Transmission, Distribution & Storage

This study systematically investigates the fracture behavior of X80 pipeline steel welded joints under hydrogen-induced cracking (HIC) conditions through combined experimental characterization and numerical simulation. Microstructural observations and Vickers hardness testing reveal significant heterogeneity in the base metal heat-affected zone (HAZ) and weld metal (WM) resulting in spatially non-uniform mechanical properties. A userdefined subroutine (USDFLD) was employed to assign continuous material property distributions within the finite element model accurately capturing mechanical heterogeneity and its influence on crack-tip mechanical fields and crack propagation paths. Results show that welding thermal cycles induce pronounced microstructural evolution significantly altering hardness and strength distributions which in turn affect the evolution of crack-tip stress and plastic strain fields. Crack propagation preferentially occurs toward regions of higher yield strength where limited plasticity leads to intensified cracktip stress concentration accelerating crack growth and extending propagation paths. Moreover crack growth is accompanied by local unloading near the crack tip reducing peak stress and strain compared to the initial stationary crack tip. The stress and strain field reconfiguration are primarily localized near the crack tip while the far-field mechanical response remains largely stable.

Metal organic frameworks (MOFs) exhibit exceptional efficacy in hydrogen storage owing to their distinctive characteristics including elevated gravimetric densities rapid kinetics and reversibility. An in-depth look at existing literature indicates that while there are many studies using machine learning (ML) algorithms to develop predictive models for estimating hydrogen uptake by MOFs a great number of these models are not explainable. The novelty of this work lies in the integration of explainability approaches and ML models providing both accuracy and interpretability which is rarely addressed in existing studies. To fill this gap this paper attempts to develop explainable ML models for forecasting the hydrogen storage capacity of MOFs using three ML techniques including Bayesian regularized neural networks (BRANN) least squares support vector machines (LSSVM) and the extra tree algorithm (ET). An MOF databank comprising 1729 data points was assembled from literature. Surface area temperature pore volume and pressure were employed as input variables in this database. The findings demonstrate that of the three algorithms the ET intelligent model attained exceptional performance yielding precise estimates with a root mean square error (RMSE) of 0.1445 mean absolute error (MAE) of 0.0762 and a correlation coefficient (R2 ) of 0.995. In addition a novel contribution of this study is the generation of an explicit formula derived from BRANN enabling straightforward implementation of hydrogen storage predictions without requiring retraining of complex models. The sensitivity analysis employing Shapley Additive Explanation technique revealed that pressure and surface area were the most significant features influencing hydrogen storage with relevance values of 0.84 and 0.59 respectively. Furthermore the outlier detection evaluation using the leverage method showed that approximately 98 % of the utilized MOFs data are trustworthy and fell within the acceptable range. Altogether this work establishes a distinctive framework that combines accuracy interpretability and practical usability advancing the state of predictive modelling for hydrogen storage in MOFs.

Underground Hydrogen Storage (UHS) has gathered interest over the past decade as an efficient means of storing energy. Although a significant number of research and demonstration projects have sought to understand the associated technical challenges it is yet to be achieved on commercial scales. We highlight case studies from town gas and blended hydrogen storage focusing on leakage pathways and hydrogen reactivity. Experience from helium storage serves as an analogue for the containment security of hydrogen as the two gases share physiochemical similarities including small molecular size and high diffusivity. Natural gas storage case studies are also investigated to highlight well integrity and safety challenges. Technical parameters identified as having adverse effects on storage containment security efficiency and hydrogen reactivity were then used to develop high-level and site-specific screening criteria. Thirty-two depleted offshore hydrocarbon reservoirs in the UK Continental Shelf (UKCS) are identified as potential storage formations based on the application of our high-level criteria. The screened fields reflect large hydrogen energy capacities low cushion gas requirements and proximity to offshore wind farms thereby highlighting the widespread geographic availability and potential for efficient UHS in the UKCS. Following the initial screening we propose that analysis of existing helium concentrations and investigation of local tectonic settings are key site-specific criteria for identifying containment security of depleted fields for stored hydrogen.

