Renewable energy sources (RESs) are generally connected to the grid through power electronic interfaces, which generate electrical power instantaneously with little inertia. With the increasing penetration of RESs, the grid will gradually develop into a low inertia and underdamped power system, which results in serious grid frequency stabilization problems. The virtual synchronous generator (VSG) is an emerging technology that mimics the operation characteristics of traditional synchronous generators (SGs). Virtual inertia and damping are therefore introduced, which help to stabilize grid frequency. This paper gives a comprehensive overview of the VSG. The basic operation principle of VSG is introduced and analyzed in depth. The key issues related to VSG are summarized and discussed, including hardware configuration, software control strategies, energy supporting methods, and typical applications.

This paper proposes a novel consequent-pole-type PM motor having a structure different from that of conventional consequent-pole-type PM motors. The proposed rotor structure is composed of a magnetic pole pair using a permanent magnet and an image-pole pair using a high permeability core. The windings facing the magnetic pole pair and the image-pole pair are connected in series in the rotor structure, the three-phase synchronous impedance is balanced, and the d-axis inductance is increased. Therefore, compared with the conventional consequent-pole type, the field weakening operation can be performed efficiently with a lower d-axis current. These advantages make it possible to expand the operating range during field weakening. Furthermore, to fix the driving control method of the proposed consequent-pole PM motor, the voltage equation of the proposed motor is derived and verified by analysis and experiment. In addition, the essential characteristics of the proposed motor were compared w... [more]

In modern complex industrial processes, mode changes cause unplanned shutdowns, potentially shortening the lifespan of key equipment and incurring significant maintenance costs. To avoid this problem, a method that can detect the fault of equipment operating in various modes is required. Therefore, we propose a novel fault detection method that uses the k-nearest neighbor normalization-based weight local outlier factor (WLOF). The proposed method performs local normalization using neighbors to consider possible mode changes in the normal data and WLOF is used for fault detection. In contrast to statistical methods, such as principal component analysis (PCA) and independent component analysis (ICA), the local outlier factor (LOF) uses the density of neighbors. However, because LOF is significantly affected by the distance between its neighbors, the weight is multiplied proportionally to the distance between each neighbor to improve the fault detection performance of the LOF. The efficie... [more]

Electromobility is one form of transport that is suitable for achieving the goals of carbon neutrality. Therefore, if stakeholders want to be informed, the aim of the article is to examine trends in the field of electromobility. Trends are explored using a systematic literature review. The selected areas are specific factors affecting electromobility, which are market characteristics and value-added services. A specific area of inquiry is important for the reason that if businesses providing or dealing with electromobility are successful in the market, it is necessary to analyse their market position or characteristics of the market in which they operate. If it is clear which laws apply in the market, the company can adapt its offer to the trends that affect the given business segment. The same applies to policy makers, new knowledge can be applied in policy making. Data, about the market and services that are offered on the market, provide knowledge to stakeholders that focus their ac... [more]

High power electromagnetics (HPEMs) pose a potential threatening risk to the wireless communication system, especially according to the main coupling path of the RF front-end channel. SPICE modeling of the responses coupled on the RF channel is crucial for the EM risk assessment, which helps us learn more about how the pulse conducts on the RF channel. A simplified linear RF channel with pyramid horn antenna is taken as an example by the selection of the key electronic modules of the actual wireless system. This paper proposes a system-level SPICE circuit model for the simplified RF channel according to the hybrid methods of the antenna electromagnetic simulation and SPICE modeling of the RF circuit. The equivalent circuits of the horn antenna illuminated by HPEMs are established with the Vector Fitting method based on Thevenin and Norton theorems. The short current response as the excitation files for the SPICE models are obtained by the commercial electromagnetic simulation of the ho... [more]

According to the requirements of carbon-neutral development, this study explores the comparison and new discussion of replacing nitrogen with carbon dioxide in the conventional two-phase microfluid flow. Thus, carbon dioxide application in various fields can be more precise and convenient. This research uses an artificially continuously tapering micro model to mimic the natural rock channel in low permeability formation, where the liquid imbibition process is entirely under surface tension-dominant. The tested capillary number decreased to 8.49 × 10−6, and the thinnest observed liquid film was reduced to 2 μm. The comparison results in two gas groups (nitrogen and carbon dioxide) show that CO2 gas fluid in microscopic porous media would have more tendency to snap off and leave fewer residual bubbles blocked between the constrictions. However, the N2 gas fluid forms smaller isolated gas bubbles after snap-off. By combining the experimental data and numerical output with the theoretical... [more]

