CA1084790A

CA1084790A - Economic solar energy concentration and collection

Info

Publication number: CA1084790A
Application number: CA282,211A
Authority: CA
Inventors: Virgil Stark; Alexandre Vayda; Paul Rousset
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-07-09
Filing date: 1977-07-07
Publication date: 1980-09-02
Also published as: CH626159A5; ES473531A1; GB1590842A; JPS577332B2; GB1590841A; JPS5334148A; ES460584A1; IL52482A; GB1590843A; ES473530A1

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

7~1~

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/or electrical energy ~o be used for many pur-5 poses. The present invention also relates to the storage ;
and use of heat energy during hours without sun or with reduced sun. The present invention further relates to the treatment of water containing salt and/or other substances using fixed and portable apparatus and methods according to the invention. More particularly, the invention relates to 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.
}t is well known that surfaces exposed to the sun collect at leas~ to some degree the solar radiation and that the absorption of this radiation results in a heating of the ;~
m(at~ial constituting the surface. It is also known that electricity can be produced by photoelectric devices exposed 25 to the sun's raysO `~
There have been many attempts in the past to collect and utilize pollution-free and essentially non-. ~ "~
consumable solar ener~y to meet many energy needs. Muchattention has been directed to the conversion and utilization of solar energy in the past few years because of the realization -3~

~0~34~9() that fossil fuels are exhaustable and that a burning of these fuels produces pollution. Solar energy, on the othex hand, is inexhaustable and available above the clouds at an average energy level of approximately 1350 watts per 5 horizontal square me~er. 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 10 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, ~uels are still a lesser expensive source of energy and the same problems of ;
high capital cost and the cyclic nature of the sun requiring ~`
storage capability have still not been satisfactoriIy solved. For example, refringent lens focusing systems, most using reflecting collectors and most including sun-tracking 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 80C 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. It is also known to improve the efficiency of these 25 systems by placing one or more glass plates above the panels -to produce a greenhouse effect for reducing heat losses.
However, the efficiency of these~panel systems is lowl from about 30% to about 40~, and they require large spaces resulting in large heat losses, and they also require a high capital inves~ment. The use o Fresnel-type lenses ': ' ~0134791D

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; 1,081,098; Japanese Patent No. 28-2130, and Australian Patent No. 131,069.
However, none of the known systems is capable o~ 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. ~he prior art also does not disclose obtaining temp~ratures in 10 the order of a few hundred degrees C while also obtaining ~ ;
at the same time 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 periodsof interrupted solar energy `
for any length of time and which also is capable of pro-viding diferent 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; howeverl there is the disadvantage that the increased heat in the photo-voltaic cell resulting from the concentration will also limit the cell output. Known photovoltaic devices produce a ~aximum of about one watt per hour per cell. Assuming a cost of $10 ~5 per photovoltaic cell, a system using non-concentrated solar energy to generate about 1 kilowatt per hour requires a ~-capital cost of at least $10,000 which is not competitive for normal uses.
With respect to solar stills, known stills used for distillation of seawater have low efficiencies and the . .

.

7~

cost of heating the water is high 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 art drawbacks and disadvantages are substantially overcome and additional advantages realized.
~ he present invention relates to methods and apparatus for concentrating, collecting, storing and utilizing solar energy. In accordance with the invention, refringent lens means concentrate the solar energy along a length at elongated collector means containing at least one fluid therein. Further in accordance wi~h the invention, the lens means comprise economical fluid or Fresnal-type lenses and lens systems which focus the solar energy substantially along the length at the collector means along substantially continuous lines or in lines of substantially discrete points. Thus, the at least one 1uid in the elongated collector may be efficiently heated to high temperatures in the order of a few hundred degrees C. The 1uid 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 similar to ~lass or plastic bottles. The fluid within the lenses preferably has an index of refraation similar to that of lens plates. The enclosure in the lens containing the fluid is advantageously communicated with the collector means to enhance performance.
Still further in accordance with the inventionj -the elongated collector means comprises a plurality of fluids, adiacent ones of which are contiguous. The fluids . .

. . .. - , . : ~ ~

~8~1790 are preferably isolated and disposed in adjacent conduits and the fluids preferably differ and have varying boiling points. The theoretical ocus or foci of the lens means are preferably on the surface of or within the hi~her or highest boiling point liquid. In a preferred embodiment, 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 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 daxkened depending on the location of the lens means focus. By solar energy trans-mitting it is meant that the solar rays are substantially transmitted 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 assists in providing different temperatures which may be utilized for different purposes. ~rrangement of multiple conduits carrying multiple 1uids in accordance with the invention can provide energy for many different uses including a vapor and super-heated vapor for mechanical devices including turbines. Advantageously, the lower boiliny 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 periods of solar energy to a temperature substantially higher than that of the lower ~;

. ~

~01514~90 " . ~

boiling point fluid which may be used as a working ~luid.
Heat is removed from the higher boiling temperature fluid by, for example, circulating the lower boiling point fluid 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 posslble.
Still further in accordance with the invention, both the infrared and luminous rays of the sun may be 10 simultaneously utilized. Photoelectric cells specifically ; `~
photovoltaic cells, can be disposed at the collector means such ~hat 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 khat 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 invention liquids, particularly water, may be distilled by locating the collector means in the liquid to be distilled, above which is positioned lens means and a downwardly sloping substantially smooth, preferably planar surface, whereby liquid is evaporated and condenses on the smooth surface which carries the condensed liquid to a collecting vessel ; positioned below 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 .

