Showing papers on "Turbine published in 2010"
TL;DR: In this paper, a suite of large eddy simulations (LES), in which wind turbines are modeled using the classical "drag disk" concept, is performed for various wind-turbine arrangements, turbine loading factors, and surface roughness values.
Abstract: It is well known that when wind turbines are deployed in large arrays, their efficiency decreases due to complex interactions among themselves and with the atmospheric boundary layer (ABL). For wind farms whose length exceeds the height of the ABL by over an order of magnitude, a “fully developed” flow regime can be established. In this asymptotic regime, changes in the streamwise direction can be neglected and the relevant exchanges occur in the vertical direction. Such a fully developed wind-turbine array boundary layer (WTABL) has not been studied systematically before. A suite of large eddy simulations (LES), in which wind turbines are modeled using the classical “drag disk” concept, is performed for various wind-turbine arrangements, turbine loading factors, and surface roughness values. The results are used to quantify the vertical transport of momentum and kinetic energy across the boundary layer. It is shown that the vertical fluxes of kinetic energy are of the same order of magnitude as the power...
807 citations
TL;DR: In this article, a combined experimental and computational study into the aerodynamics and performance of a small scale vertical axis wind turbine (VAWT) was presented, where wind tunnel tests were carried out to ascertain overall performance of the turbine and two-and three-dimensional unsteady computational fluid dynamics (CFD) models were generated to help understand the aerodynamic of this performance.
631 citations
TL;DR: A review of the state of the art and present status of active aeroelastic rotor control research for wind turbines is presented in this paper, where the authors discuss the potential of load reduction using smart rotor control concepts.
491 citations
TL;DR: In this paper, the authors present a control strategy for the generator-side converter with maximum power extraction, where the potential excess of power is dissipated in the dump-load resistor with the chopper control, and the dc-link voltage is maintained.
Abstract: This paper presents a novel control strategy for the operation of a direct-drive permanent-magnet synchronous-generator-based stand-alone variable-speed wind turbine. The control strategy for the generator-side converter with maximum power extraction is presented. The stand-alone control is featured with output voltage and frequency controller that is capable of handling variable load. The potential excess of power is dissipated in the dump-load resistor with the chopper control, and the dc-link voltage is maintained. Dynamic representation of dc bus and small-signal analysis are presented. Simulation results show that the controllers can extract maximum power and regulate the voltage and frequency under varying wind and load conditions. The controller shows very good dynamic and steady-state performance.
460 citations
TL;DR: In this article, a model for wind turbine placement based on the wind distribution is presented to maximize the wind energy capture, which considers wake loss, which can be calculated based on wind turbine locations, and wind direction.
449 citations
TL;DR: The WindFloat as discussed by the authors is a three-legged floating foundation for multimegawatt offshore wind turbines, which is designed to accommodate a wind turbine, 5 MW or larger, on one of the columns of the hull with minimal modifications to the nacelle and rotor.
Abstract: This manuscript summarizes the feasibility study conducted for the WindFloat technology. The WindFloat is a three-legged floating foundation for multimegawatt offshore wind turbines. It is designed to accommodate a wind turbine, 5 MW or larger, on one of the columns of the hull with minimal modifications to the nacelle and rotor. Potential redesign of the tower and of the turbine control software can be expected. Technologies for floating foundations for offshore wind turbines are evolving. It is agreed by most experts that the offshore wind industry will see a significant increase in activity in the near future. Fixed offshore turbines are limited in water depth to ∼30–50 m. Market transition to deeper waters is inevitable, provided that suitable technologies can be developed. Despite the increase in complexity, a floating foundation offers the following distinct advantages: Flexibility in site location; access to superior wind resources further offshore; ability to locate in coastal regions with limited shallow continental shelf; ability to locate further offshore to eliminate visual impacts; an integrated hull, without a need to redesign the transition piece between the tower and the submerged structure for every project; simplified offshore installation procedures. Anchors are significantly cheaper to install than fixed foundations and large diameter towers. This paper focuses first on the design basis for wind turbine floating foundations and explores the requirements that must be addressed by design teams in this new field. It shows that the design of the hull for a large wind turbine must draw on the synergies with oil and gas offshore platform technology, while accounting for the different design requirements and functionality of the wind turbine. This paper describes next the hydrodynamic analysis of the hull, as well as ongoing work consisting of coupling hull hydrodynamics with wind turbine aerodynamic forces. Three main approaches are presented: The numerical hydrodynamic model of the platform and its mooring system; wave tank testing of a scale model of the platform with simplified aerodynamic simulation of the wind turbine; FAST, an aeroservoelastic software package for wind turbine analysis with the ability to be coupled to the hydrodynamic model. Finally, this paper focuses on the structural engineering that was performed as part of the feasibility study conducted for qualification of the technology. Specifically, the preliminary scantling is described and the strength and fatigue analysis methodologies are explained, focusing on the following aspects: The coupling between the wind turbine and the hull and the interface between the hydrodynamic loading and the structural response.
