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Energies, Volume 14, Issue 6 (March-2 2021) – 279 articles

Cover Story (view full-size image): Photovoltaic (PV) power generation represents a glimmer of light in a world plagued by climate change. PV plants are spreading out in both industrial and customer applications, and diagnostics tools are desired today more than ever. In this paper, EMPHASIS is proposed as a fault detection method that, for the first time, accurately predicts the cell-level generated power without the need for interrupting the energy production of the PV plant. The approach is based on a power balance equation applied to temperature maps—like those taken by drones—and promptly detects even minimal malfunctioning, evaluating the effects on energy production. View this paper.
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Article
Increasing Access to Electricity: An Assessment of the Energy and Power Generation Potential from Biomass Waste Residues in Tanzania
Energies 2021, 14(6), 1793; https://doi.org/10.3390/en14061793 - 23 Mar 2021
Cited by 2 | Viewed by 905
Abstract
Tanzania has a high rural population, of which many rely on off-grid diesel generators to produce electricity. The focus of this paper is to assess if the waste biomass residues in Tanzania have sufficient energy potential to produce renewable electrical energy for small-scale [...] Read more.
Tanzania has a high rural population, of which many rely on off-grid diesel generators to produce electricity. The focus of this paper is to assess if the waste biomass residues in Tanzania have sufficient energy potential to produce renewable electrical energy for small-scale electricity generation using off-grid diesel generators coupled with anaerobic digestion (AD) and/or gasification. The gaseous fuel produced can then be used to substitute diesel fuel used in small-scale dual fuel diesel gen-sets; thus, providing more affordable electricity whilst reducing dependency on fossil fuels. The biomass waste streams estimated are those arising from agriculture, forestry, livestock, and urban human waste. To answer this question, the energy potentials of each of these biomass waste streams are quantified, followed by further calculations to determine the electricity generation capacity per stream based on overall efficiencies of 10 and 25%. The results show that combined these waste streams have an energy potential of 385 PJ (for the base year of 2018) generated from 26,924 kilotonnes (kt). Collectively, these residues can produce at least 1.2 times the electricity generated nationally in 2018 using AD and gasification coupled with a diesel gen-set engine. Full article
(This article belongs to the Special Issue Residual Biomass Conversion to Bioenergy)
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Article
Three-Dimensional Electro-Thermal Analysis of a New Type Current Transformer Design for Power Distribution Networks
Energies 2021, 14(6), 1792; https://doi.org/10.3390/en14061792 - 23 Mar 2021
Viewed by 604
Abstract
In recent years, the new type design of current transformer with bushing structure has been widely used in the distribution network system due to its advantages of miniaturization, high mechanical strength, maintenance-free, safety and environmental protection. The internal temperature field distribution is an [...] Read more.
In recent years, the new type design of current transformer with bushing structure has been widely used in the distribution network system due to its advantages of miniaturization, high mechanical strength, maintenance-free, safety and environmental protection. The internal temperature field distribution is an important characteristic parameter to characterize the thermal insulation and aging performance of the transformer, and the internal temperature field distribution is mainly derived from the joule heat generated by the primary side guide rod after flowing through the current. Since the electric environment is a transient field and the thermal environment changes slowly with time as a steady field under the actual conditions, it is more complex and necessary to study the electrothermal coupling field of current transformer (CT). In this paper, a 3D simulation model of a new type design of current transformer for distribution network based on electric-thermal coupling is established by using finite element method (FEM) software. Considering that the actual thermal conduction process of CT is mainly by conduction, convection and radiation, three different kinds of boundary conditions such as solid heat transfer boundary condition, heat convection boundary condition and surface radiation boundary condition are applied to the CT. Through the model created above, the temperature rise process and the distribution characteristics of temperature gradient of the inner conductor under different current, different ambient temperatures and different core diameters conditions are studied. Meanwhile, the hottest temperature and the maximum temperature gradient difference are calculated. According to this, the position of weak insulation of the transformer is determined. The research results can provide a reference for the factory production of new type design of current transformer. Full article
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Article
Adaptive Robust Fault-Tolerant Control Design for Wind Turbines Subject to Pitch Actuator Faults
Energies 2021, 14(6), 1791; https://doi.org/10.3390/en14061791 - 23 Mar 2021
Cited by 3 | Viewed by 656
Abstract
This paper proposes an adaptive fault tolerant control (FTC) design for a variable speed wind turbine (WT) operating in the high wind speeds region. It aims at mitigating pitch actuator faults and regulating the generator power to its rated value, thereby reducing the [...] Read more.
This paper proposes an adaptive fault tolerant control (FTC) design for a variable speed wind turbine (WT) operating in the high wind speeds region. It aims at mitigating pitch actuator faults and regulating the generator power to its rated value, thereby reducing the mechanical stress in the high wind speeds region. The proposed FTC design implements a sliding mode control (SMC) approach with an adaptation law that estimates the upper bounds of the uncertainties. System stability and uniform boundedness of the outputs was proven using the Lyapunov stability theory. The proposed approach was validated on a 5 MW three-blade wind turbine modeled using the National Renewable Energy Laboratory’s (NREL) Fatigue, Aerodynamics, Structures and Turbulence (FAST) wind turbine simulator. The controller’s performance was assessed in the presence of several pitch actuator faults and turbulent wind conditions. Its performance was also compared to that of a standard SMC approach. Mitigation of blade pitch actuator faults, generation of uniform power, smoother pitching actions and reduced chattering compared to standard SMC approach are among the main features of the proposed design. Full article
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Article
Enhancement of Food Waste Management and Its Environmental Consequences
Energies 2021, 14(6), 1790; https://doi.org/10.3390/en14061790 - 23 Mar 2021
Cited by 2 | Viewed by 762
Abstract
This paper assesses the potential environmental effects of the optimization of the kitchen waste management in Opole. The separate collection of kitchen waste is improved by distribution of separate collection kits consisting of an in-home bin and 10 L biodegradable bags. The surplus [...] Read more.
