United Kingdom

The United Kingdom has a vast scientific base across the entire Hydrogen and Fuel Cell research landscape with a world class academic community coupled with significant industrial activity from both UK-based Hydrogen and Fuel Cell companies and global companies with a strong presence within the country. The Hydrogen and Fuel Cell (H2FC) SUPERGEN Hub funded by the Engineering and Physical Sciences Research Council (EPSRC) was established in 2012 as a five-year programme to bring the UK's H2FC research community together. Here we present the UK's current Hydrogen and Fuel Cell activities along with the role of the H2FC SUPERGEN Hub.

In many processes where hydrogen may be released from below a liquid surface there has been concern regarding how such releases might ultimately disperse in an ullage space. Knowledge of the extent and persistence of any flammable volume formed is needed for hazardous area classification as well as for validation of explosion modelling or experiments. Following an initial release of hydrogen the overall process can be subdivided into three stages (i) rise and possible break-up of a bubble in the liquid (ii) formation and bursting of a thin gas-liquid-gas interface at the liquid surface and (iii) dispersion of the released gas. An apparatus based on a large glass sided water tank has been constructed which employs two synchronised high-speed imaging systems to record the behaviour of hydrogen bubble release and dispersion. A high-speed digital video system records the rising of the bubbles and the formation and bursting of the gas-liquid-gas interface at the liquid surface. An additional schlieren system is used to visualise the hydrogen release as bubbles burst at the liquid surface. The bubble burst mechanism can clearly be described from the results obtained. Following the nucleation of a hole surface tension causes the liquid film to peel back rapidly forming a ring/torus of liquid around the enlarging hole. This process lasts only a few milliseconds. Although some hydrogen can be seen to be expelled from the bubble much seems to remain in place as the film peels away. To assess the extent of the flammable plume following a bubble burst the apparatus was modified to include an electric-arc igniter. In order to identify plumes coincident in space with the igniter a schlieren system was built capable of recording simultaneously in two orthogonal directions. This confirmed that clouds undetected by the schlerien imaging could not be ignited with the electric arc igniter.

Decarbonization of the shipping sector is inevitable and can be made by transitioning into low‐ or zero‐carbon marine fuels. This paper reviews 22 potential pathways including conventional Heavy Fuel Oil (HFO) marine fuel as a reference case “blue” alternative fuel produced from natural gas and “green” fuels produced from biomass and solar energy. Carbon capture technology (CCS) is installed for fossil fuels (HFO and liquefied natural gas (LNG)). The pathways are compared in terms of quantifiable parameters including (i) fuel mass (ii) fuel volume (iii) life cycle (Well‐To‐ Wake—WTW) energy intensity (iv) WTW cost (v) WTW greenhouse gas (GHG) emission and (vi) non‐GHG emissions estimated from the literature and ASPEN HYSYS modelling. From an energy perspective renewable electricity with battery technology is the most efficient route albeit still impractical for long‐distance shipping due to the low energy density of today’s batteries. The next best is fossil fuels with CCS (assuming 90% removal efficiency) which also happens to be the lowest cost solution although the long‐term storage and utilization of CO2 are still unresolved. Biofuels offer a good compromise in terms of cost availability and technology readiness level (TRL); however the non‐GHG emissions are not eliminated. Hydrogen and ammonia are among the worst in terms of overall energy and cost needed and may also need NOx clean‐up measures. Methanol from LNG needs CCS for decarbonization while methanol from biomass does not and also seems to be a good candidate in terms of energy financial cost and TRL. The present analysis consistently compares the various options and is useful for stakeholders involved in shipping decarbonization.

