WO2009089371A1

WO2009089371A1 - Solar distillation systems and methods

Info

Publication number: WO2009089371A1
Application number: PCT/US2009/030466
Authority: WO
Inventors: Mike Wofsey
Original assignee: University Of Alabama
Priority date: 2008-01-08
Filing date: 2009-01-08
Publication date: 2009-07-16

Abstract

The present disclosure generally pertains to solar distillation systems and methods for purifying seawater, polluted water, or other types of water. In accordance with one exemplary embodiment of the present disclosure, raw water, such as seawater or polluted water, is pumped or otherwise provided to a solar distillation system (25) having an array of distillation chambers (35). For each chamber, sunlight passing into the chamber heats the raw water causing it to evaporate and condense on a ceiling (39) of the chamber. The condensed water is mostly free of salt or pollutants in the raw water and is potable. The potable water that condenses on the chamber ceiling is pulled by gravity into a collection channel (52), which runs to an outlet (53) where the potable water can be collected or dispersed.

Description

SOLAR DISTILLATION SYSTEMS AND METHODS

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U S Provisional Patent Application No

61/010,402, entitled "Solar Distillation Systems and Methods," and filed on January 8, 2008, which is incorporated herein by reference.

RELATED ART

[0002] Solar distillation has been used to provide clean drinking water and can be particularly useful in third world countries or rural areas where potable water is not always readily available In addition, there is typically a need for potable water in the wake of natural disasters, such as hurricanes and earthquakes, which can disrupt drinking water channels.

[0003] However, the evaporation rate of water is generally slow, and providing large volumes of potable water via solar distillation can be problematic. Previous solar distillation systems capable of producing significant amounts of potable water have typically been bulky, often immobile, and expensive to manufacture

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The disclosure can be better understood with reference to the following drawings The elements of the drawings are not necessarily to scale relative to each other, emphasis instead being placed upon clearly illustrating the principles of the disclosure. Furthermore, like reference numerals designate corresponding parts throughout the several views.

[0005] FIG. 1 is a block diagram illustrating a water purification system in accordance with an exemplary embodiment of the present disclosure. [0006] FIG 2 is a three-dimensional view illustrating an exemplary solar distillation system, such as is depicted in FIG 1

[0007] FIG 3 is a front view of the solar distillation system of FIG 2

[0008] FIG 4 is a three-dimensional view illustrating a tray of the solar distillation system depicted in FIG 2

[0009] FIG 5 is a top view illustrating the tray of FIG 4

[0010] FIG 6 is a three-dimensional view illustrating a barrier of the solar distillation system depicted in FIG 2

[0011] FIG 7 is a three-dimensional view illustrating the barrier of FIG 6

[0012] FIG 8 is a back view illustrating the barrier of FIG 6

[0013] FIG 9 is a front view illustrating the barrier of FIG 6

[0014] FIG 10 is a top view illustrating the barrier of FIG 6

[0015] FIG 11 is a three-dimensional view illustrating the barrier of FIG 6

[0016] FIG 12 is a three-dimensional view illustrating the tray of FIG 4

[0017] FIG 13 is a three-dimensional view illustrating the barrier of FIG 6

[0018] FIG 14 is a cross-sectional view illustrating an exemplary solar distillation system positioned above a sloped surface, such as a roof of a building

DETAILED DESCRIPTION

[0019] The present disclosure generally pertains to solar distillation systems and methods for purifying seawater, polluted water, or other types of water In accordance with one exemplary embodiment of the present disclosure, raw water, such as seawater or polluted water, is pumped or otherwise provided to a solar distillation system having an array of distillation chambers For each chamber, sunlight passing into the chamber heats the raw water causing it to evaporate and condense on a ceiling of the chamber The condensed water is mostly free of salt or pollutants in the raw water and is potable The potable water that condenses on the chamber ceiling is pulled by gravity into a collection channel, which runs to an outlet where the potable water can be collected or dispersed.

