The Italian National Recovery and Resilience Plan (NRRP) includes, among other measures, investments in hydrogen vehicle refuelling stations, intending to promote the use of fuel cell electric vehicles (FCEVs) for long-haul freight transport. This paper evaluates the impact that this action could have on CO2 emissions and fuel consumption, focusing on a case study of the Campania region. The proposed approach, which can also be transferred to other geographical contexts, requires the implementation of a freight road transport simulation model; this model is based on the construction of a supply model, the estimation of road freight demand, and an assignment procedure for computing traffic flows. This study covers the period from 2025 to 2040, according to the forecasts of the NRRP and some assumptions on the action effects; moreover, it is assumed that hydrogen is entirely produced from renewable sources (green hydrogen). The key findings from three different scenarios show that saving... [more]

This paper reports the critical reviews on the gassing tendency of different insulating fluids along with the precautionary measures to be considered during their fault diagnosis in transformer insulation. The experimental techniques and procedures for identifying the gassing due to electrical and thermal stress along with the stray gassing phenomenon has been elucidated. The different interpretation schemes used for determining the faults in transformers results in unexpected errors when the historical data relating to mineral oil is used for the other alternative fluids. Mineral oil and natural ester show a positive gassing tendency compared to synthetic ester which exhibit a negative gassing tendency. The stray gases are mostly due to breakage of C-C bonds under normal operating temperature of transformer. Among the different hydrocarbons, hydrogen and ethylene are more predominantly formed under lower temperatures. The silicone oil and ester fluids are more stable even under locali... [more]

The emissions from direct injection (DI) diesel engines remain a serious setback from the viewpoint of environmental pollution, especially for those who have been persuaded to use biofuel as an alternative fuel. The main drawbacks of using biofuels and their mixtures in DI diesel engines are increased emissions and decreased brake thermal efficiency (BTE) compared to using neat diesel fuel. The current study analyses the biodiesel made from cashew nut shell liquid (CNSL) using a single-cylinder, direct-injection diesel engine to validate the engine’s performance and discharge characteristics. In addition to the improved CNSL and a twin-fuel engine that runs on hydrogen, ethanol was added to the fuel at rates of 5%, 10%, and 15%. The investigation was conducted using a single-cylinder direct injection diesel engine at steady-state settings, above the sustained engine speed (1500 RPM). Several performance parameters and pollutant emissions, such as hydrocarbons (HC), carbon monoxide (CO)... [more]

The effects of hydrolysis methods (hydrothermal, acid, alkali, hydrothermal-enzyme, acid-enzyme, and alkali-enzyme) on hydrolysate characteristics and photo fermentative hydrogen production (PFHP) of corn straw (CS) and sorghum straw (SS) were investigated. The optimum production of reducing the sugar of straw in different solvent environments was studied by one-step hydrolysis and co-enzymatic hydrolysis pretreatment through a 3,5-dinitrosalicylic acid method. The hydrogen production process by photolytic fermentation of hydrolysates of Rhodobacter sphaeroides HY01 was further analyzed through a gas chromatograph, including the differences in accumulated PFHP yield, chemical oxygen consumption (COD), and volatile fatty acid (VFA) composition. The results showed that the highest reducing sugar yield was obtained by the acid method among one-step hydrolysis. In contrast, acid-enzyme hydrolysis can further increase the reducing sugar yield, which reached 0.42 g·g−1-straw of both straws.... [more]

In the current study, plain and lignin loaded with Zeolite Y, hydrogen was decomposed in a pyrolysis chamber. The reaction parameters were optimized and 390 °C, 3% catalyst with a reaction time of 40 min were observed as the most suitable conditions for better oil yield. The bio-oil collected from the catalyzed and non-catalyzed pyrolytic reactions was analyzed by gas chromatography mass spectrometry (GCMS). Catalytic pyrolysis resulted in the production of bio-oil consisting of 15 components ranging from C3 to C18 with a high percentage of fuel range benzene derivatives. Non-catalytic pyrolysis produced bio-oil that consists of 58 components ranging from C3 to C24; however, the number and quantity of fuel range hydrocarbons were lower than in the catalyzed products. The pyrolysis reaction was studied kinetically for both samples using thermogravimetry at heating rates of 5, 10, 15 and 20 °C/min in the temperature range 20−600 °C. The activation energies and pre-exponential factors wer... [more]

