Following the international trend of using hydrogen as combustible in many industry branches, this paper investigates the impact of mixing methane gas with 23% hydrogen (G222) on condensing boilers’ operation. After modeling and testing several boilers with heat exchange surface different designs, the authors gathered enough information to introduce a new concept, namely High-Performance Condensing Boiler (HPCB). All the boilers that fit into this approach have the same operational parameters at nominal heat load, including the CO2 concentrations in flue gases. After testing a flattened pipes condensing boiler, a CO2 emission reduction coefficient of 1.1 was determined when converting from methane gas to G222 as combustible. Thus, by inserting into the national grid a G222 mixture, an important reduction in greenhouse gases can be achieved. For a 28 kW condensing boiler, the annual reduction in CO2 emissions averages 1.26 tons, value which was experimentally obtained and is consistent... [more]

The comparison of the results obtained using two methods for measuring the radio disturbance emissions produced by compact lighting drivers in the frequency range of 30 to 300 MHz has been presented in this paper. Any electrical and electronic equipment used within the EU must comply with Directive 2014/30/EC and harmonised standards. For lighting equipment, the dedicated standard is EN-IEC 55015:2019-11E. In this standard, for tests in the frequency range of 30 to 300 MHz, two equivalent test methods are allowed for lighting drivers, i.e., the traditional method in which disturbance emissions are measured in a semianechoic chamber SAC and the alternative CDNE (Coupling Decoupling Network Emission) method. Each method is characterised by a different measurement technique. For this reason, this paper aims to compare the results obtained by the two methods and to find out whether the CDNE and SAC methods, despite the difference in measurement technique, can be considered equivalent. The... [more]

Hydrogen is a key enabler of a sustainable society. Refurbishment of the existing natural gas infrastructure for up to 100% H2 is considered one of the most energy- and resource-efficient energy transportation methods. The question remains whether the transportation of 100% H2 with reasonable adaptions of the infrastructure and comparable energy amounts to natural gas is possible. The well-known critical components for refurbishment, such as increased compressor power, reduced linepack as well as pipeline transport efficiencies, and their influencing factors were considered based on thermodynamic calculations with a step-by-step overview. A H2 content of 20−30% results in comparable operation parameters to pure natural gas. In addition to transport in pipelines, decentralized H2 production will also play an important role in addressing future demands.

The partial recovery of kinetic energy during braking allows the vehicle’s battery to be additionally charged and thus extends the range of an electric vehicle. Because of the different operating strategies of the braking energy recovery system, it is important to understand the factors influencing the level of recovered energy. The driving conditions at the place of use have a direct impact on the energy efficiency of an electric vehicle. The purpose of this paper was to analyze the energy recovered during braking in different driving conditions. The tests were based on the parameters of actual trips made along urban and suburban routes, and express roads. The collected actual speed profiles were used for the simulation studies. AVL cruise vehicle simulation software was used in the study. Simulation tests revealed that the levels of energy recovered during braking in an electric vehicle were the highest in urban conditions. The amount of energy recovered during urban driving can acco... [more]

Horizontal axis wind turbines (HAWTs) experience yaw misalignments due to the physical limitations of yaw controllers and various novel active yaw controls. Moreover, the motion of floating offshore wind turbines (FOWTs) accelerates yaw misalignment. The blade element momentum (BEM) method is widely used due to its computational efficiency for the design of HAWTs. Momentum theory, the basis of BEM, assumes steady flow and uniform induction field at the disc. Those assumptions are relaxed by engineering models to capture yaw and unsteady effects. Current yaw engineering models, however, are inaccurate since they do not capture the asymmetric wake expansion effect. Dynamic inflow models have been developed for non-yawed flow. Furthermore, the AVATAR project shows that BEM using fully coupled engineering models, the current yaw, dynamic inflow and various engineering models, suffers from significant deficiencies. This purpose of this paper, therefore, is to investigate dynamic effects for... [more]

The subject of the model research contained in this paper is an application of a motion energy−harvesting device on a crane-hoisting mechanism to power independent measurement devices. Numerical experiments focused on the selected motion energy−harvesting device (M-EHS) and its configuration properties in the context of energy-harvesting efficiency in the case of using it on a crane. The results of the computer simulations were limited to the initial specified conditions for the harvester and the movement of the conditions of the crane-hoisting mechanism. The article compares the energy efficiency for the selected construction and parameters of the harvester for specific hoisting speed and the arm length of the motion conversion system. For this purpose, the initial conditions for the crane and the configuration of parameters of the energy harvester were assumed. The results are visualized on the diagram of RMS voltage induced on piezoelectric elements, showing the impact of individual... [more]

