On April 18, 2022, the Chandler lithium battery storage facility in Arizona, USA, began to smoke and smolder, triggering a fire alarm. This situation lasted for nearly a week, and the local fire department used robots to continuously open the storage facility to discharge the chemicals produced inside the facility. According to relevant news reports, the facility is owned by Applied Energy Services (AES) and houses over 3200 lithium-ion batteries with a total energy of 10MW. The specific cause of the fire is still under investigation. According to the person in charge of AES, the fire suppression system inside the facility has been working, but the situation has not improved. Smoking and suffocation have continued, causing emergency evacuation of people within a quarter mile radius. The local fire department is also closely monitoring the further situation of the lithium battery storage facility, which once again raises questions about the safety of this clean energy among the local people.

As a representative of new energy power batteries, lithium-ion batteries have sparked a new revolution in the development of power battery vehicles. Therefore, more and more people are also thinking about their potential applications and possibilities in energy storage. At present, with the continuous development of lithium-ion battery technology, the development of lithium-ion batteries in energy storage is very rapid, and their applications have also entered the stage of commercial operation. However, with the continuous occurrence of lithium-ion battery explosion accidents, people's concerns about its safety have always been a major threshold and obstacle for its large-scale application and rapid development. In previous articles, it has been analyzed from the perspective of reaction mechanism that lithium-ion batteries have strong combustion and explosion conditions inside. Flammable materials such as low melting point flammable organic compounds and graphite negative electrode materials will become corresponding "fuels". Improper thermal management during charging, discharging, and operation will become the ultimate trigger for safety accidents in lithium-ion batteries, leading to combustion and explosion accidents. The following figure vividly illustrates the process of thermal runaway.

Image originates from the network

Currently, due to its high energy density and long service life, lithium-ion batteries are widely used as power batteries and are also considered as core components of new energy electric vehicles. However, in recent years, reports of lithium-ion battery explosion accidents have been heard repeatedly. The research report of the Electric School summarized the causes of electric vehicle explosions from 2014 to 2019. The main causes of electric vehicle explosions listed in the article include: battery self ignition, car collisions, equipment failures, charging, cable aging, component short circuits, water immersion, and human operation factors (as shown in the figure). Under the influence of these factors, electric vehicle thermal runaway is caused, resulting in explosions. According to the Fire Rescue Bureau of the Ministry of Emergency Management of China, from January 2021 to July 2021, there were a total of 6462 electric vehicle fires and explosions, with an average of over 900 electric vehicle accidents per month. 80% of electric bicycle fires occurred while charging, and the vast majority of accidents were caused by lithium battery explosions. According to the National Big Data Alliance for New Energy Vehicles, compared to 2019, the increase in fire accidents in 2020 reached 47%, with a total of 124 incidents. In the first half of 2021, there were 56 reported incidents of electric vehicle fires and explosions. With the gradual promotion of new energy vehicles, the public's anxiety about lithium-ion battery explosions is increasing.

     There have also been considerable reports of fires and explosions in lithium battery energy storage stations. According to incomplete statistics, there have been over 30 incidents of fire and explosion at energy storage plants worldwide in the past 10 years. According to incomplete statistics from the National Energy Information Platform, there have been a total of 32 incidents of fire and explosion at energy storage plants worldwide, including 1 in Japan, 2 in the United States, 1 in Belgium, 3 in China, and 24 in South Korea. And the fire and explosion of energy storage stations have certain characteristics, mainly including: the types of accident batteries are mostly ternary lithium-ion batteries, and most of them occur during charging and rest periods. The number of fire and explosion accidents in energy storage stations in South Korea is the most prominent, which may be related to the mainstream application of ternary lithium-ion batteries. This article will focus on a detailed summary and sorting of the serious explosion accidents in the lithium-ion battery energy storage field in the past three years, mainly including McMicken from the United States

BESS energy storage power station explosion accident, fire and explosion accident of the "photovoltaic+energy storage" system in Hongcheng, Chungcheongnam do, South Korea, fire and explosion accident of the Beijing Jimei Dahongmen 25MWh DC photovoltaic storage and charging integrated project, fire accident of the "Victoria Battery" (VBB) project, and battery melting incident of the Moslandin lithium-ion storage station facility.

Image originates from the network



On June 11, 2019, the South Korean Ministry of Commerce, Industry and Resources released the investigation results of a high incidence of energy storage plant fires in South Korea. The results report did not accurately identify the cause of the accident, but attributed it to uncertain factors caused by the world's first large-scale energy storage plant being put into operation. Among the 23 reported fire stations, battery manufacturer LG Chem supplied 12, Samsung SDI supplied 8, and the other 3 were supplied by other battery manufacturers. The possible causes of the accident in the report are summarized as follows:

(1) Battery system defects: When there are defects in the manufacturing of the battery system, the possibility of fire occurring due to internal short circuits in the battery increases during overcharging;

(2) The protection system for electric shock is incomplete: when overvoltage or overcurrent flows through the battery system, it may cause a short circuit in the battery and cause it to catch fire;

(3) Inadequate management and setup of operating environment: Energy storage devices installed in mountainous or seaside areas may experience repeated condensation and dust adsorption under high day and night temperature differences, which may lead to damage to the insulation layer of the grounding part between the battery and module casing, causing a fire;

(4) Lack of comprehensive management system for energy storage system: The lack of comprehensive system design and protection for energy storage power stations is also an important reason for the fire problem.

