Field of the invention

Disclosed herein is a wave-powered pump. In particular, the pump is configured as an oscillating water column device operable to pump water up from a first depth for depositing at a second, shallower depth. Corresponding systems and methods are also disclosed.

Backa round

Compared with shallow or surface sea water, deep sea water is typically lower in temperature and richer with nutrients, including elements such as magnesium, calcium, potassium, chromium, selenium, zinc, and vanadium. There is a desire to harness the nutritional value of deep sea water in aquaculture and aquafarming applications, including the cultivation of aquatic plants such as kelp.

To help kelp thrive, it is known to anchor kelp to a substrate in relatively shallow water such that the kelt can receive adequate sunlight. However, in open oceans, the sunlit surface layer lacks the nutrients more abundant in deeper water. In a previous study, researchers have used a 'kelp elevator' to depth-cycle the kelp such that the kelp is raised to shallower depths to receive sunlight during the day, and lowered at night to absorb the nutrients in deeper sea water. However, such depth-cycling techniques would utilise relatively complex devices with moving parts that are often electrically powered. Such techniques may also be relatively energy, cost and labour-intensive to set up and maintain and scale.

There is a need to address the above, and/or at least provide a useful alternative.

According to a first aspect of the present invention, there is provided an oscillating water column pump operable to draw water upwardly from a first depth and deposit the drawn water at a second shallower depth, the pump comprising: a chamber configured to be partially submerged in a body of water such that an open bottom of the chamber is below the water level so as to trap a pocket of air thereabove within the chamber; a one-way air outlet through which air trapped in the chamber is forced out when the water level within the chamber rises, the outlet inhibiting the return of air into the chamber when the water level therein falls, thereby creating a vacuum within the chamber above the water level therein; and a conduit configured to draw water at the first depth upwardly through the conduit and deposit it at the second depth, wherein the suction in the chamber causes the water to be drawn up the conduit from the first depth to the second depth.

The conduit may have a water inlet via which water at the first depth can be drawn upwardly through the conduit and toward the chamber and a water outlet via which the drawn water flows into the chamber above the water level in the chamber and is deposited from the chamber through the open bottom thereof.

The pump may further comprise: an aperture in the chamber through which air is drawn as the water level falls; an air turbine through which the air passes as it is drawn into the chamber via the aperture, and a propeller in the conduit, the propeller being coupled to the air turbine and operable to draw water through the conduit as air is drawn through the turbine and into the chamber.

The pump can have a water inlet via which water at the first depth can be drawn upwardly through the conduit and toward the chamber and a water outlet via which the drawn water flows, the conduit extending through the chamber so that the water outlet is external of the chamber.

The pump can further comprise an aperture formed in the chamber, wherein air drawn into the chamber through the aperture passes through a venturi, the venturi being in fluid communication with the conduit so that as air passes through the venturi, water is drawn upwardly through the conduit.

The pump can further comprise an accumulator at an upper end of the conduit, the accumulator being in fluid communication with the venturi for creating a suction effect within the accumulator for drawing water upwardly through the conduit.

The accumulator may have two adjacent fluid chambers through which the water is drawn, each chamber having an outlet with a one way valve, wherein the accumulator is connected to the venturi via an air line connected to the second chamber, so that, in use, the accumulator regulates pressure and flow of the water.

According to another aspect of the present invention, there is provided an oscillating water column pump operable to draw water upwardly from a first depth and deposit the drawn water at a second shallower depth, the pump comprising: a chamber configured to be partially submerged in a body of water such that an open bottom of the chamber is below the water level so as to trap a pocket of air thereabove within the chamber; a one-way air outlet through which air trapped in the chamber is forced out when the water level within the chamber rises, the outlet inhibiting the return of air into the chamber when the water level therein falls, thereby creating a vacuum within the chamber above the water level therein; and a conduit comprising: a water inlet via which water at the first depth can be drawn upwardly through the conduit and toward the chamber by the vacuum created therein; and a water outlet via which the drawn water flows into the chamber above the water level therein and is deposited from the chamber through the open bottom thereof.

The chamber of the pump may comprise a generally closed top via which air trapped in the chamber is forced out through the one-way air outlet. In certain embodiments, the chamber is substantially hollow and supported such that in use, the closed top of the partially submerged chamber is maintained above the water level.

It is envisaged that the conduit extends from the chamber to the first depth and is configured with one or more one-way valves for inhibiting backflow of water drawn through the conduit.