~B4795~

being located directly in khe liquid. Means are provided to completely enclose the apparatus while permitting move-ment of the lens or the entire system to track the sun seasonally or daily. It is prefsrred that the lens system for the liquid distilling apparatus comprise fluid lens means which include said smooth surface and in which the solar energy transmitting fluid forming part of the lens ~ ;~
means is circulated within the collector means to advan-tageously utilize 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 quantlty o~ 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 ~rom the ~ale thereo~ to lower the overall cost of obtaining distilled water. ~ccording to one embodiment o ~0- the invention, the still is portable and is easily assembled and disassembled. Ad~antageously, the stills are operative to distill seawater and brackish water and may be used at sea, for example, on life boats, and in desert areas.
The apparatus may be enclosed according to the invention to reduce heat losses and form enclosed systems.
Apparatus according to the invetnion can advan-tageously be combined with a con~entional heat pump producing and storing additional heat from the surroundin~ air or ~-water. This may be particularly significant during winter months when lower sun energy is av~ilable and there is more `~ :
_9~

~0~4~0 consurnption of energy for heating.
These and other aspects of the presenk 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 o 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 FIG. 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-communicating the enclosure of the lens with other lenses, this arrangement being utilizable to arrange a plurality of longitudinally juxtaposed lenses where single lens is now shown;
FIG. 3 is a perspective view of a lens system according 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 is~a cross-section view of the lens and :
frame of FIG. 3 taken along line 4-4;

~0~47~0 FIG. 5 is a schematic perspective diagram similar to that of FIG. 1 showing another system according to the -~
invention in which the system is enclosed, the single lens is movable to follow the seasonal location of the sun and :~
5 in which the collector comprises a single fluid-carrying ~;
conduit;
FIG. 6 is a schematic perspective diagram showiny another system according to the invention comprising an elongated, planar Fresnel.-type lens having a linear focus 10 and a collector comprising three fluid-carrying conduits.
in which an outer 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 conduitj FIG. ~ is a schematic perspective diagram showing yet another system according to the invention comprising an elongated curvilinear Fresnel-type lens and a collector comprising a single rectangular fluid-carrying conduit;
.FIG. 9 is a schematic perspective dia~ram of a composite system according to the invention for distilling water comprising individual systems each comprising two .
Z5 elongated fluld lenses and a collector located in the water :
to be distilled comprising two fluid-carrying conduits, one enclosed in the other; ~ .
FIG. 10 is a schematic perspective diagram o~ an-other system according:to the invention ~or distilling water comprising a single elongated fluid lens and a ' .'';
~ , , 9o collector comprising a single fluid-carrying conauit;
FIG. 11 is a schematic perspective diagram of a portable easily assembled and disassembled system having Fresnel lenses for distilling water according to the invention; and FIG. 12 is a cross-section view of a photoelectric cell positioned in a fluid-carrying conduit to produce electricity from solar energy according to the invention with fluid circulating inside and/or outside the conauit to remove heat.
In FIG. 1 is shown a solar energy collecting system comprising a refringent fluid lens concentrator and a 1uid-con-tainin~ olar ~energy~coll~Gtor. System 20 comprises an elongated fluid lens concentrator ~2 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 energy transmitting fluid 31. In the embodiment shown in FIG. 1, upper lens plate 26 is convex and lower plate 28 is planar. The respective sides 32, 34 o~ lens plates 2~, 28 and the ends of the lens plates ~not shown in FIG. 1) are sealed to be ~luid-tlght in manners which will be described hereinafter. Alternatively, means not shown in FIG. 1 for adding and removing or circulating fluid 31 and air are provided in the sides and/or ends of the lens plates.
Additionally, means also not shown in FIG. 1 for longitudinally and transversely (radially) juxtaposing lenses may be provided and will also be described hereinafter. In the embodiment shown in FIG. 1, collector 24 comprises an outer -elongated conduit 36 enclosing an inner elongated conduit ~(~847~g~

