Japan

Premature delamination failure characterized by the white structure flaking (WSF) or the white etching crack (WEC) often occurs in rolling element bearings and it deteriorates the durability of bearing substantially. It is known that this failure is caused by shear-mode (Mode II and Mode III) crack growth in conjunction with evolution and invasion of hydrogen into material during operation. To ensure the structural integrity associated with rolling element bearing it is important to clarify the effect of hydrogen on the shear-mode fatigue crack growth behavior near the threshold level.<br/>In our previous study the effect of hydrogen on the shear-mode fatigue crack growth behavior in a bearing steel of JIS SUJ2 was examined near the threshold level. Consequently it was shown that the threshold stress intensity factor (SIF) range for shear-mode fatigue crack growth decreased significantly by action of hydrogen. However the investigation was made only for a crack with a surface length of about 900 mm. To thoroughly understand the critical condition for delamination failure it is important to investigate the crack size dependency of the threshold level for a shear-mode small fatigue crack in the presence of hydrogen. In the present study correspondingly the threshold SIF ranges for a shear-mode crack with different length were additionally measured in the same material by using a novel technique that enables continuous charging of hydrogen in a specimen during long-term fatigue test. Then a clear reduction in crack growth rate and a crack size dependency of the threshold SIF range were observed under the environmental condition of continuous hydrogen charging.

We evaluated the strain rate sensitivity of the micro-damage evolution behavior in a ferrite/martensite dual-phase steel. The micro-damage evolution behavior can be divided into three regimes: damage incubation damage arrest and damage growth. All regimes are associated with local deformability. Thus the total elongation of DP steels is determined by a combination of plastic damage initiation resistance and damage growth arrestability. This fact implies that hydrogen must have a critical effect on the damage evolution because hydrogen enhances strain localization and lowers crack resistance. In this context the strain rate must be an important factor because it affects the time for microstructural hydrogen diffusion/segregation at a specific microstructural location or at the damage tip. In this study tensile tests were carried out on a DP steel with different strain rates of 10^{− 2} and 10^{− 4} s⁻¹. We performed the damage quantification microstructure characterization and fractography. Specifically the quantitative data of the damage evolution was analyzed using the classification of the damage evolution regimes in order to separately elucidate the effects of the hydrogen on damage initiation resistance and damage arrestability. In this study we obtained the following conclusions with respect to the strain rate. Lowering the strain rate increased the damage nucleation rate at martensite and reduced the critical strain for fracture through shortening the damage arrest regime. However the failure occurred via ductile modes regardless of strain rate.

Japan’s energy consumption derives mostly from fossil fuels which are un-secure and release a much greenhouse gas emissions. To meet goals of reducing GHG hydrogen gas can be utilized in power generation in hydrogen fired and firing / co-combustion power plants. This paper analyses the impact of hydrogen in the power generation sector using the MARKAL-TIMES Japan optimization model framework. Two models are used: a base scenario without hydrogen and hydrogen scenario in which hydrogen is supplied from 2020 onwards. In the hydrogen scenario other processes which are normally supplied by natural gas are reduced because the gas is instead used to generate power. Adding hydrogen to the energy supply leads to a decrease in projected use of fossil fuels. The hydrogen scenario produces fewer emissions than the base scenario; by 2050 the hydrogen scenario’s estimated 388 metric tons of CO2 emissions is over 250 tons less than the base scenario’s emissions of 588 metric tons.

The presented research focuses on an optimization design of a catalyst distribution inside a small-scale methane/steam reforming reactor. A genetic algorithm was used for the multiobjective optimization which included the search for an optimum of methane conversion rate and a minimum of the difference between highest and lowest temperatures in the reactor. For the sake of computational time the maximal number of the segment with different catalyst densities was set to be thirty in this study. During the entire optimization process every part of the reactor could be filled either with a catalyst material or non-catalytic metallic foam. In both cases the porosity and pore size was also specified. The impact of the porosity and pore size on the active reaction surface and permeability was incorporated using graph theory and three-dimensional digital material representation. Calculations start with the generation of a random set of possible reactors each with a different catalyst distribution. The algorithm calls reforming simulation over each of the reactors and after obtaining concentration and temperature fields the algorithms calculated fitness function. The properties of the best reactors are combined to generate a new population of solutions. The procedure is repeated and after meeting the coverage criteria the optimal catalyst distribution was proposed. The paper is summarized with the optimal catalyst distribution for the given size and working conditions of the system.

