Energies

21 pages, 6303 KiB

Open AccessArticle

A New Approach for Long-Term Stability Estimation Based on Voltage Profile Assessment for a Power Grid

by Alireza Pourdaryaei, Amidaddin Shahriari, Mohammad Mohammadi, Mohammad Reza Aghamohammadi, Mazaher Karimi and Kimmo Kauhaniemi

Energies 2023, 16(5), 2508; https://doi.org/10.3390/en16052508 - 6 Mar 2023

Cited by 3 | Viewed by 2095

Abstract

Load flow solutions refer to the steady-state stability of power systems and have a crucial role in the design and planning of slow-changing elements; e.g., in online tab changing actions, automatic generation control, over-excitation limiters and the power recovery characteristics of a load. [...] Read more.

Load flow solutions refer to the steady-state stability of power systems and have a crucial role in the design and planning of slow-changing elements; e.g., in online tab changing actions, automatic generation control, over-excitation limiters and the power recovery characteristics of a load. Therefore, the purpose of this work was to show the connectivity between load flow analysis and long-term voltage stability using a generator model by introducing a novel voltage stability assessment based on the multi-machine dynamic model along with the load flow study for a power grid. The Euclidean distance (ED) was used to introduce a new voltage stability index based on the voltage phasor profile for real-time monitoring purposes. The effects of reactive power compensation, in addition to load-generation patterns and network topology changes in the system behavior, could be seen clearly on the voltage profiles of the buses. Thus, the increased values for the EDs of the buses’ voltage amplitudes—from 0 to around 1.5 (p.u.)—implied that the system was approaching the voltage collapse point, corresponding to the Jacobian matrix singularity of the load flow equation. Moreover, the weakest load bus with respect to any system change was also identified. Indeed, the criticality of any network interruption was in direct proportion to this voltage stability index. The proposed method was validated using the IEEE 118-bus test system. Full article

(This article belongs to the Special Issue Stability Issues and Challenges in Modern Electric Power Systems)

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17 pages, 19801 KiB

Open AccessArticle

An FCS-MPC Strategy for Series APF Based on Deadbeat Direct Compensation

by Guifeng Wang, Xujie Gao and Chunjie Li

Energies 2023, 16(5), 2507; https://doi.org/10.3390/en16052507 - 6 Mar 2023

Viewed by 1538

Abstract

Aiming at the delay caused by the phase-locked loop (PLL) and harmonic detection in the traditional control of a series active power filter (SAPF), a deadbeat direct control (DBDC)-based finite control set model predictive control (FCS-MPC) strategy for the SAPF is proposed in [...] Read more.

Aiming at the delay caused by the phase-locked loop (PLL) and harmonic detection in the traditional control of a series active power filter (SAPF), a deadbeat direct control (DBDC)-based finite control set model predictive control (FCS-MPC) strategy for the SAPF is proposed in this work. Firstly, a reference voltage generation mechanism based on direct control is established, which avoids the delay in harmonic detection, thus improving the dynamic response performance of the system. Secondly, the reference current generation mechanism suitable for the SAPF is derived and established using the deadbeat control (DBC) in the αβ coordinate system, based on which the FCS-MPC system is constructed. It eliminates the complex coordinate transformation and PLL and effectively compensates for the full-frequency harmonic voltage. Finally, the proposed control strategy is verified by a simulation and an experiment. The results suggest that the proposed control strategy can effectively compensate for the load voltage and suppress harmonic distortion for the temporary swell and sag of the grid voltage, sudden load changes, and harmonic distortion conditions. Full article

(This article belongs to the Collection Advanced Control and Applications of Power Electronics and Power Converters)

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20 pages, 2449 KiB

Open AccessArticle

Optimal Scheduling Strategy of Regional Power System Dominated by Renewable Energy Considering Physical and Virtual Shared Energy Storage

by Zhe Chai, Junhui Liu, Yihan Zhang, Yuge Chen, Kunming Zhang, Chang Liu, Meng Yang, Shuo Yin, Weiqiang Qiu, Zhenzhi Lin and Li Yang

Energies 2023, 16(5), 2506; https://doi.org/10.3390/en16052506 - 6 Mar 2023

Cited by 1 | Viewed by 1699

Abstract

In view of the current situation of the global energy crisis and environmental pollution, the energy industry transition and environmental governance are urgently needed. To deal with the problem above, the construction of a power system dominated by renewable energy (PSDRE) with wind [...] Read more.

In view of the current situation of the global energy crisis and environmental pollution, the energy industry transition and environmental governance are urgently needed. To deal with the problem above, the construction of a power system dominated by renewable energy (PSDRE) with wind turbine (WT), photovoltaic (PV), biomass power (BP), and other clean, low-carbon, renewable energy sources as the principal part has become a consensus all over the world. However, the random and uncertain power output of renewable energy will not only put pressure on the power system but also lead to the unreasonable and insufficient usage of renewable energy. In this context, the energy storage (ES) effects of flexible resources, such as physical energy storage of batteries and demand response (DR), are analyzed first. Next, a modeling method for the operational characteristics of physical and virtual shared energy storage (PVSES) in regional PSDRE (RPSDRE) is proposed. Finally, an optimal scheduling strategy for RPSDRE that considers PVSES is proposed to achieve coordination of WT, PV, PVSES, and other flexible resources. The case study on RPSDRE in Lankao county, Kaifeng city, Henan province of China verifies the effectiveness and practicability of the proposed strategy. Full article

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21 pages, 9492 KiB

Open AccessArticle

A Numerical Model for Pressure Analysis of a Well in Unconventional Fractured Reservoirs

by Jiwei He, Qin Li, Guodong Jin, Sihai Li, Kunpeng Shi and Huilin Xing

Energies 2023, 16(5), 2505; https://doi.org/10.3390/en16052505 - 6 Mar 2023

Viewed by 2058

Abstract

Fractured reservoirs are highly heterogeneous in both matrix and fracture properties, which results in significant variations in well production. Assessing and quantifying the influence of fractures on fluid flow is essential for developing unconventional reservoirs. The complicated effects of fractures in unconventional fractured [...] Read more.

Fractured reservoirs are highly heterogeneous in both matrix and fracture properties, which results in significant variations in well production. Assessing and quantifying the influence of fractures on fluid flow is essential for developing unconventional reservoirs. The complicated effects of fractures in unconventional fractured reservoirs on fluid flow highly depend on fracture geometry, fracture distribution, and fracture properties, which can be reflected in pressure transient testing. The biggest challenge lies in delineating the pre-existing natural fracture distribution pattern, density, azimuth, and connectivity. Using the advanced finite element method, this paper builds a finely characterized near-wellbore model to numerically simulate the pressure transient testing process in naturally fractured reservoirs and further evaluates fracture-related effects to obtain a more accurate solution. First, the numerical program is benchmarked by the analytical solutions and numerical results of Eclipse. Next, different fracture models with single fractures or fracture networks are set up to investigate the effects of fracture parameters numerically (e.g., fracture location, fracture dip angle, fracture spacing, the ratio of fracture permeability to matrix permeability, fracture network orientation, horizontal fracture distribution, etc.) on pressure transient behaviors in naturally fractured reservoirs. Velocity and pressure profiles are presented to visualize and analyze their effects, and new features in the flow regimes of the derivative plots of the bottom-hole pressure are identified and discussed. Finally, based on geological and geophysical data, including image logs, core descriptions, wireline logs, and seismic and well test data, a practical fractured model of the Dalwogan 2 well in the Surat basin is built, analyzed, and compared with homogenous and measured data. The results show significance in characterizing the complex fracture networks in near-wellbore models of unconventional fractured reservoirs. Full article

