Patent Application
20210062785
Embodiments disclosed herein relate generally to a wind turbine including a plurality of foldable rotor blades that provide for a reduction in a static load on the rotor of the wind turbine when wind speeds exceed a rated value.
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 wind turbine may be configured as an upwind turbine, or a downwind turbine, dependent on placement of the rotor relative to the nacelle. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy 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.
Rotor blades are typically precisely designed and manufactured to efficiently transfer wind energy into rotational motion, thereby providing the generator with sufficient rotational energy for power generation. Blade efficiency is generally dependent upon blade shape and surface smoothness. Unfortunately, during operation, wind turbines may encounter varying wind conditions. Rotor blades may be designed for operation in wind conditions not exceeding a rated value. Rated wind value is defined as lowest wind speed at which wind turbine produces amount of power on the turbine nameplate. As the wind conditions exceed this rated value, the wind turbine may be caused to turn at too fast a speed, causing mechanical damage to the wind turbine components, including, but not limited to the rotor blades. Damage may include bending or breaking of the blades, damage to the support tower, or the like. In addition, wind conditions may vary at the same location, making designing of the rotor blades for a specific condition inefficient.
Accordingly, there is a need for a rotor blades that is adaptable for operation in varying wind conditions. A rotor blade that can perform in a wide variety of environmental conditions would be desired.
These and other shortcomings of the prior art are addressed by the present disclosure, which provides a foldable rotor blade for a wind turbine.
In accordance with an embodiment, provided is a wind turbine configured for extracting energy from a fluid flow. The wind turbine including a rotor comprising a rotatable hub, a plurality of foldable rotor blades coupled to the hub and a mechanical actuation structure coupled to the plurality of foldable rotor blades. The plurality of foldable rotor blades are rotatable about horizontal rotor axis. Each of the plurality of foldable rotor blades has a single fixed rotation point at a blade root. The mechanical actuation structure is coupled to the plurality of foldable rotor blades and moves the plurality of foldable rotor blades between a deployed state and a non-deployed state in response to an incoming fluid flow. The mechanical actuation structure comprises a plurality of toothed wheels, a threaded rod and a spring. Each of the plurality of foldable rotor blades is coupled to one of the plurality of toothed wheels at the single fixed rotation point. The threaded rod is disposed in cooperative engagement with each of the plurality of toothed wheels. The spring is disposed proximate the threaded rod and configured to compensate for the static wind load on each of the plurality of foldable rotor blades.
In accordance with another embodiment, provided is a wind turbine configured for extracting energy from a fluid flow. The wind turbine including a rotor comprising a rotatable hub, a plurality of foldable rotor blades and a mechanical actuation structure coupled to the plurality of foldable rotor blades. The plurality of foldable rotor blades are coupled to the hub and rotatable about a horizontal rotor axis. Each of the plurality of foldable rotor blades has a single fixed rotation point at a blade root. The mechanical actuation structure moves the plurality of foldable rotor blades to a deployed state, substantially perpendicular to the horizontal rotor axis, to capture kinetic energy from an incoming fluid flow and moves the plurality of foldable rotor blades to a non-deployed state, substantially parallel to the horizontal rotor axis. The mechanical actuation structure comprises a plurality of toothed wheels, a threaded rod and a spring. Each of the plurality of foldable rotor blades is coupled to one of the plurality of toothed wheels at the single fixed rotation point and rotatable in response to an incoming fluid flow. The threaded rod is disposed in cooperative engagement with each of the plurality of toothed wheels. The spring is disposed proximate the threaded rod and configured to compensate for the static wind load on each of the plurality of foldable rotor blades. Rotation of each of the plurality of toothed wheels applies a force on the threaded rod in a direction opposed to the incoming fluid flow and compression of the spring by the threaded rod.
