The electrification of transportation has been developed to support energy efficiency and CO2 reduction. As a result, electric vehicles (EVs) have become more popular in the current transport system to create more efficient energy. In recent years, this increase in EVs as well as renewable energy resources (RERs) has led to a major issue for power system networks. This paper studies electrical vehicles (EVs) and their applications in the smart grid and provides practical solutions for EV charging strategies in a smart power system to overcome the issues associated with large-scale EV penetrations. The research first reviews the EV battery infrastructure and charging strategies and introduces the main impacts of uncontrolled charging on the power grid. Then, it provides a practical overview of the existing and future solutions to manage the large-scale integration of EVs into the network. The simulation results for two controlled strategies of maximum sensitivity selection (MSS) and gen... [more]

This paper describes the algorithm for optimal distribution network reconfiguration using the combination of a heuristic approach and genetic algorithms. Although similar approaches have been developed so far, they usually had issues with poor convergence rate and long computational time, and were often applicable only to the small scale distribution networks. Unlike these approaches, the algorithm described in this paper brings a number of uniqueness and improvements that allow its application to the distribution networks of real size with a high degree of topology complexity. The optimal distribution network reconfiguration is formulated for the two different objective functions: minimization of total power/energy losses and minimization of network loading index. In doing so, the algorithm maintains the radial structure of the distribution network through the entire process and assures the fulfilment of various physical and operational network constraints. With a few minor modificati... [more]

Accurate prediction of crude oil prices is meaningful for reducing firm risks, stabilizing commodity prices and maintaining national financial security. Wrong crude oil price forecasts can bring huge losses to governments, enterprises, investors and even cause economic and social instability. Many classic econometrics and computational approaches show good performance for the ordinary time series prediction tasks, but not satisfactory in crude oil price predictions. They ignore the characteristics of non-linearity and non-stationarity of crude oil prices data, which hinder an accurate prediction and eventually lead to poor accuracy or the wrong result. Empirical mode decomposition (EMD) and ensemble EMD (EEMD) solve the problems of non-stationary time series forecasting, but they also generate new problems of mode mixing and reconstruction errors. We propose a hybrid method that is combination of the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and multi... [more]

The aim of this work is to analyze the effect of using diethyl ether (DEE) as an oxygenated additive of straight vegetable oils (SVOs) in triple blends with fossil diesel, to be used in current compression ignition (C.I.) engines, in order to implement the current process of replacing fossil fuels with others of a renewable nature. The use of DEE is considered taking into account the favorable properties for blending with SVO and fossil diesel, such as its very low kinematic viscosity, high oxygen content, low autoignition temperature, broad flammability limits (it works as a cold start aid for engines), and very low values of cloud and pour point. Therefore, DEE can be used as a solvent of vegetable oils to reduce the viscosity of the blends and to improve cold flow properties. Besides, DEE is considered renewable, since it can be easily obtained from bioethanol, which is produced from biomass through a dehydration process. The vegetable oils evaluated in the mixtures with DEE were ca... [more]

The Directive 2010/31/EU on the energy performance of buildings has introduced the standard of “nearly zero-energy buildings” (NZEBs). European requirements place the obligation to reduce energy consumption on all European Union Member States, particularly in sectors with significant energy consumption indicators. Construction is one such sector, as it is responsible for around 40% of overall energy consumption. Apart from a building’s mass and its material and installation solutions, its energy consumption is also affected by its placement relative to other buildings. A proper urban layout can also lead to a reduction in project development and occupancy costs. The goal of this article is to present a method of optimising single-family house complexes that takes elements such as direct construction costs, construction site organisation, urban layout and occupancy costs into consideration in the context of sustainability. Its authors have analysed different proposals of the placement o... [more]

Energy efficiency improvement in industrial companies is an essential prerequisite for the enhancement of their competitive positions in the national and global markets. Yet, the approaches currently employed in respect of the energy management do not fully utilize the innovative potential of energy technologies to achieve strategic goals. One way to further develop energy management is theoretical justification of the use of new approaches based on the suggested concept of the energy saving and energy efficiency processes’ positioning in the system of a company’s management priorities. In this article, we consider the applied use of the developed conceptual approach from the perspective of the energy saving and energy efficiency program development at the company. The main purpose of this paper is to justify the relations between energy management and strategic decision making in industrial companies. The results of the research conducted, firstly, make a certain contribution into the... [more]

