Abstract:
A portable, collapsible still includes an upper reservoir for coolant water, an intermediate condensing chamber, and a lower reservoir of an aqueous solution, for example, seawater. A condenser coil is in fluid communication with the headspace in the lower reservoir above its fluid level, with the coil extending into the condenser chamber and to an external fluid port. A reflector is positioned below the lower reservoir, to reflect sunlight onto the lower reservoir to heat it. As the water vapor pressure in the lower reservoir increases as a result of the solar heating, the water vapor enters the coil, which is bathed in the lower temperature coolant water from the upper reservoir, causing the water vapor to condense inside the coil and thus be available for drinking.

Description:
[0001]    This application claims priority to U.S. Provisional App. No. 61/907,709, filed 22 Nov. 2013, by Robert Johnston, the entirety of which is incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    Field of Endeavor 
         [0003]    The present invention relates to devices, systems, and processes useful for water distillation, and more specifically to portable, collapsible water stills. 
         [0004]    Brief Description of the Related Art 
         [0005]    Ocean voyagers are always wary of the risk of running out of potable water. Tankage on cruising boats is often inadequate for long passages, and water stored in portable tanks (e.g., ‘Jerry Jugs’) is at risk of spoiling. While there is plenty of ocean water, it is not drinkable. 
         [0006]    Many boats are equipped with water makers using reverse osmosis (RO) to separate the salts from the water. However, these require large amounts of electrical power, which, at times, may not be available (an electrical charger breakdown, battery failure, engine failure). 
         [0007]    In addition, there is always the unlikely event of the main vessel sinking, and being left in a life raft with a very meager supply, if any, of fresh water. Again, hand powered RO watermakers are available, but are expensive, and may not be readily available when the ship goes down. 
         [0008]    Similarly, many cross-country hikers, back-packers, and those traveling by automobile or horseback through arid country (e.g., Nevada), may need a convenient, portable system for making fresh water from meager, often contaminated or saline water. Water filters are commonly commercially available, which can remove bacteria from contaminated water, but cannot remove viruses, many chemicals, and salts. 
         [0009]    Much of recreational ocean cruising is carried out in warm climates with ample sunshine (often too much!). It is reasonable then, to consider using that power to create fresh water from salt water through distillation. 
       SUMMARY 
       [0010]    According to a first aspect of the invention, a low cost, portable, collapsible, rust free, light weight distillation apparatus is capable of generating small but adequate quantities of fresh water relying only on solar power. The product may be made to be self-supporting (free standing) or (more simply, and lighter) to be hanged from a makeshift stand or other elevated object (the boom on a boat, the rigging, a tree branch, or a tripod of sticks or oars, etc.). It is best used where there is no, or very limited, shade, as direct sunlight will be far more effective than ambient heat to produce the desired outcome. It is designed to be collapsed to fit into a fabric container 12″ in diameter and no more than 3″ high; it weighs no more than 2 pounds. 
         [0011]    Still other aspects, features, and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of embodiments constructed in accordance therewith, taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention of the present application will now be described in more detail with reference to exemplary embodiments of the apparatus and method, given only by way of example, and with reference to the accompanying drawings, in which: 
           [0013]      FIG. 1  illustrates a side elevational view of an exemplary distillation device; 
           [0014]      FIG. 2  illustrates a top plan view of the device of  FIG. 1 ; 
           [0015]      FIG. 3  illustrates a side elevational view of another exemplary distillation device; and 
           [0016]      FIG. 4  illustrates a top plan view of the device of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0017]    Referring to the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures. 
         [0018]    The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a solvent” includes reference to one or more of such solvents, and reference to “the dispersant” includes reference to one or more of such dispersants. 
         [0019]    Concentrations, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. 
         [0020]    For example, a range of 1 to 5 should be interpreted to include not only the explicitly recited limits of 1 and 5, but also to include individual values such as 2, 2.7, 3.6, 4.2, and sub-ranges such as 1-2.5, 1.8-3.2, 2.6-4.9, etc. This interpretation should apply regardless of the breadth of the range or the characteristic being described, and also applies to open-ended ranges reciting only one end point, such as “greater than 25,” or “less than 10.” 
         [0021]    Exemplary embodiments of portable, collapsible, distillation apparatus can have a number of features including, but not limited to: 
         [0022]    Portability, using light weight, plastic components 
         [0023]    Fit into fabric a container of, e.g., 12″ diameter, 2″ thick 
         [0024]    Weight less than 2 lbs. 
         [0025]    Collapsible, all rigid members fold or disassemble 
         [0026]    All rigid members less than 1 foot long 
         [0027]    Principle containers are formed of heavy duty polyethylene (or equivalent) 
         [0028]    Rust free, having no metallic fixtures/joints/fasteners, or formed of non-corrosive materials, such as aluminum, titanium, stainless steel, and the like 
         [0029]    Distillation purpose: to provide emergency device or creating fresh water (potable) from salt or contaminated water using the sun as only energy source. 
