Publications

There has recently been a concerted effort to commence a transition to fuel cell vehicles (FCVs) in Europe. A coalition of companies released an influential McKinsey-coordinated report in 2010 which concluded that FCVs are ready for commercial deployment. Public–private H2Mobility programmes have subsequently been established across Europe to develop business cases for the introduction of FCVs. In this paper we examine the conclusions of these studies from an energy systems perspective using the UK as a case study. Other UK energy system studies have identified only a minor role for FCVs after 2030 but we reconcile these views by showing that the differences are primarily driven by different data assumptions rather than methodological differences. Some energy system models do not start a transition to FCVs until around 2040 as they do not account for the time normally taken for the diffusion of new powertrains. We show that applying dynamic growth constraints to the UK MARKAL energy system model more realistically represents insights from innovation theory. We conclude that the optimum deployment of FCVs from an energy systems perspective is broadly in line with the roadmap developed by UK H2Mobility and that a transition needs to commence soon if FCVs are to become widespread by 2050.

This work is driven by the need to understand the hazards resulting from the rapid ignited release of hydrogen from onboard storage tanks through a thermally activated pressure relief device (TPRD) inside a garage-like enclosure with low natural ventilation i.e. the consequences of a jet fire which has been immediately ignited. The resultant overpressure is of particular interest. Previous work [1] focused on an unignited release in a garage with minimum ventilation. This initial work demonstrated that high flow rates of unignited hydrogen through a thermally activated pressure relief device (TPRD) in ventilated enclosures with low air change per hour can generate overpressures above the limit of 10- 15 kPa which a typical civil structure like a garage could withstand. This is due to the pressure peaking phenomenon. Both numerical and phenomenological models were developed for an unignited release and this has been recently validated experimentally [2]. However it could be expected that the majority of unexpected releases through a TPRD may be ignited; leading to even greater overpressures and to date whilst there has been some work on fires in enclosures the pressure peaking phenomenon for an ignited release has yet to be studied or compared with that for an equivalent unignited release. A numerical model for ignited releases in enclosures has been developed and computational fluid dynamics has then been used to examine the pressure dynamics of an ignited hydrogen release in a real scale garage. The scenario considered involves a high mass flow rate release from an onboard hydrogen storage tank at 700 bar through a 3.34 mm diameter orifice representing the TPRD in a small garage with a single vent equivalent in area to small window. It is shown that whilst this vent size garage volume and TPRD configuration may be considered “safe” from overpressures in the event of an unignited release the overpressure resulting from an ignited release is two orders of magnitude greater and would destroy the structure. Whilst further investigation is needed the results clearly indicate the presence of a highly dangerous situation which should be accounted for in regulations codes and standards. The hazard relates to the volume of hydrogen released in a given timeframe thus the application of this work extends beyond TPRDs and is relevant where there is a rapid ignited release of hydrogen in an enclosure with limited ventilation.

"The current practise of focusing the periodic retesting of composite cylinders primarily on the hydraulic pressure test has to be evaluated as critical - with regard to the damage of the specimen as well as in terms of their significance. This is justified by micro damages caused to the specimen by the test itself and by a lack of informative values. Thus BAM Federal Institute of Materials Research and Testing (Germany) uses a new approach of validation of composite for the determination of re-test periods. It enables the description of the state of a population of composite cylinders based on destructive tests parallel to operation.<br/>An essential aspect of this approach is the prediction of residual safe service life. In cases where it cannot be estimated by means of hydraulic load cycle tests as a replacement the creep or burst test remains. As a combination of these two test procedures BAM suggests the ""slow burst test SBT"". On this a variety of about 150 burst test results on three design types of cylinders with plastic liners are presented. For this purpose both the parameters of the test protocol as well as the nature and intensity of the pre-damage artificially aged test samples are analysed statistically. This leads first to an evaluation of the different types of artificial ageing but also to the clear recommendation that conventional burst tests be substituted totally if indented for assessment of composite pressure receptacles."

This paper presents a case study concerning a plant for hydrogen production and storage having a daily capacity of 100kg. The plant is located in Cluj-Napoca Romania. It produces hydrogen by means of water electrolysis while the energy is provided using solar energy. We performed the calculations for four different technical solutions used for the hydrogen production and storage plant and also we considered three scenarios regarding the sub-systems of the hydrogen production and storage plant efficiency. The conclusion of this study is that one can maximize the conversion of solar radiation into chemical energy in the form of hydrogen by hybridizing the solar hydrogen production system namely using both electrical energy as well as thermal energy in the form of steam.

This paper presents results of an experimental investigation on detonation wave propagation in semi-confined geometries. Large scale experiments were performed in layers up to 0.6 m filled with uniform and non-uniform hydrogen–air mixtures in a rectangular channel (width 3 m; length 9 m) which is open from below. A semi confined driver section is used to accelerate hydrogen flames from weak ignition to detonation. The detonation propagation was observed in a 7 m long unobstructed part of the channel. Pressure measurements ionization probes soot-records and high speed imaging were used to observe the detonation propagation. Critical conditions for detonation propagation in different layer thicknesses are presented for uniform H2/air-mixtures as well as experiments with uniform H2/O2 mixtures in a down scaled transparent channel. Finally detail investigations on the detonation wave propagation in H2/air-mixtures with concentration gradients are shown.

Jet fires develop on release of hydrogen from pressurized storage depending on orifice pressures and volumes. Risks arise from flame contact dispersion of hot gases and heat radiation. The latter varies strongly in time at short scales down to milliseconds caused by turbulent air entrainment and fluctuations. These jets emit bands of OH in the UV and water in the NIR and IR spectral range. These spectra enable the temperature measurement and the estimation of the air number of the measuring spot which can be used to estimate the total radiation at least from the bright combustion zones. Compared to video and IR camera frames the radiation enables to estimate species and temperatures distributions and total emissions. Impurities generate continuum radiation and the emission of CO2 in the IR indicates air entrainment which can be compared to CHEMKIN II calculation of the reaction with air.

