GB2550062A

GB2550062A - Harnessing of energy from water flow

Info

Publication number: GB2550062A
Application number: GB1706652.3A
Authority: GB
Inventors: Ivar Hansen Jan
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-02-20
Filing date: 2017-04-26
Publication date: 2017-11-08
Anticipated expiration: 2037-04-26
Also published as: GB201706652D0; GB201702705D0; GB2547555A; GB2550062B; GB2547555B

Abstract

Apparatus for extracting electrical energy from a flow of water 10, comprises a buoyant support structure having a hull 20 carrying arrangements for extracting electrical energy from a flow of water. An endless belt arrangement 30 is mounted for travelling in either direction around a pair of end guide rollers (102, 104, 106, 108 figure 6) defining upper and lower portions of the belt, and a plurality of projections (110) fixed with respect to the belt protections extending generally perpendicular to the portions. A turbine arrangement(s) 40, 42, 46 is mounted for rotation about a horizontal axis parallel to the direction of travel of the belt upper and lower surfaces, mounted in an open-ended horizontally extending housing forming part of the hull. The energy-extracting arrangements being carried by the hull such that when the apparatus is located in water the lower belt portion of the belt arrangement is immersed and the upper belt portion is above the water surface, and the turbine is fully immersed.

Description

Title: Harnessing of Energy from Water Flow Field of the Invention

This invention concerns harnessing of energy from water flow with particular, but not exclusive, application to tidal flow.

Background to the Invention

There is currently much interest in exploiting sources of renewable energy, including harnessing energy from flowing fluids such as wind, wave and tidal motion. Tidal streams and currents represent a potentially very powerful, clean and reliable source of energy, with benefits of predictability, but the technology is still in its infancy and most proposals, prototypes and installations so far suffer from high installation costs and low efficiency.

Many such proposals use submerged turbines secured to the seabed by a pile or other bottom fixed support structure: see e.g. WO 2004/048774. A disadvantage of seabed or bottom mounted devices is that current velocity tends to reduce with depth below the water surface, thus reducing potential energy capture. Such devices are also potentially difficult, dangerous and expensive to install, particularly in areas of strong tidal flow. Maintenance of such submerged devices is also difficult and expensive, and is generally not possible in situ. In addition, the desirability of extracting energy efficiently from tidal flow in both flow directions presents further challenges.

Summary of the Invention

In accordance with the invention there is provided apparatus for extracting electrical energy from a flow of water, comprising a buoyant support structure having a hull carrying a plurality of arrangements for extracting energy from a flow of water, including an endless belt energy-extracting arrangement mounted for travelling in either direction around a pair of end guide rollers, defining upper and lower portions of the belt, and a plurality of projections fixed with respect to the belt to travel therewith, with the projections extending generally perpendicular to upper and lower portions of the belt; and a turbine energy-extracting arrangement having a turbine mounted for rotation in either sense about an axis parallel to the direction of travel of the belt upper and lower surfaces, the turbine being mounted in an open-ended turbine housing forming part of the hull, the energy-extracting arrangements being carried by the hull such that when the apparatus is located in water the lower belt portion of the belt arrangement is immersed and the upper belt portion is above the water surface, and the turbine is fully immersed.

In use, the apparatus is located in water. On calm, flat water, the upper and lower belt portions are oriented horizontally, with the lower belt portion being immersed in water and the upper belt portion being above the water surface. The turbine is fully immersed, with the turbine axis extending horizontally and with the turbine housing extending horizontally.

When the apparatus is positioned in a flow of water, such as a tidal flow, river flow etc., with the flow direction generally aligned with the direction of travel of the belt and the turbine axis, the flow will act to push the submerged projections of the belt lower portion, driving the belt to travel around the rollers, causing rotary movement of the rollers, and also causing rotary movement of the turbine. This rotary movement (of one or both the belt rollers and of the turbine) can be used to produce electrical energy, e.g. from an electrical generator in known manner. For example the roller(s) can be linked via an appropriate transmission arrangement to an electrical generator. The turbine can be similarly linked via an appropriate transmission arrangement to an electrical generator. Preferably, a separate, respective generator is associated with each energy-extraction arrangement. In this case, in the event of maintenance work being required on a generator, only the associated energy-extraction arrangement will need to be shut down, while the remaining arrangements can continue functioning.