This research proposes a methodology for the optimal location and sizing of reactive compensation in an electrical transmission system through a deep neural network (DNN) by considering the smallest cost for compensation. An electrical power system (EPS) is subjected to unexpected increases in loads which are physically translated as an increment of users in the EPS. This phenomenon decreases voltage profiles in the whole system which also decreases the EPS’s reliability. One strategy to face this problem is reactive compensation; however, finding the optimal location and sizing of this compensation is not an easy task. Different algorithms and techniques such as genetic algorithms and non-linear programming have been used to find an optimal solution for this problem; however, these techniques generally need big processing power and the processing time is usually considerable. That being stated, this paper’s methodology aims to improve the voltage profile in the whole transmission syst... [more]

Despite offering promising opportunities for wind energy harvesting in urban environments, vertical axis wind turbines face limitations in terms of poor starting characteristics. In this study, we focus on analyzing improvements offered by dual-stage turbines for a range of wind velocities. Numerical simulations are performed for different phase angles between the rotors (a measure of relative angular positions of the blades in the two rotors) to quantify the response time for their starting behavior. These simulations rely on a through sliding mesh technique coupled with flow-induced rotations. We find that for U∞=4m/s, the phase angles of 30∘ and 90∘ substantially reduce starting time in comparison to a single-stage turbine. Dual-stage turbines with a phase angle of 90∘ exhibit similar or better starting behavior for other wind speeds. The phase angle of 0∘ in double-rotor turbines shows the poorest starting response. Moreover, it is revealed that stabilization of shear layers genera... [more]

As plug-in electric vehicles (PEVs) become more and more popular, there is a growing interest in the management of their charging power. Many models exist nowadays to manage the charging of plug-in electric vehicles, and it is important that these models are implemented in a better way. This paper investigates a price-driven charging management model in which all plug-in electric vehicles are informed of the charging strategies of neighboring plug-in electric vehicles and adjust their own strategies to minimize the cost, while an aggregator determines the unit price based on overall electricity consumption to coordinate the charging strategies of the plug-in electric vehicles. In this article, we used an asynchronous distributed generalized Nash game algorithm to investigate a charging management model for plug-in electric vehicles in a smart charging station (SCS). In a charging management model, we need to consider constraints on the charge and discharge rates of plug-in electric veh... [more]

Nowadays, power systems’ Protection, Automation, and Control (PAC) functionalities are often deployed in different constrained devices (Intelligent Electronic Devices) following a coupled hardware/software design. However, with the increase in distributed energy resources, more customized controllers will be required. These devices have high operational and deployment costs with long development, testing, and complex upgrade cycles. Addressing these challenges requires that a ’revolution’ in power system PAC design takes place. Decoupling from hardware-dependent implementations by virtualizing the functionalities facilitates the transition from a traditional power grid into a software-defined smart grid. This article presents a survey of recent literature on software-defined PAC for power systems, covering the concepts, main academic works, industrial proof of concepts, and the latest standardization efforts in this rising area. Finally, we summarize the expected future technical, indu... [more]

To understand the change in overburden structure after coal seam group mining, we investigated the overburden characteristics and bearing capacity of abandoned coal mines in a coal seam group. We provide a theoretical basis for the construction and utilization of a coal mining subsidence area under a complex geological environment. This paper takes the construction project of Zhongtie Huizhi Square in Zhangqiu District, Jinan City, Shandong Province as the engineering background. According to the occurrence conditions of the study area, theoretical analysis, similar simulation, numerical simulation, and engineering practice verification are used. The overburden structure characteristics of abandoned mines in a shallow-buried coal seam group were studied. The results show that the development height of the water-carrying fractured zone after the mining of the 3#, 4#, and 9# coal seams is 17 m, 19.5 m, and 27.1 m, respectively, which shows that the height of water flow in the fractured z... [more]

An improved analytical method was developed for identifying sulfide compounds from aromatic fractions in Lungu atmospheric residue (LGAR). Sulfides in residue aromatics were selectively oxidized into sulfoxides using tetrabutyl ammonium periodate (TBAP) and identified by positive-ion Electrospray Ionization Source (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Results showed that sulfides with lower polarity in LGAR aromatics could effectively ionize in ESI using this approach. Additionally, the oxidized sulfides were mainly S1 and S2 class species. The most abundant oxidation-generated sulfoxides O1S1 and O1S2 in LGAR aromatics had DBE values of 3~10 and 8~12, respectively. The S2 class species, whose condensation degree was higher than that of S1, were likely in the form of containing both cyclic sulfides and thiophenic compounds.

