Search Results (48)

The surge in photovoltaic (PV) power generation has made it increasingly difficult to integrate the intermittent PV industry into the power grid while maintaining grid stability. The solution is to use the seasonal surplus of PV electricity to produce “green” hydrogen through water electrolysis and then use the hydrogen as an energy source or as a reactant in chemical processes in the chemical industry to produce value-added products. However, the development of advanced hydrogen storage technologies to ensure the safe handling, transportation, and distribution of H₂ is a major issue. The use of stable liquid organic hydrogen carriers (LOHCs) has emerged as a suitable technology for hydrogen storage. This review highlights prospective LOHC technologies based on reversible catalytic hydrogenation–dehydrogenation cycles of liquid organic molecules for hydrogen storage and release under mild temperature and pressure conditions. The state-of-the-art LOHC systems are critically reviewed, highlighting the most effective heterogeneous catalytic systems. Full article

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 cost-effective 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, cryo-compressed 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 cost-effectiveness, and accelerate the deployment of hydrogen as a clean energy vector. Full article

Increasing energy demand and limited non-renewable energy resources have raised energy security concerns within the European Union. With the EU’s commitment to becoming the first climate-neutral continent, transitioning to renewable energy sources has become essential. While wind and solar energy are intermittent, consistent and reliable green energy sources, such as biogas and biomethane, offer promising alternatives. Biogas and biomethane production from biomass address key challenges, including grid stability (“supply on demand”), decentralized energy production, energy density, and efficient storage and transportation via existing natural gas infrastructure. This study examines technologies for converting woody biomass into biomethane and proposes a conceptual design utilizing the best available technologies. The system, situated in Slovenia’s Kočevje region—one of Europe’s richest forest habitats—was scaled based on the availability of low-quality woody biomass unsuitable for other applications. Combining biomass gasification, catalytic methanation, and biomethanation, supplemented by hydrogen from electrolysis, provides an effective method for converting wood to biomethane. Despite the system’s complexity and current technological limitations in energy efficiency, the findings highlight biomethane’s potential as a reliable energy carrier for domestic and industrial applications. Full article

For decades, fossil fuels have been the backbone of reliable energy systems, offering unmatched energy density and flexibility. However, as the world shifts toward renewable energy, overcoming the limitations of intermittent power sources requires a bold reimagining of energy storage and integration. Power-to-X (PtX) technologies, which convert excess renewable electricity into storable energy carriers, offer a promising solution for long-term energy storage and sector coupling. Recent advancements in machine learning (ML) have revolutionized PtX systems by enhancing efficiency, scalability, and sustainability. This review provides a detailed analysis of how ML techniques, such as deep reinforcement learning, data-driven optimization, and predictive diagnostics, are driving innovation in Power-to-Gas (PtG), Power-to-Liquid (PtL), and Power-to-Heat (PtH) systems. For example, deep reinforcement learning has improved real-time decision-making in PtG systems, reducing operational costs and improving grid stability. Additionally, predictive diagnostics powered by ML have increased system reliability by identifying early failures in critical components such as proton exchange membrane fuel cells (PEMFCs). Despite these advancements, challenges such as data quality, real-time processing, and scalability remain, presenting future research opportunities. These advancements are critical to decarbonizing hard-to-electrify sectors, such as heavy industry, transportation, and aviation, aligning with global sustainability goals. Full article

It is well known that the widespread utilization of fossil fuels contributes to climate change, so exploring new sustainable energy sources is more important than ever for energy transition pathways. The variability and intermittency of solar and wind sources are of concern. Hydrogen (H₂) utilization as an energy carrier can address this issue. The technology for producing hydrogen from biomass gasification has not yet reached a high level of technological maturity. The main novelty of this work is to evaluate the state of the art of the technologies for producing H₂ from solid biomass, taking into account technological, economic, and environmental indicators and the results of a bibliometric study, and also the calculation of the technical potential for hydrogen production through biomass gasification on a worldwide and Brazilian scale. The most frequently mentioned technology to boost H₂ production efficiency is the addition of catalysts to the gasifier. Primary catalyst utilized in biomass gasification for hydrogen enhancing enhancement, such as olivine, CaO, and CeO₂-Ni-CaO are reviewed in the article. As a result, the syngas had an H₂ content rise of 511%, 659.6%, and 853.4%, respectively. According to the reviewed literature, the levelized cost of hydrogen production can reach an average value of USD3.15/kg of H₂, and the average yield is 0.1 kg-H₂/kg-biomass. The worldwide potential for hydrogen production from solid biomass in an optimal trends scenario for 2050 is estimated to be 45.03 EJ, and Brazil’s potential is 6.5 EJ. Full article