The electrical energy so produced by the generators can be conveyed to shore, e.g. by one or more cables, preferably by a single common cable for reasons of economy. The apparatus thus in effect constitutes a floating power station.

The apparatus lends itself well to use in tidal flows, as the belt can travel in either direction and the turbine can rotate in either sense. Thus the belt travel direction and turbine rotation sense will simply reverse in response to water flow in the opposite direction, such as with tidal flow, without the need to reposition or adjust the apparatus in any way.

The apparatus can thus enable very efficient extraction of energy from a flow of water, particularly a tidal flow, tidal flow having the benefits of regularity, reliability and predictability.

The endless belt arrangement is preferably such that each projection is mounted for pivoting movement with respect to the belt about an axis transverse to the direction of travel, with the projections extending generally perpendicular to the upper and lower portions of the belt and undergoing pivoting movement in a downwards direction when passing around the rollers.

With such an arrangement, when a submerged projection reaches the downstream roller, and starts to move upwardly in a curved path, passing around the roller, the projection will pivot downwardly relative to the belt about a generally horizontal axis (typically under the action of gravity) so that the projection is no longer perpendicular to the belt. The projection is in a downwardly pointing orientation when it exits the water, facilitating a smoother transition from water to air, with less resistance, drag and potential turbulence that would be the case with a projection still perpendicular to the belt, thus increasing the efficiency of the transition and so reducing the drag on the roller, with enhanced ability for energy generation.

The projection returns to an orientation perpendicular to the upper belt portion after passing fully around the downstream roller and is conveyed upstream above the water in this orientation. When the projection reaches the upstream roller it will again pivot downwardly relative to the belt about a generally horizontal axis (in the opposite sense to pivoting at the downstream roller) so that it enters the water in a downwardly pointing orientation, again improving the efficiency of the transition between air and water. The projections pivot in similar manner at both end rollers, regardless of the belt travel direction, providing a symmetrical arrangement in which the belt travel direction and blade movement will simply reverse in response to water flow in the opposite direction, such as with a tidal flow, without the need to reposition or adjust the apparatus in any way.

The apparatus is preferably symmetrical about a mid-plane perpendicular to the length of the belt.

The belt is typically elongate in a direction aligned with the direction of travel of the belt.

The belt may be of openwork or continuous constructions, e.g. comprising a continuous flexible belt, a plurality of adjacent (contiguous or spaced) cross slats, two or more parallel chains etc., with appropriate guide means e.g. intervening guide rollers, supports etc. Suitable belt constructions, such as those used in the mining industry etc. will be well known to those skilled in the art.

The end rollers are typically of circular cross section. The rollers may extend across the full width of the belt, with a single roller at each end, or a respective roller wheel may be provided at each side of the belt, with a pair of aligned roller wheels at each end.

The projections are desirably symmetrical about a plane perpendicular to the belt and transverse to the belt. In a simple case, the projections are planar with parallel major faces. The projections may alternatively be biconcave, defining dished surfaces on either side for engagement by flowing water.

The projections preferably extend across the full width of the belt.

The projections of the apparatus are typically all the same or closely similar to each other, although this is not essential.

The projections are desirably pivotally mounted with respect to the belt, for pivoting movement in either direction (i.e. clockwise or anti-clockwise) from vertical. The pivoting movement is typically of limited extent and symmetrical in either direction.

The pivot axis is typically spaced from the plane of the belt.

Each projection is conveniently fixed to the belt by a mounting arrangement that defines the pivot axis and permits appropriate pivoting movement. The mounting arrangement may comprise a simple pivotal linkage between the projection and belt that cooperates directly with the projection and belt. More typically, the mounting arrangement includes an intervening component or components, e.g. one or more mounting plates fixed to the projection and/or belt. A single pivot may be provided, e.g. extending across the full width or the projection/belt, or aligned pivots may be provided, e g. a pair of pivots, once adjacent each side of the projection at or near the edge of the belt.

