A growing number of fire authorities and life safety system experts are addressing the issue of thermal runaway by recommending technology that provides a warning far earlier than traditional monitoring and detection methods. This can help stop thermal runaway before it begins.
The approach is increasingly being adopted by fire authorities for lithium-ion (Li-ion) Battery Energy Storage Systems (BESS) applications. Comprised of an interconnected series of batteries, BESS are self-contained, rechargeable battery units that store energy, which they can then disperse in case of power loss.
Unfortunately, in Li-ion BESS scenarios thermal runaway can occur due to thermal abuse or overcharging. The increase in heat can cause the electrolyte solution inside of a Li-ion battery to begin to turn into a vapor. If left unchecked by built-in system protections or the Battery Management System, this process can eventually cause the battery cell separator to melt down and degrade. This stage of Li-ion battery failure is referred to as “off-gassing” or “initial cell venting.”
Failure to address the continued increase in heat at this stage will result in the internal temperature of the battery continuing to rise until a point of thermal runaway, which can propagate into fires in adjacent cells and other combustibles in the area.
Although smoke and gas detectors are required by code in BESS, smoke detectors are searching for particles of combustion, which are not present until thermal runaway occurs. Most gas detectors are designed to manage threats in lead-acid battery BESS and so detect either a generic hydrocarbon gas or quantity of gas at one physical location.
Due to these factors, traditional smoke and gas detectors used in a Li-ion BESS may only indicate a thermal runaway event once it is already occurring inside the container, rather than providing sufficient warning to prevent a fire.
Now, a combination of technologies is increasingly being installed in Battery Energy Storage Systems to help tame the dangers of thermal runaway before it starts:
• Li-ion Tamer by Honeywell utilizes a network of off-gas sensors to monitor Li-ion BESS and provide an alert to the initial venting of electrolyte solvent vapors. The early warning increases time to shut down the charge to the affected rack(s) in the estimated 8-15 minutes between off-gassing of the electrolyte vapors and the beginning of thermal runaway. The controller diagnoses when and where the off-gassing of electrolyte vapors is occurring, with an electrolyte solvent release of just a single battery cell. This enables quick alarm initiation and immediate mitigation measures.
• VESDA aspirating smoke detectors provide early warning smoke detection because the heat from a combustion fire in the BESS can trigger a Li-ion thermal runaway event. The VESDA VLF continuously draws in small samples of air through holes in piping or tubing and evaluates it for smoke particles at a central location.
“When combined, VESDA, fire suppression system elements, and Li-ion Tamer provide the tools and the interface needed to protect BESS essentially anywhere they are installed. Li-ion Tamer is a flexible, effective option that can take the place of traditional gas detection,” says Randy Snow, Managing Principal at Progressive Edge Technologies, a Phoenix, Arizona-based fire and life safety system consulting firm.
For more information, email: Dawn Wotapka, Director of External Communications at Honeywell: [email protected].