Korea, Republic of

This study experimentally investigates the effect of hydrogen addition on combustion and thermal characteristics of impinging non-premixed jet flames for low-heating values gases (LHVGs). We evaluate the flame morphology and stability using a concentric non-premixed combustor with an impingement plate. OH radicals are visualized using the OH* chemiluminescence and OH-planar laser-induced fluorescence (OH-PLIF) system. Emission characteristics are investigated by calculating CO and NOx emission indices. The results show that the flame stability region narrows as the heating value decreases but expands as hydrogen has been added. The low-OH radical intensity of LHVGs increases with the hydrogen addition. EICO and EINOx decrease with the reduction of heating values. EICO rapidly declines near the lifted flame limit due to the premixing of fuel and air downstream of the flame region. The effect of the hydrogen addition on EINOx is insignificant and shows very low emissions. The heat transfer rate into cooling water indicates a linear tendency with thermal power regardless of the fuel type. These findings show that LHVGs can be employed in existing-impinging flame systems so long as they remain within flame sta bility regions. Furthermore hydrogen addition positively affects the expansion of flame stability enhancing the utility of LHVGs.

An on-site hydrogen refueling station (HRS) directly supplies hydrogen to vehicles using an on-site hydrogen production method such as electrolysis. For the efficient operation of an on-site HRS it is essential to optimize the entire process from hydrogen production to supply. However most existing approaches focus on the efficiency of hydrogen production. This study proposes an optimal operation model for a renewable-energy-integrated on-site HRS which considers the degradation of electrolyzers and operation of compressors. The proposed model maximizes profit by considering the hydrogen revenue electricity costs and energy storage system degradation. It estimates hydrogen production using a voltage equation models compressor power using a shaft power equation and considers electrolyzer degradation using an empirical voltage model. The effectiveness of the proposed model is evaluated through simulation. Comparison with a conventional control strategy shows an increase of over 56% in the operating revenue.

This study presents a hybrid power system comprising a fuel cell (FC) and a lithium-ion battery (LIB) for liquid hydrogen (LH2) carriers which is expected to increase globally due to the production cost gap of green hydrogen between renewable-rich and renewable-poor countries. The LH2 carrier has a key challenge in handling the inevitably considerable boil-off hydrogen (BOH). As a target ship of a 50000 m3 LH2 carrier with a boil-off rate (BOR) of 0.4% per day this study employs an optimization tool to determine the economic power dispatch between the FC and LIB aimed at minimizing the lifetime cost of the ship. The BOH is used as fuel for FC during the voyage. Moreover when the ship is under cargo loading and unloading operations at the port the considerable surplus BOH is utilized to generate electricity and then sold to the shore grid (StG). The results indicate that 45.2% of the BOH can be utilized as fuel for the FC and the StG system can effectively reduce the total lifetime cost by 32.0%. Further the paper presents the outcomes of a sensitivity analysis conducted on critical parameters. This study provides new insights into the BOH issue of LH2 carriers and helps to increase the international green hydrogen market.

The current fossil fuel-based generation of energy has led to large-scale industrial development. However the reliance on fossil fuels leads to the significant depletion of natural resources of buried combustible geologic deposits and to negative effects on the global climate with emissions of greenhouse gases. Accordingly enormous efforts are directed to transition from fossil fuels to nonpolluting and renewable energy sources. One potential alternative is biohydrogen (H2) a clean energy carrier with high-energy yields; upon the combustion of H2 H2O is the only major by-product. In recent decades the attractive and renewable characteristics of H2 led us to develop a variety of biological routes for the production of H2. Based on the mode of H2 generation the biological routes for H2 production are categorized into four groups: photobiological fermentation anaerobic fermentation enzymatic and microbial electrolysis and a combination of these processes. Thus this review primarily focuses on the evaluation of the biological routes for the production of H2. In particular we assess the efficiency and feasibility of these bioprocesses with respect to the factors that affect operations and we delineate the limitations. Additionally alternative options such as bioaugmentation multiple process integration and microbial electrolysis to improve process efficiency are discussed to address industrial-level applications.

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.

The integration of hydrogen energy systems into nearly zero-emission buildings (nZEB) is emerging as a viable strategy to curtail greenhouse gas emissions associated with energy use in these buildings. However the indoor or outdoor placement of certain hydrogen system components or equipment necessitates stringent safety measures particularly in confined environments. This study aims to investigate the dynamics of hydrogen dispersion within an enclosure featuring forced ventilation analyzing the interplay between leakage flow rates and ventilation efficiency both experimentally and numerically. To simulate hydrogen's behavior helium gas which shares similar physical characteristics with hydrogen was utilized in experiments conducted at leakage flows of 4 8 and 10 L/min alongside a ventilation rate of 30 air changes per hour (ACH). The experiments revealed that irrespective of the leakage rate the oxygen concentration returned to its initial level approximately 11 min post-leakage at a ventilation rate of 30 ACH. This study also encompasses a numerical analysis to validate the experimental findings and assess the congruence between helium and hydrogen behaviors. Additionally the impact of varying ACH rates (30 45 60 75) on the concentrations of oxygen and hydrogen was quantified through numerical analysis for different hydrogen leakage rates (4 8 10 20 L/min). The insights derived from this research offer valuable guidance for building facility engineers on designing ventilation systems that ensure hydrogen and oxygen concentrations remain within safe limits in hydrogen-utilizing indoor environments.

