Wind turbine rotor blade pre-staged for retrofitting with a replacement blade tip segment

A method for manufacturing a wind turbine blade that is pre-staged for subsequent retrofitting with a replacement blade tip segment includes providing the wind turbine blade with a continuous spar structure from a root end to a tip end of the wind turbine blade. At a pre-defined span-wise location, one of a span-wise extending beam structure or span-wise extending receiver section is configured with the spar structure.

FIELD

The present subject matter relates generally to wind turbine rotor blades and, more particularly, to a method for field retrofit of the existing blade tip segment with a replacement blade tip segment.

BACKGROUND

Wind turbine rotor blades generally include a body shell formed by two shell halves of a composite laminate material. The shell halves are generally manufactured using molding processes and then coupled together along the corresponding ends of the rotor blade. In general, the body shell is relatively lightweight and has structural properties (e.g., stiffness, buckling resistance, and strength) which are not configured to withstand the bending moments and other loads exerted on the rotor blade during operation.

In certain situations, it may be desirable to modify a rotor blade on an operational field wind turbine. For example, it may be desired to change the physical characteristics of the blade for noise reduction benefits, or to change the power characteristics of the blade. Such modification may call for replacement of the existing blade tip with a different blade tip segment. However, retrofit of an existing blade tip is a difficult and challenging process, particularly if the process is conducted in the field (at the wind turbine site). In addition, the joint between the replacement blade tip segment and the existing blade root segment typically dictates the maximum load limit for the blade. Thus, retrofitted blade tip segments have been limited to relatively short lengths.

As the size of wind turbine rotor blades have significantly increased in recent years, difficulties have emerged in the integral manufacture as well as conveyance and transport of the blades to a site. In response, the industry is developing sectional wind turbine rotor blades wherein separate blade segments are manufactured and transported to a site for assembly into a complete blade (a “jointed” blade). In certain constructions, the blade segments are joined together by a beam structure that extends span-wise from one blade segment into a receiver section of the other blade segment. Reference is made, for example, to US Patent Publication No. 2015/0369211, which describes a first blade segment with a beam structure extending lengthways that structurally connects with a second blade segment at a receiver section. The beam structure forms a portion of the internal spar structure for the blade and includes a shear web connected with a suction side spar cap and a pressure side spar cap. Multiple bolt joints are provided on the beam structure for connecting with the receiver section in the second blade segment, as well as multiple bolt joints located at the chord-wise joint between the blade segments.

Similarly, US Patent Publication No. 2011/0091326 describes a jointed blade wherein a first blade portion and a second blade portion extend in opposite directions from a joint. Each blade portion includes a spar section forming a structural member of the blade and running lengthways, wherein the first blade portion and the second blade portion are structurally connected by a spar bridge that joins the spar sections.

With the conventional blade structures and retrofitting processes, extensive and time consuming processes are involved in modifying the existing blade to receive the replacement blade tip. The industry would benefit from a wind turbine rotor blade that is “pre-staged” for subsequent retrofitting with a replacement blade tip, wherein such pre-staging involves configuration of spar structure within the blade that may not be necessary to the existing spar structure and is specifically provided to reduce the steps, time, and complexity for retrofitting of the replacement blade tip.

BRIEF DESCRIPTION

In one aspect, the present invention encompasses a method for manufacturing a wind turbine blade that is pre-staged for subsequent retrofitting with a replacement blade tip segment. An embodiment of this method includes providing the wind turbine blade with a continuous spar structure from a root section to a tip section of the blade. This spar structure may include, for example, opposite shear webs and opposite spar caps that define a box-beam spar structure. At a pre-defined span-wise location, one of a span-wise extending beam structure or a span-wise extending receiver section is incorporated with the spar structure by fixing a root-end of the beam structure or receiver section with the spar structure. A tip end of the beam structure or the receiver section is free of (not fixed) the spar structure. The beam structure has a size for insertion into a mating receiver section within the replacement blade tip segment at a later time. Likewise, the receiver section is sized for receipt of a mating beam structure extending from the replacement blade tip segment. In the embodiment wherein the spar structure includes opposite shear webs, the root-end of the beam structure or receiver section may be fixed between the shear webs, for example with an adhesive.

