The paper presents the study of a three-phase system coupling a DC power source to a power grid. This study, based on an FPGA, implements a real-time control system and digital models of the power circuit. The proposed proportional−resonant (P+R) controller with a modified structure was part of the system, which can be used as an alternative controller to traditional ones, e.g., in photovoltaic systems. Due to difficulties in implementing resonant controllers, a P+R with a new structure using a PI controller was elaborated. With an appropriate approach to the generation of phase current patterns, it is possible to set the reactive current and, thus, compensate for the reactive power. The operation of the system for typical operating conditions (e.g., system startup, change in preset load) was characterized and compared with a classical solution using a PI controller.

The purpose of this paper was to develop a simulation model that allows simultaneous analysis of airport screening lane performance and power consumption per passenger served. These two issues have not yet been considered simultaneously in the scientific literature. So far, the focus has been placed on process performance. However, this paper shows, by performing an empirical study and applying the proposed model, that it is important to consider these two issues simultaneously. This will allow for the sustainable development of air transport. As a case study, three system configurations for single, dual and single fast screening lanes were analyzed. For each configuration, 3 different types of X-ray devices were checked, and the results were compared. The results showed that for example calculations with 2 million passengers handled per year, the gains could be as high as 4614 kWh/year. This article therefore shows that it is important to manage the process with power consumption in m... [more]

The Agrophotovoltaic (APV) system is a novel concept in the field of Renewable Energy Systems. This system enables the generation of solar energy via photo-voltaic (PV) modules above crops, to mitigate harmful impact on food production. This study aims to develop a performance evaluation model for an APV system in a temperate climate region, such as South Korea. To this end, both traditional electricity generation models (solar radiation-based model and climate-based model) of PV modules and two major machine learning (ML) techniques (i.e., polynomial regression and deep learning) have been considered. Electricity generation data was collected via remote sensors installed in the APV system at Jeollanam-do Agricultural Research and Extension Services in South Korea. Moreover, economic analysis in terms of cost and benefit of the subject APV system was conducted to provide information about the return on investment to farmers and government agencies. As a result, farmers, agronomists, an... [more]

Current electric vehicle (EV) charging systems have limited smart functionality, and most research focuses on load-balancing the national or regional grid. In this article, we focus on supporting the early design of a smart charging system that can effectively and efficiently charge a company’s EV fleet, maximizing the use of self-generated Photo-Voltaic energy. The support takes place in the form of the Vehicle Charging Simulation (VeCS) model. System performance is determined by operational costs, CO2 emissions and employee satisfaction. Two impactful smart charging functions concern adaptive charging speeds and charging point management. Simulation algorithms for these functions are developed. The VeCS model is developed to simulate implementation of a smart charging system incorporating both charging infrastructure and local Photo-Voltaics input, using a company’s travel and energy data, prior to having the EVs in place. The model takes into account travel behaviour, energy input a... [more]

A detailed literature analysis depicts that artificial neural networks are rarely used for the power consumption estimation in the mobile robotics field. Instead, researchers prefer to develop analytical models of investigated robots. This manuscript presents a comparison of mathematical models and non-complex artificial neural networks in energy prediction tasks for differential and skid-steer drive robots which move over various types of surfaces. The results show that both methods could be used interchangeably but AI methods are more universal, do not depend on the kinematic structure of a robot and are tolerant for designers not having a complex knowledge about the system.

Current distribution anomaly can be used to indicate the onset of package-related failures modes in Silicon Carbide power MOSFET modules. In this paper, we propose to obtain the wire bond’s magnetic field profile using an array of Tunnel Magneto-Resistance (TMR) sensors, and characterise the small changes in the current density distribution to find the onset of the wire bond degradation processes, including wire bond lift-off, wire bond cracking, and wire bond fracture. We propose a novel condition monitoring technique where a non-galvanic high-bandwidth sensing and a reliability model monitor the health of the power switches. We designed a dedicated calibration set-up to examine the sensor array and calibrated to demonstrate the adequate sensitivity to a minimum 5% current anomaly detection in a single wire bond of the switching devices operating with 50 kHz switching frequency. We use a hardware-in-the-loop (HIL) experimental set-up to replicate wire bond-related failures in a 1200 V... [more]

In recent years, several researchers have studied the potential use of ammonia (NH3) as an energy vector, focused on the techno-economic advantages and challenges for full global deployment. The use of ammonia as fuel is seen as a strategy to support decarbonization; however, to confirm the sustainability of the shift to ammonia as fuel in thermal engines, a study of the environmental profile is needed. This paper aims to assess the environmental life cycle impacts of ammonia-based electricity generated in a combined heat and power cycle for different ammonia production pathways. A cradle-to-gate assessment was developed for both ammonia production and ammonia-based electricity generation. The results show that electrolysis-based ammonia from renewable and nuclear energy have a better profile in terms of global warming potential (0.09−0.70 t CO2-eq/t NH3), fossil depletion potential (3.62−213.56 kg oil-eq/t NH3), and ozone depletion potential (0.001−0.082 g CFC-11-eq/t NH3). In additio... [more]

