U.S. patent application number 11/793041 was filed with the patent office on 2008-08-28 for electromagnetic radiation collector.
Invention is credited to Garry Chambers, Alastair McIndoe Hodges.
Application Number | 20080202500 11/793041 |
Document ID | / |
Family ID | 36588252 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080202500 |
Kind Code |
A1 |
Hodges; Alastair McIndoe ;
et al. |
August 28, 2008 |
Electromagnetic Radiation Collector
Abstract
An electromagnetic radiation collector is provided. The
electromagnetic radiation collector has a concentration chamber for
collecting and concentrating electromagnetic radiation and
directing it to a target, the concentration chamber having at least
one inlet opening, the inlet opening having a cross-sectional area.
The collector also has a channeling area having an entry end for
receiving the electromagnetic radiation, the entry end having a
cross-sectional area, an exit end adjacent to the inlet opening of
the concentration chamber, and at least one reflective wall between
the entry end and the exit end. The cross-sectional area of the
inlet opening is smaller than the cross-sectional area of the entry
end of the channeling area.
Inventors: |
Hodges; Alastair McIndoe;
(Blackburn South, AU) ; Chambers; Garry; (Vermont,
AU) |
Correspondence
Address: |
VENABLE LLP
P.O. BOX 34385
WASHINGTON
DC
20043-9998
US
|
Family ID: |
36588252 |
Appl. No.: |
11/793041 |
Filed: |
December 16, 2005 |
PCT Filed: |
December 16, 2005 |
PCT NO: |
PCT/IB05/03838 |
371 Date: |
June 15, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60636652 |
Dec 17, 2004 |
|
|
|
Current U.S.
Class: |
126/684 |
Current CPC
Class: |
Y02E 10/42 20130101;
F24S 2023/88 20180501; Y02E 10/40 20130101; F24S 23/71 20180501;
F24S 23/12 20180501; F24S 23/30 20180501 |
Class at
Publication: |
126/684 |
International
Class: |
F24J 2/10 20060101
F24J002/10 |
Claims
1. An electromagnetic radiation collector, comprising: a
concentration chamber for collecting and concentrating
electromagnetic radiation and directing it to a target, the
concentration chamber having at least one inlet opening, the inlet
opening having a cross-sectional area; and a channeling area having
an entry end for receiving the electromagnetic radiation, the entry
end having a cross-sectional area, an exit end adjacent to the
inlet opening of the concentration chamber, and at least one
reflective wall between the entry end and the exit end, wherein the
cross-sectional area of the inlet opening is smaller than the
cross-sectional area of the entry end of the channeling area.
2. The collector of claim 1, wherein the concentration chamber has
a top and a bottom that are not parallel to each other.
3. The collector of claim 2, wherein the concentration chamber is
for directing the collected and concentrated electromagnetic
radiation in the direction of the diverging ends of the top and
bottom.
4. The collector of claim 1, comprising a plurality of the
channeling areas.
5. The collector of claim 4, wherein the entry ends of the
plurality of channeling areas are adjacent to each other and the
exit ends of the plurality of channeling areas are adjacent to each
other.
6. The collector of claim 1, wherein the channeling area is formed
by a first surface for reflecting the electromagnetic radiation,
and a second surface opposite the first surface.
7. The collector of claim 1, wherein the entry end has a central
axis along a first direction, and the cross-sectional area of the
entry end is perpendicular to the first direction, and the exit end
has a central axis along a second direction, and a cross-sectional
area perpendicular to the second direction, the cross-sectional
area of the entry end is larger than the cross-sectional area of
the exit end, and the second direction is not parallel to the first
direction.
8. The collector of claim 7, wherein the second direction is
substantially perpendicular to the first direction.
9. The collector of claim 1, further comprising a target positioned
adjacent to the exit end of the concentration chamber, the target
being positioned to receive the electromagnetic radiation.
10. The collector of claim 1, wherein the channeling area is a
solid element.
11. The collector of claim 9, wherein an outside surface of the
solid element is coated with a coating that is adapted to reflect
the electromagnetic radiation.
