Passive safety of lithium-ion battery energy storage power stations refers to the measures taken to activate the fire protection system as early as possible after a fire or explosion occurs in the energy storage power station in order to reduce economic losses and ensure the personal safety of operators. It is the last line of defense for the safety of energy storage power stations.
Fires caused by thermal runaway of energy storage lithium-ion batteries are classified as electrical fires, characterized by rapid fire spread, difficulty in extinguishing, and high risk.
Based on the different fuels used for thermal runaway fires in lithium batteries, energy storage lithium battery fires can be mainly classified into the following five categories: First, solid fires using lithium battery negative electrode materials as fuel; second, liquid fires using lithium battery electrolyte as fuel; third, gas fires using large amounts of flammable gases generated by the electrochemical reaction of lithium battery thermal runaway as fuel; fourth, metal fires using lithium intercalated inside the battery and other metal materials as fuel; and fifth, electrical fires using the entire lithium battery energy storage power station system (including various equipment, battery module clusters, etc.) as fuel.
Currently, the main method for extinguishing lithium-ion battery fires is water-based extinguishing agents, while gaseous and solid extinguishing agents have more limitations and are less effective.
Common types of water-based fire extinguishing agents include water, AF-31, AF-32, and ABD fire extinguishing agents. The fire extinguishing principle is that water evaporates and carries away a large amount of heat, forming a water film to isolate oxygen, cool down and inhibit combustion.
Based on reports of fires at energy storage power stations, fire brigades typically use large amounts of water to extinguish them. The advantages of water-based fire extinguishing agents are low cost and more significant fire-extinguishing and cooling effects; the disadvantages are the risk of causing short circuits or electrical equipment failures, which could disrupt the normal operation of the energy storage power station. The applicable scope and boundary conditions for fire protection systems for energy storage power stations based on water-based fire extinguishing agents need further clarification.
Researchers have found that fine water mist can effectively extinguish fires involving containerized lithium iron phosphate batteries, showing significant advantages in extinguishing open flames and rapidly reducing the temperature of the battery modules. The most critical influencing factor is the pressure of the fine water mist; increased pressure significantly improves both fire extinguishing and cooling efficiency, but also rapidly increases costs.
There are three common types of gaseous fire extinguishing agents based on their extinguishing principles: First, halon 1301 and halon 1211, which extinguish by decomposing free radicals produced during combustion and synthesizing low-activity free radicals. However, their cooling effect is not significant, making them ineffective at extinguishing electrical fires, and they also damage the ozone layer, leading to their complete ban in my country. Second, CO2, IG-541, and IG-100, which extinguish by diluting the oxygen content of the air and inhibiting combustion. However, their extinguishing efficiency is poor, they require a sealed environment, and they can easily damage electrical equipment. Third, clean gases such as heptafluoropropane and hexafluoropropane, which extinguish by rapidly cooling through molecular vaporization and diluting the air to inhibit combustion. However, this method produces large amounts of toxic gases such as hydrogen fluoride in the early stages of a fire.
Currently, most fire extinguishing measures in energy storage compartments of energy storage power stations are based on relevant Japanese battery energy storage standards and use gaseous fire extinguishing agents, primarily heptafluoropropane. The advantages are no gas residue, environmental friendliness, and no impact on subsequent equipment operation; the disadvantages are limited cooling effect, long battery module cooling time, and difficulty in extinguishing fires promptly.
Traditional solid fire extinguishing agents, such as dry powder fire extinguishing agents, are generally ineffective at extinguishing fires in energy storage power stations because electrical fires burn rapidly at high temperatures, while dry powder fire extinguishing agents do not have a cooling effect.
