Note: Descriptions are shown in the official language in which they were submitted.
~ ~ ~t7~
The present invention relates to methods and
apparatus for concentrating and collecting solar energY
for many uses including the conversion thereof to heat
energy and/~r electrical energy to be used for many pur-
poses. The present invention also relates to the storageand use of heat energy during hours without Cun or with
reduced sun. The present invention further relates to the
treatment of water containing salt and/or other substances
using fixed and porta~le apparatus and methods according
to the invention. More particularly, the invention relates
.o methods and apparatus using fluid and/or Fresnel concen-
trating lenses and lens systems and elongated collectors
comprising at least one fluid-carrying conduit located at
the foci of the lenses.
The energy emitted by the sun corresponds to a
high temperature in the order of 6000C, and is emitted in
the form of radiation which arrives at the earth with a
wavelength distribution comprising about 3~ ultraviolet
rays, 42~ visible light rays, and about 55~ infrared rays.
It is well known that surfaces exposed to the sun collect
at least to some degree the solar radiation and that the
absorption of this radiation results in a heatin~ of the
m~at~rial c~nstituting the surface. It is also known that
electricity can be produced by photoelectric devices exposed
to the sun's rays. 7
There have been many attempts in the past to
collect and utilize pollution-free and essentially non-
consumable solar energy to meet many energy needs. Much
attention has been directed to the conversion ana utilization
of solar ener~y in the past few years because of the realizatlo
-3- ~
1~17~7~
that fossil fuels are exhaustable and that a burning of
these fuels produces pollution. Solar energy, on ~he other
hand, is inexhaustable and available above the clouds at
an average energy level of approxLmately 1350 watts per
horizontal square meter. A percentage of this energy,
depending on atmospheric and weather conditions, dust,
pollution, etc., is available at the surface of the earth
during periods of sunshine which vary up to about 4000 hours
per year depending on location. Even more recently, the
shortage of fossil fuels particularly oil and the high cost
thereof have sparked new attempts to harness the energy
of the sun. As in the past, however, fuels are still a
lesser expensive source of energy and the same problems of
high capital cost and the cyclic nature of the sun reguiring
storage capability have still not been satisfactorily
solved. For example, refringent lens focusing systems, most
using reflecting collectors and most including sun-trackinq
systems, have heretofore been used but are uneconomical and
impractical because of the high cost involved. A conventional
way for obtaining lower temperatures up to about 80CC con-
sists of using dark-colored panels which absorb the solar
radiation, and combining these panels with means circulating
a heat-carrying fluid in a heat-exchanging manner with the
panels. lt is also known to improve the efficiency of these
systems by placing one or more glass pl~tes above the panels
to produce a greenhouse effect for reducing heat losses.
Howevex, the effieien~y of these panel systems is low, from
a~out 30~ to about 40%, and they require large spaces
resulting in large heat losses, ~nd they also require a
hig~ capital investment. ~he use of Fresnel-type lenses
~L7~!7~
and fluid lenses is known in the art for focusing solar
energy. See, for example, U.S. Patents 3,915,148; 3,125,091;
937,013; 3,965,683; 3,901,036; 60,109 1,081,09~; Japanese
Patent No. 28-2130, and Australian Patent No. 131,069.
However, none of the known systems is capable of converting
and storing solar energy efficiently and none can produce
heat at an economical capital investment such that the use
of solar energy is competitive with other energies. The
prior art also does not disclose obtaining temperatures in
the order of a few hundred degrees C while also obtaining
at the same tjme lower temperatures usable for home heating
and water heating or other purposes. Nor is there in the
prior art a system which is capable of storing heat energy
from solar energy during perio~ of interrupted solar energy
for any length of time and which also is capable of pro-
viding different temperatures simultaneously and also utilizing
the luminous and infrared rays of the sun.
With respect to electrical generation, it is known
that concentrating the solar energy at a photovoltaic cell
will increase the electrical output of cell; however, there
is the disadvantage that the increased heat in the photo-
voltaic cell resulting from the concentration will also limit
the cell output. Known photov~ltaic devices produce a maximur,
o~ about one watt per hour per cell. Assuming a cost of Slo
per phot~voltaic cell, a system using non-concentrated solar
energy to generate about 1 kilowatt per hour requires a
capital cost of at least S10, ooo which is not competitive
for normal uses.
With respect to ~olar stills, known stills used
for distillation of ~eawater have low efficiencies and the
~17~!'7~
cost of heating the water is hi~h as the least amount of heat
required to vaporize the water is not recovered from the
condensation but rather is lost.
In accordance with the invention the prior ~rt
draw~acks and disadvantages are substantially overcome and
additional advantages realized.
The present invention relates to methods and
apparatus for concentratinq, collecting, storing and utilizin~
solar energy. In accordance with the invention, refringent
lens means concentrate the solar energy along a length at
elongated collector means cont~!ning at least one fluid
therein. Further in accordance with the invention, the
lens means comprise economical fluid or Fresnal-type lenses
and lens systems which focus the ~olar energy ~ubstantially
along the length at the collector means along substantially
continuous lines or in lines of substantially discrete
points. Thus, the at least one fluid in the elongated
collector may be efficiently heated to high temperatures
in the order of a few hundred degrees C. The fluid lenses
are advantageously made from separate upper and lower solar
energy transmitting plates which are installed in frame
means in a fluid-tight manner, or the fluid lenses may be
welded, extruded, or blown ~Lmilar to gl~ss or plastic
bottles. The fluid within the lenses preferably has ~n
$ndex of refraction similar to that of lens plates. The
- enclosure in the lens containing the fluid is advantageously
communicated with the collector means to enhance performance.
