GB2459499A

GB2459499A - Wind turbine inlet duct

Info

Publication number: GB2459499A
Application number: GB0807548A
Authority: GB
Inventors: Michael Leslie John Coombs
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-04-25
Filing date: 2008-04-25
Publication date: 2009-10-28
Also published as: GB0807548D0

Abstract

A duct structure (12, figures 1 and 2), suitable for use as a wind turbine inlet, comprises a plurality of ducts (13, figure 3) arranged substantially in a circle. Each duct (13) comprises a relatively wider horizontal part 14 and a relatively narrower vertical part (15, figure 3) connected thereto. In use air enters the horizontal part 14 of the duct (13) and is then passed into the vertical part (15). The air then exits the vertical part (15) of the duct (13) and enters an air space 19 which is bounded, at least in part, by panels 18 extending from the exit ends of the vertical parts (15) of each duct (13). A vertical axis, but axial flow, turbine 20, 21 may be enclosed in the air space 19, a generator or alternator 22 being driven by rotation thereof. Restrictor means (figures 8-11) responsive to wind speed may be provided to control the amount of air that passes into the duct structure (12).

Description

I

Duct Structure for a Wind Turbine The present invention relates to a duct structure for enhancing the performance of a wind turbine.

Wind turbines usually comprise a propeller mounted for rotation in a vertical plane around a horizontal axis. Such wind turbines have inherent disadvantages. Among these disadvantages are the following: the propellers need to be of relatively large diameter to take advantage of the wind speeds which occur at higher levels above the ground; moreover, the propeller needs to be mounted to rotate about a vertical axis so that it can face into the wind. Wind speeds usually increase with height above the ground, and the propellers of wind turbines are usually sited as high as practicable, resulting in increased difficulty for access and maintenance.

An object of the invention is to provide a duct structure for a wind turbine which mitigates problems arising with conventional wind turbines.

The present invention provides a structure as defined in claim 1 of the set of claims following the present description. Preferred and/or optional features of the structure are the subject of other claims in the set of claims and/or are disclosed in the

description.

An objective of the present invention is to enhance the use of existing wind conditions so that a wind turbine using the duct structure of the invention will start producing power at lower ambient wind speeds. Another objective is to obviate the need to rotate the axis of the turbine or any mounting thereof to face the wind. Another objective is to hide the propeller of a wind turbine structure so that its movement is hidden and noise therefrom is reduced.

The invention is now further described by way of a non-limitative example and with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a side elevation of a duct structure of the invention; Figure 2 is a plan view of the duct structure of Figure 1; Figure 3 is a front view of a duct forming part of the structure of Figures 1 and 2; Figure 4 is an underneath view of the duct of Figure 3 in the directions of arrows A-A; Figure 5 is a side view of the duct shown in Figures 3 and 4; Figure 6 is a plan view of the duct of the duct of Figure 5; Figure 7 is a vertical cross-sectional view of a structure of the invention incorporating a horizontal wind turbine; Figure 8 shows the duct of Figure 5 equipped with a wind restrictor in its open position; Figure 9 is a front view of the duct of Figure 8; Figure 10 shows the duct of Figure 8 with the wind restrictor in a partially closed position; and Figure 11 is a front view of the duct of Figure 10.

Reference is made to Figures 1 and 2 in which a duct structure according to the invention is generally indicated by reference 12. The duct structure 12 comprises a plurality of identical ducts 13 arranged side-by-side in a circle. Referring also to Figures 3 to 6, each duct 13 has a relatively wide horizontally-directed opening 14 for the ingress of air to the structure 12. Each duct 13 also has a relatively narrow vertical part 15 and a connecting part 16 which connects the radially-inner end of the horizontally-directed opening part 14 to the top region of the vertical part 15, preferably in a smoothly-curving fashion. Thus, air passing into the relatively wide opening 14 is smoothly directed into the top of the narrow vertical part 15. Air passing downwardly via the vertical part is discharged from the bottom of the vertical part 15 via discharge outlet 17. The radially outer wall of the narrow vertical part is continued downwardly below the level of the discharge outlet so as to define part 18 of the boundary of a cylindrical space 19 in the structure 12 below the level of the discharge outlets from all the narrow vertical parts 15 of the duct 13.

