Utility-scale BESS: Best practices to mitigate hazards

Leeward Renewable Energy, a Dallas-based owner of US solar, wind, and battery storage projects, has released a report on BESS hazards to highlight the causes of thermal runaway and fires in lithium-ion batteries and to place them in context. The study, by Thomas Ebel, senior manager of BESS engineering at Leeward, examined potential causes of BESS hazards, the effects of different battery chemistry, and lessons learned from previous incidents.

The report did not factor in mechanical damage from accidents or natural events such as earthquakes and tornadoes.

Various scenarios considered BESS hazards including spikes or short-circuits running through electrodes from mechanical and/or electrochemical stress inside battery cells. The report found such stresses tend to result from electrolyte degradation or improper voltage forced into a battery system. Such events result in excessive heat that can cause thermal runaway.

The document stated battery chemistry can have a major effect on the frequency, severity, and results of voltage events. The authors of the study said lithium-ion battery chemistry can be differentiated by ratios of cobalt and nickel. Battery chemistries with higher amounts of cobalt tend to be more stable and more expensive. Devices with higher nickel ratios are less stable and more economical.

The report said, “Unfortunately, due to economic and technical reasons, the latter was the preferred method and the industry had to suffer some unwelcome consequences.”

The adoption of lithium ferro-phosphate (LFP) material in cell cathodes, as the industry standard for utility-scale BESS, is alleviating thermal runaway problems, the report said. LFP designs tend to have lower energy density, and thus are larger, and have lower flash points and lower overall heating rates compared to earlier nickel-manganese-cobalt (NMC; also abbreviated NCM) and nickel-cobalt-aluminum (NCA) formulations. LFP-based designs tend to be less expensive.

The report’s authors said the number of BESS failure incidents fell 97% between 2018 and 2023. That was attributed to safer operating performance of LFP batteries compared with NCM designs and the fact that LFP’s lower cost enables operators to equip storage facilities with better fault detection and fire suppression systems.

The report concluded that a battery management system is important for reducing incidents and limiting their effects, as well as dialog with fire departments and first responders about BESS installations.

Some BESS manufacturers are focusing on battery management system design and operation procedures, to improve safety. In May 2024, Sungrow conducted a fire demonstration to show the thermal containment and response capabilities of its PowerTitan grid energy storage system. Fluence America said battery management is just a start and expertise needs to flow readily between suppliers, contractors, operators, and first responders to prevent thermal events from making sensationalist headlines and warping public perceptions of lithium-ion battery safety.

From pv magazine USA.