CA1117070A - Economic solar energy concentration and collection - Google Patents

Abstract

ECONOMIC SOLAR ENERGY CONCENTRATION AND COLLECTION
Abstract of the Disclosure Apparatus and methods for concentrating and collect-ing solar energy are disclosed. In accordance with the in-vention, solar energy is concentrated by economical refringent lenses or lens systems including fluid lenses and/or Fresnel-type lenses. The lenses concentrate the solar energy pre-ferably along lines in continuous linear foci or in discrete foci at an elongated collector comprising one or more fluid-carrying conduits and one or more fluids therein. In one embodiment, a plurality of photoelectric cells are located in or on the collector along the linear foci or at the discrete foci and operate at increased efficiency with heat being removed by the collector. A first fluid in the collector is heated by the concentrated solar energy and in a preferred embodiment is used to heat a second fluid contiguous to the first fluid, the first fluid having a boiling point exceed-ing that of the second fluid. In a preferred embodiment, the first fluid is carried in an inner conduit while the second fluid is carried by an outer conduit which encloses the inner conduit and first fluid. Thus, the two fluids can be heated to different temperatures by a single concentrating system and used for different purposes. Additionally, the invention provides for the storage of energy using two fluids of different boiling points. Also disclosed are methods and fixed and portable apparatus for distilling water containing salt or other substances by evaporation of the water and con-densation of the water vapor wherein preferably the heat of condensation is recovered. The invention also provides for assemblies of individual systems to form larger systems.
The present invention provides heat from solar energy at a cost competitive with heat produced from fuels.

Description

~ ~ ~t7~

The present invention relates to methods and apparatus for concentrating and collecting solar energY
for many uses including the conversion thereof to heat energy and/~r electrical energy to be used for many pur-poses. The present invention also relates to the storageand use of heat energy during hours without Cun or with reduced sun. The present invention further relates to the treatment of water containing salt and/or other substances using fixed and porta~le apparatus and methods according to the invention. More particularly, the invention relates .o methods and apparatus using fluid and/or Fresnel concen-trating lenses and lens systems and elongated collectors comprising at least one fluid-carrying conduit located at the foci of the lenses.
The energy emitted by the sun corresponds to a high temperature in the order of 6000C, and is emitted in the form of radiation which arrives at the earth with a wavelength distribution comprising about 3~ ultraviolet rays, 42~ visible light rays, and about 55~ infrared rays.
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 heatin~ of the m~at~rial c~nstituting the surface. It is also known that electricity can be produced by photoelectric devices exposed to the sun's rays. 7 There have been many attempts in the past to collect and utilize pollution-free and essentially non-consumable solar energy to meet many energy needs. Much attention has been directed to the conversion ana utilization of solar ener~y in the past few years because of the realizatlo -3- ~

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that fossil fuels are exhaustable and that a burning of these fuels produces pollution. Solar energy, on ~he other hand, is inexhaustable and available above the clouds at an average energy level of approxLmately 1350 watts per horizontal square meter. A percentage of this energy, depending on atmospheric and weather conditions, dust, pollution, etc., is available at the surface of the earth during periods of sunshine which vary up to about 4000 hours per year depending on location. Even more recently, the shortage of fossil fuels particularly oil and the high cost thereof have sparked new attempts to harness the energy of the sun. As in the past, however, fuels are still a lesser expensive source of energy and the same problems of high capital cost and the cyclic nature of the sun reguiring storage capability have still not been satisfactorily solved. For example, refringent lens focusing systems, most using reflecting collectors and most including sun-trackinq systems, have heretofore been used but are uneconomical and impractical because of the high cost involved. A conventional way for obtaining lower temperatures up to about 80CC con-sists of using dark-colored panels which absorb the solar radiation, and combining these panels with means circulating a heat-carrying fluid in a heat-exchanging manner with the panels. lt is also known to improve the efficiency of these systems by placing one or more glass pl~tes above the panels to produce a greenhouse effect for reducing heat losses.
Howevex, the effieien~y of these panel systems is low, from a~out 30~ to about 40%, and they require large spaces resulting in large heat losses, ~nd they also require a hig~ capital investment. ~he use of Fresnel-type lenses ~L7~!7~

and fluid lenses is known in the art for focusing solar energy. See, for example, U.S. Patents 3,915,148; 3,125,091;
937,013; 3,965,683; 3,901,036; 60,109 1,081,09~; Japanese Patent No. 28-2130, and Australian Patent No. 131,069.
However, none of the known systems is capable of converting and storing solar energy efficiently and none can produce heat at an economical capital investment such that the use of solar energy is competitive with other energies. The prior art also does not disclose obtaining temperatures in the order of a few hundred degrees C while also obtaining at the same tjme lower temperatures usable for home heating and water heating or other purposes. Nor is there in the prior art a system which is capable of storing heat energy from solar energy during perio~ of interrupted solar energy for any length of time and which also is capable of pro-viding different temperatures simultaneously and also utilizing the luminous and infrared rays of the sun.
With respect to electrical generation, it is known that concentrating the solar energy at a photovoltaic cell will increase the electrical output of cell; however, there is the disadvantage that the increased heat in the photo-voltaic cell resulting from the concentration will also limit the cell output. Known photov~ltaic devices produce a maximur, o~ about one watt per hour per cell. Assuming a cost of Slo per phot~voltaic cell, a system using non-concentrated solar energy to generate about 1 kilowatt per hour requires a capital cost of at least S10, ooo which is not competitive for normal uses.
With respect to ~olar stills, known stills used for distillation of ~eawater have low efficiencies and the ~17~!'7~

