GB1590843A

GB1590843A - Solar energy distillation apparatus

Info

Publication number: GB1590843A
Application number: GB42601/79A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-07-09
Filing date: 1977-07-07
Publication date: 1981-06-10
Also published as: GB1590841A; ES473531A1; IL52482A; ES460584A1; GB1590842A; JPS5334148A; ES473530A1; JPS577332B2; CA1084790A; CH626159A5

Description

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ii S 154 J xj ' 1 PATENT SPECIFICATION ( 21) Application No 42601/79 ( 22) Filed 7 July 1977 ( 62) Divided Out of No 1 590 841 ( 31) Convention Application Nos.

7 620 986 ( 32) Filed 9 July 1976 7630248 8 Oct 1976 746 065 30 Nov 1976 in ( 11) ( 33) France (FR) France (FR) United States of America (US) ( 44) Complete Specification published 10 June 1981 ( 51) INT CL 3 B Ol D 3/02 ( 52) Index at acceptance Bl B 601715 GD F 4 U 60 ( 54) SOLAR ENERGY DISTILLATION APPARATUS ( 71) I, VIRGIL STARK, of 936 Fifth Avenue, New York N Y 10021, United States of America, a citizen of the United States of America do hereby declare the invention, for which I pray that a patent may be granted to me and the method by which it is to be performed, to be particularly described in and by the following statemen:The present invention relates to methods and apparatus for distilling liquids including water, using solar energy The invention further relates in preferred embodiments to the treatment of liquids including water containing salt and/or other substances using fixed or portable apparatus In particular embodiments of the invention relates to methods and apparatus using fluid and/or Fresnel concentrating lenses and lens systems and elongated collectors comprising at least one fluid-carrying conduit located at the foci of the lenses.

It is well known that surfaces exposed to the sun collect at least to some degree the solar radiation and that the absorption of this radiation results in a heating of the material constituting the surface.

With respect to solar stills, known stills used for distillation of seawater have low efficiencies and the cost of heating the water is high as the least amount of heat required to vaporize the water is not recovered from condensation but rather is lost.

The present invention provides in one aspect apparatus for distilling liquids including water using solar energy, said apparatus comprising a container for holding liquid to be distilled, elongate lens means disposed above said container for concentrating solar energy in a liquid in said container, said apparatus including an elongate member having a substantially smooth surface disposed above the container and which is solar energy transmitting at least in part, said member being positioned such that solar energy is transmitted therethrough to said container and rising evaporated liquid from said container impinges upon said surface and is condensed thereon, said surface including a portion inclined with respect to the horizontal such that condensed liquid flows along said surface to a vertically lower portion thereof and is discharged therefrom, and liquid collecting means disposed below said lower portion of said smooth surface for 55 collecting condensed liquid discharged from said lower portion.

In another aspect the invention provides a method for distilling liquids including water using solar energy comprising concentrating 60 solar energy through elongate lens means along at least one elongate focus located in the liquid to be distilled to thereby evaporate liquid therefrom, condensing the liquid on a planar elongated surface located bet 65 ween the liquid and the lens means and having an axis substantially parallel to that of the elongated focus, and including a portion inclined with respect to the horizontal such that condensed liquid flows along said sur 70 face to a vertically lower portion thereof and collecting the condensed liquid discharged from said vertically lower portion of the planar surface Preferably, refringent lens means concentrate the solar energy along a 75 length at elongate collector means containing at least one fluid therein The lens means may comprise economical fluid and/or Fresnel-type lenses (sometimes referred to as Fresnel lenses) and lens systems which 80 focus the solar energy substantially along continuous lines or in lines of substantially discrete points Means are preferably provided to maintain the focus lines or discrete foci within conduit means comprising the 85 elongated collector means regardless of the seasonal and preferably also the hourly (daily) location of the sun and/or means may be provided for seasonally and preferably also hourly (daily) tracking the sun Thus, 90 the fluid in the elongated collector means may be efficiently heated to high temperatures in order of a few hundred degrees C.

Preferred apparatus of this type is described in more detail and claimed in the parent 95 application No 28560/77 (Serial No.

1590841) from which this application is divided.

The fluid lenses when used suitably comprise upper and lower solar energy transmit 100 r REPRINTED SPE Ci Fi CA-r GN' REPLAC'ING i NAL INCORRE Ci T 71 m c 1 590 843 1 590 843 ting plates which are advantageously separate plates installed in a frame in a fluidtight manner, or the fluid lenses including the plates may be formed by gluing, welding, extruding, or being blown in a manner similar to that for glass or plastic bottles.

