NFPA Journal - Fall 2021 - 41

" What the Surprise incident highlights is that there is still
a tremendous lack of knowledge in many, many areas " of
this technology, said Stephen Kerber, director of the UL Fire
Safety Research Institute (formerly the Firefighter Safety
Research Institute) and co-author of the UL paper on the
McMicken battery explosion. " With so many stakeholders
involved, this event seemed like the perfect case study. That's
why we invested so many resources towards this project-so
we can learn and keep this from happening again. "
Power Struggle
Debate continues over whether
utility companies should be exempt from
the provisions of NFPA 855
THE DETAILS OF SURPRISE
The UL report on the Surprise incident paints a picture of a
knowledgeable fire department put in a no-win situation.
Clare and the Peoria HAZMAT team arrived at the
McMicken facility at about 6:30 p.m. on April 19, 2019, an
hour or so after a team from Surprise Fire-Medical Department,
who were dispatched after a passerby on the highway
reported seeing smoke in the area. Firefighters from Surprise
had assumed the source of the
smoke was a brush fire and arrived
with a tanker/tender truck and
wildland firefighting gear. Instead,
they found a structure 50 feet long,
13 feet wide, and 12 feet high surrounded
by a chain-link fence. The
words " Battery Storage Array " were
stenciled on its corrugated metal
exterior.
The lithium-ion ESS inside conNFPA.ORG/
GUIDANCE
Coming
soon:
Listen to an
upcoming NFPA
Podcast featuring
Peoria Fire Chief
Bobby Ruiz and
researchers from UL
discussing the
battery explosion in
Surprise, Arizona.
Read the full UL
report on the
Surprise battery
explosion.
Read past NFPA
Journal coverage
on ESS, stranded
energy, and electric
vehicles.
sisted of 27 vertical racks of battery
modules, separated into two rows
on either side of a 3-foot hallway.
APS used the battery to store solar
power collected during the day, then
discharged the energy into the electrical
grid for customer use at night.
At about 5 p.m., the battery's management system detected
a problem in rack 15. Voltage began to rapidly decrease, and
sensors at the top of the rack registered rapidly rising air
temperatures, peaking at more than 120 degrees F. A pair of
battery cells in module 2 of rack 15 had gone into thermal
runaway, the APS report concluded.
While it's unclear what triggered thermal runaway in
Surprise, its effects followed a predictable course. The
failure caused heat to build rapidly in the lithium-ion cell
and spread to surrounding cells, triggering them to go into
thermal runaway-a cascading effect that is difficult to stop.
About a minute after the initial failure, the McMicken battery's
suppression system was triggered. Rather than water,
as is now recommended, the ESS was equipped with a clean
agent gas system, which in 10 seconds filled the entire structure
with 713 pounds of the gas Novec 1230. By design, the
gas made conditions inside the container inhospitable for
active flames-but did nothing to stop the rising heat from
the chemical reaction happening inside the battery. The thermal
runaway went on unabated.
A utility-owned ESS facility in Ontario, California.
ONE OF THE MOST CONTROVERSIAL topics during the
creation of NFPA 855, Standard for the Installation of Stationary
Energy Storage Systems-and one that persists to
this day-is whether the standard's requirements should
apply to ESS owned and operated by utility companies.
Utilities have long maintained that, because they are
federally regulated and have their own safety procedures,
engineers, and technologies, they should not
be subject to outside rules. This idea was vigorously
debated at the NFPA technical meeting in 2019 during
a proposed amendment aimed at specifically excluding
utilities from the scope of NFPA 855. Although membership
voted in favor of the exclusion, the standard's
technical committee disagreed and, as a result, an official
scope was never published for the standard. The
issue remains unresolved, making NFPA 855 perhaps the
only NFPA document without an official scope.
The authors of the UL report on the Surprise ESS battery
explosion incident argued that this special carve-out
for utilities could contribute to unsafe conditions and
recommended that NFPA 855 apply to everyone. " It
seems that firefighters are going to be responding to ESS
that are owned and operated by electrical utilities the
same as they are for other entities, " the report's co-author,
Mark McKinnon, told NFPA Journal. " It doesn't seem
like a reasonable carve-out for the electrical utilities. "
Jim Biggins, the chair of the NFPA 855 technical
committee, conceded that there may be some rules
that utilities can make a legitimate argument against
having to follow. But he doesn't think they should be fully
excluded from most of the requirements in NFPA 855.
" Realistically, any energy storage system, regardless of
who it's owned by, has the same hazards and it should
be treated the same, particularly the areas related to personnel
safety and the safety of first responders, " he said.
" But there still is disagreement within the committee on
that point, and you can see that from the first revision
comments to the next edition of the standard. "
The next edition of NFPA 855 is scheduled for release
in 2023, meaning it could come up for discussion at the
2022 technical session in Boston. The first revision of the
document for the 2023 edition received more than 500
public inputs-many were from utilities requesting more
exclusions, Biggins said. " I'm sure as the second revision
comments come in, there'll be more and more discussion, "
he added. " And I wouldn't be at all surprised to see
it go to [a vote on] the floor again next year. " -J.R.
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NFPA Journal - Fall 2021

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