A BLADE

BACKGROUND OF THE INVENTION

[0001] This invention relates to a blade for a wind generator or a wind turbine.

[0002] Wind generators or turbines are known and are used for generating electrical power. As a result of varying wind speeds wind generators are designed for peak performance at specific wind speeds.

[0003] At low or intermittent wind speeds wind generators cannot always function to their optimum as an initial rotation force is required in order to rotate a generator used in a wind generator and relative limited electricity can be generated at low wind speeds as the relative rotation speed between a rotor and a stator of the generator remains low.

[0004] At high wind speeds wind generators can overheat and fail catastrophically if the rotation speed of the blades and generator of the wind generator is not kept below maximum speeds.

[0005] Manual and mechanical speed limiters and brakes are prone to failure and often require manual intervention.

SUMMARY OF THE INVENTION

[0006] The invention aims to provide an alternative blade for a wind generator or a wind turbine which might alleviate some of the aforementioned problems.

[0007] The invention provides a blade for a wind generator which is rotatable in a rotation plane and which includes a connection member which is connectable to a generator, an elongate, flexible blade body which extends from the connection member, which has a first end which is attached to the connection member, which has a second opposing end and which has a first elongate aerofoil section which has a leading end at the second end, a first cord length which is at a minimum at the leading end, a first cord line which is at a first varying angle to the rotation plane and a first aerodynamic force line which extends from the first end to the second end in a first direction and a blade end section which extends from the leading end to an end tip and which has a second aerofoil section which has a second cord length which has a maximum length at a position between the leading end and the end tip which is longer than the first cord length at the leading end.

[0008] The first cord length preferably varies and may reduce from the first end to the second end.

[0009] The first varying angle preferably reduces from the first end to the second end.

[0010] The second aerofoil section may include a second cord line which is at a second varying angle to the rotation plane. The second varying angle may be dynamically variable depending on a rotation speed of the blade end section.

[0011] The second aerofoil section may include a second aerodynamic force line which extends from the leading end to the end tip in at least a second direction which is different from the first direction. Preferably the second direction extends at least partially in the direction of travel of the blade end section. Preferably the second

W direction extends forwardly from the first direction relatively to the direction of travel of the blade end section.

[0012] The second aerofoil section may include a leading edge which is ahead of the body relatively to the direction of travel of the blade end section. The second aerofoil section may include a trailing edge which is behind the body relatively to the direction of travel of the blade end section.

[0013] Preferably the second aerofoil section may be twistable relatively to the body.

[0014] Preferably the body has a first centre of pressure and the blade end section has a second centre of pressure which second centre of pressure is ahead of the first centre of pressure relatively to the direction of travel of the body and the end section.

[0015] The invention also provides a wind generator which includes a base, a housing which is rotatably attached to the base, a generator assembly which is positioned in the housing and a plurality of the aforesaid blades, each of which is connected to the generator assembly.

[0016] The generator assembly may include a stationary stator and a rotatable rotor which is connected to the blades. The generator assembly may include a regulator. The generator assembly may include permanent or electromagnetic magnets.

[0017] The wind generator preferably includes a rudder formation which extends from the housing.

[0018] The invention also provides a wind generator which includes a base, a housing which has a pivot point, which is rotatably attached to the base at the pivot point and which has a first leading end and an opposite second trailing end, a generator assembly which is positioned in the housing, a first set of blades which is engaged with the leading end, which is connected to the generator assembly and which rotates in a first direction and a second set of blades which is engaged with the trailing end, which is connected to the generator assembly and which rotates in a second direction which is opposite to the first direction.

[0019] The leading end may be spaced a first distance from the pivot point and the trailing end may be spaced a second distance from the pivot point which second distance is greater than the first distance.

[0020] The housing may include a rudder formation which extends at least partially between the pivot point and the trailing end.

[0021] The generator assembly may include a rotatable stator and a rotatable rotor which stator and rotor are rotatable relatively to one another. The stator is preferably connected to the first set of blades and the rotor is preferably connected to the second set of blades.

