FIELD OF THE INVENTION

The invention relates to the construction of solar liquid treatment devices including solar stills intended to produce clean water condensate from saline, brackish or contaminated water supplies, with the use of solar energy.

BACKGROUND OF THE INVENTION

International patent application no. PCT/AU2009/000503 discloses a solar still module of the above mentioned type having a treatment chamber defined essentially by spaced upper and lower sheets of flexible plastics material with preformed edge regions secured together by a number of tubular connector members. The upper flexible plastics material sheet is substantially clear so as to pass solar energy through the upper sheet into the treatment chamber in the space between the sheets. The solar still module has a treatment member conveniently formed as a tray mounted within the space between the upper and lower sheets of flexible plastic material. A flexible fabric material layer is placed on the tray surface and the upwardly facing internal base surface of the tray and fabric material layer faces the upper substantially clear flexible sheet of plastics material and is spaced below same to receive the solar energy passing through the upper wall defined by the upper flexible plastics material sheet. The solar still module is, in use, mounted to be inclined such that water or other liquid to be treated is delivered to an upper end region of the base surface of the tray and flows downwardly on the base surface covered by the fabric material layer to be subjected to solar energy, the moisture being evaporated and then condensed on the inner surface of the upper flexible plastics material sheet to flow downwardly thereon. This condensate or clean water may then be collected via the tubular connector member at the lower end of the solar still module. The disclosure of PCT/AU2009/000503, as far as is necessary to understand the following, is included in the present specification by this reference thereto.

The construction and performance of the solar still module arrangements disclosed in International patent application no. PCT/AU2009/000503 for solar still modules work satisfactorily, however, it is desired to improve the efficiency of producing clean condensate from such stills. Other forms of solar treatment devices exist where the devices introduce heat from solar energy into a treatment liquid including solar water heaters, salt production cells and decontamination devices for killing toxins or similar in water or other liquids.

The present invention aims at improving the performance of solar stills and other solar treatment devices of the above-mentioned kind.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a treatment member for use in a solar treatment device to be placed in a treatment liquid flow subject to solar energy radiation received by said solar treatment device, said treatment member comprising at least one layer of a material and a metal dispersed substantially across said at least one material layer.

Conveniently in one preferred embodiment an upper and a lower said material layer is provided on either side of a second layer that includes or comprises dispersed metal. The dispersed metal may be in the form of a wire mesh of any configuration or in the form of dispersed metal particles or discrete metal fibres. In another possible embodiment uniformly dispersed metal particles may be contained within a single fabric material layer forming the treatment member. It has been found that by providing a dispersed metal layer as defined above, added heat can be introduced into the treatment liquid flow and can improve the treatment process including the efficiency of producing clean condensate in a solar still when compared to a solar still having a single fabric layer as disclosed in PCT/AU2009/000503.

Conveniently the upper material layer is bonded to the lower material layer by adhesive means. The adhesive means at least partially bonds the upper layer to the lower layer through the intermediate layer. In a preferred arrangement, at least one and preferably both said upper material layer and said lower material layer is thermoplastic with said upper material layer being bonded to said lower material layer by application of heat. Preferably, at least the upper material layer is substantially hydrophilic relative to the treatment liquid flow. The material layer or layers are preferably non-woven. Conveniently, the metal in the intermediate layer is substantially non corroding when in the environment of the treatment liquid flow and may be selected from at least one of aluminium, copper, stainless steel or alloys thereof.

Potential alternatives for the dispersed metal in the treatment member, particularly when used as an intermediate layer, are metal sheet or foil being continuous or perforated.

The present invention also anticipates providing a treatment device having a metal web providing an upwardly facing surface in use in a solar treatment device, the arrangement including a treatment member as described above. Conveniently, the metal web includes upstanding opposed side walls on either side of the upwardly facing surface to provide a tray or chute like structure. Preferably the treatment member is adhered to or bonded to the upwardly facing surface.

The present invention also provides a solar treatment device (including solar still modules) including a treatment member or device as described above.

Preferred embodiments will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig 1 is a lower edge sectional view of a solar energy still including a treatment member according to the present invention;

Fig 2 is an exploded perspective view of a preferred treatment member according to this invention;

Fig 3 is a schematic cross-sectional view of the treatment member shown in Fig 2; and

Fig 4 is a schematic flow diagram showing a method of making a preferred treatment member according to this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig 1 represents a longitudinal section of a lower end region of a solar treatment device 10 represented as a still module constructed with extruded edge members 1 1 defining a square or rectangular perimeter frame and upper and lower sheet members 12, 13, the upper sheet member 12 at least being substantially clear or highly translucent to allow solar energy to enter the internal zone 14 of the solar still module 10. The upper and lower sheet members 12, 13 may be secured in place by strip retainers 15 that engage into grooved recesses 21 , 22 formed in the edge members 1 1 . The retainers 15 engage and press inwardly a preformed folded edge 16, 17 of the upper and lower sheet members 12, 13. The retainers 15 also include projecting ribs 18 that engage with a lip protuberance 19 on an inner wall of the grooved recesses 21 , 22 to hold the retainer 15 in a desired position or allow the sheet members 12, 13 to be stretched more tightly by pressing the retainers 15 further into the grooved recesses 16, 17. Seal members 20 may be provided associated with each of the retainers 15.

