Battery thermal management method and battery thermal management system

Abstract

The invention discloses a method and a system for battery thermal management. The method comprises the following steps: acquiring an operation state, a battery temperature, an environment temperature and a thermal storage unit temperature of a battery system; the thermal load state is determined based on the battery temperature, and the active temperature control unit is called to execute a refrigeration or heating strategy; an energy storage strategy is judged and executed based on multiple parameters, and after battery charging and discharging are finished, waste heat is used for storing heat for a heat storage unit; when the temperature control strategy is executed, if the temperature of the heat storage unit meets the auxiliary condition, the heat storage unit is connected into the loop through the control valve, and cold / heat is released to cooperate with the active temperature control unit to adjust the temperature. The system comprises a battery cluster, an active temperature control unit, a heat storage unit, a control valve, a sensor group and a controller. According to the system, waste heat recovery and cooperative temperature control are achieved, the low-temperature starting speed is remarkably increased, and the system energy consumption is reduced.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and in particular to a method and a battery thermal management system for battery thermal management. Background Technology

[0002] With the widespread application of electrochemical energy storage on both the grid and user sides, its thermal management efficiency, especially its performance in low-temperature environments, has become a key factor restricting system reliability and economy. Currently, traditional battery liquid-cooled thermal management systems typically employ simple control logic based on battery temperature thresholds: when the battery temperature is below the lower limit T_MIN, an electric heater is activated to heat the coolant, which then heats the battery cell via a liquid cooling plate; when the battery temperature is above the upper limit T_MAX, a cooling unit is activated to cool the coolant. However, this approach has significant drawbacks: firstly, during low-temperature startup, the high thermal resistance of the high-capacity coolant during heat conduction results in slow system heating and significant startup delay; secondly, in cold environments, frequent activation of electric heating is necessary to maintain system temperature, leading to high energy consumption; more importantly, during the charge-discharge cycle of the battery cell, a "heating before cooling" phenomenon frequently occurs, where the waste heat generated during cell charging and discharging is not effectively utilized but directly dissipated through the cooling system, resulting in severe energy waste. Therefore, there is an urgent need for a new thermal management solution that can comprehensively utilize the waste heat of the battery cells, improve low-temperature performance, and reduce overall energy consumption. Summary of the Invention

[0003] To address the problems of long start-up delay, high operating energy consumption, and serious waste of residual heat during battery cell charging and discharging in existing liquid-cooled energy storage systems at low temperatures, this invention proposes a method and a battery thermal management system for battery thermal management.

[0004] The specific technical solution is as follows: A method for battery thermal management, comprising the following steps:

[0005] Acquire the operating status of the battery system, battery temperature, ambient temperature, and the temperature of the heat storage unit;

[0006] Based on the battery temperature, determine the thermal load status of the system;

[0007] Based on the heat load state, the active temperature control unit is invoked to execute the corresponding active temperature control strategy, which includes a cooling strategy and a heating strategy.

[0008] Based on the operating status, the ambient temperature, and the temperature of the heat storage unit, it is determined whether to execute the energy storage strategy. The energy storage strategy includes using the residual heat from the battery's charging and discharging to store heat in the heat storage unit after the battery charging and discharging process is completed.

[0009] When the active temperature control strategy is executed, if the temperature of the heat storage unit and the battery temperature meet the preset auxiliary conditions, the heat storage unit is connected to the circulation loop by controlling the control valve connected to the heat storage unit, so as to control the heat storage unit to release the cold or heat it stores, and cooperate with the active temperature control unit to perform temperature control regulation.

[0010] The auxiliary conditions include: when executing the cooling strategy, the temperature of the heat storage unit is lower than the battery temperature; when executing the heating strategy, the temperature of the heat storage unit is higher than the battery temperature. By connecting the heat storage unit to the system for coordinated temperature control when the temperature conditions are met, the temperature control efficiency is effectively improved, especially during low-temperature startup, where heat can be quickly replenished, significantly shortening the startup time. Utilizing the residual heat after battery charging and discharging completes to store energy in the heat storage unit converts previously wasted heat into a useful stored heat source, achieving energy recycling and fundamentally reducing the system's heating energy consumption.

[0011] Furthermore, when executing the cooling strategy, the cold source is dynamically allocated based on the difference between the battery temperature and the cooling load threshold T_MIN:

[0012] When the battery temperature is higher than T_MIN but the difference between it and T_MIN is less than or equal to a set threshold ΔT, the cooling capacity is provided preferentially or solely by the heat storage unit.

[0013] When the difference is greater than ΔT, the active temperature control unit and the heat storage unit work together to provide cooling. This achieves refined and intelligent management of the cold source. When the heat load is low, the stored free cold source is used first, reducing the operating frequency and power consumption of the cooling unit. When the heat load is high, the high-power active cooling unit is activated. The two work together to ensure cooling capacity while maximizing energy savings.

