Hybrid water / power generation system

Abstract

A water and power generating system is disclosed, comprising at least one renewable energy generator, at least one submerged or floating desalination apparatus configured to be at least partially powered by the renewable energy generator, a controller, a desalinated water output conduit, and an electrical power output. The controller is configured to dynamically adjust the operation of the desalination apparatus in response to variations in available renewable energy and fluctuating demands for desalinated water and electrical power. Also disclosed is a water desalination system comprising a docking platform with a substantially tubular housing, mooring attachments, and ballast for vertical orientation. The docking platform may be connected to multiple floating desalination buoys. The platform may further include electrical and water distribution hubs for interconnection with the buoys and shore-based infrastructure. The desalination buoys may incorporate intake bubble curtain devices and brine dispersal systems to enhance intake quality and manage brine discharge.

Description

[0001] HYBRID WATER / POWER GENERATION SYSTEM

[0002] 1. FIELD OF THE TECHNOLOGY

[0003] The present invention relates to systems and apparatus for desalinating water, and in particular to systems and apparatus which include offshore components.

[0004] 2. BACKGROUND TO THE TECHNOLOGY

[0005] Climate change is altering the hydrologic cycles in many coastal regions where water basins and aquifers are depleted or being exhausted. Half the global population lives within 100 miles of the coastlines, where sea water desalination could remedy water scarcity. Conventional desalination plants trend toward massive scale, that require long costly pipelines for coverage to reach and serve a coastal region. Typically, these major projects can take a around a decade to bring on line. However, for regions with water scarcity there is need for desalination systems that can be rapidly deployed.

[0006] A significant impediment to implementation of desalination systems is the cost of installation. Previous art (for example the applicant's prior PCT publication WO2019 / 098856) describes an ocean-based desalination buoy that operates with electric power transmitted from land or ocean-based generators to produce and convey freshwater to shoreside communities. These systems need to be of sufficient capacity to economically cover the cost of installation, the power cable and water pipeline to shore, and an onshore interconnection for power supply and water delivery, which means sufficient capacity to serve a population of several thousand households.

[0007] Desalination of water may be relatively energy intensive. Accordingly, it may be desirable to utilize renewable energy sources (onshore and / or offshore based) in addition to, or as an alternative to, power from a main electricity grid. It may also be desirable to provide a desalination system with battery means which can store any excess power generated by the renewable sources. However, production of desalinated water may not always be the most useful or the most economic use of the power generated and / or stored. If any excess power generated and / or stored can be used for other purposes, it may assist in amortizing the cost of the desalination system. Offshore platforms commonly run pipes to shore to deliver oil and gas, and electric power may be connected by subsea cable from the onshore grid out to the platform, but these two infrastructure elements are not comingled in a single conveyance device for a number of reasons: 1) potential for an electrical fault to cause combustion of petroleum / natural gas, 2) maintenance of oil pipelines periodically requires "pigging" to clean off residue within the pipe that would interfere with power cables laid therein, 3) intermediate valving along a pipeline would require addition complexity for power conductors to pass through or around, and 4) without the ability to easily "pull through" the power cable, installation and maintenance of the cable may be difficult and costly.

[0008] Cost-effective shipping of floating offshore desalination devices constrains the size of vessel and water treatment capacity of such devices. Greatest logistic cost efficiencies are enabled by conforming the desalination vessel to fit within standard shipping dimensions. To achieve the "economies of scale" associated with high desalination capacity and consolidated water and power conveyance infrastructure, "docking" multiple floating desalination devices together allows scaling up of desalination capacity at a single mooring point and allows for the placement of a common filtration system onboard the docking station, reducing the filtration burden on each desalination device.

[0009] The high cost of subsea infrastructure, including pipelines, power cables, and moorings indicates that aggregation of multiple installations of this infrastructure into a single set of pipeline, power cable, and moorings is economically preferred, especially as cost of a single installation of larger, higher capacity pipeline, power cable and moorings is typically far less costly than multiple discrete installations of smaller size. Subsea infrastructure cost is primarily driven by installation cost, which is dictated by the length of installation and the number of installation points, rather than material cost. Deployment of installation ships and crews sets a high day-rate for the installation process, as well as for the specialized services of divers and remote operated vehicles (ROVs) and their support vessels. The bottom conditions may require trenching and anchoring of pipeline and power cable, pile driving for moorings and the installation of ballasting materials along the pipeline length - all of which add considerable cost to the installation process.

[0010] 3. OBJECT OF THE TECHNOLOGY

[0011] It is an object of the present invention to provide a water and power generating system which can optimise generation of power and desalinated water. It is a further or alternative object to provide a water and power conveyance apparatus which provides a convenient means for conducting electrical current and a flow of water. It is a further or alternative objection to provide a docking platform for a water desalination system and / or a desalination system comprising the docking platform which functions as a common water and / or power distribution point. It is a further or alternative objection to provide a floating desalination buoy which has a bubble curtain to avoid contaminants entering the desalination apparatus and / or a brine dispersal means which prevents pooling of brine on the seafloor.

[0012] It is a further alternative object to overcome and / or ameliorate at least one problem of such systems and apparatus of the prior art.

[0013] Alternatively, it is an object of the technology to at least provide the public with a useful choice.

[0014] 4. SUMMARY OF THE TECHNOLOGY

[0015] According to one aspect of the technology there is provided a water and power conveyance apparatus, the apparatus comprising a conduit having a bore for conveying desalinated water and at least one electrically insulated electrical cable provided within the bore.

[0016] According to another aspect of the technology there is provided a water and power generating system comprising at least one renewable energy generator, at least one submerged or floating desalination apparatus configured to be at least partially powered by the at least one renewable energy generator, a controller, a desalinated water output conduit for outputting water from the at least one floating desalination apparatus and an electrical power output for outputting electrical power generated by the renewable energy generator but not used by the at least one floating desalination apparatus, wherein the controller is configured to vary the operation of the at least one floating desalination apparatus in response to changes in available power from the at least one renewable energy generator and varying desalinated water and electrical power requirements.

