Japan
Energy-efficient Conversion of Microalgae to Hydrogen and Power
Jun 2017
Publication
An integrated system for H2 production from microalgae and its storage is proposed employing enhanced process integration technology (EPI). EPI consists of two core technologies i.e. exergy recovery and process integration. The proposed system includes a supercritical water gasification H2 separation hydrogenation and combined cycle. Microalga Chlorella vulgaris is used as a material for evaluation. The produced syngas is separated to produce highly pure H2. Furthermore to store the produced H2 liquid organic H2 carrier of toluene-and-methylcyclohexane cycle is adopted. The remaining gas is used as fuel for combustion in combined cycle to generate electricity. The effects of fluidization velocity and gasification pressure to energy efficiency are evaluated. From process modelling and calculation it is shown that high total energy efficiency about 60% can be achieved. In addition about 40% of electricity generation efficiency can be realized.
Numerical investigation of hydrogen leakage from a high pressure tank and pipeline
Sep 2017
Publication
We numerically investigated high-pressure hydrogen leakage from facilities in storage and transportation phases. In storage phase assuming a tank placed in a hydrogen station we examined unsteady diffusion distance up to 100 ms after leakage. A series of simulations led us to develop an equation of unsteady hydrogen diffusion distance as a function of mass flow rate leakage opening diameter and tank pressure. These results helped us develop a safety standard for unsteady hydrogen diffusion. In transportation phase we simulated (in three dimensions) the dominant factor of steady mass flow rate from a square opening of a rectangular pipeline and the pressure distribution in the pipeline after leakage. The mass flow rate was smaller than the maximum mass flow rate and the pressure distribution converged to a steady state that was 16% higher than the pressure after the passage of expansion waves in a shock tube model. We introduced a theoretical model by dividing the flow with the leakage opening into two phases of the unsteady expansion waves’ propagation and acceleration. The simulation results showed good agreement with the modeling equation when the shrink coefficient was set to 0.8. When the leakage opening was rectangular the simulation results again showed good agreement with the modelling equation suggesting that our simulated results are independent of the leakage opening shape.
Dynamic Crush Test on Hydrogen Pressurized Cylinder
Sep 2005
Publication
It is necessary to investigate cylinder crush behavior for improvement of fuel cell vehicle crash safety. However there have been few crushing behaviour investigations of high pressurized cylinders subjected to external force. We conducted a compression test of pressurized cylinders impacted by external force. We also investigated the cylinder strength and crushing behaviour of the cylinder. The following results were obtained.
- The crush force of high pressurized cylinders is different from the direction of external force. The lateral crush force of high pressurized cylinders is larger than the external axial crush force.
- Tensile stress occurs in the boundary area between the cylinder dome and central portion when the pressurized cylinder is subjected to axial compression force and the cylinder is destroyed.
- However the high pressurized cylinders tested had a high crush force which exceeded the assumed range of vehicle crash test procedures
Exchange Current Density of Reversible Solid Oxide Cell Electrodes
Mar 2022
Publication
Reversible solid oxide cells (r-SOCs) can be operated in either solid oxide fuel cell or solid oxide electrolysis cell mode. They are expected to become important in the support of renewable energy due to their high efficiency for both power generation and hydrogen generation. The exchange current density is one of the most important parameters in the quantification of electrode performance in solid oxide cells. In this study four different fuel electrodes and two different air electrodes are fabricated using different materials and the microstructures are compared. The temperature fuel humidification and oxygen concentration at the air electrode are varied to obtain the apparent exchange current density for the different electrode materials. In contrast to ruthenium-and-gadolinia-doped ceria (Rh-GDC) as well as nickel-and-gadolinia-doped ceria (Ni-GDC) electrodes significant differences in the apparent exchange current density were observed between electrolysis and fuel cell modes for the nickel-scandia-stabilized zirconia (Ni-ScSZ) cermet. Variation of gas concentration revealed that surface adsorption sites were almost completely vacant for all these electrodes. The apparent exchange current densities obtained in this study are useful as a parameter for simulation of the internal properties of r-SOCs.