cost of heating the water is hi~h as the least amount of heat required to vaporize the water is not recovered from the condensation but rather is lost.
In accordance with the invention the prior ~rt draw~acks and disadvantages are substantially overcome and additional advantages realized.
The present invention relates to methods and apparatus for concentratinq, collecting, storing and utilizin~
solar energy. In accordance with the invention, refringent lens means concentrate the solar energy along a length at elongated collector means cont~!ning at least one fluid therein. Further in accordance with the invention, the lens means comprise economical fluid or Fresnal-type lenses and lens systems which focus the ~olar energy ~ubstantially along the length at the collector means along substantially continuous lines or in lines of substantially discrete points. Thus, the at least one fluid in the elongated collector may be efficiently heated to high temperatures in the order of a few hundred degrees C. The fluid lenses are advantageously made from separate upper and lower solar energy transmitting plates which are installed in frame means in a fluid-tight manner, or the fluid lenses may be welded, extruded, or blown ~Lmilar to gl~ss or plastic bottles. The fluid within the lenses preferably has ~n $ndex of refraction similar to that of lens plates. The - enclosure in the lens containing the fluid is advantageously communicated with the collector means to enhance performance.
Sti~l further in accordance with the invention, the elongated colle~tor means eDmprises a plurality of fluids, ad~acent ones of which are contiguous. The fluids ~17~?7~) 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 emb~diment, the elongated collector means comprises at least two con-duits; 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 ~econd boiling point.
Preferably, the solar energy is concentrated at the inner li~uid which has a boiling point which exceeds that of the outer liquid. The ~onduits and fluids are solar energy transmitting or opaque or darkened depending on the location of the lens means focus. ~y solar energy trans-mitting it is meant that the solar rays are substantiallytransmitted through the material. In this way, the fluid may be heated to different temperatures and accordingly can be utilized for different purposes, if desired. Regulation of the fluid flow rates and selection of conduit sizes and shapes a6sists in providing different temperatures which may be utilized for different purposes. Arrangement of multiple conduits carrying multiple fluids in accordance with the invention can provide energy for many different uses including a vapor and ~uper-heated vapor for mechanical devices including turbines. Advantageously, the lower boiling point fluid has a ~w latent heat of vaporization and is useful for this purpose. Additionally, heat is stored in the higher boiling point fluid by permitting its tem-perature to rise during peri~ds of ~olar energy to atemperature substantially ~igher than that of the lower 11~7~7~) boiling point fluid which may be used as a working fluid.
Heat is removed from the higher boiling temp~rature fluid by, for example, circulating the lower boiling point ~luid past the higher boiling point fluid.
The invention also provides for the union of individual systems to form larger composite systems. Thus, a high degree of concentration of solar energy is possible.
Still further in accordance with the invention, both the infrared and luminous rays of the sun may be simultaneously utilized. Photoelectri~ cells specifically photovoltaic cells, can be disposed at the collector means such ~ at the luminous rays are concentrated thereat for maximum electrical energy production while the heat generated by the concentration of the infrared rays is removed by one or more fluids in the collector means whose flow rates and volumes may be regulated. Thus, in accordance with the invention, the solar energy is concentrated by a factor in the order of up to 100 so that one of the known cells is able to produce up to 100 watts per hour instead of 1 watt per hour during periods of sunshine.
Further in accordance with the present inventior., liguids, particularly watex, may be distilled by locating the collector means in the liquid to be distilled, above which is positioned lens means and a downwardly sloping ~ubstantially smooth, preferably planar surface, whereby liquid is evaporated and condenses on the ~mooth surface which carries the condensed liquid to a collecting vessel positioned ~elow the lower side thereof. In one embodiment the vessel holding the liquid to be distilled and the liquid function as the collector means, the focus of the lens means 113~7~7i~

being located directly in the liquid. Means are provided to completely enclose the apparatus while permitting move-mer.t of the lens or the entire system to track the sun seasonally or daily. It is preferred that the lens system for the liquid distilling apparatus comprise fluid lens means which include said s~ooth sur~ace and in which the solar energy transmitting fluid forming part of the lens means is circulated within the collector means to advan-tageously utili2e the latent heat released by the vapor condensing on said smooth surface and transferred to the liquid to be distilled. The heat released by the con-densing liquid is thus not lost and returned to the system by means of the lens fluid and the circulation thereof, thereby increasing substantially the efficiency of the system and the quantity of heated liquid obtained from liquid to be distilled. In the case of seawater, salt may be produced from the resulting concentrated brine and credit obtained from the ~ale thereof to lower the overall cost of obtaining distilled water. According to one 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 may be used at sea, for example, on life boats, and in desert ~reas.
The ~pparatus may be enclosed ~ccording to the invention to reduce heat losses and form enclosed systems.
Apparatus according to the invetnion can advan-tageously be combined with a conventional heat pump producing and storing additional heat from the surrounding air or water. This ~ay be part~cularly significant during winter months when lower sun energy is available and there is more 1~7~711 consumption of energy for heating.
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 showing a system according to the invention comprising an elongated fluid lens and a collector comprising two fluid-carrying con-duits, one enclosed in the other with the focus of the lens located within the inner conduit;
FIG. lA is a cross-section view of another embodiment of the collector of FIG. 1 showing a rectangular inner con-duit on the upper surface of which is located the focus of the lens of ~IG. l;
FIG. 2 is a perspective view showing one of a series of longitudinally juxtaposed fluid lenses and its frame in cross-section and an opening for inter-communicatins the enclosure of the lens with other lenses, this arrangement being utiliza~le to arrange a plurality of longitudinally ~uxtaposed lenses where 6ingle lens is now shown;
FIG. 3 is a perspective view of a lens system nccording to the invention comprising two separate plates for enclosing a lens fluid and a frame for sealing the plates into a fluid-tight lens;
FIG. 4 i~ ~ cross-cection view of the lens and frame of FIG. 3 taken along line 4-4;

