A method for assessing the operation of analog filters installed in the measuring paths of current and voltage converters in the power supply system of a mining machine motor, using the example of the driving unit of a roadheader’s cutterhead, is presented. The suggested method is based on the identification of the fundamental harmonic of signals from the current and voltage sensors observed at the input and output of the tested filters, respectively. The identified parameters of the fundamental harmonic of signals before and after the filter allow the determination of points of the filter frequency’s characteristics and their comparison with the reference values. In the suggested method of assessing the operation of analog filters, the new approach consists of checking the frequency characteristics on the basis of identification of the basic harmonics of the signal at the input and output of the tested filter (installed in the measuring line of the electrical quantity) using data acqu... [more]

Electrification offers an opportunity to decarbonize the transport sector, but it might also increase the need for flexibility options in the energy system, as the uncoordinated charging process of battery electric vehicles (BEV) can lead to a demand with high simultaneity. However, coordinating BEV charging by means of smart charging control can also offer substantial flexibility potential. This potential is limited by restrictions resulting from individual mobility behavior and preferences. It cannot be assumed that storage capacity will be available at times when the impact of additional flexibility potential is highest from a systemic point of view. Hence, it is important to determine the flexibility available per vehicle in high temporal (and spatial) resolution. Therefore, in this paper a Markov-Chain Monte Carlo simulation is carried out based on a vast empirical data set to quantify mobility profiles as accurately as possible and to subsequently derive charging load profiles. A... [more]

The energy consumption problem has become a bottleneck hindering further development of data centers. However, the heterogeneity of servers, hybrid cooling modes, and extra energy caused by system state transitions increases the complexity of the energy optimization problem. To deal with such challenges, in this paper, an Energy Aware Task Scheduling strategy (EATS) utilizing marginal cost and task classification method is proposed that cooperatively improves the energy efficiency of servers and cooling systems. An energy consumption model for servers, cooling systems, and state transition is developed, and the energy optimization problem in data centers is formulated. The concept of marginal cost is introduced to guide the task scheduling process. The task classification method is incorporated with the idea of marginal cost to further improve resource utilization and reduce the total energy consumption of data centers. Experiments are conducted using real-world traces, and energy redu... [more]

For calculation of biological efficiency of a biogas plant (BP), it is required to determine the specific methane potential (SMP) of the substrate. A study comparing available methods for determination of SMP and the comparison with data of full-scale BPs is missing but necessary according to the differences in process conditions between both. Firstly, mass and mass associated energy balances of 33 full-scale BPs were calculated and evaluated. The results show plausible data for only 55% of the investigated BPs. Furthermore, conversion and yield efficiencies were calculated according to six different methods for SMP determination. The results show a correlation between the measured on-site specific methane yield and the calculated SMP by methods based on biological degradability. However, these methods underestimate the SMP. Calculated SMPs based on calorific values are higher, but less sensitive. A combination of biochemical and energetical methods is a promising approach to evaluate... [more]

Milling is one of the most energy consuming stages of the value production chain in many industries. To minimize the specific energy required, new and more efficient devices and circuits are designed and dedicated optimizing control strategies are applied. This research presents the results of innovative electromagnetic mill energy consumption reduction with dedicated supervisory on-line optimizing control algorithm. The paper describes an algorithm that uses the active power measurement and searches for the minimum on the active constraints of the optimization problem. The constraints follow from the product quality, mill supply voltage and magnetic induction requirements. Algorithm performance was tested in simulations, but the main validation was performed on a semi-industrial dry grinding and classification circuit equipped with an electromagnetic mill. The results of the experiments presented in this paper show that the application of the on-line optimization algorithm allows for... [more]

A beam containing a piezoelectric layer or layers is used for piezoelectric harvesting from various processes. The structure of the beam is made by gluing the piezoelectric material on one side (unimorph) or both sides (bimorph) of a carrying substrate. Two piezoelectric layers, glued on both sides of the substrate, may be electrically parallel or series connected. This paper presents an experimental analysis of the impact of parallel and series connections of two Macro Fiber Composite (MFC) MFC patches in a bimorph on the charging of a capacitor. In experiments, the effective charging process of the capacitor was obtained both for parallel and series connection of two MFC patches. The bimorph with a parallel connection generated a larger capacitor charging power than the bimorph with a series connection in the range of voltage across the capacitor from 1 to 18 V. However, the bimorph with a series connection was more effective than a parallel connection for voltage across the charged... [more]

