Reliability, availability and maintenance aspects of large-scale offshore wind farms, a concepts study

The DOWEC projects aims at implementation of large wind turbines in large scale wind farms. part of the DOWEC project a concepts study was performed regarding the achievable reliability and availability levels. A reduction with a factor of 2 with regard to the present state of the art seems fairly easy achievable. This is however not sufficient for application at more exposed sites. Availability levels are lower than targeted, but moreover the O&M cost turn out to be substantially higher than initially anticipated. The main cause for the high O&M costs is the rather frequent need for an expensive external crane vessel. A second design round is necessary to reconsider the reliability levels adopted for almost all concepts. Furthermore a more "farm like design approach" is needed to reduce major maintenance cost and increase availability.