Transmission, Distribution & Storage

This study presents the synthesis and evaluation of activated carbon derived from spent coffee grounds using three distinct activation methods namely chemical ultrasound-assisted and surface magnetized. The characterization studies of materials are used to evaluate hydrogen storage performance under varying pressure and temperature conditions. The gravimetric measurements are employed to assess the physisorption capacities while electrochemical techniques such as LSV CV and GCD evaluate hydrogen related charge storage behavior. The activation methods affect surface morphology and elemental composition of the activated carbon samples as confirmed by SEM and EDS analyses. Among the three chemically activated carbon exhibits the highest hydrogen uptake achieving 0.362 wt% at 0 ◦C and 4 kPa which is attributed to its highly porous structure. The ultrasound-assisted and surface magnetized samples exhibitmaximum capacities of 0.357 wt% and 0.339 wt% respectively. This study underlines the potential of coffee waste as a sustainable carbon precursor and introduces a dual-characterization approach.

Efficient hydrogen storage is critical for advancing hydrogen-based technologies. This study investigates the effects of pressure and surface area on hydrogen storage in three carbon-based materials: graphite graphene oxide and reduced graphene oxide. Hydrogen adsorption–desorption experiments under pressures ranging from 1 to 9 bar revealed nonlinear storage capacity responses with optimal performance at around 5 bar. The specific surface area plays a pivotal role with reduced graphene oxide and exhibiting a surface area of 70.31 m2/g outperforming graphene oxide (33.75 m2/g) and graphite (7.27 m2/g). Reduced graphene oxide achieved the highest hydrogen storage capacity with 768 sccm and a 3 wt.% increase over the other materials. In assessing proton-exchange fuel cell performance this study found that increased hydrogen storage correlates with enhanced power density with reduced graphene oxide reaching a maximum of 0.082 W/cm2 compared to 0.071 W/cm2 for graphite and 0.017 W/cm2 for graphene oxide. However desorption rates impose temporal constraints on fuel cell operation. These findings enhance our understanding of pressure–surface interactions and underscore the balance between hydrogen storage capacity surface area and practical performance in carbon-based materials offering valuable insights for hydrogen storage and fuel cell applications.

Hydrogen emissions arise from leakage during its production transport storage and use leading to an increase in atmospheric hydrogen concentrations. These emissions also cause an indirect climate effect which has been quantified in the literature with a global warming potential over 100 years (GWP100) of about 11.6 placing hydrogen between carbon dioxide (1) and methane (29.8). There is increasing debate about the climate impact of an energy transition based on hydrogen. As a case study we have therefore evaluated the expected climate impact of switching from the long-distance natural gas transmission network to the outlined future “hydrogen core network” in Germany. Our analysis focuses on the relevant sources and network components of emissions. Our results show that the emissions from the network itself represent only about 1.8% of total emissions from the transmission of hydrogen with 98% attributed to energy-related compressor emissions and only 2% to fugitive and operational hydrogen leakage. Compared to the current natural gas transmission network we calculate a 99% reduction in total network emissions and a 97% reduction in specific emissions per transported unit of energy. In the discussion we show that when considering the entire life cycle which also includes emissions from the upstream and end-use phases the switch to hydrogen reduces the overall climate impact by almost 90%. However while our results show a significantly lower climate impact of hydrogen compared to natural gas minimising any remaining emissions remains crucial to achieve carbon neutrality by 2045 as set in Germany’s Federal Climate Action Act. Hence we recommend further reducing the emissions intensity of hydrogen supply and minimising the indirect emissions associated with the energy supply of compressors.

As the need for sustainable hydrogen storage solutions increases enhancing the bonding interface between polymer liners and carbon fiber-reinforced polymer (CFRP) in Type IV hydrogen tanks is essential to ensure tank integrity and safety. This study investigates the effect of plasma treatment on polyethylene (PE) and PE/graphene nanoplatelets (GNP) composites to optimize bonding with CFRP simulating the liner-CFRP interface in hydrogen tanks. Initially plasma treatment effects on PE surfaces were assessed focusing on plasma energy and exposure time with key surface modifications characterized and bonding performance being evaluated. Plasma treatment on PE/GNP composites with increasing GNP content was then examined comparing the bonding effectiveness of untreated and plasma-treated samples. Wedge peel tests revealed that plasma treatment significantly enhanced PE-CFRP bonding with optimal conditions at 510 W and 180 s resulting in 212 % and 165 % increases in the wedge peel strength and fracture energy respectively. Plasma-treated PE/GNP composites with 0.75 wt.% GNP achieved a notable bonding enhancement with CFRP showing 528 % and 269 % improvements in strength and fracture energy over untreated neat PE-CFRP samples. These findings offer practical implications for improving the mechanical performance of hydrogen storage tanks contributing to safer and more efficient hydrogen storage systems for a sustainable energy future.

