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Energies, Volume 5, Issue 1 (January 2012) – 12 articles , Pages 1-180

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840 KiB  
Article
Steady State Assessment of Shunt Compensated EHV Insulated Cables by Means of Multiconductor Cell Analysis (MCA)
by Roberto Benato
Energies 2012, 5(1), 168-180; https://doi.org/10.3390/en5010168 - 23 Jan 2012
Cited by 4 | Viewed by 5385
Abstract
The author has already presented some papers which allow studying cable systems by means of the multiconductor cell analysis (MCA). This method considers the cable system in its real asymmetry without simplified and approximated hypotheses. The multiconductor matrix procedure based on the use [...] Read more.
The author has already presented some papers which allow studying cable systems by means of the multiconductor cell analysis (MCA). This method considers the cable system in its real asymmetry without simplified and approximated hypotheses. The multiconductor matrix procedure based on the use of admittance matrices, which account for the line cells (with earth return currents), different types of screen bonding, possible multiple circuits (single and double circuit or more), allows predicting the steady-state regime of any cable system. In the previous papers, these matrix algorithms have been presented with reference to a short extra-high voltage (EHV) double-circuit cross-bonded (CB) underground cable (UGC) system. Since the cable link was short, the shunt reactive compensation was not necessary and consequently not considered. In this paper the procedure is generalized in order to take into account three single-phase (or also one three-phase) reactors installed at the cable ends or also at intermediate locations. Full article
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Figure 1
<p>Lumped shunt compensation at the two ends.</p>
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<p>Lumped shunt compensation at the ends and at intermediate locations.</p>
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<p>No load energization at port S.</p>
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<p>Limit lengths due to the constraints (7) and (8) for cable of <a href="#energies-05-00168-t001" class="html-table">Table 1</a>.</p>
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<p>Reactive compensation degree as a function of cable length due to the constraints (7) and (8) for cable of <a href="#energies-05-00168-t001" class="html-table">Table 1</a> and <span class="html-italic">X</span>'' = 20 Ω.</p>
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<p>Admittance matrix <span class="html-italic"><span class="underline">Y</span><sub>Eξ</sub></span> for shunt reactors and screen earthing.</p>
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<p>Single-circuit CB UGC.</p>
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<p>Subdivision of the CB single-circuit cable line with indication of lumped shunt compensation locations.</p>
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<p>Phase current magnitudes along the compensated single-circuit cable, in CB with PTs.</p>
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<p>Phase voltage magnitudes along the compensated single-circuit cable in CB with PTs.</p>
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<p>Screen voltage and current magnitudes along the compensated single-circuit cable in CB with PTs.</p>
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<p>Phase current magnitudes along the compensated UGC in CB with PTs at no-load.</p>
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<p>Screen voltage magnitudes along the compensated single-circuit cable in CB with PTs at no-load.</p>
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<p>Phase current magnitudes along the compensated single-circuit cable in CB without PTs.</p>
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<p>Phase voltage magnitudes along the compensated single-circuit cable in CB without PTs.</p>
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<p>Ground return current magnitude for CB UGC without PTs.</p>
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<p>Phase current magnitudes along the compensated single-circuit cable in CB without PTs and compensated only at the two ends (as in <a href="#energies-05-00168-f001" class="html-fig">Figure 1</a>).</p>
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796 KiB  
Article
A Two-Dimensional Cloud Model for Condition Assessment of HVDC Converter Transformers
by Jian Li, Zhiman He, Youyuan Wang, Jinzhuang Lv and Linjie Zhao
Energies 2012, 5(1), 157-167; https://doi.org/10.3390/en5010157 - 23 Jan 2012
Cited by 9 | Viewed by 6143
Abstract
Converter transformers are the key and the most important components in high voltage direct current (HVDC) power transmission systems. Statistics show that the failure rate of HVDC converter transformers is approximately twice of that of transformers in AC power systems. This paper presents [...] Read more.