[0020] FIG. 1 depicts a water purification system 10 in accordance with one exemplary embodiment of the present disclosure. The system 10 has a pump 12 that pumps water from a water source 15, such as an ocean, lake, river, stream, well, or other source of water. In one exemplary embodiment, the pump 12 is coupled to a hose 18 that extends to the water source 15 and through which water is drawn from such water source 15. As shown by FIG. 1 , the pump 12 is also coupled to a hose 21 that extends to a solar distillation system 25. The pump 12 forces water through the hose 21 to the solar distillation system 25, which purifies the water in order to provide potable water, as will be described in more detail hereafter.

[0021] Potable water flows from the solar distillation system 25 through a hose 26 to a potable water reservoir 31 , such as a tank for holding the potable water for later use. In one exemplary embodiment, the solar distillation system 25 is coupled to additional hoses 24, 28, which will be described in more detail hereafter.

[0022] FIGS. 2 and 3 depict a solar distillation system 25 in accordance with one exemplary embodiment of the present disclosure. The system 25 has a tray 27 on which a transparent barrier 30 rests. In one exemplary embodiment, both the tray 27 and the barrier 30 are composed of thermoformed plastic (e.g., acrylic or polyethylene terephthalate (PET) plastic), but other types of materials are possible in other embodiments. In addition, the tray 27 has a dark color, such as black, which helps to increase the amount of sunlight absorbed by the tray 27, relative to lighter colors, thereby helping to increase the evaporation rate of raw water, as will be described in more detail hereafter.

[0023] The system 25 has at least one distillation chamber 35. The exemplary embodiment shown by FIG. 1 has an array of three chambers 35, but other numbers of chambers 35 are possible in other embodiments. The bottom of each chamber 35 is defined by the upper surface 36 (FIGS 4 and 5) of the tray 27 The ceiling of each chamber 35 is defined by the lower surface 39 (FIG 6) of the barrier 30 In addition, the sides of each chamber 35 are defined by chamber walls 42, which are formed in the tray 27, as shown by FIGS 4 and 5 The walls 42 of each chamber 35 form a respective opening 46, which allows raw water to flow into the chamber 35 from a common water feed area 47 The common water feed area 47 is defined by the chamber walls 42 and a wall 49 that separates the common water feed area 47 from a feed water overflow area 51 , which will be described in more detail hereafter In addition, the top surface of each wall 42 has a channel 52, referred to as the "condensed water collection channel," for guiding potable water to an outlet 53 (FIG 5), referred to as the 'condensed water collection outlet " In one exemplary embodiment, the channel 52 is slightly sloped so that potable water at any point along the channel 52 is pulled by gravity toward the outlet 53, where the potable water eventually exits the system 25

[0024] Various sizes of the solar distillation system 25 are possible In one exemplary embodiment, the length, width, and height of the system are all on the order of about one meter or less For example, the length may be about thirty-three (33) inches, the width may be about twenty-nine (29) inches, and the height may be about eight (8) inches Other dimensions are possible in other embodiments Using thermoformed plastic, such as acrylic or PET, at such dimensions provides a weight on the order of just a few pounds, and the system 25 can be carried by hand or otherwise transported

[0025] FIG 7 depicts the barrier 30 The barrier 30 has a holding apparatus 55 for holding the hose 21 (FIG 1) that is coupled to the pump 12 In this regard, as shown by FIG 8, the holding apparatus 55 has a notch 57 for receiving the hose 21 The notch 57 is dimensioned such that the hose 21 fits snugly in the notch 57, and friction helps to hold the hose 21 in place [0026] The hose 21 is positioned such that raw water flows from the hose 21 into a channel 60, referred to as the "feed water channel," formed on a top surface of the barrier 30. The channel 60 is of sufficiently shallow depth such that raw water overflows the channel 60 and runs along sloped surfaces 61 of the barrier 30 into channels 62 (FIGS. 9 and 10) formed by the barrier 30 between the chambers 35. The channels 62 guide the raw water to the common water feed area 47. Once in the common water feed area 47, the raw water may flow into the distillation chambers 35 through the openings 46 (FIG. 5).

[0027] As shown by FIGS. 10 and 11 , the barrier 30 has a wall 72 that extends around the barrier 30 such that the chambers 35, as a group, are surrounded by the wall 72. A channel 74 (FIG. 11 ) runs between the wall 72 and a chamber 35 such that feed water flowing over a sloped surface 61 of the chamber 35 is collected in the channel 74. The wall 72 has slots 77 that allow water in the channel 74 to egress into the feed water overflow area 51 , which surrounds the chambers 35 and the wall 72 of the barrier 30.

