Publications

This study evaluates the potential of hydrogen as a clean additive to conventional diesel fuel. Experiments were carried out on a single-cylinder air-cooled diesel engine under half- and full-load conditions across engine speeds ranging from 1000 to 3000 rpm. Hydrogen produced on site via a proton exchange membrane electrolyser was supplied to the engine at a constant flow rate of 0.5 L/min. Compared to pure diesel the hydrogen–diesel blend reduced specific fuel consumption by 10% and increased brake thermal efficiency by 10% at full load. Emissions of carbon monoxide and carbon dioxide decreased by 13% and 17% respectively at half load. Additionally nitrogen oxide emissions dropped by 17%. These results highlight the potential of hydrogen to improve combustion efficiency while significantly mitigating emissions offering a viable transitional solution for cleaner power generation using existing diesel infrastructure.

Hydrogen energy as a medium for long-term energy storage needs to ensure the continuous and stable operation of the electrolyzer during the production of green hydrogen using wind energy. In this paper based on the overall model of a wind power hydrogen production system an integrated control strategy aimed at improving the quality of wind power generation smoothing the hydrogen production process and enhancing the stability of the system is proposed. The strategy combines key measures such as the maximum power point tracking control of the wind turbine and the adaptive coordinated control of the electrochemical energy storage system which can not only efficiently utilize the wind resources but also effectively ensure the stability of the bus voltage and the smoothness of the hydrogen production process. The simulation results show that the electrolyzer can operate at full power to produce hydrogen while the energy storage device is charging when wind energy is sufficient; the electrolyzer continuously produces hydrogen according to the wind energy when the wind speed is normal; and the energy storage device will take on the task of maintaining the operation of the electrolyzer when the wind speed is insufficient to ensure the stability and reliability of the system.

Hydrogen storage remains the main barrier to the broader use of hydrogen as an energy carrier despite hydrogen’s high energy density and clean combustion. This study presents a comparative evaluation of conventional and emerging storage methods integrating thermodynamic kinetic economic and environmental metrics to assess capacity efficiency cost and reversibility. Physisorption analysis reveals that metal organic frameworks can achieve storage capacities up to 14.0 mmol/g. Chemical storage systems are evaluated including nanostructured MgH2 (7.6 wt%) catalyzed reversible complex hydrides liquid organic hydrogen carriers and clathrate hydrates. Techno-economic analysis shows storage costs from $500–700/kg H2 to $30–50/kg H2 with energy efficiencies of 50%–90%. Life cycle assessment identifies manufacturing as the primary source of emissions with carbon footprints varying from 150 to 2057 kg CO2 -eq/kg H2 . Cryo-compressed is the most practical transportation option while metal hydrides suit stationary use. This study provides a quantitative foundation to guide material selection and system design for next-generation hydrogen storage technologies.

Hydrogen tanks used in transportation are equipped with thermal pressure relief devices to prevent a tank rapture in case of fire exposure. The opening of the pressure relief valve in such a scenario would likely result in an impinging and (semi-) confined hydrogen jet fire. Therefore twelve largescale experiments of hydrogen jet fires and one large-scale propane reference experiment have been conducted with various degrees of confinement orientations of the jet and distances from the nozzle to the impinging surface. Infrared and visible light videos temperatures heat fluxes and mass flow rate of hydrogen or propane were recorded in each experiment. It was found that the hydrogen flame can be visible under certain conditions. The main difference between an open impinging jet and an enclosed impinging jet fire is the extent of the high-temperature region in the steel target. During the impinging jet fire test 51% of the exposed target area exceeded 400C while 80% of the comparable area exceeded 400C during the confined jet fire test. A comparison was also made to an enclosed propane jet fire. The temperature distribution during the propane fire was more uniform than during the hydrogen jet fire and the localized hot spot in the impact region as seen in the hydrogen jet fires was not recorded.

The article presents the results of an experimental study on the influence of hydrogen as gaseous fuel on the combustion process parameters of a single-cylinder diesel engine operating in dual-fuel mode. The study is conducted at an average engine speed of n = 2000 min⁻ 1 four engine load levels and two different diesel fuel injection timing angles. Indicator diagrams are recorded for each operating mode at varying hydrogen mass fractions in the total fuel supplied to the engine. The data from the indicator diagrams are processed using a developed software that enables the determination of combustion process parameters. The analysis of the experimental results focuses on changes in cylinder temperature the coefficients of total and active heat release the rate of heat release the duration of the combustion process phases and other parameters as a function of the hydrogen mass fraction in the total fuel mixture.

Hydrogen as fuel in civil aviation gas turbines is promising due to its no-carbon content and higher net specific energy. For an entry-level market and cost-saving strategy it is advisable to consider reusing existing engine components whenever possible and retrofitting existing engines with hydrogen. Feasible strategies of retrofitting state-of-theart Jet A-1 fuelled turbofan engines with hydrogen while applying minimum changes to hardware are considered in the present study. The findings demonstrate that hydrogen retrofitted engines can deliver advantages in terms of core temperature levels and efficiency. However the engine operability assessment showed that retrofitting with minimum changes leads to a ~5% increase in the HP spool rotational speed for the same thrust at take-off which poses an issue in terms of certification for the HP spool rotational speed overspeed margin.

This review article provides an overview of the use of hydrogen and tyre pyrolysis oil as fuels for homogeneous charge compression ignition (HCCI) engines. It discusses their properties the ways they are produced and their sustainability which is of particular importance in the present moment. Both fuels have certain advantages but also throw up many challenges which complicate their application in HCCI engines. The paper scrutinises engine performance with hydrogen and tyre pyrolysis oil respectively and compares the fuels’ emissions a crucial focus from an environmental perspective. It also surveys related technologies that have recently emerged their effects and environmental impacts and the rules and regulations that are starting to become established in these areas. Furthermore it provides a comparative discussion of various engine performance data in terms of combustion behaviour emission levels fuel economy and potential costs or savings in real terms. The analysis reveals significant research gaps and recommendations are provided as to areas for future study. The paper argues that hydrogen and tyre pyrolysis oil might sometimes be used together or in complementary ways to benefit HCCI engine performance. The importance of life-cycle assessment is noted acknowledging also the requirements of the circular economy. The major findings are summarised with some comments on future perspectives for the use of sustainable fuels in HCCI engines. This review article provides a helpful reference for researchers working in this area and for policymakers concerned with establishing relevant legal frameworks as well as for companies in the sustainable transport sector.

