ENDOW: Efficient Development of Offshore Windfarms

Abstract

The objective of the ENDOW project is to evaluate, enhance and interface wake and boundary-layer models for utilisation in developing offshore windfarms. The model hierarchy will form the basis of design tools for use by wind energy developers and turbine manufacturers to optimise power output from offshore wind farms through minimised wake effects immediately downwind of wind turbines and optimal grid connections. The initial focus of the project was to use databases from existing offshore wind farms (Vindeby and Bockstigen) for the first comprehensive evaluation of offshore wake model performances. The six wake models vary in complexity from empirical solutions to the most advanced models based on solutions of the Navier-Stokes equations using eddy viscosity or k-epsilon turbulence closure. One of the wake models is also being coupled with a full aeroelastic model for the calculation of wind loads on the turbines. Parallel research includes comparison of a local-scale stability/roughness model with a mesoscale model focusing on boundary-layer development within and over a large offshore wind farm, and particularly the influence of large scale thermal flows. A new experiment was conducted using SODAR immediately downwind of offshore wind turbines to examine vertical wind speed profiles to hub-height and beyond in near-wake conditions and wake dispersion to assist in model development and evaluation.