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Energies, Volume 8, Issue 10 (October 2015), Pages 10558-12313

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Open AccessArticle Effects of CO2 Bubble Size, CO2 Flow Rate and Calcium Source on the Size and Specific Surface Area of CaCO3 Particles
Energies 2015, 8(10), 12304-12313; https://doi.org/10.3390/en81012304
Received: 18 August 2015 / Revised: 18 October 2015 / Accepted: 19 October 2015 / Published: 27 October 2015
Cited by 5 | Viewed by 1610 | PDF Full-text (2189 KB) | HTML Full-text | XML Full-text
Abstract
The effects of CO2 flow rate and calcium source on the particle size (PS) and specific surface area (SSA) of CaCO3 particles were evaluated using microbubble generator (MBG) and air diffuser (AD) systems. The carbonate mineralization (CM) and precipitated calcium carbonate
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The effects of CO2 flow rate and calcium source on the particle size (PS) and specific surface area (SSA) of CaCO3 particles were evaluated using microbubble generator (MBG) and air diffuser (AD) systems. The carbonate mineralization (CM) and precipitated calcium carbonate (PCC) methods were employed to produce CaCO3 using gypsum and Ca(OH)2 as the calcium sources, respectively. The CaCO3 particles prepared using the MBG were smaller (with larger specific surface area) than those obtained using the conventional AD, regardless of the calcium source. The average PSs were 2–3 and 7–9 μm for the MBG and AD systems, respectively. Moreover, the PS and SSA of the particles prepared using the MBG were not greatly affected by the CO2 injection rate. This study clearly demonstrates that the use of an MBG ensures the stable production of fine CaCO3 particles using various calcium sources and a wider range of CO2 flow rates. Full article
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Open AccessArticle Model Property Based Material Balance and Energy Conservation Analysis for Process Industry Energy Transfer Systems
Energies 2015, 8(10), 12283-12303; https://doi.org/10.3390/en81012283
Received: 23 June 2015 / Revised: 2 October 2015 / Accepted: 17 October 2015 / Published: 27 October 2015
Viewed by 1771 | PDF Full-text (323 KB) | HTML Full-text | XML Full-text
Abstract
Conventional historical data based material and energy balance analyses are static and isolated computations. Such methods cannot embody the cross-coupling effect of energy flow, material flow and information flow in the process industry; furthermore, they cannot easily realize the effective evaluation and comparison
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Conventional historical data based material and energy balance analyses are static and isolated computations. Such methods cannot embody the cross-coupling effect of energy flow, material flow and information flow in the process industry; furthermore, they cannot easily realize the effective evaluation and comparison of different energy transfer processes by alternating the model module. In this paper, a novel method for material balance and energy conservation analysis of process industry energy transfer system is developed based on model property. Firstly, a reconfigurable energy transfer process model, which is independent of energy types and energy-consuming equipment, is presented from the viewpoint of the cross-coupling effect of energy flow, material flow and information flow. Thereafter the material balance determination is proposed based on both a dynamic incidence matrix and dynamic balance quantity. Moreover, the model-weighted conservation determination theorem is proved, and the energy efficiency analysis method is also discussed. Results confirmed the efficacy of the proposed methods, confirming its potential for use by process industry in energy efficiency analyses. Full article
(This article belongs to the Special Issue Applied Energy System Modeling 2015)
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Open AccessArticle A First-Order Study of Reduced Energy Consumption via Increased Thermal Capacitance with Thermal Storage Management in a Micro-Building
Energies 2015, 8(10), 12266-12282; https://doi.org/10.3390/en81012266
Received: 15 July 2015 / Revised: 18 September 2015 / Accepted: 19 October 2015 / Published: 27 October 2015
Cited by 4 | Viewed by 1720 | PDF Full-text (744 KB) | HTML Full-text | XML Full-text
Abstract
This study uses a first-order approximation of a micro-building to investigate the major factors determining how increased thermal capacitance (ITC) with thermal storage management (TSM) can reduce energy consumption in locations with relatively mild weather conditions such as the southeastern part of the
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This study uses a first-order approximation of a micro-building to investigate the major factors determining how increased thermal capacitance (ITC) with thermal storage management (TSM) can reduce energy consumption in locations with relatively mild weather conditions such as the southeastern part of the United States of America. In this study, ITC is achieved through water circulation between a large storage tank and pipes embedded within the building envelope. Although ITC results in a larger dominant time constant for the thermal response of a building, an adaptive allocation and control of the added capacitance through TSM significantly improves the benefits of the extra capacitance. This paper compares two first-order models for a micro-building: a reference case model with a single lumped thermal capacitance associated with the building, and another model, with the building’s capacitance plus the capacitance of the water system. Results showed that the ITC/TSM system reduced the cost of conditioning the building by reducing the operating time of both the cooling and the heating systems. May through September, the air conditioning operating time was reduced by an average of 70%, and October through April, the operation of the heating system was reduced by an average of 25%. Full article
(This article belongs to the Special Issue Energy Efficient Building Design 2016)
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Open AccessArticle Electricity Customer Clustering Following Experts’ Principle for Demand Response Applications
Energies 2015, 8(10), 12242-12265; https://doi.org/10.3390/en81012242
Received: 15 September 2015 / Revised: 15 October 2015 / Accepted: 20 October 2015 / Published: 27 October 2015
Cited by 8 | Viewed by 1596 | PDF Full-text (2241 KB) | HTML Full-text | XML Full-text
Abstract
The clustering of electricity customers might have an effective meaning if, and only if, it is verified by domain experts. Most of the previous studies on customer clustering, however, do not consider real applications, but only the structure of clusters. Therefore, there is
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The clustering of electricity customers might have an effective meaning if, and only if, it is verified by domain experts. Most of the previous studies on customer clustering, however, do not consider real applications, but only the structure of clusters. Therefore, there is no guarantee that the clustering results are applicable to real domains. In other words, the results might not coincide with those of domain experts. In this paper, we focus on formulating clusters that are applicable to real applications based on domain expert knowledge. More specifically, we try to define a distance between customers that generates clusters that are applicable to demand response applications. First, the k-sliding distance, which is a new distance between two electricity customers, is proposed for customer clustering. The effect of k-sliding distance is verified by expert knowledge. Second, a genetic programming framework is proposed to automatically determine a more improved distance measure. The distance measure generated by our framework can be considered as a reflection of the clustering principles of domain experts. The results of the genetic programming demonstrate the possibility of deriving clustering principles. Full article
(This article belongs to the collection Smart Grid)
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Open AccessArticle Echo State Network with Bayesian Regularization for Forecasting Short-Term Power Production of Small Hydropower Plants
Energies 2015, 8(10), 12228-12241; https://doi.org/10.3390/en81012228
Received: 7 May 2015 / Revised: 10 October 2015 / Accepted: 16 October 2015 / Published: 27 October 2015
Cited by 4 | Viewed by 2092 | PDF Full-text (1026 KB) | HTML Full-text | XML Full-text
Abstract
As a novel recurrent neural network (RNN), an echo state network (ESN) that utilizes a reservoir with many randomly connected internal units and only trains the readout, avoids increased complexity of training procedures faced by traditional RNN. The ESN can cope with complex
