Abstract:
Apparatus for generating energy in which an oscillating air column created by wave motion continuously drives a turbine in one direction.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to the generation of energy from a moving fluid. 
     A number of systems have been proposed for extracting energy from waves. Reference is made in this respect to US2011/0101696; US2012/0038163 and U.S. Pat. No. 4,271,668. The last-mentioned case discloses a counter-rotating turbine which converts energy from an alternating air flow above a water surface into mechanical energy. In US2012/0038163 use is made of a dual rotor turbine configuration responsive to bidirectional air flow. US2011/0101696 makes use of an air turbine which rotates in one direction for an incident air flow received from opposite directions. 
     Oscillating water column devices for converting wave energy into usable electrical or mechanical energy are normally on shore, near shore or off shore, units which are rigidly erected on the ocean floor or which are tethered in a rigid manner to the ocean floor. During storm conditions these devices are vulnerable to damage and destruction. 
     The present invention is concerned with apparatus of simplified construction which can generate energy from fluid which flows alternately in opposite directions, and which has an enhanced capability to withstand the effects of stormy conditions. 
     SUMMARY OF THE INVENTION 
     The invention provides apparatus for generating energy which includes a housing, a passage which extends through the housing, which has a first end and a second end and which forms a path for fluid flow between the first end and the second end, and a turbine which is mounted at a location inside the passage for rotation about an axis which, at the location, is generally transverse to the fluid flow path, and wherein the passage is shaped to direct fluid flow, when the fluid is flowing from the first end towards the second end, onto the turbine thereby to cause the turbine to rotate about the axis in an operational direction and to direct fluid flow, when the fluid is flowing from the second end towards the first end, onto the turbine thereby to cause the turbine to rotate in the operational direction. 
     The turbine may include a plurality of vanes with respective outer edge sections and the passage may be shaped to direct fluid flow from either side of the turbine primarily onto the outer edge sections. 
     The passage is preferably shaped, by means of at least a first deflecting formation between the turbine and the first end, to direct fluid flow primarily onto a first region of the turbine which is displaced from the axis and is further shaped, by means of at least a second deflecting formation between the turbine and the second end, to direct fluid flow primarily onto a second region of the turbine which is displaced from the axis and wherein the second region is generally diametrically opposed to the first region. 
     The first end may be higher than the second end. The first end may be open to atmosphere. 
     The fluid is preferably air. 
     The apparatus may include a vessel which defines a chamber, a port at a lower end of the vessel which allows water to enter and then leave the chamber, a connection at an upper end of the vessel to the housing whereby the second end of the passage is placed in fluid flow communication with the chamber, and a mechanism for anchoring the vessel at a desired position. 
     The apparatus may include at least one buoyancy member fixed to the vessel. 
     The vessel preferably comprises a cylinder which is generally vertically orientated with a closure connected to an upper end of the cylinder. The port may be constituted by an open lower end of the cylinder. The anchor mechanism may comprise one or a plurality of flexible lines which are fixed to the cylinder and to one or more anchors. The buoyancy member may be fixed to an outer side of the cylinder. The housing may be connected to the vessel on the closure. 
     The turbine may be connected directly or indirectly to an electrical generator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is further described by way of example with reference to the accompanying drawings in which: 
         FIG. 1  illustrates in perspective apparatus for generating energy according to one form of the invention; and 
         FIG. 2  illustrates on an enlarged scale and in cross-section from one side, an upper portion of the apparatus of  FIG. 1 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  of the accompanying drawings illustrates in perspective apparatus  10  according to one form of the invention. The apparatus includes a vessel  12  of circular cylindrical form, with a lower end  14  and an upper end  16 . The lower end is open and faces downwardly. The upper end has fixed to it a conical closure  18 . A housing  20  is fixed to an opening  22  at an apex of the conical closure. 
     A buoyancy ring  30  is secured to an outer surface of the vessel  12 . 
     A plurality of tethering chains or ropes or cables  34  are fixed to reinforced mounting locations  36  at peripheral positions at the lower end  14  of the vessel. The tethering cables extend to a robust and substantial anchor  38  formed by a large mass. The anchor rests on an ocean bed  40 . 
     The water above the bed has what may be referred to as a still water level  42  which is above the buoyancy member  30 . Under calm conditions a longitudinal axis  48 , which extends through the apparatus, is generally vertical. A section of the apparatus is in the air above the still water level. 
       FIG. 2  illustrates from one side and in cross-section, on a substantially enlarged scale, a part of the conical closure  18  and the housing  20 . A passage  50  extends through the housing. The passage has a first end  52  which is lowermost and a second end  54  which is uppermost and which is open to atmosphere. The passage forms an air flow path  60  which is indicated by means of a dotted line between the first end and the second end. 
