Vertical Axis Wind Turbine and Method for Operating Such a Turbine

Abstract

A vertical axis wind turbine includes two or more cells arranged one above the other along a vertical machine axis, in which each of the cells includes a plurality of vertical blades which are arranged within the cell distributed on a concentric circle about the machine axis and which are connected so as to be able to move together on this circle and which are rotationally fixed with a main shaft, and in which the blades in the cell are each individually mounted so as to be able to rotate about a vertical axis of rotation which in particular runs internally through them. Assigned to each of the blades are means by which the blade is made to adopt, a rotational position, about its axis of rotation, which is predetermined and can be changed at any time.

Claims

1. A vertical wind turbine, comprising two or more cells, which are positioned one above the other along a vertical machine axis, wherein each cell comprises a plurality of vertical blades, which are distributed on a concentric circle inside each cell round the machine axis and which are connected so as to be able to move together on the circle and which are rotationally fixed with a main shaft, and wherein the blades in each cell are each individually mounted so as to be able to rotate about a vertical axis of rotation which runs internally through them, wherein, to each of the blades, means are associated, by which the blade is made to adopt, during circulation about the machine axis and independently of the other blades, a rotational position, about its axis of rotation, which is predetermined and can be changed at any time.

2. The vertical wind turbine according to claim 1, wherein each cell comprises a first and second ring, which are concentrically positioned with respect to the machine axis, which rings delimit the cell in an upwards and downwards direction, and between the rings the blades of each cell are positioned in order to rotate through 360.

3. The vertical wind turbine according to claim 2, wherein the blades of a cell are rotatably supported at their ends on the first and second ring, so that the blades rotate through 360.

4. The vertical wind turbine according to claim 2, wherein neighboring cells share a common ring.

5. The vertical wind turbine according to claim 5, wherein the means for changing the angular position of the blades are positioned on the rings.

6. The vertical wind turbine according to claim 5, wherein the means for changing the angular position of the blades comprise an electrically or hydraulically driven motor.

7. The vertical wind turbine according to claim 6, wherein rotational movement of the electrically or hydraulically driven motors in the case of the electric motor is transmitted by gears or, in the case of the hydraulic motor, is directly transmitted to the corresponding blade.

8. The vertical wind turbine according to claim 7, wherein the electric or the hydraulic motor are positioned with a motor axis in a plane of the rings, and the rotational movement in the case of the electric drive is transmitted between the gears by a toothed belt.

9. The vertical wind turbine according to claim 7, wherein the electric or the hydraulic motor have a motor axis perpendicular to a plane of the rings, and that an angular gear is interposed for transmitting the rotational movement in the case of the electric drive.

10. The vertical wind turbine according to claim 1, wherein a lowermost cell has a predetermined distance from a ground surface, and the main shaft is rotatably supported between the lowermost cell and a machine house, which is near the ground surface, and at their ends.

11. The vertical wind turbine according to claim 10, wherein the main shaft comprises a plurality of portions, which are serially positioned in the axial direction, and the portions are connected to each other by flanges.

12. The vertical wind turbine according to claim 11, wherein the main shaft comprises a lower cylindrical portion, a middle portion, which conically widens in an upward direction and an upper cylindrical portion which has an outer diameter which is greater than that of the lower cylindrical portion.

13. The vertical wind turbine according to claim 12, wherein, on the lower cylindrical portion, the rotor of an electrical energy generating generator is positioned in a non-rotatable way.

14. The vertical wind turbine according to claim 10, wherein, for rotatably supporting the main shaft, a bearing pin is provided at a lower end of the main shaft and a supporting roller track is provided at an upper end of the main shaft.

15. The vertical wind turbine according to claim 10, wherein the upper bearing of the main shaft, which is a supporting roller bearing and which absorbs vertical upper reaction wind forces of the main shaft, is supported by a supporting frame, which obliquely widens up in a downward direction, on foundations, which are positioned outside the machine axis, wherein the lower axial and radial bearings of the main shaft are housed inside a generator housing, which is fixed to the upper struts inside the machine house, which is suspended from the supporting frame.

16. The vertical wind turbine according to claim 1, wherein on each cell on the upper and lower side a respective wind measurement device for measuring wind direction and speed is positioned.

