GB2249143A

GB2249143A - Vertical axis wind turbines

Info

Publication number: GB2249143A
Application number: GB9120224A
Authority: GB
Inventors: Vane Sutton-Vane
Original assignee: SUTTON VANE VANE
Current assignee: SUTTON VANE VANE
Priority date: 1990-09-27
Filing date: 1991-09-23
Publication date: 1992-04-29
Also published as: GB9021069D0; GB9120224D0

Abstract

The arms 19, 20 of a pair are inclined in opposite directions relative to the horizontal to form a truss-like structure with the rotor 18 and blade 21. The upper arm 19 of a pair is inclined downwardly from its (upper) point of connection with the rotor 18 and the lower arm 20 of the pair is inclined upwardly from its (lower) point of connection with the rotor 18. At their outer ends. the arms 19 and 20 of a pair are connected to a vertical turbine blade 21 of aerofoil shape in lateral cross-section. The arms 19 and 20 are spaced sufficiently far apart at their junction with the blade 21 to avoid mutual airflow interference. The arms are of aerofoil shape in lateral cross-section. During rotation, the pairs of arms 19 and 20 generate energy forces which assist in rotating the rotor 18. <IMAGE>

Description

VERTICAL AXIS WIND TURBINES This invention relates to vertical axis wind turbines, and is concerned with straight-bladed vertical axis wind turbines.

Straight-bladed vertical axis wind turbines are known for use in driving electrical generators and for other purposes. In such known vertical axis wind turbines, a turbine blade is usually mounted at the outer end of a horizontal arm which interconnects the blade with the vertical rotor. The horizontal arm has to be robust in order to resist bending moments, and usually has a large thickness, which results in creating drag. The drag absorbs energy generated by the rotating turbine blade, and substantially obstructs wind flow through the turbine.

The rotational speed of a vertical axis wind turbine is usually governed by either arranging for the blade(s) to stall upon reaching a predetermined rotational speed, or by allowing the blade(s) to pivot away from a vertical position under a predetermined centrifugal force, or by forming the blade(s) in two parts, each part pivotably mounted so as to pivot away from a vertical position in which the two parts are vertically aligned under a predetermined centrifugal force. The first mentioned type of vertical axis wind turbine is usually known as a stall regulated wind turbine. The second mentioned type is usually known as a variable geometry regulated wind turbine, and the third mentioned type is usually known as an arrow-head regulated wind turbine.

The present invention can be applied to any of the types of regulated vertical axis wind turbines referred to above.

According to the present invention, there is provided a vertical axis wind turbine in which a turbine blade is connected to a vertical rotor by a pair of vertically spaced apart arms, each of aerofoil shape in lateral cross-section, the arms being inclined in opposite directions relative to the horizontal to form a truss-like structure, and which during rotation about the vertical axis, generate additional energy forces which are transmitted to the rotor so as to assist in rotating it.

Preferably, the upper arm is downwardly inclined from its point of connection with the rotor and the lower arm is upwardly inclined from its point of connection with the rotor.

Some embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side elevation of part of a stall regulated straight-bladed vertical axis wind turbine embodying the present invention and constituting a first embodiment; Figure 2 is a diagrammatic side elevation of part of a variable geometry regulated straight-bladed vertical axis wind turbine embodying the present invention and constituting a second embodiment; Figure 3 is a diagrammatic side elevation of part of an arrow-head regulated straight-bladed vertical axis wind turbine embodying the present invention and constituting a third embodiment; and Figure 4 is a diagrammatic side elevation of another form of straight-bladed vertical axis wind turbine embodying the present invention and constituting a fourth embodiment.

The straight-bladed vertical axis wind turbine 1 shown in Figure 1 is of the stall regulated type and comprises a fixed tower 10 which is preferably of circular cross-section with a tapered head portion 11.

Alternatively, the tower 10 can be of lattice construction. Extending upwardly of the tower 10 is a vertically-disposed drive shaft 12 which is mounted in bearings 13 and 14. The drive shaft 12 is connected via a gear box 15 to an electrical generator 16 and is provided in addition to the main brake 17. An air brake may be provided in addition to the main brake 17. This may be in the form of an outward opening flap in the main blade 21 between the fairings 22 described hereafter. The air brake would be controlled so as only to open if the turbine overspeeds or if the brake 17 fails.

