Page | 005 Should thermal runaway conditions be detected then there should be the facility in place for the early alerting of emergency services.
Detection systems should also be in place for alerting to other fires that do not involve thermal runaway (for example, fires involving electrical wiring).
Continuous combustible gas monitoring within units should be provided. Gas detectors should alarm at the presence of flammable gas (yes/no), shut down the ESS, and cause the switchover to full exhaust of the ventilation system3. Sensor location should be appropriate for the type of gas detected e.g. hydrogen, carbon monoxide, volatile organic compounds.
External audible and visual warning devices (such as cabinet level strobing lights), as well as addressable identification at control and indicating equipment, should be to linked to:
1. Battery Management System (when a thermal runaway event is identified) 2. Detectionandsuppressionsystemactivation
This will enable first responders to understand what the warning is in relation to. This will aid in their decision-making.
Suppression systems
Suitable fixed suppression systems should be installed in units in order to help prevent or limit propagation between modules.
Where it is suggested that suppression systems are not required in the design, this choice should be supported by an evidence based justification and Emergency Response Plan that is designed with this approach in mind (for example, risk assessed controlled burn strategies, and external sprinkler systems).
Whilst gaseous suppression systems have been proposed previously, current research indicates the installation of water based suppression systems for fires involving cell modules is more effective.
The installation of gaseous suppression systems for electrical fires that do not involve cell modules may be appropriate but should be built into a wider suppression strategy.
FM Global cite the following reasons for not recommending gaseous protection systems4:
1. Efficacy relative to the hazard. As of 2019, there is no evidence that gaseous protection is effective in extinguishing or controlling a fire involving energy storage systems. Gaseous protection systems may inert or interrupt the chemical reaction of the fire, but only for the duration of the hold time. The hold time is generally ten minutes, not long enough to fully extinguish an ESS fire or to prevent thermal runaway from propagating to adjacent modules or racks.
3 FM Global (2017) Property Loss Prevention Data Sheets: Electrical Energy Storage Systems, para. 2.5.5.2 4 FM Global (2017) Property Loss Prevention Data Sheets: Electrical Energy Storage Systems, para. 3.3
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