By Ian Bartle Ian is the Managing Director of Nobel Fire Systems Ltd. He has over 30 years’ experience in the fire industry from technical sales through to senior management. He has developed significant experience in a wide range of disciplines from detailed fire equipment and systems design to product fire testing and certification across the full spectrum of fire suppression systems including lithium-ion batteries.
The increase in Lithium-Ion batteries (LIB) technology is affecting every walk of life as we become surrounded by a myriad of differing formats and chemistries. With the millions of batteries already in circulation and the ever-increasing demand, incidents involving lithium-ion batteries are inevitably, becoming more common place. There is currently a thirst for knowledge around battery technology which means as incidents occur, they are very much thrust into the spotlight. We should however get some perspective around these incidents, acknowledging the quantity of them is still relatively small, and look to rationalise the reasons behind them.
The task of gathering incident information on these worldwide events is both difficult and time consuming and I am pleased to be able to include a link that provides some of the pertinent statistics at https://www.evfiresafe.com/. Thank you to EV Fire Safety for sharing these important facts with us and allowing the link so readers can view the information you have gathered. The events that we see in the media are predominantly linked to more domestic use of Lithium-Ion batteries such as E-scooters and E-bikes. Incidents of this type have become very prominent and continue to grow in number prompting authorities such as Transport for London to issue a ban on them across their transport network. EV incidents are growing in number and as their global uptake increases so will the quantity of reported incidents.
This shouldn’t come as any great surprise as this type of battery energy storage technology is subject to a wider, less controlled, and regulated circulation in a domestic setting where owners can be completely oblivious to the potential risk that these devices can pose. This isn’t their fault necessarily as there is scant information available around key safety factors.
Familiarity with phones, laptops and hand tools with their ease of use and charging also breeds complacency and an expectation that you can treat them any way you please. This lack of understanding has translated into major incidents and now sadly deaths.
Larger more commercial and industrial energy storage system failures do happen. Take for instance the BESS installation in McMicken Arizona, and the Orsted BESS installation in Liverpool, as well as the sinking of the cargo ship Felicity Ace carrying thousands of EVs to name just a few. All of these were highly publicised due to their early occurrence in this emerging technology each with a large, hazardous, uncontrolled, and protracted nature.
That isn’t to say there are lots of these types of incidents, which again is understandable as they are borne from highly regulated and responsible industries that are wise to the risks and mitigate Battery technologies are evolving with various reports stating there are changes around energy density, safer chemistry and battery structure, while some of these benefits will get to us sooner, some may be 5-10 years in development. Battery manufacturers are in search of nirvana, a safe, ultra-stable product that stores huge amounts of energy in the smallest format possible. They must be able to release that stored energy on demand in a controlled and safe manner with the greatest possible resistance to shock and vibration. They have to cope with greatly varying environmental challenges around temperature and humidity and they must have the ability to recharge as rapidly as possible. This is an impatient world we live in. Marine applications can amplify some if not all of these challenges. Temperature changes can be wider and more rapid, with moisture levels a continual battle. Batteries, during their charge and discharge function produce heat which needs to be adequately catered for whilst maintaining an ability to resist water ingress. against creating issues which could escalate to the point of thermal runaway. When you consider the reasons why LIB’s enter thermal runaway, physical abuse tops the charts as the most likely cause of failure, followed by other forms of “abuse”. These can include mischarging, thermal overheat fluctuations, battery management and control, manufacturing faults or their environmental conditions. The latter of these reasons are particularly pertinent for fixed installations, be they installed in land or marine applications.
Fires of this nature create headlines, far more than their traditionally fuelled counterparts. We have simply become a little desensitised to car, boat and house fires which experience fire in the more “traditional” sense.
The one overriding reason that LIB fires hit the headlines is down to their ferocity. Fires are intense, destructive, and protracted. The level and duration of fire service attendance required is invariably extensive and expensive. The Felicity Ace incident demonstrated the potentially destructive results which can occur when limited fast and decisive firefighting interaction is hindered.
Battery technologies are evolving with various reports stating there are changes around energy density, safer chemistry and battery structure, while some of these benefits will get to us sooner, some may be 5-10 years in development. Battery manufacturers are in search of nirvana, a safe, ultra-stable product that stores huge amounts of energy in the smallest format possible. They must be able to release that stored energy on demand in a controlled and safe manner with the greatest possible resistance to shock and vibration. They have to cope with greatly varying environmental challenges around temperature and humidity and they must have the ability to recharge as rapidly as possible. This is an impatient world we live in.
Marine applications can amplify some if not all of these challenges. Temperature changes can be wider and more rapid, with moisture levels a continual battle. Lithium-ion Batteries, during their charge and discharge function produce heat which needs to be adequately catered for whilst maintaining an ability to resist water ingress.
Electrically energised equipment fires are nothing new and there are both manual and automated fixed fire suppression methods which can deal with these “standard” electrical risks admirably. Lithium-Ion battery fires however, present significant additional risks to standard energised control rooms and plant. The term “thermal runaway” being the final and destructive outcome to be avoided at all costs.
Thermal runaway is a cycle of ever-increasing temperature within the structure of the battery cell that once initiated self perpetuates irreversibly into the release of toxic and explosive gas vapours. This is the thermal runaway process which can happen gradually or explosively producing high volumes of gaseous vapours with the appearance of a very thick smoke cloud. This initial localised failure affects surrounding cells and structures very quickly, resulting in an incident that is both self-sustaining and deep seated in nature.
