Abstract:
A solar distiller with a two part distilling chamber and a concentrating mirror which is designed to be lightweight and compact for ease of transport. The distilling chamber has two main parts; a trough for holding a liquid that will be distilled, and a condensing roof on which the liquid will condense that has channels for collecting the distilled liquid. The two part distilling chamber allows for simple operation and easy maintenance. The concentrating mirror is made from a flexible reflective sheet, which is formed into a nearly parabolic shape by the mirror frame. The mirror is designed so that it can be easily assembled and then later disassembled for storage or transport. A stand holds the distilling chamber at the approximate focus of the concentrating mirror. The concentrating mirror allows a relatively large amount of sunlight to be focused onto the distilling chamber producing a proportionately large amount of distilled liquid. The solar distiller is made from inexpensive materials and can be assembled and disassembled multiple times.

Description:
BACKGROUND 
       [0001]    1. Field of Invention 
         [0002]    This invention relates to an apparatus, which uses the radiant energy of sunlight to distill liquids, such as generating fresh water from salty or otherwise undrinkable water. In particular it relates to a simple portable distiller that uses a flexible mirror to increase the amount of water distilled. 
         [0003]    2. Discussion of Prior Art 
         [0004]    There is a continuing, and in some cases increasing, need for additional clean water resources in many countries around the world. In addition to temporary interruptions to water supply caused by natural disasters, which occur with equal likelihood everywhere, there are also chronic supply problems in many regions, especially in developing countries. Solar energy is a cheap and readily available resource that can be used to produce large amounts of fresh water provided a simple and inexpensive means is devised to harness it. The prior art contains many inventions that use sunlight to heat and distill water, brine, seawater, or other liquids. Broadly speaking these devices can be classified as using one or a combination of the following configurations: heat absorbing plates, box stills, multiple effect stills, or concentrating devices using either lenses or mirrors. Such inventions strive to utilize the diffuse but substantial energy contained in sunlight to evaporate the input water and then condense and collect the distilled water. Unfortunately the inventions disclosed in the prior art are overly complex, expensive to manufacture, wasteful of material or sunlight, difficult or costly to operate and maintain, cumbersome to transport, or some combination of the above. 
         [0005]    In general terms solar devices produce in proportion to the amount of sunlight they intercept. A number of solar devices like box stills and heat absorbing plates try to make the best use of the sunlight that naturally falls on them. One disadvantage of these devices is their tendency to reradiate out of the device a substantial fraction of the energy they absorb. In order to overcome this disadvantage many inventors design additional features or mechanisms thereby increasing the overall complexity of the device and adding to the cost of maintenance or operation. The prior art contains many examples of each type, U.S. Pat. No. 5,628,879, to Woodruff discloses a box still type and U.S. Pat. No. 6,001,222 to Klein discloses a heat absorbing plate type. While these may be useful devices, they and all devices like them are wasteful of material in that they don&#39;t attempt to concentrate the sunlight falling on them before converting and/or using the solar energy. If instead they concentrated the sunlight that falls on them they would either produce more for a given area (i.e. amount of material) or they could be made with less material. 
         [0006]    The prior art also contains disclosure of a large number of devices, which use concentrating mechanisms. Disadvantages of devices that rely on concentration, using either lenses or mirrors, include complex design, a need for precision placement or motion of parts, high cost of manufacture and parts due to tight tolerances or exacting surface requirements, or excessive bulk or weight which make them cumbersome to transport, and ongoing high costs needed to operate or maintain them. 
         [0007]    One reason for the extra cost and complexity of concentrating devices is the tendency to design and use parabolic surfaces which require a high quality and precise surface figure to work optimally. Parabolic surfaces generally focus light to a very narrow point, spot, or line where the heat is generally absorbed and transferred to a liquid or fluid such as water. Unfortunately high quality and precise parabolic or even circular surfaces are relatively expensive to manufacture and require extra care and expense to maintain. 
         [0008]    Also disclosed in the prior art are a number of devices, for concentrating solar energy, that use a flexible sheet of aluminum coated plastic, such as aluminized Mylar, to form the concentration surface. These inventions each disclose a unique geometry and arrangement of structural supports, bars, members, connections, ribs, wires, etc., used to form the desired concentrating surface (i.e parabolic, catenary, cylindrical, etc.). Unfortunately each of the inventions which relate to flexible Mylar sheets in particular, contain excessive or redundant parts, the manufacture of complex shapes, and costly mechanisms to fine tune or perfect the shape of the desired concentrating surface. While not all related to solar distillation the following patents all disclose concentrating devices that exhibit at least one and often some combination of the above noted disadvantages, U.S. Pat. No. 4,611,575 (1986) to Powell, U.S. Pat. No. 4,504,362 (1985) to Kruse, U.S. Pat. No. 4,312,709 (1982) to Stark, U.S. Pat. No. 4,293,192 (1981) to Bronstein, U.S. Pat. No. 4,240,406 (1980) to Hutchinson, U.S. Pat. No. 4,173,397 (1979) to Simpson, U.S. Pat. No. 4,168,696 (1979) to Kelly, and U.S. Pat. No. 4,119,365 (1978) to Powell. 
       SUMMARY OF THE INVENTION 
       [0009]    The concentrating solar distiller of this invention uses a simple two part distilling chamber, and a flexible sheet mirror supported such that the distilling chamber is at the approximate focus of the mirror. The two part distilling chamber allows the user to easily disassemble the device for compact storage or cleaning. The flexible sheet mirror is made from inexpensive and lightweight materials, which can be rolled up or stacked compactly for shipping and yet is easy to assemble. The mirror is assembled into a bow shape (i.e. nearly parabolic in one dimension) such that it concentrates sunlight on the distilling chamber. The mirror increases the amount of sunlight falling on the distilling chamber several fold, increasing by several times the amount of water that may be distilled in a given amount of time. Because of the geometry involved, the surface of the mirror does not have to conform exactly to a precise curve, which allows lower cost materials, loser tolerances, and simplified shapes to be employed in its manufacture. 
       Objects and Advantages: 
     Accordingly several objects and advantages of my invention are 
       [0000]    
       