     A turbine  62  is mounted at a location  64  inside the passage  50 . The turbine has a central axis  66  which extends transversely to the path  60 , at least at the location  64 . The turbine has fixed to it, an electrical generator  68  which is notionally shown only. This generator may take on any suitable form known in the art and for this reason is not further described. The turbine includes a plurality of vanes  70  which extend radially from the axis  66 . Each vein is curved in a manner which is determined by taking into account fluid flow dynamics and has a thin leading edge  74  and a rounded thickened trailing edge  76 . From  FIG. 2  it is apparent that the turbine in cross-section has a circular profile. In a direction which is parallel to the axis  66  the turbine is elongate. The axis  66  and the vanes  70 , extend laterally inside the passage substantially between opposing walls of the housing  20 . 
     The housing has an inner wall  80  which is shaped, in two dimensions along the depth of the housing. A first inner surface  82  forms a first deflecting formation  84 , between the turbine and the first end  52  which extends inwardly in a gradual arc  88  so that the width  90  of the passage gradually decreases to a minimum dimension  94  adjacent the turbine. At this point a curved surface  96  of substantially circular shape is close to an outer rotational path  98  of the turbine. 
     A second deflecting formation  100  is formed between the second end  54  and the turbine. This deflecting formation is substantially in the form of a mirror image of the deflecting formation  84 . Thus, moving away from the second end  54  towards the turbine, the width  104  of the passage  50  decreases gradually along the length of a curved surface  106  of the deflecting formation. The surface  106  terminates close to the outer rotational path  98  of the turbine and is then linked to a curved surface section  108  of the wall  84  which is closely spaced from the path  98 , which bounds the path  98 . 
     The apparatus  10  is anchored at a suitable location on the ocean floor as shown in  FIG. 1 . The tethering devices  34  have lengths which allow the still water level  42  to be well above the buoyancy member  30 . As noted the lower end  14  of the vessel  14  is open and, under calm conditions, the water in the vessel is more or less at the level  42 . Air occupies the interior of the vessel, the conical section  18  and the housing  20 , above the water level  42 . 
     With wave action the level  42  oscillates up and down inside the vessel  12 . As the water level rises a column of air is expelled upwardly from the vessel and moves through the housing. As the water level drops the air flows through the housing  20  into the vessel  12 . Thus an interior of the housing is subjected to air flow which moves upwardly and downwardly, i.e. in opposite directions through the passage  50 . 
     When the air moves upwardly the air flow is deflected by the formation  88  to the left of the passage  50  (referring to  FIG. 2 ). As the cross-sectional area of the passage is reduced, moving towards the turbine, the air flow is accelerated and diverted to the left of the turbine i.e. the air flow impinges at a higher velocity on the outer edge sections of the vanes in a region  110 . Rotational movement is thus imparted to the turbine in a clockwise direction  112 , referred to as an operational rotational direction. The air passes with and around the turbine and then moves upwardly, above the turbine, to atmosphere through the open upper end  54 . As the water level in the vessel drops air flows in the reverse direction through the passage. Air enters at the second end  54  and is deflected by the formation  100  to the right, relative to the turbine and, in a similar manner to what has been described, the air velocity is increased due to the reducing cross-section of the passage as the air approaches the turbine. The air flow is thus directed primarily to the outer edge sections  114  of the vanes in a region  116  which is more or less diametrically opposed to the region  110 . Thus, the turbine is subjected to air flow which causes the turbine to continue rotating in the operational direction  112 . 
     The arrangement of the housing is thus one in which, irrespective of the direction of air flow through the housing, the turbine is forced to move by the air flow continuously in one direction. 
     In stormy conditions the oscillating water column contained inside the vessel  12  is moved to some extent laterally although it is restrained in a vertical direction. The flotation device  30  continuously urges the apparatus upwardly while the anchor  38  tethers the apparatus to the ocean bed. Thus, to a substantial extent, maximum use is continuously made of the oscillation of the water which is due to wave movement. 
     As used herein “wave” means any movement of water due to a swell which causes the water level to vary relative to the ocean bed, and, in particular, includes a wave swell. 
     The vanes are shaped so that negative pressure on the leading sides of the vanes provide rotational movement in the direction  112  as the accelerated air passes upwardly through the housing, and enters the atmosphere. Similarly, as a wave recedes, negative pressure within the upper region of the chamber draws air back through the passage where it is accelerated and deflected by the formation  106  onto the outer edges of the vanes. The negative pressure on the leading sides of the vanes continues to provide rotational movement in the direction  112  as the accelerated air passes and enters the upper region of the chamber.