WO2014100674A1

WO2014100674A1 - Integrated wave-powered desalination system

Info

Publication number: WO2014100674A1
Application number: PCT/US2013/077107
Authority: WO
Inventors: Olivier CEBERIO; Pasquale REZZA, Jr.; Arthur R. Williams
Original assignee: Resolute Marine Energy, Inc.
Priority date: 2012-12-21
Filing date: 2013-12-20
Publication date: 2014-06-26

Abstract

A wave-powered desalination system includes a wave-energy-converter subsystem, a pressurization subsystem, a reverse-osmosis chamber, an energy-recovery subsystem. The wave-energy-converter subsystem converts power carried by waves propagating on a body of water into mechanical power. The pressurization subsystem pressurizes an input seawater flow in at most two steps by at most two pressurization stages. The reverse-osmosis chamber includes a membrane having a plurality of passages disposed therein, receives the pressurized seawater, and divides the pressurized seawater into a permeate flow of purified water and a pressurized brine flow that carries away particles that did not pass through the membrane. The energy-recovery subsystem captures power carried by the pressurized brine flow that exits the reverse-osmosis chamber and delivers the captured power to the pressurization subsystem.

Description

INTEGRATED WAVE-POWERED DESALINATION SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 61/848,026 filed on December 21, 2012, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to the capture and conversion of the energy carried by waves propagating at the surface of large bodies of water, and the use of this energy to desalinate sea water by reverse osmosis. The wave energy is captured by a Wave-Energy Converter (WEC).

BACKGROUND OF THE INVENTION

[0003] This section is intended to provide a background or context to the invention recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.

[0004] The most efficient and most commonly used method of desalination is reverse-osmosis which requires very high pressure to force sea water through a membrane characterized by passages sufficiently small to block the unwanted sodium and chlorine ions. Desalination by reverse-osmosis requires that a flow of sea water be pressurized to a level sufficient to drive a substantial portion of the flow through membranes in a reverse-osmosis (RO) chamber. An example of an RO process is illustrated schematically in Fig. 1. The RO process divides the input seawater flow into two output flows, one of permeate (i.e., potable water) and one of brine (i.e., sea water of increased salinity) that is normally returned to the sea. The pressure supplied by a pump in the desalination system must be sufficient (-800 psi) to overcome an osmotic pressure created by a salinity gradient across the RO membrane. In addition, the flow along (as opposed to through) the membrane must be sufficient to remove particles blocking the membrane. Without a rapid flow along (i.e., tangential to) the membrane, the membrane quickly clogs. But, the magnitude of the flow required to prevent clogging is often comparable to, or greater than, the flow through the membrane. As illustrated in Figs. 1-4, the membrane may be a diagonal membrane. In this configuration, the flows through and along the membrane occur at the same pressure, and thus, the power in the "flushing" flow along the membrane is usually greater than the power consumed by the RO process per se. Efficiently recovering and reusing the flushing power is, therefore, not a minor challenge of RO desalination; it is a central challenge.

[0005] In some embodiments, as illustrated in Figs. 8-11, 14 and 15, a plurality of membranes may be utilized in a RO chamber. Each RO chamber includes a membrane unit having an input for high pressure seawater and two outputs, one for fresh water (i.e., permeate) and one for high pressurized brine. The membrane unit further includes a membrane. In preferred embodiments, the membrane is oriented diagonally, while in other embodiments, the membrane may be oriented horizontally or vertically.

[0006] Referring now to Fig. 1, as the relative sizes of the arrows indicate, the brine flow is usually greater than the permeate flow. For example, as seen in Fig. 1 , the brine flow may be twice that of the permeate flow, which is typical. In Fig. 1 there are three flows: pressurized seawater flow that is then divided by the RO membrane into two flows: 1) low-pressure permeate (desalinated water) flow; and 2) high-pressure brine flow. The low-pressure permeate flow and the high-pressure brine flow are output from locations disposed at opposing sides of the RO membrane.

[0007] Fig. 2 illustrates the principle that conversion of fluid-motion power into other forms of power is reversible - in the absence of irreversible losses. In the absence of irreversible losses, such as those due to friction and viscosity, the power consumed by the reverse osmosis is the product of the pressure and the rate of desalinated flow. The power actually consumed is, of course, greater due to inevitable inefficiencies. The required power is so great that it is the principal obstacle to the widespread exploitation of the technology.

[0008] The pump shown in Fig. 1 provides the required pressure. As indicated in Fig. 2, the pump consumes power. The form of the power can be electrical, mechanical or fluid, for example. The amount of power consumed in this way is proportional to the product of the pressure increase and the flow rate. Additionally, the quantity of power consumed is

proportional to the efficiency of the device.

[0009] Hydraulic motors, such as turbines, act like pumps in reverse in that hydraulic motors lower the pressure of the flow and produce, rather than consume, power. Again, the power can be mechanical, fluid or electrical. Additionally, mechanical power produced in this way can be linear or rotational. Fig. 2 shows energy-conservation relations describing this power conversion. While those for motors are similar to those shown for pumps, efficiency factors in a similar, but importantly different way. The conversion of power from one form to another is always less than perfectly efficient.

[0010] Desalination systems combine pumps and motors in a variety of ways. Each component device is imperfectly efficient. Reducing the number of such components is one of the important issues in this context.

[0011] Two lines of development:

[0012] There are two general ways of assisting in the desalination of water: recovery and wave energy. Because the brine flow produced by the RO process is both rapid and highly

pressurized, it carries substantial power, usually more power than is consumed by the RO process per se. The capture and reuse of the brine power is called recovery. As illustrated in Fig. 3, brine power capture can be performed by a fluid motor, such as a turbine. Again, as shown in Fig. 3, the captured power can be used to contribute to the pressurization of the input seawater flow. [0013] The second line of development is the exploitation of wave energy which is both abundant and accessible in coastal areas. The power available in ocean waves is symbiotic with the often especially great need for potable water in near-shore communities, including vacation resorts, but even with wave power the benefits of efficiency in both capital and operating costs are substantial. Wave energy may be used to drive a pump that pressurizes water introduced into the RO system for desalination.

[0014] Recovery integration and efficiency

[0015] Fig. 3 shows schematically the recovery process. A motor in the brine flow captures the very substantial power carried by the brine flow, and uses this captured power to drive a pump that contributes to the pressurization of the sea water entering the RO chamber. This pump is sometimes referred to as a booster pump, despite the fact that it usually adds more power to the seawater flow than the "primary" pump.

[0016] The motor that captures the power from the brine and the pump that is powered by such a motor may be integrated into one unit. A unit integrating both the motor and the pump is often referred to as a "Clark pump" and is described by U.S. Pat. 5,628,198, which is hereby incorporated by reference in its entirety. Throughout the remainder of this application the term "Clark pump" refers to the combination of a motor that captures power from the brine exiting an RO system with a pump that is driven by the motor. A "Clark pump" device integrates the recovery motor-pump combination shown in Fig. 3 into a single device, as shown in Fig. 4. The consolidation of the motor and pump reduces both the manufacturing and deployment costs, and improves the efficiency of the recovery process.

