GB2275970A

GB2275970A - Vertical axis wind turbines

Info

Publication number: GB2275970A
Application number: GB9404163A
Authority: GB
Inventors: Kenneth Morgan Davies
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-03-13
Filing date: 1994-03-04
Publication date: 1994-09-14
Anticipated expiration: 2014-03-04
Also published as: GB9305218D0; GB9404163D0; GB2275970B

Abstract

A building of rotunda form provides a stator within which a rotor 4 is mounted. The stator includes a series of funnels 7 which collect air flow from the windward side of the building and direct it inwardly and upwardly to impinge on the blades 6 of the rotor 4 to turn it. The rotor blades of the rotor are such that the blade root regions define a circle which is a substantial proportion of the overall rotor diameter. The rotor blades may be pivotally mounted. Other embodiments are taught wherein the funnelled wind is directed onto the blades horizontally. <IMAGE>

Description

"IMPROVEMENTS RELATING TO VERTICAL AXIS WIND TURBINES" This invention relates to Vertical Axis Wind Turbines or VAWTs. It is primarily concerned with those for driving electrical generators, and will be described in those terms, but it should be understood that it could have other applications, such as pumping.

Using the wind for the generation of electricity has been long established and in some countries, notably Denmark and the U.S.A., some parts of the countryside are forested with tall masts carrying huge two or three bladed propellers.

There is no doubt that these are useful contributors to the National electricity supply, but the structures are obtrusive and expensive.

Far less common, although there have been several proposals and a few built, are VAWTs. They have the advantage that they do not require means for turning them to face the wind. But large versions of these, which are necessary for generating a useful amount of power, are almost as obtrusive as the propeller variety and it is believed that, so far, no-one has made them as efficient.

It is the aim of this invention to provide a VAWT which should go a substantial way towards overcoming these drawbacks.

According to the present invention there is provided a VAWT comprising a rotor and a stator providing a housing for the rotor with ducts for capturing and funnelling wind onto the rotor blades and for allowing air to escape after having passed through or around said rotor, the rotor blades being mounted such that the diameter of the circle defined by the blade root regions is a substantial proportion of the overall rotor diameter.

In one form, the blades may be angled with respect to the vertical and the wind may be funnelled with a substantially upward component onto them. Alternatively, the blades may be radial and in a vertical plane, and the wind may be funnelled generally horizontally on to them with a substantial tangential as well as a radial component.

Preferably, the stator housing will hold the rotor in an elevated position well clear of the ground. The housing may be roofed and give the appearance of a rotunda, which can disguise the function of the building and give scope for architectural elegance or fancy. When used for generating electricity, the necessary gearing and generator may be housed centrally within this, directly below the rotor.

For a better understanding of the invention, some embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a divided horizontal section and plan view of a VAWT driven generator, Figure 2 is a divided section and elevation on the line II-II of Figure 1, Figure 3 is a part section on the line III-III of Figure 1, Figure 4 is a divided horizontal section and plan view of another VAWT driven generator, Figure 5 is a divided section and elevation on the line V-V of Figure 4, Figure 6 is a part vertical section of yet another VAWT-driven generator, Figure 7 is a perspective view from above of a component of the rotor of the VAWT of Figure 6, Figure 8 is a part vertical section of a further VAWT driven generator, Figure 9 is a detailed plan view of a variable pitch mechanism for governing the output speed of the VAWT, Figure 10 is a radial section view through the mechanism of Figure 9, Figure 11 is a view on arrows XI-XI of Figure 10; Figure 12 is a radial section view through an alternative form of variable pitch mechanism for governing the output speed of the VAWT, and Figure 13 is a divided vertical half section of a VAWT comprising a stacked cascade of rotors.

Referring to Figures 1, 2 and 3, a building 1 of rotunda form has a shallow conical roof 2 and provides a stator in which a VAWT is mounted to drive an electrical generator 3.

