Patent Grant
9168576
This application is a national phase application filed under 35 USC §371 of PCT Application No. PCT/EP2011/058768 with an International filing date of May 27, 2011, which claims priority of TR 2011/04141 filed Apr. 27, 2011. Each of these applications is herein incorporated by reference in their entirety for all purposes.
This invention relates to a production method of towers employed in wind turbines.
Diminishing fossil fuel resources and rising environmental pollution have turned the tendency towards clean energy resources into a need. Clean energy resources are those resources which do not bring about any emission of carbonaceous compounds when used. One of these most known and mostly preferred resources is the wind energy.
This energy source, the so-called wind energy, is obtained basically by turning the kinetic energy of wind into an exploitable form by means of turbines (mechanical turbine rotors). This mechanical energy is widely converted into electrical energy by means of electrical generators. The turbines are preferably disposed on towers at a plane which is vertical to the towers.
Since the wind speed increases with an increasing elevation from the sea level, the amount of energy obtainable from the wind enhances with rising the length of a tower. This mechanical effect generated by the wind, however, likewise influences the tower that carries the turbine. For this reason, it becomes crucial to provide the towers with a robust structure and to render them compliant with the operational conditions.
Towers of various structures have been in use for turbines. One of the most commonly used towers is the lattice-type tower. In the lattice type, the tower is composed of vertical or near-vertical bearing members and bracing elements coupling these members together. The lattice structure is advantageous for the production of lighter and robust towers with lower air resistance. On the other hand, since the lattice structure provides an open structure, any devices or equipment disposed within the lattice become exposed to external influences. Additionally, since the lattice structure allows birds to settle thereon, the revolving turbines generally cause the death of birds. And finally, as pointed above, the fact that the lattice structure is open against external influences brings about difficulties for the maintenance work in the tower and prolongs and endangers the same.
Therefore, close-structure turbine towers are preferred in wind turbines due to the drawbacks referred to hereinabove. One type of tower widely used in closed-type towers is the conical tower. In conical towers, the towers have a circular cross-section and therefore suffer lower air resistance. This circular cross-section also ensures a uniform distribution of tensile and compressive forces directed to the base of the tower. Since conical towers have a closed structure, they do not show the drawbacks encountered in lattice towers. Since the cross-sectional radius of the tower decreases with the length of the tower increasing, the strength of the tower suffices against the increasing wind speed at higher elevations.
The conical towers are manufactured in various forms. The most common method known in the prior art comprises the production of the lateral surface of a tower structure by cutting sheet metals of defined sizes in a proper manner, and bending and joining the same. However, the entirety of these operations cannot be performed at a single production site. Since such a tower is produced as a result of the joining operation that is too large to be transported, it becomes indispensable to conduct this operation at the site of installation. Preferably, the tower is produced in the form of components with horizontal upper and lower bases and these components are assembled at the production site. In this production method, however, almost half of the sheet metals used are cut and so become waste.
It is necessary to shape a web of sheet metal, i.e. a sheet metal coil, before it is cut in order to avoid material wastes and production handicaps. In the patent document JP 58/70918 A, in which a continuous conical structure production technique is disclosed, while a web of sheet metal is rolled with bending rollers, the angle between the line indicating the direction of movement of the sheet metal and the normal of the base of the tower is changed to yield a conical form. In that production method, however, it is not possible to produce wind turbines produced from thicker materials.
For the aforementioned reasons, a heretofore unaddressed need exists in the industry to develop a production method which eliminates such drawbacks.
The tower production method developed with the present invention comprises a first production stage including the steps of unrolling and bringing into a planar state a sheet metal wound around a coil; bending the planar sheet metal at the lateral direction at varying bending radii; and winding the bent sheet metal into a conical coil, as well as a final production stage yielding the tower and including the steps of feeding the sheet metal unrolled from the conical coil to at least one winding machine, and bending and winding the bent sheet metal in the winding machine around a central bending axis parallel to one surface thereof so that a defined initial winding radius and the angle between a longer edge thereof and the axis are kept constant and the longer edge of the sheet metal is joined over itself.