[0022] The first and second sets of blades may each include a plurality of the aforesaid blades.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The invention is further described by way of examples with reference to the accompanying drawings in which :

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Figure 1 is a perspective view of a wind generator or wind turbine according to the invention;

Figure 2 is a partially sectioned side view of the turbine of Figure 2;

Figure 3 is a perspective view of a blade used in the turbine of Figure 1 ;

Figure 4 is a plan view of the blade of Figure 3;

Figure 5 is a front side view of the blade of Figure 3;

Figure 6 is a side end view of the blade of Figure 3;

Figure 7 is a perspective view of a wind turbine according to another form of the invention; and

Figure 8 is a partially sectioned side view of the turbine of Figure 7.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0024] Figures 1 and 2 illustrate a wind generator or wind turbine 10 which has a base 12 which is in the form of a post, a housing 14 which is rotatably attached to the post 12, a set of blades 16 which is connected to a first forward or leading end 18 of the housing 14 and a rudder 20 which extends from a second rear or trailing end 22 of the housing 14 which rear end 22 is opposite from the forward end 18.

[0025] The post 12 is made from any appropriate material and an appropriate bearing 24 is located between the post 12 and the housing 14 in order to allow the housing 14 to rotate freely on the post 12.

[0026] The housing 14 is made from an appropriate metal or plastics material and encloses a generator 26 which is located inside the housing 14. The generator 26 is known and has a stator 28 and a rotor 30 which rotates inside the stator 28. The

^ ^■ ta»- O= w i g ¹ ^J -%β yj Kf T stator 28 is stationary and fixed to the housing 14 and the rotor 30 is connected to the set of blades 16. The generator 26 can have other known components such as a regulator and can have permanent or electromagnetic magnets. Wiring 32 extends from the generator 26 through the housing 14 and post 12 to a known power pack 34 where electricity generated by the generator 26 is stored prior to the use thereof by an appliance 36. Known contacts 38 in the form of slip rings are used on the wiring 32 at the junction of the post 12 and the housing 14.

[0027] The set of blades 16 has three radially extending blades 40 which are centrally attached to a circular bracket 42. A shaft 44 extends from the bracket 42 and is connected to the rotor 30. Appropriate bearings 24A are positioned between the shaft 44 and the housing 14 to allow free rotation of the blades 16 and rotor 30 relatively to the housing 14 and the stator 28.

[0028] An aerodynamically shaped nosecone 46 is fitted over the bracket 42.

[0029] The rudder 20 has an elongate beam 48 which is fixed to the housing 14 and which extends from the rear end 22. A vertically extending tailpiece 50 is fixed to the beam 48.

[0030] The rudder 20 keeps the housing 14 aligned into a prevailing wind 52 so that the forward end 18 and nosecone 46 point directly into the wind 52. The wind 52 actuates the blade 16 which rotates in an anticlockwise rotation direction 54 in a rotation plane 56. The rotation plane 56 is perpendicular to the wind direction 52. The rotation of the set of blades 16 results in the rotation of the rotor 30 and the generation of electricity in a known manner. The electricity is fed to the power pack 34 through the wiring 32 where the electricity is stored for use by the appliance 36.

[0031] As is shown in Figures 3 to 6 each blade 40 has a connection member or connector 60 with which the blade 40 is attached to the bracket 42 and connected to the generator 26, an elongate, flexible blade body 62 which extends from the connector 60, which has a first end 64 which is attached to the connector 60 and a second opposing end 66 which is remote from the first end 64 and a blade end section 68 which extends from the second end 66.

[0032] The connector 60 can be of any appropriate shape and the junction between the connector 60 and the body 62 can be reinforced in any appropriate manner.

[0033] The body 62 has a first elongate aerofoil section 70 which extends from the first end 64 to the second end 66 where it terminates at a leading end 72. The first aerofoil section 70 has a first cord length W which varies, which reduces from the first end 64 to the second end 66 and which is at a minimum at the leading end 72, a first cord line 74 which is at a first varying angle 76 to the rotation plane 56, a first aerodynamic force line 78 which extends from the first end to the second end in a first force line direction 80, a first leading edge 82 which faces the rotation direction

54 which is the direction of travel of the blade 40 and an opposing trailing edge 84.

[0034] The end section 68 extends from the leading end 72 to an end tip 86 and has a second aerofoil section 88. The second aerofoil section 88 has a second cord length W which is variable and which has a maximum length which is longer than the first cord length W at the leading end 72, a second cord line 90 which is at a second varying angle 92 to the rotation plane 56, a second aerodynamic force line 94 which extends from the leading end 72 to the end tip 86 in at least a second force line direction 96 which is different from the first force line direction 80, a second leading edge 98 and a second trailing edge 100.

