Publications

The substitution of hydrogen for natural gas within a gas network has implications for the potential rate of leakage from pipes and the distribution of gas flow driven by such leaks. This paper presents theoretical analyses of low-pressure flow through porous ground in a range of circumstances and practical experimental work at a realistic scale using natural gas hydrogen or nitrogen for selected cases. This study considers flow and distribution of 100% hydrogen. A series of eight generic flow regimes have been analysed theoretically e.g. (i) a crack in uncovered ground (ii) a crack under a semi-permeable cover in a high porosity channel (along a service line or road). In all cases the analyses yield both the change in flow rate when hydrogen leaks and the change in distance to which hydrogen gas can travel at a dangerous rate compared to natural gas. In some scenarios a change to hydrogen gas from natural gas makes minimal difference to the range (i.e. distance from the leak) at which significant gas flows will occur. However in cases where the leak is covered by an impermeable membrane a change to hydrogen from natural gas may extend the range of significant gas flow by tens or even hundreds of metres above that of natural gas. Experimental work has been undertaken in specific cases to investigate the following: (i) Flow rate vs pressure curves for leaks into media with different permeability (ii) Effects of the water content of the ground on gas flow (iii) Distribution of surface gas flux near a buried leak

Hydrogen is a valuable option of clean fuel to keep the global temperature rise below 2°C. However one of the main barriers in its transport and use is to ensure safety levels that are comparable with traditional fuels. In particular liquid hydrogen accidents may not be fully understood (yet) and excluded by relevant risk assessment. For instance as hydrogen is cryogenically liquefied to increase its energy density during transport Boiling Liquid Expanding Vapor Explosions (BLEVE) is a potential and critical event that is important addressing in the hazard identification phase. Two past BLEVE accidents involving liquid hydrogen support such thesis. For this reason results from consequence analysis of hydrogen BLEVE will not only improve the understanding of the related physical phenomenon but also influence future risk assessment studies. This study aims to show the extent of consequence analysis influence on overall quantitative risk assessment of hydrogen technologies and propose a systematic approach for integration of overall results. The Dynamic Procedure for Atypical Scenario Identification (DyPASI) is used for this purpose. The work specifically focuses on consequence models that are originally developed for other substances and adapted for liquid hydrogen. Particular attention is given to the parameters affecting the magnitude of the accident as currently investigated by a number of research projects on hydrogen safety worldwide. A representative example of consequence analysis for liquid hydrogen release is employed in this study. Critical conditions detected by the numerical simulation models are accurately identified and considered for subsequent update of the overall system risk assessment.

This paper reports a new approach for exposing materials including solar cell structures to atomic hydrogen. This method is dubbed Shielded Hydrogen Passivation (SHP) and has a number of unique features offering high levels of atomic hydrogen at low temperature whilst inducing no damage. SHP uses a thin metallic layer in this work palladium between a hydrogen generating plasma and the sample which shields the silicon sample from damaging UV and energetic ions while releasing low energy neutral atomic hydrogen onto the sample. In this paper the importance of the preparation of the metallic shield either to remove a native oxide or to contaminate intentionally the surface are shown to be potential methods for increasing the amount of atomic hydrogen released. Excellent damage free surface passivation of thin oxides is observed by combining SHP and corona discharge obtaining minority carrier lifetimes of 2.2 ms and J0 values below 5.47 fA/cm2. This opens up a number of exciting opportunities for the passivation of advanced cell architectures such as passivated contacts and heterojunctions.

Australian regional communities are moving ahead of governments. Enterprising individuals are pushing ahead to find global solutions to local issues that governments (local or state or federal) have abandoned stalled mothballed or failed to resolve. We are faced with a flaw in retail of hydrogen economy as fatal as Walgett running dry or a million fish killed in Murray-Darling. The challenge in Australian regional communities will be to interpret safety assurance requirements in an appropriate manner even in severe economic swings such as drought bushfire or floods. In this context the efficacious cultural embrace by regional communities of three key program elements is essential - Australian Hydrogen Safety Panel Hydrogen Safety Knowledge Tools and Dissemination Hydrogen Safety First Responder Training. What are the odds of no accident in retailing hydrogen for examples to vehicles? Place is everything in regional communities of Australia because in nature (as in the ocean) there is no spin. This paper examines the safety assurance issues associated with the cultural integration of Hydrogen’s three key program elements in a country Australia that is fed-up with government.