The drive shaft 12 extends coaxially within and is connected to a tubular rotor 18 to which are connected vertically-spaced pairs of arms 19 and 20 which are of aerofoil shape in lateral cross-section. The arms 19 and 20 of each pair of arms are in the same vertical plane.

The arms 19, 20 of a pair are inclined in opposite directions relative to the horizontal to form a trusslike structure with the rotor 18. The upper arm 19 of a pair is inclined downwardly from its (upper) point of connection with the rotor 18 and the lower arm 20 of the pair is inclined upwardly from its (lower) point of connection with the rotor 18. At their outer ends, the arms 19 and 20 of a pair are connected to a vertical turbine blade 21 of aerofoil shape in lateral crosssection. The arms 19 and 20 are spaced sufficiently far apart at their junction with the blade 21 to avoid mutual airflow interference. Preferably, the spacing of the arms 19, 20 at their junction with the blade 21, is greater than four times the chord of an arm.

The junctions of the arms 19 and 20 with the blade 21 are provided with fairings 22 of circular lateral cross-section and aerofoil or streamlined longitudinal cross-section. The aerofoil sections of the blades 21, the arms 19 and 20 and the fairings 22 all face the direction of rotation of the turbine 1.

During rotation, the pairs of arms 19 and 20 generate energy forces which assist in rotating the rotor 18.

The vertical axis wind turbine 1 may be provided with a single blade 21 or with two or more blades 21.

In a non-illustrated modification of the Figure 1 arrangement, the lower arm 20 of a pair extends substantially horizontally and the upper arm 19 thereof extends upwardly and outwardly from their points of attachment to the rotor 18.

The vertical axis wind turbine 2 shown in Figure 2 is of the variable geometry regulated type. The general layout is the same as in the stall regulated type as described with reference to Figure 1, but there are the following variations.

The blades 21 in this embodiment are each pivotally connected to the arms, being hinged at a point 23. This allows the blades 21 to move, under the influence of centrifugal force, to the inclined position indicated by broken lines, in order to govern or regulate the rotational speed of the turbine 2.

Pivotal movement of the blades towards the inclined position shown in broken lines is constrained by a means comprising a spring and cable system 24 contained within the associated lower arm 20.

Alternatively, the blade constraining system can be pneumatic or hydraulic.

The structural integrity of the truss-like structure formed by the arms 19 and 20 and rotor 18 is maintained by a vertically-extending half-aerofoil section structural member 25 of hollow form, which extends between the outer ends of each pair of arms 19 and 20. The hollow defined by the member 25 is disposed outward so as to allow the associated blade 21 to fit closely within it, when the blade 21 is in the vertical position. The vertical member 25 produces drag when the blade 21 is disposed other than vertical, thus improving the governing of the wind turbine 2.

The vertical axis wind turbine 3 shown in Figure 3 is of the arrow-head regulated type. The general layout is the same as in the stall regulated type described with reference to Figure 1 but there are the following variations.

Each blade 21 comprises two half blade portions 26 and 27 instead of a continuous one piece blade, the blade portions being pivotally connected to the arms 19, 20. The half blade portion 26 is hinged at point 28 to the associated arm 19, and the half blade portion 27 is hinged at point 29 to the associated arm 20. The lower end part of the half blade portion 26 and the upper end part of the half blade portion 27 are of hollow halfaerofoil section with the hollow side inboard. When the half blade portions 26 and 27 are in the vertical operating position, the hollow half-aerofoil sections thereof marry with a vertical hollow half-aerofoil section structural member 30 which extends between the outer ends of the arms 19 and 20, so as to combine with the blade portions 26, 27 in forming a complete aerofoil.

The half blade portions 26 and 27 are each connected to a mechanical or pneumatic or hydraulic system 31 contained within the vertical hollow halfaerofoil section member 30. The actuating system 31 comprises means, such as rams, operable to force the blade portions 26, 27 out of the vertical, against centrifugal force.

