Energies

605 KiB

Open AccessArticle

Sustainability Impact Assessment on the Production and Use of Different Wood and Fossil Fuels Employed for Energy Production in North Karelia, Finland

by Michael Den Herder, Marja Kolström, Marcus Lindner, Tommi Suominen, Diana Tuomasjukka and Matias Pekkanen

Energies 2012, 5(11), 4870-4891; https://doi.org/10.3390/en5114870 - 21 Nov 2012

Cited by 33 | Viewed by 8905

Abstract

The utilization rate of woody biomass in eastern Finland is high and expected to increase further in the near future as set out in several regional, national and European policies and strategies. The aim of this study was to assess the sustainability impacts [...] Read more.

The utilization rate of woody biomass in eastern Finland is high and expected to increase further in the near future as set out in several regional, national and European policies and strategies. The aim of this study was to assess the sustainability impacts of changes in fuel consumption patterns. We investigated fossil and woody biomass-based energy production chains in the region of North Karelia, focusing on some economic, environmental and social indicators. Indicators were selected based on stakeholder preferences and evaluated using the Tool for Sustainability Impact Assessment (ToSIA). The analysis was based on representative values from National Forest Inventory data, scientific publications, national and regional statistics, databases, published policy targets and expert opinion. From the results it became evident that shifting from fossil to wood-based energy production implies some trade-offs. Replacing oil with woody biomass in energy production would increase the local value added remaining in the region, create employment opportunities and would reduce total GHG emissions. However, firewood, wood chips from small-diameter trees from early thinning and wood pellets have high production costs. Moreover, large greenhouse gas emission resulted from wood pellet production. The case study generated valuable reference data for future sustainability assessments and demonstrated the usefulness of ToSIA as a tool presenting existing knowledge on sustainability impacts of alternative energy supply chains to inform decision making. Full article

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

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1481 KiB

Open AccessArticle

An Industrial System Powered by Wind and Coal for Aluminum Production: A Case Study of Technical Demonstration and Economic Feasibility

by Yuan-Zhang Sun, Jin Lin, Yong-Hua Song, Jian Xu, Xiao-Ming Li and Jian-Xun Dong

Energies 2012, 5(11), 4844-4869; https://doi.org/10.3390/en5114844 - 21 Nov 2012

Cited by 16 | Viewed by 6273

Abstract

This paper presents a case study of an isolated industrial power system for aluminum production. The novel concept is that the cost of aluminum electrolysis can be significantly reduced by innovative application of hybrid systems incorporating wind energy and low-grade coal. In addition, [...] Read more.

This paper presents a case study of an isolated industrial power system for aluminum production. The novel concept is that the cost of aluminum electrolysis can be significantly reduced by innovative application of hybrid systems incorporating wind energy and low-grade coal. In addition, the low-grade coal, which sale is not profitable in the market, can be locally consumed by the isolated power system. The power system thus fully utilizes the local resources in an effective and economic manner. However, several technical and economic issues are still of concern because the industrial system is isolated from the state grid. This paper hence discusses these issues and demonstrates the feasibility of such a hybrid power system from the technical and economic perspectives. Full article

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672 KiB

Open AccessArticle

Distributed Semantic Architecture for Smart Grids

by Yoseba K. Penya, Juan Carlos Nieves, Angelina Espinoza, Cruz E. Borges, Aitor Peña and Mariano Ortega

Energies 2012, 5(11), 4824-4843; https://doi.org/10.3390/en5114824 - 20 Nov 2012

Cited by 17 | Viewed by 8294

Abstract

The smart grid revolution demands a huge effort in redesigning and enhancing current power networks, as well as integrating emerging scenarios such as distributed generation, renewable energies or the electric vehicle. This novel situation will cause a huge flood of data that can [...] Read more.

The smart grid revolution demands a huge effort in redesigning and enhancing current power networks, as well as integrating emerging scenarios such as distributed generation, renewable energies or the electric vehicle. This novel situation will cause a huge flood of data that can only be handled, processed and exploited in real-time with the help of cutting-edge ICT (Information and Communication Technologies). We present here a new architecture that, contrary to the previous centralised and static model, distributes the intelligence all over the grid by means of individual intelligent nodes controlling a number of electric assets. The nodes own a profile of the standard smart grid ontology stored in the knowledge base with the inferred information about their environment in RDF triples. Since the system does not have a central registry or a service directory, the connectivity emerges from the view of the world semantically encoded by each individual intelligent node (i.e., profile + inferred information). We have described a use-case both with and without real-time requirements to illustrate and validate this novel approach. Full article

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

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322 KiB

Open AccessArticle

Optimal Bidding Strategies for Wind Power Producers in the Day-ahead Electricity Market

by Haifeng Zhang, Feng Gao, Jiang Wu, Kun Liu and Xiaolin Liu

Energies 2012, 5(11), 4804-4823; https://doi.org/10.3390/en5114804 - 20 Nov 2012

Cited by 20 | Viewed by 7017

Abstract

Wind Power Producers (WPPs) seek to maximize profit and minimize the imbalance costs when bidding into the day-ahead market, but uncertainties in the hourly available wind and forecasting errors make the bidding risky. This paper assumes that hourly wind power output given by [...] Read more.

