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Energies, Volume 7, Issue 3 (March 2014), Pages 1098-1851

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Open AccessArticle An Artificial Neural Network Compensated Output Feedback Power-Level Control for Modular High Temperature Gas-Cooled Reactors
Energies 2014, 7(3), 1149-1170; doi:10.3390/en7031149
Received: 25 December 2013 / Revised: 6 February 2014 / Accepted: 10 February 2014 / Published: 26 February 2014
Cited by 6 | PDF Full-text (621 KB) | HTML Full-text | XML Full-text
Abstract
Small modular reactors (SMRs) could be beneficial in providing electricity power safely and also be viable for applications such as seawater desalination and heat production. Due to its inherent safety features, the modular high temperature gas-cooled reactor (MHTGR) has been seen as one
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Small modular reactors (SMRs) could be beneficial in providing electricity power safely and also be viable for applications such as seawater desalination and heat production. Due to its inherent safety features, the modular high temperature gas-cooled reactor (MHTGR) has been seen as one of the best candidates for building SMR-based nuclear power plants. Since the MHTGR dynamics display high nonlinearity and parameter uncertainty, it is necessary to develop a nonlinear adaptive power-level control law which is not only beneficial to the safe, stable, efficient and autonomous operation of the MHTGR, but also easy to implement practically. In this paper, based on the concept of shifted-ectropy and the physically-based control design approach, it is proved theoretically that the simple proportional-differential (PD) output-feedback power-level control can provide asymptotic closed-loop stability. Then, based on the strong approximation capability of the multi-layer perceptron (MLP) artificial neural network (ANN), a compensator is established to suppress the negative influence caused by system parameter uncertainty. It is also proved that the MLP-compensated PD power-level control law constituted by an experientially-tuned PD regulator and this MLP-based compensator can guarantee bounded closed-loop stability. Numerical simulation results not only verify the theoretical results, but also illustrate the high performance of this MLP-compensated PD power-level controller in suppressing the oscillation of process variables caused by system parameter uncertainty. Full article
Open AccessArticle Appraising Bioenergy Alternatives in Uganda Using Strengths, Weaknesses, Opportunities and Threats (SWOT)-Analytical Hierarchy Process (AHP) and a Desirability Functions Approach
Energies 2014, 7(3), 1171-1192; doi:10.3390/en7031171
Received: 27 November 2013 / Revised: 16 January 2014 / Accepted: 7 February 2014 / Published: 26 February 2014
Cited by 5 | PDF Full-text (1045 KB) | HTML Full-text | XML Full-text
Abstract
Poor access to clean and reliable energy technologies is a major challenge to most developing countries. The decision to introduce new technologies is often faced by low adoption rates or even public opposition. In addition, the data required for effective decision making is
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Poor access to clean and reliable energy technologies is a major challenge to most developing countries. The decision to introduce new technologies is often faced by low adoption rates or even public opposition. In addition, the data required for effective decision making is often inadequate or even lacking, thus constraining the planning process. In this study, a methodology for participatory appraisal of technologies, integrating desirability functions to the strengths, weaknesses, opportunities and threats (SWOT)-analytical hierarchy process (AHP) methodology was developed. Application of the methodology was illustrated with an example for participatory appraisal of four bioenergy technologies in Uganda. Results showed that the methodology is effective in evaluating stakeholder preferences for bioenergy technologies. It showed a high potential to be used to identify and rate factors that stakeholders take into consideration when selecting bioenergy systems. The method could be used as a tool for technology screening, or reaching consensus in a participatory setup in a transparent manner. Full article
(This article belongs to the Special Issue Biomass and Biofuels 2013)
Open AccessArticle Study of the Vertical Distribution of Air Temperature in Warehouses
Energies 2014, 7(3), 1193-1206; doi:10.3390/en7031193
Received: 9 January 2014 / Revised: 6 February 2014 / Accepted: 12 February 2014 / Published: 27 February 2014
Cited by 4 | PDF Full-text (1120 KB) | HTML Full-text | XML Full-text
Abstract
Warehouses are usually large, plain industrial buildings commonly used for storage of goods. Vertical distribution of air temperature is an important aspect for indoor environment design, which must be taken into account by architects and engineers in the early stages of warehouse design.
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Warehouses are usually large, plain industrial buildings commonly used for storage of goods. Vertical distribution of air temperature is an important aspect for indoor environment design, which must be taken into account by architects and engineers in the early stages of warehouse design. The aim of this work is to analyze the vertical temperature gradients existing in warehouses, quantifying their value and analyzing their evolution along the year. To do so, the study outlines the monitoring of several warehouses with different building typology and height located in different areas of Spain for a complete annual cycle. The results obtained when applying a simple linear regression analysis to 175,200 vertical temperature profiles show that there is a strong influence of the outdoor temperature over the stratification of the indoor air. During warm months, the ceiling and the upper strata get warmer, whereas the cold air accumulates in the lower levels, increasing the stratification of indoor air (maximum values between 0.3 °C/m and 0.7 °C/m). During cold months, the ceiling gets cold due to its contact with the outdoor air, therefore, the colder, heavier air moves down to the lower strata, registering insignificant vertical temperature differences. Air conditioning of the warehouse, besides controlling the temperature, limits the influence of the outdoor environment on the stratification of temperatures. The results of the study may be of great use for warehouses for products sensitive to temperature, which may suffer a different evolution, conservation or maturation when the temperature differences are maintained for a long time. Full article
(This article belongs to the Special Issue Energy Efficient Building Design and Operation 2014)
Open AccessArticle Planning Minimum Interurban Fast Charging Infrastructure for Electric Vehicles: Methodology and Application to Spain
Energies 2014, 7(3), 1207-1229; doi:10.3390/en7031207
Received: 25 December 2013 / Revised: 2 February 2014 / Accepted: 8 February 2014 / Published: 27 February 2014
Cited by 3 | PDF Full-text (1201 KB) | HTML Full-text | XML Full-text
Abstract
The goal of the research is to assess the minimum requirement of fast charging infrastructure to allow country-wide interurban electric vehicle (EV) mobility. Charging times comparable to fueling times in conventional internal combustion vehicles are nowadays feasible, given the current availability of fast
[...] Read more.
