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This paper presents a framework for the efficient design and evaluation of a standalone hybrid renewable energy system (HRES) to meet the energy requirements of a rural community in the north-eastern region of Nigeria. The proposed microgrid system incorporates solar photovoltaic, wind turbines, biomass gasifier, fuel cell, and Battery storage. The sizing of each component is determined through the utilization of real local meteorological data and the load demand over a year, employing the Levy flight-salp swarm algorithms (LF-SSA). The optimization objective is to minimize the annualized system cost (ASC) of the HRES, while also considering the reliability constraint of Loss of power supply probability (LPSP). The comparative outcomes demonstrate that the LF-SSA surpasses other examined algorithms, namely the salp swarm, genetic algorithm, and HOMER software by achieving substantial cost savings of $29033, $50796, $191771 respectively in relation to the proposed HRES. The result further shows that, the LF-SSA provides the lowest LCOE of $0.933162/kWh, in contrast to SSA at $0.947737/kWh, GA at $0.958660/kWh, and HOMER at $1.075351/kWh. Additionally, the results indicate that the implemented Energy Management System (EMS) has successfully facilitated the establishment of an environmentally friendly and cost-effective energy system. • An efficient energy storage system is essential for managing intermittent energy supply. • The fuel cell can generate DC power by combining hydrogen with oxygen. • The amount of power generated by a PV panel depends on temperature and solar radiation intensity. • Deterministic rule-based controllers operate based on pre-defined rules. • Energy Management System coordinate the flow of power between different components. [ABSTRACT FROM AUTHOR]

On the path to a net-zero-carbon economy, large-scale energy storage will be an essential part of a renewable energy system. Hydrogen generated from renewable or zero-carbon sources has significant potential as an energy storage medium, by allowing for long-duration and high-capacity energy storage. At the volumes anticipated, however, underground storage systems will likely be essential. Much like the current natural gas system, underground hydrogen storage would provide a safe and cost-effective complement to smaller surface storage infrastructure. Recently, there has been significant interest in the possibility of converting existing gas storage systems to hydrogen storage, though many uncertainties exist in such a process. This paper explores the reservoir dynamics of natural gas/hydrogen gas mixtures and the resulting impacts on storage conversion and gas deliverability. Two specific topics are addressed. First, a novel viscosity model for hydrogen-containing gas mixtures is developed, which shows better agreement with experimental measurements than the widely-used Lohrenz-Bray-Clark model. Second, detailed reservoir simulations are used to investigate cost-effective injection/withdrawal strategies for converting a natural gas storage system to one that stores hydrogen/natural-gas blends. The critical role of buoyancy and gravity override is described, and recommendations are made regarding key reservoir characteristics and injection strategies for managing this behavior. • This study focuses on the conversion of an operational natural gas storage field to hydrogen storage. • A novel viscosity model is developed for hydrogen-containing gas mixtures. • Reservoir simulations evaluate the effect of geologic and engineering parameters on composition and rate of recovered gas. • Gravity segregation significantly influences the severity of fluctuations in the produced gas composition. [ABSTRACT FROM AUTHOR]

The safety of hydrogen directly affects the use of hydrogen refueling stations and public acceptance of hydrogen energy. This paper presented a methodology for the optimal design of the minimum height, width, and safety distance of the firewall of the hydrogen refueling station under various leakage pressures. The obtained relationship between distances and different hydrogen storage pressures is essential for directing the design of hydrogen refueling stations and firefighters to carry out the rescue. Results from numerical simulation showed that the firewall should be 2 m taller than the leakage hole to prevent the hydrogen jet fire from spreading back. The distance before and behind the firewall presented a linear relationship with the leakage pressure. The specific safe distances behind the firewall were 8.4, 8.5, 9.2, and 9.3 m. The firewall width exhibited a non-linear relationship with the leakage pressure. The specific values were 2.5 m for 35 or 45 MPa and 3 m for 70 or 90 MPa. • Methodology for the optimal design of firewalls in hydrogen refueling stations is determined. • The firewall should be 2 m higher than the leakage hole. • Firewalls can deflect flames and prevent them from spreading behind walls. • The distance before and behind the firewall increases with the increase of hydrogen storage pressures. [ABSTRACT FROM AUTHOR]

Hydrogen, as a clean energy source, has been widely used in the automotive industry. However, considering the difficulties of hydrogen storage and transportation, the in-situ production process has received increasing attention. In this paper, a hydrogen production system for dimethyl ether self-heating steam reforming is proposed, using a spiral tube reactor in which the oxidation of dimethyl ether occurs in the spiral tube, and the exothermic oxidation of dimethyl ether is used to provide heat for the dimethyl ether steam reforming hydrogen production reaction. A numerical model of the hydrogen production system for dimethyl ether self-heating reforming is developed, the model is simulated and analyzed, the accuracy of the model is verified through experiments, the influence of various parameters and on the system is analyzed, and the system is optimized. The results show that the proposed system can solve the problems of high energy consumption, low hydrogen yield and difficult reaction control faced by traditional autothermal reforming hydrogen production, and the system can achieve 87.79% dimethyl ether conversion rate, 84.94% hydrogen yield and 85.94% system thermal efficiency. [Display omitted] • Designed a self-heating hydrogen production reaction system for dimethyl ether reforming. • Derive the numerical model and control equation inside the reactor. • Effect of oxygen-to-ether ratio on reforming hydrogen production system is studied. • Effect of steam-to-ether Ratio on reforming hydrogen production system is studied. • Effect of reaction temperature on reforming hydrogen production system is studied. [ABSTRACT FROM AUTHOR]

Cryogenic supercritical hydrogen storage technology is a high-density physical hydrogen storage method, which is a highly promising hydrogen storage approach. However, existing research has mainly focused on the development of storage devices for cryogenic supercritical hydrogen, with limited research on the cooling process of supercritical hydrogen. Therefore, a novel cooling process for cryogenic supercritical hydrogen production based on helium expansion cycle with liquid nitrogen (LN 2) pre-cooling is proposed in this paper. In this process, after being compressed and cooled in multiple stages, the feed hydrogen is pre-cooled by LN 2. Then, cryogenic supercritical hydrogen (10 MPa, −235.15 °C, 63.36 g/L) is obtained by helium multi-stage expansion refrigeration. The process is simulated by Aspen HYSYS and optimized by genetic algorithm (GA) to obtain lower specific energy consumption (SEC). Thermodynamic analyses are conducted to evaluate the process. And compared with the conventional hydrogen liquefaction process, the results show that the proposed process is reasonable and superior. The SEC 0 , figure of merit (FOM), and the total exergy loss of the system are 5.432 kWh/kg H2 , 43.88%, and 289.69 kW respectively. This study indicates that the proposed process has significant implications for the hydrogen industry and provides valuable information for cryogenic supercritical hydrogen storage systems. • A novel high-density cryogenic supercritical hydrogen storage system is proposed. • Twelve key variables in the process are optimized to reduce the energy consumption. • The process has higher exergy efficiency than conventional LH 2 plants. • The volume storage density of hydrogen can reach 63.36 kg/m3 in the system. [ABSTRACT FROM AUTHOR]

Nitrogen heterocyclic organics are promising hydrogen storage carriers with the advantage of being capable of large-scale transportation over long distances using existing oil and gas facilities. However, traditional methods for the hydrogenation and dehydrogenation of organic hydrogen carriers usually require high temperature and pressure conditions and external hydrogen supplies, which hinder their large-scale applications, as well as having certain safety risks. In this paper, a reversible electrochemical hydrogen storage system using quinoxaline as a hydrogen carrier was developed with potential for use at room temperature and atmospheric pressure. Experiments revealed that the hydrogenation conversion of quinoxaline reached 95% within 120 min at −0.20 V vs. RHE, and the dehydrogenation conversion of 1,2,3,4-tetrahydroquinoxaline reached 100% within 30 min at 1.30 V vs. RHE. This means that the system achieved quick and efficient reversible hydrogen storage. The Pd/NF dual-function electrode prepared by spontaneous redox reaction still showed high catalytic activity after 8 cycles, indicating its good long-term stability. The proton donor in the electrochemical hydrogenation process of quinoxaline was water, which completely eliminates the safety risk from the use of external hydrogen. This work provides a simple and reliable strategy for efficient hydrogen storage using nitrogen heterocyclic organics. [Display omitted] • The hydrogenation conversion of quinoxaline reached 95%. • The optimum dehydrogenation conversion of 1,2,3,4-tetrahydroquinoxaline was 100%. • Pd/NF electrode was operated as a dual-function electrocatalyst. • Efficient reversible hydrogen storage was achieved at 25 °C and atmospheric pressure. • The H∗ required for the electrochemical hydrogenation of quinoxaline came from H 2 O. [ABSTRACT FROM AUTHOR]