Wind Power Producers (WPPs) seek to maximize profit and minimize the imbalance costs when bidding into the day-ahead market, but uncertainties in the hourly available wind and forecasting errors make the bidding risky. This paper assumes that hourly wind power output given by the forecast follows a normal distribution, and proposes three different bidding strategies, i.e., the expected profit-maximization strategy (EPS), the chance-constrained programming-based strategy (CPS) and the multi-objective bidding strategy (ECPS). Analytical solutions under the three strategies are obtained. Comparisons among the three strategies are conducted on a hypothetical wind farm which follows the Spanish market rules. Results show that bid under the EPS is highly dependent on market clearing price, imbalance prices, and also the mean value and standard deviation of wind forecast, and that bid under the CPS is largely driven by risk parameters and the mean value and standard deviation of the wind forecast. The ECPS combining both EPS and CPS tends to choose a compromise bid. Furthermore, the ECPS can effectively control the tradeoff between expected profit and target profit for WPPs operating in volatile electricity markets. Full article

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1351 KiB

Open AccessArticle

Non Breaking Wave Forces at the Front Face of Seawave Slotcone Generators

by Mariano Buccino, Davide Banfi, Diego Vicinanza, Mario Calabrese, Giuseppe Del Giudice and Armando Carravetta

Energies 2012, 5(11), 4779-4803; https://doi.org/10.3390/en5114779 - 19 Nov 2012

Cited by 43 | Viewed by 7075

Abstract

The Seawave Slotcone Generator (WAVEnergy SAS, 2003) is a wave energy converter based on the overtopping principle. Although it has been effectively researched during the last decade, no design tool has been supplied to estimate the hydrodynamic loads the waves exert on its [...] Read more.

The Seawave Slotcone Generator (WAVEnergy SAS, 2003) is a wave energy converter based on the overtopping principle. Although it has been effectively researched during the last decade, no design tool has been supplied to estimate the hydrodynamic loads the waves exert on its front face. In this article a set of well reliable 3D experiments has been re-analyzed, in order to get indications on possible calculation methods. It is shown that the Japanese design tools for monolithic sea dikes may be reasonably adapted to the present case. Finally a new approach is presented, which is based on the so called momentum flux principle; the resulting predictive equation fits the experimental data remarkably well. Full article

(This article belongs to the Special Issue Energy from the Ocean - Wave and Tidal Energy)

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2031 KiB

Open AccessArticle

Proportional-Resonant Control of Doubly-Fed Induction Generator Wind Turbines for Low-Voltage Ride-Through Enhancement

by Yan Yan, Meng Wang, Zhan-Feng Song and Chang-Liang Xia

Energies 2012, 5(11), 4758-4778; https://doi.org/10.3390/en5114758 - 19 Nov 2012

Cited by 23 | Viewed by 8499

Abstract

A novel control strategy is proposed in this paper for the rotor side converter (RSC) of doubly-fed induction generator (DFIG)-based wind power generation systems. It is supposed to enhance the low-voltage ride-through (LVRT) capability of DFIGs during great-level grid voltage dips. The strategy [...] Read more.

A novel control strategy is proposed in this paper for the rotor side converter (RSC) of doubly-fed induction generator (DFIG)-based wind power generation systems. It is supposed to enhance the low-voltage ride-through (LVRT) capability of DFIGs during great-level grid voltage dips. The strategy consists of a proportional-resonant (PR) controller and auxiliary PR controllers. The auxiliary controllers compensate the output voltage of the RSC in case of grid faults, thus limiting the rotor inrush current of DFIG and meeting the requirements of LVRT. Sequential-component decompositions of current are not required in the control system to improve the response of system. Since the resonant compensator is a double-side integrator, the auxiliary controllers can be simplified through coordinate transformation. The feasibility of the control strategy is validated by simulation on a 1.5 MW wind-turbine driven DFIG system. The impact of the RSC converter voltage rating on the LVRT capability of DFIG is investigated. Meanwhile, the influence of angular frequency detection and control parameters are also discussed. Compared with traditional vector control schemes based on PI current controllers, the presented control strategy effectively suppress rotor current and reduce oscillations of DFIG power and torque under grid faults. Full article

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997 KiB

Open AccessArticle

Optimization of Key Factors Affecting Methane Production from Acidic Effluent Coming from the Sugarcane Juice Hydrogen Fermentation Process

by Alissara Reungsang, Sakchai Pattra and Sureewan Sittijunda

Energies 2012, 5(11), 4746-4757; https://doi.org/10.3390/en5114746 - 19 Nov 2012

Cited by 55 | Viewed by 6769

Abstract

Response surface methodology with a central composite design was applied to optimize the key factors affecting methane production from the acidic effluent coming from the sugarcane juice hydrogen fermentation process. The parameters studied were substrate concentration, ratio of NaHCO₃ to substrate concentration [...] Read more.

Response surface methodology with a central composite design was applied to optimize the key factors affecting methane production from the acidic effluent coming from the sugarcane juice hydrogen fermentation process. The parameters studied were substrate concentration, ratio of NaHCO₃ to substrate concentration and initial pH. The experimental results showed that substrate concentration and initial pH had significant individual (p < 0.05) effect on methane yield (MY). However, there was no interactive effect between these variables (p > 0.05). The maximum MY of 367 mL CH₄/g-volatile solid (VS)_added was obtained at the optimum conditions of 13,823 mg-COD/L, an NaHCO₃ to substrate concentration ratio of 3.09 and an initial pH of 7.07. Under the optimum conditions, MY was enhanced 4.4-fold in comparison to raw effluent. Full article

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521 KiB

Open AccessArticle

Concept Development of Optimal Mine Site Energy Supply

by Monica Carvalho and Dean L. Millar

Energies 2012, 5(11), 4726-4745; https://doi.org/10.3390/en5114726 - 19 Nov 2012

Cited by 15 | Viewed by 6876

Abstract

This paper reports on early work and concept development for Optimal Mine Site Energy Supply, where the specific energy supply requirements and constraints for mineral production operations are considered against methodologies that have been applied for other sectors and in other energy policy [...] Read more.

