China, People’s Republic

Green hydrogen plays a pivotal role in decarbonizing our energy system and achieving the Net-Zero Emissions goal by 2050. Offshore wind farms (OWFs) dedicated to green hydrogen production are currently recognized as the most feasible solution for scaling up the production of cost-effective electrolytic hydrogen. However the cost associated with distribution and transmission systems constitute a significant portion of the total cost in the large-scale wind-hydrogen system. This study pioneers the simultaneous optimization of the inter-array cable routing of OWFs and the location and capacity of offshore hydrogen production platforms (OHPPs) aiming to minimize the total cost of distribution and transmission systems. Considering the characteristics of hydrogen production efficiency this paper constructs a novel mathematical model for OHPPs across diverse wind scenarios. Subsequently we formulate the joint planning problem as a relaxed mixed-integer second-order cone programming (MISOCP) model and employ the Benders decomposition algorithm for the solution introducing three valid inequalities to expedite convergence. Through validation on real-world large-scale OWFs we demonstrate the validity and rapid convergence of our approach. Moreover we identify hydrogen production efficiency as a major bottleneck cost factor for the joint planning problem it decreases by 1.01% of total cost for every 1% increase in hydrogen production efficiency.

Water electrolyzers play a crucial role in green hydrogen production. However their efficiency and scalability are often compromised by bubble dynamics across various scales from nanoscale to macroscale components. This review explores multi-scale modeling as a tool to visualize multi-phase flow and improve mass transport in water electrolyzers. At the nanoscale molecular dynamics (MD) simulations reveal how electrode surface features and wettability influence nanobubble nucleation and stability. Moving to the mesoscale models such as volume of fluid (VOF) and lattice Boltzmann method (LBM) shed light on bubble transport in porous transport layers (PTLs). These insights inform innovative designs including gradient porosity and hydrophilic-hydrophobic patterning aimed at minimizing gas saturation. At the macroscale VOF simulations elucidate two-phase flow regimes within channels showing how flow field geometry and wettability affect bubble discharging. Moreover artificial intelligence (AI)-driven surrogate models expedite the optimization process allowing for rapid exploration of structural parameters in channel-rib flow fields and porous flow field designs. By integrating these approaches we can bridge theoretical insights with experimental validation ultimately enhancing water electrolyzer performance reducing costs and advancing affordable highefficiency hydrogen production.

Hydrogen as a clean energy source has gradually become an important choice for the energy transformation in the world. Utilizing existing natural gas pipelines for hydrogen-blended transportation is one of the most economical and effective ways to achieve large-scale hydrogen transportation. However hydrogen can easily penetrate into the pipe material during the hydrogen-blended transportation process causing damage to the properties of the pipe. The heat-affected zone (HAZ) of the weld being the weakest part of the pipeline is highly sensitive to hydrogen embrittlement. The microstructure and properties of the grains in the heat-affected zone undergoes changes during the welding process. Therefore this paper divides the HAZ of X80 welded pipes into three sub-HAZ namely the coarse-grained HAZ fine-grained HAZ and intercritical HAZ to study the hydrogen behavior. The results show that the degree of hydrogen damage in each sub-HAZ varies significantly at different strain rates. The coarse-grained HAZ has the highest hydrogen embrittlement sensitivity at low strain rates while the intercritical HAZ experiences the greatest hydrogen damage at high strain rates. By combining the microstructural differences within each sub-HAZ the plastic damage mechanism of hydrogen in each sub-HAZ is analyzed with the aim of providing a scientific basis for the feasibility of using X80 welded pipes in hydrogen-blended transportation.

This study investigates the effects of secondary jet-guided combustion on the combustion and emissions of a hydrogen direct-injection engine through numerical simulations. The results show that secondary jet-guided combustion which involves injecting and igniting the hydrogen jet at the end of the compression stroke significantly shortens the delay period improves combustion stability and brings the combustion center closer to the top dead center (TDC) achieving a maximum indicative thermal efficiency (ITE) of 46.55% (λ = 2.4). However this strategy results in higher NOx emissions due to high-temperature combustion. In contrast single and double injections lead to worsened combustion and reduced thermal efficiency under lean-burn conditions but with relatively lower NOx emissions. This study demonstrates that secondary jet-guided combustion can effectively enhance hydrogen engine performance by optimizing mixture stratification and flame propagation providing theoretical support for clean and efficient combustion.

To ensure the safe and reliable operation of hydrogen-blended natural gas (HBNG) pipelines in urban utility tunnels this study conducted a comprehensive CFD simulation of the leakage and diffusion characteristics of HBNG in confined underground environments. Utilizing ANSYS CFD software (2024R1) a three-dimensional physical model of a utility tunnel was developed to investigate the influence of key parameters such as leak sizes (4 mm 6 mm and 8 mm)—selected based on common small-orifice defects in utility tunnel pipelines (e.g. corrosion-induced pinholes and minor mechanical damage) and hydrogen blending ratios (HBR) ranging from 0% to 20%—a range aligned with current global HBNG demonstration projects (e.g. China’s “Medium-Term and Long-Term Plan for Hydrogen Energy Industry Development”) and ISO standards prioritizing 20% as a technically feasible upper limit for existing infrastructure on HBNG diffusion behavior. The study also evaluated the adequacy of current accident ventilation standards. The findings show that as leak orifice size increases the diffusion range of HBNG expands significantly with a 31.5% increase in diffusion distance and an 18.5% reduction in alarm time as the orifice diameter grows from 4 mm to 8 mm. Furthermore hydrogen blending accelerates gas diffusion with each 5% increase in HBR shortening the alarm time by approximately 1.6 s and increasing equilibrium concentrations by 0.4% vol. The current ventilation standard (12 h−1 ) was found to be insufficient to suppress concentrations below the 1% safety threshold when the HBR exceeds 5% or the orifice diameter exceeds 4 mm—thresholds derived from simulations showing that under 12 h−1 ventilation equilibrium concentrations exceed the 1% safety threshold under these conditions. To address these gaps this study proposes an adaptive ventilation strategy that uses variable-frequency drives to adjust ventilation rates in real time based on sensor feedback of gas concentrations ensuring alignment with leakage conditions thereby ensuring enhanced safety. These results provide crucial theoretical insights for the safe design of HBNG pipelines and ventilation optimization in utility tunnels.

