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Battery Fire Safety

Photo credit to NEC Energy Solutions.

Introduction

As lithium-ion energy storage systems proliferate across the country, safety concerns are, reasonably, being raised. GI Energy is in the process of installing four 1 MWh / 1 MW systems across New York City. We developed them in close coordination with the New York City Fire Department (FDNY), the Department of Buildings (DOB), and NEC Energy Solutions (NEC ES), our energy storage system integrator. This project is a collaboration with Con Edison and builds on the utility’s previous battery safety testing efforts. Each system is equipped with state-of-the-art fire suppression systems, including several new safety features developed through the FDNY process.

Cell, Module, and Rack Safety

One of the key factors GIE assesses when selecting energy storage integration partners is their product design safety record and commitment to safety innovation. NEC ES’s containerized solution is certified to UL 9540, the Standard for Energy Storage Systems and Equipment, the go-to benchmark for energy storage system safety in North America. This is the minimum qualification we expect. The standard sets forth performance-based safety requirements for the energy storage system design. The new UL 9540A test method determines the actual propagation of thermal runaway in an energy storage system from the smallest scale at the cell level, through battery module, battery rack, and finally up to installation-level sizes if required. (Our energy storage projects in New York City have gone through both UL 9540 certification and UL 9540A testing.)

NEC ES’s system also contains multiple levels of controls designed to prevent fire events in the first place. Their battery management system (BMS) is one of the first to be certified to operate in accordance with Safety Integrity Level 2 (SIL 2) under the IEC 61508 Functional Safety Standard, which is the first quantitative safety standard from which the nuclear, machinery, and process sectors developed their own specific standards. For more information on NEC’s safety features, check out their website.

Fire Suppression and First Responder Safety Features

Thoughtful system design meeting all current certifications drastically reduces the chance of a fire event occurring. But even the best design is not infallible; so, what happens if a thermal runaway event were to occur? We collaborated with the FDNY to ensure our systems include additional features designed to minimize damage and prevent propagation in the unlikely event that a fire does occur. In addition, the local fire station first responders conduct a walkthrough of the system and controls to ensure understanding of the system operation and safety protocols.

  • An automatically activated clean agent-based fire suppression system is inside the container. If smoke is detected the clean agent system will activate and will stop or slow fire propagation. Standards on clean agent fire extinguishing systems are maintained by the National Fire Protection Association® (NFPA) code known as NFPA 2001; an overview of a typical system is available here.

  • A water-based secondary fire suppression system is also installed. The inside of the container is outfitted with a sprinkler system, which is piped to a standard fire-hose connection (so-called Siamese connection) a safe distance away from each battery. Each connection is located within reach of an existing fire hydrant. In the event of a fire inside the container, the FDNY can connect their standard hoses and pump water through to the sprinkler system. This process can continue until the container is flooded with water and the fire is extinguished.

  • Multiple “deflagration vents” have been installed on the roof of the battery system containers, along with flared deflection shields, as seen in the photo above. These vents remain closed during normal operation. If the pressure in the containers rises beyond a designed threshold, potentially due to fire or cell off gassing, the vents will open “up and away” allowing the pressure to be released safely, away from first responders or bystanders. The deflagration vents prevent a situation where an explosion could cause the doors of the container to blow outwards.

  • ”E-Stop” emergency button feature allows first responders to remotely cut power into and out of the battery, while keeping fire suppression and safety features powered.

  • Finally, our systems are outfitted with a manually activated ventilation fan. When first responders arrive on the scene, they will be able to turn on the fan (again, from a safe distance away) and vent the container allowing accumulated gases in the system to be vented in a controlled fashion and avoiding the need to open the container without knowing the composition of the air inside.

Conclusion

Battery energy storage systems, which pack lots of energy into a dense footprint, create inherent risks that must be managed. By partnering with reputable and experienced suppliers and collaborating closely with fire departments and other authorities having jurisdiction (AHJs), we are confident that our projects are safe for all stakeholders, including local communities and first responders. All players in the energy storage industry including equipment providers, project developers, and asset owners must work together with responsible authorities to ensure that battery energy storage systems are safe. Only then can battery storage reach its true potential and unlock the vast benefits this exciting technology promises for the grid and the future of sustainable power.