Publications

Buoyant round vertical jet had been investigated using Large Eddy Simulations at low Mach number. For the purpose of comparison with in-house experimental data in the present work helium has been used as a substitute for hydrogen. The influence of the transient concentration fields on the volume of gas with concentration within flammability limits has been investigated and their evolution and relation with average fields ad been characterized. Transient concentration fields created during initial jet development had been considered. Numerical results have been compared with in-house experiments and data published in the literature.

High pressure hydrogen leak is one of the top safety issues presently. This study elucidates the physics and mechanism of high pressure hydrogen jet ignition when the hydrogen suddenly spouts into the air. The experimental work was done elsewhere while we did the numerical work on this high pressure hydrogen leak problem. The direct numerical simulation based on the compressible fluid dynamics considering viscous effect was carried out with the two-dimensional axisymmetric coordinate system A detailed model of hydrogen reaction is applied and a narrow tube attached to a high pressure reservoir is assumed in the numerical simulation. The exit of the tube is opened in the atmosphere. When high pressure hydrogen is passing through the tube filled by atmospheric air a strong shock wave is formed and heats up hydrogen behind the shock wave by compression effect. The leading shock wave is expanded widely after the exit hydrogen then mixed with air by several vortices generated around the exit of the tube. As a result a couple of auto-ignitions of hydrogen occur. It is found that there is a certain relationship between the auto-ignition and tube length. When the tube becomes longer the tendency of auto-ignition is increased. Additionally other type of auto-ignitions is predicted. An explosion is also occurred in the tube under a certain condition. Vortex is generated behind the shock wave in the long tube. There is a possibility of an auto-ignition induced by vortices.

One of the main benefits sought by including hydrogen in the alternative fuels mix is emissions reduction – eventually by 100%. However in the near term there is a very significant cost differential between fossil fuels and hydrogen. Hythane (a blend of hydrogen and natural gas) can act as a viable next step on the path to an ultimate hydrogen economy as a fuel blend consisting of 8−30 % hydrogen in methane can reduce emissions while not requiring significant changes in existing infrastructure. This work seeks to evaluate whether hythane may be safer than both hydrogen and methane under certain conditions. This is due to the fact hythane combines the positive safety properties of hydrogen (strong buoyancy high diffusivity) and methane (much lower flame speeds and narrower flammability limits as compared to hydrogen). For this purpose several different mixture compositions (e.g. 8 % 20 % and 30 % hydrogen) are considered. The evaluation of (a) dispersion characteristics (which are more positive than for methane) (b) combustion characteristics (which are closer to methane than hydrogen) and (c) Combined dispersion + explosion risk is performed. This risk is expected to be comparable to that of pure methane possibly lower in some situations and definitely lower than for pure hydrogen. The work is performed using the CFD software FLACS that has been well-validated for safety studies of both natural gas/methane and hydrogen systems. The first part of the work will involve validating the flame speeds and flammability limits predicted by FLACS against values available in literature. The next part of the work involves validating the overpressures predicted by the CFD tool for combustion of premixed mixtures of methane and hydrogen with air against available experimental data. In the end practical systems such as vehicular tunnels garages etc. is used to demonstrate positive safety benefits of hythane with comparisons to similar simulations for both hydrogen and methane.

Computational Fluid Dynamics solvers are developed for explosion modelling and hazards analysis in Hydrogen air mixtures. The work is presented in two parts. These include firstly a numerical approach to simulate flame acceleration and deflagration to detonation transition (DDT) in hydrogen–air mixture and the second part presents comparisons between two approaches to detonation modelling. The detonation models are coded and the predictions in identical scenarios are compared. The DDT model which is presented here solves fully compressible multidimensional transient reactive Navier–Stokes equations with a chemical reaction mechanism for different stages of flame propagation and acceleration from a laminar flame to a highly turbulent flame and subsequent transition from deflagration to detonation. The model has been used to simulate flame acceleration (FA) and DDT in a 2-D symmetric rectangular channel with 0.04 m height and 1 m length which is filled with obstacles. Comparison has been made between the predictions using a 21-step detailed chemistry as well as a single step reaction mechanism. The effect of initial temperature on the run-up distances to DDT has also been investigated. Comparative study has also been carried out for two detonation solvers. one detonation solver is developed based on the solution of the reactive Euler equations while the other solver has a simpler approach based on Chapman–Jouguet model and the programmed CJ burn method. Comparison has shown that the relatively simple CJ burn approach is unable to capture some very important features of detonation when there are obstacles present in the cloud.

The possibility of using a risk based approach for the safe installation and siting of stationary fuel cell systems depends upon the availability of normative data and guidance on potential hazards and the probabilities of their occurrence. Such guidance data is readily available for most common hydrocarbon fuels. For hydrogen however data is still required on the hazards associated with different release scenarios. This data can then be related to the probability of different types of scenarios from historical fault data to allow safety distances to be defined and controlled using different techniques. Some data on releases has started to appear but this data generally relates to hydrogen vehicle refuelling systems that are designed for larger throughput higher pressures and the general use of larger pipe diameters than are likely to be used for small fuel cell systems.