(This article belongs to the Special Issue Exploring Hydrocarbons in Carbonate Reservoirs)

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18 pages, 4121 KiB

Open AccessArticle

Thermal Environment and Animal Comfort of Aviary Prototypes with Photovoltaic Solar Panel on the Roof

by Charles Paranhos Oliveira, Fernanda Campos de Sousa, Gabriel Machado Dallago, Jocássia Reis Silva, Paulo Henrique Reis Furtado Campos, Maria Clara de Carvalho Guimarães and Fernando da Costa Baêta

Energies 2023, 16(5), 2504; https://doi.org/10.3390/en16052504 - 6 Mar 2023

Cited by 1 | Viewed by 2520

Abstract

The areas on the roofs of animal production facilities present great potential for generating solar energy. However, the impact that the addition of new material on the roof can generate on the installation’s thermal environment is still poorly studied. Thus, this study aims [...] Read more.

The areas on the roofs of animal production facilities present great potential for generating solar energy. However, the impact that the addition of new material on the roof can generate on the installation’s thermal environment is still poorly studied. Thus, this study aims to investigate the effect of the application of photovoltaic panels in the roofs of prototypes, in reduced-scale aviaries, on the thermal environment, and on the animal comfort condition inside the prototypes. For this, six prototypes of aviaries on a reduced 1:5 scale are used. They are equipped with three types of tiles (ceramic, fiber-cement, and metal), with and without a photovoltaic panel. The effect of applying the photovoltaic panel is verified by evaluating the air temperature, the surface temperature of the roofs, the temperature and humidity index (THI), the black globe humidity index (BGHI), and the radiation heat load (RHL). The results show that applying the photovoltaic panel on the roof, regardless of the type of tile, is efficient in reducing the air temperature by about 0.4 °C, the BGHI by about 0.7, and the RHL about 4 W/m². As for THI, there is only a 4.8 reduction in fiber-cement roofs. Full article

(This article belongs to the Special Issue Building Design, Solar Energy and Thermal Comfort)

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33 pages, 4046 KiB

Open AccessReview

A Comprehensive Review of the Bidirectional Converter Topologies for the Vehicle-to-Grid System

by Suresh Panchanathan, Pradeep Vishnuram, Narayanamoorthi Rajamanickam, Mohit Bajaj, Vojtech Blazek, Lukas Prokop and Stanislav Misak

Energies 2023, 16(5), 2503; https://doi.org/10.3390/en16052503 - 6 Mar 2023

Cited by 27 | Viewed by 6579

Abstract

Over the past decade, there has been a great interest in the changeover from cars powered by gasoline to electric vehicles, both within the automotive industry and among customers. The electric vehicle–grid (V2G) technology is a noteworthy innovation that enables the battery of [...] Read more.

Over the past decade, there has been a great interest in the changeover from cars powered by gasoline to electric vehicles, both within the automotive industry and among customers. The electric vehicle–grid (V2G) technology is a noteworthy innovation that enables the battery of an electric vehicle during idling conditions or parked can function as an energy source that can store or release energy whenever required. This results in energy exchange between the grid and EV batteries. This article reviews various bidirectional converter topologies used in the V2G system. Additionally, it can reduce the cost of charging for electric utilities, thus increasing profits for EV owners. Normally electric grid and the battery of an electric vehicle can be connected through power electronic converters, especially a bidirectional converter, which allows power to flow in both directions. The majority of research work is carried out over the converters for V2G applications and concerns utilizing two conversion stages, such as the AC-DC conversion stage used for correcting the power factor and the DC-DC conversion stage for matching the terminal voltage. Furthermore, a bidirectional conversion can be made for an active power transfer between grid–vehicle (G2V) and V2G effectively. This review explores and examines several topologies of bidirectional converters which make it possible for active power flow between the grid and the vehicle and vice versa. Moreover, different types of charging and discharging systems, such as integrated/non-integrated and on/off board, etc., which have been used for electric vehicle applications, are also discussed. A comparison study is carried out based on several other factors that have been suggested. The utilization of semiconductors in power converters and non-conventional resources in charging and discharging applications are the two improving technologies for electric vehicles. Full article

(This article belongs to the Special Issue Advanced Coordinated Optimization Strategy of Electric Vehicle and Smart Grids)

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36 pages, 8859 KiB

Open AccessReview

Conservation Voltage Reduction in Modern Power Systems: Applications, Implementation, Quantification, and AI-Assisted Techniques

by Alireza Gorjian, Mohsen Eskandari and Mohammad H. Moradi

Energies 2023, 16(5), 2502; https://doi.org/10.3390/en16052502 - 6 Mar 2023

Cited by 6 | Viewed by 4121

Abstract

Conservation voltage reduction (CVR) is a potentially effective and efficient technique for inertia synthesis and frequency support in modern grids comprising power electronics (PE)-based components, aiming to improve dynamic stability. However, due to the complexities of PE-based grids, implementing the CVR methods cannot [...] Read more.

Conservation voltage reduction (CVR) is a potentially effective and efficient technique for inertia synthesis and frequency support in modern grids comprising power electronics (PE)-based components, aiming to improve dynamic stability. However, due to the complexities of PE-based grids, implementing the CVR methods cannot be performed using traditional techniques as in conventional power systems. Further, quantifying the CVR impacts in modern grids, while focusing on dynamic time scales, is critical, consequently making the traditional methods deficient. This is an important issue as CVR utilization/quantification depends on grid conditions and CVR applications. Considering these concerns, this work offers a thorough analysis of CVR applications, implementation, and quantification strategies, including data-driven AI-based methods in PE-based modern grids. To assess the CVR applications from a new perspective, aiming to choose the proper implementation and quantification techniques, they are divided into categories depending on various time scales. CVR implementation methods are categorized into techniques applied to PE-based grids and islanded microgrids (MGs) where different control systems are adopted. Additionally, to address the evaluation issues in modern grids, CVR quantification techniques, including machine learning- and deep learning-based techniques and online perturbation-based methods are evaluated and divided based on the CVR application. Concerns with the further utilizing and measuring of CVR impacts in modern power systems are discussed in the future trends section, where new research areas are suggested. Full article

(This article belongs to the Special Issue Stability Issues and Challenges in Modern Electric Power Systems)

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21 pages, 11409 KiB

Open AccessArticle

Path-Following Control for Thrust-Vectored Hypersonic Aircraft

by Nezar Sahbon, Mariusz Jacewicz, Piotr Lichota and Katarzyna Strzelecka

Energies 2023, 16(5), 2501; https://doi.org/10.3390/en16052501 - 6 Mar 2023

Cited by 5 | Viewed by 2884

Abstract

Thrust vector control (TVC) might be used to control aircraft at large altitudes and in post-stall conditions when aerodynamic control surfaces are ineffective. This study demonstrated that the implementation of the TVC on high-speed aircraft is a reasonable solution and might be an [...] Read more.