This paper assesses the potential environmental effects of the optimization of the kitchen waste management in Opole. The separate collection of kitchen waste is improved by distribution of separate collection kits consisting of an in-home bin and 10 L biodegradable bags. The surplus of collected kitchen waste is diverted from treatment in a mechanical-biological pretreatment (MBP) along with the residual waste to anaerobic digestion (AD) with the biowaste. This has positive effects on European and Polish goals, ambitions, and targets, such as (i) increasing the level of renewables in the primary energy supply, (ii) decreasing the level of greenhouse gas (GHG) emissions, (iii) increasing the level of preparation for reuse and recycling of municipal waste. The environmental effects of 1 ton additionally separately collected and treated kitchen waste are determined by using life cycle assessment. It was shown that in all selected impact categories (global warming potential, marine eutrophication potential, acidification potential, and ozone depletion potential) a clear environmental benefit can be achieved. These benefits are mainly caused by the avoided emissions of electricity and heat from the Polish production mix, which are substituted by energy generation from biogas combustion. Optimization of the waste management system by diversion of kitchen waste from mechanical-biological pretreatment to anaerobic digestion can lead to considerable saving of 448 kg CO2-eq/t of waste diverted. With an estimated optimization potential for the demonstration site of 40 kg/inh·year for the city of Opole, this would lead to 680,000 t CO2-eq savings per year for the whole of Poland. The sensitivity analysis showed that with a choice for cleaner energy sources the results would, albeit lower, show a significant savings potential. Full article
(This article belongs to the Special Issue Enhanced Biogas Production)
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Article
Analysis of Multi-Stream Fuel Injector Flow Using Zonal Proper Orthogonal Decomposition
Energies 2021, 14(6), 1789; https://doi.org/10.3390/en14061789 - 23 Mar 2021
Cited by 1 | Viewed by 641
Abstract
The 3-component velocity distribution of two lean-burn gas turbine fuel injectors are measured at a planar location near and parallel to the injector outlet. The two injectors are nominally the same design, but one features blocked central passages to study the effects of [...] Read more.
The 3-component velocity distribution of two lean-burn gas turbine fuel injectors are measured at a planar location near and parallel to the injector outlet. The two injectors are nominally the same design, but one features blocked central passages to study the effects of the presence of multi-streams and reveal the single stream characteristics embedded within the multi-stream configuration. Stereoscopic particle image velocimetry is used in an isothermal, non-reacting water analogue flow facility at an engine relevant Reynolds number. The velocity data is analysed using proper orthogonal decomposition (POD) and the work introduces the concept of Zonal POD. This is the splitting of the velocity field into zones prior to the calculation of POD modes to better identify prominent structures and features associated with each zone. Because modes are sorted by the area averaged energy contribution, zoning of a velocity field of interest may change the individual modes and will almost certainly change their order for anything other than trivial flow fields. Analysis of ensemble average and velocity fluctuation profiles reveals a radial shift outboard of the mains flow with the presence of the pilot as well as a general increase in RMS across the intermediate region between the pilot and mains flows. Analysis of POD temporal coefficients in the frequency domain reveals a low-frequency peak is evident in the mains flow region, but which may be affected by the presence of pilot flow. Furthermore, application of the ZPOD technique results in a closer representation of the velocity data for a given number of modes. This shows the behaviour of the unsteady pilot flow and reveals that a significant proportion of the fluctuating energy, RMS, is caused by this characteristic. Full article
(This article belongs to the Special Issue Advances in Gas Turbine Performance, Heat Transfer and Aerodynamics)
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Article
An Intelligent Task Scheduling Mechanism for Autonomous Vehicles via Deep Learning
Energies 2021, 14(6), 1788; https://doi.org/10.3390/en14061788 - 23 Mar 2021
Cited by 1 | Viewed by 867
Abstract
With the rapid development of the Internet of Things (IoT) and artificial intelligence, autonomous vehicles have received much attention in recent years. Safe driving is one of the essential concerns of self-driving cars. The main problem in providing better safe driving requires an [...] Read more.
With the rapid development of the Internet of Things (IoT) and artificial intelligence, autonomous vehicles have received much attention in recent years. Safe driving is one of the essential concerns of self-driving cars. The main problem in providing better safe driving requires an efficient inference system for real-time task management and autonomous control. Due to limited battery life and computing power, reducing execution time and resource consumption can be a daunting process. This paper addressed these challenges and developed an intelligent task management system for IoT-based autonomous vehicles. For each task processing, a supervised resource predictor is invoked for optimal hardware cluster selection. Tasks are executed based on the earliest hyper period first (EHF) scheduler to achieve optimal task error rate and schedule length performance. The single-layer feedforward neural network (SLFN) and lightweight learning approaches are designed to distribute each task to the appropriate processor based on their emergency and CPU utilization. We developed this intelligent task management module in python and experimentally tested it on multicore SoCs (Odroid Xu4 and NVIDIA Jetson embedded platforms). Connected Autonomous Vehicles (CAV) and Internet of Medical Things (IoMT) benchmarks are used for training and testing purposes. The proposed modules are validated by observing the task miss rate, resource utilization, and energy consumption metrics compared with state-of-art heuristics. SLFN-EHF task scheduler achieved better results in an average of 98% accuracy, and in an average of 20–27% reduced in execution time and 32–45% in task miss rate metric than conventional methods. Full article
(This article belongs to the Section A: Electrical Engineering)
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Article
Price-Response Matrices Design Methodology for Electrical Energy Management Systems Based on DC Bus Signalling
Energies 2021, 14(6), 1787; https://doi.org/10.3390/en14061787 - 23 Mar 2021
Viewed by 737
Abstract
Prosumers’ electrical installations (PEIs), as nanogrids and low-voltage microgrids, have gained importance in recent years following the development of standards such as the IEC 60364-8 series. In these systems, all distributed energy resources (DERs) are usually integrated using dc bus coupling. The IEC [...] Read more.
Prosumers’ electrical installations (PEIs), as nanogrids and low-voltage microgrids, have gained importance in recent years following the development of standards such as the IEC 60364-8 series. In these systems, all distributed energy resources (DERs) are usually integrated using dc bus coupling. The IEC 60364-8-3 predicts an electrical energy management system (EEMS) for power-sharing. The overall research framework of this paper is the nanogrid power management, where complex algorithms are required, as well as the conventional state machines and hierarchical controls. However, the addition of new DERs in such systems is not straightforward due to the complicated parameter settings for energy usage optimization. A different control strategy, named price-based power management, has been conceived to make the EEMS scalable to include new sources and simplify parameterization. Since it is analogous to economic markets, most users understand the concepts and feel comfortable tuning parameters according to their own cost/benefits goals. This paper proposes a price-based power management algorithm for EEMS to automatically design the price-response matrices (PRMs). The PRMs are a way to organize power management, considering new DERs and variable price of energy. The main contribution is the methodology to design the PRMs. Experimental results are carried out to demonstrate the effectiveness of the proposed strategy. The results were obtained with a 1.5 kW prototype composed of a PV generator, battery energy storage, loads, and grid connection. Full article
(This article belongs to the Special Issue Smart Power Management of Renewable Power System)
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Article
Energy Efficiency Analysis of Copper Ore Ball Mill Drive Systems
Energies 2021, 14(6), 1786; https://doi.org/10.3390/en14061786 - 23 Mar 2021
Cited by 7 | Viewed by 808
Abstract
Milling is among the most energy-consuming technological stages of copper ore processing. It is performed in mills, which are machines of high rotational masses. The start of a mill filled to capacity requires appropriate solutions that mitigate the overloading. One method for increasing [...] Read more.
