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Energies, Volume 3, Issue 6 (June 2010), Pages 1049-1334

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Research

Jump to: Review

Open AccessArticle Transient Response Improvement of Microgrids Exploiting the Inertia of a Doubly-Fed Induction Generator (DFIG)
Energies 2010, 3(6), 1049-1066; doi:10.3390/en30601049
Received: 12 April 2010 / Revised: 26 April 2010 / Accepted: 30 April 2010 / Published: 1 June 2010
Cited by 9 | PDF Full-text (871 KB) | HTML Full-text | XML Full-text
Abstract
Storage devices are introduced in microgrids in order to secure their power quality, power regularity and offer ancillary services in a transient period. In the transition period of a low voltage microgrid, from the connected mode of operation to the islanded mode [...] Read more.
Storage devices are introduced in microgrids in order to secure their power quality, power regularity and offer ancillary services in a transient period. In the transition period of a low voltage microgrid, from the connected mode of operation to the islanded mode of operation, the power unbalance can be partly covered by the inertia energy of the existing power sources. This paper proposes fuzzy local controllers exploiting the inertia of a Wind Turbine (WT) with a Doubly Fed Induction Generator (DFIG), if such a machine exists in the microgrid, in order to decrease the necessary storage devices and the drawbacks that arise. The proposed controllers are based in fuzzy logic due to the non linear and stochastic behavior of the system. Two cases are studied and compared during the transient period where the microgrid architecture and the DFIG controller differ. In the first case, the understudy microgrid includes a hybrid fuel cell system (FCS)-battery system and a WT with a DFIGURE. The DFIG local controller in this case is also based in fuzzy logic and follows the classical optimum power absorption scenario for the WT. The transition of the microgrid from the connected mode of operation to the islanded mode is evaluated and, especially, the battery contribution is estimated. In the second case, the battery is eliminated. The fuzzy controller of the DFIG during the transition provides primary frequency control and local bus voltage support exploiting the WT inertia. The response of the system is estimated in both cases using MATLAB/Simulink software package. Full article
(This article belongs to the Special Issue Wind Energy)
Open AccessArticle Expanding Horizons with Chameleon: Team Missouri’s Innovative Home Automation System
Energies 2010, 3(6), 1142-1153; doi:10.3390/en3061142
Received: 7 April 2010 / Revised: 20 May 2010 / Accepted: 1 June 2010 / Published: 4 June 2010
PDF Full-text (1194 KB) | HTML Full-text | XML Full-text
Abstract
Team Missouri’s 2009 Solar Decathlon entry featured a revolutionary home automation system, Chameleon, promoting both convenience and energy savings. This was accomplished using the typical controls of a convenience based automation system, while maintaining user set points, such as a home’s ambient [...] Read more.
Team Missouri’s 2009 Solar Decathlon entry featured a revolutionary home automation system, Chameleon, promoting both convenience and energy savings. This was accomplished using the typical controls of a convenience based automation system, while maintaining user set points, such as a home’s ambient temperature, in the most energy efficient manner. Environmental features of the system include controls for home heating, ventilation and air conditioning, lighting, windows, shades, appliances, indoor air quality, as well as indoor and outdoor irrigation. Further analysis and refinement to the prototype system displayed at the competition is also presented in this paper. Full article
(This article belongs to the Special Issue 2009 Solar Decathlon)
Open AccessArticle Rapid Gas Hydrate Formation Processes: Will They Work?
Energies 2010, 3(6), 1154-1175; doi:10.3390/en3061154
Received: 8 April 2010 / Revised: 20 May 2010 / Accepted: 2 June 2010 / Published: 7 June 2010
Cited by 13 | PDF Full-text (1654 KB) | HTML Full-text | XML Full-text
Abstract
Researchers at DOE’s National Energy Technology Laboratory (NETL) have been investigating the formation of synthetic gas hydrates, with an emphasis on rapid and continuous hydrate formation techniques. The investigations focused on unconventional methods to reduce dissolution, induction, nucleation and crystallization times associated [...] Read more.
