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The effect of boron substitution (x = 0, 0.005, 0.010, 0.015) on the structural and magnetic properties of Sm(Co(sub 0.86-x)Fe0.1Zr0.04B(sub x))7.5 and Sm(Co(sub 0.74-x)Fe0.1Cu0.12Zr0.04B(sub x))7.5 melt-spun samples is examined. Coercivity of 16.3 kOe was obtained for copper containing samples in as-spun ribbons with x = 0.015 while coercivity of 12 kOe was obtained in samples without copper after short annealing.

In this study, the effects of partial substitution of Fe, in the ZrFe 2 -system alloys, by Cr or V are presented. The two studied alloys, ZrFe 1.8 V 0.2 and ZrFe 1.8 Cr 0.2 , have been synthesized by high frequency induction-levitation melting under inert Ar atmosphere. The induction furnace was equipped with a water-cooled copper crucible that permits the rapid solidification of the alloy after the melting. The crystal structures of the investigated alloys have been studied by the Rietveld analysis of the obtained X-ray diffraction (XRD) patterns. The microstructure has been observed by a scanning electron microscope (SEM) on polished samples of the alloys. Their hydriding properties have been studied with a high pressure Sievert's type apparatus, up to 200 bar. All pressure–composition–temperature (PCT) measurements have been obtained at 20, 60 and 90 °C. Two high temperature activation cycles have been conducted prior to PCT measurements. The results showed almost the same uptake for the alloys after identical activation and lowering of the plateau pressure in both cases. [ABSTRACT FROM AUTHOR]

This paper presents the results of numerical simulations examining the thermodynamic processes during hydraulic hydrogen compression, using COMSOL Multiphysics® 6.0. These simulations focus on the application of hydrogen compression systems, particularly in hydrogen refueling stations. The computational models employ the CFD and heat transfer modules, along with deforming mesh technology, to simulate gas compression and heat transfer dynamics. The superposition method was applied to simplify the analysis of hydrogen and liquid piston interactions within a stainless-steel chamber, accounting for heat exchange between the hydrogen, the oil (working fluid), and the cylinder walls. The study investigates the effects of varying compression stroke durations and initial hydrogen pressures, providing detailed insights into temperature distributions and energy consumption under different conditions. The results reveal that the upper region of the chamber experiences significant heating, highlighting the need for efficient cooling systems. Additionally, the simulations show that longer compression strokes reduce the power requirement for the liquid pump, offering potential for optimizing system design and reducing equipment costs. This study offers crucial data for enhancing the efficiency of hydraulic hydrogen compression systems, paving the way for improved energy consumption and thermal management in high-pressure applications. [ABSTRACT FROM AUTHOR]

Over the last few years, hydrogen has emerged as a promising solution for problems related to energy sources and pollution concerns. The integration of hydrogen in the transport sector is one of the possible various applications and involves the implementation of hydrogen refueling stations (HRSs). A key obstacle for HRS deployment, in addition to the need for well-developed technologies, is the economic factor since these infrastructures require high capital investments costs and are largely dependent on annual operating costs. In this study, we review hydrogen's application as a fuel, summarizing the principal systems involved in HRS, from production to the final refueling stage. In addition, we also analyze the main equipment involved in the production, compression and storage processes of hydrogen. The current work also highlights the main refueling processes that impact energy consumption and the methodologies presented in the literature for energy management strategies in HRSs. With the aim of reducing energy costs due to processes that require high energy consumption, most energy management strategies are based on the use of renewable energy sources, in addition to the use of the power grid. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) have become an integral part of modern life, serving both civilian and military applications across various sectors. However, existing power supply systems, such as batteries, often fail to provide stable, long-duration flights, limiting their applications. Previous studies have primarily focused on battery-based power, which offers limited flight endurance due to lower energy densities and higher system mass. Proton exchange membrane (PEM) fuel cells present a promising alternative, providing high power and efficiency without noise, vibrations, or greenhouse gas emissions. Due to hydrogen's high specific energy, which is substantially higher than that of combustion engines and battery-based alternatives, UAV operational time can be significantly extended. This paper investigates the potential of PEM fuel cells as an alternative power source for electric propulsion in UAVs. This study introduces an adaptive, fully functioning PEM fuel cell model, developed using a reduced-order modeling approach and optimized for UAV applications. This research demonstrates that PEM fuel cells can effectively double the flight endurance of UAVs compared to traditional battery systems, achieving energy densities of around 1700 Wh/kg versus 150–250 Wh/kg for batteries. Despite a slight increase in system mass, fuel cells enable significantly longer UAV operations. The scope of this study encompasses the comparison of battery-based and fuel cell-based propulsion systems in terms of power, mass, and flight endurance. This paper identifies the limitations and optimal applications for fuel cells, providing strong evidence for their use in UAVs where extended flight time and efficiency are critical. [ABSTRACT FROM AUTHOR]

