Publications

The integration of wind and solar energy with green hydrogen technologies represents an innovative approach toward achieving sustainable energy solutions. This review examines state-ofthe-art strategies for synthesizing renewable energy sources aimed at improving the efficiency of hydrogen (H2 ) generation storage and utilization. The complementary characteristics of solar and wind energy where solar power typically peaks during daylight hours while wind energy becomes more accessible at night or during overcast conditions facilitate more reliable and stable hydrogen production. Quantitatively hybrid systems can realize a reduction in the levelized cost of hydrogen (LCOH) ranging from EUR 3.5 to EUR 8.9 per kilogram thereby maximizing the use of renewable resources but also minimizing the overall H2 production and infrastructure costs. Furthermore advancements such as enhanced electrolysis technologies with overall efficiencies rising from 6% in 2008 to over 20% in the near future illustrate significant progress in this domain. The review also addresses operational challenges including intermittency and scalability and introduces system topologies that enhance both efficiency and performance. However it is essential to consider these challenges carefully because they can significantly impact the overall effectiveness of hydrogen production systems. By providing a comprehensive assessment of these hybrid systems (which are gaining traction) this study highlights their potential to address the increasing global energy demands. However it also aims to support the transition toward a carbon-neutral future. This potential is significant because it aligns with both environmental goals and energy requirements. Although challenges remain the promise of these systems is evident.

The advancement of sustainable solutions through renewable energy sources is crucial to mitigate carbon emissions. This study reports a novel system for an airport utilizing geothermal biomass and PV solar energy sources. The proposed system is capable of producing five useful outputs including electrical power hot water hydrogen kerosene and space heating. In open literature there has been no system reported with these combination of energy sources and outputs. The system is considered for Vancouver Airport using the most recent statistics available. The geothermal sub-system introduced is also unique which utilizes carbon dioxide captured as the heat transfer medium for power generation and heating. The present system is considered using thermodynamic analysis through energetic and exergetic approaches to determine the variation in system performance based on different annual climate conditions. Biomass gasification and kerosene production are evaluated based on the Aspen Plus models. The efficiencies of the geothermal system with the carbon dioxide reservoir are found to have energetic and energetic efficiencies of 78 % and 37 % respectively. The total hydrogen production projection is obtained to be 452 tons on an annual basis. The kerosene production mass flow rate is reported as 0.112 kg/s. The overall energetic and exergetic efficiencies of the system are found to be 41.8 % and 32.9 % respectively. This study offers crucial information for the aviation sector to adopt sustainable solutions more effectively.

Hydrogen has emerged as a promising alternative to meet the growing demand for sustainable and renewable energy sources. Underground hydrogen storage (UHS) in depleted gas reservoirs holds significant potential for large-scale energy storage and the seamless integration of intermittent renewable energy sources due to its capacity to address challenges associated with the intermittent nature of renewable energy sources ensuring a steady and reliable energy supply. Leveraging the existing infrastructure and well-characterized geological formations depleted gas reservoirs offer an attractive option for large-scale hydrogen storage implementation. However significant knowledge gaps regarding storage performance hinder the commercialization of UHS operation. Hydrogen deliverability hydrogen trapping and the equation of state are key areas with limited understanding. This literature review critically analyzes and synthesizes existing research on hydrogen storage performance during underground storage in depleted gas reservoirs; it then provides a high-level risk assessment and an overview of the techno-economics of UHS. The significance of this review lies in its consolidation of current knowledge highlighting unresolved issues and proposing areas for future research. Addressing these gaps will advance hydrogen-based energy systems and support the transition to a sustainable energy landscape. Facilitating efficient and safe deployment of UHS in depleted gas reservoirs will assist in unlocking hydrogen’s full potential as a clean and renewable energy carrier. In addition this review aids policymakers and the scientific community in making informed decisions regarding hydrogen storage technologies.

