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The anticipated surge in hydrogen energy adoption underscores the pivotal role of social acceptance in determining the viability of hydrogen technologies (HTs). This review provides a comprehensive overview of acceptance research on HT, evaluating measurement tools and utilized models, identifying influencing factors, and analyzing academic discourse on HT diffusion. Drawing from 39 studies, it highlights key acceptance factors: trust, environmental attitudes, subjective knowledge, and perceived risks. Discourse analysis uncovers perceived barriers like trust deficits, infrastructural challenges, and financial constraints, while strategic considerations such as timing and transparency are identified as drivers. The findings emphasize an individual-centred perspective, heterogeneous operationalizations, and a lack of longitudinal studies. The authors propose increased downstream research, focusing on societal reactions to implemented technologies and considering both psychological and contextual factors. Adoption of multi-level and institutional perspectives is essential. • Environmental attitude is the most studied factor influencing H2 technology acceptance. • Education campaigns and support schemes are frequently cited to drive H2 adoption. • Focus on upstream research neglects acceptance dynamics. • 70% of studies reference established models; many detach theory from studied factors. • Adoption of multi-level perspectives and an increase in longitudinal studies needed. [ABSTRACT FROM AUTHOR]

Transitioning to a sustainable energy future necessitates innovative storage solutions for renewable energies, where hydrogen (H₂) emerges as a pivotal energy carrier for its low emission potential. This paper explores unlined rock caverns (URCs) as a promising alternative for underground hydrogen storage (UHS), overcoming the geographical and technical limitations of UHS methods like salt rock caverns and porous media. Drawing from the experiences of natural gas (NG) and compressed air energy storage (CAES) in URCs, we explore the viability of URCs for storing hydrogen at gigawatt-hour scales (>100 GWh). Despite challenges such as potential uplift failures (at a depth of approximately less than 1000 m) and hydrogen reactivity with storage materials at typical conditions (below temperatures of 100°C and pressures of 15 MPa), URCs present a flexible, scalable option closely allied with green hydrogen production from renewable sources. Our comprehensive review identifies critical design considerations, including hydraulic containment and the integrity of fracture sealing materials under UHS conditions. Addressing identified knowledge gaps, particularly around the design of hydraulic containment systems and the interaction of hydrogen with cavern materials, will be crucial for advancing URC technology. The paper underscores the need for further experimental and numerical studies to refine URC suitability for hydrogen storage, highlighting the role of URCs in enhancing the compatibility of renewable energy sources with the grid. • Detailed exploration of unlined rock cavern (URC) technology. • Analysis of URCs' potential for large-scale hydrogen storage. • Insights from historical use of URCs in compressed gas storage. • Examination of the opportunities and challenges in using URCs for hydrogen storage. [ABSTRACT FROM AUTHOR]

The main performance indicators of hydrogen energy production should be improved. However, improving these factors also increase the operational costs of the companies. Because of this issue, there is a need for a priority analysis so that it can be possible to focus on more important factors. Accordingly, the purpose of this study is to evaluate hydrogen production methods for global energy transition. In this process, a four-stage model has been proposed by getting evaluations from three different experts. Firstly, artificial intelligence-based decision-making can be implemented for expert prioritization. In the second stage, recommender system is conducted with collaborative filtering to complete the missing evaluations. Thirdly, selected criteria are weighted by using M-SWARA with QPFRS. Finally, method alternatives for hydrogen production are ranked via quantum picture fuzzy rough sets adopted VIKOR. The biggest contribution for doing this study is that artificial intelligence technique is integrated into the model and experts' importance coefficients are can be computed. Additionally, by using the collaborative filtering technique, empty evaluations can be filled scientifically. This contributes to the quality of the analysis process in many ways. Thanks to this technique, experts are given the opportunity not to answer questions they are not very sure about. The findings indicate that renewable energy expansion, energy efficiency and sustainable development are the most important criteria for global energy transition in hydrogen production. On the other side, the ranking results give information that thermal processes including steam methane reforming and biomass gasification is the most appropriate method alternatives for hydrogen production. Based on these analysis results, it is strongly recommended that research and development activities should be improved to increase the efficiency and effectiveness of the renewable energy projects. With the help of this issue, it can be much easier to increase the performance of hydrogen production process. • Hydrogen production methods are evaluated for global energy transition. • A four-stage model has been proposed. • Selected criteria are weighted by using M-SWARA. • Method alternatives for hydrogen production are ranked via VIKOR. • Renewable energy expansion is the most important criteria. [ABSTRACT FROM AUTHOR]

The catastrophic effects of climate change can be mitigated by transitioning to renewable energy sources such as wind, solar, and hydropower while utilizing hydrogen (H 2) as an energy carrier. As renewable fuel sources are intermittent and location-specific, large-scale, long-term storage options for H 2 must be explored with high necessity. Subsurface hydrogen storage in saline aquifers provides a vital scope to store H 2 gas in available pore voids with minimal environmental risk. In this work, a highly heterogeneous porous micromodel was used to study the immiscible two-phase dynamics at high-temperature, high-pressure saline aquifer conditions using computational fluid dynamics (CFD) simulation based on volume of fluid (VOF) method. A set of microfluidic experiments were carried out under atmospheric conditions to validate the numerical model. The VOF model was observed to show good agreement with microfluidic experiments. An unstable displacement pattern with viscous fingering was observed during various flow conditions that captured high pressure (15 and 25 MPa) and temperature conditions (323 and 343 K). It was observed that fingering displacement of brine limits the storage spaces for hydrogen, which consequently follows the high permeable path. As a result, only 0.272 fraction of brine was invaded by the H 2 at a temperature of 323 K and pressure of 15 MPa. A comparison between H 2 -brine and nitrogen (N 2)-brine flow dynamics revealed a 46% less storage capacity of porous media for H 2. Formations bearing high temperature (343 K) showed an 11.27% increase in H 2 storage capacity, while pressure increase had negligible effect. At low capillary number (Ca), more snap-off effects resulted in higher trapping of H 2 gas. This study aims to provide meaningful insights into the complexities of flow dynamics and displacement patterns that are crucial for optimizing hydrogen storage efficiency in saline aquifers and for potential 'white' hydrogen production. [Display omitted] • Hydrogen-brine two-phase flow was simulated in a heterogeneous porous media. • Simulation captures pressure and temperature conditions of geological aquifers. • Microfluidic experiments were carried out to validate the numerical model. • Viscous fingering under high-pressure and temperature limits hydrogen storage. • More snap-off effects lead to increased hydrogen trapping in porous media. [ABSTRACT FROM AUTHOR]