Embodiments of the present pump may further comprise a control system for maintaining a pressure of the air pocket within the chamber above a predetermined minimum. For example, the control system may be configured to admit air into the chamber to maintain a pressure of the air pocket above the predetermined minimum.

In certain embodiments, the pump may further comprise an additive inlet via which an additive can be mixed with the drawn water so as to be deposited therewith through the open bottom of the chamber.

According to a second aspect of the present invention, there is provided a method of drawing water up from a first depth and depositing it at a shallower second depth using an oscillating water column pump according to a first aspect of the present invention.

Brief description of the drawings

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic side view showing an oscillating water column pump according to a first embodiment of the present invention in situ wherein nutrient rich deep sea water is pumped up thereby for deposition therefrom above a kelp farm fixed at a shallower depth;

Figures 2A to 3B are a sequence of schematic side views illustrating the working principle underlying the present pump;

Figure 4 is a top perspective view of the pump of Figure 1;

Figure 5 is a schematic side view of an oscillating water column pump according to another embodiment of the invention;

Figure 6 is a schematic side view of an oscillating water column pump according to a further embodiment of the invention;

Figure 7 is a schematic side view of system having a plurality of oscillating water column pumps;

Figure 8 is a schematic side view of an oscillating water column pump according to a further embodiment of the invention; and

Figure 9 is a schematic side view of an oscillating water column pump according to a further embodiment of the invention.

Detailed

Figure 1 shows an example of how an oscillating water column pump 2 according to a first embodiment of the present invention may be deployed and utilised to pump or draw nutrient rich, colder and denser, deep seawater 4 upwardly so that it can be deposited at a shallower depth 6 over a kelp farm 8. Advantageously, the kelp farm 8 can remain fixed at a certain depth where it is able to receive sunlight during the daytime, and yet is also able to absorb nutrients from the deep seawater 4 deposited thereabove by the pump 2.

Advantageously, the pump 2 is substantially powered by naturally occurring wave energy and is configured to be relatively simple with few or no moving parts or no electrical systems. To the extent that any electricity is required, it is envisaged that it may be generated and/or stored via wave or solar energy.

As will be discussed in more detail, it is envisaged that the present pump 2 comprises a substantially hollow chamber 10 having a generally closed top 12 and an open bottom. Referring to Figure 2A, in use the chamber 10 is configured to be partially submerged in a body of water such that the open bottom thereof is below the water level 14, thereby trapping a pocket of air 16 within the chamber 10 and above the water level 14.

Chamber 10 preferably has a relatively sharp inside edge at its base which creates eddys 40 (Figure 3B) from the action of the waves which promote mixing of the seawater 4 being pumped. A mixing means may be provided within or below the chamber to further facilitate mixing of the seawater 4 being pumped.

The pump 2 also comprises a conduit 18 such as an elongate piping or tubing that extends downwardly from the chamber 10. The conduit comprises a water inlet 34 (Figure 1) positioned at the depth from which the deep seawater 4 is to be pumped. In use, the deep seawater 4 is drawn upwardly through the conduit 18 and into the chamber 10 so is to be deposited through the open bottom thereof over the kelp farm 8 (or any other suitable aquaculture application).

The working principle underlying the present pump 2 will now be discussed with reference to Figures 2A to 3B. Figure 2A shows the partially submerged chamber 10 wherein the water level 14 inside the chamber 10 substantially corresponds with the calm or still water level 20 of the body of water in which it is submerged. A pocket of air 16 is trapped within the chamber 10 above the water level 14 therein. Waves 22 are shown approaching the chamber 10.

Figure 2B shows the pump 10 as the crest of a wave (22a of Figure 2A) moves through it. As the wave 22a travels through the chamber 10, a column of water rises within the chamber 10, resulting in the water level 14 within the chamber 10 to rise to a height that is greater than a height of the water level 20 of the body of water in which it is submerged. The rising column of water acts to displace the air 16 trapped within the chamber 10. To this end, the pump 2 comprises a one way air outlet 38 through which air 16 trapped in the chamber 10 is forced out of the chamber 10 during this 'upstroke' of the water column as it rises within the chamber 10. In the depicted example, the otherwise closed top 12 of the chamber 10 is configured with a non-return valve through which air can escape to the atmosphere as the water level rises within the chamber 10.