Milling is among the most energy-consuming technological stages of copper ore processing. It is performed in mills, which are machines of high rotational masses. The start of a mill filled to capacity requires appropriate solutions that mitigate the overloading. One method for increasing the energy efficiency of ball mills is to optimize their drive systems. This article looks at two variants of drive systems with efficiencies higher than the already existing solutions. The first variant is a low-speed synchronous motor with permanent magnets without a gearbox, and the second variant is an asynchronous high-efficiency motor with a gearbox and a fluid coupling. The energy performance analysis of the three solutions was based on the average energy consumption indicator per mass unit of the milled material and on the energy consumption per hour. The investigations required models of the drive systems and analyses with the use of the Monte Carlo methods. The highest energy efficiency is observed in the case of the solution based on the permanent magnet motor. However, the drive system with the high-speed motor offers a gentle start-up possibility owing to the fluid coupling. Full article
(This article belongs to the Special Issue Mining Technologies Innovative Development)
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Article
Behavior of Residual Current Devices at Frequencies up to 50 kHz
Energies 2021, 14(6), 1785; https://doi.org/10.3390/en14061785 - 23 Mar 2021
Cited by 4 | Viewed by 694
Abstract
The use of residual current devices (RCDs) is obligatory in many types of low-voltage circuits. They are devices that ensure protection against electric shock in the case of indirect contact and may ensure additional protection in the case of direct contact. For the [...] Read more.
The use of residual current devices (RCDs) is obligatory in many types of low-voltage circuits. They are devices that ensure protection against electric shock in the case of indirect contact and may ensure additional protection in the case of direct contact. For the latter purpose of protection, only RCDs of a rated residual operating current not exceeding 30 mA are suitable. Unfortunately, modem current-using equipment supplied via electronic converters with a pulse width modulation produces earth fault currents composed of high-frequency components. Frequency of these components may have even several dozen kHz. Such components negatively influence the RCDs’ tripping level and, hence, protection against electric shock may be ineffective. This paper presents the results of the RCDs’ tripping test for frequencies up to 50 kHz. The results of the test have shown that many RCDs offered on the market are not able to trip for such frequencies. Such behavior was also noted for F-type and B-type RCDs which are recommended for the circuits of high-frequency components. Results of the test have been related to the requirements of the standards concerning RCDs operation. The conclusion is that these requirements are not sufficient nowadays and should be modified. Proposals for their modification are presented. Full article
(This article belongs to the Special Issue Analysis and Experiment for Electric Power Quality)
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Article
A Parametrical Study on Convective Heat Transfer between High-Temperature Gas and Regenerative Cooling Panel
Energies 2021, 14(6), 1784; https://doi.org/10.3390/en14061784 - 23 Mar 2021
Cited by 1 | Viewed by 533
Abstract
Thermal protection is still one of the key challenges for successful scramjet operations. In this study, the three-dimensional coupled heat transfer between high-temperature gas and regenerative cooling panel with kerosene of supercritical pressure flowing in the cooling channels was numerically investigated to reveal [...] Read more.
Thermal protection is still one of the key challenges for successful scramjet operations. In this study, the three-dimensional coupled heat transfer between high-temperature gas and regenerative cooling panel with kerosene of supercritical pressure flowing in the cooling channels was numerically investigated to reveal the fundamental characteristics of regenerative cooling as well as its influencing factors. The SST k-ω turbulence model with low-Reynolds-number correction provided by the pressure-based solver of Fluent 19.2 is adopted for simulation. It was found that the heat flux of the gas heated surface is in the order of 106 W/m2, and it declines along the flow direction of gas due to the development of boundary layer. Compared with cocurrent flow, the temperature peak of the gas heated surface in counter flow is much higher. The temperature and heat flux of the gas heated surface both rises with the static pressure and total temperature of gas. The heat flux of the gas heated surface increases with the mass flow rate of kerosene, and it hardly changes with the pressure of kerosene. Results herein could help to understand the real heat transfer process of regenerative cooling and guide the design of thermal protection systems. Full article
(This article belongs to the Section E: Thermal Management)
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Article
Laboratory Testing of Fracture Conductivity Damage by Foam-Based Fracturing Fluids in Low Permeability Tight Gas Formations
Energies 2021, 14(6), 1783; https://doi.org/10.3390/en14061783 - 23 Mar 2021
Viewed by 555
Abstract
In the case of fracturing of the reservoirs using fracturing fluids, the size of damage to the proppant conductivity caused by treatment fluids is significant, which greatly influence the effective execution of hydraulic fracturing operations. The fracturing fluid should be characterized by the [...] Read more.
