Search

It is well known that the development of dual-purpose materials is more significant and valuable than single-use materials due to the diversity of their use purposes. Based on density functional theory (DFT), the hydrogen evolution/hydrogen storage characteristics of two-dimensional (2D) B 7 P 2 monolayer are systematically studied in this paper, focusing on the key word of clean energy-"hydrogen". The results show that the B 7 P 2 monolayer can be used as a stable metal-free decorated catalyst for hydrogen evolution reaction (HER), which is renewable and environmentally friendly. The calculated Gibbs free energy (Δ G H∗) is 0.06 eV, which is comparable or even better than that of Pt catalyst (Δ G H∗ = −0.09 eV). In addition, we also found that the increase of hydrogen coverage and strain driving (−2%–2%) did not further enhance the HER activity of B 7 P 2 monolayer, showing a poor Δ G H∗. In the aspect of hydrogen storage, we have investigated the hydrogen storage performances of alkali-metal (Li, Na and K) doped B 7 P 2. It is found that in the fully loaded case, B 7 P 2 Li 6 is a promising hydrogen storage material with a 7.5 wt% H 2 content and 0.15 eV/H 2 average hydrogen adsorption energy (E ave). Moreover, ab initio molecular dynamics (AIMD) calculations show that there is no dynamic barrier for H 2 desorption of Li-decorated B 7 P 2 monolayer. In conclusion, our results indicate that the B 7 P 2 monolayer is not only an excellent catalyst for HER, but also a promising hydrogen storage medium. [Display omitted] • Li-decorated B 7 P 2 monolayer is promising as hydrogen storage material. • Hydrogen storage densities is up to 7.5 wt%, higher than DOE's target of 5.5 wt%. • The calculated Δ G H∗ of B 7 P 2 monolayer is 0.06 eV, which is lower than that of Pt catalyst (−0.09 eV). • B 7 P 2 monolayer is a new two-dimensional material with dual-purpose. [ABSTRACT FROM AUTHOR]

The growing demand for type IV hydrogen tanks with long life, lightweight, high hydrogen storage density characteristics has posed new issues for liners. The paper discusses the causes of liner failure in terms of hydrogen permeation, thermal instability, and mechanical damage, as well as a focused analysis of alternative material optimization strategies. Through a detailed investigation of aggregate state structures, formulations and processes, the principles of material modification, primarily inorganic functional filler/polymer filler filling composite and laminated orientation, and their enhancing effects are sorted out. Besides, the benefits and drawbacks of blow molding, injection and welding, and the rotating technique, which were employed by some manufacturers are contrasted in the article, for overcome the problematic molding of hollow plastic liners with metal BOSS structures. This text will be a valuable resource for material exploitation as well as efficient and reliable molding of various liners. • Improve hydrogen storage density and application range by material modification. • The failure modes of the plastic liner material are discussed. • Hydrogen barrier, mechanical and thermal properties modify measures were reviewed. • Molding methods for synthetic liners containing metal inserts are compared. • The recommendations for future liner materials design and molding are presented. [ABSTRACT FROM AUTHOR]

Hydrogen is an energy carrier that will certainly make an important and decisive contribution to the global energy transition and lead to a significant reduction in greenhouse gas (GHG) emissions over the coming decades. It is estimated that 60% of GHG emission reductions in the last phase of the energy transition could come from renewables, green hydrogen and electrification based on green energy development. Coordinated efforts by governments, industry and investors, as well as substantial investment in the energy sector, will be required to develop the hydrogen value chain on a global scale. This paper summarizes the technical and technological advances involved in the production, purification, compression, transportation and use of hydrogen. We also describe the roadmaps and strategies that have been developed in recent years in different countries for large-scale hydrogen production. • Green hydrogen's competitiveness has launched an unprecedented movement in the energy world. • Technical and technological advances related to green hydrogen are outlined. • Strategies and roadmaps of different countries around the world for hydrogen development are discussed. [ABSTRACT FROM AUTHOR]

In this paper, the robust capability of HOMER and Criteria-COPRAS is deployed to explore the prospect of selecting a renewable energy system. The energy system consisting of wind turbines, solar photovoltaic (PV), fuel cell (FC), electrolyzer, hydrogen storage, and battery energy storage is intended to power a residential load in Lagos Nigeria. Based on the economic metric, the results show that the optimal system is a PV-Battery whose total net present cost (TNPC) and initial investment cost are $9060 and $3,818, respectively. However, if the energy systems are ranked based on multiple criteria (economic, technical and environmental aspects), the most preferred of the feasible energy systems is a hybrid PV-FC-wind-battery (TNPC-$10,324, initial cost: $7670). The study results indicate that, for viability in the adoption of hydrogen energy storage as part of the hybrid energy system, the selection metric should be based on more than one criterion. [Display omitted] • Optimal sizing of off-grid hybrid renewable energy systems for a residential building is presented. • A combination of hydrogen tank and battery were proposed as backups. • Energy systems were ranked using complex proportional assessment (COPRAS). • PV-battery was ranked best using single criterion. • Hybrid combination of Photovoltaic-Wind Turbine-Fuel cell-Battery was ranked best based on multiple criterion. [ABSTRACT FROM AUTHOR]

