Patent Application
20130081342
This application claims priority of European Patent Office application No. 11183465.1 filed Sep. 30, 2011. All of the applications are incorporated by reference herein in their entirety.
The illustrated embodiments relate to a wind turbine tower.
Wind turbine towers, especially tubular steel towers for large wind turbines, are large in diameter and weight. This may cause difficulties concerning the transportation of a tower to the wind farm and the used infrastructure.
Slip forming for construction is a method of continuously pouring concrete into a form of mould that moves up vertically, normally with the assistance of hydraulic or screw jacks. As the forming of the structure progress, the section of previously poured concrete hardens and forms a kind of support wall that is strong enough to withstand the concrete poured over the top of it. Pouring continues until the desired height of the structure is reached, allowing for a type of concrete structure that is positioned on top of a foundation and completely hollow inside. U.S. Pat. No. 4,314,798 illustrate such a slip forming system.
The slip forming process is known in the art as being used to build wind turbine towers.
The casted concrete structure may comprise solid iron or stainless steel bars or grids for reinforcement.
It is also known to use fibers as reinforcement of concrete in wind turbine towers. US2009/0307998 is one such example. The Fiber Reinforced Concrete (FRC) is a technology which can be used together with different types of fibers such as plastics, metal, glass etc. Normally chopped fibers are mixed with the concrete to enhance the tensile properties.
It is desirable to provide a wind turbine tower with prolonged lifetime and reduced costs.
This objective is solved by the features of the independent claim(s).
The depending claims define further embodiments.
The technical problem which is solved by the illustrated embodiments may be regarded as the provision of an improved concrete wind turbine tower with lower weight and same strength as known concrete wind turbine towers.
The embodiments relate to a reinforced concrete wind turbine tower comprising fibre rovings as reinforcement.
In one embodiment, the fibre rovings are glass fibre rovings, armid fibre rovings and/or carbon fibre rovings.
A glass fiber roving is a bundle of multiple parallel oriented glass fibers its shape being similar to a thin rope.
In one embodiment, the carbon fibre diameter is in the range of 5 μm to 10 μm, and/or the number of carbon fibres in the roving is between 5000 and 30000, and/or the glass fibre diameter is in the range between 10 μm and 30 μm, and/or the number of glass fibres in the roving is between 500 and 2000, and/or the fibre roving weight is between 0.20 and 30 kg/km.
In one embodiment, the fibre rovings will be embedded in concrete during the slip forming process.
In one embodiment, the fibre rovings are anchored in the concrete already at the bottom of the tower and it ends at the top of the tower.
In one embodiment, some of the fibre rovings will be “winded” around the tower, e.g. in an ±25 deg. angle relative to the longitudinal (vertical) axis of the tower.
In one embodiment, some of the fibre rovings will be embedded in e.g. 85 deg. angle relative to the longitudinal axis so that they basically follow the circumference of the tower.
In one embodiment, the rovings may also be placed in the concrete in a 0 deg. angle relative to the longitudinal axis of the tower.
At the top of the tower, where the tower has to adapt to either a yaw-construction or to some transition piece between the tower and the yaw-construction, fibre rovings may be placed in other paths in order to cope with the intensive tensions and stresses which act on this part of the tower.
In one embodiment, the rovings or fibre rovings are “pre-tensioned” when placed in the concrete during the slip moulding process in order not to create any wrinkles on the rovings or in order to strengthen the tower.
In one embodiment, the fibre rovings can be embedded as a supplement to conventional iron bar reinforcement or the conventional iron bar reinforcement can be embedded as a supplement to fibre rovings.
By providing that fibre rovings are lighter than the corresponding iron bars, the whole tower construction will resultantly become lighter than conventional.
By providing that (glass) fiber rovings do not corrode, the properties of the tower will be maintained during the lifetime. Furthermore the lifetime is prolonged.
The glass fibers have higher tensile strength than steel or iron and are even cheaper.
An even further feature is that rovings are flexible and can be delivered on drums in desired lengths and they are thereby very easy to handle—especially compared to conventional reinforcement steel rods which are solid, un-flexible and difficult to handle.
Wind turbine towers with fibre reinforced concrete can achieve a height of 120 m and more.
Further features, properties and advantages will become clear from the following description of embodiments in conjunction with the accompanying drawing, wherein:
The reinforced concrete 3 of the a wind turbine tower 1 has as reinforcements fibre rovings 2,8,9,10 as reinforcements. In
The fibre rovings 2,8,9,10 nay be glass fibre rovings 2, but can also consist of carbon fibre rovings 2,8,9,10. A fibre roving 2,8,9,10 is a bundle of multiple parallel oriented fibers with around 200 fibers forming a thin rope.
The tower 1 is produced in a slip forming process or slip moulding process. Slip forming for construction is a method of continuously pouring concrete into a form of mould that moves up vertically, normally with the assistance of hydraulic or screw jacks. As the forming of the tower structure progress, the section of previously poured concrete hardens and forms a kind of support wall that is strong enough to withstand the concrete poured over the top of it. Pouring continues until the desired height of the structure is reached, allowing for a type of concrete structure that is positioned on top of a foundation and completely hollow inside. The fibre rovings 2,8,9,10 will be embedded in the concrete 3 during the slip forming process.
The fibre rovings 2,8,9,10 can be anchored in the concrete 3 at the bottom 5 and at the top 4 of the wind turbine tower 1.
Some fibre rovings 2,8,9,10 are winded around the wind turbine tower 1 in a given angle α, β relative to the longitudinal (vertical) axis A of the wind turbine tower 1
Some fibre rovings 8 are in an angle of α=±25 degree.
Some fibre rovings are in an angle of β=±85 degree so that they basically follow the circumference of the tower wind turbine tower 1.
Some fibre rovings 10 are placed in the concrete 3 in a zero degree angle relative to the longitudinal axis A of the tower 1, optionally under pretension.
At the top 4 of the wind turbine tower 1, the tower 1 adapts to either a yaw-construction or to some transition piece 11 between the tower 1 and the yaw-construction 11.
The fibre rovings 12 are placed in paths in order to cope with the intensive tensions and stresses which act on this part of the tower 1.
The fibre rovings 2,8,9,10 are pre-tensioned when placed in the concrete 3 during the slip moulding process in order not to create any wrinkles on the rovings or in order to stabilise the tower 1.
The fibre rovings 2,8,9,10 can be embedded as a supplement to conventional iron bar reinforcement 6 or the conventional iron bar reinforcement 6 can be embedded as a supplement to the fibre rovings 2.
| Number | Date | Country | Kind |
|---|---|---|---|
| 11183465.1 | Sep 2011 | EP | regional |