Converter transformers are the key and the most important components in high voltage direct current (HVDC) power transmission systems. Statistics show that the failure rate of HVDC converter transformers is approximately twice of that of transformers in AC power systems. This paper presents an approach integrated with a two-dimensional cloud model and an entropy-based weight model to evaluate the condition of HVDC converter transformers. The integrated approach can describe the complexity of HVDC converter transformers and achieve an effective assessment of their condition. Data from electrical testing, DGA, oil testing, and visual inspection were chosen to form the double-level assessment index system. Analysis results show that the integrated approach is capable of providing a relevant and effective assessment which in turn, provides valuable information for the maintenance of HVDC converter transformers. Full article
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<p>Level 1 assessment index system.</p>
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<p>Level 2 assessing index system.</p>
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<p>Image of “about 20” TDCM.</p>
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<p>Sketch of TDCM membership degree functions.</p>
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1622 KiB  
Article
Standardization Work for BEV and HEV Applications: Critical Appraisal of Recent Traction Battery Documents
by Noshin Omar, Mohamed Daowd, Omar Hegazy, Grietus Mulder, Jean-Marc Timmermans, Thierry Coosemans, Peter Van den Bossche and Joeri Van Mierlo
Energies 2012, 5(1), 138-156; https://doi.org/10.3390/en5010138 - 19 Jan 2012
Cited by 69 | Viewed by 12906
Abstract
The increased activity in the field of Battery Electric Vehicles (BEVs) and Hybrid Electric Vehicles (HEVs) have led to an increase in standardization work, performed by both world-wide organizations like the IEC or the ISO, as by regional and national bodies such as [...] Read more.
The increased activity in the field of Battery Electric Vehicles (BEVs) and Hybrid Electric Vehicles (HEVs) have led to an increase in standardization work, performed by both world-wide organizations like the IEC or the ISO, as by regional and national bodies such as CEN, CENELEC, SAE or JEVA. The issues of these standards cover several topics: safety, performance and operational/dimension issues. This paper reports a brief overview of current standardization activities of lithium batteries based on IEC 62660-1/2 and ISO 12405-1/2. Furthermore, in this paper, a series of innovative test procedures for lithium-ion batteries are presented. Thanks to these tests, the general characteristics of a battery such as charge and discharge capabilities, power performances and life cycle can be determined. Then, a new approach for extracting the life cycle of a battery in function of depth of discharge has been developed. Full article
(This article belongs to the Special Issue Electric and Hybrid Vehicles)
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<p>Rangone plot [<a href="#B3-energies-05-00138" class="html-bibr">3</a>].</p>
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<p>Voltage duration of various lithium-ion chemistries.</p>
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<p>Battery pack system [<a href="#B27-energies-05-00138" class="html-bibr">27</a>].</p>
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<p>Dynamic Discharge Performance Test [<a href="#B30-energies-05-00138" class="html-bibr">30</a>].</p>
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<p>Newly developed energy and capacity test at different current rates.</p>
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<p>Charge efficiency during CC phase at cell level.</p>
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<p>State of charge estimation including Peukert and efficiency.</p>
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<p>Second order battery model.</p>
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<p>Extended Hybrid Pulse Power Characterization Test.</p>
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<p>Butler-Volmer phenomenon at lithium-ion cell level.</p>
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<p>IEC micro-cycle for battery electric vehicle (profileB) [<a href="#B27-energies-05-00138" class="html-bibr">27</a>].</p>
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<p>Novel life cycle topology.</p>
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<p>Experimental results of the Punch topology.</p>
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<p>Increasing of variation between the cells during constant current charge without balancing.</p>
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<p>IEC micro-cycle discharge rich profile for battery electric vehicle [<a href="#B28-energies-05-00138" class="html-bibr">28</a>].</p>
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<p>New life cycle method for high power applications [<a href="#B28-energies-05-00138" class="html-bibr">28</a>].</p>
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<p>An example of the initial charge and discharge micro cycles.</p>
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526 KiB  
Article
Performance Analysis and Simulation of a Novel Brushless Double Rotor Machine for Power-Split HEV Applications
by Ping Zheng, Qian Wu, Jing Zhao, Chengde Tong, Jingang Bai and Quanbin Zhao
Energies 2012, 5(1), 119-137; https://doi.org/10.3390/en5010119 - 19 Jan 2012
Cited by 14 | Viewed by 7858
Abstract
A new type of brushless double rotor machine (BDRM) is proposed in this paper. The BDRM is an important component in compound-structure permanent-magnet synchronous machine (CS-PMSM) systems, which are promising for power-split hybrid electric vehicle (HEV) applications. The BDRM can realize the speed [...] Read more.
