The geometry of a conventional two-bladed Savonius rotor was used in this study based on a report available in the literature. A two-dimensional rotor model consisting of two buckets and an overlap ratio of 0.1 was prepared. The unsteady Reynolds averaged Navier-Stokes (URANS) equations and the eddy-viscosity turbulence model SST k-ω were employed in order to solve the fluid motion equations numerically. Instantaneous velocities and pressures were calculated at defined points around the rotor and then averaged. The research shows that the operating rotor significantly modifies the flow on the downwind part of the rotor and in the wake, but the impact of the tip speed ratio on the average velocity distribution is small. This parameter has a much greater influence on the characteristics of the aerodynamic moment and the distribution of static pressure in the wake. In the upwind part of the rotor, the average velocity parallel to the direction of undisturbed flow is 29% lower than in the... [more]

This paper presents a low-cost/high-precision smart power supply for application on data loggers. The microprocessor unit is the brain of the system and manages the events and was optimized to provide electrical energy to the electronic devices under normal operation and under the presence of disruptive events. The measurements showed that when switching either from battery to AC or from AC to battery, neither caused the shutdown of the power supply nor affected the behavior of the power supply. The power supply was able to charge 80% of the battery on a fast recharge of 1 h and the remaining 20% on a slow recharge of 2 h. The current allocated to the battery did not affect the operation of the power supply. The tests also showed that the power supply was able to transmit relevant information about its operation to external computers through a serial connection. This information includes the voltages at the battery and at the output of the voltage regulators, the voltage level of the A... [more]

The connection between Earth’s global temperature and carbon dioxide (CO2) emissions is one of the highest challenges in climate change science since there is some controversy about the real impact of CO2 emissions on the increase of global temperature. This work contributes to the existing literature by analyzing the relationship between CO2 emissions and the Earth’s global temperature for 61 years, providing a recent review of the emerging literature as well. Through a statistical approach based on maximum entropy, this study supports the results of other techniques that identify a positive impact of CO2 in the increase of the Earth’s global temperature. Given the well-known difficulties in the measurement of global temperature and CO2 emissions with high precision, this statistical approach is particularly appealing around climate change science, as it allows the replication of the original time series with the subsequent construction of confidence intervals for the model parameters... [more]

Smart buildings are becoming a new standard in construction, which allows for many possibilities to introduce ergonomics and energy savings. These contain simple improvements, such as controlling lights and optimizing heating or air conditioning systems in the building, but also more complex ones, such as indoor movement tracking of building users. One of the necessary components is an indoor localization system, especially without any device worn by the person being located. These types of solutions are important in locating people inside smart buildings, managing hospitals of the future and other similar institutions. The article presents a prototype of an innovative energy-efficient device for radio tomography, in which the hardware and software layers of the solution are presented. The presented example consists of 32 radio sensors based on a Bluetooth 5 protocol controlled by a central unit. The preciseness of the system was verified both visually and quantitatively by the image r... [more]

Nowadays, electric load forecasting through a data analytic approach has become one of the most active and emerging research areas. It provides future consumption patterns of electric load. Since there are large fluctuations in both electricity production and use, it is a difficult task to achieve a balance between electric load and demand. By analyzing past electric consumption records to estimate the upcoming electricity load, the issue of fluctuating behavior can be resolved. In this study, a framework for feature selection, extraction, and regression is put forward to carry out the electric load prediction. The feature selection phase uses a combination of extreme gradient boosting (XGB) and random forest (RF) to determine the significance of each feature. Redundant features in the feature extraction approach are removed by applying recursive feature elimination (RFE). We propose an enhanced support vector machine (ESVM) and an enhanced convolutional neural network (ECNN) for the r... [more]

Supplying shipping vessels with electricity at the ports can improve the air quality of the ports, reduce the greenhouse gas emissions from the shipping industry, contribute to the economic growth, and increase the political dependency of the countries by reducing the dependence on conventional fossil fuels. Several countries promote supplying the vessels when they are docking at ports from renewable energy systems by establishing dedicated funding mechanisms to remove the obstacles facing the shore power systems. In this context, this paper presents a new modular power electronic converter for shore power systems at shipping ports, which can perform three functions. Firstly, it will harvest the energy from a renewable energy source, such as hydroelectric and solar photovoltaic (PV) sources and ensure maximum energy extraction. Secondly, it will control the power flow from these sources to the battery storage. Finally, it will control the power flow from the battery to the vessels and/... [more]

