Patent Application
20200072188
The present disclosure relates generally to wind turbines, and more particularly to a counterweight assembly for use during single blade installation of a wind turbine.
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 airfoil 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.
Typically, to initially install a rotor blade onto the wind turbine hub, a significantly large crane must be transported to the wind turbine site in order to provide a means for raising the rotor blade relative to the hub. Unfortunately, it is often extremely expensive to both transport the crane to the wind turbine site and operate the crane for the amount of time necessary to install the rotor blade(s). As a result, the costs of employing such large cranes currently accounts for a significant portion of the overall costs associated with initial wind turbine installations.
In addition, as wind turbines continue to increase in size, cranes having the capacity to lift a fully-assembled rotor to certain tower heights are often unavailable in certain geographic locations. Therefore, in such locations, a single blade installation (SBI) process is required. In the SBI process, the hub and rotor blades are installed atop the tower sequentially in consecutive lifts. More specifically, an unbalanced rotor turning gear (URTG) drive is typically installed on the backside of the main gearbox which meshes with the teeth on the brake disc. One or more cranes then lift the hub atop the tower so that the hub can be secured to the nacelle. The entire drivetrain is then rotated using the URTG drive such that a first axis of the hub is positioned horizontally and a rotor lock is applied. A first rotor blade can then be installed in a horizontal position. After the first rotor blade is secured and the crane(s) have released the blade, the URTG device is used to rotate the hub through 120° so that the next rotor blade can be installed. This process is repeated until all rotor blades have been installed.
During the SBI process, however, the static and aerodynamic load of the unbalanced rotor (e.g. when only one or two rotor blades have been installed) may exceed capacity of the Unbalanced Rotor Turning Gear. For example, the highest static load on the drivetrain typically occurs when there is only one rotor blade positioned horizontally or two rotor blades in a “sideways-V” position.
Accordingly, improved methods and related systems the SBI process that utilizes a counterweight assembly to address the aforementioned issues would be welcomed in the art.
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 aspect, the present disclosure is directed to a method for installing a plurality of rotor blades to a rotatable hub secured atop a tower of a wind turbine. The method includes providing a counterweight assembly having, at least, an arm member and a counterweight mass secured at a distal end of the mounting assembly. The method also includes securing the arm member of the counterweight assembly to the hub of the wind turbine. Further, the method includes consecutively installing the plurality of rotor blades onto the hub of the wind turbine. Moreover, the method includes rotating the arm member about a rotation axis of the hub to continuously adjust a position of the counterweight mass between each consecutive installation of the plurality of rotor blades to change a center of gravity of the hub and maintain a balanced rotor of the wind turbine during installation of the plurality of rotor blades.
In one embodiment, the step of rotating the arm member about the rotation axis of the hub to continuously adjust the position of the counterweight mass may include affixing an outer race of a slewing ring bearing to the hub and allowing an inner race of the slewing ring bearing to rotate with respect to the outer race and mounting the arm member to the inner race of the slewing ring bearing. As such, rotation of the inner race of the slewing ring bearing allows for rotation of the arm member and the counterweight mass. In another embodiment, the inner race of the slewing ring bearing may include gear teeth that mesh with a drive mechanism. Thus, the drive mechanism is configured to drive rotation of the inner race with respect to the outer race.
In further embodiments, the method may include affixing the outer race of the slewing ring bearing to a front, exterior location of the hub. In additional embodiments, the counterweight mass may be initially suspended in a six o'clock position. In such embodiments, the drive mechanism is configured to rotate the arm member from the six o'clock position to any position around the inner race of the slewing ring bearing. In several embodiments, the method may also include locking the counterweight mass in a predetermined position via the drive mechanism.
In particular embodiments, the counterweight mass may include, at least in part, a reservoir filled at least partially with a fluid. In such embodiments, the method may further include varying an amount of the fluid in the reservoir to vary the weight of the counterweight mass. More specifically, in one embodiment, the step of varying the amount of the fluid in the reservoir may include pumping in or draining out the fluid from the reservoir via at least one conduit that extends from the reservoir through the arm member and into the hub.
In another embodiment, the method may include monitoring a moment and/or torque exerted onto the hub via at least one sensor (such as a strain gauge) mounted on the arm member and controlling the amount of fluid in the reservoir based on the moment and/or torque. In such embodiments, the sensor(s) is configured to continuously monitor the actual moment and/or torque exerted onto the hub, i.e. zero in the 6 o'clock position and maximum in the 3- or 9 o'clock position. In further embodiments, the method may also include monitoring the amount of the fluid pumped into the reservoir via at least one of a fill-level sight glass or a water meter.