The enclosure in the lens containing the fluid may advantageously be communicate with suitable collector or heat exchange means to enhance performance The fluid within the fluid lenses when used preferably has a high index of refraction The lens fluid and the distance between the lens plates may be chosen to absorb varying amounts of infrared solar energy passing through the fluid for example, more infrared solar energy will be absorbed using water as the lens fluid and less will be absorbed using a suitable transparent and colorless chemical product having a high index of refraction.

The heat absorbed by the lens fluid may be recovered and used to preheat or heat fluid in the collector means or for other purposes.

An antifreeze product may be added to the lens fluid to prevent freezing of the lens fluid when it is used in certain locations.

The elongate collector means when used preferably comprises a plurality of fluids, adjacent ones of which are contiguous The fluids are preferably isolated and disposed in adjacent conduits and the fluids preferably differ and have varying boiling points.

The theoretical focus or foci of the lens means are preferably on the surface of or within the higher or highest boiling point liquid In a preferred embodiment, the elongated collector means comprises at least two conduits; one of the conduits containing a first fluid having a first boiling point is located within a second conduit containing a second fluid having a second boiling point.

Preferably, the solar energy is concentrated at the inner liquid which has a boiling point which exceeds that of the outer liquid the conduits and fluids are solar energy transmitting or opaque or darkened depending on the location of the lens means focus By solar energy transmitting it is meant that the solar rays are substantially transmitted through the material.

In a disclosed embodiment, in which several concentrators are arranged to have a common focus, a system of lenses concentrates the solar energy along a substantially common focal line located in or on the elongated collector means during the different seasons and preferably during the different times of day without using sun tracking means This system includes an elongated central Fresnel-type or fluid lens concentrating the solar energy along a focal line, and elongated Fresnel-type lenses located adjacent to and at an angle with respect to the central lens, the adjacent Fresnel-type lenses being provided with engravings angled to direct the solar energy to the focus of the central lens The lenses are oriented so that they are alongated generally in the east-west direction A given lens or lenses primarily concentrates the solar energy 70 along the focal line for given times of the year For example, the central lens primarily concentrates the solar energy during the time closely before and closely after the equinoxes while one adjacent lens primarily 75 concentrates the solar energy up to one solstice and the other adjacent lens during the time up to the other solstice In the embodiment in which the central lens is a Fresneltype lens, the lens system preferably 80 includes sets of Fresnel-type lenses in the elongated or east-west direction The Fresnel-type lenses located towards the extreme east and west ends of the lens system are positioned at an angle with respect 85 to the inner lenses so that a given lens or lenses primarily concentrates the solar energy along the focus at given times of the day However, such lenses may also be located intermediate the east and west ends 90 in a lens system comprised of many lenses oriented along the east-west direction Thus, at different times of the day and year, one or more lenses will primarily concentrate the solar energy along the focal line without 95 using sun tracking equipment It is preferred in these embodiments that the elongated collector means comprise two or more adjacent elongated fluid-carrying conduits each of which enclose another fluid-carrying con 100 duit.

Water or other liquids may be distilled by locating the lens means focus in the water or liquid to be distilled, above which is positioned the lens means and a down 105 wardly sloping substantially smooth, preferably planar surface, whereby the liquid is evaporated and condenses on the smooth surface which carries the condensed liquid to a collecting vessel positioned below the 110 lower side thereof The planar surface is inclined relative to the horizontal, for example at about 150, and is cooled to enhance condensation thereon It is preferred that the lens means for the water distil 115 ling apparatus comprise a fluid lens which includes and preferably cools said smooth surface In some embodiments, conduit means are located in the liquid to be distilled It is preferred that the fluid forming 120 part of the fluid lens is circulated within the conduit means where one is employed to advantageously utilize the latent heat released by the vapor condensing on said smooth surface and transferred to the liquid 125 to be distilled It is preferred that the lens fluid be the same liquid as the one being distilled, salt water for example, and be circulated in the vessel containing the liquid to be distilled to heat or preheat the liquid in 130 1 590 843 the vessel In a disclosed embodiment, distillation apparatus includes both fluid and Fresnel lenses in which the fluid lens is fixed and the Fresnel lens is, if desired, movable.

The heat released by the condensing liquid on said smooth lens means surface is not lost and returned to the system in the conduit means in the vessel containing liquid to be distilled, or elsewhere, and/or the heat absorbed and recuperated by the lens fluid may be used to preheat or heat the incoming liquid to be distilled in the distillation apparatus or used for other purposes such as producing electricity by superheating suitable low boiling temperature fluids and expanding them in expansion means such as turbines and engines, thereby increasing substantially the efficiency of the system.

