OA11702A

OA11702A - Solar water still.

Info

Publication number: OA11702A
Application number: OA1200100006A
Authority: OA
Inventors: Husson Frank D Jr; Carl J S Lenox; Luis M Piek; Brian S Hunnicutt; Bradley L Spare
Original assignee: Solar Solutions Llc
Priority date: 1998-07-17
Filing date: 1999-07-07
Publication date: 2005-01-13
Also published as: TW548387B; AU5314299A; AP1532A; AP2001002034A0; PE20000496A1; DZ2847A1; CO4991009A1; AR019914A1; EG22043A; CN1220541C; WO2000003779A1; ID28523A; MA25139A1; CN1333703A; BR9912115A

Abstract

A solar water still (10) includes an enclosure assembly (12) and an evaporation assembly (14) that float on a body of source water and that are readily collapsed and folded for storage or transport. The enclosure assembly includes a transparent conical dome (20) covering a collection reservoir (18) and an inner float ring (16). The evaporation assembly is placed in the center of the inner float ring. During operation, solar radiation induces water to evaporate from the evaporation assembly. The water vapor is then condensed and collected by the enclosure assembly.

Description

117 0 2 1

SQLAR WATER STILL FIELD OF THE INVENTION ,

The présent invention relates to solar water stills and, more particularly, to aportable solar water still that may be readily transported and stored.

BACKGROUND OF THE INVENTION 5 Existing solar water stills generally include a bulky structure that prevents the still from being readily transported and stored or that complicates the structure andincreases its manufactunng costs. Further. the structural components tend to reduce the reliability of the solar water still and give rise to the possibility that the still could * be rendered inopérable by relatively minor structural damage. Additionally, existing 10 solar water stills hâve complicated undistilled water loading mechanisms or otherconfigurations that give rise to the possibility of contamination of the resultingdistilled water by the undistilled water.

Accordingly, there exists a definite need for a solar water still that is readilytransportable, easily stored, and that has a simple, cost-effective design for providing 15 a supply of potable water. The présent invention satisfies these needs and providesfurther related advantages.

SUMMARY OF THE INVENTION

The présent invention provides a solar water still having a simple inflatabledesign for providing a renewable supply of drinking water to a person. Moreover, the 20 construction of the invention water still renders the still relatively inexpensive tomanufacture, trouble-free and reliable in use, and readily collapsed and folded forstorage or transport.

The invention is embodied in a solar water still having an enclosure assemblyand an évaporation assembly. The enclosure assembly has an inneï float barrier that 117 0 2 2 surrounds an évaporation area, a collection réservoir that surrounds the inner floatbamer for collecting distilled water, and a dôme that is substantially transparent tosolar radiation and that encloses the collection réservoir, the inner float barrier, andthe évaporation area. The évaporation assembly is located in the évaporation area andhas an evaporative surface. Water that evaporates from the evaporative surfacecondenses on the interior surface of the dôme and flows into the collection réservoiras distilled water.

In another feature of the invention, the enclosure assembly floats on a body ofundistilled source water and the évaporation assembly includes a buoyant insulatorand a wick material. The buoyant insulator floats on the source water and issubstantially fiat, having a top surface and a bottom surface. The top surface isthermally insulated from the bottom surface and forms the evaporative surface. Thewick material extends from the top evaporative surface toward the bottom surface fortransporting source water to the evaporative surface. Solar radiation incident on theevaporative surface causes water to be evaporated from the evaporative surface. Theevaporated water is replaced by source water transported to the top surface by thewick.

In an alternative embodiment of the invention, the solar water still includes acollection réservoir, a bamer, and an enclosure. The collection réservoir collectsdistilled water and the barrier séparâtes the collection réservoir from an évaporationarea. The bamer has a fîrst wall surface that contacts undistilled source water in theévaporation area and a second wall surface that contacts distilled water in thecollection réservoir. The barrier extends above the évaporation area and above thecollection réservoir to prevent liquid flow between the évaporation area and thecollection réservoir. The enclosure is substantially transparent to solar radiation andencloses the collection réservoir, the barrier, and the évaporation area. The enclosureis configured such that source water that evaporates from the évaporation area andthat condenses on an interior surface of the enclosure flows into the collectionréservoir. 117 02 3

Other features and advantages of the présent invention should be apparentfrom the following description of the preferred embodiments, taken in conjunctionwith the accompanying drawings, which illustrate, by way of example, the principlesof the invention.

