Design Criteria for Electric-Powered Buses?

9/29/2022

Does anyone have experience protecting buses inside a parking garage that use lithium ion batteries?

I can't find any specifics on design criteria (or perhaps even looking at clean agent) for these types of large commercial vehicles.

Thanks in advance!

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12 Comments

Justin Phillip Milne link

9/29/2022 08:06:30 am

Yes, I would strongly caution the direction being proposed, i.e. clean agent systems. BEBs can be a performance based effort. Reach out here if you need help.

Connor

9/29/2022 08:15:40 am

These buses likely have battery banks similar in size to a small lithium battery energy storage system (ESS). You may want to look at NPFA 855: Standard for the Installation of Stationary Energy Storage Systems for a starting point.

The DOD's UFC 3-600-01 has some requirements for ESS regarding not only sprinkler protection but also room construction. They require a 3-hour rated room around the ESS. For sprinkler, the standard requires 0.6 gpm/sq ft over the entire room with 500 gpm hose stream and 120 minute duration. A density this high would require K11.2 sprinklers at a minimum. More water is better.

The thread from a few days ago regarding electric bicycle storage also has some info which may be useful to you. One upcoming project from NFPA is looking into the issue of EV parking:

https://www.nfpa.org/-/media/Files/News-and-Research/Resources/Research-Foundation/Current-projects/ProjectSummaryEVParkingGarages.ashx

Jesse

9/29/2022 08:30:29 am

I don't think clean agent is a viable option. I'm not sure how you'd be able to effectively seal the garage. And I'm not sure if you were meaning protecting inside the battery compartment of the bus - which would put it back to the manufacturer.

There was a discussion a few days ago on here about e-bike storage. Many of us were thinking along the line of EH1. There is no specific standard yet.

Franck

9/29/2022 08:48:03 am

I concur with your point.
I know that NFPA 855 leave the door open to protect battery rooms (ESS) with clean gas extinguishing systems, but I don't have return of experience of such system being efficient on such fires.
I have at least one example where it wasn't... (NOVEC 1230 protection):

https://www.smart-energy.com/storage/aps-completes-investigation-following-2019-battery-storage-fire-disaster/

Conclusion from the report was:
"The total flooding clean agent fire suppression system installed in the BESS operated early in the incident and in accordance with its design. However, clean agent fire suppression systems are designed to extinguish incipient fires in ordinary combustibles. Such systems are not capable of preventing or stopping cascading thermal runaway in a BESS."

So to be used carefully...

Franck

9/29/2022 08:42:27 am

No specific standard for electric buses so far, to my knowledge. There's none either for electric car so far.
But you would definitely need huge amount of water.
I would say, as much as you reasonably can provide.
All events reported related to EV fires required huge amount of water, and experienced several fire restart, even hours after the beginning of the vent.
Li-ion batteries can be really problematic when involved in a fire.

Minimum density from NFPA 855 should be 0.3 gpm/sq ft over 2500 sq ft, which is more or less the direction taken by NFPA to protect parking structures (for normal fuel vehicles, having in mind EV might be a bigger concern).
I don't know if this would be fine as well for buses (more batteries = more potential for thermal runaway) as batteries are normally hidden from the water spray and combustible load inside a bus is much higher than inside a car (seats).

Fire walls between buses would be an additional safety factor, but maybe not really practical for large parking bus areas.

There has been some "interesting" fire events involving electric buses recently:

China
June 2021
The incident took place on a university campus in southern China’s Guangxi Zhuang Autonomous Region and was caught on security camera.

https://www.youtube.com/watch?v=T71cVhxG_v4

Paris (France)
On April 4 and 29, 2022, 2 electric buses took fire while being in operation.
The cause is apparently related to a manufacturing defect from an electronic component.
In both incidents, the buses were destroyed, but no injuries were reported.
After the 2d fire, the company removed from service its 148 electric buses.

https://twitter.com/i/status/1520156512294948866
https://www.youtube.com/watch?v=FMSvg_H-ZCA

Dan Wilder

9/29/2022 09:05:46 am

Closest thing will be from 855 (0.30/2500) to contain but a clean agent isn't going to help under normal concentrations (not to mention how to keep containment)...Li-Ion off gas their own flammable gasses so preventing and keeping the larger concentration of inert gas becomes very difficult. The larger battery packs also create a greater ability for a single cell event to extend through multiple adjacent cells. Even if you can prevent the fire from igniting, without stopping the cascading thermal runaway, you risk ignition/reignition hours or day later).

