Simulations of emergency states and tests of resistance of electrical devices to emergencies are performed in specialized high-power laboratories, the so-called short-circuit laboratories. For most electrical power devices, such measurements are required by international standards. The basic equipment of short-circuit testing laboratories consists of current transformers for measuring short-circuit currents. These transformers should not only enable the accurate conversion of sinusoidal currents—which is typical for conventional current transformers, but also asymmetrical short-circuit currents containing an aperiodic component, which classic current transformers cannot reproduce. Therefore, manufacturers and designers try to meet the market demands and design these special class 0.2 current transformers. To meet the high technical requirements, the field-circuit method with three-dimensional space−time analysis of electromagnetic fields was used during design, considering physical phe... [more]

In the current paper, an analysis of the influence of cooling system selection on the thermal parameters of two thermally coupled power MOSFETs is presented. The required measurements of the thermal parameters were performed using the indirect electrical method at different values of power dissipated in the investigated transistors and various supply conditions for the active parts of their cooling systems. The results of the investigations are analysed and discussed. Functions modelling the observed dependences of thermal parameters of the investigated MOSFETs on the power that was dissipated in them as well as the supply conditions of the active parts of their cooling systems are proposed. A good agreement between the results of the measurements and the computations was obtained. It is shown that the use of active cooling systems makes it possible to reduce the value of the thermal resistance of the tested transistor up to 20 times. In each of the tested systems, the self- and transf... [more]

Bidirectional electric vehicle supply equipment and charging stations (EVSE) offer new business models and can provide services to the electrical grid. The smart grid lab in Vienna gives unique testing possibilities of future smart grids, as different type of electrical equipment can be operated at a reconstructed, well-known distribution grid. In this work the harmonic and supraharmonic emissions of a bidirectional EVSE are measured according to IEC61000-4-7 and IEC61000-4-30 Ed3 standard as well as the high-frequency grid impedance. In addition, the efficiency and the power factor are determined at various operating points. Although THDi at nominal power (10 kW) is very low and the efficiency and power factor is very high, at low power levels the opposite situation arise. Supraharmonic emissions remain stable independent of the charging/discharging power, and both wideband and narrowband emissions occur. The additional capacitance when connecting the EVSE impacts the high-frequency g... [more]

The zirconia solid electrolyte SOFC (solid oxide fuel cell) has the characteristics of oxygen ion conduction function, high-temperature resistance, thermoelectric coupling effect, etc. A NOx sensor based on zirconia solid electrolyte has common characteristics and problems with the SOFC in principle and application. The research objective of this paper is to solve the application problems of smart NOx sensors in diesel vehicles or gasoline vehicles. Improvements in the application performance of the NOx sensor can help the NOx emissions of gasoline vehicles or diesel vehicles better meet the requirements of emission regulations. The smart NOx sensor is a regulatory sensor required by vehicles for China’s Phase VI Vehicle Exhaust Emission Regulations or Euro Phase VI Vehicle Exhaust Emission Regulations. The smart NOx sensor is a key sensor device for improving fuel efficiency and reducing pollution. Moreover, its measurement performance includes dynamic immunity to interference, respon... [more]

With the rapid growth of the oil and gas storage, transportation, and pipeline industries, it is necessary to improve the construction process of oil and gas pipelines. By combining the technical advantages of horizontal directional drilling and pipe jacking construction, the direct pipe laying method is suitable for pipeline crossing in different strata in the oil and gas, water conservancy and hydropower, and municipal industries due to its advantages of less construction land, high speed, and reversibility. Using the rapid jacking and laying of pipelines crossing Nanjuma River in the ‘Jingshihan’ gas pipeline double line project as a case study, this paper investigates the application status of the direct pipe laying method, summarizes the project, and introduces the construction of the working well, equipment selection, guiding control technology, supporting equipment installation, and drag reduction measures, as well as analyzes the influencing factors of thrust force and trajecto... [more]

The relationship between the presented work and energy conservation is direct and indirect. Most of the literature related to energy-saving focuses on reducing the aerodynamic drag of cars, which typically leads to the appearance of vehicle motion instabilities at high speeds. Typically, this instability is compensated for by moving aerodynamic body components activated above a certain speed and left in that position until the vehicle speed drops. This change in vehicle configuration results in a significant increase in drag at high velocities. The presented study shows a fully coupled approach to fluid−structure interaction analyses of a car during a high-speed braking-in-turn manoeuvre. The results show how the aerodynamic configuration of a vehicle affects its dynamic behaviour. In this work, we used a novel approach, combining Computational Fluid Dynamics (CFD) analysis with the Multibody Dynamic System. The utilisation of an overset technique allows for car movement in the computa... [more]

