Lithium battery energy storage system fire-fighting method based on multistage cooperative detection and fixed-point spraying

Abstract

The invention discloses a lithium battery energy storage system fire-fighting method based on multi-stage cooperative detection and fixed-point spraying, which comprises the following steps: firstly, acquiring battery cell temperature, concentration of hydrogen, CO and oxygen in a module and infrared thermal imaging data in a cabin, then judging whether the working state of the current energy storage system is normal or not by a BMS (Battery Management System) by analyzing the data acquired by a composite detection system, and if not, judging whether the working state of the current energy storage system is normal or not; if yes, grading is carried out according to predefined fire-fighting grades, and fire-fighting instructions corresponding to the corresponding fire-fighting grades are issued to the master control PLC; if the response is the first-level response, local strong exhaust is started, low-concentration cooling mist is sprayed to the target PACK, and sound-light alarm (yellow lamp flickering) is carried out; if the response is the second-level response, a ventilation system is closed, perfluorohexanone liquid jet and sound-light alarm upgrading (red light flickers and buzzing is carried out) are started, and the BMS uploads a fire signal to the cloud. And when the real-time detection data is lower than a preset safety threshold value, the BMS judges that the alarm is removed and controls the master control PLC with the fault PACK to stop corresponding measures.

Description

Technical Field

[0001] This invention belongs to the field of power system technology, and more specifically, relates to a fire protection method for lithium battery energy storage systems based on multi-level collaborative detection and fixed-point spraying. Background Technology

[0002] With the transformation of the global energy structure and the rapid development of renewable energy, electrochemical energy storage power stations, as an efficient and flexible energy storage method, play an important role in regulating grid load, balancing supply and demand, and improving energy utilization efficiency. However, the safety issues of electrochemical energy storage power stations, especially the risk of fire, have become one of the key factors restricting their widespread application. Particularly in high-altitude environments, due to the thin oxygen and other special conditions, the combustion characteristics and fire suppression difficulties of energy storage power stations differ significantly from those in conventional environments, posing new challenges to the design of fire protection systems. Domestic and international scholars have conducted extensive research on the design of fire protection systems for electrochemical energy storage power stations, proposing various fire detection and suppression technologies. However, most existing research focuses on energy storage power stations in conventional environments, with relatively little research on fire protection system design in the special environments of high altitudes. The thin oxygen at high altitudes leads to changes in combustion characteristics, making traditional total flooding fire suppression systems (such as heptafluoropropane) unable to suppress reignition. In addition, existing fire protection systems have technical defects in early warning and prevention of lithium battery thermal runaway fires, such as high false alarm rate of single detectors, excessively large fire suppression coverage of compartments, independent operation of BMS system and fire protection system and inability to actively isolate faulty units, which cannot effectively meet the special requirements of high-altitude environment.

[0003] Therefore, achieving accurate early warning and effective targeted fire suppression for energy storage systems in high-altitude environments is of great engineering value in addressing the safety issues of energy storage systems caused by the thermal runaway risk of lithium iron phosphate batteries. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a fire-fighting method for lithium battery energy storage systems based on multi-level collaborative detection and fixed-point spraying. This method helps to reduce the losses caused by fire accidents in large-scale energy storage systems at high altitudes due to cell thermal runaway, and helps to solve the fire-fighting problems of inaccurate fire warnings and imprecise spraying ranges in energy storage systems.

[0005] To achieve the above-mentioned objectives, the present invention provides a fire-fighting method for lithium battery energy storage systems based on multi-level collaborative detection and fixed-point spraying, characterized by comprising the following steps:

[0006] (1) Define the response levels of the fire protection system, and the triggering and deactivation conditions under each response level;

[0007] (2) Deploy composite detection and fire protection systems on lithium battery energy storage systems;

[0008] (3) Collect detection data using detectors at each level of the composite detection system, and then upload it to the battery management system (BMS);

[0009] (4) The BMS system analyzes and processes the detection data collected by the composite detection system to determine the response level of the fire protection system;

[0010] (5) The BMS system controls the fire protection system to perform the corresponding fire protection task according to the corresponding response level, and monitors the uploaded detection data in real time during the fire protection process. When the detection data is lower than the set release condition, the fire protection task ends.