Green growth is about merging environmental and social protection with economic growth. The OECD countries follow the progress toward greening though a set of indicators. The aim of the study is to analyze the condition and development of the OECD countries using a set of green growth indicators. The univariate and multivariate statistical approach was used to identify the main features of green growth development in two time spans. The achieved success of the OECD countries toward the green growth was measured from period 1 (years 2000−2009) to period 2 (years 2010−2019). For stimulant indicators, an increase was achieved, while for the destimulant variables, a decrease was reached between the analyzed periods. CO2 productivity increased by more than 31%, material productivity by 25%, and the energy productivity by nearly 21%. From the ecological point of view, a positive sign was achieved by an intensive increase of the percentage of municipal waste treatment by recycling or composti... [more]

Goal 7 of the UN’s Sustainable Development Goals, adopted in 2015, sets out universal access to affordable, reliable and sustainable energy, but even in developed countries, this is still difficult to achieve. European comparative studies show that in Mediterranean and Central European countries, including Hungary, access to adequate energy remains a serious problem for certain social groups. The aim of the study is to examine the inequalities in access to and consumption of energy in Hungary. We pay special attention to presenting changes over time and examine what changes have taken place in household energy consumption since the years before the global economic crisis. We also explore the major socio-economic and building-related factors that increase the risk of possible energy vulnerability. For our analysis, we draw on data from a large sample survey conducted in 2007, 2013 and 2018 on a representative probability sample. Our results showed on the one hand the fundamental role of... [more]

This paper frames itself in the realm of smart energy technologies that can be utilized to satisfy the electricity demand of consumers. In this environment, demand response programs and the intelligent management of energy consumption that are offered by utility providers will play a significant role in implementing smart energy. One of the approaches to implementing smart energy is to analyze consumption data and provide targeted contracts to consumers based on their individual consumption characteristics. To that end, the identification of individual consumption features is important for suppliers and utilities. Given the complexity of smart home load profiles, an appliance-based identification is nearly impossible. In this paper, we propose a different approach by grouping appliances based on their rooms; thus, we provide a room-based identification of energy consumption. To this end, this paper presents and tests an intelligent consumption identification methodology, that can be im... [more]

Shale gas accumulates in reservoirs that have favorable characteristics and associated organic geochemistry. The Wufeng-Longmaxi formation of Well Yucan-6 in Southeast Chongqing, SW China was used as a representative example to analyze the organic geochemical and reservoir characteristics of various shale intervals. Total organic carbon (TOC), vitrinite reflectance (Ro), rock pyrolysis, scanning electron microscopy (SEM), and nitrogen adsorption analyses were conducted, and a vertical coupling variation law was established. Results showed the following: the Wufeng-Longmaxi formation shale contains kerogen types I and II2; the average TOC value at the bottom of the formation is 3.04% (and the average value overall is 0.78%); the average Ro value is 1.94%; the organic matter is in a post mature thermal evolutionary stage; the shale minerals are mainly quartz and clay; and the pores are mainly intergranular, intragranular dissolved pores, organic matter pores and micro fractures. In addit... [more]

Under certain circumstances, after connecting a superconducting transformer to the power network, a high value current may flow through its windings. This current can exceed the critical value of the superconductor many times and cause the windings to lose their superconductive state. Loss of superconductive state of the windings may result in thermal interruption of their continuity as a result of conduction of a current of very high density. The mathematical relationships used to calculate the inrush current of conventional transformers do not work well for the calculation of superconducting transformers. This is due to the properties of superconducting materials used in the windings, first of all to the stepwise changes of the windings’ resistance when exiting the superconducting state and when returning to this state. The article presents the mathematical dependencies allowing to calculate the pulse waveforms of the inrush current of these transformers are derived. Basic electrical... [more]

Since both ethanol and acetone are the main components in many alternative fuels, research on the burning characteristics of ethanol-acetone blends is important to understand the combustion phenomena of these alternative fuels. In the present study, the burning characteristics of ethanol-acetone fuel blends are investigated at a temperature of 358 K and pressure of 0.1 MPa with equivalence ratios ranging from 0.7 to 1.4. Ethanol at 100% vol., 25% vol. ethanol/75% vol. acetone, 50% vol. ethanol/50% vol. acetone, 75% vol. ethanol/25% vol. acetone, and 100% vol. acetone are studied by the constant volume combustion chamber (CVCC) method. The results show that the laminar burning velocities of the fuel blends are between that of 100% vol. acetone and 100% vol. ethanol. As the ethanol content increases, the laminar burning velocities of the mixed fuels increase. Furthermore, a detailed chemical kinetic mechanism (AramcoMech 3.0) is used for simulating the burning characteristics of the mixt... [more]

