This study examines the roles of resource consumption accounting and competitive prices in attaining sustainable profitability. The objectives were (1) to determine whether the adoption of resource consumption accounting practices yields significant improvements in competitive strategies in a highly competitive situation where activity-based costing has proved to be insignificant, and (2) to ascertain if the positive relationship between competitive pricing and sustainable profitability is increased by the extent to which resource consumption accounting exerts pressure for sustainability profitability. A PLS-SEM procedure was applied in analysing 129 of the top 30 performing companies’ structured questionnaire responses drawn from five industries in Kurdistan from 2021. The empirical results demonstrated that competitive pricing models involving resource consumption accounting systems provide superior price forecasting, error reduction and profit maximisation capabilities than existing... [more]

This paper studies the effects of different exhaust gas recirculation (EGR) rates (0%, 5%, 10%, and 15%) on the combustion, performance, and emission characteristics of a biodiesel−diesel (20% biodiesel + 80% diesel) blended fuel engine. This paper mainly analyzes the effects on engine cylinder temperature, cylinder pressure, brake thermal efficiency (BTE), brake-specific fuel consumption (BSFC), NOx emissions, carbon monoxide (CO) emissions, hydrocarbon (HC) emissions, and soot emissions. Firstly, a 3D-CFD model was established by using CONVERGE software, combined with an improved chemical kinetic mechanism including 98 species and 314 reactions, and the accuracy of the simulation model was verified by experimental results. Secondly, the effects of different EGR rates on the combustion, performance, and emission characteristics of biodiesel−diesel blended fuel were studied. The results showed that with the increase in the EGR rate, the cylinder pressure and cylinder temperature in the... [more]

Pipes can be subjected to external transient impacts such as accidental collision, which affects the safe operation of storage and transportation systems for liquid hydrogen. Fluid−structure coupling calculation for a pipe under external transient impact is performed, and the flow characteristics of liquid hydrogen in the pipe are analyzed. The pipe deforms and vibrates when suffering from external transient impact. Liquid hydrogen pressure in a cross-section plane increases along the pipe deformation direction. Additionally, external transient impact enhances the disturbance of liquid hydrogen near the pipe wall. The increased flow resistance and the energy induced by the deformed pipe both affect the flow of liquid hydrogen, and contribute to the fluctuated characteristics of liquid pressure drop. In addition, the phase state of liquid hydrogen remains unchanged in the pipe, indicating that little of the induced energy is transformed into the internal energy of liquid hydrogen. The w... [more]

Microbial fuel cells (MFCs) are a kind of bioreactor for generating electricity, facilitated by exoelectrogens while treating wastewater. The present article focuses on the performance of an air cathode plexiglass MFC in terms of chemical oxygen demand (COD) removal efficiency and power output by performing two sets of experiments. The proton exchange membrane and electrode materials were Nafion 117 and carbon felts, whereas, for stable biofilm formation on the anode surface, a pure culture of Shewanella baltica 20 was used. Firstly, sterile Luria-Bertani (LB) media containing lactate, ranging from 20 to 100 mM, was continuously fed to an MFC, and a maximum power density of 55 mW/m2 was observed. Similarly, artificial wastewater with COD ranging from 3250 mg/L to 10,272 mg/L was supplied to the MFC in the second set of experiments. In this case, the maximum power density and COD removal efficiency were 12 mW/m2 and 57%, respectively. In both cases, the hydraulic retention time (HRT) wa... [more]

The move towards a greener energy mix to fight climate change propels investments in converter-interfaced resources such as wind and photovoltaics, energy storage systems and electric vehicles. The ongoing evolution of the power system is occurring at a very fast pace, challenging transmission and distribution system operators to seek solutions that are not only adequate for this moment but also for future scenarios. Ongoing research in the fields of power electronics, power systems and control aims at developing control strategies that will help the energy transition to occur, while keeping a stable, secure and reliable power system. The objective of this paper is to present a critical review of the control strategies developed for grid-connected power converters found in renewable energy systems, energy storage systems and electric vehicles. The impact of grid-connected converters on the stability of power grids is also reviewed, highlighting the promising control strategies for enha... [more]