This paper reports on early work and concept development for Optimal Mine Site Energy Supply, where the specific energy supply requirements and constraints for mineral production operations are considered against methodologies that have been applied for other sectors and in other energy policy regimes. The primary motivation for this research is to help ensure that Canadian mineral producers will achieve reduced production costs through improvements in the efficiency with which they consume energy resources. Heat has not yet been considered for the mining sector in an integrated manner, which makes polygeneration of great interest. The methodology that optimizes configuration of polygeneration systems for mine sites has not been reported before. The variety of mining circumstances, temporal variations in energy prices, institutional inertia, and conservatism in design for mines are some of the reasons for this. This paper reviews some aspects of precedent energy management practice in mineral operations, which highlights energy challenges characteristic of the sector and sets out the initial formulation of optimal mine site energy supply. The review indicates the additional benefits of energy supply systems for mine sites that concurrently meet all utilities. 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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708 KiB

Open AccessArticle

Day-Ahead Electricity Price Forecasting Using a Hybrid Principal Component Analysis Network

by Ying-Yi Hong and Ching-Ping Wu

Energies 2012, 5(11), 4711-4725; https://doi.org/10.3390/en5114711 - 19 Nov 2012

Cited by 42 | Viewed by 7492

Abstract

Bidding competition is one of the main transaction approaches in a deregulated electricity market. Locational marginal prices (LMPs) resulting from bidding competition and system operation conditions indicate electricity values at a node or in an area. The LMP reveals important information for market [...] Read more.

Bidding competition is one of the main transaction approaches in a deregulated electricity market. Locational marginal prices (LMPs) resulting from bidding competition and system operation conditions indicate electricity values at a node or in an area. The LMP reveals important information for market participants in developing their bidding strategies. Moreover, LMP is also a vital indicator for the Security Coordinator to perform market redispatch for congestion management. This paper presents a method using a principal component analysis (PCA) network cascaded with a multi-layer feedforward (MLF) network for forecasting LMPs in a day-ahead market. The PCA network extracts essential features from periodic information in the market. These features serve as inputs to the MLF network for forecasting LMPs. The historical LMPs in the PJM market are employed to test the proposed method. It is found that the proposed method is capable of forecasting day-ahead LMP values efficiently. Full article

(This article belongs to the Special Issue Hybrid Advanced Techniques for Forecasting in Energy Sector)

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568 KiB

Open AccessArticle

Combined Optimal Sizing and Control for a Hybrid Tracked Vehicle

by Yuan Zou, Fengchun Sun, Xiaosong Hu, Lino Guzzella and Huei Peng

Energies 2012, 5(11), 4697-4710; https://doi.org/10.3390/en5114697 - 19 Nov 2012

Cited by 61 | Viewed by 8698

Abstract

The optimal sizing and control of a hybrid tracked vehicle is presented and solved in this paper. A driving schedule obtained from field tests is used to represent typical tracked vehicle operations. Dynamics of the diesel engine-permanent magnetic AC synchronous generator set, the [...] Read more.

The optimal sizing and control of a hybrid tracked vehicle is presented and solved in this paper. A driving schedule obtained from field tests is used to represent typical tracked vehicle operations. Dynamics of the diesel engine-permanent magnetic AC synchronous generator set, the lithium-ion battery pack, and the power split between them are modeled and validated through experiments. Two coupled optimizations, one for the plant parameters, forming the outer optimization loop and one for the control strategy, forming the inner optimization loop, are used to achieve minimum fuel consumption under the selected driving schedule. The dynamic programming technique is applied to find the optimal controller in the inner loop while the component parameters are optimized iteratively in the outer loop. The results are analyzed, and the relationship between the key parameters is observed to keep the optimal sizing and control simultaneously. Full article

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1389 KiB

Open AccessArticle

Structural Optimization Design of Horizontal-Axis Wind Turbine Blades Using a Particle Swarm Optimization Algorithm and Finite Element Method

by Xin Cai, Jie Zhu, Pan Pan and Rongrong Gu

Energies 2012, 5(11), 4683-4696; https://doi.org/10.3390/en5114683 - 16 Nov 2012

Cited by 24 | Viewed by 10326

Abstract

This paper presents an optimization method for the structural design of horizontal-axis wind turbine (HAWT) blades based on the particle swarm optimization algorithm (PSO) combined with the finite element method (FEM). The main goal is to create an optimization tool and to demonstrate [...] Read more.

This paper presents an optimization method for the structural design of horizontal-axis wind turbine (HAWT) blades based on the particle swarm optimization algorithm (PSO) combined with the finite element method (FEM). The main goal is to create an optimization tool and to demonstrate the potential improvements that could be brought to the structural design of HAWT blades. A multi-criteria constrained optimization design model pursued with respect to minimum mass of the blade is developed. The number and the location of layers in the spar cap and the positions of the shear webs are employed as the design variables, while the strain limit, blade/tower clearance limit and vibration limit are taken into account as the constraint conditions. The optimization of the design of a commercial 1.5 MW HAWT blade is carried out by combining the above method and design model under ultimate (extreme) flap-wise load conditions. The optimization results are described and compared with the original design. It shows that the method used in this study is efficient and produces improved designs. Full article

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781 KiB

Open AccessArticle

A PEV Charging Service Model for Smart Grids

by Khaled Shuaib, Liren Zhang, Ahmed Gaouda and Mohammed Abdel-Hafez

Energies 2012, 5(11), 4665-4682; https://doi.org/10.3390/en5114665 - 16 Nov 2012

Cited by 15 | Viewed by 6370

Abstract

Plug-in Electric Vehicles (PEVs) are envisioned to be more popular during the next decade as part of Smart Grid implementations. Charging multiple PEVs at the same time within a power distribution area constitutes a major challenge for energy service providers. This paper discusses [...] Read more.

