Tesla huge energy storage catches fire

Safety accident of energy storage project occurred in the United States

The US energy storage project has safety accident. This safety accident occurred in Monterey, California, USA, which was caused by the fire of Tesla Megapack energy storage system equipment in Elkhorn battery energy storage project operated by California Pacific Gas&Electric Company (PG&E). In this article, after talking about the fire accident of energy storage, we will analyze the reasons and discuss the ways to improve the safety of energy storage.

After the fire, the nearby residents were evacuated in an emergency, and the nearby roads were also blocked in an emergency, causing no casualties at the scene. As of 2:00 p.m. local time on Tuesday, the open fire on site had not been completely extinguished.

However, the fire did not cause power interruption. PG&E said that the reason was that Tesla Megapack battery storage could enable power companies to transmit and store redundant power across regions, and use the stored power resources when local power demand was high or the grid was unexpectedly cut off.

Elkhorn battery energy storage project is operated by PG&E and jointly designed, built and maintained by Tesla and PG&E. The energy storage system includes 256 Tesla Megapack battery energy storage systems on 33 concrete slabs with an installed capacity of 182.5MW, which was put into operation in April this year.

Purpose Compared with Powerpack, Megapack is a new energy storage product with larger capacity and higher integration. It occupies 40% less space and requires only one tenth of the parts.

Recently, Tesla also updated the Megapack order page data. The size of a single Megapack has increased by 50% compared with the previous one. Now, the energy storage capacity of each Megapack is 3.9 MWh and the rated power is 1.9 MW.

The largest energy storage project in Australia caught fire in July last year

It is worth mentioning that in July last year, the largest energy storage project in Australia, the Victoria Large Battery Energy Storage Project, also had a fire event during equipment commissioning. The fire source was the complete ignition of a 13 ton lithium battery in a container, which caused the burning of two Megapack energy storage systems at the project site.

The investigation results of the fire accident show that the short circuit caused by the leakage in the cooling system, which led to the energy storage fire, and the failure of the monitoring system to operate 24 hours as required is another internal cause of the accident.

At that time, Tesla also adjusted and optimized Megapack’s process, software and hardware, and structure to improve its design from many aspects, such as coolant leakage protection, Pyrofuse work strategy and power off measures, and fire protection design of vent.

Data shows that in 2021, Tesla’s energy storage business had 3992MWh of installed capacity in the whole year, up 32% year on year. In 2021, the cumulative installed capacity of global electrochemical energy storage was 25.1GWh, from which it can be preliminarily inferred that Tesla has now occupied about 16% of the global energy storage market share.

Previously, Tesla also mentioned in its 2021 Impact Report. By 2030, Tesla aims to sell 20 million electric vehicles every year and deploy 1500GWh energy storage projects every year to accelerate the global transformation to sustainable energy.

According to statistics, in the first half of this year, there have been about 17 global energy storage fires, including three in South Korea, four in China, six in the United States, one in Australia, one in Nigeria, one in Germany, and one in France. The United States is one of the regions with the largest number of fire incidents in energy storage power plant projects.

Fire incident of energy storage power plant project in the United States

On February 13, an accident occurred in the Moss Landing energy storage power plant project in California, USA, which is the second accident in less than half a year after the battery overheating accident occurred in the project on September 4, 2021;

On March 13, a fire broke out in a family at the corner of East Madison Avenue and Depew Street in the United States. It was caused by a faulty lithium battery;

On April 5, a small fire broke out in the Terra Gen battery energy storage project in Valley Center, California;

On April 18, a fire broke out in the energy storage facility of Yanhe substation in Arizona, the United States. The fire smoldered for 5 days and continued to emit white smoke;

On April 25, a fire broke out in the lithium ion battery energy storage system of Salt River Project (10MW);

On May 8, a user side photovoltaic energy storage system exploded in Althengstett, Karff District, Germany.

Before the fire of Tesla Megapack energy storage system equipment, another local energy storage project operated by Vistra also experienced two overheating events. In July, Vistra restarted its energy storage facilities and operated at about 98% of its maximum capacity.

At present, Vistra is building the third phase expansion project with a capacity of 350MW, and plans to increase the power station capacity to 1500MW through the fourth phase expansion project.

Because the causes of fire in the energy storage system are often very complex, for companies, what they need to do is to take precautions and put safety first. With the penetration of lithium ion battery and the development of energy storage industry, the fire safety market will also be mainly concerned.

Analysis of the causes of fire in electrochemical energy storage

Up to now, there have been more than 60 electrochemical energy storage fire accidents in the world. Most of the energy storage batteries use ternary lithium batteries. The accident occurs mainly in the equipment commissioning stage and the rest after charging and discharging.

There are many reasons for the fire in the electrochemical energy storage power station, including the quality problems of batteries and electrical equipment, the incomplete design of system protection measures, the poor coordination of control and protection functions between PCS, BMS, EMS and other systems, and the quality problems in the construction process.

However, although there are many reasons for the fire in the energy storage plant, the thermal runaway of the battery itself and the thermal runaway diffusion of the battery modules and systems are the focus of the industry at present.

The general causes of battery thermal runaway include internal and external causes. Internal causes include battery aging, such as increased internal resistance due to polarization, lithium metal deposition piercing the diaphragm, and internal impurities piercing the diaphragm.

External causes include mechanical structure damage of battery caused by accidents, local heating of battery, overcharge and discharge of battery, overvoltage, external short circuit, etc. In the battery module, after the thermal runaway of the battery cell occurs, it triggers the thermal runaway of the battery cell adjacent to it or in other parts, which is called thermal runaway diffusion. 

Uncontrolled thermal diffusion may be conducted through energy, such as thermal energy, electrical energy, and mechanical energy, or it can be accelerated by the fire of ejecta. Further accumulation of heat may also lead to fire, gas release and explosion.

How to improve the safety of energy storage

First of all, in order to prevent thermal runaway of the battery from the material and structure of the battery, it is important to improve the electrolyte, diaphragm and cathode materials.

● Electrolyte:

It is necessary to develop nonflammable and incombustible electrolyte.

● Cathode materials:

Cathode materials need to be doped or wrapped to improve the stability of metal oxides.

● Diaphragms:

The melting temperature of battery diaphragms is currently between 120-140 ℃. Once the diaphragms melt the batteries, internal short circuits will occur instantly.

Therefore, high temperature resistant diaphragms, such as organic diaphragms and inorganic ceramic diaphragms, should be developed.

In addition, improving the consistency of the battery, selecting safe and efficient thermal management system, suppressing the temperature rise of the battery, embedding foam metal and covering phase change materials to achieve passive cooling of the battery are also the focus of improving the safety of battery applications in the future.

In terms of active safety of the energy storage power station, it is necessary to improve the level of monitoring, operation and maintenance based on digital technology and monitor the hardware status of the overall power station in real time.

Furthermore, achieving real-time notification in case of abnormal faults, improving the accuracy of fault diagnosis and automatic processing efficiency, and doing a good job in early warning of the system safety status are important, so as to avoid the battery from failure to thermal runaway status.

In the future, the energy storage battery management system needs to improve the accuracy of temperature and safety parameter detection and respond in a timely manner to achieve efficient and reliable safety status analysis as well as early warning functions. Providing active balanced management and system safety protection measures are also important. The wireless battery management system should also be put on the agenda.