A key element in the safe operation of a modern gas distribution system is gas detection. The addition of hydrogen to natural gas will alter the characteristics of the fuel and therefore its impact on gas detection must be considered. It is important that gas detectors remain sufficiently sensitive to the presence of hydrogen and natural gas mixtures and that they do not lead to false readings. This paper presents analyses of work performed as part of the Office for Gas and Energy Markets (OFGEM) funded HyDeploy project on the response of various natural gas industry detectors to blended mixtures up to 20 volume percent (vol%) of hydrogen in natural gas. The scope of the detectors under test included survey instruments and personal monitors that are used in the gas industry. Four blend ratios were analysed (0 10 15 and 20 vol% hydrogen in natural gas). The laboratory testing undertaken investigated the following:

• Flammable response to blends in the ppm range (0-0.2 vol%);
• Flammable response to blends in the lower explosion limit range (0.2-5 vol%);
• Flammable response to blends in the volume percent range (5-100 vol%);
• Oxygen response to blends in the volume percent range (0-25 vol%); and
• Carbon monoxide response to blends in the ppm range (0-1000 ppm).

Catalytic and thermal conductivity based flammable detectors in the volume percent range are as expected affected in the form of a relative increase in output. All of the carbon monoxide detectors tested were found to be cross-sensitive to hydrogen in the blended mixtures tested at levels which have the potential to cause false alarms at current permissible leakage rates. In summary a number of measurement ranges across multiple detectors commonly used in the gas industry have been found to be cross-sensitive to hydrogen in natural gas blends to differing degrees. This required the HyDeploy project to select alternative instruments for the purpose of gas detection as part of the trial. This paper relates to the preparatory work to introduce hydrogen into the Keele closed network.

As the offshore energy landscape transitions to renewable energy useful decommissioned or abandoned oil and gas infrastructure can be repurposed in the context of the circular economy. Oil and gas platforms for example offer opportunity for hydrogen (H2) production by desalination and electrolysis of sea water using offshore wind power. However as H2 storage and transport may prove challenging this study proposes to react this H2 with the carbon dioxide (CO2) stored in depleted reservoirs. Thus producing a more transportable energy carriers like methane or methanol in the reservoir. This paper presents a novel thermodynamic analysis of the Goldeneye reservoir in the North Sea in Aspen Plus. For Goldeneye which can store 30 Mt of CO2 at full capacity if connected to a 4.45 GW wind farm it has the potential to produce 2.10 Mt of methane annually and abate 4.51 Mt of CO2 from wind energy in the grid.

Spontaneous ignition of compressed hydrogen release through a length of tube with different internal geometries is numerically investigated using our previously developed model. Four types of internal geometries are considered: local contraction local enlargement abrupt contraction and abrupt enlargement. The presence of internal geometries was found to significantly increase the propensity to spontaneous ignition. Shock reflections from the surfaces of the internal geometries and the subsequent shock interactions further increase the temperature of the combustible mixture at the contact region. The presence of the internal geometry stimulates turbulence enhanced mixing between the shock-heated air and the escaping hydrogen resulting in the formation of more flammable mixture. It was also found that forward-facing vertical planes are more likely to cause spontaneous ignition by producing the highest heating to the flammable mixture than backward-facing vertical planes.

The paper describes CFD modelling of lean hydrogen mixture deflagrations. Large eddy simulation (LES) premixed combustion model developed at the University of Ulster to account phenomena related to large-scale deflagrations was adjusted specifically for lean hydrogen-air flames. Experiments by Kumar (2006) on lean hydrogen-air mixture deflagrations in a 120 m3  vessel at initially quiescent conditions were simulated. 10% by volume hydrogen-air mixture was chosen for simulation to provide stable downward flame propagation; experiments with the smallest vent area 0.55 m2  were used as having the least apparent flame instabilities affecting the pressure dynamics. Deflagrations with igniter located centrally near vent and at far from the vent wall were simulated. Analysis of simulation results and experimental pressure dynamics demonstrated that flame instabilities developing after vent opening made the significant contribution to maximum overpressure in the considered experiments. Potential causes of flame instabilities are discussed and their comparative role for different igniter locations is demonstrated.

A numerical approach is developed to simulate detonation propagation attenuation failure and re-initiation in hydrogen–air mixture. The aim is to study the condition under which detonations may fail or re-initiate in bifurcated tubes which is important for risk assessment in industrial accidents. A code is developed to solve compressible multidimensional transient reactive Navier–Stokes equations. An Implicit Large Eddy Simulation approach is used to model the turbulence. The code is developed and tested to ensure both deflagrations (when detonation fails) and detonations are simulated correctly. The code can correctly predict the flame properties as well as detonation dynamic parameters. The detonation propagation predictions in bifurcated tubes are validated against the experimental work of Wang et al. [12] and found to be in good agreement with experimental observations.