Hydrogen storage in general is an indispensable prerequisite for the introduction of a hydrogen energy-based infrastructure. In this respect, high-pressure metal hydride (MH) tank systems appear to be one of the most promising hydrogen storage techniques for automotive applications using proton exchange membrane (PEM) fuel cells. These systems bear the potential of achieving a beneficial compromise concerning the comparably large volumetric storage density, wide working temperature range, comparably low liberation of heat, and increased safety. The debatable term "unstable metal hydride" is used in the literature in reference to metal hydrides with high dissociation pressure at a comparably low temperature. Such compounds may help to improve the merits of high-pressure MH tank systems. Consequently, in the last few years, some materials for possible on-board applications in such tank systems have been developed. This review summarizes the state-of-the-art developments of these metal hydrides, mainly including intermetallic compounds and complex hydrides, and offers some guidelines for future developments. Since typical laboratory hydrogen uptake measurements are limited to 200 bar, a possible threshold for defining unstable hydrides could be a value of their equilibrium pressure of peq > 200 bar for T < 100 °C. However, these values would mark a technological future target and most current materials, and those reported in this review, do not fulfill these requirements and need to be seen as current stages of development toward the intended target. For each of the aforementioned categories in this review, special care is taken to not only cover the pioneering and classic research but also to portray the current status and latest advances. For intermetallic compounds, key aspects focus on the influence of partial substitution on the absorption/desorption plateau pressure, hydrogen storage capacity and hysteresis properties. For complex hydrides, the preparation procedures, thermodynamics and theoretical calculation are presented. In addition, challenges, perspectives, and development tendencies in this field are also discussed. [ABSTRACT FROM AUTHOR]

The application of hydrogen in heavy-duty vehicles or trains has been suggested as a promising solution to decarbonize the transportation sector. In this study, a one-dimensional engine modeling is employed to evaluate the potential of hydrogen as a fuel for railway applications. A turbocharged diesel engine is simulated as the baseline unit, and the results are validated with experimental data. The same engine is converted to become compatible with hydrogen through some modifications in the turbocharger group and the injection and ignition systems to preserve the performance of the baseline configuration. The findings show that the engine traction power is reduced from 600 to 400 kW, indicating an inferior performance for the hydrogen-fueled engine. The energy consumption of the hydrogen-fueled engine on a real train mission profile is almost two times the diesel version. However, our Life Cycle Assessment analysis with a Well-to-Wheel system boundary shows a 56% reduction in equivalent CO2 emissions for the engine fueled with photovoltaic-based green hydrogen. Substituting diesel with low-carbon hydrogen can decrease the train's carbon footprint from 4.27 to even less than 2 kg CO2 eq./km, suggesting that moderately modified engines are a promising solution for decarbonizing non-feasibly electrified railway sections. [ABSTRACT FROM AUTHOR]

