Publications

In the context of mounting concerns over carbon emissions and the need to accelerate the energy transition green hydrogen has emerged as a strategic solution for decarbonizing hard-to-abate sectors. This paper introduces a methodological innovation by proposing the Green Hydrogen Efficiency Index (GHEI) a unified and quantitative framework that integrates multiple stages of the hydrogen value chain into a single comparative metric. The index encompasses six core criteria: electricity source water treatment electrolysis efficiency compression end-use conversion and associated greenhouse gas emissions. Each are normalized and weighted to reflect different performance priorities. Two weighting profiles are adopted: a first profile which assigns equal importance to all criteria referred to as the balanced profile and a second profile derived using the analytic hierarchy process (AHP) based on structured expert judgment named the AHP profile. The methodology was developed through a systematic literature review and was applied to four representative case studies sourced from the academic literature covering diverse configurations and geographies. The results demonstrate the GHEI’s capacity to distinguish the energy performance of different green hydrogen routes and support strategic decisions related to technology selection site planning and logistics optimization. The results highlight the potential of the index to contribute to more sustainable hydrogen value chains and advance decarbonization goals by identifying pathways that minimize energy losses and maximize system efficiency

As the global transition to carbon neutrality accelerates hydrogen energy has emerged as a key alternative to fossil fuels due to its potential to reduce carbon emissions. Many countries including Korea are constructing hydrogen refueling stations; however safety concerns persist due to accidents caused by equipment failures and human errors. While various accident analysis models exist the application of the root cause analysis (RCA) technique to hydrogen refueling station accidents remains largely unexplored. This study develops an RCA modeling map specifically for hydrogen refueling stations to identify not only direct and indirect causes of accidents but also root causes and applies it to actual accident cases to provide basic data for identifying the root causes of future hydrogen refueling station accidents. The RCA modeling map developed in this study uses accident cause investigation data from accident investigation reports over the past five years which include information on the organizational structure and operational status of hydrogen refueling stations as well as the RCA handbook. The primary defect sources identified were equipment defect personal defect and other defects. The problem categories which were the substructures of the primary defect source “equipment defect” consisted of four categories: the equipment design problem the equipment installation/fabrication problem the equipment reliability program problem and the equipment misuse problem. Additionally the problem categories which were the substructures of the primary defect source “personal defect” consisted of two categories: the company employee problem and the contract employee problem. The problem categories which were the substructures of the primary defect source “other defects” consisted of three categories: sabotage/horseplay natural phenomena and other. Compared to existing accident investigation reports which identified only three primary causes the RCA modeling map revealed nine distinct causes demonstrating its superior analytical capability. In conclusion the proposed RCA modeling map provides a more systematic and comprehensive approach for investigating accident causes at hydrogen refueling stations which could significantly improve safety practices and assist in quickly identifying root causes more efficiently in future incidents.

The integration of Variable Renewable Energy (VRE) sources in power systems is increased for a sustainable environment. However due to the intermittent nature of VRE sources formulating efficient economic dispatching strategies becomes challenging. This systematic review aims to elucidate the economic value creation of Artificial Intelligence (AI) in supporting the integration of VRE sources into power systems by reviewing the role of AI in mitigating costs related to balancing profile and grid with a focus on its applications for generation and demand forecasting market design demand response storage solutions power quality enhancement and predictive maintenance. The proposed study evaluates the AI potential in economic efficiency and operational reliability improvement by analyzing the use cases with various Renewable Energy Resources (RERs) including wind solar geothermal hydro ocean bioenergy hydrogen and hybrid systems. Furthermore the study also highlights the development and limitations of AI-driven approaches in renewable energy sector. The findings of this review aim to highlight AI’s critical role in optimizing VRE integration ultimately informing policymakers researchers and industry stakeholders about the potential of AI for an economically sustainable and resilient energy infrastructure.