406 citations
TL;DR: In this article, the inlet condition of the working fluid entering turbine is assumed to be in saturated vapor phase and the main purpose is to identify suitable working fluids which may yield high system efficiencies in an organic Rankine cycle (ORC) system.
405 citations
TL;DR: In this article, a detailed data ensembles of power losses due to wakes at the large wind farms at Nysted and Horns Rev are presented and analyzed, and a number of ensemble averages are simulated with a range of wind farm and computational fluid dynamics models and compared to observed wake losses.
Abstract: There is an urgent need to develop and optimize tools for designing large wind farm arrays for deployment offshore. This research is focused on improving the understanding of, and modeling of, wind turbine wakes in order to make more accurate power output predictions for large offshore wind farms. Detailed data ensembles of power losses due to wakes at the large wind farms at Nysted and Horns Rev are presented and analyzed. Differences in turbine spacing (10.5 versus 7 rotor diameters) are not differentiable in wake-related power losses from the two wind farms. This is partly due to the high variability in the data despite careful data screening. A number of ensemble averages are simulated with a range of wind farm and computational fluid dynamics models and compared to observed wake losses. All models were able to capture wake width to some degree, and some models also captured the decrease of power output moving through the wind farm. Root-mean-square errors indicate a generally better model pe...
382 citations
TL;DR: The failure modes and effects analysis (FMEA) method has been used to study the reliability of many different power generation systems as mentioned in this paper, and it has been applied to a wind turbine (WT) system using a proprietary software reliability analysis tool.
357 citations
TL;DR: A WT condition monitoring technique that uses the generator output power and rotational speed to derive a fault detection signal and uses a continuous-wavelet-transform-based adaptive filter to track the energy in the prescribed time-varying fault-related frequency bands in the power signal.
Abstract: Cost-effective wind turbine (WT) condition monitoring assumes more importance as turbine sizes increase and they are placed in more remote locations, for example, offshore. Conventional condition monitoring techniques, such as vibration, lubrication oil, and generator current signal analysis, require the deployment of a variety of sensors and computationally intensive analysis techniques. This paper describes a WT condition monitoring technique that uses the generator output power and rotational speed to derive a fault detection signal. The detection algorithm uses a continuous-wavelet-transform-based adaptive filter to track the energy in the prescribed time-varying fault-related frequency bands in the power signal. The central frequency of the filter is controlled by the generator speed, and the filter bandwidth is adapted to the speed fluctuation. Using this technique, fault features can be extracted, with low calculation times, from direct- or indirect-drive fixed- or variable-speed WTs. The proposed technique has been validated experimentally on a WT drive train test rig. A synchronous or induction generator was successively installed on the test rig, and both mechanical and electrical fault like perturbations were successfully detected when applied to the test rig.
350 citations
Book•
03 Aug 2010
TL;DR: In this article, the authors present a detailed history of wind turbine technology and its application in a wide range of applications, including wind turbines, wind farms, and wind energy conversion.