In response to escalating environmental challenges, this research underscores the pivotal role of sustainable construction practices, particularly focusing on bioclimatic design as a foundational element within the realm of sustainable architecture and environmental upgrading of buildings, within the broader context of sustainable urban planning. The study delves into the perspectives of residents in Cyprus concerning bioclimatic building design. Employing a quantitative methodology, the investigation aims to comprehensively assess homeowner views on the benefits, motivations, concerns, and preferred techniques associated with bioclimatic design. By comprehending these perspectives and contextual factors, this study identifies obstacles hindering broader implementation and illuminates why adoption remains limited, despite the potential for substantial energy and emissions reductions. The research also examines the background of respondents, such as heating/cooling systems, energy expenses, and upgrade preferences, to provide essential context for the findings. A structured questionnaire was administered to a stratified sample of 150 pedestrians in the Pafos area, ensuring a representative cross-section of the local population. This method allowed for a robust examination of demographic influences on opinions and an in-depth analysis of the impact of residential characteristics. The findings reveal a substantial influence of cost considerations in shaping decisions related to residential property development and the renovation of existing structures, contributing to the limitation of widespread adoption across the island. This influence persists even as a majority of respondents express a readiness to undertake building energy upgrades, among which, the most popular actions include the installation of specialized glass, the replacement of traditional air conditioning units with inverters, and the adoption of energy-efficient lighting. The research culminates in the proposal that introducing financial incentives has the potential to enhance homeowner participation in bioclimatic and energy upgrades. This recommendation is particularly salient in the climatic context of Cyprus, where the implementation of solar control measures emerges as a promising avenue for bolstering energy efficiency. In considering the socio-economic dimensions implicit in these findings, it becomes evident that the interplay between financial considerations and sustainable construction practices is a critical aspect. The identified barriers underscore the necessity for nuanced strategies and policy frameworks that address the socio-economic dimensions of bioclimatic design adoption. In this context, the study contributes to the existing body of knowledge by shedding light on the intricate relationship between financial factors and sustainable architectural practices, offering implications for future research endeavors and potential avenues for policy interventions. [ABSTRACT FROM AUTHOR]

Featured Application: The results obtained in the study were used by the designers of the racing car with which the Transilvania University of Brașov participated in the Student Formula competitions. During car races, strong vibrations appear in the chassis of the vehicle, due to the high power created by the engine which are then transmitted and, therefore, affect the driver's condition. The study of these vibrations is a subject frequently addressed by researchers, analyzing the influence of different parameters on the forces to which the pilot's body or certain sensitive body parts are subjected. In this paper, we analyze the particular case of a racing car made to meet safety requirements in the event of an accident. For the analysis of the forced vibrations induced by the running track, the finite element method was used. This method proved to be a useful and stable modeling and analysis method, validated by practical applications. A standard-equipped racing car with a mannequin inside was studied. Once the natural frequencies of the structure were determined, the response of some points of the mannequin's body to the movement caused by the running track or the engine was analyzed. Modeling and discretization were performed using well-known classical procedures. The obtained results revealed the parameters that can negatively influence the body of the mannequin which were communicated to the design team. The conclusion of this study is a racing car that was successfully used in Formula Student competitions. [ABSTRACT FROM AUTHOR]

The efficient operation of a metal hydride reactor depends on the hydrogen sorption and desorption reaction rate. In this regard, special attention is paid to heat management solutions when designing metal hydride hydrogen storage systems. One of the effective solutions for improving the heat and mass transfer effect in metal hydride beds is the use of heat exchangers. The design of modern cylindrical-shaped reactors makes it possible to optimize the number of heat exchange elements, design of fins and cooling tubes, filter arrangement and geometrical distribution of metal hydride bed elements. Thus, the development of a metal hydride reactor design with optimal weight and size characteristics, taking into account the efficiency of heat transfer and metal hydride bed design, is the relevant task. This paper discusses the influence of different configurations of heat exchangers and metal hydride bed for modern solid-state hydrogen storage systems. The main advantages and disadvantages of various configurations are considered in terms of heat transfer as well as weight and size characteristics. A comparative analysis of the heat exchangers, fins and other solutions efficiency has been performed, which makes it possible to summarize and facilitate the choice of the reactor configuration in the future. [ABSTRACT FROM AUTHOR]