The goal of the research is to assess the minimum requirement of fast charging infrastructure to allow country-wide interurban electric vehicle (EV) mobility. Charging times comparable to fueling times in conventional internal combustion vehicles are nowadays feasible, given the current availability of fast charging technologies. The main contribution of this paper is the analysis of the planning method and the investment requirements for the necessary infrastructure, including the definition of the Maximum Distance between Fast Charge (MDFC) and the Basic Highway Charging Infrastructure (BHCI) concepts. According to the calculations, distance between stations will be region-dependent, influenced primarily by weather conditions. The study considers that the initial investment should be sufficient to promote the EV adoption, proposing an initial state-financed public infrastructure and, once the adoption rate for EVs increases, additional infrastructure will be likely developed through private investment. The Spanish network of state highways is used as a case study to demonstrate the methodology and calculate the investment required. Further, the results are discussed and quantitatively compared to other incentives and policies supporting EV technology adoption in the light-vehicle sector. Full article
(This article belongs to the Special Issue Advances in Hybrid Vehicles)
Open AccessArticle An Equivalent Emission Minimization Strategy for Causal Optimal Control of Diesel Engines
Energies 2014, 7(3), 1230-1250; doi:10.3390/en7031230
Received: 9 December 2013 / Revised: 18 February 2014 / Accepted: 21 February 2014 / Published: 27 February 2014
Cited by 1 | PDF Full-text (372 KB) | HTML Full-text | XML Full-text
Abstract
One of the main challenges during the development of operating strategies for modern diesel engines is the reduction of the CO2 emissions, while complying with ever more stringent limits for the pollutant emissions. The inherent trade-off between the emissions of CO2
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One of the main challenges during the development of operating strategies for modern diesel engines is the reduction of the CO2 emissions, while complying with ever more stringent limits for the pollutant emissions. The inherent trade-off between the emissions of CO2 and pollutants renders a simultaneous reduction difficult. Therefore, an optimal operating strategy is sought that yields minimal CO2 emissions, while holding the cumulative pollutant emissions at the allowed level. Such an operating strategy can be obtained offline by solving a constrained optimal control problem. However, the final-value constraint on the cumulated pollutant emissions prevents this approach from being adopted for causal control. This paper proposes a framework for causal optimal control of diesel engines. The optimization problem can be solved online when the constrained minimization of the CO2 emissions is reformulated as an unconstrained minimization of the CO2 emissions and the weighted pollutant emissions (i.e., equivalent emissions). However, the weighting factors are not known a priori. A method for the online calculation of these weighting factors is proposed. It is based on the Hamilton–Jacobi–Bellman (HJB) equation and a physically motivated approximation of the optimal cost-to-go. A case study shows that the causal control strategy defined by the online calculation of the equivalence factor and the minimization of the equivalent emissions is only slightly inferior to the non-causal offline optimization, while being applicable to online control. Full article
Open AccessArticle Simulated Effects of Land Cover Conversion on the Surface Energy Budget in the Southwest of China
Energies 2014, 7(3), 1251-1264; doi:10.3390/en7031251
Received: 6 November 2013 / Revised: 23 December 2013 / Accepted: 26 February 2014 / Published: 3 March 2014
PDF Full-text (1605 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the coupled WRF/SSiB model, accompanied by a Karst Rocky Desertification (KRD) map of the Guizhou Karst Plateau (GKP) of China, was applied to detect how the changed vegetation and soil characteristics over the GKP modify the energy balance at the
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In this paper, the coupled WRF/SSiB model, accompanied by a Karst Rocky Desertification (KRD) map of the Guizhou Karst Plateau (GKP) of China, was applied to detect how the changed vegetation and soil characteristics over the GKP modify the energy balance at the land surface. The results indicated that land degradation led to reduced net radiation by inducing more upward shortwave and longwave radiation, which were associated with increasing surface albedo and temperature, respectively. The KRD also resulted in changed surface energy partitioning into sensible and latent heat fluxes. The latent heat flux at land surface was reduced substantially due to the higher surface albedo and stomatal resistance, the lower Leaf Area Index (LAI) and roughness length in the degradation experiment, while the sensible heat flux increased, mainly because of the higher surface temperature. Furthermore, the moisture flux convergence was reduced, owing to the lower atmospheric heating and the relative subsidence. However, compared with the reduced evaporation, the decrease in moisture flux convergence contributed much less to the reduced precipitation. Precipitation strongly affects soil moisture, vegetation growth and phenology, and thus evaporation and convective latent heating, so when precipitation was changed, a feedback loop was created. Full article
(This article belongs to the Special Issue Large Scale LUCC, Surface Energy Fluxes and Energy Use)
Open AccessArticle Research on a 20-Slot/22-Pole Five-Phase Fault-Tolerant PMSM Used for Four-Wheel-Drive Electric Vehicles
Energies 2014, 7(3), 1265-1287; doi:10.3390/en7031265
Received: 15 December 2013 / Revised: 20 February 2014 / Accepted: 26 February 2014 / Published: 3 March 2014
Cited by 8 | PDF Full-text (661 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a five-phase fault-tolerant permanent-magnet synchronous machine (PMSM) used for electric vehicles. In multiphase fault-tolerant PMSMs equipped with fractional-slot concentrated windings, excessive magneto-motive force (MMF) harmonics can lead to thermal demagnetization of the permanent magnets (PMs). In order to reduce the
[...] Read more.
This paper presents a five-phase fault-tolerant permanent-magnet synchronous machine (PMSM) used for electric vehicles. In multiphase fault-tolerant PMSMs equipped with fractional-slot concentrated windings, excessive magneto-motive force (MMF) harmonics can lead to thermal demagnetization of the permanent magnets (PMs). In order to reduce the lower-order harmonics, the origins of the 2-pole harmonic in conventional winding configurations are investigated, and an unequal-turn winding configuration is applied to cancel the lower-order harmonics. The main electromagnetic performances of the unequal-turn winding configuration are investigated and compared with conventional winding topologies. Based on the principle of maintaining constant instantaneous power, the fault-tolerant control strategies for open-circuits of up to two phases are developed. All of the investigations are verified by finite element analysis (FEA) results. Full article
(This article belongs to the Special Issue Advances in Hybrid Vehicles)
Open AccessArticle A Fast Solution for the Lagrange Multiplier-Based Electric Power Network Parameter Error Identification Model
Energies 2014, 7(3), 1288-1299; doi:10.3390/en7031288
Received: 23 October 2013 / Revised: 13 February 2014 / Accepted: 28 February 2014 / Published: 4 March 2014
Cited by 2 | PDF Full-text (365 KB) | HTML Full-text | XML Full-text
Abstract
The Lagrange multiplier-based method is an effective network parameter error identification method. However, two full matrices with high-dimensions are involved in the calculation procedure; these create huge computational burdens for large-scale power systems. To solve this problem, a fast solution is proposed in
[...] Read more.
The Lagrange multiplier-based method is an effective network parameter error identification method. However, two full matrices with high-dimensions are involved in the calculation procedure; these create huge computational burdens for large-scale power systems. To solve this problem, a fast solution is proposed in this paper, where special treatment techniques for full matrices are used to dramatically improve the calculation efficiency. A practical parameter error identification program has been developed and used in many electric power control centers. In this paper, the results for test systems and on-site applications are given, which show that the proposed approach is very efficient. Full article
Open AccessArticle Impacts of Irrigation on the Heat Fluxes and Near-Surface Temperature in an Inland Irrigation Area of Northern China
Energies 2014, 7(3), 1300-1317; doi:10.3390/en7031300
Received: 20 December 2013 / Revised: 11 February 2014 / Accepted: 19 February 2014 / Published: 4 March 2014
Cited by 4 | PDF Full-text (1931 KB) | HTML Full-text | XML Full-text
Abstract
Irrigated agriculture has the potential to alter regional to global climate significantly. We investigate how irrigation will affect regional climate in the future in an inland irrigation area of northern China, focusing on its effects on heat fluxes and near-surface temperature. Using the
[...] Read more.
