Sun tracking solar energy collector system

A sun tracking solar energy collector system comprising a plurality of light focusing elements disposed side by side in the form of a surface array, providing a linear array of foci; and a metallic heat exchanger tube having externally a high absorbtivity, low reflectivity coating containing a working fluid such as water, air, hydrogen or helium, to which a substantial portion of the energy in the focused light is imparted. The system includes an insulator tube external to the heat exchanger and providing small apertures covered by glass to allow the light focused by each focusing element to enter the interior of the insulator tube, where the light may impinge directly on the heat exchanger tube or on solar cells attached to the heat exchanger and facing the apertures, for conversion of a portion of the focused light energy directly into electricity, while the greater portion of the energy focused through the apertures ends up as heat through the heat exchanger tube into the working fluid, capable of raising its temperature to a desirable temperature. A highly reflective internal surface of the insulator tube serves to reflect toward the heat exchanger radiation reaching it from the solar cells and the heat exchanger, so that with the reflective internal surface being much larger than the surface covered by the apertures a very small percentage of the radiated energy is allowed to escape to space through the apertures. A vacuum maintained between the heat exchanger and the external insulator tube serves to minimize conductive losses.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates in general to solar energy collectors for capturing 
solar energy falling over a surface area, in terms of heat, raising the 
temperature of a fluid, and particularly to a sun tracking solar energy 
collector system means for increasing the temperature of the fluid and the 
efficiency of solar energy capture per unit of area using focussing means, 
solar tracking means, solar cells and an internal type heat exchanger 
means. 
2. Description of the Prior Art and of Optimizing Factors 
There has been a number of devices for capturing and utilizing heat energy 
from the sunlight. One type of such devices is the passive non tracking 
solar energy collecting panels providing in effect heat exchanging means 
between a highly light absorbing coating and water which is used for 
heating during the winter and for faucet hot water the year around. 
Coatings with much higher absorbitivity than emissivity in the range of 
the solar spectrum have been developed. The principle of what is commonly 
known as the "hot house effect" whereby visible light is easily 
transmitted through a transparent sheet, such as glass or acrylic plastic, 
imparting heat energy onto the absorbing surface at relatively low 
temperatures, so that the surface then can only radiate in the infrared 
spectrum which is only partially transmitted through said sheet, is 
beneficially used to retain the captured heat. The main drawbacks of this 
type of solar collecting devices are: 
1. Lacking sun tracking the surface where the light collecting device is 
installed is inefficiently used due to the cosine law, capturing only a 
small portion of its potential energy capture. 
2. The temperature at which the water can be raised is relatively low 
(about 145.degree. F.). While low temperature is useful for heating and 
for hot water, it cannot be used efficiently for the generation of 
electricity or to provide for air-conditioning through an absorption type 
refrigeration unit. 
3. Despite the "hot house effect" a considerable amount of the captured 
heat is being re-radiated into space, or lost through conduction to the 
outside air. 
4. Defining a price quality factor as the yearly dollar benefit derived by 
the device, divided by the overall cost of the installation, it has been 
found that such factor is relatively low for this type of solar 
collectors. 
A second type of solar collecting devices may be referred to as line focus 
solar energy collecting devices which use optical means such as Fresnel 
lenses or cylindrical paraboloidal reflectors to concentrate the sun light 
along a narrow focal line. This type may or may not include sun tracking 
means. 
The main benefit of the line focus solar collectors is that they provide 
sufficient light concentration to heat working fluid such as water to an 
intermediate temperature such as between 200 and 300.degree. F. Such water 
temperatures are capable of efficiently providing heat to an absorption 
type air conditioning system besides providing heating during the winter 
and hot water. 
The main drawback of the line focus solar collectors is the relatively high 
percentage or radiation losses, as a relatively high percentage of the 
heat exchanger receiving the radiation is exposed to radiate back into 
space. Difficulties also exist in keeping a vacuum between an inner heat 
exchanger and an outer shield when a slot along the outer shield must 
remain transparent for the solar radiation to enter. Attempting to cover 
the slot with a transparent substance such as glass while keeping the 
glass sealed surrounding a metallic inner heat exchanger, and at a wide 
range of temperatures, while maintaining a vacuum between the glass shield 
and the metallic heat exchanger. 
