WO2008092191A1

WO2008092191A1 - A wind turbine

Info

Publication number: WO2008092191A1
Application number: PCT/AU2008/000091
Authority: WO
Inventors: Maxwell Edmund Whisson
Original assignee: Water Un Limited
Priority date: 2007-02-01
Filing date: 2008-01-29
Publication date: 2008-08-07

Abstract

A wind turbine apparatus (10) has a plurality of blades (18) spaced from a central axis (12) and extending non-radially relative to the central axis (12).

Description

TITLE

"A WIND TURBINE"'

FIELD OF THE INVENTION The present invention relates to a wind turbine

BACKGROUND OF THE INVENTION

It has been discovered that enhanced efficiency can be obtained from a wind turbine that has blades which are spaced from a central axis and which do not extend radially relative thereto.

SUMMARY OF THE INVETION

In accordance with one aspect of the present invention there is provided a wind turbine comprising a central axis about which the turbine is arranged to rotate, and a plurality of blades extending outwardly of the central axis, the blades being spaced apart from the central axis and extending non radially relative to the central axis.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic cross-section of a wind turbine in accordance with the present invention; Figure 2 is a schematic cross-section of a first embodiment of a blade of the apparatus of Figure 1;

Figure 3 is a schematic cross-section of a second embodiment of a blade of the apparatus of Figure 1; Figure 4 is a schematic representation of an apparatus containing wind turbine similar to that shown in Figure 1 ;

Figure 5 is a schematic representation of an apparatus similar to that shown in Figure

4 containing blades which are longitudinally curved.

Figure 6 is a schematic illustration of a plurality of wind turbines in accordance with the present invention arranged in a bank;

Figure 7 is a schematic plan view of a further embodiment of a wind turbine in accordance with the present invention; and

Figure 8 is a side elevation of an apparatus using the wind turbine of Figure 7.

DESCRIPTION OF THE INVENTION

Referring to Figures 1 to 3 of the drawings, there is shown a cross-axis wind turbine 10 having a central axis 12 and a circular periphery 14. There is also a number of radially extending lines 16 to demonstrate radial directions from the axis 12. The wind turbine 10 comprises a plurality of blades 18 which are spaced apart from the axis 12 and extend outwardly to the periphery 14.

As shown, the blades 18 do not extend in alignment with the radially extending lines 16 of the wind turbine 10. Each of the blades 18, in fact, extends at an angle to a radial direction. The orientation of the blades 18 relative to the radial directions is preferably similar, and the blades are preferably disposed at substantially equiangularly spaced relative to the central axis 12.

Further, as shown each blade 18 is preferably transversely curved and has a transverse convex side 19 and a transverse concave side 21 as shown in Figure 2.

The wind turbine 10 may contain from three to eleven of the blades 18, preferably from five to seven. However, the optimum number of blades of the wind turbine 10 depends partly on a diameter of the wind turbine 10, the intended use thereof and anticipated wind speeds.

As can best be seen in Figure 2, each of the blades 18 is preferably orientated so as to have a base chord angle 20 in the range of 28° to 32° from a radial direction, preferably about 30° from a radial direction. The base chord angle is faced by the concave side 21 of the blade 18 as can be seen in Figure 2.

Further, a transverse width of the blades 18 is preferably between 0.60 and 0.75 of a radius of the turbine 10, preferably about 0.67 of the radius of the turbine 10. Also, a transverse curve of the blades 18 is preferably from 0.5 to 0.6 of the radius of the turbine 10, more preferably about 0.55 of the said radius of the turbine 10.

Still further, a base chord length 22 of the blades 18 is preferably in the range from 0.33 to 0.37 of a diameter of outer edges of the blades 18 most preferably about 0.35 of the said diameter of the outer edge of the blades 18. A blade chord height 24 is preferably in the range from 0.16 to 0.22 times of the base chord length 22, most preferably about 0.18 times of the said base chord length 22.

Yet still further, a diameter of outer edges of the blades 18 is preferably 1200 mm or less, more preferably in the range from 400 to 700 mm, so as to achieve a satisfactory rotation speed of the blades 18. For most applications and for a turbine diameter of

400 to 500 mm the number of blades 18 is preferably 7. For larger turbines having diameters of 500 to 1500 mm a larger number of blades 18 is preferred. The maximum number of blades 18 envisaged is 14 with the upper limit being imposed by viscous resistance to flow of air entering the turbine 10 between the blades 18.

