Document Type

Honors Project On-Campus Access Only

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Advisors:

Dr. James Heyman, Macalester College

Dr. Sanjay Arwade, University of Massachusetts Amherst

Abstract

Large offshore wind turbines (OWTs) offer an attractive renewable energy option for the coastal United States, but their support structures’ high costs remain a concern. Current OWT designs largely ignore damping from foundation-soil interactions, although small increases in damping can significantly reduce the materials cost for OWT support structures. This study examines how incorporating foundation damping into turbine models affects structural demands in a monopile-supported OWT with yaw error. Simulations in the aeroelastic code FAST model the dynamic behavior of the monopile-supported NREL 5 MW reference turbine under wind and wave loads. Structural demand and reduction of such demand is studied for the full range of yaw errors (–180° to +180°), three levels of foundation damping, and four wind-wave combinations. Including foundation damping reduces structural demands regardless of yaw angle and wind-wave combination, although percent reductions are lowest at yaw angles with high initial demand. However, for scenarios important to the design process, incorporating foundation damping reduces structural demands by 0.3% to 18.6% (with most reductions at a few percent), depending on the scenario. This suggests that incorporating foundation damping into OWT design guidelines could moderately reduce the maximum structural demands required of designs, consequently lowering the cost of OWTs.

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