The mounting arrangement may comprise an elongate member, e.g. rod, fixed with respect to the base of the projection, extending along the belt in both upstream and downstream directions. One such member may be fixed to each edge of the projection, adjacent the edges of the belt. The member may carry a preferably semicircular side plate or support, so that the projection is held between two side plates. This arrangement acts to limit the extent of pivoting that is possible. The two side plates associated with a particular projection may be connected by one or more cross members extending across the width of the belt, for additional rigidity.

As noted above, the pivot axis is typically spaced from the plane of the belt. In this case the mounting arrangement may comprise one or more spacer members for maintaining the projection in appropriate orientation relative to the belt, spaced from the belt. For example, with the arrangement described above, the elongate member may carry spacer members at or near either end thereof, dimensioned to hold the projection perpendicular to the upper and lower portions of the belt.

The possible degree of pivoting of the projection is determined by the geometry of the arrangement, depending on factors including the spacing of the pivot from the belt and the extent, in the direction of travel of the belt, of the projection and/or mounting arrangement e g. an elongate member thereof as referred to above. Appropriate geometry can be selected to suit requirements.

The belt arrangement preferably comprises a multiplicity of projections that are preferably closely spaced with respect to each other, for example being spaced apart by a distance equal to or less than two times the vertical extent of each projection.

The apparatus of the invention may carry more than one endless belt arrangement, each such arrangement being of the same, similar or different construction. Further, the apparatus may carry more than one turbine arrangement, each being of the same, similar or different construction.

The or each turbine desirable comprises multiple, angled blades, e.g. of being the general construction shown in UK Design Registration No. 4020892. Such a turbine has a plurality, e g. 12, of planar blades mounted on a pivot shaft for alignment with the fluid flow direction. Each blade is conveniently generally in the form of a sector of a circle, with two planar sides extending at an angle, e.g. in the range about 30° to about 45°, and a circular side. The blades are mounted with the planar surface inclined, e.g. at an angle in the range about 30° to about 60°, with respect to a plane perpendicular to the flow direction, with adjacent blades overlapping each other. The angle of inclination may be adjustable. The number and dimensions of the blades is desirably such that the total surface area of the blades is greater than the area of a circle with a radius equal to the length of the planar sides of the blades.

The turbine housing conveniently comprises an open-ended, horizontally extending cylindrical or square section box.

The housing may include an outwardly flared tapered flow guide at each open end, preferably with sharp end edges, for guiding water flow to the turbine and causing the speed of flow of the water to increase, for increased efficiency. A respective turbine (of the same, similar or different construction) may be mounted at or near each open end of the housing, preferably within a tapered flow guide. The axes of the turbine are preferably aligned.

The turbine housing preferably comprises opposed vertical side walls, e g. forming part of a horizontally extending square or rectangular section open-ended box, and preferably terminating in sharp vertical end edges.

The hull preferably includes one or more cylindrical buoyancy hulls at the base of the turbine housing, extending horizontally in a fore-aft direction, parallel to the turbine axis.

The hull conveniently includes a horizontal, lower hull portion, forming a lower wall of the turbine housing, and preferably terminating in a sharp horizontal end edge. This portion may extend between two cylindrical buoyancy hulls, as discussed above.

Electrical equipment e g. electrical generators etc. is typically installed on the apparatus, enabling maintenance on site, if required, without the need to take the equipment onshore.

The buoyant structure may comprise one or more hull units, e.g. having one, two, three or more hull units. The hull units of a particular support structure may be of generally similar construction, but this is not essential. Each hull unit desirably comprises an open-ended horizontally extending turbine housing for one or more turbines, e.g. as discussed above.