To meet the projected increase in global demand for energy while tackling sustainability concerns, the widespread adoption of renewable energy is inevitable. Once harnessed, exports of this renewable energy from regions with excess resources are anticipated to those that will require imports of energy. The shipping sector will thus play a pivotal role in enabling such trade through energy carriers such as hydrogen, ammonia, methanol, and liquid organic hydrogen carriers. Furthermore, in addition to these energy carriers, carbon dioxide is also expected to become an important maritime trade commodity to achieve climate targets. Through the deployment of carbon capture utilization and storage, and more recently, negative emission technologies, carbon dioxide will need to be transported to regions with the appropriate infrastructure and resources necessary for their anticipated implementation. Presently, in light of these circumstances, the lack of experience in shipping a number of these energy carriers and carbon dioxide must be addressed. As such, an understanding of the techno-economic and environmental feasibility of the large-scale shipping of these commodities must be established at all scales of operation. Accordingly, this work proposes the use of process systems engineering based approaches to enable the marine transportation of these future energy carriers and carbon dioxide from a multi-scale perspective. To lay the foundation in support of this initiative, a framework that considers the multiple scales involved is then presented for the design and operation of progressive ships and their supply chains as part of a decarbonized energy system. [Display omitted] • Discussed the potential of shipping energy carriers and carbon in achieving climate targets. • Identified feasibility challenges surrounding the large-scale shipping of hydrogen carriers. • Proposed a multi-scale framework for the design of ships and supply chains. [ABSTRACT FROM AUTHOR]

Hydrogen exploration in the municipality of Maricá (Rio de Janeiro State, Brazil) indicates that important hydrogen and helium gas fluxes are emitted through reactivated faults. The gas concentrations in the soils, and the modelled gas fluxes, are among the most intense measured so far in the world. This exploration has shown new surface expression of hydrogen micro-seeps, observed along reactivated large tectonic accidents instead of "fairy circles", most common proxy for hydrogen systems in cratonic formation. The geology of Maricá, consisting in Neoproterozoic metamorphic rocks without any already documented evidence of hydrogen-prone formations, appears as a very new field of investigation for natural hydrogen. Results indicate the presence of systematic hydrogen saturation of the usual detectors plugged at 80 cm depth, as well as a permanent recharge of hydrogen through time, without relaxation time. Moreover, positive helium anomalies are associated with this hydrogen soil gas, proving the existence of a gas flux coming from deep horizons of the subsurface. This reduces the risk of misinterpretation of surface hydrogen measurement, since the fear of drill bit metamorphism or superficial biological activity inducing hydrogen artefacts is always a possibility. These hydrogen and helium micro-seeps are associated with positive thorium concentration superficial anomalies, as it was already observed in other places associated with hydrogen exudations. We present a model of soil gas behavior, with a differential process of adsorption/desorption of each gas compound (N 2 , O 2 , Ne, H 2 and He), associated with a deep flux of hydrogen and helium. It is possible to assess a quantification of hydrogen flux of 0.32 m3 m−2.day−1. The surface flux ratio He/H 2 is much higher than any published value of generative flux. This may be explained by a subsurface accumulation, where hydrogen is severely altered whereas helium is preserved, increasing the relative proportion of helium versus hydrogen. [Display omitted] • The Marica municipality (Brazil) reveals important potential for natural hydrogen. • Reactivated faults are excellent proxies for natural hydrogen exploration. • Hydrogen seeping out of reactivated faults may be larger than in fairy circles. • Association of hydrogen and helium in soils indicates that no artefact concerns the hydrogen measurements in soils. • Metamorphic formations may be excellent candidates for hydrogen exploration. [ABSTRACT FROM AUTHOR]

Hydrogen-fuelled technologies for home heating and cooking may provide a low-carbon solution for decarbonising parts of the global housing stock. For the transition to transpire, the attitudes and perceptions of consumers must be factored into policy making efforts. However, empirical studies are yet to explore potential levels of consumer heterogeneity regarding domestic hydrogen acceptance. In response, this study explores a wide spectrum of consumer responses towards the prospect of hydrogen homes. The proposed spectrum is conceptualised in terms of the 'domestic hydrogen acceptance matrix', which is examined through a nationally representative online survey conducted in the United Kingdom. The results draw attention to the importance of interest and engagement in environmental issues, knowledge and awareness of renewable energy technologies, and early adoption potential, as key drivers of domestic hydrogen acceptance. Critically, strategic measures should be taken to convert hydrogen scepticism and pessimism into hope and optimism by recognising the multi-dimensional nature of consumer acceptance. To this end, resources should be dedicated towards increasing the observability and trialability of hydrogen homes in proximity to industrial clusters and hubs, where the stakes for consumer acceptance are highest. Progress towards realising a net-zero society can be supported by early stakeholder engagement with the domestic hydrogen acceptance matrix. • Domestic hydrogen acceptance entails a spectrum of multi-dimensional responses. • Interest and engagement in environmental issues enhances hydrogen acceptance. • Knowledge and awareness of renewables promotes hydrogen optimism. • Consumer innovativeness is associated with support for hydrogen homes. • Consumer-orientated research can help steer the domestic hydrogen transition. [ABSTRACT FROM AUTHOR]

Subsurface porous rocks hold significant hydrogen (H 2) storage potential to support an H 2 -based energy future. Understanding H 2 flow and trapping in subsurface rocks is crucial to reliably evaluate their storage efficiency. In this work, we perform cyclic H 2 flow visualization experiments on a layered rock sample with varying pore and throat sizes. During drainage, H 2 follows a path consisting of large pores and throats, through a low permeability rock layer, substantially reducing H 2 storage capacity. Moreover, due to the rock heterogeneity and depending on the experimental flow strategy, imbibition unexpectedly results in higher H 2 saturation compared to drainage. These results emphasize that small-scale rock heterogeneity, which is often unaccounted for in reservoir-scale models, plays a vital role in H 2 displacement and trapping in subsurface porous media, with implications for efficient storage strategies. [Display omitted] • Pore-scale heterogeneity impacts H 2 flow and trapping in sandstones. • Flow direction has a pronounced effect on H 2 trapping in heterogeneous rocks. • Understanding small-scale rock heterogeneity is crucial to build reservoir models. [ABSTRACT FROM AUTHOR]

