Importance sampling of severe wind gusts

An important problem that arises during the design of wind turbines is estimating extreme loads with sufficient accuracy. This is especially difficult during iterative design phases when computational resources are scarce. Over the years, many methods have been proposed to extrapolate extreme load distributions from relatively short time series...

Towards spatially constrained gust models

With the trend of moving towards 10-20MW turbines, rotor diameters are growing beyond the size of the largest turbulent structures in the atmospheric boundary layer. As a consequence, the fully uniform transients that are commonly used to predict extreme gust loads are losing their connection to reality and may lead to gross over dimensioning....

Self-starting of a small urban Darrieus rotor: Strategies to boost performance in low-Reynolds-number flows

Like many vertical-axis wind turbines (vawts) of the Darrieus type, Turby fails to achieve a fully passive start-up. Experiments indicate that there is a band of negative torque—often referred to as dead band in literature—somewhere in the tip speed range 0.5 B l B 1.6. The reason behind this is that, unfortunately, the power coefficient...

Feasibility study of the WindNok: a wind turbine integrated in the roof of a farm building