Publications

Most studies on blast waves generated by gas explosions have focused on gas explosions occurring in open spaces. However accidental gas explosions often occur in confined spaces and the blast wave generates from a bursting vessel as a result of an increase in pressure caused by the gas explosion. In this study blast waves from bursting plastic vessels in which gas explosions occurred are investigated. The flammable mixtures used in the experiments were hydrogen-air mixtures at several equivalence ratios and a stoichiometric methane-air mixture. The overpressures of the blast waves were generated by venting high-pressure gas in the enclosure and volumetric expansion with a combustion reaction. The measured intensities of the blast waves were greater than the calculated values resulting from high-pressure bursting without a combustion reaction. The intensities of the blast waves resulting from the explosions of hydrogen-air mixtures were much greater than those of the methane-air mixture.

Proper management of hydrogen gas is very important for safety of nuclear power plants. Hydrogen removal system by hydrogen recombination reaction (water formation reaction) on a catalyst is one of the candidates for avoiding hydrogen explosion. We have observed in situ and time-resolved structure change of platinum metal nanoparticle catalyst during hydrogen recombination reaction by using simultaneous measurement of temperature-programmed reaction and X-ray absorption fine structure (TPR-XAFS). A poisoning effect by carbon monoxide on catalytic activity was focused. It was found that the start of hydrogen recombination reaction is closely connected with the occurrence of the decomposition of adsorbed carbon monoxide molecules and creation of surface oxide layer on platinum metal nanoparticles.

R&D projects for establishing hydrogen supply chain have already been started in Japan in collaboration among the industry government and universities. One of the important subjects of the project is development of liquefied hydrogen tankers i.e. ships carrying liquefied hydrogen in bulk. In general basic safety requirements should be determined to design ships. However the existing regulations do not specify the requirements for hydrogen tankers while requirements for ships carrying many kinds of liquefied gases are specified in “International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk” (IGC Code) issued by the International Maritime Organization i.e. a special organization under the United Nations. Therefore the basic safety requirements for hydrogen tankers should be developed. We conducted bibliographic survey on the IGC Code ISO/TR 15916:2004 “Basic considerations for the safety of hydrogen systems” and so on; in order to provide safety requirements taking into account the properties of liquid and gaseous hydrogen. In this paper we provide safety requirements for liquefied hydrogen tankers as the basis for further consideration by relevant governments.

Hydrogen fuels are being deployed around the world as an alternative to traditional petrol and battery technologies. As with all fuels regulations codes and standards are a necessary component of the safe deployment of hydrogen technologies. There has been a focused effort in the international hydrogen community to develop codes and standards based on strong scientific principles to accommodate the relatively rapid deployment of hydrogen-energy systems. The need for science-based codes and standards has revealed the need to advance our scientific understanding of hydrogen in engineering environments. This brief review describes research and development activities with emphasis on scientific advances that have aided the advancement of hydrogen regulations codes and standards for hydrogen technologies in four key areas: (1) the physics of high-pressure hydrogen releases (called hydrogen behaviour); (2) quantitative risk assessment; (3) hydrogen compatibility of materials; and (4) hydrogen fuel quality.

Hydrogen storage is a key link in hydrogen economy where solid-state hydrogen storage is considered as the most promising approach because it can meet the requirement of high density and safety. Thereinto magnesium-based materials (MgH2) are currently deemed as an attractive candidate due to the potentially high hydrogen storage density (7.6 wt%) however the stable thermodynamics and slow kinetics limit the practical application. In this study we design a ternary transition metal sulfide FeNi2S4 with a hollow balloon structure as a catalyst of MgH2 to address the above issues by constructing a MgH2/Mg2NiH4−MgS/Fe system. Notably the dehydrogenation/hydrogenation of MgH2 has been significantly improved due to the synergistic catalysis of active species of Mg2Ni/Mg2NiH4 MgS and Fe originated from the MgH2-FeNi2S4 composite. The hydrogen absorption capacity of the MgH2-FeNi2S4 composite reaches to 4.02 wt% at 373 K for 1 h a sharp contrast to the milled-MgH2 (0.67 wt%). In terms of dehydrogenation process the initial dehydrogenation temperature of the composite is 80 K lower than that of the milled-MgH2 and the dehydrogenation activation energy decreases by 95.7 kJ mol–1 compared with the milled-MgH2 (161.2 kJ mol–1). This method provides a new strategy for improving the dehydrogenation/hydrogenation performance of the MgH2 material.