Referring to Figure 3A, as the wave 22a moves past the chamber 10 of the pump 2 (for example, when the chamber is generally situated in the trough between two waves), the water level or column within the chamber 10 falls. In prior art oscillating water column systems and devices, this 'downstroke' of the water column has been utilised to draw air past a turbine for electricity generation (it is also known to use the upstroke for electricity generation). However, in the present case, the one-way air outlet 38 prevents air from entering the chamber 10 during the downstroke of the water column, thereby creating a vacuum in the unoccupied pocket of space above the water level 14 inside the chamber 10. The generated pressure differential acts to suck or draw deep seawater 4 upwardly through the conduit 18, which drawn water 4 can exit through a water outlet 24 of the conduit 18 and enter the chamber 10 so as to be deposited therefrom through the open bottom and over the kelp farm 8, as illustrated in Figure 1.

An illustrative embodiment of the present pump 2 is shown in Figure 4. The chamber 10 is formed as a generally cylindrical body with a substantially closed top 12 and an open bottom. The body of the chamber 10 is preferably formed from a relatively rigid and rust-resistant material capable of withstanding the vacuum pressures generated therein.

The closed top 12 of the chamber 10 may be provided with the one-way air outlet 38 through which air can flow out of but not into the chamber 10. In the depicted example, the air outlet may be in the form of a through-hole which is selectively closed or sealed by a movable cover 26, such as a flap. During the upstroke, the cover 26 may be blown open by the escaping air. During the downstroke, the cover 26 may return to a closed position in which it seals the air outlet 38, thereby preventing air from returning into the chamber 10 through the air outlet during the downstroke. For example, the cover 26 maybe biased (e.g., spring biased) to assume the closed position.

The closed top 12 of the chamber 10 may be provided with a small air inlet 28 via which air may slowly enter the chamber 10, particularly to ensure the vacuum pressure therein is maintained within a predetermined range such that the chamber 10 does not collapse in on itself.

In certain embodiments, the pump 2 may also comprise a control system 30 for maintaining the pressure within the chamber above a predetermined minimum. For example, the system 30 may continuously or periodically take pressure measurements of the air pocket 16 within the chamber 10, and, if the pressure therein is determined to be too low, the system 30 may be configured to admit air into a chamber 10, such as through the previously described air inlet 28 (which may, for example, be selectively closeable).

The elongate conduit 18 of the pump 2 may also be provided with one or more non-return valves 32 along its length which are configured to prevent the backflow of water as it is drawn through the conduit 18. In this way, as waves 22 move through the chamber 10, deep seawater 4 is successively sucked up through the conduit 18 and toward the chamber 10 and is prevented from escaping the conduit 18 through the water inlet 34 thereof.

As can be seen in Figure 4, the conduit 18 terminates in a water outlet 24 which enters into the chamber 10, through a side of the chamber 10, at a height that is above the water level 14 therein. The conduit 18 may also have one or more additive inlets 36, via which an additive, such as a nutrient mixture, may be mixed with the deep seawater 4 drawn through the conduit 18 so is to be deposited through the open bottom of the chamber 10. In addition, a spray nozzle may be provided to spray water entering the chamber through the water outlet 24 to facilitate oxygenation of the water entering the chamber.

An oscillating water column pump 102 according to a second embodiment of the present invention is illustrated in Figure 5. Pump 102 is also configured to draw nutrient rich, colder and denser, deep seawater 104 upwardly so that it can be deposited at a shallower depth 106, for example over a kelp farm. Pump 102 is similarly configured to pump 2 with like reference numerals incremented by 100 used to denote like features.

Pump 102 also comprises a substantially hollow chamber 110 having a generally closed top 112 and an open bottom. In use the chamber 110 is configured to be partially submerged in a body of water such that the open bottom thereof is below the water level 114, thereby trapping a pocket of air 116 within the chamber 110 and above the water level 114.

Chamber 110 preferably has a relatively sharp inside edge at its base which creates eddys similar to those shown in Figure 3B from the action of the waves which promote mixing of the seawater 104 being pumped. A mixing means may be provided within or below the chamber to further facilitate mixing of the seawater 104 being pumped.

The pump 102 also comprises a conduit 118 such as an elongate piping or tubing that extends downwardly from the chamber 110. The conduit comprises a water inlet 134 positioned at the depth from which the deep seawater 104 is to be pumped. In use, the deep seawater 104 is drawn upwardly through the conduit 118 and into the chamber 110 so as to be deposited through the open bottom thereof over the kelp farm (or any other suitable aquaculture application). Conduit 118 extends up through an open bottom of chamber 10 and terminates at outlet 124 above the water level. Pump 102 may operate generally in accordance with pump 2 described above. In particular, falling water height within the chamber 110 creates a vacuum which causes water to be drawn along the conduit 118. Pump 102 also operates by the vacuum in the chamber 110 causing the water to be drawn up the conduit 118, in this case by syphoning.

