Analysis of loads for wind turbines in inhomogeneous terrain

The different load-generating mechanisms resulting in increased loads on wind turbines erected in a complex terrain wind farm are investigated. The analysis is based on measurements carried out on two Danish Danwin 23 - 180 kW wind turbines in the Alta Mesa wind farm in San Gorgonio Pass near Palm Springs, California.

The wind turbines are represented by one in the front row of the wind farm and one inside the wind farm. The terrain in the wind farm and around it is severely inhomogeneous and thus the wind inflow to the two turbines is highly affected by both the complex terrain and for the turbine inside the wind farm also by the wakes from the turbines in front.

This wind inflow is analyzed in detail and major differences are observed compared to the wind inflow to a wind turbine errected in homogeneous terrain. These differences concerns the vertical wind shear, the variation in wind direction and the turbulence characteristics in all directions. A detailed analysis of the structural loads corresponding to the different wind inflow characteristics, leads to the conclusion for this wind farm layout that the most important parameter in the wind inflow is the turbulence intensity in the longitudinal direction. (au) (8 tabs., 115 ills., 14 refs.).