(12) United States Patent
(10) Patent No.:
US
6,612,705 B1
(45) Date of Patent:
Sep.2, 2003
(54)
MINI-OPTICS SOLAR ENERGY CONCENTRATOR
(76) Inventors:
Mark Davidson
807 Rorke Way, Palo Alto, CA (US) 94303
Mario Rabinowitz
715 Lakemead Way, Redwood City, CA (US) 94062-3922
Notice:
Subject to any disclaimer, the term of this patent is extended or
adjusted
under 35 U.S.C. 154(b) by 8 days.
(21) Appl. No.:
10/079,168 28 Claims, 5 Drawing Sheets
(22) Filed:
Feb.19,2002
(51) Int. C1.7 .......................G02B
7/182
(52) U.S. Cl . ……………... 359/851; 359/853;
359/873; 359/872
(58) Field of Search
359/851,853, 359/873, 872, 220, 221, 223, 224, 225,
226; 126/600, 684
(56) References Cited
U.S. PATENT DOCUMENTS
4,210,463 A * 7/1980 Escher ……… 136/246
4,402,575 A * 9/1983 Jacobs ……… 359/225
5,751,490 A * 5/1998 Johnson ……..359/605
5,851,309 A * 1V1998 Kousa ……… 136/248
* cited by examiner
Primary Examiner-Mohammad Sikder
(57) ABSTRACT
This invention deals with the broad general concept for
focusing light. A
mini-optics tracking and focusing system is presented for solar power
conversion that ranges from an individual's portable system to solar conversion
of electrical power that can be used in large scale power plants for
environmentally clean energy. It can be rolled up, transported, and attached to
existing man-made, or natural structures. It allows the solar energy conversion
system to be low in capital cost and inexpensive to install as it can be
attached to existing structures since it does not require the construction of a
superstructure of its own. This novel system is uniquely distinct and different
from other solar tracking and focusing processes allowing it to be more
economical and practical. Furthermore, in its capacity as a power producer, it
can be utilized with far greater safety, simplicity, economy, and efficiency in
the conversion of solar energy.
28 Claims, 5 Drawing Sheets
MINI-OPTICS SOLAR ENERGY CONCENTRATOR
BACKGROUND OF THE INVENTION
1. Field of the Invention
Due to an ever growing shortage of conventional energy sources, there is an
increasingly intense interest in harnessing solar energy. A limiting factor in
the utilization of solar energy is the high cost of energy converters such as
photovoltaic cells. Our invention provides a low cost means for achieving
affordable solar energy by greatly reducing the cost of solar concentrators
which increase (concentrate) the density of solar energy incident on the solar
energy converter.
For example, for the purpose of generating electricity, a large area of
expensive solar cells may be replaced by a small area of high-grade photovoltaic
solar cells operating in conjunction with the inexpensive intelligent
mini-optics of our invention. Thus our invention can contribute to the goal of
achieving environmentally clean energy on a large enough scale to be competitive
with conventional energy sources.
Our invention is less expensive than conventional solar concentrators for two
reasons. First due to miniaturization, the amount of material needed for the
optical system is much 2S less. Second, because our mini-optical solar
concentrator is light-weight and flexible, it can easily be attached to existing
structures. This is a great economic advantage over all existing solar
concentrators which require the construction of a separate structure to support
and orient them to intercept and properly reflect sunlight. Such separate
structures must be able to survive gusts, windstorms, earthquakes, etc. The
instant invention utilizes existing structureswhich are already capable of
withstanding such inclement vicissitudes of nature.
2. Description of the Prior Art
There are many prior art patents that deal with twisting balls (gyricon)
displays or separable balls displays. Electric or magnetic fields are used to
orient or move these polarized or charged balls. To our knowledge none of the
prior art utilizes the balls to optically concentrate (focus) light as in our
invention. Furthermore the prior art neither teaches nor anticipates our
application of the conversion of solar energy to electricity or any other form
of energy. In one embodiment our invention incorporates balls with a shiny
planar reflecting surface such as a metallic coating to give a high coefficient
of reflectance. When the prior art refers to superior reflectance
characteristics, they mean this in the context of displays with bi-colored balls
e.g. black and white; or separable colored balls. In fact, the gyricon and
separable so ball prior art do not teach the focusing of light in any capacity.
These verities are evident from an examination of the prior art. A large
representative sample of the prior art will now be enumerated and described.
This together with the references contained therein constitutes a comprehensive
compendium of the prior art.
U.S. Pat. No. 5,754,332 issued to J. M. Crowley on May 19, 1998 deals with
gyricon bi-colored balls whose reflectance is comparable with white paper. Ile
object is to produce a monolayer gyricon display.
