Italy

Vented deflagration tests were conducted by UNIPI at B. Guerrini Laboratory during the experimental campaign for HySEA project. Experiments included homogeneous hydrogen-air mixture in a 10-18% vol. range of concentrations contained in an about 1 m3 enclosure called SSE (Small Scale Enclosure). Displacement measurements of a test plate were taken in order to acquire useful data for the validation of FE model developed by IMPETUS Afea. In this paper experimental facility displacement measurement system and FE model are briefly described then comparison between experimental data and simulation results is discussed.

The paper presents the outcomes of the HyResponse project i.e. the European Hydrogen Safety Training Programme for first responders. The threefold training is described: the content of the educational training is presented the operational training platform and its mock-up real scale transport and hydrogen stationary installations are detailed and the innovative virtual tools and training exercises are highlighted. The paper underlines the outcomes the three pilot sessions as well as the Emergency Response Guide available on the HyResponse’s public website. The next steps for widespread dissemination into the community are discussed.

Explosion relief panels or doors are often used in industrial buildings to reduce damages caused by gas explosions. Decades of research have contributed to the understanding of the phenomena involved in gas explosions in order to establish an effective method to predict reliably the explosion overpressure. All the methods predict a monotonic increase of the overpressure with the concentration of the gas in the range from the lower explosion limit to the stoichiometric one. Nevertheless in few cases a non-monotonic behaviour of the maximum developed pressure as a function of hydrogen concentration was reported in the literature. The non-monotonic behaviour was also observed during experimental tests performed at the Scalbatraio laboratory at the University of Pisa in a 25 m3 vented combustion test facility with a vent area of 112 m2. This paper presents the results obtained during the tests and investigates the possible explanations of the phenomena.

In this paper a study on the comparison between the different methodologies for the determination of the safety distances proposed by Standard Organizations and national Regulations is presented. The application of the risk-informed approach is one of the methodologies used for the determination of safety distances together with the risk-based approach. One of the main differences between the various methodologies is the risk criterion chosen. In fact a critical point is which level of risk should be used and then which are the harm events that must be considered. The harm distances are evaluated for a specified leak diameter that is a consequence of some parameters used in the various methodologies. The values of the safety distances proposed by Standard Organizations and national Regulations are a demonstration of the different approaches of the various methodologies especially in the choice of the leak diameter considered.

In our society the use of hydrogen is continually growing and there will be a widespread installation of plants with high capacity storages in our towns as automotive refuelling stations. For this reason it is necessary to make accurate studies on the safety of these kinds of plants to protect our town inhabitants Moreover hydrogen is a highly flammable chemical that can be particularly dangerous in case of release since its mixing with air in the presence of an ignition source could lead to fires or explosions. Generally most simulation models whether or not concerned with fluid dynamics used in safety and risk studies are not validated for hydrogen use. This aspect may imply that the results of studies on safety cannot be too accurate and realistic. This paper introduces an experimental activity which was performed by the Department of Energetics of Politecnico of Torino with the collaboration of the University of Pisa. Accidental hydrogen release and dispersion were studied in order to acquire a set of experimental data to validate simulation models for such studies. At the laboratories of the Department of Mechanical Nuclear and Production Engineering of the University of Pisa a pilot plant called Hydrogen Pipe Break Test was built. The apparatus consisted of a 12 m3 tank which was fed by high pressure cylinders. A 50 m long pipe moved from the tank to an open space and at the far end of the pipe there was an automatic release system that could be operated by remote control. During the experimental activity data was acquired regarding hydrogen concentration as a function of distance from the release hole also lengthwise and vertically. In this paper some of the experimental data acquired during the activity have been compared with the integral models Effects and Phast. In the future experimental results will be used to calibrate a more sophisticated model to atmospheric dispersion studies.

