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Energies, Volume 9, Issue 7 (July 2016)

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Cover Story (view full-size image) A promising route for ensuring long-term energy and environmental security is by reducing the [...] Read more.
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Open AccessCorrection
Correction: Juan, A.A.; Mendez, C.A.; Faulin, J.; de Armas, J.; Grasman, S.E. Electric Vehicles in Logistics and Transportation: A Survey on Emerging Environmental, Strategic, and Operational Challenges. Energies 2016, 9, 86
Energies 2016, 9(7), 546; https://doi.org/10.3390/en9070546
Received: 30 June 2016 / Accepted: 30 June 2016 / Published: 22 July 2016
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Abstract
The authors wish to make the following changes to the published paper [1].[...] Full article
(This article belongs to the collection Electric and Hybrid Vehicles Collection)
Open AccessArticle
Numerical Investigation of Aerodynamic Performance and Loads of a Novel Dual Rotor Wind Turbine
Energies 2016, 9(7), 571; https://doi.org/10.3390/en9070571
Received: 15 April 2016 / Revised: 6 July 2016 / Accepted: 6 July 2016 / Published: 21 July 2016
Cited by 6 | Viewed by 2384 | PDF Full-text (9333 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this paper is to numerically investigate the effects of the atmospheric boundary layer on the aerodynamic performance and loads of a novel dual-rotor wind turbine (DRWT). Large eddy simulations are carried out with the turbines operating in the atmospheric boundary [...] Read more.
The objective of this paper is to numerically investigate the effects of the atmospheric boundary layer on the aerodynamic performance and loads of a novel dual-rotor wind turbine (DRWT). Large eddy simulations are carried out with the turbines operating in the atmospheric boundary layer (ABL) and in a uniform inflow. Two stability conditions corresponding to neutral and slightly stable atmospheres are investigated. The turbines are modeled using the actuator line method where the rotor blades are modeled as body forces. Comparisons are drawn between the DRWT and a comparable conventional single-rotor wind turbine (SRWT) to assess changes in aerodynamic efficiency and loads, as well as wake mixing and momentum and kinetic energy entrainment into the turbine wake layer. The results show that the DRWT improves isolated turbine aerodynamic performance by about 5%–6%. The DRWT also enhances turbulent axial momentum entrainment by about 3.3 %. The highest entrainment is observed in the neutral stability case when the turbulence in the ABL is moderately high. Aerodynamic loads for the DRWT, measured as out-of-plane blade root bending moment, are marginally reduced. Spectral analyses of ABL cases show peaks in unsteady loads at the rotor passing frequency and its harmonics for both rotors of the DRWT. Full article
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Open AccessReview
A Review of Research on Large Scale Modern Vertical Axis Wind Turbines at Uppsala University
Energies 2016, 9(7), 570; https://doi.org/10.3390/en9070570
Received: 30 May 2016 / Revised: 6 July 2016 / Accepted: 11 July 2016 / Published: 21 July 2016
Cited by 7 | Viewed by 3585 | PDF Full-text (2657 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a review of over a decade of research on Vertical Axis Wind Turbines (VAWTs) conducted at Uppsala University. The paper presents, among others, an overview of the 200 kW VAWT located in Falkenberg, Sweden, as well as a description of [...] Read more.
This paper presents a review of over a decade of research on Vertical Axis Wind Turbines (VAWTs) conducted at Uppsala University. The paper presents, among others, an overview of the 200 kW VAWT located in Falkenberg, Sweden, as well as a description of the work done on the 12 kW prototype VAWT in Marsta, Sweden. Several key aspects have been tested and successfully demonstrated at our two experimental research sites. The effort of the VAWT research has been aimed at developing a robust large scale VAWT technology based on an electrical control system with a direct driven energy converter. This approach allows for a simplification where most or all of the control of the turbines can be managed by the electrical converter system, reducing investment cost and need for maintenance. The concept features an H-rotor that is omnidirectional in regards to wind direction, meaning that it can extract energy from all wind directions without the need for a yaw system. The turbine is connected to a direct driven permanent magnet synchronous generator (PMSG), located at ground level, that is specifically developed to control and extract power from the turbine. The research is ongoing and aims for a multi-megawatt VAWT in the near future. Full article
(This article belongs to the collection Wind Turbines) Printed Edition available
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Open AccessArticle
Broadband PLC for Clustered Advanced Metering Infrastructure (AMI) Architecture
Energies 2016, 9(7), 569; https://doi.org/10.3390/en9070569
Received: 16 April 2016 / Revised: 11 July 2016 / Accepted: 12 July 2016 / Published: 21 July 2016
Cited by 21 | Viewed by 2790 | PDF Full-text (791 KB) | HTML Full-text | XML Full-text
Abstract
Advanced metering infrastructure (AMI) subsystems monitor and control energy distribution through exchange of information between smart meters and utility networks. A key challenge is how to select a cost-effective communication system without compromising the performance of the applications. Current communication technologies were developed [...] Read more.
Advanced metering infrastructure (AMI) subsystems monitor and control energy distribution through exchange of information between smart meters and utility networks. A key challenge is how to select a cost-effective communication system without compromising the performance of the applications. Current communication technologies were developed for conventional data networks with different requirements. It is therefore necessary to investigate how much of existing communication technologies can be retrofitted into the new energy infrastructure to cost-effectively deliver acceptable level of service. This paper investigates broadband power line communications (BPLC) as a backhaul solution in AMI. By applying the disparate traffic characteristics of selected AMI applications, the network performance is evaluated. This study also examines the communication network response to changes in application configurations in terms of packet sizes. In each case, the network is stress-tested and performance is assessed against acceptable thresholds documented in the literature. Results show that, like every other communication technology, BPLC has certain limitations; however, with some modifications in the network topology, it indeed can fulfill most AMI traffic requirements for flexible and time-bounded applications. These opportunities, if tapped, can significantly improve fiscal and operational efficiencies in AMI services. Simulation results also reveal that BPLC as a backhaul can support flat and clustered AMI structures with cluster size ranging from 1 to 150 smart meters. Full article
(This article belongs to the collection Smart Grid)
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Open AccessArticle
Multislot Simultaneous Spectrum Sensing and Energy Harvesting in Cognitive Radio
Energies 2016, 9(7), 568; https://doi.org/10.3390/en9070568
Received: 8 June 2016 / Revised: 6 July 2016 / Accepted: 15 July 2016 / Published: 21 July 2016
Cited by 4 | Viewed by 1968 | PDF Full-text (838 KB) | HTML Full-text | XML Full-text
Abstract
In cognitive radio (CR), the spectrum sensing of the primary user (PU) may consume some electrical power from the battery capacity of the secondary user (SU), resulting in a decrease in the transmission power of the SU. In this paper, a multislot simultaneous [...] Read more.
