
doi: 10.1115/1.4046567
Abstract For a turbine mounted on a floating platform, extreme induced loads can be increased by up to 1.6 times those experienced by a turbine situated on a fixed base. If these loads cannot be reduced, towers must be strengthened which will result in increased costs and weight. These tower loads would be additionally exasperated for a pitch-to-feather controlled turbine by a phenomenon generally referred to as “negative damping,” if it were not avoided. Preventing negative damping from occurring on a pitch-to-feather controlled floating platform negatively affects rotor speed control and regulated power performance. However, minimizing the blade bending moment response can result in a reduction in the tower fore-aft moment response, which can increase the tower life. A variable-speed, variable pitch-to-stall (VSVP-S) floating semi-submersible wind turbine, which does not suffer from the negative damping and hence provides a more regulated power output, is presented. This incorporates a back twist blade profile such that the blade twist, starting at the root, initially twists toward stall and, at some pre-determined “initiation” point, changes direction to twist back toward feather until the tip. Wind frequency weighting was applied to the tower axial fatigue life trends of different blade profiles and a preferred blade back twist profile was identified. This had a back twist angle of −3 deg and started at 87.5% along the blade length and achieved a 5.1% increase in the tower fatigue life.
690, Hydraulic engineering. Ocean engineering, 600, tower axial fatigue life, dynamics of structures, blade back twist, 620, structural mechanics and foundation, pitch-to-stall, design of offshore structures, ocean energy technology, floating offshore wind turbine (FOWT), TC, floating and moored production systems
690, Hydraulic engineering. Ocean engineering, 600, tower axial fatigue life, dynamics of structures, blade back twist, 620, structural mechanics and foundation, pitch-to-stall, design of offshore structures, ocean energy technology, floating offshore wind turbine (FOWT), TC, floating and moored production systems
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