Publications

The development and promulgation of codes and standards are essential to establish a market-receptive environment for commercial hydrogen-based products and systems. The focus of the U.S. Department of Energy (DOE) is to conduct the research and development (R&D) needed to strengthen the scientific basis for technical requirements incorporated in national and international standards codes and regulations. In the U.S. the DOE and its industry partners have formed a Codes and Standards Tech Team (CSTT) to help guide the R&D. The CSTT has adopted an R&D Roadmap to achieve a substantial and verified database of the properties and behaviour of hydrogen and the performance characteristics of emerging hydrogen technology applications sufficient to enable the development of effective codes and standards for these applications. However to develop a more structured approach to the R&D described above the CSTT conducted a workshop on Risk Assessment for Hydrogen Codes and Standards in March 2005. The purpose of the workshop was to attain a consensus among invited experts on the protocols and data needed to address the development of risk-informed standards codes and regulations for hydrogen used as an energy carrier by consumers. Participants at the workshop identified and assessed requirements methodologies and applicability of risk assessment (RA) tools to develop a framework to conduct RA activities to address for example hydrogen fuel distribution delivery on-site storage and dispensing and hydrogen vehicle servicing and parking. The CSTT was particularly interested in obtaining the advice of RA experts and representatives of standards and model code developing organizations and industry on how data generated by R&D can be turned into information that is suitable for hydrogen codes and standards development. The paper reports on the results of the workshop and the RA activities that the DOE’s program on hydrogen safety codes and standards will undertake. These RA activities will help structure a comprehensive R&D effort that the DOE and its industry partners are undertaking to obtain the data and conduct the analysis and testing needed to establish a scientific and technical basis for hydrogen standards codes and regulations.

Reliable and effective sensors for the accurate detection of hydrogen concentrations in air are essential for the safe operation of fuel cells hydrogen fuelled systems (e.g. vehicles) and hydrogen production distribution and storage facilities. The present paper describes the activity on-going at JRC for the establishment of a facility that can be used for testing and validating the performance of hydrogen sensors under a range of conditions representative of those to be encountered in service. Potential aspects to be investigated in relation to the sensors performances are the influence of temperature humidity and pressure (simulating variations in altitude) the sensitivity to target gas and the cross sensitivity to other gases/vapours the reaction and recovery time and the sensors’ lifetime. The facility set up at JRC for the execution of these tests is described including the program for its commissioning. The results of a preliminary test are presented and discussed as an example.

This paper presents an analysis of computational fluid dynamic models of compressed hydrogen gas leaks into the air under different conditions to determine the volume of the hydrogen/air mixture and the extents of the lower flammable limit. The necessary hole size was calculated to determine a reasonably expected hydrogen leak rate from a valve or a fitting of 5 and 20 cfm under 400 bars resulting in a 0.1 and 0.2 mm effective diameter hole respectively. The results were compared to calculated hypothetical volumes from IEC 60079-10 for the same mass flowrate and in most cases the CFD results produced significantly smaller hydrogen/air volumes than the IEC standard. Prescriptive electrical classification distances in existing standards for hydrogen and compressed natural gas were examined but they do not consider storage pressure and there appears to be no scientific basis for the distance determination. A proposed table of electrical classification distances incorporating hydrogen storage volume and pressure was produced based on the hydrogen LFL extents from a 0.2 mm diameter hole and the requirements of existing standards. The PHOENICS CFD software package was used to solve the continuity momentum and concentration equations with the appropriate boundary conditions buoyancy model and turbulence models. Numerical results on hydrogen concentration predictions were obtained in the real industrial environment typical for a hydrogen refuelling or energy station.<br/><br/>

