Publications

Green hydrogen generation technologies are currently the most pressing worldwide issues ofering promising alternatives to existing fossil fuels that endanger the globe with growing global warming. The current research focuses on the creation of green hydrogen in alkaline electrolytes utilizing a Ni-Co-nano-graphene thin flm cathode with a low overvoltage. The recommended conditions for creating the target cathode were studied by electrodepositing a thin Ni-Co-nano-graphene flm in a glycinate bath over an iron surface coated with a thin copper interlayer. Using a scanning electron microscope (SEM) and energy-dispersive X-ray (EDX) mapping analysis the obtained electrode is physically and chemically characterized. These tests confrm that Ni Co and nano-graphene are homogeneously dispersed resulting in a lower electrolysis voltage in green hydrogen generation. Tafel plots obtained to analyze electrode stability revealed that the Ni-Co-nano-graphene cathode was directed to the noble direction with the lowest corrosion rate. The Ni-Co-nano-graphene generated was used to generate green hydrogen in a 25% KOH solution. For the production of 1 kg of green hydrogen utilizing Ni-Co-nano-graphene electrode the electrolysis efciency was 95.6% with a power consumption of 52 kwt h−1 whereas it was 56.212. kwt h−1 for pure nickel thin flm cathode and 54. kwt h−1 for nickel cobalt thin flm cathode respectively.

Climate change has become a major agenda item in international relations and in national energy policy-making circles around the world. This review studies the surprising evolution of the energy policy and more particularly the energy transition currently happening in the Arabian Gulf region which features some of the world’s largest exporters of oil and gas. Qatar Saudi Arabia and other neighboring energy exporters plan to export blue and green hydrogen across Asia as well as towards Europe in the years and decades to come. Although poorly known and understood abroad this recent strategy does not threaten the current exports of oil and gas (still needed for a few decades) but prepares the evolution of their national energy industries toward the future decarbonized energy demand of their main customers in East and South Asia and beyond. The world’s largest exporter of Liquefied Natural Gas Qatar has established industrial policies and projects to upscale CCUS which can enable blue hydrogen production as well as natural carbon sinks domestically via afforestation projects.

The cost of green hydrogen production is very dependent on the price of electricity. A control system that can schedule hydrogen production based on forecast wind speed and electricity price should therefore be advantageous for large-scale wind-hydrogen systems. This work presents a novel price-based control system integrated in a techno-economic analysis of hydrogen production from offshore wind. A polynomial regression model that predicts wind power production from wind speed input was developed and tested with real-world datasets from a 2.3 MW floating offshore wind turbine. This was combined with a mathematical model of a PEM electrolyzer and used to simulate hydrogen production. A novel price-based control system was developed to decide when the system should produce hydrogen and when it should sell electricity to the grid. The model and control system can be used in real-world wind-hydrogen systems and require only the forecast wind speed electricity price and selling price of hydrogen as inputs. 11 test scenarios based on 10 years of real-world wind speed and electricity price data are proposed and used to evaluate the effect the price-based control system has on the levelized cost of hydrogen (LCOH). Both current and future (2050) costs and technologies are used and the results show that the novel control system lowered the LCOH in all scenarios by 10–46%. The lowest LCOH achieved with current technology and costs was 6.04 $/kg H2. Using the most optimistic forecasts for technology improvements and cost reductions in 2050 the model estimated a LCOH of 0.96 $/kg H2 for a grid-connected offshore wind farm and onshore hydrogen production 0.82 $/kg H2 using grid electricity (onshore) and 4.96 $/kg H2 with an offgrid offshore wind-hydrogen system. When the electricity price from the period 2013–2022 was used on the 2050 scenarios the resulting LCOH was approximately twice as high.

Though being attractive on railway decarbonisation for regional lines excessive cost caused by immature hydrogen supply chain is one of the significant hurdles for promoting hydrogen traction to rolling stocks. Therefore we conduct bespoke research on the UK’s hydrogen supply chain for railway concentrating on hydrogen transportation. Firstly a map for the planned hydrogen production plants and potential hydrogen lines is developed with the location capacity and usage. A spatially explicit model for the hydrogen supply chain is then introduced which optimises the existing grid-based methodology on accuracy and applicability. Compressed hydrogen at three pressures and liquid hydrogen are considered as the mediums incorporating by road and rail transport. Furthermore three scenarios for hydrogen rail penetration are simulated respectively to discuss the levelised cost and the most suitable national transport network. The results show that the developed model with mix-integer linear programming (MILP) can well design the UK’s hydrogen distribution for railway traction. Moreover the hydrogen transport medium and vehicle should adjust to suit for different era where the penetration of hydrogen traction varies. The levelised cost of hydrogen (LCOH) decreases from 6.13 £/kg to 5.13 £/kg on average from the conservative scenario to the radical scenario. Applying different transport combinations according to the specific situation can satisfy the demand while reducing cost for multi-supplier and multitargeting hydrogen transport.

