NFPA Journal - Fall 2021 - 45

FULLY CHARGED Ever-larger and more powerful ESS are
being built across the world to capture energy for use
later. The biggest so far is a 300-megawatt system near
Monterey, California, which came online in 2021.
changes within a battery system in time to take action to prevent
thermal runaway. Some, like Ruiz, are bullish on the new
technology, while others caution that it's unproven. Whatever
the solution entails, " we've got to apply technology so the fire
service can get the intel it needs and so it has the ability to
intervene in these events remotely, " Kerber said.
One of the main critiques of NFPA 855 in the APS report
is the utility's assertion that the standard does not go nearly
far enough in trying to prevent thermal runaway from happening
in the first place. The report argues that the standard
should require battery designs and installations that can
prevent thermal runaway or at least stop it from spreading
beyond a single cell. " Although, cascading thermal runaway
is mentioned 37 times in at least one NFPA 855 draft, no
requirements were written to address it, " the APS report says.
" It is perhaps time for the industry to collectively acknowledge
that cascading thermal runaway should be stopped or
mitigated at the smallest unit possible. The next iteration of
standards should finally acknowledge this in codified form. "
While the APS report points to new battery designs that
separate individual cells with aluminum plates, high-temperature-resistant
plastics, and even air gaps to limit heat
transfer and stop the spread of thermal runaway, Biggins
says that it's wishful thinking to believe that current technologies
could allow the technical committee to essentially
prevent thermal runaway from occurring.
" I don't think you can develop a lithium-ion battery
system that's not going to have a thermal runaway issue, and
even if you could, you may have energy-density problems, "
he said. Taking the step in NFPA 855 to require an ESS
design that prevents thermal runaway, he said, would be like
NFPA's sprinkler installation standards requiring that " only
noncombustible items be stored in a warehouse so you don't
have a warehouse fire. "
CHALLENGES AND OPTIMISM
When it comes to the issue of ESS safety, there is promising
news on the horizon-and a steady stream of emerging challenges
that keep firefighters and battery designers awake at
night.
Firmly in the second category is the fact that there is still
no proven suppression strategy to stop thermal runaway in
a battery cell. Every measure tried thus far has limitations,
and only " address the symptoms rather than the cause of the
problem, " as the APS report put it.
Water systems in lithium-ion batteries work effectively to
cool the battery and can stop the spread of thermal runaway,
but as soon as the faucet shuts off, heat quickly builds and
the process resumes. Since thermal runaway can last for
days and even weeks, many jurisdictions like Surprise do not
have the water supply to adequately handle such a situation.
Gas suppression systems like the one used in the McMicken
facility are now generally acknowledged to do virtually nothing
to stop thermal runaway. Biggins is hopeful that perhaps
water mist suppression systems can " provide cooling and
maybe even have some ability to knock gas generation down
to the floor, " but testing, thus far, is limited. For now, the
problem remains unsolved.
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NFPA Journal - Fall 2021

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