GB2040363A - Vertical axis wind turbine - Google Patents

Abstract

The or each blade 10 of the turbine is connected to an arm 13, which rotates about a vertical axis 15, by a hinge 12 located at a position intermediate the ends of the blade 10 and spaced from the centre of mass of the blade, the axis of the hinge 12 in plan view lying at an angle to the longitudinal centre line 17 of the arm 13 and in elevation lying at an angle to the longitudinal axis of the blade so that in use of the turbine when the blade pivots about the hinge 12 due to centrifugal force towards a horizontal position it assumes a spoiling attitude whereby its power is reduced and rotational speed of the turbine modified. <IMAGE>

Description

SPECIFICATION Vertical axis wind turbines This invention relates to vertical axis wind turbines.

Vertical axis wind turbines require to be controlled in such a manner as to prevent over speeding. One method of control is to mount the or each blade to a support member at a position substantially intermediate the ends of the blade, but spaced from the centre of mass of the blade, by means of a hinge whose axis is tangential to a circle having said vertical axis as its centre, so that the or each blade rotates away from a vertical position due to centrifugal forces and so reduce the swept area.

Another method is to mount the or each blade so that it can be moved about its longitudinal axis in order to alter the angle of attack of the blade relative to the wind direction and thus reduce its rotational driving force.

According to the present invention there is provided a vertical axis wind turbine comprising at least one blade, support means mounting the or each blade to rotate around the vertical axis, the or each blade being hinged to the support means at a position spaced from the centre of mass of the blade by a hinge whose axis in plan view lies at an angle to the longitudinal centre line of the support means and in elevation lies at an angle to the longitudinal axis of the blades.

An embodiment of the invention will now be described, by way of an example, with reference to the accompanying drawing, in which: Figure lisa diagrmmatic partial plan view of a vertical axis wind turbine embodying the invention, with the blade shown in a vertical position, Figure 2 is a side view of the structure shown in Figure 1 taken in the direction of arrow 2, Figure 3 is a plan view similar to Figure 1 but with the blade shown in an angled position, and Figure 4 is a side view of the structure of Figure 3 taken in the direction of arrow 4.

The vertical wind turbine comprises a blade 10 in the form of a straight aerofoil section symmetrical about a chord line 11. The blade 10 is secured to one part of a hinge 12 whose other part is fixed to one end of an arm 13 extending from a hub 14. The arm 13 and hub 14 form part of support means, the remainder of which is not shown, that mounts the blade 10 to enable the blade to rotate around a vertical axis 15 of the wind turbine in the direction of arrow 16. The support means may be of a form well known to those skilled in the art of wind turbines and may comprise, for example, a shaft connected to the hub 14 and extending along the vertical axis 15to drive a device to be powered by the wind turbine, for example an electrical generator.

The hinge 12 is spaced from the centre of mass of the blade 10 and the axis of the hinge 12 in plan view, as viewed in Figures 1 and 3, lies at an angle to the longitudinal centre line 17 of the arm 13 and in elevation, as viewed in Figure 2, lies at an angle to the longitudinal axis 18 of the blade 10. The axis of the hinge 12 is therefore skewed and is not tangential to a circle having the axis 15 as its centre as in the known arrangements.

Accordingly, when the wind turbine is in use, the blade 10 will tend to pivot about the hinge 12 due to centrifugal force and as the blade 10 swings about the axis of the hinge 12 the chord line 11 of the blade 10 moves away from the normal tangential position which it has when the blade is vertical and also moves upwards or downwards causing the blade 10 to have a blade spoiling attitude, i.e. have aerodynamic drag, whereby its power is reduced and the rotational rate of the turbine modified. The blade 10 will be counterbalanced by an opposite arm provided with a weight.

Although the wind turbine shown in the drawing is described above as having only one blade 10, it will be evident that one or more further blades 10 and arms 13 could be provided.

The or each blade 10 is maintained at an optimum angle of inclination to the vertical axis so as to produce maximum outout, and is inclined from the optimum angle, to reduce the ratio of turbine speed to wind speed, and reduce stressing the blade, if the wind speed increases above a threshold value.

1. A vertical axis wind turbine comprising at least one blade, support means mounting the or each blade to rotate around the vertical axis, the or each blade being hinged to the support means at a position intermediate the ends of the blade and spaced from the centre of mass of the blade by a hinge whose axis in plan view lies at an angle to the longitudinal centre line of the support means and in elevation lies at an angle to the longitudinal axis of the blade.

2. A vertical axis wind turbine as claimed in claim 1, in which the or each blade is of an aerofoil section symmetrical about a chord line.

