Publications

Renewing a vision for European aviation: Europe today leads the world in civil aviation and air traffic management (ATM). This success should not be taken for granted particularly as the sector undergoes decarbonisation and digitalisation in today’s challenging geopolitical context. Significant value is at stake and capturing this value – for the sake of Europe’s competitiveness sustainability and sovereignty – is contingent on substantial investment in aviation research and innovation (R&I) and support to market uptake of new technologies to avoid the “valley of death” between technological development and product entry-into-service. Aviation is a major socio-economic contributor to Europe: The aviation industry is a vital component of Europe’s economy contri buting significantly to jobs gross domestic product (GDP) and trade. Overall the European aviation sector supports 15 million jobs and contributes EUR 1.1 trillion to European economic activity. The aviation sector is also critical to the EU single market European integration and global connectivity. It drives innovation and enhances Europe’s global influence and security through its combined focus on sustainability and competitiveness. The importance of aviation in achieving these fundamental goals for Europe is underscored by the findings of the Draghi report.

Indonesia’s energy sector faces critical challenges due to its heavy reliance on coal as the dominant power source which contributes to environmental degradation and rising CO2 emissions resulting into transition needs for renewable energy as targeted inside Nationally Determined Contribution (NDCs) 2060. In addition to these hydrogen energy also shows great potential for Indonesia’s energy needs. However to date there are no extensive research in Indonesia that simulate the effect of hydrogen incorporation and coal phase-out policy for 2050 power generation system making this research a critical contribution to the exploration of Indonesia's energy landscape. This study utilizes the Low Emissions Analysis Platform (LEAP). There are four simulated power generation scenarios in this study: the business-as-usual (BAU) scenario the hydrogen incorporation (HYD) scenario the coal phase-out (CPO) scenario and the progressive (PRO) scenario. The analysis indicates that the BAU scenario emerges as the most cost-effective approach for meeting Indonesia’s future electricity demand. However due to its inability to fulfill NDCs the CPO scenario is shown to be more viable from practical and cost perspectives requiring 406.9 GW capacity and USD 114.6 billion investment. On the contrary The HYD scenario largely aligns Indonesia’s hydrogen target potentially contributing 1-5% of energy demand and reducing coal reliance. Additionally while the PRO scenario has the highest investment cost (USD 151.4 billion) it also provides the lowest plant capacities (367.1 GW) offering the highest outputto-capacity ratio. The result suggests the necessity to enact government collaboration and construct feasibility analysis to implement renewable energy development.

Green hydrogen is critical for decarbonizing hard-to-electrify sectors but it faces high costs and investment risks. Here we defne and quantify the green hydrogen ambition and implementation gap showing that meeting hydrogen expectations will remain challenging despite surging announcements of projects and subsidies. Tracking 190 projects over 3 years we identify a wide 2023 implementation gap with only 7% of global capacity announcements fnished on schedule. In contrast the 2030 ambition gap towards 1.5 °C scenarios has been gradually closing as the announced project pipeline has nearly tripled to 422 GW within 3 years. However we estimate that without carbon pricing realizing all these projects would require global subsidies of US$1.3 trillion (US$0.8–2.6 trillion range) far exceeding announced subsidies. Given past and future implementation gaps policymakers must prepare for prolonged green hydrogen scarcity. Policy support needs to secure hydrogen investments but should focus on applications where hydrogen is indispensable.

Greenhouse gas anthropogenic emissions have triggered global warming with increasingly alarming consequences motivating the development of carbon-free energy systems. Hydrogen is proposed as an environmentally benign energy vector to implement this strategy but safe and efficient large-scale hydrogen storage technologies are still lacking to develop a competitive Hydrogen economy. LOHC (Liquid Organic Hydrogen Carrier) improves the storage and handling of hydrogen by covalently binding it to a liquid organic framework through catalytic exothermic hydrogenation and endothermic dehydrogenation reactions. LOHCs are oil-like materials that are compatible with the current oil and gas infrastructures. Nevertheless their high dehydrogenation enthalpy platinoid-based catalysts and thermal stability are bottlenecks to the emergence of this technology. In this review hydrogen storage technologies and in particular LOHC are presented. Moreover potential reactivities to design innovative LOHC are discussed.