Tunisia's rapid industrial expansion and population growth have created a pressing energy deficit despite the country's significant yet largely untapped renewable energy potential. This study addressed this challenge by developing a comprehensive framework to identify and evaluate strategies for promoting green hydrogen production from renewable energy sources in Tunisia. A Strength Weakness Opportunity and Threat (SWOT) analysis incorporating social economic and environmental dimensions was conducted to formulate potential solutions. The Step-wise Weight Assessment Ratio Analysis (SWARA) method facilitated the weighting of SWOT factors and subfactors. Subsequently a multi-criteria decision-making approach employing the gray technique for order preference by similarity to ideal solution (TOPSIS-G) method (validated by gray additive ratio assessment (ARAS-G) gray complex proportional assessment (COPRAS-G) and gray multi-objective optimization by ratio analysis (MOORA-G) was used to rank the identified strategies. The SWOT analysis revealed "Strengths" as the most influential factor with a relative weight of 47.3% followed by "Weaknesses" (26.5%) "Threats" (15.6%) and "Opportunities" (10.6%). Specifically experts emphasized Tunisia's renewable energy potential (21.89%) and robust power system (12.11%) as primary strengths. Conversely high investment costs (11.2%) and political instability (7.77%) posed substantial threat. Positive socio-economic impacts represented a key opportunity with a score of 5.2%. As for the strategies prioritizing criteria production cost ranked first with a score of 13.5% followed by environmental impact (12.8%) renewable energy potential (12.0%) and mitigation costs (11.3%). The gray TOPSIS analysis identified two key strategies: leveraging Tunisia's wind and solar resources and fostering regional cooperation for project implementation. The robustness of these strategies is confirmed by the strong correlation between TOPSIS-G ARAS-G COPRAS-G and MOORA-G results. Overall the study provides a comprehensive roadmap and expert-informed decision-support tools offering valuable insights for policymakers investors and stakeholders in Tunisia and other emerging economies facing similar energy challenges.

The use of hydrogen as an energy carrier within the scope of the decarbonisation of the world’s energy production and utilisation is seen by many as an integral part of this endeavour. However the discussion around hydrogen technologies often lacks some perspective on the currently available technologies their Technology Readiness Level (TRL) scope of application and important performance parameters such as energy density or conversion efficiency. This makes it difficult for the policy makers and investors to evaluate the technologies that are most promising. The present study aims to provide help in this respect by assessing the available technologies in which hydrogen is used as an energy carrier including its main challenges needs and opportunities in a scenario in which fossil fuels still dominate global energy sources but in which renewables are expected to assume a progressively vital role in the future. The production of green hydrogen using water electrolysis technologies is described in detail. Various methods of hydrogen storage are referred including underground storage physical storage and material-based storage. Hydrogen transportation technologies are examined taking into account different storage methods volume requirements and transportation distances. Lastly an assessment of well-known technologies for harnessing energy from hydrogen is undertaken including gas turbines reciprocating internal combustion engines and fuel cells. It seems that the many of the technologies assessed have already achieved a satisfactory degree of development such as several solutions for high-pressure hydrogen storage while others still require some maturation such as the still limited life and/or excessive cost of the various fuel cell technologies or the suitable operation of gas turbines and reciprocating internal combustion engines operating with hydrogen. Costs below 200 USD/kWproduced lives above 50 kh and conversion efficiencies approaching 80% are being aimed at green hydrogen production or electricity production from hydrogen fuel cells. Nonetheless notable advances have been achieved in these technologies in recent years. For instance electrolysis with solid oxide cells may now sometimes reach up to 85% efficiency although with a life still in the range of 20 kh. Conversely proton exchange membrane fuel cells (PEMFCs) working as electrolysers are able to sometimes achieve a life in the range of 80 kh with efficiencies up to 68%. Regarding electricity production from hydrogen the maximum efficiencies are slightly lower (72% and 55% respectively). The combination of the energy losses due to hydrogen production compression storage and electricity production yields overall efficiencies that could be as low as 25% although smart applications such as those that can use available process or waste heat could substantially improve the overall energy efficiency figures. Despite the challenges the foreseeable future seems to hold significant potential for hydrogen as a clean energy carrier as the demand for hydrogen continues to grow particularly in transportation building heating and power generation new business prospects emerge. However this should be done with careful regard to the fact that many of these technologies still need to increase their technological readiness level before they become viable options. For this an emphasis needs to be put on research innovation and collaboration among industry academia and policymakers to unlock the full potential of hydrogen as an energy vector in the sustainable economy.