A third type of solar collecting devices may be referred to as superimposed 
focusing collectors providing focusing of a multiplicity of sun tracking 
reflectors commonly referred to as heliostats, on to same area of a heat 
exchanger, where substantially high temperature can be sustained. 
The main advantage of the superimproved focussing solar collectors in that 
they can gather substantial amounts of solar energy per day, measured in 
megawatt hrs. per day. A drawback is that only a small portion of the 
heliostats is contributing efficiently to the common heat exchanger at any 
time. Also because of the high temperatures involved at the heat exchanger 
radiation losses can be considerable. This type of system can be 
acceptable in areas with high intensity of sun-light and inexpensive land. 
While the solar energy now falling over the roofs of houses and industrial 
buildings is almost entirely being wasted, as the price of oil will 
increase, the value of this energy will also increase. Solar energy 
collectors which may appear to provide a benefit in terms of hot water to 
a homeowner today may be determined to be wasteful a few years from now 
when the cost of thermal energy will have substantially been increased. 
It should be noted that it is not only the number of BTU's collected per 
year per unit area of surface that counts but also the temperature at 
which these BTU's are counted. The higher the temperature of the working 
fluid the higher the value of the energy because the heat in the hotter 
working fluid can be converted into more valuable forms of energy such as 
electricity, at a higher efficiency. From Carnot's cycle considerations 
the maximum thermal efficiency possible in a heat engine is 
EQU nc=1-T.sub.L /T.sub.H ( 1) 
Where T.sub.H and T.sub.L are the high and low temperatures between which 
the engine operates, expressed as absolute temperatures. If T.sub.L is 
taken to be the ambient temperature, which is usually the case, the 
efficiency n.sub.c deteriorates as T.sub.H is approaching T.sub.L. While 
n.sub.c is unattainable in practical engines, the expression (1-T.sub.L 
/T.sub.H) turns out to be a controlling factor in the expression of the 
efficiency of heat engines. It is for this reason that BTU's at relatively 
low temperature gases such as the gases from the flute of oil burners and 
the exhaust of the automobiles are allowed to excape because the 
temperature of such gases is too low compared to the high temperature of 
the system. 
Another desirable feature of a solar energy collection system is the 
evenness of energy output during a normal sunny day. The smaller the 
variation of energy output during the day the less energy storage will be 
required by the system. 
On these basis it will be useful that a qualification factor "q" of a solar 
energy collection system be defined in such a way as to include all 
relevant factors, such as shown in the following equation: 
EQU q=(1-T.sub.A/ T.sub.H).times.K /(A.times.C.times..sigma.) (2) 
Where 
T.sub.A is the average absolute ambient Temperature; 
T.sub.H is the high temperature of the working fluid; 
K is the ratio of the amount of energy retained by the collector divided by 
the amount of energy incident per unit area at normal incidence; 
A is the area of ground or roof utilized by the solar collecting device; 
C is total cost in dollars for implementing the system; and 
.sigma. is the standard deviation of BTU output per hour per unit area of 
collector during the 12 sunny hourly intervals, 6 a.m. to 6 p.m. daily. 
QUALITY FACTORS OPTIMIZED BY INVENTION 
The present invention aims at optimizing a qualification factor such as q, 
by optimizing each of its factors as follows: 
K is being optimized by the invention's providing means for sun tracking 
for both daily motion of the sun and the seasonal declination of latitude 
.+-.23.5.degree.. K is further being optimized by the invention's 
providing means for minimizing radiation losses. (1-T.sub.A /T.sub.H) is 
being improved by the invention increasing the temperature of the working 
fluid through focussing of the solar energy, preferably through lenses; 
A is being minimized by the invention by positioning a multiplicity of 
focussing lenses on a single platform thereby tracking the sun in unison 
and precluding shading of one lense by another as it usually occurs in 
other systems during the early morning and late afternoon hours. 
.sigma. is being minimized by the sun tracking and by avoiding shading 
through the single platform principle. 