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As a novel recurrent neural network (RNN), an echo state network (ESN) that utilizes a reservoir with many randomly connected internal units and only trains the readout, avoids increased complexity of training procedures faced by traditional RNN. The ESN can cope with complex nonlinear systems because of its dynamical properties and has been applied in hydrological forecasting and load forecasting. Due to the linear regression algorithm usually adopted by generic ESN to train the output weights, an ill-conditioned solution might occur, degrading the generalization ability of the ESN. In this study, the ESN with Bayesian regularization (BESN) is proposed for short-term power production forecasting of small hydropower (SHP) plants. According to the Bayesian theory, the weights distribution in space is considered and the optimal output weights are obtained by maximizing the posterior probabilistic distribution. The evidence procedure is employed to gain optimal hyperparameters for the BESN model. The recorded data obtained from the SHP plants in two different counties, located in Yunnan Province, China, are utilized to validate the proposed model. For comparison, the feed-forward neural networks with Levenberg-Marquardt algorithm (LM-FNN) and the generic ESN are also employed. The results indicate that BESN outperforms both LM-FNN and ESN. Full article
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Open AccessArticle Economically Efficient Power Storage Operation by Dealing with the Non-Normality of Power Prediction
Energies 2015, 8(10), 12211-12227; https://doi.org/10.3390/en81012211
Received: 26 July 2015 / Revised: 4 October 2015 / Accepted: 20 October 2015 / Published: 27 October 2015
Cited by 2 | Viewed by 1350 | PDF Full-text (324 KB) | HTML Full-text | XML Full-text
Abstract
Various predictive models about the residential energy demand and residential renewable energy production have been proposed. Recent studies have confirmed that they are not normally distributed over time. The increase in renewable energy installation has brought the issue of energy storage charge and
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Various predictive models about the residential energy demand and residential renewable energy production have been proposed. Recent studies have confirmed that they are not normally distributed over time. The increase in renewable energy installation has brought the issue of energy storage charge and discharge control. Thus, storage control methods that properly address non-normality are required. In this paper, we formulated the economically optimal storage control problem using Markov decision process (MDP) and the conditional value at risk (CVaR) measure to deal with the non-normality of predictive distribution about the household’s net load. The CVaR measure was employed to treat with the chance constraint on the battery capacitor, in other words, overcharge risk and over-discharge risk. We conducted a simulation to compare the annual economic saving performances between two MDPs: one is the MDP with a Gaussian predictive distribution and the other is the MDP with a normalized frequency distribution (non-normal). We used the real time series of 35 residential energy consumption and PV generation data in Japan. The importance of addressing the non-normality of random variables was shown by our simulation. Full article
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Open AccessReview Recent Progress on the Resilience of Complex Networks
Energies 2015, 8(10), 12187-12210; https://doi.org/10.3390/en81012187
Received: 2 July 2015 / Revised: 18 September 2015 / Accepted: 9 October 2015 / Published: 27 October 2015
Cited by 21 | Viewed by 2345 | PDF Full-text (6837 KB) | HTML Full-text | XML Full-text
Abstract
Many complex systems in the real world can be modeled as complex networks, which has captured in recent years enormous attention from researchers of diverse fields ranging from natural sciences to engineering. The extinction of species in ecosystems and the blackouts of power
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Many complex systems in the real world can be modeled as complex networks, which has captured in recent years enormous attention from researchers of diverse fields ranging from natural sciences to engineering. The extinction of species in ecosystems and the blackouts of power girds in engineering exhibit the vulnerability of complex networks, investigated by empirical data and analyzed by theoretical models. For studying the resilience of complex networks, three main factors should be focused on: the network structure, the network dynamics and the failure mechanism. In this review, we will introduce recent progress on the resilience of complex networks based on these three aspects. For the network structure, increasing evidence shows that biological and ecological networks are coupled with each other and that diverse critical infrastructures interact with each other, triggering a new research hotspot of “networks of networks” (NON), where a network is formed by interdependent or interconnected networks. The resilience of complex networks is deeply influenced by its interdependence with other networks, which can be analyzed and predicted by percolation theory. This review paper shows that the analytic framework for Energies 2015, 8 12188 NON yields novel percolation laws for n interdependent networks and also shows that the percolation theory of a single network studied extensively in physics and mathematics in the last 60 years is a specific limited case of the more general case of n interacting networks. Due to spatial constraints inherent in critical infrastructures, including the power gird, we also review the progress on the study of spatially-embedded interdependent networks, exhibiting extreme vulnerabilities compared to their non-embedded counterparts, especially in the case of localized attack. For the network dynamics, we illustrate the percolation framework and methods using an example of a real transportation system, where the analysis based on network dynamics is significantly different from the structural static analysis. For the failure mechanism, we here review recent progress on the spontaneous recovery after network collapse. These findings can help us to understand, realize and hopefully mitigate the increasing risk in the resilience of complex networks. Full article
(This article belongs to the Special Issue Resilience of Energy Systems)
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Open AccessReview Effect of Loads and Other Key Factors on Oil-Transformer Ageing: Sustainability Benefits and Challenges
Energies 2015, 8(10), 12147-12186; https://doi.org/10.3390/en81012147
Received: 4 August 2015 / Revised: 22 September 2015 / Accepted: 16 October 2015 / Published: 27 October 2015
Cited by 32 | Viewed by 1686 | PDF Full-text (490 KB) | HTML Full-text | XML Full-text
Abstract
Transformers are one of the more expensive pieces of equipment found in a distribution network. The transformer’s role has not changed over the last decades. With simple construction and at the same time mechanically robust, they offer long term service that on average
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Transformers are one of the more expensive pieces of equipment found in a distribution network. The transformer’s role has not changed over the last decades. With simple construction and at the same time mechanically robust, they offer long term service that on average can reach half a century. Today, with the ongoing trend to supply a growing number of non-linear loads along with the notion of distributed generation (DG), a new challenge has arisen in terms of transformer sustainability, with one of the possible consequences being accelerated ageing. In this paper we carefully review the existing studies in the literature of the effect of loads and other key factors on oil-transformer ageing. The state-of-the-art is reviewed, each factor is analysed in detail, and in the end a smart transformer protection method is sought in order to monitor and protect it from upcoming challenges. Full article
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Open AccessArticle Dual Search Maximum Power Point (DSMPP) Algorithm Based on Mathematical Analysis under Shaded Conditions
Energies 2015, 8(10), 12116-12146; https://doi.org/10.3390/en81012116
Received: 25 August 2015 / Revised: 8 October 2015 / Accepted: 13 October 2015 / Published: 27 October 2015
Cited by 4 | Viewed by 1899 | PDF Full-text (921 KB) | HTML Full-text | XML Full-text
Abstract
Photovoltaic (PV) systems represent a clean, renewable source of energy that has non-linear current-voltage (I-V) and power-voltage (P-V) characteristics. To increase the efficiency, a PV system must operate at the maximum power point (MPP) to
[...] Read more.
