The dynamic behavior and energy transformation mechanism of the multi-period evolution of bubbles collapsing near a wall have been essential considerations in bubble dynamics research. In this study, a compressible two-phase solver considering thermodynamics and phase transitions is developed on OpenFOAM (version v2112). This model is validated via comparison with analytical solutions and experimental results. The dynamics of the multi-period evolution of bubbles collapse process at different dimensionless stand-off distances (γ) were accurately reproduced. The results indicate that the shock wave emitted by the collapse of cavitation bubbles impacts the wall, causing the fluid temperature along the wall to increase. Moreover, the liquid jet has a dual effect on the wall temperature increase, depending on the initial stand-off distance between the bubble and the wall. When γ is small, the jet carries the low-temperature fluid to occupy the high-temperature region, and when γ is large,... [more]

The continued commissioning of DC microgrids in an effort to achieve net-zero carbon levels in the atmosphere demands the large-scale deployment of converters to make the power from renewable energy sources, such as solar PV, usable. To control these inherently non-linear converters using classical linear control methods, averaged modelling techniques are employed. These methods are laborious and easily become intractable when applied to converters with increased energy storage elements. A modular modelling approach is proposed. This approach is based on the synthesis of converters using refined basic building blocks. The refined basic building blocks are independently modelled as two-port networks and used in a circuit synthesis-oriented manner to derive power stage models of commonly used DC-DC converters. It is found that most of the converters considered in the study can be described as a cascade combination of these basic building blocks. As such, transmission parameters are mainl... [more]

Lithium-ion batteries are currently the pioneers of green transition in the transportation sector. The nickel-manganese-cobalt (NMC) technology, in particular, has the largest market share in electric vehicles (EVs), offering high specific energy, optimized power performance, and lifetime. The aging of different lithium-ion battery technologies has been a major research topic in the last decade, either to study the degradation behavior, identify the associated aging mechanisms, or to develop health prediction models. However, the lab-scale standard test protocols are mostly utilized for aging characterization, which was deemed not useful since batteries are supposed to age dynamically in real life, leading to aging heterogeneity. In this research, a commercial NMC variation (4-4-2) was aged with a pragmatic standard-drive profile to study aging behavior. The characterized measurable parameters were statistically investigated before performing an autopsy on the aged battery. Harvested s... [more]

The threat of global warming has increased due to industrialization, urbanization, population expansion, and changes in lifestyle among the Group of Seven(G7) Carbon dioxide emissions (CO2) directly affect how much electricity can be generated from various sources. This research aims to identify environmental hazards associated with various energy sources. Analyzing the impact of various energy sources on CO2 emissions from electricity and heat production using data from the G7. The data is analyzed using quantile regression (QR), generalized method of moments (GMM), random effects (RE), and fixed effects (FE). Our results indicate a substantial positive impact on CO2 emissions regardless of the technology used to generate coal and gas power. Coal-fired power plants have a larger impact on the environment than other sources of emissions. Also, all coal and gas coefficients are significant in FE, RE, GMM, and QR. Oil coefficients have a negative impact on environmental degradation and a... [more]

For the boiler-turbine unit in power systems, a coordinated control structure plays a crucial role in maintaining the balance in supply and demand of energy, reducing pollutant emissions and optimizing energy efficiency. The matching requirements of the turbine and boiler, the wide range of load changes, and the cooperative operation of many devices in the power system pose many challenges to designing a coordinated control system for the boiler turbine system, thus making the control design a difficult task. In this paper, iterative learning control (ILC) is used to maintain the throttle pressure and megawatt output power of a boiler turbine at the desired set points by controlling the hybrid pattern design structure. Simulation results show that the proposed approach can maintain the desired set points, and the desired response can also be obtained faster by using the proposed approach compared to the ones available in the literature.

Solar photovoltaics (PV) are susceptible to environmental and operational stresses due to their operation in an open atmosphere. Early detection and treatment of stress prevents hotspots and the total failure of solar panels. In response, the literature has proposed several approaches, each with its own limitations, such as high processing system requirements, large amounts of memory, long execution times, fewer types of faults diagnosed, failure to extract relevant features, and so on. Therefore, this research proposes a fast framework with the least memory and computing system requirements for the six different faults of a solar panel. Infrared thermographs from solar panels are fed into intense and architecturally complex deep convolutional networks capable of differentiating one million images into 1000 classes. Features without backpropagation are calculated to reduce execution time. Afterward, deep features are fed to shallow classifiers due to their fast training time. The propo... [more]