U.S. Pat. No. 5,808,783 issued to J. M. Crowley on Sep. 15, 1998 deals with
gyricon bi-colored balls "having superior reflectance characteristics
comparing favorably with those of white paper." Again the objective
is a display application.
U.S. Pat. No. 5,914,805 issued to J. M. Crowley on Jun. 22,1999 utilizes two
sets of gyricon bi-colored balls "having superior reflectance
charactreristics comparing favorably with those of white paper" for display
purposes.
U.S. Pat. No. 6,055,091 issued to N. K. Sheridon and J. M. Crowley on Apr. 25,
2000 utilizes gyricon bi-colored cylinders. Again the objective is a display
application.
U.S. Pat. No. 6,072,621 issued to E. Kishi, T. Yagi aud T. Ikeda on Jun. 6, 2000
utilizes sets of different mono-colored polarized balls which are separable for
a display device.
U.S. Pat. No. 6,097,531 issued to N. K. Sheridon on Aug.1, 2000 teaches a method
for making magnetized elements (balls or cylinders) for a gyricon display.
U.S. Pat. No. 6,120.588 issued to J. M. Jacobson on Sep. 19, 2000 describes a
display device which uses mono-colored elements that are electronically
addressable to change the pattern of the display.
U.S. Pat. No. 6,174,153 issued to N. K. Sheridon on Jan. 16, 2001 teaches
apparatus for this purpose for a gyricon display.
U.S. Pat. No. 6,192.890 B1 issued to D. H. Levy and J.-P. F. Cherry on Feb. 27,
2001 is for a changeable tattoo display using magnetic or electric fields to
manipulate particles in the display.
U.S. Pat. No. 6,211,998 BI issued to N. K. Sheridon on Apr. 3, 2001 teaches a
method of addressing a display by a combination of magnetic and electric means.
U.S. Pat. No. 6,262,707 B I issued to N. K. Sheridon on Jul. 17, 2001 has a
similar teaching for a gyricon display.
A large number of prior art devices have been described, all of which are
directed at addressing and changing the pattern of a display device. While there
are other such prior art teachings, none of them teaches or anticipates our
invention.
DEFINITIONS
"Bipolar" refers herein to either a magnetic assemblage with the two
poles north and south, or an electric system with + and - charges separated as
in an electret.
"Collector" as used herein denotes any device for the conversion of
solar energy into other forms such as electricity, heat, pressure, concentrated
light, etc.
"Compaction" refers to increasing the density of a collection
(ensemble) of objects by geometrical arrangement or other means.
"Elastomer" is a material such as synthetic rubber or plastic, which
at ordinary temperatures can be stretched substantially under low stress, and
upon immediate release of the stress, will return with force to approximately
its original length.
"Electret" refers to a solid dielectric possessing persistent electric
polarization, by virtue of a long time constant for decay of charge separation.
"Electrophoresis or Electrophoretie," is an electrochemical process in
which colloidal particles or macromolecules with a net electric charge migrate
in a solution under the influence of an electric current. It is also known as
catapboresis.
"Focusing planar mirror," is a thin almost planar mirror constructed
with stepped varying angles so as to have the optical properties of a
much thicker concave (or convex) mirror. It can heuristically be thought of
somewhat as the projection of thin equi-angular segments of small
portions of a thick mirror upon a planar surface. It is a focusing planar
reflecting surface much like a planar Fresnel lens is a focusing transmitting
surface. The tracking-focusing property of an ensemble of tiny elements which
make up the focusing planar mirror are an essential feature of the instant
invention.
"Heliostat" denotes a clock-driven mounting for automatically and
continuously pointing apparatus in the direction of the sun.
"Immiscible" herein refers to two fluids which are incapable of
mixing.
"Packing fraction" herein refers to the fraction of an available
volume or area occupied by a collection (ensemble) of objects.
"Polar gradient" as used herein relates to magnetic optical elements
that are controlled in the non-gyricon mode such as in the magnetic field
gradient mode.
"Monopolar" as used herein denotes mono-charged optical elements that
are controlled in the non-gyricon mode such as the electrophoretic mode.
"Rayleigh limit" relates to the optical limit of resolution which can
be used to determine the smallest size of the elements that constitute a
mini-mirror. Lord Rayleigh discovered this limit from a study of the appearance
of the diffraction patterns of closely spaced point sources.
"Spin glass" refers to a wide variety of materials which contain
interacting atomic magnetic moments. They possess a form of disorder, in which
the magnetic susceptability undergoes an abrupt change at what is called the
freezing temperature for the spin system.
"Thermoplastic" refers to materials with a molecular structure that
will soften when heated and harden when cooled. This includes materials such as
vinyls, nylons, elastomers, fuorocarbons, polyethylenes, styrene, acrylics,
cellulosics, etc.
