Publications

Zero-emission fuels are expected to drive the maritime sector decarbonisation with hydrogen emerging as a long-term solution. This study aims to investigate by using CFD modelling a hydrogen fuelled marine dual-fuel engine to identify operating settings ranges for different hydrogen energy fractions (HEF) as well as parametrically optimise the diesel fuel injection timing and temperature at inlet valve closing (IVC). A large marine four-stroke engine with nominal power of 10.5 MW at 500 rev/m is considered assuming operation at 90 % load and hydrogen injection in the cylinders intake ports. CFD models are developed for several operating scenarios in both diesel and dual-fuel modes. The models are validated against measured data for the engine diesel mode and literature data for a hydrogen-fuelled light-duty engine. A convergence study is conducted to select the grid compromising between computational effort and accuracy. Parametric runs for 20 % 40 % and 60 % HEF with different IVC temperature and diesel start of injection are modelled to quantify the engine performance emissions and combustion characteristics. A single parameter optimisation is conducted to determine the most effective pilot diesel injection timings. The results reveal the IVC temperature range for stable hydrogen combustion to avoid incomplete combustion at low IVC temperature and knocking above 360 K. The proposed settings lead to higher peak heat release rate and in-cylinder pressure compared to the diesel mode without exceeding the permissible in-cylinder pressure rise limits for 60 % HEF. However NOx emissions increase to 12.9 g/kWh in the dual-fuel mode. The optimal start of injection (SOI) for the diesel fuel in the case of 60 % HEF is found 8 ◦CA BTDC resulting in an indicated thermal efficiency of 43.2 % and stable combustion. Advancing SOI beyond the optimal value results in incomplete combustion. This is the first study on hydrogen use in large marine four-stroke engines providing insights for the engine design and operation and as such it contributes to the maritime industry decarbonisation efforts.

In this paper developed in the context of the Clean Sky 2 project SIENA (Scalability Investigation of hybrid-Electric concepts for Next-generation Aircraft) an extensive analysis is carried out to identify and accelerate the development of innovative propulsion technologies and architectures that can be scaled across five aircraft categories from small General Aviation airplanes to long-range airliners. The assessed propulsive architectures consider various components such as batteries and fuel cells to provide electricity as well as electric motors and jet engines to provide thrust combined to find feasible aircraft architectures that satisfy certification constraints and deliver the required performance. The results provide a comprehensive analysis of the impact of key technology performance indicators on aircraft performance. They also highlight technology switching points as well as the potential for scaling up technologies from smaller to larger aircraft based on different hypotheses and assumptions concerning the upcoming technological advancements of components crucial for the decarbonization of aviation. Given the considered scenarios the common denominator of the obtained results is hydrogen as the main energy source. The presented work shows that for the underlying models and technology assumptions hydrogen can be efficiently used by fuel cells for propulsive and system power for smaller aircraft (General Aviation commuter and regional) typically driven by propellers. For short- to long-range jet aircraft direct combustion of hydrogen combined with a fuel cell to power the on-board subsystems appears favorable. The results are obtained for two different temporal scenarios 2030 and 2050 and are assessed using Payload-Range Energy Efficiency as the key performance indicator. Naturally introducing such innovative architectures will face a lack of applicable regulation which could hamper a smooth entry into service. These regulatory gaps are assessed detailing the level of maturity in current regulations for the different technologies and aircraft categories.

The year 2024 saw a year of important developments for the Clean Hydrogen JU continuing built on the achievements of previous years and intensifying the efforts on hydrogen valleys. With a total operational commitment of EUR 203 million and the launch of 22 new projects the overall portfolio reached a total number of 147 projects under active management towards the end of the year. The budget execution reached the outstanding level of 98% in for commitments and 84% in payments in line with previous year showing the JU’s continued effort to use the available credits. In 2024 the JU launched a call for proposals with a budget of EUR 113.5 million covering R&I activities across the whole hydrogen value chain to which was added an amount of EUR 60 million from the RePowerEU plan focusing on hydrogen valleys. That amount served for valleys-related grants and the “Hydrogen Valleys Facility” tender designed for project development assistance that will support Hydrogen Valleys at different levels of maturity. The Hydrogen Valleys concept has become a key instrument for the European Commission to scale up hydrogen technology deployment and establish interconnections between hydrogen ecosystems. At the end of 2024 the Clean Hydrogen JU has already funded 20 hydrogen valleys. This support was complemented by additional credits from third countries and the optimal use- of leftover credits from previous years allowing the award of 29 new grants from the call for 2024.