It is believed that hydrogen will play an essential role in energy transition and achieving the net-zero target by 2050. Currently global hydrogen production mostly relies on processing fossil fuels such as coal and natural gas commonly referred to as grey hydrogen production while releasing substantial amounts of carbon dioxide (CO2). Developing economically and technologically viable pathways for hydrogen production while eliminating CO2 emissions becomes paramount. In this critical review we examine the common grey hydrogen production techniques by analyzing their technical characteristics production efficiency and costs. We further analyze the integration of carbon capture utilization and storage (CCUS) technology establishing the zero-carbon strategy transiting from grey to blue hydrogen production with CO2 capture and either utilized or permanently stored. Today grey hydrogen production exhibits technological diversities with various commercial maturities. Most methods rely on the effectiveness of catalysts necessitating a solution to address catalyst fouling and sintering in practice. Although CCUS captures utilizes or stores CO2 during grey hydrogen production its wide application faces multiple challenges regarding the technological complexity cost and environmental benefits. It is urgent to develop technologically mature low-cost and low-energy-consumption CCUS technology implementing extensive large-scale integrated pilot projects.

Hydrogen is a critical energy carrier in the transition to sustainable energy but its properties such as high diffusivity wide flammability range and low ignition energy present unique safety challenges during transportation. This study aims to improve on-road hydrogen transport safety by developing a dynamic traffic-dependent risk assessment framework for both Compressed Gaseous Hydrogen (CGH₂) tube trailers and Liquid Hydrogen (LH₂). A key advancement in this study is the use of dynamic occupancy data capturing variations in traffic density throughout the day instead of relying on average traffic density to estimate ignition source distribution. Additionally a qualitative Hazard and Operability (HAZOP) study was conducted for a potential central distribution terminal in Fort Saskatchewan Alberta Canada to systematically identify process hazards during the loading of hydrogen on-road carriers. Results reveal that the ignition probability for minor CGH2 leaks significantly increases with road occupancy rising from 0.003 at 0.1% to 0.149 at 5% emphasizing the importance of scheduling transport during off-peak hours Vapor Cloud Explosions (VCE) from LH2 extend up to 257 meters compared to 122.42 meters for CGH₂ underscoring the need for stricter land-use planning in densely populated areas. The analysis suggests prioritizing lower-traffic rural routes which exhibit lower release frequencies (e.g. 1.80E-05 per year) over high-traffic urban routes with higher release frequencies (e.g. 6.47E-05 per year).

Even if the aviation sector only accounts for 2% of global energy-related CO2 emissions and is the most challenging sector to decarbonize. As aviation demand grows and the need for sustainable jet fuels becomes urgent green hydrogen could substitute conventional fossil fuels thereby enabling carbon-free flights. This study investigates a techno-economic analysis of onsite versus off-site green hydrogen supply chains. A case study at the Toulouse-Blagnac airport (Europe’s first station for the production and distribution of renewable hydrogen) in France is developed to meet commercial aviation's hydrogen fuel demand between 2025 and 2050. Demand of hydrogen is projected based on the trend of jet fuel consumption. First the cost of solar-based renewable electricity is estimated at the two green hydrogen production sites using levelized cost of electricity production. Second levelized cost of hydrogen (LCOH) is evaluated for three value chain scenarios: one on-site (Toulouse airport) and two off-site (Marseille) for gaseous and cryogenic transportation of liquid hydrogen (LH2). A relative cost advantage is shown for the off-site case with cryogenic truck transportation at LCOH of €9.43/kg.LH2. This study also reveals the importance of electricity price investment costs operation costs economies of scale and transportation distance in different scenarios.

MgH2 shows significant potential for a solid-state hydrogen storage medium due to the advantages of high hydrogen capacity excellent reversibility and low cost. However its large-scale application still requires overcoming significant thermodynamic and kinetic hurdles. Catalyst design and optimization enhancements are crucial for the hydrogen storage properties of MgH2 wherein single-atom catalysts characterized by their small size and high proportion of unsaturated coordination sites have recently demonstrated a significant advance and considerable promise in this regard. This review presents recent progress on state-of-the-art single-atom catalysts for enhancing MgH2 hydrogen storage examining both supported and unsupported catalyst types i.e. transition metal @ N-modified carbon materials and transition metal @ transition metal compounds and metallene-derived compounds and single-atom alloys respectively. We systematically discussed the single-atom catalysts in MgH2 hydrogen storage systems focusing on synthesis strategies characterization techniques catalytic mechanisms as well as existing challenges and future perspectives. We aimed to provide a comprehensive and cohesive understanding for researchers in the field and promote the development of single-atom catalysts and their significant optimization of the hydrogen storage performance of MgH2.

In the pursuit of establishing a sustainable fuel cell (FC) energy system this review highlights the necessity of examining the operational principles technical details environmental consequences and economic concerns collectively. By adopting an integrated approach the review research into various fuel cells types extending their applications beyond transportation and evaluating their potential for seamless integration into sustainable practices. A detailed analysis of the technical aspects including FC membranes performance and applications is presented. The environmental impact of hydrogen generation through fuel cell/electrolyzer is quantitatively assessed emphasizing a comparative emission footprint against traditional hydrogen generation methods. Economic considerations of fuel cell technology adoption are explored through an extensive examination of market growth and forecasts and investments into the FC systems. Some flagship commercial projects of FC technology are also discussed along with their future prospective. The article concludes with a thorough analysis of challenges associated with FC adoption encompassing membrane research performance hurdles infrastructure development and application-specific challenges. This all-round review serves as an indispensable tool for academicians and policymakers providing a directed and comprehensive FC perspective.

In the twenty-first century global energy consumption is rapidly increasing particularly in emerging nations hastening the depletion of fossil fuel reserves and emphasizing the vital need for sustainable and renewable energy sources. This study aims to analyze hybrid renewable energy systems (HRESs) that use solid waste to generate power focusing on difficulties linked to intermittent renewable sources using a techno-economic framework. Employing the HOMER Pro software prefeasibility analysis is performed to meet the energy needs of an Indian community. System architecture optimization depends on factors like minimizing net present cost (NPC) achieving the lowest cost of energy (COE) and maximizing renewable source utilization. This study evaluates the technical economic and environmental feasibility of a hybrid renewable energy system (HRES) comprising a 400-kW solar photovoltaic (PV) array a 100-kW wind turbine (WT) a 100-kW electrolyzer 918 number of 12V batteries a 200-kW converter a 200-kW reformer and a 15-kg hydrogen tank (H-tank). This optimal configuration has the lowest NPC of $26.8 million and COE of $4.32 per kilowatt-hour and a Renewable Fraction (RF) of 100%. It can provide a dependable power supply and satisfy 94% of the daily onsite load demand which is 1080 kilowatt-hours per day. The required electricity is sourced to load demand entirely from renewable energy at the given location. Additionally the study highlights the benefits of HRES in solid waste management considering technological advancements and regulatory frameworks. Furthermore sensitivity analysis is conducted to measure economic factors that influence HRES accounting for fluctuations in load demand project lifespan diesel fuel costs and interest rates. Installing an HRES custom-made to the local environmental conditions would provide a long-lasting reliable and cost-effective energy source. The results show that the optimal HRES system performs well and is a viable option for sustainable electrification in rural communities.

