WO1994025750A1

WO1994025750A1 - Windmill

Info

Publication number: WO1994025750A1
Application number: PCT/SE1994/000404
Authority: WO
Inventors: Per Collin
Original assignee: Nonox Engineering Ab
Priority date: 1993-05-03
Filing date: 1994-05-03
Publication date: 1994-11-10
Also published as: EP0702753A1; AU6661994A; SE501270C2; SE9301525D0; SE9301525L

Abstract

Windmill with turbine with vertical central shaft and wings parallel or near parallel to said shaft conditionally rotatable around their own shaft, which wind turbine is composed of several part turbines arranged on the top of each other with suitably identical design, the central shafts (1.2) of which are connected with couplings (1.3), which partly centre the central shafts in relation to each other, partly are so designed that generated torque is transferred from turbine to turbine even if small angle differences exist between the centre lines of the central shafts, wherein the central shafts of the part turbines (1.2) have a supporting bearing in one end, which suitably is integrated with the coupling half of this end and which is held in position in the horizontal plane by at least three preferably symmetrically distributed preferably prestressed horizontal stay wires (1.4) extending to supporting masts (1.5), preferably guyed at the same level, located at a distance from the central shaft of the wind turbine, which suitably exceeds twice the part turbine radius.

Description

WINDMILL.

The present invention comprises a device, which uses wind energy for production of electric power (windmill, wind power plant), which has the advantage that it can be built for much higher capacity than today's commercial windmills, wich mostly have a capacity of «3000 KW. The upper limit in capacity for a windmill according to the invention is difficult to judge today, but it exceeds very likely 20 MW.

Wind is a kind of energy with low intensity per area unit, thus the turbine of a large windmill must sweep large areas. All commercial windmills of today are of propeller type, wich severely limits their maximum capacity because large propeller diameters cause severe structural strength poblems. Currently the only way to bring about large effect based on wind at one location is a farm with a large number of propeller mills. Such a farm very much interferes with and disturbes the landscape and also results in high investment cost per installed KW.

As the wind velocity increases with altitude above ground/sea level, it is an advantage to make a windmill high instead of wide. The variation of wind velocity with altitude above ground or sea level can be represented by the formula

where VJJ = the wind velocity at altitude H, Q^ = the velocity at the altitude of

the measuring device above ground/sea level and K is a constant approximately = 0,1.

The formula gives that nomally the wind velocity at altitude +250m is 20% higher than at +40m level. As the exstractable specific effect (KW/πr swept area) is proportional to third power of wind velocity, 70% larger specific effect can be extracted at the higher level, a fact that this invention makes use of. A windmill according to this invention is thus built tall and has a turbine with a vertical central shaft. The wings of the turbine are, contrary to for instance the wings of the Darrieus-turbine, straight and parallell or nearly parallell to the turbine shaft and also rotate individually around their own axis (the* wing shaft). The invention thus relates to a windmill with large effect, preferably at least 1 MW, especially > 3 MW. The turbine of the windmill has a vertical central shaft and is constructed of several part turbines assembled on top of each other. The turbines are suitably of essentially identical design, which simplifies manufacture and maintenance, but the turbines can be individually designed for instance in order to adapt them to the wind velocity at different levels. The part turbines have wings, which preferably are parallell or near parallell with the central shaft The wings are rotateable around their own axis, which preferably describes a circular orbit around the central shaft when the wind turbine rotates. The part turbine's central shaft (part central shaft) are arranged along a basically straight, vertical line, preferably with limited angular deviations between the part central shafts of two adjecent turbines. The part central shafts are preferably connected to each other with couplings, which are designed to transfer generated torque from part tubine to part turbine even though small angular deviations may exist between the centerlines of the part shafts. The central shafts of the part tubines are suitably centered relative each other by for instance appropriate design of the couplings between the part turbines or with special centering devices. The central shaft of the wind turbine is supported by collar bearings counteracting movement in the horizontal direction. Preferably every part turbine has its own collar bearing. Such a collar bearing is suitably located in one of the ends of the part central shafts and can be integrated with the coupling device (coupling half) of this end for connection of the part tubine with adjecent part tubine. The collar bearing can be held in the horizontal plane with preferably at least three radially pointing stay wires, wich preferably are prestressed and connected to neighbouring supporting masts and/or neighbouring windmills. These stay wires are preferably symmetrically distributed around the circumference of the collor bearing, and the supporting masts or other windmills to which the stay wires extend, are likewise preferably symmetrically distributed around said wind turbine. The stay wires from the collar bearing extend preferably mainly horizontally to the neighbouring masts respectivly windmills. A prefered embodiment of the invention implies that a wind turbine is surrounded by at least three support masts, which preferably are symmetrically arranged around the wind turbine. The support masts are preferably in their turn guyed with guy wires extending to those levels, where the stay wires from the collar bearings of the wind turbine are fastened to the support masts. Normally inclined guy wires extend from the same levels of the support masts to anchoring points at ground level. The support masts are preferably designed for low drag, particularly as lattice masts, which suitably can be built mainly from pipes. Such masts are per se wellknown and usually designated ^Mmasts of TV-type^M. As example of suitable masts can be mentioned lattice masts manufactured by AB WIBE, Mora, Sweden, of which relevant types are series 1000 with maximum height 150m, series 1500 with maximum height 250m and particularly series 2400 with maximum height 335m, the latter type having triangular lattice work with side of 2,4m, 1,8m and 1,0m. Also higher or lower such masts can be used. The distance between the wind turbine and nearest support mast and/or windmills, to wich the collar bearings are stayed, can vary but is preferably at least the double radius of the wind turbine and at most five times the radius.