Additionally, it is preferred that the condensed liquid be circulated in the conduit means in the vessel containing liquid to be distilled or elsewhere to utilize heat contained in the condensed water The solution of salt (Na Cl) dissolved in water absorbs less infrared rays than water alone Thus, where it is desired to reduce absorption of infrared rays in the lens fluid, a salt/water solution is preferably used as the lens fluid When desalinating sea water, the sea water is preferably used as the lens fluid and preferably is also introduced preheated into the container holding the water to be distilled.

In the case of sea water, salt may be produced from the resulting concentrated brine and credit obtained from the sale thereof to lower the overall cost of obtaining distilled water Heat may also be recovered from the heated brine discharged from time to time from the system Combination concentrator systems including both fluid and Fresnel lenses can be advantageously used In one such combination system, one set of fluid lens concentrators is inclined, for example, south at 150 with the horizontal, with the bottom plates of the lenses being cooled by fluid circulating within the lenses whereby the vapor condenses on the cooled bottom plates and flow therealong into an adjacent vessel Another set of Fresnel concentrators or fluid lenses are provided to receive the sun's rays during hours of sunshine to primarily heat fluids having high boiling temperatures to over 200 C in conduit means in the vessel containing liquid to be distilled The heat in the high boiling temperature fluids is stored and used primarily during periods without sunshine whereby evaporation and condensation of the vapor on the cooled bottom plates of the fluid lenses continues during periods without sunshine The Fresnel lenses or a separate set of fluid lenses used to heat the high boiling temperature fluids to store heat are preferably provided with tracking means to follow the seasonal and preferably also the hourly location of the sun According to one embodiment of the invention, the distillation apparatus comprises a plurality of sets of fluid lenses One set of lenses has a lens plate separation at the point of maximum 70 separation of, for example, one inch for minimum absorption of infrared rays and maximum evaporation of the water to be distilled during periods of sunshine This set comprises smooth surface bottom lens 75 plates for condensing the vapor thereon which are inclined to flow the condensate into a vessel located below the edges thereof The lens fluid in this set of lenses will cool the bottom lens plates to provoke 80 condensation thereon Another set of lenses having a lens plate separation at the point of maximum separation for example of four inches is used for high absorption of infrared rays and contains a high boiling point (for 85 example about 200 C) lens fluid which is communicated with a plurality of conduits located in the water to be distilled This set of lenses and conduits is used primarily for storing heat as described hereinbefore to be 90 used during periods without sunshine to continue the distillation The lens fluids for both sets of lenses recuperate heat absorbed by the lens fluids as described hereinbefore.

The use of the different fluid lenses 95 increases production of distilled water and increases the efficiency of the system.

According to one embodiment, the lens or lens system focus is located in the water to be distilled such that the location of the 100 focus remains in the water to be distilled with the changing location of the sun This eliminates the need for means to move the lens or lens system to maintain the focus thereof in or on an elongated collector In 105 another embodiment of the invention, the still is portable and is easily assembled and disassembled Advantageously, the stills are operative to distill seawater and brackish water and the portable stills in particular 110 may be used at sea, for example, on life boats, and in desert areas.

Lenses may also be combined so that the solar rays pass through the lenses serially and can shorten the focus of the lens system 115 and can provide a sharper focus of the lens system.

Apparatus according to some embodiments of the invention may be used to electrolyze water and salt recovered from distil 120 lation Hydrogen, sodium and chlorine may be recovered from the electrolysis The recovery of these products further increases the economic efficiency of the apparatus.

Additionally, the hydrogen may be used as a 125 non-polluting fuel or used with carbon monoxide to produce methanol, or with nitrogen of the air to produce ammonia fertilizer and other nitrogen products such as nitric acid and urea 130 1 590 843 By means of the invention, apparatus and methods having high efficiency and low cost for concentrating, collecting and converting solar energy are disclosed.

These and other aspects of the present invention will be more apparent from the following description of the preferred embodiments thereof when considered with the accompanying drawings.

The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings in which like numerals refer to like parts and in which:

FIG 1 is a schematic perspective diagram of a composite system for distilling water comprising individual systems each including three elongated fluid lenses, two lenses being located on the same plane and the third at an angle to the two, the foci of the lenses being located in a vessel containing the water to be distilled at different locations therein; FIG 2 is a schematic perspective diagram of a portable easily assembled and disassembled system having Fresnel lenses for distilling water; FIG 3 is a schematic perspective diagram showing a system for substantially continuous distillation of water in which the lens system comprises Fresnel and fluid lenses and has a plurality of foci located at different depths in the water to be distilled, a Fresnel lens and collector being movable to track the seasonal location of the sun and a set of lenses for preheating the incoming water to be distilled and FIG 4 is a schematic perspective diagram showing another system for distilling water in which the lens system comprises two fluid lenses and a plurality of conduits to provide substantially continuous operation.

