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Amid fire concerns, Tesla defends lithium-ion battery safety

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Amid fire concerns, Tesla defends lithium-ion battery safety

SNL Image

A Tesla battery system stores power at a solar farm in Arizona. A company official says the technology is safe despite a spate
of recent fires at energy storage systems.
Source: Salt River Project.

As recent battery fires have highlighted the risks associated with lithium-ion battery systems, Tesla Inc., one of the most prominent builders and distributors of energy storage systems, has stepped up its public support for the technology.

Most recently, in an Aug. 19 letter responding to an Arizona Corporation Commission member's scathing critique of lithium-ion battery safety, a Tesla official attempted to correct what she called "a number of apparent misunderstandings" about lithium-ion batteries.

"It is important to recognize how far energy storage technology and the related safety codes and standards have come over the last several years as the energy storage industry has grown exponentially," Sarah Van Cleve, Tesla's U.S. energy policy manager, said in the letter.

Alarmed by a major explosion at a 2-MW Arizona Public Service Co. facility in April, the state's second such incident, ACC member Sandra Kennedy, the agency's lone Democrat, blasted the "unacceptable hazards and risks" of lithium-ion batteries and urged Arizona to explore more sustainable alternatives. But standards recently updated and under development at the National Fire Protection Association and the International Code Council, Van Cleve countered, "would now preclude the types of storage systems that have had fire incidents in Arizona over the last several years."

The dispute over safety comes as Tesla ramps up its energy storage business as part of a global market expansion. The risks associated with lithium-ion batteries "are not dissimilar from those posed by standard utility equipment," Van Cleve said, calling fire danger "part of the normal course of business when dealing with electrical equipment."

Lithium-ion systems "are the only widely used grid-scale storage technologies available today other than pumped hydro storage," Van Cleve argued. However, several competing technologies have made significant recent progress, including flow and sodium-sulfur batteries, both of which are available commercially.

'We don't know anything about it yet'

Tesla's claims that lithium-ion batteries are getting safer notwithstanding, the lessons from Arizona Public Service's latest battery system fire and explosion, which remains under investigation, are not yet clear.

Only after the specific cause is identified can the findings from the explosion be incorporated into codes and standards, said Christian Dubay, a vice president and chief engineer at the National Fire Protection Association. "We don't know anything about it yet."

Donald Brandt, CEO of Arizona Public Service, a Pinnacle West Capital Corp. subsidiary, said on Aug. 8 that the company would delay its ambitious energy storage plans to learn from the accident.

The fire in Surprise, Ariz., sent several firefighters to the hospital, resulted in "extreme" damage, affecting 75% to 100% of the building in which the batteries were housed, and released hazardous gases before the explosion, according to a City of Surprise fire department report obtained by S&P Global Market Intelligence through a public records request.

AES Corp. supplied the system, which relied on batteries from South Korean supplier LG Chem Ltd., according to the incident report.

LG Chem and other South Korean energy storage companies this year came under pressure following fires at roughly two dozen projects in their domestic market. That led to a temporary market shutdown during a government investigation. South Korea's battery storage sector is eyeing a comeback in the second half of 2019, accompanied by enhanced safety standards.

Still, Kennedy's claim that lithium-ion batteries can "easily" catch fire is "simply not true," wrote Van Cleve, arguing that current standards "are designed to prevent propagation of fire between cells and packs, thus preventing major fires or explosions."

Lithium-ion batteries are, in general, "a very safe technology," said Ken Boyce, a principal engineer at safety certification, testing and advisory firm UL LLC, which has helped develop the new requirements. But the technology's flammable electrolyte can cause "thermal runaway," when defective or damaged cells overheat and trigger a cascading problem, Boyce acknowledged.

UL is among 46 companies and organizations, including LG Chem and Arizona Public Service, that had, as of Aug. 8, signed an energy storage industry corporate responsibility pledge, intended in part to reduce safety risks. Tesla itself has not signed the document, but Panasonic Corp., Tesla's battery cell supplier and manufacturing partner, has.