The study presents the development of a novel integrated wind-biomass energy system designed for sustainable urban development leveraging municipality waste and wind power energy sources. This innovative system is capable of producing multiple forms of energy including electricity cooling heat and hydrogen addressing the diverse energy needs of urban communities. It integrates advanced thermodynamic cycles like Kalina and water electrolysis via an alkaline electrolyzer. In addition the system uniquely combines power and refrigeration while utilizing landfills as an energy source. The designed system is thermodynamically modeled using the Engineering Equation Solver and process wise simulated by the Aspen Plus software to ensure better performance. By integrating advanced thermodynamic cycles such as the Kalina and combined power and refrigeration system the overall system is designed to maximize the utilization of biomass energy content and enhances overall performance. The thermodynamic analysis results reveal that the system achieved remarkable results with an energy efficiency of 67.60% and an exergy efficiency of 59.7% demonstrating its tangible performance compared to other standalone energy systems. The refrigeration system itself achieves an energetic COP of 5.41 and an exergetic COP of 1.7. Additionally the system's hydrogen production facilitated by an alkaline electrolyzer reaches a rate of 5.38 kg/h highlighting its potential to contribute to clean hydrogen energy solutions. Moreover the exergo-environmental assessment shows that the system is environmentally friendly. The cost assessment shows that the system reaches profitability in 7 years and demonstrates growth achieving a substantial NPV of 192.39 million by 30 years highlighting its long-term financial viability.

Hydrogen is a promising carbon-free energy carrier for large-scale applications yet its adoption faces unique safety challenges. Microscopic physicochemical properties such as high diffusivity low ignition energy and distinct chemical pathways alter the safety of hydrogen systems. Analyzing the HIAD 2.0 incident database an occurrence-based review of past hydrogen incidents shows that 59% arise from general industrial failures common to other hydrocarbon carrier systems. Of the remaining 41% only 15% are unequivocally linked to the fuel’s unique properties. This study systematically isolates hazards driven by hydrogen’s intrinsic properties by filtering out confounding factors and provides an original clear characterization of the different failure mechanisms of hydrogen systems. These hydrogen-specific cases are often poorly described limiting their contribution to safety strategies and regulations improvement. A case study on pipeline failures illustrates how distinguishing hydrogen-specific hazards supports targeted risk mitigation. The findings highlight the need for evidence-based regulation over broadly precautionary approaches.

The teams sits down with Johannah Christensen to discuss regulatory policies and risk mitigation for vessel owners switching to green fuels and what we can do to encourage that jump as well as ensure a Just Transition.

The podcast can be found on their website.

Hydrogen-fueled Internal Combustion Engines (H2-ICEs) are typically operated with lean mixtures to minimize NOx emissions and reduce the risk of abnormal combustion events. Due to hydrogen’s low Lewis number premixed hydrogen-air flames in lean conditions exhibit strong thermodiffusive instabilities which make the numerical simulation of the combustion process particularly challenging. Indeed the intensity of these instabilities is significantly influenced by thermodynamic parameters – such as mixture temperature pressure and dilution rate – resulting in substantial variations in combustion behaviour across different operating conditions. Therefore they have to be properly considered not only to ensure model robustness but also to improve model accuracy over a wider range of operations. In this study the combustion process in a Direct Injection H2-ICE was analyzed using 3D-CFD simulations relying on a flamelet-based combustion model. Two sets of lookup flame speed maps were defined: laminar flame speed (SL) maps derived from standard 1D-CFD simulations in homogeneous reactor and freely propagating flame speed (SM) maps which account for the effects of thermodiffusive instabilities. The model that uses SL maps required the recalibration of some combustion model parameters when changing the dilution rate to ensure consistency with experimental data. Instead the model relying on SM maps featured a noticeable accuracy across different air-to-fuel ratios without the need for recalibration any combustion model parameter highlighting the key role of thermodiffusive flame instabilities on the combustion process. Based on these findings the impact of such instabilities was evaluated throughout the entire combustion process from both global and local perspectives. The relevance of thermodiffusive instabilities was observed to increase with the air-to-fuel ratio thereby enhancing combustion speed in leaner mixtures. Additionally the implementation of thermodiffusive instabilities was found to affect also preferred direction of flame propagation as stronger instabilities were identified in the leanest and low-temperature portions of the flame front. Novelty and significance This study addresses a critical knowledge gap regarding the role of thermodiffusive flame instabilities in accurately replicating the combustion process of a direct-injection internal combustion engine within a RANS simulation framework. Indeed while these instabilities have been shown to significantly enhance the mixture consumption rate in quiescent environments at low to moderate pressures and temperatures particularly in lean mixtures their impact on the burn rate under engine-like conditions has not yet been systematically investigated to the best of the authors’ knowledge. This work provides a comprehensive analysis of the significance of these instabilities in the combustion process of a direct-injection hydrogen internal combustion engine. The analysis is conducted from both a global perspective assessing their overall influence on the combustion process and a local perspective examining how they alter flame front characteristics when incorporated into the model.

Alternative fuel opportunities can satisfy energy security and reduce carbon emissions. In this regard the hydrogen fuel is derived from the source of environmental pollutants like sewage and algae wastewater through hydrothermal gasification technique using a KOH catalyst with varied gasification process parameters of duration and temperature of 6–30 min and 500-800 ◦C. The novelty of the work is to identify the optimum gasification process parameter for obtaining the maximum hydrogen yield using a KOH catalyst as an alternative fuel for agricultural engine applications. Influences of gasification processing time and temperature on H2 selectivity Carbon gasification efficiency (CE) Lower heating value (LHV) Hydrogen yield potential (HYP) and gasification efficiency (GE) were studied. Its results showed that the gasifier operated at 800 ◦C for 30 min offering maximum hydrogen yield (26 mol/kg) and gasification efficiency (58 %). The synthesized H2 was an alternative fuel blended with diesel fuel/TiO2 nanoparticles. It was experimentally studied using an internal combustion engine. Influences of H2 on engine perfor mance like brake-specific fuel consumption brake thermal efficiency and emission performances were measured and compared with diesel fuel. The results showed that DH20T has the least (420g/kWh) brake-specific fuel consumption (BSFC) and superior brake thermal efficiency of about 25.2 %. The emission results revealed that the DH20T blend showed the NOX value increased by almost 10.97 % compared to diesel fuel whereas the CO UHC and smoke values reduced by roughly 31.25 28.34 and 42.35 %. The optimum fuel blend (DH20T) result is rec ommended for agricultural engine applications.