Pump 102 also comprises a one way air outlet 138 through which air 116 trapped in the chamber 110 is forced out of the chamber 110 during an upstroke of the water column as it rises within the chamber 110. As the water falls due to the wave motion, a vacuum is created within the chamber 110.

An aperture 142 is provided in an upper part of the chamber 110 and through which air can flow due to the vacuum in the chamber 110. A turbine 144 is mounted within the aperture 142 and configured to rotate due to air passing through the aperture due to the vacuum created in the chamber 110. It will be appreciated that the turbine 144 may also be mounted remotely from the chamber in fluid communication with the aperture 142 via a further conduit or ducting.

Turbine 144 is coupled to a propeller 146 mounted within the conduit 118 and configured so that rotation of the turbine 144 causes rotation of the propeller 146 to pump water through the conduit. In the illustrated embodiment, the turbine 144 and the propeller 146 are coupled directly via a shaft, through an optional gearbox 147, though other forms of coupling are also possible. For example, the turbine 144 and propeller 146 may be electrically coupled with the turbine driving a generator to generate electricity which is then distributed to an electric motor which drives the propeller 146.

In one form of operation, the pump 102 is configured so that the vacuum within the chamber solely draws air through the turbine to drive it. In other forms, the vacuum is partially used to drive the turbine and partially used to draw water through the conduit 118. Conduit 118 is configured with one or more one-way valves 132 for inhibiting backflow of water drawn through the conduit. Although the one-way valve 132 is shown near water inlet 134, it may be positioned at other locations in the conduit 118.

Another oscillating water column pump 202 is illustrated in Figure 5, pump 202 according to a further embodiment of the present invention. Pump 202 is also configured to draw nutrient rich, colder and denser, deep seawater 204 upwardly so that it can be deposited at a shallower depth 206, for example over a kelp farm. Pump 202 is similarly configured to pumps 2, 102 with like reference numerals incremented by 100,200 used to denote like features.

Pump 202 also comprises a substantially hollow chamber 210 having a generally closed top 212 and an open bottom. In use the chamber 210 is configured to be partially submerged in a body of water such that the open bottom thereof is below the water level 214, thereby trapping a pocket of air 216 within the chamber 210 and above the water level 214.

The pump 202 also comprises a conduit 218 such as an elongate piping or tubing that extends downwardly from the chamber 210. The conduit comprises a water inlet 234 positioned at the depth from which the deep seawater 204 is to be pumped. In use, the deep seawater 204 is drawn upwardly through the conduit 218 and into the chamber 210 so as to be deposited through the open bottom thereof over the kelp farm (or any other suitable aquaculture application).

Pump 202 may operate in a similar manner to pumps 2, 102 described above. In this regard, falling water height within the chamber 210 creates a vacuum within the chamber 210 and this vacuum is used to cause water to be drawn along the conduit 218. Again, the vacuum generated in the chamber 210 indirectly causes water to be pumped through conduit 218. Pump 202 also comprises a one way air outlet 238 through which air 216 trapped in the chamber 210 is forced out of the chamber 210 during an upstroke of the water column as it rises within the chamber 210. As the water falls due to the wave motion, a vacuum is created within the chamber 210.

Where pump 202 differs from pumps 2 and 102 is by the mechanism which causes the water to be drawn along conduit 218. In this regard, the vacuum within chamber 210 is not directly used to draw water through the conduit, but indirectly causes pumping of the water. In this regard, instead the vacuum is used to drive an air turbine 244 (described below) to generate mechanical power which is used to pump the dep seawater upwardly.

Furthermore, conduit 218 extends through the chamber 210 but does not terminate within the chamber 210, with water outlet 224 being external of the chamber 210.

An aperture 242 is provided in an upper part of the chamber 210 and through which air can flow due to the vacuum in the chamber 210. A turbine 244 is mounted within the aperture 242 and configured to rotate due to air passing through the aperture due to the vacuum created in the chamber 210. It will be appreciated that the turbine 244 may also be mounted remotely from the chamber in fluid communication with the aperture 242 via a further conduit or ducting.

