United Kingdom

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.

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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.