GB2051252A

GB2051252A - Apparatus for Extracting Energy from a Fluid Current

Info

Publication number: GB2051252A
Application number: GB7921376A
Authority: GB
Original assignee: Jordan C G
Current assignee: Jordan C G
Priority date: 1979-06-19
Filing date: 1979-06-19
Publication date: 1981-01-14

Abstract

The apparatus comprises a shaft (1) mounted for rotation about a vertical axis (A-A) and carrying at least one vane assembly (2) having first and second vanes (3 and 4) and mounting arms (5), the vanes being affixed to the arms (5) so that, in the absence of exposure to a fluid current, the vanes (3 and 4) both depend from the arms (5) and are angularly offset from the vertical in opposite directions. When exposed to a fluid current, e.g. wind, the vanes (3 and 4) both move relative to the vertical, in the same angular direction. <IMAGE>

Description

SPECIFICATION Apparatus for Extracting Energy From a Fluid Current This invention relates to apparatus for extracting energy from a fluid current and is especially, although not exclusively, concerned with wind-driven power generators.

Most wind-driven power generators proposed hitherto have employed a sail arrangement comprising an array of two or more sails or vanes .connected to a substantially horizontal drive shaft, and arranged so that when the drive shaft axis is substantially aligned with the wind direction, the sails or vanes can be driven thereby so as to sweep through a substantially vertical plane and turn the drive shaft about its axis. The need to provide such power generators with means to keep the drive shaft axis substantially aligned with the wind direction adds to the bulk, cost and complication of this type of generator.

Furthermore, whenever there is a change of wind direction, there is a delay before the sail array can be reoriented to face into the new wind direction, and during this time the generator is operating with reduced wind-power absorbing efficiency.

There have been some proposals to deal with this problem by employing an arrangement having a substantially vertical drive shaft driven by a sail or vane arrangement which is such that it will cause the drive shaft to rotate, in a predetermined direction, whatever the direction of the wind (assuming that it is generally horizontal). One power generator of this type is based on the well-known cup anemometer.

Another is the Savonius generator (U.S. Patent Specification No. 1,697,574, published in 1929).

In these generators, the reverse of the windcatching surfaces of the vanes or sails have to move against the wind for half of their rotational travel. These reverse surfaces are, of course, shaped so as to reduce their wind resistance, but nevertheless they do give rise to sufficient wind resistance as substantially to impair the efficiency of the generators, and at present vertical axis wind-driven power generators are employed for a very small number of purposes, such as for driving small generators on sailing vessels, where relatively small amounts of power are required and where the generator efficiency is not of great importance.

According to the present invention, there is provided apparatus for extracting energy from a fluid current, the apparatus comprising a drive shaft mounted for axial rotation about a substantially vertical axis, and at least one vane assembly mounted on said drive shaft for rotation therewith, said vane assembly comprising a first vane and a second vane and means mounting said first and second vanes on opposite sides of said drive shaft, said first and second vanes being affixed to said mounting means so that, in the absence of exposure to a fluid current, said vanes both depend from the mounting means and are angularly offset from the vertical in opposite directions, and said mounting means being arranged to operate so as to permit rotational movement of said vanes when exposed to a fluid current, such that said vanes are both moved relative to the vertical in the same angular direction.

In common with the prior power generators mentioned above having a vertical drive shaft axis, the apparatus of the present invention is multi-directional in that it does not require means to adjust the attitude of the drive shaft when the direction of the fluid current changes, so long as the latter direction continues to lie substantially in a plane which is perpendicular to the axis of the drive shaft, i.e. so long as it continues to lie in a horizontal plane when the apparatus has been set up in its normal operating attitude, with the drive shaft axis vertical.

Unlike those prior vertical drive shaft axis generators, the apparatus of my present invention has vanes which, in operation of the apparatus, can automatically adjust so as to increase the area presented to the fluid current when being driven by it and also decrease the area presented to the fluid current when returning against it.

