WO2020216965A1

WO2020216965A1 - Wind turbine with wind guide system with load reduction means

Info

Publication number: WO2020216965A1
Application number: PCT/EP2020/061655
Authority: WO
Inventors: Peter Grabau
Original assignee: Winnowave Sl
Current assignee: Winnowave Sl
Priority date: 2019-04-25
Filing date: 2020-04-27
Publication date: 2020-10-29
Anticipated expiration: 2021-10-25

Abstract

A wind guide system (2) to speed up wind to improve the energy production from wind turbines (6) is introduced. The wind guide (2) has a geometry and/or porosity that result in less turbulence induced loads on the wind turbine rotor. The length L of the wind guide is longer than the diameter of the rotor D whereby the vortices (4) from the wind guide (2) will not hit the rotor blades (8).

Description

Title

Wind Turbine with Wind Guide System with Load Reduction Means

Introduction

The present invention relates to a system and method for optimizing the climatic wind conditions of a site in order to increase the energy production rate of wind turbines and at the same time reduce the wind induced load. The present invention more particularly relates to a system and a method to speed up the wind in an area in front of the rotor and/or behind of the turbine rotor in order to increase the energy production rate of wind turbines and at the same time reduce turbulence induced wind loads on wind turbine

Prior art

The Danish patent DK177082B1 discloses a method and a system for increasing the output of a wind turbine, wherein one or more flow surfaces are placed at a wind turbine. At lower wind speeds, the flow surfaces are set to guide the wind up towards the rotor of the wind turbine and hence take advantage of the Venturi effect in the rotor. DK177082B1 shows how to install speed-increasing surfaces around a wind farm to exploit the Venturi effect to increase the wind speed in front of the turbine and/or to expand the wake behind the turbine.

However, it would be desirable to find other systems that enable such wind speed increase and at the same time reduce the vortex induced turbulence generated by the flow surfaces and thereby reduce the loads on the wind turbine.

One problem associated with the above mentioned is that the turbulent wind flow generated by the flow surfaces in some cases will hit the rotor of the wind turbine and thereby increase the fatigue loads on the turbine. A further problem is that turbines are designed for and erected at sites with expected wind conditions within the design load envelope for the wind turbine. Therefore, adding flow surfaces to an existing wind turbine may result in overloading the wind turbine. In case the wind turbine has been designed for the flow surface operating conditions, it will still be an advantage to reduce the turbulence induced loads on the wind turbine and thereby reduce the cost of the turbine or extend the lifetime of the wind turbine.

Object of the invention

It is therefore an object of the present invention to provide a system and a method including a wind guide system to guide the wind into an area in front of and/or behind the wind turbine rotor to improve the wind turbine energy production rate and at the same time reduce the turbulence induced wind loads on the wind turbine caused by pressure differences across certain parts of the wind guide system by ensuring that the major parts of the vortex induced turbulence generated from the wind guide system, will not hit the rotor of the wind turbine

It is a further object of the present invention to provide a system and a method to reduce the strength in the vortices generated by the ends of the wind guide system

At least one of the above objects, or at least one of the further objects which will be evident from the below description of the present invention, is according to a first aspect of the present invention achieved by a wind guide system as defined in claim 1.

Description of the invention

In a first aspect, a wind guide system for guiding the wind in front of a wind turbine from a first direction to a second direction. The wind turbine comprising a tower and a rotor provided with a number of rotor blades defining a rotor swept area. The wind guide system comprising a ground- based wind guide with a horizontal width, a vertical height, a thickness and with at least two ends, arranged and configured to receive wind from an altitude below the rotor swept area and to direct the wind so the wind leaving the wind guide has another direction than the wind before the wind guide. The wind guide system is arranged and configured to direct the wind to an area in front of and/or behind the rotor swept area. In addition, the ground- based wind guide is extending in a horizontal length larger than the diameter of the rotor of the wind turbine, whereby the vortices generated close to the ends of the wind guide system will not be able to reach the wind turbine rotor, and thereby reducing the wind induced loads on the wind turbine and/or on neighbouring wind turbines.

