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Safe on the seabed

We can see what sticks up out of the sea – a big tower with rotor blades that are seventy meters long. But what does it look like underwater?

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Norway has Europe’s largest wind power potential. The energy resources represented by wind power are ten times greater than the country’s existing hydropower resources. And wind power offers as much energy potential as the oil Norway currently pumps out of the North Sea.

Extracting energy from wind results in virtually no CO2 emissions, and support for renewable energy is strong. Sea-based windmills are invisible from the land, have a modest effect on the environment, and are supported by most political groups.

But realizing this dream of reliable and competitive offshore windmills requires massive investments in research and development. Anchoring a 100-150 meter high windmill tower to the sea floor is usually more expensive and technically more demanding than pouring a foundation on land. In particular, the weight of the nacelle (the nose-shaped protrusion where the blades and the generator are mounted) has to be reduced to build wind power plants to produce 10 MW each, which is considered the optimum. New technology shows this is possible.

Today, the most common design for offshore wind turbines uses a monopile technology, including the offshore windmill park at Hornsrev in Denmark. The Owec Tower has been developed in Norway, and is being used in a pilot project outside Scotland in water depths of up to 45 meters. Hywind and Sway are technologies that have been designed for the depths and weather conditions found in the North Sea. StatoilHydro has ownership interests in both. Sway is expected to install a full-scale offshore windmill between 2010 and 2012.

These technological advances are comparable to the advances made in Norwegian oil and gas production in the North Sea and in the far north. What was considered to be technologically impossible or unprofitable 20 years ago is now a reality.

Text: Tor Harald Monsen
Graphic: Mads Nordtvedt
Source: Professors Geir Moe and Tore Undeland, NTNU

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