This study investigates the nexus of income inequality, economic growth, and CO2 emissions based on the environmental Kuznets curve (EKC) hypothesis for 38 OECD countries during 1990−2015. The indices of income inequality include the Gini coefficient and the top income share. The main objective of this study is to re-examine the effects of income inequality and economic growth on CO2 emissions based on the Environmental Kuznets Curve (EKC) hypothesis. The panel analysis for OECD countries is examined using country fixed effects and Granger causality including pre-tests for unit root, cointegration, and stationarity. The main findings of this study are as follows. First, the effects of economic growth on CO2 emissions have an inverted U-shaped relationship, and the effects of income inequality on CO2 emission also have an inverted U-shaped relationship. Second, the Gini coefficient and the top income share represented by the income inequality index are well-defined tools for analyzing t... [more]

Issues related to safe and abundant energy production have been prominent in recent years. This is particularly true when society considers how to increase the quality of life by providing low-cost energy to citizens. A significant concern of the Gulf Cooperation Council (GCC) relates to the environmental effects of energy production and energy use associated with climate change. Efforts to reduce fossil fuel use and increase the use of renewable energy, together with the price volatility of fossil fuels, have seriously impacted the economics of many oil-producing countries, particularly the Gulf States, which has led to efforts to make their economies more diverse and less dependent on oil production. In this article, we introduce a multidisciplinary energy economics course developed at the Missouri University of Science and Technology that can be easily adopted by GCC universities to enhance future generations’ understanding of energy challenges.

There are a huge number of harmonics in the railway power supply system. Accurately estimating the harmonic impedance of the system is the key to evaluating the harmonic emission level of the power supply system. A harmonic impedance estimation method is proposed in this paper, which takes the Gaussian mixture regression (GMR) as the main idea, and is dedicated to calculating the harmonic impedance when the load changes or the background harmonic changes in the traction power supply system. First, the harmonic voltages and currents are measured at the point of common coupling (PCC); secondly, a Gaussian mixture model (GMM) is established and optimized parameters are obtained through the EM algorithm; finally, a Gaussian mixture regression is performed to obtain the utility side harmonic impedance. In the simulation study, different harmonic impedance estimation models with uniform distribution and Gaussian distribution are established, respectively, and the harmonic impedance changes c... [more]

The traditional optimum modes of gas-lift production are usually established by taking the injected gas rate as a decision variable and maximum oil production as the objective function. After solving the model, the injected gas rates of single wells are obtained, and then the oil productions of single wells, the total oil productions of well groups and economic profit can be obtained. However, the models do not take both different types of gas-lift performance curves (GLPCs) and the cost factors of gas-lift production technique into account. On the basis of GLPCs, this paper introduces the factors of a gas-lift production technique, which includes the water cut of crude oil, cost of gas injection and water treatment, and oil and gas prices. The concept of a gas-lift economic performance curve (GLEPC) is proposed, and an optimum gas allocation model is established, considering different types of GLPCs and taking economic benefits as the objective, and the model is solved by the method o... [more]

This study investigates the thermal-stress characteristics of a bi-metallic Ti-6Al-4V-Nitinol butt joints manufactured via laser welding. Particularly, the thermal profile along the weld interface and the deformation profile of the finished welded workpiece. A decoupled transient thermomechanical simulation model was constructed to recreate the welding process. This decoupled thermomechanical simulation model consisted of two transient simulation models. A transient thermal simulation model and a transient structural simulation model, with the thermal history of the transient thermal model being fed into the transient structural model. Both the thermal and structural portions of the model utilized temperature-dependent thermal and structural properties of Ti-6Al-4V and Nitinol. The temperature profile of the transient thermal-stress model aligns with the experimental thermal profile within 5% error. The deformation profile also matches the experimental results within 5% error. This app... [more]

Considering the specific heat characteristics of working fluid and existence of various losses in a porous medium (PM) cycle, this paper applies finite time thermodynamic theory to study its efficient power performance with nonlinear variable specific heat model. Range of the cycle pre-expansion ratio is obtained by solving the equation, and PM cycle is converted to Otto cycle by choosing appropriate pre-expansion ratio. Influences of pre-expansion ratio, specific heat characteristics, temperature ratio, and various losses on cycle performances are investigated. Thermal efficiencies are compared at operating points of the maximum power output and efficient power. The results show that PM cycle has better performance than Otto cycle. Under certain conditions of parameters, thermal efficiencies at the maximum efficient power and maximum power output operating points are 50.45% and 47.05%, respectively, and the former is 7.22% higher than the latter. The engine designed with the maximum e... [more]

