GB2541871A - Counter rotating wind turbine - Google Patents

Counter rotating wind turbine Download PDF

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Publication number
GB2541871A
GB2541871A GB1515095.6A GB201515095A GB2541871A GB 2541871 A GB2541871 A GB 2541871A GB 201515095 A GB201515095 A GB 201515095A GB 2541871 A GB2541871 A GB 2541871A
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GB
United Kingdom
Prior art keywords
blade assembly
wind turbine
vertical axis
blade
threshold
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB1515095.6A
Other versions
GB201515095D0 (en
Inventor
Young Alex
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Summit Associates Ltd
Original Assignee
Summit Associates Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Summit Associates Ltd filed Critical Summit Associates Ltd
Priority to GB1515095.6A priority Critical patent/GB2541871A/en
Publication of GB201515095D0 publication Critical patent/GB201515095D0/en
Publication of GB2541871A publication Critical patent/GB2541871A/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D9/00—Adaptations of wind motors for special use; Combinations of wind motors with apparatus driven thereby; Wind motors specially adapted for installation in particular locations
    • F03D9/20—Wind motors characterised by the driven apparatus
    • F03D9/25—Wind motors characterised by the driven apparatus the apparatus being an electrical generator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D3/00—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor 
    • F03D3/02—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor  having a plurality of rotors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D3/00—Wind motors with rotation axis substantially perpendicular to the air flow entering the rotor 
    • F03D3/06—Rotors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D7/00—Controlling wind motors 
    • F03D7/06—Controlling wind motors  the wind motors having rotation axis substantially perpendicular to the air flow entering the rotor
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/18—Structural association of electric generators with mechanical driving motors, e.g. with turbines
    • H02K7/1807—Rotary generators
    • H02K7/1823—Rotary generators structurally associated with turbines or similar engines
    • H02K7/183—Rotary generators structurally associated with turbines or similar engines wherein the turbine is a wind turbine
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/20—Rotors
    • F05B2240/21—Rotors for wind turbines
    • F05B2240/211—Rotors for wind turbines with vertical axis
    • F05B2240/212—Rotors for wind turbines with vertical axis of the Darrieus type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/20—Rotors
    • F05B2240/21—Rotors for wind turbines
    • F05B2240/211—Rotors for wind turbines with vertical axis
    • F05B2240/213—Rotors for wind turbines with vertical axis of the Savonius type
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/74—Wind turbines with rotation axis perpendicular to the wind direction

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Wind Motors (AREA)

Abstract

A twin rotor vertical axis wind turbine comprises two mechanically decoupled blade assemblies 1, 6 that rotate in different directions and are aligned around the same axis 8. One rotor is coupled to a generator magnet 5 and the other to an electrical coil 9, such that the magnet and armature winding rotate in opposite directions, increasing the relative velocity. The turbines are configured such that such that the first blade assembly will rotate when the wind speed is above a first threshold and the second blade assembly will counter rotate when the wind speed is below a second threshold. There may be a brake 12, 15 associated with one or both rotors, which could be exclusively or a combination of lift or drag based devices, such as Darrieus or Savonius rotors. There may also be a control system to control the brakes.