Sti~l further in accordance with the invention,
the elongated colle~tor means eDmprises a plurality of
fluids, ad~acent ones of which are contiguous. The fluids
~17~?7~)
are preferably isolated and disposed in adjacent conduits
and the fluids preferably differ And have varying boiling
points. The theoretical focus or foci of the lens means
are preferably on the surface of or within the higher or
highest boiling point liquid. In a preferred emb~diment,
the elongated collector means comprises at least two con-
duits; one of the conduits containing a first fluid having
a first boiling point is located within a second conduit
containing a second fluid having a ~econd boiling point.
Preferably, the solar energy is concentrated at the inner
li~uid which has a boiling point which exceeds that of
the outer liquid. The ~onduits and fluids are solar
energy transmitting or opaque or darkened depending on the
location of the lens means focus. ~y solar energy trans-
mitting it is meant that the solar rays are substantiallytransmitted through the material. In this way, the fluid
may be heated to different temperatures and accordingly
can be utilized for different purposes, if desired. Regulation
of the fluid flow rates and selection of conduit sizes
and shapes a6sists in providing different temperatures
which may be utilized for different purposes. Arrangement
of multiple conduits carrying multiple fluids in accordance
with the invention can provide energy for many different
uses including a vapor and ~uper-heated vapor for mechanical
devices including turbines. Advantageously, the lower
boiling point fluid has a ~w latent heat of vaporization
and is useful for this purpose. Additionally, heat is stored
in the higher boiling point fluid by permitting its tem-
perature to rise during peri~ds of ~olar energy to atemperature substantially ~igher than that of the lower
-7-
11~7~7~)
boiling point fluid which may be used as a working fluid.
Heat is removed from the higher boiling temp~rature fluid
by, for example, circulating the lower boiling point
~luid past the higher boiling point fluid.
The invention also provides for the union of
individual systems to form larger composite systems. Thus,
a high degree of concentration of solar energy is possible.
Still further in accordance with the invention,
both the infrared and luminous rays of the sun may be
simultaneously utilized. Photoelectri~ cells specifically
photovoltaic cells, can be disposed at the collector means
such ~ at the luminous rays are concentrated thereat for
maximum electrical energy production while the heat generated
by the concentration of the infrared rays is removed by
one or more fluids in the collector means whose flow rates
and volumes may be regulated. Thus, in accordance with the
invention, the solar energy is concentrated by a factor
in the order of up to 100 so that one of the known cells
is able to produce up to 100 watts per hour instead of 1
watt per hour during periods of sunshine.
Further in accordance with the present inventior.,
liguids, particularly watex, may be distilled by locating
the collector means in the liquid to be distilled, above
which is positioned lens means and a downwardly sloping
~ubstantially smooth, preferably planar surface, whereby
liquid is evaporated and condenses on the ~mooth surface
which carries the condensed liquid to a collecting vessel
positioned ~elow the lower side thereof. In one embodiment
the vessel holding the liquid to be distilled and the liquid
function as the collector means, the focus of the lens means
113~7~7i~
being located directly in the liquid. Means are provided
to completely enclose the apparatus while permitting move-
mer.t of the lens or the entire system to track the sun
seasonally or daily. It is preferred that the lens system
for the liquid distilling apparatus comprise fluid lens
means which include said s~ooth sur~ace and in which the
solar energy transmitting fluid forming part of the lens
means is circulated within the collector means to advan-
tageously utili2e the latent heat released by the vapor
condensing on said smooth surface and transferred to the
liquid to be distilled. The heat released by the con-
densing liquid is thus not lost and returned to the system
by means of the lens fluid and the circulation thereof,
thereby increasing substantially the efficiency of the
system and the quantity of heated liquid obtained from
liquid to be distilled. In the case of seawater, salt may
be produced from the resulting concentrated brine and credit
obtained from the ~ale thereof to lower the overall cost of
obtaining distilled water. According to one embodiment of
the invention, the still is portable and is easily assembled
and disassembled. Advantageously, the stills are operative
to distill seawater and brackish water and may be used
at sea, for example, on life boats, and in desert ~reas.
The ~pparatus may be enclosed ~ccording to the
invention to reduce heat losses and form enclosed systems.
Apparatus according to the invetnion can advan-
tageously be combined with a conventional heat pump producing
and storing additional heat from the surrounding air or
water. This ~ay be part~cularly significant during winter
months when lower sun energy is available and there is more
1~7~711
consumption of energy for heating.
These and other aspects of the present invention will
be more Apparent from the following description of the
preferred embodiments thereof when considered with the
accompanying drawings.