Plug-in Electric Vehicles (PEVs) are envisioned to be more popular during the next decade as part of Smart Grid implementations. Charging multiple PEVs at the same time within a power distribution area constitutes a major challenge for energy service providers. This paper discusses a priority-based approach for charging PEVs in a Smart Grid environment. In this work, ideas from the communication network paradigm are being utilized and tailored toward achieving the desired objective of monitoring and controlling PEVs electric load in Smart Grid. A detailed example is given to show how uncontrolled penetration of PEVs can impact distribution transformer reliability. The paper introduces the concept of Charging Quality of Service (CQoS) as a smart electric vehicle charging scheme and models it using a priority-controlled leaky bucket approach. The performance of such a model is investigated under the umbrella of a Smart Grid environment. Full article

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

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763 KiB

Open AccessArticle

Development of a Terminal Control System with Variable Minimum Airflow Rate

by Young-Hum Cho

Energies 2012, 5(11), 4643-4664; https://doi.org/10.3390/en5114643 - 15 Nov 2012

Cited by 8 | Viewed by 6591

Abstract

A constant minimum airflow rate is used in conventional Single Duct Variable Air Volume Terminal Box control sequences. This control sequence can cause occupant discomfort or use excessive energy under partial load conditions. If the minimum airflow rate is higher than required; terminal [...] Read more.

A constant minimum airflow rate is used in conventional Single Duct Variable Air Volume Terminal Box control sequences. This control sequence can cause occupant discomfort or use excessive energy under partial load conditions. If the minimum airflow rate is higher than required; terminal boxes will have significantly more simultaneous heating and cooling; and AHUs will consume more fan power. Buildings will have indoor air quality problems if the minimum airflow rate is less than required. Many engineers and researchers have investigated advanced variable air volume terminal box control algorithms without a system retrofit for thermal comfort; indoor air quality and energy savings. In this study a developed control system with variable minimum airflow rate for Single Duct Variable Air Volume Terminal Boxes was applied and validated using an actual building and evaluated for comfort; indoor air quality and energy consumption. The energy consumption and thermal performance of terminal boxes using the conventional and proposed control algorithms were compared. Full article

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

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891 KiB

Open AccessArticle

Novel Speed Bumps Design and Optimization for Vehicles' Energy Recovery in Smart Cities

by Andrea Pirisi, Francesco Grimaccia, Marco Mussetta and Riccardo E. Zich

Energies 2012, 5(11), 4624-4642; https://doi.org/10.3390/en5114624 - 14 Nov 2012

Cited by 31 | Viewed by 10237

Abstract

Recently the technology development and increasing amounts of investment in renewables has led to a growing interest towards design and optimization of green energy systems. In this context, advanced Computational Intelligence (CI) techniques can be applied by engineers to several technical problems in [...] Read more.

Recently the technology development and increasing amounts of investment in renewables has led to a growing interest towards design and optimization of green energy systems. In this context, advanced Computational Intelligence (CI) techniques can be applied by engineers to several technical problems in order to find out the best structure and to improve efficiency in energy recovery. This research promises to give new impulse to using innovative unconventional renewable sources and to develop the so-called Energy Harvesting Devices (EHDs). In this paper, the optimization of a Tubular Permanent Magnet-Linear Generator for energy harvesting from vehicles to grid is presented. The optimization process is developed by means of hybrid evolutionary algorithms to reach the best overall system efficiency and the impact on the environment and transportation systems. Finally, an experimental validation of the designed EHD prototype is presented. Full article

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

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1014 KiB

Open AccessArticle

Asymmetrical Interleaved DC/DC Switching Converters for Photovoltaic and Fuel Cell Applications—Part 1: Circuit Generation, Analysis and Design

by Eliana Arango, Carlos Andres Ramos-Paja, Javier Calvente, Roberto Giral and Sergio Serna

Energies 2012, 5(11), 4590-4623; https://doi.org/10.3390/en5114590 - 14 Nov 2012

Cited by 31 | Viewed by 7704

Abstract

A novel asymmetrical interleaved dc/dc switching converters family intended for photovoltaic and fuel cell applications is presented in this paper. The main requirements on such applications are small ripples in the generator and load, as well as high voltage conversion ratio. Therefore, interleaved [...] Read more.

A novel asymmetrical interleaved dc/dc switching converters family intended for photovoltaic and fuel cell applications is presented in this paper. The main requirements on such applications are small ripples in the generator and load, as well as high voltage conversion ratio. Therefore, interleaved structures and voltage multiplier cells have been asymmetrically combined to generate new converters, which inherently operate indiscontinuous conduction mode. The novel family is derived from boost, buck-boost and flyback-based structures. This converter family is analyzed to obtain the design equations and synthesize a design process based on the typical requirements of photovoltaic and fuel cell applications. Finally, the experimental results validate the characteristics and usefulness of the asymmetrical interleaved converter family. Full article

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2020 KiB

Open AccessArticle

Non-Intrusive Demand Monitoring and Load Identification for Energy Management Systems Based on Transient Feature Analyses

by Hsueh-Hsien Chang

Energies 2012, 5(11), 4569-4589; https://doi.org/10.3390/en5114569 - 14 Nov 2012

Cited by 141 | Viewed by 9880

Abstract

Energy management systems strive to use energy resources efficiently, save energy, and reduce carbon output. This study proposes transient feature analyses of the transient response time and transient energy on the power signatures of non-intrusive demand monitoring and load identification to detect the [...] Read more.