Thrust vector control (TVC) might be used to control aircraft at large altitudes and in post-stall conditions when aerodynamic control surfaces are ineffective. This study demonstrated that the implementation of the TVC on high-speed aircraft is a reasonable solution and might be an alternative when compared to the complicated reaction control system or large aerodynamic control surfaces. The numerical flight dynamics model of the X-15 experimental aircraft was developed and implemented in MATLAB/Simulink and then used to investigate the proposed solution. The obtained results indicate that the aircraft, equipped with full 3D thrust vectoring and two independent horizontal stabilizers to control the roll angle, was able to achieve flight along the path that was defined by a set of waypoints. This paper also highlights the potential benefits and challenges of using TVC as a control method for aircraft. The results of this study contribute to the growing body of research on aircraft control and simulation. Future work can explore the use of TVC for other aircraft with unique configurations and low maneuverability features. Full article

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19 pages, 5107 KiB

Open AccessArticle

Categorizing 15 kV High-Voltage HDPE Insulator’s Leakage Current Surges Based on Convolution Neural Network Gated Recurrent Unit

by Wen-Bin Liu, Phuong Nguyen Thanh, Ming-Yuan Cho and Thao Nguyen Da

Energies 2023, 16(5), 2500; https://doi.org/10.3390/en16052500 - 6 Mar 2023

Cited by 2 | Viewed by 1769

Abstract

The leakage currents are appropriate for determining the contamination level of insulators in the power distribution system, which are efficiently cleaned or replaced during the maintenance schedule. In this research, the hybrid convolution neural network and gated recurrent unit model (CNN-GRU) are developed [...] Read more.

The leakage currents are appropriate for determining the contamination level of insulators in the power distribution system, which are efficiently cleaned or replaced during the maintenance schedule. In this research, the hybrid convolution neural network and gated recurrent unit model (CNN-GRU) are developed to categorize the leakage current pulse of the 15 kV HDPE insulator in the transmission towers in Taiwan. Many weather parameters are accumulated in the online monitoring system, which is installed in different transmission towers in coastal areas that suffer from heavy pollution. The Pearson correlation matrix is computed for selecting the high correlative features with the leakage current. Hyperparameter optimization is employed to decide the enhancing framework of the CNN-GRU methodology. The performance of the CNN-GRU is completely analyzed with other deep learning algorithms, which comprise the GRU, bidirectional GRU, LSTM, and bidirectional LSTM. The developed CNN-GRU acquired the most remarkable improvements of 79.48% CRE, 83.54% validating CRE, 14.14% CP, 20.89% validating CP, 66.24% MAE, 63.59% validating MAE, 73.24% MSE, and 71.59% validating MSE benchmarks compared with other methodologies. Therefore, the hybrid CNN-GRU methodology provides comprehensive information about the contamination degrees of insulator surfaces derived from the property of leakage currents. Full article

(This article belongs to the Special Issue Application of Intelligent Techniques in Power System Stability, Control and Protection)

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19 pages, 2294 KiB

Open AccessReview

Indirect Effects of High-Performance Buildings at Household and Community Level: A Systematic Literature Review

by Lorenza Pistore, Francesca Tintinaglia, Roberta Pernetti, Pietro Stivanello and Wilmer Pasut

Energies 2023, 16(5), 2499; https://doi.org/10.3390/en16052499 - 6 Mar 2023

Cited by 3 | Viewed by 2001

Abstract

Towards a carbon-neutral society, the building sector has a pivotal role with still a great potential for improvement. A new generation of buildings is rising but, to set a more ambitious shift in the paradigm and to fully justify the additional efforts (technological [...] Read more.

Towards a carbon-neutral society, the building sector has a pivotal role with still a great potential for improvement. A new generation of buildings is rising but, to set a more ambitious shift in the paradigm and to fully justify the additional efforts (technological and economic) needed to fill the gap between net zero and plus energy performances, it is essential to consider not only the direct effects, but also all the indirect impacts. However, research conducted in the last decade solely focuses on the direct effects, mainly energy savings, while the indirect impacts neither have a clear identity nor terminology and a defined list of the impacts and methodologies for their quantification is still missing. With these premises, a systematic literature review on the current state of the art was performed in this work, with the aim of (i) investigating the heterogeneous terminology used for such indirect effects, (ii) identifying a final potential list of impacts both at the household and at the community level and (iii) their macro-categorizations, and (iv) exploring the current implemented methodologies and indicators for an economic quantification. As a final result of the analysis, the authors propose a unique terminology for addressing the indirect effects of high-performance buildings. This paper sets the needed basis and common ground for future research in this field, meant to economically quantify the indirect effects in the building sector. Full article

(This article belongs to the Special Issue Energy Evaluation and Energy-Savings for Sustainable Buildings)

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15 pages, 14124 KiB

Open AccessArticle

Employing the Peltier Effect to Control Motor Operating Temperatures

by Stephen Lucas, Romeo Marian, Michael Lucas, Titilayo Ogunwa and Javaan Chahl

Energies 2023, 16(5), 2498; https://doi.org/10.3390/en16052498 - 6 Mar 2023

Cited by 3 | Viewed by 1937

Abstract

Electrical insulation failure is the most common failure mechanism in electrical machines (motors and generators). High temperatures and/or temperature gradients (HTTG) are the main drivers of insulation failure in electrical machines. HTTG combine with and augment other destructive effects from over-voltage, to voltage [...] Read more.

Electrical insulation failure is the most common failure mechanism in electrical machines (motors and generators). High temperatures and/or temperature gradients (HTTG) are the main drivers of insulation failure in electrical machines. HTTG combine with and augment other destructive effects from over-voltage, to voltage transients, overload and load variations, poor construction techniques, and thermal cycling. These operating conditions cause insulation damage that leads to electrical insulation failure. The insulation failure process is greatly accelerated by pollutants and moisture absorption. A simple and robust way to reduce HTTG and moisture adsorption is by maintaining constant internal temperatures. The current method to maintain elevated internal temperatures and reduce condensation issues is by internal electrical heating elements. This paper examines the effectiveness of applying thermoelectric coolers (TECs), solid-state heat pumps (Peltier devices), as heaters to raise a motor’s internal temperature by pumping heat into the motor core rather than heating the internal air. TEC technology is relatively new, and the application of TECs to heat a motor’s internal volume has not previously been explored. In this paper, we explore the hypothesis that TECs can pump heat into a motor when out of service, reducing the HTTG by maintaining high winding slot temperatures and eliminating condensation issues. This paper describes a test motor setup with simple resistive heating (traditional method), compared with the application of TECs with heat sinks, heat pipes, and a water circulation heat exchanger, to gauge the capability of TECs to heat the inner core or winding area. In this paper, we demonstrate the full integration of TECs into a motor. The results show that each of the systems incorporating the TECs would effectively pump heat into the core and keep the winding hot, eliminating condensation issues and water ingress due to thermal cycling. Full article

(This article belongs to the Special Issue Advanced Studies of Thermoelectric Systems)

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19 pages, 944 KiB

Open AccessArticle

Numerical Investigation of the Long-Term Load Shifting Behaviors within the Borehole Heat Exchanger Array System

by Haijiang Zou, Siyu Guo, Ruifeng Wang, Fenghao Wang, Zhenxing Shen and Wanlong Cai

Energies 2023, 16(5), 2497; https://doi.org/10.3390/en16052497 - 6 Mar 2023

Viewed by 1725

Abstract

In the process of development and utilization of a large-scale borehole heat exchanger (BHE) array system, the phenomenon of load shifting within BHE array can be observed. In this paper, OpenGeoSys software coupled with TESPy toolkit is used to establish a comprehensive numerical [...] Read more.

