Korea, Republic of
Safe Ventilation Methods against Leaks in Hydrogen Fuel Cell Rooms in Homes
Jul 2022
Publication
Hydrogen which has a high energy density and does not emit pollutants is considered an alternative energy source to replace fossil fuels. Herein we report an experimental study on hydrogen leaks and ventilation methods for preventing damage caused by leaks from hydrogen fuel cell rooms in homes among various uses of hydrogen. This experiment was conducted in a temporary space with a volume of 11.484 m3 . The supplied pressure leak-hole size and leakage amount were adjusted as the experimental conditions. The resulting hydrogen concentrations which changed according to the operation of the ventilation openings ventilation fan and supplied shutoff valve were measured. The experimental results showed that the reductions in the hydrogen concentration due to the shutoff valve were the most significant. The maximum hydrogen concentration could be reduced by 80% or more if it is 100 times that of the leakage volume or higher. The shutoff valve ventilation fan and ventilation openings were required to reduce the concentrations of the fuel cell room hydrogen in a spatially uniform manner. Although the hydrogen concentration in a small hydrogen fuel cell room for home use can rapidly increase a rapid reduction in the concentration of hydrogen with an appropriate ventilation system has been experimentally proven.
On-Board Cold Thermal Energy Storage System for Hydrogen Fueling Process
Feb 2019
Publication
The hydrogen storage pressure in fuel cell vehicles has been increased from 35 MPa to 70 MPa in order to accommodate longer driving range. On the downside such pressure increase results in significant temperature rise inside the hydrogen tank during fast filling at a fueling station which may pose safety issues. Installation of a chiller often mitigates this concern because it cools the hydrogen gas before its deposition into the tank. To address both the energy efficiency improvement and safety concerns this paper proposed an on-board cold thermal energy storage (CTES) system cooled by expanded hydrogen. During the driving cycle the proposed system uses an expander instead of a pressure regulator to generate additional power and cold hydrogen gas. Moreover CTES is equipped with phase change materials (PCM) to recover the cold energy of the expanded hydrogen gas which is later used in the next filling to cool the high-pressure hydrogen gas from the fueling station.
Annealing Effects on SnO2 Thin Film for H2 Gas Sensing
Sep 2022
Publication
Hydrogen (H2 ) is attracting attention as a renewable energy source in various fields. However H2 has a potential danger that it can easily cause a backfire or explosion owing to minor external factors. Therefore H2 gas monitoring is significant particularly near the lower explosive limit. Herein tin dioxide (SnO2 ) thin films were annealed at different times. The as-obtained thin films were used as sensing materials for H2 gas. Here the performance of the SnO2 thin film sensor was studied to understand the effect of annealing and operating temperature conditions of gas sensors to further improve their performance. The gas sensing properties exhibited by the 3-h annealed SnO2 thin film showed the highest response compared to the unannealed SnO2 thin film by approximately 1.5 times. The as-deposited SnO2 thin film showed a high response and fast response time to 5% H2 gas at 300 ◦C of 257.34% and 3 s respectively.
Carbon-free Green Hydrogen Production Process with Induction Heating-based Ammonia Decomposition Reactor
Dec 2022
Publication
This study presents an induction heating-based reactor for ammonia decomposition and to achieve a 150 Nm3 /h carbon-free green hydrogen production process. The developed metallic monolith reactor acts by increasing the reactor temperature through an electromagnetic induction method using renewable-based electricity. As a result hydrogen is produced without the generation of air pollutants such as CO2 which are formed via the conventional production pathway. Furthermore techno-economic analysis was conducted based on exergy and economic analysis to evaluate the feasibility of the developed process. Experimentally the proposed reactor showed an ammonia conversion of 90.0 % at 600 ℃ and 7 barg. Exergy analysis indicated that the total unused exergy accounted for 45.79 % of the total exergy input giving an exergy efficiency of 54.21 % for the overall process. Furthermore the CAPEX and OPEX values are calculated as 1599567 USD and 644719 USD/y respectively; therefore the levelized cost of hydrogen (LCOH) was calculated to be 6.98 USD/kgH2. This study also demonstrated that the LCOH varies with the ammonia feed price and the process capacity and so it would be expected to decrease from 6.98 to 5.33 USD/kgH2 as the hydrogen production capacity is increased from 150 to 500 Nm3 / h. Overall our results confirm the feasibility of carbon-free green hydrogen production on on-site hydrogen refueling stations and they will be expected to advance the development of an environmental hydrogen economy.