At the DIMNP (Department of Mechanical Nuclear and Production Engineering) laboratories of University of Pisa (Italy) a pilot plant called HPBT (Hydrogen Pipe Break Test) was built in cooperation with the Italian Fire Brigade Department. The apparatus consists of a 12 m3 tank connected with a 50 m long pipe. At the far end of the pipeline a couple of flanges have been used to house a disc with a hole of the defined diameter. The plant has been used to carry out experiments of hydrogen release. During the experimental activity data have been acquired about the gas concentration and the length of release as function of internal pressure and release hole diameter. The information obtained by the experimental activity will be the basis for the development of a new specific normative framework arranged to prevent fire and applied to hydrogen. This study is focused on hydrogen concentration as function of wind velocity and direction. Experimental data have been compared with theoretical and computer models (such as CFD simulations)

Application of Solid Oxide Fuel Cells (SOFC) in gasification-based power plants would represent a turning point in the power generation sector allowing to considerably increase the electric efficiency of coal-fired power stations while reducing CO2 and other pollutant emissions. The aim of this paper is the thermodynamic assessment of a SOFC-based IGFC plant with methanation reactor hydrogen post-firing and CO2 capture by physical absorption. The configuration proposed allows to obtain a very high net efficiency (51.6%) overcoming the main limits of configurations assessed in previous works.

Gas sensors are applied for facilitating the safe use of hydrogen in for example fuel cell and hydrogen fuelled vehicles. New sensor developments aimed at meeting the increasingly stringent performance requirements in emerging applications are presented based on in-house technical developments and a literature study. The strategy of combining different detection principles i.e. sensors based on electrochemical cells semiconductors or field effects in combination with thermal conductivity sensor or catalytic combustion elements in one new measuring system is reported. This extends the dynamic measuring range of the sensor while improving sensor reliability to achieve higher safety integrity through diverse redundancy. The application of new nanoscaled materials nano wires carbon tubes and graphene as well as the improvements in electronic components of field-effect resistive-type and optical systems are evaluated in view of key operating parameters such as sensor response time low energy consumption and low working temperature.

In industrial buildings explosion relief panels or doors are often used to reduce damages caused by gas explosion. Decades of research produced a significant contribution to the understanding of the phenomena involved nevertheless among the aspects that need further research interaction between acoustic oscillation and the flame front is one of the more important. Interaction between the flame front and acoustic oscillation has raised technical problem in lots of combustion applications as well and had been studied theoretically and experimentally in such cases. Pressure oscillation had been observed in vented deflagration and in certain cases they are responsible for the highest pressure peak generated during the event. At Scalbatraio laboratory of Pisa University CVE test facility was built in order to investigate vented hydrogen deflagration. This paper is aimed to present an overview of the results obtained during several experimental campaigns which tests are analysed with the focus on the investigation of flame acoustic interaction phenomenon. Qualitative and quantitative analysis is presented and the possible physic generating the phenomenon investigated.

The use of hydrogen in small scale gas turbines is currently limited by several issues. Blending hydrogen with methane or other gaseous fuels can be considered a low medium-term viable solution with the goal of reducing greenhouse gas emissions. In fact only small amounts can be mixed with methane in premixed combustors due to the risk of flashback. The aim of this article is to investigate the injection of small quantities of steam as a method of increasing the maximum permissible hydrogen content in a mixture with methane. The proposed approach involves introducing the steam directly into the combustion chamber into the main fuel feeding system of a Turbec T100. The study is carried out by means of CFD analysis of the combustion process. A thermodynamic analysis of the energy system is used to determine boundary conditions. The combustion chamber is discretized using a three-dimensional mesh consisting of 4.7 million nodes and the RANS RSM model is used to simulate the effects of turbulence. The results show that the addition of steam may triple the permissible percentage of hydrogen in the mixture for the considered MGT passing from 10% to over 30% by volume also leading to a reduction in NOx emissions without a significant variation in CO emissions.