In cognitive radio (CR), the spectrum sensing of the primary user (PU) may consume some electrical power from the battery capacity of the secondary user (SU), resulting in a decrease in the transmission power of the SU. In this paper, a multislot simultaneous spectrum sensing and energy harvesting model is proposed, which uses the harvested radio frequency (RF) energy of the PU signal to supply the spectrum sensing. In the proposed model, the sensing duration is divided into multiple sensing slots consisting of one local-sensing subslot and one energy-harvesting subslot. If the PU is detected to be present in the local-sensing subslot, the SU will harvest RF energy of the PU signal in the energy-harvesting slot, otherwise, the SU will continue spectrum sensing. The global decision on the presence of the PU is obtained through combining local sensing results from all the sensing slots by adopting “Or-logic Rule”. A joint optimization problem of sensing time and time splitter factor is proposed to maximize the throughput of the SU under the constraints of probabilities of false alarm and detection and energy harvesting. The simulation results have shown that the proposed model can clearly improve the maximal throughput of the SU compared to the traditional sensing-throughput tradeoff model. Full article
(This article belongs to the Special Issue Wireless Power Transfer 2016)
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Open AccessArticle
A WebGIS Decision Support System for Management of Abandoned Mines
Energies 2016, 9(7), 567; https://doi.org/10.3390/en9070567
Received: 26 May 2016 / Revised: 23 June 2016 / Accepted: 12 July 2016 / Published: 21 July 2016
Cited by 3 | Viewed by 2104 | PDF Full-text (4001 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the development of a WebGIS application aimed at providing safe and reliable data needed for reclamation of abandoned mines in national parks and other protected areas in Vojvodina in compliance with existing legal regulations. The geodatabase model for this application [...] Read more.
This paper presents the development of a WebGIS application aimed at providing safe and reliable data needed for reclamation of abandoned mines in national parks and other protected areas in Vojvodina in compliance with existing legal regulations. The geodatabase model for this application has been developed using UML and the CASE tool Microsoft Visio featuring an interface with ArcGIS. The WebGIS application was developed using GeoServer, an open source tool in the Java programming language, with integrated PostgreSQL DB and the possibility of generating and publishing WMS, WFS and KML services. The WebGIS application is publicly available, based on an appropriate central database, which for the first time encompasses all available data on abandoned mines in Vojvodina, and as such may serve as a model for similar databases on the territory of the Republic of Serbia. Full article
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Open AccessArticle
A Comparative Study of Multiple-Criteria Decision-Making Methods under Stochastic Inputs
Energies 2016, 9(7), 566; https://doi.org/10.3390/en9070566
Received: 21 April 2016 / Revised: 4 July 2016 / Accepted: 7 July 2016 / Published: 21 July 2016
Cited by 34 | Viewed by 3086 | PDF Full-text (1581 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an application and extension of multiple-criteria decision-making (MCDM) methods to account for stochastic input variables. More in particular, a comparative study is carried out among well-known and widely-applied methods in MCDM, when applied to the reference problem of the selection [...] Read more.
This paper presents an application and extension of multiple-criteria decision-making (MCDM) methods to account for stochastic input variables. More in particular, a comparative study is carried out among well-known and widely-applied methods in MCDM, when applied to the reference problem of the selection of wind turbine support structures for a given deployment location. Along with data from industrial experts, six deterministic MCDM methods are studied, so as to determine the best alternative among the available options, assessed against selected criteria with a view toward assigning confidence levels to each option. Following an overview of the literature around MCDM problems, the best practice implementation of each method is presented aiming to assist stakeholders and decision-makers to support decisions in real-world applications, where many and often conflicting criteria are present within uncertain environments. The outcomes of this research highlight that more sophisticated methods, such as technique for the order of preference by similarity to the ideal solution (TOPSIS) and Preference Ranking Organization method for enrichment evaluation (PROMETHEE), better predict the optimum design alternative. Full article
(This article belongs to the collection Wind Turbines) Printed Edition available
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Open AccessArticle
EMD-Based Feature Extraction for Power Quality Disturbance Classification Using Moments
Energies 2016, 9(7), 565; https://doi.org/10.3390/en9070565
Received: 30 May 2016 / Revised: 4 July 2016 / Accepted: 12 July 2016 / Published: 20 July 2016
Cited by 10 | Viewed by 1977 | PDF Full-text (5393 KB) | HTML Full-text | XML Full-text
Abstract
In electric power systems, there are always power quality disturbances (PQDs). Usually, noise contamination interferes with their detection and classification. Common methods perform frequency or time-frequency analyses on the power distribution signal for detecting and classifying a limited number of PQDs with some [...] Read more.
