To better understand the mass transfer behaviors in CaC2 production from CaO and coke, this paper studies the diffusion behaviors of CaO and graphite, with or without ash, at 1500 and 1700 °C. CaO and graphite are pressed into tablets and heated alone or in close contact. Physical and chemical changes in these tablets are analyzed by XRD and SEM+EDX. In some experiments, thin Mo wires are placed between the closely contacted CaO and graphite tablets to identify the diffusion direction. It is found that the diffusion between CaO and low-ash graphite is very limited. SiO2 in a high-ash graphite diffuses into CaO tablet and reacts with CaO to form Ca2SiO4, which then diffuses into the graphite tablet easily and leads to CaC2 formation at 1700 °C.

Analyses were conducted on 10 grass species from permanent grasslands in the Noteć Leniwa and Noteć Bystra valley. Their chemical composition was assayed, and their heat of combustion and heating value were determined. The cellulose content ranged from 33.38% to 38.68%, while the content of lignin ranged from 15.42% to 21.99%, and that of hemicellulose from 30.27% to 34.31%. The heating value of grasses was comparable to that of wood from 2- to 3-year-old willows and other fast-growing energy crops. However, the calorific value of naturally dried grasses may be slightly lower. The quantities of minerals in these grasses, exceeding those in wood, did not result in a lowering of their heat of combustion. The analyses clearly showed that the investigated grass species may be successfully used for energy generation purposes.

Sonic log compressional and shear-wave velocities combined with logged bulk density can be used to calculate dynamic elastic moduli in organic shale reservoirs. We use linear multivariate regression to investigate modulus prediction when shear-wave velocities are not available in seven unconventional shale reservoirs. Using only P-wave modulus derived from logged compressional-wave velocity and density as a predictor of dynamic shear modulus in a single bivariate regression equation for all seven shale reservoirs results in prediction standard error of less than 1 GPa. By incorporating compositional variables in addition to P-wave modulus in the regression, the prediction standard error is reduced to less than 0.8 GPa with a single equation for all formations. Relationships between formation bulk and shear moduli are less well defined. Regressing against formation composition only, we find the two most important variables in predicting average formation moduli to be fractional volume o... [more]

Most research about Light and elevated Temperature Induced Degradation (LeTID) is focused on multicrystalline silicon (mc-Si). In this work, the degradation kinetics of Czochralski-grown monocrystalline silicon (Cz-Si) induced by light at an elevated temperature were studied in detail. The lifetime evolutions over time during (1) light soaking (LS), (2) dark annealing−light soaking (DA−LS), and (3) DA−LS cycling experiments were analyzed. Ratios of the capture coefficients for the electrons and holes (k-values) were used to characterize the possible defects responsible for degradation. We found that the behavior of degradation and recovery under light soaking with or without a dark annealing treatment was mostly like boron−oxygen (BO)-related degradation but gave k-values from 19 to 25. In the DA−LS cycling experiment, the max degradation amplitudes hardly changed from the second cycle, and the k-values decreased with an increase in the cycling number. We then analyzed the possible rea... [more]

This paper describes the synthesis, crystal structure, and NH3 sorption properties of Mg1-xMnx(NH3)6Cl2 (x = 0−1) mixed metal halide ammines, with reversible NH3 storage capacity in the temperature range 20−350 °C. The stoichiometry (x) dependent NH3 desorption temperatures were monitored using in situ synchrotron radiation powder X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. The thermal analyses reveal that the NH3 release temperatures decrease in the mixed metal halide ammines in comparison to pure Mg(NH3)6Cl2, approaching the values of Mn(NH3)6Cl2. Desorption occurs in three steps of four, one and one NH3 moles, with the corresponding activation energies of 54.8 kJ⋅mol-1, 73.2 kJ⋅mol-1 and 91.0 kJ⋅mol-1 in Mg0.5Mn0.5(NH3)6Cl2, which is significantly lower than the NH3 release activation energies of Mg(NH3)6Cl2 (Ea = 60.8 kJ⋅mol-1, 74.8 kJ⋅mol-1 and 91.8 kJ⋅mol-1). This work shows that Mg1-xMnx(NH3)yCl2 (x = 0 to 1, y = 0 to 6) is stable within... [more]