Development of High-pressure Hydrogen Gas Barrier Materials
Oct 2015
Publication
We prepared several gas barrier resins based on amorphous PVA derivative that has the T1C (13C spin-lattice relaxation time) of a long time component in amorphous phase. We confirmed it was important to control state in amorphous phase of gas barrier resin in order to achieve both moldability and good gas barrier property. Polymer alloy was designed to improve flexibility. Polymer alloy made of amorphous PVA and elastomer resin showed good hydrogen resistance. Even after its polymer alloy were repeatedly exposed to 70MPa hydrogen gas the influence on higher-order structure in amorphous phase was in negligible level.
Hydrogen Technologies and Developments in Japan
Jan 2019
Publication
The successful development of hydrogen-energy technologies has several advantages and benefits. Hydrogen energy development could prevent global warming as well as ensure energy security for countries without adequate energy resources. The successful development of hydrogen would provide energy for transportation and electric power. It is a unique energy carrier as it can be produced from various energy sources such as wind fossil fuels and biomass and when it is combusted it emits no CO2 emissions. The other advantage is the wide distribution of resources globally that can be used to produce hydrogen. In Japan the Ministry of Economy Trade and Industry (METI) published a ‘Strategic Roadmap for Hydrogen and Fuel Cells’ in 2014 with a revised update published in March 2016. The goal of the roadmap is to achieve a hydrogen society. The roadmap aims to resolve technical problems and secure economic efficiency. The roadmap has been organized into the following three phases: Phase 1—Installation of fuel cells; Phase 2—Hydrogen power plant/mass supply chain; Phase 3—CO2- free hydrogen. This paper reports on the current status of fuel cells and fuel-cell vehicles in Japan and gives a description and status of the R&D programmes along with the results of global energy model study towards 2050.
Heuristic Design of Advanced Martensitic Steels That Are Highly Resistant to Hydrogen Embrittlement by ε-Carbide
Feb 2021
Publication
Many advanced steels are based on tempered martensitic microstructures. Their mechanical strength is characterized by fine sub-grain structures with a high density of free dislocations and metallic carbides and/or nitrides. However the strength for practical use has been limited mostly to below 1400 MPa owing to delayed fractures that are caused by hydrogen. A literature survey suggests that ε-carbide in the tempered martensite is effective for strengthening. A preliminary experimental survey of the hydrogen absorption and hydrogen embrittlement of a tempered martensitic steel with ε-carbide precipitates suggested that the proper use of carbides in steels can promote a high resistance to hydrogen embrittlement. Based on the surveys martensitic steels that are highly resistant to hydrogen embrittlement and that have high strength and toughness are proposed. The heuristic design of the steels includes alloying elements necessary to stabilize the ε-carbide and procedures to introduce inoculants for the controlled nucleation of ε-carbide.
A field explosion test of hydrogen-air mixtures
Sep 2005
Publication
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.
Hazid for CO2-free Hydrogen Supply Chain Feed (Front End Engineering Design)
Oct 2015
Publication
We at Kawasaki have proposed a “CO2 free H2 chain” using the abundant brown coal of Australia as a hydrogen source. We developed the basic design package and finished the Front End Engineering Design (FEED) in 2014. There are not only the hazards of the processing plant system but also the characteristic hazards of a hydrogen plant system. We considered and carried out Hazard Identification (HAZID) as the most appropriate approach for safety design in this stage. This paper describes the safety design and HAZID which we practiced for the CO2-Free Hydrogen Supply Chain FEED.
Security Risk Analysis of a Hydrogen Fueling Station with an On-site Hydrogen Production System Involving Methylcyclohexane
Sep 2017
Publication
Although many studies have looked at safety issues relating to hydrogen fuelling stations few studies have analyzed the security risks such as deliberate attack of the station by threats such as terrorists and disgruntled employees. The purpose of this study is to analyze security risks for a hydrogen fuelling station with an on-site production of hydrogen from methylcyclohexane. We qualitatively conducted a security risk analysis using American Petroleum Institute Standard 780 as a reference for the analysis. The analysis identified 93 scenarios including pool fires. We quantitatively simulated a pool fire scenario unique to the station to analyze attack consequences. Based on the analysis and the simulation we recommend countermeasures to prevent and mitigate deliberate attacks.