[0011] The objective of this invention is achieved as follows:

[0012] This invention relates to a fire-fighting method for lithium battery energy storage systems based on multi-level collaborative detection and targeted spraying. First, it collects data on cell temperature, hydrogen, CO, and oxygen concentrations within the module, and infrared thermal imaging data of the chamber. Then, the BMS analyzes the data collected by the composite detection system to determine if the current operating status of the energy storage system is normal. If abnormal, it classifies the system according to a predefined fire-fighting level and issues corresponding fire-fighting commands to the main control PLC. For a Level 1 response, it activates local forced ventilation, sprays low-concentration cooling mist onto the target PACK, and issues an audible and visual alarm (flashing yellow light). For a Level 2 response, it shuts down the ventilation system, activates perfluorohexanone liquid jet, upgrades the audible and visual alarm (flashing red light accompanied by a buzzer), and the BMS uploads the fire signal to the cloud. When the real-time detection data falls below a pre-set safety threshold, the BMS determines that the alarm is cleared and controls the main control PLC of the faulty PACK to stop the corresponding measures.

[0013] Meanwhile, the fire-fighting method for lithium battery energy storage systems based on multi-level coordinated detection and fixed-point spraying of this invention also has the following beneficial effects:

[0014] (1) Through the three-level coordinated detection of cell-level fiber optic temperature sensor, PACK-level gas detector and cabin-level infrared thermal imaging, timely and accurate early warning and cooling intervention for thermal runaway can be achieved.

[0015] (2) By using PACK-level fixed-point spraying (each PACK is equipped with an independent nozzle), the inhibitor is released only on the faulty PACK, avoiding contact between the battery in the non-faulty area and the extinguishing agent. Compared with the traditional full-cabin immersion scheme, this greatly reduces the damage rate of normal batteries.

[0016] (3) A new type of fire nozzle was adopted, which has a better spray angle and atomization degree, and can better adapt to the high-altitude environment, thus solving the problem of the decline in fire-fighting efficiency of ordinary fire nozzles in the high-altitude environment. Attached Figure Description

[0017] Figure 1It is a diagram of the battery compartment and the arrangement of the internal battery cells;

[0018] Figure 2 This is a flowchart of the fire-fighting method for lithium battery energy storage systems based on multi-level collaborative detection and fixed-point spraying, as described in this invention.

[0019] Figure 3 This is a structural diagram of a fire nozzle;

[0020] Figure 4 This shows the temperature distribution of Pack 1 when it triggers a thermal runaway warning (Level 1 response);

[0021] Figure 5 This shows the temperature distribution of Pack 1 when the thermal runaway warning (Level 1 response) is lifted;

[0022] Figure 6 It is the curve of the thermal runaway combustible gas generation rate of a single battery cell as a function of time;

[0023] Figure 7 It is the coupling relationship between the rate of gas generation during thermal runaway and the cell temperature;

[0024] Figure 8 This is the curve showing the highest temperature change in the space during the process of PACK 2 triggering a thermal runaway fire alarm (Level 2 response). Detailed Implementation

[0025] The specific embodiments of the present invention will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand the invention. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of the invention will be omitted here.

[0026] Example

[0027] In this embodiment, taking a lithium iron phosphate battery compartment in a 1C energy storage power station in a plateau region as an example, the internal structure is as follows: Figure 1 As shown, the battery module is composed of 2×7 cells arranged in a PACK. Each PACK contains 8 220Ah cells, and the heat dissipation power of a single cell at a 1C charge / discharge rate is 36.1kW / m. 3 .

[0028] When the lithium iron phosphate battery compartment malfunctions, such as Figure 2 As shown, the specific process of fire fighting based on the lithium battery energy storage system of this invention, which utilizes multi-level collaborative detection and fixed-point spraying, is as follows:

[0029] (1) Define the response levels of the fire protection system, and the triggering and deactivation conditions under each response level;

[0030] In this embodiment, the fire protection system response level includes two levels, where the first level response is the early thermal runaway warning stage and the second level response is the thermal runaway fire alarm stage.