The transition to sustainable energy has ushered in the era of electrofuels (e-fuels) which are synthesised using electricity from renewable sources water and CO2 as a sustainable alternative to fossil fuels. This paper presents a systematic review of the techno-economic (TEA) and life cycle assessments (LCAs) of e-fuel production. We critically evaluate advancements in production technologies economic feasibility environmental implications and potential societal impacts. Our findings indicate that while e-fuels offer a promising solution to reduce carbon emissions their economic viability depends on optimising production processes and reducing input material costs. The LCA highlights the necessity of using renewable energy for hydrogen production to ensure the genuine sustainability of e-fuels. This review also identifies knowledge gaps suggesting areas for future research and policy intervention. As the world moves toward a greener future understanding the holistic implications of e-fuels becomes paramount. This review aims to provide a comprehensive overview to guide stakeholders in their decision-making processes.

This work presents a comparative novel evaluation of two distinct fuels methanol and hydrogen production and power generation routes via fuel cells. The first route includes the methanol production from direct partial oxidation of methane to methanol where the methanol is condensed stored and sent to a direct methanol fuel cell. The second route is hydrogen production from solar methane cracking (named as turquoise hydrogen) where heat is supplied from concentrated solar power and hydrogen is stored and directed to a hydrogen fuel cell. This study aims to provide insights into these fuel's production conditions storage methods energy and exergy efficiencies. The proposed system is simulated using the Engineering Equation Solver software and a thermodynamic analysis of the entire system including all the equipment and process streams is performed. The methanol and hydrogen route's overall energy and exergy efficiencies are 39.75% 38.35% 35.84% and 34.58% respectively. The highest exergy destruction rate of 1605 kW is observed for the partial oxidation of methane to methanol. The methanol and hydrogen routes generate 32.087 MWh and 11.582 MWh of electricity for 16-hour of fuel cell operation respectively. Sensitivity analysis has been performed to observe the effects of different parameters such as operating temperature and mass flow rate of fuels on the electricity production and energy efficiencies of the systems.

The work carried out in this paper focused on “Machine learning models for the prediction of turbulent combustion speed for hydrogen-natural gas spark ignition engines”. The aim of this work is to develop and verify the ability of machine learning models to solve the problem of estimating the turbulent flame speed for a spark-ignition internal combustion engine operating with a hydrogen-natural gas mixture then evaluate the relevance of these models in relation to the usual approaches. The novelty of this work is the possibility of a direct calculation of turbulent combustion speed with a good precision using only machine learning model. The obtained models are also compared to each other by considering in turn as a comparison criterion: the precision of the result calculation time and the ability to assimilate original data (which has not undergone preprocessing). An important particularity of this work is that the input variables of the machine learning models were chosen among the variables directly measurable experimentally based on the opinion of experts in combustion in internal combustion engines and not on the usual approaches to dimensionality reduction on a dataset. The data used for this work was taken from a MINSEL 380 a 380-cc single-cylinder engine. The results show that all the machine learning models obtained are significantly faster than the usual approach and Random Forest (R2: R-squared = 0.9939 and RMSE: Root Mean Square Error = 0.4274) gives the best results. With a forecasting accuracy of over 90 % both approaches can make reasonable predictions for most industrial applications such as designing engine monitoring and control systems firefighting systems simulation and prototyping tools.