Under government funded project: "Development for Safe Utilization and Infrastructure of Hydrogen" entrusted by New Energy and Industrial Technology Development Organization (NEDO) special material testing equipment with heavy walled pressure vessel under 45MPa gaseous hydrogen is facilitated. Tensile properties strain controlled low-cycle and high-cycle fatigue and fatigue crack growth tests on CrMo steel (SCM435 (JIS G 4105)) which will be applied for the storage gas cylinders in Japanese hydrogen fuel stations are investigated. The results of the tensile tests under 45MPa ultra high purity hydrogen gas (O2<1ppm) at room temperature shows that there are no difference in yield and maximum tensile strength with those tested in air. However the reduced ductilities with brittle fracture surface were observed which indicates the occurrence of hydrogen environment embrittlement. It was also found by tensile tests that the embrittling origin is not only caused by machined traces on surface but also by the non-metallic inclusions dispersed on surface. Further discussions on surface treatment effects will be presented. In low cycle fatigue tests considerable reductions in cycles to failure in 45MPa ultra high purity hydrogen gas were observed. However there are tendencies that the effect of hydrogen environment embrittlement becomes not so significant as the plastic strain range decreases. It was demonstrated that there was no effect of hydrogen on fatigue limit and this implies that CrMo gas cylinders can be operated in limited fatigue safe condition. Another series of hydrogen test results temperature effect fatigue crack growth rate delayed fracture test using wedge opening loaded specimens and fatigue test of CrMo gas cylinders under repeated internal pressure with artificial crack will be presented.

The aim of the presented article is to analyse the influence of synthesis gas composition on the power economic and internal parameters of an atmospheric two-cylinder spark-ignition internal combustion engine (displacement of 686 cm3 ) designed for a micro-cogeneration unit. Synthesis gases produced mainly from waste contain combustible components as their basic material (methane hydrogen and carbon monoxide) as well as inert gases (carbon dioxide and nitrogen). A total of twelve synthesis gases were analysed that fall into the category of medium-energy gases with lower heating value in the range from 8 to 12 MJ/kg. All of the resulting parameters from the operation of the combustion engine powered by synthesis gases were compared with the reference fuel methane. The results show a decrease in the performance parameters for all operating loads and an increase in hourly fuel consumption. Specifically for the operating speed of the micro-cogeneration unit (1500 L/min) the decrease in power parameters was in the range of 7.1–23.5%; however the increase in hourly fuel consumption was higher by 270% to 420%. The decrease in effective efficiency ranged from 0.4 to 4.6% which in percentage terms represented a decrease from 1.3% to 14.5%. The process of fuel combustion was most strongly influenced by the proportion of hydrogen and inert gases in the mixture. It can be concluded that setting up the synthesis gas production in the waste gasification process in order to achieve optimum performance and economic parameters of the combustion engine for a micro cogeneration unit has an influential role and is of crucial importance.

The FLACS CFD-tool for consequence prediction has been developed continuously since 1980. The initial focus was explosion safety on offshore oil platforms in recent years the tool is also applied to study dispersion hydrogen safety dust explosions and more. A development project sponsored by Norsk Hydro Statoil and Ishikawajima Heavy Industries (IHI) was carried out to improve the modelling and validation of hydrogen dispersion and explosions. In this project GexCon carried out 200 small-scale experiments on dispersion and explosion with H₂ and mixtures with H₂ and CO or N₂. Experiments with varying confinement congestion concentration and ignition location were performed. Since the main purpose of the tests was to produce good validation data all tests were simulated with the FLACS-HYDROGEN tool. The simulations confirmed the ability to predict explosions effects for the wide range of scenarios studied. A few examples of comparisons will be shown. To build confidence in a consequence prediction model it is important that the scales used for validation are as close as possible to reality. Since the hazard to people and facilities and the risk will generally increase with scale validation against large-scale experiments is important. In the 1980s a series of large-scale explosion experiments with H2 was carried out in the Sandia FLAME facility and sponsored by the US Nuclear Regulatory Commission. The FLAME facility is a 30.5m x 1.83m x 2.44m channel tests were performed with H2 concentrations from 7% to 30% with varying degree of top venting (0% 13% and 50%) and congestion (with or without baffles blocking 33% of the channel cross-section). A wide range of flame speeds and overpressures were observed. Comparisons are made between FLACS simulations and FLAME tests. The main conclusion from this validation study is that the precision when predicting H2 explosion consequences with FLACS has been improved to a very acceptable level

Air pollution and traffic congestion are two of the major issues affecting public authorities policy makers and citizens not only in Italy and European Union but worldwide; this is nowadays witnessed by always more frequent limitations to the traffic in most of Italian cities for instance. Hydrogen use in automotive appears to offer a viable solution in medium-long term; this new perspective involves the need to carry out adequate infrastructures for distribution and refuelling and consequently the need to improve knowledge on hydrogen technologies from a safety point of view. In the present work possible different configurations for gaseous hydrogen refuelling station has been compared: “stand-alone” and “multi-fuel”. These two alternative scenarios has been taken into consideration each of one with specific hypotheses: “stand-alone” configuration based on the hypothesis of a potential model consisting of a hydrogen refuelling station composed by on-site hydrogen production via electrolysis a trailer of compressed gas for back-up compressor unit intermediate storage unit and dispenser. In this model it is assumed that no other refuelling equipment and/or dispenser of traditional fuel is present in the same site. “multi-fuel” configuration where it is assumed that the same components for hydrogen refuelling station are placed in the same site beside one or more refuelling equipment and/or dispenser of traditional fuel. Comparisons have been carried out from the point of view of specific risk assessment which have been conducted on both the two alternative scenarios.

