plate (which serves as an evaporator), and finally returns to the compressor via the gas-liquid separator. In the heating mode, the four-way reversing valve guides the refrigerant to be discharged from the compressor, and flows sequentially through the battery direct cooling plate (which serves as a condenser), the electronic expansion valve, the outdoor heat exchanger (which serves as an evaporator), and finally returns to the compressor via the gas-liquid separator.

6. A method for direct cooling and heating management of refrigerant in an energy storage system, characterized in that, The refrigerant direct cooling and heating management system applied to the energy storage system according to any one of claims 1-5 includes the following steps: Mode determination steps: Obtain the temperature parameters of the battery module and the ambient temperature. Based on the comparison result of the temperature parameters and the preset threshold, control the four-way reversing valve to switch the refrigerant flow direction so that the system enters the cooling mode or the heating mode. Temperature difference priority control steps: Real-time monitoring of the difference between the highest and lowest temperatures in the battery module. When the difference exceeds the preset temperature difference threshold, priority is given to adjusting the opening of the electronic expansion valve to optimize the distribution of refrigerant in the battery direct cooling plate. Temperature target control steps: Under the premise of satisfying the temperature difference priority control steps, the operating frequency of the compressor is adjusted according to the deviation between the temperature parameters of the battery module and the set target temperature.

7. The refrigerant direct cooling and heating management method for an energy storage system according to claim 6, characterized in that, In the cooling mode, the temperature target control step specifically includes: The target evaporation temperature is dynamically calculated based on the highest temperature of the battery module. The target evaporation temperature is negatively correlated with the highest temperature, that is, when the highest temperature increases, the target evaporation temperature decreases. The method further includes an overheat protection step: calculating the refrigerant overheat at the compressor suction port in real time, and reducing the opening of the electronic expansion valve when the overheat is lower than a preset safety threshold to prevent liquid refrigerant from entering the compressor.

8. A refrigerant direct cooling and heating management method for an energy storage system according to claim 6, characterized in that, In the heating mode, the temperature target control step specifically includes: The operating frequency of the compressor is adjusted according to the deviation between the lowest temperature of the battery module and the preset heating target temperature. The method further includes a defrosting control step: real-time monitoring of the coil temperature of the outdoor heat exchanger; when the coil temperature is lower than the preset frosting threshold and the duration exceeds the preset time, controlling the four-way reversing valve to switch to the cooling mode for defrosting until the coil temperature rises back to the defrosting exit threshold.

9. A refrigerant direct cooling and heating management method for an energy storage system according to claim 6, characterized in that, It also includes a fan speed control step: real-time acquisition of the system's exhaust pressure value or the mid-temperature value of the outdoor heat exchanger; Based on the deviation between the exhaust pressure value or the mid-temperature value and the preset target value, the rotational speed of the fan configured on the outdoor heat exchanger is dynamically adjusted to maintain the condensing pressure of the system within the preset high-efficiency operating range.

10. A refrigerant direct cooling and heating management method for an energy storage system according to claim 6, characterized in that, It also includes system security protection steps, which include at least one of the following logics: When the system's exhaust pressure or the compressor's exhaust temperature is detected to exceed the preset safety limit, a degradation protection strategy is executed, which reduces the compressor's operating frequency, increases the opening of the electronic expansion valve, and adjusts the fan speed configured on the outdoor heat exchanger to the maximum value. When the system's low pressure is detected to be lower than the lower limit of the saturation pressure corresponding to the current evaporation temperature and this continues for a preset time, a refrigerant leak alarm is triggered. When the difference between the highest and lowest temperatures of the battery module exceeds a preset alarm threshold and persists for a preset duration, a battery consistency alarm is triggered or a power reduction request is sent.

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