Safety technology for hydrogen infrastructure underground
As an energy source that would help countries achieve carbon neutrality and energy security, hydrogen energy is being sought after globally as the energy source of the future. To this end, the European Union(EU) has introduced its strategy on hydrogen, implementing its plan to invest €470 billion(623 trillion Korean won) in 10 years to build a hydrogen-based society in the region. Germany, one of the most ardent supporters of global green initiatives, has put forward a national hydrogen strategy to invest a total of 1.2 trillion Korean won by 2030. The South Korean government is also investing in hydrogen city projects and infrastructure construction to inch closer to getting the hydrogen economy up and running.
The Korea Institute of Civil Engineering and Building Technology (KICT, President Kim Byung-suk) has announced its plan to develop technologies pertaining to the entire course of an underground hydrogen infrastructure project, from its design and construction to its operation and management. Such technologies would fundamentally improve the safety of hydrogen facilities. The construction of new infrastructure in the CBD area may bring a more efficient integration with other renewable energy networks and help the development of source technologies for hydrogen infrastructure construction, technologies for which South Korea has depended on sourcing from other advanced countries.
Safe and reliable infrastructure is crucial to the establishment of a hydrogen ecosystem. However, any ground-level hydrogen facility project tends to face fierce opposition from local residents, and the alternative of building them peripherally makes the project less cost-effective and efficient.
Dr. Kim Yangkyun of the Hydrogen-infrastructure Research Cluster at KICT has developed the core safety engineering technologies for building reliable hydrogen infrastructure underground along with an active control system to mitigate the impact of possible hydrogen leaks and blasts. The new system can help control the ambient hydrogen concentration within an underground facility at all times via forced ventilation and can reduce risk up to 80% compared with similar above-ground facilities thanks to the introduction of roof-type vents that minimize blast overpressure in times of an emergency.
Basically, any underground hydrogen infrastructure is an enclosed space. All risks of a potential blast should be eliminated by keeping the ambient hydrogen concentration below the Lower Flammable Limit (LFL) whenever a leak occurs. The active control system that Dr. Kim Yangkyun’s research team proposed maintains the quality of the atmosphere of the enclosed space to a normal level and can prevent blast accidents at times of emergency hydrogen gas leaks. An optimized interpretation was used, including multiple factors (shape, location, intake, and outtake capacities of the inlet/outlet) to formulate the conditions for ordinary times and for an emergency where the concentration of hydrogen gas in the facility is kept below the LFL or 4% of hydrogen by volume.
If the active control system malfunctions and an explosion occurs, such an impact should be minimal. The roof-type vent of the deflagration venting system can reduce damage from blast overpressure inside the facility to a 20th. The real-scale experiment of vented deflagration conducted at KICT in 2021 showed that the maximum overpressure reduction effect could be obtained due to a sudden drop in blast overpressure when the explosion vent is bigger than the vent coefficient standard of 2.2. The effectiveness remained constant regardless of the hydrogen concentration or point of the deflagration. Another model was presented to calculate the size of the roof-type vent for the safe design of the underground hydrogen facility. The improved model was built on the minimum vent size model specified in guide NFPA68 of the US National Fire Protection Association to apply to underground hydrogen facilities.
The research team focused on the fusion of functions: ventilations in normal time and after a blast accident. Dr. Kim Yangkyun, the head of the research team said: “The dual system of active control ventilation and the roof type vent is an integrated security technology for both emergency and non-emergency situations responding to all risks incurred in an accident by making the most of the limited cross-section area of the vent.”