Metal organic frameworks (MOFs) exhibit exceptional efficacy in hydrogen storage owing to their distinctive characteristics including elevated gravimetric densities rapid kinetics and reversibility. An in-depth look at existing literature indicates that while there are many studies using machine learning (ML) algorithms to develop predictive models for estimating hydrogen uptake by MOFs a great number of these models are not explainable. The novelty of this work lies in the integration of explainability approaches and ML models providing both accuracy and interpretability which is rarely addressed in existing studies. To fill this gap this paper attempts to develop explainable ML models for forecasting the hydrogen storage capacity of MOFs using three ML techniques including Bayesian regularized neural networks (BRANN) least squares support vector machines (LSSVM) and the extra tree algorithm (ET). An MOF databank comprising 1729 data points was assembled from literature. Surface area temperature pore volume and pressure were employed as input variables in this database. The findings demonstrate that of the three algorithms the ET intelligent model attained exceptional performance yielding precise estimates with a root mean square error (RMSE) of 0.1445 mean absolute error (MAE) of 0.0762 and a correlation coefficient (R2 ) of 0.995. In addition a novel contribution of this study is the generation of an explicit formula derived from BRANN enabling straightforward implementation of hydrogen storage predictions without requiring retraining of complex models. The sensitivity analysis employing Shapley Additive Explanation technique revealed that pressure and surface area were the most significant features influencing hydrogen storage with relevance values of 0.84 and 0.59 respectively. Furthermore the outlier detection evaluation using the leverage method showed that approximately 98 % of the utilized MOFs data are trustworthy and fell within the acceptable range. Altogether this work establishes a distinctive framework that combines accuracy interpretability and practical usability advancing the state of predictive modelling for hydrogen storage in MOFs.

The study provides a study on energy storage technologies for photovoltaic and wind systems in response to the growing demand for low-carbon transportation. Energy storage systems (ESSs) have become an emerging area of renewed interest as a critical factor in renewable energy systems. The technology choice depends essentially on system requirements cost and performance characteristics. Common types of ESSs for renewable energy sources include electrochemical energy storage (batteries fuel cells for hydrogen storage and flow batteries) mechanical energy storage (including pumped hydroelectric energy storage (PHES) gravity energy storage (GES) compressed air energy storage (CAES) and flywheel energy storage) electrical energy storage (such as supercapacitor energy storage (SES) superconducting magnetic energy storage (SMES) and thermal energy storage (TES)) and hybrid or multi-storage systems that combine two or more technologies such as integrating batteries with pumped hydroelectric storage or using supercapacitors and thermal energy storage. These different categories of ESS enable the storage and release of excess energy from renewable sources to ensure a reliable and stable supply of renewable energy. The optimal storage technology for a specific application in photovoltaic and wind systems will depend on the specific requirements of the system. It is important to carefully evaluate these needs and consider factors such as power and energy requirements efficiency cost scalability and durability when selecting an ESS technology.

As an energy carrier characterized by its high energy density and eco-friendliness hydrogen holds a pivotal position in energy transition. This paper elaborates on the scientific foundations and recent progress of photo- and electro-catalytic water splitting including the corresponding mechanism material design and optimization and the economy of hydrogen production. It systematically reviews the research progress in photo(electro)catalytic materials including oxides sulfides nitrides noble metals nonnoble metal and some novel photocatalysts and provides an in-depth analysis of strategies for optimizing these materials through material design component adjustment and surface modification. In particular it is pointed out that nanostructure regulation dimensional engineering defect introduction doping alloying and surface functionalization can remarkably improve the catalyst performance. The importance of adjusting reaction conditions such as pH and the addition of sacrificial agents to boost catalytic efficiency is also discussed along with a comparison of the cost-effectiveness of different hydrogen production technologies. Despite the significant scientific advancements made in photo(electro)catalytic water splitting technology this paper also highlights the challenges faced by this field including the development of more efficient and stable photo(electro)catalysts the improvement of system energy conversion efficiency cost reduction the promotion of technology industrialization and addressing environmental issues.

