Berlin 2012 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 17: Focus Session: Alternative energies – Compensation of long- and short-term fluctuations (jointly with DY)

DF 17.1: Topical Talk

Thursday, March 29, 2012, 15:00–15:30, EB 107

Wind energy - Characterization and modeling of short-term fluctuations in incoming wind and power output — •Michael Hölling, Matthias Wächter, Allan Morales, Patrick Milan, and Joachim Peinke — ForWind - Center for Wind Energy Research, Institute of Physics, University of Oldenburg

One inherent characteristic of turbulent atmospheric wind fields is their correlation in time and space, which results in intermittent behavior of velocity increments on a wide range from very small to very large scales. Wind energy converters work in this highly intermittent environment and transfer these fluctuations to the generator and the power output, respectively. With a significantly increased wind power production in the future, there is a need to better understand the interaction of turbulent wind fields with wind turbines. We present methods to describe and model these intermittent characteristics of atmospheric flows and power output of wind turbines using stochastic analysis. Data from wind tunnel experiments on blade segments with respect to lift forces under turbulent wind conditions show dynamic stall like behavior with an increased maximum lift force shifted to higher angles of attack compared to laminar inflow conditions. In addition an increase in the standard deviation in the acting lift forces is observed, which leads to dynamic changes in loads, that have to be accounted for e.g. in the design process of the wind turbine. Also the power output from wind turbines shows intermittent behavior resulting from the turbulent wind fields. The presented methods can help to describe and predict power fluctuations and to make the machines last longer.