In a preferred embodiment of the invention, or in a separate inventive concept as an alternative to the wind guide extending in a horizontal length larger than the diameter of the rotor of the wind turbine, the wind guide system is porous in at least a part of the structure causing the pressure difference between the windward and the leeward side of the wind guide system to be reduced and thereby also the strength of the vortices generated by the pressure difference will be reduced.

In a preferred embodiment of the invention, or in a separate inventive concept forming an alternative to the wind guide extending in a horizontal length larger than the diameter of the rotor of the wind turbine, the wind guide system is arranged so it primarily direct the wind to the area behind the rotor swept area.

In a preferred embodiment of the invention, or in a separate inventive concept forming an alternative to the wind guide extending in a horizontal length larger than the diameter of the rotor of the wind turbine, the wind guide system is tapered towards the ends resulting in lower wind guide system vertical height at the area close to the ends which results in less area with pressure difference to generate to vortices resulting in less turbulence generated by the wind guide system resulting in a load reduction on the wind turbine.

In a preferred embodiment of the invention, or in a separate inventive concept forming an alternative to the wind guide extending in a horizontal length larger than the diameter of the rotor of the wind turbine, the wind guide system is aligned with the wind turbine tower to ensure that turbulence generated by the wind guide system will end up behind the wind turbine and therefore not hit the rotor of the wind turbine and therefore not generate extra loads on the wind turbine rotor.

In a preferred embodiment of the invention the wind guide system porosity is actively and/or passively adjustable whereby the strength in the vortices can also be adjusted so when the turbulence generated by the vortices will not hit the turbine rotor, the porosity can be less.

In a preferred embodiment of the invention the wind guide system is angled less than 10 degrees relative to vertical since this has proven to be the most cost-effective solution

In a preferred embodiment of the invention, or in a separate inventive concept forming an alternative to the wind guide extending in a horizontal length larger than the diameter of the rotor of the wind turbine, the wind guide system comprises one or more additional wind turbines arranged at the horizontal ends of the wind guide, preferably one or two additional wind turbines at each end and preferably smaller than the main wind turbine behind the wind guide. By the additional wind turbines the amount of wind let through at the ends can be controlled to reduce or adjust undesired vortex generation at the ends. At the same time, the additional wind turbines may generate additional power, in particular as the wind blows around the ends of the wind guide with high wind speed. In particular, it is preferred that the form of the wind guide is adapted at its ends to the form of the additional wind turbines, in particular to the rotor swept areas of the additional wind turbines, to reduce, in particular to minimize, leakage between the additional wind turbines and the wind guide.

It is further preferred that the additional wind turbines comprise a rotor mounted to the wind guide. In such a way, the additional wind turbines are independent from the ground and can be pre-mounted to the wind guide to simplify installation.

Alternatively, it is preferred that the additional wind turbines are formed as common, i.e. traditional wind turbines having a rotor mounted to a tower based on the ground. In such a way, the additional wind turbines are independent from the wind guide and can be installed before or after the wind guide.

It is also preferred that the additional wind turbines are configured to yaw to adapt to the actual wind direction. In such a way, efficiency of the additional wind turbines can be improved.

It is further preferred that a control unit is provided configured to control rotation of the rotor of the additional wind turbines to control the amount of wind passing the rotors of the additional wind turbines, in particular by turning the wind turbines on or off or by adjusting the induction of the additional wind turbines, similar to a porosity that is actively adjustable. By controlling the amount of wind passing the rotors of the additional wind turbines, the amount of undesired vortices forming at the ends can be controlled.

In a preferred embodiment of the invention, or in a separate inventive concept forming an alternative to the wind guide extending in a horizontal length larger than the diameter of the rotor of the wind turbine, the wind guide system comprises one or more trees arranged at the horizontal ends of the wind guide, preferably one tree at each end. By the trees the amount of wind let through at the ends can be controlled to reduce or adjust undesired vortex generation at the ends.

