Korea, Republic of
Quantitative Risk Assessment of Hydrogen Refueling Station in Cheonan City of South Korea
Oct 2023
Publication
The average temperature of the Earth has risen due to the accumulation of greenhouse gases emitted from the usage of fossil fuels. The consequential climate changes have caused various problems fueling the growing demand for environmentally friendly energy sources that can replace fossil fuels. Batteries and hydrogen have thus been utilized as substitute energy sources for automobiles to reduce fossil fuel consumption. Consequently the number of hydrogen refueling stations is increasing due to an increase in the number of hydrogen-powered vehicles. However several incidents have been reported in the United States of America and Japan where hydrogen refueling stations have been operating for a long time. A risk assessment of hydrogen refueling stations operating in urban areas was performed in this study by calculating the risk effect range using a process hazard analysis tool (PHAST) v8.7 from DNV-GL and a hydrogen risk assessment model (HyRAM) from Sandia National Laboratories (SNL). The societal risk was assessed through a probit model based on the calculation results. The assessment results showed that the risk caused by jet fire and overpressure in an incident is lower than the ‘as low as reasonably practicable’ (ALARP) level.
The Effect of Ventilation on the Hazards of Hydrogen Release in Enclosed Areas of Hydrogen-fueled Ship
Aug 2023
Publication
This paper presents a systematic investigation that encompasses the safety assessment of a fuel preparation room (FPR) intended for a hydrogen-fueled ship. The primary objective is to determine the appropriate ventilation strategy to mitigate the risks associated with potential hydrogen leakage. The study focuses on a case involving an FPR measuring 10.2 m × 5.3 m × 2.65 m which is part of a 750 DWT hydrogen-powered fishing vessel. To identify the potential events leading to hydrogen dispersion an event tree analysis is conducted. Additionally existing regulations and guidelines related to the safety assessments of hydrogen leakage in enclosed areas are summarized and analyzed. Computational fluid dynamics FLACS-CFD are utilized for the consequence analysis in order to evaluate the impact of ventilation on hydrogen dispersion and concentration within the FPR. The research findings indicate significant effects of ventilation on the hazards and safety assessments of FPRs and high-pressure fuel gas supply systems. The study highlights that hydrogen vapor tends to accumulate at the ceiling and in the corners and spaces created by the equipment. The position and size of ventilation openings greatly influence the dispersion of hydrogen leakage. Proper ventilation design including top inlet ventilation and outlet ventilation on the opposite side helps to maintain a safe FPR by facilitating the efficient dispersion of hydrogen vapor. Moreover locating inlet ventilation on the same side as the outlet ventilation is found to hinder dispersion while the cross-ventilation achieved by placing inlets and outlets on opposite sides enhances airflow and dispersion. Consequently it is recommended to prioritize the structural design of FPRs and implement enhanced safety measures. Additionally updating the relevant regulations to address these concerns is strongly advised.
Assessment of Greenhouse Gas Emissions from Hydrogen Production Processes: Turquoise Hydrogen vs. Steam Methane Reforming
Nov 2022
Publication
Hydrogen has received substantial attention because of its diverse application in the energy sector. Steam methane reforming (SMR) dominates the current hydrogen production and is the least expensive endothermic reaction to produce grey hydrogen. This technology provides the advantages of low cost and high energy efficiency; however it emits an enormous amount of CO2. Carbon capture storage (CCS) technology helps reduce these emissions by 47% to 53% producing blue hydrogen. Methane pyrolysis is an alternative to SMR that produces (ideally) CO2-free turquoise hydrogen. In practice methane pyrolysis reduces CO2 emissions by 71% compared to grey hydrogen and 46% compared to blue hydrogen. While carbon dioxide emissions decrease with CCS fugitive methane emissions (FMEs) for blue and turquoise hydrogen are higher than those for grey hydrogen because of the increased use of natural gas to power carbon capture. We undertake FMEs of 3.6% of natural gas consumption for individual processes. In this study we also explore the utilization of biogas as a feedstock and additional Boudouard reactions for efficient utilization of solid carbon from methane pyrolysis and carbon dioxide from biogas. The present study focuses on possible ways to reduce overall emissions from turquoise hydrogen to provide solutions for a sustainable low-CO2 energy source.
