GB2185289A - Wind energy convertor - Google Patents

Abstract

A wind energy convertor comprises an upstanding support having a central vertical axis, a circular turbine which is supported by an uppermost part of the support in such a way that the turbine is freely rotatable about the vertical axis and which comprises a plurality of circumferentially spaced blades extending lengthwise with respect to the support; and an annular body which is carried by the support and which is coaxial with and is positioned adjacent to the upper end of the turbine. The upper surface of the annular body is above the turbine and is so shaped as to cause the velocity of the wind that blows against this surface to increase as it passes over the surface, thereby creating a reduction in air pressure in the circular space bounded by the annular body so that wind blowing against the blades of the turbine is drawn upwardly within the turbine and out of the central space to drive the turbine rotatably about the vertical axis, thereby converting the energy of the wind into rotational mechanical energy. The blades may be pivotally mounted and variable in pitch due to centrifugal force acting against restraining means.

Description

SPECIFICATION An improved wind energy convertor This invention relates to apparatus forconverting the energy ofthe wind into mechanical energy for use in the generation of electricity or other source of power and, for convenience, such apparatus will hereinafter be referred to by the generic expression "wind energy convertor".

In the specification of Patent No: 2083564B, there is described and claimed a wind energy convertor comprising an upstanding column; a fan which is supported on the upper end of the column in such a waythatthefan is freely rotatable about the axis of the column and which comprises a plurality of circumferentiallyspaced, radially extending blades; a substantiallycircularturbinewhich surrounds and is radially spaced from an uppermost part of, and is supported by, and freely rotatable about the axis of, the column, andwhich comprises a plurality of circumferential ly spaced blades extending lengthwise with respectto the column, and an annular body which is supported by the column and which is coaxial with and which is positioned adjacenttothe outer circumferential edge ofthefan, the upper surface of the annular body being abovethefanand being so shaped as to cause the velocity of wind that blows against the surface to increase as it passes overthe surface, thereby creating a reduction in air pressure in the circular space bounded by the annular body so that wind blowing against the blades oftheturbine and driving the turbine rotatably abouttheaxis ofthe column is drawn upwardly within theturbineto drive the fan rotatably about the axis of the column in the same rotational direction as the turbine, thereby converting the energy ofthe wind into rotational mechanical energy.

It is an object ofthe present invention to provide a simple wind energy convertor which works on the same principle as the wind energy convertor ofthe aforesaid patentto convent into mechanical energy the energyofawind blowing in substantially any direction but which costs less than the wind energy convertorofthe aforesaid patent.

According to the present invention, the simple wind energy convertorcomprises an upstanding support having a central vertical axis; a substantially circular turbinewhich is directly or indirectly supported by an uppermost part of the support in such a way that the turbine is freely rotatable about said vertical axis and which comprises a plurality of circumferentially spaced blades extending lengthwise with respectto the support; and an annularbodywhich is carried by the support and which is coaxial with and is positioned adjacent to the upper end of the turbine, the upper surface ofthe annular body being above the turbine and being so shaped as to cause the velocity of wind that blows againstthis surface to increase as it passes overthesurface, thereby creating a reduction in air pressure in the circular space bounded by the annular body so that wind blowing against the blades ofthe turbines is drawn upwardlywithintheturbine and out of said central space to drive the turbine rotatably about said vertical axis, thereby converting the energy ofthewind into rotational mechanical energy.

Due to the omission at the upper end ofthe upstanding supportof afreely rotatablefan compris- ing a plurality of circumferentially spaced, radially extending blades, as used in the wind energy convertor of the aforesaid patent, the simple wind energy convertor of the present invention will be less efficient than the wind energy convertor ofthe aforesaid patent and will not self-start at wind speeds as low as those at which the wind energyconvertordescribed and claimed in the aforesaid patent will self-start. Prefer ably, to compensate for the absence ofsuch a fan, each of at least some ofthe plurality of circumferentially spaced, lengthwise extending blades of the turbine is pivotally mounted about a substantially vertical axis passing through the blade and each has associated means for automatically restraining pivotal movement of said blade about its vertical axis, the arrangment being such that, asthevelocity of wind directed on outwardlyfacing surfaces ofthe pivotable turbine blades gradually increases and hence the speed of rotation oftheturbine gradually increases from zero to a predeterminedvalue,the resultant gradually increasing centrifugal force on the pivotable turbine blades causes each pivotableturbine blade to pivot about its vertical axis against the action of its associated restraining means,the restraining means being of such a form that, as the velocity of the wind gradually increases until the rotational speed ofthe turbine reaches said predetermined value, each pivotable blade is permitted to pivot smoothly against incrementai restraintfrom an initial position in which it lies at a positive acute angle to a tangent ofthe circle passing through the vertical rotational axes ofthe pivotable turbine blades to a normal running position in which it lies along orat a small angleto said tangent, and, as the velocity ofthe wind increasesfurtherto or above a maximum acceptable value, each pivotable blade is permitted to pivot smoothly from the said normal running position to a "feathering" position in which it lies at a negative acute angle to said tangent, thereby ensuring that, as the velocity ofthe wind reaches or exceeds said maximum acceptablevalue, the torque and the ratio of peripheral turbine speed to wind speed are reduced to maintain substantially constant power and to ensure that the rotational speed of the turbine is not increased to an undesirable extent.

