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The Pr and Sm co-doped ceria (with up to 20 mol.% of dopants) compounds were examined as catalytic layers on the surface of SOFC anode directly fed by biogas to increase a lifetime and the efficiency of commercially available DIR-SOFC without the usage of an external reformer.

The XRD SEM and EDX methods were used to investigate the structural properties and the composition of fabricated materials. Furthermore the electrical properties of SOFCs with catalytic layers deposited on the Ni-YSZ anode were examined by a current density-time and current density-voltage dependence measurements in hydrogen (24 h) and biogas (90 h). Composition of the outlet gasses was in situ analysed by the FTIR-based unit.

It has been found out that Ce_0.9Sm_0.1O_2-δ and Ce_0.8Pr_0.05Sm_0.15O_2-δ catalytic layers show the highest stability over time and thus are the most attractive candidates as catalytic materials in comparison with other investigated lanthanide-doped ceria enhancing direct internal reforming of biogas in SOFCs.

Power-to-Power is a process whereby the surplus of renewable power is stored as chemical energy in the form of hydrogen. Hydrogen can be used in situ or transported to the consumption node. When power is needed again hydrogen can be consumed for power generation. Each of these processes incurs energy losses leading to a certain round-trip efficiency (Energy Out/Energy In). Round-trip efficiency is calculated considering the following processes; water electrolysis for hydrogen production compressed liquefied or metal-hydride for hydrogen storage fuel-cell-electric-truck for hydrogen distribution and micro-gas turbine for hydrogen power generation. The maximum achievable round-trip efficiency is of 29% when considering solid oxide electrolysis along with metal hydride storage. This number goes sharply down when using either alkaline or proton exchange membrane electrolyzers 22.2% and 21.8% respectively. Round-trip efficiency is further reduced if considering other storage media such as compressed- or liquefied-H2. However the aim of the paper is to highlight there is still a large margin to increase Power-to-Power round-trip efficiency mainly from the hydrogen production and power generation blocks which could lead to round-trip efficiencies of around 40%e42% in the next decade for Power-to-Power energy storage systems with micro-gas turbines.

Gaseous hydrogen for fuel cell electric vehicles must meet quality standards such as ISO 14687:2019 which contains maximal control thresholds for several impurities which could damage the fuel cells or the infrastructure. A review of analytical techniques for impurities analysis has already been carried out by Murugan et al. in 2014. Similarly this document intends to review the sampling of hydrogen and the available analytical methods together with a survey of laboratories performing the analysis of hydrogen about the techniques being used. Most impurities are addressed however some of them are challenging especially the halogenated compounds since only some halogenated compounds are covered not all of them. The analysis of impurities following ISO 14687:2019 remains expensive and complex enhancing the need for further research in this area. Novel and promising analyzers have been developed which need to be validated according to ISO 21087:2019 requirements.

Hydrogen-based energy storage and generation is an increasingly used technology especially in renewable systems because they are non-polluting devices. Fuel cells are complex nonlinear systems so a good model is required to establish efficient control strategies. This paper presents a hybrid model to predict the variation of H2 flow of a hydrogen fuel cell. This model combining clusters’ techniques to get multiple Artificial Neural Networks models whose results are merged by Polynomial Regression algorithms to obtain a more accurate estimate. The model proposed in this article use the power generated by the fuel cell the hydrogen inlet flow and the desired power variation to predict the necessary variation of the hydrogen flow that allows the stack to reach the desired working point. The proposed algorithm has been tested on a real proton exchange membrane fuel cell and the results show a great precision of the model so that it can be very useful to improve the efficiency of the fuel cell system.

