Energies

1530 KiB

Open AccessArticle

Power Quality and Harmonic Analysis of End User Devices

by Alberto Dolara and Sonia Leva

Energies 2012, 5(12), 5453-5466; https://doi.org/10.3390/en5125453 - 19 Dec 2012

Cited by 68 | Viewed by 7670

Among the non-linear loads used in household, Compact Fluorescent Lamps (CFLs) and LED lamps are becoming more widespread, while incandescent lamps are intended to be replaced by these types of lighting devices. LEDs and CFLs are significantly more efficient and economical than incandescent [...] Read more.

Among the non-linear loads used in household, Compact Fluorescent Lamps (CFLs) and LED lamps are becoming more widespread, while incandescent lamps are intended to be replaced by these types of lighting devices. LEDs and CFLs are significantly more efficient and economical than incandescent lamps, and are expected to be used in 100% of residential lighting in the future. As nonlinear loads, LEDs and CFLs produce highly distorted currents. A large number of customers using LEDs or CFLs for domestic, commercial and industrial lighting could determine important Power Quality problems. The paper reports experimental measurement results regarding Power Quality in indoor lighting systems. The harmonic absorptions of several types of luminaries are analyzed, highlighting the impact behavior of different lamps function of used luminaries’ technologies. The recorded harmonic absorption allows characterizing the harmonic spectrum variability of the investigated lamps. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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242 KiB

Open AccessArticle

A New Battery Energy Storage Charging/Discharging Scheme for Wind Power Producers in Real-Time Markets

by Minh Y Nguyen, Dinh Hung Nguyen and Yong Tae Yoon

Energies 2012, 5(12), 5439-5452; https://doi.org/10.3390/en5125439 - 19 Dec 2012

Cited by 40 | Viewed by 7310

Abstract

Under a deregulated environment, wind power producers are subject to many regulation costs due to the intermittence of natural resources and the accuracy limits of existing prediction tools. This paper addresses the operation (charging/discharging) problem of battery energy storage installed in a wind [...] Read more.

Under a deregulated environment, wind power producers are subject to many regulation costs due to the intermittence of natural resources and the accuracy limits of existing prediction tools. This paper addresses the operation (charging/discharging) problem of battery energy storage installed in a wind generation system in order to improve the value of wind power in the real-time market. Depending on the prediction of market prices and the probabilistic information of wind generation, wind power producers can schedule the battery energy storage for the next day in order to maximize the profit. In addition, by taking into account the expenses of using batteries, the proposed charging/discharging scheme is able to avoid the detrimental operation of battery energy storage which can lead to a significant reduction of battery lifetime, i.e., uneconomical operation. The problem is formulated in a dynamic programming framework and solved by a dynamic programming backward algorithm. The proposed scheme is then applied to the study cases, and the results of simulation show its effectiveness. Full article

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743 KiB

Open AccessArticle

Fuel-N Evolution during the Pyrolysis of Industrial Biomass Wastes with High Nitrogen Content

by Hongfang Chen, Yin Wang, Guangwen Xu and Kunio Yoshikawa

Energies 2012, 5(12), 5418-5438; https://doi.org/10.3390/en5125418 - 19 Dec 2012

Cited by 76 | Viewed by 7325

Abstract

In this study, sewage sludge and mycelial waste from antibiotic production were pyrolyzed in a batch scale fixed-bed reactor as examples of two kinds of typical industrial biomass wastes with high nitrogen content. A series of experiments were conducted on the rapid pyrolysis [...] Read more.

In this study, sewage sludge and mycelial waste from antibiotic production were pyrolyzed in a batch scale fixed-bed reactor as examples of two kinds of typical industrial biomass wastes with high nitrogen content. A series of experiments were conducted on the rapid pyrolysis and the slow pyrolysis of these wastes in the temperature range from 500–800 °C to investigate the Fuel-N transformation behavior among pyrolysis products. The results showed that Fuel-N conversion to Char-N intimately depended on the pyrolysis temperature and the yield of Char-N reduced with the increase of the pyrolysis temperature. Under the same pyrolysis conditions, Tar-N production mainly depended on complex properties of the different biomasses, including volatile matter, nitrogen content and biomass functional groups. HCN was the predominant NO_x precursor in the rapid pyrolysis of biomass, whereas in the slow pyrolysis of mycelial waste, more NH₃ was produced than HCN due to the additional NH₃ formation through the hydrogenation reaction of Char-N, HCN and H radicals. At the same time, some part of the char was analyzed by Fourier Transform infrared spectroscopy (FTIR) to get more information on the nitrogen functionality changes and the tar was also characterized by Gas Chromatography and Mass Spectrometry (GCMS) to identify typical nitrogenous tar compounds. Finally, the whole nitrogen distribution in products was discussed. Full article

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604 KiB

Open AccessReview

Commercial Biomass Syngas Fermentation

by James Daniell, Michael Köpke and Séan Dennis Simpson

Energies 2012, 5(12), 5372-5417; https://doi.org/10.3390/en5125372 - 19 Dec 2012

Cited by 342 | Viewed by 25732

Abstract

The use of gas fermentation for the production of low carbon biofuels such as ethanol or butanol from lignocellulosic biomass is an area currently undergoing intensive research and development, with the first commercial units expected to commence operation in the near future. In [...] Read more.