The current energy system is subject to a fundamental transformation: A system that is oriented towards a constant energy supply by means of fossil fuels is now expected to integrate increasing amounts of renewable energy to achieve overall a more sustainable energy supply. The challenges arising from this paradigm shift are currently most obvious in the area of electric power supply. However it affects all areas of the energy system albeit with different results. Within the energy system various independent grids fulfill the function of transporting and spatially distributing energy or energy carriers and the demand-oriented supply ensures that energy demands are met at all times. However renewable energy sources generally supply their energy independently from any specific energy demand. Their contribution to the overall energy system is expected to increase significantly.<br/>Energy storage technologies are one option for temporal matching of energy supply and demand. Energy storage systems have the ability to take up a certain amount of energy store it in a storage medium for a suitable period of time and release it in a controlled manner after a certain time delay. Energy storage systems can also be constructed as process chains by combining unit operations each of which cover different aspects of these functions. Large-scale mechanical storage of electric power is currently almost exclusively achieved by pumped-storage hydroelectric power stations.<br/>These systems may be supplemented in the future by compressed-air energy storage and possibly air separation plants. In the area of electrochemical storage various technologies are currently in various stages of research development and demonstration of their suitability for large-scale electrical energy storage. Thermal energy storage technologies are based on the storage of sensible heat exploitation of phase transitions adsorption/desorption processes and chemical reactions. The latter offer the possibility of permanent and loss-free storage of heat. The storage of energy in chemical bonds involves compounds that can act as energy carriers or as chemical feedstocks. Thus they are in direct economic competition with established (fossil fuel) supply routes. The key technology here – now and for the foreseeable future – is the electrolysis of water to produce hydrogen and oxygen.<br/>Hydrogen can be transformed by various processes into other energy carriers which can be exploited in different sectors of the energy system and/or as raw materials for energy-intensive industrial processes. Some functions of energy storage systems can be taken over by industrial processes. Within the overall energy system chemical energy storage technologies open up opportunities to link and interweave the various energy streams and sectors. Chemical energy storage not only offers means for greater integration of renewable energy outside the electric power sector it also creates new opportunities for increased flexibility novel synergies and additional optimization.<br/>Several examples of specific energy utilization are discussed and evaluated with respect to energy storage applications. The article describes various technologies for energy storage and their potential applications in the context of Germany’s Energiewende i.e. the transition towards a more sustainable energy system. Therefore the existing legal framework defines some of the discussions and findings within the article specifically the compensation for renewable electricity providers defined by the German Renewable Energy Sources Act which is under constant reformation. While the article is written from a German perspective the authors hope this article will be of general interest for anyone working in the areas of energy systems or energy technology.

Hydrogen may play a crucial part in delivering a net zero emissions future. Currently hydrogen production storage transport and utilisation are being explored to scope opportunities and to reduce barriers to market activation. One such barrier could be negative public response to hydrogen technologies. Previous research around socio-technical risks finds that public acceptance issues are particularly challenging for emerging remote technical sensitive uncertain or unfamiliar technologies - such as hydrogen. Thus while the hydrogen value chain could offer a range of potential environmental economic and social benefits each will have perceived risks that could challenge the introduction and subsequent roll-out of hydrogen. These potential issues must be identified and managed so that the hydrogen sector can develop adapt or respond appropriately. Geological storage of hydrogen could present challenges in terms of perceived safety. Valuable lessons can be learned from international research and practice of CO2 and natural gas storage in geological formations (for carbon capture and storage CCS and for power respectively). Here we explore these learnings. We consider the similarities and differences between these technologies and how these may affect perceived risks. We also reflect on lessons for effective communication and community engagement. We draw on this to present potential risks to the perceived safety of - and public acceptability of – the geological storage of hydrogen. One of the key lessons learned from CCS and natural gas storage is that progress is most effective when risk communication and public acceptability is considered from the early stages of technology development.

When hydrogen flows through a small finite length constant exit area nozzle the viscous effects create a fluid throat which acts as a converging-diverging nozzle and lead to Mach number greater than one at the exit if the jet is under-expanded. This phenomenon influences the mass flow rate and the dispersion cloud size. In this study the boundary layer effect on the unsteady hydrogen sonic jet flow through a 1 mm diameter pipe from a high pressure reservoir (up to 70 MPa) is studied using computational fluid dynamics with a large eddy simulation turbulence model. This viscous flow simulation is compared with a non-viscous simulation to demonstrate that the velocity is supersonic at the exit of a small exit nozzle and that the mass flow is reduced.

Community support and acceptance is part of the licence to operate for any industry. The hydrogen industry is no different and we will need to have strong support from the broad community to establish a viable hydrogen economy in Australia.<br/>As Woodside progresses our plans for bulk hydrogen export and associated domestic opportunities stakeholder engagement throughout will be critical to success. This talk will share Woodside’s approach to community engagement and local opportunities and how we plan to draw on more than 30 years’ experience operating liquefied natural gas plants in Western Australia’s Pilbara region.<br/>At this early stage of our hydrogen work we are beginning with the end in mind: engaging the customer. We’ve worked with local Australian businesses to help raise public awareness and interest in hydrogen by producing prototype consumer products. We will share experiences from this work that underscore the value of early engagement with all stakeholders: government regulators industrial and community neighbours and end consumers to enable the hydrogen economy vision for Australia. This paper will present information on community engagement and acceptance of hydrogen in Australia.<br/>This information has come from Woodside Energy Ltd by engaging with small businesses government regulators and the community at large. As we establish community acceptance for hydrogen as an energy carrier in Australia Woodside has been working in parallel to have standards and regulations established for hydrogen in Australia. Through our work with Hydrogen Mobility Australia we are advocating the adoption of ISO standards unless there is a specific geographic or health safety and environment reason not to.