SUMMARY OF THE INVENTION 
The present invention provides a sun tracking solar energy collection 
system preferably utilizing parallel strips of the central area of a 
focusing element such as Fresnal lenses, disposed side by side to form a 
surface array, providing a linear array of foci for focusing the 
intercepted energy on substantially circular spots on an internal tubular 
metallic heat exchanger, or on solar cells thermally connected and 
supported with the heat exchanger, the light beams of each focusing 
element being allowed to enter an outer insulating tube, covering the heat 
exchanger tube, through a small circular aperture covered by a transparent 
material such as glass, on the external insulating tube. The external tube 
provides insulation against re-radiation by having its internal surface 
highly reflective in order that it reflects energy radiated outwardly back 
towards the inner heat exchanger tube. In this manner, while the collected 
energy reaches the solar cells or the heat exchanger, the radiation 
emitted by the solar cells and the heat exchanger, that can escape back 
into space, is proportional to the ratio of the total area of the 
apertures, divided by the total insulator tube surface. This ratio depends 
on the spacing between apertures and the size of each aperture. As the 
ratio can be designed to be very small the invention provides for improved 
retention of the collected energy. The invention also provides insulation 
against conductive losses by providing a vacuum between inner and outer 
tubes. A single solar tracking platform supporting the focusing panels and 
the energy gathering components provides a most efficient light gathering 
utilisation of a building roof or other surface. 
Accordingly an object of the present invention is to provide a sun tracking 
solar energy collector comprising: 
optical focusing means for concentrating sunlight falling on rectangular 
surface strips of optical focusing elements onto a much smaller area in 
the vicinity of the focus of the optical focusing means: 
a tubular metallic heat exchanger for containing a working fluid such as 
water or a gas and running along the foci of the optical focusing means 
thereby transferring the heat received by the concentrated sunlight to the 
working fluid; 
an insulating tube preferably metallic placed around the heat exchanger and 
presenting a highly reflective internal surface towards the metalic heat 
exchanger for reflecting back radiation emitted by the heat exchanger; 
small circular openings on the insulating tube covered with a transparent 
material such as glass for allowing the focused sunlight to enter the 
insulating tube and to reach the heat exchanger, the apertures 
constituting only a small portion of the total surface of the insulating 
tube; 
a vacuum maintained between the heat exchanger and the insulating tube for 
lowering conductive heat losses between the heat exchanger and the outside 
air; and 
a solar tracking platform for supporting the solar focusing means, the heat 
exchanger, and the insulating tube so that the optical axis of the optical 
focusing means remains substantially alligned with the direction of the 
sun. 
A further object of the present invention is to provide a solar energy 
collector of high surface utilization. 
A still further object of the present invention is to provide a solar 
energy collector capable of raising the temperature of the working fluid 
to a useful temperature preferably above the boiling temperature of water. 
A still further object of the present invention is to minimize shading of 
one focusing means by another focusing means. 
Another object of the invention is to efficiently utilize the height 
immediately above the solar energy collector by including a multiplicity 
of said light focusing means on same sun tracking platform. 
Still another object of the invention is to provide a solar collector 
exhibiting an efficient retention of the captured heat energy by providing 
insulating means to minimize both radiative and conductive losses. 
A still further object of the present invention is to provide a solar 
energy collector with efficient heat transfer properties to the working 
fluid. 
Another object of the present invention is to convert a portion of focused 
sunlight energy directly into electricity by use of solar cells, while 
converting a substantial portion of the remaining energy into heat for 
house heating, air conditioning and faucet hot water, by having solar 
cells receive focused sunlight while a heat exchanger, supporting the 
cells, acts as their heat sink, absorbing the non converted energy as 
heat. 
Another object of the present invention is to convert a portion of focused 
sunlight energy directly into electricity by use of solar cells, supported 
by a heat exchanger which is used as a heat sink, the cells being 
protected from mechanical damage by a tubular insulator external to the 
solar cells and the heat exchanger, and also protected from moisture 
damage through a vacuum maintained inside the tubular insulator. 
Another object of the present invention is to provide a solar collector 
with minimum variation of heat energy output during the 12 hours of daily 
sunshine. 
Still another object of the present invention is to provide a relatively 
light weight solar collector at relatively low cost compared to the yearly 
monetary benefit. 
