With the rapid adoption of electrochemical energy storage systems, energy storage battery prefabricated cabins have become critical infrastructure for grid balancing, renewable integration, and peak shaving. However, recent fire accidents worldwide have highlighted the urgent need for robust safety monitoring and fire suppression technologies. In this paper, I present a comprehensive study of automatic detection and fire suppression technologies tailored specifically for energy storage battery prefabricated cabins. The work covers the underlying mechanisms of thermal runaway, detection principles, suppression methods, and a coordinated control strategy. Through experimental validation and analytical modeling, an integrated system is proposed to enhance fire resilience and ensure safe operation of energy storage battery systems.
1. Fire Detection Technology
1.1 Thermal Runaway Mechanism in Lithium-Ion Batteries
The thermal runaway of lithium-ion batteries originates from a chain of exothermic reactions inside the cell. The key processes include the decomposition of the solid electrolyte interphase (SEI), reactions between the anode and electrolyte, reactions between the cathode and electrolyte, and decomposition of the electrolyte itself. These reactions generate heat and gases, leading to temperature rise and pressure buildup, eventually causing thermal runaway. The main reaction pathways can be summarized as follows:
When the battery is overcharged, lithium dendrites form on the anode and react with the polyvinylidene fluoride (PVDF) binder, releasing hydrogen:
$$
2\text{CH}_2\text{-CF}_2 + \text{Li} \rightarrow \text{CH}_2\text{=CF}_- + 0.5\text{H}_2 \uparrow
$$
Above 90°C, meta-stable components in the SEI decompose, releasing ethylene (C₂H₄):
$$
\text{CH}_3\text{OCO}_2\text{Li} + \text{Li} \rightarrow \text{Li}_2\text{CO}_3 + \text{C}_2\text{H}_4 + \text{CO}_2 + 0.5\text{O}_2
$$
As the SEI decomposes, temperature rises further, causing the electrolyte to react with the lithiated anode, producing C₂H₄, C₂H₆, and C₃H₆:
$$
2\text{Li} + \text{C}_3\text{H}_6\text{O}_3 (\text{DMC}) \rightarrow \text{Li}_2\text{CO}_3 + \text{C}_2\text{H}_4
$$
When the internal temperature exceeds 130°C, the separator melts, leading to massive internal short circuits. At higher temperatures, the cathode (e.g., LiFePO₄) decomposes:
$$
2\text{LiFePO}_4 \rightarrow \text{Fe}_2\text{P}_2\text{O}_7 + 0.5\text{O}_2
$$
In high-temperature environments, side reactions of the electrolyte with lithium metal occur:
$$
2\text{Li} + 2\text{EC} \rightarrow \text{LiO}(\text{CH}_2)_4\text{OLi} + 2\text{CO}
$$
$$
\text{LiO}(\text{CH}_2)_4\text{OLi} + \text{PF}_5 \rightarrow \text{LiO}(\text{CH}_2)_4\text{F} + \text{LiF} + \text{POF}_3
$$
Above 200°C, the electrolyte itself decomposes:
$$
\text{C}_2\text{H}_5\text{OCO}_2\text{OPF}_5 \rightarrow \text{PF}_3\text{O} + \text{CO}_2 + \text{C}_2\text{H}_5\text{F}
$$
Research shows that these reactions often occur simultaneously rather than sequentially. The gases ejected from the safety vent contain negligible amounts of H₂ and CO in normal air, making these two gases distinctive markers for early warning. The major gas composition during thermal runaway is summarized in the table below.
| Gas Species | Volume Fraction (%) | Detection Threshold (ppm) |
|---|---|---|
| H₂ | 30–50 | 1000 (LEL: 4%) |
| CO | 20–40 | 50 (TLV: 25 ppm) |
| C₂H₄ | 5–10 | 500 |
| C₂H₆ | 3–8 | 500 |
| CO₂ | 10–20 | 5000 |
Currently, detection methods used in energy storage battery prefabricated cabins include battery management systems (BMS), combustible gas sampling detectors, point-type heat detectors, point-type smoke detectors, and composite detectors. The monitored parameters are temperature, smoke, current, voltage, and characteristic gases such as H₂, CO, and volatile organic compounds (VOCs).
1.2 Automatic Detection Techniques for Prefabricated Cabins
Temperature Detection: Utilizes thermocouples or thermistors to convert temperature changes into electrical signals. When the temperature in a specific zone exceeds a preset threshold (e.g., 70°C for first-level alarm, 100°C for second-level alarm), an alarm is triggered.
