APPARATUS FOR EXTRACTING POWER FROM WAVE MOTION

Abstract: An axial flow turbine (15) having separate flow paths (38, 39) controlled by non-return valves (47, 53) at outlets, for extracting power from fluid flow induced in a duct (11) by wave motion in a body of water (13) such as the ocean.

Description: APPARATϋS FOR EXTRACTING POWER FROM WAVE MOTION THIS INVENTION relates to apparatus for extracting power from the energy of waves generated in a body of water such as the ocean. It is an object of this invention to utilise wave motion in a body of water to generate mechanical power. In one form the invention resides in apparatus for extrac¬ ting power from wave motion in a body of water, said apparatus comprising : a duct located in the body of water whereby a fluid flow is induced through the duct as a result of wave motion in the body of water; and an axial flow turbine mounted to the duct such that the fluid flow passes through said turbine. According to a preferred feature of the invention the axial flow turbine comprises : a first and a -second vane assembly; a first fluid flow control means associated with one vane assembly to permit the fluid flow to act on the one vane assembly exclusively when the fluid flow is in one direction through the duct; and a second fluid flow control means associated with the other vane assembly to permit the fluid flow to act exclusively on the other vane assembly when the fluid flow is in the other direction. According to a further preferred feature of the invention the vane assemblies are connected to an output drive shaft such that said output drive shaft will undergo uni-direc- tional rotation as a result of rotation of said vane assemblies. According to a preferred feature of the invention defined in the immediately preceding paragraph, the first and second vane assemblies are mounted concentrically one about the other on the output drive shaft. With this arrangement, the axial flow turbine preferably includes inner, intermediate and outer shrouds concentric with the output shaft, the inner shroud being mounted on or formed integral with said output shaft, the inner shroud being in spaced relation to the intermediate shroud and the outer shroud being in spaced relation to the intermediate shroud, wherein the first vane assembly comprises a plu¬ rality of circumferentially spaced vanes extending between the inner and intermediate shrouds, and the second vane assembly comprises a plurality of circumferentially spaced vanes extending between the intermediate and outer shrouds. The invention will be better understood by reference to the following description of one specific embodiment as shown in the accompanying drawings in which : - Figure 1 is a plan view of the upper side of an axial flow turbine of apparatus according to the embodiment; Figure 2 is a plan view of the underside of the tubine of Figure 1; Figure 3 is a sectional elevation of the turbine with the fluid flow being shown in said other direction; Figure 4 is a sectional elevation of the turbine with the fluid flow being shown in-said one direction; Figure 5 is a section on 5-5 of Figure 1; Figure 6 is a section on 6-6 of Figure 1; Figure 7 is a plan view of the first and second vane assemblies; Figure 8 is a sectional elevation of an alternative arrangement of the axial flow turbine, with said fluid flow being shown in one direction; Figure 9 is a sectional elevation of the turbine of Figure 8 with the fluid flow being shown in the other direction; Figure 10 is a schematic view of the arrangement of the vanes of the first vane assembly of the turbine . of Figures 8 and 9; Figure 11 is a schematic view of the arrangement of the vanes of the second vane assembly of the turbin of Figures 8 and 9; Figure 12 is a sectional elevation of a further alternative arrangement of axial flow turbine, with fluid flow in one direction; Figure 13 is a sectional elevation of the turbine of Figure 12 with the fluid flow in the other direc¬ tion; Figure 14 is a schematic elevation of one arrange¬ ment of the duct of apparatus according to the embodiment; Figure 15 is a schematic elevation of a further arrangement of the duct; and Figure 16 is a schematic elevation of a still fur¬ ther arrangement of the duct. Referring to the drawings, a duct 11 is located in a body of water 13, such as the sea, in a manner whereby an alternating fluid flow is induced through the duct as a result of wave motion in the body of water. An axial flow turbine 15 is mounted to the duct 11 such that the fluid flow passes through the turbine. In the arrangement