Vattenfall Hails Installation of One of World’s Largest Offshore Wind Turbines (UK)

Vattenfall yesterday hailed a world class engineering achievement with the installation off Cumbria of one of the world’s largest offshore wind turbines.

The 153 metre wind turbine, weighing in at 661 tonnes, is the first of 30 to be installed in the coming months at the Ormonde Offshore Wind Farm. At night on the 22 March the REpower 5M 5 megawatt (MW) wind turbine was installed by the crew of the SeaJack, the specially designed wind turbine installation vessel, and a team of Vattenfall and REpower engineers.

The SeaJack, carrying components for two wind turbines, will now move onto a second foundation and install the other turbine in its cargo.

Vattenfall’s Project Manager for Ormonde Matthew Green said: “Safely and carefully installing a 661 tonne, 153 metre wind turbine, in the Irish Sea is a world class engineering achievement. I would like to thank everyone on the project for their professionalism as we now look to make good progress towards completing the project in 2011.”

He added: “The efficient installation of these wind turbines, some of the most powerful ever installed, has required us to make advances in the way we transport them to site. Never before have two turbines of this scale been assembled and then transported in a single trip and we are very proud of this achievement.”

Frank Zimmermann, Head of the Offshore Business Unit of REpower Systems AG: “We had the opportunity to install our first offshore wind turbines in the UK, Germany and Belgium, far shore and in deep water. Benefitting from this experience we are now taking the first step towards large scale wind farms at an industrial level, with installing 30 turbines in Ormonde. One particular challenge is to coordinate the numerous different parties out on the open water together with Vattenfall. Here, the profound and detailed planning of methods and interface handling, done over the last almost two years, is paying off!”

The REpower 5M is among the largest offshore wind turbines in the world and the Ormonde Offshore Wind Farm will be the largest commercial deployment of the wind turbine.

The installation process

The two REpower 5M Turbines were sailed from Harland & Wolff, Belfast on board the installation vessel SeaJack. Each shipment of two turbines consists of two nacelles, two lower tower sections, two upper tower sections and two fully assembled rotors (hubs and blades) which are ‘seafastened’ horizontally on top of a specially designed tower.

Upon arrival at the first turbine location the vessel was positioned alongside the pre-installed foundation carefully so as to avoid seabed cables. When the installation barge was at the desired location the vessel was jacked up on four legs to raise the hull, crane and cargo clear of the sea. Personnel were then transferred onto the turbine foundation via a foot bridge and preparations were made to receive the first lower tower section. The tower sections, each weighing over 100 tonnes, were lifted using pre-installed lift beams from the deck of the SeaJack to the foundation transition piece. Once in place, the technicians on board the foundations started the bolting operation which makes up the flanged connections securing the towers in place. Once both tower sections were in place, the 315 tonne nacelle was the next component to be installed to the top of the tower, 95m above sea level.

The 126m diameter rotor lift completed the installation of the turbine and due to its size was the most critical lift. When operational, the swept area of the rotor is greater than two football pitches, so when lifting this size of blade from horizontal to vertical it was necessary that the wind was moderate and that the nacelle was orientated to minimise the area exposed to the wind. Once the rotor hub was presented to the face of the nacelle, the final series of connections were made to complete the installation.

As soon as the rotor is safely secured, the installation vessel will leave the site to install another turbine at the next planned location. Technicians will remain on site to complete the turbine mechanical works and will spend the subsequent days working out of Barrow to ensure that the turbine is able to generate power as soon as is possible.

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Source: vattenfall, March23, 2011