Fire Hazard of Lithium-ion Battery Energy Storage Systems: 1. Module to Rack-scale Fire Tests

Lithium-ion batteries (LIB) are being increasingly deployed in energy storage systems (ESS) due to a high energy density. However, the inherent flammability of current LIBs presents a new challenge to fire protection system design. While bench-scale testing has focused on the hazard of a single battery, or small collection of batteries, the more complex burning behavior of a commercially design module (collection of batteries) or rack (collection of modules) is still largely unknown. In this study, a series of small- to large-scale free burn fire tests were conducted on ESS comprised of either iron phosphate (LFP) or lithium nickel oxide/lithium manganese oxide (LNO/LMO) batteries. Small-scale tests showed that a thermal runaway event could lead to a self-propagating fire for both the LFP and LNO/LMO batteries with a significantly greater heat release rate (HRR) generated from the LNO/LMO battery. Intermediate- and large-scale tests showed that the burning of a single module was sufficient to involve all other modules within the same ESS rack for both types of battery chemistries. The different burning behavior of the two battery chemistries was further demonstrated with the LNO/LMO battery generating a maximum HRR nearly three times that of the LFP battery. To better understand the hazard associated with these fires, a multi-point source model was used to analyze the radiative heat exposure to the environment. The end result is an experimentally validated data set that can be used to estimate the heat exposure to objects surrounding an ESS fire, such as ESS racks across an aisle space in a large deployment, or other nearby combustibles. These data also provide the basis for evaluating the effectiveness of sprinkler protection at reducing the fire hazard and protecting the surroundings.