A Theoretical Study on the Hydrogen Filling Process of the On-board Storage Cylinder in Hydrogen Refueling Station
May 2023
Publication
With the development of the hydrogen fuel automobile industry higher requirements are put forward for the construction of hydrogen energy infrastructure the matching of parameters and the control strategy of hydrogen filling rate in the hydrogen charging process of hydrogen refueling stations. At present the technological difficulty of hydrogen fueling is mainly reflected in the balanced treatment of reducing the temperature rise of hydrogen and shortening the filling time during the fast filling process. Vehicle hydrogen storage cylinder (VHSC) is one of the important components of hydrogen fuel cell vehicles. This study proposed a theoretical model for calculating the temperature rise in the VHSC during the high pressure refueling process and revealed the hydrogen temperature rise during refueling. A hydrogen temperature rise prediction model was constructed to elucidate the relationship between filling parameters and temperature rise. The filling process of VHSC was analyzed from the theoretical method. The theoretical analysis results were consistent with the simulation and experimental analysis results which provided a theoretical basis for the current hydrogen temperature control algorithm of the gas source in the hydrogen refueling station and then reduced the energy consumption required for hydrogen cooling in the hydrogen refueling station.
Design and Analysis of Cryogenic Cooling System for Electric Propulsion System Using Liquid Hydrogen
Jan 2023
Publication
As the demand for eco-friendly energy increases hydrogen energy and liquid hydrogen storage technologies are being developed as an alternative. Hydrogen has a lower liquefaction point and higher thermal conductivity than nitrogen or neon used in general cryogenic systems. Therefore the application of hydrogen to cryogenic systems can increase efficiency and stability. This paper describes the design and analysis of a cryogenic cooling system for an electric propulsion system using liquid hydrogen as a refrigerant and energy source. The proposed aviation propulsion system (APS) consists of a hydrogen fuel cell a battery a power distribution system and a motor. For a lab-scale 5 kW superconducting motor using a 2G high-temperature superconducting (HTS) wire the HTS motor and cooling system were analyzed for electromagnetic and thermal characteristics using a finite element method-based analysis program. The liquid hydrogen-based cooling system consists of a pre-cooling system a hydrogen liquefaction system and an HTS coil cooling system. Based on the thermal load analysis results of the HTS coil the target temperature for hydrogen gas pre-cooling the number of buffer layers and the cryo-cooler capacity were selected to minimize the thermal load of the hydrogen liquefaction system. As a result the hydrogen was stably liquefied and the temperature of the HTS coil corresponding to the thermal load of the designed lab-scale HTS motor was maintained at 30 K.
Oxy-fuel Combustion-based Blue Hydrogen Production with the Integration of Water Electrolysis
Jun 2023
Publication
Blue hydrogen is gaining attention as an intermediate step toward achieving eco-friendly green hydrogen production. However the general blue hydrogen production requires an energy-intensive process for carbon capture and storage resulting in low process efficiency. Additionally the hydrogen production processes steam methane reforming (SMR) and electrolysis emits waste heat and byproduct oxygen respectively. To solve these problems this study proposes an oxy-fuel combustion-based blue hydrogen production process that integrates fossil fuel-based hydrogen production and electrolysis processes. The proposed processes are SMR + SOEC and SMR + PEMEC whereas SMR solid oxide electrolysis cell (SOEC) and proton exchange membrane electrolysis cell (PEMEC) are also examined for comparison. In the proposed processes the oxygen produced by the electrolyzer is utilized for oxy-fuel combustion in the SMR process and the resulting flue gas containing CO2 and H2O is condensed to easily separate CO2. Additionally the waste heat from the SMR process is recovered to heat the feed water for the electrolyzer thereby maximizing the process efficiency. Techno-economic sensitivity and greenhouse gas (GHG) analyses were conducted to evaluate the efficiency and feasibility of the proposed processes. The results show that SMR + SOEC demonstrated the highest thermal efficiency (85.2%) and exergy efficiency (80.5%) exceeding the efficiency of the SMR process (78.4% and 70.4% for thermal and exergy efficiencies respectively). Furthermore the SMR + SOEC process showed the lowest levelized cost of hydrogen of 6.21 USD/kgH2. Lastly the SMR + SOEC demonstrated the lowest life cycle GHG emissions. In conclusion the proposed SMR + SOEC process is expected to be a suitable technology for the transition from gray to green hydrogen.
