GB2469120A

GB2469120A - System and method of transferring water to shore

Info

Publication number: GB2469120A
Application number: GB0905826A
Authority: GB
Inventors: Alvin Smith
Original assignee: Dartmouth Wave Energy Ltd
Current assignee: Dartmouth Wave Energy Ltd
Priority date: 2009-04-03
Filing date: 2009-04-03
Publication date: 2010-10-06
Also published as: GB2469120A8; GB0905826D0

Abstract

The invention relates to a system and method of transferring water to shore. The system comprises a structure 10 located offshore and arranged to support water above the surface of the body of water 12 to create an offshore head of water. Water from the body of water is pumped into the structure, preferably by wave-powered pumping devices 18. Alternately, tidal movement may be used to transfer water into the structure. A duct 14 extends between the structure and an onshore location such as a reservoir 14 and is used to convey water from the structure to the onshore location. The offshore head of water is higher than the onshore location such that water is transferred from the structure via the duct to the onshore location under gravity. The onshore reservoir creates a head of water onshore and allows stored water to be used for the generation of hydroelectricity, desalination, irrigation, agriculture, cooling of machinery, heat pump circulation, heat sinking of air conditioning apparatus, leisure pool or salt production.

Description

TRANSFERRING WATER TO SHORE

Field of the invention

The present invention relates to transferring water from a body of water to shore. Once the water has been transferred to shore, it may be used in various applications, including the generation of hydroelectricity.

Background

Wave-powered pumping devices are known. These devices typically comprise a float arranged at the surface of a body of water above a submerged platform. A pump acts between the platform and the float. Surface waves in the body of water cause the float to move reciprocally in the water with respect to the submerged platform. This reciprocal movement drives the pump, which pressurises water in a pumping chamber of the pump.

An example of a wave-powered pumping device is described in UK Patent GB2445951.

It is known to use wave-powered pumping devices to pump water to shore, for example to fill an onshore reservoir. Water in the onshore reservoir may then be used in a number of applications, including the controlled generation of hydroelectric energy.

Typically, water is pumped to shore through long pipes that extend between individual pumping devices and the shore. Long pipes result in high line friction. To reduce line friction, these pipes generally have a large diameter. Multiple long pipes of large diameter are expensive and may be difficult to install.

It is desirable to locate the pumping devices at a significant distance offshore in order to benefit from larger waves. However, the pumping devices can be difficult to see and hence are susceptible to damage from collisions with passing vessels. Further problems may be caused by having several long pipes leading back to the shore from the respective pumps.

Against this background, the present invention aims to provide an alternative method of transferring water to shore.

Summary of the invention

The invention provides a system for transferring water from a body of water to an onshore location, the system comprising: a structure located offshore, the structure being arranged to support water above the surface of the body of water to create an offshore head of water; at least one pumping device arranged to pump water from the body of water into the structure; and a duct extending between the structure and the onshore location, the duct being arranged to convey water from the structure to the onshore location; wherein the offshore head of water is higher than the onshore location such that water is transferred from the structure via the duct to the onshore location under gravity.

In contrast to the prior art described above, the present invention does not pump water to shore. Instead, the water is transferred to shore under gravity from the offshore head of water.

The or each pumping device may be wave-powered. Alternatively, the pumping devices may be powered by other sources, for example by the wind.

Rather than water being pumped into the structure, it is envisaged that tidal movement could be utilised to create an offshore head of water. Accordingly, the invention also provides a system for transferring water from a body of water to an onshore location, the system comprising: a structure located offshore, the structure being arranged to create an offshore head of water by capturing water from the body of water as the depth of the body of water increases and supporting the captured water above the surface of the body of water as the depth of the body of water decreases; and a duct extending between the structure and the onshore location, the duct being arranged to convey water from the structure to the onshore location; the system being arranged such that the offshore head of water is higher than the onshore location such that water is transferred from the structure via the duct to the onshore location under gravity.

Once the water has been transferred to shore, it may be used for generating hydroelectricity. To this end, the system may comprise at least one hydroelectric generator through which the water passes once it has been transferred to shore.

Subsequently, the system may be arranged to return the water to the body of water or to a suitable alternative destination.

The system may be arranged to transfer water from the offshore head of water to an onshore reservoir. Here, the water may be stored for later use. The or each hydroelectric generator may be located below the level of the water in the reservoir such that the reservoir defines a head of water onshore. The system may be arranged to convey water under gravity from the reservoir to the or each hydroelectric generator.

