The present disclosure relates in general to wind turbine rotor blades, and more particularly to coatings applied to the rotor blades to protect the rotor blades from erosion.
Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known foil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
During the operation of a wind turbine, the rotor blades may be subjected to a wide variety of environmental conditions. In many cases, such as when the wind turbines are located in coastal or desert areas, the rotor blades may be subjected to environmental conditions that include abrasive materials, such as sand particles and/or rain droplets. The interaction of these abrasive materials with the rotor blades may cause portions of the rotor blades to erode. In particular, the leading edges of rotor blades may be highly susceptible to erosion. Erosion of the various portions of the rotor blades limits the maximum rotational speed of the rotor blades, thus limiting the power output of the wind turbine.
One prior art solution for reducing similar erosion issues involves the use of a thick ceramic cap mounted to a blade. This prior art cap has a thickness greater than 10 millimeters, and is preferably in the range from 10 millimeters to 1,000 millimeters. However, the use of such a cap has a variety of disadvantages when applied to wind turbine rotor blades. For example, as the size of the wind turbines and rotor blades increases, the size of the cap must also increase. Such a large, thick cap would be extremely heavy, increasing the stress on and limiting the speed of the rotor blades. Further, these prior art caps would be particularly susceptible to cracking due to vibrations during the continuous operation of the wind turbine.
Thus, an improved erosion protection coating for a rotor blade would be desired. For example, an erosion protection coating that is relatively thin and light would be advantageous. Additionally, an erosion protection coating that includes components for reducing the transmission of rotor blade stress and strain to the erosion protection coating would be desired. Further, an erosion protection coating that includes components for the prevention of fouling during operation of the rotor blade would be desired.
Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In one embodiment, a rotor blade assembly for a wind turbine is disclosed. The rotor blade assembly includes a rotor blade having surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending between a tip and a root. The rotor blade assembly further includes an erosion protection coating configured on a surface of the rotor blade. The erosion protection coating includes a ceramic layer, the ceramic layer having a thickness of less than approximately 10 millimeters. The ceramic layer is configured to reduce erosion of the rotor blade.
In another embodiment, a rotor blade assembly for a wind turbine is disclosed. The rotor blade assembly includes a rotor blade having surfaces defining a pressure side, a suction side, a leading edge, and a trailing edge extending between a tip and a root. The rotor blade assembly further includes an erosion protection coating configured on the leading edge of the rotor blade and extending in the generally span-wise direction along substantially the entire outer half of the rotor blade. The erosion protection coating includes a ceramic layer. The ceramic layer is configured to reduce erosion of the rotor blade.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
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In some embodiments, the rotor blade 16 may include a plurality of individual blade segments aligned in an end-to-end order from the blade tip 32 to the blade root 34. Each of the individual blade segments may be uniquely configured so that the plurality of blade segments define a complete rotor blade 16 having a designed aerodynamic profile, length, and other desired characteristics. For example, each of the blade segments may have an aerodynamic profile that corresponds to the aerodynamic profile of adjacent blade segments. Thus, the aerodynamic profiles of the blade segments may form a continuous aerodynamic profile of the rotor blade 16. Alternatively, the rotor blade 16 may be formed as a singular, unitary blade having the designed aerodynamic profile, length, and other desired characteristics.
The rotor blade 16 may, in exemplary embodiments, be curved. Curving of the rotor blade 16 may entail bending the rotor blade 16 in a generally flapwise direction and/or in a generally edgewise direction. The flapwise direction may generally be construed as the direction (or the opposite direction) in which the aerodynamic lift acts on the rotor blade 16. The edgewise direction is generally perpendicular to the flapwise direction. Flapwise curvature of the rotor blade 16 is also known as pre-bend, while edgewise curvature is also known as sweep. Thus, a curved rotor blade 16 may be pre-bent and/or swept. Curving may enable the rotor blade 16 to better withstand flapwise and edgewise loads during operation of the wind turbine 10, and may further provide clearance for the rotor blade 16 from the tower 12 during operation of the wind turbine 10.