The provision of pivotable turbine blades in the simplewindenergyconvertorhastheimportant advantagethatthewindenergyconvertorhasa high starting torque and that, since each pivotable turbine blade is restrained from pivoting beyond a normal running position until the velocity ofthe wind reaches or exceeds a maxim u m accepta ble value and, when the wind reaches or exceeds said maximum accept able value each blade is permitted to pivot smooth ly to a "feathering" position, the rotational speed of the turbine will neverexceeda predetermined maximum safe value, irrespective ofthe velocity ofthe wind as the aerodynamic characteristics of the converter automatically change.A simple wind energy conver torwith pivotableturbine blades will, therefore, operate satisfactorily over a wide range of wind velocities, preferably as a variable speed device, but capable of operating as a constant speed device, if required.

The restraining means associated with each pivotable turbine blade may beasingle restraining device which will permit controlled pivotal movement ofthe blade unitl the centrifugal force on the blade reaches a predetermined value and which will then resistfurther pivota! movement ofthe blade until the velocity ofthe wind reaches or exceeds said maximum acceptable value when the restraining device will permit further pivotal movement of the blade to the "feathering" position, but, for ease of manufacture, preferably the restraining means associated with each pivotable turbine blade comprises two restraining devices independent of one another, one restraining device permitting controlled pivotal movementofthe blade from the start position to the normal full speed running position andtheother restraining device resisting pivotal movement of the blade until the velocity of the wind reaches or exceeds said maximum acceptable value when the blade is permitted to pivot to the "feathering" position. Preferably, the first of said two restraining devices comprises a spring or springs connected to the pivotable turbine blade and the second of said two restraining devices is either a furtherspring or an elongate torsion member arranged along the vertical pivotal axis ofthe blade and fixed at one or both of its ends. The elongate torsion member may be a bar ortube of steel, of resin bonded carbon fibres or of other suitable composite materials.Alternatively, each of said two restraining devices may be an elongate torsion member, the first restraining device being a torsion tube and the second restraining device being a torsion bar surrounded by and coaxial with the torsion tube, the axes ofthe torsion tube and torsion barlying along the vertical pivotal axis ofthe blade and the torsion tube and the torsion bar each being fixed at one or both of its ends.

Preferably, each turbine blade has a transverse cross-section of substantially aerofoil shape; preferably, also, the leading edge of each turbine blade is inclined radially outwardly in the direction of rotation oftheturbine.

The circularturbine ofthe simple wind energy convertor may have at least two groups ofcircum- ferentiallyspaced, lengthwise extending blades, each ofwhich groups of lengthwise extending blades is spaced lengthwise with respect to the or each other group of blades and is rigidlysecuredtothe oreach adjacent group of blades, the circumferentiallyspaced blades ozone group being circumferentially staggered with respect to the circumferentially spaced blades of the othergroup or of at least one ofthe other groups.

Circumferential staggering ofthe lengthwise extend ing blades of adjacent groups of blades oftheturbine provides beneficial dynamic characteristics resulting in agreaterpoweroutputthan would be obtained, undersimilarwind conditions, with a substantially circularturbine having a single group ofcircum- ferentially spaced, lengthwise extending blades.

Preferably, to accelerate a largervolume of wind between the blades oftheturbine and thereby increase still furtherthe amountofwind energy availableforconversion,thewind energy convertor further includes, radially outwardly of and surrounding the turbine, a plurality of circumferentially spaced blades which extend lengthwise with respecttoand are supported by the support and which define, between adjacent blades, a plurality ofventuri through which wind is directed on to the blades ofthe turbine, the surfaces of the venturi blades being so shaped as to direct the wind on to the blades of the turbine and, at the same time, to shield from the wind the downwind blades of the turbine, thereby substantially reducing the drag on the turbine and enabling the turbine to rotate such that its peripheral velocity preferably does not exceed twice the linearvelocity of the wind. Preferably, theventuri blades extend downwardly from the underside ofthe annular body and are secured between the annular body and a second annular body coaxial with and spaced below the first annular body. The radially outward edges of the venturi blades may extend substantially vertically but, preferably, they are inclined radially outwardly in a direction towards the upper end ofthe convertor.