12. The collector of claim 1, wherein the channeling area is a
tube, the entry end being an opening of the tube, and the exit end
being an opening of the tube.
13. The collector of claim 12, wherein at least one of an inside
surface of the tube and an outside surface of the tube is coated
with a coating that is adapted to reflect the electromagnetic
radiation inside the tube.
14. The collector of claim 1, wherein the channeling area has a
circular cross-section.
15. The collector of claim 1, wherein the channeling area has a
rectangular cross-section.
16. The collector of claim 1, wherein the channeling area has a
square cross-section.
17. The collector of claim 2, wherein the entry ends of the
channeling areas are staggered relative to each other.
18. The collector of claim 1, wherein the channeling area has a
length from the entry end to the exit end, and the entry end has a
maximum width, the length of the channeling area being between 2
and 1000 times as large as the maximum width of the entry end.
19. The collector of claim 18, wherein the length of the channeling
area is between 5 and 100 times as large as the maximum width of
the entry end.
20. The collector of claim 19, wherein the length of the channeling
area is between 10 and 50 times as large as the maximum width of
the entry end.
21. The collector of claim 1, further comprising a flap protruding
into the concentration chamber adjacent to the inlet opening, the
flap being for directing at least a portion of the electromagnetic
radiation toward the target.
22. The collector of claim 21, wherein the reflective wall of the
channeling area is parabolic and the focal point of the parabolic
reflective wall is on one of the flaps.
23. The collector of claim 1, wherein the at least one reflective
wall of the channeling area is parabolic and the focal point of the
parabolic reflective wall is in the inlet opening of the
concentration chamber.
24. A method of collecting electromagnetic radiation, comprising:
channeling-electromagnetic radiation in a channeling area, the
channeling area having an entry end for receiving the
electromagnetic radiation, an exit end, and at least one reflective
wall between the entry end and the exit end, the entry end having a
cross-sectional area, collecting and concentrating the
electromagnetic radiation in a concentration chamber, the
concentration chamber having at least one inlet opening adjacent
the exit end of the channeling area, the inlet opening having a
cross-sectional area; and directing the collected and concentrated
electromagnetic radiation to a target, wherein the cross-sectional
area of the inlet opening is smaller than the cross-sectional area
of the entry end of the channeling area.
25. The method of claim 24, wherein the electromagnetic radiation
is received by a plurality of the channeling areas.
26. The method of claim 24, wherein the channeling area is
solid.
27. The method of claim 24, wherein the channeling area is tubular,
the entry end is an opening, and the exit end is an opening.
28. The method of claim 24, wherein the at least one reflective
wall of the channeling area is parabolic.
29. An electromagnetic radiation collector, comprising: a tapering
element having an entry end for receiving electromagnetic
radiation, the entry end having a central axis along a first
direction, and a cross-sectional area perpendicular to the first
direction; an exit end having a central axis along a second
direction, and a cross-sectional area perpendicular to the second
direction; and a wall connecting the entry end to the exit end, the
wall being capable of channeling the electromagnetic radiation
received by the entry end to the exit end, wherein the
cross-sectional area of the entry end is larger than the
cross-sectional area of the exit end, and the second direction is
not parallel to the first direction.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to electromagnetic
radiation collection.
[0003] 2. Related Art
[0004] The collection and concentration of electromagnetic (EM)
radiation is well known. Radio waves are typically collected and
concentrated using parabolic dishes. Solar radiation is collected
and concentrated using parabolic mirrors or lenses. The former
devices suffer from requiring a relatively high
height-to-collection area ratio and the latter being expensive,
heavy and fragile. Both these types of device also suffer from the
requirement to track the source in order to function properly.
BRIEF SUMMARY OF THE INVENTION
[0005] The invention seeks to overcome at least some of the
deficiencies in the prior art by providing an EM radiation
collection and concentration device which can cover a large area,
have a low profile, have no requirement to track the source and be
constructed so as to be relatively light and inexpensive.