Description

COUNTER ROTATING WIND TURBINE
Field of the Invention
The present invention relates to the field of wind turbine design, in particular to a vertical axis wind turbine having a first blade assembly and a second blade assembly.
Background of the Invention
This invention improves the electrical generation properties of a vertical axis wind turbine, in particular the optimisation of energy harvested from the wind in gusty, turbulent environment.
The energy available in gusts of wind is often unharvested by wind turbines due to the inertia of large blades and the damaging effect that sudden variation in force can have upon turbines, but these gusts can be a significant source of energy in the wind.
Most designs for wind turbines are designed for either low, medium or high, non-turbulent wind speeds, so delivering either consistent but low electrical generation or inconsistent but high electrical generation. GB2404227A discusses the design of vertical axis wind turbine blades. In particular, GB2404227A discusses the use of blades wherein the upper end and the lower end of the blade are rotationally off-set about the axis of rotation forming a helix-like shape. It is proposed that these blades will increase the efficiency of the system by smoothing the torque produced by the blades around the whole rotation. US2010/0133829 discusses the use of a regenerative drive system in combination with a wind turbine to control the speed of the blades during gusty conditions. It is proposed that this would increase the capture of energy in gusty conditions and allow the generator to act as a motor to start the high wind speed blades. JP2007113562A discusses a wind turbine with a combination of two blade types. The blades are mechanically connected by a complex system of gears. The blades may rotate in opposite directions utilising a planetary gearing system to convert the counter-rotation into electrical energy via a generator. US 20120148403 A1 discusses a wind turbine with a combination of two blade systems to form an alternator. One of the blade systems is the rotor and the other of the blade systems acts as the stator of the alternator. The two blades may be axially aligned and disposed on the same shaft and rotate in opposite directions.
It is the object of this invention to deliver the capability to harvest energy from the wind in a wide range of wind speeds and levels of turbulence.
Summary of the Invention
Accordingly, the present invention aims to solve the above problems by providing, according to a first aspect, a vertical axis wind turbine for generating electricity comprising a first blade assembly, a second blade assembly and a generator. The first blade assembly and the second blade assembly rotate about the same axis and are mechanically decoupled. The first blade assembly is configured to rotate in a first direction when the wind speed is above a first threshold and the second blade assembly is configured to rotate in the opposite direction when the wind speed is below a second threshold. The generator has a magnet and an electrical coil wherein the magnet is coupled to one of the first blade assembly or the second blade assembly and the coil is coupled to the other of the first blade assembly and the second blade assembly.
The first threshold is lower than or equal to the second threshold. Optionally the first threshold is lower than the second threshold.
In this way the vertical axis wind turbine of the present invention can convert wind energy into electrical energy over a wide range of wind speeds and can also convert the wind energy efficiently. At low wind speeds, below the first threshold, the second blade assembly may rotate and generate electrical energy. At high wind speeds, above the first threshold, the first blade assembly may rotate and generate electrical energy.
This arrangement provides electrical generation capability over a wide range of wind speeds.
The second blade assembly is operational at wind speeds below the second threshold and so will generate electricity in low wind conditions. The first blade assembly is capable of generating more torque than the second blade assembly at wind speeds above the first threshold. The first blade assembly does not operate below the first threshold.
The combination of the two blade assemblies rotating in the opposite direction to one another generates electricity over a wide range of wind speeds.
The counter rotation of the first blade assembly and the second blade assembly also reduces the vibrations of the turbine, as the vibrations of the blade assemblies are out of phase.
Optional features of the invention will now be set out. These are applicable singly or in any combination with any aspect of the invention.
In some embodiments a first brake mechanism is provided for mechanically locking the first blade assembly. In this way, when the wind is below the first threshold the first blade assembly can be mechanically locked so it does not rotate.
When the first blade assembly is locked the counter rotation of the second blade assembly does not result in the first blade assembly rotating in the same direction as the second blade assembly as a result of magnetic attraction within the generator. If the first blade assembly were allowed to rotate some of the energy captured by the second blade assembly would be used to rotate the first blade and therefore less energy would be converted to electricity by the generator.
In some embodiments a second brake mechanism is provided for mechanically locking the second blade assembly. In use when the wind is above the second threshold the second blade assembly is mechanically locked and does not rotate.