Electric vehicles (EVs) have become popular in the last decade because of their advantages compared to conventional vehicles. The market offers dozens of EV models in a large range of prices, performances, and specifications. This paper presents an expert system we developed to support sellers and customers in choosing an EV that matches the customers' specifications. The system enables ranking-specific EVs according to the customers' specifications and counting the number of mismatches. The paper analyzes a database of 53 different EVs, each with 22 different characteristics, enabling customers to choose the EV that best suits their most important specifications. Based on the customer's requirements and the principle of fuzzy sets, the system assigns a matching value to each criterion. These matching values are the input matrix for the TOPSIS procedure that ranks all the EVs according to their matching scores for a specific customer. The applicability of the proposed method is demonstrated for one customer with specific preferred EV requirements. A Python code of this method is also available herein. [ABSTRACT FROM AUTHOR]

The mass storage of hydrogen is a challenge considering large industrial applications and continuous distribution, e.g., for domestic use as a future energy carrier that respects the environment. For a long time, molecular hydrogen was stored and distributed, either as a gas (pressurized up to 75 MPa) or as a cryogenic liquid (20.4 K). Furthermore, the atomic storage of hydrogen in the solid-state form via metallic or covalent compounds is still the subject of intense research and limited to a small scale for some practical developments. In addition, other type H chemical storage routes are being tested, such as ammonia and LOHC (Liquid Organic Hydrogen Carrier), etc. In any case, the main constraint remains security. However, Hydrogen Solid State Storage (HSSS) using MgH2 bodies has been shown to be feasible in terms of process and safety. Furthermore, its intrinsic volumetric densification was proven to be much better performing with 106:70:45 kgH2/m3 for solid (RT):LH (20.4 K):gas (75 MPa), respectively. Very early on, fairly reactive MgH2-based pellets were produced (for max. ~27 tons/year) at McPhy Energy using a series of unique and self-built installations. Thus, the design of large instrumented reservoirs was undertaken thanks to fundamental research first carried out at the CNRS. So, prototypes of storage units from 100 to ~5500 kWh have been produced. However, McPhy took other routes a few years ago (smelting and refueling stations) because the HSSS market was not merging at that time. Today, a new operator, Jomi–Leman, therefore, decided to try the challenge again focusing on applications with on-site production and mass HSSS. [ABSTRACT FROM AUTHOR]

Due to its high hydrogen storage efficiency and safety, Mg/MgH2 stands out from many solid hydrogen storage materials and is considered as one of the most promising solid hydrogen storage materials. However, thermodynamic/kinetic deficiencies of the performance of Mg/MgH2 limit its practical applications for which a series of improvements have been carried out by scholars. This paper summarizes, analyzes and organizes the current research status of the hydrogen storage performance of Mg/MgH2 and its improvement measures, discusses in detail the hot studies on improving the hydrogen storage performance of Mg/MgH2 (improvement measures, such as alloying treatment, nano-treatment and catalyst doping), and focuses on the discussion and in-depth analysis of the catalytic effects and mechanisms of various metal-based catalysts on the kinetic and cyclic performance of Mg/MgH2. Finally, the challenges and opportunities faced by Mg/MgH2 are discussed, and strategies to improve its hydrogen storage performance are proposed to provide ideas and help for the next research in Mg/MgH2 and the whole field of hydrogen storage. [ABSTRACT FROM AUTHOR]

The retrofit of the most energy-intensive buildings represents an opportunity to improve their energy efficiency or to reduce their energy demand. This paper proposes combining computer-aided design (CAD) modeling and the use of energy efficiency software to build a methodology for calculating, visualizing and analyzing building parameters in order to provide retrofit scenarios. Five retrofit scenarios were implemented using the energy software, including the initial operating cost, capital cost and payback period to be evaluated. At the same time, a three-dimensional CAD model was created to perform daylighting and shading simulations to visualize and design the role of building orientation under actual use conditions. These retrofit scenarios were evaluated individually and then combined to examine their performance in terms of cost-effectiveness and energy efficiency. The simulation results show the importance of the building's orientation, as this directly affects the thermal properties of the walls and openings, as well as the daylighting areas. The simulation results were also used to define the parameters that affect the interoperability of the retrofit solutions. Finally, in addition to the significant reduction in calculation time, the coupling of the CAD software with the energy efficiency software allowed access to information that was not available at the outset. [ABSTRACT FROM AUTHOR]

