Publications

The power to weight ratio of power plants is an important consideration especially in the design of Unmanned Aircraft System (UAS). In this paper a UAS with an MTOW of 35.3 kg equipped with a fuel cell as a prime power supply to provide electrical power to the propulsion system is considered. A pressure vessel design that can estimate and determine the total size and weight of the combined power plant of a fuel cell stack with hydrogen and air/oxygen vessels and the propulsion system of the UAS for highaltitude operation is proposed. Two scenarios are adopted to determine the size and weight of the pressure vessels required to supply oxygen to the fuel cell stack. Different types of stainless-steel materials are used in the design of the pressure vessel in order to find an appropriate material that provides low size and weight advantages. Also the design of a hydrogen pressure vessel and mass estimation are also considered. The estimated sizes and weights of the hydrogen and oxygen vessels of the power plant and propulsion system in this research offer a maximum of four hours of flying time for the UAS mission; this is based on a Horizon (H-1000) Proton Exchange Membrane (PEM) stack.

Natural hydrogen (H2) holds promising potential as a clean energy source but its exploration remains challenging due to limited knowledge and a lack of quantitative tools. In this context identifying active H2 seepage areas is crucial for advancing exploration efforts. Here we focus on sub-circular depressions (SCDs) that often mark high H2 concentration in soils thought to correspond to deeper fluxes seeping at the surface making them promising targets for exploration. Coupling open-access Google Earth© images and in-field H2 measurement data an artificial intelligence model was trained to detect seepage zones. The model achieves an average precision of 95 % detects and maps seepage zones in new regions like Kazakhstan and South Africa highlighting its potential for global application. Moreover preliminary spatial analyses show that geological features control the distribution of H2-SCDs that can emit billions of tons of H2 at the scale of a sedimentary basin. This study paves the way for a faster and more efficient methodology for selecting H2 exploration targets. Plain Language Summary. Natural hydrogen is a promising clean energy source but it remains difficult to explore due to a lack of accessible tools. In this study we used free satellite images (Google Earth©) and in-field hydrogen measurements to identify specific surface features - small sub-circular depressions (SCDs) - that often mark areas where hydrogen is seeping from underground. We trained an artificial intelligence model to detect these depressions using a dataset of confirmed hydrogen-emitting SCDs collected across five countries. Thanks to this diversity in the training data the model can be applied at a global scale having learned to recognize a wide variety of structures associated with hydrogen seepage. To validate its effectiveness the model was tested on two random regions - in Kazakhstan and South Africa - and successfully identified over a thousand new potential hydrogen-emitting depressions. With an average precision of 95 % this tool offers a fast and reliable way to map natural hydrogen seepage zones helping guide future exploration efforts worldwide.

The increasing adoption of liquid hydrogen (LH2) as a clean energy carrier presents significant safety challenges particularly in confined underground spaces like tunnels. LH2′s unique properties including high energy density and cryogenic temperatures amplify the risks of leaks and explosions which can lead to catastrophic overpressures and extreme temperatures. This study addresses these challenges by investigating the diffusion and explosion behaviour of LH2 leaks in tunnels providing critical insights into disaster prevention and structural resilience for underground infrastructure. Using advanced numerical simulations validated through theoretical calculations and experimental analogies the study analyses hydrogen diffusion patterns overpressure dynamics and thermal impacts following an LH2 tank rupture. Results show that LH2 explosions generate overpressures exceeding 50 bar and temperatures surpassing 2500 ◦C far exceeding the hazards posed by gaseous hydrogen leaks. Mitigation measures such as suction ventilation and high humidity significantly reduce explosion impacts underscoring their value for tunnel safety. This research advances understanding of hydrogen safety in confined spaces demonstrating the importance of integrating mitigation measures into tunnel design. The findings contribute to disaster prevention strategies offer insights into optimizing safety protocols and support the development of resilient infrastructure capable of accommodating hydrogen technologies in a rapidly evolving energy landscape.