5 BRIEF DESCRIPTION OF THE DRAWINGS * FIG. 1 is a cross-sectional élévation view of a conical solar water still, inaccordance with the invention. FIG. 2 is a plan view of the solar water still of FIG. 1, further showing afloating évaporation assembly. 10 FIG. 3 is a plan view of another embodiment of a floating évaporation assembly having additional wicking holes, in accordance with the invention. FIG. 4 is a cross sectional élévation view of an embodiment of a solar waterstill, in accordance with the invention, with an inflatable évaporation assembly havingcorrugated surfaces. 15 FIG. 5 is a cross-sectional élévation view of an embodiment of a conical solar water still, in accordance with the invention, showing a plurality of inflation rings, asolid or inflatable support structure and a buoyant évaporation assembly having adraped wicking material. FIG. 6 is a cross-sectional élévation view of an embodiment of a conical solar 20 water still, in accordance with the invention, including a catch basin for collectingrain water, a skirt and weights for use in océan or rough waters. FIG. 7 is a cross-sectional élévation view of an embodiment of a conical solarwater still, in accordance with the invention, showing two inflatable pools, for use ofthe solar still on land. 25 FIG. 8 is a cross-sectional élévation view of an embodiment of a conical solar. water still, in accordance with the invention, showing an integrated inflatable support 117 0 2 4

System for maintaining the still inflated during extreme weather conditions or duringuse on land. FIGS. 9A-9D are cross-sectional élévation views of an embodiment of aconical solar water still, in accordance with the invention, showing an extemal rigidsupport System for use during extreme weather conditions or during use on land.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the invention, there is provided a solar water stillcomprising an enclosure assembly having an inner float barrier that surrounds anévaporation area, a collection réservoir that surrounds the inner float barrier forcollecting distilled water, a dôme that is substantially transparent to solar radiationand that encloses she collection réservoir, the inner float barrier, and the évaporationarea; and an évaporation assembly located in the évaporation area and having anevaporative surface.

In a preferred embodiment of the invention, the enclosure assembly isconfigured to float on a body of source water; and the évaporation assemblycomprises a buoyant insulator that is configured to float on the source water, theinsulator being substantially fiat and having a top surface and a bottom surface,wherein the top surface is thermally insulated from the bottom surface and forms theevaporative surface and comprises a wick material that extends from the topevaporative surface toward the bottom surface for transporting source water to theevaporative surface.

In accordance with the invention, there is provided a solar water stillaltematively comprising a collection réservoir; a barrier that séparâtes the collectionréservoir from an évaporation area, wherein the barrier has a first wall surface thatcontacts source water in the évaporation area and a second wall surface that contactsdistilled water in the collection réservoir, and wherein the barrier extends above theévaporation area and above the collection réservoir to prevent liquid flow between the 117 0 2 5 évaporation area and the collection réservoir; an enclosure that is substantiallytransparent to solar radiation, that encloses the collection réservoir, the barrier, andthe évaporation area, wherein the enclosure is configured such that source water thatevaporates from the évaporation area and that condenses on an interior surface of the 5 enclosure flows into the collection réservoir.

As shown in the drawings, the présent invention is embodied in a solar waterstill 10 having a simple inflatable design for providing a renewable supply of distilledwater to a person in a daily survival or emergency situation. The still may bemanufactured from relatively inexpensive materials and may be designed to float on a 10 body of source water.

With reference now to FIGS. 1 and 2, the still 10 includes an enclosureassembly 12 and an évaporation assembly 14 which are readily collapsed and foldedfor storage or transport. During operation, solar radiation induces water to evaporatefrom the évaporation assembly. The resulting water vapor is then condensed and 15 collected by the enclosure assembly.