This study investigates the production of biobased carbon materials from potato waste and its application in energy storage systems such as supercapacitors. Three different categories of carbons were produced: hydrochar (HC) from hydrothermal carbonization (HTC) at three different temperatures (200 °C, 220 °C, 240 °C) and two different duration times (two hours and five hours), pyrolyzed hydrochar (PHC) obtained via pyrolysis of the HTC chars at 600 °C and 900 °C for two hours and pyrochar from the pyrolysis of biomass at 600 °C and 900 °C for two hours. The carbon samples were analysed regarding their physico-chemical properties such as elemental composition, specific surface area, bulk density and surface functionalities as well as their electrochemical characteristics such as electric conductivity and specific capacity via cyclic voltammetry. N- and O-enriched carbon materials with promising specific surface areas of up to 330 m2 g−1 containing high shares of microporosity were prod... [more]

The aim of this study is to comprehensively evaluate the energy consumption in the automotive industry, clarifying the effect of its productive processes. For this propose, the material flow of the vehicles has been elaborated, from mining to vehicle assembly. Initially, processes where each type of material was used, and the relationship between them, were clarified. Subsequently, material flow was elaborated, while considering materials input in each process. Consequently, the consumption of energy resources (i.e., oil, natural gas, coal, and electricity) was calculated. Open data were utilized, and the effects on the Japanese vehicle market were analyzed as a case study. Our results indicate that the energy that is required for vehicle production is 41.8 MJ/kg per vehicle, where mining and material production processes represent 68% of the total consumption. Moreover, 5.23 kg of raw materials and energy resources are required to produce 1 kg of vehicle. Finally, this study proposed... [more]

Nowadays, the high share of electricity production from renewables drives coal-fired power plants to adopt a more flexible operation scheme and, at the same time, maintain flue gas emissions within respective standards. A 500 kWth pulverized coal furnace was used to study pre-dried lignite combustion or co-combustion as an available option for these plants. Bituminous coal from Czech Republic and pre-dried lignite from Greece were blended for the experiments. Particle emissions measurements with a heated Electrical Low Pressure Impactor (ELPI+) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS) analyses were performed. The effect of the pre-dried lignite proportions in the fuel feed and the combustion conditions regarding the combustion air staging were the two parameters selected for this study. Skeletal density values were measured from the cyclone prior to the impactor. Results are depicted with respect to the aerodynamic and Stokes diameter for impactor... [more]

To optimize the thermal design of AlGaN-GaN high-electron-mobility transistors (HEMTs), which incorporate high power densities, an accurate prediction of the underlying thermal transport mechanisms is crucial. Here, a HEMT-structure (Al0.17Ga0.83N, GaN, Al0.32Ga0.68N and AlN on a Si substrate) was investigated using a time-domain thermoreflectance (TDTR) setup. The different scattering contributions were investigated in the framework of phonon transport models (Callaway, Holland and Born-von-Karman). The thermal conductivities of all layers were found to decrease with a temperature between 300 K and 773 K, due to Umklapp scattering. The measurement showed that the AlN and GaN thermal conductivities were a magnitude higher than the thermal conductivity of Al0.32Ga0.68N and Al0.17Ga0.83N due to defect scattering. The layer thicknesses of the HEMT structure are in the length scale of the phonon mean free path, causing a reduction of their intrinsic thermal conductivity. The size-effect of... [more]

. has received attention from the research and industrial field as a biomass crop because of its fast growth and high productivity. The features of this species match with the increasing demand for wood for energy production. Commonly, the wood used for energy production is converted in chips, a material susceptible to microbial degradation and energy losses if not properly stored before conversion. This study aims at investigating two outdoor storage systems of Eucalyptus wood chips (covered vs. uncovered), assessing the variation in moisture content, dry matter losses and fuel characteristics. The class size of the material was P16, which was obtained using a commercial chipper appositely searched to conduct the study. The results highlighted how the different storage methods were influenced by the climatic condition: the woody biomass covered showed the best performances in terms of dry matter losses achieving 2.7% losses vs. the 8.5% of the uncovered systems. However, fuel characte... [more]