In another aspect, the present disclosure is directed to a counterweight assembly for maintaining balance of a rotor of a wind turbine during installation of a plurality of rotor blades onto a rotatable hub secured atop a tower of the wind turbine. The counterweight assembly includes a counterweight mass configured to be moved to multiple positions between consecutive installations of the plurality of rotor blades to continuously change a center of gravity of the hub and maintain balance of the rotor during installation of the plurality of rotor blades. In addition, the counterweight assembly includes a rotatable arm member comprising a proximal end and a distal end. Further, the counterweight mass is secured at the distal end such that, when the arm member is secured to the hub, the counterweight mass remains spaced apart a predetermined distance from the hub, the proximal end configured for affixing the arm member at a front, exterior location of the hub forward of the plurality of rotor blades. As such, the rotatable arm member is configured to rotate about a rotation axis of the hub to continuously adjust a position of the counterweight mass between consecutive installations of the plurality of rotor blades to change a center of gravity of the hub and maintain a balanced rotor of the wind turbine during installation of the plurality of rotor blades. It should be understood that the counterweight assembly may further include any of the additional features and/or embodiments described herein.
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.
Generally, the present subject matter is directed to various methods for consecutively installing a plurality of rotor blades to a rotatable hub secured atop a tower of a wind turbine. Specifically, as will become apparent from the description provided below, the disclosed methods utilize a counterweight assembly that can change the center of gravity of the rotor of the wind turbine in order to drive the rotor forward without putting new demands on components.
Referring now to the drawings,
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Each rotor blade 22 may also include a pitch adjustment mechanism 34 configured to rotate each rotor blade 22 about its pitch axis 36. Further, each pitch adjustment mechanism 34 may include a pitch drive motor 38 (e.g., any suitable electric, hydraulic, or pneumatic motor), a pitch drive gearbox 40, and a pitch drive pinion 42. In such embodiments, the pitch drive motor 38 may be coupled to the pitch drive gearbox 40 so that the pitch drive motor 38 imparts mechanical force to the pitch drive gearbox 40. Similarly, the pitch drive gearbox 40 may be coupled to the pitch drive pinion 42 for rotation therewith. The pitch drive pinion 42 may, in turn, be in rotational engagement with a pitch bearing 44 coupled between the hub 20 and a corresponding rotor blade 22 such that rotation of the pitch drive pinion 42 causes rotation of the pitch bearing 44. Thus, in such embodiments, rotation of the pitch drive motor 38 drives the pitch drive gearbox 40 and the pitch drive pinion 42, thereby rotating the pitch bearing 44 and the rotor blade 22 about the pitch axis 36. Similarly, the wind turbine 10 may include one or more yaw drive mechanisms 46 configured to change the angle of the nacelle 16 relative to the wind (e.g., by engaging a yaw bearing 48 of the wind turbine 10).
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As shown at 102, the method 100 includes providing a counterweight assembly 80 having, at least, an arm member 84 and a counterweight mass 86 secured at a distal end of the arm member 84. As shown at 104, the method 100 may include securing the arm member 84 of the counterweight assembly 80 to the hub 20 of the wind turbine 10. As shown at 106, the method 100 may include consecutively installing the plurality of rotor blades 22 onto the hub 20 of the wind turbine 10. As shown at 108, the method 100 may include rotating the arm member 84 about a rotation axis of the hub 20 to continuously adjust a position of the counterweight mass 86 between each consecutive installation of the rotor blades 22 to change a center of gravity 82 of the hub 20 and maintain a balanced rotor 18 of the wind turbine 10 during installation of the rotor blades 22.
The method 100 of
In particular embodiments, the counterweight mass 86 may be a hollow mass or a solid mass. For example, in one embodiment, the solid mass may be any suitable material, including, e.g. steel. In alternative embodiments, the hollow mass may be a reservoir or tank optionally filled, at least in part, with a fluid. In such embodiments, an empty counterweight mass 86 can be easily transported to the wind turbine 10 and then subsequently filled on site to minimize shipping costs. If crane capacity allows, the counterweight mass 86 may be filled with the fluid, e.g. water, on the ground before lifting the mass uptower. In such embodiments, the amount of fluid in the reservoir may be varied to adjust a weight of the counterweight mass 86. As such, the weight of the counterweight mass 86 can be adjusted as needed based on various factors including but not limited to crane size availability, rotor blade size, tower height, rotor dimensions, etc. More specifically, as shown in
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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.