[0006] There is a pressing need to be able to generate energy from
renewable energy sources. Solar energy is one such resource which
has potential to be exploited. Conventional devices for collecting
radiant energy to generate energy in a useful form suffer from a
high capital cost and/or the inability to generate high enough
temperatures to be useful for many applications. The invention
seeks to overcome these deficiencies in the prior art by providing
a radiant energy concentration device that can gather energy from a
relatively large area and concentrate it onto a small target area.
The device is relatively inexpensive to produce, can be light in
construction and has the potential to generate high target
temperatures or, in the case of conversion to electricity by
photovoltaic cells, require only a small area of cells, thus saving
cost.
[0007] The invention is directed to a device that can cover
relatively large collections areas at relatively low cost, does not
necessarily require materials of particular refractive index, can
be made of light construction and can concentrate the radiation
onto a single target area.
[0008] The invention is capable of being less massive and having a
lower profile than prior art concentration devices. It is also
capable of having high concentration factors. It is suitable in any
application where it is desired to collect and concentrate EM
radiation, with particular utility in the collection and
concentration of solar radiation. In the case of solar radiation, a
device in accordance with the invention can be used in conjunction
with photovoltaic cells or to heat a fluid to harness the solar
energy for a desired purpose. In the case of radio frequency
radiation, the subject device could be used to collect, focus and
tune the radiation.
[0009] An example of the device has an assembly of channeling areas
that are used to collect and concentrate the incident EM radiation.
Also disclosed are methods for manufacturing the subject
devices.
[0010] Particular embodiments of the invention provide an
electromagnetic radiation collector having a concentration chamber
for collecting and concentrating electromagnetic radiation and
directing it to a target, the concentration chamber having at least
one inlet opening, the inlet opening having a cross-sectional area.
The collector also has a channeling area having an entry end for
receiving the electromagnetic radiation, the entry end having a
cross-sectional area, an exit end adjacent to the inlet opening of
the concentration chamber, and at least one reflective wall between
the entry end and the exit end. The cross-sectional area of the
inlet opening is smaller than the cross-sectional area of the entry
end of the channeling area.
[0011] Other embodiments of the invention provide a method of
collecting electromagnetic radiation. The method includes
channeling electromagnetic radiation in a channeling area, the
channeling area having an entry end for receiving the
electromagnetic radiation, an exit end, and at least one reflective
wall between the entry end and the exit end, the entry end having a
cross-sectional area; collecting and concentrating the
electromagnetic radiation in a concentration chamber, the
concentration chamber having at least one inlet opening adjacent
the exit end of the channeling area, the inlet opening having a
cross-sectional area; and directing the collected and concentrated
electromagnetic radiation to a target. The cross-sectional area of
the inlet opening is smaller than the cross-sectional area of the
entry end of the channeling area.
[0012] Still other embodiments of the invention provide an
electromagnetic radiation collector that has a tapering element
having an entry end for receiving electromagnetic radiation, the
entry end having a central axis along a first direction, and a
cross-sectional area perpendicular to the first direction; an exit
end having a central axis along a second direction, and a
cross-sectional area perpendicular to the second direction; and a
wall connecting the entry end to the exit end, the wall being
capable of channeling the electromagnetic radiation received by the
entry end to the exit end. The cross-sectional area of the entry
end is larger than the cross-sectional area of the exit end, and
the second direction is not parallel to the first direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The foregoing and other features and advantages of the
invention will be apparent from the following, more particular
description of preferred embodiments of the invention, as
illustrated in the accompanying drawings wherein like reference
numbers generally indicate identical, functionally similar, and/or
structurally similar elements.
[0014] FIG. 1 shows an example of a first embodiment of the
invention;
[0015] FIG. 2 shows an example of a second embodiment of the
invention;
[0016] FIG. 3 shows an example of a third embodiment of the
invention;
[0017] FIG. 4 shows a cross-sectional view of fourth embodiment of
the invention;
[0018] FIG. 5 shows a cross-sectional view of fifth embodiment of
the invention;
[0019] FIG. 6 shows a sixth embodiment of the invention; and
[0020] FIG. 7 shows a seventh embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] An exemplary embodiment of the invention is shown in the
drawings and described herein.