[0028] As shown by FIG. 11 , the wall 72 also has slots 78 at the front of the barrier

30 to allow feed water to egress from the channels 62 that run between the chambers 35. The feed water that passes through the slots 62 flows into the common water feed area 47 (FIG. 4) and replenishes feed water that evaporates from this area 47.

[0029] In one exemplary embodiment, the wall 72 is hollow to facilitate coupling of the barrier 30 to the tray 27. In this regard, as described above, the tray 27 has walls 42 (FIG. 4) that define the chambers 35 and the condensed water collection channel 52. As shown by FIGS. 4 and 12, a groove 81 runs along an outer perimeter of the wall 42. The barrier 30 is positioned such that portions of the tray wall 42 along such outer perimeter fit within the hollow wall 72 of the barrier 30, and the hollow wall 72, therefore, overlays the tray wall 42 along such perimeter. The wall 42 of the tray 27 is dimensioned along the groove 81 such that the wall 42 fits snugly within the hollow wall 72 of the barrier 30. The mating of the walls 42, 72 along the length of the groove 81 seals the chambers 35 (and the condensed water collection channel 52 within the chambers 35) except for the openings 46 (FIG. 4) that allow feed water to enter the chambers 35.

[0030] As shown by FIG. 13, an indention 82 is formed in the bottom of the barrier

30 thereby forming an interior rim 84 that runs along a perimeter of the barrier 30. The rim 84 is dimensioned to fit snugly in the groove 81 (FIG. 12) of the tray 27. As the barrier 30 is being positioned on the tray 27, the rim 84 presses against the tray wall 42 until the rim 84 reaches the groove 81. When the groove 81 is reached, the rim 84 slides into the groove 81. The snug fit of the rim 84 in the groove 81 helps to resist movement of the barrier 30 relative to the tray 27 thereby helping to maintain a coupling between the barrier 30 and the tray 27. That is, positioning the barrier 30 such that the rim 84 is inserted into the groove 81 detachably couples the barrier 31 to the tray 27. The barrier 30 can be removed from the tray 27 by hand, if desired, by forcing the rim 84 out of the groove 81 and lifting the barrier 30.

[0031] As shown by FIGS. 8 and 11 , the barrier 30 has a flap 83 that extends from the wall 72 of the barrier 30 into the common water feed area 47. The flap 83 extends sufficiently far into the common water feed area 47 such that the surface of the feed water within this area 47 is higher than the bottom of the flap 83. That is, at least a portion of the flap 83 is submerged in the feed water in the area 47. Therefore, the chambers 35 are sealed such that ambient air is prevented from entering the chambers 35.

[0032] In this regard, as described above, there are openings 46 that allow water to enter the chambers 35. The portions of the openings 46 above the waterline are covered by the flap 83, and the portions of the openings 46 below the waterline are sealed by the feed water in the area 47. That is, the water seals the portions of the openings 46 below the flap 83. Thus, ambient air is prevented from entering the chambers 35 through the openings 46. Further, there are no other openings that allow ambient air to flow into the chambers 35, and the chambers 35 are effectively sealed from the ambient air.

[0033] By sealing the chambers 35, the humidity inside of the chambers 35 can be much higher than that outside the chambers 35 helping to enhance the condensation of water within the chambers 35. In fact, it is possible for the humidity within the chambers 35 to approach close to saturation or 100%. In addition, sealing of the chambers 35 helps to reduce the amount of heat that escapes the chambers 35 thereby helping to enhance the evaporation rate within the chambers 35. Note that it is unnecessary for the chamber seals to be hermetic. In this regard, small leaks in the seams of the chambers 35 should not have a significant impact to the humidity and condensation rate within the chambers 35. Nevertheless, sealing of the chambers 35 and particularly the openings 46 that allow feed water to flow into the chambers 35 helps to improve the efficiency of the system 25.

[0034] Sunlight and/or other light passes through the transparent barrier 30 and into each chamber 35. The light heats the interior region of each chamber 35, and the barrier 30 traps such heat within the chambers 35, similar to a greenhouse. Thus, the temperatures within the chambers 35 likely exceed the atmospheric temperatures outside of the system 25 helping to increase the evaporation rate of the raw water within the chambers 35.