This paper describes experimental and numerical modelling results from an investigation into the flammability profiles associated with high pressure hydrogen jets released in close proximity to surfaces. This work was performed under a Transnational Access Agreement activity funded by the European Research Infrastructure project H2FC.<br/>The experimental programme involved ignited and unignited releases of hydrogen at pressures of 150 and 425 barg through nozzles of 1.06 and 0.64 mm respectively. The proximity of the release to a ceiling or the ground was varied and the results compared with an equivalent free-jet test. During the unignited experiments concentration profiles were measured using hydrogen sensors. During the ignited releases thermal radiation was measured using radiometers and an infra-red camera. The results show that the flammable volume and flame length increase when the release is in close proximity to a surface. The increases are quantified and the safety implications discussed.<br/>Selected experiments were modelled using the CFD model FLACS for validation purposes and a comparison of the results is also included in this paper. Similarly to experiments the CFD results show an increase in flammable volume when the release is close to a surface. The unstable atmospheric conditions during the experiments are shown to have a significant impact on the results.

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.

We analyze the feasibility of a novel hydrogen fuel cell electric generator to provide power with zero noise and emissions for myriad ground based applications. The hydrogen fuel cell electric generator utilizes a novel scalable apparatus that safely generates 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 sodium hydroxide (NaOH) byproduct of the hydrogen producing reaction is collected within the apparatus for later reprocessing by electrolysis to recover the Na reactant. The detailed analysis shows that the novel hydrogen fuel cell electric generator will be capable of meeting the clean power requirements for residential and commercial buildings including single family homes and light commercial establishments under a wide range of geographic and climatic conditions.

The site at the Health and Safety Executive’s Science and Research Centre in Buxton will carry out controlled tests to establish the critical safety evidence proving that a 100% hydrogen gas network is equally as safe as the natural gas grid heating our homes and businesses today. The results will be critical in determining if it is safe to convert millions of homes across the country from natural gas to hydrogen. H21 which is led by Northern Gas Networks (NGN) the gas distributor for the North of England in partnership with Cadent SGN and Wales & West Utilities HSE Science and Research Centre and DNV-GL is part of a number of gas industry projects designed to support conversion of the UK gas networks to carry 100% hydrogen. Currently about 30% of UK carbon emissions are from the heating of homes businesses and industry. H21 states that a large-scale conversion of the gas grid from natural gas to hydrogen is vital to meeting the Government’s Net Zero targets.

The issue of spontaneous ignition of highly pressurized hydrogen release is of important safety concern e.g. in the assessment of risk and design of safety measures. This paper reports on recent numerical investigation of this phenomenon through releases via a length of tube. This mimics a potential accidental scenario involving release through instrument line. The implicit large eddy simulation (ILES) approach was used with the 5th-order weighted essentially non-oscillatory (WENO) scheme. A mixture-averaged multi-component approach was used for accurate calculation of molecular transport. The thin flame was resolved with fine grid resolution and the autoignition and combustion chemistry were accounted for using a 21-step kinetic scheme.<br/>The numerical study revealed that the finite rupture process of the initial pressure boundary plays an important role in the spontaneous ignition. The rupture process induces significant turbulent mixing at the contact region via shock reflections and interactions. The predicted leading shock velocity inside the tube increases during the early stages of the release and then stabilizes at a nearly constant value which is higher than that predicted by one-dimensional analysis. The air behind the leading shock is shock-heated and mixes with the released hydrogen in the contact region. Ignition is firstly initiated inside the tube and then a partially premixed flame is developed. Significant amount of shock-heated air and well developed partially premixed flames are two major factors providing potential energy to overcome the strong under-expansion and flow divergence following spouting from the tube.<br/>Parametric studies were also conducted to investigate the effect of rupture time release pressure tube length and diameter on the likelihood of spontaneous ignition. It was found that a slower rupture time and a lower release pressure will lead to increases in ignition delay time and hence reduces the likelihood of spontaneous ignition. If the tube length is smaller than a certain value even though ignition could take place inside the tube the flame is unlikely to be sufficiently strong to overcome under-expansion and flow divergence after spouting from the tube and hence is likely to be quenched.