Background: The issue of renewable energy (RE) source intermittency, such as wind and solar, along with the geographically uneven distribution of the global RE potential, makes it imperative to establish an energy transport medium to balance the energy demand and supply areas. A promising energy vector to address this situation is hydrogen, which is considered a clean energy carrier for various mobile and portable applications. Unfortunately, at standard pressure and temperature, its energy content per volume is very low (0.01 kJ/L). This necessitates alternative storage technologies to achieve reasonable capacities and enable economically viable long-distance transportation. Among the hydrogen storage technologies using chemical methods, liquid organic hydrogen carrier (LOHC) systems are considered a promising solution. They can be easily managed under ambient conditions, the H₂ storage/release processes are carbon-free, and the carrier liquid is reusable. However, the evolution of the proposals from the carrier liquid type and catalyst elemental composition point of view is scarcely studied, considering that both are critical in the performance of the system (operational parameters, kinetic of the reactions, gravimetric hydrogen content, and others) and impact in the final cost of the technology deployed. The latter is due to the use of the Pt group elements (PGEs) in the catalyst that, for example, have a high demand in the hydrogen production sector, particularly for polymer electrolyte membrane (PEM) water electrolysis. With that in mind, our objective was to examine the evolution and the focus of the research in recent years related to proposals of LOHCs and catalysts for hydrogenation and dehydrogenation reactions in LOHC systems which can be useful in defining routes/strategies for new participants interested in becoming involved in the development of this technology. Data sources: For this systematic review, we searched the SCOPUS database and forward and backward citations for studies published in the database between January 2011 and December 2022. Eligibility criteria: The criteria include articles which assessed or studied the effect of the type of catalyst, type of organic liquid, reactor design(s)/configuration(s), and modification of the reactor operational parameters, among others, over the performance of the LOHC system (de/hydrogenation reaction(s)). Data extraction and analysis: The relevant data from each reviewed study were collected and organized into a pre-designed table on an Excel spreadsheet, categorized by reference, year, carrier organic liquid, reaction (hydrogenation and/or dehydrogenation), investigated catalyst, and primary catalyst element. For processing the data obtained from the selected scientific publications, the data analysis software Orbit Intellixir was employed. Results: For the study, 233 studies were included. For the liquid carrier side, benzyltoluene and carbazole dominate the research strategies. Meanwhile, platinum (Pt) and palladium (Pd) are the most employed catalysts for dehydrogenation reactions, while ruthenium (Ru) is preferred for hydrogenation reactions. Conclusions: From the investigated liquid carrier, those based on benzyltoluene and carbazole together account for over 50% of the total scientific publications. Proposals based on indole, biphenyl, cyclohexane, and cyclohexyl could be considered to be emerging within the time considered in this review, and, therefore, should be monitored for their evolution. A great activity was detected in the development of catalysts oriented toward the dehydrogenation reaction, because this reaction requires high temperatures and presents slow H₂ release kinetics, conditioning the success of the implementation of the technology. Finally, from the perspective of the catalyst composition (monometallic and/or bimetallic), it was identified that, for the dehydrogenation reaction, the most used elements are platinum (Pt) and palladium (Pd), while, for the hydrogenation reaction, ruthenium (Ru) widely leads its use in the different catalyst designs. Therefore, the near-term initiatives driving progress in this field are expected to focus on the development of new or improved catalysts for the dehydrogenation reaction of organic liquids based on benzyltoluene and carbazole. Full article

The compound p-Nitrophenol (p-NP) is widely recognized as a highly toxic nitro-aromatic substance that urgently requires emission control. Reducing p-NP to p-aminophenol (p-AP) not only decreases its toxicity and mineralization properties in nature but also provides a key raw material for the chemical and pharmaceutical industries. The study used coal fly ash (CFA) as a catalyst carrier for synthesizing the p-NP reduction catalyst. Using CFA as an alternative option not only reduces costs but also achieves the objective of treating waste with waste compared to utilizing commercial solid materials for synthesizing catalysts. By employing hydrochloric acid and sodium hydroxide pretreatment methods, the physicochemical properties of CFA are significantly improved, enhancing the dispersion of palladium (Pd) nanoparticles. The structural features of the prepared samples were characterized using various surface analysis techniques, and both intermittent and continuous modes were experimentally tested for the model catalytic reaction involving the sodium borohydride (NaBH₄)-mediated reduction of p-NP. The results demonstrate that CFA has potential in wastewater treatment. Full article