In the process of development and utilization of a large-scale borehole heat exchanger (BHE) array system, the phenomenon of load shifting within BHE array can be observed. In this paper, OpenGeoSys software coupled with TESPy toolkit is used to establish a comprehensive numerical model of BHE system (without depicting the heat pump part), and the behaviors of load shifting between BHEs with different design parameters are studied. The results show that the outlet temperature of single BHE and BHE array is generally rising, and the soil temperature around the BHE has accumulated unbalanced heat. The soil temperature near the BHEs array fluctuates more obviously than the single BHE system, and the distribution is uneven. At the end of the 15th year, the soil temperature near the center BHE increased by 2 °C compared with the initial soil temperature, which was more favorable in winter, but was not conducive to the performance improvement in summer. Further analysis by changing the inter-borehole spacing shows that with the increase of the inter-borehole spacing, the load shifting behaviors are gradually weakened, and the maximum shifted load of the central BHE is linear with the change of the inter-borehole spacing. After changing the layout methods, we observe that the more intensive the layout is, the more load shifting behavior is, and the unbalanced rate of soil temperature distribution around the linear layout is lower than other layouts. With the increase in the number of BHEs, the load shifting behaviors are further enhanced. By analyzing the proportion of shifted load amount relative to the average value, it is found that the system will take a longer time to reach heat balance with the increase of BHEs’ number. A shutdown of part of BHEs for a certain period of time will help to improve the long-term operational efficiency of the large-scale shallow ground source heat pump (GSHP) system. Full article

(This article belongs to the Topic Heat Exchanger Design and Heat Pump Efficiency)

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28 pages, 36261 KiB

Open AccessFeature PaperArticle

Evaluation of a Three-Parameter Gearshift Strategy for a Two-Speed Transmission System in Electric Vehicles

by Md Ragib Ahssan, Mehran Ektesabi and Saman Gorji

Energies 2023, 16(5), 2496; https://doi.org/10.3390/en16052496 - 6 Mar 2023

Cited by 4 | Viewed by 1900

Abstract

This paper proposes a three-parameter gearshift scheduling strategy that has been implemented on both large and small electric vehicles with two-speed transmission systems. The new strategy evaluates vehicle performance under varying driving conditions on flat and hilly roads by assessing the vehicle speed, [...] Read more.

This paper proposes a three-parameter gearshift scheduling strategy that has been implemented on both large and small electric vehicles with two-speed transmission systems. The new strategy evaluates vehicle performance under varying driving conditions on flat and hilly roads by assessing the vehicle speed, acceleration, and road grade. A heuristic approach is used to develop two gearshift schedules for vehicle acceleration and road grade, and gradient descent and pattern search methods are applied to optimize the gear ratios and primary gearshift schedules. The results show that the proposed gearshift strategy saves 16.5% of energy on hilly roads compared to conventional approaches. Optimal gearshift schedules for acceleration provide more room for second gear operation, while optimized gearshift schedules for the road grade increase the buffer zone for larger vehicles and allow more space for the second gear operating area. The experimental results validate the proposed approach’s performance for both large and small electric vehicles. Full article

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30 pages, 8820 KiB

Open AccessReview

Transient Stability Analysis and Enhancement Techniques of Renewable-Rich Power Grids

by Albert Poulose and Soobae Kim

Energies 2023, 16(5), 2495; https://doi.org/10.3390/en16052495 - 6 Mar 2023

Cited by 6 | Viewed by 3647

Abstract

New techniques and approaches are constantly being introduced to analyze and enhance the transient stability of renewable energy-source-dominated power systems. This review article extensively discusses recent papers that have proposed novel and innovative techniques for analyzing and enhancing the renewable source-dominated power system’s [...] Read more.

New techniques and approaches are constantly being introduced to analyze and enhance the transient stability of renewable energy-source-dominated power systems. This review article extensively discusses recent papers that have proposed novel and innovative techniques for analyzing and enhancing the renewable source-dominated power system’s transient stability. The inherent low-inertia characteristics of renewable energy sources combined with fast-acting power electronic devices pose new challenges in power systems. Different stability concerns exist for grid-following and subsequent grid-forming converter/inverter connections to power grids; hence, distinct solutions for enhancing the transient stability have been devised for each. Moreover, the fundamental concepts and characteristics of converter/inverter topologies are briefly discussed in this study. Recent discussions and reviews of analysis and enhancement techniques in transient stability could lead to new ways to solve problems in power systems that rely primarily on renewable energy sources. Full article

(This article belongs to the Special Issue Studies on Power System Dynamics and Stability)

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12 pages, 4293 KiB

Open AccessArticle

Multi-Scroll Attractor and Multi-Stable Dynamics of a Three-Dimensional Jerk System

by Fudong Li and Jingru Zeng

Energies 2023, 16(5), 2494; https://doi.org/10.3390/en16052494 - 6 Mar 2023

Cited by 8 | Viewed by 1787

Abstract

A multi-scroll attractor reflects the structural diversity of the dynamic system, and multi-stability behavior reflects its state diversity. Multi-scroll and multi-stability chaotic systems can produce complex random sequences, which have important application values in the field of data security. However, current works on [...] Read more.

A multi-scroll attractor reflects the structural diversity of the dynamic system, and multi-stability behavior reflects its state diversity. Multi-scroll and multi-stability chaotic systems can produce complex random sequences, which have important application values in the field of data security. However, current works on multi-scroll–multi-steady behavior have been carried out separately, rather than simultaneously. This paper considers a three-dimensional Jerk system with a sinusoidal nonlinear term. The basic dynamic behaviors, such as the stability of equilibrium points, bifurcation of parameters and initial values, phase diagrams, and basins of attraction, were analyzed. It was found that the system has infinite equilibrium points. Moreover, the system not only generates complex dynamics, such as single-scroll, double-scroll, and multi-scroll but also realizes the self-reproduction of these dynamic characteristics by controlling the initial value of the system. Therefore, by expanding the equilibrium point, the effective controls of the system’s structural diversity and state diversity are realized at the same time, having important theoretical significance and application value. Full article

(This article belongs to the Special Issue Machine Learning for Cyber-Physical Energy Systems)

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19 pages, 2070 KiB

Open AccessArticle

Air Conditioning Operation Strategies for Comfort and Indoor Air Quality in Taiwan’s Elementary Schools

by Ling-Yi Chang and Tong-Bou Chang

Energies 2023, 16(5), 2493; https://doi.org/10.3390/en16052493 - 6 Mar 2023

Cited by 3 | Viewed by 1742

Abstract

The Executive Yuan in Taiwan plans to install air-conditioning (A/C) in all elementary schools within two years. However, besides the associated energy consumption and environmental issues, the use of A/C will inevitably result in the doors and windows of the classroom being closed, [...] Read more.

