Wind energy plants are increasingly built offshore. Their installation is carried out by giant special vessels. During the second and third quarter of 2012, two such jackup vessels will be launched in Dubai. They will be the first vessels of this kind fitted with three Voith Schneider Propellers (VSP) each.
The identical jackup vessels will be approximately 131 meters long, 39 metres wide, have an input power of 11.4 MW, 5300 tons maximum load, an operating platform covering some 3200 square meters and an installation crane capable of lifting loads weighing up to 800 tons up to a height of 24 meters. Three VSP ensure propulsion and accurate positioning and bring the naval giants to a sailing speed of 12 knots during crossings.
Installing Wind Energy Plants in the North Sea
The vessels will be built by the Dubai shipyard Lamprell Energy and will transport and install offshore wind energy plants, especially in the North Sea. Delivery to the owner, Fred Olsen Windcarrier AS in Norway, is planned in May and September 2012.
Advantages in Maintenance, Maneuverability and Efficiency
A typical design characteristic of these vessels are the four columns or “jackup legs“, which can be lowered to the bottom of the sea, lift the vessel and turn it into a stable operating platform in the sea. For this process, the vessels have to hold their position with extreme precision. This is where the advantages of the VSP in direct combination with the dynamic positioning system come in. It only takes three seconds for the drives to reverse. This prevents the ship from making leeway, which is normally inevitable due to the swell of the sea. The moment when the vessel is lifted from the water is particularly critical.
Hydrodynamically Efficient
The VSP also allow a simple hull shape creating a hydrodynamically efficient design, which has a positive impact on consumption figures and emissions. Another feature is the intelligent Voith Roll Stabilization (VRS). If weather conditions are difficult the VSP reduce rolling motions.
One of the Windiest Regions in the World
Together with regions such as Cape Horn at the southernmost end of Argentina, the North Sea belongs to the world’s windiest areas. 90 percent of the time there are winds with speeds of more than four meters per second. This makes feeding energy from wind parks into the grid commercially viable. The energy yield on the high seas is 50 percent higher than that of plants on the mainland. This advantage in efficiency plus the fact that they have a lesser impact on the scenery of coastlines and shorelands make offshore wind parks increasingly attractive for electricity companies.