[0017] In examples, the controller assigns a notional value to the amount of power being output at the electrical power output and a notional value to the amount of water being output to the desalinated water output, and the controller varies the operation of the at least one floating desalination apparatus to maximise the sum of the notional values of the power output and the water output. In examples, the controller operates the desalination apparatus to produce at least a minimum flow rate of desalinated water unless a predetermined condition occurs.

[0018] In examples, the controller varies the operation of the desalination apparatus such that the system supplies at least a minimum electrical output to the electrical power output unless a predetermined condition occurs.

[0019] In examples, at least one of the renewable energy generators is located offshore.

[0020] In examples, at least one of the renewable energy generators is located onshore.

[0021] In examples, the system comprises a connection to an onshore mains power grid.

[0022] In examples, the system is configured to receive power from the mains power grid and / or to supply power to the mains power grid.

[0023] In examples, the system comprises at least one battery for storing power from the renewable energy generator and / or from the mains power grid.

[0024] According to another form of the technology there is provided a docking platform comprising; a substantially tubular outer housing; at least one mooring attachment means; a ballast volume configured to cause the tubular housing to maintain a substantially vertical orientation in use; and at least one of: a) an electrical distribution hub configured for connection to a plurality of electrical conductors; and b) a water distribution hub configured for connection to a plurality of water carrying conduits.

[0025] In examples, the docking platform is configured to dock with a plurality of offshore desalination buoys.

[0026] In examples, the docking platform comprises attachment links for connecting the desalination buoys to the docking platform. In examples, the clocking platform is configured to dock with six offshore desalination buoys arranged circumferentially around the tubular housing.

[0027] In examples, the electrical distribution hub is configured to interconnect with the offshore desalination buoys via buoy power cables.

[0028] In examples, the water distribution hub is configured to receive desalinated water from the offshore desalination buoys via buoy water lines.

[0029] In examples, the water distribution hub is configured for connection to a flexible water hose for conveying desalinated water from the offshore desalination buoys to shore.

[0030] In examples, the electrical distribution hub is configured for connection to a flexible power umbilical for conveying electrical power to or from shore.

[0031] In examples, the flexible power umbilical passes through the flexible water hose and the water distribution hub to the electrical distribution hub.

[0032] In examples, the docking platform is configured to receive control signals from a remote controller via a communications cable.

[0033] In examples, the docking platform comprises a water filtration system for filtering water received by the water distribution hub.

[0034] According to another form of the technology there is provided a water desalination system comprising : a docking platform comprising; a substantially tubular outer housing; at least one mooring attachment means; a ballast volume configured to cause the tubular housing to maintain a substantially vertical orientation in use; and at least one of: a) an electrical distribution hub configured for connection to a plurality of electrical conductors; and b) a water distribution hub configured for connection to a plurality of water carrying conduits ; and a plurality of floating desalination devices connected to the docking platform.

[0035] In examples, the docking platform is substantially cylindrical and the floating desalination devices are substantially cylindrical.

[0036] In examples, a diameter of each of the floating desalination devices is substantially equal to a diameter of the docking platform.

[0037] In examples, the docking platform comprises an electrical distribution hub and a water distribution hub, wherein each floating desalination device is connected to the electrical distribution hub by an electrical connector and each floating desalination device is connected to the water distribution hub by conduit.

[0038] In examples, the docking platform comprises a water filtration system for filtering water received by the water distribution hub.

[0039] In examples, the floating desalination devices do not include water filters for filtering desalinated water.

[0040] In examples, the docking platform comprises a controller configured to receive control signals and to control the operation of the electrical distribution hub and / or the water distribution hub based on the control signals.

[0041] In examples, the controller is connected to the desalination buoys by communication cables and is configured to control the operation of the offshore desalination buoys.

[0042] In examples, a floatation raft is provided around the desalination buoys and is connected to the desalination buoys and / or the docking platform, to thereby decrease the draft of water desalination system.

[0043] According to another form of the technology there is provided a floating desalination buoy comprising a seawater intake, a desalination apparatus, a brine outlet, and a desalinated water outlet, the desalination buoy further comprising an intake bubble curtain device configured to generate a curtain of bubbles immediately upstream of the seawater intake.

[0044] In examples, the intake bubble curtain device is positioned such that the bubbles do not enter the seawater intake port.

[0045] In examples, the bubbles are microbubbles.

[0046] According to another form of the technology there is provided a floating desalination buoy comprising a seawater intake, a desalination apparatus, a desalinated water outlet, and a brine dispersal means comprising a pipe configured as a ring around the desalination buoy, the pipe comprising a plurality of brine outlet apertures,

[0047] According to another form of the technology there is provided a water desalination system comprising:

[0048] • a docking platform;

[0049] • a plurality of floating desalination devices connected to the docking platform, each floating desalination buoy comprising a seawater intake, a desalination apparatus, a desalinated water outlet;

[0050] • the system further comprising a brine dispersal means comprising a pipe configured as a ring around the outside of each desalination buoy, the pipe comprising a plurality of brine outlet apertures,

[0051] • wherein the brine dispersal means is in fluid communication with a brine outlet for each of the floating desalination buoys.

[0052] Further aspects of the technology, which should be considered in all its novel aspects, will become apparent to those skilled in the art upon reading of the following description which provides at least one example of a practical application of the technology.

[0053] 5. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] One or more embodiments of the technology will be described below by way of example only, and without intending to be limiting, with reference to the following drawings, in which: Figure 1 A Is a diagrammatic view of a water and power generating system according to one form of technology.

[0055] Figure 1 B is a diagrammatic view of the power switching terminal shown in Figure 1 A.

[0056] Figure 2 is a diagrammatic drawing of a water and power conveyance apparatus according to one form of the technology.

[0057] Figure 3 is an isometric view of one form of power conductor for use with the water and power conveyance apparatus of Figure 2.

[0058] Figure 4 is a diagrammatic perspective view of a water desalination system (POD device) of one form of the technology connected to six desalination buoys.