~117~7~) FIG. 5 is a schematic perspective diagram similar to that of FIG. 1 showing another system according to the lnvention in which the ~ystem is enclosed, the single lens is movable to follow the seasonal location of the sun and in which the collector comprises a single fluid-carrying conduit;
FIG. 6 is a schematic perspec~ive diagram showing another system according to the invention comprisiny an elongated, planar Fresnel-type lens having a linear focus and a collector comprising three fluid-carrying conduits in which an oute~ conduit encloses two inner conduits and in which the focus of the lens is located within the outer conduit;
FIG. 7 is a cross-section view of part of another collector comprising three fluid-carrying conduits in which the innermost conduit is enclosed by the intermediate conduit which is enclosed by the outermost conduit;
FIG. 8 is a ~chematic perspective diagram showing yet another system according to the invention comprising an elongated curvilinear ~resnel-type lens and a collector comprising a single rectangular fluid-carrying conduit;
FIG. 9 is a schematic perspective diagram of a composite system according to the invention for distilling water comprising individual ~ystems each comprising two elongated fluid lenses and a collector located in the w~ter to be distilled comprising two fluid-carrying conduits, one enclosed în the otherJ
~ IG. 10 i~ a sch2matic perspective diagram of an-other system a~cording to the invention for distilling water c~mprising a single elongated fluid lens and a ~L7~7~

collector comprising a single fluid-carrying conduit;
FIG. 11 is a schematic perspective diagram of a portable easily assembled and disassembled system having ~resnel lenses for distilling water according to the invention; and FIG. 12 is a cross-sectio~ view of a photoele~tric cell positioned in a fluid-carrying c~nduit to produce electricity from solar energy according to the invention with fluid circulating inside and/or outside the conduit to remove heat.
In FIG. 1 is shown a sol~r energy collecting system comprising a refringent fluid lens concentrator and a fluid-containing sDlar energy collector. System 20 comprises an elongated fluid lens concentrator 22 and collector 24 in the form of elongated fluid-containing conduits.
Elongated fluid lens 22 comprises solar energy transmitting plates 26, 28 mounted in frame 30 and spaced to enclose solar ener~y transmitting fluid 31. In the embodiment shown in FI~. 1, upper lens plate 26 is convex and lower plate 28 is planar. The respective sides 32, 34 of lens plates 26, 28 and the ends of the lens plates (not ~hown in FIG. 1) are sealed to be fluid-tight in manners which will be described hereinafter. Alternatively, means not shown in PIG. 1 for adding and remo~ing or circulating fluid 31 and air are provided in the ~ides and/or ends of the lens plates.
Additionally, mèans also not shown in FIG. 1 for longitudinally and transversely ~radially) juxtaposing lenses may be provided and will slso be described ~ereinafter. In the embodiment shown $n FIG. ~, collector 24 comprises an outer elongated conduit 36 enclosing an inner elongated conduit 1~7~7~) 38, both shown to be tubular in shape. Conduit 36 is placed in insulating container 40 and is surrounded by insulating ~aterial 42 except for a longitudinally extending opening 44 located above conduit 36. Opening 44 is closed off by solar energy transmitting and heat insulating plate 46.
~late 46 is suitably made of glass or plastic and the insulating material 42 is suitably a foam such as poly-ethylene foam. Collector 24 is located below lens 22 and the theoretical linear focus 48 is located at or along the collector for substantially all of ~he daylight hours.
The space between the lens and collector is enclosed hy side panels SO which if rigid can also serve to support lens 22 and frame 30 in cooperation with support member 52.
For optimum concentration of solar energy at collector 24, lens 22 is oriented at a preselected angle A with the horizontal, the longitudinal axis of the lens (and of the system) is oriented along the east-west direction and the con-vex upper lens plate 26 is oriented to face south ~northern hemisphereJ. The optimum value for angle A depends upon the location of the system 20, and for a fixed system is chosen to give optimum concentration on an annual basis.
For movable systems, which will be described hereinafter, angle A is selected for optimum seasonal 601ar energy c~ncentration or for optimum concentration for even shorter periods of time.
As mentioned hereinbefore, the collector 24 is located at tbe theoret$cal focus 48 of the lens 22 and in the embod~ment of FIG. 1, conduits 36 and 38 are solar energy transmitting, the theoretical focus 48 being located within the inner conduit 3~. Conduits 36 and 38 contain ~3 7~!7i~

heat-carrying fluids 54 and 56, respectively. Since the concentration of the solar energy will be greatest in the fluid within the c~nduit at which the lens theoretical focus is located, i.e., in fluid 56 within conduit 3B, fluid 56 may be heated to a relatively high temperature and is therefore chosen to have a relatively high boiling point, for example, from about 150C to about 350C. Such fluids may comprise by way of example and not llmitation lubricating oils, glycerine, olive oil, paraffin oils, etc. Thus, during periods of sunshine, fluid 56 is heated to a tem-perature which may be in excess of 100C, for example, 200C
the precise temperature attained depending on many factors such as the flow rate of fluids 54, 56, the dlameters of conduits 36, 38 sun intensity and position, insulation, heat exchange rates, etc. Fluid 54 is selected to have a boiling point which is less than the boiling point of fluid 56, preferably at least 50C less than the boiling point of fluid 56, and preferably in the temperature range of from about -62C to about 100C. Such a fluid is suitably water. It is also preferred-that fluid 54 have a low latent heat of vaporization, for example, from about 20 calories per kilogram to about 270 calories per kilogram, and such fluids may comprise by way of example and not li~itation fre~n, butane, propane, ammonia, ethyl ether, methyl alcohol, etc.
In operation, solar energy is concentrated in fluid 56 (chosen to ~e lubricating oil) within conduit 38 and raises the temperature of the oil ~o about 200C. Since the focus to lens 22 is theoretically linear, ~luid 56 will be ~on-tinually heated as it traverses the linear focus. Fluid 54 '7V