An experimental study of a hydrogen-containing jet’s impact on a palladium-based catalyst in an air atmosphere was carried out. High-intensity temperature fluctuations on the catalyst surface are obtained in the case when large-scale vortex structures are contained in the jet. These superstructures have a longitudinal size of 20−30 initial jet diameters and a transverse size of about 3−4 diameters. To form such structures, it is necessary to use long, round tubes in the Reynolds number range of 2000−3000 as a source of the impinging jet when a laminar-turbulent transition occurs in the channel according to the intermittency scenario. This effect was obtained at a low hydrogen content in the mixture (XH2 = 3…15%) and a low initial temperature of the catalyst (180 °C). It is shown that the smallest temperature fluctuations are obtained for the laminar flow in the tube (<1.5%), and they are more significant (<4%) for the turbulent regime at low Reynolds numbers (Re < 6000). The g... [more]

Given the increase in population and energy demand worldwide, alternative methods have been adopted for the production of hydrogen as a clean energy source. This energy offers an alternative energy source due to its high energy content, and without emissions to the environment. In this bibliometric analysis of energy production using electrolysis and taking into account the different forms of energy production. In this analysis, it was possible to evaluate the research trends based on the literature in the Scopus database during the years 2011−2021. The results showed a growing interest in hydrogen production from electrolysis and other mechanisms, with China being the country with the highest number of publications and the United States TOP in citations. The trend shows that during the first four years of this study (2011−2014), the average number of publications was 74 articles per year, from 2015 to 2021 where the growth is an average of 209 articles, the journal that published the... [more]

In this paper, the effect of rotating magnetic fields on hydrogen generation from water electrolysis is analyzed, aiming to provide a research reference for hydrogen production and improving hydrogen production efficiency. The electrolytic environment is formed by alkaline solutions and special electrolytic cells. The two electrolytic cells are connected to each other in the form of several pipes. The ring magnets are used to surround the pipes and rotate the magnets so that the pipes move relative to the magnets within the ring magnetic field area. Experimentally, the electrolysis reaction of an alkaline solution was studied by using a rotating magnetic field, and the effect of magnetic field rotation speed on the electrolysis reaction was analyzed using detected voltage data. The experimental phenomenon showed that the faster the rotation speed of the rotating magnetic field, the faster the production speed of hydrogen gas.

To become sustainable, the production of electricity has been oriented towards the adoption of local and renewable sources. Distributed electric and thermal energy generation is more suitable to avoid any possible waste, and the Micro Gas Turbine (MGT) can play a key role in this scenario. Due to the intrinsic properties and the high flexibility of operation of this energy conversion system, the exploitation of alternative fuels and the integration of the MGT itself with other energy conversion systems (solar field, ORC, fuel cells) represent one of the most effective strategies to achieve higher conversion efficiencies and to reduce emissions from power systems. The present work aims to review the results obtained by the researchers in the last years. The different technologies are analyzed in detail, both separately and under a more complete view, considering two or more solutions embedded in micro-grid configurations.

Solid oxide cells represent one of the most efficient and promising electrochemical technologies for hydrogen energy conversion. Understanding and monitoring degradation is essential for their full development and wide diffusion. Techniques based on electrochemical impedance spectroscopy and distribution of relaxation times of physicochemical processes occurring in solid oxide cells have attracted interest for the operando diagnosis of degradation. This research paper aims to validate the methodology developed by the authors in a previous paper, showing how such a diagnostic tool may be practically implemented. The validation methodology is based on applying an a priori known stress agent to a solid oxide cell operated in laboratory conditions and on the discrete measurement and deconvolution of electrochemical impedance spectra. Finally, experimental evidence obtained from a fully operando approach was counterchecked through ex-post material characterization.