Photovoltaic (PV) systems represent a clean, renewable source of energy that has non-linear current-voltage (I-V) and power-voltage (P-V) characteristics. To increase the efficiency, a PV system must operate at the maximum power point (MPP) to produce the maximum available power. Under uniform conditions, there is only a single MPP in the P-V curve of a PV system; however, determining the MPP is more complicated under partially shaded conditions (PSCs) because multiple peak power points exist. In recent years, various studies have been performed to obtain the highest peak power point under PSCs, which is referred to as the global maximum power point (GMPP). In this paper, a novel method based on mathematical analysis that reduces the search zone and simultaneously identifies the possible MPPs in the specified zone is proposed; this proposed method is called the dual search maximum power point (DSMPP) algorithm. To evaluate the effectiveness of the proposed method, simulation and hardware implementations are carried out. The results show that the search time of GMPP is significantly reduced and the GMPP is detected in the minimum amount of time with high accuracy and minimum oscillation in the power produced. Full article
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Open AccessArticle Integrating Auto-Associative Neural Networks with Hotelling T2 Control Charts for Wind Turbine Fault Detection
Energies 2015, 8(10), 12100-12115; https://doi.org/10.3390/en81012100
Received: 6 September 2015 / Revised: 9 October 2015 / Accepted: 19 October 2015 / Published: 23 October 2015
Cited by 7 | Viewed by 1902 | PDF Full-text (1073 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel methodology to detect a set of more suitable attributes that may potentially contribute to emerging faults of a wind turbine. The set of attributes were selected from one-year historical data for analysis. The methodology uses the k-means
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This paper presents a novel methodology to detect a set of more suitable attributes that may potentially contribute to emerging faults of a wind turbine. The set of attributes were selected from one-year historical data for analysis. The methodology uses the k-means clustering method to process outlier data and verifies the clustering results by comparing quartiles of boxplots, and applies the auto-associative neural networks to implement the residual approach that transforms the data to be approximately normally distributed. Hotelling T2 multivariate quality control charts are constructed for monitoring the turbine’s performance and relative contribution of each attribute is calculated for the data points out of upper limits to determine the set of potential attributes. A case using the historical data and the alarm log is given and illustrates that our methodology has the advantage of detecting a set of susceptible attributes at the same time compared with only one independent attribute is monitored. Full article
(This article belongs to the Special Issue Wind Turbine 2015)
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Open AccessArticle Forecasting China’s Annual Biofuel Production Using an Improved Grey Model
Energies 2015, 8(10), 12080-12099; https://doi.org/10.3390/en81012080
Received: 12 July 2015 / Revised: 11 October 2015 / Accepted: 19 October 2015 / Published: 23 October 2015
Cited by 9 | Viewed by 1749 | PDF Full-text (292 KB) | HTML Full-text | XML Full-text
Abstract
Biofuel production in China suffers from many uncertainties due to concerns about the government’s support policy and supply of biofuel raw material. Predicting biofuel production is critical to the development of this energy industry. Depending on the biofuel’s characteristics, we improve the prediction
[...] Read more.