[0017] Powering desalination with wave energy, without recovery

[0018] The straightforward introduction of wave power into the desalination context is illustrated by Fig. 5. Fig. 5 is a schematic drawing showing the elements of a reverse-osmosis desalination system 100 powered by wave energy. In Fig. 5, the reverse-osmosis desalination system 100 includes a reverse-osmosis desalination device 101 that includes a chamber 114 which receives a pressurized water flow to be desalinated 102 which is divided by the reverse- osmosis device 101 into two flows, a desalinated water flow 103 and a brine flow 108 of increased salinity. The system comprises two fluid flows, both of which enter the system from the ocean. One flow comprises the fluid to be desalinated (water flow 102). A substantial fraction of this flow leaves the system as desalinated water 103; the remainder is returned to the ocean (water flow 108). The second flow 111 also enters the system from the ocean, is pressurized by the wave-energy-conversion (WEC) subsystem 109, which powers the primary pump 104 that pressurizes the water flow to be desalinated 102. The WEC subsystem 109 is powered by ocean waves. An example is a so-called surge-type wave-energy converter (WEC) , which could power the WEC subsystem 109, such as those described in more detail with respect to Figs. 12a and 12b.

SUMMARY OF THE INVENTION

[0019] One embodiment relates to a wave-powered desalination system including a wave- energy-converter subsystem, a pressurization subsystem, a reverse-osmosis chamber, an energy- recovery subsystem and passive conduits. The wave-energy-converter subsystem convert powers carried by waves propagating on a body of water into mechanical power. The pressurization subsystem pressurizes an input seawater flow in at most two steps by at most two pressurization stages. The reverse-osmosis chamber includes a membrane having a plurality of passages disposed therein, receives the pressurized seawater, and divides the pressurized seawater into a permeate flow of purified water and a pressurized brine flow that carries away particles that did not pass through the membrane. The energy-recovery subsystem captures power carried by the pressurized brine flow that exits the reverse-osmosis chamber and delivers the captured power to the pressurization subsystem. The passive conduits carry the input seawater, the pressurized brine, and the purified water between the body of water and components of the wave-powered desalination system without changing a pressure, a

composition or a magnitude of a flow of each of the input seawater, the pressurized brine and the purified water. [0020] Another embodiment relates to a method for desalinating seawater with a wave-powered desalination system. The method includes converting power carried by waves propagating on a body of water into mechanical power via a wave-energy-converter subsystem, pressurizing an input seawater flow in at most two steps by at most two pressurization stages, receiving the pressurized seawater and dividing the pressurized seawater, in a reverse-osmosis chamber including a membrane having a plurality of passages disposed therein, into a permeate flow of purified water and a pressurized brine flow that carries away particles that did not pass through the membrane, capturing power carried by the pressurized brine flow that exits the reverse- osmosis chamber, and delivering the captured power to the pressurization subsystem. The pressurized brine and the purified water are carried between the body of water and components of the wave-powered desalination system by passive conduits without changing a pressure, a composition or a magnitude of a flow of each of the input seawater, the pressurized brine and the purified water.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, in which:

[0022] Fig. 1 is a diagram of a conventional desalination system.

[0023] Fig. 2 is a diagram illustrating that conversion of fluid-motion power into other forms of power is reversible.

[0024] Fig. 3 is a diagram illustrating recovery power from the brine exiting the RO system.

[0025] Fig. 4 is a diagram illustrating the integration of a recovery motor and a pump powered by the recovery motor into a single unit.

[0026] Fig. 5 is a diagram of a conventional WEC-powered reverse-osmosis desalination system. [0027] Fig. 6 is a diagram providing a comparison of three embodiments of the present disclosure. The embodiments differ in the way in which wave and recovery power are used to pressurize the seawater flow.

[0028] Fig. 7 is a diagram illustrating Two-Stage Pressurization, as well as Upstream vs. Downstream Recovery-Powered Pressurization.

[0029] Fig. 8 is a diagram illustrating Two-Stage Pressurization, as well as Recovery pressurization downstream and discrete (motor + pump).

[0030] Fig. 9 is a diagram illustrating Two-Stage Pressurization, as well as Recovery pressurization downstream and integrated.

[0031] Fig. 10 is a diagram illustrating Two-Stage Pressurization, as well as Recovery- powered pressurization upstream and discrete.

[0032] Fig. 11 is a diagram illustrating Two-Stage Pressurization, as well as Recovery- powered pressurization upstream and integrated.

[0033] Fig. 12a is a diagram of a surgeWEC Paddle that converts fluid wave power into translational mechanical power.

[0034] Fig. 12b is a diagram of a surgeWEC Paddle that converts fluid wave power into rotational mechanical power.

[0035] Fig. 13 is a diagram illustrating conversion of brine-flow power into translational mechanical power.

[0036] Fig. 14 is a diagram of a Single-stage wave-powered desalination system illustrating discrete components mounted to a common translational power transmission. [0037] Fig. 15 is a diagram of a Single-stage wave-powered desalination system illustrating integration into a single device all three components, wave and brine power capture and pressurization of the seawater flow.

[0038] Fig. 16 is an illustration of the single integrated device appearing in Fig 15. Fig. 16 illustrates a WEC-assisted Clark pump.

[0039] Fig. 17 is an illustration of an Oscillating Rotary Vane Pump (or Motor) comprising a single rotor-stator pair.

[0040] Fig. 18 is an illustration of an Oscillating Rotary Vane Pump & Motor comprising a double rotor-stator vane pair.

[0041] Fig. 19 is a schematic cross section of a WEC-assisted Clark pump showing how the ratio of brine flow to seawater flow is controlled by the diameter of the connection between the two Clark pump pistons.

[0042] Fig. 20 is a schematic cross section of a WEC-assisted Clark pump in which the ratio of the brine flow to the seawater flow is controlled by the diameters of the right- and left-hand cylinders comprising the form of the WEC-assisted Clark pump.

[0043] Fig. 21 is a schematic cross section of a two-rotor-stator pair WEC-assisted Clark pump. Fig. 21 illustrates an oscillating rotary vane pump or motor with a double rotor-stator pair, and unequal brine and seawater flows.

DETAILED DESCRIPTION

[0044] As discussed above, wave-powered desalination requires capturing the power available from both wave motion and the brine flow, and using this captured power to pressurize the seawater entering the RO chamber. Thus all of the embodiments described below involve devices that capture the fluid-motion power in two flows, the wave motion and the high-pressure brine flow, and that use the captured power to pressurize the seawater flow. The embodiments described all combine capture and pressurization devices in different ways.

[0045] As Fig. 5 indicates, RO desalination involves three fluid flows. The power available in two of these flows, wave motion and the flushing brine flow, are captured and used to pressurize the seawater flow into the RO chamber. This fundamental structure leads to the one- and two- stage alternatives shown in Fig. 6. The wave and brine power sources can be applied to the seawater flow either together or independently. If applied independently, the two power sources can be applied to the seawater stream in either order, leading to the three configurations shown in Fig. 6. Each of the three configurations shown in Fig. 6 has its advantages. Below we describe the issues relevant to these configurations and the embodiments that exploit them.

[0046] Among the configurations described below is a single-stage pressurization in which the WEC is synthesized with a Clark pump. This synthesis combination provides the entire pressurization required by RO desalination in a single, integrated device.

[0047] Embodiment Options: Number of pressurization stages

[0048] Fig. 6 is a diagram providing a comparison of three embodiments of the present disclosure. The embodiments differ in the ways in which wave and recovery power are used to pressurize the seawater flow.

[0049] As Fig. 6 indicates, a distinction among the disclosed embodiments is whether seawater pressurization is accomplished in two stages or one. One aspect of the distinction between single-stage and two-stage pressurization is that two-stage pressurization allows the straightforward exploitation of the very efficient Clark pump.