The Executive Yuan in Taiwan plans to install air-conditioning (A/C) in all elementary schools within two years. However, besides the associated energy consumption and environmental issues, the use of A/C will inevitably result in the doors and windows of the classroom being closed, which will increase the accumulation of carbon dioxide (CO₂) within the classroom. An excessive indoor CO₂ concentration can result in reduced cognitive performance and an impaired learning efficiency. Therefore, the moderate introduction of external air into the classroom is essential to increase the air exchange rate (AER) and reduce the CO₂ concentration level. Accordingly, the present study conducts a numerical investigation into the effects of various A/C operation strategies on the CO₂ concentration within the classroom given different proportions of students remaining in the classroom during the recess. Overall, the results indicate that the optimal usage strategy is to operate the A/C over the full school day (08:00~15:50 p.m.) in conjunction with a mechanical ventilation system providing a fresh air exchange rate of 5 l/s for every person in the room. However, the use of a mechanical ventilation system inevitably incurs an additional hardware and energy consumption. Thus, an alternative recommendation is also proposed, in which the windows are opened and the air conditioner is turned off at every recess and during the lunchtime period. It is shown that the resulting CO₂ concentration in the classroom is still consistent with the Taiwan Environmental Protection Administration (EPA) regulations and the thermal comfort of the students is achieved for more than three-quarters of the school day. Full article

(This article belongs to the Section B: Energy and Environment)

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21 pages, 5319 KiB

Open AccessArticle

Pyrolysis Oil Derived from Plastic Bottle Caps: Characterization of Combustion and Emissions in a Diesel Engine

by Somkiat Maithomklang, Ekarong Sukjit, Jiraphon Srisertpol, Niti Klinkaew and Khatha Wathakit

Energies 2023, 16(5), 2492; https://doi.org/10.3390/en16052492 - 6 Mar 2023

Cited by 7 | Viewed by 2868

Abstract

Recycling used plastic can help reduce the amount of plastic waste generated. Existing methods, namely the process of pyrolysis, are chemical heating processes that decompose plastics in the absence of oxygen. This decomposes the plastics in a controlled environment in order to produce [...] Read more.

Recycling used plastic can help reduce the amount of plastic waste generated. Existing methods, namely the process of pyrolysis, are chemical heating processes that decompose plastics in the absence of oxygen. This decomposes the plastics in a controlled environment in order to produce fuel from waste. The present study consequently investigated the physical and chemical properties of pyrolysis oil derived from plastic bottle caps (WPBCO) and the effects on the engine performance and emission characteristics of a diesel engine operating on WPBCO. The experiments were conducted with a single-cylinder diesel engine operating at a constant 1500 rpm under various engine loading conditions. The experimental results of the chemical properties of test fuels indicated that WPBCO and diesel fuels have similar functional groups and chemical components. In comparison, WPBCO has a lower kinematic viscosity, density, specific gravity, flash point, fire point, cetane index, and distillation behavior than diesel fuel. However, WPBCO has a high gross calorific value, which makes it a suitable replacement for fossil fuel. In comparison to diesel fuel, the use of WPBCO in diesel engines results in increased brake-specific fuel consumption (BSFC) and brake thermal efficiency (BTE) under all load conditions. The combustion characteristics of the engine indicate that the use of WPBCO resulted in decreased in-cylinder pressure (ICP), rate of heat release (RoHR), and combustion stability compared to diesel fuel. In addition, the combustion of WPBCO advances the start of combustion more strongly than diesel fuel. The use of WPBCO increased emissions of NO_X, CO, HC, and smoke. In addition, the particulate matter (PM) analysis showed that the combustion of WPBCO generated a higher PM concentration than diesel fuel. When WPBCO was combusted, the maximum rate of soot oxidation required a lower temperature, meaning that oxidizing the soot took less energy and that it was easier to break down the soot. Full article

(This article belongs to the Special Issue Energy Trends of Fuel Combustion in Diesel Engine)

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23 pages, 8888 KiB

Open AccessArticle

Algorithm for Fast Detection of Stator Turn Faultsin Variable-Speed Synchronous Generators

by Rodolfo V. Rocha and Renato M. Monaro

Energies 2023, 16(5), 2491; https://doi.org/10.3390/en16052491 - 6 Mar 2023

Cited by 1 | Viewed by 1636

Abstract

Faults between stator winding turns of synchronous generators have led to specific changes in the harmonic content of currents. In this paper, these changes are used to detect faults in variable-speed synchronous generators connected to three-level converters during their operation. Currents typically measured [...] Read more.

Faults between stator winding turns of synchronous generators have led to specific changes in the harmonic content of currents. In this paper, these changes are used to detect faults in variable-speed synchronous generators connected to three-level converters during their operation. Currents typically measured for control purposes are used to avoid installation of additional sensors. The neutral point current of the three-level converter is also evaluated under faults in the generator. Encoder-tuned dynamic filters based on Park transformation and Fourier coefficients together with low-pass filters are used to detect the selected harmonics under variable speeds. The geometric loci of these components are proposed as a method to distinguish between healthy and faulty conditions. Simulation and experimental data are used to test sensitivity, selectivity and detection time of the proposed technique for different fault types. Generalization for a different generator is also presented and tested. Most fault cases were detected using the harmonics. Full article

(This article belongs to the Special Issue Fault Detection and Diagnosis of Electrical Power System Equipments)

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15 pages, 5512 KiB

Open AccessArticle

A Self-Powered Dual-Stage Boost Converter Circuit for Piezoelectric Energy Harvesting Systems

by Abdul Haseeb, Mahesh Edla, Ahmed Mostafa Thabet, Mikio Deguchi and Muhammad Kamran

Energies 2023, 16(5), 2490; https://doi.org/10.3390/en16052490 - 6 Mar 2023

Cited by 3 | Viewed by 1960

Abstract

Miniaturised piezoelectric devices are emerging energy harvesting sources that are appropriate for various implantable and wearable applications. However, these piezoelectric devices exhibit considerable internal resistance due to their internal impedance, which leads to self-start and low-energy conversion failures. This paper describes a dual-stage [...] Read more.

Miniaturised piezoelectric devices are emerging energy harvesting sources that are appropriate for various implantable and wearable applications. However, these piezoelectric devices exhibit considerable internal resistance due to their internal impedance, which leads to self-start and low-energy conversion failures. This paper describes a dual-stage boost converter circuit by facilitating self-powering features and boosting the low voltage harvested by the piezoelectric devices into dc. The proposed circuit comprises conversion stages of ac-dc and dc-dc in Stages I and II, respectively. In addition, the proposed circuit does not require employing the auxiliary circuits to generate the train pulses by triggering the bidirectional switches to envelop the current being stored in Stage II and kick-start the self-powered circuit for piezoelectric energy harvesting systems. Theoretical assumptions and control strategies were tested and verified with ideal and impedance input sources. The proposed circuit could convert a low voltage of 3 V_ac into 19 V_dc. The maximum attained output power by the proposed circuit was 3.61 mW. The outcome depicted that the proposed circuit boosted the low voltage and outperformed the existing literature circuits in terms of output voltage and power. Full article

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17 pages, 1972 KiB

Open AccessEditor’s ChoiceArticle

SGAM-Based Analysis for the Capacity Optimization of Smart Grids Utilizing e-Mobility: The Use Case of Booking a Charge Session

by Moisés Antón García, Ana Isabel Martínez García, Stylianos Karatzas, Athanasios Chassiakos and Olympia Ageli

Energies 2023, 16(5), 2489; https://doi.org/10.3390/en16052489 - 6 Mar 2023

Cited by 2 | Viewed by 2085

Abstract

The description of the functionality of a smart grid’s architectural concept, analyzing different Smart Grid (SG) scenarios without disrupting the smooth operation of the individual processes, is a major challenge. The field of smart energy grids has been increasing in complexity since there [...] Read more.

