Australia

Hydrogen storage in depleted gas reservoirs triggers geochemical and microbiological reactions at the caprockreservoir interface yielding significant implications on storage integrity. Acetogenesis is a microbial reaction observed during underground hydrogen storage (UHS) that produces acetate and converts it into acetic acid under protonation potentially impacting the UHS process integrity. For the first time this research explores the impact of the acetic acid + brine + caprock reaction on shale caprock mineralogy microstructure and physicochemical properties where this preliminary study has been conducted under ambient conditions to obtain an initial assessment of the impact. A comprehensive mineralogical and micro-structural characterization including scanning electron microscopy (SEM) energy dispersive X-ray spectroscopy (EDS) X-ray fluorescence (XRF) Xray diffraction (XRD) micro-computed tomography (micro-CT) and inductively coupled plasma mass spectrometry (ICP-MS) have been conducted to assess the mineralogical and microstructural changes in shale specimens saturated with brine solutions with a range of acetic acid percentages (5 % 10 % and 20 %) to find the maximum possible impact. According to the conducted mineralogical analysis (EDS XRF and XRD) there is a significant primary mineral dissolution during the acetic acid interaction where calcite and dolomite are the predominant minerals dissolved evidencing the significant impact of the acetic acid reaction on carbonate-rich caprock systems during UHS. However secondary mineral precipitation happened at high acidic concentrations (20 %). Interestingly other common minerals in reservoir rocks (e.g. mica pyrite) did not demonstrate rapid interactions with acetic acid compared to carbonates. The impact of these mineralogical changes on the caprock microstructure was then investigated through SEM and micro-CT and the results demonstrate substantial enhancements in porosity and microcracks in the rock matrix due to the calcite and dolomite dissolutions despite some microcracks being closed by secondary precipitations. This preliminary study evidences the significant impact of acidification on caprock integrity which may occur during the acetogenesis reaction in UHS environments. These effects should be carefully considered in field UHS projects to eliminate the risks.

Hydrogen can play a significant role in Australian economy and Australia has set an ambitious goal to become a global leader in hydrogen industry as outlined in the National Hydrogen Strategy 2024. Hydrogen is an efficient energy carrier that can be used for both transporting and storing energy. Underground hydrogen storage (UHS) in aquifers depleted gas and oil reservoirs and salt caverns have been considered as a low-cost option for largescale storage of hydrogen. In this study a method for hydrogen storage in engineered (shallow) lenses is proposed where a lens is created in a very low permeability layered formation such as shales via opening the layers by a pressurised fluid. A preliminary overview of the Australian basins is presented focussing on the most suitable/obvious units for the purpose of creating engineered lenses for storage of hydrogen. Major engineering aspects of lenses such as size volume storage capacity storage time and hydrogen loss are reviewed followed by a Techno-Economic Analysis for the proposed hydrogen storage method. Initial modelling shows that up to 250 tonnes of hydrogen can be stored in shallow engineered lenses incurring a capital cost of 35.7 US$/kg and total annual operational cost of 7 US$/kg making the proposed storage method a competitive option against salt and lined rock caverns. Finally Monitoring and Verification (M&V) as part of storage assurance practice has been discussed and successful examples are presented.

Green hydrogen is a promising energy carrier for the decarbonization of hard-toabate sectors and supporting renewable energy integration aligning with carbon neutrality goals like the European Green Deal. Iceland’s abundant renewable energy and decarbonized electricity system position it as a strong candidate for green hydrogen production. Despite early initiatives its hydrogen economy has yet to significantly expand. This study evaluated Iceland’s hydrogen development through stakeholder interviews and a techno-economic analysis of alkaline and PEM electrolyzers. Stakeholders were driven by decarbonization goals economic opportunities and energy security but faced technological economic and governance challenges. Recommendations include building stakeholder confidence financial incentives and creating hydrogen-based chemicals to boost demand. Currently alkaline electrolyzers are more cost-effective (EUR 1.5–2.8/kg) than PEMs (EUR 2.1–3.6/kg) though the future costs for both could drop below EUR 1.5/kg. Iceland’s low electricity costs and high electrolyzer capacity provide a competitive edge. However this advantage may shrink as solar and wind costs decline globally particularly in regions like Australia. This work’s findings emphasize the need for strategic planning to sustain competitiveness and offer transferable insights for other regions introducing hydrogen into ecosystems lacking infrastructure.