The design and implementation of an asynchronous coilgun’s structure is relatively simple compared with other types of linear induction launchers. In order to drive rotating electrical machines, multilevel converter structures have attracted much attention in recent decades as a result of their unique advantages. A linear induction launcher has an identical theoretical background to rotating electrical machines; therefore, multilevel converter structures can be applied to them as well. The stator of a launcher can be excited by generators or capacitor groups whose voltage and frequency might be fixed or changeable by a power conditioner. The aim of this study is to design and simulate a novel power conditioner as a multilevel converter topology for the power source of an asynchronous coilgun. Cascaded H-Bridge multilevel converter topology constitutes the proposed power conditioner in which a level-shifted pulse-width modulation method is used to generate appropriate pulses for the pow... [more]

Renewable energy sources are intended to support the decarbonisation process of the Polish economy. Since 2005, the share of renewable energy in total electricity in Poland has been increasing. The number of photovoltaic panels installed by prosumers as part of micro-installations increased particularly strongly. The aim of this research is an assessment of the impact of government programmes on the development of RES micro-installations in Poland. A regression discontinuity design was used in the analysis. It is a model from the group of average impact effect models used in evaluation studies. The added value of the presented study is its application in the assessment of the impact of implemented programmes on the number and output of micro-installations in Poland. In the study, it is shown that there had been no increase in the number and output of micro-installations at the adopted threshold (2019Q4). On the other hand, there was a sharp increase in them over the whole period starti... [more]

Sea wave energy is being increasingly regarded as one of the most promising sources of renewable energy. This paper deals with the modeling and simulation of an onshore wave energy converter system designed by UMBRA GROUP SpA. Several topics are addressed. Starting from the multibody modeling strategy, this paper delves more deeply into the mechanical efficiency evaluation of the ball-screw in the elastohydrodynamic lubrication regime, the core of the energy conversion process, as well as the thermal characterization of the power take-off module, based on the lumped-parameter and finite element method models. High values of ball-screw indirect efficiency have been observed, ranging from 73% to 97%; these results appear even more encouraging when compared to the performance of alternative energy-consuming technologies. Thermal analysis, on the other hand, provided a maximum temperature increase of 40 °C, allowing for the aversion of any structural collapse and the realistic identificati... [more]

In an era where sustainability is becoming the main driving force for research and development, supercritical fluids-based techniques are presented as a very efficient alternative technology to conventional extraction, purification, and recrystallization processes. Supercritical antisolvent (SAS) precipitation is a novel technique that can replace liquid antisolvent precipitation techniques. Additionally, through the optimization of precipitation operating conditions, morphology, particle size, and particle size distribution of nanoparticles can be controlled. As an antisolvent, supercritical carbon dioxide (scCO2) is far more sustainable than its conventional liquid counterparts; not only does it have a critical point (304 K and 73.8 bar) on its phase diagram that allows for the precipitation processes to be developed so close to room temperature, but also its recovery and, consequently, the precipitated solute purification stage is considerably simpler. This technique can be used eff... [more]

Air conditioning loads (ACLs) are potential flexible resources that can provide various grid services to the power system. Recent studies have attempted to represent their flexibility using a virtual battery (VB) model for quantification, but the modeling process requires information on thermal parameters and heat disturbances (e.g., solar irradiation and internal heat load) that are difficult to measure. In this paper, we present a new method that models a VB without prior knowledge of such information. First, we construct a thermal dynamic model of an individual ACL using historical input-output data. The linear regression model parameters are identified without using the measurements of disturbances. Second, we derive a VB model from the linear regression parameters using a change of variable technique. We show that the VB can be directly modeled from the regression model of thermal dynamics without estimating the exact thermal parameters and heat disturbances. Third, aggregation of... [more]

Compression by shock waves is a specific way of compressing gases. It has been practically applied for many years in supersonic flying objects. The idea of using this method in rotary engines is extremely appealing because one disk can replace several or a dozen disks of an axial compressor, significantly reducing the weight and production costs of the engine and lowering the fuel consumption due to possible increased compression ratio. This paper presents a review of existing technical solutions and the results of published research devoted to the construction of shock wave compression rotary engines: patents, scientific publications describing various research methods, numerical calculations, and the experimental results of unusual technical solutions. The characteristic solutions and problems that arose during the implementation of these methods are presented and described. Judging from the presented overview, these have wide application possibilities, and an enormous intellectual a... [more]

Vertical axis wind turbines are an emerging and in-development wind energy technology which are characterized by their complicated aerodynamics. Detached flow conditions, which are typically developed at operational tip speed ratios, demand a rigorous characterization of the airfoils for an accurate prediction of the turbine performance. In this work, a custom-built, three-component external strain gauge balance, specifically developed for airfoil testing, is validated. The physical reasons responsible for discrepancies with reference data are also analyzed. Two- and three-dimensional flat plates, as well as the DU06-W-200 airfoil, are tested in a wind tunnel. Lift and drag coefficients and pitching moments are obtained for a wide angular range at Re = 200,000. The results are compared with data from the bibliography and CFD simulations, performed with the recently developed GEKO (generalized k-omega) turbulence model, achieving remarkable agreement. Instantaneous forces are also analy... [more]