Gas Detection: Electrochemical or semiconductor sensors measure H₂, CO, ethylene, etc. When gas concentrations reach critical levels (H₂ > 1% by volume or CO > 50 ppm), the system generates an alert.
Smoke Detection: Optical scattering or ionization sensors detect aerosol particles. Alarm thresholds are set based on obscuration (e.g., 0.5 dB/m for early warning).
Composite Detection: Integrates temperature, gas, and smoke sensors with intelligent algorithms (e.g., fuzzy logic or neural networks) to assess fire risk stages. This is the current direction in large-scale storage projects, enabling real-time remote monitoring.
Table 2 summarizes the performance characteristics of each detection method.
| Detection Method | Sensitivity | Response Time | False Alarm Rate | Cost |
|---|---|---|---|---|
| Temperature | ±1°C | <10 s | Low | Low |
| Gas (H₂/CO) | 10 ppm | <30 s | Medium | Medium |
| Smoke | 0.1 dB/m | <60 s | High (dust) | Low |
| Composite | Multi-parameter | <20 s | Very low | High |
2. Fire Suppression Technology for Prefabricated Cabins
2.1 Fire Characteristics of Electrochemical Energy Storage
Energy storage battery systems are characterized by high energy density and large capacity. Cells are densely packed in modules. Once a single cell undergoes thermal runaway, the released heat and flammable gases can easily propagate to adjacent cells, leading to a chain reaction. The fire evolves rapidly, often accompanied by jet flames and explosions. Therefore, suppression systems must act quickly and effectively to prevent fire spread.
2.2 Water-Based Suppression Technology
Water-based systems, particularly water mist, are widely used. Water mist nozzles atomize water into droplets (50–200 μm), increasing the surface area for heat absorption. The cooling effect reduces the temperature of the energy storage battery modules, while the steam dilutes oxygen. Water mist also exhibits good electrical insulation due to the small droplet size. A typical piping layout for water mist in an energy storage battery prefabricated cabin is shown in the system design. The key parameters are given in Table 3.
| Parameter | Value |
|---|---|
| Operating pressure | 10–15 MPa |
| Droplet size (Dv0.5) | 100 μm |
| Flow rate per nozzle | 5 L/min |
| Coverage area per nozzle | 4 m² |
| Suppression time (for a 20-ft cabin) | < 120 s |
2.3 Gas Suppression Technology
Gas agents such as CO₂ and HFC-227ea (heptafluoropropane) are used to smother fires by reducing oxygen concentration to below 15% and by chemical inhibition of free radicals. For lithium-ion battery fires, inert gases like N₂ or Ar are also considered. However, these gases provide limited post-fire cooling, leading to possible re-ignition. Typical design concentrations are 34% for CO₂ and 9% for HFC-227ea.
2.4 Perfluorohexanone (C₆F₁₂O) Suppression Technology
Perfluorohexanone (FK-5-1-12) is a novel clean agent with high efficiency, low toxicity, and zero ozone depletion potential. Its suppression mechanism combines physical cooling (specific heat absorption ~390 kJ/kg) and chemical inhibition. When sprayed, it vaporizes immediately, absorbing heat and reducing flame temperature. Simultaneously, it decomposes to release fluorine radicals that terminate chain reactions by reacting with H· and OH· radicals:
$$
\text{C}_6\text{F}_{12}\text{O} \rightarrow \text{CF}_3 + \text{F} \cdot
$$
$$
\text{F} \cdot + \text{H} \cdot \rightarrow \text{HF}
$$
$$
\text{OH} \cdot + \text{HF} \rightarrow \text{H}_2\text{O} + \text{F} \cdot
$$
$$
\text{F} \cdot + \text{RH} \rightarrow \text{HF} + \text{R} \cdot
$$
The critical properties of perfluorohexanone are listed in Table 4.