(chosen to be water) which surrounds the oil and conduit 38 is heated primarily by the oil primarily through con-duction. Both fluids, oil and water, are circulated ~t predetermined rates to obtain desired temperatures and ~zy be used for different heat applications. For example, the water may be heated to about 70DC - 80C or more and used for space and hot water heating. ~he water may be heated to lower temperatures and used, for example, in swimming pools. The higher temperature oil may be used for applications requiring higher temperatures including industrial applications or may be used merely to heat the water. Since the temperature of fluid 56 increases as it traverses the lens focus, fluids at many different tem-peratures are realizable by providing taps for fluid outlet and/or inlet at different points along the focus.
Fluid 54 may be evaporated and the vapor or superheated vapor used to produce mechanical power in a turbine or engine which, in turn, may generate electricity. Preferably, a closed system (not shown~ is employed in which the con-densed fluid is returned to collector 24. In such applications,fluids such as Freon*, butane, propane, ethyl ether, methyl alcoh~l, ammonia and the like may constitute fluid 54.
As mentioned hereinbefore, a ~erious drawback of ~olar energy sy~tems in general and known systems in particular relates to the ~torage of energy during periods in which there i~ no ~unshine or the intensity thereof is low, ~s for example during the night or during periods of cloudy weather. In accordance with the present invention, heat i5 ~tored for use ~n those period~ in fluid 56 which is heated during ~ormal ~y~tem operation to n temperature ; * Trademark of E.I. duPont de Nemours & Co., Inc.

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which is at least about 50C higher than the temperature of fluid 54. Therefore, even when fluid 56 is not being heated by solar energy or being heated at a reduced rate, it stores heat and will continue to supply heat to fluid 54 due to the temperature difference between the two fluids. Preferably, the circulation of fluid 56 is stopped for those periods. Fluid 56 continues to trans-fer heat to fluid 54 until the difference in the temperature of the two fluids is relatively small. The time that fluid 56 will transfer and/or store heat depends upon the initial temperature of fluid 56, the differerce in temperatures between the fluids, the volumes of the fluid, the character-istics (specific heat, boiling point, latent heat, etc.) of the fluids, the use to which fluid 54 is put, etc.
Further in accordance with the inventi~n, the fluid 31 in lens 22 may be communicated (not shown) with collector 24 through conduit 36 or 38 or through another separate conduit to remove heat from the lens fluid, thereby maintaining it at a suitable temperature while utilizing solar energy absorbed by the lens fluid.
In FIG . 1, collector 24 was shown to comprise tubular conduits 36, 38. However, the conduits need not be tubular and in some instances other configurations are preferre~. For example, referring to FIG. lA, collector 58 comprises rectangular inner conduit 59. The rectangular configuration may be desirable when the theoretical focus varies excessively with seasons and the time of day in a single lens system ~s shown in FIG. 1. Providing a rectangular shape will all~w movement of focus 48 while still maintainin~ it at conduit 59. Focus 48 has bee~ ~hown on 1~17C!70 the surface of conduit 49, and in such a case, the surface of conduit 49 need not be solar energy transmitting and is preferably darkened. Fluid 56 inside conduit 59, as in FIG. 1, has a higher boiling point than outer fluid 54 since the concentration of the solar energy will be at the conduit containing fluid 56.
It is to be understood that the systems shown in the remaining figures and described hereinafter are longi-tudinally oriented in an east-west direction and faced towards the sun preferably by plus or minus 15 (plus in winter, minus in ~ummer) c r the latitude of the location in order to achieve an optimum concentration of solar energy, seasonally or for shorter periods of time. It is to be further understood that the elongated lenses or lens system and the elongated collectors and conduits thereof are arranged substantially along parallel longitudinal axes. Description will be made hereinafter of mcvable lens systems for track-ing the sun; manual and automatic means for effecting track-ing movement of systems and/or lenses on a seasonal basis are known. ~he refringent lenses according to the invention are operative to also concentrate diffuse solar energy which may repres~nt up to about 50~ of the solar energy at the system. While only part of a single lens is shown in FIG. 1, it is to ke understood that many lenses may be longitudinally and radially juxtaposed. Use of many lenses results in 4 system with a high degree of solar energy concentration which is achieved quite economically.
In the embodiment shown in FIG. 1, heating is accomplished by heat exchange between fluids 54 and 56 with-out the necessity of an external heat exchanger which reducec 1~17C~7~

heat losses. Side panels 50 which are made of an insulatingmaterial further reduce heat losses. Additionally, plate 46 provides a greenhouse effect in the collectors to furt~er reduce heat losses. Collector 24 is also preferably made of insulating material~ The reduction in heat loss is especially important during periods of no or reduced sunshine. It is preferred that the theoretical focus of the lenses be located at the inner fluid to further reduce heat losses since the outer fluid will act as an insulator. The solar energy transmitting tubes are preferably made of colorless and trarsparent glass or plastic and the tubes which need not transmit solar energy there-through are preferably metal, preferably steel, copper or aluminum, and preferably have darkened outer surfaces.
According to the invention, the area of the collector surfaces may be much smaller than the area of the concentrators and may be only from about 1~ to about 10%
of the area of the concentra~ors, thus reducing the heat losses accordingly. As less material is required in the collector, the cost will be reduced.
As will be more apparent hereinafter, the collector systems may comprise a number of cond~its other than two and configurations other than tubular, and the lenses and lens systems may be other than that shown in FIG. 1 and may be movable and also track the sun.
Fluid lenses according to the invention may have configurations other than that shown in FIG. 1. The lens plates may be economically made of glass or plastic and are joined in a fluid-tight manner as by welding. Alternatively, the lens may be extruded with the sides integrally joined.

