Stabilization of Offshore Semi-Submersible Wind Platform with Tuned Mass and Tuned Inerter Dampers
Background
Wind tends to be stronger, and more reliable over the ocean than on land, and many wind turbine manufacturers are developing increasingly larger offshore wind turbines and platforms. Offshore wind also brings wind closer to the 80% of the US’s electrical demand occurring in coastal or Great Lakes regions. Floating platforms are required for depths greater than 60 m, but vibrations of these platforms result in much higher turbine fatigue and stresses compared to onshore turbines. Around 80-95% of offshore wind is expected to be installed on floating semi-submersible structures, and thus reducing vibrations of this platform structure is critical.
Innovation
A Tuned Inerter Damper design reduces weight of the secondary mass and may provide a backup source of power to run essential turbine systems or contribute additional power to the grid
Modification of OpenFAST source code to incorporate further structural control (both tuned mass and tuned inerter damper)
1/50th-scale testing with both tuned-mass and tuned-inerter damper prototypes
Approach
Lagrangian analysis in MATLAB was be used to compare pitch and heave movement between baseline, TMD, and TID configurations in regular wave conditions with no wind.
Design of TMD and TID state space models in OpenFAST’s structural control module were implemented to compare pitch and heave measurements between these configurations under both wind- and wave- load.
Test of a 1/50th Scale-Model in a wave tank in three configurations (baseline, TMD, and TID) and under both free decay and regular wave conditions.
Achievement
Both the MATLAB and OpenFAST models perform as expected and show good agreement.
Optimization of TID parameters in MATLAB shows promising results for OpenFAST and scale testing moving forward.
Future Work
Continued development of MATLAB code to incorporate wind forces and estimate energy output from TID
Prototype testing with TMD and TID in regular wave conditions and with ducted fan fan at pre-determined speeds to simulate wind thrust