Hydrogen technologies are expected to play a key role in implementing the transition from a fossil fuel- based to a more sustainable lower-carbon energy system. To facilitate their widespread deployment the safe operation and hydrogen systems needs to be ensured together with the evaluation of the associated risk.<br/>HIAD has been designed to be a collaborative and communicative web-based information platform holding high quality information of accidents and incidents related to hydrogen technologies. The main goal of HIAD was to become not only a standard industrial accident database but also an open communication platform suitable for safety lessons learned and risk communication as well as a potential data source for risk assessment; it has been set up to improve the understanding of hydrogen unintended events to identify measures and strategies to avoid incidents/accidents and to reduce the consequence if an accident occurs.<br/>In order to achieve that goal the data collection is characterized by a significant degree of detail and information about recorded events (e.g. causes physical consequences lesson learned). Data are related not only to real incident and accidents but also to hazardous situations.<br/>The concept of a hydrogen accident database was generated in the frame of the project HySafe an EC co-funded NoE of the 6th Frame Work Programme. HIAD was built by EC-JRC and populated by many HySafe partners. After the end of the project the database has been maintained and populated by JRC with publicly available events. The original idea was to provide a tool also for quantitative risk assessment able to conduct simple analyses of the events; unfortunately that goal could not be reached because of a lack of required statistics: it was not possible to establish a link with potential event providers coming from private sector not willing to share information considered confidential. Starting from June 2016 JRC has been developing a new version of the database (i.e. HIAD 2.0); the structure of the database and the web-interface have been redefined and simplified resulting in a streamlined user interface compared to the previous version of HIAD. The new version is mainly focused to facilitate the sharing of lessons learned and other relevant information related to hydrogen technology; the database will be public and the events will be anonymized. The database will contribute to improve the safety awareness fostering the users to benefit from the experiences of others as well as to share information from their own experiences.

A series of experiments on hydrogen flame propagation in a thin layer geometry is presented. Premixed hydrogen-air compositions in the range from 6 to 15%(vol.) H2 are tested. Semi-open vertical combustion chamber consists of two transparent Plexiglas side walls with main dimensions of 90x20 cm with a gap from 1 to 10 mm in between. Test mixtures are ignited at the open end of the chamber so that the flame propagates towards the closed end. Ignition position changes from top to bottom in order to take into account an effect of gravity on flame propagation regimes. High-speed shadow imaging is used to visualize and record the combustion process. Thermal-diffusion and Darrieus-Landau instabilities are governing the general flame behaviour. Heat losses to side walls and viscous friction in a thin layer may fully suppress the flame propagation with local or global extinction. The sensitivity to heat losses can be characterized using a Peclet number as a ratio of layer thickness to laminar flame thickness. Approaching to critical Peclet number Pec = 42 the planar or wrinkled flame surface degradants to one-or two-heads "finger" flame propagating straight (for two-heads flame) or chaotic (for one-head "finger" flame). Such a "fingering" of the flame is found for the first time for gaseous systems and very similar to that reported for smouldering or filtering combustion of solid materials and also under micro-gravity conditions. The distance between "fingers" may depend on deficit of limiting component. The processes investigated can be very important from academic and practical points of view with respect to safety of hydrogen fuel cells.

The unconfined release of high-pressure hydrogen can create a large flammable jet with the potential to generate significant damage. To properly understand the separation distances necessary to protect the immediate surroundings it is important to accurately assess the potential consequences. In these events the possibility for a detonation cannot be excluded and would generally result in the worst case scenario from the standpoint of damaging overpressure. The strong concentration gradients created by a jet release however raises the question of what portion of the flammable cloud should be considered. Often all of the fuel within the limits of fast-flame acceleration or even all of the fuel within the flammability range is considered which typically comprises the majority of the flammable cloud. In this work prior detonation studies are reviewed to illustrate the inherently unstable nature of detonations with a focus on the critical dimensions and concentration gradients that can support a propagating detonation wave. These criteria are then applied to the flammable cloud concentration distributions generated by an unconfined jet release of hydrogen. By evaluating these limits it is found that the portion of the flammable cloud that is likely to participate is significantly reduced. These results are compared with existing experimental data on the ignition of unconfined hydrogen releases and the peak pressures that were measured are consistent with a detonation of a mass of fuel that is equivalent to the model prediction for the mass of fuel within the detonable limits. This work demonstrates how the critical conditions for detonation propagation can be used to estimate the portion of a hydrogen release that could participates in a detonation and how these criteria can be readily incorporated into existing dispersion modelling approaches.

Correlative engineering models (Linden 1994) are compared to recent published (Cariteau et al. (2009) Pitts et al. (2009) Barley and Gawlick (2009) Swain et al. (1999) Merilo et al. (2010)) and unpublished (CEA experiments in a 1 m3  with two openings) experimental hydrogen or helium distribution in enclosures (with one and two openings). The modelling-experiments comparison is carried out in transient and in steady state conditions. On this basis recommendations and limits of use of these models are proposed.

The work is dedicated to the possibility of using hydrogen-powered vehicles in urban transport systems. Due to the need to look for alternative solutions for vehicles with conventional drive in cities hydrogen-powered cars are one of the practical possibilities of realizing the sustainable transport assumptions and independence from oil imports - which is one of the main priorities of the European Union. This paper presents a literature analysis the analysis of the current state and development of use hydrogen-powered vehicles in the world.<br/>The article refers to the possibilities of use hydrogen-vehicles in different ways of mobility: individual vehicles taxis and shared mobility. In addition the author focused on showing the advantages and disadvantages of using hydrogen-powered vehicles in urban transport systems.