The use of gas fermentation for the production of low carbon biofuels such as ethanol or butanol from lignocellulosic biomass is an area currently undergoing intensive research and development, with the first commercial units expected to commence operation in the near future. In this process, biomass is first converted into carbon monoxide (CO) and hydrogen (H₂)-rich synthesis gas (syngas) via gasification, and subsequently fermented to hydrocarbons by acetogenic bacteria. Several studies have been performed over the last few years to optimise both biomass gasification and syngas fermentation with significant progress being reported in both areas. While challenges associated with the scale-up and operation of this novel process remain, this strategy offers numerous advantages compared with established fermentation and purely thermochemical approaches to biofuel production in terms of feedstock flexibility and production cost. In recent times, metabolic engineering and synthetic biology techniques have been applied to gas fermenting organisms, paving the way for gases to be used as the feedstock for the commercial production of increasingly energy dense fuels and more valuable chemicals. Full article

(This article belongs to the Special Issue Wood to Energy)

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1612 KiB

Open AccessArticle

Electrodeposition of a Au-Dy₂O₃ Composite Solid Oxide Fuel Cell Catalyst from Eutectic Urea/Choline Chloride Ionic Liquid

by Claudio Mele and Benedetto Bozzini

Energies 2012, 5(12), 5363-5371; https://doi.org/10.3390/en5125363 - 19 Dec 2012

Cited by 6 | Viewed by 6251

Abstract

In this research we have fabricated and tested Au/Dy₂O₃ composites for applications as Solid Oxide Fuel Cell (SOFC) electrocatalysts. The material was obtained by a process involving electrodeposition of a Au-Dy alloy from a urea/choline chloride ionic liquid electrolyte, followed [...] Read more.

In this research we have fabricated and tested Au/Dy₂O₃ composites for applications as Solid Oxide Fuel Cell (SOFC) electrocatalysts. The material was obtained by a process involving electrodeposition of a Au-Dy alloy from a urea/choline chloride ionic liquid electrolyte, followed by selective oxidation of Dy to Dy₂O₃ in air at high temperature. The electrochemical kinetics of the electrodeposition bath were studied by cyclic voltammetry, whence optimal electrodeposition conditions were identified. The heat-treated material was characterised from the morphological (scanning electron microscopy), compositional (X-ray fluorescence spectroscopy) and structural (X-ray diffractometry) points of view. The electrocatalytic activity towards H₂ oxidation and O₂ reduction was tested at 650 °C by electrochemical impedance spectrometry. Our composite electrodes exhibit an anodic activity that compares favourably with the only literature result available at the time of this writing for Dy₂O₃ and an even better cathodic performance. Full article

(This article belongs to the Special Issue Hydrogen Energy and Fuel Cells)

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1606 KiB

Open AccessArticle

Atmospheric Turbulence Effects on Wind-Turbine Wakes: An LES Study

by Yu-Ting Wu and Fernando Porté-Agel

Energies 2012, 5(12), 5340-5362; https://doi.org/10.3390/en5125340 - 17 Dec 2012

Cited by 267 | Viewed by 18180

Abstract

A numerical study of atmospheric turbulence effects on wind-turbine wakes is presented. Large-eddy simulations of neutrally-stratified atmospheric boundary layer flows through stand-alone wind turbines were performed over homogeneous flat surfaces with four different aerodynamic roughness lengths. Emphasis is placed on the structure and [...] Read more.

A numerical study of atmospheric turbulence effects on wind-turbine wakes is presented. Large-eddy simulations of neutrally-stratified atmospheric boundary layer flows through stand-alone wind turbines were performed over homogeneous flat surfaces with four different aerodynamic roughness lengths. Emphasis is placed on the structure and characteristics of turbine wakes in the cases where the incident flows to the turbine have the same mean velocity at the hub height but different mean wind shears and turbulence intensity levels. The simulation results show that the different turbulence intensity levels of the incoming flow lead to considerable influence on the spatial distribution of the mean velocity deficit, turbulence intensity, and turbulent shear stress in the wake region. In particular, when the turbulence intensity level of the incoming flow is higher, the turbine-induced wake (velocity deficit) recovers faster, and the locations of the maximum turbulence intensity and turbulent stress are closer to the turbine. A detailed analysis of the turbulence kinetic energy budget in the wakes reveals also an important effect of the incoming flow turbulence level on the magnitude and spatial distribution of the shear production and transport terms. Full article

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1268 KiB

Open AccessArticle

Establishing an Integration-Energy-Practice Model for Improving Energy Performance Indicators in ISO 50001 Energy Management Systems

by Tsung-Yung Chiu, Shang-Lien Lo and Yung-Yin Tsai

Energies 2012, 5(12), 5324-5339; https://doi.org/10.3390/en5125324 - 17 Dec 2012

Cited by 45 | Viewed by 12434

Abstract

Global energy sources are gradually becoming scarce and prices are continually rising. Governments and businesses in various countries are actively developing technologies for energy management and developing new sources of energy. On 15 June 2011, the International Organization for Standardization (ISO) announced the [...] Read more.

Global energy sources are gradually becoming scarce and prices are continually rising. Governments and businesses in various countries are actively developing technologies for energy management and developing new sources of energy. On 15 June 2011, the International Organization for Standardization (ISO) announced the ISO 50001 standard for energy management systems. Organizations and enterprises are confronted with challenges associated with enhancing energy performance indicators, continuing to improve energy consumption efficiency, and managing third-party international certifications. This study conducted cases studies of businesses that have introduced an ISO 50001 energy management system by using an integration-energy-practice model to improve energy performance indicators and to complete the international auditing and certification procedures for ISO 50001 energy management systems. Based on case study results, the achievement rates for annual energy performance indicators increased, thereby enhancing the energy intensity efficiency. Establishing an integration-energy-practice model for introducing an ISO 50001 energy management system can efficiently meet demands for energy performance indicators and pass the international certification for ISO 50001 energy management systems. The proposed model efficiently provides enterprises with methods for developing sustainable energy management. It integrates internal and external technical resources to establish energy technology think tanks, for promoting successful technology and experiences to various sectors, thereby allowing enterprises to integrate energy management, increase energy efficiency, and meet the ISO 50001 international standard for energy management systems. Full article

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419 KiB

Open AccessArticle

A Simple Sizing Algorithm for Stand-Alone PV/Wind/Battery Hybrid Microgrids

by Jing Li, Wei Wei and Ji Xiang

Energies 2012, 5(12), 5307-5323; https://doi.org/10.3390/en5125307 - 14 Dec 2012

Cited by 141 | Viewed by 9518

Abstract

In this paper, we develop a simple algorithm to determine the required number of generating units of wind-turbine generator and photovoltaic array, and the associated storage capacity for stand-alone hybrid microgrid. The algorithm is based on the observation that the state of charge [...] Read more.