38, both shown ~o be kubular in shape. Conduit 36 is placed in insulating container 40 and is surrounded by insulating material 42 except for a longitudinally extending opening 44 located above conduit 36. Opening 44 is closed off by 5 solar energy transmitting and heat insulating plate 46.
Plate 46 is suitably made of glass or plastic and the insulating material 42 is suitably a ~oam such as poly-ethylene foam. Collector 24 is located below lens 22 and the theoretical linear focus 48 is located at or along the 10 collector for substantially all of the daylight hours.
The space between the lens and collector is enclosed by side panels 50 which if rigid can also serve to support ?
lens 22 and fxame 30 in cooperation with support member 52.
For optimum concentration of solar energy at collector 24, 15 lens 22 is oriented at a preselected angle A with the horizontal, the longitudinal axis o 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 (nor~hern hemisphere). The optimum value for angle A depends upon 20 the location o 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 solar energy concentration or for optimum concentration for even shorter 25 periods of time.
As mentioned hereinbefore, the collector 24 is located at the theoretical focus 48 of the lens 22 and in ;~
the embodiment o FIG. 1, conduits 36 and 38 are solar energy transmitting, the theoretical focus 48 being located within the inner conduit 38. Conduits 36 and 38 contain . : . .
.: ', " ,' -13- ~
'.,: , ~';
- . -. ... . ,. . ,, ,. . , , : . ~

~ 34~ 0 heat-carrying fluids 54 and 56, respectively. Since the concentration of the solar energy will be greatest in the fluid within the conduit at which the lens theoretical focus is located, i.e., in fluid 56 within conduit 38, fluid 56 may be heated to a relatively high temperature and : is therefore chosen to have a relatively high ~oiling point, for example, ~rom about 150C to about 350C. Such fluids ~ `
may comprise by way of example and not limitation lubricating :
oils, glycerine, olive oil, para~fin 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 factorssuch as the flow rate of fluids 54, 56, the diameters 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 vaporiæation, 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 limitation freon, butane, propane, ammonia, ethyl ether, methyl alcohol, etc.
:` In operation, solar energy is concentrated in fluid ~.
56 (chosen to be lubricating oil) within conduit 38 and raises the temperature of the oil to about 200C. Since the focus to lens 22 is theoretically linear, fluid 56 will be con-tinually heated as it traverses the linear focus. Fluid 54 .

-14- :

'791D

~chosen to he 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 at predetermined rates to obtain desired temperatures and may be used for different heat applications. For example, the water may be heated to about 70C - 80C or more and used for space and hot water heating. The 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 di~ferent tem-perakures 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,~luids such as ~reonl butane, propane, ethyl ether, methyl alcohol, ammonia and the like may cons~itute ~luid 54.
As mentioned hereinbefore, a serious drawback of solar energy systems in general and known systems in 25 particular relates to the storage o~ energy during periods -in which there is no sunshine or the lntensity thereof is ~
low, as for example during the night or during periods of ~-cloudy weather. In accordance with the present invention, heat is stored ~or use in those periods in fluid 56 which is heated during normal system operation to a temperature ,; . ,., ~ , . . . .

~0847~0 ~

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 difference 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 invention, 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 preferred. For example, referring to FIG. lA, collector 25 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 as shown in FIG. 1. Providing a rectangular shape will allow movement of focus 48 while still maintaining it at conduit 59. Focus 48 has been shown on .

~8~q9~ .

the surface of conduit 49, and in such a case, the surface of conduit 49 need not be solar energy transmittiny 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 o~ the solar energy will be at the conduit containing fluid 56.
It is to be understood that the systems shown in the remaining igures 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 summer) of 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 movable 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. The refringent lenses according to the invention are operative to also concentrate difuse solar energy which may represent 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 be understood that many lenses may be 25 longitudinally and radially juxtaposed. Use of many lenses ;~
results in a system with a high degree of solar energy concentration which is achieved quite economically.
\ In the embodiment shown in FIG. 1, heating `
I is accomplished by heat exchange between fluids 54 and 56 with- -out the necessity of an external heat exchanger which reduces ~ ;;

:
- - : . ... .. . .. ... ..

~47~0 heat losses. Side panels 50 which are made o~ an insulating material further reduce heat losses. Additionally, plate 46 provides a greenhouse effect in the collectors to further reduce heat losses. Collector 24 is also preferably made o~ 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 transparent 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 concentrators, thus reducing the heat losses accordingly. As less material is re~uired in the collector, the cost will be reduced.
~ will be more apparent hereinafter, the collector systems may comprise a number of conduits 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 25 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, -~ 30 the lens may be extruded with the sides integrally joined.

. . . . : .-.; . . . .. .

~o~ o The ends of the lenses may similarly be welded or extruded or formed from a bulb o~ glass or plastic as by blowing as, for example, in the manufacture of glass or plastic bottles.
The lens shown in FIG 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. ~ -~s 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 FIGS. 3 and 4, upper curvilinear plate 26 and lower planar plate 28 are separate pieces and are joined in a ~luid-tight manner by means of ~rame 104. Frame 104 comprises two longitudinal grooves 106, 108. The upper groove 106 is curvilinear and sized to accommodate upper curvilinear plate 26 while the ~; `
lower ~roove is linear and sized to accommodate planar plate 28. The edges of the respective separate plates are in-serted into the respective grooves along with sealing ` -,~
material 110. The ends of the plates are similarly joined.
The material 110 may comprise a gasket or similar flexible piece and/or deformable material such as silicone to form -; 30 fluid-tight joints. Thus, the lenses according to the in- `
:~

.. , .. . .,. - - . . . . . ~ .. , , ... . - - .

