Abstract:
A wind turbine blade internal structure system is disclosed herein. A representative system includes span wise spar elements, thru thickness web elements, and an aerodynamic shell. In particular embodiments, the spars may be constructed of pre-cured planks and either adhesively bonded together or assembled using layers of laminates between planks. The laminate layers may be used for structural purposes either to increase the stiffness of the spar, increase the effective bond area of the spar to the shell, or to form a transition region at the plank termination. The spars can be incorporated into the shell assembly layup. The shear web may contain segmentation along the span wise axis of the blade, splitting the shear web into pressure and suction halves that are joined by a connector element that allows for alignment between the web halves in the span wise, chord wise, and thickens directions. The spar and web design elements discussed herein can be applied to either a segments or monolithic blade assembly.

Description:
TECHNICAL FIELD 
       [0001]    The present technology is directed generally to efficient wind turbine blades and wind turbine blade structures, including segmented and/or otherwise modular wind turbine blades, and segmented shear webs. 
       BACKGROUND 
       [0002]    As fossil fuels become scarcer and more expensive to extract and process, energy producers and users are becoming increasingly interested in other forms of energy. One such energy form that has recently seen a resurgence is wind energy. Wind energy is typically harvested by placing a multitude of wind turbines in geographical areas that tend to experience steady, moderate winds. Modern wind turbines typically include an electric generator connected to one or more wind-driven turbine blades, which rotate about a vertical axis or a horizontal axis. 
         [0003]    In general, larger (e.g., longer) wind turbine blades produce energy more efficiently than do short blades. Accordingly, there is a desire in the wind turbine blade industry to make blades as long as possible. However, long blades create several challenges. For example, long blades are heavy and therefore have a significant amount of inertia, which can reduce the efficiency with which the blades produce energy, particularly at low wind conditions. In addition, long blades are difficult to manufacture and in many cases are also difficult to transport. Accordingly, a need remains for large, efficient, lightweight wind turbine blades. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is a partially schematic, isometric illustration of a wind turbine system having blades configured in accordance with an embodiment of the presently disclosed technology. 
           [0005]      FIG. 2  is a partially schematic, isometric illustration of a wind turbine blade configured in accordance with an embodiment of the presently disclosed technology. 
           [0006]      FIG. 3  is an illustration of an embodiment of the wind turbine blade shown in  FIG. 2 , with portions of the outer skin of the blade removed and/or translucent for purposes of illustration. 
           [0007]      FIGS. 4A-4B  show a cross sectional view of an embodiment of the wind turbine blade in which the spars are internal to the shell structure, with  FIG. 4A  displaying the entire blade assembly and  FIG. 4B  showing a detailed view of the spar cap within the skin build. 
           [0008]      FIGS. 5A-5D  illustrate several steps in a manufacturing method for encapsulating a rectangular layered spar within an aerodynamic shell. 
           [0009]      FIGS. 6A-6C  illustrate several different materials that can be used as an adhesive layer between the pre-cured sections of the rectangular layered spar, in accordance with embodiments of the presently disclosed technology. 
           [0010]      FIGS. 7A-7B  illustrate the use of interleaved laminate layers between precured spar planks to provide an increased strength connection between the spar and the shell, in accordance with embodiments of the presently disclosed technology. 
           [0011]      FIG. 8  illustrates a spar joint for a modular blade extending from a segment in which the spar is encapsulated within the aerodynamic shell, in accordance with embodiments of the presently disclosed technology. 
           [0012]      FIG. 9  illustrates a segmented shear web installation having a split line that runs along the spanwise axis of the blade, in accordance with embodiments of the presently disclosed technology. 
           [0013]      FIG. 10  shows a manufacturing method for a wind turbine blade in which two halves are completed and then mated together, in accordance with an embodiment of the present technology. 
           [0014]      FIG. 11  shows a partially schematic, isometric view of a representative transition between spar planks of one width and spar planks of another width, in accordance with an embodiment of the present technology. 
