The wind turbines
Vattenfall has opted for the world's most powerful wind turbine, MHI Vestas V164-8.0 MW as the windmill of choice for Horns Rev 3. This wind turbine type has been tested in the test centre in Østerild in Thy, Denmark. In October 2014, this type of turbine set the world record for wind turbines by generating 192,000 kWh in the space of one day.
With its wingspan of 164 metres, the V164-8.0 MW is stroked by the wind over an area corresponding to 21 large villa plots, or roughly 21,000 square metres. The hub height will be 105 metres, while the nacelle (engine housing) is roughly 20 metres long and 8 x 8 metres in height and breadth. The nacelle is designed so that the main bearings, clutch, gearbox and generator can be lifted out of the housing in connection with maintenance.
The Horns Rev 3 wind turbines will stand on solid foundations of monopiles, which, using a special vessel, are struck around 25-39 metres down into the seabed. Each monopile is between 50-70 metres long and weighs between 420 and 706 tonnes.
On the monopile, an approx. 32 metre-long transition piece is placed. The monopile and the transition piece are connected with a flange joint, which is secured with large nuts and bolts that combined extend the monopile by 26.2 metres. The lowest segment of the tower is fastened securely onto the transition piece, after which the other components of the wind turbine are installed.
In connection with the installation of the transition piece one must take care to ensure it will stand completely vertical, if the monopile has not to been struck completely straight down into the seabed. The transition piece is installed over the sea's surface with a variety of installations such as boat landing, ladders and interior and exterior work platforms as well as pipes for the submarine cables.
The transformer platform and the cables
Energinet.dk is responsible for building and operating the installations that will lead the power from Horns Rev 3 to land. These consist of:
- A transformer platform, which collects the power from the turbines and turns up the electrical voltage from the turbines from 33 kV to 220 kV.
- A 220 kV submarine cable for the transporting of the wind energy to land.
- A cable station for the regulation of the electrical voltage at the transition from submarine cable to land cable.
- A land cable for transporting the wind energy to an existing substation on land.
During the construction of the wind turbines, they will also be connected by cables to the transformer platform, which is constructed in the sea in the middle of the farm. From there, the current is transported via a 30 centimetre-thick submarine cable, which is hosed or dug about a metre down under the seabed. The cable is led to shore at Houstrup Strand just outside Blåbjerg Klitplantage. On the final stretch in to the beach, the cable is hosed deeper in order to avoid the sea currents and waves exposing the cable.
On land, the cable is dug even deeper down under the beach and the cliffs and further underground to a substation 50 kilometres from the coast and from there onwards to the substation in Holsted. From here, the current goes up into the air and is transported onwards to the electricity utilities via an overhead power line on high voltage masts.