Thermochemical hydrogen production process is one of the candidates of industrial fossil fuel free hydrogen production. Japan Atomic Energy Agency (JAEA) has been conducting R&D of the thermochemical water splitting iodine-sulfur (IS) process since the end of 1980s. This paper presents the recent study on the IS process in JAEA. In 2005-2009 test-fabrication of components collection of design database improvement of process components for higher thermal efficiency and proposition of composition measurement method were carried out. On the basis of them the integrity test of process components is carried out in 2010-2014 to examine their integrities in severe process environments. At present a Bunsen reactor which produces acids and incidental equipments has been already manufactured using corrosion resistant materials such as glass lining steel and fluoroplastic lining steel. Flow tests to examine the functionality and integrity of the materials are planned in 2012.

Hydrogen-induced cracking behavior in high-strength steel mainly composed of martensite was analyzed by acoustic emission (AE) technique and finite element method (FEM) in slow strain-rate tensile (SSRT) tests and welding tests. The crack initiation was detected by the AE signals and the time evolution of stress concentration and hydrogen diffusion were calculated by FEM. The effect of hardness and plastic strain on the hydrogen diffusion coefficientwas explicitly introduced into the governing equation in FEM. The criterion and indicator parameter for the crack initiation were derived as a function of maximum principal stress and locally accumulated hydrogen concentration. The results showed that the cracking criterion derived by AE and FEM is useful for predicting the cold cracking behavior and determining the critical preheat temperature to prevent hydrogeninduced cracking.

The authors have proposed a new combustion process called the Plume Ignition Combustion Concept (PCC) in which with an optimal combination of hydrogen injection timing and controlled jet geometry the plume of the hydrogen jet is spark-ignited to accomplish combustion of a rich mixture. This combustion process markedly improves thermal efficiency by reducing cooling loss which is essential for increasing thermal efficiency in a hydrogen engine while maintaining high power. In order to improve thermal efficiency and reduce NOx formation further PCC was applied to a lean-burn regime to burn a leaner mixture globally. In this study the effect of supercharging which was applied to recover the reduced output power due to the leaner mixture on improving thermal efficiency was confirmed along with clarifying the cause.

This research qualitatively reviews literature regarding energy system modeling in Japan specific to the future hydrogen economy leveraging quantitative model outcomes to establish the potential future deployment of hydrogen in Japan. The analysis focuses on the four key sectors of storage supplementing the gas grid power generation and transportation detailing the potential range of hydrogen technologies which are expected to penetrate Japanese energy markets up to 2050 and beyond. Alongside key model outcomes the appropriate policy settings governance and market mechanisms are described which underpin the potential hydrogen economy future for Japan. We find that transportation gas grid supplementation and storage end-uses may emerge in significant quantities due to policies which encourage ambitious implementation targets investment in technologies and research and development and the emergence of a future carbon pricing regime. On the other hand for Japan which will initially be dependent on imported hydrogen the cost of imports appears critical to the emergence of broad hydrogen usage particularly in the power generation sector. Further the consideration of demographics in Japan recognizing the aging shrinking population and peoples’ energy use preferences will likely be instrumental in realizing a smooth transition toward a hydrogen economy.

By using a newly constructed bench-scale hydrogen energy system with renewable energy ‘Pure Hydrogen Energy System’ the present study demonstrates the operations of a metal hydride (MH) tank for hydrogen compression as implemented through the use solar thermal energy. Solar thermal energy is used to generate hot water as a heat source of the MH tank. Thus 70 kg of LaNi5 one of the most typical alloys used for hydrogen storage was placed in the MH tank. We present low and high hydrogen flow rate operations. Then the operations under winter conditions are discussed along with numerical simulations conducted from the thermal point of view. Results show that a large amount of heat (>100 MJ) is generated and the MH hydrogen compression is available.