Biomass gasification for energy purposes has several advantages, such as the mitigation of global warming and national energy independency. In the present work, the data from an innovative and intensified steam/oxygen biomass gasification process, integrating a gas filtration step directly inside the reactor, are presented. The produced gas at the outlet of the 1 MWth gasification pilot plant was analysed in terms of its main gaseous products (hydrogen, carbon monoxide, carbon dioxide, and methane) and contaminants. Experimental test sets were carried out at 0.25−0.28 Equivalence Ratio (ER), 0.4−0.5 Steam/Biomass (S/B), and 780−850 °C gasification temperature. Almond shells were selected as biomass feedstock and supplied to the reactor at approximately 120 and 150 kgdry/h. Based on the collected data, the in-vessel filtration system showed a dust removal efficiency higher than 99%-wt. A gas yield of 1.2 Nm3dry/kgdaf and a producer gas with a dry composition of 27−33%v H2, 23−29%v CO, 3... [more]

The use of lignocellulosic biomass to obtain biofuels and chemicals produces a large amount of lignin as a byproduct. Lignin valorization into chemicals needs efficient conversion processes to be developed. In this work, hydrocracking of organosolv lignin was performed by using nickel Raney catalyst. Organosolv lignin was obtained from the pretreatment of eucalyptus wood at 170 °C for 1 h by using 1/100/100 (w/v/v) ratio of biomass/oxalic acid solution (0.4% w/w)/1-butanol. The resulting organic phase of lignin in 1-butanol was used in hydrogenation tests. The conversion of lignin was carried out with a batch reactor equipped with a 0.3 L vessel with adjustable internal stirrer and heat control. The reactor was pressurized at 5 bar with hydrogen at room temperature, and then the temperature was raised to 250 °C and kept for 30 min. Operative conditions were optimized to achieve high conversion in monomers and to minimize the loss of solvent. At the best performance conditions, about 10... [more]

Hydrogen is mainly produced by steam reforming of natural gas, a nonrenewable resource. Alternative and renewable routes for hydrogen production play an important role in reducing dependence on oil and minimizing the emission of greenhouse gases. In this work, butanol, a model compound of bio-oil, was employed for hydrogen production by steam reforming. The reaction was evaluated for 30 h in a tubular quartz reactor at 500 °C, atmospheric pressure, GHSV of 500,000 h−1, and an aqueous solution feed of 10% v/v butanol. For this reaction, catalysts with 20 wt.% NiO were prepared by wet impregnation using three supports: γ-alumina and alumina modified with 10 wt.% of cerium and lanthanum oxides. Both promoters increased the reduction degree of the catalysts and decreased catalyst acidity, which is closely related to coke formation and deactivation. Ni/La2O3−Al2O3 presented a higher nickel dispersion (14.6%) which, combined with other properties, led to a higher stability, higher mean hydro... [more]

This article presents the results of the development of membrane-catalytic methods for obtaining purified hydrogen of various degrees of purity required for feeding high-, medium-, and low-temperature fuel cells. In order to conduct this, porous ceramic catalytic converters were obtained using self-propagating high-temperature synthesis. These converters are suitable for high-speed processes for producing synthesis gas with different carbon monoxide content (0.08−0.1 vol. %), which can be used to feed fuel cells of various types. Using a hybrid catalytic membrane reactor, in which the stage of catalytic conversion of organic substrates was combined with the stage of selective extraction of ultrapure hydrogen (content of H2 was not less than 99.9999 vol. %) from the reaction zone, combined carbon dioxide and steam reforming of organic substrates of various origins were carried out. The result of the work was the creation of a prototype of a small-sized electric generator plant in which... [more]

The graphitic carbon nitride (g-C3N4) is a class of two-dimensional layered material. The ever-growing research on this fascinating material is due to its unique visible light absorption, surface, electrocatalytic, and other physicochemical properties that can be useful to different energy conversion and storage applications. Photoelectrochemical (PEC) water splitting reaction is one of the promising applications of g-C3N4, wherein it acts as a durable catalyst support material. Very recently, the construction of g-C3N4-based binary and ternary heterostructures exhibited superior PEC water splitting performance owing to its reduced reunion of e-/h+ pairs and the fast transfer of charge carriers at the heterostructure interface. This review compiles the recent advances and challenges on g-C3N4-based heterostructured photocatalysts for the PEC water splitting reaction. After an overview of the available literature, we presume that g-C3N4-based photocatalysts showed enhanced PEC water spl... [more]