I would suggest consulting an FPE and engage the local FD/AHJ for a solution...FM Global has some info available for batteries, but not specific to this scenario.

Some good research on the off gassing and use of clean agent from the FAA

http://www.tc.faa.gov/its/worldpac/techrpt/tc15-59.pdf

Brian Cockburn

9/29/2022 06:50:15 pm

There's a similar forum post about e-bike Li-Ion batteries: https://www.meyerfire.com/daily/best-practice-to-address-e-bike-fire-concerns#comments

Battery banks in busses, especially several e-busses parked close together, might begin to resemble an Energy Storage System (ESS) as per NFPA 855 (my opinion). It requires Extra-Hazard 1 protection at a minimum.

Parking garages are normally Ordinary Hazard 1 but increasing numbers of electric busses or cars might create a fire hazard that could overwhelm an OH1 system.

It occurred to me that if it's possible to park the electric busses in a separate area, that surrounding them with a water curtain might help contain flame and heat if a fire happens. Engaging a code consultant and the fire department would be a good idea.

Franck

9/30/2022 04:19:59 am

In the latest edition of NFPA 13 (2022), car parking even moved to OH Gr 2.

A.4.3.3.2
Ordinary hazard (Group 2) occupancies include occupancies having uses and conditions similar to the following:

(1) Agricultural facilities

(2) Automobile parking garages

...

Current discussions within NFPA even think to move it to EH Gr 1.
The reason is that modern vehicles (not to speak EV) have more and more plastic parts and electronic components representing a higher fire load, in addition to the fact that the fuel tank itself is now mostly done with plastic where it was metal in the good old time (quickest fire spread as it becomes a pool fire when the car is fully involved in a fire).

Brian Cockburn

9/30/2022 11:31:04 am

I've seen those changes too. Here in BC, Canada we will use the 2013 ed. and we're moving to 2019 (eventually), but that still uses OH1 for parking garages.

Protecting future parking garages to OH2 might make sense for the reasons you said - increased combustibility and fuel load, but taking it to EH1 would be a real challenge.

Many parking areas have dry systems so that means a 3,250 sq.ft design area if using EH1, which could be reduced by using high temp sprinklers to ~ 2440 sq.ft. This still results in a 2.5x increase in water requirements compared to OH1. Extended coverage sprinklers (Tyco EC-14 for example) aren't typically listed for EH applications so that means standard 8.0k sprinklers or CMDA/CMSA sprinklers of some kind. Pipe sizes will increase considerably, looped systems would likely be the norm, and fire pumps would often become necessary even in small buildings where you'd never expect to need one. All this can be done but the cost will be substantial, which would be paid for by even higher mortgages and rents.

If this is how things go then I hope sprinkler manufacturers respond with new sprinklers for these applications, or maybe we need to re-think blindly adopting EVs the way we are.

Franck

9/30/2022 09:27:15 am

Another "intere'sting" loss for electric buses in Germany:

https://climate-science.press/2021/10/23/fire-in-stuttgart-bus-depot-could-have-been-caused-by-e-bus-charging-munich-takes-8-e-buses-out-of-service/

David Williams

10/11/2022 10:06:07 am

Note that the insurance rating agency may have a more restrictive requirement than NFPA or other standards. We have experience where FM is calling for a higher rating than the language in NFPA Codes.

Melanie Willhite

8/26/2023 10:50:31 am

I am seeing the same thing as David on the FM requirements being more restrictive than the NFPA codes. My research on this similar topic (specifically for EV charging stations in parking garages) revealed the following:

NFPA 13-2019 - OH1 in parking garages
NFPA 13-2022 - OH2 in parking garages
FM Global Data Sheet 3-26 - HC-3

I found two white papers I thought I would share:
"White Paper - Fire Safety in parking Garages with electric vehicles - 6-6-2023" published by Siemens that recommends a solution of high-pressure water mist to help control the EV fire.

https://www.siemens.com/global/en/products/buildings/contact/white-paper-fire-protection-electric-vehicles.html

NFPA Research Foundation - Modern Vehicle Hazards in Parking Structures and Vehicle Carriers - July 2020

https://www.nfpa.org/News-and-Research/Data-research-and-tools/Building-and-Life-Safety/Modern-Vehicle-Hazards-in-Parking-Garages-Vehicle-Carriers

Does anyone have any more information to the recommended fire solution to control an EV fire in a parking garage?

Thank you everyone for the posts above on this topic, very helpful!

Design Criteria for Electric-Powered Buses?

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