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Highlights

The Monin-Obukhov similarity theory has been used to extrapolate the wind speed with height in MABL.

For the development of the method and its validation, data were taken from the FINO 3 research platform.

The observed deviations are acceptable for neutral and unstable atmospheric stability.

The application of the energy calculation of a commercial wind turbine presents satisfactory results.

Abstract

Offshore wind energy has more favorable wind conditions than its terrestrial counterpart, so a reliable estimate of the wind potential in the atmospheric boundary layer is of great importance to justify the energy viability of new offshore wind farms. In this paper a method is developed to determine the annual energy production of a wind turbine in open sea, which takes into account the continuous variations of the atmospheric stability and the roughness of the sea surface, from the measurements made with masts of measurements, where meteorological data are obtained at levels much lower than those of the hub. As an application, the wind speed is first extrapolated with the height, from the measurements obtained in the German research platform FINO 3, in the North Sea, during the years 2015, 2016 and 2017. Then, it is applied to the calculation of the electrical energy of a 3.0 MW commercial wind turbine, with the hub at 80 m above the sea surface. The results obtained were compared with the data of the wind speed provided at this height by the platform, and its application to the calculation of the energy, presenting acceptable deviations in all the years of study.

Keywords

Wind energy

Offshore wind farms

Atmospheric stability

Sea surface roughness

Energy production

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