Projektbericht
Betrieb von Windenergieanlagen unter Vereisungsbedingungen

Available only in German Language

Ergebnisse und Empfehlungen aus einem EU-Forschungsprojekt

Einleitung

Die zunehmende Anzahl der an vereisungsgefährdeten Standorten aufgestellten Windenergieanlagen (WEA) fordert praxisgerechte Lösungen, um den Betrieb mit Vereisung zu erkennen und eine Gefährdung der Umgebung und der Anlage selbst zu verhindern. In Deutschland wurden allein im ersten Halbjahr 1999 über 50 % der in diesem Zeitraum aufgestellten Windenergieanlagen und fast 50 % der im gleichen Zeitraum installierten Leistung im Binnenland errichtet.

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A RECIPE TO ESTIMATE AERODYNAMICS AND LOADS ON ICED ROTOR BLADES

Abstract

Wind tunnel tests have been carried out using "artificial" iced profiles with various types and amount of ice accretion gained from real iced rotor blades. This information has be used as an input for aerodynamic load calculation and power output prediction. Coefficients of lift, drag and aerodynamical moment were measured at the original clean airfoil and with added leading edge ice models in an angle of attack range between -10° to 30° degrees. A recipe has been developed to transfer the wind tunnel test results to any other airfoil used on wind turbine rotor blades and furthermore an extrapolation method is given to predict the behaviour of iced airfoils in the high angle of attack range. Finally, an approach to estimate the aerodynamic and mass loads due to icing and to predict the loss of energy caused by an iced rotor is given.

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AERODYNAMICS OF ICED AIRFOILS AND THEIR INFLUENCE ON LOADS AND POWER PRODUCTION

Abstract

Typical types of ice fragments were removed from the blade of a small wind turbine and preserved. Before harvesting the ice pieces measurements of loads and power output as well as the meteorological conditions had been performed during partial power operation. From these ice fragments two dimensional wind tunnel models were built. The coordinates of the "clean" airfoil were not taken from the catalogue but moulded directly from the rotor blade. The clean airfoil was investigated with and without ice at the leading edge in the wind tunnel of the University of Braunschweig. Using the results (aerodynamic coefficients cl, cd, and cm) the power curves for the clean and iced rotor of a stall and pitch controlled 300 kW turbine were calculated and the loss of energy production estimated. Finally, measurements of unsteady behaviour of both iced and non-iced profiles including dynamic stall effects were carried out in the wind tunnel. The ice accretion investigated is similar to that collected from large turbines and the Reynolds number effect on the resulting coefficients is negligible. Therefore, the values found may be transferred to larger turbines.

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