In Poland, there has been a steady increase in the share of wind-generated energy in the overall energy balance of the country. However, wind power plants belong to unstable energy sources—the amount of generated power is variable in time. Variable generation may cause problems with the quality of energy transmitted in electricity networks. Therefore, this article presents the results of field tests of the impact of the Vestas V90 2 MW wind turbine on selected voltage quality parameters occurring in the grid. Due to the multifaceted influence of the power plant on the parameters of the grid to which it is connected, the article focuses only on four selected parameters: voltage value, zero and reverse asymmetry, and the value of the voltage distortion factor. The research conducted by the authors confirmed the positive influence of the operation of the wind power plant on the quality parameters of the electricity transmitted through the power grid. An increase in the power generated in... [more]

As the proportion of large-scale wind farms and distributed wind power connected to the power grid increases annually, the effects of their intermittent and random characteristics on the active and reactive power fluctuations of the power grid are becoming increasingly evident, causing frequent voltage fluctuations at the grid-connected point. To solve these problems, this study proposes a new topology of an electromagnetic var compensator (EVC) based on a rotary phase-shifting transformer (RPST). The EVC can work under capacitive and inductive conditions to compensate for inductive and capacitive power, respectively. In accordance with the parallel steady-state mathematical model of the EVC, a double closed-loop control strategy with high precision and considerable robustness is proposed for the EVC on the basis of instantaneous reactive power theory. Finally, simulations show that the topology of the proposed EVC exhibits bidirectional and continuous adjustment capability that can me... [more]

The pulsating flow is one of the techniques that can enhance heat transfer, therefore leading to energy saving in tubular heat exchangers. This paper investigated the heat transfer and flow characteristics in a two-dimensional in-line tube bundle with the pulsating flow by a numerical method using the Ansys Fluent. Numerical simulation was performed for the Reynolds number Re = 500 with different frequencies and amplitude of pulsation. Heat transfer enhancement was estimated from the central tube of the tube bundle. Pulsation velocity had an asymmetrical character with a reciprocating flow. The technique developed by the authors to obtain asymmetric pulsations was used. This technique allows simulating an asymmetric flow in heat exchangers equipped with a pulsation generation system. Increase in both the amplitude and the frequency of the pulsations had a significant effect on the heat transfer enhancement. Heat transfer enhancement is mainly observed in the front and back of the cylin... [more]

Experimental studies have shown that bioethanol production from biomass sources has been reported to be influenced by several process parameters. It is not entirely known, however, how the interaction of these factors affects the concentration of bioethanol production. In this study, the use of Gaussian Process Regression (GPR) in predictive modeling of bioethanol production from fountain grass has been investigated. Parametric analysis showing the interaction effect of time, pH, temperature, and yeast extract on the bioethanol production was examined. The effect of kernel functions on the performance of the GPR in modeling the prediction of bioenergy output was also examined. The study shows that the kernel function, namely, rotational quadratic (RQGPR), squared exponential (SEGPR), Matern 5/2 (MGPR), exponential (EGPR), and the optimizable (Opt.GPR.), had varying effects on the performance of the GPR. Coefficients of determination (R2) of 0.648, 0.670, 0.667, 0.762, and 0.993 were ob... [more]

Current distortion degrades power quality and affects system performance, especially for sensitive loads that require pure sinusoidal waves. Owing to its excellent dynamic response, a well-designed active power filter (APF) can achieve a total harmonic distortion (THD) within the acceptable limits defined by IEEE 3002 standards through compensating harmonic distortions. The APF consists of two main modules: a reference signal extraction module and a modulation module. This paper adapts the matrix pencil method, a well-known model-based parameter estimation technique, to the problem of reference extraction. Contrary to conventional time-domain methods such as the synchronous reference frame (SRF) and the reactive power theory (PQ theory) that rely on low-pass filters in their implementations, the proposed method does not use a filter. However, it extracts the reference signal by first decomposing the load current into its constituent frequency components, and then subtracting the pure s... [more]