shown in Figures 1 to 7, the axial flow turbine 15 comprises a first vane assembly 17 and a second vane assembly 19 each connected to an output drive shaft 21. ' The vane assemblies 17 and 19 are located in a chamber 22 defined within a housing 23 which comprises a substantially circular side wall 25 and a pair of end walls 27. The output drive shaft 21 is journalled in bearings 29 which in the illustrated arrangement are carried by the end walls 27. An inner shroud 31, an intermediate shroud 33 and an outer shroud 35 are located in the chamber 22 concentric with the output drive shaft 21, the inner shroud being integral with the output drive shaft. The intermediate shroud 33 is spaced from the inner shroud 31 and the outer shroud 35 is spaced from the intermediate shroud 33. The inter¬ mediate shroud thus divides the chamber 22 into inner and outer annular sub-chambers 37 and 38 respectively. The first vane assembly 17 comprises a plurality of curcum- ferentially spaced vanes 41 mounted between the inner end intermediate shrouds, and the second vane assembly com¬ prises a plurality of circumferentially spaced vanes 43 mounted between the intermediate and outer shrouds. The vanes 41 are thus located within the inner sub-chamber 37 and the vanes 43 located within the outer sub-chamber 45. The respective vanes of the first and second vane assem- blies are mounted in opposed relation with respect to each other (as shown in Figures 5 and 6), the purpose of which will become apparent later. Means may be provided for selectively varying the pitch of the respective vanes of the first and second vane assem¬ blies. A plurality of first apertures 45 are formed in each end wall 27 of the housing for fluid communication with the inner sub-chamber 37. The set of first apertures 45 in the end wall 27a are each provided with valve means 47 arranged to permit fluid flow through first sub-chamber (i.e. over the first vane assembly) only when fluid flows through the duct 11 in one direction (as depicted by the arrows 48). When fluid flow is in the other direction, the valve means 47. close their respective apertures 45 against fluid flow and thereby do not allow the fluid flow to act on the first vane assembly. A plurality of second apertures 51 are formed in each end wall 27 of the housing for fluid communication with the outer sub-chamber 38» The set of second apertures 51 in the end wall 27b are each provided with valve means 53 arranged to permit fluid flow through the outer sub- chamber 38 (i.e. over the second vane assembly) only when the fluid flows in said other direction (as depicted by the arrows 54). When the fluid flows in said one direc¬ tion, the valve- means close their respective apertures 51 and thereby do not allow the fluid flow to act on the second vane assembly. The operation of the respective vane means 47 and 53 in the illustrated arrangement is controlled by the fluid flow itself. The valve means 47 comprise hinged flaps which move with the fluid flow in said one direction to open the apertures and in the other direction to close the apertures. Similarly, the valve means 53 may also comp¬ rise hinged flaps which move with fluid flow in said other direction to open the aperture and in said one direction to close the apertures. From the aforegoing, it is evident that when the fluid flow is in said one direction, it acts exclusively on the first vane assembly and thereby imparts rotational torque to that vane assembly and thus to the output drive shaft 21. When the fluid flow is in said other direction, it acts exclusively on the second vane assembly and imparts rotational torque to that vane assembly and thus to the output drive shaft. However, because the vanes of the second vane assembly are mounted in opposed relation to the vanes of the first vane assembly, the direction of the rotational torque applied to the output drive shaft when the fluid acts on the second vane assembly is the same as that applied to the outer drive shaft when the fluid acts on the first vane assembly. In other words, the output drive shaft undergoes uni-directional rotation as a result of rotation of the vane assemblies. In an alternative arrangement, the vanes of the first and second vane assemblies may be arranged in multi-stage formation, with stator vanes being provided for directing fluid flow onto the respective vanes at each stage of the first and second vane assemblies. Referring now to Figures 8 to 11, there is shown an arrangement of the first and second vane assemblies 117 and 119 respectively having two stages. Stator vanes 