The problems that arise during the transmission of control commands for key elements and data on their execution via communication systems over long distances at energy facilities are considered. The necessity of a new approach to solving this problem using a fiber-optic communication line (FOCL) is substantiated. A new design of analog FOCL has been developed for transmitting control commands for key elements of substations and switching data. A new method for forming an optical signal in a laser transmitting module using direct current modulation is proposed. The advantages of using a new method for generating commands for control signals and switching data using a sequence of command codes compared with digital signals currently used in control and monitoring systems are substantiated. The main parameters of the developed analog FOCL have been calculated. An experimental prototype of an analog FOCL was assembled, and research was conducted. The results of calculations and experiment... [more]

Fans as industrial devices are among the most significant single recipients of driving energy. Therefore, they represent an important area of energy savings to reduce CO2 emissions. The ubiquity of fans and their operation under conditions different from the optimum provides an opportunity for more significant global reductions in the energy used to drive them. The second important aspect, besides energy efficiency, related to the operation of fans is the noise they generate. This article studies fans in various operating configurations, emphasizing improving operating efficiency and reducing noise emissions. The subject matter undertaken is based on the current trends and needs of the industry, notably the ventilation and power industry. The article attempts a detailed literature review taking into account just these aspects. The paper is divided into three main sections, with an analysis of the literature in the areas of energy efficiency, considering the operation of fans with the n... [more]

With the increasing size and complexity of power systems, it is crucial to have an effective protection system in place to ensure its reliability. One of the important components of the protection system are relays. It is important for a relay to operate dependably and securely so that any fault can be cleared in time to minimize damages to the power network. However, it is important to test a relay in a realistic environment before commissioning it to the network. Testing a relay in the actual network can be expensive with limited fault scenarios. Hence, Hardware-in-the-Loop (HIL) testing is an efficient method to perform closed-loop testing of a relay since numerous fault cases can be simulated to provide a realistic operating environment for the relay under test. This paper sheds light on the HIL testing done for protective relays using a sample distribution system using RTDS. Two SEL-351 relays have been used in this experiment, and proper settings for the relays are calculated for... [more]

The porosity of rocks is an important parameter used in rock mechanics and underground mining. It affects the movement of fluids in the rock mass and the internal processes taking place (the ability to store water or gases), allowing us to characterize the type of rock and determine possible future applications. Conventional porosity testing methods (e.g., test drill cores in the laboratory) are complex and time-consuming. On the other hand, more modern technologies, such as computed tomography, are high-cost. In the presented study, a core sample with karst and porous structures inside was used. This core sample was poured with resin to reinforce the outer surfaces of the core and make it easier to cut with a rock saw. It was then cut into 3 mm thickness slices in preparation for the next step—the 3D optical scanning. Measurements were made with the ATOS CORE 500 optical scanner. Data processing was then performed in open-source software using popular and commonly used modeling method... [more]

With the large-scale development of wind turbines, large flexible blades bear heavier loads. In the actual rotating work of blades, the coupling of structural deformation and motion produces a dynamic stiffening effect and spin softening effect, which affects the dynamic characteristics of blades. In this study, the finite element method is used to model the NREL 5MW blade, and the dynamic stiffening and spin softening effects are investigated using the modal analysis. The influence of rotating effects on the blade’s natural frequency is revealed. It is concluded that the effect of dynamic stiffening is more significant than that of spin softening, and the comprehensive result of the two effects is not simply the superposition of them but presents obvious nonlinearity.

At present, China’s high-speed rail is in a period of rapid development. Most of the refrigerants used in Chinese motor train units at this stage are still R134a and R407c, which have an impact on the environment. In response to the environmental protection concept of green travel, it is of great significance to study the air conditioning system of motor train units using CO2 refrigerant. Using CFD simulation analysis technology, the heat transfer performance of the air side of the CO2 finned tube evaporator used in the air conditioning system of the motor train unit is studied. We select the air outlet temperature, pressure drop, heat transfer factor, and resistance factor as the objective function, in addition, monitoring points are set up in the air flow channel to monitor the turbulent flow field and pipe wall pressure. Our research shows that the cooling capacity of the CO2 evaporator can reach up to 29.76 kW, which can meet the heat exchange required in the air conditioning syste... [more]

Distributed energy resources (DERs) based on renewable power, such as photovoltaic (PV), have been increasing worldwide. To support this growth, some technologies have been developed to increase the hosting capacity (HC) of distribution networks (DNs), such as the Soft Open Point (SOP), which can replace normally open switches in DNs with the advantage of allowing power and voltage control. The benefits of SOPs in terms of increasing distributed generation (DG) hosting capacity can be enhanced by network reconfiguration (NR). In this work, an optimization-based approach is proposed for placing SOP in DN with simultaneous NR; that is, the proposed algorithm consists of a promising alternative to previous works in the literature that deal with SOP placement and NR in an iteratively way or in a two-step procedure, considering that better results can be obtained by simultaneously handling both options, as shown in the introduced case studies. The optimization problem is modeled as nonlinea... [more]

