Petroleum hydrocarbons, heavy metals and agricultural pesticides have mutagenic, carcinogenic, immunotoxic and teratogenic effects and cause drastic changes in soil physicochemical and microbiological characteristics, thereby representing a serious danger to health and environment. Therefore, soil pollution urgently requires the application of a series of physicochemical and biological techniques and treatments to minimize the extent of damage. Among them, bioremediation has been shown to be an alternative that can offer an economically viable way to restore polluted areas. Due to the difficulty in choosing the best bioremediation technique for each type of pollutant and the paucity of literature on soil bioremediation enhanced by the use of specific additives, we reviewed the main in situ and ex situ methods, their current properties and applications. The first section discusses the characteristics of each class of pollutants in detail, while the second section presents current biorem... [more]

This paper presents a complete study of a standalone photovoltaic (PV) system including a maximum power tracker (MPPT) driving a DC boost converter to feed a resistive load. Here, a new MPPT approach using a modification on the original perturb and observe (P&O) algorithm is proposed; the improved algorithm is founded on a variable step size (VSZ). This novel algorithm is realized and efficiently implemented in the PV system. The proposed VSZ algorithm is compared both in simulation and in real time to the P&O algorithm. The stability analysis for the VSZ algorithm is performed using Lyapunov’s stability theory. In this paper, a detailed study and explanation of the modified P&O MPPT controller is presented to ensure high PV system performance. The proposed algorithm is practically implemented using a DSP1104 for real-time testing. Significant results are achieved, proving the validity of the proposed PV system control scheme. The obtained results show that the proposed VSZ succeeds at... [more]

Due to use of the metallic cans in the air gap, the electromagnetic shielding effect is formed, which is the prominent characteristic of the canned motor. In the flux field, eddy current induction occurs on both cans that thus affects the characteristic of the air gap flux field, and generates a loss that is the highest loss of the canned motor. In this paper, a combination method is proposed and stressed to analyze the shielding effect, based on a typical canned permanent magnet synchronous motor. First, the dq vector decomposition of the eddy current is studied. Second, the effect of the load angle on the loss distribution is studied. Finally, compared with the ordinary motor, the feature of can loss due to rotor speed and conductivity variation is shown. The three-dimensional finite element method is adopted, considering the end effect.

Co-combustion of biomass and solid fuels from wastes in existing highly efficient power plants is a low-cost solution that can be applied quickly and with low effort to mitigate climate change. Circulating fluidized bed combustion has several advantages when it comes to co-combustion, such as high fuel flexibility. The operational flexibility of circulating fluidized bed (CFB) co-combustion is investigated in a 1 MWth pilot plant. Straw pellets and refuse-derived fuel (RDF) are co-combusted with lignite at full load and part loads. This study focusses on the impact on the hydrodynamic conditions in the fluidized bed, on the heat transfer to the water/steam side of the boiler, and on the flue gas composition. The study demonstrates the flexibility of CFB combustion for three low-rank fuels that differ greatly in their properties. The co-combustion of RDF and straw does not have a negative effect on hydrodynamic stability. How the hydrodynamic conditions determine the temperature and pre... [more]

Lightning stroke on a transmission tower structure is one of the major reasons that results in high voltages at the tower arms due to the excessive lightning current flowing through the transmission tower to earth. The Surge voltage seen at the tower cross arm on the first tower close to a substation is the worst case. If this voltage is higher than the withstand level of the insulator string, the insulation of substation equipment will be exposed to transient over-voltage called fast front back-flashover (FFBF). The peak of this transient overvoltage is affected by the value of the system’s earthing resistance. This paper studies the effect of reducing the grounding resistance of both the surge arrestor (SA) and the first transmission line tower adjacent to a 66 kV substation on FFBF. Three case studies using PSCAD/EMTDC software are presented to simulate the variation of the potential sire at the substation equipment with different resistance values for the first tower and SA earthin... [more]

