The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Sanjoy Roy - One of the best experts on this subject based on the ideXlab platform.
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power output by active pitch regulated Wind turbine in presence of short duration Wind Variations
IEEE Transactions on Energy Conversion, 2013Co-Authors: Sanjoy RoyAbstract:The inexact power output from a pitch angle-controlled (PAC) horizontal-axis turbine, as influenced by short duration Wind Variations like turbulence and gusts, has been the subject of well-documented experimental and empirical studies. In this paper, an analytical interpretation of the phenomena is presented under assumption of two-parameter Weibull statistics for short duration Wind Variations. The popular concept of turbulence intensity is used as a parametric measure for randomness of Wind speed. The formulations culminate in analytical expressions for two distinct metrics of power distortion, namely: (a) the short duration output power from the turbine as a mean distinct from corresponding ideal zero-turbulence value; and (b) the output power variability as a quantification of randomness around the mean. Estimates of both metrics are presented for operating conditions in accordance with the well-known IEC 61400-1 standards. Trends indicated by computed estimates are found to be consistent with empirically observed data from field studies that are reported in the literature.
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Inclusion of Short Duration Wind Variations in Economic Load Dispatch
IEEE Transactions on Sustainable Energy, 2012Co-Authors: Sanjoy RoyAbstract:Randomness of Wind speed around a short-duration-stable mean value is commonly referred to as short duration Wind variation. This paper investigates the effect of substantial Wind-based capacity inclusion on optimal load dispatch, with the source Wind susceptible to short duration Variations. Analytical formulation of the economic load dispatch (ELD) problem inclusive of Wind power generation is presented separately for cases with and without representation of transmission losses. In each formulation, the effect of short duration Wind Variations is included as an aggregate, thereby avoiding the complexity of stochastic models. Three-generator and 20-generator study cases are discussed to illustrate two distinct aspects of the ELD problem. First, the optimal cost, losses, and system- λ are presented across a range of short-duration-stable mean Wind speed. Thereafter, the sensitivity of all three metrics is discussed with reference to different levels of short duration Wind Variations.
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Impact of Short Duration Wind Variations on Output of a Pitch Angle Controlled Turbine
IEEE Transactions on Sustainable Energy, 2012Co-Authors: Sanjoy RoyAbstract:The distorted output of a pitch angle controlled (PAC) horizontal axis turbine, as influenced by short duration Wind Variations like turbulence and gusts, is analyzed under the assumption of two-parameter Weibull statistics. The well accepted concept of turbulence intensity is used as a parametric measure of short duration Wind Variations. Analytical expressions are formulated and used to estimate the short duration aggregate power output from a turbine, together with the fractional deviations from corresponding ideal zero-turbulence values. Operating conditions of constant turbulence intensity, and constant Wind speed standard deviation, are considered separately for the studies. Sensitivity of turbine output power to cut-in and rated values of Wind speed are evaluated and discussed.
Michael J Mcphaden - One of the best experts on this subject based on the ideXlab platform.
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dynamics of Wind forced intraseasonal zonal current Variations in the equatorial indian ocean
Journal of Geophysical Research, 2011Co-Authors: Iskhaq Iskandar, Michael J McphadenAbstract:[1] This study examines the structure and dynamics of Wind-forced intraseasonal zonal current variability in the equatorial Indian Ocean. We take advantage of a variety of satellite and in situ data sets, including unprecedented 4–8 year-long velocity time series records from the Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction (RAMA) program. Spectral analysis reveals prominent intraseasonal zonal currents Variations along the equator with periods of 30–70 days. These oscillations are vertically in phase above the thermocline and propagate eastward with the local zonal Winds. In the thermocline, intraseasonal zonal velocity Variations also propagate eastward across a broad range of phase speeds expected for low baroclinic equatorial Kelvin waves; amplitudes decrease with depth, with deeper levels leading those near surface. Collectively, these results suggest that the near-surface layer responds directly to intraseasonal zonal Wind stress forcing and that subsequently energy radiates downward and eastward in the thermocline in the form of Wind-forced equatorial Kelvin waves. In addition, intraseasonal zonal current variability on the equator is coherent with off-equatorial sea surface height fluctuations in the eastern and central of the basin. This coherence is primarily due to the fact that equatorial zonal Wind Variations are associated with off-equatorial Wind stress curls that can generate local Ekman pumping and westward propagating Rossby waves.
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decadal phase change in large scale sea level and Winds in the indo pacific region at the end of the 20th century
Geophysical Research Letters, 2008Co-Authors: Michael J McphadenAbstract:[1] Satellite observations of sea surface height (SSH) and Wind stress for the period of 1993–2006 reveal a near-coherent large-scale decadal variability in much of the Indo-Pacific region with a phase change at the turn of the 20th century. Trade Wind Variations in the tropical Pacific and South Indian Ocean are anti-correlated with each other as are SSH differences across these two basins, implying anti-correlated variation of the subtropical cells in the two oceans. Decadal changes in large-scale SSH in the extra-tropics are mostly associated with well-defined patterns of Wind stress curl indicating a near-coherent decadal variation in the strength of subtropical and subpolar gyres. Together, these Variations reflect a linkage in the circulation of the Pacific and Indian Oceans via atmospheric and oceanic bridges. The phase change in the tropical Pacific tends to occur earlier than elsewhere, suggesting a potential role of the tropical Pacific in regulating decadal variability of the entire region.
Shang-ping Xie - One of the best experts on this subject based on the ideXlab platform.