The various features of novelty which characterize the invention are 
pointed out with partialarity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its uses, reference 
should behad to the accompanying drawings and descriptive matter in which 
there is illustrated a preferred embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings and particular to FIG. 1 and 8 a sun tracking 
solar energy collector system comprises light focusing means 10 rigidly 
supported by a sun tracking platform 20. The platform 20 is rotatably 
supported at the ends of a shaft 40 so that it can be continuously 
tracking the sun during its daily motion from East to West. 
The sunlight is being concentrated by the focusing means 10, onto circular 
apertures 32 on a tubular insulator 33, allowing the light to reach an 
internal heat exchanger tube 36, shown in detail in FIGS. 7a & 7b. The 
solar light may reach an aperture such as aperture 34 directly as shown in 
FIG. 5 and FIGS. 7a and 7b by sun ray 38, or through a reflection on 
mirrors, such as mirrors 50, as shown in FIG. 6. In FIG. 6. In FIG. 6 the 
focus is effectively being displaced from a point 51 to a new point 52 
symmetric to the point 51 with respect to the reflecting mirror 54. 
As in the type of FIG. 5a heat exchanger 31 is supported internally of tube 
insulator 33 in the type where mirrors 50 are used. The heat exchanger 31 
receiving the rays reflected by the mirrors 50, lies much closer to the 
focusing means 10. The circular aperture, such as apertures 32 allowing 
the concentrated light to reach the internal heat exchanger 36, are facing 
downwards, towards the mirrors 50, and therefore are not shown in FIG. 8. 
Therefore, FIG. 8 shows two types of focusing. Direct focusing onto energy 
receiving means 75 as shown in FIG. 5 or indirect focusing through mirrors 
50 onto energy receiving means 76, as shown in FIG. 6. 
Referring now to FIGS. 2a and 2b a reflector 26 with focusing properties 
such as that of a paraboloid or a spherical surface, is used as the basis 
for the derivation of an element 29 which amounts to a relatively narrow 
strip along the center portion of the reflector. FIG. 2b shows light rays 
27 and 28 being focused towards aperture 32. 
While the reflective focusing means of FIGS. 2a and 2b could concentrate 
the solar light onto a linear array of focal points 51, as shown in FIG. 
8, such reflectors would be harder to manufacture, to support and to keep 
properly alligned on the sun tracking platform 20. Full plano-convex or 
double convex refractive lenses, while desirable, would be extremely 
expensive and heavy for this application. The preferred type and 
particularly the basic element of the focusing means is a portion of a 
Fresnel lens the derivation of which is shown in FIGS. 3a and 3b. 
Turning now to FIGS. 3a and 3b a Fresnel lens 11 having a cross section 12 
may be defined in terms of the following parameters: 
the diameter of the aperture of the lens D; 
the radius R; 
the height of the ridges h; 
the minimum thickness t; and 
the refractive index of the material of the lens u. 
From the known lens equation, 
EQU 1/f=(u-1)(1/R.sub.1 +1/R.sub.2) (3) 
where f is the focal length of the lens and R.sub.1 and R.sub.2 are the 
radii of the two convex surfaces of the lens. 
Assuming R.sub.1 =R and R.sub.2 infinite, implying a plano-convex lens so 
that ridges will have to be formed only on one side of the lens, and 
assuming a refractive index about 1.5, the equation (2) may be written as, 
EQU f=2R (3a) 
By setting 
EQU R=KD/2 (4) 
equation (3a) becomes 
EQU f=KD or f/D=K (5) 
indicating that K, the ratio of the radius R to half the apertures (D/2), 
is equal to the focal length to aperture ratio. Since the smallest value 
that R can take is D/2 at which value the lens becomes a hemisphere, K=1 
the shortest focal length possible according to the equation (3a) is F=D, 
a focal length equal to the aperture. As values of K greater than unity 
would be preferable the resulting focal length is expected to be slightly 
greater than the aperture of the lens. In FIG. 3b a value of K=1.1 has 
been chosen, thereby R=0.55D and f=1.1D. For example, if aperture D of the 
lens were to be 5 ft. the focal length would be 5.5 ft. 
