A modern pulp mill generates a variety of different by-products and waste streams, some of these can be recycled, refined, sold, or used on-site for energy production. However, some, such as chemical and biological sludges produced in wastewater treatment cannot be reused or disposed of easily, mainly due to their high moisture content and poor drying characteristics. Tightening legislation regarding waste disposal as well as the growing need to increase the process efficiencies of pulp mills act as driving forces to find environmentally friendly and energy-efficient techniques for pulp mill sludge treatment. This study summarizes the current methods for pulp mill sludge handling and evaluates the potential of hydrothermal carbonization (HTC), a conversion process through which wet organic substrates can be transformed into a carbonaceous material (hydrochar). Depending on the process parameters, the material’s structure is modified, enabling hydrochar use in energy, soil conditioning... [more]

Demand and need for the application of high voltage direct current (HVDC) are increasing because of high capacity and long-distance transmission. Research on polypropylene (PP) that can increase the operation temperature compared to existing insulation is constantly being considered. This study aimed to evaluate the electrical performance and estimate the life of HVDC application of PP. In this study, a DC V-t characteristic tests were conducted on three types of PP sheets at a temperature of 110 °C. In addition, a life estimation formula based on the electrical stress was derived and the electrical performances were evaluated. The experimental results show that the life exponent of material mixed with block copolymer, homo polymer and high density polyethylene (HDPE) was 23 and the electrical performance was 17% better than block copolymer, thereby demonstrating the reliability and electrical performance for application of HVDC.

Herein, a pair of inexpensive and eco-friendly polymers were blended and formulated based on poly (ethylene oxide) (PEO) and poly (vinyl alcohol) (PVA). FTIR, XRD, EDX and TEM techniques were used to describe a Phosphated titanium oxide (PO4TiO2) nanotube synthesised using a straightforward impregnation-calcination procedure. For the first time, the produced nanoparticles were inserted as a doping agent into this polymeric matrix at a concentration of (1−3) wt.%. FTIR, TGA, DSC and XRD were used to identify the formed composite membranes. Furthermore, because there are more hydrogen bonds generated between the polymer’s functional groups and oxygen functional groups PO4TiO2, oxidative stability and tensile strength are improved with increasing doping addition and obtain better results than Nafion117. The permeability of methanol reduced as the weight % of PO4TiO2 increased. In addition, the ionic conductivity of the membrane with 3 wt.% PO4-TiO2 is raised to (28 mS cm−1). The optimised... [more]

With the fast evolution in greenhouse gas (GHG) emissions (e.g., CO2, N2O) caused by fossil fuel combustion and global warming, climate change has been identified as a critical threat to the sustainable development of human society, public health, and the environment. To reduce GHG emissions, besides minimizing waste heat production at the source, an integrated approach should be adopted for waste heat management, namely, waste heat collection and recycling. One solution to enable waste heat capture and conversion into useful energy forms (e.g., electricity) is employing solid-state energy converters, such as thermoelectric generators (TEGs). The simplicity of thermoelectric generators enables them to be applied in various industries, specifically those that generate heat as the primary waste product at a temperature of several hundred degrees. Nevertheless, thermoelectric generators can be used over a broad range of temperatures for various applications; for example, at low tempe... [more]

The implementation of renewable energy sources is rapidly growing in the electrical sector. This is a major step for civilization since it will reduce the carbon footprint and ensure a sustainable future. Nevertheless, these sources of energy are far from perfect and require complementary technologies to ensure dispatchable energy and this requires storage. In the last few decades, redox flow batteries (RFB) have been revealed to be an interesting alternative for this application, mainly due to their versatility and scalability. This technology has been the focus of intense research and great advances in the last decade. This review aims to summarize the most relevant advances achieved in the last few years, i.e., from 2015 until the middle of 2021. A synopsis of the different types of RFB technology will be conducted. Particular attention will be given to vanadium redox flow batteries (VRFB), the most mature RFB technology, but also to the emerging most promising chemistries. An in-de... [more]

