Spain

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 decarbonization of the maritime sector represents a priority in the energy policy agendas of the majority of Countries worldwide and the International Maritime Organization (IMO) has recently revised its strategy aiming for an ambitious zero-emissions scenario by 2050. In these regards there is a broad consensus on hydrogen as one of the most promising clean energy vectors for maritime transport and a key towards that goal. However to date an international regulatory framework for the use of hydrogen on-board of ships is absent this posing a severe limitation to the adoption of hydrogen technologies in this sector. To cope with this issue this paper presents a preliminary gap assessment analysis for the International Code of Safety for Ship Using Gases or other Low-flashpoint Fuels (IGF Code) with relation to hydrogen as a fuel. The analysis is structured according to the IGF Code chapters and a bottom-up approach is followed to review the code content and assess its relevance to hydrogen. The risks related to hydrogen are accounted for in assessing the gaps and providing a first level set of recommendations for IGF Code updates. By this means this work settles the basis for further research over the identified gaps towards the identification of a final set of recommendations for the IGF Code update.

Energy communities led by local citizens are vital for achieving the European energy transition goals. This study examines the design of a regional energy community in a rural area of Spain aiming to address the pressing issue of rural depopulation. Seven villages were selected based on criteria such as size energy demand population and proximity to infrastructure. Three energy valorization scenarios generating eight subscenarios were analyzed: (1) self-consumption including direct sale (1A) net billing (1B) and selling to other consumers (1C); (2) battery storage including storing for self-consumption (2A) battery-to-grid (2B) and electric vehicle recharging points (2C); and (3) advanced options such as hydrogen refueling stations (3A) and hydrogen-based fertilizer production (3B). The findings underscore that designing rural energy communities with a focus on social impact—especially in relation to depopulation—requires an innovative approach to both their design and operation. Although none of the scenarios alone can fully reverse depopulation trends or drive systemic change they can significantly mitigate the issue if social impact is embedded as a core principle. For rural energy communities to effectively tackle depopulation strategies such as acting as an energy retailer or aggregating individual villages into a single unified energy community structure are crucial. These approaches align with the primary objective of revitalizing rural communities through the energy transition.

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.

The global economic growth the increase in thepopulation and advances in technology lead to an increment in theglobal primary energy demand. Considering that most of thisenergy is currently supplied by fossil fuels a considerable amountof greenhouse gases are emitted contributing to climate changewhich is the reason why the next European Union bindingagreement is focused on reducing carbon emissions usinghydrogen. This study reviews different technologies for hydrogenproduction using renewable and non-renewable resources.Furthermore a comparative analysis is performed on renewable-based technologies to evaluate which technologies are economically and energetically more promising. The results show howbiomass-based technologies allow for a similar hydrogen yield compared to those obtained with water-based technologies but withhigher energy efficiencies and lower operational costs. More specifically biomass gasification and steam reforming obtained a properbalance between the studied parameters with gasification being the technique that allows for higher hydrogen yields while steamreforming is more energy-efficient. Nevertheless the application of hydrogen as the energy vector of the future requires both the useof renewable feedstocks with a sustainable energy source. This combination would potentially produce green hydrogen whilereducing carbon dioxide emissions limiting global climate change and thus achieving the so-called hydrogen economy.

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.

Decarbonizing the steel industry will require a shift towards renewable energy. However costs and emissions associated with the long-distance transport of renewable energy carriers may incentivize the relocation of steel production closer to renewable energy sources. This “green relocation” would affect regional economic structures and global trade patterns. Nevertheless the macroeconomic and environmental impacts of alternative industry location options remain underexplored. This study compares the impacts on value-added prices and emissions under two options for decarbonizing the Dutch steel industry: importing green hydrogen from Brazil to produce green steel in the Netherlands versus relocating production to Brazil and transporting green steel to the Netherlands. Impacts are analyzed by combining a price and a quantity model within an environmentally extended multiregional input-output (EE-MRIO) framework. Results suggest that the relocation option brings the greatest synergies between climate and economic goals at the global level as it leads to lower production costs smaller price effects and greater emissions reductions. However relocation also results in stronger distributive impacts across global regions. Higher carbon prices would be insufficient to counteract relocation incentives. This calls for policymakers in industrialized countries to systematically consider the possibility of green relocation when designing decarbonization and industrial competitiveness strategies.