Once the parameters of the lens have been determined the curved surfaces 
AB, CD, Ef, etc as shown in FIG. 3b are drawn between lines 13 and 14, 
which determine the height of the ridges, as arcs with centers C.sub.A, 
C.sub.C, C.sub.E, etc. respectively, where the distance between any two 
consecutive centers is h. Preferably the value h is chosen to be an 
integral number of the medium wavelength of the solar spectrum. The lines 
joining the ends of the above arcs such as BC, DE, FG, etc are lines 13, 
14 and 15 parallel to the surface of the lens and normal to the optical 
axis 16 of lens 11. This geometrical construction may be used to guide the 
method of construction of the original die, which can then be used for 
mass production of the lenses, by stamping, casting or injection. 
In accordance with this method the sheet of metal used to make the die can 
be rotated about optical axis 16, shown in FIG. 3a and 3b while the 
cutting tool is effectively being pivoted from the centers such as 
C.sub.A, C.sub.C, C.sub.E etc. It may be noted that the cutting tool will 
cut, in an identical manner, if it is guided by an arc of radius greater 
than R, having centers at C.sub.A, C.sub.C, C.sub.E etc, but the tool and 
arc being conveniently located on the ridged side of the lens 11, while 
the actual distance of the cutting tool from the arc centers is being 
maintained at the value of R. 
Referring now to FIG. 3a the lens 11 comprises circular ridges with radii 
corresponding to the distances from the optical axis 16 of the points A, 
C, E, etc. The distance of the nth such circular ridge from the optical 
axis 16 can be expressed as 
##EQU1## 
It should be noted that equation (3) while it provides an approximate 
solution to the lens performance it is not absolutely accurate. Spherical 
aberration, comma, and astigmatism are names describing lens errors which 
are not apparent from the equation(3). With today's availability of 
computers the shape of the lens surface can be computed to provide optimum 
performance. 
According to the principles of optics focusing is accomplished by each 
element of the focusing means. This implies that the shape and size of the 
image of an object formed, for example, by a lens, especially at normal 
incidence, remains the same, regardless of what portion of the lens is 
actually being used. What changes when smaller portions of the lens are 
used is the intensity of the image. In the case of solar energy focusing, 
the object is the sun, effectively located at infinity, so that its image 
is being formed at the focus of the lens. 
To accomplish the aim of relatively high temperature high concentration of 
sunlight is needed, which can be achieved by a relatively large lens 
aperture D. In order that the foci of adjacent lenses are spaced at 
sufficiently short intervals on the heat exchanger tube so that the 
impinging heat can easily spread by conduction over the entire body of the 
heat exchanger tube, only narrow strips such as the strip W X Y Z of the 
lens 11 shown in FIG. 3a are to be used as a focusing element means. As 
mentioned above this will not affect the shape of the image, which in the 
case of the sun as the object, will be a small circle. 
FIG. 4 shows a W X Y Z rectangular section of a lens, identical to the W X 
Y Z element shown derived in FIG. 3a, now repeated 5 times to form a 
rectangular panel array 17 of W X Y Z lens elements. The axis BB' divides 
the array 17 into two identical square panels 18 and 19, symmetrically 
disposed with respect to the axis BB'. It is easier for the array 17 to be 
manufactured and be handled in terms of two square panels 18, 19 rather 
than a single rectangular panel 17. 
FIG. 5 shows the array of focusing elements of FIG. 4, as two array panels 
77, 78, concentrating the sun light, which is normally impinging on to the 
lens surfaces, on to five discrete foci formed on to the tubular heat 
exchanger 36. 
FIG. 6 shows focusing array 17 as array panels 79, 80 with ray 39 after 
being refracted by the W X Y Z focusing element, as ray 41 being reflected 
by a mirror 54 to the new focus point 52, located symmetrically to the 
original focus 51 with respect to the mirror 54. 
The benefits of the arrangement involving mirrors, as shown in FIG. 6 are: 
(1) the actual position of the heat exchanger 36 can be closer to the 
focusing means 17 and (2) mirrors 54 may contain screw adjustment (not 
shown) for a fine adjustment and therefore centering the light beam in an 
apertures such as aperture 53. 
Referring now to FIG. 7a, the heat exchanger 36 is a metallic type, 
preferably made out of a high heat conductivity material such as copper, 
containing a working fluid 25, such as water, air, hydrogen, or helium. 