"This paper investigates hydrogen storage and refueling technologies that were used in rail vehicles over the past 20 years as well as planned activities as part of demonstration projects or feasibility studies. Presented are details of the currently available technology and its vehicle integration market availability as well as standardization and research and development activities. A total of 80 international studies corporate announcements as well as vehicle and refueling demonstration projects were evaluated with regard to storage and refueling technology pressure level hydrogen amount and installation concepts inside rolling stock. Furthermore current hydrogen storage systems of worldwide manufacturers were analyzed in terms of technical data.<br/>We found that large fleets of hydrogen-fueled passenger railcars are currently being commissioned or are about to enter service along with many more vehicles on order worldwide. 35 MPa compressed gaseous storage system technology currently dominates in implementation projects. In terms of hydrogen storage requirements for railcars sufficient energy content and range are not a major barrier at present (assuming enough installation space is available). For this reason also hydrogen refueling stations required for 35 MPa vehicle operation are currently being set up worldwide.<br/>A wide variety of hydrogen demonstration and retrofit projects are currently underway for freight locomotive applications around the world in addition to completed and ongoing feasibility studies. Up to now no prevailing hydrogen storage technology emerged especially because line-haul locomotives are required to carry significantly more energy than passenger trains. The 35 MPa compressed storage systems commonly used in passenger trains offer too little energy density for mainline locomotive operation - alternative storage technologies are not yet established. Energy tender solutions could be an option to increase hydrogen storage capacity here."

The increasing energy demand and the subsequent climate change consequences are supporting the search for sustainable alternatives to fossil fuels. In this scenario the link between hydrogen and renewable energy is playing a key role and unitized hydrogen-chlorine (H2-Cl2) regenerative cells (RFCs) have become promising candidates for renewable energy storage. Described herein are the recent advances in cell configurations and catalysts for the different reactions that may take place in these systems that work in both modes: electrolysis and fuel cell. It has been found that platinum (Pt)-based catalysts are the best choice for the electrode where hydrogen is involved whereas for the case of chlorine ruthenium (Ru)-based catalysts are the best candidates. Only a few studies were found where the catalysts had been tested in both modes and recent advances are focused on decreasing the amount of precious metals contained in the catalysts. Moreover the durability of the catalysts tested under realistic conditions has not been thoroughly assessed becoming a key and mandatory step to evaluate the commercial viability of the H2-Cl2 RFC technology.

The electrification of final energy uses is a key strategy to reach the desired scenario with zero greenhouse gas emissions. Many of them can be electrified with more or less difficulty but there is a part that is difficult to electrify at a competitive cost: heavy road transport maritime and air transport and some industrial processes are some examples. For this reason the possibility of using other energy vectors rather than electricity should be explored. Hydrogen can be considered a real alternative especially considering that this transition should not be carried out immediately because initially the electrification would be carried out in those energy uses that are considered most feasible for this conversion. The Canary Islands’ government is making considerable efforts to promote a carbon-free energy mix starting with renewable energy for electricity generation. Still in the early–mid 2030s it will be necessary to substitute heavy transport fossil fuel. For this purpose HOMER software was used to analyze the feasibility of hydrogen production using surplus electricity produced by the future electricity system. The results of previous research on the optimal generation MIX for Grand Canary Island based exclusively on renewable sources were used. This previous research considers three possible scenarios where electricity surplus is in the range of 2.3–4.9 TWh/year. Several optimized scenarios using demand-side management techniques were also studied. Therefore based on the electricity surpluses of these scenarios the optimization of hydrogen production and storage systems was carried out always covering at least the final hydrogen demand of the island. As a result it is concluded that it would be possible to produce 3.5 × 104 to 7.68 × 104 t of H2/year. In these scenarios 3.15 × 105 to 6.91 × 105 t of water per year would be required and there could be a potential production of 2.8 × 105 to 6.14 × 105 t of O2 per year.