Baking Effect on Desorption of Diffusible Hydrogen and Hydrogen Embrittlement on Hot-Stamped Boron Martensitic Steel
Jun 2019
Publication
Recently hot stamping technology has been increasingly used in automotive structural parts with ultrahigh strength to meet the standards of both high fuel efficiency and crashworthiness. However one issue of concern regarding these martensitic steels which are fabricated using a hot stamping procedure is that the steel is highly vulnerable to hydrogen delayed cracking caused by the diffusible hydrogen flow through the surface reaction of the coating in a furnace atmosphere. One way to make progress in understanding hydrogen delayed fractures is to elucidate an interaction for desorption with diffusible hydrogen behavior. The role of diffusible hydrogen on delayed fractures was studied for different baking times and temperatures in a range of automotive processes for hot-stamped martensitic steel with aluminum- and silicon-coated surfaces. It was clear that the release of diffusible hydrogen is effective at higher temperatures and longer times making the steel less susceptible to hydrogen delayed fractures. Using thermal desorption spectroscopy the phenomenon of the hydrogen delayed fracture was attributed to reversible hydrogen in microstructure sites with low trapping energy.
Charpy Impact Properties of Hydrogen-Exposed 316L Stainless Steel at Ambient and Cryogenic Temperatures
May 2019
Publication
316L stainless steel is a promising material candidate for a hydrogen containment system. However when in contact with hydrogen the material could be degraded by hydrogen embrittlement (HE). Moreover the mechanism and the effect of HE on 316L stainless steel have not been clearly studied. This study investigated the effect of hydrogen exposure on the impact toughness of 316L stainless steel to understand the relation between hydrogen charging time and fracture toughness at ambient and cryogenic temperatures. In this study 316L stainless steel specimens were exposed to hydrogen in different durations. Charpy V-notch (CVN) impact tests were conducted at ambient and low temperatures to study the effect of HE on the impact properties and fracture toughness of 316L stainless steel under the tested temperatures. Hydrogen analysis and scanning electron microscopy (SEM) were conducted to find the effect of charging time on the hydrogen concentration and surface morphology respectively. The result indicated that exposure to hydrogen decreased the absorbed energy and ductility of 316L stainless steel at all tested temperatures but not much difference was found among the pre-charging times. Another academic insight is that low temperatures diminished the absorbed energy by lowering the ductility of 316L stainless steel
Review of the Durability of Polymer Electrolyte Membrane Fuel Cell in Long-Term Operation: Main Influencing Parameters and Testing Protocols
Jul 2021
Publication
Durability is the most pressing issue preventing the efficient commercialization of polymer electrolyte membrane fuel cell (PEMFC) stationary and transportation applications. A big barrier to overcoming the durability limitations is gaining a better understanding of failure modes for user profiles. In addition durability test protocols for determining the lifetime of PEMFCs are important factors in the development of the technology. These methods are designed to gather enough data about the cell/stack to understand its efficiency and durability without causing it to fail. They also provide some indication of the cell/stack’s age in terms of changes in performance over time. Based on a study of the literature the fundamental factors influencing PEMFC long-term durability and the durability test protocols for both PEMFC stationary and transportation applications were discussed and outlined in depth in this review. This brief analysis should provide engineers and researchers with a fast overview as well as a useful toolbox for investigating PEMFC durability issues.
Risk Assessment Method Combining Independent Protection Layers (IPL) of Layer of Protection Analysis (LOPA) and RISKCURVES Software: Case Study of Hydrogen Refueling Stations in Urban Areas
Jul 2021
Publication
The commercialization of eco-friendly hydrogen vehicles has elicited attempts to expand hydrogen refueling stations in urban areas; however safety measures to reduce the risk of jet fires have not been established. The RISKCURVES software was used to evaluate the individual and societal risks of hydrogen refueling stations in urban areas and the F–N (Frequency–Number of fatalities) curve was used to compare whether the safety measures satisfied international standards. From the results of the analysis it was found that there is a risk of explosion in the expansion of hydrogen refueling stations in urban areas and safety measures should be considered. To lower the risk of hydrogen refueling stations this study applied the passive and active independent protection layers (IPLs) of LOPA (Layer of Protection Analysis) and confirmed that these measures significantly reduced societal risk as well as individual risk and met international standards. In particular such measures could effectively reduce the impact of jet fire in dispensers and tube trailers that had a high risk. Measures employing both IPL types were efficient in meeting international standard criteria; however passive IPLs were found to have a greater risk reduction effect than active IPLs. The combination of RISKCURVES and LOPA is an appropriate risk assessment method that can reduce work time and mitigate risks through protective measures compared to existing risk assessment methods. This method can be applied to risk assessment and risk mitigation not only for hydrogen facilities but also for hazardous materials with high fire or explosion risk.