The successful and fast start-up of proton exchange membrane fuel cells (PEMFCs) at subfreezing temperatures (cold start) is very important for the use of PEMFCs as energy sources for automotive applications. The effective thermal management of PEMFCs is of major importance. When hydrogen is stored in hydride-forming intermetallics, significant amounts of heat are released due to the exothermic nature of the reaction. This excess of heat can potentially be used for PEMFC thermal management and to accelerate the cold start. In the current work, this possibility is extensively studied. Three hydride-forming intermetallics are introduced and their hydrogenation behavior is evaluated. In addition, five thermal management scenarios of the metal hydride beds are studied in order to enhance the kinetics of the hydrogenation. The optimum combination of the intermetallic, hydrogenation behavior, weight and complexity of the thermal management system was chosen for the study of thermal coupling with the PEMFCs. A 1D GT-SUITE model was built to stimulate the thermal coupling of a 100 kW fuel cell stack with the metal hydride. The results show that the use of the heat from the metal hydride system was able to reduce the cold start by up to 8.2%. [ABSTRACT FROM AUTHOR]

Liquid organic hydrogen carriers (LOHCs) are an interesting alternative for hydrogen storage as the method is based on the reversibility of hydrogenation and dehydrogenation reactions to produce liquid and safe components at room temperature. As hydrogen storage involves a large amount of hydrogen and pure compounds, the design of a three-phase reactor requires the study of gas and liquid-phase kinetics. The gas-phase hydrogenation kinetics of LOHC γ-butyrolactone/1,4-butanediol on a copper-zinc catalyst are investigated here. The experiments were performed with data, taken from the literature, in the temperature and pressure ranges 200–240 °C and 25–35 bar, respectively, for a H2/γ-butyrolactone molar ratio at the reactor inlet of about 90. The best kinetic law takes into account the thermodynamic chemical equilibrium, is based on the associative hydrogen adsorption and is able to simulate temperature and pressure effects. For this model, the confidence intervals are at most 28% for the pre-exponential factors and 4% for the activation energies. Finally, this model will be included in a larger reactor model in order to evaluate the selectivity of the reactions, which may differ depending on whether the reaction takes place in the liquid or gas phase. [ABSTRACT FROM AUTHOR]

In the present scenario, much importance has been provided to hydrogen energy systems (HES) in the energy sector because of their clean and green behavior during utilization. The developments of novel techniques and materials have focused on overcoming the practical difficulties in the HES (production, storage and utilization). Comparatively, considerable attention needs to be provided in the hydrogen storage systems (HSS) because of physical-based storage (compressed gas, cold/cryo compressed and liquid) issues such as low gravimetric/volumetric density, storage conditions/parameters and safety. In material-based HSS, a high amount of hydrogen can be effectively stored in materials via physical or chemical bonds. In different hydride materials, Mg-based hydrides (Mg–H) showed considerable benefits such as low density, hydrogen uptake and reversibility. However, the inferior sorption kinetics and severe oxidation/contamination at exposure to air limit its benefits. There are numerous kinds of efforts, like the inclusion of catalysts that have been made for Mg–H to alter the thermodynamic-related issues. Still, those efforts do not overcome the oxidation/contamination-related issues. The developments of Mg–H encapsulated by gas-selective polymers can effectively and positively influence hydrogen sorption kinetics and prevent the Mg–H from contaminating (air and moisture). In this review, the impact of different polymers (carboxymethyl cellulose, polystyrene, polyimide, polypyrrole, polyvinylpyrrolidone, polyvinylidene fluoride, polymethylpentene, and poly(methyl methacrylate)) with Mg–H systems has been systematically reviewed. In polymer-encapsulated Mg–H, the polymers act as a barrier for the reaction between Mg–H and O2/H2O, selectively allowing the H2 gas and preventing the aggregation of hydride nanoparticles. Thus, the H2 uptake amount and sorption kinetics improved considerably in Mg–H. [ABSTRACT FROM AUTHOR]