Multi-speed transmission can greatly improve the power and economic performance of electric vehicles (EVs) compared with single-speed transmission. Gear ratio is the key design parameter of multi-speed transmission. Optimizing gear ratios can further improve vehicle performance. Most of the existing optimization methods of gear ratios take the power and economy of vehicles in gear as the optimization objectives, but rarely consider the shift performance of the transmission, such as shift time, friction, and shift jerk. Considering the shift performance in the process of gear ratio optimization can not only optimize the vehicle performance in gear, but also improve the shift performance of the transmission. Therefore, this paper proposes a multi-objective optimization method of gear ratios considering the shift performance. Firstly, a seamless three-speed automated manual transmission (AMT) of EVs is selected as the research object, the structure and the shift process without power inte... [more]

This study experimentally investigated the performance of a PVT air collector coupled with a triangular block. The triangular block, newly suggested by the authors, is a triangular-shaped obstacle and was inserted at the bottom of the PVT air collector to enhance the heat transfer performance of the collector. The experiment was carried out in actual climate conditions in Korea with two air mass flow rate conditions: 0.03606 kg/m2 s and 0.06948 kg/m2 s. Results show the average values of electrical efficiency of the collector during the test period to be 16.15% and 16.43% for each air mass flow rate, while thermal efficiencies were 28.83% and 38.36%, respectively. The average values of total energy efficiencies were found to be 44.99% and 54.79%, respectively. The results show that air mass flow rate has a large impact on thermal and total energy efficiency, while it has a small impact on electrical efficiency. Furthermore, it was confirmed that the PVT air collector coupled with a tri... [more]

Promoting the development and utilization of solar energy is a practical way to alleviate the energy crisis and achieve the goal of carbon neutrality. Recently, interest has arisen in the dual-functional active solar thermal façade (ASTF) system that produces hot water throughout the whole year and reduces cooling and heating load as a function of the building façade. Here, a mathematical model of the ASTF system is built and validated by the experimental data, and the annual performance of the ASTF system in representative cities in three climate regions is evaluated. The results are that compared with the common solar water system, the ASTF system adds passive energy savings, which accounts for 5.8%, 7.2% and 11.4% of the total primary energy savings of the system for Shanghai, Beijing and Lanzhou. Compared with the traditional wall, the ASTF saves 16.4% and 23.0% of cooling energy consumption and 102.3% and 92.4% of heating energy consumption for Shanghai and Beijing, respectively.... [more]

This paper aims to present the gained experience in modeling and simulating bottom-up power system restoration processes. In a system with low inertia, such as a restoration path, the Common Information Models for the regulation systems appear to no longer be suitable for the estimation of the frequency behavior, and thus a detailed model must be considered. On the other hand, due to the predominantly inductive behavior of the HV transmission network, the assumption of decoupling the power-frequency behavior to study the restoration stability seems to be licit. All these issues are discussed and justified in the paper by means of the use of different software packages and of the comparison with on-field recordings.

Capturing particulate matter (PM) is an important issue due to the protection of human health and the quality of their life. This paper describes the innovation of an affordable particulate matter capture device for small heat sources to reduce particulate matter emissions. The design of two investigated variants of the device is based on the principle of a tubular electrostatic precipitator with one charging electrode placed in the chimney. The design of the precipitators is aimed at increasing the area of the collecting electrodes by elements dividing precipitation space, with a simultaneously increased number of charging electrodes. The influence of the elements’ application on the pressure drop and the gas flow velocity through the devices is analyzed by computational fluid dynamics (CFD). The work is further focused on the economic evaluation of precipitators and design adjustments for lower energy consumption. The achieved results show the right direction of efforts to improve th... [more]

