Master thesis : Fatigue Methodology of Floating Offshore Wind Turbine Platform & Tower in Composite Materials

Abstract

The offshore wind power industry is gaining popularity for generating large amount of electricity around the globe. In recent years, it has developed wind turbine and floater technologies, where abundant wind resources and open sea areas are ideal for developing wind farms. A wind turbine needs a reliable structural design to harvest energy from surrounding environmental loads. However, it is common for offshore wind turbines to be exposed to high dynamic loads, eventually causing fatigue in their substructure. To overcome the above limitation, a composite material for the wind turbine is a practical alternative. It reduces the maintenance and upkeep costs associated with the steel offshore. It also reduces the tower mass and, the support mass. In this master thesis, methodology for the fatigue assessment of a composite wind turbine tower that can be used on a floating offshore platform has been discussed and finite element models are developed. Additionally, different dynamic analyses and finite element routines are incorporated into the design process of the turbine tower model. The thesis report has presented the fatigue methodology for the Floating Offshore Wind Power Platform and Turbine Tower in Composite Materials. First, it explains why fatigue life modelling methods for metals and alloys, already developed and validated, cannot be directly applied to composites. Hence, to develop an efficient fatigue model for composite materials, it is imperative to understand the specific mechanisms that cause the damage to a composite material under fatigue and static loading. Next, a particular emphasis has been placed on designing and developing turbine towers using composite materials. The model developed has been run under different load conditions. The repetitive environment load is analysed using BV's in-house software OPERA to evaluate global structural response. At last, the SN curves and CFL diagrams have been used to figure out fatigue life damage using the python script.