Abstract: Chronological History of Wind Turbine Technology Major Benefits and Problems Associated with Alternate Energy Sources Benefits and Disadvantages of Wind Turbine Technology Worldwide Utilization of Wind Turbines Operating Principles of Wind Turbines Wind Turbine Classifications Wind Farm Developers Design Configurations Next Generation Wind Turbines with Unique Features Typical Wind Power Estimates for United States Design Aspects and Performance Requirements Types of Wind Turbines Modern Wind Turbines Off-Design Performance Techniques for Capturing Large Amounts of Wind Energy Annual Energy Acquisition from Specified Wind Turbine Site Estimating Annual Hours of Capturing Wind Energy Design Aspects and Performance Capabilities of Wind Turbine Rotors One-Dimensional Theory for Ideal Rotor Two-Dimensional Aerodynamic Model Three-Dimensional Aerodynamic Model for Wing of Finite Length Rotor Design Requirements for Wind Farm Applications Hydrodynamic Analysis of Flow over Rotor Wind Turbine Blade Design Requirements Analysis of Performance of Propeller Blades Blade Performance Application of Beam Theory to Various Turbine Blade Configurations Material Requirements for Blades Critical Features of Blade Section Sensors and Control Devices Required for Dynamic Stability and Improved Performance under Variable Wind Environments Regulation Control Systems Sensors for Monitoring Wind Parameters Transmission Systems Electrical Generators Performance Capabilities and Limitations of Synchronous Generators Critical Rotor Performance Parameters Impacts of Airfoil Characteristics on Blade and Turbine Performance Automatic Shut-Down Capability Critical Design Aspects of HAWT and VAWT Rotors Low Harmonic Content Electrical Generators for Improving Efficiency Impacts of Loadings on Structural Integrity of Wind Turbine Stand-Alone Wind Turbine Systems Historical Background: Use at Remote Sites Configurations of Stand-Alone Systems Stand-Alone Systems for Remote Sites Sizing of System Components Stand-Alone Systems with Utility Power Back-Up Stand-Alone Wind TurbineBased Systems for Various Applications Hybrid Systems for Village Electrification Multitasking Wind Turbines Wind Energy Conversion Techniques in Built Environments Concentrator Configuration Requirements Energy Design Buildings Local Wind Characteristics in Built Environments Impact of Built Environment on BAWT Performance Environmental Issues and Economic Factors Affecting Wind Turbine Installation Environmental Factors and Other Critical Issues Problems Arising from Large Windstream Diameters Estimating Critical Performance Parameters Using Classical BEM Theory Justification of Wind Turbine Installation Based on Economics Estimated Costs of Critical Components and Subsystems Wind Turbine Towers Index Each chapter begins with an Introduction and concludes with a Summary and References.
TL;DR: In this paper, the authors presented dynamic behavior and simulation results in a stand-alone hybrid power generation system of wind turbine, microturbine, solar array and battery storage.
TL;DR: In this article, the authors quantify the relationship between wind farm efficiency and wind speed, direction, turbulence and atmospheric stability using power output from the large offshore wind farm at Nysted in Denmark.
Abstract: Here, we quantify relationships between wind farm efficiency and wind speed, direction, turbulence and atmospheric stability using power output from the large offshore wind farm at Nysted in Denmark. Wake losses are, as expected, most strongly related to wind speed variations through the turbine thrust coefficient; with direction, atmospheric stability and turbulence as important second order effects. While the wind farm efficiency is highly dependent on the distribution of wind speeds and wind direction, it is shown that the impact of turbine spacing on wake losses and turbine efficiency can be quantified, albeit with relatively large uncertainty due to stochastic effects in the data. There is evidence of the ‘deep array effect’ in that wake losses in the centre of the wind farm are under-estimated by the wind farm model WAsP, although overall efficiency of the wind farm is well predicted due to compensating edge effects. Copyright © 2010 John Wiley & Sons, Ltd.
TL;DR: In this paper, a diffuser shroud with a broad-ring brim at the exit periphery and a wind turbine inside it is used to augment the power of a single wind turbine by a factor of about 2-5 compared with a bare wind turbine.
Abstract: We have developed a new wind turbine system that consists of a diffuser shroud with a broad-ring brim at the exit periphery and a wind turbine inside it. The shrouded wind turbine with a brimmed diffuser has demonstrated power augmentation by a factor of about 2–5 compared with a bare wind turbine, for a given turbine diameter and wind speed. This is because a low-pressure region, due to a strong vortex formation behind the broad brim, draws more mass flow to the wind turbine inside the diffuser shroud.
