Detection, prevention, and control of fires in electrochemical energy storage systems
Jul 18,2024
In recent years, fires caused by electrochemical energy storage have become a focus of news, and people are increasingly paying attention to the detection, prevention, and extinguishing of electrochemical energy storage fires.
Electrochemical energy storage fires are caused by thermal runaway of batteries. The general causes of thermal runaway of batteries are internal and external factors. The internal factors mainly include battery aging, while the external factors include mechanical structural damage caused by accidents, heating of partial batteries, overcharging and discharging of batteries, overvoltage, external short circuits, etc. In the battery module, after the thermal runaway of the battery cell, the thermal runaway of the battery cell adjacent to it or other parts is triggered, resulting in thermal runaway propagation. Thermal runaway propagation can be accelerated either by energy conduction or by ejecta fire. Further accumulation of heat can lead to fires and explosions.
In order to deal with the electrochemical energy storage fire, the energy storage power station should be equipped with fire alarm system, ventilation system, fire extinguishing system and secondary sprinkler cooling system.
Fire Alarm System
The alarm system should be equipped with comprehensive combustible gas detectors, which can jointly determine battery thermal runaway through smoke, heat, and fire alarm signals. The exhaust gas generated by lithium batteries should be considered as a warning signal for taking measures to prevent thermal runaway. Independent testing results show that the average time interval from the detection of exhaust gas to the occurrence of thermal runaway is 11 to 12 minutes. Detecting the stage when lithium batteries begin to produce exhaust gas can provide early warning for the control of battery energy storage systems. By sending a signal to the battery management system to turn off the battery power, it can prevent further temperature rise of the battery cells and keep them below the thermal runaway point. If necessary, ventilation treatment can be used to eliminate the accumulation of combustible gases generated by batteries.
Ventilation System
The ventilation system of the energy storage power station should be able to limit the combustible gas to below 25% of the minimum explosion limit. Explosion-proof blowers are used in the ventilation system, and the combustible gas detection system is linked with the ventilation system to prevent the explosion caused by gas accumulation in the process of thermal runaway, especially after the open flame is extinguished.
Fire Extinguishing System
The fire extinguishing system shall be set up in the battery area in accordance with the regulations and interlinked with the fire alarm system. There are many kinds of fire extinguishing agents in the fire extinguishing system, including perfluorohexanone, heptafluoropropane, carbon dioxide and aerosol, etc. Gas extinguishing agents mainly extinguish open fires, water-based extinguishing agents have the best cooling effect, and aerosols can provide additional protection for the battery to prevent fire reignition, and in the case of a battery fire, it can also reduce the oxygen content in the closed environment.
Cooling System
The fire of lithium battery is likely to reignite even if it appears to have been extinguished. Therefore, it is necessary to install a water-cooling system with a sprinkler nozzle, which can be directly connected to the water supply system, or install a specific water pump outside the battery energy storage system water tank.
In order to enhance the safety of electrochemical energy storage power stations, relevant standards have been issued. In November 2017, UL issued the UL9540A standard “Evaluation of Thermal Runaway Fire Propagation in Batteries and Energy Storage Systems”, specifically to address the problem of fire propagation due to thermal runaway in battery energy storage systems. Three revised versions of the standard have been released, and it is expected that the regulatory environment will become increasingly improved.
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