The effect of the blades 18 is to cause the wind to flow at higher velocity over the convex surfaces 19 such that there is a tendency for an increased pressure on the concave surfaces 21 on the downwind and upwind sides of the turbine 10. Another effect tending to increase efficiency has been found to be rotational momentum of air emerging from an inner edge of downwind moving blades flowing across axes of the blades 18 meeting with edges of upwind blades 18 so adding wind power tending to drive the latter blades 18 upwind.

Also, as shown in Figure 3, it is preferred for the blades 18 to have a variable thickness in longitudinal cross section, preferably according to aerofoil principles, with a thicker leading edge 26 and a longer air path over the convex surface 19. In Figure 4 of the accompanying drawings there is shown an apparatus 30 which comprises a cross-axis wind turbine 10 in accordance with the present invention mounted about a central axis 32 with stub members 33. As shown in Figure 4, the apparatus 30 comprises an upper disc 34, an intermediate disc 36 and a lower disc 38. The blades 18 of the turbine 10 are mounted in curved slots 40 cut in the discs 34, 36 and 38. The blades 18 are preferably welded to the discs 34, 36 and 38 at the slots 40. As can be seen the stubs 33 do not extend into the centre of the apparatus 30 but simply extend outwardly from respective discs 34 and 38.

It has been found surprisingly that a cross-axis wind turbine in accordance with the present invention has enhanced drag and aerodynamic lift compared to previously known cross-axis wind turbines which leads to greater efficiency in converting wind power to rotary mechanical power.

Preferably the blades 18 of the wind turbine 10 of the present invention are arranged to be refrigerated to cause cooling of wind air passing through the wind turbine 10. This facilitates precipitation of moisture from the wind air.

The wind turbine 10 of the present invention may be used singly or in a bank containing a plurality of the wind turbines. Increased efficiency has been surprisingly found in banks of closely spaced turbines turning in the same direction.

In Figure 5, there is shown an apparatus 50 which is similar to the apparatus of Figure 4, except that the blades 18 are longitudinally curved so as to bulge out slightly. This arrangement assists in confining wind energy towards the center of the turbine 10. Also, in this embodiment a central axis 52 extends right through the apparatus 50.

The wind turbine of the present invention is of general applicability in harnessing wind power. For example, it may be used in relation to the inventions of International

Patent Applications PCT/AU2005/001219, PCT/AU2006/001023 and PCT/AU2006/001900 also in the name of the present applicant.

In Figure 6 there is shown a wind turbine apparatus 60 comprising three wind turbines 10 in accordance with the present invention arranged in parallel in a bank equispaced around a central axis 62. As shown, the wind turbines 10 are connected to the central axis 62 by means of upper and lower struts 61. Further, the turbines 10 are interconnected at their lower ends by a static ring gear 64 having a respective planetary gear 66 mounted to an axis 68 of each wind turbine 10. Whilst the ring gear 64 is static the remainder of the apparatus 60 rotates axially.

Other forms of drive arrangement may be used. Further, the number of blades is preferably 5 to 7 in. each turbine 10. The number of turbines may be increased if desired such as to five or more. The arrangement of the upright turbines shown in Figure 6 is substantially independent of horizontal wind direction. Also, the turbines

10 could be arranged substantially horizontally. The turbines 10 in the apparatus of Figure 6 all rotate in the same direction as shown by the arrows 67 whether the wind blows from the front or the back and efficiency of conversion of wind power to rotary mechanical power is relatively high. The absence of a need for full rotation to face the wind is an advantage.

In operation rotation of the turbine 10 causes the apparatus 60 as a whole to rotate axially about the ring gear 64 as shown by the arrow 69. This has the advantage that all of the turbines 10 are upwind for part of the rotation. It has now been found that rotation of the turbine bank is driven by an aerodynamic lateral force generated by a higher velocity of air on a downwind side of a spinning cylinder. In Figure 6, the lateral component of the wind power is to the right on the two nearest turbines 10 with wind approaching from the foreground (the observer). Change in wind direction emerging from the two turbines tends to reduce lateral action on the downwind turbine which causes the whole turbine bank 60 to rotate in the same direction as the individual turbines but at a lower speed.

