The discussion about the hazards and risks arising from fires involving lithium-ion batteries and electric vehicles continues to hit the global headlines with much debate on the topic. You only need to look at the media reports and stories about serious fires, 看到受伤和死亡的风险是非常真实的, 不管这种火灾发生的频率如何. 去年五月, the International Association of Fire and Rescue 服务 reported that ‘the frequency of fires had increased over the past six years’.
随着锂离子供电设备的普及, it is also likely that the potential for fire (thermal events) will also increase. The consumer is generally not aware of the actual hazards associated with a thermal event involving e-mobility or other devices. When such an event does happen, the situation is difficult to bring under control and make safe. Larger batteries mean greater challenges for the fire and rescue service.
危险是什么??
把这个问题看成两个事件也许是值得的. The first is thermal runaway where a lithium-ion battery enters an uncontrollable self-heating state. 在这个阶段, 产生高温, 有毒和腐蚀性气体可从电池排出。, 弹片或发光的微粒会喷射出来, 气体可以点燃, 有时从细胞中喷出火焰射流.
The gases released are both heavier and lighter than air, forming two separate layers. 许多人把它描述为烟雾，但事实并非如此. The heavier gasses will seek out the lowest areas, flowing some distance from the source. If either layer comes into contact with an ignition source, it is likely that an unconfined vapour cloud explosion (UVCE) will occur.
The second part of the equation is when the surrounding (normal) combustibles become involved and a fire occurs. 这可能与家庭住宅有关, a business or an electric vehicle when the plastics/fabrics used in construction ignite.
Whilst I have described this as two events (for the sake of discussion), the development of thermal runaway to a fully involved fire can be both rapid and devastating. 紧急救援人员, fire engineers and researchers around the world are trying to keep pace with the issue of fires involving battery powered devices, 能源储存系统和车辆. 目前还没有灵丹妙药.
Whilst the fires associated with or resulting from these thermal events can be extinguished, 热失控更难解决. 以车辆为例, many thousands of liters of water are required in an attempt to cool the cell(s) involved. 即使火焰已经熄灭, thermal runaway continues and so too will the production of flammable gases, 从而增加了UVCE发生的风险.
海事部门
Now transfer this risk to the marine environment, specifically an electric vehicle on a car deck. The battery pack is larger and the volume of any gas produced is greater. It is around this time that the alarm may be raised and crew respond. At this point, thermal runaway is progressing through the cells. The gases may have ignited, and the normal combustibles used in construction may be alight.
By this time the drenchers should be in operation, reducing the fire and heat being released. 同时火势的蔓延可能会减少, the construction of the vehicle will have shielded the battery pack from the cooling effects of any water, leaving a question mark over the control of the thermal runaway. If flames are absent and flammable gasses are still venting near hot surfaces – or come into contact with other ignition sources – the consequences could be fatal.
Much research is being undertaken to ascertain how lithium-ion batteries and electric vehicles can be safely transported, 如果需要的话, 如何管理热或火灾事件. There are different views about the complexities and dangers associated with transporting this type of cargo. 在天平的一端, there is little difference between a fire involving electric vehicles compared to a fire in a vehicle with an internal combustion engine. 在另一端, some might say from ‘real world experience’ that the hazards are significant and vessels and crew are ill-equipped to deal with the event.
Looking at this from the perspective of a former firefighter and current marine casualty investigator, it appears to me that there is a gap in knowledge between the research field and the experiences of emergency responders. If we are to improve not only consumer safety but also the safety of those seafarers who transport goods around the globe, there needs to be much closer alignment between the two worlds.