The present invention is illustrated by way of
example and not limitation in the figures of the accompanying
drawings in which like numerals refer to like parts and
in which:
FIG. 1 is a schematic perspective diagram showing
a system according to the invention comprising an elongated
fluid lens and a collector comprising two fluid-carrying con-
duits, one enclosed in the other with the focus of the lens
located within the inner conduit;
FIG. lA is a cross-section view of another embodiment
of the collector of FIG. 1 showing a rectangular inner con-
duit on the upper surface of which is located the focus of
the lens of ~IG. l;
FIG. 2 is a perspective view showing one of a
series of longitudinally juxtaposed fluid lenses and its
frame in cross-section and an opening for inter-communicatins
the enclosure of the lens with other lenses, this arrangement
being utiliza~le to arrange a plurality of longitudinally
~uxtaposed lenses where 6ingle lens is now shown;
FIG. 3 is a perspective view of a lens system
nccording to the invention comprising two separate plates
for enclosing a lens fluid and a frame for sealing the plates
into a fluid-tight lens;
FIG. 4 i~ ~ cross-cection view of the lens and
frame of FIG. 3 taken along line 4-4;
--10--
~117~7~)
FIG. 5 is a schematic perspective diagram similar
to that of FIG. 1 showing another system according to the
lnvention in which the ~ystem is enclosed, the single lens
is movable to follow the seasonal location of the sun and
in which the collector comprises a single fluid-carrying
conduit;
FIG. 6 is a schematic perspec~ive diagram showing
another system according to the invention comprisiny an
elongated, planar Fresnel-type lens having a linear focus
and a collector comprising three fluid-carrying conduits
in which an oute~ conduit encloses two inner conduits and in
which the focus of the lens is located within the outer
conduit;
FIG. 7 is a cross-section view of part of another
collector comprising three fluid-carrying conduits in which
the innermost conduit is enclosed by the intermediate
conduit which is enclosed by the outermost conduit;
FIG. 8 is a ~chematic perspective diagram showing
yet another system according to the invention comprising
an elongated curvilinear ~resnel-type lens and a collector
comprising a single rectangular fluid-carrying conduit;
FIG. 9 is a schematic perspective diagram of a
composite system according to the invention for distilling
water comprising individual ~ystems each comprising two
elongated fluid lenses and a collector located in the w~ter
to be distilled comprising two fluid-carrying conduits, one
enclosed în the otherJ
~ IG. 10 i~ a sch2matic perspective diagram of an-
other system a~cording to the invention for distilling
water c~mprising a single elongated fluid lens and a
~L7~7~
collector comprising a single fluid-carrying conduit;
FIG. 11 is a schematic perspective diagram of a
portable easily assembled and disassembled system having
~resnel lenses for distilling water according to the
invention; and
FIG. 12 is a cross-sectio~ view of a photoele~tric
cell positioned in a fluid-carrying c~nduit to produce
electricity from solar energy according to the invention
with fluid circulating inside and/or outside the conduit
to remove heat.
In FIG. 1 is shown a sol~r energy collecting
system comprising a refringent fluid lens concentrator
and a fluid-containing sDlar energy collector. System 20
comprises an elongated fluid lens concentrator 22 and collector
24 in the form of elongated fluid-containing conduits.
Elongated fluid lens 22 comprises solar energy transmitting
plates 26, 28 mounted in frame 30 and spaced to enclose
solar ener~y transmitting fluid 31. In the embodiment
shown in FI~. 1, upper lens plate 26 is convex and lower plate
28 is planar. The respective sides 32, 34 of lens plates 26,
28 and the ends of the lens plates (not ~hown in FIG. 1) are
sealed to be fluid-tight in manners which will be described
hereinafter. Alternatively, means not shown in PIG. 1 for
adding and remo~ing or circulating fluid 31 and air are
provided in the ~ides and/or ends of the lens plates.
Additionally, mèans also not shown in FIG. 1 for longitudinally
and transversely ~radially) juxtaposing lenses may be
provided and will slso be described ~ereinafter. In the
embodiment shown $n FIG. ~, collector 24 comprises an outer
elongated conduit 36 enclosing an inner elongated conduit
-12-
1~7~7~)
38, both shown to be tubular in shape. Conduit 36 is placed
in insulating container 40 and is surrounded by insulating
~aterial 42 except for a longitudinally extending opening
44 located above conduit 36. Opening 44 is closed off by
solar energy transmitting and heat insulating plate 46.
~late 46 is suitably made of glass or plastic and the
insulating material 42 is suitably a foam such as poly-
ethylene foam. Collector 24 is located below lens 22 and the
theoretical linear focus 48 is located at or along the
collector for substantially all of ~he daylight hours.
The space between the lens and collector is enclosed hy
side panels SO which if rigid can also serve to support
lens 22 and frame 30 in cooperation with support member 52.
For optimum concentration of solar energy at collector 24,
lens 22 is oriented at a preselected angle A with the
horizontal, the longitudinal axis of the lens (and of the
system) is oriented along the east-west direction and the con-
vex upper lens plate 26 is oriented to face south ~northern
hemisphereJ. The optimum value for angle A depends upon
the location of the system 20, and for a fixed system is
chosen to give optimum concentration on an annual basis.
For movable systems, which will be described hereinafter,
angle A is selected for optimum seasonal 601ar energy
c~ncentration or for optimum concentration for even shorter
periods of time.
As mentioned hereinbefore, the collector 24 is
located at tbe theoret$cal focus 48 of the lens 22 and in
the embod~ment of FIG. 1, conduits 36 and 38 are solar
energy transmitting, the theoretical focus 48 being located
within the inner conduit 3~. Conduits 36 and 38 contain
~3 7~!7i~
heat-carrying fluids 54 and 56, respectively. Since the
concentration of the solar energy will be greatest in
the fluid within the c~nduit at which the lens theoretical
focus is located, i.e., in fluid 56 within conduit 3B, fluid
56 may be heated to a relatively high temperature and
is therefore chosen to have a relatively high boiling point,
for example, from about 150C to about 350C. Such fluids
may comprise by way of example and not llmitation lubricating
oils, glycerine, olive oil, paraffin oils, etc. Thus,
during periods of sunshine, fluid 56 is heated to a tem-
perature which may be in excess of 100C, for example, 200C
the precise temperature attained depending on many factors
such as the flow rate of fluids 54, 56, the dlameters of
conduits 36, 38 sun intensity and position, insulation,
heat exchange rates, etc. Fluid 54 is selected to have
a boiling point which is less than the boiling point of
fluid 56, preferably at least 50C less than the boiling
point of fluid 56, and preferably in the temperature range of
from about -62C to about 100C. Such a fluid is suitably
water. It is also preferred-that fluid 54 have a low
latent heat of vaporization, for example, from about 20
calories per kilogram to about 270 calories per kilogram,
and such fluids may comprise by way of example and not
li~itation fre~n, butane, propane, ammonia, ethyl ether,
methyl alcohol, etc.