Energy management systems strive to use energy resources efficiently, save energy, and reduce carbon output. This study proposes transient feature analyses of the transient response time and transient energy on the power signatures of non-intrusive demand monitoring and load identification to detect the power demand and load operation. This study uses the wavelet transform (WT) of the time-frequency domain to analyze and detect the transient physical behavior of loads during the load identification. The experimental results show the transient response time and transient energy are better than the steady-state features to improve the recognition accuracy and reduces computation requirements in non-intrusive load monitoring (NILM) systems. The discrete wavelet transform (DWT) is more suitable than short-time Fourier transform (STFT) for transient load analyses. Full article

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

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1676 KiB

Open AccessArticle

Electrical Double-Layer Capacitors in Hybrid Topologies —Assessment and Evaluation of Their Performance

by Noshin Omar, Mohamed Daowd, Omar Hegazy, Peter Van den Bossche, Thierry Coosemans and Joeri Van Mierlo

Energies 2012, 5(11), 4533-4568; https://doi.org/10.3390/en5114533 - 14 Nov 2012

Cited by 47 | Viewed by 8916

Abstract

PHEVs and BEVs make use of battery cells optimized for high energy rather than for high power. This means that the power abilities of these batteries are limited. In order to enhance their performance, a hybrid Rechargeable Energy Storage System (RESS) architecture can [...] Read more.

PHEVs and BEVs make use of battery cells optimized for high energy rather than for high power. This means that the power abilities of these batteries are limited. In order to enhance their performance, a hybrid Rechargeable Energy Storage System (RESS) architecture can be used combining batteries with electrical-double layer capacitors (EDLCs). Such a hybridized architecture can be accomplished using passive or active systems. In this paper, the characteristics of these topologies have been analyzed and compared based on a newly developed hybridization simulation tool for association of lithium-ion batteries and EDLCs. The analysis shows that the beneficial impact of the EDLCs brings about enhanced battery performances in terms of energy efficiency and voltage drops, rather than extension of vehicle range. These issues have been particularly studied for the passive and active hybrid topologies. The classical passive and active topologies being expensive and less beneficial in term of cost, volume and weight, a new hybrid configuration based on the parallel combination of lithium-ion and EDLCs on cell level has been proposed in this article. This topology allows reducing cost, volume, and weight and system complexity in a significant way. Furthermore, a number of experimental setups have illustrated the power of the novel topology in terms of battery capacity increase and power capabilities during charging and discharging. Finally, a unique cycle life test campaign demonstrated that the lifetime of highly optimized lithium-ion batteries can be extended up to 30%–40%. Full article

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876 KiB

Open AccessArticle

Demand Side Management for Stand-Alone Hybrid Power Systems Based on Load Identification

by Félix Iglesias, Peter Palensky, Sergio Cantos and Friederich Kupzog

Energies 2012, 5(11), 4517-4532; https://doi.org/10.3390/en5114517 - 13 Nov 2012

Cited by 21 | Viewed by 7606

Abstract

Within the field of Distributed Generation (DG), stand-alone Hybrid Power Systems (HPS) are a suitable solution to provide energy to isolated facilities where the connection to a centralized grid is not affordable. The logical evolution of such systems involves the optimization of power [...] Read more.

Within the field of Distributed Generation (DG), stand-alone Hybrid Power Systems (HPS) are a suitable solution to provide energy to isolated facilities where the connection to a centralized grid is not affordable. The logical evolution of such systems involves the optimization of power resources and related control strategies, but also enhancements concerning the management of energy loads. This paper introduces Demand Side Management (DSM) strategies specially designed for HPS. They are applied on a real and patented HPS that consists of PV panels, a diesel generator, an inverter and a set of batteries. DSM strategies are built up on a framework of distributed endpointdevices connected to a central control application where loads are identified according to their behavior. System network components, load definitions, the control application and DSM strategies are depicted. Finally, simulations show illustrative savings achieved by the application of some of the proposed strategies. Full article

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1515 KiB

Open AccessArticle

An Energy and Water Resource Demand Estimation Model for Multi-Family Housing Complexes in Korea

by Dongjun Suh and Seongju Chang

Energies 2012, 5(11), 4497-4516; https://doi.org/10.3390/en5114497 - 13 Nov 2012

Cited by 13 | Viewed by 6630

Abstract

This paper proposes and develops a residential energy and resource consumption estimation model in the context of multi-family residential housing in Korea using a multi-layer perceptron (MLP) neural network. Eight indicators are introduced which affect the energy and water resource usage characteristics of [...] Read more.

This paper proposes and develops a residential energy and resource consumption estimation model in the context of multi-family residential housing in Korea using a multi-layer perceptron (MLP) neural network. Eight indicators are introduced which affect the energy and water resource usage characteristics of Korean residential complexes. The proposed model precisely estimated the electricity, gas energy and water consumption for each examined residential complex. In terms of validation, the results showed the highest level of agreement with actually collected datasets. The model shows promising prospects in providing necessary estimations, not only for optimally scaling and sizing energy- and water-related infrastructures, but also to promote reliable energy and resource savings through greenhouse gas (GHG) reduction planning in multi-family housing complexes. The model could also be of use in framing guidelines for the better planning of national or regional energy and resource policies and for forming a foundation of decision-making with definite references regarding the facility management of each apartment complex to enhance the energy and resource use efficiency at these locations. Full article

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

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462 KiB

Open AccessArticle

Supplementary Controller Design for SSR Damping in a Series-Compensated DFIG-Based Wind Farm

by Zaijun Wu, Chanxia Zhu and Minqiang Hu

Energies 2012, 5(11), 4481-4496; https://doi.org/10.3390/en5114481 - 13 Nov 2012

Cited by 6 | Viewed by 5917

Abstract

The increasing presence of wind power in power systems will likely drive the integration of large wind farms with electrical networks that are series-compensated to sustain large power flows. This may potentially lead to subsynchronous resonance (SSR) issues. In this paper, a supplementary [...] Read more.