[0050] For single-stage pressurization, the wave and brine power must be combined. It might appear to be necessary therefore to convert the power carried by both fluid flows into mechanical power (a common axle, for example), so that they can be readily combined. As described below, this need not be the case. [0051] Two-stage pressurization: Order of WEC-powered and Recovery-powered pressurization

[0052] Fig. 7 focuses on the differences between the two sequential orderings of wave- powered and brine-powered pressurization that are available in two-stage pressurization. The two orderings are labeled upstream and downstream, indicating where in the seawater flow the recovery-powered pressurization 702 occurs relative to the WEC-powered pressurization 701. If the recovery-powered pressurization 702 is downstream of the WEC-powered pressurization 701, it can be performed entirely on land. If it is performed upstream, then the pressurized output of the recovery-powered pressurization 701 must be piped to provide input to the underwater WEC device 703. Fig. 7 demonstrates that pressurization can be done in two different sequential orders. Pressurization powered by waves and by recovery can be done in either order.

[0053] Two-stage pressurization, downstream recovery-powered pressurization.

[0054] Fig. 8 illustrates the two-stage configuration in which recovery-powered pressurization 802 occurs downstream of the WEC-powered pressurization 801. In the system illustrated in Fig. 8, pressurization powered by waves occurs before (upstream) a second stage powered by recovery. Output from the recovery-powered pressurization 802 flows to the RO chamber 803. Fig. 8 shows details of a realistic system using this configuration. The additional detail includes an accumulator 804, additional filters 805, a storage container as well as other components. The accumulator 804 acts as both pressure smoothing device and as a fly wheel. The accumulator 804 is an energy storage device that captures and stores energy when the pressure in the flow is high, and returns the captured energy to the flow when the pressure in the flow is low. A typical accumulator is described in the patent GB 1,104,527 and in the more recent international patent application WO 2004043576, each of which are hereby incorporated by reference in their entirety. In certain embodiments, the accumulator functions by allowing a flow to occupy a flexible bladder whose expansion and contraction changes the volume available to a fixed quantity of compressible gas. Pressure fluctuations in the incompressible flow are thereby reduced. The additional filters 805 remove relatively large impurities from the seawater flow. Additional components in the illustrated embodiment of Fig. 8, including the brine-dilution tank 806 and the calcium-neutralizer tank 816, are generic components of desalination facilities.

[0055] The function of the Fig. 8 embodiment may be explained by considering the various illustrated flows. Starting first with the upstream WEC-powered pressurization 801 , low pressure seawater 807 is filtered by filters 805 and provided to a wave-energy-conversion (WEC) subsystem 808, which powers two conventional linear displacement pumps 809 that pressurize the low pressure seawater 807 into medium pressure seawater 810. The WEC subsystem 808 is powered by ocean waves, and may include a so-called surge-type wave-energy converter (surgeWEC), such as those described in more detail with respect to Figs. 12a and 12b, and as illustrated in the Fig. 8 embodiment. In the embodiment illustrated in Fig. 8, the conventional linear pumps 809 are attached to a surgeWEC paddle 817, which oscillates in response to waves propagating at the surface of large bodies of water. In the embodiment illustrated in Fig. 8, the medium pressure seawater 810 flows to accumulator 804 (described above), and ultimately flows to a recovery booster pump 811. The recovery booster pump 811 adds further pressure to the medium pressure seawater 810 which then flows to the RO chamber 803 as high pressure seawater 812. As explained above with reference Figs. 3 and 5, the high pressure seawater 812 then flows through the RO chamber 803 to generate two flows: 1) low-pressure permeate (desalinated water / fresh water) 813 and 2) high pressure brine 814.

[0056] As also generally explained above with reference to Figs. 3 and 5, the high pressure brine 814 powers a motor 815 (such as a turbine), and that captured energy can be used to drive booster pump 811 which contributes to the pressurization of medium pressure seawater 810 into high pressure seawater 812 that flows to the RO chamber 803 to generate low-pressure permeate (desalinated water / fresh water) 813. In this embodiment, the energy-recovery subsystem comprises the motor 815, which is configured to convert power carried by the high pressure brine flow 814 into power configured to drive the booster pump 811, and the booster pump 811 is configured to assist in pressurizing the medium pressure seawater 810. In particular, the booster pump 811 may be configured to transfer a pressure of the high pressure brine flow 814 directly to the medium pressure seawater 810 without conversion into, and back out of, mechanical power.

[0057] Whereas Fig. 8 illustrates recovery as independent capture and pressurization devices, Fig. 9 shows these devices as integrated into a Clark pump.

[0058] Fig. 9 illustrates the two-stage configuration in which recovery-powered pressurization 902 occurs downstream of the WEC-powered pressurization 901. In the system illustrated in Fig. 9, pressurization powered by waves occurs before (upstream) a second stage powered by recovery. Output from the recovery-powered pressurization 902 flows to the RO chamber 903. In the embodiment of Fig. 9, the recovery-powered pressurization 902 is achieved using a Clark pump. Fig. 9 shows details of a realistic system using this configuration. The additional detail includes an accumulator 904, additional filters 905, a storage container as well as other components. The accumulator 904 acts as both pressure smoothing device and as a fly wheel. The accumulator 904 is an energy storage device that captures and stores energy when the pressure in the flow is high, and returns the captured energy to the flow when the pressure in the flow is low. In certain embodiments, the accumulator functions by allowing a flow to occupy a flexible bladder whose expansion and contraction changes the volume available to a fixed quantity of compressible gas. Pressure fluctuations in the incompressible flow are thereby reduced. The additional filters 905 remove relatively large impurities from the seawater flow. Additional components in the illustrated embodiment of Fig. 9, including the brine-dilution tank 906 and the calcium-neutralizer tank 916, are generic components of desalination facilities.

[0059] The operation of the Fig. 9 embodiment may be explained by considering the various illustrated flows. Starting first with the upstream WEC-powered pressurization 901, low pressure seawater 907 is filtered by filters 905 and provided to a wave-energy-conversion (WEC) subsystem 908, which powers two conventional linear displacement pumps 909 that pressurize the low pressure seawater 907 into medium pressure seawater 910. The WEC subsystem 908 is powered by ocean waves, and may include a so-called surge-type wave-energy converter (surgeWEC), such as those described in more detail with respect to Figs. 12a and 12b, and as illustrated in the Fig. 9 embodiment. In the embodiment illustrated in Fig. 9, the conventional linear pumps 909 are attached to a surgeWEC paddle 917, which oscillates in response to waves propagating at the surface of large bodies of water. In the embodiment illustrated in Fig. 9, the medium pressure seawater 910 flows to accumulator 904 (described above), and ultimately flows to a Clark pump 911. Operation of the Clark pump 911 will be discussed in further detail below. The recovery Clark pump 911 adds further pressure to the medium pressure seawater 910 which then flows to the RO chamber 903 as high pressure seawater 912. As explained above with reference Fig. 4, the high pressure seawater 912 then flows through the RO chamber 903 to generate two flows: 1) low-pressure permeate (desalinated water / fresh water) 913 and 2) high pressure brine 914.

[0060] As also generally explained above with reference to Fig. 4, the high pressure brine 914 is introduced into the Clark pump 911, which comprises a motor (such as a a piston

arrangement), and a booster pump that contributes to the pressurization of medium pressure seawater 910 into high pressure seawater 912 that flows to the RO chamber 903 to generate low- pressure permeate (desalinated water / fresh water) 913.