"Translucent" as used herein refers to materials that pass light of
only certain wavelengths so that the transmitted light is colored.
SUMMARY OF THE INVENTION
There are many aspects and applications of this invention. Primarily this
invention deals with the broad general concept of method and apparatus for
focusing light. A particularly important application is the focusing of
sunlight for power conversion and production.
It is a general object of this invention to provide a focusing planar
mini-optic system for reflecting light with a substantially higher power density
than the incident light.
One object is to provide an inexpensive, light-weight, and flexible mini-optical
light concentrator that can easily be attached to existing structures, and thus
does not require the construction of a superstructure of its own.
Another objective is to provide a solar energy conversion system that is not
only low capital cost, but that is also inexpensive to install.
A particularly important object is to provide a unique tracking and focusing
system for solar power conversion.
Another object is to provide a system that holds or locks the mini-mirror
elements in rigid orientation with minimal to no-power expenditure between
rotational focusing operations.
Another object is to provide a means for unlocking the mini-mirror elements so
that they may rotate freely when being guided into the proper orientation.
Another object is to provide an inexpensive system for photovoltaic conversion.
Another objective is to provide daily peaking power when the load is highest on
the conventional power grid.
Another objective is to provide electricity to remote villages or rural
settlements.
Another object is to provide a rugged system for conversion of solar energy to
heat.
Another objective is to provide electricity for communications installations.
Another object is to provide large-scale environmentally clean energy.
Another objective is to help in the industrialization of developing countries.
Another object is to provide a low-cost, tough, lightweight, concentrated
efficient solare energy converter that is highly portable.
Another objective is to provide a minitiarized planar heliostat field
configuration that can either track the sun temporally, or follow the sun with a
photomultiplier which searches for a maximum output.
Another object is to provide a portable system that can easily go anywhere man
can go, to track and concentrate the sun's energy.
Other objects and advantages of the invention will be apparent in a description
of specific embodiments thereof, given by way of example only, to enable one
skilled in the art to readily practice the invention as described hereinafter
with reference to the accompanying drawings.
In accordance with the illustrated preferred embodiments, method and apparatus
are presented that are capable of producing and maintaining a high concentration
of light relative to the original source such as sunlight. The embodiments are
all capable of secure attachment to sturdy existing structures to provide an
inexpensive application with a long and trouble-free life.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of an electrically charged bipolar sphere
with an equatorial flat reflecting surface. This sphere is one of a multitude of
optical elements which track the sun and focus the sun's light beam onto a
collector.
FIG. 2 is a cross-sectional view of a magnetically charged bipolar sphere with
an equatorial flat reflecting surface. This sphere is one of a multitude of
optical elements, which track the sun and focus the sun's light beam onto a
collector.
FIG. 3 is a cross-sectional view of a circular disk with a backside-reflecting
surface. This disk is one of a multitude of optical elements which track the sun
and focus the sun's light beam onto a collector.
FIG. 4 is a cross-sectional view of a cylinder with an internal flat reflecting
surface. This cylinder is one of a multitude of optical elements which track the
sun and focus the sun's light beam onto a collector.
FIG. 5 is a cross-sectional view of a circular disk with a frontside reflecting
surface. This disk is one of a multitude of optical elements which track the sun
and focus the sun's light beam onto a collector.
FIG. 6 is a cross-sectional view of a monopolar electric cell filled with two
immiscible fluids, and shiny charged particles of the same sign in the bottom
one. 'Ibis cell is one of a multitude of optical elements which track the sun
and focus the sun's light beam onto a collector.
FIG. 7 is a cross-sectional view of a ferrofluid cell partially filled with a
colloidal suspension of shiny ferromagnetic particles in a fluid. This cell is
one of a multitude of optical elements which track the sun and focus the sun's
light beam onto a collector.
FIG. 8 is a cross-sectional view of a mini-optics ensemble of elements of two or
more populations of sizes to increase the packing fraction and hence the
reflectance. Each element tracks the sun and focuses the sun's light beam onto a
collector.
FIG. 9 is a cross-sectional view of a mini-optics ensemble of elements showing
the overlay of a transparent ground plane on top and a resistive grid on the
bottom to locally produce varying mini-electric fields for orienting the
mini-mirrors to focus the incident light onto a collector.
FIG. 10 is a perspective view of a two-dimensional array of the rotatable
elements of a focusing planar mirror.
FIG. 11 is a schematic top view showing the electronic control grid for rotating
the reflecting elements of a focusing planar mirror.
FIG. 12 illustrates method and apparatus for significantly increasing the degree
of concentration of solar energy reaching the collector by utilizing two or more
focusing planar mirrors.