Irrigated agriculture has the potential to alter regional to global climate significantly. We investigate how irrigation will affect regional climate in the future in an inland irrigation area of northern China, focusing on its effects on heat fluxes and near-surface temperature. Using the Weather Research and Forecasting (WRF) model, we compare simulations among three land cover scenarios: the control scenario (CON), the irrigation scenario (IRR), and the irrigated cropland expansion scenario (ICE). Our results show that the surface energy budgets and temperature are sensitive to changes in the extent and spatial pattern of irrigated land. Conversion to irrigated agriculture at the contemporary scale leads to an increase in annual mean latent heat fluxes of 12.10 W m−2, a decrease in annual mean sensible heat fluxes of 8.85 W m−2, and a decrease in annual mean temperature of 1.3 °C across the study region. Further expansion of irrigated land increases annual mean latent heat fluxes by 18.08 W m−2, decreases annual mean sensible heat fluxes by 12.31 W m−2, and decreases annual mean temperature by 1.7 °C. Our simulated effects of irrigation show that changes in land use management such as irrigation can be an important component of climate change and need to be considered together with greenhouse forcing in climate change assessments. Full article
(This article belongs to the Special Issue Large Scale LUCC, Surface Energy Fluxes and Energy Use)
Open AccessArticle Energy and Cost Saving of a Photovoltaic-Phase Change Materials (PV-PCM) System through Temperature Regulation and Performance Enhancement of Photovoltaics
Energies 2014, 7(3), 1318-1331; doi:10.3390/en7031318
Received: 22 October 2013 / Revised: 17 February 2014 / Accepted: 19 February 2014 / Published: 5 March 2014
Cited by 20 | PDF Full-text (459 KB) | HTML Full-text | XML Full-text
Abstract
The current research seeks to maintain high photovoltaic (PV) efficiency and increased operating PV life by maintaining them at a lower temperature. Solid-liquid phase change materials (PCM) are integrated into PV panels to absorb excess heat by latent heat absorption mechanism and regulate
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The current research seeks to maintain high photovoltaic (PV) efficiency and increased operating PV life by maintaining them at a lower temperature. Solid-liquid phase change materials (PCM) are integrated into PV panels to absorb excess heat by latent heat absorption mechanism and regulate PV temperature. Electrical and thermal energy efficiency analysis of PV-PCM systems is conducted to evaluate their effectiveness in two different climates. Finally costs incurred due to inclusion of PCM into PV system and the resulting benefits are discussed in this paper. The results show that such systems are financially viable in higher temperature and higher solar radiation environment. Full article
Open AccessArticle The Development and Empirical Evaluation of the Korean Smart Distribution Management System
Energies 2014, 7(3), 1332-1362; doi:10.3390/en7031332
Received: 13 November 2013 / Revised: 22 February 2014 / Accepted: 25 February 2014 / Published: 5 March 2014
Cited by 5 | PDF Full-text (6774 KB) | HTML Full-text | XML Full-text
Abstract
This paper introduces the development and actual test results of the Korean Smart Distribution Management System (KSDMS). The KSDMS has been designed and developed to cope with the lack of interconnection capability of the Dispersed Energy Resource (DER), to provide standardization and compatibility,
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This paper introduces the development and actual test results of the Korean Smart Distribution Management System (KSDMS). The KSDMS has been designed and developed to cope with the lack of interconnection capability of the Dispersed Energy Resource (DER), to provide standardization and compatibility, and to implement automatic processing of service restoration, in the existing Distribution Automation System (DAS) in Korea. First, real-time system analysis and control application programs were developed, to solve the problems of the existing DAS; and the Distribution Management System (DMS) platform was developed, to run the developed application programs. Second, international standard-based communication, platform, and database structures were adopted, for standardization and compatibility. Third, a platform and application program functions were developed to process faults automatically; and a communication device and an intelligent electronic device (IED) were developed to automate fault restoration, through communication between devices. The KSDMS was evaluated by three tests: unit function test, platform and application program integration test, and empirical test. The first two were conducted on both small and large demonstration systems. The empirical test was performed at the Power Testing Center (PTC) in Gochang, and on a real system, at the Korea Electric Power Corporation (KEPCO), on Jeju Island. The test results verified that the KSDMS can actively resolve the problems of the existing DAS. Full article
(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)
Open AccessArticle Comparative Analysis of Milled Wood Lignins (MWLs) Isolated from Sugar Maple (SM) and Hot-Water Extracted Sugar Maple (ESM)
Energies 2014, 7(3), 1363-1375; doi:10.3390/en7031363
Received: 20 November 2013 / Revised: 1 February 2014 / Accepted: 18 February 2014 / Published: 5 March 2014
Cited by 4 | PDF Full-text (842 KB) | HTML Full-text | XML Full-text
Abstract
To further elucidate the advantageous effects of hot-water extraction (HWE) on delignification, milled wood lignin (MWL) was isolated from sugar maple (SM) and from hot-water extracted sugar maple (ESM). Ball-milled wood was analyzed for particle size distribution (PSD) before and after dioxane:water (DW)
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To further elucidate the advantageous effects of hot-water extraction (HWE) on delignification, milled wood lignin (MWL) was isolated from sugar maple (SM) and from hot-water extracted sugar maple (ESM). Ball-milled wood was analyzed for particle size distribution (PSD) before and after dioxane:water (DW) extraction. The MWL samples were analyzed by analytical and spectral methods. The results indicated that the MWL isolated from SM and ESM was mainly released from the middle lamella (ML) and the secondary wall (SW), respectively. The cleavage of dibenzodioxocin (DB) and spirodienone (SD) lignin substructures during HWE is suggested. The removal of lignin during acetone:water (AW) extraction of hot-water extracted wood indicates that including an additional operation in a hardwood HWE-based biorefinery would be beneficial for processing of wood. Full article
(This article belongs to the Special Issue Biomass and Biofuels 2013)
Open AccessArticle Design and Control of a Multi-Functional Energy Recovery Power Accumulator Battery Pack Testing System for Electric Vehicles
Energies 2014, 7(3), 1376-1392; doi:10.3390/en7031376
Received: 3 January 2014 / Revised: 10 February 2014 / Accepted: 21 February 2014 / Published: 5 March 2014
Cited by 6 | PDF Full-text (912 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, aiming at the energy loss and harmonic problems in the conventional power accumulator battery pack testing system (PABPTS), an improved multi-functional energy recovery PABPTS (ERPABPTS) for electric vehicles (EVs) was proposed. The improved system has the functions of harmonic detection,
[...] Read more.
In this paper, aiming at the energy loss and harmonic problems in the conventional power accumulator battery pack testing system (PABPTS), an improved multi-functional energy recovery PABPTS (ERPABPTS) for electric vehicles (EVs) was proposed. The improved system has the functions of harmonic detection, suppression, reactive compensation and energy recovery. The ERPABPTS, which contains a bi-directional buck-boost direct current (DC)-DC converter and a bi-directional alternating current (AC)-DC converter with an inductor-capacitor-inductor (LCL) type filter interfacing to the AC-grid, is proposed. System configuration and operation principle of the combined system are discussed first, then, the reactive compensation and harmonic suppression controller under balanced grid-voltage condition are presented. Design of a fourth order band-pass Butterworth filter for current harmonic detection is put forward, and the reactive compensator design procedure considering the non-linear load is also illustrated. The proposed scheme is implemented in a 175-kW prototype in the laboratory. Simulation and experimental results show that the combined configuration can effectively realize energy recovery for high accuracy current test requirement, meanwhile, can effectively achieve reactive compensation and current harmonic suppression. Full article
(This article belongs to the Special Issue Advances in Hybrid Vehicles)
Open AccessArticle Investigation of the Cooling and Thermal-Measuring System of a Compound-Structure Permanent-Magnet Synchronous Machine
Energies 2014, 7(3), 1393-1426; doi:10.3390/en7031393
Received: 17 October 2013 / Revised: 18 February 2014 / Accepted: 19 February 2014 / Published: 7 March 2014
Cited by 7 | PDF Full-text (1503 KB) | HTML Full-text | XML Full-text
Abstract
The compound-structure permanent-magnet synchronous machine (CS-PMSM) is a power-split device which can enable the internal combustion engine (ICE) to operate at optimum efficiency during all driving conditions by controlling its torque and speed. However, the CS-PMSM has more serious temperature rise and heat
[...] Read more.