A new type of brushless double rotor machine (BDRM) is proposed in this paper. The BDRM is an important component in compound-structure permanent-magnet synchronous machine (CS-PMSM) systems, which are promising for power-split hybrid electric vehicle (HEV) applications. The BDRM can realize the speed adjustment between claw-pole rotor and permanent-magnet rotor without brushes and slip rings. The structural characteristics of the BDRM are described and its magnetic circuit model is built. Reactance parameters of the BDRM are deduced by an analytical method. It is found that the size characteristics of the BDRM are different from those of conventional machines. The new sizing and torque equations are analyzed and the theoretical results are used in the optimization process. Studies of the analytical magnetic circuit and finite element method (FEM) model show that the BDRM tends to have high leakage flux and low power factor, and then the method to obtain high power factor is discussed. Furthermore, a practical methodology of the BDRM design is developed, which includes an analytical tool, 2D field calculation and performance evaluation by 3D field calculation. Finally, different topologies of the BDRM are compared and an optimum prototype is designed. Full article
(This article belongs to the Special Issue Electric and Hybrid Vehicles)
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Graphical abstract

Graphical abstract
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<p>CS-PMSM system.</p>
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<p>Brushless CS-PMSM system.</p>
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<p>Power flow path in the brushless CS-PMSM system.</p>
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<p>Typical operation states of the power-split hybrid drive system: (<b>a</b>) Pure electric mode; (<b>b</b>) ICE starter mode; (<b>c</b>) CVT mode; (<b>d</b>) Acceleration and hill climbing mode; (<b>e</b>) Braking mode.</p>
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<p>Flux path in one pole of the BDRM.</p>
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<p>Equivalent magnetic circuit diagrams with load: (<b>a</b>) d-axis; (<b>b</b>) q-axis.</p>
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<p>Simplified magnetic circuit.</p>
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<p>Phasor diagram when <span class="html-italic">I</span><span class="html-italic"><sub>d</sub></span> = 0.</p>
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<p>Power factor <span class="html-italic">versus</span> <math display="inline"> <semantics> <mi>ψ</mi> </semantics> </math>.</p>
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<p>3D BDRM model.</p>
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<p>The flux-linkage and BEMF in one-phase at no-load.</p>
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<p>FEM calculated torque curve of the BDRM.</p>
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<p>The 2D equivalent model.</p>
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<p>Inner air gap flux density from 2D and 3D FEM.</p>
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<p>BEMF from 2D and 3D FEM.</p>
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<p>No-load BEMF and average torque from 2D FEM and 3D FEM: (<b>a</b>) Models with different pole arc coefficients of the claw tip; (<b>b</b>) Models with different axial lengths of single-phase; (<b>c</b>) Models with different thickness of stator cores.</p>
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<p>Flowchart of the design methodology.</p>
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<p>Variation of BEMF and average torque with the pole-pair number.</p>
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<p>Variation of average torque and torque ripple with pole arc coefficient of the claw tip.</p>
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<p>Variation of average torque and torque ripple with pole arc coefficient of the claw root.</p>
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<p>No-load flux density distribution of the claw at maximum linked flux.</p>
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<p>Inner air gap flux density: (<b>a</b>) Radial surface-mounted structure; (<b>b</b>) Radial embedding structure; (<b>c</b>) Tangential embedding structure.</p>
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2587 KiB  
Article
Modeling of Turbine Cycles Using a Neuro-Fuzzy Based Approach to Predict Turbine-Generator Output for Nuclear Power Plants
by Yea-Kuang Chan and Jyh-Cherng Gu
Energies 2012, 5(1), 101-118; https://doi.org/10.3390/en5010101 - 19 Jan 2012
Cited by 16 | Viewed by 6769
Abstract
Due to the very complex sets of component systems, interrelated thermodynamic processes and seasonal change in operating conditions, it is relatively difficult to find an accurate model for turbine cycle of nuclear power plants (NPPs). This paper deals with the modeling of turbine [...] Read more.