The present invention may be utilized in many fields for treatment of water by evaporation and condensation thereof Typically, the water is seawater or brackish water and is to be desalinated, or water containing minerals or other substances, or water such as industrial waste water or polluted water which is to be purified and distilled.

Refringent concentrators and collectors can be arranged in systems operative to distil water, preferably recovering the heat of condensation and preferably recovering heat in the condensed water and discharged brine as described hereinafter.

The system 160 shown in FIG 1 comprises a plurality of sub-systems 162, each employing a three lens arrangement 164.

Each lens system 164 is supported above an elongated, central, channel 166 and parallel, elongated, side channels 168 such that the central part of the lens system is above the central channels and the outer longitudinal edges of the outer two lenses are above the side channels Each lens is inclined and the bottom lens plates 28 are planar The water to be distilled is filled in the central channel to a predetermined height Within channel 166 are located the elongated foci F 70 of the lenses, preferably at different locations and different heights, the different heights corresponding to different water depths in channel 166 In FIG 1, lens fluid 31 is advantageously salt water The solu 75 tion of salt (Na Cl) dissolved in water absorbs less infrared rays than water alone.

Thus, where it is desired to reduce absorption of infrared rays in the lens fluid, a salt/water solution is preferably used as the 80 lens fluid When desalinating seawater, the seawater is preferably used as the lens fluid and preferably is also introduced preheated into the container holding the water to be distilled Valving is provided in the conduits 85 to control draining and to regulate circulation of the fluids In operation, the water to be distilled is heated due to the solar energy concentrated at foci F and the water is vaporized The vapor strikes the 90 lower plates 28, is condensed thereon and flows therealong to be discharged at or dropped from the edges thereof into side channel 168 The interiors of the fluid lenses are communicated with the interior of chan 95 nels 166 by conduits 177 (only one set of which are shown) as well as being intercommunicated Heat exchange means 179 may be provided inside channel 166, particularly for transferring heat from the con 100 densed water in channel 168 to the water in channel 166 The water in the fluid lenses is circulated through the lenses and channels.

In this way, the heat released by condensation of the vapor is transmitted through 105 plates 28 to the water in the lenses and the heat absorbed by the water in the lens from the condensing vapor is returned to the system in the channels Thus, the water to be distilled may be heated or preheated The 110 lenses 22 are arranged so that the foci F remain within channels 166 regardless of the seasonal and daytime location of the sun, the foci moving along the paths indicated in channel 166 by the broken lines 115 Thus, the foci will not be displaced outside channels 166 and it is therefore not necessary to provide means to move the lenses to follow the location of the sun Heat in the distilled water may also be utilized to pre 120 heat or heat the water to be distilled The distilled water may only be a few degrees less than the vapor temperature The recovered heat may also be used for other purposes and the lens fluid and/or condensate 125 can be circulated through heat-exchanging means to remove the heat therefrom This is significant because the latent heat required to vaporize the water 170 of about 540 calories per gram in addition to the sensible 130 1 590 843 heat are released by condensation of the vapor and are substantially recuperated from the condensate and substantially returned to the system by the circulated water in the lenses upon which the vapor condenses This latent heat and the sensible heat are substantial and would otherwise be lost This results in much higher efficiency of the system compared with solar stills where channels filled with water to be treated are covered with only glass or plastic plates or sheets which receive the solar rays Circulating the water in the lenses also cools the lower lens plates 28 thereby assisting condensation thereon Conduits 175 and 176 are provided for filling and emptying the respective channels The water 170 to be distilled may be held between predetermined heights by a float system comprising float 178 and relays 180 and 182 Movement of the float activates respective relays to start and stop a pump or motor valve (not shown) A similar arrangement may be used in side channels 168 or a gravitational drain arrangement may be employed to maintain the height of distilled water in the side channels between predetermined heights.

The respective channels are communicated to provide approximately equal levels in each of the respective channels Advantageously, the channels are made of concrete or asbestos cement and are preferably insulated on the outer sides Means other than the lens itself may be used to condense the vapor such as substantially smooth preferably planar plates located below the lenses 164 In such a case, the lens fluid may not recover substantially all of the latent heat unless the plate is proximate thereto Alternatively, means associated with the plate may be used to recover the latent heat.