Paper mill sludge (PMS) solids are predominantly comprised of cellulosic fibers and fillers rejected during the pulping or paper making process. Most sludges are dewatered and discharged into landfills or land spread at a cost to the mill; creating large economic and environmental burdens. This lignocellulosic residual stream can be used as a source of sugars for microbial fermentation to renewable chemicals. The aim of this study was to determine the possibility of converting mill sludge to sugars and then fermentation to either isoprene or ethanol. Chemical analysis indicated that the cellulosic fiber composition between 28 to 68% and hemicellulose content ranged from 8.4 to 10.7%. Calcium carbonate concentration in the sludge ranged from 0.4 to 34%. Sludge samples were enzyme hydrolyzed to convert cellulose fibers to glucose, percent conversion ranged from 10.5 to 98%. Calcium carbonate present with the sludge resulted in low hydrolysis rates; washing of sludge with hydrochloric aci... [more]

This study explores the international natural gas market integration using the Engle−Granger cointegration and error correction model. Previous studies have suggested that liquefied natural gas (LNG) and oil-linked pricing with a long-term contract have played key roles in gas market integration, especially between European and Asian markets. There is, however, little discussion of the role of the emergence of a swing supplier. A swing supplier, e.g., Qatar or Russia, is flexible to unexpected changes in supply and demand in both European and Asian markets and adapts the gas production/exports swiftly to meet the changes in the markets. Qatar has been a swing supplier since 2005 in the global natural gas market. In 2009, Qatar’s global LNG export share reached above 30% and has remained around 25% since then. Empirical results indirectly support that the emergence of a swing supplier may tighten market integration between Europe and Asia. The swing supplier may have accelerated the deg... [more]

Operating temperature is an important parameter of thyristors to ensure the stable operation of power electronic devices. Thermal management technology is of great significance for improving the reliability of thyristors. In this study, the performance of a phase change material (PCM) mesh-finned heat sink is investigated for the thermal management of thyristors. A multi-physical coupling model of the PCM mesh-finned heat sink is established to analyze the effects of different power losses, air velocities, heights of fins, and thickness of PCM on the thermal performance of the PCM heat sink. The influence of thermal and flow fields on PCM is considered in this model. Furthermore, the heat sink design is optimized to improve the thermal performance based on the calculation results of thermal network parameters. The results show that the power losses, the air velocity, the height of fins, and the thickness of PCM significantly affect the protection ability of the PCM heat sink. After opt... [more]

5-Hydroxymethylfurfural, which can be derived from lignocellulosic biomass, can be transformed via the hydrodeoxygenation process to potential biofuels, such as 2,5 dimethylfuran or other chemicals of industrial importance. Non-noble metal catalysts constitute a robust and cheap solution for this process. In this work, the modification of the Ni/TiO2 catalyst by the addition of iron and support modification was evaluated. It was shown that bimetallic Ni-Fe catalysts are more selective and stable than their monometallic counterparts. This improvement in properties depends on the Ni:Fe ratio, but the support plays an equally important role—namely the high surface area anatase titania support improves the metal dispersion, resulting in a higher catalytic activity, and the formation of NiFe alloy facilitates the C=O bond cleavage. Such catalysts are active and stable and can be easily separated from the reaction mixture thanks to their magnetic properties.

Si/PEDOT: PSS solar cell is an important alternative for photovoltaic device due to its anticipated high theoretical efficiency and simple manufacturing process. In this study, processing silicon substrate with diluted NaOH aqueous solution was found to be an effective method for improving device performance, one that notably improves junction quality and light trapping ability. When immersed in diluted NaOH aqueous solution, the junction quality was improved according to the enlarged fill factor, reduced series resistance, and enhanced minor carrier lifetime. The diluted NaOH aqueous solution immersion etched the silicon surface and helped with the enhancement of light trapping ability, further improving the short-circuit current density. Although diluted NaOH aqueous solution immersion for bare silicon could improve the performance of devices, proper immersion time was needed. The influence of immersion time on device performances was investigated. The photovoltaic conversion efficie... [more]