The article deals with the issue of modern challenges in the development of the fuel and energy complex, including the oil and gas industry as its basis in terms of the volume of tax revenues to the budget. Industry technological priorities have been identified: the creation of domestic equipment and technologies for the traditional upstream fuel and energy complex, digital transformation and the development of Industry 4.0 technologies, the development of technological competencies in key areas of energy transition, and the development of technologies in terms of ecology and industrial safety. The world experience of supporting the development of scientific research in industry is analyzed on the example of the USA, Norway and China. An analysis of the challenges of the institutional development of the fuel and energy complex at all stages from research to serial production is presented. The covenants of the state in the field of developing human resources for the implementation of the energy transition of the domestic fuel and energy complex, independent of external circumstances, have been determined. Proceeding from the analysis of internal barriers and successful international practices, proposals were made for the development of state technology policy. The National Program of the Russian Federation formulates directions for the development of the industry in the medium term. The technological development of the Russian Federation in the medium term will be influenced, on the one hand, by a number of external and internal threats of technological backwardness and degradation of the Russian economy, and on the other, by emerging new opportunities. Russia has a serious scientific and technical foundation in the field of hydrogen energy, scientific and technical personnel, operating facilities in the hydrogen industry, intellectual property, standard base, design and operational documentation, experience in creating the world's largest hydrogen filling station for launch vehicles and spacecraft ("Energy- Buran") guarantee the successful completion of assigned tasks in the medium term. Huge reserves of biomass, hydro resources, wind resources, geothermal resources, wave energy of the seas and oceans, solar energy provide enormous opportunities for the export of hydrogen to all interested countries, as well as the widespread use of hydrogen in the national economy, primarily for converting aviation to environmentally friendly fuel and preserving the environment megacities and large urban agglomerations. [ABSTRACT FROM AUTHOR]

Researchers and policymakers are seeking alternatives to oil products. Hydrogen and electricity could be the answer. This review compares both carriers and their technologies across the production chain. This study indicates electricity is more mature and advanced on a large scale. It also presents greater Energy Returns on Investment (EROI) over hydrogen, which portends a viable alternative to oil products. Hydrogen is not adaptable to traditional uses and comes with significant transportation losses, so it's recommended as an energy storage option instead of a carrier. It is a competitive option in areas where grid extension is not feasible and is hard to abate industries. The primary resource of carriers is crucial for their energy and environmental sustainability. Therefore, clean energy and carbon capture and storage technologies and their hybridization across the production chain could define the future energy landscape. • Electricity present greater maturity, energy and environmental advantages. • Hydrogen is proposed as an energy storage medium rather than a carrier. • Energy source of alternatives critical determinant of sustainability. • Renewables, nuclear energy, CCS and technology hybrids define the future of energy. [ABSTRACT FROM AUTHOR]

The envisioned role for Türkiye in the context of Europe's energy strategies should be crucial. By promoting countries like Türkiye can contribute significantly to global efforts in advancing sustainable energy transitions. Moreover, Incorporating Türkiye into Europe's energy strategies can reduce reliance on external energy suppliers and enhance energy security. The findings of this study offer fresh perspectives on the intricacies of the energy system dynamics and make valuable contributions to the ongoing discourse surrounding transition routes. The study takes into account several key aspects, including the current state of hydrogen in Türkiye, the country's potential for renewable energy, the existing policy and regulatory framework, and the necessary infrastructure and market conditions required for the establishment of a hydrogen hub. These insights shed light on the feasibility and viability of hydrogen as an indispensable component within the context of Türkiye 's energy landscape, offering valuable guidance for policymakers, industry stakeholders, and researchers involved in shaping the future of the energy sector. • The envisioned role for Türkiye in the context of Europe's energy strategies. • Insights and perspectives on energy dynamics, enrich discourse on transition routes. • EU-Türkiye green Hydrogen collaboration overcomes political setbacks, forging a transformative alliance. • Türkiye has the potential to seize a significant market share and enhance the value of its expansive territory. • Türkiye and Europe can develop clean energy by transporting pure hydrogen or blending it with natural gas. [ABSTRACT FROM AUTHOR]

The global imperative to transition from fossil fuels to renewable sources is addressed, with hydrogen identified as a pivotal energy carrier. Departing from qualitative approaches, quantitative methodologies are employed to understand the challenges comprehensively. Qualitative insights are quantitatively assessed through a novel index, enabling a nuanced analysis of strengths and weaknesses. The resulting model is a precise tool for informed decision-making in energy transition efforts. Notably, Chile, New Zealand, and Morocco are identified as high-potential economies for hydrogen development, aligning with expert opinions. Conflict demonstrates an overall negative correlation with technological progress, while regulatory quality emerges as a strong positive correlation with the state of hydrogen in policy. This quantitative model offers a robust framework for future research and application, including incorporating additional data and subnational-level analysis. The study provides a quantitative foundation for advancing hydrogen development and sustainable energy transition. • A numerical index can be beneficial to studying the ongoing energy transition. • We present a novel way of quantizing hydrogen development using various indicators. • Results show that there are several "hidden champions" with high growth potential. • Indicators based on varying dimensions of development offer a clear picture forward. [ABSTRACT FROM AUTHOR]

In response to the pressing need for sustainable and greener energy alternatives, this study investigates into the exploration of hydrogen energy as a promising solution. The purpose of this study is to identify the common challenges and potential solutions in hydrogen energy transition and to validate their applicability in Malaysia through expert interviews. This research utilizes various methods: literature review identifies challenges and solutions, bibliometric analysis validates findings, and interviews with Malaysian hydrogen experts validate their applicability for the country. Thematic coding analysis using NVivo software is used to analyse the interview data. From this study, top three challenges are identified as the most applicable in Malaysia: high cost, ambiguous policy and limited infrastructure. Additionally, three potential solutions are considered as the most relevant: establishment of clear policy, encouragement of public-private partnerships, as well as investment in technologies and infrastructure. [ABSTRACT FROM AUTHOR]

Social entrepreneurship plays a crucial role in global sustainable development, enhancing the quality of life and preserving environmental, human, and social capital. However, when it comes to the energy transition, it faces numerous challenges and experiences conflicts in terms of costs, technological innovation, and public policies. This study seeks to illustrate one of the new alternative energy schemes which could replace fossil fuels in the future: hydrogen. This transformation would result in significant social impacts, leading to the question, "how should it be done?" Social entrepreneurship can integrate socio-economic actors and agents and help them to devise and implement new forms of energy innovation. Therefore, a descriptive qualitative methodology was implemented, that allows us to analyze the process of building entrepreneurship with a social vision and to propose a model that enables the transition from fossil economies to the hydrogen economies. Among the most significant results, the importance of the support of the three primary axes of each country and the role of social entrepreneurship as a key element for the transition stand out. The discussion contributes to the debate on the path that academia should lead, and the fundamental role of entrepreneurship based on social conscience as a driver of change. • Hydrogen can replace fossil fuels and reduce emissions. • Proposed model for Hydrogen transition with key role of social entrepreneurship. • Academia's role in social entrepreneurship as driver for change, redefining entrepreneurship to meet societal needs. [ABSTRACT FROM AUTHOR]