A Web-based Decision Support System (DSS) for Hydrogen Refueling Station Location and Supply Chain Optimisation
Jun 2023
Publication
This study presents a novel web-based decision support system (DSS) that optimizes the locations of hydrogen refueling stations (HRSs) and hydrogen supply chains (HSCs). The system is developed with a design science approach that identifies key design requirements and features through interviews and literature reviews. Based on the findings a system architecture and data model were designed incorporating scenario management optimization model visualization and data management components. The DSS provides a two-stage solution model that links demand to HRSs and production facilities to HRSs. A prototype is demonstrated with a plan for 2025 and 2030 in the Republic of Korea where 450 to 660 stations were deployed nationwide and linked to production facilities. User evaluation confirmed the effectiveness of the DSS in solving optimization problems and its potential to assist the government and municipalities in planning hydrogen infrastructure.
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.
Environmental Assessment of Hydrogen Utilization in Various Applications and Alternative Renewable Sources for Hydrogen Production: A Review
May 2023
Publication
Rapid industrialization is consuming too much energy and non-renewable energy resources are currently supplying the world’s majority of energy requirements. As a result the global energy mix is being pushed towards renewable and sustainable energy sources by the world’s future energy plan and climate change. Thus hydrogen has been suggested as a potential energy source for sustainable development. Currently the production of hydrogen from fossil fuels is dominant in the world and its utilization is increasing daily. As discussed in the paper a large amount of hydrogen is used in rocket engines oil refining ammonia production and many other processes. This paper also analyzes the environmental impacts of hydrogen utilization in various applications such as iron and steel production rocket engines ammonia production and hydrogenation. It is predicted that all of our fossil fuels will run out soon if we continue to consume them at our current pace of consumption. Hydrogen is only ecologically friendly when it is produced from renewable energy. Therefore a transition towards hydrogen production from renewable energy resources such as solar geothermal and wind is necessary. However many things need to be achieved before we can transition from a fossil-fuel-driven economy to one based on renewable energy
Review on Bubble Dynamics in Proton Exchange Membrane Water Electrolysis: Towards Optimal Green Hydrogen Yield
Dec 2023
Publication
Water electrolysis using a proton exchange membrane (PEM) holds substantial promise to produce green hydrogen with zero carbon discharge. Although various techniques are available to produce hydrogen gas the water electrolysis process tends to be more cost-effective with greater advantages for energy storage devices. However one of the challenges associated with PEM water electrolysis is the accumulation of gas bubbles which can impair cell performance and result in lower hydrogen output. Achieving an in-depth knowledge of bubble dynamics during electrolysis is essential for optimal cell performance. This review paper discusses bubble behaviors measuring techniques and other aspects of bubble dynamics in PEM water electrolysis. It also examines bubble behavior under different operating conditions as well as the system geometry. The current review paper will further improve the understanding of bubble dynamics in PEM water electrolysis facilitating more competent inexpensive and feasible green hydrogen production.
