Given the difficulty of early warning of coal spontaneous combustion caused by continuous abnormal exceedance of CO in the tailgate corner of a low metamorphic coal seam and taking the 1305-working face of the Dananhu No.1 coal mine in Hami, Xinjiang as an example, this paper studies the abnormal CO-exceedance phenomenon based on field measurements, experimental research, and numerical simulation. The research shows that the abnormal CO-exceedance phenomenon is not caused by spontaneous combustion oxidation but by ambient-temperature oxidation of coal in the goaf. Factors, such as higher amounts of residual coal and higher degrees of fragmentation of the goaf, provide opportunities for the ambient-temperature oxidation of residual coal in the 1305 goaf. The 1305 coal oxidation characteristics at ambient temperature are examined, and the abnormal CO-exceedance mechanism is analyzed in depth. A CO-early-warning-limit model in the tailgate corner for coal spontaneous combustion in the 130... [more]

In this article, we present the possibility of applying the concept of elasticity in the system of sustainable energy development through the use of wood biomass. We used a dual (socio-ecological and economic) approach to sustainable energy development. The research was carried out using the methods of reduction reasoning, scientific observation, and examination of source documents. We identified crisis threats in the context of sustainable energy development. Then, we analyzed the supply of wood biomass in Poland, taking into account its geographical location. As a result, we identified and characterized the causal relationships between the assumptions of the concept of resistance and the sustainable development of energy with the use of wood biomass. We found that the concepts of resilience can be adapted to assessing energy sustainability. This adaptation is based on resilience, flexibility, and strategic ability to revitalize the country. We found that five key threats (extreme wea... [more]

Duqm is located in the Al Wasta Governorate in Oman and is currently fed by 10 diesel generators with a total capacity of around 76 MW and other rental power sources with a size of 18 MW. To make the electric power supply come completely from renewables, one novel solution is to replace the diesel with hydrogen. The extra energy coming from the PV-wind system can be utilized to produce green hydrogen that will be utilized by the fuel cell. Measured data of solar insolation, hourly wind speeds, and hourly load consumption are used in the proposed system. Finding an ideal configuration that can match the load demand and be suitable from an economic and environmental point of view was the main objective of this research. The Hybrid Optimization Model for Multiple Energy Resources (HOMER Pro) microgrid software was used to evaluate the technical and financial performance. The findings demonstrated that the suggested hybrid system (PV-wind-fuel cell) will remove CO2 emissions at a cost of e... [more]

According to various estimates, street lighting in Poland consumes between 1.500 and 2.500 GWh per year and is responsible for some greenhouse gas emissions from electricity generation. Also on the basis of estimates, it is estimated that approximately 3.3 million road and street luminaires are used in Poland. The increase in electricity costs, on the one hand, and the technical possibilities in the field of lighting, on the other, force the search for new solutions aimed at saving during the operation of electrical devices and installations, including road lighting installations. One of the methods of saving electricity is to replace the luminaires with energy-saving ones with LED sources, but also with new sodium and metal halide sources. The latter solution is cheaper and allows us to keep existing poles, electrical installation and luminaire heads if their technical parameters have not been degraded. The new and already used luminaires with discharge sources can be used in road lig... [more]

Polyphenols that are abundant in various organic wastes can inhibit anaerobic degradation of these wastes. This study investigated the effect of the concentration of individual phenolic acids (p-OH benzoic, vanillic, ferulic, sinapic, syringic, and p-coumaric acids) and their mixture on the methane potential of distillery stillage. An increase in phenolic acid concentration adversely affected biogas production and composition, as well as the methane-production rate. The inhibition constants for methane production were 0.5−1.0 g/L of individual phenolic acids and 1.5 g/L of the mixture of these acids. At lower concentrations, the phenolic acids were utilized as a carbon source, but the process was impeded when their concentrations exceeded the threshold value, due to their negative effect on microbial growth. When distillery stillage was spiked with vanillic acid, two-phase methane production was observed. Spiking distillery stillage with vanillic, p-coumaric, syringic, or ferulic acids... [more]