DETAILED DESCRIPTION OF THE PRESENTLY
PREFERRED EMBODIMENTS
FIG. 1 shows a rotatable element 1 of a
focusing planar mini-mirror with an
equatorial flat reflecting surface 2 which 25 reflects
a wave beam of sunlight 3. The element I shown is a cross-sectional view of an
electrically charged bipolar sphere 4 with charge +q in one hemisphere and
charge -q in the opposite hemisphere, that is operated in the well-known
electrical gyricon mode. This sphere 4 is one of a multitude of rotatable
optical elements 1 which track the sun and focus the sun's light wave beam onto
a collector by means of an electric field E.
FIG. 2 shows a rotatable element 1 of a focusing planar mini-mirror with a flat
equatorial reflecting surface 2 which reflects a wave beam of sunlight 3. The
element 1 shown is a cross-sectional view of a magnetically charged bipolar
sphere 4 with north magnetic field N in one hemisphere and south magnetic field
S in the other hemisphere, that is operated in the well-known magnetic gyricon
mode. This sphere 4 is one of a multitude of rotatable optical elements 1 which
track the sun and focus the sun's light beam onto a collector by means of a
magnetic field B.
FIG. 3 shows a rotatable element 1 of a focusing planar mini-mirror with a
backside reflecting surface 2 which reflects a light wave beam 3. The element I
shown is a cross-sectional view of a circular disk 5 with rounded edges, that is
operated in any of the well-known modes, such as gyricon, electrical monopolar,
magnetic, polar gradient, etc. Ibis disk 5 is one of a multitude of rotatable
optical elements 50 1 which track the sun and focus
the sun's light wave beam onto a collector by means of an electric field or
magnetic field, or combination thereof. It should benoted that in display modes,
a spherical or cylindrical shape is necessary for the elements, as they must be
able to rotate 180 degrees without binding up in order to display a black or
white side up. In the instant invention, a 90 degree rotation of the element I
is more than sufficient as this produces a 180 degree reflection of the beam of
sunlight. Since the angle of reflection is equal to the angle of incidence on
the reflecting element 1, a doubling of the angle is produced.
FIG. 4 shows a rotatable element I of a focusing planar mini-mirror with an
internal flat reflecting surface 2 in the plane of the hemicylinders which
reflects a wave beam of sunlight 3. The element 1 shown is a
cross-sectional view of a cylinder 6 that is operated in any of the well-known
modes, such as gyricon, electrical monopolar, magnetic, polar gradient, etc.
This cylinder 6 is one of a multitude of rotatable optical elements I which
track the sun and focus the sun's light beam onto a collector by means of an
electricfield or magnetic field, or combination thereof.
In the case of non-front-surface reflection such as shown in FIGS. 1-4, the
material of element 1 needs to be clear or transparent so the incident light can
easily reach the reflecting surface 2.
FIG. 5 shows a rotatable element 1 of a focusing planar mini-mirror with a
frontside reflecting surface 2 which reflects a light wave beam 3. This is a
presently preferred embodiment of the rotatable element 1. The element I shown
is a cross sectional view of a circular disk 5, with rounded edges that is
operated in any of the well-known modes, such as gyricon, electrical monopolar,
magnetic, polar gradient, etc. Ibis disk 5 is one of a multitude of optical
elements 1 which track the sun and focus the sun's light wave beam onto a
collector by means of an electric field E or magnetic field B, or combination
thereof. The case is illustrated where two-axis control is possible in mutually
orthogonal directions by means of embedded charge +q and -q at top andbottom,
and embedded magnetic field with north magnetic field N at one end and south
magnetic field S in the other as shown. TWo-axis control can also be
accomplished with either an E or B field singly.
It should be noted that in prior art display modes, a spherical or cylindrical
shape is necessary for the elements, as they must be able to rotate 180 degrees
without binding up in order to display a black or white side up. In the instant
invention, a 90 degree rotation of the element I is more than sufficient as this
produces a 180 degree reflection of the beam of sunlight, since the angle of
reflection is equal to the angle of incidence on the reflecting element 1. Thus
a doubling of the angle is produced herein.
FIG. 6 shows a fixed element 10 of a focusing planar mini-miffor which is a
cross-sectional view of a monopolar electric cell 2 partially filled with a
bottom fluid 7 with shiny charged particles 8 of the same sign (shown here as +,
but which could also all be -), and a top transparent fluid 70. The two fluids
are immiscible. When an electromagnetic field E' is applied, the particles 8
coalesce to form a flat reflecting surface at the interface between fluid 7 and
fluid 70, as also influenced by surface tension and meniscus. Fluid 70 could be
air, but a transparent fluid of substantially less density than fluid 7 is
preferred so that gravity will act to maintain their relative top/bottom
orientations. If the particles 8 are small enough to form a colloidal
suspension, the density of the particles 8 and the fluid 7 may differ. However,
it is generally preferable to have the density of the particles 8 approximately
matched to the fluid 7.