Direct air capture of carbon dioxide (CO 2) is technically a feasible solution for reducing atmospheric CO 2 concentrations at scale, building on decades of global research. However, powering such systems even partially with CO 2 -intensive fossil fuels results in more CO 2 emissions. This paper presents a novel energy management strategy (EMS) to further explore modular offshore wind energy off Canada's West Coast via power-to-direct air capture and power-to-gas systems. The system architecture includes a 15 MW wind turbine paired with a hydrogen energy storage system, i.e. hydrogen production and storage, and direct air capture (DAC) units. Hydrogen production from wind generation is stored and used to offer two key benefits: to deliver the thermal loads of the DAC system, and to meet hydrogen demand for external consumers. The proposed EMS offers an extra degree of freedom to operate the designed system by setting the priority either to maximize the amount of CO 2 capture or to maximize the amount of H 2 production for external consumers. In particular, the study incorporates dynamic mathematical modeling and constraints formulation for the aforementioned scenarios; DAC priority for CO 2 capture and H 2 for external hydrogen demand satisfaction. The effectiveness of the proposed EMS is shown through extensive simulations with different seasonal conditions. • Detailed mathematical dynamical models for offshore power-to-DAC and power-to-gas systems. • Green hydrogen production for two-fold benefits; H 2 for meeting DAC thermal loads, and H 2 as fuel for external consumers. • Scenario 1 prioritize the CO 2 capture rate, while scenario 2 maximizes the H 2 production for external consumers. • Design of EMS shows the correct unit commitment of the CO 2 capture rate and H 2 tracking. [ABSTRACT FROM AUTHOR]

This paper aims to provide a holistic analysis of the role of hydrogen for achieving greenhouse gas neutrality in Germany. For that purpose, we apply an integrated energy system model which includes all demand sectors of the German energy system and optimizes the transformation pathway from today's energy system to a future cost-optimal energy system. We show that 412 TWh of hydrogen are needed in the year 2045, mostly in the industry and transport sector. Particularly, the use of about 267 TWh of hydrogen in industry is essential as there are no cost-effective alternatives for the required emission reduction in the chemical industry or in steel production. Furthermore, we illustrate that the German hydrogen supply in the year 2045 requires both an expansion of domestic electrolyzer capacity to 71 GW H2 and hydrogen imports from other European countries and Northern Africa of about 196 TWh. Moreover, flexible operation of electrolyzers is cost-optimal and crucial for balancing the intermittent nature of volatile renewable energy sources. Additionally, a conducted sensitivity analysis shows that full domestic hydrogen supply in Germany is possible but requires an electrolyzer capacity of 111 GW H2. • 412 TWh of hydrogen demand in a greenhouse gas neutral Germany in the year 2045. • Hydrogen usage is crucial for defossilization of chemical and steel industry. • 47% of hydrogen is imported from other European countries and Northern Africa. • 71 GW H2 of electrolyzer capacity in Germany with flexible operation. • 35 TWh of hydrogen storage in salt caverns for security of supply. [ABSTRACT FROM AUTHOR]

The storage of hydrogen in metal hydride reactors is examined experimentally and numerically in this paper. In this respect, as-received LaNi 5 powders are coated with different amounts of copper by using copper sulphate solution to accelerate the hydrogen charging processes. The thermal conductivity of the copper-coated storage material is found to reach up to 8 times of the uncoated powders. A two-dimensional axisymmetric model regarding complex heat and mass transfer occurring during hydrogen charging process in metal hydride reactors is numerically solved at macro level. The developed model is validated by using experimental data related to the amount of hydrogen stored and the reactor temperatures. In accordance with the experimental results, the simulation results show that more homogenous temperature distribution in the reactor can be obtained with the copper coating due to improved thermal properties. Moreover, charging time is also improved by the copper coating. However, since the reactor is loaded with coated/uncoated LaNi 5 powders at the same weight of 65 g, the total amount of hydrogen stored decreases with the copper coating due to reduced amount of LaNi 5. • LaNi 5 powders are coated with copper to improve hydrogen storage performance. • Thermal conductivity is notably improved with copper additive. • Hydrogen charging time is significantly shortened with copper additive. • A 2D axisymmetrical model is developed to simulate the hydrogen storage. • The experimental and numerical results are in good agreement. [ABSTRACT FROM AUTHOR]

Optimal energy management of microgrids enables efficient integration of renewable energies by considering all system flexibilities. For systems with significant seasonal imbalance between energy production and demand, it may be necessary to integrate seasonal storage in order to achieve fully decarbonized operation. This paper develops a novel model predictive control strategy for a renewable microgrid with seasonal hydrogen storage. The strategy relies on data-based prediction of the energy production and consumption of an industrial power plant and finds optimized energy flows using a digital twin optimizer. To enable seasonal operation, incentives for long-term energy shifts are provided by assigning a cost value to the storage charge and adding it to the optimization target function. A hybrid control scheme based on rule-based heuristics compensates for imperfect predictions. With only 6% oversizing compared to the optimal system layout, the strategy manages to deliver enough energy to meet all demand while achieving balanced hydrogen production and consumption throughout the year. • PV with seasonal H 2 storage enables fully sustainable operation of industrial microgrids. • Model predictive control overcomes perfect foresight limitation in energy management. • H 2 production for long-term storage is incentivized by adding an extra cost term. • Hybrid predictive control enables a low cost system with nearly perfect yearly operation. [Display omitted] [ABSTRACT FROM AUTHOR]

Liquid organic hydrogen carriers (LOHCs) are considered a promising hydrogen storage technology. Heat must be exchanged with an external medium, such as a heat transfer fluid, for the required chemical reactions to occur. Batch reactors are simple but useful solutions for small-scale storage applications, which can be modelled with a lumped-parameter approach, adequately reproducing their dynamic performance. For such reactors, power is consumed to circulate the external heat transfer fluid and stir the organic liquid inside the reactor, and heat transfer performance and power consumption are two key parameters in reactor optimisation. Therefore, with reference to the hydrogen release phase, this paper describes a procedure to optimise the reactor thermal design, based on a lumped-parameter model, in terms of heat transfer performance and minimum power consumption. Two batch reactors are analysed: a conventional jacketed reactor with agitation nozzles and a half-pipe coil reactor. Heat transfer performance is evaluated by introducing a newly defined dimensionless parameter, the Heat Transfer Ratio (HTR), whose value directly correlates to the heat rate required by the carrier's dehydrogenation reaction. The resulting model is a valid tool for adequately reproducing the hydrogen storage behaviour within dynamic models of complex and detailed energy systems. • Thermal design of hydrogen storage systems based on LOHC batch reactors is analysed • Design is optimised to ensure effective heat transfer and minimum power consumption • Novel dimensionless parameter (Heat Transfer Ratio, HTR) is introduced • A threshold HTR value is identified, above which only marginal gains are achieved • The lumped-parameter model can be deployed in complex energy system dynamic models [ABSTRACT FROM AUTHOR]

In the present scenario, hydrogen has become a prominent alternative of fossil fuel that motivated us to develop more advanced nanomaterials to store efficient hydrogen for future use. This paper studies the hydrogen storage performance of Li-decorated Ѱ-graphene by conducting density functional theory simulations involving van der Waals corrections. Psi (Ѱ)-graphene is an advanced two-dimensional carbon allotrope that comprises pentagon, hexagon, and heptagon carbon rings. The simulation outcome reveals that the Li atom is bounded strongly to Ѱ-graphene with −2.63 eV binding energy through 0.89e charge transfer from Li-2s orbital to C-2p orbitals. Ѱ-graphene system decorated with the Li atom can bind seven hydrogen molecules with a suitable average binding energy of −0.31 eV/H 2 , high H 2 gravimetric capacity of 15.15 wt%, and optimal average desorption temperature of 384 K. As per the Bader charge portioning, ∼0.09e charge is transferred from the Li-2s orbital to the H-1s orbital after hydrogen adsorption on Li + Ѱ-graphene. The hydrogen molecules are adsorbed on Li + Ѱ-graphene via a polarization mechanism. The high Li diffusion barrier of 0.78 eV and structural integrity of Li + Ѱ-graphene configuration at high temperature predicts that the system is a suitable candidate for high-capacity hydrogen storage applications. [Display omitted] • The Li atom attached to Ѱ-graphene with binding energy of −2.54 eV. • A single Li-decorated Ѱ-graphene system can adsorb 7H 2 molecules leading to 15.15 gravimetric wt % of hydrogen. • The desorption temperature of 384K is obtained, which is ideal for reversible H 2 storage. • Stability of the structure is validated through MD simulations. • The diffusion energy barrier of 0.78 eV is obtained, sufficient to prevent the system from metal-metal clustering. [ABSTRACT FROM AUTHOR]