[0031] The trigger condition for a Level 1 response is: T b_ij > T b_tr M H2_i > M H2_tr M CO_i > M CO_tr ΔT i >ΔT tr The condition for lifting a Level 1 response is: T b_ij < T b_s ΔM H2_i < 0ppm / s, ΔM CO_i < 0ppm / s, ΔT i <ΔT tr ;

[0032] Among them, T b_ij M represents the surface temperature of the j-th cell in the i-th cell module PACK of the lithium battery energy storage system, where i represents the PACK number and j represents the cell number; H2_i M CO_i ΔT represents the mass concentrations of H2 and CO gases in the i-th PACK; i T represents the maximum temperature difference on the surface of the i-th PACK group; b_tr M represents the temperature-level trigger threshold. H2_tr M CO_tr The mass concentration of H2 and CO gases represents the first-level trigger threshold; ΔT tr Indicates the first-level trigger threshold for temperature difference; T b_s This indicates the temperature-level threshold for release.

[0033] The trigger condition for a level 2 response is: T b_ij > T b_tr2 The conditions for lifting a Level 2 response are: T b_ij < T b_s2 ΔM H2_i < 0ppm / s, ΔM CO_i < 0ppm / s;

[0034] Among them, T b_tr2 T represents the secondary temperature trigger threshold. b_s2 This indicates the temperature-level secondary release threshold.

[0035] In this embodiment, T b_tr = 65℃, M H2_tr = 250ppm, M CO_tr = 300ppm, ΔTtr = 5℃, T b_s = 40℃, T b_tr2 = 120℃, T b_s2 = 100℃;

[0036] (2) Deploy composite detection and fire protection systems on lithium battery energy storage systems;

[0037] In this embodiment, the composite detection system comprises three levels of detectors: cell-level, PACK-level, and battery compartment-level.

[0038] Among them, the cell-level detector uses a fiber optic temperature sensor. One fiber optic temperature sensor is deployed on the surface of the cell in each PACK, and the surface temperature T of the cell is collected using the fiber optic temperature sensor. b_ij Where i represents the PACK number and j represents the cell number;

[0039] The PACK-level detectors are combustible gas detectors, with one combustible gas detector deployed at the top of each PACK. These detectors collect the mass concentrations M of H2 and CO gases. H2_i and M CO_i ;

[0040] The battery compartment detector uses an infrared thermal imager. One infrared thermal imager is deployed on the surface of each PACK to collect the temperature distribution on the PACK surface, and then the maximum temperature difference ΔT is calculated. i。

[0041] The fire suppression system includes a forced exhaust fan located on the side of the battery cell module PACK and fire nozzles located at the top inside the battery cell module.

[0042] In this embodiment, the fire nozzle is a high-pressure atomizing nozzle suitable for high-altitude environments, and its mechanical structure is as follows: Figure 2 As shown in Table 1, the components of the fire nozzle are as follows. Its special mechanical structure can compensate for the atomization effect, thereby overcoming the problem of poor atomization effect caused by the easy liquefaction of perfluorohexanone in high-altitude environments. The fire nozzle is placed on top of each PACK so that all cells are within the effective range.

[0043] Table 1: Names of Components of a Fire Nozzle

[0044] Serial Number name 1 nozzle body 2 valve core 3 O-ring rubber seal 4 spring 5 nozzle 6 O-ring rubber seal 7 silicone gaskets 8 cover plate 9 Phillips head hex bolts 10 flat washers 11 Standard elastic washer

[0045] (3) Collect detection data using detectors at each level of the composite detection system, and then upload it to the battery management system (BMS);

[0046] In this embodiment, the dataset of PACK 1 collected by the composite detection system is: the set of cell temperatures (°C) T collected by the cell temperature sensor. b1 = [47, 50, 59, 68, 54, 52, 45, 42]、The PACK internal gas detector detected a combustible gas solute concentration M. H2_1 = 273ppm, M CO_1 = 341ppm, the infrared thermal imager scanned the maximum temperature difference of the PACK from the outside, ΔT1 = 8℃.