In this paper, we develop a simple algorithm to determine the required number of generating units of wind-turbine generator and photovoltaic array, and the associated storage capacity for stand-alone hybrid microgrid. The algorithm is based on the observation that the state of charge of battery should be periodically invariant. The optimal sizing of hybrid microgrid is given in the sense that the life cycle cost of system is minimized while the given load power demand can be satisfied without load rejection. We also report a case study to show the efficacy of the developed algorithm. Full article

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1289 KiB

Open AccessArticle

An Efficient Drift-Flux Closure Relationship to Estimate Liquid Holdups of Gas-Liquid Two-Phase Flow in Pipes

by Jinho Choi, Eduardo Pereyra, Cem Sarica, Changhyup Park and Joe M. Kang

Energies 2012, 5(12), 5294-5306; https://doi.org/10.3390/en5125294 - 14 Dec 2012

Cited by 94 | Viewed by 8917

Abstract

The reliable predictions of liquid holdup and pressure drop are essential for pipeline design in oil and gas industry. In this study, the drift-flux approach is utilized to calculate liquid holdups. This approach has been widely used in formulation of the basic equations [...] Read more.

The reliable predictions of liquid holdup and pressure drop are essential for pipeline design in oil and gas industry. In this study, the drift-flux approach is utilized to calculate liquid holdups. This approach has been widely used in formulation of the basic equations for multiphase flow in pipelines. Most of the drift-flux models have been developed on an empirical basis from the experimental data. Even though, previous studies showed that these models can be applied to different flow pattern and pipe inclination, when the distribution parameter is flow pattern dependent. They are limited to a set of fluid properties, pipe geometries and operational conditions. The objective of this study is to develop a new drift-flux closure relationship for prediction of liquid holdups in pipes that can be easily applied to a wide range of flow conditions. The developed correlation is compared with nine available correlations from literatures, and validated using the TUFFP (Fluid Flow Projects of University of Tulsa) experimental datasets and OLGA (OiL and GAs simulator supplied by SPTgroup) steady-state synthetic data generated by OLGA Multiphase Toolkit. The developed correlation performs better in predicting liquid holdups than the available correlations for a wide range of flow conditions. Full article

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259 KiB

Open AccessArticle

Wind Turbine Tower Vibration Modeling and Monitoring by the Nonlinear State Estimation Technique (NSET)

by Peng Guo and David Infield

Energies 2012, 5(12), 5279-5293; https://doi.org/10.3390/en5125279 - 14 Dec 2012

Cited by 37 | Viewed by 6916

Abstract

With appropriate vibration modeling and analysis the incipient failure of key components such as the tower, drive train and rotor of a large wind turbine can be detected. In this paper, the Nonlinear State Estimation Technique (NSET) has been applied to model turbine [...] Read more.

With appropriate vibration modeling and analysis the incipient failure of key components such as the tower, drive train and rotor of a large wind turbine can be detected. In this paper, the Nonlinear State Estimation Technique (NSET) has been applied to model turbine tower vibration to good effect, providing an understanding of the tower vibration dynamic characteristics and the main factors influencing these. The developed tower vibration model comprises two different parts: a sub-model used for below rated wind speed; and another for above rated wind speed. Supervisory control and data acquisition system (SCADA) data from a single wind turbine collected from March to April 2006 is used in the modeling. Model validation has been subsequently undertaken and is presented. This research has demonstrated the effectiveness of the NSET approach to tower vibration; in particular its conceptual simplicity, clear physical interpretation and high accuracy. The developed and validated tower vibration model was then used to successfully detect blade angle asymmetry that is a common fault that should be remedied promptly to improve turbine performance and limit fatigue damage. The work also shows that condition monitoring is improved significantly if the information from the vibration signals is complemented by analysis of other relevant SCADA data such as power performance, wind speed, and rotor loads. Full article

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2787 KiB

Open AccessArticle

A Building Energy Efficiency Optimization Method by Evaluating the Effective Thermal Zones Occupancy

by Anna Laura Pisello, Michael Bobker and Franco Cotana

Energies 2012, 5(12), 5257-5278; https://doi.org/10.3390/en5125257 - 13 Dec 2012

Cited by 61 | Viewed by 9227

Abstract

Building energy efficiency is strongly linked to the operations and control systems, together with the integrated performance of passive and active systems. In new high quality buildings in particular, where these two latter aspects have been already implemented at the design stage, users’ [...] Read more.

Building energy efficiency is strongly linked to the operations and control systems, together with the integrated performance of passive and active systems. In new high quality buildings in particular, where these two latter aspects have been already implemented at the design stage, users’ perspective, obtained through post-occupancy assessment, has to be considered to reduce whole energy requirement during service life. This research presents an innovative and low-cost methodology to reduce buildings’ energy requirements through post-occupancy assessment and optimization of energy operations using effective users’ attitudes and requirements as feedback. As a meaningful example, the proposed method is applied to a multipurpose building located in New York City, NY, USA, where real occupancy conditions are assessed. The effectiveness of the method is tested through dynamic simulations using a numerical model of the case study, calibrated through real monitoring data collected on the building. Results show that, for the chosen case study, the method provides optimized building energy operations which allow a reduction of primary energy requirements for HVAC, lighting, room-electricity, and auxiliary supply by about 21%. This paper shows that the proposed strategy represents an effective way to reduce buildings’ energy waste, in particular in those complex and high-efficiency buildings that are not performing as well as expected during the concept-design-commissioning stage, in particular due to the lack of feedback after the building handover. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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219 KiB

Open AccessArticle

Chemical Profiles of Wood Components of Poplar Clones for Their Energy Utilization

by František Kačík, Jaroslav Ďurkovič and Danica Kačíková

Energies 2012, 5(12), 5243-5256; https://doi.org/10.3390/en5125243 - 13 Dec 2012

Cited by 43 | Viewed by 6523

Abstract

Selected and tested poplar clones are very suitable biomass resources for various applications such as biofuels, the pulp and paper industry as well as chemicals production. In this study, we determined the content of lignin, cellulose, holocellulose, and extractives, syringyl to guaiacyl (S/G) [...] Read more.