In high wind speeds, higher than the second threshold, the torque generated by the first blade assembly may be sufficiently high to overcome the torque of the second blade assembly and force the second blade assembly to rotate in the same direction as the first blade assembly (against the wind). The result is that less electricity is generated as the first blade assembly is working against the second blade assembly and both the coil and magnet are rotating in the same direction. The second brake mechanism can be used to mechanically lock the second blade assembly to prevent this.
In some embodiments the vertical axis wind turbine also has a control system. The control system has a detector for monitoring the wind speed, a means for controlling the first brake mechanism and a means for controlling the second brake mechanism.
This allows the locking of each of the first and second blade assemblies at certain wind speeds and provides a mechanism for controlling the brake system.
The combination of a first brake system and a second brake system mean that at low wind speeds, below the first threshold, the second blade assembly can catch the wind and apply torque to the generator without dragging the first blade assembly through the air and ensures that at high wind speeds the first blade assembly can catch the wind and apply a torque to the generator without dragging the second blade assembly through the air.
The only interaction between the two blade systems is the air disturbance from the blades and the attraction between the magnet and the wire coil within the generator.
In some embodiments the generator comprises an array of magnets that is mechanically coupled to one or other of the first blade assembly and the second blade assembly.
In some embodiments the generator is switchable from a first configuration to a second configuration. In the first configuration the generator converts mechanical energy into electrical energy and in the second configuration the generator is a motor.
In use, when the wind is above the first threshold, the generator is switched to the second configuration and the motor applies a torque to the first blade assembly and when the first blade assembly reaches a self-sustaining speed of rotation the generator is switched to the first configuration.
In this way the generator can be used to power up the first blade system.
In some embodiments the vertical axis wind turbine has a coordination system having a plurality of sensors and a means for controlling the switching of the generator between the first and second configuration. The plurality of sensors monitor the wind speed and the speed of rotation of the first blade assembly. The plurality of sensors may also monitor the speed of rotation of the second blade assembly.
In this way the powering up of the first blade assembly can be controlled and achieved using the minimum amount of energy.
In some embodiments when the generator is in the second configuration the second blade assembly is mechanically locked by the second brake mechanism.
In this configuration the torque applied to power up the first blade assembly does not act against the torque generated by the second blade assembly’s rotation.
In some embodiments when the generator is in the second configuration (i.e. when it is acting as a motor) the second blade assembly is not mechanically locked by the second brake mechanism. In use, the motor applies a torque to the second blade assembly and applies an opposite torque to the first blade assembly. Optionally the torque applied to the first blade assembly is equal and opposite to the force applied to the second blade assembly.
The rotation of the second blade assembly is utilised to assist in the powering up of the first blade assembly. The motor applies a torque such that the first blade assembly is accelerated in the desired direction of rotation and the second blade assembly is accelerated in the opposite direction. The second blade is accelerated so that it travels faster than the wind speed. This causes the wind to act against the direction of rotation of the second blade assembly and provides the reaction force. This reaction force is utilised to accelerate the first blade assembly. In this way the motor accelerates the first blade assembly to a self-sustaining speed.
When a torque is applied by the motor, the torque is applied in equal and opposite measure to the first blade assembly and the second blade assembly. This torque will cause the blades to accelerate in opposite rotational directions.
When a torque is applied to the second blade assembly (e.g. Savonius blades), the second blade assembly will rotate and an equal and opposite torque is applied to the first blade assembly. If the first blade assembly (e.g. the Darrieus blades) is not mechanically locked, the first blade assembly will begin to rotate in the opposite direction to the second blade assembly.
This is in line with Newton’s 3rd law which states that any force applied results in an equal and opposite reaction force.
When the second blade assembly is rotating at less than the speed of the wind the torque applied to the second blade assembly is low. Therefore, the torque applied to the first blade assembly will also be small.
When the torque applied to the second blade assembly is increased the second blade assembly will rotate faster and the torque applied to the first blade assembly will also increase.
When the second blade assembly is rotating faster than the speed of the wind, the wind will apply a reaction force to the second blade assembly. The reaction force resists the rotation of the second blade assembly whilst the second blade assembly is rotating faster than the wind speed.
The result of this reaction force which opposes the rotation of the second blade assembly is that a greater torque is applied to the first blade assembly via the coil and magnet of the generator. This results in the first blade assembly being accelerated. The relative rotational speed between the two blade assemblies increases.