Due to the very complex sets of component systems, interrelated thermodynamic processes and seasonal change in operating conditions, it is relatively difficult to find an accurate model for turbine cycle of nuclear power plants (NPPs). This paper deals with the modeling of turbine cycles to predict turbine-generator output using an adaptive neuro-fuzzy inference system (ANFIS) for Unit 1 of the Kuosheng NPP in Taiwan. Plant operation data obtained from Kuosheng NPP between 2006 and 2011 were verified using a linear regression model with a 95% confidence interval. The key parameters of turbine cycle, including turbine throttle pressure, condenser backpressure, feedwater flow rate and final feedwater temperature are selected as inputs for the ANFIS based turbine cycle model. In addition, a thermodynamic turbine cycle model was developed using the commercial software PEPSE® to compare the performance of the ANFIS based turbine cycle model. The results show that the proposed ANFIS based turbine cycle model is capable of accurately estimating turbine-generator output and providing more reliable results than the PEPSE® based turbine cycle models. Moreover, test results show that the ANFIS performed better than the artificial neural network (ANN), which has also being tried to model the turbine cycle. The effectiveness of the proposed neuro-fuzzy based turbine cycle model was demonstrated using the actual operating data of Kuosheng NPP. Furthermore, the results also provide an alternative approach to evaluate the thermal performance of nuclear power plants. Full article
(This article belongs to the Special Issue Intelligent Energy Demand Forecasting)
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<p>Simplified schematics of the overall BWR nuclear power plant.</p>
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<p>PEPSE<sup>®</sup> turbine cycle model for Unit 1 of the Kuosheng NPP.</p>
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<p>(<b>a</b>) Two-input first-order Sugeno fuzzy model with two rules. (<b>b</b>) Equivalent ANFIS architecture [<a href="#B8-energies-05-00101" class="html-bibr">8</a>].</p>
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<p>A typical architecture of multilayered feedforward ANN.</p>
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<p>Overall structure for plant operating data acquisition and processing system.</p>
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<p>Regression model of condenser backpressure versus circulating water inlet temperature.</p>
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<p>Trend data for generator output, turbine throttle pressure, condenser backpressure, feedwater flow rate, and final feedwater temperature.</p>
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<p>Turbine-generator output versus condenser backpressure.</p>
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<p>Structure of the ANFIS based turbine cycle model for the Kuosheng NPP.</p>
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<p>(<b>a</b>) Training results for the ANFIS based turbine cycle model; (<b>b</b>) Comparison between the measured values and the validated results of the ANFIS model.</p>
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<p>(<b>a</b>) Estimated results under winter operating conditions (Case 1); (<b>b</b>) Estimated results with wider variations in condenser backpressure (Case 2).</p>
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620 KiB  
Article
Correlation of the Growth Rate of the Hydrate Layer at a Guest/Liquid-Water Interface to Mass Transfer Resistance
by Masatoshi Kishimoto and Ryo Ohmura
Energies 2012, 5(1), 92-100; https://doi.org/10.3390/en5010092 - 18 Jan 2012
Cited by 23 | Viewed by 6852
Abstract
Growth rate of a hydrate layer at the guest/liquid-water interface is analyzed considering the conjugate process of the mass-transfer and hydrate crystal growth. Hydrate-layer growth rate data in the literature are often compiled according to the system subcooling (∆T Teq [...] Read more.
Growth rate of a hydrate layer at the guest/liquid-water interface is analyzed considering the conjugate process of the mass-transfer and hydrate crystal growth. Hydrate-layer growth rate data in the literature are often compiled according to the system subcooling (∆T TeqTex, where Teq is the equilibrium dissociation temperature of the hydrate and Tex is the system temperature), suggesting predominant heat transfer limitations. In this paper, we investigate how the existing data on hydrate-layer growth is better correlated to mass transfer of the guest species in liquid water in three-phase equilibrium with bulk guest fluid and hydrate. We have analyzed the conjugate processes of mass-transfer/hydrate-layer-growth following our previous study on the hydrate crystal growth into liquid water saturated with a guest substance. A dimensionless parameter representing the hydrate-layer growth rate is derived from the analysis. This analysis is based on the idea that the growth rate is controlled by the mass transfer of the hydrate-guest substance, dissolved in the bulk of liquid water, to the front of the growing hydrate-layer along the guest/water interface. The variations in the hydrate-layer growth rate observed in the previous studies are related to the dimensionless parameter. Full article
(This article belongs to the Special Issue Natural Gas Hydrate 2011)
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Graphical abstract

Graphical abstract
