Records Added in February 2019
Records added in February 2019
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Showing records 26 to 50 of 179. [First] Page: 1 2 3 4 5 6 Last
Decoupling Design and Verification of a Free-Piston Linear Generator
Peng Sun, Chi Zhang, Jinhua Chen, Fei Zhao, Youyong Liao, Guilin Yang, Chinyin Chen
February 27, 2019 (v1)
Keywords: decoupling design, free-piston, linear generator, power and efficiency distribution
This paper proposes a decoupling design approach for a free-piston linear generator (FPLG) constituted of three key components, including a combustion chamber, a linear generator and a gas spring serving as rebounding device. The approach is based on the distribution of the system power and efficiency, which provides a theoretical design method from the viewpoint of the overall power and efficiency demands. The energy flow and conversion processes of the FPLG are analyzed, and the power and efficiency demands of the thermal-mechanical and mechanical-electrical energy conversion are confirmed. The energy and efficiency distributions of the expansion and compression strokes within a single stable operation cycle are analyzed and determined. Detailed design methodologies of crucial geometric dimensions and operational parameters of each key component are described. The feasibility of the proposed decoupling design approach is validated through several design examples with different output... [more]
Green Small Cell Operation of Ultra-Dense Networks Using Device Assistance
Gilsoo Lee, Hongseok Kim
February 27, 2019 (v1)
Keywords: belief propagation, cellular networks, Energy Efficiency, Optimization, small cell
As higher performance is demanded in 5G networks, energy consumption in wireless networks increases along with the advances of various technologies, so enhancing energy efficiency also becomes an important goal to implement 5G wireless networks. In this paper, we study the energy efficiency maximization problem focused on finding a suitable set of turned-on small cell access points (APs). Finding the suitable on/off states of APs is challenging since the APs can be deployed by users while centralized network planning is not always possible. Therefore, when APs in small cells are randomly deployed and thus redundant in many cases, a mechanism of dynamic AP turning-on/off is required. We propose a device-assisted framework that exploits feedback messages from the user equipment (UE). To solve the problem, we apply an optimization method using belief propagation (BP) on a factor graph. Then, we propose a family of online algorithms inspired by BP, called DANCE, that requires low computati... [more]
Fault-Ride through Strategy for Permanent-Magnet Synchronous Generators in Variable-Speed Wind Turbines
Mohamed Abdelrahem, Ralph Kennel
February 27, 2019 (v1)
Keywords: fault-ride through, Model Predictive Control, permanent-magnet synchronous generator, wind turbine
Currently, the electric power production by wind energy conversion systems (WECSs) has increased significantly. Consequently, wind turbine (WT) generators are requested to fulfill the grid code (GC) requirements stated by network operators. In case of grid faults/voltage dips, a mismatch between the generated active power from the wind generator and the active power delivered to the grid is produced. The conventional approach is using a braking chopper (BC) in the DC-link to dissipate this active power. This paper proposes a fault-ride through (FRT) strategy for variable-speed WECSs based on permanent magnet synchronous generators (PMSGs). The proposed strategy exploits the rotor inertia of the WECS (inertia of the WT and PMSG) to store the surplus active power during the grid faults/voltage dips. Thus, no additional hardware components are requested. Furthermore, a direct model predictive control (DMPC) scheme for the PMSG is proposed in order to enhance the dynamic behavior of the WE... [more]
Realistic Quantum Control of Energy Transfer in Photosynthetic Processes
Reda M. El-Shishtawy, Robert Haddon, Saleh Al-Heniti, Bahaaudin Raffah, Sayed Abdel-Khalek, Kamal Berrada, Yas Al-Hadeethi
February 27, 2019 (v1)
Keywords: dipole-dipole interaction, energy transfer, quantum correlations, quantum effects in biology, time-dependent coupling effect