The high potential of hydrogen as a key factor on the pathway towards a climate neutral economy leads to rising demand in technical applications where gaseous hydrogen is used. For several metals hydrogen-metal interactions could cause a degradation of the material properties. This is especially valid for low carbon and highstrength structural steels as they are commonly used in natural gas pipelines and analyzed in this work. This work provides an insight to the impact of hydrogen on the mechanical properties of an API 5L X65 pipeline steel tested in 60 bar gaseous hydrogen atmosphere. The analyses were performed using the hollow specimen technique with slow strain rate testing (SSRT). The nature of the crack was visualized thereafter utilizing μCT imaging of the sample pressurized with gaseous hydrogen in comparison to one tested in an inert atmosphere. The combination of the results from non-conventional mechanical testing procedures and nondestructive imaging techniques has shown unambiguously how the exposure to hydrogen under realistic service pressure influences the mechanical properties of the material and the appearance of failure.

Green hydrogen represents a promising solution for renewable energy application and carbon footprint reduc tion. However its production through renewable energy powered water electrolysis is hindered by significant cost arising from repair maintenance and economic losses due to unexpected downtimes. Although reliability engineering is highly effective in addressing such issues there is limited research on its application in the hydrogen field. To present the state-of-the-art research this study aims to explore the potential of reducing these events through reliability engineering a widely adopted approach in various industries. For this purpose it examines past accidents occurred in water electrolysis plants from the hydrogen incident and accident database (HIAD 2.1). Besides a literature review is performed to analyze the state-of-the-art application of reliability engineering techniques such as failure analysis reliability assessment and reliability-centered maintenance in the hydrogen sector and similar industries. The study highlights the contributions and potentials of reliability engineering for efficient and stable green hydrogen production while also discussing the gaps in applying this approach. The unique challenges posed by hydrogen’s physical properties and innovative technologies in water electrolysis plants necessitate advancement and specialized approaches for reliability engineering.

Shipping corridors act as the arteries of the global economy. The maritime shipping sector is also a major source of greenhouse gas emissions accounting for 2.9% of the global total. The international nature of the shipping sector combined with issues surrounding the use of battery technology means that these emissions are considered difficult to eliminate. This work explores the transition to renewable fuels by examining the use of electrofuels (in the form of liquid hydrogen methane methanol ammonia and Fischer-Tropsch fuel) to decarbonise large container ships from a technical economic and environmental perspective. For an equivalent range to current fossil fuel vessels the cargo capacity of vessels powered by electrofuels decreases by between 3% and 16% depending on the fuel of choice due to the lower energy density compared with conventional marine fuels. If vessel operators are willing to sacrifice range cargo space can be preserved by downsizing onboard energy storage which necessitates more frequent refuelling. For a realistic green hydrogen cost of €3.5/kg (10.5 €c/kWh) in 2030 the use of electrofuels in the shipping sector results in an increase in the total cost of ownership of between 124% and 731% with liquid hydrogen in an internal combustion engine being the most expensive and methanol in an internal combustion engine resulting in the lowest cost increase. Despite this we find that the increased transportation costs of some consumer goods to be relatively small adding for example less than €3.27 to the cost of a laptop. In general fuels which do not require cryogenic storage and can be used in internal combustion engines result in the lowest cost increases. For policymakers reducing the environmental impact of the shipping sector is a key priority. The use of liquid hydrogen which results in the largest cost increase offers a 70% reduction in GHG emissions for an electricity carbon intensity of 80 gCO2e/ kWh which is the greatest reduction of all fuels assessed in this work. A minimum carbon price of €400/tCO2 is required to allow these fuels to reach parity with conventional shipping operations. To meet European Union emissions reductions targets electricity with an emissions intensity below 40 gCO2e/kWh is required which suggests that for electrofuels to be truly sustainable direct connection with a source of renewable electricity is required.

The Mediterranean basin has been characterized by a net flow of fossil commodities from the North African shore to Southern Europe and the Middle East for decades; however decarbonizing the energy system implies to substantially modify this situation turning the current “black dialogue” into a “green dialogue” (i.e. based on the exchange of renewable electricity and green hydrogen). This paper presents a feasibility study conducted to estimate the potential green hydrogen production by electrolysis in three Tunisian sites. It shows and compares several plant layouts varying the size and typology of renewable electricity generators and electrolyzers. The work adopts local weather data and technical features of the technologies in the computations and accounts for site specific topographical and infrastructural constraints such as land available for construction and local power grid connection capacities. It shows that configurations able to produce large quantities of green hydrogen may not be compliant with such constraints basically nullifying their contribution in any hydrogen strategy. Finally results show that the LCOH lies in the range 1.34 $/kgH2 and 4.06 $/kgH2 depending on both the location and the combination of renewable electricity generators and electrolyzers.