Comparative Life Cycle Greenhouse Gas Analysis of Clean Hydrogen Pathways: Assessing Domestic Production and Overseas Import in South Korea
Sep 2023
Publication
The development of a Clean Hydrogen Standard based on life-cycle greenhouse gas (GHG) emissions is gaining prominence on the international agenda. Thus a framework for assessing life-cycle GHG emissions for clean hydrogen pathways is necessary. In this study the comprehensive datasets and effects of various scenarios encompassing hydrogen production carriers (liquid hydrogen ammonia methylcyclohexane) carbon capture and storage (CCS) target analysis year (2021 2030) to reflect trends of greening grid electricity and potential import countries on aggregated life-cycle GHG emissions were presented. South Korea was chosen as a case study region and the low-carbon alternatives were suggested for reducing aggregated emissions to meet the Korean standard (5 kgCO2e/kgH2). First capturing and storing nearly entire (>90%) CO2 from fossil- and waste-based production pathways is deemed essential. Second when repurposing the use of hydrogen that was otherwise used internally applying a penalty for substitution is appropriate leading to results notably exceeding the standard. Third for electrolysis-based hydrogen using renewable or nuclear electricity is essential. Lastly when hydrogen is imported in a well-to-point-of-delivery (WtP) perspective using renewable electricity during hydrogen conversion into a carrier and reusing the produced hydrogen for endothermic reconversion reaction are recommended. By implementing the developed calculation framework to other countries' cases it was observed that importing hydrogen to regions having scope of WtP or above (e.g. well-to-wheel) might not meet the threshold due to additional emissions from importation processes. Additionally for hydrogen carriers undergoing the endothermic reconversion the approach to reduce WtP emissions (reusing produced hydrogen) may conflict with the approach to reduce well-to-gate (WtG) emission (using external fossilbased fuel). The discrepancy highlights the need to set a broader scope of emissions assessment to effectively promote the life-cycle emission reduction efforts of hydrogen importers. This study contributes to the field of clean hydrogen GHG emission assessment offering a robust database and calculation framework while addressing the effects of greening grid electricity and CCS implementation proposing low-carbon alternatives and GHG assessment scope to achieve global GHG reduction.
A Review on the Research Progress and Application of Compressed Hydrogen in the Marine Hydrogen Fuel Cell Power System
Jan 2024
Publication
The urgency to mitigate greenhouse gas emissions from maritime vessels has intensified due to the increasingly stringent directives set forth by the International Maritime Organization (IMO). These directives specifically address energy efficiency enhancements and emissions reduction within the shipping industry. In this context hydrogen is the much sought after fuel for all the global economies and its applications for transportation and propulsion in particular is crucial for cutting down carbon emissions. Nevertheless the realization of hydrogen-powered vessels is confronted by substantial technical hurdles that necessitate thorough examination. This study undertakes a comprehensive analysis encompassing diverse facets including distinct variations of hydrogen fuel cells hydrogen internal combustion engines safety protocols associated with energy storage as well as the array of policies and commercialization endeavors undertaken globally for the advancement of hydrogen-propelled ships. By amalgamating insights from these multifaceted dimensions this paper adeptly encapsulates the myriad challenges intrinsic to the evolution of hydrogen-fueled maritime vessels while concurrently casting a forward-looking gaze on their prospective trajectory.
Deep Reinforcement Learning-Based Energy Management for Liquid Hydrogen-Fueled Hybrid Electric Ship Propulsion System
Oct 2023
Publication
This study proposed a deep reinforcement learning-based energy management strategy (DRL-EMS) that can be applied to a hybrid electric ship propulsion system (HSPS) integrating liquid hydrogen (LH2 ) fuel gas supply system (FGSS) proton-exchange membrane fuel cell (PEMFC) and lithium-ion battery systems. This study analyzed the optimized performance of the DRL-EMS and the operational strategy of the LH2 -HSPS. To train the proposed DRL-EMS a reward function was defined based on fuel consumption and degradation of power sources during operation. Fuel consumption for ship propulsion was estimated with the power for balance of plant (BOP) of the LH2 FGSS and PEMFC system. DRL-EMS demonstrated superior global and real-time optimality compared to benchmark algorithms namely dynamic programming (DP) and sequential quadratic programming (SQP)-based EMS. For various operation cases not used in training DRL-EMS resulted in 0.7% to 9.2% higher operating expenditure compared to DP-EMS. Additionally DRL-EMS was trained to operate 60% of the total operation time in the maximum efficiency range of the PEMFC system. Different hydrogen fuel costs did not affect the optimized operational strategy although the operating expenditure (OPEX) was dependent on the hydrogen fuel cost. Different capacities of the battery system did not considerably change the OPEX.
