Wind turbine blade

Abstract

A wind turbine blade is disclosed, at least 50% of the surface of which is covered with a self-adhesive, thermoplastic film. A method of manufacturing and repairing such a wind turbine blade is also disclosed. A two layer thermoplastic film suitable for covering the surface of a wind turbine blade is also disclosed. The film comprises a surface layer and a lower layer. The surface layer comprises 50% to 85% of polyvinylidene fluoride (PVDF), wherein up to 30% of the polyvinylidene fluoride may be replaced by hexafluoropropylene (HFP); and 10% to 45% polymethyl methacrylate (PMMA). The lower layer comprises 10% to 45% of a polyvinylidene fluoride (PVDF) polymer, wherein up to 30% of the polyvinylidene fluoride may be replaced by hexafluoropropylene (HFP); and 50% to 85% PMMA. Optionally the surface and/or lower layer comprises up to 8% UV stabilisers/absorbers; up to 10% matting agent; and up to 40% of an inorganic pigment. The film has an initial gloss of less than 30% when measured with a reflectometer at a angle of 60 degrees.

1 .- 38 . (canceled) 
     
     
         39 . A wind turbine blade at least 50% of the surface of which is covered with a self-adhesive, thermoplastic film, wherein the film is applied in a number of strips. 
     
     
         40 . The wind turbine blade according to  claim 39 , wherein the film is applied in a number of strips arranged to reduce the complexity of curvature of each strip. 
     
     
         41 . The wind turbine blade according to  claim 39 , wherein the edge of one strip overlaps with the edge of an adjacent strip. 
     
     
         42 . The wind turbine blade according to  claim 39 , wherein edges of adjacent strip do not overlap and the join is covered with a further strip of thermoplastic film. 
     
     
         43 . The wind turbine blade according to  claim 39 , wherein edges of adjacent strips do not overlap and the join is painted with a PVDF paint. 
     
     
         44 . The wind turbine blade according to  claim 39 , wherein the thermoplastic film comprises at least one of an aliphatic polyurethane, a vinyl, an acrylic or a fluorinated thermoplastic. 
     
     
         45 . The wind turbine blade according to  claim 39 , wherein substantially all of the blade is covered with the film covering. 
     
     
         46 . The wind turbine blade according to  claim 39 , wherein the thermoplastic film comprises a two layer structure having an outer layer with enhanced weather resistant properties compared to the inner layer. 
     
     
         47 . The wind turbine blade according to  claim 46 , wherein the inner layer has enhanced adhesion properties compared to the outer layer. 
     
     
         48 . The wind turbine blade according to  claim 46 , wherein the inner and outer layers include polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA) with the outer layer having more PVDF than PMMA and the inner layer having more PMMA than PVDF. 
     
     
         49 . The wind turbine blade according to  claims 46 , wherein the layers are co-extruded. 
     
     
         50 . The wind turbine blade according to  claim 39 , wherein the thermoplastic film has an initial gloss of less than 30% when measured with a reflectometer at an angle of 60° with respect to the film surface. 
     
     
         51 . The wind turbine blade according to  claim 39 , wherein the thermoplastic film is less than 300˜m thick, and preferably from 50 to 150˜m thick. 
     
     
         52 . The wind turbine blade according to  claim 39 , wherein the thermoplastic film is porous such that it is air permeable and water impermeable. 
     
     
         53 . The wind turbine blade according to  claim 39 , wherein the adhesive is an acrylic or silicon based adhesive. 
     
     
         54 . A method of manufacturing a wind turbine blade comprising moulding the blade body and adhering a thermoplastic film to at least 50% of the surface of the body, wherein the film is applied in a number of strips. 
     
     
         55 . A method of repairing a wind turbine blade comprising adhering a thermoplastic film to at least 50% of the surface of a worn blade body, wherein the film is applied in a number of strips running between the leading and trailing edges of the blade. 
     
     
         56 . The method of manufacturing or repair according to  claim 54 , wherein the film is applied in a number of strips arranged to reduce the complexity of curvature of each strip. 
     
     
         57 . The method of manufacturing or repair according to  claim 54 , wherein the edge of one strip overlaps with the edge of an adjacent strip. 
     
     
         58 . The method of manufacturing or repair according to  claim 54 , wherein edges of adjacent strip do not overlap and the join is covered with a further strip of thermoplastic film. 
     
     
         59 . The method of manufacturing or repair according to  claim 54 , wherein edges of adjacent strips do not overlap and the join is painted with a PVDF paint. 
     
     
         60 . The method of manufacturing or repair according to  claim 54 , wherein the thermoplastic film is heated shortly before and/or during its application to the blade body. 
     
     
         61 . A wind turbine blade manufactured according to the method of  claim 54 .