The compound-structure permanent-magnet synchronous machine (CS-PMSM) is a power-split device which can enable the internal combustion engine (ICE) to operate at optimum efficiency during all driving conditions by controlling its torque and speed. However, the CS-PMSM has more serious temperature rise and heat dissipation problems than conventional permanent-magnet (PM) machines, especially when the CS-PMSM is running at low speed and under full load conditions. As the thermal resistance of double-layer air gaps is quite big, the hot spot proves to be in the inner winding rotor. To ensure the safe operation of the CS-PMSM, the use of forced-air and water cooling in the inner winding rotor are investigated. The study shows that the water cooling can provide a better cooling effect, but require a complicated mechanical structure. Considering the complexity of the high efficiency cooling system, a real-time temperature monitoring method is proposed and a temperature measuring system which can accurately measure the real-time temperature of multiple key points in the machine is developed to promptly adjust the operating and cooling conditions based on the measured temperature results. Finally, the temperature rise experiment of the CS-PMSM prototype is done and the simulation results are partly validated by the experimental data. Full article
(This article belongs to the Special Issue Advances in Hybrid Vehicles)
Open AccessArticle Energy Efficiency in Greenhouse Evaporative Cooling Techniques: Cooling Boxes versus Cellulose Pads
Energies 2014, 7(3), 1427-1447; doi:10.3390/en7031427
Received: 17 December 2013 / Revised: 20 February 2014 / Accepted: 3 March 2014 / Published: 7 March 2014
Cited by 5 | PDF Full-text (1171 KB) | HTML Full-text | XML Full-text
Abstract
Evaporative cooling systems using a combination of evaporative pads and extractor fans require greenhouses to be hermetic. The greatest concentration of greenhouses in the world is located in southeast Spain, but these tend not to be hermetic structures and consequently can only rely
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Evaporative cooling systems using a combination of evaporative pads and extractor fans require greenhouses to be hermetic. The greatest concentration of greenhouses in the world is located in southeast Spain, but these tend not to be hermetic structures and consequently can only rely on fogging systems as evaporative cooling techniques. Evaporative cooling boxes provide an alternative to such systems. Using a low-speed wind tunnel, the present work has compared the performance of this system with four pads of differing geometry and thickness manufactured by two different companies. The results obtained show that the plastic packing in the cooling unit produces a pressure drop of 11.05 Pa at 2 m·s−1, which is between 51.27% and 94.87% lower than that produced by the cellulose pads. This pressure drop was not influenced by increases in the water flow. The evaporative cooling boxes presented greater saturation efficiency at the same flow, namely 82.63%, as opposed to an average figure of 65% for the cellulose pads; and also had a lower specific consumption of water, at around 3.05 L·h−1·m−2·°C−1. Consequently, we conclude that evaporative cooling boxes are a good option for cooling non-hermetic greenhouses such as those most frequently used in the Mediterranean basin. Full article
Open AccessArticle Performance Evaluation of a Solar Adsorption Refrigeration System with a Wing Type Compound Parabolic Concentrator
Energies 2014, 7(3), 1448-1466; doi:10.3390/en7031448
Received: 14 January 2014 / Revised: 20 February 2014 / Accepted: 27 February 2014 / Published: 11 March 2014
Cited by 5 | PDF Full-text (702 KB) | HTML Full-text | XML Full-text
Abstract
Simulation study of a solar adsorption refrigeration system using a wing type compound parabolic concentrator (CPC) is presented. The system consists of the wing type collector set at optimum angles, adsorption bed, a condenser and a refrigerator. The wing type collector captures the
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Simulation study of a solar adsorption refrigeration system using a wing type compound parabolic concentrator (CPC) is presented. The system consists of the wing type collector set at optimum angles, adsorption bed, a condenser and a refrigerator. The wing type collector captures the solar energy efficiently in the morning and afternoon and provides the effective temperature for a longer period of time compared to that achieved by a linear collector. The objectives of the study were to evaluate the system behavior, the effect of wing length, and to compare the performance of the systems with wing type and linear CPCs. A detailed dynamic simulation model was developed based on mass and energy balance equations. The simulation results show that the system performance with wing type CPC increases by up to 6% in the summer and up to 2% in the winter, compared to the performance with a linear CPC having same collector length. The ice production also increases up to 13% in the summer with the wing type CPC. This shows that the wing type CPC is helpful to increase the performance of the system compared to the linear CPC with the same collector length and without the need for tracking. Full article
Open AccessArticle A Range-Based Vehicle Life Cycle Assessment Incorporating Variability in the Environmental Assessment of Different Vehicle Technologies and Fuels
Energies 2014, 7(3), 1467-1482; doi:10.3390/en7031467
Received: 4 December 2013 / Revised: 25 February 2014 / Accepted: 3 March 2014 / Published: 11 March 2014
Cited by 18 | PDF Full-text (323 KB) | HTML Full-text | XML Full-text
Abstract
How to compare the environmental performance of different vehicle technologies? Vehicles with lower tailpipe emissions are perceived as cleaner. However, does it make sense to look only to tailpipe emissions? Limiting the comparison only to these emissions denies the fact that there are
[...] Read more.
How to compare the environmental performance of different vehicle technologies? Vehicles with lower tailpipe emissions are perceived as cleaner. However, does it make sense to look only to tailpipe emissions? Limiting the comparison only to these emissions denies the fact that there are emissions involved during the production of a fuel and this approach gives too much advantage to zero-tailpipe vehicles like battery electric vehicles (BEV) and fuel cell electric vehicle (FCEV). Would it be enough to combine fuel production and tailpipe emissions? Especially when comparing the environmental performance of alternative vehicle technologies, the emissions during production of the specific components and their appropriate end-of-life treatment processes should also be taken into account. Therefore, the complete life cycle of the vehicle should be included in order to avoid problem shifting from one life stage to another. In this article, a full life cycle assessment (LCA) of petrol, diesel, fuel cell electric (FCEV), compressed natural gas (CNG), liquefied petroleum gas (LPG), hybrid electric, battery electric (BEV), bio-diesel and bio-ethanol vehicles has been performed. The aim of the manuscript is to investigate the impact of the different vehicle technologies on the environment and to develop a range-based modeling system that enables a more robust interpretation of the LCA results for a group of vehicles. Results are shown for climate change, respiratory effects, acidification and mineral extraction damage of the different vehicle technologies. A broad range of results is obtained due to the variability within the car market. It is concluded that it is essential to take into account the influence of all the vehicle parameters on the LCA results. Full article
(This article belongs to the Special Issue Advances in Hybrid Vehicles)
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Open AccessArticle A Magnetless Axial-Flux Machine for Range-Extended Electric Vehicles
Energies 2014, 7(3), 1483-1499; doi:10.3390/en7031483
Received: 10 January 2014 / Revised: 11 February 2014 / Accepted: 27 February 2014 / Published: 11 March 2014
Cited by 13 | PDF Full-text (4317 KB) | HTML Full-text | XML Full-text
Abstract
A new magnetless axial-flux doubly-salient DC-field (AF-DSDC) machine is proposed and implemented into the application of a range-extended electric vehicle (RE-EV). By employing the radial active part for the torque production, the proposed machine can produce satisfactory torque density to fulfill the requirements
[...] Read more.
A new magnetless axial-flux doubly-salient DC-field (AF-DSDC) machine is proposed and implemented into the application of a range-extended electric vehicle (RE-EV). By employing the radial active part for the torque production, the proposed machine can produce satisfactory torque density to fulfill the requirements of the RE-EV system. With the support of the 3D finite element method (3D-FEM), the performances of the proposed machine are calculated and compared with the requirements of the typical passenger RE-EV applications. To offer a more comprehensive illustration, the common radial-flux (RF) machines are included for comparison. Full article
(This article belongs to the Special Issue Advances in Hybrid Vehicles)
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Open AccessArticle A Proposal for Typical Artificial Light Sources for the Characterization of Indoor Photovoltaic Applications
Energies 2014, 7(3), 1500-1516; doi:10.3390/en7031500
Received: 16 January 2014 / Revised: 26 February 2014 / Accepted: 6 March 2014 / Published: 12 March 2014
Cited by 8 | PDF Full-text (836 KB) | HTML Full-text | XML Full-text
Abstract
There are currently no international norms which define a method for characterizing photovoltaic solar cells for indoor applications. The current standard test conditions are not relevant indoors. By performing efficiency simulations based on the quantum efficiency of typical solar cells and the light
[...] Read more.