[0059] Figure 5 is a top view of the POD device and desalination buoys of Figure 4.

[0060] Figure 6 is a diagrammatic perspective view of the POD device shown in Figure 4.

[0061] Figure 7 is a diagrammatic perspective view of a POD device of one form of the technology connected to two desalination buoys.

[0062] Figure 8 is schematic diagram showing power and control signal lines in a POD device.

[0063] Figure 9 is a diagrammatic perspective view of a water desalination system provided with a floatation raft of the present technology.

[0064] Figure 10A is a diagrammatic perspective view of a water desalination system provided with a brine dispersal means of the present technology.

[0065] Figure 10B shows a side view of a partial section of brine diffuser ring of the brine dispersal means of Figure 10A. Figure 1 1 A is a front view of a lower portion of a desalination buoy with an intake bubble curtain according to one form of the technology.

[0066] Figure 1 1 B is a cut-away side view of the seawater intake port of the desalination buoy of Figure 11 A.

[0067] 6. BRIEF DESCRIPTION OF EXEMPLARY FORMS OF THE TECHNOLOGY

[0068] 6.1. Water and power generating system

[0069] 6. 1. 1. Overview

[0070] A water and power generating system according to one form of the present technology comprises at least one submerged or floating desalination apparatus (e.g. offshore desalination buoy 401 ) and at least one renewable energy generator (e.g. one or more of solar power system 105, wind power system 105, wave energy converter 420, ocean current energy device 421 and / or other land or offshore based renewable energy generators). The submerged or floating desalination apparatus can be at least partially powered by at the least one renewable energy generator. The system further comprises an electrical power output (e.g. onshore external cable 250) for outputting electrical power generated by the at least one renewable energy generator but not used by the at least one floating or submerged desalination apparatus.

[0071] The system further comprises a controller (e.g. water-power microgrid controller 300) which is configured to vary the operation of the at least one floating submerged or floating desalination apparatus in response to changes in one or more of: available power from the at least one renewable energy generator; varying desalinated water requirements; and varying electrical power requirements.

[0072] The controller may also vary operation of the at least one floating submerged or floating desalination apparatus in response to changes in other variables, as described further below. In some cases, the controller may vary electrical power flows without changing operation of the at least one floating submerged or floating desalination apparatus, or it may change power flows at the same time as varying the operation of the at least one floating submerged or floating desalination apparatus. The controller may be a single apparatus, or its functions may be distributed between a plurality of physically separate apparatus.

[0073] In examples, the controller assigns a notional value to the amount of power being output at the electrical power output and a notional value to the amount of water being output to the desalinated water output, and the controller varies the operation of the at least one floating desalination apparatus to maximise the sum of the notional values of the power output and the water output.

[0074] 6. 1.2. Example system

[0075] A water and power generating system according to one form of the technology is described in more detail below, with reference to Figures 1 a and 1 b.

[0076] Desalinated water 450 is produced by a desalination system 410 located onboard an offshore desalination buoy 401 and is conveyed by way of a water pipeline 200 to an onshore receiving station 405. Electric power 260 is conveyed to and from an offshore terminal 220 and an onshore terminal 225 by way of a power conductor cable 210. Fig. 1 B shows detail of the offshore terminal 220, which is a device that acts to switch and interconnect the power circuits connected to it to achieve desired power flows, and may operate with direct current (DC) or alternating current (AC). Referring back to Figure 1 A, the offshore terminal 220 may be located within the offshore desalination buoy 401 , or within a separate housing such as docking platform 510, described further below. An onshore terminal 225 is located within an onshore facility (not shown). In examples, a plurality of offshore desalination buoys 401 may be provided. The desalinated water from the plurality of offshore desalination buoys 401 may be transported directly to one or more onshore receiving stations 405 by parallel water pipelines 200, or to a single onshore receiving station 405 by a single water pipeline 200.

[0077] In addition to its connection to power conductor cable 210 by way of offshore external cable 250, offshore terminal 220 may be connected to desalination system 410 by way of a desalination power cable 212 and (optionally) to an offshore battery 108 via an offshore battery power cable 213. The offshore terminal 220 may also be connected to one or more marine renewable energy devices, such as a wave energy converter 420 connected via wave energy power cable 107, an ocean current energy device 421 connected via ocean current power cable 1 10, a floating solar array (not shown), an offshore wind turbine (not shown), or other marine renewable energy devices (not shown). An offshore terminal 220 may also be provided. The offshore terminal 220 acts to switch and interconnect the power circuits (e.g. from offshore renewable power sources, power conductor cable etc) connected to it to achieve desired power flows and may operate with direct current (DC) or alternating current (AC).

[0078] In addition to its connection to power conductor cable 210 by way of onshore external cable 251, the onshore terminal 225 may be connected to a grid power source 104 by way of a grid power cable 113 and to an onshore battery 103 via an onshore battery power cable 112. Onshore terminal 225 may also be connected to one or more onshore renewable energy devices such as a solar power system 105 or a wind power system 106 by way of an onshore renewable power cable 11 1 . The onshore terminal 225 may act to switch and interconnect the power circuits connected to it to achieve desired power flows and may operate with direct current (DC) or alternating current (AC). The existence of electric energy storage device(s) and the local power grid onshore allows for improvement of electric power reliability for the offshore desalination devices(s) as well as other power uses connected to the hybrid microgrid system.

[0079] A controller (referred to herein as a water-power microgrid controller 300) performs as a master controller that monitors and controls the operation of the marine water-power microgrid 100. In the example shown the controller may issue commands and receive data from an offshore controller 310 through an offshore control circuit 307, adjusting the interconnection configurations of onshore terminal 225 through an onshore control circuit 306, and operating the onshore receiving station 405 through receiving control circuit 305. Offshore controller 310 responds to commands from water-power microgrid controller 300, adjusts the interconnection configurations of offshore terminal 220 through an offshore control circuit 309, and adjusts the operation of the desalination system 410 through a desalination control circuit 308.