Turbine 244 is coupled to a propeller 246 mounted within the conduit 218 and configured so that rotation of the turbine 244 causes rotation of the propeller 246 to pump water through the conduit. In the illustrated embodiment, the turbine 244 and the propeller 246 are coupled directly via a shaft, through an optional gearbox 247, though other forms of coupling are also possible. For example, the turbine 244 and propeller 246 may be electrically coupled with the turbine driving a generator to generate electricity which is then distributed to an electric motor which drives the propeller 246. Conduit 218 is also configured with one or more one-way valves for inhibiting backflow of water drawn through the conduit. Although the one-way valve is shown near water inlet 234, it may be positioned at other locations in the conduit 218.

Figure 7 illustrates a system 300 according to another embodiment of the invention. System 300 includes an oscillating water column pump 202 in combination with an oscillating water column pump 2.

Oscillating water column pump 202 is used to draw deep seawater 304 upwardly. To increase the performance of of pump 202, it is used in combination with pump 2 by extending the conduit 218 into pump 2, with water outlet 224 being located within chamber 10 of pump 2. This results in increased pumping performance and a higher volume of fluid being drawn upwardly.

Another oscillating water column pump 302 according to a further embodiment of the present invention is illustrated in Figure 8. Pump 302 is also configured to draw nutrient rich, colder and denser, deep seawater 304 upwardly so that it can be deposited at a shallower depth 306, for example over a kelp farm. Pump 302 is similarly configured to pumps 2, 102, 202 with like reference numerals incremented by 100, 200, 300 used to denote like features.

Pump 302 also comprises a substantially hollow chamber 310 having a generally closed top 312 and an open bottom. In use the chamber 310 is configured to be partially submerged in a body of water such that the open bottom thereof is below the water level 314, thereby trapping a pocket of air 316 within the chamber 310 and above the water level 314.

The pump 302 works in conjunction with an external conduit 318, such as an elongate piping or tubing that extends to the deep seawater 304. The conduit comprises a water inlet 334 positioned at the depth from which the deep seawater 304 is to be pumped. A water outlet 324 is provided external of the chamber 310. In use, the deep seawater 304 is drawn upwardly through the conduit so as to be deposited over the kelp farm (or any other suitable aquaculture application).

Pump 302 may operate in a similar manner to pumps 2, 102, 202 described above. In this regard, falling water height within the chamber 310 creates a vacuum within the chamber 310 and this vacuum is used to cause water to be drawn along the conduit 318. Again, the vacuum generated in the chamber 310 indirectly causes water to be pumped through conduit 318.

Pump 302 also comprises a one way air outlet 338 through which air 316 trapped in the chamber 310 is forced out of the chamber 310 during an upstroke of the water column as it rises within the chamber 310. As the water falls due to the wave motion, a vacuum is created within the chamber 310.

Pump 302 differs from the above pumps in that it includes a pressure modifying component 348. The pressure modifying component 348 is provided for reducing the pressure and increasing the velocity of the air being drawn into the chamber 10 due to the vacuum, which is used to draw the water through the conduit 348. In the illustrated embodiment, the pressure modifying component is an external venturi 348, though it will be appreciated that may be possible to use alternative devices. Venturi 349 is provided to increase the speed and lower the pressure of air entering the chamber 310 during an inhalation phase of the pump, i.e. as the water recedes in the chamber 310. This is expected to increase the overall efficiency of the pump 302. The venturi 348 may be directly mounted to chamber 310 or may be external to it and connected by an intermediate pipe (not shown). Venturi 348 is connected to the conduit 318 via an air pipe 350. In this arrangement, the vacuum in the chamber 310 creates a low pressure air flow in the venturi 348, which draws air through the conduit 318, syphoning water along the conduit, from the deep location 304 to the shallower location 306. Conduit 318 is also configured with one or more one-way valves 332 for inhibiting backflow of water drawn through the conduit. Although the one-way valve is shown near water inlet 334, it may be positioned at other locations in the conduit 318.

Another oscillating water column pump 402 according to a further embodiment of the present invention is illustrated in Figure 9. Pump 402 is also configured to draw nutrient rich, colder and denser, deep seawater 404 upwardly so that it can be deposited at a shallower depth 406, for example over a kelp farm. Pump 402 is similarly configured to pump 302 with like reference numerals incremented by 100 used to denote like features.

Pump 402 also comprises a substantially hollow chamber 410 having a generally closed top 412 and an open bottom. In use the chamber 410 is configured to be partially submerged in a body of water such that the open bottom thereof is below the water level 414, thereby trapping a pocket of air 416 within the chamber 410 and above the water level 414.