Despite many years having passed since it was discovered, FeTi alloys remain one of the most important low-temperature hydrogen storage alloys due to its high capacity, characteristics and low price. However, the main technological issue is its initial activation, which is usually conducted at relatively high temperature and pressure. This paper is the first to show that the complicated process can be replaced by intense movement of the powder or even chunks of alloy under hydrogen pressure without any additional grinding media. The newly discovered process, named self-shearing reactive milling (SSRM), leads to the full hydrogenation of FeTi alloys. The wear of particles, which is caused by their movement, causes the exposure of a fresh active alloy surface that is active enough to absorb hydrogen without any thermal treatment or evacuation. The resultant material, despite simply being strongly stirred, evolves from large chunks to an extremally fine spongy structure containing particle with sizes of tens of nanometers that combine to form large agglomerates. This result is an enormous improvement for the potential use of FeTi alloys and all other AB-type alloys in commercial applications by extraordinarily simplifying hydrogen storage vessels, which will not have to withstand high-temperature and pressure activation. [Display omitted] • FeTi alloy is activated mechanically at room temperature. • The wear of the surface of particles under H 2 leads to spontaneous hydrogenation. • The method can be applied even for big chunks. • No additives are required. • Alloy is fully hydrogenated. [ABSTRACT FROM AUTHOR]

The construction of hydrogenation infrastructure is important to promote the large-scale development of hydrogen energy industry. The technical performance of hydrogen refueling station (HRS) largely determines the refueling efficiency and cost of hydrogen fuel cell vehicles. This paper systematically lists the hydrogen refueling process and the key equipment applicable in the HRS. It comprehensively reviews the key equipment configuration from the hydrogen supply, compression, storage and refueling of the HRS. On the basis of the parameter selection and quantity configuration method, the process optimization technology related to the equipment utilization efficiency and construction cost was quantitatively evaluated. Besides, the existing problems and prospects are put forward, which lays the foundation for further research on the technical economy of HRSs. • The key equipment and process flow of the HRSs are discussed. • The hydrogen supply system configuration is analyzed from three hydrogen sources. • The configuration and optimization of hydrogen storage vessels are presented. • The compressor configuration matched with hydrogen storage are described. • The empirical and queuing method of hydrogen dispenser configuration are explained. [ABSTRACT FROM AUTHOR]

In this paper, a proposal for a novel integrated Brayton cycle, supercritical plant, trans critical plant and organic Rankine cycle-based power systems for multi-generation applications are presented and analyzed thermodynamically. The plant can generate power, heating-cooling for residential applications, and hydrogen simultaneously from a single energy source. Both energetic and exergetic analyses are conducted on this multi-generation plant and its subsystems in order to evaluate and compare them thermodynamically, in terms of their useful product capabilities. The energetic and exergetic effectiveness of the multi-generation system are computed as 44.69% and 42.03%, respectively. After that, a parametric study on each of the subsystems of the proposed combined system is given in order to provide a deeper understanding of the working of these subsystems under different states. Lastly, environmental impact assessments are provided to raise environmental concerns for several operating conditions. For the base working condition, the results illustrate that the proposed plant has 0.5961, 0.0442, 0.6265 and 1.678 of exergo-environmental impact factor, exergy sustainability index, exergy stability factor and sustainability index, respectively. • To offer a novel integrated power plant with multigeneration. • To make a comprehensive energy and exergy analyses for more effective system design. • The energy and exergy efficiencies are found to be 44.69% and 42.03%, respectively. • To evaluate the impact of working conditions on integrated system effectiveness. [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) are crystalline, hybrid, materials containing metal ions and organic molecules; components that together form three-dimensional structures. At the present, the large-scale production necessary for the commercialization of MOFs based industrial processes seems to be the greatest challenge, mainly due to the fact that MOFs require harsh operating conditions and large amounts of toxic solvents during their synthesis which result in added production costs and raise safety and environmental related concerns. This review provides an overview on the recent developments in the synthesis of MOFs and their green applications. The currently used solvothermal processes for the synthesis of MOFs necessitate the use of hazardous and non-renewable solvents such as such as dimethylformamide (DMF), dimethylformamide (DEF), methanol, ethanol, and acetonitrile. Green and economical routes for MOFs synthesis that are non-solvent based have been rigorously under study to facilitate the commercialization of synthesis processes that are safe and environmentally benign. Such processes include water-based MOF synthesis, mechanochemical MOFs synthesis and the use of super-critical fluids and ionic liquids as solvents to replace the conventionally used ones. The paper also discusses the recent developments in the applications of MOFs in innovative and vital applications such as hydrogen production, fuel cells, and water desalination. Challenges and corrective actions attributed to the use of MOFs in these applications are also presented and discussed. [Display omitted] • Most recent progresses in green synthesis of organic frameworks are discussed. • Green energy applications of MOFs in hydrogen production and fuel cell are tackled. • Recent developments of MOFs in desalination are summarized. • Challenges in future development, synthesis and applications of MOFs are addressed. [ABSTRACT FROM AUTHOR]

In this paper, the TiFe-based master alloy Ti 1.04 Fe 0.7 Ni 0.1 Zr 0.1 Mn 0.1 Pr 0.06 was fabricated by conventional induction melting with high purity helium as the protective gas. After that, the as-cast specimens were mechanically milled with nickel powders to synthesize the as-milled Ti 1.04 Fe 0.7 Ni 0.1 Zr 0.1 Mn 0.1 Pr 0.06 + 10 wt.% Ni composites with excellent electrochemical characteristics. The master alloy is composed of TiFe, Ti 2 Fe and Pr phases, which has a typical crystal structure. Mechanically milling the master alloy with nickel powder leads to the reductions of the grain size and particle size, even forming amorphous structure. The experimental results showed that the specimens after ball-milling treatment can be used to hydriding and dehydriding by electrochemistry, getting the maximal discharge capacity in the first cycle, and no activation was required. The discharge capacity of the as-milled composites declined from 264.2 to 133.6 mAh/g with the milling duration extending from 5 to 30 h. The electrochemical kinetics markedly declined with prolonging milling duration. However, the electrochemical cycling stability of the specimens reduced firstly and then increased with the prolongation of grinding duration. • The ferrotitanium alloy +10 wt.% Ni were prepared by mechanical milling. • The as-milled (5 h) specimen has the maximal discharge capacity of 264.2 mAh/g. • The electrochemical kinetics are worse with the prolongation of milling duration. [ABSTRACT FROM AUTHOR]

