Korea, Republic of

In the maritime domain hydrogen fuel cell propulsion and autonomous vessels are two important issues that are yet to be implemented together because of a few challenges. It is obvious that there are several individual safety studies on Maritime Autonomous Surface Ships and hydrogen storage as well as fuel cells based on various risk assessment tools but the combined safety studies that include hydrogen fuel cells on autonomous vessels with recent risk analysis methods are extremely limited. This research chooses the “System-Theoretic Process Analysis” (STPA) method which is a recent method for potential risk identification and mitigation. Both hydrogen and autonomous vessels are analyzed and assessed together with the STPA method. Results are not speculative but rather flexible compared to conventional systems. The study finds a total of 44 unsafe control actions (UCAs) evolved from human and central control unit controllers through STPA. Further the loss scenarios (LS) are identified that lead to those UCAs so that loss scenarios can be assessed and UCAs can be mitigated for safe operation. The objective of this study is to ensure adequate safety for hydrogen fuel cell propulsion on autonomous vessels.

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.

Industrial sectors pivotal for the economic prosperity of nations rely heavily on affordable reliable and environmentally friendly energy sources. Industries like iron and steel oil refineries and coal-fired power plants while instrumental to national economies are also the most significant contributors to waste gases that contain substantial volumes of carbon monoxide (CO). CO can be converted to a highly efficient and carbon free fuel hydrogen (H2) through a well-known water gas shift reaction. However the untapped potential of H2 from waste industrial streams is yet to be explored. This is the first article that investigates the potential of H2 production from industrial waste gases. The available resource (i.e. CO) and its H2 production potential are estimated. The article also provides insights into the principal challenges and potential avenues for long-term adoption. The results showed that 249.14 MTPY of CO are available to produce 17.44 MTPY of H2 annually. This suggests a significant potential for H2 production from waste gases to revolutionize industrial waste management and contribute significantly towards Sustainable Development Goals 7 9 and 13ensuring access to affordable reliable sustainable and modern energy for all and taking decisive climate action respectively.

In this study we examined the effect of CO2 injection into deep saline aquifers considering impurities present in blue hydrogen production. A fluid model was designed for reservoir conditions with impurity concentrations of 3.5 and 20%. The results showed that methane caused density decreases of 95.16 and 76.16% at 3.5 and 20% respectively whereas H2S caused decreases of 99.56 and 98.77% respectively. Viscosity decreased from 0.045 to 0.037 cp with increasing methane content up to 20%; however H2S did not affect the viscosity. Notably CO2 with H2S impacted these properties less than methane. Our simulation model was based on the Gorae-V properties and simulated injections for 10 years followed by 100 years of monitoring. Compared with the pure CO2 injection methane reached its maximum pressure after eight years and eleven months at 3.5% and eight years at 20% whereas H2S reached maximum pressure after nine years and two months and nine years and six months respectively. These timings affected the amount of CO2 injected. With methane as an impurity injection efficiency decreased up to 73.16% whereas with H2S it decreased up to 81.99% with increasing impurity concentration. The efficiency of CO2 storage in the dissolution and residual traps was analyzed to examine the impact of impurities. The residual trap efficiency consistently decreased with methane but increased with H2S. At 20% concentration the methane trap exhibited higher efficiency at the end of injection; however H2S had a higher efficiency at the monitoring endpoint. In carbon capture and storage projects methane impurities require removal whereas H2S may not necessitate desulfurization due to its minimal impact on CO2 storage efficiency. Thus the application of carbon capture and storage (CCS) to CO2 emissions containing H2S as an impurity may enable economically viable operations by reducing additional costs.

Hydrogen as fuel has been considered as a feasible energy carry and which offers a clean and efficient alternative for transportation. During the high pressure filling the temperature in the hydrogen storage tank (HST) may rise rapidly due to the hydrogen compression. The high temperature may lead to safety problem. Thus for fast and safely refueling the hydrogen several key factors need to be considered. In the present study by the thermodynamics theories a mathematical model is established to simulate and analyze the high pressure filling process of the storage tank for the hydrogen station. In the analysis the physical parameters of normal hydrogen are introduced to make the simulation close to the actual process. By the numerical simulation for 50 MPa compressed hydrogen tank the temperature and pressure trends during filling are obtained. The simulation results for non-adiabatic filling were compared with the theoretically calculated ones for adiabatic conditions and the simulation results for non-adiabatic filling were compared with the simulation ones for adiabatic conditions. Then the influence of working pressure initial temperature mass flow rate initial pressure and inlet temperature on the temperature rise were analyzed. This study provides a theoretical research basis for high pressure hydrogen energy storage and hydrogenation technology.