This paper presents the properties of fractional-order magnetic coupling. The difficulties connected with the analysis of two coils in dynamic states, resulting from the classical approach, provided motivation for studying the properties of fractional-order magnetic coupling. These difficulties arise from failure to comply with the commutation laws, i.e., a sudden power disappearance in the primary winding caused by a switch-mode power supply. Theoretically, under ideal conditions, a sudden power disappearance in the coil is, according to the classical method, manifested by a sudden voltage surge in the form of the Dirac delta function. As is well-known, it is difficult to obtain such ideal conditions in practice; the time of current disappearance does not equal zero due to the circuit breaker’s imperfection (even when electronic circuit breakers are used, the time equals several hundred nanoseconds). Furthermore, it is necessary to take into account phenomena occurring in real inducta... [more]

This paper presents a robust repowering approach to the structural response of tubular steel wind turbine towers enhanced by internal stiffening rings. First, a structural response simulation model was validated by comparison with the existing experimental data. This was then followed with a mesh density sensitivity analysis to obtain the optimum element size. When the outdated wind turbine system needs to be upgraded, the wall thickness, the mid-section width-to-thickness ratio and the spacing of the stiffening rings of wind turbine tower were considered as the critical design variables for repowering. The efficiency repowering range of these design variables of wind turbine towers of various heights between 50 and 250 m can be provided through the numerical analysis. Finally, the results of efficiency repowering range of design variables can be used to propose a new optimum design of the wind turbine system when repowering a wind farm.

Aiming at problems of power allocation and economic scheduling for independent multi-microgrid systems, a bi-level optimization method based on optimal power flow and consensus algorithm is proposed. The novelty of the method is that an independent multi-microgrid system is divided into two layers: in the upper layer, with the predicted output range of the microgrids as the input data, each microgrid is considered as a virtual power supply or virtual load, and taking the minimum network loss as the goal, the energy mutual aid and power allocation among the microgrids are transformed into solving the optimal power flow; in the lower layer, taking the upper layer power distribution scheme as the constraint condition, considering load fluctuation and wind/solar generation uncertainty, the optimal dispatch model of the controllable distributed generator is established based on the distributed theory and the consensus algorithm of equal cost increment, and the "plug and play" of the distrib... [more]

Microalgae biofilm-based culture has attracted much interest due to its high harvest efficiency and low energy requirements. Using light-emitting diodes (LEDs) as light source for microalgae culture has been considered as a promising choice to enhance the economic feasibility of microalgae-based commodities. In this work, the LED power conversion capability and CO2 fixation rate of microalgae biofilms (Chlorella ellipsoidea and Chlorella pyrenoidosa) cultured under different light spectra (white, blue, green and red) were studied. The results indicated that the power-to-biomass conversion capabilities of these two microalgae biofilms cultured under blue and white LEDs were much higher than those under green and red LEDs (C. ellipsoidea: 32%−33% higher, C. pyrenoidosa: 34%−46% higher), and their power-to-lipid conversion capabilities cultured under blue LEDs were 61%−66% higher than those under green LEDs. The CO2 fixation rates of these two biofilms cultured under blue LEDs were 13% an... [more]

The interest in studying energy systems’ resilience is increasing due to a rising awareness of the importance of having a secure energy supply. This growing trend is a result of a series of recent disruptions, among others also affecting electricity systems. Therefore, it is of crucial importance for policymakers to determine whether their country has a resilient electricity supply. Starting from a set of 12 indicators, this paper uses data envelopment analysis (DEA) to comprehensively evaluate the electricity supply resilience of 140 countries worldwide. Two DEA models are applied: (1) the original ratio-based Charnes, Cooper, and Rhodes (CCR) model and (2) a novel hybrid framework for robust efficiency analysis incorporating linear programming and Monte Carlo simulations. Results show that the CCR model deems 31 countries as efficient and hence lacks the capability to differentiate them. Furthermore, the CCR model considers only the best weight vectors for each country, which are not... [more]

This study developed a NH3 emission factor for bituminous coal power plants in South Korea in order to investigate the NH3 emission characteristics. The NH3 concentration analysis results showed that emissions from the selected bituminous coal power plants were in the range of 0.21−0.99 ppm, and that the difference in NH3 concentration was affected by NOx concentration. The NH3 emission factor was found to be 0.0029 kg NH3/ton, which demonstrated that the difference in the values obtained from the research conducted in South Korea was lower than the difference in the emission factor provided by the U.S. EPA, which is currently applied in the statistics of South Korea. NH3 emissions were compared by using the NH3 emission factor developed in this study alongside the EPA’s NH3 emission factor that is currently applied in South Korea’s statistics; the difference was found to be 206 NH3 ton/year. This implies that an emission factor that reflects the national characteristics of South Korea... [more]