The explosive development of electrical engineering in the early 19th century marked the birth of the 2nd industrial revolution, with the use of electrical energy in place of steam power, as well as changing the history of human development. The versatility of electricity allows people to apply it to a multitude of fields such as transportation, heat applications, lighting, telecommunications, and computers. Nowadays, with the breakout development of science and technology, electric energy sources are formed by many different technologies such as hydroelectricity, solar power, wind power, coal power, etc. These energy sources are connected to form grid systems to transmit electricity to cities, businesses and homes for life and work. Electrical energy today has become the backbone of all modern technologies. To ensure the safe, reliable and energy-efficient operation of the grid, a wide range of grid management applications have been proposed. However, a significant challenge for monit... [more]

Experiments on the convection heat transfer and pressure drop of supercritical carbon dioxide in a mini vertical upward flow were investigated in a smooth tube with an inner diameter of 2 mm. The experiments were conducted with pressures ranging from 7.62 to 8.44 MPa, mass fluxes ranging from 600 to 1600 kg·m−2·s−1, and heat flux ranging from 49.3 to 152.3 kW·m−2. Results show that the peak of heat transfer occurs when the bulk fluid temperature is below the proposed critical temperature and the wall temperature is above the proposed critical temperature. For the 2 mm vertical upward flow, the radial buoyancy effects are relatively weak, and the axial thermal acceleration effect cannot be negligible. In this study, a new modified Jackson correlation for the supercritical carbon dioxide is proposed for convective heat transfer. To reflect the effect of flow acceleration on heat transfer, a dimensionless heat flux was introduced to construct a new semi-correlation of heat transfer. The n... [more]

With the increase of energy demand, energy wasteful behavior is inevitable. To reduce energy waste, it is crucial to understand users’ electricity consumption habits and detect abnormal usage behavior in a timely manner. This study proposes a high-dimensional energy consumption anomaly detection method based on deep learning. The method uses high-dimensional energy consumption related data to predict users’ electricity consumption in real time and for anomaly detection. The test results of the method on a publicly available dataset show that it can effectively detect abnormal electricity usage behavior of users. The results show that the method is useful in establishing a real-time anomaly detection system in buildings, helping building managers to identify abnormal electricity usage by users. In addition, users can also use the system to understand their electricity usage and reduce energy waste.

New methods for state estimation are required due to the complexity of the topology of transmission and distribution systems, and the predictability in the management of prosumer dispatch. This paper describes a pilot project in Greece that, in accordance with OneNet’s architecture, addresses the challenges of congestion and balancing management that system operators face due to the high penetration of renewable energy sources. The respective data requirements and the IT/OT environment are described, as well as the interconnections among the various modules and functionalities. Available resources of the grid’s flexibility are identified, and the implementation of an integrated monitoring system based on efficient forecasting of volatile generation and demand is addressed. Congestion management and frequency and voltage control are in the center of interest of the demonstrator where, in close collaboration with system operators, respective network models are being developed.

Over the years, cities have undergone transformations that, invariably, overload and even compromise the functioning of an energy matrix dependent on increasingly scarce resources. The high demand for energy has challenged stakeholders to invest in more sustainable alternatives, such as bioenergy, which, in addition, helps to reduce the pressure for finite resources, enable the energy recovery of waste and contribute to the mitigation of carbon emissions. For these improvements to be successful, stakeholders need specific technological strategies, requiring tools, methods and solutions that support the decision-making process. In this perspective, the current work aimed to develop a framework optimizing the evaluation of waste bioenergy projects through the application of algorithms. Therefore, a literature review was carried out to select the algorithms and identify the sectors/areas and stages in which they are applied. These algorithms were then grouped into two sequential phases. T... [more]

In this study, a method for the bacterial disinfection of drinking water in the water storage systems based on the electric potential generated from a piezoelectric wind energy harvester is presented. First, an efficient galloping piezoelectric wind energy harvester is designed by adding curve- shaped attachments to the bluff body of the harvester. The simulated output voltage of the harvester is validated by performing different sets of experiments on an open environment. Later, the output voltage of the harvester is enhanced, using copper oxide nanowires (CuONWs) grown perpendicular to the surface of the center copper wire. The enhanced electric field is able to disinfect the bacterial water in a 25 min time period. The bacterial removal log efficiency of 2.33 is obtained with a supplied rms voltage of 0.1 V from the harvester. The findings of this study will help to provide alternate means to water treatment that are efficient, reliable, and also free from disinfection by-products.