Hydrogen energy is valued for its diverse sources and clean low-carbon nature and is a promising secondary energy source with wide-ranging applications and a significant role in the global energy transition. Nonetheless hydrogen’s low energy density makes its largescale storage and transport challenging. Liquid hydrogen with its high energy density and easier transport offers a practical solution. This study examines the global hydrogen liquefaction methods with a particular emphasis on the liquid nitrogen pre-cooling Claude cycle process. It also examines the factors in the helium refrigeration cycle—such as the helium compressor inlet temperature outlet pressure and mass—that affect energy consumption in this process. Using HYSYS software the hydrogen liquefaction process is simulated and a complete process system is developed. Based on theoretical principles this study explores the pre-cooling refrigeration and normal-to-secondary hydrogen conversion processes. By calculating and analyzing the process’s energy consumption an optimized flow scheme for hydrogen liquefaction is proposed to reduce the total power used by energy equipment. The study shows that the hydrogen mass flow rate and key helium cycle parameters—like the compressor inlet temperature outlet pressure and flow rate—mainly affect energy consumption. By optimizing these parameters notable decreases in both the total and specific energy consumption were attained. The total energy consumption dropped by 7.266% from the initial 714.3 kW and the specific energy consumption was reduced by 11.94% from 11.338 kWh/kg.

Hydrogen has the potential to revolutionize how we power our lives from transportation to energy production. This study aims to compare the climate change impacts and the main factors affecting them for different categories of hydrogen production including grey hydrogen (SMR) blue hydrogen (SMR-CCS) turquoise hydrogen (TDM) and green hydrogen (PEM electrolysis). Grey hydrogen blue hydrogen and turquoise hydrogen which are derived from fossil sources are produced using natural gas and green hydrogen is produced from water and renewable electricity sources. When considering natural gas as a feedstock it is sourced from the pipeline route connected to Russia and through the liquefied natural gas (LNG) route from the USA. The life cycle assessment (LCA) result showed that grey hydrogen had the highest emissions with the LNG route showing higher emissions 13.9 kg CO2 eq. per kg H2 compared to the pipeline route 12.3 kg CO2 eq. per kg H2. Blue hydrogen had lower emissions due to the implementation of carbon capture technology (7.6 kg CO2 eq. per kg H2 for the pipeline route and 9.3 kg CO2 eq. per kg H2 for the LNG route) while turquoise hydrogen had the lowest emissions (6.1 kg CO2 eq. per kg H2 for the pipeline route and 8.3 kg CO2 eq. per kg H2 for the LNG route). The climate change impact showed a 12–25% increase for GWP20 compared to GWP100 for grey blue and turquoise hydrogen. The production of green hydrogen using wind energy resulted in the lowest emissions (0.6 kg CO2 eq. per kg H2) while solar energy resulted in higher emissions (2.5 kg CO2 eq. per kg H2). This article emphasizes the need to consider upstream emissions associated with natural gas and LNG extraction compression liquefaction transmission and regasification in assessing the sustainability of blue and turquoise hydrogen compared to green hydrogen.

The use of hydrogen as fuel presents many safety challenges due to its flammability and explosive nature combined with its lack of color taste and odor. The purpose of this paper is to present an electrochemical sensor that can achieve rapid and accurate detection of hydrogen leakage. This paper presents both the component elements of the sensor like sensing material sensing element and signal conditioning as well as the electronic protection and signaling module of the critical concentrations of H2. The sensing material consists of a catalyst type Vulcan XC72 40% Pt from FuelCellStore (Bryan TX USA). The sensing element is based on a membrane electrode assembly (MEA) system that includes a cathode electrode an ion-conducting membrane type Nafion 117 from FuelCellStore (Bryan TX USA). and an anode electrode mounted in a coin cell type CR2016 from Xiamen Tob New Energy Technology Co. Ltd (Xiamen City Fujian Province China). The electronic block for electrical signal conditioning which is delivered by the sensing element uses an INA111 from Burr-Brown by Texas Instruments Corporation (Dallas TX USA). instrumentation operational amplifier. The main characteristics of the electrochemical sensor for hydrogen leakage detection are operation at room temperature so it does not require a heater maximum amperometric response time of 1 s fast recovery time of maximum 1 s and extended range of hydrogen concentrations detection in a range of up to 20%.

