Japan

We at Kawasaki Heavy Industries have proposed a "CO2-Free H2 supply chain" using abundant brown coal of Australian origin as the energy source. This chain will store CO2 generated during the process for producing hydrogen from brown coal in a project (Carbon Net) that the Australia Government is promoting. Thus Japan can import CO2-free hydrogen. The supply chain consists of the hydrogen production system the hydrogen transport/storage system and the hydrogen use system. Related to their designs we have to consider their hazards polluted scenarios and safety measures via a safety assessment process that is compliant with international risk assessment standards. To verify safety designs related experiments and analyses will be conducted. This paper describes the approach to safety design for especially the related liquid hydrogen facilities.

Compressed hydrogen is delivered by trailers in steel cylinders at 19.6 MPa in Japan. Kawasaki Heavy Industries Ltd. developed two compressed hydrogen trailers with composite cylinders in collaboration with JX Nippon Oil in a project of the New Energy and Industrial Technology Development Organization (NEDO).<br/>The first trailer which was the first hydrogen trailer with composite cylinder in Japan has 35 MPa cylinders and the second trailer has 45 MPa cylinders. These trailers have been operated transporting hydrogen and feedstock to hydrogen refuelling stations without the accident. This paper describes the safety design including compliance with regulations the influence of vibrations and safety verification in case of a collision.

The objective of this study is to gain a basic understanding of the effect of hydrogen on the fatigue limit. The material was a low-alloy steel modified to be sensitive to hydrogen embrittlement by heat treatment. A statistical fatigue test was carried out using smooth and deep-notched specimens at a loading frequency of 20 Hz. The environment was laboratory air and hydrogen gas. The hydrogen gas pressure was 0.1 MPa in gauge pressure. The fatigue limit of the smooth specimen was higher in the hydrogen gas than that in air although the material showed severe hydrogen embrittlement during the SSRT (Slow Strain Rate Test). The fatigue limit of the deep-notched specimen in the hydrogen gas was the same as that in air. For the smooth specimen the fatigue limit was determined by whether or not a crack was initiated. For the deep-notched specimen the fatigue limit was determined by whether or not a crack propagated. The results can be interpreted as that hydrogen has no significant effect on crack initiation in the high-cycle fatigue regime and affected the threshold of the crack propagation.

A high-pressure hydrogen jet released into the air has the possibility of igniting in a tube without any ignition source. The mechanism of this phenomenon called spontaneous ignition is considered to be that hydrogen diffuses into the hot air caused by the shock wave from diaphragm rupture and the hydrogen-oxidizer mixed region is formed enough to start chemical reaction. Recently flow visualization studies on the spontaneous ignition process have been conducted to understand its detailed mechanism but such ignition has not yet been well clarified. In this study the spontaneous ignition phenomenon was observed in a rectangular tube. The results confirm the presence of a flame at the wall of the tube when the shock wave pressure reaches 1.2–1.5 MPa in more than 9 MPa burst pressure and that ignition occurs near the wall followed by multiple ignitions as the shock wave propagates with the ignitions eventually combining to form a flame.

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.

Global climate change concerns have pushed international governmental actions to reduce greenhouse gas emissions by adopting cleaner technologies hoping to transition to a more sustainable society. The hydrogen economy is one potential long-term option for enabling deep decarbonization for the future energy landscape. Progress towards an operating hydrogen economy is discouragingly slow despite global efforts to accelerate it. There are major mismatches between the present situation surrounding the hydrogen economy and previous proposed milestones that are far from being reached. The overall aim of this study is to understand whether there has been significant real progress in the achievement of a hydrogen economy or whether the current interest is overly exaggerated (hype). This study uses bibliometric analysis and content analysis to historically map the hydrogen economy’s development from 1972 to 2020 by quantifying and analyzing three sets of interconnected data. Findings indicate that interest in the hydrogen economy has significantly progressed over the past five decades based on the growing numbers of academic publications media coverage and projects. However various endogenous and exogenous factors have influenced the development of the hydrogen economy and created hype at different points in time. The consolidated results explore the changing trends and how specific events or actors have influenced the development of the hydrogen economy with their agendas the emergence of hype cycles and the expectations of a future hydrogen economy.

We utilized nanoporous mayenite (12CaO·7Al₂O₃) a cost-effective material in the hydride state (H⁻) to explore the possibility of its use for hydrogen storage and transportation. Hydrogen desorption occurs by a simple reaction of mayenite with water and the nanocage structure transforms into a calcium aluminate hydrate. This reaction enables easy desorption of H⁻ ions trapped in the structure which could allow the use of this material in future portable applications. Additionally this material is 100% recyclable because the cage structure can be recovered by heat treatment after hydrogen desorption. The presence of hydrogen molecules as H⁻ ions was confirmed by ¹H-NMR gas chromatography and neutron diffraction analyses. We confirmed the hydrogen state stability inside the mayenite cage by the first-principles calculations to understand the adsorption mechanism and storage capacity and to provide a key for the use of mayenite as a portable hydrogen storage material. Further we succeeded in introducing H⁻ directly from OH⁻ by a simple process compared with previous studies that used long treatment durations and required careful control of humidity and oxygen gas to form O² species before the introduction of H⁻.

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.

Large-scale deflagration and detonation experiments of hydrogen and air mixtures provide fundamental data needed to address accident scenarios and to help in the evaluation and validation of numerical models. Several different experiments of this type were performed. Measurements included flame front time of arrival (TOA) using ionization probes blast pressure heat flux high-speed video standard video and infrared video. The large-scale open-space tests used a hemispherical 300-m3 facility that confined the mixture within a thin plastic tent that was cut prior to initiating a deflagration. Initial homogeneous hydrogen concentrations varied from 15% to 30%. An array of large cylindrical obstacles was placed within the mixture for some experiments to explore turbulent enhancement of the combustion. All tests were ignited at the bottom center of the facility using either a spark or in one case a small quantity of high explosive to generate a detonation. Spark-initiated deflagration tests were performed within the tunnel using homogeneous hydrogen mixtures. Several experiments were performed in which 0.1 kg and 2.2 kg of hydrogen were released into the tunnel with and without ventilation. For some tunnel tests obstacles representing vehicles were used to investigate turbulent enhancement. A test was performed to investigate any enhancement of the deflagration due to partial confinement produced by a narrow gap between aluminium plates. The attenuation of a blast wave was investigated using a 4-m-tall protective blast wall. Finally a large-scale hydrogen jet experiment was performed in which 27 kg of hydrogen was released vertically into the open atmosphere in a period of about 30 seconds. The hydrogen plume spontaneously ignited early in the release.

This paper shows the experimental results and findings of field explosion tests conducted to obtain fundamental data concerning the explosion of hydrogen-air mixtures. A tent covered with thin plastic sheets was filled with hydrogen/air mixed gas and subsequently ignited by an electric-spark or explosives to induce deflagration and/or detonation. Several experiments with different concentrations and/or volumes of mixture were carried out. The static overpressure of blast waves was measured using piezoelectric pressure sensors. The recorded data show that the shape of the pressure-time histories of the resulting blast waves depends on the difference in the ignition method used. The pictures of the explosion phenomenon (deflagration and/or detonation) were taken by high-speed cameras.