When a gaseous working fluid is used it may be highly pressurized so that 
it can carry a greater amount of energy. The preferred working fluid is 
here assumed to be air at a midrange pressure such as would be a pressure 
between 100 and 250 pounds per square inch. In case of a small leak the 
desired pressure can be easily maintained through a standby pump (not 
shown). 
The heat exchanger 36 is preferably coated on its outer surface by a high 
absorbtivity low emissivity coating. Such coatings with an absorptivity as 
high as 95 and an emissivity of only 0.05 in the center of the solar 
spectrum have been reported to be available. 
The heat exchanger 36 is being supported inside insulator tube 33, through 
supporting washers 24 made out of insulative material such as ceramics. 
The primary function of the insulator tube 33 is to provide an insulating 
space 22 between it and the heat exchanger tube 36. As a vacuum the 
insulating space 22 will provide maximum insulation. While various 
materials, including glass, could be used to make up the insulator tube 
33, highest strength and reliability will be provided if the tube 33 is 
made of metal. The air-tight connection at the ends of each straight run, 
needed for sealing the space between the tubes 36, 33, is preferably made 
of metal which can easily be welded or brazed to each of said tubes. Since 
tube 33 is also made of metal it provide proper mechanical support and 
protection for the heat exchanger tube 36. 
The tube 33 is provided with internal reflective surface 35, for reflecting 
back towards the heat exchanger tube 36 the radiation emitted by the hot 
heat exchanger tube 36. The insulator tube 33, therefore, provides dual 
insulation; conductive insulation by establishing the vacuum space 22 and 
radiative insulation through its reflective surface 35. 
Apertures 34 spaced substantially equally along the length of the insulator 
tube 33 provide passage of the focused sun ray 38 to reach the heat 
exchanger tube 36, at a focus region 42. 
A transparent aperture cover 21 preferably made out of glass is used to 
provide a solid surface across the apertures 34. The edge of the glass may 
be sealed directly against the body of the tube 33 through special 
sealants. Since such sealants usually need high temperature treatment, it 
may be easier for the glass to be fabricated and sealed as a unit with a 
holder 41 as a separate process. The holder 41 with the glass can then be 
attached to the tube 33 with the combination of a screw thread and an 
anearobic sealant, for maintaining of a vacuum within space 22. 
It may be noted that while a substantial amount of radiation is incident on 
a small area of the focus region 42 the high conductivity of the body of 
the heat exchanger 36 is used to quickly conduct the incident heat away 
for the entire body of the heat exchanger thereby maintaining a uniform 
temperature. Heat will travel from the point of incidence of focus region 
42 towards its opposite side along the length of the tube 36. 
A cross section of the wall of the tube 36, other then a uniform wall, may 
exist, which will optimally distribute the heat in the body of the heat 
exchanger tube 36. It is the basis of a substantially uniform temperature 
over the body of the heat exchanger 36, that will help lower radiative 
losses from the heat exchanger 36 through the aperture cover glass 21 to 
the outer space, being that the greater portion of such radiation, falling 
on to the reflective inner surface 35 will be returned to the heat 
exchanger 36. 
FIG. 7b shows a second embodiment of the invention wherein the concentrated 
solar light illuminates a solar cell 43, whereby a significant percentage 
of the solar energy is directly converted into electricity. Part of the 
light will be reflected by the surface of the solar cell and part of the 
reflected light will escape back towards space through the aperture 34. A 
substantial amount of such radiation will remain inside the tube 33 by 
being re-reflected from the surface 35, of the tube 33, to the solar cell 
43. 
Solar cells are usually photovoltaic cells comprising a photosensitive 
surface 45, made out of N-type silicon, a P-type layer 46 which also 
provides the positive connection plate 47 and a negative connection 48. 
When the cell 43 is illuminated the light quanta penetrate to exite the 
junction between the two layers 45 and 46 allowing electrons to flow from 
the negative connection 48 to the positive connection plate of heat sink 
47. 
An external circuit connected between the connection 48, 47 can utilize the 
electron current flow as electrical energy. A series parallel connection 
of a large number of cells can bring both the working voltage and current 
to operating levels. 
