Arup produces EV fire safety guidelines for covered car parks

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Thousands of covered car parks may need retrofitting, along with new considerations for new-builds, to reflect the different fire safety implications of electric vehicles compared to combustion engines.

Working with the UK’s Office for Zero Emissions Vehicles (OZEV), Arup has produced interim safety guidance to support parking and/or charging of electric vehicles within covered car parks.

The full transition to electric vehicles (EVs) will be one of the most important actions to achieve the net zero. In the UK, new sales of non-electric vehicles will be banned from 2030, and to make that happen, infrastructure needs to be upgraded to meet the needs of large numbers of electric passenger vehicles and vans.

One of the main challenges is the need to provide sufficient charging capacity, and in the UK, grant programmes have been undertaken to accelerate EV charge point installation. However, until now, there has been limited guidance on safety around fire risk at charge points. 

EV fires are rare but need different responses
EV fires are rare. Data reported by Arup shows that in Norway, where EVs make up almost ten percent of cars, they make up less than three percent of vehicle fires.

At the same time, Thatcham Research, the UK motor insurers’ research centre, conducted research cited by Arup, the Motor Insurance Anti-Fraud and Theft Register from 2018 to 2020. They found that 0.001% of plug-in hybrids and 0.003% of range extended electric vehicles were subject of fire claims. That was lower than the 0.007% of petrol vehicles and 0.011% of diesel vehicles. 

Arup’s new guidance, however, explains why even such rare incidents require a very different approach to fire safety because of the nature of the fires involved. An EV battery can undergo thermal runaway and is influenced by factors such as size of battery, battery chemistry and state of charge. Thermal runaway is a process within battery cells which leads to the decomposition of battery elements and can lead to the onset of fire within the battery. 

This can overcome the cooling systems within the battery and can result in ignition. If ignition occurs, it can cause adjacent battery cells to heat up and undergo thermal runaway. The greater the number of battery cells undergoing thermal runaway within the battery pack, the greater the likelihood of fire starting in successive cells. This can potentially lead to the failure of the entire
battery.
 
Measures proposed to enhance safety
Arup’s report outlines an extensive series of measures that can be taken in the development or retrofitting of covered car parks to improve safety. These include some structural aspects that can help to prevent spread of fires when they happen – such as increasing the distance between parked cars or constructing barriers between bays to limit heat-spread. 
 
Just as importantly, the report highlights technology options such as thermal monitoring cameras positioned at ground level to identify early indications of rising battery temperatures that would allow action to be taken.
 
Perhaps the most important advice, however, is to ensure that EV charging points are installed with safety in mind as charging itself can be a potential risk factor. So the report highlights the value of setting a clear standard for EV charge points to be adhered to, ensuring those installing or maintaining them are highly competent, a putting in place a manual over-ride function to allow people to cut power to chargers if an EV goes into thermal runaway. 
 
To read Arup’s Covered car parks – fire safety guidance for electric vehicles Click here