[0061] The illustrated embodiment of a Clark pump 911 uses two opposing cylinders A and B, with pistons that share a single rod that passes through a center block. A reversing valve, which is controlled by a pilot valve that may be mechanically actuated by the pistons, allows the two opposing cylinders to alternate between driving and pressurizing. As illustrated in Fig. 9, feed pressure from the high pressure brine 914 is directed into cylinder A and pushes against the piston proximate to cylinder A, pushing the rod through the center block. The brine in cylinder B, which has gone through the RO chamber 903 on the previous stroke, is discharged. Cylinder A starts to pressurize when the piston and rod are forced into it. As the rod pushes the piston proximate to cylinder A within cylinder A, medium pressure seawater 910 entering cylinder A of the Clark pump 911 is pressurized and becomes high pressure seawater 912. The high pressure seawater 912 circulates through the RO chamber 903 and the high pressure brine 914 output from the RO chamber 903 on the subsequent stroke enters the Clark pump 91 1 through the reversing valve. Although the subsequent stroke is not illustrated in Fig. 9, one of ordinary skill in the art will appreciate that on the subsequent stroke, the reversing valve changes position such that the high pressure brine 914 from the subsequent stroke is directed into cylinder B and pushes against the piston proximate to cylinder B, pushing the rod through the center block in a reverse direction. The brine in cylinder A, which went through the RO chamber 903 on the previous stroke, is discharged. Cylinder B starts to pressurize when the piston and rod are forced into it. As the rod pushes the piston proximate to cylinder B within cylinder B, medium pressure seawater 910 entering cylinder B of the Clark pump 911 is pressurized and becomes high pressure seawater 912. The high pressure seawater 912 circulates through the RO chamber 903 and the high pressure brine 914 output from the RO chamber 903 on the subsequent stroke enters the Clark pump 911 through the reversing valve, which again changes position. The processes described above are then repeated.

[0062] In the embodiments of Figs. 8 and 9 a pressure of low pressure seawater is increased in a first step powered by wave energy converted by a WEC subsystem and a second step powered by power recovered from a pressurized brine flow by the energy-recovery subsystem (i.e., the motor and booster pump of Fig. 8 or the Clark pump of Fig. 9).

[0063] Two-stage pressurization, upstream recovery-powered pressurization.

[0064] Fig. 10 illustrates two-stage pressurization in which the recovery-powered

pressurization 1002 is upstream of the WEC-powered pressurization 1001. The recovery- powered pressurization may occur onshore, as illustrated in Fig. 10. In Fig. 10, as in Fig. 8, the recovery-powered pressurization is shown as two independent devices, a motor 1015 (such as a turbine) that converts the brine-flow power into mechanical power, and a booster pump 1011 that converts this mechanical power into pressurization of the seawater flow.

[0065] Fig. 10 shows details of a realistic system using this configuration. The additional detail includes an accumulator 1004, additional filters 1005, a storage container as well as other components. The accumulator 1004 acts as both pressure smoothing device and as a fly wheel. The accumulator 1004 is an energy storage device that captures and stores energy when the pressure in the flow is high, and returns the captured energy to the flow when the pressure in the flow is low. In certain embodiments, the accumulator functions by allowing a flow to occupy a flexible bladder whose expansion and contraction changes the volume available to a fixed quantity of compressible gas. Pressure fluctuations in the incompressible flow are thereby reduced. The additional filters 1005 remove relatively large impurities from the seawater flow. Additional components in the illustrated embodiment of Fig. 10, including the calcium- neutralizer tank 1016, are generic components of desalination facilities.

[0066] The operation of the Fig. 10 embodiment may be explained by considering the various illustrated flows. Starting first with the upstream recovery step, high pressure brine 1014 exiting the RO chamber 1003 powers a motor 1015 (such as a turbine), and that captured energy can be used to drive booster pump 1011 which contributes to the pressurization of low pressure seawater 1007 into medium pressure seawater 1010. The medium pressure seawater 1010 is filtered by filters 1005 and provided to a wave-energy-conversion (WEC) subsystem 1008, which powers two conventional linear displacement pumps 1009 that pressurize the medium pressure seawater 1010 into high pressure seawater 1012. The WEC subsystem 1008 is powered by ocean waves, and may include a so-called surge-type wave-energy converter (surgeWEC), such as those described in more detail with respect to Figs. 12a and 12b, and as illustrated in the Fig. 10 embodiment. In the embodiment illustrated in Fig. 10, the conventional linear pumps 1009 are attached to a surgeWEC paddle 1017, which oscillates in response to waves

propagating at the surface of large bodies of water. In the embodiment illustrated in Fig. 10, the high pressure seawater 1012 flows to accumulator 1004 (described above), and ultimately flows to the RO chamber 1003. As explained above with reference to the upstream recovery portion of Fig. 7, the high pressure seawater 1012 flows through the RO chamber 1003 to generate two flows: 1) low-pressure permeate (desalinated water / fresh water) 1013 and 2) high pressure brine 1014. The high pressure brine 1014 is then used in another cycle of the upstream recovery step.

[0067] In the system illustrated in Fig. 10, recovery-powered pressurization occurs first (upstream) and onshore. Output of the recovery-pressurization is piped to the submerged surgeWEC. [0068] Fig. 11 illustrates a system in which recovery-powered pressurization occurs onshore and first (upstream). Operation of the system of Fig. 11 is similar to that of Fig. 10, except that in the system of Fig. 11, the motor 1015 and the drive booster pump 1011 of Fig. 10 are replaced with a Clark pump 1111. Fig. 11 shows details of a realistic system using this configuration. The additional detail includes an accumulator 1104, additional filters 1105, a storage container as well as other components. The accumulator 1104 acts as both pressure smoothing device and as a fly wheel. The accumulator 1004 is an energy storage device that captures and stores energy when the pressure in the flow is high, and returns the captured energy to the flow when the pressure in the flow is low. In certain embodiments, the accumulator 1104 functions by allowing a flow to occupy a flexible bladder whose expansion and contraction changes the volume available to a fixed quantity of compressible gas. Pressure fluctuations in the incompressible flow are thereby reduced. The additional filters 1105 remove relatively large impurities from the seawater flow. Additional components in the illustrated embodiment of Fig. 11, including the calcium-neutralizer tank 1116, are generic components of desalination facilities.

[0069] The operation of the Fig. 11 embodiment may be explained by considering the various illustrated flows. Starting first with the upstream recovery step, high pressure brine 1114 exiting the RO chamber 1103 powers a Clark pump 11 11 which contributes to the pressurization of low pressure seawater 1107 into medium pressure seawater 1110. The medium pressure seawater 1110 is filtered by filters 1105 and provided to a wave-energy-conversion (WEC) subsystem 1108, which powers two conventional linear displacement pumps 1109 that pressurize the medium pressure seawater 1110 into high pressure seawater 1112. The WEC subsystem 1108 is powered by ocean waves, and may include a so-called surge-type wave-energy converter (surgeWEC), such as those described in more detail with respect to Figs. 12a and 12b, and as illustrated in the Fig. 11 embodiment. In the embodiment illustrated in Fig. 11, the conventional linear pumps 1109 are attached to a surgeWEC paddle 1117, which oscillates in response to waves propagating at the surface of large bodies of water. In the embodiment illustrated in Fig. 11, the high pressure seawater 1112 flows to accumulator 1104 (described above), and ultimately flows to the RO chamber 1103. As explained above with reference to the upstream recovery portion of Fig. 7, the high pressure seawater 1112 flows through the RO chamber 1103 to generate two flows: 1) low-pressure permeate (desalinated water / fresh water) 1113 and 2) high pressure brine 1014. The high pressure brine 1114 is then used in another cycle of the upstream recovery step.