[0080] Water-power microgrid controller 300 commands the flow of electric power and desalinated water production throughout marine water-power microgrid 100. Control software running within water-power microgrid controller 300 dictates the use of available electric power from all electric energy sources connected to the offshore terminal 220 and to the onshore terminal 225 to produce desalinated water 450, or, as required, the curtailment of desalinated water 450 production in favour of maximizing available power within marine water-power microgrid 100 to satisfy higher value demands of the available electric power. The water-power microgrid controller 300 may configure power flows to balance intermittent renewable energy such as that produced by wave energy converter 420, ocean current energy device 421 , solar power system 105, wind power system 106 or other renewable energy sources (not shown) with stored battery energy within offshore battery 108 and onshore battery 103, and grid power source 104. Water-power microgrid controller 300 may command the charging and discharging of offshore battery 108 and onshore battery 103. Water-power microgrid controller 300 may be programmed to optimize (for conditions at the present time) the combined value of desalinated water 450 and electric power 260 (relative to cost of production) by modifying the delivery quantities of either or both, including being responsive to real-time and future market values for both desalinated water and electric power, and including consideration of present and forecasted availability of energy resources for renewable energy generation devices connected to offshore terminal 220 and onshore terminal 225. The notional value assigned to the desalinated water and / or the electrical power may be current (or expected) market value, or it may vary from actual market value if either water production or power production is to be prioritised.

[0081] In some instances, an onshore power outage (or shortage) may result in the controller prioritising delivery of marine renewable energy to shoreside demands and deprioritize water delivery. In other instances, marine renewable resources may be insufficient to drive the marine renewable energy generating devices, and power is provided to the offshore desalination devices from the electric energy storage devices (e.g. batteries) or from a grid connection. In another instance, all renewable energy generated by the marine renewable energy devices is utilized by the offshore desalination devices and no electrical power is delivered onshore. In still other cases, both electrical power and water are delivered to shore in relative amounts calculated to optimize economic returns. In yet another case, where power generated by the renewable energy devices (on and offshore) is insufficient to drive the desalination equipment, the onshore and offshore batteries are depleted, and the cost of mains power is high, it may not be economic to operate the desalination system, and neither electrical power nor water are delivered to shore. In some cases, the system may supply at least a minimum flow of desalinated water and / or of electrical power unless certain conditions are met (e.g. if there is insufficient energy available to do so, if the minimum power output is not required at certain times of day, certain times of the year, etc).

[0082] Where individual floating submerged or floating desalination apparatus 401 have been described above, a POD device 500 as described herein below may be substituted.

[0083] The submerged or floating desalination apparatus described above may also include a floating desalination apparatus such as the example described in PCT publication WO2019 / 098856. 6.2. Water and power conveyance apparatus

[0084] According to another aspect of the technology there is provided a water and power conveyance apparatus 215. In examples, the apparatus 215 is configured for use in a saline / marine environment. The apparatus 215 may be used with a water and power generating system such as that described above. The apparatus 215 comprises a conduit 200 having a bore 201 for conveying desalinated water and at least one electrically insulated electrical cable 210 provided within the bore 201 .

[0085] One example of such a water and power conveyance apparatus 215 is shown in Figs. 1 A and 2. A water and power conveyance apparatus 215 comprises a power conductor cable 210 residing within water pipeline 200, creating a hybrid conveyance system that may be lower cost than a conventional powerwater conveyance system whereby a power conductor cable resides outside of a water pipeline. The presence of desalinated water 450 within water pipeline 200 reduces the potential for electric faults of power conductor cable 210 with low concentrations of free ions, compared with fault conditions of the power conductor exposed to seawater.

[0086] Fig. 2 shows a more detailed view of the water and power conveyance apparatus 215 including water pipeline 200, power conductor cable 210, through-pipe contacts 230, offshore external cable 250 and onshore external cable 251 . Through-pipe contacts 230 penetrate the sidewall of water pipeline 200 and are sealed to prevent water leakage and serve to provide electrical connection between power conductor cable 210, offshore external cable 250 and onshore external cable 251.

[0087] Fig. 3 shows a cutaway view of power conductor cable 210, including a multiplicity of individual wire conductors 211 within an insulation material 270. Power being conducted through power conductor cable 210 may be in the form of direct current (DC) or alternating current (AC) including three-phase power. Control signal cables such as offshore control circuit 307 (not shown in Fig. 3) may also be included as metallic or fiber-optic cables within power cable conductor 210.

[0088] The water and power conveyance apparatus embodies several advantages over conventional marine power and pipeline systems, which are typically separate infrastructure elements installed in distinctly separate pathways. Advantages include: 1) containment and protection of the power cable 210 within the pipeline 200, 2) consolidation of water and power infrastructure in one pathway, 3) reduced armoring requirement for power cable 210 and thus lower cable cost; 4) ability to use the pipeline 200 as a "pull through" conduit for the power cable 210 to avoid costly cable laying on the seafloor; 5) in the case where earth drilling is required to create an underground and / or under seafloor passageway to insert the pipeline 200, allowance for both electrical and water conveyance infrastructure elements to be consolidated to a single borehole, and 6) potential for greater regulator acceptance and reduced permitting timeline and costs association with less environmental disturbance than with two infrastructure pathways. Because desalinated water is largely devoid of dissolved minerals and salts, its electrical conductivity is greatly reduced, making the water environment within the pipeline surrounding the power cable a far better electrical insulator than is the case of an electrical cable submersed in seawater. The purified, demineralized nature of the desalinated water being conveyed within the pipeline also eliminates the potential for scaling or fouling within the pipeline , thus eliminating the need to "pig" the pipe as a maintenance procedure.