The heat transfer analysis in the filling process of compressed on-board hydrogen storage tank has been the focus of hydrogen storage research. The initial conditions mass flow rate and heat transfer coefficient have certain influence on the hydrogen filling performance. In this paper the effects of mass flow rate and heat transfer coefficient on hydrogen filling performance are mainly studied. A thermodynamic model of the compressed hydrogen storage tank was established by Matlab/Simulink. This 0D model is utilized to predict the hydrogen temperature hydrogen pressure tank wall temperature and SOC (State of Charge) during filling process. Comparing the simulated results with the experimental data the practicability of the model can be verified. The simulated results have certain meaning for improving the hydrogenation parameters in real filling process. And the model has a great significance to the study of hydrogen filling and purification.

The deployment of hydrogen technologies particularly the deployment of hydrogen dispensing systems for passenger vehicles requires that hydrogen components perform reliably in environments where they have to meet the following performance parameters:

• Perform safely where the consumer will be operating the dispensing equipment
• Dispense hydrogen at volumes comparable to gasoline dispensing stations in timeframes comparable to gasoline stations
• Deliver a fueling performance that is within the boundaries of consumer tolerance
• Perform with maintenance/incident frequencies comparable to gasoline dispensing systems

This paper will describe the typical components of a hydrogen dispensing and storage system describe the hazards associated with these systems and components describe safety measures currently in place in codes and standards identify outstanding areas of safety concern and measures to address the outstanding areas of concern.

The paper will use incident frequency data from NREL’s Technology Validation project to more quantitatively identify safety concerns in hydrogen dispensing and storage systems.

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.

HyDeploy is a pioneering hydrogen energy project designed to help reduce UK CO2 emissions and reach the Government’s net zero target for 2050.

As the first ever live demonstration of hydrogen in homes HyDeploy aims to prove that blending up to 20% volume of hydrogen with natural gas is a safe and greener alternative to the gas we use now.  It is  providing evidence on how customers don’t have to change their cooking or heating appliances to take the blend which means less disruption and cost for them.  It is also confirming initial findings that customers don’t notice any difference when using the hydrogen blend.

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)

The efficiency of gas sensor application for facilitating the safe use of hydrogen depends to a considerable extent on the response time of the sensor to change in hydrogen concentration. The response and recovery times have been measured for five different hydrogen sensors three commercially available and two promising prototypes which operate at room temperature. Experiments according to ISO 26142 show that most of the sensors surpass much for a concentration change from clean to hydrogen containing air the demands of the standard for the response times t(90) and values of 2 to 16 s were estimated. For an opposite shift to clean air the recovery times t(10) are from 7 to 70 s. Results of transient behaviour can be fitted with an exponential approach. It can be demonstrated that results on transient behaviour depend not only from investigation method and the experimental conditions like gas changing rate and concentration jump as well as from operating parameters of sensors. In comparison to commercial MOS and MIS-FET hydrogen sensors new sensor prototypes operating at room temperature possesses in particular longer recovery times.

Faced with key obstacles such as the short driving range long charging time and limited volume allowance of battery−−powered electric light scooters in Asian cities the aim of this study is to present a passive fuel cell/battery hybrid system without DC−−DC to ensure a compact volume and low cost. A novel topology structure of the passive fuel cell/battery power system for the electric light scooter is proposed and the passive power system runs only on hydrogen. The power performance and efficiency of the passive power system are evaluated by a self−developed test bench before installation into the scooters. The results of this study reveal that the characteristics of stable power output quick response and the average efficiency are as high as 88% during the Shanghainese urban driving cycle and 89.5% during the Chinese standard driving cycle. The results pre‐ sent the possibility that this passive fuel cell/battery hybrid powertrain system without DC−DC is practical for commercial scooters.

This study addresses one of knowledge gaps in hydrogen safety science and engineering i.e. a predictive model for calculation of deterministic separation distances defined by the parameters of a blast wave generated by a high-pressure gas storage tank rupture in a fire. An overview of existing methods to calculate stored in a tank internal (mechanical) energy and a blast wave decay is presented. Predictions by the existing technique and an original model developed in this study which accounts for the real gas effects and combustion of the flammable gas released into the air (chemical energy) are compared against experimental data on high-pressure hydrogen tank rupture in the bonfire test. The main reason for a poor predictive capability of the existing models is the absence of combustion contribution to the blast wave strength. The developed methodology is able to reproduce experimental data on a blast wave decay after rupture of a stand-alone hydrogen tank and a tank under a vehicle. In this study the chemical energy is dynamically added to the mechanical energy and is accounted for in the energy-scaled non-dimensional distance. The fraction of the total chemical energy of combustion released to feed the blast wave is 5% and 9% however it is 1.4 and 30 times larger than the mechanical energy in the stand-alone tank test and the under-vehicle tank test respectively. The model is applied as a safety engineering tool to four typical hydrogen storage applications including onboard vehicle storage tanks and a stand-alone refuelling station storage tank. Harm criteria to people and damage criteria for buildings from a blast wave are selected by the authors from literature to demonstrate the calculation of deterministic separation distances. Safety strategies should exclude effects of fire on stationary storage vessels and require thermal protection of on-board storage to prevent dangerous consequences of high-pressure tank rupture in a fire.