A suitable embodiment of the invention implies that the central shaft is arranged to be supported at least at one place, preferably at several places or at every part turbine with a device similar to a roller bearing, particularly active for carryingthe wind pressure on the turbine, preferably adjecent to or integrated with the couplings between the part turbines. The support is attained through a force absorbing outer bearing brace, which surrounds the central shaft and suitably is essentially concentric with the same and has the centre line mainly parallell to the central shaft The brace can be kept in position preferably by prestressed stay wires extending to neighbouring support masts and/or windmills, preferably mainly horizontally. The supporting force is tranferred to the central shaft by circular rolling elements, e.g. wheels, preferably auto wheels such as truck wheels, preferably with gasfilled tyres. The axles of the elements (axles of rotation, wheel axles) can be arranged on pivotally hinged arms, the pivots of which are fixed to the central shaft The pivots can be essentially parallell to the central shaft, thus by turning of the hinged arms the rolling elements can be brought to bear against the inner surface of the brace ring facing the central shaft By turning the arms in opposite direction the rolling elements can be disengaged from the brace ring and suitably be brought to a free position, where a rolling element or part of it as the wheel or the tyre can be exchanged. The pivots for the rolling elements can be essentially parallell with he central shaft, but as well somewhat inclined in relation to the central shaft e.g. with the pivots converging upward and/or downward in direction towards the central shaft, especially if the inner sufaces of the brace ring is constructed conically tapered in direction upwards and/or downwards in order to enable the rolling elements to carry part of the weight of a brace ring or to govern the brace ring at right level.

The invention enables the exploitation of very tall windmills. Suitable heights are > 100m, generally >150 or >200m and especially > 250 or >300m. The support mast or masts, which are located closest to the wind turbine are suitably at least of the same height as the wind turbine and preferably they are higher, suitably so much higher that the difference in height corresponds to the height of the lowest part turbine. This will facilitate the mounting of this part turbine after the other turbines coupled together have been hoisted hanging in cables from the support masts. Suitable difference in height can be >20m, or >40 or >60m.

The height of a part tubine can vary within wide limits. Suitable heights can be >20m, >30m, >40m or at least 50m. These minimum heights can refer to all part turbines or e.g. those part tubines, that represent the main part of the height of the wind turbine. All part turbines can have essentially the same height and essentially the same general design as diameter etc, which can facilitate and reduce manufacturing and maintenance costs. Possibly can those part tubines close to the lower end of the wind turbine be designed to carry heavier weight loads and those close to the upper end be designed for heavier wind loads. The ratio between height and diameter of the wind turbine can suitably be at least 2, often >4, >6 or >8.

The invention is generally defined in the attached claims.

The invention is illustrated in more detail with an embodiment with reference to attached drawings and figures. The invention is however not limited to the embodiments, which intend to illustrate the invention without limiting it

The attached drawings show:

FIG 1 a view of a windmill according to the invention,

FIG 1A a view from above of the wind mill according to FIG 1,

FIG 2 a view from above of a part turbine of a windmill according to the invention, FIG 3+4 diagrams of the variations of certain parameters during one revolution of a turbine (0°< α <360°) respectivly a part of one revolution,

FIG 5 a wing, partly sectionalized,

FIG 6 the lowest part of a wind turbine, partly sectionalized

FIG 7 design of a part of a collar bearing for the central shaft, partly sectionalized FIG 8 outlines of a diagram for a control lsystem of a windmill according to the invention. In order to illustrate the invention in more detail, an embodiment of a windmill according to the design outlined in FIG 1 with a capacity of 12 MW will be described below. The wind turbine of the windmill consists of 6 part turbines (1.1) assembled on top of each other and suitably of identical design: The central shaft of the part turbines (1.2) are shaped as wide tubes and interconnected with couplings (1.3), which partly centers the shafts relative each other, and transfer the generated torque from turbine to turbine even though small angular deviations my exist between the centre lines of the turbine shafts, and partly suitably are integrated with the collar bearings of the central shaft, whereby the shafts are held in position with, for each bearing, at least 3 symmetrically arranged radial and horizontal prestressed stay wires (1.4) to vertical support masts being guyed at the same level, the masts being located at a distance from the shaft, which suitably exceeds twice the part tubine radius.

