Alpha Ventus offshore project: major milestone accomplished

AREVA Multibrid has successfully completed an important milestone in the installation of the Alpha Ventus project, Germany’s first offshore wind farm.
Six tripods, the foundation structures for the 5 MW M5000 wind turbines, now tower out of the water 45 kilometers off the island of Borkum.

"This successful milestone results from AREVA’s efforts to propose innovative, reliable and cost-effective solutions for the wind offshore market. Lessons learnt from this first Alpha-Ventus erection phase already benefit all players involved and will help the wind offshore development in Germany." declared Felix Debierre, Managing Director of AREVA Multibrid.

The Alpha Ventus wind farm is a pioneering offshore joint project for the energy suppliers EWE, E.ON Climate & Renewables and Vattenfall companies. Almost 70 people worked tirelessly from April 17 to June 1 to install the 6 foundation structures at a depth of 30 meters.

Alpha Ventus is the first German wind farm to be built at sea under real offshore conditions. The construction, erection, operation and integration into the power grid that will be tested in the Alpha Ventus research project will provide essential experience in developing future commercial offshore wind farms.  In 2008, German authorities approved a total of 32 projects.

Major components such as the tripod foundation structures, the nacelle, the hub and the blades are transported to Eemshaven in the Netherlands, the nearest seaport to the Alpha Ventus wind farm.

The M5000 turbine has since the very outset been developed for use under harsh conditions on the open sea.

The blades are manufactured by PN Rotor in Stade, Germany. They are loaded onto the “Mega Motti” barge and transported to the port of Eemshaven.

The length of a blade reaches 56.3 m. The rotor blades catch the wind over an area about the size of one and a half football fields.

A floating crane lifts the 710-ton, 45m-high tripod foundations one-by-one, transports them to the anchoring area and sets them down on the sea bed.

The tripods are being used as a foundation structure for the very first time.

Truly a world first!

The "jack-up" barge is a platform that rides the swell and is used to ram the piles and assemble the wind turbine. Once “jacked up”, the platform stands anchored to the sea bed on its four supporting columns and houses a work platform approximately 10 meters above the water level, with an underwater ram for anchoring the foundations to the sea bed. The three legs of the tripods are “nailed” to the sea bed with a 35-40 meter-long pile, and embedded in the pile sleeve by filling it with concrete.

The next steps will be to secure the steel tower segments to the foundation before installing the turbine, nacelle and rotor.

The tower consists of three parts.

The lower tower section will be joined to the substructure with a steel flange and to the foundation, one after the other, and fixed together.

Source: http://www.multibrid.com/index.php?id=4&L=1

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