Water Flooding (WF) and CO 2 Foam Flooding EOR (CFF) processes are exergy intensive and CO 2 emissive in nature. Hence, the objective of this work is to investigate the ways to attain decarbonization and to evaluate hydrogen requirement for attaining energy transition during WF and CFF processes under different operational conditions. This was performed by using exergy-based evaluation metrics (i.e., Exergy-Return on Exergy-Investment (ERoEI), carbon emissions and hydrogen intensity). It was found that CFF process was 1.69 times more exergy intensive than WF process. Further, for every barrel of oil produced, WF process had net-CO 2 emission of 5.18 kg, while CFF process had net-CO 2 sequestration of 814.5 kg. Moreover, during CFF process, reducing the surfactant concentration from 2.5 wt% to 0.5 wt% had correspondingly decreased CO 2 emissions from 70% to 31%. Further, to attain energy transition during production operations, it was evaluated that WF process requires 1.7 times more hydrogen than CFF process. [Display omitted] • Decarbonization & energy transition was carried out on CO 2 foam flooding EOR process. • Performed sensitivity analysis on various field operations using evaluation metrics. • Manufacturing of surfactants & Injection pumps consumed 66% of total exergy invested. • By using H 2 as fuel source in field operations, the CO 2 emissions are reduced by 62%. • CO 2 foam flooding EOR process sequestrated 27 times more mass of CO 2 than it emitted. [ABSTRACT FROM AUTHOR]

This study investigated the impact of cushion gas type and presence on the performance of underground hydrogen storage (UHS) in an offshore North Sea aquifer. Using numerical simulation, the relationship between cushion gas type and UHS performance was comprehensively evaluated, providing valuable insights for designing an efficient UHS project delivery. Results indicated that cushion gas type can significantly impact the process's recovery efficiency and hydrogen purity. CO 2 was found to have the highest storage capacity, while lighter gases like N 2 and CH 4 exhibited better recovery efficiency. Utilising CH 4 as a cushion gas can lead to a higher recovery efficiency of 80%. It was also determined that utilising either of these cushion gases was always more beneficial than hydrogen storage alone, leading to an incremental hydrogen recovery up to 7%. Additionally, hydrogen purity degraded as each cycle progressed, but improved over time. This study contributes to a better understanding of factors affecting UHS performance and can inform the selection of cushion gas type and optimal operational strategies. • Compositional numerical simulation of underground hydrogen storage in a North Sea aquifer utilising CMG-GEM. • Hydrogen recovery efficiency improves with the utilisation of cushion gas. • CO 2 exhibits highest storage capacity; N 2 and CH 4 improve recovery efficiency. • CH 4 as cushion gas leads to 80% recovery efficiency, minimizing lateral spreading and viscous fingering. • Cushion gas density dictates the efficiency of the underground hydrogen storage scheme. [ABSTRACT FROM AUTHOR]

This study presents a systematic workflow for estimating hydrogen storage capacity for a smooth energy transition from natural gas market to hydrogen market to achieve net-zero emissions. The workflow establishes maximum and minimum thresholds for hydrogen storage and considers appropriate storage techniques, including underground or surface facilities. The technique assesses environmental footprint of each storage technique and evaluates associated emission reductions. We apply this workflow to energy market in Alberta and project minimum and maximum storage thresholds of 0.28 and 5 megatonne/year (Mt/year) by 2050. Under three distinct storage scenarios, the storage capacity necessitates 128 salt caverns, 10 million compressed gas tanks, or 78,150 cryogenic liquefied tanks. Salt cavern storage emerges as a promising choice owing to its relatively lower emissions of 0.16 MtCO 2 e/year and a land footprint of 2.56 km2. The net emission reduction achieved is 1.47 MtCO 2 e/year, equivalent to 0.8% of Canada's target emission reduction of 190 MtCO 2 e/year by 2050. • A workflow is developed to forecast required hydrogen storage capacity in Alberta. • Salt caverns emerge as a reliable and practical technique for large-scale hydrogen storage. • The workflow projects the required number of salt caverns for hydrogen storage. • Supplying stored hydrogen to market reduces 1.5 megatonne/year of GHG emissions. [ABSTRACT FROM AUTHOR]

In aiding India's effort to become carbon neutral, this research focusses on its Southeastern (SE) region, investigating its potential for decarbonization and using of green hydrogen as alternate fuel for industrial operations. The study analyzed the total CO 2 emissions from the power and industrial sectors in the region, and estimated an annual emissions of 307.8 million tonnes. Considering different GDP growth scenarios, this study estimated the demand for energy and green hydrogen until 2050 for achieving energy transition. Based on the region's renewable energy capacity, an optimal energy mix of 5% small hydro, 45% wind and 50% solar power is recommended for green hydrogen production. This study found that the Cauvery and Krishna-Godavari basins have the storage potential to continuously deliver the stored hydrogen for seven years to the region, ensuring energy security. Finally, by decarbonizing industrial operations in SE region, the global temperature rise could be reduced by 0.003842 °C. [Display omitted] • Power plants are the leading CO 2 emitters, contributing to 64% of total CO 2 emissions. • Energy demand projected till 2050, with Andhra Pradesh as leading consumer. • Quantified green hydrogen and solar energy demand to achieve energy transition. • Hydrogen storage capacity of Cauvery and KG basins for energy security are assessed. • Cauvery and KG basins can potentially deliver the stored H 2 continuously for 6 years. [ABSTRACT FROM AUTHOR]

The transition to a low-carbon energy system can be depicted as a "great reconfiguration" from a socio-technical perspective that carries the risk of impact shifts. Electrification with the objective of achieving rapidly deep decarbonisation must be accompanied by effective efficiency and flexibility measures. Hydrogen can be a preferred option in the decarbonisation process where electrification of end-uses is difficult or impractical as well as for long-term storage in energy infrastructure characterised by a large penetration of renewable energy sources. Notwithstanding the current uncertainties regarding costs, environmental impact and the inherent difficulties of increasing rapidly supply capacity, hydrogen can represent a solution to be used in multi-energy systems with combined heat and power (CHP), in particular in urban energy districts. In fact, while achieving carbon savings with natural gas fuelled CHP is not possible when low grid carbon intensity factors are present, it may still be possible to use it to provide flexibility services and to reduce emissions further with switch from natural gas to hydrogen. In this paper, a commercially established urban district energy scheme located in Southampton (United Kingdom) is analysed with the goal of exploring potential variations in its energy demand. The study proposes the use of scalable data-driven methods and probabilistic simulation to generate seasonal energy demand patterns representing the potential short-term and long-term evolution of the energy district. • Hydrogen role in the transition to low carbon energy systems for urban energy district. • Data-driven urban energy modelling using regression-based approaches. • Probabilistic modelling of energy demand in terms of electricity and fuels. • Climate change impact and energy efficiency measures accounting. • Seasonal variations of energy demand patterns from short-term to long-term scenarios. [ABSTRACT FROM AUTHOR]