Hydrogen is commonly perceived as the key player in the transition towards a low-carbon future. Nevertheless H2 low energy density hinders its easy storage and transportation. To address this issue different alternatives (liquefied hydrogen ammonia and liquid organic hydrogen carriers) are explored as hydrogen vectors. The techno-economic assessment of H2 transport through these carriers is strongly dependent on the basis of design adopted such that it is difficult to draw general conclusions. In this respect this work is aimed at performing a sensitivity analysis on the hypotheses introduced in the layout of H2 value chains. Different scenarios are discussed depending on harbour-to-harbour distances cost of utilities and raw materials and H2 application to the industrial or mobility sector. The most cost-effective carrier is selected for each case-study: NH3 is the most advantageous for industrial sector while LH2 holds promises for mobility. Critical issues are pointed out for future large-scale applications.

This Review provides an overview of the emerging concepts of catalystsmembranes and membrane electrode assemblies (MEAs) for water electrolyzers with anion-exchange membranes (AEMs) also known as zero-gap alkaline water electrolyzers. Much ofthe recent progress is due to improvements in materials chemistry MEA designs andoptimized operation conditions. Research on anion-exchange polymers (AEPs) has focusedon the cationic head/backbone/side-chain structures and key properties such as ionicconductivity and alkaline stability. Several approaches such as cross-linking microphase andorganic/inorganic composites have been proposed to improve the anion-exchangeperformance and the chemical and mechanical stability of AEMs. Numerous AEMs nowexceed values of 0.1 S/cm (at 60−80 °C) although the stability specifically at temperaturesexceeding 60 °C needs further enhancement. The oxygen evolution reaction (OER) is still alimiting factor. An analysis of thin-layer OER data suggests that NiFe-type catalysts have thehighest activity. There is debate on the active-site mechanism of the NiFe catalysts and their long-term stability needs to beunderstood. Addition of Co to NiFe increases the conductivity of these catalysts. The same analysis for the hydrogen evolutionreaction (HER) shows carbon-supported Pt to be dominating although PtNi alloys and clusters of Ni(OH) 2 on Pt show competitiveactivities. Recent advances in forming and embedding well-dispersed Ru nanoparticles on functionalized high-surface-area carbonsupports show promising HER activities. However the stability of these catalysts under actual AEMWE operating conditions needsto be proven. The field is advancing rapidly but could benefit through the adaptation of new in situ techniques standardizedevaluation protocols for AEMWE conditions and innovative catalyst-structure designs. Nevertheless single AEM water electrolyzercells have been operated for several thousand hours at temperatures and current densities as high as 60 °C and 1 A/cm 2 respectively.

Hydrogen production from electrolytic water based on Renewable Energy has been found as a vital method for the local consumption of new energy and the utilization of hydrogen energy. In this paper the hydrogen production power supply matching the working characteristics of electrolytic water production was investigated. Through the analysis of the correlation between the electrolysis current and temperature of the proton exchange membrane electrolyzer and the electrolyzer port voltage energy efficiency and hydrogen production speed it was concluded that the hydrogen production power supply should be characterized by low output current ripple high output current and wide range voltage output. To meet the requirements of the system of hydrogen production from electrolytic water based on new energy a hydrogen production power supply scheme was proposed based on Y which is the type three is the phase staggered parallel LLC topology. In the proposed scheme the cavity with three is the phase staggered parallel output is resonated to meet the operating characteristics (high current and low ripple) of the electrolyzer and pulse frequency control is adopted to achieve resonant soft in the switching operation and increase conversion efficiency. Lastly a simulation model and a 6kW experimental prototype were built to verify the rationality and feasibility of the proposed scheme.

Hydrogen has emerged as a promising new energy source that can be produced in renewable mode for example from biomass derivatives reforming or water splitting. However the conventional catalysts used for hydrogen production in renewable mode suffer from limitations in activity selectivity and/or stability. To overcome these limitations nanostructured catalysts with multicomponent active phases particularly trimetallic catalysts are being explored. This catalyst formulation significantly enhances catalyst activity and effectively suppresses the undesired production of CO CH4 or coke during the reforming of biomass derivatives for hydrogen formation. Moreover the success of this approach extends to water splitting catalysis where trimetallic based catalysts have demonstrated good performance in hydrogen production. Notably trimetallic catalysts composed of Ni Fe and a third metal prove to be highly efficient in water splitting bypassing the problems associated with traditional catalysts. That is the high material costs of state-of-the-art catalysts as well as the limited activity and stability of alternative ones. Furthermore theoretical methods play a vital role in understanding catalyst activity and/or selectivity as well as in the design of catalysts with improved characteristics. These enable a comprehensive study of the complete reaction mechanism on a target catalyst and help in identifying potential reaction descriptors allowing for efficient screening and selection of catalysts for enhanced hydrogen production. Overall this critical review shows how the exploration of trimetallic catalysts combined with the insights from theoretical methods holds great promise in advancing hydrogen production through renewable means paving the way for sustainable and efficient energy solutions.