Electrical Vehicles (EVs) have gained popularity in recent years in the automotive field. They are seen as a way to reduce the CO2 footprint of vehicles. Although EVs have witnessed significant advancement in recent years, they still have two major setbacks: limited autonomy and long recharging time. Dynamic Inductive Power Transfer (DIPT) systems permit charging EVs while driving, provide unlimited autonomy, and eliminate stationary charging time and lower battery dependency. Multiple transmitters are required to achieve DIPT; thus, dealing with transient phases is essential because every time a receiver crosses over from one transmitter to another, it experiences a new transient phase. This article presents a novel control strategy for multi-transmitter DIPT systems that ensures a continuous and stable power transfer to a moving EV. The proposed control strategy eliminates drop and inrush currents during transient phases. The control integrates a soft start feature and a degraded ope... [more]

A theoretical framework to implement multi-sensor data fusion methods for kinematic quantities is proposed. All methods defined through the framework allow the combination of signals obtained from position, velocity and acceleration sensors addressing the same target, and improvement in the observation of the kinematics of the target. Differently from several alternative methods, the considered ones need no dynamic and/or error models to operate and can be implemented with low computational burden. In fact, they gain measurements by summing filtered versions of the heterogeneous kinematic quantities. In particular, in the case of position measurement, the use of filters with finite impulse responses, all characterized by finite gain throughout the bandwidth, in place of straightforward time-integrative operators, prevents the drift that is typically produced by the offset and low-frequency noise affecting velocity and acceleration data. A simulated scenario shows that the adopted metho... [more]

Coal-fired power plants are widely used to achieve a power balance in grids with renewable energy, which leads to new requirements for speediness in load dispatch. This paper presents a nondominated-sorting grey wolf optimizer algorithm (NSGWO) for the multiobjective load dispatch of coal-fired power plants that employed efficient nondominated sorting, a reference-point selection strategy, and a simulated binary crossover operator. The optimization results of the benchmark functions indicated that the NSGWO algorithm had a better accuracy and a better distribution than the traditional multiobjective grey wolf optimizer algorithm. Regarding the load dispatch of economy, environmental protection, and speediness strategies, the NSGWO had the best performance of all the simulated algorithms. The optimal-compromise solutions of the economy and speediness strategies of the NSGWO algorithm had a good distribution, which elucidated that this novel algorithm was favorable to allowing coal-fired... [more]

The use of hydrogen in small scale gas turbines is currently limited by several issues. Blending hydrogen with methane or other gaseous fuels can be considered a low medium-term viable solution, with the goal of reducing greenhouse gas emissions. In fact, only small amounts can be mixed with methane in premixed combustors, due to the risk of flashback. The aim of this article is to investigate the injection of small quantities of steam as a method of increasing the maximum permissible hydrogen content in a mixture with methane. The proposed approach involves introducing the steam directly into the combustion chamber into the main fuel feeding system of a Turbec T100. The study is carried out by means of CFD analysis of the combustion process. A thermodynamic analysis of the energy system is used to determine boundary conditions. The combustion chamber is discretized using a three-dimensional mesh consisting of 4.7 million nodes and the RANS RSM model is used to simulate the effects of... [more]

Geothermal surface manifestations (GSMs) are direct clues towards hydrothermal activities of a geothermal system in the subsurface and significant indications for geothermal resource exploration. It is essential to recognize various GSMs for potential geothermal energy exploration. However, there is a lack of work to fulfill this task using deep learning (DL), which has achieved unprecedented successes in computer vision and image interpretation. This study aims to explore the feasibility of using a DL model to fulfill the recognition of GSMs with photographs. A new image dataset was created for the GSM recognition by preprocessing and visual interpretation with expert knowledge and a high-quality check after downloading images from the Internet. The dataset consists of seven GSM types, i.e., warm spring, hot spring, geyser, fumarole, mud pot, hydrothermal alteration, crater lake, and one type of none GSM, including 500 images of different photographs for each type. The recognition res... [more]

Microalgae-based technologies have huge potential for application in the environment sector and the bio-energy industry. However, their cost-efficiency has to be improved by drawing on design and operation data for large-scale installations. This paper presents a technical concept of an installation for large-scale microalgae culture on digestate liquor, and the results of a pilot-scale study to test its performance. The quality of non-treated digestate has been shown to be insufficient for direct use as a growth medium due to excess suspended solids, turbidity, and organic matter content, which need to be reduced. To that end, this paper proposes a system based on mechanical separation, flotation, and pre-treatment on a biofilter. The culture medium fed into photobioreactors had the following parameters after the processing: COD—340 mgO2/dm3, BOD5—100 mgO2/dm3, TN—900 mg/dm3, and TP—70 mg/dm3. The installation can produce approx. 720 kgVS/day of microalgal biomass. A membrane unit and... [more]

