Offshore wind turbines

Cotes Overpressure System


The patented Cotes Wind Overpressure System works by ensuring that the air pressure inside wind turbines is greater than the surrounding air, thus preventing moist, salt-laden air from entering through the many openings.

This specialist Cotes setup also mixes moist, salty air entering the structure with a flow of dry air. This makes the moisture evaporate, and the salt crystallises, making it easy to filter out. The drier, de-salted air can then be used to help protect delicate electronics and other equipment.

Cotes Wind dehumidifiers are compact, lightweight units specially configured for installation inside the nacelles and towers of wind turbines. The dehumidifier is automatically turned on and off in order to maintain any designated relative humidity set point.


How it works


As the name implies, the Cotes Overpressure System works by helping make sure the air pressure inside offshore wind turbines is greater than the surrounding air — thus preventing moist, salt-laden air from entering nacelles and towers through the many gaps and openings.

Salt filtration prevent corrosion

The combined dehumidifier and  desalter at the heart of the Cotes Overpressure System works by mixing the moisture-laden, salty air entering the turbine with dry air.

This then makes the water component in the sea water droplets evaporate, leaving the salts behind in crystalline form. These crystals are like dry dust, making it much easier to filter them out.

These units feature a filter cassette with an exceptionally large filter area as well as an unusually long service life. This prevents the filters from getting blocked by wet, salt-laden air.

Additional cooling

Combining the Cotes Overpressure System with an add-on heat exchanger unit provides a straightforward, reliable way to keep the air around sensitive mechanical equipment and electronics under consistent, controlled conditions.

The air from the overpressure system is cooled with cold air taken from the upper part of the tower and cooled still further by passing over the tower wall.

A 1000m3/hour Cotes Overpressure System can provide as much as 40KWh of cooling effect, with a flow of dry air that’s also free of corrosive salts.

Dealing with humidity and salt

A visual explanation of Cotes Wind Overpressure system.


The Cotes Overpressure System has been nominated as one of 5 major Danish technical innovations for Danish Industry’s 2014 Product Prize.

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