The orientation of this flat reflecting surface can be controlled by E to
reflect light 3. Until the electric field E is applied, as an optional
capability the particles 8 and the fluid 7 can function as a transparent window
when the particles 8 are nanosize i.e. much smaller than the wavelength of the
incident light and the fluid 7 is transparent or translucent while they are
dispersed in the fluid 7. For the case of dispersed transparency' the particles
8 should be <<4000 A (4x 10-7 in). This cell 2 is one of a
multitude of optical elements I which track the sun and focus the sun's wave
beam onto a collector. 7be particles 8 may include a wide variety of
electomagnetically interactive materials such as electret, optoelectric,
conducting, thermoelectric, electrophoretic, resistive, serniconductive,
insulating, piezoelectric, magnetic, ferromagnetic, paramagnetic, diamagnetic,
or spin (e.g. spin glass) materials. It should be noted that the reflecting area
remains constant for spherical and circular-cylindrical cells, as the
orientation of the reflecting surface changes. However, the increase in
reflecting area is not a serious problem for the non-spherical, non-4ircular
cell geometry shown.
FIG. 7 shows a fixed element 11 of a focusing planar mini-mirror which is a
cross-sectional view of a ferrofluid cell 3 partially filled with a ferrofluid 9
containing shiny ferromagnetic particles 10 of high permeability, shown here as
u, and a top transparent fluid 90. The two fluids are immiscible. When an
inhomogeneous electromagnetic field B of increasing gradient is applied, the
particles 10 are drawn to the region of increasing gradient and coalesce to form
a flat reflecting surface at the interface between fluid 9 and fluid 90, as also
influenced by surface tension and meniscus. Fluid 90 could be air or a
transparent fluid of substantially less density than fluid 9 so that gravity
will act to maintain their relative top/bottom orientations. The orientation of
the flat reflecting surface can be controlled by B to reflect light 3. This cell
3 is one of a multitude of optical elements I which track the sun and focus the
sun's wave beam onto a collector. The particles 10 are small enough to form a
colloidal suspension, and are coated to prevent coalescence until B is applied,
as is well known in the art. It should be noted that the reflecting area remains
constant 20 for spherical and circular-cylindrical cells, as the orientation of
the reflecting surface changes. However, the increase in reflecting area is not
a serious problem for the non-spherical, non-circular cell geometry shown.
FIG. 8 is a cross-sectional view of a mini-optics ensemble 4 of rotatable
elements 1 of two or more populations of particle sizes to increase the packing
fraction and hence increase the energy of the reflected wave 30. The particles
are contained between two elastomer sheets 11 of which the top sheet 11' is
transparent. The large particles 12 and the small particles 13 can already be
rotatable, or rendered rotatable by expanding the clastomers. 11 by the
application of a fluid thereto. TU small particles 13 are disposed in the
interstices of the monolayer arrangement of the large particles 12. Thus the
small particles 13 just fit into the small pockets created by theconjunction of
the large particles 12, to create more reflecting area than the very small area
that these small particles 13 block of the large particles 12. Each element I
tracks the sun and focuses the sun's light beam onto a collector.
Let us here consider the packing (compaction) of spheres in broad terms so that
we may better understand the various trade-offs that may be undertaken in the
choice of one set of particles 12 versus two sets of particles 12 and 13, or
more; and the relative advantages that are also a function of the packing array.
(The spheres are chosen for convenience. We could equally well be discussing
circular disks as in FIGS. 3 and 5) With one set of particles 12 of radius R in
a square monolayer array in which any adjacent four particles have their centers
at the comers of a square, the maximum packing fraction of the circular mirrors
is
This means that as much as 21% the reflecting area is wasted, with less
than 79% of the area available for reflection. If a second population of
particles 13 are put into the interstices, their radii would need to be just
slightly greater than
so that they would fill the interstices of a monolayer of spheres (first
population), and yet not fall through the openings. The maximum packing fraction
in square array of two such sets of circular mirrors is
Thus just by the addition of a second population of particles 13, of the
right size, the reflecting area can increase from about 79% to about 92% in a
square array.
Now lot us consider one set of particles 12 of radius R in a hexagonal monolayer
array in which any adjacent six particles have their centers at the comers of a
hexagon. In this case, the maximum packing fraction of the circular is mirrors
is
This means that only about 10% the reflecting area is wasted, with about
90% of the area available for reflection with one population of particles 12, by
just going to a hexagonal array. If a second population of particles 13 are put
into the interstices, their radii would need to be just slightly greater than
so that they would fill the interstices of a monolayer of an hexagonal aff ay of
spheres (first population of particles 12), and yet not fall through the
openings. The maximum packing fraction in hexagonal array of two such sets of
circular mirrors is
Thus just by the addition of a second population of particles 13, of the right
size, the reflecting area can increase from about 90% to about 95% in an
hexagonal array.