           [0015]      FIG. 12  shows a side view of a representative transition between spar planks of one width and spar planks of another width, in accordance with an embodiment of the present technology. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The presently disclosed technology is directed generally to efficient, modular wind turbine blade shear webs and other structures, and associated systems and methods for manufacture, assembly, and use. Several details describing structures and/or processes that are well-known and often associated with wind turbine blades and rotors are not set forth in the following description to avoid unnecessarily obscuring the description of the various embodiments of the technology. Moreover, although the following disclosure sets forth several representative embodiments, several other embodiments can have different configurations and/or different components than those described in this section. In particular, other embodiments may have additional elements and/or may lack one or more of the elements described below with reference to  FIGS. 1-12 . In  FIGS. 1-12 , many of the elements are not drawn to scale for purposes of clarity and/or illustration. In several instances, elements referred to individually by a reference number followed by a letter (e.g.,  110   a ,  110   b ,  110   c ) are referred to collectively by the reference number without the letter (e.g.,  110 ). 
         [0017]      FIG. 1  is a partially schematic, isometric illustration of an overall system  100  that includes a wind turbine  103  having blades  110  configured in accordance with an embodiment of the present technology. The wind turbine  103  includes a tower  101  (a portion of which is shown in  FIG. 1 ), a housing or nacelle  102  carried at the top of the tower  101 , and a generator  104  positioned within the housing  102 . The generator  104  is connected to a shaft or spindle carrying a hub  105  that projects outside the housing  102 . The blades  110  each include a hub attachment portion  112  at which the blades  110  are connected to the hub  105 , and a tip  111  positioned radially or longitudinally outwardly from the hub  105 . In an embodiment shown in  FIG. 1 , the wind turbine  103  includes three blades connected to a horizontally-oriented shaft. Accordingly, each blade  110  is subjected to cyclically varying loads as it rotates among the 12:00, 3:00, 6:00 and 9:00 positions, because the effect of gravity on the blade is different at each position. In other embodiments, the wind turbine  103  can include other numbers of blades connected to a horizontally-oriented shaft, or the wind turbine  103  can have a shaft with a vertical or other orientation. In any of these embodiments, the blades  110  and the hub  105  can together form a rotor  106 . The blades  110  can be manufactured and/or assembled in situ, in the field, or otherwise near the tower  101  to reduce the expense and inconvenience of transporting large, fully-assembled blades. 
         [0018]      FIG. 2  is partially schematic, isometric illustration of a representative one of the blades  110  described above with reference to  FIG. 1 . The blade  110  includes multiple segments  113 , for example a first segment  113   a , a second segment  113   b , and a third segment  113   c . The segments extend along a spanwise, longitudinal, or axial axis from the hub attachment portion  112  to the tip portion  111 . The spanwise axis is represented in  FIG. 2  as extending in hub direction H and tip direction T. The blade  110  also extends along a thickness axis in pressure direction P and a suction direction S, and further extends along a chordwise axis in a forward direction F and an aft direction A. The outer surface of the blade  110  is formed by a skin or shell  150  that can include several skin or shell sections. These sections can include a suction side skin or shell  151 , a pressure side skin or shell  152 , and a trailing edge skin or shell  154 . The internal structure of the blade  110 , the connections between the internal structure and the skin/shell  150 , and the connections between neighboring segments  113  are described further below. 
         [0019]      FIG. 3  illustrates the blade  110  with portions of the skin removed or translucent for purposes of illustration. In this embodiment, the blade  110  includes multiple ribs  160  located at each of the segments  113   a ,  113   b , and  113   c . The ribs  160  are connected to three spars  116  (shown as first spar  116   a , second spar  116   b , and a third spar  116   c ) that extend along the length of the blade  110 . Accordingly, each of the spars  116  includes a first portion  118   a  at the first segment  113   a , a second spar portion  118   b  at the second segment  113   b , and a third spar portion  118   c  at the third segment  113   c . Each segment  113  also includes a corresponding shear web  117 , illustrated as a first shear web  117   a , a second shear web  117   b , and a third shear web  117   c . Each segment  113  may also contain an aft shear web  119  to connect the third spar,  116   c , to the shell, illustrated as a first aft shear web  119   a , a second aft shear web  119   b , and a third aft shear web  119   c . The spar portions  118  in neighboring sections  113  are connected at two connection regions  114   a ,  114   b  to transmit loads from one segment  113  to the next. The shear webs  117  are not continuous across the connection regions  114 . Instead, truss structures  140  (shown as first structure  140   a  and second truss structure  140   b ) at each connection  114  are connected between neighboring segments  113  to transmit shear loads from one segment  113  to the next. 