This report describes the direct electrolysis of treated wastewater (as a catholyte) to produce hydrogen and potentially reuse the water. To suppress the negative shift of the cathodic potential due to an increase in pH by the hydrogen evolution reaction (HER) the treated wastewater is acidified using the synergetic effect of protons generated from the bipolar membrane and inor ganic precipitation occurred at the surface of the cathode during the HER. Natural seawater as an accessible source for Mg2+ ions was added to the treated wastewater because the concentration of Mg2+ ions contained in the original wastewater was too low for acidification to occur. The mixture of treated wastewater with seawater was acidified to pH 3 allowing the initial cathode potential to be maintained for more than 100 h. The amount of inorganic precipitates formed on the cathode surface is greater than that in the control case (adding 0.5 M NaCl instead of seawater) but does not adversely affect the cathodic potential and Faradaic efficiency for H2 production. Additionally it was confirmed that less organic matter was adsorbed to the inorganic deposits under acidic conditions. These indicate that acidification plays an important role in improving the performance and stability of low-grade water electrolysis. Considering that the treated wastewater is discharged near the ocean acidification-based electrolysis of the effluent with seawater can be a water reuse technology for green hydrogen production enhancing water resilience and contributing to the circular economy of water resources.

Hydrogen is a promising environmentally friendly fuel with the potential for zero-carbon emissions particularly in maritime applications. However owing to its wide flammability range (4–75%) significant safety concerns persist. In confined spaces hydrogen leaks can lead to explosions posing a risk to both lives and assets. This study conducts a numerical analysis to investigate hydrogen flow within hydrogen storage rooms aboard ships with the goal of developing efficient ventilation strategies. Through simulations performed using ANSYS-CFX this research evaluates hydrogen diffusion stratification and ventilation performance. A vertex angle of 120◦ at the ceiling demonstrated superior ventilation efficiency compared to that at 177◦ while air inlets positioned on side-wall floors or mid-sections proved more effective than those located near the ceiling. The most efficient ventilation occurred at a velocity of 1.82 m/s achieving 20 air exchanges per hour. These findings provide valuable insights for the design of safer hydrogen vessel operations.

This study proposes the SMR Smart Net-Zero City (SSNC) framework—a scalable model for achieving carbon neutrality by integrating Small Modular Reactors (SMRs) renewable energy sources and sector coupling within a microgrid architecture. As deploying renewables alone would require economically and technically impractical energy storage systems SMRs provide a reliable and flexible baseload power source. Sector coupling systems—such as hydrogen production and heat generation—enhance grid stability by absorbing surplus energy and supporting the decarbonization of non-electric sectors. The core contribution of this study lies in its real-time data emulation framework which overcomes a critical limitation in the current energy landscape: the absence of operational data for future technologies such as SMRs and their coupled hydrogen production systems. As these technologies are still in the pre-commercial stage direct physical integration and validation are not yet feasible. To address this the researchers leveraged real-time data from an existing commercial microgrid specifically focusing on the import of grid electricity during energy shortfalls and export during solar surpluses. These patterns were repurposed to simulate the real-time operational behavior of future SMRs (ProxySMR) and sector coupling loads. This physically grounded simulation approach enables highfidelity approximation of unavailable technologies and introduces a novel methodology to characterize their dynamic response within operational contexts. A key element of the SSNC control logic is a day–night strategy: maximum SMR output and minimal hydrogen production at night and minimal SMR output with maximum hydrogen production during the day—balancing supply and demand while maintaining high SMR utilization for economic efficiency. The SSNC testbed was validated through a seven-day continuous operation in Busan demonstrating stable performance and approximately 75% SMR utilization thereby supporting the feasibility of this proxy-based method. Importantly to the best of our knowledge this study represents the first publicly reported attempt to emulate the real-time dynamics of a net-zero city concept based on not-yet-commercial SMRs and sector coupling systems using live operational data. This simulation-based framework offers a forward-looking data-driven pathway to inform the development and control of next-generation carbon-neutral energy systems.

This study employs the FLACS code to analyze hydrogen leakage vapor dispersion and subsequent explosions. Utilizing pseudo-source models a liquid pool model and a hybrid model combining both we investigate dispersion processes for varying leak mass flow rates (0.225 kg/s and 0.73 kg/s) in a large open space. We also evaluate explosion hazards based on overpressure and impulse effects on humans. The computational results compared with experimental data demonstrated reasonable hydrogen vapor cloud concentration predictions especially aligned with the wind direction. For higher mass flow rate of 0.73 kg/s the pseudo-source model exhibited the most reasonable predictive performance for locations near the leak source despite the hybrid model yielded similar results to the pseudo-source model while the liquid pool model was more suitable for lower mass flow rate of 0.225 kg/s. Regarding explosion analyses using overpressure-impulse diagram higher mass flow rates leaded to potentially fatal overpressure and impulse effects on humans. However lower mass flow rates may cause severe eardrum damage at the maximum overpressure point.