Patent Description:
Generally, a wind turbine includes a wind tower, a nacelle mounted on the wind tower, and a rotor coupled to the nacelle. The rotor generally includes a rotatable hub and a plurality of rotor blades coupled to and extending outwardly from the hub. Each rotor blade may be spaced about the hub so as to facilitate rotating the rotor to enable kinetic energy to be converted into usable mechanical energy, which may then be transmitted to an electric generator disposed within the nacelle for the production of electrical energy. Typically, a gearbox is used to drive the electric generator in response to rotation of the rotor. For instance, the gearbox may be configured to convert a low speed, high torque input provided by the rotor to a high speed, low torque output that may drive the electric generator.

Most wind turbines include support towers that include a plurality of tubular-shaped tower support sections. Adjacent tower support sections are coupled at structural connections using welding and/or mechanical fastening of ring flanges to form support tower assemblies. Wind towers are subject to large cyclic loading, which results in a large displacement of tower support sections and increased bending stresses and torsional stresses induced to the tower support members. The flanges of the structural connection between tower sections are preloaded by the bolted connections, such that a compressive stress is generated under the bolt head and nut, which exceeds any fluctuating loads experienced by the tower connection under functional loads, including generator reactive torque, gyroscopic loads due to change of direction of the turbine rotational axis, and dynamic loads due to imbalance or resonance. The mating flange faces are loaded under the nut and bolt, with the loading being relaxed between bolted connections. Axial loads transmitted through the tower about an axis parallel with the vertical axis of the tower are resisted by the friction generated between the flange faces under the clamping load of the bolts by the coefficient of friction between the flanges.

Some support tower members may be subjected to stresses that cause fatigue cracking and/or failure, particularly at the joint between adjacent support tower members and between the tower top and the yaw bearing. The primary mode of failure in the structural connections of wind tower joints can be bolt failure by the compromise of bolt preload. The bolts begin to experience fluctuating loads and stresses once the bolt preload is reduced, and this fluctuating load leads to fatigue failure of the bolt as well as fatigue cracking of nearby steel. Conventional methods for repairing support tower members include disassembling the entire support tower, replacing support tower members, and reassembling the support tower, which is expensive and time consuming. <CIT> describes a structural flange connection system and method; <CIT> describes in particular an adapting flange.

In one aspect, a reinforcement assembly for a tower of a wind turbine is disclosed as having at least one generally cylindrical tower section with an exterior wall and an interior wall defining a height and a thickness therebetween, the at least generally cylindrical tower section comprising a non-cylindrical, ovalized, out-of-round portion.

At least one generally cylindrical tower flange is coupled to the tower section, the tower flange having at least one vertical flange portion and at least one horizontal flange portion. At least one adjustable generally cylindrical reinforcing member has, at least one vertical member portion comprising flexible portions coupled to the exterior wall of the tower section, and at least one horizontal member portion adjustably engaged with at least one adjusting spacer. Adjustment of the adjusting spacer aligns the reinforcing member with an adjacent tower flange. The flexible portions are configured be bent to a non-cylindrical shape to match the tower section profile thereby allowing direct contact between the flexible portions and the wind tower section.

In another aspect, a method for reinforcing a tower of a wind turbine is disclosed by: disengaging a top portion of a tower section at a generally cylindrical flanged connection, the flanged connection having at least one upper tower flange and at least one lower tower flange; placing at least one adjusting spacer in a horizontal flange portion of the lower tower flange; engaging the at least one adjusting spacer with a horizontal member portion of a generally cylindrical adjustable reinforcing member; positioning the reinforcing member atop the lower tower flange; and, adjusting the at least one adjusting spacer to align the reinforcing member with the upper tower flange; tightening at least one adjusting nut onto the adjusting spacer to secure the reinforcing member; coupling a vertical member flexible portion of the reinforcing member with the tower section; and reengaging the top portion of the tower section by fastening the upper tower flange to the reinforcing member.

