Dive Brief:

  • Problems with system components other than battery cells and modules were responsible for most battery energy storage system failures examined in a joint study by battery analytics software provider TWAICE, the Electric Power Research Institute and the Pacific Northwest National Laboratory, TWAICE said Wednesday.
  • The study looked at 81 incidents cataloged in EPRI’s BESS Failure Incident Database, which has tracked publicly reported battery fires, explosions and other safety events since 2011. It classified events by root cause – design, manufacturing, integration/assembly/construction and operation – and failed element – cells/modules, controls and balance-of-system components.
  • The results show that the “common storyline…that failures are almost all attributable to battery modules” is inaccurate, TWAICE Senior Technical Solution Engineer Ryan Franks said.

Dive Insight:

Concerns about the safety of stationary lithium-ion batteries flared after a 2019 explosion at a BESS facility in Surprise, Ariz., which owner Arizona Public Service attributed to a faulty battery cell. 

The incident came after a spate of fires at South Korean BESS facilities from 2017 to 2019, 27 of which were examined in the TWAICE/EPRI/PNNL report. An expert panel blamed those incidents on shoddy installations, poor operating procedures, inadequate or missing electrical safety systems and missing system controls, according to S&P Global. 

The South Korea incidents followed a surge in BESS installations there “[that] was not accompanied by robust safety standards and regulations, which contributed to the failures,” the report said. 

Notwithstanding the 2019 APS incident, the varied causes of the BESS fires in South Korea and elsewhere cut against the narrative that manufacturing defects or lithium-ion chemistry itself are responsible for the bulk of battery safety events, Franks said. 

“Batteries are [often] the victims” of BESS safety incidents, he said.

Franks noted that overall BESS safety has improved dramatically in recent years, despite high-profile incidents like the APS fire. The TWAICE/EPRI/PNNL report found a 97% global decline in grid-scale battery failures between 2018 and 2023 due in part to “very robust…consideration of safety [that] has mitigated some of the concern around design and manufacturing,” he said.

Still, “integration, assembly and construction” was the most common root cause of BESS failures, accounting for 10 of the 26 incidents for which researchers had enough information to assign blame. BESS components like DC and AC wiring and HVAC and fire suppression subsystems are often supplied by different vendors and “are not necessarily designed to work together,” heightening the stakes of proper integration and assembly, the report notes.

BESS integration, assembly and construction still involves a “human factor” that can lead to error, Franks said. He noted the report’s finding that 72% of failures in systems whose age is known occurred during construction, the commissioning process or within two years of becoming operational. 

However, since utility-scale BESS remains in an “adolescent stage,” the sample of older systems is sparse, limiting insight into how they age, Franks said. 

Other data-related issues that limit understanding of BESS failures include incomplete visibility into failure modes — only 36% of failures after 2017 that were analyzed in the report had enough information to ascertain a cause — and the fact that battery fires or explosions may be especially likely to destroy evidence of manufacturing defects, the report said.

The report’s recommendations include better site-specific hazard assessments, improved sensing and monitoring during the design phase; better workforce training, quality checks and system-level failure analysis during installation and construction; better quality controls in component manufacturing facilities; and better monitoring and analytics during operation to spot potential failures earlier.

A more stringent oversight framework similar to those governing aviation and ground transportation could produce better insights into BESS failures and further improve safety, Franks said. That framework could build on the North American Electric Reliability Corporation’s existing data collection on generating asset availability and reliability, he said.