This paper presents pulse multiplication technology based on an optimal Pulse Doubling Technique (PDT) to upgrade a 28-Pulse Rectifier (28-PR) to a 56-PR. The optimal PDT comprises a Tapped Interphase Reactor (TIPR) with a low kVA-rating and two diodes. The number of pulses can be increased from 28 to 56 using the PDT so that the input current harmonics are reasonably mitigated. Additionally, the 14-phase Polygon-Connected Autotransformer (PCA) is designed in such a way that it can be used for retrofit applications. A detailed simulation analysis in the MATLAB/Simulink environment is carried out, and the results show that the improved quality indices of the final AC input and DC output power are equivalent to the IEEE 519-2014 standard and meet sensitive industrial application requirements with an input current Total Harmonic Distortion (THD) lower than 3%. Moreover, the power factor also maintained unity for a wide operating range. The optimal PDT scheme is affordable and easy to impl... [more]

Enzyme-induced carbonate precipitation (EICP) is a new biogeotechnical ground improvement technique that uses calcium carbonate (CaCO3) formed by biochemical processes to increase soil strength and stiffness. In this paper, crude urease extracted from soybeans was employed to catalyze the precipitation of CaCO3 in sand. To optimize the urease extraction efficiency, factors affecting the soybean crude urease extraction, including the powdered soybean particle size, concentration, soaking time, and soaking temperature, were addressed. This paper also provided further insight regarding the impact of the urease activity of soybean crude extract on the chemical conversion efficiency and the biocementation performance in EICP. The findings revealed that the powdered soybean concentration and the particle size were the two most important factors affecting the urease activity of the soybean crude extract. The enzyme activity utilized in the EICP process might further lead to different reactant... [more]

The framework of energy transition poses significant challenges in subtransmission network development, where the increased renewable energy generation is collected, in order to efficiently convey power production, avoiding limitations in a range of operating conditions. In this paper, a method to evaluate possible margins for further renewable penetration due to electric network development is assessed, by means of scenario evaluation for the concretisation of renewable initiatives, combined producibility analysis, and load flow studies, accounting for operation islands in subtransmission network organisation, carried out in N and N-1 conditions. The method is applied to a provisional model of the southern part of the Italian power system.

Utilities are increasingly interested in integrating energy efficiency and demand response measures as a strategic approach that aims to achieve an increasingly reliable, dynamic, and integrated electric system. The concepts of energy efficiency (EE), demand response (DR), and system reliability (ESR) have been mainly studied from a different perspective, dealing only with the interaction between EE and DR and between EE and ESR. This paper aims to improve knowledge and demonstrate the validity of EE interventions (EEIs) through the use of a tool for evaluating the benefits of energy efficiency measures (EEMs) in the environmental sphere and in terms of DR and ESR. In order to evaluate this interaction, a quantitative method is proposed and validated on real results in an Italian case scenario, taking into account the analysis of smart meters data for residential users located in southern Italy in Calabria. Based on the collected data, an aggregation of users was evaluated with real ho... [more]

The focus of this work is on developing a nonlinear grey model for the laminar flow regime of carrier fluid across the flat plate collector. The trust region reflective algorithm was used to solve the nonlinear laminar flow problem and handle the sparse matrix. The stream function, dimensionless velocity, gradients of velocity components, carrier fluid temperature, and the absorber plate temperature were estimated for a flat plate collector operated with and without a circular chimney. Similarly, the same technique was adopted to determine a model for heat transfer across the absorber plate. The numerically obtained solution was also compared with the parameters obtained through the instrumental measurement. The relative tolerance was kept at 10−5 for the white and grey box solutions. The developed model was noticed to have a smaller deviation than the conventional analytical model to predict the experimental values. The slip condition was observed for the proposed scheme. The uncertai... [more]

