Siemens low noise wind turbine blades inspired by silent flight of the owl

Silent operation of turbines is crucial for the success of many onshore wind projects. Siemens has therefore conducted extensive R&D over the last years to further reduce the noise of its wind turbines. An important breakthrough has now been achieved with the launch of a new generation of Siemens’ so-called DinoTail, an aerodynamic blade add-on. The trailing edge fringe of an owl’s wing provided the inspiration for this noise-reducing component.

Owls are silent hunters. Flying without noise allows them to stealthily approach their prey – primarily smaller rodents. This is enabled by a particular structure of the owl’s wings: A serrated, fringed structure at the trailing edge, and small combs at the leading edge of the wings are believed to mitigate the noise of the air flow by generating fine vortices. This effect is now used by a new Siemens invention which optimizes the aeroacoustic performance of rotor blades.

In addition to vortex generators on the blade surface, Siemens now equips trailing edges with a combination of serrations and combs. This combed teeth concept creates fine vortices at the point where the fast air stream from above the blade profile meets the slower flow from below. As a result, the aerodynamic noise from the trailing edge of the blade is reduced significantly.

“In our wind tunnel measurements and field tests, the combed teeth showed a substantial reduction in wind turbine noise at all wind speeds,” reports Stefan Oerlemans, Key Expert, Aeroacoustics, at the technology department of Siemens Wind Power. “This structure that was inspired by owl wings does not compromise the aerodynamic performance.”

As a consequence the noise mitigation does not affect the annual energy production of a wind turbine, Oerlemans explained at a presentation of the concept during the WindEnergy Hamburg 2016 trade show. For noise-constrained sites, the new technology can be used to increase energy production without increasing noise emissions.

The new combed teeth blade add-on will largely replace Siemens’ first generation DinoTail for onshore wind turbines. Serial manufacturing will start soon as part of the Low Noise equipment of the new Siemens wind turbine SWT-3.3-130LN. The new DinoTail Next Generation will also be applied at further new turbine models.