ZnMn2O4 spinels are prepared by a simple hydrothermal route with control of the reaction time, ranging from 6 h to 18 h. The evolution of the structural and morphological parameters under the effect of time was analyzed by XRD, ATR-FTIR, XPS, and SEM-EDS. The XRD results show that for longer reaction times (18 h), the ZnMn2O4 spinel samples present a tetragonal structure with high crystallinity and an average crystallite size of 32.3 ± 1.7 nm, larger than those obtained for 6 h and 12 h. The ATR-FTIR spectra confirm the structural results, with well-defined peaks related to stretching vibrations of M-O (M = Zn, Mn) functional groups. XPS reveals the co-existence of several metal oxides and hydroxides at the outermost surface. SEM analysis shows that the samples present a pyramid morphology, better defined at 18 h, with an average particle size of 6.2 ± 1.5 µm. EDS analysis of ZnMn2O4 (18 h) reveals atomic ratios of 0.45, 0.22, and 0.50 for Zn/Mn, Zn/O, and Mn/O, respectively, in good a... [more]

Secure data aggregation is an important process that enables a smart meter to perform efficiently and accurately. However, the fault tolerance and privacy of the user data are the most serious concerns in this process. While the security issues of Smart Grids are extensively studied, these two issues have been ignored so far. Therefore, in this paper, we present a comprehensive survey of fault-tolerant and differential privacy schemes for the Smart Gird. We selected papers from 2010 to 2021 and studied the schemes that are specifically related to fault tolerance and differential privacy. We divided all existing schemes based on the security properties, performance evaluation, and security attacks. We provide a comparative analysis for each scheme based on the cryptographic approach used. One of the drawbacks of existing surveys on the Smart Grid is that they have not discussed fault tolerance and differential privacy as a major area and consider them only as a part of privacy preservat... [more]

This paper presents the effect of baffle geometry on the charging process of a low-temperature heat storage unit. Four different geometry variants were considered for this purpose. Each of them was simulated and the results were compared. The following parameters were selected as comparison criteria: the charging time of the heat storage unit, the change in the liquid and solid fractions of the phase change material, and the change in its temperature over time. The analysis showed that, independent from the heat transfer fluid velocity, the use of baffles did not significantly affect the charging time. Furthermore, the application of baffles of all studied types did not bring an essential decrease in charging time. It was found that the optimal solution was to use the simplest construction. Tuning of the HTF flow by the use of baffles is applicable to shell and tube heat exchangers; however, it adds no significant effects in the case of heat storage units of the proposed design. The ab... [more]

This paper presents an algorithm for solving the power flow (PF) problem of droop-regulated AC microgrids (DRACMs) operating in isolated mode. These systems are based on radial distribution networks without having a slack bus to facilitate conventional computations. Moreover, distributed generation units have to distribute the power and voltage regulation among themselves as a function of operating frequency and voltage droop rather than having a slack bus that regulates voltage and power demands. Based on the conventional backward/forward sweep algorithm (BFS), the proposed method is a derivative-free PF algorithm. To manage the absence of a slack bus in the system, the BFS algorithm introduces new loops, equations, and self-adaptation procedures to its computation procedures. A comparison is presented between the proposed BFS algorithm and other state-of-the-art PF algorithms, as well as PSCAD/EMTDC. In comparison to existing algorithms, the proposed approach is fast, simple, accurat... [more]

Drying is a complex process of simultaneous heat, mass, and momentum transport phenomena with continuous phase changes. Numerical modelling is one of the most effective tools to mechanistically express the different physics of drying processes for accurately predicting the drying kinetics and understanding the morphological changes during drying. However, the mathematical modelling of drying processes is complex and computationally very expensive due to multiphysics and the multiscale nature of heat and mass transfer during drying. Physics-informed machine learning (PIML)-based modelling has the potential to overcome these drawbacks and could be an exciting new addition to drying research for describing drying processes by embedding fundamental transport laws and constraints in machine learning models. To develop such a novel PIML-based model for drying applications, it is necessary to have a fundamental understanding of heat, mass, and momentum transfer processes and their mathematica... [more]

With the background of implementing carbon peaking and carbon neutralization, identifying methods to realize energy-saving and carbon reduction effectively has become an important issue in the intelligent energy-conservation manufacturing industry. During the process of achieving this goal, determining an optimal location for a low-carbon and intelligent manufacturing industrial park is a foremost decision-making problem for manufacturing corporations’ energy-efficient development. The article established a multi-criteria decision framework to assist manufacturing companies when selecting suitable industrial park sites. To begin with, an evaluation criteria framework is confirmed by literature search. Then, a fuzzy optimization model, which combines the fuzzy Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and the fuzzy VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) is presented, where fuzzy TOPSIS is used to determine the decision-maker criteri... [more]