In some embodiments the coordination system further comprises a means for controlling the torque applied to the second blade assembly. In this way the amount of energy used in starting-up the first blade assembly can be controlled and minimised.
For example, when the generator is acting as a motor it may be controlled via power electronics to increase or decrease the relative rotational speed of the coil and magnet of the generator in response to changing wind conditions. The control of the coil and magnet increases or decreases the relative rotational speed of the first blade assembly and the second blade assembly.
For wind speeds that are high enough to cause damage to the wind turbine, an additional resistive load can be applied to the electrical output to apply additional generator torque to slow the rotational speed. In this way the system is able to continue to convert wind energy to electricity in an even wider range of wind speeds.
In even higher wind speeds the first brake mechanism and the second brake mechanism can be applied to slow both of the first blade assembly and the second blade assembly to a stop.
In some embodiments the first blade assembly is mechanically coupled to the magnet and the second blade assembly is mechanically coupled to the coil. In some embodiments the second blade assembly is mechanically coupled to the magnet and the first blade assembly is mechanically coupled to the coil.
The first threshold may be between 2-30 m/s. For example, the first threshold may be from 2-20 m/s. It may be from 2-15 m/s. It may be from 2-10 m/s. It may be from 5-30 m/s. It may be from 5-20 m/s. It may be from 5-15 m/s. It may be from 5-10 m/s. It may be from 10-30 m/s. It may be from 10-20 m/s. It may be from 10-15 m/s. It may be from 15-30 m/s.
It may be from 15-20 m/s. It may be from 20-30 m/s.
The second threshold may be between 1-70 m/s. For example, the second threshold may be from 3-70 m/s. It may be from 5-70 m/s. It may be from 10-70 m/s. It may be from 20-70 m/s. It may be from 30-70 m/s. It may be from 40-70 m/s. It may be from 50-70 m/s. It may be from 60-70 m/s. It may be from 5-60 m/s. It may be from 10-60 m/s. It may be from 20-60 m/s. It may be from 30-60 m/s. It may be from 40-60 m/s. It may be from 50-60 m/s. It may be from 5-50 m/s. It may be from 10-50 m/s. It may be from 20-50 m/s. It may be from 30-50 m/s. It may be from 40-50 m/s. It may be from 5-40 m/s. It may be from 10-40 m/s.
It may be from 20-40 m/s. It may be from 30-40 m/s. It may be from 3-30 m/s. It may be from 5-30 m/s. It may be from 10-30 m/s. It may be from 20-30 m/s. It may be from 3-20 m/s. It may be from 5-20 m/s. It may be from 10-20 m/s. It may be from 3-15 m/s. It may be from 5-15 m/s.
In this way the wind turbine of the present invention provides a wind turbine that can convert wind energy into electricity over a wide range of wind speeds. At lower wind speeds, below the first threshold, the second blade assembly can rotate and generate power. At high wind speeds, above the second threshold, the first blade assembly can rotate and generate power. There may be wind speeds between the first threshold and the second threshold whereby both the first blade assembly and the second blade assembly can rotate and generate power.
In some embodiments the first blade assembly comprises a lift operated blade. Preferably there are a plurality of blades forming the first blade assembly, with a minimum of one blade. Preferably, if there is more than one blade, the blades are equidistant apart.
The first blade assembly may comprise blades that are helically formed around the central vertical axis. This arrangement means that all possible angles of attack to the oncoming wind can act on the blade, thus providing smooth torque throughout the rotation cycle.
In some embodiments the first blade assembly may comprise a Darrieus-type blade. Preferably, the first blade assembly has three darrieus-type blades.
The planar cross section of a Darrieus blade is an aerofoil shape, with the chord length arranged to lie at a constant radius from the central axis of rotation.
The chord length of the blade remains at a consistent distance from the central axis through the length of the blade from base to tip.
The first blade assembly may be connected to the generator via struts attached to the lower section of each blade.
The first blade assembly may also be rotably connected to the central shaft at the top of the blades via struts.
In some embodiments the second blade assembly may be a drag operated blade. For example, the second blade assembly may comprise a blade or blades designed for low wind speeds the blade being helically formed using at least two discreet baffles to limit the air flow in planes that are not the plane of rotation. For example, the second blade assembly may comprise a Savonius blade or Savonius blades.
In some embodiments the first blade assembly is a lift operated blade and the second blade assembly is a drag operated blade. For example, the first blade assembly may be a Darrieus blade and the second blade assembly may be a Savonius blade, preferably the Darrieus blade system is mechanically couple to the magnet and the Savonius blade is mechanically coupled to the coil. Preferably, the second blade assembly is encompassed within the envelope of rotation of the first blade assembly.
Further optional features of the invention are set out below.
Brief Description of the Drawings
Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:
Figure 1 shows a cut away view of a generator and blade arrangement of an embodiment of the present invention.
Figure 2 shows an external view of a wind turbine of the present invention.