TL;DR: In this paper, the relationship between the total stored turbine kinetic energy and the total system power production for wind is studied in detail using simplified frequency control models and extensive simulations of wind penetration scenarios over an extended multi-year timeframe.
Abstract: Rising wind generation penetrations and the distinctive inertial characteristics of associated turbine technology will impact system frequency control. While wind production will displace conventional synchronous plant, empirical study data presented also suggest that the relationship between the total stored turbine kinetic energy and the total system power production for wind is a variable that exhibits significant nonlinearity. Changing trends in system frequency behavior of a power system following the loss of the largest generator are studied in detail here, using simplified frequency control models and extensive simulations of wind penetration scenarios over an extended multiyear timeframe. The system frequency response is characterized by the rate of change of frequency and the frequency nadir. Results show that increasing levels of doubly fed induction generators and high-voltage dc interconnection alter the frequency behavior significantly, and that system operators may have to be proactive in developing solutions to meet these challenges.
TL;DR: In this paper, the wake of a wind turbine operating in a uniform inflow at various tip speed ratios is simulated using a numerical method, which combines large eddy simulations with an actuator line technique.
Abstract: The wake of a wind turbine operating in a uniform inflow at various tip speed ratios is simulated using a numerical method, which combines large eddy simulations with an actuator line technique. The computations are carried out in a numerical mesh with about 8.4·106 grid points distributed to facilitate detailed studies of basic features of both the near and far wake, including distributions of interference factors, vortex structures and formation of instabilities. Copyright © 2009 John Wiley & Sons, Ltd.
TL;DR: In this article, the authors have discussed various aspects related to cavitation in hydro turbines, different causes for the declined performance and efficiency of the hydro turbines and suitable remedial measures suggested by various investigators have been discussed.
Abstract: Reaction turbines basically Francis turbines and propeller/Kaplan turbines are suitable for medium and low head hydropower sites. The management of the small hydropower plants is an important factor, for achieving higher efficiency of hydro turbines with time. Turbines show declined performance after few years of operation, as they get severely damaged due to various reasons. One of the important reasons is erosive wear of the turbines due to cavitation. Reaction turbines, however are more prone to cavitation especially Francis turbines where a zone in the operating range is seriously affected by cavitation and considered as forbidden zone. Cavitation is a phenomenon which manifests itself in the pitting of the metallic surfaces of turbine parts because of the formation of cavities. In the present paper, studies undertaken in this field by several investigators have been discussed extensively. Based on literature survey various aspects related to cavitation in hydro turbines, different causes for the declined performance and efficiency of the hydro turbines and suitable remedial measures suggested by various investigators have been discussed.
TL;DR: In this article, the authors identify and provide an understanding of the principal parameters that govern the downstream wake structure and its recovery to the free-stream velocity profile, and demonstrate that there are a number of interdependent variables that affect the rate of wake recovery and will have a significant impact on the spacing of marine current turbines within an array.
TL;DR: In this paper, a thermodynamic analysis of a subcritical boiler-turbine generator is performed for a 32MW coal-fired power plant, where both energy and exergy formulations are developed for the system.
TL;DR: In this paper, the authors used the continuous wavelet transformation (CWT) to filter useless noise in raw vibration signals, and auto terms window (ATW) function is used to suppress the cross terms in WVD, which can not only remove cross terms faraway from the auto terms, but also keep high energy close to every instantaneous frequency.
TL;DR: In this article, the effects of surface roughness on gas turbine performance are reviewed based on publications in the open literature over the past 60 years, and the conclusion remains that considerable research is yet necessary to fully understand the role of roughness in gas turbines.
Abstract: The effects of surface roughness on gas turbine performance are reviewed based on publications in the open literature over the past 60 years. Empirical roughness correlations routinely employed for drag and heat transfer estimates are summarized and found wanting. No single correlation appears to capture all of the relevant physics for both engineered and service-related (e.g., wear or environmentally induced) roughness. Roughness influences engine performance by causing earlier boundary layer transition, increased boundary layer momentum loss (i.e., thickness), and/or flow separation. Roughness effects in the compressor and turbine are dependent on Reynolds number, roughness size, and to a lesser extent Mach number. At low Re, roughness can eliminate laminar separation bubbles (thus reducing loss) while at high Re (when the boundary layer is already turbulent), roughness can thicken the boundary layer to the point of separation (thus increasing loss). In the turbine, roughness has the added effect of augmenting convective heat transfer. While this is desirable in an internal turbine coolant channel, it is clearly undesirable on the external turbine surface. Recent advances in roughness modeling for computational fluid dynamics are also reviewed. The conclusion remains that considerable research is yet necessary to fully understand the role of roughness in gas turbines.