17. The vertical wind turbine according to claim 1, wherein on each cell on the upper and/or lower side at a blade bearing, a force measurement device for measuring the radial and tangential force direction is provided.

18. A method for operating a vertical wind turbine according to claim 1, wherein an angular position of the individual blade of the wind turbine around its axis of rotation is actively controlled, independently from each other, according to measured values of wind speed, wind direction, rotational speed of wind turbine and position of blades along the blades circulation around the machine axis.

19. The method according to claim 18, wherein, for the blade angle, which describes a deviation of the blade from a base position, in a tangential direction with respect to the circulation circle around the machine axis, virtual cam discs are provided, which define a variation of the blade angle with the position of the blades on the circulation circle, and that the active control of individual blades is performed according to the virtual cam discs.

20. The method according to claim 19, wherein, for selecting the virtual cam discs used for the active control of blades, a tip-speed ratio of the wind turbine is continually determined, wherein the tip-speed ratio indicates a ratio of a peripheral velocity of blades to wind speed, and that according to the determined tip-speed ratio the virtual cam disc used for active control of the blades is selected or different virtual cam discs are exchanged.

21. The method according to claim 19, wherein the virtual cam discs are referred to a zero position of the wind turbine, and the zero position depends on the wind direction.

22. The method according to claim 18, wherein for each cell its own wind speed is determined, which depends on a height above a ground surface, and the angular position of the individual blades of cell around their axis of rotation (12) is actively controlled according to the wind speed determined for the cell.

23. The vertical wind turbine according to claim 16, wherein the wind measurement device is an ultrasound anemometer.

Description

BRIEF DESCRIPTION OF FIGURES

[0038] The invention is explained in the following by means of exemplary embodiments in connection with the drawing. In particular:

[0039] FIG. 1 is a simplified side view of an example of the vertical wind turbine according to the invention with two cells and the lower bearing of main shaft inside a suspended machine house;

[0040] FIGS. 2-4 are a view from above (a) and a side view (b) of the three rings for supporting the blade in the turbine of FIG. 1;

[0041] FIG. 5 is a side view of the main shaft of turbine of FIG. 1;

[0042] FIG. 6 is a side view of a blade with an upper and lower bearing of turbines according to FIG. 1;

[0043] FIG. 7 is a perspective view of a detail of two different types of mounting an electric motor for blade adjustment on the lower blade supporting ring;

[0044] FIG. 8 is a further view of an electric motor mounted on a horizontal lower ring for blade adjustment, which is protected by a cover;

[0045] FIG. 9 shows the calculated optimal blade position through a 360 rotation of turbine with a tip-speed ratio of 0.4 in diagram (a) and in the axial view from above (b);

[0046] FIG. 10 shows neutralized blade control curves, which consider the technical limits of driving means;

[0047] FIG. 11 shows a block diagram of the electromechanical control of the blade position according to an example of the invention; and

[0048] FIG. 12 shows a block diagram of the electromechanical control of the blade position according to another example of the invention.

MODES FOR CARRYING OUT THE INVENTION

[0049] In FIG. 1 a simplified side view of an example of the vertical wind turbine according to the invention is provided.

[0050] The wind turbine 10 of FIG. 1 comprises two cells Z1 and Z2, which are positioned one above the other along a vertical machine axis MA. Each of cells Z1, Z2 has two horizontal rings 11, 16 and 16, 19, which are concentric to the machine axis MA, between which a plurality (in example 3) of vertical blades 13 are rotatably supported, each about its own axis of rotation 12. The middle ring 16 is equally associated to both cells Z1 and Z2.

[0051] The structure of rings 11, 16 and 19 is obtained from FIGS. 2, 3 and 4. Each of rings 11, 16 and 19 is an equilateral triangle or a regular polygon, whose corners support the blades 13 by means of a corresponding bearing support 38 (see also FIG. 7). The periphery is provided by rods 33, which are connected to a vertical central pipe 35 by means of radial rods 31 and pipes 32. On the underside of rings, flat irons 34 are used as pulling struts. Radial ribs 37 are positioned around the central pipe 35, wherein the ribs support flanges 36 which are provided at the ends of pipe 35.