This study measures the connectedness of natural gas and electricity spot returns to their futures returns with different maturities. We employ the Henry Hub and the Pennsylvania, New Jersey, and Maryland (PJM) Western Hub Peak as the natural gas price indicator and the wholesale electricity price indicator, respectively. We also use each commodity’s spot prices and 12 types of futures prices with one to twelve months maturities and realize results in fourfold. First, we observe mutual spillover effects between natural gas futures returns and learn that the natural gas futures market is integrated. Second, we observe the spillover effects from natural gas futures returns to natural gas spot returns (however, the same is not evident for natural gas spot returns to natural gas futures returns). We find that futures markets have better natural gas price discovery capabilities than spot markets. Third, we observe the spillover effects from natural gas spot returns to electricity spot retur... [more]

In this study, P25-titanium dioxide (TiO2) was doped with ruthenium (Ru) by systematically varying the Ru content at 0.15, 0.30, 0.45 and 0.6 mol%. The synthesized Ru-doped TiO2 nanomaterials have been characterized by X-ray diffraction (XRD), Raman spectroscopy, energy-dispersive X-ray (EDX) analysis, UV-visible (UV−Vis) spectroscopy, and electrochemical impedance (EIS) spectroscopy. The XRD patterns of undoped and Ru-doped TiO2 nanomaterials confirm the presence of mixed anatase and rutile phases of TiO2 while EDX spectrum confirms the presence of Ti, O and Ru. Further, UV-visible absorption spectra of doped TiO2 nanomaterial reveal a slight red shift on Ru-doping. The short circuit current density (JSC) of the cells fabricated using the Ru-doped TiO2 photoanode was found to be dependent on the amount of Ru present in TiO2. Optimized cells with 0.3 mol% Ru-doped TiO2 electrodes showed efficiency which is 20% more than the efficiency of the control cell (η = 5.8%) under stimulated ill... [more]

Fixed exposure will lead to underexposure or overexposure of collected flame radiation images using CCD, which has a great influence on the temperature measuring accuracy. A temperature measurement method was proposed by image fusion with multi-exposure, which can eliminate the influence of insufficient underexposure and overexposure. The approach was first to acquire a group of flame radiation images during different exposures. Then a partial region with good exposure effect in each radiation image was obtained by segmentation, with which the complete flame image can be spliced together. An experimental system was built to calibrate the temperature measurement parameters by two-color pyrometry through a blackbody furnace. The relation between exposure time and monochromatic gray level, as well as the relation between the temperature and temperature measurement coefficient were obtained. A candle flame was selected as the measuring object and the complete and accurate flame temperature... [more]

We introduce the problem of load nowcasting to the energy forecasting literature. The recent load of the objective area is predicted based on limited available metering data within this area. Thus, slightly different from load forecasting, we are predicting the recent past using limited available metering data from the supply side of the system. Next, to an industry benchmark model, we introduce multiple high-dimensional models for providing more accurate predictions. They evaluate metered interconnector and generation unit data of different types like wind and solar power, storages, and nuclear and fossil power plants. Additionally, we augment the model by seasonal and autoregressive components to improve the nowcasting performance. We consider multiple estimation techniques based on the lassoand ridge and study the impact of the choice of the training/calibration period. The methodology is applied to a European TSO dataset from 2014 to 2019. The overall results show that in compariso... [more]

La1-xCexNi5 alloys (x = 0, 0.09, 0.25 and 0.5) were investigated in terms of their structures, phase contents, hydrogen storage properties and microhardness. It was confirmed that a cerium addition to the reference (LaNi5) alloy caused structural changes such as lattice shrinkage and, as a result, changed both the absorption and desorption pressures and the enthalpies of formation and decomposition. The alloy with the highest cerium content was found to possess a two-phase structure, probably as a result of nonequilibrium cooling conditions during its manufacturing process. The microhardness was found to increase to some extent with the cerium content and decrease for samples with the highest cerium content.

In this paper, the boiling synchronization of two-phase flow patterns in two parallel minichannels of 1 mm in diameter with connected compressible volumes was analyzed. The analysis was performed using images recorded with a high-speed camera. The degree of synchronization between channels was evaluated by assessing the presence of liquid flow in the small part of the minichannels. It can be concluded that boiling is synchronized when small bubble flow or wavy annular flow occur in neighboring channels. The occurrence of slug flow in one channel causes the boiling in neighboring channels to become unsynchronized. The result of the image analysis shows that the correlation coefficient based on the evaluation of the presence of liquid flow in the small part of the minichannels over a long enough time period allows for the detection of boiling synchronization.