The presence of distributed energy sources in integrated energy systems make it difficult to meet the real-time balance between supply and demand, requiring the deployment of energy storage systems. Hydrogen storage can compensate for the lack of electrochemical energy storage in the energy, time and space dimensions. Meanwhile, the cooperative operation of participants within an integrated energy system, compared to individual operation, can help generate additional benefits and reduce carbon emissions. Therefore, this paper proposes a method for optimising the operation of integrated energy systems based on a cooperative game containing hydrogen energy storage systems. Firstly, a model for optimising the operation of an integrated energy system with hydrogen storage energy system considering the revenue from hydrogen sales is constructed. Secondly, a benefit allocation mechanism for the cooperative game based on the shapley value method is proposed. Finally, the BPSO-SA optimisation algorithm is proposed for solution. The total operating cost of the collaborative operation scenario is reduced by 22.96% and the carbon emissions are reduced by 80.11% compared to the independent operation scenario, the operating cost savings and carbon emissions reduction are allocated to the participants according to their contribution, encourage participants to build integrated energy systems through collaboration. • A model for optimising the operation of an IES containing hydrogen energy storage system is developed. • A multi-participant cooperative game benefit allocation mechanism within the IES is developed. • A hybrid particle swarm optimisation-simulated annealing based on beetle antennae search strategy (BPSO-SA) is proposed. [ABSTRACT FROM AUTHOR]

With hydrogen contents 6.69 and 7.49 wt%, Sn(AlH 4) 4 and Zr(AlH 4) 4 were experimentally synthesized, but their structures, bonding natures and hydrogen storage properties were not further investigated. This paper determines the low energy structures of Sn(AlH 4) 4 and Zr(AlH 4) 4 crystals by using global optimization algorithm combined with density functional theories, and analyze their electronic structures and bonding properties. The most stable structures of Sn(AlH 4) 4 and Zr(AlH 4) 4 contain isolated H 2 molecules. The formation enthalpies of Zr(AlH 4) 4 reaches 1.0 eV and the value of Sn(AlH 4) 4 is a little smaller. In Zr(AlH 4) 4 , the AlH 5 , AlH 6 and Al 2 H 6 units are connected tightly by Zr atoms through H bridges. In Sn(AlH 4) 4 , the AlH 6 units form a net structure, and the Sn atom exists in SnH 3 with one shared H atom. The bonding characteristics are analyzed by calculating charge populations and crystal orbital hamilton population (COHP). The metal components (Al, Sn, Zr) and H atoms form polarized covalent bonds. The covalent contributions are close for Sn–H and Al–H bonds but the charge values on the Sn atoms are much smaller. For the Zr–H bonds, both the charges on the Zr atoms and the covalent contributions are smaller than the values of the Al–H bonds. Combining the bonding natures and the structure features, it suggests that proper electronegativity of the metal atoms (Sn and Zr here) is the key factor for the stabilities and reversible hydrogen storage properties of metal aluminum hydrides. • The crystal phases of Sn(AlH 4) 4 and Zr(AlH 4) 4 are predicted. • The metal components (Al, Sn, Zr) and H atoms form polarized covalent bonds. • In Zr(AlH 4) 4 , Polarized covalent Zr–H bond is weaker than Al–H bond. • Hydrogen storage capacity in Sn(AlH 4) 4 and Zr(AlH 4) 4 reaches 6.69 and 7.49 wt%,respectively. • The electronegativity of metal atoms in aluminum hydrides is related to structural stability and reversible hydrogen storage. [ABSTRACT FROM AUTHOR]

In this paper, using density functional theory (DFT), we investigate the impact of mechanical treatment in terms of uniaxial and biaxial strains on both hydrogenation states of magnesium compounds i.e. H 2 -free magnesium (Mg) and preliminarily hydrogenated magnesium (MgH 2). The thermodynamic properties calculation shows that applying uniaxial and biaxial strains on the H 2 -free magnesium does not significantly affect the formation enthalpy and decomposition temperature of the hydride phase. On the other hand, strain energy contributions on preliminarily hydrogenated magnesium are found able to decrease and improve the formation enthalpy and the decomposition temperature, making it feasible for the operational conditions of proton exchange membrane (PEM) fuel cells at 289 – 393 K. Also, the findings demonstrate that the kinetic properties in terms of hydrogen atom diffusion show a decrease in the activation energy barrier, which means an improvement in the kinetics properties faster than that of strain-free magnesium hydride. These results potentially provide better clues for the development of a magnesium-based metal hydride for hydrogen storage applications. [Display omitted] • Magnesium hydride has high thermodynamic properties and slow kinetics. • Strains on H 2 -free Magnesium does not affect its thermodynamic properties. • Pre-hydrogenated Magnesium under strain shows better thermodynamic properties. • The achieved results meet practical requirements for H 2 -storage in PEM fuel cells. [ABSTRACT FROM AUTHOR]

This paper describes a model of hydrogen blowdown dynamics for storage tanks needed for hydrogen safety engineering to accurately represent incident scenarios. Heat transfer through a tank and pipe walls affects the temperature and pressure transients inside the storage vessel and at the nozzle exit, and thus the characteristics of the resulting hydrogen jet in the case of loss of containment. Current non-adiabatic blowdown models are validated against experiments performed with hydrogen storage tanks at only ambient temperature. The effect of heat transfer for cryo-compressed hydrogen is more significant due to a larger difference of temperature between the stored hydrogen and the surrounding atmosphere, especially in case of equipment insulation failure during an incident. Our previous work demonstrated that the heat transfer through a discharge pipe wall can significantly affect the mass flow rate of cryogenic hydrogen releases. Thoroughly validated models of non-adiabatic blowdown dynamics for cryo-compressed hydrogen are missing at the moment. This work develops further the non-adiabatic blowdown model at ambient temperature using the under-expanded jet theory developed at Ulster University, to expand it to cryo-compressed hydrogen storage tanks. The non-ideal behaviour of cryo-compressed hydrogen due to low temperatures is taken into account through the high-accuracy Helmholtz energy formulations. The developed model includes effect of heat transfer at both the tank and the discharge pipe walls. The model is thoroughly validated against sixteen tests on blowdown of hydrogen storage tanks with initial pressure 0.6–20 MPa ab and temperature 80–310 K, through release nozzle of diameter in the range 0.5–4.0 mm, performed within the PRESLHY project. The model well reproduces the experimental pressure and temperature recordings in the storage tank during the entire blowdown duration for the whole set of sixteen tests. In conjunction with the volumetric source model, explained in detail, the physical model allows to perform CFD simulations accurately reproducing the temperature distribution in time and space for the cryogenic hydrogen jet experiment. • Physical model of blowdown dynamics for cryo-compressed hydrogen storage tanks. • The model accounts for heat transfer at both the tank and the discharge pipe walls. • The model employs the high-accuracy Helmholtz energy formulations. • Validation against tests with pressure 0.6–20 MPa and temperature 80–310 K. [ABSTRACT FROM AUTHOR]

The paper proposes the analysis of four different scenarios of renewables penetration (40%, 60%, 80%, and 100%) with the most affordable generators: photovoltaic panels and wind turbines. The synergy of two storage technologies, such as Li-Ion batteries and the hydrogen power-to-power solution (electrolyzer, H 2 tank, and fuel cells), is evaluated to ensure the balance of the power-grid. The paper discusses the numerical Trnsys-based modeling of the smart grid. A detailed performance evaluation of each component, according to operational maps provided by manufacturers, has been performed to meet an electrical load (10 MW peak - 54 GW h annual). The results of the analysis show the crucial role of the H 2 system in the goal of achieving a higher renewable fraction, mainly due to the possibility of seasonal storage without the self-discharge limitation of batteries. In the 100% renewable solution the contribution of H 2 is equal to 30% of the electric load. • The synergy of Li-Ion batteries and hydrogen is evaluated to ensure grid balance. • Hydrogen integration has been evaluated in the path to 100% renewable energy. • The optimum solution is a tradeoff between renewable share and system cost. • A fully renewable system would cost $0.42/kWh with a 30% hydrogen contribution. • Hydrogen power-to-power system is strongly limited by high cost. [ABSTRACT FROM AUTHOR]