In general, the present subject matter discloses a reinforced wind tower flanged connection using a reinforcing member attached to an existing wind tower section as a retrofit. The reinforcing member can have enough structural capability to withstand fatigue and extreme tower loads that are higher than the original tower flange. The reinforcing member can attach like a "cap" on the existing wind tower thereby forming a reinforcing top flange for the wind turbine. The directional legend on the drawings defines vertical (V) and horizontal (H) directions as used herein.

<FIG> illustrates a wind turbine <NUM> of conventional construction. The wind turbine <NUM> includes a wind tower <NUM> with a nacelle <NUM> mounted thereon. A plurality of rotor blades <NUM> are mounted to a rotor hub <NUM>, which is in turn connected to a main flange that turns a main rotor shaft, as discussed below. The wind turbine power generation and control components are housed within the nacelle <NUM>. The view of <FIG> is provided for illustrative purposes only to place the present invention in an exemplary field of use. It should be appreciated that the invention is not limited to any particular type of wind turbine configuration.

As further shown in <FIG>, the wind tower <NUM> according to the present disclosure may be formed from a plurality of wind tower sections <NUM>. Each of the plurality of wind tower sections <NUM> may be disposed adjacent and coupled to another of the plurality of wind tower sections <NUM> to at least partially form the wind tower <NUM>. In exemplary embodiments, the wind tower sections <NUM> may be formed from a suitable metal or metal alloy, such as carbon steel. Alternatively, however, the wind tower sections <NUM> may be formed from any suitable materials, such as, for example, various suitable composite materials.

<FIG> illustrates one embodiment of a wind tower section <NUM> according to the present disclosure. As shown, in exemplary embodiments, the wind tower section <NUM> may be a generally cylindrical wind tower section <NUM>. For example, the cross-sectional shape of the wind tower section <NUM> may be generally circular, tubular or oval. Further, in some embodiments, the cross-sectional shape of the wind tower section <NUM> may be generally polygonal, having a plurality of sides such that the polygonal cross-section approximates a generally circular, tubular or oval cross-section.

The wind tower section <NUM> according to the present disclosure has an exterior wall <NUM> and an interior wall <NUM>. The exterior wall <NUM> and the interior wall <NUM> may each be generally cylindrical with regard to the wind tower section <NUM> in general. The exterior wall <NUM> and interior wall <NUM> may generally define a height <NUM> of the wind tower section <NUM>. The exterior wall <NUM> and interior wall <NUM> may further generally define a thickness <NUM> (see <FIG>) of the wind tower section <NUM> therebetween.

As further shown in <FIG>, each of the wind tower sections <NUM> may, in some embodiments, comprises a plurality of wind tower cans <NUM>. Each of the wind tower cans <NUM> may be a generally cylindrical portion of the wind tower section <NUM>, and may define a portion of the height <NUM> of the wind tower section <NUM> as well as the thickness <NUM> of the wind tower section <NUM>. Each of the plurality of wind tower cans <NUM> may be disposed adjacent and coupled to another of the plurality of wind tower cans <NUM> to at least partially form the wind tower section <NUM>. For example, a plurality of wind tower cans <NUM> may be stacked end to end to form the wind tower section <NUM>. Further, the wind tower cans <NUM> may be coupled together by, for example, welding the wind tower cans <NUM> together at intersections <NUM> between the adjacent wind tower cans <NUM>. It should be understood, however, that the present disclosure is not limited to welding, and that any suitable fastening device or method may be utilized to couple the wind tower cans <NUM> together, for example bolted flanges.

It should be understood that the cross-sectional area of the wind tower section <NUM>, and thus the wind tower cans <NUM>, may remain constant or may taper through the height <NUM> of the wind tower section or portions thereof. For example, in some embodiments, the cross-sectional area of each of the wind tower cans <NUM> and wind tower sections <NUM> may decrease through the height <NUM> or a portion thereof. Further, it should be understood that the wind tower sections <NUM>, that make up the wind tower <NUM>, may all taper or may all have generally constant cross-sections, or one or more of the wind tower sections <NUM> may taper while other of the wind tower sections <NUM> may have generally constant cross-sections.