The dependence of distributed generations (DGs) on climate conditions and fluctuating load demands are the challenges for the implementation of battery energy storage systems (BESSs) in islanded microgrids. BESS participation in system frequency regulation becomes one of the solutions to those challenges. Frequency regulation by BESS can be realized by applying the load-frequency control (LFC) in BESS. However, this participation clearly poses problems for the battery state of charge (SOC), as the battery is often overcharged or undercharged. In this paper, a control that maintains SOC at a certain level is introduced. This control strategy focuses on the battery operation function, which is determined from five control scenarios. All scenarios are achieved by applying the droop reference shifting method in the LFC to allow battery operation change. Control verification is carried out on an islanded microgrid system that experiences load demand changes and photovoltaic (PV) output powe... [more]

This paper aims to conduct a parametric study for five gas turbine cycles (namely, simple, heat exchanged, free turbine and simple cycle, evaporative, and humidified) using a CO2-argon-steam-oxyfuel (CARSOXY) mixture as a working fluid to identify their optimal working conditions with respect to cycle efficiency and specific work output. The performance of the five cycles using CARSOXY is estimated for wet and dry compression, and a cycle is suggested for each range of working conditions. The results of this paper are based on MATLAB codes, which have been developed to conduct the cycle analysis for CARSOXY gas turbines, assuming a stoichiometric condition with an equivalence ratio of 1.0. Analyses are based on the higher heating value (HHV) of methane as fuel. This paper also identifies domains of operating conditions for each cycle, where the efficiency of CARSOXY cycles can be increased by up to 12% compared to air-driven cycles. The CARSOXY heat exchanged cycle has the highest effi... [more]

In this paper, the amount of SF6 decomposition gases due to the partial discharge (PD) was studied in the SF6 gas-insulated transformer. The long-term PD degradation experiment was performed while controlling the discharge magnitude using the surface discharge, and the gas generation amount was measured by using gas chromatography for SO2F2, SOF2, SO2, CO, and CF4. In addition, to investigate the relationship between the partial discharge energy and the decomposed gas generation amount, partial discharge energy was calculated by a data processing program and converted to the unit of joule per mole. With the finite element method (FEM), the electric field distribution and SF6 gas decomposition mechanism were explained for the partial discharge energy effect on the gas generation. This study helps understand the relationship between the partial discharge energy and the decomposed gas generation ratio with the experimental results and can be used for the diagnosis of PD and maintenance pr... [more]

In this research, the modeling, simulation, and analysis of the energy conversion equations that describe the behavior of a hybrid photovoltaic and wind turbine system that supplies electrical energy to an average organic architecture is performed. Organic constructions have a philosophy that seeks to understand and integrate into the site, taking advantage of the natural potentials and their resources of the surrounding areas so that they form part of a unified and correlated composition. The rooms in these buildings are designed similar to a bean, inspired by the uterus of a mother and her child who are comfortable, at rest, and alive. We are left with the task of spreading this research to integrate its energy potential from the surroundings and transform it into autonomous electrical energy. In this article, a numerical model based on the fundamental equations was developed and coded, and the results compared with experimental data with a real airplane-type system located in a remo... [more]

This article presents the results of a three-year experiment involving a multi-criteria evaluation (productivity, economic and energy balance) of the effectiveness of nitrogen (N) and sulfur (S) fertilization in different cultivars of winter oilseed rape (open-pollinated, semi-dwarf hybrid, long-stem hybrid) grown in north-eastern (NE) Poland. The yield of the semi-dwarf cultivar was 11% lower than the yield of the long-stem hybrid cultivar and 18% higher than the yield of the open-pollinated cultivar. In all cultivars, N fertilization improved yields up to a rate of 180 kg ha−1 and up to a rate of 230 kg ha−1 in years with low precipitation in spring and summer. Seed yield increased in all cultivars in response to S fertilization at 40 kg ha−1. Higher rates of N fertilizer decreased the content of crude fat and glucosinolates (GLS) and increased the concentration of total protein in all cultivars. Sulfur fertilization increased the content of total protein (in long-stem cultivars) and... [more]