Development of Visible-Light-Driven Rh–TiO2-CeO2 Hybrid Photocatalysts for Hydrogen Production
Jul 2021
Publication
Visible-light-driven hydrogen production through photocatalysis has attracted enormous interest owing to its great potential to address energy and environmental issues. However photocatalysis possesses several limitations to overcome for practical applications such as low light absorption efficiency rapid charge recombination and poor stability of photocatalysts. Here the preparation of efficient noble metal–semiconductor hybrid photocatalysts for photocatalytic hydrogen production is presented. The prepared ternary Rh–TiO2–CeO2 hybrid photocatalysts exhibited excellent photocatalytic performance toward the hydrogen production reaction compared with their counterparts ascribed to the synergistic combination of Rh TiO2 and CeO2.
Research and Development Investment and Collaboration Framework for the Hydrogen Economy in South Korea
Sep 2021
Publication
South Korea developed its hydrogen strategies to achieve carbon neutrality and dominate the hydrogen economy amidst and with the impetus of the coronavirus disease 2019 (COVID-19) pandemic. The government strives toward the goal via continuous investment in green hydrogen technologies as well as strategic collaborations. To facilitate the transition into the hydrogen economy this study presents a research and development (R&D) investment and collaboration framework as a national strategy. The framework offers abundant information to elucidate the technology R&D spectrum and regional dimensions of the strategy. Furthermore the proposed framework was applied to the Korean hydrogen economy comprising 955 nationally funded projects worth USD 565.7 million. The statuses and trends of the government’s investment in nationally funded research projects are illustrated with regard to the value chains of the hydrogen economies of 16 regions as well as nine technology clusters relating to the hydrogen economy thereby determining the research organizations that played crucial roles in each cluster of the 16 regions between 2015 and 2020. The results indicate that the research organizations in Daejeon acquired the highest government R&D funding in many hydrogen-economy-related research fields and that an R&D spectrum-based research/strategic collaboration is required to accomplish specialized complexes in the regions.
Prediction of Hydrogen Concentration in Containment During Severe Accidents Using Fuzzy Neural Network
Jan 2015
Publication
Recently severe accidents in nuclear power plants (NPPs) have become a global concern. The aim of this paper is to predict the hydrogen buildup within containment resulting from severe accidents. The prediction was based on NPPs of an optimized power reactor 1000. The increase in the hydrogen concentration in severe accidents is one of the major factors that threaten the integrity of the containment. A method using a fuzzy neural network (FNN) was applied to predict the hydrogen concentration in the containment. The FNN model was developed and verified based on simulation data acquired by simulating MAAP4 code for optimized power reactor 1000. The FNN model is expected to assist operators to prevent a hydrogen explosion in severe accident situations and manage the accident properly because they are able to predict the changes in the trend of hydrogen concentration at the beginning of real accidents by using the developed FNN model.
Hydrogen Stress Cracking Behaviour in Dissimilar Welded Joints of Duplex Stainless Steel and Carbon Steel
Jun 2021
Publication
As the need for duplex stainless steel (DSS) increases it is necessary to evaluate hydrogen stress cracking (HSC) in dissimilar welded joints (WJs) of DSS and carbon steel. This study aims to investigate the effect of the weld microstructure on the HSC behaviour of dissimilar gas-tungsten arc welds of DSS and carbon steel. In situ slow-strain rate testing (SSRT) with hydrogen charging was conducted for transverse WJs which fractured in the softened heat-affected zone of the carbon steel under hydrogen-free conditions. However HSC occurred at the martensite band and the interface of the austenite and martensite bands in the type-II boundary. The band acted as an HSC initiation site because of the presence of a large amount of trapped hydrogen and a high strain concentration during the SSRT with hydrogen charging. Even though some weld microstructures such as the austenite and martensite bands in type-II boundaries were harmless under normal hydrogen-free conditions they had a negative effect in a hydrogen atmosphere resulting in the premature rupture of the weld. Eventually a premature fracture occurred during the in situ SSRT in the type-II boundary because of the hydrogen-enhanced strain-induced void (HESIV) and hydrogen-enhanced localised plasticity (HELP) mechanisms.