The FCH 2 JU launched the European Hydrogen Safety Panel (EHSP) initiative in 2017. The mission of the EHSP is to assist the FCH 2 JU both at programme and at project level in assuring that hydrogen safety is adequately managed and to promote and disseminate H2 safety culture within and outside of the FCH 2 JU programme. The EHSP is composed of a multidisciplinary pool of safety experts grouped in ad-hoc working groups (task forces) according to the tasks to be performed and to expertise. The scope and activities of the EHSP are structured around four main areas:

This study is aimed at the validation of the pressure peaking phenomenon against laboratory-scale experiments. The phenomenon was discovered recently as a result of analytical and numerical studies performed at Ulster University. The phenomenon is characterized by the existence of a peak on the overpressure transient in an enclosure with vent(s) at some conditions. The peak overpressure can significantly exceed the steady-state pressure and jeopardise a civil structure integrity causing serious life safety and property protection problems. However the experimental validation of the phenomenon was absent until recently. The validation experiments were performed at Karlsruhe Institute of Technology within the framework of the HyIndoor project. Tests were carried out with release of three different gases (air helium and hydrogen) within a laboratory-scale enclosure of about 1 m3 volume with a vent of comparatively small size. The model of pressure peaking phenomenon reproduced closely the experimental pressure dynamics within the enclosure for all three used gases. The prediction of pressure peaking phenomenon consists of two steps which are explained in detail. Examples of calculation for typical hydrogen applications are presented.

The UK has an extensive natural gas pipeline network supplying 84% of homes. Previous studies of decarbonisation pathways using the UK MARKAL energy system model have concluded that the low ­pressure gas networks should be mostly abandoned by 2050. yet most of the iron pipes near buildings are currently being replaced early for safety reasons. Our study suggests that this programme will not lock-in the use of gas in the long-term. We examine potential future uses of the gas network in the UK energy system using an improved version of UK MARKAL that introduces a number of decarbonisation options for the gas network including bio-methane hydrogen injection to the natural gas and conversion of the network to deliver hydrogen.<br/>We conclude that hydrogen conversion is the only gas decarbonisa­tion option that might enable the gas networks to continue supplying energy to most buildings in the long-term from a cost-optimal perspective. There is an opportunity for the government to adopt a long­t erm strategy for the gas distribution networks that either curtails the iron mains replacement programme or alters it to prepare the network for hydrogen conversion; both options could substantially reduce the long-term cost of supplying heat to UK buildings.

Self-acceleration of a spherically expanding hydrogen-air flame was experimentally investigated in a closed dual-chamber apparatus with the quartz windows enabled to a flame diameter with up to 240 mm. The flame radius and flame speed in lean hydrogen-air mixtures at elevated pressure were evaluated using a high speed Schlieren photography. The experimental results from hydrogen-air explosion at elevated pressure validated the prediction model for self-similar propagation. The flame radius and its speed calculated by the prediction models agree well with the experimental results of hydrogen-air explosions at elevated pressure. Furthermore the acceleration exponent α is evaluated by plotting the flame radius with time. The results show the α value increase with the dimensionless flame radius r/rcl. It is indicated that the self-acceleration and the transition regime to self-similar propagation exist in the spherically expanding hydrogen-air flame.

The dynamics of detonation transmission from a straight channel into a curved chamber was investigated as a function of initial pressure using a combined experimental and numerical study. Hi-speed Schlieren and *OH chemiluminescense were used for flow visualization; numerical simulations considered the two-dimensional reactive Euler equations with detailed chemistry. Results show the highly transient sequence of events (i.e. detonation diffraction re-initiation attempts and wave reflections) that precede the formation of a steadily rotating Mach detonation along the outer wall of the chamber. An increase in pressure from 15 kPa to 26 kPa expectedly resulted in detonations that are less sensitive to diffraction. Local quenching of the initial detonation occurred for all pressures considered. The location where this decoupling occurred along the inner wall determined the location where transition from regular reflection to a rather complex wave structure occurred along the outer wall. This complex wave structure includes a steadily rotating Mach detonation (stem) an incident decoupled shock-reaction zone region and a transverse detonation that propagates in pre-shocked mixture.

A core theme of the UK Government's new Industrial Strategy is exploiting opportunities for domestic supply chain development. This extends to a special ‘Automotive Sector Deal’ that focuses on the shift to low emissions vehicles (LEVs). Here attention is on electric vehicle and battery production and innovation. In this paper we argue that a more straightforward gain in terms of framing policy around potential economic benefits may be made through supply chain activity to support refuelling of battery/hydrogen vehicles. We set this in the context of LEV refuelling supply chains potentially replicating the strength of domestic upstream linkages observed in the UK electricity and/or gas industries. We use input-output multiplier analysis to deconstruct and assess the structure of these supply chains relative to that of more import-intensive petrol and diesel supply. A crucial multiplier result is that for every £1million of spending on electricity (or gas) 8 full-time equivalent jobs are supported throughout the UK. This compares to less than 3 in the case of petrol/diesel supply. Moreover the importance of service industries becomes apparent with 67% of indirect and induced supply chain employment to support electricity generation being located in services industries. The comparable figure for GDP is 42%.

The use of hydrogen as fuel should always be accompanied by a safety assessment in case of an accidental release. To evaluate the potential hazards in a spill accident both experiments and simulations are performed. In the present work the CFD code ADREA-HF is used to simulate the liquefied hydrogen (LH2) spill experiments (test 5 6 7) conducted by the Health and Safety Laboratory (HSL). In these tests LH2 was spilled at a fixed rate of 60lt/min in several directions and for several durations. The factors that influence the vapor dispersion under cryogenic release conditions that were examined in this study are: the air humidity the wind direction and the slip effect of droplets formed by both the cryogenic liquid and the condensation of air humidity. The numerical results were compared with the experimental measurements and the effect of each abovementioned factors in the vapor dispersion is being discussed.

A hydrogen purification system based on the technology of the electrochemical hydrogen compression and purification is introduced. This system is developed within the scope of the project MEMPHYS. Therefore the project its targets and the different work stages are presented. The technology of the electrochemical purification and the state of the art of hydrogen purification are described. Early measurements in the project have been carried out and the results are shown and discussed. The ability of the technology to recover hydrogen from a gas mixture can be recognized and an outlook into further optimizations shows the future potential. A big advantage is the simultaneous compression of the purified hydrogen up to 200 bar therefore facilitating the transportation and storage.