The description of the functionality of a smart grid’s architectural concept, analyzing different Smart Grid (SG) scenarios without disrupting the smooth operation of the individual processes, is a major challenge. The field of smart energy grids has been increasing in complexity since there are many stakeholder entities with diverse roles. Electric Vehicles (EVs) can transform the stress on the energy grid into an opportunity to act as a flexible asset. Smart charging through an external control system can have benefits for the energy sector, both in grid management and environmental terms. A suitable model for analyzing and visualizing smart grid use cases in a technology-neutral manner is required. This paper presents a flexible architecture for the potential implementation of electromobility as a distributed storage asset for the grid’s capacity optimization by applying the Use Case and Smart Grid Architecture Model (SGAM) methodologies. The use case scenario of booking a charge session through a mobile application, as part of the TwinERGY Horizon 2020 project, is deployed to structure the SGAM framework layers and investigate the applicability of the SGAM framework in the integration of electromobility as a distributed storage asset into electricity grids with the objective of enhanced flexibility and decarbonization. Full article

(This article belongs to the Special Issue Integration of Renewable Energy and Plug-In Electric Vehicles into Power Networks)

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21 pages, 8201 KiB

Open AccessArticle

Application of Miller Cycle and Net-Zero Fuel(s) to Diesel Engine: Effect on the Performance and NOx Emissions of a Single-Cylinder Engine

by Motong Yang and Yaodong Wang

Energies 2023, 16(5), 2488; https://doi.org/10.3390/en16052488 - 6 Mar 2023

Cited by 2 | Viewed by 3576

Abstract

Diesel engines play a very significant role in the automotive industry, but the total emissions of diesel engines are more than 1.8 times that of petrol engines. It is therefore important for diesel engines to control emissions. Theoretically, the Miller cycle can be [...] Read more.

Diesel engines play a very significant role in the automotive industry, but the total emissions of diesel engines are more than 1.8 times that of petrol engines. It is therefore important for diesel engines to control emissions. Theoretically, the Miller cycle can be used to achieve NOx reductions by changing the effective compression ratio, while it has become increasingly popular in recent years with the increasing maturity of current turbocharging technology. Based on Ricardo WAVE software, this paper analyses the NOx emissions and engine performance of diesel engines by modelling and simulating their operation under different loads with two types of Miller cycles (EIVC and LIVC) at different degrees. Simulation of engines operating under different loads allows a more comprehensive study of the effects of the Miller cycle on the engine, and a specific analysis in the context of the actual engine operating environment. The result is that both versions of the Miller cycle are most effective in reducing NOx emissions at 10% load, showing a maximum reduction of 21% for EIVC and 37% for LIVC. However, as the Miller cycle decreases engine power, the paper further investigates the application of turbocharger systems in the EIVC Miller cycle, with results showing a 32% increase in brake power at 10% load and −25% EIVC Miller cycle degree. Both ethanol-fueled diesel-cycle and Miller cycle engines were also analyzed, and a reduction in NOx emissions was observed, as well as hydrogen engine performance and NOx emissions. Full article

(This article belongs to the Special Issue 100% Clean, Renewable Energy and Storage Solutions to Air Pollution and Global Warming)

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24 pages, 2876 KiB

Open AccessArticle

An Energy-Efficient Data Aggregation Clustering Algorithm for Wireless Sensor Networks Using Hybrid PSO

by Sharmin Sharmin, Ismail Ahmedy and Rafidah Md Noor

Energies 2023, 16(5), 2487; https://doi.org/10.3390/en16052487 - 6 Mar 2023

Cited by 32 | Viewed by 4358

Abstract

Extending the lifetime of wireless sensor networks (WSNs) and minimizing energy costs are the two most significant concerns for data transmission. Sensor nodes are powered by their own battery capacity, allowing them to perform critical tasks and interact with other nodes. The quantity [...] Read more.

Extending the lifetime of wireless sensor networks (WSNs) and minimizing energy costs are the two most significant concerns for data transmission. Sensor nodes are powered by their own battery capacity, allowing them to perform critical tasks and interact with other nodes. The quantity of electricity saved from each sensor together in a WSN has been strongly linked to the network’s longevity. Clustering conserves the most power in wireless transmission, but the absence of a mechanism for selecting the most suitable cluster head (CH) node increases the complexity of data collection and the power usage of the sensor nodes. Additionally, the disparity in energy consumption can lead to the premature demise of nodes, reducing the network’s lifetime. Metaheuristics are used to solve non-deterministic polynomial (NP) lossy clustering problems. The primary purpose of this research is to enhance the energy efficiency and network endurance of WSNs. To address this issue, this work proposes a solution where hybrid particle swarm optimization (HPSO) is paired with improved low-energy adaptive clustering hierarchy (HPSO-ILEACH) for CH selection in cases of data aggregation in order to increase energy efficiency and maximize the network stability of the WSN. In this approach, HPSO determines the CH, the distance between the cluster’s member nodes, and the residual energy of the nodes. Then, ILEACH is used to minimize energy expenditure during the clustering process by adjusting the CH. Finally, the HPSO-ILEACH algorithm was successfully implemented for aggregating data and saving energy, and its performance was compared with three other algorithms: low energy-adaptive clustering hierarchy (LEACH), improved low energy adaptive clustering hierarchy (ILEACH), and enhanced PSO-LEACH (ESO-LEACH). The results of the simulation studies show that HPSO-ILEACH increased the network lifetime, with an average of 55% of nodes staying alive, while reducing energy consumption average by 28% compared to the other mentioned techniques. Full article

(This article belongs to the Special Issue Empowering Future Generation Smart Grid Using Electric Vehicles (EV))

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20 pages, 6071 KiB

Open AccessArticle

Federated-Learning-Based Energy-Efficient Load Balancing for UAV-Enabled MEC System in Vehicular Networks

by Ayoung Shin and Yujin Lim

Energies 2023, 16(5), 2486; https://doi.org/10.3390/en16052486 - 6 Mar 2023

Cited by 6 | Viewed by 2288

Abstract

At present, with the intelligence that has been achieved in computer and communication technologies, vehicles can provide many convenient functions to users. However, it is difficult for a vehicle to deal with computationally intensive and latency-sensitive tasks occurring in the vehicle environment by [...] Read more.