[0022] An example of a device in accordance with the invention has
an assembly of channeling areas wherein the EM radiation can be
internally reflected within the channeling areas. The channeling
areas are constructed such that at least some of the EM radiation
that enters a broad end of the channeling areas will be steered
within the channeling areas to exit a narrow end of the channeling
areas at a direction different to that which it entered. The broad
ends of the channeling areas are assembled to form a surface that
is herein termed the collection surface. EM radiation falls on the
collection surface and enters the broad ends of the channeling
areas. The EM radiation is reflected from the walls of the
channeling areas so as to be directed to exit from the narrow end
of the channeling areas. This is achieved by ensuring that at each
reflection point the angle of incidence of the EM radiation to the
reflecting surface is less than 90.degree.. A method for ensuring
that this is the case for a wide arc of angles of the EM radiation
incident on the collection surface is to shape the channeling areas
such that they are much longer than they are broad at their broad
end. This provides, in some embodiments, a small angle of taper of
the walls of the channeling area thus fulfilling the reflection
angle requirements for a broader range of incident EM radiation
angles. The ratio of length of the channeling area to the breadth
of its broad end should desirably be between 2 and 1000, more
preferably between 5 and 100, and most preferably between 10 and
50. FIG. 1 shows an example of a single channeling area and a
typical path 20 that EM radiation might take within the area.
[0023] The channeling areas can be made of solid material that is
capable of transmitting the EM radiation that is to be collected
and concentrated and with walls that reflect the EM radiation back
into the channeling area. In another embodiment of the invention,
the channeling areas are formed as cavities, where the walls of the
cavities are capable of reflecting the EM radiation back into the
cavity.
[0024] In one embodiment of the invention, the narrow ends of an
assembly of channeling areas are gathered together into an area
that is smaller than the area of the broad ends of assembled
channeling areas. In such an example, the EM radiation collected
over the broad ends area is concentrated into the narrow ends area.
An example of this embodiment is shown in FIG. 2.
[0025] In a particular embodiment of the invention, the narrow ends
of the channeling areas open into a concentration chamber which
serves to further concentrate the radiation exiting from the narrow
ends of the channeling areas. The narrow ends of the channeling
areas open onto one face of the concentration chamber wherein the
faces of the concentration chamber are capable of reflecting the EM
radiation. At least one, and preferably only one, of the faces of
the concentration chamber is transmissive to or absorptive of the
EM radiation with all other faces being reflective of the EM
radiation. The face of the concentration chamber that is
transmissive or absorptive, termed herein the exit port, is the
port though which the concentrated EM radiation can exit the device
or be absorbed and utilized in the desired manner. In one
embodiment, a target that utilizes the EM radiation is placed at
the exit port. The narrow ends of the channeling areas opening into
the concentration chamber are configured such that the EM radiation
exiting the narrow ends of the channeling areas is directed toward
the exit port, either directly or via one or more reflections from
the reflective faces of the concentration chamber. An example of
such a configuration is given in FIG. 3, which shows a schematic
cross-section of a portion of the device. In FIG. 3, the device 100
has channeling areas 120 having broad ends 130 and narrow ends 140.
A concentration chamber 200 has entry ports 210 and an exit port
220. Also shown in FIG. 3 is an indicative path 22 that a beam of
EM radiation might take through the device. In an alternative
embodiment, the concentration chamber 200 may have an additional
exit port 230 at its other end such that any EM radiation which is
reflected toward that end of the concentration chamber could also
be utilized. This could add somewhat to the cost of the device but
could serve to increase its efficiency.
[0026] In order that the EM radiation entering the concentration
chamber is directed toward the exit port, while also providing a
device with a low profile, it is desirable to steer the EM
radiation within the channeling areas such that the direction
normal to the plane of the narrow end of the channeling areas
different from the direction normal to the collection surface. One
way to achieve this is to curve the channeling areas as shown, for
example, in FIG. 3. In a particular embodiment, the angle of
curvature of the channeling areas is approximately equal along
their length to enhance the manufacturability of the device,
however this is not necessary for the device to function.