At Woodside Energy Ltd (Woodside) safety is built into everything we do and progressing hydrogen opportunities is no exception. This paper will present information from the macro level of process safety for hydrogen at a plant level through to the consumer experience. Examples of the benefits of an integrated process safety approach will be used from Woodside’s experience pioneering the liquefied natural gas industry in Australia.<br/>This paper will underscore the reasons why Australia needs to adopt robust safety standards for hydrogen as quickly as possible in order to advance the hydrogen economy across all sectors. Focus areas requiring attention during development of standards and potential mechanisms to close will be proposed. Establishing a hydrogen economy in Australia could lower carbon emissions stabilise power grids increase renewable energy penetration and create jobs. Developing Australian standards that are fully aligned with international standards will facilitate Australia taking a leading role in the global hydrogen economy.

A hydrogen fuel is expected to expand its demand in the future. However hydrogen has to be treated with enough caution because of wide combustible conditions and easiness to ignite. Detonation accidents are caused in hydrogen gas such as the explosion accident in Fukushima first nuclear plant (2011). Therefore it is necessary to comprehend initiation conditions of detonation to prevent its detonation explosion. In the present study cylindrical detonation induced by direct initiation is simulated to understand the dependency of equivalence ratios in hydrogen-oxygen mixture. The several detailed kinetic models are compared to select the most appropriate model for detonation in a wide range of equivalence ratios. The Petersen-Hanson model is used in the present study due to the best agreement among the other models. In the numerical results of cylindrical detonation induced by direct initiation a cellular structure which is similar to the experimental smoked foil record is observed. The local pressure is up to 12 MPa under the condition at the standard state. The ignition process of cylindrical detonation has two stages. At the first stage the normalized cell width /L1/2 at each equivalence ratio increases linearly. At the second stage cell bifurcations appear due to a generation of new transverse waves. It is observed that a transverse wave transforms to a transverse detonation at the end of the first stage and after that some disturbance is developed to be a new transverse wave at the beginning of the second stage.

Hydrogen energy based vehicles or power generators are expected to come into widespread use in the near future. Safety information is of major importance to support the successful public acceptance of hydrogen as an energy carrier. One of the most important issues in terms of safety is the use of such system in closed area such as a private garage in which a fuel cell car may be parked. This kind of situation leads to the fundamental problem of the dispersion of hydrogen due to a simple vertical source in an enclosure. Many numerical and experimental studies have already been conducted on this problem showing the formation of a stably stratified distribution of concentration. Most of them consider the cases of accidental situation in which the flow rate is relatively important (of the order of 10Nl/min to 100Nl/min). We present a set of experiments conducted on a full scale facility of the size of a typical private garage with helium as a model gas for hydrogen. In this study we focus on the low flow rates that can be characteristic of chronic leaks that may not be detected by security devices of the system (of the order of 0.1Nl/min to 10Nl/min). The facility allows changing natural ventilation conditions and experiments have been conducted from the tightest which is less than 0.01ACH to that typical of a real garage say of the order of 0.1ACH.

A three-dimensional mathematical model of gaseous hydrogen deflagration in the enclosed space is developed. The process is described by the system of gas dynamics differential equations. Thermodynamic parameters of the mixture and its components are defined as functions of the local temperature and mixture composition. The concentration changes of the fuel and combustion products are determined using conservation laws taking into account rates of component disappearance and formation and turbulent diffusion. It is assumed that the chemical reaction takes place only in the volume where the fuel concentration is within the limits of inflammability. The mathematical model is validated during an intercomparison test to predict deflagration of a large-scale hydrogen-air mixture in open atmosphere. An algorithm of numerical solution based on the Godunov method is developed. A computer system of engineering analysis of gas-dynamic processes of hydrogen-air mixture formation and combustion in enclosed space with natural ventilation is created. It allows predicting the history of the changes of overpressure temperature concentrations of hydrogen and combustion products and other thermogasdynamic parameters of the mixture in space. This prognosis can be used to estimate dangerous zones of destruction and recommend some safety measures.

<br/>Cyclic Voltammetry Measurements performed on a Cobaloxime Catalyst designed for photochemical hydrogen production.

The test data of static burst strength and load cycle strength of composite pressure vessels are often described by GAUSSian normal or WEIBULL distribution function to perform safety analyses. The goodness of assumed distribution function plays a significant role in the inferential statistics to predict the population properties by using limited test data. Often GAUSSian and WEIBULL probability nets are empirical methods used to validate the distribution function; Anderson-Darling and Kolmogorov-Smirnov tests are the mostly favorable approaches for Goodness of Fit. However the different approaches used to determine the parameters of distribution function lead mostly to different conclusions for safety assessments.<br/>In this study six different methods are investigated to show the variations on the rates for accepting the composite pressure vessels according to GTR No. 13 life test procedure. The six methods are: a) Norm- Log based method b) Least squares regression c) Weighted least squares regression d) A linear approach based on good linear unbiased estimators e) Maximum likelihood estimation and f) The method of moments estimation. In addition various approaches of ranking function are considered. In the study Monte Carlo simulations are conducted to generate basic populations based on the distribution functions which are determined using different methods. Then the samples are extracted randomly from a population and evaluated to obtain acceptance rate. Here the “populations” and “samples” are corresponding to the burst strength or load cycle strength of the pressure vessels made from composite material and a plastic liner (type 4) for the storage of hydrogen. To the end the results are discussed and the best reliable methods are proposed.

