Wind Power Plant

The invention relates to a wind power plant, comprising a rotor that can be rotated about a vertical axis, said rotor between two horizontal bearing planes disposed at a distance on top of each other comprising a plurality of rotor blades, which are disposed distributed on a circumferential circle, can each be pivoted about a vertical pivot axis, and the pivot range of which is delimited on both sides by a stop. In such a wind power plant, an improvement in the energy yield, while simultaneously ensuring another operation, is enabled in that the width of the rotor blades is smaller than approximately ⅓ the radius of the circumferential circle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a highly simplified schematic illustration of a wind power installation in the form of a vertical rotor based on the drag principle and having two rotors one above the other, as is suitable for implementation of the invention. The wind power installation10has a vertical axis11about which two rotors12and12′ rotate. Further rotors may, of course, also be provided, which rotate about the axis11. However, it is just as possible to provide only a single rotor12. The rotor or rotors12,12′ is or are connected via a shaft16to a generator unit17, which can also contain a gearbox in order to change the rotation speed. Instead of the shaft16, a shaft train comprising a plurality of individual shafts located concentrically one inside the other can be provided, via which the individual rotors12,12′ are coupled to the generator unit17independently of their rotation. This is particularly advantageous when the aim is to optimally tap off flow strata with different wind speeds by means of rotors12,12′ located at different heights.

Each of the rotors12,12′ is equipped with a plurality of vertically arranged rotor blades15which are mounted in a distributed manner, such that they can pivot, on a circumferential circle between a lower mounting plane14and an upper mounting plane13. For the sake of simplicity and clarity, only the front rotor blades are in each case shown inFIG. 1.FIG. 2shows a plan view from above of a rotor12according to one preferred exemplary embodiment of the invention, showing the interaction of the rotor12and of the rotor blades15accommodated therein, with an air flow (wind)20. The upper mounting plane13is in this case omitted in order to allow the rotor blades15to be seen without any impediment. Overall, twelve rotor blades15are arranged distributed uniformly on the circumferential circle27and can each pivot about a vertical pivoting axis18. The pivoting range of each rotor15, which is shown in detail inFIGS. 5and comprises an angle β of about 100° to 115°, is in each case bounded by a single stop19which is in the form of a post and is placed a short distance away from the pivoting axis18within the circumferential circle27.

Each rotor blade15is straight and has a leading edge25and a trailing edge26(FIG. 7). The pivoting axes18of the rotor blades15are arranged within the rotor blades15, in the vicinity of, but at a distance from, the leading edge25. At one limit position of the pivoting range (FIG. 6), that section of the rotor blade which is located between the pivoting axis18and the leading edge25pivots against the stop19. In the other limit position (FIG. 7), that section of the rotor blade15which is located between the pivoting axis18and the trailing edge26pivots against the stop19. As can be seen fromFIG. 5, in one limit position of the pivoting range (β), the rotor blades15each include an angle α of about 50° with the radius vector of the circumferential circle27which passes through the pivoting axis18, and in the other limit position of the pivoting range (β), include an angle 180°-γ of about 150° to 165°.

In another refinement, which is shown by way of example inFIGS. 3 and 4, the pivoting axes18of the rotor blades15are arranged directly in the leading edges25of the rotor blades15. In this case, the pivoting range (β) of the rotor blades15is in each case defined by a limiting element21which is in the form of a circular arc and concentrically surrounds the pivoting axis18, and whose ends each form a stop22and23.

The comparatively narrow width b of the individual rotor blades15is essential for the invention (FIG. 5). The width b is less than approximately ⅓ of the radius R of the circumferential circle27. This allows a comparatively large number of rotor blades15to be accommodated on the circumferential circle27without having to limit the pivoting range to do so. The interaction of the rotor12and of the rotor blades15with the air flow is thus subdivided to a greater extent, thus leading to better utilization in the volume, and to smoother running.

The size and position of the pivoting range of the rotor blades as shown inFIG. 5are also important. When the rotor12is revolving in the clockwise direction as shown inFIG. 2and with the wind direction shown there, this results in changing rotor blade positions, which can be subdivided into and associated with different angle ranges A to D: in a first angle range A, which can be referred to as the drive range, the rotor blades15rest on the stop19and are positioned transversely with respect to the air flow20, thus resulting in a driving torque. In the angle range B, the situation with respect to the position of the rotor blade15is unstable, because this is where the blade starts to separate from the stop19. In the angle range C, the rotor blade15pivots outward and strikes against the stop19from the other side. Once again, this results in a driving torque. Because of the effect of the air flow20, a driving torque is also applied in an additional drive range (angle range D) as a result of the chosen position of the pivoting range (see alsoFIGS. 4aand4b) until, later, the rotor blade is separated from the stop19and is positioned parallel to the air flow (right-hand side ofFIG. 2andFIG. 3) in order to enter the angle range A again even later (see alsoFIG. 4c).