         [0020]      FIG. 4A  illustrates a cross sectional view of a representative segment  113  of the blade  110  configured in accordance with an embodiment of the present technology. The first and second spars,  116   a  and  116   b , are shown as layered pre-cured spars which are encapsulated within the aerodynamic shells  151  and  152 . The first and second spars  116   a ,  116   b  are connected through the thickness direction by the shear web  117 . This embodiment illustrates the third spar  116   c  as a pre-cured spar connected to the suction side skin  151  and the pressure side skin  152  through the aft shear web  119 , though in other embodiments, the third spar  116   c  can have other arrangements. For clarity, the spars  116  have been shown as rectangular elements, but the spars  116  can have other shapes in other embodiments. In general, the spars  116  are made up of a single stack of flat, pre-cured elements, with each element having the same chordwise width in some embodiments and different widths in other embodiments. 
         [0021]      FIG. 4B  shows a detailed diagram of the second spar  116   b  and the suction shell  151 . The component configuration is similar to that of the first spar  116   a  and the pressure side shell  152 . In this embodiment, the shell  151  includes an outer face sheet  203 , e.g., formed from a number of laminate plies along the exterior face of the aerodynamic shell. The shell  151  further includes an inner face sheet  204 , e.g., formed from a number of laminate plies along the interior face of the aerodynamic shell, and a core body or layer  205  between the two face sheets  203 ,  204 . In a typical embodiment, the face sheets  203 ,  204  are fiber reinforced composite laminates (e.g. fiberglass) and the core  205  is a low density material such as balsa wood or foam, though in other embodiments, these components can be formed from other materials. 
         [0022]    The second spar  116   b  is formed from layers of pre-cured laminate planks  201  that are flat in one direction (e.g., a generally chordwise direction), and are bonded with adhesive layers  202 . In a particular embodiment, the layers forming individual planks  201  are constructed of pultruded fiberglass, and in other embodiments they can be made of other composites using other fibers (e.g. carbon fibers) with different resins (e.g. epoxy, polyester and/or others), or even homogeneous materials (e.g. wood and/or metal). 
         [0023]    In a particular embodiment, the second spar  116   b  is encapsulated between the face sheets  203  and  204  in place of the core layer  205  at that location. To fit the rectangular second spar  116   b  against the curved aerodynamic shell  151 , a filler component  207  is placed between the second spar  116   b  and the internal surface of the suction side shell  151 . The filler component  207  can be or include a non-structural material such as foam or pure polymer, but may in other embodiments be a structural material such as a fiber-reinforced composite in order to add to the structural performance of the blade  110 . 
         [0024]    To eliminate a sharp bend in the inner face sheet  204  when the second spar  116   b  and the core  205  do not have the same thickness, ramp elements  206  may be added to the core  205  adjacent to the spar  116   b . The ramp elements  206  may be manufactured from low cost, lightweight materials. In other embodiments, the plies of the face sheets  203  and  204  may follow paths different than those shown in  FIG. 4B . For example the inner face sheets  204  can go around the outside of the second spar  116   b  such that in the area over the second spar  116   b , the inner face sheet  204  is near the outer surface of the shell  151 . In another embodiment, some plies of the outer face sheet  203  wrap around the inside of the second spar  116   b , or some plies of the face sheets  203  and  204  follow paths through intermediate bondlines inside the second spar  116   b . The selection of which configuration is suitable for a given application can be made based on criteria such as stress, manufacturing, and/or reliability. 
         [0025]      FIGS. 5A-5D  illustrate a representative manufacturing method for encapsulating the rectangular layered second spar  116   b  within the aerodynamic suction side shell  151 . The pressure side shell  152  and first spar  116   a  can be made in accordance with a similar manufacturing method. In  FIG. 5A , the outer face sheet laminate plies  203  are first laid up against a female mold  209 .  FIG. 5B  shows a detailed view of the spar landing region. In this embodiment, the filler component  207  is constructed of a multitude of laminate plies cut to varying widths to fill the gap between the outer face sheet  203  and the layered spar assembly of planks  201  and adhesive layers  202 . By making the filler component  207  from a unidirectional laminate, with the fiber direction oriented along the spanwise axis of the blade, the manufacturer can increase the bending stiffness of the blade  110 . In this embodiment, a fiber mat layer  208  is placed between the spar assembly  116   b  and the filler plies  207  to promote resin flow through the region. In other embodiments, this gap may be filled with other materials such as adhesive or resin, or a pre-cured component shaped such that it fits inside the available space.  FIG. 5C  illustrates the placement of the core layer  205 , and the optional core ramps  206  around the spar assembly  116   b  against the outer face sheet  203 .  FIG. 5D  illustrates a process for completing the layup with the addition of the inner face sheet  204 . The layup diagrams described in  FIGS. 5A-5D  can be used with any suitable layup manufacturing method including the use of pre-preg laminates, wet layup, and infusion. Furthermore, variations in the sequence of operations may be made in order to produce the variations in configuration described in the preceding paragraph. 