Ammonia is an industrial chemical and the basic building block for the fertilizer industry. Lately attention has shifted towards using ammonia as a carbon-free energy vector due to the ease of transportation and storage in liquid state at − 33 ◦C and atmospheric pressure. This study evaluates the prospects of blue and green ammonia as future energy carriers; specifically the gas switching reforming (GSR) concept for H2 and N2 co-production from natural gas with inherent CO2 capture (blue) and H2 generation through an optimized value chain of wind and solar power electrolysers cryogenic N2 supply and various options for energy storage (green). These longer term concepts are benchmarked against conventional technologies integrating CO2 capture: the Kellogg Braun & Root (KBR) Purifier process and the Linde Ammonia Concept (LAC). All modelled plants utilize the same ammonia synthesis loop for a consistent comparison. A cash flow analysis showed that the GSR concept achieved an attractive levelized cost of ammonia (LCOA) of 332.1 €/ton relative to 385.1–385.9 €/ton for the conventional plants at European energy prices (6.5 €/GJ natural gas and 60 €/MWh electricity). Optimal technology integration for green ammonia using technology costs representative of 2050 was considerably more expensive: 484.7–772.1 €/ton when varying the location from Saudi Arabia to Germany. Furthermore the LCOA of the GSR technology drops to 192.7 €/ton when benefitting from low Saudi Arabian energy costs (2 €/GJ natural gas and 40 €/MWh electricity). This cost difference between green and blue ammonia remained robust in sensitivity analyses where input energy cost (natural gas or wind/solar power) was the most influential parameter. Given its low production costs and the techno-economic feasibility of international ammonia trade advanced blue ammonia production from GSR offers an attractive pathway for natural gas exporting regions to contribute to global decarbonization.

This paper deals with the integration of a Power-to-Power Energy Storage System (P2P-ESS) based on a hydrogen driven micro gas turbine (mGT) for an off-grid application with a continuous demand of 30 kWe for three European cities: Palermo Frankfurt and Newcastle. In the first part of the analysis the results show that the latitude of the location is a very strong driver in determining the size of the system (hence footprint) and the amount of seasonal storage. The rated capacity of the PV plant and electrolyzer are 37%/41% and 58%/64% higher in Frankfurt and Newcastle respectively as compared to the original design for Palermo. And not only this but seasonal storage also increases largely from 3125 kg H2 to 5023 and 5920 kg H2 . As a consequence of this LCOE takes values of 0.86 e/kWh 1.26 e/kWh and 1.5 e/kWh for the three cities respectively whilst round-trip efficiency is approximately 15.7% for the three designs at the 3 cities. Finally with the aim to reduce the footprint and rating of the different systems a final assessment of the system hybridised with battery storage shows a 20% LCOE reduction and a 10% higher round-trip efficiency.

Climate change and environmental degradation are growing concerns in today’s society which has led to greater awareness and responsibility regarding the need to adopt sustainable practices. The European Union has established the goal of achieving climate neutrality by 2050 which implies a significant reduction in greenhouse gas emissions in all sectors. To achieve this goal renewable energies the circular economy and energy efficiency are being promoted. A major source of emissions is the use of fossil fuels in different types of ships (from transport ships to those used by national navies). Among these it highlights the growing interest of the defense sector in trying to reduce these emissions. The Spanish Ministry of Defense is also involved in this effort and is taking steps to reduce the carbon footprint in military operations and improve sustainability in equipment acquisition and maintenance. The objective of this study is to identify the most promising alternative fuel among those under development for possible implementation on Spanish Navy ships in order to reduce greenhouse gas emissions and improve its capabilities. To achieve this a multi-criteria decision-making method will be used to determine the most viable fuel option. The data provided by the officers of the Spanish Navy is of great importance thanks to their long careers in front of the ships. The analysis revealed that hydrogen was the most suitable fuel with the highest priority ahead of LNG and scored the highest in most of the sections of the officials’ ratings. These fuels are less polluting and would allow a significant reduction in emissions during the navigation of ships. However a further study would also have to be carried out on the costs of adapting to their use and the safety of their use.

This bibliometric study examines the evolution of compressed-hydrogen storage technologies over the last 20 years revealing exponential growth in research and highlighting key advancements in compressed-hydrogen storage materials-based solutions and integration with renewable energy systems. The analysis highlights the pivotal role of composite material tanks and the filament-winding process in revolutionizing storage technology. These innovations have enhanced safety reduced weight and facilitated adaptation for use in automotive and industrial applications. Global research efforts are characterized by substantial international collaboration spearheaded by a small cohort of highly productive researchers and supported by a broader network of contributors. Notwithstanding the ongoing challenges pertaining to safety considerations and cost scalability the potential of hydrogen as a clean energy carrier and its role in balancing renewable energy systems serve to reinforce its importance in the transition to sustainable energy.