The depletion of fossil energy reserves has intensified the interest in renewable energy sources, such as solar energy. Solar water heating represents an environmentally clean technology, with an abundant, permanent, renewable energy source that does not pollute or harm the ecosystem. In this context, the objective of the work was to revisit the theme of residential solar heating in relation to the use of flat-plate solar collectors. This study combined bibliometrics techniques and a systematic literature review. The results indicated that by considering the period from 1993 to 2020, we could find several publications revealing that the interest in this subject still remains high and current. Themes related to water heating and ambient cooling showed consistency in the publications, while studies focused on integrating solar thermal energy with other chemical processes, such as distillation or desalination, indicated that significant research is required in this area.

Bioethanol-derived biomass is a green sustainable source of energy that is highly recommended as an efficient alternative to the replacement of fossil fuels. However, this type of bioethanol production is always expensive with very low bioethanol concentration. Therefore, this work aims to represent a facile and green approach for bioethanol production with high concentration and purity as well as reasonable cost from corn stover (CS). The goal of this study is to characterize CS and its treated samples with maleic acid (CSM) using various characterization analyses, such as proximate and ultimate analysis, HHV, TGA, FTIR, SEM, and CHNS. The bioethanol production stages: Pretreatment, enzymatic degradation, fermentation, and finally bioethanol separation and purification via the pervaporation process, which have been investigated and optimized are associated with the economic analysis. The optimum operating condition of the pretreatment process was 2% maleic acid, 1:20 solid-to-liquid r... [more]

Renewable energy transition creates unprecedented issues in power system control, operation and protection [...]

This paper deals with voltage control in a buck DC-DC converter. In fact, dynamic mathematical equations describing the principle behavior of the above system have been derived. Due to the nonlinearity of the established model, a nonlinear control algorithm is adopted. It is based on the sliding mode control approach. To highlight the performance of the latter, a comparative study with four control algorithms is carried out. The validity of the model and the performance of the conceived algorithms are verified in simulation. Both the system and the algorithm controls are implemented in the Matlab/Simulink environment. Extensive results under different operational conditions are presented and discussed.

Pneumatic conveying is widely used in coal mining. As the lowest conveying velocity of materials, the pickup velocity is the key to the study of gas−solid two-phase flow. In this study, the pickup velocity of pebble particles was experimentally investigated. When the particle size is 3−9 mm, the airflow velocity was found to suitably describe the results as a function of the pickup velocity and have a high correlation. When the swirl number is 0.2, the optimal swirl number was found for which the highest particle pickup ratio was observed. Based on four different methods, namely, visual observation, mass weighing, coefficient of difference analysis, and determination of the peak-average ratio of the pressure drop in the flow field to measure the pickup velocity of the spraying material, the results showed that the accuracy of the particle pickup velocity obtained through visual observation was the lowest, and when the mass−loss rate of the particle was selected as the measurement index... [more]

The current work presents an effective fault detection and diagnosis (FDD) technique in wind energy converter (WEC) systems. The proposed FDD framework merges the benefits of kernel principal component analysis (KPCA) model and the bidirectional long short-term memory (BiLSTM) classifier. In the developed FDD approach, the KPCA model is applied to extract and select the most effective features, while the BiLSTM is utilized for classification purposes. The developed KPCA-based BiLSTM approach involves two main steps: feature extraction and selection, and fault classification. The KPCA model is developed in order to select and extract the most efficient features and the final features are fed to the BiLSTM to distinguish between different working modes. Different simulation scenarios are considered in this study in order to show the robustness and performance of the developed technique when compared to the conventional FDD methods. To evaluate the effectiveness of the proposed KPCA-based... [more]

Wind turbine wake redirection drawn by a yaw control has been proposed as a strategy to improve the performance of wind farms. However, the characteristics and the development of the curled wake structure deformed by the yaw action of the rotor are not well understood. In the present study, the structure of the wake behind a wind turbine imparted with various yaw angles subjected to uniform inflow was investigated using large-eddy simulation. The NREL 5MW reference wind turbine was modeled with an actuator disk with rotation to study the deformation process of the curled wake. The source of the vertical asymmetry in the wake deformation was found to be based on the interaction of global wake rotation and a counter-rotating vortex pair induced by the yaw angle. The yaw angle had a profound influence on the distortion of the wake and its trajectory, whose effect was naturally mitigated with downstream distance.

