Static and Fatigue Analysis of Composite Turbine Blades Under Random Ocean Current Loading

Abstract

The objective of this paper is to investigate how U.S. National Renewable Energy Laboratory (NREL)‐designed modeling tools commonly used for wind turbine blade design and analysis can be applied to the design of ocean current turbines (OCT). Design, static analysis, and fatigue life predictions of a horizontal-axis, ocean current turbine composite blade were investigated using NREL’s PreCom, BModes, AeroDyn, FAST with seawater conditions. PreComp was used to compute section properties of this OCT blade. BModes calculated mode shapes and frequencies of the blade. Loading on a turbine blade in the Gulf Stream at a South Florida location (26^o4.3’N 79^o50.5’W, 25-m depth) was calculated with AeroDyn. FAST was then used to obtain the dynamic response of the blade, including flap and edge bending moment distribution with respect to blade rotation. Static analysis was performed by using a combination of Sandia’s NuMAD and ANSYS. Palmgren-Miner’s cumulative fatigue damage model was employed with damage estimation based on the material fatigue property data in DOE/MSU Composite Material Fatigue Database. During service life, OCT blades are subjected to cyclic loads and random ocean current loading. Hence, the blades experience repeated and alternating stresses, which can lead to fatigue failure. These loads were weighted by rate of occurrence from a histogram analysis of in situ measurements conducted by the Southeast National Marine Renewable Energy Center (SNMREC).