This review critically examines hydrogen energy systems highlighting their capacity to transform the global energy framework and mitigate climate change. Hydrogen showcases a high energy density of 120 MJ/kg providing a robust alternative to fossil fuels. Adoption at scale could decrease global CO2 emissions by up to 830 million tonnes annually. Despite its potential the expansion of hydrogen technology is curtailed by the inefficiency of current electrolysis methods and high production costs. Presently electrolysis efficiencies range between 60 % and 80 % with hydrogen production costs around $5 per kilogram. Strategic advancements are necessary to reduce these costs below $2 per kilogram and push efficiencies above 80 %. Additionally hydrogen storage poses its own challenges requiring conditions of up to 700 bar or temperatures below −253 °C. These storage conditions necessitate the development of advanced materials and infrastructure improvements. The findings of this study emphasize the need for comprehensive strategic planning and interdisciplinary efforts to maximize hydrogen's role as a sustainable energy source. Enhancing the economic viability and market integration of hydrogen will depend critically on overcoming these technological and infrastructural challenges supported by robust regulatory frameworks. This comprehensive approach will ensure that hydrogen energy can significantly contribute to a sustainable and low-carbon future.

In order to reduce carbon emissions the effects of gas composition and initial turbulence on the premixed flame dynamics of hydrogen-blended natural gas were investigated. The results show that an increase in hydrogen content leads to earlier formation of flame wrinkles. When the equivalence ratio is 1 and hydrogen blending ratio is below 20% Tulip flames appear approximately 2.25 m away from the ignition point. When hydrogen blending ratio exceeds 20% Tulip flames appear approximately 1.3 m away from the ignition point and twisted Tulip flames appear approximately 2.5 m away from the ignition position. During the 0.05 m process of flame propagation downstream from ignition point flame propagation velocity increases by about 2 m/s for every 10% increase in hydrogen content. The increase in hydrogen content has the most significant impact on the flame propagation velocity during the ignition stage. The average flame propagation velocity increases with the increase of hydrogen blending ratio. The greater the initial turbulence the more obvious the stretching deformation of flame front structure. With the increase of wind speed the flame propagation velocity first increases and then decreases. At a wind speed of 3 m/s the flame propagation velocity reaches its maximum value.

Hydrogen (2 ) has a big role to play in energy transition to achieve net-zero carbon emissions by 2050. For 2 to compete with other fuels in the energy market more research is required to mitigate key issues like greenhouse gas (GHG) emissions safety and end-use costs. For these reasons a software-supported technical overview of 2 production storage transportation and utilisation is introduced. Drawbacks and mitigation approaches for 2 technologies were highlighted. The recommended areas include solar thermal or renewable-powered plasma systems for feedstock preheating and oxy-hydrogen combustion to meet operating temperatures and heat duties due to losses; integration of electrolysis of 2 into hydrocarbon reforming methods to replace air separation unit (ASU); use of renewable power sources for electrical units and the introduction of thermoelectric units to maximise the overall efficiency. Furthermore a battolyser system for small-scale energy storage; new synthetic hydrides with lower absorption and desorption energy; controlled parameters and steam addition to the combustor/cylinder and combustors with fitted heat exchangers to reduce emissions and improve the overall efficiency are also required. This work also provided detailed information on any of these systems implementations based on location factors and established a roadmap for 2 production and utilisation. The proposed 2 production technologies are hybrid pyrolysis-electrolysis and integrated AD-MEC and DR systems using renewable bioelectrochemical and low-carbon energy systems. Production and utilisation of synthetic natural gas (NG) using renewablepowered electrolysis of 2 oxy-fuel and direct air capture (DAC) is another proposed 2 energy system for a sustainable 2 economy. By providing these factors and information researchers can work towards pilot development and further efficiency enhancement.