The occurrence of coherence phenomenon as a result of the interference of the probability amplitude terms is among the principle features of quantum mechanics concepts. Current experiments display the presence of quantum techniques whose coherence is supplied over large interval times. Specifically, photosynthetic mechanisms in light-harvesting complexes furnish oscillatory behaviors owing to quantum coherence. In this manuscript, we study the coherent quantum energy transfer for a single-excitation and nonlocal correlation in a dimer system (donor+acceptor) displayed by two-level systems (TLSs), interacting with a cavity field with a time-dependent coupling effect considering the realistic situation of coupling between each TLS and the cavity field. We analyze and explore the specific conditions which are viable with real experimental realization for the ultimate transfer of quantum energy and nonlocal quantum correlation. We show that the enhancement of the probability for a single-e... [more]
AC Voltage Control of DC/DC Converters Based on Modular Multilevel Converters in Multi-Terminal High-Voltage Direct Current Transmission Systems
Rui Li, John E. Fletcher
February 27, 2019 (v1)
Keywords: AC voltage control, DC fault protection, DC/DC converter, modular multilevel converter (MMC), multi-terminal high-voltage direct current (HVDC) system
The AC voltage control of a DC/DC converter based on the modular multilevel converter (MMC) is considered under normal operation and during a local DC fault. By actively setting the AC voltage according to the two DC voltages of the DC/DC converter, the modulation index can be near unity, and the DC voltage is effectively utilized to output higher AC voltage. This significantly decreases submodule (SM) capacitance and conduction losses of the DC/DC converter, yielding reduced capital cost, volume, and higher efficiency. Additionally, the AC voltage is limited in the controllable range of both the MMCs in the DC/DC converter; thus, over-modulation and uncontrolled currents are actively avoided. The AC voltage control of the DC/DC converter during local DC faults, i.e., standby operation, is also proposed, where only the MMC connected on the faulty cable is blocked, while the other MMC remains operational with zero AC voltage output. Thus, the capacitor voltages can be regulated at the r... [more]
An Analysis Based on SD Model for Energy-Related CO₂ Mitigation in the Chinese Household Sector
Xingpeng Chen, Guokui Wang, Xiaojia Guo, Jinxiu Fu
February 27, 2019 (v1)
Keywords: CO2 emissions, household sector, system dynamics
Reducing carbon dioxide (CO₂) emissions has become a global consensus in response to global warming and climate change, especially to China, the largest CO₂ emitter in the world. Most studies have focused on CO₂ emissions from the production sector, however, the household sector plays an important role in the total energy-related CO₂ emissions. This study formulates an integrated model based on logarithmic mean Divisia index methodology and a system dynamics model to dynamically simulate household energy consumption and CO₂ emissions under different conditions. Results show the following: (1) the integrated model performs well in calculating the contribution of influencing factors on household CO₂ emissions and analyzing the options for CO₂ emission mitigation; (2) the increase in income is the dominant driving force of household CO₂ emissions, and as a result of the improved standard of living in China a sustained increase in household CO₂ emissions can be expected; (3) with decreasin... [more]
Classification of Gene Expression Data Using Multiobjective Differential Evolution
Shijing Ma, Xiangtao Li, Yunhe Wang
February 27, 2019 (v1)
Keywords: binary differential evolution, binary optimization, differential evolution algorithm, multiobjective method
Gene expression data are usually redundant, and only a subset of them presents distinct profiles for different classes of samples. Thus, selecting high discriminative genes from gene expression data has become increasingly interesting in bioinformatics. In this paper, a multiobjective binary differential evolution method (MOBDE) is proposed to select a small subset of informative genes relevant to the classification. In the proposed method, firstly, the Fisher-Markov selector is used to choose top features of gene expression data. Secondly, to make differential evolution suitable for the binary problem, a novel binary mutation method is proposed to balance the exploration and exploitation ability. Thirdly, the multiobjective binary differential evolution is proposed by integrating the summation of normalized objectives and diversity selection into the binary differential evolution algorithm. Finally, the MOBDE algorithm is used for feature selection, and support vector machine (SVM) is... [more]
Project Management for a Wind Turbine Construction by Applying Fuzzy Multiple Objective Linear Programming Models
He-Yau Kang, Amy H. I. Lee, Tzu-Ting Huang