~VB~ 9~

vention in which two independent pla~es are joined or the lenses are exkruded or blown, are relativel~ eas~ 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 shown comprising a single tubular inner conduit in which the focus 120 is located.
Description of preferred embodiments of the invention has been made hereinbefore with reerence to linear theoretical focus fluid lenses. However, in accordance with the invention, the solar energy may be concentrated by focal point lenses. In FIG. ll is shown a plane refringent element 126 comprising a rigid frame surrounding a sheet or plate of plastic or glass material in which are formed by impressions or molding concentric closely spaced rings o~ microprisms whose pitch, for example, corresponds to about 3 to about 6 microprisms per millimeter. The plane =- 30 refringent element 126 acts like a plane Fresnel lens. Solar "

energy striking the reEringent element 126 is concentrated by the microprisms into a theoretical point focus. Refringent eLements 126 may be positioned longitudinally juxtaposed and/or radially juxtaposed. The system may be arranged 5 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 ~orming, in effect, a linear focus composed of dis- ;
crete point foci, or as shown in FIG.lI in a liquid being ;
10 distilled.
System 130 of FIGo 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. Pro~iding three conduits permits use of three diferent fluids and allows ~or use of the fluids at varying temperatures or many di~eren~ applications.
FIG. 7 shows another arrangement Eor three conduits in which the inner conduit 139 i9 enclosed by intermediate conduit 141 which in turn is 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 collector lS0 depending upon the seasonal location ;
: ` `
o the sun. Collector 150 is located eask-west so it is oriented to collect solar~energy during daily movement of the sun, and comprises a single solar energy transmitting, ~(18479V

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 lS0 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 and insulating material 42 into overlapping engage-~ent. 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 reracting the rays of the sun, the micro-prisms also provide reflection o rays such as 156. The inside sides of element 146 may also be suitably angled -and made reflective to reflect any rays impinging thereon L5 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. Typically, the liquid is water and the water is seawater or brackish water and is to be d~salinated, or water containing minerals or other substances such as industrial waste water or polluted water which is to be purified and distilled. Further in accordance with the invention, 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.
The system 160 shown in FIG. 9 comprises a plurality of sub-systems 162, each employing a two lens . ~ ~ . - - , .

arrangement 164. Each lens pair 164 is supported above an elongated, central, rectangularly configured channel 166 and parallel, elongated rec~anyularly configured, side channels 168 such that the central part of the pair of S lenses is above the central channels and the outer ~
longitudinal 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 10 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. ~. The ocus 64 of the lens pair 164 is located within inner conduit 38. Pre-15 ferably, the interior of lenses 22 is communicated with `
collector 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 1uid in the inner conduit 38 is a higher boiling point fluid as described hereinbe~ore. In operation, the water 170 to be distilled i9 heated by collector 172 due to the solar energy ' concentrated thereat and the water 170 is vaporized. The vapor strikes the lower plates 28, is condensed thereon and flows therealong to be discharged at or dropped from the edges thereof into side channel I68. In accordance with the ~-invention, the water in the fluid lenses is circulated through collector 172. In this way, the heat released by condensation of the vapor is transmitted through the plate -~30 28 to the water in the lenses and the heat absorbed by the .

o 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 539 calories per liter (975 BTU per kilogram) in addition to the sensible heat is substantially returned to the system by the circulated water in the lense6 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 which 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 10at 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 9: ' .' may be used in side channels 168 or a gravitational drain arrangement may be employed to maintain ~he height of distilled water in the side channels between predetermined heights. The respective channels are communicated to provide approximately e~ual levels in each o the respective channels. Advan~
tageously, the channels are made o concrete or asbestos cement. 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 the latent heat unless the plate is proximate thereto. Alternatively, means associated . .
. .

.
.

~)8~9~ ~:
,, ~' "
with the plate may be used to recover the latent heat.
The system shown in FIG. 9 is substantially : : -enclosed by the c~el panels to reduce heat loss as ,.. . .
described hereinbefore. The two-conduit collector 172 is 5 particularly advantageous since the fluid in the inner ;~
.
conduit 38 may be raised to a high temperature and used to stare heat as described hereinbefore. This adds a very important capability to the system in that it can operate during the night and during periods o~ reduced sunshine. This is very important in that it provides the advantage of substantially continuous operation resulting in increased system output at reduced cost. The recovery of the lat~nt heat of the condensing vapor by the lens fluid assists in providing a continuous operation system 15 since heat losses are reduced. ;~
In FIG. 10, a single lens system, single conduit .; : , .
system 196 is shown which is similar to those described hereinbe~ore. The adjacent channels 198, 200 for the water 170 to be distLlled and the distilled water, respectively are trough-shaped and may advantageousLy be formed from~adj~cent plates. The 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 to . .
; track the sun. An expandable material, as dbscr~` for FIG. 5, forms the side panels of each compartment of such a system. Ad~antageously, the material is of plastic.
In FIG. 11 is shown an embodiment of a portabIe 3Q water distillation system 330 which is easily assembled and ~0 !3479~