For prohibiting a global warming fuel-cell systems without carbon dioxide emissions are a one of the promising technique. In case of a fuel-cell vehicle (FCV) high-pressure H₂ gas is indispensable for a long running range. Although there are lot of paper for studying a hydrogen embrittlement (HE) there are few paper referred to the effect of high-pressure H₂on the HE phenomenon.

In this study an effect of high-pressure H₂ gas on tensile & fatigue properties of stainless steel SUS316L were investigated by means of the internal high-pressure H₂ gas technique. Main findings of this study are as follows;

• Although there are almost no hydrogen embrittlement effect on the 0.2 % proof stress and tensile strength elongation and reduction of area decrease in H₂ gas environment
• For case of low Ni_eq material fatigue life and fatigue limit decrease in H₂ gas environment
• For case of low Ni_eq material not a few α’ martensitic phase generated on the fatigue fractured specimen.

In this paper we propose and verify a novel method to simulate crack propagation without propagating a crack by finite element method. We propose this method for elastoplastic analysis coupled with convection-diffusion. In the previous study we succeeded in performing elastoplastic analysis coupled with convection-diffusion of hydrogen for a material with a crack under tensile loading. This research extends the successful method to fatigue crack propagation. In convection-diffusion analysis in order to simulate the invasion and release of elements through the free surface the crack tip is expressed by using a notch with a sufficiently small radius. Therefore the node release method conventionally used to simulate crack propagation cannot be applied. Hence instead of crack propagation based on an analytical model we propose a novel method that can reproduce the influence of the vicinity of the crack tip on a crack. We moved the stress field near the crack tip in the direction opposite to that of crack propagation by an amount corresponding to the crack propagation length. When we extend the previous method to fatigue crack propagation simulation we must consider the difference in strain due to loading and unloading. This problem was solved by considering the strain due to loading as a displacement. Instead of moving the strain due to loading we moved the displacement. First we performed a simple tensile load analysis on the model and output the displacement of all the nodes of the model at maximum load. Then the displacement was moved in the direction opposite to that of crack propagation. Finally the stress field was reproduced by forcibly moving all the nodes by the displacement amount. The strain due to unloading was reproduced by removing the displacement. Furthermore we verified the equivalence of the crack propagation simulation and the proposed method.

In the literature different energy carriers are proposed in future long-distance hydrogen value chains. Hydrogen can be stored and transported in different forms e.g. as compressed dense-phase hydrogen liquefied hydrogen and in chemically bound forms as different chemical hydrides. Recently different high-level value chain studies have made extrapolative investigations and compared such options with respect to energy efficiency and cost. Three recent journal papers overlap as the liquid hydrogen option has been considered in all three studies. The studies are not fully aligned in terms of underlying assumptions and battery limits. A comparison reveals partly vast differences in results for chain energy efficiency for long-distance liquid hydrogen transport which are attributable to distinct differences in the set of assumptions. Our comparison pinpoints the boiloff ratio i.e. evaporation losses due to heat ingress in liquid hydrogen storage tanks as the main cause of the differences and this assumption is further discussed. A review of spherical tank size and attributed boiloff ratios is presented for existing tanks of different vintage as well as for recently proposed designs. Furthermore the prospect for further extension of tanks size and reduction of boiloff ratio is discussed with a complementary discussion about the use of economic assumptions in extrapolative and predictive studies. Finally we discuss the impact of battery limits in hydrogen value chain studies and pinpoint knowledge needs and the need for a detailed bottom-up approach as a prerequisite for improving the understanding for pros and cons of the different hydrogen energy carriers.