February 27, 2019 (v1)
Subject: Energy Policy
Keywords: fuzzy multiple objective linear programming (FMOLP), program evaluation and review technique (PERT), project management, Renewable and Sustainable Energy, wind turbine
Meeting the demand of energy is a challenge for many countries these days, and generating electricity from renewable resources has become a main trend for future economic development. The construction of a renewable energy plant is costly and timely; therefore, a good project management model is essential. In this paper, a fuzzy multiple objective linear programming (FMOLP) model is constructed based on program evaluation and review technique (PERT) first. With the consideration of the different degrees of importance of the multiple objectives, a fuzzy multiple weighted-objective linear programming (FMWOLP) model is constructed next. Through each proposed model, a compromise solution can be devised to maximize the total degree of satisfaction while considering multiple objectives. The results can provide references for the management on what activities and how long these activities should be crashed, how much the total project cost should be, and how long the total project duration tim... [more]
Multi-Attribute Technological Modeling of Coal Deposits Based on the Fuzzy TOPSIS and C-Mean Clustering Algorithms
Miloš Gligorić, Zoran Gligorić, Čedomir Beljić, Slavko Torbica, Svetlana Štrbac Savić, Jasmina Nedeljković Ostojić
February 27, 2019 (v1)
Keywords: adjusted Rand index, block model, coal deposit, entropy, Fukuyama-Sugeno validity functional, fuzzy C-mean clustering, fuzzy TOPSIS, technological model
The main aim of a coal deposit model is to provide an effective basis for mine production planning. The most applied approach is related to block modeling as a reasonable global representation of the coal deposit. By selection of adequate block size, deposits can be well represented. A block has a location in XYZ space and is characterized by adequate attributes obtained from drill holes data. From a technological point of view, i.e., a thermal power plant’s requirements, heating value, sulfur and ash content are the most important attributes of coal. Distribution of attributes’ values within a coal deposit can vary significantly over space and within each block as well. To decrease the uncertainty of attributes’ values within blocks the concept of fuzzy triangular numbers is applied. Production planning in such an environment is a very hard task, especially in the presence of requirements. Such requirements are considered as target values while the values of block attributes are the a... [more]
Energy Conversion: A Comparison of Fix- and Self-Referenced Wave Energy Converters
Wanan Sheng, Tony Lewis
February 27, 2019 (v1)
Keywords: oscillating water column, point absorber, power take-off optimization, wave energy converter, WEC deployment
The paper presents an investigation of fix-referenced and self-referenced wave energy converters and a comparison of their corresponding wave energy conversion capacities from real seas. For conducting the comparisons, two popular wave energy converters, point absorber and oscillating water column, and their power conversion capacities in the fixed-referenced and self-referenced forms have been numerically studied and compared. In the numerical models, the device’s power extractions from seas are maximized using the correspondingly optimized power take-offs in different sea states, thus their power conversion capacities can be calculated and compared. From the comparisons and analyses, it is shown that the energy conversion capacities of the self-referenced devices can be significantly increased if the motions of the device itself can be utilized for wave energy conversion; and the self-referenced devices can be possibly designed to be compliant in long waves, which could be a very ben... [more]
Adaptive Droop Control for Microgrids Based on the Synergetic Control of Multi-Agent Systems
Zhiwen Yu, Qian Ai, Xing He, Longjian Piao
February 27, 2019 (v1)
Keywords: adaptive droop control, globally asymptotical stability, microgrid, multi-agent system, time-delays
In this paper, a distributed synergetic control based on multi-agent systems is proposed to solve the problems of frequency and voltage errors, system stability and power sharing accuracy in the traditional droop control of microgrids. Starting with power flow equations, we build the secondary-order dynamic model of DG, which consists of three parts: (1) active power allocation; (2) active power-frequency; and (3) reactive power-voltage droop control. Considering time-delays in communication networks, a leaderless synergetic control algorithm is proposed to allocate the active power in inverse proportion to the droop coefficient, and the synergetic control with a virtual leader is proposed to control the system frequency and voltage to keep at the expected value. Besides, the direct Lyapunov method is introduced to verify the globally asymptotical stability. Moreover, the impacts of communication disturbance are also discussed from the aspects of control precision and system stability.... [more]