There are currently no international norms which define a method for characterizing photovoltaic solar cells for indoor applications. The current standard test conditions are not relevant indoors. By performing efficiency simulations based on the quantum efficiency of typical solar cells and the light spectra of typical artificial light sources, we are able to propose the first step for developing a standard by determining which light sources are relevant for indoor PV characterization and which are not or are redundant. Our simulations lead us to conclude that indoor light sources can be divided into three different categories. For the characterization of photovoltaic solar cells in indoor environments, we propose that solar cells be measured under one light source from each group. Full article
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Open AccessArticle Extended Distributed State Estimation: A Detection Method against Tolerable False Data Injection Attacks in Smart Grids
Energies 2014, 7(3), 1517-1538; doi:10.3390/en7031517
Received: 6 November 2013 / Revised: 7 February 2014 / Accepted: 27 February 2014 / Published: 12 March 2014
Cited by 18 | PDF Full-text (492 KB) | HTML Full-text | XML Full-text
Abstract
False data injection (FDI) is considered to be one of the most dangerous cyber-attacks in smart grids, as it may lead to energy theft from end users, false dispatch in the distribution process, and device breakdown during power generation. In this paper, a
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False data injection (FDI) is considered to be one of the most dangerous cyber-attacks in smart grids, as it may lead to energy theft from end users, false dispatch in the distribution process, and device breakdown during power generation. In this paper, a novel kind of FDI attack, named tolerable false data injection (TFDI), is constructed. Such attacks exploit the traditional detector’s tolerance of observation errors to bypass the traditional bad data detection. Then, a method based on extended distributed state estimation (EDSE) is proposed to detect TFDI in smart grids. The smart grid is decomposed into several subsystems, exploiting graph partition algorithms. Each subsystem is extended outward to include the adjacent buses and tie lines, and generate the extended subsystem. The Chi-squares test is applied to detect the false data in each extended subsystem. Through decomposition, the false data stands out distinctively from normal observation errors and the detection sensitivity is increased. Extensive TFDI attack cases are simulated in the Institute of Electrical and Electronics Engineers (IEEE) 14-, 39-, 118- and 300-bus systems. Simulation results show that the detection precision of the EDSE-based method is much higher than that of the traditional method, while the proposed method significantly reduces the associated computational costs. Full article
(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)
Open AccessArticle Electromagnetic Design of a New Electrically Controlled Magnetic Variable-Speed Gearing Machine
Energies 2014, 7(3), 1539-1554; doi:10.3390/en7031539
Received: 13 December 2013 / Revised: 18 February 2014 / Accepted: 27 February 2014 / Published: 13 March 2014
Cited by 5 | PDF Full-text (1105 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a new electrically controlled magnetic variable-speed gearing (EC-MVSG) machine, which is capable of providing controllable gear ratios for hybrid electric vehicle (HEV) applications. The key design feature involves the adoption of a magnetic gearing structure and acceptance of the memory
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This paper proposes a new electrically controlled magnetic variable-speed gearing (EC-MVSG) machine, which is capable of providing controllable gear ratios for hybrid electric vehicle (HEV) applications. The key design feature involves the adoption of a magnetic gearing structure and acceptance of the memory machine flux-mnemonic concept. Hence, the proposed machine can not only offer a gear-shifting mechanism for torque and speed transmission, but also provide variable gear ratios for torque and speed variation. The electromagnetic design is studied and discussed. The finite-element method is developed with the hysteresis model to verify the validity of the machine design. Full article
(This article belongs to the Special Issue Advances in Hybrid Vehicles)
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Open AccessArticle Differences in Public Perceptions of Geothermal Energy Technology in Australia
Energies 2014, 7(3), 1555-1575; doi:10.3390/en7031555
Received: 26 November 2013 / Revised: 13 February 2014 / Accepted: 27 February 2014 / Published: 14 March 2014
Cited by 6 | PDF Full-text (236 KB) | HTML Full-text | XML Full-text
Abstract
In Australia, geothermal energy technology is still considered an emerging technology for energy generation. Like other emerging energy technologies, how the public perceive the technology and under what conditions they are likely to accept or oppose the technology, remains relatively unknown. In response,
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In Australia, geothermal energy technology is still considered an emerging technology for energy generation. Like other emerging energy technologies, how the public perceive the technology and under what conditions they are likely to accept or oppose the technology, remains relatively unknown. In response, this exploratory research utilised online focus groups to identify: (1) the extent of agreement with geothermal technology before and after information, including media reports focusing on a range of the technology’s attributes; and (2) how the characteristics of individuals with different levels of agreement vary. After information, within the sample of 101 participants, fewer reported being unsure, the minority disagreed and the majority agreed. Overall, the preference was for projects to be located away from communities. Participants that disagreed or were unsure, were more likely to report lower subjective knowledge of the technology, lower perceived benefits and higher risks, and were less likely to believe people in their community would have the opportunity to participate in consultation. These characteristics suggest there are advances to be made by analyzing what contributes to different levels of acceptance. The findings also suggest that the location of projects will be an important consideration and that the conditions of acceptance are likely to vary amongst community members. Full article
Open AccessArticle Artificial Neural Network for Short-Term Load Forecasting in Distribution Systems
Energies 2014, 7(3), 1576-1598; doi:10.3390/en7031576
Received: 7 February 2014 / Revised: 7 March 2014 / Accepted: 10 March 2014 / Published: 17 March 2014
Cited by 6 | PDF Full-text (2249 KB) | HTML Full-text | XML Full-text
Abstract
The new paradigms and latest developments in the Electrical Grid are based on the introduction of distributed intelligence at several stages of its physical layer, giving birth to concepts such as Smart Grids, Virtual Power Plants, microgrids, Smart Buildings and
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The new paradigms and latest developments in the Electrical Grid are based on the introduction of distributed intelligence at several stages of its physical layer, giving birth to concepts such as Smart Grids, Virtual Power Plants, microgrids, Smart Buildings and Smart Environments. Distributed Generation (DG) is a philosophy in which energy is no longer produced exclusively in huge centralized plants, but also in smaller premises which take advantage of local conditions in order to minimize transmission losses and optimize production and consumption. This represents a new opportunity for renewable energy, because small elements such as solar panels and wind turbines are expected to be scattered along the grid, feeding local installations or selling energy to the grid depending on their local generation/consumption conditions. The introduction of these highly dynamic elements will lead to a substantial change in the curves of demanded energy. The aim of this paper is to apply Short-Term Load Forecasting (STLF) in microgrid environments with curves and similar behaviours, using two different data sets: the first one packing electricity consumption information during four years and six months in a microgrid along with calendar data, while the second one will be just four months of the previous parameters along with the solar radiation from the site. For the first set of data different STLF models will be discussed, studying the effect of each variable, in order to identify the best one. That model will be employed with the second set of data, in order to make a comparison with a new model that takes into account the solar radiation, since the photovoltaic installations of the microgrid will cause the power demand to fluctuate depending on the solar radiation. Full article
(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)
Open AccessArticle Coordinated Control of Distributed and Bulk Energy Storage for Alleviation of Post-Contingency Overloads
Energies 2014, 7(3), 1599-1620; doi:10.3390/en7031599
Received: 13 January 2014 / Revised: 9 March 2014 / Accepted: 11 March 2014 / Published: 17 March 2014
Cited by 3 | PDF Full-text (491 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a novel corrective control strategy that can effectively coordinate distributed and bulk energy storage to relieve post-contingency overloads. Immediately following a contingency, distributed batteries are implemented to provide fast corrective actions to reduce power flows below their short-term emergency ratings.
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This paper presents a novel corrective control strategy that can effectively coordinate distributed and bulk energy storage to relieve post-contingency overloads. Immediately following a contingency, distributed batteries are implemented to provide fast corrective actions to reduce power flows below their short-term emergency ratings. During the long-term period, Pumped Hydro Storage units work in pumping or generation mode to aid conventional generating units keep line flows below the normal ratings. This problem is formulated as a multi-stage Corrective Security-constrained OPF (CSCOPF). An algorithm based on Benders decomposition was proposed to find the optimal base case solution and seek feasible corrective actions to handle all contingencies. Case studies based on a modified RTS-96 system demonstrate the performance and effectiveness of the proposed control strategy. Full article
(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)
Open AccessArticle Methods to Increase the Robustness of Finite-Volume Flow Models in Thermodynamic Systems
Energies 2014, 7(3), 1621-1640; doi:10.3390/en7031621
Received: 27 September 2013 / Revised: 7 March 2014 / Accepted: 10 March 2014 / Published: 18 March 2014
Cited by 8 | PDF Full-text (409 KB) | HTML Full-text | XML Full-text
Abstract
This paper addresses the issues linked to simulation failures during integration in finite-volume flow models, especially those involving a two-phase state. This kind of model is particularly useful when modeling 1D heat exchangers or piping, e.g., in thermodynamic cycles involving a phase change.