Selected and tested poplar clones are very suitable biomass resources for various applications such as biofuels, the pulp and paper industry as well as chemicals production. In this study, we determined the content of lignin, cellulose, holocellulose, and extractives, syringyl to guaiacyl (S/G) ratio in lignin, and also calculated higher heating values (HHV) among eight examined clones of Populus grown on three different experimental sites. The highest lignin content for all the examined sites was determined in ‘I-214’ and ‘Baka 5’ clones, whereas the highest content of extractives was found in ‘Villafranca’ and ‘Baka 5’ clones. The highest S/G ratio for all the examined sites was determined in ‘Villafranca’ and ‘Agathe F’ clones. The chemical profiles of main wood components, extractives, and the S/G ratio in lignin were also influenced by both the experimental site and the clone × site interaction. Higher heating values, derived from calculations based on the contents of lignin and extractives (or lignin only), were in close agreement with the previously published data. The highest heating values were found for ‘Baka 5’ and ‘I-214’ clones. The optimal method of poplar biomass utilization can be chosen on basis of the lignocellulosics chemical composition and the S/G ratio in lignin. Full article

(This article belongs to the Special Issue Wood to Energy)

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Open AccessArticle

Behavior of the Blade Tip Vortices of a Wind Turbine Equipped with a Brimmed-Diffuser Shroud

by Shuhei Takahashi, Yuya Hata, Yuji Ohya, Takashi Karasudani and Takanori Uchida

Energies 2012, 5(12), 5229-5242; https://doi.org/10.3390/en5125229 - 13 Dec 2012

Cited by 45 | Viewed by 11517

Abstract

To clarify the behavior of the blade tip vortices of a wind turbine equipped with a brimmed-diffuser shroud, called a “Wind-Lens turbine”, we conducted a three-dimensional numerical simulation using a large eddy simulation (LES). Since this unique wind turbine consists of not only [...] Read more.

To clarify the behavior of the blade tip vortices of a wind turbine equipped with a brimmed-diffuser shroud, called a “Wind-Lens turbine”, we conducted a three-dimensional numerical simulation using a large eddy simulation (LES). Since this unique wind turbine consists of not only rotating blades but also a diffuser shroud with a broad-ring brim at the exit periphery, the flow field around the turbine is highly complex and unsteady. Previously, our research group conducted numerical simulations using an actuator-disc approximation, in which the rotating blades were simply modeled as an external force on the fluid. Therefore, the detailed flow patterns around the rotating blades and the shroud, including the blade tip vortices, could not be simulated. Instead of an actuator-disc approximation, we used a moving boundary technique in the present CFD simulation to simulate the flow around a rotating blade in order to focus especially on blade tip vortices. The simulation results showed a pair of vortices consisting of a blade tip vortex and a counter-rotating vortex which was generated between the blade tip and the inner surface of the diffuser. Since these vortices interacted with each other, the blade tip vortex was weakened by the counter-rotating vortex. The results showed good agreement with past wind tunnel experiments. Full article

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3304 KiB

Open AccessArticle

Classification and Clustering of Electricity Demand Patterns in Industrial Parks

by Luis Hernández, Carlos Baladrón, Javier M. Aguiar, Belén Carro and Antonio Sánchez-Esguevillas

Energies 2012, 5(12), 5215-5228; https://doi.org/10.3390/en5125215 - 12 Dec 2012

Cited by 98 | Viewed by 7951

Abstract

Understanding of energy consumption patterns is extremely important for optimization of resources and application of green trends. Traditionally, analyses were performed for large environments like regions and nations. However, with the advent of Smart Grids, the study of the behavior of smaller environments [...] Read more.

Understanding of energy consumption patterns is extremely important for optimization of resources and application of green trends. Traditionally, analyses were performed for large environments like regions and nations. However, with the advent of Smart Grids, the study of the behavior of smaller environments has become a necessity to allow a deeper micromanagement of the energy grid. This paper presents a data processing system to analyze energy consumption patterns in industrial parks, based on the cascade application of a Self-Organizing Map (SOM) and the clustering k-means algorithm. The system is validated with real load data from an industrial park in Spain. The validation results show that the system adequately finds different behavior patterns which are meaningful, and is capable of doing so without supervision, and without any prior knowledge about the data. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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948 KiB

Open AccessArticle

Electric Energy Consumption of the Full Scale Research Biogas Plant “Unterer Lindenhof”: Results of Longterm and Full Detail Measurements

by Hans-Joachim Naegele, Andreas Lemmer, Hans Oechsner and Thomas Jungbluth

Energies 2012, 5(12), 5198-5214; https://doi.org/10.3390/en5125198 - 10 Dec 2012

Cited by 59 | Viewed by 8733

Abstract

This work thoroughly evaluates the electric power consumption of a full scale, 3 × 923 m³ complete stirred tank reactor (CSTR) research biogas plant with a production capacity of 186 kW of electric power. The plant was fed with a mixture of [...] Read more.

