ENERGY STORAGE SYSTEMS AND FIRE PROTECTION
New recommendations for lithium-ion battery-based energy storage systems
Lithium-ion battery-based energy storage systems (ESS) are in increasing demand for supplying energy to buildings and power grids. However, they are also under scrutiny after a number of recent fires and explosions. It has become clear that lithium-ion batteries are vulnerable to thermal runaway, leading to a venting of flammable gases and subsequent combustion, and creating new fire protection challenges.
To increase awareness of what can be done to improve safety around this technology, commercial property insurer FM Global has publicly released groundbreaking research and recommendations. These are based on small- to large-scale fire tests recently conducted on ESS sized for commercial applications, such as manufacturing, office buildings, power generation and utility use.
The good news is that the research shows that ESS deployments can be made safer through the combination of automatic sprinklers and the careful spacing of ESS racks.
Determining the fire hazard
From a fire protection standpoint, the overall fire hazard of any ESS is a combination of all the combustible system components, including battery chemistry, battery format (e.g., cylindrical, prismatic or polymer pouch), electrical capacity and energy density. Materials of construction and the design of components such as batteries and modules also play a part in determining hazard levels.
The fire testing was conducted at the FM Global Research Campus in Rhode Island, USA, and the ESS composed of either lithium iron phosphate (LFP) or nickel manganese cobalt oxide (NMC) batteries. Both of the ESS tested had solid metal side and back walls, an open front—and contained 16 modules of prismatic batteries arranged in eight levels of two modules. The LFP system had a rating of 83.6 kWh, while the NMC system had a rating of 125 kWh.
At all test scales, which ranged from a single-battery module to full ESS racks containing 16 modules each, the ESS composed of LFP batteries was found to have a lower overall fire hazard. In the sprinklered tests where a single sprinkler operation was sufficient to contain the fire to the rack where it ignited, the fire did not significantly affect any of the modules in the adjacent rack.
Under the same conditions, a test involving a system comprised of NMC batteries resulted in the fire spreading to an adjacent rack, and the number of sprinkler operations represented a demand area greater than 230 square meters (2,475 square feet).
Delay or prevent
Despite the design of the racks effectively shielding the fire from sprinkler water, the fire tests proved that sprinklers could delay or prevent fire spread to adjacent racks. Coupled with adequate separation from nearby combustibles and the addition of thermal barriers between racks, the hazard can be reduced even more. However, without a protection system that can suppress the fire in the early stages, a prolonged burn, high water demand and damage to surroundings are likely.
We recommend protection coupling sprinkler system design and ESS installation guidance, such as the appropriate separation distance, to keep the fire hazard within acceptable levels.
To learn more, download the full research report from the FM Global website at fmglobal.com/researchreports.