[0052] Cells Z1, Z2 are non-rotatably connected with their blades 13 through a central pipe 15 and 18 to a vertical main axis 20, which is rotatably supported underneath cells, so that they may rotate about the machine axis MA together with the main axis 20. The main axis 20 is rotatably supported at the upper end in a bearing support 23 with support rollers, which is supported by a frame of obliquely downwards spread pipes 24 on external foundations 29. In the example of FIG. 1, the lower vertical and radial bearings are housed in the generator housing, which is fixed in the machine house 26, which is suspended to the frame 24. In this way more weight can be transferred to the external foundations 29, whereby the stability moment of the entire construction may be increased. Height H1 may for example be 75 m or more (over 200 m, for example). The diameter d1 of the circle, on which the blades 13 are moving with their axis of rotation 12, is 20 m, for example. Each of cells Z1, Z2 experiences, because of its different height, its own wind speed v.sub.w.sup.1 and v.sub.w.sup.2.

[0053] The main axis 20 is composed, in the example of FIG. 5, of a lower cylindrical portion 45 of small diameter, a middle portion 43, which conically widens in an upward direction, and an upper cylindrical portion 41 of greater diameter. Portions 41, 43 and 45 are fastened to each other by flanges 42 and 44. At the upper end of the lower cylindrical portion a supporting roller track 40 is provided, at the lower end of the lower cylindrical portion 45 a bearing pin 46 is provided. Portions have lengths h1, h2 and h3 of, for example, 4 m, 11 m and 0.5 m, respectively.

[0054] As is shown in FIG. 1, the lower cylindrical portion 45 supports a rotor 22 of a generator as well as a brake 21, which are both housed in the machine house 26. Cells Z1 and Z2 form, together with the main axis, the rotor of the wind turbine, which rotates about the machine axis MA.

[0055] In FIG. 2(a) the position of one of actuators 38 associated to each blade 13 is shown, as an example. The actuator 39 is positioned, in this case, in parallel to rod 33 of ring 19, in direct proximity to bearing support 38 of corresponding blade. This is more clearly shown in the enlarged detail of FIG. 7, where one of actuators, actuator 39a, is parallel to rod 33. The corresponding blade 13 is provided, on its axis of rotation above the bearing support 38 with a first gear 49. The actuator 39a, in this case an electric servomotor, acts through an angular gear 52 upon a second gear 50, which is positioned at the same height of the first gear 49 and which is drivingly connected with the same through a toothed belt (not shown). If the use of an angular gear has to be avoided, the actuator (39b) may also be vertically mounted, however giving rise to an increased flow resistance. The horizontal actuator 39a according to FIG. 8 may be simply provided with a cover 51 for protecting it from environmental agents.

[0056] Energy is supplied to actuators 39 or 39a,b through corresponding lines by a central supply unit and these are controlled by control signals according to the settings of a control unit. If hydraulic actuators (motors) are used instead of electric motors, the energy is provided by a central hydraulic unit through corresponding hydraulic conduits.

[0057] An overview of the concept of active blade control is provided in block diagram of FIG. 11.

[0058] Blades 13 or F1-F6 of cells Z1 and Z2 are actively rotated by actuators 39a (through angular gears 52) or 39b (directly) about their longitudinal axis. Any blade angle (angle between the tangent to the circulation circle of rotor and a cord of blade) may be individually set for each blade in each position on the circulation circle.

[0059] The object of the active blade control is to operate with all (example 12) blades 13 or F1-F6 in both cells with a blade angle which varies with the rotor position. Depending on the wind speed and rotational speed of rotor another curve of blade angles with respect to rotor position is operated. To this end, various virtual cam discs are generated, which are stored in a memory. The blade angle then follows the edge curve of the selected virtual cam disc. The zero point of the rotor position is a function of the wind direction. Wind direction and wind speed are measured by an wind speed sensor 67 and a wind direction sensor 68.

[0060] The wind measurement is of particular importance in the present turbine of FIG. 1. A vertical wind turbine 10 of the type shown in FIG. 1 has blades 13 which are uniformly shaped along the entire active height of rotor, which, during each rotor rotation may be individually controlled in an optimal way. The angle of attack of blade 13 with respect to relative wind flow should be controlled at each time during the rotor rotation. The blades fly during the rotor rotation almost along a circular path having rotor radius, around the rotor center or the machine axis MA and generate a lift in a radial direction and a thrust in a tangential direction. The thrust should be optimized at any given moment so that the turbine 10 experiences a maximum drive.

