WO2012123968A2

WO2012123968A2 - System and method of nacelle mounting enabling stacking/cascading of airfoil blade(s) in wind turbine

Info

Publication number: WO2012123968A2
Application number: PCT/IN2012/000172
Authority: WO
Inventors: Raghunathan VALAGAM RAJAGOPAL
Original assignee: Valagam Rajagopal Raghunathan
Priority date: 2011-03-14
Filing date: 2012-03-13
Publication date: 2012-09-20
Also published as: WO2012123968A3

Abstract

The present invention discloses a system and method of mounting nacelle(5) over the turbine(T) at inverted position and the generation of power by stacking the airfoil blade(s) (1) on top of each other. The wind turbine along with the rotor(2) is mounted on the tower with bearings for accommodating any axial misalignment. The nacelle(5) at inverted position is mounted over the turbine(T) rather than mounting it beneath the turbine. A support plate (6) holds the nacelle(5) and it transmits the vibration of the nacelle(5) to the ground by means of guy wires(7). The rotor(2) has provisions for stacking the airfoil blade(s) (1) for more generation of power according to the need. Since the guy wires(7) are anchored to the tip of the turbine at the nacelle support plate or truss(6), the wobbling action of the turbine(T) is considerably reduced thereby it enhances rigidity to the structure.

Description

SYSTEM AND METHOD OF NACELLE MOUNTING ENABLING STACKING/CASCADING OF AIRFOIL BLADE(S) IN WIND TURBINE

Field of the Invention

This invention relates to the wind turbine with the state of art method of enabling stacking of the airfoil blades by means of system and method of placing nacelle over the turbine. The existing wind turbines have the airfoil blades mounted on the rotor which creates wobbling while the turbine is being operated and generates stress on the tower and turbine structures. Although it can be avoided to some extent by sturdier design it is accomplished at the expense of material cost. The present invention of inverted mounting the nacelle over the turbine reduces the wobbling action besides enhancing the structural support to the turbine. Also, it paves the way if required, in multi stage for stacking of the airfoil blade(s) one over the other thereby enabling the design of turbine to be modularized and further bring flexibility to the design of vertical axis wind turbines

Background and prior art of the Invention

The ever increasing global demand for electricity and the effect the generation of such has on the ecosystem, in concert with the lack of natural resources to keep up with growing demand. It has provided new impetus to look toward the development of alternative and renewable energy sources. The wind turbine is the revolutionary invention for the generation of electricity from the alternate or renewable energy resources thereby achieving the sustainable development which is the need at present to preserve the ecosystem. A wind turbine is a device for converting the kinetic energy in wind into the mechanical energy of a rotating shaft. Usually that rotating mechanical energy is converted immediately by a generator into electrical energy. In the large turbines, there is generally a generator on top of the tower. The generator is usually connected to the turbine shaft through gears which turn the generator at a different speed than the turbine shaft. Fancy power electronic controls convert the electricity into the correct frequency and voltage to feed intolhe power grid. The first law of thermodynamics tells us the energy out of the wind turbine over a certain amount of time (power) has to equal the energy that went into the turbine during the same amount of time (also power). The "energy in" is the kinetic energy from the wind's velocity and air density that flows into the area swept by the turbine blade(s). It is not possible to convert all of the wind's kinetic energy into mechanical energy. Some energy must remain in the air leaving the turbine. The "energy out" is the energy converted by the turbine blades into mechanical energy (which is then usually turned into electricity), plus whatever energy is left in the air after it passes through the turbine rotors. A component of lift force causes rotor rotation and a component of drag force opposes rotation. The rotor torque will be positive as long as the driving component of the lift force exceeds the opposing component of the drag force. With such a system the aerodynamic performance is poor at low wind speeds and the blade(s) tend to stall at low rotational speeds. Consequently, some type of auxiliary device such as a nacelle must be employed to start the system. The integral piece of a wind turbine is the wind turbine nacelle, also known as the generator. This is the piece that is turned by the windmill blade(s) to generate power.

Today's windmill designs have problems of gyroscopic vibration when the machine veers with changing wind direction. Since the nacelle is mounted below the turbine, the airfoil blade(s) in the turbine tend to sag or wobble while the turbine is operated. So, the turbine on the tower acts like a lateral point load on the cantilever beam which is not safe. The lateral load leading to enormous bending moment at the base of the tower and airfoil blade(s) as each blade passes by the wind- shade of the supporting mast as wheel as when being braked during tempest conditions. These bending moments lead to frequent blade replacements and high maintenance costs. The stability of the tower is also affected by the above said phenomena. The bending moment enhances while the airfoil blade(s) are stacked or cascaded for more generation of power.