         
           
             a) to provide a simple to use solar distillation apparatus which can be made of inexpensive materials; 
             b) to provide a portable solar distillation apparatus which can be stored compactly for ease of transport; 
             c) to provide an easily manufactured and assembled solar distillation apparatus; 
             d) to provide a solar distillation apparatus that is easy to operate and inexpensive to maintain; 
             e) to provide a solar distillation apparatus which uses a concentrating mirror to minimize waste of material and solar energy; 
           
         
       
     
       Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description. 
       [0000]      
     
     
       DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  shows a perspective view of the solar distillation apparatus with arrows indicating the flow of liquid into and out of the distilling chamber. 
           [0016]      FIG. 1A  shows a cross section of the mirror frame. 
           [0017]      FIG. 2  shows a perspective view of the preferred embodiment of the solar distillation chamber. 
           [0018]      FIG. 3  shows a side view of the preferred embodiment of the solar distillation chamber. 
           [0019]      FIG. 4  shows a cross section of the condensing roof shown in  FIG. 2 . 
           [0020]      FIG. 5  shows a perspective view of the evaporating basin which forms the bottom half of the distillation chamber shown in  FIG. 2  and  FIG. 3 . 
       
    
    
       [0021]    Several illustrations and drawings have been presented to better aid in the understanding of the present invention. The scope of the present invention is not limited to what the figures show. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    An embodiment of the concentrating solar distiller of this invention is illustrated in  FIG. 1 . There are two principle elements shown, a distilling chamber  10  and a concentrating mirror  40 . 
         [0023]    The distillation of liquids, which may commonly be water for drinking, occurs in the distilling chamber  10 . Distilling chamber  10  consists of two main parts, an evaporating basin  12  which fits under a condensing roof  14 . 
         [0024]    Evaporating basin  12 , shown as an elongated shallow trough in  FIG. 5 , must be able to hold water and should be made of a material that conducts thermal energy from its exterior surface  32  to the raw water inside. Evaporating basin  12  has leg brackets  37  (for attaching legs  68 ) protruding horizontally from each end. In the preferred embodiment, evaporating basin  12  is made from aluminum, although other materials such as plastic, tin or stainless steel may be used, and has its exterior surface  32  darkened to absorb solar radiation. 
         [0025]    Condensing roof  14 , shown in  FIG. 4  as a lopsided “M”, along with the two end caps  17 , should form a substantially airtight seal where it meets evaporating basin  12 . Condensing roof  14  can be made from a single extruded sheet or can be comprised of a plurality of strips of material joined together at various advantageous locations, like the shoulders of the “M”, such that an airtight seal is formed. Also present if condensing roof  14  is made with a plurality of strips joined together is at least one cooling fin  15 , which is a heat conducting metal sheet, such as aluminum, running the length of condensing roof  14  with most of its surface area outside the distilling chamber  10  but a small amount of its surface area inside. Cooling fin  15  helps to transfer excess heat from the interior of condensing roof  14  to the outside environment. 
         [0026]    Also running the length of condensing roof  14  are two inward and upward curving edges, or channels  16 , shown as dashed lines in  FIG. 4 . Each of the two channels  16 , which form the bottom portion of condensing roof  14 , connect to an exit tube  18  where the distilled liquid exits distilling chamber  10  and enters a distilled water reservoir (not shown). Condensing roof  14  is made of a transparent plastic in the preferred embodiment, but may be made using an opaque plastic or metal material. End caps  17  are flat plates of a plastic or metal material and are joined to condensing roof  14  using a manufacturing process or adhesive. The airtight seal between condensing roof  14  and evaporating basin  12  may be enhanced by inserting between them a gasket  38  made from a material such as cork, foam, or rubber. 
