Wind Power In Stormy Waters

Wind Power In Stormy Waters


14 kilometres off Denmark’s West coast in the North Sea, in some of Europe’s roughest waters, the world’s first major offshore wind power plant has since December 2002 produced enough energy to run 150,000 Danish households. Eighty 2.0 MW turbines from the world’s leading wind turbine manufacturer Vestas are sited across an area of 20 sq. km.

With a water depth between 6.5 and 13.5 metres and frequently rough conditions, the Horn’s Reef project (named after the area in the North Sea) is a dream come true, as well as a challenge which has demanded a combination of experience and new thinking.

“There are other offshore wind parks in the world but everybody agrees that Horn’s Reef is the first ’real’ offshore wind park because of its size and its placement in the North Sea. So far, all other offshore parks have been placed close to land in protected waters“, says project manager Jens Bonefeldt of the engineering company Tech-wise. “The North Sea is considered to be one of the roughest stretches of water in the world.”

The Horn’s Reef project has proved innovative on several fronts. The turbine foundations, which were supplied by MT Højgaard, are mono-pile foundations that have been installed in the seabed by a huge hydraulic hammer. Vestas itself has been responsible for setting up the turbines. In cooperation with the transport company A2SEA, Vestas created a special ship which can hold steady while the turbines are being set up, and besides that has also developed a brand new on-line monitoring system.

The turbines on Horn’s Reef are serviced by specially trained technicians. If conditions are too rough for them to reach the turbines by sea, they can be flown out to them instead. This is possible because the nacelles are equipped with special platforms on the top, so that the technicians can be winched down onto the turbine. All the necessary tools are inside the nacelle, and there are bunks for an overnight stay should it be necessary. There are food rations, a radio, lifejackets and other emergency equipment.

Just as servicing offshore turbines presents an extra challenge, the same can be said of monitoring them. All the turbines at Horn’s Reef are equipped with an advanced remote monitoring system called VestasOnline™. The new system is able to process and transfer large amounts of vital data to the wind farm’s main control centre – and then operate the wind farm as a power plant.

“The new system is a great advance in wind farm management and makes it possible to manage remote sites, both onshore and offshore,” Jens Bonefeldt says.

During the installation of Horn’s Reef, Vestas has been building up further expertise in its Offshore Knowledge Center. “The great thing about Horn’s Reef is that up to now, most of our offshore knowledge has either been quite theoretical or has come from very small projects in protected waters,” says Egon Poulsen, head of Offshore at Vestas Group. “At Horn’s Reef, we have actually had a chance to test our vision and all the theories, and most of the planning was pretty much on target.”

The proof, according to Egon Poulsen, is a new contract for the first offshore wind farm in the UK. The farm will be installed during the summer of 2003, 7 kilometers off the coast of Wales near Rhyll, where the average water depth is 12 meters and the tide-water difference is 8 meters. The farm, which will comprise 30 Vestas V80-2.0 MW will be owned and operated by National Wind Power Ltd. The farm is the first of 18 projected offshore wind farms that are being planned for installation around Great Britain and Northern Ireland.