For example, a single hull unit hull may comprise a turbine housing, e.g. as discussed above, with a belt arrangement mounted on an upper portion thereof, and also carrying one or more turbines on lower portions thereof The hull unit may also carry one or more side turbines, typically one on each side of the hull unit, in a symmetrical arrangement. A dual hull unit hull may comprise two similar side-by-side hull units, each with an associated belt apparatus and two end turbines, with side turbines on each side of the overall hull construction. Adjacent hull units may share a common vertical side wall and cylindrical buoyancy hull.

Similarly, a triple hull unit hull may comprise three similar side-by-side hull units.

The size and construction of the buoyant support structure, particularly the hull thereof, can be designed as appropriate, having regard to the nature and number of energy harnessing arrangements (belt or turbine) it is intended to carry, the intended location of use, etc.

The apparatus typically carries appropriate ancillary equipment including, e.g. navigation lights, foghorns and safety equipment such as rafts, lifeboats and helipads, installed according to marine guidelines; a position finding system and a communication system with shore; an anchoring system comprising anchors, chain and winches; electrical cables for shore delivery; valves, pumps and pipes sufficient for a working ballast system; at least one hydraulic crane installed on the deck/topside of the structure, in order to allow any submerged turbine to be hoisted up onto the deck where any repairs or maintenance work can be carried out; an appropriately sized battery bank to supply energy in case of an emergency ‘black-out’; sufficient accommodation units in case maintenance teams have to stay overnight and also where they can have their breaks and meals whilst working on the structure. In this way, any necessary maintenance and repairs can be carried out in situ.

The apparatus may be designed to be in a fixed position for the working life of the apparatus. Alternatively, the apparatus may be movable, being self-propelled or by being towed or otherwise transported. The apparatus may be secured in position of use, permanently or temporarily, e g. by use of at least four anchors and chains.

The apparatus can be produced in a range of different sizes, to suit different requirements.

The apparatus of the invention can be of simple and robust construction, and enable improved efficiency in energy harnessing, and is well suited to use in tidal flows. A schematic outline of typical embodiments of apparatus in accordance with the invention will now be described, by way of illustration, with reference to the accompanying drawings, in which:

Figure 1 is a schematic top view of apparatus in accordance with the invention;

Figure 2 is a schematic end view of the apparatus of Figure 1, in the direction of the arrow 2 in Figure 1;

Figure 3 is a schematic side view of the apparatus of Figure 1, in the direction of the arrow 3 in Figure 1;

Figure 4 is a further schematic side view of the apparatus of Figure 1, in the direction of the arrow 3 in Figure 1, with parts removed;

Figure 5 is a further schematic side view of the apparatus of Figure 1, in the direction of the arrow 3 in Figure 1, with parts removed, illustrating the hull;

Figure 6 is a schematic perspective view of a belt arrangement of apparatus in accordance with the invention;

Figure 7 is a schematic side view of the belt arrangement of Figure 6;

Figure 8 is a perspective view of part of the Figure 6 arrangement;

Figure 9 is an enlarged scale detail of a hinge arrangement suitable for use in the belt arrangement of Figures 6 to 8;

Figures 10 A, B and C illustrate hinging movement of the hinge shown in Figure 9;

Figures 11 A and B illustrate further the hinge of Figures 9 and 10;

Figure 12 is a plan view of a washer plate forming part of the Figure 9 arrangement;

Figure 13 is a side view illustrating the construction of a turbine suitable for use with the apparatus of the invention;

Figure 14 is an end view of the turbine of Figure 13;

Figure 15 is a schematic view, similar to Figure 2, of a dual hull unit hull apparatus in accordance with the invention;

Figure 16 is a schematic view, similar to Figure 2, of a triple hull unit hull apparatus in accordance with the invention, with side turbines not shown; and

Figure 17 is a schematic top view of the apparatus of Figure 16, shown at a smaller scale.

Detailed Description of the Drawings

It is to be understood that the drawings are very schematic, and are intended to illustrate the principle of the invention.