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<p>Dependence of hydrate-layer growth rate on the subcooling ∆<span class="html-italic">T</span> for several reported studies: (□) methane at 5.60 MPa [<a href="#B12-energies-05-00092" class="html-bibr">12</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="blue"> <mo>○</mo> </mstyle> </mrow> </semantics> </math>) methane at 8.15 MPa [<a href="#B12-energies-05-00092" class="html-bibr">12</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="green"> <mo>◇</mo> </mstyle> </mrow> </semantics> </math>) methane at 10.56 MPa [<a href="#B12-energies-05-00092" class="html-bibr">12</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="red"> <mo>△</mo> </mstyle> </mrow> </semantics> </math>) propane at 0.31 MPa [<a href="#B12-energies-05-00092" class="html-bibr">12</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="#CC99FF"> <mo>-</mo> </mstyle> </mrow> </semantics> </math>) propane at 0.41 MPa [<a href="#B12-energies-05-00092" class="html-bibr">12</a>]; (■) propane at 0.51 MPa [<a href="#B12-energies-05-00092" class="html-bibr">12</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="olive"> <mo>●</mo> </mstyle> </mrow> </semantics> </math>) methane [<a href="#B13-energies-05-00092" class="html-bibr">13</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="green"> <mo>◆</mo> </mstyle> </mrow> </semantics> </math>) CO<sub>2</sub>(vapor) at 3 MPa [<a href="#B14-energies-05-00092" class="html-bibr">14</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="red"> <mo>▲</mo> </mstyle> </mrow> </semantics> </math>) CO<sub>2</sub>(gas) at 5 MPa [<a href="#B14-energies-05-00092" class="html-bibr">14</a>].</p>
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<p>Illustration of hydrate-layer growth at the guest/liquid-water interface.</p>
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<p>Schematic of solubility curves of guest species in liquid-water.</p>
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<p>Dependence of hydrate-layer growth rate on the <span class="html-italic">n</span>∆<span class="html-italic">x</span><sub>g</sub> for the systems in <a href="#energies-05-00092-f001" class="html-fig">Figure 1</a>: (□) methane at 5.60 MPa [<a href="#B12-energies-05-00092" class="html-bibr">12</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="blue"> <mo>○</mo> </mstyle> </mrow> </semantics> </math>) methane at 8.15 MPa [<a href="#B12-energies-05-00092" class="html-bibr">12</a>]; (◇) methane at 10.56 MPa [<a href="#B12-energies-05-00092" class="html-bibr">12</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="red"> <mo>△</mo> </mstyle> </mrow> </semantics> </math>) propane at 0.31 MPa [<a href="#B12-energies-05-00092" class="html-bibr">12</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="#CC99FF"> <mo>-</mo> </mstyle> </mrow> </semantics> </math>) propane at 0.41 MPa [<a href="#B12-energies-05-00092" class="html-bibr">12</a>]; (■) propane at 0.51 MPa [<a href="#B12-energies-05-00092" class="html-bibr">12</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="olive"> <mo>●</mo> </mstyle> </mrow> </semantics> </math>) methane [<a href="#B13-energies-05-00092" class="html-bibr">13</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="green"> <mo>◆</mo> </mstyle> </mrow> </semantics> </math>) CO<sub>2</sub>(vapor) at 3 MPa [<a href="#B14-energies-05-00092" class="html-bibr">14</a>]; (<math display="inline"> <semantics> <mrow> <mstyle mathcolor="red"> <mo>▲</mo> </mstyle> </mrow> </semantics> </math>) CO<sub>2</sub>(gas) at 5 MPa [<a href="#B14-energies-05-00092" class="html-bibr">14</a>].</p>
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575 KiB  
Article
Is the Electric Vehicle an Attractive Option for Customers?
by Israel García and Luis Javier Miguel
Energies 2012, 5(1), 71-91; https://doi.org/10.3390/en5010071 - 12 Jan 2012
Cited by 15 | Viewed by 8870
Abstract
As a new technology, electric mobility has the potential to achieve a reduction in CO2 emissions and contribute to the transition from the current transportation system to a better one, environmentally speaking. The objective of the paper is to aid the necessary [...] Read more.
As a new technology, electric mobility has the potential to achieve a reduction in CO2 emissions and contribute to the transition from the current transportation system to a better one, environmentally speaking. The objective of the paper is to aid the necessary decision-making for the adoption and development of electric vehicles in Spain, taking the time horizon of 2020. This will be achieved by building a System Dynamics model for various scenarios that will be used for the analysis and comparison of various dynamic variables, as well as to determine how, and to what extent, they will influence the number of electric vehicles that will run on Spanish roads in the coming years, focusing on the cost variable. Full article
(This article belongs to the Special Issue Electric and Hybrid Vehicles)
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<p>Casual loop diagram example.</p>
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<p>General model schema.</p>
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<p>Schema of the electric vehicle block.</p>
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<p>Electric vehicle schema.</p>
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<p>Forecast of the battery price [<a href="#B19-energies-05-00071" class="html-bibr">19</a>].</p>
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<p>Oil price evolution [<a href="#B25-energies-05-00071" class="html-bibr">25</a>].</p>
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<p>Driving patterns [<a href="#B21-energies-05-00071" class="html-bibr">21</a>].</p>
