Patent Application
20130299277
The present disclosure generally relates to wind turbines and, more particularly, relates to wind turbine towers for optimized mounting of tower internal components.
A utility-scale wind turbine typically includes a set of two or three large rotor blades mounted to a rotor hub. The rotor blades and the rotor hub together are referred to as the rotor. The rotor blades aerodynamically interact with the wind and create lift, which is then translated into a driving torque by the rotor. The rotor is attached to and drives a main shaft, which in turn is operatively connected via a drive train to a generator or a set of generators that produce electric power. The main shaft, the drive train and the generator(s) may all be situated within a nacelle, which in turn is situated on top of a wind turbine tower.
The most common type of wind turbine tower today is a steel tube tower constructed of several individual tower sections. Each tower section is essentially a steel shell attached to internal top and bottom flanges, and the top flange of one section is bolted to the bottom flange of an adjacent section to form the tower. While typically a wind turbine tower is composed of three or four tower sections, the number of tower sections may vary depending upon the hub height of the wind turbine tower.
Inside the wind turbine tower are tower internals that may include a ladder, a lift, platforms spaced at various tower heights, lights, and electrical conduits and wires. The platforms may be provided just below each flange joint between tower sections and are primarily provided as a working surface for technicians to complete the flange bolted joints during construction of the tower, and to inspect and service these bolted joints throughout the tower's life. The ladder extends from the bottom of the tower to the top and is the means by which technicians reach the nacelle on top of the tower. Various wires and electrical cables also run up and down the tower.
The tower internals are typically supported by brackets that are welded to the inside surface (e.g., the inside wall) of the wind turbine tower. The brackets for all of the platforms, cable trays and other wire attachments, the ladder, the lights, etc., can add up to a lot of brackets to weld to the inside of the wind turbine tower. Each welded bracket reduces the fatigue strength of the steel shell of the wind turbine tower. In order to account for the reduced fatigue strength due to the welded brackets, the steel shell has to be of an increased thickness to meet certain design requirements and to effectively resist wind turbine loads. The thicker the steel shell is, the more expensive it is and the more it weighs, adding to the overall weight and cost of the wind turbine.
Accordingly, it would be beneficial if a mechanism to effectively mount tower internals within a wind turbine tower without compromising its strength is developed. It would additionally be beneficial if such a mechanism is cost effective and weighs less relative to existing mechanisms in traditional wind turbine towers.
In accordance with one aspect of the present disclosure, a tubular wind turbine tower section is disclosed. The tubular wind turbine tower section may comprise a top flange, a bottom flange, a bottom can attached to the bottom flange, a top can attached to the top flange, a plurality of intermediate cans axially joined together between and attached to the bottom can and the top can, and a plurality of support brackets welded to the top can and the bottom cans. At least some of the intermediate cans may have a thickness less than the thickness of the top can, and no support brackets are welded to said intermediate cans.
In accordance with another aspect of the present disclosure, a wind turbine tower section is disclosed. The wind turbine tower section may comprise a top flange, a bottom flange, a bottom can attached to the bottom flange, a top can attached to the top flange, a plurality of intermediate cans axially joined together between and attached to the bottom can and the top can, and a support system for supporting tower internals inside of the tower section. The support system may be attached to support brackets mounted to the top can and the bottom can. No support brackets are welded to the intermediate cans.
In accordance with yet another aspect of the present disclosure, a tubular wind turbine tower section is disclosed. The tubular wind turbine tower section may comprise a top flange, a bottom flange, a bottom can attached to the bottom flange, a top can attached to the top flange, a plurality of intermediate cans axially joined together between and attached to the bottom can and the top can, and a plurality of support brackets welded to the top can and the bottom cans. No support brackets are welded to at least some of the intermediate cans, and each of the intermediate cans without welded support brackets may have a thickness less than the thickness of said intermediate can if said can had a support bracket welded to it.
Other advantages and features will be apparent from the following detailed description when read in conjunction with the attached drawings.
For a more complete understanding of the disclosed methods and apparatuses, reference should be made to the embodiments illustrated in greater detail on the accompanying drawings, wherein:
While the following detailed description has been given and will be provided with respect to certain specific embodiments, it is to be understood that the scope of the disclosure should not be limited to such embodiments, but that the same are provided simply for enablement and best mode purposes. The breadth and spirit of the present disclosure is broader than the embodiments specifically disclosed and encompassed within the claims eventually appended hereto.
Referring to
Ladders, platforms, lights, electrical conduits, and several other components may be mounted within the wind turbine tower 4, in a manner described in
Turning now to
Each of the tower sections 30 may include a top flange 32 and a bottom flange 34, for mounting to adjacent tower sections, the base foundation 28 (e.g., the bottom flange of the bottommost tower section may be connected to the base foundation), or the nacelle 6 (e.g., the top flange of the topmost tower section may be connected to the nacelle). Between the top flange 32 and the bottom flange 34 of each individual tower section 30 may be multiple shells or cans 36 that may be welded (or connected by other mechanisms) at their axial ends to one another or to one of the top or the bottom flanges to form each tower section. Each of the cans 36 may be constructed of a single piece of steel plate bent, formed, or rolled into a substantially cylindrical (or other) shape and welded on its ends. Other materials or alloys may also be suitable for constructing the wind turbine tower 4 in addition to steel plate.