Usage of hydrogen as fuel gives rise to possible accidental risks due to leakage and dispersion. A risk from hydrogen leak is the formation of a large volume of the hydrogen-air mixture which could be ignited and leading up to a severe explosion. Prevention and control of formation and ignition of combustible hydrogen cloud necessitate sufficient knowledge of mechanisms of the hydrogen leak dispersion ignition and over-pressures generated during combustion. This paper aims to investigate the momentum-controlled jet the buoyancy-controlled wave and the parameters influencing hydrogen concentration distribution in an elongated space. It demonstrates experimental results and analysis from helium and hydrogen dispersion in a channel. A set of experiments were carried out for the release of helium and hydrogen jets in a 3 m long channel to record their concentrations in the cloud by concentration sensors at different horizontal and vertical positions. Flow visualization technique was applied using shadowgraph to image the mixing process next to the release point and the helium- hydrogen-air cloud shape at the middle of the channel. Moreover results were used for comparison of helium and hydrogen concentration gradients. The results of the experiments show that swift mixing occurs at higher flow rates smaller nozzle sizes and downward release direction. Higher concentration recorded in the channel with negative inclination. Results also confirmed that hydrogen/helium behavior pattern in the channel accords with mutual intrusion theory about gravity currents.

Carbon materials such as graphene nanoflakes carbon nanotubes and fullerene can be widely used to store hydrogen and doping these materials with lithium (Li) generally increases their H2 -storage densities. Unfortunately Li is expensive; therefore alternative metals are required to realize a hydrogen-based society. Sodium (Na) is an inexpensive element with chemical properties that are similar to those of lithium. In this study we used density functional theory to systematically investigate how hydrogen molecules interact with Na-doped graphene nanoflakes. A graphene nanoflake (GR) was modeled by a large polycyclic aromatic hydrocarbon composed of 37 benzene rings with GR-Na-(H2 )n and GR-Na+ -(H2 )n (n = 0–12) clusters used as hydrogen storage systems. Data obtained for the Na system were compared with those of the Li system. The single-H2 GR-Li and GR-Na systems (n = 1) exhibited binding energies (per H2 molecule) of 3.83 and 2.72 kcal/mol respectively revealing that the Li system has a high hydrogen-storage ability. This relationship is reversed from n = 4 onwards; the Na systems exhibited larger or similar binding energies for n = 4–12 than the Li-systems. The present study strongly suggests that Na can be used as an alternative metal to Li in H2 -storage applications. The H2 -storage mechanism in the Na system is also discussed based on the calculated results.

This work programme was focused on identifying a suitable odorant for use in a 100% hydrogen gas grid (domestic use such as boilers and cookers). The research involved a review of existing odorants (used primarily for natural gas) and the selection of five suitable odorants based on available literature. One odorant was selected based on possible suitability with a Polymer Electrolyte Membrane (PEM) based fuel cell vehicle which could in future be a possible end-user of grid hydrogen. NPL prepared Primary Reference Materials containing the five odorants in hydrogen at the relevant amount fraction levels (as would be found in the grid) including ones provided by Robinson Brothers (the supplier of odorants for natural gas in the UK). These mixtures were used by NPL to perform tests to understand the effects of the mixtures on pipeline (metal and plastic) appliances (a hydrogen boiler provided by Worcester Bosch) and PEM fuel cells. HSE investigated the health and environmental impact of these odorants in hydrogen. Olfactory testing was performed by Air Spectrum to characterise the ‘smell’ of each odorant. Finally an economic analysis was performed by E4tech. The results confirm that Odorant NB would be a suitable odorant for use in a 100% hydrogen gas grid for combustion applications but further research would be required if the intention is to supply grid hydrogen to stationery fuel cells or fuel cell vehicles. In this case further testing would need to be performed to measure the extent of fuel cell degradation caused by the non-sulphur odorant obtained as part of this work programme and also other UK projects such as the Hydrogen Grid to Vehicle (HG2V) project would provide important information about whether a purification step would be required regardless of the odorant before the hydrogen purity would be suitable for a PEM fuel cell vehicle. If purification was required it would be fine to use Odorant NB as this would be removed during the purification step.

