Spain

Although alkaline water electrolysis (AWE) is the most widespread technology for hydrogen production by electrolysis its electrochemical and fluid dynamic optimization has rarely been addressed simultaneously using Computational Fluid Dynamics (CFD) simulation. In this regard a two-dimensional (2D) CFD model of an AWE cell has been developed using COMSOL® software and then experimentally validated. The model involves transport equations for both liquid and gas phases as well as equations for the electric current conservation. This multiphysics approach allows the model to simultaneously analyze the fluid dynamic and electrochemical phenomena involved in an electrolysis cell. The electrical response was evaluated in terms of polarization curve (voltage vs. current density) at different operating conditions: temperature electrolyte conductivity and electrode-diaphragm distance. For all cases the model fits very well with the experimental data with an error of less than 1% for the polarization curves. Moreover the model successfully simulates the changes on gas profiles along the cell according to current density electrolyte flow rate and electrode-diaphragm distance. The combination of electrochemical and fluid dynamics studies provides comprehensive information and makes the model a promising tool for electrolysis cell design.

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.

The hydrogen sector is envisaged as one of the key enablers of the energy transition that the European Union is facing to accomplish its decarbonization targets. However regarding the technologies that enable the deployment of a hydrogen economy a growing concern exists about potential burden-shifting across sustainability dimensions. In this sense social life cycle assessment arises as a promising methodology to evaluate the social implications of hydrogen technologies along their supply chains. In the context of the European projects eGHOST and SH2E this study seeks to advance on key methodological aspects of social life cycle assessment when it comes to guiding the ecodesign of two relevant hydrogen-related products: a 5 kW solid oxide electrolysis cell stack for hydrogen production and a 48 kW proton-exchange membrane fuel cell stack for mobility applications. Based on the social life cycle assessment results for both case studies under alternative approaches the definition of a product-specific supply chain making use of appropriate cut-off criteria was found to be the preferable choice when addressing system boundaries definition. Moreover performing calculations according to the activity variable approach was found to provide valuable results in terms of social hotspots identification to support subsequent decision-making processes on ecodesign while the direct calculation approach is foreseen as a complement to ease the interpretation of social scores. It is concluded that advancements in the formalization of such suitable practices could foster the integration of social metrics into the sustainable-by-design framework of hydrogen-related products.

The production of biohydrogen with negative CO2 emissions through the steam methane reforming of biomethane coupled with carbon capture and storage represents a promising technology particularly for industries that are difficult to electrify. In spite of the maturity of this technology which is currently employed in the production of grey and blue hydrogen a detailed cost model that considers the entire supply chain is lacking in the literature. This study addresses this gap by applying correlations derived from actual facilities producing grey and blue hydrogen to calculate the CAPEX while exploring various feedstock combinations for biogas generation to assess the OPEX. The analysis also includes logistic aspects such as decentralised biogas production and the transportation and storage of CO2 . The levelized cost of golden hydrogen is estimated to range from EUR 1.84 to 2.88/kg compared to EUR 1.47/kg for grey hydrogen and EUR 1.93/kg for blue hydrogen assuming a natural gas cost of EUR 25/MWh and excluding the CO2 tax. This range increases to between 3.84 and 2.92 with a natural gas cost of EUR 40/MWh with the inclusion of the CO2 tax. A comparison with conventional green hydrogen is performed highlighting both prices and potential thereby offering valuable information for decision-making.

Energy Intensive Industries (EII) are high users of energy and some of these facilities are extremely dependent on Natural Gas for processing heat production. In European countries where Natural Gas is mostly imported from external producers the increase in international Natural Gas prices is making it difficult for some industries to deliver the required financial results. Therefore they are facing complex challenges that could cause their delocalization in regions with lower energy costs. European countries lack on-site Natural Gas resources and the plans to reduce greenhouse gas emissions in the industrial sector make it necessary to find an alternative. Many different processes cannot be electrified and in these cases synthetic methane is one of the solutions and also represents an opportunity to reduce external energy supply dependency. This study analyzes the current development of power-to-gas technological solutions that could be implemented in large industrial consumers to produce Synthetic Methane using Green Hydrogen as a raw source and using Renewable Energy electricity mainly produced with photovoltaic or wind energy. The study also reviews the triple bottom line impact and the current development status and associated costs for each key component of a power-to-gas plant and the requirements to be fulfilled in the coming years to develop a cost-competitive solution available for commercial use.