Each of the plurality of wind tower sections <NUM> may be disposed adjacent and coupled to another of the plurality of wind tower sections <NUM> to at least partially form the wind tower <NUM>. For example, a plurality of wind tower sections <NUM> may be stacked end to end to form the wind tower <NUM>. Further, each of the wind tower sections <NUM> may comprise at least one flange <NUM> or a plurality of flanges <NUM>. The horizontal flange portion of flanges <NUM> may be oriented radially inward or radially outward from the centerline of the wind tower <NUM>. The flanges <NUM> may be configured to couple the wind tower section <NUM> to an adjacent wind tower section <NUM>. For example, each flange <NUM> may be disposed at an end of the wind tower section <NUM>. In exemplary embodiments, the flange <NUM> may define a plurality of bore holes <NUM>. The bore holes <NUM> may be spaced generally circumferentially about the flange <NUM>. The bore holes <NUM> may be configured to accept a mechanical fastener <NUM>, such as a nut and bolt combination, a rivet, a screw, or any other suitable mechanical fastener <NUM>, therethrough. To couple the wind tower section <NUM> to an adjacent wind tower section <NUM>, the flange <NUM> may be mated with an adjacent flange <NUM> of the adjacent wind tower section <NUM>, and the bore holes <NUM> of the mating flanges <NUM> aligned. For example, an upper tower flange <NUM> can be aligned with a lower tower flange <NUM> for mechanically bonding a tower flanged connection using mechanical fasteners <NUM>, for example, bolts and nuts. Mechanical fasteners <NUM> may be placed through at least a portion of the mating bore holes <NUM> to couple the wind tower sections <NUM> together thereby making a bolted flange connection. It should be understood, however, that the present disclosure is not limited to wind tower sections <NUM> having flanges <NUM> as described above, and rather that any suitable fastening device or method may be utilized to couple the wind tower sections <NUM> together.

Some support wind tower members may be subjected to stresses that cause fatigue cracking and/or failure, particularly at the intersection <NUM> between adjacent support wind tower members, particularly between the wind tower top flange <NUM> and the yaw bearing <NUM> that is attached to the nacelle <NUM>, as seen in <FIG>. Thus, a reinforcement system <NUM> for the wind tower <NUM> is disclosed. The reinforcement system <NUM> allows for a wind tower <NUM> to be retrofitted for a wind turbine <NUM> that might be experiencing fatigue cracking or that has been upgraded thereby creating larger structural loading on the wind tower <NUM>. The reinforcement system <NUM> allows for the efficient and cost-effective retrofit of wind towers <NUM> which may be used in various locations with various environmental conditions. Further, the reinforcement system <NUM> may allow for existing wind turbines <NUM> to be upgraded with, for example, heavier components, without requiring replacement of the wind tower <NUM>. Rather, before, during, or after the upgrade, the reinforcement system <NUM> may be retrofitted on the wind tower <NUM> to tailor the wind tower <NUM> for the upgrade.