The part turbines (see FIG 2+2A) have 3 wings (2.1) which are rotatably mounted at the outer end of the spoke arms (2.3), which are fixed near the couplings (1.3) of the central shaft (2.2). In consideration of the torque a wing exerts and the air drag caused by the rotation of a turbine, the arms are designed with a double symmetrical section with low aerodynamic drag. The number of wings can be either smaller or larger than 3, e.g. 2, 4, 5, 6 or more.

The lowest part turbine, the avarage +altitude of which is +40m, is via the tube shaft (1.6) connected to devices for transformation of the wind turbine effect to electric power, for instance delivered to the public grid. The effect exstracted from the generator is according to the invention preferably controlled in such a way, that the rotary velocity of the wings (2.1) around the turbine centre will be less than twice the undisturbed wind velocity, suitably 30-150% of it This is a much smaller velocity than what e.g. is specified in the German patent No. 892 130 (350-1500% of the undisturbed wind velocity). A wind tubine with large effect built according to said patent would get problems from the high stresses, which the centrifugal forces would exert due to the dimensions needed to give sufficiently large sweep area. The rotary velocity of the wings around the turbine centre of the embodiment of the invention in question is in FIG 2 approximately 63% of the undisturbed wind velocity, and in spite the wings being long and slender, they will not cause structural problems.

In order to get a high extraction efficiency of the energy in the wind with a windmill according to the invention, the part turbine wings are preferably all forced to rotate around their individual axis (below = wing rotation) in a direction opposite that of the turbine's, the rotation being individually controlled by servo devices, e.g. frequency controlled electric motors or hydraulic motors. The control of the servo devices are based on measuring results of turbine rpm and shaft torque, the strength (velocity) and direction of the undisturbed wind, the latter suitably measured with sensors located at the average altitude above ground/sea level for each individual part turbine. The sensor signals control the servo devices, which set the angle of incidence of each wing relative the apparent wind direction in such a way that maximum possible lift force is created for every position a wing takes during one turbine revolution.

To illusterate the "work'' of a wing during one revolution of the turbine FIG 2, 2a, 3, and 4 are given. FIG 2 shows the local wind vectors for the wind for a 3- winged turbine, which rotates counter clockwise and with the undisturbed wind parallell to the X-axis and when wing A is in windward position. The setting of the wings (2.1) in respective position are also shown with an angle of incidence of 12° relative the apparent wind (VX). The resulting lift force (L) this angle creates and the components of it, tangentially (T) and radially (R), are exemplified for wing C in FIG 2. FIG 2a shows the same part turbine in angular perspective. FIG 3, for which the same symbols are valid as in FIG 2, is based on the following assumed data :

# Utilization efficiency of the inherent total effect of the undisturbed wind

= 49%

# Total design effect = 12 MW y

# 6 part turbines with total swept aera = SlOOnr^*'

# .Altitude of the centre of part turbine 6 = +225,5m

# Part turbine radius (to the wing shaft) = 18,5m

# Wing chord = 3,3m

# Wing aspect ratio = 11

# Wing section lift coefficient C = 2,0

Lmax

# Undisturbed maximum wind velocity = 16m/sec

# Tangential velocity for the wing shaft = 10 m/sec

Based on these data FIG 3 shows the calulated variations during one turbine revolution (0° < α <360°) for the following parameters for wing A:

2 TA = Tangential component of the lift force N/m βA = The angle between undisturbed and apparent wind velocity vector α>A = .Angular velocity (rad/sek) for the clockwise rotation of wing A around its own shaft to secure desired angle of incidence.

From FIG 3 it can be seen that the tangential force TA, and thus the moment a wing exerts on the turbine shaft has strong vaiations during one turbine revolution. A good smoothing will be gained if the part turbine is provided with three wings, as shown i FIG 4, where the curves for the tangential forces (TA, TB, TC) of the individual wings are separately shown together with the aggregate curve for all wings (TABC). In order to secure a nearly constant torque for a complete wind turbine according to the invention, the shafts of the part turbines (1.1) can be " phase shifted" relative to each other in the couplings (13) between the shafts (1.2).