The rotation of the whole turbine bank is driven by the wind and adds power which is additional to the power of the rotating turbines. In this case, the change in momentum of wind diverted around the turbine bank is partly converted into power driving the whole turbine bank around.

Rotation of the central axis 62 may be used to obtain useable mechanical or electrical power. Further, the turbines 10 may be used for cooling purposes. In this case, there can be provided a non-rotating refrigerant tube with radially extending cooling fins. The turbine blades would operate outside of the cooling fins and would cause cooling of the refrigerant tube by extracting heat from the fins. No sealing would be needed in an arrangement of this sort. Such an arrangement is shown in Figures 7 and 8.

In Figures 7 and 8 there is shown a wind turbine apparatus 70 which is similar to the wind turbine apparatuses 10, 30 and 50 and like reference numbers denote like parts.

In this case the central shaft 72 is fixed and is hollow. The shaft 72 is arranged to contain refrigerant. A plurality of discs 74 are mounted about the shaft 72 and the discs 74 are surrounded by blades 18. This embodiment of the present inventions is made possible by the fact that there is a gap between the axis of the wind turbine apparatus 70 and inner edge of the blades 18. Also, the discs 74 are in line with, or parallel to, the wind, whether it is just blowing through the turbine or spinning in a vortex toward concave surfaces of downwind blades.

As can be seen in Figure 8, the discs 74 are spaced from one another. Discs 74 are mounted to the shaft 72 for the whole length thereof.

In operation, refrigerant liquid flows along the shaft 72 as shown by the arrows 76. Refrigerant tubes could be mounted in the discs 74 if preferred so as to keep the discs 74 cool.

The action of the turbine 10, in accordance with the present invention, is independent of wind direction and does not need assistance of a wind guidance vane, but an upwind vane may increase power by sheltering the upwind blades and diverting wind slightly toward the downwind blades. The turbine 10 may have increased power if the axial length thereof is increased.

Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

Claims

1. A wind turbine comprising a central axis about which the turbine is arranged to rotate, and a plurality of blades extending outwardly of the central axis, the blades being spaced apart from the central axis and extending non-radially relative to the central axis.

2. A wind turbine according to claim 1, wherein the turbine contains from 3 to 11 blades.

3. A wind turbine apparatus according to claim 2, wherein the turbine contains from 5 to 7 blades.

4. A wind turbine apparatus according to any one of the preceding claims, wherein each blade is transversely curved having a transverse convex side and a transverse concave side.

5. A wind turbine apparatus according to any claim 4, in which each blade has a base chord angle in the range from 28° to 32° from a radial direction.

6. A wind turbine apparatus according to claim 5, wherein the base chord angle is faced by the concave side of each blade.

7. A wind turbine apparatus according to any one of claims 4 to 6, wherein a transverse width of each blade is between 0.60 and 0.75 of a radius of the turbine.

8. A wind turbine apparatus according to any one of claims 4 to 7, wherein a transverse curve of each blade is from 0.5 to 0.6 of the radius of the turbine.

9. A wind turbine apparatus according to any one of claims 4 to 8, wherein a base chord length of each blade is in the range from 0.33 to 0.37 of a diameter of outer edge of the blades.

10. A wind turbine apparatus according to claim 9, wherein a base chord height of each blade is in the range from 0.16 to 0.22 times the base chord length thereof.

11. A wind turbine according to any one of claims 4 to 10, wherein the blades each have an aerofoil cross section.

12. A wind turbine according to any one of the preceding claims, wherein a diameter of outer edges of the blades is 1 ,200 mm or less.

13. A wind turbine according to claim 12 in which the diameter of the outer edges of the blades is in the range from 500 to 700 mm.

14. A wind turbine according to any one of the preceding claims wherein each of the blades is longitudinally curved so as to bulge out.

15. A wind turbine apparatus comprising a plurality of wind turbines in accordance with any one of the preceding claims arranged in parallel in a bank.

16. A wind turbine apparatus according to claim 15, in which the bank comprises a central axis allowing the wind turbines to rotate and the turbine bank as a whole to rotate more slowly in the same direction.