In electric power systems, there are always power quality disturbances (PQDs). Usually, noise contamination interferes with their detection and classification. Common methods perform frequency or time-frequency analyses on the power distribution signal for detecting and classifying a limited number of PQDs with some difficulties at low signal-to-noise ratio (SNR). In this regard, recently proposed methodologies for PQD detection estimate several parameters and apply distinct signal processing techniques to improve the detection of PQD. In this work, a novel methodology that merges empirical mode decomposition (EMD), the moments of a random variable, and an artificial neural network (ANN) is proposed for detecting and classifying different PQD. The proposed method estimates skewness, kurtosis, and Shannon entropy from the EMD of one-phase voltage/current signal. Then, an ANN is in charge of classifying the input signal into one of nine different classes for PQD, receiving these parameters as inputs. The effectiveness of the proposed method was verified through computer simulations and experimentation with real data. Obtained results demonstrate its high effectiveness reaching an outstanding 100% of accuracy in detecting and classifying all treated PQD through a few number of parameters, outperforming most of previously proposed approaches. Full article
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Open AccessArticle
Thermal Hydraulic Performance in a Solar Air Heater Channel with Multi V-Type Perforated Baffles
Energies 2016, 9(7), 564; https://doi.org/10.3390/en9070564
Received: 6 June 2016 / Revised: 11 July 2016 / Accepted: 14 July 2016 / Published: 20 July 2016
Cited by 13 | Viewed by 1840 | PDF Full-text (13727 KB) | HTML Full-text | XML Full-text
Abstract
This article presents heat transfer and fluid flow characteristics in a solar air heater (SAH) channel with multi V-type perforated baffles. The flow passage has an aspect ratio of 10. The relative baffle height, relative pitch, relative baffle hole position, flow attack angle, [...] Read more.
This article presents heat transfer and fluid flow characteristics in a solar air heater (SAH) channel with multi V-type perforated baffles. The flow passage has an aspect ratio of 10. The relative baffle height, relative pitch, relative baffle hole position, flow attack angle, and baffle open area ratio are 0.6, 8.0, 0.42, 60°, and 12%, respectively. The Reynolds numbers considered in the study was in the range of 3000–10,000. The re-normalization group (RNG) k-ε turbulence model has been used for numerical analysis, and the optimum relative baffle width has been investigated considering relative baffle widths of 1.0–7.0.The numerical results are in good agreement with the experimental data for the range considered in the study. Multi V-type perforated baffles are shown to have better thermal performance as compared to other baffle shapes in a rectangular passage. The overall thermal hydraulic performance shows the maximum value at the relative baffle width of 5.0. Full article
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Open AccessEditor’s ChoiceArticle
New Electro-Thermal Battery Pack Model of an Electric Vehicle
Energies 2016, 9(7), 563; https://doi.org/10.3390/en9070563
Received: 30 May 2016 / Revised: 4 July 2016 / Accepted: 12 July 2016 / Published: 20 July 2016
Cited by 8 | Viewed by 4595 | PDF Full-text (5016 KB) | HTML Full-text | XML Full-text
Abstract
Since the evolution of the electric and hybrid vehicle, the analysis of batteries’ characteristics and influence on driving range has become essential. This fact advocates the necessity of accurate simulation modeling for batteries. Different models for the Li-ion battery cell are reviewed in [...] Read more.
Since the evolution of the electric and hybrid vehicle, the analysis of batteries’ characteristics and influence on driving range has become essential. This fact advocates the necessity of accurate simulation modeling for batteries. Different models for the Li-ion battery cell are reviewed in this paper and a group of the highly dynamic models is selected for comparison. A new open circuit voltage (OCV) model is proposed. The new model can simulate the OCV curves of lithium iron magnesium phosphate (LiFeMgPO4) battery type at different temperatures. It also considers both charging and discharging cases. The most remarkable features from different models, in addition to the proposed OCV model, are integrated in a single hybrid electrical model. A lumped thermal model is implemented to simulate the temperature development in the battery cell. The synthesized electro-thermal battery cell model is extended to model a battery pack of an actual electric vehicle. Experimental tests on the battery, as well as drive tests on the vehicle are performed. The proposed model demonstrates a higher modeling accuracy, for the battery pack voltage, than the constituent models under extreme maneuver drive tests. Full article
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Open AccessArticle
Energy Management in Prosumer Communities: A Coordinated Approach
Energies 2016, 9(7), 562; https://doi.org/10.3390/en9070562
Received: 30 November 2015 / Revised: 9 February 2016 / Accepted: 27 June 2016 / Published: 20 July 2016
Cited by 13 | Viewed by 2527 | PDF Full-text (3199 KB) | HTML Full-text | XML Full-text
Abstract
The introduction of uncontrollable renewable energy is having a positive impact on our health, the climate, and the economy, but it is also pushing the limits of the power system. The main reason for this is that, in any power system, the generation [...] Read more.
The introduction of uncontrollable renewable energy is having a positive impact on our health, the climate, and the economy, but it is also pushing the limits of the power system. The main reason for this is that, in any power system, the generation and consumption must match each other at all times. Thus, if we want to further introduce uncontrollable generation, we need a large ability to manage the demand. However, the ability to control the power consumption of existing demand management approaches is limited, and most of these approaches cannot contribute to the introduction of reneweables, because they do not consider distributed uncontrolled consumption and generation in the control. Furthermore, these methods do not allow users to exchange or jointly manage their power generation and consumption. In this context, we propose an augmented energy management model for prosumers (i.e., producer and consumer). This model considers controlled and uncontrolled generation and consumption, as well as the prosumer’s ability (i) to plan the intended power consumption; and (ii) to manage real-time deviations from the intended consumption. We apply this model to the energy management of prosumer communities, by allowing the prosumers to coordinate their power consumption plan, to manage the deviations from the intended consumption, and to help each other by compensating deviations. The proposed approach seeks to enhance the power system, and to enable a prosumer society that takes account social and environmental issues, as well as each prosumer’s quality of life. Full article
(This article belongs to the Special Issue Multi-Disciplinary Perspectives on Energy and Sustainable Development)
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Open AccessArticle
Battery Grouping with Time Series Clustering Based on Affinity Propagation
Energies 2016, 9(7), 561; https://doi.org/10.3390/en9070561
Received: 11 April 2016 / Revised: 19 June 2016 / Accepted: 12 July 2016 / Published: 19 July 2016
Cited by 5 | Viewed by 1468 | PDF Full-text (5389 KB) | HTML Full-text | XML Full-text
Abstract
Battery grouping is a technology widely used to improve the performance of battery packs. In this paper, we propose a time series clustering based battery grouping method. The proposed method utilizes the whole battery charge/discharge sequence for battery grouping. The time sequences are [...] Read more.