The phase shift angle depends on the number of wings per part turbine ( m ) and the number of part turbines ( n ) and is, when measured in degrees, preferably 360°/n.m, i.e. in the shown embodiment of the invention 20°. Superposition of 6 individual 20° phase shifted curves of the type TABC in FIG 4 gives an almost straight line with small variations < +/- 1%, i.e. giving a wind turbine with almost constant torque. Phase shift angles other than 360/n.m is possible but give less good smoothing of the turbine moment

The curve for the angular velocity of the wing rotation ( ωA) has suitably, as shown in FIG 3, two marked peaks in the intervals 75°< α < 105° and 260° < α < 280°. The reason for this is the shift between the under- and overpressure side of a wing, which is necessary in order to get the tangential component (TA) of the lift force to act in the desired turbine rotational direction, a shift wich suitably is brought about in the mentioned intervals, where the lift force is near ^***• 0. The shift is brought about by an increase of the wing's rotational angular velocity beyond what is required due to the turning of the apparent wind in these intervals (dashed part of the curve for ωA). In order to get a wing with as small angular momentum as possible, and with a lift force coinciding with its centre of gravity and/or axis of rotation and thereby minimizing the servo power necessary for the wing rotation, the wing is given a section, which has coinciding or near coinciding centre of pressure and centre of gravity and/or axis of rotation, large moment of resistance and a high lift coefficient This gives a slender wing with low weight (angular momentum) and low servo power requirement According to the invention the above mentioned characteristics can be obtained by giving the wing a double symmetrical aerodynamic section, e.g. an elliptical section with a thickness = 15-25% of the wing chord and/or by providing the wing with leading and trailing edge flaps. FIG 5 gives an example of such a section (5.1) with ellictical shape, 20% thickness and with centre of pressure and centre of gravity near coinciding with the symmetri axis of the wing.

As shown in FIG 5 the leading edge flap (5.2) has single symmetrical aerodynamic section and is limited ly rotatable between stops and suspended pivotably in, preferably hollow, pivots (5.3) in front of the leading edge of the wing. The pivots are mounted in bearings fixed in pylons (5.4) protruding from the wing in such a way that the flap can swing freely in front of the leading edge of the wing (5.5).

The trailing edge flap (5.6) is single symmetrical and integrated with the trailing edge of the wing in such a way that it is limitedly rotatable around pivots (5.7) located in the centre of the preferably halfcylinder shaped nose (5.8) of the flap and mounted in bearings inside the rear opening of the wing in such a way that the flap can swing > +/- 20° relative the wing chord.

In order to reduce the tendency for boundary layer separation over the suction side of the trailing edge flap and thus enable increased angle of incidence of the wing and a high CLmax, an air jet (5.9) can, according to the invention, be blown along the suction side of the flap through the slot formed by the edges of the openings and the nose of the flap being suspended in adapted bearings inside the rear opening of the wing. The "driving force" for the jet is provided by the overpressure, which according to the invention is maintained inside the wing. A suitable fan connected to the central shaft of the wind turbine can provide overpressure in the inner of the central shaft of the wind tubine. Through the shaft and the tube shaped spoke arms (2.3), which carry the wings (2.1), and the tube shaped wing pivots (5.10), the air is fed to the inner of the-wings. A wing in principle shaped as in FIG 5 with 3,3m chord and a 5mm slot opening has a CLmax >2,0 when an overpressure of 1000 Pa is maintained inside the wing. The power consumption of the fan will correspond to <2% of the total produced power.

In order to further increase the aerodynamic efficiency of the wings they can according to the invention be equipped with discs (tip vanes) at the ends, the shape of wich preferably are circular wirth a diameter = wing cord.

The air supply to the wings has according to the invention, besides the lift increasing effect, the important function of counteracting icing. According to the invention the distributed air thus can be heated under those meteorological conditions, which can cause icing, which efTectively will prevent icing. Especially exposed to the risk of icing is the nose of the leding edge flap (5.2), which according to the invention can be protected in the way, that the pylons (5.4) and the flap pivots (5.3) are built hollow so that air from the inner of the wing can flow through the flap, whereby the air first is forced to flow along the flap nose and then drained through holes or slots in the trailing edge of the flap.

The heat energy needed for heating the air to the wings is according to the invention primarily covered by the heat losses from the main generators) of the wind turbine.

During rotation of a windturbine according to the invention the under- and overpressure sides of the individual wings are shifted during the intervals 75°<α<105° respectively 260°<α<280° (see FIG 3) (whereby α is the angle in the turbine's direction of rotation between a radius from the turbine centre directed windward and a radius from the centre directed towards the wing rotation centre, whereby a complete revolution of the turbine corresponds to α = 360°), which means that a full repositioning of the flaps must occur during those intervals. If according to the invention, the leading and trailing end flaps are interconnected, for instance mechanically by adapted angle gears and a shaft, the flap repositioning will occur automatically during the intervals stated above during which the additional wing rotation beyond that which is caused by the change of apparent wind direction, will force the leading edge flap across the chord and thereby force the trailing edge flap in the opposite direction.