The system may be configured to convey water to the or each hydroelectric generator simultaneously from two sources, for example from the reservoir and simultaneously from the offshore structure via respective paths. In one embodiment of the invention described in detail later, the system is configured to convey water to the hydroelectric generators from the reservoir and simultaneously directly from the offshore structure.

The offshore structure may be a dedicated structure or an existing structure such as an oilrig. The structure may be supported by the seabed or on a floating platform or vessel.

The structure may comprise a tower supporting a water storage tank above the surface of the body of water. Alternatively, the offshore structure may comprise a tower having an internal chamber for supporting water from the body of water above the surface of the body of water. The chamber may extend substantially the full height of the tower.

An outlet for communicating with the duct may be located above the base of the tower such that a lower region of the chamber is defined below the outlet. Conveniently, the lower region of the chamber is flooded in use and serves to stabilise the tower in the body of water. The lower region may also collect sediment and other debris, thereby reducing the amount of debris passing through the outlet to the duct. A service hatch or similar entry point may be provided in the structure to access the lower region for cleaning and servicing purposes.

The pumping devices may be located a significant distance offshore, typically between about two hundred metres to about five miles off shore. This allows the pumping devices to benefit from larger swell relative to locations closer to shore, thus allowing the pumping devices to operate more efficiently.

The pumping devices may be located close to the offshore structure, whilst being located a significant distance offshore. Whereas prior art systems are required to pump water back to the shore, the present system is only required to pump water to the nearby structure. Consequently, the distance over which water is pumped can be minimised and is significantly less than in the prior art. This allows shorter pipes of smaller diameter to be used because line friction is less acute than in prior art systems. As a result, cost is reduced.

When multiple wave-powered pumping devices are employed, these may be clustered around the offshore structure. The significant size of the structure makes this arrangement easily visible in the water and hence serves to protect the pumping devices from boats and other passing vessels. Clustering the pumping devices close to or around the structure is also convenient for servicing purposes.

The duct may comprise a single pipeline for transferring water to shore from the offshore structure. This arrangement is advantageous because only one pipeline would need to be laid between the offshore structure and the onshore location. This is in contrast to prior art systems that require multiple pipes extending all the way to shore from the respective pumping devices. One relatively large diameter pipeline for this purpose would be more efficient and cost-effective. A penstock pipe is suitable. The pipeline may be buried or ploughed into the seabed.

If the diameter of the pipeline is sufficiently large, a remotely operated vehicle (ROV) may travel through the pipeline for cleaning and surveying purposes. Prior to the ROV being deployed, the water may be pumped out of the pipeline so that the ROV can perform a dry survey or cleaning operation.

Aside from the generation of hydroelectricity, the water transferred to shore may be used for other purposes, for example: desalination and irrigation; aquaculture; cooling of machinery; heat pump circulation; heat sinking of air conditioning apparatus; salt production or for leisure activities.

The invention also provides a method of transferring water from a body of water to an onshore location, the method comprising: transferring water from the body of water into an offshore structure; raising the water level within the offshore structure to a height that is greater than the height of the onshore location; and transferring the water from within the offshore structure under gravity to the onshore location via a duct extending between the two.

The method may comprise pumping water from the body of water into the structure, for example by means of wave-powered pumping devices. Alternatively or additionally, the method may comprise allowing water to flow into the structure as the depth of the body of water increases and supporting that water above the surface of the body of water as the depth of the body of water decreases.

It will be appreciated that optional features described above in relation to the system are equally applicable to the method. However, these features have not been repeated for reasons of conciseness.

Brief description of the drawings

Specific embodiments of the invention will now be described, by way of example only and without limitation to the scope of the invention, with reference to the following figures, in which: Figure 1 shows a system comprising a water tower located offshore in a body of water, the system being arranged to transfer water under gravity from the water tower to an onshore reservoir; Figure 2 shows a system comprising a water tower located offshore in the sea, the system being arranged to transfer water under gravity from the water tower to an onshore reservoir, wherein water from the onshore reservoir is passed through one or more hydroelectric generators before being returned to the sea; Figure 3 shows a variant of the system of Figure 2, in which the system is configured to transfer water from the water tower directly to the one or more hydroelectric generators or to the onshore reservoir; Figure 4 shows a system comprising a water tower located offshore in the sea and arranged to transfer water under gravity to one or more hydroelectric generators located onshore; and Figure 5 shows a variant of the system of Figure 4, in which the water tower is supported on a floating structure.