Tire normal forces are difficult to measure, but information on the vehicle normal force can be used in many automotive engineering applications, e.g., rollover detection and vehicle and wheel stability. Previous papers use algebraic equations to estimate the tire normal force. In this article, the estimation of tire normal force is formulated as an input estimation problem. Two observers are proposed to solve this problem by using a quarter-car suspension model. First, the Youla Controller Output Observer framework is presented. It converts the estimation problem into a control problem and produces a Youla parameterized controller as observer. Second, a Kalman filter approach is taken and the input estimation problem is addressed with an Unbiased Minimum Variance Filter. Both methods use accelerometer and suspension deflection sensors to determine the vehicle normal force. The design of the observers is validated in simulation and a sensitivity analysis is performed to evaluate their... [more]

New semiconductor technology is enabling the design of more reliable and high-performance power converters. In particular, wide bandgap (WBG) silicon carbide (SiC) and gallium nitride (GaN) technologies provide faster switching times, higher operating temperature, and higher blocking voltage. Recently, high-voltage GaN devices have opened the design window to new applications with high performance and cost-effective implementation. However, one of the main drawbacks is that these devices require accurate base current control to ensure safe and efficient operation. As a consequence, the base drive circuit becomes more complex and the final efficiency is decreased. This paper presents an improved gate driver circuit for GaN devices based on the use of a constant current regulator (CCR). The proposed circuit achieves constant current regardless of the operating conditions, solving variations with temperature, aging and operating conditions that may degrade the converter performance. Besid... [more]

This paper proposes a new compact electrothermal model of the Insulated Gate Bipolar Transistors (IGBT) dedicated for SPICE (Simulation Program with Integrated Circuit Emphasis). This model makes it possible to compute the non-isothermal DC characteristics of the considered transistor and the waveforms of terminal voltages and currents of the investigated device and its internal temperature at transients. This model takes into account the nonlinearity of thermal phenomena in this device. The form of the formulated model is described and the problem of estimating its parameter values is discussed. The correctness of the proposed model was verified experimentally both at DC operation and at transients. The obtained results are compared to the results of computations performed with the use of the classical literature model. A very good agreement between the results of measurements and computations performed with the new model is obtained at different cooling conditions and in a wide range... [more]

Automatic generation control (AGC) is primarily responsible for ensuring the smooth and efficient operation of an electric power system. The main goal of AGC is to keep the operating frequency under prescribed limits and maintain the interchange power at the intended level. Therefore, an AGC system must be supplemented with modern and intelligent control techniques to provide adequate power supply. This paper provides a comprehensive overview of various AGC models in diverse configurations of the power system. Initially, the history of power system AGC models is explored and the basic operation of AGC in a multi-area interconnected power system is presented. An in-depth analysis of various control methods used to mitigate the AGC issues is provided. Application of fast-acting energy storage devices, high voltage direct current (HVDC) interconnections, and flexible AC transmission systems (FACTS) devices in the AGC systems are investigated. Furthermore, AGC systems employed in different... [more]

Electro-hydraulic compact drives (ECDs) are an emerging technology for linear actuation in a wide range of applications. Especially within the low power range of 5−10 kW, the plug-and-play capability, good energy efficiency and small space requirements of ECDs render this technology a promising alternative to replace conventional valve-controlled linear drive solutions. In this power range, ECDs generally rely on passive cooling to keep oil and system temperatures within the tolerated range. When expanding the application range to larger power classes, passive cooling may not be sufficient. Research investigating the thermal behaviour of ECDs is limited but indeed required for a successful expansion of the application range. In order to obtain valuable insights into the thermal behaviour of ECDs, thermo-hydraulic simulation is an important tool. This may enable system design engineers to simulate thermal behaviour and thus develop proper thermal designs during the early design phase, e... [more]

This article discusses the current state and trends in the development of the electric power industry in Kazakhstan. An analysis of the energy supply and energy intensity of Kazakhstan’s GDP is provided in this paper. The results of the foresight of the risks and opportunities of the energy industry are described. This study identifies the relationship between the traditional development of the energy industry and the development of alternative energy sources. In addition, the work examines the risks and consequences of various trends in the development of national and global energy. Previous studies have shown that government efforts are insufficient in developing an alternative energy sector in Kazakhstan. The research results show that there is a need to transform energy production from traditional sources towards greater efficiency and environmental friendliness, as well as the active involvement of the business community in the development of an alternative energy market. This is... [more]

The circular economy (CE) as an idea involves applying the concept of sustainable development that has been gaining worldwide support. This shift in perception of energy and resource-use from its linear to circular forms creates a specific business environment, which constitutes the subject of this research. This article aims to analyze the impact of a manager’s energy on organizational wisdom, focusing on its circular business model activity. In the beginning, the article focuses on presenting ideas of the circular economy, emphasizing the manager’s activity in implementing strategic and operational tasks. These activities are identified as energy to launch mechanisms for developing organizational wisdom for sustainable enterprise. Assuming that organizational wisdom consists of two dimensions, organizational learning, and absorptive capacity, the research identifies relationships between them. The study was conducted at VIVE Textile Recycling Ltd., (Kielce, Poland). Empirical data we... [more]

