The effect of ocean waves on offshore wind turbines

The Ocean has a varying surface roughness where the roughness length is determined by the characteristics of the waves. In this paper, a method is established where the roughness length of the ocean is calculated from the wind speed and the fetch length. The fetch length depends on the wind direction and a case study is performed for a wind turbine exposed to wind blowing in two opposite directions: from the shore and the sea. For each case, the vertical wind speed distribution is calculated in order to study the influence that the direction of the wind has on the annual energy production. The potential for using a site-specific offshore turbine design, dependent on the prevailing wind direction, is also explored.

Keywords: ocean waves, offshore wind turbines, wind speed-calculations