The enclosure assembly 12 includes an inner float tube or ring 16, a catchbasin or collection réservoir 18, and a conical dôme 20. The dôme may beconstructed of a variety of flexible, optically transparent materials, e.g., flexible filmsof such materials as clear vinyl (e.g., polyvinyl chloride), urethanes, polyesters (e.g., 20 polyethylene terephthalate), polyamides, polysiloxanes, polyalkylenes (e.g.,polyethylene), polycarbonates, and the like, as well as blends thereof (e.g.,polyethylene-nylon), laminates thereof, and the like, formed in a conical shape thatallows solar radiation to pass through the dôme and heat the wick assembly 14. Asdefined herein, the term dôme is defined to include a variety of shapes, such as the 25 conical structure shown in FIG. 1, and is not limited to hemispherical structures.

The inner float ring is a flexible toroidal ring of flexible film and includes aninflation valve 22 for inflating the ring and providing shape and structural strength tothe bottom of the enclosure assembly. The collection réservoir may.be a pocket of 117 0 2 6 flexible film attached between the inner float ring and the conical dôme such that theréservoir loops outside and attaches to the inner float ring. Accordingly, the 'collection réservoir water is separated from the source water by the float ring and theflexible film. 5 The reservoir’s flexible film is attached to the inner float ring and the conical dôme by any suitable means, e.g. by a radio frequency (RF) seal, sonie weld, by aheat seal, or the like, to form an air and water tight seal within the enclosureassembly. Accordingly, when the inner float ring is floating on a body of sourcewater, the air within the enclosure assembly is trapped within the still 10 because the 10 source water prevents the air from exiting through the center of the inner float ring.The réservoir may rest at the surface of the water line or extend below the water lineof the source water and, as it fills with distilled water, may further act as a condenserbecause it is adjacent to and cooled by the source water.

The réservoir may include a drain valve or capped spout 24 having a cap, or a 15 clamp. Also, a straw 25, having a removable cap 26, may be attached through asealed opening in the conical dôme 20 at a location that lies above the water line ofthe source water. Opposite the straw, within the dôme, may be a tube 19 that extendsdown into the réservoir 18 and that is pliable and flexible to avoid puncturing the still10 during operation and when folding the still for storage or transport. A suitable 20 device for providing the sealed opening into the réservoir or dôme may be a seal, suchas, for example, part number CARMO 3-802, available from KABAR ManufacturingCorp. of Farmington, New York.

The évaporation assembly 14 has a fiat disk-like shape and may be attached tothe outside of the inner collection réservoir 18 in contact with the source water by a 25 suitable means, e.g., a hook and loop fastener such as Velcro (not shown). The wick assembly may be formed of a buoyant insulator 35 made of suitable material, e.g., open or closed-cell foam, and may hâve a hole 28 placed therethrough. Good thermal insulation between the buoyant insulator’s top evaporative surface 30 and its bottom 117 0 2 7 surface 32 is particularly valuable for increasing the effectiveness of the évaporationassembly.

As shown in FIG. 3, the évaporation assembly 14 mav include additional holes 36 to facilitate the conveyance of moisture front the source water to a top evaporative5 surface 30. The holes, 28 and 36, may be left open or may be filled with suitable transport media, e.g., a sponge material, open-cell urethane foam, or other materialthat exhibits wicking or capillary action for transporting source water to the topevaporative surface which is covered with a black wick material such as felt, fibrouscarpet, cloth, or the like, having fine hair-like fibers. For example, the evaporative 10 surface may be covered with crest black carpet which is available front Bretlin, Inc. ofDalton, Georgia.

Altematively, as shown ïn FIG. 4, an évaporation wick assembly 14’ may beformed of an inflatable assembly made of flexible film, which likewise insulates theevaporative surface 30 front the source water on which the évaporation assembly 15 floats. The évaporation assembly preferably has a relatively fiat top surface 30’having corrugated surface features forming dépréssions 34 for holding smallquantities of source water initially placed or wicked onto the evaporative surface.

As shown in FIG. 5, an évaporation assembly 14” may be formed with carpet 37 having flaps 38 for contacting the source water. The flaps enable the carpet to 20 better wick the source water to the top evaporative surface 30 for heating. The buoyant insulator may include the central hole 28 and the carpet may hang or sagdown into the hole and contact the source water for improved water transport to thetop evaporative surface through the carpet.