[0014] Furthermore, during the battery system startup phase, the method further includes:

[0015] Determine the permissible charge / discharge rate based on the current battery temperature;

[0016] The battery is charged and discharged at this rate, utilizing its self-generated heat, combined with the heat provided by the heating strategy executed by the active temperature control unit and the heat released by the heat storage unit, to preheat the battery. This triple heating source specifically addresses the pain point of slow system startup in low-temperature environments, achieving rapid and uniform preheating and ensuring the energy storage system's rapid response capability under frigid conditions.

[0017] Furthermore, the determination of the system's thermal load state based on battery temperature includes:

[0018] When the battery's maximum temperature exceeds the first temperature threshold T_MAX, it is determined to be in a thermal load state.

[0019] When the lowest battery temperature is less than the second temperature threshold T_MIN, it is judged to be in a cold load state.

[0020] When the battery temperature is between T_MIN and T_MAX, it is determined to be in a no-load state. This makes the judgment criteria of the control strategy clear and explicit, easy to program and implement in the controller, and ensures the reliability and stability of the system control.

[0021] Furthermore, when the cooling strategy is executed due to a heat load condition, the step of controlling the heat storage unit to release cooling capacity further includes:

[0022] Determine whether the temperature of the heat storage unit is lower than the target cooling temperature T_COOL;

[0023] When the temperature of the heat storage unit is lower than T_COOL, the step of controlling the release of cold energy by the heat storage unit is executed. This ensures the quality of the released cold energy, avoids problems such as poor auxiliary cooling effect or even reverse heating due to excessively high temperature of the heat storage unit, and guarantees the efficiency and effectiveness of the synergistic cooling process.

[0024] Furthermore, when the heating strategy is executed under a cold load condition, the step of controlling the heat storage unit to release heat further includes:

[0025] Determine whether the temperature of the heat storage unit is higher than the target heating temperature T_HEAT;

[0026] When the temperature of the heat storage unit is higher than T_HEAT, the step of controlling the heat storage unit to release heat is executed. This ensures the quality of the released heat, avoids ineffective or reverting auxiliary heating, and ensures the reliability and efficiency of the synergistic heating process.

[0027] Furthermore, the operating state includes charging / discharging state and standby state.

[0028] A battery thermal management system for implementing a method for battery thermal management, comprising:

[0029] Battery clusters;

[0030] An active temperature control unit is used to cool or heat the circulating medium;

[0031] A thermal storage unit is used to store cold or heat energy.

[0032] A control valve is used to control the on / off state of the heat storage unit and the circulation loop;

[0033] The sensor array is used to acquire the operating status of the battery system, battery temperature, ambient temperature, and the temperature of the heat storage unit;

[0034] The controller is configured to perform the steps of the method.

[0035] Furthermore, the heat storage unit is a liquid storage tank, and the active temperature control unit is a refrigeration and heating unit. The liquid storage tank and the refrigeration and heating unit are connected in parallel on the pipeline. The pipeline design with the liquid storage tank and the refrigeration and heating unit connected in parallel allows the heat storage unit to be flexibly connected to or isolated from the main circulation. It has a simple structure, is easy to control, and is easy to modify and integrate on the basis of existing liquid cooling systems.

[0036] Furthermore, the storage tank stores energy using the specific heat capacity of the working fluid. Utilizing the specific heat capacity of the working fluid for sensible heat storage is a reliable, low-cost, and technologically mature energy storage method according to this invention, which is beneficial for the promotion and implementation of the solution.

[0037] The above technical solution has the following advantages or technical effects:

[0038] 1. This invention achieves efficient energy recycling by recovering and utilizing the waste heat from the charging and discharging of battery cells for heat storage, and by utilizing ambient cold sources for cold storage. This significantly reduces the external energy consumption of the system during the cooling and heating process and improves the overall energy efficiency of the energy storage system.

[0039] 2. This invention combines the self-heating of the battery cell, the heat stored in the active heating unit and the heat storage unit for synergistic preheating, which greatly improves the start-up performance of the energy storage system in low-temperature environments, effectively shortens the start-up time, and ensures the system's rapid response and reliable operation under frigid conditions.