This article reviews the different topologies compatible with V2G feature and control approaches of integrated onboard charger (iOBC) systems for battery electric vehicles (BEVs). The integrated topologies are presented, analyzed, and compared in terms of component count, switching frequency, total harmonic distortion (THD), charging and traction efficiencies, controllability, reliability and multifunctionality. This paper also analyzes different control approaches for charging and traction modes. Moreover, the performance indices such as setting time, rise time, overshoot, etc., are summarized for charging and traction operations. Additionally, the feasibility of a Level 3 charging (AC fast charging with 400 Vac) of up to 44 kW iOBC is discussed in terms of converter efficiencies with different switching frequencies and switch technologies such as SiC and GaN. Finally, this paper explores the power density trends of different commercial integrated charging systems. The power density t... [more]

The electricity load forecasting plays a pivotal role in the operation of power utility companies precise forecasting and is crucial to mitigate the challenges of supply and demand in the smart grid. More recently, the hybrid models combining signal decomposition and artificial neural networks have received popularity due to their applicability to reduce the difficulty of prediction. However, the commonly used decomposition algorithms and recurrent neural network-based models still confront some dilemmas such as boundary effects, time consumption, etc. Therefore, a hybrid prediction model combining variational mode decomposition (VMD), a temporal convolutional network (TCN), and an error correction strategy is proposed. To address the difficulty in determining the decomposition number and penalty factor for VMD decomposition, the idea of weighted permutation entropy is introduced. The decomposition hyperparameters are optimized by using a comprehensive indicator that takes account of t... [more]

Nonlinear composite materials serve to homogenize electric fields and can effectively improve the local concentration of the electric field in power systems. In order to study the nonlinear surface conductivity properties of micro-nano epoxy composites, two types of epoxy micro-nano composite specimens were prepared in the laboratory using the co-blending method. The surface conductivity of the composites was tested under different conditions using a high-voltage DC surface conductivity test system. The results show that the surface conductivity of micro-nano structured composites increases and then decreases with the rise of nanofiller doping concentration. The nonlinear coefficient was 1.781 at 4 wt% of doped nanostructured SiC, which was the most significant nonlinear coefficient compared to other doping contents. For the same doping concentration, the micro-nano structured composites doped with nanostructured SiC have more significant surface conductivity at the same test temperatu... [more]

To address the problem of pipeline blockage detection, a mathematical model of pipeline blockage detection is established based on fluid oscillation theory. This paper proposes a governing equation of the water hammer of fluid motion in a pipeline with a blockage point, and The Dirac function is introduced for dimensionlessness and linearization. The amplitude of the harmonic of each component in different periods is expressed by a Fourier series. The blocking position can be determined by the ratio of the two-component harmonics, and the blocking magnitude can be determined by the blocking attenuation parameters of each component’s harmonics. The numerical simulation and experimental results show that the application of fluid oscillation theory to detect the location and magnitude of pipeline blockages is effective, and the accuracy of the detection method is verified, which lays a theoretical foundation for the application of the proposed method in engineering practice.

In this study, an operation strategy is introduced for distributed energy resources (DERs) in reconfigurable microgrids (MGs) to improve voltage profiles, minimize power losses, and boost the system performance. The proposed methodology aims to minimize power loss and energy not supplied (ENS) in MGs with an intelligent share of DERs and network reconfiguration in grid-connected and islanded modes. Due to the inherent uncertain nature of renewable DERs, these sources’ power output is considered as an uncertain parameter, and its effect on the system characteristics is analyzed. The state-of-the-art information gap decision theory (IGDT) approach is utilized to explore different decision-making strategies in the energy scheduling of reconfigurable MGs to deal with such uncertainty. To validate the effectiveness of the proposed method, the IEEE 33-bus radial system is utilized as the test MG. The simulation results show the importance of energy storage systems and reconfiguration in deal... [more]