The most important hydrogen energy storage technologies, developed between 1974 and 2022, now enable the quality operation of global power grids that integrate alternative energy facilities (wind power, solar power, geothermal power, etc.). With the continuous large-scale penetration of converter-interfaced generation (CIG), based on the combined use of renewable energy sources (RES) and hydrogen energy storage systems (ESS), into practical power systems, the dynamic characteristics of the latter change significantly. New challenges with the power system control and stability arise due to the specific CIG properties. A positive-sequence time-domain simulation is frequently used to solve them. However, the known simplifications and limitations are inevitably applied in case of such simulation. These become critical for the CIG with RES and hydrogen ESS models due to their fast dynamics. Therefore, the validation of such simulation results becomes relevant. This paper proposes a novel validation approach based on the use of a benchmark tool Hybrid Real-Time Power System Simulator (HRTSim) instead of field measurements. A major feature of the proposed approach is the possibility of a guaranteed validation of the benchmark tool using any state of the modeled power system. A hybrid implementation of a detailed three-phase model of CIG is also developed for the HRTSim, which provides an adequate simulation of the full range of dynamic processes. The results of validation of a positive-sequence simulation of a practical power system with CIG, which includes both RES and hydrogen ESS, using the developed approach presented in this paper have allowed to identify the causes of calculation errors, as well as factors affecting them. [ABSTRACT FROM AUTHOR]

Hydrogen energy storage system (HESS) has excellent potential in high-proportion renewable energy systems due to its high energy density and seasonal storage characteristics. After detailing the volatility of wind speed, irradiance and load, this paper proposes a bi-level optimization model to analyze the economic operation of the wind-photovoltaic-hydrogen hybrid system (WPH-HS). First, the relationship between the source-load output matching and operating conditions of HESS is studied, two evaluation indicators are described, which can be adjusted by wind-solar complementarity on the source side and demand response on the load side. Second, considering the levelized cost of storage (LCOS), the total annual cost (TAC) calculation method of WPH-HS is presented, and this paper provides a new hybrid optimization technology of chaotic search, particle swarm optimization and non-dominated sorting genetic algorithm2. Finally, the system is simulated with the MATLAB software to determine the optimal sizing of components and minimize the LCOS while ensuring the optimal TAC. The simulation results are elaborated in detail. In particular, the added source-load interaction reduces the TAC and LCOS by 7.3% and 10.3%. When two indicators reach 0.03 and 0.1745, the system is economically viable with the LCOS of 0.276 USD/kWh. The hybrid optimization algorithm can achieve better result in fewer iterations. • The cross-season utilization of the hydrogen energy storage system is discussed. • A price bi-level model about the levelized cost of storage and the total annual cost is established. • Evaluation indicators are presented to promote the source-load interaction. • Effects of wind speed, irradiance, and loads are investigated for the levelized cost of storage. • A hybrid optimization algorithm based on three common algorithms is designed. [ABSTRACT FROM AUTHOR]

The paper describes the breakthrough microleaks-no-burst (μLNB) safety technology of explosion free in fire self-venting hydrogen tanks that do not require thermally-activate pressure relief devices (TPRD). The technology implies melting of the hydrogen-tight liner before hydrogen-leaky double-composite wall loses its load-bearing ability. Hydrogen then flows through the wall's microchannels and either burns in microflames on its own or together with resin. The experimental validation of the technology is presented for 7 prototypes with the nominal working pressure of 70 MPa made of carbon-carbon or carbon-glass composites. The prototypes are fire tested at the specific heat release rate HRR/A = 1 MW/m2 characteristic for gasoline/diesel spill fires. The μLNB technology eliminates catastrophic consequences of tank rupture in fire: blast waves, fireballs, and projectiles. The technology limits hydrogen accumulation in naturally ventilated enclosures. It reduces the risk of hydrogen-powered vehicles to an acceptable level below that for fossil fuel automobiles, including underground parking and tunnels. It provides an unprecedented level of life safety and property protection. • Breakthrough safety technology of explosion free in fire tank is introduced. • The tank made of 2 composites is self-venting in fire and does not require TPRD. • The microleaks-no-burst concept of tank performance in fire is explained. • 4 carbon-carbon and 3 carbon-glass tanks are successfully tested in 1 MW/m2 fire. [ABSTRACT FROM AUTHOR]

Due to the uncertainty of structure and material parameters, reliability analysis of hydrogen storage composite pressure vessel (CPV) is an important issue. In this paper, reliability analysis of hydrogen storage CPV is carried out based on kriging surrogate model with two types of random-interval uncertainties. First, progressive failure behavior is analyzed based on finite element model (FEM) of CPV. Second, the kriging model is built to surrogate the burst pressure. Then, global sensitivity analysis is conducted using Sobol method. Finally, uncertainty analysis and reliability analysis of CPV are carried out with two types of random-interval uncertainties. The results show that longitudinal tensile strength, thicknesses of the hoop layers and the helical layers are important factors of the CPV burst. Besides, the reliability of CPV is low (0.048) with random-interval uncertainties, which should be improved to increase the safety of CPV. The proposed method provides a general solution to the reliability analysis of CPV with two types of random-interval uncertainties, which would co-exist in the hydrogen storage CPV. [Display omitted] • The kriging model of hydrogen storage vessel burst is established and verified. • The global sensitivity analysis of burst is carried out by Sobol method. • Longitudinal tensile strength and layer thickness are important influencing factors. • Reliability analysis is carried out with random-interval uncertainties. • Reliability is smaller with hybrid uncertainties than with only random uncertainty. [ABSTRACT FROM AUTHOR]

The paper proposes a methodology for designing intelligent systems of autonomous distributed hybrid power complexes (ADHPC) ensuring a minimum level of energy consumption from the national external grid as well as diesel power plants used to deliver the power to regional households, and industrial consumers. It will be realized because of the effective use of generated energy from renewable energy sources in such ADHPC systems by considering their both normal and emergency operating modes. In doing so, ADHPC will not only help offload the existing power grid during peak demand, but also allow for significant process efficiencies in energy production from renewable energy sources (RES), including "green" hydrogen: for instance, the excess energy is accumulated during the period of its excess and is provided back to power consumers in the period of shortage, the electricity losses are reduced since effective management is applied for power flows circulating in the ADHPC systems. The methodology includes the following stages (subtasks): development of the structure of a distributed hybrid system for generating and transporting electricity from sources to consumers; development of a system for diagnostics of failures of generating units and wire breaks in sections of local power transportation networks and management based on the diagnostics results of power flows circulating in the ADHPC systems for both normal and emergency modes. Therefore, a balance of power capacities and minimization of their losses are ensured. [ABSTRACT FROM AUTHOR]

Long-term and large-scale H 2 storage is vital for a sustainable H 2 economy. Research in underground H 2 storage (UHS) in porous media is emerging, but the understanding of H 2 reconnection and recovery mechanisms under cyclic loading is not yet adequate. This paper reports a qualitative and quantitative investigation of H 2 reconnection and recovery mechanisms in repeated injection-withdrawal cycles. Here we use microfluidics to experimentally investigate up to 5 cycles of H 2 injection and withdrawal under a range of injection rates at shallow reservoir storage conditions. We find that H 2 storage capacities increase with increasing injection rate and range between ∼10% and 60%. The residual H 2 saturation is in the same range between cycles (30–40%), but its distribution in the pore space visually appears to be hysteretic. In most cases, the residually trapped H 2 reconnects in the subsequent injection cycle, predominantly in proximity to the large pore clusters. Our results provide valuable experimental data to advance the understanding of multiple H 2 injection cycles in UHS schemes. [Display omitted] • Microfluidics for examination of cyclic hydrogen injections. • Microscopic hydrogen storage capacities up to 60% of the pore space. • Reproducible residual hydrogen saturation between the injection cycles. • Efficient reconnection of residually trapped hydrogen in the next drainage cycle. [ABSTRACT FROM AUTHOR]

Integration of renewable energy sources (RES) together with energy storage systems (ESS) changes processes in electric power systems (EPS) significantly. Specifically, rate of change and the lowest values of operating conditions during the emergencies are got influenced. Such changes can cause incorrect actions of relay protection (RP) as it was designed and adjusted with no regard for influence of RES and ESS. Detailed research on processes during the different normal and abnormal modes in both EPS and primary transducers and also in RP devices should be done to take preventive actions. To do this research mathematical modeling based on detailed and authentic models of all elements including RP should be used. HRTSim (which was developed by authors) software for simulating EPS provides the opportunity to create such models of EPS of any size without simplifications and limits. Using of this instrument together with detailed mathematical models of RP which were developed before provided the opportunity to investigate them rigorously in RES-integrated EPS. Settings providing adequate action of RP in certain conditions were performed as a result of this investigation. Fragments of these investigations are performed in this paper. Results of these investigations would be useful for designing new methods and tools of RP adjustment. General structure of a grid-connected combined renewable energy system with a hydrogen storage system. [Display omitted] [ABSTRACT FROM AUTHOR]

The paper discusses the suitability of bedded salt deposits for underground hydrogen storage facilities. The presented research is an example of multi-criteria decision analysis coupled with spatial data analysis undertaken using GIS (Geographic Information System). The aim of this study is to develop a methodology for selecting the best locations for hydrogen storage in salt caverns. In the analysis, we take into account the results of previous studies of the storage capacity of rock salt deposits. The presented methodology allows the creation of rock salt deposit suitability maps for underground hydrogen storage. The results show that the applied method significantly influences the resulting map image, helping to identify optimal locations for hydrogen storage facilities. The presented approach may be of value to governmental institutions considering underground hydrogen storage, geological services, power plants producing electricity from renewable energy sources, and chemical and petrochemical plants. • A site-selection method was developed for hydrogen storage in salt caverns. • The method is based on the analyses of multi-criteria decision and spatial data. • The method was applied in a case study, the results of which are presented here. • The case study result allowed to identify favorable locations for hydrogen storage. [ABSTRACT FROM AUTHOR]

Large-scale application of hydrogen requires safe, reliable and efficient storage technologies. Among the existing hydrogen storage technologies, cryo-compressed hydrogen (CcH 2) storage has the advantages of high hydrogen storage density, low energy consumption and no ortho-para hydrogen conversion. But it still needs higher hydrogen storage pressure when reaching higher hydrogen storage density. In order to reduce hydrogen storage pressure and improve storage density, solid adsorption technology is introduced in CcH 2. Activated carbon and metal-organic framework materials (MOFs) are employed as adsorbents in this paper. The gravimetric/volumetric hydrogen storage capacities of different adsorption tanks are studied and compared with the hydrogen storage conditions of 1–55 MPa at 77–298 K. The results show that the hydrogen storage density of CcH 2 combined with adsorption is higher than that of pure adsorption hydrogen storage, and the storage pressure is lower than that of pure CcH 2 under the same hydrogen storage capacity. And the combination of two hydrogen storage technologies can achieve a high hydrogen storage capacity equivalent to that of liquid hydrogen at a lower pressure. • CcH 2 combined with adsorption can reach higher density with lower storage pressure. • AX-21 plays a negative role when exceed the specific pressure (24 MPa at 77K). • MOFs can significantly improve the density of CcH 2 in a wide range. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the hydrogen storage capacity of OLi 3 decorated graphyne and graphdiyne using density functional theory calculation. The optimization results showed that the OLi 3 superalkalis were anchored strongly on the graphyne and graphdiyne with the adsorption energy of −3.82 and −4.04 eV, respectively. The binding energy between OLi 3 and carbon nanosheet is much higher than that between two OLi 3 superalkalis, indicating their uniform dispersion over the carbon material surface without any aggregation. The thermal stability has also been verified by ab inito molecular dynamics simulation. Decorating with OLi 3 can effectively improve the hydrogen storage capacity of carbon monolayers. The hydrogen storage capacities of 4OLi 3 /GY and 8OLi 3 /GDY complexes are 7.23 and 8.87 w. t. %, with the average hydrogen adsorption energy of −0.252 and −0.218 eV per H 2. The binding energy between Li and its neighboring H 2 is contributed by the electron transfer and some orbital hybridization. The results suggest the complexes with reversible hydrogen storage properties at ambient temperature, indicating their potential use as promising hydrogen storage candidates. • Large binding energy and electrostatic repulsion hinder the clustering of OLi 3. • The decoration with OLi 3 significantly increase the HSC of graphyne and graphdiyne. • The hydrogen adsorption energy of 4OLi 3 /GY and 8OLi 3 /GDY are −0.252 and −0.218 eV. • The T D ensure 4OLi 3 /GY to be hydrogen storage medium under moderate temperature. [ABSTRACT FROM AUTHOR]

Based on the density functional theory, we investigate the electronic properties of the clusters M 2 B 7 (M = Be, Mg, Ca) and their hydrogen storage properties systematically in this paper. Extensive global search results show that the global minimal structures of the three systems (Be 2 B 7 , Mg 2 B 7 and Ca 2 B 7) are heptagonal biconical structure, and the two alkaline earth metals are located at the top of the biconical. Chemical bonding analyses show that M 2 B 7 clusters have 6σ and 6π delocalized electrons, which are doubly aromatic. At the wB97XD level, the three systems have good hydrogen storage capabilities. The hydrogen storage density of Be 2 B 7 is as high as 23.03 wt%, while Mg 2 B 7 and Ca 2 B 7 also far exceed the hydrogen storage target set by the U.S. Department of Energy in 2017. Their average adsorption energies of H 2 molecules all ranged from 0.1 eV/H 2 to 0.48 eV/H 2 , which is fall in between physisorption and chemisorption. Extensive Born Oppenheimer molecular dynamics (BOMD) simulations show that the H 2 molecules of the three systems can be completely released at a certain temperature. Therefore, M 2 B 7 systems can achieve reversible adsorption of H 2 molecules at normal temperature and pressure. It can be seen that the B 7 clusters modified by alkaline earth metals may become a promising new nano-hydrogen storage material. [Display omitted] • The M 2 B 7 clusters exhibit the high capacity hydrogen storage and release. • Be 2 B 7 can adsorb 14H 2 and achieve the theoretical 23.03 wt% gravimetric density. • The gravimetric density is as high as 13.87 wt% for Mg 2 B 7 and 13.36 wt% for Ca 2 B 7. • The alkali earth metal doped B 7 clusters can be used as hydrogen storage materials. [ABSTRACT FROM AUTHOR]

Environmentally friendly and pollution-free hydrogen cell, battery and supercapacitor hybrid power system has taken the attention of scientists in recent years. Several notable advancements in energy storage mechanisms with hybrid power systems have been made during the last decade, influencing innovation, research, and the possible direction for improving energy storage technologies. This paper represents a quantitative analysis of all knowledge carriers with mathematical and statistical methods of hydrogen energy storage to establish a hybrid power system. For selecting the top cited papers in this topic, related articles on energy storage mechanisms for hybrid power systems were searched in the Scopus database under specified predetermined parameters. The selection technique of the most cited paper was based on filtered keywords in the hybrid hydrogen energy storage-based hybrid power system and related research during 2008–2021. About 48% of all articles have been published between 2016 and 2019; 21% will have originated from China; and 29% of the papers have used batteries as a form of energy storage in the application of electric vehicles. Most of the articles contain experimental work (25.11%) followed by simulation analysis (25%) and systematic and nonsystematic review (18.75%). Related publications with the most citations were published in 35 different impactful journals from different publishers and nations. This research found that integrating hydrogen energy storage with battery and supercapacitor to establish a hybrid power system has provided valuable insights into the field's progress and development. Moreover, it is a thriving and expanding subject of study. Bibliometric analysis was used to identify the most significant research publications on the subject of hybrid energy storage, mapping the multidisciplinary character, illustrating nature and trends, and outlining areas for further research. The process of collecting, selecting, and analyzing the most cited articles is expected to contribute to a methodical foundation for future developments of hydrogen energy storage systems and provide viable research paths toward attaining a hybrid power system. • Hydrogen-battery-supercapacitor hybrid power system made notable advancements. • A statistical analysis of hydrogen storage integrated hybrid system is demonstrated. • Top cited papers were searched in Scopus database under predetermined parameters. • Challenges and recommendations are highlighted for future energy applications. • Bibliometric analysis was used to identify potentials for future research directions. [ABSTRACT FROM AUTHOR]

Considering the high calorific value and low-carbon characteristics of hydrogen energy, it will play an important role in replacing fossil energy sources. The production of hydrogen from renewable energy sources for electricity generation and electrolysis of water is an important process to obtain green hydrogen compared with classic low-carbon hydrogen production methods. However, the challenges in this process include the high cost of liquefied hydrogen and the difficulty of storing hydrogen on a large scale. In this paper, we propose a new route for hydrogen storage in metals, namely, electricity generation from renewable energy sources, electrolysis to obtain metals, and subsequent hydrogen production from metals and water. Metal monomers facilitate large-scale and long-term storage and transportation, and metals can be used as large-scale hydrogen storage carriers in the future. In this technical route, the reaction between metal and water for hydrogen production is an important link. In this paper, we systematically summarize the research progress, development trend, and challenges in the field of metal to hydrogen production. This study aim to aid in the development of this field. • A new route for hydrogen storage and production via metals on a large scale is proposed. • Electrolysis to obtain metals by green electricity, and subsequent hydrogen production from metals and water. • Metal monomers facilitate large-scale and long-term storage and transportation. • Metals can be used as large-scale hydrogen storage carriers in the future. • Metal-water hydrogen production can make full use of renewable energy without carbon dioxide. [ABSTRACT FROM AUTHOR]