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The ends of the lenses may similarly be welded or extruded or formed from a bulb of glass or plastic as by blowing as, for example, in the manufacture of glass or plastic bottles.
The lens shown in ~IG. 1 is supported by suitable frames and structural members. For example, lens 80 is supported by frame 88 shown in FIG. 2. As there shown, one of a plurality of lenses 80 are longitudinally juxtaposed at ends 90 and supported by longitudinal support stringers 92 and transverse support stringers 94. The lenses may be ;10 secured to the frame by, for example, adhesives. The theoretical focus 96 of the lenses is at and along collector 98. Means in the form of openings 100 are provided to add and remove fluid 31 and/or air and the openings may be communicated by, for example, tubes to provide for circualtion of the fluid. The openings may be provided in other locations.

As mentioned hereinbefore, the plates forming the lenses may be integrally extruded or blown or may comprise separate plates joined as by welding. Referring now to ~IGS. 3 and 4, upper curvilinear plate 26 and lower planar plate 28 are separate pieces and are joined in a fluid-tight manner by means of frame 104. Frame 104 comprises two longitudinal grooves 1~6, 108. The upper groove 106 is curvilinear and sized to accommodate upper curvilinear plate 26 while the lower groove is linear And ~i2ed to accommodate planar plate 28. ~he edges of the respective ~eparate plates are in-fierted into the respective grooves along with sealingmaterial 110. The ends of the plates are similarly joined.
The material 110 may camprise a gasket or similar flexible piece and/or deforma~le ~aterial such as silicone to form fluid-tight joints. Thus, the lenses according to the in-1~17~!?71) vention in which two independent plates are joined or thelenses are extruded or blown, are relatively easy to manufacture and are relatively inexpensive.
As mentioned hereinbefore, lens 22 may be movable to track the seasonal movement of the sun. In FIG. 5, system 112 is shown in which the side walls 114, 116 are made of expandable plastic whereby the system remains enclosed as described hereinbefore upon movement of lens 22 along a radial axis of the collector. With lens 22 in the positions designated by solid lines, walls 114, 116 assume first positions connected between respective bottomsides of collector 118 and sides 32, 34 of the lens. Upon counter-clockwise rotation of the lens to the position designated by the broken lines, the lengths of the walls are changed and the system remains enclosed. Thus, a simple, inexpensive, enclosed system is provided in which the lens may be moved to track the seasonal location of the sun. Still referring to FIG. 5, collector 118 is ~hown comprising a ~ingle tubular inn~r conduit in which the focus 120 is located.
Description of preferred embodiments of the invention has been made hereinbefore with reference to linear theoretical focus fluid lenses. However, in accordance with the invention, the solar energy may be concentrated by focal point lenses. In FI~. 11 is shown a plane refr$ngent element 126 comprising a rigid frame surrounding a sheet or plate o~ plastic or glass material in which are formed by imp~essions or molding concentric closely spaced rings of microprisms whose pitch, for ex2mple, corresponds to about 3 to about 6 nicroprisms per mill$meter. The plane refringent element 126 acts like a plane Fresnel lens. Solar '7~

energy striking the refringent element 126 is concentrated by the microprisms into a theoretical point focus. Refringent elements 126 may l~e ~ositioned longitudinally juxtaposed and/or radially juxtaposed. The system may be arranged so that the point foci of lenses 126 are located within or at the surface of conduits 36, 38, 59 as described hereinbefore, the series of discrete point foci along a length forming, in effect, a linear focus composed of dis-crete point foci, or as shown in FI~.ll in a liquid being distilled.
System 130 of FIG. 6 is shown employing an elongated refringent element 132 having longitudinal micro-prisms 134 acting as a longitudinal Fresnel lens. The lens 132 and collector 136 are arranged so that the linear focus is located at collector 136 which is similar to collector 24 in FIG. 1 except that two inner conduits 138, 140 are enclosed in outer conduit 36. Linear focus 142 is located within conduit 36. Providing three conduits permits use of three different fluids and allows for use of the fluids at varying temperatures for many dif~erent applications.
FIG. 7 shows another arrangement for three conduits in which the inner conduit 139 is enclosed by intermediate conduit 141 which in turn iE enclosed by outer conduit 36.
System 144 in FIG. 8 shows a rectilinear refringent element 146 formed with longitudinal microprisms 148 which direct the solar energy to different linear foci F, Fl, F2 located at col~ector 150 depending upon the seasonal location of t~e sun. Collector 150 is located east-west so it is oriented to c~llect ~lar energy during daily movement of the ~un, and comprises a single solar energy transmitting, 7~

at least at upper part 152, rectangular fluid conduit 154 which is surrounded in part by insulating material 42. Parts of system 144 are not shown to proportion. In particular, collector 150 is shown in larger proportion for clarity and is less than about 10% of the size of lens 146. A closed system is achieved by extending the sides of refringent ele-ment 146 an~ insulating material 42 into overlappi~g engage-ment. As described hereinbefore, use of a rectangular conduit 154 facilitates location of a moving focus such as F, Fl, F2 within the conduit. Although element 146 focuses primarily by refracting the rays of the sun, the micro-prisms also provide reflection of rays such as 156. ~he inside sides of element 146 may also be suitably angled and made reflective to reflect any rays impinging thereon to the focus.
The present invention may be utilized for many energy applications as described hereinbefore and may also be advantageously used to distill or otherwise treat liquids particularly water by evaporation and condensation thereof. ~ypically, the liquid is water and the water is seawater or brackish water and is to be desalinated, or water containing minerals or other substances such as industrial waste water or polluted water which is to be purified ~nd di~tilled. Further in accordance with the inventi~n, the refringent concentrators and collectors according to the invention are arranged in systems operative to distill water, preferably recovering the heat of condensation as described hereinafter.
~he ~ystem 160 shown i~ FIG. 9 comprises a plurality of sub-systems 162, each employing a two lens 1117~!7V