The rotation speed of water at the inlet of the low hump outlet conduit has a great effect on its hydraulic performance. Therefore, the influence of different inlet water rotation speeds on hydraulic loss and flow pattern of low hump outlet conduit is studied in this paper. By solving RANS equations and the RNG k-ε turbulence model, the hydraulic loss and 3D flow field of the low hump outlet conduit were calculated under different inlet water rotation speeds. To verify the numerical results, the model tests of low hump outlet conduit with different guide vanes were conducted. The results show that along with the growth of inlet water rotation speed, the hydraulic loss of outlet conduit will firstly decrease by degrees and then increase dramatically, the vortex location moves from the whole bottom of the descent segment to the right bottom of descent segment and the vortex area becomes smaller, the flow pattern of the whole conduit is improved obviously. The hydraulic loss and flow fiel... [more]

A postulated progressing severe accident scenario has been simulated using MAAP5 code with the focus on ex-vessel cooling of molten corium in the reactor cavity. Various parameters associated with the prediction of molten corium−concrete interaction (MCCI) are identified. Accordingly, a sensitivity analysis is performed to assess the impact of these parameters on the predicted cavity floor erosion depth during this MCCI postulated accident. The sensitivity index of each variable parameter is determined using the Cotter indices method and Sobol′ indices method. At the early stage of the accident, the predicted cavity floor erosion depth is found to be highly sensitive to the downward heat transfer coefficient parameter with Cotter and Sobol′ indices of 94% and 50%, respectively. At the late phase of the accident, however, the cavity floor erosion depth becomes sensitive to melt eruption (Cotter index of 40%), water ingression (Cotter index of 13%), and particulate bed (Cotter index of 1... [more]

This paper presents the results of a survey concerning energy literacy conducted among a group of 913 students at the Cracow University of Economics in Poland—a country whose power system is still primarily based on burning coal and where the prospects of the closure of the mining sector present particularly difficult challenges. The aim of the study was to investigate specific aspects of energy literacy such as knowledge, behaviour, attitudes, and self-efficacy, and to determine what affects them using multivariate linear regression analysis. According to the findings, the primary factors determining energy literacy are gender, going away from home to study, and the experience of energy poverty. Self-efficacy, attitude, and the pro-ecological elements of both attitude and knowledge are the factors that have the most impact on students’ behaviour. The absence of a statistically significant impact of general knowledge on behaviour is a critical presumption for developing the premises of... [more]

In this paper, a microscopic oil displacement visualization experiment based on the glass etching model to simulate the tight oil reservoir of underground rocks is carried out. At present, water flooding technology is widely used in the development of oil and gas fields, and the remaining oil content is still very high after water flooding. It is the key to improving oil recovery to identify and study the remaining oil form distribution after water flooding. The experiment result shows there are five types of residual oil after water flooding: columnar residual oil, membranous residual oil, oil droplet residual oil, blind terminal residual oil and cluster residual oil. A convolution neural network is suitable for complex image characteristics with good robustness. In recent years, it has made a breakthrough in a set of small and efficient neural networks with SqueezeNet, Google Inception and the flattened network method put forward. In order to solve the problems of low automation, low... [more]

Conducting polymers, such as polyaniline (PANi) and polypyrrole (PPy), and their nanocomposites, are desired in a wide range of applications, including supercapacitors, lithium ion battery, chemical sensors, biosensors, barrier thin films, and coatings, because of their interesting electrical and electrochemical properties. It is well known that the properties of polymer nanocomposites depend on their chemical structure, as well as their microstructure, yet scientists and engineers have not fully understood how to properly control the structure of polymer nanocomposites. In this study, it is shown that the structure of polyaniline−montmorillonite clay nanocomposites (PACN) can be controlled by varying the ammonium persulfate (APS, oxidant) concentration. The structure of polyaniline and Cloisite 20A clay are, therefore, profoundly affected during the synthesis of PACN nanocomposites. The thickness of polyaniline crystal decreased with increasing oxidant concentration. Fourier transform... [more]