Large-scale hydrogen underground storage is widely considered as an important solution for energy transition to mitigate global warming, however, our understanding on the various chemical and physical processes leading to H 2 loss during geo-storage remains largely unknown. We conducted adsorption isotherms measurements of H 2 , CH 4 and CO 2 on Cretaceous Cameo coal at 35, 50 and 65 °C, to explore adsorption mechanisms of H 2 and deciphering the effect of cushion gas (e.g., CH 4 , CO 2) on H 2 loss in the subsurface. The adsorbed amounts of H 2 are just 12% and 6% of CH 4 and CO 2 at temperature of 35 °C and pressure of 2.3 MPa, respectively, and H 2 adsorption behavior on Cameo coal can be described well by Langmuir monolayer theory. The extremely high Langmuir pressures (35–49 MPa) for H 2 indicate very weak affinity with coal, compared to CH 4 and CO 2. Differences of Langmuir adsorption capacities suggest that the gas adsorption of H 2 and CH 4 are mainly by physical interactions while both physical and chemical bonding with coal structures occurs for CO 2. The affinity with solid materials for the three gases can be quantitatively evaluated by the heat of adsorption, which was determined to be ∼9.2 kJ/mol for H 2. Extrapolation of our experimental results to natural coal seams indicates that H 2 presents much smaller adsorption amounts at depth up to 2000 m, corresponding to temperatures lower than 65 °C and pressure less than 30 MPa, geological conditions that are suitable for hydrogen underground storage. This study confirms that the injection of CH 4 or CO 2 as cushion gas can largely reduce the H 2 loss by adsorption in the subsurface. Empirical calculation suggests H 2 adsorption will be insignificant with chemical composition of CH 4 above 8% or CO 2 above 2% at the storage sites (e.g., abandoned mines, depleted coal seams). Our study lays a foundation on the understanding of the risk of H 2 loss in large-scale hydrogen underground storage. • Adsorbed amounts of H 2 are much smaller than CH 4 and CO 2. • Weak affinity of H 2 with coals is quantitatively evaluated. • H 2 loss by adsorption during geological storage can be significantly reduced by the injection of CH 4 or CO 2 as cushion gas. [ABSTRACT FROM AUTHOR]

Underground hydrogen storage (UHS) in aquifers, salt caverns and depleted hydrocarbon reservoirs allows for the storage of larger volumes of H 2 compared to surface storage in vessels. In this work, we investigate the impact of aquifer-related mechanisms and parameters on the performance of UHS in an associated North Sea aquifer using 3D numerical compositional simulations. Simulation results revealed that the aquifer's permeability heterogeneity has a significant impact on the H 2 recovery efficiency where a more homogenous rock would lead to improved H 2 productivity. The inclusion of relative permeability hysteresis resulted in a drop in the H 2 injectivity and recovery due to H 2 discontinuity inside the aquifer which leads to residual H 2 during the withdrawal periods. In contrast, the effects of hydrogen solubility and hydrogen diffusion were negligible when studied each in isolation from other factors. Hence, it is essential to properly account for hysteresis and heterogeneity when evaluating UHS in aquifers. • Numerical compositional simulation utilising CMG-GEM of underground hydrogen storage in a North Sea aquifer. • Hydrogen recovery efficiency improves as the storage cycles increase. • Heterogeneity and hysteresis are the most impactful mechanisms on underground hydrogen storage. • Hydrogen solubility and diffusion in water have a minimal impact on the storage process when studied separately. • Solubility and diffusion effects become more pronounced when studied in combination with each other and hysteresis. [ABSTRACT FROM AUTHOR]

As energy system research into high shares of renewables has developed, so have the perspectives of the fundamental nature of a highly renewable economy. Early energy system transition research suggested that current fossil fuel energy systems would transition to a 'Hydrogen Economy', whereas more recent insights suggest that a 'Power-to-X Economy' may be a more appropriate term, as renewable electricity will become both the most important primary and final energy carrier through various Power-to-X conversion routes across the energy system. This paper provides a detailed overview on research insights of recent years on the core elements of the Power-to-X Economy and the role of hydrogen based on latest research results. These results suggest that, by 2050, upwards of 61,737 TWh LHV of hydrogen will be required to fully defossilise the global energy-industry system. Hydrogen, therefore, emerges as a central intermediate energy carrier and its relevance is driven by significant cost reductions in renewable electricity, especially of solar photovoltaics and wind power. Efficiency and cost drivers position direct electrification as the primary solution for defossilisation of the global energy-industry system; however, electron-to-molecule routes are essential for the large subset of remaining energy-related demands including chemical production, marine and aviation fuels, and steelmaking. [Display omitted] • The term 'Hydrogen Economy' insufficiently describes future energy systems. • 'Power-to-X Economy' better highlights the essential role of renewable electricity. • The highest reported demand for e-hydrogen is presented at over 60 PWh H2,LHV. [ABSTRACT FROM AUTHOR]

Green hydrogen offers a promising solution to energy transition challenges. However, a comprehensive understanding of its scenario in Brazil is lacking, hampering the formulation of strategies to enhance domestic market competitiveness. This article identifies Brazil's panorama of green hydrogen, the barriers, drivers, and investment potential for developing this market. It also proposes strategies to stimulate the growth of this industry at the national level. Based on qualitative methods, including literature analysis and interviews with 17 experts, the study reveals that regulatory and political issues and infrastructure readiness necessitate collaborative efforts between the public and private sectors. Overcoming technical hurdles like cost-effective large-scale production and efficient storage demands research investments. Challenges like high production costs and an underdeveloped national industry impede market expansion. By fostering players' collaboration, Brazil could harness its potential in the green hydrogen sector, promoting economic growth, job creation, and environmental sustainability to attain a global leadership position. • The panorama of green hydrogen in Brazil was presented. • Barriers that limit the development of the green hydrogen chain were analyzed. • Strategies to strengthen the green hydrogen market were presented. • Reasons for investing in green hydrogen in Brazil were discussed. • Brazil can become one of the leading exporters of green hydrogen. [ABSTRACT FROM AUTHOR]

Green hydrogen potential as a clean energy carrier presents promising prospects in the fight against climate change. The most efficient method of producing decarbonized hydrogen is through electrolysis, which involves splitting water molecules using renewable sources of electricity. Morocco boasts various advantages that enable it to play a pivotal role in bringing this vision to fruition. Lately, the nation has devised an ambitious strategy for green hydrogen and implemented significant changes related to industry and water resource management. This document presents a thorough examination of Morocco's energy sector, with a special focus on the substantial hurdles that must be surmounted to establish an economy centered on green hydrogen, with the capacity to generate employment opportunities and achieve carbon neutrality. Numerous impediments require cooperation with Europe and other international allies to establish a green hydrogen industry in Morocco. These challenges encompass bolstering the competitiveness of green hydrogen, scaling up production, and cultivating the requisite expertise. • Morocco is identified as one of the countries with the highest potential for green hydrogen export. • Green hydrogen roadmap for Morocco is presented and analyzed. • Technological, economical, environmental and societal challenges for green hydrogen development in Morocco are outlined. [ABSTRACT FROM AUTHOR]