The report addresses the environmental challenges faced by European sea ports and aims to provide guidance to smaller ports for improving their environmental performance while achieving sustainability goals through experiences gained by implementing noteworthy green initiatives in practice. Larger ports possess significant advantages in terms of financial resources risk tolerance and organisational capacity. They often have the means to invest in innovative solutions and actively participate in research and development projects leading to co-funded pilot implementation of green initiatives. They typically have more skilled personnel stronger influence and stakeholder leverage which position them better to lead the way in sustainability efforts. Finally larger ports often form robust collaborations to drive collective action towards sustainable goals. Smaller ports face unique challenges stemming from typically limited resources and risk aversion. They often prioritise mature solutions relying on tested practices to mitigate potential risks. They may lack internal expertise requiring guidance and capacity-building programmes to navigate the selection and implementation of green practices. Also they require financial and technical support particularly as they may underutilise available funding mechanisms and have limited participation in R&D programmes. They may benefit from partnerships with other ports and stakeholders to create synergies and gain experience from their lessons learned to boost their capacity to implement green practices

To inject green hydrogen (H2) into the existing natural gas (NG) infrastructure is one way to decarbonize the European energy system. However asset readiness is necessary to be successful. Preliminary analysis and experimental results about the compatibility of hydrogen and natural gas mixtures (H2NG) with the actual gas grids make the scientific community confident about the feasibility. Nevertheless specific technical questions need more research. A significant topic of debate is the impact of H2NG mixtures on the performance of state-ofthe-art fiscal measuring devices which are essential for accurate billing. Identifying and addressing any potential degradation in their metrological performance due to H2NG is critical for decision-making. However the literature lacks data about the gas meters’ technologies currently installed in the NG grids such as a comprehensive overview of their readiness at different concentrations while data are fragmented among different sources. This paper addresses these gaps by analyzing the main characteristics and categorizing more than 20000 gas meters installed in THOTH2 project partners’ grids and by summarizing the performance of traditional technologies with H2NG mixtures and pure H2 based on literature review operators experience and manufacturers knowledge. Based on these insights recommendations are given to stakeholders on overcoming the identified barriers to facilitate a smooth transition.

This article presents the concept of green transformation of the coal mining sector. Pump stations that belong to Spółka Restrukturyzacji Kopal´n S.A. (SRK S.A. Bytom Poland) pump out approximately 100 million m3 of mine water annually. These pump stations protect neighboring mines and lower-lying areas from flooding and protect subsurface aquifers from contamination. The largest cost component of maintaining a pumping station is the expenditure for purchasing electricity. Investment towards renewable energy sources will reduce the environmental footprint of pumping station operation by reducing greenhouse gas emissions. The concept of liquidation of an exemplary mining site in the context of a circular economy by proposing the development/revitalization of a coal mine site is presented. This concept involves the construction of a complex consisting of photovoltaic farms combined with efficient energy storage in the form of green hydrogen produced by water electrolysis. For this purpose the potential of liquidated mining sites will be utilized including the use of pumped mine wastewater. This article is conceptual. In order to reach the stated objective a body of literature and legal regulations was analyzed and an empirical study was conducted. Various scenarios for the operation of mine pumping stations have been proposed. The options presented provide full or nearly full energy self-sufficiency of the proposed pumping station operation concept. The effect of applying any option for upgrading the pumping station could result in the creation of jobs that are alternatives to mining jobs and a guarantee of efficient asset management.

The number of species and elementary reactions needed for describing the oxidation of fuels increases with the size of the molecule and in turn the complexity of detailed mechanisms. Although the kinetics for conventional fuels (H2 CH4 C3H8...) are somewhat well-established chemical integration in detonation applications remains a major challenge. Significant efforts have been made to develop reduction techniques that aim to keep the predictive capabilities of detailed mechanisms intact while minimizing the number of species and reactions required. However as their starting point of development is based on homogeneous reactors or ZND profiles reduced mechanisms comprising a few species and reactions are not predictive. The methodology presented here relies on defining virtual chemical species such that the thermodynamic equilibrium of the ZND structure is properly recovered thereby circumventing the need to account for minor intermediate species. A classical asymptotic expression relating the ignition delay time with the reaction rate constant is then used to fit the Arrhenius coefficients targeting computations carried out with detailed kinetics. The methodology was extended to develop a three-step mechanism in which the Arrhenius coefficients were optimized to accurately reproduce the one-dimensional laminar ZND structure and the D−κ curves for slightly-curved quasi-steady detonation waves. Two-dimensional simulations performed with the three-step mechanism successfully reproduce the spectrum of length scales present in soot foils computed with detailed kinetics (i.e. cell regularity and size). Results attest for the robustness of the proposed methodology/approximation and its flexibility to be adapted to different configurations.