Zero-export photovoltaic systems are an option to transition to Smart Grids. They decarbonize the sector without affecting third parties. This paper proposes the analysis of a zero-export PVS with a green hydrogen generation and storage system. This configuration is feasible to apply by any selfgeneration entity; it allows the user to increase their resilience and independence from the electrical network. The technical issue is simplified because the grid supplies no power. The main challenge is finding an economic balance between the savings in electricity billing proportional to the local electricity rate and the complete system’s investment operation and maintenance expenses. This manuscript presents the effects of the power sizing on the efficacy of economic savings in billing (ηSaving ) and the effects of the cost reduction on the levelized cost of energy (LCOE) and a discounted payback period (DPP) based on net present value. In addition this study established an analytical relationship between LCOE and DPP. The designed methodology pro poses to size and selects systems to use and store green hydrogen from the zero-export photo voltaic system. The input data in the case study are obtained experimentally from the Autonomous University of the State of Quintana Roo located on Mexico’s southern border. The maximum power of the load is LPmax = 500 kW and the average power is LPmean = 250 kW; the tariff of the electricity network operator has hourly conditions for a medium voltage demand. A suggested semi-empirical equation allows for determining the efficiency of the fuel cell and electrolyzer as a function of the local operating conditions and the nominal power of the com ponents. The analytical strategy the energy balance equations and the identity functions that delimit the operating conditions are detailed to be generalized to other case studies. The results are obtained by a computer code programmed in C++ language. According to our boundary conditions results show no significant savings generated by the installation of the hydrogen system when the zero-export photovoltaic system Power ≤ LPmax and DPP ≤ 20 years is possible only with LCOE ≤ 0.1 $/kWh. Specifically for the Mexico University case study zero-export photovoltaic system cost must be less than 310 $/kW fuel cell cost less than 395 $/kW and electrolyzer cost less than 460 $/kW.

A composite hydrogen storage vessel (CHSV) is one key component of the hydrogen fuel cell vehicle which always suffers random vibration during transportation resulting in fatigue failure and a reduction in service life. In this paper firstly the free and constrained modes of CHSV are experimentally studied and numerically simulated. Subsequently the random vibration simulation of CHSV is carried out to predict the stress distribution while Steinberg’s method and Dirlik’s method are used to predict the fatigue life of CHSV based on the results of stress distribution. In the end the optimization of ply parameters of the composite winding layer was conducted to improve the stress distribution and fatigue life of CHSV. The results show that the vibration pattern and frequency of the free and constrained modes of CHSV obtained from the experiment tests and the numerical predictions show a good agreement. The maximum difference in the value of the vibration frequency of the free and constrained modes of CHSV from the FEA and experiment tests are respectively 8.9% and 8.0% verifying the accuracy of the finite element model of CHSV. There is no obvious difference between the fatigue life of the winding layer and the inner liner calculated by Steinberg’s method and Dirlik’s method indicating the accuracy of FEA of fatigue life in the software Fe-safe. Without the optimization the maximum stresses of the winding layer and the inner liner are found to be near the head section by 469.4 MPa and 173.0 MPa respectively and the numbers of life cycles of the winding layer and the inner liner obtained based on the Dirlik’s method are around 1.66 × 106 and 3.06 × 106 respectively. Through the optimization of ply parameters of the composite winding layer the maximum stresses of the winding layer and the inner liner are reduced by 66% and 85% respectively while the numbers of life cycles of the winding layer and the inner liner both are increased to 1 × 107 (high cycle fatigue life standard). The results of the study provide theoretical guidance for the design and optimization of CHSV under random vibration.

