Exploding thoughts: a brief take on a BESS explosion - The Beijing, China case

Those whom I have worked with in the past know that I am an advocate for explosion safety and prevention in BESS during the design, construction and in operational stages. I recently got asked if an explosion was less likely to happen than a fire. My gut feeling is that it might be. Still, I reckon that the impact of a blast could be more harmful than that of fire due to the unknowns and the high degree of uncertainties in thermal runaway gas mixture, explosion behaviour and shock wave impact, and more importantly the surprise and silent effect. This is one of the main issues that I have with the “let it burn” approach.

I recently read an excellent paper “An analysis of li-ion induced potential incidents in battery electrical energy storage system by use of computational fluid dynamics modeling and simulations: The Beijing April 2021 case study” by authors in the reference below*. 

My interpretation is that sadly, two lives were lost in 2021 in an explosion involving Li-ion BESS (LFP type) in Beijing, China. Apart from the sad loss of two lives (firefighters), what left my mouth wide open reading the paper was that the fire originated in one building and the explosion happened in a separate building around 20 m apart, almost 2.5 hours after the fire initiation. I definitely recommend giving it a read, it is a worthwhile investment (unfortunately it is not an open source).

Key intakes that I learned from reading this paper:

• The craziest point, that I hadn't thought about, but it's entirely logical, is that explosive gas can travel through underground cable trenches/ducting from your BESS containers to other rooms. This is particularly important for those housing equipment in buildings.
• “...batteries in high SOC release more types of thermal runaway gas, with higher fire and explosion risks…” I never thought about this from this angle. This emphasises the importance of having UL9540A tests carried out at the system level and not only at the cell or module levels.
• 50-100 kPa and over 100 kPa (14.5 psi or 1 bar) blast pressures are enough to either harm you for life or take your life completely. From reading the paper, I interpreted that the pressure estimated at the location of the lost firefighters was around 70 kPa; when near the ignition source, it was estimated at 37 kPa. 
• Shock waves can lead to greater overpressure risk and damage than at the source of initiation. I believe that overpressure release panels sometimes do not work due to the quick pressure overbuilt that overwhelms the pressure rating of these protection devices. Relaying only to this type of prevention is only a sweetener, in my opinion. Therefore, there should be more thoughts about it and my issues with the NFPA 68. Open for debate.
• There is a stigma around LFP being fire-safer than NMC battery chemistry. This is not necessarily true. Both chemistries are highly sensitive to mechanical and thermal abuses. Or in other words, how we operate them. Human-lead errors.
• The importance of computational fluid dynamics from BESS OEMs first, following the entire project quantitative risk assessments for fires and explosions (including different overpressure curve scenarios). These should be a planning requirement alongside full fire and explosion prevention and suppression safety systems in design, construction and operation. In addition to emergency response plans before and after an explosion/fire event. Independent technical experts (such as Blanboz) and fire brigades must previously authorise these.

Could this explosion event in Beijing have been prevented? Probably yes. How? In-Country regulations and requirements specifically applied to the BESS in the design, construction and operational stages. In addition to the critical role that standards and safety certifications play in the BESS industry. Are the NFPA 68 and 69 the best? Well in my personal opinion, they aren't. But these standards are probably the best we currently have in the industry which can also open debate for further improvement. Nevertheless, the role that emergency response plans play and the responsibilities that the BESS OEM shares in the HSE of a project. Remember that we all have a role in the success and safety of this industry. 

*Paper’s reference: 

Xingyu Shen, Qianran Hu, Qi Zhang, Dan Wang, Shuai Yuan, Juncheng Jiang, Xinming Qian, Mengqi Yuan. An analysis of li-ion induced potential incidents in battery electrical energy storage system by use of computational fluid dynamics modeling and simulations: The Beijing April 2021 case study.Engineering Failure Analysis,Volume 151,2023,107384,ISSN 1350-630.

https://doi.org/10.1016/j.engfailanal.2023.107384

About the author:

Andres Blanco – Project Consultant | Managing Director at Blanboz, I’m an engineer with almost 15 years of experience in the renewable energy field, with the last seven to eight of these years fully dedicated to BESS through the full project life cycle. I am also passionate about explosion and fire prevention and suppression’s implementation in BESS.  Electricity for all - Batteries lead the charge. Further information at www.blanboz.com , if you want to contact me, please do so at a.blanco@blanboz.com , www.linkedin.com/in/andresblanco77