Effective multiphase flow and transport simulations are a critical tool for screening, selection, and operation of geological CO2 storage sites. The relative permeability curve assumed for these simulations can introduce a large source of uncertainty. It significantly impacts forecasts of all aspects of the reservoir simulation, from CO2 trapping efficiency and phase behavior to volumes of oil, water, and gas produced. Careful consideration must be given to this relationship, so a primary goal of this study is to evaluate the impacts on CO2-EOR model forecasts of a wide range of relevant relative permeability curves, from near linear to highly curved. The Farnsworth Unit (FWU) is an active CO2-EOR operation in the Texas Panhandle and the location of our study site. The Morrow ‘B’ Sandstone, a clastic formation composed of medium to coarse sands, is the target storage formation. Results indicate that uncertainty in the relative permeability curve can impart a significant impact on model... [more]

The problem of energy recovery in braking of an electric vehicle is solved here, which ensures high quality blended deceleration using electrical and friction brakes. A model reference controller is offered, capable to meet the conflicting requirements of intensive and gradual braking scenarios at changing road surfaces. In this study, the neural network controller provides torque gradient control without a tire model, resulting in the return of maximal energy to the hybrid energy storage during braking. The torque allocation algorithm determines how to share the driver’s request between the friction and electrical brakes in such a way as to enable regeneration for all braking modes, except when the battery state of charge and voltage levels are saturated, and a solo friction brake has to be used. The simulation demonstrates the effectiveness of the proposed coupled two-layer neural network capable of capturing various dynamic behaviors that could not be included in the simplified phys... [more]

The development of data driven methods for Li-ion battery diagnosis and prognosis is a growing field of research for the battery community. A big limitation is usually the size of the training datasets which are typically not fully representative of the real usage of the cells. Synthetic datasets were proposed to circumvent this issue. This publication provides improved datasets for three major battery chemistries, LiFePO4, Nickel Aluminum Cobalt Oxide, and Nickel Manganese Cobalt Oxide 811. These datasets can be used for statistical or deep learning methods. This work also provides a detailed statistical analysis of the datasets. Accurate diagnosis as well as early prognosis comparable with state of the art, while providing physical interpretability, were demonstrated by using the combined information of three learnable parameters.

Gas migration in oil and gas wells is defined as gases and/or fluids from adjacent formations invading a freshly cemented annulus. During well completions, gas and/or fluids can migrate to zones with lower pressure or even to the surface. Static gel strength (SGS), related to the yield stress of the cement, is a widely accepted measurement used to predict and minimize gas migration. In this review article, we look at the mechanisms and some possible solutions to gas migration during oil and gas well cementing. The use of static gel strength (SGS) and experimental measurements for SGS and wellbore pressure reduction are discussed. Rheological properties, including the yield stress and the viscosity of cement slurries, are also briefly discussed. Understanding the rheological properties of cement is complex since its material properties depend on cement type, as well as the shape and size distribution of cement particles. From this brief review, it is evident that in order to reduce free... [more]

We report the design, fabrication, and characterization of a prototype that meets the form, fit, and function of a household 1.5 V AA battery, but which can be wirelessly recharged without removal from the host device. The prototype system comprises a low-frequency electrodynamic wireless power transmission (EWPT) receiver, a lithium polymer energy storage cell, and a power management circuit (PMC), all contained within a 3D-printed package. The EWPT receiver and overall system are experimentally characterized using a 238 Hz sinusoidal magnetic charging field and either a 1000 µF electrolytic capacitor or a lithium polymer (LiPo) cell as the storage cell. The system demonstrates a minimal operating field as low as 50 µTrms (similar in magnitude to Earth’s magnetic field). At this minimum charging field, the prototype transfers a maximum dc current of 50 µA to the capacitor, corresponding to a power delivery of 118 µW. The power effectiveness of the power management system is approximat... [more]

In this paper, a sliding mode control is presented for direct torque and stator flux control of interior permanent magnet synchronous motor in a rotor speed sensorless drive system. The control scheme is developed in a specific synchronous rotating reference frame (X-Y) in which the stator current space vector coincides with the direct (X) axis. For this control technique no need to have any knowledge of machine parameters such as stator two-axis inductances, rotor permanent magnets flux linkage, and even the rotor initial position. However, the on-line actual stator resistance value is required to estimate the stator flux components in the stator stationary two-axis reference frame. In this control strategy, two simple methods are described for estimating the rotor speed and stator resistance. Some simulation and experimental results are presented to support the validity and effectiveness of the proposed control scheme.