This paper explores the effectiveness of metal recovery and values of gaseous emissions during thermal e-waste processing followed by magnetic separation. The thermal process of conversion of this kind of waste is difficult due to the uncertainty of the operation when compared to the processing of homogeneous materials. This is due to their complex and heterogeneous structure. The adoption of the fluidized bed reactor makes the process feasible, stabilizing it significantly and limiting emissions of harmful gases. Mobile cellphones were used as the raw input material of 450 g total mass. During the thermal transformation, the exhaust gases such as: CO, CO2, NOx, SO2, HCI, HBr, HCN, NH3, phenol, hydrocarbons, HF and COCI2 were analysed. The thermal treatment resulted in 333.6 g of solids in the fluidized bed. They were fragmented into grains smaller than 1 mm and 0.5 mm. The process of magnetic enrichment was used next on grains greater than 1 mm and smaller than 0.5 mm. The process was... [more]

Dielectric electroactive polymers have been widely used in recent applications based on smart materials. The many advantages of dielectric membranes, such as softness and responsiveness to electric stimuli, have lead to their application in actuators. Recently, researchers have aimed to improve the design of dielectric electroactive polymer actuators. The modifications of DEAP actuators are designed to change the bias mechanism, such as spring, pneumatic, and additional mass, or to provide a double cone configuration. In this work, the modification of the shape of the actuator was analyzed. In the standard approach, a circular shape is often used, while this research uses an elliptical shape for the actuator. In this study, it was shown that this construction allows a wider range of movement. The paper describes a new design of the device and its model. Further, the device is verified by the measurements.

This paper is focused on the extraction of the noise parameters of a linear active device by exploiting both forward and reverse noise power measurements associated with different terminations. In order for load-pull measurements to yield a significant marginal improvement (as compared to forward measurements only) it is expected that the device under test should appreciably deviate from unidirectionality. For this reason, the source/load-pull technique is applied to frequencies at which the considered devices are still usable but their reverse noise factor exhibits a measurable dependence on the output terminations. Details on the test bench set up to the purpose, covering the 20−40 GHz frequency range, are provided. A characterization campaign on a 60 nm gate length, 4×35 µm GaN-on-Si HEMT fabricated by OMMIC is illustrated.

Poultry waste is increasingly used as a substrate for the methane fermentation process in a biogas plant. However, not all waste materials processed in the meat industry meet the criteria for optimal process management and cost-effective methane efficiency. An example may be centrifuged biological sludge, etc. Treatment of such material used as a substrate by introducing new metabolically and enzymatically active strains of bacteria could be beneficial for the fermentation process in a biogas plant and provide increased energy efficiency. The aim of the study was to compare the amount and quality of biogas obtained from biological sludge from the processing of poultry vaccinated with metabolically diversified bacterial inoculum after initial incubation of the batch before the actual process in a biofermenter. Laboratory tests were carried out in accordance with the guidelines contained in the DIN 38 414-S8 and VDI 4630 standards. Based on the obtained results, it was found that the opt... [more]

As the utilization and consumption of lignocellulosic biomass increases, so too will the need for an adequate supply of feedstock. To meet these needs, novel waste feedstock materials will need to be utilized. Exploitation of these novel feedstocks will require information both on the effects of solvent extraction on the succeeding analysis of potential novel feedstocks and how accurate current methodologies are in determining the composition of novel lignocellulosic feedstocks, particularly the carbohydrate and lignin fractions. In this study, the effects of solvent extraction on novel feedstocks, including tree foliage, tree bark and spent mushroom compost, with 95% ethanol, water and both sequentially were examined. Chemical analyses were carried out to determine the moisture content, ash, extractives, post-hydrolysis sugars, Klason lignin (KL) and acid-soluble lignin (ASL) within the selected feedstocks. The result of extraction could be seen most strongly for Klason lignin, with a... [more]