Biofuel production in China suffers from many uncertainties due to concerns about the government’s support policy and supply of biofuel raw material. Predicting biofuel production is critical to the development of this energy industry. Depending on the biofuel’s characteristics, we improve the prediction precision of the conventional prediction method by creating a dynamic fuzzy grey–Markov prediction model. Our model divides random time series decomposition into a change trend sequence and a fluctuation sequence. It comprises two improvements. We overcome the problem of considering the status of future time from a static angle in the traditional grey model by using the grey equal dimension new information and equal dimension increasing models to create a dynamic grey prediction model. To resolve the influence of random fluctuation data and weak anti-interference ability in the Markov chain model, we improve the traditional grey–Markov model with classification of states using the fuzzy set theory. Finally, we use real data to test the dynamic fuzzy prediction model. The results prove that the model can effectively improve the accuracy of forecast data and can be applied to predict biofuel production. However, there are still some defects in our model. The modeling approach used here predicts biofuel production levels based upon past production levels dictated by economics, governmental policies, and technological developments but none of which can be forecast accurately based upon past events. Full article
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Open AccessArticle Numerical Analysis on the Optimization of Hydraulic Fracture Networks
Energies 2015, 8(10), 12061-12079; https://doi.org/10.3390/en81012061
Received: 8 September 2015 / Revised: 15 October 2015 / Accepted: 20 October 2015 / Published: 23 October 2015
Cited by 20 | Viewed by 2012 | PDF Full-text (2771 KB) | HTML Full-text | XML Full-text
Abstract
The clear understanding of hydraulic fracture network complexity and the optimization of fracture network configuration are important to the hydraulic fracturing treatment of shale gas reservoirs. For the prediction of hydraulic fracture network configuration, one of the problems is the accurate representation of
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The clear understanding of hydraulic fracture network complexity and the optimization of fracture network configuration are important to the hydraulic fracturing treatment of shale gas reservoirs. For the prediction of hydraulic fracture network configuration, one of the problems is the accurate representation of natural fractures. In this work, a real natural fracture network is reconstructed from shale samples. Moreover, a virtual fracture system is proposed to simulate the large number of small fractures that are difficult to identify. A numerical model based on the displacement discontinuity method is developed to simulate the fluid-rock coupling system. A dimensionless stress difference that is normalized by rock strength is proposed to quantify the anisotropy of crustal stress. The hydraulic fracturing processes under different stress conditions are simulated. The most complex fracture configurations are obtained when the maximum principle stress direction is perpendicular to the principle natural fracture direction. In contrast, the worst results are obtained when these two directions are parallel to each other. Moreover, the side effects of the unfavorable geological conditions caused by crustal stress anisotropy can be partly suppressed by increasing the viscous effect of the fluid. Full article
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Open AccessArticle A Comparison of Techniques for Reducing Unicast Traffic in HSR Networks
Energies 2015, 8(10), 12029-12060; https://doi.org/10.3390/en81012029
Received: 7 August 2015 / Revised: 14 September 2015 / Accepted: 20 October 2015 / Published: 23 October 2015
Cited by 2 | Viewed by 1507 | PDF Full-text (2269 KB) | HTML Full-text | XML Full-text
Abstract
This paper investigates several existing techniques for reducing high-availability seamless redundancy (HSR) unicast traffic in HSR networks for substation automation systems (SAS). HSR is a redundancy protocol for Ethernet networks that provides duplicate frames for separate physical paths with zero recovery time. This
[...] Read more.
This paper investigates several existing techniques for reducing high-availability seamless redundancy (HSR) unicast traffic in HSR networks for substation automation systems (SAS). HSR is a redundancy protocol for Ethernet networks that provides duplicate frames for separate physical paths with zero recovery time. This feature of HSR makes it very suited for real-time and mission-critical applications such as SAS systems. HSR is one of the redundancy protocols selected for SAS systems. However, the standard HSR protocol generates too much unnecessary redundant unicast traffic in connected-ring networks. This drawback degrades network performance and may cause congestion and delay. Several techniques have been proposed to reduce the redundant unicast traffic, resulting in the improvement of network performance in HSR networks. These HSR traffic reduction techniques are broadly classified into two categories based on their traffic reduction manner, including traffic filtering-based techniques and predefined path-based techniques. In this paper, we provide an overview and comparison of these HSR traffic reduction techniques found in the literature. The concepts, operational principles, network performance, advantages, and disadvantages of these techniques are investigated, summarized. We also provide a comparison of the traffic performance of these HSR traffic reduction techniques. Full article
(This article belongs to the collection Smart Grid)
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Open AccessArticle Expression of Heat Shock Proteins in Human Fibroblast Cells under Magnetic Resonant Coupling Wireless Power Transfer
Energies 2015, 8(10), 12020-12028; https://doi.org/10.3390/en81012020
Received: 27 July 2015 / Revised: 22 September 2015 / Accepted: 16 October 2015 / Published: 22 October 2015
Cited by 1 | Viewed by 1459 | PDF Full-text (681 KB) | HTML Full-text | XML Full-text
Abstract
Since 2007, resonant coupling wireless power transfer (WPT) technology has been attracting attention and has been widely researched for practical use. Moreover, dosimetric evaluation has also been discussed to evaluate the potential health risks of the electromagnetic field from this WPT technology based
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Since 2007, resonant coupling wireless power transfer (WPT) technology has been attracting attention and has been widely researched for practical use. Moreover, dosimetric evaluation has also been discussed to evaluate the potential health risks of the electromagnetic field from this WPT technology based on the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. However, there has not been much experimental evaluation of the potential health risks of this WPT technology. In this study, to evaluate whether magnetic resonant coupling WPT induces cellular stress, we focused on heat shock proteins (Hsps) and determined the expression level of Hsps 27, 70 and 90 in WI38VA13 subcloned 2RA human fibroblast cells using a western blotting method. The expression level of Hsps under conditions of magnetic resonant coupling WPT for 24 h was not significantly different compared with control cells, although the expression level of Hsps for cells exposed to heat stress conditions was significantly increased. These results suggested that exposure to magnetic resonant coupling WPT did not cause detectable cell stress. Full article
(This article belongs to the Special Issue Wireless Power Transfer)
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Open AccessArticle Analysing Performance Characteristics of Biomass Haulage in Ireland for Bioenergy Markets with GPS, GIS and Fuel Diagnostic Tools
Energies 2015, 8(10), 12004-12019; https://doi.org/10.3390/en81012004
Received: 20 August 2015 / Revised: 30 September 2015 / Accepted: 14 October 2015 / Published: 22 October 2015
Cited by 3 | Viewed by 1463 | PDF Full-text (645 KB) | HTML Full-text | XML Full-text