In operation, solar energy is concentrated in fluid
56 (chosen to ~e lubricating oil) within conduit 38 and raises
the temperature of the oil ~o about 200C. Since the focus
to lens 22 is theoretically linear, ~luid 56 will be ~on-
tinually heated as it traverses the linear focus. Fluid 54
-14
'7V
(chosen to be water) which surrounds the oil and conduit
38 is heated primarily by the oil primarily through con-
duction. Both fluids, oil and water, are circulated ~t
predetermined rates to obtain desired temperatures and ~zy
be used for different heat applications. For example,
the water may be heated to about 70DC - 80C or more and
used for space and hot water heating. ~he water may be
heated to lower temperatures and used, for example, in
swimming pools. The higher temperature oil may be used
for applications requiring higher temperatures including
industrial applications or may be used merely to heat the
water. Since the temperature of fluid 56 increases as it
traverses the lens focus, fluids at many different tem-
peratures are realizable by providing taps for fluid
outlet and/or inlet at different points along the focus.
Fluid 54 may be evaporated and the vapor or superheated
vapor used to produce mechanical power in a turbine or
engine which, in turn, may generate electricity. Preferably,
a closed system (not shown~ is employed in which the con-
densed fluid is returned to collector 24. In such applications,fluids such as Freon*, butane, propane, ethyl ether, methyl
alcoh~l, ammonia and the like may constitute fluid 54.
As mentioned hereinbefore, a ~erious drawback
of ~olar energy sy~tems in general and known systems in
particular relates to the ~torage of energy during periods
in which there i~ no ~unshine or the intensity thereof is
low, ~s for example during the night or during periods of
cloudy weather. In accordance with the present invention,
heat i5 ~tored for use ~n those period~ in fluid 56 which is
heated during ~ormal ~y~tem operation to n temperature
; * Trademark of E.I. duPont de Nemours & Co., Inc.
-15-
1~17~!7V
which is at least about 50C higher than the temperature
of fluid 54. Therefore, even when fluid 56 is not being
heated by solar energy or being heated at a reduced rate,
it stores heat and will continue to supply heat to fluid
54 due to the temperature difference between the two
fluids. Preferably, the circulation of fluid 56 is
stopped for those periods. Fluid 56 continues to trans-
fer heat to fluid 54 until the difference in the temperature
of the two fluids is relatively small. The time that
fluid 56 will transfer and/or store heat depends upon the
initial temperature of fluid 56, the differerce in temperatures
between the fluids, the volumes of the fluid, the character-
istics (specific heat, boiling point, latent heat, etc.)
of the fluids, the use to which fluid 54 is put, etc.
Further in accordance with the inventi~n, the
fluid 31 in lens 22 may be communicated (not shown) with
collector 24 through conduit 36 or 38 or through another
separate conduit to remove heat from the lens fluid,
thereby maintaining it at a suitable temperature while
utilizing solar energy absorbed by the lens fluid.
In FIG . 1, collector 24 was shown to comprise
tubular conduits 36, 38. However, the conduits need not
be tubular and in some instances other configurations are
preferre~. For example, referring to FIG. lA, collector
58 comprises rectangular inner conduit 59. The rectangular
configuration may be desirable when the theoretical focus
varies excessively with seasons and the time of day in
a single lens system ~s shown in FIG. 1. Providing a
rectangular shape will all~w movement of focus 48 while still
maintainin~ it at conduit 59. Focus 48 has bee~ ~hown on
1~17C!70
the surface of conduit 49, and in such a case, the surface
of conduit 49 need not be solar energy transmitting and
is preferably darkened. Fluid 56 inside conduit 59, as in
FIG. 1, has a higher boiling point than outer fluid 54 since
the concentration of the solar energy will be at the conduit
containing fluid 56.
It is to be understood that the systems shown in
the remaining figures and described hereinafter are longi-
tudinally oriented in an east-west direction and faced towards
the sun preferably by plus or minus 15 (plus in winter,
minus in ~ummer) c r the latitude of the location in order
to achieve an optimum concentration of solar energy, seasonally
or for shorter periods of time. It is to be further
understood that the elongated lenses or lens system and the
elongated collectors and conduits thereof are arranged
substantially along parallel longitudinal axes. Description
will be made hereinafter of mcvable lens systems for track-
ing the sun; manual and automatic means for effecting track-
ing movement of systems and/or lenses on a seasonal basis
are known. ~he refringent lenses according to the invention
are operative to also concentrate diffuse solar energy which
may repres~nt up to about 50~ of the solar energy at
the system. While only part of a single lens is shown
in FIG. 1, it is to ke understood that many lenses may be
longitudinally and radially juxtaposed. Use of many lenses
results in 4 system with a high degree of solar energy
concentration which is achieved quite economically.
In the embodiment shown in FIG. 1, heating
is accomplished by heat exchange between fluids 54 and 56 with-
out the necessity of an external heat exchanger which reducec
1~17C~7~
heat losses. Side panels 50 which are made of an insulatingmaterial further reduce heat losses. Additionally, plate
46 provides a greenhouse effect in the collectors to
furt~er reduce heat losses. Collector 24 is also preferably
made of insulating material~ The reduction in heat loss
is especially important during periods of no or reduced
sunshine. It is preferred that the theoretical focus
of the lenses be located at the inner fluid to further
reduce heat losses since the outer fluid will act as an
insulator. The solar energy transmitting tubes are
preferably made of colorless and trarsparent glass or plastic
and the tubes which need not transmit solar energy there-
through are preferably metal, preferably steel, copper or
aluminum, and preferably have darkened outer surfaces.