[0089] The hybrid water and power conveyance device may consist of polymer piping such as high-density polyethylene (HDPE) or polyvinyl chloride (PVC) or other suitable material with sufficient mechanical strength, pressure resistance, durability, and chemical resistance to convey pressurized desalinated water. The hybrid water and power conveyance device may also consist of multiple power conductors within the power cable with sufficient conductivity to minimize electrical losses, insulated to prevent conduction between conductors and corrosion of the conductor metal by desalinated water. The electrical insulation materials may consist of a polymer or other non-conductive jacketing sufficient to prevent faults from occurring based on the rated voltage of the power being conducted. The power cable may also include mechanical cable elements with sufficient tensile strength to enable pull-through of the cable within the hybrid water / power conveyance device piping and may contain a fiber optic or other type signal conductors.

[0090] When used as part of a water and power generating system such as that described above, the water / power conveyance system 200 may inherently amortize infrastructure costs between the marine renewable energy device(s) and the offshore desalination device(s), and may increase the reliability of water delivery.

[0091] 6.3. Docking Platform and Pooled Offshore Desalination Device

[0092] In one form of the technology a docking platform may be provided. Multiple floating desalination devices may attach to the docking platform. The docking platform may provide an anchor point for the floating desalination devices connected to it, such that each desalination device does not need its own independent mooring. In examples, each desalination device may be substantially cylindrical, although other form factors are possible. The docking platform may also be substantially cylindrical, although other form factors are possible. A water desalination system comprising the combination of a docking platform and a plurality of floating desalination devices is referred to herein as a Pooled Offshore Desalination device (POD).

[0093] The docking platform of the POD device may function as a receiving point for desalinated water from multiple floating desalination devices for conveyance in a single subsea pipeline to shore. Likewise, a single subsea power cable may connect to a common distribution point on the docking platform, where multiple desalination devices may connect to serve their onboard power requirements. In the case of a hybrid water-power microgrid configuration, this subsea power cable may reside within the desalinated water pipeline and power may be received from adjacent marine renewable energy devices as well as from the grid onshore. Of course, more than one subsea pipeline and / or power cable may be used if required.

[0094] In examples, the docking platform may comprise an outer housing in the form of a cylindrical tube of the same diameter as the floating destination devices and may receive up to six floating desalination devices affixed to its perimeter. In examples where the docking platform has the same diameter as the floating desalination devices, the geometry of equilateral triangles dictates that exactly six floating desalination devices arranged side-by-side and contacting the POD device's exterior surface may occupy the space. Alternatively, two, three, four, five, or six floating desalination devices may be attached to the exterior of the docking platform, arranged symmetrically to achieve a balanced, vertical orientation while floating.

[0095] Fig. 4 shows a POD device 500 comprising a docking platform 510 having an outer housing in the form of a tubular vessel. A plurality of offshore desalination buoys 401 are attached to the docking platform 510. The docking platform 510 may provide a common mooring point for the offshore desalination buoys 401.

[0096] Docking platform 510 contains a buoyancy volume 514 and a ballast volume 511 enabling docking platform 510 to float with a vertical orientation (e.g. with a substantially vertical centroidal axis) by causing its center of gravity to be located below its center of buoyancy along its centroidal axis. Docking platform 510 may be moored to the seafloor by at least one mooring 523, each mooring 523 anchored to the sea bottom with an anchor 524. In examples, a plurality of moorings 523 and anchors 524 are provided. In one embodiment, docking platform 510 may function as a connection point for a water pipeline 200 by way of a flexible water hose 520 and power conductor cable 210 by way of flexible power umbilical 521 . On board docking platform 510, flexible water hose 520 may connect to a water filtration stage 515 that connects to water distribution hub 512. Individual offshore desalination buoys 401 may connect to the water distribution hub 512 to deliver desalinated water into flexible water hose 520. In another embodiment (not shown), flexible water hose 520 may connect directly to water distribution hub 512 without water filtration stage 515. Providing the water filtration stage 515 to the docking platform 510 means that the offshore desalination buoys 401 can have reduced filtration capacity relative to what would otherwise be required, or in some cases it may eliminate the need for the offshore desalination buoys 401 to have any filtration means for the desalinated water.

[0097] In examples, a power distribution hub 513 provided to docking platform 510 may serve as an interconnection point for individual offshore desalination buoys 401 to connect to flexible power umbilical 521 to receive electric power 260.

[0098] Fig. 5 shows a top view of the geometric relationship between offshore desalination buoys 401 with an outside diameter D and docking platform 510 with the same outside diameter D. Equilateral triangle sides 530 terminating at the centroids 531 of offshore desalination buoys 401 and docking platform 510 demonstrate that a maximum of exactly six offshore desalination buoys 401 may surround docking platform 510 while contacting its outer circumference.

[0099] Fig.6 shows an embodiment of a water-power distribution station 570 within docking platform 510 whereby a flexible water hose 520 connects to water distribution hub 512, which also connects to as many as six (two are shown for simplicity) buoy water lines 552 which receive desalinated water 450 from adjacent offshore desalination buoys 401 . The desalination buoys may be mechanically attached to docking platform 510 by attachment links 540. Water-power distribution station 570 may also contain a power distribution hub 513 (e.g. equivalent to offshore terminal 220), whereby electrical power 260 may be delivered or received through flexible power umbilical 521 that may pass through flexible water hose 520 and water distribution hub 512 to power distribution hub 513 and terminate in POD terminal 550. POD terminal 550 may function to interconnect, switch, and regulate power flows 560 to and / or from as many as six (two are shown for simplicity) offshore desalination buoys 401 . Power flows through buoy power cables 551, flexible power umbilical 521, wave energy power cable 107, and / or ocean current power cable 110 may be switched and / or regulated. Communications cable 561 may convey signals from a water-power microgrid controller 300 to POD terminal 550 to command its switching and power regulation functions.

[0100] Fig. 7 shows an embodiment of POD device 500 configured with two offshore desalination buoys 401, joined together with a plurality of attachment links 540. Also shown are moorings 523 and anchors 524 connecting POD device 500 to the sea floor (via docking platform 510), as well as flexible water hose 520 and flexible power umbilical 521.