Figures 1 to 5 show schematically apparatus 10 in accordance with the invention, comprising a floating single hull unit hull 20 carrying an endless belt arrangement 30 and also four similar turbine arrangements 40, 42, 44, 46 for extracting energy from a flow of water. The apparatus 10 is shown floating in water, with the water surface shown at 50, and the direction of tidal flow indicated by arrow 60, with the turbines 40, 42, 44, 46 fully submerged and the belt arrangement 30 partially submerged. Each of the belt arrangement and turbines has associated therewith a respective electricity generator (not shown).

The hull 20 comprises a main elongate hull 70 of generally open-ended, open-topped rectangular box-like form, constituting a housing for turbines 44 and 46, as is apparent e.g. from Figure 2, orientated with the length of the hull extending in a fore-aft direction between hull ends, aligned with the tidal flow direction 60. A pair of similar elongate, cylindrical horizontal buoyancy hulls 72, 74 with rounded ends are incorporated into the base of the main hull 70, extending in a fore-aft direction. The size, particularly diameter, of the buoyancy hulls is selected to provide appropriate buoyancy/ballast for the specific arrangement. The buoyancy is set so the belt arrangement and turbines are always in the correct position to harness energy from tidal flow, regardless of the state of the tide.

The main hull 70 comprises two vertical hull portions 71 constituting vertical side walls of the turbine housing and a horizontal lower hull portion 71a constituting a lower wall of the turbine housing. The hull portions are compartmented. The lower hull portion 71a functions as a physical support between the vertical hull portions 71 (also forming part of the flow guide as discussed below) and also has ballasting and damping functions, reducing vertical pitching and rolling movements of the apparatus 10 in high waves. When the apparatus is ballasted down to the correct level, several thousand tons of water will be ‘trapped’ between the vertical hull portions 71 and the horizontal hull portion 71a. When wave forces try to either lift or lower the apparatus in the sea or cause pitch or roll, this ‘trapped’ water will function as a ballast, and will have to be displaced either in or out depending on the buoyancy power in the sea. By the time this water has been displaced, the wave causing this problem will have passed, and no serious vertical movement will have been registered. Considering an embodiment in which the hull is 30m long, 25m high with 21m between the vertical side walls, the contained volume is 15,750m^ which contains 15,750 tonnes of water.

The belt arrangement 30 is carried on an upper portion of hull 70, with the belt extending in a fore-aft direction. Two end turbines 44, 46 are carried near the open ends of the hull 70. A deck (not shown) is provided and the hull 70 on which appropriate ancillary equipment may be carried. A pair of similar side frameworks 76, 78 extend outwardly from the hull 70, and these carry the side turbines 40, 42.

The hull 70 is shaped at the ends to form an outwardly flared tapered flow guide at each open end, with sharp end edges, surrounding the end turbines, as shown at 80, 82 in the figures, with the side walls and bottom wall all being outwardly inclined as shown in Figure 5. This configuration acts to guide water to the end turbines 44, 46. The bottom wall upper and lower faces both have inclined ends, meeting at an acute angle to form a horizontally extending sharp edge 90, 92 at each end, constituting a sharp end edge at the bottom of the turbine housing. The inclined ends of the side wall inner faces meet the side wall outer faces at an acute angle, forming vertically extending sharp edges 94, 95, 96, 97 at each side of the turbine housing, constituting further sharp end edges.

The belt arrangement 30 represented in Figures 1, 2 and 4 is shown in more detail in Figures 6 to 12. The arrangement comprises an elongate endless belt 100, e.g. a continuous belt of robust, flexible material such as is used in the mining industry etc., mounted for travelling around end guide roller wheels 102, 104, 106, 108, with a pair of aligned roller wheels defining a roller (represented by the circles in Figure 1) at each end, so that the belt can travel in either elongate direction.

