wind turbine blade

Abstract

There is provided a wind turbine blade at least 50% of the surface of which is covered with a self-adhesive thermoplastic film. By applying a self-adhesive thermoplastic film to the blade, the need for a gelcoat or the paint is eliminated. It is estimated that the thermoplastic film will take a similar time to apply as the gelcoat and/or paint. However, it does not require any further treatment once it has been applied thereby reducing significantly the work involved in finishing the blade. Also, the thickness of the film is precisely controlled in advance of its application to the blade ensuring that a surface with a uniform thickness is produced.

1 . A wind turbine blade at least 50% of the surface of which is covered with a self-adhesive, thermoplastic film. 
     
     
         2 . The blade according to  claim 1 , wherein substantially all of the blade is covered with the film. 
     
     
         3 . The blade according to  claim 1 , wherein the thermoplastic film comprises a two layer structure having an outer layer with enhanced weather resistant properties compared to the inner layer. 
     
     
         4 . The blade according to  claim 3 , wherein the inner layer has enhanced adhesion properties compared to the outer layer. 
     
     
         5 . The blade according to  claim 3 , 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. 
     
     
         6 . The blade according to  claim 3 , wherein the layers are co-extruded. 
     
     
         7 . The blade according to  claim 1 , 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. 
     
     
         8 . The blade according to  claim 1 , wherein the thermoplastic layer is less than 300 μm thick. 
     
     
         9 . The blade according to  claim 1 , wherein the film is porous such that it is air permeable and water impermeable. 
     
     
         10 . The blade according to  claim 1 , wherein the adhesive is an acrylic adhesive. 
     
     
         11 . 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. 
     
     
         12 . The method of manufacturing according to  claim 11 , wherein the film is applied in a number of strips running between the leading and trailing edges of the blade. 
     
     
         13 . The method of manufacturing according to  claim 11 , wherein the film is applied in a number of strips arranged to reduce the complexity of curvature of each strip. 
     
     
         14 . The method of manufacturing according to  claim 12 , wherein the edge of one strip overlaps with the edge of an adjacent strip. 
     
     
         15 . The method of manufacturing according to  claim 12 , wherein edges of adjacent strip do not overlap and the join is covered with a further strip of thermoplastic film. 
     
     
         16 . The method of manufacturing according to  claim 12 , wherein edges of adjacent strip do not overlap and the join is painted with a PVDF paint. 
     
     
         17 . The method of manufacturing according to  claim 11 , wherein the thermoplastic film is heated shortly before and/or during its application to the blade body. 
     
     
         18 . The method of manufacturing according to  claim 11 , wherein the blade body is wetted with a suitable fluid shortly before the application of the thermoplastic film to the blade body. 
     
     
         19 . The method of manufacturing according to  claim 11 , wherein the film is trimmed before its application to the blade body. 
     
     
         20 . The method of manufacturing according to  claim 11  of making a blade according to  claim 1 . 
     
     
         21 . A two layer thermoplastic film comprising an upper layer and a lower layer, wherein:
 the upper layer comprising   (a) 50% to 85% of polyvinylidene fluoride (PVDF), wherein up to 30% of the polyvinylidene fluoride may be replaced by hexafluoropropylene (HFP);   (b) 10% to 45% polymethyl methacrylate (PMMA);   (c) optionally up to 8% UV stabilisers and/or absorbers;   (d) optionally up to 10% matting agent; and   (e) optionally up to 40% of an inorganic pigment.   the lower layer comprising   (f) a polymer of 10% to 45% of (PVDF), wherein up to 30% of the polyvinylidene fluoride may be replaced by hexafluoropropylene (HFP);   (g) 50% to 85% PMMA;   (h) optionally up to 8% UV stabilisers/absorbers;   (i) optionally up to 10% matting agent; and   (j) optionally up to 40% of an inorganic pigment;   wherein the film has an initial gloss of less than 30% when measured with a reflectometer at an angle of 60 degrees.   
     
     
         22 . The two layer film according to  claim 21  wherein the upper layer has a thickness between 40 and 240 μm and the lower layer has a thickness between 10 and 60 μm. 
     
     
         23 . The two layer film according to  claim 21 , wherein the UV stabilisers are based on ultrafine ‘nano’ titanium dioxide materials containing surface modified inorganic oxide particles. 
     
     
         24 . The two layer film according to  claim 21 , wherein the PVDF contains up to 30% HFP. 
     
     
         25 . The two layer film according to  claim 21 , further comprising adhesive on the lower layer. 
     
     
         26 . The two layer film according to  claim 21 , wherein there is at least 0.5% matting agent in at least one layer.