Riblet coating is also referred to as shark skin coating because, like the skin of sharks, it features microscopically small grooves that reduce the formation of vortices and, in turn, frictional resistance. The coating was developed at the Fraunhofer I nstitute for Manufacturing Technology and Advanced Materials IFAM in Bremen and tested for the first time on the blades of a wind turbine as part of the EU-funded project riblet4wind .
Wind tunnel tests had previously shown an impressive 10% increase in aerodynamic efficiency. The coating has now been tested on an older turbine in Bremerhaven that does not yet have an adjustable angle of attack. The seven project partners also developed an automated process for applying the riblet coating to the turbine’s rotor blades. According to the Fraunhofer IFAM , although the exceptional weather conditions during the five-month test phase prevented clear quantification of the increased output, an improvement was nevertheless evident. Further tests with newer and more modern turbines are scheduled to follow.