Battery grouping is a technology widely used to improve the performance of battery packs. In this paper, we propose a time series clustering based battery grouping method. The proposed method utilizes the whole battery charge/discharge sequence for battery grouping. The time sequences are first denoised with a wavelet denoising technique. The similarity matrix is then computed with the dynamic time warping distance, and finally the time series are clustered with the affinity propagation algorithm according to the calculated similarity matrices. The silhouette index is utilized for assessing the performance of the proposed battery grouping method. Test results show that the proposed battery grouping method is effective. Full article
(This article belongs to the Special Issue Energy Time Series Forecasting)
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Open AccessArticle
Risk Assessment of Distribution Networks Considering the Charging-Discharging Behaviors of Electric Vehicles
Energies 2016, 9(7), 560; https://doi.org/10.3390/en9070560
Received: 29 May 2016 / Revised: 3 July 2016 / Accepted: 10 July 2016 / Published: 19 July 2016
Cited by 6 | Viewed by 2190 | PDF Full-text (5850 KB) | HTML Full-text | XML Full-text
Abstract
Electric vehicles (EVs) have received wide attention due to their higher energy efficiency and lower emissions. However, the random charging and discharging behaviors of substantial numbers of EVs may lead to safety risk problems in a distribution network. Reasonable price incentives can guide [...] Read more.
Electric vehicles (EVs) have received wide attention due to their higher energy efficiency and lower emissions. However, the random charging and discharging behaviors of substantial numbers of EVs may lead to safety risk problems in a distribution network. Reasonable price incentives can guide EVs through orderly charging and discharging, and further provide a feasible solution to reduce the operational risk of the distribution network. Considering three typical electricity prices, EV charging/discharging load models are built. Then, a Probabilistic Load Flow (PLF) method using cumulants and Gram-Charlier series is proposed to obtain the power flow of the distribution network including massive numbers of EVs. In terms of the risk indexes of node voltage and line flow, the operational risk of the distribution network can be estimated in detail. From the simulations of an IEEE-33 bus system and an IEEE 69-bus system, the demonstrated results show that reasonable charging and discharging prices are conducive to reducing the peak-valley difference, and consequently the risks of the distribution network can be decreased to a certain extent. Full article
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Open AccessArticle
Understanding the Contribution of Mining and Transportation to the Total Life Cycle Impacts of Coal Exported from the United States
Energies 2016, 9(7), 559; https://doi.org/10.3390/en9070559
Received: 15 April 2016 / Revised: 17 June 2016 / Accepted: 30 June 2016 / Published: 19 July 2016
Cited by 3 | Viewed by 1971 | PDF Full-text (2497 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The construction of two marine bulk terminals in the Pacific Northwest region of the United States are currently under review and would open up additional thermal coal exports to Asia on the order of almost 100 million additional tonnes per year. The major [...] Read more.
The construction of two marine bulk terminals in the Pacific Northwest region of the United States are currently under review and would open up additional thermal coal exports to Asia on the order of almost 100 million additional tonnes per year. The major exporters of coal to Asian markets include Indonesia and Australia. This life cycle analysis (LCA) seeks to understand the role of transportation and mining in the cradle-to-busbar environmental impacts of coal exports from the Powder River Basin (PRB) to Asian countries, when compared to the competitor countries. This LCA shows that: (1) the most significant greenhouse gas (GHG) impacts in the cradle-to-busbar life cycle of coal for power generation come from the combustion of coal in a power plant, even when 90% carbon capture is applied; (2) for non-GHG air impacts, power plant combustion impacts are less dominant and variations in upstream impacts (mining and transportation) are more important; and (3) when comparing impacts between countries, upstream impacts vary for both GHG and non-GHG results, but conclusions that rank countries cannot be made. Future research should include expansion to include non-air impacts, potential consequential effects of coal exports, and a better understanding around the characterization of non-GHG ocean transport impacts. Full article
(This article belongs to the Special Issue Life-Cycle Assessment of Energy Systems in Current and Evolving Grids)
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Open AccessArticle
Indirect Load Control for Energy Storage Systems Using Incentive Pricing under Time-of-Use Tariff
Energies 2016, 9(7), 558; https://doi.org/10.3390/en9070558
Received: 1 May 2016 / Revised: 24 June 2016 / Accepted: 14 July 2016 / Published: 19 July 2016
Cited by 5 | Viewed by 2040 | PDF Full-text (4920 KB) | HTML Full-text | XML Full-text
Abstract
Indirect load control (ILC) is a method by which the customer determines load reduction of electricity by using a price signal. One of the ILCs is a time-of-use (TOU) tariff, which is the most commonly used time-varying retail pricing. Under the TOU tariff, [...] Read more.