In operation, the user unrolls the still’s enclosure assembly 12 and évaporation 25 assembly 14’ from a package. The évaporation assembly is inflated, pre-wetted by theuser, and placed upon the surface of the source water. The user inflates the inner floatring 16 and then holds the still by the tip of the conical dôme 20 and drops the stillenclosure assembly over the évaporation assembly to inflate the dôme. The dôme ”702 8 remains inflated by the air trapped within the still and further inflates as the enclosedair heats up and water evaporates and will thus retain its conical shape.

Optionally, as shown in FIGS. 5, 6, 8 and 9, the dôme may include structuralmembers in the form of rigid rods, inflatable support tubes 62, or the like that may be 5 placed inside the solar still or inserted into pockets on the conical dôme 20, to ensurethat the conical dôme does not deflate in the presence of an air leak. As shown inFIG. 5, the inflatable support tube 62 has one end that is placed in the apex of theconical dôme and an opposite end that is attached to the evaporative assembly bysuitable means, e.g., a hook and loop fastener. The user secures the évaporation 10 assembly to the enclosure assembly by suitable means, e.g., a hook and loop fastenerto prevent the évaporation assembly front floating away ffom the still. The user alsosecures the still to ^prevent the still from floating away from the user’s location orfront being overtumed in high winds.

Refemng to FIGS. 1 and 4, the still 10 opérâtes during the daylight hours. 15 Solar radiation passing through the conical dôme 20 strikes and heats the evaporativesurface 30. The source water is wicked to the evaporative surface as incident solarradiation heats and evaporates the water on the black wick material. The evaporatedwater vapor saturâtes the air inside the conical dôme and some of the water vaporcondenses on the rnner surface of the dôme 40 and flows down the inner surface into 20 the collection réservoir 18. At the end of a day, or other suitable time period, thedistilled water is removed from the collection réservoir.

The distilled water may be sucked directly out of the collection réservoir 18using the straw 25. Altematively, the distilled water may be drained ffom thecollection réservoir into a container by detaching the évaporation assembly 14 ffom 25 the still 10 and pouring the distilled water out of the valve or spout 24. Whendraining distilled water from the still in this manner, the enclosure assembly 12 istipped so that the distilled water collects at the head of the drain valve. The valve isthen opened and the distilled water drains from the collection réservoir into thecontainer. After the distilled water is removed, the still can either be-placed back on ”702 9 the water and left ovemight so that production can begin again early the next day, orthe enclosure assembly may be refolded and the évaporation assembly may be'rolledaround the enclosure assembly to form a relatively small package for storage or travel. A still 10 having a dôme 20 with a height of about 76 centimeters (30 inches) 5 and a wick assembly 14 having a diameter of about 79 centimeters (31 inches) has been found to produce about 1.5-2.5 liters of distilled water a day while floating on afresh water lake under direct exposure to sunlight, depending on weather conditions.The still’s inner float tube 16 has a radius of about 15.3 centimeters (6 inches) and thecollection réservoir 18 has a semicircular radius of about 20 centimeters (8 inches). 10 The évaporation assembly is formed of an inflatable device made of clear vinyl 0.6millimeters (12 mils) thick. The clear urethane of the dôme has a thickness of about0.15 millimeters (ô^mils), although more economical (and less durable) embodimentsof the invention may hâve a thickness of 3 mils or less.

An alternative embodiment of the solar still 10” is shown in FIG. 6. The 15 features shown in addition to FIG. 5 are advantageous for increasing the effectivenessof the solar water still in more adverse conditions. These additional features may beincluded in the still individually or collectively in accordance with the cost andrequirements that various applications of the invention may dictate.

The enclosure assembly 12’ may further include arain catch basin 50 for 20 collecting rain on a rainy day. The rain catch basin is formed of a cylindrical ring offlexible material or film, which is attached to the conical dôme 20. The rain catchbasin may be attached to the conical dôme so that the catch basin is slightly slanted inorder for the rainwater to accumulate toward one side 52 of the catch basin. Thecatch basin may also include a drain hose 54 or straw for ease of emptying the catch 25 basin.