140a are arranged to direct fluid flow (when in said one direction) onto the vanes 141a at the first stage of the first vane assembly and stator vanes 140b are arranged to direct fluid flow onto the vanes 141b at the second stage. Similarly stator vanes 142b are arranged to direct fluid flow (when in said -fXJRE ^ other direction) onto the vanes 143b at the first stage o the second vane assembly and stator vanes 142a ar arranged to direct fluid flow onto the vanes 143a at th second stage of the second vane assembly. The arrangemen of the stator vanes 140a and 140b with respect to th vanes 141a and 141b is illustrated in Figure 10, and th arrangement of the stator vanes 142a and 142b with respec to the vanes 143a and 143b is illustrated in Figure 11. Referring now to the arrangement shown in Figures 12 an 13 of the drawings, a first vane assembly 217 is mounte on a first drive shaft 218 and a second vane assembly 21 is mounted on a second drive shaft 220. The second driv shaft 220 is tubular and has the first drive shaft 218 i rotatably mounted concentrically therein. The respectiv vanes of the first and second vane assemblies may be s arranged relative to each other that rotational torqu applied to the first and second drive shafts is uni directional. In such a case the first and second driv shafts may be coupled to the output drive shaft (no shown). Alternatively, the respective vanes of the firs and second vane assemblies may be so arranged relative t each other that the rotational torque applied to the firs shaft is opposite in direction to that applied to th second shaft. One of the contra-rotating shafts 218 an 220 may be coupled directly to the output drive shaft an the outer shaft may be coupled to the output drive shaf through a motion conversion mechanism which changes the direction of rotation of said other shaft. In a further arrangement (not shown) the first and second vane assemblies may be mounted one beside the other on a common output drive shaft.. In this case, the respective vanes of the first and second vane assemblies are in opposed relation so that uni-directional rotation is applied to the output drive shaft as the fluid flow acts exclusively on the first vane assembly when flow is in said one direction and exclusively on the second vane assembly when flow in said other direction. As mentioned beforehand, the duct 11 is located in the body of water 13 in a manner whereby an alternating fluid flow is induced through the duct as a result of wave motion in the body of water. In the arrangement illustrated in Figure 14, the duct 11 is formed underground in an area of land 71 margining the body of water 13. The lower end 73 of the duct communi¬ cates with the body of water and is located sufficiently far below the troughs of waves and minimum tide level to ensure that it remains fully submerged. A screen 75 is fitted onto the lower end of the duct to filter water entering the duct through that end. The upper end 77 of the duct communicates with atmospheric air. Water 79, which has entered the duct from the body of water, adopts a level corresponding to the water level of the body of water at the point directly above the lower end of the duct. Atmospheric air is contained in that part of the duct above the water 79. The axial flow turbine 15 is mounted at the upper end of the duct. Wave motion in the body of water induces fluid flow in the duct 11 and such fluid flow acts on the turbine 15. More specifically, wave motion in the water successively increases and decreases the depth of water above the lower end 73 of the duct, which leads to corresponding changes in the hydrostatic pressure at the inlet of the duct and in turn successive increases and decreases in the level of the water 79 in the duct. As the level of the water in the duct rises, the air in the duct is compressed somewhat and consequently part of it is expelled to atmosphere. As the level of the water in the duct falls, the remaining air in the duct is expanded and replenishment air is induced into the duct from atmosphere. This induced air flow in the duct, moving successively in one direction and then in the other direction, passes through the turbine, acting upon the turbine in a manner described herein¬ before. In the arrangement illustrated in Figure 15 of the dra¬ wings, the duct 11 is positioned off-shore and is suppor¬ ted in combination by the bed 81 of the body of water and a support structure 83 embedded or otherwise rigidly anchored to the bed 81. The lower end 73 of the duct communicates with the body of water 13 and the