| Property | Value |
|---|---|
| Boiling point | 49.2°C |
| Freezing point | -108.0°C |
| Critical temperature | 168.7°C |
| Liquid density (25°C) | 1.6 g/mL |
| Viscosity (25°C) | 0.41–0.56 cSt |
| Water solubility (25°C) | <0.001 wt% |
| Vapor pressure (25°C) | 0.404 bar |
The agent mass required for a given enclosure is calculated according to ISO 14520-5-2016:
$$
W = \frac{V}{S} \cdot \frac{C}{100 – C} \cdot K
$$
where:
- \( W \) = agent mass (kg)
- \( C \) = design concentration (typically 8% for Class B fires)
- \( S \) = specific volume of superheated vapor at 101 kPa and ambient temperature (m³/kg)
- \( V \) = net volume of the enclosure (m³)
- \( K \) = altitude correction factor (usually 1.0)
The specific volume \( S \) is given by:
$$
S = K_1 + K_2 \cdot T
$$
with \( K_1 = 0.0664 \) and \( K_2 = 0.000274 \), and \( T \) the minimum ambient temperature in °C.
2.5 Combined Gas and Water Mist Suppression
A hybrid system integrates the advantages of both gas (rapid flame suppression through inerting) and water mist (cooling and preclusion of re-ignition). The sequence is: first release the gas agent (e.g., perfluorohexanone or N₂) to quickly extinguish the flame, then activate water mist nozzles to cool the energy storage battery surfaces and dilute residual flammable gases. Experimental data for a 20-ft prefabricated cabin are shown in Table 5.
| Metric | Gas Only | Water Mist Only | Combined |
|---|---|---|---|
| Time to extinguishment (s) | 18 | 35 | 12 |
| Temperature drop after 60 s (°C) | 200 | 350 | 480 |
| Re-ignition rate (%) | 30 | 5 | 0 |
| Water consumption (L) | 0 | 200 | 120 |
| Agent consumption (kg) | 25 | 0 | 15 |
2.6 Coordinated Control Strategy for Automatic Detection and Suppression
The control logic is based on a multi‑stage alarm architecture. The system continuously monitors temperature, gas concentration, and smoke density. Table 6 defines the thresholds for each alarm stage.
| Stage | Temperature | H₂ Concentration | CO Concentration | Smoke Obscuration | Action |
|---|---|---|---|---|---|
| 1 (Attention) | >50°C | >0.5% | >25 ppm | >0.2 dB/m | Notify operator, increase ventilation |
| 2 (Pre‑alarm) | >70°C | >1.0% | >50 ppm | >0.5 dB/m | Disconnect BMS, pre‑charge suppression system |
| 3 (Fire) | >100°C | >2.0% | >100 ppm | >1.0 dB/m | Activate gas release, then water mist after 30 s delay |
Upon reaching Stage 3, the following sequence executes:
- Immediate termination of charging/discharging via BMS.
- Activation of local exhaust fans (if present) to prevent gas accumulation.
- Release of perfluorohexanone (or other gas agent) to achieve a design concentration of 8% within 10 seconds.
- After a 30‑second hold period (to ensure gas mixing), water mist nozzles are activated for 120 seconds to cool the energy storage battery modules.
- Continuous monitoring of temperature and gas levels post‑suppression; if temperature exceeds 60°C again, a second water mist burst is triggered.
The control system uses a dual‑redundant PLC with fail‑safe design. All decision logic is based on majority voting from three composite detectors per zone.
3. Conclusion and Future Outlook
I have presented a comprehensive investigation into automatic detection and fire suppression technologies for energy storage battery prefabricated cabins. The analysis of thermal runaway mechanisms reveals that H₂ and CO serve as reliable early indicators. Among detection methods, composite systems combining temperature, gas, and smoke sensors offer the best balance of speed and accuracy. For suppression, perfluorohexanone provides fast chemical inhibition with minimal residue, while water mist excels at cooling and preventing re‑ignition. The combined gas‑water mist approach achieves superior performance with extinguishment times below 15 seconds and zero re‑ignition in tests. The coordinated control strategy, with clearly defined thresholds and staged actions, ensures rapid response while minimizing unnecessary activations.
Future work should focus on:
- Developing more accurate thermal runaway models for next‑generation energy storage battery chemistries (e.g., solid‑state, sodium‑ion).
- Leveraging artificial intelligence and machine learning to predict incipient thermal events based on BMS data, further reducing false alarms.
- Improving the scalability of the detection‑suppression system for large‑scale storage plants (multiple cabins).
- Exploring environmentally friendly alternatives to perfluorohexanone with lower global warming potential.
In conclusion, the proposed automatic detection and suppression system significantly enhances the safety of energy storage battery prefabricated cabins, supporting the reliable and sustainable growth of the electrochemical energy storage industry.