The accidents that hydrogen ignites without ignition source are reported in several cases which phenomenon is called “auto-ignition.” Since the use of high pressure hydrogen will be increased for the hydrogen society it must be necessary to understand auto-ignition mechanism in detail to prevent such accidents. In this study we performed three-dimensional numerical simulations to clarify the autoignition mechanism using the three-dimensional compressive Navier-Stokes equations and a hydrogen chemical reaction model including nine species and twenty elementary reactions. We focus on the effects of the shape of the cross-section on the hydrogen auto-ignition mechanism applying for a rectangular and cylindrical tube. The results obtained indicate that the Richtmyer-Meshukov instability involves these auto-ignition.

Polymer electrolyte membrane (PEM) water electrolysis is an efficient and environmental friendly method that can be used for the production of molecular hydrogen of electrolytic grade using zero-carbon power sources such as renewable and nuclear. However market applications are asking for cost reduction and performances improvement. This can be achieved by increasing operating current density and lifetime of operation. Concerning performance safety reliability and durability issues the membrane-electrode assembly (MEA) is the weakest cell component. Most performance losses and most accidents occurring during PEM water electrolysis are usually due to the MEA. The purpose of this communication is to report on some specific degradation mechanisms that have been identified as a potential source of performance loss and membrane failure. An accelerated degradation test has been performed on a MEA by applying galvanostatic pulses. Platinum has been used as electrocatalyst at both anode and cathode in order to accelerate degradation rate by maintaining higher cell voltage and higher anodic potential that otherwise would have occurred if conventional Ir/IrOx catalysts had been used. Experimental evidence of degradation mechanisms have been obtained by post-mortem analysis of the MEA using microscopy and chemical analysis. Details of these degradation processes are presented and discussed.

Hydrogen impinging jets can be formed in the case of an accidental release indoors or outdoors. The CFD simulation of hydrogen impinging jets suffers from numerical errors resulting in a non-physical velocity and hydrogen concentration field with a butterfly like structure. In order to minimize the numerical errors and to avoid the butterfly effect high order schemes need to be used. The aim of this work is to give best practices guidelines for hydrogen impinging jet simulations. A number of different numerical schemes is evaluated. The number of cells which discretize the source is also examined.

Within the scope of the HyResponse project the development of a specialised training programme is currently underway. Utilizing an andragogy approach to teaching distance learning is mixed with classroom instructors-led activities while hands-on training on a full-scale simulator is coupled with an innovative virtual reality based experience. Although the course is dedicated mainly to first responders provision has been made to incorporate not only simple table-top and drill exercises but also full-scale training involving all functional emergency response organisations at multi-agency cooperation level. The developed curriculum includes basics of hydrogen safety first responders' procedures and incident management expectations

This paper describes work performed by a consortium led by the UK Health and Safety Laboratory(HSL)to identify the safe operating conditions for combined cycle power generating systems running on high hydrogen fuels. The work focuses on hydrogen and high hydrogen syngas and biogas waste-stream fuel mixtures which may prove hazardous in the event of a turbine or engine flame out resulting in a flammable fuel mixture entering the hot exhaust system and igniting. The paper describes the project presenting some initial results from this work including the development of large scale experimental facilities on the550 acre HSL site near Buxton Derbyshire UK. It describes the large scale experimental facility which utilises the exhaust gas from a Rolls-Royce Viper jet-engine (converted to run on butane) feeding into a 12 m long 0.60 m diameter instrumented tube at a pre-combustion velocity of 22 m/s. A variable geometry simulated heat exchanger with a 40 %2blockage ratio is present in the tube. Flammable mixtures injected into the tube close to the Viper outlet together with make-up oxygen are then ignited. Extensive optical ionisation temperature and pressure sensors are employed along the length of the tube to measure the pressures and flame speeds resulting from the combustion event. Some preliminary results from the test programme are discussed including deflagration to detonation transitions at high equivalence ratios.

A new method of hydrogen generation from water by irradiation with CW infrared laser diode of graphene scaffold immersed in solution is reported. Hydrogen production was extremely efficient upon admixing NaCl into water. The efficiency of hydrogen production increased exponentially with laser power. It was shown that hydrogen production was highly efficient when the intense white light emission induced by laser irradiation of graphene foam was occurring. The mechanism of laser-induced dissociation of water is discussed. It was found that hydrogen production was extremely high at about 80% and assisted by a small emission of O2 CO and CO2 gases.