         [0026]      FIGS. 6A-6C  illustrates configurations in accordance with further embodiments for bonding the pre-cured layers  201  together into a spar, using different types of fiber-reinforced layers to function as the adhesive layers  202  between the precured plank layers  201 . In some embodiments, a pure adhesive is used, and in others, any of the fiber-reinforced materials  202  shown in  FIGS. 6A-6C  are used. Pre-preg, wet layup, infusion, and/or other suitable methods can be used to make suitable fiber-reinforced materials  202 . The spar assembly of pre-cured planks  201  and laminate adhesive layers  202  can be cured as a sub-assembly and then used in full blade assemblies, or the adhesive layers  202  can be co-cured with the shells if the spars are encapsulated as shown in  FIG. 4A-5D . 
         [0027]    Three representative embodiments for forming representative spar assemblies are shown in  FIGS. 6A-6C . In  FIG. 6A , the adhesive layers  202  are made of a unidirectional laminate, having a fiber alignment that runs along the spanwise axis of the blade. The use of a unidirectional laminate as the adhesive layer can significantly increase the axial stiffness and strength of the resulting spar assembly. In  FIG. 6B , the adhesive layers  202  are made of a biaxial laminate which can significantly increase the shear load capability of the spar assembly.  FIG. 6C  shows a triaxial laminate used for the adhesive layers  202 , which combines the benefits of both the unidirectional and biaxial laminates. This method can be used on any suitable size and number of planks for a spar assembly, though only three planks are shown in  FIGS. 6A-6C  for purposes of illustration. 
         [0028]      FIGS. 7A-7B  illustrate techniques for positioning laminates (used as the adhesive layers  202 ) between pre-cured spar planks to increase the bond area of the spar assembly. In this embodiment,  FIG. 7A  is a cross sectional view of a representative second spar  116   b . The laminate adhesive layers  202 , extend beyond the width of the planks  201 . In  FIG. 7A , all the laminate layers  202  are gathered on one side or opposing sides of the spar assembly to create a flange. This flange can increase the bond area if the spar assembly is bonded to a finished skin shell, or if the spar is encapsulated within the shell as shown in  FIGS. 4A-4B .  FIG. 7B  illustrates another embodiment in which some of the laminate layers  202  pass along or adjacent to the outer face sheet  203 , and the remainder pass along or adjacent to the inner face sheet  204 . The extended plies also aid in reinforcing the skin shell locally where extra strength may be beneficial for transferring loads to and from the spar. Only three planks are shown in  FIGS. 7A-7B  to simplify the illustrations but these methods can be used for embodiments of any suitable spar size and/or plank count. 
         [0029]    In a similar manner, fiber-reinforced adhesive layers  202  may extend past the ends of the pre-cured planks  201  in the longitudinal direction, e.g. toward the blade tip or toward the hub, into and out of the plane of  FIGS. 7A and 7B . The plies can be used as one or more transition elements from the spars to the hub attachment or root region  112  ( FIG. 2 ). The plies can also be utilized in the extreme outboard section of the blade  110  to transition from a layered plank spar to a traditional spar layup. 
         [0030]      FIG. 8  illustrates a representative manner in which a layered spar encapsulated within the aerodynamic shell can be used in a modular wind turbine blade. In particular,  FIG. 8  illustrates a portion of the first spar  116   a  shown in  FIG. 4A  at a joint region of the overall blade  110  (e.g., the first joint region  114   a  shown in  FIG. 3 ). The precured planks  201  that form the first spar  116   a  extend longitudinally past the end of the pressure side shell  152 . The planks terminate at varying longitudinal locations creating a pattern of projections and recesses. These will align with corresponding recesses and projections, respectively, from the plank termination points of and adjacent spar in the spanwise adjoining section to form a finger lap joint which can be bonded by applying an adhesive. Suitable techniques for forming such joints are included in U.S. Patent Publication No. US2012/0082555, incorporated herein by reference. To the extent the foregoing application and/or any other materials incorporated herein by reference conflict with the present disclosure, the present disclosure controls. The foregoing arrangement can provide a high strength joint between the spars located in different spanwise sections of the blade. Additional structure may be used or required to carry shear and torsion loads, such as a truss structure or an additional shear web and associated skin panels. 