[0070] The illustrated embodiment of a Clark pump 1111 uses two opposing cylinders A and B, with pistons that share a single rod that passes through a center block. A reversing valve, which is controlled by a pilot valve that may be mechanically actuated by the pistons, allows the two opposing cylinders to alternate between driving and pressurizing. As illustrated in Fig. 11, feed pressure from the high pressure brine 1114 is directed into cylinder A and pushes against the piston proximate to cylinder A, pushing the rod through the center block. The brine in cylinder B, which has gone through the RO chamber 1103 on the previous stroke, is discharged. Cylinder A starts to pressurize when the piston and rod are forced into it. As the rod pushes the piston proximate to cylinder A within cylinder A, low pressure seawater 1107 entering cylinder A of the Clark pump 1111 is pressurized and becomes medium pressure seawater 1110. The medium pressure seawater 1110 circulates through the WEC subsystem 1108, where it is pressurized and becomes high pressure seawater 1112 that is introduced to the RO chamber 1103. The high pressure brine 1114 output from the RO chamber 1103 on the subsequent stroke enters the Clark pump 1111 through the reversing valve. Although the subsequent stroke is not illustrated in Fig. 11, one of ordinary skill in the art will appreciate that on the subsequent stroke, the reversing valve changes position such that the high pressure brine 114 from the subsequent stroke is directed into cylinder B and pushes against the piston proximate to cylinder B, pushing the rod through the center block in a reverse direction. The brine in cylinder A, which went through the RO chamber 1103 on the previous stroke, is discharged. Cylinder B starts to pressurize when the piston and rod are forced into it. As the rod pushes the piston proximate to cylinder B within cylinder B, low pressure seawater 1107 entering cylinder A of the Clark pump 1111 is pressurized and becomes medium pressure seawater 1110. The medium pressure seawater 1110 circulates through the WEC subsystem 1108, where it is pressurized and becomes high pressure seawater 1112 that is introduced to the RO chamber 1103. The high pressure brine 1114 output from the RO chamber 1103 on the subsequent stroke enters the Clark pump 1111 through the reversing valve, which again changes position. The processes described above are then repeated.

[0071] In the embodiments of Figs. 10 and 11, a pressure of low pressure seawater is increased in a first step powered by power recovered from the high pressure brine flow by the energy- recovery subsystem (i.e., the motor and booster pump of Fig. 10 or the Clark pump of Fig. 11) and a second step powered by wave energy converted by the wave-energy-converter subsystem.

[0072] Single-stage pressurization (common drive)

[0073] Referring to the 1 -stage portion of Fig. 6 and Figs. 14 and 15, pressurization of the seawater flow can be accomplished in a single step or stage. This consolidation of wave- powered and brine-powered pressurization can be accomplished in two ways. Embodiments of both types are described. First, the power in the wave motion and that in the brine flow can both be converted into mechanical power, where they can be combined to power a pump that pressurizes the seawater flow. This approach is labeled single-stage, discrete recovery, reflecting the fact that it comprises independent conversion devices all mounted to a common power- transfer device. In other words, the wave-energy-converter subsystem and the energy-recovery subsystem are configured to convert fluid-motion power into mechanical power that is delivered by a common transmission shaft to a pump configured to pressurize the seawater flow. An alternative approach comprises assisting, or amplifying, the pressure transfer provided by a Clark pump with power captured from wave motion. Embodiments illustrating both approaches are described below.

[0074] Translational vs. rotational stroke

[0075] The mechanical power used in a single-stage system includes translation mechanical power or rotational mechanical power. Consider first the conversion of the two fluid-power sources, the waves and the brine flow, into mechanical power. The capture and conversion of the fluid-motion power of waves into mechanical power can produce power in several forms, such as electrical or mechanical. Mechanical power produced by a WEC can itself be of two types, translational or rotational. The two types of mechanical power that can be produced by a surgeWEC are contrasted in Figs. 12a and 12b. Figs. 12a and 12b show a surgeWEC paddle 1201 oscillating rotationally about the hinge which is attached to a sea-bed platform 1204. If a surgeWEC paddle 1201 is attached to a conventional linear displacement pump 1202, as shown in Fig. 12a, the motion of the piston in such a system is translational. If the surgeWEC paddle 1201 is attached to a rotary vane pump 1203, as shown in Fig. 12b, the mechanical power is rotational. Fig. 12a shows additionally that translational motion along multiple axes is available. Synthesis of wave-powered and brine-powered pressurization can use either form. Embodiments utilizing both power forms are described below.

[0076] Fig. 13 illustrates the type of linear-displacement fluid motor that can be used to capture and convert the power in the high-pressure brine flow. The diagram of Fig. 13 illustrates a fluid motor that converts the power carried by the high-pressure brine flow into translational mechanical power. The valves of Fig. 13 are not passive check (one-way) valves. Instead, the valves controlling the entry of the brine flow are piloted (controlled) switch valves, while the valves controlling the exit of the brine flow are piloted check valves.

[0077] In the case of Fig. 13, the high-pressure brine flow is converted into a translational force on the surgeWEC paddle. In this way, wave power and brine power are combined to drive the surgeWEC paddle, which then drives a linear-displacement pump that pressurizes the seawater flow in a single step or stage. Fig. 14 illustrates a system operating in this manner.

[0078] The system illustrated in Fig. 14 exploits single-stage pressurization. The additional detail includes an accumulator 1404, additional filters 1405, a storage container as well as other components. The accumulator 1404 acts as both pressure smoothing device and as a fly wheel. The accumulator 1404 is an energy storage device that captures and stores energy when the pressure in the flow is high, and returns the captured energy to the flow when the pressure in the flow is low. In certain embodiments, the accumulator 1404 functions by allowing a flow to occupy a flexible bladder whose expansion and contraction changes the volume available to a fixed quantity of compressible gas. Pressure fluctuations in the incompressible flow are thereby reduced. The additional filters 1405 remove relatively large impurities from the low pressure seawater flow 1407. Additional components in the illustrated embodiment of Fig. 14, including the calcium-neutralizer tank 1416, are generic components of desalination facilities.

[0079] As illustrated in Fig. 14, low pressure seawater flow (i.e., input seawater flow) 1407 enters the system through a beach well 1419, is filtered by filters 1405 and is provided to a wave- energy-conversion (WEC) subsystem 1408, which powers a conventional linear displacement pumps 1409 and a modified Clark pressure-transfer device 1411. The linear displacement pump 1409 and the modified Clark pressure-transfer device 1411 pressurize the low pressure seawater 1407 into high pressure seawater 1412. Unlike a conventional Clark pump, the modified Clark pressure -transfer device 1411 includes a translationally oscillating drive shaft 1418 extending outside of a housing of the pump. The WEC subsystem 1408 is powered by ocean waves, and may include a so-called surge-type wave-energy converter (surge WEC), such as those described in more detail with respect to Figs. 12a and 12b, and as illustrated in the Fig. 14 embodiment. The translationally oscillating drive shaft 1418 is coupled at one end to a surgeWEC paddle

1417, which oscillates in response to waves propagating at the surface of large bodies of water. The linear-displacement pump 1409 is generally powered when the illustrated surgeWEC paddle 1417 is moving forward (towards the accumulator 1404 in the illustrated embodiment of Fig. 13) in response to incident wave action propagating at the surface of large bodies of water.

[0080] The power carried by the high pressure brine flow 1414 is converted to mechanical power by a component like that described in Fig. 13. In Fig. 14, a pressure of the low pressure seawater 1407 is increased in a single step in which power carried by the high pressure brine flow 1414 is converted to translational mechanical power, which assists in the powering of the linear displacement pump 1409. The translational mechanical power is carried by a

translationally oscillating drive shaft 1418 configured to assist in the powering of the linear- displacement pump 1409, which pressurizes the low pressure seawater flow 1407. In particular, the high pressure brine flow 1414 pushes an end of the translationally oscillating drive shaft

1418, for example, in a forward direction (i.e., away from the surgeWEC paddle 1417), when the surgeWEC paddle 1417 is already moving forward in response to incident wave action. Because one end of the linear pump 1409 is coupled to the surgeWEC paddle 1417, as the surgeWEC paddle 1417 moves in the forward direction, assisted by the additional translational power supplied by the translationally oscillating drive shaft 1418, the low pressure seawater flow 1407 is pressured. The WEC subsystem may also be configured to power the translationally oscillating drive shaft 1418.