CO2 emissions associated with hydrogen production can be reduced replacing steam methane reforming with electrolysis using renewable electricity with a trade-off of increasing energy consumption water consumption and cost. In this research a linear programming optimization model of a hydrogen production system that considers simultaneously energy consumption water consumption CO2 emissions and cost on a cradle-to-gate basis was developed. The model was used to evaluate the impact of CO2 intensity on the optimum design of a hydrogen production system for Japan considering different stakeholders’ priorities. Hydrogen is produced using steam methane reforming and electrolysis. Electricity sources include grid wind solar photovoltaic geothermal and hydro. Independent of the stakeholders’ priorities steam methane reforming dominates hydrogen production for cradle-to-gate CO2 intensities larger than 9 kg CO2/kg H2 while electrolysis using renewable electricity dominates for lower cradle-to-gate CO2 intensities. Reducing the cradle-to-gate CO2 intensity increases energy consumption water consumption and specific cost of hydrogen production. For a cradle-to-gate CO2 intensity of 0 kg CO2/kg H2 the specific cost of hydrogen production varies between 8.81 and 13.6 USD/kg H2; higher than the specific cost of hydrogen production targeted by the Japanese government in 2030 of 30 JPY/Nm3 3.19 USD/kg H2.

Ensuring the energy transition in order to decrease CO2 and volatile organic compounds emissions and improve the efficiency of energy processes requires the development of advanced materials and technologies for the electrical energy sector. The article reviews superconducting materials functional nanomaterials used in the power industry mainly due to their magnetic electrical optical and dielectric properties and the thin layers of amorphous carbon nitride which properties make them an important material from the point of view of environmental protection optoelectronic photovoltaic and energy storage. The superconductivity-based technologies material processing and thermal and nonthermal plasma generation have been reviewed as technologies that can be a solution to chosen problems in the electrical energy sector and environment. The study explains directly both—the basics and application potential of low and high-temperature superconductors as well as peculiarities of the related manufacturing technologies for Roebel cables 1G and 2G HTS tapes and superconductor coil systems. Among the superconducting materials particular attention was paid to the magnesium di-boride MgB2 and its potential applications in the power industry. The benefits of the use of carbon films with amorphous structures in electronics sensing technologies solar cells FETs and memory devices were discussed. The article provides the information about most interesting from the R&D point of view groups of materials for PV applications. It summarises the advantages and disadvantages of their use regarding commercial requirements such as efficiency lifetime light absorption impact on the environment costs of production and weather dependency. Silicon processing inkjet printing vacuum deposition and evaporation technologies that allow obtaining improved and strengthened materials for solar cell manufacturing are also described. In the case of the widely developed plasma generation field waste-to-hydrogen technology including both thermal and non-thermal plasma techniques has been discussed. The review aims to draw attention to the problems faced by the modern power industry and to encourage research in this area because many of these problems can only be solved within the framework of interdisciplinary and international cooperation.

Hydrogen is a promising energy carrier especially for transportation owing to its unique physical and chemical properties. Moreover the combustion of hydrogen gas generates only pure water; thus its wide utilization can positively affect human society to achieve global net zero CO2 emissions by 2050. This review summarizes the characteristics of the primary hydrogen carriers such as water methane methanol ammonia and formic acid and their corresponding hydrogen production methods. Additionally state-of-the-art studies and hydrogen energy applications in recent years are also included in this review. In addition in the conclusion section we summarize the advantages and disadvantages of hydrogen carriers and hydrogen production techniques and suggest the challenging tasks for future research.

The roll-out of hydrogen refuelling stations is a key step in the transition to a hydrogen economy. Since Japan has been shifting from the demonstration stage to the implementation stage of a hydrogen economy a near-term city-level roll-out plan is required. The aim of this study is to plan near-term locations for building hydrogen refuelling stations in Yokohama City from a safety perspective. Our planning provides location information for hydrogen refuelling stations in Yokohama City for the period 2020–2030. Mobile type and parallel siting type refuelling stations have been considered in our planning and locations were determined by matching supply and demand to safety concerns. Supply and demand were estimated from hybrid vehicle ownership data and from space availability in existing gas stations. The results reaffirmed the importance of hydrogen station location planning and showed that use of mobile type stations is a suitable solution in response to the uncertain fuel cell vehicle fuel demand level during the implementation stage of a hydrogen economy.