Laser beam machining (LBM) has proven its applications and advantages over almost all the range of engineering materials. It offers its competences from macro-machining to micro- and nano-machining of simple-to-complex shapes. The hybrid approaches in laser ablation have demonstrated much improved results in terms of material removal rate, surface integrity, geometrical tolerances, thermal damage, metallurgical alterations, and many more. The flipside of LBM is the existence of universal problems associated with its thermal ablation mechanism. In order to alleviate or reduce the inherent problems of LBM, a massive research has been done during the past decade in order to build a relatively new route of laser-hybrid processes. This paper reviews the research work carried out so far in the area of LBM and its hybrid processes for different materials and shapes. The article also highlights the research gaps and future research directions in the context of laser and laser-hybrid ablation. [ABSTRACT FROM AUTHOR]

Abstract: Titanium borates show promising hydrogen storage characteristics. Structural relaxation around individual hydrogen atoms and the binding energies are studied by means of the density functional theory methods for a number of hydrogenated TiB2 , TiB and Ti2B structures. Starting with the possible symmetric hydrogen sites a random structure searching has been performed, in addition to locate all energetically stable adsorption sites. It is shown that for the three bulk compounds considered, the lowest binding energies are obtained for TiB2 (in the 0.3–1.8 eV range), the largest for Ti2B (in the 3.9–4.7 eV range), while for TiB they are intermediate (in the 2.8–3.5 eV range). Calculations performed on hydrogenated Ti2B result in two energetically stable sites for two different starting environments, suggesting a possible soft mode solution. [Copyright &y& Elsevier]

Hydrogen energy is a very attractive option in dealing with the existing energy crisis. For the development of a hydrogen energy economy, hydrogen storage technology must be improved to over the storage limitations. Compared with traditional hydrogen storage technology, the prospect of hydrogen storage materials is broader. Among all types of hydrogen storage materials, solid hydrogen storage materials are most promising and have the most safety security. Solid hydrogen storage materials include high surface area physical adsorption materials and interstitial and non-interstitial hydrides. Among them, interstitial hydrides, also called intermetallic hydrides, are hydrides formed by transition metals or their alloys. The main alloy types are A 2 B, AB, AB 2 , AB 3 , A 2 B 7 , AB 5 , and BCC. A is a hydride that easily forms metal (such as Ti, V, Zr, and Y), while B is a non-hydride forming metal (such as Cr, Mn, and Fe). The development of intermetallic compounds as hydrogen storage materials is very attractive because their volumetric capacity is much higher (80–160 kgH 2 m − 3 ) than the gaseous storage method and the liquid storage method in a cryogenic tank (40 and 71 kgH 2 m − 3 ). Additionally, for hydrogen absorption and desorption reactions, the environmental requirements are lower than that of physical adsorption materials (ultra-low temperature) and the simplicity of the procedure is higher than that of non-interstitial hydrogen storage materials (multiple steps and a complex catalyst). In addition, there are abundant raw materials and diverse ingredients. For the synthesis and optimization of intermetallic compounds, in addition to traditional melting methods, mechanical alloying is a very important synthesis method, which has a unique synthesis mechanism and advantages. This review focuses on the application of mechanical alloying methods in the field of solid hydrogen storage materials. [ABSTRACT FROM AUTHOR]

Hydrogen-induced disproportionation (HID) during the cycles of absorption and desorption leads to a serious decline in the storage capacity of the ZrCo alloy, which has been recognized as the biggest obstacle to its application. Therefore, the prerequisite of a ZrCo application is to solve its anti-disproportionation problem in the field of rapid hydrogen isotope storage. Beyond surface modification and nanoball milling, this work systematically reviews the method of element substitution, which can obviously improve the anti-disproportionation. From a micro angle, as hydrogen atoms that occupy the 8e site in the ZrCoH3 lattice are instable and are considered to be the driving force of disproportionation, researchers believe that element substitution by changing the occupation of hydrogen atoms at the 8e site can improve the anti-disproportionation of the alloy. At present, Ti/Nb substitutions for the Zr terminal among substitute elements have an excellent anti-disproportionation performance. In this work, up-to-date research studies on anti-disproportionation and its disproportionation mechanism of the ZrCo alloy are introduced by combining experiments and simulations. Moreover, the optimization of the alloy based on the occupation mechanism of 8e sites is expected to improve the anti-disproportionation of the ZrCo alloy. [ABSTRACT FROM AUTHOR]