In this paper, the authors propose to use batteries to improve the performance of grid-connected photovoltaic plants when their photovoltaic fields are subject to partial shading phenomena. Particular attention is devoted to predictable and repetitive partial shadings, such as those that often appear in urban residential environments. Firstly, battery packs with proper nominal voltage and capacity are connected in parallel to partially shaded photovoltaic submodules. Then, the shaded photovoltaic submodules are properly disconnected and connected to the respective photovoltaic string by using a “battery control unit”, which is operated by taking into account characteristics of the specific partial shading phenomenon to cope with. To demonstrate the effectiveness of the proposed technique, an experimental study is performed to compare the performances of two identical prototypal grid-connected photovoltaic generators subject to identical artificial and repetitive partial shadings. Only... [more]

In this paper, flat plate film cooling with two rows of compound angle cylindrical film cooling holes was investigated. A data processing method was evaluated which could determine the film cooling effectiveness and heat transfer coefficient simultaneously from the transient wall temperature data. The method was based on solving an inverse problem of the one-dimensional transient heat conduction equation. To evaluate the performance of the method, wall temperature data were obtained using the known film cooling effectiveness and heat transfer coefficient data as the convection boundary condition. Then, the method was applied to calculate the film cooling effectiveness and heat transfer coefficient based on the wall temperature data. Different blowing ratios, heat transfer coefficients, mainstream temperatures, and material thermal conductivities were investigated. In general, the data and calculation were in good agreement. It was found that the error decreased when the heat transfer c... [more]

Microwave treatment is an emerging technique for biomass tar elimination. The electric and thermal fields of the microwave reactor are the key to high elimination efficiency and energy utilization. In this work, we simulated the electric and thermal fields of a microwave reactor with various parameters including irradiation feed position, microwave power, silicon carbide length and flow velocity. Results show that the irradiation feed position that locates 5 mm vertically to the central plane can obtain the highest electric intensity and silicon carbide temperature (ca. 1100 K) after wave absorbing. Both the electric and thermal fields are strengthened when microwave power is increased. Extending the silicon carbide bed length will decrease the bed temperature and heating rate. A high flow velocity leads to non-uniform temperature distribution of the silicon carbide. For the purpose of achieving a high microwave energy utilization and uniform bed temperature, suitable irradiation feed... [more]

The problem of rising energy prices stems from the weakening of economies operating in the realities of the COVID-19 coronavirus pandemic, as well as from the rising cost of CO2 emission allowances in connection with the European Union’s environmental policy. The outbreak of war in Ukraine has deepened the energy crisis in European countries, which, to a significant extent, benefit from hydrocarbon resources imported from Russia. This problem is particularly acute in countries that are heavily dependent on conventional forms of energy production (e.g., Poland). In light of the problems observed, the need to develop a market for renewable energy has become more urgent than ever. Although this problem affects a number of countries, the authors of the study decided that it is particularly important in the region of the countries neighbouring the line of the ongoing armed conflict in Ukraine, i.e., Poland and the Baltic States (Lithuania, Latvia and Estonia). The choice of the research are... [more]

Non-intrusive load monitoring takes place in residential and industrial contexts to disaggregate and identify loads connected to a distribution grid. This work studies the applicability and effectiveness for AC railways, considering the highly dynamic behavior of rolling stock as an electric load, immersed in varying contexts of moving loads. Both voltage−current diagrams and harmonic spectra were considered for identification and extraction of features relevant to classification and clustering. Principal components were extracted, approaching the problem using principal component analysis (PCA) and partial least square regression (PLSR). Clustering methods were then discussed, verifying separability performance and applicability to the railway context, checking the performance by means of the balanced accuracy index. Based on more than one hundred measured spectra, PLSR has been confirmed with superior performance and lower complexity. Independent verification based on dispersion and... [more]