         [0030]    Benefits include that no external fuels are required 
         [0031]    No complex, heavy machinery required (e.g., reverse osmosis water maker) 
         [0032]    Low cost 
         [0033]    Design Considerations 
         [0034]    One goal is to produce a portable (lightweight, small), collapsible (to reduce volume), rust free (due to intentional presence of water fresh and salt), effective system for making potable water from that which is available in situations of distress in which no fresh water is at hand. 
         [0035]    An exemplary unit can be packed into a fabric container 12″ in diameter and not more than 3″ in height. These parameters are somewhat arbitrary and not an essential quality of the system. Size may be varied in order to improve portability, tune the production to the need, or other considerations (e.g., materials costs). An additional objective is affordability, as current RO hand-operated units cost upward of $400.00. Commonly commercially available filters are less expensive, but have only limited applicability, as discussed above. 
         [0036]    The system capitalizes on the fact that sunlight (and especially the infra-red end of the spectrum) is differentially absorbed by materials of different color. The device includes two reservoirs, for the coolant (e.g., fresh, cool sea water, which can also be water yet to be distilled, that is, source water), and for the source water (e.g., sea water, stream water, stagnant water), with a condensing chamber between then, where the coolant from the coolant reservoir surrounds a coiled, thermally conductive conduit for the vapor from the source reservoir. The coolant reservoir is surrounded by a reflective surfaced, flexible plastic wall (to reduce heat absorption) and the source water reservoir is surrounded by a black flexible plastic wall (to enhance absorption of infrared and other solar energy). In addition, the whole unit is topped by a reflective (e.g., aluminized) shade, additionally reducing energy input to the coolant reservoir; and the unit rests upon or within a reflective curved plastic power collector, designed to amplify the amount of light energy reaching the source water reservoir. 
         [0037]    It is expected that by using water drawn from at least five (5) feet under the surface of the water (in tropical zones) in the coolant reservoir (75 degrees Fahrenheit), and by using surface water in the source water reservoir (80 to 85 degrees Fahrenheit), during the daytime, a temperature differential of at least 60 degrees Fahrenheit may be achieved (approximately 140 degrees Fahrenheit in the exposed source water reservoir). While this will not boil the water, it will substantially increase the vaporization rate. 
         [0038]    The vapor from the source water reservoir will ascend into a coiled tube within the condensing chamber, where it is surrounded by coolant (optionally flowing at a controlled rate suited to the need and availability from the above coolant chamber). The output of that condensing tube will flow to a suitable potable water container. The output of the condensing chamber (used coolant) will in turn be moved to the evaporation reservoir, thus preserving heat absorbed from the condensation process. 
         [0039]    Turning now to the drawing figures, specific design features will be discussed with reference thereto. The unit  10  is topped by an eye or hanger  20  suitable to support the unit, including the water in the filled unit. Surrounding and radiating from the eye  20  are a plurality, e.g., eight, equally spaced support units or braces  24  securing an upper ring  26  of an upper, coolant reservoir  12  to the eye, and extending beyond the ring to provide support to an overhanging shade  16 . 
         [0040]    The shade  16 , which is advantageously reflective, fits loosely over the frame formed by the braces  24 , with spacing between it and the underlying coolant reservoir  12  to allow adequate air flow. The shade  16  preferably includes at least one, e.g., four, apertures  22  near the apex of the shade to allow for thermal convection of air beneath the shade. 
         [0041]    From the upper ring  26  of the coolant reservoir  12  will hang the remaining components, advantageously in a cylindrical form, requiring only sufficient material strength in the walls to support the weight of the water contents and the unit. For rigidity of form, the bottom of the coolant reservoir  12  and the top and bottom of the lower, source water reservoir  14  will also be formed around a rigid (plastic) ring (not illustrated). The upper  12  and lower  14  reservoirs each have an aperture, near the top and another near the bottom in the side walls of each, suitable for connecting an external fill tube and an external drain tube, as needed, for the purpose of filling and emptying the reservoirs. These external tubes (not illustrated) are also advantageously fitted with valves to control the flow of fluid through the apertures and tubes. 
         [0042]    The upper (coolant) reservoir  12  has a drain port  48  near its bottom, and a small (e.g., approximately ½″) aperture  50  in its floor directly connecting it to a condensing chamber  30 . The condensing chamber  30  is formed by the taught, flat bottom of the coolant reservoir  12  on top, and the upward tented top  32  of the underlying source water reservoir  14 , and is secured to the bottom of the upper reservoir centrally. A fitting suitable to provide vapor escape from the evaporating (source water) chamber  14  into a thin walled (preferably) clear plastic tube  34  (see  FIG. 2 ), which acts as a condenser coil, is on or near the apex of the condensing chamber floor  32 . The clear plastic (condensing) tube  34  spirals or otherwise follows a complex path around the center of the top  32 , proceeding outward from the inlet fitting from the headspace above the water in the lower, source reservoir, until it joins the side wall fitting  34  suitable for connecting a fresh water output hose or tube. The purpose is thus to provide heat exchange to condense vapor from the reservoir and preheat water for later evaporation. 
         [0043]    The side wall of the condensing chamber  30  includes a fitting  36  near the top suitable for an adjustable valve to allow control of discharge of warmed coolant from the condensing chamber. 