Hydrogen is an important clean renewable energy carrier and has the advantages of high calorific value, low environmental impact, and wide availability. Magnesium hydride (MgH 2) has attracted extensive attention due to its high hydrogen storage density; however, its poor hydrolysis kinetics limit its application. In this paper, the hydrolysis performance of MgH 2 was studied in a self-made hydrolysis reactor, which included both a single tube structure and a plate tower structure. The hydrolysis reactor with the plate tower structure was conducive to achieving controllable and continuous MgH 2 hydrolysis. Specifically, the plate tower structure can effectively strengthen the distribution of MgH 2 materials, improve the liquid–solid mass transfer and reduce the surface coating. The results of this paper can expand the application of traditional reactors and provide a novel approach for the design of hydrolysis reactors for controllable continuous MgH 2 hydrolysis. [Display omitted] • A new MgH 2 hydrolysis reactor was proposed. • MgH 2 was modified to realize long-time dehydrogenation. • The controllable and continuous hydrolysis function of MgH 2 is realized. • The application of traditional plate reactor has been further expanded. [ABSTRACT FROM AUTHOR]

The substitution of fossil fuels with renewable energy sources such as hydrogen is a decisive factor in making aviation environmentally compatible. A key parameter for the use of hydrogen is the storage system. In the design of a flight-capable storage system, not only the mass but especially the volume of the hydrogen has to be considered. Therefore, in this paper different techniques are compared and evaluated from the point of view of their application in aircraft design. The analyses are performed on two reference aircraft, the Airbus A320 and the Embraer E 190, in the short- and medium-haul range. Simplified, it is assumed that the respective max. Take-off mass (MTOM) remains constant. The change of the necessary periphery has no influence on the MTOM. A tank concept could be designed, which can find applications in today's conventional aircraft design. • Energy consumption calculated for A320 and E 190. • Flight data evaluation. • Comparison of different storage methods. • Calculation of volumes for different storage methods and ambient pressures. • Discussion about possible constructive misplacement. [ABSTRACT FROM AUTHOR]

Novel metal hydride (MH) hydrogen storage tanks for fuel cell electric forklifts have been presented in this paper. The tanks comprise a shell side equipped with 6 baffles and a tube side filled with 120 kg AB 5 alloy and 10 copper fins. The alloy manufactured by vacuum induction melting has good hydrogen storage performance, with high storage capacity of 1.6 wt% and low equilibrium pressure of 4 MPa at ambient temperature. Two types of copper fins, including disk fins and corrugated fins, and three kinds of baffles, including segmental baffles, diagonal baffles and hole baffles, were applied to enhance the heat transfer in metal hydride tanks. We used the finite element method to simulate the hydrogen refueling process in MH tanks. It was found that the optimized tank with corrugated fins only took 630 s to reach 1.5 wt% saturation level. The intensification on the tube side of tanks is an effective method to improve hydrogen storage performance. Moreover, the shell side flow field and hydrogen refueling time in MH tanks with different baffles were compared, and the simulated refueling time is in good agreement with the experimental data. The metal hydride tank with diagonal baffles shows the shortest hydrogen refueling time because of the highest velocity of cooling water. Finally, correlations regarding the effect of cooling water flow rate on the refueling time in metal hydride tanks were proposed for future industrial design. • Novel MH hydrogen storage tanks for fuel cell electric forklift were simulated. • Simulations were validated by the experimental data on refueling time. • Optimized MH tank only took 630 s to reach 1.5 wt% saturation level. • Dimensionless correlations were proposed to estimate the hydrogen refueling time. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study of two cases of metal hydride hydrogen storage units working on (i) LaNi 5 (ii) Compacts of LaNi 5 incorporated with expanded natural graphite (ENG). It has been observed from the previous studies that the hydriding/dehydriding reactions eventually causes large strain changes, due to which the hydride forming metal alloys disintegrate and form a powder bed. Such reactor beds usually have a low thermal conductivity which minimizes the heat transfer phenomenon occurring during the absorption of hydrogen gas. Therefore, there is a need to implement heat augmentation methods to significantly enhance the thermal conductivity. The objective of this research is to present a 2-D numerical model using Finite Volume Method (FVM) and estimate the hydrogen storage performance of a cylindrical metal hydride bed for both the cases, i.e. powdered metal hydride bed and ENG compacts-based reactor bed at different values of inlet pressure and heat transfer fluid temperature. In this study, a detailed investigation on the absorption process reveals that reactor beds with compacted disks of LaNi 5 and ENG demonstrate an enhanced effective thermal conductivity and efficient mass transfer. The simulation results show that a remarkable improvement in the heat transfer and hydrogen storage capacity with reduced absorption time can be achieved by using LaNi 5 and ENG compacts. It was observed that the average reactor bed temperature dropped from 345.13 K to 337.37 K when the ENG based compacted disks was introduced into the reactor bed. Moreover, for supply pressure of 24 bar and fluid temperature of 293 K, the time taken to absorb hydrogen into the rector to achieve stabilized hydrogen storage capacity was estimated to be 446s and 232 s for the case of metal hydride and ENG compacts-based bed, respectively. • A 2-D numerical model was developed to estimate the hydrogen system performance. • Comparative performance analysis is carried out for two different cases. • The absorption time of hydrogen is 446s and 232s for cases (i) and (ii). • Maximum average bed temperature is reduced by 7.76 K. [ABSTRACT FROM AUTHOR]

Dealing with the conflict between the temperature/pressure rise and the total mass of hydrogen is a key challenge for rapid hydrogen filling of the hydrogen storage tank (HST). The temperature/pressure rise and total mass of hydrogen cause safety risks because of the former and limited cruise as the result of the latter. Therefore, safe hydrogen filling strategy is essential for the promotion of hydrogen fuel cell vehicles (FCVs). The existing thermodynamic model of the hydrogen storage tank is simplified either in the hydrogen state or the heat conduction of the HST wall, which can be hardly used as the real-time and accurate references for developing the filling strategy. To solve this problem, this paper works out the mathematical expression of a HST thermodynamic model. With the proposed HST thermodynamic model, a variable mass flow hydrogen filling strategy is developed. The results show that at the mass flow (12 g/s), the errors of the thermodynamic model are 7.1% and 6.8% for the temperature and pressure rise, compared with the computational fluid dynamics (CFD) model. At the mass flow (4.84 g/s), the thermodynamic model errors are 8.3% and 7.1% for the temperature and pressure rise, compared with the experimental data. Also, compared with the rule-based hydrogen filling strategies, the final state of charge (SoC) with the new filling strategy improve by 3%, 3.7%, and 2.7% at different initial temperatures, different volumes, and initial SoCs, respectively. • A real-time thermodynamic HST model with strong convergence is proposed. • The wall's unsteady heat transfer and hydrogen real properties are considered. • Variable mass flow is applied in the development of the filling strategy first. • The mass flow is determined by reinforcement learning, not rule-based. [ABSTRACT FROM AUTHOR]

Hydrogen storage and release process of metal hydride (MH) accompany with large amount of reaction heat. The thermal management is very important to improve the comprehensive performance of hydrogen storage unit. In present paper, thermochemical material (TCM) is used to storage and release the reaction heat, and a new sandwich configuration reaction bed of MH-TCM system was proposed and its superior hydrogen and thermal storage performance were numerically validated. Firstly, the optimum TCM distribution with a volume ratio (TCM in inner layer to total) of 0.4 was derived for the sandwich bed. Then, comparisons between the sandwich reaction bed and the traditional reaction bed were performed. The results show that the sandwich MH-TCM system has faster heat transfer and reaction rate due to its larger heat transfer area and smaller thermal resistance, which results in the hydrogen storage time is shortened by 61.1%. The heat transfer in the reaction beds have significant effects on performance of MH-TCM systems. Increasing the thermal conductivity of the reaction beds can further reduce the hydrogen storage time. Moreover, improving the hydrogen inflation pressure can result in higher equilibrium temperature, which is beneficial for the enhancing heat transfer and hydrogen absorption rates. •Integrating TCM in MH hydrogen storage reactor can recycle the reaction heat. •A new sandwich configuration reaction bed of MH-TCM system was proposed. •The new reaction bed can shorten hydrogen storage time by 61.1%. •Improving TCM thermal conductivity or H 2 pressure are efficient ways to accelerate hydrogen storage rate. [ABSTRACT FROM AUTHOR]