[0040] 3. Based on a multi-parameter intelligent collaborative temperature control strategy, this invention achieves rapid, accurate and uniform adjustment of battery temperature, effectively avoiding local overheating or overcooling of the battery cell, which helps to extend the battery's service life and improve the stability and safety of system operation. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the battery thermal management system of the present invention;

[0042] Figure 2 This is a flowchart of the thermal management method of the present invention;

[0043] Figure 3 This is a flowchart of the battery system operation status and load judgment of the present invention;

[0044] Figure 4 This is a flowchart illustrating the collaborative execution of the cooling strategy of this invention;

[0045] Figure 5 This is a flowchart of the heat storage strategy of the present invention. Detailed Implementation

[0046] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] Example 1

[0048] A method for battery thermal management, the method by means of... Figure 1 The system hardware implementation shown is as follows: Figure 2 As shown, the steps of this method include:

[0049] The controller monitors the status of the battery system and acquires its parameters. It continuously acquires the operating status of the battery system, including charging / discharging and standby states; it also acquires the battery temperature, ambient temperature, and the temperature of the heat storage unit, with the battery temperature including at least the highest and lowest temperatures of the battery cells.

[0050] Determine the thermal load status and basic strategy. Based on the acquired battery temperature, the controller compares it with a preset operating temperature range to determine the system's thermal load status. For example... Figure 3 As shown, specifically, this includes: when the battery's highest temperature exceeds a first temperature threshold T_MAX, it is determined to be a hot load state; when the battery's lowest temperature is less than a second temperature threshold T_MIN, it is determined to be a cold load state; when the battery temperature is between T_MIN and T_MAX, it is determined to be a no-load state. Based on the determined hot load state, the controller calls the active temperature control unit to execute the corresponding active temperature control strategy, where the hot load state corresponds to a cooling strategy, the cold load state corresponds to a heating strategy, and the no-load state corresponds to a cyclic strategy.

[0051] Coordinated temperature control is implemented to determine the energy storage strategy. The controller determines whether to execute the energy storage strategy based on the operating status, ambient temperature, and the temperature of the heat storage unit. The energy storage strategy involves utilizing the residual heat from the battery's charging and discharging process to store heat in the heat storage unit. Triggering this strategy requires two conditions to be met simultaneously: the ambient temperature must be below the preset shutdown temperature limit T_MAX_SUSPEND, and the battery outlet working fluid temperature must be above the temperature of the heat storage unit.

[0052] When implementing the active temperature control strategy, if the temperature of the heat storage unit and the battery temperature meet preset auxiliary conditions, the control valve connected to the heat storage unit is controlled to connect the heat storage unit to the circulation loop, controlling it to release the stored cold or heat energy, and cooperating with the active temperature control unit to perform temperature regulation. Auxiliary conditions include: when implementing the cooling strategy, the temperature of the heat storage unit is lower than the battery temperature; when implementing the heating strategy, the temperature of the heat storage unit is higher than the battery temperature.

[0053] Introduce a dynamic cold source allocation mechanism, such as Figure 4As shown, when executing the cooling strategy, the cooling source is dynamically allocated based on the difference between the battery temperature and the cooling load threshold T_MIN: when the battery temperature is higher than T_MIN but the difference between it and T_MIN is less than or equal to the set threshold ΔT, the cooling capacity is provided preferentially or solely by the heat storage unit; when the difference is greater than ΔT, the cooling is provided jointly by the active temperature control unit and the heat storage unit. When the cooling strategy is executed due to a heat load condition, the step of controlling the release of cooling capacity by the heat storage unit also includes determining whether the temperature of the heat storage unit is lower than the cooling target temperature T_COOL; the step of releasing cooling capacity is only executed when it is lower than T_COOL.

[0054] The battery system startup phase also includes a collaborative preheating step: the allowable charge / discharge rate is determined based on the current battery temperature, and the battery is charged and discharged at this rate. The battery's self-generated heat is used, combined with the heat provided by the active temperature control unit's heating strategy and the heat released by the heat storage unit, to preheat the battery together.

[0055] like Figure 5 As shown, waste heat recovery after charging and discharging is achieved through a heat storage strategy. The controller determines whether the ambient temperature is lower than the shutdown temperature limit T_MAX_SUSPEND and whether the outlet temperature of the energy storage unit is higher than the working fluid temperature of the storage tank. When both conditions are met, the electric valve is opened and the water pump is kept running to pump the high-temperature working fluid from the battery outlet into the storage tank for heat storage. When the temperature of the storage tank approaches the battery return water temperature, the electric valve is closed to stop heat storage.

[0056] Example 2

[0057] like Figure 1 As shown, a battery thermal management system for implementing Embodiment 1 includes:

[0058] Battery clusters constitute the energy storage units of the system;

[0059] An active temperature control unit is used to cool or heat the circulating medium, and can be implemented in the form of a cooling and heating unit;

[0060] A heat storage unit, used to store cold or heat, is preferably a liquid storage tank, which stores energy through the specific heat capacity of the working fluid;

[0061] The control valve, specifically an electric valve, is used to control the on / off state of the liquid storage tank and the circulation loop. The water pump provides the circulation power, and the liquid storage tank and the refrigeration and heating unit are connected in parallel on the pipeline.