The VAWT has a rotor 4 comprising a central drum 5 from which blades 6 radiate. The drum 5 is of substantial radius, greater than the length of each blade 6. These blades are all angled similarly to the vertical and air is directed onto them in a generally upward and inward direction through funnels 7 in the housing 1. This is illustrated by the arrows in Figure 2. Also, towards the end of the funnels 7 the flow is deflected so that it impinges more squarely on the rotor blades 6, as shown in Figure 3. Grilles 8 are positioned in the funnels 7 for safety and to prevent ingress of large foreign bodies. It will be appreciated that, with the wind blowing from one direction, no more than half these funnels 8 will actually be directing air flow on to the rotor 4, and some will be capturing more wind than others.But collectively this will cause the rotor to spin, and used air will be carried round and escape through the corresponding funnels 8 on the lee side. It will not matter which direction the wind comes from, and shifts, sudden or otherwise, will have little or no effect.

The generator 3 is housed in a room below the drum 5 and is coupled to the rotor 4 via a gear box 9 and a central vertical shaft 11 surrounded by a split shroud 10. Bearings are indicated at 12 and 13. A platform 14 at first floor level gives access to these parts. Braking arrangements are not shown, but can be provided, and two forms of variable pitch mechanism are described below.

The funnels 8 overlie a circular arcade 15 surrounding the generator room. Arches and columns forming this arcade are primarily structural, but they can give interest and elegance to what could otherwise be a somewhat prosaic building.

Turning to Figures 4 and 5, equivalent parts are similarly referenced, but here the rotor 4 has a different blade arrangement and the funnels are correspondingly different. The rotor blades 16 are radial and in a vertical plane. The funnels 17 are defined by alternating vanes 18 and roof-supporting members 19, but all with substantially the same radial and tangential attitude so that airflow is directed as shown in Figure 4 to impinge on one side only of the blades 16.

In Figure 6, the funnels and rotor blades are similar to those of the first embodiment, but the hub 21 of the rotor is somewhat different. It is generally dished and journalled on a massive fixed column which is anchored to the floor. There is no support or stabilising provided by the roof structure. The hub 21 is carried at its upper end by bearings 22 and is supported by further bearings 23 on a thrust ring 24. The rotor is conveniently built up of sections as shown in Figure 7, these being mutually bolted together and to the hub 21. Immediately below this, the hub provides a disc 25 with which a brake 26 co-operates. At its lower end, the hub 21 has a gear ring 27 by which drive is transmitted to a gear 28 on a shaft 29 to the generator (not shown).

In Figure 8, the central stationary column 30 is extended upwards to be anchored in the roof structure. There are two rotors 4 stacked one on top of the other, both being of the Figure 6 type, with similar funnelling arrangements.

The rotors are no longer dished, but extend horizontally from their respective hubs. But otherwise, the arrangement is similar to that of Figure 6 and similar parts are correspondingly referenced.

The components may be fabricated from any suitable material, but it is envisaged that the funnels and blades in particular may be of moulded plastics, and smoothly contoured. Not only could this improve air flow and efficiency, but corrosion problems that can arise with metal are eliminated.

The rotors are all shown just centrally supported. This may suffice, but if sag is a problem there could be an annular bearing ring at or near the outer periphery.

Referring now to Figures 9, 10 and 11, there is illustrated a centrifugally actuated variable pitch mechanism for the blades 6 of the rotor 4. Each blade 6 is rotably supported by means of a blade spindle 38 carried in a mounting sleeve 31. A double-lugged collar 32 is secured to the spindle end and both may rotate through about 600.

A push rod 33 connects one of the lugs of the collar 32 to a governor rod 34 pivoted to the rotor structure at its radially inner end and formed with a bob weight at the outer end. The other lug of the collar 32 is connected to a collar 36 secured to the spindle end of an adjacent blade by a link rod 35. Thus, when the centrifugal force experienced by the governor rod overcomes the aerodynamic back pressure on the rotor blades, the blades will be moved towards a feathered position, thus limiting or reducing the rotor speed to a safe level. In this arrangement, pairs of adjacent blades share a governor rod, but the ratio of blades to governor rods may be adjusted as required.