TL;DR: In this paper, the position of an obstacle shielding the returning blade of the Savonius turbine and possibly leading to a better flow orientation toward the advancing blade is optimized. And the optimization process takes into account the output power coefficient as target function, considers the position and the angle of the shield as optimization parameters, and relies on Evolutionary Algorithms.
TL;DR: In this paper, a combined heat and power plant for cogeneration purposes that produces 50MW of electricity and 33.3 kg/s of saturated steam at 13 bar is optimized using genetic algorithm.
TL;DR: In this article, an energy and exergy analysis is performed on four different wind power systems, including both horizontal and vertical axis wind turbines, with respect to both the first and second laws of thermodynamics.
TL;DR: In this paper, the authors developed a periodic state space controller that utilizes individual blade pitching to improve power output and reduce platform motions in above rated wind speed region, and simulation results using a high-fidelity nonlinear turbine model show that the individual blade pitch controller reduces power fluctuations, platform rolling rate and platform pitching rate by 44, 39% and 43%, respectively, relative to a baseline controller developed specifically for floating wind turbine systems.
Abstract: Floating wind turbines offer a feasible solution for going further offshore into deeper waters. However, using a floating platform introduces additional motions that must be taken into account in the design stage. Therefore, the control system becomes an important component in controlling these motions. Several controllers have been developed specifically for floating wind turbines. Some controllers were designed to avoid structural resonance, while others were used to regulate rotor speed and platform pitching. The development of a periodic state space controller that utilizes individual blade pitching to improve power output and reduce platform motions in above rated wind speed region is presented. Individual blade pitching creates asymmetric aerodynamic loads in addition to the symmetric loads created by collective blade pitching to increase the platform restoring moments. Simulation results using a high-fidelity non-linear turbine model show that the individual blade pitch controller reduces power fluctuations, platform rolling rate and platform pitching rate by 44%, 39% and 43%, respectively, relative to a baseline controller (gain scheduled proportional–integral blade pitch controller) developed specifically for floating wind turbine systems. Turbine fatigue loads were also reduced; tower side–side fatigue loads were reduced by 39%. Copyright © 2009 John Wiley & Sons, Ltd.
TL;DR: In this paper, the power output of a variable-speed wind turbine generator is monitored using a wavelet in order to extract the strength of particular frequency components, characteristic of faults.
Abstract: With an increasing number of wind turbines being erected offshore, there is a need for cost-effective, predictive, and proactive maintenance. A large fraction of wind turbine downtime is due to bearing failures, particularly in the generator and gearbox. One way of assessing impending problems is to install vibration sensors in key positions on these subassemblies. Such equipment can be costly and requires sophisticated software for analysis of the data. An alternative approach, which does not require extra sensors, is investigated in this paper. This involves monitoring the power output of a variable-speed wind turbine generator and processing the data using a wavelet in order to extract the strength of particular frequency components, characteristic of faults. This has been done for doubly fed induction generators (DFIGs), commonly used in modern variable-speed wind turbines. The technique is first validated on a test rig under controlled fault conditions and then is applied to two operational wind turbine DFIGs where generator shaft misalignment was detected. For one of these turbines, the technique detected a problem 3 months before a bearing failure was recorded.
25 Jul 2010
TL;DR: In this article, the impact of increased penetration of DIFG-based wind turbines on transient and small signal stability of a large power system is analyzed. And the proposed technique is tested on a large test system representing the Midwestern portion of the U.S. interconnection.
