Publications

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.

The next decade will see fundamental changes in how people heat their homes. The global energy system is changing in response to the need to transition away from fossil-based generation towards more environmentally sustainable alternatives.

Hydrogen offers one such alternative but currently there is limited understanding of public perceptions of hydrogen the information that people need in order to make an informed choice about using hydrogen in their homes and how misunderstandings could present barriers to the uptake of hydrogen technology. This is crucial to ensure the success of future policy and investment. The H21 concept is to convert the UK gas distribution network to 100% hydrogen over time thereby decarbonising heat and supporting decarbonisation of electric large industrials and transport. This would be achieved using the existing UK gas grid network and technology available across the world today whilst maintaining the benefits of gas and the gas networks in the energy mix for the long-term future. Additionally this would maintain choice of energy for customers i.e. they would be able to use both gas and electricity. The H21 project is being delivered by the UK gas distribution networks Northern Gas Networks Cadent Wales & West Utilities and SGN. As part of the H21 project Leeds Beckett University has been working with Northern Gas Networks to gain insight into public perceptions of hydrogen as a domestic fuel. Using innovative social science methods the research team has explored for the first time public perceptions of moving the UK domestic fuel supply to 100% hydrogen. We identify what people think and feel about a potential conversion the concerns and questions that they have and how to address them clearly. The findings presented in this report will ensure that issues around the current perception of hydrogen are identified and addressed prior to any large-scale technology rollout.

The first stage of the project comprised a series of discovery interviews which explored how to talk to people about hydrogen and the H21 project. We interviewed 12 participants selected to ensure we included people with a range of experiences and domestic settings for example people who live in urban and rural areas those who live alone those who live with children or a partner those who live in their own home and those who rent. Most participants had given very little thought about where their gas and electric comes from and other than switching supplier to get a better tariff had very little interest in it. They had not previously considered their domestic heating as a source of carbon emissions and were surprised that there may be a need in the future to change their gas supply. From the discovery interviews we identified several key areas to explore in the next stage of the work:

• Beliefs about the environment
• Beliefs about inconvenience and cost
• Beliefs about safety
• Beliefs about the economic impact

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.

Hydrogen (H2 ) has become an important energy vector for mitigating the effects of climate change since it can be obtained from renewable sources and can be fed to fuel cells for producing power. Bioethanol can become a green H2 source via Ethanol Steam Reforming (ESR) but several variables influence the power production in the fuel cell. Herein we explored and optimized the main variables that affect this power production. The process includes biomass fermentation bioethanol purification H2 production via ESR syngas cleaning by a CO-removal reactor and power production in a high temperature proton exchange membrane fuel cell (HT-PEMFC). Among the explored variables the steam-to-ethanol molar ratio (S/E) employed in the ESR has the strongest influence on power production process efficiency and energy consumption. This effect is followed by other variables such as the inlet ethanol concentration and the ESR temperature. Although the CO-removal reactor did not show a significant effect on power production it is key to increase the voltage on the fuel cell and consequently the power production. Optimization was carried out by the response surface methodology (RSM) and showed a maximum power of 0.07 kWh kg−1 of bioethanol with an efficiency of 17% when ESR temperature is 700 ◦C. These values can be reached from different bioethanol sources as the S/E and CO-removal temperature are changed accordingly with the inlet ethanol concentration. Because there is a linear correlation between S/E and ethanol concentration it is possible to select a proper S/E and CO-removal temperature to maximize the power generation in the HT-PEMFC via ESR. This study serves as a starting point to diversify the sources for producing H2 and moving towards a H2 -economy.

Hydrogen stations and supply systems for public transport have been demonstrated in a number of European cities during the last four years. The first refuelling facility was put into operation in Reykjavik in April 2003. Experience from the four years of operation shows that safety related incidents are more frequent in the user interface than in the other parts of the hydrogen refuelling station (HRS). This might be expected taking into account the fact that the refuelling is manually operated and that according to industrial statistics human failures normally stand for more than 80% of all safety related incidents. On the other hand the HRS experience needs special attention since the refuelling at the existing stations is carried out by well trained personnel and that procedures and systems are followed closely. So far the quality and safety approach to hydrogen refuelling stations has been based on industrial experience. This paper addresses the challenge related to the development of safe robust and easy to operate refuelling systems. Such systems require well adapted components and system solutions as well as user procedures. The challenge to adapt the industrial based quality and safety philosophy and methodologies to new hydrogen applications and customers in the public sector is addressed. Risk based safety management and risk acceptance criteria relevant to users and third party are discussed in this context. Human factors and the use of incident reporting as a tool for continuous improvement are also addressed. The paper is based on internal development programmes for hydrogen refuelling stations in Hydro and on participation in international EU and IPHE projects such as CUTE HyFLEET:CUTE HySafe and HyApproval.

