Overview
As global warming continues and the crisis caused by climate change grows, international efforts to resolve this problem are strengthening. In relation to this, many countries have introduced strict regulatory measures to reduce the exhaust gas of Internal Combustion Engine Vehicles (ICEVs) and have promoted the distribution of green vehicles through policies such as Electric Vehicle (EV) subsidies. According to the Global EV Outlook 2023 published by the International Energy Agency (IEA), the number of EVs operating worldwide is expected to increase from about 30 million in 2022 to about 240 million in 2030, showing an annual growth rate of about 30%.

In addition, the sales of EVs, which accounted for less than 5% of the total new car sales worldwide (2020), are increasing to 9% (2021) and 14% (2022) (expected to account for 30% in 2030), and the sales ratio of EVs in the total new car market is rapidly rising. As the ownership and sales of EVs increase worldwide, the number of EVs transported by Pure Car and Truck Carrier (hereinafter, PCTC) is also increasing significantly. Therefore, accidents related to EV transportation, such as EV fires on PCTC, are also inevitably expected to increase.

To prevent and minimize the damage of accidents related to EV fires on PCTC, KR conducted a HAZID (Hazard Identification) workshop (KR headquarters, 2024.01.23) with experts from various organizations such as shipping companies and shipyards. The HAZID analysis procedure is shown in [Figure 1] below, and through this analysis, major hazards and their causes and consequences were identified, and safety measures to reduce the risk level were systematically derived.

[Figure 1] HAZID Study Procedure

Characteristics of EV Fires on PCTC
Lithium-ion batteries, the power source of EVs, have many advantages such as high energy/power density, long life, and high efficiency. However, compared to other battery technologies, they have the disadvantages of having a narrow range of voltage and temperature for normal operation, being composed of flammable organic materials for the battery electrolyte, and having a very high reactivity of the main component, lithium.

The battery temperature can rise due to causes such as impact, overheating, overcharging, etc., which can cause gas emission or thermal runaway generating heat. If thermal runaway occurs in one cell, it can propagate to adjacent cells, causing jet fire, gas emission, and in severe cases, explosion.

Especially, once thermal runaway starts, even without oxygen supply from the outside, the fire can continue and lead to explosion through heat, flammable/toxic gas, and oxygen generation from the battery itself. The fire caused by thermal runaway shows different patterns depending on the SoC (State of Charge) level of the battery, as shown in [Figure 2].

This HAZID analysis focused on EV fires that can occur on PCTCs during transportation and cargo loading/unloading operations. PCTC operation modes are divided into two modes, transporting operation (Mode 1) and loading/unloading operation (Mode 2), for more effective discussions, and analyzed the risk types for human and asset aspects.

  · Mode 1 – Transporting Operation (Cargo Management Onboard)
  · Mode 2 – Loading/Unloading Operation (including Cargo Lashing Operation)

In addition, Fire Safety Functions of PCTC are divided into five functions as follows, and potential risk scenarios related to the functions are discussed.

  · Function 1 – Fire Protection Scheme
  · Function 2 – Fire Prevention
  · Function 3 – Fire Detection & Confirmation 
  · Function 4 – Fire Suppression (Firefighting & Containment)
  · Function 5 – Means of Escape

The distribution of the total 18 hazardous scenarios identified through the HAZID workshop is compared according to the risk level by operation mode (Mode 1 vs Mode 2) and the risk type (Human risk vs Asset risk) as shown in [Figure 4]. The risk scenarios related to the cargo management and transporting operation (Mode 1) show a higher risk level than the cargo loading/unloading operation (Mode 2) overall.

In particular, it is shown that the frequency of the risk scenarios by mode was not significantly different, but the severity of the consequences when an accident occurred in Mode 1 is more serious. As per the distribution of the risk scenarios in terms of human and asset risk, it can be noted that the severity of the asset risk-related scenarios is slightly higher.

        (a) Mode 1 vs Mode 2                                 (b) Human risk vs Asset risk

[Figure 4] Hazardous Scenario Distribution by Operation Mode & Risk Type

Main Discussions for EV Fires on PCTC
Through the HAZID workshop, various hazard scenarios related to EV fires on PCTC were identified, which could occur during the transporting operation (Mode 1) and loading/unloading operation (Mode 2). In relation to this, fire safety functions were discussed in detail, and the summary of the discussion is as follows.

1) Provide fire protection scheme clearly considering EV fires characteristics
  · For Operation Mode 1: e.g., Establish a fire protection strategy for EV fire during transportation to minimize the spread of fire onboard until external support (onshore) can be received, etc.
  · For Operation Mode 2: e.g., Establish a fire protection strategy for EV fire during loading and unloading operation to support land-based professional firefighters, and EV fire response during loading and unloading operation is performed by land-based professional firefighters, etc.

2) Cooperation among stakeholders is necessary to reduce risks of EV fires on PCTC
  · SoC limitations of EV battery (identified as a key issue for reducing the risk of EV fires): e.g., governments, shippers, shipowners, etc.
  · Loading ICEVs and EVs separately on PCTC: e.g., cargo terminals, shippers, shipowners, etc.   
  · Involving shore-based firefighting services for loading/unloading operation mode: e.g., cargo terminals, nearby fire stations (professional firefighters), shipowners, etc.
  · Training procedures for crew, stevedores, shore-based firefighters: e.g., governments, cargo terminals, shipowners, etc.

3) Revitalize research and information sharing related to EV maritime transportation & fire characteristics
  · Fire characteristics of EV battery according to SoC level and SoC limit criteria for maritime transportation
  · Temperature change characteristics of PCTC car deck according to transporting environment
  · PCTC fire simulation: ventilation effect, smoke flow characteristics, impact of EV fire on fire & safety system, etc.
  · Ship’s stability impact by PCTC fire: effect of firefighting water used, weight change of burning vehicles, adverse weather conditions, etc.

Conclusions
KR identified potential risk factors related to EV fires during transportation and loading/unloading operations of PCTC through the risk analysis (HAZID), and derived appropriate safety measures to reduce the risk level for a total of 18 risk scenarios. These should be reasonably reviewed and implemented in the establishment of EV fire response strategy or PCTC design stage considering the operation of transporting and loading/unloading of EVs on PCTC in the future.
[Source: Risk Analysis for EV Fires on PCTC, HAZID Report, KR-HSE-HAZD-RPT-092, Rev.0, 2024]

KR will continue to monitor the trends and results of related R&D projects and provide customers with safety improvement and technical support for PCTC EV fire protection in line with the latest technology and regulatory trends.

※ We would like to express our gratitude to the experts from the companies and organizations below who attended the HAZID workshop and provided many significant opinions for reducing the risk level of EV fires on PCTC.