Indirect load control (ILC) is a method by which the customer determines load reduction of electricity by using a price signal. One of the ILCs is a time-of-use (TOU) tariff, which is the most commonly used time-varying retail pricing. Under the TOU tariff, the customer can reduce the energy cost through an energy storage system (ESS). However, because this tariff is fixed for several months, the ESS operation does not truly reflect the wholesale market price, which could widely fluctuate. To overcome this limitation, this paper proposes an incentive pricing method in which the load-serving entity (LSE) gives the incentive pricing signal to the customers with ESSs. Because the ESS charging schedule is determined by the customer through ILC, a bilevel optimization problem that includes the customer optimization problem is utilized to determine the incentive pricing signal. Further, the bilevel optimization problem is reformulated into a one-level problem to be solved by an interior point method. In the proposed incentive scheme: (1) the social welfare increases and (2) the increased social welfare can be equitably divided between the LSE and the customer; and (3) the proposed incentive scheme leads the customer to voluntarily follow the pricing signal. Full article
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Open AccessArticle
A Novel Method to Magnetic Flux Linkage Optimization of Direct-Driven Surface-Mounted Permanent Magnet Synchronous Generator Based on Nonlinear Dynamic Analysis
Energies 2016, 9(7), 557; https://doi.org/10.3390/en9070557
Received: 19 June 2016 / Revised: 8 July 2016 / Accepted: 9 July 2016 / Published: 19 July 2016
Cited by 2 | Viewed by 1688 | PDF Full-text (6210 KB) | HTML Full-text | XML Full-text
Abstract
This paper pays attention to magnetic flux linkage optimization of a direct-driven surface-mounted permanent magnet synchronous generator (D-SPMSG). A new compact representation of the D-SPMSG nonlinear dynamic differential equations to reduce system parameters is established. Furthermore, the nonlinear dynamic characteristics of new D-SPMSG [...] Read more.
This paper pays attention to magnetic flux linkage optimization of a direct-driven surface-mounted permanent magnet synchronous generator (D-SPMSG). A new compact representation of the D-SPMSG nonlinear dynamic differential equations to reduce system parameters is established. Furthermore, the nonlinear dynamic characteristics of new D-SPMSG equations in the process of varying magnetic flux linkage are considered, which are illustrated by Lyapunov exponent spectrums, phase orbits, Poincaré maps, time waveforms and bifurcation diagrams, and the magnetic flux linkage stable region of D-SPMSG is acquired concurrently. Based on the above modeling and analyses, a novel method of magnetic flux linkage optimization is presented. In addition, a 2 MW D-SPMSG 2D/3D model is designed by ANSYS software according to the practical design requirements. Finally, five cases of D-SPMSG models with different magnetic flux linkages are simulated by using the finite element analysis (FEA) method. The nephograms of magnetic flux density are agreement with theoretical analysis, which both confirm the correctness and effectiveness of the proposed approach. Full article
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Open AccessArticle
A Laboratory Study of the Effects of Interbeds on Hydraulic Fracture Propagation in Shale Formation
Energies 2016, 9(7), 556; https://doi.org/10.3390/en9070556
Received: 18 April 2016 / Revised: 24 June 2016 / Accepted: 12 July 2016 / Published: 19 July 2016
Cited by 6 | Viewed by 2042 | PDF Full-text (5667 KB) | HTML Full-text | XML Full-text
Abstract
To investigate how the characteristics of interbeds affect hydraulic fracture propagation in the continental shale formation, a series of 300 mm × 300 mm × 300 mm concrete blocks with varying interbeds, based on outcrop observation and core measurement of Chang 7-2 shale [...] Read more.
To investigate how the characteristics of interbeds affect hydraulic fracture propagation in the continental shale formation, a series of 300 mm × 300 mm × 300 mm concrete blocks with varying interbeds, based on outcrop observation and core measurement of Chang 7-2 shale formation, were prepared to conduct the hydraulic fracturing experiments. The results reveal that the breakdown pressure increases with the rise of thickness and strength of interbeds under the same in-situ field stress and injection rate. In addition, for the model blocks with thick and high strength interbeds, the hydraulic fracture has difficulty crossing the interbeds and is prone to divert along the bedding faces, and the fracturing effectiveness is not good. However, for the model blocks with thin and low strength interbeds, more long branches are generated along the main fracture, which is beneficial to the formation of the fracture network. What is more, combining the macroscopic descriptions with microscopic observations, the blocks with thinner and lower strength interbeds tend to generate more micro-fractures, and the width of the fractures is relatively larger on the main fracture planes. Based on the experiments, it is indicated that the propagation of hydraulic fractures is strongly influenced by the characteristics of interbeds, and the results are instructive to the understanding and evaluation of the fracability in the continental shale formation. Full article
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Open AccessArticle
A Novel Strategy for Optimising Decentralised Energy Exchange for Prosumers
Energies 2016, 9(7), 554; https://doi.org/10.3390/en9070554
Received: 30 April 2016 / Revised: 1 July 2016 / Accepted: 12 July 2016 / Published: 18 July 2016
Cited by 8 | Viewed by 2021 | PDF Full-text (563 KB) | HTML Full-text | XML Full-text
Abstract
The realization of the Smart Grid vision will change the way of producing and distributing electrical energy. It paves the road for end-users to become pro-active in the distribution system and, equipped with renewable energy generators such as a photovoltaic panel, to become [...] Read more.
The realization of the Smart Grid vision will change the way of producing and distributing electrical energy. It paves the road for end-users to become pro-active in the distribution system and, equipped with renewable energy generators such as a photovoltaic panel, to become a so called “prosumer”. The prosumer is engaged in both energy production and consumption. Prosumers’ energy can be transmitted and exchanged as a commodity between end-users, disrupting the traditional utility model. The appeal of such scenario lies in the engagement of the end user, in facilitating the introduction and optimization of renewables, and in engaging the end-user in its energy management. To facilitate the transition to a prosumers’ governed grid, we propose a novel strategy for optimizing decentralized energy exchange in digitalized power grids, i.e., the Smart Grid. The strategy considers prosumer’s involvement, energy loss of delivery, network topology, and physical constraints of distribution networks. To evaluate the solution, we build a simulation program and design three meaningful evaluation cases according to different energy flow patterns. The simulation results indicate that, compared to traditional power distribution system, the maximum reduction of energy loss, energy costs, energy provided by the electric utility based using the proposed strategy can reach 51 % , 66 % , 97.5 % , depending on the strategy. Moreover, the proportion of energy self-satisfaction approaches reaches 98 % . Full article
(This article belongs to the Special Issue Decentralized Management of Energy Streams in Smart Grids)
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Open AccessArticle
Comparative Life Cycle Cost Analysis of Hardening Options for Critical Loads
Energies 2016, 9(7), 553; https://doi.org/10.3390/en9070553
Received: 15 February 2016 / Revised: 6 July 2016 / Accepted: 13 July 2016 / Published: 18 July 2016
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Abstract
In order to determine the most cost effective alternative among hardening options of power systems, the direct monetary benefits should be evaluated above all other things. Therefore, this paper presents a life-cycle cost model which describes total monetary costs experienced in annual time [...] Read more.
