The characteristics of offshore winds are becoming increasingly attractive for the development of wind energy in the coastal areas. Stronger and less gusty winds allow to produce more wind power than on land. In addition, offshore wind farms solve the problem of shortage of land areas (especially near big cities consuming a lot of electricity) and do not alter the habitual surrounding landscapes.
With the introduction of floating wind turbines, offshore wind energy is no longer limited to the construction of wind farms within the depths of up to 30-40 meters (the construction of foundation bases at great depths make the projects unprofitable). The floating feature of design adds a number of advantages: high mobility, maintainability and ease of recycling.
The coastline often doesn’t have enough space for placement of stationary turbines (with bases driven into the sea bed) due to steep underwater coastal slopes or other local features.
The potential of floating wind farms is huge. Structures are assembled on land, and then towed to such marine areas, where wind characteristics allow to obtain a capacity factor of about 50%.
The installed unit capacity of floating wind turbines starts at 2 MW (Statoil’s projects in the North Sea) and reaches up to 7 MW (the project of consortium of Japanese producers off the coast of Fukushima).
Constructions of floating bases for wind turbines are divided into three types:
1. Semi-submersible on a triangular platform.
Wide platform using water as ballast provides high stability of the structure and resistance during wind storms.
2. TLP – Tension-leg platform.
Tense steel ropes attached to the sea bed, keep the floating platform and diagonal guywires make the structure more rigid.
3. SPAR-platforms, platforms with underwater bases of cylindrical type.
A large cylinder or rod fixed and floating by means of ropes. Thanks to the large counterweight, SPAR-base has the highest possible stability.
China, the USA, Japan, Great Britain and Portugal intend to actively develop offshore wind energy using floating wind farms.
It is assumed that it is due to the floating wind turbine technology, the cost of offshore electricity will drop to the level of “land”.