Patent Application
20090085355
The present invention is related to the field of self-acting variable pitch vertical axis wind turbines, and is more particularly directed to such turbines employed for generating power.
Self-acting variable pitch vertical axis wind turbines (SAVPVAWTs) are known and have been developed to compensate for wind direction variations to the extent that approximately constant and predicable performance may be achieved with improved efficiency.
For example US Patent Application Publication No. 20070014658 to Mollinger describes a windmill provided with a vertical shaft from which radially extend four arms at right angles to each other, each of the four arms having attached thereto a variable pitch, flat three section blade mounted on a vertical axis and a booster curtain within a structural frame located next to the blade. The pitch of the blade is changed by a variable-speed electric motor and the booster curtain is opened or closed by a bi-directional electric motor, the speed and the direction of the electric motors being controlled by a weather vane so as to maintain maximum torque on the vertical shaft from wind blowing from any horizontal direction. As will readily be appreciated, the cost and complexity of such equipment with concomitant maintenance requirements render it of doubtful commercial viability.
Accordingly, there is a need for a simpler improved SAPVAWT.
It is therefore a general object of the present invention to provide an improved self-acting variable pitch vertical axis wind turbine.
A further object of the present invention is to provide a simple mechanical means of effecting a variation in turbine blade pitch without the need for external and power consumptive actuation.
A still further object of the present invention is to provide a SAVPVAWT coupled to a generator for generating electrical power.
According to the present invention there is provided a self-acting variable pitch vertical axis wind turbine which comprises:
In one embodiment, the rotor is formed of a split casing including two complementary top and bottom halves, the stator is enclosed within the split casing of the rotor, and the wind turbine further includes:
In one embodiment, each paddle defines a paddle plane and each blade is rotatable about the respective spindle axis between first and second blade position, with the paddle plane being substantially parallel to the turbine axis when in the first blade position and with the paddle plane being substantially perpendicular to the turbine axis when in the second blade position. The first and second blade positions being typically limited by the rotational displacement of the cam within the cavity of the mounting.
The fixed shaft may conveniently be hollow and one or more power take-off cables may be accommodated therein for conveying electrical power to a load, for example a light bulb, radio receiver or any other appropriate appliance.
The stator may be of any convenient and conventional construction and of a size to be fitted within the casing of the rotor.
The split casing of the rotor is in two halves and each half in combination constitutes the commutator of the generator, whereby rotation of the rotor in use generates power within the windings of the stator and that power is fed to a load by the cable(s) as aforesaid. The rotor casing is mounted on the shaft for rotation thereabout and a ball bearing race is provided for that purpose on either side of the stator.
Each half of the split casing is provided with for example four mating halves of blade mountings, each mounting advantageously being of aerodynamic shape and orientation. In one embodiment of the present invention, four such mountings are provided equidistantly spaced about the circumference of the casing and each mates with its corresponding half such that the spindle of a blade is held therewithin in rotatable manner, the angular range of such rotation being limited as indicated supra. In this latter respect, the quadrant-shaped cam in use moves within the hemi-cylindrical cavity, thus giving a 90° range of movement. The two halves of the rotor casing are secured one to the other by suitable fixtures, such as screws or nuts and bolts.
The blade paddles are asymmetrically mounted on a respective spindle such that the centre of gravity of each blade is offset from the mid-point of the paddle for a purpose to be hereinafter described. Each spindle may advantageously be mounted in at least one ball bearing race.
The blade paddles may be of generally rectangular form or may in the alternative be curved or may be provided with surface embellishments such as in relief or intaglio. Further the paddles may be of shapes representative of different interests such as sport, nature, politics and/or may be adorned with slogans or advertising material in general.
Other objects and advantages of the present invention will become apparent from a careful reading of the detailed description provided herein, with appropriate reference to the accompanying drawings.
Other objects and advantages of the present invention will become apparent from a careful reading of the detailed description provided herein, with appropriate reference to the accompanying drawings, in which similar references used in different Figures denote similar components, and wherein:
a is a similar view to that of
a and 4b are schematic cross sectional views of a blade mounting (not to scale relative to the blade paddle) taken along line 4-4 of
With reference to the annexed drawings the preferred embodiment of the present invention will be herein described for indicative purpose and by no means as of limitation.
Now referring to
The generator 12 comprises a stator 14 and a rotor 16, which latter consists of a split casing 18 having an upper half and a complementary lower half 20, 22 respectively. The stator 14 and the rotor 16, rotating about a generally vertical turbine axis 17, are provided with appropriate windings (not shown) in conventional manner.
A hollow fixed mounting shaft 24 accommodates the cables 13 and is secured within a central bore 26 formed in the base 2, the shaft and the base being fixed such for example by a set screw (not shown). The stator 14 is rigid with the shaft 24, the stator being enclosed within the two halves 20, 22 of the casing 18 of the rotor 16. The casing halves 20, 22 are secured together by suitable fixtures (not shown).
Each half 20, 22 of the rotor casing 18 is provided externally thereof with five blade mountings 30 spaced apart equally about the periphery thereof and are aerodynamically contoured from the periphery towards the centre of the hub 10. At the end of each mounting 30, remote from the centre of the hub 10 at the periphery thereof, there is defined a clamping region 32 (see
Each blade paddle 8 is of generally rectangular shape and is asymmetrically fixed to its respective spindle 34 as can clearly be seen from
In use, the SAVPVAWT is located on the pylon 4 in an appropriate site to take advantage of the wind element. The wind turns the impeller 6 and electrical power is generated by the generator 12 with electricity being delivered by the cables 13 to a load (not shown). The mode of operation of the present invention is as follows.
With the wind direction as indicated by arrows A in
It will be understood that the surface area of each paddle and the location of its centre of gravity are important parameters in terms of how and when the paddle moves in response to the torque and/or the desired rotational speed.
Although the blade paddles 8 have been described in the specific embodiment as being planar, their shape and surface embellishment may be different and may be customized, provided that the required asymmetry and rotational capability are maintained.
Although the present invention has been described with a certain degree of particularity, it is to be understood that the disclosure has been made by way of example only and that the present invention is not limited to the features of the embodiments described and illustrated herein, but includes all variations and modifications within the scope and spirit of the invention as hereinafter claimed.
