Research Information

Technology for Fire Safety in Underground Spaces to Support the Commercialization of Fuel Cell Electric Vehicles
  • Date2021-03-30
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Technology for Fire Safety in Underground Spaces to Support the Commercialization of Fuel Cell Electric Vehicles

 

 

▲ Research Fellow Yoo Yong-ho, Department of Fire Safety Research

 

 

Foreword


The two keywords that best summarize the trend of today's global automotive market are "electric" and "self-driving." These paradigms, which can be observed in the automotive industry of the EU, the US, and also Korea, sum up a strategy pursued by developed nations seeking to lead the future car industry to induce investment and create jobs in related manufacturing and service industries, which would function as a national growth engine. As the key nations of the world, with the exception of the US, are in support of the Paris Agreement, the shift toward electric vehicles is in line with their efforts to reduce vehicle-emitted carbon dioxide in order to meet their individual energy efficiency improvement and pollutant emission reduction targets.


Also notable are the large-scale underground developments taking place around the world in response to a continuing increase in the demand for mobility, and to environmental changes in metropolitan areas. The idea is to keep above-ground environments pleasant and to make use of deep-underground spaces as a sustainable development option. Today, in Korea, traffic inefficiency in Seoul its surrounding area is a serious issue causing economic losses that amount to KRW 12.5 trillion each year (OECD Territorial Reviews for Seoul, 2002). Statistics from the Korea Transport DataBase of the Korea Transport Institute indicate that this cost will increase at a rate of 5.88% each year to reach a staggering KRW 16 trillion by 2031. As such, underground developments in Korea are expected to be accelerated.


This report outlines the present and future of environment-friendly vehicles. In particular, safety technology for underground developments taking place in support of the hydrogen economy and the increased use of hydrogen vehicles are examined.

 

Table 1. Different Types of Environment-friendly Vehicles

 

 

Korea's Fuel Cell Electric Vehicle Industry


A commitment to reducing carbon dioxide emission requires a switch from fossil fuel-run combustion engine vehicles to electric vehicles. Through systemic reforms, the key nations are aiming for the elimination of internal combustion engine vehicles by 2030, or by 2040 at the latest. As can be seen in Table 1, the different types of electric vehicles include battery electric vehicles, plug-in hybrid electric vehicles, hybrid electric vehicles, and fuel cell electric vehicles. A fuel cell electric vehicle, powered by electricity generated using hydrogen, uses fuel cells in place of a battery or combines fuel cells with a battery or a supercapacitor to supply electricity to its onboard motor. By sucking in air from the atmosphere, it induces a chemical reaction between oxygen and hydrogen in its fuel cells to generate electrical energy and run its motor. Unlike other electric vehicles, a fuel cell electric vehicle uses fuel cells for power generation and a secondary battery for power storage. As the secondary battery is for storing just a small quantity of energy, it characteristically has a small capacity.


Some notable facts about the Korean hydrogen vehicle industry are that it was responsible for the world’s first mass production of hydrogen vehicles in 2013, and produces hydrogen vehicles capable of the longest driving range in the world. In addition, 99% of the core parts used in Korean-made hydrogen vehicles are produced domestically. Korea's developed petrochemical industry and extensive experience in the running of industrial plants mean that the Korean hydrogen vehicle industry has access to the hydrogen pipelines and high-purity hydrogen production technology required for hydrogen supply (approximately 1.64 million tons a year as of January 2019), that it is capable of creating sufficient demand for hydrogen and achieving economic efficiency of hydrogen, and that through facility expansion and process conversion, it will be capable of supplying by-product hydrogen on a large scale. In its "Roadmap to a Hydrogen Economy" announced January 2019, the Korean government expressed its vision of an industrial ecosystem that would foster a hydrogen economy largely constituted of hydrogen vehicles and fuel cells. As can be seen in Figure 1, plans are in place to increase the number of fuel cell electric vehicles in use from 889 in 2018 to 81,000 (65,000 in Korea alone) by 2022, and to 6.2 million (2.9 million in Korea alone) by 2040. Plans are being formed to supply buses, taxis, and commercial trucks that run on hydrogen.