In this study we employ an optimization model to optimally design a self-sufficient independent of any imports and exports hydrogen infrastructure for Austria by 2030. Our approach integrates key hydrogen technologies within a detailed spatial investment and operation model – coupled with a European scale electricity market model. We focus on optimizing diverse infrastructure componentsincluding trailers pipelines electrolyzers and storages to meet Austria's projected hydrogen demand. To accurately estimate this demand in hourly resolution we combine existing hydrogen strategies and projections to account for developments in various industrial sectors consider demand driven by the transport sector and integrate hydrogen demand arising from its use in gas-powered plants. Accounting for the inherent uncertainty linked to such projections we run the analysis for two complementary scenarios. Our approach addresses the challenges of integrating large quantities of renewable hydrogen into a future energy system by recognizing the critical role of domestic production in the early market stages. The main contribution of this work is to address the gap in optimizing hydrogen infrastructure for effective integration of domestic renewable hydrogen production in Austria by 2030 considering sector coupling potentials optimal electrolyzer placement and the design of local hydrogen networks.

Clean energy vehicles (CEVs) e.g. battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs) are being adopted gradually to substitute for internal combustion engine vehicles (ICEVs) around the world. The fueling infrastructure is one of the key drivers for the development of the CEV market. When the government develops funding policies to support the fueling infrastructure development for FCEVs and BEVs it has to assess the effectiveness of different policy options and identify the optimal policy combination which is very challenging in transportation research. In this paper we develop a system dynamics model to study the feedback mechanism between the fueling infrastructure funding policies and the medium- to long-term diffusion of FCEVs and BEVs and the competition between FCEVs and BEVs based on relevant policy and market data in Guangzhou China. The results of the modeling analysis are as follows. (1) Funding hydrogen refueling stations and public charging piles has positive implications for achieving the substitution of CEVs for ICEVs. (2) Adjusting the funding ratio of hydrogen refueling stations and public charging piles or increasing the funding budget and extending the funding cycle does not have a significant impact on the overall substitution of CEVs for ICEVs but only impacts the relative competitive advantage between FCEVs and BEVs. (3) An equal share of funding for hydrogen refueling stations and public charging piles would have better strategic value for future net-zero-emissions urban transportation. (4) Making a moderate-level full investment in hydrogen refueling stations coupled with hydrogen refueling subsidies can provide the ideal conditions for FCEV diffusion.

Hydrogen (H2 ) is positioned as a key solution to the decarbonization challenge in both the energy and transportation sectors. While hydrogen is a clean and versatile energy carrier it poses significant safety risks due to its wide flammability range and high detonation potential. Hydrogen leaks can occur throughout the hydrogen value chain including production storage transportation and utilization. Thus effective leak detection systems are essential for the safe handling storage and transportation of hydrogen. This review aims to survey relevant codes and standards governing hydrogen-leak detection and evaluate various sensing technologies based on their working principles and effectiveness. Our analysis highlights the strengths and limitations of the current detection technologies emphasizing the challenges in achieving sensitive and specific hydrogen detection. The results of this review provide critical insights into the existing technologies and regulatory frameworks informing future advancements in hydrogen safety protocols.