In a preferred embodiment of the invention, or in a separate inventive concept forming an alternative to the wind guide extending in a horizontal length larger than the diameter of the rotor of the wind turbine, the wind guide at its horizontal ends comprises projections, in particular formed as kinks, to the lee side and/or to the luff side of the wind guide. The projections might be perpendicular to the main direction of extension of the wind guide or might extend with an acute angle to the main direction of extension of the wind guide. By such projections, vortices forming at the ends can be widely reduced. This design is similar to winglets used on airplane wings and on some wind turbine blades. The design also improves the stability of the wind guide system to wind loads and it improves the efficiency of the wind guide system almost as much as a corresponding length extension of the wind guide system.

In a preferred embodiment of the invention, or in a separate inventive concept forming an alternative to the wind guide extending in a horizontal length larger than the diameter of the rotor of the wind turbine, the wind guide at its horizontal ends comprises one or more leakage gaps for letting wind through the wind guide. By leaking wind through the wind guide at its ends, the formation of vortices at the ends can be reduced.

In particular, it is preferred that the leakage gaps extend mainly in the horizontal direction. The leakage gaps might be formed as cut-out in the outer ends of the wind guide. Such leakage gaps efficiently reduce undesired vortices at the ends. Alternatively, it is preferred that the leakage gaps extend mainly in the vertical direction. The leakage gaps might be formed as cut-out in the upper side or at the lower side or through the entire vertical extension of the wind guide at the ends. Such leakage gaps efficiently reduce undesired vortices at the ends.

In particular, it is preferred that the leakage gaps are adjustable to adjust the amount of wind passing through the leakage gaps. In such a way, the amount or strength of undesired vortices forming at the ends can be adjusted.

It is further preferred that the wind guide at its horizontal ends comprises one or more adjustable vanes that are rotatably adjustable about horizontal axes, so that horizontal leakage gaps between two adjacent vanes can be adjusted by adjusting the angular position of the vanes about their axes. By such adjustable vanes, the amount or strength of undesired vortices forming at the ends can be effectively adjusted. When the vanes are positioned vertically, the leakage will be close to zero. The vanes can lead the wind flow upwardly in order to improve the wind farm efficiency by leading wind into the wake of the wind turbine. Alternatively, the vanes can lead the wind flow downwardly and thereby keep the turbulent air caused by the vortices closer to the ground to reduce the effect of turbulent flow hitting the wind turbine or a neighbouring wind turbine. The vanes can be actively controlled, or they can be passively controlled by exploiting the wind force to open or close.

In a preferred embodiment of the invention the maximum electrical power output from the wind turbine is within the interval 15 kW to 12 MW

In a preferred embodiment of the invention the wind turbine rotor diameter is within the interval 5 meters to 220 meters A preferred embodiment of the invention implies a wind guide system for a wind turbine system according to any of the embodiment described above, for guiding the wind in front of a wind turbine from a first direction to a second direction. The wind turbine comprising a tower and a rotor provided with a number of rotor blades defining a rotor swept area. The wind guide system comprising a ground-based wind guide with a horizontal width, a vertical height, a thickness and with at least two ends, arranged and configured to receive wind from an altitude below the rotor swept area and to direct the wind so the wind leaving the wind guide has another direction than the wind received by the wind guide. The wind guide system is arranged and configured to direct the wind to an area in front of and/or behind the rotor swept area. The ground-based wind guide is extending in a horizontal length larger than the diameter of the rotor of the wind turbine, and thereby reducing the wind induced loads on the wind turbine and/or on neighbouring wind turbines.