In the wake of unprecedented global weather events and the ever-pressing urgency of climate change the discourse around energy transition has become more critical than ever.<br/>The United Kingdom once at the forefront of the energy transition movement finds itself at a crossroads. The initial rapid progress towards a low-carbon future is now facing hurdles threatening the achievement of the 'net zero by 2050' target.<br/>This revelation comes from the third edition of our UK Energy Transition Outlook (ETO) which leverages an independent model incorporating the UK's energy system's extensive connections with Europe and beyond.<br/>This report has a comprehensive analysis of:<br/>♦ Renewable energy technology scaling and costs<br/>♦ The continuing dependence on fossil fuel and need to decarbonize<br/>♦ Energy demand by sector and source<br/>♦ Energy efficiency<br/>♦ Energy supply<br/>♦ Electricity and infrastructure<br/>♦ Hydrogen<br/>♦ Energy expenditure<br/>♦ Policies driving the transition<br/>♦ Digitalization.

The decarbonization of heavy industries demands large volumes of green hydrogen. To produce green hydrogen via electrolysis the EU’s Renewable Energy Directive II imposes rules to ensure the use of renewable electricity. Hydrogen producers can use portfolios of power purchase agreements (PPAs) to buy renewable electricity. These portfolios must meet hydrogen demand cost-effectively and battery storage can help by shifting excess renewable generation. However high uncertainty around future electricity prices and demand complicates optimal portfolio design. Current literature lacks comprehensive models that evaluate such portfolio optimization under uncertainty for real-world case studies including battery storage. This work addresses the gap by introducing a stochastic mixed-integer linear programming model tailored to industrial applications. We demonstrate the model using a real-world glass manufacturing site in Germany. Our findings show that portfolio optimization alone can reduce the levelized cost of hydrogen (LCOH) by 6.24% under EU rules. Adding a battery further cuts costs achieving an LCOH of 11.8 e2024 kg−1 . Exploring different temporal matching schemes reveals that weekly matching reduces LCOH by 2 e2024kg−1 while maintaining a high share of renewable energy. The model offers a flexible tool for optimizing PPA portfolios in various industrial settings.

Green ammonia is a promising hydrogen derivative which enables intercontinental transport of dispatchable renewable energy. This research describes the development of a model which optimizes a global green ammonia network considering the costs of production storage and transport. In generating the model we show economies of scale for green ammonia production are small beyond 1 million tonnes per annum (MMTPA) although benefits accrue up to a production rate of 10 MMTPA if a production facility is serviced by a new port or requires a long pipeline. The model demonstrates that optimal sites for ammonia production require not only an excellent renewable resource but also ample land from which energy can be harvested. Land limitations constrain project size in otherwise optimal locations and force production to more expensive sites. Comparison of current crude oil markets to future ammonia markets reveals a trend away from global supply hubs and toward demand centers serviced by regional production.

The transition toward low-carbon energy systems requires reliable tools for assessing renewable-based hydrogen production under real-world climatic and economic conditions. This study presents a novel probabilistic framework integrating the following three complementary elements: (1) a Photovoltaic Geographical Information System (PVGIS) for high-resolution location-specific solar energy data; (2) Metalog probability distributions for advanced modeling of variability and uncertainty in photovoltaic (PV) energy generation; and (3) Levelized Cost of Hydrogen (LCOH) calculations to evaluate the economic viability of hydrogen production systems. The methodology is applied to three diverse European locations—Lublin (Poland) Budapest (Hungary) and Malaga (Spain)—to demonstrate regional differences in hydrogen production potential. The results indicate annual PV energy yields of 108.3 MWh 124.6 MWh and 170.95 MWh respectively which translate into LCOH values of EUR 9.67/kg (Poland) EUR 8.40/kg (Hungary) and EUR 6.13/kg (Spain). The probabilistic analysis reveals seasonal production risks and quantifies the probability of achieving specific monthly energy thresholds providing critical insights for designing systems with continuous hydrogen output. This combined use of a PVGIS Metalog and LCOH calculations offers a unique decision-support tool for investors policymakers and SMEs planning green hydrogen projects. The proposed methodology is scalable and adaptable to other renewable energy systems enabling informed investment decisions and improved regional energy transition strategies.