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<p>Electricity price forecast [<a href="#B29-energies-05-00071" class="html-bibr">29</a>].</p>
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<p>Electric vehicles on Spanish roads (the authors’ calculations).</p>
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<p>TON of CO<sub>2</sub> not emitted (the authors’ calculations).</p>
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<p>Forecast of battery cost in the optimistic, pessimistic and baseline scenarios (own calculations).</p>
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<p>Electric vehicles on roads for the optimistic, pessimistic and baseline scenarios (the authors’ calculations).</p>
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<p>Electric vehicle price for the optimistic, pessimistic and baseline scenarios (own calculations).</p>
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<p>Electric vehicle fleet compared to the Government target for the optimistic scenario without subsidies in 2013 (the authors’ calculations).</p>
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<p>Electric vehicle fleet compared to the Government target for the optimistic scenario with subsidies until 2020 (the authors’ calculations).</p>
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<p>Electric vehicle fleet compared to the Government target for the optimistic scenario with optimal subsidies until 2020 (the authors’ calculations).</p>
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<p>Electric vehicle fleet compared to the Government target for the pessimistic scenario without subsidies until 2020 (the authors’ calculations).</p>
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<p>Electric vehicle fleet compared to the Government target for the pessimistic scenario with the optimal subsidies until 2020 (the authors’ calculations).</p>
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593 KiB  
Article
The Potential of a Surfactant/Polymer Flood in a Middle Eastern Reservoir
by Ridha Gharbi, Abdullah Alajmi and Meshal Algharaib
Energies 2012, 5(1), 58-70; https://doi.org/10.3390/en5010058 - 11 Jan 2012
Cited by 15 | Viewed by 7422
Abstract
An integrated full-field reservoir simulation study has been performed to determine the reservoir management and production strategies in a mature sandstone reservoir. The reservoir is a candidate for an enhanced oil recovery process or otherwise subject to abandonment. Based on its charateristics, the [...] Read more.
An integrated full-field reservoir simulation study has been performed to determine the reservoir management and production strategies in a mature sandstone reservoir. The reservoir is a candidate for an enhanced oil recovery process or otherwise subject to abandonment. Based on its charateristics, the reservoir was found to be most suited for a surfactant/polymer (SP) flood. The study started with a large data gathering and the building of a full-field three-dimensional geological model. Subsequently, a full field simulation model was built and used to history match the water flood. The history match of the water flood emphasizes the areas with remaining high oil saturations, establishes the initial condition of the reservoir for an SP flood, and generates a forecast of reserves for continued water flood operations. A sector model was constructed from the full field model and then used to study different design parameters to maximize the project profitability from the SP flood. An economic model, based on the estimated recovery, residual oil in-place, oil price, and operating costs, has been implemented in order to optimize the project profitability. The study resulted in the selection of surfactant and polymer concentrations and slug size that yielded the best economic returns when applied in this reservoir. The study shows that, in today’s oil prices, surfactant/polymer flood when applied in this reservoir has increased the ultimate oil recovery and provide a significant financial returns. Full article
(This article belongs to the Special Issue Advances in Petroleum Engineering)
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<p>Optimization process used for surfactant/polymer flood.</p>
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<p>Permeability map of the sector model.</p>
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<p>Variation of NPV with the amount of surfactant used for different surfactant concentrations (polymer conc. = 2800 ppm).</p>
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<p>Variation of NPV with polymer concentration (surf. conc = 0.15 vol.%).</p>
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<p>Variation of NPV with crude oil price.</p>
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<p>Variation of NPV with oil price under various permeability realizations.</p>
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721 KiB  
Article
Modeling and Control of a Flux-Modulated Compound-Structure Permanent-Magnet Synchronous Machine for Hybrid Electric Vehicles
by Ping Zheng, Chengde Tong, Jingang Bai, Jing Zhao, Yi Sui and Zhiyi Song
Energies 2012, 5(1), 45-57; https://doi.org/10.3390/en5010045 - 5 Jan 2012
Cited by 8 | Viewed by 10218
Abstract
The compound-structure permanent-magnet synchronous machine (CS-PMSM), comprising a double rotor machine (DRM) and a permanent-magnet (PM) motor, is a promising electronic-continuously variable transmission (e-CVT) concept for hybrid electric vehicles (HEVs). By CS-PMSM, independent speed and torque control of the vehicle engine is realized [...] Read more.