Within the internal zone 14, a treatment tray member 23 is provided supported by at least one cross support member 24. The tray member 23 has a base wall 26 with an upwardly facing surface 27 and opposed upwardly directed side walls 25. Treatment liquid 28 which may be saline water or similar is delivered to the top end (not shown) of the tray member 23 to flow downwardly on the upwardly facing surface 27. In use the solar still module 10 is supported in an upwardly inclined manner to allow this flow of the treatment liquid 28 on the surface 27. Any treatment water that reaches the lower end 29 of the surface 27 can be collected in zone 50 and discharged through an outlet 51 in a side edge member 1 1 and recycled to the module 10 or a similar module if there are more than one such module in an installation. Solar energy entering the zone 14 evaporates water from the treatment liquid 28 which condenses on the inner surface 30 of both the upper and lower sheet members 12, 13 which also flows downwardly thereon to be suitably collected in a clean condensate collection and discharge arrangement (not illustrated). Further details of the general structure of such solar stills may be seen from PCT/AU2009/000503 and from Australian provisional patent application no. 2009905616 filed on 18 November 2009. The subject matter disclosure of the specification of the above identified patent applications is also included in the present specification by this reference thereto.

In accordance with a preferred aspect of the present invention, it is proposed to position a treatment member 40 covering at least part of and preferably a substantial part of the upwardly facing surface 27. The treatment member 40, as shown in Figs 2 and 3 may comprise upper and lower layers or sheets 41 , 42 of a material, preferably a non-woven material that is hydrophilic to the treatment liquid 28. The treatment member may be bonded to or adhesively secured to at least part of and preferably all of the surface 27 covered by the treatment member 40. The material may be viscose, polyester, polypropylene, or blends of these materials. Between the upper and lower layers 41 , 42 is a second layer 43 that is substantially formed by a metal that is non corroding in the environment of the treatment liquid 28. For saline water being the treatment liquid, aluminium, aluminium alloys, copper and copper alloys and stainless steel are all suitable metal materials. In a preferred embodiment, an aluminium wire mesh is utilized for the second layer 43. Alternatively thin metal sheet material or metal foil could be used, either perforated or not. In a further alternative, dispersed metal particles or discrete fibres could be employed as the second layer 43. Preferably an adhesive bonding material is used between the inner surfaces of the upper and lower layers 41 , 42 to bond these two layers together through the perforations in the metallic second layer 43. In yet another possible arrangement the layers 41 , 42 (or at least one of the layers 41 , 42) might be made from a thermoplastic material so as to mutually bond through the second layer 43 to one another or at least around the perimeter edges 52 (Fig 3) to contain the second layer 43 therebetween. In yet another possible arrangement metal particles or discrete fibres might be dispersed through a single material layer that presents a hydrophilic surface to the treatment liquid 28. The material of the layer is preferably non-woven viscose, polyester, polypropylene or blends thereof.

Fig 4 discloses, in a schematic manner, a method of manufacturing the treatment member 40 and the tray member 23. A roll of metal foil material 60 adapted for forming the tray member 23 is provided and dispensed at 61 as a flat web of foil material. This typically might be aluminium / aluminium foil but could be other metal foil. The foil has sufficient thickness to be substantially self supporting as a base wall 26 of the tray member 23 as described earlier. Thereafter rolls 62, 63 of material to form layers 41 , 42 are provided separated by a roll 64 of metal mesh material to form a layer 43. Each of the rolls 62, 63, 64 dispense their material onto a central surface portion 65 of the metal foil web 61 . Laminating rolls 65 are provided to laminate the layers 41 , 42, 43 to the central surface portion 66 of the metal foil web 61 . This may be achieved by applying suitable adhesive materials or if the layers 41 , 42 are thermoplastic materials, by applying heat to bend the layers together and to the foil web 61 . This produces a flat web material 67 with the layers 41 , 42, 43 bonded to the central surface portion 66 with flat edge zones 68, 69 or either side of metal foil material. Subsequently, at least a portion of the edge zones 68, 69 are bent upwardly as shown at 70 to form the upwardly configured side edge walls 25 of the tray member 23. Thereafter the material 70 is transversely cut to form required discrete lengths for use as the tray members 23 as depicted in Fig 1 .

The material for the layers 41 , 42 may be a blend of 50% viscose and polyester or polypropylene or alternatively 100% viscose. It may have a weight of 50 gm / square metre. It has been found that provision of such a treatment member 40 gives a 20% increase in condensate formed and collected compared to that which is collected without such a member.