[0101] One or more POD devices 500 may form part of the water and power generating system described above. Fig. 8 shows a control scheme whereby power flows and system control may be regulated by water-power microgrid controller 300 through commands and data conveyed by communications cable 561 to POD terminal 550. In one embodiment, POD terminal 550 may be connected through buoy communication cables 553 to offshore controllers 310 located in each offshore desalination buoy 401 and may relay data and control commands between water-power microgrid controller 300 and offshore controllers 310.

[0102] In one embodiment, electric power 260 may flow from power distribution hub 513 through flexible power umbilical 521, power conductor cable 210, and onshore external cable 251 to onshore terminal 255. In another embodiment, electric power 260 may flow from onshore terminal 255 towards power distribution hub 513 through onshore external cable 251 , power conductor cable 210, and flexible power umbilical 521 . In another embodiment, electric power 260 may not flow in either direction.

[0103] In one embodiment, electric power 260 may be received by power distribution hub 513 from flexible power umbilical 521 and delivered to offshore desalination buoys 401 to meet buoy load 560 through buoy power cables 551 based on commands from water-power microgrid controller 300 and POD terminal 550. The net power flows in this embodiment may be expressed as follows: N times buoy load 560 is equal to electric power 260, where N is equal to the number of offshore desalination buoys 401 attached to docking platform 510.

[0104] In another embodiment, electric power may be received by power distribution hub 513 from wave energy power cable 107, ocean current power cable 110, and / or flexible power umbilical 521 and delivered to offshore desalination PODs 401 through buoy power cables 551 based on commands from water-power microgrid controller 300 and POD terminal 550. The net power flows in this embodiment may be expressed as follows: N times buoy load 560 is equal to the sum of wave power 571 and ocean current power 572 and electric power 260.

[0105] In another embodiment, commands from water-power microgrid controller 300 and POD terminal 550 may direct power distribution hub 513 to deliver electric power received from wave energy power cable 107 and ocean current power cable 110 to offshore desalination PODs 401 through buoy power cables 551 and to flexible power umbilical 521 for delivery to shore. The net power flows in this embodiment may be expressed as follows: N times buoy load 560 plus electric power 260 is equal to the sum of wave power 571 and ocean current power 572.

[0106] 6.4. Shallow Water System

[0107] In cases of shallow water deployment, additional flotation is required to reduce the draft of vertically oriented desalination buoys or POD devices. Simply reducing ballast to raise the desalination buoy may cause the center of ballast to approach or rise above the center of buoyancy, reducing seaworthiness with unstable vertical floatation and creating potential for the desalination buoy to tip over.

[0108] The current invention allows for a single desalination buoy or a POD device comprising multiple desalination buoys to reduce draft without causing unstable floatation in the water column. In examples the shallow water system comprises a flotation raft (e.g. a pontoon or float) surrounding the desalination buoy or POD device, and a variable ballast system within the base of the desalination buoy and / or docking platform. In one form of the technology a flotation raft is attached to the desalination buoy and / or POD device enabling the buoyancy of the flotation raft to raise and reduce the draft of the desalination buoy or POD device. Stability is also improved with the greater lateral support provided by flotation raft, similar to the stability provided by outriggers on a canoe. The flotation raft may be made of any suitable material or combination of materials to provide structural support and flotation in ocean conditions, configured to cause positive net buoyancy.

[0109] The variable ballast system allows for the system to be tuned for specific site conditions, including the expected roughness of sea conditions, wave height, nominal water depth, and tidal depth changes. The ballast may take the form of freshwater or seawater that may be pumped in or out of ballast tanks dynamically, or a massive material which is loaded into the desalination buoy or docking platform upon installation as fixed ballast. Fig. 9 shows flotation system 580 applied to a POD device 500, comprising a flotation raft 585, attachment fixtures 586 and a variable ballast 581. Flotation raft 585 may surround POD device 500 and attach to POD device 500 with attachment fixtures 586. In one embodiment, POD device 500 is raised above its natural flotation level (i.e. its draft is decreased) with added buoyancy provided by flotation raft 585. In another embodiment, flotation raft 585 may be attached to POD device 500 and variable ballast 581 added to increase stability and achieve a desired bottom clearance BC between the distal end of the POD device 500 and the sea floor. In another embodiment, the displacement of flotation raft 585 may be sized to achieve bottom clearance BC without adjustment of variable ballast 581. In another embodiment, bottom clearance BC may be adjusted dynamically by pumping water or seawater in or out of tanks comprising variable ballast 581.

[0110] 6.5. Brine Discharge Device

[0111] Desalination devices typically produce brine as a consequence of separating salt from saline water (e.g seawater). Typically, a desalination device (e.g. offshore desalination buoy 401) comprises at least an inlet for saline water, a desalination apparatus (e.g. one or more reverse osmosis (RO) columns), a brine outlet and a desalinated water outlet.

[0112] Brine is, by its nature, denser than seawater, so tends to descend when introduced into the ocean. Conventional brine disposal from onshore desalination plants requires piping the brine some distance offshore in seafloor pipes to brine diffusors designed to prevent pooling of brine on the seafloor, where it may harm marine life. Energy is required to pressurize the brine flow for ejection from diffuser nozzles, and brine piping and diffusers are costly to install. In addition, the high velocity shear at the ejection nozzles may cause additional harm to sea life.

[0113] Brine produced by the desalination system on board the desalination buoy may be discharged directly into the ocean at the top of the water column at low pressure and without nozzles. Brine descending from the top of the water column mixes naturally as it descends, and may reach ambient salinity before it reaches the seafloor.

[0114] One form of the technology comprises a brine dispersal means for broadly dispersing brine produced by a desalination buoy or POD device. Perforated piping may be located below the water surface with an array of brine outlet holes through its sidewall to allow brine to escape into surrounding seawater. Brine may be introduced into the perforated piping from diffuser lines emanating from an individual desalination buoy 401 or the desalination buoys 401 of a POD device. The form of this diffuser pipe is intended to achieve at least one of the following 1) broad area diffusion to avoid high concentrations of brine salinity in the immediate vicinity of the diffuser pipe, 2) very low pressure drop to minimize energy consumption, and 3) adequate diffusion over a broad area of water column that the salinity of desalination buoy intake water is not increased by the presence of brine near the intake.