According to the invention, the area of the
collector surfaces may be much smaller than the area of the
concentrators and may be only from about 1~ to about 10%
of the area of the concentra~ors, thus reducing the heat
losses accordingly. As less material is required in the
collector, the cost will be reduced.
As will be more apparent hereinafter, the collector
systems may comprise a number of cond~its other than two and
configurations other than tubular, and the lenses and lens
systems may be other than that shown in FIG. 1 and may be
movable and also track the sun.
Fluid lenses according to the invention may have
configurations other than that shown in FIG. 1. The lens
plates may be economically made of glass or plastic and are
joined in a fluid-tight manner as by welding. Alternatively,
the lens may be extruded with the sides integrally joined.
-18-
1~7~7~
The ends of the lenses may similarly be welded or extruded
or formed from a bulb of glass or plastic as by blowing as,
for example, in the manufacture of glass or plastic bottles.
The lens shown in ~IG. 1 is supported by suitable frames
and structural members. For example, lens 80 is supported
by frame 88 shown in FIG. 2. As there shown, one of a
plurality of lenses 80 are longitudinally juxtaposed at
ends 90 and supported by longitudinal support stringers 92
and transverse support stringers 94. The lenses may be
;10 secured to the frame by, for example, adhesives. The
theoretical focus 96 of the lenses is at and along collector
98. Means in the form of openings 100 are provided to
add and remove fluid 31 and/or air and the openings may be
communicated by, for example, tubes to provide for circualtion
of the fluid. The openings may be provided in other locations.
As mentioned hereinbefore, the plates forming the lenses
may be integrally extruded or blown or may comprise separate
plates joined as by welding. Referring now to ~IGS. 3 and
4, upper curvilinear plate 26 and lower planar plate 28
are separate pieces and are joined in a fluid-tight manner by
means of frame 104. Frame 104 comprises two longitudinal
grooves 1~6, 108. The upper groove 106 is curvilinear and
sized to accommodate upper curvilinear plate 26 while the
lower groove is linear And ~i2ed to accommodate planar plate
28. ~he edges of the respective ~eparate plates are in-
fierted into the respective grooves along with sealingmaterial 110. The ends of the plates are similarly joined.
The material 110 may camprise a gasket or similar flexible
piece and/or deforma~le ~aterial such as silicone to form
fluid-tight joints. Thus, the lenses according to the in-
--19--
1~17~!?71)
vention in which two independent plates are joined or thelenses are extruded or blown, are relatively easy to
manufacture and are relatively inexpensive.
As mentioned hereinbefore, lens 22 may be movable
to track the seasonal movement of the sun. In FIG. 5,
system 112 is shown in which the side walls 114, 116 are
made of expandable plastic whereby the system remains
enclosed as described hereinbefore upon movement of lens
22 along a radial axis of the collector. With lens 22 in
the positions designated by solid lines, walls 114, 116 assume
first positions connected between respective bottomsides
of collector 118 and sides 32, 34 of the lens. Upon counter-
clockwise rotation of the lens to the position designated
by the broken lines, the lengths of the walls are changed and
the system remains enclosed. Thus, a simple, inexpensive,
enclosed system is provided in which the lens may be moved
to track the seasonal location of the sun. Still referring
to FIG. 5, collector 118 is ~hown comprising a ~ingle tubular
inn~r conduit in which the focus 120 is located.
Description of preferred embodiments of the
invention has been made hereinbefore with reference to
linear theoretical focus fluid lenses. However, in accordance
with the invention, the solar energy may be concentrated by
focal point lenses. In FI~. 11 is shown a plane refr$ngent
element 126 comprising a rigid frame surrounding a sheet
or plate o~ plastic or glass material in which are formed
by imp~essions or molding concentric closely spaced rings
of microprisms whose pitch, for ex2mple, corresponds to
about 3 to about 6 nicroprisms per mill$meter. The plane
refringent element 126 acts like a plane Fresnel lens. Solar
-20-
'7~
energy striking the refringent element 126 is concentrated
by the microprisms into a theoretical point focus. Refringent
elements 126 may l~e ~ositioned longitudinally juxtaposed
and/or radially juxtaposed. The system may be arranged
so that the point foci of lenses 126 are located within
or at the surface of conduits 36, 38, 59 as described
hereinbefore, the series of discrete point foci along a
length forming, in effect, a linear focus composed of dis-
crete point foci, or as shown in FI~.ll in a liquid being
distilled.
System 130 of FIG. 6 is shown employing an
elongated refringent element 132 having longitudinal micro-
prisms 134 acting as a longitudinal Fresnel lens. The lens
132 and collector 136 are arranged so that the linear focus
is located at collector 136 which is similar to collector
24 in FIG. 1 except that two inner conduits 138, 140 are
enclosed in outer conduit 36. Linear focus 142 is located
within conduit 36. Providing three conduits permits use
of three different fluids and allows for use of the fluids
at varying temperatures for many dif~erent applications.
FIG. 7 shows another arrangement for three conduits in which
the inner conduit 139 is enclosed by intermediate conduit
141 which in turn iE enclosed by outer conduit 36.
