Thanks for taking the time to read my responses and pinning my YouTube comment.
They are letting it burn itself out overnight, so will be interesting to see how many banks were hit. Looks like at least two, maybe 3.
This is will actually provide valuable data on fire spread in these types of systems.
Maybe they already have data on this and it's a basic cost/benefit trade-off?
IMO it should be either "safe" or a no go. The only cost/benefit trade-off is pay for it to be safe or not at all.
"Resistant" is not the same as guaranteed never to happen ever.
Standards and certification to them are not perfect.
It's all good to boast about that track record, until Murphy bites you on the arse and the incredibly unlikely thing happens.
I'm not saying it's a cell, but I wouldn't rule it out. It is afterall one of the primary, if not the primary cause of possible fire in such systems, that's why the standards exist in the first place to try and prevent it happening.
From my knowledge designing and testing for failure propagation, the main thing that can cause a compliant design to go non-compliant is elevated ambient temperature. If a whole pack is sitting toasty up at >90°C and one goes off then they're all going off. Given it's winter here right now I don't think elevated environmental ambient temperatures are the cause (
16.5°C top in Moorabol today). Multiple cells being in close proximity and on the edge of failure such that a failure cluster with sufficient energy to set off the whole pack occurs seems also seems statistically pretty unlikely to me.
Even with cell failures, in liquid cooled systems it is extremely difficult to initiate any significant thermal runaway to begin with because even without coolant being pumped, once temperature hits 100°C the water based coolant boils off and hard limits the temperature rise. It generally (depending on construction and exact chemistry) takes temperatures around 120°C in a short amount of time to get cells to do something violent instead of safely venting. Having a sustained fault sufficient to deplete (boil off) coolant to the point where still volatile cells can get hot enough start significant and self-propagating fires seems also unlikely. If the coolant system was intact and filled I strongly believe there would be no fire, particularly of this scale. Perhaps some venting of a few overheated cells but that's it. Perhaps a really sustained failure event where safety monitoring systems failed to pick up a deviation and shut things down??
I would have presumed that the system would have a safety charging/discharge cutoff for a pack and/or cabinet in the event of a lack of coolant or coolant system failure, as the odds of something going wrong with a coolant pumping system would be orders of magntiude higher than cell failure. That would be bread-and-butter safety stuff in the design of such a system. So I'd be surprised if it's that.
What has caused the various Tesla battery car fires? There must be a lot of data on that by now?
Yes, will be very interesting to find out the actual cause.
You make a fair point about cut-offs for detecting coolant system failures but other than a coolant failure I don't really see how it could have gone up in flames... In the case of fiery Tesla car and battery pack failures I've looked at in the past, that all also appear related to some breach or failure of the coolant system or were otherwise exposed to a burning ICE car long enough to boil off all the coolant. My best guess is still that something went shitty with the coolant system and it wasn't caught. [Edit: I don't think actually seen the coolant monitoring systems on the Tesla packs, I mostly look at the electrical stuff and air cooled systems]
I'll ask some colleagues what they think next week. There are some other experienced lithium ion battery system engineers on this forum too so hopefully they can check what I'm saying.
I wonder how they are going to deal with all the toxic waste from that one, quietly bury it on the adjacent farmland ?
It's a lithium ion based system not a NiCd or lead acid. The most toxic substance is the electrolyte which will be well burned off. The hazard in lithium ion battery disposal is batteries starting fires.
https://en.wikipedia.org/wiki/Environmental_impacts_of_lithium-ion_batteries
Edit: Also not sure what that "toxic smoke warning issued by authorities" is that's plastered on a few news sites. If it actually happened then it was taken down quick. Lithium ion battery fires just produce "normal" smoke. Official source: "There is currently no threat to the community though residents and motorists will notice smoke in the area. An Advice message has been issued." - https://www.frv.vic.gov.au/large-battery-fire-moorabool
Sounds pretty toxic to me:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5577247/#:~:text=Lithium%2Dion%20battery%20fires%20generate,amounts%20of%20gas%20and%20smoke.&text=Fluoride%20gas%20emission%20can%20pose,large%20Li%2Dion%20battery%20packs.
How far that spreads, though, no idea.
I guess that's why they are taking it seriously
"A FRV HAZMAT appliance is on scene conducting atmospheric monitoring with a Scientific Officer in support. FRV’s specialist RPAS (drones) unit has also been deployed.
UL 1973 includes a clause for toxic emissions. As I mentioned before, the most toxic substance is the electrolyte which is generally fluorine based so can produce some toxic gasses when burnt. The amount is pretty miniscule though, particularly for an outdoor system so that's why it's generally not a problem. It can be a problem for large batteries in a confined space as that paper (and others) point out but I'd also be equally worried about general electronics smoke in that scenario. Not saying there are zero hazards and right by the emergency services to act with caution and get their own data.
Also the rest of the fire safety section you screenshoted:
They make design efforts to help prevent spread of fire from pack-to-pack as you would hope. I think it's possible we'll see only the one bank burned tomorrow (though more will need replacing for safety).
What could be a worry though is if this event turns out relatively inconsequential people will get too complacent with large battery systems. Not every system is designed like the Tesla Megapacks to such high levels of compliance. I've seen some real dodgy stuff out there. I hope it doesn't hurt the renewable industry sector but I also hope people don't get lax either.