The high potential in renewable energy sources (RES) and the availability of strategic minerals for green hydrogen technologies place Africa in a promising position for the development of a climate-compatible economy leveraging on hydrogen. This study reviews the potential hydrogen value chain in Africa considering production and final uses while addressing perspectives on policies possible infrastructures and facilities for hydrogen logistics. Through scientific studies research and searching in relevant repositories this review features the collection analysis of technical data and georeferenced information about key aspects of the hydrogen value chain. Detailed maps and technical data for gas transport infrastructure and liquefaction terminals in the continent are reported to inform and elaborate findings about readiness for hydrogen trading and domestic use in Africa. Specific maps and technical data have been also collected for the identification of potential hydrogen offtakers focusing on individual industrial installations to produce iron and steel chemicals and oil refineries. Finally georeferenced data are presented for main road and railway corridors as well as for most important African ports as further end-use and logistic platforms. Beyond technical information this study collects and discusses more recent perspectives about policies and implementation initiatives specifically addressing hydrogen production logistics and final use also introducing potential criticalities associated with environmental and social impacts.

Hydrogen production by seawater electrolysis is significantly hindered by high energy costs and undesirable detrimental chlorine chemistry in seawater. In this work energy-saving hydrogen production is reported by chlorine-free seawater splitting coupling tip-enhanced electric field promoted electrocatalytic sulfion oxidation reaction. We present a bifunctional needle-like Co3S4 catalyst grown on nickel foam with a unique tip structure that enhances the kinetic rate by improving the current density in the tip region. The assembled hybrid seawater electrolyzer combines thermodynamically favorable sulfion oxidation and cathodic seawater reduction can enable sustainable hydrogen production at a current density of 100 mA cm−2 for up to 504 h. The hybrid seawater electrolyzer has the potential for scale-up industrial implementation of hydrogen production by seawater electrolysis which is promising to achieve high economic efficiency and environmental remediation.

This article describes an example of using the measurement data from photovoltaic systems and wind turbines to perform practical probabilistic calculations around green hydrogen generation. First the power generated in one month by a ground-mounted photovoltaic system with a peak power of 3 MWp is described. Using the Metalog family of probability distributions the probability of generating selected power levels corresponding to the amount of green hydrogen produced is calculated. Identical calculations are performed for the simulation data allowing us to determine the power produced by a wind turbine with a maximum power of 3.45 MW. After interpolating both time series of the power generated by the renewable energy sources to a common sampling time they are summed. For the sum of the power produced by the photovoltaic system and the wind turbine the probability of generating selected power levels corresponding to the amount of green hydrogen produced is again calculated. The presented calculations allow us to determine with probability distribution accuracy the amount of hydrogen generated from the energy sources constituting a mix of photovoltaics and wind. The green hydrogen production model includes the hardware and the geographic context. It can be used to determine the preliminary assumptions related to the production of large amounts of green hydrogen in selected locations. The calculations presented in this article are a practical example of Business Intelligence.

This study explores the integration and optimization of battery energy storage systems (BESSs) and hydrogen energy storage systems (HESSs) within an energy management system (EMS) using Kangwon National University’s Samcheok campus as a case study. This research focuses on designing BESSs and HESSs with specific technical specifications such as energy capacities and power ratings and their integration into the EMS. By employing MATLAB-based simulations this study analyzes energy dynamics grid interactions and load management strategies under various operational scenarios. Real-time data from the campus are utilized to examine energy consumption renewable energy generation grid power fluctuations and pricing dynamics providing key insights for system optimization. This study finds that a BESS manages energy fluctuations between 0.5 kWh and 3.7 kWh over a 24 h period with battery power remaining close to 4 W for extended periods. Grid power fluctuates between −5 kW and 75 kW while grid prices range from 75 to 120 USD/kWh peaking at 111 USD/kWh. Hydrogen energy storage varies from 1 kWh to 8 kWh with hydrogen power ranging from −40 kW to 40 kW. Load management keeps power stable at around 35 kW and PV power integration peaks at 48 kW by the 10th h. The findings highlight that BESSs and HESSs effectively manage energy distribution and storage improving system efficiency reducing energy costs by approximately 15% and enhancing grid stability by 20%. This study underscores the potential of BESSs and HESSs in stabilizing grid operations and integrating renewable energy. Future directions include advancements in storage technologies enhanced EMS capabilities through artificial intelligence and machine learning and the development of smart grid infrastructures. Policy recommendations stress the importance of regulatory support and stakeholder collaboration to drive innovation and scale deployment ensuring a sustainable energy future.