         [0044]    The source water reservoir  14  has a top  32  which is tented or otherwise forms a sloped surface, from a generally central apex down to lower peripheral edges, and is fenestrated, as previously described. The reservoir  14  includes a fill port  38  and a drain port  40  in the side wall as described above. 
         [0045]    Beneath the lower reservoir  14 , an up-curved (upside-down-umbrella shaped), preferably octagonal, reflective sheet  42  is positioned, and is designed to increase the energy delivery from the sun to the lower reservoir. The sheet  42  is reflective on the inside or top surface  44 , and held in place by removable, flexible plastic ribs  46  ( FIG. 2 ) which secure to the bottom ring of the source water reservoir  14  and into pockets at the rim of the sheet. The ribs produce enough tension to hold the assembly in place with the unit hanging from the eye  20 . 
         [0046]    According to another exemplary embodiment, illustrated in  FIGS. 3 and 4 , a free standing unit  100  includes the structures as described above with reference to  FIGS. 1 and 2 , with the exceptions which follow. The unit  100  includes a plurality of, e.g., eight, folding, locking vertical members  102  connecting the upper ring of the coolant reservoir  12  with the bottom ring of the source water reservoir  14 . A plurality of, e.g., four, folding angle braces  104  are positioned so as to alternate in the direction of the angled portions to provide lateral stability of the unit. Additional bracing units may be used as needed, depending on size, stability, lateral stresses encountered. 
         [0047]    In addition to the foregoing, additional components can optionally be included in a system as described herein. All fluid ports should be suitable for attachment of ⅜″ I.D. clear plastic tubing suitable for drinking water. A small hand pump can be provided, suitable to lift water at least six (6) feet and pump it with limited resistance another three (3) feet up, and moving about four (4) fluid ounces per stroke, with input and output connectors suited to the ⅜″ I.D. tubing above. The hand pump can be particularly useful when using a system as described herein on a boat, particularly a sailboat, as the pump permits a single user to pump seawater from below the waterline of the vessel and into the coolant reservoir  12 , to replenish the coolant as it is heated from heat exchange with the condensing water vapor from the source water reservoir in the condensing coil. For such uses, a 10 foot length of ⅜″ I.D. (clear) plastic tubing for coolant water (a sufficient length to get at least five feet beneath the surface of the water) is also provided and attached to the pump inlet. A six (6) foot length of ⅜″ I.D. clear plastic tubing is provided for source water, and condenser coolant output. A three (3) foot length of ⅜″ I.D. clear plastic tubing is provided for the pump output to reservoir inlet. A two (2) foot length of ⅜″ I.D. clear plastic tubing is provided for the condenser (fresh water) output. Advantageously, a fabric container is suitable for all components. The overall design is such that the forces of gravity and the shaping of the flexible structural material provide the unit with dimensional stability. The spring/elasticity in the braces  46 , along with the fabric shaping, provide the necessary dimensional stability of the reflective sheet, much as the spring metal and material form an umbrella. The fluid reservoirs are advantageously made of a collapsible, water impervious material. 
         [0048]    In operation, the upper reservoir  12  is filled, at least partially, with a liquid coolant, which is easily achieved with sea-, lake-, or stream-water, and the lower reservoir  14  is at least partially filled with source water, e.g., sea-, lake-, or stream-water, which is not (yet) potable. The unit is placed in the sun, so that sunlight is reflected off of the inner, reflective, curved surface  44  of the sheet  42 , and onto the exterior wall of the lower reservoir  14 . The liquid coolant from the reservoir  12  is permitted to flow from the reservoir  12  into the condensing chamber  30 , via the opening  50  between them, and thus at least partially, and preferably completely, covers the exterior surface of the condensing coil  34 . Optionally, the opening  50  is closed by a valve which is can be opened and closed by the user. As the source water in the lower reservoir  14  is heated by the intensified sunlight from the reflector sheet  42 , the coolant (water) from the upper reservoir remains essentially the same temperature, in part because of the reflective outer surface of the outer reservoir  12  and the shade  16 . Water vapor is generated at increasing rates in the lower reservoir because of the increased heat transfer to the water in the lower reservoir, and the water vapor rises up through the fitting in the apex of the top of the lower reservoir and into the condensing coil  34 . The condensing coil  34  is at a lower temperature than the water vapor from the source reservoir, and thus liquid water condenses on the inner surface of the tube forming the coil. Because the uppermost portion of the condensing coil  34  is positioned at its connection to the reservoir  14 , the resultant condensate water is free to flow down the coil and away from the reservoir  14 , towards the fresh water outlet  34 . As the heat transfer between the condenser coil  34  and the coolant (water) surrounding it, from the energy released from condensing the water vapor, increases the temperature of the coolant, the coolant can be bled off at the coolant outlet  36 , with new, cooler coolant flowing into the condenser chamber from the reservoir  12 , and the warmed, used coolant transferred to the lower reservoir for later distillation. For thus purpose, the condensing chamber can be in fluid communication, e.g., via a tube (not illustrated), optionally fitted with a valve, with the source reservoir. 
         [0049]    While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein.