Search Results (3,661)

Hydrogen combustion engine vehicles have the potential to rapidly enter the market and reduce greenhouse gas emissions (GHG) compared to conventional engines. The ability to provide a rapid market deployment is linked to the fact that the industry would take advantage of the existing internal combustion engine production chain. The aim of this paper is twofold. First, it aims to develop a methodology for applying life-cycle assessment (LCA) to internal combustion engines to estimate their life-cycle GHG emissions. Also, it aims to investigate the decarbonization potential of hydrogen engines produced by exploiting existing diesel engine technology and assuming diverse hydrogen production routes. The boundary of the LCA is cradle-to-grave, and the assessment is entirely based on primary data. The products under study are two monofuel engines: a hydrogen engine and a diesel engine. The hydrogen engine has been redesigned using the diesel engine as a base. The engines being studied are versatile and can be used for a wide range of uses such as automotive, cogeneration, maritime, off-road, and railway; however, this study focuses on their application in pickup trucks. As part of the redesign process, certain subsystems (e.g., combustion, injection, ignition, exhaust gas recirculation, and exhaust gas aftertreatment) have been modified to make the engine run on hydrogen. Results revealed that employing a hydrogen engine using green hydrogen (i.e., generated from water electrolysis using wind-based electricity) might reduce GHG emission by over 90% compared to the diesel engine This study showed that the benefits of the new hydrogen engine solution outweigh the increase of emissions related to the redesign process, making it a potentially beneficial solution also for reconditioning current and used internal combustion engines. Full article

This article analyzes the processes of compressing hydrogen in the gaseous state, an aspect considered important due to its contribution to the greater diffusion of hydrogen in both the civil and industrial sectors. This article begins by providing a concise overview and comparison of diverse hydrogen-storage methodologies, laying the groundwork with an in-depth analysis of hydrogen’s thermophysical properties. It scrutinizes plausible configurations for hydrogen compression, aiming to strike a delicate balance between energy consumption, derived from the fuel itself, and the requisite number of compression stages. Notably, to render hydrogen storage competitive in terms of volume, pressures of at least 350 bar are deemed essential, albeit at an energy cost amounting to approximately 10% of the fuel’s calorific value. Multi-stage compression emerges as a crucial strategy, not solely for energy efficiency, but also to curtail temperature rises, with an upper limit set at 200 °C. This nuanced approach is underlined by the exploration of compression levels commonly cited in the literature, particularly 350 bar and 700 bar. The study advocates for a three-stage compression system as a pragmatic compromise, capable of achieving high-pressure solutions while keeping compression work below 10 MJ/kg, a threshold indicative of sustainable energy utilization. Full article

The use of Atmospheric Pressure Plasma Jet (APPJ) technology for surface treatment of carbon fabrics is investigated to estimate the increase in the fracture toughness of carbon-fiber composite materials. Nitrogen and a nitrogen–hydrogen gas mixture were used to size the carbon fabrics by preliminarily optimizing the process parameters. The effects of the APPJ on the carbon fabrics were investigated by using optical and chemical characterizations. Optical Emission Spectroscopy, Fourier Transform Infrared-Attenuated Total Reflection, X-ray Photoelectron Spectroscopy and micro-Raman spectroscopy were adopted to assess the effectiveness of ablation and etching effects of the treatment, in terms of grafting of new functional groups and active sites. The treated samples showed an increase in chemical groups grafted onto the surfaces, and a change in carbon structure was influential in the case of chemical interaction with epoxy groups of the epoxy resin adopted. Flexural test, Double Cantilever Beam and End-Notched Flexure tests were then carried out to characterize the composite and evaluate the fracture toughness in Mode I and Mode II, respectively. N₂/H₂ specimens showed significant increases in G_IC and G_IIC, compared to the untreated specimens, and slight increases in P_max at the first crack propagation. Full article

The use of existing natural gas pipelines for the transport of hydrogen/natural gas mixtures can achieve large-scale, long-distance and low-cost hydrogen transportation. A jet fire induced by the leakage of high-pressure pure hydrogen and hydrogen-blended natural gas pipelines may pose a severe threat to life and property. Based on the Abel–Nobel equation of state and a notional nozzle model, an equivalent pipe leakage model is established to simulate high-pressure pipeline gas leakage jet fire accidents. Large-scale high-pressure hydrogen and natural gas/hydrogen mixture jet fires are simulated, showing the jet impingement process and obtaining an accurate and effective simulation framework. This framework is validated by comparing the simulated and experimental measured results of flame height, flame appearance and thermal radiation. Several combustion models are compared, and the simulated data show that the non-premixed chemical equilibrium combustion model is superior to other combustion models. The influence of the pipe pressure and the hydrogen blending ratio on the consequences of natural gas/hydrogen mixture pipeline leakage jet fire accidents is explored. It is found that when the hydrogen blending ratio is lower than 22%, the increase in the hydrogen blending ratio has little effect on the decrease in the thermal radiation hazard distance. Full article

In light of growing concerns regarding greenhouse gas emissions and the increasingly severe impacts of climate change, the global situation demands immediate action to transition towards sustainable energy solutions. In this sense, hydrogen could play a fundamental role in the energy transition, offering a potential clean and versatile energy carrier. This paper reviews the recent results of Life Cycle Assessment studies of different hydrogen production pathways, which are trying to define the routes that can guarantee the least environmental burdens. Steam methane reforming was considered as the benchmark for Global Warming Potential, with an average emission of 11 kg_CO2eq/kg_H2. Hydrogen produced from water electrolysis powered by renewable energy (green H₂) or nuclear energy (pink H₂) showed the average lowest impacts, with mean values of 2.02 kg_CO2eq/kg_H2 and 0.41 kg_CO2eq/kg_H2, respectively. The use of grid electricity to power the electrolyzer (yellow H₂) raised the mean carbon footprint up to 17.2 kg_CO2eq/kg_H2, with a peak of 41.4 kg_CO2eq/kg_H2 in the case of countries with low renewable energy production. Waste pyrolysis and/or gasification presented average emissions three times higher than steam methane reforming, while the recourse to residual biomass and biowaste significantly lowered greenhouse gas emissions. The acidification potential presents comparable results for all the technologies studied, except for biomass gasification which showed significantly higher and more scattered values. Regarding the abiotic depletion potential (mineral), the main issue is the lack of an established recycling strategy, especially for electrolysis technologies that hamper the inclusion of the End of Life stage in LCA computation. Whenever data were available, hotspots for each hydrogen production process were identified. Full article

HSG (high-sulfur gas) reservoirs are prevalent globally, yet their exploitation is hindered by elevated levels of hydrogen sulfide. A decrease in temperature and pressure may result in the formation of sulfur deposits, thereby exerting a notable influence on gas production. Test instruments are susceptible to significant corrosion due to the presence of hydrogen sulfide, resulting in challenges in obtaining bottom hole temperature and pressure test data. Consequently, a WTD (wellbore temperature distribution) model incorporating sulfur precipitation was developed based on PPP (physical property parameter), heat transfer, and GSTP (gas–solid two-phase) flow models. The comparison of a 2.53% temperature error and a 4.80% pressure error with actual field test data indicates that the established model exhibits high accuracy. An analysis is conducted on the impact of various factors, such as production, sulfur layer thickness, reservoir temperature, and reservoir pressure, on the distribution of the wellbore temperature field and pressure field. Increased gas production leads to higher wellhead temperatures. The presence of sulfur deposits reduces the flow area and wellhead pressure. A 40% concentration of hydrogen sulfide results in a 2 MPa pressure drop compared to a 20% concentration. Decreased reservoir pressure and temperature facilitate the formation of sulfur deposits at the wellhead. Full article

This study focuses on the heavily Mg-doped GaN in which the passivation effect of hydrogen and the compensation effect of nitrogen vacancies (V_N) impede its further development. To investigate those two factors, H ion implantation followed by thermal annealing was performed on the material. The evolution of relevant defects (H and V_N) was revealed, and their distinct behaviors during thermal annealing were compared between different atmospheres (N₂/NH₃). The concentration of H and its associated yellow luminescence (YL) band intensity decrease as the thermal annealing temperature rises, regardless of the atmosphere being N₂ or NH₃. However, during thermal annealing in NH₃, the decrease in H concentration is notably faster compared to N₂. Furthermore, a distinct trend is observed in the behavior of the blue luminescence (BL) band under N₂ and NH₃. Through a comprehensive analysis of surface properties, we deduce that the decomposition of NH₃ during thermal annealing not only promotes the out-diffusion of H ions from the material, but also facilitates the repair of V_N on the surface of heavily Mg-doped GaN. This research could provide crucial insights into the post-growth process of heavily Mg-doped GaN. Full article

N-Hydroxyurea (HU) is an important chemotherapeutic agent used as a first-line treatment in conditions such as sickle cell disease and $\beta$-thalassemia, among others. To date, its properties as a hydrated molecule in the blood plasma or cytoplasm are dramatically understudied, although they may be crucial to the binding of HU to the radical catalytic site of ribonucleotide reductase, its molecular target. The purpose of this work is the comprehensive exploration of HU hydration. The topic is studied using ab initio molecular dynamic (AIMD) simulations that apply a first principles representation of the electron density of the system. This allows for the calculation of infrared spectra, which may be decomposed spatially to better capture the spectral signatures of solute–solvent interactions. The studied molecule is found to be strongly hydrated and tightly bound to the first shell water molecules. The analysis of the distance-dependent spectra of HU shows that the E and Z conformers spectrally affect, on average, 3.4 and 2.5 of the closest H₂O molecules, respectively, in spheres of radii of 3.7 Å and 3.5 Å, respectively. The distance-dependent spectra corresponding to these cutoff radii show increased absorbance in the red-shifted part of the water OH stretching vibration band, indicating local enhancement of the solvent’s hydrogen bond network. The radially resolved IR spectra also demonstrate that HU effortlessly incorporates into the hydrogen bond network of water and has an enhancing effect on this network. Metadynamics simulations based on AIMD methodology provide a picture of the conformational equilibria of HU in solution. Contrary to previous investigations of an isolated HU molecule in the gas phase, the Z conformer of HU is found here to be more stable by 17.4 kJ·mol⁻¹ than the E conformer, pointing at the crucial role that hydration plays in determining the conformational stability of solutes. The potential energy surface for the OH group rotation in HU indicates that there is no intramolecular hydrogen bond in Z-HU in water, in stark contrast to the isolated solute in the gas phase. Instead, the preferred orientation of the hydroxyl group is perpendicular to the molecular plane of the solute. In view of the known chaotropic effect of urea and its N-alkyl-substituted derivatives, N-hydroxyurea emerges as a unique urea derivative that exhibits a kosmotropic ordering of nearby water. This property may be of crucial importance for its binding to the catalytic site of ribonucleotide reductase with a concomitant displacement of a water molecule. Full article

Ejector-based proton exchange membrane fuel cells (PEMFCs) are of great interest due to their simplicity and feasibility. Thus, proton exchange membrane fuel cells are considered the most suitable technology for in-vehicle systems, industrial applications, etc. Despite the passive characteristics of the ejector, active control of the hydrogen supply system is needed to ensure sufficient hydrogen, maintain the stack pressure, and ensure effective entrainment. In this research, a novel semi-empirical model is proposed to accurately predict the entrainment performance of the ejector with an 80 kW fuel cell system. According to the precise semi-empirical model, the hydrogen supply system and the anode channel are modeled. Then, a fuzzy logic controller (FLC) is developed to supply sufficient and adequate gas flow and maintain the rapid dynamic response. Compared to the conventional proportional–integral–derivative controller, the fuzzy logic controller could reduce the anode pressure variability by 5% during a stepped case and 2% during a dynamic case. Full article

The range is one of the most important performance indicators for fuel-cell electric vehicles. This article focuses on the analysis of GB/T 43252-2023 “Energy Consumption and Range Test Methods for Fuel-Cell Electric Vehicles” from the perspective of a standard analysis, and conducts actual vehicle tests on the range test method and process. It introduces the measurement method of hydrogen gas filling for test vehicles, and explains the main content of the new standard revision and the main differences between the new and old standards. This article takes the fuel-cell dump truck as an example, and analyzed the relationship between the output power of fuel-cell stacks and power batteries during vehicle operation and driving conditions, as well as the proportion of fuel cell output power. The results show that the optimal output power range of fuel cells is 20–40 kW, accounting for 45.2% of the total operating time. When driving at high speeds, the output power of fuel cells is greater than that of power batteries. Full article

Currently, the process of creating industrial installations is associated with digital technologies and must involve the stage of developing digital models. It is also necessary to combine installations with different properties, functions, and operational principles into a single system. Some tasks require the use of predictive modeling and the creation of “digital twins”. The main processes during the fuel cell modeling involve electrochemical transformations as well as the movement of heat and mass flows, including monitoring and control processes. Numerical methods are utilized in addressing various challenges related to fuel cells, such as electrochemical modeling, collector design, performance evaluation, electrode microstructure impact, thermal stress analysis, and the innovation of structural components and materials. A digital model of the membrane-electrode unit for a solid oxide fuel cell (SOFC) is presented in the article, incorporating factors like fluid dynamics, mass transfer, and electrochemical and thermal effects within the cell structure. The mathematical model encompasses equations for momentum, mass, mode, heat and charge transfer, and electrochemical and reforming reactions. Experimental data validates the model, with a computational mesh of 55 million cells ensuring numerical stability and simulation capability. Detailed insights on chemical flow distribution, temperature, current density, and more are unveiled. Through a numerical model, the influence of various fuel types on SOFC efficiency was explored, highlighting the promising performance of petrochemical production waste as a high-efficiency, low-reagent consumption fuel with a superior fuel utilization factor. The recommended voltage range is 0.6–0.7 V, with operating temperatures of 900–1300 K to reduce temperature stresses on the cell when using synthesis gas from petrochemical waste. The molar ratio of supplied air to fuel is 6.74 when operating on synthesis gas. With these parameters, the utilization rate of methane is 0.36, carbon monoxide CO is 0.4, and hydrogen is 0.43, respectively. The molar ratio of water to synthesis gas is 2.0. These results provide an opportunity to achieve electrical efficiency of the fuel cell of 49.8% and a thermal power of 54.6 W when using synthesis gas as fuel. It was demonstrated that a high-temperature fuel cell can provide consumers with heat and electricity using fuel from waste from petrochemical production. Full article