Large-scale experiments examining spherical-flame acceleration in lean hydrogen-air mixtures were performed in a 64 m3 constant-pressure enclosure. Equivalence ratios ranging from 0.33 to 0.57 were examined using detailed front tracking for flame diameters up to 1.2 m through the use of a Background Oriented Schlieren (BOS) technique. From these measurements the critical radii for onset of instability for these mixtures on the order of 2–3 cm were obtained. In addition the laminar burning velocity and rate of flame acceleration as a function of radius were also measured.

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

Building a network of hydrogen refuelling stations is essential to develop the hydrogen economy within transport. Additional hydrogen is regarded a likely key component to store and convert back excess electrical power to secure future energy supply and to improve the quality of biomass-based fuels. Therefore future hydrogen supply and distribution chains will have to address several objectives. Such a complexity is a challenge for risk assessment and risk management of these chains because of the increasing interactions. Improved methods are needed to assess the supply chain as a whole. The method of “Functional modelling” is discussed in this paper. It will be shown how it could be a basis for other decision support methods for comprehensive risk and sustainability assessments.

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

Computational fluid dynamic simulations have been performed in order to study the consequences of a hydrogen release from a pressure swing adsorption installation operating at 30 barg. The simulations were performed using FLACS-Hydrogen software from GexCon. The impact of obstruction partial confinement leak orientation and wind on the explosive cloud formation (size and explosive mass) and on explosion consequences is investigated. Overpressures resulting from ignition are calculated as a function of the time to ignition.

NFPA 2 Hydrogen Technologies Code allows the use of risk-informed approaches to permitting hydrogen fuelling installations through the use of performance-based evaluations of specific hydrogen hazards. However the hydrogen fuelling industry in the United States has been reluctant to implement the performance-based option because the perception is that the required effort is cost prohibitive and there is no guarantee that the Authority Having Jurisdiction (AHJ) would accept the results. This report provides a methodology for implementing a performance-based design of an outdoor hydrogen refuelling station that does not comply with specific prescriptive separation distances. Performance-based designs are a code-compliant alternative to meeting prescriptive requirements. Compliance is demonstrated by evaluating a compliant prescriptive-based refuelling station design with a performance-based design approach using Quantitative Risk Assessment (QRA) methods and hydrogen risk tools. This template utilizes the Sandia-developed QRA tool Hydrogen Risk Analysis Model (HyRAM) to calculate risk values when developing risk-equivalent designs. HyRAM combines reduced-order deterministic models that characterize hydrogen release and flame behaviour with probabilistic risk models to quantify risk values. Each project is unique and this template is not intended to cover unique site-specific characteristics. Instead example content and a methodology are provided for a representative hydrogen refuelling site which can be built upon for new hydrogen applications.

Propagation characteristics of hydrogen-air deflagration need to be understood for an accurate risk assessment. Especially flame propagation velocity is one of the most important factors. Propagation velocity of outwardly propagating flame has been estimated from burning velocity of a flat flame considering influence of thermal expansion at a flame front; however this conventional method is not enough to estimate an actual propagation velocity because flame propagation is accelerated owing to cellular flame front caused by intrinsic instability in hydrogen-air deflagration. Therefore it is important to understand the dynamic propagation characteristics of hydrogen-air deflagration. We performed explosion tests in a closed chamber which has 300 mm diameter windows and observed flame propagation phenomena by using Schlieren photography. In the explosion experiments hydrogen-air mixtures were ignited at atmospheric pressure and room temperature and in the range of equivalence ratio from 0.2 to 1.0. Analyzing the obtained Schlieren images flame radius and flame propagation velocity were measured. As the result cellular flame fronts formed and flame propagations of hydrogen–air mixture were accelerated at the all equivalence ratios. In the case of equivalent ratio φ = 0.2 a flame floated up and could not propagate downward because the influence of buoyancy exceeded a laminar burning velocity. Based upon these propagation characteristics a favorable estimation method of flame propagation velocity including influence of flame acceleration was proposed. Moreover the influence of intrinsic instability on propagation characteristics was elucidated.

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.

An energy production from the combination of dehydrogenation and combined cycle power generation is proposed. The delivered system is established from three main modules: dehydrogenation combustion and combined cycle. The heat in the system is circulated thoroughly to enhance the energy efficiency due to optimum energy recovery. The Pt/Al2O3 catalyst is applied in the dehydrogenation module due to superior activity to accelerate the dehydrogenation of MCH. The toluene emitted from the MCH is recirculated to the hydrogenation plant while the hydrogen is further utilized as the fuel in the combustion. Although the high-temperature condition is necessary to perform high yield dehydrogenation the proposed system is capable of carrying out self-heating mechanism with no external heat. With the optimum configuration the delivered system can produce 100.0 MW of electricity from 100 t/h of MCH with 50.19% of energy efficiency.