Researchers at DOE’s National Energy Technology Laboratory (NETL) have been investigating the formation of synthetic gas hydrates, with an emphasis on rapid and continuous hydrate formation techniques. The investigations focused on unconventional methods to reduce dissolution, induction, nucleation and crystallization times associated with natural and synthetic hydrates studies conducted in the laboratory. Numerous experiments were conducted with various high-pressure cells equipped with instrumentation to study rapid and continuous hydrate formation. The cells ranged in size from 100 mL for screening studies to proof-of-concept studies with NETL’s 15-Liter Hydrate Cell. Results from this work demonstrate that the rapid and continuous formation of methane hydrate is possible at predetermined temperatures and pressures within the stability zone of a Methane Hydrate Stability Curve (see Figure 1). Full article
(This article belongs to the Special Issue Natural Gas Hydrate)
Open AccessArticle Residential Energy Performance Metrics
Energies 2010, 3(6), 1194-1211; doi:10.3390/en3061194
Received: 28 April 2010 / Revised: 24 May 2010 / Accepted: 3 June 2010 / Published: 9 June 2010
Cited by 2 | PDF Full-text (1145 KB) | HTML Full-text | XML Full-text
Abstract
Techniques for residential energy monitoring are an emerging field that is currently drawing significant attention. This paper is a description of the current efforts to monitor and compare the performance of three solar powered homes built at Missouri University of Science and [...] Read more.
Techniques for residential energy monitoring are an emerging field that is currently drawing significant attention. This paper is a description of the current efforts to monitor and compare the performance of three solar powered homes built at Missouri University of Science and Technology. The homes are outfitted with an array of sensors and a data logger system to measure and record electricity production, system energy use, internal home temperature and humidity, hot water production, and exterior ambient conditions the houses are experiencing. Data is being collected to measure the performance of the houses, compare to energy modeling programs, design and develop cost effective sensor systems for energy monitoring, and produce a cost effective home control system. Full article
(This article belongs to the Special Issue 2009 Solar Decathlon)
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Open AccessArticle Simulation Prototyping of an Experimental Solar House
Energies 2010, 3(6), 1251-1262; doi:10.3390/en3061251
Received: 19 May 2010 / Revised: 2 June 2010 / Accepted: 14 June 2010 / Published: 17 June 2010
PDF Full-text (349 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a comparative analysis between an energy simulation model and an actual solar home. The case study used was the Team Missouri’s 2009 Solar Decathlon entry. The home was evaluated using the predicted data developed with the use of Energy-10 [...] Read more.
This paper presents a comparative analysis between an energy simulation model and an actual solar home. The case study used was the Team Missouri’s 2009 Solar Decathlon entry. The home was evaluated using the predicted data developed with the use of Energy-10 Version 1.8. The software simulates the energy use performance of building strategies ranging from building envelope and system efficiency options. The performance data used was collected during the 2009 Solar Decathlon competition. Results comparing energy efficient strategies, consumption and generation are explored with future implications discussed. Full article
(This article belongs to the Special Issue 2009 Solar Decathlon)
Open AccessArticle An Examination of AC/HVDC Power Circuits for Interconnecting Bulk Wind Generation with the Electric Grid
Energies 2010, 3(6), 1263-1289; doi:10.3390/en3061263
Received: 15 April 2010 / Accepted: 20 May 2010 / Published: 18 June 2010
Cited by 9 | PDF Full-text (279 KB) | HTML Full-text | XML Full-text
Abstract
The application of high voltage dc (HVDC) transmission for integrating large scale and/or off-shore wind generation systems with the electric grid is attractive in comparison to extra high voltage (EHV) ac transmission due to a variety of reasons. While the technology of [...] Read more.
The application of high voltage dc (HVDC) transmission for integrating large scale and/or off-shore wind generation systems with the electric grid is attractive in comparison to extra high voltage (EHV) ac transmission due to a variety of reasons. While the technology of classical current sourced converters (CSC) using thyristors is well established for realization of large HVDC systems, the technology of voltage sourced converters (VSC) is emerging to be an alternative approach, particularly suitable for multi-terminal interconnections. More recently, a more modular scheme that may be termed ‘bridge of bridge’ converters (BoBC) has been introduced to realize HVDC systems. While all these three approaches are functionally capable of realizing HVDC systems, the converter power circuit design trade-offs between these alternatives are not readily apparent. This paper presents an examination of these topologies from the point of view of power semiconductor requirements, reactive component requirements, operating losses, fault tolerance, multi-terminal operation, modularity, complexity, etc. Detailed analytical models will be used along with a benchmark application to develop a comparative evaluation of the alternatives that maybe used by wind energy/bulk transmission developers for performing engineering trade-off studies. Full article
(This article belongs to the Special Issue Wind Energy)
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Review

Jump to: Research

Open AccessReview Fifty Years of Magnetic Fusion Research (1958–2008): Brief Historical Overview and Discussion of Future Trends
Energies 2010, 3(6), 1067-1086; doi:10.3390/en30601067
Received: 3 March 2010 / Revised: 29 April 2010 / Accepted: 10 May 2010 / Published: 1 June 2010
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Abstract