This work thoroughly evaluates the electric power consumption of a full scale, 3 × 923 m³ complete stirred tank reactor (CSTR) research biogas plant with a production capacity of 186 kW of electric power. The plant was fed with a mixture of livestock manure and renewable energy crops and was operated under mesophilic conditions. This paper will provide an insight into precise electric energy consumption measurements of a full scale biogas plant over a period of two years. The results showed that a percentage of 8.5% (in 2010) and 8.7% (in 2011) of the produced electric energy was consumed by the combined heat and power unit (CHP), which was required to operate the biogas plant. The consumer unit agitators with 4.3% (in 2010) and 4.0% (in 2011) and CHP unit with 2.5% (in 2010 and 2011) accounted for the highest electrical power demand, in relation to the electric energy produced by the CHP unit. Calculations show that 51% (in 2010) and 46% (in 2011) of the total electric energy demand was due to the agitators. The results finally showed the need for permanent measurements to identify and quantify the electric energy saving potentials of full scale biogas plants. Full article

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243 KiB

Open AccessArticle

Improved Cyclability of Liquid Electrolyte Lithium/Sulfur Batteries by Optimizing Electrolyte/Sulfur Ratio

by Sheng S. Zhang

Energies 2012, 5(12), 5190-5197; https://doi.org/10.3390/en5125190 - 07 Dec 2012

Cited by 194 | Viewed by 13686

Abstract

A liquid electrolyte lithium/sulfur (Li/S) cell is a liquid electrochemical system. In discharge, sulfur is first reduced to highly soluble Li₂S₈, which dissolves into the organic electrolyte and serves as the liquid cathode. In solution, lithium polysulfide (PS) undergoes [...] Read more.

A liquid electrolyte lithium/sulfur (Li/S) cell is a liquid electrochemical system. In discharge, sulfur is first reduced to highly soluble Li₂S₈, which dissolves into the organic electrolyte and serves as the liquid cathode. In solution, lithium polysulfide (PS) undergoes a series of complicated disproportionations, whose chemical equilibriums vary with the PS concentration and affect the cell’s performance. Since the PS concentration relates to a certain electrolyte/sulfur (E/S) ratio, there is an optimized E/S ratio for the cyclability of each Li/S cell system. In this work, we study the optimized E/S ratio by measuring the cycling performance of Li/S cells, and propose an empirical method for determination of the optimized E/S ratio. By employing an electrolyte of 0.25 m LiSO₃CF₃-0.25 m LiNO₃ dissolved in a 1:1 (wt:wt) mixture of dimethyl ether (DME) and 1,3-dioxolane (DOL) in an optimized E/S ratio, we show that the Li/S cell with a cathode containing 72% sulfur and 2 mg cm⁻² sulfur loading is able to retain a specific capacity of 780 mAh g⁻¹ after 100 cycles at 0.5 mA cm⁻² between 1.7 V and 2.8 V. Full article

(This article belongs to the Special Issue Li-ion Batteries and Energy Storage Devices)

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729 KiB

Open AccessReview

Ash Deposition in Biomass Combustion or Co-Firing for Power/Heat Generation

by Yuanyuan Shao, Jinsheng Wang, Fernando Preto, Jesse Zhu and Chunbao Xu

Energies 2012, 5(12), 5171-5189; https://doi.org/10.3390/en5125171 - 07 Dec 2012

Cited by 143 | Viewed by 11610

Abstract

This paper presents a concise overview of ash deposition in combustion or co-firing of biomass (woody biomass, agricultural residues, peat, etc.) with other fuels for power/heat generation. In this article, the following five research aspects on biomass combustion ash deposition are reviewed [...] Read more.

This paper presents a concise overview of ash deposition in combustion or co-firing of biomass (woody biomass, agricultural residues, peat, etc.) with other fuels for power/heat generation. In this article, the following five research aspects on biomass combustion ash deposition are reviewed and discussed: influence of biomass fuel characteristics, deposit-related challenges, ash deposition monitoring and analysis of ash deposits, mechanisms and chemistry of fly ash deposition, and key technologies for reducing ash deposition and corrosion in biomass-involved combustion. Full article

(This article belongs to the Special Issue Wood to Energy)

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882 KiB

Open AccessArticle

A High Step-Down Interleaved Buck Converter with Active-Clamp Circuits for Wind Turbines

by Cheng-Tao Tsai and Chih-Lung Shen

Energies 2012, 5(12), 5150-5170; https://doi.org/10.3390/en5125150 - 06 Dec 2012

Cited by 11 | Viewed by 7588

Abstract

In this paper, a high step-down interleaved buck coupled-inductor converter (IBCC) with active-clamp circuits for wind energy conversion has been studied. In high step-down voltage applications, an IBCC can extend duty ratio and reduce voltage stresses on active switches. In order to reduce [...] Read more.

In this paper, a high step-down interleaved buck coupled-inductor converter (IBCC) with active-clamp circuits for wind energy conversion has been studied. In high step-down voltage applications, an IBCC can extend duty ratio and reduce voltage stresses on active switches. In order to reduce switching losses of active switches to improve conversion efficiency, a IBCC with soft-switching techniques is usually required. Compared with passive-clamp circuits, the IBCC with active-clamp circuits have lower switching losses and minimum ringing voltage of the active switches. Thus, the proposed IBCC with active-clamp circuits for wind energy conversion can significantly increase conversion efficiency. Finally, a 240 W prototype of the proposed IBCC with active-clamp circuits was built and implemented. Experimental results have shown that efficiency can reach as high as 91%. The proposed IBCC with active-clamp circuits is presented in high step-down voltage applications to verify the performance and the feasibility for energy conversion of wind turbines. Full article

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561 KiB

Open AccessArticle

Diesel Consumption of Agriculture in China

by Nan Li, Hailin Mu, Huanan Li and Shusen Gui

Energies 2012, 5(12), 5126-5149; https://doi.org/10.3390/en5125126 - 06 Dec 2012

Cited by 15 | Viewed by 6059

Abstract

As agricultural mechanization accelerates the development of agriculture in China, to control the growth of the resulting energy consumption of mechanized agriculture without negatively affecting economic development has become a major challenge. A systematic analysis of the factors (total power, unit diesel consumption, [...] Read more.

