Massive Moss Landing battery “still smoking” as authorities probe cause of devastating fire

About 80 per cent of the Moss Landing battery facility in California has been destroyed in a fire which started on Thursday afternoon, said North County Fire Protection District Chief Joel Mendoza over the weekend.

The battery energy storage system (BESS), about 80km south of San Francisco, was still smoking by Saturday but Monterey County officials said air quality monitoring showed no levels of hydrocarbon fluoride gas, a key concern for lithium-ion battery fires.

Evacuation orders over fears about air quality were lifted over the weekend as well, allowing some 1500 people to return to their homes. 

Neither owner Vistra Corp nor Monterey County officials know what caused the fire, nor why the facility’s fire suppression system didn’t work.

The Moss Landing BESS is the third largest operating battery in the world at 750 megawatt (MW) / 3000 MWh. It was designed as a now-rare indoor facility at an old PG&E power station in the Elkhorn Slough coastal reserve wetlands. 

PG&E has its own Eikhorn 183MW BESS on the site which uses Telsa Megapacks and is still operating – although that also had a small fire in 2022.

The fire broke out at around 3pm on Thursday last week in the 300 MW / 1,200 MWh section of the site which was the first phase to be commissioned in 2020, inside a former turbine hall. No one has been reported injured or killed in the incident.

Vistra later added a second phase of 100 MW/​400 MWh and expanded with a third phase in 2023 of 350 MW/1400MWh, although this follows current best practice of being outside.

The LG Chem JH4 battery cells use NMC (nickel manganese cobalt) technology, a combination that is being swapped out for LFP (lithium iron phosphate) in utility scale batteries.

LFP technology has a lower thermal runaway onset temperature which means the cells can handle higher heat before catching on fire, said battery expert and Power Switch managing director Drew Lebowitz on LinkedIn.

About 80 per cent of utility scale batteries are now made with LFP technology, he says. 

“The industry has made enormous strides in safety, learning from its successes and its failures, in product design, codes, standards, training, and other fields,” Lebowitz says on LinkedIn.

Vistra director Brad Watson said fires had occurred at the facility twice since 2019 after water caused batteries to overheat.

“Those projects were brought down for quite a long time. Once we went in, investigated, and learned what the causes were, in some cases had to redesign and reconfigure equipment. And months went by and we lived up to our commitment that we would share all that information on what the root cause was and what we did to correct it, to put the projects back online,” Watson said.

Watson says after the fire is out the company will do an “exacting” investigation to find out what happened and said there is a “high probability it will not happen again.”