This article explores how the implementation of solar PV and transportation infrastructure – grid or hydrogen pipeline – has implications for various aspects of security cooperation and geopolitical powershifts. Highlighting the emerging intra-European green hydrogen pipeline project H2Med we examine the Portuguese geopolitical ambitions related to their geographical advantage for solar PV energy production. Using media and document analysis we identified two main axes of solar PV implementation in Portugal – one centered on resilience and one on exports – and further explored underlying and resulting tensions in neighboring countries’ energy strategies and cleantech innovation policies. Our analysis revealed that policy prioritizations in solar PV diffusion result in unequal effects on resilience energy security and power shifts. In particular solar PV implementations such as individual to local or regional grid-based ‘prosumption’ setups result in notably different geopolitical effects compared to large-scale solar PV to green hydrogen-production for storage and export. Thereby emerging possibilities of storage and long-distance trade of renewable energies have more significant implications on geopolitics and energy security than what is typically recognized.

The growing demand for sustainable solutions in the transportation sector and global decarbonization goals have fueled debate on using hydrogen as an energy source. Although hydrogen’s potential is recognized in Brazil its application in heavy-duty vehicles still faces structural and technological barriers. This study aimed to analyze the viability of hydrogen as an energy alternative for trucks in Brazil. The research adopted an exploratory qualitative approach based on the expert analysis method through semi-structured interviews with development engineers representatives of heavy-duty vehicle manufacturers and researchers specializing in hydrogen technologies. The data were organized into a thematic framework and interpreted using content analysis. The results show that although there is growing interest and ongoing initiatives challenges such as the cost of fuel cells the lack of refueling infrastructure and low technological maturity hinder large-scale adoption. From a theoretical perspective the study contributes by integrating specialized literature with practical insights from key industry players broadening the understanding of the energy transition. In practical terms it outlines some strategic paths such as expanding technological development and forming partnerships. From a social perspective it emphasizes the importance of hydrogen as a pillar for sustainable low-carbon mobility capable of positively impacting public health and mitigating climate change.

This report includes information on European training programmes educational materials and the trends and patterns of research and innovation activity in the hydrogen sector with data of patent registrations and publications. It is based on the information available at the European Hydrogen Observatory (EHO) website (https://observatory.cleanhydrogen.europa.eu/) the leading source of hydrogen data in Europe. The data presented in this report is based on research conducted until the end of August 2024. The training programmes section provides insights into major European training initiatives categorized by location. It allows filtering by type of training focus area and language. It covers a wide range of opportunities such as vocational and professional trainings summer schools and Bachelor's or Master's programmes. The education materials chapter summarizes the publicly accessible educational materials available online. Documents can be searched by educational level by course subject by language or by the year of release. The section referring to research and innovation activity analyses trends and patterns in the hydrogen sector using aggregated datasets of patent registrations and publications by country.