In order to determine the most cost effective alternative among hardening options of power systems, the direct monetary benefits should be evaluated above all other things. Therefore, this paper presents a life-cycle cost model which describes total monetary costs experienced in annual time increments during the project with consideration for the time value of money. In addition, to minimize the risks associated with estimated cost errors due to uncertainties of input data, the stochastic input data are considered. Using the Monte Carlo method, the probabilities and cost ranges in the case studies can be predicted, in turn resulting in better decisions in the selection of hardening options which are cost effective. Full article
(This article belongs to the Special Issue Microgrids 2016)
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Open AccessArticle
Industrial Energy Consumption in Northeast China under the Revitalisation Strategy: A Decomposition and Policy Analysis
Energies 2016, 9(7), 549; https://doi.org/10.3390/en9070549
Received: 21 April 2016 / Revised: 15 June 2016 / Accepted: 7 July 2016 / Published: 18 July 2016
Cited by 10 | Viewed by 1706 | PDF Full-text (4069 KB) | HTML Full-text | XML Full-text
Abstract
While previous studies have examined China’s changing industrial energy consumption at the national level, this study argues that it is more useful, from a policy standpoint, to conduct a regional-level analysis owing to the significant regional disparity in industrialisation in the country. This [...] Read more.
While previous studies have examined China’s changing industrial energy consumption at the national level, this study argues that it is more useful, from a policy standpoint, to conduct a regional-level analysis owing to the significant regional disparity in industrialisation in the country. This study focuses particularly on Northeast China, where the implementation of the Northeast Revitalisation Strategy in 2003 has contributed to rapid reindustrialisation, which has a serious implication for industrial energy consumption. We decompose the region’s energy consumption changes into activity, structure, and intensity effects. Our results show that the intensity effect is not the only negative factor impacting industrial energy consumption during 2003–2012. The structure effect also has a negative impact on industrial energy consumption between 2005 and 2012. However, the negative impact of the two factors is weakening and not strong enough to counter the positive impact of the activity effect. This result highlights the problem of uncoordinated policy-making in Northeast China. The development strategy, which still depends highly on traditional heavy industries, is in conflict with the national strategy of energy conservation. The two conflicting objectives of industrial revitalization and energy conservation must be reconciled for sustainability in the long term. The study concludes with policy recommendations on how to achieve such reconciliation. Full article
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Open AccessArticle
Earliest Deadline Control of a Group of Heat Pumps with a Single Energy Source
Energies 2016, 9(7), 552; https://doi.org/10.3390/en9070552
Received: 4 May 2016 / Revised: 18 June 2016 / Accepted: 5 July 2016 / Published: 15 July 2016
Cited by 2 | Viewed by 1448 | PDF Full-text (766 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we develop and investigate the optimal control of a group of 104 heat pumps and a central Combined Heat and Power unit (CHP). The heat pumps supply space heating and domestic hot water to households. Each house has a buffer [...] Read more.
In this paper, we develop and investigate the optimal control of a group of 104 heat pumps and a central Combined Heat and Power unit (CHP). The heat pumps supply space heating and domestic hot water to households. Each house has a buffer for domestic hot water and a floor heating system for space heating. Electricity for the heat pumps is generated by a central CHP unit, which also provides thermal energy to a district heating system. The paper reviews recent smart grid control approaches for central and distributed levels. An online algorithm is described based on the earliest deadline first theory that can be used on the aggregator level to control the CHP and to give signals to the heat pump controllers if they should start or should wait. The central controller requires only a limited amount of privacy-insensitive information from the heat pump controllers about their deadlines, which the heat pump controllers calculate for themselves by model predictions. In this way, a robust heat pump and CHP control is obtained, which is able to minimize energy demand and results in the desired thermal comfort for the households. The simulations demonstrate fast computation times due to minor computational and communication overheads. Full article
(This article belongs to the Special Issue Decentralized Management of Energy Streams in Smart Grids)
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Open AccessArticle
Artist Photovoltaic Modules
Energies 2016, 9(7), 551; https://doi.org/10.3390/en9070551
Received: 23 May 2016 / Revised: 9 July 2016 / Accepted: 11 July 2016 / Published: 15 July 2016
Cited by 2 | Viewed by 1677 | PDF Full-text (5525 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a full-color photovoltaic (PV) module, called the artist PV module, is developed by laser processes. A full-color image source is printed on the back of a protective glass using an inkjet printer, and a brightened grayscale mask is used to [...] Read more.
In this paper, a full-color photovoltaic (PV) module, called the artist PV module, is developed by laser processes. A full-color image source is printed on the back of a protective glass using an inkjet printer, and a brightened grayscale mask is used to precisely define regions on the module where colors need to be revealed. Artist PV modules with 1.1 × 1.4 m2 area have high a retaining power output of 139 W and an aesthetic appearance making them more competitive than other building-integrated photovoltaic (BIPV) products. Furthermore, the installation of artist PV modules as curtain walls without metal frames is also demonstrated. This type of installation offers an aesthetic advantage by introducing supporting fittings, originating from the field of glass technology. Hence, this paper is expected to elevate BIPV modules to an art form and generate research interests in developing more functional PV modules. Full article
(This article belongs to the Special Issue Nano-Structured Solar Cells)
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Open AccessArticle
Thermal Perception in the Mediterranean Area: Comparing the Mediterranean Outdoor Comfort Index (MOCI) to Other Outdoor Thermal Comfort Indices
Energies 2016, 9(7), 550; https://doi.org/10.3390/en9070550
Received: 30 May 2016 / Revised: 7 July 2016 / Accepted: 8 July 2016 / Published: 15 July 2016
Cited by 19 | Viewed by 1738 | PDF Full-text (4189 KB) | HTML Full-text | XML Full-text
Abstract
Outdoor thermal comfort is an essential factor of people’s everyday life and deeply affects the habitability of outdoor spaces. However the indices used for its evaluation were usually developed for indoor environments assuming still air conditions and absence of solar radiation and were [...] Read more.