disassembled. System 330 comprises planar Fresnel lenses 126 having concentric microprisms causing the solar energy to be concentrated at point foci. Lenses 126 are longitudinally and transversely juxtaposed to form a com-posite lens assembly of six Fresnel lenses which is inclinedwith respect ko the horizontal, six being chosen ~or purposes of illustration. The lenses are formed into an assembly by, for example, securin~ them as by adhesives to a solar energy transmitting glass or plastic plate 332 which, in the case of plastic, may be folded along 1exible partition lines 334~ Each Fresnel lens may be about 9 inahes by about 7 inches. The point foci of the lenses are located in the water to be distilled in ~lexible container or bag 336 made of plastic or other plyable material. Flexible container or bag 338 made o~ plastic or other flexible material located belo~ 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 i ; ~ -connected to frame 346 at one end and are secured at the othex end in indentations in platform 348, or the legs may be secured ~n the ground or otherwise 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 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. Means such as 3Q transparent tubes 322, 324 connected to the bottom o~ the ~ ~ .

108479~ ~ ~

containers are used to indicate water levels therein. The ~`
lens assembly, support assembly and containers are easily assembled and disassembled. The foci located in the water to be distilled in container 336 heat the water and cause 5 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 soIar energy is used to generate electricity lO by means of photoelectric cells. More particularly, the ~, luminous rays o the sun are concentrated on photovoltaic cells. Referring to FIG. 12, photovoltaîc cells 398 made of silicon or cadmium or other materials are disposed in the interior of inner fluid-carrying conduit 400 shown advan-tageously to be of rectangular cross-section. The theoretical ocus 402 of the lens is at the cells and preferably on the outer surface thereof. The cells may be juxtaposed if~the theor~tical focus 402 is linear or spaced if the theoretical foaus 402 is a point ocus. The concentrated luminous rays are converted to electricity by the cells while the heat absorbed by the cells rom the inrared rays is removed by the circulating fluid 404 and also by the fluid 406 circulating within the outer conduit 408. The removal of heat can be controlled by 25 the size of the conduits 402, 406 and by the volume and - , rate at which the fluid are circulated. PreferabIy 1uid ~
: :
404 is substantially eIectrically non-conductive such as air or other gases and liquids. Means (not shown) are provided for connecting the cells in parallel or series and for removing the generated electricity. If 1uid 404 is : , ~ -27-3L~)3~4L790 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 ~ .
5 made of transparent material if the theoretical ocus ~ .
402 is linear or transparent apertures may be provided above the cells if the theoretical focus 402 is at a point.
The upper part of outer conduit 408 is also transparent.
The details of inner and outer conduits have been describad .
hereinbefore.
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 15 increased heat energy is dissipated and removed by the fluids -in the conduits. Electricity may be generated ln conjunction ~ ~:
with other uses of solar eneryy. For example, referring to : FIG. l, 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: i .
A lens concentration system is combined with a ~ .
25 conduit collector system in which the surface area of the .;` :.. `
concentrating system exposed to the sun is from about 10 to about 100 times larger than the surface area of the collecting ~ .
system through which the energy is concentrated. As a result heat losses are reduced substantially since the ~ .
collector has an area of, for example, only from about 1%

-28- : :

o to about 10% oP conventional flat plate collector systems and the overall surface area is about half that of conventional flat plate systems. Thus, the efficiency over conventional `
flat plate systems is in the order of abo~t 50% higher.
This reduction in surface æea reduces correspondingly the material requirements per unit of surface area exposed to ~ ;-the sun and the inves~ment cost is also reduced correspondingly by about one-hal.
More solar energy can be coIlected by the method and apparatus according to the invention since the collector conduits are oriènted east-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 lS the sun. This positioning of ~he lenses can represent up to 50% 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 much less than;
known solar systems, but the operating costs of obtaining h~at energy is lower. Also the cost o~ heat derived from solar energy according to the lnvention is lower and may be up to one-third lower than the cost of petroleum fuels ;
.:
based on the usable heat content. This is of great importance to oil importing countries~ Additionally, solar energy is inexhaustable and does not produce pollution as does the burning of ather fuels.

