Design of support structures for offshore wind turbines - Wind Power Generation and Wind Turbine Design - page 567

Typically the support structure is divided in two main parts:

1. The turbine tower

2. The foundation

The turbine tower normally consists of two or three sections. The design of the
tower is usually provided by the turbine manufacturer. The tower is often installed
in the same shift as the nacelle and the rotor.
The term foundation here refers to the turbine support structure, excluding the
tower. It is essentially located below and at the water level. The function of the
foundation is to direct the loads on the support structure into the seabed.
Many types of foundation for offshore wind turbines already exist. Essentially,
the manner in which they are connected to the seabed determines how they are
classifi ed. The choice of foundation type depends primarily on the local water
depth at the proposed site.

3.2 Foundation types

3.2.1 Monopile
The most frequently used foundation type is the monopile. It commonly consists
of a foundation pile and a transition piece, on top of which the turbine tower is
placed, as shown in Fig. 12.
Foundation piles are made from steel plates which are rolled and welded together
to form a cylindrical section. The conventional method of installation (see Fig. 13)

Figure 12: Foundation types, from left to right: monopole, tripod, jacket, GBS,
fl oating.