Fifty years ago, the secrecy surrounding magnetically controlled thermonuclear fusion had been lifted allowing researchers to freely share technical results and discuss the challenges of harnessing fusion power. There were only four magnetic confinement fusion concepts pursued internationally: tokamak, stellarator, pinch, and mirror. Since the early 1970s, numerous fusion designs have been developed for the four original and three new approaches: spherical torus, field-reversed configuration, and spheromak. At present, the tokamak is regarded worldwide as the most viable candidate to demonstrate fusion energy generation. Numerous power plant studies (>50), extensive R&D programs, more than 100 operating experiments, and an impressive international collaboration led to the current wealth of fusion information and understanding. As a result, fusion promises to be a major part of the energy mix in the 21st century. The fusion roadmaps developed to date take different approaches, depending on the anticipated power plant concept and the degree of extrapolation beyond ITER. Several Demos with differing approaches will be built in the US, EU, Japan, China, Russia, Korea, India, and other countries to cover the wide range of near-term and advanced fusion systems. Full article
(This article belongs to the Special Issue Nuclear Fusion)
Open AccessReview State of the Art and Trends in Wind Resource Assessment
Energies 2010, 3(6), 1087-1141; doi:10.3390/en3061087
Received: 1 April 2010 / Revised: 4 May 2010 / Accepted: 21 May 2010 / Published: 3 June 2010
Cited by 15 | PDF Full-text (1064 KB) | HTML Full-text | XML Full-text
Abstract
Given the significant rise of the utilization of wind energy the accurate assessment of the wind potential is becoming increasingly important. Direct applications of wind assessment techniques include the creation of wind maps on a local scale (typically 5 20 km) and [...] Read more.
Given the significant rise of the utilization of wind energy the accurate assessment of the wind potential is becoming increasingly important. Direct applications of wind assessment techniques include the creation of wind maps on a local scale (typically 5 20 km) and the micrositing of wind turbines, the estimation of vertical wind speed variations, prospecting on a regional scale (>100 km), estimation of the long-term wind resource at a given site, and forecasting. The measurement of wind speed and direction still widely relies on cup anemometers, though sonic anemometers are becoming increasingly popular. Moreover, remote sensing by Doppler techniques using the backscattering of either sonic beams (SODAR) or light (LIDAR) allowing for vertical profiling well beyond hub height are quickly moving into the mainstream. Local wind maps are based on the predicted modification of the regional wind flow pattern by the local atmospheric boundary layer which in turn depends on both topographic and roughness features and the measured wind rose obtained from one or several measurement towers within the boundaries of the planned development site. Initial models were based on linearized versions of the Navier-Stokes equations, whereas more recently full CFD models have been applied to wind farm micrositing. Linear models tend to perform well for terrain slopes lower than about 25% and have the advantage of short execution times. Long-term performance is frequently estimated from correlations with nearby reference stations with concurrent information and continuous time series over a period of at least 10 years. Simple methods consider only point-to-point linear correlations; more advanced methods like multiple regression techniques and methods based on the theory of distributions will be discussed. Both for early prospecting in regions where only scarce or unreliable reference information is available, wind flow modeling on a larger scale (mesoscale) is becoming increasingly popular. Full article
(This article belongs to the Special Issue Wind Energy)
Open AccessReview New Laser Fusion and Its Gain by Intense Laser
Energies 2010, 3(6), 1176-1193; doi:10.3390/en3061176
Received: 5 April 2010 / Accepted: 28 April 2010 / Published: 8 June 2010
Cited by 2 | PDF Full-text (601 KB) | HTML Full-text | XML Full-text
Abstract
The feasibility of a new approach of laser fusion in plasma without implosion has been proposed and is discussed using an intense laser. The cross section of the nuclear reaction is increased by enhancing the penetrability of nuclei through the Coulomb barrier. [...] Read more.
The feasibility of a new approach of laser fusion in plasma without implosion has been proposed and is discussed using an intense laser. The cross section of the nuclear reaction is increased by enhancing the penetrability of nuclei through the Coulomb barrier. In this approach, an intense laser field of more than 100 PW was required to distort the Coulomb barrier to obtain enough penetrability. An energy gain even with Deuterium-Deuterium (D-D) reaction can be obtained using this scheme in Deuterium plasma. A reactor with neutron and direct conversion of charged particle beam individually is proposed. Charged particles from D-D reaction are guided to the end of the reactor and are directly converted by a MHD scheme into electric energy. The energy recovery rate is high and requires a small amount of laser energy, which may make the energy cost cheaper than that of a fission reactor. Full article
(This article belongs to the Special Issue Nuclear Fusion)
Open AccessReview Designs and Architectures for the Next Generation of Organic Solar Cells
Energies 2010, 3(6), 1212-1250; doi:10.3390/en3061212
Received: 5 May 2010 / Accepted: 9 June 2010 / Published: 14 June 2010
Cited by 43 | PDF Full-text (509 KB) | HTML Full-text | XML Full-text
Abstract
Organic solar cells show great promise as an economically and environmentally friendly technology to utilize solar energy because of their simple fabrication processes and minimal material usage. However, new innovations and breakthroughs are needed for organic solar cell technology to become competitive [...] Read more.