Penetration of renewable energy sources (RESs) in power systems increase all over the world to overcome current challenges, most importantly environmental issues. Beside advantages of RESs, their integration into the power systems have imposed various challenges considering uncertain and intermitted power output. To cope with these challenges, utilizing energy storage systems with renewable energy sources alongside the demand response (DR) programs are considered as reliable solutions. On the other hand, in an uncertain environment, minimizing worst-case cost or regret is counted as an important criterion to evaluate operation of any system under uncertain parameters. Therefore, in this paper, optimal operation of power systems is solved under penetration of wind turbines, hydrogen storage system, and DR programs in an uncertain environment. To guarantee robust operation of the system under the worst-case scenario, a novel stochastic p-robust optimization method (SPROM) is proposed which combines both stochastic programming and robust optimization approaches where minimizes the worst-case cost or regret level. The performance of the developed model is evaluated considering a six-bus test system under two cases as stochastic optimization (SO) and SPROM. Obtained results show that the maximum regret level is reduced considerably using the proposed SPROM comparing with pure stochastic method. • Security-constraint unit commitment problem is solved considering wind generation. • Hydrogen storage system and renewable energy sources are integrated in power system. • Stochastic p-robust optimization method is proposed to get robust operation. • Expected total operating cost of the system is minimized under worst-case scenario. • Maximum level of relative regret in system is minimized under worst-case scenario. [ABSTRACT FROM AUTHOR]

Hydrogen storage plays a fundamental role in the future hydrogen energy system, and carbon aerogel is one of the most potential hydrogen storage materials because of its high gravimetric and volumetric density on hydrogen adsorption. In this paper, the amorphous structure of carbon, obtained by a numerical simulation process by using the molecular dynamic and Monte Carlo methods, as well as the primary unit method, was intercepted as a sphere structure for numerical annealing to build a carbon nanosphere, which serves as the basic unit to reconstruct the carbon aerogel's skeleton by the Diffusion Limited Cluster Aggregation (DLCA) method. The hydrogen adsorption in carbon aerogel was simulated by using the self-coding parallel grand canonical Monte Carlo (GCMC) method. The influences of particle diameter, density, temperature, pressure, and specific surface area on the hydrogen adsorbing capacity in carbon aerogel were analyzed in detail. The results showed that the carbon aerogel's hydrogen storage capacity with a specific surface area of 2680 m2/g could reach 4.52 wt % at 77 K and 3.0 MPa. • A 3-D network and nanosphere amorphous structure of carbon aerogel is rebuilt. • Hydrogen adsorption on carbon nanosphere and carbon aerogel is simulated by GCMC. • Multilayer adsorption occurs on the nanosphere's surface gradually layer by layer. • Hydrogen storage capacity is 4.52 wt % at P = 3.0 MPa, T = 77 K, and SSA = 2680 m2/g. [ABSTRACT FROM AUTHOR]

High dehydrogenation temperature and slow dehydrogenation kinetics impede the practical application of magnesium hydride (MgH 2) serving as a potential hydrogen storage medium. In this paper, Fe–Ni catalyst modified three-dimensional graphene was added to MgH 2 by ball milling to optimize the hydrogen storage performance, the impacts and mechanisms of which are systematically investigated based on the thermodynamic and kinetic analysis. The MgH 2 +10 wt%Fe–Ni@3DG composite system can absorb 6.35 wt% within 100 s (300 °C, 50 atm H 2 pressure) and release 5.13 wt% within 500 s (300 °C, 0.5 atm H 2 pressure). In addition, it can absorb 6.5 wt% and release 5.7 wt% within 10 min during 7 cycles, exhibiting excellent cycle stability without degradation. The absorption-desorption mechanism of MgH 2 can be changed by the synergistic effects of the two catalyst materials, which significantly promotes the improvement of kinetic performance of dehydrogenation process and reduces the hydrogen desorption temperature. [Display omitted] • Synergistic effects of graphene and iron based catalysts have been investigated. • Remarkable features revealed via XRD, SEM, EDS, HRTEM, PCT and DSC. • The conversion of Mg 2 Ni and Mg 2 NiH 4 enhances the performance of hydride storage. • The MgH 2 -10 wt% Fe–Ni @3DG sample releases 5.13 wt% H 2 within 500 s at 300 °C. [ABSTRACT FROM AUTHOR]