Non-precious Electrocatalysts for Oxygen Evolution Reaction in Anion Exchange Membrane Water Electrolysis: A Mini Review
Sep 2021
Publication
Anion exchange membrane water electrolysis (AEMWE) is considered the next generation of green hydrogen production method because it uses low-cost non-noble metal oxide electrocatalyst electrodes and can store highpurity hydrogen under high pressure. However the commercialization of AEMWE with non-precious metal oxide electrocatalysts is challenging due to low electrocatalytic activity and durability. Overcoming the low kinetics caused by four-electron transfer is vital in addressing the low activity of non-noble metal oxide electrocatalysts for oxygen evolution reaction. This article overviews the synthesis methods and related techniques for various anode electrodes applied to AEMWE systems. We highlight effective strategies that have been developed to improve the performance and durability of the non-precious electrocatalysts and ensure the stable operation of AEMWE followed by a critical perspective to encourage the development of this technology.
Complex Hydrides for Hydrogen Storage – New Perspectives
Apr 2014
Publication
Since the 1970s hydrogen has been considered as a possible energy carrier for the storage of renewable energy. The main focus has been on addressing the ultimate challenge: developing an environmentally friendly successor for gasoline. This very ambitious goal has not yet been fully reached as discussed in this review but a range of new lightweight hydrogen-containing materials has been discovered with fascinating properties. State-of-the-art and future perspectives for hydrogen-containing solids will be discussed with a focus on metal borohydrides which reveal significant structural flexibility and may have a range of new interesting properties combined with very high hydrogen densities.
Techno-economic Analysis of On-site Blue Hydrogen Production Based on Vacuum Pressure Adsorption: Practical Application to Real-world Hydrogen Refueling Stations
Feb 2023
Publication
Although climate change can be efficiently curbed by shifting to low-carbon (blue) hydrogen as an energy carrier to achieve carbon neutrality current hydrogen production mainly proceeds via the gray pathway i.e. generates large amounts of CO2 as a byproduct. To address the need for cleaner hydrogen production we herein propose novel CO2 capture processes based on the integration of vacuum pressure swing adsorption into a gray hydrogen production process and perform retrofitting to a blue hydrogen production process for on-site hydrogen refueling stations. Techno-economic analysis reveals that the implementation of the proposed capture processes allows one to significantly reduce CO2 emission while preserving thermal efficiency and the economic feasibility of this implementation in different scenarios is determined by computing the levelized cost of hydrogen. As a result blue hydrogen is shown to hold great promise for the realization of sustainable energy usage and the net-zero transition.
Urban Hydrogen Production Model Using Environmental Infrastructures to Achieve the Net Zero Goal
Dec 2022
Publication
Land available for energy production is limited in cities owing to high population density. To reach the net zero goal cities contributing 70% of overall greenhouse gas emissions need to dramatically reduce emissions and increase self-sufficiency in energy production. Environmental infrastructures such as sewage treatment and incineration plants can be used as energy production facilities in cities. This study attempted to examine the effect of using environmental infrastructure such as energy production facilities to contribute toward the carbon neutrality goal through urban energy systems. In particular since the facilities are suitable for hydrogen supply in cities the analysis was conducted focusing on the possibility of hydrogen production. First the current status of energy supply and demand and additional energy production potential in sewage treatment and incineration plants in Seoul were analyzed. Then the role of these environmental infrastructures toward energy self-sufficiency in the urban system was examined. This study confirmed that the facilities can contribute to the city’s energy self-sufficiency and the achievement of its net-zero goal.
Economic Evaluation of an Ammonia-Fueled Ammonia Carrier Depending on Methods of Ammonia Fuel Storage
Dec 2021
Publication
This study proposed two concepts for ammonia fuel storage for an ammonia-fueled ammonia carrier and evaluated these concepts in terms of economics. The first concept was to use ammonia in the cargo tank as fuel and the second concept was to install an additional independent fuel tank in the vessel. When more fuel tanks were installed there was no cargo loss. However there were extra costs for fuel tanks. The target ship was an 84000 m3 ammonia carrier (very large gas carrier VLGC). It traveled from Kuwait to South Korea. The capacity of fuel tanks was 4170 m3 which is the required amount for the round trip. This study conducted an economic evaluation to compare the two proposed concepts. Profits were estimated based on sales and life cycle cost (LCC). Results showed that sales were USD 1223 million for the first concept and USD 1287 million for the second concept. Profits for the first and second concepts were USD 684.3 million and USD 739.5 million respectively. The second concept showed a USD 53.1 million higher profit than the first concept. This means that the second concept which installed additional independent fuel tanks was better than the first concept in terms of economics. Sensitivity analysis was performed to investigate the influence of given parameters on the results. When the ammonia fuel price was changed by ±25% there was a 15% change in the profits and if the ammonia (transport) fee was changed by ±25% there was a 45% change in the profits. The ammonia fuel price and ammonia (cargo) transport fee had a substantial influence on the business of ammonia carriers.