A novel approach has been developed for quantitative evaluation of the susceptibility of steels and alloys to hydrogen embrittlement. The approach uses a combination of hydrogen thermal desorption spectroscopy (TDS) analysis with recent advances in machine learning technology to develop a regression artificial neural network (ANN) model predicting hydrogen-induced degradation of mechanical properties of steels. We describe the thermal desorption data processing artificial neural network architecture development and the learning process beneficial for the accuracy of the developed artificial neural network model. A data augmentation procedure was proposed to increase the diversity of the input data and improve the generalization of the model. The study of the relationship between thermal desorption spectroscopy data and the mechanical properties of steel evidences a strong correlation of their corresponding parameters. A prototype software application based on the developed model is introduced and is openly available. The developed prototype based on TDS analysis coupled with ANN is shown to be a valuable engineering tool for steel characterization and quantitative prediction of the degradation of steel properties caused by hydrogen.

Developing renewable energy-driven water splitting for sustainable hydrogen production plays a key role in achieving the carbon neutrality goal. Nevertheless the efficiency of traditional pure water electrolysis is severely hampered by the anodic oxygen evolution reaction (OER) due to its sluggish kinetics. In this context replacing OER with thermodynamically more favorable oxidation reactions to produce hydrogen via hybrid water electrolysis becomes an energy-saving hydrogen production scheme. Here the recent advances in hybrid water electrolysis are critically reviewed. First the fundamentals of electrochemical oxidation of typical organic molecules such as urea hydrazine and biomass are presented. Then the recent achievements in electrocatalysts for hybrid water electrolysis are introduced with an emphasis on outlining catalyst design strategies and the correlation between catalyst structure and performance. Finally future perspectives in this field for a sustainable hydrogen economy are proposed.

The term ‘decarbonised gas’ refers to biogases hydrogen and carbon capture utilisation and storage (CCUS). This strategy paper sets out how decarbonised gas can help to get net zero done by tackling the hard-to-decarbonise sectors – industry heavy transport and domestic heating – which together account for around 40% of UK greenhouse gas emissions. It also illustrates the crucial importance of supportive public opinion and sets out in detail how decarbonised gas can help to ensure that net zero is achieved with public support. The report is based on extensive quantitative and qualitative opinion research on climate change in general net zero emissions in the UK and the specific decarbonised gas solutions in homes transport and industry. The full quantitative data is contained in the Supplements tab.<br/><a href="https://www.dgalliance.org/wp-content/uploads/2020/05/DGA-Getting-Net-Zero-Done-final-May-2020.pdf"/><a href="https://www.dgalliance.org/wp-content/uploads/2020/05/DGA-Getting-Net-Zero-Done-final-May-2020.pdf"/>

Thermally sprayed aluminium (TSA) coatings provide protection to offshore steel structures without the use of external cathodic protection (CP) systems. These coatings provide sacrificial protection in the same way as a galvanic anode and thus hydrogen embrittlement (HE) becomes a major concern with the use of high strength steels. The effect of TSA on the HE of steel seems to remain largely unknown. Further the location of hydrogen in TSA-coated steel has not been explored. To address the above knowledge gap API 5L X80 and AISI 4137 steel coupons with and without TSA were prepared and the amount of hydrogen present in these steels when cathodically polarised to −1.1 V (Ag/AgCl) for 30 days in synthetic seawater was determined. One set of TSA-coated specimens was left at open circuit potential (OCP). The study indicates that the amount of hydrogen present in TSA-coated steel is ~100 times more than the amount found in uncoated steel and that the hydrogen seems to be largely localised in the TSA layer.

In the last years different Italian hydrogen projects provided for gaseous hydrogen motor vehicles refuelling stations. Motivated by the lack of suitable set of rules in the year 2002 Italian National Firecorps (Institute under the Italian Ministry of the Interior) formed an Ad Hoc Working Group asked to regulate the above-said stations as regards fire prevention and protection safety. This Working Group consists of members coming from both Firecorps and academic world (Pisa University). Throughout his work this Group produced a technical rule covering the fire prevention requirements for design construction and operation of gaseous hydrogen refuelling stations. This document has been approved by the Ministry’s Technical Scientific Central Committee for fire prevention (C.C.T.S.) and now it has to carry out the “Community procedure for the provision of information”. This paper describes the main safety contents of the technical rule.

Although today hydrogen is distributed mainly by trailers in the long terms pipeline distribution will be more suitable if large amounts of hydrogen are produced on industrial scale. Therefore from the safety point of view it is essential to compare hydrogen pipelines to natural gas pipelines which are well established today. Within the paper we compare safety implications in accidental situations. We do not look into technological aspects such as compressors or seals.<br/>Using a CFD (Computational Fluid Dynamics) tool it is possible to investigate the effects of different properties (density diffusivity viscosity and flammability limits) of hydrogen and methane on the dispersion process. In addition CFD tools allow studying the influence of different release scenarios geometrical configurations and atmospheric conditions. An accidental release from a pipeline is modelled. The release is simulated as a flow though a small hole between the high-pressure pipeline and the environment. A part of the pipeline is included in the simulations as high-pressure reservoir. Due to the large pressure difference between the pipeline and the environment the flow conditions at the release become critical.<br/>For the assumed scenarios larger amount of flammable mixture could be observed in case of hydrogen release. On the other hand because of buoyancy and a higher sonic speed at the release the hydrogen clouds are farther from the ground level or buildings than in case of the methane clouds decreasing the probability of ignition and reducing the flame acceleration due to obstacles in case of ignition. Results on the effect of wind in the release scenarios are also described.