Hydrogen, as a carbon-free energy carrier, has emerged as a crucial component in the decarbonization of the energy system, serving as both an energy storage option and fuel for dispatchable power generation to mitigate the intermittent nature of renewable energy sources. However, the unique physical and combustion characteristics of hydrogen, which differ from conventional gaseous fuels such as biogas and natural gas, present new challenges that must be addressed. To fully integrate hydrogen as an energy carrier in the energy system, the development of low-emission and highly reliable technologies capable of handling hydrogen combustion is imperative. This study presents a ground-breaking achievement - the first successful test of a micro gas turbine running on 100% hydrogen with NOx emissions below the standard limits. Furthermore, the combustor of the micro gas turbine demonstrates exceptional fuel flexibility, allowing for the use of various blends of hydrogen, biogas, and natural gas, covering a wide range of heating values. In addition to a comprehensive presentation of the test rig and its instrumentation, this paper illuminates the challenges of hydrogen combustion and offers real-world operational data from engine operation with 100% hydrogen and its blends with methane. • Hydrogen's potential as an alternative, carbon-free fuel for micro gas turbines is assessed. • The obstacles of utilizing hydrogen fuel in a micro gas turbine are addressed and the necessary modifications are presented. • Data from successful tests of a micro gas turbine running on hydrogen blends ranging up to 100% hydrogen is presented. • NOx emissions below the standard limits were achieved with the new setup. • The study's outcomes could aid researchers and developers in incorporating hydrogen as a carbon-free energy carrier. [ABSTRACT FROM AUTHOR]

Argentina has a wide availability of renewable resources, which provides important advantages for the hydrogen vector incorporation. The province of Córdoba is an excellent model case for the study of the rapid incorporation of hydrogen as fuel, to replace 20% V/V of natural gas consumed in vehicular use. This does not involve major changes in infrastructure or modifications to the vehicles. This paper computes and analyzes the levelized cost of hydrogen with the emissions associated for each part of the complete hydrogen supply chain. Two different production sources were used: renewable energies sources and the Argentine electrical grid; and two production pathways: in situ and centralized production. Comparing the same volume of proposed hydrogen compressed natural gas and current CNG, a cost decrease in the majority of the scenarios and a CO 2 eq emission reduction ranging from 19.5 to 8.2% are achieved, even if the hydrogen is produced using the carbon-intensive grid electricity. • The Production of hydrogen to replace part of the CNG used in vehicles is proposed. • Levelized cost of hydrogen and the emissions associated was assessed. • The study includes the entire supply chain from production to the filling station. • The use of HCNG results in a reduction of emissions in all the studied scenarios. • The new fuel is economically favorable, becoming relevant for rapid energy transition. [ABSTRACT FROM AUTHOR]

The rapidly increasing production volume of clean hydrogen creates challenges for transport infrastructure. This study improves understanding of hydrogen transport options in Europe and provides more detailed analysis on the prospects for hydrogen transport in Finland. Previous studies and ongoing pipeline projects were reviewed to identify potential and barriers to hydrogen transport. A fatigue life assessment tool was built because material challenges have been one of the main concerns of hydrogen transportation. Many European countries aim at utilizing existing gas infrastructure for hydrogen. Conducted studies and pilot facilities have provided promising results. Hydrogen reduces the fatigue life of the pipeline, but existing pipelines can be used for hydrogen if pressure variation is maintained at a reasonable level and the maximum operation pressure is limited. Moreover, the use of existing pipelines can reduce hydrogen transport costs, but the suitability of every pipeline for hydrogen must be analyzed, and several issues such as leakage, leakage detection, effects of hydrogen on pipeline assets and end users, corrosion, maintenance, and metering of gas flow must be considered. The development of hydrogen transport will vary within countries depending on the structure of the existing gas infrastructure, and on the future hydrogen use profile. [Display omitted] • H 2 pipeline transportation projects in Europe were reviewed. • Use of linear elastic fracture mechanics fatigue assessment tool was demonstrated. • 80 bar natural gas pipeline could be converted to 45–55 bar H 2 pipeline. • Existing natural gas network will be utilized for H 2 transportation in the future. • Further research needed to ensure feasibility of H 2 transportation in existing grid. [ABSTRACT FROM AUTHOR]

Substantial changes in the energy system are necessary to achieve greenhouse gas neutrality. Green hydrogen is a key to defossilisation. Politicians frequently mention the use of hydrogen in the building sector to supply decentrally produced heat as a potential field of application. An advantage repeatedly mentioned is that the existing gas distribution network infrastructure is an important asset that could still be used in the future. However, there is a lack of analyses of the conversion of gas distribution networks to hydrogen focussing on the economic implications on the costs of the distribution network infrastructure. The paper provides insights using a techno-economic model network analysis (MNA) tool called gas Distribution grId modelliNg tOol (DINO). The analysis is carried out for Germany and considers hydrogen use in all counties. The results are compared to a synthetic methane and electrification scenario. In the hydrogen scenario, the total need for distribution grids is decreasing until 2050 by at least 130,000 km. The network length of the synthetic methane scenario is slightly lower and that of the electrification scenario drops to zero. The annual operation costs are lower in all scenarios as gas demand and infrastructure are reduced. Nevertheless, the total annual cost in the hydrogen scenario is potentially two times higher than in the case of the synthetic methane scenario and more than four times higher than in the electrification scenario. Based on the present results, it is questionable whether an advantage of the continued use of the existing gas distribution grid infrastructure in case of synthetic gas or hydrogen scenarios exists. • Impact of the energy transition on gas distribution networks by comparing three defossilisation pathways. • Application of a model network analysis to the use of hydrogen to derive the cost-optimal gas distribution networks. • First nationwide analysis of hydrogen in gas distribution grids based on the German case at the county level. • Decreasing demand for gas distribution infrastructure in all scenarios and highest costs in the case of hydrogen use. • Questionable advantage of continued infrastructure use in case of conversion of existing gas distribution networks. [ABSTRACT FROM AUTHOR]

