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Electrified Not Burned: Balancing The Power of Lithium-ion Batteries and Fire Code Impacts

7x24 Exchange Fall Magazine 2020 | Electrified But Not Burned: Balancing The Power of Lithium-ion Batteries and Fire Code Impacts

By Simon Xie, PE

Energy is getting electrified. As for the reason, you’ve guessed it right: efficiency, cost, sustainability and more. The benefits of the lithium-ion battery are driving this transition. Compared to other types of batteries that are readily available on the market, lithium-ion batteries easily win with a clear advantage – high energy density. We can realize this advantage both gravimetrically and volumetrically, resulting in a low life cycle cost. This makes lithium-ion batteries an ideal choice for mission critical facilities.

Many mission critical designers are implementing the use of Lithium Ion Batteries for UPS systems due to the lower weight, smaller footprint, longer life, and equivalent cost when compared to valve regulated lead acid (VRLA) batteries. As designers and builders of Mission Critical facilities continue to evaluate the suitability of this technology, it is important to understand the fire code related impacts.

Although lithium-ion batteries do not contain water-reactive metal lithium, there are safety concerns. The electrolyte in a lithium-ion battery cell contains a cocktail of flammable liquids. These chemicals can be transformed into flammable gases if battery cells malfunction. For example, Li-dendrites, needle-like structures, can form within the battery cell, growing from the surface of the anode, through the electrolyte, penetrating the separator that otherwise safely keeps the electrolytes on the anode and cathode separated. This creates a risk of an internal short circuit. The shorted battery can then go through a cascade of exothermal processes that decompose the materials within the cell, build up the pressure in the cell, and produce flammable gases and toxic gases. If these gases are released through pinholes or larger ruptures on the battery cell enclosure, a fire or an explosion becomes a serious risk.

Prior to the release of the 2018 edition of the International Fire Code (IFC) and International Building Code (IBC), these guidelines primarily focused on lead-acid battery systems as they applied to standby or emergency power applications commonly found in today’s data centers. Besides the electrical hazards, lead-acid batteries and nickel batteries (e.g. Ni-Cad, Ni-MH, and Ni-Zn batteries) can lead to hydrogen off-gassing and corrosive electrolytes. Earlier codes did not adequately address the safety concerns stemming from lithium-ion batteries. For example, earlier versions such as the 2015 IFC only require the compliance with battery system requirements1 when the batteries are used for standby power, emergency power, or UPS applications and only when the electrolyte or the battery weight is over the threshold. If a lithium-ion battery system is not used for these applications, or even if these thresholds are exceeded, one could still argue that IFC battery system requirements are not applicable.

Another example that previous editions of IFC/IBC were not adequately addressing batteries is the use of Group H (high-hazard) occupancy classifications. Group H occupancy classifications requires the space to be designed and constructed with the highest fire safety provisions. Although energized batteries can be hazardous, a Group H occupancy classification could still be triggered if batteries are not used in standby/emergency power or UPS applications when the total electrolytes exceed the maximum allowable quantities for hazardous materials in Chapter 3 of IBC (e.g. if the batteries are in storage and not energized).

The 2018 IFC and IBC eliminated these deficiencies by addressing hazards from lithium-ion batteries and other technologies. The 2018 IFC clearly states that battery systems used for standby/emergency power, UPS, power-shedding, power-sharing, and all similar uses are governed by the storage battery system requirements in IFC Chapter 12.

Another important change made in the 2018 IFC is that the former thresholds using the total volume of the electrolyte and the weight of the lithium-ion batteries are completely abandoned. Instead, a set of the electrical outputs (in kWh) of each type of battery is used to establish the threshold. This is a necessary change since many battery systems have electrolytes unlike the ones in lead-acid or nickel batteries. This is also an important change for lithium-ion batteries because a higher kWh usually means a larger quantity of combustible electrolytes, which could lead to a fire spreading rapidly from one lithium-ion battery rack to another2. The 2018 IFC also introduces a new set of threshold kWh values for the battery systems. Once this threshold is exceeded, this space will be considered as a Group H occupancy. For example, a lithium-ion battery system of more than 20 kWh must comply with the 2018 IFC battery requirements in Section 1206 (600 kWh); once the lithium-ion battery system exceeds 600 kWh, such space is classified as a Group H-2 occupancy and must comply with additional Group H-2 requirements.

Among all the 2018 IFC updates, new requirements3 for battery array layout can have more impacts on room design. In a nutshell, battery systems must be arranged so that a single array does not exceed 50 kWh and separated at least 3 feet from the adjacent array.

Finally, the 2018 IFC provides a compliance path for battery system installations under three special conditions. The first is if the project includes battery technologies that are not specifically covered in IFC; secondly, the project uses multiple battery technologies that may result in adverse interactions; and thirdly, the project needs to include a battery system that exceeds the output threshold, triggering a Group H occupancy, but the project budget cannot afford the requirements of such occupancy classification. To follow an alternative path, a hazard mitigation analysis that includes battery system failure mode and effect analysis must be provided to the Authorities Having Jurisdiction (AHJ) for approval.

The 2018 IFC and IBC have taken significant steps to address the hazards of battery systems. However, there are still a lot of special circumstances not addressed. For example, there are buildings dedicated to battery systems. These types of buildings are not well addressed in 2018 IFC and IBC. Fires and explosions within these types of buildings have occurred. For example, Arizona Public Service’s McMicken Energy Storage Facility suffered a lithium-ion battery fire and explosion in April of 2019, which injured four firefighters.

Fortunately, solutions for many of these special circumstances are addressed in the first edition of NFPA 855 (2020 Edition), Standard for the Installation of Stationary Energy Storage Systems. It is expected that the upcoming 2021 IFC and IBC will contain similar provisions from NFPA 855 and will reference NFPA 855 for fire and life safety on energy storage systems.

In addition to the model code and standard development, we should also recognize the different rates of clean energy adoption among different localities. Ambitious clean energy goals will inevitably drive the local jurisdictions to accelerate the adoption of stringent regulations around battery systems.

While our society is benefiting from lithium-ion batteries, the new safety challenges must be recognized and addressed through design. As battery technologies evolve, improvements and benefits are realized. The glass/ceramic solid-state lithium-ion battery, free of any combustible electrolytes, could offer fire hazard-free solutions in the future. Sharing the knowledge of the applications and benefits of this wave of electrification offers exciting opportunities for mission critical facilities.

Like all new technologies, manufacturers are working to address issues and to find solutions that will mitigate past safety issues and concerns, including better battery management systems which are intended to prevent the possibility of thermal runaway. It is incumbent on owners and engineers to review risks and available technologies to determine the best solution for the project and owner’s needs.

1Requirements are contained in Section 608 of 2015 IFC.
2Li-Ion battery Energy Storage Systems: Effect of Separation Distances Based on a Radiation Heat Transfer Analysis, 12 June, 2017
(https://www.wpi.edu/sites/default/files/docs/Departments-Programs/Fire-Protection/Final_ESS_Report.pdf)
3See more detailed requirements and specific exceptions in Section 1206.2.8.3 of 2018 IFC.

Simon Xie, PE is Fire Protection Engineer of Swanson Rink, Inc. He can be reached at xie@swansonrink.com.

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