In accordance with yet another embodiment, provided is a method of using of a wind turbine. The method comprises providing a wind turbine including a hub and a plurality of foldable rotor blades coupled to the hub and rotatable about a horizontal rotor axis, rotating the at least one rotor blade about its longitudinal axis to generate energy, determining if the incoming fluid flow exceeds a rated value, actuating a mechanical actuation structure coupled to each of the plurality of foldable rotor blades in the presence of an incoming fluid flow that exceeds the rated value to move the plurality of foldable rotor blades to a non-deployed state, substantially parallel to the horizontal rotor axis, determining if the incoming fluid flow exceeds the rated value, actuating the mechanical actuation structure in the presence of an incoming fluid flow that does not exceed the rated value to move the plurality of foldable rotor blades to a deployed state, substantially perpendicular to the horizontal rotor axis, to capture kinetic energy from an incoming fluid flow that is within a rated value. Each of the plurality of foldable rotor blades has a single fixed rotation point at a blade root. The mechanical actuation structure comprises a plurality of toothed wheels, a threaded rod and a spring. Each of the plurality of foldable rotor blades is coupled to one of the plurality of toothed wheels at the single fixed rotation point. The threaded rod is disposed in cooperative engagement with each of the plurality of toothed wheels. The spring is disposed proximate the threaded rod and configured to compensate for the static wind load on each of the plurality of foldable rotor blades.
Other objects and advantages of the present disclosure will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings.
The above and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein
The invention will be described for the purposes of illustration only in connection with certain embodiments; however, it is to be understood that other objects and advantages of the present disclosure will be made apparent by the following description of the drawings according to the disclosure. While preferred embodiments are disclosed, they are not intended to be limiting. Rather, the general principles set forth herein are considered to be merely illustrative of the scope of the present disclosure and it is to be further understood that numerous changes may be made without straying from the scope of the present disclosure.
Reference will now be made in detail to the various embodiments of the invention, one or more examples of which are illustrated in the figures. Each example is provided by way of explanation of the invention, and is not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the present invention includes such modifications and variations.
The plurality of foldable rotor blades 108 may be fabricated of any suitable material including, but not limited to stretchable fabric, tensionable fabric, plastic, metal, carbon fiber and/or other construction material. In an embodiment of the plurality of foldable rotor blades 108, including an underlying support structure where included, the structure may be fabricated of any suitable material, including, but not limited to carbon fiber and/or other material capable of lending support to the plurality of foldable rotor blades.
The rotor blades 108 and the hub 106 form a rotor 110 of the wind turbine 100. In operation the incoming prevailing fluid flow 112, imparts a rotation on the rotor 110 due to an aerodynamic profile on the plurality of foldable rotor blades 108. More specifically, in the illustrated embodiment, the rotor 110 turns around the substantially horizontal rotor axis 114, which is substantially parallel to the direction of the incoming prevailing fluid flow 112. The rotor 110 drives the generator, such that electrical energy is produced from the kinetic energy of the incoming prevailing fluid flow 112.
It should be noted that relative adjectives like in front, backward, behind and rear are defined with respect to the wind direction, and more particularly the incoming prevailing fluid flow 112, related to the wind turbine 100 in operation, i.e. when the wind turbine 100 produces electrical energy. That means that the incoming prevailing fluid flow 112 flows from a front end 116 to a back end 118 of the wind turbine 100. In addition, the terms axial or radial relate to the horizontal rotor axis 114 of the hub 106, when the wind turbine 100 produces electrical energy. Thus, as described above, the horizontal rotor axis 114 is substantially parallel to the incoming prevailing fluid flow 112 direction.