The modern-day urban energy sector possesses the integrated operation of various microgrids located in a vicinity, named cluster microgrids, which helps to reduce the utility grid burden. However, these cluster microgrids require a precise electric load projection to manage the operations, as the integrated operation of multiple microgrids leads to dynamic load demand. Thus, load forecasting is a complicated operation that requires more than statistical methods. There are different machine learning methods available in the literature that are applied to single microgrid cases. In this line, the cluster microgrids concept is a new application, which is very limitedly discussed in the literature. Thus, to identify the best load forecasting method in cluster microgrids, this article implements a variety of machine learning algorithms, including linear regression (quadratic), support vector machines, long short-term memory, and artificial neural networks (ANN) to forecast the load demand i... [more]

Numerous numerical and experimental studies have been conducted regarding the Concentrated Photovoltaic Thermal (CPVT) system because of its significant potential for efficient conversion of solar energy. The overall efficiency of the CPVT system is strongly dependent on the device, which extracts excess heat from photovoltaic cells. The most efficient cooling technology involves active cooling, which means that heat is collected from the PV cell via the forced flow of heat transfer fluid. This research paper provides an extensive discussion on devices dedicated to active-cooling CPVT systems, taking into account the latest solutions. First, a short introduction regarding CPVT systems and their main components is presented. The second part of this study presents state-of-the-art solutions in the field of heat extraction devices for the active cooling of photovoltaic cells. The available solutions are classified into two main groups depending on the scale of internal channels: macro- an... [more]

Due to their large and increasing size and the corrosive nature of salt water and high wind speeds, offshore wind turbines are required to be more robust, more rugged and more reliable than their onshore counterparts. The dynamic characteristics of the blade and its response to applied forces may be influenced dramatically by rotor rotational speed, which may even threaten the stability of the wind turbine. An accurate and computationally efficient structural dynamics model is essential for offshore wind turbines. A comprehensive model that takes the centrifugal stiffening effect into consideration could make rapid and accurate decisions with live data sensed from the structure. Moreover, this can enhance both the performance and reliability of wind turbines. When a rotating blade deflects in its plane of rotation or perpendicular to it, the centrifugal force exerts an inertia force that increases the natural frequencies and changes the mode shapes, leading to changes in the dynamic re... [more]

In the development of deep geological repositories (DGRs), performance assessment modeling is used to evaluate the integrity and performance of the engineered and geological barriers for thousands or millions of years of evolution of the disposal system. To evaluate the suitability of a site for a DGR, geoscientific data from dedicated site investigation programs are integrated into site-specific assessments. This paper presents the development and implementation of a modeling workflow aimed at comparing three potential siting areas for a DGR in Switzerland from the viewpoint of long-term safety and technical feasibility. The workflow follows the guidelines of the national regulator addressing safety relevant criteria such as the barrier efficiency of the host rock and its mechanical and chemical integrity in response to repository-induced influences and the long-term stability of the repository site over geological scales. In the regulatory requirements, the role of parametric, concep... [more]

Compared with oil, natural gas has been the focus of the energy industry in recent years. Renewable energy is the goal and trend of future developments, and it has made considerable progress; however, it has not reached the ideal popularization rate. Therefore, natural gas is still very important so far. In this paper, the influence of thermal gas injection and room temperature gas injection on gas reservoir recovery is analyzed, and the method of water plugging by hot gas injection in tight gas reservoir is put forward. Indoor simulation experiments were carried out to evaluate the effect of hot-gas injection in cut pore water and the degree of water blockage. On this basis, the numerical simulation of removing water blockage by hot-gas injection was carried out. The changes in core temperature and remaining water saturation were discussed by using simulation models. Results of this study can provide a theoretical basis for removing water blockage in actual oil and gas reservoirs.

In the pursuit of more efficient vehicles on the world’s roads, the vehicle thermal management system has become a limiting factor when it comes to EV range and battery life. In extreme climates, if the thermal system cannot pull down or warm up the EV powertrain in a timely manner, the battery is at serious risk of capacity loss or accelerated degradation. As waste heat is inherently limited with EVs, the way in which we provide the heat for warm-up must be as efficient as possible to reduce the load on the battery. In this paper, a revolutionary waste heat recovery (WHR) thermal management system designed by Tesla, nicknamed the ‘Octovalve’, is described, modelled, and simulated. This paper contributes to collective knowledge by presenting an in-depth breakdown of the key operating modes and outlining the potential benefits. Modelled in the multidomain Simulink Simscape software, the octovalve’s performance is directly compared to a typical EV WHR thermal management system. The syste... [more]