According to the invention, the central shaft of the part turbine can be designed as a tube and in the embodiment it has a diameter = 2,5m. The six spoke arms of the part turbine, which support the three wings, are fastened to the central shaft near the integrated unit of shaft coupling and bearing (1.3), the latter with advantage being of type reversed "hydrostatic shoe bearing" with "shoes" acting radially outwardly against a stable ring held i position by stay wires (1.4) to the main supporting masts (1.5). Suitable collar bearings are also such of a type with rolling elements, which are described below.

The servo device for the wing rotation, for instance frequency controlled electric motor with attached gear is, according to the embodiment, installed in the central shaft at the root of the spoke arm. The force from the servo device can be transmitted via a shaft mounted on bearings in the spoke arm to the pinion of the angle gear, the crown wheel of which is attached to the tube shaped pivot of the wing (5.10).

To facilitate maintenance of the servo devices and other equipment installed in the central shaft (1.2) this, according to the invention, can be made with a diameter sufficiently large to permit an internal lift. Also the spoke arms (2.3) can have such dimensions that a person can pass to reach the bearing and angle gear for wing rotation at the outer end of an arm.

The wind turbine effect can, from the lowest part turbine shaft,, via adapted mechanical gear(-s), be transmitted to one or more generators, suitably asynchron generators. The generated electric power, which depending on the wind velocity variations will get varying frequency, can be converted in a converter with an intermediate direct current step and be delivered with public grid frequency. A windmill according to the invention can with this arrangement extract 49% of the wind's total inherent effect (85% of theoretical maximum) for the entire wind velocity interval 4-16 m/sec, the higer figure corresponding to the windmill's nominal capacity. At a wind velocity >16 m/sec (or other suitable maximum wind velocity e.g. at most 10 m/sec or at most 20 m/sec) the angle of incidence of the wings can be adjusted down so that the capacity remains nominal. If for a windmill according to the invention of nominally 12 MW the alternative with only one generator is chosen, a step up gear in several steps is necessary and for instance, with conventional tecnique, a first step with an angle gear of 1:5, the crown wheel of wich with a diameter of approx. 3m combined with a planetary gear tuned to the generator rpm. Such a special gear will be heavy and surely expensive.

According to the invention another alternative for converting the wind turbine effect to electric power is prefered, which means the use of adapted number of "generating units", each consisting of a generator, preferably an asynchronous generator, for instance of 400 KW. The generator can be coupled to a gear connected to driving wheels, which roll on and are driven by a rotating circular body, preferably a cylinder, joined to the wind turbine. The generator can for instance be directly connected to the pinion of a standard rear axle for a heavy truck or similar, which can be equipped with wheels of railroad type with adapted diameter. The necessary number of units are electrically connected to for instance converting equipment including an intermediate direct current step, wherefrom the power can be fed to the public grid.

For this purpose converting units already existing on the market and originally designed for electric railroad locomotives with an electric braking capacity of for instance 2400 KW can be advantageously used, whereby 6 "generating units" can be connected in parallel to one converting unit possibly modified from 16 2/3 to 50/60 Hz.

In order to transmit the wind turbine effect to the "generating units" can, according to the in FIG 6 exemplified and shown alternative, the lower end of the central shaft (6.6) of the wind turbine be fastened to the centre of a pontoonlike cylinder (6.7) with large diameter, in the shown embodiment 30m, on the vertical cylinder wall of which a railroad track (6.8) is mounted, and against which the wheels of the "generating units" are pressed, suitably hydraulically. The units are suspended in stationary, but vertically adjustable, devices equally spaced around the pontoon perimeter. At 16 m/sec undisturbed wind velocity, the moving railroad track is electrically braked, by feeding power to the grid, and slowed down to a suitable velocity, for instance 45 km/h, whereby 30 units will feed 12 MW to the grid. The alternative with mutiple "generating units" is very flexible from capacity point of view and futhermore cheaper than the alternative with a specially designed large generator and multiple step gear.