The enclosure assembly 12’ may further include a double tube inner float ring16’ for greater séparation of the distilled water in the collection réservoir 18 from thesource water. The double tube inner float ring is formed of two inflatable attached 117 0 2 10 tubes. Altemativeiy, the tube 16’ may also hâve a non-circular shape such as an ovalshape for providing such séparation.

The enclosure assembly 12’ may further include a skirt or flap 56 forimproving the sealing of the enclosure and the stability of the still 10’ in the presence 5 of rough or wavy waters. The skirt may be a flexible flap formed of flexible film orthe like which is attached to the inner float ring 16’ or to the collection réservoir 18.Further, the skirt may include weights 58 that maintain the cylindrical shape of theskirt 56 to prevent air from escaping out of the dôme 20 as the still floats on a wavywater surface. Ιθ Other modifications to the solar water still 10’ may be made in accordance with the présent invention. For example, the tube 54 may be attached through a smallwater collection cône for facilitating emptying the respective basins 18 and 52.Further, the collection réservoir may include an inflatable ring for maintaining thecollection reservoir’s shape with respect to the inner float ring. 15 Also, the dôme may be a semi-spherical dôme having intégral Fresnel lenses stamped into the dôme for concentrating the incoming solar radiation on theévaporation assembly to create localized spots of increased water vaporization.

As shown in FIG. 7, for land use, the solar water still 10’ may be placed in aninflatable wading pool 64 or the like. Likewise, a small tub or inflatable wading pool 20 64 may be placed in the center of the inner float ring 16 and an appropriately sized évaporation assembly may be placed in the tub. Altemativeiy, moisture ladenmaterial, such as leaves, grass, or the like, may be placed in the center of the innerfloat ring 16 for évaporation of the material’s moisture content. The efficiency of aland use still may be reduced because of the lack of cooling outside of the dôme 25 provided by évaporation from the Iake or océan surface.

Referring to FIG. 8 and FIGS. 9A — 9D, an extemal support System may beprovided to prevent the solar still from deflating in extreme weather conditions. The 117 0 2 11 support System may consist of a plurality (e.g., three) of inflatable tubes 65 sealed intothe dôme 20 (FIG. 8), each tube including an inflation valve 66. Altemativelÿ, rigidrods 67 (FIGS 9A - 9D) made of suitable rigid material, e.g., fîberglass, plastic,bamboo, or the like, may be attached to the outer portion of the solar still by suitable 5 means, e.g., by tabs 68 located along the height of the dôme and by a mountinggrommet 72 at the apex of the dôme. The ends of the rigid pôles may be attached tothe lower portion of the solar still using suitable means, e.g., flaps 70 with mountinggrommets 72 (FIG. 9D). The tabs may be in the form of a strip of flexible film sealedto the dôme (FIG. 9B), as tabs reinforced with grommets 72, attached to the dôme and 10 that then may be tied onto the rigid pôles using string 74 (FIG. 9C), or the like.

While the foregoing has been with reference to spécifie embodiments of theinvention, it will be appreciated by those skilled in the art that these are illustrationsonly and that changes in these embodiments can be made without departing from theprinciples of the invention, the scope of which is defined by the appended daims.

Claims

117 0 2 12

1. A solar water still, comprising:an enclosure assembly having an inner float barrier that surrounds an évaporation area,a collection réservoir that surrounds the inner float barrier for 5 collecting distilled water, a dôme that is substantiallv transparent to solar radiation and that encloses the collection réservoir, the inner float barrier, and theévaporation area; and an évaporation assembly located in the évaporation area and having an 10 evaporative surface.

2. A^solar water still as defined in claim 1, wherein: the enclosure assembly is configured to float on a body of sourcewater; and 15 the évaporation assembly comprises: a buoyant insulator that is configured to float on the source water, the insulator being substantiallv fiat and having a top surfaceand a bottom surface, wherein the top surface is thermally insulatedfrom the bottom surface and forms the evaporative surface; 20 a wick material that extends from the top evaporative surface toward the bottom surface for transporting source water to theevaporative surface.

3. A solar water still as defined in claim 2, wherein the evaporative 25 surface is corrugated to form dépréssions that collect and hold source water placed onthe evaporative surface.