Outdoor thermal comfort is an essential factor of people’s everyday life and deeply affects the habitability of outdoor spaces. However the indices used for its evaluation were usually developed for indoor environments assuming still air conditions and absence of solar radiation and were only later adapted to outdoor spaces. For this reason, in a previous study the Mediterranean Outdoor Comfort Index (MOCI) was developed, which is an empirical index able to estimate the thermal perception of people living in the Mediterranean area. In this study it was compared numerically (by using the data obtained through a field survey) with other selected thermal indices. This comparison, performed in terms of Spearman’s rho correlation coefficient, association Gamma, percentage of correct predictions and cross-tabulation analysis, led to identify the MOCI as the most suitable index to examine outdoor thermal comfort in the interested area. As a matter of fact it showed a total percentage of correct predictions of 35.5%. Good performances were reported even in thermophysiological indices as the Physiological Equivalent Temperature (PET) and Predicted Mean Vote (PMV). Moreover it was revealed that adaptation and acclimatization phenomena tend to have a certain influence as well. Full article
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Open AccessArticle
A New Fault Diagnosis Algorithm for PMSG Wind Turbine Power Converters under Variable Wind Speed Conditions
Energies 2016, 9(7), 548; https://doi.org/10.3390/en9070548
Received: 3 May 2016 / Revised: 7 July 2016 / Accepted: 8 July 2016 / Published: 15 July 2016
Cited by 11 | Viewed by 2375 | PDF Full-text (2937 KB) | HTML Full-text | XML Full-text
Abstract
Although Permanent Magnet Synchronous Generator (PMSG) wind turbines (WTs) mitigate gearbox impacts, they requires high reliability of generators and converters. Statistical analysis shows that the failure rate of direct-drive PMSG wind turbines’ generators and inverters are high. Intelligent fault diagnosis algorithms to detect [...] Read more.
Although Permanent Magnet Synchronous Generator (PMSG) wind turbines (WTs) mitigate gearbox impacts, they requires high reliability of generators and converters. Statistical analysis shows that the failure rate of direct-drive PMSG wind turbines’ generators and inverters are high. Intelligent fault diagnosis algorithms to detect inverters faults is a premise for the condition monitoring system aimed at improving wind turbines’ reliability and availability. The influences of random wind speed and diversified control strategies lead to challenges for developing intelligent fault diagnosis algorithms for converters. This paper studies open-circuit fault features of wind turbine converters in variable wind speed situations through systematic simulation and experiment. A new fault diagnosis algorithm named Wind Speed Based Normalized Current Trajectory is proposed and used to accurately detect and locate faulted IGBT in the circuit arms. It is compared to direct current monitoring and current vector trajectory pattern approaches. The results show that the proposed method has advantages in the accuracy of fault diagnosis and has superior anti-noise capability in variable wind speed situations. The impact of the control strategy is also identified. Experimental results demonstrate its applicability on practical WT condition monitoring system which is used to improve wind turbine reliability and reduce their maintenance cost. Full article
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Open AccessArticle
Harnessing the Flexibility of Thermostatic Loads in Microgrids with Solar Power Generation
Energies 2016, 9(7), 547; https://doi.org/10.3390/en9070547
Received: 21 April 2016 / Revised: 15 June 2016 / Accepted: 7 July 2016 / Published: 15 July 2016
Cited by 4 | Viewed by 1883 | PDF Full-text (779 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a demand response (DR) framework that intertwines thermodynamic building models with a genetic algorithm (GA)-based optimization method. The framework optimizes heating/cooling schedules of end-users inside a business park microgrid with local distributed generation from renewable energy sources (DG-RES) based on [...] Read more.
This paper presents a demand response (DR) framework that intertwines thermodynamic building models with a genetic algorithm (GA)-based optimization method. The framework optimizes heating/cooling schedules of end-users inside a business park microgrid with local distributed generation from renewable energy sources (DG-RES) based on two separate objectives: net load minimization and electricity cost minimization. DG-RES is treated as a curtailable resource in anticipation of future scenarios where the infeed of DG-RES to the regional distribution network could be limited. We test the DR framework with a case study of a refrigerated warehouse and an office building located in a business park with local PV generation. Results show the technical potential of the DR framework in harnessing the flexibility of the thermal masses from end-user sites in order to: (1) reduce the energy exchange at the point of connection; (2) reduce the cost of electricity for the microgrid end-users; and (3) increase the local utilization of DG-RES in cases where DG-RES exports to the grid are restricted. The results of this work can aid end-users and distribution network operators to reduce energy costs and energy consumption. Full article
(This article belongs to the Special Issue Decentralized Management of Energy Streams in Smart Grids)
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Open AccessEditorial
Electrical Power and Energy Systems for Transportation Applications
Energies 2016, 9(7), 545; https://doi.org/10.3390/en9070545
Received: 11 July 2016 / Accepted: 13 July 2016 / Published: 14 July 2016
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Abstract
This book contains the successful invited submissions [1–25] to a Special Issue of Energies on the subject area of “Electrical Power and Energy Systems for Transportation Applications”. Full article
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Open AccessArticle
Solar Energy as a Form Giver for Future Cities
Energies 2016, 9(7), 544; https://doi.org/10.3390/en9070544
Received: 1 May 2016 / Revised: 6 July 2016 / Accepted: 7 July 2016 / Published: 14 July 2016
Cited by 6 | Viewed by 2052 | PDF Full-text (2892 KB) | HTML Full-text | XML Full-text
Abstract
Energy is considered as a main influence on urban configurations. However, there is a difficulty on translating the city models based on theoretical renewable energy concepts into practical applications. This study considers the possibility of understanding this future model as a transformation of [...] Read more.
