Wind turbine comprising means to alter the size of the surface of the blades

Technical Field

The present invention relates to a wind turbine with vertical rotor shaft according to the preamble of claims 1 and 11.

Background of the Invention

A wind turbine is an arrangement by means of which the kinetic energy of the wind is transformed into electric energy. This is usually achieved by capturing the power of the wind using rotors or blades/shovels, and through mechanical constructions transform the captured wind power, by means of one or a plurality of electric generators to electric energy, which is transferred for further consumption.

The most common type of wind turbine is the one with a horizontal rotor shaft. In such wind turbine the shaft of the rotor is arranged horizontally. Usually these types of wind turbines have two or three rotors, but designs with one rotor exist. For large wind turbines with horizontal rotor shaft the rotors tend to get very large.

Another type of wind turbine is the ones with vertical rotor shaft. Examples of wind turbines with vertical rotor shaft are wind turbines of the Savonius and Darrieus types. US 3942909 shows, in one embodiment a rotor of the Savonius type comprising a plurality of blades, wherein the positions of the blades are changed using a complex construction of pivots, weights and springs.

Existing types of wind turbines as described above have drawbacks such as having low efficiency, having to be stopped at low or high wind forces, being costly to produce, being difficult to transport, and furthermore being complicated and costly to maintain and serve.

Summary of the Invention

The object of the present invention is to provide an improved wind turbine which solves the above mentioned problems, completely or in part.

The object is achieved by means of a wind turbine comprising at least one substantially vertical rotatable shaft and at least one blade module, which is connected to the shaft in order to rotate with the shaft. The blade module comprises at least one substantially vertically

arranged blade, wherein the blade has at least one surface exposed to the wind and is being arranged to rotate the shaft when influenced by wind. Furthermore, the blade module comprises means by means of which the size of the surface exposed to the wind of the blade can be varied to adapt the size of the surface exposed to the wind of the blade to wind velocity and/or power output.

The size of the surface exposed to the wind of the blade can be varied by means which are pivot means and at least a portion of the blade is pivoted, wherein the pivoted portion can be turned and thereby the size of the surface exposed to the wind of the blade can be varied. The blade can be pivoted vertically or horizontally, and can also be pivoted substantially diagonally.

In one embodiment of the invention the blade comprises at least a first portion and a second portion, and the first portion is displaceable in relation to the second portion, wherein the size of the surface exposed to the wind of the first portion, and therefore also the surface exposed to the wind of the blade, can be varied. The displacement is achieved by means being displaceable means.

Furthermore, a wind turbine according to the invention is modular, wherein the wind turbine comprises at least one substantially vertical rotatable shaft, and at least one blade module which is connected to the shaft in order to rotate with the shaft. The blade module comprises at least one substantially vertically arranged blade, wherein the blade comprises at least one surface exposed to the wind and is arranged to rotate the shaft when influenced by the wind. The wind turbine furthermore comprises additional blade modules to form a modular wind turbine, wherein the additional blade modules may be connected to each other and arranged at the shaft to rotate the shaft.

Furthermore, the blade modules in the modular wind turbine may comprise means by means of which the size of the surface exposed to the wind of the blade can be varied to adapt the size of the surface exposed to the wind of the blade to wind velocity and/or power output.

The present invention provides a wind turbine which can supply electricity even at low and high wind forces, and is adaptable with regard to the size of the wind turbine and the supplied power output. Furthermore, the wind turbine is inexpensive to produce, easy to transport and assemble, and easy to serve and maintain.

Further advantages with the present invention will be apparent from the following detailed description.

Brief Description of the Drawings

In the following description embodiments of the invention will be described with reference to the appended figures, in which:

- Figure 1 schematically shows a wind turbine according to the present invention;

- Figure 2 shows a blade module where a portion of the blades are folded out; Figure 3 shows a blade module where a portion of the blades are folded in;

Figure 4 schematically shows a blade, wherein a portion of the blade is displaceable; and

Figure 5 schematically shows a wind turbine according to the present invention comprising a support module.