The concept of sustainability and green energy has become increasingly relevant in our lives especially in the face of climate change and the growing demand for sustainable solutions in the energy sector. Driven by renewable energies there is a continuous effort to research and develop alternative energy sources and fuels. In this context the European Union (EU) Strategy for Hydrogen (H) has emerged placing this source as one of the central pillars in the fight against climate change. Hydrogen is seen as a potential fuel and energy source of the future. However in addition to political and structural challenges this new approach also faces significant technical obstacles. With the increase in population and human needs the need for energy continues to grow. The world population is projected to reach ten billion people by the year 2050 (Tarhan and Çil 2021). To meet this growing demand and promote a transition to clean energies many countries are incorporating renewable energy sources into their energy mix while still relying on fossil fuels. Developed countries are gradually reducing their use of fossil fuels in energy production. Considering that 80 per cent of our daily energy needs are still met by these sources the complete transition is complex and not immediate but it is an achievable goal.

Maintaining frequency stability is one of the biggest challenges facing future power systems due to the increasing penetration levels of inverter-based renewable resources. This investigation experimentally validates the frequency provision capabilities of a real Polymer Electrolyte Membrane (PEM) hydrogen electrolyser (HE) using a power hardware-in-the-loop (PHIL) setup. The PHIL consists of a custom 3-level interleaved buck converter and a hardware platform for real-time control of the converter and conducting grid simulation associated with the modelling of the future Iberian Peninsula (IP) and Continental Europe (CE) systems. The investigation had the aim of validating earlier simulation work and testing new responses from the electrolyser when providing different frequency services at different provision volumes. The experimental results corroborate earlier simulation results and capture extra electrolyser dynamics as the double-layer capacitance effect which was absent in the simulations. Frequency Containment Reserve (FCR) and Fast Frequency Response (FFR) were provided successfully from the HE at different provision percentages enhancing the nadir and the rate of change of frequency (RoCoF) in the power system when facing a large disturbance compared to conventional support only. The results verify that HE can surely contribute to frequency services paving the way for future grid support studies beyond simulations.

An important component of the deep decarbonization of the worldwide energy system is to build up the large-scale utilization of hydrogen to substitute for fossil fuels in all sectors including industry the electricity sector transportation and heating. Hence apart from reducing hydrogen production costs establishing an efficient and suitable infrastructure for the storage transportation and distribution of hydrogen becomes essential. This article provides a technically detailed overview of the state-of-the-art technologies for hydrogen infrastructure including the physical- and material-based hydrogen storage technologies. Physical-based storage means the storage of hydrogen in its compressed gaseous liquid or supercritical state. Hydrogen storage in the form of liquid-organic hydrogen carriers metal hydrides or power fuels is denoted as material-based storage. Furthermore primary ways to transport hydrogen such as land transportation via trailer and pipeline overseas shipping and some related commercial data are reviewed. As the key results of this article hydrogen storage and transportation technologies are compared with each other. This comparison provides recommendations for building appropriate hydrogen infrastructure systems according to different application scenarios.

Green hydrogen is widely recognised as a key enabler for decarbonising heavy industry and long-haul transport. However producing it cost-competitively from variable renewable energy sources presents design challenges. In this study a mixed-integer linear programming (MILP) optimisation framework is developed to minimise the levelised cost of hydrogen (LCOH) from renewable-powered electrolysers. The analysis covers all European countries and explores how wind and solar resource availability influences the optimal sizing of renewable generators electrolysers hydrogen storage and batteries under both current and future scenarios. Results show that renewable resource quality strongly affects system design and hydrogen costs. At present solar-only systems yield LCOH values of 7.4–24.7 €/kg whereas wind-only systems achieve lower costs (5.1–17.1 €/kg) due to higher capacity factors and reduced storage requirements. Hybrid systems combining solar and wind emerge as the most cost-effective solution reducing average LCOH by 57 % compared to solar-only systems and 25 % compared to wind-only systems effectively narrowing geographical cost disparities. In the future scenario LCOH declines to 3–4 €/kg confirming renewable hydrogen’s potential to become economically competitive throughout Europe. A key contribution of this work is the derivation of design guidelines by correlating renewable resource quality with technical energy and economic indicators.