Fuel cell vehicles (FCVs) should control the energy management between two energy sources for fuel economy using the stored energy in a battery or generation of energy through a fuel cell system. The fuel economy for an FCV includes trip costs for hydrogen consumption and the lifetime of two energy sources. This paper proposes an implementable energy management control strategy for an FCV to reduce trip costs. The concept of the proposed control strategy is first to analyze the allowable current of a fuel cell system from the optimal strategies for various initial battery state of charge (SOC) conditions using dynamic programming (DP) and second to find a modulation ratio determining the current of a fuel cell system for driving a vehicle using the particle swarm optimization method. The control strategy presents the on/off moment of a fuel cell system and the proper modulation ratio of the turned-on fuel cell system with respect to the battery SOC and the power demand. The proposed strategy reduces trip costs in real-time similar to the DP-based optimal strategy and more than the simple energy control strategy of switching a fuel cell system on/off at the battery SOC boundary conditions even for long-term driving cycles.

This study introduces a machine learning approach to predict the effect of alloying elements and test conditions on the hydrogen environment embrittlement (HEE) index of austenitic steels for the first time. The correlation between input features and the HEE index was analyzed with Pearson's correlation coefficient (PCC) and Maximum Information Coefficient (MIC) algorithms. The correlation analysis results identified Ni and Mo as dominant features influencing the HEE index of austenitic steels. Based on the analysis results the performance of the four representative machine learning models as a function of the number of top-ranked features was evaluated: random forest (RF) linear regression (LR) Bayesian ridge (BR) and support vector machine (SVM). Regardless of the type and the number of top-ranking features the RF model had the highest accuracy among various models. The machine learning-based approach is expected to be useful in designing new steels having mechanical properties required for hydrogen applications.

In the present scenario much importance has been provided to hydrogen energy systems (HES) in the energy sector because of their clean and green behavior during utilization. The developments of novel techniques and materials have focused on overcoming the practical difficulties in the HES (production storage and utilization). Comparatively considerable attention needs to be provided in the hydrogen storage systems (HSS) because of physical-based storage (compressed gas cold/cryo compressed and liquid) issues such as low gravimetric/volumetric density storage conditions/parameters and safety. In material-based HSS a high amount of hydrogen can be effectively stored in materials via physical or chemical bonds. In different hydride materials Mg-based hydrides (Mg–H) showed considerable benefits such as low density hydrogen uptake and reversibility. However the inferior sorption kinetics and severe oxidation/contamination at exposure to air limit its benefits. There are numerous kinds of efforts like the inclusion of catalysts that have been made for Mg–H to alter the thermodynamic-related issues. Still those efforts do not overcome the oxidation/contamination-related issues. The developments of Mg–H encapsulated by gas-selective polymers can effectively and positively influence hydrogen sorption kinetics and prevent the Mg–H from contaminating (air and moisture). In this review the impact of different polymers (carboxymethyl cellulose polystyrene polyimide polypyrrole polyvinylpyrrolidone polyvinylidene fluoride polymethylpentene and poly(methyl methacrylate)) with Mg–H systems has been systematically reviewed. In polymer-encapsulated Mg–H the polymers act as a barrier for the reaction between Mg–H and O2/H2O selectively allowing the H2 gas and preventing the aggregation of hydride nanoparticles. Thus the H2 uptake amount and sorption kinetics improved considerably in Mg–H.

This study has developed traceable standards for evaluating impurities in hydrogen fuel according to ISO 14687. Impurities in raw H2 including sub mmol/mol levels of CO CO2 and CH4 were analyzed using multiple detectors while avoiding contamination. The gravimetric standards prepared included mixtures of the following nominal concentrations: 1 2 3e5 8e11 17e23 and 47e65 mmol/mol for CO2 CH4 and CO O2 N2 Ar and He respectively. The expanded uncertainty ranges were 0.8% for Ar N2 and He 1% for CH4 and CO and 2% for CO2 and O2. These standards were stable while that for CO varied by only 0.5% during a time span of three years. The prepared standards are useful for evaluating the compliance of H2 fuel in service stations with ISO 14687 quality requirements.

Decarbonizing the planet is one of the major goals that countries around the world have set for 2050 to mitigate the effects of climate change. To achieve these goals green hydrogen that can be produced from the electrolysis of water is an important key solution to tackle global decarbonization. Consequently in recent years there is an increase in interest towards green hydrogen production through the electrolysis process for large-scale implementation of renewable energy based power plants and other industrial and transportation applications. The main objective of this study was to provide a comprehensive review of various green hydrogen production technologies especially on water electrolysis. In this review various water electrolysis technologies and their techno-commercial prospects including hydrogen production cost along with recent developments in electrode materials and their challenges were summarized. Further some of the most successful results also were described. Moreover this review aims to identify the gaps in water electrolysis research and development towards the techno-commercial perspective. In addition some of the commercial electrolyzer performances and their limitations also were described along with possible solutions for cost-effective hydrogen production Finally we outlined our ideas and possible solutions for driving cost-effective green hydrogen production for commercial applications. This information will provide future research directions and a road map for the development/implementation of commercially viable green hydrogen projects.