This paper investigates innovative solutions to enhance the performance and lifespan of standalone photovoltaic (PV)-based microgrids with a particular emphasis on off-grid communities. A major challenge in these systems is the limited lifespan of batteries. To overcome this issue researchers have created hybrid energy storage systems (HESS) along with advanced power management strategies. This study introduces innovative multi-level HESS approaches and a related energy management strategy designed to alleviate the charge/discharge stress on batteries. Comprehensive Matlab Simulink models of various HESS topologies within standalone PV microgrids are utilized to evaluate system performance under diverse weather conditions and load profiles for rural site. The findings reveal that the proposed HESS significantly extends battery life expectancy compared to existing solutions. Furthermore the paper presents a novel energy management strategy based on the Reduced Fractional Gradient Descent (RFGD) algorithm optimization tailored for hybrid systems that include photovoltaic fuel cell battery and supercapacitor components. This strategy aims to minimize hydrogen consumption of Fuel Cells (FCs) thereby supporting the production of green ammonia for local industrial use. The RFGD algorithm is selected for its minimal user-defined parameters and high convergence efficiency. The proposed method is compared with other algorithms such as the Lyrebird Optimization Algorithm (LOA) and Osprey Optimization Algorithm (OOA). The RFGD algorithm exhibits superior accuracy in optimizing energy management achieving a 15% reduction in hydrogen consumption. Its efficiency is evident from the reduced computational time compared to conventional algorithms. Although minor losses in computational resources were observed they were substantially lower than those associated with traditional optimization techniques. Overall the RFGD algorithm offers a robust and efficient solution for enhancing the performance of hybrid energy systems.

The derivation of an efficient operational strategy for storing intermittent renewable energies using a hybrid battery-hydrogen energy storage system is a difficult task. One approach for deriving an efficient operational strategy is using mathematical optimization in the context of model predictive control. However mathematical optimization derives an operational strategy based on a non-exact mathematical system representation for a specified prediction horizon to optimize a specified target. Thus the resulting operational strategies can vary depending on the optimization settings. This work focuses on evaluating potential improvements in the operational strategy for a hybrid batteryhydrogen energy storage system using mathematical optimization. To investigate the operation a simulation model of a hybrid energy storage system and a tailor-made mixed integer linear programming optimization model of this specific system are utilized in the context of a model predictive control framework. The resulting operational strategies for different settings of the model predictive control framework are compared to a rule-based controller to show the potential benefits of model predictive control compared to a conventional approach. Furthermore an in-depth analysis of different factors that impact the effectiveness of the model predictive controller is done. Therefore a sensitivity analysis of the effect of different electricity demands and resource sizes on the performance relative to a rule-based controller is conducted. The model predictive controller reduced the energy consumption by at least 3.9 % and up to 17.9% compared to a rule-based controller. Finally Pareto fronts for multi-objective optimizations with different prediction and control horizons are derived and compared to the results of a rule-based controller. A cost reduction of up to 47 % is achieved by a model predictive controller with a prediction horizon of 7 days and perfect foresight. Keywords: Model Predictive Control Optimization Mixed Integer Linear Programming Hybrid Battery-Hydrogen Energy Storage System

With the question of ‘can short messages be effective in increasing public support for a complex new technology (hydrogen)?‘ this study uses a representative national survey in Australia to analyze the differences and variations in subjective support for hydrogen in response to four differently framed short messages. The findings of this study show that short messages can increase social acceptance but the effects depend on how strongly the message is framed in terms of its alignment with either an economic or environmental values framework. Furthermore the effects depend on the social and cultural context of the receiver of the message.