[0115] In one form of the technology, the perforated piping may take the form of a ring around the desalination buoy or POD device to create a broad area of brine diffusion, minimize energy consumption and avoid brine contamination of intake water.

[0116] Fig. 10A shows a brine dispersal means comprising a brine diffusion ring 590 surrounding POD device 500, with diffuser lines 591 supplying brine from offshore desalination buoys 401 for diffusion into the surrounding ocean. Brine diffuser ring 590 comprises a pipe formed into a ring of sufficient diameter to encompass an offshore desalination buoy 401 , in the case of individual buoy deployments (not shown), or POD device 500 as shown. The brine diffusion ring 590 comprises a multiplicity of perforations into the sidewall of the pipe allowing brine 592 to be discharged. The perforations may extend around substantially the entire ring. Supply of brine 592 from desalination buoys 401 to brine diffusion ring 590 may be conducted by at least one brine diffuser line 591.

[0117] In one embodiment, discharged brine 592 diffuses and mixes with surrounding seawater 597 in the near vicinity of brine diffuser ring 590 and does not raise the salinity of intake seawater 596 being let into seawater intake ports 595, due to brine diffuser ring 590 being separated vertically from seawater intake ports 596 by a sufficient diffusion distance DD in the water column (shown in Fig. 10B).

[0118] In another embodiment, brine diffusion ring 590 may be increased in diameter to increase its lateral separation from seawater intake ports 595 to further cause separation of brine 592 being injected into seawater 597 from seawater intake ports 595.

[0119] Fig. 10B shows a side view of a partial section of brine diffuser ring 590 adjacent to offshore desalination buoy 401 , that may be individually deployed or a component of POD device 500, indicating a level of submersion below the water surface 594 with brine 592 being ejected downward from brine diffuser ring 590 positioned at a ring depth RD below the surface. The sum of ring depth RD and diffusion depth DD equals the depth of seawater intake port 595 below water surface 594.

[0120] 6.6. Intake Bubble Curtain

[0121] Desalination plants intaking raw seawater are vulnerable to ocean algae blooms, which typically interrupt operation due to biofouling of intake filters. The offshore desalination buoy is also subject to intake fouling from suspended contaminants and microorganisms such as algae.

[0122] In one form of the technology an air bubble curtain may be generated in front of the seawater intake of a desalination buoy to reduce the loading of suspended particles and microorganisms from the incoming seawater. By design, the seawater intake for an offshore desalination buoy is accessible and readily supplied with air from within the buoy.

[0123] In examples, the bubble emitter is located at or below the lower edge of the seawater intake port. This may enable micro bubbles to be emitted at close proximity to each other. The micro bubbles rise due to their buoyancy, providing a stream of bubbles with substantial contact area to the incoming seawater stream and any suspended particles of microorganisms therein. Upon contact with these suspended bodies, surface tension at the bubble's surface tends to attach the bodies to the bubbles, causing the bodies to rise with the bubble stream. With positioning of the bubble curtain ahead of the intake port, the rising bubbles with attached bodies will pass the upper edge of the intake port and not be drawn inside. Above the upper edge of the intake port, the bubbles and attached bodies will continue to rise to the surface and avoid being drawn into the intake port.

[0124] Referring next to Fig. 1 1A, an intake bubble curtain device 600 comprises a bubble emitter 610 and pressurized air supply (not shown). Bubble emitter 610 comprises a hollow tube for the conductance of pressurized air, with a multiplicity of hole penetrations provide to the tube. In examples, the holes are provided in the top radius of the tube. The holes may be sized for the formation of micro bubbles 605 (e.g. bubbles smaller than one hundredth of a millimetre in diameter, but larger than one micrometre) . The holes may be spaced in close proximity to each other along bubble emitter 610 to form a nearly continuous "bubble curtain" across the seawater intake port 595.

[0125] Fig. 11 B shows a cut-away side view of a seawater intake port 595 (e.g. of an offshore desalination buoy 401 ) and an intake bubble curtain device 600. As shown, bubble emitter 610 may be spaced a distance S from the mouth of seawater intake port 595. Distance S may be selected to allow for intake seawater 596 with a flow velocity 599 to displace microbubbles 605 towards seawater intake port 595 without causing micro bubbles 605 to be carried into seawater intake port 605 (that is, the bubbles rise above the level of the upper edge of the seawater intake port before they reach the seawater intake port). Assuming uniform flow velocity 599 across intake seawater 596, the distance S must be greater than intake port height H times the ratio of the flow velocity 599 divided by bubble rise velocity 612 in order to avoid microbubbles entering the intake port 605

[0126] Offshore desalination buoys 401 of the present technology may comprise one or more of the floatation system 580, brine dispersal means and intake bubble curtain device 600 described above.

[0127] 6.7. Other Remarks

[0128] Those skilled in the art will appreciate that various forms of the present technology provide apparatus and systems for desalinating water which increase the economic viability of such systems and apparatus, and which allow for more convenient transportation.

[0129] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to".

[0130] The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference.

[0131] Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavour in any country in the world.

[0132] The technology may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features. Where in the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth.

[0133] It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the technology and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be included within the present technology.

Claims

7. CLAIMS1 . A water and power generating system comprising at least one renewable energy generator, at least one submerged or floating desalination apparatus configured to be at least partially powered by the at least one renewable energy generator, a controller, a desalinated water output conduit for outputting water from the at least one floating desalination apparatus and an electrical power output for outputting electrical power generated by the renewable energy generator but not used by the at least one floating desalination apparatus, wherein the controller is configured to vary the operation of the at least one floating desalination apparatus in response to changes in available power from the at least one renewable energy generator and varying desalinated water and electrical power requirements.

2. The system of claim 1 , wherein the controller assigns a notional value to the amount of power being output at the electrical power output and a notional value to the amount of water being output to the desalinated water output, and varies the operation of the at least one desalination apparatus to maximise the sum of the notional values.