As fire engineers we have a number of fire suppression agents that can be deployed, however the potentially explosive gas release coupled to the escalating heat production and self-sustaining deep-seated risk eliminates the use of so many and makes containment and suppression of that incident difficult and protracted. There is no one agent that encompasses all of the virtues needed to deal with a fire of this nature although some get close. The fires are invariably deep seated and obscured sources preventing direct access for cooling, flame front attack or chemical interaction. This in turn means that the fires have an ability to escalate and become more intense before suppression agents have chance to exhibit their worth.
Some agents can be applied from fixed equipment automatically and some through hand portable devices such as extinguishers. I personally prefer the fixed route as I believe the exposure of untrained personnel to such a high risk is a health and safety hazard too far. Even the best trained fire fighters need to evaluate the developing f ire to stop, start and reposition to get the best out of the portable device and agent idiosyncrasies. This must also be done in breathing apparatus and protective firefighting kit from as safe a location as possible.
Guidance documents and standards are in continual development with various agencies around the world. As the understanding and best practices evolve leading documents such as UL 9540a and NFPA 855 will encompass these changes and set out clearer guidelines and assistance. In addition to those global standards, testing of various firefighting agents will establish application rates and deployment methods in “Type testing” scenarios. These are usually completed by manufacturers of fire systems and undertaken by independently assessed test houses to some form of recognised bench marking process. These include and are not limited to authorities such as DNV, UL, BSI, MCA, IMO etc.
As a fire company we believe prevention is always better than the cure and we also believe there should a multistage approach to fire protection. With this particular type of fire risk there is no one fire suppression agent or application method that provides 100% security. Part of that protection package is to provide an early warning signal that detects when batteries are approaching the point of thermal runaway, the point of no return. This early warning symptom is known as the “Off Gas” stage which occurs in the short period just before thermal runaway commences.
The Off Gas element of battery breakdown consists of very specific types of gases and there is now a detector available which is designed specifically to be sensitive and reactive to these gases. Testing has shown that if these gases are sensed early enough and the charge or discharge process of that battery can be isolated then invariably thermal runaway can be prevented.
Typically, those “off gases” pre-thermal runaway are Carbon Monoxide, Methane, Ethane and Ethylene and as thermal runaway commences those gases and vapours can include Hydrogen Chloride, Hydrogen Fluoride and Hydrogen. The production of these usually leads to a fire which could be in an explosive or deflagration format involving further exposed cells usually resulting in an everincreasing intense fire as thermal runaway rolls through packs of cells or pouches.
Independent testing of these detectors and their controls has been undertaken to establish, sensitivity, speed of reaction, and repeatability of that function coupled to long term reliability. The following graph shows the variable time potential for intervention before thermal runaway becomes unavoidable. What also becomes visible is the issue with the time taken for standard detection methods to receive their initiating conditions of both heat and smoke production. It is clear both are too close to the point thermal runaway commences, to prevent it.
The primary course of action is to send a signal to the Battery Management System to shut off power to batteries, with the aim of preventing any further increase in battery cell temperature, i.e. lower than the point of thermal runaway. Also, ventilation activation to remove flammable gas accumulation, if required.
UL 9540a recognizes and quantifies off-gas events as pre-cursors to thermal runaway, while independent testing by DNV-GL has concluded that Li-ion Tamer® can prevent thermal runaway after a two-year battery failure testing program.
Fire suppression and containment becomes the next phase of protection. Some fire suppression agents are reliant on the reduction of oxygen, some on a chemical gas producing a cooling effect whilst others provide a chemical reaction with the burning material. A number of fixed system agents have undergone fire testing by independent authorities to an established set of risk parameters and an established battery installation set up to set a performance benchmark.
We utilise two of those agents to provide a second and third level of protection. Initially we utilise Stat-X a condensed aerosol that has been tested to UL 9540a and DNV which imparts a penetrative gaseous suspension of Potassium Nitrate particulate into the deep-seated battery configuration to suppress and contain the fire chemically.
DNV testing has concluded that Stat-X® can put out a lithium-ion battery fire, that residual Stat-X® airborne aerosol in the hazard will provide additional extended protection against a re-flash of the fire, and that Stat-X® can reduce oxygen in an enclosed environment during a battery fire. (Fireaway DNV report March 2017) It is however essential to remember that access of the agent to the point of ignition of the fire is greatly restricted by the structures and enclosures around the affected battery cell, so the chances of getting agent to the seat of the fire are greatly constrained.
Every battery installation and ESS set up should be subject to an individual assessment of risk and it cannot be assumed that even though some products have undergone very successful fire testing that it will be successful when set up in a generalised configuration.
All parameters that could inhibit effective detection and the suppression agent’s successful deployment must be considered.
It is these restrictive influences that prompts the consideration of a third level of protection, water-based containment. This provides cooling to the affected area and also sets up a physical barrier of water spray that should be designed to create a larger area of entrainment to encompass the affected area whilst providing cooling to the surrounding structures. Water mist lends itself better to marine applications than standard sprinklers due to their superior heat absorption capabilities and lower water volume demand.
When those fire suppression resources are to be deployed would be determined by a detailed understanding of the environment into which those batteries are contained, coupled to an effective fire detection management system.
For more information visit the company’s website at https://nobel-fire-systems.com/.