Characteristics of Hydrogen Leakage Sound from a Fuel-cell Vehicle by Hearing
Oct 2015
Publication
Fuel-cell vehicle run on hydrogen is known that it has better energy efficiency than existing gasoline cars. The vehicles are designed so that hydrogen leaks from the tank are stopped automatically upon detection of hydrogen leakage or detection of impact in a collision. However we investigated the characteristics of hydrogen leakage sound from a hydrogen-leaking vehicle and the threshold of discrimination of hydrogen leakage from noise at a crossing with much traffic to examine a method to rescue people safely depending on the sense of hearing in the event of a continuous hydrogen leak. Here in the discrimination threshold test we conducted the test by using helium which is alternative gas of hydrogen leakage sound. We clarified that hydrogen leakage sound from vehicles has directivity height dependence and distance dependence. Furthermore we confirmed the threshold flow rate for distinguishing hydrogen gas when hydrogen leakage is heard at a distance of 5–10 m from the center of the hydrogen leaking vehicle in a 74 dB traffic noise environment.
An Experimental Study on Mechanism of Self-ignition of High-pressure Hydrogen
Oct 2015
Publication
In the present study the self-ignition of high-pressure hydrogen released in atmospheric air through a diaphragm is visualized under various test conditions. The experimental results indicate that the hydrogen that jets through the rupturing diaphragm is mixed with the heated air near the tube wall. The self-ignition event originated from this mixing. The self-ignition was strongly dependent on the strength of an incident shock wave generated at the diaphragm rupture. As a result a cylindrical flame that formed after the self-ignition shows a tendency to become longer as it propagates in the downstream direction. The head velocities of the hydrogen-air mixture and the cylindrical flame are consistent with that of a contact surface calculated from the measured shock speed. A modified self-ignition mechanism is proposed based on the experimental observations.
Update on Regulation Review for HRS Construction and Operations in Japan
Oct 2015
Publication
In 2005 the Japanese High-pressure Gas Safety Act the Fire Service Act and the Building Standards Act were revised to establish the requirements for 35 MPa hydrogen stations. And in 2012-2014 revisions were made to the High-pressure Gas Safety Act and the Fire Service Act to provide the regulatory requirements for 70 MPa hydrogen stations. We conducted a study on materials that may contribute to prepare technical standards concerning the major 4 items 12 additional items and 13 new items which may affect the costs from the point of view of promoting the hydrogen infrastructure.
Fundamental Safety Testing and Analysis of Solid State Hydrogen Storage Materials and Systems
Sep 2007
Publication
Hydrogen is seen as the future automobile energy storage media due to its inherent cleanliness upon oxidation and its ready utilization in fuel cell applications. Its physical storage in light weight low volume systems is a key technical requirement. In searching for ever higher gravimetric and volumetric density hydrogen storage materials and systems it is inevitable that higher energy density materials will be studied and used. To make safe and commercially acceptable systems it is important to understand quantitatively the risks involved in using and handling these materials and to develop appropriate risk mitigation strategies to handle unforeseen accidental events. To evaluate these materials and systems an IPHE sanctioned program was initiated in 2006 partnering laboratories from Europe North America and Japan. The objective of this international program is to understanding the physical risks involved in synthesis handling and utilization of solid state hydrogen storage materials and to develop methods to mitigate these risks. This understanding will support ultimate acceptance of commercially high density hydrogen storage system designs. An overview of the approaches to be taken to achieve this objective will be given. Initial experimental results will be presented on environmental exposure of NaAlH4 a candidate high density hydrogen storage compound. The tests to be shown are based on United Nations recommendations for the transport of hazardous materials and include air and water exposure of the hydride at three hydrogen charge levels in various physical configurations. Additional tests developed by the American Society for Testing and Materials were used to quantify the dust cloud ignition characteristics of this material which may result from accidental high energy impacts and system breach. Results of these tests are shown along with necessary risk mitigation techniques used in the synthesis and fabrication of a prototype hydrogen storage system.