Hydrogen storage alloys are usually susceptible to poisoning by O 2 , CO, CO 2 , etc., which decreases the hydrogen storage property sharply. In this paper, the adsorption characteristics of oxygen on the ZrCo(110) surface were investigated, and the effect of oxygen occupying an active site on the surface on the hydrogen adsorption behavior was discussed. The results show that the dissociation barrier of H 2 is increased by more than 26% after O occupies the active sites on the ZrCo(110) surface, and the probability of H 2 adsorption and dissociation decreases significantly. The adsorption energy of H atoms on the O–ZrCo(110) surface decreased by 18–56%, and the adsorption stability of H decreased. In addition, H atom diffusion on the surface and into bulk are prevented with higher reaction energetic barriers by O occupying active sites. Eventually, the ability of the ZrCo surface to adsorb hydrogen is seriously reduced. [Display omitted] • Oxygen molecules are easily adsorbed and dissociated on the ZrCo surface. • The O atoms stably occupy active sites on the ZrCo surface. • The O atoms reduce the adsorption and dissociation ability of H 2 on ZrCo surface. • The O atoms hinder that diffusion and inward penetration of H on ZrCo surface. [ABSTRACT FROM AUTHOR]

Establishing an industrial park-integrated energy system (IN-IES) is an effective way to reduce carbon emission, reduce energy supply cost and improve system flexibility. However, the modeling of hydrogen storage in traditional IN-IES is relatively rough. In order to solve this problem, an IN-IES with hydrogen energy industry chain (HEIC) is proposed in this paper. Hydrogen production, transportation, and storage technologies are applied in HEIC. Firstly, a novel long-term hydrogen storage model considering different time steps is presented. Secondly, hydrogen compressor models considering different pressure ratios are further employed. On this basis, the impact of the HEIC on the planning and operation results of IN-IES is studied. Finally, the superiority and the effectiveness of the proposed model and planning method are verified by simulation cases. • The hydrogen energy industry chain including hydrogen production, storage, and transportation technologies. • A novel long-term hydrogen storage model is proposed that considers different time steps. • Different hydrogen compression levels are utilized to hydrogen compressor models. [ABSTRACT FROM AUTHOR]

The increasing pollution caused by conventional cars and the problems caused by the use of fossil fuels have drawn the attention of researchers and manufacturers to the design of cars that use clean fuels. Electric vehicles connected to the network have a significant impact on reducing environmental pollution and transportation costs, especially in big cities. The cost of supplying loads to subscribers in the distribution network also includes generation and transmission costs. These costs are directly related to the intelligence of the distribution network and the total amount of energy of electric vehicles. The contribution of each generation unit and each transmission line must be calculated to determine the generation and transmission costs. In this research, in order to maximize the profit of the parking lot owner, improve voltage drop and load factor, a comprehensive framework for optimal energy management in a parking lot is presented, which can provide a method to control the charging of electric vehicles, in addition to meeting the needs of their owners, only as a series of controllable loads that they need to receive electrical energy to charge their batteries. In the next step, considering the inherent characteristic of electric cars, i.e. having a battery, and looking at them as a series of storage resources that can return the electric energy in their battery to the grid if necessary, a method to simultaneously control their charging and discharging is provided. In the final step of the paper, it is assumed that hydrogen storage systems will also enter the circuit, and thus, a comprehensive method for energy management is proposed. Finally, the linearized model of demand response and the proposed scheme along with the modeling of hydrogen storage and electric vehicles are considered to be part of contribution to improve the operation and economic situation of the network. • In practice, the high cost that battery depreciation imposes on car owners when using the V2G feature makes the use of this feature not economically justified. • A comprehensive framework for optimal energy management in a parking lot with the aim of maximizing the profit of the parking lot owner, improving the voltage drop and network power factor is provided. • The proposed method for energy management in the presence of hydrogenous storage systems was applied in a sample parking lot and how it works. • Considering the hydrogenous storage systems, while significantly increasing the profit of the parking lot owner, it also significantly reduces the power received from the network during the peak hours of the network. [ABSTRACT FROM AUTHOR]

Hydrogen storage can help achieve climate change and reduce greenhouse gas emissions. This paper presents a first assessment of the suitability of northeastern Italy for underground hydrogen storage (UHS). The study focuses on the analysis of publicly available well data, which allowed identifying geological formations potentially suitable for UHS. The most promising area, known as the "Treviso Area" consists of both saline aquifers and depleted gas fields. One of the key petrophysical properties, i.e. porosity, was calculated for each of the five wells revealing conditions potentially suitable for UHS by applying empirical formulas to geophysical log data. For the two depleted gas fields, a hydrogen injection simulation was also performed. This work is a pioneer study and lays the foundation for hopeful further analyses, which could help implement the recently launched "North Adriatic Hydrogen Valley" initiative. [Display omitted] • A first assessment of underground hydrogen storage (UHS) in Italy is provided. • In NE Italy, saline aquifers and depleted gas fields are potentially suitable for UHS. • A key petrophysical property for UHS, porosity, is calculated from geophysical logs. • A simulation of hydrogen injection and production is provided. [ABSTRACT FROM AUTHOR]

This article presents an analysis of the permeation tests established in the current regulations for the type-approval of on board tanks in hydrogen vehicles. The analysis is done from the point of view of a test maker, regarding the preparation for the execution of a permeation test. The article contains a description of the required instrumentation and set-up to carry out a permeation test according to the applicable standards and regulations. Tank conditions at the beginning of the test, configuration of permeation chamber, duration of the test, or permeation rate to be reported, are aspects that are not well-defined in regulations. In this paper we examine the challenges when carrying out a permeation test and propose possible solutions to overcome them, with the intention of supporting test makers and helping the development of permeation test guidelines. • Regulations for type approval of hydrogen and fuel cell vehicles. • Regulations and standards requirements for permeation of on-board vehicle compressed hydrogen storage. • Lack of guidelines to set-up the permeation test for hydrogen tanks. • Approach to ensure replicability and repeatability of the permeation test. [ABSTRACT FROM AUTHOR]

In this paper, based on first-principles calculations, the effects of Nb/Ta modified ZrCo(110) surfaces on the adsorption, dissociation and diffusion of hydrogen are discussed. It is demonstrated that for the pure ZrCo(110) surface, H easily dissociates spontaneously, and is then captured by the holes on the surface. After entering the subsurface, H tends to fill the subsurface and continue to diffuse inward instead of escaping. After Nb/Ta doping, the maximum dissociation energy barrier of hydrogen decreases by 12.3%/37.0%, respectively. The diffusion energy barrier of H on the surface decreased by 15.8%/12.4%, and that on the subsurface decreased by 16.7%/24.1%. Charge transfer and density of states analysis showed that the bonding strength of H in the surface is improved after Nb/Ta doping. The results confirm that Nb/Ta doping can improve the hydrogen storage performance of ZrCo. [Display omitted] • Nb/Ta doping facilitates the dissociation of hydrogen on the ZrCo(110) surface. • Reduced hindrance for H 2 to dissociate to H and be trapped by the surface. • The migration barrier of H on the surface is reduced. • The diffusion of H on the subsurface is easier. • Nb/Ta doping enhances the hydrogen storage performance of ZrCo alloy. [ABSTRACT FROM AUTHOR]

Filament winding (FW) technique determines the production efficiency of wound products and the bearing capacity of composite layers, so the development and innovation of winding technique and equipment have become the focus of scientific researchers. This paper analyzes the influence of fiber crossing on the composite layers in the single filament winding (SFW) technique, proposes a multi-filament winding (MFW) technique. Firstly, the constitutive model of fiber cross region is constructed from mesoscopic scale, and the influence of this phenomenon on the design of composite layers is illustrated using netting theory. Then, the MFW technique is designed and developed, and the three-point bending test of CFRP is carried out with digital image correlation (DIC) technology, indicating that the MFW technique exhibits superior flexural strength of 483.71 MPa. Finally, a 35 MPa type III vessel is taken as the object for comparative numerical simulation, the results show the stress adopting the MFW technique in the dome section is reduced by 1418 MPa, and is smaller and more evenly distributed in the cylinder section. The MFW technique takes full advantage of the CFRP properties, improves the pressure bearing capacity of composite layers, meets the American DOT-CFFC standard requirements, and reduces the carbon fiber usage. The lightweight design of high-pressure hydrogen storage vessels is realized with a novel idea, and the winding efficiency is greatly improved compared with SFW technique. [Display omitted] • The disadvantages of traditional filament winding technique are revealed. • Multi-filament winding (MFW) technique is proposed innovatively. • The theory of variable yarn thickness and variable yarn width is developed. • The composite layers with MFW technique have a better bearing performance. • MFW technique realizes lighter and more efficient manufacturing of pressure vessels. [ABSTRACT FROM AUTHOR]