The buckling tendency of an offshore pipeline buried in a liquefiable soil aggravates under earthquake situations. Moreover, to understand the upheaval displacement behavior of an offshore pipeline under dynamic loading, it is crucial to understand the variation of liquefaction potential within the soil bed. Thus, in the present study, the variation of the liquefaction potential within the soil body and its effect on the pipeline upheaval displacement (u) and post-shake uplift resistance (Vup) is investigated using a finite element package called PLAXIS 2D. The study was performed for different seismic and soil conditions. To define the soil, two advanced constitutive models are used. The static stages are modelled with the ‘Hardening Soil Model with small strain’ (HSS model), while the dynamic stage is modelled with the PM4Sand model. Moreover, the problem is defined as a 2d plane strain problem. The pipe is considered to be covered with Nevada sand. Several parameters such as a sand-... [more]

Voltage sag detection is utilized to capture the sag occurrence moment and calculate the sag depth of power grid voltage in real time, so as to generate reference voltage for controlling voltage interactive equipment such as dynamic voltage restorers (DVRs). However, the traditional voltage sag detection methods based on synchronously rotating frames (SRFs) are unable to acquire high-precision sag information under nonideal grid conditions such as unbalance or harmonic interference. In order to enhance the immunity of the sag detection, a method based on a selective harmonic extraction algorithm (SHEA) is proposed in this paper. Firstly, the state-space model of SHEA is established using discrete orthogonal basis to decouple and separate the signal of target frequency and the signal of interference frequency. The controllability, stability and convergence of SHEA are analyzed theoretically and serve as the criteria for parameter tuning. Moreover, a gain compensator (GC) is used to impr... [more]

The synchronous integration of numerous input and output loads is possible with multi-input (MI) and multi-output (MO) DC−DC converters. In this paper, the non-isolated DC−DC converter described, which has a high step-up capability and multiple ports for outputs and inputs for energy storage system (ESS) applications. The voltage level of the converter is changeable. The capacity to provide the large voltage increases with a low duty cycle portion, the ease with which each duty cycle can be controlled, and minimal power losses are all advantages of the proposed design. The proposed system offers advantages for applications requiring energy storage. In the continuous conduction mode (CCM), the operation principles, steady-state evaluation, and extracting of the voltage and current coefficients are performed. The supply sources can be inserted or withdrawn without causing a cross-regulation issue in the proposed converter. Ultimately, the functionality of the proposed structure is examin... [more]

In underground projects such as mining and tunneling, the presence of coal rock columns plays a certain supporting role, and the instability of coal rock columns is often related to their size and shape of presence. Therefore, in order to investigate the compressive damage characteristics and damage evolution law of rocks of different sizes, uniaxial compression tests were conducted on sandstones with different height−diameter ratios to explore the mechanical properties and damage characteristics of sandstones with different height−diameter ratios, analyze the connection between acoustic emission ringing count rate, accumulated energy, peak frequency, and b-value changes and height−diameter ratio, and analyze the evolution law of sandstones during damage based on damage variables, and draw the following conclusions. As the height-to-diameter ratio increases, the less affected by the end effect, the rock strength shows a nonlinear decreasing trend, and the decreasing trend becomes slow.... [more]

Liquid fuel can be an alternative to solid fuel in non-gasified locations. The mazout for municipal-energy boiler plants is much cheaper than fuel oil. However, this relates to the problem of wastewater disposal from such a boiler plant. A proprietary system for the disposal of bottom water and other sewage-containing mazout has been developed. The solution depends on the proper preparation and burning of a water−mazout emulsion (WME). The emulsion is prepared in a specially designed and developed dosing ejector. By burning the emulsion using the developed system, an efficiency increase of 2−3% was achieved for boilers operating on the mazout fuel. Such a result was achieved due to a reduction in the excess air factor. Moreover, emissions of nitrogen oxides and carbon monoxide were reduced by 30−35% and 70−80%, respectively. In addition due to cleaning the heat-exchange surfaces obtained when working on the WME, the amount of time for productive and more efficient use of the equipment... [more]

