United Kingdom

To advance hydrogen into the energy market it is necessary to consider risk assessment for scenarios that are complicated by accidental hydrogen release mixing with other combustible hydrocarbon fuels. The paper is aimed at examining the effect of mixing the hydrocarbon and inert gas into the hydrogen flame on the kinetic mechanisms the laminar burning velocity and the flame stability. The influences of hydrogen concentration on the flame burning velocity were determined for the hydrogen/propane (H2-C3H8) hydrogen/ethane (H2-C2H6) hydrogen/methane (H2-CH4) and hydrogen/carbon dioxide (H2-CO2) mixtures. Experimental tests were carried out to determine the lift-off blow-out and blowoff stability limits of H2 H2-C3H8 H2-C2H6 H2-CH4 and H2-CO2 jet flames in a 2 mm diameter burner. The kinetic mechanisms of hydrogen interacting with C3 C2 and C1 fuels is analysed using the kinetic mechanisms for hydrocarbon combustion.

Numerical simulations have been carried out for pressurised hydrogen release through a nozzle in a simulated vehicle refilling environment of an experiment carried out in a joint industry project by Shell bp Exxon and the UK HSE Shirvill[1]. The computational domain mimics the experimental set up for a vertical downwards release in a vehicle refuelling environment. Due to lack of detailed data on pressure decay in the storage cylinder following the release a simple analytical model has also been developed to provide the transient pressure conditions at nozzle exit. The modelling is carried out using the traditional Computational fluid dynamics (CFD) approach based on Reynolds averaged Navier Stokes equations. The Pseudo diameter approach is used to bypass the shock-laden flow structure in the immediate vicinity of the nozzle. For combustion the Turbulent Flame Closure (TFC) model is used while the shear stress transport (SST) model is used for turbulence

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 report provides the Committee on Climate Change’s response to the UK Government’s Clean Growth Strategy.

The report finds that:

• The Government has made a strong commitment to achieving the UK’s climate change targets.

• Policies and proposals set out in the Clean Growth Strategy will need to be firmed up.

• Gaps to meeting the fourth and fifth carbon budgets remain. These gaps must be closed.

• Risks of under-delivery must be addressed and carbon budgets met on time.

This report for the CCC by Madano and Element Energy assesses the public acceptability of two alternative low-carbon technologies for heating the home: hydrogen heating and heat pumps.

These technologies could potentially replace natural gas in many UK households as part of the government’s efforts to decrease carbon emissions in the UK.

The report’s key findings are:

• carbon emissions reduction is viewed as an important issue but there is limited awareness of the need to decarbonise household heating or the implications of switching over to low-carbon heating technologies
• acceptability of both heating technologies is limited by a lack of perceived tangible consumer benefit which has the potential to drive scepticism towards the switch over more generally
• heating technology preferences are not fixed at this stage although heat pumps appear to be the favoured option in this research studythree overarching factors were identified as influencing preferences for heating technologies.

These factors manifested differently for different people meaning that the same factor could lead one person to prefer heat pumps and another to prefer hydrogen depending on their overall heating preferences and understanding of the two technologies. The factors are:

• perceptions of the negative installation burden
• familiarity with the lived experience of using the technologies for heating
• perceptions of how well the technologies would meet modern heating needs both hydrogen heating and heat pumps face significant challenges to secure public acceptability

This is the Committee’s seventh report on Scotland’s progress towards meetings emissions targets as requested by Scottish Ministers under the Climate Change (Scotland) Act 2009.

Overall Scotland continues to outperform the rest of the UK in reducing its greenhouse gas emissions but successful strategies for energy and waste mask a lack of progress in other parts of the Scottish economy.

The report shows that Scotland’s total emissions fell by 10% in 2016 compared to 2015. The lion’s share of this latest drop in emissions came from electricity generation.