     On April 19, 2019 local time, a fire and explosion occurred at the McMicken BESS energy storage plant owned by Arizona Public Service Company (APS), the largest power company in Arizona, USA, resulting in four serious injuries. The energy storage power station started construction in June 2016 and was officially put into operation in March 2017, with a scale of 2 MW/2 MWh. There are a total of 27 battery racks in the energy storage container, with 14 lithium-ion battery modules stacked in each rack and 28 lithium-ion batteries placed in each module. The system caught fire and exploded after 25 months of safe operation. According to Utility

The accident investigation report released by Arizona Public Service shows that the general contractor for the energy storage station project is AES Corporation
(AES), the battery supplier is LG Chem, which uses a nickel manganese cobalt ternary lithium battery (NMC) with an energy density exceeding 200Wh/kg. It was caused by a thermal runaway caused by a malfunction of one battery on the battery rack. The cause of the battery malfunction has been identified as an internal defect in the battery. During the operation of the lithium-ion battery, unusual deposition and dendritic growth of lithium metal occurred. After the battery failed and experienced thermal runaway, the fire extinguishing system installed inside the energy storage container was unable to suppress the thermal runaway of the lithium battery. Additionally, due to the lack of heat blocking materials between the batteries on each individual battery rack, heat was transmitted to each battery in the rack, releasing flammable gases and reaching explosive concentrations. The flammable gas came into contact with air when firefighters opened the container door, causing an explosion. The study also reported that other battery racks were not affected by accident batteries due to their appropriate and safe placement distance (the installation diagram of energy storage container components is shown below). Lithium ion battery dendrites are a well-known failure mode for lithium-ion batteries, but they rarely occur in energy storage batteries that have only been in operation for about two years.

Installation diagram of energy storage container components 1

Installation diagram of energy storage container components 2

Post accident photos of McMicken BESS energy storage power plant

On April 6, 2021 local time, a fire and explosion occurred in the Hongcheng photovoltaic and energy storage system in Chungcheongnam do, South Korea. The energy storage system was installed and put into operation in 2018, with a photovoltaic power generation capacity of 3.4MW and a storage capacity of 10MWh. The explosion destroyed 0.5MW of energy storage batteries. It is understood that the lithium-ion battery cell supplier of the energy storage station is LG New Energy. According to the investigation conclusion released by the South Korean side, the causes of the lithium battery fire include three major reasons: insufficient battery overvoltage protection, the need for improvement in the operating environment (humidity and dust) and installation process, and insufficient experience in ESS.

Photo of fire and explosion in the Hongcheng photovoltaic and energy storage system in Chungcheongnam do, South Korea

On April 16, 2021, Beijing time, a fire and explosion occurred in the Beijing Jimei Dahongmen 25MWh DC optical storage and charging integrated project located at No.14 Ximachang A, Fengtai District. The accident resulted in three deaths and one serious injury. The developer of this project is Beijing Fuwei Oil and Gas Technology Co., Ltd. The project started construction in October 2017, and the first phase was delivered and put into operation in March 2019. The second phase of construction and renovation began in May 2021. Prior to the incident, it was in the equipment debugging stage and was the largest commercial user side energy storage power station in the center of Beijing. It is also the largest demonstration project for solar energy storage and charging in Beijing. According to the official investigation report on the 4.16 major fire accident in Fengtai District, the first phase that has been put into use includes a rooftop distributed photovoltaic 1.4MW, 4MW/12MWh energy storage, and 12.5MWh charging piles. The direct cause of the fire in the south building of the accident was determined to be due to an internal short circuit fault in the lithium iron phosphate battery in the battery room, causing thermal runaway and the fire of the battery. The report also reported subsequent experiments that found that thermal runaway of lithium iron phosphate batteries would produce ejecta, mainly methyl ethyl carbonate vapor and hydrogen, methane, carbon monoxide, carbon dioxide, etc., most of which were flammable gases. The direct cause of the explosion in the north building is believed to be the flammable and explosive components generated by the thermal runaway of the south building entering the energy storage room of the north building through the cable trench and diffusing, mixing with air to form explosive gases, which explode when exposed to electrical sparks. According to the "Accident Analysis of Beijing Jimei Dahongmen 25MWh DC Light Storage and Charging Integrated Power Station Project" released by the Electric Power Research Institute, the battery used in the power station is Guoxuan High tech's lithium iron phosphate battery. The report from the Electric Power Station pointed out that due to limited information, an accurate conclusion cannot be made on the cause of the battery's thermal runaway. But the possible reasons may be internal battery cell defects or dendritic lithium caused by long-term charging and discharging, which can lead to battery failure, or external electrical and thermal shocks that cause irreversible heat release inside the battery and cause thermal runaway. It also mentioned in the suggestion the need to accelerate the development of new intrinsic safety energy storage batteries to effectively ensure the safe operation of energy storage stations.