[0081] Here, the reversing valve of the modified Clark pressure-transfer device 1411, which is itself controlled by a pilot valve, may be mechanically controlled or may be controlled by an electronic control system. For example, in a mechanical embodiment, the reversing valve is configured to move into position to allow the application of high pressure brine flow 1414 against an end of the translationally oscillating drive shaft 1418 in response to initial movement of the surgeWEC paddle 1417 into the forward direction to power the linear-displacement pump 1409 (as discussed above). In an electrically controlled embodiment, the surgeWEC paddle 1417 or the hinge to which the surgeWEC paddle 1417 is attached includes a sensor to sense initial movement of the surgeWEC paddle 1417 in a forward direction, at which point an mechanical solenoid configures the reversing valve to move into position to allow the application of high pressure brine flow 1414 against an end of the translationally oscillating drive shaft 1418. In a further electrically controlled embodiment, the electronic control system includes prediction algorithms to predict the incident wave action propagating at the surface of the body of water, and a mechanical solenoid configures the reversing valve to move into position to allow the application of high pressure brine flow 1414 against an end of the translationally oscillating drive shaft 1418 at time when the surgeWEC paddle 1417 is predicted to begin moving forward in response to wave action.

[0082] In the embodiment illustrated in Fig. 14, the high pressure seawater 1412 flows to accumulator 1404 (described above), and then flows through the RO chamber 1403 to generate two flows: 1) low-pressure permeate (desalinated water / fresh water) 1413 and 2) high pressure brine 1414. The high pressure brine 1414 is then introduced into the modified Clark pressure- transfer device 1411. [0083] Fig. 12a and 14 also illustrate the fact that, although both wave and brine power are converted to translational mechanical power, this power is not transmitted along a common axis. One aspect of this approach of combining wave and brine power is that the surge WEC paddle, the brine-powered fluid motor (i.e., the modified Clark pressure-transfer device) and the piston of the linear displacement pump all move synchronously with negligible loss in the transfer of power among the discrete components.

[0084] Single, Integrated Pressurization Device

[0085] In contrast to the desalination system shown in Fig. 14, Fig. 15 illustrates the alternative approach in which the Clark pressure-transfer device is assisted by captured wave power.

[0086] The integration described above is enabled by the integration of the three principal functionalities: pressurization, recovery and wave-energy capture. While the Clark-pump technology illustrated in Fig. 4 contributes to the integration, it may be extended in several ways. These extensions are described as follows.

[0087] Fig. 15 is a diagram of a Single-stage wave-powered desalination system illustrating integration into a single device all three components: wave and brine power capture and pressurization of the seawater flow. The system illustrated in Fig. 15 employs a wave-power amplified Clark pressure-transfer device (i.e., a modified Clark pump or modified Clark pressure -transfer device). Fig. 16 expands the view of the single integrated device appearing in Fig 15. In the embodiment of Fig. 15, a pressure of the low pressure seawater flow 1507 is increased in a single step wherein a pressure of the high pressure brine flow 1514 is transferred directly to the low pressure seawater flow 1507 by the modified Clark pressure-transfer device (i.e., a Clark pump) 1511, and pressurization of the low pressure seawater flow 1507 by the modified Clark pressure-transfer device 1511 is amplified by an addition of wave power to a translationally oscillating motion of the pressure-transfer device. In other words, movement of the WEC forwards and backwards affects the translation of pistons within the Clark pump, that in turn affect the high pressure brine flow and the high pressure seawater flow. [0088] The system illustrated in Fig. 15 exploits single-stage pressurization. The additional detail includes an accumulator 1504, additional filters 1505, a storage container as well as other components. The accumulator 1504 acts as both pressure smoothing device and as a fly wheel. The accumulator 1504 is an energy storage device that captures and stores energy when the pressure in the flow is high, and returns the captured energy to the flow when the pressure in the flow is low. In certain embodiments, the accumulator 1504 functions by allowing a flow to occupy a flexible bladder whose expansion and contraction changes the volume available to a fixed quantity of compressible gas. Pressure fluctuations in the incompressible flow are thereby reduced. The additional filters 1505 remove relatively large impurities from the low pressure seawater flow 1507. Additional components in the illustrated embodiment of Fig. 15, including the calcium-neutralizer tank 1516, are generic components of desalination facilities.

[0089] As illustrated in Fig. 15, low pressure seawater flow (i.e., input seawater flow) 1507 is filtered by filters 1505 and is provided to a wave-energy-conversion (WEC) subsystem 1508, which powers two modified Clark pressure-transfer devices 1511 configured to pressurize the low pressure seawater 1507 into high pressure seawater 1512. Unlike a conventional Clark pump, the modified Clark pressure-transfer devices 1511 each include a translationally oscillating drive shaft 1518 extending outside of a housing of the pump. The WEC subsystem 1508 is powered by ocean waves, and may include a so-called surge-type wave-energy converter (surgeWEC), such as those described in more detail with respect to Figs. 12a and 12b, and as illustrated in the Fig. 15 embodiment. Each translationally oscillating drive shaft 1518 is coupled at one end to a surgeWEC paddle 1517, which oscillates in response to waves propagating at the surface of large bodies of water.

[0090] The power carried by the high pressure brine flow 1514 is converted to mechanical power by a component like that described in Fig. 13. In Fig. 15, a pressure of the low pressure seawater 1507 is increased in a single step in which power carried by the high pressure brine flow 1514 is converted to translational mechanical power. The high pressure brine flow 1514 can enter one or both of the modified Clark pressure -transfer devices 1511, depending on a configuration of a pilot switch control (see Fig. 16) that modifies a position of a pilot switch. Each modified Clark pressure -transfer device 1511 may include a pilot switch control, or the modified Clark pressure-transfer devices 1511 may share the same pilot switch control. The pilot switch control may modify the position of the pilot switch automatically based, for example, on pressure within the modified Clark pressure-transfer device or a position of a translationally oscillating drive shaft. Alternatively, the pilot switch control may modify the position of the pilot switch based on manual input of an operator.

[0091] Each modified Clark pressure-transfer device includes a translationally oscillating drive shaft 1518 and an dog-bone-shaped piston 1519. As used herein, "dog-bone-shaped" refers to a shape having substantially horizontal, elongated mid-section having enlarged ends (i.e., ends of the piston have a larger circumference than the mid-section). A first end of the translationally oscillating drive shaft 1518 is coupled to the surgeWEC paddle 1517, and a second end of the translationally oscillating drive shaft 1518 is coupled to the dog-bone-shaped piston 1519. The translational mechanical power is carried by the translationally oscillating drive shaft 1518 and the dog-bone-shaped piston 1519 in order to pressurize the low pressure seawater flow 1507. In particular, the high pressure brine flow 1514 pushes an end of the dog-bone-shaped piston 1519, for example, in a forward direction (i.e., away from the surgeWEC paddle 1517). Because the translationally oscillating drive shaft is coupled to both the surgeWEC paddle 1517 and the dog- bone-shaped piston 1519, as the surgeWEC paddle 1517 moves in the forward direction, the low pressure seawater flow 1507 is pressured. One of ordinary skill in the art will appreciate that in Figs. 15 and 16, the surgeWEC paddle 1517 is moving in the forward direction, but at other times, the surge WEC paddle 1517 may be moving in a backward direction. When the surgeWEC paddle 1517 moves in a backward direction, the translationally oscillating drive shaft

1518 and the dog-bone-shaped piston 1519 move towards the surgeWEC paddle 1517. The orientation (i.e., open or closed) position of the valves in the passive conduits can be changed such that when the translationally oscillating drive shaft 1518 and the dog-bone-shaped piston

1519 move backwards, the seawater disposed in the portion proximate to a connection point between the translationally oscillating drive shaft 1518 and the dog-bone-shaped piston 1519 is pressurized, while low pressure seawater 1507 is introduced at the other side of the dog-bone- shaped piston 1519. In other words, the portion labeled low pressure seawater 1507 and the portion labeled high pressure seawater 1512 within the modified Clark pressure-transfer devices 1511 are inverted. The WEC subsystem may also be configured to power the translationally oscillating drive shaft 1518.