A further aspect of the invention implies a method for guiding the wind in front of a wind turbine from a first direction to a second direction. The wind turbine comprising a tower and a rotor provided with a number of rotor blades defining a rotor swept area. The wind guide system comprising a ground- based wind guide with a horizontal width, a vertical height, a thickness and with at least two ends, arranged and configured to receive wind from an altitude below the rotor swept area and to direct the wind so the wind leaving the wind guide has another direction than the wind before the wind guide. The wind guide system is arranged and configured to direct the wind to an area in front of and/or behind the rotor swept area. In addition, the ground- based wind guide system is extending in a horizontal length larger than the diameter of the rotor of the wind turbine, and thereby reducing the wind induced loads on the wind turbine and/or on neighbouring wind turbines. Figures

The invention will be better understood by reading the following description, given solely by way of non-limiting examples and with reference to the drawings, in which:

Fig. 1 shows a wind guide system in front of a wind turbine. The horizontal length of the wind guide system is exceeding the diameter of the rotor. The vortices generated at the ends of the wind guide system is also shown. Since L is larger than D, the vortices do not hit the rotor.

Fig. 2 shows a wind guide system with leakages close to its ends. The wind guide system is in front of a wind turbine.

Fig. 3 shows a wind guide system that is aligned with the wind turbine tower, so the wind is primarily increased behind the turbine rotor.

Fig. 4 shows a wind guide system that is tapered towards the ends and located in front of a wind turbine.

Fig. 5 shows a front view of a wind guide system with additional wind turbines at the ends of the wind guide.

Fig. 6 shows a front view of a wind guide system with additional wind turbines and the form of the ends of the wind guide adapted to the rotors of the additional wind guides.

Fig. 7 shows a top view of a wind guide system with additional wind turbines that can adapt to the wind direction. Fig. 8 shows a front view of a wind guide system with additional wind turbines formed as common wind turbines with rotor and tower.

Fig. 9 shows a front view of a wind guide system with trees at the ends of the wind guide.

Fig. 10 shows a top view of a wind guide system with luff projections at the ends of the wind guide.

Fig. 1 1 shows a top view of a wind guide system with lee projections at the ends of the wind guide.

Fig. 12 shows a top view of a wind guide system with perpendicular luff and lee projections at the ends of the wind guide.

Fig. 13 shows a top view of a wind guide system with acute angled luff and lee projections at the ends of the wind guide.

Fig. 14 shows a front view of a wind guide system with horizontal leakage gaps at the ends of the wind guide.

Fig. 15 shows a front view of a wind guide system with vertical leakage gaps at the ends of the wind guide.

Fig. 16 shows a front view of a wind guide system with horizontal leakage gaps adjustable by rotatable vanes at the ends of the wind guide.

Fig. 17 shows a cross sectional view of the wind guide system of Fig. 16. List of positions numbers

2 Wind guide

4 Vortices

6 Wind turbine

8 Blade for wind turbine

10 Hole (porosity)

12 T apered area of Wind guide

14 additional wind turbine

16 tree

18 projection

20 leakage gap

22 vane

Detailed description

In Fig. 1 a wind guide system is seen where vortices are shed from its ends. The vortices can be stable tip vortices or alternating vortices often called von Karman vortices. Regardless of the kind of vortices, they will create turbulence that will be carried by the wind towards the wind turbine. In case this turbulence hit the wind turbine rotor the fatigue loads on the turbine will be increased which is not desirable. Therefore, according to the invention, the horizontal length, L, should be larger than the rotor diameter, D, to avoid the turbulence from hitting the wind turbine rotor. In case the wind direction changes so it is not perpendicular to the wind guide, the turbulence from one end of the wind guide system will be more likely to hit the wind turbine rotor, resulting in the necessity of an even larger L.

In Fig. 2 the strength of the vortices is decreased by including holes (porosity) through the wind guide and thereby reducing the pressure difference between the high pressure (wind ward) side and the low pressure (lee ward) side. In Fig. 3 the wind guide is aligned with the wind turbine tower resulting in a, increase in wind speed primarily behind the wind turbine rotor. This way the vortices will also disappear behind the wind turbine rotor and therefore they will not have any load impact on the wind turbine rotor, although they might have an impact on neighbouring turbines.

In Fig. 4 the wind guide is tapered towards the ends resulting in less area with pressure difference that create the vortices and therefore the strength of the vortices will be reduced resulting in less turbulence resulting in less fatigue loads on the wind turbine rotor.

