Detailed analysis of a waked turbine using a high-resolution scanning lidar

Abstract

Sandia National Laboratories and the National Renewable Energy Laboratory conducted a wake-steering field campaign at the Scaled Wind Farm Technology facility. The campaign included the use of two highly instrumented V27 wind turbines, an upstream met tower, and high-resolution wake measurements of the upstream wind turbine using a customized scanning lidar from the Technical University of Denmark (DTU). The present work investigates the impact of the upstream wake on the downstream turbine power and blade loads as the wake swept across the rotor in various waked conditions. The wake position was tracked using the DTU SpinnerLidar and synchronized to the met tower and turbine sensors. Fully and partially waked conditions reduced the power output and increased the fatigue loading on the downstream wind turbine. Partial wake impingement was found to result in a 10% increase in fatigue loading over the fully waked condition. Rotational sampling of the blade root bending moments revealed that the fatigue damage accrued during full turbine waking, was primarily caused by turbulence within the wake rather than velocity shear, while the partially waked turbine experienced a large 1-per revolution fatigue due to shear. The development of a power to fatigue load metric curve indicated the wake positions where shifting the wake has the most benefit for the waked turbine.