Industrial applications of hydrogen are key to the transition towards a sustainable lowcarbon economy. Hydrogen has the potential to decarbonize industrial sectors that currently rely heavily on fossil fuels. Hydrogen with its unique and versatile properties has several in-industrial applications that are fundamental for sustainability and energy efficiency such as the following: (i) chemical industry; (ii) metallurgical sector; (iii) transport; (iv) energy sector; and (v) agrifood sector. The development of a bibliometric analysis of industrial hydrogen applications in Europe is crucial to understand and guide developments in this emerging field. Such an analysis can identify research trends collaborations between institutions and countries and the areas of greatest impact and growth. By examining the scientific literature and comparing it with final hydrogen consumption in different regions of Europe the main actors and technologies that are driving innovation in industrial hydrogen use on the continent can be identified. The results obtained allow for an assessment of the knowledge gaps and technological challenges that need to be addressed to accelerate the uptake of hydrogen in various industrial sectors. This is essential to guide future investments and public policies towards strategic areas that maximize the economic and environmental impact of industrial hydrogen applications in Europe.

Nowadays there is an intense debate in the European Union (EU) regarding the limits to achieve the European Green Deal to make Europe the first climate-neutral continent in the world. In this context there are also different opinions about the role that thermal engines should play. Furhermore there is no clear proposal regarding the possibilities of the use of green hydrogen in the transport decarbonization process even though it should be a key element. Thus there are still no precise guidelines regarding the role of green hydrogen with it being exclusively used as a raw material to produce E-fuels. This review aims to evaluate the possibilities of applying the different alternative technologies available to successfully complete the process already underway to achieve Climate Neutrality by about 2050 depending on the maturity of the technologies currently available and those anticipated to be available in the coming decades.

With renewable energy sources projected to become the dominant source of electricity hydrogen has emerged as a crucial energy carrier to mitigate their intermittency issues. Water electrolysis is the most developed alternative to generate green hydrogen so far. However in the past two decades steam electrolysis has attracted increasing interest and aims to become a key player in the portfolio of electrolytic hydrogen. In practice steam electrolysis follows two distinct operational approaches: Solid Oxide Electrolysis Cell (SOEC) and Proton Exchange Membrane (PEM) at high temperature. For both technologies this work analyses critical cell components outlining material characteristics and degradation issues. The influence of operational conditions on the performance and cell durability of both technologies is thoroughly reviewed. The analytical comparison of the two electrolysis alternatives underscores their distinct advantages and drawbacks highlighting their niche of applications: SOECs thrive in high temperature industries like steel production and nuclear power plants whereas PEM steam electrolysis suits lower temperature applications such as textile and paper. Being PEM steam electrolysis less explored this work ends up by suggesting research lines in the domain of i) cell components (membranes catalysts and gas diffusion layers) to optimize and scale the technology ii) integration strategies with renewable energies and iii) use of seawater as feedstock for green hydrogen production.

In recent years there has been a significant increase in the adoption of autonomous vehicles for marine and submarine missions. The advancement of emerging imaging navigation and communication technologies has greatly expanded the range of operational capabilities and opportunities available. The ENDURUNS project is a European research endeavor focused on identifying strategies for achieving minimal environmental impact. To measure these facts this article evaluates the product impacts employing the Life Cycle Assessment methodology for the first time following the ISO 14040 standard. In this analysis the quantitative values of Damage and Environmental Impact using the Eco-Indicator 99 methodology in SimaPro software are presented. The results report that the main contributors in environmental impact terms have been placed during the manufacturing phase. Thus one of the challenges is accomplished avoiding the use phase emissions that are the focus to reduce nowadays in the marine industry.