Design, Modeling and Control of Magnetic Bearings for a Ring-Type Flywheel Energy Storage System
Chow-Shing Toh, Shyh-Leh Chen
February 27, 2019 (v1)
Keywords: flywheel battery, Halbach array, magnetic bearing, nonlinear control
This study is concerned with the magnetic force models of magnetic bearing in a flywheel energy storage system (FESS). The magnetic bearing is of hybrid type, with axial passive magnetic bearing (PMB) and radial hybrid magnetic bearing (HMB). For the PMB, a pair of ring-type Halbach arrays of permanent magnets are arranged vertically to support the rotor weight. For the HMB, a set of ring-type Halbach array is placed on the rotor side, which corresponds to coil sets on the stator side. The HMB can produce both attraction and repulsion forces on the radial direction, depending on the direction of the coil currents. It is found that the ring-type configuration and the differential winding scheme for coil sets can yield linear magnetic force models for both PMB and HMB. Based on the obtained magnetic force model, an integral sliding mode controller is designed for the stable rotor levitation in the radial direction. The experimental results show that the rotor can be stabilized to the bea... [more]
Membrane Permeability Rates of Vanadium Ions and Their Effects on Temperature Variation in Vanadium Redox Batteries
Liuyue Cao, Anders Kronander, Ao Tang, Da-Wei Wang, Maria Skyllas-Kazacos
February 27, 2019 (v1)
Subject: Materials
Keywords: capacity, crossover, diffusion, ion exchange membrane, permeability rates, side reactions, vanadium redox flow batteries (VRFBs)
The inevitable diffusion of vanadium ions across the membrane can cause considerable capacity loss and temperature increase in vanadium redox flow batteries (VRFBs) over long term operation. Reliable experimental data of the permeability rates of vanadium ions are needed for membrane selection and for use in mathematical models to predict long-term behavior. In this paper a number of ion exchange membranes were selected for detailed evaluation using a modified approach to obtain more accurate permeation rates of V2+, V3+, VO2+ and VO₂⁺ ions. Three commercial ion exchange membranes—FAP450, VB2 and F930—are investigated. The obtained diffusion coefficients are then employed in dynamic models to predict the thermal behavior under specific operating conditions. The simulation results prove that smaller and more balanced permeability rates of V2+ and VO₂⁺ ions are more important to avoid large temperature increases in the cell stack during stand-by periods at high states-of-charge with pump... [more]
Evaluation of Strategies to Improve the Thermal Performance of Steel Frames in Curtain Wall Systems
Ji Hyun Oh, Hyun Jung Yoo, Sun Sook Kim
February 27, 2019 (v1)
Keywords: curtain wall, hot-box test, steel frame, thermal transmittance, U-value
Recently, metal curtain wall systems have been widely used in high-rise buildings due to many advantages, including being lightweight, rapid construction, and aesthetic features. Since the metal frame may lead to lower energy performance, thermal discomfort, and condensation risk due to the high thermal conductivity, its thermal performance can be important for the improvement of the overall thermal performance of the curtain wall system, as well as the energy efficiency of the building envelope. This study aims to evaluate variety of design strategies to improve the thermal performance of steel curtain wall frames. Five base cases and three further steps were selected for two different head profile shapes based on a state-of-the art technology review, and their thermal transmittances were calculated through simulations according to the ISO 12631 standard which is an international standard for calculating thermal transmittance of curtain wall system. Measured results that were obtained... [more]
Supporting Renewables’ Penetration in Remote Areas through the Transformation of Non-Powered Dams
Thomas Patsialis, Ioannis Kougias, Nerantzis Kazakis, Nicolaos Theodossiou, Peter Droege
February 27, 2019 (v1)
Subject: Energy Policy