3. A vertical axis wind turbine as claimed in claim 1 or claim 2, in which the support means comprises an arm having at its end remote from the hinge a hub connected to a vertical shaft arranged to drive a device to be powered by the turbine.

4. A vertical axis wind turbine as claimed in any preceding claim, having a plurality of blades and support means.

5. A vertical axis wind turbine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Vertical axis wind turbines This invention relates to vertical axis wind turbines. Vertical axis wind turbines require to be controlled in such a manner as to prevent over speeding. One method of control is to mount the or each blade to a support member at a position substantially intermediate the ends of the blade, but spaced from the centre of mass of the blade, by means of a hinge whose axis is tangential to a circle having said vertical axis as its centre, so that the or each blade rotates away from a vertical position due to centrifugal forces and so reduce the swept area. Another method is to mount the or each blade so that it can be moved about its longitudinal axis in order to alter the angle of attack of the blade relative to the wind direction and thus reduce its rotational driving force. According to the present invention there is provided a vertical axis wind turbine comprising at least one blade, support means mounting the or each blade to rotate around the vertical axis, the or each blade being hinged to the support means at a position spaced from the centre of mass of the blade by a hinge whose axis in plan view lies at an angle to the longitudinal centre line of the support means and in elevation lies at an angle to the longitudinal axis of the blades. An embodiment of the invention will now be described, by way of an example, with reference to the accompanying drawing, in which: Figure lisa diagrmmatic partial plan view of a vertical axis wind turbine embodying the invention, with the blade shown in a vertical position, Figure 2 is a side view of the structure shown in Figure 1 taken in the direction of arrow 2, Figure 3 is a plan view similar to Figure 1 but with the blade shown in an angled position, and Figure 4 is a side view of the structure of Figure 3 taken in the direction of arrow 4. The vertical wind turbine comprises a blade 10 in the form of a straight aerofoil section symmetrical about a chord line 11. The blade 10 is secured to one part of a hinge 12 whose other part is fixed to one end of an arm 13 extending from a hub 14. The arm 13 and hub 14 form part of support means, the remainder of which is not shown, that mounts the blade 10 to enable the blade to rotate around a vertical axis 15 of the wind turbine in the direction of arrow 16. The support means may be of a form well known to those skilled in the art of wind turbines and may comprise, for example, a shaft connected to the hub 14 and extending along the vertical axis 15to drive a device to be powered by the wind turbine, for example an electrical generator. The hinge 12 is spaced from the centre of mass of the blade 10 and the axis of the hinge 12 in plan view, as viewed in Figures 1 and 3, lies at an angle to the longitudinal centre line 17 of the arm 13 and in elevation, as viewed in Figure 2, lies at an angle to the longitudinal axis 18 of the blade 10. The axis of the hinge 12 is therefore skewed and is not tangential to a circle having the axis 15 as its centre as in the known arrangements. Accordingly, when the wind turbine is in use, the blade 10 will tend to pivot about the hinge 12 due to centrifugal force and as the blade 10 swings about the axis of the hinge 12 the chord line 11 of the blade 10 moves away from the normal tangential position which it has when the blade is vertical and also moves upwards or downwards causing the blade 10 to have a blade spoiling attitude, i.e. have aerodynamic drag, whereby its power is reduced and the rotational rate of the turbine modified. The blade 10 will be counterbalanced by an opposite arm provided with a weight. Although the wind turbine shown in the drawing is described above as having only one blade 10, it will be evident that one or more further blades 10 and arms 13 could be provided. The or each blade 10 is maintained at an optimum angle of inclination to the vertical axis so as to produce maximum outout, and is inclined from the optimum angle, to reduce the ratio of turbine speed to wind speed, and reduce stressing the blade, if the wind speed increases above a threshold value. CLAIMS

1. A vertical axis wind turbine comprising at least one blade, support means mounting the or each blade to rotate around the vertical axis, the or each blade being hinged to the support means at a position intermediate the ends of the blade and spaced from the centre of mass of the blade by a hinge whose axis in plan view lies at an angle to the longitudinal centre line of the support means and in elevation lies at an angle to the longitudinal axis of the blade.

2. A vertical axis wind turbine as claimed in claim 1, in which the or each blade is of an aerofoil section symmetrical about a chord line.

3. A vertical axis wind turbine as claimed in claim 1 or claim 2, in which the support means comprises an arm having at its end remote from the hinge a hub connected to a vertical shaft arranged to drive a device to be powered by the turbine.

4. A vertical axis wind turbine as claimed in any preceding claim, having a plurality of blades and support means.

5. A vertical axis wind turbine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.