This numerical study investigates the effects of adding a small amount of ignition promoters for controlling the wedge-induced oblique shock wave (OSW) to oblique detonation wave (ODW) transition in a premixed hydrogen−air mixture at hypersonic speeds. The time-dependent two-dimensional compressible Euler equations for multiple thermally perfect species with a reactive source term are solved using adaptive mesh refinement and detailed chemical kinetics. The wedge with a fixed angle of 26° exhibits abrupt to smooth transitions for freestream Mach numbers 7−9 (speeds 2.8−3.2 km/s) at a pressure of 20 kPa and a temperature of 300 K. The small amount (1000 PPM by vol.) of H2O2 and O3 is found to be effective at significantly reducing the initiation length for the oblique detonation transition for all Mach numbers, which suggests a practical approach to increase the operating flight range for oblique detonation wave engine with a finite length wedge. At Mach number 8, the abrupt OSW to ODW... [more]

This paper proposes the implementation, analysis and comparison of the control techniques Proportional, Integral and Derivative, Nonlinear Predictive, Fuzzy control and Sliding Mode Control technique applied to the speed control of an independent excited DC motor driven by a three-phase fully controlled rectifier of six pulses. The methodology proposes the design of the bench, modeling of the real system by the system identification method and the adjustments of the parameters of the controllers using an optimization process. Comparisons are made between the techniques, highlighting their characteristics and performances when executed under similar conditions. The robustness of each control, when acting on a nonlinear system, is investigated. All control techniques are applied in three different tests: (i) reference signal of step type without load application, (ii) reference signal with amplitude variation without load application and (iii) reference signal of step type with load appl... [more]

Many environmental parameters affect the performance of solar photovoltaics (PV), such as dust and temperature. In this paper, three PV technologies have been investigated and experimentally analyzed (mono, poly, and flexible monocrystalline) in terms of the impact of dust and thermal energy on PV behavior. Furthermore, a modular neural network is designed to test the effects of dust and temperature on the PV power production of six PV modules installed at Sohar city, Oman. These experiments employed three pairs of PV modules (one cleaned daily and one kept dusty for 30 days). The performance of the PV power production was evaluated and examined for the three PV modules (monocrystalline, polycrystalline, and flexible), which achieved 30.24%, 28.94%, and 36.21%, respectively. Moreover, the dust reduces the solar irradiance approaching the PV module and reduces the temperature, on the other hand. The neural network and practical models’ performance were compared using different indicator... [more]

The consensus control method based on a multi-agent system has been widely applied in the distributed control and optimization of microgrids. However, the following drawbacks are still common in current research: (1) ignoring the influence of consensus control commands on the synchronization stability of the physical grid under primary control; (2) only focusing on improving one property ofcontrol performance, lacking comprehensive considerations of multiple properties. With the aim of solving these problems, in this paper we propose a weight-adaptive robust control strategy for implementing distributed frequency regulation of islanded microgrids. Firstly, the frequency synchronization stability of the physical layer is analyzed by means of a coupled oscillator theory and the design objectives of the controllable parameters for the information layer are formed. Subsequently, the relationship between the weight coefficients and the two important control performances of convergence speed... [more]

Effective prediction of wind power output intervals can capture the trend of uncertain wind output power in the form of probability, which not only can avoid the impact of randomness and volatility on grid security, but also can provide supportable information for grid dispatching and grid planning. To address the problem of the low accuracy of traditional wind power interval prediction, a new interval prediction method of wind power is proposed based on PSR-BLS-QR with adaptive rolling error correction. First, one-dimensional wind power data are mapped to high-dimensional space by phase space reconstruction (PSR) to achieve data reconstruction and the input and output of the broad learning system (BLS) model are constructed. Second, the training set and the test set are divided according to the input and output data. The BLS model is trained by the training set and the initial power interval of training data is constructed by quantile regression (QR). Then, the error distribution of n... [more]