Accurately predicting the breakdown pressure in horizontal sections is essential when designing and optimizing fracturing jobs for horizontal wells in tight gas reservoirs. Taking the Sulige block in the Ordos Basin as an example, for different completion methods combined with indoor rock experience data and well data, a new method for predicting breakdown pressure based on a linear regression model is proposed. Based on the Hossain horizontal well stress field model, this paper established a calculation model of breakdown pressure under different completion methods by using experimental and well data. The average error between the calculation results and the actual breakdown pressure at the initiation point is 3.67%. A Pearson correlation analysis was conducted for eight sensitive factors of horizontal well stress, which showed that the maximum horizontal principal stress, minimum horizontal principal stress, tensile strength, and elastic modulus had strong linear correlations with br... [more]

This paper discusses fuel cell electric vehicles and, more specifically, the challenges and development of hydrogen-fueled buses for people accessing this transportation in cities and urban environments. The study reveals the main innovations and challenges in the field of hydrogen bus deployment, and identifies the most common approaches and errors in this area by extracting and critically appraising data from sources important to the energy perspective. Three aspects of the development and horizons of fuel cell electric buses are reviewed, namely energy consumption, energy efficiency, and energy production. The first is associated with the need to ensure a useful and sustainable climate-neutral public transport. Herewith, the properties of the hydrogen supply of electric buses and their benefits over gasoline, gas, and battery vehicles are discussed. The efficiency issue is related to the ratio of consumed and produced fuel in view of energy losses. Four types of engines−gasoline, di... [more]

Accurately capturing wind speed fluctuations and quantifying the uncertainties has important implications for energy planning and management. This paper proposes a novel hybrid machine learning model to solve the problem of probabilistic prediction of wind speed. The model couples the light gradient boosting machine (LGB) model with the Gaussian process regression (GPR) model, where the LGB model can provide high-precision deterministic wind speed prediction results, and the GPR model can provide reliable probabilistic prediction results. The proposed model was applied to predict wind speeds for a real wind farm in the United States. The eight contrasting models are compared in terms of deterministic prediction and probabilistic prediction, respectively. The experimental results show that the LGB-GPR model improves the point forecast accuracy (RMSE) by up to 20.0% and improves the probabilistic forecast reliability (CRPS) by up to 21.5% compared to a single GPR model. This research is... [more]

In the control of DC/AC switched power converters (SPC), one of the most important aspects to be considered is the selection of the real-time control platform. The real-time control platform must be able to meet the high performance efficiency and regulation requirements of the DC/AC SPC, as these typically operate at switching frequencies in the order of kHz to MHz. For this reason, the hardware characteristics of the ADC and PWM, and the processing capacity of the real-time control platform are of vital importance when implementing advanced digital controllers that maintain voltage and current levels within regulatory standards. In this context, we aimed to perform a comparative study of the computation times of different real-time control platforms when implementing different control strategies for DC/AC switched power converters. We also analyzed the impact of the real-time control platforms on the THD of the voltages generated by the DC/AC switched power converters. With the help... [more]

Employment and the competencies of employees in the energy sector are coming into particular prominence in economies around the world. It is one of the few sectors positively affected by the COVID-19 pandemic. As a result, a significant global change in the awareness of society occurred in favor of increasing pro-health and pro-environmental activities, which can be seen in the green transformation. Poland can also boast such changes in recent years, as evidenced by the dynamic development of renewable energy sources (boom for photovoltaics) and the increase in prosumption. Correlated with this is the increase in demand for employees with specific competencies, the so-called multi-competencies that are a compilation of technical, business, and soft and hard competencies, as well as interdisciplinary ones. The paper emphasizes the need to better adjust the education system to the real needs of the labor market in a turbulent environment with the use of the Sectoral Qualifications Framew... [more]

Renewable energy has received a lot of attention. In recent years, offshore wind power has received particular attention among renewable energies. Fixed-type offshore wind turbines are now the most popular. However, because of the deep seas surrounding Japan, floating types are more preferable. The floating system is one of the factors that raises the cost of floating wind turbines. Vertical axis wind turbines (VAWT) have a low center of gravity and can tilt their rotors. As a result, a smaller floating body and a lower cost are expected. A mechanism called a floating axis wind turbine (FAWT) is expected to further reduce the cost. FAWT actively employs the features of VAWT in order to specialize itself in the area of offshore floating-type wind turbines. The lifting line theory simulation was used in this study to discuss the performance of the FAWT under the tilted conditions and its wake field. The results show that a tilted VAWT recovers faster than an upright VAWT. This suggests t... [more]

Presented in this paper is a method of bidirectional real and reactive power control of a three-phase grid-connected inverter under unbalanced grid situations. Unbalanced three-phase load and unbalanced grid impedance are illustrations of unbalanced grid issues that have been investigated. As a result, both grid currents and point-of-common-coupling (PCC) voltages will be unbalanced. The real and reactive power that is delivered to the grid oscillates by a significant amount in these unbalanced conditions. A time-domain symmetrical components extraction approach is used to calculate the inverter’s reference currents from the negative- and zero-sequence components of the measured currents. The suggested approach corrects unbalanced grid currents and unbalanced PCC voltages, and provides the desired real and reactive power to the grid when unbalanced situations exist. As a consequence, power oscillations will be eliminated, and power control will be possible. The suggested method’s perfo... [more]