Researchers at many different institutions around the world study voltage and current waveform distortions in power networks using a variety of techniques. Due to the uncontrolled growing number of nonlinear devices supplied by electrical energy, more severe supraharmonic pollution has been observed. A bibliometric analysis of the topic development between 2013 and 2022 is presented in the paper. Using the selected search tools, a comparative review of articles published in the last three years was conducted. It organizes the existing knowledge about supraharmonic pollution generated by nonlinear devices and identifies current research challenges associated with the spread of these disturbances in electrical networks. The most frequently discussed topics by researchers are those that deal with the level of emissions generated by supraharmonic sources and their effects on components of the power system. The second most prominent research direction is the detection, measurement, analysis... [more]

The analysis of public attitudes towards nuclear energy represents an issue that is commonly investigated, especially considering the new context of classifying some nuclear power plants as green investments under the European Green Deal. The importance of this topic is critical to the future of nuclear power generation. The purpose of this study is to identify the relationships that exist between the different factors and the attitude of the public towards nuclear energy in the context of the European Green Deal. The article identifies and analyzes the main factors that influence this relationship. In this context, a questionnaire-based survey was conducted regarding the identification of the relationship between public knowledge, degree of cooperation, perceived risks, trust and attitude towards nuclear energy. The sample was chosen using the snowball method. The analysis was made up of 578 respondents from different segments of age, gender, place of residence, field of activity, wor... [more]

Accurate estimation of the thermal conductivity of porous materials is crucial for the modeling of heat transfer and energy consumption calculation in energy, aerospace, biomedicine and chemical engineering, etc. The series-parallel model is a simple and direct method and is usually used in the prediction of the effective thermal conductivity (ETC) of porous materials. In this work, the weighted coefficients of the series and parallel section were obtained based on the tortuosity of the porous materials. Then, the physical model of the ETC of the porous materials was established. Furthermore, the ETC of the porous materials was developed using the fractal model to calculate the pore cross-sectional area of the porous materials. Finally, quantitative analysis of the characteristic parameters, e.g., porosity, tortuosity, tortuous fractal dimension and pore diameter distribution, of the ETC of the porous materials was conducted. The results show that the proposed model can provide an accu... [more]

The adoption of smart grids is becoming a common reality worldwide. This new reality is starting to impact energy customers as they face a dynamic grid in which they can actively participate. However, if energy customers are not prepared to participate actively, they can have their energy costs increased. This paper provides a review of acceptance models and customer surveys around the world made to assess the customers’ perception and willingness to participate in smart grids. Contributing to this assessment, this paper presents a survey undertaken in Portugal. The survey results demonstrate a willingness, from the customer’s end, to actively participate in smart grid initiatives. It was found that 92.9% of participants are willing to plan their energy usage to face hourly energy prices and that 95.0% of participants are willing to accept an external control of at least one appliance, enabling direct load control demand response programs. Also, the results identified two cognitive ten... [more]

Inverters with Quasi-Z-Source Networks (QZSN) provide DC-DC boosting and DC-AC conversion in a single stage. It offers reduced cost, complexity, and volume compared with the classical two-stage conversion system, which is composed of a boost converter followed by a Voltage-Source-Inverter (VSI). Further, QZSI provides superior conversion characteristics for single-stage grid-connected photovoltaic transformerless systems. However, the absence of galvanic isolation in these systems makes it possible to allow leakage current through these systems’ parasitic capacitances due to the high-frequency Common-Mode Voltage (CMV) generated by the Pulse Width Modulation (PWM) nature of the inverter output voltages. As a result of this current, critical safety issues may arise with PV systems. Many PWM techniques have been presented in recent years for QZSIs. This paper is intended to provide a comprehensive analysis and review study of the characteristics of most of these PWM techniques in terms o... [more]

To solve the optimization issues of interior permanent magnet synchronous motors (IPMSMs) and ensure a large output torque while minimizing torque ripple and core loss, the multi-objective optimization strategy should be employed. In this study, we took an 8-pole, 48-slot IPMSM as a specimen. First, the width and thickness of the permanent magnet (PM) and the rotor bridge structures were pre-selected as optimization parameters, while torque ripple and core loss were taken as optimization targets. Then, the Taguchi method to perform orthogonal experiments was employed to select the multi-parameter combinations that make the experimental results stable and with little fluctuation. To ensure the optimal results, the function equations were obtained by multivariate nonlinear fitting, while the parameters were optimized by particle swarm optimization (PSO). Finally, the optimal results were verified by the Finite Element Method (FEM). The results show that our proposed hybrid method can pro... [more]

Changes in the energy sector, associated with the move away from fossil fuels, pose a challenge for appropriate thermal energy management in residential buildings. The important element to deal with the variability of renewable energy in thermal systems is latent heat thermal energy storage. Due to the low thermal conductivity of phase change materials, a number of techniques are proposed to enhance the heat transfer process. In this research, the global sensitivity of fin geometrical parameters on the melting and solidification times and energy efficiency of these processes was investigated. The computational model of the phase change was developed using the finite volume method with the enthalpy-porosity model and Boussinesq approximation. Numerical simulations were carried out according to the design of experiments technique. The multi-dimensional response surface was developed, and the multi-objective optimisation was done. The research shows that the melting process is most influe... [more]