System 144 in FIG. 8 shows a rectilinear refringent
element 146 formed with longitudinal microprisms 148 which
direct the solar energy to different linear foci F, Fl, F2
located at col~ector 150 depending upon the seasonal location
of t~e sun. Collector 150 is located east-west so it is
oriented to c~llect ~lar energy during daily movement of
the ~un, and comprises a single solar energy transmitting,
-21-
7~
at least at upper part 152, rectangular fluid conduit 154 which
is surrounded in part by insulating material 42. Parts
of system 144 are not shown to proportion. In particular,
collector 150 is shown in larger proportion for clarity
and is less than about 10% of the size of lens 146. A closed
system is achieved by extending the sides of refringent ele-
ment 146 an~ insulating material 42 into overlappi~g engage-
ment. As described hereinbefore, use of a rectangular
conduit 154 facilitates location of a moving focus such
as F, Fl, F2 within the conduit. Although element 146 focuses
primarily by refracting the rays of the sun, the micro-
prisms also provide reflection of rays such as 156. ~he
inside sides of element 146 may also be suitably angled
and made reflective to reflect any rays impinging thereon
to the focus.
The present invention may be utilized for many
energy applications as described hereinbefore and may
also be advantageously used to distill or otherwise treat
liquids particularly water by evaporation and condensation
thereof. ~ypically, the liquid is water and the water
is seawater or brackish water and is to be desalinated,
or water containing minerals or other substances such
as industrial waste water or polluted water which is to
be purified ~nd di~tilled. Further in accordance with
the inventi~n, the refringent concentrators and collectors
according to the invention are arranged in systems
operative to distill water, preferably recovering the
heat of condensation as described hereinafter.
~he ~ystem 160 shown i~ FIG. 9 comprises a
plurality of sub-systems 162, each employing a two lens
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1117~!7V
arrangement 164. Each lens pair lS4 is supported above
~n elongated, central, rectangularly configured channel
166 and parallel, elongated rectangularly configured, side
channels 168 such that the central part of the pair of
lenses is above the central channels and the outer
lonait~dinal edges of the lenses are above the side channels.
Each individual lens is inclined and additionally the pair
of lenses is rotated slightly in a clockwise direction such
that adjacent pairs are overlapping. The bottom lens
plates 28 are planar. The water 170 to be distilled is
filled in the central channel to a predetermined height.
Within channel 166 is positioned collector 172 which com-
prises conduits 36, 38 as in FIG. 1. The focus 64 of the
lens pair 164 is located within inner conduit 38. Pre-
ferably, the interior of lenses 22 is communicated withcollector 172. In the embodiment shown in FIG. 9, lens
fluid 31 is advantageously water and the interior of the
lenses is communicated by conduit 174 with outer conduit
36 in which the fluid is also water. The fluid in the
inner conduit 38 is a higher boiling point fluid as described
hereinbefore. In operation, the water 170 to be distilled
is heated by collector 172 due to the solar enexgy
concentrated thereat and the water 170 is vaporized. The
vapor strikes the lower plates 28, is condensed thereon and
flows therealon~ to be discharged at or dropped from the
edges thereof into æide channel 168. In accordance with the
invention, the water in the fluid lenses is circulated
throu~h collector 172. In this way, the heat released by
condensation of the vspor is transmitted through the plate
28 to the water in the lenses and the heat absorbed by the
-23-
i~7~7~)
water in the lens from the condensing vapor is returned
to the system through conduit 36. This is significant
because the latent heat required to vaporize the water
170 of about ~39 calories per liter (975 BTU per
kilogram) in additi~n to the sensible heat is substantially
returned to the system by the circulated water in the
lenses upon which the vapor condenses. This latent heat
is substantial and would otherwise be lost. This results
in a much higher efficiency of the system compared with
solar stills where channels filled with water to be treated
are covered with only glass plates w~ich receive the solar
rays. Circulating the water in the lenses also cools the
lower lens plate 28 thereby assisting condensation thereon.
Conduits 175 and 176 are provided for filling and emptying
the respective channels. The water 170 to be distilled may
be held between predetermined heights by a float system
comprising float 17R and relays 180 and 182. Movement of
the float activates respective relays to start and stop
a pump or motor valve (not shown). A similar arrangement
may be used in side channels 168 or a gravitational drain
arrangement may be employed to maintain the height of distilled
water in the side channels between predetermined heights. The
respective channels are communicated to provide ~pproximately
equal levels in each of the respective channels. Advan-
tageously, the channels are made of concrete or asbestoscement. ~eans other than the lens itself may be used to
condense the Yapor such ~s substantially smooth preferably
planar plates located below the lenses 164. In such a case,
the lens fluid may not rec~ver the latent heat unless the
plate is proximate thereto. Alternatively, means associated
~7~
with the plate may be used to recover the latent heat.
The system shown in FIG. 9 is substantially
enclosed by the ~nel panels to reduce heat loss as
described hereinbefore. The two-conduit collector 172 is
particularly advantageous since the fluid in the inner
conduit 38 may be raised to a high temperature and used
to store heat as described hereinbefore. This adds a
very important capability to the system in that it can
operate during the night and during periods of reduced
In sunshine. This is very important in that it provides the
advantage of substantially continuous operation resulting
in increased system output at reduced cost. The rscovery
of the latent heat of the condensing vapor by the lens
fluid assists in providing a continuous operation system
since heat losses are reduced.
In FIG. 10, a single lens system, single conduit
system 196 is shown which is similar to those described
hereinbefore. The adjacent channels 198, 200 for the
water 170 to be distilled and ~he distilled water, respectively
are trough-shaped and may advantageously be formed from adjacent
plates. ~he inclined lens 22 is above channels 198, 200
and the lower part of lens 202 terminates above channel
200 to permit the condensed water to fall therein.
According to the invention, systems may be main-
tained essentially enclosed while lenses 22 are moved totrack the ~un. An expandable material, as de ~ ~ for
FI~. 5, forms the side panels of each compartment of such a
system. ~dvantageously, the material is of plastic.