         [0027]    A pair of screws (not shown), or equivalent reversible means, is located at either end of distilling chamber  10 , to positively and reversibly hold condensing roof  14  against evaporating basin  12 , with gasket  38  between, to ensure the substantially airtight seal described above. Also a basin liner  30 , which can be made of a disposable material, is used to line the interior of evaporating basin  12 , to prevent excess buildup of scale, salt or dirt within evaporating basin  12 , and thereby facilitate cleaning. Also a wicking material  34  may rest on the bottom of evaporating basin  12  or on top of the basin liner  30 . The wicking material  34  is made of a fabric, sponge, or sponge-like material that effectively increases the amount of water to air surface area thereby enhancing evaporation. 
         [0028]      FIG. 1  and  FIG. 1A  show details of concentrating mirror  40  used to collect sunlight from a relatively large area and focus the sunlight onto evaporating basin  12 . Concentrating mirror  40  consists of a reflective sheet  42 , a pair of mirror frames  44 , and a pair of shaping wires  46 , to support and shape the reflective sheet  42 . In the preferred embodiment reflective sheet  42  consists of a sheet of reflectively coated thin polymer material, such as aluminized Mylar™, held in a nearly parabolic shape by mirror frames  44  and shaping wires  46  as will be described. An optional backing sheet  58 , made of plastic, aluminum or similar material may be included behind the reflective sheet  42  to help maintain the desired mirror shape. 
         [0029]    Nearly parabolic is intended to mean a shape that closely approximates a parabolic trough, sometimes called a linear parabolic reflector, such that almost all of the incoming sunlight is focused onto the area of the evaporating basin&#39;s exterior surface  32 . Since evaporating basin  12  has a finite width and height, a perfect parabolic trough surface capable of focusing sunlight to a line, is not needed. Instead the reflecting surface need only be good enough (i.e. nearly parabolic) at focusing light that almost all of the light be intercepted by evaporating basin  12 . 
         [0030]    As  FIG. 1  shows each mirror frame  44  is composed of at least two longitudinal members  50  of equal length and at least two transverse members  52  of equal length. All members of mirror frame  44  are made of thin aluminum strips in the preferred embodiment, although steel, plastic, wood, or other materials can be substituted as appropriate. Each member of mirror frame  44  has a plurality of holes at roughly equal distances along them to allow joining using a bolt  54  and a nut  56  or equivalent reversible means. The longitudinal members  50 , should flex without breaking when the ends are pulled a short distance toward each other. 
         [0031]    The longitudinal and transverse members of mirror frame  44  are arranged to create a rectangle covering the outside edge of reflective sheet  42  such that reflective sheet  42  fills the interior area without significant obstruction. In the preferred embodiment, reflective sheet  42  and an optional backing sheet  58  are captured between two mirror frames  44  using a plurality of bolts  54  and nuts  56  (as shown in  FIG. 1A ), or equivalent joining device, such that mirror frames  44  and reflective sheet  42  may be separated if desired. Additional transverse members  52  may connect longitudinal members  50  along the underside of reflective sheet  42 , or backing sheet  58  if used, at roughly equal distances from the other transverse members  52  to provide additional support for reflective sheet  42 . Two shaping wires  46  of equal but shorter length than the longitudinal members  50 , are secured to either end of each of the longitudinal members  50 , causing the ends of longitudinal members  50  to bend up forming reflective sheet  42  into a nearly parabolic concentrator, as shown in  FIG. 1 . 
         [0032]      FIG. 1  and  FIG. 2  show leg brackets  37  which protrude from each end of evaporating basin  12  primarily allowing legs  68  to be attached that hold and support distilling chamber  10  at the approximate focus of concentrating mirror  40 . Each leg bracket  37  should accommodate at least one and preferably two legs  68  such that the legs  68  hold one end of distilling chamber  10 . The legs  68  can be made from a light weight tubular metal or plastic material and is made with aluminum tubing in the preferred embodiment. The end of distilling chamber  10  with exit tubes  18 , should be at a slightly lower elevation from the other end, so the distilled water collected in the channels  16  will by force of gravity flow out exit tubes  18 . Each leg  68  also has at least one mirror frame connection  66  where mirror frame  44  may be connected. Each leg  68  must be tall enough to support evaporating basin  12  at the approximate focus of concentrating mirror  40 . 