[0062] The sensor group collects all the parameters required for the system to operate, including various sensors used to obtain the operating status of the battery system, battery temperature, ambient temperature and the temperature of the heat storage unit. The liquid cooling system parameters include the coolant temperature at the inlet and outlet of the energy storage unit, pipeline flow rate and the working fluid temperature inside the storage tank.

[0063] The controller, communicatively connected to the battery management system, is configured to perform the steps of any of the battery thermal management methods described in Embodiment 1. The controller receives all data from the sensor array and outputs control commands to the cooling / heating unit, water pump, and electric valve.

[0064] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for battery thermal management, characterized in that the steps include... include: Acquire the operating status of the battery system, battery temperature, ambient temperature, and the temperature of the heat storage unit; Based on the battery temperature, determine the thermal load status of the system; Based on the heat load state, the active temperature control unit is invoked to execute the corresponding active temperature control strategy, which includes a cooling strategy and a heating strategy. Based on the operating status, the ambient temperature, and the temperature of the heat storage unit, it is determined whether to execute the energy storage strategy. The energy storage strategy includes using the residual heat from the battery's charging and discharging to store heat in the heat storage unit after the battery charging and discharging process is completed. When the active temperature control strategy is executed, if the temperature of the heat storage unit and the battery temperature meet the preset auxiliary conditions, the heat storage unit is connected to the circulation loop by controlling the control valve connected to the heat storage unit, so as to control the heat storage unit to release the cold or heat it stores, and cooperate with the active temperature control unit to perform temperature control regulation. The auxiliary conditions include: when the cooling strategy is executed, the temperature of the heat storage unit is lower than the battery temperature; When the heating strategy is executed, the temperature of the heat storage unit is higher than the battery temperature.

2. The method for battery thermal management according to claim 1, characterized in that, When implementing the cooling strategy, the cooling source is dynamically allocated based on the difference between the battery temperature and the cooling load threshold T_MIN: When the battery temperature is higher than T_MIN but the difference between it and T_MIN is less than or equal to a set threshold ΔT, the cooling capacity is provided preferentially or solely by the heat storage unit. When the difference is greater than ΔT, the active temperature control unit and the heat storage unit work together to provide cooling.

3. The method for battery thermal management according to claim 1, characterized in that, During the battery system startup phase, the method further includes: Determine the permissible charge / discharge rate based on the current battery temperature; The battery is charged and discharged at this rate, utilizing its self-generated heat, combined with the heat provided by the heating strategy executed by the active temperature control unit and the heat released by the heat storage unit, to preheat the battery.

4. The method for battery thermal management according to claim 1, characterized in that, The method for determining the thermal load status of the system based on battery temperature includes: When the battery's maximum temperature exceeds the first temperature threshold T_MAX, it is determined to be in a thermal load state. When the lowest battery temperature is less than the second temperature threshold T_MIN, it is judged to be in a cold load state. When the battery temperature is between T_MIN and T_MAX, it is considered to be in a no-load state.

5. A method for battery thermal management according to claim 4, characterized in that, When the cooling strategy is executed based on the determination of a heat load state, the step of controlling the heat storage unit to release cooling capacity further includes: Determine whether the temperature of the heat storage unit is lower than the target cooling temperature T_COOL; When the temperature of the heat storage unit is lower than T_COOL, the step of controlling the heat storage unit to release cold energy is executed.

6. A method for battery thermal management according to claim 4, characterized in that, When the heating strategy is executed based on the determination of a cooling load state, the step of controlling the heat storage unit to release heat further includes: Determine whether the temperature of the heat storage unit is higher than the target heating temperature T_HEAT; When the temperature of the heat storage unit is higher than T_HEAT, the step of controlling the heat storage unit to release heat is executed.

7. A method for battery thermal management according to claim 1, characterized in that, The operating states include charging / discharging state and standby state.

8. A battery thermal management system for implementing the method for battery thermal management according to any one of claims 1 to 7, characterized in that, include: Battery clusters; An active temperature control unit is used to cool or heat the circulating medium; A thermal storage unit is used to store cold or heat energy. A control valve is used to control the on / off state of the heat storage unit and the circulation loop; The sensor array is used to acquire the operating status of the battery system, battery temperature, ambient temperature, and the temperature of the heat storage unit; The controller is configured to perform the steps of the method as described in any one of claims 1 to 7.

9. A battery thermal management system according to claim 8, characterized in that, The heat storage unit is a liquid storage tank, and the active temperature control unit is a refrigeration and heating unit. The liquid storage tank and the refrigeration and heating unit are connected in parallel on the pipeline.

10. A battery thermal management system according to claim 9, characterized in that, The storage tank stores energy using the specific heat capacity of the working fluid.

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