The compound-structure permanent-magnet synchronous machine (CS-PMSM), comprising a double rotor machine (DRM) and a permanent-magnet (PM) motor, is a promising electronic-continuously variable transmission (e-CVT) concept for hybrid electric vehicles (HEVs). By CS-PMSM, independent speed and torque control of the vehicle engine is realized without a planetary gear unit. However, the slip rings and brushes of the conventional CS-PMSM are considered a major drawback for vehicle application. In this paper, a brushless flux-modulated CS-PMSM is investigated. The operating principle and basic working modes of the CS-PMSM are discussed. Mathematical models of the CS-PMSM system are given, and joint control of the two integrated machines is proposed. As one rotor of the DRM is mechanically connected with the rotor of the PM motor, special rotor position detection and torque allocation methods are required. Simulation is carried out by Matlab/Simulink, and the feasibility of the control system is proven. Considering the complexity of the controller, a single digital signal processor (DSP) is used to perform the interconnected control of dual machines instead of two separate ones, and a typical hardware implementation is proposed. Full article
(This article belongs to the Special Issue Electric and Hybrid Vehicles)
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<p>Schematic diagram of a hybrid electric drive system based on CS-PMSM.</p>
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<p>(<b>a</b>) The flux-modulated CS-PMSM; (<b>b</b>) The cross section of the brushless DRM.</p>
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<p>Energy transducing diagram of the flux-modulated CS-PMSM.</p>
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<p>Control diagram of the flux-modulated CS-PMSM system.</p>
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<p>System model of the flux-modulated CS-PMSM system in Matlab/Simulink.</p>
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<p>Simulated speed and torque waveforms: (<b>a</b>) Speeds of output shaft, ICE and rotating magnetic field generated by stator-1; (<b>b</b>) Torque delivered from ICE, electromagnetic torque of stator-1, torque delivered to modulating ring, electromagnetic torque of motor-2 and torque of output shaft.</p>
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<p>Phase voltage and current waveforms of DRM and motor-2: (<b>a</b>) DRM; (<b>b</b>) Motor-2.</p>
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<p>Historical speed-torque points: (<b>a</b>) Stator-1 and motor-2 operating points; (<b>b</b>) ICE, output load and transferred ICE operating points.</p>
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<p>Hardware implementation of the flux-modulated CS-PMSM controller.</p>
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<p>Photograph of the CS-PMSM controller.</p>
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1114 KiB  
Article
On the Establishment of Climatic Zones in Europe with Regard to the Energy Performance of Buildings
by Katerina Tsikaloudaki, Kostas Laskos and Dimitrios Bikas
Energies 2012, 5(1), 32-44; https://doi.org/10.3390/en5010032 - 29 Dec 2011
Cited by 73 | Viewed by 7503
Abstract
Nowadays, subjects such as eco-design requirements, product rating or code compliance with regard to energy efficiency are expanding towards a pan-European level. This leads to the necessity of defining zones within the European region, which share common climatic characteristics and will further facilitate [...] Read more.
Nowadays, subjects such as eco-design requirements, product rating or code compliance with regard to energy efficiency are expanding towards a pan-European level. This leads to the necessity of defining zones within the European region, which share common climatic characteristics and will further facilitate the quick estimation of building energy performance. Towards this direction stands the current paper; it presents an approach for defining climatic zones in Europe on the basis of the amount of heating and cooling degree days. It is applied for the climate classification of selected European cities and is compared with the conventional scheme based solely on heating degree days. Since the approach is orientated mainly towards the assessment of building energy performance, its outcomes are evaluated with regard to the actual heating and cooling energy needs of a reference building unit with office use located in representative cities of the proposed climatic zones and facing the four cardinal orientations. The classification of climatic zones on the basis of both heating and cooling degree days leads to more realistic results, since nowadays cooling needs form a substantial part of the energy balance of the building, especially in the Mediterranean regions. Full article
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<p>The geographical distribution of selected cities for establishing climatic zones in the European region. Map: European Commission (<a href="http://ec.europa.eu/avservices/" target="_blank">http://ec.europa.eu/avservices/</a>), © European Union, 2011.</p>
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<p>The distribution of Cooling Degree Days at a base temperature 18 °C (CDD18) plotted against Heating Degree Days at a base temperature of 18 °C (HDD18).</p>
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<p>The areas representing high, medium and low heating and cooling needs according to the first approach (<b>a</b>) and the second approach (<b>b</b>), also presented in <a href="#energies-05-00032-t001" class="html-table">Table 1</a>.</p>
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<p>The geographical distribution of selected cities and their classification into climatic zones on the basis of CDD and HDD approach. Map: European Commission (<a href="http://ec.europa.eu/avservices/" target="_blank">http://ec.europa.eu/avservices/</a>), © European Union, 2011.</p>
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<p>Axonometric plan of the reference room [<a href="#B3-energies-05-00032" class="html-bibr">3</a>].</p>
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<p>The area weighted heating needs of the building unit located in the 15 selected cities, with regard to their amount of Heating Degree Days.</p>
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<p>The area weighted cooling needs of the building unit located in the 15 selected cities, with regard to their amount of Cooling Degree Days.</p>
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277 KiB  
Article
Changing Lifestyles Towards a Low Carbon Economy: An IPAT Analysis for China
by Klaus Hubacek, Kuishuang Feng and Bin Chen
Energies 2012, 5(1), 22-31; https://doi.org/10.3390/en5010022 - 27 Dec 2011
Cited by 78 | Viewed by 10140
Abstract
China has achieved notable success in developing its economy with approximate 10 percent average annual GDP growth over the last two decades. At the same time, energy consumption and CO2 emissions almost doubled every five years, which led China to be the [...] Read more.