Keywords: energy autarky, remote areas’ electrification, renewable energy sources (RES) penetration, small-scale hydropower (SHP), solar photovoltaic systems (SPVS)
Supplying power to remote areas may be a challenge, even for those communities already connected to the main grid. Power is often transmitted from long distances, under adverse weather conditions, and with aged equipment. As a rule, modernizing grid infrastructure in such areas to make it more resilient faces certain financial limitations. Local distribution may face stability issues and disruptions through the year and—equally important—it cannot absorb significant amounts of locally-produced power. The European policy has underlined the importance of energy production in local level towards meeting energy security and climate targets. However, the current status of these areas makes the utilization of the local potential prohibitive. This study builds on the observation that in the vicinity of such mountainous areas, irrigation dams often cover different non energy-related needs (e.g., irrigation, drinking water). Transforming these dams to small-scale hydropower (SHP) facilities can... [more]
Profitability Variations of a Solar System with an Evacuated Tube Collector According to Schedules and Frequency of Hot Water Demand
Carlos J. Porras-Prieto, Susana Benedicto-Schönemann, Fernando R. Mazarrón, Rosa M. Benavente
February 27, 2019 (v1)
Keywords: active solar water-heating system, evacuated-tube collector, hot water, profitability, schedule of demand
The use of solar water heating systems with evacuated tube collectors has been experiencing a rapid growth in recent years. Times when there is demand for hot water, the days of use and the volumes demanded may determine the profitability of these systems, even within the same city. Therefore, this paper characterizes the behavior of a solar system with active circulation with the objective of determining the profitability variations according to the timing and schedule of demand. Through a simplified methodology based on regression equations, calculated for each hour of the day based on data from an experimental facility, the useful energy is estimated from the time and frequency of the demand for hot water at 60 °C. The analysis of the potential profitability of the system in more than 1000 scenarios analyzed shows huge differences depending on the number of days when the water is demanded, the time when demand occurs, the irradiation and the average price of energy. In cities with h... [more]
Research and Application of a Hybrid Forecasting Model Based on Data Decomposition for Electrical Load Forecasting
Yuqi Dong, Xuejiao Ma, Chenchen Ma, Jianzhou Wang
February 27, 2019 (v1)
Keywords: data decomposition, electrical load forecasting, generalized regression neural network, Genetic Algorithm
Accurate short-term electrical load forecasting plays a pivotal role in the national economy and people’s livelihood through providing effective future plans and ensuring a reliable supply of sustainable electricity. Although considerable work has been done to select suitable models and optimize the model parameters to forecast the short-term electrical load, few models are built based on the characteristics of time series, which will have a great impact on the forecasting accuracy. For that reason, this paper proposes a hybrid model based on data decomposition considering periodicity, trend and randomness of the original electrical load time series data. Through preprocessing and analyzing the original time series, the generalized regression neural network optimized by genetic algorithm is used to forecast the short-term electrical load. The experimental results demonstrate that the proposed hybrid model can not only achieve a good fitting ability, but it can also approximate the actu... [more]
On the Reliability of Optimization Results for Trigeneration Systems in Buildings, in the Presence of Price Uncertainties and Erroneous Load Estimation
Antonio Piacentino, Roberto Gallea, Pietro Catrini, Fabio Cardona, Domenico Panno
February 27, 2019 (v1)
Keywords: buildings, cogeneration, energy loads, linear programming, Optimization, prices, sensitivity, stochastic, trigeneration, uncertainty