Oil recovery using modified/smart water technology can be maximized by optimizing the composition of the injected water. Brine optimization is also believed to improve polymer flooding performance. This chapter assesses and defines the potential impact of combining low-salt-modified water with polymer flooding, based on the presence of sulfate in the injection water. Hence, we evaluated the influence of sodium sulfate on (1) polymer viscoelasticity, under the assumption that the phenomena exists, and (2) oil recovery and pressure response. Mainly, a comprehensive rheological evaluation and two-phase core flood experiments are the focus of this work. Composition of injection brine is optimized after having synthetic seawater as a base brine. Core-flood experiments were performed in a secondary, tertiary and a sort of post-tertiary (quaternary) mode to evaluate the feasibility of applying both processes (modified water and polymer flood). Obtained data was subsequently cross-analyzed and... [more]

Lithium nickelate (LiNiO2) and materials based on it are attractive positive electrode materials for lithium-ion batteries, owing to their large capacity. In this paper, the results of atomic layer deposition (ALD) of lithium−nickel−silicon oxide thin films using lithium hexamethyldisilazide (LiHMDS) and bis(cyclopentadienyl) nickel (II) (NiCp2) as precursors and remote oxygen plasma as a counter-reagent are reported. Two approaches were studied: ALD using supercycles and ALD of the multilayered structure of lithium oxide, lithium nickel oxide, and nickel oxides followed by annealing. The prepared films were studied by scanning electron microscopy, spectral ellipsometry, X-ray diffraction, X-ray reflectivity, X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and selected-area electron diffraction. The pulse ratio of LiHMDS/Ni(Cp)2 precursors in one supercycle ranged from 1/1 to 1/10.... [more]

One of the most important techniques for energy harvesting is the clean energy collection from the ambient vibration. Piezoelectric energy harvesting systems became a hot topic in the literature and attracted most researchers. The reason behind this attraction is that piezoelectric materials are a simple structure and provide a higher power density among other mechanisms (electromagnetic and electrostatic). The aim of this manuscript is to succinctly review and present the state of the art of different existing vibrational applications utilizing piezoelectric energy harvesting technique. Meanwhile, the main concentration is harvesting energy from a vehicle suspension system. There is a significant amount of dissipated energy from the suspension dampers that is worthy of being harvested. Different mathematical car models with their experimental setup are presented, discussed, and compared. The piezoelectric material can be mounted in different locations such as suspension springs, dampe... [more]

This editorial note is dedicated to the 1st International Conference on Nanofluids (ICNf19), which was organized under the auspices of Nanouptake COST Action in June 2019, in Castelló (Spain). After a brief report about the conference issues, the successful selected contributions to this Special Issue of Energies about the ICNf19 are introduced.

Pretreatment of waste materials could help in more efficient waste management. Various pretreatment methods exist, each one having its own advantages and disadvantages. Moreover, a certain pretreatment technique might be efficient and economical for one feedstock while not for another. Thus, it is important to analyze how parameters change during pretreatment. In this study, two different pretreatment techniques were applied: thermal at lower and higher temperatures (38.6 °C and 80 °C) and biological, using cattle rumen fluid at ruminal temperature (≈38.6 °C). Two different feedstock materials were chosen: sewage sludge and riverbank grass (Typha latifolia), and their combinations (in a ratio of 1:1) were also analyzed. Various parameters were analyzed in the liquid phase before and after pretreatment, and in the gas phase after pretreatment. In the liquid phase, some of the parameters that are relevant to water quality were measured, while in the gas phase composition of biogas was me... [more]

