Energy & physicsPaper· 2021Published
Floating offshore wind turbines
Where to place dampers on the platform of a floating wind turbine to reduce its vibrations. Published in Energies.
Full paperIn short
Floating wind turbines sway with wind and waves, and those vibrations wear them down and cost them efficiency. One way to damp them is with tuned mass dampers (TMDs), which usually sit in the nacelle or the tower, where space and weight are tightly limited.
In this work we moved them to the floating platform. Using NREL's 5 MW barge-type model, simulated in FAST, we studied how the turbine's response changes when one or two dampers are placed in different positions and orientations.
On the platform, the dampers mainly reduce the platform's pitch and, to a lesser extent, the tower's vibrations. The platform can carry heavier dampers, but every added mass breaks the symmetry, so position matters, and two dampers placed symmetrically stabilise better than one.
As a next step we propose replacing them with wave energy converters, forming a hybrid wind and marine system that generates energy as well as stabilising the turbine.
Abstract
Floating offshore wind turbines (FOWT) are subjected to strong loads, mainly due to wind and waves. These disturbances cause undesirable vibrations that affect the structure of these devices, increasing the fatigue and reducing its energy efficiency. Among others, a possible way to enhance the performance of these wind energy devices installed in deep waters is to combine them with other marine energy systems, which may, in addition, improve its stability.
The purpose of this work is to analyze the effects that installing some devices on the platform of a barge-type wind turbine have on the vibrations of the structure. To do so, two passive control devices, TMD (Tuned Mass Damper), have been installed on the platform of the floating device, with different positions and orientations. TMDs are usually installed in the nacelle or in the tower, which imposes space, weight, and size hard constraints. An analysis has been carried out, using the FAST software model of the NREL-5MW FOWT. The results of the suppression rate of the tower top displacement and the platform pitch have been obtained for different locations of the structural control devices. They have been compared with the system without TMD.
As a conclusion, it is possible to say that these passive devices can improve the stability of the FOWT and reduce the vibrations of the marine turbine. However, it is indispensable to carry out a previous analysis to find the optimal orientation and position of the TMDs on the platform.