Detailed Description of Embodiments of the Invention

Figure 1 shows a wind turbine 1 according to the present invention. In the embodiment in Figure 1 the wind turbine 1 comprises a vertical shaft 2 and a plurality of blade modules 3. Said shaft 2 is rotatable, and rotationally journalled in a base module 10. The blade module 3 is connected to the shaft 2 and is arranged to rotate the shaft 2 when influenced by the wind. As shown in Figure 2 the blade module 3 comprises blades/vanes 4 having the function of absorbing the power of the wind, hence the function of the blade module 3 is to transform the power of the wind to a rotational motion which makes the shaft 2 to rotate when said shaft 2 is connected with the blade module 3.

The blade module 3 absorbs the power of the wind by comprising substantially vertically arranged blades 4 having a surface exposed to the wind. With a "surface exposed to the wind" it is understood the surface of the blade 4 upon which the power of the wind impacts and contributes to the rotational movement of the blade module 3, and therefore also to the rotational movement of the shaft 2. A large surface exposed to the wind makes a large contribution to the rotational movement of the blade module 3 and a small surface exposed to the wind makes a small contribution to the rotational movement of the blade module 3, ceteris paribus. The total surface exposed to the wind can include a plurality of surfaces exposed to the wind.

In Figure 2 an embodiment of the invention is shown in which the blades 4 are pivoted. In this embodiment the blades 4 comprises two portions, one outer portion and one inner portion that are pivoted in relation to each other, wherein the outer vertically pivoted portion can be turned inwards or outwards thereby adapt the size of the surface exposed to the wind of the blade 4, and hence the wind turbine can be adapted to wind velocity and/or desired power output. It is often desirable at low wind forces to have a large surface exposed to the wind and have a small surface exposed to the wind at high wind forces. Furthermore, the power output from the wind turbine 1 can be adapted by varying the size of the surface exposed to the wind of the blades 4, where a large surface exposed to the wind gives more power and a small surface exposed to the wind gives less power, ceteris paribus.

In wind turbines, according to prior art, the rotor is usually blocked if the wind is light, usually approximately at 3 m/s, or too strong, usually at 25 m/s, which means that no electricity is generated by these wind turbines during said wind conditions. With a wind turbine 1 according to the invention, electricity is generated also at wind forces lower or higher than the above mentioned since the surface exposed to the wind can be varied. The blades 4 in Figure 2 have a large surface exposed to the wind because the pivoted portion of the blade 4 in this example is completely folded out. On the other hand in Figure 3 an example is shown where the pivoted portion of the blade 4 is fully folded in, why the surface exposed to the wind of the blade is minimal. In such a situation the wind turbine 1 can still continue to generate electricity even if the wind force is very high. Of course the blade modules 3 can be arranged to be blocked if desired.

In another embodiment of the invention at least a first portion of the blade 4 is displaceable in relation to a second portion, which is not displaceable, wherein the size of the surface exposed to the wind of the first portion can be varied by displacement of the first portion. In Figure 4 a blade 4 is shown, where the first portion of the blade 4 is displaceable in relation to the second portion. In this example, the size of the surface exposed to the wind of the blade 4 is enlarged because the displaceable portion is displaced outwards in the radial direction of the shaft. With a reversed procedure, where the displaceable portion is displaced inwards in the radial direction of the shaft, the size of the surface exposed to the wind of the blade 4 is reduced.

The person skilled in the art realises that the different embodiments above for adaptation of the surface exposed to the wind of the blade 4 can be combined, wherein at least one portion of the blade 4 can be pivoted and at least one portion can be displaceable, which means that

one and the same portion of the blade 4 can both pivoted and displaced at the same time, or that different portions of the blade 4 are pivoted and displaced, respectively. With such a design of a blade 4, a blade 4 is provided where the surface exposed to the wind can be varied in many different ways to adapt the wind turbine 1 to different wind conditions and/or power output, or other relevant factors.