The development of the bus rapid transit system (BRTS) is tremendously growing in developing countries of the world. In large cities, the projection of transportation intends to enhance economic growth and changes the image of the city for both residents and outsiders. The purpose of this research was to study the application of alternative options for energy efficient BRTS in developing countries. The BRTS has some of its accessibility patterns that relate to the socio-economic strata. A decision-making efficiency analysis methodology has been applied to analyze the comparative analysis of both conventional fuel and hybrid bus systems for the Multan city of Pakistan. The section-wise application of a hybrid energy-based bus system has been analyzed in comparison to the conventional bus system. Out of 21 stations, the efficiency-wise hybrid bus system remained superior or equivalent to the standard value of 1 except one midpoint section. The finding of the analysis indicates that the h... [more]

The stochastic point reactor with random parameters is considered in this work. The hybrid uncertain variations—noise and random parameters—are analyzed with the spectral techniques for the efficiency and high rates of convergence. The proposed hybrid technique enables one to derive an equivalent deterministic system that can be solved to get the mean solution and deviations due to each uncertainty. The contributions of different sources uncertainties can be decomposed and quantified. The deviations in the thermal hydraulics are also computed in the current work. Two model reactors are tested with the proposed technique and the comparisons show the advantages and efficiency compared with the other techniques.

Taking the hydraulic wind turbine as the research object, the method is studied to improve the utilization ratio of wind energy for hydraulic wind turbine, when the wind speed is lower than the rated wind speed. The hydraulic fixed displacement pump speed and generating power can be used as control output to realize the maximum power point tracking control. The characteristics of the maximum power point tracking control are analyzed for hydraulic wind turbine, and the hydraulic output power is taken as control output based on the comprehensive performance requirements. Because the hydraulic wind turbine is a strong multiplication nonlinear system, the system is globally linearized based the feedback linearization method, and the maximum power point tracking control law is obtained. The simulation and experiment results show that the system has good dynamic performance with the proposed control law. The control provides theoretical guidance for optimal power tracking control law applica... [more]

The space-borne manipulator has been playing an important part in docking tasks. Docking collision can easily lead to instability of both the manipulator and floating base. Aiming at the problem of soft capture, a novel soft-contact joint with dual working modes is developed, especially to buffer and unload the spatial collision momentum. Furthermore, considering a series-wound soft-capture manipulator with multi-joints, a generalized modeling method was established by using the Kane approach. Both the benefits of soft-contact joint and the effectiveness of dynamics equations are verified in MATLAB and Adams software by simulations of a two-joint manipulator with eight-DOF. The comparative simulation results showed the advantages of the proposed soft-contact joint in reducing instability from spatial impact.

A new circuit structure and control method for a high power interleaved dual-buck inverter are proposed. The proposed inverter consists of six switches, four diodes and two inductors, uses a dual-buck structure to eliminate zero-cross distortion, and operates in an interleaved mode to reduce the current stress of switch. To reduce the total harmonic distortion at low output power, the inverter is controlled using discontinuous-current-mode control combined with continuous-current-mode control. The experimental inverter had a power-conversion efficiency of 98.5% at output power = 1300 W and 98.3% at output power = 2 kW, when the inverter was operated at an input voltage of 400 VDC, output voltage of 220 VAC/60 Hz, and switching frequency of 20 kHz. The total harmonic distortion was < 0.66%, which demonstrates that the inverter is suitable for high-power dc-ac power conversion.

In this research, the idea of multicomponent, one-vessel cleaning of syngas through simultaneous dedusting and adsorption is described. Data presented were obtained with the use of a pilot-scale 60 kWth fixed-bed GazEla reactor, coupled with a dry gas cleaning unit where mineral sorbents are injected into raw syngas at 500−650 °C, before dedusting at ceramic filters. The research primarily presents results of the application of four calcined sorbents, i.e., chalk (CaO), dolomite (MgO−CaO), halloysite (AlO−MgO−FeO), and kaolinite (AlO−MgO) for high-temperature (HT) adsorption of impurities contained in syngas from gasification of biomass. An emphasis on data regarding the stability of the filtration process is provided since the addition of coating and co-filtering materials is often necessary for keeping the filtration of syngas stable, in industrial applications.

In recent years, different off-the-shelf solutions for the rapid control prototyping of power electronics converters have been commercialised. The main benefits of those systems are based on a fast and easy-to-use environment due to high-level programming. However, most of those systems are very expensive and are closed software and hardware solutions. In this context, this paper presents the design and implementation of a control platform targeting at the segment in between expensive off-the-shelf control platforms and low-cost controllers. The control platform is based on the Launchpad TMS320F28379D from Texas Instruments, and it is equipped with an expansion board that provide analogue-to-digital measurements, switching signals and hardware protections. The performance of the control platform is experimentally tested on a 20 kVA power converter.