Publications

Present work describes the failure analysis of cooling duct of a fighter aircraft. The analyzed chemical composition of cooling duct indicates that it is manufactured from Al-based alloy (AA 3003 or its equivalent). Microstructure of cooling duct displays the presence of two phases namely matrix and insoluble particles. The hardness values at different locations within damaged area of cooling duct reflect nearly same and consistent. The fracture surface of the cooling duct exhibits transgranular features and cracks with little branching. The analyzed hydrogen content in cooling duct is significantly higher (∼ 12 ppm) than the specified one (< 1 ppm). However the alloy used to fabricate cooling duct is not susceptible to typical hydrogen embrittlement. This shows hydrogen pick up during operation. The presence of cracks with branching does reflect features of hydrogen embrittlement. In addition striations indicative of fatigue features are also observed. It thus appears that the cooling duct has failed due to pick up of large amount of hydrogen as well as vibrational fatigue.

Hydrogen presents an attractive option to decarbonise the present energy system. Hydrogen can extend the usage of the existing gas infrastructure with low-cost energy storability and flexibility. Excess electricity generated by renewables can be converted into hydrogen. In this paper a novel multi-energy systems optimisation model was proposed to maximise investment and operating synergy in the electricity heating and transport sectors considering the integration of a hydrogen system to minimise the overall costs. The model considers two hydrogen production processes: (i) gas-to-gas (G2G) with carbon capture and storage (CCS) and (ii) power-to-gas (P2G). The proposed model was applied in a future Great Britain (GB) system. Through a comparison with the system without hydrogen the results showed that the G2G process could reduce £3.9 bn/year and that the P2G process could bring £2.1 bn/year in cost-savings under a 30 Mt carbon target. The results also demonstrate the system implications of the two hydrogen production processes on the investment and operation of other energy sectors. The G2G process can reduce the total power generation capacity from 71 GW to 53 GW and the P2G process can promote the integration of wind power from 83 GW to 130 GW under a 30 Mt carbon target. The results also demonstrate the changes in the heating strategies driven by the different hydrogen production processes.

This work reports a numerical investigation of microcombustion in an undulate microchannel using premixed hydrogen and air to understand the effect of the burner design on the flame in order to obtain stability of the flame. The simulations were performed for a fixed equivalence ratio and a hyperbolic temperature profile imposed at the microchannel walls in order to mimic the heat external losses occurred in experimental setups. Due to the complexity of the flow dynamics combined with the combustion behavior the present study focuses on understanding the effect of the fuel inlet rate on the flame characteristics keeping other parameters constant. The results presented stable flame structure regardless of the inlet velocity for this type of design meaning that a significant reduction in the heat flux losses through the walls occurred allowing the design of new simpler systems. The increase in inlet velocity increased the flame extension with the flame being stretched along the microchannel. For higher velocities flame separation was observed with two detected different combustion zones and the temperature profiles along the burner centerline presented a non-monotonic decrease due to the dynamics of the vortices observed in the convex regions of the undulated geometry walls. The geometry effects on the flame structure flow field thermal evolution and species distribution for different inlet velocities are reported and discussed.

To meet the needs of public and private stakeholders involved in the development construction and operation of hydrogen fuelling stations needed to support the widespread roll-out of hydrogen fuel cell electric vehicles this work presents publicly available station templates and analyses. These ‘Reference Stations’ help reduce the cost and speed the deployment of hydrogen stations by providing a common baseline with which to start a design enable quick assessment of potential sites for a hydrogen station identify contributors to poor economics and suggest areas of research. This work presents layouts bills of materials piping and instrumentation diagrams and detailed analyses of five new station designs. In the near term delivered hydrogen results in a lower cost of hydrogen compared to on-site production via steam methane reforming or electrolysis although the on-site production methods have other advantages. Modular station concepts including on-site production can reduce lot sizes from conventional assemble-on-site stations.

This study was conducted for a group of 15 clients in the public and private sectors interested in potential pathways for decarbonising residential heating and the impact of these pathways on the energy system. The ambition for all new heating installations to be low carbon from 2035 is essential to meeting the net zero target in 2050 and our study found that electricity demand for home heating is set to quadruple by 2050 as part of the shift away from gas-fired boilers.

The key findings from the study include:

• Phasing out natural gas boiler installations by 2035 is crucial for eliminating CO2 from home heating; delaying to 2040 could leave us with ¼ of today’s home heat emissions in 2050
• Achieving deployment of 600k heat pumps per year by 2028 will require policy intervention both to lower costs and to inform and protect consumers Almost £40bn could be saved in cumulative system costs by 2050 through adoption of more efficient and flexible electric heating technologies like networked heat pumps and storage
• Electricity demand from heating could quadruple by 2050 to over 100TWh per year almost a third of Great Britain’s current total annual electricity demand Using hydrogen for a share of heating could lower peak power demand although producing most of this hydrogen from electrolysis would raise overall power demand.