Referring again to the drawings wherein, as previously stated, identical reference numerals denote the same elements throughout the various views,
As illustrated in
In the embodiment of
The threaded rod/stud 134 is coupled to the preloaded spring 136 which is preloaded such that until which time the prevailing fluid flow 112 exceeds the rated value, the plurality of rotor blades 108 remain substantially perpendicular to the incoming prevailing fluid flow 112 and operational, as illustrated in
Referring now to
The tension of the preloaded spring 136 is selected such that when the speed of the incoming prevailing fluid flow 112 reaches the rated value, the preloaded spring 136 travels a distance equal to a quarter of a circumference of the toothed wheel 132, thereby allowing the toothed wheel 132 to rotate 90 degrees. At the end of the 90 degree toothed wheel rotation, the plurality of rotor blades 108 are folded in a manner so as to be oriented horizontally, as best illustrated in
The mechanical actuation structure 130 is operable to deploy and retract any number of rotor blades, such as the plurality of rotor blades 108. Each of the plurality of rotor blades 108 is coupled to the single threaded rod/stud 134 of the mechanical actuation structure 130 with a single toothed wheel, of the plurality of toothed wheels 132. Accordingly, the degree of folding/retraction (defined as an angle θ between the horizontal rotor axis 114 and a spanwise axis 117) of each of the plurality of rotor blades 108 is always the same. This is important since non-uniformity of the plurality of rotor blades 108 will result in an unbalanced condition of the rotor 110, resulting in potential damage to the overall wind turbine 100.
The mechanical actuation structure 130 as disclosed does not require active control, in that the degree of folding/retraction of the plurality of rotor blades 108 in response to incoming prevailing fluid flow 112 is defined by the preloaded spring 136 parameters and the degree of preloading. More particularly, the mechanical actuation structure 130 provides complete mechanical automation of the blades 108.
The plurality of foldable rotor blades 108 are in a typical embodiment symmetrically placed with respect to the turning axis, and more particularly the horizontal rotor axis 114, when coupled to the wind turbine 100. When deployed as in
In
In a step 206, a determination is made whether incoming fluid flow exceeds a rated value. If the incoming fluid flow (wind) does not exceed the rated value, the plurality of foldable rotor blades are allowed to continue to operate in the deployed state, as in step 204. If the incoming fluid flow exceeds the rated value, a mechanical actuation structure coupled to the plurality of foldable rotor blades is actuated, in a step 208, to move the plurality of foldable rotor blades to a non-deployed state, substantially parallel to the horizontal rotor axis. By positioning the plurality of foldable rotor blades substantially horizontal to the rotor axis, the incoming fluid flow that exceeds the rated value are allowed flow downstream, unobstructed, about the plurality of foldable rotor blades. Next, in a step 210, the incoming fluid flow is continually monitored, in a step 210, to determine if they exceed the rated value. If it is determined the incoming fluid flow continues to exceed the rated value, the foldable rotor blades are maintained in a non-deployed state, in a step 212, until such time the incoming fluid flow is determined in step 210, to not exceed the rated value. If it is determined in step 210 that the incoming fluid flow does not exceed the rated value, the mechanical actuation structure is actuated, in a step 214, to move the plurality of foldable rotor blades to the deployed state, substantially perpendicular to the horizontal rotor axis, and operated as in step 204. The foldable rotor blades are maintained in the deployed state until such time the incoming fluid flow is determined, in step 206, to exceed the rated value.
Accordingly, disclosed is a plurality of foldable rotor blades for enhanced performance of a wind turbine. The plurality of foldable rotor blades are caused to retract, or move to a non-deployed state upon actuation of a mechanical actuation structure, in the presence of an incoming fluid flow that exceeds the rated value for the blade design. The plurality of foldable rotor blades are caused to move to a deployed state upon actuation of a mechanical actuation structure, in the presence of an incoming fluid flow that does not exceed the rated value for the blade design.
The plurality of foldable rotor blades may be fabricated of any suitable material including, but not limited to stretchable fabric, tensionable fabric, plastic, metal, carbon fiber and/or other construction material. In an embodiment of the plurality of foldable rotor blades, including an underlying support structure where included, the structure may be fabricated of any suitable material, including, but not limited to carbon fiber and/or other material capable of lending support to the plurality of foldable rotor blades.
It will be understood that the previous apparatus configurations and modes of operation described herein are merely examples of proposed apparatus configurations and operating conditions. What is significant is the apparatus provides for enhanced performance and thus increased efficiency of a wind turbine.
The foregoing has described an apparatus and method of performance enhancement of a wind turbine. While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the disclosure as described herein. While the present disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the disclosure. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure.