As agricultural mechanization accelerates the development of agriculture in China, to control the growth of the resulting energy consumption of mechanized agriculture without negatively affecting economic development has become a major challenge. A systematic analysis of the factors (total power, unit diesel consumption, etc.) influencing diesel consumption using the SECA model, combined with simulations on agricultural diesel flows in China between 1996 and 2010 is performed in this work. Seven agricultural subsectors, fifteen categories of agricultural machinery and five farm operations are considered. The results show that farming and transportation are the two largest diesel consumers, accounting for 86.23% of the total diesel consumption in agriculture in 2010. Technological progress has led to a decrease in the unit diesel consumption and an increase in the unit productivity of all machinery, and there is still much potential for future progress. Additionally, the annual average working hours have decreased rapidly for most agricultural machinery, thereby influencing the development of mechanized agriculture. Full article

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290 KiB

Open AccessArticle

Linear Active Disturbance Rejection Control of Waste Heat Recovery Systems with Organic Rankine Cycles

by Jianhua Zhang, Jiancun Feng, Yeli Zhou, Fang Fang and Hong Yue

Energies 2012, 5(12), 5111-5125; https://doi.org/10.3390/en5125111 - 04 Dec 2012

Cited by 30 | Viewed by 6774

Abstract

In this paper, a linear active disturbance rejection controller is proposed for a waste heat recovery system using an organic Rankine cycle process, whose model is obtained by applying the system identification technique. The disturbances imposed on the waste heat recovery system are [...] Read more.

In this paper, a linear active disturbance rejection controller is proposed for a waste heat recovery system using an organic Rankine cycle process, whose model is obtained by applying the system identification technique. The disturbances imposed on the waste heat recovery system are estimated through an extended linear state observer and then compensated by a linear feedback control strategy. The proposed control strategy is applied to a 100 kW waste heat recovery system to handle the power demand variations of grid and process disturbances. The effectiveness of this controller is verified via a simulation study, and the results demonstrate that the proposed strategy can provide satisfactory tracking performance and disturbance rejection. Full article

(This article belongs to the Special Issue Waste to Energy Technologies)

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575 KiB

Open AccessArticle

Integrated Simulation Model for Energy Security Evaluation

by Yudha Prambudia and Masaru Nakano

Energies 2012, 5(12), 5086-5110; https://doi.org/10.3390/en5125086 - 04 Dec 2012

Cited by 25 | Viewed by 6532

Abstract

Energy security is a difficult issue to evaluate due to its polysemic and multifaceted nature. Recent studies have evaluated energy security by considering a multitude of dimensions (i.e., availability, affordability, etc.). However, these works lack coherence, as performance in one [...] Read more.

Energy security is a difficult issue to evaluate due to its polysemic and multifaceted nature. Recent studies have evaluated energy security by considering a multitude of dimensions (i.e., availability, affordability, etc.). However, these works lack coherence, as performance in one dimension is not necessarily relevant to performance in others. Due to this consideration, an ex-ante evaluation (i.e., policy analysis) of energy security cannot be reliably performed. This paper proposes an integrated simulation approach to address this apparent shortcoming. We consider energy security performance as a feature that emerges from interactions between the components of energy security dimensions. Integration is completed by identifying and establishing relationships between these components. A model is developed for the simulation that uses system dynamics as a modeling tool. The evaluation of Indonesia’s energy security is presented as an example. It is found that the policies intended to improve Indonesia’s energy security may conflict with each other. Increasing energy production will maintain the performance of the availability dimension at a high level in the short term, but this benefit is outweighed by the resulting degradation to the performance of the acceptability dimension. Subsidy elimination will increase the availability of energy due to lower energy consumption at the expense of maintaining energy affordability for the public. This study shows that the interrelationships between the dimensions of energy security is an important aspect to consider in energy security evaluations, as they can reveal tradeoffs between policies and improve the reliability of analyses. Full article

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1749 KiB

Open AccessArticle

Modeling Woody Biomass Procurement for Bioenergy Production at the Atikokan Generating Station in Northwestern Ontario, Canada

by Md. Bedarul Alam, Reino Pulkki, Chander Shahi and Thakur Upadhyay

Energies 2012, 5(12), 5065-5085; https://doi.org/10.3390/en5125065 - 03 Dec 2012

Cited by 18 | Viewed by 6726

Abstract

Efficient procurement and utilization of woody biomass for bioenergy production requires a good understanding of biomass supply chains. In this paper, a dynamic optimization model has been developed and applied to estimate monthly supply and procurement costs of woody biomass required for the [...] Read more.

Efficient procurement and utilization of woody biomass for bioenergy production requires a good understanding of biomass supply chains. In this paper, a dynamic optimization model has been developed and applied to estimate monthly supply and procurement costs of woody biomass required for the Atikokan Generating Station (AGS) in northwestern Ontario, based on its monthly electricity production schedule. The decision variables in the model are monthly harvest levels of two types of woody biomass, forest harvest residues and unutilized biomass, from 19,315 forest depletion cells (each 1 km²) for a one year planning horizon. Sixteen scenarios are tested to examine the sensitivity of the cost minimization model to changing economic and technological parameters. Reduction in moisture content and improvement of conversion efficiency showed relatively higher reductions in monthly and total costs of woody biomass feedstock for the AGS. The results of this study help in understanding and designing decision support systems for optimal biomass supply chains under dynamic operational frameworks. Full article

(This article belongs to the Special Issue Wood to Energy)

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245 KiB

Open AccessArticle

Short-Run and Long-Run Elasticities of Diesel Demand in Korea

by Kyoung-Min Lim, Myunghwan Kim, Chang Seob Kim and Seung-Hoon Yoo

Energies 2012, 5(12), 5055-5064; https://doi.org/10.3390/en5125055 - 28 Nov 2012

Cited by 11 | Viewed by 6414

Abstract

This paper investigates the demand function for diesel in Korea covering the period 1986–2011. The short-run and long-run elasticities of diesel demand with respect to price and income are empirically examined using a co-integration and error-correction model. The short-run and long-run price elasticities [...] Read more.

