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

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Open AccessArticle Power Quality and Harmonic Analysis of End User Devices
Energies 2012, 5(12), 5453-5466; https://doi.org/10.3390/en5125453
Received: 8 October 2012 / Revised: 13 December 2012 / Accepted: 14 December 2012 / Published: 19 December 2012
Cited by 29 | PDF Full-text (1530 KB) | HTML Full-text | XML Full-text
Abstract
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
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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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Open AccessArticle A New Battery Energy Storage Charging/Discharging Scheme for Wind Power Producers in Real-Time Markets
Energies 2012, 5(12), 5439-5452; https://doi.org/10.3390/en5125439
Received: 12 September 2012 / Revised: 2 November 2012 / Accepted: 7 December 2012 / Published: 19 December 2012
Cited by 14 | PDF Full-text (242 KB) | HTML Full-text | XML Full-text
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
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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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Open AccessArticle Fuel-N Evolution during the Pyrolysis of Industrial Biomass Wastes with High Nitrogen Content
Energies 2012, 5(12), 5418-5438; https://doi.org/10.3390/en5125418
Received: 10 September 2012 / Revised: 14 December 2012 / Accepted: 14 December 2012 / Published: 19 December 2012
Cited by 26 | PDF Full-text (743 KB) | HTML Full-text | XML Full-text
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
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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 NOx 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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Open AccessReview Commercial Biomass Syngas Fermentation
Energies 2012, 5(12), 5372-5417; https://doi.org/10.3390/en5125372
Received: 3 September 2012 / Revised: 31 October 2012 / Accepted: 5 December 2012 / Published: 19 December 2012
Cited by 134 | PDF Full-text (604 KB) | HTML Full-text | XML Full-text
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
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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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Open AccessArticle Electrodeposition of a Au-Dy2O3 Composite Solid Oxide Fuel Cell Catalyst from Eutectic Urea/Choline Chloride Ionic Liquid
Energies 2012, 5(12), 5363-5371; https://doi.org/10.3390/en5125363
Received: 15 August 2012 / Revised: 20 October 2012 / Accepted: 7 December 2012 / Published: 19 December 2012
Cited by 2 | PDF Full-text (1612 KB) | HTML Full-text | XML Full-text
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
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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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Open AccessArticle Atmospheric Turbulence Effects on Wind-Turbine Wakes: An LES Study
Energies 2012, 5(12), 5340-5362; https://doi.org/10.3390/en5125340
Received: 10 October 2012 / Revised: 28 November 2012 / Accepted: 11 December 2012 / Published: 17 December 2012
Cited by 72 | PDF Full-text (1606 KB) | HTML Full-text | XML Full-text
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
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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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Open AccessArticle Establishing an Integration-Energy-Practice Model for Improving Energy Performance Indicators in ISO 50001 Energy Management Systems
Energies 2012, 5(12), 5324-5339; https://doi.org/10.3390/en5125324
Received: 18 September 2012 / Revised: 10 December 2012 / Accepted: 12 December 2012 / Published: 17 December 2012
Cited by 16 | PDF Full-text (1268 KB) | HTML Full-text | XML Full-text
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
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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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Open AccessArticle A Simple Sizing Algorithm for Stand-Alone PV/Wind/Battery Hybrid Microgrids
Energies 2012, 5(12), 5307-5323; https://doi.org/10.3390/en5125307
Received: 13 September 2012 / Revised: 19 November 2012 / Accepted: 29 November 2012 / Published: 14 December 2012
Cited by 61 | PDF Full-text (419 KB) | HTML Full-text | XML Full-text
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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Open AccessArticle An Efficient Drift-Flux Closure Relationship to Estimate Liquid Holdups of Gas-Liquid Two-Phase Flow in Pipes
Energies 2012, 5(12), 5294-5306; https://doi.org/10.3390/en5125294
Received: 31 October 2012 / Revised: 3 December 2012 / Accepted: 11 December 2012 / Published: 14 December 2012
Cited by 28 | PDF Full-text (1289 KB) | HTML Full-text | XML Full-text
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
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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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Open AccessArticle Wind Turbine Tower Vibration Modeling and Monitoring by the Nonlinear State Estimation Technique (NSET)
Energies 2012, 5(12), 5279-5293; https://doi.org/10.3390/en5125279
Received: 7 September 2012 / Revised: 29 November 2012 / Accepted: 30 November 2012 / Published: 14 December 2012
Cited by 13 | PDF Full-text (259 KB) | HTML Full-text | XML Full-text
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
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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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Open AccessArticle A Building Energy Efficiency Optimization Method by Evaluating the Effective Thermal Zones Occupancy
Energies 2012, 5(12), 5257-5278; https://doi.org/10.3390/en5125257
Received: 29 October 2012 / Revised: 22 November 2012 / Accepted: 6 December 2012 / Published: 13 December 2012
Cited by 41 | PDF Full-text (2787 KB) | HTML Full-text | XML Full-text
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’
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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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Open AccessArticle Chemical Profiles of Wood Components of Poplar Clones for Their Energy Utilization
Energies 2012, 5(12), 5243-5256; https://doi.org/10.3390/en5125243
Received: 30 August 2012 / Revised: 26 November 2012 / Accepted: 7 December 2012 / Published: 13 December 2012
Cited by 18 | PDF Full-text (219 KB) | HTML Full-text | XML Full-text
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)
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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)
Open AccessArticle Behavior of the Blade Tip Vortices of a Wind Turbine Equipped with a Brimmed-Diffuser Shroud
Energies 2012, 5(12), 5229-5242; https://doi.org/10.3390/en5125229
Received: 3 November 2012 / Revised: 30 November 2012 / Accepted: 10 December 2012 / Published: 13 December 2012
Cited by 10 | PDF Full-text (1524 KB) | HTML Full-text | XML Full-text
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
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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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Open AccessArticle Classification and Clustering of Electricity Demand Patterns in Industrial Parks
Energies 2012, 5(12), 5215-5228; https://doi.org/10.3390/en5125215
Received: 9 October 2012 / Revised: 26 November 2012 / Accepted: 6 December 2012 / Published: 12 December 2012
Cited by 32 | PDF Full-text (3304 KB) | HTML Full-text | XML Full-text
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
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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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Open AccessArticle Electric Energy Consumption of the Full Scale Research Biogas Plant “Unterer Lindenhof”: Results of Longterm and Full Detail Measurements
Energies 2012, 5(12), 5198-5214; https://doi.org/10.3390/en5125198
Received: 31 August 2012 / Revised: 30 October 2012 / Accepted: 29 November 2012 / Published: 10 December 2012
Cited by 14 | PDF Full-text (948 KB) | HTML Full-text | XML Full-text
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
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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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