To provide more practical data for safety assessments a systematic study of explosion and combustion processes which can take place in mixtures produced by jet releases in realistic environmental conditions is required. The presented work is aimed to make step forward in this direction binding three inter-connected tasks: (i) study of horizontal and vertical jets (ii) study of the burnable clouds formed by jets in different geometry configurations and (iii) examination of combustion and explosion processes initiated in such mixtures. Test matrix for the jet experiments included variation of the release pressure and nozzle diameter with the aim to study details of the resulting hydrogen concentration and velocity profiles depending on the release conditions. In this study the following parameters were varied: mass flow rate jet nozzle diameter (to alter gas speed) and geometry of the hood located on top of the jet. The carried out experiments provided data on detailed structure for under-expanded horizontal and buoyant vertical jets and data on pressure loads resulted from deflagration of various mixtures formed by jet releases. The data on pressures waves generated in the conditions under consideration provides conservative estimation of pressure loads for realistic leaks.

Several today’s and future applications in energy technology bear the risk of the formation of flammable hydrogen/air mixtures either due to the direct use of hydrogen or due to hydrogen appearing as a by-product. If there’s the possibility of hydrogen being released accidentally into closed areas countermeasures have to be implemented in order to mitigate the threat of an explosion. In the field of nuclear safety passive auto-catalytic recombiners (PAR) are well-known devices for reducing the risk of a hydrogen detonation in a nuclear power plant in the course of a severe accident. Hydrogen and oxygen react on catalyst materials like platinum or palladium already far below conventional flammability limits. The most important concern with regard to the utilization of hydrogen  recombiners is the adequate removal of the reaction heat. Already low hydrogen concentrations may increase the system temperature beyond the self-ignition limit of hydrogen/air mixtures and may lead to an unintended ignition on hot parts of the PAR.<br/>Starting from the nuclear application since several years IEF-6 and LRST perform joint research in the field of passive auto-catalytic recombiners including experimental studies modelling and development of new design concepts. Recently approaches on specifically designed catalysts and on passive cooling devices have been successfully tested. In a design study both approaches are combined in order to provide means for efficient and safe removal of hydrogen. The paper summarizes results achieved so far and possible designs for future applications.

To make “Hydrogen vehicles and refuelling station systems” fit for public use research on hydrogen safety and designing mitigative measures are significant. For compact storage it is planned to store under high pressure (40MPa) at the refuelling stations so that the safety for the handling of high-pressurized hydrogen is essential. This paper describes the experimental investigation on the hypothetical dispersion and explosion of high-pressurized hydrogen gas which leaks through a large scale break in piping and blows down to atmosphere. At first we investigated time history of distribution of gas concentration in order to comprehend the behaviour of the dispersion of high-pressurized hydrogen gas before explosion experiments. The explosion experiments were carried out with changing the time of ignition after the start of dispersion. Hydrogen gas with the initial pressure of 40MPa was released through a nozzle of 10mm diameter. Through these experiments it was clarified that the explosion power depends not only on the concentration and volume of hydrogen/air pre-mixture but also on the turbulence characteristics before ignition. To clarify the explosion mechanism the numerical computer simulation about the same experimental conditions was performed. The initial conditions such as hydrogen distribution and turbulent characteristics were given by the results of the atmospheric diffusion simulation. By the verification of these experiments the results of CFD were fully improved.