upper end 77 extends out of the water so as to communicate with atmospheric air. The upper end 77 of the duct is prefe¬ rably located above the crests of waves and maximum tide level so as to remain exposed to atmospheric air at all times. The axial flow turbine 15 is mounted at the lower end of the duct. As before, wave motion ' in the body of water induces fluid flow in the duct 11 and such fluid flow acts on the tur¬ bine. However in contrast to the arrangement illustrated in Figure 9, it is the induced water flow, moving succes¬ sively in one direction and then in the other direction, rather than air flow, that acts on the turbine. Referring now to the arrangement illustrated in Figure 16 of the drawings, the duct 11 is located off-shore and is supported on a support structure 87 embedded or otherwise rigidly secured to the bed 81 of the body of water. The lower end of the duct 11 communicates with the body of water and the upper end communicates with atmospheric air. The axial flow turbine 15 is mounted at the upper end of the duct. The fluid flow induced in the duct as a result OMPI of wave motion acts on the turbine in the manner described previously. The fluid flow in this arrangement may com¬ prise an air flow or a combination of air and water flow; in the latter case, the air-water interface would pass through the turbine. In a further arrangement (not shown) the duct may be disposed at an angle inclined to the vertical, with the lower end of the duct in communication with the body of water and the upper end in communication with either the body of water or atmospheric air. In a still further arrangement (not shown), the duct may be disposed at a generally horizontal attitude, preferably resting or supported on the bed of the body of water. The ends of the duct are spaced according to the typical wave lengths of the wave motion in the body of water so that one end is located beneath a wave crest while the other end is located beneath a wave trough, and vice versa. It should be appreciated that the scope of the invention is not limited to the scope of the embodiment described. In particular the fluid in the duct which acts on the turbine may comprise water from the body of water, air from atmosphere, or a combination of a column of water and a column of air the interface of which passes through the turbine with fluid flow. Alternatively, the duct may contain a fluid, such as oil, having a density lower than that of the body of water and greater than that of atmospheric air.

Claims: The Claims defining the invention are as follows :- ' 1. Apparatus for extracting power from wave motion in a body of water, said apparatus comprising : a duct located in the body of water whereby a fluid flow is induced through the duct as a result of wave motion in the body of water; and an axial flow turbine mounted to the duct such that the fluid flow passes through said turbine. 2. Apparatus as claimed in claim 1 wherein the axial flow turbine comprises : a first and a second vane assem¬ bly; a first fluid flow control means associated with one vane assembly to permit the fluid flow to act on the one vane assembly exclusively when the fluid flow is in one direction through the duct; and a second fluid flow control means associated with the other vane assembly to permit the fluid flow to act exclusively on the other vane assembly when the fluid flow is in the other direction. 3. Apparatus as claimed in claim 2 wherein the vane assemblies are connected to an output drive shaft such that said output drive shaft will undergo uni-directional rotation as a result of rotation of said vane assemblies. 4. Apparatus as claimed in any one of the preceding claims wherein the first vane assembly is located in a first fluid chamber and the second vane assembly is loca¬ ted in a second fluid chamber. 5. Apparatus as claimed in claim 4 wherein said first fluid flow control means comprises one or more first fluid inlet apertures and one or more first fluid outlet aper¬ tures associated with the first fluid chamber, and first valve means associated with said first fluid inlet aper¬ tures and/or said first fluid outlet apertures said first valve means being adapted to permit fluid flow through the first fluid chamber so as to act on the first vane assem¬ bly only when the fluid flow is in said one direction. 