Sönke Siegfriedsen

Preventing corrosion in offshore wind energy facilities

Technical field
Engines, pumps, turbines
A European pioneer of wind energy, Sönke Siegfriedsen developed a system that protects offshore wind units from corrosive sea air, making possible Germany's first offshore wind park.

Siegfriedsen is a wind energy fanatic. As a young student at the Lübeck University of Applied Sciences in 1979, he built his first wind energy system from spare car parts and placed it on the roof of the school. The unit had an output of only 0.5 kilowatts - and was so loud that professors forbade him to run it during class hours. By the late 1990s, the wind expert from northern Germany had already formed his own company, Aerodyn, to engineer wind-energy solutions for manufacturers all over the country. It's no surprise, then, that Siegfriedsen in 1998 was one of the first German engineers to tackle the issue of offshore wind energy.

Siegfriedsen knew that harsh conditions at planned offshore wind park locations called not simply for adapted land wind units, but for entirely new solutions. With that in mind, he set out to develop a completely different system capable of coping with the corrosive salt air that blows at sea. As it was, sea air was terrible for a wind unit's generator and gear areas and regularly caused short circuits, making long-term maintenance very costly.

Once they set to their task, the research team led by Siegfriedsen had a brilliant idea: a system housed inside the wind unit takes in outside air and filters out salt and any other particles using an air processing system similar to that used at semiconductor plants. The treated air builds up inside the tower, creating a positive pressure that prevents untreated outside air from entering the unit.

In 2007, wind energy plant manufacturer Multibrid, based in Bremerhaven, acquired all the patent rights to Siegfriedsen's system. However, Siegfriedsen has kept for himself the right to exploit the anti-corrosive patent commercially in China, a market he deems too exciting to pass up. In February 2008, Siegfriedsen moved into his new office in Shanghai, where Aerodyn plans to grow significantly in the coming years.

How it works

The basic precondition for the long life of an offshore unit is its permanent protection form the corrosive sea atmosphere. That's why in Multibrid's key unit that uses Siegfriedsen's protection system, the Multibrid M5000,  the nacelle and hub are hermetically sealed against ambient air.

An air treatment system is located at the bottom of the tower, taking in ambient air and filtering out water and salt particles. Using the treated air, a level of overpressure is built up inside the tower, securing a controlled volume flow through the entire turbine with the help of a pressure-difference monitoring system.

The internal air pressure prevents the intrusion of any untreated air from outside. In addition, the temperature in the nacelle can be adjusted by varying the pressurised airflow.


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