In the case of fracturing of the reservoirs using fracturing fluids, the size of damage to the proppant conductivity caused by treatment fluids is significant, which greatly influence the effective execution of hydraulic fracturing operations. The fracturing fluid should be characterized by the minimum damage to the conductivity of a fracture filled with proppant. A laboratory research procedure has been developed to study the damage effect caused by foamed and non-foamed fracturing fluids in the fractures filled with proppant material. The paper discusses the results for high quality foamed guar-based linear gels, which is an innovative aspect of the work compared to the non-foamed frac described in most of the studies and simulations. The tests were performed for the fracturing fluid based on a linear polymer (HPG—hydroxypropyl guar, in liquid and powder form). The rheology of nitrogen foamed-based fracturing fluids (FF) with a quality of 70% was investigated. The quartz sand and ceramic light proppant LCP proppant was placed between two Ohio sandstone rock slabs and subjected to a given compressive stress of 4000–6000 psi, at a temperature of 60 °C for 5 h. A significant reduction in damage to the quartz proppant was observed for the foamed fluid compared to that damaged by the 7.5 L/m3 natural polymer-based non-foamed linear fluid. The damage was 72.3% for the non-foamed fluid and 31.5% for the 70% foamed fluid, which are superior to the guar gum non-foamed fracturing fluid system. For tests based on a polymer concentration of 4.88 g/L, the damage to the fracture conductivity by the non-foamed fluid was 64.8%, and 26.3% for the foamed fluid. These results lead to the conclusion that foamed fluids could damage the fracture filled with proppant much less during hydraulic fracturing treatment. At the same time, when using foamed fluids, the viscosity coefficient increases a few times compared to the use of non-foamed fluids, which is necessary for proppant carrying capacities and properly conducted stimulation treatment. The research results can be beneficial for optimizing the type and performance of fracturing fluid for hydraulic fracturing in tight gas formations. Full article
(This article belongs to the Section G: Geo-Energy)
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Article
Determination of Fuel Properties of Char Obtained during the Pyrolysis of Waste Pharmaceutical Blisters
Energies 2021, 14(6), 1782; https://doi.org/10.3390/en14061782 - 23 Mar 2021
Viewed by 736
Abstract
The research presented in this manuscript is focused on the pyrolysis of waste pharmaceutical blisters, which are a large and neglected group of waste, that could be possibly recovered. The studies were focused on the analysis of the chemical composition, as well as [...] Read more.
The research presented in this manuscript is focused on the pyrolysis of waste pharmaceutical blisters, which are a large and neglected group of waste, that could be possibly recovered. The studies were focused on the analysis of the chemical composition, as well as fuel properties of the char generated during the process and its possible applications. The process temperatures (400, 425, and 450 °C) were determined based on the thermogravimetric study that was performed prior to the pyrolysis tests. The selected materials included the pre- and post-consumer waste pharmaceutical blisters in order to determine the possible influence of impurities on the final products. The tests were performed on a laboratory scale fixed bed reactor. The obtained solid fractions (metal and char) were separated. Char was subjected to elemental analysis (C, H, N, Cl, S), as well as the heat of combustion and fuel-related properties (content of flammable, non-flammable, and volatile components) were determined. The results were used to compare the properties of char to the properties of active carbon. The market potential was analyzed. Full article
(This article belongs to the Special Issue Thermal Methods for Waste Utilization)
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Article
Model-Based Analysis of Flow Separation Control in a Curved Diffuser by a Vibration Wall
Energies 2021, 14(6), 1781; https://doi.org/10.3390/en14061781 - 23 Mar 2021
Viewed by 522
Abstract
Vibration wall control is an important active flow control technique studied by many researchers. Although current researches have shown that the control performance is greatly affected by the frequency and amplitude of the vibration wall, the mechanism hiding behind the phenomena is still [...] Read more.
Vibration wall control is an important active flow control technique studied by many researchers. Although current researches have shown that the control performance is greatly affected by the frequency and amplitude of the vibration wall, the mechanism hiding behind the phenomena is still not clear, due to the complex interaction between the vibration wall and flow separation. To reveal the control mechanism of vibration walls, we propose a simplified model to help us understand the interaction between the forced excitation (from the vibration wall) and self-excitation (from flow instability). The simplified model can explain vibration wall flow control behaviors obtained by numerical simulation, which show that the control performance will be optimized at a certain reduced vibration frequency or amplitude. Also, it is shown by the analysis of maximal Lyapunov exponents that the vibration wall is able to change the flow field from a disordered one into an ordered one. Consistent with these phenomena and bringing more physical insight, the simplified model implies that the tuned vibration frequency and amplitude will lock in the unsteady flow separation, promote momentum transfer from the main stream to the separation zone, and make the flow field more orderly and less chaotic, resulting in a reduction of flow loss. Full article
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Article
Assessment of High-Electrification UK Scenarios with Varying Levels of Nuclear Power and Associated Post-Fault Behaviour
Energies 2021, 14(6), 1780; https://doi.org/10.3390/en14061780 - 23 Mar 2021
Cited by 1 | Viewed by 1079
Abstract
Renewable integration into the electricity system of Great Britain (GB) is causing considerable demand for additional flexibility from plants. In particular, a considerable share of this flexibility may be dispatched to secure post-fault transient frequency dynamics. Pursuant to the unprecedented changes to the [...] Read more.
Renewable integration into the electricity system of Great Britain (GB) is causing considerable demand for additional flexibility from plants. In particular, a considerable share of this flexibility may be dispatched to secure post-fault transient frequency dynamics. Pursuant to the unprecedented changes to the traditional portfolio of generation sources, this work presents a detailed analysis of the potential system-level value of unlocking flexibility from nuclear electricity production. A rigorous enhanced mixed integer linear programming (MILP) unit commitment formulation is adopted to simulate several generation-demand scenarios where different layers of flexibility are associated to the operation of nuclear power plants. Moreover, the proposed optimisation model is able to assess the benefit of the large contribution to the system inertial response provided by nuclear power plants. This is made possible by considering a set of linearised inertia-dependent and multi-speed constraints on post fault frequency dynamics. Several case studies are introduced considering 2050 GB low-carbon scenarios. The value of operating the nuclear fleet under more flexible paradigms is assessed, including environmental considerations quantified in terms of system-level CO2 emissions’ reduction. Full article
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Article
Experimental and Numerical-Driven Prediction of Automotive Shredder Residue Pyrolysis Pathways toward Gaseous Products
Energies 2021, 14(6), 1779; https://doi.org/10.3390/en14061779 - 23 Mar 2021
Cited by 2 | Viewed by 656
Abstract
There has been a gradual increase in the field of parts recovery from cars that are withdrawn from use. However, the disposal of automotive shredder residue (ASR) still remains a significant problem. ASR is refuse derived fuel (RDF), which contains mainly plastics, fiber [...] Read more.