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In the present work the effect of artificial ageing of AA2024-T3 on the tensile mechanical properties and fracture toughness degradation due to corrosion exposure will be investigated. Tensile and fracture toughness specimens were artificially aged to tempers that correspond to Under-Ageing (UA) Peak-Ageing (PA) and Over-Ageing (OA) conditions and then were subsequently exposed to exfoliation corrosion environment. The corrosion exposure time was selected to be the least possible according to the experimental work of Alexopoulos et al. (2016) so as to avoid the formation of large surface pits trying to simulate the hydrogen embrittlement degradation only. The mechanical test results show that minimum corrosion-induced decrease in elongation at fracture was achieved for the peak-ageing condition while maximum was noticed at the under-ageing and over-ageing conditions. Yield stress decrease due to corrosion is less sensitive to tempering; fracture toughness decrease was sensitive to ageing heat treatment thus proving that the S΄ particles play a significant role on the corrosion-induced degradation.

In the last two years or so there has been increasing interest in hydrogen as an energy source in Australia and around the world. Notably this is not the first time that hydrogen has caught our collective interest. Most recently the 2000s saw a substantial investment in hydrogen research development and demonstration around the world. Prior to that the oil crises of the 1970s also stimulated significant investment in hydrogen and earlier still the literature on hydrogen was not lacking. And yet the hydrogen economy is still an idea only.<br/>So what if anything might be different this time?<br/>This is an important question that we all need to ask and for which the author can only give two potential answers. First our need to make dramatic reductions in greenhouse gas (GHG) emissions has become more pressing since these previous waves of interest. Second renewable energy is considerably more affordable now than it was before and it has consistently outperformed expectations in terms of cost reductions by even its strongest supporters.<br/>While this dramatic and ongoing reduction in the cost of renewables is very promising our need to achieve substantial GHG emission reductions is the crucial challenge. Moreover meeting this challenge needs to be achieved with as little adverse social and economic impact as possible.<br/>When considering what role hydrogen might play we should first think carefully about the massive scale and complexity of our global energy system and the typical prices of the major energy commodities. This provides insights into what opportunities hydrogen may have. Considering a temperate country with a small population like Australia we see that domestic natural gas and transport fuel markets are comparable to and even larger than the electricity market on an energy basis.

Microalloyed steels have evolved in terms of their chemical composition processing and metallurgical characteristics since the beginning of the 20th century in the function of fabrication costs and mechanical properties required to obtain high-performance materials needed to accommodate for the growing demands of gas and hydrocarbons transport. As a result of this microalloyed steels present a good combination of high strength and ductility obtained through the addition of microalloying elements thermomechanical processing and controlled cooling processes capable of producing complex microstructures that improve the mechanical properties of steels. These controlled microstructures can be severely affected and result in catastrophic failures due to the atomic hydrogen diffusion that occurs during the corrosion process of pipeline steel. Recently a martensite–bainite microstructure with acicular ferrite has been chosen as a viable candidate to be used in environments with the presence of hydrogen. The aim of this review is to summarize the main changes of chemical composition processing techniques and the evolution of the mechanical properties throughout recent history on the use of microalloying in high strength low alloy steels as well as the effects of hydrogen in newly created pipelines examining the causes behind the mechanisms of hydrogen embrittlement in these steels.

As nations around the world seek to reduce carbon dioxide emissions in order to mitigate climate change risks there has been a resurgence of interest in the use of hydrogen as a zero-emissions energy carrier. Hydrogen can be produced from diverse feedstocks via a range of low-emissions pathways and has broad potential in the process of decarbonization across the energy transport and industrial sectors.<br/>With an abundance of both renewable and fossil fuel energy resources a comparatively low national energy demand and excellent existing regional resource trading links Australia is well positioned to pursue industrial-scale hydrogen production for both domestic and export purposes. In this paper we present an overview of the progress at the government industry and research levels currently undertaken to enable a large-scale hydrogen industry for Australia.

The cost of the hydrogen value chain needs to be reduced to allow the widespread development of hydrogen applications. Mechanical compressors widely used for compressing hydrogen to date account for more than 50% of the CAPEX (capital expenditure) in a hydrogen refuelling station. Moreover mechanical compressors have several disadvantages such as the presence of many moving parts hydrogen embrittlement and high consumption of energy. Non-mechanical hydrogen compressors have proven to be a valid alternative to mechanical compressors. Among these electrochemical compressors allow isothermal and therefore highly efficient compression of hydrogen. On the other hand adsorption-desorption compressors allow hydrogen to be compressed through cooling/heating cycles using highly microporous materials as hydrogen adsorbents. A non-mechanical hybrid hydrogen compressor consisting of a first electrochemical stage followed by a second stage driven by adsorption-desorption of hydrogen on activated carbons allows hydrogen to be produced at 70 MPa a value currently required for the development of hydrogen automotive applications. This system has several advantages over mechanical compressors such as the absence of moving parts and high compactness. Its use in decentralized hydrogen facilities such as hydrogen refuelling stations can be considered