[0061] Because of static and dynamic loads on blades, the rotor is subdivided, along the active height, according to size of wind turbine, into one to four cells (two cells Z1 and Z2 in the example of FIG. 1). Each cell Z1, Z2 contains three blades 13, respectively, which are rotatably supported, on the upper and lower side, at the end of a radial arm, so that they are fixedly connected to the center of the rotor. The three arms form a respective fictitious ring on the upper and lower side of each cell.

[0062] Since all rotor cells are fixedly connected to the rotor, they also rotate with the same speed of the rotor. The wind direction and speed may however greatly vary along the active height of rotor, in particular in the case of huge (tall) turbines. In order to ensure an optimal thrust control, at each moment during the rotor rotation, the speed and direction of the relative wind flow of each blade should be exactly known. By a static wind measurement, the wind speed and direction may be measured along the height in a vertical direction and at a distance from the rotor (wind measurement pole). Since the wind measurement pole is at a fixed distance from the turbine, in case of an unfavorable wind direction, it will be in the wind shadow of the turbine, and, also because of the distance, will provide incorrect measurements, which do not correspond to the real conditions on the blades.

[0063] It is therefore proposed to fix, for each ring, externally on each ring arm, a respective wind measurement device W1-W3 (FIG. 1). The wind measurement device W1-W3 will now determine, in each instant in time, during rotor rotation, the exact relative wind flow direction and speed, with respect to the arm and therefore to the blade. The wind measurement device should preferably contain no mechanical-dynamical measurement component, such as wind vane and wind wheel, but instead measure wind direction and wind speed through ultrasound (ultrasound anemometer), since mechanical measurement components may provide incorrect results due to centrifugal acceleration on rotor. The wind measurement device W1-W3 should be at a distance from the arm end, which is sufficient to avoid any influence from the air turbulence zone of the arm end.

[0064] It is known that the wind direction and speed may greatly vary along the active height of rotor (wind shear and turbulences). If such phenomena can not be locally and temporally measured with sufficient precision, in order to optimally control the blade 13, the turbine will have a highly reduced aerodynamic efficiency. If the measurement takes place in each cell Z1, Z2 on the upper and lower side of circumference, in a dynamic and temporally proximate way, each blade may also be always controlled at an optimal relative angle of attack. In order to determine the wind conditions at middle height of blade, the respective wind measurements on the upper and lower side of blade have to be mediated, in order to provide the blade control signal. From the measurement of the relative flow, at each moment of time, through the rotor peripheral speed, the absolute wind speed and direction may also be calculated by trigonometric means. Based on these measurements, the optimal tip-speed ratio of turbine and the optimal corresponding blade angle of attack may be determined in a very short time frame.

[0065] The measurement device may also determine brief high local turbulences which may lead to a blade and turbine overload. Consequently, an optional relieving blade adjustment or a complete blade disconnection (release) may be performed. Measurements with wind measurement devices W1-W3 on each arm for each ring allow to individually control each cell with their respective blades in an independent manner.

[0066] It is also proposed to install on each cell Z1, Z2 on the lower or upper ring, on each arm, at the blade bearing, a force measurement device K1-K3 for radial and tangential force direction. Through the tangential force measurement, together with the wind measurement device W1-W3, the blade propulsion and therefore the turbine efficiency may be optimized. Signals from both these measurement devices W1-W3 and K1-K3 shall adaptively improve the efficiency of the turbine by use of a self-learning control program.

[0067] The radial force measurement signal should, together with the tangential force measurement signal, constantly monitor the load profile of blade. Through this measurement the frequency and intensity of blade load and therefore of residual operating life of blade may be determined.

[0068] As an alternative or in addition to above said force measurement for determining the blade load, a strain gauge may also be provided at blade central surface (for example for blade 13: DM in FIG. 1), which, together with a measurement system measures the frequency and intensity of bending stresses in blade 13. These measurements can then define the residual operating life of blade 13. The method may be complicated by the fact that the measurement signal has to be transmitted from the rotating blade to the ring arm. The strain gauge device should however be exclusively used for measuring the blade load, and not for optimization of blade propulsion.

