The final rotor blade of the 24th wind turbine was successfully installed at the Nordsee Ost offshore wind farm over the weekend. This marks the halfway milestone of the total 48 wind turbines at RWE’s offshore wind farm, three months after the installation kicked off.
“In a football match we would now have reached halftime. At the Nordsee Ost wind farm, however, the second half is already in full swing without interruption because, apart from the 24 completely installed turbines, all towers with the associated nacelles already stand in the water,” explained Marcel Sunier, Project Director for the Nordsee Ost wind farm at RWE Innogy. “Thanks to the good cooperation especially on our installation vessel ‘Victoria Mathias’ we successfully concluded the installation of the tower segments and nacelles early in October.”
Since the Victoria Mathias installed the towers and nacelles in the past few months, the second installation vessel Friedrich Ernestine is installing the rotor blades of the wind turbines. For the first time the decision was taken to use the so-called single-blade assembly, a process in which the rotor blades are not installed as pre-assembled rotor star, but all the rotor blades are fitted individually to the hub at sea.
The restrictions under maritime law on the Weser River had only granted restricted permission for the installation vessel’s departure with a pre-installed rotor star on board due to its width. The three rotor blades of the 6 MW turbine, built by Senvion, cover an area of 126 meters. This is the equivalent of about two football fields.
“Meanwhile the conditions have changed in favour of the rotor star assembly,” Sunier explained. The local authorities are now in favour of the installation vessel leaving with the pre-installed rotor star. “
The marine police have now granted a permit for seven departures each with two rotor stars on board. We are now in a position to assemble the rotor star from the ‘Victoria Mathias’ in the traditional way. We expect this to save additional time. End of last week our installation vessel left the base port for the first time with two pre-installed rotor stars on board and reached the construction site during the weekend, where installation started immediately. The installation of the first rotor star is already finished. Weather permitting, we should have installed all the wind power systems completely by the end of the year.”
The individual components of the 6 MW turbine of the company Senvion are impressive with their huge dimensions: At a height of some 160 meters from sea level to the tip of the blade the wind power system is higher than the Cologne cathedral. The nacelle has a weight of approx. 320 tons and about the size of a single-family home. It accommodates the machine components such as transmission and generator. The tower consists of two individual segments and has a total length of 70 meters and a weight of over 240 tons. Each rotor blade is 60 meters long and weighs some 23 tons. This is equivalent to the weight of about six full-grown elephants.
“The construction of the Nordsee Ost wind farm is making good headway,” Sunier emphasised. “Since the middle of March, all the foundations have been anchored firmly in the seabed, in June we completed the inter-array cables and in July the substation was erected at sea. We intend to commission the wind farm completely next spring. However, the first wind power systems are due to be put into service and to feed power into the grid as early as this autumn.”
Following its completion, the Nordsee Ost offshore wind farm will have an installed capacity of some 295 MW and supply the equivalent of some 300,000 residential households with electricity per year. Equipped with the currently most powerful offshore turbines, Nordsee Ost ranks among the largest commercial wind power projects off the German coast.