As a typical wide bandgap semiconductor, ZnO has received a great deal of attention from researchers because of its strong physicochemical characteristics. During the past few years, great progress has been made in the optoelectronic applications of ZnO, particularly in the photocatalysis and photodetection fields. To enable further improvements in the material’s optoelectronic performance, construction of a variety of ZnO-based composite structures will be essential. In this paper, we review recent progress in the growth of different ZnO−graphene nanocomposite structures. The related band structures and photocatalysis and photoresponse properties of these nanocomposites are discussed. Additionally, specific examples of the materials are included to provide an insight into the common general physical properties and carrier transport characteristics involved in these unique nanocomposite structures. Finally, further directions for the development of ZnO−graphene nanocomposite materials... [more]

Hydrogen storage in magnesium-based composites has been an outstanding research area including a remarkable improvement of the H-sorption properties of this system in the last 5 years. Numerous additives of various morphologies have been applied with great success to accelerate the absorption/desorption reactions. Different combinations of catalysts and preparation conditions have also been explored to synthesize better hydrogen storing materials. At the same time, ball milling is still commonly and effectively applied for the fabrication of Mg-based alloys and composites in order to reduce the grain size to nanometric dimensions and to disperse the catalyst particles over the surface of the host material. In this review, we present the very recent progress, from 2016 to 2021, on catalyzing the hydrogen sorption of Mg-based materials by ball milling. The various catalyzing routes enhancing the hydrogenation performance, including in situ formation of catalysts and synergistic improveme... [more]

Nuclear graphite can be used in fission and fusion systems due to its excellent nuclear performance and mechanical properties where the ability of oxidation resistance is usually concerned. Although the excellent performance of new graphite ET-10 was revealed by previous experiments regarding the accident conditions of a fission reactor, further studies are needed to oxidize the graphite under the conditions recommended by the ASTM D7542 standard. A test facility was designed and developed to oxidize the cylindrical specimen with a 10 L/min airflow. According to oxidation rates and microstructures of specimens, the chemical kinetics-controlled regime was determined as 675−750 °C, where the activation energy was obtained as 172.52 kJ/mol. The experiment results revealed the excellent ability of graphite ET-10 for oxidation resistance with lower oxidation rates and longer oxidation times compared with some mainstream graphite. The main reasons are the low contents of some impurities and... [more]

The intermittent nature of renewable sources, such as solar and wind, leads to the need for a hybrid renewable energy system (HRES) that can provide uninterrupted and reliable energy to a remote and off-grid location with the use of a biogas generator and battery. In the present study, conventional PV panels have been integrated with phase change material (PCM) for power enhancement. In addition, various configurations (i. PV-Wind-Battery system, ii. PV-PCM-Wind-Battery, iii. PV-Wind-Biogas-Battery and iv. PV-PCM-Wind-Biogas-Battery) have been compared for the hot and humid climatic location of Chennai, India. Optimization has been carried out to minimize the cost of energy and the net present cost has also been computed. It has been found that the integration of PCM with the PV-Wind-Biogas-Battery-based off-grid system results in savings of USD 0.22 million in terms of net present cost and reduces the cost of energy from USD 0.099/kWh to USD 0.094/kWh. Similarly, for another off-grid... [more]

A new porous system in power plants allowing the management of the crisis of heat exchange at boiling water in porous structures has been investigated. This study refers to the thermal power plants of electrical power stations and devices for cutting natural and artificial mineral media. Combustion chambers and supersonic nozzles were cooled by different porous structures. The optimum cell sizes of the porous structures were determined and data on the heat transfer capacity for the (critical) heat flow were obtained. A thermal device in the form of a rocket-type burner with a detonation jet showed high efficiency for capillary-porous and flow-through cooling systems. The economic effect per burner is not less than 200−300 dollars, and the coolant consumption is reduced by dozens of times, which is environmentally important. A comparative evaluation of the investigated structures and coatings has advantages over other cooling systems. The integration of mesh structures with capillary-po... [more]