The pontoonlike cylinder, to which the central shaft of the windturbine is fastened, can according to the invention, apart from the function as a gear between the central shaft and the generating units, also have the very important function as axial bearing for the entire wind turbine. To fill this function the pontoon is equipped with a ring shaped float (6.10), suitably with the same diameter as the pontoon, attached under its bottom. The pontoon-float is installed in a circular water basin (6:11) and in the space under the pontoon bottom and inside the float ring, an air cushion is maintained (6.12) with so adjusted pressure, that the pontoon with the wind turbine will be air-suspended (hovering). A small flow of pressurized air is continously supplied under the pontoon bottom and the exess air bubbles out into the basin under the float ring, whereby the water level (6.13) in the basin is ajusted in such a way that the radial collar bearings of the wind turbine are held at correct level.

When the wind turbine + pontoon rotates in the water, the entire water ring between the pontoon and the basin wall also rotates. Due to the absence of displacement wave the rotational resistance will be very low (compare boat moving concurrently in a river). It will mainly be caused by the shear forces in the water ring. Due to the low viscosity of water, especially at raised temperature, these are very low and the pontoon-float works as an uncomplicated very efficient axial bearing.

Another preferred embodiment of the supporting collar bearings (1.3), which is as efficient as the above mentioned shoe type bearing but considerably less costly, is shown in FIG 7. The bearing in question has a certain similarity with a roller bearing, the rolling elements however being truck wheels or similar wheels. The wheels (7.1), which in the embodiment are 15 in number in each support bearing (1.3), are rolling^' inside a heavy outer race ring (7.2) fixed in position by the three horizontal stay wires (1.4) to the supporting masts (1.5). Each wheel is mounted in a bearing on a pivot (7.3) welded to a heavy arm (7.4) pivoting in the horizontal plane in a hinge fastened to the central shaft (7.6). A partly threaded axle (7.7), governed by and running in a sleeve (7.8) fastened to the central shaft (7.6), is pressing against the arm (7.4) with one end by the action of a nut (7.9) on the threaded part of the axle (7.7) pressing against a stop (7.10) fixed to the sleeve (7.8). By means of a torque wrench the nuts (7.9) can be tightened in such a way that all wheels (7.1) get the same adapted pressure against the outer race (7.2). It is also possible, but more costly, to get the wanted wheel pressure by means of a hydraulic device acting on the arm (7.4). Shifting of wheels, when .the mill is in operation, is possible by vertical lift of the wheel from the pivot (7.3) when the wheel has been moved to the indicated disengaged position (7.11).

FIG 8 shows an example of a circuit diagram for the control system of the wing rotation. In a computer unit (8.1) measuring test results are stored for the torque of the turbine shaft (8.2), the turbine rpm (8.3) and the undisturbed wind velocity (8.4). The sensor for the shaft torque is unique for each part turbine and can for instance be strain gauges on the couplings between the part turbines. The sensor (8.2) is connected to a computer unit (8.5) suitably set up for computing a rolling average of the shaft torque, for instance a 10 minutes average. The sensor for the turbine rpm can for instance be a tachometer for the generator. The sensor (8.3) is connected to a computer unit (8.6) which in a similar manner can be arranged to calculate a rolling average, e.g. for 10 minutes, of the rpm. The sensor for the undisturbed wind velocity (8.4) is unique for each part tubine and can be a anemometer. The sensor (8.4) is connected to a computer unit (8.7) similarity set up for computing a rolling average of the wind velocity, for instance a 10 minutes average. The wind velocity, the rpm and shaft torque of the part turbine make up the input data for computing an output signal (8.8), which corresponds to the angle of incidence of the wings in relation to the apparent wind vector and can be considered represent the "work" the part turbine will develop.

In the computing unit (8.9) measuring test results for the undisturbed wind direction (8.10), the angle of rotation (8.11) and the signal (8.8) are collected. The sensor of the undisturbed wind direction is unique for each part tubine and can e.g. consist of a. syngon sensor. The sensor (8.10) is connected to a computing unit (8.12), which, for instance, can be set up for computing a rolling, e.g.10 minutes, average of the wind direction. Computer (8.9) calculates the angle the wing momentarily must have and which results in the output signal (8.13) to the servo device of the wing.

The three supporting masts (1.5) for holding the the bearings of the wind turbine (1.3) in the horizontal plane can, as said above, be of standard design marketed for TV-transmitters etc and which are manufactured for heights up to > 300m. On the masts sensors for direction and velocity of the undisturbed wind are mounted at levels of the part turbines. Each part turbine's wings thus are controlled on basis of wind data at its own level, which makes it possible to adjust the wing rotation for optimum utilization of the wind at all levels. The test data from the sensors can advantageously be transmitted with opto cable + infralink to the the central computer inside the central shaft controlling the wing rotation. The measuring test results for wind direction, wind velocity etc can as well be taken up by sensors at a distance from the wind mill, for instance at distances at least 100m, at least 500m or at least 1000m.