Detailed Description and Further Optional Features of the Invention
Figure 1 shows a cut away view of a generator and blade arrangement of an embodiment of the present invention.
The first blade assembly 1 consists of a plurality of blades 2. Each blade 2 is an aerofoil rotably fixed to a central shaft 8 via struts at the top of the assembly (not shown). Each blade 2 is also affixed to the magnet 5 via the struts 3. In this way when the first blade assembly catches the wind and rotates, the magnet also rotates.
The magnet 5 may take the form of an array of magnets.
The second blade assembly 6 comprises the blades 7. Each blade 7 is a drag type blade fixed to a shaft 8. Each blade 7 is connected to a wire coil 9 via the shaft 8 and is supported by the bearings 10. In this way when the second blade assembly catches the wind and rotates, the wire coil also rotates.
The generator 11 consists of the wire coil 9 and the magnet 5. The wire coil 9 is partially surrounded by the magnet 5. In this way when there is relative movement between the coil and magnet, electricity is generated. A first brake mechanism 12 is directly connected to the magnet 5. The first blade assembly is connected to the first brake mechanism 12 via the magnet 5. The first brake mechanism has a brake disk 13 and a brake calliper 14. In this way, in low wind speeds the blades 2 can be mechanically locked into position by the first brake mechanism so that the counter rotation of the low speed blades 7 does not result in the blades 2 rotating in the same direction as a result of magnetic attraction within the generator 11.
When the wind speed reaches a level such that the blades 2 can sustain rotation through the lift generated from the wind (wind speeds above the first threshold) the first brake mechanism 12 can be released. A second brake mechanism 15 is connected to the coil 9 and the shaft 8. The blades 7 can be mechanically locked into position by the second brake mechanism. In this way, in high wind speeds (above the second threshold) the blades 2 do not drag the blades 7 in the same direction as the blades 2.
The combination of first brake mechanism and second brake mechanism allows the movement of the first blade assembly 1 to be uncoupled from the movement of the counter rotating second blade assembly 6. This ensures that at low wind speeds, below the first threshold, the blades 7 can catch the wind and apply torque to the generator without dragging the blades 2 through the air. It also ensures that at high wind speeds, above the second threshold, the blades 2 can catch the wind and apply a torque to the generator without dragging the blades 7 through the air.
The only interaction between the two blade assemblies is the air disturbance from the blades and the attraction between the permanent magnets and the wire coil within the generator. A control system 16 is provided. When the control system 16 detects wind speeds above the first threshold the generator 11 will be switched to act as a motor to spin up the first blade assembly 1.
In a first embodiment, the second blade assembly 6 will be mechanically locked into position using the second brake mechanism 15 whilst the motor rotates the high speed blades to a rotational speed at which the rotation is self sustaining. At this point the second brake mechanism 15 is released and the generator is switched back to operate as a generator.
In a second embodiment, the second blade assembly 6 is not mechanically locked. The generator 11 is switched to motor mode and applies an equal torque to both the coil 9 and the permanent magnet array 5. This torque increases the rotational speed of the blades 7 such that the wind provides resistance to further increases in rotational speed. This torque provokes an equal and opposite torque application to the magnet 5 such that the blades 2 increase in rotational speed, but counter rotate with reference to the the blade 7.
This second embodiment requires the control system 16 to report the speed of the blades 2 and blades 7 so that the correct torque is applied to the coil 9 and the magnet 5. Once the blades 2 have reached a speed at which the rotation is self sustaining the generator is switched back to operate as a generator.
In both the first and second embodiments described above the generator can be used to spin-up the first blade assembly. In this way the barrier to reaching a sustainable rotation speed for blades, in particular high torque blades, can be overcome.
Figure 2 shows an external view of a wind turbine of the present invention.
The turbine consists of a first blade assembly 21, a second blade assembly 24 and a generator 27.
The first blade assembly has three blades 22. Each blade 22 is a Darrieus type blade and is arranged in a helical shape such that every angle of attack to the oncoming wind is represented within the blade system. The blades 22 are configured to rotate in a first direction. This arrangement provides a smooth torque generation through the rotation cycle.
The first blade assembly is mechanically connected to the magnet of the generator 27 via the struts 23. In this way when the first blade assembly rotates the magnet will also rotate.
The second blade assembly 24 is a Savonius type blade 25. The blade 25 is configured to rotate in a second direction, opposite to the direction of rotation of the blades 22. The second blade assembly 24 is mechanically connected to the coil of the generator 27 via the central shaft 26. In this way when the second blade assembly 24 rotates the coil will also rotate. The second blade assembly 24 is encompassed within the envelope of rotation of the first blade assembly 21.
While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.
All references referred to above are hereby incorporated by reference.