[0027] In some embodiments of the invention, the channeling areas
are tapered in only one dimension, that is they take the form of
tapered slots. In other embodiments, the channeling areas are
tapered in two dimensions so that they take the form of tapered
rods, where the rods can be of any cross-sectional shape that is
suitable for packing together at high density. Examples of such
shapes are circles, squares, rectangles, triangles and other
multi-sided polygons.
[0028] When the channeling areas take the form of tapered rods, to
aid in accommodating the curvature or the rods, maintain a high
packing density for the broad ends of the channeling areas and
enhance the strength of an assembly of the channeling areas, the
channeling areas can be assembled such that each channeling area is
staggered relative to its neighbors. In a particular embodiment of
this aspect of the invention, rows of channeling areas are
assembled such that the channeling areas in each row are offset
from the row in front such that the narrow end of each channeling
area is between the narrow ends of the neighboring channeling areas
in the rows immediately in front of and behind the subject row. By
assembling the channeling areas in this way it is possible for the
narrow end of each channeling area to curve into the space between
the neighboring channeling areas in the row in front of it. This
allows the channeling areas to be curved while maintaining high
packing density of the broad ends of the channeling areas.
[0029] It is desirable to maintain a high packing density of the
broad ends of the channeling areas at the collecting surface so
that the highest fraction of the EM radiation incident on the
collecting surface enters a channeling area and is not reflected
back.
[0030] In one embodiment of the invention, the channeling areas are
circular in cross-section and the broad ends are assembled in a
packing arrangement as is shown in FIG. 4, where a top view of the
assembled rows of the broad ends of the circular channeling areas
are shown offset from one another. Triangles are superimposed on
the view to show the relationship of the centers of the circular
ends. This arrangement increases packing density and allows space
for the channeling areas to be curved as disclosed above. With this
arrangement, a maximum fraction of .pi./2 3 (approx. 90%) of the
incident radiation is collected. In a particular embodiment of this
aspect of the invention, channeling areas with a square or
rectangular cross-section are used. A top view of this arrangement
is shown in FIG. 5. With this shape of channeling area, the broad
ends of the channeling areas can be packed such that close to 100%
of the incident radiation enters the channeling areas and is thus
collected. Note that in the embodiment shown in FIG. 5 it is
possible, but not necessary, for the channeling areas to be of
rectangular cross-section down their full length. For example, the
channeling areas may be square or rectangular at the collecting
surface but then transition to a circular area as we move down the
channeling area toward its tip.
[0031] Devices in accordance with the invention are useful in
applications where EM radiation concentration devices have been
used in the prior art, in particular solar radiation and radio
frequency radiation. Examples of such uses particularly relevant to
the collection and concentration of solar radiation are to heat
fluid circulating through a tube or pipe, to generate electricity
directly using photovoltaic cells or to produce hydrogen from
water. Note that the invention has particular utility in the
application of producing electricity using photovoltaic cells as it
allows the light to be collected from an extended area using the
relatively inexpensive device of the invention and concentrate it
on to a relatively small area of the relatively expensive
photovoltaic cells. This potentially allows electricity to be
generated at lower capital cost. Also, this device addresses
deficiencies in the conventional art when attempting to use a
concentrator with photovoltaic cells. Apart from expense and
weight, the conventional devices suffer from relatively low
concentration factors of typically less than 10 and the problem of
the photovoltaic cells overheating and becoming less efficient. The
invention can have high concentration factors. For example, for a
panel according to the embodiment shown in FIG. 3 that is two
meters long with an exit port normal to the axis of its length,
running the full width of the panel and 2 mm high, the calculated
concentration factor is 1000. Also, for an embodiment as shown in
FIG. 3, the photovoltaic cells would be placed adjacent to and
facing the exit port, such that the back of the panel of
photovoltaic cells is in free space rather than against a surface
such as a roof as would usually be the case in the conventional
art. In this configuration, the back of the panel of photovoltaic
cells is thus easily accessible to cooling means such as finned
heat-sinks, pads onto which water could be dripped and evaporated
by ambient air currents, or other cooling devices.