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This paper addresses the issues linked to simulation failures during integration in finite-volume flow models, especially those involving a two-phase state. This kind of model is particularly useful when modeling 1D heat exchangers or piping, e.g., in thermodynamic cycles involving a phase change. Issues, such as chattering or stiff systems, can lead to low simulation speed, instabilities and simulation failures. In the particular case of two-phase flow models, they are usually linked to a discontinuity in the density derivative between the liquid and two-phase zones. In this work, several methods to tackle numerical problems are developed, described, implemented and compared. In addition, methods available in the literature are also implemented and compared to the proposed approaches. Results suggest that the robustness of the models can be significantly increased with these different methods, at the price of a small increase of the error in the mass and energy balances. Full article
Open AccessArticle Some Aspects of Ice-Hydropower Interaction in a Changing Climate
Energies 2014, 7(3), 1641-1655; doi:10.3390/en7031641
Received: 27 December 2013 / Revised: 27 February 2014 / Accepted: 28 February 2014 / Published: 18 March 2014
Cited by 4 | PDF Full-text (738 KB) | HTML Full-text | XML Full-text
Abstract
Ice formation and related processes in rivers and lakes/reservoirs influence the operation of hydropower plants in cold regions. It is a matter of interest to the scientific community and hydropower operators alike how existing ice effects and problems will manifest themselves in a
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Ice formation and related processes in rivers and lakes/reservoirs influence the operation of hydropower plants in cold regions. It is a matter of interest to the scientific community and hydropower operators alike how existing ice effects and problems will manifest themselves in a future changed climate. In this paper, we use different modeling results to investigate future freshwater ice conditions. The modeling approaches include using temperature derived winter indices, using one-dimensional (1D) hydrodynamic and ice cover model on three case study reservoirs, and using a 1D river hydrodynamic and ice cover model for a river reach. The analysis shows that changes in river and reservoir ice regimes due to climate change scenarios may have both positive and negative consequences for hydropower operation. Positive consequences emerge from reduction in ice season and reduced static ice loads. Negative consequences or challenges are attributed to unstable winters that may lead to increased frequency of freeze-thaw episodes with a shortened winter season. These aspects are discussed in more detail in the paper. Full article
Open AccessArticle Comparison between Underground Cable and Overhead Line for a Low-Voltage Direct Current Distribution Network Serving Communication Repeater
Energies 2014, 7(3), 1656-1672; doi:10.3390/en7031656
Received: 6 November 2013 / Revised: 3 March 2014 / Accepted: 4 March 2014 / Published: 20 March 2014
PDF Full-text (756 KB) | HTML Full-text | XML Full-text
Abstract
This paper compares the differences in economic feasibility and dynamic characteristics between underground (U/G) cable and overhead (O/H) line for low-voltage direct current (LVDC) distribution. Numerous low loaded long-distance distribution networks served by medium-voltage alternative current (MVAC) distribution lines exist in the Korean
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This paper compares the differences in economic feasibility and dynamic characteristics between underground (U/G) cable and overhead (O/H) line for low-voltage direct current (LVDC) distribution. Numerous low loaded long-distance distribution networks served by medium-voltage alternative current (MVAC) distribution lines exist in the Korean distribution network. This is an unavoidable choice to compensate voltage drop, therefore, excessive cost is expended for the amount of electrical power load. The Korean Electric Power Corporation (KEPCO) is consequently seeking a solution to replace the MVAC distribution line with a LVDC distribution line, reducing costs and providing better quality direct current (DC) electricity. A LVDC distribution network can be installed with U/G cables or O/H lines. In this paper, a realistic MVAC distribution network in a mountainous area was selected as the target model to replace with LVDC. A 30 year net present value (NPV) analysis of the economic feasibility was conducted to compare the cost of the two types of distribution line. A simulation study compared the results of the DC line fault with the power system computer aided design/electro-magnetic transient direct current (PSCAD/EMTDC). The economic feasibility evaluation and simulation study results will be used to select the applicable type of LVDC distribution network. Full article
(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)
Open AccessArticle Multi-Stage Control of Waste Heat Recovery from High Temperature Slags Based on Time Temperature Transformation Curves
Energies 2014, 7(3), 1673-1684; doi:10.3390/en7031673
Received: 20 January 2014 / Revised: 7 March 2014 / Accepted: 14 March 2014 / Published: 20 March 2014
Cited by 14 | PDF Full-text (980 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a significant method and a basic idea of waste heat recovery from high temperature slags based on Time Temperature Transformation (TTT) curves. Three samples with a fixed CaO/SiO2 ratio of 1.05 and different levels of Al2O3
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This paper presents a significant method and a basic idea of waste heat recovery from high temperature slags based on Time Temperature Transformation (TTT) curves. Three samples with a fixed CaO/SiO2 ratio of 1.05 and different levels of Al2O3 were designed and isothermal experiments were performed using a Single Hot Thermocouple Technique (SHTT). The TTT curves established through SHTT experiments described well the variation of slag properties during isothermal processes. In this study, we propose a multi-stage control method for waste heat recovery from high temperature slags, in which the whole temperature range from 1500 °C to 25 °C was divided into three regions, i.e., Liquid region, Crystallization region and Solid region, based on the TTT curves. Accordingly, we put forward an industrial prototype plant for the purpose of waste heat recovery and the potential of waste heat recovery was then calculated. The multi-stage control method provided not only a significant prototype, but also a basic idea to simultaneously extract high quality waste heat and obtain glassy phases on high temperature slags, which may fill the gap between slag properties and practical waste heat recovery processes. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
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Open AccessArticle Evaluation of Visitor Counting Technologies and Their Energy Saving Potential through Demand-Controlled Ventilation
Energies 2014, 7(3), 1685-1705; doi:10.3390/en7031685
Received: 8 February 2014 / Revised: 18 March 2014 / Accepted: 19 March 2014 / Published: 21 March 2014
Cited by 2 | PDF Full-text (964 KB) | HTML Full-text | XML Full-text
Abstract
Direction-sensitive visitor counting sensors can be used in demand-controlled ventilation (DCV). The counting performance of two light beam sensors and three camera sensors, all direction sensitive, was simultaneously evaluated at an indoor location. Direction insensitive sensors (two mat sensors and one light beam