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indian ocean variability in the cmip5 multimodel ensemble the basin mode
Journal of Climate, 2013Co-Authors: Shang-ping Xie, Xiao-tong Zheng, Yali Yang, Lin Liu, Gang HuangAbstract:This study evaluates the simulation of the Indian Ocean Basin (IOB) mode and relevant physical processes in models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). Historical runs from 20 CMIP5 models are available for the analysis. They reproduce the IOB mode and its close relationship to El Nino-Southern Oscillation (ENSO). Half of the models capture key IOB processes: a downwelling oceanic Rossby wave in the southern tropical Indian Ocean (TIO) precedes the IOB development in boreal fall and triggers an antisymmetric Wind anomaly pattern across the equator in the following spring. The anomalous Wind pattern induces a second warming in the north Indian Ocean (NIO) through summer and sustains anticyclonic Wind anomalies in the northwest Pacific by radiating a warm tropospheric Kelvin wave. The second warming in the NIO is indicative of ocean-atmosphere interaction in the interior TIO. More than half of the models display a double peak in NIO warming, as observed following El Nino, while the rest show only one winter peak. The intermodel diversity in the characteristics of the IOB mode seems related to the thermocline adjustment in the south TIO to ENSO-induced Wind Variations. Almost all the models show multidecadal Variations in IOB variance, possibly modulated by ENSO.
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Importance of Ocean Dynamics for the Skewness of the Indian Ocean Dipole Mode
Journal of Climate, 2013Co-Authors: Tomomichi Ogata, Shang-ping Xie, Jian Lan, Xiao-tong ZhengAbstract:AbstractInterannual anomalies of sea surface temperature (SST), Wind, and cloudiness in the southeastern tropical Indian Ocean (SE-TIO) show negative skewness. In this research, asymmetry between warm and cold episodes in the SE-TIO and the importance of ocean dynamics are investigated. A coupled model simulation and observations show an asymmetric relationship between SST and the thermocline depth in the SE-TIO where SST is more sensitive to an anomalous shoaling than to deepening of the thermocline. This asymmetric thermocline feedback on SST is a result of a deep mean thermocline. Sensitivity experiments with an ocean general circulation model (OGCM) show that a negative SST skewness arises in response to sinusoidal zonal Wind Variations that are symmetric between the westerly and easterly phases. Heat budget analysis with an OGCM hindcast also supports the importance of ocean dynamics for SST skewness off Sumatra and Java.
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sst induced surface Wind Variations over the brazil malvinas confluence satellite and in situ observations
Journal of Climate, 2005Co-Authors: Hiroki Tokinaga, Youichi Tanimoto, Shang-ping XieAbstract:Abstract The confluence of the Brazil–Malvinas Currents maintains strong sea surface temperature (SST) fronts in the midlatitude southwestern Atlantic year-round. SST effects on near-surface stability and surface Wind Variations are examined in this region using satellite and in situ datasets. Satellite observations show strong (weak) surface Wind speeds over the warm Brazil (cold Malvinas) Current. A novel feature of this study is the construction of a high-resolution surface meteorological dataset that is based on historical ship observations. Analysis of this new in situ dataset reveals an increased (reduced) sea–air temperature difference over the Brazil (Malvinas) Current, indicating destabilization (stabilization) in the atmospheric boundary layer. These results are consistent with the SST-induced vertical mixing mechanism for Wind adjustment. The SST effect on the near-surface atmosphere is observed both in the climatology and on interannual time scales in the Brazil–Malvinas confluence. Along a zo...
Henrik Lundstedt - One of the best experts on this subject based on the ideXlab platform.
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solar Wind Variations related to fluctuations of the north atlantic oscillation
Geophysical Research Letters, 2002Co-Authors: Fredrik Boberg, Henrik LundstedtAbstract:A study on a possible solar Wind interaction with the North AtlanticOscillation (NAO) is performed. Results are presented suggesting arelationship between the NAO index and the electric field strength E ofthe solar Wind. A possible scenario for the suggested interaction isthat an electromagnetic disturbance is generated by the solar Wind inthe global electric circuit of the ionosphere. This disturbance is thendynamically propagating downward through the atmosphere and subsequentlyinfluencing the large-scale pressure system in the North Atlanticregion. A relationship is also evident on longer time-scales when usingthe group sunspot number as a proxy for the solar Wind. (Art. No. 1718)
K. S. Barr - One of the best experts on this subject based on the ideXlab platform.
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Coherent Doppler lidar for Wind farm characterization
Wind Energy, 2013Co-Authors: Ram Krishnamurthy, Jennifer Fine, Ronald Calhoun, Aditya Choukulkar, A Oliver, K. S. BarrAbstract:Coherent Doppler lidar measurements are of increasing interest for the Wind energy industry. Wind measurements are fundamental inputs for the evaluation of potential energy yield and performance of Wind farms. Three-dimensional scanning Doppler lidar may provide a new basis for Wind farm site selection, design and optimization. In this paper, the authors discuss Doppler lidar measurements obtained for a Wind energy development. The possibility of using lidar measurements to more fully characterize the Wind field is discussed, specifically terrain effects, spatial variation of Winds, power density and the effect of shear at different layers within the rotor swept area. Vector retrieval methods have been applied to the lidar data, and results are presented on an elevated terrain-following surface at hub height. The vector retrieval estimates are compared with tower measurements, after interpolation to the appropriate level. Doppler lidar data are used to estimate the spatial power density at hub height (for the period of the deployment). An example Wind farm layout is presented for demonstration purposes based purely on lidar measurement, even though the lidar data acquisition period cannot be considered climatological. The strength of this approach is the ability to directly measure spatial Variations of the Wind field over the Wind farm. Also, because Doppler lidar can measure Winds at different vertical levels, an approach for estimating Wind power density over the rotor swept area (rather than only the hub height) is explored. Finally, advanced vector retrieval algorithms have been applied to better characterize local Wind Variations and shear. Copyright {©} 2012 John Wiley {&} Sons, Ltd.