The system shown in FIG 1 is substantially enclosed by the channel panels to reduce heat loss, the panels preferably being made of an expandable material to accommodate movement of the lenses Additionally, as mentioned, by removing from the lens fluid the heat of condensation recovered by it, for example, the circulating it in channels 166, the lens fluid will be cooled, in turn cooling the lower lens plate and assisting in condensing any vapor impinging thereon As described hereinbefore, the lens fluid will be heated by direct and indirect absorption of infrared radiation and by heating of the lens plates, and this heat may also be recovered from the lens fluid The heat recovered from the lens fluid and condensed water may be used to preheat water to be distilled before entering channel 166 or to preheat and heat the water to be distilled in channel 166 by heat exchange means The efficiency of the system can be further increased by recovering the heat contained in the brine discharged from channel 166 from time to time The heat which is recovered from the condensing vapor, the condensed water, the brine and the lens fluid can be used for other purposes such as producing electricity by superheating and 70 expanding fluids having low boiling temperatures and low heats of vaporization The water distillation systems described hereinafter operate in similar manner and description thereof will therefore be more 75 limited.

In FIG 2 is shown an embodiment of a portable water distillation system 330 which is easily assembled and disassembled In system 330, the lens means comprises an elon 80 gate array of planar Fresnel Lenses 126 having concentric microprisms causing the solar energy to be concentrated at point foci A longitudial Fresnel lens or lenses may also be used Lenses 126 are longitudinally and 85 transversely juxtaposed to form a composite lens assembly of six Fresnel lenses which is inclined with respect to the horizontal, six being chosen for purposes of illustration.

The lenses are formed into an assembly by, 90 for example, securing them as by adhesives to a solar energy transmitting glass or plastics plate 332 which, in the case of plastics, may be folded along flexible partition lines 334 Each Fresnel lens may be about 9 95 inches by about 7 inches The point foci of the lenses are located in the water to be distilled in flexible container of bag 336 made of plastics or other pliable material Flexible container or bag 338 made of plastics or 100 other flexible material located below and extending beyond container 336 is used to collect condensate from plate 332 The lens assembly and containers are supported by support assembly 340 comprising pairs of 105 legs 342, 344, frame 346 and platform 348.

The legs are pivotably connected to frame 346 at one end and are secured at the other end in indentations in platform 348, or the legs may be secured in the ground or other 110 wise where no platform is used Thus, the legs may be moved to adjust the angle of incline of the lens assembly to follow the seasonal location of the sun The containers or bags have side panels 350, 352 which 115 extend upwards to plates 332 to form an enclosed system as described hereinbefore.

An opening is provided in side panel 352 at the lower side of plate 332 to allow the condensate to drop into the collector bag 338 120 Means such as transparent tubes 322, 324 connected to the bottom the containers are used to indicate water levels therein The lens assembly, support assembly and containers are easily assembled and disassem 125 bled The foci located in the water to be distilled in container 336 heat the water and cause it to evaporate, condensing on the bottom of planar plates 332 The condensate moves along plates 332 and falls into 130 1 590 843 container 338.

Fluid lenses having upper and lower plates are generally of large size and consequently have long focal lengths which are generally longer than the width of the plates Longitudinal Fresnel lenses having longitudinal microprisms are generally of smaller size and have shorter focal lengths.

Since the longitudinal microprisms decrease in height toward the center of the lens, the lens width is limited Also, the width of the glass or plastics sheets used for the Fresnel lenses is limited This can be used to great advantage.

Fluid lenses are larger than Fresnel lenses and are less efficient, absorbing and reflecting more solar energy than Fresnel lenses.

Thus, a system comprised entirely of fluid lenses is generally less efficient than a system having only Fresnel lenses or at least one Fresnel lens combines with at least one fluid lens In one preferred embodiment of the invention, systems are provided which include fluid and Fresnel lenses Such systems can be used to great advantage in distilling water where fluid lenses increase overall efficiency by recovering the heat of vaporization of the water being distilled Referring to FIG 3, such a system 450 is shown.

System 450 comprises fluid lens 22 and Fresnel lenses 132 A and 132 B Each lens has a different focus within channel 166 containing the water 170 to be distilled.

Channel 166 is trough-shaped to provide varying depths of water and the different foci are located at different depths A narrow Fresnel concentrator 132 A is positioned over the area in channel 166 inwhich water to be distilled is introduced, which area is reference by 451 Due to the single-conduit collector 188, and the location and size of lens 132 A, collector 188 and lens 132 A are used to preheat water introduced into channel 166, for example to 40 WC As a result, almost no condensation occurs at such location Highly efficient Fresnel lens 132 B is inclined at a steep angle with the horizontal facing north, and is focused inside the inner conduit in collector 172 which is of the two conduit type Collector 172 and Fresnel lens 132 B are connected and the lens is supported so as to be movable to track the seasonal and hourly location of the sun The support may be of the type described in the parent application No 28560/77 (Serial No 1590841) Preferably, flexible sheets 452, 453 are provided and attached on one side to the support for the Fresnel lens 132 A and on the other side at the support structure for the fluid lens 22.