This paper investigates the demand function for diesel in Korea covering the period 1986–2011. The short-run and long-run elasticities of diesel demand with respect to price and income are empirically examined using a co-integration and error-correction model. The short-run and long-run price elasticities are estimated to be −0.357 and −0.547, respectively. The short-run and long-run income elasticities are computed to be 1.589 and 1.478, respectively. Thus, diesel demand is relatively inelastic to price change and elastic to income change in both the short-run and long-run. Therefore, a demand-side management through raising the price of diesel will be ineffective and tightening the regulation of using diesel more efficiently appears to be more effective in Korea. The demand for diesel is expected to continuously increase as the economy grows. Full article

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105 KiB

Open AccessCorrection

Correction: Long, H. et al. More Wind Power Integration with Adjusted Energy Carriers for Space Heating in Northern China. Energies 2012, 5, 3279-3294.

by Hongyu Long, Kunyao Xu, Ruilin Xu, Jianjun He, Kai Wu and Li Guo

Energies 2012, 5(12), 5053-5054; https://doi.org/10.3390/en5125053 - 27 Nov 2012

Viewed by 4666

Abstract

In the original version of the article published in Energies [1], insufficient acknowledgement was given for the contributors Mr. Li Guo and Prof. Kai Wu in Xi’an Jiaotong University. The main work was completed by the research group in Xi’an Jiaotong University led [...] Read more.

In the original version of the article published in Energies [1], insufficient acknowledgement was given for the contributors Mr. Li Guo and Prof. Kai Wu in Xi’an Jiaotong University. The main work was completed by the research group in Xi’an Jiaotong University led by Prof. Kai Wu. Mr. Li Guo was his master student who gave a lot of efforts in the measurement of daily loads of heating and electricity in different families, and his data was used in Section 2.1. Prof. Kai Wu was involved in the whole work; he put forward the basic idea, made the research plan and participated in the detailed discussion about the algorithm for calculation. [...] Full article

255 KiB

Open AccessArticle

Degradation Characteristics of Wood Using Supercritical Alcohols

by Jeeban Poudel and Sea Cheon Oh

Energies 2012, 5(12), 5038-5052; https://doi.org/10.3390/en5125038 - 27 Nov 2012

Cited by 6 | Viewed by 5265

Abstract

In this work, the characteristics of wood degradation using supercritical alcohols have been studied. Supercritical ethanol and supercritical methanol were used as solvents. The kinetics of wood degradation were analyzed using the nonisothermal weight loss technique with heating rates of 3.1, 9.8, and [...] Read more.

In this work, the characteristics of wood degradation using supercritical alcohols have been studied. Supercritical ethanol and supercritical methanol were used as solvents. The kinetics of wood degradation were analyzed using the nonisothermal weight loss technique with heating rates of 3.1, 9.8, and 14.5 °C/min for ethanol and 5.2, 11.3, and 16.3 °C/min for methanol. Three different kinetic analysis methods were implemented to obtain the apparent activation energy and the overall reaction order for wood degradation using supercritical alcohols. These were used to compare with previous data for supercritical methanol. From this work, the activation energies of wood degradation in supercritical ethanol were obtained as 78.0–86.0, 40.1–48.1, and 114 kJ/mol for the different kinetic analysis methods used in this work. The activation energies of wood degradation in supercritical ethanol were obtained as 78.0–86.0, 40.1–48.1, and 114 kJ/mol. This paper also includes the analysis of the liquid products obtained from this work. The characteristic analysis of liquid products on increasing reaction temperature and time has been performed by GC-MS. The liquid products were categorized according to carbon numbers and aromatic/aliphatic components. It was found that higher conversion in supercritical ethanol occurs at a lower temperature than that of supercritical methanol. The product analysis shows that the majority of products fall in the 2 to 15 carbon number range. Full article

(This article belongs to the Special Issue Wood to Energy)

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Open AccessArticle

Impact of PHEVs Penetration on Ontario’s Electricity Grid and Environmental Considerations

by Lena Ahmadi, Eric Croiset, Ali Elkamel, Peter L. Douglas, Woramon Unbangluang and Evgueniy Entchev

Energies 2012, 5(12), 5019-5037; https://doi.org/10.3390/en5125019 - 27 Nov 2012

Cited by 13 | Viewed by 6832

Abstract

Plug-in hybrid electric vehicles (PHEVs) have a large potential to reduce greenhouse gases emissions and increase fuel economy and fuel flexibility. PHEVs are propelled by the energy from both gasoline and electric power sources. Penetration of PHEVs into the automobile market affects the [...] Read more.

Plug-in hybrid electric vehicles (PHEVs) have a large potential to reduce greenhouse gases emissions and increase fuel economy and fuel flexibility. PHEVs are propelled by the energy from both gasoline and electric power sources. Penetration of PHEVs into the automobile market affects the electrical grid through an increase in electricity demand. This paper studies effects of the wide spread adoption of PHEVs on peak and base load demands in Ontario, Canada. Long-term forecasting models of peak and base load demands and the number of light-duty vehicles sold were developed. To create proper forecasting models, both linear regression (LR) and non-linear regression (NLR) techniques were employed, considering different ranges in the demographic, climate and economic variables. The results from the LR and NLR models were compared and the most accurate one was selected. Furthermore, forecasting the effects of PHEVs penetration is done through consideration of various scenarios of penetration levels, such as mild, normal and aggressive ones. Finally, the additional electricity demand on the Ontario electricity grid from charging PHEVs is incorporated for electricity production planning purposes. Full article

(This article belongs to the Special Issue Vehicle to Grid)

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265 KiB

Open AccessArticle

Fault Location in Power Electrical Traction Line System

by Yimin Zhou, Guoqing Xu and Yanfeng Chen

Energies 2012, 5(12), 5002-5018; https://doi.org/10.3390/en5125002 - 26 Nov 2012

Cited by 14 | Viewed by 7051

Abstract

In this paper, methods of fault location are discussed in electrical traction single-end direct power supply network systems. Based on the distributed parameter model of the system, the position of the short-circuit fault can be located with the aid of the current and [...] Read more.

