Assessing Low Frequency Variations in Solar and Wind Power and Their Climatic Teleconnections

2021 ◽  
Author(s):  
Emilio Bianchi ◽  
Tomas Guozden ◽  
Roberto Kozulj
Keyword(s):  
Wind Power ◽  
Low Frequency ◽  
Frequency Variations

Dynamic Stability of a Water Brake Dynamometer

1998 ◽  
Vol 120 (1) ◽  
pp. 89-96 ◽  
Author(s):  
R. A. Van den Braembussche ◽  
H. Malys
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Lumped Parameter Model ◽  
Stable Operation ◽  
Pressure Oscillations ◽  
Lumped Parameter ◽  
Flow Oscillations ◽  
Brake Dynamometer ◽  
Low Torque ◽  
Frequency Variations

A lumped parameter model to predict the high frequency pressure oscillations observed in a water brake dynamometer is presented. It explains how the measured low frequency variations of the torque are a consequence of the variation in amplitude of the high frequency flow oscillations. Based on this model, geometrical modifications were defined, aiming to suppress the oscillations while maintaining mechanical integrity of the device. An experimental verification demonstrated the validity of the model and showed a very stable operation of the modified dynamometer even at very low torque.

Removing Spurious Low-Frequency Variability in Drifter Velocities

2013 ◽  
Vol 30 (2) ◽  
pp. 353-360 ◽  
Author(s):  
Rick Lumpkin ◽  
Semyon A. Grodsky ◽  
Luca Centurioni ◽  
Marie-Helene Rio ◽  
James A. Carton ◽  
...  
Keyword(s):  
Low Frequency ◽  
Original Data ◽  
Strain Sensors ◽  
Wind Forcing ◽  
Stokes Drift ◽  
Interannual Variations ◽  
Transmission Frequency ◽  
Low Frequency Variability ◽  
Frequency Variations ◽  
Drifting Buoys

Abstract Satellite-tracked drifting buoys of the Global Drifter Program have drogues, centered at 15-m depth, to minimize direct wind forcing and Stokes drift. Drogue presence has historically been determined from submergence or tether strain records. However, recent studies have revealed that a significant fraction of drifters believed to be drogued have actually lost their drogues, a problem that peaked in the mid-2000s before the majority of drifters in the global array switched from submergence to tether strain sensors. In this study, a methodology is applied to the data to automatically reanalyze drogue presence based on anomalous downwind ageostrophic motion. Results indicate that the downwind slip of undrogued drifters is approximately 50% higher than previously believed. The reanalyzed results no longer exhibit the dramatic and spurious interannual variations seen in the original data. These results, along with information from submergence/tether strain and transmission frequency variations, are now being used to conduct a systematic manual reevaluation of drogue presence for each drifter in the post-1992 dataset.

Output Power Correlation Between Nearby Wind Power Plants

2003 ◽  
Author(s):  
Yih-Huei Wan ◽  
Michael Milligan ◽  
Brian Parsons
Keyword(s):  
Power Plant ◽  
Wind Power ◽  
Power Output ◽  
High Frequency ◽  
Power Plants ◽  
Meteorological Data ◽  
Low Frequency ◽  
Spatial Separation ◽  
Wind Power Plant ◽  
Wind Power Plants

The National Renewable Energy Laboratory (NREL) started a project in 2000 to record long-term, high-frequency (1-Hz) wind power output data from large commercial wind power plants. Outputs from about 330 MW of wind generating capacity from wind power plants in Buffalo Ridge, Minnesota, and Storm Lake, Iowa, are being recorded. Analysis of the collected data shows that although very short-term wind power fluctuations are stochastic, the persistent nature of wind and the large number of turbines in a wind power plant tend to limit the magnitudes and rates of changes in the levels of wind power. Analyses of power data confirm that spatial separation greatly reduces variations in the combined wind power output relative to output from a single wind power plant. Data show that high frequency variations of wind power from two wind power plants 200 km apart are independent of each other, but low frequency power changes can be highly correlated. This fact suggests that time-synchronized power data and meteorological data can aid in the development of statistical models for wind power forecasting.

scholarly journals Trapped Planetary (Rossby) Waves Observed in the Indian Ocean by Satellite Borne Altimeters

2017 ◽  
Author(s):  
Yair De-Leon ◽  
Nathan Paldor
Keyword(s):  
Indian Ocean ◽  
Rossby Waves ◽  
Low Frequency ◽  
Propagation Speed ◽  
Wave Theory ◽  
Planetary Waves ◽  
Sea Surface ◽  
Trapped Wave ◽  
The Indian Ocean ◽  
Frequency Variations