This study comprehensively reviews the state-of-the-art laboratory-scale fracture mechanics testing methods to assess their suitability for investigating stress-induced critical cracks and geochemically induced subcritical cracks in caprock during underground hydrogen storage. Subcritical crack propagation is primarily examined using empirical techniques such as double torsion and constant stress-rate methods. Both methods determine stress intensity factors and crack velocities without requiring crack length measurements. Comparatively the double torsion method provides advantages such as simple sample preparation and pre-cracking process continuous data acquisition and fracture toughness measurements which makes it more reliable for caprockrelated studies. The International Society for Rock Mechanics recommends four standard methods for critical crack propagation to determine fracture toughness values. Chevron-notched specimens including the Chevron Bend specimen Short Rod specimen and Cracked Chevron Notched Brazilian Disk specimen exhibit higher uncertainty in fracture toughness data due to specimen size effects additional fixture requirements and undesirable crack formations. In contrast the Semi-Circular Bend specimen method is frequently employed due to its smaller specimen size simplified testing and well-balanced dynamic forces. Despite these advancements studies on multiple cracking behaviour in caprock under subsurface hydrogen storage conditions remain limited. The conventional methods discussed in this review are primarily designed to function at ambient conditions making it challenging to replicate subsurface geochemical interactions. Future studies should focus more on developing new laboratory techniques and enhancing existing specimen configurations by incorporating specialised apparatus such as high-pressure cells and reaction chambers to implement typical subsurface conditions observed during underground hydrogen storage. Additionally more parametric studies on caprock samples are recommended to generate a comprehensive dataset on subcritical and critical crack propagation and validate the reliability of these testing methods for underground hydrogen storage applications.

Unlocking the potential of offshore renewables for green hydrogen (GH2) production can be a game-changer empowering economies with their visionary clean energy policies amplifying energy security and promoting economic growth. However their novelty entails uncertainty and risk necessitating a robust framework for facility deployment and infrastructure planning. To optimize offshore GH2 infrastructure placement this work proposes a novel and robust GIS-based multi-criteria decision-making (MCDM) framework. Encompassing thirtytwo techno-socio-economic-safety factors and ocean environmental impact analysis this methodology facilitates informed decision-making for sustainable and safe GH2 development. Utilizing the synergies between offshore wind and solar resources this study investigates the potential of hybrid ocean technologies to enhance space utilization and optimize efficiency. To illustrate the practical application of the proposed framework a case study examining a GH2 system in Australia's marine region and its potential nexus with nearby offshore industries has been conducted. The performed life cycle assessment (LCA) explored various configurations of GH2 production storage and transportation technologies. A Bayesian objective weight integrating technique has been introduced and contrasted statistically with the hybrid CRITIC Entropy MEREC and MARCOS-based MCDM approaches. Various locations are ranked based on the net present value of life cycle cost GH2 production capacity risk availability and environment sustainability factors illustrating their compatibility. A sensitivity analysis is conducted to confirm that a Bayesian approach improves the decision-making outcomes through identifying optimal criteria weights and alternative ranks more effectively. Empowering strategic GH2 decisions globally the proposed approach optimizes system performances cost sustainability and safety excelling in harsh environments.

The purpose of this Hydrogen Pipeline System COP is to provide guidance based on current knowledge for the design construction and operation of transmission pipeline systems transporting gaseous hydrogen or blends of hydrogen and hydrocarbon fluids.<br/>The objective of the code is to provide guidance for the safe reliable and efficient transportation and storage of hydrogen in transmission pipeline systems that are required to conform to the AS(/NZS) 2885 series. The document also references adoption of other international codes where suitable guidance is available.<br/>This document is intended to be updated with revised design criteria and methods as research and experience improves the understanding of hydrogen service in transmission pipelines. Although the CoP may be further developed into a published standard in the future within the AS(/NSZ) 2885 series framework this current revision of the CoP is not equivalent to a formal published Australian standard. The document also includes expanded commentary and background information as an informative code of practice that is more extensive than is typically covered in a standard.