The paper investigates the stability and bifurcation phenomena that can occur in membrane reactors for the production of hydrogen by ammonia decomposition. A simplified mixed model of the membrane reactor is studied and two expressions of hydrogen permeation are investigated. The effect of the model design and operating parameters on the existence of steady state multiplicity is discussed. In this regard, it is shown that the adsorption-inhibition effect caused by the competitive adsorption of ammonia can lead to the occurrence of multiple steady states in the model. The steady state multiplicity exists for a wide range of feed ammonia concentration and reactor residence time. The effect of the adsorption constant, the membrane surface area and its permeability on the steady state multiplicity is delineated. The analysis also shows that no Hopf bifurcation can occur in the studied model.

An ultrasonic spray pyrolysis (USP) device consists of an evaporation and two reaction zones of equal length, into which an aerosol with a precursor compound enters, and where nanoparticles are formed in the final stage. As part of this research, we simulated the geometry of a side inlet, where the reaction gas (H2) enters into the reaction tube of the device by using numerical methods. Mixing with the carrier gas (N2) occurs at the entry of the H2. In the initial part, we performed a theoretical calculation with a numerical simulation using ANSYS CFX, while the geometries of the basic and studied models were prepared with Solidworks. The inlet geometry of the H2 included a study of the position and radius of the inlet with respect to the reaction tube of the USP device, as well as a study of the angle and diameter of the inlet. In the simulation, we chose the typical flows of both gases (N2, H2) in the range of 5 L/min to 15 L/min. The results show that the best geometry is with the H... [more]

To improve the reactor efficiency, this study investigated the influence of temperature on the biological hydrogen methanation (BHM) in trickle-bed reactors (TBR). Rising temperatures increase the metabolic activity of methanogenic microorganisms, thus leading to higher reactor specific methane formation rates (MFR). In order to quantify the potential for improved performance, experiments with four different operating temperatures ranging from 40 to 55 °C were carried out. Methane content increased from 88.29 ± 2.12 vol % at 40 °C to 94.99 ± 0.81 vol % at 55 °C with a stable biological process. Furthermore, a reactor specific methane formation rate (MFR) of up to 8.85 ± 0.45 m³ m−3 d−1 was achieved. It could be shown that the microorganisms were able to adapt to higher temperatures within hours. The tests showed that TBR performance with regard to BHM can be significantly increased by increasing the operating temperature.

Climate change primarily caused by the greenhouse gases emitted as a result of the consumption of carbon-based fossil fuels is considered one of the biggest challenges that humanity has ever faced. Moreover, the Ukrainian crisis in 2022 has complicated the global energy and food status quo more than ever. The permanency of this multifaceted fragility implies the need for increased efforts to have energy independence and requires long-term solutions without fossil fuels through the use of clean, zero-carbon renewables energies. Hydrogen technologies have a strong potential to emerge as an energy eco-system in its production-storage-distribution-utilization stages, with its synergistic integration with solar-wind-hydraulic-nuclear and other zero-carbon, clean renewable energy resources, and with the existing energy infrastructure. In this paper, we provide a global review of hydrogen energy need, related policies, practices, and state of the art for hydrogen production, transportation, s... [more]

Hydrogen is a promising fuel to decarbonize aviation, but macroeconomic studies are currently missing. Computable general equilibrium (CGE) models are suitable to conduct macroeconomic analyses and are frequently employed in hydrogen and aviation research. The main objective of this paper is to investigate existing CGE studies related to (a) hydrogen and (b) aviation to derive a macroeconomic research agenda for hydrogen-powered aviation. Therefore, the well-established method of systematic literature review is conducted. First, we provide an overview of 18 hydrogen-related and 27 aviation-related CGE studies and analyze the literature with respect to appropriate categories. Second, we highlight key insights and identify research gaps for both the hydrogen- and aviation-related CGE literature. Our findings comprise, inter alia, hydrogen’s current lack of cost competitiveness and the macroeconomic relevance of air transportation. Research gaps include, among others, a stronger focus on... [more]

