The increased volume of Lithium-ion batteries
Lithium-ion (Li-ion) batteries power much of our modern world: laptops, smartphones and, all the more, electrical vehicles (EVs). Li-ion batteries exhibit high energy density, low self-discharge rates, lack of memory effect, fast charging capabilities, and long lifespans, proving them to be efficient energy storage solutions.
The mechanism behind it is ingenious: Each battery unit is packed with hundreds of Li-ion cells with a positive cathode at one end, consisting of lithium compounds such as lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide or lithium nickel manganese cobalt oxide. At the other end is a negative anode made of graphite or other carbon materials. To ensure the flow of charge carriers, the space between the electrodes is filled with ion-conducting electrolytes. Electrical isolation between the electrodes is achieved through a separator that is permeable to ions. As you charge it, electrons flow from the cathode to the anode, which will store them. As you use your device, i.e. discharge the battery, those electrons flow through an external circuit, such as an EV engine, back to the cathode.
Since EVs are gaining traction as a critical component in the fight against climate change and as replacement for internal combustion engine (ICE) vehicles, global numbers are likely to increase. And the question arises: How can building owners and operators reduce fire risks in EV parking garages?
Fire safety for EV charging stations
As with any new and evolving technology there are legitimate safety concerns, particularly the emotive, but real, danger of fire.
However, current data suggests EVs are less likely to ignite than ICEs. A 2022 Swedish government study found only 3.8 fires per 100,000 electric or hybrid cars compared to 68 per 100,000 cars of all types1. Similarly, an Australian study found that the chance of a passenger EV battery igniting is only 0.0012 percent, compared to 0.1 percent for an ICE car.
The rare case when EV batteries do ignite the storage of so much power in such small spaces can get quite serious. The reason: EV battery incendiaries burn up to three times hotter and longer than ICE car fires. And they are more likely to reignite and will produce toxic, sometimes lethal, heavy metal-laden smoke. The risk is most serious in densely parked locations, where a ‘thermal runaway’ – caused by heat generation, a potential ignition of electrolyte vapor, and a subsequent spread of heat to adjacent cells – may happen. Trends of larger cars, smaller parking spaces and a vehicle’s increased combustible plastic content are all contributors to this hazard too. Parking garages concentrate these risks, also adding those of potential emergency service access restrictions and building destruction.
Six steps to reduce fire safety risks
As the global fleet of EVs not only continues to grow, but also to age, the danger of an EV battery-ignited major car park fire is likely to increase as well. Also, the charging infrastructure presents an additional potential fire hazard. To reduce this risk, it is important to act before issues even occur. A few suggestions:
- Norms and standards are in evolution, but it is hard for them to keep pace with change in e-mobility so all stakeholders need to be proactive.
- Design and battery management systems are advancing in terms of safety, e.g., improved battery casing. However, commercial pressure to boost charge levels means that danger cannot be eliminated completely.
- The primary focus should be on minimizing risks to people, including garage occupants and firefighters, as well as to buildings themselves. After any incident, it is important to ensure a swift return to service.
- The first means to better protect people and buildings is through detection. This needs to be accurate: detecting smoke at an early stage and avoiding false alarms in potentially dirty environments with ICE exhaust fumes. The alarms must be audible and visible to nearby individuals, and facility managers need to be alerted with precise information regarding the fire origin.
- In the event of a fire, it is necessary to be able to control and suppress it until emergency services arrive. This is essential to reduce chances of a thermal runaway that will spread from one vehicle to another.
- Existing real estate should be modernized with appropriate safety solutions as much as possible. For future garages, fire safety systems should be integrated with smart charging and digital building management systems.
The technological solutions: Early detection and effective suppression
Early detection and effective suppression are two key innovation areas that building owners and operators need to look into when it comes to fire safety in parking garages.Early detection with smoke detectors
Multi-criteria detectors using Advanced Signal Analysis are highly suitable for garage environments. They function even in settings with significant ambient pollution. These detectors are able to recognize the early smoldering stage of fires accurately, while providing priceless time for an effective response. An example: During a simulation of EV battery fires in Denmark in 2023 an incipient fire was identified within one to three minutes. As a basis, detectors need to be positioned in the most effective way – depending on garage size and layout. In this case, the power to chargers is shut off, garage occupants will be guided to the exit, additional vehicles will be prevented from entering, and the fire service will be contacted – all automatically.Effective fire suppression
A second key area concerns the effective containing of fires. Although a fire extinguisher can be used to put out a charging unit fire, it may not always be feasible, particularly in the case of a vehicle fire, and especially one that involves an EV battery. To address this issue, a reliable mechanism for suppressing vehicle fires can be activated automatically by the detection system. A recently conducted study by the Danish Institute of Fire Security and Technology (DBI), Danfoss and Siemens determined an effective technology for fire suppression2. The SEM-SAFE mist sprays kept fires limited, allowing sufficient time for fire service arrival, typically within 30 minutes. They also prevented multi-vehicle spread and avoided the high temperatures that can wreak structural damage. The specially engineered nozzles operate at 50 bars, which is significantly higher than the pressure of a typical home shower. These nozzles discharge droplets that are typically between 50-100 μm in size. The flame heat both attracts the droplets and quickly causes them to evaporate. But in so doing, the tiny watery heroes expand by a minimum of 1,700 times, which simultaneously cools the fire and deprives it of oxygen.
Outlook: Improved fire safety protocols
Ultimately, additional measures can be taken to enhance garage fire safety protocols, particularly in terms of integrating building technology. For instance, video surveillance can be utilized to switch to a control center for visual monitoring in case of a fire. And it’s obvious in the end: reliable, rapid detection and appropriate fire suppression technologies can reduce the EV battery fire risk in garages, massively.
References
- https://www.msb.se/sv/publikationer/demonstration-av-slackmetod-for-litiumjonbatterier.-metodtillampning-pa-olika-aggregationsnivaer–modul-sub-batteri-elbilspack-och-fordonsniva/
- https://www.siemens.com/global/en/products/buildings/contact/white-paper-fire-protection-electric-vehicles.html