This article provides an overview of the requirements for a grid-oriented integration of hydrogen energy storage (HES) and components into the power grid. Considering the general definition of HES and the possible components this paper presents future hydrogen demand electrolysis performance and storage capacity. These parameters were determined through various overall system studies aiming for climate neutrality by the year 2045. In Germany the targeted expansion of renewable energy generation capacity necessitates grid expansion to transport electricity from north to south and due to existing grid congestions. Therefore electrolysis systems could be used to improve the integration of renewable energy systems by reducing energy curtailment and providing grid services when needed. Currently however there are hardly any incentives for a grid-friendly allocation and operation of electrolysis or power-to-gas plants. Two possible locations for hydrogen plants from two current research projects HyCavMobil (Hydrogen Cavern for Mobility) and H2-ReNoWe (Hydrogen Region of north-western Lower Saxony) are presented as practical examples. Using power grid models the integration of electrolysis systems at these locations in the current high and extra-high voltage grid is examined. The presented results of load flow calculations assess power line utilization and sensitivity for different case scenarios. Firstly the results show that power lines in these locations will not be overloaded which would mean an uncritical operation of the power grid. While the overall grid stability remains unaffected in this case selecting suitable locations is vital to prevent negative effects on the local grid.

This article presents an innovative approach to address the optimization and planning of hydrogen network transmission focusing on minimizing computational and operational costs including capital operational and maintenance expenses. The mathematical models developed for gas flow rate pipelines junctions and storage form the basis for the optimization problem which aims to reduce costs while satisfying equality inequality and binary constraints. To achieve this we implement a dynamic algorithm incorporating 100 scenarios to account for uncertainty. Unlike conventional successive linear programming methods our approach solves successive piecewise problems and allows comparisons with other techniques including stochastic and deterministic methods. Our method significantly reduces computational time (56 iterations) compared to deterministic (92 iterations) and stochastic (77 iterations) methods. The non-convex nature of the model necessitates careful selection of starting points to avoid local optimal solutions which is addressed by transforming the primal problem into a linear program by fixing the integer variable. The LP problem is then efficiently solved using the Complex Linear Programming Expert (CPLEX) solver enhanced by Monte Carlo simulations for 100 scenarios achieving a 39.13% reduction in computational time. In addition to computational efficiency this approach leads to operational cost savings of 25.02% by optimizing the selection of compressors (42.8571% decreased) and storage facilities. The model’s practicality is validated through realworld simulations on the Belgian gas network demonstrating its potential in solving large-scale hydrogen network transmission planning and optimization challenges.

This work consists of a systematic review showing recent progress and trends in the development of high entropy alloys (HEA) for solid-state hydrogen storage. The information was compiled from academic papers from the following databases: Google Scholar ScienceDirect Springer SCOPUS American Chemical Society MDPI; as well as the patent banks United States Patent and Trademark Office Google Patent and lens.org. This article discusses key aspects such as HEA design (elements used thermodynamic and geometric characteristics thermodynamic simulations and synthesis methods); HEA evaluation focusing on crystallinity thermal behavior and hydrogen storage; HEA-related trends including MgH2 modification the advancement of lightweight alloys and the use of machine learning.

The reliance on hydrogen as part of the transition towards a low-carbon economy will require developing dedicated pipeline infrastructure. This deployment will be shaped by regulatory frameworks governing investment and access conditions ultimately structuring how the commodity is traded. The paper assesses the market design for hydrogen infrastructure assuming the application of unbundling requirements. For this purpose it develops a general economic framework for regulating pipeline infrastructure focusing on asset specificity market power and access rules. The paper assesses the scope of application of infrastructure regulation which can be set to individual pipelines or to entire networks. When treated as entire networks the infrastructure can provide flexibility to enhance market liquidity. However this requires establishing network monopolies which rely on central planning and reduce the overall dynamic efficiency of the sector. The paper further compares the regulation applied to US and EU natural gas pipeline infrastructure. Based on the different challenges faced by the EU hydrogen sector including absence of wholesale concentration and large infrastructure needs the paper draws lessons for a regulatory framework establishing the main building blocks of a hydrogen target model. The paper recommends a review of the current EU regulatory framework in the Hydrogen and Decarbonised Gas Package to enable i) the application of regulation to individual pipelines rather than entire networks; ii) the use of negotiated third-party access light-touch regulation and possibly marketbased coordination mechanisms for the access to the infrastructure and iii) a more significant role for long-term capacity contracts to underpin infrastructure investments.

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.

