Offshore wind turbines

DONG nysted offshore wind farm

Less downtime and longer service life


The Nysted Offshore Wind Farm (Nysted Havmøllepark) lies about 10 km out to sea off the southeastern tip of Denmark. It is one of the world’s largest wind farms, and consists of eight rows of nine Siemens Wind Power 2.3CS MW turbines.
The Nysted wind farm began commercial operations in December 2003, and is operated by DONG Energy, one of the leading energy groups in northern Europe.


If not tackled effectively, the high levels of moisture in sea air – often saturated with corrosive salts due to the offshore environment – can have serious effects on the structures, operating uptime and maintenance budgets of offshore wind turbines.
DONG Energy is responsible for the operation and maintenance of the Nysted facility, and therefore has a special interest in the reliability and durability of these wind turbines. Sending technicians out by boat to undertake service and repairs is time-consuming and can be dangerous – and always involves substantial costs.

High reliability, minimal maintenance

Despite now having been in non-stop service for more than a decade, less than half of the dehumidifier units have ever shown faults. According to Jesper Nielsen, the DONG Energy manager responsible for maintenance of the Nysted wind turbines, “They’re strongly built and service-friendly. They just keep on working as intended, and we rarely see anything wrong.”
The only maintenance the Cotes dehumidifiers normally require is the changing of the filters once a year, carried out in conjunction with the annual maintenance visit. If anything is wrong, technicians simply replace the whole dehumidifier with a spare and take the one needing attention back to the workshop on land. This helps DONG Energy keep its maintenance costs to a bare minimum.

“There is no sign of corrosion, condensation or any problems of that kind. Inside, our wind turbines and the electrical installations are pretty much in as good a state as the day they were commissioned.”

Jesper Nielsen, DONG Energy


  • Stable, controlled conditions inside nacelles and towers
  • Lower ISO 9223 classification requirements mean lower costs for materials, coatings and components
  • Fewer service interruptions and less downtime
  • Longer service life, higher, more stable revenue and better return on investment
  • Significantly lower service and maintenance costs


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For more about tackling humidity in offshore wind turbines,
please contact Mogens S. Nielsen +45 5167 2903