In the frame of a sustainable development investigations dealing with massive Hydrogen production by means of nuclear heating are carried out at CEA. For nuclear safety thermodynamic efficiency and waste minimization purposes the technological solution privileged is the coupling of a gas cooled Very High Temperature Reactor (VHTR) with a plant producing Hydrogen from an Iodine/Sulfur (I/S) thermochemical cycle. Each of the aforementioned facilities presents different risks resulting from the operation of a nuclear reactor (VHTR) and from a chemical plant including Hydrogen other flammable and/or explosible substances as well as toxic ones. Due to these various risks the safety approach is an important concern. Therefore this paper deals with the preliminary CEA investigations on the safety issues devoted to the whole plant focusing on the safety questions related to the coupling between the nuclear reactor and the Hydrogen production facility. Actually the H2 production process and the energy distribution network between the plants are currently at a preliminary design stage. A general safety approach is proposed based on a Defence In Depth (DID) principle permitting to analyze all the system configurations successively in normal incidental and accidental expected operating conditions. More precisely the dynamic answer of an installation to a perturbation affecting the other one during the previous conditions as well as the potential aggressions of the chemical plant towards the nuclear reactor have to be considered. The methodology presented in this paper is intended to help the designer to take into account the coupling safety constraints and to provide some recommendations on the global architecture of both plants especially on their coupling system. As a result the design of a VHTR combined to a H2 production process will require an iterative process between design and safety requirements.

Hydrogen energy is very promising as it ensures a high efficiency and ecological cleanliness of energy conversion. The goal of the present work is to provide the analysis of hydrogen safety aspects and to prescribe methods of safety operation with hydrogen. The authors conducted a hazard analysis of hydrogen operation and storage in comparison with other fuels. Good ventilation is the main hydrogen operation requirement. Besides an effective way of protection against propagation of hazards (for instance leaks) is neutralization of dangerous hydrogen-air mixtures by a method of controlled catalytic combustion inside special devices so-called recombiners [1-3]. The basis of these devices is a high porosity cell material (HPCM) activated by platinum deposition. Apart from recombiners HPCM was also applied for development of hydrogen detectors intended for measurement and analysis of hydrogen concentration for hydrogen-driven transport and objects of hydrogen infrastructure (including vapor-air media at high pressure and  temperatures). A system of hydrogen safety based on hydrogen detectors and hydrogen catalytic recombiners was developed. Experimental and theoretical studies of hydrogen combustion processes heat- and mass transfer and also gas flows in catalytic-activated HPCM allowed for a design optimization of recombiners and their location. Pilot hydrogen detectors and hydrogen catalytic recombiners were fabricated and their laboratory tests were successfully performed. Thus it was indicated that on condition of following the  appropriate passive and active safety measures hydrogen is just as safe as the other fuels. This conclusion represents another incentive for a transition to the hydrogen energy.

Within the framework of the internal project HyQRA of the HYSAFE Network of Excellence (NoE) funded by the European Commission (EC) the participating partners were requested to apply their Quantitative Risk Assessment (QRA) methodologies on a predefined hypothetical gaseous H₂ refuelling station named BBC (Benchmark Base Case). The overall aim of the HyQRA project was to perform an inter-comparison of the various QRA approaches and to identify the knowledge gaps on data and information needed in the QRA steps specifically related to H₂. Partners NCSRD and UNIPI collaborated on a common QRA. UNIPI identified the hazards on site selected the most critical ones defined the events that could be the primary cause of an accident and provided to NCSRD the scenarios listed in risk order for the evaluation of the consequences. NCSRD performed the quantitative analysis using the ADREA-HF CFD code. The predicted risk assessment parameters (flammable H₂ mass and volume time histories and maximum horizontal and vertical distances of the LFL from the source) were provided to UNIPI to analyze the consequences and to evaluate the risk and distances of damage. In total 15 scenarios were simulated. Five of them were H₂ releases in confined ventilated spaces (inside the compression and the purification/drying buildings). The remaining 10 scenarios were releases in open/semi-confined spaces (in the storage cabinet storage bank and refuelling hose of one dispenser). This paper presents the CFD methodology applied for the quantitative analysis of the common UNIPI/NCSRD QRA and discusses the results obtained from the performed calculations.

Based on the increasing need of energy for the future and the related risks to the environments due to burning of fossils fuels hydrogen is seen as an efficient and application related clean energy carrier that may be derived from renewable energy sources. A variety of applications connected with production and use of hydrogen and the related risks have been identified and a survey has been conducted among a number of experts as an internet exercise for unveiling the potential lack of necessary knowledge in order to handle hydrogen in a safe way concerning the various applications. The main results concern hazardous situations related to release and explosions of hydrogen in confined and semi-confined areas tunnels and garages and mitigation of hazardous situations i.e. preventions of accidents and reduction of consequences from accidents happening anyway.