One of the topics for the revision deliberation of GTR13 on hydrogen and fuel cell vehicles is the study of an appropriate initial burst pressure of the containers. The purpose of this study is to investigate the influence of the hydraulic sequential tests on the residual burst pressure in order to examine the appropriate initial burst pressure correlated with the provisions for the residual burst pressure at the Endof-Life (EOL). Specifically we evaluated any deterioration and variations of burst pressure due to hydraulic sequential tests on 70MPa compressed-hydrogen containers. When the burst pressure after the hydraulic sequential testing (EOL) was compared with the initial burst pressure at the beginning of life (BOL) the pressure proved to have decreased by a few percent while the variation increased. In the burst test it was observed that the rupture originated in the cylindrical part in all the BOL containers while in some of the EOL containers the rupture originated in the dome part. Since the dome part is a section that suffers an impact of vertical drop test it is conceivable that some sort of damage occurred in the CFRP. Therefore it was assumed that this damage was the main causal factor for the decrease in the burst pressure and the increase of the burst pressure variation at the dome part.

Magnesium hydride owns the largest share of publications on solid materials for hydrogen storage. The “Magnesium group” of international experts contributing to IEA Task 32 “Hydrogen Based Energy Storage” recently published two review papers presenting the activities of the group focused on magnesium hydride based materials and on Mg based compounds for hydrogen and energy storage. This review article not only overviews the latest activities on both fundamental aspects of Mg-based hydrides and their applications but also presents a historic overview on the topic and outlines projected future developments. Particular attention is paid to the theoretical and experimental studies of Mg-H system at extreme pressures kinetics and thermodynamics of the systems based on MgH₂ nanostructuring new Mg-based compounds and novel composites and catalysis in the Mg based H storage systems. Finally thermal energy storage and upscaled H storage systems accommodating MgH₂ are presented.

In the context of the fatigue life design of components particularly those destined for use in hydrogen refuelling stations and fuel cell vehicles it is important to understand the hydrogen-induced fatigue crack growth (FCG) acceleration in steels. As such the mechanisms for acceleration and its influencing factors are reviewed and discussed in this paper with a special focus on the peculiar frequency dependence of the hydrogen-induced FCG acceleration. Further this frequency dependence is debated by introducing some potentially responsible elements along with new experimental data obtained by the authors.

This article is part of the themed issue ‘The challenges of hydrogen and metals’.

Link to document download on Royal Society Website

Hydrothermal gasification (HTG) experiments were carried out to extract hydrogen from biomass. Although extensive research has been conducted on hydrogen production with HTG limited research exists on the use of biochar as a raw material. In this study woodland residues (wood chip) and biochar from wood-chip pyrolysis were used in HTG treatment to generate hydrogen. This research investigated the effect of temperature (300–425 °C) and biomass/water (0.5–10) ratio on gas composition. A higher temperature promoted hydrogen production because the water–gas shift reaction and steam-reforming reaction were promoted with an increase in temperature. The methane concentration was related positively to temperature because of the methanation and hydrogenation reactions. A lower biomass/water ratio promoted hydrogen production but suppressed carbon-monoxide production. Most reactions that produce hydrogen consume water but water also affects the water–gas shift reaction balance which decreases the carbon-monoxide concentration. By focusing on the practical application of HTG we attempted biochar treatment by pyrolysis (temperature of heating part: 700 °C) and syngas was obtained from hydrothermal treatment above 425 °C.

Unlike four-wheel fuel-cell vehicles fuel-cell motorcycles have little semi-closure space corresponding to the engine compartment of four-wheel fuel-cell vehicles. Furthermore motorcycles may fall while parked or running. We conducted hydrogen concentration measurement and ignition tests to evaluate the feasibility of detecting leaks when hydrogen gas leaked from a fuel-cell motorcycle as well as the risk of ignition. We found that the installation of hydrogen leak detectors is effective because it is possible to detect minute hydrogen leaks by installing leak detectors at appropriate points on the fuel cell motorcycle and risks can be reduced by interrupting the hydrogen leak immediately after detection.