The volatility of renewable energy sources (RES) poses a growing problem for operation of electricity grids. In contrary, the necessary decarbonisation of sectors such as heat supply and transport requires a rapid expansion of RES. Load management in the context of power-to-heat systems can help to simultaneously couple the electricity and heat sectors and stabilise the electricity grid, thus enabling a higher share of RES. In addition power-to-hydrogen offers the possibility of long-term energy storage options. Within this work, we present a novel optimization approach for heat pump operation with the aim to counteract the volatility and enable a higher usage of RES. For this purpose, a detailed simulation model of buildings and their energy supply systems is created, calibrated and validated based on a plus energy settlement. Subsequently, the potential of optimized operation is determined with regard to PV and small wind turbine self-consumption. In addition, the potential of season... [more]

This paper presents basic principles of built-environment physics’ modelling, and it reviews common computational tools and capabilities in a scope of practical design approaches for retrofitting purposes. Well-established simulation models and methods, with applications found mainly in the international scientific literature, are described by means of strengths and weaknesses as regards related tools’ availability, easiness to use, and reliability towards the determination of the optimal blends of retrofit measures for building energy upgrading and Urban Heat Island (UHI) mitigation. The various characteristics of computational approaches are listed and collated by means of comparison among the principal modelling methods as well as among the respective computational tools that may be used for simulation and decision-making purposes. Insights of coupling between building energy and urban microclimate models are also presented. The main goal was to provide a comprehensive overview of a... [more]

Literature and manuals refer to biomass gasification as one of the most efficient processes for power generation, highlighting features, such as residual biomass use, distributed generation and carbon sequestration, that perfectly incorporate gasification into circular economies and sustainable development goals. Despite these features, small scale applications struggle to succeed as a leading solution for sustainable development. The aim of this review is to investigate the existing technological barriers that limit the spreading of biomass gasification from a socio-technical point of view. The review outlines how existing technologies originated from under feed-in-tariff regimes and highlights where the current design goals strongly differ from what will be needed in the near future. Relevant market-ready small-scale gasification systems are analyzed under this lens, leading to an analysis of the reactor and filtration design. To help understand the economical sustainability of these... [more]

A fuel cell is an electrochemical device that converts the chemical energy of a fuel and oxidant into electricity. Cation-exchange and anion-exchange membranes play an important role in hydrogen fed proton-exchange membrane (PEM) and anion-exchange membrane (AEM) fuel cells, respectively. Over the past 10 years, there has been growing interest in using nanofiber electrospinning to fabricate fuel cell PEMs and AEMs with improved properties, e.g., a high ion conductivity with low in-plane water swelling and good mechanical strength under wet and dry conditions. Electrospinning is used to create either reinforcing scaffolds that can be pore-filled with an ionomer or precursor mats of interwoven ionomer and reinforcing polymers, which after suitable processing (densification) form a functional membrane. In this review paper, methods of nanofiber composite PEMs and AEMs fabrication are reviewed and the properties of these membranes are discussed and contrasted with the properties of fuel ce... [more]

The small modular dual fluid reactor is a novel variant of the Generation IV molten salt reactor and liquid metal fast reactor. In the primary circuit, molten salt or liquid eutectic metal (U-Pu-Cr) is employed as fuel, and liquid lead works as the coolant in the secondary circuit. To design the control system of such an advanced reactor, the uncertainties of the employed computer model and the physicochemical properties of the materials must be considered. In this paper, a one-dimensional model of a core is established based on the equivalent parameters achieved via the coupled three-dimensional model, taking into account delayed neutron precursor drifting, and a power control system is developed. The performance of the designed controllers is assessed, taking into account the model and property uncertainties. The achieved results show that the designed control system is able to maintain the stability of the system and regulate the power as expected. Among the considered uncertain par... [more]

Self-sensing techniques are a commonly used approach for electromagnetic actuators since they allow the removal of position sensors. Thus, costs, space requirements, and system complexity of actuation systems can be reduced. A widely used parameter for self-sensing is the position-dependent incremental inductance. Nevertheless, this parameter is strongly affected by electromagnetic hysteresis, which reduces the performance of self-sensing. This work focuses on the design of a hysteresis-compensated self-sensing algorithm with low computational effort. In particular, the Integrator-Based Direct Inductance Measurement (IDIM) technique is used for the resource-efficient estimation of the incremental inductance. Since the incremental inductance exhibits a hysteresis with butterfly characteristics, it first needs to be transformed into a B-H curve-like hysteresis. Then, a modified Prandtl−Ishlinskii (MPI) approach is used for modeling this hysteretic behavior. By using a lumped magnetic cir... [more]