This paper describes a large eddy simulation model of hydrogen spontaneous ignition in a T-shaped channel filled with air following an inertial flat burst disk rupture. This is the first time when 3D simulations of the phenomenon are performed and reproduced experimental results by Golub et al. (2010). The eddy dissipation concept with a full hydrogen oxidation in air scheme is applied as a sub-grid scale combustion model to enable use of a comparatively coarse grid to undertake 3D simulations. The renormalization group theory is used for sub-grid scale turbulence modelling. Simulation results are compared against test data on hydrogen release into a T-shaped channel at pressure 1.2–2.9 MPa and helped to explain experimental observations. Transitional phenomena of hydrogen ignition and self-extinction at the lower pressure limit are simulated for a range of storage pressure. It is shown that there is no ignition at storage pressure of 1.35 MPa. Sudden release at pressure 1.65 MPa and 2.43 MPa has a localised spot ignition of a hydrogen-air mixture that quickly self-extinguishes. There is an ignition and development of combustion in a flammable mixture cocoon outside the T-shaped channel only at the highest simulated pressure of 2.9 MPa. Both simulated phenomena i.e. the initiation of chemical reactions followed by the extinction and the progressive development of combustion in the T-shape channel and outside have provided an insight into interpretation of the experimental data. The model can be used as a tool for hydrogen safety engineering in particular for development of innovative pressure relief devices with controlled ignition.

Bioenergy with carbon capture and storage (BECCS) removes carbon dioxide (CO2) from the atmosphere i.e. negative CO2 emissions. It will likely have an important role in the transition to a net-zero economy by offsetting hard-to-abate greenhouse gas emissions. However there are concerns about the sustainability of large scale BECCS deployment using bioenergy from predominantly primary biomass sources (i.e. dedicated energy crops). Secondary sources of biomass (e.g. waste biomass municipal solid wastes forest/agricultural residues) are potentially an economical and sustainable alternative resource. Furthermore supplementing primary biomass demand with secondary sources could enable the supply of biomass from solely indigenous sources (i.e. from the UK) which could provide economic advantages in a growing global bio-economy.<br/><br/>There is also a growing interest in biomass-derived hydrogen production with CCS (BHCCS) which generates hydrogen and removes CO2 from the atmosphere. Hydrogen could help decarbonise fuel-dependent sectors such as heat industry or transportation. The aim of this study was to determine whether BHCCS could possibly deliver net negative CO2 emissions making comparisons against the other BECCS technologies.

In this podcast David Ledesma talks to Martin Lambert Head of OIES Hydrogen Research about the key messages from the recent European Hydrogen Conference and how they fit with the ongoing research in OIES.   In particular they cover the heightened energy security concerns following the Russian invasion of Ukraine and hydrogen ambitions in the REPowerEU document published by the European Commission in early March 2002.   They then go on to talk about the growing realism about where hydrogen is more likely to play a role and some of the key challenges to be overcome. Addressing the challenges of creating business cases for use of hydrogen in specific sectors and for transporting it to customers the conversation also addresses the importance of hydrogen storage and the recognition that this area needs more focus both technically and commercially.   Finally they talk about the geopolitics of hydrogen and how energy security concerns may influence future development pathways.

