Modelling the Impact of Leading Edge Erosion Progression on the Electricity Produced by Wind Turbines

Abstract

This thesis discusses the development of a model to predict the progression of erosion on a wind turbine blade with time, and the effects that progressive erosion has on wind turbine Annual Energy Production (AEP). An Erosion Progression Model (EPM) has been produced which can predict the erosion due to rain droplet impacts on a wind turbine blade as a function of time, mean wind speed, and rainfall intensity. Novel methods to predict the erosion affected area, and to incorporate distributed erosion have been developed to predict realistic eroded blade surface geometries. Blade inspection data, provided by rsted, from two operational wind farms was used to validate EPM predictions. An experimental campaign, using pressure, force balance and infra-red thermography measurements, was undertaken to validate a method for testing a blade section with Detachable Leading Edges (DLEs) in the Durham 2m wind tunnel. Results from wind tunnel tests using DLEs with an eroded geometry, predicted by the EPM, were used to validate a two-dimensional Computational Fluid Dynamics (CFD) method for calculating aerodynamic forces on aerofoils with distributed erosion. Simulations of 205 combinations of mean wind speed, annual rainfall intensity and operating time were conducted using the validated CFD method. Blade Element Momentum (BEM) calculations of the DTU 10MW RWT, over 10 years of operation, when coupled with an annual wind distribution for Anholt offshore wind farm, showed that increases in both mean wind speed and annual rainfall intensity result in an increase in the percentage AEP loss. AEP losses of 0.4-1.6 may be expected after 10 years, depending on the environmental conditions.