Hydrogen is considered to be a very promising potential energy carrier due to its excellent characteristics such as abundant resources high fuel value clean and renewable. Its safety features greatly influence the potential use. Several safety problems need to be analyzed before using in transportation industry. With the development of the tunnel transportation technology the safe use of hydrogen in tunnels will receive a lot of research attentions. In this article the risk associated with hydrogen release from onboard high-pressure vessels and the induced combustion in tunnels was analyzed using the Partially Averaged Navier–Stokes (PANS) turbulence model. The influences of the tunnel ventilation facilities on the hydrogen flow characteristics and the flammable hydrogen cloud sizes were studied. The tunnel layouts were designed according to the subsea tunnel. And a range of longitudinal ventilation conditions had been considered to investigate the hydrogen releases and the sizes of the flammable hydrogen cloud. Then the hydrogen combustion simulation was carried out after the fixed leaking time. The overpressures induced after the ignition of leaking hydrogen were studied. The influences of ventilation and ignition delay time on the overpressure were also investigated. The main aim was to research the phenomena of hydrogen releases and combustion risk inside subsea tunnels and to lay the foundation of risk assessment methodology developed for hydrogen energy applications on transportation.

HyRAM is a methodology and accompanying software toolkit which is being developed to provide a platform for integration of state-of-the-art validated science and engineering models and data relevant to hydrogen safety. As such the HyRAM software toolkit establishes a standard methodology for conducting quantitative risk assessment (QRA) and consequence analysis relevant to assessing the safety of hydrogen fueling and storage infrastructure. The HyRAM toolkit integrates fast-running deterministic and probabilistic models for quantifying risk of accident scenarios for predicting physical effects and for characterizing the impact of hydrogen hazards (thermal effects from jet fires thermal and pressure effects from deflagrations and detonations). HyRAM incorporates generic probabilities for equipment failures for nine types of hydrogen system components generic probabilities for hydrogen ignition and probabilistic models for the impact of heat flux and pressure on humans and structures. These are combined with fast-running computationally and experimentally validated models of hydrogen release and flame behaviour. HyRAM can be extended in scope via user contributed models and data. The QRA approach in HyRAM can be used for multiple types of analyses including codes and standards development code compliance safety basis development and facility safety planning. This manuscript discusses the current status and vision for HyRAM.

This paper describes an experimental programme on vented hydrogen deflagrations which formed part of the Hyindoor project carried out for the EU Fuel Cells and Hydrogen Joint Undertaking. The purpose of this study was to investigate the validity of analytical models used to calculate overpressures following a low concentration hydrogen deflagration. Other aspects of safety were also investigated such as lateral flame length resulting from explosion venting. The experimental programme included the investigation of vented hydrogen deflagrations from a 31 m3 enclosure with a maximum internal overpressure target of 10 kPa (100 mbar). The explosion relief was provided by lightly covered openings in the roof or sidewalls. Uniform and stratified initial hydrogen distributions were included in the test matrix and the location of the ignition source was also varied. The maximum hydrogen concentration used within the enclosure was 14% v/v. The hydrogen concentration profile within the enclosure was measured as were the internal and external pressures. Infrared video images were obtained of the gases vented during the deflagrations. Findings show that the analytical models were generally conservative for overpressure predictions. Flame lengths were found to be far less than suggested by some guidance. Along with the findings the methodology test conditions and corresponding results are presented.

The debate on low-carbon heat in Europe has become focused on a narrow range of technological options and has largely neglected hydrogen and fuel cell technologies despite these receiving strong support towards commercialisation in Asia. This review examines the potential benefits of these technologies across different markets particularly the current state of development and performance of fuel cell micro-CHP. Fuel cells offer some important benefits over other low-carbon heating technologies and steady cost reductions through innovation are bringing fuel cells close to commercialisation in several countries. Moreover fuel cells offer wider energy system benefits for high-latitude countries with peak electricity demands in winter. Hydrogen is a zero-carbon alternative to natural gas which could be particularly valuable for those countries with extensive natural gas distribution networks but many national energy system models examine neither hydrogen nor fuel cells for heating. There is a need to include hydrogen and fuel cell heating technologies in future scenario analyses and for policymakers to take into account the full value of the potential contribution of hydrogen and fuel cells to low-carbon energy systems.

Hydrogen stored or transported as ammonia has been proposed as a sustainable carbon-free alternative for fossil-fuels in high-temperature industrial processes including power generation. Although ammonia itself is toxic and exhibits both a low flame speed and calorific value it rapidly decomposes to hydrogen in high temperature environments suggesting the potential use in applications which incorporate fuel preheating. In this work the rate of ammonia-to-hydrogen decomposition is initially simulated at elevated temperatures to indicate the proportion of fuel conversion in conditions similar to gas pipelines gas-turbines or furnaces with exhaust-gas recirculation. Following this different proportions of hydrogen and ammonia are numerically simulated in independent zero-dimensional plug-flow-reactors at pressures ranging from atmospheric to 50 MPa and pre-heating temperatures from 600 K to 1600 K. Deflagration of very-lean-to-fuel-rich mixtures was investigated employing air as the oxidant stream. Analyses of these reactors provide estimates of autoignition thresholds of the hydrogen/ammonia blends which are relevant for the safe implementation and operation of hydrogen/ammonia blends or pure ammonia as a fuel source. Further operational considerations are subsequently identified for using ammonia or hydrogen/ammonia blends as a hydrogen fuel carrier by quantifying residual concentrations of hydrogen and ammonia fuel products as well as other toxic emissions within the hot exhaust products.

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

This paper describes a 1-D numerical model for the prediction of heat and mass transfer through an intumescent paint that is applied to an on-board high-pressure GH2 storage tank. The intumescent paint is treated as a composite system consisting of three general components decomposing in accordance with independent finite reaction rates. A moving mesh that is employed for a better prediction of the expansion process of the intumescent paint is based on the local changes of heat and mass. The numerical model is validated against experiments by Cagliostro et al. (1975). The overall model results are used to estimate effect of intumescent paint on fire resistance of carbon-fibre reinforced GH2 storage.