The podcast can be found on their website

The absorption of CO2 is of importance in carbon capture utilization and storage technology for greenhouse gas control. In the present work we clarified the mechanism of how metal-based ionic liquids (MBILs) Bmim[XCln]m (X is the metal atom) enhance the CO2 absorption capacity of ILs via performing molecular dynamics simulations. The sparse hydrogen bond interaction network constructed by CO2 and MBILs was identified through the radial distribution function and interaction energy of CO2-ion pairs which increase the absorption capacity of CO2 in MBILs. Then the dynamical properties including residence time and self-diffusion coefficient confirmed that MBILs could also promote the diffusion process of CO2 in ILs. That's to say the MBILs can enhance the CO2 absorption capacity and the diffusive ability simultaneously. Based on the analysis of structural energetic and dynamical properties the CO2 absorption capacity of MBILs increases in the order Cl− → [ZnCl4]2-→ [CuCl4]2-→ [CrCl4]- → [FeCl4]- revealing the fact that the short metal–Cl bond length and small anion volume could facilitate the performance of CO2 absorbing process. These findings show that the metal–Cl bond length and effective volume of the anion can be the effective factors to regulate the CO2 absorption process which can also shed light on the rational molecular design of MBILs for CO2 capture and other key chemical engineering processes such as IL-based gas sensors nano-electrical devices and so on.

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.

To facilitate the transition to the hydrogen economy the EU project NATURALHY is studying the potential for the existing natural gas pipeline networks to transport hydrogen together with natural gas to end-users. Hydrogen may then be extracted for hydrogen fuel-cell applications or the mixture used directly by consumers in existing gas-fired equipment with the benefit of lower carbon emissions. The existing gas pipeline networks are designed constructed and operated to safely transport natural gas mostly methane. However hydrogen has significantly different properties that may adversely affect both the integrity of the network and thereby increase the likelihood of an accidental leak and the consequences if the leak finds a source of ignition. Consequently a major part of the NATURALHY project is focused on assessing how much hydrogen could be introduced into the network without adversely impacting on the safety of the network and the risk to the public. Hydrogen is more reactive than natural gas so the severity of an explosion following an accidental leak may be increased. This paper describes field-scale experiments conducted to measure the overpressures generated by ignition of methane/hydrogen/air mixtures in a congested but unconfined region. Such regions may be found in the gas handling and metering stations of the pipeline networks. The 3 m x 3 m x 2 m high congested region studied contained layers of pipes. The composition of the methane/hydrogen mixture used was varied from 0% hydrogen to 100% hydrogen. On the basis of the experiments performed the maximum overpressures generated by methane/hydrogen mixtures with 25% (by volume) or less hydrogen content are not likely to be much more than those generated by methane alone. Greater percentages of hydrogen did significantly increase the explosion overpressure.

We analytically investigated the influence of light hydrocarbons on turbulent premixed H2/air atmospheric flames under lean conditions in view of safe handling of H2 systems applications in H2 powered IC engines and gas turbines and also with an orientation towards modelling of H2 combustion. For this purpose an algebraic flame surface wrinkling model included with pressure and fuel type effects is used. The model predictions of turbulent premixed flames are compared with the set of corresponding experimental data of Kido et al. (Kido Nakahara et al. 2002). These expanding spherical flame data include H2–air mixtures doped with CH4 and C3H8 while the overall equivalence ratio of all the fuel/air mixtures is fixed at 0.8 for constant unstretched laminar flame speed of 25 cm/s by varying N2 composition. The model predictions show that there is little variation in turbulent flame speed ST for C3H8 additions up to 20-vol%. However for 50 vol% doping flame speed decreases by as much as 30 % from 250 cm/s that of pure H2–air mixtures for turbulence intensity of 200 cm/s. With respect to CH4 for 50 vol% doping ST reduces by only 6 % cf. pure H2/air mixture. In the first instance the substantial decrease of ST with C3H8 addition may be attributed to the increase in the Lewis number of the dual-fuel mixture and proportional restriction of molecular mobility of H2. That is this decrease in flame speed can be explained using the concept of leading edges of the turbulent flame brush (Lipatnikov and Chomiak 2005). As these leading edges have mostly positive curvature (convex to the unburned side) preferential-diffusive-thermal instabilities cause recognizable impact on flame speed at higher levels of turbulence with the effect being very strong for lean H2 mixtures. The lighter hydrocarbon substitutions tend to suppress the leading flame edges and possibly transition to detonation in confined structures and promote flame front stability of lean turbulent premixed flames. Thus there is a necessity to develop a predictive reaction model to quantitatively show the strong influence of molecular transport coefficients on ST.