The combination of traditional reactor and permeable membrane is beneficial to increase the production rate of the target product. How to design a high efficiency and energy saving membrane reactor is one of the key problems to be solved urgently. This paper utilizes finite-time thermodynamics and nonlinear programming to solve the optimal configurations of the membrane reactor of steam methane reforming (MR-SMR) for two optimization objectives that is heat exchange rate minimization and power consumption minimization. The exterior wall temperature and fixed hydrogen production rate are regarded as the control variable and constraint respectively. The results indicate that the hydrogen production rate and heat exchange rate in MR-SMR are increased by 108.58% and 58.42% respectively while the power consumption is reduced by 33.44% compared with those in the traditional reactor under the same condition. Compared with the results in reference reactor (MR-SMR obtained with initial values) the heat exchange rate is reduced by 1.40% by optimizing the exterior wall temperature and the power consumption is reduced by 5.10% by optimizing the exterior wall temperature and molar flow rate of sweep gas. The optimal distributions of exterior wall temperatures in the optimal reactors of minimum heat exchange rate and power consumption have a theoretical guiding significance for the thermal design of the membrane reactors.

In the past material innovation has changed society through new material-induced technologies adding a new value to society. In the present world engineers and scientists are expected to invent new materials to solve the global problem of climate change. For the transport sector the challenge for material engineers is to change the oil-based world into a sustainable world. After witnessing the recent high oil price and its adverse impact on the global economy it is time to accelerate our efforts towards this change.

Industries are tackling global energy issues such as oil and CO₂ as well as local environmental problems such as NOx and particulate matter. Hydrogen is the most promising candidate to provide carbon-free emission-free and oil-free mobility. As such engineers are working very hard to bring this technology into the real society. This paper describes recent progress of vehicle technologies as well as hydrogen-storage technologies to extend the cruise range and ensure the easiness of refuelling and requesting material scientists to collaborate with industry to fight against global warming.

Link to document download on Royal Society Website  

The energy transition – which represents the efforts undertaken and results achieved on renewable energy expansion and energy efficiency – is our basis for a clean secure and affordable energy supply which is essential for all our lives. By adopting the 2030 Climate Action Plan the Federal Government has paved the way for meeting its climate targets for 2030. Its long-term goal is to achieve carbon neutrality in line with the targets agreed under the Paris Agreement which seeks to keep global warming well below 2 degrees and if possible below 1.5 degrees. In addition Germany has committed itself together with the other European Member States to achieving greenhouse gas (GHG) neutrality by 2050. Apart from phasing out coal-fired power for which Germany has already taken the relevant decisions this means preventing emissions which are particularly hard to reduce such as process-related GHG emissions from the industrial sector.<br/>In order for the energy transition to be successful security of supply affordability and environmental compatibility need to be combined with innovative and smart climate action. This means that the fossil fuels we are currently using need to be replaced by alternative options. This applies in particular to gaseous and liquid energy sources which will continue to be an integral part of Germany’s energy supply. Against this backdrop hydrogen will play a key role in enhancing and completing the energy transition.

Fast depletion of fossil fuels and their detrimental effect to the environment is demanding an urgent need of alternative fuels for meeting sustainable energy demand with minimum environmental impact.  Expert studies indicate hydrogen is one of the most promising energy carriers for the future due to its superior combustion qualities and availability. The use of hydrogen in spark ignition internal combustion engine may be part of an integrated solution to the problem of depletion of fossil fuels and pollution of the environment. The broader flammability limits and fast flame propagation velocity of hydrogen ensures complete combustion of fuel and allows engine to be operated at lean ranges. Lean burn operation comparatively maintains NOx CO and HC emissions at a very low level. In the present work oxyhydrogen (HHO) gas is produced in leak proof plexiglass reactor by electrolysis of water using potassium hydroxide as electrolyte.  The HHO gas generator is attached to a spark ignition engine currently operating on the road without any modifications of the engine. The HHO gas produced is then added to the air which is being drawn into the engine.  Experiments were conducted on a 4-stroke single cylinder natural air cooled spark ignition engine to determine total fuel consumption specific fuel consumption air fuel ratio brake power and brake thermal efficiency and emissions CO CO₂ O2 NOx HC at different loads with and without addition of HHO gas to gasoline for lower speeds ranging from 700 rpm to 1500 rpm. Also mileage tests were conducted to find the speed at which the fuel consumption is optimum.

A turbulent combustion model based on the Linear Eddy Model for Large Eddy Simulation (LEM- LES) is currently proposed to study self-ignition events of rapidly expanding hydrogen jets. The model is a one-dimensional treatment of a diffusion-reaction system within each multi-dimensional LES cell. This reduces the expense of solving a complete multi-dimensional problem while preserving micro-scale hotspots and their effects on ignition. The current approach features a Lagrangian description of fluid particles on the sub-grid for increased accuracy. Also Adaptive Mesh Refinement (AMR) is implemented for increased computational efficiency. In this paper the model is validated for various inviscid laminar 1-D mixing and ignition problems shock tube problems flames and detonations.

This paper shows numerical investigation related to hydrogen-air deflagration venting. The aim of this study is to clarify the influence of concentration gradient on the pressure histories and peak pressures in a chamber. The numerical analysis target is a 27 m3 cubic chamber which has 2.6 m2 vent area on the sidewall. The vent opening pressure is set to be gauge 10 kPa. Two different conditions of the hydrogen concentration are assumed which are uniform and gradient. In the uniform case 15 20 25 30 and 35 vol.% concentrations are assumed. In the gradient case the concentration linearly increases from 0 vol.% (at the ground) to 30 40 50 60 70 vol.% (at the ceiling). The initial total mass of hydrogen inside the chamber is the same as the uniform case. Moreover three different ignition points are assumed: on the rear center and the front of the chamber relative to the vent. The deflagrations are initiated by a single ignition source. In most gradient cases the highest peak is lower than in the uniform case though the initial total mass of hydrogen inside the chamber is the same as in the uniform case. This is because the generated burned gas per time is smaller in the gradient case than in the uniform case. In 15 vol.% gradient case however the peak pressure gets higher than in the uniform case. This is because in 15 vol.% gradient case the burning velocity around the ignition point gets faster and the flame surface gets larger which induces larger amount of burned gas per time.

