One of the key decision in a wind farm is the type of tower that will be used to reach the desired hub high.
In the infancy of the wind industry, lattice towers where used – you can still see them in very old wind farm, for instance in southern Spain.
However, this technology was not really a good fit when the hub high reached 50+ meters. The following step has been to switch to tubular steel tower with a circular section, which has been (and still is) the standard technical solution.
In parallel, the concrete tower solution has been developing. This can be either hybrid (the lower part of the tower is made of concrete and the upper section of still) or a full concrete solution (except for a small element on top of the tower that act as a sort of adapter between the last section and the nacelle.
The components of the tower can be either precast in an existing factory or cast in situ in a factory specifically built for the project, usually in the wind farm area. Obviously, this second alternative make sense in big wind farms, with dozens of wind turbines.
Regarding the assembly process, there are different technical solutions in the market. However, in general each tower section is composed by several elements (usually from 2 to 6) that must be assembled together with vertical joints to compose a complete tower section.
After, the different tower sections are assembled together and united with horizontal joints.
The joints are usually filled with grout, and a system of cables run through the tower usually all the way down to the foundation.
The foundation of a concrete tower is usually smaller and different from the standard shallow foundations used for steel towers.
Is a concrete tower a good choice?
As often, the answer depends on many factors.
From an economical point of view, to simplify the problem, concrete towers are usually competitive when the wind turbine is high (100 m. and above).
From the technical perspective, there are several advantages of concrete over steel:
- No restriction in the geometric design
- Greater stiffness (good for resonance) and damping
- Greater maximum hub height possible
- Smaller foundation due to increased weight
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Obviously, this second alternative make sense in big wind farms, with dozens of wind turbines.