 

Figure 1. The Present and Future of the Korean Hydrogen Vehicle Industry

 

 

Use of Underground Space in Various Countries


Countries around the world, recognizing the importance of underground development for the future benefit of the environment, are engaged in the building of underground infrastructure, underground future cities, and underground expressways. In Europe and the US, roads are being built deep under downtown areas as a starting point for the conservation of above-ground green areas, to solve the problem of traffic congestion, and to promote sustainable development and green growth. Prime examples include The “Big Dig" of Boston (US); the Shinjuku Central Loop Line of Tokyo (Japan); and the A86 Underground Ring Expressway of Paris (France). In Korea, a proposal was developed in 2009 to construct underground expressways that would meet the rapidly increasing demand for expressways in the Seoul area and reduce traffic congestion in the existing road network by increasing road capacities. Table 2 shows the wide range of large-scale underground road construction projects currently being planned and under review in Korea.

 

Table 2. Planned Underground Road Projects of Korea

 

 

Dangers of Fire and Explosions in an Underground Space


Underground developments are particularly vulnerable to fire. In the last five years, a total of 130 cases of accidents involving fire in a tunnel, roughly 26 a year, were reported in Korea (National Fire Data System). A notable one occurred in Dalseong Tunnel 2, in which a fire started by an overheated brake lining of a vehicle carrying a missile spread to the wooden encasement containing the missile and caused an explosion, resulting in damages to the tunnel ceiling that included longitudinal and net-shaped cracks 0.3 mm to 1 mm wide, scaling, and spalling, as well as surface scaling in paved surfaces.


Underground developments are particularly vulnerable to fire. In the last five years, a total of 130 cases of accidents involving fire in a tunnel, roughly 26 a year, were reported in Korea (National Fire Data System). A notable one occurred in Dalseong Tunnel 2, in which a fire started by an overheated brake lining of a vehicle carrying a missile spread to the wooden encasement containing the missile and caused an explosion, resulting in damages to the tunnel ceiling that included longitudinal and net-shaped cracks 0.3 mm to 1 mm wide, scaling, and spalling, as well as surface scaling in paved surfaces.

 

Figure 2. Fire Experiment on a Hydrogen Vehicle

 

 

Safety Technology for Response to Leakages, Fires, and Explosions Involving a Fuel Cell Electric Vehicle in a Semi-enclosed Underground Space


As a nation anticipating the mass commercialization of fuel cell electric vehicles, we should identify and develop countermeasures to address the risks associated with the operation of fuel cell electric vehicles, and with accidents involving a fuel cell electric vehicle, including the characteristics of a fire occurring in a typical underground space. Hydrogen is a gas with no color, scent, taste, or toxicity. Hydrogen is also the lightest the element. At one-fourteenth the weight of oxygen, when released into the atmosphere hydrogen characteristically disperses at a high speed of 20m/s. Due to its low minimum ignition energy level of 0.02 MJ, static electricity can ignite hydrogen to cause a fire. With a flammability limit of 4% to 75%, hydrogen can cause a fire or explosion in a wide range of conditions. Today's typical fuel cell electric vehicle comes with 2 or 3 pressurized 700 bar hydrogen tanks fitted under the rear seats or the trunk. Each of these tanks supplies hydrogen to a fuel cell stack. Each hydrogen tank is equipped with a thermally activated pressure relief device, an essential safety device, which on detecting abnormal temperature or pressure, automatically opens the valve to release pressurized hydrogen from the tank to adjust the pressure inside the tank. For such a system, a technology that addresses the risk of gas leakage or a jet fire/explosion caused by a malfunction of the safety device or damage to a hydrogen tank in a car accident is needed. In recognition of the research trend in this technology in key nations around the world, the National Fire Agency of Korea commissioned research and development related to response to fires caused directly or indirectly by a fuel cell electric vehicle in a semi-enclosed underground space. The Korea Institute of Civil Engineering and Building Technology (KICT) is currently spearheading said research and development endeavors, in which fire safety technology for an improved field response to fires and explosions caused by a fuel cell electric vehicle in an underground space such as a tunnel or an underground parking lot is being researched and developed as shown in Figure 3. The KICT is concurrently carrying out research in the formation of standard operating procedures for the optimal control of different types of fire and in the risks of leakage and fire posed by different types of hydrogen charging stations to provide the future hydrogen industry with valuable and essential safety technology.

 

Figure 3. Development of Technologies to Respond to Gas Leakages and Fires Involving an FCEV in a Semi-enclosed Space Under Different Conditions

 

 

Conclusion


Hydrogen is a green energy source that can be the solution to humanity's energy and environmental issues, and we must prepare to make a switch to a hydrogen-based society. Such a change would align with the paradigm shift of phasing out fossil fuel use and nuclear power generation, while achieving greenhouse gas reduction targets. Of all the technologies required for a hydrogen society, safety technology is paramount. In consideration of this, safety reviews based on qualitative and quantitative risk assessments and analyses should be prioritized.

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