Institution of Gas Engineers & Managers

With the rapid development of hydrogen pipelines their safety issues have become increasingly prominent. In order to evaluate the properties of pipeline materials under a highpressure hydrogen environment this study investigates the hydrogen embrittlement sensitivity of X70 welded pipe in a 10 MPa high-pressure hydrogen environment using slow strain rate testing (SSRT) and low-cycle fatigue (LCF) analysis. The microstructure slow tensile and fatigue fracture morphology of base metal (BM) and weld metal (WM) were characterized and analyzed by means of ultra-depth microscope scanning electron microscope (SEM) electron backscattering diffraction (EBSD) and transmission electron microscope (TEM). Results indicate that while the high-pressure hydrogen environment has minimal impact on ultimate tensile strength (UTS) for both BM and WM it significantly decreases reduction of area (RA) and elongation (EL) with RA reduction in WM exceeding that in BM. Under the nitrogen environment the slow tensile fracture of X70 pipeline steel BM and WM is a typical ductile fracture while under the high-pressure hydrogen environment the unevenness of the slow tensile fracture increased and a large number of microcracks appeared on the fracture surface and edges with the fracture mode changing to ductile fracture + quasicleavage fracture. In addition the high-pressure hydrogen environment reduces the fatigue life of the BM and WM of X70 pipeline steel and the fatigue life of the WM decreases more than that of the BM as well. Compared to the nitrogen environment the fatigue fracture specimens of BM and WM in the hydrogen environment showed quasi-cleavage fracture patterns and the fracture area in the instantaneous fracture zone (IFZ) was significantly reduced. Compared with the BM of X70 pipeline steel although the effective grain size of the WM is smaller WM’s microstructure with larger Martensite/austenite (M/A) constituents and MnS and Al-rich oxides contributes to a heightened embrittlement sensitivity. In contrast the second-phase precipitation of nanosized Nb V and Ti composite carbon-nitride in the BM acts as an effective irreversible hydrogen trap which can significantly reduce the hydrogen embrittlement sensitivity

Hydrogen energy technologies are envisioned to play a critical supporting role in global decarbonisation. While low-carbon hydrogen is primarily targeted for reducing industrial emissions alongside decarbonising parts of the transport sector environmental benefits could also be achieved in the residential context. Presently gasdependent countries such as Japan and the United Kingdom are assessing the feasibility of deploying hydrogen home appliances as part of their national energy strategies. However prospects for the transition will hinge on consumer acceptance alongside an array of other socio-technical factors. To support potential ambitions for large-scale and sustained technology diffusion this study advances a Unified Theory of Domestic Hydrogen Acceptance. Through an integrative comparative literature review targeting hydrogen and domestic energy studies the paper proposes a novel Domestic Hydrogen Acceptance Model (DHAM) which accounts for the cognitive and emotional dimensions of human perceptions. Through this dual interplay the proposed framework can increase the predictive power of hydrogen acceptance models.

Hydrogen as a primary carbon-free energy carrier is confronted by challenges in storage and transportation. However liquid organic hydrogen carriers (LOHCs) present a promising solution for storing and transporting hydrogen at ambient temperature and atmospheric pressure. Unlike circular energy carriers such as methanol ammonia and synthetic natural gas LOHCs do not produce by-products during hydrogen recovery. LOHCs only act as hydrogen carriers and the carriers can also be recycled for reuse. Although there are considerable advantages to LOHCs there are also some drawbacks especially relative to the energy consumption during the dehydrogenation step of the LOHC recycling. This review summarizes the recent progresses in LOHC technologies focusing on catalyst developments process and reactor designs applications and techno-economic assessments (TEA). LOHC technologies can potentially offer significant benefits to Australia especially in terms of hydrogen as an export commodity. LOHCs can help avoid capital costs associated with infrastructure such as transportation vessels while reducing hydrogen loss during transportation such as in the case of liquid hydrogen (LH2). Additionally it minimises CO2 emissions as observed in methane and methanol reforming. Thus it is essential to dedicate more efforts to explore and develop LOHC technologies in the Australian context.