By, according to the invention, making the supporting masts (1.5) higher over the ground level than the aggregate sum of the part turbines' heights, the masts beside the function as supports also fill the important function of enabling easy erection of the wind turbine. This is carried through by successivly connecting from below of the part turbines complete with wings, servo devices etc and by finally connecting the entire hanging wind turbine to the devices at ground level for the transfomation of the the wind turbine power to electricity.

Claims

PATENT CLAIMS.

1. Windmill with large effect, preferably at least 3 MW, the wind turbine of which has a vertical central shaft and is built up of several part turbines (1.1) arranged on top of each other suitably of identical design, with wings (2.1) parallel or near parallel to the central shaft (1.2), which are rotatable around their own axis (5.10), characterized in the central shafts of the part turbines (1.2) being connected to each other with couplings (1.3), which are designed to transfer generated tourqe from part turbine to part turbine even though small angular deviations may exist between the centre lines of the part turbines' shafts and with centering of the part turbines' shafts in relation to each other, the entral shafts of the part turbines having a collar (support) bearing (1.3) in one end, which bearing suitably is integrated with the coupling half (1.3) of this end and which is held in position in the horizontal plane by at least three, preferably symmetrically distributed, radial, preferably prestressed, stays (1.4) to guyed supporting masts (1.5), preferably of TV-mast type guyed at the same level, located at a distance from the central shaft, which suitably exeeds twice the part turbine radius.

2. Windmill according to claim 1, characterized in that the wind turbine is built up of n part turbines with each m wings, wherein m preferably has the same numerical value for all, or the predominant number of, the part turbines and at least one of, suitably a predominant number of, and preferably all, the part turbines being phase-shifted in relation to each other in the shaft couplings (1.3) so that the wings of a rotating reference turbine moves a specified ηumber of degrees, preferably 360/n.m degrees, ahead respectivly behind the nearest wing in another part turbine, preferably the neigbouring part turbines.

3. Windmill according to claims 1 or 2, characterized in that the rpm of the complete wind turbine through adaptation of the power outlet from a generator engaged to the central shaft of the lowest part turbine, is controlled in such a way, that the wings velocity of rotation around the centre of the central shaft is maintained at a velocity < twice the velocity of the undisturbed wind, suitably 30 - 150 % of the same.

4. Windmill according to one or more of claims 1-3, characterized in that the wings of the part turbines are arranged to positively rotate around their own axis, preferably in a direction of rotation opposite to that of the wind turbine, by means of individual servo devices controlled on basis of measurment test results of rpm and central shaft torque of the wind turbine and the velocity of the undisturbed wind, suitably measured at the average altitude over ground/sea level of the individual part turbine, whereby the servo devices preferably control the angular velocity (3.ω) of each wing in such way that its angle of incidence (5.11) in relation to the direction of the apparent wind (2.VX) gives the wing optimal lift force acting in the turbine's direction of rotation (lift force component (T) acting tangentially) in every position of the wing during one revolution of the turbine, and whereby the servo devices preferably are arranged to shift under- and overpressure side of the wings in the intervals 75°<α<105° and 260°<α<280° respectivly during one revolution of the turbine, preferably with maximum angular velocity around the wing's own shaft (ωA) within these intervals.

5. Windmill according to one or more of claims 1-4, characterized in that the wings of the part turbines have double symmetrical aerodynamic section (5.1) and are equipped with aerodynamically adapted leading- as well trailing edge flaps giving a wing of high lift and low angular momentum in order to minimize the necessary servo power for the rotation of a wing by coinciding or nearly coinciding centre of pressure, gravity and shaft 6. Windmill according to claim 5 characterized in that the leading edge flap (5.2) has single symmetrical section and is suspended in and limitediy rotatable around preferably hollow pivots (5.3) in front of the wings leading edge (5.5), which pivots are mounted in bearings in pylons (5.4) protruding from the leading edge (5.5) to the extent, that the flap can swing freely past the edge, while the single symmetrical trailing edge flap (5.

6) is integrated with the trailing edge of the wing in such a way that the flap is limitediy rotatable around pivots (5.7), located in the centre of the suitably halfcylinder shaped nose (5.8) of the flap, mounted in bearings inside an opening in the trailing edge of the wing, preferably in such a way that the flap can swing ""^**+^•/- 20° relative the wing chord.

7. Windmill according to claim 5 or 6, characterized in that the slot, which is formed between the nose of the trailing edge flap (5.8) and one or the other of the edges of the rear opening of the wing, is utilized as nozzle for air, which can be blown out through the nozzle when overpressure is maintained inside the wing and blow along the suction side of the flap, accelrating the boundary layer there, enabling large angle of incidence.