Global climate policy commitments are encouraging the development of EU energy policies aimed at paving the way for cleaner energy systems. This article reviews key decarbonization drivers for Italy considering higher environmental targets from recent European Union climate policies. Energy efficiency, the electrification of final consumption, the development of green fuels, increasing the share of renewable energy sources in the electric system, and carbon capture and storage are reviewed. A 2030 scenario is designed to forecast the role of decarbonization drivers in future energy systems and to compare their implementation with that in the current situation. Energy efficiency measures will reduce final energy consumption by 15.6%, as primary energy consumption will decrease by 19.8%. The electrification of final consumption is expected to increase by 6.08%. The use of green fuels is estimated to triple as innovative fuels may go to market at scale to uphold the ambitious decarbonizat... [more]

Hydrogen can be considered an innovative fuel that will revolutionize the energy sector and enable even more complete use of the potential of renewable sources. The aim of the paper is to present the challenges faced by companies and economies that will produce and use hydrogen. Thanks to the use of hydrogen in the energy, transport and construction sectors, it will be possible to achieve climate neutrality by 2050. By 2050, global demand for hydrogen will increase to 614 million metric tons a year, and thanks to the use of hydrogen in energy, transport and construction, it will be possible to achieve climate neutrality. Depending on the method of hydrogen production, the processes used and the final effects, several groups can be distinguished, marked with different colors. It is in this area of obtaining friendly hydrogen that innovative possibilities for its production open up. The costs of hydrogen production are also affected by network fees, national tax systems, availability and... [more]

Hydrogen is emerging as a new energy vector outside of its traditional role and gaining more recognition internationally as a viable fuel route. This review paper offers a crisp analysis of the most recent developments in hydrogen production techniques using conventional and renewable energy sources, in addition to key challenges in the production of Hydrogen. Among the most potential renewable energy sources for hydrogen production are solar and wind. The production of H2 from renewable sources derived from agricultural or other waste streams increases the flexibility and improves the economics of distributed and semi-centralized reforming with little or no net greenhouse gas emissions. Water electrolysis equipment driven by off-grid solar or wind energy can also be employed in remote areas that are away from the grid. Each H2 manufacturing technique has technological challenges. These challenges include feedstock type, conversion efficiency, and the need for the safe integration of H... [more]

Hydrogen is expected to be a next-generation energy source that does not emit carbon dioxide, but when used as a fuel, the issue is the increase in the amount of NOx that is caused by the increase in flame temperature. In this study, we experimentally investigated NOx emissions rate when hydrogen was burned in a hydrocarbon gas burner, which is used in a wide temperature range. As a result of the experiments, the amount of NOx when burning hydrogen in a nozzle mixed burner was twice as high as when burning city gas. However, by increasing the flow velocity of the combustion air, the amount of NOx could be reduced. In addition, by reducing the number of combustion air nozzles rather than decreasing the diameter of the air nozzles, a larger recirculation flow could be formed into the furnace, and the amount of NOx could be reduced by up to 51%. Furthermore, the amount of exhaust gas recirculation was estimated from the reduction rate of NOx, and the validity was confirmed by the relation... [more]

In the context of hydrogen production from biomass or organic waste with dark fermentation, this study analysed 55 studies (339 experiments) in the literature looking for the effect of operating parameters on the process performance of dark fermentation. The effect of substrate concentration, pH, temperature, and residence time on hydrogen yield, productivity, and content in the biogas was analysed. In addition, a linear regression model was developed to also account for the effect of nature and pretreatment of the substrate, inhibition of methanogenesis, and continuous or batch operating mode. The analysis showed that the hydrogen yield was mainly affected by pH and residence time, with the highest yields obtained for low pH and short residence time. High hydrogen productivity was favoured by high feed concentration, short residence time, and low pH. More modest was the effect on the hydrogen content. The mean values of hydrogen yield, productivity, and content were, respectively, 6.4... [more]