Underground hydrogen storage has gained interest in recent years due to the enormous demand for clean energy. Hydrogen is more diffusive than air with a smaller density and lower viscosity. These unique properties introduce distinctive hydrodynamic phenomena in hydrogen storage one of which is fingering. Fingering could induce the fluid trapped in small clusters of pores leading to a dramatic decrease in hydrogen saturation and a lower recovery rate. In this study numerical simulations are performed at the microscopic scale to understand the evolution of hydrogen saturation and the impacts of injection and withdrawal cycles. Two sets of micromodels with different porosity (0.362 and 0.426) and minimum sizes of pore throats (0.362 mm and 0.181 mm) are developed in the numerical model. A parameter analysis is then conducted to understand the influence of injection velocity (in the range of 10-2 m/s to 10-5 m/s) and porous structure on the fingering pattern followed by an image analysis to capture the evolution of the fingering pattern. Viscous fingering capillary fingering and crossover fingering are observed and identified under different boundary conditions. The fractal dimension specific area mean angle and entropy of fingers are proposed as geometric descriptors to characterize the shape of the fingering pattern. When porosity increases from 0.362 to 0.426 the saturation of hydrogen increases by 26.2%. Narrower pore throats elevate capillary resistance which hinders fluid invasion. These results underscore the importance of pore structures and the interaction between viscous and capillary forces for hydrogen recovery efficiency. This work illuminates the influence of the pore structures and the fluid properties on the immiscible displacement of hydrogen and can be further extended to optimize the injection strategy of hydrogen in underground hydrogen storage.

Hydrogen is a promising clean energy source that can be a promising alternative to fossil fuels without toxic emissions. It can be generated from formic acid (FA) through an FA dehydrogenation reaction using an active catalyst. Activated carbon-supported palladium (Pd/C) catalyst has superior activity properties for FA dehydrogenation and can be reused after deactivation. This study focuses on predicting the FA conversion to H2 (%) in the presence of Pd/C using machine learning techniques and experimental data (1544 data points). Six different machine learning algorithms are employed including random forest (RF) extremely randomized trees (ET) decision tree (DT) K nearest neighbors (KNN) support vector machine (SVM) and linear regression (LR). Temperature time FA concentration catalyst size catalyst weight sodium formate (SF) concentration and solution volume are considered as the input data while the FA conversion to H2 (%) is the target value. Based on the train and test outcomes the ET is the most accurate model for the prediction of FA conversion to H2 (%) and its accuracy is assessed by root mean squared error (RMSE) R-squared (R2 ) and mean absolute error (MAE) which are 3.16 0.97 and 0.75 respectively. In addition the results reveal that solution volume is the most significant feature in the model development process that affects the amount of FA conversion to H2 (%). These techniques can be used to assess the efficiency of other catalysts in terms of type size weight percentage and their effects on the amount of FA conversion to H2 (%). Moreover the results of this study can be used to optimize the energy cost and environmental aspects of the FA dehydrogenation process.

Scaling up water electrolyzers for green hydrogen production poses challenges in predicting megawatt-to gigawatt (MW/GW)-class system behavior under renewable energy power fluctuations. A fundamental evaluation is warranted to connect the characteristics of W- to kW-class laboratory electrolyzers with those of MW- to GW-class systems in practical applications. This study evaluates a 50 kW-class proton exchange membrane water electrolyzer with 30 cells using an accelerated degradation test protocol a simulated renewable energy power and a constant current of 800 A (1.33 A cm− 2 ) and the results show average degradation rates per cell of 40.4 27.2 and 5.6 μV h− 1 respectively. Evidently a voltage as approximate indicator exists for each cell to effectively suppress degradation. Durability tests reveal reductions in anode catalyst loading on the membrane electrode assemblies and inhomogeneous oxidation of the anode current collector. The findings contribute to predicting the stacking performance of electrolyzers for practical applications.