6. Apparatus as claimed in claim 4 and 5 wherein said second fluid flow control means comprises one or more second fluid inlet apertures and one or more second fluid outlet apertures associated with the second fluid chamber, and second valve means associated with said second fluid inlet apertures and/or said second fluid outlet apertures, said second valve means being adapted to permit fluid flow through the second fluid chamber so as to act on the second vane assembly only when the fluid flow is in said other direction. 7. Apparatus as claimed in claim 5 or 6 wherein opera¬ tion ' of the first and second valve means is controlled by the fluid flow. 8. Apparatus as claimed in any one of the preceding claims wherein the first and second vane assemblies are mounted one about the other on the output drive shaft. 9. Apparatus as claimed in claim 8 wherein the axial flow turbine comprises inner, intermediate and outer shrouds concentric with the output shaft, the inner shroud being mounted on or formed integral with said output shaft, the inner shroud being in spaced relation to the intermediate shroud and the outer shroud being in spaced relation to the intermediate shroud, wherein the first vane assembly comprises a plurality " of circumferentially spaced vanes extending between the inner and intermediate shrouds, and the second vane assembly comprises a plura¬ lity of circumferentially spaced vanes extending between the intermediate and outer shrouds. 10. Apparatus as claimed in claim 9 wherein the first an second vane assemblies are located within a chamber defined by a substantially circular side wall and a pair of end walls, said intermediate shroud dividing the cham¬ ber into said first and second chambers. 11. Apparatus as claimed in claim 10 wherein said first fluid inlet apertures and said second fluid outlet aper¬ tures are formed in one of said end walls, and said first fluid outlet apertures and said second fluid inlet aper¬ tures are formed in the other of said end walls. 12. Apparatus as claimed in any one of claims 1 to 7 wherein the first and second vane assemblies are mounted one beside the other on the output drive shaft. 13. Apparatus as claimed in any one of claims 2 to 7 wherein the first vane assembly is mounted on a first drive shaft and the second vane assembly is mounted on a second drive shaft. 14. Apparatus as claimed in claim 13 wherein the respec¬ tive vanes of the first and second vane assemblies are so arranged relative to each other that the first and second shafts are adapted to * undergo rotation in the same direction, and wherein the first and second shafts are coupled to said output drive shaft. 15. Apparatus as claimed in claim 13 wherein the respec¬ tive vanes of the first and second vane assemblies are so arranged relative to each other that the first and second shafts are adapted to undergo rotation in opposite direc¬ tions, and wherein one of the shafts is. coupled directly to the output drive shaft and the other is coupled to the output drive shaft through a motion conversion device which reverses the direction of rotation of said other shaft. O PI 16. Apparatus as claimed in any one of the preceding claims wherein the first and second vanes are arranged in a multi-stage formation. 17. Apparatus as claimed in any one of the preceding claims wherein one end of the duct communicates with the body of water and the other end of the duct communicates with atmospheric air. 18. Apparatus as claimed in any one of claims 1 to 16 wherein both ends of the duct communicates with the body of water and wherein one end of the duct is at a higher level than the other. 19. Apparatus as claimed in any one of claims 1 to 16 wherein the duct is submerged in the body of water and is disposed at a substantially horizontal, attitude, and ends of the duct being spaced according to the typical wave lengths of the wave motion in the body of water. 20. Apparatus as claimed in any one of the preceding claims wherein the fluid which acts on the axial flow turbine is water from the body of water. 21. Apparatus as claimed in any one of claims 1 to 19 wherein the fluid which acts on the axial flow turbine is atmospheric air. 22. Apparatus as claimed in any one of the preceding claims wherein the fluid which acts on the axial flow turbine comprises a column of water and a column of air. 23. Apparatus as claimed in claims 17 wherein the fluid which acts on the axial flow turbine comprises a fluid of density lower than that of the body of water and greater than that of atmospheric air. 24. Apparatus substantially as herein described wi reference to the accompanying drawings.

Inventors: FLEAY WILLIAM ARNOLD, FLEAY, WILLIAM, ARNOLD
Applicants: FLEAY WILLIAM ARNOLD, FLEAY, WILLIAM, ARNOLD
Application year: 1981
Main classification: E02B9
IPC codes: F03B13