Referring to Figure 11, the variable pitch mechanism here comprises the blade spindle 38 again supported for rotation to adjust the pitch of the blade. The spindle 38 is carried in a mounting sleeve 44 with its inner end supported in a bearer bracket 43. The intermediate portion of the spindle 38 carries a helical groove 42 which cooperates with a slidable block 41 having a pin which engages the groove 42. Radial movement of the block 41 outwardly moves the blade towards a feathered position. The block is urged towards its inner position by a spring 39. The spring characteristics and mass of the block are chosen to cause the blades to be feathered at a particular speed range, thus limiting the operational speed of the rotor.

Figure 13 shows a multi-storey arrangement comprising three stator/rotor arrangements of the type described with reference to Figures 4 and 5, of progressively smaller diameter stacked one above the other and above a stator/rotor arrangement of the type described with reference to Figures 1 and 2, and all driving a common shaft using locating rings and keyed sleeves.

An important feature of the arrangements disclosed herein is that the rotors are of relatively large diameter.

This has several significant aspects; the differential speed between the wind speed and the blade speed can be reduced, without requiring an excessive output shaft speed; the effective length of the funnels may be reduced, thus reducing the drag and aerodynamic losses before the wind reaches the rotor; the increased diameter increases the effective catchment area for wind and so ensures a high mass flow and thus energy conversion.

Claims

1. A VAWT comprising a rotor and a stator providing a housing for the rotor with ducts for capturing and funnel ling wind onto the rotor blades and for allowing air to escape after having passed through or around said rotor, the rotor blades being mounted such that the diameter of the circle defined by the blade root regions is a substantial proportion of the overall rotor diameter.

2. A VAWT according to claim 1, wherein the blades are mounted on a drum.

3. A VAWT according to claim 1 or 2, wherein said blades are angled with respect to the vertical and the stator is adapted in use to funnel the wind with a substantially upward component onto said blades.

4. A VAWT according to claim 3, wherein said stator is adapted in use also to impart to the wind a velocity component in the direction of rotation of said rotor.

5. A VAWT according to claim 1 or claim 2, wherein said stator is adapted in use to funnel the wind horizontally onto the blades, with a substantial horizontal as well as a radial component.

6. A VAWT according to claim 5, wherein said rotor blades are generally radial and in a generally vertical plane.

7. A VAWT according to any preceding claims, including means for varying the pitch of the blades on the rotor.

8. A VAWT according to claim 7 wherein said pitch varying means includes a drive member responsive to centrifugal force for varying the pitch of said blades, thereby to govern the speed of the rotor.

9. A VAWT according to any preceding claim, including one or more rotors stacked vertically above said first mentioned stator, and imparting drive to a common shaft.

10. A VAWT according to any of claims 1 to 8 including one or more stator/rotor combinations stacked vertically above said first mentioned stator and imparting drive to a common shaft.

11. A VAWT according to any preceding claim, wherein said blade root diameter is at least one half the overall diameter of the rotor.

12. A VAWT according to any preceding claim, wherein said stator in use holds said rotor in an elevated position from the ground.

13. A VAWT substantially as hereinbefore described with reference to and as illustrated in any of the accompanying drawings.

Amendments to the claims have been filed as follows 1. A VAWT comprising a rotor and a stator providing a housing for the rotor with ducts for capturing and funnelling wind onto the rotor blades and for allowing air to escape after having passed through or around said rotor, the rotor blades being mounted such that the diameter of the circle defined by the blade root regions is a substantial proportion of the overall rotor diameter.

2. A VAWT according to claim 1, wherein the blades are mounted on a drum.

9. A VAWT according to any preceding claim, including one or more rotors stacked vertically above said first mentioned stator, and imparting drive to a common hub.

10. A VAWT according to any of claims 1 to 8 including one or more stator/rotor combinations stacked vertically above said first mentioned stator and imparting drive to a common hub, 11. A VAWT according to any preceding claim, wherein said blade root diameter is at least one half the overall diameter of the rotor.