Owing to the massive expansion and intermittent nature of renewable power, green hydrogen production, storage, and transportation technologies with improved economic returns need to be developed. Moreover, the slowness of the dehydrogenation reaction is a primary barrier to the commercialization of liquid organic hydrogen carrier (LOHC) technology. The present study focused on increasing the speed of dehydrogenation, resulting in the proposal of a triple-loop dehydrogenation system comprising reaction, heating, and chilling loops. The reactor has a rotating cage containing a packed bed of catalyst pellets, which is designed to enhance both heat and mass transfer by helping to detach precipitated hydrogen bubbles from the catalyst surface. In addition, the centrifugal force aids in isolating the gas phase from the LOHC liquid. A dehydrogenation experiment was conducted using the reaction and chilling loops, which revealed that the average hydrogen production rate during the first hour was 52.6 LPM (liter per minute) from 26.3 L of perhydro-dibenzyl-toluene with 1.5 kg of 0.5 wt% Pt/Al₂O₃ catalyst. This was approximately 48% more than the value predicted with the reaction kinetics measured with a small-scale plug flow dehydrogenation reactor with less than 1.0 g of 5.0 wt% Pt/Al₂O₃ catalyst. The concept, construction methods, and results of the preliminary gas infiltration, flow visualization, and reactor pumping experiments are also described in this paper. Full article

Due to the specificity, high efficiency, and gentleness of enzyme catalysis, the industrial utilization of enzymes has attracted more and more attention. Immobilized enzymes can be recovered/recycled easily compared to their free forms. The primary benefit of immobilization is protection of the enzymes from harsh environmental conditions (e.g., elevated temperatures, extreme pH values, etc.). In this paper, catalase was successfully immobilized in a poly(aryl ether sulfone) carrier (PAES-C) with tunable pore structure as well as carboxylic acid side chains. Moreover, immobilization factors like temperature, time, and free-enzyme dosage were optimized to maximize the value of the carrier and enzyme. Compared with free enzyme, the immobilized-enzyme exhibited higher enzymatic activity (188.75 U g⁻¹, at 30 °C and pH 7) and better thermal stability (at 60 °C). The adsorption capacity of enzyme protein per unit mass carrier was 4.685 mg. Hydrogen peroxide decomposition carried out in a continuous-flow reactor was selected as a model reaction to investigate the performance of immobilized catalase. Immobilized-enzymes showed a higher conversion rate (90% at 8 mL/min, 1 h and 0.2 g) compared to intermittent operation. In addition, PAES-C has been synthesized using dichlorodiphenyl sulfone and the renewable resource bisphenolic acid, which meets the requirements of green chemistry. These results suggest that PAES-C as a carrier for immobilized catalase could improve the catalytic activity and stability of catalase, simplify the separation of enzymes, and exhibit good stability and reusability. Full article

Mycoplasma bovis (M. bovis) is a significant pathogen responsible for highly transmissible mastitis in cattle globally. It primarily spreads through colostrum, milk, and semen. Cows with persistent infections act as carriers, intermittently releasing the pathogen, making their milk a pivotal factor in infection transmission. Given the limited seroprevalence surveys in Serbia, this study aimed to detect M. bovis presence in bulk tank milk (BTM), determine route shedding, and evaluate infection risks. BTM samples were collected from 115 dairy farms across Serbia, with M. bovis DNA detected in 11 out of the 115 samples by real-time PCR. Additionally, M. bovis was detected in 1.30% of nasal swabs sampled from apparently healthy animals. A univariate analysis of the risk factors associated with M. bovis presence in the BTM samples revealed correlations with factors such as the breed, farm seropositivity, pre-milking and post-milking disinfection practices, farm type, cow population, milk yield, number of cows in the BTM samples, and parity. Seropositive farms exhibited the highest likelihood of M. bovis presence in milk. Moreover, pre- and post-milking disinfection practices and highly productive cows yielding over 8000 L of milk were identified as risk factors for PCR-positive BTM. In a multivariable mixed regression analysis, a risk factor for the presence of M. bovis infection in the BTM sample was the Holstein breed. These findings underscore a relatively high prevalence of M. bovis in BTM within Serbian dairy farms, suggesting a potential risk for M. bovis spreading through milk and oral route of calves’ infection. Full article

As the global energy landscape transitions towards a more sustainable future, hydrogen has emerged as a promising energy carrier due to its potential to decarbonize various sectors. However, the economic competitiveness of hydrogen production by water electrolysis strongly depends on renewable energy source (RES) availability. Thus, it is necessary to overcome the challenges related to the intermittent nature of RESs. This paper presents a comprehensive techno-economic analysis of complementing green hydrogen production with grid electricity. An evaluation model for the levelized cost of hydrogen (LCOH) is proposed, considering both CO₂ emissions and the influence of RES fluctuations on electrolyzers. A minimum load restriction is required to avoid crossover gas. Moreover, a new operation strategy is developed for hydrogen production plants to determine optimal bidding in the grid electricity market to minimize the LCOH. We evaluate the feasibility of the proposed approach with a case study based on data from the Kyushu area in Japan. The results show that the proposed method can reduce the LCOH by 11% to 33%, and increase hydrogen productivity by 86% to 140%, without significantly increasing CO₂ emission levels. Full article