This paper describes the efficient preparation of an Mg 2 Ni alloy for hydrogen storage via high-energy ball milling mechanical alloying for 2 h. The degree of alloy amorphisation increases with increasing ball-milling time. Ball milling for 4 h affords partially amorphous alloys exhibiting the best hydrogen storage performance. Partial substitution of Ni with Cr and Mn improves the hydrogen absorption/desorption thermodynamics, kinetics and cycling performance of the alloy. Specifically, partial Mn substitution improves the cycling performance and reduces the activation energy of the hydrogen desorption reaction, effectively improving the hydrogen desorption kinetic performance. Mg 2 Ni 0.8 Mn 0.2 shows the best cycling and hydrogen absorption/desorption kinetic performances. Partial Cr substitution reduces the entropy and enthalpy changes of the hydrogen absorption/desorption reaction and effectively reduces the temperature of the initial hydrogen absorption/desorption reaction. In particular, Mg 2 Ni 0.9 Cr 0.1 shows the best thermodynamic performance. [Display omitted] • An optimised method for fabricating Mg 2 Ni alloys for hydrogen storage was developed • Mn addition effectively improves the cycle and kinetic performance of Mg 2 Ni alloys • Cr addition improves the thermodynamic properties of Mg 2 Ni alloys [ABSTRACT FROM AUTHOR]

This research paper describes a simplified and quick method for determining the exchange current densities of the H 2 O/H 2 system on powder composite electrodes made of hydrogen storage intermetallics. The method is based on the hydrogen storage electrode potential jump upon its galvanostatic overswitching from the cathodic to the anodic direction for low- and high charge/discharge rates. Indeed, research findings indicate that the discharge rate/exchange current density quotient depends either linearly or exponentially on the potential jump for low- and high-charge/discharge rates. This study also defines the applicability ranges for both types of dependencies with the best accuracy for calculating exchange currents (relative experimental error ≤5%) corresponding to potential jumps of up to 0.037 V (discharge rates of up to 0.2C) and 0.08–0.20 V (discharge rates over 0.3C). Furthermore, this study presents other instances of determining exchange currents versus cycling determination for different intermetallics and discusses the effect of the hydride material surface modification and charge/discharge rate conditions on the exchange current density. [Display omitted] • The exchange current density of the H 2 O/H 2 system, i H 2 O / H 2 0 , will be determined from the overswitch potential jump, Δ E (j) . • At low charge/discharge rate (up to 0.2C), the i H 2 O / H 2 0 increase linearly with a decrease in the Δ E (j) . • At high charge/discharge rate (above 0.3C), the i H 2 O / H 2 0 increase exponentially with a decrease in the Δ E (j) . [ABSTRACT FROM AUTHOR]

The most critical development in conventional underwater applications in recent years is to use hydrogen energy systems, including Air Independent Propulsion (AIP) systems. Proton Exchange Membrane (PEM) fuel cell-powered AIP systems increase interest worldwide. They offer many advantages such as longer endurance time without going to the surface for 2–3 weeks or without snorkeling with an average speed, perfectly silent operation, environmentally friendly process, high efficiency, and low thermal dissipation underwater. PEM fuel cells require a continuous source of hydrogen and oxygen as reactants to sustain a chemical reaction to produce electrical energy. Hydrogen storage is the critical challenge regarding the quality of supplied hydrogen, system weight, and volume. This paper reviewed hydrogen/oxygen storage preferences coupled with PEM Fuel Cell applications in the literature for unmanned underwater vehicles. Since underwater vehicles have different volume and weight requirements, no single hydrogen storage technique is the best for all underwater applications. • Hydrogen is the preferred fuel for underwater vehicles. • Underwater vehicles use hydrogen energy systems having Air Independent Propulsion (AIP) systems. • This paper review H 2 /O 2 storage preferences coupled with PEM Fuel Cell applications for unmanned underwater vehicles. • Compressed, and metal hydride-based H 2 storages are suitable for small to medium submarines. [ABSTRACT FROM AUTHOR]

Hydrogen embrittlement is a widely known phenomenon in high-strength and storage materials. Hydrogen embrittlement is responsible for subcritical crack growth in material, fracture initiation, subsequent loss in mechanical properties, and catastrophic failure. Hydrogen is induced in the material during an electrochemical reaction between the hydrogen, storage materials, and high-pressure gaseous hydrogen environment. Various mechanisms which are responsible for crack development, growth, and fracture have been deliberated and reported. However, the fundamental mechanism of hydrogen embrittlement remains unclear. Several techniques such as linearly increasing stress test techniques (LIST), constant extension rate test (CERT) and slow strain rate testing (SSRT), thermal desorption spectroscopy (TDS), permeation testing (PT), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been utilized to determine the amount of hydrogen diffused and available in the hydrogen storage material. The review intends to categorize and provide a clear understanding of the degradation mechanism that occurs during hydrogen embrittlement. The improvement in mitigating the hydrogen embrittlement degradation as a function of modifying the structure and surfaces of the material is established. Prospects for addressing hydrogen embrittlement degradation through further experimental and numerical research are suggested. Lastly, this paper through recommendation endeavors to prevent hydrogen storage tank degradation and reduces high costs associated with the replacement of the component in renewable energy applications. • Hydrogen storage tank is critical in renewable energy. • Hydrogen tank performance can be enhanced by appropriate material selection. • Microstructural modification reduces the hydrogen embrittlement. • Embrittlement degradation mechanism affects hydrogen tank storage. [ABSTRACT FROM AUTHOR]

Graphene can been used to improve the hydrogen storage performance of magnesium based materials because of its outstanding electrical conductivity, high specific surface area, and good mechanical qualities. In this paper, mechanical ball milling method was utilized to prepare the CeMg 12 /Ni alloy combined with graphene in order to investigate the impact of graphene on microstructure, kinetics, and thermodynamic properties of alloy. The results reveal that the addition of graphene can refine the grains of alloy, increase the surface defects of alloy particles and promote Ni to be dissolved in the main phase of the alloy. The absolute value of enthalpy drops from 65.27 kJ/mol to 60.3 kJ/mol when Graphene is added at a higher concentration. The addition of graphene improves the dehydrogenation performance of alloy hydride by lowering its thermal stability. Because of a minimum dehydrogenation activation energy of 85.23 kJ/mol and dehydrogenation characteristic time of 1090s, the alloy with 6 wt% Graphene exhibits the best dehydrogenation kinetic performances. • 1 The structural feature of Graphene is profit to increase the surface activity. • 2 Addition of Graphene is beneficial for improving thermodynamic performance. • 3 Adding Graphene can reduce the apparent activation energy of hydrogen releasing. • 4 The structure of Graphene is good for ameliorating the hydrogen sorption properties. [ABSTRACT FROM AUTHOR]

The estimation of storage capacity is crucial for underground hydrogen storage. Shale gas reservoirs have low permeability and porosity, so it is the potential site for hydrogen storage. The study is based on the depleted shale gas reservoirs with multiple flow mechanisms (diffusion, desorption and seepage). Firstly, this paper, using Laplace transformation, point source function and Stehfest inversion, presents a semi-analytical solution for bottom-hole pressure response with hydrogen duration injection. Then we, considering the multiple flow mechanisms, deduce a material balance equation specifically for shale gas reservoirs and plot modified type curves based on the Blasingame decline analysis theory. Furthermore, we discuss the effects of different critical parameters related to hydrogen storage capacity on type curves. In the final part, we describe in detail the method of obtaining hydrogen reserves using type curves. The proposed one can estimate the hydrogen volume in fractures and matrix systems, and get the actual underground storage volume through pressure response, compared with the hydrogen storage capacity calculated by the volumetric method. This study is helpful for the hydrogen capacity estimation of shale gas underground storage on-site. • Theoretical derivation addresses the bottom-hole pressure during the hydrogen injection for shale reservoirs. • Building the modified Blasingame type curves estimates the hydrogen storage capacity. • Fractures' parameters and adsorption index affect the capacity estimation result and reflect in typical curves. [ABSTRACT FROM AUTHOR]

The combustion calorific value of hydrogen is three times of gasoline and the burning product of hydrogen is water, which makes hydrogen the representative of clean energy. The hollow part of single-walled carbon nanotube (SWNT) is an excellent container space, which has great potential as hydrogen storage materials. This paper considers the micro-scale effect of SWNT based on Eringen's nonlocal elastic theory, and constructs a nanobeam model and analyzes the nonlinear dynamic characteristics. Based on these, the effects of different modification components on hydrogen storage properties of SWNT is discussed. The analysis exhibits that different modification positions also have a great influence on the hydrogen storage efficiency. The results of theoretical analysis and numerical simulation show that the modification components' optimization plays a certain role in improving the hydrogen storage efficiency of SWNT. The maximum increase hydrogen storage efficiency can be 12.7% by selecting appropriate decorative elements and appropriate positions. • Propose a new kind of Ni/Mg modified single wall carbon nanotube structure. • Study the influence of different modification positions on storage efficiency. • The tests shows that the modification components' optimization plays a certain role. • The max increase storage efficiency can be 12.7% by selecting appropriate positions. [ABSTRACT FROM AUTHOR]