Climate change and global warming concerns promote interest in alternative fuels especially zero-carbon fuels like hydrogen. Modifying existing combustion engines for dual-fuel operation can decrease emissions of vehicles that are already on the road. The procedure of a deep learning-based model predictive control as a machine learning implementation practical for complex nonlinear systems with input and state constraints has been developed and tested on a hydrogen/diesel dual-fuel (HDDF) engine application. A nonlinear model predictive controller (NMPC) utilizing a deep neural network (DNN) process model is proposed to control the injected hydrogen and diesel. This DNN model has eight inputs and four outputs and has a short computational time compared to the physics-based model. The architecture and hyperparameters of the DNN model of the HDDF process are optimized through a two-stage Bayesian optimization to achieve high accuracy while minimizing the complexity of the model described. The final DNN architecture has two hidden layers with 31 and 23 neurons. A modified engine capable of HDDF operation is compared to standard diesel operation to evaluate the engine performance and emissions. During experimental engine testing the controller required an average computational time of 2 ms per cycle on a low-cost processor satisfying the real-time requirements and was faster than recurrent networks. The control performance of the DNN-NMPC for the HDDF engine showed a mean absolute error of 0.19 bar in load tracking while maximizing average hydrogen energy share (68%) and reducing emissions. Specifically the particulate matter emissions decrease by 87% compared to diesel operation.

An increasing demand for energy coupled with rising pollution levels is driving the search for environmentally clean alternative energy resources to replace fossil fuels. Hydrogen has emerged as a promising clean energy carrier and raw material for various applications. However its environmental benefits depend on sustainable production methods. The rapid development of nanomaterials (NMs) has opened new avenues for the conversion and utilization of renewable energy (RE). NMs are becoming increasingly important in addressing challenges related to hydrogen (H₂) generation. This review provides an overview of current advancements in H₂ production from biomass via thermochemical (TC) and biological (BL) processes including associated costs and explores the applications of nanomaterials in these methods. Research indicates that biological hydrogen (BL-H₂) production remains costly. The challenges associated with the TC conversion process are examined along with potential strategies for improvement. Finally the technical and economic obstacles that must be overcome before hydrogen can be widely adopted as a fuel are discussed.

As Europe transitions away from natural gas dependency and accelerates its adoption of renewable energy 12 green hydrogen has emerged as a key energy carrier for industrial and automotive applications. Similarly plans 13 to export hydrogen and ammonia from resource-rich regions like Australia and the Middle East to major importers 14 such as Japan and South Korea underline the global commitment to decarbonization. Central to these efforts is 15 the advancement of efficient hydrogen compression technologies which are essential for establishing a 16 sustainable hydrogen supply chain. This study provides a comparative analysis of two key hydrogen compression 17 technologies categorized under positive displacement and non-mechanical systems. The evaluation emphasizes 18 the technical characteristics energy efficiency and potential applications of these systems in the emerging 19 hydrogen economy. Special focus is placed on electric motor-driven compressors which integrate advanced 20 materials and optimized designs to enhance efficiency and minimize energy consumption. By addressing the gap 21 in comparative evaluations this paper offers insights into the performance and sustainability of these technologies 22 contributing to the development of cost-effective and reliable hydrogen supply systems.

The FuelEU Maritime Regulation part of the European Union’s (EU’s) Fit for 55 initiative aims to achieve significant reductions in greenhouse gas (GHG) emissions within the maritime sector. This study assesses the feasibility of alternative fuels for the Estonian pilot fleet using a Well-to-Wake (WtW) life cycle assessment (LCA) methodology. Operational data from 18 vessels sourced from the Estonian State Fleet’s records were analyzed including technical specifications fuel consumption patterns and operational scenarios. The study focused on marine diesel oil (MDO) biomethane hydrogen biodiesel ammonia and hydrotreated vegetable oil (HVO) each presenting distinct trade-offs. Biomethane achieved a 59% GHG emissions reduction but required a volumetric storage capacity up to 353% higher compared to MDO. Biodiesel reduced GHG emissions by 41.2% offering moderate compatibility with existing systems while requiring up to 23% larger storage volumes. HVO demonstrated a 43.6% emissions reduction with seamless integration into existing marine engines. Ammonia showed strong potential for long-term decarbonization but its adoption is hindered by low energy density and complex storage requirements. This research underscores the importance of a holistic evaluation of alternative fuels taking into account technical economic and environmental factors specific to regional and operational contexts. The findings offer a quantitative basis for policymakers and maritime stakeholders to develop effective decarbonization strategies for the Baltic Sea region.

This study explores the potential of renewable seafood shell waste for sustainable energy conversion and longterm storage particularly for isolated communities. Despite its rich chitin and protein composition seafood shell waste is often neglected. The research evaluates and compares three advanced gasification technologies: biomass gasification plasma gasification and chemical looping to convert seafood shell waste into syngas and H2. The study uses validated Aspen Plus models to optimize feedstock blending ratios and operational parameters. Results show that feedstocks high in lobster and shrimp shells yield higher H2 outputs and improved syngas quality compared to clam-dominated blends. For instance biomass gasification at 1200 ◦C yielded approximately 500 kg/h of H2 from pure lobster or shrimp feeds while plasma gasification at 4500 ◦C achieved yields near 730 kg/ h. Plasma gasification when integrated with fuel cell conversion and heat recovery systems can generate over 10000 kWh during a 6-hour peak period enough to power over 1100 single-detached homes. Its levelized cost of hydrogen (LCOH) varies from $5.72-$8.37/kg H2 making it less expensive than chemical looping and biomass gasification. Plasma gasification also has the lowest global warming potential (GWP) at 6 kg CO2e/kg H2. Combining plasma gasification with carbon capture and storage may reduce GWP to 0.3 kg CO2e/kg H2 and can be further explored. These findings underscore the technical and economic viability of converting seafood shell renewable waste into H2 advancing sustainable energy transitions and supporting net-zero goals.

Dark fermentation (DF) has gained increasing interest over the past two decades as a sustainable route for biohydrogen production; however understanding how reproducible the process can be both from macro- and microbiological perspectives remains limited. This study assessed the reproducibility of a parallel continuous DF system using fruit-vegetable waste as a substrate under strictly controlled operational conditions. Three stirred-tank reactors were operated in parallel for 90 days monitoring key process performance indicators. In addition to baseline operation different process enhancement strategies were tested including bioaugmentation supplementation with nutrients and/or additional fermentable carbohydrates and modification of key operational parameters such as pH and hydraulic retention time all widely used in the field to improve DF performance. Microbial community structure was also analyzed to evaluate its reproducibility and potential relationship with process performance and metabolic patterns. Under these conditions key performance indicators and core microbial features were reproducible to a large extent yet full consistency across reactors was not achieved. During operation unforeseen operational issues such as feed line clogging pH control failures and mixing interruptions were encountered. Despite these disturbances the system maintained an average hydrogen productivity of 3.2 NL H2/L-d with peak values exceeding 6 NL H2/L-d under optimal conditions. The dominant microbial core included Bacteroides Lactobacillus Veillonella Enterococcus Eubacterium and Clostridium though their relative abundances varied notably over time and between reactors. An inverse correlation was observed between lactate concentration in the fermentation broth and the amount of hydrogen produced suggesting it can serve as a precursor for hydrogen. Overall the findings presented here demonstrate that DF processes can be resilient and broadly reproducible. However they also emphasize the sensitivity of these processes to operational disturbances and microbial shifts. This underscores the necessity for refined control strategies and further systematic research to translate these insights into stable high-performance real-world systems.