The increasing presence of wind power in power systems will likely drive the integration of large wind farms with electrical networks that are series-compensated to sustain large power flows. This may potentially lead to subsynchronous resonance (SSR) issues. In this paper, a supplementary controller on the grid-side converter (GSC) control loop is designed to mitigate SSR for wind power systems based on doubly fed induction generators (DFIGs) with back-to-back converters. Different supplementary controller feedback signals and modulated-voltage injecting points are proposed and compared based on modal analysis and verified through root locus analysis to identify the optimal feedback signal and the most effective control location for SSR damping. The validity and effectiveness of the proposed supplemental control are demonstrated on the IEEE first benchmark model for computer simulations of SSR by means of time domain simulation analysis using Matlab/Simulink. Full article

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

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1652 KiB

Open AccessArticle

A DFuzzy-DAHP Decision-Making Model for Evaluating Energy-Saving Design Strategies for Residential Buildings

by Kuang-Sheng Liu, Sung-Lin Hsueh, Wen-Chen Wu and Yu-Lung Chen

Energies 2012, 5(11), 4462-4480; https://doi.org/10.3390/en5114462 - 9 Nov 2012

Cited by 33 | Viewed by 8020

Abstract

The construction industry is a high-pollution and high-energy-consumption industry. Energy-saving designs for residential buildings not only reduce the energy consumed during construction, but also reduce long-term energy consumption in completed residential buildings. Because building design affects investment costs, designs are often influenced by [...] Read more.

The construction industry is a high-pollution and high-energy-consumption industry. Energy-saving designs for residential buildings not only reduce the energy consumed during construction, but also reduce long-term energy consumption in completed residential buildings. Because building design affects investment costs, designs are often influenced by investors’ decisions. A set of appropriate decision-support tools for residential buildings are required to examine how building design influences corporations externally and internally. From the perspective of energy savings and environmental protection, we combined three methods to develop a unique model for evaluating the energy-saving design of residential buildings. Among these methods, the Delphi group decision-making method provides a co-design feature, the analytical hierarchy process (AHP) includes multi-criteria decision-making techniques, and fuzzy logic theory can simplify complex internal and external factors into easy-to-understand numbers or ratios that facilitate decisions. The results of this study show that incorporating solar building materials, double-skin facades, and green roof designs can effectively provide high energy-saving building designs. Full article

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

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714 KiB

Open AccessArticle

Combustion Characteristics of Chlorine-Free Solid Fuel Produced from Municipal Solid Waste by Hydrothermal Processing

by Bayu Indrawan, Pandji Prawisudha and Kunio Yoshikawa

Energies 2012, 5(11), 4446-4461; https://doi.org/10.3390/en5114446 - 8 Nov 2012

Cited by 16 | Viewed by 7873

Abstract

An experimental study on converting municipal solid waste (MSW) into chlorine-free solid fuel using a combination of hydrothermal processing and water-washing has been performed. After the product was extracted from the reactor, water-washing experiments were then conducted to obtain chlorine-free products with less [...] Read more.

An experimental study on converting municipal solid waste (MSW) into chlorine-free solid fuel using a combination of hydrothermal processing and water-washing has been performed. After the product was extracted from the reactor, water-washing experiments were then conducted to obtain chlorine-free products with less than 3000 ppm total chlorine content. A series of combustion experiments were then performed for the products before and after the washing process to determine the chlorine content in the exhaust gas and those left in the ash after the combustion process at a certain temperature. A series of thermogravimetric analyses were also conducted to compare the combustion characteristics of the products before and after the washing process. Due to the loss of ash and some volatile matter after washing process, there were increases in the fixed carbon content and the heating value of the product. Considering the possible chlorine emission, the washing process after the hydrothermal treatment should be necessary only if the furnace temperature is more than 800 °C. Full article

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

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361 KiB

Open AccessArticle

Annual Electric Load Forecasting by a Least Squares Support Vector Machine with a Fruit Fly Optimization Algorithm

by Hongze Li, Sen Guo, Huiru Zhao, Chenbo Su and Bao Wang

Energies 2012, 5(11), 4430-4445; https://doi.org/10.3390/en5114430 - 8 Nov 2012

Cited by 118 | Viewed by 9462

Abstract

The accuracy of annual electric load forecasting plays an important role in the economic and social benefits of electric power systems. The least squares support vector machine (LSSVM) has been proven to offer strong potential in forecasting issues, particularly by employing an appropriate [...] Read more.

The accuracy of annual electric load forecasting plays an important role in the economic and social benefits of electric power systems. The least squares support vector machine (LSSVM) has been proven to offer strong potential in forecasting issues, particularly by employing an appropriate meta-heuristic algorithm to determine the values of its two parameters. However, these meta-heuristic algorithms have the drawbacks of being hard to understand and reaching the global optimal solution slowly. As a novel meta-heuristic and evolutionary algorithm, the fruit fly optimization algorithm (FOA) has the advantages of being easy to understand and fast convergence to the global optimal solution. Therefore, to improve the forecasting performance, this paper proposes a LSSVM-based annual electric load forecasting model that uses FOA to automatically determine the appropriate values of the two parameters for the LSSVM model. By taking the annual electricity consumption of China as an instance, the computational result shows that the LSSVM combined with FOA (LSSVM-FOA) outperforms other alternative methods, namely single LSSVM, LSSVM combined with coupled simulated annealing algorithm (LSSVM-CSA), generalized regression neural network (GRNN) and regression model. Full article

(This article belongs to the Special Issue Hybrid Advanced Techniques for Forecasting in Energy Sector)

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309 KiB

Open AccessArticle

Coherency Identification of Generators Using a PAM Algorithm for Dynamic Reduction of Power Systems

by Gi-Chan Pyo, Jin-Woo Park and Seung-Il Moon

Energies 2012, 5(11), 4417-4429; https://doi.org/10.3390/en5114417 - 8 Nov 2012

Cited by 6 | Viewed by 7710

Abstract

This paper presents a new coherency identification method for dynamic reduction of a power system. To achieve dynamic reduction, coherency-based equivalence techniques divide generators into groups according to coherency, and then aggregate them. In order to minimize the changes in the dynamic response [...] Read more.