Detailed description

Referring to Figure 1, a water tower 10 stands offshore in the sea 12 and is connected via a transfer pipe 14 to an onshore reservoir 16. The water tower 10 serves to define an offshore head of water. A plurality of wave-powered pumping devices 18 are positioned in the sea 12 adjacent to the water tower 10. As described in further detail later, water is pumped into the water tower 10 and subsequently transferred under gravity from the water tower 10 to the onshore reservoir 16 via the transfer pipe 14. In this example, the transfer pipe 14 is a penstock pipe, which is formed by welding a series of rings together.

The onshore reservoir 16 creates a head of water onshore and allows the stored water to be used for the controlled generation of hydroelectricity. Other uses for the water in the reservoir 16 include: desalination and irrigation; aquaculture; cooling of machinery; heat pump circulation; heat sinking of air conditioning apparatus; use as a leisure pool or use for salt production. An overflow channel 20 is provided for preventing the onshore reservoir 16 from filling beyond a maximum fill level 22. The overflow channel 20 conveys excess water 24 back into the sea 12 as shown, although the ultimate destination of the excess water 24 is not important.

Referring now to Figure 1 in more detail: the water tower 10 extends vertically from a base 26 below the surface 28 of the sea 12, to an upper end 30 above the surface 28 of the sea 12. The base 26 is sunk into the seabed 32 and is wider than the upper end 30 to provide stability. The tower 10 is hollow and has a frustoconical outer wall 34 that defines an internal chamber 36 for storing water 38. The internal chamber 36 extends substantially the full height of the tower 10 in order to maximise the water-storing capacity of the tower 10.

An outlet 40 for transferring water to the onshore reservoir 16 is provided in a lower portion 42 of the tower 10. The outlet 40 is provided in the outer wall 34 above the base 26 such that a lower region 44 of the internal chamber is defined below the outlet 40.

The lower region 44 is constantly flooded in use and hence stabilises the tower 10 in the sea 12. Service hatches 46 are provided in the lower portion 42 of the tower 10 for maintenance and cleaning purposes, e.g. to remove any sediment of other debris that may collect in the lower region 44. The service hatches 46 may also be used to pump water out of the tower 10, or to allow water into the tower 10 to sink the tower 10 when it is initially installed after, for example, being floated into position.

An overflow pipe 48 for preventing the tower 10 from filling above a maximum fill level 50 is provided in an upper portion 52 of the water tower 10. It will be appreciated that in alternative embodiments, the overflow pipe 48 may be omitted so that excess water is allowed simply to spill over the upper end 30 of the tower 10.

The plurality of wave-powered pumping devices 18 are clustered close to the base 26 of the water tower 10. In this example, the pumping devices 18 each comprise a surface float assembly 54 arranged to float at the surface 28 of the sea 12 and a platform 56 that is disposed below the surface 28. The submerged platforms 56 are attached to the seabed 32 by tethers 58. A pump 60 is supported on each platform 56 and acts between that platform 56 and the respective surface float assembly 54. Surface waves 62 cause the surface float assembly 54 to move reciprocally in the sea 12 with respect to the submerged platform 56; this reciprocal movement drives the pump 60, causing water from the sea 12 to be drawn into a pumping chamber 64 and pressurised. It will be appreciated that pumping devices other than those specifically described herein are suitable for this purpose.

A plurality of riser pipes 66 extend vertically up the outer wall 34 of the water tower 10. A lower end 68 of each riser 66 is connected to an outlet of a respective pumping device 18, and an upper end 70 of each riser 66 is disposed at the upper end 30 of the water tower 10. The upper ends 70 of the riser pipes 66 include outlets that communicate with the internal chamber 36 of the water tower 10. These outlets are positioned such that water 72 is expelled into the internal chamber 36 of the tower 10.

The transfer pipe 14 communicates with the internal chamber 36 of the water tower 10 and extends between the water tower 10 and the onshore reservoir 16. A first section 74 of the transfer pipe 14 is connected to the outlet 40 in the lower portion 42 of the tower and hence extends outwardly from the outer wall 34. A second section 76 of the transfer pipe 14 is buried beneath the seabed 32 and extends in a generally horizontal direction from the water tower 10 towards the shore 78. A third section 80 of the transfer pipe 14 extends onshore between the second section 76 and the onshore reservoir 16.