The growing interest in hydrogen as an alternative fuel has stimulated research into methods that enable the global shift to sustainable green energy. One promising pathway is the production of green hydrogen via electrolysis particularly when coupled with renewable energy sources like solar power. Integrating a proton exchange membrane (PEM) electrolyzer with solar energy can aid this transition. Using treated sewage effluent instead of deionized water can make the process more economical and sustainable. Thus the objective of this research is to demonstrate that an integrated electrolysis-water treatmentsolar energy system can be a viable candidate for producing green hydrogen in a sustainable manner. This study assesses different combinations of water pretreatment (RO and UF) and solar energy input (PV ST and PTC) evaluating their techno-economic feasibility efficiencies environmental impact and sustainability. The study shows that CSP scenarios have the highest CAPEX roughly fourfold that of PV cases and sevenfold that of national grid cases. Using solar energy sources like PV ST and PTC results in high material efficiency (94.87%) and environmental efficiency (98.34%) while also reducing CO2 emissions by approximately 88% compared to the national grid. The process’s economic sustainability averages 57% but it could reach 90% if hydrogen production costs fall to $2.08-$2.27 per kg. The outcome of this study is to provide a green hydrogen production pathway that is technically feasible environmentally sustainable and economically viable.

Efficient hydrogen storage is critical for advancing hydrogen-based technologies. This study investigates the effects of pressure and surface area on hydrogen storage in three carbon-based materials: graphite graphene oxide and reduced graphene oxide. Hydrogen adsorption–desorption experiments under pressures ranging from 1 to 9 bar revealed nonlinear storage capacity responses with optimal performance at around 5 bar. The specific surface area plays a pivotal role with reduced graphene oxide and exhibiting a surface area of 70.31 m2/g outperforming graphene oxide (33.75 m2/g) and graphite (7.27 m2/g). Reduced graphene oxide achieved the highest hydrogen storage capacity with 768 sccm and a 3 wt.% increase over the other materials. In assessing proton-exchange fuel cell performance this study found that increased hydrogen storage correlates with enhanced power density with reduced graphene oxide reaching a maximum of 0.082 W/cm2 compared to 0.071 W/cm2 for graphite and 0.017 W/cm2 for graphene oxide. However desorption rates impose temporal constraints on fuel cell operation. These findings enhance our understanding of pressure–surface interactions and underscore the balance between hydrogen storage capacity surface area and practical performance in carbon-based materials offering valuable insights for hydrogen storage and fuel cell applications.

Water electrolyzers play a crucial role in green hydrogen production. However their efficiency and scalability are often compromised by bubble dynamics across various scales from nanoscale to macroscale components. This review explores multi-scale modeling as a tool to visualize multi-phase flow and improve mass transport in water electrolyzers. At the nanoscale molecular dynamics (MD) simulations reveal how electrode surface features and wettability influence nanobubble nucleation and stability. Moving to the mesoscale models such as volume of fluid (VOF) and lattice Boltzmann method (LBM) shed light on bubble transport in porous transport layers (PTLs). These insights inform innovative designs including gradient porosity and hydrophilic-hydrophobic patterning aimed at minimizing gas saturation. At the macroscale VOF simulations elucidate two-phase flow regimes within channels showing how flow field geometry and wettability affect bubble discharging. Moreover artificial intelligence (AI)-driven surrogate models expedite the optimization process allowing for rapid exploration of structural parameters in channel-rib flow fields and porous flow field designs. By integrating these approaches we can bridge theoretical insights with experimental validation ultimately enhancing water electrolyzer performance reducing costs and advancing affordable highefficiency hydrogen production.

The global shipping industry is transitioning toward decarbonization with hydrogen-powered vessels emerging as a key solution to meet international emission reduction targets particularly the IMO’s goal of reducing emissions by 50% by 2050. As a zero-emission fuel hydrogen aligns with international regulations such as the IMO’s greenhouse gas reduction strategy the MARPOL Convention and regional policies like the EU’s Emissions Trading System. Despite regulatory support and advancements in hydrogen fuel cell technology challenges remain in hydrogen storage fuel cell integration and operational safety. Currently high-pressure gaseous hydrogen storage is the most viable option but its spatial and safety limitations must be addressed. Alternative storage methods including cryogenic liquid hydrogen organic liquid hydrogen carriers and metal hydride storage hold potential for application but still face technical and integration barriers. Overcoming these challenges requires continued innovation in vessel design fuel cell technology and storage systems supported by comprehensive safety standards and regulations. The successful commercialization of hydrogen-powered vessels will be instrumental in decarbonizing global shipping and achieving climate goals.

The UK has set an ambitious target of delivering clean power by 2030. Low carbon dispatchable power generation using hydrogen will play a key role in a clean power system by providing flexibility and other services for system operability and also by providing supply adequacy during extended periods of low renewable output decarbonising the role currently performed by an aging portfolio of unabated natural gas power generation. While some 100% hydrogen to power (H2P) commercial projects are already being deployed globally using multi megawatt fuel cells alongside blending hydrogen into existing gas turbines and new hydrogen ready turbines industrial scale 100% H2P projects face additional challenges of deploying new technology into a nascent system one which requires significant volumes of hydrogen storage with long lead times. To achieve the 2030 clean power system ambition and lay the foundations for a clean resilient and secure power system beyond 2030 it is critical that the new government takes resolute actions now to support H2P at scale. A clear strategic plan should be developed within the first 12 months of the new administration with clarity being given on policy business models and deployment rates for hydrogen to power (H2P) and its enabling infrastructure. This report produced by Hydrogen UK’s Power Generation Working Group explores the role that H2P will play in the decarbonised power system of the future the barriers to deployment and recommendations for overcoming them.

This paper can be found on their website.

Hydrogen as a clean energy source has gradually become an important choice for the energy transformation in the world. Utilizing existing natural gas pipelines for hydrogen-blended transportation is one of the most economical and effective ways to achieve large-scale hydrogen transportation. However hydrogen can easily penetrate into the pipe material during the hydrogen-blended transportation process causing damage to the properties of the pipe. The heat-affected zone (HAZ) of the weld being the weakest part of the pipeline is highly sensitive to hydrogen embrittlement. The microstructure and properties of the grains in the heat-affected zone undergoes changes during the welding process. Therefore this paper divides the HAZ of X80 welded pipes into three sub-HAZ namely the coarse-grained HAZ fine-grained HAZ and intercritical HAZ to study the hydrogen behavior. The results show that the degree of hydrogen damage in each sub-HAZ varies significantly at different strain rates. The coarse-grained HAZ has the highest hydrogen embrittlement sensitivity at low strain rates while the intercritical HAZ experiences the greatest hydrogen damage at high strain rates. By combining the microstructural differences within each sub-HAZ the plastic damage mechanism of hydrogen in each sub-HAZ is analyzed with the aim of providing a scientific basis for the feasibility of using X80 welded pipes in hydrogen-blended transportation.