This paper focuses on an experimental study of the explosive decompression on representative samples of the hyperbaric type IV hydrogen storage vessels. The adhesion of the composite to the liner is achieved by different adhesives. The bond behavior of liner-to-composite bonded joint considerably depends on the properties of adhesives, as well as the assembly process. X-ray tomography allows determining the damages before and after explosive decompression tests. Tomographic observations have revealed a certain level of porosity due to the assembly process with plasma treatment. This porosity influences the damage mechanisms induced by explosive decompression. Results show that 1) the increasing of the maximum hydrogen pressure (differential pressure induced during the depressurization step between the liner/adhesive interface or the adhesive/composite) increases the risk of liner collapse for the same gas exposure conditions, 2) Compared with soft adhesive, the stiff adhesive has proven better adhesion between the composite and the liner, 3) the flame treatment improved the surface energy of the PA6 and subsequently increased the collapse limit pressure, 4) adhesive RCA-20 with plasma preparation can be defined as a kind of low strength to collapse adhesive with a collapse limit pressure less than 2 MPa, 5)adhesive RCA-2000 with flame treatment can be defined as a kind of high strength to collapse adhesive in the present report with a collapse limit pressure between 15 MPa and 17.5 MPa. • Rapid decompression resistance of liner/composite adhesive joints. • The stiffness of the adhesive is the main parameter affecting liner collapse. • A flame treatment has improved the performance of the structure. • The adhesive's thickness has less influence on the occurrence of the collapse. • Porosity of the samples have less influence on the occurrence of the collapse. [ABSTRACT FROM AUTHOR]

Mg-based hydrogen storage alloys have become a research hotspot in recent years owing to their high hydrogen storage capacity, good reversibility of hydrogen absorption/desorption, low cost, and abundant resources. However, its high thermodynamic stability and slow kinetics limit its application, so the modification of Mg-based hydrogen storage alloys has become the development direction of Mg-based alloys. Transition metals can be used as catalysts for the dehydrogenation of hydrogen storage alloys due to their excellent structural, electrical, and magnetic properties. Graphene, because of its unique sp2 hybrid structure, excellent chemical stability, and a specific surface area of up to 2600 m2/g, can be used as a support for transition metal catalysts. In this paper, the internal mechanism of graphene as a catalyst for the catalysis of Mg-based hydrogen storage alloys was analyzed, and the hydrogen storage properties of graphene-catalyzed Mg-based hydrogen storage alloys were reviewed. The effects of graphene-supported different catalysts (transition metal, transition metal oxides, and transition metal compounds) on the hydrogen storage properties of Mg-based hydrogen storage alloys were also reviewed. The results showed that graphene played the roles of catalysis, co-catalysis, and inhibition of grain aggregation and growth in Mg-based hydrogen storage materials. • The catalytic mechanism of graphene is electron transfer between Mg and C. • Graphene has shown excellent results in maintaining good cycling stability. • Graphene can catalyze, co-catalyze, and inhibit grain growth. • Composite nanometer transition metal alloys with graphene are promising catalysts. [ABSTRACT FROM AUTHOR]

Additive doping is one of the effective methods to overcome the shortcomings of MgH 2 on the aspect of relatively high operating temperatures and slow desorption kinetics. In this paper, hollow g-C 3 N 4 (TCN) tubes with a diameter of 2 μm are synthesized through the hydrothermal and high-temperature pyrolysis methods, and then nickel is chemically reduced onto TCN to form Ni/TCN composite at 278 K. Ni/TCN is then introduced into the MgH 2 /Mg system by means of hydriding combustion and ball milling. The MgH 2 –Ni/TCN composite starts to release hydrogen at 535 K, which is 116 K lower than the as-milled MgH 2 (651 K). The MgH 2 –Ni/TCN composite absorbs 5.24 wt% H 2 within 3500 s at 423 K, and takes up 3.56 wt% H 2 within 3500 s, even at a temperature as low as 373 K. The apparent activation energy (E a) of the MgH 2 decreases from 161.1 to 82.6 kJ/mol by the addition of Ni/TCN. Moreover, the MgH 2 –Ni/TCN sample shows excellent cycle stability, with a dehydrogenation capacity retention rate of 98.0% after 10 cycles. The carbon material enhances sorption kinetics by dispersing and stabilizating MgH 2. Otherwise, the phase transformation between Mg 2 NiH 4 and Mg 2 NiH 0.3 accelerates the re/dehydrogenation reaction of the composite. • Ni/tubular g-C 3 N 4 was synthesized and introduced into MgH 2. • Ni/TCN compound lowers onset desorption temperature of MgH 2 by 116 K. • Ni/TCN compound decreases desoption activation energy from 161.1 to 82.6 kJ/mol. [ABSTRACT FROM AUTHOR]

A systematic study of the interactions between hydrogen and Mg–Ag alloys prepared by mechanical alloying is presented in this paper. The alloys were chosen to cover both the two-phase limited solubility and hypoeutectic regions (3, 5, 10, 20 wt. % Ag in Mg) as well as the intermetallic phases (γ′-AgMg 4 , ε-AgMg 3 and AgMg). The hydrogen-absorption abilities of the samples were investigated for the two states: directly after mechanical alloying and after annealing. It was found that all of the chosen alloys could be very effectively synthesized with mechanical alloying, a process that also was found to extend the solubility limits compared to those on known phase diagrams. The synthesis is greatly enhanced by further annealing which allows us to obtain well crystallized samples with phase compositions in accordance with these phase diagrams. In most cases, the obtained alloys were able to absorb significant amounts of hydrogen while magnesium hydride and AgMg intermetallics were formed as a residual product and phase, respectively, that did not react with hydrogen under the chosen conditions. The magnesium hydride formed in such reactions seemed to have a very similar decomposition temperature and was not significantly influenced by the silver additive, which was not found to greatly catalyze the MgH 2 decomposition reaction in such cases. Samples characterized directly after ball milling showed higher reaction kinetics with hydrogen. • Mg–Ag alloys were successfully synthesized by mechanical alloying. • Mechanical alloying leads to increase in Ag solubility in Mg. • Synthesized alloys except AgMg phase reacted with hydrogen. • The kinetics of reaction of alloys with hydrogen is faster for non-annealed samples. [ABSTRACT FROM AUTHOR]