3. The system of any one of claims 1 or 2, wherein the controller operates the desalination apparatus to produce at least a minimum flow rate of desalinated water unless a first predetermined condition occurs.

4. The system of any one of claims 1 to 3, wherein the controller varies the operation of the desalination apparatus such that the system supplies at least a minimum electrical output to the electrical power output unless a second predetermined condition occurs.

5. The system of any one of claims 1 to 4, wherein at least one of the renewable energy generators is located offshore.

6. The system of any one of claims 1 to 5, wherein at least one of the renewable energy generators is located onshore.

7. The system of any one of claims 1 to 6, further comprising a connection to an onshore mains power grid.

8. The system of claim 7, wherein the system is configured to receive power from the mains power grid and / or to supply power to the mains power grid.

9. The system of any one of claims 1 to 8, further comprising at least one battery for storing power from the renewable energy generator and / or from the mains power grid.

10. A water and power conveyance apparatus, the apparatus comprising a conduit having a bore for conveying desalinated water and at least one electrically insulated electrical cable provided within the bore, the at least one electrically insulated electrical cable comprising an insulation material and a wire conductor within the insulation material.1 1 . The apparatus of claim 10, wherein the conduit is configured for use in a saline or marine environment.

12. The apparatus of any one of claims 10 to 1 1, wherein the conduit is formed from a polymer material selected from high-density polyethylene (HDPE) or polyvinyl chloride (PVC).

13. The apparatus of any one of claims 10 to 12, wherein at least one signal conductor is provided within the insulation material.

14. The apparatus of claim 1 3 wherein the signal conductor comprises a fiber-optic cable.

15. The apparatus of any one of claims 10 to 14, wherein a mechanical cable element is provided within the insulation material for pull-through installation of the electrically insulated electrical cable within the conduit.

16. A docking platform comprising: an outer housing; at least one mooring attachment means; a ballast volume configured to cause the outer housing to maintain a substantially vertical orientation in use; and at least one of: a) an electrical distribution hub configured for connection to a plurality of electrical conductors; and b) a water distribution hub configured for connection to a plurality of water carrying conduits.

17. The docking platform of claim 16, wherein the docking platform is configured to dock with a plurality of offshore desalination buoys.

18. The docking platform of any one of claims 16 to 17, comprising attachment links for connecting the desalination buoys to the docking platform.

19. The clocking platform of any one of claims 16 to 18, wherein the outer housing of the clocking platform is substantially cylindrical and the docking platform is configured to dock with six offshore desalination buoys arranged circumferentially around the tubular housing.

20. The docking platform of any one of claims 16 to 19, wherein the electrical distribution hub is configured to interconnect with the offshore desalination buoys via buoy power cables.

21. The docking platform of claim 20, wherein the electrical distribution hub is configured for connection to a flexible power umbilical for conveying electrical power to or from shore.

22. The docking platform of any one of claims 16 to 21, wherein the water distribution hub is configured to receive desalinated water from the offshore desalination buoys via buoy water lines.

23. The docking platform of any claim 22, wherein the water distribution hub is configured for connection to a flexible water hose for conveying desalinated water from the offshore desalination buoys to shore.

24. The docking platform of claim 23 when dependent on claim 21 , wherein the flexible power umbilical passes through the flexible water hose and the water distribution hub to the electrical distribution hub.

25. The docking platform of any one of claims 16 to 24, configured to receive control signals from a remote controller via a communications cable.

26. A water desalination system comprising: a docking platform comprising: an outer housing; at least one mooring attachment means; a ballast volume configured to cause the outer housing to maintain a substantially vertical orientation in use; and at least one of: a) an electrical distribution hub configured for connection to a plurality of electrical conductors; and b) a water distribution hub configured for connection to a plurality of water carrying conduits; and a plurality of floating desalination devices connected to the docking platform.

27. The water desalination system of claim 26, the outer housing of the docking platform and the floating desalination devices are substantially cylindrical.

28. The water desalination system of claim 27, wherein a diameter of each of the floating desalination devices is substantially equal to a diameter of the docking platform.

29. The water desalination system of any one of claims 26 to 28, wherein the docking platform comprises an electrical distribution hub and a water distribution hub, and each floating desalination device is connected to the electrical distribution hub by an electrical connector and to the water distribution hub by a conduit.

30. The water desalination system of any one of claims 26 to 29, wherein the docking platform comprises a controller configured to receive control signals and to control the operation of the electrical distribution hub and / or the water distribution hub based on the control signals.31 . The water desalination system of claim 30, wherein the controller is connected to the desalination buoys by communication cables and is configured to control the operation of the offshore desalination buoys.

32. The water desalination system of any one of claims 26 to 31, further comprising a flotation raft provided around the desalination buoys and connected to the desalination buoys and / or the docking platform to decrease the draft of the water desalination system.

33. A floating desalination buoy comprising: a seawater intake; a desalination apparatus; a brine outlet; a desalinated water outlet; and an intake bubble curtain device configured to generate a curtain of bubbles immediately upstream of the seawater intake.

34. The floating desalination buoy of claim 33, wherein the intake bubble curtain device is positioned such that the bubbles do not enter the seawater intake port.

35. The floating desalination buoy of claim 33 or 34, wherein the bubbles are microbubbles.

36. A floating desalination buoy comprising: a seawater intake; a desalination apparatus; a desalinated water outlet; and a brine dispersal means comprising a pipe configured as a ring around the desalination buoy, the pipe comprising a plurality of brine outlet apertures.

37. A water desalination system comprising: a docking platform; a plurality of floating desalination devices connected to the docking platform, each floating desalination buoy comprising a seawater intake, a desalination apparatus, and a desalinated water outlet; a brine dispersal means comprising a pipe configured as a ring around the outside of each 1desalination buoy, the pipe comprising a plurality of brine outlet apertures; wherein the brine dispersal means is in fluid communication with a brine outlet for each of the floating desalination buoys.

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