The inner conduit carries a high boiling point fluid which is capable of being heated to a high temperature of, for example, C This, in turn, heats the lower boiling point fluid in the outer conduit to, for example, 80 WC Because of its steep angle, because it is not cooled by a fluid as is a fluid lens, little vapor condenses on lens 132 B. Fluid lens 22, having a lower efficiency than lens 132 B, is inclined at a slight angle with 70 the horizontal facing south of, for example, which is sufficient to cause condensate to flow along lower plate 28 and be discharged into channel 168 Lens 22 is focused directly in channel 166 so that its 75 focus will be in water 170 regardless of the sun's seasonal and daytime location A substantial amount of the vapor will impinge on lens 22 because of its location The Fresnel/fluid lens combination shown in FIG 3 80 has the following advantages using a plurality of lenses, and collectors and foci at varying water depths permits heating the water to different temperatures at different depths to set up currents which assist in overall 85 water heating and evaporation, thereby increasing system efficiency Employing Fresnel lenses to heat the water while providing a fluid lens on which the vapor condenses permits recuperation of the heat of 90 vaporization by the lens fluid while still employing the more efficient movable Fresnel lenses The fluid lens is not movable since a suitable angle of inclination must be maintained for the condensate to flow along 95 the bottom plate of the lens The focus of lens 22 will always be in channel 166 regardless of season Using a two conduit collector 172 at the focus of the efficient Fresnel lens and including a high boiling point fluid per 100 mits raising the temperature of that fluid to about 200 C whereby heat may be stored as described hereinbefore and used during the night Locating the focus of lens 22 directly in the channel heats up the water quickly 105 and provides heat to the water 170 during periods of sunshine During periods without sunshine (and even during periods of sunshine when heat is removed from the lens fluid), the lens fluid is cool and will provoke 110 greater condensation of vapor This combination permits continuous operation, the focus of lens 22 directly in the channel providing evaporation of water during periods of sunshine and collector 172 in which fluids 115 are heated to 200 C in the inner conduit and WC in the outer conduit storing heat and providing for evaporation of water during periods with and without sunshine assisted by a lower lens plate 28 cooled by the lens 120 fluid.

Another embodiment for distilling water similar to the apparatus shown in FIG 3 is shown in FIG 4 However, in FIG 4, two sets of double plate fluid lenses are pro 125 vided One set of lenses 22 A is inclined south at, for example, 15 with the horizontal and has a smaller distance between plates of, for example 1 inch at the point of maximum separation Such plates will have 130 1 590 843 sloped, cooled bottom plates to allow the vapor to condense on such plates and to flow toward and be discharged into channel 168 Ahother set of lenses 22 B contains circulating lens fluid having preferably a boiling temperature over 200 C and high infrared ray absorption characteristics This fluid is circulated from the lens system into the inner conduits 38 of a series of preferably metallic interconnected collectors 172, 172 A, 172 B, 172 C A plurality of interconnected collectors is provided to increase the overall collector surface area in channel 166 The inner conduits 38 are inserted in outer conduits 36 Another fluid such as water flows in outer conduits 36 about conduit 38 The fluid circulated in conduit 36 will be heated to, for example, 90 WC to heat the water 170 contained in the vessel 166.

The flow of the high temperature fluid in conduits 36 is stopped during hours without sunshine and the fluid with high temperature is stored in the inner conduits 38 and continues to heat the fluid in the outer conduits 36 The outer conduits 36 will in turn heat the water to be distilled during hours without sun Lenses 22 A with cooled bottom plates 28 will condense the water vapor so produced and also during hours without sunshine, and discharge the condensate into the channel 168 During hours with sunshine, lenses 22 A provide heat for vaporization of the water to be distilled In the system described above, and shown in FIG 14, the lenses need not be made movable to track the sun since the foci of the lenses will always be in the vessel containing the water to be distilled As mentioned hereinabove, preferably a salt/water solution and preferably seawater is used as the lens fluid, and in the case of distillation of seawater, the seawater from the lens being introduced into the vessel preheated.

Where the invention is used for distilling brine, the salt from the concentrated brine may also be recovered and sold or electrolyzed The invention provides for portable dismountable distillation units which could be used to distil seawater in life boats or brackish water in arid desert areas thereby possibly saving lives The invention also contemplates a floating installation at sea on a large ship such as a previously mothballed aircraft carrier located in a warm, sunny climate whereby seawater can efficiently and inexpensively be distilled.