The hollow half-aerofoil sections of the blade portions 26 and 27 and the member 30 produce drag when the blade portions 26, 27 are other than verticallydisposed, thus improving the governing of the turbine 3.

The vertical axis wind turbine 4 shown in Figure 4 has the same general layout of the previous embodiments but with the following variations.

A blade 21 is mounted on a pair of convergent/divergent arms 19, 20 which have extensions l9a, 20a of shorter length than arms 19, 20. The outer ends of the extensions l9a, 20a, support a verticallydisposed elongate member 40 of aerofoil (lateral) crosssection. The member 40 serves as a counterweight means which balance the blade 21.

An air brake may be provided, rather like the air brake described above in connection with Figure 1. In this embodiment however, the air brake, (which may also comprise an outward opening flap), may be disposed in the central part of the blade 21, intermediate the points of connection between the blade 21 and arms 19, 20.

The arms 19 in all embodiments form an inverted Vee rotor and the arms 20 form a Vee rotor which produce useful amounts of power as opposed to vertical axis wind turbines with horizontal arms which only produce drag.

The arms 19 and 20 also reduce blade bending moments.

The area of the tower 10 and arms 19, 20 is reduced compared with known designs and do not substantially obstruct wind flow through the wind turbine, giving improved air flow and reduced turbulence effects of the down-wind blade compared with known designs.

The arms 19, 20 form a frame structure which is lighter in weight and more rigid than a single horizontal arm and should be cheaper to produce.

The configuration allows the generator 16, gear box 15 and brake 17 to be at a lower level.

When the invention is applied to variable geometry and arrow-head regulated types of wind turbines, there are no drag producing cables, struts etc during normal operation of the turbines, resulting in improved efficiency.

Vertical axis wind turbines with blades have a self-starting capability, even if only one blade is provided. However, the greater the number of blades, the better the self-starting capability.

The tower 10 may be less costly to produce compared with known towers.

On very large wind turbines it may be necessary to provide a vertical aerofoil-section strut between a pair of arms 19, 20 at half radius.

Claims

1. A vertical axis wind turbine in which a turbine blade is connected to a vertical rotor by a pair of vertically spaced apart arms, each of aerofoil shape in lateral cross-section, the arms being inclined in opposite directions relative to the horizontal to form a truss-like structure, and which during rotation about the vertical axis, generate additional energy forces which are transmitted to the rotor so as to assist in rotating it.

2. A wind turbine as claimed in Claim 1, wherein the upper arm is downwardly inclined from its point of connection to the rotor.

3. A wind turbine as claimed in Claim 1 or Claim 2, wherein the lower arm is upwardly inclined from its point of connection to the rotor.

4. A wind turbine as claimed in Claim 1, 2 or 3, provided with counterweight means which balance the blade.

5. A wind turbine as claimed in Claim 4, wherein the counterweight means is supported by extensions of the upper and lower arms.

6. A wind turbine as claimed in Claim 1, wherein the lower arm extends substantially horizontally and the upper arm extends upwardly and outwardly from their points of attachment to the rotor.

7. A wind turbine as claimed in Claim 1, 2 or 3, provided with means pivotally connecting the blade to the arms whereby the blade can move under the influence of centrifugal force in order to regulate the rotational speed of the turbine.

8. A wind turbine as claimed in Claim 7, provided with means constraining pivotal movement of the blade.

9. A wind turbine as claimed in Claim 7 or 8, provided with structure extending between the arms and defining a hollow for locating the blade when disposed in a vertical position.

10. A wind turbine as claimed in Claim 1, 2 or 3, wherein the blade is formed by blade portions pivotally connected to the arms.

11. A wind turbine as claimed in Claim 10, wherein the blade is formed by two portions, one blade portion being pivotally connected to the upper arm and the other blade portion being pivotally connected to the lower arm.

12. A wind turbine as claimed in Claim 10 or 11, provided with activating means operable to force the blade portions out of the vertical, against centrifugal force.

13. A wind turbine as claimed in Claim 10, 11 or 12, provided with structure extending between the arms so as to combine with the blade portions in forming a complete aerofoil.

14. A wind turbine substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

15. A wind turbine substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.

16. A wind turbine substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.

17. A wind turbine substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.