LNG carriers play a crucial role in the shipping industry meeting the global demand for natural gas (NG). However the energy losses resulting from the propulsion system and the excess boil-off gas (BOG) cannot be overlooked. The present article investigates the H2 production on board LNG carriers employing both the engine's waste heat (WH) and the excess BOG. Conventional (ORC) and dual-pressure (2P-ORC) organic Rankine cycles coupled separately with a solid oxide electrolysis (SOEC) have been simulated and compared. The hydrogen (H2) produced is then compressed at 150 bar for subsequent use as required. According to the results the 2P-ORC generates 14.79 % more power compared to ORC allowing for an increased energy supply to the SOEC; hence producing more H2 (34.47 kg/h compared to 31.14 kg/h). Including the 2P-ORC in the H2 production plant results in a cheaper H2 cost by 0.04 $/kgH2 compared to ORC a 1.13 %LHV higher system efficiency when leveraging all the available waste heat. The plant including 2P-ORC exploits more than 86 % of the of the available waste compared to 70 % when using ORC. Excluding the compression system decreases the capital cost by almost the half regardless of the WH recovery system used yet it plays in favour of the plant with ORC making the cost of H2 cheaper by 0.29 $/kgH2 in this case. Onboard H2 production is a versatile process independent from the propulsion system ensuring the ship's safety and availability throughout a sea journey.

Renewable hydrogen is emerging as the key to a sustainable energy transition with multiple applications and uses. In the field of transport in addition to fuel cell vehicles it is necessary to develop an extensive network of hydrogen refueling stations (hereafter HRSs). The characteristics and properties of hydrogen make ensuring the safe operation of these facilities a crucial element for their successful deployment and implementation. This paper shows the outcomes of an analysis of hydrogen incidents and accidents considering their potential application to HRSs. For this purpose the HIAD 2.0 was reviewed and a total of 224 events that could be repeated in any of the major industrial processes related to hydrogen refueling stations were analyzed. This analysis was carried out using a mixed methodology of quantitative and qualitative techniques considering the following hydrogen value chain: production storage delivery and industrial use. The results provide general information segmented by event frequency damage classes and failure typology. The analysis shows the main processes of the value chain allow the identification of key aspects for the safety management of refueling facilities.

The use of compression ignition engines (CIEs) is associated with increased greenhouse gas emissions. It is therefore necessary to research sustainable solutions and reduce the negative environmental impact of these engines. A widely studied alternative is the use of H2 in dual-fuel mode. This review has been developed to include the most recent studies on the subject to collect and compare their main conclusions on performance and emissions. Moreover this study includes most relevant emission control strategies that have not been extensively analyzed in other reviews on the subject. The main conclusion drawn from the literature is the negative effect of the addition of H2 on NOx. This is due to the increase in temperature during combustion which increases NOx formation as the thermal mechanism predominates. Therefore to reduce these emissions three strategies have been studied namely exhaust gas recirculation (EGR) water injection (WI) and compression ratio (CR) reduction. The effect of these techniques on NOx reduction together with their effect on other analyzed performance parameters have been deeply analyzed. The studies reviewed in this work indicate that hydrogen is an alternative fuel for CIEs when used in conjunction with techniques that have proven to be effective in reducing NOx.