8. Windmill according to one or more of claims 5-7, characterized in that the pylons of a wing and and its leading edge flap are so designed that when overpressure is maintained in the inner of the wing an air stream therefrom flows through the pylons as well as the flap.

9. Windmill according to one or more of claims 5-8, characterized in that the leading edge and trailing edge flap with suitably designed devices, preferably of mechanical type, are interconnected in such a way that deflection of the leading edge flap results in deflection of the trailing edge flap in the opposite direction.

10. Windmill according to one or more of claims 1-9, characterized in that the wings of the wind turbine are provided with tip vanes with circular form and with a diameter = wing chord.

11. Windmill according to one or more of claims 1-10, characterized in that the mill comprises a pontoon like cylinder with large diameter and preferably vertical cylinder wall (6.7) floating in a circular water basin (6.11), wherein the central shaft (6.6) of the wind turbine is fastened in the centre of the cylinder and wherein a ring shaped float (6.10), with preferably the same outer diameter as the pontoon, is fastened under the bottom of the cylinder and wherein a small flow of compressed air is continously fed to the space inside the float ring under the bottom of the pontoon, where an air cushion (6.12) is maintained, bringing the pontoon with the wind turbine to be air-suspended (hovering), preferably with the excess air bubbling out under the float ring, and wherein an adapted water level (6.13) simultaneously can be maintained in the water basin, thus bringing the support bearings (1.3) to take the appropiate level.

12. Windmill according to one or more of claims 1-11, characterized in that the effect of the wind turbine is converted into electric power in an adapted number of generating units (6.9), preferably comprising an asynchronous generator connected to the wind turbine by a mechanical gear, for instance directly connected to the pinion of the rear axle of a heavy truck or similar equipped with wheels, for instance of railroad type with adapted diameter, wherein the wheels are brought to rotate by being pressed against a circular track, for instance a rail road track (6.8) with large diameter impelled by the wind turbine, wherein the the track (6.8) can be attached to the preferably vertical mantle wall of the pontoon like cylinder.

13. Windmill according to one or more of claims 1-12, characterized in that the central shaft of the part turbines are tubes with preferably the same diameter, wich is large enough to permit installation of a lift and that the spoke arms mounted on the central shaft, which support the wings, likwise are preferably tube shaped with a section preferably with low aerodynamic drag.

14. Windmill according to one or more of claims 1-13, characterized in that a fan maintains overpressure in the central shaft (1.2) and its arms (2.3), whereby air, possibly somewhat heated, via the the tube shaped pivots (5.10) is fed to the inner of the wings.

15. Windmill according to one or more of claims 1-14, characterized in that the length of the supporting masts (1.5) is so much larger than the aggregate length of the part turbines, that the masts can be utilized for erecting the wind turbine, whereby part turbines completly mounted at ground level sucessivly can be connected from below and the entire wind turbine can hang in the masts when being connected to the devices on ground level for converting the wind turbine power to electric power.

16. Windmill according to any of the preceding claims, characterized in that the central shaft is arranged for being supported in the horizontal direction at several levels, for the purpose of carrying the wind pressure on the turbine, preferably close to the couplings between the part turbines, against an outer supporting circular collar ring (7.2), which is arranged around the central shaft and with its axis essentially parallel with the central shaft and held in position by stays, e.g. prestressed stay wires (1.4), extending to the supporting masts, whereby the supporting forces are transmitted to the central shaft by circular rolling elements e.g. wheels (7.1), preferably auto wheels, such as truck wheels with gasfilled tyres, the wheel axles of the elements (7.3) being arranged on hinged arms (7.4), which are rotatably mounted on pivots (7.5) connected to the central shaft and with their axles of rotation principally parallel to the central shaft in such a way, that the rolling elements by turning of the arms can be brought to contact with pressure the side of the collar ring facing the central shaft and roll on it, and by turning the arms in the opposite direction can be moved to a disengaged position (7.11) in which the rolling elements are free from contact with the collar ring and thus the element or part thereof e.g. a wheel or a tyre can be replaced.

17. Method for controlling a windmill according to any of the preceding claims, characterized in that on the basis of measurement test results, as rpm and shaft torque of the turbine and the direction and velocity of the undisturbed wind, suitably measured at the idividual average altitude of each part turbine, each wing's angular velocity is controlled in such a way that its angle of incidence in relation to the direction of the apparent wind gives the wing optimal lift force (lift force component) acting in the direction of rotation in every position during the revolution.

18. Erection of a wind turbine according to any of the claims 1-15, characterized in that the mounting of the wind turbine is made with supporting masts higher than the aggregate height of the part turbines by sucessivly connecting the part turbines from below to the hanging wind turbine and connection of the wind turbine with devices at ground level for converting the wind turbine power to elctric power.