When a wind blows at the location of the structure, air blows into the wide entrance openings 14 of those ducts which fully and partially face into the wind. The air is conducted through the ducts 13, initially horizontally, and is then turned vertically downwardly by the smoothly curving connecting parts 16 so that it then passes into and through the relatively narrow vertical parts 15 and is discharged therefrom via the outlets 17 into the cylindrical space 19 bounded by the wall parts 18. As the amount of air entering the wide horizontal entrance openings 14 is substantially equal to the amount of air passing through and discharged from the narrow vertical parts 15 of the duct, the speed of the air passing through the vertical parts 15 will be greater than the speed of air entering the ducts 13. For example, if the horizontal openings 14 have twice the cross-sectional area of the discharge outlets 17 of the vertical parts 15 of the ducts, air blowing into the horizontal entrance openings 14 will pass out of the discharge outlets 17 at about twice the speed of the incoming air. As depicted in Figure 7, a propeller can be located in the structure 12, in the cylindrical space 16, so that its blades 20 are situated in the fast-moving streams of air passing downwardly from the discharge outlets 17 on one side of the space 16, causing the propeller to rotate a central shaft 21 and thereby causing a generator or alternator 22 driven by the shaft 21 to produce electricity.

As is apparent from the foregoing, the ducts 13 have their entrance openings 14 facing in all directions around the central axis of the structure 12. This 3600 arrangement of the entrance openings 14 of the ducts 13 ensures that whichever direction wind blows from, air will always enter one or more of the entrance openings 14 of the intake ducts 13 and be conducted into the vertical duct for discharge onto the blades 20 of the propeller. The air flow passing the propeller is always in the same direction (e.g., vertically downwards as shown), and it is therefore unnecessary to change the axis of rotation of the propeller when the wind direction changes (as is the case with present conventional wind turbines). The number of bearings for the propeller can therefore be reduced (as compared to conventional wind turbines), e.g., to two bearings, such as upper and lower bearings (not shown) of the shaft supporting the propeller.

The structure of the invention comprises means for preventing self-destruction of the propeller when wind speeds are very high by restricting the area of the entrance opening 14 of each duct 13 in high winds. As shown in Figs. 8,9, 10 and 11, the restriction is realised by vanes which each have the general form of the letter "Z" and which are each attached by a hinge 23 to the top of the entrance 14 of each duct 13.

The "Z"-shaped vanes each comprise three flat parts 22, 26 27, and each part 22, 26 and 27 of each vane is at right angles to the adjoining part thereof. The base part 22 of the vane is inside the respective entrance opening 14 of the duct 13, and the upright S 3 part 26 and top part 27 are outside the entrance opening 14. The combined areas of the outer part 26 and top part 27 of the vane are greater than the area of the inner part 22. A weight 25 is attached by a support rod 24 to the outside part 26 of the vane to bias the vane to an open position in which the base 22 lies against the inside of the top of the opening 14 of the duct 13, as shown in Figs. 8 and 9. When the wind speed increases beyond a certain value, the outside part 26 of the vane (together with the attached fin-like or blade-like top part 27) is pivoted around the hinge 23 causing the inner part 22 to restrict the entrance 14 of the duct 13 (as shown in Figs. 10 and 11).

The ratio of the areas of the inner part 22 to the outside and top parts 26, 27 of the vane, together with the magnitude of the weight, ensures that at high wind speeds, the intake area is restricted (but not closed). Accordingly, air will pass to the propeller causing electricity generation even at very high wind speeds.

The structure of the invention would be mounted above and spaced apart from the ground by any suitable means.

For any location, the structure according to the invention will (compared to a conventional wind turbine) enable lower wind speeds to be utilised for electricity generation by a wind turbine, using fewer moving parts, and hiding or screening movement of the propeller 20.