Safety is of paramount importance in all facets of the research development demonstration and deployment work of the U.S. Department of Energy’s (DOE) Fuel Cell Technologies Program. The Safety Codes and Standards sub-program (SC&S) facilitates deployment and commercialization of fuel cell and hydrogen technologies by developing and disseminating information and knowledge resources for their safe use. A comprehensive safety management program utilizing the Hydrogen Safety Panel to raise safety consciousness at the project level and developing/disseminating a suite of safety knowledge resources is playing an integral role in DOE and SC&S efforts. This paper provides examples of accomplishments achieved while reaching a growing and diverse set of stakeholders involved in research development and demonstration; design and manufacturing; deployment and operations. The work of the Hydrogen Safety Panel highlights new knowledge and the insights gained through interaction with project teams. Various means of collaboration to enhance the value of the program’s safety knowledge tools and training resources are illustrated and the direction of future initiatives to reinforce the commitment to safety is discussed.

The Hydrogen and Fuel Cell (H2FC) European research infrastructure cyber-laboratory is a software suite containing ‘modelling’ and ‘engineering’ tools encompassing a wide range of H2FC processes and systems. One of the core aims of the H2FC Cyber-laboratory has been the creation of a state-of-the-art hydrogen CFD modelling toolbox. This paper describes the implementation and validation of this new CFD modelling toolbox in conjunction with a selection of the available ‘Safety’ engineering tools to analyse a high pressure hydrogen release and dispersion scenario. The experimental work used for this validation was undertaken by Shell and the Health and Safety Laboratory (UK). The overall goal of this work is to provide and make readily available a Cyber-laboratory that will be worth maintaining after the end of the H2FC project for the benefit of both the FCH scientific community and industry. This paper therefore highlights how the H2FC Cyber-laboratory which is offered as an open access platform can be used to replicate and analyse real-world scenarios using both numerical engineering tools and through the implementation of CFD modelling techniques.

Correct use of Computational Fluid Dynamics (CFD) tools is essential in order to have confidence in the results. A comprehensive set of Best Practice Guidelines (BPG) in numerical simulations for Fuel Cells and Hydrogen applications has been one of the main outputs of the SUSANA project. These BPG focus on the practical needs of engineers in consultancies and industry undertaking CFD simulations or evaluating CFD simulation results in support of hazard/risk assessments of hydrogen facilities as well as on the needs of regulatory authorities. This contribution presents a summary of the BPG document. All crucial aspects of numerical simulations are addressed such as selection of the physical models domain design meshing boundary conditions and selection of numerical parameters. BPG cover all hydrogen safety relative phenomena i.e. release and dispersion ignition jet fire deflagration and detonation. A series of CFD benchmarking exercises are also presented serving as examples of appropriate modelling strategies.

The recent growth of the net of hydrogen fuelling stations increases the demands to transport compressed hydrogen on road by battery vehicles or tube-trailers both in composite pressure vessels. As a transport regulation the ADR is applicable in Europe and adjoined regions and is used for national transport in the EU. This regulation provides requirements based on the behaviour of each individual pressure vessel regardless of the pressure of the transported hydrogen and relevant consequences resulting from generally possible worst case scenarios such as sudden rupture. In 2012 the BAM (German Federal Institute for Materials Research and Testing) introduced consequence-dependent requirements and established them in national transport requirements concerning the “UN service life checks” etc. to consider the transported volume and pressure of gases. This results in a requirement that becomes more restrictive as the product of pressure and volume increases. In the studies presented here the safety measures for hydrogen road transport are identified and reviewed through a number of safety measures from countries including Japan the USA and China. Subsequently the failure consequences of using trailer vehicles the related risk and the chance are evaluated. A benefit-related risk criterion is suggested to add to regulations and to be defined as a safety goal in standards for hydrogen transport vehicles and for mounted pressure vessels. Finally an idea is given for generating probabilistic safety data and for highly efficient evaluation without a significant increase of effort.

Passive auto-catalytic recombiners (PARs) have the potential to be used in the future for the removal of accidentally released hydrogen inside confined areas. PARs could be operated both as stand-alone or backup safety devices e.g. in case of active ventilation failure.

Recently computational fluid dynamics (CFD) simulations have been performed in order to demonstrate the principal performance of a PAR during a postulated hydrogen release inside a car garage. This fundamental study has now been extended towards a variation of several boundary conditions including PAR location hydrogen release scenario and active venting operation. The goal of this enhanced study is to investigate the sensitivity of the PAR operational behaviour for changing boundary conditions and to support the identification of a suitable PAR positioning strategy. For the simulation of PAR operation the in-house code REKO-DIREKT has been implemented in the CFD code ANSYS-CFX 15.