According to the traditional voltage and current double closed-loop control mode, the inverter management strategy for photovoltaic grid connection has insufficient anti-interference ability and slow response. This paper proposes a control strategy that applies adaptive-linear active disturbance rejection control (A−LADRC) to the outer loop control to achieve the purpose of anti-interference. The control strategy uses the linear extended state observer (LESO) to evaluate external interference caused by the change of external conditions and the internal disturbance caused by parameter uncertainty. PD controller compensates the disturbances and adds adaptive control to simplify parameter adjustment. Finally, this paper takes advantage of Lyapunov theory to conduct stability analysis. Compared with the traditional linear active disturbance rejection control (LADRC), the superiority of this control strategy is verified. The experimental results show that the system has better control perfo... [more]

The subject of this study was a distribution substation that feeds 14 fast DC chargers (80 kW) located at the bus depot in Lublin, Poland. The voltage variations were determined to be within the PN-EN 50160 standard limit values (±10% Un). There were several events registered when 4th, 6th, 8th, and 10th voltage harmonics were above the PN-EN 50160 limit during the charging of the electric buses. The obtained maximum 10 min average values of the total voltage harmonic distortion (THD) were 3.36%, 2.27%, and 2.89% for the first, second, and third phase, respectively, i.e., below the limit value of 8% required by PN-EN 50160. Due to the exceedance of the 6th voltage harmonic, the PN-EN 50160 requirements were not met.

In order to achieve climate goals and limit the global temperature rise, an increasing share of renewable-energy sources (RESs) is required. However, technologies for the use of RESs need to be integrated into the landscape and ecological heritage to ensure a fully sustainable energy transition. This work aims to develop a scalable technique for integrating the estimation of rooftop PV and wind potential into spatial planning, providing a framework to support decision-makers in developing energy policies. The methodology is applied to the minor Sicilian islands, which are characterised by significant environmental and landscape constraints. The methodology is used to identify the areas eligible for the installation of onshore wind turbines and the usable roof surfaces for the installation of PV systems. It is shown that the available technical potential of rooftop PV installations could ensure a higher production than the actual consumption on 13 of the 14 islands studied. Nevertheless... [more]

In 2021, the residential sector had an electricity consumption of around 39% in México. Householders influence the quantity of energy they manage in a home due to their preferences, culture, and economy. Hence, profiling the householders’ behavior in communities allows designers or engineers to build strategies that promote energy reductions. The household socially connected products ease routine tasks and help profile the householder. Furthermore, gamification strategies model householders’ habits by enhancing services through ludic experiences. Therefore, a gamified smart community concept emerged during this research as an understanding that this type of community does not need a physical location but has similar characteristics. Thus, this paper proposes a three-step framework to tailor interfaces. During the first step, the householder type and consumption level were analyzed using available online databases for Mexico. Then, two artificial neural networks were built, trained, and... [more]

Heat exchangers, devices for the transfer of heat between two or more working fluids, are extensively used in cooling applications and heating applications. Heat exchangers in buildings are typically components of space-conditioning systems, as well as of water-heating applications. Heat exchangers are also sometimes used in applications that require storage and release of energy at specific times. Phase change materials (PCMs) enhance these heat-exchange processes, given their ability to melt and solidify at a fixed range of temperatures, absorbing or releasing significant amounts of latent heat. Five different configurations of PCM−air heat exchangers for thermal control in buildings are analyzed in this work. The heat exchangers were fitted with PCM encapsulated in plastic and composite pouches of various shapes, and packaged in stackable panel layers. Three-dimensional computational fluid dynamics (CFD) modeling of coupled incompressible fluid and conjugate heat transfer were perfo... [more]