An important component of the deep decarbonization of the worldwide energy system is to build up the large-scale utilization of hydrogen to substitute for fossil fuels in all sectors including industry the electricity sector transportation and heating. Hence apart from reducing hydrogen production costs establishing an efficient and suitable infrastructure for the storage transportation and distribution of hydrogen becomes essential. This article provides a technically detailed overview of the state-of-the-art technologies for hydrogen infrastructure including the physical- and material-based hydrogen storage technologies. Physical-based storage means the storage of hydrogen in its compressed gaseous liquid or supercritical state. Hydrogen storage in the form of liquid-organic hydrogen carriers metal hydrides or power fuels is denoted as material-based storage. Furthermore primary ways to transport hydrogen such as land transportation via trailer and pipeline overseas shipping and some related commercial data are reviewed. As the key results of this article hydrogen storage and transportation technologies are compared with each other. This comparison provides recommendations for building appropriate hydrogen infrastructure systems according to different application scenarios.

Hydrogen production from renewable energy sources has the potential to significantly reduce the carbon footprint of critical economic sectors that rely heavily on fossil fuels. Liquid organic hydrogen carrier (LOHC) technology has the capability to overcome the limitations associated with conventional hydrogen storage technologies. To date dibenzyltoluene and benzyltoluene are the benchmark LOHC molecules due to the unique hydrogen storage properties. However the reaction temperature for dehydrogenation reaction is high and catalysts need to be further developed so that efficient release of hydrogen can be realized. Exploration of various catalyst preparation methods such as supercritical carbon-dioxide deposition the selection on support material with relevant textural and chemical properties and optimization of catalyst modifiers are rewarding approaches of improving the catalyst performance. In addition to this the lowering of the dehydrogenation temperature by employing electrochemical methods and reactive distillation approaches are strategies that will make the LOHC technology competitive.

Recent studies on additive manufacturing (AM) have indicated the necessity of understanding the hydrogen embrittlement (HE) of high-strength steels fabricated by AM due to the different microstructure obtained compared to their conventionally processed counterparts. This study investigated the influence of post-AM tempering (at 205 ◦C 315 ◦C and 425 ◦C) on the HE resistance of AM-fabricated AISI 4340 steel a representative ultrahigh-strength medium-carbon low-alloy steel. The present results show that tempering effectively reduced the HE sensitivity of the steel. When tested in air tempering at a low temperature of 205 ◦C slightly increased both the yield strength (YS) and ultimate tensile strength (UTS) accompanied by a reduction in elongation (EL). This behaviour is attributed to the precipitation of carbides. In contrast higher tempering temperatures of 315 ◦C and 425 ◦C resulted in a progressive decrease in both YS and UTS as anticipated. However when tested in a hydrogen-rich environment although the HE dramatically reduced the ductility and YS could not even be determined for the samples tempered at 205 ◦C and 315 ◦C the tempered samples retained higher UTS and EL compared to the as-AM-fabricated samples because of the increased HE resistance by tempering. Microstructural examination indicated that tempering at 205 ◦C and 315 ◦C retained the bainitic microstructure while promoting the formation of fine carbide precipitates which softened the bainitic ferrite matrix enhancing the hydrogen trapping capacity. Tempering at 425 ◦C promoted recovery of the AM-fabricated steel reducing dislocation density producing a lower subsurface hydrogen concentration and higher hydrogen diffusivity which led to an enhanced HE resistance. As a result testing of the samples tempered at 425 ◦C in hydrogen resulted in a high YS (~1200 MPa) and only a ~5 % reduction in UTS and a 64 % reduction in EL compared with the untempered samples of which the reductions were 31 % in UTS and 79 % in EL. Furthermore this study underscores the critical role of the trap character in governing the HE behaviour offering a pathway toward optimised heat treatment strategies for improved HE resistance of additively manufactured high-strength steels.

This paper examines the techno-economic feasibility of utilising salt caverns for large-scale hydrogen storage in Ireland leveraging wind energy and proton exchange membrane (PEM) electrolysers. The analysis focuses on optimising the integration of wind power with hydrogen production and storage addressing key challenges such as energy curtailment grid transmission constraints and renewable energy intermittency. Findings highlight significant economic considerations with a single hydrogen storage cavern requiring an initial investment of approximately €240 million where geological site preparation and compressor systems constitute the largest cost components. Annual operational expenses (OPEX) are estimated at €4.6 million largely due to compressor energy consumption and cooling requirements. The study emphasizes the critical impact of electrolyser scale on economic viability. Small-scale systems such as a 20 MW PEM electrolyser are economically unfeasible with a levelised cost of hydrogen (LCOH) of around €10/kg and filling times extending up to 2.5 years. However scaling up to a 200 MW PEM electrolyser dramatically improves cost efficiency lowering the LCOH to approximately €0.83/kg and reducing filling times to just 90 days. This research provides a comprehensive framework for hydrogen storage development offering key insights for policymakers and industry stakeholders to drive the renewable energy transition and enhance energy security through cost-effective and sustainable storage solutions.

