Rotary Tower:

The offshore wind power plant of power output 5 MW with a rotary tower, which is showed on Drawing 1 and Drawing 2, is 90 - 100 metres high and the axis of the tower's tilt under the force of the wind is +10 metres. The amount of steel necessary to produce that tower is comparable to an amount needed for a stationary tower, so no cost savings can be achieved in this respect.
A service platform is at the level of +15m.
The advantage of using the rotary tower consists in that it may be put in a vertical position, together with the entire power plant, on its foundation with the use of a winch. It is a cheap and absolutely safe method.
A rotary tower for an offshore wind power plant with the power output of 2x5=10 MW shall be approx. 150m high and the consumption of steel per each unit of rated power in the case of that tower will be approx. 40% bigger than in the case of the tower described above.
The structure of an offshore wind power plant with two rotors positioned one above the other has the following advantages as compared to single-rotor facilities:

• higher concentration of power output on one foundation;
• double rated power output per 1 ha of the wind farm area;
• shorter cable connections within the wind farm area;
• higher production of electrical energy by the rotor the hub of which is situated at the level of approx. +210m.

(more information)

The enclosed Drawing 1 and Drawing 2 present an offshore wind power plant with one power generating set fixed firmly on the rotary tower. The power plant positions itself, together with the rotor, perpendicularly to the wind direction, steered by a back rudder. The tower, shaped as a frame, rests via bearings mounted on horizontal pins which are part of the rotary sleeve. The rotary sleeve rests on the foundation via a thrust bearing, whereas two radial bearings hold the sleeve in a vertical position. Through the sleeve runs an stationary pipe which cases the cable transmitting the power out. The rotary sleeve construction is presented on Drawing 3. The back part of the tower rests on two double floats, which during strong wind go deeper into the water and when the weather is calm return to the surface, but which, however, cannot detach themselves from the water surface due to the application of water ballast.
The rotary tower is made from commercial steel tubes of enhanced strenght.
For a power plant of output 5 MW, the diameter of the tubes is within the range of 800 - 1200 mm.
For a power plant of output 2x5 MW, the diameter of the tubes is within the range of 800 - 1500 mm.