The wind speed profile at offshore wind farm sites

Using Monin-Obukhov theory the vertical wind speed profile can be predicted from the wind speed at one height, when the two parameters Monin-Obukhov length and sea surface roughness are known. The applicability of this theory for wind power prediction at offshore sites is investigated using data from the measurement program Rdsand in the Danish Baltic Sea. Different methods to estimate the two parameters are discussed and compared. Significant deviations to the theory are found for near-neutral and stable conditions, where the measured wind shear is larger than predicted. A simple correction method to account for this effect has been developed and tested. As