Publications

Hydrogen tanks used in transportation are equipped with thermal pressure relief devices to prevent a tank rapture in case of fire exposure. The opening of the pressure relief valve in such a scenario would likely result in an impinging and (semi-) confined hydrogen jet fire. Therefore twelve largescale experiments of hydrogen jet fires and one large-scale propane reference experiment have been conducted with various degrees of confinement orientations of the jet and distances from the nozzle to the impinging surface. Infrared and visible light videos temperatures heat fluxes and mass flow rate of hydrogen or propane were recorded in each experiment. It was found that the hydrogen flame can be visible under certain conditions. The main difference between an open impinging jet and an enclosed impinging jet fire is the extent of the high-temperature region in the steel target. During the impinging jet fire test 51% of the exposed target area exceeded 400C while 80% of the comparable area exceeded 400C during the confined jet fire test. A comparison was also made to an enclosed propane jet fire. The temperature distribution during the propane fire was more uniform than during the hydrogen jet fire and the localized hot spot in the impact region as seen in the hydrogen jet fires was not recorded.

This paper examines the changes in the performance level and pollutant emissions of a combustion chamber for turbofan engines. Two different fuels are compared: a conventional liquid fuel of the JET-A (kerosene) class and a hydrogen-based gaseous fuel. A turbofan engine delivering a 70 kN thrust at cruise conditions and 375 kN thrust at takeoff is considered. The comparison is carried out by investigating the combustion pattern with different boundary conditions the latter assigned along a typical flight mission. The calculations rely on a combined approach with a preliminary lumped parameter estimation of the engine performance and thermodynamic properties under different flight conditions (i.e. take-off climbing and cruise) and a CFD-based combustion simulation employing as boundary conditions the outputs obtained from the 0-D computations. The results are discussed in terms of performance thermal properties distributions throughout the combustor and of pollutant concentration at the combustor outflow. The results demonstrate that replacing the JET-A fuel with hydrogen does not affect the overall engine performance significantly and stable and efficient combustion takes place inside the burner although a different temperature regime is observable causing a relevant increase in thermal NO emissions.

China has emerged as a global leader in promoting new energy vehicles; however the impact of these efforts on the commercial vehicle sector remains limited. Hydrogen fuel cell vehicles are crucial for improving the environmental performance of commercial vehicles in China. This study evaluates the effectiveness of China’s Hydrogen fuel cell vehicle policies. Firstly an evaluation index system for hydrogen fuel cell vehicle policies is established quantifying the policy through two key metrics: policy comprehensiveness and policy synergy. Subsequently city-level data from 84 municipalities (2018-2022) are analyzed to assess policy impacts on hydrogen fuel cell vehicles adoption. The results show that both policy comprehensiveness and synergy significantly drive hydrogen fuel cell vehicle sales growth. Early sales figures also strongly influence current trends. Therefore promoting growth in hydrogen fuel cell vehicle sales can further enhance policy efforts while also accounting for the cumulative effects of initial promotional activities.

The burgeoning adoption of photovoltaic and wind energy has limitations of volatility and intermittency which hinder their application. Electro-hydrogen coupling energy storage systems emerge as a promising solution to address this issue. This technology combines renewable energy power generation with hydrogen production through water electrolysis and hydrogen fuel cell power generation effectively enabling the consumption and peak load management of renewable energy sources. This paper presents a power system with a 10 kW photovoltaic system and lithium battery energy storage system designed for hydrogen-electric coupled energy storage validated through the physical experiments. The results demonstrate the system's effectiveness in mitigating the impact of randomness and volatility in photovoltaic power generation. Moreover the energy management system can adjust bus power based on load demand. Testing the system in the absence of photovoltaic power generation reveals its capability to supply energy to the load for three hours with a minimum operating load power of 3 kW even under weather conditions unsuitable for photovoltaic power generation. These findings showed the potential of electro-hydrogen coupling energy storage systems in addressing the challenges associated with renewable energy integration paving the way for a reliable and sustainable energy supply.