Cogeneration and trigeneration plants are widely recognized as promising technologies for increasing energy efficiency in buildings. However, their overall potential is scarcely exploited, due to the difficulties in achieving economic viability and the risk of investment related to uncertainties in future energy loads and prices. Several stochastic optimization models have been proposed in the literature to account for uncertainties, but these instruments share in a common reliance on user-defined probability functions for each stochastic parameter. Being such functions hard to predict, in this paper an analysis of the influence of erroneous estimation of the uncertain energy loads and prices on the optimal plant design and operation is proposed. With reference to a hotel building, a number of realistic scenarios is developed, exploring all the most frequent errors occurring in the estimation of energy loads and prices. Then, profit-oriented optimizations are performed for the examined... [more]
Comparison of Two Processes Forming CaCO₃ Precipitates by Electrolysis
Hyun Sic Park, JunYoung Han, Ju Sung Lee, Kwang-Mo Kim, Hyung Jun Jo, Byoung Ryul Min
February 27, 2019 (v1)
Keywords: CaCO3, electrolysis, mineral carbonation
As one of the carbon capture and utilization (CCU) technologies, mineral carbonation which has been introduced to reduce the carbon dioxide (CO₂) concentration in the atmosphere is a technology that makes it possible to capture CO₂ and recycle byproducts as resources. However, existing mineral carbonation requires additional energy and costs, as it entails high temperature and high pressure reaction conditions. This study compared two processes which electrolyze NaCl and CaCl₂ solution to produce CO₂ absorbent needed to generate CaCO₃, and which were conducted at room temperature and pressure unlike existing mineral carbonation. As a result, high-purity calcite was obtained through Process 1 using NaCl solution, and aragonite and portlandite were obtained in addition to calcite through Process 2 (two steps) using CaCl₂ solution.
Modeling and Forecasting Electricity Demand in Azerbaijan Using Cointegration Techniques
Fakhri J. Hasanov, Lester C. Hunt, Ceyhun I. Mikayilov
February 27, 2019 (v1)
Keywords: Azerbaijan electricity demand, cointegration and error correction models, forecast scenarios, time series analysis
Policymakers in developing and transitional economies require sound models to: (i) understand the drivers of rapidly growing energy consumption and (ii) produce forecasts of future energy demand. This paper attempts to model electricity demand in Azerbaijan and provide future forecast scenarios—as far as we are aware this is the first such attempt for Azerbaijan using a comprehensive modelling framework. Electricity consumption increased and decreased considerably in Azerbaijan from 1995 to 2013 (the period used for the empirical analysis)—it increased on average by about 4% per annum from 1995 to 2006 but decreased by about 4½% per annum from 2006 to 2010 and increased thereafter. It is therefore vital that Azerbaijani planners and policymakers understand what drives electricity demand and be able to forecast how it will grow in order to plan for future power production. However, modeling electricity demand for such a country has many challenges. Azerbaijan is rich in energy resources... [more]
Validation of Generic Models for Variable Speed Operation Wind Turbines Following the Recent Guidelines Issued by IEC 61400-27
Andrés Honrubia-Escribano, Francisco Jiménez-Buendía, Emilio Gómez-Lázaro, Jens Fortmann
February 27, 2019 (v1)
Keywords: doubly-fed induction machine (DFIG), full-scale converter (FSC), generic model, IEC 61400-27, model validation, power system stability, standard model
Considerable efforts are currently being made by several international working groups focused on the development of generic, also known as simplified or standard, wind turbine models for power system stability studies. In this sense, the first edition of International Electrotechnical Commission (IEC) 61400-27-1, which defines generic dynamic simulation models for wind turbines, was published in February 2015. Nevertheless, the correlations of the IEC generic models with respect to specific wind turbine manufacturer models are required by the wind power industry to validate the accuracy and corresponding usability of these standard models. The present work conducts the validation of the two topologies of variable speed wind turbines that present not only the largest market share, but also the most technological advances. Specifically, the doubly-fed induction machine and the full-scale converter (FSC) topology are modeled based on the IEC 61400-27-1 guidelines. The models are simulated... [more]
Structural Dynamic Analysis of Semi-Submersible Floating Vertical Axis Wind Turbines
Jeremiah Ishie, Kai Wang, Muk Chen Ong
February 27, 2019 (v1)
Keywords: coupled non-linear time domain simulation, fatigue analysis, finite element method, semi-submersible substructure, Simo-Riflex-DMS, structural dynamics, wind turbine