Photovoltaic (PV) systems have been used extensively worldwide over the past few years due to the mitigation of fossils fuels; it is the best source because of its eco-friendly nature. In PV systems, the main research area concerns its performance under partial shading (PS) and complex partial shading (CPS) conditions. PV sources perform perfectly under ideal conditions, but under practical conditions, their performance depends upon many factors, including shading conditions, temperature, irradiance, and the angle of inclination, which can bring a photovoltaic or solar system into a PS or CPS condition. In these conditions, many power peaks appear, and it is hard to find the global peak among many local peaks. The ability to track the maximum power peak and maintain it to avoid fluctuations depends on the maximum power point tracking (MPPT) technique used in a photovoltaic system. This article is based on the implementation of a hybrid algorithm, combining Harris hawk’s optimization (H... [more]

This paper, submitted to the special issue of Energies “Future of Road Vehicle Aerodynamics”, proposes and justifies the use of an old idea of generating downforce by actively drawing air from under the car body and exhausting it to the outside. Instead of traditional moving mechanical-curtain elements, a new method for sealing the clearance under the body with an air curtain is proposed. Basic information on the geometry and flow characteristics of such a solution suitable for use in automobiles is presented. The performance of such a fan-driven device generating downforce is studied over a wide range of driving speeds. The device allows for significantly improved vehicle acceleration, shorter braking distances, and extension of the range of safe cornering speeds. The paper shows the successive stages of development of the idea, from the 2D model to the 3D model, and an attempt to implement the device on a sports car. The distributions of pressure, velocity, pathlines and values of ae... [more]

Micro-cogeneration (micro-combined heat and power) is a technology that simultaneously produces decentralized thermal and electrical energy with a power of less than 50 kWel. This technology consists of using the waste heat generated by a thermodynamic process to meet the heating and hot water demands of buildings. The use of biomass as a fuel offers important advantages: use of a renewable energy, carbon neutrality, availability, and low cost. Furthermore, the analysis and optimization of hybrid energy systems, which include existing micro-cogeneration systems powered by renewable energy, is a scientific challenge needing experimental characterization of such micro-cogeneration systems. In this context, a biomass Stirling micro-CHP unit (μCHP), was tested to characterize its energy performance. A dynamic model based on these experimental investigations was developed to evaluate its thermal power output and energy efficiencies. The dependence of the nominal load on the water flow rate... [more]

The development of district heating systems results in a search for alternative heat sources. One of these is low-enthalpy geothermic energy, more available than traditional geothermal energy. However, utilization of these resources is difficult, due to the low quality of the produced heat. To utilize them, the heat pump system can be used. Such a system was designed for this case study of a city in a region of the Polish Lowlands. The data necessary for the design came from the project of the borehole and operational parameters of the existing heating plant. Four heat pump-cycle designs were proposed, modeled, and simulated using Ebsilon software. Afterward, the designs were optimized to achieve maximum coefficient of performance (COP) value. As a result of the simulation, the efficiency of each design was determined and the seasonal COP value was calculated with the annual measured heat demand of the plant. The system based on the cascade design proved the most efficient, with a seas... [more]

In recent years, container-based virtualization technology for edge and cloud computing has advanced dramatically. Virtualization solutions based on Docker Containers provide a more lightweight and efficient virtual environment for Edge and cloud-based applications. Because their use is growing on its own and is still in its early phases, these technologies will face a slew of security issues. Vulnerabilities and malware in Docker container images are two serious security concerns. The risk of privilege escalation is increased because Docker containers share the Linux kernel. This study presents a distributed system framework called Safe Docker Image Sharing with Homomorphic Encryption and Blockchain (SeDIS-HEB). Through homomorphic encryption, authentication, and access management, SeDIS-HEB provides secure docker image sharing. The SeDIS-HEB framework prioritizes the following three major functions: (1) secure docker image upload, (2) secure docker image sharing, and (3) secure docke... [more]