Only a small portion of the light absorbed by the cell 43 is converted to 
electrical energy, the balance manifests itself as heat. Further, only a 
small portion of this heat will escape through the aperture 34 back into 
space. The balance will take two routes. In the first route heat will be 
conducted from the cell 43 to its heat sink such as the heat exchanger 36 
while in the second route heat radiated from the cell 43 arrives and is 
substantially absorbed by the plate or heat sink 47 and heat exchanger 36 
via one or more reflections from the reflective surface 35. 
While normal solar cells will not withstand the high concentrations of 
light referred to by the invention recently developed cells, referred to 
as "concentrator cells" can process light concentrations up to 200. With 
normal solar cells rated up to a temperature of 257 degrees F. the 
concentrator cells which withstand higher temperatures can be used to 
provide temperatures in the working fluid which will be adequate for home 
heating and air-conditioning, hot water and even production of additional 
electricity using the pressure of the working fluid in the heat exchanger 
36, to drive a turbine or an engine. 
While the size of the aperture 34 is desired to be small so that only a 
small portion of the reflected and re-radiated energy will escape back to 
space, it may be desirable to spread the radiation through the aperture on 
to a larger surface such as the surface of the solar cell 43. 
Spreading of the light beam can be easily accomplished if the transparent 
aperture cover 21 of aperture 34 is made in the form of a concave lens 44 
as shown in FIG. 7b. 
Refering again to FIG. 8 and to FIG. 9 platform 20 supports a multiplicity 
of the light focusing means 10, in the form of square panels such as 18 
and 19. The platform 20 is constructed around the shaft or spine member 40 
which is also used as a support spine for the main portion for sun 
tracking system. The spine member and structure is shown in greater detail 
in FIG. 9. Cantilever members 59, 60 extend from the spine member 40 on 
each side. Each pair of the cantilever members 59, 60 can be fabricated 
from a single "I" shape extruded aluminum seperable in two so that each 
half will be tapered toward the end. After separation the two "T" shaped 
beams 59, 60 are joined through a splice 64. A circumferential adaptor 
section 67 attach the pair of cantilever beams 59, 60 onto the spine shaft 
40. Securing means such as a through bolt 65 and tightening bolt 66 may be 
used for securing the adaptor section 67 to the spine shaft 40. 
Aluminum spot welding may also provide further strength to the connection 
between the adaptor section 67 and the spine 40. The splice member 64 and 
the adaptor section 67 may be preferably cast as one piece out of a 
suitable metal. Webs 69 formed by the top of the "T" beams provide 
rigidity of the cantilever members 59, 60 along the plane of the platform 
20. In addition webs 69 provide a convenient means for securing the panels 
18, 19 on to the platform 20 by screws 70 shown in FIG. 8 through holes 68 
provide on the web 69 as shown in FIG. 9. Accurate positioning and further 
rigidity of the cantilever members 59, 60 in the plane of the platform 20, 
is provided by brace members 62 interposed between and secure with the 
cantilever members by means of brackets 63. 
While one type of focusing, either direct focusing such as shown in FIG. 5 
or focusing through mirrors 50 such as shown in FIG. 6, may be used 
throughout the platform, FIG. 8 shows both types of focusing used with the 
same platform. Thus, the array panels 77 and 78 are directly focusing 
light into an array of foci formed along the heat energy receiving means 
75. The heat energy receiving means 75 is supported by the cantilever 
members 60 of the platform 20, through supporting members 71. 
Panels 79 and 80 gather focused light by combining their focusing through 
mirrors 50 at the new focal point 52. The energy receiving means 76 
comprises heat exchanger 31 and heat exchanger tube 36 inside the 
insulator 33. Apertures such as apertures 53 of insulator 33 are facing 
towards the mirrors 59 and therefore cannot be seen in FIG. 8. The mirrors 
50 previously described in FIG. 6 are supported by support members 72 in 
conjunction with a mirror supporting platform 58. 
A connecting section 74 connect the energy receiving means 75, 76 to permit 
heat interaction therebetween. The section 74 comprises an inner tube such 
as 36 and an insulator tube such as 33 but no apertures. Energy receiving 
means 76, 75, and 81, 82 shown in FIG. 8 may be connected in series or in 
parallel depending on sizes and temperatures involved in a particular 
system. 