Global attention is being given to hydrogen as it is seen as a versatile energy carrier and a flexible energy vector in transitioning to a low-carbon economy. Hydrogen production/storage/conveyance is metal intensive and it is crucial to understand if there is material availability to fulfil the committed plans. Using the material intensity of electrolysers pipelines and desalinators along with the projected Portuguese and European Union roadmaps we are able to identify possible bottlenecks in the supply chains. The availability of the vast majority of raw materials does not represent a threat to hydrogen technologies implementation with electrolysers requiring almost up to 3 Mt of raw materials and pipelines up to 2.5 Mt. The evident exception is iridium although representing less than 0.001 % of the material requirements it may hinder the widespread implementation of proton exchange membrane electrolysers. Desalinators have the least material footprint of the studied infrastructure.

As global economies seek to transition to low-carbon energy systems to achieve net zero targets hydrogen has potential to play a key role to decarbonise sectors that are unsuited to electrification or where long-term energy storage is required. Hydrogen can also assist in enabling decentralized renewable power generation to satisfy higher electricity demand to match the scale-up of electrified technologies. In this context suitable transport storage and distribution networks will be essential to connect hydrogen generation and utilisation sites. This paper presents a techno-economic impact evaluation of international marine hydrogen transportation between Canada and the Netherlands comparing liquid hydrogen ammonia and a dibenzyl toluene liquid organic hydrogen carrier (LOHC) as potential transport vectors. Economic costs energy consumption and losses in each phase of the transportation system were analysed for each vector. Based on the devised scenarios our model suggests levelised costs of hydrogen of 6.35–9.49 $2022/kgH2 and pathway efficiencies of 55.6–71.9%. While liquid hydrogen was identified as the most cost-competitive carrier sensitivity analysis revealed a merit order for system optimisation strategies based upon which LOHC could outperform both liquid hydrogen and ammonia in the future.

This study addresses cost-optimal sizing and energy management of a grid-integrated solar photovoltaic wind turbine hybrid renewable energy system integrated with electrolyzer and hydrogen storage tank to simultaneously meet electricity and hydrogen demands considering the case study of Dijon France. Mixed Integer Linear Programming optimization problem is formulated to evaluate two objective case scenarios: single objective and multi-objective minimizing total annual costs and grid carbon emission footprint. The study incorporates various technical economic and environmental indicators focusing on the impact of sensitivity lying on various grid electricity purchase rates within the French electricity market prices. The results highlight that rising grid prices drive increased integration of renewable sources while lower prices favor ultimate grid dependency. Constant hydrogen demand necessitates the installation of two electrolyzers. Notably grid electricity prices above 60 e/MWh result increase in the size of the hydrogen tank and electrolyzer operation to prevent renewable energy losses. Grid prices above 140 e/MWh depict 70% of electrical and 80% of electrolyzer demand provided by the renewable generation resulting in a carbon emission below 0.0416 Mt of CO2 and 0.643 kgCO2 /kgH2 . Conversely grid prices below 20 e/MWh lead ultimately to 100% grid dependency with a higher carbon emission of approximately 0.14 Mt of CO2 and 4.13 kgCO2 /kgH2 reducing the total annual cost to 41.63 Million e. Increase in grid prices from 20e/MWh to 180 e/MWh resulted in increase of hydrogen specific costs from 1.23 to 3.58 e/kgH2 . Finally the Pareto front diagram is employed to illustrate the trade-off between total annual cost and carbon emission due to grid imports aiding in informed decision-making.