Compared with the medium voltage ac (MVAC) collection system, the medium voltage dc (MVDC) one for renewable energy sources has many advantages. High-power dc/dc converters are one of the key stages of the MVDC collection system to boost the voltage generated by photovoltaic or wind turbine. A novel hybrid three-level dc/dc converter utilizing a blocking capacitor to realize zero-voltage zero-current-switching (ZVZCS) is proposed. A higher overall efficiency can be achieved by reducing conduction losses. Detailed experimental results on a scaled-down hardware prototype rated at 150 V/750 V/1 kW are demonstrated to verify the proposed converter performance.

Electrical machines are commonly used in industries and transport and are manufactured with enameled wire coils with polymer insulation. In extreme conditions, as in aeronautics and aerospace, where temperatures exceed 280 °C, the organic insulation deteriorates and it is necessary to find another way to insulate winding wires, in order to ensure a longer life duration of the insulation system and a better operating reliability of electric motors in these environments. Ceramics are more resistant to high temperatures than polymers and the proposed study focuses on the temperature dependence of the dielectric properties of anodized aluminum strips for use in high-temperature electrical machine windings. Different dielectric parameters are measured during thermal constraint. The purpose is to determine the temperature index of the anodized strip and propose a thermal stress life model.

Nanostructured materials remarkably improve the overall properties of thermoelectric devices, mainly due to the increase in the surface-to-volume ratio. This behavior is attributed to an increased number of scattered phonons at the interfaces and boundaries of the nanostructures. Among many other materials, nanostructured Si was used to expand the power generation compared to bulk crystalline Si, which leads to a reduction in thermal conductivity. However, the use of nanostructured Si leads to a reduction in the electrical conductivity due to the formation of low dimensional features in the heavily doped Si regions. Accordingly, the fabrication of hybrid nanostructures based on nanostructured Si and other different nanostructured materials constitutes another strategy to combine a reduction in the thermal conductivity while keeping the good electrical conduction properties. This review deals with the properties of Si-based thermoelectric devices modified by different nanostructures and... [more]

This study aims to investigate the impact of dual credit policy on the diffusion of new energy vehicles (NEVs) from the perspective of complex interactions among heterogeneous manufacturers. Thus, the market competition and credit cooperation relationships, constituting the complex interrelated system in NEV diffusion, are considered in this paper. To this end, we established a double-layer complex network to depict the asymmetric competition and cooperation structure, and developed an evolution game model on network, revealing the diffusion rule and trend of NEVs among manufacturers. Simulation results show that the existence of credit cooperation relationship can effectively improve the diffusion of NEVs, especially when implementing cooperative strategy that prioritizes helping manufacturers with low sale profits. Such a cooperative strategy is effective for maintaining high diffusion of NEVs even under low NEV credit’s trading price. Meanwhile, the monopoly competitive structure ch... [more]

This paper presents an energy-saving strategy that was applied to a parallel variable frequency pump system of a water circulation pumping station. Firstly, the mathematical model of shaft power consumption for the parallel pump system was established using quadratic polynomial fitting, with some constraints configured according to the system’s water supply demands. Then, the algorithm program was designed with the goal of minimizing the energy consumption through the application of an improved differential evolution algorithm. Additionally, the energy consumption model and constraints were integrated and simplified in order to adapt to the algorithm calculation. In the end, the algorithm was implemented according to the pump design parameters and supply targets of the pumping station. Meanwhile, a comparison was done between the differential evolution (DE) algorithm and the genetic algorithm (GA). Furthermore, an experimental test was conducted in an aluminum company in order to verif... [more]