The following two tables summarize the above results on packing fractions.
|
TABLE 1
|
|
Comparison of Hexagonal and Square Packing Fractions
|
|
|
PF1
|
PF2
|
PF2/PF1
|
|
Hexagonal Packing
|
0.907
|
0.951
|
1.049
|
|
Square Packing
|
0.785
|
0.920
|
1.172
|
|
|
TABLE 2
|
|
Relative Gain of Hexagonal vs. Square Packing |
|
PFh1/PFs1 |
PFh2/PFs2
|
PFh2/PFs1
|
|
|
1.155 |
1.034 |
1.211 |
|
|
0.785
|
0.920
|
1.172
|
|
Interesting conclusions can be drawn from TABLES 1 and 2 which can be guides for
design tradeoffs even though the calculated quantities are upper limits of what
can be attained in practice. TABLE 2 shows that just by going from a square
monolayer array to an hexagonal monolayer array the reflecting area can be
increased by about 16%. When two populations of particles 12 and 13 are used,
there is only about a 3% improvement by going to an hexagonal array. The largest
improvement is about 21% for a two population hexagonal array comparedwith a one
population square array.
FIG. 9 is a cross-sectional view of a mini-optics ensemble 5 of an individually
rotatable monolayer of elements I showing the overlay of a transparent ground
plane 14 on top and a resistive grid 15 on the bottom to locally produce varying
mini-electric fields for orienting the mini-mirrors 2 to focus the incident
light 3 as concentrated light of the reflected wave 30 onto a collector 16. The
collector 16 as used herein denotes any device for the conversion of solar
energy such as electricity, heal, pressure, concentrated light, etc. The
rotatable elements 1 are situated in ridged cells 17 15 between
two elastomer sheets. For spherical or cylindrical elements A the ridged
cellular structure 17 is conducive but not necessary to hold the elements in
grid position in the array structure. For elements 1 of disk shape 5 as in FIGS.
3 and 5, the ridged cells 17 are a valuable adjunct in maintaining the array
structure and avoiding binding between the elements 1.
Because the mini-optics system is tough and light-weight it is highly portable
unlike existing light concentrating optical systems that are heavy, bulky, and
cumbersome. Furthermore, the mini-optics system can easily be mass produced at
low cost since it is mainly two sheets of thin lastic with millions of
smart-beads sandwiched between the sheets. The mini-optics system can be rolled
up, transported, and attached to existing man-made, or natural structures such
as trees, rocks, hillsides, and mountain tops. Therefore, in addition to
providing solar energy in conventional urban settings, the mini-optics system is
also ideally suited for rugged terrain and can be used by campers, mountain
climbers, explorers, etc. It is unmatched as a portable system that can easily
go anywhere man can go, and track and concentrate the sun's energy.
When rotation of the elements I is desired, the effect of the torque applied by
the field can be augmented by injecting a fluid 18 from a plenum reservoir 19 by
a pressure applying means 20 to expand the separation of the sheets 11. In the
case of non-front-surface reflection such as shown in FIGS. 1-4, it is desirable
to utilize a fluid 18 whose index of refraction matches the clear hemisphere or
clear hemicylinder. In addition to providing a means to pressure the elastomer
sheets 11 apart, the fluid 18 acts as a lubricant to permit the elements 1 to
rotate freely when being guided into the proper orientation.
The ridged cells 17 can be created in thermoplastic elastomer sheets 11 by
heating the sheets 11 to a slightly elevated temperature and applying pressure
with the elements 1 between the sheets 1. In the case of elements 1 of disk
shape 5, the ridged cells 17 can be created on each sheet individually. This
gives twice the height for the cells, when two such sheets are put together to
hold the elements 1.
A presently preferred maximum for the diameter of elements 1 is -10 mm or more
for this figure and for FIGS. 1-5. The minimum diameter of elements I can be
assessed from the Rayleigh limit
where d is the minimum diameter of elements 1, λ ~
4000 A is the minimum visible wavelength, n is the index of refraction -1 of
element I (the medium in which the incident light is reflected), and u is the
half angle admitted by elements 1. Thus d ~ 40,000 A (4 x l0-6 m)
is the minimum diameter of elements 1.
If the focusing planar mini-mirrors concentrate the solar radiation by a factor
of 100, the total increase in power density reaching the collector would be 100
times greater than the incident power of the sun. Thus the collector area need
be only ~ 1% the size of one receiving solar radiation directly. Although the
total capital and installation cost of this improved system may be more than 1%
of a direct system, there will nevertheless be substantial savings.