This paper presents a new coherency identification method for dynamic reduction of a power system. To achieve dynamic reduction, coherency-based equivalence techniques divide generators into groups according to coherency, and then aggregate them. In order to minimize the changes in the dynamic response of the reduced equivalent system, coherency identification of the generators should be clearly defined. The objective of the proposed coherency identification method is to determine the optimal coherent groups of generators with respect to the dynamic response, using the Partitioning Around Medoids (PAM) algorithm. For this purpose, the coherency between generators is first evaluated from the dynamic simulation time response, and in the proposed method this result is then used to define a dissimilarity index. Based on the PAM algorithm, the coherent generator groups are then determined so that the sum of the index in each group is minimized. This approach ensures that the dynamic characteristics of the original system are preserved, by providing the optimized coherency identification. To validate the effectiveness of the technique, simulated cases with an IEEE 39-bus test system are evaluated using PSS/E. The proposed method is compared with an existing coherency identification method, which uses the K-means algorithm, and is found to provide a better estimate of the original system. Full article

(This article belongs to the Special Issue Electrical Power and Energy Systems)

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1621 KiB

Open AccessArticle

Analytical Investigation and Control System Set-up of Medium Scale PV Plants for Power Flow Management

by Antonino Oscar Di Tommaso, Fabio Genduso and Rosario Miceli

Energies 2012, 5(11), 4399-4416; https://doi.org/10.3390/en5114399 - 8 Nov 2012

Cited by 39 | Viewed by 6510

Abstract

In the field of photovoltaic (PV) plants and energy conversion from renewable sources, a large part of the technical literature is more devoted to practical aspects (new solar cells, electrically driven PV panels, safety, reduction of parasitic currents, etc.) than to theoretical investigations. [...] Read more.

In the field of photovoltaic (PV) plants and energy conversion from renewable sources, a large part of the technical literature is more devoted to practical aspects (new solar cells, electrically driven PV panels, safety, reduction of parasitic currents, etc.) than to theoretical investigations. Despite this tendency, this paper presents a mathematical analysis of a medium scale photovoltaic power generation system connected to the distribution network and of its control system. In such a system, the conversion stage is unique due to the absence of a boost chopper. The conducted analysis leads to the interesting conclusion that the inverter used in the plant presents two degrees of freedom, easy to exploit in a control system in which the inverter simultaneously realizes the interconnection to the grid and the MPPT control. The structure of the control system is then presented, discussed and validated by means of numerical simulations. Full article

(This article belongs to the Special Issue Solar Energy Systems and Materials)

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200 KiB

Open AccessArticle

Regulatory Promotion of Waste Wood Reused as an Energy Source and the Environmental Concerns about Ash Residue in the Industrial Sector of Taiwan

by Wen-Tien Tsai

Energies 2012, 5(11), 4390-4398; https://doi.org/10.3390/en5114390 - 2 Nov 2012

Cited by 2 | Viewed by 6156

Abstract

The objective of this paper was to provide a preliminary analysis of the utilization of energy derived from waste wood in Taiwan, a highly industrialized country with a high dependence (over 99%) on imported energy. The discussion focuses on the status of waste [...] Read more.

The objective of this paper was to provide a preliminary analysis of the utilization of energy derived from waste wood in Taiwan, a highly industrialized country with a high dependence (over 99%) on imported energy. The discussion focuses on the status of waste wood generation and its management over the past decade. Findings show that the quantities of biomass waste collected for reuse purposes in the industrial sectors of Taiwan has exhibited an increasing trend, from about 4000 tons in 2001 to over 52,000 tons in 2010. Although waste wood can be reused as a fuel and raw material for a variety of applications based on regulatory promotion, the most commonly used end use is to directly utilize it as an auxiliary fuel in industrial utilities (e.g., boilers, heaters and furnaces) for the purpose of co-firing with coal/fuel oil. The most progressive measure for promoting biomass-to-power is to introduce the feed-in tariff (FIT) mechanism according to the Renewable Energy Development Act passed in June 2009. The financial support for biomass power generation has been increasing over the years from 0.070 US$/kWh in 2010 to 0.094 US$/kWh in 2012. On the other hand, the environmental regulations in Taiwan regarding the hazard identification of wood-combusted ash (especially in filter fly-ash) and its options for disposal and utilization are further discussed in the paper, suggesting that waste wood impregnated with chromated copper arsenate (CCA) and other copper-based preservatives should be excluded from the wood-to-energy system. Finally, some recommendations for promoting wood-to-energy in the near future of Taiwan are addressed. Full article

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

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627 KiB

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A Novel Miniature Culture System to Screen CO₂-Sequestering Microalgae

by Wei Han, Chunying Li, Xiaoling Miao and Guangxin Yu

Energies 2012, 5(11), 4372-4389; https://doi.org/10.3390/en5114372 - 1 Nov 2012

Cited by 18 | Viewed by 7368

Abstract

In this study, a novel 96-well microplate swivel system (M96SS) was built for high-throughput screening of microalgal strains for CO₂ fixation. Cell growth under different CO₂ supply conditions (0.2, 0.4, 0.8, and 1.2 gL⁻¹d⁻¹), residual nitrate, [...] Read more.