Energy is considered as a main influence on urban configurations. However, there is a difficulty on translating the city models based on theoretical renewable energy concepts into practical applications. This study considers the possibility of understanding this future model as a transformation of the existing urban centres. With this objective, a methodology to intervene in existing cities based on the study of solar access is developed. Therefore, an analysis of solar potential in relation with urban morphology is carried on through a simulation software in l’Eixample, a neighbourhood of Barcelona. The distribution of the sun factor in the different areas of the building blocks envelope displays possible morphological modifications that would facilitate solar energy collection. Consequently, the analytical method presented could be applied to regulate urban interventions with the aim of obtaining more solar energy based cities. Full article
(This article belongs to the Special Issue Energy Efficient City)
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Open AccessArticle
Electricity Self-Sufficient Community Clustering for Energy Resilience
Energies 2016, 9(7), 543; https://doi.org/10.3390/en9070543
Received: 23 April 2016 / Revised: 25 June 2016 / Accepted: 7 July 2016 / Published: 14 July 2016
Cited by 5 | Viewed by 2144 | PDF Full-text (5317 KB) | HTML Full-text | XML Full-text
Abstract
Local electricity generation and sharing has been given considerable attention recently for its disaster resilience and other reasons. However, the process of designing local sharing communities (or local grids) is still unclear. Thus, this study empirically compares algorithms for electricity sharing community clustering [...] Read more.
Local electricity generation and sharing has been given considerable attention recently for its disaster resilience and other reasons. However, the process of designing local sharing communities (or local grids) is still unclear. Thus, this study empirically compares algorithms for electricity sharing community clustering in terms of self-sufficiency, sharing cost, and stability. The comparison is performed for all 12 months of a typical year in Yokohama, Japan. The analysis results indicate that, while each individual algorithm has some advantages, an exhaustive algorithm provides clusters that are highly self-sufficient. The exhaustive algorithm further demonstrates that a clustering result optimized for one month is available across many months without losing self-sufficiency. In fact, the clusters achieve complete self-sufficiency for five months in spring and autumn, when electricity demands are lower. Full article
(This article belongs to the Special Issue Decentralized Management of Energy Streams in Smart Grids)
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Open AccessArticle
Real Time Information Based Energy Management Using Customer Preferences and Dynamic Pricing in Smart Homes
Energies 2016, 9(7), 542; https://doi.org/10.3390/en9070542
Received: 10 March 2016 / Revised: 26 June 2016 / Accepted: 5 July 2016 / Published: 14 July 2016
Cited by 17 | Viewed by 2669 | PDF Full-text (1082 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents real time information based energy management algorithms to reduce electricity cost and peak to average ratio (PAR) while preserving user comfort in a smart home. We categorize household appliances into thermostatically controlled (tc), user aware (ua), [...] Read more.
This paper presents real time information based energy management algorithms to reduce electricity cost and peak to average ratio (PAR) while preserving user comfort in a smart home. We categorize household appliances into thermostatically controlled (tc), user aware (ua), elastic (el), inelastic (iel) and regular (r) appliances/loads. An optimization problem is formulated to reduce electricity cost by determining the optimal use of household appliances. The operational schedules of these appliances are optimized in response to the electricity price signals and customer preferences to maximize electricity cost saving and user comfort while minimizing curtailed energy. Mathematical optimization models of tc appliances, i.e., air-conditioner and refrigerator, are proposed which are solved by using intelligent programmable communication thermostat ( iPCT). We add extra intelligence to conventional programmable communication thermostat (CPCT) by using genetic algorithm (GA) to control tc appliances under comfort constraints. The optimization models for ua, el, and iel appliances are solved subject to electricity cost minimization and PAR reduction. Considering user comfort, el appliances are considered where users can adjust appliance waiting time to increase or decrease their comfort level. Furthermore, energy demand of r appliances is fulfilled via local supply where the major objective is to reduce the fuel cost of various generators by proper scheduling. Simulation results show that the proposed algorithms efficiently schedule the energy demand of all types of appliances by considering identified constraints (i.e., PAR, variable prices, temperature, capacity limit and waiting time). Full article
(This article belongs to the Special Issue Decentralized Management of Energy Streams in Smart Grids)
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Open AccessArticle
Thermoelectric Generators on Satellites—An Approach for Waste Heat Recovery in Space
Energies 2016, 9(7), 541; https://doi.org/10.3390/en9070541
Received: 29 January 2016 / Revised: 17 June 2016 / Accepted: 30 June 2016 / Published: 14 July 2016
Cited by 6 | Viewed by 2252 | PDF Full-text (4010 KB) | HTML Full-text | XML Full-text
Abstract
Environmental radiation in space (from the Sun, etc.) and operational thermal loads result in heat flows inside the structure of satellites. Today these heat flows remain unused and are collected, transported to a radiator and emitted to space to prevent the satellite from [...] Read more.
Environmental radiation in space (from the Sun, etc.) and operational thermal loads result in heat flows inside the structure of satellites. Today these heat flows remain unused and are collected, transported to a radiator and emitted to space to prevent the satellite from overheating, but they hold a huge potential to generate electrical power independently of solar panels. Thermoelectric generators are a promising approach for such applications because of their solid state characteristics. As they do not have any moving parts, they do not cause any vibrations in the satellite. They are said to be maintenance-free and highly reliable. Due to the expected small heat flows modern devices based on BiTe have to be considered, but these devices have no flight heritage. Furthermore, energy harvesting on space systems is a new approach for increasing the efficiency and reliability. In this paper, different systems studies and applications are discussed based some experimental characterisation of the electrical behaviour and their dependence on thermal cycles and vibration. Full article
(This article belongs to the Special Issue Space Power and Propulsion)
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