[0069] The basic concept of an active blade control is shown in block diagram in FIG. 11. Components, which are surrounded by a dotted line (rotor block 53 in FIG. 11), are mounted inside an electrical cabinet on the rotor. The communication with the tower control and the data acquisition run over a Wi-Fi connection with corresponding Wi-Fi transmitters 57 and 66. The power supply by an alternating current voltage supply 71 (3400VAC, 1 neutral and 1 ground) runs through a collector ring 62. Functional blocks provided on rotor are supplied by a 24 VDC-voltage supply 56. An analog 24VDC voltage supply 65 is also provided outside the rotor.

[0070] The virtual cam discs (different blade angle curves according to rotor position) are stored on the rotor (motion controller 58). They may also be changed through the Wi-Fi connection. Wind speed, wind direction and rotor speed are processed on the tower (not rotating) through an I/O of a programmable logic controller (PLC) 64, which is operating with a computer 70. The virtual cam disc which has to be taken, is communicated through the Wi-Fi connection to the motion controller 58 on rotor. I/O are available on the rotor as well as on the tower.

[0071] The 6 actuators 39a or 39b in the simplest case follow the same cam disc, however with an angular offset of 120 (for example with 3 blades for each cell). The zero value of the rotor position depends on the wind direction. If, in case of higher systems, and/or with more than two cells, the wind speeds for the cells are very different from each other, for each of cells a corresponding virtual cam disc is selected according to the corresponding wind speed. For each cell Z1, Z2 a corresponding wind speed (v.sub.w) is determined, depending on the height above ground, and the angular position of individual blades 13, F1-F6 of cell is actively controlled according to the wind speed (v.sub.w) determined for the cell. Since the dependence of the wind speed from height over ground follows a standard curve, it is sufficient to measure the wind speed at a height, in order to determine on its basis the values for other heights. All cells have the same rotational speed about the machine axis MA, but because of the different heights, they have different wind speeds. Correspondingly different tip-speed ratios are obtained, which then are averaged for the entire system and have to ensure a maximum of energy production.

[0072] The electric cabinet with the motion controller 58 is provided on the rotor. The rotor position should also be sensed on the rotor. To this end, a corresponding encoder may be used. In the example of FIG. 11, a transducer for zero position 54 is instead provided. The rotor rotational speed is determined on the tower. The resulting step impulses are read through an PLC 64 and are transmitted through the Wi-Fi connection to the motion controller 58 on the rotor.

[0073] The active blade control receives a plurality of incoming signals, directly from a measurement system, which comprises the wind speed sensor 67, the wind direction sensor 68 and possibly a rotor torque sensor 69. In addition, impulses for the rotational speed are supplied. Based on these input signals, the blade control 64 determines how the individual blades have to be controlled (which cam discs are used, where is the zero point of the rotor position). The control signals from the motion controller 58 flow through a power module 59 to an output module 60 and from here through a distribution box 55 to the individual actuators 39a and 39b .

[0074] The profile of blade angle is periodically newly selected (different cam discs). The wind direction defines the zero position of rotor. Based on the input signals required for adjustment, a median over a predetermined time is calculated. Both the refresh time and the time window for the averaging of the adjustment parameters should be freely selectable. A specific control 61 may provide commands for the switching off of turbine or rotational speed reduction.

[0075] The maximum number of different blade angle profiles (virtual cam discs), which may be defined, is limited by the motion controller 58 and may for example be equal to 99. The blade angle profile to be used depends on the operating conditions and the tip-speed ratio of the turbine. The tip-speed ratio is calculated in a way known per se, from the wind speed v.sub.w and the rotor speed (or the rotor peripheral velocity).

[0076] The theoretical optimal blade angle profile for a blade 13 has been calculated by means of an analytical model for different tip-speed ratios. An example of a tip-speed ratio of 0.4 (a) together with a schematic view of the physical positions of blades each 30 (b) is shown in FIG. 9.

[0077] It is to be noted that the maximal accelerations in FIG. 9 are not reached in reality. The optimal blade angle profiles are therefore neutralized and the resulting characteristics are compared with typical proprieties of available drive motors. An example of two different neutralizations is shown in FIG. 10.