With greater power density, a hybrid power source that combines supercapacitors and batteries has a wide range of applications in pulse-operated power systems. In this paper, a supercapacitor/battery semi-active hybrid energy storage system (HESS) with a full current-type control strategy is presented. The studied HESS is composed of batteries, supercapacitors, and a bidirectional buck−boost converter. The converter is controlled such that supercapacitors supply load power pulses, and batteries provide the power in steady state. To realize the fast compensation of the supercapacitors to the load power pulses, a power distribution module based on hysteresis control theory is designed in the control system. Moreover, the control strategy does not require the model parameters of the converter and supercapacitors, so the control system is simplified. A complete configuration scheme and cost analysis of the proposed HESS are also presented. Obtained results show that the proposed supercapac... [more]

Investigations into the connectivity and complexity of pore systems in shales are essential for understanding the flow of shale gas and the capacities of the associated reservoirs. In the present study, eight shale samples from the Wufeng-Longmaxi (WF-LMX) Formation that were collected from Well Yucan-6 in the southeast of the Sichuan Basin were analyzed for microstructural, pore network, and pore connectivity characteristics. The measurement results of low-pressure nitrogen adsorption illustrated that all shale samples contain micropores, mesopores, and macropores. Micropores and mesopores account for a high proportion of the total pores, and the dominant pore throat size is in the range of 2−6 nm. High-pressure mercury injection tests reveal that the porosity, total pore volume, and total specific surface area of pores for samples from the WF Formation are higher than those for samples from the LMX Formation. In spontaneous absorption experiments, the slopes of the absorption curves... [more]

For large-scale and sustainable water electrolysis, it is of great significance to develop cheap and efficient electrocatalysts that can replace platinum. Currently, it is difficult for most catalysts to combine high activity and stability. To solve this problem, we use cobalt to regulate the electronic structure of ruthenium to achieve high activity, and use carbon matrix to protect alloy nanoparticles to achieve high stability. Herein, based on the zeolitic imidazolate frameworks (ZIFs), a novel hybrid composed of RuCo alloy nano-particles and N-doped carbon was prepared via a facile pyrolysis-displacement-sintering strategy. Due to the unique porous structure and multi-component synergy, the optimal RuCo500@NC750 material in both acidic and alkaline media exhibited eminent HER catalytic activity. Notably, the 3-RuCo500@NC750 obtained a current density of 10 mA cm−2 at 22 mV and 31 mV in 0.5 M H2SO4 and 1.0 M KOH, respectively, comparable to that of the reference Pt/C catalyst. Furth... [more]

A tunnel boring machine (TBM) is an important large-scale engineering machine, which is widely applied in tunnel construction. Precise cutterhead torque prediction plays an essential role in the cost estimation of energy consumption and safety operation in the tunneling process, since it directly influences the adaptable adjustment of excavation parameters. Complicated and variable geological conditions, leading to operational and status parameters of the TBM, usually exhibit some spatio-temporally varying characteristic, which poses a serious challenge to conventional data-based methods for dynamic cutterhead torque prediction. In this study, a novel hybrid transfer learning framework, namely TRLS-SVR, is proposed to transfer knowledge from a historical dataset that may contain multiple working patterns and alleviate fresh data noise interference when addressing dynamic cutterhead torque prediction issues. Compared with conventional data-driven algorithms, TRLS-SVR considers long-ago... [more]

There is a growing research interest in studying microgrids as a way to overcome the lack of access to energy. These microgrids could be the key to global energy access because of their many advantages related to flexibility, efficiency, and reliability. Despite all these qualities, microgrids remain challenging to implement in a sustainable and resilient way without a clear consensus on what causes these failures. To this end, this work proposes a new paradigm to make a multidisciplinary and comprehensive review of the operation of microgrids. By reconciling the different fields inherent to microgrids, this review enables the study of microgrids within a unified framework. Microgrids will be presented through energy, information, financial, and social fields to provide the necessary elements for their systemic understanding. Each field will be presented with its internal elements, architecture, and significant issues. By elaborating on this new vision of microgrids, this article hopes... [more]

SO2 and NOx in flue gas are serious environmental pollutants. As an excellent adsorbent, activated coke has good application potential in flue gas desulfurization and denitrification. In this study, different concentrations of NH3 and K2CO3 solutions were used to modify the activated coke made from biomass and coal, and then separate and coordinated desulfurization and denitrification experiments were carried out. The adsorption efficiency of activated coke and the adsorption capacity of SO2 and NO were compared, and the adsorption relationship between SO2 and NO was clarified. The changes of the surface functional groups of activated coke before and after adsorption and the forms of SO2 and NO after adsorption were analyzed by Fourier transform infrared spectrometer and X-ray diffractometer patterns. Results show that K2CO3 and NH3 modification can promote the adsorption of SO2 and NO in activated coke, and K2CO3 modification is more significant for improving the denitrification and d... [more]