Various methods may be employed for having the platform 20 supported and 
tracking the sun. While it may be easier to have the platform 20 supported 
and positioned, so that its surface remains substantially normal to the 
rays of the sun, be means attached to the roof of the building, it will be 
preferable if the platform 20 is supported by a tower based on solid 
ground. Such independent means of supporting and positioning the platform 
20 will preclude the danger of damage to the house structure by the 
platform. 
FIG. 1 shows such a preferred arrangement where a platform 20 is supported 
over the southern part of the house roof of a house 1. The platform 20 
carrying optical panels 18, 19, is being supported by a tower 2, having a 
foundation 3. 
A greater detail about the preferred method of support and positioning of 
the platform 20 is shown in FIG. 10. 
Referring now to FIG. 10, the tower 2 provides an inclined truss 90, which 
provides a pivot 105 about which the platform 20 can be tilted to point 
toward the sun as its seasonal southern declination varies. The truss 90 
is internally reinforced by cross members 106, 107. The truss 90 is 
structurally re-inforced by a support member 91, rigidly connected to the 
tower 2. The spine shaft 40 is rotatably supported by a yoke formed by a 
"U" beam 92 and two angle brackets 93. A gear 94 is rigidly attached to 
the shaft 40 so that, in conjunction with a worm gear 95, the shaft 40 and 
therefore the entire platform 20 can be rotated to track the sun during 
its daily movement. The worm gear 95 is rotatably supported by extenions 
96, 97 of the U beam 92. Rotation of the worm gear 95 is provided by a 
drive motor, (not shown), providing rotation to a drive spracket 99, which 
is connected through a chain or belt 100 to a second spracket 98 coaxially 
and rigidly attached to same shaft as the worm gear 95. 
Sun tracking due to the southern seasonal declination of the sun is 
accomplished by drive motor, not shown, driving through a gear train, a 
gear 104 which adjusts the angle of the "U" beam 92 about pivot 105, 
through a toothed arced member 102. 
Automatic tracking is achieved by the rise of an error voltage when the 
normal to the platform is displaced from the line to the sun. Two pairs of 
photosensitive elements such as phototransistors are employed to detect 
North/South and East/West deviations. Thus phototransistors 5 and 8 
positioned next to an aperture northward and southward, respectively, can 
provide a North/South error in terms of a voltage developed as a 
difference of currents provided by the phototransistors. When the platform 
it tilted too much to the South the transistor 8 will provide more current 
than transistor 5 causing the motor driving the gear 104 to rotate in the 
direction that will tilt the platform 20 Northwardly thus eliminating the 
error. A second pair comprising phototransistors 6 and 7 operate in a 
similar way for East/West positioning of the platform. Box 9 in the 
vicinity of the phototransistors 5, 6, 7, 8 serves to house the proper 
power supply and the electronic circuitry which is commercially available. 
An omnidirectional light detector, not shown, can provide signal to the 
electronic circuitry in box 9 when the sun rises in the morning or the sun 
reappears during a cloudy day. Such signal can provide sweep signals to 
the control circuitry so that the direction of the platform towards the 
sun can be re-initiated. 
Referring now to FIG. 11, a second method is shown for supporting and 
guiding the platform 20, to track the sun. A truss 121, supported on to 
the roof of the house 1, provides a swivel ball joint for rotatably 
supporting the shaft 40 at the upper side. At the lower side the shaft 40 
is permitted to be displaced between two members 125 and 126 forming an 
arc about a center located at the swivel ball joint 122. The members 125 
and 126 restrict the shaft 40 from side movement but permit it to rotate 
about its axis. They also provide an effective slot in which the shaft 40 
can be displaced vertically along the arc. This can be accomplished in 
terms of a cable 56 which is wound or unwound around a winch 129 by the 
action of a drive motor 57. Structural members 127, 123 and 124 provide 
support for the weight thrust which the platform exerts mainly towards the 
ground support members. East/West rotation of the platform is accomplished 
substantially similarly as previously described in terms of a worm drive 
95 and worm gear 94 shown in FIG. 10. Guidance signals are provided as 
previously described in terms of the phototransistors 5, 6, 7, 8, and the 
electronic circuitry in box 9. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the principles of the 
invention, it will be understood that the invention may be embodied 
otherwise without departing from such principles.