In FIG. 11 is ~own an embodiment of a portable
water distillation ~yste~ 330 which is easily assembled and
7~!7i~)
disassembled. System 330 comprises planar Fresnel
lenses 126 having concentric microprisms causing the ~olar
energy to be concentrated at point foci. Lenses 126 are
longitudinally and transversely ju~taposed to form a com-
posite lens assembly of six Fresnel lenses which is inclinedwith respect to the horizontal, six being chosen for purposes
of illustration. The lenses are formed into an assembly
by, for example, securing them as by adhesives to a solar
energy transmitting glass or plastic plate 332 which, in the
case of plastic, may be folded along flexible partition
lines 334. Each Fresnel lens ~ay be about 9 inches by about
7 inches. The point foci of the lenses are located in the
water to be distilled in flexible container or bag 336 made
of plastic or other plyable material. Flexible container
or bag 338 made of plastic or other flexible material located
below and extending beyond container 336 is used to collect
condensate from plate 332. The lens assembly and containers
are supported by support assembly 340 comprising pairs of legs
342, 344, frame 346 and platform 348. The legs are pivotably
connected to frame 346 at one end and are secured at the
other end in indentations in platform 348, or the legs may
be secured in the ground or otherwise where no platform is
used. Thu-~, the legs may be moved to adjust the angle of
incline of the lens assembly to follow the seasonal location
o~ the sun. The containers or ~ags have side panels 350l
352 which extend upwards to plates 332 to form an enclosed
system as described hereinbefore. An opening is provided in
side pane~ 352 at the lower side of plate 332 to allow the
condensate to ~rop into the collector bag 338. ~eans such as
transparent tubes 322, 324 connected to the bottom of the
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1~17~7~
c:ontainers are used to indicate water levels therein. The
lens assembly, support assembly and containers are easily
~ssembled and disassembled. The foci located in the water
to be distilled in container 336 heat the water and cause
it to evaporate, condensing on the bottom of planar plates
332. The condensate moves along plates 332 and falls into
container 338.
According to another aspect of the invention, the
concentrated solar energy is used to generate electricity
by means of photoelectric cells. More particularly, the
luminous rays of the sun are concentrated on photovoltaic
cells. Referring to FIG. 12, photovsltaic cells 398 made of
silicon or cadmium or other materials are disposed in the
interior of inner ~luid-carrying conduit 400 shown advan-
tageously to be of rectangular cross section. Thetheoretical focus 402 of the lens is at the cells and
preferably on the outer surface thereof. The cells may be
juxtaposed if the theoretical focus 402 is linear or
spaced if the theoretical focus 402 is a point focus. The
concentrated luminous rays are converted to electricity by
the cells while the heat absorbed by the cells from the
infrared rays is removed by the circulating fluid 404
and also by the fluid 406 circulating within the outer
~onduit 40~. The removal of heat can be ~ontrolled ~y
the size of the conduits 402, 406 and by the volume and
rate at which the fluid are circulated. Preferably fluid
404 is substantially electrically non-conductive such as air
or other g~ses and liquids. Means (not shown) are provided
for connecting the cells in parallel or series and for
removins the generated electricity. If fluid 404 is
1~7~7~
is electrically conducting, means (not shown) are provided
for electrically insulating the cells and the means for
interconnecting the cells and for removing the generated
electricity. Conduit 402 has at least its upper surface
made of transparent material if the theoretical focus
402 is linear or transparent apertures may be provided
above the cells if the theoretical focus 402 is at a point.
~he upper part of outer conduit 408 is also transparent.
The details of inner and outer conduits have b en described
hereinbefoxe.
As mentioned hereinbefore, in accordance with the
invention, concentrating the luminous energy of the sun with
a concentration of up to about 100 permits electricity to be
generated at up to about 100 times more power while the
increased heat energy is dissipated and removed by the fluids
in the conduits. Electricity may be qenerated in conjunction
with other uses of ~olar energy. For example, referring to
FIG. 1, using a dual fluid carrying collector, photovoltaic
cells may be inserted therein as just described and electricity
generated while the heat energy is being used to heat a
structure.
Prominent aspects and advantages of the invention
may be summarized as follows:
A lens concentration ~ystem is combined with a
conduit collector 6ystem in which the surface area of the
concentrating sy tem exposed to the sun is from about 10 to
about 100 times larger than the surface area of the collecting
syst~ through which the energy i~ concentrated. As a
result heat losses are reduced ~ubstantially fiince the
collector has an area of, for example, only from about 1%
-28-
~Lil7~7~)
to about 10~ of oonventional flat plate collector systems and
the overall surface area is about half that of conventional
flat plate systems. Thus, the efficiency over conventicnal
flat plate systems is in the order of about 50~ higher.
This reduction in surfacearea reduces correspondingly the
material requirements per unit of surface area exposed to
the sun and the investment cost is also reduced correspondingly
by about one-half.
More solar energy can be collected by the method
and apparatus according to the invention since the collector
conduits are oriented e~st-west thereby being located at the
foci of the lenses throughout the day and, according to the
invention, the lenses can be moved and positioned at various
inclinations to optimally follow the seasonable location of
the sun. This positioning of the lenses can represent up to
504 higher solar energy collection. Even using auxiliary
equipment to adjust the inclination of the lenses, the
reduction in investment is in the order of a third over flat
panel systems. Not only is the investment cost ~uch less than
known solar systems, but the operating costs of obtaining
heat energy is lower. Also the cost of heat derived from
solar energy according to the invention is lower and may
be up to one-third lower than the cost of petroleum fuels
bhsed on the usable heat content. This is of great importance
to oil importing countries. Additionally, solar e~ergy is
~nexhaustable and does not produce pollution as does the
burning of other fuels.