Abstract
In Ireland, truck transport by road dominates and will remain the main transportation mode of biomass. Cost efficiency and flexibility of forest transport can be typically improved by optimising routes. It is important to know every process and attributes within the workflow of
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In Ireland, truck transport by road dominates and will remain the main transportation mode of biomass. Cost efficiency and flexibility of forest transport can be typically improved by optimising routes. It is important to know every process and attributes within the workflow of roundwood transport. This study aimed to analyse characteristics of timber trucking in Ireland, and to estimate the least-cost route for the distribution of biomass with the use of geographic information systems (GIS). Firstly, a tracking system that recorded the truck’s movements and fuel consumption was installed. A total of 152 trips were recorded, routes were chosen by the truck driver. The recorded information was used to analyse the distances and times travelled loaded and unloaded per road class, breaks, loading and unloading times as well as fuel consumption. Secondly, the routes taken by the truck where compared with routes created using Network Analyst (NA), an extension of ArcGIS. Four scenarios based on route selection criteria were selected: shortest distance (S1), shorted time (S2), and prioritising high-class roads with shortest distance (S3) and time (S4). Results from the analysis of the tracking system data showed that driving both loaded and unloaded occupied on average 69% of the driver’s working shift; with an average time driving loaded of 49%. The travel distance per trip varied from 112 km and 197 km, with the truck driver using mostly national and regional roads. An average 2% of the total distance and 11% of the total time was spent driving on forest roads. In general, the truck’s speed recorded on the different road classes was on average 30% lower than the legal maximum speed. The average fuel consumption was 0.64 L/km. In terms of the route comparison, the driving directions from the truck routes coincided with 77% of the directions of the routes based on shortest driving time (S2 and S4). All the routes chosen by the driver had 22% longer distance than the routes in S1 (shortest distance). The routes selected based on shortest distance (S1 and S3) had the longest travelling time, approximately 19% more than the ones taken by the truck and 30% more than S2 and S4. The average running cost for the truck was 0.83 €/km. Choosing the shortest distance routes (S1 and S3) not only implies reducing travelling costs but also a reduction of CO2 emissions by 12% in comparison to routes in S2 and S4. However, when selecting the routes, travel time can be a much more crucial parameter to analyse rather than distance in terms of transportation costs. Choosing the routes generated in scenario S2 over S1 implied an increase in distance by 12% but a decrease in time of 30%. Less driving time translates into better driving conditions across higher classes or roads; less wear and tear of trucks; and lesser fuel used. It also complies with local authorities preferences of having timber trucks move on higher road types in order to minimise the expenses associated with road maintenance. Full article
(This article belongs to the Special Issue Economics of Bioenergy 2015)
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Open AccessArticle An Efficient Model for NPD Performance Evaluation Using DEMATEL and Fuzzy ANP—Applied to the TFT-LCD Touch Panel Industry in Taiwan
Energies 2015, 8(10), 11973-12003; https://doi.org/10.3390/en81011973
Received: 9 June 2015 / Revised: 18 September 2015 / Accepted: 12 October 2015 / Published: 22 October 2015
Cited by 4 | Viewed by 1407 | PDF Full-text (2335 KB) | HTML Full-text | XML Full-text
Abstract
As the competitive market nowadays shortens the life cycle of products, new products should be designed to meet the customer’s demand under a dynamic marketing environment so as to efficiently enhance the product strength of new products with maximization of profit. Hence, the
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As the competitive market nowadays shortens the life cycle of products, new products should be designed to meet the customer’s demand under a dynamic marketing environment so as to efficiently enhance the product strength of new products with maximization of profit. Hence, the key solution for enterprises to succeed will be the precise evaluation of new product development (NPD) performance, particularly for those who manage to survive in the intensely competitive market in Taiwan. This study is to identify the thin film transistor-liquid crystal display (TFT-LCD) touch panel industry and then establish an integrated model of NPD performance evaluation for enterprises. Firstly, literature review and interviews with experts are conducted to select the four aspects and 15 criteria as the main factors affecting NDP performance evaluation. Secondly, Decision Making Trial and Evaluation Laboratory (DEMATEL) is employed to identify the interrelationships among those factors. Finally, a Fuzzy theory is applied to resolve the linguistic hedges and an Analytic Network Process (ANP) is adopted to obtain the weights of all factors. A case study is performed to validate the proposed model in a Taiwanese TFT-LCD company. It not only provides the decision maker with a guidance system but also increases the competitive advantages for the TFT-LCD industry to design new products in the future. Full article
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Open AccessArticle An Experimental Study on the Effects ofWinglets on the Wake and Performance of a ModelWind Turbine
Energies 2015, 8(10), 11955-11972; https://doi.org/10.3390/en81011955
Received: 25 August 2015 / Revised: 25 September 2015 / Accepted: 3 October 2015 / Published: 21 October 2015
Cited by 8 | Viewed by 1715 | PDF Full-text (2852 KB) | HTML Full-text | XML Full-text
Abstract
Wind tunnel experiments were performed to investigate the effects of downstream-facing winglets on the wake dynamics, power and thrust of a model wind turbine. Two similar turbines with and without winglets were operated under the same conditions. Results show an increase in the
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Wind tunnel experiments were performed to investigate the effects of downstream-facing winglets on the wake dynamics, power and thrust of a model wind turbine. Two similar turbines with and without winglets were operated under the same conditions. Results show an increase in the power and thrust coefficients of 8.2% and 15.0% for the wingletted case. A simple theoretical treatment of a two-turbine system suggests a possible positive tradeoff between increasing power and thrust coefficients at a wind farm scale. The higher thrust coefficient created a region of enhanced mean shear and turbulence in the outer portion of the wake. The winglets did not significantly change the tip-vortex strength, but higher levels of turbulence in the far wake decreased the tip-vortex strength. Because of the increased mean shear in the wingletted turbine’s wake, the Reynolds stresses were higher, potentially leading to a higher energy flux downstream. Full article
(This article belongs to the Special Issue Wind Turbine 2015)
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Open AccessArticle Techno-Economic Performance Evaluation for Olive Mills Powered by Grid-Connected Photovoltaic Systems
Energies 2015, 8(10), 11939-11954; https://doi.org/10.3390/en81011939
Received: 16 September 2015 / Revised: 5 October 2015 / Accepted: 14 October 2015 / Published: 21 October 2015
Cited by 2 | Viewed by 1502 | PDF Full-text (547 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, due to the rise in petroleum prices and greenhouse gas emissions, renewable energy has been recommended as a power source for different types of facilities. For the period 2010 to 2020 the European Commission has established three key objectives related