[0047] The datasets for PACK 2 are: cell temperature (°C) data collected by the cell temperature sensor T b1 =[54, 61, 76, 156, 71, 58, 53, 52]、The PACK internal gas detector detected a combustible gas solute concentration M. H2_1 =565ppm, M CO_1 = 891ppm, and the infrared thermal imager scanned the maximum temperature difference ΔT1 of the PACK from the outside, which was 76℃.

[0048] (4) The BMS system analyzes and processes the detection data collected by the composite detection system to determine the response level of the fire protection system;

[0049] In this embodiment, based on the data collected from Pack 1, it can be inferred that Cell 4 of this Pack has overheated, and the maximum temperature difference ΔT on the outer surface of the Pack is greater than ΔT. tr = 5℃, and accompanied by a value higher than the threshold (M H2_tr = 250ppm, M CO_tr The release of combustible gases H2 and CO (300 ppm) meets the triggering conditions for a Level 1 response of the fire protection system.

[0050] Based on the data collected from Pack 2, it can be inferred that the temperature of cell 4 in this pack has exceeded the first-level response range, reaching 156℃, which is higher than the second-level response trigger threshold T. b_tr2 = 120℃. Based on the temperature difference of up to 76℃ on the outer surface of PACK 2, it can be inferred that an open flame had appeared inside at this time.

[0051] (5) The BMS system controls the fire protection system to perform the corresponding fire protection task according to the corresponding response level, and monitors the uploaded detection data in real time during the fire protection process. When the detection data is lower than the set release condition, the fire protection task ends.

[0052] In this embodiment, the process of performing a firefighting task is as follows:

[0053] (5.1) When any fire response level is triggered, the BMS system triggers the thermal runaway prevention mechanism and actively disconnects the circuit of the faulty PACK;

[0054] (5.2) For different alarm levels that occur in PACK 1 and PACK 2, BMS issues corresponding instructions to the main control PLC of the two PACKs respectively.

[0055] Based on the data collected from Pack 1, it can be inferred that Pack 1 has triggered the Level 1 response conditions. This triggers local forced ventilation, fire nozzles spraying low-concentration perfluorohexanone aerosol onto the faulty Pack, audible and visual alarms, and uploading a fire signal to the cloud. In this embodiment, the local forced ventilation speed is 10 m / s, and the low-concentration perfluorohexanone aerosol is 30 g / m³. 3 ;

[0056] Based on the data collected from PACK 2, it can be inferred that PACK 2 triggers the secondary response conditions, which would involve shutting down the ventilation system, activating fire nozzles to spray liquid perfluorohexanone, triggering an audible and visual alarm accompanied by a buzzer, and uploading the fire signal to the cloud.

[0057] (5.3) During the firefighting process, the BMS system monitors the uploaded detection data in real time. When the real-time detection data is lower than the release condition under each response level, the BMS system controls the fire protection system to stop the firefighting task.

[0058] In this embodiment, based on the data collected from Pack 1, it can be inferred that Cell 4 of this Pack has overheated, and the maximum temperature difference ΔT on the outer surface of the Pack is greater than ΔT. tr = 5℃, and accompanied by a value higher than the threshold (M H2_tr = 250ppm, M CO_tr The release of combustible gases H2 and CO (approximately 300 ppm) meets the triggering conditions for a Level 1 fire suppression system response. At this time, the temperature distribution of all cells inside Pack 1 is as follows: Figure 4 As shown, the cell with the highest temperature at this time is cell number 4, reaching 68℃. Therefore, the BMS control system for PACK 1 initiates the Level 1 response measures, activating the PACK forced ventilation system with a wind speed of 10m / s; the fire nozzles release a low-concentration perfluorohexanone mist (30g / m³). 3 ).

[0059] After 316 seconds, the highest temperature of the battery cell dropped to 40℃, reaching the safe threshold T. b_s At this point, the maximum temperature difference on the surface of PACK 1 is 3°C, reaching the safety threshold value ΔT. s The amounts of combustible gases H2 and CO no longer increase. The specific temperature distribution at this point is as follows: Figure 5 As shown. Figure 5To determine the temperature distribution of all cells within the same PACK at the time of the Level 1 response, the cell with the highest temperature at this point was cell number 2, reaching 40℃, while the temperature of cell number 4 had dropped to 38℃. At this point, the criteria for deactivating the alarm had been met, and all cells within PACK 1 had returned to their normal operating temperature range.

