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.

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]

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.

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]

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]

As research on wind energy has progressed, it has broadened from a focus on the wind turbine to include the entire wind farm. In particular, methods to mitigate the negative effects of upstream wakes on downstream turbines have received significant attention. One such mitigation method is axial induction control (AIC) in which upstream turbines are derated to reduce the momentum deficits in their wakes, leaving higher speed flow for downstream turbines. If performed correctly, it is theorized that the power production gains in downstream turbines can compensate for the power sacrificed by derating upstream turbines. Previous work has indicated that the “excess” energy left in the wake of the derated turbine is along the edges of the wake such that a turbine placed directly downstream will see little to no increase in power. To address this hypothesis, we performed a control and treatment experiment with model-scale turbines in a wide flume. Five turbines were arranged in three successi... [more]

Electric vehicles have a promising development prospect. As its core component, lithium-ion power battery plays a crucial role in different application scenarios. Aiming at the availability and safety of square ternary lithium batteries at different ambient temperatures and different current rates, charge-discharge cycle experiments are carried out to study the voltage, temperature and capacity changes of lithium batteries. The voltage plateau characteristics of lithium batteries under different working conditions are explored. The results show that when discharging at current rates of 0.1C, 0.25C, 0.5C, 0.75C, and 1C under the ambient temperature of −5 °C, 10 °C, 25 °C, and 40 °C, the terminal voltage of the battery changes smoothly during the voltage plateau period, the rise of the surface temperature has not reached the peak value, and the discharge capacity accounts for about 50%. The battery has better working performance. While at the ambient temperature of −20 °C, the discharge... [more]

In this study, we present an analytical modeling framework for wind turbine wakes under an arbitrary pressure gradient imposed by the base flow. The model is based on the conservation of the streamwise momentum and self-similarity of the wake velocity deficit. It builds on the model proposed by Shamsoddin and Porté-Agel, which only accounted for the imposed pressure gradient in the far wake. The effect of the imposed pressure gradient on the near wake velocity is estimated by using Bernoulli’s equation. Using the estimated near wake velocity as the starting point, the model then solves an ordinary differential equation to compute the streamwise evolution of the maximum velocity deficit in the turbine far wake. The model is validated against experimental data of wind turbine wakes on escarpments of varying geometries. In addition, a comparison is performed with a pressure gradient model which only accounts for the imposed pressure gradient in the far wake, and with a model that does not... [more]

This work is devoted to the formulation of innovative SCADA-based methods for wind turbine performance analysis and interpretation. The work is organized as an academia−industry collaboration: three test cases are analyzed, two with hydraulic pitch control (Vestas V90 and V100) and one with electric pitch control (Senvion MM92). The investigation is based on the method of bins, on a polynomial regression applied to operation curves that have never been analyzed in detail in the literature before, and on correlation and causality analysis. A key point is the analysis of measurement channels related to the blade pitch control and to the rotor: pitch manifold pressure, pitch piston traveled distance and tower vibrations for the hydraulic pitch wind turbines, and blade pitch current for the electric pitch wind turbines. The main result of this study is that cases of noticeable under-performance are observed for the hydraulic pitch wind turbines, which are associated with pitch pressure dec... [more]

In this paper, an algorithm for the maximum extraction of energy generated by photovoltaic (PV) systems was presented. The tracking of the global maximum point of the system is complex due to the non-linearity of the current-voltage (I-V) characteristic curve of the photovoltaic modules, as they vary according to the temperature and solar irradiation in the module. To obtain the best energy efficiency in these systems, it is important that the generation is delivering the maximum power available through the arrangement. In order to solve such problems, in this work an efficient MPPT-FA method was proposed, which showed good traceability when compared to traditional methods. Most traditional MPPT techniques are not able to find the global maximum point to extract the maximum power provided by the PV system. Finally, the Firefly Metaheuristic MPPT method proved to be robust against several partial shading scenarios. Simulations were presented to demonstrate the effectiveness of the propo... [more]

This paper proposes the application of generation adequacy analysis for reliability evaluation of an insulated power generation system that supplies a FPSO (Floating Production Storage and Offloading) oil and gas production platform. The frequency and duration method was adopted for generating system reliability evaluation. The historical reliability data of the floating production storage and offloading platform power system and the continuous Markov process are used to determine the generator’s reliability model. The load model was also based on the platform daily peak load variation curve. The system risk indexes were obtained using Monte Carlo simulation. Two system scenarios were simulated using different failure data for one of the generators and the software PowerFactory© has been used as a tool for this simulation. For a complete generation system modeling, frequency and duration methods were developed to calculate the probabilities, frequencies and duration of the system state... [more]