The effectiveness of shot peening in suppressing hydrogen embrittlement (HE) of the heat-treated steels with different strength levels 790 MPa (115 ksi) and 930 MPa (135 ksi) was comprehensively investigated. A plastically deformed layer on the surface facilitated an increased number of dislocations and refined grain morphology. This hindered hydrogen transportation as confirmed by the results of electrochemical permeation exhibiting a decrease in the effective diffusion coefficient up to 47 %. The trapping behaviour of the steels scrutinized through Thermal Desorption Spectroscopy (TDS) proposed that dislocations are primary traps. Along with this residual compressive stresses (RCS) were introduced into the materials reaching a maximum of − 650 MPa and a depth of 250 μm. This prevented fracture of the steels under constant load in a plastic regime (1.05xYS) and 120 bar H2 environment. Slow Strain Rate Tensile (SSRT) tests indicated superior mechanical properties of the shot-peened steels under electrochemical charging reducing HE susceptibility by 15 %. Fracture morphology confirmed the protective nature of the plastically deformed layer highlighting a higher ductility of the fracture. RCS has been indicated as a determining factor in suppressing HE by shot peening regardless of the strength level of the steel.

Global demand for clean energy carriers like hydrogen (H2) is rising under carbon-reduction policies. While domestic H2 projects are progressing international trade presents significant opportunities for countries with abundant renewables or advanced production capabilities. Yet establishing H2 as a viable global commodity requires overcoming supply chain challenges in flexibility efficiency and cost. This review examines hydrogen supply chain network design (HSCND) studies and highlights key research gaps in export-oriented systems. Current work often focuses on transport technologies but lacks integrated analyses combining technical economic and policy dimensions. Notable gaps include limited research on retrofitting infrastructure for H2 derivatives underexplored roles of ports as export hubs and insufficient evaluation of regulatory frameworks and financial risks. This review proposes a methodological approach to guide HSCND for export supporting data collection and strategic planning. Future research should integrate technical geopolitical and social factors into models backed by methodological innovation and empirical evidence.

With the accelerating global transition to clean energy underground hydrogen storage (UHS) has gained significant attention as a flexible and renewable energy storage technology. Ontario Canada as a pioneer in energy transition offers substantial underground storage potential with its geological conditions of salt limestone and sandstone providing diverse options for hydrogen storage. However the hydrogen transport characteristics of different rock media significantly affect the feasibility and safety of energy storage projects warranting in-depth research. This study simulates the hydrogen flow and transport characteristics in typical energy storage digital rock core models (salt rock limestone and sandstone) from Ontario using the improved quartet structure generation set (I-QSGS) and the lattice Boltzmann method (LBM). The study systematically investigates the distribution of flow velocity fields directional characteristics and permeability differences covering the impact of hydraulic changes on storage capacity and the mesoscopic flow behavior of hydrogen in porous media. The results show that salt rock due to its dense structure has the lowest permeability and airtightness with extremely low hydrogen transport velocity that is minimally affected by pressure differences. The microfracture structure of limestone provides uneven transport pathways exhibiting moderate permeability and fracture-dominated transport characteristics. Sandstone with its higher porosity and good connectivity has a significantly higher transport rate compared to the other two media showing local high-velocity preferential flow paths. Directional analysis reveals that salt rock and sandstone exhibit significant anisotropy while limestone’s transport characteristics are more uniform. Based on these findings salt rock with its superior sealing ability demonstrates the best hydrogen storage performance while limestone and sandstone also exhibit potential for storage under specific conditions though further optimization and validation are required. This study provides a theoretical basis for site selection and operational parameter optimization for underground hydrogen storage in Ontario and offers valuable insights for energy storage projects in similar geological settings globally.