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In recent years, due to the rise in petroleum prices and greenhouse gas emissions, renewable energy has been recommended as a power source for different types of facilities. For the period 2010 to 2020 the European Commission has established three key objectives related to climatic change and energy sustainability, such as reductions of CO2 emissions, increases in the use of renewable energy, and improvements in energy efficiency. A key industry is olive oil production in olive mills, where there is a great opportunity to reduce electricity consumption, increase additional profits related to the reduction of technologies that are harmful to the environment, and to cut back maintenance costs. For this reason, a feasibility study of grid-connected photovoltaics (PV) systems has been carried out for different types of olive mills in Andalusia (southern Spain). This region is highly energy dependent, but has an abundance of “green” resources to be exploited. The results of this study contemplate a reduction in spending on electrical power of between 2% and 37%, and an increase in the use of renewable energy of between 2% and 26%. These results are according to the self-consumption or net metering policy and the production capacity of olive oil. Full article
(This article belongs to the Special Issue Energy for Agriculture)
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Open AccessArticle A Solution Based on Bluetooth Low Energy for Smart Home Energy Management
Energies 2015, 8(10), 11916-11938; https://doi.org/10.3390/en81011916
Received: 28 August 2015 / Revised: 28 September 2015 / Accepted: 3 October 2015 / Published: 21 October 2015
Cited by 33 | Viewed by 2832 | PDF Full-text (646 KB) | HTML Full-text | XML Full-text
Abstract
The research and the implementation of home automation are getting more popular because the Internet of Things holds promise for making homes smarter through wireless technologies. The installation of systems based on wireless networks can play a key role also in the extension
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The research and the implementation of home automation are getting more popular because the Internet of Things holds promise for making homes smarter through wireless technologies. The installation of systems based on wireless networks can play a key role also in the extension of the smart grid towards smart homes, that can be deemed as one of the most important components of smart grids. This paper proposes a fuzzy-based solution for smart energy management in a home automation wireless network. The approach, by using Bluetooth Low Energy (BLE), introduces a Fuzzy Logic Controller (FLC) in order to improve a Home Energy Management (HEM) scheme, addressing the power load of standby appliances and their loads in different hours of the day. Since the consumer is involved in the choice of switching on/off of home appliances, the approach introduced in this work proposes a fuzzy-based solution in order to manage the consumer feedbacks. Simulation results show that the proposed solution is efficient in terms of reducing peak load demand, electricity consumption charges with an increase comfort level of consumers. The performance of the proposed BLE-based wireless network scenario are validated in terms of packet delivery ratio, delay, and jitter and are compared to IEEE 802.15.4 technology. Full article
(This article belongs to the Special Issue Energy Efficient Building Design 2016)
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Open AccessReview State of the Art Authentication, Access Control, and Secure Integration in Smart Grid
Energies 2015, 8(10), 11883-11915; https://doi.org/10.3390/en81011883
Received: 16 July 2015 / Revised: 10 October 2015 / Accepted: 12 October 2015 / Published: 21 October 2015
Cited by 13 | Viewed by 2659 | PDF Full-text (306 KB) | HTML Full-text | XML Full-text
Abstract
The smart grid (SG) is a promising platform for providing more reliable, efficient, and cost effective electricity to the consumers in a secure manner. Numerous initiatives across the globe are taken by both industry and academia in order to compile various security issues
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The smart grid (SG) is a promising platform for providing more reliable, efficient, and cost effective electricity to the consumers in a secure manner. Numerous initiatives across the globe are taken by both industry and academia in order to compile various security issues in the smart grid network. Unfortunately, there is no impactful survey paper available in the literature on authentications in the smart grid network. Therefore, this paper addresses the required objectives of an authentication protocol in the smart grid network along with the focus on mutual authentication, access control, and secure integration among different SG components. We review the existing authentication protocols, and analyze mutual authentication, privacy, trust, integrity, and confidentiality of communicating information in the smart grid network. We review authentications between the communicated entities in the smart grid, such as smart appliance, smart meter, energy provider, control center (CC), and home/building/neighborhood area network gateways (GW). We also review the existing authentication schemes for the vehicle-to-grid (V2G) communication network along with various available secure integration and access control schemes. We also discuss the importance of the mutual authentication among SG entities while providing confidentiality and privacy preservation, seamless integration, and required access control with lower overhead, cost, and delay. This paper will help to provide a better understanding of current authentication, authorization, and secure integration issues in the smart grid network and directions to create interest among researchers to further explore these promising areas. Full article
(This article belongs to the collection Smart Grid)
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Open AccessArticle Optimal Subinterval Selection Approach for Power System Transient Stability Simulation
Energies 2015, 8(10), 11871-11882; https://doi.org/10.3390/en81011871
Received: 2 September 2015 / Revised: 14 October 2015 / Accepted: 16 October 2015 / Published: 21 October 2015
Cited by 2 | Viewed by 1565 | PDF Full-text (333 KB) | HTML Full-text | XML Full-text
Abstract
Power system transient stability analysis requires an appropriate integration time step to avoid numerical instability as well as to reduce computational demands. For fast system dynamics, which vary more rapidly than what the time step covers, a fraction of the time step, called
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Power system transient stability analysis requires an appropriate integration time step to avoid numerical instability as well as to reduce computational demands. For fast system dynamics, which vary more rapidly than what the time step covers, a fraction of the time step, called a subinterval, is used. However, the optimal value of this subinterval is not easily determined because the analysis of the system dynamics might be required. This selection is usually made from engineering experiences, and perhaps trial and error. This paper proposes an optimal subinterval selection approach for power system transient stability analysis, which is based on modal analysis using a single machine infinite bus (SMIB) system. Fast system dynamics are identified with the modal analysis and the SMIB system is used focusing on fast local modes. An appropriate subinterval time step from the proposed approach can reduce computational burden and achieve accurate simulation responses as well. The performance of the proposed method is demonstrated with the GSO 37-bus system. Full article
(This article belongs to the Special Issue Electric Power Systems Research) Printed Edition available
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Open AccessArticle A New Building-Integrated Wind Turbine System Utilizing the Building
Energies 2015, 8(10), 11846-11870; https://doi.org/10.3390/en81011846
Received: 10 August 2015 / Revised: 13 October 2015 / Accepted: 15 October 2015 / Published: 21 October 2015