In the traditional coal-mine gas-concentration prediction process, problems such as low timeliness of data and low efficiency of the prediction model in learning data features result in low accuracy of the final prediction. To solve these problems, a gas-concentration prediction method driven by the Spark Streaming framework is proposed. In this research study, the Spark Streaming framework, autoregressive integrated moving average (ARIMA) model and support vector machine (SVM) model are used to construct a new prediction model called the SPARS model. The Spark Streaming framework is used to process large batches of real-time streaming data in a short period of time, and the model can be used to intermittently update and optimize the prediction model so that the model can fully learn the characteristics of the data. At the same time, the advantages of the ARIMA model and SVM model for processing linear data and nonlinear data are combined to improve the model’s prediction efficiency an... [more]

An accurate understanding of molecular structure evolution during pyrolysis is essential for the clean utilization of coal. In this study, middle-rank coal was taken as the research subject, and vitrinite and inertinite samples were stripped from coal using a hand picking and sink−float separation process. In situ Fourier transform infrared (FTIR) spectroscopy and in situ X-ray diffraction (XRD) were performed to compare the macromolecular structure changes between vitrinite and inertinite during pyrolysis. The results show that the aromaticity (I), the polycondensation degree of aromatic rings (DOC), the average lateral sizes (La) of basic structure unit (BSU), and the stacking heights (Lc) of BSU in both vitrinite and inertinite during pyrolysis increase continuously with increasing temperature. The values of these parameters for inertinite are higher than those of vitrinite, suggesting that the aromatization degree of inertinite has always been higher than that of vitrinite. In situ... [more]

Considering the battery-failure-induced catastrophic events reported frequently, the early fault warning of batteries is essential to the safety of electric vehicles (EVs). Motivated by this, a novel data-driven method for early-stage battery-fault warning is proposed in this paper by the fusion of the short-text mining and the grey correlation. In particular, the short-text mining approach is exploited to identify the fault information recorded in the maintenance and service documents and further to analyze the categories of battery faults in EVs statistically. The grey correlation algorithm is employed to build the relevance between the vehicle states and typical battery faults, which contributes to extracting the key features of corresponding failures. A key fault-prediction model of electric buses based on big data is then established on the key feature variables. Different selections of kernel functions and hyperparameters are scrutinized to optimize the performance of warning. Th... [more]

Aiming to accurately identify the state of health (SOH) and the remaining useful life (RUL) of lithium-ion batteries, in this paper, we propose an algorithm for the health factor extraction and SOH prediction of the batteries based on discrete wavelet transform and the Cauchy−Gaussian variation tent sparrow search algorithm (DWT-CGTSSA). Firstly, concerning the inconsistent data length, discrete wavelet transform (DWT) was adopted to decompose the battery’s signals and extract features. Then, the Cauchy−Gaussian variation tent sparrow search algorithm (CGTSSA) was utilized to extract features and obtain the optimal feature subset after encoding. Finally, the optimal feature subset was used to establish a prediction model based on CatBoost for predicting the SOH of lithium-ion batteries. Experiments were conducted for verification. The experimental results showed that the model established in this research is capable of realizing the prediction between different battery packs. The B0005... [more]

This work is a survey of current trends in applications of PMUs. PMUs have the potential to solve major problems in the areas of power system estimation, protection, and stability. A variety of methods are being used for these purposes, including statistical techniques, mathematical transformations, probability, and AI. The results produced by the techniques reviewed in this work are promising, but there is work to be performed in the context of implementation and standardization. As the smart grid initiative continues to advance, the number of intelligent devices monitoring the power grid continues to increase. PMUs are at the center of this initiative, and as a result, each year more PMUs are deployed across the grid. Since their introduction, myriad solutions based on PMU-technology have been suggested. The high sampling rates and synchronized measurements provided by PMUs are expected to drive significant advancements across multiple fields, such as the protection, estimation, and... [more]

The noncontact heating technology of IH targets heat directly where it is needed through the electromagnetic energy adsorption and conversion of magnetic materials. Unlike conventional heating methods, the heat generated by electromagnetic induction of magnetic materials can be applied directly into the reactor without heating the entire device; this new heating method is not only more energy efficient but also safer, cleaner and more sustainable if renewable electricity is adopted; moreover, magnetic catalysts can be recovered and reused by separating chemical reactants and products from the catalyst by the application of a magnetic field, and it can provide the required heat source for the reaction without altering its catalytic properties. Magnetic catalysts with an electric field have been applied to some industrial areas, such as the preparation of new materials, catalytic oxidation reactions, and high-temperature heat absorption reactions. It is a trend that is used in the hydrog... [more]