A few patents are typical of the known prior art attempting to improve the stability of the tower and the turbine by various methods. For example, U.S Pat. No. 5252029 to Barnes discloses a wind turbine which includes a vertically extending hollow rotor shaft mounted on a support structure with two, three or four rotor blades of troposkein configuration on the rotor shaft for rotating the shaft in response to wind energy and thereby drive a generator to produce electrical power. The turbine includes an erection hinge and gin pole which permits the turbine to be cable hoisted using a simple winch mounted at or bear ground level. An additional set of guy wires are provided to hold the central support structure and lower bearing in a vertical position. The above invention improves overall cost effectiveness of construction, installation and maintenance cost.

While U.S Pat. No: 4204805 to Bolie discloses a method comprising of rotating assembly attached to central hub, which is supported for rotation in a horizontal plane about a vertical axis, in a bearing on top of the tower of selected elevation. The rotating assembly comprises at least two radial spokes or arms positioned from each other at equal angles in a horizontal plane. The outer ends of the arms are attached to a connector assembly which generally is in the form of a u-shaped member lying in a vertical plane. The above invention concerns the structural problems of vertical axis windmills.

But, none of the prior art documents disclose a simplified and economical method of enhancing the structural rigidity of the turbine and the tower with the provision of stacking the airfoil blade(s) if required for multi stage mode of operation. Further, the prior art has not dealt with the placing of nacelle, to enhance the structural support of the turbine and tower, thereby enabling the provision of stacking airfoil blade(s). If required for multi stage mode of operation

Summary of the Invention

According to aspect of present invention, there is provided a system and method for mounting the nacelle in an inverted position over the turbine with the aid of guy wires for cost effective method of power generation. The nacelle in an inverted position is mounted over the turbine and is supported by guy wires from the base. The nacelle is fixed to the support plate which is held in place by means of guy wires from the base. The bearing mounted beneath the nacelle accommodates for the misalignment and minimizes the friction. The nacelle provides structural support to the tower and turbine structure and also it prevents the turbine from inducing a wobbling effect which may develop undesirable stress on the rotor and the tower. The position of nacelle enables provision of stacking the airfoil blade(s) one above the other in case of any need, to enhance the generation of power. Thus the present invention besides modularizing the design of turbine also ensures structural stability to the tower and turbine structure by reducing the wobbling action in an economical manner, without incurring the further expense of material.

Object of the Invention

It is an object of the invention to provide a cost effective method and system of inverted mounting of the nacelle over the turbine and thereby enabling stacking the airfoil blade(s) of the wind turbine if required in multi-stage mode of operation. It is an object of the invention to provide a cost effective method and system of mounting the nacelle at an inverted position over the turbine for the structural rigidity of the tower and turbine structure.

It is an object of the invention to enable stacking of the airfoil blade(s) one above the other if required in multi-stage mode of operation by means of mounting the nacelle at an inverted position over the turbine, to increase the power generating capacity of the wind turbine.

It is an object of the invention to fix the nacelle with the support plate to secure the nacelle in place and for preventing the nacelle from rotating along with the turbine, by means of guy wires from the base anchored to the support plate,

It is an object of invention to minimize wobbling of the turbine on the structure by means of mounting the nacelle at an inverted position over the turbine thereby providing structural support to it. It is an object of invention to modularize the design of the turbine by means of mounting the nacelle at an inverted position over the turbine thereby bringing flexibility to its design.

It is an object of invention to prevent discrepancies like wobbling of turbine, which is the source for the development of stress.t is yet another object of invention to minimize the gyroscopic vibration when the machine veers with changing wind direction and its effect on the turbine and tower structure, by relieving the stress acting upon them

It is yet another object of invention to minimize the stress developing on the tower and turbine structure due to misalignment by having a single rotating structure. The stress is minimized by means of mounting the nacelle at an inverted position over the turbine

Statement of the Invention

The system of mounting the nacelle at inverted position enabling stacking the airfoil blade(s), said system comprising of:

A. The stackable/cascade able airfoil blade (1) for generating the power from the approaching wind., said stacking/cascading being carried out, depending on whether the mode of arrangement of airfoil blade is single stage or multistage,

B. The rotor (2), said rotor for transmitting the power generated by the turbine (T) to the generator.

C. The arms (3), said arms for holding the airfoil blade(s) (1) are attached to the rotor (2).

D. The tower (4), said tower for housing the turbine (^"I ) along with the totor (2) and to withstand against the wind.

E. The nacelle (5), said nacelle for driving the turbine (T) and to receive the power generated from the turbine (T).

F. The nacelle support plate (6), said plate supporting the nacelle for preventing the nacelle from rotating along with the turbine (T). G. The guy wires (7), said guy wire's one end is anchored to the support plate (6) and whose other end at the anchor enables holding the support plate (6) in position.