Hydrogen spark-ignition direct-injection engines result in no carbon emissions at use but NOX remains a challenge. This study demonstrates that with lean combustion (ϕ < 0.38) in-cylinder NOX can be reduced to a quarter of the current maritime regulatory limit. An original contribution of this work is the use of speciesresolved emissions formation across multiple engine load conditions. A novel chemically detailed combustion modelling framework was developed in CHEMKIN-Pro incorporating the evolution of the CRECK C1–C3 NOX mechanism for improved high-pressure accuracy. The framework was extensively validated using crank-angleresolved data across 9–18 bar loads. The model accurately reproduced pressure traces heat release angles and NOX. Mechanistic analysis revealed a shift from thermal Zeldovich NOX to intermediate-species (notably N2Odriven) as equivalence ratio and pressure varied. The findings highlighted the use of a high-fidelity chemical kinetic modelling framework not only to match experimental results but to gain physically grounded insight into actionable near-zero emission strategies.

Thermo-catalytic decomposition (TCD) presents a promising pathway for producing hydrogen from natural gas without emitting CO2. This process represents a form of fossil fuel decarbonization where the byproduct rather than being a greenhouse gas is a solid carbon material with potential for commercial value. This study examines the dynamic behavior of TCD showing that carbon formed during the reaction first enhances and later dominates methane decomposition. Three types of carbon materials were employed as starting catalysts. Methane decomposition was continuously monitored using on-line Fourier transform infrared (FT-IR) spectroscopy. The concentration and nature of surface-active sites were determined using a two-step approach: oxygen chemisorption followed by elemental analysis through X-ray photoelectron spectroscopy (XPS). Changes in the morphology and nanostructure of the carbon catalysts both before and after TCD were examined using high-resolution transmission electron microscopy (HRTEM). Thermogravimetric analysis (TGA) was used to study the reactivity of the TCD deposits in relation to the initial catalysts. Partial oxidation altered the structural and surface chemistry of the initial carbon catalysts resulting in activation energies of 69.7–136.7 kJ/mol for methane. The presence of C2 and C3 species doubled methane decomposition (12% → 24%). TCD carbon displayed higher reactivity than the nascent catalysts and sustained long-term activity.

The resilience and sustainable development of modern power distribution systems faces escalating challenges due to increasing renewable integration and extreme events. Traditional single-system approaches often overlook the spatiotemporal coordination of cross-domain restoration resources. In this paper we propose a multi-stage resilience enhancement method that employs transportation and hydrogen energy systems. This approach coordinates the pre-event preventive allocation and multi-stage collaborative scheduling of diverse restoration resources including remote-controlled switches (RCSs) mobile hydrogen emergency resources (MHERs) and hydrogen production and refueling stations (HPRSs). The proposed framework supports cross-stage dynamic optimization scheduling enabling the development of adaptive resource dispatch strategies tailored to the characteristics of different stages including prevention fault isolation and service restoration. The model is applicable to complex scenarios involving dynamically changing network topologies and is formulated as a mixed-integer linear programming (MILP) problem. Case studies based on the IEEE 33-bus system show that the proposed method can restore a distribution system’s resilience to approximately 87% of its normal level following extreme events.

This report aims to summarise the status of the European hydrogen policy landscape. It is based on the information available at the European Hydrogen Observatory (EHO) website the leading source of data on hydrogen in Europe. The data presented in this report is based on research conducted by Hydrogen Europe until the end of July 2024 but also goes beyond this timeline for major policies legislations or standards implemented recently. This report builds upon the previous version published in April 2024 which reflected data as of August 2023 providing updated insights on European policies and legislation national strategies national policies and legislation and codes and standards. Interactive data dashboards can be accessed on the website: https://observatory.cleanhydrogen.europa.eu/ The EU policies and legislation section provides insights into the main European policies and legislation relevant to the hydrogen sector which are briefly summarized on content and their potential impact to the sector. The national hydrogen strategies chapter offers a comprehensive examination of the hydrogen strategies adopted in Europe. It summarizes the quantitative indicators that have been published (targets and estimates) and provides brief summaries of the different national strategies that have been adopted. The section referring to national policies and legislation focuses on the policy framework measures incentives and targets in place that have an impact on the development of the respective national hydrogen markets within Europe. The codes and standards section provides information on current European standards and initiatives developed by the standardisation bodies including CEN CENELEC ISO IEC OIML The standards are categorised according to the different stages of the hydrogen value chain: production distribution and storage and end-use applications.