The third section 80 inclines upwardly from the second section 76 and terminates at an outlet end 82 positioned above the maximum fill level 22 of the reservoir 16. The outlet end 82 of the transfer pipe 14 is lower than the maximum fill level 50 of the water tower 10, and so is arranged to expel water 84 into the reservoir 16 when the water tower 10 is full. A service port 86 for accessing the transfer pipe 14 for cleaning and maintenance purposes is provided at the junction between the second and third sections 76, 80 of the transfer pipe 14.

In use, surface waves 62 in the sea 12 cause the wave-powered pumping devices 18 to pump water from the sea 12 up through the risers 66 and into the internal chamber 36 of the water tower 10. Initially, water entering the tower 10 fills the lower region 44 of the internal chamber 36, below the outlet 40. As more water is pumped into the tower 10, the water level in the tower 10 rises until in reaches the level of the outlet 40. As the wave-powered pumps 18 continue to operate, water flows through the outlet 40, down through the first section 74 of the transfer pipe 14, along the horizontal second section 76 to shore 78, and up through the third section 80 of the transfer pipe 14 to a height substantially level with the outlet 40 of the tower 10. Pumping more water into the tower causes the water level in the tower 10 to rise, and the weight of the water 38 in the tower 10 forces more water through the transfer pipe 14. The water level in the third section 80 of the transfer pipe 14 rises in step with the water level in the tower 10. Once the water level in the tower 10 rises above the height of the outlet end 82 of the third section 80 of the transfer pipe 14, water 84 begins to flow out from the outlet end 82 of the transfer pipe 14 to fill the onshore reservoir 16.

The reservoir 16 continues to fill as the wave-powered pumping devices 18 continue to operate. Once the water level in the reservoir 16 reaches the maximum fill level 22, excess water 24 flows through the overflow pipe 20 and back into the sea 12 to prevent the reservoir 16 from overfilling.

Referring to Figure 2, in a second example, a tower 110 having an open cross-braced lattice structure stands offshore in the sea 112. The tower 110 is supported on a concrete foundation 126 that is sunk into the seabed 132. The tower 110 supports a water tank 111 at an upper end 130, the water tank 111 defining an offshore head of water. The water tank 111 has an outlet 140 for communicating water 113 to an onshore reservoir 116 via a transfer pipe 114. An overspill pipe 148 is provided on the tank 111 for preventing the tank 111 from filling beyond a maximum fill level 150. Similarly, the onshore reservoir 116 includes an overflow channel 120 for preventing the reservoir 116 from filling beyond a maximum fill level 122.

The transfer pipe 114 has a first section 174 connected to the outlet 140 of the water tank Ill and extending downwardly through the tower 110. The first section 174 of the transfer pipe 114 connects to a second section 176, which is buried beneath the seabed 132. The second section 176 extends in a generally horizontal direction between the tower 110 and the shore 178. A third section 180 of the transfer pipe 114 extends onshore between the second section 176 and the onshore reservoir 116. The third section 180 inclines upwardly from the second section 176 and terminates at an outlet end 182 positioned above the maximum fill level 122 of the reservoir 116. The outlet end 182 is arranged to expel water 184 into the reservoir 116. A service port 186 for accessing the transfer pipe 114 for cleaning and maintenance purposes is provided at the junction between the second and third sections 176, 180 of the transfer pipe 114.

As described above with reference to Figure 1, wave-powered pumping devices 118 are arranged close to a lower end 142 of the tower 110 and configured to pump water into the water tank 111 via risers 166 extending up the tower 110. That water eventually flows into the reservoir 116.

The system shown in Figure 2 is configured to generate hydroelectricity. As described in further detail below, this is achieved by channelling water from the onshore reservoir 116 through one or more hydroelectric generators 188 of a hydroelectric power plant.

The hydroelectric generators 188 are operated by water returning under gravity from the reservoir 116 to the sea 112 via a return path 190. The return path 190 is defined in part by an outflow pipe 192 that inclines downwardly from the onshore reservoir 116 towards the sea 112. A first end 194 of the outflow pipe 192 communicates with the reservoir 116, and a second end 196 of the outflow pipe 192 is arranged to expel water 198 into the sea 112. The hydroelectric generators 188 include turbines located adjacent the second end 196 of the outflow pipe 192.

A shut-off valve 200 is provided in the outflow pipe 192, upstream of the generators 188.

The shut-off valve 200 may be operated to block the flow of water in the outflow pipe 192 to the generators 188 when it is not required to generate hydroelectricity. A surge pipe 201 extends vertically upwards from a section of the outflow pipe 192 upstream of the shut-off valve 200. A surge pond 202 is located above the surge pipe 201 and communicates with the surge pipe 201. The surge pipe 201 and surge pond 202 provide a path for water to flow when the shut-off valve 200 is closed, thereby mitigating potentially damaging water hammer1 or pressure wave effects caused by the rapidly changing momentum of the water in the transfer pipe 192 on closing of the shut-off valve 200.