Risk Identification for the Introduction of Advanced Science and Technology: A Case Study of a Hydrogen Energy System for Smooth Social Implementation
May 2020
Publication
A method of risk identification is developed by comparing existing and advanced technologies from the viewpoint of comprehensive social risk. First to analyze these values from a multifaceted perspective we constructed a questionnaire based on 24 individual values and 26 infrastructural values determined in a previous study. Seven engineering experts and six social science experts were then asked to complete the questionnaire to compare and analyze a hydrogen energy system (HES) and a gasoline energy system (GES). Finally the responses were weighted using the analytic hierarchy process. Three important points were identified and focused upon: the distinct disadvantages of the HES compared to the GES judgments that were divided between experts in the engineering and social sciences fields and judgments that were divided among experts in the same field. These are important risks that should be evaluated when making decisions related to the implementation of advanced science and technology.
Assessing Uncertainties of Life-Cycle CO2 Emissions Using Hydrogen Energy for Power Generation
Oct 2021
Publication
Hydrogen and its energy carriers such as liquid hydrogen (LH2) methylcyclohexane (MCH) and ammonia (NH3) are essential components of low-carbon energy systems. To utilize hydrogen energy the complete environmental merits of its supply chain should be evaluated. To understand the expected environmental benefit under the uncertainty of hydrogen technology development we conducted life-cycle inventory analysis and calculated CO2 emissions and their uncertainties attributed to the entire supply chain of hydrogen and NH3 power generation (co-firing and mono-firing) in Japan. Hydrogen was assumed to be produced from overseas renewable energy sources with LH2/MCH as the carrier and NH3 from natural gas or renewable energy sources. The Japanese life-cycle inventory database was used to calculate emissions. Monte Carlo simulations were performed to evaluate emission uncertainty and mitigation factors using hydrogen energy. For LH2 CO2 emission uncertainty during hydrogen liquefaction can be reduced by using low-carbon fuel. For MCH CO2 emissions were not significantly affected by power consumption of overseas processes; however it can be reduced by implementing low-carbon fuel and waste-heat utilization during MCH dehydrogenation. Low-carbon NH3 production processes significantly affected power generation whereas carbon capture and storage during NH3 production showed the greatest reduction in CO2 emission. In conclusion reducing CO2 emissions during the production of hydrogen and NH3 is key to realize low-carbon hydrogen energy systems.
A Study of Decrease Burst Strength on Compressed-hydrogen Containers by Drop Test
Sep 2019
Publication
We investigate an appropriate initial burst pressure of compressed hydrogen containers that correlates with a residual burst pressure requirement at the end of life (EOL) and report an influence of hydraulic sequential tests on residual burst pressure. Results indicate that a container damage caused by a drop test during hydraulic sequential tests has a large influence on burst pressure. The container damage induced through hydraulic sequential tests is investigated using non-destructive evaluations to clarify a strength decreasing mechanism. An ultrasonic flaw detection analysis is conducted before and after the drop test and indicated that the damage occurred at the cylindrical and dome parts of the container after the drop test. An X-ray computed tomography imaging identifies a delamination inside laminated structure made of carbon fiber reinforced plastics (CFRP) layer with some degree of delamination reaching the end boss of the container. Results suggest that a load profile fluctuates in the CFRP layer at the dome part and that a burst strength of the dome part decreases. Therefore an observed decreasing in drop damage at the dome part can be used to prevent a degradation of EOL container burst strength.