This article presents the possibility of improving combustion using the effect of releasing hydrogen from a solution with nucleation of gas bubbles. This concept consists in dissolving hydrogen in diesel fuel until the equilibrium state of the solution is reached. At a later stage, the phenomenon is reversed, and this gas is released from the solution during its injection into the combustion chamber with a strong swirl. A characteristic feature of the solution is that when lowering the pressure (opening the atomizers), there is a decrease in the equilibrium thermodynamic potential, which results in the excess, dissolved hydrogen being released spontaneously, and this process is of a volumetric nature. This article is a continuation of the work carried out at Poznan University of Technology on the development of this concept. This article presents the results of tests for the impact of hydrogen dissolved in diesel fuel on the combustion process within a turbulent-flow environment. The tests were conducted in the combustion chamber of an engine equipped with a toroidal combustion chamber and direct injection. During the tests, the following factors were measured: the main indicators of motor operation, emission of hydrocarbons, carbon monoxide, nitrogen oxides, and particulate matters. Full article

Global population growth requires the use of various natural resources to satisfy the basic needs of humanity. Fossil fuels are mainly used to produce electricity, transportation and the artificial air conditioning of habitats. Nevertheless, countries around the world are looking for alternative energy sources due to the decrease in the availability of these fuels and their high environmental impact. The mixture of hydrogen and carbon monoxide (H₂ + CO), commonly called syngas, is a high-value feedstock for various industrial applications. By varying the composition of syngas, especially the H₂/CO molar ratio, it can be used to produce methanol, fuels or synthetic natural gas. However, when this ratio is very low, the separation of this gas usually represents a great problem when making the energy balance, which is why it is proposed to adapt a combustion process in chemical cycles, taking advantage of the energy of this gas, reducing the energy impact of the process. During the present project, mass and energy balances were developed for combustion in chemical cycles, using ilmenite as a carrier, integrating heat exchangers to take advantage of the residual energy at the output of the process, to preheat the inlet current in the regenerator. Here, a comparative was made at different temperatures of the air stream and evaluating the mechanism of the ilmenite when a syngas stream is used as fuel. Full article

Hydrogen sulfide (H₂S), a novel gas signaling molecule, has been shown to enhance plant resistance to various abiotic stresses. Here, we investigated the effect of sodium hydrosulfide (NaHS, a H₂S donor) on the growth, photosynthetic parameters, and enzyme activities related to carbon and nitrogen metabolism, as well as the levels of carbohydrates and nitrogen metabolites in foxtail millet seedlings subjected to drought stress conditions in pots. The findings revealed that drought stress led to a significant 41.2% decline in the total dry weight (DW) after 12 days of treatment, whereas plants treated with NaHS showed a lesser reduction of 18.7% in total DW. Under drought stress, exogenous NaHS was found to enhance carbon metabolism in foxtail millet seedlings by significantly enhancing photosynthetic capacity, starch, and sucrose content. Additionally, exogenous NaHS was observed to improve nitrogen metabolism by substantially increasing soluble protein content, nitrogen assimilate activity, and synthesis of nitrogen-containing compounds in foxtail millet seedlings. In summary, the exogenous application of NaHS stimulated seedling growth and enhanced drought resistance in foxtail millet by modulating carbon and nitrogen metabolism processes affected by drought stress. Full article

The high demand for carbon-based products within pyrometallurgy is placing the industry in an increasingly challenging position to meet stringent requirements. To transition away from fossil carbon carriers, biochar emerges as a sustainable and CO₂-neutral alternative, presenting a viable solution without necessitating fundamental adjustments to plant technology, unlike hydrogen as an alternative reducing agent. Prior investigations have underscored the potential of woody biomass pyrolysis products for CO₂-neutral metallurgy. Nonetheless, it is imperative to recognize that biochar must meet distinct requirements across various metallurgical processes. This paper conducts a comparative analysis between biochar and petroleum coke using thermogravimetric analyses, surface measurements, reactivity assessments, and scanning electron microscopy. Furthermore, the performance in a furnace for simulating the Waelz process, specifically regarding ZnO reduction, is scrutinized. The results illustrate the optical differences between petroleum coke and biochar and the significantly higher reactivity and specific surface area of biochar. When used in solid–gas reactors, it is observed that due to its high reactivity, biochar reacts more vigorously and carbon is completely consumed. However, during the reduction of ZnO, only minor differences were monitored, making biochar comparable to petroleum coke. Therefore, under certain constraints, biochar can be considered a potential substitute for metallurgical solid–gas reactions. Full article