The European Union has adopted legislation aimed to increase the use of renewable energy and improve the effectiveness of conventional-form energy use. Additional structure insulation helps to decrease heat energy loss. Airtightness of the building envelope (building airtightness) is an additional factor that determines comfortable and energy-saving living environment. The conformity of heat energy loss with the object’s design energy class is one of the mandatory indicators used in the obligatory building energy performance certification procedure. Optionally, the objects to be certified are the entire buildings or separate units (flats). There is an issue of concern whether a flat assessed as a separate housing unit would meet the requirements of design energy class depending on the location of the unit in the building. The study is aimed to determine the change in heat loss of end units in terraced houses (townhouses) as a result of various factors, leading to uneven airtightness of... [more]

The city of Aripuana is one of the largest wood producer in the state of Mato Grosso, Brazil. Wood residues are used in the electricity generation at three thermoelectric plants in this region. However, the plants have high costs in transporting the wood residues (due to poor road conditions). Hence, this paper compares the energy performance of wood residues in natura and compacted as briquettes by calculating the heating value and determining the influence of moisture content on the energy characteristics of wood residues. The goal is to demonstrate the viability of using briquettes in order to improve thermoelectric generation. The wood residues from this region are affected by the high humidity of the biome. An alternative to improve the use of energy contained in the wood residues is to produce briquettes with lower humidity. This allows one to maintain high levels of heat energy in a lower volume, facilitating handling and storage. The results show that the use of briquettes impr... [more]

In the photovoltaic industry, there is great interest in increasing the power output of solar cells to achieve grid parity and to promote the widespread use of solar cells. However, despite many developments, a phenomenon called light-induced degradation causes the efficiency of solar cells to deteriorate over time. This study proposes a treatment that can be applied to cells within solar modules. It uses a half-bridge resonance circuit to induce a magnetic field and selectively heat Al electrodes in the solar cells. The electrical state of a solar module was measured in real time as it was being heated, and the results were combined with a kinetics simulation using a cyclic reaction. As the temperature of the solar module increased, the time taken to reach the saturation point and the recovery time decreased. Moreover, the value of the saturation point increased. The light-induced degradation activation energy was similar to results in the existing literature, suggesting that the kine... [more]

A new type of Water Lead Lithium Cooled (WLLC) blanket that adopts the modular design scheme, water cooling the structure components, liquid PbLi as breeder and coolant, and SiC as the thermal insulator between PbLi and structures is under development as a candidate blanket concept for the Chinese Fusion Engineering Test Reactor (CFETR). Based on a poloidal-radial slice model, thermal hydraulic analysis is performed for this blanket to validate the feasibility of design goals. Results show that the present design can achieve the outlet temperature in the range of 600−700 °C, with all the material temperatures safely below the upper limits. A series of sensitivity analyses are also carried out. It indicates that the thermal conductivity (TC) of SiC would have a significant influence on the temperature field, streamlines and pressure drop; that is, lower TC of SiC can maintain the temperature of PbLi at a high level, and induce an increased number of vortices in the liquid PbLi flow as w... [more]

The mechanical loads that gas diffusion layers (GDLs) withstand in polymer electrolyte membrane fuel cell (PEMFC) stacks are sensitive to the assembly and working conditions. The mechanical properties of GDLs mostly depend on their composition materials, microstructural characteristics, operation conditions, etc. An accurate and comprehensive understanding of the mechanical performance of GDLs is significant for predicting the stress distribution and improving the assembly technology of PEMFC stacks. This study presented a novel 3-D nonlinear and orthotropic constitutive model of a carbon paper GDL to represent the material stiffness matrix with its compressive, tensile, and shear properties. Numerical simulations were performed based on the 3-D constitutive model, and the proposed 3-D model was validated against the experimental data reported previously. It is found that the simulation results of the 3-D constitutive model show a good agreement with the experimental results. Besides,... [more]