Thus, in the, or each, vane assembly of my apparatus, when the first vane (say) is angularly offset from the vertical so as to face into the fluid current, the effect of the fluid current on the first vane will be to cause it to rotate towards the vertical, thus increasing the area presented by the first vane to the fluid current; this rotation of the first vane causes, through the mounting means, rotation of the second vane, in the same angular direction, so that it rotates further away from the vertical, and the area presented by the second vane to the fluid current decreases. The effect of the fluid current on the second vane is to reinforce the turning effect on the vanes.

Preferably, in a vane assembly of an apparatus in accordance with my invention, the driven surface of the first and second vanes is substantially continuous. I also prefer that the first and second vanes should both be substantially planar. I have also found it desirable that each of the first and second vanes should generally lie in a plane which is perpendicular to that in which the other vane generally lies: with this arrangement, when one of the two vanes presents its driven face fully to the fluid current, the other, returning vane is edge-on to the fluid current.

In a preferred arrangement the mounting means for the first and second vanes comprises link means connecting the first and second vanes to each other, the link means being journalled so as to permit rotational movement about a substantially horizontal axis which runs generally lengthwise of the link means. This is a simple yet effective way to arrange that the vanes can undergo the required rotational movement when exposed to a fluid current. The link means may be positioned so that its substantially horizontal axis intersects the substantially vertical axis of the drive shaft; again, the arrangement is simple yet effective.

For smoothness and evenness of operation, and also to increase the power output available from the apparatus, I prefer to mount a plurality of the vane assemblies on the drive shaft. Preferably the vane assemblies are mounted in a stack configuration. I have found that greater efficiency can be achieved when the successive vane assemblies in the stack configuration are spirally staggered on the drive shaft.

Whenever there are a plurality of vane assemblies, I find it best that each vane assembly should be balanced by another vane assembly which is offset relative to it by one quarter of a revolution about the axis of rotation of the drive shaft.

In order that the invention may be more fully understood, some embodiments in accordance therewith will now be described with reference to the accompanying drawings, wherein: Figure 1 is a schematic, partial, perspective view of a wind-powered apparatus in accordance with the present invention having a single vane assembly; Figures 2 to 6 are a series of views of the apparatus shown in Figure 1 in different rotational positions during operation; Figure 7 is a schematic, partial, perspective view of a wind-powered apparatus in accordance with the invention having two vane assemblies; and Figure 8 is a schematic, partial, perspective view of a wind-powered apparatus in accordance with the invention having several vane assemblies, arranged in a spiral, stack configuration.

In each of the Figures, the respective apparatus is shown with its vanes oriented by a wind flowing from the right to the left side of the drawings; and the same or similar parts are shown by corresponding reference numerals and letters.

Referring firstly to Figure 1, the apparatus shown therein is primarily intended for extracting energy from the wind, and comprises a drive shaft 1 and a vane assembly shown generally at 2. The drive shaft 1 is mounted for axial rotation about a vertical axis A-A, by means of a suitably supported bearing at its top and another at its bottom end; the bearings and the means of supporting them are of conventional design and are not shown.

Vane assembly 2 comprises a first vane 3 and a second vane 4 mounted on opposite sides of the drive shaft 1 by a mounting means in the form of a link 5 to which the vanes 3 and 4 are fixedly attached so that, in the absence of exposure to the wind, vanes 3 and 4 depend from the link 5 and are angularly offset from the vertical in opposite directions; the attitude of the vanes in the absence of exposure to the wind is the same as that shown in Figure 4. Vanes 3 and 4 are both in the form of sheet-like rectangular members, so that in each case the driven surface is substantially continuous and the vane is planar. It will be seen that the respective planes in which vanes 3 and 4 lie are perpendicular to each other.

Link 5 is journalled in the drive shaft 1 at 6 so as to permit rotational movement, in the directions indicated by the double-headed arrow 7, about a substantially horizontal axis B-B which runs lengthwise of the link 5. Axis B-B intersects axis A-A.

In operation, wind acting on the vane assembly 2 in a generally horizontal direction causes the drive shaft 1 to turn in the direction of arrow 8, regardless of from which angle the wind is blowing. If rotation in the reverse direction is required, the attitudes of the vanes 3 and 4 are reversed, i.e. as viewed in the upper diagram of Figure 4, the attitude of vane 3 is reversed so that it projects towards, instead of away from, the observer, and the attitude of vane 4 is reversed so that it projects away from, instead of towards, the observer.