The increased frequency of heat-related mortality and morbidity in urban environments indicates the importance of urban climate studies. As most of the world’s population lives in cities, the education of designers, planners and policy makers is crucial to promote urban sustainability This paper, firstly, focuses on the different factors causing the urban heat islands in large cities. Secondly, it considers how these factors are reflected in higher education programmes. Examples are shown from courses in UK higher education, explaining the common software tools used for simulating urban spaces, and student field measurements are drawn on to illustrate how urban climate studies are included in higher education curricula. Urban metabolism is used to conceptualise the main approach to systemic resource-use assessments and as a holistic framework to investigate the main drivers of the urban heat island phenomenon. To sum up, this paper reflects on the importance of training climatically-aw... [more]

This paper aims to study the effect of cyclic heating and flowing-water cooling conditions on the physical properties of granite. Ultrasonic tests, gas measured porosity, permeability, and microscope observations were conducted on granite after thermal treatment. The results showed that the velocity of P- and S-waves decreased as the number of thermal cycles increased. The porosity increased with the number of the thermal cycles attained at 600 °C, while no apparent changes were observed at 200 and 400 °C. The permeability increased with the increasing number of thermal cycles. Furthermore, microscope observations showed that degradation of the granite after thermal treatment was attributed to a large network of microcracks induced by thermal stress. As the number of thermal cycles increased, the number of transgranular microcracks gradually increased, as well as their length and width. The quantification of microcracks from cast thin section (CTS) images supported the visual observati... [more]

Biomass occupies a significant proportion of municipal solid waste. For the high-value processing of waste biomass, a hydrothermal-carbonization method was chosen because of the advantages of effective and mild conditions. Four typical types of waste biomass (banana peel, mangosteen peel, orange peel, and pomelo peel) were used in this work to prepare high-value carbon aerogels (CA) via hydrothermal-carbonization treatment for cracking ethanol. Four kinds of CA all had good performances in the ethanol cracking reaction and improved the yield of H2 from 21 wt% to about 40 wt%. The banana peel-based carbon aerogel (BPCA) showed the best performance in the reaction; it cracked ethanol and obtained 41.86 wt% of H2. The mechanism of ethanol cracking by CA was revealed: On one hand, the self-cracking of ethanol was improved due to the extension of residence time, which benefited from the abundant pores in CA. On the other hand, the heterogeneous reaction occurred on the surface of CA where t... [more]

Although numerous investigations have revealed the gas physisorption characteristics of porous media, the essence of physisorption behavior of gas within nanoscale space is still indistinct. We speculated that the physisorption behavior of a complex molecular system (e.g., CH4 and CO2) exhibits a quantum effect due to the confinement effect of nanopores. Gas molecules occur in varied orbitals following certain probabilities and, therefore, have separate energy levels inside a nanoscale space. Energy level transition of molecules from excited state to ground state triggers gas physisorption, while non-uniform spatial distribution of energy-quantized molecules within nanopores dominates the gas physisorption behavior. The spatial distribution of gas molecules can be adjusted by temperature, pressure and potential energy field. Based on the quantum effect, we developed a physisorption equation from the perspective of quantum mechanics to re-understand the basic principles of gas physisorp... [more]

This paper investigates how the pre-treatment of the growth solution with ultrasonic energy affects the annealing temperatures and the growth temperatures of zinc oxide (ZnO) nanorods. The ultrasonic pre-treatment of the growth solution resulted in the successful growth of ZnO nanorods at a very low annealing temperature of 40 °C. The size and density of ZnO nanorods were found to increase proportionally with the increasing duration of pre-ultrasonic treatment, as indicated by characterisations performed with a scanning electron microscope (SEM). At an annealing temperature of 40 °C, coupled with ultrasonic waves, the SEM results showed that ZnO nanorods’ length and diameter increased by 37 and 25%. A similar pattern was also observed at an annealing temperature of 60 and 80 °C, where the length and diameter of ZnO nanorods increased. In addition, the conductivity and acidity of the aqueous solution that had been sonicated were measured. The results showed that solution conductivity an... [more]