Hydrogen is a promising energy carrier in the clean energy systems currently being developed. However its effectiveness in mitigating greenhouse gas (GHG) emissions requires conducting a lifecycle analysis of the process by which hydrogen is produced and supplied. This study focuses on the hydrogen for the transport sector in particular renewable hydrogen that is produced from wind- or solar PV-powered electrolysis. A life cycle inventory analysis is conducted to evaluate the Well-to-Tank (WtT) GHG emissions from various renewable hydrogen supply chains. The stages of the supply chains include hydrogen being produced overseas converted into a transportable hydrogen carrier (liquid hydrogen or methylcyclohexane) imported to Japan by sea distributed to hydrogen filling stations restored from the hydrogen carrier to hydrogen and filled into fuel cell vehicles. For comparison an analysis is also carried out with hydrogen produced by steam reforming of natural gas. Foreground data related to the hydrogen supply chains are collected by literature surveys and the Japanese life cycle inventory database is used as the background data. The analysis results indicate that some of renewable hydrogen supply chains using liquid hydrogen exhibited significantly lower WtT GHG emissions than those of a supply chain of hydrogen produced by reforming of natural gas. A significant piece of the work is to consider the impacts of variations in the energy and material inputs by performing a probabilistic uncertainty analysis. This suggests that the production of renewable hydrogen its liquefaction the dehydrogenation of methylcyclohexane and the compression of hydrogen at the filling station are the GHG-intensive stages in the target supply chains.

To efficiently convert and utilize intermittent solar energy a novel solar-driven ethanol steam reforming (ESR) system integrated with a membrane reactor is proposed. It has the potential to convert low-grade solar thermal energy into high energy level chemical energy. Driven by chemical potential hydrogen permeation membranes (HPM) can separate the generated hydrogen and shift the ESR equilibrium forward to increase conversion and thermodynamic efficiency. The thermodynamic and environmental performances are analyzed via numerical simulation under a reaction temperature range of 100–400 ◦C with permeate pressures of 0.01–0.75 bar. The highest theoretical conversion rate is 98.3% at 100 ◦C and 0.01 bar while the highest first-law efficiency solar-to-fuel efficiency and exergy efficiency are 82.3% 45.3% and 70.4% at 215 ◦C and 0.20 bar. The standard coal saving rate (SCSR) and carbon dioxide reduction rate (CDRR) are maximums of 101 g·m−2 ·h −1 and 247 g·m−2 ·h −1 at 200 ◦C and 0.20 bar with a hydrogen generation rate of 22.4 mol·m−2 ·h −1 . This study illustrates the feasibility of solar-driven ESR integrated with a membrane reactor and distinguishes a novel approach for distributed hydrogen generation and solar energy utilization and upgradation.

Hydrogen energy as clean and efcient energy is considered signifcant support for the construction of a sustainable society in the face of global climate change and the looming energy revolution. Hydrogen is one of the most important chemical substances on earth and can be obtained through various techniques using renewable and nonrenewable energy sources. However the necessity for a gradual transition to renewable energy sources signifcantly hampers eforts to identify and implement green hydrogen production paths. Therefore this paper’s objective is to provide a technological review of the systems of hydrogen production from solar and wind energy utilizing several types of water electrolyzers. The current paper starts with a short brief about the diferent production techniques. A detailed comparison between water electrolyzer types and a complete illustration of hydrogen production techniques using solar and wind are presented with examples after which an economic assessment of green hydrogen production by comparing the costs of the discussed renewable sources with other production methods. Finally the challenges that face the mentioned production methods are illuminated in the current review.

Fossil resources are unevenly distributed on the earth and are finite primary energy which is widely used in the fields of industry transportation and power generation etc.<br/>Primary energies that can replace fossil resources include renewable energy and nuclear energy. Hydrogen has the potential to be secondary energy that can be widely used in industry for various purposes. Nuclear energy can be used for producing hydrogen; it is becoming more important to convert this primary energies into hydrogen. This paper describes the roles of nuclear energy as a primary energy in hydrogen production from the viewpoint of the basics of energy form conversion.