4. À solar water still as defined in claim 2, wherein the evaporativesurface is covered wilh black carpet. 117 0 2 13

5. A solar water still as defined in claim 4, wherein the black carpet is thewick material and covers the evaporative surface.

6. A solar water still as defined in claim 5, wherein the black carpet hangs 5 over the edge of the buoyant insulator for contacting the source water.

7. A solar water still as defined in claim 5, wherein the buoyant insulatorincludes at least one hole near the center of the insulator and the black carpet droopsinto the hole at the center of the buoyant insulator for contacting the source water. 10

8. A solar water still as defined in claim 2, wherein the buoyant insulatoris formed of open or closed cell foam. *

9. A solar water still as defined in claim 2, wherein the buoyant insulator15 is an inflatable vinyl chamber and the enclosure assembly is formed of urethane.

10. A solar water still as defined in claim 1, wherein the dôme is a conicaldôme formed of optically transparent film. 20

11. A solar water still as defined in claim 1, wherein the inner float bamer is an inflatable toroidal tube formed of flexible film.

12. A solar water still as defined in claim 11, wherein the inflatabletoroidal tube includes an inflation valve. 25

13. A solar water still as defined in claim 1, wherein the inner float bameris formed of two attached tubes which are inflatable for separating the collectionréservoir from the évaporation area. 30

14. A solar water still as defined in claim 1, wherein the collection réservoir sits at or below the surface of the water line when the solar water still isfloating on a body of source water. 117 0 2 14

15. A solar water still as defïned in claim 1, wherein the collectionréservoir includes a drain hose for removing distilled water from the collectionréservoir. 5

16. A solar water still as defined in claim 1, wherein the dôme includes a resealable spout located on the dôme at a location above a water line.

17. A solar water still as defined in claim 1, further comprising a straw forsucking water out of the collection réservoir. 10

18. A solar water still as defined in claim 1, further comprising a rain water catch basin formed of a ring of flexible film that extends around an outside * surface of the conical dôme to form a catch basin. 15

19. A solar water still as defined in claim 1, further comprising a skirt attached below the enclosure assembly for use in océan waters, wherein the skirt isformed of a flap of flexible film.

20. A solar water still as defined in claim 19, further comprising weights 20 attached to the skirt to maintain the skirt in a cylindrical shape to prevent air escaping from within the dôme as the still floats on a wavy surface.

21. A solar water still as defined in claim 1, wherein the enclosureassembly is attached to the évaporation assembly using a hook and loop fastener. 25

22. A solar water still as defïned by claim 1, further comprising a supportpôle located in the center of the dôme between an apex of the dôme and theévaporation assembly to maintain the shape of the dôme. 117 0 2 15

23. A solar water still as defined by claim 1, further comprising a pluralityof infiatable support members that are sealed onto the dôme between the collectionréservoir and a top portion of the dôme to maintain the shape of the dôme. 5

24. A solar water still as defined by claim 1, further comprising a plurality of rigid rods which are located on the outside of the dôme and attached to the dômeby suitable means.

25. A solar water still as defined by claim 1 wherein said suitable means 10 comprises tabs and mounting grommets adéquate to maintain the shape of the dôme.

26. A solar water still, comprising:a collection réservoir: a bamer that séparâtes the collection réservoir from an évaporationarea, wherein the bamer has a first wall surface that contacts source water inthe évaporation area and a second wall surface that contacts distilled water in i the collection réservoir, and wherein the barrier extends above the évaporationarea and above the collection réservoir to prevent liquid flow between theévaporation area and the collection réservoir; an enclosure that is substantially transparent to solar radiation, thatencloses the collection réservoir, the barrier, and the évaporation area, whereinthe enclosure is configured such that source water that evaporates ffom theévaporation area and that condenses on an interior surface of the enclosureflows into the collection réservoir. 25

27. An évaporation assembly for use in a solar water still, comprising:a buoyant insulator that is configured to float on a body of source water, the insulator being substantially fiat and having an evaporative topsurface and a bottom surface, wherein the evaporative top surface is thermally 30 insulated from the bottom surface; a wick material that extends from the evaporative top surface toward the bottom surface for transporting source water to the evaporative top surface.