With the production method developed, the production stages of a tower and particularly of a conical tower are divided into two and the preproduction of the material composing the tower is performed at a plant. Following the first stage, the material that is turned into a coil is easily transported to the site of final production with lower costs and the final production stage is performed at the site to complete the tower production process. Thus, it becomes possible to produce towers of larger sizes while lowering production costs.
The object of the present invention is to develop a tower production method for a conical tower.
Another object of the present invention is to develop a tower production method, making use of a web of sheet metal, i.e. sheet metal coil.
A further object of the present invention is to develop a tower production method, allowing for a continuous production process.
Still another object of the present invention is to develop a tower production method, which allows for easier transportation than prior art methods.
Yet another object of the present invention is to develop a tower production method allowing production of a tower with higher mechanical strength than prior art towers.
Still a further object of the present invention is to develop a tower production method that minimizes waste material.
Yet a further object of the present invention is to develop a method for producing an inexpensive tower, which is easily produced, transported, and assembled.
A system, in which is used a tower production method developed according to the present invention, as well as representative embodiments of towers produced according to this method are illustrated in the annexed figures briefly described as following.
The parts in said figures are individually referenced as following.
As differing from the tower production methods according to the prior art, the tower production method developed with the present invention comprises a first production stage, in which a coil (A) of an unprocessed sheet metal (B) is made planar; and the planar sheet metal (B) is bent at the lateral direction so as to yield a bent sheet metal (B′) and is wound into a conical coil (A′); and a final production stage (C), in which a conical coil (A′) is unwound and is wound and joined in the form of a conical spiral (C) to produce a tower (C). The first production stage in which the sheet metal (B) is bent and brought into a conical coil (A′) is preferably conduced at a production facility. The produced conical coil (A′) is then transported to the site where the tower (C) is to be erected and is wound at that site to give a tower (C). Since the load is uniformly distributed at the joining edges of the wound sheet metal (B′) in a conical spiral tower (C) formed in this way, the mechanical strength of the tower is increased and a tower (C) is produced with high mechanical strength by making use of sheet metals (B) even with a lower thickness.
According to the method developed, the sheet metal (B) is bent at the lateral direction, as illustrated in
In said bending operation, when the sheet metal (B) is wound, it is bent so that a conical spiral tower is formed. Since the spiral pitch in the conical spiral is constant, bending a sheet metal with a constant shorter edge (B2) to form a conical spiral produces a conical structure in which the longer edges (B3) of the sheet metal (B) abut one over the other so that no gap remains there between. In order to form a conical spiral, the bending equation (f) of the sheet metal (B) bent on the lateral direction will preferably be as follows:
wherein “K(t)” stands for the bending function, “t” for the distance of a point on which a bending operation is conducted to one end of the sheet metal (B), “a” for the angular frequency, and “r” for the radius of the spiral (base of the tower). Since the edges (B3) of the sheet metal (B) are bent so as to be closed over themselves in producing a tower (C), the angular frequency (a) will be indirectly proportional to the width of the sheet metal (w). The spiral radius (r) in turn is equal to the lower radius of the tower (C). Thus, the bending radius (d) is determined with this equation (f) and the sheet metal (B) is bent at the lateral direction so as to form a conical spiral, i.e. the tower (C).
The bent sheet metal (B′), having underwent the first production stages, is preferably wound around an accumulator (7) before it is wound around the conical coil (A′). The accumulator (7) allows for subjecting the sheet metal (B′) to any of a plurality of operations while it is in a stationary state, before it is wound around the coil (A′). The painting and drying operations, for instance, can be conducted at the accumulator (7) with manpower while the sheet metal (B′) is wound around the accumulator (7). Additionally, the accumulator (7) allows space to be saved at the site of production.