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 embrittlement is one of the largest obstacles against the commercialisation of ultra-high strength quenching and partitioning (Q&P) steels with ultimate tensile strength over 1500 MPa including the hot stamped steel parts that have undergone a Q&P treatment. In this work the influence of partitioning temperature on hydrogen embrittlement of ultra-high strength Q&P steels is studied by pre-charged tensile tests with both dog-bone and notched samples. It is found that hydrogen embrittlement resistance is enhanced by the higher partitioning temperature. Then the hydrogen embrittlement mechanism is analysed in terms of hydrogen retained austenite and martensite matrix. Thermal desorption analysis (TDA) shows that the hydrogen trapping properties are similar in the Q&P steels which cannot explain the enhancement of hydrogen embrittlement resistance. On the contrary it is found that the relatively low retained austenite stability after the higher temperature partitioning ensures more sufficient TRIP effect before hydrogen-induced fracture. Additionally dislocation recovery and solute carbon depletion at the higher partitioning temperature can reduce the flow stress of the martensite matrix improving its intrinsic toughness and reducing its hydrogen sensitivity both of which result in the higher hydrogen embrittlement resistance.

Time is rapidly running out to make the crucial planning decisions and secure investment to keep the UK on track to deliver a reliable affordable and decarbonised energy system to meet future emissions regulation enshrined in the 2008 Climate Change Act according to a report published today by the Royal Academy of Engineering.

Prepared for the Prime Minister's Council for Science and Technology A critical time for UK energy policy details the actions needed now to create a secure and affordable low carbon energy system for 2030 and beyond.

The study looks at the future evolution of the UK’s energy system in the short to medium term. It considers how the system is expected to develop across a range of possible trajectories identified through modelling and scenarios.

The following actions for government are identified as a matter of urgency:

• enable local or regional whole-system large scale pilot projects to establish real-world examples of how the future system will work. These must move beyond  current single technology demonstrators and include all aspects of the energy systems along with consumer behaviour and financial mechanisms
• drive forward new capacity in the three main low carbon electricity generating technologies: nuclear carbon capture and storage (CCS) and offshore wind
• develop policies to accelerate demand reduction especially in domestic heating and introduce smarter demand management
• clarify and stabilise market mechanisms and incentives in order to give industry the confidence to invest.

New technologies could become unexpectedly significant – such as solar PV which has recently become much cheaper. But large scale deployment of novel technologies would take decades and the system cannot be planned on promises and aspirations alone. The Academy calls instead for a combination of known technologies to be scaled up to unprecedented levels and integrated in smarter ways.

The report notes that the addition of shale gas or tight oil is unlikely to have a major impact on the evolution of the UK's energy system as we already have secure and diverse supplies of hydrocarbons from multiple sources.

Dr David Clarke FREng who led the group that produced the report says: “Updating the UK energy system to meet the ‘trilemma’ of decarbonisation security and affordability is a massive undertaking. Meeting national targets affordably requires substantial decarbonisation of the electricity system by 2030 through a mix of nuclear power CCS and renewables with gas generation for balancing. Beyond 2030 we must then largely decarbonise heat and transport potentially through electrification but also using other options such as hydrogen and biofuels. We also need to adapt our transmission and distribution networks to become ‘smarter’”.

"Failure to plan the development of the whole energy system carefully will result at best in huge increases in the cost of delivery or at worst a failure to deliver. Substantial investment is needed and current investment capacity is fragile. For example in the last month projects like Carlton’s new Trafford CCGT plant have announced further financing delays and the hoped-for investment by Drax in the White Rose CCS demonstrator has been withdrawn. The UK has also dropped four places to 11th in EY’s renewable energy country attractiveness index.”

Link to document download on Royal Society Website

A set of original experiments is presented covering the topic of hydrogen-air mixture ignition by a hot surface. The hot surface is a 30 mm long/10 mm diameter heated coil which temperature is controlled by IR techniques. The coil is placed into the flowing stream of hydrogen air mixtures. The variable parameters are the composition of the flammable atmosphere (4 to 75% H2 v/v) the flow speed (from 0.5 m/s to 30 m/s) and its temperature (from -110°C to ambient). The experimental techniques and results are presented and a tentative interpretation is proposed based on ignition theories and highspeed video recordings. It is shown that the ignition temperature (600°C) is insensitive to flowing conditions which is a very unexpected result.