The HyDeploy Project seeks to address a key issue for UK customers: how to reduce the carbon they emit in heating their homes. The UK has a world class gas grid delivering heat conveniently and safely to over 83% of homes. Emissions could be reduced by lowering the carbon content of gas through blending with hydrogen. Compared with solutions such as heat pumps this means that customers would not need disruptive and expensive changes in their homes. This Network Innovation Competition (NIC) funded project seeks to establish the level of hydrogen that can be safely blended with natural gas for transport and use in a UK network.

Under its Smart Energy Network Demonstration innovation programme Keele University is establishing its electricity and gas networks as facilities to drive forward innovation in the energy sector. The objective of HyDeploy is to trial natural gas blended with potentially up to 20% volume of hydrogen in a part of the Keele gas network. Before any hydrogen can be blended with natural gas in the network the percentage of hydrogen to be delivered must be approved by the Health and Safety Executive (HSE). It must be satisfied that the approved blended gas will be as safe to use as normal gas. Any approval will be given as an exemption to the Gas Safety (Management) Regulations. These regulations ensure the safe use and management of gas through the gas network in the UK. The evidence presented to the HSE comprises critically appraised literature combined with the results from a specifically commissioned experimental and testing programme. Based on engagement with all local customers this includes detailed safety checks on the network appliances and installations at Keele. Subject to approval by the HSE the hydrogen production and grid injection units will be installed and an extensive trial programme of blending will be undertaken. If hydrogen were blended at 20% volume with natural gas across the UK it would save around 6 million tonnes of carbon dioxide emissions every year the equivalent of taking 2.5 million cars off the road.

This report and any attachment is freely available on the ENA Smarter Networks Portal here. IGEM Members can download the report and any attachment directly by clicking on the pdf icon above.

Fuel Cell Vehicles (FCVs) are a disruptive innovation and are currently looking towards niche market entry. However commercialisation has been unsuccessful thus far and there is a limited amount of literature that can guide their market entry. In this paper a historical case study is undertaken which looks at Tesla Motors high-end encroachment market entry strategy. FCVs have been compared to Tesla vehicles due to their similarities; both are disruptive innovations both are high cost and both are zero emission vehicles. Therefore this paper looks at what can be learned form Tesla Motors successful market entry strategy and proposes a market entry strategy for FCVs. It was found that FCVs need to enact a paradigm shift from their current market entry strategy to one of high-end encroachment. When this has been achieved FCVs will have greater potential for market penetration.

As the UK’s largest emitter of greenhouse gases the supply of domestic industrial and commercial heat must be decarbonised if the UK is to meet its climate change targets.<br/><br/>This report publishes the outcomes from Phase 1 of the Energy Technologies Institute’s Smart Systems and Heat programme highlighting that for the UK to transition to a low carbon heating system it must understand consumer needs and behaviours while connecting this with the development and integration of technologies and new business models.<br/><br/>Written by the ETI with support from the Energy Systems Catapult this report tackles three interconnected areas: heating needs and controls within the home; heating infrastructure and building retrofit at a local level; and the operation and governance of the whole system.<br/><br/>The research also shows that as part of a low carbon heating system upgrade advanced controls are critical to performance sizing and operating costs enabling smaller appliances and lower peak electricity demands and maximising the efficiency of existing infrastructure. With significant fabric retrofits potentially required in around 10 million of the existing 28 million dwellings in the UK housing stock the report recommends that building new homes to be both very efficient and “low carbon ready” is a low regret decision which should be progressed with some urgency.

Portable H2 sensor was made by using mass spectrometer for the outside monitoring experiment: the leak test the replacement test of gas pipe line the combustion test the explosion experiment the H2 diffusion experiment and the recent issue of the exhaust gas of Fuel Cell Vehicle. In order to check the real time concentration of H2 in various conditions even in the highly humid condition the system volume of the sampling route was minimized with attaching the humidifier. Also to calibrate H2 concentration automatically the specific concentration H2 small cylinder was mounted in the system. In the experiment when H2 gas was introduced in the N2 flow or air in the tube or the high-pressure bottle highly concentrated H2 phases were observed by this sensor without diffusion. This H2 sensor can provide the real time information of the hydrogen molecules and the clouds. The basic characterization of this sensor showed 0-100% H2 concentrations within 2ms. Our observation showed the size of the high concentration phase of H2 and the low concentration phase after mixing process. The mixed and unmixed H2 unintended concentration of cloud gas the high speed small cluster of hydrogen molecules in purged gas were explored by this real time monitoring system.

With the anticipated introduction of hydrogen fuel cell vehicles to the market there is an increasing need to address the fire resistance of hydrogen cylinders for onboard storage. Sufficient fire resistance is essential to ensure safe evacuation in the event of car fire accidents. The authors have developed a Finite Element (FE) model for predicting the thermal response of composite hydrogen cylinders within the frame of the open source FE code Elmer. The model accounts for the decomposition of the polymer matrix and effects of volatile gas transport in the composite. Model comparison with experimental data has been conducted using a classical one-dimensional test case of polymer composite subjected to fire. The validated model was then used to analyze a type-4 hydrogen cylinder subjected to an engulfing external propane fire mimicking a published cylinder fire experiment. The external flame is modelled and simulated using the open source code FireFOAM. A simplified failure criteria based on internal pressure increase is subsequently used to determine the cylinder fire resistance.