The reinforcement system <NUM>, as shown in <FIG>, includes a reinforcement assembly <NUM>, and at least one wind tower section <NUM> with an existing tower flange <NUM> that can be the top tower flange <NUM>. Further, the reinforcement system <NUM> includes at least one reinforcing member <NUM> or a plurality of reinforcing members <NUM>. The reinforcing member <NUM> can be broken into segmented reinforcing member portions <NUM>, such as segmented portions of a ring flange positioned end-to-end, for easier installation of the reinforcement assembly <NUM>. The segmented reinforcing member portions <NUM> can be shaped to a specific tower irregularity. The reinforcing member <NUM> interacts with the at least one wind tower section <NUM> to reinforce the at least one wind tower section <NUM>. The reinforcement assembly <NUM> can be attached to the exterior wall <NUM> of the wind tower section <NUM> by drilling holes in the existing wind tower section <NUM> and fastening with maintenance free fasteners. The geometry of the reinforcing member <NUM> can be shaped as an unequal leg angle with a vertical member portion <NUM> and a horizontal member portion <NUM>. The vertical member portion <NUM> can be descriptively referred to as a 'skirt' portion as it extends to cover a damaged portion of the tower. The reinforcing member <NUM> can be oriented in any direction necessary to mate with the existing flanged connection. For example, to reinforce an upper flange <NUM>, flexible portions <NUM> can be disposed vertically upward and secured to an upper portion of the tower section <NUM>, with adjusting spacers <NUM>, for example jacking bolts or shims, extending above or below the horizontal member portion <NUM> for providing position adjustment of the reinforcing member <NUM>.

Additionally, the vertical member portion <NUM> of the reinforcing member <NUM> can extend both vertically upward and vertically downward, as seen in <FIG>, with the upward portion secured to an upper portion of the tower section <NUM> and the downward portion secured to a lower portion of the tower section <NUM>. Also, two (first and second) separate reinforcing members <NUM> can be stacked on top of each other in a dual inverted or flipped fashion such that the upper surface of the horizontal member portions <NUM> of each dual reinforcing member <NUM> are in direct contact. In the dual configuration, the vertical member portion <NUM> of the first reinforcing member <NUM> points vertically upward and the vertical member portion <NUM> on the second reinforcing member <NUM> points vertically downward.

The reinforcement assembly <NUM> can have at least one generally cylindrical wind tower section <NUM> with an exterior wall <NUM> and an interior wall <NUM> defining a height <NUM> and a thickness <NUM> therebetween. At least one generally cylindrical tower flange <NUM> can be coupled to the wind tower section <NUM>, for example, by welding at the intersection <NUM>. The tower flange <NUM> can have at least one vertical flange portion <NUM> and at least one horizontal flange portion <NUM>. At least one adjustable generally cylindrical reinforcing member <NUM>, can have at least one vertical member portion <NUM> adjustably coupled to the exterior wall <NUM> of the wind tower section <NUM>, and, at least one horizontal member portion <NUM> adjustably engaged, for example threaded, with at least one jacking bolt or shim <NUM>, such that the adjusting spacer <NUM> is adjusted to align the reinforcing member <NUM> with an adjacent tower flange for mechanical bonding.

The adjusting spacer <NUM> can be positioned atop a adjusting pad <NUM> which can be centered atop a adjusting portion of the bore holes <NUM> in the horizontal flange portion <NUM> of the tower flange <NUM>. The adjusting portion can include the bore holes <NUM> portion unoccupied by mechanical fasteners <NUM>. The adjusting portion position can alternate with mechanical fasteners <NUM> around the perimeter of the reinforcing member <NUM>. The at least one adjusting spacer <NUM> can be threadably engaged with a adjusting nut <NUM> configured for securing the position of the adjustable reinforcing member <NUM>. The vertical member portion <NUM> of the reinforcing member <NUM> can have a scalloped edge thereby forming vertical member portion flexible portions <NUM> for mechanically coupling to a non-cylindrical, ovalized, or out-of-round portion of the wind tower section <NUM>. The flexible portions <NUM> can be configured using any appropriate profile or shape modification that enables bending portions, such as notches, cuts, slits, scallops, or other irregular shaping. The flexible portions <NUM> can be bent to a non-cylindrical shape to match the tower section <NUM> profile thereby allowing direct contact between the flexible portions <NUM> the wind tower section <NUM>. The flexible portions <NUM> are them mechanically coupled to the tower section <NUM> using any suitable mechanical fasteners. The reinforcing member <NUM> can be threadably engaged with a yaw bearing assembly <NUM> that is coupled to a nacelle <NUM> of the wind turbine <NUM>.