There has been a gradual increase in the field of parts recovery from cars that are withdrawn from use. However, the disposal of automotive shredder residue (ASR) still remains a significant problem. ASR is refuse derived fuel (RDF), which contains mainly plastics, fiber sponges, and rubbers in different proportions, and therefore a thermal treatment of selected waste samples is applied. The presented research includes thermogravimetry (TG) analysis and differential thermogravimetric (DTG) analysis, as well as a proximate and an ultimate analysis of the ASR samples. The obtained results were processed and used as an input for modelling. The numerical calculations focused on the identification of the ASR’s average composition, the raw pyrolysis process product, its dry pyrolytic gas composition, and the combustible properties of the pyrolytic gases. The TGA analysis with three heating rate levels covered the temperature range from ambient to 800 °C. The thermal decomposition of the studied samples was in three stages confirmed with three peaks observed at the temperatures 280, 470, and 670 °C. The amount of solid residue grew with the heating rates and was in the range of 27–32 wt%. The numerical calculation of the pyrolysis process showed that only 0.46 kg of dry gas were formed from 1 kg of ASR. The gas yield increased with the rising temperature, and, at the same time, its calorific value decreased from 19.22 down to 14.16 MJ/m3. This is due to the decomposition of C6+ hydrocarbons and the promotion of CO formation. The thermodynamic parameters of the combustion process for a pyrolytic gas air mixture, such as the adiabatic flame temperature and laminar flame speed, were higher than for methane and were, respectively, 2073 °C and 1.02 m/s. Full article
(This article belongs to the Special Issue Computational Thermal, Energy, and Environmental Engineering)
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Article
Experimentally Verified Flow Distribution Model for a Composite Modelling System
Energies 2021, 14(6), 1778; https://doi.org/10.3390/en14061778 - 23 Mar 2021
Cited by 1 | Viewed by 568
Abstract
Requirements of modern process and power technologies for compact and highly efficient equipment for transferring large heat fluxes lead to designing these apparatuses as dense parallel flow systems, ranging from conventional to minichannel dimensions according to the specific industrial application. To avoid operating [...] Read more.
Requirements of modern process and power technologies for compact and highly efficient equipment for transferring large heat fluxes lead to designing these apparatuses as dense parallel flow systems, ranging from conventional to minichannel dimensions according to the specific industrial application. To avoid operating issues in such complex equipment, it is vital to identify not only the local distribution of heat flux in individual parts of the heat transfer surface but also the uniformity of fluid flow distribution inside individual parallel channels of the flow system. A composite modelling system is currently being developed for accurate design of such complex heat transfer equipment. The modeling approach requires a flow distribution model enabling to yield accurate-enough predictions in reasonable time frames. The paper presents the results of complex experimental and modeling investigation of fluid flow distribution in dividing headers of tubular-type equipment. Different modeling approaches were examined on a set of header geometries. Predictions obtained via analytical and numerical models were validated using data from the experiments conducted on additively manufactured header samples. Two case studies employing parallel flow systems (mini-scale systems and a conventional-size heat exchanger) demonstrated the applicability of the distribution model and the accuracy of the composite modelling system. Full article
(This article belongs to the Special Issue Heat and Mass Transfer Issues in Mini Gaps)
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Experts versus Algorithms? Optimized Fuzzy Logic Energy Management of Autonomous PV Hybrid Systems with Battery and H2 Storage
Energies 2021, 14(6), 1777; https://doi.org/10.3390/en14061777 - 23 Mar 2021
Cited by 1 | Viewed by 569
Abstract
Off-grid applications based on intermittent solar power benefit greatly from hybrid energy storage systems consisting of a battery short-term and a hydrogen long-term storage path. An intelligent energy management is required to balance short-, intermediate- and long-term fluctuations in electricity demand and supply, [...] Read more.
Off-grid applications based on intermittent solar power benefit greatly from hybrid energy storage systems consisting of a battery short-term and a hydrogen long-term storage path. An intelligent energy management is required to balance short-, intermediate- and long-term fluctuations in electricity demand and supply, while maximizing system efficiency and minimizing component stress. An energy management was developed that combines the benefits of an expert-knowledge based fuzzy logic approach with a metaheuristic particle swarm optimization. Unlike in most existing work, interpretability of the optimized fuzzy logic controller is maintained, allowing the expert to evaluate and adjust it if deemed necessary. The energy management was tested with 65 1-year household load datasets. It was shown that the expert tuned controller is more robust to changes in load pattern then the optimized controller. However, simple readjustments restore robustness, while largely retaining the benefits achieved through optimization. Nevertheless, it was demonstrated that there is no one-size-fits-all tuning. Especially, large power peaks on the demand-side require overly conservative tunings. This is not desirable in situations where such peaks can be avoided through other means. Full article
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Article
Research on Optimal Charging of Power Lithium-Ion Batteries in Wide Temperature Range Based on Variable Weighting Factors
Energies 2021, 14(6), 1776; https://doi.org/10.3390/en14061776 - 23 Mar 2021
Viewed by 496
Abstract
With the popularity of electric vehicles (EV), the charging technology has become one of the bottleneck problems that limit the large-scale deployment of EVs. In this paper, a charging method using multi-stage constant current based on SOC (MCCS) is proposed, and then the [...] Read more.
With the popularity of electric vehicles (EV), the charging technology has become one of the bottleneck problems that limit the large-scale deployment of EVs. In this paper, a charging method using multi-stage constant current based on SOC (MCCS) is proposed, and then the charging time, charging capacity and temperature increase of the battery are optimized by multi-objective particle swarm optimization (MOPSO) algorithm. The influence of the number of charging stages, the cut-off voltage, the combination of different target weight factors and the ambient temperature on the charging strategy is further compared and discussed. Finally, according to the ambient temperature and users’ requirements of charging time, a charging strategy suitable for the specific situation is obtained by adjusting the weight factors, and the results are analyzed and justified on the basis of the experiments. The results show that the proposed strategy can intelligently make more reasonable adjustments according to the ambient temperature on the basis of meeting the charging demands of users. Full article
(This article belongs to the Special Issue Electric Vehicle Charging: Social and Technical Issues)
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Article
Inverse Optimal Control in State Derivative Space System with Applications in Motor Control
Energies 2021, 14(6), 1775; https://doi.org/10.3390/en14061775 - 23 Mar 2021
Cited by 1 | Viewed by 478
Abstract
This paper mathematically explains how state derivative space (SDS) system form with state derivative related feedback can supplement standard state space system with state related feedback in control designs. Practically, inverse optimal control is attractive because it can construct a stable closed-loop system [...] Read more.