This paper aims to present an overview of the current state of hydrogen storage methods and materials assess the potential benefits and challenges of various storage techniques and outline future research directions towards achieving effective economical safe and scalable storage solutions. Hydrogen is recognized as a clean secure and costeffective green energy carrier with zero emissions at the point of use offering significant contributions to reaching carbon neutrality goals by 2050. Hydrogen as an energy vector bridges the gap between fossil fuels which produce greenhouse gas emissions global climate change and negatively impact health and renewable energy sources which are often intermittent and lack sustainability. However widespread acceptance of hydrogen as a fuel source is hindered by storage challenges. Crucially the development of compact lightweight safe and cost-effective storage solutions is vital for realizing a hydrogen economy. Various storage methods including compressed gas liquefied hydrogen cryocompressed storage underground storage and solid-state storage (material-based) each present unique advantages and challenges. Literature suggests that compressed hydrogen storage holds promise for mobile applications. However further optimization is desired to resolve concerns such as low volumetric density safety worries and cost. Cryo-compressed hydrogen storage also is seen as optimal for storing hydrogen onboard and offers notable benefits for storage due to its combination of benefits from compressed gas and liquefied hydrogen storage by tackling issues related to slow refueling boil-off and high energy consumption. Material-based storage methods offer advantages in terms of energy densities safety and weight reduction but challenges remain in achieving optimal stability and capacities. Both physical and material-based storage approaches are being researched in parallel to meet diverse hydrogen application needs. Currently no single storage method is universally efficient robust and economical for every sector especially for transportation to use hydrogen as a fuel with each method having its own advantages and limitations. Moreover future research should focus on developing novel materials and engineering approaches in order to overcome existing limitations provide higher energy density than compressed hydrogen and cryo-compressed hydrogen storage at 70 MPa enhance costeffectiveness and accelerate the deployment of hydrogen as a clean energy vector.

Hydrogen valleys are envisaged (imagined) integrated industrial systems where hydrogen is produced stored and utilized. Here we show how hydrogen valleys as sociotechnical imaginaries are differentiated in terms of their specific configurations but homogenous in terms of reflecting the interests of large industrial fossil fuel suppliers and consumers. This path dependence is anticipated in sociotechnical transitions theory which emphasises the power of incumbents with vested interests to maintain basic templates or regimes of production and consumption. The simultaneously heterogeneous and homogenous nature of hydrogen valley imaginaries can be thought of as a form of glocalisation for which we draw on Roudometof's theory of glocalisation as involving the local refraction of diffusing global tendencies. To illustrate this we compare two hydrogen valleys one in the north of the Netherlands and one in southern Spain. In the north Netherlands the hydrogen valley imaginary comprises use of offshore windpower to electrolyse hydrogen for transport fuel and as feedstock to heavy industry in proximate regions including northern Germany and Belgium. This is consistent with existing gas distribution networks connecting industrial consumers. In the southern Spanish case the imaginary positions Spain as a major exporter of green hydrogen to the rest of Europe via onshore renewable electrolysis with export including via ocean tankers and chemical refining in existing infrastructure in Rotterdam. Overall the study explores empirically theoretically-informed themes concerning the interrelationship of mutually supportive local and global imaginaries – hence our term glocalised imaginaries.

With the fast-growing implementation of renewable energy projects Morocco is positioned as a pioneer in green and sustainable development aiming to achieve 52% of its electricity production from renewable sources by 2030. This ambitious target faces challenges due to the intermittent nature of renewable energy which impacts grid stability. Hydrogen offers a promising solution but identifying the most cost-effective production configurations is critical due to high investment costs. Despite the growing interest in renewable energy systems the techno-economic analysis of (Concentrating Solar PowerPhotovoltaic) CSP-PV hybrid configurations remain insufficiently explored. Addressing this gap is critical for optimizing hybrid systems to ensure cost-effective and scalable hydrogen production. This study advances the field by conducting a detailed technoeconomic assessment of CSP-PV hybrid systems for hydrogen production at selected locations in Morocco leveraging high-precision meteorological data to enhance the accuracy and reliability of the analysis. Three configurations are analyzed: (i) a standalone 10 MW PV plant (ii) a standalone 10 MW Stirling dish CSP plant and (iii) a 10 MW hybrid system combining 5 MW from each technology. Results reveal that hybrid CSP-PV systems with single-axis PV tracking achieve the lowest levelized cost of hydrogen (LCOH2) reducing costs by up to 11.19% and increasing hydrogen output by approximately 10% compared to non-tracking systems. Additionally the hybrid configuration boosts annual hydrogen production by 2.5–11.2% compared to PV-only setups and reduces production costs by ~25% compared to standalone CSP systems. These findings demonstrate the potential of hybrid solar systems for cost-efficient hydrogen production in regions with abundant solar resources.