China has achieved notable success in developing its economy with approximate 10 percent average annual GDP growth over the last two decades. At the same time, energy consumption and CO2 emissions almost doubled every five years, which led China to be the world top emitter in 2007. In response, China’s government has put forward a carbon mitigation target of 40%–45% reduction of CO2 emission intensity by 2020. To better understand the potential for success or failure of such a policy, it is essential to assess different driving forces such as population, lifestyle and technology and their associated CO2 emissions. This study confirms that increase of affluence has been the main driving force for China’s CO2 emissions since the late 1970s, which outweighs reductions achieved through technical progress. Meanwhile, the contribution of population growth to CO2 emissions was relatively small. We also found a huge disparity between urban and rural households in terms of changes of lifestyle and consumption patterns. Lifestyles in urban China are beginning to resemble Western lifestyles, and approaching their level of CO2 emissions. Therefore, in addition to the apparent inefficiencies in terms of production technologies there is also a lot of room for improvement on the consumption side especially in interaction of current infrastructure investments and future consumption. Full article
(This article belongs to the Special Issue Low Carbon Transitions Worldwide)
2330 KiB  
Article
Mid-Term Energy Demand Forecasting by Hybrid Neuro-Fuzzy Models
by Hossein Iranmanesh, Majid Abdollahzade and Arash Miranian
Energies 2012, 5(1), 1-21; https://doi.org/10.3390/en5010001 - 22 Dec 2011
Cited by 25 | Viewed by 7561
Abstract
This paper proposes a structure for long-term energy demand forecasting. The proposed hybrid approach, called HPLLNF, uses the local linear neuro-fuzzy (LLNF) model as the forecaster and utilizes the Hodrick–Prescott (HP) filter for extraction of the trend and cyclic components of the energy [...] Read more.
This paper proposes a structure for long-term energy demand forecasting. The proposed hybrid approach, called HPLLNF, uses the local linear neuro-fuzzy (LLNF) model as the forecaster and utilizes the Hodrick–Prescott (HP) filter for extraction of the trend and cyclic components of the energy demand series. Besides, the sophisticated technique of mutual information (MI) is employed to select the most relevant input features with least possible redundancies for the forecast model. Each generated component by the HP filter is then modeled through an LLNF model. Starting from an optimal least square estimation, the local linear model tree (LOLIMOT) learning algorithm increases the complexity of the LLNF model as long as its performance is improved. The proposed HPLLNF model with MI-based input selection is applied to the problem of long-term energy forecasting in three different case studies, including forecasting of the gasoline, crude oil and natural gas demand over the next 12 months. The obtained forecasting results reveal the noteworthy performance of the proposed approach for long-term energy demand forecasting applications. Full article
(This article belongs to the Special Issue Intelligent Energy Demand Forecasting)
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<p>Structure of the proposed forecasting approach.</p>
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<p>Structure of the LLNF model.</p>
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<p>Operation of LOLIMOT in the first four iterations in a two-dimensional input space.</p>
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<p>Illustration of input selection algorithm.</p>
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<p>Validation error <span class="html-italic">versus</span> number of inputs for LLNF<sub>τ</sub>—first case study.</p>
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<p>Validation error <span class="html-italic">versus</span> number of inputs for LLNF<sub>c</sub>—first case study.</p>
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<p>Actual and forecasted gasoline demand for 2010 (HPLLNF + MI).</p>
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<p>Actual and forecasted crude oil demand for 2009 (HPLLNF (global) + MI).</p>
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<p>Original and trend component of the natural gas demand from January 1992 to December 2007.</p>
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<p>Natural gas demand cyclic component from January 1992 to December 2007.</p>
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<p>Natural gas demand cyclic component from January 1994 to December 1997.</p>
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<p>Actual and forecasted natural gas demand for 2008 (HPLLNF (global) + MI).</p>
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<p>Comparison of test MAPE in different case studies.</p>
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