Low-frequency vibrations of the entire wind turbine generator (WTG) can cause high stresses on the tower. These stresses can significantly reduce the lifetime of the tower structure. Furthermore, if the vibrations are too high in the assembly state, e.g. the installation of the rotor blades may become impossible or may only be carried out in a narrow time frame due to weather conditions. Resonant vibrations in particular can be (cost-)effectively reduced by tuned mass dampers.
In bridge construction, dampers have long been tried and tested. Wölfel has designed and delivered dampers for bridges already in the 1970s. In the wind energy sector, the demand for dampers has continuously increased over the past few years.
The following scenarios, in which a TMD.Tower can be used, have emerged:
- Resonance case due to rotor speed and higher harmonics: When starting a WTG, often a resonance is passed through or the WTG should be operated in such a way that the excitations from the rotor (1P, 2P or 3P etc.) are close to a natural frequency of the WTG.
- Excitation by periodic vortex shedding: At certain wind speeds, vortices can periodically detach from the tower of a WTG. Typically, this can become critical for WTGs in the assembled state (without nacelle or rotor blades) or for slender WTGs with a low second tower bending natural frequency.
- Wave excitation in offshore WTGs: Wave excitation can become critical if the first natural frequency of a WTG is very low because the energy of the wave excitation is particularly high at these frequencies. The trend towards more and more powerful WTGs in greater water depths and the retention of the monopile foundation concept intensify this problem.
Depending on the type of wind turbine and the overall context, it has to be assessed whether the expected vibrations are problematic and which solution is the most suitable for vibration reduction.
The passive dampers used by Wölfel are characterized by a high robustness. Tailored to the specific application, we offer individually adapted dampers to successfully solve the respective problem.
- Support in the conception of the WTG
- Concept development for different variants/series of WTGs
- Detailed design including relevant aspects, such as:
- Component selection
- Selection and design of the optimal damping concept
- Braking or locking mechanism
- Optional frequency adjustment
- Thermal proof
- Complete documentation, including proof of structural integrity etc.
- Support with any necessary certifications
- Prototype construction
- Experimental verification
- Serial delivery
Particularly notable is the direct contact within a cooperation with LISEGA, which makes it possible to provide large production capacities of the highest quality at short notice.
Today’s slender and high wind turbine towers are increasingly subject to vibrations, which are typically caused by wind and wave loads or rotor imbalances. A leading german wind turbine OEM requested for Wölfel to develop and manufacture a solution for vortex induced vibrations (VIV) in the 2nd tower bending mode for turbines in wind farms across the world. The aim is to reduce critical fatigue loads during vortex shedding events. Relatively high tower frequencies above one hertz, a cost efficient design and fast delivery are only some of the challenges within this project.
Please contact us personally
We would be pleased to support you in solving your problem concerning "Wind turbine vibrations" and advise you on questions regarding our system and service offerings in the areas of structural health monitoring, vibration reduction, sound and noise as well as structural design.