: Hydrogen is a clean non-polluting fuel and a key player in decarbonizing the energy sector. Interest in hydrogen production has grown due to climate change concerns and the need for sustainable alternatives. Despite advancements in waste-to-hydrogen technologies the efficient conversion of mixed plastic waste via an integrated thermochemical process remains insufficiently explored. This study introduces a novel multi-stage pyrolysis-reforming framework to maximize hydrogen yield from mixed plastic waste including polyethylene (HDPE) polypropylene (PP) and polystyrene (PS). Hydrogen yield optimization is achieved through the integration of two water–gas shift reactors and a pressure swing adsorption unit enabling hydrogen production rates of up to 31.85 kmol/h (64.21 kg/h) from 300 kg/h of mixed plastic wastes consisting of 100 kg/h each of HDPE PP and PS. Key process parameters were evaluated revealing that increasing reforming temperature from 500 ◦C to 1000 ◦C boosts hydrogen yield by 83.53% although gains beyond 700 ◦C are minimal. Higher reforming pressures reduce hydrogen and carbon monoxide yields while a steam-to-plastic ratio of two enhances production efficiency. This work highlights a novel scalable and thermochemically efficient strategy for valorizing mixed plastic waste into hydrogen contributing to circular economy goals and sustainable energy transition.

The underlying physical mechanisms leading to the generation of blast waves after liquid hydrogen (LH2) storage tank rupture in a fire are not yet fully understood. This makes it difficult to develop predictive models and validate them against a very limited number of experiments. This study aims at the development of a CFD model able to predict maximum pressure in the blast wave after the LH2 storage tank rupture in a fire. The performed critical review of previous works and the thorough numerical analysis of BMW experiments (LH2 storage pressure in the range 2.0e11.3 bar abs) allowed us to conclude that the maximum pressure in the blast wave is generated by gaseous phase starting shock enhanced by combustion reaction of hydrogen at the contact surface with heated by the shock air. The boiling liquid expanding vapour explosion (BLEVE) pressure peak follows the gaseous phase blast and is smaller in amplitude. The CFD model validated recently against high-pressure hydrogen storage tank rupture in fire experiments is essentially updated in this study to account for cryogenic conditions of LH2 storage. The simulation results provided insight into the blast wave and combustion dynamics demonstrating that combustion at the contact surface contributes significantly to the generated blast wave increasing the overpressure at 3 m from the tank up to 5 times. The developed CFD model can be used as a contemporary tool for hydrogen safety engineering e.g. for assessment of hazard distances from LH2 storage.

Green hydrogen is critical for decarbonizing hard-to-electrify sectors but it faces high costs and investment risks. Here we defne and quantify the green hydrogen ambition and implementation gap showing that meeting hydrogen expectations will remain challenging despite surging announcements of projects and subsidies. Tracking 190 projects over 3 years we identify a wide 2023 implementation gap with only 7% of global capacity announcements fnished on schedule. In contrast the 2030 ambition gap towards 1.5 °C scenarios has been gradually closing as the announced project pipeline has nearly tripled to 422 GW within 3 years. However we estimate that without carbon pricing realizing all these projects would require global subsidies of US$1.3 trillion (US$0.8–2.6 trillion range) far exceeding announced subsidies. Given past and future implementation gaps policymakers must prepare for prolonged green hydrogen scarcity. Policy support needs to secure hydrogen investments but should focus on applications where hydrogen is indispensable.