[0092] Here, the reversing valve of the modified Clark pressure-transfer device 1511, which is itself controlled by a pilot valve, may be mechanically controlled or may be controlled by an electronic control system. For example, in a mechanical embodiment, the reversing valve is configured to move into position to allow the application of high pressure brine flow 1514 against an end of the translationally oscillating drive shaft 1518 in response to initial movement of the surgeWEC paddle 1517 into the forward direction. In an electrically controlled embodiment, the surgeWEC paddle 1517 or the hinge to which the surgeWEC paddle 1517 is attached includes a sensor to sense initial movement of the surgeWEC paddle 1517 in a forward direction, at which point an mechanical solenoid configures the reversing valve to move into position to allow the application of high pressure brine flow 1514 against an end of the translationally oscillating drive shaft 1518. In a further electrically controlled embodiment, the electronic control system includes prediction algorithms to predict the incident wave action propagating at the surface of the body of water, and a mechanical solenoid configures the reversing valve to move into position to allow the application of high pressure brine flow 1514 against an end of the translationally oscillating drive shaft 1518 at time when the surgeWEC paddle 1517 is predicted to begin moving forward in response to wave action.

[0093] In the embodiment illustrated in Fig. 15, the high pressure seawater 1512 exits the modified Clark pressure -transfer devices 1511 and flows to accumulator 1504 (described above), and then flows through the RO chamber 1503 to generate two flows: 1) low-pressure permeate (desalinated water / fresh water) 1513 and 2) high pressure brine 1514. The high pressure brine 1514 is then introduced into the modified Clark pressure -transfer devices 1511, thereby repeating the cycle.

[0094] Rotational [0095] As mentioned above, in connection with Figs. 12a and 12b, capture and conversion of the power in both waves and the high-pressure brine flow can result in either of two forms of mechanical power: translational and rotational. Rotational power can be exploited in similar ways to those used to exploit translational power, although the devices providing the required functionalities are different.

[0096] Single rotor-stator pair

[0097] As Fig. 12b indicates, a surge WEC paddle oscillates rotationally about the hinge by which it is attached to a platform. Analogous to a linear-displacement pump for the conversion of translational mechanical power, a vane pump provides the same functionality for rotational mechanical power. The piston of the linear-displacement pump is replaced by a rotating vane which is attached to the hinge of the oscillating surgeWEC paddle. As shown in Fig. 17, like the piston, the powered vane drives and pressurizes the water in front of it. A stationary vane blocks the rotor-propelled water, forcing it to exit through a controlled valve, as shown in Fig. 17.

[0098] A vane extending radially outward from a rotor radially drives the fluid confined in front of the vane angularly within a confining cylinder. A second vane extending radially inward from the confining cylinder blocks the angular flow, forcing the flow out of the cylinder through a controlled valve. Fig. 17 illustrates the operation of such a pump. Note that such a pump or motor must oscillate; it cannot rotate freely, as the vanes would collide. The maximum angular stroke of the device shown in Fig. 17 is less than 360° (180° in both directions). Finite vane thickness safety margins, etc., render the practical maximum angular stroke to 140° in both directions.

[0099] The same configuration operates as a fluid motor when high-pressure fluid enters the cylinder through a valve creating a pressure difference across the rotor-attached vane, thereby providing a torque on the rotor. Power is transferred from a high-pressure flow to a low-pressure flow by two of the devices illustrated in Fig. 17 mounted on a common shaft. The fact that the vane pump and vane motor are mounted to a common shaft makes this configuration naturally compatible with surgeWEC geometry and operation. [0100] Double rotor-stator pair

[0101] Fig. 18 illustrates a Vane pump (or motor) comprising two rotor-stator pairs. Note that the maximum stroke of the configuration shown in Fig. 17 is twice that of the configuration shown in Fig. 18. A maximum stroke of 90° or more can be exploited to lock the surgeWEC paddle in a nominally horizontal position during dangerously violent weather.

[0102] Controlling the ratio of brine and seawater flows

[0103] The relative magnitude of the brine and seawater flows is controlled by the volumes occupied by each in the wave-assisted Clark pump. If the pistons of the system move in both volumes, then the volumes can be rendered different by the volume occupied by the shaft connecting the two pistons, as shown in Fig. 19. Fig. 19 is a schematic cross section of WEC- assisted Clark pump showing how the ratio of brine flow to seawater flow is controlled by the diameter of the connection between the two Clark-pump pistons. In other words, a ratio of the high pressure brine flow to the low pressure seawater flow is fixed by a ratio of a diameter of a connection between two pistons of the Clark pump (i.e., pressure -transfer device) to a diameter of a cylinder in which the two pistons move.

[0104] Thin brine cylinder

[0105] If the pistons of the wave-assisted Clark pump move in different cylinders, then the required brine/seawater volume difference can be created by varying a diameter of the cylinders. For example, cylinders having different diameters may be utilized. Fig. 20 is a schematic cross section of a WEC-assisted Clark pump in which the ratio of the brine flow to the seawater flow is controlled by the diameters of the right- and left-hand cylinders comprising the form of the WEC-assisted Clark pump. In other words, a ratio of the high pressure brine flow to the low pressure seawater flow may be fixed by a ratio of diameters of two coaxial cylinders in which two pistons of the Clark pump possess different diameters, and move in cylinders possessing different diameters.

[0106] Single-vane [0107] The single-rotor-stator-pair configuration lends itself to a straightforward method of controlling the ratio of the brine and seawater flows. Just as a piston in a cylinder can act either as a pump or a fluid motor, the single -rotor-stator pair device shown in Fig. 17 can act either as a positive displacement pump or as a rotary fluid motor. Thus, two devices like those shown in Fig. 17 mounted on a common axle, one acting as a fluid motor, the other acting as a pump can, in combination, function as a pressure-transfer device, transferring pressure from the brine flow to the seawater flow. The radius of the two single-rotor-pair device shown in Fig. 17 implies the fluid volume and therefore the flow rate. Thus the two single-rotor-stator-pair devices, one acting as a motor the other as a pump can have different radii, and different flow rates. In other words, in this embodiment, a conversion of fluid-motion power into oscillatory rotational power and/or a conversion of oscillatory rotational power into fluid-motion power may be effected by a vane pump-motor pair, each vane pump in the vane pump-motor pair comprising a single rotor- stator pair. A ratio of the high pressure brine flow to the low pressure seawater flow may be fixed by a ratio of diameters of two coaxial single-rotor-stator-pair vane pumps.

[0108] When the double-rotor-pair configuration is employed, the required volume difference can be achieved by different cylinder diameters in the two subvolumes in which the brine and seawater rotor vanes move.

