DONG Energy has completed the decommissioning of the world’s first offshore wind farm, the 4.95MW Vindeby built in the Danish Baltic Sea near the island of Lolland in 1991.
Vindeby offshore wind farm was constructed as a demonstration project which was to prove whether it was possible to generate green power offshore.
Following more than 25 years of successful operational life, DONG Energy decided to decommission the wind farm. In March 2017, contractors commenced the dismantling of the eleven wind turbines.
Blades, nacelles and towers were dismantled and 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, DONG said.
"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," said Leif Winther, Senior Lead Business Developer in DONG Energy.
"In cooperation with the winning contractors, we developed the dismantling method and entered a long process with the authorities to obtain all necessary permits."
Throughout the dismantling process, up to 20 workers took part in the work, which took place in periods when the weather permitted offshore work. Water depths of only two to five metres added to the challenging conditions, as only a limited selection of vessels were able to work in the area, DONG said.
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 a noise barrier concept. Prior to this, however, some of the blades will become part of a research project at DTU Risø. Components that are not immediately reusable have been transported to a certified recovery company.
"And the tale of the world's first offshore wind farm off Vindeby on Lolland will be preserved for posterity with one wind turbine from Vindeby Offshore Wind Farm becoming part of the exhibition at the Danish Museum of Energy in Bjerringbro in Jutland," said Winther.
During its entire lifetime, Vindeby offshore wind farm had generated 243GWh of power. This corresponds to what seven of the largest offshore wind turbines today can generate in a single year - or what DONG Energy's largest project to date, Hornsea One, can generate in 17 days.
Photo and video: DONG Energy