Achieving the goal of net zero emissions targeted by many governments and businesses around the world will require an economical zero-emissions fuel, such as hydrogen. Currently, the high production cost of zero emission 'renewable' hydrogen, produced from electrolysis powered by renewable electricity, is hindering its adoption. In this paper, we examine the role of uncertainties in projections of techno-economic factors on the transition from hydrogen produced from fossil fuels to renewable hydrogen. We propose an integrated framework, linking techno-economic and Monte-Carlo based uncertainty analysis with quantitative hydrogen supply-demand modelling, to examine hydrogen production by different technologies, and the associated greenhouse gas (GHG) emissions from both the feedstock supply and the production process. The results show that the uncertainty around the cost of electrolyser systems, the capacity factor, and the gas price are the most critical factors affecting the timing of the transition to renewable H 2. We find that hydrogen production will likely be dominated by fossil fuels for the next few decades if the cost of carbon emissions are not accounted for, resulting in cumulative emissions from hydrogen production of 650 Mt CO 2 -e by 2050. However, implementing a price on carbon emissions can significantly expedite the transition to renewable hydrogen and cut the cumulative emissions significantly. • The impacts of uncertainty on the transition to renewable hydrogen are quantified. • System cost of electrolyser, the capacity factor and gas price are critical factors. • Cumulative emissions from hydrogen production by 2050 can be very significant. • Carbon price can significantly advance the transition and cut cumulative emissions. [ABSTRACT FROM AUTHOR]

Hydrogen gas (H 2) is currently widely investigated in the context of the energy transition as a means of storing energy production in particular from renewable and intermittent sources. However, such manufactured H 2 is not a primary energy source but an energy carrier of other primary sources. The idea that natural H 2 sources could exist on Earth and represent a potential source of primary energy had long been neglected in absence of empirical evidence. Recent geological surveys in many parts of the world provide increasing evidence that specific geological processes can lead to significant natural H 2 generation. The objectives of this study are to synthetize information on natural H 2 generation patterns based on geoscience literature and discuss societal implications, from an interdisciplinary perspective, of potential large-scale deployment of natural H 2 operations. Based on current knowledge, we suggest that natural H 2 presents contrasting features compared to current dominant energy sources, and may potentially contribute to a gradual emergence of energy system decentralization. We discuss differences and common features between natural and manufactured H 2 systems and point out technical, social and economic opportunities and challenges. Overall, we argue that natural H 2 is an emerging primary energy source with promising opportunities for the energy transition, and may involve a change of paradigm in the interplay between society and energy systems. • Specific geological processes can lead significant H 2 generation. • Natural H 2 is a new primary energy source with distinctive features compared to current sources. • Natural H 2 may represent a new and potentially significant supply of low carbon energy. • Energy system decentralization can improve efficiency and reduce cost for natural H 2. • System approaches are essential in supporting sustainable natural H 2 operations. [ABSTRACT FROM AUTHOR]

The quest for a low-carbon energy transition has grown in recent years as concerns about the effects of climate change have grown. In this context, several governments around the world are concerned about hydrogen's possible role in a decarbonized energy system. As a result, this paper will provide a high-level overview of the hydrogen value chain, as well as an analysis of current and emerging trends in the global hydrogen market, particularly in the Middle East and North Africa (MENA), which are considered the cornerstone of the current global energy system traditional fossil fuel. Egypt, as a case study, could instruct other emerging countries in general, and natural gas suppliers in particular, how to maximize gains by switching from current imports to blue hydrogen made from natural gas. Policymakers who are responsible for Egypt's national hydrogen strategy should focus on global energy insights, international experience, and natural gas-sourced blue hydrogen as a step to renewables-sourced green hydrogen. • The role of hydrogen energy in carbon-post age. • Perspectives into different low hydrogen technologies. • Blue hydrogen is a step to green hydrogen. • Egypt should formulate a national hydrogen strategy. [ABSTRACT FROM AUTHOR]

Hydrogen is regarded as a key component of future low-carbon energy systems. Yet, for the implementation of hydrogen technologies on a large scale it is necessary to consider social acceptance. Studies on acceptance of hydrogen technologies have resulted in neutral to positive evaluations. This paper extends previous studies by focusing on large-scale hydrogen infrastructure. Within the project ELEGANCY, quantitative data on the acceptance was gathered among the German population. The results confirm the positive perception of hydrogen on a general level. However, the high level of acceptance is decreasing when it comes to infrastructure implementation in the own neighbourhood. In this paper, the gap between acceptance of hydrogen technology on a general level and the level of its infrastructural implementation is analysed, focusing on new pipeline infrastructure. The results show that sociodemographic factors, especially the variable age, as well as project-related factors, especially trust in stakeholders, have a high explanatory power. • Hydrogen technology is highly accepted in the German population. • Acceptance is decreasing, when it comes to large-scale infrastructure. • Effects of NIMBY are related to project-related, personal and place-based factors. • NIMBYism can be addressed through increasing trust in stakeholders. [ABSTRACT FROM AUTHOR]

Green ammonia production as an important application for propelling the upcoming hydrogen economy has not been paid much attention by China, the world's largest ammonia producer. As a result, related studies are limited. This paper explores potential supply chain design and planning strategies of green ammonia production in the next decade of China with a case study in Inner Mongolia. A hybrid optimization-based simulation approach is applied, considering traditional optimization approaches are insufficient to address uncertainties and dynamics in a long-term energy transition. Results show that the production cost of green ammonia will be at least twice that of the current level due to higher costs of hydrogen supply. Production accounts for the largest share of the total expense of green hydrogen (~80 %). The decline of electricity and electrolyser prices are key in driving down the overall costs. In addition, by-product oxygen is also considered in the model to assess its economic benefits. We found that by-product oxygen sales could partly reduce the total expense of green hydrogen (~12 % at a price of USD 85/t), but it also should be noted that the volatile price of oxygen may pose uncertainties and risks to the effectiveness of the offset. Since the case study may represent the favourable conditions in China due to the abundant renewable energy resources and large-scale ammonia industry in this region, we propose to take a moderate step towards green ammonia production, and policies should be focused on reducing the electricity price and capital investments in green hydrogen production. We assume the findings and implications are informative to planning future green ammonia production in China. • The H 2 -based energy transition in China's ammonia industry is explored. • A hybrid approach for green ammonia supply chain design and planning is proposed. • The cost of green ammonia will be at least twice that of the current level. • Electricity price and expenses in electrolysers are key impacts to the total cost. • Storing and selling by-product oxygen can partly reduce the total cost. [ABSTRACT FROM AUTHOR]

