Off-shore foundations of wind turbines

The experimental wind farms at Vindeby and Tunø are both founded on concrete caissons and the task at hand therefore was to develop alternatives for use in greater water depths and construction in a greater number than the 11 and 10 resp. in the experimental wind farms. Based on data from the two locations, Rødsand and Horns Rev, foundations have been developed for use in water depths of 5-11 m and for wind farm sizes of approx. 100 windturbines. The main results are that steel is the most cost-effectiver material and that prices only rise slightly with increasing depth in the interval of 5-11 m. A study of the installation procedure indicates that it is realistic to plan with an installation period of one summer season for a wind farm consisting of 100 windturbines. Three different types of foundations have been developed: Monopile, tripod and gravity foundations. The price difference between the three types is insignificant at the depths investigated. The project progressed according to schedule and the results have been studied with interest both in Denmark and abroad