A method for reinforcing a tower of a wind turbine <NUM> can include the steps of; disengaging a top portion of a wind tower section <NUM> at a generally cylindrical flanged connection, the flanged connection can have at least one upper tower flange <NUM> and at least one lower tower flange <NUM>; placing at least one adjusting spacer <NUM> atop a adjusting pad <NUM> that is generally positioned atop a adjusting portion of the bore holes <NUM> in a horizontal flange portion <NUM> of the least one lower tower flange <NUM>; engaging the adjusting spacer <NUM> with a horizontal member portion <NUM> of a generally cylindrical adjustable reinforcing member <NUM>; positioning the reinforcing member <NUM> atop the lower tower flange <NUM>; and aligning the reinforcing member <NUM> into final position by adjusting at least one adjusting spacer <NUM>.

Additional method steps can include tightening at least one adjusting nut <NUM> onto the adjusting spacer <NUM> to hold final position of the reinforcing member <NUM>. Then coupling the vertical member portion <NUM> of the reinforcing member <NUM> with the wind tower section <NUM>, for example, using maintenance-free mechanical fasteners. And finally reengaging the top portion of the wind tower section <NUM> by fastening the upper tower flange <NUM> to the reinforcing member <NUM> with mechanical fasteners <NUM>. The upper tower flange <NUM> can be integrated with a yaw bearing assembly <NUM> thereby positioning the reinforced flanged connection at the top of the wind tower <NUM>.

A wind turbine <NUM> is also disclosed as having a nacelle <NUM>, a rotor <NUM> coupled to the nacelle <NUM>, the rotor <NUM> having one or more rotor blades <NUM> attached thereto, and a tower <NUM> supporting the nacelle. The tower <NUM> can have a reinforcement system <NUM> as disclosed herein.

It should be appreciated that the reinforcement system <NUM> disclosed herein can be applied to any flanged wind tower connection, for example, the reinforcing member <NUM> can be applied to an upper tower flange <NUM>, a lower tower flange <NUM>, an intermediate tower flange, and/or a foundation flange. The reinforcing member <NUM> also can be oriented with the scalloped edges and flexible portions <NUM> pointed upward or downward for connection to a tower section <NUM>. Also, the reinforcing member can have multiple horizontal member portions <NUM> and multiple vertical member portions <NUM> pointed in both upward and downward directions for providing more secured attachment to the tower section <NUM>. Additionally, the reinforcing member can take the shape of a wide flange or similar structural shape to provide additional structural support.

Claim 1:
A reinforcement assembly (<NUM>) for a tower (<NUM>) of a wind turbine (<NUM>), comprising:
at least one generally cylindrical tower section (<NUM>) comprising an exterior wall (<NUM>) and an interior wall (<NUM>) defining a height (<NUM>) and a thickness (<NUM>) therebetween;
the at least generally cylindrical tower section (<NUM>) comprising a non-cylindrical, ovalized, out-of-round portion;
at least one generally cylindrical tower flange (<NUM>) coupled to the tower section (<NUM>), the tower flange (<NUM>) comprising at least one vertical flange portion (<NUM>) and at least one horizontal flange portion (<NUM>); and,
at least one adjustable generally cylindrical reinforcing member (<NUM>), the reinforcing member (<NUM>) comprising at least one vertical member portion (<NUM>), the vertical member portion (<NUM>) comprising flexible portions (<NUM>) coupled to the exterior wall (<NUM>) of the tower section (<NUM>), and at least one horizontal member portion (<NUM>) adjustably engaged with at least one adjusting spacer (<NUM>),
wherein adjustment of the adjusting spacer (<NUM>) aligns the reinforcing member (<NUM>) with an adjacent tower flange (<NUM>); and wherein the flexible portions (<NUM>) are configured be bent to a non-cylindrical shape to match the non-cylindrical portion of the tower section thereby allowing direct contact between the flexible portions (<NUM>) and the wind tower section (<NUM>).