The energy transition is not something that awaits us in the next decade. On the contrary, it is a process in which we are already deeply enrolled. The main step towards the creation of a carbon-neutral society is the implementation of renewable energy sources (RES) as replacements for fossil fuels. Given the intermittency of RES, energy storage has an essential role to play in this transition. Hydrogen technology with its many advances was recognized to be the most promising choice. As multiple hydrogen applications were researched relatively recently, the current development of its technology is not yet on the large-scale implementation level. With the increasing number of studies and initiated projects, the utilization of hydrogen's immense ecological potential is to be expected in the next few decades. New innovative solutions of hydrogen technology that includes hydrogen production, storage, distribution, and usage, are permeating all industry sectors. In a rapidly changing world, technological advances bring forth public discussions, that are a deciding factor whether society will be able to adapt and accept those new contributions or reject them. Currently, hydrogen is the best associated with fuel cell electric vehicles which emit only water vapour and warm air, producing no harmful tailpipe emissions. As various scientists are stressing the gravity of climate change effects that are reaching the physical environment, ecosystems, and humanity in general, concern for the future is becoming the main global topic. Consequently, governments are implementing new sustainable policies that promote RES as a substitute for fossil fuels. Increasing progress in hydrogen technology instigated nations worldwide to incorporate hydrogen in their energy legislations and national development plans, which resulted in numerous national hydrogen strategies. This work shows the progress of hydrogen taking its place as a key factor of the future green energy society. It reviews recent developments of hydrogen technologies, their social, industrial, and environmental standing, as well as the stage of transitioning economies of both advanced and beginner countries. An example of the ongoing energy transition is Croatia, which is in the process of implementing a hydrogen strategy with the ambition to be able to one day equally participates in the rapidly emerging hydrogen market. • Hydrogen is the flagship of the green energy transition. • National policies and directives are focused on supporting carbon-neutral society based on hydrogen. • Progress of hydrogen usage is evident in the expansion of hydrogen infrastructure. • Social acceptance of hydrogen technology is steadily increasing. • The hydrogen economy is expected to grow by carrying out current energy strategies. [ABSTRACT FROM AUTHOR]

The paper provides an assessment of the current wind energy potential in Ukraine, and discusses developmental prospects for wind-hydrogen power generation in the country. Hydrogen utilization is a highly promising option for Ukraine's energy system, environment, and business. In Ukraine, an optimal way towards clean zero-carbon energy production is through the development of the wind-hydrogen sector. In order to make it possible, the energy potential of industrial hydrogen production and use has to be studied thoroughly. Ukraine possesses huge resources for wind energy supply. At the beginning of 2020, the total installed capacity of Ukrainian wind farms was 1.17 GW. Wind power generation in Ukraine has significant advantages in comparison to the use of traditional sources such as thermal and nuclear energy. In this work, an assessment of the wind resource potential in Ukraine is made via the geographical approach suggested by the authors, and according to the «Methodical guidelines for the assessment of average annual power generation by a wind turbine based on the long-term wind speed observation data». The paper analyses the long-term dynamics of average annual wind speed at 40 Ukrainian weather stations that provide valid data. The parameter for the vertical wind profile model is calculated based on the data reanalysis for 10 m and 50 m altitudes. The capacity factor (CF) for modern wind turbine generators is determined. The CF spatial distribution for an average 3 MW wind turbine and the power generation potential for the wind power plants across the territory of Ukraine are mapped. Based on the wind energy potential assessment, the equivalent possible production of water electrolysis-derived green hydrogen is estimated. The potential average annual production of green hydrogen across the territory of Ukraine is mapped. It is concluded that Ukraine can potentially establish wind power plants with a total capacity of 688 GW on its territory. The average annual electricity production of this system is supposed to reach up to 2174 bln kWh. Thus, it can provide an average annual production of 483 billion Nm3 (43 million tons) of green hydrogen by electrolysis. The social efficiency of investments in wind-hydrogen electricity is presented. Image 1 • Assessment of wind potential and electrolysis of green hydrogen in Ukraine. • Ukraine has the potential to build 688 GW of WPP capacity on its territory. • Ukraine can provide 43 m tons of green hydrogen annual production by electrolysis. • Map of potential distribution of annual green hydrogen production in Ukraine. • Investments' social efficiency of in wind-hydrogen electricity. [ABSTRACT FROM AUTHOR]

We report a techno-economic modelling for the flexible production of hydrogen and ammonia from water and optimally combined solar and wind energy. We use hourly data in four locations with world-class solar in the Atacama desert and wind in Patagonia steppes. We find that hybridization of wind and solar can reduce hydrogen production costs by a few percents, when the effect of increasing the load factor on the electrolyser overweighs the electricity cost increase. For ammonia production, the gains by hybridization can be substantially larger, because it reduces the power variability, which is costly, due to the need for intermediate storage of hydrogen between the flexible electrolyser and the less flexible ammonia synthesis unit. Our modelling reveals the crucial role in the synthesis of flexibility, which cuts the cost of variability, especially for the more variable wind power. Our estimated near-term production costs for green hydrogen, around 2 USD/kg, and green ammonia, below 500 USD/t, are encouragingly close to competitiveness against fossil-fuel alternatives. • World-class solar and wind in Chile and Argentina allow for competitive green H 2 and NH 3 production. • Combining wind and solar can reduce costs especially for NH 3 production. • Renewable power variability is a major cost driver for NH 3 synthesis. • Flexibiliy in NH 3 synthesis is key to manage the variability. [ABSTRACT FROM AUTHOR]

The Plan-DelyKaD project focused on an in-depth comparison of relevant electrolysis technologies, identified criteria for and selected most relevant salt cavern sites in Germany, studied business case potentials for applying hydrogen taken from storage to different end-users and engaged in identifying the future role of hydrogen from large scale storage in the German energy system. The focus of this paper is on the latter three topics above. The bottom-up investigation of most suitable salt cavern sites was used as input for a model-based analysis of microeconomic and macroeconomic aspects. The results identify dimensions and locations of possible hydrogen storages mostly in Northern Germany with ample potential to support the integration of fluctuating renewable electricity into the German power system. The microeconomic analysis demonstrates that the most promising early business case for hydrogen energy from large scale storage is its application as a fuel for the mobility sector. From a system perspective the analysis reveals that an optimized implementation of hydrogen generation via electrolysis and storage in salt caverns will have a positive impact on the power system in terms of reduced curtailments of wind power plants and lower residual peak loads. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports on a stakeholder dialogue project on the possible contribution of hydrogen to the Dutch energy transition. Dialogue methodology aims at articulating and exploring competing perspectives, including views that are in the margin of the energy policy subsystem. Three dialogue groups explored trajectories labeled Hydrogen for Transport, Hydrogen for the Built Environment and Hydrogen in the existing natural gas grid. The groups identified barriers and opportunities for the trajectories through back casting and assessed its pros and cons as compared to a non-hydrogen alternative. Referees from abroad contributed to a confrontation workshop, where the groups exchanged and discussed their first findings. The dialogue reveals that stakeholders are strongly divided with respect to small-scale domestic as well as the concept of a flexible natural gas infrastructure. We find a conflict between knowledge claims that either support or challenge the status quo. This is referred to as institutionalized knowledge conflict. [Copyright &y& Elsevier]