I attended an online conference on Wednesday 16th September for 2 hours entitled “Electric Vehicles, Fire and Security”
This was mainly driven by three large fires which were in Netherlands, Denmark and United Kingdom.
Dr. Ing. Nils Rosmuller
Applied Professor for Energy and Transport Safety, Instituut Fysieke Veiligheid (IFV)
Senior Advisor and Test Manager, Norsk elbilforening/ Norwegian EV Association
Senior Representative, DOET/Dutch Organisation for Electric Transportation
Secretary General, AVERE
- An overview of the latest innovation in fire safety technologies in EVs
- Experts insight in the risk management of the security of electric vehicles
- A review of measures to deal with the specific EV risks
There were a number of excellent questions discussed by this great enthusiastic panel.
- Is it acceptable to charge an EV up to 750 KW in a carpark environment, it would not be acceptable to fill up a petrol tank in this environment
- Should better/more sophisticated fire detection be in place where EVs are charged
- Did EVs cause the fires in UK, Netherlands and Denmark
The lithium-ion (Li-ion) battery technology can enable a broad introduction of electrified vehicles mainly due to its high energy capacity.
Li-ion batteries also have other important properties, e.g. long life time and the possibility of fast charging. However, lithium-ion batteries have a drawback compared to most other battery technologies in that the electrolyte is flammable and the battery may go into a thermal runaway, that is, the battery may self-heat, resulting in a rapid pressure and temperature increase in the cell, which will release flammable and toxic gases but can also cause projectiles and fire.
This may happen moving out of the stable operating window of the Li-ion cell and can be caused by e.g. short circuiting, overheating, overcharging or mechanical damage.
The electrified vehicle has a potential to be safer than conventional combustion engine cars, simply because the main fire source, gasoline/diesel is removed.
The safety of a battery system depends on several things, e.g. cell chemistry, cell design and system design, including thermal management system and control strategies.
Many battery systems for automotive applications use less stable chemistries in order to obtain higher energy density for example. Abuse test results from cell level are presented and their impact is discussed on battery system and vehicle level.
The gases released during a from a Li-ion battery cell can be toxic, e.g. CO, but the fluoride emissions are of most concern. Hydrogen fluoride (HF) is one of them, but there are also others, e.g. phosphorous oxyfluoride (POF3). They are formed from the fluorine content used in the Li-ion cell, the binder (e.g. PVdF) and the commonly used Li-salt, hexafluorophosphate (LiPF6).
There is good knowledge about the safety risks and safety devices used in consumer cells. Using Li-ion in the automotive sector puts higher demands on the battery since the batteries are significantly larger and with harsher environmental conditions, e.g. vibrations, humidity, larger temperature variations.
The different Li-ion chemistries show diverse hazards where the LFP is less reactive but still safety measures are needed for all Li-ion batteries. High safety is achieved by adding several safety layers from cell to vehicle level, however the risk for a cascading fire in a complete battery pack starting from a single cell is not yet well studied and the knowledge about possible counteractions is thus also limited. Sometimes things go wrong even though smart safety strategies are used. The exploded cylindrical cell due to a cell vent malfunction showed this and this fact underlines the importance of using many safety layers.
The toxic gas emissions from Li-ion batteries, e.g. HF and POF3, can pose a serious risk for persons. A replacement of the Li-salt LiPF6 to a non-fluorine salt and change of fluorine binder could resolve this risk.
Research is ongoing in this field but the required properties for a Li-ion battery in a xEVs are complex and demanding.
Worldwide, wildly differing estimates suggest there are well over 1 billion cars in use. Of these approximately 3 million are Electric or hybrid vehicles.
Estimates of the availability of carbon fossil fuels suggest there is less than sixty years of oil and gas reserves, and, depending on which statistics we read there will be between 200 and 3,000 years of coal.
These figures demonstrate several things. Firstly, all the statistics need careful scrutiny and interpretation, secondly, whatever figures we work with, they all lead to the fact that one day fossil fuels will not be available. Thirdly, the use of carbon fossil fuels may come to an end before the resources are fully used up; it has been said that the Stone Age did not come to an end because of a lack of stone.
Despite these difficulties more EV are appearing on the roads and the parking industry will need to catch up with the realities of charging these vehicles within their carparks, requiring not only large infrastructure changes but an awareness of the changing risks involved with the new systems and new EV energy technologies. http://www.ev-volumes.com has an article showing we are in an exponential curve which suggests by 2027 half the world’s new car sales will be EV. The UK government has set goals to eliminate Internal Combustion Engines (ICE) by 2040, and governments around the world are proactively encouraging the use of EV, which, like a game of hide and seek, are coming, ready or not.
An EV faces the biggest risk of fire from its batteries. Battery technology is improving all the time, with safety systems being added as fast as legislation is brought in to cover the new technologies, and vice versa. Charging controls and battery management systems are becoming more intelligent, the use of better fire calming chemicals within the battery compartments, including external intumescent barriers designed to resist thermal runaway and isolate the batteries from each other. Battery cooling systems have been installed to attempt to limit the chances of spontaneous ignition of the batteries, which in some cases can occur as low as 66.5°c.
ICE vehicles have had 192 years of development (the first ICE was produced on the 1st April 1826) and much is understood about the fire risks they present. Methods of extinguishing ICE fires are well advanced and are still advancing, with new ideas about firefighting techniques and methodologies constantly being developed. Despite this, serious fire events continue to occur in car parks with devastating results, although these are rare. The unknown risks presented by EV are to be added into the methodology of risk assessments which must consider we have very little accurate data and even less information about how to deal with an EV fire event.
There is much that is unknown and much to learn about the evolving EV technology and how to deal
with the new challenges they bring for the parking industry, particularly in emergency situations; we
need to inform and educate ourselves to answer the questions outlined above and develop solutions
for fire containment and extinction of EV batteries. However, should someone find a way to split the
water molecule cheaply, battery cars, along with fossil fuel cars, will be a thing of the past, not the