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:

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.

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

In the event of a fire the TPRD (Thermally activated Pressure Relief Device) prevents the high-pressure full composite cylinder from bursting by detecting high temperatures and releasing the pressurized gas. The current safety performance of both the vessel and the TPRD is demonstrated by an engulfing bonfire test. However there is no requirement concerning the effect of the TPRD release which may produce a hazardous hydrogen flame due to the high flow-rate of the TPRD. It is necessary to understand better the behavior of an unprotected composite cylinder exposed to fire in order to design appropriate protection for it and to be able to reduce the length of any potential hydrogen flame. For that purpose a test campaign was performed on a 36 L cylinder with a design pressure of 70 MPa. The time from fire exposure to the bursting of this cylinder (the burst delay) was measured. The influence of the fire type (partial or global) and the influence of the pressure in the cylinder during the exposure were studied. It was found that the TPRD orifice diameter should be significantly reduced compared to current practice.

Due to its promising potential to overcome the challenge of thermal endurance of liquid hydrogen storage systems cryo-compressed hydrogen storage (CcH2) is regarded as a verypromising physical storage solution in particular for use in larger passenger vehicles with high energy and long range requirements. A probabilistic approach for validation of safe operation of CcH2 storage systems under automotive requirements and experimental results on life-cycle testing is presented. The operational regime of BMW's CcH2 storage covers pressures of up to 35 MPa and temperatures from +65 C down to -240 C applying high loads on composite and metallic materials of the cryogenic pressure vesselcompared to ambient carbon fiber reinforced pressure vessels. Thus the proof of fatigue strength under combined pressure and deep temperature cyclic loads remains a challenging exercise. Furthermore it will be shown that the typical automotive safety and life-cycle requirements can be fulfilled by the CcH2 vehicle storage system and moreover that the CcH2 storage system can even feature safety advantages over a CGH2 storage system mainly due to the advantageous thermodynamic properties of cryogenic hydrogen the lower storage pressure and due to the intrinsic protection against intrusion through the double-shell design.

In recent years new-found interest in the hydrogen economy from both industry and academia has helped to shed light on its potential. Hydrogen can enable an energy revolution by providing much needed flexibility in renewable energy systems. As a clean energy carrier hydrogen offers a range of benefits for simultaneously decarbonizing the transport residential commercial and industrial sectors. Hydrogen is shown here to have synergies with other low-carbon alternatives and can enable a more cost-effective transition to de-carbonized and cleaner energy systems. This paper presents the opportunities for the use of hydrogen in key sectors of the economy and identifies the benefits and challenges within the hydrogen supply chain for power-to-gas power-to-power and gas-to-gas supply pathways. While industry players have already started the market introduction of hydrogen fuel cell systems including fuel cell electric vehicles and micro-combined heat and power devices the use of hydrogen at grid scale requires the challenges of clean hydrogen production bulk storage and distribution to be resolved. Ultimately greater government support in partnership with industry and academia is still needed to realize hydrogen's potential across all economic sectors.

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There are new safety challenges with an increased use of hydrogen e.g. that people may not see dangerous jet flames in case of an incident. Compared to conventional fuels hydrogen has very different characteristics and physical properties and is stored at very high pressure or at very low temperatures. Thus the nature of hazard scenarios will be very different. Consequence modelling of ventilation releases explosions and fires can be used to predict and thus understand hazards. In order to describe the detailed development of a hazard scenario and evaluate ways of mitigation 3D Computational Fluid Dynamics (CFD) models will be required. Even with accurate modelling the communication of risk can be challenging. For this visualization in virtual reality (VR) may be of good help in which the CFD model predictions are presented in a realistic 3D environment with the possibility to include sounds like noise from a high pressure release explosion or fire. In cooperation with Statoil Christian Michelsen Research (CMR) and GexCon have developed the VRSafety application. VRSafety can visualize simulation results from FLACS (and another CFD-tool KFX) in an immersive VR-lab or on a PC. VRSafety can further be used to interactively control and start new CFD-simulations during the sessions. The combination of accurate CFD-modelling visualization and interactive use through VRSafety represents a powerful toolbox for safety training and risk communication to first-responders employees media and other stakeholders. It can also be used for lessons learned sessions studying incidents and accidents and to demonstrate what went wrong and how mitigation could have prevented accidents from happening. This paper will describe possibilities with VRSafety and give examples of use.