arrangement 164. Each lens pair lS4 is supported above ~n elongated, central, rectangularly configured channel 166 and parallel, elongated rectangularly configured, side channels 168 such that the central part of the pair of lenses is above the central channels and the outer lonait~dinal edges of the lenses are above the side channels.
Each individual lens is inclined and additionally the pair of lenses is rotated slightly in a clockwise direction such that adjacent pairs are overlapping. The bottom lens plates 28 are planar. The water 170 to be distilled is filled in the central channel to a predetermined height.
Within channel 166 is positioned collector 172 which com-prises conduits 36, 38 as in FIG. 1. The focus 64 of the lens pair 164 is located within inner conduit 38. Pre-ferably, the interior of lenses 22 is communicated withcollector 172. In the embodiment shown in FIG. 9, lens fluid 31 is advantageously water and the interior of the lenses is communicated by conduit 174 with outer conduit 36 in which the fluid is also water. The fluid in the inner conduit 38 is a higher boiling point fluid as described hereinbefore. In operation, the water 170 to be distilled is heated by collector 172 due to the solar enexgy concentrated thereat and the water 170 is vaporized. The vapor strikes the lower plates 28, is condensed thereon and flows therealon~ to be discharged at or dropped from the edges thereof into æide channel 168. In accordance with the invention, the water in the fluid lenses is circulated throu~h collector 172. In this way, the heat released by condensation of the vspor is transmitted through the plate 28 to the water in the lenses and the heat absorbed by the i~7~7~) water in the lens from the condensing vapor is returned to the system through conduit 36. This is significant because the latent heat required to vaporize the water 170 of about ~39 calories per liter (975 BTU per kilogram) in additi~n to the sensible heat is substantially returned to the system by the circulated water in the lenses upon which the vapor condenses. This latent heat is substantial and would otherwise be lost. This results in a much higher efficiency of the system compared with solar stills where channels filled with water to be treated are covered with only glass plates w~ich receive the solar rays. Circulating the water in the lenses also cools the lower lens plate 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 17R 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 ~pproximately equal levels in each of the respective channels. Advan-tageously, the channels are made of concrete or asbestoscement. ~eans other than the lens itself may be used to condense the Yapor such ~s substantially smooth preferably planar plates located below the lenses 164. In such a case, the lens fluid may not rec~ver the latent heat unless the plate is proximate thereto. Alternatively, means associated ~7~

with the plate may be used to recover the latent heat.
The system shown in FIG. 9 is substantially enclosed by the ~nel panels to reduce heat loss as described hereinbefore. The two-conduit collector 172 is particularly advantageous since the fluid in the inner conduit 38 may be raised to a high temperature and used to store heat as described hereinbefore. This adds a very important capability to the system in that it can operate during the night and during periods of reduced In sunshine. This is very important in that it provides the advantage of substantially continuous operation resulting in increased system output at reduced cost. The rscovery of the latent heat of the condensing vapor by the lens fluid assists in providing a continuous operation system since heat losses are reduced.
In FIG. 10, a single lens system, single conduit system 196 is shown which is similar to those described hereinbefore. The adjacent channels 198, 200 for the water 170 to be distilled and ~he distilled water, respectively are trough-shaped and may advantageously be formed from adjacent plates. ~he inclined lens 22 is above channels 198, 200 and the lower part of lens 202 terminates above channel 200 to permit the condensed water to fall therein.
According to the invention, systems may be main-tained essentially enclosed while lenses 22 are moved totrack the ~un. An expandable material, as de ~ ~ for FI~. 5, forms the side panels of each compartment of such a system. ~dvantageously, the material is of plastic.
In FIG. 11 is ~own an embodiment of a portable water distillation ~yste~ 330 which is easily assembled and 7~!7i~) disassembled. System 330 comprises planar Fresnel lenses 126 having concentric microprisms causing the ~olar energy to be concentrated at point foci. Lenses 126 are longitudinally and transversely ju~taposed to form a com-posite lens assembly of six Fresnel lenses which is inclinedwith respect to the horizontal, six being chosen for purposes of illustration. The lenses are formed into an assembly by, for example, securing them as by adhesives to a solar energy transmitting glass or plastic plate 332 which, in the case of plastic, may be folded along flexible partition lines 334. Each Fresnel lens ~ay be about 9 inches by about 7 inches. The point foci of the lenses are located in the water to be distilled in flexible container or bag 336 made of plastic or other plyable material. Flexible container or bag 338 made of plastic or 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 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 otherwise where no platform is used. Thu-~, the legs may be moved to adjust the angle of incline of the lens assembly to follow the seasonal location o~ the sun. The containers or ~ags have side panels 350l 352 which extend upwards to plates 332 to form an enclosed system as described hereinbefore. An opening is provided in side pane~ 352 at the lower side of plate 332 to allow the condensate to ~rop into the collector bag 338. ~eans such as transparent tubes 322, 324 connected to the bottom of the 1~17~7~

c:ontainers are used to indicate water levels therein. The lens assembly, support assembly and containers are easily ~ssembled and disassembled. 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 container 338.
According to another aspect of the invention, the concentrated solar energy is used to generate electricity by means of photoelectric cells. More particularly, the luminous rays of the sun are concentrated on photovoltaic cells. Referring to FIG. 12, photovsltaic cells 398 made of silicon or cadmium or other materials are disposed in the interior of inner ~luid-carrying conduit 400 shown advan-tageously to be of rectangular cross section. Thetheoretical focus 402 of the lens is at the cells and preferably on the outer surface thereof. The cells may be juxtaposed if the theoretical focus 402 is linear or spaced if the theoretical focus 402 is a point focus. The concentrated luminous rays are converted to electricity by the cells while the heat absorbed by the cells from the infrared rays is removed by the circulating fluid 404 and also by the fluid 406 circulating within the outer ~onduit 40~. The removal of heat can be ~ontrolled ~y the size of the conduits 402, 406 and by the volume and rate at which the fluid are circulated. Preferably fluid 404 is substantially electrically non-conductive such as air or other g~ses and liquids. Means (not shown) are provided for connecting the cells in parallel or series and for removins the generated electricity. If fluid 404 is 1~7~7~