The molecular structure of cationic surfactants is closely related to their flotation performance. In this paper, three cationic surfactants with different head group structures were selected as collectors of kaolinite, and the substituent effects were studied by the DFT method. The DFT calculation results showed that increasing the number of substituents in the dodecylamine head group can significantly increase its surface and head group charge. Dodecylamine has the lowest LUMO orbital energy, so dodecylamine has the strongest electron attraction ability and the strongest interaction with kaolinite. Electron density differential showed that there was an area of electron aggregation between the collector and the surface of the kaolinite. The interaction energy of DDA on kaolinite surfaces was greater than that of the other two collectors, indicating that the adsorption of DDA on the surface of kaolinite was more stable. Flotation results showed that higher a kaolinite yield was obtaine... [more]

Photovoltaic (PV) systems are well-known systems that convert solar energy into electrical energy. Increases in operating temperature induce a drop in conversion efficiency and, thus, in the output power produced by the panel. This paper investigates the effectiveness of using Phase Change Materials (PCMs) in cooling PV modules. Due to its high storage density with limited temperature fluctuations, the latent heat storage in a PCM is an important factor. This depends on the thermophysical properties of PCMs such as the melting point, specific heat capacity, latent heat, density, etc. This paper aims to make a comparison between four types of PCM with different melting points and physical properties. Indoor experimental studies were performed using five prototypes. A halogen lamp was used as a solar simulator to ensure that experiments were carried out under the same irradiance. The first prototype was the reference, which consisted of a PV panel, a stand, and an electric circuit withou... [more]

Six supplementary cementitious materials (SCMs) were identified to be incorporated in concrete exposed to high-temperature cycling conditions within the thermal energy storage literature. The selected SCMs are bauxite, chamotte, ground granulated blast furnace slag, iron silicate, silica fume, and steel slag. A microstructural characterization was carried out through an optical microscope, X-ray diffraction analysis, and FT-IR. Also, a pozzolanic test was performed to study the reaction of SCMs silico-aluminous components. The formation of calcium silica hydrate was observed in all SCMs pozzolanic test. Steel slag, iron silicate, and ground granulated blast furnace slag required further milling to enhance cement reaction. Moreover, the tensile strength of three fibers (polypropylene, steel, and glass fibers) was tested after exposure to an alkalinity environment at ambient temperature during one and three months. Results show an alkaline environment entails a tensile strength decrease... [more]

High energetic efficiency is a major requirement in industrial processes. The poor thermal conductivity of conventional working fluids stands as a limitation for high thermal efficiency in thermal applications. Nanofluids tackle this limitation by their tunable and enhanced thermal conductivities compared to their base fluid counterparts. In particular, carbon-based nanoparticles (e.g., carbon nanotubes, graphene nanoplatelets, etc.) have attracted attention since they exhibit thermal conductivities much greater than those of metal-oxide and metallic nanoparticles. In this work, thermal conductivity data from the literature are processed by employing rigorous statistical methodology. A high-accuracy regression equation is developed for the prediction of thermal conductivity of graphene nanoplatelet-water nanofluids, based on the temperature (15−60 °C), nanoparticle weight fraction (0.025−0.1 wt.%), and graphene nanoparticle specific surface area (300−750 m2/g). The strength of the impa... [more]

To improve the utilization of steel slag (SS) in CO2 capture and making building materials, the paper mainly discussed the effects of desulphurization gypsum (DG) and w/s ratio on strength development and CO2 capture capability of high Al content SS. It showed that 10 wt% DG enhanced the strength of hydration-curing SS by 262% at 28 days. Similarly, adding 6 wt% DG in carbonation-curing SS contributed to increases in strength and CO2 uptake by 283% and 33.54%, reaching 42.68 MPa and 19.12%, respectively. Strength decreases and CO2 uptake increases with w/s. Microanalysis (QXRD, SEM-EDS, TG-DTG, FTIR, XPS, and MIP) revealed that the main hydration products of SS were C-S-H gel and C4AH13, which transformed to ettringite with DG addition. The carbonation products were mainly calcite and aragonite. Additionally, the amount of aragonite, mechanically weaker than calcite, decreased and calcite increased significantly when DG was added in carbonation-curing samples, providing a denser struct... [more]