H. The anchor (8) for withholding the nacelle support plate (6) by means of guy wires (7).

While operating the turbine, the airfoil blade(s) attached to the rotor by means of arms tends to sag and it induces a wobbling effect which develops stress on the tower and turbine structure. Also when the airfoil blade(s) are cascaded while there is a need for excess generation of power, the stress developed and the wobbling of turbine is further increased. The present invention minimizes the stress by mounting the nacelle above the turbine and reduces the wobbling effect which is the factor for development of stress. Since the nacelle is mounted above the turbine, it paves the way for stacking the airfoil blades without any undesirable factors like wobbling and thereby the power generation can be increased economically.

Stacking of Airfoil Blade(s):

Wind turbine generates power by the kinetic energy of approaching wind which causes the rotation of airfoil blade(s). The generation of the power can be increased by many factors provided the swept area is increased by them. By increasing the number of stages of airfoil blade(s) the power generation can be increased. So, the airfoil blades are cascaded or stacked one above the other as per the need and thereby the power generation can be increased which is said to be stacking of airfoil blade(s). It is well known that the generation of power from the wind turbine will increase with the increase in stages of blades since the swept area is increased accordingly.

Wobbling of turbine:

When the turbine is mounted on the nacelle in the existing cases, the turbine is supported freely and it is subjected to sagging which tends to increase while it is being operated. The turbine mounted on the tower acts like a cantilever beam with the weight of the turbine acting as lateral point load on the structure. So the turbine tends to wobble during its operation due to the misalignment of the rotating components which may develops undesirable stress, bending moment and noise. The above phenomenon is said to be wobbling of turbine.

Working conditions:

The present invention discloses method of mounting the nacelle on the turbine at inverted position thereby enabling stacking the airfoil blade(s). The stacking of airfoil blade(s) comprises of two modes. A. Single stage mode

B. Stacking or Cascading mode(if there is a need for more power generation)

Single stage mode: As shown in the fig.1 the turbine is mounted on the tower with the nacelle mounted at inverted position with the airfoil blade(s) in a single stage. The nacelle is fixed with the support plate which is held in place by means of guy wires. The guy wires anchored at the base at one end and to the support plate at the other prevents the rotation of nacelle and transmits vibration while the turbine is being operated. The airfoil blade(s) mounted below the nacelle is mounted in a single stage as per the need of the power.

Stacking or Cascading mode:

As shown in the fig.2 the turbine is mounted on the tower with the nacelle mounted at inverted position with the airfoil blade(s) in a multi stage. There may be case to increase the generation of power from the turbine which can be accomplished by increasing the swept area. By having many stages of airfoil blades one above the other more power can be generated which is said to be stacking or cascading mode. The method of mounting the nacelle on the turbine at inverted position thereby mounting the airfoil blade(s) in single stage, said method comprises of:

A. Fixing the airfoil blade (1) in a single stage to the arms (3) which is in turn attached to the rotor (2).

B. Mounting the turbine (T) along with the rotor (2) on the tower (4).

C. Mounting the nacelle (5) concentrically above the turbine (T) to prevent the wobbling and development of stress.

D. Attaching the nacelle support plate (6) to the nacelle (5) for securing in position during the operation of turbine (T).

E. Anchoring the guy wires (7) to the anchor at one end and the other end to the nacelle support plate (6).

F. Deploying the guy wires (7) to prevent the movement of nacelle (5) while the turbine (T) is operated thereby minimizing the sagging of the turbine.

G. Deploying the anchor (0) for withholding the nacelle support plate (6) by means of guy wires (7).

The method of mounting the nacelle on the turbine at inverted position and the airfoil blades in multi stage, said method comprises of:

A. Fixing the airfoil blade (1) in a multi-stage to the arms (3) which in turn is attached to the rotor (2).

B. Mounting the turbine (T) along with the rotor on the tower (4).

C. Mounting the nacelle (5) concentrically above the turbine (T) and in inverted position to prevent the wobbling and development of stress.

E. Anchoring guy wires (7) to the anchor at one end and to the nacelle support plate (6) at the other end.. F. Deploying the guy wires (7) to prevent the movement of nacelle (5) while the turbine (T) is operated and minimizing the sagging of the turbine.

G. Cascading or stacking the airfoil blade(s) (1) if there is a need for more generation of power and mode of arrangement is multi stage..

