ESS, other energy storage manufacturers announce safety certification for competitive edge

Julia Song, ESS co-founder and chief technology officer, said the certification process tests materials to support claims that decay or degradation over time are not issues. Certification also examines chemicals related to electrolytes and other components, engages in mechanical testing that focuses on vibration and examinations looking at electrical currents, shocks and short-circuiting, she said.

"The UL 9540 covers a lot of different issues," she said. "But I think people talk about fire a lot because that's happening frequently with lithium batteries."

Fire and lithium batteries are not an issue with ESS, which makes iron flow technology for storage applications that require up to 12 hours of energy capacity. Its systems are used for utility-scale renewable energy installations, remote solar and storage microgrids, solar load-shifting and peak shaving and other ancillary grid services.

Few manufacturers have gone through the multi-year process, but many others are expected to be certified in the coming years, Hugh McDermott, senior vice president of business development and sales at ESS, said in an interview.

"Eventually, we have to believe everybody is going to be out there getting it," he said.

Many jurisdictions in North America don't specifically require UL 9540, but the same tests and standards are "effectively incorporated" into a National Fire Protection Association standard called NFPA 855, McDermott said.

Other companies have announced safety testing.

Wärtsilä recently said it completed large-scale fire safety testing of its energy storage system, designed to simulate a worst-case scenario.

Under test conditions, a fire was ignited in a ventilated unit and burned for more than eight hours, the Helsinki, Finland-based company said. A fire would remain contained in the initiating unit, doors would remain closed and the fire would not spread, the company said.

And EnerVenue said it has completed UL 9540A thermal runaway fire propagation testing at the level of cells, modules and units. The Fremont, California-based company said its energy storage vessels completed UL 9540A testing at the cell level with no flames observed during induced thermal runaway.

Chief Technology Officer Majid Keshavarz said the test results confirm its battery chemistry as a "leading option" for customers concerned about eliminating the possibility of fires or thermal hazards at grid-scale installations.