Fire and explosion scene of Beijing Jimei Dahongmen 25MWh DC optical storage and charging integrated project

At 10:15 am local time on July 30, 2021, a fire occurred during construction of the Tesla Megapack energy storage system installed on one of the world's largest energy storage projects, the Victoria Battery (VBB) project, located in Victoria, Australia. The Victoria Battery project aims to help Victoria, Australia achieve its renewable energy targets of 40% by 2025 and 50% by 2030. Construction began in December 2020 and the project officially began operation on December 8, 2021. This project consists of 212 Tesla Megapacks, with a project scale of 300 MW/450 MWh. The official investigation report from the Victoria Energy Security Agency shows that the cause of the fire was initially determined to be a short circuit in two specific battery circuits at the same time caused by coolant leakage outside the battery compartment. This fault is a rare type of fault and was not detected in a timely manner, leading to the fire. The fire involved slow self ignition of two container systems and did not cause an explosion. The independent reports of Fisher Engineering Inc (FEI) and ESRG also provided the same report on the cause of the accident, stating that the main cause of the accident was the thermal management loss of the lithium battery caused by coolant leakage, which could potentially lead to the combustion of another adjacent energy storage system under the influence of wind. Tesla also stated that it will strengthen connection firmware management, complete monitoring and process improvement, and improve detectability and related fault handling mechanisms for such rare events. The project is owned and operated by French renewable energy producer Neoen, with Tesla as the general contractor. The battery used in the project is Tesla's Megapack, which consists of battery modules, power generation devices, thermal management systems, and control systems. Each unit can store more than 3 MWh of energy and be placed in a 7.2m * 1.6 m * 2.5 m container. According to relevant reports, the Megapack system currently uses square lithium iron phosphate batteries, which do not require nickel or cobalt to reduce battery costs.

Pictures of the scene of the Victoria battery explosion accident

In addition, in February of this year, the world's largest Moslandin lithium-ion storage facility located in Vistra Energy, California, triggered a fire due to the complete melting of 10 battery packs. Due to the timely cooling treatment of the batteries by the cooling device, there was no greater disaster. The Vistra Energy battery pack melting event was less than 5 months after the melting event in September 2021, when as many as 7000 battery packs were melted, accounting for 7% of all nearly 100000 battery packs. According to a statement released by Vistra Energy in January this year, the battery pack melting incident that occurred in September last year was due to the thermal management system mistakenly starting at extremely low smoke levels, and a few joints on some flexible hoses and pipes in the system malfunctioning, causing the system to mistakenly spray water to cool down, resulting in battery damage and overheating. The scale of some power stations in the accident was 300MW/1200MWh, and the second phase power station (100MW/400MWh) was not affected. According to its official claim, the low-level smoke was generated due to a bearing failure in the air handling device, and the smoke was not caused by the battery. The first phase of the Moslandin lithium-ion energy storage station project started construction in November 2018 and began operation in December 2020. The second phase of the project started construction in September 2020 and was delivered for commissioning in July 2021. Its battery supplier is LG New Energy, which mainly produces nickel cobalt manganese ternary lithium batteries. The system integration and engineering contractor is Fluence, which currently has a total capacity of 400MW/1600MWh and is also the world's largest battery storage facility. The battery melting phenomenon in February this year is still under further investigation.

With the increasing scale of energy storage on the power generation side, safety requirements are becoming higher and higher. Improving the safety management of lithium batteries is one option, but safer liquid flow batteries, compressed air, and other new energy storage technologies will have more market opportunities.

Reference materials:

[1]
Arizona Public Service. McMicken Battery Energy Storage System Event
Technical Analysis and Recommendations [R] America：Arizona Public
Service，2020.

[2] Beijing Municipal Emergency Management Bureau Investigation Report on the "4.16" Major Fire Accident in Fengtai District [R] Beijing: Beijing Municipal Emergency Management Bureau, 2021

[3] China Academy of Electric Power Sciences Research Co., Ltd Accident Analysis of Beijing Jimei Dahongmen 25MWh DC Optical Storage and Charging Integrated Power Station Project [R] Beijing: China Academy of Electric Power Sciences Research Co., Ltd., 2021

[4] AND BLUM, PE, CFEI. Victorian Big Battery Fire: July 30, 2021 [R] Australia：Fisher Engineering, Inc.，2021.




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