:

. `

~ccording to the invention, by concentrat- .
ing -the solar energy at elongated conduits, higher temperatures, for example, exceeding 200C (392F) are attainable using high boiling temperature fluids in the conduits such as lubricating oil, glycerine, etc. This is to be compared with to about 80C
(176F) attainable by flat plate systems. Accord-ing to the invention, multiple conduits, either con-duit receiving the ~oci of the lenses, and the higher temperatures attainable allow storing solar heat to be used for hours without sunshine. The in- : :~
vention provides ~or storage of heated ~luids 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 s~rage volume required by the higher temperature fluid over fluids at about 80C. For example, for the same fluid, 2-1/2 times `
less space is required to store the same heat at 200C
20 than at 80C. ~ccording to the invention, low boil- :
ing point and low latent heat o~ vaporization flu.ids .
such as ~reon, 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 than using fuel.
Electricity may also be produced according to the invention with photovoltaic cells where the increased solar energy concentration of up to 100 times increases substantially the electric produc-. ~ :
. , : : .. . ~ . .

i(~8479D

tion and correspondingly reduces the cost o~ elec-tricity. Several circulating fluids in several con-duits are employed to remove the heat developed by ~
the concentrated infraredl solar rays. The present i;
invention has the advantage of generating electric-ity, producing heat simultaneously or separately and storing heat and is useful in many applications, ~ ~ ;
thus increasing system efficiency, utilization and .
amortizing the cost of the system.
Employing several fIuids according to the invention permits simultaneous use for many purposes such as heating water, heating buildings, air con-ditioning, producing electricity, etc.
An advantage of the present invention is that di~fuse sun ener~y 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-20 cording to the inventlon and recovering a large part ;
o~ the latent heat o~ vaporization and sensible heat ~about 1100 ~UT/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 ln the conduit in the water to be distilled thereby heating the water to be distilled. The salt from the concentrated 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 irrigation purposes. The inven-7~0 tion provides for portable dismountable distilla-tion units which could be used to distill sea water in life boats or brackish water in ari~ desert areas thereby possibly 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 10 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 15 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 descri.bed hereinbefore could be combined with known heat pumps to further utilize the collected solar en- :
erby in combination with the heat provided by the heat pumps, particularly for refrigeration systems.
In addition to providing ener~y for heating, the sys-tems according to the invention could be used for air conditioning and, as just mentioned, in refrigera- .
25 tion systems. Also, the multi-conduit collectors and ~ :
fluids are capable of providing temperatures o~ about .:
70C to about 80C for heating rooms and for heating water, and at higher temperatures, for example, about ~ :
I80C to about 200C, for heat storage applications ~ ~
30 and to produce electricity. :

-32~

;~:

~L~)84790 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 - 5 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.
For 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 producer for example, one pound of distilled water for every square meter (about 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.

: ' ~

:~:

.. . . . .. . . . . . .. .. . , - .. :: -17gl~ :

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 5 storage provided by systems according to the inven- , tion is a feature which also makes the'se 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 ~
10 where clean water i5 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 cha'nges 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.

' ' . .

'.; '' ' -34- ' - , , ~

Claims

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

1. Apparatus for collecting solar energy comprising collector means including at least two elongated conduits adapted to pass fluids therethrough, said conduits having substantially parallel axes and being disposed so that an inner first of said conduits adapted to pass a fluid there-through is enclosed by an outermost conduit adapted to pass a fluid therethrough with the fluids in said inner and outer-most conduits being in a heat exchanging relationship, said inner and outermost conduits being transparent at least in part, said apparatus further comprising elongated lens means having an axis extending substantially parallel to said axes of said conduits and being disposed to concentrate solar energy through transparent portions of said inner and outermost con-duits to an elongated focus located substantially on or within and substantially along the length of said inner conduit.

2. The apparatus of claim 1, wherein said lens means comprises a plurality of longitudinally disposed point focus lenses for concentrating the solar energy in substantially discrete points.

3. The apparatus of claim 1, wherein said lens means include at least one fluid lens which comprises a solar energy transmitting lens fluid and spaced, solar energy-transmitting lens plates enclosing said lens fluid, said lens fluid and said lens plates being selected to transmit therethrough substantially undiminished the infrared solar energy.

4. The apparatus of claim 3 and further comprising means for connecting said fluid lens with one of said inner and outermost conduits for transmitting said solar energy transmitting fluid between said lens and one of said inner and outermost conduits.

5. The apparatus of claim 1, wherein said lens means comprises at least one Fresnel lens.

6. The apparatus of claim 1, wherein said lens means comprises a plurality of lenses positioned along the axis of said lens means.

7. The apparatus of claim 1, wherein said lens means comprises a plurality of lenses positioned along an arcuate axis tranverse to the axis of said lens means.

8. The apparatus of claim 1, wherein said inner and outermost conduits are substantially tubular.

9. The apparatus of claim 1, wherein at least one of said inner and outermost conduits is rectangular at least in part.

10. The apparatus as recited in claim 1, and including the fluids which are passed through said inner and outermost conduits.

11. The apparatus as recited in claim 10, wherein the fluids are different.

12. The apparatus of claim 11, wherein the fluid within said inner conduit has a higher boiling point than the fluid in said outermost conduit.

13. The apparatus of claim 12, wherein the boiling points of said two fluids are separated by more than 50° C.

14. The apparatus of claim 12, wherein the fluid hav-ing the higher boiling point has a boiling point in excess of about 150° C.