In recent decades, the steady increase of energy consumption from building construction and operations cause atmospheric pollution and significant financial burden, mainly due to the high costs imposed from energy production. This study examines ways under which modern designs of a building can be applied on construction and domestication while following conventional methods of construction, compared to a building that has been constructed and domesticated under bioclimatic architecture. Particularly, two buildings were investigated in terms of the energy consumption incurred, being built on the same seaside area and period of construction and at adjacent plots of the same distance from sea for ease of comparison. The first building (A1) was constructed under the principles of bioclimatic architecture, being also facilitated with green and smart technologies. The second building (A2) was constructed under conventional construction techniques. The energy efficiency of both buildings was calculated by the "TEE KENAK" software, while specific parameters were recorded. Energy classifications of both buildings were valued and a proposed scenario and interventions unveiled the energy classification upgrading from A2 to A1. Our analysis revealed, as also found in the literature, that during thermal energy oscillating conditions, corresponding relative humidity stresses were observed, indicating that the vapor pressure handling should be taken into account towards comfort. The preliminary incremental cost evaluation and comparison of A1 and A2 energy upgrading under the criterion of simple payback period were critically discussed. [ABSTRACT FROM AUTHOR]

Hydride-forming alloys are currently considered reliable and suitable hydrogen storage materials because of their relatively high volumetric densities, and reversible H2 absorption/desorption kinetics, with high storage capacity. Nonetheless, their practical use is obstructed by several factors, including deterioration and slow hydrogen absorption/desorption kinetics resulting from the surface chemical action of gas impurities. Lately, common strategies, such as spark plasma sintering, mechanical alloying, melt spinning, surface modification and alloying with other elements have been exploited, in order to overcome kinetic barriers. Through these techniques, improvements in hydriding kinetics has been achieved, however, it is still far from that required in practical application. In this review, we provide a critical overview on the effect of mechanical alloying of various metal hydrides (MHs), ranging from binary hydrides (CaH2, MgH2, etc) to ternary hydrides (examples being Ti-Mn-N and Ca-La-Mg-based systems), that are used in solid-state hydrogen storage, while we also deliver comparative study on how the aforementioned alloy preparation techniques affect H2 absorption/desorption kinetics of different MHs. Comparisons have been made on the resultant material phases attained by mechanical alloying with those of melt spinning and spark plasma sintering techniques. The reaction mechanism, surface modification techniques and hydrogen storage properties of these various MHs were discussed in detail. We also discussed the remaining challenges and proposed some suggestions to the emerging research of MHs. Based on the findings obtained in this review, the combination of two or more compatible techniques, e.g., synthesis of metal alloy materials through mechanical alloying followed by surface modification (metal deposition, metal-metal co-deposition or fluorination), may provide better hydriding kinetics. [ABSTRACT FROM AUTHOR]

The paper explores the influence of planetary milling on the temperature and velocity of Al-Ti-B powder mixture combustion and also on the structure and phase composition of the reaction products. It is found that the time increase of planetary milling modifies the structure of the powder particles, improves the density of compacted specimens, and increases the temperature and velocity of their combustion. These time dependences are extreme, with maximum values during 180 s planetary milling. Experiments show that the reaction products consist of an aluminum matrix with uniformly distributed particles of titanium diboride of not over 1 µm in size. The average particle size changes with the increase in the time of the planetary milling of the initial powder mixture. [ABSTRACT FROM AUTHOR]