As global demand for green hydrogen rises potential hydrogen exporters move into the spotlight. While exports can bring countries revenue large-scale on-grid hydrogen electrolysis for export can profoundly impact domestic energy prices and energy-related emissions. Our investigation explores the interplay of hydrogen exports domestic energy transition and temporal hydrogen regulation employing a sector-coupled energy model in Morocco. We find substantial co-benefits of domestic carbon dioxide mitigation and hydrogen exports whereby exports can reduce market-based costs for domestic electricity consumers while mitigation reduces costs for hydrogen exporters. However increasing hydrogen exports in a fossil-dominated system can substantially raise market-based costs for domestic electricity consumers but surprisingly temporal matching of hydrogen production can lower these costs by up to 31% with minimal impact on exporters. Here we show that this policy instrument can steer the welfare (re-)distribution between hydrogen exporting firms hydrogen importers and domestic electricity consumers and hereby increases acceptance among actors.

This report supports the European Commission (DG ENER) in the design and implementation of a European import auction for renewable hydrogen and its derivatives under the European Hydrogen Bank (EHB). The EHB aims to contribute to the EU's climate neutrality goal by 2050. While domestic auctions have already been launched under the EHB its international leg focusing on renewable fuels of non-biological origin (RFNBO) imports from third countries remains to be designed. This report offers strategic recommendations based on hydrogen market analyses the assessment of existing and planned hydrogen auction schemes in Europe and beyond as well as preliminary considerations on auction design. The analysis highlights the potential for hydrogen imports from regions like North America Australia Latin America and the MENA region. It includes concrete case studies on both pipeline-based imports of pure hydrogen and ship-based imports of key derivatives (ammonia methanol and synthetic aviation fuels (eSAF) to reflect Member State preferences and provides a concrete starting point for further defining import auctions. Priority considerations for auction design include ensuring fair competition between domestic production and imports addressing geopolitical risks and achieving cost efficiency. The case studies serve as a flexible blueprint for implementing EHB import auctions considering Member State interests and aligning with the EU's broader objectives.

This study compares qualitative risk analyses of compressed hydrogen gas (GH2) and liquid hydrogen (LH2) fuel gas supply systems (FGSSs) for eco-friendly marine vessels. Using hazard identification (HAZID) and hazard and operability (HAZOP) methodologies the study systematically identifies and compares the unique risks and safety strategies for GH2 and LH2 FGSS. For GH2-FGSS HAZID identifies 22 hazards with one unacceptable risk related to potential explosions from high-pressure hydrogen accumulation due to ventilation failure. HAZOP identifies 27 hazards all categorized as acceptable or ALARP. Recommended safety measures include pressure protection devices real-time alarms and enhanced piping durability. For LH2-FGSS HAZID identifies 38 hazards without any unacceptable risks though cryogenic icing and overpressure remain significant concerns. HAZOP reveals 43 hazards with one unacceptable risk involving thermal contraction and piping damage from repeated operations posing fire hazards. Suggested mitigations include improved cooling and purge gas procedures along with rigorous insulation management. Primary differences in safety management focus on high explosion risk of GH2-FGSS from high-pressure storage and the piping damage risk of LH2-FGSS from icing and thermal contraction. To enhance risk management for each system future research implements an operational simulation-based quantitative risk assessment. This study provides foundational safety strategies and guidelines for future vessels supporting the adoption of eco-friendly fuels in the maritime industry.

Hydrogen’s promise as a transformative energy solution has been consistently unfulfilled. This perspective article suggests that the primary barrier is not necessarily technological but a systemic failure to apply holistic systems thinking and genuine interdisciplinary collaboration. Through historical analysis and contemporary case studies we argue that only by integrating technical economic policy and social expertise within a holistic systems framework across the entire value chain can hydrogen overcome its boom-and-bust cycles and become a foundational component of the low-carbon energy future.

As global demand for clean energy continues to rise hydrogen as an ideal energy carrier plays a crucial role in the energy transition. Traditional hydrogen production methods predominantly rely on fossil fuels leading to environmental pollution and energy inefficiency. In contrast plasma-assisted hydrogen production as an emerging technology has gained significant attention due to its high efficiency environmental friendliness and flexibility. Plasma technology generates high-energy electrons or ions by exciting gas molecules which under specific conditions effectively decompose water vapor or hydrocarbon gases to produce hydrogen. This review systematically summarizes the basic principles technological routes research progress and potential applications of plasmaassisted hydrogen production. It focuses on various plasma-based hydrogen production methods such as water vapor decomposition hydrocarbon cracking arc discharge and microwave discharge highlighting their advantages and challenges. Additionally it addresses key issues facing plasma-assisted hydrogen production including energy efficiency improvement reactor stability and cost optimization and discusses the future prospects of these technologies. With ongoing advancements plasma-assisted hydrogen production is expected to become a mainstream technology for hydrogen production contributing to global goals of zero carbon emissions and sustainable energy development.

Hydrogen emissions arise from leakage during its production transport storage and use leading to an increase in atmospheric hydrogen concentrations. These emissions also cause an indirect climate effect which has been quantified in the literature with a global warming potential over 100 years (GWP100) of about 11.6 placing hydrogen between carbon dioxide (1) and methane (29.8). There is increasing debate about the climate impact of an energy transition based on hydrogen. As a case study we have therefore evaluated the expected climate impact of switching from the long-distance natural gas transmission network to the outlined future “hydrogen core network” in Germany. Our analysis focuses on the relevant sources and network components of emissions. Our results show that the emissions from the network itself represent only about 1.8% of total emissions from the transmission of hydrogen with 98% attributed to energy-related compressor emissions and only 2% to fugitive and operational hydrogen leakage. Compared to the current natural gas transmission network we calculate a 99% reduction in total network emissions and a 97% reduction in specific emissions per transported unit of energy. In the discussion we show that when considering the entire life cycle which also includes emissions from the upstream and end-use phases the switch to hydrogen reduces the overall climate impact by almost 90%. However while our results show a significantly lower climate impact of hydrogen compared to natural gas minimising any remaining emissions remains crucial to achieve carbon neutrality by 2045 as set in Germany’s Federal Climate Action Act. Hence we recommend further reducing the emissions intensity of hydrogen supply and minimising the indirect emissions associated with the energy supply of compressors.