The belt 100 carries a multiplicity of similar projecting blades 110, fixed with respect to the belt to travel therewith. The blades are closely spaced with respect to each other, with adjacent blades being spaced by a distance approximately equal to two times the vertical extent of each blade, as shown in Figure 6. Each blade 110 is of planar form, having two parallel major opposed rectangular faces, extending across the full width of the belt. Each blade 110 has a respective elongate member 120, 122 rigidly fixed to the base thereof, the elongate member extending by an equal distance along the length of the belt in both upstream and downstream directions Each such member carries a semi-circular side plate 130, 132, with the plates connected by a framework of cross members 136 to provide a rigid structure, as best shown in Figure 8. The side plates 130, 132 also function to hold or trap water on the blade, for improved efficiency.

This rigid structure, incorporating blade 110, is pivotally mounted with respect to the belt for limited pivoting movement in either clockwise or anti-clockwise direction, as represented in Figure 7, by a hinge arrangement 140 e g. as shown in Figures 9 to 11, with one such arrangement at each side of the belt.

The hinge arrangement of Figures 9 to 11 comprises a pair of apertured mounting plates 150, 152, each having a base member 154 and three apertured upstanding link members 156, 156’ with aligned openings 158, 158’ therethrough. As shown in Figure 9, one plate 150 is secured rigidly with respect to the adjacent elongate member 120 or 122 by means of bolts 170 extending through aligned apertures therein, and the other plate 152 is rigidly secured with respect to the belt 100 by means of bolts 172 extending though aligned apertures therein, with an associated flexible washer plate 174 having side strips 176 (Figure 12). The link members 156 are interleaved with each other as shown in Figure 1 IB, with a pivot bolt 180 passed through the aligned openings 158, 158’ to define a pivot axis permitting relative pivoting of the plates 150, 152 in either clockwise or anti-clockwise senses, as shown in Figures 10 A, B, C. In this way, the associated blade 110 can pivot relative to the belt 100.

The blade 110 (and associated supporting structure) is thus pivotally mounted with respect to the belt above a pivot axis defined by bolt 180 that extends across the width of the belt and is slight spaced from the plane of the belt.

The members 120, 122 each carry a spacer member 190, 192 at each end thereof. The spacer members have a height equal to the spacing of the pivot axis from the belt, and so function to hold the blade 110 perpendicular to horizontal portions of the belt 100. However, when the belt 100 passes in a curved path around end roller wheels 102, 104, 106, 108, the blades 110 and associated structure can pivot with respect to the belt, pivoting in a downward direction, e.g. as shown at the right-hand side of Figure 7, under the action of gravity.

The belt arrangement 30 is mounted on the hull 20 so that the belt has upper and lower horizontal portions, with the upper portion above the water surface and the lower portion submerged, e g. as shown in Figures 4 and 7.

In use, the apparatus 10 is positioned in flowing water, e.g. a body of water subject to a tidal flow, with the length of the belt aligned with the flow direction 60.

When the apparatus is positioned in a flow of water, with the flow direction 60 generally aligned with the direction of movement of the belt 100, the flow will act to push the submerged blades 110 of the belt lower portion, driving the belt to travel around the end rollers, causing rotary movement of the rollers. The rotary movement of one or both of the end rollers is used to produce energy, from an electrical generator (not shown) in known manner. For example, the roller(s) can be linked via an appropriate transmission arrangement to an electrical generator. When a submerged blade reaches the downstream roller, and starts to move upwardly in a curved path, passing around the roller, the blade will pivot downwardly relative to the belt about a generally horizontal axis, so that the projection is no longer perpendicular to the belt. The blade is in a downwardly pointing orientation when it exits the water, as shown at the right-hand side of Figure 7, facilitating a smoother transition from water to air, with less resistance, drag and potential turbulence that would be the case with a blade still perpendicular to the belt, thus increasing the efficiency of the transition and so reducing the drag on the roller, with enhanced ability for energy generation.

The blade returns to an orientation perpendicular to the upper belt portion after passing fully around the downstream roller and is conveyed upstream above the water in this orientation. When the blade reaches the upstream roller it will again pivot downwardly relative to the belt about a generally horizontal axis (in the opposite sense to pivoting at the downstream roller) so that it enters the water in a downwardly pointing orientation, again improving the efficiency of the transition between air and water.

