Field-test of nacelle-based lidar to explore its applications for Vattenfall as wind park operator

Abstract

The market share of wind energy is related to many factors, including politics, social acceptance and financial feasibility. In light of reducing the Levelised Energy Cost (LEC) generated from wind energy, power company Vattenfall is continuously looking for new ways of monitoring and improving wind turbine yield. Recent publications have shown nacelle-based lidar to be a valuable tool for research, capturing the interest of Vattenfall's Wind Resource team. To gain more insight in the applications of nacelle-based lidar and their benefits to Vattenfall as operator, a measurement campaign was conducted at wind park Slufterdam West. More specifically, a Wind Iris was installed on the nacelle of the most southern wind turbine (type GE 1.5s) and a sodar of type AQ500 was installed 235m to the southeast of this turbine. The Wind Iris proved to be a useful instrument for measurement of the power curve and mean yaw misalignment. The former was found to be in accordance with the contracted power curve and the latter turned out to be 1.5 degrees. In the wind regime where it is most relevant to the power curve (4-13 m/s), yaw misalignment was found to have no clear relationship with rotor speed and wind speed. Two methods were used to investigate the impact of yaw misalignment on the power curve, but no definitive conclusions could be drawn. Moreover, the Wind Iris was found to be a useful tool for investigating the blockage effect and results were in accordance with theory. Finally, a financial case study was carried out to evaluate implementation of the Wind Iris at Slufterdam. However, since there is no evidence that the turbines have yaw misalignment nor that small yaw misalignment is harming the power curve, implementation is currently not recommended. However, if the impact of yaw misalignment on the power curve can be quantified accurately, implementation can be financially viable.