The energy extracted by the apparatus from the wind, due to the angular momentum of the rotation of the apparatus about the axis A-A, may be harnessed by coupling the shaft, either directly or through step-up gearing, for example, to any suitable apparatus, for example an electric generator.

I shall now describe, with reference to Figures 2 to 6, the manner in which the attitude of the vane assembly 2 varies during operation of the apparatus shown in Figure 1. In each of Figures 2 to 5, the upper diagram is a schematic, partial, perspective view similar to that of Figure 1 and taken from the same position, showing the apparatus at successive stages during one half revolution of the drive shaft 1 during normal operation of the apparatus, when the wind speed is nearly the maximum for which the apparatus has been designed, and the lower diagram shows the attitude of the vanes 3 and 4 at the respective stage, as seen by looking along axis B-B from vane 4 towards vane 3. The diagrams of Figure 6 are corresponding views of the vane assembly 2 when the apparatus has been struck by an abnormally high gust of wind.It will be recalled that in all of the Figures, the wind is blowing from right to left.

In the position shown in Figure 2, the vane assembly 2 is almost fully facing into the wind, and, as a result of the force due to the pressure exerted by the wind on the driven surface (surface 9) of the vane 3, as well as that due to the pressure exerted on the obverse surface (surface 10) of the vane 4, the assembly 2 is held in the position shown most clearly in the lower diagram, the moments of the two forces mentioned above being in balance with those due to the weights of the vanes 3 and 4. Thus, the driven vane, vane 3, presents almost a maximum area to the wind, and the returning vane, vane 4 presents almost a minimum area to the wind, being nearly in its edge-on position. It will be appreciated that for the vanes 3 and 4 to balance in the attitude shown in Figure 2, they will need to be of substantial weight (the precise value depending upon the optimum wind speed for which the apparatus is designed) so that they can therefore be of rubust construction and resistant to wind damage.

When the apparatus has rotated to the position shown in Figure 3, it is about half way between the head-on position shown in Figure 2 and the side-on position shown in Figure 4, and, as the wind pressure forces on surfaces 9 and 10 are lower than in the Figure 1 position, the vane 3 has rotated by a few degrees from the near-vertical position it occupied in the Figure 2 position to project it into the wind and the vane 4 has dropped by the same angular amount from its near edge-on position.

By the time the apparatus has rotated into the position shown in Figure 4, it is in its side-on position, and neither vane receives any turning force from the wind, and they have the attitude shown most clearly in the lower diagram, which attitude is the same as that when no wind is blowing. As soon as the apparatus has rotated under its own momentum past the Figure 4 position, it again begins to be driven by the wind, with the vane 4 being the driven one and the vane 3 being the returning one, so that the surfaces now acted on directly by the wind are the driven surface 11 of the vane 4 and the obverse face 12 of the vane 3.

If the apparatus is struck by an abnormally high gust of wind, the vanes adopt the attitude illustrated in Figure 6, the wind force acting on driven surface 9 of vane 3 being sufficiently great to take the vane assembly past the Figure 2 attitude to the attitude shown in Figure 6. When the vane assembly 2 is in that attitude, the turning moment acting on the shaft 2 due to the wind pressure on the driven surface 9 of vane 3 is lower than it would have been in the Figure 2 attitude, and furthermore it is opposed by a turning moment which is due to the wind pressure on the driven surface 11 of the vane 4.

Thus, the power extracting efficiency of the apparatus is automatically reduced in high winds.

It will be appreciated that the vane assembly 2 can automatically ease the rotational strain on the shaft 1 if it is governed or braked when the wind speed is greater than the optimum one for which the vane assembly has been designed, since under such conditions the vane assembly will adopt the attitude illustrated in Figure 6 to reduce the turning moment on the shaft 1.