The efficiency of tunnels systems is often evaluated using numerical simulations. This concerns both to normal and emergency mode of tunnel systems operation. Therefore the safety level of tunnel users may depend on the quality of numerical models being built. The most often studied areas cover the researches on natural and forced airflows in the normal mode and on fire development and smoke spreading in the emergency mode as well as modeling of fan operation. Thus, many software packages implementing Computational Fluid Dynamics (CFD) are applied here. Despite the available software is recognized as reliable, the problem arises because the built numerical models should be validated at least partially with experimental data. There is a shortage of experimental data from real tunnels due to high costs and many organizational or formal difficulties. Some researchers use data from scaled experiments, but this leads to problems connected with scaling. The paper presents the application of... [more]

Considering the necessity of achieving economic development by keeping the quality of the environment, the aim of this paper is to study the impact of economic growth on GHG emissions in a sample of Central and Eastern European (CEE) countries (V4 countries, Bulgaria and Romania) in the period of 1996−2019. In the context of dynamic ARDL panel and environmental Kuznets curve (EKC), the relationship between GHG and GDP is N-shaped. A U-shaped relationship was obtained in the renewable Kuznets curve (RKC). Energy consumption, domestic credit to the private sector, and labor productivity contribute to pollution, while renewable energy consumption reduces the GHG emissions. However, more efforts are required for promoting renewable energy in the analyzed countries.

Cost reductions in nascent forms of Renewable Energy Technology (RET) are essential for them to contribute to the energy mix. Policy intervention can facilitate this cost reduction; however, this may require a significant investment from the public sector. These cost reductions fall into two broad categories: (1) incremental cost reductions through continual improvements to existing technologies, and (2) radical innovation where technologies that significantly differ from the incumbents are developed. This study presents a modelling methodology to integrate radical innovation in RET experience curve and learning investment analysis, using wave energy as an example nascent RET. This aims to quantify the potential effects of radical innovation on the learning investment, allowing the value of successful innovation to be better analysed. The study highlights the value offered by radical innovations in long-term deployment scenarios for wave energy. This suggests that high-risk R&D efforts... [more]

This study was performed to analyze the spray, combustion, and air pollutant characteristic of JP-5 fuel for naval aircraft in a spray visualization system and a single-cylinder CRDI diesel engine that can be visualized. The analysis results of JP-5 fuel were compared with DF. The spray tip penetration of JP-5 showed diminished results as the spray developed. JP-5 had the highest ROHR and ROPR regardless of the fuel injection timings. The physicochemical characteristics of JP-5, such as its excellent vaporization and low cetane number, were analyzed to prolong the ignition delay. Overall, the longer combustion period and the lower heat loss of the DF raised the engine torque and the IMEP. JP-5 showed higher O2 and lower CO2 levels than the DF fuel. The CO emission level increased as the injection timing was advanced in two test fuels, and the CO emitted from the DF fuel, which has a longer combustion period than JP-5, turned out to be lower. NOx also reduced as the fuel injection timin... [more]

Coal combustion is an anthropogenic source of mercury (Hg) emissions to the atmosphere. The strong toxicity and bioaccumulation potential have prompted attention to the control of mercury emissions. Pyrolysis has been regarded as an efficient Hg removal technology before coal combustion and other utilization processes. In this work, the Hg speciation in coal and its thermal stability were investigated by combined sequential chemical extraction and temperature programmed decomposition methods; the effect of coal rank on Hg speciation distribution and Hg release characteristics were clarified based on the weight loss of coal; the amount of Hg released; and the emission of sulfur-containing gases during coal pyrolysis. Five species of mercury were determined in this study: exchangeable Hg (F1), carbonate + sulfate + oxide bound Hg (F2), silicate + aluminosilicate bound Hg (F3), sulfide bound Hg (F4), and residual Hg (F5), which are quite distinct in different rank coals. Generally, Hg enr... [more]

Vehicle exhaust emission tests use exhaust sampling systems that dilute the exhaust gas with ambient air. The dilution factor DF is calculated assuming that the combustion is complete, and that the engine is operated at a stoichiometric air-fuel ratio (AFR). These assumptions are not always met. This is especially true for diesel engines. This article discusses the tests to find out what the average lambda (λ) over the ARTEMIS, WLTC and NEDC driving cycles is and how this affects the result of the emission measurements. Measurements were carried out on a chassis dynamometer equipped with a standard emission measurement system used during the homologation. The λ was calculated using the Brettschneider equation. The dilution ratio DR was also determined by measuring the CO2 concentration in the raw exhaust gas. The CO2-tracer method used for this was modified. The median of the λ for a CI vehicle was 1.23−3.31, which makes the relative percentage difference between the DF and DR (ΔDF) in... [more]