In use, surface waves 162 in the sea 112 cause the wave-powered pumping devices 118 to pump water from the sea 112, up through the risers 166, and into the water tank 111.

Water 113 that is pumped into the tank 111 flows under gravity through the outlet 130 of the tank 111 and down through the first section 174 of the transfer pipe 114. As water continues to be pumped into the tank 111, the transfer pipe 114 conveys that water to the onshore reservoir 116 in much the same way as described above with reference to Figure 1.

To generate hydroelectric energy, the shut-off valve 200 is opened to allow water from the onshore reservoir 116 to flow under gravity down through the outflow pipe 192 and out through the second end 196 of the outflow pipe 192 into the sea 112 via the hydroelectric generator(s) 188. When hydroelectric generation is no longer required, the shut-off valve 200 is closed. Closing the shut-off valve 200 causes water flowing in the outflow pipe 192 to divert up through the surge pipe 201 and collect in the surge pond 202. Whilst the shut-off valve 200 remains closed, the level of water in the surge pond 202 will rise and fall periodically as water oscillates between the reservoir 116 and the surge pond 202; eventually this movement will be damped by friction and fluid circulation until the oscillation ceases.

The reservoir 116 continues to fill via the transfer pipe 114 whilst the shut-off valve 200 is closed. If the level of water in the reservoir 116 exceeds the maximum fill level 122, then excess water 124 is returned to the sea 112 via the overflow channel 120. When the shut-off valve 200 is reopened, any water in the surge pond 202 will fall back down the surge pipe 201 under gravity, and will flow down through the outflow pipe 192 together with water from the reservoir 116 to the sea 112 via the hydroelectric generators 188.

Figure 2 shows water 198 returning to the sea 112 via a return outlet 203 located above the surface 128 of the sea 112. It will be appreciated that in other variants of the invention, the return outlet 203 may be under the surface of the sea 112. In such a configuration, the hydroelectric generators 188 may be operated in reverse, i.e. to pump water from the sea 112 up through the outflow pipe 192 and into the onshore reservoir 116. This may be desirable as a way of storing energy when there is a surplus of available electricity from other sources, i.e. a pumped storage scheme.

Figure 3 shows a variant of the system described above with reference to Figure 2.

Referring to Figure 3, the onshore reservoir 116 fills via a common channel 204 and empties through the turbines 188 via that channel 204. The common channel 204 is defined by a section of pipe 205 extending between the reservoir 116 and the buried second section 176 of the transfer pipe 114. The surge pipe 201 communicates with this section of pipe 205.

The section of pipe 205 includes an outflow branch 206 for diverting water towards the hydroelectric generators 188 and back to the sea 112. In this example, a shut-off valve 207 is located at the junction between the common channel 204 and the outflow branch 206. Closing the shut-off valve 207 blocks the flow to the outflow branch 206 while leaving the section of pipe 205 in communication with the transfer pipe 114 so that water is caused to flow under gravity from the offshore water tank 111, through the transfer pipe 114, and up through the common channel 204 to fill the onshore reservoir 116.

Opening the shut-off valve 207 opens the outflow branch 206 causing water to flow from the onshore reservoir 116, down through the common channel 204, through the outflow branch 206 and back to the sea 112 via the hydroelectric generators 188. When the shut-off valve 207 is open in this way, water from the offshore water tank 111 also flows directly to the generators 188. It will therefore be apparent that in this situation water is provided to the hydroelectric generators 188 from two sources, which boosts the power output from the generators 188.

Figure 4 shows a further example of the invention. The system shown in Figure 4 utilises the same offshore tower arrangement described above in relation to Figures 2 and 3.

However, in contrast to the systems of Figures 2 and 3, the system of Figure 4 does not include an onshore reservoir. Instead, a transfer pipe 214 extends between the offshore water tank 111 and hydroelectric generators 288 located onshore. The transfer pipe 214 is arranged to convey water directly to the onshore generators 288 from the offshore water tank 111.

In use, the wave-powered pumping devices 118 pump water into the water tank 111 supported at the upper end 130 of the offshore tower 110. Water 113 in the tank 111 falls under gravity down through the first section 174 of the transfer pipe 214 and is forced along the transfer pipe 214 to shore 178 by the weight of water in the storage tank 111. Water from the transfer pipe 214 is returned to the sea 112 via the hydroelectric generators 288.