For some types of operation, it is desirable to moderate the ease with which the vane assembly 2 can change its attitude under varying wind conditions, and in such circumstances I prefer to design the mounting means so that the rotational movement of the vanes 3 and 4 is damped, by hydraulic or other means, In theory, if the apparatus is in the Figure 4 position relative to the wind when it begins to blow, it will not be possible for the apparatus to begin to turn. In practice, the wind does not blow in a straight line manner, and, provided the apparatus is not subjected to excessive frictional forces or to too great an initial ioad, the wind will still be able to get the apparatus started.

Nevertheless, it will be appreciated from the foregoing description that the rate of power production, even in a steady wind, is far from constant and for this reason, and also to increase the rate of energy extraction, I prefer to employ a plurality of vane assemblies on the drive shaft.

Figure 7 shows an embodiment in which there are two vane assemblies, assemblies 2 and 2a.

Assembly 2 is the same as assembly 2 of the apparatus shown in Figure 1, and is mounted in the same manner on a drive shaft, which is again designated by numeral 1, the same reference numerals being used in Figure 7 as in Figure 1 for common features. Assembly 2a is the same as assembly 2, and its features are indicated by corresponding numerals with the suffix "a". As will be seen from Figure 7, assembly 2 is stacked above assembly 2a and is offset relative to it by one quarter of a revolution about the axis A-A of rotation of the drive shaft 1, the axes of the links 5 and 5a, axes B-B and B1-B1 respectively, being perpendicular to each other, so that the two assemblies balance one another.

For still greater wind energy-collecting efficiency, I prefer the arrangement shown in Figure 8, wherein the apparatus comprises several vane assemblies, 2, 2a, etc., mounted on a shaft 1 in a stack configuration, the successive link axes B-B, B,B1, B -B2, B3-B3, etc. being arranged in a spiral manner. Again, the axes B-B and B1-B1 of assemblies 2 and 2a are perpendicular to each other, and this is also so with each succeeding pair of axes, B2-B2 and B3-B3, etc. However, the displacement of each succeeding pair relative to its predecessor is not necessarily ninety degrees.The actual displacement is conveniently substantially less, and of the order of thirty degrees or even less, depending in part on the total number of assemblies in the stack to achieve a balanced system. Figure 8 diagrammatically illustrates a suitable support structure for the drive shaft 1 , the structure comprising a tripod support structure shown at 13, an upper bearing 14, and a lower bearing (not shown) for the foot of the shaft 1.

While the apparatus of the invention has been described with reference to its use for extracting energy from the wind, it will be appreciated that it can be employed to extract energy from any generally horizontally moving fluid, and in particular for extracting energy from rivers and sea waves.

As indicated earlier, the energy extracted by the apparatus of the invention, which initially appears as the energy of rotation of the apparatus about the drive shaft axis, may be harnessed by coupling the apparatus to an electric generator or any other suitable apparatus. By way of example only, I would mention use of my apparatus to propel small boats or large ships by directly transmitting the power to conventional water screws. This could give economies of sail without the complexities associated with sails, rigging and constant adjustment, tacking, etc. In fact, one could "sail" directly into wind and have normal rudder control.

Claims

1. Apparatus for extracting energy from a fluid current, the apparatus comprising a drive shaft mounted for axial rotation about a substantially vertical axis, and at least one vane assembly mounted on said drive shaft for rotation therewith, said vane assembly comprising a first vane and a second vane and means mounting said first and second vanes on opposite sides of said drive shaft, said first and second vanes being affixed to said mounting means so that, in the absence of exposure to a fluid current, said vanes both depend from the mounting means, and are angularly offset from the vertical in opposite directions, and said mounting means being arranged to operate so as to permit rotational movement of said vanes when exposed to a fluid current, such that said vanes are both moved relative to the vertical in the same angular direction.

2. Apparatus according to claim 1, wherein the driven surface of each of said first and second vanes is substantially continuous.

3. Apparatus according to claim 1 or claim 2, wherein said first and second vanes are substantially planar.

4. Apparatus according to any one of claims 1 to 3, wherein each of said first and second vanes generally lies in a plane which is perpendicular to that in which the other said vane generally lies.

5. Apparatus according to any one of claims 1 to 4, wherein said mounting means comprises link means connecting said first and second vanes to each other, said link means being journalled so as to permit rotational movement about a substantially horizontal axis which runs generally lengthwise of said link means.