The hydrogen economy is receiving increasing attention as a complement to electrification in the global energy transition. Clean hydrogen production is often viewed as a competition between natural gas reforming with CO2 capture and electrolysis using renewable electricity. However solid fuel gasification with CO2 capture presents another viable alternative especially when considering the potential of biomass to achieve negative CO2 emissions. This study investigates the techno-economic potential of hydrogen production from large-scale coal/ biomass co-gasification plants with CO2 capture. With a CO2 price of 50 €/ton the benchmark plant using commercially available technologies achieved an attractive hydrogen production cost of 1.78 €/kg with higher CO2 prices leading to considerable cost reductions. Advanced configurations employing hot gas clean-up membrane-assisted water-gas shift and more efficient gasification with slurry vaporization and a chemical quench reduced the hydrogen production cost to 1.50–1.62 €/kg with up to 100% CO2 capture. Without contingencies added to the pre-commercial technologies the lowest cost reduces to 1.43 €/kg. It was also possible to recover waste heat in the form of hot water at 120 ◦C for district heating potentially unlocking further cost reductions to 1.24 €/kg. In conclusion gasification of locally available solid fuels should be seriously considered next to natural gas and electrolysis for supplying the emerging hydrogen economy.

Alkaline electrolysis is already a proven technology on land with a high maturity level and good economic performance. However at sea little is known about its economic performance toward hydrogen production. Alkaline electrolysis units operate with purified water to split its molecules into hydrogen and oxygen. Purified water and especially that sourced from the sea has a variable cost that ultimately depends on its quality. However the impurities present in that purified water have a deleterious effect on the electrolyte of alkaline electrolysis units that cause them to drop their energy efficiency. This in turn implies a source of economic losses resulting from the cost of electricity. In addition at sea there are various options regarding the electrolyte management of which the cost depends on various factors. All these factors ultimately impact on the levelized cost of the produced hydrogen. This article aims to shed some light on the economic performance of alkaline electrolysis units operating under sea conditions highlighting the knowledge gaps in the literature and initiating a debate in the field.

This study proposes a predictive equivalent consumption minimization strategy (P-ECMS) that utilizes velocity prediction and considers various dynamic constraints to mitigate fuel cell degradation assessed using a dedicated sub-model. The objective is to reduce fuel consumption in real-world conditions without prior knowledge of the driving mission. The P-ECMS incorporates a velocity prediction layer into the Energy Management System. Comparative evaluations with a conventional adaptive-ECMS (A-ECMS) a standard ECMS with a well-tuned constant equivalence factor and a rule-based strategy (RBS) are conducted across two driving cycles and three fuel cell dynamic restrictions (|∕| ≤ 0.1 0.01 and 0.001 A∕cm2 ). The proposed strategy achieves H2 consumption reductions ranging from 1.4% to 3.0% compared to A-ECMS and fuel consumption reductions of up to 6.1% when compared to RBS. Increasing dynamic limitations lead to increased H2 consumption and durability by up to 200% for all tested strategies.

HyResponder is a European Hydrogen Train the Trainer programme for responders. This paper describes the key outputs of the project and the steps taken to develop and implement a long-term sustainable train the trainer programme in hydrogen safety for responders across Europe and beyond. This FCH2 JU (now Clean Hydrogen Joint Undertaking) funded project has built on the successful outcomes of the previous HyResponse project. HyResponder has developed further and updated educational operational and virtual reality training for trainers of responders to reflect the state-of-the-art in hydrogen safety including liquid hydrogen and expand the programme across Europe and specifically within the 10 countries represented directly within the project consortium: Austria Belgium the Czech Republic France Germany Italy Norway Spain Switzerland and the United Kingdom. For the first time four levels of educational materials from fire fighter through to specialist have been developed. The digital training resources are available on the e-Platform (https://hyresponder.eu/e-platform/). The revised European Emergency Response Guide is now available to all stakeholders. The resources are intended to be used to support national training programs. They are available in 8 languages: Czech Dutch English French German Italian Norwegian and Spanish. Through the HyResponder activities trainers from across Europe have undertaken joint actions which are in turn being used to inform the delivery of regional and national training both within and beyond the project. The established pan-European network of trainers is shaping the future in the important for inherently safer deployment of hydrogen systems and infrastructure across Europe and enhancing the reach and impact of the programme.

