of Offshore Wind Parks
The picture to the right shows the Danish electrical transmission grid.
Major power stations are shown in yellow.
Total generating capacity was some 10,000 MW in 1998.
Present and future offshore wind parks with a total of some 4,100 MW
are shown in white and blue.
The western and eastern part of the country are not directly connected,
but are connected to the German and Swedish electrical transmission systems
using AC (alternating currency transmission lines). The rest of the connections
to Sweden, Norway, and Germany are DC (direct current) connections.
Grid connection of offshore wind parks is not a major technical problem
per se, in the sense that the technologies which are involved are
well known. Optimising these technologies for remote offshore sites will
be important, however, to ensure reasonable economics.
The first commercial-sized offshore wind farms in Denmark will be located
some 15-40 km (10-25 miles) from shore, at water depths from 5 to 10, possibly
15 metres. The park sizes will range from 120 to 150 MW. The first parks
(year 2002) will be built using the present 1.5 MW generation of wind turbines,
which by then will have been through an onshore operational period of some
Undersea cabling connecting offshore parks to the main electrical grid is
a well known technology. Undersea cables will have to be buried in order
to reduce the risk of damage due to fishing equipment, anchors, etc. If
bottom conditions permit, it will be most economic to wash cables into the
seabed (using high pressure water jets) rather than digging or ploughing
cables into the bottom of the sea.
Inside the large 120-150 MW wind parks being planned in Denmark, it is likely
that 30-33 kV connections will be used. In the middle of each park there
will probably be a platform with a 30 to 150 kV transformer station, plus
possibly a number of service facilities.
Connection to the mainland will be done using 150 kV connections.