Hydrogen Economy and Cyclic Economy are advocated together with the use of perennial (solar wind hydro geo-power SWHG) and renewable (biomass) energy sources for defossilizing anthropic activities and mitigating climate change. Each option has intrinsic limits that prevent a stand-alone success in reaching the target. Humans have recycled goods (metals water paper and now plastics) to a different extent since very long time. Recycling carbon (which is already performed at the industrial level in the form of CO2 utilization and with recycling paper and plastics) is a key point for the future. The conversion of CO2 into chemicals and materials is carried out since the late 1800s (Solvay process) and is today performed at scale of 230 Mt/y. It is time to implement on a scale of several Gt/y the conversion of CO2 into energy products possibly mimicking Nature which does not use hydrogen. In the short term a few conditions must be met to make operative on a large scale the production of fuels from recycled-C namely the availability of low-cost: i. abundant pure concentrated streams of CO2 ii. non-fossil primary energy sources and iii. non-fossil-hydrogen. The large-scale production of hydrogen by Methane Steam Reforming with CO2 capture (Blue-H2) seems to be a realistic and sustainable solution. Green-H2 could in principle be produced on a large scale through the electrolysis of water powered by perennial primary sources but hurdles such as the availability of materials for the construction of long-living robust electrochemical cells (membranes electrodes) must be abated for a substantial scale-up with respect to existing capacity. The actual political situation makes difficult to rely on external supplies. Supposed that cheap hydrogen will be available its direct use in energy production can be confronted with the indirect use that implies the hydrogenation of CO2 into fuels (E-fuels) an almost ready technology. The two strategies have both pros and cons and can be integrated. E-Fuels can also represent an option for storing the energy of intermittent sources. In the medium-long term the direct co-processing of CO2 and water via co-electrolysis may avoid the production/transport/ use of hydrogen. In the long term coprocessing of CO2 and H2O to fuels via photochemical or photoelectrochemical processes can become a strategic technology.

South Korea has drawn up plans to reduce greenhouse gases by 29.7 million tons by supplying 4.5 million electric and hydrogen cars by 2030 to implement the “2050 carbon neutrality” goal. This article gathers data on public preferences for electric cars (ECs) over hydrogen cars (HCs) in the commercial vehicle transportation sector through a survey of 1000 people. Moreover the strength of the preference was evaluated on a five-point scale. Of all respondents 60.0 percent preferred ECs and 21.0 percent HCs the former being 2.86 times greater than the latter. On the other hand the strength of the preference for HCs was 1.42 times greater than that for ECs. Factors influencing the preference for ECs over HCs were also explored through adopting the ordered probit model which is useful in examining ordinal preference rather than cardinal preference. The analyzed factors which are related to respondents’ characteristics experiences and perceptions can be usefully employed for developing strategies of promoting carbon neutrality in the commercial vehicle transportation sector and preparing policies to improve public acceptance thereof.

Hydrogen Fuel Cell Electric Vehicles (HFC EVs) represent an alternative to replace current internal combustion engine vehicles. The use of these vehicles with storage of compressed gaseous hydrogen (CGH2) in confined spaces such as tunnels underground car parks etc. creates new challenges to ensure the protection of people and property and to keep the risk at an acceptable level. The HYTUNNEL-CS project sponsored by the FCH-JU was launched to develop validated hazard and risk assessment tools for the behavior of hydrogen leaks in tunnels. Among the experiments carried out in support of the validation tools the CEA has conducted tests on gas dispersion in a full-scale tunnel geometry. In the tests carried out hydrogen is replaced by helium under a pressure of 70 MPa in a 78 liter tank. The car is simulated by a flat plate called chassis and the discharges are made either downwards under the chassis or upwards to take into account a rollover of the car during the accident. Different thermally activated pressure relief device (TPRD) diameters are examined as well as different orientations of the discharge. Finally the mixing transient of helium with air is measured for distances between -50 and +50m from the release. Performing CFD simulations of such an under-expanded jet in an environment as large as a road tunnel demands a compressible flow solver and so a large computational cost. To optimize this cost a notional nozzle approach is generally used to replace the under-expanded jet by a subsonic jet that has the same concentration dilution behavior. The physics at the injection point is then not resolved and a model of these boundary conditions has to be implemented. This article first reviews the main experimental results. Then a model of boundary conditions is proposed to have a subsonic hydrogen jet that matches the dilution characteristics of an under-expanded jet. Furthermore this model is implemented in the TRUST LES computer code and in the Neptune-CFD RANS computer code in order to simulate some helium dispersion experiments. Finally results from the CFD simulations are compared to the experimental results and the effect of the exact shape of the tunnel is also assessed by comparing simulations with idealized flat walls and real scanned walls.