The use of aluminum-based products is widespread and growing particularly in industries such as automotive food packaging and construction. Obtaining aluminum is expensive and energy-intensive making the recycling of existing products essential for economic and environmental viability. This work explores the potential of using green hydrogen as a replacement for natural gas in the smelting and refining furnaces in aluminum recycling facilities. The adoption of green hydrogen has the potential to curtail approximately 4.54 Ktons/year of CO2 emissions rendering it a sustainable and economically advantageous solution. The work evaluates the economic viability of a case study through assessing the Net Present Value (NPV) and the Internal Rate of Return (IRR). Furthermore it is employed single- and multi-parameter sensitivity analyses to obtain insight on the most relevant conditions to achieve economic viability. Results demonstrate that integrating on-site green hydrogen generation yields a favorable NPV of €57370 an IRR of 9.83% and a 19.63-year payback period. The primary factors influencing NPV are the initial electricity consumption stack and the H2 price.

H2 production via membrane-assisted steam methane reforming (MA-SMR) can ensure higher energy efficiency and lower emissions compared to conventional reforming processes (SMR). Ceramic-supported Pd–Ag membranes have been extensively investigated for membrane-assisted steam methane reforming applications with outstanding performance. However costs sealings for integration in the reactor structure and resistance to solicitations remain challenging issues. In this work the surface quality of a low-cost porous Hastelloy-X filter is improved by asymmetric filling with α-Al2O3 of decreasing size and deposition of γ-Al2O3 as an interdiffusion barrier. On the modified support a thin Pd–Ag layer was deposited via electroless plating (ELP) resulting in a membrane with H2/N2 selectivity >10000. The permeation characteristics of the membrane were studied followed by testing for membrane-assisted methane steam reforming. The results showed the ability of the membrane reactor to overcome thermodynamic conversion of the conventional process for all explored operating conditions as well as ensuring 99.3% H2 purity in the permeate stream at 500 ◦C and 4 bar.

Innovative green vehicle concepts have become increasingly prevailing in consumer purchasing habits as technology evolves. The global transition towards sustainable transportation indicates an increase in new-generation vehicles including both fuel-cell electric vehicles (FCEVs) and plug-in electric vehicles (PEVs) that will take on roads in the future. This change requires new-generation stations to support electrification. This study introduced a prominent multi-energy system concept with a hydrogen refueling station. The proposed multi-energy system (MES) consists of green hydrogen production a hydrogen refueling station for FCEVs hydrogen injection into natural gas (NG) and a charging station for PEVs. An on-site renewable system projected at the station and a polymer electrolyte membrane electrolyzer (PEM) to produce hydrogen for two significant consumers support MES. In addition the MES offers the ability to conduct two-way trade with the grid if renewable energy systems are insufficient. This study develops a comprehensive multi-energy system with an economically optimized energy management model using a mixed-integer linear programming (MILP) approach. The determinative datasets of vehicles are generated in a Python environment using Gauss distribution. The fleet of FCEVs and PEVs are currently available on the market. The study includes fleets of the most common models from well-known brands. The results indicate that profits increase when the storage capacity of the hydrogen tank is higher and natural gas injections are limitless. Optimization results for all cases tend to choose higher-priced natural gas injections over hydrogen refueling because of the difference in costs of refueling and injection expenses. The analyses reveal the highest hydrogen sales to the natural gas (NG) grid by consuming 2214.31 kg generating a revenue of $6966 and in contrast the lowest hydrogen sales to the natural gas grid at 1045.38 kg resulting in a revenue of $3286. Regarding electricity the highest sales represent revenue of $7701 and $2375 for distribution system consumption and electric vehicles (EV) respectively. Conversely Cases 1 and 2 have achieved sales to EV of $2286 and $2349 respectively but do not have any sales to distribution system consumption regarding the constraints. Overall the optimization results show that the solution is optimal for a multi-energy system operator to achieve higher profits and that all end-user parties are satisfied.