Magnesium-based materials are promising as hydrogen storage media due to their high theoretical hydrogen absorption capacity, abundance and low price. The subject of this study are the hydrogen sorption characteristics of the composites 80 wt % MgH2-15 wt % Ni-5 wt % activated carbon (synthesized from polyolefin wax, a waste product of polyethylene production at low pressure which will be denoted further in the text as POW) and 90 wt % MgH2-5 wt % Ni-5 wt % POW, prepared by ball milling under argon atmosphere. Structure, phase and surface composition of the samples before and after hydrogenation are determined by XRD and TEM. The maximum absorption capacity value of the composites at a temperature 573 K and after 60 min. of hydrogenation are 5.3 wt % H2 for the material with higher Ni content and 5.5 wt % H2 for the other sample. The presence of both additives—nickel and activated carbon derived from POW—has a positive impact on hydrogenation kinetics and the capacity achieved. The results from TEM characterization, e.g., the polycrystalline SAED (selected area electron diffraction) show the presence of graphite, Mg and monoclinic Mg2NiH4. [ABSTRACT FROM AUTHOR]

Innovative renewable routes are potentially able to sustain the transition to a decarbonized energy economy. Green synthetic fuels, including hydrogen and natural gas, are considered viable alternatives to fossil fuels. Indeed, they play a fundamental role in those sectors that are difficult to electrify (e.g., road mobility or high-heat industrial processes), are capable of mitigating problems related to flexibility and instantaneous balance of the electric grid, are suitable for large-size and long-term storage and can be transported through the gas network. This article is an overview of the overall supply chain, including production, transport, storage and end uses. Available fuel conversion technologies use renewable energy for the catalytic conversion of non-fossil feedstocks into hydrogen and syngas. We will show how relevant technologies involve thermochemical, electrochemical and photochemical processes. The syngas quality can be improved by catalytic CO and CO2 methanation reactions for the generation of synthetic natural gas. Finally, the produced gaseous fuels could follow several pathways for transport and lead to different final uses. Therefore, storage alternatives and gas interchangeability requirements for the safe injection of green fuels in the natural gas network and fuel cells are outlined. Nevertheless, the effects of gas quality on combustion emissions and safety are considered. [ABSTRACT FROM AUTHOR]

This paper describes the design process of the monocoque for IDRAkronos, a three-wheeler hydrogen prototype focused on fuel efficiency, made to compete at the Shell Eco-Marathon event. The vehicle takes advantage of the lightweight and high mechanical performance of carbon fiber to achieve minimal mass and optimized fuel consumption. Based on previous experiences and background knowledge, the authors describe their work toward a design that integrates aerodynamic performance, style, structural resistance and stiffness. A portrayal of the objectives, load cases, simulations and production process—that lead to a final vehicle winner of the Design Award and 1st place general at the 2016 competition—is presented and discussed. [ABSTRACT FROM AUTHOR]

The development of the chassis for the hydrogen fuel cell powered car has been involved in the designing and manufacturing aspects, while taking into consideration the mass, strength, stiffness, centre of gravity (COG), and manufacturing cost requirements. Towards this direction, a chassis design is proposed employing a space frame structure and constructed by an aluminium alloy with great strength. The structural design has been derived through the lightweight engineering approaches in conjunction with the part consolidation, Design for Assembly (DFA) and Design for Manufacture methods. Moreover, it has been performed in compliance with the safety regulations of the Shell Eco Marathon racing competition. The material’s principal characteristics are the great strength, the low mass, as well as the great workability, machinability, and weldability. Following the national and global environmental issues, the recyclable characteristics of the aluminium alloy are an extra asset. Furthermore, the existence of aluminium alloy manufacturers around the fabricating area provides low cost supply and fast delivery benefits. The integration of the fuel cell powered vehicle is obtained through the designing and the manufacturing processes of the chassis and the parts fitted on the chassis. The manufacturing procedures are described thoroughly; mainly consisting of the cutting and welding processes and the assembling of the parts that are fitted on the chassis. Additionally, the proper welding parameters for the custom chassis design are investigated and are selected after deductive reasoning. The quality control of the weld joints is conducted by non-destructive methods (NDT) ensuring the required structural properties of the welds. A combination of the selected material, the specific type of the chassis, and the manufacturing processes lead to construction simplicity in a low manufacturing cost by using the existing laboratory equipment. Furthermore, the designing and manufacturing parameters lead to a stiff with a low centre of gravity, and the most lightweight chassis of the urban concept category at the Shell Eco Marathon race. [ABSTRACT FROM AUTHOR]