Open Air-Cooled Generators for the Use in Wind Turbines

The wind power industry continuously searches for cost reduction measures to reduce the LCoE (levelized cost of energy) of wind turbines. This paper shows how the method of cooling the generator may contribute to a further reduction of the LCoE. In the past it was usual to use completely closed generators with air-to-air cooler or air-to-water cooler like it is standard in larger industrial motors. In a further development step, open aircooling uses the ambient air directly as primary coolant. While changing to an open aircooling several advantages help to reduce investment costs, but this approach also opens up risks, which have to be handled carefully.In this paper the advantages are listed and all important risks are addressed. For each risk adequate counter-measures are presented to mitigate or completely avoid these risks.