Hydrogen (H2 ) can be a promising energy carrier for decarbonizing the economy and especially the transport sector which is considered as one of the sectors with high carbon emissions due to the extensive use of fossil fuels. H2 is a nontoxic energy carrier that could replace fossil fuels. Fuel Cell Electric Vehicles (FCEVs) can decrease air pollution and reduce greenhouse gases when H2 is produced from Renewable Energy Sources (RES) and at the same time being accessible through a widespread network of Hydrogen Refueling Stations (HRSs). In this study both the sizing of the equipment and financial analysis were performed for an HRS supplied with H2 from the excess electrical energy of a 10 MW wind park. The aim was to determine the optimum configuration of an HRS under the investigation of six different scenarios with various numbers of FCEVs and monthly demands as well as ascertaining the economic viability of each examined scenario. The effect of the number of vehicles that the installation can refuel to balance the initial cost of the investment and the fuel cost in remote regions was investigated. The results showed that a wind-powered HRS could be a viable solution when sized appropriately and H2 can be used as a storage mean for the rejected wind energy. It was concluded that scenarios with low FCEVs penetration have low economic performance since the payback period presented significantly high values.

"Because of the contrasting chemical kinetics of methane and hydrogen combustion the development of blending laws for laminar burning velocity ul and Markstein length for constituent mixtures of CH₄/air and H₂/air presents a formidable challenge. Guidance is sought through a study of analytical expressions for laminar burning velocity. For the prediction of burning velocities of blends six blending laws were scrutinised. The predictions were compared with the measured burning velocities made by Hu et al. under atmospheric conditions. These covered equivalence ratios ranging from 0.6 to 1.3 and the full fuel range for H₂ addition to CH₄. This enabled assessments to be made of the predictive accuracy of the six laws. The most successful law is one developed in the course of the present study involving the mass fraction weighting of the product of ul density heat of reaction and specific heat divided by the thermal conductivity of the mixture. There was less success from attempts to obtain a comparably successful blending law for the flame speed Markstein length Lb despite scrutiny of several possibilities. Details are given of two possible approaches one based on the fractional mole concentration of the deficient reactant. A satisfactory empirical law employs mass fraction weighting of the product ulLb.

This study is driven by the need to understand requirements to safe blow-down of hydrogen onboard storage tanks through a pressure relief device (PRD) inside a garage-like enclosure with low natural ventilation. Current composite tanks for high pressure hydrogen storage have been shown to rupture in 3.5–6.5 min in fire conditions. As a result a large PRD venting area is currently used to release hydrogen from the tank before its catastrophic failure. However even if unignited the release of hydrogen from such PRDs has been shown in our previous studies to result in unacceptable overpressures within the garage capable of causing major damage and possible collapse of the structure. Thus to prevent collapse of the garage in the case of a malfunction of the PRD and an unignited hydrogen release there is a clear need to increase blow-down time by reducing PRD venting area. Calculations of PRD diameter to safely blow-down storage tanks with inventories of 1 5 and 13 kg hydrogen are considered here for a range of garage volumes and natural ventilation expressed in air changes per hour (ACH). The phenomenological model is used to examine the pressure dynamics within a garage with low natural ventilation down to the known minimum of 0.03 ACH. Thus with moderate hydrogen flow rate from the PRD and small vents providing ventilation of the enclosure there will be only outflow from the garage without any air intake from outside. The PRD diameter which ensures that the pressure in the garage does not exceed a value of 20 kPa (accepted in this study as a safe overpressure for civil structures) was calculated for varying garage volumes and natural ventilation (ACH). The results are presented in the form of simple to use engineering nomograms. The conclusion is drawn that PRDs currently available for hydrogen-powered vehicles should be redesigned along with either a change of requirements for the fire resistance rating or innovative design of the onboard storage system as hydrogen-powered vehicles are intended for garage parking. Further research is needed to develop safety strategies and engineering solutions to tackle the problem of fire resistance of onboard storage tanks and requirements to PRD performance. Regulation codes and standards in the field should address this issue.

The scenario of detonative ignition in shocked mixture is significant because it is a contributor to deflagration to detonation transition for example following shock reflections. However even in one dimension simulation of ignition between a contact surface or a flame and a shock moving into a combustible mixture is difficult because of the singular nature of the initial conditions. Initially as the shock starts moving into reactive mixture the region filled with reactive mixture has zero thickness. On a fixed grid the number of grid points between the shock and the contact surface increases as the shock moves away from the latter. Due to initial lack of resolution in the region of interest staircasing may occur whereby the resulting plots consist of jumps between few values a few grid points and these numerical artifacts are amplified by the chemistry which is very sensitive to temperature leading to unreliable results. The formulation is transformed replacing time and space by time and space over time as the independent variables. This frame of reference corresponds to the self-similar formulation in which the non-reactive problem remains stationary and the initial conditions are well-resolved. Additionally a solution obtained from short time perturbation is used as initial condition at a time still short enough for the perturbation to be very accurate but long enough so that there is sufficient resolution. The numerical solution to the transformed problem is obtained using an essentially non-oscillatory algorithm which is adequate not only for the early part of the process but also for the latter part when chemistry leads to appearance of a shock and eventually a detonation wave is formed. A validation study was performed and the results were compared with the literature for single step Arrhenius chemistry. The method and its implementation were found to be effective. Results are presented for values of activation energy ranging from mild to stiff.