Abstract. Using 20 years of accurately calibrated, high resolution, observations of Sea Surface Height Anomalies (SSHA) by satellite ‎borne altimeters we show that in the Indian Ocean south of the Australian coast the low frequency variations of SSHA are ‎dominated by westward propagating, trapped, i.e. non-harmonic, planetary waves. Our results demonstrate that the ‎meridional-dependent amplitudes of the SSHA are large only within a few degrees of latitude next to the South-Australian ‎coast while farther in the ocean they are uniformly small. This meridional variation of the SSHA signal is typical of the ‎amplitude structure in the trapped wave theory. The westward propagation speed of the SSHA signals is analyzed by ‎employing three different methods of estimation. Each one of these methods yields speed estimates that can vary widely ‎between adjacent latitudes but the combination of at least two of the three methods yields much smoother variation. The ‎estimates obtained in this manner show that the observed phase speeds at different latitudes exceed the phase speeds of ‎harmonic Rossby (Planetary) waves by 140 % to 200 %. In contrast, the theory of trapped Rossby (Planetary) waves in a ‎domain bounded by a wall on its equatorward side yields phase speeds that approximate more closely the observed phase ‎speeds.‎

scholarly journals Multidecadal to millennial marine climate oscillations across the Denmark Strait (~ 66° N) over the last 2000 cal yr BP

2014 ◽  
Vol 10 (1) ◽  
pp. 325-343 ◽  
Author(s):  
J. T. Andrews ◽  
A. E. Jennings
Keyword(s):  
North Atlantic ◽  
Low Frequency ◽  
Atlantic Water ◽  
Ice Age ◽  
The North ◽  
Denmark Strait ◽  
Water Stratification ◽  
The North Atlantic Oscillation ◽  
Frequency Variations ◽  
Marine Climate

Abstract. In the area of Denmark Strait (~66° N), the two modes of the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) are expressed in changes of the northward flux of Atlantic water and the southward advection of polar water in the East Iceland current. Proxies from marine cores along an environmental gradient from extensive to little or no drift ice, capture low frequency variations over the last 2000 cal yr BP. Key proxies are the weight% of calcite, a measure of surface water stratification and nutrient supply, the weight% of quartz, a measure of drift ice transport, and grain size. Records from Nansen and Kangerlussuaq fjords show variable ice-rafted debris (IRD) records but have distinct mineralogy associated with differences in the fjord catchment bedrock. A comparison between cores on either side of the Denmark Strait (MD99-2322 and MD99-2269) show a remarkable millennial-scale similarity in the trends of the weight% of calcite with a trough reached during the Little Ice Age. However, the quartz records from these two sites are quite different. The calcite records from the Denmark Strait parallel the 2000 yr Arctic summer-temperature reconstructions; analysis of the detrended calcite and quartz data reveal significant multi-decadal–century periodicities superimposed on a major environmental shift occurring ca. 1450 AD.

Control Strategies of HESS for the Application of Directly Driven WTG

2012 ◽  
Vol 512-515 ◽  
pp. 694-699 ◽  
Author(s):  
Li Wang ◽  
Yan Li ◽  
Mei Wei Sheng ◽  
Yi Shan Xu ◽  
Zeng Tao Yang ◽  
...  
Keyword(s):  
Wind Power ◽  
System Analysis ◽  
Control Strategies ◽  
Storage System ◽  
Low Frequency ◽  
Energy Storage System ◽  
Hybrid Energy ◽  
Hybrid Energy Storage ◽  
Hybrid Energy Storage System ◽  
Management Algorithm

Wind power is the most fast growing energy source in the world while its intermittency and uncertainty generate stability, reliability and power quality problems in the electric grid. A battery/supercapacitor Hybrid Energy Storage System (HESS) is integrated to the directly driven Wind Turbine Generation (WTG) system to achieve a better wind power output characteristic. When integrated to a grid connected WTG, the supercapacitor and battery respectively absorbs the high frequency part and low frequency part of the wind fluctuations. Feedback elements are added to achieve a better performance of this management algorithm. While for a HESS applied to the stand-alone WTG system, the supercapacitor supports the frequency of the isolated system after the islanded operation and PI controllers are used. The control models are developed by the User Definition (UD) module on Power System Analysis Software Package (PSASP). Simulations are carried out to verify the control strategies effective and feasible.

High and low frequency variations and the cyclical behaviour of real wages

2005 ◽  
Vol 37 (5) ◽  
pp. 571-579 ◽  
Author(s):  
Ahmad. B. Afrasiabi * ◽  
Tomas W. Nonnenmacher
Keyword(s):  
Low Frequency ◽  
Real Wages ◽  
Cyclical Behaviour ◽  
Frequency Variations
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