Recently, emerging third-generation photovoltaic technologies have shown rapid progress in device performance; the power conversion efficiencies (PCEs) of organic bulk heterojunction (BHJ) and perovskite solar cells (PSCs) are now surpassing 19% and 25%, respectively. Despite this dramatic enhancement, their efficiencies are theoretically limited based on the detailed balance model which accounts for inevitable loss mechanisms under operational conditions. Integrated solar cells, formed by monolithically integrating two photoactive layers of perovskite and BHJ with complementary absorption, provide a promising platform for further improvement in solar cell efficiency. In perovskite/BHJ integrated solar cells (POISCs), high bandgap perovskite offers high open-circuit voltage with minimal losses while low bandgap organic BHJ extends absorption bandwidth by covering the near-infrared region, resulting in additional photocurrent gain. Different from conventional tandem solar cells, integra... [more]

Homogeneous charge compression ignition is considered a promising solution to face the increasing regulations imposed by the legislator in the transport sector, thanks to pollutant and CO2 emissions reduction. In this work, a quasi-dimensional multi-zone HCCI model integrated with 1D commercial software is developed and validated. It is based on the control mass Lagrangian approach and computes the mixture chemistry evolution through offline tabulation of chemical kinetics (tabulated kinetic of ignition). Thus, the simulation can predict mixture auto-ignition with reduced computational effort and high accuracy. Multi-zone schematization mimics the typical thermal stratification of HCCI engines, controlling the combustion evolution. The model is coupled to sub-models for pollutant emissions estimation. Initially, the tabulated chemistry approach is validated against a chemical kinetics solver applied to a constant-volume homogeneous reactor, considering various fuel blends. The model is... [more]

Data sets of internal resistances and open-circuit voltage of a particular battery are needed in ANSYS Fluent program to predict the heat generation accurately. However, one set of available data, called Chen’s original, does not cover all types and shapes of batteries. Therefore, this research was intended to study the effects of shapes and polarization chemistries on heat generation in Li-ion batteries. Two kinds of material chemistries (nickel manganese cobalt oxide, NMC, and lithium iron phosphate, LFP) and three forms (cylindrical, pouch, and prismatic) were studied and validated with the experiment. Internal resistance was unique to each cell battery. Differences in shapes affected the magnitude of internal resistance, affecting the amount of heat generation. Pouch and prismatic cells had lower internal resistance than cylindrical cells. This may be the result of the forming pattern, in which the anode, cathode, and separator are rolled up, making electrons difficult to move. In... [more]

Well interference has drawn great attention in the development of shale gas reservoirs. In the W shale gas reservoir, well interference increased from 27% to 63% between 2016 and 2019, but the gas production recovery of parent wells was only about 40% between 2018 and 2019. Therefore, the mechanism and influencing factor of well interference degree were analyzed in this study. A numerical model of the W shale gas reservoir was developed for history matching, and the mechanisms of well interference and production recovery were analyzed. Sensitivity analysis about the effect of different parameters on well interference was carried out. Furthermore, the feasibility and effectiveness of gas injection pressure boosting to prevent interference were demonstrated. The results show that the main causes of inter-well interference are: the reservoir energy of the parent well before hydraulic fractures of the child well, well spacing, the fracture connection, etc. The fracture could open under hig... [more]

The variations in the boiler operation conditions have a great effect on the combustion characteristics and the pollutant formation in furnaces. This work aims to investigate the effects of operational parameters on NOx formation and its distribution in furnaces using the numerical simulation method to obtain the optimum control strategy for reducing NOx emissions. The numerical simulation models of pulverized coal combustion in furnaces involving flow, heat transfer, combustion and NOx formation are established. Taking a 600 MW supercritical opposed firing pulverized coal boiler as the study object, a full-scale three-dimensional physical model of the boiler is constructed with Gambit software. On this basis, the pulverized coal combustion and the NOx formation under various boiler loads are numerically simulated using the software of Ansys Fluent 2021R1, and the accuracy and the reliability of the models established are verified by comparing the simulation data with the field test da... [more]