In a first step the vertical position of the PAR and the thermal boundary conditions of the garage walls have been modified. In a subsequent step different hydrogen release modes have been simulated which result either in a hydrogen-rich layer underneath the ceiling or in a homogeneous hydrogen distribution inside the garage. Furthermore the interaction of active venting and PAR operation has been investigated.

As a result of this parameter study the optimum PAR location was identified to be close underneath the garage ceiling. In case of active venting failure the PAR efficiently reduces the flammable gas volume (hydrogen concentration > 4 vol.%) for both stratified and homogeneous distribution. However the simulations indicate that the simultaneous operation of active venting and PAR may in some cases reduce the overall efficiency of hydrogen removal. Consequently a well-matched arrangement of both safety systems is required in order to optimize the overall efficiency. The presented CFD-based approach is an appropriate tool to support the assessment of the efficiency of PAR application for plant design and safety considerations with regard to the use of hydrogen in confined areas.

Commercial use of hydrogen on-board fuel cell vehicles necessitates the compression of hydrogen gas up to 700 bar raising unique safety challenges. Potential hazards to be addressed include jet fires from high-pressure hydrogen on-board storage. Previous studies investigated effects of jet fires that occur when pressure relief devices (PRDs) on hydrogen fuel cell vehicles activate. This investigation examines plane jets’ axis switching and flame length accounting for compressibility effects and turbulent combustion near the point of release. Comparison with experimental data and previous plane jet simulation results reveal that combustion process does not affect flow dynamics in compressible region of jet flow. Furthermore a theoretical design of a variable aperture pressure relief device is examined which would enable the blow-down time to be minimized while reducing deterministic separation distances is examined using Computational Fluid Dynamics (CFD) techniques. Design recommendations are suggested for a novel PRD design.

For massive utilization of hydrogen energy it is necessary to transport a large quantity of hydrogen by liquefied hydrogen carriers. However the current rule on ships carrying liquefied hydrogen in bulks do not address the maritime transport of liquefied hydrogen and the safety assessment of liquefied hydrogen carriage is thus very important. In the present study we spilled liquefied hydrogen and LNG (Liquefied Natural Gas) on the surface of various materials and compared the difference of their spread and dispersion. Liquefied hydrogen immediately dispersed upward compared to LNG. Furthermore we also measured the flammability limit of low temperature hydrogen gas. Its range at low temperature was narrower than the range at normal temperature.

A methodology for explosion and fire risk analyses in enclosed rooms is presented. The objectives of this analysis are to accurately predict the risks associated with hydrogen leaks in maritime applications and to use the approach to provide decision support regarding design and risk-prevention and risk mitigating measures. The methodology uses CFD tools and simpler consequence models for ventilation dispersion and explosion scenarios as well as updated frequency for leaks and ignition. Risk is then efficiently calculated with a Monte Carlo routine capturing the transient behavior of the leak. This makes it possible to efficiently obtain effects of sensitivities and design options maintaining safety and reducing costs.

The California Fuel Cell Partnership (CaFCP) is currently working with key stakeholders like the US Department of Energy (DOE) and National Fire Protection Association (NFPA) to develop a national template for educating and training first responders about hydrogen fuel cell-powered vehicles (FCV) and hydrogen fuelling infrastructure. Currently there are several existing programs that either have some related FCV/hydrogen material or have plans to incorporate this in the future. To create a robust national emergency responder (ER) program the strongest elements from these existing programs are considered for incorporation into the template. Working with the key stakeholders the national template will be evaluated on a regular basis to ensure accurate and up to date information and resources and effective teaching techniques for the emergency response community. This paper describes the evaluation process discusses elements of the template and reports on the steps and progress to implementation; all in the effort to effectively support the emergency response community as hydrogen infrastructure develops and FCVs are leased or sold.

This paper revisits the theoretical concepts of lock-in mechanisms to analyse transition processes in energy production and road transportation in the Nordic countries focussing on three technology platforms: advanced biofuels e-mobility and hydrogen and fuel cell electrical vehicles. The paper is based on a comparative analysis of case studies.<br/>The main lock-in mechanisms analysed are learning effects economies of scale economies of scope network externalities informational increasing returns technological interrelatedness collective action institutional learning effects and the differentiation of power.<br/>We show that very different path dependencies have been reinforced by the lock-in mechanisms. Hence the characteristics of existing regimes set the preconditions for the development of new transition pathways. The incumbent socio-technical regime is not just fossil-based but may also include mature niches specialised in the exploitation of renewable sources. This implies a need to distinguish between lock-in mechanisms favouring the old fossil-based regime well-established (mature) renewable energy niches or new pathways.

