When talking about fire protection for a BESS, many people only think of automatic fire suppression systems. However, a fire extinguisher, no matter how advanced, is only the last line of defense. A truly effective safety strategy must be built on the philosophy of “Defense-in-Depth”.
It is a multi-layered approach, where each layer of protection supports and backs up the others, creating a comprehensive safety system that can prevent failures early and minimize damage if they occur. Let’s explore the four core layers of defense in a professionally designed BESS container.
Layer 1: Prevention – The Root of Safety
The most effective defense is to prevent a problem from happening in the first place. The goal of this layer is to keep the battery cells operating within safe limits and never reach a point where thermal runaway begins. The “soldiers” in this layer include:
- Battery Management System (BMS): Continuously monitor the voltage, current and temperature of each battery cell, proactively disconnecting if any abnormal signs are detected.
- Thermal Management System (HVAC): Maintains optimal operating temperature environment, eliminating one of the main causes of heat loss.
Grade 2: Early Detection – Vigilant Eyes and Ears
If the containment fails and a battery cell begins to thermally runaway, the next goal is to detect it as early as possible. The early stages of thermal runaway often release flammable gases before smoke and fire appear. Therefore, a comprehensive early detection system would include:
- Off-gas Detection: Highly sensitive sensors are capable of detecting characteristic gases (such as Hydrogen, Carbon Monoxide) released in the early stages of an incident. This is the earliest warning line.
- Smoke Detectors: Detects smoke particles in the air.
- Heat Detectors: Detects sudden temperature increase in container.
When any sensor is triggered, the system immediately sends an alert to the operator and can automatically take actions such as disconnecting the entire BESS system.
Class 3: Suppression – Timely Intervention
Only when there is a clear sign of fire (smoke or high temperature) will the third layer of defense be activated. This is when automatic fire extinguishing system with clean gas (like Novec 1230) works.
The system will spray gas to extinguish the fire, preventing it from spreading from one battery module to another or to external equipment. It should be noted that the clean air system can extinguish the fire, but it cannot stop the chemical reaction of the thermal runaway process taking place inside a damaged battery cell. Its role is to control the fire and “buy time” for further response measures.
Class 4: Damage Control (Containment & Venting)
This final layer of defense is designed to minimize the consequences in the worst case scenario, should a major explosion or fire occur.
- Explosion Venting: If flammable gases build up and explode, the pressure inside the container will increase suddenly. Explosion vents are designed to inflate at a certain pressure, releasing the pressure in a controlled and directed manner to a safe area, avoiding damage to the container structure.
- Fire-rated Walls: The container shell and internal partitions can be designed with fire-resistant materials, capable of withstanding high temperatures for a certain period of time (e.g. 2 hours), helping to prevent fire from spreading to adjacent BESS containers or neighboring structures.
Fire safety for BESS is not a single product, but a system strategy. By applying the philosophy of “Defense in Depth”, a well-designed BESS container will create a maximum safety operating environment, with multiple layers of protection that back up each other. This is the difference between a basic BESS solution and a professionally designed, reliable system.