Figures 13 and 14 illustrate a turbine construction suitable for use as turbines 40, 42, 44, 46. This is as covered in UK Design Registration No. 4020892.

The illustrated turbine comprises 12 similar planar blades 200 mounted on a pivot shaft 210 for alignment with the fluid flow direction 60. Each blade 200 is generally in the form of a sector of a circle, with two planar sides extending at an angle of about 45°, and a circular side. The blades are mounted with the planar surface inclined e.g. at an angle in the range about 30° to about 60°, with respect to a plane perpendicular to the flow direction 60, with adjacent blades overlapping each other. The number and dimensions of the blades is such that the total surface area of the blades is greater than the area of a circle with a radius equal to the length of the planar sides of the blades. The angle of inclination of the blades can be adjusted to optimise energy recovery. The turbine can rotate in either sense, clockwise or anti-clockwise. The shaft is linked via an appropriate transmission arrangement to an electricity generator (not shown).

This turbine construction enables very efTicient harvesting of energy from flowing water.

In use, the turbines 40, 42, 44, 46 and the belt wheels 102, 104, 106, 108 will rotate around their respective axes when the water current flows. The energy gathered in their axes can be transferred to hydraulic pumps (not shown) on the hull deck and a hydraulic system will then activate generators/dynamos. The method for transferring this energy from the turbines etc. to the pumps can be via a gear (cogwheel) on the turbine axis and a shaft from the gearbox to the pump. Alternative methods include either a belt drive or a chain drive from an axis up to the hydraulic pump. Other arrangements for transferring the rotary motion to electricity generators, not necessarily involving hydraulic pumps, may also be employed.

The respective generators associated with each of the turbine arrangements and the belt arrangement are connected to a single, common cable to convey the electricity to shore, for reasons of economy.

The hull may carry optional ancillary equipment (not shown) e.g. as discussed above.

In a typical embodiment the hull has an overall height of about 30 to 40 meters, an overall side-to-side width of about 70 to 75 meters, and a fore-aft length of about 30 to 35 meters, with each turbine having a diameter of about 20 meters, and the belt apparatus having a width of about 20 meters and a length of about 25 meters. The end guide roller wheels 102, 104, 106, 108 each have a diameter of about 4 meters, and the blades 110 have a width of about 20 meters and a height of about 2 meters.

Apparatus of other sizes and constructions can also be provided, e.g. having one or additional belt apparatuses, and/or additional turbines suitably mounted thereon.

The components of the belt arrangement and turbines are typically made of metal, e.g. aluminium, steel etc., for robustness.

Figure 15 illustrates a dual hull unit hull apparatus, that is generally similar to the single hull unit hull embodiment of the previous Figures but has two similar side-by-side hull units 300, 310 and carries an additional belt arrangement and two additional turbines. Adjacent hull units share a common vertical side wall and cylindrical buoyancy hull. Each belt arrangement and turbine preferably has a respective electricity generator associated therewith, linked to a single, common cable for conveying electricity to shore.

Figures 16 and 17 similarly illustrate a triple hull unit hull apparatus with three similar side-by-side hull arrangements 320, 330, 340, with each hull unit carrying three aligned belt units 350 and also additional intervening turbines 360. The apparatus also includes side turbines corresponding to turbines 40, 42 of the apparatus of Figures 1 to 5, with two on each side, but these are not shown in Figure 16. Again, each belt arrangement and turbine preferably has a respective electricity generator associated therewith, linked to a single, common cable for conveying electricity to shore.

In multi hull unit hull embodiments, the common vertical side wall outer faces both have inclined ends, meeting at an acute angle to form a vertically extending sharp edge, e.g. as shown at 370 in Figure 17, constituting a sharped end edge of a turbine housing.