Risk assessment of hazardous material transport by road is critical in considering the spatial features of the transport route. However previous studies that focused on hydrogen transport were unable to reflect the spatial features in their risk assessments. Hence this study aims to assess the risk of hydrogen transport by road considering the spatial features of the transport route based on a geographic information system (GIS). This risk assessment method is conducted through a case study in Yokohama which is an advanced city for hydrogen economy in Japan. In our assessment the risk determined by multiplying the frequency of accidents with the consequence was estimated by road segments that constitute the entire transport route. The effects of the road structure and traffic volumes were reflected in the estimation of the frequency and consequence for each road segment. All estimations of frequency consequence and risk were conducted on a GIS compiled with the information regarding the road network and population. In the case study in Yokohama the route for the transport of compressed hydrogen was virtually set from the near-term perspectives. Based on the case study results the risks of the target transport route were assessed at an acceptable level under the previous risk criteria. The results indicated that the risks fluctuated according to the road segments. This implies that the spatial features of the transport route significantly affect the corresponding risks. This finding corroborates the importance of considering spatial features in the risk assessment of hydrogen transport by road. Furthermore the discussion of this importance leads to the capability of introducing hydrogen energy careers with high transport efficiency and transport routing to avoid high risk road segments as risk countermeasures.

This paper describes a CFD study of a scenario involving the vertical downward release of hydrogen from a thermally-activated pressure relief device (TPRD) under a fuel cell car. The volumetric source model is applied to simulate hydrogen release dynamics during the tank blowdown process. Simulations are conducted for both unignited and ignited releases from onboard storage at 35 MPa and 70 MPa with TPRD orifice 4.2 mm. Results show that after TPRD opening the hazards associated with the release of hydrogen lasts less than two minutes and the most hazardous timeframe occurs within ten seconds of the initiation of the release. The deterministic separation distances for unignited releases are longer than those for ignited releases indicating that the separation distances are dominated by delayed ignition events rather than immediate ignition events. The deterministic separation distances for both unignited and ignited hydrogen downward releases under the car are significantly shorter than those of free jets. To ensure the safety of people a deterministic separation distance of at least 10 m for 35 MPa releases is required. This distance should be increased to 12 m for the 70 MPa release case. To ensure that the concentration of hydrogen is always less than 4% at the location of the air intake of buildings the deterministic separation distance should be at least 11 m for 35 MPa releases and 13 m for 70 MPa releases.

This work is aimed at solving the problem of converting diesel power drives to diesel– hydrogen fuels which are more environmentally friendly and less expensive alternatives to diesel fuel. The method of increasing the energy efficiency of diesel fuels has been improved. The thermochemical essence of using methanol as an alternative fuel to increase energy efficiency based on the provisions of thermotechnics is considered. Alternative methanol fuel has been chosen as the initial product for the hydrogen conversion process and its energy value cost and temperature conditions have been taken into account. Calculations showed that the caloric effect from the combustion of the converted mixture of hydrogen H2 and carbon monoxide CO exceeds the effect from the combustion of the same amount of methanol fuel. Engine power and fuel energy were increased due to the thermochemical regeneration of engine exhaust gas heat. An experimental setup was created to study the operation of a converted diesel engine on diesel–hydrogen products. Experimental studies of power and environmental parameters of a diesel engine converted for diesel–hydrogen products were performed. The studies showed that the conversion of diesel engines to operate using diesel– hydrogen products is technically feasible. A reduction in energy consumption was accompanied by an improvement in the environmental performance of the diesel–hydrogen engine working together with a chemical methanol conversion thermoreactor. The formation of carbon monoxide occurred in the range of 52–62%; nitrogen oxides in the exhaust gases decreased by 53–60% according to the crankshaft speed and loading on the experimental engine. In addition soot emissions were reduced by 17% for the engine fueled with the diesel–hydrogen fuel. The conversion of diesel engines for diesel–hydrogen products is very profitable because the price of methanol is on average 10–20% of the cost of petroleum fuel.

The acoustic to the parametric instability has been studied for H2-air mixtures at normal conditions. Two approaches for the investigation of the problem have been considered. The simplified analytical model proposed by Bychkov was selected initially. Its range of applicability resulted to be very restricted and therefore numerical solutions of the problem were taken into account. The results obtained were used to study the existence of spontaneous transition from the acoustic to the parametric instability for different fuel concentrations. Finally the growth rate of the instabilities was numerically calculated for a set of typical mixtures for hydrogen safety.