The thickness of the steel plate and the resulting thickness of the cans 36 constructed from that steel plate may be selected according to established design principles. To reduce weight and cost, the cans 36 that have internal components welded to them may be made of thicker steel plates compared to the cans that have no additional welding aside from the longitudinal and circumferential welds that are used to join the cans. Specifically, inside the wind turbine tower 4 are disposed various components generically referred to as tower internals. These tower internals may include ladders, lifts and platforms for maintenance and for reaching the nacelle 6, cables for power transmission and controls, lighting, etc., all of which may be mounted to and/or supported by the inside walls of the cans 36 through welding. For example, a ladder may be fixed to brackets, which in turn may be welded to the inside walls of one or more of the cans 36. One of the design variables that affects the thickness of the steel plate required for constructing the cans 36 is the effect of welding. For a given load on, the wind turbine tower 4, the addition of welds at various locations on the inner walls of the cans 36 reduces the fatigue strength of the can walls, which increases the thickness requirement. The welding of a bracket, for example, to the inner wall of the cans 36 not only creates stress risers and changes the metallurgy of the parent material (e.g., steel plate) in the heat affected zone, it also applies additional point loads to the tower wall, etc. All of these effects increase the need for the steel plate of the cans 36 to be thicker in order to meet the design requirements.
In order to reduce weight and cost of the wind turbine tower 4 (and the wind turbine 2), the present disclosure proposes that the welding of tower internals to the cans 36 be limited to only certain cans of each tower section 30 so that only the cans having welding will be made of thicker steel plates, while the remaining ones of the cans may be made of thinner steel plates.
Referring now to
The tower section 40 may be mounted via its bottom flange 34 to the base foundation 28. As shown best in
The thickness of each of the cans 36 within the tower sections 40 and 42 may be customized to reduce weight of the wind turbine tower 4 and the cost of the steel plate making up those cans. Specifically, the steel plate of the cans 36 that do not have any welding from mounting of tower internals on their inner walls may be thinner, cheaper and lighter than the steel plate of the cans which do have any internal welding (from mounting tower internals).
In at least some embodiments and, as shown, the tower internals may be attached only to a top can 44 and a bottom can 46 within each of the tower sections 40 and 42. For the top can 44 and the bottom can 46, the steel plate employed for constructing those cans may be thicker to permit welding and meet all design requirements, while all intermediate cans 48 (which have no welding) may be constructed of thinner steel plate that is not thick enough to permit welding but yet meets all design requirements. In order to facilitate attachment of the tower internals to the top can 44 and the bottom can 46, a plurality of support brackets 50 welded to the top and the bottom cans and/or a support system 52 supported by the support brackets may be employed. Both the support brackets 50 and the support system 52 are described below.
With respect to the support system 52, it may include one or more tubes (e.g., rectangular tubes) or rods 54 that may be connected (e.g., by bolts) to and supported by the support brackets 50 welded to the top can 44 and the bottom can 46 of each of the tower sections 40 and 42. In addition to tubes or rods, truss sub-assemblies or cables may also be possible instead of rods 54. While two (See
The support system 52 may be supported by way of the support brackets 50 welded to the inner walls of one or both of the top can 44 and the bottom can 46 of each tower section. As shown specifically in
The support system 52 can function as a “backbone” inside the tower for the attachment of and support of tower internals, and structures other than those illustrated or described could constitute this backbone. Together the support brackets 50 and the support system 52 may be employed as attachment points to support the various tower internals, such as, one or more ladders 60, buss bars, cables, outlets, lights, platforms and other components (not shown). Similar to the tubes 54, some of the tower internals may additionally be supported laterally against swaying, if necessary, by utilizing brackets attached to the inner walls of the intermediate cans 48 by ways other than welding such as bolts, glue or magnets.
By virtue of using only the top can 44 and the bottom can 46 for welding, these cans may be constructed of thicker steel plates compared to steel plates of the intermediate cans 48, thereby facilitating a reduced weight and cheaper wind turbine tower 4. Each can without welding of support brackets for mounting tower internals may have a reduced thickness, less than the thickness would have been if there were attachment points welded to it. The cans with welding of support brackets for mounting tower internals may advantageously include only the top can 44 and the bottom can 46. Any one or more of the intermediate cans 48 may also have welding of support brackets for mounting tower internals, if necessary. By designing a wind turbine tower having each of its tower sections with this can configuration, the overall weight and cost of construction is lowered, while maintaining the fatigue strength of the wind turbine tower.
Thus, depending upon the size and weight of the various tower internals, the thickness of the cans 36 in any given tower section 30 may be customized to have thicker steel plates where welding is desired and thinner steel plates in all remaining cans. Furthermore, each of the tower sections 30 may be individually customized depending upon the requirements of the tower internals mounted therein. For example, one tower section may have only the top and the bottom cans 44 and 46, respectively, with increased thickness, while another tower section may have top two and bottom two cans with increased thickness, and so on.
Thus, the present disclosure sets forth a wind turbine tower with customized thickness of cans or shells composing each of the plurality of tower sections. The cans having tower internals mounted (e.g., welded) thereon may be constructed of thicker steel plates while the cans with no welding may be constructed of thinner steel plates to save cost and to reduce the overall weight of the wind turbine tower without compromising the fatigue strength of the wind turbine tower while meeting all design requirements.
While only certain embodiments have been set forth, alternatives and modifications will be apparent from the above description to those skilled in the art. These and other alternatives are considered equivalents and within the spirit and scope of this disclosure and the appended claims.
