Design optimization of hull size for spar-based floating offshore wind turbines
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© 2018, Springer Nature Switzerland AG. A newly evolving concept in utility-scale floating wind turbines is investigated through design optimization. The ideal hull length is selected from seven new designs, based on optimizing the trade-off between minimizing structural weight and maximizing electricity harvest. The seven new spar-buoy designs have drafts ranging from 62 to 120 m. Each floater hull has been developed in conformance with industry-standard structural guide API Bulletin 2U. Performance is assessed with the Loose software using time-domain analysis and irregular winds and waves. The simulation method is based on multi-body theory in Euler space, which does not rely on small-angle assumptions. Nonlinear hydrostatic restoring forces and moments are derived for large rotational angles in the pitch-roll-yaw Euler angle sequence. Environmental forcing by wind is computed using aero-elastic theory. A new individual pitch control (IPC) method based on DISCON control routine (Jonkman) is investigated as a possible means to improve generating efficiency. The pitch angle of each blade is individually controlled relative to a mean angle computed by DISCON to maintain the ideal angle of attack by removing the angle change caused by inclining tower. A comparison of the generating efficiency between IPC and traditional collective pitch control shows that IPC is not an effective way to increase output power.
author list (cited authors)
Gao, J. u., & Sweetman, B.