The uppersurface ofthe annular body preferably is of such a shape asto encourage accelerated flow of the wind over its surface. In a preferred embodiment, the angle of inclination ofthe uppersurfaceto said vertical axis ofthe support increases smoothly in an upward direction. The accelerated flow ofthe wind overthe uppersurface of andthe circularspace bounded by the annular body causes a reduction in air pressure in and above the circu lar space which increases the velocity of wind flowing upwardly through the circular space, with the resultthat the inherent resistance ofthe turbine to the rate of flow of airthroughtheturbine is reduced.

The upstanding support may be a single column as described in the specification ofthe aforesaid patent or, where the simple wind energy convertor is to be of a substantially larger construction than the wind energy convertor ofthe aforesaid patent, as described in the specification of co-pending PatentApplication No: 85/15324 the support may comprise a plurality of upstanding elongate members uniformly spaced around said central vertical axis,theturbine being rotatably supported at at least one of its ends by said upstanding members. The plurality of upstanding elongate members may be the legs of a latticework tower or pylon but, in a preferred embodiment, the plurality of upstanding elongate members are vertical columns on orwith respect to which the annular body is slidably or otherwise so mounted that it can be raised or lowered when required, the turbine is carried by and is freely rotatable with respect to the annular body so that it is indirectly supported by the vertical columns, and the vertical columns have associated means for raising or lowering the annular body, and the turbine carried thereby, with respect to the columns andforlocking the annular body with respect tothe columns when it is in the desired position.The aforesaid preferred embodiment has the important advantagethattheannularbody,andtheturbine carried thereby, can be raised with respect to the columns to the desired position without the use of a heavy crane and, as a consequence, in weather conditionswhenthe use of a cranewould be too dangerous andiorthe site inaccessible to cranes and other lifting devices The lifting means associated with the vertical columns may take any convenient form but preferably each column has at its upper and lower ends pulleys around which at least one hawser connected to lower parts ofthe annular bodycanbe drawn byat least one associated motor or other drive means.Each vertical column preferably also carries locking means by which the annular body can be mechanically locked to the column when the annular body is in the desired position.

The electrical generators and/orotherancillary equipment associated with the generation of electric ity or other source of power may be located in a housing atthe foot ofthe support but, in the preferred embodiment, the electrical generator is an integral part ofthe wind energy convertor.

The simple wind energy convertor of the present invention ensuresthattheenergyofthewind is converted into rotational mechanical energy without inhibiting to any great extent the natural movement of thewind. Furthermore,the plurality of iongitudinally extending blades ofthe turbine, when pivotally mounted about vertical axes, providethe important advantage thatthe simple wind energy convertor can be self-starting, even at low wind speeds. Additionally, the simple wind energy convertor is pleasing to the eye and can therefore be installed in areas of natural beauty without being any more obstrusive than the conventional sail mill.

Claims (17)

1. Awind energy convertorcomprising an upstanding support having a central vertical axis; a substantially circularturbine which is directly or indirectly supported by an uppermost part ofthe support in such a way that the turbine is freely rotatable about said vertical axis and which comprises a plurality of circumferentially spaced blades extending lengthwise with respect to the support; and an annular body which is carried by the support and which is coaxial with and is positioned adjacent to the upper end ofthe turbine, the uppersurface ofthe annular body being above the turbine and being so shaped as to cause the velocity of wind that blows against this surface to increase as it passes over the surface,thereby creating a reduction in air pressure in the circular space bounded by the annular body so that wind blowing against the blades ofthe turbine is drawn upwardly within theturbine and out of said central space to drive the turbine rotatably about said vertical axis, thereby converting the energy ofthe wind into rotational mechanical energy.

2. Awindervergy convertor as claimed in Claim 1, wherein each of at least some of the plurality of circumferentially spaced, lengthwise extending blades of the turbine is pivotally mounted about a substantially vertical axis passing through the blade and each has associated means for automatically restraining pivotal movement of said blade about its vertical axis, the arrrangement being such that, as the velocity of wind directed on outwardly facing surfaces ofthe pivotable turbine blades gradually increases and hencethespeed of rotation oftheturbine gradually increases from zero to a predetermined value, the resultant gradually increasing centrifugal force on the pivotableturbine blades causes each pivotable turbine blade to pivot about its vertical axis against the action of its associated restraining means, the restraining means being ofsuchaform that, as the velocity ofthe wind gradually increases until the rotational speed oftheturbine reaches said predetermined value, each pivotable blade is permitted to pivot smoothly against incremental restraint from an initial position in which it lies at a positive acute angle to a tangent of the circle passing through the rotational axes ofthe pivotableturbine blades to a normal running position in which it lies along or at a small angle to said tangent, and, asthe velocity ofthe wind increasesfurtherto or above a maximum acceptable value, each pivotable blade is permitted to pivot smoothly from the said normal running position to a "feathering" position in which it lies at a negative acute angle to said tangent, thereby ensuring that, as the velocity ofthe wind reaches or exceeds said maximum acceptablevalue,thetorqueandtheratio of peripheral turbine speed to wind speed are reduced to maintain substantially constant power and to ensure that the rotational speed oftheturbine is not increased to an undesirable extent.