In 2016 for the first time a polymer electrolyte fuel cell free of Pt electrocatalysts was shown to deliver more than 0.5 W cm-2 of peak power density from H2 and air (CO2 free). This was achieved with a silver-based oxygen reduction (ORR) cathode and a Pd-CeO2 hydrogen oxidation reaction (HOR) anodic electrocatalyst. The poor kinetics of the HOR under alkaline conditions is a considerable challenge to Anion Exchange Membrane Fuel Cell (AEMFC) development as high Pt loadings are still required to achieve reasonable performance. Previously the ameliorative combination of Pd and CeO2 nanocomposites has been exploited mostly in heterogeneous catalysis where the positive interaction is well documented. Carbon supported PdCeO2 HOR catalysts have now been prepared by different synthetic techniques and employed in AEMFCs as alternative to Pt and PtRu standards. Important research has also been recently reported delving into the origin of the HOR enhancement on Pd-CeO2. Such work has highlighted the importance of the bifunctional mechanism of the HOR at high pHs. Carefully prepared nano-structures of Pd and CeO2 that promote the formation of the Pd-O-Ce interface provide optimal binding of both Had and OHad species aspects which are crucial for enhanced HOR kinetics. This review paper discusses the recent advances in Pd-CeO2 electrocatalysts for AEMFC anodes.

The use of stationary H2 and fuel cell systems is expected to increase rapidly in the future. In order to facilitate the safe introduction of this new technology the HyPer project funded by the EC developed a public harmonized Installation Permitting Guidance (IPG) document for the installation of small stationary H2 and fuel cell systems for use in various environments. The present contribution focuses on the safety assessment of a facility inside which a small H2 fuel cell system (4.8 kWe) is installed and operated. Dispersion experiments were designed and performed by partner UNIPI. The scenarios considered cover releases occurring inside the fuel cell at the valve of the inlet gas pipeline just before the pressure regulator which controls the H2 flow to the fuel cell system. H2 was expected to leak out of the fuel cell into the facility and then outdoors through the ventilation system. The initial leakage diameter was chosen based on the Italian technical guidelines for the enforcement of the ATEX European directive. Several natural ventilation configurations were examined. The performed tests were simulated by NCSRD using the ADREA-HF code. The numerical analysis took into account the full interior of the fuel cell in order to investigate for any potential accumulation effects. Comparisons between predicted and experimental H2 concentrations at 4 sensor locations inside the facility are reported. Finally an overall assessment of the ventilation efficiency was made based on the simulations and experiments.

The present paper illustrates an innovative steel processing route developed by employing hydrogen direct reduced pellets and an open slag bath furnace. The paper illustrates the direct reduction reactor employing hydrogen as reductant on an industrial scale. The solution allows for the production of steel from blast furnace pellets transformed in the direct reduction reactor. The reduced pellets are then melted in open slag bath furnaces allowing carburization for further refining. The proposed solution is clean for the decarbonization of the steel industry. The kinetic chemical and thermodynamic issues are detailed with particular attention paid to the slag conditions. The proposed solution is also supported by the economic evaluation compared to traditional routes.

This experimental work analyzes the hydrogen embrittlement mechanism in quenched and tempered low-alloyed steels. Experimental tests were performed to study hydrogen diffusion under applied cyclic loading. The permeation curves were fitted by considering literature models in order to evaluate the role of trapping—both reversible and irreversible—on the diffusion mechanism. Under loading conditions a marked shift to the right of the permeation curves was noticed mainly at values exceeding the tensile yield stress. In the presence of a relevant plastic strain the curve changes due to the presence of irreversible traps which efficiently subtract diffusible atomic hydrogen. A significant reduction in the apparent diffusion coefficient and a considerable increase in the number of traps were noticed as the maximum load exceeded the yield strength. Cyclic loading at a tensile stress slightly higher than the yield strength of the material increases the hydrogen entrapment phenomena. The tensile stress causes a marked and instant reduction in the concentration of mobile hydrogen within the metal lattice from 55% of the yield strength and it increases significantly in the plastic field.