is electrically conducting, means (not shown) are provided for electrically insulating the cells and the means for interconnecting the cells and for removing the generated electricity. Conduit 402 has at least its upper surface made of transparent material if the theoretical focus 402 is linear or transparent apertures may be provided above the cells if the theoretical focus 402 is at a point.
~he upper part of outer conduit 408 is also transparent.
The details of inner and outer conduits have b en described hereinbefoxe.
As mentioned hereinbefore, in accordance with the invention, concentrating the luminous energy of the sun with a concentration of up to about 100 permits electricity to be generated at up to about 100 times more power while the increased heat energy is dissipated and removed by the fluids in the conduits. Electricity may be qenerated in conjunction with other uses of ~olar energy. For example, referring to FIG. 1, using a dual fluid carrying collector, photovoltaic cells may be inserted therein as just described and electricity generated while the heat energy is being used to heat a structure.
Prominent aspects and advantages of the invention may be summarized as follows:
A lens concentration ~ystem is combined with a conduit collector 6ystem in which the surface area of the concentrating sy tem exposed to the sun is from about 10 to about 100 times larger than the surface area of the collecting syst~ through which the energy i~ concentrated. As a result heat losses are reduced ~ubstantially fiince the collector has an area of, for example, only from about 1%

~Lil7~7~) to about 10~ of oonventional flat plate collector systems and the overall surface area is about half that of conventional flat plate systems. Thus, the efficiency over conventicnal flat plate systems is in the order of about 50~ higher.
This reduction in surfacearea reduces correspondingly the material requirements per unit of surface area exposed to the sun and the investment cost is also reduced correspondingly by about one-half.
More solar energy can be collected by the method and apparatus according to the invention since the collector conduits are oriented e~st-west thereby being located at the foci of the lenses throughout the day and, according to the invention, the lenses can be moved and positioned at various inclinations to optimally follow the seasonable location of the sun. This positioning of the lenses can represent up to 504 higher solar energy collection. Even using auxiliary equipment to adjust the inclination of the lenses, the reduction in investment is in the order of a third over flat panel systems. Not only is the investment cost ~uch less than known solar systems, but the operating costs of obtaining heat energy is lower. Also the cost of heat derived from solar energy according to the invention is lower and may be up to one-third lower than the cost of petroleum fuels bhsed on the usable heat content. This is of great importance to oil importing countries. Additionally, solar e~ergy is ~nexhaustable and does not produce pollution as does the burning of other fuels.

1~7~7~

According to the invention, by concentrat-ing the solar energy at elongated conduits, higher temperatures, for example, exceeding 200~C (392F) are attainable using high boiling temperature ~luids in the conduits such as lubricating oil, glycerine, etc. This is to be compared with to about 80C
(176DF) attainable by flat plate systems~ Accord-ing to the invention, multiple conduits, either con-duit receiving the foci of the lenses, and the higher temperatures attainable allow storing solar hea~ to be used for hours without sunshine. The in-vention provides for storage of heated fluids in the inner conduit at high temperature, for example, over 200C which heats the outside fluid to lower temperatures, for example, 80C. Using this arrange-ment permits a reduction in storage volume re~uired by the higher temperature fluid over fluids at about 80C. For example, for the same fluid, 2-1/2 ti~es less space is required to store the same heat at 200C
than at 80C. According to the invention, low boil-ing point and low latent heat of vaporization fluids such as freon, ether, etc. are used in the conduits which fluids are vaporized and superheated by the solar energy and used to produce electricity in ex-pansion motors such as turbines at lower cost thanusing fuel.
Electricity may also be produced according to the invention with photovoltaic cells where the increased solar energy concentration of up to 100 times i~creases substantially the electric produc-1~17C!7~) tion and correspondingly reduces the cost of elec-tricity. Several circulating 1uids in several con-duits are employed to remove the heat developed by the concentrated infrared solar rays. The present invention has the advantage of generating electric-ity, producing heat simultaneously or separately and storinq heat and is useful in many applications, thus increasing system efficiency, utilization and amortizing the cost of the system.
Employin~ several fluids according to the invention permits simultaneous use for many purposes such as heating water, heating buildings, air con-ditioning, producing electricity, etc.
An advantaoe of the present invention is that diffuse sun energy of up to about 50~ can be collected.
Further according to the invention water containing salt or other substances is distilled using solar energy collection and concentration ac-cording to the invention and recovering a large partof the latent heat of vaporization and sensible heat (about 1100 BUT/lb or 600 cal/kg). This is accom-plished by using the fluid circulating in the lens system to recover the latent heat and circulating the fluid in tbe conduit in the water to be distilled thereby heating the water to be distilled. The ~alt from the ~oncentrated brine may also be recov-ered and sold or electrolyzed. Distillation accord-ing to the invention is at low cost such that water may be produced for irrig~tion purposes. me inven-1~7~!7~

tion provides for portable dismountable distilla-tion units which could be used to distill sea water in life boats or brackish water in arid desert areas t~ereby possi~ly saving lives.
While specific applications of the inven-tion have been described, many are uses of the col-lected solar energy are possible. For example, the salt by-product of desalination may be collected and sold to reduce the over-all operating cost of the system. Additionally, the salt may be separated in-to sodium and chlorine by electrolysis by electric-ity generated by the solar energy collecting system.
In this respect, water can be separated into hydrogen and oxygen also by electrolysis, the hydrogen of which in turn may be used in the manufacture of liquid meth-anol which is easily transported and may be used as fuel for automobiles, airplanes, etc. The system described hereinbefore could be combined with known heat pumps to further utilize the collected solar en-erby in combination with the heat provided by theheat pumps, particularly for refrigeration systems.
In addition to providing energy for heating, the sys-tems according to the invention could be used for air conditioning and, as just mentioned, in refrigera-tion systems. Also, the multi-conduit collectors and fluids are capable of providing temperatures of about 70C to about 80C for heating rooms and for heating water, and at higher temperatures, for example, about 180C to about 200C, for heat ~torage applications and to produce electricity.