[0035] The barrier 30, which is exposed to the atmospheric conditions, is likely at lower temperatures than those within the chambers 35. Moreover, for each chamber 35, the evaporated raw water condenses on the interior surface 39 (FIG. 6) of the barrier 30. Gravity causes the condensed water, which is free of salt and pollutants, to run along the interior surface 39 of the barrier 30 until it reaches the collection channel 52. Potable water flows through the channel 52 to the outlet 53. [0036] As shown by FIGS. 9 and 11 , the front of each chamber 35 has a curved groove 93 that spans across a respective opening 46 (FIG. 4). For each chamber 35, a respective groove 93 forms a sloped ledge 95 (FIG. 6) on the interior surface of the chamber 35. Condensed water runs along the ledge 95 to the condensed water collection channel 52. The presence of the ledge 95 redirects condensed water that would otherwise drip into the common water feed area 47 at the opening 46 such that the condensed water instead flows to the condensed water feed channel 52 thereby increasing the amount of potable water collected in this channel 52.

[0037] Note that the raw water flowing from the feed water channel 60 on top of the barrier 30 helps to cool the barrier 30 thereby increasing the condensation rate of the evaporated water within the chambers 35. In one exemplary embodiment, feed water is continuously fed over the sloped surfaces 61 such that the feed water in the common water feed area 47 overflows the wall 49 (FIG. 4) into the feed water overflow area 51. The surface of the tray 27 defining this area 51 is sloped such that the feed water in the area 51 runs to an outlet 66 (FIG. 5), referred to as the "feed water overflow collection outlet." In one exemplary embodiment, the outlet 67 is coupled to a hose 28 (FIG. 1) from which water can flow back to the water source 15 or other location.

[0038] In one exemplary embodiment, the hose 28 is coupled to a valve 69 that controls whether water from the hose 28 travels through a hose 70 to the water source 15 or through a hose 71 to the potable water reservoir 31. For normal solar distilling operations, the valve 69 is set such that the water from the hose 28 is directed to the water source 15. In other embodiments, water from the outlet 66 can be directed to other locations.

[0039] The exemplary solar distillation system 25 shown by FIGS. 2-13 can be manufactured at a relatively low cost using thermoforming techniques or other low cost manufacturing techniques. In addition, manufacturing the system 25 with acrylic, PET or other lightweight materials generally facilitates transportation of the system 25. Moreover, the barrier 30 can be carried by hand and laid on the tray 27 without using support beams or other types of support structures thereby simplifying implementation of the system 25 and reducing the overall cost of the system 25. Further, the system 25 can have a relatively low profile or height. The system 25 can also be configured with a sloping baseline to allow direct connection to pitched roofs Multiple systems 25 can be arrayed, positioned side-by-side to cover a relatively large horizontal area, such as a large field or a rooftop of a building, thereby increasing production of distilled, potable water. In addition, multiple systems 25 can be arrayed end-to-end with elevated stands to position directly over crop furrows and feed distilled water to drip-irrigation systems while still allowing sunlight to pass through the systems 25 to the underlying crops. As shown by FIG. 3, the tray 27 has holes 101 for receiving coupling devices, such as screws or nails, that can be used to couple the tray 27 to a stand or table (not shown).

[0040] In addition to the outlet 66, the system 25 has another outlet 67 (FIGS. 4 and

5), referred to as the "feed water collection outlet." For normal solar distilling operations, the outlet 67 is closed so that raw water does not flow through it. However, when it rams, the system 25 can be used to collect rainwater by opening the outlet 67. Any rainwater that falls on the chambers 35 should flow into the common water feed area 47. Thus, any such rainwater, as well as rainwater that falls on the common water feed area 47, flows out of the system 25 through the outlet 67. During periods of rain, particularly heavy rain, it is likely that the system 25 could produce more freshwater by collecting rainwater and dispensing such rainwater through the outlet 67 or otherwise rather than by distilling water alone

[0041] To operate in such a mode, referred to hereafter as the "rainwater collection mode," the input of raw water to the feed water channel 60 is stopped (e g , the pump 12 (FIG. 1 ) is turned off), and the outlet 67 is opened. Initially, the water flowing through the outlet 67 is feed water previously input to the system 25 for solar distillation. Such water is prevented from flowing to the potable water reservoir 31.