When introducing hydrogen-fuelled vehicles an evaluation of the potential change in risk level should be performed. It is widely accepted that outdoor accidental releases of hydrogen from single vehicles will disperse quickly and not lead to any significant explosion hazard. The situation may be different for more confined situations such as parking garages workshops or tunnels. Experiments and computer modelling are both important for understanding the situation better. This paper reports a simulation study to examine what if any is the explosion risk associated with hydrogen vehicles in tunnels. Its aim was to further our understanding of the phenomena surrounding hydrogen releases and combustion inside road tunnels and furthermore to demonstrate how a risk assessment methodology developed for the offshore industry could be applied to the current task. This work is contributing to the EU Sixth Framework (Network of Excellence) project HySafe aiding the overall understanding that is also being collected from previous studies new experiments and other modelling activities. Releases from hydrogen cars (containing 700 bar gas tanks releasing either upwards or downwards or liquid hydrogen tanks releasing only upwards) and buses (containing 350 bar gas tanks releasing upwards) for two different tunnel layouts and a range of longitudinal ventilation conditions have been studied. The largest release modelled was 20 kg H2 from four cylinders in a bus (via one vent) in 50 seconds with an initial release rate around 1000 g/s. Comparisons with natural gas (CNG) fuelled vehicles have also been performed. The study suggests that for hydrogen vehicles a typical worst-case risk assessment approach assuming the full gas inventory being mixed homogeneously at stoichiometry could lead to severe explosion loads. However a more extensive study with more realistic release scenarios reduced the predicted hazard significantly. The flammable gas cloud sizes were still large for some of the scenarios but if the actual reactivity of the predicted clouds is taken into account very moderate worst-case explosion pressures are predicted. As a final step of the risk assessment approach a probabilistic QRA study is performed in which probabilities are assigned to different scenarios time dependent ignition modelling is applied and equivalent stoichiometric gas clouds are used to translate reactivity of dispersed nonhomogeneous clouds. The probabilistic risk assessment study is based on over 200 dispersion and explosion CFD calculations using the commercially available tool FLACS. The risk assessment suggested a maximum likely pressure level of 0.1-0.3 barg at the pressure sensors that were used in the study. Somewhat higher pressures are seen elsewhere due to reflections (e.g. under the vehicles). Several other interesting observations were found in the study. For example the study suggests that for hydrogen releases the level of longitudinal tunnel ventilation has only a marginal impact on the predicted risk since the momentum of the releases and buoyancy of hydrogen dominates the mixing and dilution processes.

A method for determination of hazardous zones for hydrogen installations has been studied. This work has been carried out within the NoE HySafe. The method is based on the Italian Method outlined in Guide 31-30(2004) Guide 31–35(2001) Guide 31-35/A(2001) and Guide 31-35/A; V1(2003). Hazardous zones for a “generic hydrogen refuelling station”(HRS) are assessed based on this method. The method is consistent with the EU directive 1999/92/EC “Safety and Health Protection of Workers potentially at risk from explosive atmospheres” which is the basis for determination of hazardous zones in Europe. This regulation is focused on protection of workers and is relevant for hydrogen installations such as hydrogen refuelling stations repair shops and other stationary installations where some type of work operations will be involved. The method is also based on the IEC standard and European norm IEC/EN60079-10 “Electrical apparatus for explosive gas atmospheres. Part 10 Classification of hazardous areas”. This is a widely acknowledged international standard/norm and it is accepted/approved by Fire and Safety Authorities in Europe and also internationally. Results from the HySafe work and other studies relevant for hydrogen and hydrogen installations have been included in the case study. Sensitivity studies have been carried out to examine the effect of varying equipment failure frequencies and leak sizes as well as environmental condition (ventilation obstacles etc.). The discharge and gas dispersion calculations in the Italian Method are based on simple mathematical formulas. However in this work also CFD (Computational Fluid Dynamics) and other simpler numerical tools have been used to quantitatively estimate the effect of ventilation and of different release locations on the size of the flammable gas cloud. Concentration limits for hydrogen to be used as basis for the extent of the hazardous zones in different situations are discussed.

