Spain

This paper presents an improved Equivalent Consumption Minimization Strategy (ECMS) designed to optimize energy management for the hybrid hydrogen fuel power setups in multirotor drones. The proposed strategy aims to reduce hydrogen consumption and enhance the performance of the system consisting of Proton Exchange Membrane Fuel Cells (PEMFCs) and lithium batteries. Multirotor drones experience rapid power fluctuations due to their agile maneuvering but PEMFCs are unable to meet these demands swiftly due to their inherent limitations. To address this lithium batteries supplement peak power requirements and absorb excess energy on the DC bus. However this can lead to energy loss if the batteries are charged when not required. Our improved ECMS considers these inefficiencies and adjusts energy distribution to reduce hydrogen consumption and optimize the system’s performance. The proposed strategy effectively maintains the lithium batteries’ State of Charge (SOC) reduces hydrogen usage and enhances overall system efficiency when compared to traditional ECMS approaches.

Cement industry due to the decomposition of CaCO3 and the production of clinker emits large amounts of CO2 into the atmosphere. This anthropogenic gas can be captured and through its synthesis with green hydrogen methanol and finally synthetic fuels are achieved. By using e-fuel Europe’s climate neutrality objectives could be achieved. However the energy transition still lacks a clear roadmap and decisions are strongly affected by the geopolitical situation the energy demand and the economy. Therefore different scenarios are analysed to assess the influence of key factors on the overall economic viability of the process: 1) A business-as-usual scenario EU perspectives 2) allowing e-fuels and 3) improving H2 production processes. The technical feasibility of the production of synthetic fuels is verified. The most optimistic projections indicate future production costs of synthetic fuels will be lower than those of fossil fuels. This is directly related to the cost of green hydrogen production.

The reliance on fossil fuels for electricity production in insular regions creates critical environmental economic and logistical challenges particularly for ecologically fragile islands. Transitioning to renewable energy is essential to mitigate these impacts enhance energy security and preserve unique ecosystems. This systematic review addresses key research questions: what practical strategies have proven effective in reducing fossil fuel dependency in island contexts and what barriers hinder their widespread adoption? By applying the PRISMA methodology this study examines a decade (2014–2024) of research on renewable energy systems highlighting successful initiatives such as the integration of solar and wind systems in Hawaii energy storage advancements in La Graciosa hybrid renewable grids in the Galápagos Islands and others. Specific barriers include high upfront costs regulatory challenges and technical limitations such as grid instability due to renewable energy intermittency. This review contributes by synthesizing lessons from diverse case studies and identifying innovative approaches like hydrogen storage predictive control systems and community-driven renewable projects. The findings offer actionable insights for policymakers and researchers to accelerate the transition towards sustainable energy systems in island environments.

This review article provides a comprehensive overview of the pivotal role that nanomaterials particularly graphene and its derivatives play in advancing hydrogen energy technologies with a focus on storage production and transport. As the quest for sustainable energy solutions intensifies the use of nanoscale materials to store hydrogen in solid form emerges as a promising strategy toward mitigate challenges related to traditional storage methods. We begin by summarizing standard methods for producing modified graphene derivatives at the nanoscale and their impact on structural characteristics and properties. The article highlights recent advancements in hydrogen storage capacities achieved through innovative nanocomposite architectures for example multi-level porous graphene structures containing embedded nickel particles at nanoscale dimensions. The discussion covers the distinctive characteristics of these nanomaterials particularly their expansive surface area and the hydrogen spillover effect which enhance their effectiveness in energy storage applications including supercapacitors and batteries. In addition to storage capabilities this review explores the role of nanomaterials as efficient catalysts in the hydrogen evolution reaction (HER) emphasizing the potential of metal oxides and other composites to boost hydrogen production. The integration of nanomaterials in hydrogen transport systems is also examined showcasing innovations that enhance safety and efficiency. As we move toward a hydrogen economy the review underscores the urgent need for continued research aimed at optimizing existing materials and developing novel nanostructured systems. Addressing the primary challenges and potential future directions this article aims to serve as a roadmap to enable scientists and industry experts to maximize the capabilities of nanomaterials for transforming hydrogen-based energy systems thus contributing significantly to global sustainability efforts.

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.

As a result of international agreements on the reduction of CO2 emissions new technologies using hydrogen are being developed. Hydrogen despite being the most abundant element in Nature cannot be found in its pure state. Water is one of the most abundant sources of hydrogen on the planet. The proposal here is to use energy from the sea in order to obtain hydrogen from water. If plants to obtain hydrogen were to be placed in the ocean the impact of long submarines piping to the coast will be reduced. Further this will open the way for the development of ships propelled by hydrogen. This paper discusses the feasibility of an offshore installation to obtain hydrogen from the sea using ocean wave energy.

Hydrogen production via water electrolysis and renewable electricity is expected to play a pivotal role as an energy carrier in the energy transition. This fuel emerges as the most environmentally sustainable energy vector for non-electric applications and is devoid of CO2 emissions. However an electrolyzer´s infrastructure relies on scarce and energyintensive metals such as platinum palladium iridium (PGM) silicon rare earth elements and silver. Under this context this paper explores the exergy cost i.e. the exergy destroyed to obtain one kW of hydrogen. We disaggregated it into non-renewable and renewable contributions to assess its renewability. We analyzed four types of electrolyzers alkaline water electrolysis (AWE) proton exchange membrane (PEM) solid oxide electrolysis cells (SOEC) and anion exchange membrane (AEM) in several exergy cost electricity scenarios based on different technologies namely hydro (HYD) wind (WIND) and solar photovoltaic (PV) as well as the different International Energy Agency projections up to 2050. Electricity sources account for the largest share of the exergy cost. Between 2025 and 2050 for each kW of hydrogen generated between 1.38 and 1.22 kW will be required for the SOEC-hydro combination while between 2.9 and 1.4 kW will be required for the PV-PEM combination. A Grassmann diagram describes how non-renewable and renewable exergy costs are split up between all processes. Although the hybridization between renewables and the electricity grid allows for stable hydrogen production there are higher non-renewable exergy costs from fossil fuel contributions to the grid. This paper highlights the importance of nonrenewable exergy cost in infrastructure which is required for hydrogen production via electrolysis and the necessity for cleaner production methods and material recycling to increase the renewability of this crucial fuel in the energy transition.