If the hydrogen economy is to progress more hydrogen refuelling stations are required. In the short term in the absence of a hydrogen distribution network the most likely means of supplying the refuelling stations will be by liquid hydrogen road tanker. This development will clearly increase the number of tanker offloading operations significantly and these may need to be performed in more challenging environments with close proximity to the general public. The work described in this paper was commissioned in order to determine the hazards associated with liquid hydrogen spills onto the ground at rates typical for a tanker hose failure during offloading.

Experiments have been performed to investigate spills of liquid hydrogen at a rate of 60 litres per minute. Measurements were made on both unignited and ignited releases.

These include:

• Concentration of hydrogen in air thermal gradient in the concrete substrate liquid pool formation and temperatures within the pool
• Flame velocity within the cloud thermal radiation IR and visible spectrum video records.
• Sound pressure measurements
• An estimation of the extent of the flammable cloud was made from visual observation video IR camera footage and use of a variable position ignition source.

Hydrogen dispersion in an enclosure is numerically studied using simple analytical solutions and a large-eddy-simulation based CFD code. In simple calculations the interface height and temperature rise of the upper layer are obtained based on mass and energy conservation and the centreline hydrogen volume fraction is derived from similarity solutions of buoyant jets. The calculated centreline hydrogen volume fraction using the two methods agree with each other; however discrepancies are found for the calculated total flammable volume as a result of the inability of simple calculations in taking into account local mixing and diffusion. The CFD model in contrast is found to be capable of correctly reproducing the diffusion and stratification phenomena during the mixing stage.

This is the tenth consecutive year of the World Energy Council’s (the Council) annual survey of key challenges and opportunities facing energy leaders in managing and shaping Energy Transitions. This year’s Issues Monitor report provides seven global maps six regional maps and fifty national maps.

These maps have been developed by analysing the responses of nearly 2300 energy leaders drawn from across the Council’s diverse and truly global energy community.

The Council’s Issues Monitor identifies the strategic energy landscape of specific countries and regions in the world through an analysis of 42 energy issues and 4 digitalisation-specific issues affecting the energy system. It provides a unique reality check and horizon scanning of persistent and emerging concerns involved in whole energy systems transition. This year’s report welcomes a significant increase in both the participation of global leaders (up over 75% from 1300 to nearly 2300) as well as the participation of 86 countries.

Each Issue Map provides a visual snapshot of the uncertainties and action priorities that energy policymakers CEOs and leading experts strive to address to shape and manage successful Energy

Transitions. Maps can be used in the following ways:

• To promote a shared understanding of successful Energy Transitions
• To appreciate and contrast regional variations to better understand differing priorities and areas of concern
• To follow the evolution of specific technology trends related to the energy sector

Underground or partial underground tunnels form a very important part of modern road transportation systems. As the development of hydrogen cars advancing into the markets it is unavoidable in the near future that hydrogen cars would become the users of ordinary road tunnels. This paper discusses potential fire scenarios and fire hazards of hydrogen cars in road tunnels and implications on the fire safety measures and ventilation systems in existing tunnels. The information needed for carry out risk assessment of hydrogen cars in road tunnels are discussed. hydrogen has a low ignition energy and wide flammable range suggesting that leaks have a high probability of ignition and result hydrogen flame. CFD simulations of hydrogen fires in a full scale 5m by 5m square cross-section tunnel were carried out. The effect of the ventilation on controlling the back-layering and the downstream flame are discussed.

Uptake of hydrogen vehicles is an ideal solution for countries that face challenging targets for carbon dioxide reduction. The advantage of hydrogen fuel cell electric vehicles is that they behave in a very similar way to petrol engines yet they do not emit any carbon containing products during operation. The hydrogen industry currently faces the dilemma that they must meet certain measurement requirements (set by European legislation) but cannot do so due to a lack of available methods and standards. This paper outlines the four biggest measurement challenges that are faced by the hydrogen industry including flow metering quality assurance quality control and sampling.