The method may further include retrofitting the wind turbine blade with the replacement blade tip segment at a time subsequent to manufacture of the wind turbine blade by cutting the existing blade tip segment from the wind turbine blade at a chord-wise joint line such that the tip-end of the beam structure extends span-wise from a remaining blade root segment beyond the chord-wise joint line, or the receiver section is exposed at the chord-wise joint line. Spar structure in the blade root segment that extends along the tip-end of the beam structure or receiver section may also be removed such that only the beam structure extends from the blade root segment or the receiver section is exposed at the chord-wise joint line. Then, the replacement blade tip segment is aligned and connected with the blade root segment in a span-wise direction so that the beam structure moves into the receiver section of the replacement blade tip segment, or a beam structure extending from the replacement tip segment slides into the receiver section. A finish surface can then be provided to the blade shell components of the blade root segment and the replacement tip segment at the joint line.

As discussed above, the spar structure may include opposite shear webs, wherein the root-end of the beam structure or receiver section is between and fixed to the shear webs, and wherein the process of removing of the spar structure includes cutting away the shear webs along the tip-end of the beam structure or the tip end of the receiver section.

The wind turbine blade may be operational on a wind turbine at a field site, wherein the method includes removing and lowering the wind turbine bade from a rotor hub of the wind turbine and performing the retrofitting process with the wind turbine blade in a down-tower position relative to the rotor hub.

The method may also include producing and maintaining an inventory of the replacement blade tip segments, wherein for the retrofitting process, one of the replacement blade tip segments is selected from the inventory and transported to the field site.

The invention also encompasses various embodiments of a wind turbine blade that is pre-staged for subsequent retrofitting with a replacement blade tip segment, wherein the blade includes a pressure side shell, and a suction side shell joined to the pressure side shell along a leading edge and a trailing edge such that an interior cavity is defined between the pressure side shell and the suction side shell. A continuous spar structure is configured within the interior cavity from a root end to a tip end of the wind turbine blade. At a pre-defined span-wise location, one of a span-wise extending beam structure or span-wise extending receiver section is configured with the spar structure. The span-wise extending beam structure is configured for insertion into a mating receiver section in a replacement blade tip segment, or the receiver section is configured for receipt of a mating beam structure extending from a replacement blade tip segment.

In a particular embodiment of the wind turbine blade, the beam structure includes a root end fixed to the spar structure and a tip-end that is adjacent and unfixed to the spar structure, wherein the spar structure can be removed from alongside the tip-end of the beam structure when retrofitting the wind turbine blade with the replacement blade tip segment. Alternatively, the section includes a root end fixed to the spar structure such that the receiver section extends at least to a location of a chord-wise joint line where the replacement blade tip segment will be retrofitted.

The spar structure may include opposite shear webs, wherein a root-end of the beam structure or root-end of the span-wise extending receiver section is configured between the shear webs.

DETAILED DESCRIPTION OF THE INVENTION

Generally, the present subject matter is directed to methods for manufacturing wind turbine rotor blades (and the resulting blades) that are pre-staged for subsequent retrofitting with a replacement blade tip segment.

Referring now to the drawings,FIG. 1is a side view of an exemplary wind turbine10having a plurality of rotor blades28that may be retrofitted in accordance with aspects of the present disclosure. The illustrated wind turbine10is a horizontal-axis wind turbine. Alternatively, the wind turbine10may be a vertical-axis wind turbine. The wind turbine10includes a tower12that extends from a support surface14, a nacelle16mounted on the tower12, a generator18positioned within the nacelle16, a gearbox20coupled to the generator18, and a rotor22that is rotationally coupled to the gearbox20with a rotor shaft24. The rotor22includes a rotatable hub26, with the rotor blades28coupled to and extending outward from the rotatable hub26. Each rotor blade28includes a blade tip17and a blade root19, and corresponding root-end blade segment32and a tip-end blade segment29.

FIG. 2is a view of a retrofitted wind turbine blade70that was made by modifying a pre-staged blade28ofFIGS. 4a-4csuch that the root-end blade segment32of pre-staged rotor blade28is retrofitted with a replacement blade tip segment30that extends in the opposite span-wise direction from a chord-wise joint34. Each of the blade segments30,32includes a pressure side shell member31and a suction side shell member33. The blade segments30,32are connected by internal joint structure36extending into both blade segments30,32to facilitate joining of the blade segments30,32, as described in greater detail below. The blade70includes a leading edge74and a trailing edge76, as well as the root portion19and tip portion17, with the upper and lower shell member31,33joined together at the leading edge74and trailing edge76. The pre-staged blade28and retrofitted blade70include an internal cavity in which various structural members, such as spar caps46and shear webs44are configured. The construction and function of the internal structural components of the blade70are well known to those skilled in the art and need not be described in detail herein for an understanding and appreciation of the present invention.