Heat pumps, an example of one of the most environmentally friendly technologies, can play a key role in the future of sustainable energy. Due to the European Union’s ambitious goals to achieve climate neutrality by 2050, research is currently focused on finding solutions to increase the energy and economic efficiency of heating and cooling with heat pumps to benefit the environment. This paper presents the results of energy simulations for a single-family building located in selected cities—Warsaw (Poland), Madrid (Spain), Riga (Latvia), and Rome (Italy)—as a case study for different climate conditions and energy policy. In each variant, ground and air source heat pumps are considered for heating, cooling, ventilation, and air conditioning (HVAC) purposes. Moreover, we conducted an economic estimation including investment and operating costs, as well as an ecological analysis of carbon dioxide (CO2) emissions. Results show that heat pumps as an energy source for HVAC systems seem to be... [more]

The tightness of a borehole is essential for its long-term durability. For this purpose, the column of the pipe is sealed with cement slurry. After contacting the slurry, mud in the borehole is removed. However, the slurry does not effectively remove the remaining drilling mud. Therefore, the annular space is cleaned with a wash. Effectively cleaning the borehole presents quite a problem, as many variables that affect the stability of the borehole need to be considered. The time of contact between the borehole and the wash is very important. On the one hand, insufficient contact time does not guarantee proper removal of the mud. On the other hand, a long contact time may destroy the wall of the borehole. To address these problems, studies were carried out to assess the effect of the wash contact time on annular space cleaning. When determining the time of washing, a compromise between effective cleaning and the stability of the borehole wall is required. In the research presented in th... [more]

The substantial improvements in transmission voltage, which have been adopted to meet fast-growing energy demands, require more reliable power equipment and higher-quality insulating materials. The polytetrafluoroethylene (PTFE) nozzle, as the key part of a high-voltage circuit breaker, is often subjected to arc ablation and breakdown phenomena. Thus, it is very urgent to develop nozzles with better performance. In this study, PTFE/boron nitride (BN) composites were prepared. The relationships among the BN filler loading, thermal transition properties, spectral reflectance properties, arc ablation resistance, and AC dielectric breakdown performances, as well as their corresponding mechanisms, were studied. Experimental results show that the thermal conductivity and thermal diffusivity of PTFE/BN composites increased monotonously with BN loading, and that both parameters were improved by 41% and 44%, respectively, for 11 wt % composites compared with pure PTFE. Moreover, PTFE/BN composi... [more]

Due to rapidly progressing development in the field of materials used in the automotive industry, research methods enabling the validation of the properties of materials used in specific applications, e.g., engines, are gaining importance. One such method is dilatometry, which belongs to a branch of physics dealing with methods of measuring the thermal expansion of bodies. It includes assessment study of the dependence of body measurements on external conditions. The authors propose that dilatometric methods could be used to diagnose damage and the causes of engine damage that has already occurred. This is a novel approach in diagnostic methods. The aim of the paper was to validate the proposed method for diagnosing of combustion engine components. Two cases of malfunction of this type of device are presented. In the first case, the subject of research is needle-nozzle holder precision pairs used in engines with a power of 150 kW. The main achievement of the research is revealing the o... [more]

In order to explore the influences of fault dislocations on tunnel stability under seismic action, a nonlinear dynamic simulation method for the rock−fault contact system is proposed. First, considering the deterioration effect of seismic action on the ultimate bearing load of the contact interface between rock mass and fault, a mathematical model is established reflecting the seismic deterioration laws of the contact interface. Then, based on the traditional point-to-point contact type in a geometric mesh, a point-to-surface contact type is also considered, and an improved dynamic contact force method is established, which considers the large sliding characteristics of the contact interface. According to the proposed method, a dynamic finite element calculation for the flow of the rock−fault contact system is designed, and the accuracy of the method is verified by taking a sliding elastic block as an example. Finally, a three-dimensional (3D) calculation model for a deep tunnel throug... [more]

The distribution network is the most exposed part of the electrical power system relative to different abnormal events; therefore, it reports the highest occurrence rates in terms of electrical and mechanical failures. The present project describes a strategy for restoring faulty areas after the occurrence of an abnormal event causing an outage; consequently, the proposed algorithm is not only focused on the maximization of the connected loads but also deals with the minimization of the switching operations by considering technical operational constraints. The remarked study has two stages: The first one finds an initial set of tie-line candidates using the spanning tree technique, while the second stage applies a genetic algorithm to determine the optimal solution considering all the constraints. Three cases studies have been used to test the proposed algorithm, then the simulation and results of IEEE 13, 37 and 94 node feeders depict the effectiveness of the restoration strategy.