Fraunhofer IWES Testing Large Wind Turbine Aerodynamics

German research institute Fraunhofer IWES is measuring the aerodynamics of wind turbines with a rated power of more than five megawatts (MW), said to be the first-ever validation of its kind in the world.

The aerodynamic properties of the Adwen AD 8 wind turbine, with a rated power of 8MW and a rotor diameter of 180 metres, are being measured at the site in Bremerhaven and compared against complex models in the scope of the “HighRe” research and development project.

The project is funded by the Federal Ministry for Economic Affairs and Energy (BMWi) with a budget of EUR 4 million. This way it shall be assessed whether the model calculations used to date are also valid for large wind turbines, which will primarily be built offshore in the future, the institute said.

The “HighRe” project (aerodynamics with high Reynolds numbers for the large offshore wind turbines of the future) conducts complex measurements of the wind field and the aerodynamic reaction of the wind turbine in the near future. With these findings of real wind conditions both in front of and on a wind turbine, it will become possible to analyze and understand the precise aerodynamic effect on rotor blades at such large dimensions. The wind field is scanned using three overlapping LiDAR laser scanners in front of the wind turbine and complemented with additional wind measurements in front of and behind the turbine. At the same time, sensors are installed on the turbine and rotor blades to record these conditions precisely.

Even prior to the start of the HighRe project, Fraunhofer IWES was able to demonstrate that there are significant deviations in the models of yawing large wind turbines. The model used for such cases was developed almost 20 years ago on considerably smaller turbines. The picture is similar for a large number of wind turbine aerodynamics models. The model calculations are based on small turbines. To compensate for this, computational fluid dynamics (CFD) methods are being used increasingly. However, to date, it has only been possible to check the accuracy of CFD methods on small model turbines. The HighRe project changes this deficit in wind energy aerodynamics completely, according to Fraunhofer IWES.

“The HighRe project is a great opportunity for wind energy research and the wind energy industry. With this project, the safety and accuracy of wind energy aerodynamics can be adapted to real turbine development. This represents a huge potential for the wind energy industry,” said project manager Dr. Bernhard Stoevesandt, summarizing the prospects of this project.