The BESS challenge: learning to let it burn

With the government’s increasing drive for clean energy, it’s no surprise that along with solar farms, wind installations and grid substations, battery energy storage systems (BESS) are making an appearance with increasing frequency across the country.

BESS are highly engineered and deceptively simple in appearance. Nevertheless, in this edition of Fire we show how the rapid proliferation of BESS is starting to outpace the fire safety legislation that has been designed to keep sites, communities and firefighters from harm.

FireKnowledge Insights this month provides a detailed account of BESS fires – and why they need to be a treated very differently from other incidents the fire service encounters.

At the centre of a BESS fire is the thermal runaway. Very simplistically, this is the uncontrolled increase in temperature in the battery cell that triggers a chain reaction that spreads outwards to neighbouring cells and modules. Once started, the process generates large volumes of flammable and highly toxic gases, which includes carbon monoxide, hydrogen, methane, hydrogen fluoride, hydrogen cyanide. The result is not just fire, but explosions and secondary fires. Thermal runaway has a host of causes: overcharging, impact damage, manufacturing faults, internal short circuits and even water penetration through poorly maintained seals.

And critically, BESS fires will keep burning till every cell in the battery has exhausted itself. When water is applied it is not extinguishing the fire, it is simply cooling the outside.

At a recent conference, Jon Bird, station manager at Gloucestershire Fire and Rescue Service, took the audience through a recent BESS fire incident on a solar farm near Cirencester.

The first problem was finding the location. Local fire crews had had no knowledge of its whereabouts.

Crucially, there were also no internal fire detection systems. Once on the scene, Bird said the decision was made not to apply water directly to the burning containers: “It isn’t worth putting water on these things as it will just contaminate the land.”

Instead, curtain sprays were deployed to protect nearby containers. After about an hour, the doors of a second container burst open under pressure. Luckily, all the crew were behind the cordon and no one was injured. Within a few hours, the incident was scaled back and the controlled burn strategy had clearly worked.

Nevertheless, the knowledge gaps it revealed are worth noting. BESS sites need to be mapped by local fire services and integrated into risk information systems. Importantly, site operators have to engage with the FRS as a condition of responsible deployment. Currently, it appears to be an afterthought – reactive not proactive. Meanwhile, fire services need to enhance their on-scene environmental assessments – there had been no field-testing of run-off at Cirencester.

Elsewhere in this edition of Fire magazine, Cleveland CFO Peter Rickard talks about his experience of how the fire service can build community engagement in areas of extreme poverty. His 13-week programme for young people with special educational needs – rated outstanding by Ofsted – and his plans for care leavers are examples of how much good work the service can provide beyond the incident ground.

And on a lighter note – but no less important as a way to help with leadership, community and mental health – South Yorkshire CFO Chris Kirby is spearheading a revival of Fire Sport UK, culminating in a Festival of Sport in Sheffield on April 22-23. For Kirby, the festival is an prime example of what fire and rescue can achieve as a force for good in the community.

Andrew Chilvers

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