Accelerated decarbonisation of steelmaking oil refining and petrochemical industries is essential for climate change mitigation. Drawing on three longitudinal case studies of these industries in the UK this synthesis article makes a comparative analysis of their varying low-carbon reorientation speeds. The paper uses the triple embeddedness framework to analyse five factors (policy support international competition financial health technical feasibility corporate strategy and mindset) that explain why UK oil refineries have in recent years been comparatively the fastest in their low-carbon reorientation and UK steelmakers the slowest. We find that policy support has been more beneficial for refining and petrochemicals than for steel although recent government deals with steelmakers addressed this imbalance. International competition has been high for steel and petrochemicals and comparatively lower for refining (meaning that decarbonisation costs are less detrimental for international competitiveness). Financial performance has comparatively been worst for steel and best for oil refining which shapes the economic feasibility of low-carbon options. Hydrogen and carbon-capture-and-storage are technologically feasible for refining and petrochemicals while Electric Arc Furnaces are technically feasible for steelmakers but face wider feasibility problems (with scrap steel supply electricity grids and electricity prices) which is why we question the recent government deals. Corporate strategy and perceptions changed in oil refining with firms seeing economic opportunities in decarbonisation while steelmakers and petrochemical firms still mostly see decarbonisation as a burden and threat. The paper ends with comparative conclusions a discussion of political considerations and future outlooks for the three UK industries policy and research.

Hydrogen flames are much thinner than hydrocarbon flames. They have a higher propensity to wrinkle and are subject to thermo-diffusive instabilities in lean conditions. The large scale experiments of Sherman under partially vented conditions have shown that the transition to detonation is possible with only modest flame acceleration to approximately 200 m/s which is much lower than the commonly accepted limits corresponding to choked flames. At present the reason for this transition is not known. Vented H2-air explosions have also demonstrated the role played by expansion/flame interactions in deforming the flame. The state of the art on flame burning rate enhancement by expansion waves will be provided along with the recent experimental and numerical results of head on interaction of flames with an expansion wave conducted in our group. We show that the expansion wave interaction can generate local burning rate increases by more than an order of magnitude. The role of thermo-diffusive instability is also assessed. The mechanism of flame deformation is via the vorticity generation by the misaligned pressure gradient controlled by the expansion wave and the density gradient of the flame. Expansion waves originating from the unburned gas severely elongate the cells until the flame folds burn out. Expansion waves originating from the burned gas side first invert the flames then elongate them by the same mechanism. The rate of elongation is controlled by the volumetric expansion of the gas and the curvature-enhanced growth.

In many industries low-carbon hydrogen will substitute fossil fuels in the course of the transformation to climate neutrality. This paper contributes to understanding this transformation. This paper provides an overview of energy- and emission-intensive industry sectors with great potential to defossilize their production processes with hydrogen. An assessment of future hydrogen demand for various defossilization strategies in Germany that rely on hydrogen as a feedstock or as an energy carrier to a different extent in the sectors steel chemicals cement lime glass as well as pulp and paper is carried out. Results indicate that aggregate industrial hydrogen demand in those industries would range between 197 TWh and 298 TWh if production did not relocate abroad for any industry sector. The range for hydrogen demand is mainly due to differences in the extent of hydrogen utilization as compared to alternative transformation paths for example based on electrification. The attractiveness of production abroad is then assessed based on the prospective comparative cost advantage of relocating parts of the value chain to excellent production sites for low-carbon hydrogen. Case studies are provided for the steel industry as well as the chemical industry with ethylene production through methanol and the production of urea on the basis of ammonia. The energy cost of the respective value chains in Germany is then compared to the case of value chains partly located in regions with excellent conditions for renewable energies and hydrogen production. The results illustrate that at least for some processes – as ammonia production – relocation to those favorable regions may occur due to substantial comparative cost advantages.

This paper presents work undertaken by the HSE as part of the Hytunnel-CS project a consortium investigating safety considerations for fuel cell hydrogen (FCH) vehicles in tunnels and similar confined spaces. The test programme investigating hydrogen dispersion in tunnels involved simulating releases analogous to Thermally activated Pressure Relief Devices (TPRDs) typically found on hydrogen vehicles into the HSE Tunnel facility. The releases were scaled and based upon four scenarios: cars buses and two different train designs. The basis for this scaling was the size of the tunnel and the expected initial mass flow rates of the releases scenarios. The results of the 12 tests completed have been analysed in two ways: the initial mass flow rates of the tests were calculated based upon facility measurements and the Able-Noble equations of state for comparison to the intended initial flow rate; and observations of the hydrogen dispersion in the tunnel were made based on 15 hydrogen sensors arrayed along the tunnel. The calculated mass flow rates showed reasonable agreement with the intended initial conditions showing that the scaling methodology can be used to interpret the data based on the full-scale tunnel of interest. Observations of the hydrogen dispersion show an initial turbulent mixing followed by a movement of the mixed hydrogen/air cloud down the tunnel. No vertical stratification of the cloud was observed but this effect could be possible in longer tunnels or tunnels with larger diameters. Higher ventilation rates in the tunnel resulted in a reduction of the residence time of the hydrogen and a slight increase in the dilution.