A safety study of gaseous hydrogen supply stations with 40MPa storage system is undertaken through a risk based approach. Accident scenarios are identified based on a generic model of hydrogen station. And risks of identified accident scenarios are estimated and evaluated comparing with risk acceptance criteria. Also safety measures for risk reduction are discussed. Especially for clearance distance it is proposed that the distance from high-pressurized equipment to site borders should be at least 6 meters. As a result of the study it is concluded that risks of accidental scenarios can be mitigated to acceptable level under the proposed safety measures with several exceptions. These exceptional scenarios are very unlikely to occur but expected to have extremely severe consequence once occurred.

The paper presents the results of the CFD inter-comparison exercise SBEP-V3 performed within the activity InsHyde internal project of the HYSAFE network of excellence in the framework of evaluating the capability of various CFD tools and modelling approaches in predicting the physical phenomena associated to the short and long term mixing and distribution of hydrogen releases in confined spaces. The experiment simulated was INERIS-TEST-6C performed within the InsHyde project by INERIS consisting of a 1 g/s vertical hydrogen release for 240 s from an orifice of 20 mm diameter into a rectangular room (garage) of dimensions 3.78x7.2x2.88 m in width length and height respectively. Two small openings at the front and bottom side of the room assured constant pressure conditions. During the test hydrogen concentration time histories were measured at 12 positions in the room for a period up to 5160 s after the end of release covering both the release and the subsequent diffusion phases. The benchmark was organized in two phases. The first phase consisted of blind simulations performed prior to the execution of the tests. The second phase consisted of post calculations performed after the tests were concluded and the experimental results made available. The participation in the benchmark was high: 12 different organizations (2 non-HYSAFE partners) 10 different CFD codes and 8 different turbulence models. Large variation in predicted results was found in the first phase of the benchmark between the various modelling approaches. This was attributed mainly to differences in turbulence models and numerical accuracy options (time/space resolution and discretization schemes). During the second phase of the benchmark the variation between predicted results was reduced.

Energy storage systems are required to address the fluctuating behaviour of variable renewable energy sources. The environmental sustainability of energy storage technologies should be carefully assessed together with their techno-economic feasibility. In this work an environmental analysis of a renewable hydrogen-based energy storage system has been performed making use of input parameters made available in the framework of the European REMOTE project. The analysis is applied to the case study of the Froan islands (Norway) which are representative of many other insular microgrid sites in northern Europe. The REMOTE solution is compared with other scenarios based on fossil fuels and submarine connections to the mainland grid. The highest climate impacts are found in the dieselbased configuration (1090.9 kgCO2eq/MWh) followed by the REMOTE system (148.2 kgCO2eq/MWh) and by the sea cable scenario (113.7 kgCO2eq/MWh). However the latter is biased by the very low carbon intensity of the Norwegian electricity. A sensitivity analysis is then performed on the length of the sea cable and on the CO2 emission intensity of electricity showing that local conditions have a strong impact on the results. The REMOTE system is also found to be the most cost-effective solution to provide electricity to the insular community. The in-depth and comparative (with reference to possible alternatives) assessment of the renewable hydrogen-based system aims to provide a comprehensive overview about the effectiveness and sustainability of these innovative solutions as a support for off-grid remote areas.

The following paper describes researches to evaluate the behaviour under various accidental conditions of systems of transport compressed hydrogen. Particularly have been considered gaseous tube trailer and the packages cylinders employed for the road transport which have an internal gas pressures up to 200 barg.<br/>Further to a verification of the actual safety conditions this analysis intends to propose a theme that in the next future if confirmed projects around the employment of hydrogen as possible source energetic alternative could become quite important. The general increase of the consumptions of hydrogen and the consequently probable increase of the transports of gaseous hydrogen in pressure they will make the problem of the safety of the gaseous tube trail particularly important. Gaseous tube trailers will also use as components of plant. for versatility easy availability' and inexpensiveness.<br/>The first part of the memory is related to the analysis of the accidents happened in the last year in Italy with compressed hydrogen transports and particularly an accurate study has been made on the behaviour of a gaseous tube trailer involved in fire following a motorway accident in March 2003. In the central part of the job has been done a safety analysis of the described events trying to make to also emerge the most critical elements towards the activities developed by the teams of help intervened.<br/>Finally in the last part you are been listed on the base of the picked data a series of proposals and indications of the possible structural and procedural changes that could be suggested with the purpose to guarantee more elevated safety levels.