This paper mathematically explains how state derivative space (SDS) system form with state derivative related feedback can supplement standard state space system with state related feedback in control designs. Practically, inverse optimal control is attractive because it can construct a stable closed-loop system while optimal control may not have exact solution. Unlike the previous algorithms which mainly applied state feedback, in this paper inverse optimal control are carried out utilizing state derivative alone in SDS system. The effectiveness of proposed algorithms are verified by design examples of DC motor tracking control without tachometer and very challenging control problem of singular system with impulse mode. Feedback of direct measurement of state derivatives without integrations can simplify implementation and reduce cost. In addition, the proposed design methods in SDS system with state derivative feedback are analogous to those in state space system with state feedback. Furthermore, with state derivative feedback control in SDS system, wider range of problems such as singular system control can be handled effectively. These are main advantages of carrying out control designs in SDS system. Full article
(This article belongs to the Special Issue Design and Control of Electrical Motor Drives)
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Review
Building Façade Retrofit with Solar Passive Technologies: A Literature Review
Energies 2021, 14(6), 1774; https://doi.org/10.3390/en14061774 - 23 Mar 2021
Cited by 2 | Viewed by 717
Abstract
Worldwide, buildings have been presented as one of the main energy consumers and, for that matter, there is an increased tendency to invest in policies and measures that promote more efficient buildings. Among the chosen strategies, the need to promote the use of [...] Read more.
Worldwide, buildings have been presented as one of the main energy consumers and, for that matter, there is an increased tendency to invest in policies and measures that promote more efficient buildings. Among the chosen strategies, the need to promote the use of passive solutions and retrofit the existing building stock is often pointed out. Portuguese building stock has proven to be obsolete in terms of thermal comfort, which can directly affect the energy demand for climatization purposes. Considering the great solar availability in the country, when compared to other European locations, building retrofit with solar passive technologies can be a suitable solution. This paper aims to review studies on the application of solar passive technologies to retrofit façades in the Mediterranean climate context, with a special focus on Portugal. Four retrofit passive solar technologies were reviewed, namely glazing, sun shading, sunspaces and Trombe wall technologies. Full article
(This article belongs to the Special Issue Building Thermal Envelope - New Trends and Applications)
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Article
Innovative Application of Model-Based Predictive Control for Low-Voltage Power Distribution Grids with Significant Distributed Generation
Energies 2021, 14(6), 1773; https://doi.org/10.3390/en14061773 - 23 Mar 2021
Cited by 1 | Viewed by 517
Abstract
In past decades, the deployment of renewable-energy-based power generators, namely solar photovoltaic (PV) power generators, has been projected to cause a number of new difficulties in planning, monitoring, and control of power distribution grids. In this paper, a control scheme for flexible asset [...] Read more.
In past decades, the deployment of renewable-energy-based power generators, namely solar photovoltaic (PV) power generators, has been projected to cause a number of new difficulties in planning, monitoring, and control of power distribution grids. In this paper, a control scheme for flexible asset management is proposed with the aim of closing the gap between power supply and demand in a suburban low-voltage power distribution grid with significant penetration of solar PV power generation while respecting the different systems’ operational constraints, in addition to the voltage constraints prescribed by the French distribution grid operator (ENEDIS). The premise of the proposed strategy is the use of a model-based predictive control (MPC) scheme. The flexible assets used in the case study are a biogas plant and a water tower. The mixed-integer nonlinear programming (MINLP) setting due to the water tower ON/OFF controller greatly increases the computational complexity of the optimisation problem. Thus, one of the contributions of the paper is a new formulation that solves the MINLP problem as a smooth continuous one without having recourse to relaxation. To determine the most adequate size for the proposed scheme’s sliding window, a sensitivity analysis is carried out. Then, results given by the scheme using the previously determined window size are analysed and compared to two reference strategies based on a relaxed problem formulation: a single optimisation yielding a weekly operation planning and a MPC scheme. The proposed problem formulation proves effective in terms of performance and maintenance of acceptable computational complexity. For the chosen sliding window, the control scheme drives the power supply/demand gap down from the initial one up to 38%. Full article
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Article
A Novel Multi-Area Distribution State Estimation Approach for Active Networks
Energies 2021, 14(6), 1772; https://doi.org/10.3390/en14061772 - 23 Mar 2021
Cited by 1 | Viewed by 473
Abstract
This paper presents a hierarchically distributed algorithm for the execution of distribution state estimation function in active networks equipped with some phasor measurement units. The proposed algorithm employs voltage-based state estimation in rectangular form and is well-designed for large-scale active distribution networks. For [...] Read more.
This paper presents a hierarchically distributed algorithm for the execution of distribution state estimation function in active networks equipped with some phasor measurement units. The proposed algorithm employs voltage-based state estimation in rectangular form and is well-designed for large-scale active distribution networks. For this purpose, as the first step, the distribution network is supposed to be divided into some overlapped zones and local state estimations are executed in parallel for extracting operating states of these zones. Then, using coordinators in the feeders and the substation, the estimated local voltage profiles of all zones are coordinated with the local state estimation results of their neighboring zones. In this regard, each coordinator runs a state estimation process for the border buses (overlapped buses and buses with tie-lines) of its zones and based on the results for voltage phasor of border buses, the local voltage profiles in non-border buses of its zones are modified. The performance of the proposed algorithm is tested with an active distribution network, considering different combinations of operating conditions, network topologies, network decompositions, and measurement scenarios, and the results are presented and discussed. Full article
(This article belongs to the Special Issue Load Modelling of Power Systems)
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Article
High Efficiency of the Removal Process of Pb(II) and Cu(II) Ions with the Use of Fly Ash from Incineration of Sunflower and Wood Waste Using the CFBC Technology
Energies 2021, 14(6), 1771; https://doi.org/10.3390/en14061771 - 23 Mar 2021
Cited by 2 | Viewed by 627
Abstract
In these research studies, fly ash (SW-FA) resulting from the incineration of sunflower (20%) and wood (80%) waste employing the circulating fluidized bed combustion (CFBC) technology was used to analyze the possibility of removing Pb(II) and Cu(II) ions in adsorption processes. Currently, great [...] Read more.