In this study, seven of the most commonly applied covering materials in smart farms are selected as the representative samples for analysis, namely, glass, soft film (polyethylene, PE), soft film (polyolefin, PO), rigid plastic film (ethylene tetra fluoro ethylene, ETFE), rigid plastic sheet (poly methyl methacrylate, PMMA), rigid plastic sheet (polycarbonate, PC double layer), and woven film. For each covering material, visible light transmittance and reflectivity, solar radiation transmittance and reflectivity, thickness, solar heat gain coefficient, and the coefficient of heat transmission are measured according to the test methods in the Korean Industrial Standards (KS) to derive input data for the respective materials. In addition, using the optical and thermal input data as derived above, simulations are performed on the cooling load and daylight characteristics of smart farms to derive basic reference data for the selection of adequate covering materials for the design. Based on... [more]

Microcombustion attracts interest with its promise of energy dense power generation for electronics. Yet, challenges remain to develop this technology further. Thermal management of heat losses is a known hurdle. Simultaneously, non-uniformities in heat release within the reaction regions also affect the device performance. Therefore a combination of thermal management strategies are necessary for further performance enhancements. Here, a bench top platinum nanoparticle based microcombustion reactor, coupled with thermoelectric generators is used. Methanol-air mixtures achieve room temperature ignition within a catalytic cartridge. In the current study, the reactor design is modified to incorporate two traditional thermal management strategies. By limiting enthalpic losses through the exhaust and reactor sides, using multi-pass preheating channels and heat recirculation, expected improvements are achieved. The combined strategies doubled the power output to 1.01 W when compared to the... [more]

The design of a cooling system is critical in power converters based on wide-bandgap (WBG) semiconductors. The use of gallium nitride enhancement-mode high-electron-mobility transistors (GaN e-HEMTs) is particularly challenging due to their small size and high power capability. In this paper, we model, study and compare the different heat dissipation systems proposed for high power density GaN-based power converters. Two dissipation systems are analysed in detail: bottom-side dissipation using thermal vias and top-side dissipation using different thermal interface materials. The effectiveness of both dissipation techniques is analysed using MATLAB/Simulink and PLECS. Furthermore, the impact of the dissipation system on the parasitic elements of the converter is studied using advanced design systems (ADS). The experimental results of the GaN-based converters show the effectiveness of the analysed heat dissipation systems and how top-side cooled converters have the lowest parasitic induc... [more]

The thin layers of ZnO and ZnO: Al (Al doped zinc oxide—AZO) were deposited by the atomic deposition layer (ALD) method on silicon and glass substrates. The structures were deposited using diethylzinc (DEZ) and deionized water as zinc and oxygen precursors. A precursor of trimethylaluminum (TMA) was used to introduce the aluminum dopant. The present study of ALD-deposited ZnO and AZO films was motivated by their applications in photovoltaics. We attempted to expose several properties of such films. Structural, optical (including ellipsometric measurements) and electrical investigations were performed. We discussed the relations between samples doped with different Al fractions and their properties.

Lignocellulose and starch-based raw materials are often applied in the investigations regarding biohydrogen generation using dark fermentation. Management of the arising post-fermentation broth becomes a problem. The Authors proposed sequential processes, to improve the efficiency of both hydrogen generation and by-products management carried under model conditions. During the proposed procedure, the simple sugars remaining in broth are converted into organic acids, and when these products are used as substrates for the photo fermentation process. To enhance the broth management also conditions promoting Deep Eutectic Solvents (DES) precursors synthesis are simultaneously applied. Application of Box-Behnken design allows defining of the optimal conditions for conversion to DESs precursors. During the procedure hydrogen was obtained, the concentration of hydrogen in the photo fermentation reached up to 819 mL H2/L medium/7 d, depending on the broth type, i.e., when the broth was optimiz... [more]