Contrary to several reports in the recent literature the use of oxygen sensors for indirectly monitoring ambient hydrogen concentration has serious drawbacks. This method is based on the assumption that a hydrogen release will displace oxygen which is quantified using oxygen sensors. Despite its shortcomings the draft Hydrogen Vehicle Global Technical Regulation lists this method as a means to monitor hydrogen leaks to verify vehicle fuel system integrity. Experimental evaluations that were designed to impartially compare the ability of commercial oxygen and hydrogen sensors to reliably measure and report hydrogen concentration changes are presented. Numerous drawbacks are identified and discussed.

We numerically investigated the initial behaviour of leakage and diffusion from high-pressure hydrogen storage tank assumed in hydrogen station. First calculations are carried out to validate the present numerical approach and compare with the theoretical distribution of hydrogen mass fraction to the direction which is vertical to the jet direction in the case of hydrogen leaking out from the circular injection port whose diameter is 0.25 mm. Then performing calculations about hydrogen leakage and diffusion behaviour on different tank pressures the effects are examined to reduce damage by gas explosion assumed in the hydrogen station. There is no significant difference in the diffusion distance to the jet direction from a start to 0.2 ms. After 0.2 ms it is seen the difference in the diffusion distance to the jet direction in different pressure. As tank pressures become large the hydrogen diffusion not only to the jet direction but also to the direction which is vertical to the jet direction is remarkably seen. Then according to histories of the percentage of the flammable mass to total one in the space it drastically increases up to 30%2between 0 and 0.05 ms. After 0.05 ms it uniformly increases so it is shown that the explosion risk becomes high over time. The place where mass within flammability range distributes at a certain time is shown. Hydrogen widely diffuses to jet direction and distributes in each case and time. Therefore it is found that when it is assumed that ignition occurs by some sources in place where high-pressure hydrogen is leaked and diffused the magnitude of the explosion damage can be predicted when and where ignition occurs.

Evaluations of the uncertainties resulting from risk assessment tools to predict releases from the various hydrogen storage types are important to support risk informed safety management. The tools have to predict releases from a wide range of storage pressures (up to 80 MPa) and temperatures (at 20K) e.g. the cryogenic compressed gas storage covers pressures up to 35 MPa and temperatures between 33K and 338 K. Accurate calculations of high pressure releases require real gas EOS. This paper compares a number of EOS to predict hydrogen properties typical in different storage types. The vessel dynamics are modelled to evaluate the performance of various EOS to predict exit pressures and temperatures. The results are compared to experimental data and results from CFD calculations.

Jordan's energy diversification strategy is centred around renewables which are expected will provide the low-cost reliable secure and environmentally sustainable energy required to power its new engines of economic growth – manufacturing transport construction and agriculture.

The National Energy Strategy 2020–2030 presents the evolution of the energy sector under its vision for stimulating demand achieving efficiency and improving electricity system flexibility.

This Renewables Readiness Assessment (RRA) highlights key actions for the short and medium-term that could create more conductive conditions for renewable energy development. It aims to help unlock Jordan's renewable energy potential and provide the means to meet the energy diversification goals of its national strategy.

The study was undertaken by the Ministry of Energy and Mineral Resources (MEMR) in collaboration with the International Renewable Energy Agency (IRENA).

Key recommendations:

• Provide the necessary conditions for renewables growth in the power sector.
• Foster continued growth of renewable power generation.
• Plan the integration of higher shares of renewable power.
• Incentivise the use of renewables for heating and cooling.
• Support renewable transport and mobility options.
• Catalyse renewable energy investment. Strengthen local industries and create jobs in renewables.

An increase in use of hydrogen for energy storage and clean energy supply in a future energy and mobility market will strengthen the focus on safety and the safe handling of hydrogen facilities. The ability to simulate the whole chain of physical phenomena that may occur during an accident is mandatory for future safety studies on an industrial or urban scale. Together with the RWTH Aachen University Forschungszentrum Jülich (JÜLICH) develops numerical methods to predict safety incidents connected with the release of either LH2 or GH2 using the commercial CFD code ANSYS CFX. The full sequence from the release distribution or accumulation of accidentally released hydrogen till the mitigation of accident consequences by safety devices is considered. For specific phenomena like spreading and vaporization of LH2 pools or the operational behavior of passive auto-catalytic recombiners (PAR) in-house sub-models are developed and implemented. The paper describes the current development status gives examples of the validation and concludes with future work to provide the full range of hydrogen release and recombination simulation.

The present work proposes a parametric study on the influence of the height of the release source on the helium dispersion regimes inside a naturally ventilated enclosure. Several configurations were experimentally addressed in order to improve knowledge on dispersion considering conditions close to hydrogen energy systems in terms of operating characteristics and design. Thus the varying parameters of the study were mainly the height of the release and also the releasing flow rate the volume and the geometry of the enclosure. Experimental results were compared to existing analytical models and considered through model improvements allowing a better approach of these specific cases for hydrogen systems risk assessment.

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

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.

This paper introduces the 3D risk management (3DRM) concept with particular emphasis on hydrogen installations (Hy3DRM). The 3DRM framework entails an integrated solution for risk management that combines a detailed site-specific 3D geometry model a computational fluid dynamics (CFD) tool for simulating flow-related accident scenarios methodology for frequency analysis and quantitative risk assessment (QRA) and state-of-the-art visualization techniques for risk communication and decision support. In order to reduce calculation time and to cover escalating accident scenarios involving structural collapse and projectiles the CFD-based consequence analysis can be complemented with empirical engineering models reduced order models or finite element analysis (FEA). The paper outlines the background for 3DRM and presents a proof-of-concept risk assessment for a hypothetical hydrogen filling station. The prototype focuses on dispersion fire and explosion scenarios resulting from loss of containment of gaseous hydrogen. The approach adopted here combines consequence assessments obtained with the CFD tool FLACS-Hydrogen from Gexcon and event frequencies estimated with the Hydrogen Risk Assessment Models (HyRAM) tool from Sandia to generate 3D risk contours for explosion pressure and radiation loads. For a given population density and set of harm criteria it is straightforward to extend the analysis to include personnel risk as well as risk-based design such as detector optimization. The discussion outlines main challenges and inherent limitations of the 3DRM concept as well as prospects for further development towards a fully integrated framework for risk management in organizations.