FIG. 10 is a perspective view of a two-dimensional array of the rotatable
elements 1 of a focusing planar mini-mirror with an equatorial flat reflecting
surface 2 which reflects incident light 3 and focuses it as a concentrated light
wave 30 to a collector 16.
FIG. 11 is a schematic top view showing the electronic control grid 33 for
rotating the reflecting elements of a focusing planar mini-mirror. Except for
the cylinders of FIG. 4 which have a one-axis response, the preferred
non-cylindrical geometry of each of the other elements 1, 10, or 11 is capable
of rotating in any direction (two-axis response) in response to a selectively
applied electric field by the electronic control grid 33. The electronic control
grid 33 is made of resistive components 21. The mini-mirror/lens array with
elements 1, 10, or 11 is sandwiched between the resistive electronic control
grid shown here and the transparent ground plane as shown in the cross-sectional
view of FIG. 9. The orientation of the elements 1, 10, or 11 (cf. FIGS. 1-7) is
determined by controlling the voltages V at the nodes of the grid such as those
shown V00 ,
V01 , V02 , V10 ,
V11, with
voltage Vij at the
ij th node. The voltage Vij can be controlled by a very small inexpensive computer with analog
voltage outputs. Once in operation, this system can be powered by the solar
energy conversion device which collects the concentrated light. The electronic
control grid 33 is similar in construction and function to analogous grids used
in personal computer boards, and in flat panel monitors.
The voltage between successive nodes produces an electric field in the plane of
the planar mini-mirror, and the voltage between a node and the ground plane
produces an electric field perpendicular to the planar mini-mirror to control
the orientation angle of the reflecting/focusing mini-mirrors. The number of
elements 1 , 10, or 11 per grid cell is determined by the degree of focusing
desired: the higher the degree of focusing, the fewer the number of elements
per grid cell. In the case of elements 1 which contain orthogonal electrical and
magnetic dipoles as in FIG. 7, the orientation function may be separated for
orientation in the plane and orientation perpendicular to the plane by each of
the fields.
After being positioned for optimal focusing angles of reflection, elements 1
(cf. FIGS. 1-5, and 9) may be held in place by the elastomer sheets 11 (cf.
FIGS. 8 and 9) with the voltages Vij
being turned off to eliminate unnecessary power dissipation. When a new angular
orientation of the elements I and 2 is desirable due to the sun's motion
relative to the earth, the sheets 11 (cf. FIG. 9) are separated by injecting a
fluid 18 from a plenum reservoir 19 by a pressure applying means 20. In the case
of elements 10 or 11 the reflecting angle needs to be held fixed by the control
function which is the electronic control grid 33. To minimize power dissipation
in this case it is desirable to make resistive components 21 highly resistive so
that a given voltage drop is accomplished with a minimum of current flow and
hence with a minimum of power dissipation.
FIG. 12 illustrates method and apparatus for significantly increasing the degree
of concentration of solar energy reaching the collector by utilizing two or more
focusing planar mini-mirrors. Shown are a cross-sectional view of two sets of
mini-optics ensembles 6 and 7 of rotatable elements I wherein the sunlight 3 is
incident on the first ensemble 6 and the reflected light 40 from this first
ensemble 6 is focused on the second ensemble 7 to reflect light 50 which is
further concentrated and focused on the collector 16. The mini-optics ensembles
6 and 7 are attached to a structure 100 which preferably is a pre-existing
structure such as a building.
To illustrate the magnification capability of this configuration, in the ideal
case where all theincident light is reflected without absorption or losses, if
the two sets of focusing planarmini-mirrors each concentrated the light energy
by a factor of 100, the total increase in power density reaching the collector
would be a factor of (100)' -10,000 times greater than the incident power. For n
such reflectors each feeding into the other until finally reaching the
collector, the increase would be (100r. Similarly, if two focusing planar
mini-mirrors were positioned to have n concentrating reflections between them
before the light is reflected to the collector, the increase would also be
(100r. Of course in a real case the increase would be less than this due to
losses.
The thermodynamic limit of such a scheme would be an effective temperature of
the radiation atthe collector no higher than the source temperature which in the
case of the sun is ~ 6000 K. A practical limit would occur much before this
related to temperatures well below the melting point of the materials used.
There is also an optical limit that the power per unit area per steradian cannot
be increased by a passive optical system.
A major advantage of the instant invention, is that the focusing planar
mini-mirrors can be attached to an already existing
structure 100, ranging from buildings to trees t; rocks, or even flat on the
ground. Since the necessary structural strength is already built into the
existing structure, no additional funds need be expended to construct mirror
supporting edifices which are capable of withstanding harsh winds, earthquakes,
and other natural disturbances.