In Fig. 5 the wind guide system comprises two additional wind turbines arranged at each horizontal end of the wind guide. The additional wind turbines each comprise a rotor mounted to the wind guide. The wind guide system further comprises a control unit configured to control rotation of the rotor of the additional wind turbines to control the amount of wind passing the rotors of the additional wind turbines by turning the wind turbines on or off or by adjusting the induction of the additional wind turbines.

In Fig. 6 the form of the wind guide is adapted at its ends to the rotor swept areas of the additional wind turbines to minimize leakage between the additional wind turbines and the wind guide.

In Fig. 7 the additional wind turbines are configured to yaw to adapt to the actual wind direction.

In Fig. 8 the additional wind turbines are formed as common wind turbines having a rotor mounted to a tower based on the ground.

In Fig. 9 the wind guide system comprises one tree arranged at each horizontal end of the wind guide. In Fig. 10 the wind guide at its horizontal ends comprises projections formed as kinks to the luff side of the wind guide. The projections are perpendicular to the main direction of extension of the wind guide.

In Fig. 1 1 the wind guide at its horizontal ends comprises projections formed as kinks to the lee side of the wind guide. The projections are perpendicular to the main direction of extension of the wind guide.

In Fig. 12 the wind guide at its horizontal ends comprises projections formed as kinks to the lee side and to the luff side of the wind guide. The projections are perpendicular to the main direction of extension of the wind guide.

In Fig. 13 the wind guide at its horizontal ends comprises projections formed as kinks to the lee side and to the luff side of the wind guide. The projections extend with an acute angle to the main direction of extension of the wind guide.

In Fig. 14 the wind guide at its horizontal ends comprises two horizontal leakage gaps formed as cut-out in the outer ends of the wind guide for letting wind through the wind guide.

In Fig. 15 the wind guide at its horizontal ends comprises two vertical leakage gaps formed as cut-out through the entire vertical extension of the wind guide at the ends for letting wind through the wind guide.

In Fig. 16 und Fig. 17 the leakage gaps are adjustable to adjust the amount of wind passing through the leakage gaps. The leakage gaps are adjustable by the wind guide at its horizontal ends comprising one or more adjustable vanes that are rotatably adjustable about horizontal axes, so that horizontal leakage gaps between two adjacent vanes can be adjusted by adjusting the angular position of the vanes about their axes. Clauses

In the following clauses, preferred embodiments of the invention are defined:

1. A wind guide system for guiding the wind in front of a wind turbine from a first direction to a second direction;

the wind turbine comprising a tower and a rotor provided with a number of rotor blades defining a rotor swept area;

the wind guide system comprising a ground-based wind guide with a horizontal width, a vertical height, a thickness and with at least two ends, arranged and configured to receive wind from an altitude below the rotor swept area and to direct the wind so the wind leaving the wind guide has another direction than the wind received by the wind guide;

the wind guide system is arranged and configured to direct the wind to an area in front of and/or behind the rotor swept area characterized in that the ground-based wind guide system is extending in a horizontal length larger than the diameter of the rotor of the wind turbine, and thereby reducing the wind induced loads on the wind turbine.

2. A wind guide system according to clause 1 , wherein the wind guide system is porous, in at least one part of the wind guide system.

3. A wind guide system according to clause 1 , wherein the wind guide is arranged and configured to direct wind to the area wind behind the rotor swept area.

4. A wind guide system according to clause 1 , wherein the wind guide is tapered towards the ends of the wind guide system.

5. A wind guide system according to clause 1 , wherein the wind guide is aligned with the wind turbine tower. 6. A wind turbine system according to clause 2, wherein the porosity is actively and /or passively adjustable.

7. A wind turbine comprising a wind guide system according to any of the clauses 1-6, wherein the wind guide system is angled less than 10 degrees relative to vertical.