Claims (23)

1. A vertical axis wind turbine for generating electricity comprising a first blade assembly, a second blade assembly and a generator wherein: the first blade assembly and the second blade assembly rotate about the same axis and are mechanically decoupled; the first blade assembly is configured to rotate in a first direction when the wind speed is above a first threshold and the second blade assembly is configured to rotate in the opposite direction when the wind speed is below a second threshold; and the generator has a magnet and an electrical coil wherein the magnet is coupled to one of the first blade assembly or the second blade assembly and the coil is coupled to the other of the first blade assembly and the second blade assembly.
2. The vertical axis wind turbine of claim 1 wherein the first threshold is lower than or equal to the second threshold.
3. The vertical axis wind turbine of claim 1 or claim 2 wherein a first brake mechanism is provided for mechanically locking the first blade assembly such that in use when the wind is below the first threshold the first blade assembly is mechanically locked and does not rotate.
4. The vertical axis wind turbine of any one of the preceding claims wherein a second brake mechanism is provided for mechanically locking the second blade assembly such that in use when the wind is above the second threshold the second blade assembly is mechanically locked and does not rotate.
5. The vertical axis wind turbine of claim 3 or claim 4 further comprising a control system wherein the control system has a detector for monitoring the wind speed, a means for controlling the first brake mechanism and a means for controlling the second brake mechanism.
6. The vertical axis wind turbine of any one of the preceding claims wherein the generator is switchable from a first configuration to a second configuration wherein in the first configuration the generator converts mechanical energy into electrical energy and in the second configuration the generator is a motor such that in use when the wind is above the first threshold the generator is switched to the second configuration and the motor applies a torque to the first blade assembly and when the first blade assembly reaches a self-sustaining speed of rotation the generator is switched to the first configuration.
7. The vertical axis wind turbine of claim 6 further comprising a coordination system having a plurality of sensors and a means for controlling the switching of the generator between the first and second configuration wherein the plurality of sensors monitor the wind speed and the speed of rotation of the first blade assembly.
8. The vertical axis wind turbine of claim 6 or claim 7 wherein when the generator is in the second configuration the second blade assembly is mechanically locked by the second brake mechanism.
9. The vertical axis wind turbine of claim 6 or claim 7 wherein when the generator is in the second configuration the second blade assembly is not mechanically locked by the second brake mechanism such that the motor applies a torque to the first blade assembly and the second blade assembly.
10. The vertical axis wind turbine of claim 9 wherein the coordination system further comprises a means for controlling the torque applied to the first blade assembly and the second blade assemblies.
11. The vertical axis wind turbine of any one of the preceding claims wherein the first blade assembly is mechanically coupled to the magnet and the second blade assembly is mechanically coupled to the coil.
12. The vertical axis wind turbine of any one of the preceding claims wherein the first threshold is between 2-30 m/s.
13. The vertical axis wind turbine of claim 12 wherein the first threshold is between 5-20 m/s.
14. The vertical axis wind turbine of claim 13 wherein the first threshold is between 5-15 m/s.
15. The vertical axis wind turbine of any one of the preceding claims wherein the second threshold is between 3-70 m/s.
16. The vertical axis wind turbine of claim 15 wherein the second threshold is between 5-60 m/s.
17. The vertical axis wind turbine of claim 16 wherein the second threshold is between 5-15 m/s.
18. The vertical axis wind turbine of any one of the preceding claims wherein the first blade assembly comprises a lift operated blade.
19. The vertical axis wind turbine of claim 18 wherein the first blade assembly comprises a Darrieus blade.
20. The vertical axis wind turbine of claim 19 wherein there are a plurality of Darrieus blades.
21. The vertical axis wind turbine of any one of the preceding claims wherein the second blade assembly comprises a drag operated blade.
22. The vertical axis wind turbine of claim 21 wherein the second blade assembly comprises a Savonius blade.
23. A vertical axis wind turbine substantially as herein described with reference to the description and figures.
GB1515095.6A 2015-08-25 2015-08-25 Counter rotating wind turbine Withdrawn GB2541871A (en)

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GB1515095.6A GB2541871A (en) 2015-08-25 2015-08-25 Counter rotating wind turbine

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