Using Environmental Contours to Predict Extreme Events on Wind Turbines

Abstract

This paper presents and explores estimating design loads on wind turbines using the environmental contour method. Contours promise to provide both practical reliability estimation and valuable information about the combination of joint environmental variable values, e.g. wind speed and turbulence, most critical to each specific wind turbine. We present the background of the development of environmental contours as applied to wind energy systems, and apply this theory, in three examples, to develop contours based either (1) on design code description of environmental conditions, or (2) on measured data for a site-specific application. The site-specific case is used for both stall and pitch controlled turbine examples. From these contours, and a functional description of the short-term response of the turbine, implicit FORM estimates are made for the turbine response; these estimates are compared with results obtained from numerical integration of the short-term response of the turbine over the joint distribution of wind speed and turbulence. We find that the environmental contour method provides reasonable estimates of the expected extreme load, compared with the full integration method.