Note: Descriptions are shown in the official language in which they were submitted.
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
': '
-4- -
~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
. .
-5-
.
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
~;
-7-
. ~
~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
.
-8-
~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;
--10--
~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
-11-
' .'';
~ , ,
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
-12-
~(~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
.
-16-
~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 ~ ;;
-17-
:
- - : . ... .. . .. ... ..
~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.
-18-
. . . . : .-.; . . . .. .
~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- `
:~
19
.. , .. . .,. - - . . . . . ~ .. , , ... . - - .
~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
"
-20-
790
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,
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~(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
-22-
. ~ ~ . - - , .
10847910
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
. .
. .
-24-
.
.
~)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
-25-
~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
~ ~ .
-26-
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-
30-
. ~ :
. , : : .. . ~ . .
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-
-31-
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.
: ' ~
-33-
:~:
.. . . . .. . . . . . .. .. . , - .. :: -
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.
' '
. .
'.; '' '
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- , , ~