As a developing country the Philippines must balance its rapid industrialization efforts with the realities and consequences of climate change on the country. A feasible option to achieve this is increasing the share of renewables in power generation coupled with energy storage technology. This paper examines the present situation and opportunities for development of hydrogen and fuel cell technology in the Philippines as promising alternatives with proven applications in niche energy demand sectors aside from renewables integration. Although the Philippines is considered a latecomer there is significant renewable resource potential available local experts and trained talents and enabling legislations in the country that provide opportunities in harnessing fuel cell technologies for the transition to energy self-sufficient and low-carbon society. Current advancement of the technology in the country is limited to an initial 5-year roadmap focused on component development from cheap and local materials. Provisions for large-scale hydrogen infrastructure have not yet been realized which is comparable to the early stages of development in other countries that are also pursuing fuel cell technology. Strong industry-academe partnerships should be pursued through a specific legislated agency to ensure future development of this technology for the country’s benefit. Lastly applications in distributed power generation poised to be a lucrative direction as demonstration and validation with other potential uses such as transportation remains a challenge.

Low-temperature electrolysis by using polymer electrolyte membranes (PEM) can play an important role in hydrogen energy transition. This work presents a study on the performance of a proton exchange membrane in the water electrolysis process at room temperature and atmospheric pressure. In the perspective of applications that need a device with small volume and low weight a miniaturized electrolysis cell with a 36 cm2 active area of PEM over a total surface area of 76 cm2 of the device was used. H2 and O2 production rates electrical power energy efficiency Faradaic efficiency and polarization curves were determined for all experiments. The effects of different parameters such as clamping pressure and materials of the electrodes on polarization phenomena were studied. The PEM used was a catalyst-coated membrane (Ir-Pt-Nafion™ 117 CCM). The maximum H2 production was about 0.02 g min−1 with a current density of 1.1 A cm−2 and a current power about 280 W. Clamping pressure and the type of electrode materials strongly influence the activation and ohmic polarization phenomena. High clamping pressure and electrodes in titanium compared to carbon electrodes improve the cell performance and this results in lower ohmic and activation resistances.

Experience makes a superior teacher. Sharing the details surrounding safety events is one of the best ways to help prevent their recurrence elsewhere. This approach requires an open non-punitive environment to achieve broad benefits. The Hydrogen Incident Reporting Tool (www.h2incidents.org) is intended to facilitate the sharing of lessons learned and other relevant information gained from actual experiences using and working with hydrogen and hydrogen systems. Its intended audience includes those involved in virtually any aspect of hydrogen technology systems and use with an emphasis towards energy and transportation applications. The database contains records of safety events both publicly available and/or voluntarily submitted. Typical records contain a general description of the occurrence contributing factors equipment involved and some detailing of consequences and changes that have been subsequently implemented to prevent recurrence of similar events in the future. The voluntary and confidential nature and other characteristics surrounding the database mean that any analysis of apparent trends in its contents cannot be considered statistically valid for a universal population. A large portion of reported incidents have occurred in a laboratory setting due to the typical background of the reporting projects for example. Yet some interesting trends are becoming apparent even at this early stage of the database’s existence and general lessons can already be taken away from these experiences. This paper discusses the database and a few trends that have already become apparent for the reported incidents. Anticipated future uses of this information are also described. This paper is intended to encourage wider participation and usage of the incidents reporting database and to promote the safety benefits offered by its contents.

Numerical simulations have been carried out for spontaneous ignition of pressurized hydrogen release directly into air. Results showed a possible mechanism for spontaneous ignition due to molecular diffusion. To accurately calculate the molecular transport of species momentum and energy in a multi-component gaseous mixture a mixture-averaged multi-component approach was employed in which thermal diffusion is accounted for. To reduce false numerical diffusion extremely fine meshes were used along with the ALE (Arbitrary Lagrangian-Eulerian) method. The ALE method was employed to track the moving contact surface with moving clustered grids. A detailed kinetic scheme with 21 elementary steps and 8 reactive chemical species was implemented for combustion chemistry. The scheme gives due consideration to third body reactions and reaction-rate pressure-dependant “fall-off” behavior. The autoignition of pressurized hydrogen release was previously observed in laboratory tests [2-3] and suspected as possible cause of some accidents. The present numerical study successfully captured this scenario. Autoignition was predicted to first take place at the tip region of the hydrogen-air contact surface due to mass and energy exchange between low temperature hydrogen and shock-heated air at the contact surface through molecular diffusion. The initial flame thickness is extremely thin due to the limiting molecular diffusion. The combustion region extends downward along the contact surface as it moves downstream. As the hydrogen jet developed downstream the front contact surface tends to be distorted by the developed flow of the air. Turbulence plays an important role in mixing at the region of the distorted contact surface. This is thought to be a major factor for the initial laminar flame to turn into a final stable turbulent flame.

Hydrogen production through methanol reforming processes has been stimulated over the years due to increasing interest in fuel cell technology and clean energy production. Among different types of methanol reforming the steam reforming of methanol has attracted great interest as reformate gas stream where high concentration of hydrogen is produced with a negligible amount of carbon monoxide. In this review recent progress of the main reforming processes of methanol towards hydrogen production is summarized. Different catalytic systems are reviewed for the steam reforming of methanol: mainly copper- and group 8–10-based catalysts highlighting the catalytic key properties while the promoting effect of the latter group in copper activity and selectivity is also discussed. The effect of different preparation methods different promoters/stabilizers and the formation mechanism is analyzed. Moreover the integration of methanol steam reforming process and the high temperature–polymer electrolyte membrane fuel cells (HT-PEMFCs) for the development of clean energy production is discussed.