15. The apparatus of claim 14, wherein the fluid hav-ing the higher boiling point has a boiling point less than about 350° C.

16. The apparatus of claim 12, wherein the fluid hav-ing the higher boiling point comprises at least one fluid selected from the group consisting of lubricating oils, glycerine, olive oils, and paraffin oils.

17. The apparatus of claim 12, wherein the fluid hav-ing the lower boiling point has a boiling point not greater than about 100° C.

18. The apparatus of claim 17, wherein the fluid hav-ing the lower boiling point has a boiling point in excess of about -62° C.

19. The apparatus of claim 12, wherein the fluid hav-ing the lower boiling point has a low latent heat of vaporiza-tion.

20. The apparatus of claim 19, wherein said low heat of vaporization is from about 20 calories per kilogram to about 270 calories per kilogram.

21. The apparatus of claim 12, wherein the fluid hav-ing the lower boiling point comprises at least one fluid selected from the group consisting of water, Freon, butane, propane, ethyl ether, ammonia and methyl alcohol.

22. The apparatus of claim 20, wherein the fluid hav-ing the lower boiling point comprises at least one fluid selected from the group consisting of Freon, butane, propane, ethyl ether, ammonia and methyl alcohol.

23. The apparatus of claim 10, and comprising means for circulating said fluids through said inner and outermost conduits and for controlling the circulation of said fluids and for selectively stopping the circulation of at least one of said fluids in its respective conduit.

24. The apparatus of claim 1, and further comprising insulating means for insulating said apparatus against heat loss to its environment.

25. The apparatus of claim 1, and further comprising means for moving said lens means for maintaining said focus substantially on or within and substantially along said length to track the sun's position.

26. An elongated collector for converting concen-trated solar energy into heat energy comprising an elongated container including at least two elongated conduits adapted to pass fluids therethrough, said conduits and container having substantially parallel axes, said container having an elongated opening having an axis substantially parallel to that of the container, said conduits being disposed so that an inner first of said conduits adapted to pass a fluid therethrough is en-closed by an outermost conduit adapted to pass fluid therethrough with the fluids in said inner and outermost conduits being in a heat exchanging relationship, said inner and outermost conduits being transparent at least in part, said container including said elongated opening and transparent portions of said inner and outermost conduits being aligned to permit passage of solar energy through said opening and transparent portions, whereby an elongated focus of concentrated solar energy may be located substantially on or within and substantially along the length of said inner conduit.

27. The collector of claim 26, and further comprising insulating means for insulating said collector against heat loss to its environment.

28. The collector of claim 26, wherein said collector further comprises solar energy transmitting means enclosing at least part of said collector and permitting concentration of the solar energy on or within said inner conduit and inhibiting loss of heat from said collector.

29. The collector as recited in claim 26, and including the fluids which are passed through said inner and outermost conduits.

30. The collector as recited in claim 29, wherein the fluids are different.

31. The collector of claim 30, wherein the fluid within said inner conduit has a boiling point at least about 50° C.
higher than the boiling point of the fluid in said outermost conduit.

32. The collector of claim 31, wherein the fluid hav-ing the higher boiling point has a boiling point of from about 150° C. to about 350° C.

33. The collector of claim 31, wherein the fluid hav-ing the higher boiling point comprises at least one fluid selected from the group consisting of lubricating oils, glycerine, olive oils, and paraffin oils.

34. The collector of claim 31, wherein the fluid hav-ing the lower boiling point has a boiling point of from about -62° C. to about 100° C.

35. The collector of claim 31, wherein the fluid hav-ing the lower boiling point has a low latent heat of vaporiza-tion of from about 20 calories per kilogram to about 270 calories per kilogram.

36. The collector of claim 31, wherein the fluid hav-ing the lower boiling point comprises at least one fluid selected from the group consisting of water, Freon, butane propane, ethyl ether, ammonia and methyl alcohol.

37. The collector of claim 36, wherein the fluid hav-ing the lower boiling point comprises at least one fluid selected from the group consisting of Freon, butane, propane, ethyl ether, ammonia and methyl alcohol.

38. The collector of claim 26 and including means for circulating said fluids and for controlling the circulation of said fluids and for selectively stopping the flow of at least one of said fluids in said inner and outermost conduits.

39. A method for collecting solar energy comprising concentrating solar energy in a narrow elongated focus and locating said focus on or within and substantially along the length of a first elongated conduit which is transparent at least in part, contains a first fluid therein and is enclosed by a second elongated circuit which is also transparent at least in part and contains a second different fluid therein, the axes of the conduits and the focus being substantially parallel, the me-thod including the steps of placing the two fluids in a heat ex-changing relationship, selectively circulating the fluids in a heat exchanging relationship, selectively circulating the fluids through the conduits and concentrating the solar energy through the transparent portions of the conduits to said focus.

40. The method as recited in claim 39, wherein first and second different fluids are circulated through the first and second conduits, respectively.