3. Awind energy converter as claimed in Claim 2, wherein the restraining means associated with each pivotableturbine blade is a single restraining device which will permit controlled pivotable movement of the blade until the centrifugal force on the blade reaches a predetermined value and which will then resistfurtherpivotal movementofthe blade until the velocity ofthe wind reaches or exceeds said maximum acceptable value when this restraining device will permit further pivotable movement ofthe blade to the "feathering" position.

4. Awind energy converter as claimed in Claim 2, wherein the restraining means associated with each pivotable turbine blade comprises two restraining devices independent of one another, one restraining device permitting controlled pivotable movement of the blade from the start position to the normal full speed running position and the other restraining device resisting pivotal movement of the blade until the velocity ofthe wind reaches or exceeds said maximum acceptable value when the blade is permitted to pivot to the "feathering" position.

5. A wind energy converter a claimed in Claim 4, wherein the first of said two restraining devices comprises a spring or springs connected to the pivotable turbine blade and the second of said two restraining devices is either a further spring or an elongate torsion member arranged along the vertical pivotal axis ofthe blade and fixed at one or both of its ends.

6. A wind energy converter as claimed in Claim 5, wherein the elongate torsion member is a bar ortube of steel, of resin bonded carbon fibres or of other suitable composite materials.

7. Awind energy converter as claimed in Claim 4, wherein each of said two restraining devices is an elongate torsion member, the first restraining device being a torsion tube and the second restraining device being a torsion bar surrounded by and coaxial with the torsion tube, the axes of the torsion tube and torsion bar lying along the vertical pivotal axis of the blade and the torsion tube and the torsion bar each being fixed at one or both of its ends.

8. Awindenergyconverterasclaimed in anyone ofthe preceding Claims, wherein each turbine blade has a transverse cross-section of substantially aerofoil shape.

9. Awindenergyconverterasclaimed in any one of the preceding Claims, wherein the circular turbine has at leasttwo groups of circumferentially spaced, lengthwise extending blades, each of which groups of lengthwise extending blades is spaced lengthwise with respectto the or each other group of blades and is rigidly secured to the or each adjacent group of blades, thecircumferentially spaced blades of one group being circu mferentiaily staggered with respect to the circumferentially spaced blades ofthe other group or of at least one ofthe other groups.

10. Awind energy converter as claimed in any one ofthepreceding Claims,whereintheconverterfurther includes, radially outwardly of and surrounding the turbine, a plurality of circumferentially spaced blades which extend lengthwise with respectto and are supported bythe support and which define, between adjacent blades, a plurality of venturi through which wind is directed on to the blades ofthe turbine, the surfaces of the venturi blades being so shaped as to directthe wind on to the blades oftheturbine and, at the sametime,to shieldfrom the wind the downwind blades oftheturbine, thereby substantially reducing the drag on the turbine.

11. Awind energy converter as claimed in Claim 10,wherein the venturi blades extenddownwardly from the undersurface ofthe annular body and are secured between the annular body and a second annular body coaxial with and spaced below the first annular body.

12. A wind energy converter as claimed in Claim 10 or 11, wherein the radially outward edges ofthe venturi blades are inclined radially outwardly in a direction towards the upper end ofthe converter.

13. Awindenergyconverterasclaimed in anyone of the preceding Claims, wherein the angle of inclination ofthe upper surface ofthe annular body to said vertical axis ofthe support increases smoothly in an upward direction.

14. Awindenergyconverterasclaimed in any one ofthe preceding Claims, wherein the upstanding support is a single column.

15. Awind energy converter as claimed in any one of Claims 1 to 13,wherein the upstanding support comprises a plurality of upstanding elongate mem bers uniformly spaced around said central vertical axis, the turbine being rotatably supported at at least one of its ends by said upstanding members.

16. Awind energy converter as claimed in Claim 15,whereinthepluralityofupstanding elongate members are vertical columns on orwith respect to which the annular body is slidably or otherwise so mounted that it can be raised or lowered when required, the turbine is carried by and is freely rotatable with respectto the annular body so that it is indirectly supported by the vertical columns, and the vertical columns have associated means for raising or lowering the annular body, and the turbine carried thereby, with respect to the columns and for locking the annular body with respect to the columns when it is in the desired position.

17. A wind energy converter substantially as hereinbefore described with reference to and as shown intheaccompanying drawing.