This paper presents the current results of the theoretical and experimental activity carried out by the Italian Working Group on the fire prevention safety issues in the field of the hydrogen transport in pipelines. From the theoretical point of view a draft document has been produced beginning from the regulations in force on the natural gas pipelines; these have been reviewed corrected and integrated with the instructions suitable to the use with hydrogen gas. From the experimental point of view a suitable apparatus has been designed and installed at the University of Pisa; this apparatus will allow the simulation of hydrogen releases from a pipeline with or without ignition of the hydrogen-air mixture. The experimental data will help the completion of the above-mentioned draft document with the instructions about the safety distances. However in the opinion of the Group the work on the text contents is concluded and the document is ready to be discussed with the Italian stakeholders involved in the hydrogen applications.

We performed a hydrogen combustion analysis in the Advanced Power Reactor 1400 MWe (APR1400) containment during a severe accident initiated by a small break loss of coolant accident (SBLOCA) which occurred at a lower part of the cold leg using a multi-dimensional hydrogen analysis system (MHAS) to confirm the integrity of the APR1400 containment. The MHAS was developed by combining MAAP GASFLOW and COM3D to simulate hydrogen release distribution and combustion in the containment of a nuclear power plant during the severe accidents in the containment of a nuclear power reactor. The calculated peak pressure due to the flame acceleration by the COM3D using the GASFLOW results as an initial condition of the hydrogen distribution was approximately 555 kPa which is lower than the fracture pressure 1223 kPa of the APR1400 containment. To induce a higher peak pressure resulted from a strong flame acceleration in the containment we intentionally assumed several things in developing an accident scenario of the SBLOCA. Therefore we may judge that the integrity of the APR1400 containment can be maintained even though the hydrogen combustion occurs during the severe accident initiated by the SBLOCA.

This publication by the Department for Business Energy and Industrial Strategy (BEIS) brings together heat networks investment opportunities in England and Wales. The opportunities present a wide range of projects supported through the development stages by the Heat Networks Delivery Unit (HNDU) and projects seeking capital support from the Heat Networks Investment Project (HNIP).

The publication includes a list of one-page summaries for each of the heat network projects supported by BEIS which set out details of HNDU and HNIP projects where projects have provided enough detail in time for publication.

For HNIP this represents projects which have submitted at least a pre-application to the Delivery Partner Triple Point Heat Networks Investment Management since the scheme opened in February 2019. As a number of the projects are at different stages of development some of the costs aren’t currently available or will be subject to project consent and change as they progress through the project lifecycle.

Related Document: Heat Network Detailed Project Development Resource: Guidance on Strategic and Commercial Case

Hydrogen is increasingly receiving a primary role as an energy vector in ensuring the achievement of the European decarbonization goals by 2050. In fact Hydrogen could be produced also by electrolysis of water using renewable sources such as photovoltaic and wind power being able to perform the energy storage function as well as through injection into natural gas infrastructures. However hydrogen injection directly impacts thermodynamic properties of the gas itself such as density calorific value Wobbe index sound speed etc. Consequently this practice leads to changes in metrological behavior especially in terms of volume and gas quality measurements. In this paper the authors present an overview on the impact of hydrogen injection in natural gas measurements. In particular the changes in thermodynamic properties of the gas mixtures with different H2 contents have been evaluated and the effects on the accuracy of volume conversion at standard conditions have been investigated both on the theoretical point of view and experimentally. To this end the authors present and discuss the effect of H2 injection in gas networks on static ultrasonic domestic gas meters both from a theoretical and an experimental point of view. Experimental tests demonstrated that ultrasonic gas meters are not significantly affected by H2 injection up to about 10%.

Interest in the future is not new. Economic constraints and acceptability considerations of today compel decision-makers from industry and authorities to speculate on possible safety risks originating from a hydrogen economy developed in the future. Tools that support thinking about the long-term consequences of today's actions and resulting technical systems are usually prognostic based on data from past performance of past or current systems. It has become convention to assume that the performance of future systems in future environments can be accommodated in the uncertainties of such prognostic models resulting from sensitivity studies. This paper presents an alternative approach to modelling future systems based on narratives about the future. Such narratives based on the actions and interactions of individual "agents" are powerful means for addressing anxiety about engaging the imagination in order to prepare for events that are likely to occur detect critical conditions and to thus achieve desirable outcomes. This is the methodological base of Agent-Based Models (ABM) and this paper will present the approach discuss its strengths and weaknesses and present a preliminary application to modelling safety risks related to energy scenarios in a possible future hydrogen economy.