Abstract: The targeted and current development of wind energy in various countries around the world reveals that wind power is the fastest growing power generation technology. Among the several wind generation technologies, variable speed wind turbines utilizing doubly fed induction generators (DFIGs) are gaining momentum in the power industry. With the increase in penetration of these wind turbines, the power system dominated by synchronous machines will experience a change in dynamics and operational characteristics. Given this assertion, the present paper develops an approach to analyze the impact of increased penetration of DFIG based wind turbines on transient and small signal stability of a large power system. The primary basis of the method is to convert the DFIG machines into equivalent conventional round rotor synchronous machines and then evaluate the sensitivity of the eigenvalues with respect to inertia. In this regard, modes that are both detrimentally and beneficially affected by the change in inertia are identified. These modes are then excited by appropriate disturbances and the impact of reduced inertia on transient stability performance is also examined. The proposed technique is tested on a large test system representing the Midwestern portion of the U.S. interconnection. The results obtained indicate that the proposed method effectively identifies both detrimental and beneficial impacts of increased DFIG penetration both for transient stability and small signal stability related performance.
21 Mar 2010
TL;DR: In this paper, the reliability problems associated with transmission or gearbox equipped wind turbines and the existing solutions of using direct drive gearless turbines and torque splitting, are reviewed, as well as alternative solutions such as magnetically-levitated bearings from the aerospace industry, and the consideration of Continuously Variable Transmissions (CVTs) from the automobile industry.
Abstract: The reliability problems associated with transmission or gearbox equipped wind turbines and the existing solutions of using direct drive gearless turbines and torque-splitting, are reviewed. As alternative solutions we propose the Geared Turbofan Engine (GTF) technology, and magnetically-levitated bearings from the aerospace industry, and the consideration of Continuously Variable Transmissions (CVTs) from the automobile industry, and discuss their promise in addressing the gearbox problems currently encountered by existing wind turbine technology.
TL;DR: In this article, the authors used a tri-bladed horizontal axis turbine to investigate the hydrodynamics of marine current turbines and to characterize the wake generated by the turbine.
Abstract: Experimental results of tests carried out to investigate the hydrodynamics of marine current turbines are presented. The objective is to build an experimental database in order to validate the numerical developments conducted to characterise the flow perturbations induced by marine current turbines. For that purpose, we used a tri-bladed horizontal axis turbine. The work is dedicated to measuring the behaviour of the system and to characterising the wake generated by the turbine. The efficiency of the device is quantified by the measurement of the thrust and the amount of power generated by the rotor for various inflow conditions, whereas the wake is characterised by Laser Doppler Velocimetry. Particular attention is paid to the flow characteristic effects on the performance of a 0.70 m diameter turbine. The load predictions on the structure and the measured performance of the turbine over its working range of currents and rotational speeds are presented. The results showed that this kind of turbine is sensitive to the quality of the incoming flow. The turbulence intensity effects on turbine behaviour and on its wake are also characterised in order to study how the far wake decays downstream and to estimate the effect produced in downstream turbines.
TL;DR: In this paper, a 1D model for a tidal channel is combined with a theory for turbines in a channel to show that the tuning of the flow through the turbines and the density of turbines in the channel's cross-section also interact with the larger scale flow, via the drag coefficient, to determine the power available for production.
Abstract: As tidal turbine farms grow they interact with the larger scale flow along a channel by increasing the channel's drag coefficient. This interaction limits a channel's potential to produce power. A 1D model for a tidal channel is combined with a theory for turbines in a channel to show that the tuning of the flow through the turbines and the density of turbines in a channel's cross-section also interact with the larger scale flow, via the drag coefficient, to determine the power available for production. To maximise turbine efficiency, i.e. the power available per turbine, farms must occupy the largest fraction of a channel's cross-section permitted by navigational and environmental constraints. Maximising of power available with these necessarily densely packed farms requires turbines to be tuned for a particular channel and turbine density. The optimal through-flow tuning fraction varies from near 1/3 for small farms occupying a small fraction of the cross-section, to near 1 for large farms occupying most of the cross-section. Consequently, tunings are higher than the optimal through-flow tuning of 1/3 for an isolated turbine from the classic turbine theory. Large optimally tuned farms can realise most of a channel's potential. Optimal tunings are dependent on the number of turbines per row, the number of rows, as well as the channel geometry, the background bottom friction coefficient and the tidal forcing.