Cited by 13 | Viewed by 2354 | PDF Full-text (4612 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes an innovative building-integrated wind turbine (BIWT) system by directly utilizing the building skin, which is an unused and unavailable area in all conventional BIWT systems. The proposed system has been developed by combining a guide vane that is able to
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This paper proposes an innovative building-integrated wind turbine (BIWT) system by directly utilizing the building skin, which is an unused and unavailable area in all conventional BIWT systems. The proposed system has been developed by combining a guide vane that is able to effectively collect the incoming wind and increase its speed and a rotor with an appropriate shape for specific conditions. To this end, several important design issues for the guide vane as well as the rotor were thoroughly investigated and accordingly addressed in this paper. A series of computational fluid dynamics (CFD) analyses was performed to determine the optimal configuration of the proposed system. Finally, it is demonstrated from performance evaluation tests that the prototype with the specially designed guide vane and rotor for the proposed BIWT system accelerates the wind speed to a sufficient level and consequently increases the power coefficient significantly. Thus, it was confirmed that the proposed system is a promising environment-friendly energy production system for urban areas. Full article
(This article belongs to the Special Issue Wind Turbine 2015)
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Open AccessReview Recent Advances in Osmotic Energy Generation via Pressure-Retarded Osmosis (PRO): A Review
Energies 2015, 8(10), 11821-11845; https://doi.org/10.3390/en81011821
Received: 31 August 2015 / Revised: 24 September 2015 / Accepted: 14 October 2015 / Published: 20 October 2015
Cited by 16 | Viewed by 2690 | PDF Full-text (1368 KB) | HTML Full-text | XML Full-text
Abstract
Global energy consumption has been highly dependent on fossil fuels which cause severe climate change and, therefore, the exploration of new technologies to produce effective renewable energy plays an important role in the world. Pressure-retarded osmosis (PRO) is one of the promising candidates
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Global energy consumption has been highly dependent on fossil fuels which cause severe climate change and, therefore, the exploration of new technologies to produce effective renewable energy plays an important role in the world. Pressure-retarded osmosis (PRO) is one of the promising candidates to reduce the reliance on fossil fuels by harnessing energy from the salinity gradient between seawater and fresh water. In PRO, water is transported though a semi-permeable membrane from a low-concentrated feed solution to a high-concentrated draw solution. The increased volumetric water flow then runs a hydro-turbine to generate power. PRO technology has rapidly improved in recent years; however, the commercial-scale PRO plant is yet to be developed. In this context, recent developments on the PRO process are reviewed in terms of mathematical models, membrane modules, process designs, numerical works, and fouling and cleaning. In addition, the research requirements to accelerate PRO commercialization are discussed. It is expected that this article can help comprehensively understand the PRO process and thereby provide essential information to activate further research and development. Full article
(This article belongs to the Special Issue Osmotic Power)
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Open AccessArticle Numerical Validation of a Vortex Model against ExperimentalData on a Straight-Bladed Vertical Axis Wind Turbine
Energies 2015, 8(10), 11800-11820; https://doi.org/10.3390/en81011800
Received: 3 August 2015 / Revised: 28 September 2015 / Accepted: 13 October 2015 / Published: 20 October 2015
Cited by 4 | Viewed by 2028 | PDF Full-text (1065 KB) | HTML Full-text | XML Full-text
Abstract
Cyclic blade motion during operation of vertical axis wind turbines (VAWTs) imposes challenges on the simulations models of the aerodynamics of VAWTs. A two-dimensional vortex model is validated against the new experimental data on a 12-kW straight-bladed VAWT, which is operated at an
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Cyclic blade motion during operation of vertical axis wind turbines (VAWTs) imposes challenges on the simulations models of the aerodynamics of VAWTs. A two-dimensional vortex model is validated against the new experimental data on a 12-kW straight-bladed VAWT, which is operated at an open site. The results on the normal force on one blade are analyzed. The model is assessed against the measured data in the wide range of tip speed ratios: from 1.8 to 4.6. The predicted results within one revolution have a similar shape and magnitude as the measured data, though the model does not reproduce every detail of the experimental data. The present model can be used when dimensioning the turbine for maximum loads. Full article
(This article belongs to the Special Issue Wind Turbine 2015)
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Open AccessArticle Co-Movement Analysis of Italian and Greek Electricity Market Wholesale Prices by Using a Wavelet Approach
Energies 2015, 8(10), 11770-11799; https://doi.org/10.3390/en81011770
Received: 13 August 2015 / Revised: 1 October 2015 / Accepted: 9 October 2015 / Published: 20 October 2015
Cited by 3 | Viewed by 1730 | PDF Full-text (1970 KB) | HTML Full-text | XML Full-text
Abstract
We study the co-evolution of the dynamics or co-movement of two electricity markets, the Italian and Greek, by studying the dynamics of their wholesale day-ahead prices, simultaneously in the time-frequency domain. Co-movement is alternatively referred as market integration in financial economics and markets
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We study the co-evolution of the dynamics or co-movement of two electricity markets, the Italian and Greek, by studying the dynamics of their wholesale day-ahead prices, simultaneously in the time-frequency domain. Co-movement is alternatively referred as market integration in financial economics and markets are internationally integrated if the reward for risk is identical regardless the market one trades in. The innovation of this work is the application of wavelet analysis and more specifically the wavelet coherence to estimate the dynamic interaction between these two prices. Our method is compared to other generic econometric tools used in Economics and Finance namely the dynamic correlation and coherence analysis, to study the co-movement of variables of the type related to these two fields. Our study reveals valuable information that we believe will be extremely useful to the authorities as well as other agents participating in these markets to better prepare the national markets towards the European target model, a framework in which the two markets will be coupled. Full article
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Open AccessArticle Miniaturized Air-Driven Planar Magnetic Generators
Energies 2015, 8(10), 11755-11769; https://doi.org/10.3390/en81011755
Received: 3 June 2015 / Revised: 28 July 2015 / Accepted: 14 September 2015 / Published: 19 October 2015
Cited by 2 | Viewed by 2460 | PDF Full-text (3445 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the design, analysis, fabrication and testing of two miniaturized air-driven planar magnetic generators. In order to reduce the magnetic resistance torque, Generator 1 establishes a static magnetic field by consisting a multilayer planar coil as the stator and two multi-pole
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This paper presents the design, analysis, fabrication and testing of two miniaturized air-driven planar magnetic generators. In order to reduce the magnetic resistance torque, Generator 1 establishes a static magnetic field by consisting a multilayer planar coil as the stator and two multi-pole permanent-magnet (PM) rotors on both sides of the coil. To further decrease the starting torque and save more space, Generator 2 adopts the multilayer planar coil as the rotor and the multi-pole PMs as the stator, eliminating the casing without compromising the magnetic structure or output performance. The prototypes were tested gathering energy from wind which can work at a low wind speed of 1~2 m/s. Prototype of Generator 1 is with a volume of 2.61 cm3 and its normalized voltage reaches 485 mV/krpm. Prototype of Generator 2 has a volume of 0.92 cm3 and a normalized voltage as high as 538 mV/krpm. Additionally, output voltage can be estimated at better than 96% accuracy by the theoretical model developed in this paper. The two micro generators are capable of producing substantial electricity with little volume to serve as compact power conversion devices. Full article