"This paper summarises the modelling and experimental programme in the EC FP6 project HYPER. A number of key results are presented and the relevance of these findings to installation permitting guidelines (IPG) for small stationary hydrogen and fuel cell systems is discussed. A key aim of the activities was to generate new scientific data and knowledge in the field of hydrogen safety and where possible use this data as a basis to support the recommendations in the IPG. The structure of the paper mirrors that of the work programme within HYPER in that the work is described in terms of a number of relevant scenarios as follows: 1. high pressure releases 2. small foreseeable releases 3. catastrophic releases and 4. the effects of walls and barriers. Within each scenario the key objectives activities and results are discussed.<br/>The work on high pressure releases sought to provide information for informing safety distances for high-pressure components and associated fuel storage activities on both ignited and unignited jets are reported. A study on small foreseeable releases which could potentially be controlled through forced or natural ventilation is described. The aim of the study was to determine the ventilation requirements in enclosures containing fuel cells such that in the event of a foreseeable leak the concentration of hydrogen in air for zone 2 ATEX is not exceeded. The hazard potential of a possibly catastrophic hydrogen leakage inside a fuel cell cabinet was investigated using a generic fuel cell enclosure model. The rupture of the hydrogen feed line inside the enclosure was considered and both dispersion and combustion of the resulting hydrogen air mixture were examined for a range of leak rates and blockage ratios. Key findings of this study are presented. Finally the scenario on walls and barriers is discussed; a mitigation strategy to potentially reduce the exposure to jet flames is to incorporate barriers around hydrogen storage equipment. Conclusions of experimental and modelling work which aim to provide guidance on configuration and placement of these walls to minimise overall hazards is presented. "

The purpose of the experimental work is to determine the conditions for which an enclosure can guest a fuel cell for civil use. Concerning the installation permitting guide this study allows the safe use of the fuel cell in case of small not catastrophic leakages. In fact the correct plan of the vents in the enclosure guarantees the low concentration of hydrogen (H2) below the LFL.

In this study the authors present a techno-economic assessment of on-site hydrogen refuelling stations (450 kg/day of H2 ) based on different hydrogen sources and production technologies. Green ammonia biogas and water have been considered as hydrogen sources while cracking autothermal reforming and electrolysis have been selected as the hydrogen production technologies. The electric energy requirements of the hydrogen refuelling stations (HRSs) are internally satisfied using the fuel cell technology as power units for ammonia and biogas-based configurations and the PV grid-connected power plant for the water-based one. The hydrogen purification where necessary is performed by means of a Palladium-based membrane unit. Finally the same hydrogen compression storage and distribution section are considered for all configurations. The sizing and the energy analysis of the proposed configurations have been carried out by simulation models adequately developed. Moreover the economic feasibility has been performed by applying the life cycle cost analysis. The ammonia-based configurations are the best solutions in terms of hydrogen production energy efficiency (>71% LHV) as well as from the economic point of view showing a levelized cost of hydrogen (LCOH) in the range of 6.28 EUR/kg to 6.89 EUR/kg a profitability index greater than 3.5 and a Discounted Pay Back Time less than five years.

A potentially viable solution to the problem of greenhouse gas emissions by vehicles in the transportation sector is the deployment of hydrogen as alternative fuel. A limitation to the diffusion of the hydrogen‐fuelled vehicles option is the intricate refuelling stations that vehicles will require. This study examines the practical use of hydrogen fuel within the internal combustion engine (ICE)‐powered long‐haul heavy‐duty trucking vehicles. Specifically it appraises the techno‐ economic feasibility of constructing a network of long‐haul truck refuelling stations using hydrogen fuel across Canada. Hydrogen fuel is chosen as an option for this study due to its low carbon emissions rate compared to diesel. This study also explores various operational methods including variable technology integration levels and truck traffic flows truck and pipeline delivery of hydrogen to stations and the possibility of producing hydrogen onsite. The proposed models created for this work suggest important parameters for economic development such as capital costs for station construction the selling price of fuel and the total investment cost for the infrastructure of a nation‐ wide refuelling station. Results showed that the selling price of hydrogen gas pipeline delivery op‐ tion is more economically stable. Specifically it was found that at 100% technology integration the range in selling prices was between 8.3 and 25.1 CAD$/kg. Alternatively at 10% technology integration the range was from 12.7 to 34.1 CAD$/kg. Moreover liquid hydrogen which is delivered by trucks generally had the highest selling price due to its very prohibitive storage costs. However truck‐delivered hydrogen stations provided the lowest total investment cost; the highest is shown by pipe‐delivered hydrogen and onsite hydrogen production processes using high technology integration methods. It is worth mentioning that once hydrogen technology is more developed and deployed the refuelling infrastructure cost is likely to decrease considerably. It is expected that the techno‐economic model developed in this work will be useful to design and optimize new and more efficient hydrogen refuelling stations for any ICE vehicles or fuel cell vehicles.