The use of a direct torque control (DTC) drive is a well-known control strategy that is applied frequently to induction motors. Although torque and stator flux ripples are major disadvantages of this approach, using a higher-level inverter helps to overcome these issues. In this paper, we propose a novel switching table with a modified control strategy for a three-level inverter to achieve ripple minimization, as well as smooth switching and neutral point balance; the latter features are generally ignored in many works. The proposed model is compared with a conventional DTC and an improved three-level inverter-fed voltage vector synthesis model in the Matlab/Simulink® environment with low, normal, and high-speed operation under load torque disturbances. The performance indexes and the comparative results confirm the effectiveness of the proposed model in reducing the torque and stator flux ripples by up to 70% and 78%, respectively, generating a lower total harmonic distortion (THD%) i... [more]

Combined heat and power (CHP) systems based on low-temperature proton exchange membrane fuel cells (LT-PEMFC) technology are suspected to CO poisoning on the anode side. The fuel cell CO sensitivity increases with ongoing operation time leading to high performance losses. In this paper we present the development of detection and regeneration algorithm based on air bleed to minimize voltage losses due to CO poisoning. Therefore, CO sensitivity tests with two short stacks with different operation time will be analyzed and the test results of aged membrane electrode assemblies (MEAs) will be presented for the first time. Additionally, the first results of the algorithm in operation will be shown.

In this work, we demonstrated a heterojunction Si solar cell utilizing chemically grown titanium oxide (TiOx) as an electron-selective contact layer at its rear surface. With TiOx, the rear surface was passivated to reduce carrier recombination. The reverse saturation current, which is an indicator of carrier recombination, exhibited a 4.4-fold reduction after placing a TiOx layer on the rear surface. With reduced recombination, the open-circuit voltage increased from 433 mV to 600 mV and consequently, the power conversion efficiency (PCE) increased from 9.57 to 14.70%. By X-ray photoemission spectroscopy, the surface passivation was attributed to a silicon oxide interfacial layer formed during the chemical growth process. This passivation results in a 625 cm/s surface recombination velocity for the TiOx-passivated Si surface, which is 2.4 times lower than the sample without TiOx, ensuring the carriers pass through the rear contact without extensive recombination. According to these re... [more]

This paper discusses the issues of the impact of pressure and temperature on the precipitation of paraffin deposits from reservoir fluids in the presence of previously prepared paraffin inhibitors. Using a properly modified PVT apparatus, the temperature of the beginning of paraffin precipitation (wax appearance temperature—WAT) has been determined, below which the solid paraffin phase was captured on a specialized filter in various temperatures. Based on the conducted experiments, a boundary has been established separating the paraffin area (the presence of paraffins as their solid phase) from an area without paraffin. Measurements of the amount of paraffin using the filter allowed the determination of the WPC (wax precipitation curve), due to which additional data is provided regarding the amount of precipitated paraffin deposit below the WAT. The developed methodology enables to conduct the measurements within a wide range of pressures using the sample saturated with reservoir gas,... [more]

This paper proposes a new variable structure control scheme for a variable-speed, fixed-pitch ducted wind turbine, equipped with an annular, brushless permanent-magnet synchronous generator, considering a back-to-back power converter topology. The purpose of this control scheme is to maximise the aerodynamic power over the entire wind speed range, considering the mechanical safety limits of the ducted wind turbine. The ideal power characteristics are achieved with the design of control laws aimed at performing the maximum power point tracking control in the low wind speeds region, and the constant speed, power, and torque control in the high wind speed region. The designed control laws utilize a Luenberger observer for the estimation of the aerodynamic torque and a shallow neural network for wind speed estimation. The effectiveness of the proposed method was verified through tests in a laboratory setup. Moreover, a comparison with other solutions from the literature allowed us to bette... [more]