From Figures 2 and 4 it is clear that the blades 4 of the blade module 3 are curved/arched in the radial direction. The function with curved/arched blades 4, according to the said figures, is on one the hand to provide a possibility to adapt the size of the surface of the blade, and on the other hand to increase the efficiency of the blades 4. The curved/arched surface will make the air velocity over the blade 4 to increase, why an over pressure is created which in turn results in an under pressure on the opposite side of the blade 4. The combination of over/under pressure result in that both a pushing and a suction force acts on the blade 4, and therefore the efficiency of the blade 4, and hence also the blade module 3, is increased.

The wind turbine 1 according to the invention comprises in an embodiment a rotatable drive wheel 6 (see Figure 1) with which the shaft 2 is connected and is supported to be rotated by the shaft. Around the drive wheel 6 one or a plurality of electrical generators 7 are arranged, where the shaft of the electrical generators 7 are rotated by the drive wheel 6. These electrical generators 7 are arranged to generate electricity when the drive wheel 6 is rotated. The arrangement of drive wheels 6 and electrical generators 7 is preferably arranged at ground level, which means that the lower portion of the shaft 2 is connected with the drive wheel 6. By means of an arrangement like this service, maintenance and accessibility is substantially facilitated. For example, the rotational movement of the drive wheel 6 can be transferred by means of a cog railway to a coupling for each electrical generator 7 that are arranged around the drive wheel 6. With said couplings the electrical generators 7 can be connected or unconnected while in operation independently of the rotation of the drive wheel 6. Therefore, the electrical generators 7 can be subject to maintenance or replaced without the need to stop the wind turbine 1.

Further, the inventors have realised that the drive wheel 6 (connected with blade modules and shaft) instead of being rotationally journalled in a conventional manner can be arranged to levitate, without contact, over a plurality of strong permanent magnets 8. Radial side forces can, for instance, be handled by ball bearings and/or slide bearings so as to ensure that this

arrangement is securely fixed. With an arrangement as described above a wind turbine 1 with a substantially increased efficiency due to the decreased axial friction is provided.

In yet another embodiment of the invention the wind turbine 1 can comprise one or several support modules 5 intended to support the wind turbine 1. In Figure 5 an example of a support module 5 arranged on the top of the wind turbine 1 is shown. A plurality of cables are fastened at the support module 5, and secured to the ground at the other end, wherein the wind turbine 1 is safely secured in position. It should be realised that the support module 5 can be arranged on other portions of the shaft 2 than on its top. It is also realised by the skilled person that more than one support module 5 can be arranged on the shaft 2, e.g. one on the top and one on the middle of the shaft 2. The base of the vertical shaft 2 is preferably journalled in ball bearings in a base module 10 to increase the stability of the shaft 2.

Furthermore, the wind turbine 1 according to the invention is suited to be assembled using separate modules, i.e. to form a modular assembled wind turbine 1. One or a plurality of blade modules 3 can be connected to the shaft 2. The number of blade modules 3 that are connected to the shaft 2 depends on the power output that is desired from the wind turbine 1 , but can also depend on the available area on which the wind turbine 1 is to be placed upon, or on aesthetical considerations regarding the size of the wind turbine 1 and therefore its visual impact on the local environment.

Also, other portions of the wind turbine 1, such as base, support portions and wind turbine housing can consist of modules. Further, other portions of the wind turbine can be built with modules of frame work type.

The advantage of a modular wind turbine 1 is on the one hand that transportation of the wind turbine 1 to the location at which it is to be located is substantially facilitated since the wind turbine 1 can be transported in convenient modules to be assembled on location, and on the other hand that maintenance and service of the wind turbine 1 can be performed in a simple manner, for instance by replacing individual modules. The cost of producing a wind turbine 1 according to the invention can also be kept low since the wind turbine 1 can be built using standardized modules, and hence large scale effects can be achieved.

The assembly of a modular wind turbine 1 according to the invention is simplified by placing a first blade module 3 at the shaft 2 to be lifted up, wherein a second blade module 3 is arranged at the shaft 2 and is connected to the first blade module 3. Thereafter, the first and

the second blade modules 3 are lifted so that a third blade module 3 can be arranged at the shaft 2, etc. This method has the advantage that the assembly of the wind turbine 1 is simplified.