This paper is a critical review of selected real-world energy storage systems based on hydrogen, ranging from lab-scale systems to full-scale systems in continuous operation. 15 projects are presented with a critical overview of their concept and performance. A review of research related to power electronics, control systems and energy management strategies has been added to integrate the findings with outlooks usually described in separate literature. Results show that while hydrogen energy storage systems are technically feasible, they still require large cost reductions to become commercially attractive. A challenge that affects the cost per unit of energy is the low energy efficiency of some of the system components in real-world operating conditions. Due to losses in the conversion and storage processes, hydrogen energy storage systems lose anywhere between 60 and 85% of the incoming electricity with current technology. However, there are currently very few alternatives for long-term storage of electricity in power systems so the interest in hydrogen for this application remains high from both industry and academia. Additionally, it is expected that the share of intermittent renewable energy in power systems will increase in the coming decades. This could lead to technology development and cost reductions within hydrogen technology if this technology is needed to store excess renewable energy. Results from the reviewed projects indicate that the best solution from a technical viewpoint consists in hybrid systems where hydrogen is combined with short-term energy storage technologies like batteries and supercapacitors. In these hybrid systems the advantages with each storage technology can be fully exploited to maximize efficiency if the system is specifically tailored to the given situation. The disadvantage is that this will obviously increase the complexity and total cost of the energy system. Therefore, control systems and energy management strategies are important factors to achieve optimal results, both in terms of efficiency and cost. By considering the reviewed projects and evaluating operation modes and control systems, new hybrid energy systems could be tailored to fit each situation and to reduce energy losses. • Review of 15 projects that use hydrogen as energy storage in a power system. • Hydrogen is one of very few alternatives for long-term electricity storage. • Hydrogen storage should in most cases be combined with battery storage. • Power-to-gas-to-power for hydrogen still has a low energy efficiency (15–40%). • Intermittent in-flow of energy and high costs are big challenges for these systems. [ABSTRACT FROM AUTHOR]

Hydrogen storage using the metal hydrides and complex hydrides is the most convenient method because it is safe, enables high hydrogen capacity and requires optimum operating condition. Metal hydrides and complex hydrides offer high gravimetric capacity that allows storage of large amounts of hydrogen. However, the high operating temperature and low reversibility hindered the practical implementation of the metal hydrides and complex hydrides. An approach of combining two or more hydrides, which are called reactive hydride composites (RHCs), was introduced to improve the performance of the metal hydrides and complex hydrides. The RHC system approach has significantly enhanced the hydrogen storage performance of the metal hydrides and complex hydrides by modifying the thermodynamics of the composite system through the metathesis reaction that occurred between the hydrides, hence enhancing the kinetic and reversibility performance of the composite system. In this paper, the overview of the RHC system was presented in detail. The challenges and perspectives of the RHC system are also discussed. This is the first review report on the RHC system for solid-state hydrogen storage. • Current progress in reactive hydride composite (RHC) for hydrogen storage is reviewed. • Roles of intermediate compounds in RHC system is highlighted. • Future perspectives and challenges of RHC as hydrogen storage medium are discussed. [ABSTRACT FROM AUTHOR]

Cr–Mo steel is often used as the material of the hydrogen storage vessel, but its ductility can be deteriorated by high pressure hydrogen, which makes it possible that the local area of strain concentration on the hydrogen storage vessel made of Cr–Mo steel may fail due to excessive plastic deformation. The limit criterion of local strain established according to the study of the fracture strain is the basis for local failure assessment of the vessel. However, the correlation between the fracture strain and the stress state of Cr–Mo steel in high pressure hydrogen is still unclear, so the limit criterion of local strain for hydrogen storage vessel made of Cr–Mo steel has not been established. In this paper, the slow strain rate tensile test (SSRT) of notched specimens with different notch sizes was carried out in air, 45 MPa hydrogen and 100 MPa hydrogen, respectively. Based on the test results, the whole process from tensile to fracture of the specimens was simulated by finite element method. The distribution of stress triaxiality and plastic strain during the tensile process was analyzed, and the correlations between the stress triaxiality and the fracture strain in different environments were obtained. Finally, the limit criterion of local strain for local failure assessment of 4130X hydrogen storage vessel was established. • SSRT of notched specimens made of 4130X steel were carried out in hydrogen. • The whole process from tensile to fracture of the specimens was simulated. • The correlations between the stress triaxiality and fracture strain were obtained. [ABSTRACT FROM AUTHOR]