Brief Description of the Drawings

Fig.1 illustrates the method of mounting the nacelle at inverted position deployed using the nacelle mounting system as embodied in the present invention, with the generation of power from single stage airfoil blade(s).

Fig.2 illustrates the method of mounting the nacelle at inverted position deployed using the nacelle mounting system as embodied in the present invention ,with the generation of power from multi stage airfoil blade(s) inclusive of, stacked or cascaded airfoil blades.

Fig.3 illustrates a block diagram showing the steps involved in the method of mounting the nacelle over the turbine at inverted position and enabling the airfoil blade(s) to be mounted in single or multi stage, said multi stage being inclusive of, stacked or cascaded airfoil blades resulting in generation of power air.

Detailed Description of the Drawings

The other and further features, advantages, and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings which are incorporated in and constitute a part of this invention, illustrate one of the embodiments of the invention, and together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure. It was with knowledge of the foregoing state of the technology that the present invention has been conceived and is now reduced to practice.

Fig.1 illustrates the method of mounting the nacelle at inverted position with the generation of power from single stage airfoil blades deployed using the nacelle mounting system. People skilled in the art will be aware that, the stacking of airfoil blade(s) comprises of two modes.

A. Single stage mode

B. Stacking or Cascading mode - (if there is a need for more power generation)

The airfoil blades (1) in single stage is mounted on the arms (3) and attached to the rotor (2). The nacelle (5) is mounted at inverted position over the turbine (T) and is held in place by the nacelle support plate or truss (6). The nacelle support plate (6) is anchored to the base by means of guy wires (7). The bearing is mounted for the smooth rotation of the turbine (T) and to accommodate the misalignment while the turbine is being operated. The position of the nacelle at the inverted position enhances the structural stability of the turbine (T) and it brings modularity to its design. It also prevents discrepancies like wobbling which is the source for the development of stress.

Fig.2 illustrates the method of mounting the nacelle at inverted position with the generation of power in multi-stage mode from stacked or cascaded airfoil blade(s) deployed using the nacelle mounting system. In order to generate more power from the turbine, there are cases in which the airfoil blades (1) are cascaded one above the other to generate more power by enhancing the swept area. But, cascading of airfoil blades (1) leads to sagging of the blades (1) which induce stresses in the structure and wobbling in the turbine (T). But in present invention since the nacelle(5) is mounted over the turbine (T) it acts as simply supported beam which does not induce any stress or wobbling in the turbine .The bending moment induced on the turbine is also considerably reduced since the turbine will undergo only the axial load. So, the present invention paves the way for the stacking or cascading of airfoil blades (1) without the undesirable factors explained above. Fig.3 illustrates a block diagram showing the steps involved in generation of power from single stage or multi stage inclusive of stacked/cascaded airfoil blade(s) with the nacelle mounted at inverted position.

The method of mounting the nacelle on the turbine at inverted position and the airfoil blades in single or multi stage, said method comprises of:

A. Fixing the airfoil blade (1) in a single stage to the arms (3) which in turn attached to the rotor (2).

B. Mounting the turbine (T) along with the rotor (2) on the tower (4).

D. Attaching the nacelle support plate (6) to the nacelle (5) for securing in position during the operation of turbine.

E. Anchoring the guy wires (7) to the anchor at one end and to the nacelle support plate (6) at the other end.

F. Deploying the guy wires (7) to prevent the movement of nacelle (5) while the turbine is operated and minimizing the sagging of the turbine (T).

G. Cascading/Stacking the airfoil blades (1) if there is a need for more generation of power.

The operation method of mounting the nacelle at inverted position over the turbine and the generation of power from single or multi stage blades is as follows:

While the wind turbine is mounted on the tower (4) with the nacelle (5) beneath the turbine (T), the turbine tends to sag while the turbine gains some speed during its operation. The turbine mounted on the tower (4) acts like a cantilever beam with a lateral point load (weight of turbine) at its end which generates enormous bending moment and the deflection of the entire structure. The cantilever effect will cause the turbine to sag and which generate stresses and also it tends to wobble which enhance the stress gradually. The present invention overcomes this drawback by mounting the nacelle (5) at inverted position over the turbine rather than mounting it beneath the turbine (T). The nacelle (5) mounted at inverted position is supported by nacelle support plate or truss (6) which is anchored to the ground at the anchor by means of guy wires. The nacelle is held in place by means of the guy wires and it provides structural support to the nacelle. Since the nacelle is mounted over the turbine and is held in place by guy wires(7), lateral movement of tower(4) and the turbine is minimized or avoided and the tower(4) is subjected to axial load alone which makes the tower(4) more rigid. Also, the present invention paves the way for the stacking or cascading of airfoil blade(s) (1) whenever there is a need to enhance the generation of power from the turbine (T) thereby the design of turbine can be modularized. The airfoil blade(s) (1) can be stacked or cascaded but still does not induce wobbling or stress so that the more power can be generated from the turbine as desired.