The energy in the air flow20is utilized optimally by the position and size of the pivoting range of the rotor blades. The splitting of the total rotor blade area between a multiplicity of comparatively narrow rotor blades15also contributes to this. This splitting at the same time results in the rotor12running smoothly, reducing the magnitude of the disturbance forces associated with the pivoting. A further improvement can be achieved if the thickness d of the rotor blades15is reduced in a center area24between the leading edge25and the trailing edge26(FIG. 6). In addition to the weight saved in each rotor blade15by this measure, further weight can be saved, without any loss of strength, by forming the mounting planes13,14by spoked wheels28which rotate about the axis11(FIG. 6).

However, instead of the rotor blades15shown inFIGS. 6 and 7, it is also possible to use aerodynamically optimized rotor blades15′ as shown inFIG. 9, which are distinguished by a cross-sectional profile in the form of a stretched droplet with a pointed end29and a round end30. In this case, the pivoting axis18is arranged at the round end30. A stop31is mounted in a rotationally fixed manner within the rotor blade15′ and has two stop surfaces32and32′ which are oriented at an acute angle to one another. In one limit position of the pivoting range (as shown inFIG. 9), one inner face of the rotor blade15′ rests on the lower stop surface32. In the other limit position, when the rotor blade15′ has been pivoted about the pivoting axis18in the counterclockwise direction, the other inner face of the rotor blade15′ rests on the upper stop surface32′. The internal arrangement protects the stop mechanism against external influences such as icing, dirt or damage, and at the same time improves the aerodynamics. When rotor blades15′ such as these and as shown inFIG. 8are installed in the rotor12, this results in angle ranges A and D which are larger than those shown inFIG. 2.

Since the wind does not blow uniformly and continuously at many sites where wind power installations are installed, it is advantageous for operational reasons to be able to store the energy that is produced easily and effectively, and to withdraw the energy from the storage again as required. The described rotor, which emits a high torque from the start as a drag rotor, is particularly highly suitable for operation of one or more compressors. When the compressors are used to suck in air and compress it, the compressed air that is produced can be stored in a compressed-air reservoir, and can drive a turbine or a compressed-air motor, which produces electricity via a flange-connected generator, as required. A wind power installation such as this according to the invention with a compressed-air reservoir is illustrated in the form of the preferred physical embodiment inFIG. 10, and in the form of a highly simplified installation layout inFIG. 11.

In the case of the wind power installation33shown inFIG. 10, a compressed-air reservoir40in the form of a container, composed of concrete by way of example, is introduced into the ground. The compressed-air reservoir at the same time acts as a foundation for the wind power installation built above it. Three rotors or cells35a,35band35care arranged one above the other on a mast45with a vertical central axis34and are designed, for example, as shown inFIG. 8. The mast45is anchored in a frame37which is built on the foundation, and is stabilized via a side guy36. Power transmission38, which is connected to the rotors35a, b, c,and is in the form of a wheel or turntable is arranged within the frame37, via which power transmission38compressors39which are distributed on the circumference can be driven in a manner which allows them to be connected selectively.

In the highly simplified installation layout shown inFIG. 11, the rotor35drives a compressor39via the power transmission38, which compressor39sucks in air at the inlet, compresses it and emits it at the outlet via a first controllable valve43to the compressed-air reservoir40. When it is intended to produce electrical energy, compressed air is taken from the compressed-air reservoir40via a second controllable valve44, and is expanded in a turbine41(or a compressed-air motor), in order to produce work. The turbine41drives a generator42which produces three-phase electricity and—after appropriate voltage and frequency matching—emits it to a local or superordinate grid system. When compressed air is stored and taken at the same time, the compressed-air reservoir40is used, so to speak, as a “smoothing capacitor”.

The wind power installation33shown inFIG. 10has an overall height of, for example, 90 m, which is made up of 30 m for the mast45and 60 m for the three rotors/cells35a, b, c,with a height of 20 m each. A mean wind speed of 5 m/s results in a power of 44 kW being produced, corresponding to 1056 kWh of energy per day. If the pressure reservoir40has a storage volume of 5000 m3, 1250 kWh can be stored in it at a pressure of 10 bar.

However, generators can also be arranged directly on the power transmission38and produce electrical power directly when required, without the interposition of the compressed-air reservoir, thus allowing the installation to be operated particularly flexibly, overall.

LIST OF REFERENCE SYMBOLS

10,33Wind power installation

32,32′ Stop surface

d Thickness

b Width