This paper describes the size optimization of a hybrid photovoltaic/fuel cell grid linked power system including hydrogen storage. The overall objective is the optimal sizing of a hybrid power system to satisfy the load demand of a university laboratory with an unreliable grid, with low energy cost and minimal carbon emissions. The aim is to shift from grid linked diesel power system to a clean and sustainable energy system. The optimum design architecture was established by adopting the energy-balance methods of HOMER (hybrid optimization model for electric renewables). Analysis of hourly simulations was performed to decide the optimal size, cost and performance of the hybrid system, using 22-years monthly averaged solar radiation data collected for Ambrose Alli University, Ekpoma (Lat. 6°44.3ʹN, Long. 6°4.8ʹE). The results showed that a hybrid system comprising 54.7 kW photovoltaic array, 7 kW fuel cell system, 14 kW power inverter and 3 kW electrolyzer with 8 kg hydrogen storage tank can sustainably augment the erratic grid with a very high renewable fraction of 96.7% at $0.0418/kWh. When compared with the conventional usage of grid/diesel generator system; energy cost saving of more than 88% and a return on investment of 41.3% with present worth of $308,965 can be derived in less than 3 years. The application of the optimally sized hybrid system would possibly help mitigate the rural-to-urban drift and resolve the electricity problems hindering the economic growth in Nigeria. Moreover, the hybrid system can alleviate CO 2 emissions from other power generation sources to make the environment cleaner and more eco-friendly. • The sizing of a hybrid system for an unreliable grid is presented. • Optimum architecture was established by adopting energy-balance methods. • Proposed optimum size boosts erratic grid; renewable fraction of 97% at $0.0418/kWh. • CO 2 cut by 97% and cost saving of 88% at 41% return on investment can be derived. • It can aid shift from grid/fossil option to a cleaner and sustainable energy system. [ABSTRACT FROM AUTHOR]

In the present paper, the blast furnace slag (BFS) supported Co-B catalyst were investigated in detail. The impregnation-chemical reduction method was used while hydrochloric (HCl) acid treated BFS samples (BFS+) were prepared. Catalyst samples were analyzed in three main groups as base BFS (BFS0), BFS0-Co-B and BFS+-Co-B. The effects of these catalyst samples on hydrogen production from the solid-state sodium boron hydride (NaBH 4) are analyzed in this study. The effects of some parameters such as the ingredients of blast furnace slag, the molarity of hydrochloric acid treatment, the Co percentages and the solution temperatures were investigated on the hydrolysis performance of NaBH 4. The NaBH 4 hydrolysis reaction with the BFS0 is treated by the BFS+-Co-B-20% catalyst was completed approximately 25 min and the hydrolysis reaction with the BFS0-Co-B-20% catalyst was completed approximately 20 min whereas the hydrolysis reaction of NaBH 4 was completed in 1 h 35 min. The hydrogen production rates at pre-heated to max 40, 50 and 60 °C were measured as 55.12, 64.47 and 70.41 L/min.g catalyst , respectively. According to another result of the study, the high-efficiency solid-state BFS-Co-B & NaBH 4 mixtures were covered with the PVA (Polyvinyl alcohol) film to make them more resistant to environmental effects such as humidity. • BFS was used as a catalyst for the first time within the NaBH 4 hydrolysis process. • 20% Co-B-BFS acid untreated sample improved total hydrogen production 34.7%. • 50% Co-B-BFS acid treated sample improved total hydrogen production 25.1%. • Best result in terms of "L/min.gcatalyst" was obtained by acid treated 40% Co-B-BFS. • PVA technique used to protect NaBH4 from environmental effects. [ABSTRACT FROM AUTHOR]

Hydrogen direct reduction has been proposed as a means to decarbonize primary steelmaking. Preferably, the hydrogen necessary for this process is produced via water electrolysis. A downside to electrolysis is the large electricity demand. The electricity cost of water electrolysis may be reduced by using a hydrogen storage to exploit variations in electricity price, i.e., producing more hydrogen when the electricity price is low and vice versa. In this paper we compare two kinds of hydrogen storages in the context of a hydrogen direct reduction process via simulations based on historic Swedish electricity prices: the storage of gaseous hydrogen in an underground lined rock cavern and the storage of hydrogen chemically bound in methanol. We find the methanol-based storages to be economically advantageous to lined rock caverns in several scenarios. The main advantages of methanol-based storage are the low investment cost of storage capacity and the possibility to decouple storage capacity from rate capacity. Nevertheless, no storage option is found to be profitable for historic Swedish electricity prices. For the storages to be profitable, electricity prices must be volatile with relatively frequent high peaks, which has happened rarely in Sweden in recent years. However, such scenarios may become more common with the expected increase of intermittent renewable power in the Swedish electricity system. [Display omitted] • Storage of H 2 key to lower costs of hydrogen-based steelmaking. • Storage of compressed H 2 and H 2 bound in methanol compared. • H 2 storage in methanol integrates well in hydrogen direct reduction process. • Simulations using historic electricity prices favor methanol in several scenarios. • Low-cost storage capacity, flexibility of sizing main advantages of methanol. [ABSTRACT FROM AUTHOR]

Hydrogen storage is essential in hydrogen value chains and subsurface storage may be the most suitable large-scale option. This paper reports numerical simulations of seasonal hydrogen storage in the Norne hydrocarbon field, offshore Norway. Three different storage schemes are examined by injecting pure hydrogen into the gas- , oil- , and water zones. Implementation of four annual withdrawal-injection cycles followed by one prolonged withdrawal period show that the thin gas zone is a preferred target with a final hydrogen recovery factor of 87%. The hydrogen distribution in the subsurface follow the geological structures and is restricted by fluid saturation and displacement efficiencies. Case studies show that the pre-injection of formation gas as a cushion gas efficiently increases the ultimate hydrogen recovery, but at the cost of hydrogen purity. The injection of 30% hydrogen-formation gas mixture results in a varying hydrogen fraction in the withdrawn gas. An alternative well placement down the dipping structure shows lower storage efficiency. [Display omitted] • Long-term and large-scale hydrogen storage is examined in a depleted oil and gas field. • A real full-field simulation model with site-specific parameters was used. • Preferred targets for seasonal hydrogen withdrawal were identified. • Effect of the cushion gas nature, its composition and structural geometry were assessed. [ABSTRACT FROM AUTHOR]