This paper presents the application of an active energy management strategy to a hybrid system consisting of a proton exchange membrane fuel cell (PEMFC) battery and supercapacitor. The purpose of energy management is to control the battery and supercapacitor states of charge (SOCs) as well as minimizing hydrogen consumption. Energy management should be applied to hybrid systems created in this way to increase efficiency and control working conditions. In this study optimization of an existing model in the literature with different meta-heuristic methods was further examined and results similar to those in the literature were obtained. Ant lion optimizer (ALO) moth-flame optimization (MFO) dragonfly algorithm (DA) sine cosine algorithm (SCA) multi-verse optimizer (MVO) particle swarm optimization (PSO) and whale optimization algorithm (WOA) meta-heuristic algorithms were applied to control the flow of power between sources. The optimization methods were compared in terms of hydrogen consumption and calculation time. Simulation studies were conducted in Matlab/Simulink R2020b (academic license). The contribution of the study is that the optimization methods of ant lion algorithm moth-flame algorithm and sine cosine algorithm were applied to this system for the first time. It was concluded that the most effective method in terms of hydrogen consumption and computational burden was the sine cosine algorithm. In addition the sine cosine algorithm provided better results than similar meta-heuristic algorithms in the literature in terms of hydrogen consumption. At the same time meta-heuristic optimization algorithms and equivalent consumption minimization strategy (ECMS) and classical proportional integral (PI) control strategy were compared as a benchmark study as done in the literature and it was concluded that meta-heuristic algorithms were more effective in terms of hydrogen consumption and computational time.

This study develops a semi-empirical model of an alkaline water electrolyzer (AWE) based on thermodynamic and electrochemical principles to investigate cell voltage behavior during electrolysis. By importing polarization curve test data under specific operational conditions eight undefined parameters are precisely fitted demonstrating the model’s high accuracy in describing the voltage characteristics of alkaline electrolyzers. Additionally an AWE system model is introduced to examine the influence of various operational parameters on system efficiency. This innovative approach not only provides detailed insights into the operational dynamics of AWE systems but also offers a valuable tool for optimizing performance and enhancing efficiency advancing the understanding and optimization of AWE technologies.

The global trend towards decarbonization and the demand for energy security have put hydrogen energy into the spotlight of industry politics and societies. Numerous governments worldwide are adopting policies and strategies to facilitate the transition towards hydrogen-based economies. To assess the determinants of such transition this study presents a comparative analysis of the technological innovation systems (TISs) for hydrogen technologies in Germany and South Korea both recognized as global front-runners in advancing and implementing hydrogen-based solutions. By providing a multi-dimensional assessment of pathways to the hydrogen economy our analysis introduces two novel and crucial elements to the TIS analysis: (i) We integrate the concept of ‘quality infrastructure’ given the relevance of safety and quality assurance for technology adoption and social acceptance and (ii) we emphasize the social perspective within the hydrogen TIS. To this end we conducted 24 semi-structured expert interviews applying qualitative open coding to analyze the data. Our results indicate that the hydrogen TISs in both countries have undergone significant developments across various dimensions. However several barriers still hinder the further realization of a hydrogen economy. Based on our findings we propose policy implications that can facilitate informed policy decisions for a successful hydrogen transition.

This article presents a novel approach to the analysis of heat release in a hydrogen-fueled internal combustion spark-ignition engine with exhaust gas recirculation (EGR). It also discusses aspects of thermodynamic analysis common to modeling and empirical analysis. This new approach concerns a novel method of calculating the specific heat ratio (cp/cv) and takes into account the reduction in the number of moles during combustion which is characteristic of hydrogen combustion. This reduction in the number of moles was designated as a molar contraction. This is particularly crucial when calculating the average temperature during combustion. Subsequently the outcomes of experimental tests including the heat-release rate the initial combustion phase (denoted CA0- 10) and the main combustion phase (CA10-90) are presented. Furthermore the impact of exhaust gas recirculation on the combustion process in the engine is also discussed. The efficacy of the proposed measures was validated by analyzing the heat-release rate and calculating the mean combustion temperature in the engine. The application of EGR in the range 0-40% resulted in a notable prolongation of both the initial and main combustion phases which consequently influenced the mean combustion temperature.