At present, with the intelligence that has been achieved in computer and communication technologies, vehicles can provide many convenient functions to users. However, it is difficult for a vehicle to deal with computationally intensive and latency-sensitive tasks occurring in the vehicle environment by itself. To this end, mobile edge computing (MEC) services have emerged. However, MEC servers (MECSs), which are fixed on the ground, cannot flexibly respond to temporal dynamics where tasks are temporarily increasing, such as commuting time. Therefore, research has examined the provision of edge services using additional unmanned aerial vehicles (UAV) with mobility. Since these UAVs have limited energy and computing power, it is more important to optimize energy efficiency through load balancing than it is for ground MEC servers (MECSs). Moreover, if only certain servers run out of energy, the service coverage of a MEC server (MECS) may be limited. Therefore, all UAV MEC servers (UAV MECSs) need to use energy evenly. Further, in a high-mobility vehicle environment, it is necessary to have effective task migration because the UAV MECS that provides services to the vehicle changes rapidly. Therefore, in this paper, a federated deep Q-network (DQN)-based task migration strategy that considers the load deviation and energy deviation among UAV MECSs is proposed. DQN is used to create a local model for migration optimization for each of the UAV MECSs, and federated learning creates a more effective global model based on the fact that it has common spatial features between adjacent regions. To evaluate the performance of the proposed strategy, the performance is analyzed in terms of delay constraint satisfaction, load deviation, and energy deviation. Full article

(This article belongs to the Section F2: Distributed Energy System)

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20 pages, 1445 KiB

Open AccessArticle

Clustering Electrical Customers with Source Power and Aggregation Constraints: A Reliability-Based Approach in Power Distribution Systems

by Thiago Eliandro de Oliveira Gomes, André Ross Borniatti, Vinícius Jacques Garcia, Laura Lisiane Callai dos Santos, Nelson Knak Neto and Rui Anderson Ferrarezi Garcia

Energies 2023, 16(5), 2485; https://doi.org/10.3390/en16052485 - 5 Mar 2023

Cited by 1 | Viewed by 1792

Abstract

Reliability is an important issue in electricity distribution systems, with strict regulatory policies and investments needed to improve it. This paper presents a mixed integer linear programming (MILP) model for clustering electrical customers, maximizing system reliability and minimizing outage costs. However, the evaluation [...] Read more.

Reliability is an important issue in electricity distribution systems, with strict regulatory policies and investments needed to improve it. This paper presents a mixed integer linear programming (MILP) model for clustering electrical customers, maximizing system reliability and minimizing outage costs. However, the evaluation of reliability and its corresponding nonlinear function represent a significant challenge, making the use of mathematical programming models difficult. The proposed heuristic procedure overcomes this challenge by using a linear formulation of reliability indicators and incorporating them into the MILP model for clustering electrical customers. The model is mainly defined on a density-based heuristic that constrains the set of possible medians, thus dealing with the combinatorial complexity associated with the problem of empowered p-medians. The proposed model proved to be effective in improving the reliability of real electrical distribution systems and reducing compensation costs. Three substation cluster scenarios were explored, in which the total utility compensations were reduced by approximately USD 86,000 (1.80%), USD 67,400 (1.41%), and USD 64,000 (1.3%). The solutions suggest a direct relationship between the reduction in the compensation costs and the system reliability. In addition, the alternative modeling approach to the problem served to match the performance between the distribution system reliability indicators. Full article

(This article belongs to the Special Issue Power Quality in Smart Grids: Advanced Technology for System Regulation and Analysis)

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18 pages, 727 KiB

Open AccessArticle

Application of Variable-Order Fractional Calculus to the Modeling of Calendar Aging in Lithium-Ion Batteries

by Juan Antonio López-Villanueva, Pablo Rodríguez-Iturriaga, Luis Parrilla and Salvador Rodríguez-Bolívar

Energies 2023, 16(5), 2484; https://doi.org/10.3390/en16052484 - 5 Mar 2023

Cited by 4 | Viewed by 1890

Abstract

Battery aging is one of the key challenges that electrochemical energy storage faces. Models for both cycling and calendar aging are valuable for quantitatively assessing their contribution to overall capacity loss. Since batteries are stored and employed under varying conditions of temperature and [...] Read more.

Battery aging is one of the key challenges that electrochemical energy storage faces. Models for both cycling and calendar aging are valuable for quantitatively assessing their contribution to overall capacity loss. Since batteries are stored and employed under varying conditions of temperature and state of charge in their real-life operation, the availability of a suitable model to anticipate the outcome of calendar aging in lithium-ion batteries under dynamic conditions is of great interest. In this article, we extend a novel model to predict the capacity loss due to calendar aging by using variable-order fractional calculus. For this purpose, some theoretical difficulties posed by variable-order definitions are discussed and compared by applying them to fit experimental results with a multi-parameter optimization procedure. We show that employing a variable-order model allows for a significant improvement in accuracy and predictive ability with respect to its constant-order counterpart. We conclude that variable-order models constitute an interesting alternative for reproducing complex behavior in dynamical systems, such as aging in lithium-ion batteries. Full article

(This article belongs to the Special Issue Advances in Devices for Energy Generation and Storage)

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16 pages, 3337 KiB

Open AccessArticle

Hydrothermal Carbonization of Sewage Sludge into Solid Biofuel: Influences of Process Conditions on the Energetic Properties of Hydrochar

by Siti Zaharah Roslan, Siti Fairuz Zainudin, Alijah Mohd Aris, Khor Bee Chin, Mohibah Musa, Ahmad Rafizan Mohamad Daud and Syed Shatir A. Syed Hassan

Energies 2023, 16(5), 2483; https://doi.org/10.3390/en16052483 - 5 Mar 2023

Cited by 13 | Viewed by 3190

Abstract

Hydrothermal carbonization (HTC) is an attractive, green technology for the management of sewage sludge. In this study, low-value secondary sewage sludge was subjected to an HTC treatment in a 1 L batch hydrothermal reactor and transformed into a high-energy-density hydrochar under varying HTC [...] Read more.

Hydrothermal carbonization (HTC) is an attractive, green technology for the management of sewage sludge. In this study, low-value secondary sewage sludge was subjected to an HTC treatment in a 1 L batch hydrothermal reactor and transformed into a high-energy-density hydrochar under varying HTC conditions (temperature of 150–300 °C, carbonization time of 30–150 min and a solid loading of 10–30%). The resulting hydrochar fuel characteristics were analyzed for ultimate and proximate analyses, functional group composition and energetic parameters. It was found that the hydrochar yield decreased with the increasing HTC temperature and reaction time, primarily due to the loss of organic volatile matter and functional groups. Under the optimum conditions of 150 °C, 30 min of carbonization time and 30% solid loading, 80.56% of the hydrochar was recovered, providing a maximum energy yield of 90.32% and a high heating value of 18.49 MJ/kg. Compared to the raw sewage sludge (H/C ratio of 2.67 and O/C ratio of 0.51), the hydrochar also had lower H/C and O/C atomic ratios of 1.42 and 0.18, respectively. The results suggest that significant dehydration and decarboxylation during the HTC treatment of sewage sludge have resulted in the formation of carbonaceous hydrochar with energetic properties close to the sub-bituminous coals. Full article

(This article belongs to the Special Issue Bioprocessing Technologies for Biofuel Production)

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15 pages, 4380 KiB

Open AccessArticle

Thermal Performance of Slotted Light Steel-Framed Composite Wall

by Zhijian Yang, Lisuo Sun, Bo Nan and Shunli Wei

Energies 2023, 16(5), 2482; https://doi.org/10.3390/en16052482 - 5 Mar 2023

Cited by 4 | Viewed by 1948

Abstract

In this study, calibrated hot box and finite element simulation methods were used to study the influence of a slotted web on the thermal performance of a lightweight steel stud composite wall. By comparing the results from the simulations and experiments, the accuracy [...] Read more.