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Direction-sensitive visitor counting sensors can be used in demand-controlled ventilation (DCV). The counting performance of two light beam sensors and three camera sensors, all direction sensitive, was simultaneously evaluated at an indoor location. Direction insensitive sensors (two mat sensors and one light beam sensor) were additionally tested as a reference. Bidirectional counting data of free people flow was collected for 36 days in one-hour resolution, including five hours of manual counting. Compared to the manual results, one of the light beam sensors had the most equally balanced directional overall counting errors (4.6% and 5.2%). The collected data of this sensor was used to model the air transportation energy consumption of visitor counting sensor-based DCV and constant air volume ventilation (CAV). The results suggest that potential savings in air transportation energy consumption could be gained with the modeled DCV as its total daily airflow during the test period was 54% of the total daily airflow of the modeled CAV on average. A virtually real-time control of ventilation could be realized with minute-level counting resolution. Site-specific calibration of the visitor counting sensors is advisable and they could be complemented with presence detectors to avoid unnecessary ventilation during unoccupied periods of the room. A combination of CO2 and visitor counting sensors could be exploited in DCV to always guarantee sufficient ventilation with a short response time. Full article
(This article belongs to the Special Issue Energy Efficient Building Design and Operation 2014)
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Open AccessArticle Design and Study on Sliding Mode Extremum Seeking Control of the Chaos Embedded Particle Swarm Optimization for Maximum Power Point Tracking in Wind Power Systems
Energies 2014, 7(3), 1706-1720; doi:10.3390/en7031706
Received: 26 January 2014 / Revised: 23 February 2014 / Accepted: 4 March 2014 / Published: 21 March 2014
Cited by 8 | PDF Full-text (507 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a sliding mode extremum seeking control (SMESC) of chaos embedded particle swarm optimization (CEPSO) Algorithm, applied to the design of maximum power point tracking in wind power systems. Its features are that the control parameters in SMESC are optimized by
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This paper proposes a sliding mode extremum seeking control (SMESC) of chaos embedded particle swarm optimization (CEPSO) Algorithm, applied to the design of maximum power point tracking in wind power systems. Its features are that the control parameters in SMESC are optimized by CEPSO, making it unnecessary to change the output power of different wind turbines, the designed in-repetition rate is reduced, and the system control efficiency is increased. The wind power system control is designed by simulation, in comparison with the traditional wind power control method, and the simulated dynamic response obtained by the SMESC algorithm proposed in this paper is better than the traditional hill-climbing search (HCS) and extremum seeking control (ESC) algorithms in the transient or steady states, validating the advantages and practicability of the method proposed in this paper. Full article
(This article belongs to the Special Issue Wind Turbines 2014)
Open AccessArticle Preparation of Polybenzimidazole-Based Membranes and Their Potential Applications in the Fuel Cell System
Energies 2014, 7(3), 1721-1732; doi:10.3390/en7031721
Received: 7 November 2013 / Revised: 24 February 2014 / Accepted: 5 March 2014 / Published: 24 March 2014
Cited by 4 | PDF Full-text (716 KB) | HTML Full-text | XML Full-text
Abstract
Various polybenzimidazole (PBI)-based ion-exchange films were prepared and thoroughly characterized by Fourier transform infrared (FT-IR) spectroscopy, proton conductivity, and water uptake for possible use as fuel cell membranes. Upon the increase in the flexibility of the PBI-based polymer films (e.g., poly(oxyphenylene benzimidazole) (OPBI)
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Various polybenzimidazole (PBI)-based ion-exchange films were prepared and thoroughly characterized by Fourier transform infrared (FT-IR) spectroscopy, proton conductivity, and water uptake for possible use as fuel cell membranes. Upon the increase in the flexibility of the PBI-based polymer films (e.g., poly(oxyphenylene benzimidazole) (OPBI) and sulfonated OPBI (s-OPBI)), the membranes exhibited slightly improved proton conductivity, but significantly increased dimensional changes. To reduce the dimensional changes (i.e., increase the stability), the cross-linking of the polymer films (e.g., cross-linked OPBI (c-OPBI) and sulfonated c-OPBI (sc-OPBI)) was accomplished using phosphoric acid. Interestingly, the sc-OPBI membrane possessed a greatly increased proton conductivity (0.082 S/cm), which is comparable to that of the commercially available Nafion membrane (0.09 S/cm), while still maintaining slightly better properties regarding the dimensional change and water uptake than those of the Nafion membrane. Full article
(This article belongs to the Special Issue Polymer Electrolyte Membrane Fuel Cells)
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Open AccessArticle Day-Ahead Energy Planning with 100% Electric Vehicle Penetration in the Nordic Region by 2050
Energies 2014, 7(3), 1733-1749; doi:10.3390/en7031733
Received: 8 January 2014 / Revised: 8 March 2014 / Accepted: 19 March 2014 / Published: 24 March 2014
Cited by 1 | PDF Full-text (456 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the day-ahead energy planning of passenger cars with 100% electric vehicle (EV) penetration in the Nordic region by 2050. EVs will play an important role in the future energy systems which can both reduce the greenhouse gas (GHG) emissions from
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This paper presents the day-ahead energy planning of passenger cars with 100% electric vehicle (EV) penetration in the Nordic region by 2050. EVs will play an important role in the future energy systems which can both reduce the greenhouse gas (GHG) emissions from the transport sector and provide the demand side flexibility required by smart grids. On the other hand, the EVs will increase the electricity consumption. In order to quantify the electricity consumption increase due to the 100% EV penetration in the Nordic region to facilitate the power system planning studies, the day-ahead energy planning of EVs has been investigated with different EV charging scenarios. Five EV charging scenarios have been considered in the energy planning analysis which are: uncontrolled charging all day, uncontrolled charging at home, timed charging, spot price based charging all day and spot price based charging at home. The demand profiles of the five charging analysis show that timed charging is the least favorable charging option and the spot priced based EV charging might induce high peak demands. The EV charging demand will have a considerable share of the energy consumption in the future Nordic power system. Full article
(This article belongs to the Special Issue Advances in Hybrid Vehicles)
Open AccessArticle H Fault Tolerant Control of WECS Based on the PWA Model
Energies 2014, 7(3), 1750-1769; doi:10.3390/en7031750
Received: 26 January 2014 / Revised: 13 March 2014 / Accepted: 19 March 2014 / Published: 24 March 2014
Cited by 4 | PDF Full-text (461 KB) | HTML Full-text | XML Full-text
Abstract
The main contribution of this paper is the development of H∞ fault tolerant control for a wind energy conversion system (WECS) based on the stochastic piecewise affine (PWA) model. In this paper the normal and fault stochastic PWA models for WECS including
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The main contribution of this paper is the development of H∞ fault tolerant control for a wind energy conversion system (WECS) based on the stochastic piecewise affine (PWA) model. In this paper the normal and fault stochastic PWA models for WECS including multiple working points at different wind speeds are established. A reliable piecewise linear quadratic regulator state feedback is designed for the fault tolerant actuator and sensor. A sufficient condition for the existence of the passive fault tolerant controller is derived based on some linear matrix inequalities (LMIs). It is shown that the H∞ fault tolerant controller of WECS can control the wind turbine exposed to multiple simultaneous sensor faults or actuator faults; that is, the reliability of wind turbines can be improved. Full article
(This article belongs to the Special Issue Wind Turbines 2014)
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Open AccessArticle Localized Climate and Surface Energy Flux Alterations across an Urban Gradient in the Central U.S.