[0035] The first cord length W reduces from a maximum length of 100 mm at the first end 64 to a minimum length of 65 mm at the leading end 72. The first varying angle 76 is at its greatest at the first end 64 and gradually reduces towards the leading end 72. In this example the first varying angle 76 varies from 70° at the first end 64 to 10° at the leading end 72. The first force line direction 80 extends substantially parallel to the length of the body 62.

[0036] The second cord length W varies and increases from a length of 65 mm at the leading end 72 to a maximum length of 125 mm at a position 102 which is between the leading end 72 and the end tip 86 and then reduces in length from the position 102 to the end tip 86 where the length is 23 mm. The second varying angle 92 varies from 10° at the leading end 72 to 8° at the end tip 86. The second force line direction 96 extends, at least partially, in the rotation direction 54 and the second leading edge 98 is, for at least part of its length, ahead of the first leading edge 82 and the second trailing edge 100 is behind the first trailing edge 84. This causes the second force line 94 on at least part of the second section 88 to be displaced towards the direction of travel relatively to the first force line 78.

[0037] As the length of the first and second cord lengths W, W are at a minimum at the leading end 72 a waist with a reduced torque resistance is formed at the leading end 72 and between the body 62 and the second section 88. The second section 88 and the end section 68 are resiliently deformable and twistable relatively to the body 62.

[0038] In use the set of blades 16 is stationary as the wind 52 commences its attack on each blade 40. The wind 52 applies pressure to the entire length of the blade 40 and the wind 52 is deflected from the blade 40 by the angled underside 104 of the

blade 40. As a result of the enlarged first varying angle 76 at the first end 64 the wind 52 easily forces the blade 40 in the rotation direction 54 which results in movement of the blade 40. As soon as the blade 40 starts moving lift is produced by the first and second sections 70, 88. As a result of the first and second varying angles 76, 92 the direction of the aerodynamic force applied to the blade 40 along the first and second force lines 78, 94 vary. Specifically on the end section 68 the aerodynamic force on the second force line 94 depends, at least partially in the rotation direction 54. This aerodynamic force provides additional thrust to the blade 40 in its direction of travel and increases the effectiveness of the blade 40. As a result of the combined action of the wind 52 on the underside 104 and the aerodynamic force applied to the blade 40 the rotation speed of the blade 40 increases. As the rotation speed of the blade 40 increases the aerodynamic force applied to the end section 68 on the second force line 94 causes twisting of the end section 68 relatively to the body 62. The twisting action of the end section 68 causes changes in direction of the aerodynamic force on the second force line 94. When the blade 40 reaches its optimum speed the force applied by the wind 52 on the underside 104, the aerodynamic force applied to the blade 40 and the drag on the set of blades 16 caused by friction and the weight of the bracket 42, nosecone 46, shaft 44 and rotor 30 are in equilibrium. If the wind speed 52 increases and the rotation speed of the blade 40 increases beyond the optimum rotation speed of the set of blades 16 or the turbine 10 further twisting of the end section 68 relatively to the body 62 takes place. As the speed of the blade 40 increases the twisting of the end section 68 continues which results in an increase in drag on the second section 88 and eventually the aerodynamic force exerted on the second section 88 and the end section 68 at the second force line 94 becomes negative. This results in the

0 braking of the blade 40. As the wind speed 52 further increases the braking effect caused by the twisting of the end section 68 further increases. In this manner the over speeding of the set of blades 16 is dynamically and automatically controlled by the dynamic changes in the second varying angle 92.

[0039] Depending on optimum speed requirements of the blade 40 changes can be made to the first and second cord lengths W, W, the first and second varying angles 76, 92 and the degrees of forward angle of the second force line direction 96 and the second leading edge 98. The rigidity of the material, such as for example an appropriate plastics material, from which the blade 40 is made can also be used to control the dynamic actions of the blade 40.

[0040] The fact that the cord length W is a minimum at the leading end 72 allows for the twisting of the end section 68 relatively to the body 62. The fact that the second force line 94 extends in the second force line direction 96 which is in a forward direction relatively to the first force line direction 80 and the second leading edge 98 is forward of the first leading edge 82 results in the required aerodynamic force on the end section 68 to cause the twisting effect and the dynamic changes in the second varying angle 92.

[0041] Through experimentation the applicant has found that the rotation speed of the blade 40 in varying low and moderate wind speeds is similar to conventional, commercially available blades. At high wind speeds the rotational speed of the blade 40 reaches an optimum and does not increase substantially further as the wind speed increases.