With decreasing costs of the clean technologies the balanced scales of the Sustainable Development Goal 7 targets e.g. energy equity (EE) energy security (ES) and environmental sustainability (EVS) are quickly changing. This fundamental balancing process is a key requirement for a net-zero future. Accordingly this research analyzes the regime-switching effect of Hydrogen economy as the green transition sharing economy and economic complexity as the complexity-based and geopolitical risks and energy prices as the geostrategy policies on the Goal 7 targets. To this end a Markov-switching panel vector autoregressive method with regime-heteroskedasticity is applied to study advancing the Goal 7 in the world's twenty-five large energy consumers during 2004–2020. Concerning the parameters and statistics of the model the results refer to the existence of two regimes associated with the Goal 7 corners called “upward and downward” regimes for EE and “slightly upward and sharply upward” regimes for ES and EVS. It is revealed that the vulnerability of EE and ES targets is considerably reduced when the regime switches to the dominant regime that is “downward” and “slightly upward” regimes respectively and that of the EVS target remains unaffected. Through the impulse-response analysis the findings denote that the first hypothesis of the efficiency of the Hydrogen economy in promoting the Goal 7 targets is insignificant. However the significant short-term and dynamic shock effects of the complexity-based and geostrategy policies on the Hydrogen economy are detected which will be a feasible alternative assessment in advancing the Goal 7. Further the complexity-based policies support the Goal 7 targets under different regimes especially in the short- and medium-term. Hence the second hypothesis regarding the effectiveness of the complexity-based policies in promoting Goal 7 targets is confirmed. The third hypothesis concerning the complexity of the impact of geostrategy policies on the Goal 7 targets is verified. Particularly the switching process towards the Goal 7 may not necessarily be restricted by the geopolitical risks. Moreover EE is supported through energy prices in the short-term under both regimes while they are non-conductive to promote ES and EVS through time. Accordingly the decision-makers should acknowledge adopting a regime-switching path forward for ensuring the time-varying balanced growth of the Goal 7 targets as the impact of the suggested policy instruments is asymmetric.

This paper provides a comprehensive review and outlook on power converters devised for supplying polymer electrolyte membrane (PEM) electrolyzers from photovoltaic sources. The produced hydrogen known as green hydrogen is a promising solution to mitigate the dependence on fossil fuels. The main topologies of power conversion systems are discussed and classified; a loss analysis emphasizes the issues concerning the electrolyzer supply. The attention is focused on power converters of rated power up to a tenth of a kW since it is a promising field for a short-term solution implementing green hydrogen production as a decentralized. It is also encouraged by the proliferation of relatively cheap photovoltaic low-power plants. The main converters proposed by the literature in the last few years and realized for practical applications are analyzed highlighting their key characteristics and focusing on the parameters useful for designers. Future perspectives are addressed concerning the availability of new wide-bandgap devices and hard-to-abate sectors with reference to the whole conversion chain.

In today’s world the need for sustainable energy solutions is paramount to address the ongoing crisis of increasing greenhouse gas emissions and global warming. Industries heavily reliant on fossil fuels must explore alternative energy sources. Hydrogen with its high heating value and zero direct emissions has emerged as a promising fuel for the future. Electrolytic hydrogen production has gained significance as it enables demand-side response grid stabilization using excess energy and the mitigation of curtailment from intermittent renewable energy sources (RES) such as solar and wind. Advanced combined heat and power (CHP) systems comprise of Solid oxide fuel cell (SOFC) module and a coupled reforming reactor to capture energy contained in the SOFC exhaust gases from SOFC. In present work 3D CFD model of an experimental coupled reactor used for onsite hydrogen production is developed and implemented into ANSYS Fluent® software. The study is aimed at opti mizing the reactor performance by identifying appropriate kinetic models for reforming and combustion re actions. SOFC anode off-gas (AOG) comprising mainly of unconverted hydrogen is combined with methane combustion to enhance thermal efficiency of the reactor and hence the CHP system. Kinetic models for catalytic reforming and combustion are implemented into ANSYS Fluent® through custom-built user defined functions (UDFs) written in C programming language. Simulation results are validated with experimental data and found in good agreement. AOG assisted combustion of methane shows a substantial improvement in thermal efficiency of the system. Improvement in thermal efficiency and reduction in carbon-based fuel demand AOG utilization contributes to sustainable hydrogen production and curtailment of greenhouse gas emissions.