The effective identification of the economic withholding behavior of the generators can help ensure the fair operation of the electricity market. A SCAD-logit model is proposed to improve the performance of the logit model for the massive data of electricity market. First, a social network analysis method is used to construct an equity relationship graph of the generators to obtain a set of key monitoring generators. An indicator system for identifying the economic withholding behavior of the generators is constructed based on structure conduct performance (SCP) theory. The indicators are screened by the smoothed clipped absolute deviation (SCAD) penalty regression method to reduce the collinearity and improve identification efficiency. Then, a SCAD-logit model is established to identify the economic withholding of key monitoring generators, so that the boundary contributions of each indicator to the economic withholding behavior are obtained. The confusion matrix, ROC curve, and AUC v... [more]

Power-to-Liquid (PtL) plants can viably implement carbon capture and utilization technologies in Europe. In addition, local CO2 sources can be valorized to substitute oil and gas imports. This work’s aim was to determine the PtL efficiency obtained by combining a solid oxide electrolyzer (SOEC) and Fischer−Tropsch synthesis. In addition, a recommended plant configuration to produce synthetic fuel and wax at pilot scale is established. The presented process configurations with and without a tail gas reformer were modeled and analyzed using IPSEpro as simulation software. A maximum mass flow rate of naphtha, middle distillate and wax of 57.8 kg/h can be realized by using a SOEC unit operated in co-electrolysis mode, with a rated power of 1 MWel.. A maximum PtL efficiency of 50.8% was found for the process configuration without a tail gas reformer. Implementing a tail gas reformer resulted in a maximum PtL efficiency of 62.7%. Hence, the reforming of tail gas is highly beneficial for the... [more]

In this paper, an analysis of the physico-chemical properties of diethyl ether/sunflower oil blends, as well as changes in emissions in work with AD3.152 diesel engine, were realized. The following properties of tested blends have been examined in detail: density (ρ) at 15 °C; kinematic viscosity (v) at 40 °C; cold filter plugging point (CFPP); lower heating value (LHV); flash point (FP); and surface tension (ϭ). In this research, different blends of diethyl ether (DEE) with sunflower oil (SO) in ratios of 10:90, 20:80 and 30:70% by volume were chosen. It was confirmed that DEE impacts significantly on reducing of SO viscosity. Furthermore, the density, as well as the surface tension of tested blends, have been reduced significantly when DEE was blended with SO. In this way, DEE impacts on better atomization of the SO injected into the combustion chamber. It was confirmed that DEE addition improves the low-temperature properties of SO significantly, which indicates the possibility of a... [more]

Measurements of air flow velocity are essential at every stage of the design, construction and operation of wind turbines. One of the basic measurement tools in this area is the tachometric anemometer, which is based on the simple physical phenomenon of the air kinetic energy exchange with a rotating measuring element. Tachometric anemometers have favorable operational features and good static metrological parameters. However, in the case of fast-changing flows, the measurement is burdened with a significant dynamic error, and the measured average value of the velocity is overestimated. This article presents the concept and results of pilot studies of a dynamic error correction method of tachometric anemometers. The correction consists of the precise measurement of the rotor’s rotational velocity and determination of the measured air velocity, taking into account the dynamics of the instrument. The developed method can be used in tachometric anemometers intended for laboratory, technic... [more]

This paper investigates the nonlinear modeling and stability of a doubly-fed variable speed pumped storage power station (DFVSPSPS). Firstly, the mathematical model of DFVSPSPS with surge tank considering nonlinear pump turbine characteristics was derived and established. Then, Hopf bifurcation analysis of DFVSPSPS was performed. The stable region was identified and verified by example analysis. Moreover, the effect mechanism of nonlinear pump turbine characteristics on the stability of DFVSPSPS was explored. Finally, the influence of factors on the stability and dynamic response of DFVSPSPS was studied. The results indicate that the emerged Hopf bifurcation of DFVSPSPS is supercritical and the region on the low side of the bifurcation line is the stable region. Nonlinear head characteristics have a significant influence on the stability and dynamic response of DFVSPSPS. Nonlinear speed characteristics have an obvious effect on the stability and dynamic response of DFVSPSPS only under... [more]