The unsustainable and continuous growth of anthropogenic emissions of greenhouse gases (GHG) has pushed governments private companies and stakeholders to adopt measures and policies to fight against climate change. Within this framework increasing the contribution of renewable energy sources (RES) to final consumed energy plays a key role in the planned energy transition. Regarding the residential sector in Europe 92% of GHG emissions comes from 75% of the building stock that is over 25 years old and highly inefficient. Thus this sector must raise RES penetration from the current 36% to 77% by 2050 to comply with emissions targets. In this regard the hybridization of hydrogen-based technologies and RES represents a reliable and versatile solution to facilitate decarbonization of the residential sector. This study provides an overview and analysis of standalone renewable hydrogen-based systems (RHS) focusing on the residential and buildings sector as well as critical infrastructures like telecom stations data servers etc. For detailed evaluation of RHS several pilot plants and real demonstration plants implemented worldwide are reviewed. To this end a techno-economic assessment of relevant parameters like self-sufficiency ratio levelized cost of energy and hydrogen roundtrip efficiency is provided. Moreover the performance of the different configurations is evaluated by comparing the installed power of each component and their energy contribution to cover the load over a defined period of time. Challenges ahead are identified for the wider deployment of RHS in the residential and buildings sector.

The production of hydrogen from photovoltaics (PV) has gained attention due to its potential as an energy vector. In this context there are two basic configurations for electrically coupling PV to hydrogen electrolyzers: direct and indirect. The direct configuration operates variably based on meteorological conditions but has simplicity as an advantage. The indirect configuration involves a power stage (PS) with a maximum power point tracker and a DC-DC converter maintaining an optimal power transfer from PV to electrolyzers but incurs losses at the PS. The direct configuration avoids these losses but requires a specific design of the PV generator to achieve high electrical transfer. The comparative analysis of hydrogen production between these two approaches indicates that the indirect paradigm yields a 37.5% higher hydrogen output throughout a typical meteorological year compared to the optimized direct configuration. This increase enhances the overall sunlight-to-hydrogen efficiency elevating it from 5.0% in the direct case to 6.9% in the indirect one. Furthermore the direct setup sensitive to PV power fluctuations suffers an 18% reduction in hydrogen production with just a 5% reduction in photogenerated power. Under optimal performance the direct coupling produces less hydrogen unless the DCDC converter efficiency drops 17% below commercial standards.

This work studies the efficiency and long-term viability of powered hydrogen production. For this purpose a detailed exploration of hydrogen production techniques has been undertaken involving data collection information authentication data organization and analysis. The efficiency trends environmental impact and hydrogen production costs in a landscape marked by limited data availability were investigated. The main contribution of this work is to reduce the existing data gap in the field of hydrogen production by compiling and summarizing dispersed data. The findings are expected to facilitate the decision-making process by considering regional variations energy source availability and the potential for technological advancements that may further enhance the economic viability of electrolysis. The results show that hydrogen production methods can be identified that do not cause significant harm to the environment. Photolysis stands out as the least serious offender producing 0 kg of CO2 per kg of H2 while thermolysis emerges as the major contributor to emissions with 20 kg of CO2 per kg of H2 produced.

Hydrogen is one of the main energy carriers playing a prominent role in the future decarbonization of the economy. However several aspects regarding the transport and storage of this gas are challenging. The intermediary conversion of hydrogen into high-density energy molecules may be a crucial step until technological conditions are ready to attain a significant reduction in fossil fuel use in transport and the industrial sector. The process of transforming hydrogen into methane by anaerobic digestion is reviewed showing that this technology is a feasible option for facilitating hydrogen storage and transport. The manuscript focuses on the role of anaerobic digestion as a technology driver capable of fast adaptation to current energy needs. The use of thermophilic systems and reactors capable of increasing the contact between the H2 -fuel and liquid phase demonstrated outstanding capabilities attaining higher conversion rates and increasing methane productivity. Pressure is a relevant factor of the process allowing for better hydrogen solubility and setting the basis for considering feasible underground hydrogen storage concomitant with biological methanation. This feature may allow the integration of sequestered carbon dioxide as a relevant substrate.