[0032] A low profile collector and concentrator is most desirable
in applications for radio frequency (RF) radiation. In these
applications, the device could be used to focus the RF radiation
onto an RF receiver. Also, by careful choice of the dimensions of
the channeling areas, the subject device could be used to tune the
collected RF radiation to a frequency that can be received more
easily by a receiver. For example, the device can be used to tune
the RF radiation to a higher frequency, which requires a smaller
and more easily implemented receiver.
[0033] The subject devices can be made by any suitable method. The
channeling areas can be solid elements transmissive of light and
made from materials such as polymers or glass. For these solid
elements, the walls of the elements can be coated with a reflective
material or the refractive index of the material can be such that
in most cases the incident angle of the EM to be reflected to the
wall of the element exceeds the critical angle so that total
internal reflection occurs. This embodiment has potential
advantages in ease of fabrication but can also tend to be heavy.
This embodiment could be constructed by manufacturing many elements
and assembling them into arrays as disclosed above. The broad ends
can be clamped or otherwise held together and, in the case of the
embodiment shown in FIG. 3, the narrow ends can be set so that that
they are mounted in and penetrate a plate that forms the upper
surface of the concentration chamber.
[0034] A particular embodiment is one where the channeling areas
are cavities formed in a monolithic block made of metal or polymer
material. This may be somewhat harder to fabricate but will be
lighter. A method of manufacturing this embodiment is to form an
assembly of curved elements, for example tapered elements, from a
malleable material such as copper or nickel. The assembly can be
one of individual elements or of rows of elements formed into combs
where each tapered element is a "tooth" of the comb. Each comb
forms a row or portion of a row of the elements and the "teeth" of
the combs of successive rows in the assembly are staggered to give
the arrangements shown in FIG. 4 or 5. Before being assembled into
an array, the elements can be straight or already curved. If the
elements are straight, a bar can be passed over the assembly of the
narrow ends of the elements as a convenient method of introducing
the desired curvature. The assembled elements can be held in their
assembly by being clamped into a frame or other similar device. The
curved assembled elements, in conjunction with side walls and, if
applicable, a top and/or base, can then be used as a mold for the
final monolithic shape. The shape with the desired assembly of
cavities can be molded by any applicable method. It may be cast by
pouring polymer into the mold and letting it set or by injection
molding techniques. In this process it is desirable to first coat
the mold with a suitable release agent to facilitate removal of the
mold elements from the cast shape. After the cast shape is set the
mold elements can be removed. This can most easily be achieved by
first removing the cast shape from the mold side walls, top and/or
base then unclamping the assembly of elements and removing them
separately or in groups as is most convenient and practical. Note
that in most cases the elements will need to be straightened
somewhat to be withdrawn from the cavities so it is desirable that
the material from which the tapered elements are made be malleable
so that in can undergo the straightening process without breaking
or distorting the shape of the cavity from which it is being
withdrawn. This process results in a cast shape that contains an
assembly of densely packed curved, light guiding cavities, wherein
the broad ends of the cavities all open onto one face of the shape
and the narrow ends of the cavities all open on to a different face
of the shape.
[0035] If the shape is not cast from an intrinsically reflective
material such as metal or metal filled polymer, then the external
faces of the shape and/or the walls of the cavities can to be
coated with a reflective layer. For polymer material this is most
easily achieved with an electroless metal deposition process such
as electroless chrome or nickel deposition. A further transparent
coating could be applied over the reflective coating if desired to
protect the reflective coating. The molded and coated shape can
then be assembled into a collector and concentration device by
mounting the shape in a box with a reflective internal base surface
when the face of the shape into which the narrow ends open is
spaced apart from the reflective base of the box. The base of the
box and the lower face of the shape then form the top and base of
the concentration chamber, where at the end of the box to which the
narrow ends of the cavities are directed is the opening or
transmissive portion which serves as the exit port. A sheet of
transmissive material such as glass or clear polymer sheet can be
placed over the assembled array of broad ends of the cavities that
forms the collecting surface in order to facilitate cleaning and
prevent dust, dirt or water from entering the cavities.