8. A wind guide system according to any of the clauses 1-7 wherein the wind turbine maximum power output is more than 15, 20, 50, 100, 200, 300, 500, 700, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 1 1000, 12000 kW.

9. A wind guide system according to any of the clauses 1-8 wherein the wind turbine rotor diameter is more than 5, 10, 15, 20, 50, 60, 70, 80, 90, 100, 1 10, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220 meters

10. A method for guiding the wind in front of a wind turbine from a first direction to a second direction;

Claims

1. A wind turbine system comprising a wind turbine and a wind guide system for guiding the wind in front of a wind turbine from a first direction to a second direction;

the wind guide system is arranged and configured to direct the wind to an area in front of and/or behind the rotor swept area characterized in that the ground-based wind guide is extending in a horizontal length larger than the diameter of the rotor of the wind turbine, and thereby reducing the wind induced loads on the wind turbine.

2. The wind turbine system according to claim 1 , wherein the wind guide system is porous, in at least one part of the wind guide system.

3. The wind turbine system according to claim 1 , wherein the wind guide is arranged and configured to direct wind to the area behind the rotor swept area.

4. The wind turbine system according to claim 1 , wherein the wind guide is tapered towards the ends of the wind guide system.

5. The wind turbine system according to claim 1 , wherein the wind guide is aligned with the wind turbine tower.

6. The wind turbine system according to claim 2, wherein the porosity is actively and /or passively adjustable.

7. The wind turbine system according to any of the claims 1-6, wherein the wind guide system is angled less than 10 degrees relative to vertical.

8. The wind turbine system according to any of the claims 1-7 wherein the wind guide system comprises one or more additional wind turbines arranged at the ends of the wind guide.

9. The wind turbine system according to claim 8, wherein the wind guide is adapted at its ends to the form of the additional wind turbines, to reduce leakage between the additional wind turbines and the wind guide.

10. The wind turbine system according to claim 8 or 9, wherein the additional wind turbines comprise a rotor mounted to the wind guide.

1 1 . The wind turbine system according to claim 8 or 9, wherein the additional wind turbines are formed as common wind turbines having a rotor mounted to a tower based on the ground.

12. The wind turbine system according to any of the claims 8-1 1 wherein the additional wind turbines are configured to yaw to adapt to the actual wind direction.

13. The wind turbine system according to any of the claims 8-12 wherein a control unit is provided configured to control rotation of the rotor of the additional wind turbines to control the amount of wind passing the rotors of the additional wind turbines.

14. The wind turbine system according to any of the claims 1-13 wherein the wind guide system comprises one or more trees arranged at the ends of the wind guide.

15. The wind turbine system according to any of the claims 1-14 wherein the wind guide at its ends comprises projections to the lee side and/or to the luff side.

16. The wind turbine system according to any of the claims 1-15 wherein the wind guide at its ends comprises one or more leakage gaps.

17. The wind turbine system according to claim 16, wherein the leakage gaps extend in the horizontal direction.

18. The wind turbine system according to claim 16, wherein the leakage gaps extend in the vertical direction.

19. The wind turbine system according to any of the claims 16-18 wherein the leakage gaps are adjustable to adjust the amount of wind passing through the leakage gaps.

20. The wind turbine system according to claim 19 wherein the wind guide at its ends comprises one or more adjustable vanes rotatably adjustable about horizontal axes, so that horizontal leakage gaps between two adjacent vanes can be adjusted by adjusting the angular position of the vanes about their axes.

21 . The wind turbine system according to any of the claims 1-20 wherein the wind turbine maximum power output is more than 15, 20, 50, 100, 200, 300, 500, 700, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 1 1000, 12000 kW.

22. The wind turbine system according to any of the claims 1-21 wherein the wind turbine rotor diameter is more than 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, 1 10, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220 meters.

23. A wind guide system for a wind turbine system according to any of claims 1 to 22, for guiding the wind in front of a wind turbine from a first direction to a second direction;

24. A method for guiding the wind in front of a wind turbine by a wind guide system from a first direction to a second direction;