The strong and stable wind at offshore locations and the increasing demand for energy have made the application of wind turbines in deeper water surge. A novel concept of a 5 MW baseline Floating Vertical Axis Wind Turbine (FVAWT) and a 5 MW optimised FVAWT with the DeepWind Darrieus rotor and the optimised DeepWind Darrieus rotor, respectively, were studied extensively. The structural responses, fatigue damages, platform global motions and mooring line dynamics of the FVAWTs were investigated comprehensively during normal operating conditions under steady wind and turbulent wind conditions, using a coupled non-linear aero-hydro-servo-elastic code (the Simo-Riflex-DMS code) which was developed by Wang et al. for modeling FVAWTs. This coupled code incorporates the models for the turbulent wind field, aerodynamics, hydrodynamics, structural dynamics, and generator controller. The simulation is performed in a fully coupled manner in time domain. The comparison of responses under different... [more]
Experimental Study of 6LoPLC for Home Energy Management Systems
Augustine Ikpehai, Bamidele Adebisi, Khaled M. Rabie, Russell Haggar, Mike Baker
February 27, 2019 (v1)
Keywords: 6LoPLC, 6LoWPAN, home energy management system, impulsive noise, low-power PLC, low-rate PLC, smart micro-grid
Ubiquitous connectivity is already transforming residential dwellings into smart homes. As citizens continue to embrace the smart home paradigm, a new generation of low-rate and low-power communication systems is required to leverage the mass market presented by energy management in homes. Although Power Line Communication (PLC) technology has evolved in the last decade, the adaptation of PLC for constrained networks is not fully charted. By adapting some features of IEEE 802.15.4 and IPv6 over Low-power Wireless Personal Area Network (6LoWPAN) into power lines, this paper demonstrates a low-rate, low-power PLC system over the IPv6 network (referred to as 6LoPLC), for Home Energy Management System (HEMS) applications. The overall idea is to provide a framework for assessing various scenarios that cannot be easily investigated with the limited number of evaluation hardware available. In this respect, a network model is developed in NS-3 (Version 21) to measure several important characte... [more]
Modeling and Mitigation for High Frequency Switching Transients Due to Energization in Offshore Wind Farms
Yanli Xin, Bo Liu, Wenhu Tang, Qinghua Wu
February 27, 2019 (v1)
Keywords: high frequency (HF), offshore wind farm (OWF), overvoltage mitigation, prestrikes, switching transient, vacuum circuit breaker (VCB)
This paper presents a comprehensive investigation on high frequency (HF) switching transients due to energization of vacuum circuit breakers (VCBs) in offshore wind farms (OWFs). This research not only concerns the modeling of main components in collector grids of an OWF for transient analysis (including VCBs, wind turbine transformers (WTTs), submarine cables), but also compares the effectiveness between several mainstream switching overvoltage (SOV) protection methods and a new mitigation method called smart choke. In order to accurately reproduce such HF switching transients considering the current chopping, dielectric strength (DS) recovery capability and HF quenching capability of VCBs, three models are developed, i.e., a user⁻defined VCB model, a HF transformer terminal model and a three-core (TC) frequency dependent model of submarine cables, which are validated through simulations and compared with measurements. Based on the above models and a real OWF configuration, a simulati... [more]
Cold Storage for a Single-Family House in Italy
Luigi Mongibello, Giorgio Graditi
February 27, 2019 (v1)
Keywords: cold storage, cold water, economic analysis, PCM, Simulation, single-family house
This work deals with the operation, modeling, simulation, and cost evaluation of two different cold storage systems for a single-family house in Italy, that differ from one another on the cold storage material. The two materials used to perform the numerical simulations of the cold storage systems are represented by cold water and a phase change material (PCM), and the numerical simulations have been realized by means of numerical codes written in Matlab environment. The main finding of the present work is represented by the fact that, for the considered user characteristics, and under the Italian electricity tariff policy, the use of a proper designed cold storage system characterized by an effective operation strategy could represent a viable solution from an economical point of view.
Showing records 26 to 50 of 179. [First] Page: 1 2 3 4 5 6 Last
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