The pump 402 works in conjunction with an external conduit 418, such as an elongate piping or tubing that extends to the deep seawater 404. In use, the deep seawater 404 is drawn upwardly through the conduit so as to be deposited over the kelp farm (or any other suitable aquaculture application). The conduit comprises a water inlet 434 positioned at the depth from which the deep seawater 404 is to be pumped. A water outlet 424 is provided external of the chamber 410 and at an accumulator 452, which will be described further below.

Pump 402 may operate in a similar manner to pumps 2, 102, 202, 302 described above. In this regard, falling water height within the chamber 410 creates a vacuum within the chamber 410 and this vacuum is used to cause water to be drawn along the conduit 418. Again, the vacuum generated in the chamber 410 indirectly causes water to be pumped through conduit 418. Pump 402 also comprises a one way air outlet 438 through which air 416 trapped in the chamber 410 is forced out of the chamber 410 during an upstroke of the water column as it rises within the chamber 410. As the water falls due to the wave motion, a vacuum is created within the chamber 410.

Pump 402 differs from pumps 2, 102, 202 (but is similar to pump 302) in that an external venturi 448 is provided to increase the speed and lower the pressure of air entering the chamber 410 during an inhalation phase of the pump, i.e. as the water recedes in the chamber 410. This acts to increase the efficiency of the pump 402. The venturi 448 may be directly mounted to chamber 410 or may be external to it and connected by an intermediate pipe (not shown). Venturi 448 is connected to accumulator 452 via an air pipe 450. In this arrangement, the vacuum in the chamber 410, creates a low pressure air flow in the venturi 448, which draws air through the accumulator 452 and therefore up conduit 418, syphoning water along the conduit, from the deep location 404 to the shallower location 406.

Accumulator 452 is configured to regulate pressure and flow of the water and acts to smooth out the output of the pump 402, which varies due to the inhalation and pumping phases. The accumulator 452 has two chambers 454a, 454b and each chamber is fitted with a one-way valve 456a, 456b. Air line 450 is connected to the second chamber 454b of the accumulator 452. In use, water flows into the first chamber 454a and remains until the pressure in the second chamber 454b drops to a level that causes the water to flow into the second chamber 454b. After water is drawn into the second chamber 454b, it remains there until a subsequent charge of water enters from the first chamber 454a, causing water to exit the accumulator 452.

Conduit 418 is also configured with one or more one-way valves 432 for inhibiting backflow of water drawn through the conduit. Although the one-way valve is shown near water inlet 434, it may be positioned at other locations in the conduit 418. Many modifications of the above embodiments will be apparent to those skilled in the art without departing from the scope of the present invention. For example, while the chamber 10 is depicted as having a substantially cylindrical form, it can, of course, have many other forms.

Also, although illustrated and described as having a single conduit 18, the pump 2 may be provided with multiple conduits 18, each terminating at either a common outlet 24 or individual outlets.

Furthermore, a suction effect is created within the chamber 10 as the water level around the pump 2 falls with a receding wave, which increases the height of water in the chamber 10 and acts to draw the pump 2 downwardly. It is therefore envisaged that the chamber 10 is supported in position, by a floating structure or platform for example, such that when deployed, it floats and remains partially submerged in the body of water. Of course, in other embodiments, the position of the pump 2 and chamber 10 relative to the still water level 20 may be at least partially anchored to the sea floor or external structure, or fixed by any known means. In one example, it might be that the chamber 10 is positionally anchored to the kelp farm substrate 8 such that the chamber 10 does not stray therefrom.

While the foregoing relates primarily to kelp farming, the present pump 2 can of course be used in a wide variety of different applications, including salmon farming and the revitalization of coral. The pump 2 may also be used in the reduction of undesirably high water nutrient levels from a sea or river floor.

It will be appreciated that the hydrodynamics of the pump 2, in particular parameters around the size of the chamber 10, conduit 18 and outlet 24 or the degree of closure of the air outlet 38, will be varied in accordance with the anticipated wave size profile incident on the pump 2. Prior to installation of the pump 2, the specific wave history at the site may be recorded by data loggers over a predetermined period such as 12months so that the specific parameters of the pump can be optimised. To ensure optimal operation of the pump, it may be that pump 10 is fitted with data loggers to measure the wave size profile at the site to ensure efficient operation. In addition, data around oxygen levels, nitrates and nutrient levels may also be collected. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.