In this study, a novel 96-well microplate swivel system (M96SS) was built for high-throughput screening of microalgal strains for CO₂ fixation. Cell growth under different CO₂ supply conditions (0.2, 0.4, 0.8, and 1.2 gL⁻¹d⁻¹), residual nitrate, and pH value of Chlorella sp. SJTU-3, Chlorella pyrenoidosa SJTU-2, and Scenedesmus obliquus SJTU-3 were examined in the M96SS and traditional flask cultures. The dynamic data showed there was a good agreement between the systems. Two critical problems in miniature culture systems (intra-well mixing and evaporation loss) were improved by sealed vertical mixing of the M96SS. A sample screen of six microalgal species (Chlorella sp. SJTU-3, Chlorella pyrenoidosa SJTU-2, Selenastrum capricornutum, Scenedesmus obliquus SJTU-3, Chlamydomonas sajao, Dunaliella primolecta) was carried out in flasks and the M96SS. Chlamydomonas sajao appeared to be a robust performer (highest cell density: 1.437 g L⁻¹) in anaerobic pond water with 0.8, and 1.2 gL⁻¹d⁻¹ CO₂. The reliability and efficiency of the M96SS were verified through a comparison of traditional flask culture, M96SS, Lukavský’s system, and a microplate shaker. Full article

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

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4986 KiB

Open AccessArticle

Time Domain Modeling and Analysis of Dynamic Gear Contact Force in a Wind Turbine Gearbox with Respect to Fatigue Assessment

by Wenbin Dong, Yihan Xing and Torgeir Moan

Energies 2012, 5(11), 4350-4371; https://doi.org/10.3390/en5114350 - 1 Nov 2012

Cited by 27 | Viewed by 14747

Abstract

The gearbox is one of the most expensive components of the wind turbine system. In order to refine the design and hence increase the long-term reliability, there has been increasing interest in utilizing time domain simulations in the prediction of gearbox design loads. [...] Read more.

The gearbox is one of the most expensive components of the wind turbine system. In order to refine the design and hence increase the long-term reliability, there has been increasing interest in utilizing time domain simulations in the prediction of gearbox design loads. In this study, three problems in time domain based gear contact fatigue analysis under dynamic conditions are discussed: (1) the torque reversal problem under low wind speed conditions, (2) statistical uncertainty effects due to time domain simulations and (3) simplified long term contact fatigue analysis of the gear tooth under dynamic conditions. Several recommendations to deal with these issues are proposed based on analyses of the National Renewable Energy Laboratory’s 750 kW land-based Gearbox Reliability Collaborative wind turbine. Full article

(This article belongs to the Special Issue Wind Turbines)

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757 KiB

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Design and Fabrication of a Novel Hybrid-Structure Heat Pipe for a Concentrator Photovoltaic

by Hsin-Jung Huang, Sheng-Chih Shen and Heiu-Jou Shaw

Energies 2012, 5(11), 4340-4349; https://doi.org/10.3390/en5114340 - 29 Oct 2012

Cited by 29 | Viewed by 6592

Abstract

This study presents a design method to fabricate a novel hybrid-structure flat plate heat pipe (NHSP heat pipe) for a concentrator photovoltaic. The NHSP heat pipe is composed of a flattened copper pipe and a sintered wick structure, and a coronary-stent-like rhombic copper [...] Read more.

This study presents a design method to fabricate a novel hybrid-structure flat plate heat pipe (NHSP heat pipe) for a concentrator photovoltaic. The NHSP heat pipe is composed of a flattened copper pipe and a sintered wick structure, and a coronary-stent-like rhombic copper mesh supports the structure. The coronary-stent-like supporting structure enhances the mechanical strength and shortens the reflux path of the working fluid. Experiments demonstrate that the sintered capillary heat pipe reduces the thermal resistance by approximately 72%, compared to a traditional copper mesh-screen heat pipe. Furthermore, it can reduce thermal resistance by 65% after a supporting structure is added to the heat pipe. The results show that the NHSP heat pipe provided the best performance for the concentrator photovoltaic, which can increase photoelectric conversion efficiency by approximately 3.1%, compared to an aluminum substrate. Full article

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626 KiB

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Investigation on Electrostatical Breakup of Bio-Oil Droplets

by Zhen-Tao Wang, Aleksandar M. Mitrašinović and John Z. Wen

Energies 2012, 5(11), 4323-4339; https://doi.org/10.3390/en5114323 - 29 Oct 2012

Cited by 22 | Viewed by 6132

Abstract

In electrostatic atomization, the input electrical energy causes breaking up of the droplet surface by utilizing a mutual repulsion of net charges accumulating on that surface. In this work a number of key parameters controlling the bio-oil droplet breakup process are identified and [...] Read more.

In electrostatic atomization, the input electrical energy causes breaking up of the droplet surface by utilizing a mutual repulsion of net charges accumulating on that surface. In this work a number of key parameters controlling the bio-oil droplet breakup process are identified and these correlations among the droplet size distribution, specific charges of droplets and externally applied electrical voltages are quantified. Theoretical considerations of the bag or strip breakup mechanism of biodiesel droplets experiencing electrostatic potential are compared to experimental outcomes. The theoretical analysis suggests the droplet breakup process is governed by the Rayleigh instability condition, which reveals the effects of droplets size, specific charge, surface tension force, and droplet velocities. Experiments confirm that the average droplet diameters decrease with increasing specific charges and this decreasing tendency is non-monotonic due to the motion of satellite drops in the non-uniform electrical field. The measured specific charges are found to be smaller than the theoretical values. And the energy transformation from the electrical energy to surface energy, in addition to the energy loss, Taylor instability breakup, non-excess polarization and some system errors, accounts for this discrepancy. The electrostatic force is the dominant factor controlling the mechanism of biodiesel breakup in electrostatic atomization. Full article

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Energies, Volume 5, Issue 11 (November 2012) – 33 articles , Pages 4251-4891

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