Effects of Hydrogen Mixture Ratio and Scavenging Air Temperature on Combustion and Emission Characteristics of a 2-stroke Marine Engine
Nov 2022
Publication
A numerical study was conducted to investigate the effects of hydrogen and scavenging air temperature (SAT) on the combustion and emission characteristics of a 2-stroke heavy-duty dual-fuel (DF) marine engine at full load. The engine had a 700 mm bore fuelled with hydrogen–methane (H2-CH4) mixtures. Three-dimensional simulations of the combustion and emission formation inside the engine cylinder with various H2 contents in the H2-CH4 mixture were performed. ANSYS FLUENT simulation software was used to analyse the engine performance in-cylinder pressure temperature and emission characteristics. The CFD models were validated against the measured data recorded from the engine experiments. The results showed that an increase in the in-cylinder peak pressure increased the engine power when the H2 content in the H2-CH4 mixture increased. Notably CO2 and soot emissions decreased (up to more than 65%) when the H2 content in the gaseous mixture increased to 50%. Specific NO emissions in the DF modes were lower than that of the diesel mode when the H2 content in the gaseous mixture was lower than 40%. However they increased compared to the diesel mode when the H2 content continued to increase. This limits the H2 amount that should be used in a gaseous mixture creating NO emissions. The results also showed that the SAT cooling method can further reduce emission problems while enhancing engine power. In particular reducing the SAT to 28 ◦C in the gaseous mixture with 10% H2 ensured that the DF mode emitted the lowest NO emissions compared to the diesel mode. This reduced NO emissions by 37.92% compared to the measured NO emissions of the research engine (a Tier II marine engine). This study successfully analysed the benefits of using an H2-CH4 mixture as the primary fuel and the SAT cooling method in a 2-stroke ME-GI heavy-duty marine engine.
Hydrogen Technology Development and Policy Status by Value Chain in South Korea
Nov 2022
Publication
Global transitions from carbon- to hydrogen-based economies are an essential component of curbing greenhouse gas emissions and climate change. This study provides an investigative review of the technological development trends within the overall hydrogen value chain in terms of production storage transportation and application with the aim of identifying patterns in the announcement and execution of hydrogen-based policies both domestically within Korea as well as internationally. The current status of technological trends was analyzed across the three areas of natural hydrogen carbon dioxide capture utilization and storage technology linked to blue hydrogen and green hydrogen production linked to renewable energy (e.g. water electrolysis). In Korea the establishment of underground hydrogen storage facilities is potentially highly advantageous for the storage of domestically produced and imported hydrogen providing the foundations for large-scale application as economic feasibility is the most important national factor for the provision of fuel cells. To realize a hydrogen economy pacing policy and technological development is essential in addition to establishing a roadmap for efficient policy support. In terms of technological development it is important to prioritize that which can connect the value chain all of which will ultimately play a major role in the transformation of human energy consumption.
Frequency Regulation of an Islanded Microgrid Using Hydrogen Energy Storage Systems: A Data-Driven Control Approach
Nov 2022
Publication
Hydrogen energy storage (HES) systems have recently received attention due to their potential to support real-time power balancing in a power grid. This paper proposes a data-driven model predictive control (MPC) strategy for HES systems in coordination with distributed generators (DGs) in an islanded microgrid (MG). In the proposed strategy a data-driven model of the HES system is developed to reflect interactive operations of an electrolyzer hydrogen tank and fuel cell and hence the optimal power sharing with DGs is achieved to support real-time grid frequency regulation (FR). The MG-level controller cooperates with a device-level controller of the HES system that overrides the FR support based on the level of hydrogen. Small-signal analysis is used to evaluate the contribution of FR support. Simulation case studies are also carried out to verify the accuracy of the data-driven model and the proposed strategy is effective for improving the real-time MG frequency regulation compared with the conventional PI-based strategy.
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