This article discusses possible strategies for decarbonizing the energy systems of an existing port. The approach consists in creating a complete superstructure that includes the use of renewable and fossil energy sources the import or local production of hydrogen vehicles and other equipment powered by Diesel electricity or hydrogen and the associated refuelling and storage units. Two substructures are then identified one including all these options the other considering also the addition of the energy demand of an adjacent steel industry. The goal is to select from each of these two substructures the most cost-effective configurations for 2030 and 2050 that meet the emission targets for those years under different cost scenarios for the energy sources and conversion/storage units obtained from the most reliable forecasts found in the literature. To this end the minimum total cost of all the energy conversion and storage units plus the associated infrastructures is sought by setting up a Mixed Integer Linear Programming optimization problem where integer variables handle the inclusion of the different generation and storage units and their activation in the operational phases. The comprehensive picture of possible solutions set allows identifying which options can most realistically be realized in the years to come in relation to the different assumed cost scenarios. Optimization results related to the scenario projected to 2030 indicate the key role played by Diesel hybrid and electric systems while considering the most stringent or much more stringent scenarios for emissions in 2050 almost all vehicles energy demand and industry hydrogen demand is met by hydrogen imported as ammonia by ship.

A wide range of aircraft propulsion technologies is being investigated in current research to reduce the environmental impact of commercial aviation. As the implementation of purely hydrogenpowered aircraft may encounter various challenges on the airport and vehicle side combined hydrogen and kerosene energy sources may act as an enabler for the first operations with liquid hydrogen propulsion technologies. The presented studies describe the conceptual design of such a dual-fuel regional aircraft featuring a retrofit derived from the D328eco under development by Deutsche Aircraft. By electrically assisting the sustainable aviation fuel (SAF) burning conventional turboprop engines with the power of high-temperature polymer-electrolyte fuel cells the powertrain architecture enables a reduction of SAF consumption. All aircraft were modeled and investigated using the Bauhaus Luftfahrt Aircraft Design Environment. A description of this design platform and the incorporated methods to model the hydrogen-hybrid powertrain is given. Special emphasis was laid on the implications of the hydrogen and SAF dual-fuel system design to be able to assess the potential benefits and drawbacks of various configurations with the required level of detail. Retrofit assumptions were applied particularly retaining the maximum takeoff mass while reducing payload to account for the propulsion system mass increase. A fuel cell power allocation of 20% led to a substantial 12.9% SAF consumption decrease. Nonetheless this enhancement necessitated an 18.1% payload reduction accompanied by a 34.5% increment in propulsion system mass. Various additional studies were performed to assess the influence of the power split. Under the given assumptions the design of such a retrofit was deemed viable.

As new sources of energy and advanced technologies are used there is a continuous evolution in energy supply demand and distribution. Advanced nuclear reactors and clean hydrogen have the opportunity to scale together and diversify the hydrogen production market away from fossil fuel-based production. Nevertheless the technical uncertainties surrounding nuclear hydrogen processes necessitate thorough research and a solid development effort. This paper aims to position pink hydrogen for nuclear hydrogen production at the forefront of sustainable energy-related solutions by offering a comprehensive review of recent advancements in nuclear hydrogen production covering both research endeavors and industrial applications. It delves into various pink hydrogen generation methodologies elucidating their respective merits and challenges. Furthermore this paper analyzes the evolving landscape of pink hydrogen in terms of its levelized cost by comparatively assessing different production pathways. By synthesizing insights from academic research and industrial practices this paper provides valuable perspectives for stakeholders involved in shaping the future of nuclear hydrogen production.

Updates to the separation distances between different exposures and bulk liquid hydrogen systems are included in the 2023 version of NFPA 2: Hydrogen Technologies Code. This work details the models and calculations leading to those distances. The specific models used including the flow of liquid hydrogen through an orifice within the Hydrogen Plus Other Alternative Fuels Risk Assessment Models (HyRAM+) toolkit are described and discussed to emphasize challenges specific to liquid hydrogen systems. Potential hazards and harm affecting individual exposures (e.g. ignition sources air intakes) for different unignited concentrations overpressures and heat flux levels were considered and exposures were grouped into three bins. For each group the distances to a specific hazard criteria (e.g. heat flux level) for a characteristic leak size informed by a risk-analysis led to a hazard distance. The maximum hazard distance within each group was selected to determine a table of separation distances based on internal pressure and pipe size rather than storage volume similar to the bulk gaseous separation distance tables in NFPA 2. The new separation distances are compared to the previous distances and some implications of the updated distances are given.