Nowadays, energy saving is considered a key issue worldwide, as it brings a variety of benefits: reducing greenhouse gas emissions and the demand for energy imports and lowering costs on a household and economy-wide level. Researchers and building designers are looking to optimize building efficiency by means of new energy technologies. Changes can also be made in existing buildings to reduce the energy consumption of air conditioning systems, even during operational conditions without dramatically modifying the system layout and have as low an impact as possible on the cost of the modification. These may include the usage of new heat transfer fluids based on nanofluids. In this work, an extended experimental campaign (from February 2020 to March 2021) has been carried out on the HVAC system of an educational building in the Campus of University of Salento, Lecce, Italy. The scope of the investigation was comparing the COP for the two HVAC systems (one with nanofluid and the other one... [more]

Olive oil is one excellence of the Italian food industry: around 300 kt yr−1 are produced, creating roughly the same amount of olive mill wastewater (OMW) to be disposed of. The present work describes a process to exploit OMW by converting its organic compounds to valuable gaseous biofuel. A sample OMW was characterized (COD, TOC, solids, and polyphenols) and submitted to membrane filtration tests to concentrate the organic compounds. Based on the results of the experiments, a treatment process was outlined: the retentate streams from microfiltration and ultrafiltration steps were fed to a cracking and a steam reforming reactor, respectively; the obtained syngas streams were then mixed and sent to a methanation reactor. The process was simulated with Aspen Plus (AspenTech©) software, assessing operating conditions and streams compositions: the final biofuel is around 81 mol.% methane, 4 mol.% hydrogen, and 11 mol.% carbon dioxide. The permeate stream cannot be directly disposed of, but... [more]

With the Internet of things and various information and communication technologies, a city can manage its assets in a smarter way, constituting the urban development vision of a smart city [...]

The wake dynamics of a wind turbine are influenced by the atmospheric turbulence and the wake of its upwind turbine. In this work, we investigate the wake characteristics of a waked wind turbine for four different downwind spacings and three different inflows using large-eddy simulation with a turbine parameterized using the actuator surface model. The wake statistics of the waked turbine are compared with those of the stand-alone wind turbine under the same inflow. The results show that the oncoming wake significantly affects the near wake of the waked turbine, where it accelerates the wake recovery by increasing the turbulent convection, and increases the turbulence kinetic energy. The velocity deficit and turbulence kinetic energy in the far wake, on the other hand, are fairly similar with each other for the considered different turbine spacings, and are close to those of the stand-alone wind turbine. As for the wake meandering of the waked wind turbines, it is initiated quickly and... [more]

Power quality disturbances (PQD) have a negative impact on power quality-sensitive equipment, often resulting in great financial losses. To prevent these losses, besides detecting a PQD on time, it is important to classify it, so that appropriate recovery procedures are employed. The majority of research employs machine learning model PQD classifiers on manually extracted features from simulated or real-world signals. This paper presents an end-to-end approach that circumvents the manual feature extraction and uses signals generated from mathematical voltage sag type formulas. We developed a configurable voltage sag generator that was used to form training and validation datasets. Based on the synthetic three-phase voltage signals, we trained several end-to-end LSTM classifiers that classify voltage sags according to ABC classification. The best-performing model achieved an accuracy of over 90% in the real-world dataset.

In view of reducing the number of inverter legs that provide dual-phase, three-level output voltages (as may be needed in an uninterruptible power supply), and that also provide a wide range of output frequencies (as needed in an advanced motor drive system with wide speed ranges), a three-level, dual-phase inverter topology is presented in this paper. Its three-level attribute was based on the F-type inverter topological concept, and its dual-output feature was based on the common representation of the inverter-leg concept. The proposed inverter could deliver single- and three-phase voltages to corresponding one- and three-phase loads, in common or different frequency modes of operation. A boundary between these modes of operation was established for the proposed inverter. An additional possibility of either operation in the one-phase or the three-phase system was offered by the inverter configuration. A modified carrier-based sinusoidal pulse-width modulation scheme is presented for... [more]

For the optimal high-efficiency operation of a PEM fuel cell system, the temperature, pressure, humidity and mass flow of the supplied air must be tuned to the fuel cell stack requirements. Especially for aircraft applications, this requires a thorough understanding of the fuel cell air supply system behavior and how it changes when the ambient pressure is below 1 bar(a) during flight. This work investigates the influence of low inlet pressures and varying inlet temperatures on the compression map of an electrical turbo charger. This is especially relevant in airborne fuel cell application and not much literature can be found on that topic. Compressor limits are evaluated experimentally and theoretically. The theory of mass flow and speed correction is compared to experimental findings and found to be applicable for the surge and speed limit of the investigated turbo chargers as long as the compressor map is not limited by the power of the electric motor and inverter. Based on this, a... [more]