The current study evaluates the feasibility of a forward osmosis membrane bioreactor (FO-MBR) for dark fermentation aiming at simultaneous biohydrogen production and wastewater treatment. Optimal microbial inoculation was achieved via heat-treated activated sludge enriching Clostridium sensu stricto 1 and yielding up to 2.21 mol H2.(mol hexose)− 1 in batch mode. In continuous operation a substrate concentration of 4.4 g L− 1 and a hydraulic retention time (HRT) of 12 h delivered the best results producing 1.51 mol H2.(mol hexosesupplied) − 1 . The FO-MBR configured with a 1.1 m2 hollow fiber side-stream membrane module and operated under dynamic HRT (2.5–12 h) dependent on membrane flux was integrated with intermittent CSTR (Continuous stirred tank reactor) operation to counter metabolite accumulation. This system outperformed a conventional CSTR achieving a hydrogen yield of 1.78 mol H2.(mol hexosesupplied) − 1 . Remarkable treatment efficiencies were observed with BOD5 COD and TOC removal rates of 95.32 % 99.02 % and 99.10 % respectively and an 83.8 % reduction in total waste volume. Additionally the FO-MBR demonstrated strong antifouling performance with 96.14 % water flux recovery achieved after a brief 5 min hydraulic rinse following 47.5 h of continuous highstrength broth exposure. These results highlight the FO-MBR system’s ability as a sustainable and highperformance alternative for integrated hydrogen production and effluent treatment. Further studies are recommended to address long-term fouling control and metabolite management for industrial scalability.

Photoelectrochemical (PEC) water splitting is a promising technology for green hydrogen production by harnessing solar energy. Traditionally this sustainable approach is studied under light intensity of 100 mW/cm2 mimicking the natural solar irradiation at the Earth’s surface. Sunlight can be easily concentrated using simple optical systems like Fresnel lens to enhance charge carrier generation and hydrogen production in PEC water splitting. Despite the great potentials this strategy has not been extensively studied and faces challenges related to the stability of photoelectrodes. To prompt the investigations and applications this work outlines the best practices and protocols for conducting PEC solar water splitting under concentrated sunlight illumination incorporating our recent advancements and providing some experimental guidelines. The key factors such as light source calibration photoelectrode preparation PEC cell configuration and long-term stability test are discussed to ensure reproducible and high performance. Additionally the challenges of the expected photothermal effect and the heat energy utilization strategy are discussed.

Given the climate change observed in the past few decades sustainable development and the use of renewable energy sources are urgent. In this scenario hydrogen production through electrolyzers is a promising renewable source and energy vector because of its ultralow greenhouse emissions and high energy content. Hydrogen can be used in a variety of applications from transportation to electricity generation contributing to the diversification of the energy matrix. In this context this paper presents an autonomous isolated DC microgrid system for generating and storing electrical energy to be exclusively used for feeding an electrolyzer hydrogen production plant which has been retrofitted for green hydrogen production. Experimental verification was performed at Itaipu Parquetec which consists of an alkaline electrolysis unit directly integrated with a battery energy storage system and renewable sources (e.g. photovoltaic and wind) by using an isolated DC microgrid concept based on DC/DC and AC/DC converters. Experimental results revealed that the new electrolyzer DC microgrid increases the system’s overall efficiency in comparison to the legacy thyristor-based power supply system by 26% and it autonomously controls the energy supply to the electrolyzer under optimized conditions with an extremely low output current ripple. Another advantage of the proposed DC microgrid is its ability to properly manage the startup and shutdown process of the electrolyzer plant under power generation outages. This paper is the result of activities carried out under the R&D project of ANEEL program No. PD-10381-0221/2021 entitled “Multiport DC-DC Converter and IoT System for Intelligent Energy Management” which was conducted in partnership with CTG-Brazil.

Biohydrogen production from industrial wastewater has been a focus of interest in recent years. The in depth knowledge in lab scale parameters and emerging strategies are needed to be investigated in order to implement the biohydrogen production process at large scale. The operating parameters have great influence on biohydrogen productivity. With the aim to gain major insight into biohydrogen production process this review summarizes recent updates on dark fermentation inoculum pretreatment methods operating parameters (hydraulic retention time organic loading rate pH temperature volatile fatty acids bioreactor configuration nutrient availability partial pressure etc.). The challenges and limitations associated with the biohydrogen production are lack of biohydrogen producers biomass washout and accumulation of metabolites are discussed in detail. The advancement strategies to overcome these limitations are also briefly discussed.

Hydrogen serves as a key clean-energy carrier with the main hurdles lying in safe efficient transport and storage (gas or liquid) and in end-use energy conversion. Liquid hydrogen (LH) as a high-density method of storage and transportation presents cryogenic insulation as its key technical issues. In LH storage tanks the performance of high vacuum multilayer insulation (HVMLI) will decline due to hydrogen release and leakage from the microscopic pores of steel which significantly destroy the vacuum layer. The accumulation of residual gases will accelerate thermal failure shorten the service life of storage tanks and increase safety risks. Adsorption is the most effective strategy for removing residual gases. This review aims to elucidate materials methods and design approaches related to hydrogen storage. First it summarizes adsorbents used in liquid hydrogen storage tanks including cryogenic adsorbents metal oxides zeolite molecular sieves and non-volatile compounds. Second it explores experimental testing methods and applications of hydrogen adsorbents in storage tanks analyzing key challenges faced in practical applications and corresponding countermeasures. Finally it proposes research prospects for exploring novel adsorbents and developing integrated systems.

Amidst the escalating global challenges presented by climate change carbon trading mechanisms have become critical tools for driving reductions in carbon emissions and optimizing energy systems. However existing carbon trading models constrained by fixed settlement cycles face difficulties in addressing the scheduling needs of energy systems that operate across multiple time scales. To address this challenge this paper proposes an optimal scheduling methodology for hydrogen-encompassing integrated energy systems that incorporates a multi-time-scale carbon trading mechanism. The proposed approach dynamically optimizes the scheduling and conversion of hydrogen energy electricity thermal energy and other energy forms by flexibly adjusting the carbon trading cycle. It accounts for fluctuations in energy demand and carbon emissions occurring both before and during the operational day. In the day-ahead scheduling phase a tiered carbon transaction cost model is employed to optimize the initial scheduling framework. During the day scheduling phase real-time data are utilized to dynamically adjust carbon quotas and emission ranges further refining the system’s operational strategy. Through the analysis of typical case studies this method demonstrates significant benefits in reducing carbon emission costs enhancing energy efficiency and improving system flexibility.

Hydrogen is blended with natural gas to form hydrogenated natural gas (HCNG) which is a new efficient and clean energy. CHEMKIN-PRO 19.0 software was combined with the GRI-Mech 3.0 mechanism to evaluate the capacity of H2 blending in reducing CO and CO2 emissions. Influences of H2 blending on combustion reactions of the CH4-air mixture were investigated. The results showed that the main reactants and products (CH4 CO and CO2) decreased in gradient with increasing H2 blending ratio accompanied by a shorter reaction duration and a faster reaction rate. After adding H2 important key radicals H O and OH increase significantly so that the combustion reactions become more violent. Sensitivity analysis reveals that among relevant elementary reactions of CO and CO2 R38 (with its promotional effect) and R158 (with its inhibitory effect) show the greatest sensitivity. As the H2 concentration increases the sensitivity of the two reactions (separately with promotional and inhibitory effects) decreases. Blending H2 in the natural gas can improve the combustion rate and reduce the generation of emissions CO and CO2 which is of important significance for realizing low-carbon goals and reducing air pollution.