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The erosion protection coating 110 may be configured on a surface of the rotor blade 16. In exemplary embodiments, the erosion protection coating 110 may be configured on the leading edge 26 of the rotor blade 16. Further, in embodiments wherein the erosion protection coating 110 is configured on the leading edge 26, the coating 110 may further extend at least partially onto the pressure side 22 and/or the suction side 24, as desired to provide suitable erosion protection. Additionally or alternatively, the erosion protection coating 110 may be configured on any suitable surface or surfaces of the rotor blade 16, such as the pressure side 22, the suction side 24, the trailing edge 28, the tip 32, and/or the root 34.
In some exemplary embodiments, the erosion protection coating 110 may be configured on only a portion of the rotor blade 16 along the length of the rotor blade in the generally span-wise direction. For example, the erosion protection coating 110 may be configured on approximately the outer half of the length of the rotor blade 16 or, in exemplary embodiments, approximately the outer third of the length of the rotor blade 16 (in other words, the approximate half or third of the length of the rotor blade 16 that includes the tip 32). Thus, the erosion protection coating may extend in the generally span-wise direction along substantially the entire outer half of the rotor blade 16, or along substantially the entire outer third of the rotor blade 16.
However, it should be understood that the present disclosure is not limited to the erosion protection coating 110 being configured on or extending through only a certain portion of the length of the rotor blade 16. Rather, any configuration of the erosion protection coating 110 on any portion of the length of the rotor blade 16 is within the scope and spirit of the present disclosure.
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The ceramic layer 112 according to the present disclosure is a relatively thin ceramic layer 112. Various forms of the ceramic layer 112 and various application methods, as discussed below, may be utilized to ensure that the ceramic layer 112 is relatively thin. Thus, the ceramic layer 112 of the present disclosure has a thickness 114 of less than approximately 10 millimeters. Further, the ceramic layer 112 may have a thickness 114 of equal to or less than approximately 5 millimeters, equal to or less than approximately 2 millimeters, or in exemplary embodiments equal to or less than approximately 1 millimeter. The relatively thin ceramic layer 112 of the present disclosure ensures that the erosion protection coating 110 does not add an undesirable amount of weight to the rotor blade 16, such that the stress on the rotor blade 16 is not increased and the speed of the rotor blade 16 is not decreased.
Further, in some embodiments, the thickness 114 of the ceramic layer 112, and/or of the erosion protection coating 110 in general, may taper throughout a portion of the ceramic layer 112 and erosion protection coating 110. For example, in embodiments wherein the erosion protection coating 110 is configured on the leading edge 26, a portion of the ceramic layer 112 and/or the erosion protection coating 110 extending towards or configured on the pressure side 22 and/or the suction side 24 may taper. The taper may be such that the outer surface of the rotor blade assembly 100 is generally continuous between the erosion protection coating 110 and the remaining surface of the rotor blade 16. In alternative embodiments, however, the thickness 114 of the ceramic layer 112, and/or of the erosion protection coating 110 in general, may remain generally constant, or may increase, or change as desired.
The ceramic layer 112 according to the present disclosure is a relatively hard ceramic layer 112. In some embodiments, for example, the ceramic layer 112 may have a hardness value of up to approximately 8 according to the Mohrs scale. In other embodiments, the ceramic layer 112 may have a hardness value in the range between approximately 10 gigapascals and approximately 40 gigapascals according to the Vickers scale.
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In exemplary embodiments, for example, the elastic layer 120 may comprise polyurethane. Alternatively, the elastic layer 120 may comprise any relatively elastic material that is suitable for absorbing strain from the rotor blade 16 and reducing or preventing the strain being transmitted through the elastic layer 120 to the ceramic layer 112.
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To reduce lightning damage to the rotor blade 16, the lightning protection web 140 may be operatively connected to a lightning protection device 142, as shown in
Thus, when the lightning protection web 140 and lightning protection device 142 are operatively connected, the lightning protection device 142 may protect the lightning protection web 140 and rotor blade 16 from lightning strikes. The electrical current from lightning striking the erosion protection coating 110 may flow through the lightning protection web 140 to the lightning protection device 142. In some embodiments, a conduction cable 144 or a plurality of conduction cables 144, as shown in
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In other embodiments, as shown in
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.