Element substitution is an efficient method to enhance the activation property of TiFe alloys. In this paper, Zr, Mn and Ni were utilized to replace Fe in the alloy partially, and different content rare earth Sm substitute Ti in the alloy. The alloys with nominal compositions of Ti 1.1- x Fe 0.6 Ni 0.1 Zr 0.1 Mn 0.2 Sm x (x = 0–0.08) were made through vacuum induction melting. The microstructure, composition and hydrogen storage property of alloys were measured in detail by X-ray diffraction, scanning electron microscope, high-resolution transmission electron microscopy and automatically Sievert apparatus. The results reveal that the as-cast alloys contain TiFe as major phase and Ti 2 Fe as secondary phase. Sm addition refines the grain of alloys obviously. All alloys have good activation properties and can be completely activated without any heat treatment. The activation performance can be further improved by partially replacing Ti with Sm, and the incubation period of activation can be shortened greatly. • Sm addition refines the grains of TiFe-based alloys. • The activation property of alloys can be improved obviously after adding Sm. • Introducing Sm improves the hydrogen storage kinetics of samples. • The hydrogen absorption and desorption hysteresis reduces after adding Sm. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of a hydrogen refueling system that consists of a polymer electrolyte membrane electrolyzer integrated with photovoltaic arrays, and an electrochemical compressor to increase the hydrogen pressure. The energetic and exergetic performance of the hydrogen refueling station is analyzed at different working conditions. The exergy cost of hydrogen production is studied in three different case scenarios; that consist of i) off-grid station with the photovoltaic system and a battery bank to supply the required electric power, ii) on-grid station but the required power is supplied by the electric grid only when solar energy is not available and iii) on-grid station without energy storage. The efficiency of the station significantly increases when the electric grid empowers the system. The maximum energy and exergy efficiencies of the photovoltaic system at solar irradiation of 850 W m-2 are 13.57% and 14.51%, respectively. The exergy cost of hydrogen production in the on-grid station with energy storage is almost 30% higher than the off-grid station. Moreover, the exergy cost of hydrogen in the on-grid station without energy storage is almost 4 times higher than the off-grid station and the energy and exergy efficiencies are considerably higher. [Display omitted] • A solar hydrogen refueling station is designed for remote application. • The exergy cost of hydrogen is determined in different working conditions. • An electrochemical hydrogen compressor is integrated in the hydrogen production system. • An on-grid refueling station has considerably lower hydrogen cost than off-grid. • The efficiency of off-grid refueling station is highly sensitive to the capacity. [ABSTRACT FROM AUTHOR]

The B 6 Ca 2 and B 8 Ca 2 clusters adopt interesting inverse sandwich architectures, featuring a prolate B 6 (or perfect B 8) ring jammed with two capping Ca atoms. Both clusters show the high thermodynamic stability due to the double (σ and π) electronic delocalization. In present paper, we computationally studied the hydrogen storage of them. The results suggest that each Ca site in B 6 Ca 2 and B 8 Ca 2 clusters could store up six H 2 , yielding a gravimetric density of 14.2 wt% for B 6 Ca 2 and 12.6 wt% for B 8 Ca 2. The average adsorption energy for H 2 -adsorbed B 6 Ca 2 and B 8 Ca 2 complexes is within the scope of 0.12–0.15 eV per H 2 at w B97XD level, hinting that two clusters could reversibly store and release hydrogen, which is positively confirmed by the Born-Oppenheimer molecular dynamics simulations. Both B 6 Ca 2 and B 8 Ca 2 nanoclusters are feasible hydrogen storage media under the ambient condition. The B 6 Ca 2 and B 8 Ca 2 inverse sandwiches possess high-capacity hydrogen storage and release. Each Ca site can adsorb six H 2 , yielding a gravimetric density of 14.2 wt% for B 6 Ca 2 and 12.6 wt% for B 8 Ca 2. [Display omitted] • The B 6 Ca 2 and B 8 Ca 2 inverse sandwiches have the high thermostability with the double electronic delocalization. • The B 6 Ca 2 and B 8 Ca 2 inverse sandwiches exhibit the high-capacity hydrogen storage and release. • The gravimetric density is as high as 14.2 wt% for B 6 Ca 2 and 12.6 wt% for B 8 Ca 2. • The Ca-doped boron nanostructure can be used as hydrogen storage material. [ABSTRACT FROM AUTHOR]

The dome reinforcement (DR) technology was studied to reduce the amount of carbon fiber of the type IV hydrogen storage vessel in this paper. Firstly, the influence of the angle and thickness of the dome reinforcement part on the stress distribution of the dome section is studied by finite element analysis. Secondly, the weight reduction of carbon fiber composite layer is studied based on the dome reinforcement model. The strain-based Hashin progressive damage model is used to predict the burst pressure and burst mode with user-defined material subroutine (UMAT) of ABAQUS. Finally, the dome reinforcement technology is further verified in comparison with non-dome reinforcement by burst tests. The results show that the progressive damage model can effectively represent matrix cracking and fiber fracture, and the predicted burst pressure and mode is consistent with the test results. The fiber stress near the equator of the dome section affects the burst mode, and the smaller the angle of dome reinforcement parts, the better the reinforcing effect, and the dome reinforcement technology can help to improve the fiber damage state at the dome, transfer the maximum stress to the cylinder section of the vessel, and ensure the burst mode to be a safe mode. Also, it can help to reduce the consumption of carbon fiber by up to 5.5% in composite material. [Display omitted] • The fiber stress near the equator of the dome section directly affects the burst mode. • The smaller the angle of dome reinforcement parts, the better the reinforcing effect. • The dome reinforcement parts can transfer the maximum stress to the cylinder section. • The dome reinforcement parts help to reduce carbon fiber consumption by up to 5.5%. [ABSTRACT FROM AUTHOR]