Amidst the escalating global challenges presented by climate change carbon trading mechanisms have become critical tools for driving reductions in carbon emissions and optimizing energy systems. However existing carbon trading models constrained by fixed settlement cycles face difficulties in addressing the scheduling needs of energy systems that operate across multiple time scales. To address this challenge this paper proposes an optimal scheduling methodology for hydrogen-encompassing integrated energy systems that incorporates a multi-time-scale carbon trading mechanism. The proposed approach dynamically optimizes the scheduling and conversion of hydrogen energy electricity thermal energy and other energy forms by flexibly adjusting the carbon trading cycle. It accounts for fluctuations in energy demand and carbon emissions occurring both before and during the operational day. In the day-ahead scheduling phase a tiered carbon transaction cost model is employed to optimize the initial scheduling framework. During the day scheduling phase real-time data are utilized to dynamically adjust carbon quotas and emission ranges further refining the system’s operational strategy. Through the analysis of typical case studies this method demonstrates significant benefits in reducing carbon emission costs enhancing energy efficiency and improving system flexibility.

Bio-hydrogen production (BHP) produced from renewable bio-resources is an attractive route for green energy production due to its compelling advantages of relative high efficiency cost-effectiveness and lower ecological impact. This study reviewed different BHP pathways and the most important enzymes involved in these pathways to identify technological gaps and effective approaches for process intensification in industrial applications. Among the various approaches reviewed in this study a particular focus was set on the latest methods of chemicals/metal addition for improving hydrogen generation during dark fermentation (DF) processes; the up-to-date findings of different chemicals/metal addition methods have been quantitatively evaluated and thoroughly compared in this paper. A new efficiency evaluation criterion is also proposed allowing different BHP processes to be compared with greater simplicity and validity

The widespread penetration of hydrogen in mainstream energy systems requires hydrogen production processes to be economically competent and environmentally efficient. Hydrogen if produced efficiently can play a pivotal role in decarbonizing the global energy systems. Therefore this study develops a framework which evaluates hydrogen production processes and quantifies deficiencies for improvement. The framework integrates slack-based data envelopment analysis (DEA) with fuzzy analytical hierarchy process (FAHP) and fuzzy technique for order of preference by similarity to ideal solution (FTOPSIS). The proposed framework is applied to prioritize the most efficient and sustainable hydrogen production in Pakistan. Eleven hydrogen production alternatives were analyzed under five criteria including capital cost feedstock cost O&M cost hydrogen production and CO2 emission. FAHP obtained the initial weights of criteria while FTOPSIS determined the ultimate weights of criteria for each alternative. Finally slack-based DEA computed the efficiency of alternatives. Among the 11 three alternatives (wind electrolysis PV electrolysis and biomass gasification) were found to be fully efficient and therefore can be considered as sustainable options for hydrogen production in Pakistan. The rest of the eight alternatives achieved poor efficiency scores and thus are not recommended.

Numerical simulations reveal the combustion dynamics of hydrogen-blended natural gas (H-BNG) in semi-open spaces. In the typical semi-open space scenario increasing the hydrogen blending ratio from 0% to 60% elevates peak internal pressure by 107% (259.3 kPa → 526.0 kPa) while reducing pressure rise time by 56.5% (95.8 ms → 41.7 ms). A vent size paradox emerges: 0.5 m openings generate 574.6 kPa internal overpressure whereas 2 m openings produce 36.7 kPa external overpressure. Flame propagation exhibits stabilized velocity decay (836 m/s → 154 m/s 81.6% reduction) at hydrogen concentrations ≥30% within 2–8 m distances. In street-front restaurant scenarios 80% H-BNG leaks reach alarm concentration (0.8 m height) within 120 s with sensor response times ranging from 21.6 s (proximal) to 40.2 s (distal). Forced ventilation reduces hazard duration by 8.6% (151 s → 138 s) while door status shows negligible impact on deflagration consequences (412 kPa closed vs. 409 kPa open) maintaining consistent 20.5 m hazard radius at 20 kPa overpressure threshold. These findings provide crucial theoretical insights and practical guidance for the prevention and management of H-BNG leakage and explosion incidents.

Hydrogen energy characterized by its abundant resources green and lowcarbon attributes and wide-ranging applications is a critical energy source for achieving carbon peaking and carbon neutrality goals. The operational efficiency of the hydrogen energy industrial chain is pivotal in determining the security of its supply chain and its contribution to China’s energy transition. This study investigates the efficiency of China’s hydrogen energy industrial chain by selecting 30 listed companies primarily engaged in hydrogen energy as the research sample. A three-stage data envelopment analysis (DEA) model is applied to assess the industry’s comprehensive technical efficiency pure technical efficiency and scale efficiency. Additionally kernel density estimation is utilized to analyze efficiency trends over time. Key factors influencing efficiency are identified and targeted recommendations are provided to enhance the performance and sustainability of the hydrogen energy industrial chain. These findings offer valuable insights to support the development and resilience of China’s hydrogen energy industry