Robust estimation of wind turbine design loads for service lifetimes of 30 to 50 years that are based on field measurements of a few days is a challenging problem. Estimating the long-term load distribution involves the integration of conditional distributions of extreme loads over the mean wind speed and turbulence intensity distributions. However, the accuracy of the statistical extrapolation is fairly sensitive to both model and sampling errors. Using measured inflow and structural data from the LIST program, this paper presents a comparative assessment of extreme loads using three distributions: namely, the Gumbel, Weibull and Generalized Extreme Value distributions. The paper uses L-moments, in place of traditional product moments, to reduce the sampling error. The paper discusses the application of extreme value theory and highlights its practical limitations. The proposed technique has the potential of improving estimates of the design loads for wind turbines.

All materials have an influence from the processing parameters for structural performance, but composite materials have a much more intimate materials/processing/structural performance connection due to their macroscopic inhomogeneities. In this paper, a link is provided between processing paramers, material architecture, and mechanical performance for various material architectures. In particular, a simple formula is provided to understand the fiber volume of a given part. This fiber volume is then linked with the fatigue performance. These data are indicative of the influence of processing pressures on laminate fiber volumes, independent of processing techniques and can be useful to wind turbine blade manufacturers to prepare processing conditions, a priori, to minimize expensive trial and error manufacturing development.

Full-scale wind tunnel tests of the NREL Unsteady Aerodynamics Experiment (UAE) Phase VI permitted unprecedented control and measurement of inflow to the UAE rotor. This in turn has allowed in-depth validation of the AeroDyn wind turbine aerodynamics software. This validation began with comparison of simple cases (i.e., fixed yaw, fixed pitch, no teeter), with results presented last year [2]. Among the findings of that study was the significant increase in section lift along the rotor blades due to the 3–dimensional flow over the UAE rotor. This delayed stall was not adequately accounted for in the AeroDyn model. This continued validation effort looks into delayed stall and the static and dynamic behavior of the Generalized Dynamic Wake (GDW) model in AeroDyn. Validation is accomplished through comparison of UAE data and simulation results for the following cases: • Uniform inflow (upwind, zero yaw error), • Step pitch changes on an operating rotor, • A teetering rotor at various yaw angles, and • Downwind rotor released into flee yaw from various initial yaw error positions. Results presented allow us to draw several conclusions. The Du and Selig delayed stall correction adequately models the increase in C L , but the suggested decrease in C D of that model does not agree with observations in the data. The time lag coefficient in the GDW model agrees well with observations in the rapid pitch change UAE data. The phase of teeter response for the GDW model agrees better with data than for the equilibrium wake model. Dynamic stall provides significant additional damping to the teeter motion. The choice of wake model also greatly affects the yaw rate in the yaw release simulations.