Environmental Life-Cycle Assessment of Eco-Friendly Alternative Ship Fuels (MGO, LNG, and Hydrogen) for 170 GT Nearshore Ferry
May 2022
Publication
With increasing concerns about environmental pollution the shipping industry has been considering various fuels as alternative power sources. This paper presents a study of the holistic environmental impacts of eco-friendly alternative ship fuels of marine gas oil (MGO) liquefied natural gas (LNG) and hydrogen across each of their life cycles from their production to the operation of the ship. The environmental impacts of the fuels were estimated by life-cycle assessment (LCA) analysis in the categories of well-to-tank tank-to-wake and well-to-wake phases. The LCA analysis was targeted for a 170 gross tonnage (GT) nearshore ferry operating in the ROK which was conceptually designed in the study to be equipped with the hydrogen fuel cell propulsion system. The environmental impact performance was presented with comparisons for the terms of global warming potential (GWP) acidification potential (AP) photochemical ozone creation potential (POCP) eutrophication potential (EP) and particulate matter (PM). The results showed that the hydrogen showed the highest GWP level during its life cycle due to the large amount of emissions in the hydrogen generation process through the steam methane reforming (SMR) method. The paper concludes with suggestions of an alternative fuel for the nearshore ferry and its production method based on the results of the study.
Jet Flame Risk Analysis for Safe Response to Hydrogen Vehicle Accidents
Jun 2023
Publication
With an increase in the use of eco-friendly vehicles such as hybrid electric and hydrogen vehicles in response to the global climate crisis accidents related to these vehicles have also increased. Numerical analysis was performed to optimize the safety of first responders responding to hydrogen vehicle accidents wherein hydrogen jet flames occur. The influence range of the jet flame generated through a 1.8-mm-diameter nozzle was analyzed based on five discharge angles (90 75 60 45 and 30◦ ) between the road surface and the downward vertical. As the discharge angle decreases toward the road surface the risk area that could cause damage moves from the center of the vehicle to the rear; at a discharge angle of 90◦ the range above 9.5 kW/m2 was 1.59 m and 4.09 m to the front and rear of the vehicle respectively. However at a discharge angle of 30◦ it was not generated at the front but was 10.39 m to the rear. In response to a hydrogen vehicle accident first responders should perform rescue activities approaching from a diagonal direction to the vehicle front to minimize injury risk. This study can be used in future hydrogen vehicle design to develop the response strategy of the first responders.
Risk Assessment of Explosion Accidents in Hydrogen Fuel-Cell Rooms Using Experimental Investigations and Computational Fluid Dynamics Simulations
Oct 2023
Publication
For the safe utilization and management of hydrogen energy within a fuel-cell room in a hydrogen-fueled house an explosion test was conducted to evaluate the potential hazards associated with hydrogen accident scenarios. The overpressure and heat radiation were measured for an explosion accident at distances of 1 2 3 5 and 10 m for hydrogen–air mixing ratios of 10% 25% 40% and 60%. When the hydrogen–air mixture ratio was 40% the greatest overpressure was 24.35 kPa at a distance of 1 m from the fuel-cell room. Additionally the thermal radiation was more than 1.5 kW/m2 which could cause burns at a distance of 5 m from the hydrogen fuel-cell room. Moreover a thermal radiation in excess of 1.5 kW/m2 was computed at a distance of 3 m from the hydrogen fuel-cell room when the hydrogen–air mixing ratio was 25% and 60%. Consequently an explosion in the hydrogen fuel-cell room did not considerably affect fatality levels but could affect the injury levels and temporary threshold shifts. Furthermore the degree of physical damage did not reach major structural damage levels causing only minor structural damage.