-29-
1~7~7~
According to the invention, by concentrat-
ing the solar energy at elongated conduits, higher
temperatures, for example, exceeding 200~C (392F)
are attainable using high boiling temperature ~luids
in the conduits such as lubricating oil, glycerine,
etc. This is to be compared with to about 80C
(176DF) attainable by flat plate systems~ Accord-
ing to the invention, multiple conduits, either con-
duit receiving the foci of the lenses, and the
higher temperatures attainable allow storing solar
hea~ to be used for hours without sunshine. The in-
vention provides for storage of heated fluids in
the inner conduit at high temperature, for example,
over 200C which heats the outside fluid to lower
temperatures, for example, 80C. Using this arrange-
ment permits a reduction in storage volume re~uired
by the higher temperature fluid over fluids at about
80C. For example, for the same fluid, 2-1/2 ti~es
less space is required to store the same heat at 200C
than at 80C. According to the invention, low boil-
ing point and low latent heat of vaporization fluids
such as freon, ether, etc. are used in the conduits
which fluids are vaporized and superheated by the
solar energy and used to produce electricity in ex-
pansion motors such as turbines at lower cost thanusing fuel.
Electricity may also be produced according
to the invention with photovoltaic cells where the
increased solar energy concentration of up to 100
times i~creases substantially the electric produc-
-30-
1~17C!7~)
tion and correspondingly reduces the cost of elec-
tricity. Several circulating 1uids in several con-
duits are employed to remove the heat developed by
the concentrated infrared solar rays. The present
invention has the advantage of generating electric-
ity, producing heat simultaneously or separately and
storinq heat and is useful in many applications,
thus increasing system efficiency, utilization and
amortizing the cost of the system.
Employin~ several fluids according to the
invention permits simultaneous use for many purposes
such as heating water, heating buildings, air con-
ditioning, producing electricity, etc.
An advantaoe of the present invention is
that diffuse sun energy of up to about 50~ can be
collected.
Further according to the invention water
containing salt or other substances is distilled
using solar energy collection and concentration ac-
cording to the invention and recovering a large partof the latent heat of vaporization and sensible heat
(about 1100 BUT/lb or 600 cal/kg). This is accom-
plished by using the fluid circulating in the lens
system to recover the latent heat and circulating
the fluid in tbe conduit in the water to be distilled
thereby heating the water to be distilled. The
~alt from the ~oncentrated brine may also be recov-
ered and sold or electrolyzed. Distillation accord-
ing to the invention is at low cost such that water
may be produced for irrig~tion purposes. me inven-
-31-
1~7~!7~
tion provides for portable dismountable distilla-
tion units which could be used to distill sea water
in life boats or brackish water in arid desert areas
t~ereby possi~ly saving lives.
While specific applications of the inven-
tion have been described, many are uses of the col-
lected solar energy are possible. For example, the
salt by-product of desalination may be collected and
sold to reduce the over-all operating cost of the
system. Additionally, the salt may be separated in-
to sodium and chlorine by electrolysis by electric-
ity generated by the solar energy collecting system.
In this respect, water can be separated into hydrogen
and oxygen also by electrolysis, the hydrogen of which
in turn may be used in the manufacture of liquid meth-
anol which is easily transported and may be used as
fuel for automobiles, airplanes, etc. The system
described hereinbefore could be combined with known
heat pumps to further utilize the collected solar en-
erby in combination with the heat provided by theheat pumps, particularly for refrigeration systems.
In addition to providing energy for heating, the sys-
tems according to the invention could be used for air
conditioning and, as just mentioned, in refrigera-
tion systems. Also, the multi-conduit collectors and
fluids are capable of providing temperatures of about
70C to about 80C for heating rooms and for heating
water, and at higher temperatures, for example, about
180C to about 200C, for heat ~torage applications
and to produce electricity.
-32-
7~7~)
The apparatus according to the invention
has been described primarily using schematic diagramS.
Accordingly, certain details not essential to an un-
derstanding of the invention have been omitted. For
example, the materials and support structure com-
prising the apparatus according to the invention not
described in detail will be known to those skilled in
the respective arts. The sizes of the parts of the
apparatus described hereinbefore will vary depending
on the use to which the apparatus is put. In a two conduit
collector system, where the inner fluid is lubricat-
ing oil heated to about 200C, the space required to
store an equal amount of heat will be about 2-1~2
times less than for a fluid such as water heated to
80C. Also, the multiple conduit system permits
multiple uses for the heats of the different fluids.
~or example, a fluid heated to about 200C may be
used to heat buildings and a fluid heated to about
70C to 80C may be used for heating water. Portable
distillation units may be used, for example, as men-
tioned hereinbefore, in lifeboats to distill sea
water or in desert areas to distill brackish water
and thereby possibly save lives. Portable units ac-
cording to the invention could produce, for example,
one pound of distilled water for every square meter
labout 10 square feet) of lens concentrator area ex-
posed to the sun's rays, and this without recapturing
the heat of condensation. The production of distilled
water, however, will be about six times as great if
the heat of condensation is recovered.
-33-
~17~7~
It is pointed out that the heat obtained
from the sun using the energy systems according to
the invention may be lower in cost than heat energY
obtained from fuels which may thus be replaced. Heat
storage provided by systems according to the inven-
tion is a feature which also makes these systems com-
petitive with fuels. The distillation systems accord-
ing to the invention are capable of providing dis-
tilled water at low cost and therefore are important
where clean water is scarce.
The advantagesof the present invention, as
well as certain changes and modifications of the dis-
closed embodiments thereof, will be readily apparent
to those skilled in the art. It is the applicant's
intention to cover by their claims all those changes
and modifications which could be made to the embodi-
ments of the invention herein chosen for the purposes
of the disclosure without departing from the spirit
and scope of the invention.
This application is a division of Canadian
application No. 282,211, filed July 7, 1977.
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