While specific applications of the invention have been described, many other uses are possible For example, the salt byproduct of desalination may be collected and sold to reduce the overall operating cost of the system Additionally, the salt may be separated into sodium and chlorine by electrolysis by electricity, preferably generated by an associated solar energy collecting system In this respect, water can be separated into hydrogen and oxygen also by electrolysis, from electricity preferably generated by solar energy, the hydrogen of which in turn may be used with carbon monoxide 70 in the manufacture of liquid methanol which is easily transported and may be used as fuel for automobiles, airplanes.

The apparatus according to the invention has been described primarily using schema 75 tic diagrams Accordingly, certain details not essential to an understanding of the invention have been omitted For example, the materials and support structure comprising the apparatus according to the invention 80 not described in detail will be known to those skilled in the respective arts The sizes of the parts of the apparatus described hereinbefore will vary depending on the use to which the apparatus is put 85 It is pointed out that the heat obtained from the sun using the energy systems according to the invention may be lower in cost than heat energy obtained from fuels which may thus be replaced The distillation 90 systems according to the invention are capable of providing distilled water at low cost and therefore are important where clean water is scarce.

Claims

WHAT I CLAIM IS: 95

1 Apparatus for distilling liquids including water using solar energy said apparatus comprising a container for holding liquid to be distilled, elongate lens means disposed above said container for concentrating solar 100 energy in a liquid in said container, said apparatus including an elongate member having a substantially smooth surface disposed above the container and which is solar energy transmitting at least in part, said 105 member being positioned such that solar energy is transmitted therethrough to said container and rising evaporated liquid from said container impinges upon said surface and is condensed thereon, said surface 110 including a portion inclined with respect to the horizontal such that condensed liquid flows along said surface to a vertically lower portion thereof and is discharged therefrom, and liquid collecting means disposed below 115 said lower portion of said smooth surface for collecting condensed liquid discharged from said lower portion.

2 Apparatus according to claim 1, wherein the liquid is water 120 3 Apparatus according to claim 1 or claim 2 wherein said lens means comprises at least one fluid lens comprising a solar energy-transmitting lens fluid and solar energy-transmitting lens plates enclosing 125 said fluid.

4 Apparatus according to claim 3, wherein said member having said smooth surface comprises a bottom one of said lens plates and wherein said bottom lens plate is 130 1 590 843 operative to transmit the heat of condensation from water vapor condensing thereon to said lens fluid and wherein said fluid lens includes means for admitting fluid to and withdrawing fluid from said fluid lens such that said fluid can be passed through said fluid lens.

Apparatus according to claim 4 including means for removing heat absorbed in said fluid which is passed through said fluid lens.

6 Apparatus according to claim 5, including means for removing heat absorbed by said fluid which is passed through said fluid lens and for transferring at least part of said heat to the liquid to be distilled.

7 Apparatus according to any one of claims 3 to 6, including at least one Fresnel lens positioned to provide optimal concentration of the sun's energy in the liquid to be distilled.

8 Apparatus according to any one of claims 3 to 6 comprising a plurality of spaced fluid lenses, at least two of which have spaced foci, at least one of said fluid lenses being positioned and being operative to condense fluid vapor thereon and discharge the condensed liquid from an end thereof and the other fluid lens being positioned to provide optimal concentration of the sun's energy in the liquid to be distilled.

9 The apparatus of claim 8, wherein said at least one of said fluid lenses includes opposed plates enclosing a lens fluid spaced for minimal absorption of solar energy and conversion thereof to heat by said lens fluid, and said apparatus further comprising means for circulating said lens fluid for cooling it and thereby enhancing condensation on said at least one of said fluid lenses.

Apparatus according to claim 1 or claim 2 wherein said lens means includes an elongate Fresnel lens and said member having said smooth surface is a plate disposed below said Fresnel lens.

11 Apparatus according to claim 1 or claim 2 wherein said lens means comprise a plurality of point focus Fresnel lenses arranged so that the foci of the lenses extend along at least one line, said member having said smooth surface being a plate disposed below said Fresnel lenses.

12 Apparatus according to any one of claims 1 to 10 wherein said lens means is operative to concentrate solar energy substantially along at least one line and said apparatus further comprises elongate solar energy collector means comprising at least one elongate conduit through which at least one fluid can be passed, said conduit being disposed in said container for the liquid to be distilled along an axis substantially parallel to the elongate axis of said lens means, said line being located in or on said conduit.

13 Apparatus according to claim 12 wherein said at least one conduit is solar energy transmitting at least in part and is adapted to pass concentrated solar energy therethrough such that said line is located 70 within the fluid in said conduit.

