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Foundation Structures

 

There is still a tendency to use the largest possible offshore wind turbines with higher outputs for new projects. These projects are being planned at ever greater distances from the coast and therefore often at greater depths. A suitable type of foundation must be selected for each site. The aim here is both to ensure the stability of the structure over its service life and to use cost-optimised foundations. Because: the costs of the foundations contribute to a large part of the total investment costs of offshore wind turbines. Further requirements for offshore foundations are "simple" and fast production processes, "simplified" handling during the installation process and general suitability for low-noise installation work.

For the reasons given above, the Monopile foundation concept has evolved over the years from gravity, jacket, tripod or tripile foundations to the most commonly used foundation variant. The proportion of WTGs newly built in 2018 with monopiles as foundation structures is over 90 percent. At the end of 2018, 76 percent of the offshore wind turbines were monopiles, 6 percent gravity foundations and 8 percent jackets. The foundation types Tripod (2 percent), High-Rise Pile Cap (6 percent), Tripile (1 percent) remain at a low level. This also applies to the technology of floating foundations (floating < 1 percent), although there are signs of a technology shift here.

 

 

Highcharts Example
Data source for image

 

Data source: [Fraunhofer IEE]

 

 

Die einzelnen Konstruktionen eignen sich für unterschiedliche Standortbedingungen. Schwerkraftfundamente und High- Rise Pile Caps stehen vorwiegend in küstennahen und flachen Gewässern. Die lediglich in Asien verwendeten High-Rise Pile Caps befinden sich im Schnitt in 7 Meter Wassertiefe und 9 km Küstenentfernung. Monopiles, zunächst nur in Wassertiefen bis etwa 20 Meter eingesetzt, werden inzwischen auch in Wassertiefen über 30 Meter verwendet. Die Gründungsfundamente Tripod und Tripile liegen mit durchschnittlich 96 km in größter
Entfernung zur Küste. Schwimmende Strukturen befinden sich bei durchschnittlich 85 Meter Wassertiefe zurzeit noch mit nur wenigen Einzelexemplaren in der Erprobungsphase. Die folgende Abbildung zeigt, in welchen Küstenentfernungen und Wassertiefen die unterschiedlichen Gründungsstrukturen eingesetzt werden.

 

 

 

 

Water depth and distance from the shore of different foundation designs

Data source: [4C Offshore]