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.
Approximately 131 meters in length, a width of 39 meters, an input power of 11.4 MW, 5 300 tons maximum load, an operating platform covering some 3 200 square meters and an installation crane capable of lifting loads weighing up to 800 tons up to a height of 24 meters. These are the key data of the two jackup vessels with identical design that will be built by the Dubai shipyard Lamprell Energy. Delivery is planned in May and September 2012. Their future task: transporting and installing offshore wind energy plants, especially in the North Sea. This is their intended end purpose according to their owner, Fred Olsen Windcarrier AS in Norway.
High performance, maneuverability and reliability are the key requirements for the propulsion system. This is why Fred Olsen has decided in favor of a solution with Voith Schneider Propellers: three VSP ensure propulsion and accurate positioning and bring the naval giants to a sailing speed of 12 knots during crossings.
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 into special effect. 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. During this transitional phase of lifting, the VSP delivers significantly better thrust than other propulsion concepts.
The VSP also allow a simple hull shape. These ships can thus be built with an hydrodynamically efficient design, which has a positive impact on consumption figures and emissions. Voith carried out a relevant model test, during which these advantages were successfully demonstrated. Another feature of the jackup vessel is the intelligent Voith Roll Stabilization (VRS). If weather conditions are difficult - a frequent occurrence in stormy offshore wind parks - the VSP reduces the rolling motions of the vessel.
The North Sea - 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.
Voith Turbo (voithturbo.com), the specialist for hydrodynamic drive, coupling and braking systems for road, rail and industrial applications, as well as for ship propulsion systems, is a Group Division of Voith AG.
Voith (voith.com) is setting the standard in the paper, energy, mobility, and service markets. Established on January 1, 1867, Voith is now one of the largest family-owned businesses in Europe, with 39 000 employees, 5.1 billion euro in sales, and over 280 locations worldwide. Voith is an official partner of the initiative "Germany - Land of Ideas".