[0042] In this regard, as shown by FIG. 1 , the hose 24 extending from the outlet 67 is coupled to a valve 96 that controls whether water from the hose 24 travels through a hose 98 to the water source 15 or through a hose 99 to the potable water reservoir 31. Initially, the valve 96 is set such that the water from the hose 24 is directed to the water source 15. In other embodiments, water from the outlet 66 can be directed to other locations. Once the feed water has drained to the water source and the tray 27 sufficiently flushed by rainwater, the valve 96 is adjusted such that water from the hose 24 is directed to the potable water reservoir 31 rather than the water source 15. Thus, rainwater from the common water feed area 47 passes through the outlet 67 to the potable water reservoir 31.

[0043] In addition, after the input of raw water to the system 25 has stopped in the rainwater collection mode and the raw water in the feed water overflow area 51 has drained through the outlet 66 to the water source 15, the valve 69 (FIG. 1) is adjusted such that water from the hose 28 is directed through the hose 71 to the potable water reservoir 31. Thus, rainwater from the feed water overflow area 47 is directed to the potable water reservoir 31.

[0044] The system 25 can also operate in a mode, referred to as the "zero brine mode," in order to facilitate gathering of salt crystals from evaporated seawater. In such a mode, the feed water collection output 67 is closed after the system 25 has been used for normal solar distilling operations using seawater or after the system 25 has been used for other operations that input seawater into the common water feed area 47. As an example, the system 25 may be used for an extended period of time, such as several weeks, to provide potable water by feeding the system 25 seawater as the raw water input, and the system 25 may then be transitioned into the zero brine mode to collect salt crystals that have accumulated in the common water feed area 47. In the zero brine mode, the input of raw water to the feed water channel 60 is stopped (e.g., the pump 12 (FIG. 1 ) is turned off). The seawater that remains in the tray 27 is then allowed to evaporate leaving dry salt crystals in the tray 27. The barrier 30 is lifted or otherwise removed, and the salt crystals are collected from the tray 27 (e.g., emptied into a collection hopper). After the salt crystals have been collected, the barrier 30 is placed on the tray 27, and operation of the system 25 in another mode is commenced.

[0045] For example, the system 25 may be operated in a solar distilling mode (i.e., normal solar distilling operations) and the zero brine mode in an alternating fashion to collect potable water between collections of salt crystals. For example, every month or so, the operation of the solar distilling mode may be stopped to transition temporarily into the zero brine mode. Note that the increasing salinity of feed water leading up to salt crystal collection increases desalination efficiency due to the release of heat from the salt crystallization process. Of course, the system 25 can be transitioned at any time to the rainwater collection mode or other mode, as may be desired.

[0046] Note that embodiments described above are exemplary, and various modifications to the described embodiments are possible. For example, in one exemplary embodiment, the distillation chambers are arranged in a stair-step fashion to accommodate an incline, such as a sloped roof. FIG. 14 depicts an exemplary solar distillation system 25 positioned above a roof 115 of a building.

Claims

CLAIMSNow, therefore, the following is claimed:

1. A solar distillation system (25), comprising: a transparent barrier (30) defining at least one distillation chamber (35), the transparent barrier having a first channel (60) for guiding feed water such that the feed water flows over an upper transparent surface (61 ) of the distillation chamber, wherein evaporated feed water within the distillation chamber condenses on a lower surface (39) of the distillation chamber; and a tray (27) having a first outlet (53) and a second channel (52) positioned such that condensed water on the lower surface of the distillation chamber is pulled via gravity into the second channel, wherein the second channel is sloped such that condensed water within the second channel flows to the first outlet.

2. The solar distillation system of claim 1 , wherein the barrier defines an array of distillation chambers (35).

3. The solar distillation system of claim 1 , wherein the barrier is formed via thermoforming.

4. The solar distillation system of claim 1 , wherein the barrier is detachably coupled to the tray.

5. The solar distillation system of claim 1 , wherein the tray has a second outlet (67) positioned such that water within the distillation chamber flows into the second outlet.