The share of renewable electricity generation has been growing steadily over the past few years. However not all sectors can be fully electrified to reach decarbonization goals. The maritime industry which plays a critical role in international trade is such a sector. Therefore there is a need for a global strategic approach towards the production transportation and use of synfuels enabling the maritime energy transition to benefit from economies of scale. There are potential locations around the world for renewable generation such as hydropower in Norway wind turbines in the North Sea and photovoltaics in the Sahara where synfuels can be produced and utilized within the country as well as exported to demand hubs. Given that a country's domestic production may not fully meet its demand a scenario-based analysis is essential to determine the feasibility of supply chains pillaring on the demand and supply for the respective sector of utilization. Our work demonstrates this methodology for the import of hydrogen and derived ammonia and methanol to Germany from Norway Namibia and Algeria in 2030 and 2050 utilizing the pipeline- and ship-based transport scenarios. Thereby the overall supply chain efficiency for maritime applications is analyzed based on the individual supply chain energy consumption from production to bunkering of the fuel to a vessel. The analysis showed that the efficiency of import varies from 44.6% to 53.9% between the analyzed countries. Furthermore a sensitivity analysis for green and blue hydrogen production pathways is presented along with the influence of qualitative factors like port infrastructure geopolitics etc. As an example through these analyses recommendations for supply from Norway Algeria and Namibia at the Port of Wilhelmshaven within a supply chain are examined.

Hydrogen is increasingly recognized as a key solution for decarbonizing the Dutch energy system particularly within the industrial sector. A national hydrogen network is under development to serve the five major industrial clusters in the Netherlands. However meeting the hydrogen needs of the industries outside these clusters which are collectively known as “Cluster 6” remains difficult. Regulatory unclarity and ambiguity around the hydrogen distribution infrastructure including restrictions on distribution system operators (DSOs) compound these challenges. This study investigates the complex and evolving regulatory landscape for hydrogen distribution across Cluster 6 in the Netherlands using a two-step approach of Institutional Network Analysis (INA) and stakeholder interviews. Findings outline possible pathways for delegating distribution responsibilities in current and future regulatory frameworks while stakeholders report structural and outcome uncertainty limiting their willingness to invest in hydrogen distribution initiatives. The research findings highlight the need for a more coherent regulatory and technical framework to support more effective development of physical hydrogen systems. Policy recommendations include clarification of distributor roles targeted support mechanisms and flexible regulations that can adapt to the rapidly developing hydrogen market.

In this paper we propose an alternative strategy to produce green hydrogen in a more sustainable way than standard water electrolysis where a substantial amount of the electrical energy is wasted in the oxygen evolution quite often simply released in the atmosphere. The HER (hydrogen evolution reaction) is effectively coupled with the oxidation of guaiacol at the anode leading to the simultaneous production of H2 and valuable guaiacol oligomers. Significative points i) a substantial decrease of the potential difference for the HER 0.85 V with guaiacol ii) HER is accompanied by the production of industrially appealing and sustainable guaiacol based oligomers iii) guaiacol oxidation runs efficiently on carbon-based surfaces like graphite and glassy carbon which are cheap and not-strategic materials. Then the electrochemical oxidation mechanism of guaiacol is studied in detail with in-situ EPR measurements and post-electrolysis product characterization: LC-DAD LC-MS and NMR. Experimental results and theoretical calculations suggest that guaiacol polymerization follows a Kane-Maguire mechanism.

In Spain the winery industry exerts a great influence on the national economy. Proportional to the scale of production a significant volume of waste is generated estimated at 2 million tons per year. In this work a laboratory-scale reactor was used to study the feasibility of the energetic valorization of winery effluents into hydrogen by means of dark fermentation and its subsequent conversion into electrical energy using fuel cells. First winery wastewater was characterized identifying and determining the concentration of the main organic substrates contained within it. To achieve this a synthetic winery effluent was prepared according to the composition of the winery wastewater studied. This effluent was fermented anaerobically at 26 ◦C and pH = 5.0 to produce hydrogen. The acidogenic fermentation generated a gas effluent composed of CO2 and H2 with the percentage of hydrogen being about 55% and the hydrogen yield being about 1.5 L of hydrogen at standard conditions per liter of wastewater fermented. A gas effluent with the same composition was fed into a fuel cell and the electrical current generated was monitored obtaining a power generation of 1 W·h L−1 of winery wastewater. These results indicate that it is feasible to transform winery wastewater into electricity by means of acidogenic fermentation and the subsequent oxidation of the bio-hydrogen generated in a fuel cell.