This paper investigates the decoration of superalkali NLi 4 on graphene and the hydrogen storage properties by using first principles calculations. The results show that the NLi 4 units can be stably anchored on graphene while the Li atoms are strongly bound together in the superalkali clusters. Decoration using the superalkali clusters not only solve the aggregation of metal atoms, it also provide more adsorption sites for hydrogen. Each NLi 4 unit can adsorb up to 10 H 2 molecules, and the NLi 4 decorated graphene can reach a hydrogen storage capacity 10.75 wt% with an average adsorption energy −0.21 eV/H 2. We also compute the zero-point energies and the entropy change upon adsorption based on the harmonic frequencies. After considering the entropy effect, the adsorption strengths fall in the ideal window for reversible hydrogen storage at ambient temperatures. So NLi 4 decorated graphene can be promising hydrogen storage material with high reversible storage capacities. • Superalkali NLi 4 decorated nanomaterials are proposed for hydrogen storage. • NLi 4 clusters can be stably anchored on graphene monolayer. • Superalkalis effectively solve the aggregation of metal atoms on substrate. • High reversible storage capacities can be achieved at ambient temperature. [ABSTRACT FROM AUTHOR]

Over the past years, hydrogen has been identified as the most promising carrier of clean energy. In a world that aims to replace fossil fuels to mitigate greenhouse emissions and address other environmental concerns, hydrogen generation technologies have become a main player in the energy mix. Since hydrogen is the main working medium in fuel cells and hydrogen-based energy storage systems, integrating these systems with other renewable energy systems is becoming very feasible. For example, the coupling of wind or solar systems hydrogen fuel cells as secondary energy sources is proven to enhance grid stability and secure the reliable energy supply for all times. The current demand for clean energy is unprecedented, and it seems that hydrogen can meet such demand only when produced and stored in large quantities. This paper presents an overview of the main hydrogen production and storage technologies, along with their challenges. They are presented to help identify technologies that have sufficient potential for large-scale energy applications that rely on hydrogen. Producing hydrogen from water and fossil fuels and storing it in underground formations are the best large-scale production and storage technologies. However, the local conditions of a specific region play a key role in determining the most suited production and storage methods, and there might be a need to combine multiple strategies together to allow a significant large-scale production and storage of hydrogen. • Large-scale production and storage of hydrogen are presented. • Renewable hydrogen is summarized. • Non-renewable hydrogen is discussed. • Natural underground hydrogen storage is presented. [ABSTRACT FROM AUTHOR]

NaBH 4 has been considered as one of the ideal hydrogen carriers with comparatively high hydrogen capacities towards traditional hydrogen storage materials. However, the hydrogen generation from NaBH 4 needs excess water and costly catalysts to achieve a complete and fast hydrogen release. Herein, we report an innovative strategy to use solid-state multi-hydroxyl mannitol as a reactant towards NaBH 4 , which brings fast and controllable hydrogen release below 80 °C. More than 4.1 wt% H 2 (83% of the theoretical capacity) could be released totally from the NaBH 4 -mannitol composite with high purity. Structural and morphological studies further reveal that mannitol acts as a bi-functional additive to react with NaBH 4 during hydrogen release and protect NaBH 4 from moisture during storage. This work shows potential in developing all-solid-state hydrogen production systems with high-capacity borohydrides. The NaBH 4 -mannitol composites were prepared by ball-milling, and effectively released hydrogen below 80 °C. Mannitol acts both as a carrier of proton hydrogens (Hδ+), reacting with NaBH 4 , and as a protector reducing the influence of moisture and oxygen on NaBH 4. [Display omitted] • All-solid-state NaBH 4 -mannitol composites were prepared by ball mill. • NaBH 4 -mannitol composite released hydrogen from 78.8 °C with 4.17 wt% capacity. • Bi-functional additive mannitol serves as both a reactant and a protector of NaBH 4. [ABSTRACT FROM AUTHOR]

NaBH 4 has been widely considered as a low-cost hydrogen storage material with high gravimetric hydrogen capacity of about 10 wt%. However, its strong thermodynamic stability severely hinders the application of NaBH 4 to obtain hydrogen. In this study, multi-hydroxyl xylitol, for the first time, was chosen as a protic hydrogen carrier to destabilize and react with NaBH 4. The NaBH 4 -xylitol composites were easily prepared through hand-milling, which leads to the fast liberation of hydrogen from moderate temperatures lower than 80 °C with more than 3.6 wt% hydrogen desorption capacity. Besides, over 80% of hydrogen could be efficiently released in NaBH 4 -xylitol composite. The dehydrogenation process is proved to be completely impurity-free and controllable by altering the NaBH 4 /xylitol ratios and operating temperatures. The reaction between NaBH 4 and xylitol is investigated to be similar to an alcoholysis procedure, however no observable liquid phase takes place before and after the dehydrogenation of NaBH 4 -xylitol composite, showing a great potential to produce hydrogen under low temperatures through solid-state carriers. • A new strategy to use multi-hydroxyl xylitol to destabilize NaBH 4. • NaBH 4 -xylitol composite starts to release hydrogen before 80 °C with high efficiency. • No observable liquid phase during dehydrogenation in NaBH 4 -xylitol composite, showing high volumetric capacity. [ABSTRACT FROM AUTHOR]