Page | 005 TECHNICAL INFORMATION PAPER SERIES | FIRE HAZARDS OF BATTERY ENERGY STORAGE SYSTEMS
and total damages were not reported; however, it appears that the BESS was destroyed. This was the third fire at this former power plant since it was established by PG&E in 2022 as a destination for energy storage.
REDUCING RISK OF FIRE LOSS
INVOLVING BESS
Risk from fires involving Battery Energy Storage Systems can be reduced by adhering to NFPA 855 for all new BESS installations, and by considering the following best practices found in the industry:
• Site all new BESS containers on the exterior of critical buildings, configured at a minimum of 25 feet from the nearest exterior wall or roof overhang and not in line with any building openings such as windows, doors, and vents for a horizontal distance of 25 feet from the far edge of the container.
• Place additional BESS containers at a minimum distance of 10 feet between other battery energy storage system units/containers.
• When BESS units must be placed in closer proximity to a critical building or adjacent storage units, enhance the exterior wall to meet a 2-hour fire resistance rated assembly complete with 90-minute fire rated doors or windows.
• When BESS units must be placed in closer proximity to adjacent storage units, provide a 2-hour fire wall between each to extend past each end horizontally by half the width of the largest container and extend vertically above the height of the container by a minimum 3 feet.
• Outfit BESS containers with exhaust ventilation to release off-gasses found with a developing lithium- ion battery fire, and to reduce potential for excessive heat which can lead to thermal runaway–mechanical ventilation of not less than 1 cubic foot per minute.
• Consider installation of continuous gas detection and supervision within the enclosure which would activate the mechanical exhaust system upon detection of methane, benzene, ethane, ethylene, hydrogen, hydrogen sulfide, and carbon monoxide.
• For larger capacity units, provide smoke and fire detection in accord with NFPA 72 using a VESDA (very early warning smoke detection) or radiant-type detection within the container. Provide supervision to a centrally attended location upon trouble or detection alarm condition.
• Where good water supplies exist, protect larger BESS capacityunitswithautomaticfiresprinklerprotection to enable adequate cooling and reduce the potential for the battery arrays from reaching thermal runaway.
• Where sprinkler protection is not feasible due
Source: inControl Systems, Inc.
to remoteness or poor water supply, BESS can
be protected with an approved clean agent fire suppression system to control single and double cell lithium-ion battery fires through reduction of oxygen in an enclosed and unoccupied space.
• Battery energy storage systems configured within small rooms, enclosures, or containers where flammable gas can exceed 25% of the lower flammable limit (LFL) should be protected with either explosion prevention/ suppression or deflagration venting designed and installed within requirements of NFPA 69 Standard on Explosion Prevention Systems and NFPA 68 Standard on Explosion Protection by Deflagration Venting.
• Assure that all electrical wiring, lighting, and components incorporated within portions of the BESS enclosure to be designed and installed for a hazardous location in accord with Article 500 of NFPA 72, National Electrical Code.
• Follow NFPA 855 requirements for inspection, testing and maintenance of battery energy storage system units–assure that each unit is de-energized and a system-off inspection is conducted at least annually on all components within the BESS.
• Assure that a system shut-off inspection includes a check of:
– All equipment and components
– Spacing between racks, cabinets, and trays – Equipment grounding conductors
– Battery modules and arrays
– Connections and terminations
– Monitoring and charge control
– Disconnecting means
– Interconnectionwithotherenergysources – Signage
– Ventilation
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