Definition of the equivalent atmospheric stability for wind turbine fatigue load assessment

M C Holtslag, W A A M Bierbooms, G J W van Bussel
2014 Journal of Physics, Conference Series  
In this paper the dependence of wind turbine fatigue loads on atmospheric stability is assessed. It is shown that fatigue loads depend strongly on stability, and highest loads occur for very unstable conditions. For a given hub height wind speed one can define an equivalent atmospheric stability that corresponds to the same cumulative loads as if one performs an infinite amount of simulations for all stability conditions that may occur. It is shown that stability, conditionalised to hub height
more » ... ised to hub height wind speed, is approximately normally distributed and the equivalent stability corresponds well to the mean stability for a given hub height wind speed. If one follows the IEC guidelines for offshore sites, neglecting atmospheric stability, one will compute higher cumulative lifetime fatigue loads (≈ 10%). This overestimation is caused by conservatism in both wind shear and turbulence levels, which is explicitly shown for the turbulence levels analyzed in this paper.
doi:10.1088/1742-6596/524/1/012110 fatcat:oo4m4hjv7bg6jgphlc5vodbelu