Using Li-ion Batteries for UPS Systems
Commercial building managers or project managers considering Lithium-ion Uninterruptible Power Supply (Li-ion UPS) options for new facility rooms or for replacement of existing lead acid, VRLA or NiCad "legacy" UPS systems need to be aware of the inherent risks. When making these decisions, it's important to utilize UL 9540 safety testing and UL 9540A fire testing to inform a safe overall design of the UPS in the planned compartment. However, completion of this testing does not mean the Li-ion UPS is safe to install everywhere. The Li-ion UPS, compartment design and planned hazard mitigation features must be evaluated as described in NFPA 855 and AEGIS' Li-ion white paper to ensure the arrangement adequately reduces risk to building occupants, critical business systems or facility use. Additionally, we recommend the involvement of your risk management personnel as part of this decision-making process.
The ability to upgrade an eight-hour lead acid or other UPS battery system to a 24-hour system without affecting the battery room size or structural support. If kept at the same capacity, UPS room square footage can be freed up for other uses.
Li-ion UPS may be a very attractive option for some of the more important critical facilities, such as system operations centers and data centers; however, significant safety issues must be addressed.
Legacy Battery Rooms
A typical legacy battery room is not designed to address the thermal runaway risks associated with even one rack of Li-ion batteries. Li-ion battery thermal runaway occurs when the temperature inside the battery reaches a point that causes a chemical reaction within the battery to occur, which can result in the venting of combustible gas and thermal propagation to adjacent cells. The venting of combustible gas creates the potential for a severe fire of long duration, an explosion or both in succession. Li-ion battery thermal runaway can result from factors beyond the control of a battery management system.
Once thermal runaway and venting occurs, it cannot be managed by even the best battery management system or fire protection system. Legacy battery room firewalls are generally not constructed to withstand an explosion or long-duration, high-severity fire events and may fail prematurely. Exhaust systems for legacy UPS may not be able to manage the volume of combustible gas released during Li-ion thermal runaway events. Typical battery room electrical systems are not designed for hazardous atmospheres, and many ignition sources will be present during a release. If combustible gas and an ignition source is present, then the possibility exists for a catastrophic event.
An incident involving Li-ion thermal runaway can develop rapidly and irreversibly in mixed-used occupancies. Personnel egress routes, critical business systems and critical operating centers can be affected. Building habitability can be impacted for extended durations, potentially weeks or months. In high-rise commercial buildings, even more complex factors may need to be taken into account if considering Li-ion UPS battery rooms.
Further Considerations
If a Li-ion UPS remains the technology of choice, then further consideration must be given to where to place the UPS safely. The safest option would be a specifically designed, purpose-built enclosure at least 25 feet away from the facility. A second, less preferred option is a "bunkerized" room in the facility that shares at least one or preferably two (a corner) exterior wall(s), which are built utilizing damage-limiting construction and have fire department access from the exterior. A "bunkerized" room is one where the interior walls, floor and ceiling are designed by a structural engineer for the expected blast pressure, and the exterior wall is of sufficient size and design to adequately relieve any overpressure (e.g., damage limiting construction). If using one of these options, further consideration should be given to ensure safety for any building occupants, pedestrians or traffic that may be in the vicinity. In addition, appropriate and periodic training must be provided for all first aid and emergency responders to such an event.
AEGIS's Li-ion White Paper
AEGIS's white paper on Li-ion BESS is written specifically for grid-level Li-ion BESS, but can also be applied to UPS systems. The white paper currently states, "Li-ion BESS, Li-ion Emergency Power Systems (Li-ion EPS) or Li-ion Uninterruptible Power Supply (Li-ion UPS) systems should not be installed within mixed-use occupancies such as offices, schools, hospitals or shop areas due to the significant explosion hazard potential." This message should proactively be communicated to all decision-makers for member commercial facilities. AEGIS Loss Control Property Operations is available to discuss the risks associated with any project, including those that may involve commercial facilities. You can view and download the Lithium-ion Battery Energy Storage Systems (Li-ion BESS) White Paper | November 2023 Update here.
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