Future power systems in which generation will come almost entirely from variable Renewable Energy Sources (vRES) will be characterized by weather-driven supply and flexible demand. In a simulation of the future Dutch power system we analyze whether there are sufficient incentives for market-driven investors to provide a sufficient level of security of supply considering the profit-seeking and myopic behavior of investors. We cosimulate two agent-based models (ABM) one for generation expansion and one for the operational time scale. The results suggest that in a system with a high share of vRES and flexibility prices will be set predominantly by the demand’s willingness to pay particularly by the opportunity cost of flexible hydrogen electrolyzers. The demand for electric heating could double the price of electricity in winter compared to summer and in years with low vRES could cause shortages. Simulations with stochastic weather profiles increase the year-to-year variability of cost recovery by more than threefold and the year-to-year price variability by more than tenfold compared to a scenario with no weather uncertainty. Dispatchable technologies have the most volatile annual returns due to high scarcity rents during years of low vRES production and diminished returns during years with high vRES production. We conclude that in a highly renewable EOM investors would not have sufficient incentives to ensure the reliability of the system. If they invested in such a way to ensure that demand could be met in a year with the lowest vRES yield they would not recover their fixed costs in the majority of years.

: The global demand for energy and the need to mitigate climate change require a shift from traditional fossil fuels to sustainable and renewable energy alternatives. Hydrogen is recognized as a significant component for achieving a carbon-neutral economy. This comprehensive review examines the underground hydrogen storage and particularly laboratory-scale studies related to rock– hydrogen interaction exploring current knowledge. Using bibliometric analysis of data from the Scopus and Web of Science databases this study reveals an exponential increase in scientific publications post-2015 which accounts for approximately 85.26% of total research output in this field and the relevance of laboratory experiments to understand the physicochemical interactions of hydrogen with geological formations. Processes in underground hydrogen storage are controlled by a set of multi-scale parameters including solid properties (permeability porosity composition and geomechanical properties) and fluid properties (liquid and gas density viscosity etc.) together with fluid–fluid and solid–fluid interactions (controlled by solubility wettability chemical reactions etc.). Laboratory experiments aim to characterize these parameters and their evolution simulating real-world storage conditions to enhance the reliability and applicability of findings. The review emphasizes the need to expand research efforts globally to comprehensively address the currently existing issues and knowledge gaps.

The current work presents the electro-oxidation of olive mill and biodiesel wastewaters in an alkaline medium with the aim of hydrogen production and simultaneous reduction in the organic pollution content. The process is performed at laboratory scale in an own-design single cavity electrolyzer with graphite electrodes and no membrane. The system and the procedures to generate hydrogen under ambient conditions are described. The gas flow generated is analyzed through gas chromatography. The wastewater balance in the liquid electrolyte shows a reduction in the chemical oxygen demand (COD) pointing to a decrease in the organic content. The experimental results confirm the production of hydrogen with different purity levels and the simultaneous reduction in organic contaminants. This wastewater treatment appears as a feasible process to obtain hydrogen at ambient conditions powered with renewable energy sources resulting in a more competitive hydrogen cost.

Green hydrogen production is a sustainable energy solution with great potential offering advantages such as adaptability storage capacity and ease of transport. However there are challenges such as high energy consumption production costs demand and regulation which hinder its largescale adoption. This study explores the role of simulation models in optimizing the technical and economic aspects of green hydrogen production. The proposed system which integrates photovoltaic and energy storage technologies significantly reduces the grid dependency of the electrolyzer achieving an energy self-consumption of 64 kWh per kilogram of hydrogen produced. By replacing the high-fidelity model of the electrolyzer with a reduced-order model it is possible to minimize the computational effort and simulation times for different step configurations. These findings offer relevant information to improve the economic viability and energy efficiency in green hydrogen production. This facilitates decision-making at a local level by implementing strategies to achieve a sustainable energy transition.

