CASE STUDY. The Nysted wind farm in the Baltic Sea off the Danish coast.
Photo: Gunnar Britse
WIND ENERGY | INDUSTRIAL SERVICES
some time. “To give an example, in the case of the Horns Rev wind farm off the western coast of Denmark, which was built in 2002, the coatings used were of a rather basic kind,” Damsgaard continues.
Within a few years of operation, the structure exposed extensive surface damage. That experience made it clear that coating systems must be applied in multiple layers to achieve a buffer effect. The reason is that pores and in- consistencies are not likely to occur at the same locations in each layer.
Damsgaard refers to another example: At the Nysted wind farm, 120 kilogrammes of protective zinc anodes had been embedded into the foundations. Some of the anodes became inactive but could not be located. This shows how important it is to document every construc- tion detail. With the appropriate documentation at hand, it would be possible to check other anodes from the same batch to reduce future repair efforts and costs.
The first wind farm, with a rated power of five megawatts, was built in the Baltic Sea off the Danish coast in 1991. Nevertheless, offshore wind turbines are still a relatively new and unexplored field for all parties involved. There is no extensive experience as yet. And there are no gen- eral rules or standards to rely on. “The importance of high quality standards and reliable monitoring systems cannot be overemphasized,” said Daniel Engel, Vice President Ma- terials and Products with Germanischer Lloyd.
To arrive at an optimized, economically and ecologically feasible anticorrosion concept for offshore wind turbines, experts from all industries involved must co-operate close- ly. Experience gained by one industry may benefit the oth- ers. Bimetallic corrosion, for example, can be avoided by selecting appropriate materials or integrating other protec- tive measures during the design stage.
Similarly, wind turbine designers may draw on experience gained by shipyards in implementing the challenging VOC guidelines, which limit emissions of volatile organic sub- stances. And then there is the paradigm of anticorrosion strat-
egies for offshore oil platforms. These should be adopted and modified to provide sustainable
protection for wind turbines.