Shipping is a very important source of pollution worldwide. In recent years numerous actions and measures have been developed trying to reduce the levels of greenhouse gases (GHG) from the marine exhaust emissions in the fight against climate change boosting the Sustainable Development Goal 13. Following this target the action of hydrogen as energy vector makes it a suitable alternative to be used as fuel constituting a very promising energy carrier for energy transition and decarbonization in maritime transport. The objective of this study is to develop an ex-ante environmental evaluation of two promising technologies for vessels propulsion a H2 Polymeric Electrolytic Membrane Fuel Cell (PEMFC) and a H2 Internal Combustion Engine (ICE) in order to determine their viability and eligibility compared to the traditional one a diesel ICE. The applied methodology follows the Life Cycle Assessment (LCA) guidelines considering a functional unit of 1 kWh of energy produced. LCA results reveal that both alternatives have great potential to promote the energy transition particularly the H2 ICE. However as technologies readiness level is quite low it was concluded that the assessment has been conducted at a very early stage so their sustainability and environmental performance may change as they become more widely developed and deployed which can be only achieved with political and stakeholder’s involvement and collaboration.

Hydrogen induced cracking is still a severe and current threat for several industrial applications. With the aim of providing a simple and versatile device for hydrogen detection a new instrument was designed based on solid state sensor technology. New detection technique allows to execute hydrogen permeation measurement in short time and without material surface preparation. Thanks to this innovation HELIOS offers a concrete alternative to traditional experimental methods for laboratory permeability tests. In addition it is proposed as a new system for Non Destructive Testing of components in service in hydrogenating environment. Hydrogen flux monitoring is particularly relevant for risk mitigation of elements involved in hydrogen storage and transportation. Hydrogen permeation tests were performed by means of HELIOS instruments both on a plane membrane and on the wall of a gas cylinder. Results confirmed the extreme sensitivity of the detection system and its suitability to perform measurements even on non metallic materials by means of an easy-to-handle instrument.

Hydrogen used in hydrogen fuel cell vehicles is the flammable gas which has wide flammable range and flame propagation speed is very fast. This fuel cell vehicle equipped with high-pressure vessel in the form of fuel to supply the high pressure hydrogen storage system needs to be checked carefully about a special safety design and exact weak point for high pressure repeated fatigue. 70 L liner and 70 MPa Type-3 vessel were tested using the equipments which can perform ambient hydraulic cycling test and burst test in the Korea Gas Safety Corporation. And it was performed to identify the internal external behaviour through the Finite Element Analysis (FEA) and real leakage mode for high pressure repeated fatigue when subjected to be pressurized in vessel. 70 L liner and 70 MPa Type-3 vessel were tested using the equipments which can perform ambient hydraulic cycling test and burst test in the Korea Gas Safety Corporation. And it was performed to identify the internal external behaviour through the Finite Element Analysis (FEA) and real leakage mode for high pressure repeated fatigue when subjected to be pressurized in vessel. Through this study liner of type-3 hydrogen vessel is ruptured first on cylindrical (body) part than Dome part in 8.5 MPa. Also the same Phenomena are confirmed through the Finite Element Analysis (FEA). External composite leakage mode in ambient hydraulic cycling test was occurred in different area such as the Dome Dome knuckle and cylindrical (body) parts. But cracks of inner liner for gas tight were occurred in only cylindrical (body) parts. Also in FEA results when vessel is pressurized Dome knuckle and cylindrical (body) parts is weakest among all parts because of expansion of cylindrical (body) parts.

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.

In this paper we present a detailed design study of a novel apparatus for safely generating hydrogen (H2) on demand according to a novel method using a controlled chemical reaction between water (H2O) and sodium (Na) metal that yields hydrogen gas of sufficient purity for direct use in fuel cells without risk of contaminating sensitive catalysts. The apparatus consists of a first pressure vessel filled with liquid H2O with an overpressure of nitrogen (N2) gas above the H2O reactant and a second pressure vessel that stores solid Na reactant. Hydrogen gas is generated above the solid Na when H2O reactant is introduced using a regulator that senses when the downstream pressure of H2 gas above the solid Na reactant has dropped below a threshold value. The sodium hydroxide (NaOH) byproduct of the hydrogen producing reaction is collected within the apparatus for later reprocessing by electrolysis to recover the Na reactant.

Correlating hydrogen embrittlement phenomenon with the metallic microstructural features holds the key for developing metals resistant to hydrogen-based failures. In case of fatigue failure of hydrogen charged metals in addition to the hydrogen-based failure mechanisms associated with monotonic loading such as HELP HEDE etc. microstructural features such as grain size type of grain boundary (special/random) fraction of special grain boundaries; their network and triple junctions can play a complex role. The probable sites for fatigue crack initiation in such metals can be identified as the sites of highest hydrogen concentration or accumulated plastic strain. To this end we have developed an experimental framework based on in-situ fatigue crack initiation and propagation studies under scanning electron microscope (SEM) to identify the weakest link in the metallic microstructure leading to failure. In-situ fatigue experiments are performed on carefully designed polycrystalline nickel (99.95% pure) specimens (miniaturised shallow-notched & electro-polished) using a 10 kN fatigue stage inside the SEM. Electron Back Scattering Diffraction (EBSD) map of the notched region surface helps identify the distribution of special/random grain boundaries triple junctions and grain orientation. The specimen surface in the shallow notched region for both the hydrogen charged and un-charged specimens are then carefully studied to correlate the microstructural feature associated with fatigue crack initiation sites. Such correlation of the fatigue crack initiation site and microstructural feature is further corroborated with the knowledge of hydrogen trapping and grain’s elastic anisotropicity to be either the site of high hydrogen concentration accumulated plastic slip or both.