Eneco: Hundreds of Offshore Wind Turbines Have This Chink in the Armor
- Operations & Maintenance
Following the recent media attention given to Eneco’s Princess Amalia Wind Farm (Prinses Amaliawindpark) and its grout problem, the company yesterday said that hundreds of turbines comprised in first-generation offshore wind farms are facing this issue.
The foundation construction of the Princess Amalia Wind Farm was done according to the DNV GL certified standard, including the design which was common ten years ago in the offshore wind industry.
It has been found that the design can cause sagging of the part between the foundation and the tower itself. This happens because this middle part, the so-called transition piece, is slid over the foundation and then fixed with grout, a cement adhesive.
The reason that the tower of the wind turbine was not simply bolted with a ‘flange’ to the foundation, is that it was not yet possible to install a foundation into the seabed which would stand entirely straight. The tower had to be balanced to stand straight, hence a transition piece was used to put the tower in the right position.
Due to forces of waves and wind, despite model calculations, the adhesion of the grouted connection has reduced over time, which leads to a light subsidence, ranging from millimeters to a few centimeters. There is no inclination of turbines, or loss of production, Eneco stated.
Since it involves a design flaw that needs to be repaired in time to avoid future damage or potentially unsafe situations, Eneco is recovering all wind turbines of the Princess Amalia Wind Farm. To this day, 22 out of 60 wind turbines have been repaired, and the remaining 38 turbines will be repaired this year.
Eneco will bear the cost of this recovery, totaling EUR 47 million, because the contractor was not found responsible for the reliability of the design. Moreover, this design flaw was not covered by the insurance policy. The company said that a share of these costs has already been paid in the years 2012-2014.
Eneco stressed that the grout problem did not lead to loss of production and the offshore wind farm has experienced a very high production in recent years.
The developer also explained that this “childhood disease” does not occur in new generations of offshore wind farms, such as Eneco Luchterduinen, because now an advanced design is applied ‒ a flange connection instead of a grouted one.