Under the constraints of the “dual carbon” goals accurately depicting the full life cycle carbon footprint of green hydrogen and its derivatives and quantifying the potential for emission reduction is a prerequisite for hydrogen energy policy and investment decisions. This paper constructs a unified life cycle model covering the entire process from “wind and solar power generation–electrolysis of water to producing hydrogen-synthesis of methanol/ammonia-terminal transportation” and includes the manufacturing stage of key front-end equipment and the negative carbon effect of CO2 capture within a single system boundary and also presents an empirical analysis. The results show that the full life cycle carbon emissions of wind power hydrogen production and photovoltaic hydrogen production are 1.43 kgCO2/kgH2 and 3.17 kgCO2/kgH2 respectively both lower than the 4.9 kg threshold for renewable hydrogen in China. Green hydrogen synthesis of methanol achieves a net negative emission of −0.83 kgCO2/kgCH3OH and the emission of green hydrogen synthesis of ammonia is 0.57 kgCO2/kgNH3. At the same time it is predicted that green hydrogen green ammonia and green methanol can contribute approximately 1766 66.62 and 30 million tons of CO2 emission reduction respectively by 2060 providing a quantitative basis for the large-scale layout and policy formulation of the hydrogen energy industry.

This study experimentally investigates the effect of hydrogen addition on combustion and thermal characteristics of impinging non-premixed jet flames for low-heating values gases (LHVGs). We evaluate the flame morphology and stability using a concentric non-premixed combustor with an impingement plate. OH radicals are visualized using the OH* chemiluminescence and OH-planar laser-induced fluorescence (OH-PLIF) system. Emission characteristics are investigated by calculating CO and NOx emission indices. The results show that the flame stability region narrows as the heating value decreases but expands as hydrogen has been added. The low-OH radical intensity of LHVGs increases with the hydrogen addition. EICO and EINOx decrease with the reduction of heating values. EICO rapidly declines near the lifted flame limit due to the premixing of fuel and air downstream of the flame region. The effect of the hydrogen addition on EINOx is insignificant and shows very low emissions. The heat transfer rate into cooling water indicates a linear tendency with thermal power regardless of the fuel type. These findings show that LHVGs can be employed in existing-impinging flame systems so long as they remain within flame sta bility regions. Furthermore hydrogen addition positively affects the expansion of flame stability enhancing the utility of LHVGs.

Underground hydrogen storage (UHS) in basaltic rocks offers a scalable solution for large-scale sustainable energy needs yet its efficiency is limited by poorly constrained pore-scale hysteresis during cyclic hydrogenbrine flow. While basaltic rocks have been extensively studied for carbon sequestration and critical mineral extraction the pore-scale physics governing cyclic hydrogen-brine interactions particularly the roles of snap-off wettability and hysteresis remain inadequately understood. This knowledge gap hinders the development of predictive models and optimization strategies for UHS performance. This study presents a pore-scale investigations of cyclic hydrogen-brine flow in basaltic formations combining micro-computed tomography imaging with pore network modelling. A systematic workflow is employed to evaluate the effects of repeated drainage-imbibition cycles on multiphase flow properties under varying wetting regimes with emphasis on hysteresis evolution and its influence on recoverable hydrogen. Model validation is achieved through a novel benchmarking approach that incorporates synthetic fractures and morphological scaling enabling calibration against experimental capillary pressure and relative permeability. Results show that hydrogen trapping is primarily governed by snap-off and pore-body isolation particularly within large angular pores exhibiting high aspect ratios and limited connectivity. Strong hysteresis is observed between drainage and imbibition with hydrogen saturations averaging 85% predominantly in larger pore spaces compared to a residual saturation of 61% following imbibition. Repeated cycling leads to a gradual increase in residual saturation which eventually stabilizes indicating the onset of a hysteresis equilibrium state. Wettability emerges as a critical second-order control on displacement dynamics. Shifting from strongly to weakly water-wet conditions reduces capillary entry pressures enhances brine re-invasion and increases hydrogen recovery efficiency by ∼6%. These findings offer mechanistic insights into capillary trapping and wettability effects providing a framework for optimizing UHS reactive and abundant yet underutilized basalt formations and supporting ongoing global decarbonization efforts through reliable subsurface hydrogen storage.