Battery energy storage systems (BESS) are at the heart of the clean energy transition, enabling grid stability and efficient use of renewable power. However, BESS facilities also pose a unique fire safety challenge: thermal runaway.
This chain reaction, triggered by excessive heat or internal faults, can lead to catastrophic fires, explosions, and costly downtime. As BESS deployments scale globally, preventing thermal runaway isn’t just a technical challenge, it’s a critical safety priority.
In this article, we’ll explore proven fire safety solutions that help operators mitigate thermal runaway risks, protect assets, and ensure compliance with industry standards.
Understanding Thermal Runaway
What is thermal runaway?
Thermal runaway is a self-perpetuating reaction that occurs when a battery cell’s temperature rises uncontrollably. In lithium-ion batteries (sometimes referred to as ‘li ion’), this happens when internal heat generation exceeds the system’s ability to dissipate it. Once triggered, the process accelerates rapidly, leading to cell venting, fire, or even explosion.
What causes thermal runaway?
Key triggers and causes of thermal runaway include:
- Overcharging: Excess voltage can cause chemical instability within the cell.
- Internal short circuits: Often due to manufacturing defects or physical damage.
- Mechanical stress: Impact or vibration can compromise cell integrity.
- High ambient temperatures: External heat sources or poor ventilation exacerbate risk.
Why is BESS particularly vulnerable to thermal runaway?
Battery energy storage systems contain thousands of interconnected cells. This high energy density means that a single cell failure can cascade across the system, amplifying the danger. Additionally, BESS installations often operate in remote or harsh environments, making early detection and intervention more challenging.
Early Detection & Monitoring
Preventing thermal runaway starts with identifying warning signs before they escalate. Advanced monitoring systems and predictive technologies are essential for early intervention.
Battery Management Systems (BMS)
A robust BMS is the first line of defence against lithium battery thermal runaway. It continuously tracks critical parameters such as voltage, current, and temperature across individual cells and modules. By enforcing safe operating limits and triggering alarms when anomalies occur, BMS helps prevent conditions that lead to thermal runaway.
Sensors & Diagnostics
These include:
- Thermal sensors: Detect abnormal heat buildup at the cell level.
- Gas detection: Identifies electrolyte vapours or off-gassing, which often precede thermal events.
- Voltage imbalance monitoring: Flags cells that deviate from normal performance, indicating potential internal faults.
Predictive Analytics
Modern systems leverage machine learning to analyse historical and real-time data, predicting failure patterns before they occur. This proactive approach allows operators to schedule maintenance or isolate problematic modules, reducing risk significantly.
Fire Safety Solutions for BESS
Preventing thermal runaway isn’t just about detection, it’s about having robust fire safety measures in place to contain and mitigate risks. Here are the key strategies and technologies that make a difference.
Passive Fire Protection
Passive measures are built into the system design to slow down or prevent fire spread without active intervention. These include fire-resistant enclosures made from non-combustible materials to isolate li ion battery modules and thermal barriers to prevent heat transfer between cells and modules. Large systems can also be divided into smaller, fire-resistant sections to limit propagation.
Active Fire Suppression Systems
When thermal runaway occurs, rapid suppression is critical. There are several different types of suppression systems, including:
- Water mist systems: Unlike traditional sprinklers, water mist systems use minimal water to effectively cool and control battery fires without causing electrical hazards.
- Gas-based suppression systems: Release inert or chemical gases to suppress fire, either through heat absorption or lowering the oxygen concentration. As there is no risk of water damage, gas suppression is an increasingly popular choice for BESS installations.
- Aerosol suppression systems: Compact systems that release fine particles to interrupt combustion chemistry.
- Hybrid systems: These systems are compatible with multiple extinguishing agents to ensure maximum effectiveness.
Advanced Cooling Solutions
Temperature control is essential for prevention of thermal runaway. Methods include liquid cooling, where coolant is circulated around the lithium ion battery packs to maintain an optimal temperature. A ventilation system will effectively remove excess heat and prevent hotspots, while phase-change materials absorb heat during peak loads to help keep the temperature stable.
Emergency Venting & Pressure Relief
In the event of cell failure, controlled venting prevents explosions. This can be done via pressure relief panels to allow gases to escape safely, or deflagration venting, which directs flames and pressure away from critical components.
Integrated Fire Detection
Suppression systems with integrated fire detection ensure the alarm is triggered as soon as a fire is detected. Smoke and heat detectors pick up a fire that has already started, while gas sensors can detect electrolyte vapours before ignition.
Standards & Compliance
Protecting battery energy storage systems from fire isn’t just best practice, it’s a regulatory requirement. Compliance ensures systems are designed, installed, and maintained to minimise risk and protect both people and assets.
Specific standards vary depending on location, so it’s important to check the correct legislation for your region.
Best Practices for Operators
Even with advanced technology and compliance measures, human oversight and operational discipline remain critical. Here are some practical steps every operator should implement.
- Regular maintenance and inspections: Schedule routine checks on battery modules, cooling systems, and fire suppression equipment. Inspect for physical damage, corrosion, or loose connections that could lead to faults.
- Staff training: Train personnel on thermal runaway risks and early warning signs, establish clear evacuation and response protocols and ensure staff know how to safely isolate affected modules during an incident.
- Compliance audits: Regularly review adherence to the relevant regional standards and update systems as regulations evolve.
- Choose appropriate fire protection: Partner with suppliers who specialise in energy storage safety and whose equipment is certified to EN, UL or AS standards, depending on your location. For lithium-ion batteries, prioritise clean agent or aerosol systems over traditional sprinklers.
Conclusion
Thermal runaway is one of the most serious risks facing battery energy storage systems, but it’s not inevitable. With the right combination of early detection, robust fire safety solutions, and strict compliance, operators can dramatically reduce the likelihood of catastrophic failures.
Fire safety measures, such as passive barriers, active suppression systems, advanced cooling, and emergency venting, are essential components of a safe and reliable BESS installation. Choosing certified equipment, integrating it with monitoring systems, and maintaining it through regular audits ensures that your fire protection strategy is as strong as your energy storage solution.
As the demand for energy storage grows, so does the responsibility to keep these systems safe. Investing in comprehensive fire safety solutions means protecting your assets, your people, and the future of clean energy.
How we can help
We offer a variety of BESS fire safety solutions to help mitigate the risk of thermal runaway. Discover our battery energy storage systems fire protection range.