In these research studies, fly ash (SW-FA) resulting from the incineration of sunflower (20%) and wood (80%) waste employing the circulating fluidized bed combustion (CFBC) technology was used to analyze the possibility of removing Pb(II) and Cu(II) ions in adsorption processes. Currently, great emphasis is placed on circular economy, zero waste or climate neutrality strategies. The use of low-cost SW-FA waste seems to fit well with pro-ecological, economic and energy-saving trends. Hence, this material was characterized by various techniques, such as granulation analysis, bulk density, SEM-EDX, XRD and XRF analysis, BET, BJH, thermogravimetry, zeta potential, SEM morphology and FT-IR spectrometry. As a result of the conducted research, the factors influencing the effectiveness of the adsorption process, such as adsorbent dosage, initial and equilibrium pH, initial metal concentration and contact time, were analyzed. The maximum removal efficiency were achieved at the level of 99.8% for Pb(II) and 99.6% for Cu(II), respectively. The kinetics analysis and isotherms showed that the pseudo-second-order equation and the Freundlich isotherm models better describe these processes. The experiments proved that SW-FA can act as an appropriate adsorbent for highly effective removal of lead and copper from wastewater and improvement of water quality. Full article
(This article belongs to the Special Issue Progress and Novel Applications of Fluidized Bed Technology)
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Article
In Situ Tests of the Monitoring and Diagnostic System for Individual Photovoltaic Panels
Energies 2021, 14(6), 1770; https://doi.org/10.3390/en14061770 - 22 Mar 2021
Cited by 3 | Viewed by 695
Abstract
The dynamic development of photovoltaic systems in the world and in Poland is mainly related to the drop in prices of installation components. Currently, electricity from photovoltaics is one of the cheapest renewable energy sources. The basis for effective energy generation is, first [...] Read more.
The dynamic development of photovoltaic systems in the world and in Poland is mainly related to the drop in prices of installation components. Currently, electricity from photovoltaics is one of the cheapest renewable energy sources. The basis for effective energy generation is, first of all, failure-free operation of the photovoltaic system over a long period of operation, up to 30 years. The paper presents the results of a study of a low-cost distributed system for monitoring and diagnosis of photovoltaic installations (SmartPV), capable of assessing the operating parameters of individual photovoltaic panels. The devices were tested by connecting them to an existing photovoltaic installation, allowing the measurement of operational parameters of individual photovoltaic panels as well as operating conditions such as illuminance and panel surface temperature. The data were recorded on a server using wireless Wi-Fi transmission. Interesting data were collected during the tests, confirming the usefulness of the suggested device for monitoring the photovoltaic installations. Differences in performance of the photovoltaic panel depending on solar radiation and surface temperature were recorded. The temperature coefficient of power was determined, allowing for increased accuracy in the prediction of generated power. The correct recording in different situation, i.e., shading, sensor damage or weather anomalies, was verified. Based on the collected data, rules will be defined for an expert application which, in combination with SmartPV devices, will ensure a quick response to any malfunctions of the photovoltaic system, both related to failures and those resulting from natural degradation during operation. Full article
(This article belongs to the Special Issue The IMTech 2021 Innovative Mining Technologies)
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Article
Analysis of Harmful Exhaust Gas Concentrations in Cloud behind a Vehicle with a Spark Ignition Engine
Energies 2021, 14(6), 1769; https://doi.org/10.3390/en14061769 - 22 Mar 2021
Cited by 3 | Viewed by 596
Abstract
The article presents issues related to the assessment of concentrations of harmful substances in the exhaust gas cloud behind the vehicle. In the theoretical part, considerations about the harmfulness of exhaust gases and methods of detection of chemical compounds were made, and the [...] Read more.
The article presents issues related to the assessment of concentrations of harmful substances in the exhaust gas cloud behind the vehicle. In the theoretical part, considerations about the harmfulness of exhaust gases and methods of detection of chemical compounds were made, and the issues of von Karman vortices and the Lambert-Beer law were referred to. The test object was a vehicle equipped with an SI engine meeting the Euro 3 standard. The drive unit had a capacity of 2.8 dm3, a rated power reaching 142 kW at 5500 rpm and a maximum torque of 280 Nm at 3500 rpm. The measurements of the dilution of the exhaust gas cloud behind the vehicle were made in stationary conditions (laboratory) and during actual operation in the Poznań agglomeration. In the research, technically advanced equipment from the PEMS group was used. In the analysis of the obtained results, detailed considerations were made regarding the influence of the location of the measuring probe in relation to the exhaust system. As can be seen from the obtained dependencies, the vehicle motion is favorable for the assessment of concentrations behind a moving object, because the ecological indicators at successive distances behind the exhaust system achieve better parameters in most points than in a stationary test. Full article
(This article belongs to the Special Issue Exhaust Emissions from Passenger Cars)
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Article
Conversion of Slaughterhouse Wastes to Solid Fuel Using Hydrothermal Carbonization
Energies 2021, 14(6), 1768; https://doi.org/10.3390/en14061768 - 22 Mar 2021
Cited by 1 | Viewed by 645
Abstract
In this study, cattle and pig slaughterhouse wastes (SHWs) were hydrothermally carbonized at 150–300 °C, and the properties of SHW-derived hydrochar were evaluated for its use as a solid fuel. The results demonstrated that increasing the hydrothermal carbonization (HTC) treatment temperature improved the [...] Read more.
In this study, cattle and pig slaughterhouse wastes (SHWs) were hydrothermally carbonized at 150–300 °C, and the properties of SHW-derived hydrochar were evaluated for its use as a solid fuel. The results demonstrated that increasing the hydrothermal carbonization (HTC) treatment temperature improved the energy-related properties (i.e., fuel ratio, higher heating value, and coalification degree) of both the cattle and pig SHW-derived hydrochars. However, the improvements of cattle SHW-derived hydrochars were not as dramatic as that of pig SHW-derived hydrochars, due to the lipid-rich components that do not participate in the HTC reaction. In this regard, there was no merit of using HTC treatment on cattle SHW for the production of hydrochar or using the hydrochar as a solid fuel in terms of energy retention efficiency. On the other hand, a mild HTC treatment at approximately 200 °C was deemed suitable for converting pig SHW to value-added solid fuel. The findings of this study suggest that the conversion of SHWs to hydrochar using HTC can provide an environmentally benign method for waste treatment and energy recovery from abandoned biomass. However, the efficiency of energy recovery varies depending on the chemical composition of the raw feedstock. Full article
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Article
Assessing the Level of Energy and Climate Sustainability in the European Union Countries in the Context of the European Green Deal Strategy and Agenda 2030
Energies 2021, 14(6), 1767; https://doi.org/10.3390/en14061767 - 22 Mar 2021
Cited by 10 | Viewed by 1012
Abstract
The concept of sustainable development integrates activities in the economic, environmental and social areas. Energy policy, which is very closely linked to climate protection, is of key importance for achieving the goals of the concept in question. All these elements are connected by [...] Read more.