Growing renewable energy deployment worldwide has sparked a shift in the energy landscape with far-reaching geopolitical ramifications. Hydrogen’s role as an energy carrier is central to this change facilitating global trade and the decarbonisation of hard-to-abate sectors. This analysis offers a new method for optimally sizing solar/wind-to-hydrogen systems in specifically suitable locations. These locations are limited to the onshore and offshore regions of selected countries as determined by a bespoke geospatial analysis developed to be location-agnostic. Furthermore the research focuses on determining the best configurations for such systems that minimise the cost of producing hydrogen with the optimisation algorithm expanding from the detailed computation of the classic levelised cost of hydrogen. One of the study’s main conclusions is that the best hybrid configurations obtained provide up to 70% cost savings in some areas. Such findings represent unprecedented achievements for Italy and Portugal and can be a valuable asset for economic studies of this kind carried out by local and national governments across the globe. These results validate the optimisation model’s initial premise significantly improving the credibility of this work by constructively challenging the standard way of assessing large-scale green hydrogen projects.

With the aim of reducing carbon emissions and seeking independence from Russian gas in the wake of the conflict in Ukraine the use of hydrogen in the European Union is expected to rise in the future. In this regard hydrogen transport via pipeline will become increasingly crucial either through the utilization of existing natural gas infrastructure or the construction of new dedicated hydrogen pipelines. This study investigates the effects of hydrogen blending in existing pipelines on the European energy system by the year 2050 by introducing hydrogen blending sensitivities to the Global Energy System Model (GENeSYS-MOD). Results indicate that hydrogen demand in Europe is inelastic and limited by its high costs and specific use cases with hydrogen production increasing by 0.17% for 100%-blending allowed compared to no blending allowed. The availability of hydrogen blending has been found to impact regional hydrogen production and trade with countries that can utilize existing natural gas pipelines such as Norway experiencing an increase in hydrogen and synthetic gas exports from 44.0 TWh up to 105.9 TWh in 2050 as the proportion of blending increases. Although the influence of blending on the overall production and consumption of hydrogen in Europe is minimal the impacts on the location of production and dependence on imports must be thoroughly evaluated in future planning efforts.

Hydrogen plays an important role in the global transition towards Net-Zero emission. While pipelines are a viable option to transport large quantities of compressed hydrogen over long distances it is not always practical in many applications. In such situations a viable option is to transport and deliver large quantities of hydrogen as cryogenic liquid. The liquefaction process cools hydrogen to cryogenic temperatures below its boiling point of -259.2 0C. Such extreme low temperature implies specific hazards and risks which are different from those associated with the relatively well-known compressed gaseous hydrogen. Managing these specific issues brings new challenges for the stakeholders.<br/>Furthermore the transfer of liquid hydrogen (LH2) and its technical handling is relatively well known for industrial gas or space applications. Experience with LH2 in public and populated areas such as truck and aircraft refuelling stations or port bunkering stations for example is limited or non-existent. Safety requirements in these applications which involve or are in proximity of untrained public are different from rocket/aerospace industry.<br/>The manuscript reviews knowhow already gained by the international hydrogen safety community; and on such basis elucidate the gaps which are yet to be filled to meet industry needs to design and operate inherently safe LH2 operations including the implications for regulations codes and standards (RCS). Where relevant the associated gaps in some underpinning sciences will be mentioned; and the need to contextualise the information and safety practices from NASA1/ESA2/JAXA3 to inform risk adoption will be summarised.