The efficiency of Hybrid Electric Vehicles (HEVs) may be substantially increased if the energy of the exhaust gases, which do not complete the expansion inside the cylinder of the internal combustion engine, is efficiently recovered by means of a properly designed turbogenerator and employed for vehicle propulsion; previous studies, carried out by the same authors of this work, showed a potential hybrid vehicle fuel efficiency increment up to 15% by employing a 20 kW turbine on a 100 HP rated power thermal unit. The innovative thermal unit here proposed is composed of a supercharged engine endowed with a properly designed turbogenerator, which comprises two fundamental elements: an exhaust gas turbine expressly designed and optimized for the application, and a suitable electric generator necessary to convert the recovered energy into electric energy, which can be stored in the on-board energy storage system of the vehicle. In these two parts, the realistic efficiency of the innovative... [more]

The DeepCwind floating wind turbine platform has become one of the most successful structures for accommercial floating wind farms, and the stability of it is crucial for survivability. Hence, this paper studies an anti-oscillation device with the purpose of reducing the heave and surge effects of the platform. The influence of various chamfered perforations at different sizes of the anti-heave device on the floating platform was further studied by numerical and experimental methods. Furthermore, through an analysis of the surge and heave of the pedestal with anti-heave devices with different chamfered perforations under different wave heights and wave periods, the effects on the hydrodynamic performance of the pedestal were studied. Physical experiments were conducted on a pedestal with anti-heave devices with chamfered perforations under the working conditions of different wave heights and wave periods to verify the reliability of the numerical simulation. The results show that the a... [more]

The current practice with building energy simulation software tools requires the manual entry of a large list of detailed inputs pertaining to the building characteristics, geographical region, schedule of operation, end users, occupancy, control aspects, and more. While these software tools allow the evaluation of the energy consumption of a building with various combinations of building parameters, with the manual information entry and considering the large number of parameters related to building design and operation, global optimization is extremely challenging. In the present paper, a novel approach is developed for the global optimization of building energy models (BEMs) using Python EnergyPlus. A Python-based script is developed to automate the data entry into the building energy modeling tool (EnergyPlus) and numerous possible designs that cover the desired ranges of multiple variables are simulated. The resulting datasets are then used to establish a surrogate BEM using an art... [more]

Renewable energy technologies play a crucial role in solving global energy and environmental issues, and the pace of the energy transition directly depends on improving their efficiency. Presently, the development and implementation of renewable energy systems are ensured mainly through state funding, the possibilities of which are limited. The potential of attracting private investments depends directly on their impact on companies’ profitability indicators, and the uncertainty regarding the return on investments is one of the main barriers affecting investors’ decision-making. Based on a vector autoregressive model for analysing the stationary time series, the paper explores the impact of long-term investments and research and development costs in renewable energy technologies on the financial performance of ten of the largest companies operating in this field. The study’s results showed that investments and spending on research and development positively affect such companies’ profi... [more]

Southern Africa has suffered from multiple power disruptions in the past decade due to inadequate electrical generation capacity, as well as load developments in locations that were not suitably planned for. Southern African countries are able to have reliable, sustainable, and efficient electrical power grids. The use of power interconnections for exchange power, especially for long-distance transmission networks, is important. Installing a suitable high-voltage alternating current (HVAC) with a high-voltage direct current (HVdc) will improve the active−reactive power compensation when transmitting electrical power over long distances (when transmitting bulk power is possible). Flexible alternating current transmission system (FACTS) devices are typically combinations of shunt and series converters. These approaches are capable of improving the power stability and voltage while allowing power to be transferred with minimal losses to an alternating current transmission system for the p... [more]

The aim of the article is to identify problems related to the siting of wind farms, both those that have arisen as a result of recent legislative revisions and those arising from social developments in Poland. In 2022 a map defining ‘exclusion zones’ around wind turbines, i.e., areas where residential development was prohibited, was released in Poland. It was only then that many territorial governments realised the scale of the problems generated by the entry into force of the 2016 Wind Farm Act. It turned out that this group of municipalities included towns that might suffer some consequences despite the fact that there are no or few wind farms in their area. The aim of this paper is to identify towns and cities where more than one quarter of the area is land within the H10 zones, where the construction of wind farms is banned, if their distance from the nearest building or from the boundary of a national park is less than ten times the height of the turbine mast. The example of the t... [more]

