Wind Farm, Egmond aan zee
The Egmond aan Zee wind farm is the first big wind farm build in the North Sea off the Dutch coast. The farm comprises 36 wind turbines, each with a capacity of 3 MW. Together they supply enough renewable electricity for more than 100,000 households
Each of the 36 wind turbines stand on a monopile, a big steel pile that is driven into the sea bed. The diameter of this pile is 4.6 metres and the plate thickness is 5-6 cm. The length of these monopiles varies from 40 to 50 metres, depending on the sea bed conditions and the depth of water at the site. The piles each weigh roughly 250 tons. After driving, the top of each pile will be five meters under the water table and the base around 30 metres under the sea bed.
A “transition piece”, around 25 metres high and clearing the water by around 13 metres, is placed on the pile. Attached to this transition piece are work platforms, ladders and a berthing facility for boats. The transition piece has a diameter of 4.3 metres and is lowered over the top of the monopile. The space between the monopile and the transition piece is sealed by an inflatable grout seal of Trelleborg Ridderkerk. This seal is designed to close a gap of several centimeters and simultaneously resist an internal pressure of few bars. Grouting the space above the grout seal with cement, results in a very strong joint between the transition piece and the monopile.
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A floating crane is used to install the tower and the turbine. The vessel is specially adapted to install offshore wind turbines and can lift more than 100 tons to a height of over 80 metres. The vessel berths close to a monopile and erects the 53-metre long tower onto the transition piece. The top section of the turbine – the nacelle – is then lifted onto the tower. The nacelle contains the generator of the wind turbine. |
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Source: www.noordzeewind.nl