Posters

Abstract

In energy yield assessment, special attention is always given to commercial power curves, including verifying the peak power coefficient (Cp) value and making site-specific adjustments. The power performance risk can be managed through a power curve performance warranty and verified with an IEC 61400-12-1 power curve test. However, the risk associated with the thrust coefficient (Ct) is less adressed and raises concerns: overly optimistic or even unrealistic Ct values can lead to an underestimation of wake losses. For sites with close inter-turbine distances, or with low terrain roughness, this underestimation can result in a yield gap of more than 5%. This study aims to identify an empirical range to detect Ct anomalies based on the Cp-Ct relationship and recalibrate OEM data. Firstly, examples of optimistic commercial power curves and the corresponding underestimation of wake losses are presented. A database of power curves is then used to define a realistic threshold for Ct values. Furthermore, using BEM simulations on reference wind turbines, a Cp-Ct map-based threshold is established. To investigate the margin of the empirical threshold, we are also exploring the potential benefits of dedicated blade and airfoil shapes to reduce the thrust produced. The present analysis will aim to illustrate the advantages of a flatback airfoil and how it will impact the Cp-Ct trend. To that end, a reference blade will be redesigned to introduce flatback airfoils in place of the original airfoils. Several metrics will be monitored (e.g., thrust, power, tower fore-aft displacement, blade root flapwise bending moment) and compared to the reference blade.