Referring still toFIGS. 2 and 4a-4c, the pre-staged wind turbine blade28is provided with a continuous spar structure42from the root section19to the tip section17, as with any number of conventional wind turbine blade designs. This spar structure42may include, for example, opposite shear webs44and opposite spar caps46that define a box-beam spar structure42. At a pre-defined span-wise location, a span-wise extending beam structure40is incorporated with the spar structure42during fabrication of the pre-staged blade28by fixing a root-end41of the beam structure40with the spar structure42and leaving a tip-end43of the beam structure40essentially unattached to the spar structure42. As appreciated fromFIG. 2, the beam structure40has a size for insertion into a mating receiver section54within the replacement blade tip segment30during the retrofitting process.

In the embodiment ofFIGS. 4a-4cwherein the spar structure42includes opposite shear webs44, the root-end41of the beam structure40may be fixed between the shear webs44, for example with an adhesive, mechanical means, or any other suitable means. The tip-end43of the beam structure40may lie adjacent to the shear webs44, but is unattached to the shear webs44so that the shear webs44can be easily cut away from the tip-end43, as depicted inFIGS. 4band 4c, for subsequent retrofitting with the replacement blade tip segment30. For this, as discussed above, the shell components31,33of the blade tip segment29(pre-staged blade28) are cut away at a chord-wise joint line34such that the tip-end43of the beam structure extends span-wise from the remaining blade root segment32beyond the chord-wise joint line34. The spar structure42in the blade root section32that extends along the tip-end43of the beam structure40may be removed at the same time or after cutting away of the blade shell components31,33so only the beam structure40extends from the blade root segment32, as depicted inFIG. 4c. Then, the replacement blade tip segment30can be aligned and connected with the blade root segment32in the retrofitting process wherein the tip-end43of the beam structure40slides into the mating receiver section54of the replacement blade tip segment30, as seen inFIG. 2.

The embodiment ofFIGS. 3 and 5a-5cis drawn to providing the pre-staged wind turbine blade28with a pre-staged receiver section54having a root end55fixed to the spar structure42. An opposite end of the receiver section54extends at least to the chord-wise joint line34and may be fixed to the webs44along the complete length of the receiver section54. As depicted inFIGS. 5band 5c, when the blade tip segment29is cut away from the pre-staged blade28, the spar structure, including the webs44and/or are subsequently cut back to the joint line34. If the receiver section54extends beyond the joint line34(as depicted inFIG. 5b), then this length of the receiver section54may also be trimmed to the joint line34such that an open end of the receiver section54is exposed at the joint line (FIG. 5c) for receipt of a beam structure40that extends from the replacement blade tip segment30.

FIGS. 6athrough 6esequentially depict an embodiment of the current method for retrofitting a pre-staged wind turbine rotor blade28in the field, wherein the blade28remains attached in the uptower positon to a rotor hub. Alternatively, the pre-staged wind turbine blade28can be removed and lowered from the hub26using any suitable process and the retrofitting process is performed with the wind turbine blade28in a down-tower position relative to the rotor hub26.

FIG. 6bdepicts a chord-wise cut made in the blade28at a location that defines a chord-wise joint line34. With this embodiment, the cut can made completely through the blade28, wherein the existing blade tip segment29is removed, as depicted inFIG. 6c. The remaining spar structure42is depicted in the blade root segment32(FIG. 6c). In an alternate embodiment wherein the pre-staged blade28includes a pre-staged beam structure40, the cut at the chord-wise joint line34would be made through the blade shell components31,33leaving the spar structure42(e.g., webs44and spar caps46) essentially intact (as depicted and discussed above with respect toFIG. 5b).

FIG. 6cdepicts the blade root segment32with the receiver section54exposed at the joint line34.

FIG. 6ddepicts selection of one of the preformed replacement blade tip segments30from an inventory60and span-wise connection of the segment30with the blade root segment32. In particular, as the replacement blade tip segment30is moved in the span-wise direction, the beam structure40slides into the pre-staged receiver section54within the blade root segment32. To fix the beam structure40with the receiver section54, the end pin52on the root end43of the beam structure40extends through a slot in the wall57of the receiver section54(FIG. 3), and chord-wise oriented slots in the receiver section54align with corresponding slots in the beam structure40. A chord-wise pin53is then inserted through the aligned slots, as particularly seen inFIG. 3.

FIG. 6edepicts the replacement blade tip segment30fixed to the blade root segment32and the blade shell components provided with a finish at the joint line34, for example a fiberglass, epoxy or other repair type finish that provides a relatively smooth and aerodynamic surface at the join line34between the shell components of the replacement blade tip segment30and the root-end blade segment32. The finish may include a seal band68wrapped around the blade shell components31,33at the joint line34. Thus, the blade inFIG. 6eis a complete retrofitted blade70as also depicted inFIG. 3.