Lightweight textile covering for wind turbine rotor blades

Wind turbines are composed of a rotor with several aerodynamic rotor blades extending from a hub connected to a rotatable shaft. The rotor is oriented into the wind so that as air passes over the blades of the wind turbine, a lift force is applied to each blade, causing the rotor and shaft to rotate and a generator to produce electricity.

The power output of a wind turbine is directly dependent on the effective surface area of the blades that is in contact with the air stream. Accordingly, wind turbines with longer rotor blades generate more power. However, as the size of the rotor blade increases, so does its weight. It is necessary to develop rotor blades made of lighter materials that are still strong enough to withstand the forces exerted on a rotor blade. This is particularly true for the development of the large, lightweight rotor blades required for the most advanced wind turbines in the 10 to 20 MW range.

Laminated fabrics used to cover rotor blades are lightweight but not very UV resistant, so an additional UV protection layer is required to protect the fabric from UV damage. This increases the weight of the cover. In addition, these materials are expensive and have a limited elongation, which is disadvantageous for the stretching of the covering on the support elements. Due to the limited elongation before breakage of the covering, it is recommended to add a mesh to the covering to give the covering sufficient strength. This is another extra layer that increases the weight of the covering. A coating has been applied to the covering to protect the covering and provide low air permeability. The disadvantage of such a coating is that it does not adhere well to the other layers of the laminated fabric, as a result of which the coating loses all or part of its good properties prematurely.

The present invention aims to solve at least some of the above problems or drawbacks.

The textile covering developed by Concordia Textiles has a limited weight of no more than 800 g/m2, making it extremely suitable for wind turbine rotor blades. In addition, the covering has an elongation at break of at least 20% in both warp and weft direction, as a result of which the covering can be stretched tautly over supporting elements of a rotor blade without the covering tearing. The covering further comprises a protective top layer film laminated to the fabric of the covering. The film protects the fabric and ensures a low air permeability of the covering. Because the film is laminated, the film is very strongly bonded to the fabric, so that the covering retains its good properties for very long periods.

Fire-retardant polyester weft and warp threads are advantageous because polyester yarns have a high elongation at break, which allows the fabric to be stretched taut over support elements of a rotor blade without the fabric tearing and without the need for a mesh. This reduces the weight of the rotor blade covering. Polyester yarns have a considerable resistance to UV light, which in combination with the protective top layer guarantees sufficient resistance to UV light and it is not necessary to apply an additional UV protection layer. This further reduces the weight of a rotor blade's covering. Finally, polyester yarns are cheap, which greatly reduces the material cost of a rotor blade.

This use results in a rotor blade with a very low weight and with good properties that are retained for a long period of time. The very low weight of the covering allows larger rotor blades, which leads to higher efficiency.

The invention relates to a covering for rotor blades, composed of a fabric and a protective top layer.

The fabric comprises weft and warp threads. The weft and warp threads are preferably selected from a group of para-aramids, such as Kevlar® and Twaron®, meta-aramids, such as Nomex® and Teijinconex®, and polyester yarns. These yarns have an average to high tensile strength per unit area, a low specific weight, considerable resistance to UV light, very good wear resistance and have good to very good resistance to sea water. This makes these yarns suitable for use in rotor blade coverings, even for wind turbines at sea.

The fabric has two opposing sides. The protective top layer forms an outer layer of the covering. The protective top layer is applied to one or both of the opposite sides of the fabric. Preferably, the protective top layer is applied to only one side of the fabric. This is advantageous in order to limit the weight of the covering. It will be apparent to one skilled in the art that with a covering with a protective top layer applied to only one side of the fabric, the side with the protective top layer forms an outside of the rotor blade.

The protective top layer protects the covering and in particular the fabric against external conditions, such as weather conditions, UV light, chemical reactions, etc. The protective top layer is advantageous for preserving good properties of the covering, as a result of which the life of the covering and consequently a rotor blade is extended.

The protective top layer is a film. In addition to protecting the covering and in particular the fabric, a film is also advantageous for a low air permeability of the covering, resulting in a higher efficiency in converting air flows into energy. The protective top layer is laminated to the fabric. A laminated film is particularly advantageous compared to a protective coating as a protective top layer, because the film has a very good adhesion to the fabric, resulting in a high resistance to erosion of the protective top layer under the influence of rainfall. This extends the life of the covering compared to using a coating as a protective top layer. The film is preferably of a material from a group of thermoplastic polyurethane (TPU), such as Elastollan®, ethylene-tetrafluoroethylene (ETFE), such as Tefzel®, Fluon® and Neoflon®, and polyvinyl fluoride (PVF), such as Tedlar®.