Introducing carbon trading is an essential way to decarbonize the power system. Many existing studies mainly consider source-side unilateral carbon trading (UCT). However, there are still rare studies considering source-load bilateral carbon trading (BCT). The effect of source-load BCT on system-wide carbon mitigation is worth studying. To fill this research gap, a hierarchical low-carbon economic-dispatch model with source-load BCT based on the Aumann−Shapley method was proposed. In the first layer, economic-dispatch was conducted to minimize the power-generation costs and source-side carbon-trading costs. Then, based on the carbon-emission flow (CEF) theory, the actual load carbon emissions can be obtained and passed to the second layer. At the second layer, the demand-response optimization was performed to minimize the load-side carbon-trading costs. Finally, the proposed model was tested on the modified New England 39-bus and IEEE 118-bus systems using the MATLAB/YALMIP platform wi... [more]

International oil and gas companies listed in New York must publish the information of oil and gas reserves under the SEC (United States Securities and Exchange Commission) standards every year. For greatly improving the SEC reserve, the SEC reserve value and the SEC reserve substitution rate, in this article not only the SEC reserve equations have been determined but also the SEC reserve value models have been established. The SEC reserve value models have been verified as correct. Based on these models, the multivariate function calculus method, the multivariate function limit method and the function recurrence method have been adopted to research parameter sensitivity differences rules, parameter adjustment directions, parameter adjustment degrees and SEC reserve parameter linkage adjustment rules. The research is significant, because there are great differences between SEC standards and China’s in reserve management mode, reserve estimation method system and financial management sy... [more]

This scientometric review and bibliometric analysis aimed to characterize trends in scientific research related to algae, photobioreactors and astaxanthin. Scientific articles published between 1995 and 2020 in the Web of Science and Scopus bibliographic databases were analyzed. The article presents the number of scientific articles in particular years and according to the publication type (e.g., articles, reviews and books). The most productive authors were selected in terms of the number of publications, the number of citations, the impact factor, affiliated research units and individual countries. Based on the number of keyword occurrences and a content analysis of 367 publications, seven leading areas of scientific interest (clusters) were identified: (1) techno-economic profitability of biofuels, bioenergy and pigment production in microalgae biorefineries, (2) the impact of the construction of photobioreactors and process parameters on the efficiency of microalgae cultivation, (3... [more]

An active prechamber turbulent ignition system is a forced ignition method for internal combustion engines fueled with low reactivity fuels, i.e., natural gas and gasoline, which could expand the lean-burn limit, promote flame propagation, and ensure cyclic stability. In the present study, the effects of charge concentration stratifications inside the prechamber on the jet characteristics and combustion process were numerically investigated using CONVERGE software coupled with a reduced methane mechanism by the coupling control of spark timing and prechamber global equivalence ratio. The results show that the jet characteristics and ignition mechanisms can be regulated by controlling the prechamber global equivalence ratio and spark timing. On the one hand, as the prechamber global equivalence ratio increases, the velocity of the jet increases firstly and then decreases, the temperature drops, and OH and CH2O radicals are reduced, but the stable combustion intermediates, CO and H2, are... [more]

This paper develops a multi-objective co-design optimization framework for the optimal sizing and selection of battery and power electronics in hybrid battery energy storage systems (HBESSs) connected to the grid. The co-design optimization approach is crucial for such a complex system with coupled subcomponents. To this end, a nondominated sorting genetic algorithm (NSGA-II) is used for optimal sizing and selection of technologies in the design of the HBESS, considering design parameters such as cost, efficiency, and lifetime. The interoperable framework is applied considering three first-life battery cells and one second-life battery cell for forming two independent battery packs as a hybrid battery unit and considers two power conversion architectures for interfacing the hybrid battery unit to the grid with different power stages and levels of modularity. Finally, the globally best HBESS system obtained as the output of the framework is made up of LTO first-life and LFP second-life... [more]