The recovery of energy and valuable compounds from exhaust gases in the iron and steel industry deserves specialattention due to the large power consumption and CO 2 emissions of the sector. In this sense the hydrogen content of coke oven gas(COG) has positioned it as a promising source toward a hydrogen-based economy which could lead to economic and environmentalbenefits in the iron and steel industry. COG is presently used for heating purposes in coke batteries or furnaces while in highproduction rate periods surplus COG is burnt in flares and discharged into the atmosphere. Thus the recovery of the valuablecompounds of surplus COG with a special focus on hydrogen will increase the efficiency in the iron and steel industry compared tothe conventional thermal use of COG. Different routes have been explored for the recovery of hydrogen from COG so far: i)separation/purification processes with pressure swing adsorption or membrane technology ii) conversion routes that provideadditional hydrogen from the chemical transformation of the methane contained in COG and iii) direct use of COG as fuel forinternal combustion engines or gas turbines with the aim of power generation. In this study the strengths and bottlenecks of themain hydrogen recovery routes from COG are reviewed and discussed.

Hydrogen technologies are evolving to decarbonise the transport sector. The present work focuses on the technical design of a Hydrogen Refueling Station to supply hydrogen to five buses in the city of Valencia Spain. The study deals with the technical selection of the components from production to consumption setting an efficient standardisation method. Different calculation are used to size the storage systems for 70.8 kg of hydrogen produced by the elecrolyser daily. For the high-pressure storage system massive and cascade methods are proposed being the last one more efficient (1577.53 Nm3 non usable volume compared to 9948.95 Nm3 of the massive method).

In the automotive sector hydrogen is being increasingly explored as an alternative fuel to replace conventional carbon-based fuels. Its combustion characteristics make it well-suited for adaptation to internal combustion engines. The wide flammability range of hydrogen allows for higher dilution conditions resulting in enhanced combustion efficiency. When combined with lean combustion strategies hydrogen significantly reduces environmental impact virtually eliminating carbon dioxide and nitrogen oxide emissions while maintaining high thermal efficiency. This paper aims to assess the potential of using an outwardly opening poppet valve hydrogen direct injection (DI) system in a small engine for light-duty applications. To achieve this a comparison of performance emission levels and combustion parameters is conducted on a single-cylinder spark-ignition (SI) research engine fueled by hydrogen using both port fuel injection (PFI) and this new direct injection system. Two different engine loads are measured at multiple air dilution and injection timing conditions. The results demonstrate notable efficiency improvements ranging from 0.6% to 1.1% when transitioning from PFI to DI. Accurate control of injection timing is essential for achieving optimal performance and low emissions. Delaying the start of injection results in a 7.6% reduction in compression work at low load and a 3.9% reduction at high load. This results in a 3.1-3.2% improvement in ISFC in both load conditions considered.

Hydrogen will become a key player in transitioning toward a net-zero energy system. However a clear pathway toward a unified European hydrogen infrastructure to support the rapid scale-up of hydrogen production is still under discussion. This study explores plausible pathways using a fully sector-coupled energy system model. Here we assess the emergence of hydrogen infrastructure build-outs connecting neighboring European nations through hydrogen import and domestic production centers with Western and Central European demands via four distinct hydrogen corridors. We identify a potential lock-in effect of blue hydrogen in the medium term highlighting the risk of longterm dependence on methane. In contrast we show that a self-sufficient Europe relying on domestic green hydrogen by 2050 would increase yearly expenses by around 3% and require 518 gigawatts of electrolysis capacity. This study emphasizes the importance of rapidly scaling up electrolysis capacity building hydrogen networks and storage facilities deploying renewable electricity generation and ensuring coherent coordination across European nations.

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.

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.