Ev-charging in parking structures

Best Practices

Background

The increasing adoption of electric vehicles (EVs) has brought new challenges to fire protection, insurance, and risk engineering, particularly in parking garages. This document outlines the hazards associated with EV chargers, the problems faced by fire brigades, and notable losses, followed by integrated guidelines for fire protection and risk management.

Understanding hazards of EV-Charging

EV fires are notoriously difficult to extinguish compared to conventional vehicle fires. Several factors contribute to this challenge, such as high temperatures, risk of re-ignition and toxic / flammable fumes. This is why it is important to mitigate risks associated with EV fires, especially in shopping malls and airport parking garages where many cars are parked charging closely to one another.

Lithium-ion batteries in EVs can fail and burn differently from internal combustion engine vehicles. When these batteries fail, they undergo thermal runaway, where a single cell failure can cause the production of heat, oxygen, and flammable and toxic gases. This process can spread to adjacent cells, leading to rapid fire growth or explosion due to exothermic chemical reactions.

Electrical faults, such as short circuits, can occur in EV chargers, leading to overheating and potential fires. These faults can be caused by manufacturing defects, improper installation, or damage to the charging equipment.

Overcharging and overheating of EV batteries can result in fires. Chargers that do not regulate temperature, voltage, or current correctly can cause batteries to overheat and ignite.

The electrolyte used in lithium-ion batteries is hydrocarbon-based and can lead to intense fires once ignited. These fires are very difficult to extinguish and can reignite due to ongoing exothermic chemical reactions (release of hydrofluoric acid in fire event).


Notable losses

A fire broke out in a Stuttgart bus depot in Gaisburg at the charging stations for electric buses located in the central shelter. The parking facility, measuring 140 by 100 meters, can accommodate about 100 buses, including the charging stations for electric buses. Within eight minutes of the first fire detection, the fire department confirmed that ten buses were fully engulfed in flames. Thirty-eight buses were driven directly out of the hall, while sixteen others were in the containment area or positioned in front of and next to the hall. In total, twenty-five buses were destroyed, and the parking facility was at risk of collapse but ultimately did not collapse. The damage amounts to tens of millions of euros. The cause of the fire was the charging process of an electric bus.

A fire at Stavanger Airport in Norway caused significant damage and highlighted the challenges of dealing with EV fires in parking structures. The fire brigade faced difficulties due to the confined space and the intensity of the flames. The fire is believed to have started in an electric vehicle, resulting in heavy smoke and explosions.

In another recent incident in a parking garage in a Madrid suburb, two firefighters lost their lives following a suspected explosion of accumulated fire gases from a burning electric vehicle that caught fire after a collision while parking. The parking garage reportedly had poor ventilation, which contributed to the rapid and explosive spread of the fire.


Guidelines for fire protection and risk management in enclosed parking structures

Risk Analysis

  • Conduct a detailed risk analysis of hazards and controls in place during the planning phase of EV chargers.
  • Local laws and regulations regarding the charging area must also be applied. Relevant risk topics stating the higher level of protection, whether from local laws or this best practice guide, should be followed.

Control and Regular testing

  • Integrate charging areas in monthly or weekly inspections, and perform maintenance according to the manufacturer’s instructions.
  • A protective device for overcharging and deep discharging should be considered.
  • Implement yearly testing and IR thermography inspections for all chargers. This should be conducted by a specialized contractor or specially trained employees of the electrical maintenance department.
  • For large stations, full testing, including current injection of protection relays and insulation resistance, should be conducted.

Emergency Planning

  • Install charging areas where vehicles can be easily removed and have easy access for manual firefighting, such as upper levels in underground parking. For above-ground parking structures, the charging area could be located on the top floor to prevent the lower building structure from being exposed to high temperatures in a fire event (as heat can be released easier).
     
  • Implement a response plan for any abnormal situation, such as shock, overheating, or gas release:
    • Identify the fault.
    • Disconnect from the charger, emergency shut down for chargers (refer to the manufacturer’s instructions for electrical disconnection).
    • Provide access to charging stations for emergency removal of EVs. This can allow EVs to be moved outdoors, away from buildings or combustible storage, using safe and appropriate handling devices.
    • Maintain a permanent watch until the fire service responds.
    • Manage extinguishing water to prevent pollution. Loss experience indicates that this type of fire requires a large quantity of water for continuous cooling, even after the flames have been extinguished.
       
  • Train employees on the fire risks associated with lithium-ion batteries, including potential runaway and fire scenarios, ensuring that personnel always intervene safely and without taking any risks.
     
  • The fire department should be included in the planning stages of installing EV chargers in the parking structure, enabling them to provide feedback on potential firefighting plans.

Fire Protection Considerations

  • The EV-Chargers should either be free standing or mounted to a fire resistant / non-combustible wall.
  • To limit the potential fire spread, the charging area should be divided into sections having a maximum of 8 EVs / charging spots in one section.
  • The sections should be divided using non-combustible / fire resistant materials (e.g. brickwork, concrete, etc.), alternatively the fire division could be ensured by a minimum distance of 10m free space.
  • The charging area should be well ventilated, either located near natural air source / flow or mechanically ventilated. The ventilation also must be closely coordinated with the other installed fire protection / detection systems (e.g. sprinkler system).
  • Charging areas should have automatic fire detection (e.g. thermal detectors / IR-cameras, smoke detection, or similar) to ensure immediate alarming of the fire brigade and evacuation of the area.
  • Charging areas should have gas detection, to supervise the charging operation.
  • The entire parking structure should be protected by an automatic sprinkler system with a minimum coverage of 12,2mm/min over 230m² for a wet system or 300m² for a dry system in accordance with NFPA 13 for at least a minimum of 90 minutes. The battery cooling is crucial, even if flames of fire have already been extinguished (potential risk of re-ignition).
  • Provide an adequate water supply for the sprinkler system, but also for manual firefighting (if not already available through public hydrant network). Depending on the parking structure, standpipes should be provided for fire brigade intervention.
  • Implement an interlock system to shut down electricity to chargers when fire detection, gas-detection or the sprinkler system are alerted / activated.
  • Ensure charging areas are free of combustible materials and storage.

Conclusion

The dynamic landscape of EVs and their charging infrastructure necessitates continuous updates to fire protection standards. By adhering to these guidelines and principles, designers, builders, and regulatory bodies can ensure the safety of EV users and the protection of property. Insurance companies play a crucial role in this process by assessing risks, ensuring compliance, and promoting best practices in fire protection and risk engineering.

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