The concurrent planning of multiple Distributed Generations (DGs), consisting of solar-DG and DSTATCOM with reconfiguration in IEEE 33 and 69 bus Radial Distribution Network (RDN), using Adaptive Particle Swarm Optimization (APSO) and hybrid Grey Wolf-Particle Swarm Optimization (GWO-PSO), is reported in this paper. For this planning, a novel multiple objective-based fitness-function (MOFF) is proposed based on various performance parameters of the system, such as power losses (both active, as well as reactive loss), system voltage profile, short circuit level of line current (SCLLCurrent), and system reliability. The economic perspective of the system has also been considered based on the various costs, such as fix, loss, and Energy Not Supplied (ENS) cost. Two case studies have been presented on IEEE 33 and 69 bus RDN to validate the efficacy of the proposed methodology. The results analysis of the system shows that better performance can be achieved with the proposed technique for 3... [more]

In this study, the fracture propagation characteristics and associated mechanisms of coal are investigated by using computed tomography (CT) observation and image-based simulation. The spatial distribution and the structural morphology of original fractures provide significant influences on the failure behavior of fractured coal. The fractures with small dip angles and large openings result in more-obvious fracture closure and stable propagation stages, while failure pattern is more sensitive to those with large dip angles. The coal tends to experience brittle failure, which transits from a splitting to mixed-splitting faulting mode because of the difference in original fracture distribution. The final failure fracture network originates mainly from the propagation of original fractures, driven by localized tensile stress. Fracture interaction and mineral influence tend to increase the complexity in the failure fracture network. Moreover, image-based numerical models are established on... [more]

Energy and environment form a nexus in which residents are the owners of tourism energy resources. Only a few studies have focused on the energy literacy of residents in ethnic tourism destinations and its impact on sustainable tourism. Using a qualitative research approach through field works and in-depth interviews in the Ping’an Village, Longji Terraces Scenic Area, this study explored the relationships between the energy literacy of residents and sustainable tourism in ethnic areas. The result showed that the energy literacy of the ethnic residents of Pingan village in terms of knowledge, attitude, and behavior has increased in line with the development of tourism, and both external and internal factors contribute to the improvement. Besides, the promotion of energy literacy among the residents not only has a positive impact on the tourists’ behavior but also brings about effective improvements in the local energy use structure and infrastructure, thus contributing to the sustainab... [more]

This paper proposes a high-frequency isolated current-fed dual active bridge bidirectional DC−DC series resonant converter with an inductive filter for energy storage applications, and a steady-state analysis of the converter is carried out. The performance of the proposed converter has been compared with a voltage-fed converter with a capacitive output filter. The proposed converter topology is operated in continuous conduction mode with zero circulation current (ZCC), less current stress and high efficiency. The conditions required for soft switching are determined, and it is found that the converter operates with soft switching of all switches for a wide variation in load and input voltage without loss of duty cycle. Current-fed converters are suitable for low-voltage renewable energy applications because of their inherent boosting capability. An inductive output filter is chosen to make the output current ideal for fast charging and high-power-density battery storage applications.... [more]

Lignin depolymerization has been studied for decades to produce carbon-neutral chemicals/biofuels and biopolymers. Among different chemical reaction pathways, catalytic hydrogenolysis favors reactions under relatively mild conditions, while its yield of bio-oil and high-value aromatic products is relatively high. In this study, the influence of reaction parameters on lignin hydrogenolysis are discussed by chemical process parameter mapping and modeled using three different machine learning algorithms based upon literature experimental data. The best R2 scores for solid residue and aromatic yield were 0.92 and 0.88 for xgboost, respectively. The parameter importance was examined, and it was observed that lignin-to-solvent ratio and average pore size have a larger impact on lignin hydrogenolysis results. Finally, the optimal conditions of lignin hydrogenolysis were predicted by chemical process parameter mapping using the best-fit machine learning model, which indicates that further proc... [more]

The high-voltage battery is a crucial element for EV traction systems. It is the primary energy source that must be regularly recharged to reach the autonomy declared by the manufacturer. Therefore, an EV charging system is required to ensure the battery charging process. This review thoroughly investigates the available EV charging technologies and the most popular batteries for EV applications. The contributions of this work can be summarized as follows: the classification and topologies of electric vehicle chargers are examined, an overview of the current EV charging standards is provided, the state-of-the-art of EV charging couplers is discussed, and the most widely used batteries in EV applications are reviewed.

The main purpose of the paper was to identify the most frequently discussed directions of research on green transformation. In the article, both the significant similarities in the existing studies in this field, as well as the newly emerging topics of research, are presented. For this purpose, the authors used a systematic literature review with elements of statistical analyses. This kind of approach is not popularly used in literature review papers, as it differs from the research practices employed previously, which mostly concentrated on applying qualitative methods, alternatively supported by the analysis of the co-occurrence of keywords. In this paper, the authors decided to include selected methods of dimensional analysis in the systematic literature review, namely the log-linear and correspondence analyses. The main results of the presented analyses are a more detailed division of studies related to green transformations into groups focused on the areas more difficult to distin... [more]