For longer journeys, when drivers of electric vehicles need a charge on the road, the best solution is off-board ultra-fast chargers, which offer a short charging time for electric vehicle batteries. Consequently, the ultra-fast charging of batteries is a major issue in electric mobility development globally. Current research in the area of power electronics for electric vehicle charging applications is focused on new high-power chargers. These chargers will significantly increase the charging power of electric vehicles, which will reduce the charging time. Furthermore, electric vehicles can be deployed to achieve improved efficiency and high-quality power if vehicle to microgrid (V2µG) is applied. In this paper, standards for ultra-fast charging stations and types of fast charging methods are reviewed. Various power electronic topologies, the modular design approach used in ultra-fast charging, and integration of the latter into standalone microgrids are also discussed in this paper.... [more]

Hybrid renewable energy systems (HRES) combine two or more renewable energy systems and are an interesting solution for decentralized renewable energy generation. The exergy and exergo-economic approach have proven to be useful methods to analyze hybrid renewable energy systems. The aim of this paper is to present a review of exergy and exergy-economic approaches to evaluate hybrid renewable energy systems in buildings. In the first part of the paper, the methodology of the exergy and exergo-economic analysis is introduced as well as the main performance indicators. The influence of the reference environment is analyzed, and results show that the selection of the reference environment has a high impact on the results of the exergy analysis. In the last part of the paper, different literature studies based on exergy and exergo-economic analysis applied to the photovoltaic-thermal collectors, fuel-fired micro-cogeneration systems and hybrid renewable energy systems are reviewed. It is sh... [more]

Modern societies need a constant and stable electrical supply. After relying primarily on formal mathematical modeling from operations research, control theory, and numerical analysis, power systems analysis has changed its attention toward AI prediction/forecasting tools. AI techniques have helped fix power system issues in generation, transmission, distribution, scheduling and forecasting, etc. These strategies may assist today’s large power systems which have added more interconnections to meet growing load demands. They make it simple for them to do difficult duties. Identification of problems and problem management have always necessitated the use of labor. These operations are made more sophisticated and data-intensive due to the variety and growth of the networks involved. In light of all of this, the automation of network administration is absolutely necessary. AI has the potential to improve the problem-solving and deductive reasoning approaches used in fault management. This... [more]

In this paper, a simplified and robust control strategy of an interleaved high gain DC/DC boost converter (IHGBC) is proposed in order to enhance DC bus voltage regulation in proton exchange membrane fuel cell (PEMFC) applications. The fluctuation of the energy source voltage and external load, and the change in system parameters lead to the instability of output voltage. Based on the creation of an average state space model of the DC/DC boost converter, the proposed controller is designed based on a linear active disturbance rejection control (LADRC), which has an external voltage loop and an internal current loop to meet the output voltage requirements under parameters uncertainties and disturbances. The effectiveness of the proposed approach strategy and its superiority were examined under different operating conditions and scenarios. Simulation and experiment results showed the efficiency and robustness of the suggested approach and the great effectiveness in the reference tracking... [more]

Oil production prediction plays a significant role in designing programs for hydrocarbon reservoir development, adjusting production operations and making decisions. The prediction accuracy of oil production based on single methods is limited since more and more unconventional reservoirs are being exploited. Artificial intelligence technology and data decomposition are widely implemented in multi-step forecasting strategies. In this study, a hybrid prediction model was proposed based on two-stage decomposition, sample entropy reconstruction and long short-term memory neural network (LSTM) forecasts. The original oil production data were decomposed into several intrinsic mode functions (IMFs) by complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN); then these IMFs with different sample entropy (SE) values were reconstructed based on subsequence reconstruction rules that determine the appropriate reconstruction numbers and modes. Following that, the highest-freque... [more]

The feasibility of regenerative cooling technology in scramjet engines has been verified, while the heat transfer behavior involved in the process needs further study. This paper expounds on the necessity of coupled heat-transfer analysis and summarizes its research progress. The results show that the effect of pyrolysis on heat transfer in the cooling channel depends on the heat flux and coking rate, and the coupling relationship between combustion and heat transfer is closely related to the fuel flow rate. Therefore, we confirm that regulating the cooling channel layout according to the real heat-flux distribution, suppressing coking, and accurately controlling the fuel flow rate can contribute to accomplishing the optimal collaborative design of cooling performance and combustion performance. Finally, a conjugate thermal analysis model can be used to evaluate the performance of various thermal protection systems.