This work discusses the current scenario and future growth of electrochemical energy devices, such as water electrolyzers and fuel cells. It is based on the pivotal role that hydrogen can play as an energy carrier to replace fossil fuels. Moreover, it is envisaged that the scaled-up and broader deployment of the technologies can hold the potential to address the challenges associated with intermittent renewable energy generation. From a sustainability perspective, this synergy between hydrogen and electricity from renewable sources is particularly attractive: electrolyzers convert the excess energy from renewables into green hydrogen, and fuel cells use this hydrogen to convert it back into electricity when it is needed. Although this transition endorses the ambitious goal to supply greener energy for all, it also entails increased demand for the materials that are essential for developing such cleaner energy technologies. Herein, several economic and environmental issues are highlighted, besides a critical overview regarding each technology. The aim is to raise awareness and provide the reader (a non-specialist in the field) with useful resources regarding the challenges that need to be overcome so that a green hydrogen energy transition and a better life can be fully achieved. Full article

The production of hydrogen-based dense energy carriers (DECs) has been proposed as a combined solution for the storage and dispatch of power generated through intermittent renewables. Frameworks that model and optimize the production, storage, and dispatch of generated energy are important for data-driven decision making in the energy systems space. The proposed multiperiod framework considers the evolution of technology costs under different levels of promotion through research and targeted policies, using the year 2021 as a baseline. Furthermore, carbon credits are included as proposed by the 45Q tax amendment for the capture, sequestration, and utilization of carbon. The implementation of the mixed-integer linear programming (MILP) framework is illustrated through computational case studies to meet set hydrogen demands. The trade-offs between different technology pathways and contributions to system expenditure are elucidated, and promising configurations and technology niches are identified. It is found that while carbon credits can subsidize carbon capture, utilization, and sequestration (CCUS) pathways, substantial reductions in the cost of novel processes are needed to compete with extant technology pathways. Further, research and policy push can reduce the levelized cost of hydrogen (LCOH) by upwards of 2 USD/kg. Full article

Autonomous navigation and localization are the foundations of unmanned intelligent systems, therefore, continuous, stable, and reliable position services in unknown environments are especially important for autonomous navigation and localization. Aiming at the problem where GNSS cannot continuously localize in complex environments due to weak signals, poor penetration ability, and susceptibility to interference and that visual navigation and localization are only relative, this paper proposes a GNSS-aided visual dynamic localization method that can provide global localization services in unknown environments. Taking the three frames of images and their corresponding GNSS coordinates as the constraint data, the GNSS coordinate system and world coordinate system transformation matrix are obtained through horn coordinate transformation, and the relative positions of the subsequent image sequences in the world coordinate system are obtained through epipolar geometry constraints, homography matrix transformations, and 2D–3D position and orientation solving, which ultimately yields the global position data of unmanned carriers in GNSS coordinate systems when GNSS is temporarily unavailable. Both the dataset validation and measured data validation showed that the GNSS initial-assisted positioning algorithm could be applied to situations where intermittent GNSS signals exist, and it can provide global positioning coordinates with high positioning accuracy in a short period of time; however, the algorithm would drift when used for a long period of time. We further compared the errors of the GNSS initial-assisted positioning and GNSS continuous-assisted positioning systems, and the results showed that the accuracy of the GNSS continuous-assisted positioning system was two to three times better than that of the GNSS initial-assisted positioning system, which proved that the GNSS continuous-assisted positioning algorithm could maintain positioning accuracy for a long time and it had good reliability and applicability in unknown environments. Full article

Heterogeneous catalysis ozonation technology can achieve efficient treatment of refractory organics in industrial wastewater due to its advantages including fast reaction speed, high ozone utilization rate, low catalyst loss and low cost and has a broad application prospect. The development of efficient and stable heterogeneous ozone catalytic materials is the key to promoting the application of this technology in industrial wastewater treatment. Based on this, an Mn/Al₂O₃ catalyst was successfully prepared by impregnation method using 3~5 mm γ-Al₂O₃ pellets as the carrier, and the surface morphology characteristics, elemental state and phase composition of the catalyst were investigated by SEM-EDX, XRD and XPS. The results showed that Mn was successfully loaded onto the surface of a γ-Al₂O₃ carrier. On this basis, intermittent single factor experiments were conducted to systematically investigate the effects of catalyst dosage, pH, and ozone concentration on the catalytic performance of phenol. It was found that under the optimal conditions of a catalyst dosage of 100 g (filling height of 14.2 cm), pH of 7, and ozone concentration of 4 mg/L (gas volume of 1 L/min), the removal efficiencies of 800 mL 100 mg/L of simulated phenol wastewater reached 100% after 60 min of reaction. The removal efficiencies of the catalyst still reached 95.8% within 60 min even after the fifth cycle reaction, indicating excellent reusability of the catalyst. This work provides a facile strategy for the treatment of refractory organics in industrial wastewater. Full article