Arcing is a harmful condition that can lead to electrical fires. The U.S. National Electrical Code requires the installation of electric arc breakers in all residential areas. However, such devices can fail, and therefore, may not work when needed. At present, there are no tests to confirm the correct operation of this type of device. This study aimed to propose an experimental test method to verify the proper functioning of magneto-thermal switches with an electric arc protection function for the occurrence of arc faults. The results show that the proposed method adequately detected the correct operations and tripping time by using different surge suppressors. The proposed system lays the foundations for a portable test system for the periodic checking of electrical systems in which arc fault detection devices (AFDDs) are installed.

The energy crisis and environmental pollution have attracted much attention and have promoted researches on clean and sustainable hydrogen energy resources. With the help of highly active and stable transition metal nickel-based catalysts, the production of hydrogen from water electrolysis from electrolyzed water has become an inexpensive and efficient strategy for generating hydrogen energy. In recent years, heteroatom doping has been found to be an effective strategy to improve the electrocatalytic hydrogen evolution reaction (HER) performances of nickel-based catalysts in acidic, neutral, and alkaline media. This review will highlight many recent works of inexpensive and readily available heteroatom-doped nickel-based HER catalysts. The evaluation methods for the performances of HER catalyst will be briefly described, and the role of heteroatom doping and its application in nickel-based catalyst will be summarized. This article will also point out some heteroatom doping strategies,... [more]

The movable water saturation of tight sandstone reservoirs is an important parameter in characterizing water production capacity, and there is a great need to understand the relationship between movable water saturation and water production characteristics. However, movable water behavior in this context remains unclear. In this study, four groups of tight sandstone cores from the Sulige gas field are measured to understand the movable water saturation characteristics. Then, the effects such as reservoir micropore throat, clay mineral and physical properties on movable water saturation are analyzed, and the movable water saturation and water production characteristics are discussed. The results show that higher movable water saturation will result in a greater amount of water in the gas drive. There is a critical pressure difference of the gas drive, and a large amount of movable water will flow out. Movable water saturation is independent of the porosity, permeability and initial wate... [more]

In this paper, the effect of an external ultrafast transverse magnetic field (UFTMF) on a vacuum arc in the diffused mode has been studied. According to the results of studies, a novel approach for making a zero-crossing in a DC arc current has been presented. Plasma voltage fluctuations of the vacuum arc, which are caused by UFTMF, have been investigated via finite element simulation and two-fluid description of plasma physics. By making an appropriate UFTMF through an external circuit, the arc current can be commuted successfully from the vacuum interrupter (VI) to a parallel capacitor and charge it up. In this way, a zero-crossing in the arc current can be achieved, and the current will be interrupted by the VI. Simulation results, which are supporting physical backgrounds for this analysis, have been presented in this paper while technological issues for industrial implementation of this concept have been discussed in detail.

The efficient spatial load forecasting (SLF) is of high interest for the planning of power distribution networks, mainly in areas with high rates of urbanization. The ever-present spatial error of SLF arises the need for probabilistic assessment of the long-term point forecasts. This paper introduces a probabilistic SLF framework with prediction intervals, which is based on a hierarchical trending method. More specifically, the proposed hierarchical trending method predicts the magnitude of future electric loads, while the planners’ knowledge is used to improve the allocation of future electric loads, as well as to define the year of introduction of new loads. Subsequently, the spatial error is calculated by means of root-mean-squared error along the service territory, based on which the construction of the prediction intervals of the probabilistic forecasting part takes place. The proposed probabilistic SLF is introduced to serve as a decision-making tool for regional planners and dis... [more]