[0109] Double vane

[0110] Fig. 21 is a schematic cross section of a two-rotor-stator pair WEC-assisted Clark pump. The thicker wall on the right-hand side of the cylinder renders the volume used by the brine flow smaller than that used by the seawater flow. In this embodiment, a conversion of fluid-motion power into oscillatory rotational power and/or a conversion of oscillatory rotational power into fluid-motion power are effected by at least one vane pump, the at least one vane pump comprising two rotor-stator pairs. A ratio of the high pressure brine flow to the input seawater flow is fixed by a ratio of heights of rotor vanes that move in the high pressure brine flow and the low pressure seawater flow, and a diameter of a connection between two pistons of a Clark pump to a diameter of a cylinder in which the two pistons move. [0111] In the embodiments described above, wave-energy conversion, energy recovery and seawater pressurization are integrated in various configurations to improve the efficiency of a seawater desalination system. The advantages of the embodiments described herein include, but are not limited to: exploitation of low-cost and widely-available wave energy, reduction of manufacturing and deployment costs due to the relative simplicity and integration of the system components, reduction of operational costs due the relative efficiency of the integrated components, and reduction of operational costs due the relative efficiency of systems comprised of relatively fewer system components.

[0112] Although the purification processes described herein are described in the context of purify sea water, one of ordinary skill in the art will appreciate that the purification processes can also be used to purify brackish and waste water.

[0113] The construction and arrangements of the integrated wave-powered desalination system, as shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, orientations, processing, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process, control, or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary

embodiments without departing from the scope of the present invention.

[0114] As utilized herein, the terms "approximately," "about," "substantially", and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims.

[0115] The terms "coupled," "connected," and the like as used herein mean the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another.

[0116] References herein to the positions of elements are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure.

[0117] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for the sake of clarity.

Claims

WHAT IS CLAIMED IS:

1. A wave-powered desalination system, comprising:

a wave-energy-converter subsystem configured to convert power carried by waves propagating on a body of water into mechanical power;

a pressurization subsystem configured to pressurize an input seawater flow in at most two steps by at most two pressurization stages;

a reverse-osmosis chamber including a membrane having a plurality of passages disposed therein, the reverse-osmosis chamber configured to receive the pressurized seawater and divide the pressurized seawater, via the membrane, into a permeate flow of purified water and a pressurized brine flow that carries away particles that did not pass through the membrane;

an energy-recovery subsystem configured to capture power carried by the pressurized brine flow that exits the reverse-osmosis chamber and to deliver the captured power to the pressurization subsystem; and

passive conduits configured to carry the input seawater, the pressurized brine and the purified water between the body of water and components of the wave -powered desalination system without changing a pressure, a composition or a magnitude of a flow of each of the input seawater, the pressurized brine and the purified water.

2. The wave-powered desalination system of claim 1, wherein a pressure of the input seawater flow is increased in a first step powered by wave energy converted by the wave-energy- converter subsystem and a second step powered by power recovered from the pressurized brine flow by the energy-recovery subsystem.

3. The wave-powered desalination system of claim 1, wherein the energy-recovery subsystem comprises a fluid motor configured to convert power carried by the pressurized brine flow into power configured to drive a pump, the pump configured to assist in a pressurization of the input seawater flow.

4. The wave-powered desalination system of claim 1, wherein the energy-recovery subsystem comprises a pressure-transfer device configured to transfer a pressure of the pressurized brine flow directly to the input seawater flow, without conversion into, and back out of, mechanical power.

5. The wave-powered desalination system of claim 1, wherein a pressure of the input seawater flow is increased in a first step powered by power recovered from the pressurized brine flow by the energy-recovery subsystem and a second step powered by wave energy converted by the wave-energy-converter subsystem.

6. The wave-powered desalination system as in claim 1, wherein a pressure of the input seawater flow is increased in a single step wherein the wave-energy-converter subsystem and the energy-recovery subsystem are configured to convert fluid-motion power into

mechanical power that is delivered by a common transmission shaft to a pump configured to pressurize the input seawater flow.

7. The wave-powered desalination system of claim 6, wherein the mechanical power is translational mechanical power.

8. The wave-powered desalination system of claim 6, wherein the mechanical power is rotational mechanical power.

9. The wave-powered desalination system of claim 6, wherein a pressure of the input seawater flow is increased in a single step wherein power carried by the pressurized brine flow is converted to translational mechanical power carried by a translationally oscillating drive shaft configured to assist in powering a linear-displacement pump configured to pressurize the input seawater flow.

10. The wave-powered desalination system of claim 1, wherein a pressure of the input seawater flow is increased in a single step wherein a pressure of the pressurized brine flow is transferred directly to the input seawater flow by a pressure-transfer device, and pressurization of the input seawater flow by the pressure-transfer device is amplified by an addition of wave power to a translationally oscillating motion of the pressure-transfer device.

11. The wave-powered desalination system as in claim 10, wherein a ratio of the pressurized brine flow to the input seawater flow is fixed by a ratio of a diameter of a connection between two pistons of the pressure-transfer device to a diameter of a cylinder in which the two pistons move.

12. The wave-powered desalination system of claim 10, wherein a ratio of the pressurized brine flow to the input seawater flow is fixed by a ratio of diameters of two coaxial cylinders in which two pistons of the pressure-transfer device possess different diameters, and move in cylinders possessing different diameters.

13. The wave-powered desalination system of claim 8, wherein a conversion of fluid- motion power into oscillatory rotational power and/or a conversion of oscillatory rotational power into fluid-motion power are effected by a vane pump-motor pair, each vane pump in the vane pump-motor pair comprising a single rotor-stator pair.

14. The wave-powered desalination system of claim 13, wherein a ratio of the pressurized brine flow to the input seawater flow is fixed by a ratio of diameters of two coaxial single-rotor-stator-pair vane pumps.

15. The wave-powered desalination system of claim 8, wherein a conversion of fluid- motion power into oscillatory rotational power or a conversion of oscillatory rotational power into fluid-motion power are effected by at least one vane pump, the at least one vane pump comprising two rotor-stator pairs.

16. The wave-powered desalination system of claim 15 wherein a ratio of the pressurized brine flow to the input seawater flow is fixed by a ratio of heights of rotor vanes that move in the pressurized brine flow and the input seawater flow, and a diameter of a connection between two pistons of a pressure-transfer device to a diameter of a cylinder in which the two pistons move.

17. A method for desalinating seawater with a wave-powered desalination system comprising:

converting power carried by waves propagating on a body of water into mechanical power via a wave-energy-converter subsystem;

pressurizing an input seawater flow in at most two steps by at most two pressurization stages;

receiving the pressurized seawater and dividing the pressurized seawater, in a reverse- osmosis chamber including a membrane having a plurality of passages disposed therein, into a permeate flow of purified water and a pressurized brine flow that carries away particles that did not pass through the membrane; and

capturing power carried by the pressurized brine flow that exits the reverse-osmosis chamber;

delivering the captured power to the pressurization of input seawater,

wherein the pressurized brine and the purified water are carried between the body of water and components of the wave-powered desalination system by passive conduits without changing a pressure, a composition or a magnitude of a flow of each of the input seawater, the pressurized brine and the purified water.

18. The method of claim 17, wherein the pressurizing step comprises a first step powered by wave energy converted by a wave-energy-converter subsystem and a second step powered by power recovered from the pressurized brine flow by an energy-recovery subsystem.

19. The method of claim 17, wherein the pressurizing step comprises a first step powered by power recovered from the pressurized brine flow by an energy-recovery subsystem and a second step powered by wave energy converted by a wave-energy-converter subsystem.

20. The method of claim 20, wherein the pressurizing step comprises a single step in which a wave-energy-converter subsystem and an energy-recovery subsystem convert fluid- motion power into mechanical power that is delivered by a common transmission shaft to a pump configured to pressurize the input seawater flow.