Evaluating Uncertainty in Accident Rate Estimation at Hydrogen Refueling Station Using Time Correlation Model
Nov 2018
Publication
Hydrogen as a future energy carrier is receiving a significant amount of attention in Japan. From the viewpoint of safety risk evaluation is required in order to increase the number of hydrogen refuelling stations (HRSs) implemented in Japan. Collecting data about accidents in the past will provide a hint to understand the trend in the possibility of accidents occurrence by identifying its operation time However in new technology; accident rate estimation can have a high degree of uncertainty due to absence of major accident direct data in the late operational period. The uncertainty in the estimation is proportional to the data unavailability which increases over long operation period due to decrease in number of stations. In this paper a suitable time correlation model is adopted in the estimation to reflect lack (due to the limited operation period of HRS) or abundance of accident data which is not well supported by conventional approaches. The model adopted in this paper shows that the uncertainty in the estimation increases when the operation time is long owing to the decreasing data.
Rechargeable Proton Exchange Membrane Fuel Cell Containing an Intrinsic Hydrogen Storage Polymer
Oct 2020
Publication
Proton exchange membrane fuel cells (PEMFCs) are promising clean energy conversion devices in residential transportation and portable applications. Currently a high-pressure tank is the state-of-the-art mode of hydrogen storage; however the energy cost safety and portability (or volumetric hydrogen storage capacity) presents a major barrier to the widespread dissemination of PEMFCs. Here we show an ‘all-polymer type’ rechargeable PEMFC (RCFC) that contains a hydrogen-storable polymer (HSP) which is a solid-state organic hydride as the hydrogen storage media. Use of a gas impermeable SPP-QP (a polyphenylenebased PEM) enhances the operable time reaching up to ca. 10.2 s mgHSP −1 which is more than a factor of two longer than that (3.90 s mgHSP −1) for a Nafion NRE-212 membrane cell. The RCFCs are cycleable at least up to 50 cycles. The features of this RCFC system including safety ease of handling and light weight suggest applications in mobile light-weight hydrogen-based energy devices.
Performance Tests of Catalysts for the Safe Conversion of Hydrogen Inside the Nuclear Waste Containers in Fukushima Daiichi
Sep 2019
Publication
The safe decommissioning as well as decontamination of the radioactive waste resulting from the nuclear accident in Fukushima Daiichi represents a huge task for the next decade. At present research and development on long-term safe storage containers has become an urgent task with international cooperation in Japan. One challenge is the generation of hydrogen and oxygen in significant amounts by means of radiolysis inside the containers as the nuclear waste contains a large portion of sea water. The generation of radiolysis gases may lead to a significant pressure build-up inside the containers and to the formation of flammable gases with the risk of ignition and the loss of integrity.
In the framework of the project “R&D on technology for reducing concentration of flammable gases generated in long-term waste storage containers” funded by the Japanese Ministry of Education Culture Sports Science and Technology of Japan (MEXT) the potential application of catalytic recombiner devices inside the storage containers is investigated. In this context a suitable catalyst based on the so-called intelligent automotive catalyst for use in a recombiner is under consideration. The catalyst is originally developed and mass-produced for automotive exhaust gas purification and is characterized by having a self-healing function of precious metals (Pd Pt and Rh) dissolved as a solid solution in the perovskite type oxides. The basic features of this catalyst have been tested in an experimental program. The test series in the REKO-4 facility has revealed the basic characteristics of the catalyst required for designing the recombiner system.
In the framework of the project “R&D on technology for reducing concentration of flammable gases generated in long-term waste storage containers” funded by the Japanese Ministry of Education Culture Sports Science and Technology of Japan (MEXT) the potential application of catalytic recombiner devices inside the storage containers is investigated. In this context a suitable catalyst based on the so-called intelligent automotive catalyst for use in a recombiner is under consideration. The catalyst is originally developed and mass-produced for automotive exhaust gas purification and is characterized by having a self-healing function of precious metals (Pd Pt and Rh) dissolved as a solid solution in the perovskite type oxides. The basic features of this catalyst have been tested in an experimental program. The test series in the REKO-4 facility has revealed the basic characteristics of the catalyst required for designing the recombiner system.
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