14 Apparatus according to any one of claims 1 to 10 wherein said solar energy collector means comprises a plurality of elongate conduits through each of which at least 75 one fluid can be passed, said conduits being disposed in said container for the liquid along parallel axes which are substantially parallel to the elongate axis of said lens means, an inner of said conduits being dis 80 posed within an outer of said conduits and said line being located in or one one of the inner and outer conduits.

Apparatus according to claim 14, wherein said outer conduit is solar energy 85 transmitting at least in part and is adapted to pass concentrated solar energy therethrough such that said line is located within said outer conduit.

16 Apparatus according to any one of 90 claims 12 to 15 further comprising means for communicating the interior of said fluid lens with one of said inner and outer conduits.

17 Apparatus according to any preced 95 ing claim wherein said liquid collecting means comprises a second container.

18 Apparatus according to claim 17 and further comprising means for adding water to be distilled to said first container 100 and means for removing distilled water from said second container, said means for adding water comprising means for automatically maintaining the level of water in said first container within predetermined limits, and 105 said means for removing water comprising means for automatically maintaining the level of water in said second container between predetermined limits.

19 Apparatus according to claim 17 or 110 claim 18 wherein said apparatus comprises a plurality of apparatus including a plurality of first containers for liquid to be distilled a plurality of second containers for collecting condensed liquid and a plurality of lens 115 means arranged in a parallel manner, adjacent first containers being separated by a second container which is common to adjacent apparatus.

Apparatus according to any one of 120 claims 17 to 19 further comprising insulating means for enclosedly insulating the volume between said first and second containers and said lens means.

21 Apparatus according to any preced 125 ing claim further comprising portable means for easily assembling and disassembling said apparatus for distilling water portably.

22 Apparatus according to any preceding claim wherein said lens means comprise 130 1 590 843 a plurality of lenses juxtaposed about a radial axis of said apparatus.

23 Apparatus according to any one of claims 1 to 18 wherein said lens means comprise a plurality of lenses juxtaposed along a longitudinal axis of said apparatus.

24 Apparatus according to any preceding claim wherein said lens means have a plurality of foci, said foci being located in said container for liquid to be distilled substantially regardless of the seasonal and daytime location of the sun at varying heights therein corresponding to varying liquid depths.

5 A method for distilling liquids including water using solar energy comprising concentrating solar energy through elongate lens means along at least one elongate focus located in the liquid to be distilled to thereby evaporate liquid therefrom, condensing the liquid on a planar elongated surface located between the liquid and the lens means and having an axis substantially parallel to that of the elongated focus, and including a portion inclined with respect to the horizontal such that condensed liquid flows along said surface to a vertically lower portion thereof and collecting the condensed liquid discharged from said vertically lower portion of the planar surface.

26 A method according to claim 25, wherein the elongate lens means comprises at least one fluid lens containing a lens fluid therein, said fluid lens causing the liquid being distilled to be evaporated and condensed onto the bottom of a substantially smooth surface of the fluid lens means, the condensed vapor being collected from said smooth surface, and the lens fluid being circulated to recover the latent heat of condensation and sensible heat of the vapor absorbed and recovered by the lens fluid in the fluid lens.

27 A method according to claim 26, wherein the recovered heat in the lens fluid 45 is used to heat the liquid to be distilled.

28 A method according to any one of claims 25 to 27 which includes the step of concentrating the solar energy along an elongated focus located in or on elongate 50 collector means including at least one elongate conduit which contains a fluid therein and the axis of which is substantially parallel to that of the focus, whereby the fluid is heated to assist evaporation of the liquid 55 29 A method according to claim 28, wherein the solar energy is concentrated in or on a transparent inner conduit enclosed in a transparent outer conduit, each conduit containing a different fluid therein 60 A method according to any one of claims 25 to 29 further comprising the step of recovering heat contained in the collected condensed liquid.

31 A method according to any one of 65 claims 25 to 30 further comprising recovering heat contained in the liquid remaining in the container after a substantial part thereof has been evaporated.

32 A method according to any one of 70 claims 25 to 31, further comprising focusing the solar energy directly in the liquid at a plurality of locations at varying liquid depths.

33 A method according to any one of 75 claims 25 to 32, wherein the liquid is water.

34 Apparatus for distilling liquids, substantially as herein described with reference to any one of the accompanying drawings.

A method according to claim 25 80 substantially as herein described with reference to the accompanying drawings.

R G C JENKINS & CO.

Chartered Patent Agents Chancery House 53/64 Chancery Lane London WC 2 A 1 QU Agents for the Applicants Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd, Berwick-upon-Tweed, 1981 Published at the Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.