Figure 5 shows a variant of the system described above with reference to Figure 4. In Figure 5, instead of being supported on a sunken base, the tower 110 is supported on a floating plafform 290. A portion of slack is provided in the first section 174 of the transfer pipe 114 to allow the floating structure to accommodate rising and falling sea levels.

Naturally, the floating structure would be moored, although the mooring is not shown in Figure 5.

It will be appreciated that many modifications may be made to the examples described above without departing from the scope of the invention as defined by the following claims. For example, it will be appreciated that the wave-powered pumping devices are not essential: variants of the invention are envisaged in which tidal movement causes an offshore structure to fill with water, thereby creating an offshore head of water.

Claims

Claims I. A system for transferring water from a body of water to an onshore location, the system comprising: a structure located offshore, the structure being arranged to support water above the surface of the body of water to create an offshore head of water; at least one pumping device arranged to pump water from the body of water into the structure; and a duct extending between the structure and the onshore location, the duct being arranged to convey water from the structure to the onshore location; wherein the offshore head of water is higher than the onshore location such that water is transferred from the structure via the duct to the onshore location under gravity.
2. The system of Claim 1, wherein the at least one pumping device is wave-powered.
3. The system of Claim 2, wherein the system comprises a plurality of wave-powered pumping devices clustered around the structure.
4. A system for transferring water from a body of water to an onshore location, the system comprising: a structure located offshore, the structure being arranged to create an offshore head of water by capturing water from the body of water as the depth of the body of water increases and supporting the captured water above the surface of the body of water as the depth of the body of water decreases; and a duct extending between the structure and the onshore location, the duct being arranged to convey water from the structure to the onshore location; the system being arranged such that the offshore head of water is higher than the onshore location such that water is transferred from the structure via the duct to the onshore location under gravity.
5. The system of any of preceding claim, further comprising a reservoir at the onshore location, the system being configured to transfer water from the offshore structure into the reservoir.
6. The system of any preceding claim, further comprising at least one hydroelectric generator, the system being configured to convey water directly or indirectly from the offshore structure to the or each hydroelectric generator to generate hydroelectricity.
7. The system of Claim 6, wherein the system is configured to convey water from a reservoir onshore to the or each hydroelectric generator to generate hydroelectricity.
8. The system of Claim 7, wherein the or each hydroelectric generator is located below the surface of water in the reservoir, the system being configured to convey water under gravity from the reservoir to the or each hydroelectric generator.
9. The system of any of Claims 6 to 8, wherein the system is configured to convey water to the or each hydroelectric generator simultaneously from two sources.
10. The system of Claim 9, wherein the system is configured to convey water to the or each hydroelectric generator from the reservoir onshore and simultaneously from the offshore structure via respective paths.
11. The system of any preceding claim, wherein the duct comprises a single transfer pipeline for transferring water to shore from the offshore structure.
12. The system of any preceding claim, wherein the offshore structure comprises a tower supporting a water storage tank for supporting water from the body of water above the surface of the body of water.
13. The system of any of Claims 1 to 11, wherein the offshore structure comprises a tower having an internal chamber for supporting water from the body of water above the surface of the body of water.
14. The system of Claim 13, wherein the chamber extends substantially the full height of the tower.
15. The system of Claim 14 wherein the tower includes an outlet in communication with the duct, the outlet being located above the base of the tower such that a lower region of the chamber is defined below the outlet.
16. The system of any preceding claim, wherein the structure is supported on the bed of the body of water.
17. The system of any of Claims ito 15, wherein the structure is arranged to float on the body of water.
18. A method of transferring water from a body of water to an onshore location, the method comprising: transferring water from the body of water into an offshore structure; raising the water level within the offshore structure to a height that is greater than the height of the onshore location; and transferring the water from within the offshore structure under gravity to the onshore location via a duct extending between the two.
19. The method of Claim 18, further comprising pumping water from the body of water into the structure
20. The method of Claim 19, further comprising pumping water into the structure in response to wave action.
21. The method of Claim 18, further comprising allowing water to flow into the structure as the depth of the body of water increases and supporting that water above the surface of the body of water as the depth of the body of water decreases.
22. A system for transferring water from a body of water to an onshore location substantially as herein described, with reference to or as shown in any of the accompanying drawings.
23. A method of transferring water from a body of water to an onshore location substantially as herein described, with reference to or as shown in any of the accompanying drawings.