In this study, calibrated hot box and finite element simulation methods were used to study the influence of a slotted web on the thermal performance of a lightweight steel stud composite wall. By comparing the results from the simulations and experiments, the accuracy of the finite element method was verified; this method was then used for parameter analyses. The results showed that the wall’s thermal transfer coefficient is inversely proportional to increases in the length of the slot and height of the stud web, leading to improvements in the thermal insulation effect; vice versa, the wall thermal transfer coefficient increases when the slot transverse spacing and stud thickness increase, and the insulation effect correspondingly worsens. The stud spacing influences the insulation performance of the wall by changing the proportion of studs within a certain wall. The greater the proportion of studs, the greater the stud thermal bridging, the faster the thermal loss, and the worse the insulation effect of the wall. In practice, the height of the stud web can be set as required. Preferably, for practical applications, the number of rows of slots is 5–7, the length of the slots is 70–80 mm, the transverse distance of the slots is 6–8 mm, the thickness of each stud is 1 or 1.2 mm, and the distance of each stud is 600 mm. Full article

(This article belongs to the Section G: Energy and Buildings)

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19 pages, 6985 KiB

Open AccessArticle

Discrete-Time Sliding Mode Current Control for a Seven-Level Cascade H-Bridge Converter

by Leonardo Comparatore, Magno Ayala, Yassine Kali, Jorge Rodas, Julio Pacher, Alfredo Renault and Raúl Gregor

Energies 2023, 16(5), 2481; https://doi.org/10.3390/en16052481 - 5 Mar 2023

Cited by 1 | Viewed by 2150

Abstract

This paper deals with the implementation and performance analysis of discrete-time sliding mode (DTSM) current control applied to a seven-level cascade H-bridge converter to track three-phase reference currents for a reactive load. The converter output voltages are synthesized using a modulation scheme based [...] Read more.

This paper deals with the implementation and performance analysis of discrete-time sliding mode (DTSM) current control applied to a seven-level cascade H-bridge converter to track three-phase reference currents for a reactive load. The converter output voltages are synthesized using a modulation scheme based on phase-shifted carrier modulation. Simulation and experimental tests have been added to demonstrate the performance of the proposed controller. At the same time, the effectiveness of the DTSM is verified under transient and steady-state conditions, respectively, by measuring the total harmonic distortion and the mean square error. Full article

(This article belongs to the Section F3: Power Electronics)

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22 pages, 1862 KiB

Open AccessArticle

A Hyper-Integrated Mobility as a Service (MaaS) to Gamification and Carbon Market Enterprise Architecture Framework for Sustainable Environment

by Alper Ozpinar

Energies 2023, 16(5), 2480; https://doi.org/10.3390/en16052480 - 5 Mar 2023

Cited by 3 | Viewed by 3862

Abstract

Various human activities emit greenhouse gasses (GHGs) that contribute to global climate change. These include the burning of fossil fuels for energy production, transportation, and industrial uses, and the clearing of forests to create farmland and pasture, all for urban and industrial development. [...] Read more.

Various human activities emit greenhouse gasses (GHGs) that contribute to global climate change. These include the burning of fossil fuels for energy production, transportation, and industrial uses, and the clearing of forests to create farmland and pasture, all for urban and industrial development. As a result, temperatures around the world are rising, extreme weather events are occurring more frequently, and human health is suffering because of these changes. As a result of massive traffic, agriculture, and urbanization, the natural environment is being destroyed, negatively affecting humans and other living things. Humanity plans to live in smart cities within this ecosystem as the world evolves around these mutations. A smart city uses technology and data to improve the quality of life of its citizens and the efficiency of its urban systems. Smart cities have the potential to be more sustainable because they use technology and data to improve the efficiency of urban systems and reduce the negative impact of human activities on the environment. Smart cities can also use technology to improve green transportation and waste management and reduce water consumption, which can help conserve natural resources and protect the environment. Smart cities can create livable, efficient, and sustainable urban environments using technology and data. This paper presents a new Enterprise Architecture Framework for reducing carbon emissions for environmental sustainability that combines gamification and green behavior with blockchain architecture to ensure a system that is trustworthy, secure, and scalable for shareholders, citizens, service providers, and technology vendors. In order to achieve this, the hyper-integrated framework approach explains a roadmap for how sustainability for reducing carbon emissions from transportation is based on an optimized MaaS approach improved by gamification. As part of this study, a computational model and a formulation are proposed to calculate the activity exchange values in the MaaS ecosystem for swapping, changing, and bartering for assets within the integrated system. This paper aims to propose the framework and a module interoperability approach, so numerical values for computation parameters are not included as they may belong to other research studies. In spite of this, a case study section has been provided as an example of a calculation approach. Full article

(This article belongs to the Topic Energy Management and Sustainable Development from Economic, Social and Environmental Aspects)

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12 pages, 3604 KiB

Open AccessArticle

Study on Nonlinear Dielectric Properties of Micro Silica

by Yucui Xue, Wenmin Guo, Yunlong Sun, Zhonghua Li, Yongsen Han and Hongxu Jia

Energies 2023, 16(5), 2479; https://doi.org/10.3390/en16052479 - 5 Mar 2023

Cited by 1 | Viewed by 1799

Abstract

Inorganic insulating powder can potentially be used in nuclear power plant cables, fire-resistant cables, and so on due to its high heat resistance and radiation resistance. It is of great academic and engineering value to study the dielectric properties of inorganic insulating powder. [...] Read more.

Inorganic insulating powder can potentially be used in nuclear power plant cables, fire-resistant cables, and so on due to its high heat resistance and radiation resistance. It is of great academic and engineering value to study the dielectric properties of inorganic insulating powder. In this paper, we aim to study the nonlinear dielectric properties via the measurement of the time-domain polarization current spectrum under the application of a DC electric field. Three kinds of silica powders are measured by a measurement system with adjustable pressure. The effects of powder shape, particle size, and packing pressure and temperature on the dependence of relaxation polarization and electrical conductivity on the applied electric field are studied. The experimental results show that the relationship between electrical conductivity and the electric field of inorganic insulating powder presents two different characteristics, i.e., field-induced enhancement and field-induced weakening. The relationship between conductance and temperature shows an increase with temperature. That is, the electrical conductivity increases or decreases with the increase in temperature. The inorganic powder insulation can be regarded as a composite, which is composed of inorganic powder particles and air gaps. The interface between the powder particles and air gaps contributes a lot to the polarization of inorganic insulating powder. The phenomena (including the field-induced weakening characteristic between relaxation polarization and electric field and the decrease characteristic of polarization with increasing temperature) can be explained by a simplified interface polarization mechanism. Full article

(This article belongs to the Special Issue Recent Developments in Theories, Technologies and Applications of HVDC Insulation Systems)

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