         [0031]      FIG. 9  is an illustration of the shear web  117  configured as a segmented assembly. In this embodiment, the shear web  117  is connected between the first spar  116   a  and the second spar  116   b  e.g., at the centers of the spars. The same technique can be used to join shear webs  117  to spars at other positions, including but not limited to (a) the forward edges of the first and second spars, (b) the aft edges of the first and second spars, (c) between the pressure and suction skins  152 ,  151 , but not contacting a spar, and/or (d) any combination of multiple shear webs. The shear web  117  can include a pressure side element  217   a , a suction side element  217   b , and a connector element  217   c . The split line between the pressure side element  217   a  and the suction side element  217   b  runs in a spanwise direction along the blade  110 . The connector element  217   c  can allow for alignment and/or adjustment between the suction side element  217   a  and the pressure side element  217   b  in the three blade axes, e.g., spanwise axis, thickness axis, and chordwise axis. 
         [0032]    In a particular embodiment, the connector element  217   c  has a socket type configuration, as illustrated in  FIG. 9 . For example, the connector element  217   c  can include a female element that directly receives the end of the suction side element  217   b , or that receives a corresponding male component carried by the suction side element  217   b . Connections in accordance with other suitable embodiments include but are not limited to (a) a double lap shear configuration with bridging elements carried by both the shear elements  217   a ,  217   b , (b) a single lap shear configuration with a bridging element on one side or directly bonding the two web elements  217   a ,  217   b  together, and/or (c) a double-socket “H” style joint. The connector element  217   c  can be constructed as a co-cured extension of either the pressure side element  217   a  or the suction side element  217   b , or it can be a separate part formed from any suitable material and then bonded to both web elements  217   a ,  217   b.    
         [0033]      FIG. 10  illustrates a technique for manufacturing a blade  110  in accordance with a particular embodiment of the present technology. In this embodiment, the pressure and suction halves of the blade are completed to include spars and shear web segments and are then joined together to complete the blade. As shown, the first or pressure-side spar  116   a  is encapsulated within the pressure side skin  152 , and the second or suction-side spar  116   b  is encapsulated within the suction side skin  151 . The shear web  117  is initially segmented along the spanwise direction of the blade and so includes the pressure side element  217   a , the suction side element  217   b , and the connector element  217   c . In some embodiments, an additional spar may be used at the leading and/or trailing edges of the blade  110  for increased edgewise stiffness, but these are not shown in  FIG. 10  for purposes of clarity. During assembly, the two halves (or other fractional portions) are brought together and bonded. 
         [0034]    In some embodiments, it may be advantageous to use different widths of pre-cured planks in the spars of different portions of the blade, or to use pre-cured planks in one part of the blade, and other structures (e.g. infused or prepreg structures) in another part of the blade. Accordingly, embodiments of the present technology can include a structurally efficient transition between different parts of the spar.  FIG. 11  and  FIG. 12  show a transition in accordance with one such embodiment.  FIG. 11  illustrates a transition in which the inboard portion of the spar is made of first planks  201   a , and the outboard portion of the spar is made of second planks  201   b  with the first planks  201   a  being wider (e.g., in a chordwise direction) than the second planks  201   b . Individual first planks  201   a  are butted to a corresponding second plank  201   b . Additional narrow planks may be added on top of the spar cap as necessary to maintain selected levels of stiffness and strength across the transition area. The ends of the planks may have tapers or other arrangements for reducing stress concentrations at each individual layer. In other embodiments, some or all of the first planks  201   a  may be formed from materials different than those used to form the second planks  201   b  e.g., pre-cured composites with different fibers or resins, or composites fabricated in other ways (e.g. infusion, prepreg) without being pre-cured prior to assembly.  FIG. 12  shows a side view of this transition region with the thickness direction exaggerated for clarity. 
         [0035]    From the foregoing, it will be appreciated that specific embodiments of the present technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the technology. Further, while advantages associated with certain embodiments of the technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the present technology. Accordingly, the present disclosure and associated technology can encompass other embodiments not expressly shown or described herein.