Currently there is a growing interest in increasing the power range of air-cooled fuel cells (ACFCs) as they are cheaper easier to use and maintain than water-cooled fuel cells (WCFCs). However air-cooled stacks are only available up to medium power (<10 kW). Therefore a good solution may be the development of ACFCs consisting of several stacks until the required power output is reached. This is the concept of air-cooled multi-stack fuel cell (AC-MSFC). The objective of this work is to develop a turnkey solution for the integration of AC-MSFCs in renewable microgrids specifically those with high-voltage DC (HVDC) bus. This is challenging because the AC-MSFCs must operate in the microgrid as a single ACFC with adjustable power depending on the number of stacks in operation. To achieve this the necessary power converter (ACFCs operate at low voltages so high conversion rates are required) and control loops must be developed. Unlike most designs in the literature the proposed solution is compact forming a system (AC-MSFCS) with a single input (hydrogen) and a single output (high voltage regulated power or voltage) that can be easily integrated into any microgrid and easily scalable depending on the power required. The developed AC-MSFCS integrates stacks balance of plant data acquisition and instrumentation power converters and local controllers. In addition a virtual instrument (VI)has been developed which connected to the energy management system (EMS) of the microgrid allows monitoring of the entire AC-MSFCS (operating temperature purging cell voltage monitoring for degradation evaluation stacks operating point control and alarm and event management) as well as serving as a user interface. This allows the EMS to know the degradation of each stack and to carry out energy distribution strategies or specific maintenance actions which improves efficiency lifespan and of course saves costs. The experimental results have been excellent in terms of the correct operation of the developed AC-MSFCS. Likewise the accumulated degradation of the stacks was quantified showing cells with a degradation of >80%. The excellent electrical and thermal performance of the developed power converter was also validated which allowed the correct and efficient supply of regulated power (average efficiency above 90%) to the HVDC bus according to the power setpoint defined by the EMS of the microgrid.

Green hydrogen is the term used to reflect the fact that hydrogen is generated from renewable energies. This process is commonly performed by means of water electrolysis decomposing water molecules into oxygen and hydrogen in a zero emissions process. Proton exchange membrane (PEM) electrolyzers are applied for such a purpose. These devices are complex systems with nonlinear behavior which impose the measurement and control of several magnitudes for an effective and safe operation. In this context the modern paradigm of Digital Twin (DT) is applied to represent and even predict the electrolyzer behavior under different operating conditions. To build this cyber replica a paramount previous stage consists of characterizing the device by means of the curves that relate current voltage and hydrogen flow. To this aim this paper presents a processes supervision system focused on the characterization of a experimental PEM electrolyzer. This device is integrated in a microgrid for production of green hydrogen using photovoltaic energy. Three main functions must be performed by the supervision system: measurement of the process magnitudes data acquisition and storage and real-time visualization. To accomplish these tasks firstly a set of sensors measure the process variables. In second place a programmable logic controller is responsible of acquiring the signals provided by the sensors. Finally LabVIEW implements the user interface as well as data storage functions. The process evolution is observed in real-time through the user interface composed by graphical charts and numeric indicators. The deployed process supervision system is reported together with experimental results to prove its suitability.

The current political scenario and the concerns for global warming have pushed very harsh regulations on conventional propulsion systems based on the use of fossil fuels. New technologies are being promoted but their current technological status needs further research and development for them to become a competitive substitute for the ever-present internal combustion engine. Hydrogen-fueled internal combustion engines have demonstrated the potential of being a fast way to reach full decarbonization of the transport sector but they still have to face some limitations in terms of the operating range of the engine. For this reason the present work evaluates the potential of reaching full load operation on a conventional diesel engine assuming the minimum modifications required to make it work under H2 combustion. This study shows the methodology through which the combustion model was developed and then used to evaluate a multi-cylinder engine representative of the medium to high duty transport sector. The evaluation included different strategies of dilution to control the combustion performance and the results show that the utilization of EGR brings different benefits to engine operation in terms of efficiency improvement and emissions reduction. Nonetheless the requisites defined for the needed turbocharging system are harsher than expected and result in a potential non-conventional technical solution.