The concept of sustainable development integrates activities in the economic, environmental and social areas. Energy policy, which is very closely linked to climate protection, is of key importance for achieving the goals of the concept in question. All these elements are connected by the European Green Deal strategy and Agenda 2030. Their implementation requires the evaluation of previous actions undertaken within the framework of sustainable development and the diagnosis of the current state. Therefore, this article presents the results of such research in relation to the key industry connected with this process, which is the energy sector. The research methodology was based on the analysis of 14 indicators that characterize four basic areas (dimensions) related to energy and climate sustainability. These indicators concern energy and climate as well as social and economic issues. This approach makes it possible to comprehensively assess the actions taken so far in the implementation of sustainable economic development in the energy and climate area in the European Union (EU) countries. The entropy-complex-proportional-assessment (COPRAS) methodologies, which belong to the group of multiple criteria decision-making methods, were used for this study. The conducted research allowed for the assessment of the changes in the EU countries in terms of energy and climate sustainability between 2009–2018. In addition, the effects of the introduced changes in individual years and in relation to the studied areas (dimensions) were also evaluated. Based on the results, considering the adopted criteria, the EU countries were divided into groups similar to the level of energy and climate sustainability. The results constitute a valuable set of data, which allows for a wide and in-depth multicriteria analysis. This allows for a very objective and broad assessment of the effects of sustainable development policies in the EU countries and the current state in the context of the European Green Deal strategy and Agenda 2030. Full article
(This article belongs to the Special Issue Energy Economic Analysis: Energy Transition and Sustainability)
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Review
State-of-the-Art of Strategies to Reduce Exhaust Emissions from Diesel Engine Vehicles
Energies 2021, 14(6), 1766; https://doi.org/10.3390/en14061766 - 22 Mar 2021
Cited by 8 | Viewed by 947
Abstract
Compression ignition engines play a significant role in the development of a country. They are widely used due to their innate properties such as high efficiency, high power output, and durability. However, they are considered one of the key contributors to transport-related emission [...] Read more.
Compression ignition engines play a significant role in the development of a country. They are widely used due to their innate properties such as high efficiency, high power output, and durability. However, they are considered one of the key contributors to transport-related emission and have recently been identified as carcinogenic. Thus, it is important to modify the designs and processes before, during, and after combustion to reduce the emissions to meet the strict emission regulations. The paper discusses the pros and cons of different strategies to reduce emissions of a diesel engine. An overview of various techniques to modify the pre-combustion engine design aspects has been discussed first. After that, fuel modifications techniques during combustion to improve the fuel properties to reduce the engine-out emission is discussed. Finally, post-combustion after-treatment devices are briefly discussed, which help improve the air quality of our environment. Full article
Article
Two-Step Predict and Correct Non-Intrusive Parametric Model Order Reduction for Changing Well Locations Using a Machine Learning Framework
Energies 2021, 14(6), 1765; https://doi.org/10.3390/en14061765 - 22 Mar 2021
Viewed by 630
Abstract
The objective of this paper is to develop a two-step predict and correct non-intrusive Parametric Model Order Reduction (PMOR) methodology for the problem of changing well locations in an oil field that can eventually be used for well placement optimization to gain significant [...] Read more.
The objective of this paper is to develop a two-step predict and correct non-intrusive Parametric Model Order Reduction (PMOR) methodology for the problem of changing well locations in an oil field that can eventually be used for well placement optimization to gain significant computational savings. In this work, we propose a two-step PMOR procedure, where, in the first step, a Proper Orthogonal Decomposition (POD)-based strategy that is non-intrusive to the simulator source code is introduced, as opposed to the convention of using POD as a simulator intrusive procedure. The non-intrusiveness of the proposed technique stems from formulating a novel Machine Learning (ML)-based framework used with POD. The features of the ML model (Random Forest was used here) are designed such that they take into consideration the temporal evolution of the state solutions and thereby avoid simulator access for the time dependency of the solutions. The proposed PMOR method is global, since a single reduced-order model can be used for all the well locations of interest in the reservoir. We address the major challenge of the explicit representation of the well location change as a parameter by introducing geometry-based features and flow diagnostics-inspired physics-based features. In the second step, an error correction model based on reduced model solutions is formulated to correct for discrepancies in the state solutions at well grid blocks expected from POD basis for new well locations. The error correction model proposed uses Artificial Neural Networks (ANNs) that consider the physics-based reduced model solutions as features, and is proved to reduce the error in QoI (Quantities of Interest), such as oil production rates and water cut, significantly. This workflow is applied to a simple homogeneous reservoir and a heterogeneous channelized reservoir using a section of SPE10 model that showed promising results in terms of model accuracy. Speed-ups of about 50×–100× were observed for different cases considered when running the test scenarios. The proposed workflow for Reduced-Order Modeling is “non-intrusive” and hence can increase its applicability to any simulator used. Additionally, the method is formulated such that all the simulation time steps are independent and hence can make use of parallel resources very efficiently and also avoid stability issues that can result from error accumulation over time steps. Full article
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Article
Multi-Level Multi-Input Converter for Hybrid Renewable Energy Generators
Energies 2021, 14(6), 1764; https://doi.org/10.3390/en14061764 - 22 Mar 2021
Cited by 1 | Viewed by 608
Abstract
A three-phase multi-level multi-input power converter topology is presented for grid-connected applications. It encompasses a three-phase transformer that is operated on the primary side in an open-end winding configuration. Thus, the primary winding is supplied on one side by a three-phase N-level neutral [...] Read more.
A three-phase multi-level multi-input power converter topology is presented for grid-connected applications. It encompasses a three-phase transformer that is operated on the primary side in an open-end winding configuration. Thus, the primary winding is supplied on one side by a three-phase N-level neutral point clamped inverter and, on the other side, by an auxiliary two-level inverter. A key feature of the proposed approach is that the N-level inverter is able to perform independent management of N − 1 input power sources, thus avoiding the need for additional dc/dc power converters in hybrid multi-source systems. Moreover, it can manage an energy storage system connected to the dc-bus of the two-level inverter. The N-level inverter operates at a low switching frequency and can be equipped with very low on-state voltage drop Insulated-Gate Bipolar Transistor (IGBT) devices, while the auxiliary inverter is instead operated at low voltage according to a conventional high-frequency two-level Pulse Width Modulation (PWM) technique and can be equipped with very low on-state resistance Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) devices. Simulations and experimental results confirm the effectiveness of the proposed approach and its good performance in terms of grid current harmonic content and overall efficiency. Full article
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