Green hydrogen and ammonia are forecast to play key roles in the deep decarbonization of the global economy. Here we explore the potential of using green hydrogen and ammonia to couple the energy agriculture and industrial sectors with India’s nationalscale electricity grid. India is an ideal test case as it currently has one of the most ambitious hydrogen programs in the world with projected electricity demands for hydrogen and ammonia production accounting for over 1500 TWh/yr or nearly 25% of India’s total electricity demand by 2050. We model the ambitious deep decarbonization of India’s electricity grid and half of its steel and fertilizer industries by 2050. We uncover modest risks for India from such a strategy with many benefits and opportunities. Our analysis suggests that a renewables-based energy system coupled with ammonia off-take sectors has the potential to dramatically reduce India’s greenhouse emissions reduce requirements for expensive long-duration energy storage or firm generating capacity reduce the curtailment of renewable energy provide valuable short-duration and long-duration load-shifting and system resilience to inter-annual weather variations and replace tens of billions of USD in ammonia and fuel imports each year. All this while potentially powering new multi-billion USD green steel and maritime fuel export industries. The key risk for India in relation to such a strategy lies in the potential for higher costs and reduced benefits if the rest of the world does not match their ambitious investment in renewables electrolyzers and clean storage technologies. We show that such a pessimistic outcome could result in the costs of green hydrogen and ammonia staying high for India through 2050 although still within the range of their gray counterparts. If on the other hand renewable and storage costs continue to decline further with continued global deployment all the above benefits could be achieved with a reduced levelized cost of hydrogen and ammonia (10–25%) potentially with a modest reduction in total energy system costs (5%). Such an outcome would have profound global implications given India’s central role in the future global energy economy establishing India’s global leadership in green shipping fuel agriculture and steel while creating an affordable sustainable and secure domestic energy supply.

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

The ongoing global energy transition spurred by ecological concerns and by evolving political dynamics is necessitating a significant expansion of renewable energy sources. This shift towards renewables is introducing the challenge of heightened energy supply volatility and it underscores the imperative for large-scale storage solutions in order to mitigate fluctuations in demand and supply. This study investigates the potential of Power-to-X (P2X) technologies to address this challenge and it evaluates their technical and socioeconomic implications. Using scenario simulations that leverage the maximum estimated potentials of renewable energy sources relative to demand profiles across different countries we explore the role of P2X integration in the enhancement of energy production. Our analysis highlights the pivotal role of hydrogen in the decarbonization of key industrial sectors such as steel production and heavyduty transportation in the near term. For Germany we observe a reduction in CO2 emissions from 306.26 Mt to 232.28 Mt (-24.15%) and an increase in energy independence as measured by the reduction in primary energy imports from 1150.37 TWh to 887.86 TWh (-22.82%) when comparing the baseline scenario to the most socio-economically favorable scenario. France demonstrates even greater reductions with CO2 emissions decreasing by 37.69% and primary energy imports by 40.46%. Portugal achieves similar reductions with CO2 emissions falling by 38.71% and primary energy imports by 41.81%. However none of the three countries investigated in this study (Germany France and Portugal) achieve full decarbonization and energy independence simultaneously since their respective potential for renewable energy is not sufficiently large. Drawing from these insights and accounting for the unique contexts of each of the three countries we offer tailored policy recommendations for optimizing P2X utilization and enhancing energy production efficiency.

The potential of utilizing the rejected heat of a fuel cell system to improve the aircraft propulsive efficiency is discussed for various flight conditions. The thermodynamic background of the process and the connection of power consumption in the fan of the ducted propulsor and fuel cell heat are given and a link between these two components is presented. A concept that goes beyond the known ram heat exchanger is discussed which outlines the potential benefits of integrating a fan upstream of the heat exchanger. The influence of the fan pressure ratio flight speed and altitude as well as the temperature level of the available fuel cell heat on the propulsive efficiency is presented. A correlation between the fan pressure ratio flight speed and exchangeable fuel cell heat is established providing a simplified computational approach for evaluating feasible operating conditions within this process. This paper identifies the challenges of heat exchanger integration at International Standard Atmosphere sea level conditions and its benefits for cruise flight conditions. The results show that for a flight Mach number of 0.8 and a fan pressure ratio of 1.5 at a cruising altitude of 11000 m the propulsion efficiency increases by approximately 8 percentage points compared to a ducted propulsor without heat utilization. Under sealevel conditions the concept does not offer any performance advantages over a ducted propulsor. Instead it exhibits either comparable or reduced propulsive efficiency.

Hydrogen purity plays a crucial role in the expanding hydrogen economy particularly in applications such as fuel cells and industrial processes. This review investigates the relationship between hydrogen production methods and resulting purity levels emphasizing the differences between reforming electrolysis and biomass-based techniques. Furthermore it explores state-of-the-art purification technologies including pressure swing adsorption (PSA) membrane separation and cryogenic distillation highlighting their effectiveness and limitations in achieving ultra-pure hydrogen. Analytical methods such as gas chromatography mass spectrometry and cavity ring-down spectroscopy are also discussed in terms of their accuracy and application scope for hydrogen quality assessment. By integrating findings from global and domestic studies this paper aims to provide a comprehensive understanding of the challenges and advancements in hydrogen purity offering insights into optimizing hydrogen for a sustainable energy future.

Coal replacement with hydrogen is a strategy for reducing carbon emissions from high-temperature industrial processes. Hydrogen lancing is a direct way for introducing hydrogen to existing coal-fired kilns. This work investigates the effects of hydrogen lancing on nitrogen oxides (NOx) emissions and ignition behaviour in a pilotscale furnace that employs a 30 % coal replacement with hydrogen lancing. The investigation encompasses the impacts of lancing distance angling and velocity. Advanced measurement techniques including spectrometry and monochromatic digital cameras characterise the flame and assess emissions. The results indicate that the 30 % coal replacement by hydrogen lancing enhances combustion and reduces the emissions of carbon monoxides (CO). The flame characteristics vary with the location of the hydrogen injection generally becoming more-intense than during coal combustion. NOx emissions during lancing are similar or up to double the emissions observed for pure coal combustion depending on the lancing configuration. Increasing the distance between the hydrogen lance and coal burner increases NOx emissions.

We report on the first stage of an energy systems integration project to develop hybrid renewable energy generation and storage of hydrogen for subsequent use via research-based low regret system testbeds. This study details the design and construction of a flexible plug-and-play hybrid renewable power and hydrogen system testbed with up to 50 kW capacity aimed at addressing and benchmarking the operational parameters of the system as well as key components when commissioned. The system testbed configuration includes three different solar technologies three different battery technologies two different electrolyser technologies hydrogen storage and a fuel cell for regenerative renewable power. Design constraints include the current limit of an AC microgrid regulations for grid-connected inverters power connection inefficiencies and regulated hazardous area approval. We identify and show the resolution of systems integration challenges encountered during construction that may benefit planning for the emerging pilot or testbed configurations at other sites. These testbed systems offer the opportunity for informed decisions on economic viability for commercial-scale industry applications.