Green hydrogen produced from renewable energy sources such as wind and solar is increasingly recognized as a critical enabler of the global energy transition and the decarbonization of industrial and transport sectors. The successful adoption of green hydrogen and its derivatives is closely linked to production costs which can vary substantially between countries depending not only on resource potential but also on country-specific financing conditions. These differences arise from country-specific risk factors that affect the costs of capital ultimately influencing investment decisions. However comprehensive assessments that integrate these risks with future cost projections for renewable energy green hydrogen and its synthetic downstream products are lacking. Using the Middle East and North Africa (MENA) as an example this study introduces a novel approach that allows to incorporate mainly qualitative country-specific investment risks into quantitative analyses such as costpotential and energy modelling. Our methodology calculates weighted average costs of capital (WACC) for 17 MENA countries under different risk scenarios providing a more nuanced assessment compared to traditional models that use uniform cost of capital assumptions. The results indicate significant variations in WACC such as between 4.67% in the United Arab Emirates and 24.84% in Yemen or Syria in the business-as-usual scenario. The incorporation of country-specific capital cost scenarios in quantitative analysis is demonstrated by modelling the cost-potential of Fischer-Tropsch (FT) fuels. The results show that countryspecific investment risks significantly impact costs. For instance by 2050 the starting LCOFs in high-risk scenarios can be up to 180% higher than in lowerrisk contexts. This underlines that while renewable energy potential and its cost are important it are the country-specific risk factors—captured through WACC—that have a greater influence in determining the competitiveness of exports and consequently the overall development of the renewable energy green hydrogen and synthetic fuel sectors.

Green hydrogen is increasingly recognized as a pivotal energy carrier in the global transition toward low-carbon energy systems. Beyond its established applications in industry and transportation the development of green hydrogen could accelerate its integration into the power generation sector thus enabling a more sustainable deployment of renewable energy sources. Vietnam endowed with abundant renewable energy potential—particularly solar and wind—has a strong foundation for green hydrogen. This emerging energy source holds significant potential to support the strategic objectives in recent national energy policies aligning with the country’s socio-economic development. However despite this promise the integration of green hydrogen into Vietnam’s energy system remains limited. This paper provides a critical review of the current landscape of green hydrogen in Vietnam examining both the opportunities and challenges associated with its production and deployment. Special attention is given to regulatory frameworks infrastructure readiness and economic viability. Additionally the study also explores the potential of green hydrogen in enhancing energy security within the context of the national energy transition.

Photocatalytic hydrogen (H2) production offers a promising solution to energy shortages and environmental challenges by converting solar energy into chemical energy. Hydrogen as a versatile energy carrier can be generated through photocatalysis under sunlight or via electrolysis powered by solar or wind energy. However the advancement of photocatalysis is hindered by the limited availability of effective visible light-responsive semiconductors and the challenges of charge separation and transport. To address these issues researchers are focusing on the development of novel nanostructured semiconductors and composite materials that can enhance photocatalytic performance. In this paper we provide an overview of the advanced photocatalytic materials prepared so far that can be activated by sunlight and their efficiency in H2 production. One of the key strategies in this research area concerns improving the separation and transfer of electron–hole pairs generated by light which can significantly boost H2 production. Advanced hybrid materials such as organic–inorganic hybrid composites consisting of a combination of polymers with metal oxide photocatalysts and the creation of heterojunctions are seen as effective methods to improve charge separation and interfacial interactions. The development of Schottky heterojunctions Z-type heterojunctions p–n heterojunctions from nanostructures and the incorporation of nonmetallic atoms have proven to reduce photocorrosion and enhance photocatalytic efficiency. Despite these advancements designing efficient semiconductor-based heterojunctions at the atomic scale remains a significant challenge for the realization of large-scale photocatalytic H2 production. In this review state-of-the-art advancements in photocatalytic hydrogen production are presented and discussed in detail with a focus on photocatalytic nanostructures heterojunctions and hybrid composites.

The potential for hydrogen to reshape energy systems has been recognized for over a century. Yet as decarbonization priorities have sharpened in many regions three distinct frontier areas are critical to consider: hydrogen produced from wind; hydrogen produced from nuclear power; and the development of natural hydrogen. These pathways reflect technology and policy changes including a 54% increase in the globally installed wind capacity since 2020 plus new signs of potential emerging in nuclear energy and natural hydrogen. Broadly speaking there are a considerable number of studies covering hydrogen production from electrolysis yet none systematically examine wind- and nuclear-derived hydrogen natural hydrogen or the policies that enable their adoption in key countries. This article highlights international policy and technology developments with a focus on prime movers: Germany China the US and Russia.