In the coming decades, the number of end-of-life (EoL) traction battery systems will increase sharply. The disassembly of the system to the battery module is necessary to recycle the battery modules or to be able to use them for further second-life applications. These different recovery paths are important pathways to archive a circular battery supply chain. So far, little knowledge about the disassembling of EoL batteries exists. Based on a disassembly experiment of a plug-in hybrid battery system, we present results regarding the battery set-up, including their fasteners, the necessary disassembly steps, and the sequence. Upon the experimental data, we assess the disassembly duration of the battery system under uncertainty with a fuzzy logic approach. The results indicate that a disassembling time of about 22 min is expected for the battery system in the field study if one worker conducts the process. An estimation for disassembling costs per battery system is performed for a plant i... [more]

Concentrating photovoltaic power generation technology is a highly efficient way of utilizing solar energy resources with the efficiency limited by cell cooling conditions. For the heat dissipation problem from multi-point solar cell cooling, a microchannel heat sink is used to resolve the issue. Ammonia is chosen as the working fluid and two diamond microchannel heat sinks in series for the 16 simulated solar cells cooling with typical size. The heat sink consists of 31 triangular microchannels, each with a hydraulic diameter of 237 μm and a flow path length of 40 mm. It is experimentally verified that the diamond microchannel heat sink has excellent multi-point heat source heat dissipation capability. The surface temperature of the heat source can be controlled below 65.9 °C under the heat flux of 351.5 W/cm2, and the maximum temperature difference between the multi-point heat sources is only 1.4 °C. The effects of heat flux, mass flux and inlet state on the flow boiling heat transfe... [more]

The pressure-controlled injection tool (PCIT) is the key equipment in the process of high-pressure water jet fragmentation in the solid fluidization exploitation of deep-sea natural gas hydrate (NGH). The internal flow field erosion wear numerical simulation model of PCIT is established through computational fluid dynamics software to study the influence law and main factors of the drilling fluid erosion wear of PCIT. The influence laws of different drilling fluid physical parameters and different structural parameters on PCIT erosion wear were analyzed based on the Euler−Lagrangian algorithm bidirectional coupled discrete phase model (DPM) and the solid−liquid two-phase flow model. The results show that the easily eroded areas are the cone of the sliding core, the plug transition section, the plug surface, and the axial flow passage. The sliding core inlet angle and solid particle size are the main factors affecting the PCIT erosion rate. When the inlet angle of the sliding core is 30... [more]

Computer-vision-based separation methods for coal gangue face challenges due to the harsh environmental conditions in the mines, leading to the reduction of separation accuracy. So, rather than purely depending on the image features to distinguish the coal gangue, it is meaningful to utilize fixed coal characteristics like density. This study achieves the classification of coal and gangue based on their mass, volume, and weight. A dataset of volume, weight and 3_side images is collected. By using 3_side images of coal gangue, the visual perception value of the volume is extracted (ExM) to represent the volume of the object. A Support Vector Machine (SVM) classifier receives (ExM) and the weight to perform the coal gangue classification. The proposed system eliminates computer vision problems like light intensity, dust, and heterogeneous coal sources. The proposed model was tested with a collected dataset and achieved high recognition accuracy (KNN 100%, Linear SVM 100%, RBF SVM 100%, G... [more]

Pyrolysis of crude oil is an important way to generate natural gas. However, the current analysis of pyrolysis gas carbon isotopes and the study of gas generation dynamics are not unified, and the genesis and accumulation of gas reservoirs are needed to conduct in-depth discussions. Therefore, Tarim crude oil samples in China were selected to perform thermal simulation experiments using an autoclave. The pyrolysis hydrocarbon production yield, carbon isotope characteristics and gas-generation process of crude oil samples in Tarim Basin were studied by GC-MS, FT-IR and carbon isotope analysis, respectively. The compositions of the Tarim Oilfield were determined, including the 83.69% content of hydrocarbons, the 14.08% content of aromatic compounds, and lower than 3% content of heteroatom compounds. The non-monotonic linear relationship of C2-5 isotopes may be due to the complexity of crude oil, and the formation of gaseous hydrocarbons can be divided into three stages. The results showe... [more]

Several countries are focusing their efforts on diversifying electricity generation to promote the transition towards a sustainable low-carbon energy system through the strategic development of the value chains related to renewable energy industries. In this way, the development of a national industry that helps to ensure a clean and affordable electricity supply and that also generates important socio-economic benefits, has gained relevance worldwide. This article proposes a methodology and economic model that considers technological progress and economies of scale to analyze a potential upstream development and integration of the value chain of the photovoltaic industry in Mexico. The results show that the upstream development of a national photovoltaic industry is financially viable and sustainable, and with which the national demand for photovoltaic technology could be satisfied by 76% and imports reduced by 47%, both compared to a reference scenario. This enables the generation of... [more]