[0060] Based on the data collected from Pack 2, it can be inferred that the temperature of cell 4 in this pack has exceeded the first-level response range, reaching 156℃, which is higher than the second-level response trigger threshold T. b_tr2 = 120℃. Based on the temperature difference of up to 76℃ on the outer surface of PACK 2, it can be inferred that an open flame had already appeared inside at this point. Experimental data on various gases generated during the thermal runaway process of this type of battery cell are as follows: Figure 6 As shown, (a) represents the changes in the production rates of CO2, CO, H2, and C3H6, and (b) represents the changes in the production rates of HF, CH4, C2H4, and C2H6. Based on this, multiple experiments were conducted to determine the coupling relationship between the gas production flow rate of different gases and the cell temperature, such as... Figure 7 As shown in the figure, the dots represent the actual sampling points collected during the simulation, where temperature T and gas production rate v are related. x The curve represents the coupling relationship obtained by fitting all sampling points. Subsequent fire analysis of PACK 2 will be based on this result.

[0061] Based on this, a thermal runaway simulation experiment was conducted on the thermal runaway region of PACK 2. The results show the entire process of thermal runaway fire in the internal region of PACK 2 from the onset of the fire to its extinguishing, and the flame temperature changes are as follows: Figure 8 As shown, when the temperature suddenly increases, it indicates that an open flame has appeared, causing the highest temperature in the space to be the flame temperature; when the temperature drops below the ignition point of the combustible gas, it indicates that the flame has been extinguished. Therefore, it can be concluded from the temperature curve that from the release of high-pressure perfluorohexanone gas by the fire suppression system to the extinguishing of the flame, a total of 23 seconds elapsed, and the final cell temperature was reduced to around 70°C.

[0062] In the case of PACK 2 in this scenario, since the detection time occurred sometime after the thermal runaway fire, the simulation determined that this time was t=129s. Therefore, the fire suppression system was manually shut down between 97s and 129s, and its detection and extinguishing functions were activated at 129s. This was also the moment when the emergency alarm was detected in PACK 2 in this case. By observing the temperature change curve of the highest temperature inside the PACK after 129s, it can be concluded that the open flame was extinguished 23s after the fire suppression system intervention, and there was no reignition. Ultimately, the cell temperature was reduced to around 70℃, below the secondary response deactivation threshold T. b_s2 =100℃. The alarm level is downgraded from the thermal runaway fire alarm level to the thermal runaway early warning stage.

[0063] By simulating accidents involving two PACKs in the case study, it can be concluded that the two fire suppression system response schemes proposed in this invention, targeting both high temperature and fire scenarios, can effectively solve the current problems. When the PACK is in the thermal runaway early warning stage, the fire suppression system intervention can reduce the temperature of all cells in the PACK to below 40°C, thereby eliminating the high temperature risk. When the PACK is in the thermal runaway fire alarm stage, the system intervention can quickly extinguish the open flames in the PACK and reduce the cell temperature to the warning level, followed by cooling treatment using Level 1 response measures. Experimental results show that this scheme can effectively suppress the spread of high temperature or fire to other cell modules in the battery compartment, achieving accurate early warning and targeted effective fire suppression for energy storage systems in high-altitude environments, effectively preventing further expansion of losses in thermal runaway accidents in lithium iron phosphate energy storage systems.

[0064] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A fire-fighting method for lithium battery energy storage systems based on multi-level collaborative detection and fixed-point spraying, characterized in that, Includes the following steps: (1) Define the response levels of the fire protection system, and the triggering and deactivation conditions under each response level; (2) Deploy composite detection and fire protection systems on lithium battery energy storage systems; (3) Collect detection data using detectors at each level of the composite detection system, and then upload it to the battery management system (BMS); (4) The BMS system analyzes and processes the detection data collected by the composite detection system to determine the response level of the fire protection system; (5) The BMS system controls the fire protection system to perform the corresponding fire protection task according to the corresponding response level, and monitors the uploaded detection data in real time during the fire protection process. When the detection data is lower than the set release condition, the fire protection task ends.