The DC-link capacitors in an electronic power system are the main constraint of the power density and lifespan of the power converters. Evaluating the load life of capacitors working in severely adverse circumstances plays an important role in the design stages of the next-generation power converters. In this article, an improved evaluation system for the capacitors utilized in high-power three-phase voltage source inverters is proposed. The purpose of this article is to reproduce the same encountered stresses when a DC-link capacitor is used in a high-power inverter with pulse-width modulation. Hence, an improved down-scale evaluation system for the DC-link capacitors used in high-power three-phase inverter systems under balanced and unbalanced load conditions is proposed. Moreover, AC and DC analyses in the proposed evaluation system are conducted. The equivalent circuit and transfer functions are derived to verify the proposed evaluation system. Finally, a prototype system is constr... [more]

Previously published studies on Australia’s energy security did not examine the country’s domestic energy security situation in tandem with its international energy statecraft. This paper fills this research gap. In order to provide a robust analysis of a country’s strategic options in the energy sector, it is paramount to balance domestic and international dimensions, along with internal and external factors. The paper utilizes the strengths, weaknesses, opportunities, and threats (SWOT) method to review Australia’s strategic options by balancing the inward-looking, domestic risk minimization dimension (energy security), with the outward-looking, international power projection dimension (energy statecraft). The paper also applies the 4A framework (availability, accessibility, affordability, and acceptance) to assess Australia’s energy security performance. On the one hand, the results demonstrate that Australia has many strengths and opportunities as a reliable and stable energy suppl... [more]

This paper proposes a control scheme based on an optimal triple phase-shift (TPS) control for dual active bridge (DAB) DC−DC converters to achieve maximum efficiency. This is performed by analyzing, quantifying, and minimizing the total power losses, including the high-frequency transformer (HFT) and primary and secondary power modules of the DAB converter. To analyze the converter, three operating zones were defined according to low, medium, and rated power. To obtain the optimal TPS variables, two optimization techniques were utilized. In local optimization (LO), the offline particle swarm optimization (PSO) method was used, resulting in numerical optimums. This method was used for the low and medium power regions. The Lagrange multiplier (LM) was used for global optimization (GO), resulting in closed-form expressions for rated power. Detailed analyses and experimental results are given to verify the effectiveness of the proposed method. Additionally, obtained results are compared wi... [more]

The supply chain strategy has a significant impact on energy consumption. This strategy determines the location of individual links in the chain (suppliers, producers, distributors), which affects the costs of logistics processes, including, in particular, transport processes. Currently, due to the rapid increase in fuel prices, the issue of energy consumption in the supply chains is becoming increasingly important. The aim of the article is to present the impact of the increase in fuel and energy costs on the costs of logistics processes and, as a result, on the profitability of different supply chain strategies. The profitability of changing from global to local sources of supply as a result of rising energy prices was especially taken into account. The article presents the results of interviews from enterprises carried out by the authors and the results of simulations carried out using a model developed by the authors. The need to conduct such research resulted from the existing res... [more]

With the growing cost of carbon emissions reduction, the application of industrial restructuring to suppress carbon emissions is becoming more attractive. By constructing an input-output optimization model, this study explored how industrial restructuring helps megacities synergistically achieve carbon peak and high-quality development. The results showed that through contributing 164.4% of the reduction in emissions from 2020 to 2025, industrial structure optimization significantly inhibited the growth of carbon emissions; From 2020 to 2025, the manufacturing structure continued to be high-end, which resulted in a reduction in industrial carbon emissions by 10.3%; through vigorous development of the low-carbon service industry, the carbon emission of the service industry would continue to slow down at an average annual rate of 2.4%. Industrial premiumization and the low-carbonization of the modern service sector are the key driving forces for Shenzhen to achieve low-carbon transformat... [more]

This paper explores the empirical validity of an augmented volume model for Colombian electricity price returns (in the present study, the definition of returns is simply the “rate of change” of observed prices for different periods). Of particular interest is the impact of coskewness and cokurtosis when modeling Colombian electricity price returns. We found that coskewness as an augmentation factor is highly significant and should be considered when modeling Colombian electricity price returns. The results obtained for coskewness as an augmentation factor in a volume model are consistent when using either an Ordinary Least Square (OLS) and Generalized Method of Moments (GMM) specification for the data employed. On the other hand, the effect of cokurtosis is highly irrelevant and not significant in most cases under the proposed specification.

