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The Influence of Flexible Towers on the Dynamics of Offshore Wind Turbine Gravity Base Structures

2018-09-25, O’Leary, Kieran, Pakrashi, Vikram, Kelliher, Denis

With offshore wind turbines increasing in size, there is increasing interest in non-traditional support structures. New concepts include lightweight and flexible fiberglass composite towers that have potential benefits over traditional stiff steel towers. The aim of this paper was to assess how the combination of a more flexible wind turbine tower with an offshore concrete gravity base foundation would affect the dynamic response of the structure. The results focus on how the dynamic amplification factors (DAFs) change with varying levels of foundation stiffness during an extreme event (50 year return period extreme event).

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Publication

Optimization of composite material tower for offshore wind turbine structures

2019-09, O’Leary, Kieran, Pakrashi, Vikram, Kelliher, Denis

The focus of this study was to investigate the application of lightweight fiber reinforced composite materials in the construction of offshore wind turbine support structures. A composite tower design suitable for the NREL 5 MW reference wind turbine is presented. The design is based on the most automated and low cost composite manufacturing methods (pultrusion and filament winding) and the conclusions of this study may not be applicable for offshore structures using different composite material construction techniques. The mass of the tower was minimized using gradient based optimization approach. The cost of a composite tower was calculated and levelized cost of energy (LCOE) projections are discussed in comparison with the existing steel tower cost. The study determined that while the composite tower is technically feasible and has a lower mass than a comparable steel tower, uncertainty remains in how it compares economically in terms of LCOE.