Claims

CLAIMS: 1. A duct structure comprising a plurality of ducts arranged substantially in a circle, each duct comprising a relatively wider horizontal part arranged radially and having one end open to the air, a relatively narrower vertical part having one end adjacent to the other end of the horizontal part, a connecting part which connects the said other end of the horizontal part with the said one end of the vertical part, so that air entering the open end of the horizontal part is conducted to the vertical part, and a panel extending from the other end of the vertical part to define part of the boundary of an air space for receiving air passing out from the said vertical part.
2. The structure of claim 1 wherein the open ends of the horizontal parts extend 3600 around the structure.
3. The structure of claim 1 or claim 2 wherein, for each duct, the horizontal part is at the upper end of the vertical part.
4. The structure of any of claims ito 3 wherein each duct has the approximate form, in vertical cross-section, of an "r" or an inverted "j".
5. The structure of any of claims 1 to 4 wherein the outer wall of the vertical part and the lower part of the horizontal part and the said panel are formed from a single piece of relatively rigid sheet material such as sheet metal and/or plastics material.
6. The structure of any one of claims 1 to 5 wherein the horizontal part is substantially rectangular (e.g., square) in vertical cross-section.
7. The structure of any of claims 1 to 6 wherein the vertical part is substantially triangular or frusto-triangular in horizontal cross-section.
8. The structure of any of claims ito 7 wherein the said panels extend 3600 around the structure to define a substantially cylindrical air space.
9. The structure of claim 8 comprising a propeller mounted for rotation in a horizontal plane within the cylindrical air space, the axis of the propeller being coaxial with the structure, air discharged from the vertical part of one or more ducts passing onto the blades of the propeller.
10. The structure of claim 9 comprising an electric generator or alternator arranged to be rotated by rotation of the propeller.
11. The structure of any of claims ito 10 comprising restnctor means responsive to wind speed to restrict excessive amounts of air passing into the structure.
12. The structure of claim 11 wherein the said restrictor means comprises, for each horizontal part of each duct, a vane having the general form of a Z' which is hingedly attached to the top or bottom of the open end of a respective duct such that a first part of the vane on one side of the hinge is within the open end region of the duct, and a second part of the vane on the other side of the hinge is outside the duct, whereby pivoting of the vane around the binge causes the first part to restrict the open end of the respective intake duct, and means (such as a weight or spring) biasing the vane away from its restricting disposition.

13, The structure of claim 12 wherein the first part of the said vane has a smaller area than the second part thereof 14. The structure of claim 12 or claim 13 wherein the second part of the vane comprises a main part which is hingedly attached by one edge region to the duct, the opposite edge region having a vane or fin which is substantially perpendicular to the main part, such that tilting of the main part under increased wind strength increases the area of the vane or fin perpendicular to the wind.15, A structure substantially as described with reference to the drawings.16. A wind turbine structure substantially as described with reference to the drawings.Amendmnts to the claims have been filed as follows 1. A duct structure comprising a plurality of ducts arranged substantially in a circle, each duct comprising at its upper end a relatively wider horizontal part arranged radially and having one end open to receive air blowing into the duct, a relatively narrower vertical part having its upper end adjacent to the other end of the horizontal part, a connecting part which connects the said other end of the horizontal part with the said upper end of the vertical part, so that air entering the open end of the horizontal part is conducted to the vertical part, and a panel extending downwards from the other, lower end of the vertical part to define the boundary of a cylindrical air space for receiving air passing out from the lower end of the said vertical part, and a propeller mounted for rotation in a horizontal plane within the cylindrical air space, the axis of the propeller being substantially coaxial with the axis of the structure, air discharged from the lower end(s) of the vertical parts of one or more ducts passing onto the blades of the propeller on one side of the cylindrical space.2. The structure of claim 1 wherein the open ends of the horizontal parts extend 360° around the structure.3. The structure of claim 1 or claim 2 wherein each duct has the approximate form, in vertical cross-section, of an "r" or an inverted "j".4. The structure of any one of claims 1 to 3 wherein the horizontal part is substantially rectangular (e.g., square) in vertical cross-section.5. The structure of any of claims 1 to 4 wherein the vertical part is substantially triangular or frusto-triangular in horizontal cross-section.*.. * 6. The structure of any of claims 1 to 5 wherein the said panels extend 360° around the structure to define the substantially cylindrical air space. ,.**** 7. The structure of any of claims 1 to 6 comprising an electric generator or alternator arranged to be rotated by rotation of the propeller. S.. * 8. The structure of any of claims 1 to 7 comprising restrictor means responsive to * * wind speed to restrict excessive amounts of air passing into the structure.9. The structure of claim 8 wherein the said restrictor means comprises, for each horizontal part of each duct, a vane having the general form of a Z' which is hingedly attached to the top of the open end of a respective duct such that a first part of the vane on one side of the hinge is within the open end region of the duct, and a second part of the vane on the other side of the hinge is outside the duct, whereby pivoting of the vane around the hinge causes the first part to restrict the open end of the respective intake duct, and means (such as a weight or spring) biasing the vane away from its restricting disposition.A10. The structure of claim 9 wherein the first part of the said vane has a smaller area than the second part thereof 11. The structure of claim 9 or claim 10 wherein the second part of the vane comprises a main part which is hingedly attached by one edge region to the duct, the opposite edge region having a vane or fin which is substantially perpendicular to the main part, such that tilting of the main part under increased wind strength increases the area of the vane or fin perpendicular to the wind.12. A structure substantially as described with reference to the drawings.
13. A wind turbine structure substantially as described with reference to the drawings. * I III I I... * I I* 1S3II I,.S I..I * * I *I I