7~7~) The apparatus according to the invention has been described primarily using schematic diagramS.
Accordingly, certain details not essential to an un-derstanding of the invention have been omitted. For example, the materials and support structure com-prising the apparatus according to the invention 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. In a two conduit collector system, where the inner fluid is lubricat-ing oil heated to about 200C, the space required to store an equal amount of heat will be about 2-1~2 times less than for a fluid such as water heated to 80C. Also, the multiple conduit system permits multiple uses for the heats of the different fluids.
~or example, a fluid heated to about 200C may be used to heat buildings and a fluid heated to about 70C to 80C may be used for heating water. Portable distillation units may be used, for example, as men-tioned hereinbefore, in lifeboats to distill sea water or in desert areas to distill brackish water and thereby possibly save lives. Portable units ac-cording to the invention could produce, for example, one pound of distilled water for every square meter labout 10 square feet) of lens concentrator area ex-posed to the sun's rays, and this without recapturing the heat of condensation. The production of distilled water, however, will be about six times as great if the heat of condensation is recovered.

~17~7~

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. Heat storage provided by systems according to the inven-tion is a feature which also makes these systems com-petitive with fuels. The distillation systems accord-ing to the invention are capable of providing dis-tilled water at low cost and therefore are important where clean water is scarce.
The advantagesof the present invention, as well as certain changes and modifications of the dis-closed embodiments thereof, will be readily apparent to those skilled in the art. It is the applicant's intention to cover by their claims all those changes and modifications which could be made to the embodi-ments of the invention herein chosen for the purposes of the disclosure without departing from the spirit and scope of the invention.
This application is a division of Canadian application No. 282,211, filed July 7, 1977.

Claims (15)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Apparatus for distilling liquids including water using solar energy, comprising container means for holding liquid to be distilled, an elongated fluid lens for concentrat-ing solar energy in said container means, said fluid lens hav-ing upper and lower solar energy-transmitting lens plates and a solar energy-transmitting fluid enclosed by said lens plates and means for admitting fluid to and withdrawing fluid from said fluid lens, such that said fluid can be passed through said fluid lens, said fluid lens being disposed above said container means and positioned such that rising evaporated liquid from said container means impinges upon said lower lens plate and is condensed thereon, said lower lens plate being operative to transmit at least in part the heat of condensation released by evaporated liquid condensing thereon to said fluid in said lens, and said fluid being operative to absorb at least in part the heat transmitted by said lower lens plate, said fluid lens be-ing inclined with respect to the horizontal such that condensed liquid flows along said lower lens plate to a vertically lower portion thereof and is discharged therefrom, and liquid collect-ing means disposed below said lower portion of said lower lens plate for collecting condensed liquid discharged from said lower portion.

2. The apparatus of claim 1 and including means for removing heat absorbed in said fluid which is passed through said fluid lens.

3. The apparatus of claim 1 and 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 said liquid to be distilled.

4. The apparatus of claim 3, wherein the liquid to be distilled is water.

5. The apparatus of claim 1 and further compris-ing elongated solar energy collector means comprising a plurality of elongated conduits through each of which a fluid can be passed, said conduits being disposed in said container means along parallel axes which are substantially parallel to the elongated axis of said lens means, an inner of said con-duits being disposed within an outer of said conduits and said line being located in or on one of said inner and outer con-duits.

6. The apparatus of claim 5, wherein said outer conduit is solar energy transmitting at least in part and is adapted to pass concentrated solar energy therethrough such that said line is located within said outer conduit.

7. The apparatus of claim 5, wherein said inner conduit and said outer conduit are solar energy transmitting at least in part, said solar energy-transmitting parts of said inner and outer conduits being aligned and being adapted to pass concentrated solar energy therethrough such that said line is located within said inner conduit.

8. The apparatus of claim 5 and further compris-ing means for communicating the interior of said fluid lens with one of said inner and outer conduits.

9. The apparatus of claim 4, wherein said con-tainer means comprises a first container for containing the water to be distilled and wherein said water collecting means comprises a second container.

10. The apparatus of claim 9 and further compris-ing means for adding water to be distilled to said first con-tainer 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 said means for re-moving water comprising means for automatically maintaining the level of water in said second container between predeter-mined limits.

11. The apparatus of claim 9, wherein said appa-ratus comprises a plurality of apparatus including a plura-lity of first containers, a plurality of second containers and a plurality of lens means arranged in a parallel manner, adjacent first containers being separated by a second con-tainer which is common to adjacent apparatus.

12. The apparatus of claim 9 and further compris-ing insulating means for enclosedly insulating the volume between said first and second containers and said lens means.

13. The apparatus of claim 9 and further compris-ing portable means for easily assembling and disassembling said apparatus for distilling water portably.

14. The apparatus of claim 1, wherein said fluid lens comprises a plurality of lenses juxtaposed about a radial axis of said apparatus.

15. The apparatus of claim 1, wherein said fluid lens comprises a plurality of lenses juxtaposed along a longi-tidinal axis of said apparatus.