Hydrogen (H2) fuel is one of eco-friendly resources for delivering de-carbonized and sustainable electricity supply in line with the UN’s Sustainable Development Goals 7 and 13 for affordable and clean energy and climate change action respectively. This paper presents a state-of-the art review of the H2 energy resource in terms of its history and evolution production techniques global economy market perspective and application to microgrid systems. It also introduces a systematic classification of the fuel. The production techniques examined include: the thermal approach such as the reforming gasification and thermochemical processes; the photocatalytic approach otherwise called artificial photosynthesis; the biological and photonic approach that involves the photolysis photo-fermentation dark fermentation CO gas fermentation and biomass valorization processes to produce H2 while the electrical approach is based on the chemical dissociation of electrolytes into their constituent ions by the passage of electric current. A particular attention is paid to the potential of the H2 resource in running some energy generators in microgrid systems such as the internal combustion engines microturbines and the fuel cells that are useful for combined heat and power application. The paper introduces different technical configurations topologies and processes that involve the use of green H2 fuel in generating systems and the connection of bus bars power converters battery bank and the electrical and thermal loads. The paper also presents hybrid fuel cell (FC) and PV system simulation using System Advisor Model (SAM) to showcase the use of H2 fuel in a micogrid. The paper provides insightful directions into the H2 economy smart electrical grid and the future prospects.

The increasing interest in off-grid green hydrogen production has elevated the importance of reliable techno-economic assessment (TEA) tools to support investment and planning decisions. However limited operational data and inconsistent modeling approaches across existing tools introduce significant uncertainty in cost estimations. This study presents a comprehensive review and comparative analysis of seven TEA tools—ranging from simplified calculators to advanced hourly based simulation platforms—used to estimate the Levelized Cost of Hydrogen (LCOH) in off-grid Hydrogen Production Plants (HPPs). A standardized simulation framework was developed to input consistent technical economic and financial parameters across all tools allowing for a horizontal comparison. Results revealed a substantial spread in LCOH values from EUR 5.86/kg to EUR 8.71/kg representing a 49% variation. This discrepancy is attributed to differences in modeling depth treatment of critical parameters (e.g. electrolyzer efficiency capacity factor storage and inflation) and the tools’ temporal resolution. Tools that included higher input granularity hourly data and broader system components tended to produce more conservative (higher) LCOH values highlighting the cost impact of increased modeling realism. Additionally the total project cost—more than hydrogen output—was identified as the key driver of LCOH variability across tools. This study provides the first multi-tool horizontal testing protocol a methodological benchmark for evaluating TEA tools and underscores the need for harmonized input structures and transparent modeling assumptions. These findings support the development of more consistent and reliable economic evaluations for off-grid green hydrogen projects especially as the sector moves toward commercial scale-up and policy integration.

Electrolysis of abundant seawater resources is a promising approach for hydrogen production. However the high-concentration chloride ion in seawater readily induces the chlorine evolution reaction (CER) resulting in catalyst degradation and decreased electrolysis efficiency. In recent years the electrooxidation of small organic molecules (e.g. methanol) biomass-derived compounds (e.g. 5-hydroxymethylfurfural) and plastic monomers (e.g. ethylene glycol) has been seen to occur at lower potentials to substitute for the traditional oxygen evolution reaction (OER) and CER. This alternative approach not only significantly reduces energy consumption for hydrogen production but also generates value-added products at the anode. This review provides a comprehensive summary of research advancements in value-added electrooxidation reaction-assisted seawater hydrogen production technologies and emphasizes the underlying principles of various reactions and catalyst design methodologies. Finally the current challenges in this field and potential future research directions are systematically discussed.