This study presents the application of a new sustainability assessment methodology. It aims to improve the information that can be obtained from a sustainability assessment including the concept of alternative usage impact. To prove the effectiveness of this methodology three different hydrogen production methodologies considering its consumption in transportation sector is the case of study. The methodologies considered are Steam Methane Reform using natural gas Proton Exchange Membrane electrolysis one using grid electricity and the other study case using central tower solar power plant electricity from the PS10 facility. While separately green hydrogen is the technology with less environmental impact when considering the full system and the impact of the green hydrogen on the rest of the resources the integration of green hydrogen technology is not the most environmentally sustainable. Similar behavior is observed in the economic and technical fields. The different accounting of combinations of technologies and the impact on the resource which is not used provides the sustainability performance of the overall system. These results show that in order to account the all impacts taking place in a energy technology integration its impact on the rest of resources and uses provide more valuable information.

The transition to decarbonized energy systems positions hydrogen as a critical vector for achieving climate neutrality yet its large-scale transportation and storage remain key challenges. This study presents a comprehensive life cycle assessment (LCA) and economic analysis of large-scale H2 supply chains evaluating the liquid organic hydrogen carrier (LOHC) system based on benzyltoluene/perhydro-benzyltoluene (H0-BT/H12-BT) against conventional technologies: compressed gaseous hydrogen (CGH2) liquid hydrogen (LH2) and liquid ammonia (LNH3). The analysis includes multiple H2 transportation scenarios across Europe considering the steps: conditioning sea transportation post-processing and land distribution by truck or pipeline. Environmentally LOHC currently faces higher environmental impacts than CGH2 driven by energy-intensive dehydrogenation process. Truck-based distribution further amplifies impacts particularly over long distances while pipeline-based distribution significantly reduces the environmental burdens where infrastructure exists. Sensitivity analysis reveals that using H2 for dehydrogenation heat lowers process-level impacts but increases overall supply chain impacts questioning its net environmental benefit. Economically LOHC remains competitive despite high dehydrogenation costs benefiting from low sea transportation expenses compatibility with existing fossil fuel infrastructure and potential for future CAPEX and OPEX improvements. While CGH2 outperforms LH2 and LNH3 avoiding energy-intensive liquefaction and cracking its storage requirements add considerable costs. For land distribution LOHC trucks are optimal at lower capacities whereas repurposed natural gas pipelines favour CGH2 at higher scale reducing costs by up to 84 %. Despite current trade-offs the scalability flexibility and synergies with existing infrastructure position LOHC as a promising solution for long-distance H2 transport contingent on technological maturation to mitigate dehydrogenation impacts.

The present investigation aims to provide a comparative assessment of using hydrogen-enriched wood waste-derived producer gas (PG) for a dual-fuel diesel engine fueled with a 20% Jatropha biodiesel/80% diesel blend (BD20) with the traditional mode. The experiments were conducted at 23°bTDC of injection timing 240 bar of injection pressure 17.5:1 of compression ratio and 1500 rpm of engine speed under various engine loads. Gas carburetor induction (GCI) port injection (PI) and inlet manifold injection (IMI) methods were used to supply H2-enriched PG while B20 is directly injected into the combustion chamber. Among all the combinations the IMI method provided the highest brake thermal efficiency of 30.91% the lowest CO emission of 0.08% and smoke opacity discharge of 49.26 HSU while NOx emission reached 1744.32 ppm which was lower than that of the PI mode. Furthermore the IMI method recorded the highest heat release rate of 91.17 J/°CA and peak cylinder pressure of 83.29 bar reflecting superior combustion quality. Finally using the IMI method for H2-enriched PG in dual-fuel diesel engines could improve combustion efficiency reduce greenhouse gas emissions and improve fuel economy showing that the combination of BD20 with H2-enriched PG offers a cleaner more sustainable and economically viable technology.