While the instant invention has been described with reference to presently
preferred and other embodiments, the descriptions are illustrative of the
invention and are not to be construed as limiting the
invention. Thus, various modifications and applications may occur to those
skilled in the art without departing from the true spirit and scope of the
invention as summarized by the appended claims.
What is claimed is:
1. |
A miniature optics system for
concentrating reflected sunlight, |
|
comprising: (a) an array
of miniature rotatable reflecting balls having two hemispheres positioned in
the space between two sheets holding said array of miniature reflecting
balls; (b) the top sheet of said two sheets being transparent; (c) means to
individually rotate the array of balls within said sheets; and (d) a dipole
embedded in each ball for coupling to at least one of the sheets.
|
2. |
The apparatus of claim 1, wherein
each said rotatable miniature |
|
reflector is a ball
comprising: (a) a reflector embedded in said ball; and (b) charge of opposite sign
in each said ball.
|
3. |
The apparatus of claim 1, wherein
each said rotatable miniature |
|
reflector is a ball
comprising: (a) a reflector embedded in said ball; and (b) a magnetic dipole each
said ball.
|
4. |
The apparatus of claim 1, wherein
each said rotatable miniature |
|
reflector is a disk
comprising: (a) a reflector on one of the surfaces of said disk; and (b) bipolar
charge in each disk.
|
5. |
The apparatus of claim 1, wherein
each said rotatable miniature |
|
reflector is a disk
comprising: (a) a reflector on one of the surfaces of said disk; and (b) a
magnetic dipole embedded in said disk.
|
6. |
The apparatus of claim 1, wherein
each said rotatable miniature |
|
reflector is a disk
comprising: (a) a reflector on one of the surfaces of said disk, and (b) a
magnetic dipole and an electric dipole embedded in said disk.
|
7. |
The apparatus of claim 1, wherein
each said rotatable miniature |
|
reflector is a cylinder
comprising: (a) a reflector embedded in said cylinder; and (b) means for
coupling to an electromagnetic
field.
|
8. |
The apparatus of claim 1, wherein
said sheets maintain said |
|
reflectors in fixed
azimuthal orientation.
|
9. |
The apparatus of claim I with
means for spreading apart said |
|
sheets.
|
10. |
The apparatus of claim 1, wherein the
diameter of each said |
|
rotatable
miniature reflector is in the range 4x10-6 m to 10-1 m .
|
11. |
The apparatus of claim 1, wherein at
least one sheet forms a |
|
cellular array.
|
12. |
The apparatus of claim 1, wherein said
concentrating reflected |
|
light is caused
to produce power.
|
13. |
The apparatus of claim 1, wherein said
concentrating reflected |
|
light is caused
to produce electrical power.
|
14. |
A miniature optics system for
concentrating reflected sunlight, |
|
comprising: (a) an
array of rotatable miniature reflectors positioned in the space between
two sheets; (b) means for rotating said rotatable miniature reflectors; (c) means for
tracking the source of light; (d) means for focusing said reflecting system unto a collector; and (e) a dipole
embedded in each reflector for coupling to at least one of the sheets.
|
15. |
The apparatus of claim 14, wherein each
said rotatable miniature |
|
reflector is a
body comprising: (a) a reflector embedded in said body; and (b)
field producing sources in each quadrant of said body.
|
16. |
The apparatus of claim 14, wherein the
said sheets maintain |
|
the reflectors in
fixed azimuthal orientation.
|
17. |
The apparatus of claim 14 with means
for spreading apart |
|
the sheets.
|
18. |
The apparatus of claim 14, wherein said
concentrating |
|
reflected light is caused
to produce power.
|
19. |
The apparatus of claim 14, wherein said
concentrating |
|
reflected light is caused
to produce electrical power.
|
20. |
The apparatus of claim 14 wherein the
concentrated light |
|
is used in a process
to charge a fuel cell.
|
21. |
The apparatus of claim 14 wherein the
concentrated light |
|
is used in a process
to de-salinate water.
|
22. |
The apparatus of claim 14 wherein the
concentrated light |
|
is used in a process
to charge batteries.
|
23. |
The apparatus of claim 14 wherein the
concentrated light |
|
is used in a process
to produce hydrogen fuel.
|
24. |
The apparatus of claim 14 wherein the
concentrated light |
|
is used to heat a
building.
|
25. |
The apparatus of claim 14 wherein the
concentrated light |
|
is used to melt
snow or ice.
|
26. |
The apparatus of claim 14 wherein the
concentrated light |
|
is used to heat
water.
|
27. |
The apparatus of claim 14 wherein the
concentrated light |
|
is used to provide
heat for a distillation process.
|
28. |
The apparatus of claim 14 wherein the
concentrated light |
|
is used to provide
heat or electricity for powering an ocean-going vessel. |