The key findings are:

• Overall Scotland met its annual emissions targets in 2016. 
• Scotland’s progress in reducing emissions from the power sector masks a lack of action in other areas particularly transport agriculture forestry and land use.
• Low-carbon heat transport agriculture and forestry sector policies need to improve in order to hit 2032 emissions targets.
• The Scottish Government’s Climate Change Plan – published in February 2018 – now has sensible expectations across each sector to reduce emissions.

Simulation of hydrogen-air mixture explosions in a closed large-scale vessel with uniform and nonuniform mixture compositions was performed by the group of partners within the EC funded project “Hydrogen Safety as an Energy Carrier” (HySafe). Several experiments were conducted previously by Whitehouse et al. in a 10.7 m3 vertically oriented (5.7-m high) cylindrical facility with different hydrogen-air mixture compositions. Two particular experiments were selected for simulation and comparison as a Standard Benchmark Exercise (SBEP) problem: combustion of uniform 12.8% (vol.) hydrogen-air mixture and combustion of non-uniform hydrogen-air mixture with average 12.6% (vol.) hydrogen concentration across the vessel (vertical stratification 27% vol. hydrogen at the top of the vessel 2.5% vol. hydrogen at the bottom of the vessel); both mixtures were ignited at the top of the vessel. The paper presents modelling approaches used by the partners comparison of simulation results against the experiment data and conclusions regarding the non-uniform mixture combustion modelling in real-life applications.

This paper is concerned with predicting the impact on the probability of failure of adding hydrogen to the natural gas distribution network. Hydrogen has been demonstrated to change the behaviour of crack like defects which may affect the safety of pipeline or make it more expensive to operate. A tool has been developed based on a stochastic approach to assess the failure probability of the gas pipeline due to the existence of crack-lie defects including the operational aspects of the pipeline such as inspection and repair procedures. With various parameters such as crack sizes material properties internal pressure modelled as uncertainties a reliability analysis based on failure assessment diagram is performed through direct Monte Carlo simulation. Inspection and repair procedures are included in the simulation to enable realistic pipeline maintenance scenarios to be simulated. In the data preparation process the accuracy of the probabilistic definition of the uncertainties is crucial as the results are very sensitive to certain variables such as the crack depth length and crack growth rate. The failure probabilities of each defect and the whole pipeline system can be obtained during simulation. Different inspection and repair criteria are available in the Monte Carlo simulation whereby an optimal maintenance strategy can be obtained by comparing different combinations of inspection and repair procedures. The simulation provides not only data on the probability of failure but also the predicted number of repairs required over the pipeline life thus providing data suitable for economic models of the pipeline management. This tool can be also used to satisfy certain target reliability requirement. An example is presented comparing a natural gas pipeline with a pipeline containing hydrogen.

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

The paper presents an overview of the main results of the EC NOE HySafe activity to estimate an allowable hydrogen permeation rate for automotive legal requirements and standards. The work was undertaken as part of the HySafe internal project InsHyde.<br/>A slow long term hydrogen release such as that due to permeation from a vehicle into an inadequately ventilated enclosed structure is a potential risk associated with the use of hydrogen in automotive applications. Due to its small molecular size hydrogen permeates through the containment materials found in compressed gaseous hydrogen storage systems and is an issue that requires consideration for containers with non-metallic (polymer) liners. Permeation from compressed gaseous hydrogen storage systems is a current hydrogen safety topic relevant to regulatory and standardisation activities at both global and regional levels.<br/>Various rates have been proposed in different draft legal requirements and standards based on different scenarios and the assumption that hydrogen dispenses homogeneously. This paper focuses on the development of a methodology by HySafe Partners (CEA NCSRD. University of Ulster and Volvo Technology) to estimate an allowable upper limit for hydrogen permeation in automotive applications by investigating the behaviour of hydrogen when released at small rates with a focus on European scenario. The background to the activity is explained. reasonable scenarios are identified a methodology proposed and a maximum hydrogen permeation rate from road vehicles into enclosed structures is estimated The work is based on conclusions from the experimental and numerical investigations described by CEA NCSRD and the University of Ulster in related papers.