Organic solar cells show great promise as an economically and environmentally friendly technology to utilize solar energy because of their simple fabrication processes and minimal material usage. However, new innovations and breakthroughs are needed for organic solar cell technology to become competitive in the future. This article reviews research efforts and accomplishments focusing on three issues: power conversion efficiency, device stability and processability for mass production, followed by an outlook for optimizing OSC performance through device engineering and new architecture designs to realize next generation organic solar cells. Full article
(This article belongs to the Special Issue Solar Cells)
Open AccessReview Illustration of Modern Wind Turbine Ancillary Services
Energies 2010, 3(6), 1290-1302; doi:10.3390/en3061290
Received: 6 May 2010 / Accepted: 12 June 2010 / Published: 21 June 2010
Cited by 16 | PDF Full-text (330 KB) | HTML Full-text | XML Full-text
Abstract
Increasing levels of wind power penetration in modern power systems has set intensively high standards with respect to wind turbine technology during the last years. Security issues have become rather critical and operation of wind farms as conventional power plants is becoming [...] Read more.
Increasing levels of wind power penetration in modern power systems has set intensively high standards with respect to wind turbine technology during the last years. Security issues have become rather critical and operation of wind farms as conventional power plants is becoming a necessity as wind turbines replace conventional units on the production side. This article includes a review of the basic control issues regarding the capability of the Doubly Fed Induction Generator (DFIG) wind turbine configuration to fulfill the basic technical requirements set by the system operators and contribute to power system security. An overview of ancillary services provided by wind turbine technology nowadays is provided, i.e., fault ride-through capability, reactive power supply and frequency-active power control. Full article
(This article belongs to the Special Issue Wind Energy)
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Open AccessReview Review of DC System Technologies for Large Scale Integration of Wind Energy Systems with Electricity Grids
Energies 2010, 3(6), 1303-1319; doi:10.3390/en3061303
Received: 13 May 2010 / Accepted: 12 June 2010 / Published: 22 June 2010
Cited by 12 | PDF Full-text (417 KB) | HTML Full-text | XML Full-text
Abstract
The ever increasing development and availability of power electronic systems is the underpinning technology that enables large scale integration of wind generation plants with the electricity grid. As the size and power capacity of the wind turbine continues to increase, so is [...] Read more.
The ever increasing development and availability of power electronic systems is the underpinning technology that enables large scale integration of wind generation plants with the electricity grid. As the size and power capacity of the wind turbine continues to increase, so is the need to place these significantly large structures at off-shore locations. DC grids and associated power transmission technologies provide opportunities for cost reduction and electricity grid impact minimization as the bulk power is concentrated at single point of entry. As a result, planning, optimization and impact can be studied and carefully controlled minimizing the risk of the investment as well as power system stability issues. This paper discusses the key technologies associated with DC grids for offshore wind farm applications. Full article
(This article belongs to the Special Issue Wind Energy)
Open AccessReview A Review on Concepts, Applications, and Models of Aquifer Thermal Energy Storage Systems
Energies 2010, 3(6), 1320-1334; doi:10.3390/en3061320
Received: 6 May 2010 / Accepted: 13 June 2010 / Published: 22 June 2010
Cited by 20 | PDF Full-text (245 KB) | HTML Full-text | XML Full-text
Abstract
Being a heat source or sink, aquifers have been used to store large quantities of thermal energy to match cooling and heating supply and demand on both a short-term and long-term basis. The current technical, economic, and environmental status of aquifer thermal [...] Read more.
Being a heat source or sink, aquifers have been used to store large quantities of thermal energy to match cooling and heating supply and demand on both a short-term and long-term basis. The current technical, economic, and environmental status of aquifer thermal energy storage (ATES) is promising. General information on the basic operation principles, design, and construction of ATES systems is discussed in this paper. Numerous projects in operation around the world are summarized to illustrate the present status of ATES. Hydrogeological-thermal simulation has become an integral part of predicting ATES system performance. Numerical models which are available to simulate an ATES system by modeling mass and heat transport in the aquifer have been summarized. This paper also presents an example of numerical simulation and thermohydraulic evaluation of a two-well, ATES system operating under a continuous flow regime. Full article
(This article belongs to the Special Issue Geothermal Power)
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