Research into the off-grid hybrid energy system to provide reliable electricity to a remote community has extensively been done. However simultaneous meeting electric freshwater and gas demands from the off-grid hybrid energy sources are very scarce in literature. Power- to-X (PtX) is gaining attention in recent days in the energy transition scenarios to generate green hydrogen the primary product of the process as an energy carrier which is deemed to replace conventional fuels to reach absolute carbon neutrality. In this study renew able–based hybrid energy is developed to simultaneously meet the electricity freshwater and gas (cooking gas via methanation process) demands for a remote Island in Bangladesh. In this process an energy management strategy has been developed to use the excess energy to generate both freshwater and the hydrogen where hydrogen is then converted to natural gas via methanation process. The PV wind turbine diesel generator battery and fuel cell have been optimized using non-dominating sorting algorithm-II (NSGA-II) to offer reliable cost-effective solutions of electricity freshwater and cooking gas for the end users. Results reported that the PV/ WT/DG/Batt configuration has been found the most economic configuration with the lowest COE (0.1724 $/kWh) which is 9 % lower than PV/WT/Batt configuration which has the second lowest COE. The cost of water (COW) and cost of gas (COG) of the PV/WT/DG/Batt system are also the lowest among all the four configurations and have been found 1.185 $/m3 and 3.978 $/m3 respectively.

Bio-hydrogen production (BHP) produced from renewable bio-resources is an attractive route for green energy production due to its compelling advantages of relative high efficiency cost-effectiveness and lower ecological impact. This study reviewed different BHP pathways and the most important enzymes involved in these pathways to identify technological gaps and effective approaches for process intensification in industrial applications. Among the various approaches reviewed in this study a particular focus was set on the latest methods of chemicals/metal addition for improving hydrogen generation during dark fermentation (DF) processes; the up-to-date findings of different chemicals/metal addition methods have been quantitatively evaluated and thoroughly compared in this paper. A new efficiency evaluation criterion is also proposed allowing different BHP processes to be compared with greater simplicity and validity

Massive theoretical and applied research is underway worldwide to assess the viability of transporting natural gas-hydrogen blends in pipelines. For the first time this work derives simplified but closed-form equations that describe how changes in gas properties due to hydrogen blending at different volumes map to specific changes in pressure drop compressor power and linepack. These first-of-their-kind equations which are extensively validated against transient gas flow models enabled three unprecedented and unique findings. The first finding which quantifies how a change in demand maps to a change in delay and swing on the supply side reveals that pressure swings increase monotonically with an increase in hydrogen blending volume translating into an increase in pipeline fatigue and risk of failure. The second finding crucially shows that pressure drop does not monotonically increase with an increase in hydrogen blending volume; in fact it is highest at around 85 % hydrogen volume not at 100 %. The third finding shows that the decrease in linepack as a result of an increase in hydrogen volume is not only related to the gross calorific value of the gas mixture but also to the pressure-tocompressibility factor ratio suggesting that smaller parallel pipelines can offset this linepack reduction compared to a single larger pipeline.

Green hydrogen is a promising energy vector for replacing fossil fuels in hard-to-abate sectors but its cost hinders widespread deployment. This research develops an exact MILP model to optimize the design of integrated green energy projects minimizing the total annual cost between different power configurations. The model is applied to a case study in regional Victoria Australia which supports a fleet of nine fuel cell electric buses requiring 1160 kg of hydrogen per week. The optimal system includes a 453 kW electrolyzer 212 kg of storage in compressed hydrogen vessels 704 kW of solar PV and 635 kW of wind power firmed with grid electricity. The LCOH is 14.8 A$/kg which is higher than other estimates in the literature for Australia. This is arguably due to the idle capacities resulting from intermittent hydrogen demand. Producing additional hydrogen with surplus or low-priced electricity could reduce LCOH to 12.4 A$/kg. Sensitivity analyzes confirm the robustness of the system to variations in key parameter costs resource availability and estimated energy supply and demand.