Claims

1. Apparatus for extracting electrical energy from a flow of water, comprising a buoyant support structure having a hull carrying a plurality of arrangements for extracting energy from a flow of water, including an endless belt energy-extracting arrangement mounted for travelling in either direction around a pair of end guide rollers, defining upper and lower portions of the belt, and a plurality of projections fixed with respect to the belt to travel therewith, with the projections extending generally perpendicular to upper and lower portions of the belt; and a turbine energy-extracting arrangement having a turbine mounted for rotation in either sense about a horizontal axis parallel to the direction of travel of the belt upper and lower surfaces, the turbine being mounted in an open-ended horizontally extending turbine housing forming part of the hull, the energy-extracting arrangements being carried by the hull such that when the apparatus is located in water the lower belt portion of the belt arrangement is immersed and the upper belt portion is above the water surface, and the turbine is fully immersed.

2. Apparatus according to claim 1, wherein the turbine housing has an outwardly flared, tapered flow guide at each open end.

3. Apparatus according to claim 2, wherein the flow guide has sharp end edges.

4. Apparatus according to claim 1, 2 or 3, wherein a respective turbine is mounted at or near each open end of the housing.

5. Apparatus according to claim 4, wherein the axes of the turbines are aligned.

6. Apparatus according to claim 4 or 5, wherein each turbine is mounted within a tapered flow guide of the housing.

7. Apparatus according to any one of the preceding claims, wherein the turbine housing comprises opposed vertical side walls.

8. Apparatus according to any one of the preceding claims, wherein the hull includes one or more cylindrical buoyancy hulls at the base of the housing, extending horizontally in a direction parallel to the turbine axis or axes.

9. Apparatus according to any one of the preceding claims, wherein the hull includes a horizontal, lower hull portion, forming a lower wall of the turbine housing.

10. Apparatus according to claim 9, wherein the lower hull portion extends between two cylindrical buoyancy hulls at the base of the housing, the buoyancy hulls extending horizontally in a direction parallel to the turbine axis or axes.

11. Apparatus according to any one of the preceding claims, wherein each projection of the endless belt is mounted for pivoting movement with respect to the belt about an axis transverse to the direction of travel, with the projections extending generally perpendicular to the upper and lower portions of the belt and undergoing pivoting movement in a downwards direction when passing around the rollers.

12. Apparatus according to claim 11, wherein the projection pivot axis is spaced from the plane of the belt.

13. Apparatus according to claim 11 or 12, wherein each projection is fixed to the belt by a mounting arrangement that defines the pivot axis.

14. Apparatus according to claim 13, wherein the mounting arrangement comprises one or more mounting plates fixed to the projection and/or belt.

15. Apparatus according to claim 13 or 14, wherein the mounting arrangement comprises an elongate member fixed with respect to the base of the projection, extending along the belt in both upstream and downstream directions.

16. Apparatus according to claim 15, wherein a respective elongate member is fixed to each edge of the projection, adjacent the edges of the belt.

17. Apparatus according to claim 16, wherein each member carries a side plate or support, so that the projection is held between two side plates.

18. Apparatus according to claim 17, wherein the two side plates associated with a projection are connected by one or more cross members extending across the width of the belt.

19. Apparatus according to any one of claims 13 to 18, wherein the pivot axis is spaced from the plane of the belt and the mounting arrangement comprises one or more spacer members for maintaining the projection in appropriate orientation relative to the belt, spaced from the belt.

20. Apparatus according to any one of the preceding claims, wherein the projections of the endless belt are symmetrical about a plane perpendicular to the belt and transverse to the belt.

21. Apparatus according to claim 20, wherein the projections are planar with parallel major faces.

22. Apparatus according to claim 20, wherein the projections are biconcave, defining dished surfaces on either side for engagement by flowing water.

23. Apparatus according to any one of the preceding claims, wherein the or each turbine comprises multiple, angled blades.

24. Apparatus according to any one of the preceding claims, wherein the buoyant structure comprises a hull having one or more side-by-side hull units, each hull unit comprising a horizontally extending housing for one or more turbines.

25. Apparatus according to any one of the preceding claims, including one or more electrical generators for generating electrical energy in response to movement of the endless belt and/or rotation of the turbine.

26. Apparatus according to claim 25, including a respective electrical generator associated with each of the endless belt arrangement and the or each turbine.