In recent years, China has proposed the goal of peaking carbon dioxide emissions by 2030 and achieving carbon neutrality by 2060, which will significantly alter its existing coal-based energy mix. Since coal is China’s primary source of energy and the largest contributor to carbon emissions, coal reduction is an important measure toward carbon neutrality. In order to guarantee the stable development of economy and society in the process of coal reduction, the path and cost of coal reduction need to be studied in depth. Based on coal use in China, this paper examines and measures the stages and costs of coal reduction. It also gives a definition for coal reduction costs for the first time, including economic cost, environment and ecology cost, and health cost, as well as proposes a framework for analyzing the “full cost, full process, and full scenario”. We measure the cost in combination with the KAYA formula, and take into account the time value of the cost. Based on the above measure... [more]

An underappreciated source of renewable energy is wastewater, both municipal and industrial, with global production exceeding 900 km3 a year. Wastewater is currently perceived as a waste that needs to be treated via energy-consuming processes. However, in the current environmental nexus, traditional wastewater treatment uses 1700−5100 TWh of energy on a global scale. The application of modern and innovative treatment techniques, such as microbial fuel cells (MFC), would allow the conversion of wastewater’s chemical energy into electricity without external energy input. It has been demonstrated that the chemically bound energy in globally produced wastewater exceeds 2.5 × 104 TWh, which is sufficient to meet Europe’s annual energy demand. The aim of this paper is to answer the following questions. How much energy is bound in municipal and industrial wastewaters? How much of that energy can be extracted? What benefits will result from alternative techniques of waste treatment? The main f... [more]

Repairing delamination damage is critical to guarantee the structural safety of carbon fiber-reinforced thermosetting composites. The popular repair approaches, scarf repair and injection repair, can significantly restore the in-plane mechanical performance. However, the out-of-plane properties become worse due to the sacrifice of fiber continuity in these repairing processes, leading to the materials being susceptible under service loads. Here, we propose a novel in situ delamination repair approach of controllable thermal ablation in damage removal, achieving a high repair efficiency without impairing the fiber continuity in carbon fiber/epoxy panels. The epoxy resin in the delaminated region was eliminated under the carbonization temperature in a few minutes, allowing the carbon fiber frame to retain its structural integrity. The healing agent, refilled in the damaged region, was cured by the Joule heating of designed electrodes for 30 min at 80 °C, yielding the whole repair process... [more]

This paper describes the implementation of a hydrogen-based system for an autonomous surface vehicle in an effort to reduce environmental impact and increase driving range. In a suitable computational environment, the dynamic electrical model of the entire hybrid powertrain, consisting of a proton exchange membrane fuel cell, a hydrogen metal hydride storage system, a lithium battery, two brushless DC motors, and two control subsystems, is implemented. The developed calculation tool is used to perform the dynamic analysis of the hybrid propulsion system during four different operating journeys, investigating the performance achieved to examine the obtained performance, determine the feasibility of the work runs and highlight the critical points. During the trips, the engine shows fluctuating performance trends while the energy consumption reaches 1087 Wh for the fuel cell (corresponding to 71 g of hydrogen) and 370 Wh for the battery, consuming almost all the energy stored on board.

For the past decade, research on vertical axis wind turbines (VAWTs) has garnered immense interest due to their omnidirectional characteristic, especially the lift-type VAWT. The H-rotor Darrieus VAWT operates based on the lift generated by aerofoil blades and typically possesses higher efficiency than the drag-type Savonius VAWT. However, the open-ended blades generate tip loss effects that reduce the power output. Wingtip devices such as winglets and endplates are commonly used in aerofoil design to increase performance by reducing tip losses. In this study, a CFD simulation is conducted using the sliding mesh method and the k-ω SST turbulence model on a two-bladed NACA0018 VAWT. The aerodynamic performance of a VAWT with offset, symmetric V, asymmetric and triangular endplates are presented and compared against the baseline turbine. The simulation was first validated with the wind tunnel experimental data published in the literature. The simulation showed that the endplates reduced... [more]

As the transportation industry develops new forms of energy and electrification, expressway dynamic wireless charging has become an attractive technology that has the potential to completely solve a range of anxieties associated with electric vehicles. The main objective of this paper was to analyze the economic feasibility of dynamic wireless charging projects on highways. First, the roadside cost of dynamic wireless charging was estimated in terms of equipment, construction, and maintenance costs. Then, various indicators of the national economy of expressway dynamic wireless charging were analyzed. Finally, using the GM (1,1) model, a prediction model for evaluating the associated economic benefits is proposed in this study. As a case study, a national economic evaluation of retrofitting a dynamic wireless charging infrastructure on the Guiyang to Xinzhai Expressway was calculated with the following results: the economic internal rate of return (EIRR) is 11.27% to 29.11%, the econom... [more]