An experimental study into accuracy of novel techniques in Power Curve verification

Abstract

The EU goals to decrease wind energy prices are driving the wind energy industry to give more attention to monitoring and improving turbine performance. Meanwhile, as turbines grow bigger and more are placed offshore, performance monitoring costs are increasing, making it more interesting to consider novel devices to measure turbine performance. The purpose of this study was to investigate the applicability of these devices in power performance monitoring and evaluating the potential gains which can be achieved. A comparative study of the measurement accuracies was performed of the nacelle-based Lidar (WindIris) and a spinner anemometer (iSpins) against an IEC-compliant met-mast. Accuracies of both devices in measuring wind speeds, yaw misalignment and power curves were found to be comparable to a met-mast and therefore could be worthy replacements of met-masts for power performance measurements in the future. The impact of non-ideal wind conditions, like yaw misalignment, turbulence and wind shear, on power performance was also investigated using both experimental and Bladed simulated results. No conclusive results were found on the relationship between yaw misalignment and performance loss. The ideal yaw error was found to increase with increasing wind shear, caused by higher angles of attack in the top of the rotor area. The direct impact of turbulence intensity and wind shear on power curves was found to be wind speed dependent and not that significant on overall energy production. Finally, combining the knowledge acquired about yaw misalignment and device accuracies, a financial feasibility study was performed to evaluate future implementation of the novel devices for yaw misalignment correction. Since no conclusive evidence was presented that correcting for yaw misalignment could increase power performance significantly, current implementation of such a correction campaign is not recommended. If a deliberate yaw misalignment campaign were to be performed, however, the impact of yaw misalignment on turbine performance should be quantifiable and expectations are that implementation of novel devices should be financially feasible.