Wind-turbine optimizer ROMO Wind, together with Vattenfall, carried out a performance measurement project at Nørrekær Enge wind farm in Denmark using 13 Siemens 2.3-MW wind turbines. The goal was to compare the power-curve measurement results of an IEC-compliant met mast, a nacelle LiDAR, and the iSpin spinner anemometer.
The results show that only the iSpin technology enables reliable and replicable wind-turbine performance measurements on all turbines in the wind farm. Within a confidence interval of 95%, the comparable turbines were observed to be operating within only 0.3% of AEP to each other and the power curve verified reference turbine.

The Nørrekær Enge wind farm, commissioned in 2009, consists of 13 Siemens SWT 2.3-93 wind turbines at 80-m hub height. The layout of the park is shown below together with the IEC compliant met mast.
The raw measurement data is available in an online data sharing portal and interested experts are invited to analyze and confirm all data. The systemic advantage of the iSpin spinner anemometer is that it measures the wind where it first hits the turbine – directly at the spinner.
The Nørrekær Enge data now proves that iSpin can be described as the best nacelle-based wind measurement technology and performance measurement method available today:
- The difference between iSpin and met mast AEP measurements was only 0.4%.
- The total variation in AEP among the turbines was within 2.1%. Removing outliers due to curtailment, yaw misalignment, and differing installation.
- The scatter of power curves measured by the spinner anemometer is significantly the remaining nine turbines were operating within only 0.3% of AEP to each other less than the scatter of the met mast and LiDAR measurements, as the iSpin measurements are undisturbed by terrain effects and wakes from other turbines in the wind farm.
- Using the spinner anemometer, operators can cost-effectively monitor the performance of any turbine in any wind farm at any time.
“We are more than happy with the results and the use of iSpin. We are able to precisely measure the performance of every single wind turbine in the wind farm,” said Anders Sommer, Senior R&D Engineer Wind Power at Vattenfall. “The results help us to efficiently optimize the performance of all turbines in a wind farm.“
Jan Nikolaisen, Co-CEO of ROMO Wind, commented: “The current industry standard of using a met mast is too expensive, impractical, and imprecise for the industry’s needs. With iSpin we offer a tool that can cheaply and repeatably provide transparency and verification on wind turbine performance and, more importantly, on the performance of a whole wind farm. Better performance measurements will help the entire wind industry.”
Nikolaisen added: “Our data-sharing portal, which we have established together with Vattenfall, shows the kind of collaboration we are seeking: we invite all interested specialists to verify or falsify our iSpin uses ultrasonic technology to measure the wind at the spinner. In this way, accurate information on the wind conditions in front of the rotor can be gathered. This enables operators to measure and monitor the power curves, as well as to check whether their turbines are aligned for the best possible yield.”
At the same time, the data allows for optimised wind farm management and load reduction, which prolongs the total life of the The iSpin technology was developed by the Technical University of Denmark (DTU) and has been continuously tested since 2004. iSpin is a wind measurement technology which is not dependent on a specific manufacturer, and is designed for permanent installation.
Data sharing portal: www.romowind.com/open-data
Filed Under: News