2. The fire-fighting method for lithium battery energy storage systems based on multi-level collaborative detection and fixed-point spraying according to claim 1, characterized in that, The fire protection system response levels include two levels: Level 1 response is the early warning stage of thermal runaway, and Level 2 response is the alarm stage of thermal runaway fire. The trigger condition for a Level 1 response is: T b_ij > T b_tr M H2_i > M H2_tr M CO_i > M CO_tr ΔT i >ΔT tr The condition for lifting a Level 1 response is: T b_ij < T b_s ΔM H2_i < 0ppm / s, ΔM CO_i < 0ppm / s, ΔT i <ΔT tr ; Among them, T b_ij M represents the surface temperature of the j-th cell in the i-th cell module PACK of the lithium battery energy storage system, where i represents the PACK number and j represents the cell number; H2_i M CO_i ΔT represents the mass concentrations of H2 and CO gases in the i-th PACK; i T represents the maximum temperature difference on the surface of the i-th PACK group; b_tr M represents the temperature-level trigger threshold. H2_tr M CO_tr The mass concentration of H2 and CO gases represents the first-level trigger threshold; ΔT tr Indicates the first-level trigger threshold for temperature difference; T b_s This indicates the temperature-level threshold for release. The trigger condition for a level 2 response is: T b_ij > T b_tr2 The conditions for lifting a Level 2 response are: T b_ij < T b_s2 ΔM H2_i < 0ppm / s, ΔM CO_i < 0ppm / s; Among them, T b_tr2 T represents the secondary temperature trigger threshold. b_s2 This indicates the temperature-level secondary release threshold.

3. The fire-fighting method for lithium battery energy storage systems based on multi-level collaborative detection and fixed-point spraying according to claim 1, characterized in that, The composite detection system consists of three levels of detectors: cell-level, PACK-level, and battery compartment-level. Among them, the cell-level detector uses a fiber optic temperature sensor. One fiber optic temperature sensor is deployed on the surface of the cell in each PACK, and the surface temperature T of the cell is collected using the fiber optic temperature sensor. b_ij Where i represents the PACK number and j represents the cell number; The PACK-level detectors are combustible gas detectors, with one combustible gas detector deployed at the top of each PACK. These detectors collect the mass concentrations M of H2 and CO gases. H2_i and M CO_i ; The battery compartment detector uses an infrared thermal imager. One infrared thermal imager is deployed on the surface of each PACK to collect the temperature distribution on the PACK surface, and then the maximum temperature difference ΔT is calculated. i。 4. The fire-fighting method for lithium battery energy storage systems based on multi-level collaborative detection and fixed-point spraying according to claim 1, characterized in that, The fire protection system includes a forced exhaust fan located on the side of the battery cell module PACK and a fire nozzle located at the top inside the battery cell module.

5. The fire-fighting method for lithium battery energy storage systems based on multi-level collaborative detection and fixed-point spraying according to claim 1, characterized in that, The process of performing the firefighting task in step (5) is as follows: (5.1) When any fire response level is triggered, the BMS system triggers the thermal runaway prevention mechanism and actively disconnects the circuit of the faulty PACK; (5.2) The BMS sends corresponding instructions to the main control PLC according to the corresponding response level. If a certain PACK triggers the first-level response condition, it will start local forced ventilation, fire nozzles spray low-concentration perfluorohexanone aerosol onto the faulty PACK, sound and light alarm, and upload the fire signal to the cloud. If a PACK triggers the Level 2 response condition, the ventilation system will be shut down, the fire nozzles will be activated to spray liquid perfluorohexanone, an audible and visual alarm will be set up and accompanied by a buzzer, and the fire signal will be uploaded to the cloud. (5.3) During the firefighting process, the BMS system monitors the uploaded detection data in real time. When the real-time detection data is lower than the release condition under each response level, the BMS system controls the fire protection system to stop the firefighting task.

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