World’s first offshore wind farm dismantled by Dong at Vindeby

Dong Energy has dismantled the Vindeby offshore wind farm in southeast Denmark that was built in 1991 as the world’s first demonstration project to prove it was possible to generate green electricity at sea.

The offshore wind industry has since matured into one of the fastest-growing segments of renewable energy generation worldwide with a capacity of 16.1GW. Most of that is still concentrated in northern Europe, but offshore wind is rapidly spreading to Asian markets and the US.

After generating power for more than 25 years, the 4.5MW array near the island of Lolland, Vindeby will be preserved for posterity with one wind turbine as part of an exhibition in the Danish Museum of Energy in Bjerringbro in Jutland, says Leif Winther, senior lead business developer at Dong.

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"This is the first time we're dismantling an offshore wind farm, but luckily, we've been able to draw on our vast experience from constructing offshore wind farms and working offshore," Winther says.

"In cooperation with the winning contractors, we developed the dismantling method and entered a long process with the authorities to obtain all necessary permits."

In March 2017, contractors started the dismantling of the 11 wind turbines. Blades, nacelle and tower were taken down individually by a mobile crane and placed on board a jack-up vessel.

The concrete foundations were broken down on site, mainly by hydraulic demolition shears and a hydraulic hammer, but also by breaking down the concrete using milling tools. The broken-down concrete and reinforcement structures were subsequently collected.

At water depths of only two to five metres, only a limited selection of vessels were able to work in the area.

All wind turbine components and parts from the foundations were shipped to shore in Nyborg harbour. The components will be reused as much as possible as spare parts for other wind turbines, while the blades will be reused in an innovative noise barrier concept.

During its entire lifetime, Vindeby has generated 243GWh of power. This corresponds to what seven of the largest offshore wind turbines today can generate in a single year.

Vindeby marked the humble beginnings of offshore wind power and has given a significant helping hand to the industry, which in Denmark alone employs 30,000 people, has an annual revenue of about DKr90bn ($14.4bn) and an export volume amounting to around DKr60bn.