6. The solar distillation system of claim 1 , wherein the tray defines a common water feed area (47) for holding feed water that is to replenish feed water evaporated in the distillation chamber, wherein the tray defines a feed water overflow area (51 ) that is separated from the common water feed area by at least one wall (49), wherein the tray is arranged such that feed water in the common water feed area overflowing the wall is collected in the feed water overflow area, and wherein the feed water overflow area has a second outlet (66) and is sloped such that water in the feed water overflow area flows to the second outlet.

7. The solar distillation system of claim 6, further comprising a pump (12) configured to pump water from the second outlet such that the pumped water flows over the upper transparent surface of the distillation chamber.

8. The solar distillation system of claim 6, wherein the distillation chamber has an opening (46), and wherein water within the common water feed area seals the distillation chamber.

9. The solar distillation system of claim 8, wherein the barrier is arranged such that water flowing over the upper transparent surface of the distillation chamber flows into the common water feed area.

10. The solar distillation system of claim 9, wherein the barrier defines an array of distillation chambers (35).

11. A solar distillation system (25), comprising: a tray (27); and a transparent barrier (30) detachably coupled to the tray and defining at least one distillation chamber (35), wherein the transparent barrier is composed of plastic and formed via thermoforming or injection molding, wherein the distillation chamber is arranged such that evaporated feed water within the distillation chamber condenses on a lower surface (39) of the distillation chamber and is pulled by gravity into a first channel (52), and wherein the first channel is sloped such that condensed water within the first channel flows to an outlet (53).

12. The solar distillation system of claim 11 , wherein the barrier has a second channel (60) for guiding feed water such that the guided feed water flows over an upper transparent surface (61) of the distillation chamber.

13. The solar distillation system of claim 11 , wherein the barrier defines an array of distillation chambers (35).

14. A solar distillation system (25), comprising: a tray (27) having a common water feed area (47); and a transparent barrier (30) detachably coupled to the tray, the transparent barrier defining at least one distillation chamber (35), the distillation chamber having an opening (46) for allowing feed water in the common water feed area to enter the distillation chamber, wherein the feed water in the common water feed area seals the distillation chamber, and wherein the distillation chamber is arranged such that evaporated feed water within the distillation chamber condenses on a lower surface (39) of the distillation chamber and is pulled by gravity into a first channel (52), and wherein the first channel is sloped such that condensed water within the first channel flows to an outlet (53).

15. The solar distillation system of claim 14, the barrier has a second channel (60) for guiding feed water such that the guided feed water flows over an upper transparent surface (61 ) of the distillation chamber.

16. The solar distillation system of claim 14, wherein the barrier defines an array of distillation chambers (35).

17. The solar distillation system of claim 14, wherein the transparent barrier is composed of plastic and formed via thermoforming or injection molding.

18. A method of distilling water, comprising the steps of: guiding feed water such that the guided feed water flows across a transparent surface (61) of a distillation chamber (35); inputting feed water into the distillation chamber such that the input feed water is evaporated by heat from light passing through the transparent surface and condenses on a lower surface (39) of the distillation chamber; collecting, into a channel (52), condensed water on the lower surface of the distillation chamber; and guiding the collected water to an outlet (53).

19. The method of claim 18, further comprising the step of sealing the distillation chamber via feed water.

20. The method of claim 18, further comprising the steps of: collecting the feed water in a common water feed area (47); and pumping overflow feed water from the common water feed area such that the pumped overflow feed water flows across the transparent surface of the distillation chamber.

21. The method of claim 18, further comprising the steps of: opening an outlet (67) such that feed water in the distillation chamber flows out of the distillation chamber through the outlet; and collecting rainwater in the distillation chamber.

22. The method of claim 21 , further comprising the step of coupling the outlet to a potable water reservoir (31).

23. The method of claim 18, further comprising the steps of: stopping feed water from entering the distillation chamber, the distillation chamber defined by a transparent barrier (30) and a tray (27); removing the barrier from the tray; and collecting salt crystals from the tray.

24. A method of manufacturing a solar distillation system (25), comprising the steps of: forming a transparent barrier (30) via thermoforming or injection molding, the transparent barrier defining an array of distillation chambers (35); and forming a tray (27) for use with the transparent barrier.