[0078] Blades are positioned according to a virtual lead axis. The lead axis is determined by a NULL-impulse (zero position 54) and the rotational speed. The PLC 64 stores with a predetermined frequency the current wind speed, the rotor speed and the wind direction. The median is periodically calculated based on the wind speed and rotor speed. These provide the averaged tip-speed ratio by calculation through the last time window, and the cam disc is selected. The median of the wind speed is also periodically calculated. It then allows the NULL position of the cam disc to be determined.

[0079] If the tip-speed ratio of turbine is <0.4 a constant blade angle profile is used, in order to increase the rotational speed. As soon as the tip-speed ratio is >0.4, the turbine is operative.

[0080] When the power is decreased, the wind turbine is decelerated by the generator, in order to set the speed to zero. The blade control receives from control 61 of system a signal that indicates that the operating condition ramp down has been reached and the blade drives 39a and 39b are de-energized or, in case of a hydraulic drive, the hydraulic motors are released.

[0081] The rotor speed is 0 and brakes of wind turbine are closed. The blade control is not deactivated, so that it doesn't lose the rotor position. The motors are de-energized or the hydraulic motors have no oil pressure. The blades 13 therefore align with the wind.

[0082] The wind turbine is decelerated by the brake 21 as quick as possible. The blades 13 are physically current-free or oil pressure free in case of actuation of the emergency command.

[0083] A block diagram which is analogous to FIG. 11 for the electro-hydraulic control of blades in cells is shown in FIG. 12. The hydraulic actuators HA11-HA1n and HA21-HA23, provided for actuating the individual blades and which are provided with the required valves and activation, are supplied with oil pressure through hydraulic conduits in cells by one (or more) central (positioned in the center of rotor) hydraulic aggregate(s) 73. The one or more hydraulic aggregates 73 obtain their operating current from their own voltage supply 72, which is connected to the energy transmission (collector ring 62).

[0084] The hydraulic actuators HA11-HA1n and HA21-HA23 may be particularly compact and provide high adjustment forces. By opening the corresponding valves, it is very easily possible to ensure the necessary freewheeling of blades.

LIST OF REFERENCES

[0085] 10 wind turbine (vertical) [0086] 11 upper ring [0087] 12 axis of rotation [0088] 13 blade [0089] 14, 17 rod [0090] 15, 18 pipe [0091] 16 middle ring [0092] 19 lower ring [0093] 20 main shaft [0094] 21 brake [0095] 22 rotor (generator) [0096] 23 bearing mount [0097] 24 pipe [0098] 25 rod [0099] 26 machine house [0100] 29 foundations [0101] 31, 33 rods [0102] 32 pipe [0103] 34 plane [0104] 35 pipe [0105] 36 flange [0106] 37 rib [0107] 38 bearing support [0108] 39 actuator (blade) [0109] 39a,b servomotor [0110] 40 supporting roller track [0111] 41 upper portion (cylindrical) [0112] 42, 44 flange [0113] 43 middle portion (conical) [0114] 45 lower portion (cylindrical) [0115] 46 lower bearing pin [0116] 47, 48 bearing (for example, self-aligning roller or ball bearings) [0117] 49, 50 gear [0118] 51 cover [0119] 52 angular gear [0120] 53 rotor block [0121] 54 zero position [0122] 55 distribution box [0123] 56 24VDC voltage supply [0124] 57 Wi-Fi transmitter [0125] 58 motion controller [0126] 59 power module [0127] 60 outlet module [0128] 61 control [0129] 62 collector ring [0130] 63 impulse for rotational speed [0131] 64 PLC [0132] 65 24VDC voltage power supply [0133] 66 Wi-Fi transmitter [0134] 67 wind speed sensor [0135] 68 wind direction sensor [0136] 69 rotor torque sensor [0137] 70 computer [0138] 71, 72 alternate current power supply [0139] 73 hydraulic aggregate [0140] d1 diameter [0141] DM strain gauge [0142] FP blade profile [0143] F1-F6 blades [0144] HA11 [0145] HA1n hydraulic actuators (integrated with valves and activation) [0146] HA21 [0147] HA23 hydraulic actuators (integrated with valves and activation) [0148] H1 total height [0149] h1-h3 height [0150] K1-K3 force measurement device [0151] MA machine axis [0152] W1-W3 wind measurement device [0153] Z1, Z2 cell