Hydrogen is recognized as a promising and attractive energy carrier to decarbonize the sectors responsible for global warming such as electricity production industry and transportation. However although hydrogen releases only water as a result of its reaction with oxygen through a fuel cell the hydrogen production pathway is currently a challenging issue since hydrogen is produced mainly from thermochemical processes (natural gas reforming coal gasification). On the other hand hydrogen production through water electrolysis has attracted a lot of attention as a means to reduce greenhouse gas emissions by using low-carbon sources such as renewable energy (solar wind hydro) and nuclear energy. In this context by providing an environmentally-friendly fuel instead of the currently-used fuels (unleaded petrol gasoline kerosene) hydrogen can be used in various applications such as transportation (aircraft boat vehicle and train) energy storage industry medicine and power-to-gas. This article aims to provide an overview of the main hydrogen applications (including present and future) while examining funding and barriers to building a prosperous future for the nation by addressing all the critical challenges met in all energy sectors.

In order to facilitate the introduction of a new technology as it is the utilization of hydrogen as an energy carrier development of safety codes and standards besides the conduction of demonstrative projects becomes a very important action to be realized. Useful tools of work could be the existing gaseous fuel codes (natural gas and propane) regulating the stationary and automotive applications. Some safety codes have been updated to include hydrogen but they have been based on criteria and/or data applicable for large industrial facilities making the realization of public hydrogen infrastructures prohibitive in terms of space. In order to solve the above mentioned problems others questions come out: how these safety distances have been defined? Which hazard events have been taken as reference for calculation? Is it possible to reduce the safety distances through an appropriate design of systems and components or through the predisposition of adequate mitigation measures? This paper presents an analysis of the definitions of “safety distances” and “hazardous locations” as well as a synoptic analysis of the different values in force in several States for hydrogen and natural gas. The above mentioned synoptic table will highlight the lacks and so some fields that need to be investigated in order to produce a suitable hydrogen standard.

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.

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.

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.

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%.

The release of gases heavier than air like propane at ground level or lighter than air like hydrogen close to a ceiling can both lead to fire and explosion hazards that must be carefully considered in safety analyses. Even if the simulation of accident scenarios in complex installations and long transients often appears feasible only using lumped parameter computer codes the phenomenon of denser or lighter gas dispersion is not implicitly accounted by these kind of tools. In the aim to set up an ad hoc model to be used in the computer code ECART fluid-dynamic simulations by the commercial FLUENT 6.0 CFD code are used. The reference geometry is related to cavities having variable depth (2 to 4 m) inside long tunnels filled with a gas heavier or lighter than air (propane or hydrogen). Three different geometrical configurations with a cavity width of 3 6 and 9 m are considered imposing different horizontal air stream velocities ranging from 1 to 5 m/s. A stably-stratified flow region is observed inside the cavity during gas shearing. In particular it is found that the density gradient tends to inhibit turbulent mixing thus reducing the dispersion rate. The obtained data are correlated in terms of main dimensionless groups by means of a least squares method. In particular the Sherwood number is correlated as a function of Reynolds a density ratio modified Froude numbers and in terms of the geometrical parameter obtained as a ratio between the depth of the air-dense gas interface and the length of the cavity. This correlation is implemented in the ECART code to add the possibility to simulate large installations during complex transients lasting many hours with reasonable computation time. An example of application to a typical case is presented.