While others were about to enjoy their New Year’s Eve dinner, the installation vessel Svanen started installation of the first monopile at Anholt Offshore Wind Farm, and the construction of Denmark’s largest offshore wind farm has now started.
According to the original schedule, Svanen was supposed to start work on 1 January, but the mobilisation of the installation vessel was successfully completed a few days ahead of schedule and it was ready to leave the Port of Grenaa on 27 December. Due to weather forecasts predicting high winds, the departure was delayed, but on 29 December, Svanen headed towards the position.
The next day, on 30 December at 12:25, the first monopile was lowered into the water at Bladt Industries in the Port of Aalborg and tied to a tug that headed for the wind farm. The trip from Aalborg to the offshore wind farm takes around 12 hours for a tug and upon arrival, the installation preparations could be made.
Pile driving started on New Year’s Eve at 17:00hrs and after two hours, the pile had reached its target depth.
What is a monopile?
The Anholt project is based on the well-known monopile concept. The concept entails that a single pile is driven into the seabed. The monopile foundation is a round steel pipe with a diameter of approx 5 metres and a wall thickness of 5-9cm. The length of the monopile is adjusted to the specific location and varies from 37 to 54 metres.
In order to be able to float the approx 450-tonne monopile from Aalborg to the installation site, the pile is sealed by means of two end caps. The caps are removed when the pile is erected and placed at its final position. By means of a large hydraulic hammer, the monopile is driven 18-36 metres into the seabed depending on water depth and seabed conditions.
Anholt Offshore Wind Farm
In 2012-2013, DONG Energy will be constructing Denmark’s next large-scale offshore wind farm between Djursland and the island of Anholt in the Kattegat.
The wind farm will become Denmark’s largest offshore wind farm with a capacity of 400MW and it will cover four per cent of Denmark’s total power consumption with CO2-free power.
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Offshore WIND staff, January 03, 2012; Image: dongenergy