Utility Scale Battery Energy Storage Systems

Utility Scale Battery Energy Storage Systems are designed to store energy; they charge and discharge this energy back and forth to the grid or end user. These “Storage Systems” are composed of multiple shipping (like) containers filled with layered stacks of Lithium Batteries. 

Each container may hold up to thousands of pounds of batteries based on size. 

Similar to other energy developments battery storage systems have several risks associated with them such as; noise, off gassing, fires and potential explosions. Therefore it's imperative that these facilities are sited appropriately and follow both State Fire code NFPA 855 and the Lone Star Infrastructure Protection Act to ensure the safety of the public. Lithium-ion batteries contain flammable electrolytes, which can create unique hazards when the battery cell becomes compromised and enters thermal runaway. The initiating event is frequently a short circuit which may be a result of overcharging, overheating, or mechanical abuse. During the exothermic reaction process (i.e., thermal runaway), large amounts of flammable and potentially toxic battery gas will be generated. The released gas largely contains hydrogen, which is highly flammable under a wide range of conditions. This may create an explosive atmosphere in the battery room or storage container. 

Both the battery equipment and the cooling fans makes noise, ranging in leaves fluctuating around 70-95 dba. This noise pollution can travel for several miles. To keep up, the battery systems are heavily dependent on air cooling which consists of large industrial fans on each container. These are necessary to keep the batteries at a safe operating temperature and most importantly to prevent the batteries from over heating during normal operations and going into Thermal Runaway.

Definition of Thermal Runaway provided below.  

Source: National Fire Protection Association NFPA 855 2023 edition, C.4.2 Fires Thermal Runaway Definition: Fires in electrochemical ESS are often a result of a process called thermal runaway. Thermal runaway can simply be defined as the process in which a battery creates heat but cannot dissipate that heat, resulting in dynamic temperature increase. Initial signs of thermal runaway might include pressure increase at the cell level, temperature increase, and off-gassing. As the process continues, additional signs might include vent gas ignition, exploding cells, projectile release, heat propagation, and flame propagation.

As the failure cascades, responders should also be prepared for toxic and potentially explosive gas release. Through fire and explosion testing in accordance with 9.5.3.2 to determine battery burn outcomes, including toxic gas release calculations, remains incomplete, responders should treat them as highly dangerous and use their full suite of PPE and breathing apparatus when responding.

NFPA Hazards Under Normal Operation: Fire hazards:

There can be the potential for fire hazards if there are latent defects within the cells or design issues with the controls that prevent thermal runaway of the cells. Systems need to be evaluated for their ability to prevent propagation due to these defects. Hazard for LFP batteries under emergency/abnormal conditions are as follows: Chemical hazards: There can be the potential for off-gassing of hazardous vapors under abnormal conditions depending on the size of the cells and the level of failure.