This study evaluates and compares physical chemical and dual activation methods for preparing activated carbons from spent coffee grounds to optimize their porosity for hydrogen storage. Activation processes including both one-step and two-step chemical and physical methods were investigated incorporating a novel dual activation process that combines chemical and physical activation. The findings indicate that the two-step chemical activation yields superior results producing activated carbons with a high specific surface area of 1680 m2 /g and a micropore volume of 0.616 cm3 /g. These characteristics lead to impressive hydrogen uptake capacities of 2.65 wt% and 3.66 wt% at 77 K under pressures of 1 and 70 bar respectively. The study highlights the potential of spent coffee grounds as a cost-effective precursor for producing high-performance activated carbons.

As the world shifts towards renewable energy sources the need for reliable large-scale energy storage solutions becomes increasingly critical. Underground Hydrogen Storage (UHS) emerges as a promising option to bridge this gap. However the success of UHS heavily depends on the durability of infrastructure materials particularly cement in wellbores and in unlined rock caverns (URCs) where it serves a dual role in grouting and sealing. This study explores the chemical interactions between hydrogen and cement in these environments exploring how hydrogen might compromise cement integrity over time. We employed advanced thermodynamic analyses kinetic batch tests and 1D reactive transport models to simulate the behaviour of cement when exposed to hydrogen under conditions found in two potential UHS sites: the Haje URC in the Czech Republic and a depleted gas field in the Perth Basin Western Australia. Our results reveal that while certain cement phases are vulnerable to dissolution the overall increase in porosity is minimal suggesting a lower risk of significant degradation. Notably hydrogen was found to penetrate 5 cm of cement within just 4–5 days at both sites. These insights are crucial for enhancing the design and maintenance strategies of UHS facilities. Moreover this study not only advances our understanding of material sciences in the context of hydrogen energy storage but also underscores the importance of sustainable infrastructure in the transition away from fossil fuels.

Large-scale H2 storage in depleted hydrocarbon reservoirs offers a practical way to use existing energy infra structure to address renewable energy intermittency. Cushion gases often constitute a large initial investment especially when expensive H2 is used. Cheaper alternatives such as CO2 or in-situ CH4 can reduce costs and in the case of CO2 integrate within carbon capture and storage systems. This study explored cushion and working gas dynamics through numerically modelling a range of storage scenarios in laterally extensive reservoirs – such as those in the Southern North Sea. In all simulations the cushion and working gases were separated laterally to limit contact surface area and therefore mixing. This work provides valuable insights into (i) capacity estima tions of CO2 storage and H2 withdrawal (ii) macro-scale fluid dynamics and (iii) the effects of gas mixing trends on H2 purity. The results underscore key trade-offs between CO2 storage volumes and H2 withdrawal and purity

Hydrogen energy storage systems (HESS) are increasingly recognised for their role in sustainable energy ap plications though their performance depends on efficient power electronic converter (PEC) interfaces. In this paper a multiport-isolated DC-DC converter characterised by enhanced power density reduced component count and minimal conversion stages is implemented for HESS applications. However the high-frequency multiwinding transformer in this converter introduces cross-coupling effects complicating control and result ing in large power deviations from nominal values due to step changes on other ports which adversely impact system performance. To address this issue a novel model reference-based decoupling control technique is pro posed to minimise the error between the actual plant output and an ideal decoupling reference model which represents the cross-coupling term. This model reference-based decoupling control is further extended into a hybrid decoupling control technique by integrating a decoupling matrix achieving more robust decoupling across a wider operating region. The hybrid decoupling technique mathematically ensures an improved control performance with the cross-coupling term minimised through a proportional-derivative controller. The proposed hybrid decoupling controller achieves a maximum power deviation.

Hydrogen storage plays a crucial role in achieving net-zero emissions by enabling large-scale energy storage balancing renewable energy fluctuations and ensuring a stable supply for various applications. This study provides a comprehensive analysis of hydrogen storage technologies with a particular focus on underground storage in geological formations such as salt caverns depleted gas reservoirs and aquifers. These formations offer high-capacity storage solutions with salt caverns capable of holding up to 6 TWh of hydrogen and depleted gas reservoirs exceeding 1 TWh per site. Case studies from leading projects demonstrate the feasibility of underground hydrogen storage (UHS) in reducing energy intermittency and enhancing supply security. Challenges such as hydrogen leakage groundwater contamination induced seismicity and economic constraints remain critical concerns. Our findings highlight the technical economic and regulatory considerations for integrating UHS into the oil and gas industry emphasizing its role in sustainable energy transition and decarbonization strategies.