Advocating for the replacement of the hub height wind speed with a rotor equivalent wind speed

�2 Wind profiles influence the turbine performance. We will analyze measurement campaigns in order to show the influence of the atm. conditions, the topography and the surface roughness on the wind profile. At the same time we will perform BEM simulations using both measured profiles as well as simulations using an exponential shear profile of varying exponent, in order to show possible implications of the equivalent wind speed definition used. The two formulas, representing the wind speed corresponding to the energy (REWS, 1) and mass (WAWS, 2) through the turbine rotor will be used. BEM simulations of the el. power (left figure above) vs. an exponential shear for a constant wind speed at hub height, show an increased turbine performance for shear exponents above 0.56. The right figure presents the percentage difference of the two equivalent wind speed expressions for unity speed at hub height. Obviously large performance differences may be experienced for high shear values following the two expressions which will influence on our perception of the turbine's performance.