Moss Landing BESS Facility Incident

On September 4, 2021, a Battery Energy Storage Systems (BESS) meltdown occurred within the Vistra Corporation facility's Phase I system, causing damage to approximately 7% of the facility's battery modules. According to the Monterey Herald, there have been at least three battery incidents since the company started to house batteries at the Moss Landing Power plant site. This latest incident caused the closure of Highway 1 in both directions and prompted a shelter-in-place order for the surrounding area due to the concern that the smoke from the event could contain toxins from the burning lithium-ion batteries.

Vistra Corporation owns one of the world's largest BESS with a total capacity of 1,600 megawatt-hours. The Moss Landing, California facility was rolled out in two different “phases”, a 300-megawatt Phase I system and an extra 100-megawatt Phase II system. Each system comprises many arrays that contain many rows of batteries. A fire suppression system and a water-based suppression system protected the facility.

How the Incident Began

After the smoke had been detected, the heat suppression system was activated in section 1 of the facility. The activated heat suppression system was water-based, and due to coupling failures in the suppression system, the batteries were exposed to water. This resulted in short-circuiting and arcing which are jumping electrical currents that can cause a fire. The resulting smoke produced further water suppression short-circuiting the batteries and causing additional batteries to melt. Furthermore, cracks in the floor allowed water to seep down to batteries on lower-level racks.

According to a Vistra Corporation news release, the overheating was controlled and contained without the need for outside assistance. However, consistent with Vistra’s incident response planning and out of caution, the Moss Landing team asked the local fire department, North County Fire Protection District of Monterey County, to respond to the site. No workers were injured nor did the community suffer harm.

Investigation Results

Vistra’s Findings and Corrective Actions Report reported that a programming error had allowed the suppression system to go off at smoke concentrations lower than the specified design limit. The small amount of smoke may have come from a bearing or other friction source. Prior to the incident, the battery monitoring systems showed temperatures were within appropriate limits, so it is doubtful the smoke came from the battery sources.

Additionally, it was determined that the failures on the couplings occurred in the flexible hoses along a path that was not pressure tested to withstand the suppression system, thus allowing the massive failure to take place. Vistra plans future corrective actions, including a complete pressure test on the whole system, proper programming for the suppression systems, sealing the gaps on higher floors, and various other precautionary measures.

Lessons Learned

Failure of detection and heat suppression systems led to the battery meltdown at the Moss Landing facility. The consequences of this failure highlight the crucial role that proper detection and suppression systems play in ensuring the safe operation of these BESS facilities. It must be confirmed that the suppression system functions correctly and that there are no adverse effects on potential runaways and deflagrations.

A complete battery hazard analysis and battery tests should have been performed along with studying the options for mitigation and adding Layer of Protection Analysis (LOPA), and its impacts on critical scenarios. Cell test data should have been used to understand the thermal runaway and fire potential to design appropriate mitigation strategies.

Battery Hazard Analysis

The failure of their detection and heat suppression systems led to the battery meltdown at the Moss Landing facility; the layers of protection used to help mitigate against fires were not effective. The consequences of this failure highlight the crucial role these systems play in ensuring the safe operation of BESS facilities. To assess the hazards involved, possible risks, and the effectiveness of various layers of protection, we recommend testing be performed as part of a Battery Hazard Analysis (BHA). A BHA can be used to verify the suppression system's reliability in case of a BESS failure. As part of this service, we help you identify safeguards and other mitigation strategies to reduce the risks to your facility.

While it was not an issue in the Moss Landing incident, BESS system failure frequently results in toxic gases and heat discharge. A typical action from a BHA could be that we recommend incorporating detection systems calibrated to detect specific components. Modeling the possible mechanics of deflagration due to BESS meltdowns and then sizing the right blast panels can be a last line of defense to reduce the impact of an explosion.

Finally, we recommend incorporating the various protections and BHA findings with an emergency response procedure to ensure the hazards and incidents are dealt with quickly and appropriately.

Laboratory Testing

ioKinetic can measure battery safety by simulating normal and worst-case operating conditions safely under laboratory conditions using an EVx Battery tester and calorimeter. When complying with various codes and standards such as with UL9540A tests, ioKinetic can perform the required secondary tests at the cell level, such as:

• Battery abuse testing
• Gas chromatography
• Explosivity test
• Heat capacity and thermal conductivity

If it is necessary to measure the battery component reactivity, ioKinetic can use an Accelerating Rate Calorimeter (ARC), a Differential Scanning Calorimeter (DCS), and a Thermogravimetric Analyzer (TGA) to analyze electrolyte, anode, and cathode chemistry.

We Can Help

ioKinetic has reduced process safety risk, maintained compliance and substantially increased peace of mind for our clients worldwide. To learn more about how we can help you manage risk, contact us today or call us at 1-844-ioKinetic.