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Open AccessEditorial Geothermal Energy: Delivering on the Global Potential
Energies 2015, 8(10), 11737-11754; https://doi.org/10.3390/en81011737
Received: 8 October 2015 / Accepted: 9 October 2015 / Published: 19 October 2015
Cited by 9 | Viewed by 2165 | PDF Full-text (666 KB) | HTML Full-text | XML Full-text
Abstract
Geothermal energy has been harnessed for recreational uses for millennia, but only for electricity generation for a little over a century. Although geothermal is unique amongst renewables for its baseload and renewable heat provision capabilities, uptake continues to lag far behind that of
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Geothermal energy has been harnessed for recreational uses for millennia, but only for electricity generation for a little over a century. Although geothermal is unique amongst renewables for its baseload and renewable heat provision capabilities, uptake continues to lag far behind that of solar and wind. This is mainly attributable to (i) uncertainties over resource availability in poorly-explored reservoirs and (ii) the concentration of full-lifetime costs into early-stage capital expenditure (capex). Recent advances in reservoir characterization techniques are beginning to narrow the bounds of exploration uncertainty, both by improving estimates of reservoir geometry and properties, and by providing pre-drilling estimates of temperature at depth. Advances in drilling technologies and management have potential to significantly lower initial capex, while operating expenditure is being further reduced by more effective reservoir management—supported by robust models—and increasingly efficient energy conversion systems (flash, binary and combined-heat-and-power). Advances in characterization and modelling are also improving management of shallow low-enthalpy resources that can only be exploited using heat-pump technology. Taken together with increased public appreciation of the benefits of geothermal, the technology is finally ready to take its place as a mainstream renewable technology, exploited far beyond its traditional confines in the world’s volcanic regions. Full article
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Open AccessArticle Maximum Energy Output of a DFIG Wind Turbine Using an Improved MPPT-Curve Method
Energies 2015, 8(10), 11718-11736; https://doi.org/10.3390/en81011718
Received: 1 August 2015 / Revised: 21 September 2015 / Accepted: 13 October 2015 / Published: 19 October 2015
Cited by 8 | Viewed by 2281 | PDF Full-text (637 KB) | HTML Full-text | XML Full-text
Abstract
A new method is proposed for obtaining the maximum power output of a doubly-fed induction generator (DFIG) wind turbine to control the rotor- and grid-side converters. The efficiency of maximum power point tracking that is obtained by the proposed method is theoretically guaranteed
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A new method is proposed for obtaining the maximum power output of a doubly-fed induction generator (DFIG) wind turbine to control the rotor- and grid-side converters. The efficiency of maximum power point tracking that is obtained by the proposed method is theoretically guaranteed under assumptions that represent physical conditions. Several control parameters may be adjusted to ensure the quality of control performance. In particular, a DFIG state-space model and a control technique based on the Lyapunov function are adopted to derive the control method. The effectiveness of the proposed method is verified via numerical simulations of a 1.5-MW DFIG wind turbine using MATLAB/Simulink. The simulation results show that when the proposed method is used, the wind turbine is capable of properly tracking the optimal operation point; furthermore, the generator’s available energy output is higher when the proposed method is used than it is when the conventional method is used instead. Full article
(This article belongs to the Special Issue Wind Turbine 2015)
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Open AccessArticle Linear Modeling and Regulation Quality Analysis for Hydro-Turbine Governing System with an Open Tailrace Channel
Energies 2015, 8(10), 11702-11717; https://doi.org/10.3390/en81011702
Received: 5 September 2015 / Revised: 3 October 2015 / Accepted: 13 October 2015 / Published: 19 October 2015
Cited by 6 | Viewed by 2167 | PDF Full-text (738 KB) | HTML Full-text | XML Full-text
Abstract
On the basis of the state–space method (SSM), a novel linear mathematical model of the unsteady flow for the tailrace system with an open channel is proposed. This novel model is an elastic linearized model of water hammer. The validity of the model
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On the basis of the state–space method (SSM), a novel linear mathematical model of the unsteady flow for the tailrace system with an open channel is proposed. This novel model is an elastic linearized model of water hammer. The validity of the model has been verified by several examples of numerical simulation, which are based on a finite difference technique. Then, the complete mathematical model for the hydro-turbine governing system of hydropower station with an open tailrace channel, which is used for simulating the transient process of the hydro-turbine governing system under load disturbance, is established by combining the models of hydro-turbine, generator, governor and open tailrace channel. Finally, according to the complete model, the regulation quality for hydro-turbine governing system with an open tailrace channel under load disturbance is studied, and the effects of open tailrace channel and tailrace surge tank on regulation quality are analyzed. The results indicate that: The open tailrace channel has a strong influence on the regulation quality by observing the water level fluctuations in tailrace surge tank. The surge shows a piecewise periodical change along with the variation in the length of an open channel. The open tailrace channel can be used to improve the regulation quality of hydro-turbine governing system. Full article
(This article belongs to the Special Issue Hydropower)
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Open AccessArticle A Non-Unity Torque Sharing Function for Torque Ripple Minimization of Switched Reluctance Generators in Wind Power Systems
Energies 2015, 8(10), 11685-11701; https://doi.org/10.3390/en81011685
Received: 25 August 2015 / Revised: 7 October 2015 / Accepted: 13 October 2015 / Published: 16 October 2015
Cited by 3 | Viewed by 1965 | PDF Full-text (2826 KB) | HTML Full-text | XML Full-text
Abstract
This paper deals with a new torque ripple minimization method for a Switched Reluctance Generator (SRG). Although, the SRG has many advantages including simple and robust construction, and high power density as a generator, it has not been widely employed in the industry.
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This paper deals with a new torque ripple minimization method for a Switched Reluctance Generator (SRG). Although, the SRG has many advantages including simple and robust construction, and high power density as a generator, it has not been widely employed in the industry. One of the major drawbacks of the SRG is its high torque ripple that results in high noise operation of the generator. In this paper, a non-unity Torque Sharing Function (TSF) is proposed to minimize the torque ripple over a wide speed range of operation. Simulations as well as experimental results are presented to verify the effectiveness of the proposed torque ripple minimization technique. Full article
(This article belongs to the Special Issue Wind Turbine 2015)
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