It will be obvious to a person skilled in the art that with the advance of technology, the basic idea of the invention can be implemented in a plurality of ways. The invention and its embodiments are thus not restricted to the above examples but may vary within the scope of the claims.

Further the above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.

Claims

I Claim:

1. The system of nacelle mounting at inverted position enabling stacking/cascading air-foil blades in wind turbine , said system comprising of:

A. The airfoil blade(s) (1), said airfoil blade(s) for generating the power from the approaching wind, said stacking/cascading being carried out, depending on whether the mode of arrangement of airfoil blade(s) is single stage or multistage..

B. The rotor (2), said rotor (2) for transmitting the power generated by the turbine (T) to the generator.

C. The arms (3) said arms (3) for holding the airfoil blade(s) are attached to the rotor.

D. The tower (4) said tower (4) for housing the turbine (T) along with the rotor (2) and to withstand against the wind forces.

E. The nacelle (5) said nacelle (5) for driving the turbine (T) and to support it.

F. The nacelle support plate (6) said nacelle support plate (6) or truss supporting the nacelle (5) for preventing the nacelle from rotating along with the turbine (T).

G. The guy wires (7) said guy wires (7) whose one end is anchored to the support plate (6) and whose other end at the anchor enables holding the support plate (6) in position.

H. The anchor (8) said anchor (8) for withholding the nacelle support plate (6) or truss (6) by means of guy wires (7).

2. The system as claimed in claim 1 wherein the airfoil blade(s) (1) generates power from the approaching wind.

3. The system as claimed in claim 1 wherein the rotor(2) is fixed concentric to the tower(4) for transmitting the power from the airfoil blade(s)(1) to the nacelle(5).

4. The system as claimed in claim 1 wherein the arms (3) mounting the airfoil blade(s) (1) provides structural support to the airfoil blade(s) (1).

5. The system as claimed in claim 1 wherein the tower (4) houses the turbine (T) and its accessories and withstand against the wind and also the lateral and axial load imposed by the turbine.

6. The system as claimed in claim 1 wherein the nacelle(5) mounted at inverted position over the turbine (T) and also to receive the power generated by the turbine.

7. The system as claimed in claim 1 wherein the nacelle support plate (6) or truss secures the nacelle (5) by providing structural support to it.

8. The system as claimed in claim 1 wherein the guy wires (7) anchored to the nacelle support plate (6) from the ground renders stability to the structure.

9. The system as claimed in claim 1 wherein the anchor withholds the support plate (6)by means of guy wires(7) to transmits vibration to the ground.

10. The system as claimed in claim 3 wherein the rotor(2) has provisions for stacking the airfoil blades(1) when there is a need for more generation of power and thereby the design of turbine (T) is modularized.

11. The system as claimed in claim 6 wherein the position of the nacelle (5) at inverted position restricts or minimizes the lateral load thereby minimizes the stress on the turbine (T).

12. The system as claimed in claim 11 wherein the wobbling of the turbine is minimized by the replacement of concentric members by an individual rotor (2).

13. The system as claimed in claim 6 wherein the nacelle(5) mounted at inverted position exerts only the axial load on the tower(4) which aids in structural stability of the tower(4).

14. The system as claimed in claim 7 wherein the nacelle support plate(6) transmits vibrations from the nacelle(5) to the ground by means of guy wires(7).

15. The system as claimed in claim 8 wherein the guy wires(7) transfers all the tension and the generated stress to the ground thereby adding stability to the structures.

16. The method of mounting the nacelle on the turbine (T) at inverted position and enabling the airfoil blades to be mounted in single or multi stage, said method comprising steps of:

B. Mounting the turbine (T) along with the rotor (2) on the tower (4).

C. Mounting the nacelle (5) concentrically above the turbine to prevent the wobbling and development of stress.

F. Having the guy wires (7) preventing the movement of nacelle (5) while the turbine is operated and minimizes the sagging of the turbine.

G. Stacking or cascading of the airfoil blade(s) (1) increased if there is a need for more generation of power.

17. The system as claimed in claim 1 where in mounting of nacelle (5)at inverted position above the turbine (T) with the generation of power from single or multi stage airfoil blade(s) (1) and method substantially as herein described with respect to the accompanying drawings.