Which Is Preferred between Electric or Hydrogen Cars for Carbon Neutrality in the Commercial Vehicle Transportation Sector of South Korea? Implications from a Public Opinion Survey
Feb 2024
Publication
South Korea has drawn up plans to reduce greenhouse gases by 29.7 million tons by supplying 4.5 million electric and hydrogen cars by 2030 to implement the “2050 carbon neutrality” goal. This article gathers data on public preferences for electric cars (ECs) over hydrogen cars (HCs) in the commercial vehicle transportation sector through a survey of 1000 people. Moreover the strength of the preference was evaluated on a five-point scale. Of all respondents 60.0 percent preferred ECs and 21.0 percent HCs the former being 2.86 times greater than the latter. On the other hand the strength of the preference for HCs was 1.42 times greater than that for ECs. Factors influencing the preference for ECs over HCs were also explored through adopting the ordered probit model which is useful in examining ordinal preference rather than cardinal preference. The analyzed factors which are related to respondents’ characteristics experiences and perceptions can be usefully employed for developing strategies of promoting carbon neutrality in the commercial vehicle transportation sector and preparing policies to improve public acceptance thereof.
Economic Prospects of Taxis Powered by Hydrogen Fuel Cells in Palestine
Feb 2024
Publication
Recently major problems related to fuel consumption and greenhouse gas (GHG) emissions have arisen in the transportation sector. Therefore developing transportation modes powered by alternative fuels has become one of the main targets for car manufacturers and governments around the world. This study aimed to investigate the economic prospects of using hydrogen fuel cell technology in taxi fleets in Westbank. For this purpose a model that could predict the number of taxis was developed and the expected economic implications of using hydrogen fuel cell technology in taxi fleets were determined based on the expected future fuel consumption and future fuel cost. After analysis of the results it was concluded that a slight annual increase in the number of taxis in Palestine is expected in the future due to the government restrictions on issuing new taxi permits in order to get this sector organized. Furthermore using hydrogen fuel cells in taxi fleets is expected to become more and more feasible over time due to the expected future increase in oil price and the expected significant reduction in hydrogen cost as a result of the new technologies that are expected to be used in the production and handling of hydrogen.
Experimental Analysis of the Effects of Ship Motion on Hydrogen Dispersion in an Enclosed Area
Apr 2023
Publication
This study aims to experimentally quantify the hydrogen diffusion characteristics by ship motion. Hydrogen leakage experiments were conducted under various ship motion conditions and the corresponding hydrogen concentrations for each sensor were expressed by an equation. The experimental facility was a scale model of the hydrogen fuel storage room of a ship. An experiment was conducted by implementing the roll and pitch motions of the ship as well as motion direction using a ship simulator. In the equation describing the hydrogen concentration the minimum and maximum root mean square deviations were 0.987 and 0.707 respectively and the correlations were 0.000109 and 0.0012289. Although the results differed as per the sensor location the hydrogen concentration was affected by the motion period of the ship. The experimental results and prediction equations can be useful for sensor and vent location selection by predicting the concentration when hydrogen leaks in ships in motion.
Heat Integration of Liquid Hydrogen-Fueled Hybrid Electric Ship Propulsion System
Nov 2023
Publication
This study introduced the methodology for integrating ethylene glycol/water mixture (GW) systems which supply heat energy to the liquid hydrogen (LH2 ) fuel gas supply system (FGSS) and manage the temperature conditions of the battery system. All systems were designed and simulated based on the power demand of a 2 MW class platform supply vessel assumed as the target ship. The LH2 FGSS model is based on Aspen HYSYS V14 and the cell model that makes up the battery system is implemented based on a Thevenin model with four parameters. Through three different simulation cases the integrated GW system significantly reduced electric power consumption for the GW heater during ship operations achieving reductions of 1.38% (Case 1) 16.29% (Case 2) and 27.52% (Case 3). The energy-saving ratio showed decreases of 1.86% (Case 1) 21.01% (Case 2) and 33.80% (Case 3) in overall energy usage within the GW system. Furthermore an examination of the battery system’s thermal management in the integrated GW system demonstrated stable cell temperature control within ±3 K of the target temperature making this integration a viable solution for maintaining normal operating temperatures despite relatively higher fluctuations compared to an independent GW system.
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