       OPERATION OF THE INVENTION 
       [0033]    This concentrating solar distillation apparatus has been designed and should be built in such a way that it is lightweight and compact for ease of portability as well as easy to assemble and disassemble. It may be moved from one location to a new location and reassembled in the new location and operate satisfactorily in the new location. As a result each of the parts that can be assembled and disassembled has a means by which it can and should be secured, joined, supported or connected for operation. 
         [0034]    The apparatus can be operated by first supplying water to evaporating basin  12  by adding raw water via input tube  24  manually or to an optional raw water reservoir that is connected to input tube  24  with a valve for regulating the flow of raw water into evaporating basin  12 . When concentrating mirror  40  is connected and supported by the appropriate mirror frame connection  66  such that nearly all of the solar energy is concentrated on evaporating basin  12 , solar energy will heat evaporating basin  12  which will in turn heat the raw water inside. As the raw water inside evaporating basin  12  is heated it will evaporate at an increased rate. This water vapor will condense on the inside surface of condensing roof  14 , where it will by force of gravity run down the sides of condensing roof  14  and collect in one of the two channels  16  designed to catch the distilled water. This water will then run along channel  16  and out exit tube  18  where it will finally collect in a distilled water reservoir. Concentrating mirror  40  can be repositioned using the provided mirror frame connection(s)  66  to track the sun. 
         [0035]    It is assumed that evaporating significant quantities of raw water will over time lead to a build up of minerals or salts in evaporating basin  12 . Thus distilling chamber  10  can be disassembled by removing the screws from each end and lifting the condensing roof  14 . At this point evaporating basin  12  can be cleaned or scrubbed to remove mineral and salt build-up. Additionally basin liner  30  can be used to line evaporating basin  12  and reduce the amount of mineral or salt that would otherwise accumulate on evaporating basin  12 . Basin liner  30  may then be cleaned or disposed of as the user desires. 
       DESCRIPTION AND OPERATION OF ALTERNATIVE EMBODIMENTS 
       [0036]    Depending on the season and the latitude where the concentrating solar distillation apparatus is operating some sunlight may be reflected past the end of the evaporating basin  12  and it may be desirable to add a secondary flat or “fold” mirror as an attachment to the legs  68  on the side furthest from the sun to reflect sunlight back onto the evaporating basin  12 . 
         [0037]    Depending on the circumstances it may be desirable to use only a single leg  68  attached to each leg bracket  37 , if for example the user is most concerned with securing the device against possible theft than enhancing portability. Each of the two legs  68  could then be secured to a large metal plate, embedded deep in the ground, or set in concrete. 
       CONCLUSION, RAMIFICATIONS, AND SCOPE OF INVENTION 
       [0038]    While the above description contains many specifications these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. Many other variations are possible, for example an active (i.e. automatic) sun tracking system could be employed. The active tracker could (mechanically) orient or rotate concentrating mirror  40  such that throughout a day concentrating mirror  40  would change position multiple times to reflect sunlight optimally onto evaporating basin  12  whatever the hour. 
         [0039]    Additionally the condensing roof  14  can be shaped with a sloped or multifaceted ceiling, flat or sloped sides and v-shaped channel along the bottom inside edge. Also a wicking material  34  may be used in evaporating basin  12  to enhance the evaporation of the raw water, in a manner disclosed elsewhere and consistent with the prior art. 
         [0040]    Additionally the evaporating basin  12  can have a selective coating, which is a coating designed to maximize heat absorption while minimizing heat radiation from a surface, applied to exterior surface  32  in place of, or in addition to darkening exterior surface  32 . 
         [0041]    Accordingly the scope of the invention should be determined not by the embodiment(s) illustrated, but by the appended claims and their legal equivalents.