In the first production stage of the method developed according to the present invention, the sheet metal (B) can either be processed horizontally (the wider surface (B1) thereof being parallel to the ground), or vertically (the wider surface (B1) thereof being now vertical to the ground). The vertical operation has various advantages over the horizontal one. One of these advantages is that the welding operation to join two sheet metals (B) is performed more easily as compared to the other case. The most significant difference between the horizontal and vertical operations is that the bent sheet metal (B′) is moved at the vertical or horizontal direction on the production band following the bending operation. In this context, the space required to keep the bent sheet metal (B′) within the site of production is arranged either vertically or horizontally. When a vertical production is conducted, however, the sheet metal is brought close to the horizontal with a small angle following the bending operation so that the space in which the sheet metal is kept is reduced. In this tilting operation, as exemplified in
After the sheet metal (B) is first bent and then wound in the first production stage into a conical coil (A′), it is transported to the site where the tower (C) is to be erected (and where the final production stage is implemented). This transportation operation is conducted both easily and inexpensively, since the bent sheet metal (B′) is wound into a conical coil form (A′).
In said winding operation, the sheet metal must be fed into the winding machine (8) from a correct position to result in a correctly-wound tower (C). Since the radius of a sheet metal (B′) being wound is varying especially in winding a conical tower, its position with respect to the winding machine (8) can change. For this reason, in a preferred embodiment according to the present invention, the position of the sheet metal (B′) by which it is fed to the winding machine (8) can be adjusted on the horizontal and vertical axes, as well as angularly, to conduct the winding operation in a correct manner.
In an alternative embodiment of the present invention, a tower (C) may be in the form of joining more than one sheet metal (B′) end-to-end from their shorter edges (B2) and winding the same. Particularly if a high tower (C) is to be formed, the amount of sheet metal (B′) wound around a single conical coil (A′) may not be adequate to form the entirety of the tower (C). In this case, after all of a sheet metal (B′) provided on a conical coil (A′) is fed to the winding machine (8), the next conical coil (A′) is taken and the sheet metal (B′) thereon (A′) is unwound and at least one shorter edge (B2) thereof is joined to at least one shorter edge (B2) of the former sheet metal (B′) wound in the winding machine (8). This fixation operation is preferably performed via welding. The thickness of sheet metals (B′) joined end-to-end can preferably be different as required by the size and shape of a tower (C) produced.
With the production method developed according to the present invention, the first shaping and conditioning operations of a sheet metal (B) to produce a tower (C) are performed at a production facility (plant) and the sheet metal (B) is thus brought into a conical coil (A′), so that the material to make a tower (C) can be kept at a very small volume and be transported in this form to the site of erection. Then, the final production stage is easily performed at the site by making use of this conical coil (A′). Thus, the number of equipment and operations required at the site are minimized. Additionally, since a continuous sheet metal (B) is bent and used in this manner, any waste material to occur from the sheet metal (B) as it is cut is likewise minimized.
| Number | Date | Country | Kind |
|---|---|---|---|
| a 2011 04141 | Apr 2011 | TR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/058768 | 5/27/2011 | WO | 00 | 10/25/2013 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2012/146317 | 11/1/2012 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 2751672 | Reed | Jun 1956 | A |
| 3888283 | Cauffiel | Jun 1975 | A |
| 6336583 | Wang et al. | Jan 2002 | B1 |
| 7037388 | Kan et al. | May 2006 | B2 |
| 20020114884 | Friedersdorf et al. | Aug 2002 | A1 |
| 20100095508 | Wahlen et al. | Apr 2010 | A1 |
| Number | Date | Country |
|---|---|---|
| 14 52 253 | Jan 1969 | DE |
| 58 070918 | Apr 1983 | JP |
| Entry |
|---|
| PCT Search Report dated Jan. 19, 2012 of Patent Application No. PCT/EP2011/058768 filed May 27, 2011. |
| Number | Date | Country | |
|---|---|---|---|
| 20140047696 A1 | Feb 2014 | US |