6. Apparatus according to claim 5, wherein said substantially horizontal axis intersects said substantially vertical axis of said drive shaft.

7. Apparatus according to any one of claims 1 to 6, wherein said mounting means are arranged to operate so that said rotational movement of said vanes is damped.

8. Apparatus according to claim 7, wherein said mounting means is damped hydraulically.

9. Apparatus according to any one of claims 1 to 8, wherein there are a plurality of said vane assemblies mounted as aforesaid on said drive shaft.

10. Apparatus according to claim 9, wherein said vane assemblies are mounted on said drive shaft in a stack configuration.

1 Apparatus according to claim 10, wherein the successive vane assemblies are spirally staggered on said drive shaft.

12. Apparatus according to any one of claims 9 to 11, wherein each said vane assembly is balanced by another said vane assembly which is offset relative to it by one quarter of a revolution about the axis of rotation of said drive shaft.

13. Apparatus for extracting energy from a fluid current, the apparatus being substantially as hereinbefore described with reference to, and as schematically illustrated in, Figures 1 to 6 of the accompanying drawings.

14. Apparatus for extracting energy from a fluid current, the apparatus being substantially as hereinbefore described with reference to, and as schematically illustrated in, Figure 7 of the accompanying drawings.

1 5. Apparatus for extracting energy from a fluid current, the apparatus being substantially as hereinbefore described with reference to, and as schematically illustrated in, Figure 8 of the accompanying drawings.

1 6. Each and every novel invention hereinbefore disclosed.

New Claims or Amendments to Claims filed on 19June1980.

Superseded Claims 4 to 16.

New or Amended Claims 4 to 18.

4. Apparatus according to claim 1 or claim 2, wherein said first and second vanes are curved, in such a direction that in operation of the apparatus they each present a curved surface to the fluid current which is generally convex towards the fluid current in the direction of the height of the respective vane.

5. Apparatus according to any one of claims 1 to 4, wherein each of said first and second vanes generally lies in a plane which is perpendicular to that in which the other said vane generally lies.

6. Apparatus according to any one of claims 1 to 5, wherein said mounting means comprises link means connecting said first and second vanes to each other, said link means being journalled so as to permit rotational movement about a substantially horizontal axis which runs generally lengthwise of said link means.

7. Apparatus according to claim 6, wherein said substantially horizontal axis intersects said substantially vertical axis of said drive shaft.

8. Apparatus according to any one of claims 1 to 7, wherein said mounting means are arranged to operate so that said rotational movement of said vanes is damped.

9. Apparatus according to claim 8, wherein said mounting means is damped hydraulically.

1 0. Apparatus according to any one of claims 1 to 9, wherein said rotational movement of said vanes can extend sufficiently to enable each said vane when exposed to a relatively strong fluid current to pass beyond the point of maximum power absorption.

11. Apparatus according to any one of claims 1 to 10, wherein there are plurality of said vane assemblies mounted as aforesaid on said drive shaft.

12. Apparatus according to claim 1 wherein said vane assemblies are mounted on said drive shaft in a stack configuration.

13. Apparatus according to claim 12, wherein the successive vane assemblies are spirally staggered on said drive shaft.

1 4. Apparatus according to any one of claims 11 to 13, wherein each said vane assembly is balanced by another said vane assembly which is offset relative to it by one quarter of a revolution about the axis of rotation of said drive shaft.

1 5. Apparatus for extracting energy from a fluid current, the apparatus being substantially as hereinbefore described with reference to, and as schematically illustrated in, Figures 1 to 6 of the accompanying drawings.

1 6. Apparatus for extracting energy from a fluid current, the apparatus being substantially as hereinbefore described with reference to, and as schematically illustrated in, Figure 7 of the accompanying drawings.

1 7. Apparatus for extracting energy from a fluid current, the apparatus being substantially as hereinbefore described with reference to, and as schematically illustrated in, Figure 8 of the accompanying drawings.

18. A vessel, whenever equipped with a water screw arranged to be driven by apparatus in accordance with any one of claims 1 to 1 7.