41. The method of claim 40, wherein the boiling point of said first fluid is at least about 50° C. greater than that of said second fluid.

42. The method of claim 41, wherein said first fluid is permitted to rise in temperature to be at least about 50° C. above the temperature of said second fluid and heat is selectively transferred from said first fluid to said second fluid.

43. The method of claim 42, wherein the rate of circu-lation of said first fluid is selectively controlled to trans-fer heat to said second fluid.

44. The method of claim 41, wherein said focus is located within said first fluid and said first fluid has a boiling point of from about 150° C. to about 350° C.

45. The method of claim 44, wherein the boiling point of said second fluid is from about -62° C. to about 100° C.

46. The method of claim 45, wherein said second fluid has a low latent heat of vaporization of from about 20 to about 270 cal/kg.

47. Apparatus for collecting solar energy comprising collector means including at least two elongated conduits adapted to pass liquids therethrough, said conduits having substantially parallel axes and being disposed so that an inner first of said conduits adapted to pass a liquid therethrough is enclosed by an outermost conduit which is transparent at least in part and adapted to pass a liquid therethrough, the liquids in said inner and outermost conduits being in a heat exchanging relationship, the apparatus further comprising elongated lens means having an axis extending substantially parallel to the axes of said conduits and being disposed to concentrate solar energy through a transpa-rent portion of said outermost conduit to an elongated focus located substantially on and substantially along the length of said inner conduit.

48. The apparatus of claim 47, wherein said inner conduit is transparent at least in part, the elongated focus passing through a transparent portion of said inner conduit and being located substantially within and substantially along the length of said inner conduit.

49. The apparatus as recited in claim 47, and in-cluding the liquids which are passed through said inner and outermost conduits.

50. The apparatus as recited in claim 49, wherein a first liquid is passed through said inner conduit and a different second liquid is passed through said outer conduit.

51. The apparatus of claim 50, wherein said first liquid has a higher boiling point than said second liquid.

52. The apparatus of claim 50, wherein said first liquid has a boiling point of greater than about 150° C. and said second liquid has a boiling point of less than about 100° C.

53. The apparatus of claim 50, and including means for circulating said liquids and for controlling the circula-tion of said liquids and for selectively stopping the flow of at least one of said first and second liquids in said inner and outermost conduits.

54. An elongated collector for converting concen-trated solar energy into heat energy comprising an elongated container including at least two elongated conduits adapted to pass liquids therethrough, said conduits and container having substantially parallel axes, said container having an elongated opening having an axis substantially parallel to that of the container, said conduits being disposed so that an inner first of said conduits adapted to pass a liquid therethrough is enclosed by an outermost conduit which is transparent at least in part and is adapted to pass a liquid therethrough, the liquids in said inner and outermost conduits being in a heat exchanging relationship, said container including said elongated opening and transparent portion of said outermost conduit being aligned to permit passage of solar energy through said opening and trans-parent portion, whereby an elongated focus of concentrated solar energy may be located substantially on and substantially along the length of said inner conduit.

55. The apparatus of claim 54, wherein said inner conduit is transparent at least in part with a transparent portion thereof being aligned with said transparent portion of said outer-most conduit and said opening, whereby the elongated focus may be located substantially within and substantially along the length of said inner conduit.

56. The collector as recited in claim 54, and in-cluding the liquids which are passed through said inner and outermost conduits.

57. The collector as recited in claim 56, and com-prising the liquids which are passed through said inner and outermost conduits.

58. The collector of claim 56, wherein said first liquid has a higher boiling point than said second liquid.

59. The collector of claim 56, wherein said first liquid has a boiling point of greater than about 150° C. and said second liquid has a boiling point of less than about 100°
C.

60. The collector of claim 56 and including means for circulating said liquids and for controlling the circulation of said liquids and for selectively stopping the flow of at least one of said first and second liquids in said inner and outermost conduits.

61. A method for collecting solar energy comprising concentrating solar energy in a narrow elongated focus and locating the focus on and substantially along the length of a first elongated conduit containing a liquid therein enclosed by a second elongated conduit which is transparent at least in part and contains a liquid therein, the axes of the conduits and the focus being substantially parallel, the method in-cluding the steps of placing the liquids in a heat exchanging relationship, selectively circulating the liquids through the conduits and concentrating the solar energy through a transpa-rent portion of the second conduit to said focus.

62. The method of claim 61, wherein the inner con-duit is transparent at least in part and the elongated focus is passed through a transparent portion of the inner conduit and located substantially within and substantially along the length thereof.

63. The method as recited in claim 61, wherein first and second different liquids are circulated through the first and second conduits, respectively.

64. The method of claim 63, wherein said first liquid has a higher boiling point than said second liquid.

65. The method of claim 64, wherein said first liquid has a boiling point greater than about 150° C. and said second liquid has a boiling point of less than about 100° C.

66. The method of claim 61 and including the steps of regulating the flow of liquid in the inner and outermost con-duits and selectively stopping the flow of liquid in at least one of the inner and outermost conduits.