Energies 2014, 7(3), 1770-1791; doi:10.3390/en7031770
Received: 3 January 2014 / Revised: 11 March 2014 / Accepted: 20 March 2014 / Published: 24 March 2014
Cited by 5 | PDF Full-text (2533 KB) | HTML Full-text | XML Full-text
Abstract
Long-term urban and rural climate data spanning January 1995 through October 2013 were analyzed to investigate the Urban Heat Island (UHI) effect in a representative mid-sized city of the central US. Locally distributed climate data were also collected at nested low density urban,
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Long-term urban and rural climate data spanning January 1995 through October 2013 were analyzed to investigate the Urban Heat Island (UHI) effect in a representative mid-sized city of the central US. Locally distributed climate data were also collected at nested low density urban, recently developed, and high density urban monitoring sites from June through September 2013 to improve mechanistic understanding of spatial variability of the UHI effect based upon urban land use intensity. Long-term analyses (1995–2013) indicate significant differences (p < 0.001) between average air temperature (13.47 and 12.89 °C, at the urban and rural site respectively), relative humidity (69.11% and 72.51%, urban and rural respectively), and average wind speed (2.05 and 3.15 m/s urban and rural respectively). Significant differences (p < 0.001) between urban monitoring sites indicate an urban microclimate gradient for all climate variables except precipitation. Results of analysis of net radiation and soil heat flux data suggest distinct localized alterations in urban energy budgets due to land use intensity. Study results hold important implications for urban planners and land managers seeking to improve and implement better urban management practices. Results also reinforce the need for distributed urban energy balance investigations. Full article
(This article belongs to the Special Issue Large Scale LUCC, Surface Energy Fluxes and Energy Use)
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Open AccessArticle DVP: A Novel High-Availability Seamless Redundancy (HSR) Protocol Traffic-Reduction Algorithm for a Substation Automation System Network
Energies 2014, 7(3), 1792-1810; doi:10.3390/en7031792
Received: 20 January 2014 / Revised: 17 March 2014 / Accepted: 19 March 2014 / Published: 24 March 2014
Cited by 11 | PDF Full-text (323 KB) | HTML Full-text | XML Full-text
Abstract
The high-availability seamless redundancy (HSR) protocol, a potential candidate for substation automation system (SAS) networks, provides duplicated frame copies of each sent frame, with zero fault-recovery time. This means that even in the case of node or link failure, the destination node will
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The high-availability seamless redundancy (HSR) protocol, a potential candidate for substation automation system (SAS) networks, provides duplicated frame copies of each sent frame, with zero fault-recovery time. This means that even in the case of node or link failure, the destination node will receive at least one copy of the sent frame. Consequently, there is no network operation down time. However, the forwarding process of the QuadBox node in HSR is not smart and relies solely on duplication and random forwarding of all received frames. Thus, if a unicast frame is sent in any closed-loop network, the frame copies will be spread through most of all the links in both directions until they reach the destination node, which inevitably results in significant, unnecessary network traffic. In this paper, we present an algorithm called the dual virtual paths (DVP) algorithm to solve such an HSR excessive traffic issue. The idea behind our DVP algorithm is to establish automatic DVP between each HSR node and all the other nodes in the network, except for the QuadBox node. These virtual paths will be used for DVP unicast traffic transmission, rather than using the standard HSR transmission process. Therefore, the DVP algorithm results in less traffic, because there is no duplication or random forwarding, contrary to standard HSR. For the sample networks selected in this paper, the DVP algorithm shows more than a 70% reduction in network traffic and about an 80% reduction in the discarded traffic compared to the standard HSR protocol. Full article
(This article belongs to the Special Issue Smart Grids: The Electrical Power Network and Communication System)
Open AccessArticle Inter-Seasonal Variations of Surface Temperature in the Urbanized Environment of Delhi Using Landsat Thermal Data
Energies 2014, 7(3), 1811-1828; doi:10.3390/en7031811
Received: 29 January 2014 / Revised: 13 March 2014 / Accepted: 13 March 2014 / Published: 24 March 2014
Cited by 9 | PDF Full-text (1228 KB) | HTML Full-text | XML Full-text
Abstract
Complex land use/cover patterns in urban areas significantly influence their prevailing surface temperature conditions. As a result of differential cooling and heating of various land use/cover, large temperature ranges are associated with bare land, built-up land, etc. and low ranges are found in
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Complex land use/cover patterns in urban areas significantly influence their prevailing surface temperature conditions. As a result of differential cooling and heating of various land use/cover, large temperature ranges are associated with bare land, built-up land, etc. and low ranges are found in vegetation cover and water bodies. Extremely high and low temperature conditions in built-up land have direct and negative impacts on health conditions, and therefore are imperative to study. Thus, an attempt has been made in this research to analyze seasonal variations in surface temperature in city of Delhi. Landsat Thematic Mapper (TM) 5 satellite images for the four seasons, viz., 16 January (winter), 5 March (spring), 8 May (summer) and 29 September (autumn) 2011 have been used to interpret the distribution and changes in surface temperature. A total of 80 samples from all land use/cover categories were taken to generalize the patterns along with north-south and west-east profiles. The extracted surface temperature patterns reflect the spatial and temporal dynamics of temperature over different land use/cover. The north-south and west-east gradient of temperature demonstrates that the core of Delhi has a much lower temperature and weak urban heat island (UHI) phenomenon. Full article
(This article belongs to the Special Issue Large Scale LUCC, Surface Energy Fluxes and Energy Use)
Open AccessArticle Biofuels from the Fresh Water Microalgae Chlorella vulgaris (FWM-CV) for Diesel Engines
Energies 2014, 7(3), 1829-1851; doi:10.3390/en7031829
Received: 19 February 2014 / Revised: 11 March 2014 / Accepted: 18 March 2014 / Published: 24 March 2014
Cited by 17 | PDF Full-text (1243 KB) | HTML Full-text | XML Full-text
Abstract
This work aims to investigate biofuels for diesel engines produced on a lab-scale from the fresh water microalgae Chlorella vulgaris (FWM-CV). The impact of growing conditions on the properties of biodiesel produced from FWM-CV was evaluated. The properties of FWM-CV biodiesel were found
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This work aims to investigate biofuels for diesel engines produced on a lab-scale from the fresh water microalgae Chlorella vulgaris (FWM-CV). The impact of growing conditions on the properties of biodiesel produced from FWM-CV was evaluated. The properties of FWM-CV biodiesel were found to be within the ASTM standards for biodiesel. Due to the limited amount of biodiesel produced on the lab-scale, the biomass of dry cells of FWM-CV was used to yield emulsified water fuel. The preparation of emulsion fuel with and without FWM-CV cells was conducted using ultrasound to overcome the problems of large size microalgae colonies and to form homogenized emulsions. The emulsified water fuels, prepared using ultrasound, were found to be stable and the size of FWM-CV colonies were effectively reduced to pass through the engine nozzle safely. Engine tests at 3670 rpm were conducted using three fuels: cottonseed biodiesel CS-B100, emulsified cottonseed biodiesel water fuel, water and emulsifier (CS-E20) and emulsified water containing FWM-CV cells CS-ME20. The results showed that the brake specific fuel consumption (BSFC) was increased by about 41% when the engine was fueled with emulsified water fuels compared to CS-B100. The engine power, exhaust gas temperature, NOx and CO2 were significantly lower than that produced by CS-B100. The CS-ME20 produced higher power than CS-E20 due to the heating value improvement as a result of adding FWM-CV cells to the fuel. Full article
(This article belongs to the Special Issue Renewable Energy for Agriculture)

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Open AccessReview A Review of Thermal Co-Conversion of Coal and Biomass/Waste
Energies 2014, 7(3), 1098-1148; doi:10.3390/en7031098
Received: 12 November 2013 / Revised: 21 January 2014 / Accepted: 5 February 2014 / Published: 25 February 2014
Cited by 31 | PDF Full-text (642 KB) | HTML Full-text | XML Full-text
Abstract
Biomass is relatively cleaner than coal and is the only renewable carbon resource that can be directly converted into fuel. Biomass can significantly contribute to the world’s energy needs if harnessed sustainably. However, there are also problems associated with the thermal conversion of
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Biomass is relatively cleaner than coal and is the only renewable carbon resource that can be directly converted into fuel. Biomass can significantly contribute to the world’s energy needs if harnessed sustainably. However, there are also problems associated with the thermal conversion of biomass. This paper investigates and discusses issues associated with the thermal conversion of coal and biomass as a blend. Most notable topics reviewed are slagging and fouling caused by the relatively reactive alkali and alkaline earth compounds (K2O, Na2O and CaO) found in biomass ash. The alkali and alkaline earth metals (AAEM) present and dispersed in biomass fuels induce catalytic activity during co-conversion with coal. The catalytic activity is most noticeable when blended with high rank coals. The synergy during co-conversion is still controversial although it has been theorized that biomass acts like a hydrogen donor in liquefaction. Published literature also shows that coal and biomass exhibit different mechanisms, depending on the operating conditions, for the formation of nitrogen (N) and sulfur species. Utilization aspects of fly ash from blending coal and biomass are discussed. Recommendations are made on pretreatment options to increase the energy density of biomass fuels through pelletization, torrefaction and flash pyrolysis to reduce transportation costs. Full article
(This article belongs to the Special Issue Biomass and Biofuels 2013)

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