[0042] The enlarged first varying angle 76 and the forwardly directed aerodynamic force on the end section 68 increases the torque which the blade 40 exerts on the

shaft 44. Through experimentation the applicant found that at varying wind speeds and more importantly at low and moderate wind speeds the torque exerted by the set of blades 16 on the shaft 44 is significantly higher than the torque which known commercially available blades exerts on a similar shaft under similar conditions. The additional torque is important as this allows an increase in the size, weight and magnets of the generator 26 which should result in an increase in electricity production and the effectiveness of the turbine 10. This is specifically important at low and moderate wind speeds. The increased effectiveness of the blade 40 can however result in overheating of the turbine 10 in high winds. This potential problem is however countered by the automatic braking by the blade 40 at high rotation speeds.

[0043] Accordingly the blade 40 increases the effectiveness of the turbine 10 at low and moderate wind speeds and provides a self-regulating mechanism to prevent the turbine 10 from over-speeding at high wind speeds.

[0044] Figures 7 and 8 illustrate an alternative turbine 200. Similar reference numerals are used in respect of the turbine 200 to illustrate similar components used and identified in the turbine 10 and only the differences between the turbine 200 and the turbine 10 are described.

[0045] In the turbine 200 a first set of blades 16A is connected to the housing 14A at the forward end 18 and a second set of blades 16B is connected to the housing 14 at the rear end 22. The forward end 18 of the housing 14A is spaced a first distance D from a centreline 202 or pivot point of the post 12 and the rear end 22 is spaced a second distance D' from the centreline 202 which second distance D' is greater than the first distance D. The turbine 200 has a rudder 2OB which has a vertically

extending tailpiece 5OA which extends directly from the housing 14 and faces towards the rear end 22. The tailpiece 5OA extends at least partially between the centreline 202 and the rear end 22.

[0046] The first set of blades 16A is similar to the set of blades 16. Each blade 4OA of the second set of blades 16B is inverted relatively to the blades 40 of the first set of blades 16A and the second set of blades 16B rotates in a clockwise rotation direction 104 which is opposite to the anticlockwise rotation direction 54 of the first set of blades 16A. In all other respects each blade 40A is similar to the blade 40.

[0047] The generator 26A of the turbine 200 has a stator 28A which is rotatably located in the housing 14A. Appropriate bearings 24B are used inside the housing 14A to mount the stator 28A in the housing 14A. The stator 28A is connected to the first blade section 16A by way of the shaft 44 and the rotor 30 is connected to the second set of blades 16B by a shaft 44A. Appropriate slip rings or contacts 38A are used to connect the generator 26A to the wiring 32.

[0048] When the first and second sets of blades 16A, B are rotated by wind 52 in the manner described the stator 28A is rotated in the anticlockwise rotation direction 54 and the rotor 30 is rotated in the clockwise rotation direction 104. The relative speed between the stator 28A and the rotor 30 is higher than, and a combination of, the individual speeds of the first and second sets of blades 16A, 16B.

[0049] In this manner the effectiveness of the generator 26A is increased especially in low and moderate wind conditions. The additional torque delivered by the blades 40 is specifically important in this instance as this allows the rotation of the heavy stator 28A. As the force of the wind 52 which reaches the second set of blades 16B

is reduced the additional torque delivered by the blades 4OA ensures early rotation of the rotor 30.

[0050] The rudder 2OB ensures that the first and second sets of blades 16A, 16B remains at right angles to the wind 52 under normal wind conditions.

[0051] At excessive wind speeds the blades 40, 40A act in the manner described. Additionally the relative gyromagnetic forces generated by the first and second sets of blades 16A, 16B, the stator 28A and the rotor 30 as well as the air vortex formed behind each of the first and second sets of blades 16A, 16B force the housing 14A to pivot on the post 12 and to turn away from the direction of the wind 52. This reduces the wind force being applied to the first and second sets of blades 16A, 16B. When the rotational speeds of the first and second sets of blades 16A, 16B reduce sufficiently the rudder 2OB forces the housing 14A towards its original position.

[0052] By varying the first and second distances D, D' and the size of the rudder 2OB the turbine 200 can be designed for varying optimum wind speeds.

[0053] The turbine 200 accordingly has increased efficiency in low and moderate wind speeds and has an additional automatic and dynamic rotation speed regulation capability over and above that of the blades 40, 40A.