In this paper, methods of fault location are discussed in electrical traction single-end direct power supply network systems. Based on the distributed parameter model of the system, the position of the short-circuit fault can be located with the aid of the current and voltage value at the measurement end of the electrical traction line. Furthermore, the influence of the transient resistance, the position of the locomotive, locomotive load for fault location are also discussed. MATLAB simulation tool is used for the simulation experiments. Simulation results are proved the effectiveness of the proposed algorithms. Full article

(This article belongs to the Special Issue Smart Grid and the Future Electrical Network)

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864 KiB

Open AccessReview

Biofuels Production through Biomass Pyrolysis —A Technological Review

by Mohammad I. Jahirul, Mohammad G. Rasul, Ashfaque Ahmed Chowdhury and Nanjappa Ashwath

Energies 2012, 5(12), 4952-5001; https://doi.org/10.3390/en5124952 - 23 Nov 2012

Cited by 991 | Viewed by 49591

Abstract

There has been an enormous amount of research in recent years in the area of thermo-chemical conversion of biomass into bio-fuels (bio-oil, bio-char and bio-gas) through pyrolysis technology due to its several socio-economic advantages as well as the fact it is an efficient [...] Read more.

There has been an enormous amount of research in recent years in the area of thermo-chemical conversion of biomass into bio-fuels (bio-oil, bio-char and bio-gas) through pyrolysis technology due to its several socio-economic advantages as well as the fact it is an efficient conversion method compared to other thermo-chemical conversion technologies. However, this technology is not yet fully developed with respect to its commercial applications. In this study, more than two hundred publications are reviewed, discussed and summarized, with the emphasis being placed on the current status of pyrolysis technology and its potential for commercial applications for bio-fuel production. Aspects of pyrolysis technology such as pyrolysis principles, biomass sources and characteristics, types of pyrolysis, pyrolysis reactor design, pyrolysis products and their characteristics and economics of bio-fuel production are presented. It is found from this study that conversion of biomass to bio-fuel has to overcome challenges such as understanding the trade-off between the size of the pyrolysis plant and feedstock, improvement of the reliability of pyrolysis reactors and processes to become viable for commercial applications. Further study is required to achieve a better understanding of the economics of biomass pyrolysis for bio-fuel production, as well as resolving issues related to the capabilities of this technology in practical application. Full article

(This article belongs to the Special Issue Biomass and Biofuels 2012)

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380 KiB

Open AccessArticle

Influence of Pyrolysis Temperature on Rice Husk Char Characteristics and Its Tar Adsorption Capability

by Anchan Paethanom and Kunio Yoshikawa

Energies 2012, 5(12), 4941-4951; https://doi.org/10.3390/en5124941 - 23 Nov 2012

Cited by 87 | Viewed by 8830

Abstract

A biomass waste, rice husk, was inspected by thermoanalytical investigation to evaluate its capability as an adsorbent medium for tar removal. The pyrolysis process has been applied to the rice husk material at different temperatures 600, 800 and 1000 °C with 20 °C/min [...] Read more.

A biomass waste, rice husk, was inspected by thermoanalytical investigation to evaluate its capability as an adsorbent medium for tar removal. The pyrolysis process has been applied to the rice husk material at different temperatures 600, 800 and 1000 °C with 20 °C/min heating rate, to investigate two topics: (1) influence of temperature on characterization of rice husk char and; (2) adsorption capability of rice husk char for tar removal. The results showed that subsequent to high temperature pyrolysis, rice husk char became a highly porous material, which was suitable as tar removal adsorbent with the ability to remove tar effectively. In addition, char characteristics and tar removal ability were significantly influenced by the pyrolysis temperature. Full article

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735 KiB

Open AccessArticle

Simulation of Synthesis Gas Production from Steam Oxygen Gasification of Colombian Coal Using Aspen Plus^®

by Jorge E. Preciado, John J. Ortiz-Martinez, Juan C. Gonzalez-Rivera, Rocio Sierra-Ramirez and Gerardo Gordillo

Energies 2012, 5(12), 4924-4940; https://doi.org/10.3390/en5124924 - 23 Nov 2012

Cited by 38 | Viewed by 14899

Abstract

A steady state simulation of syngas production from a Steam Oxygen Gasification process using commercial technologies was performed using Aspen Plus^®. For the simulation, the average proximate and ultimate compositions of bituminous coal obtained from the Colombian Andean region were employed. [...] Read more.

A steady state simulation of syngas production from a Steam Oxygen Gasification process using commercial technologies was performed using Aspen Plus^®. For the simulation, the average proximate and ultimate compositions of bituminous coal obtained from the Colombian Andean region were employed. The simulation was applied to conduct sensitivity analyses in the O₂ to coal mass ratio, coal slurry concentration, WGS operating temperature and WGS steam to dry gas molar ratio (SDG) over the key parameters: syngas molar composition, overall CO conversion in the WGS reactors, H₂ rich-syngas lower heating value (LHV) and thermal efficiency. The achieved information allows the selection of critical operating conditions leading to improve system efficiency and environmental performance. The results indicate that the oxygen to carbon ratio is a key variable as it affects significantly both the LHV and thermal efficiency. Nevertheless, the process becomes almost insensitive to SDG values higher than 2. Finally, a thermal efficiency of 62.6% can be reached. This result corresponds to a slurry solid concentration of 0.65, a WGS process SDG of 0.59, and a LTS reactor operating temperature of 473 K. With these fixed variables, a syngas with H₂ molar composition of 92.2% and LHV of 12 MJ Nm⁻³ was attained. Full article

(This article belongs to the Special Issue Selected Papers from the 25th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS2012))

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Energies, Volume 5, Issue 12 (December 2012) – 31 articles , Pages 4892-5466

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