[0036] An alternative method for collecting the EM radiation to
inject it into the concentration chamber is to use a series of
mirrors that focus the light into a series of spots or slots in the
top of the concentration chamber. In the case of a slot, the
optimal mirror shape is parabolic in the plane of the slot and
normal to it. In the case of spots, the mirror is optimally a
parabolic dish. The slots or spots are arranged to be at the focal
line or point of the mirror such that EM radiation reflected off
the mirror is substantially concentrated into the openings in the
top of the concentration chamber. To allow for different angles of
EM radiation incident on the mirrors, the mirrors can be rotated
about their focal line or point such that the focus of the light
remains co-incident with the openings in the concentration chamber.
A control mechanism can perform the rotation whereby a signal,
which could be the output from the EM radiation target or from a
separate sensor, is monitored and the rotation of the mirrors
performed so as to maximize the amount of EM radiation impacting
the target.
[0037] In another aspect of the invention, the concentration
chamber can be designed so that the lower face of the concentration
chamber slopes from the non-target end of the concentration chamber
to the target end, with the slope being such that the target end
has a larger height than the non-target end. This assists in
minimizing the number of reflections that are required in the
concentration chamber before the EM radiation impinges on the
target.
[0038] In another aspect, the openings in the top of the
concentration chamber can be designed such that on the edge of the
opening furthest from the target a flap is attached that hangs down
into the concentration chamber. This flap helps to deflect the EM
radiation entering the concentration chamber to shallower angles
such that it is more likely to impinge on the target with a reduced
number of reflections in the concentration chamber and helps to
prevent light that has entered the concentration chamber from being
lost through the other openings in the top of the concentration
chamber. The openings in the top of the concentration chamber can
be gaps in a solid element or alternatively they can be areas of an
integral solid element that are transparent to the EM radiation,
with other areas of the element being reflective of the EM
radiation. For example, the top of the concentration chamber can be
a glass or polymer sheet which is selectively coated with a
reflective coating in areas other than those forming the openings
to the concentration chamber. In this embodiment, the flaps could
still be flaps of material protruding into the concentration
chamber or they could be formed as the back surface of a bulge in
the top of the concentration chamber where the back surface of the
bulge is coated or otherwise made reflective, and the front surface
(that closer to the target end of the concentration chamber) is
transmissive of the EM radiation.
[0039] FIG. 6 is a cross-section schematic which depicts these
aspects. In this example, a device 300 has focusing mirrors 310,
slots or spots 320 onto which the EM radiation is focused, flaps
340 on the back edge of the slots or spots 320, a target 350 for
the EM radiation and a sloped lower face 360 of the concentration
chamber 330 that helps to direct the EM radiation toward the target
350. In order to allow for different incident angles of EM
radiation onto the mirrors 310, the mirrors 310 can be made to
rotate around their focal points or focal lines. Alternatively, the
whole device can be rotated such that the EM radiation presents a
constant incident angle to the mirrors 310 or a combination of
rotation of the whole device with rotation of the individual
mirrors 310.
[0040] A potential limitation of the embodiment shown in FIG. 6 is
that the rotation of the parabolic mirrors in an counter-clockwise
direction (as drawn in FIG. 6) can be limited if the bottom of the
mirrors collide with the top of the concentration chamber. The
effect of this limitation is that the range of angles of light
incident on the parabolic mirrors can be limited. Specifically, in
some configurations light at some angle greater than normal to the
plane of the mirror tops cannot be focused onto the entry points to
the concentration chamber as it cannot be made to intersect with
the concave parabolic surface of a mirror. To overcome, or at least
ameliorate this limitation, the back surface of the mirror
structures can be formed so as to reflect light incident at angles
past the normal onto the concave surface of the parabolic mirror
behind it at the correct angle such that the light is then focused
onto an entry point to the concentration chamber. In this aspect,
the back surface is preferably a flat mirror, at least over the
portion upon which light incident at the past normal angles to be
focused impinges. That is, the required portion of the back
reflective surface of the mirror structure is at a constant angle
relative to the incident light angle. The mirror structures can be
rotated in a clockwise direction (as drawn in FIG. 6) to ensure
that light at different incident angles past the normal are focused
onto an entry point to the concentration chamber, once they have
been reflected from the concave parabolic surface of the preceding
mirror structure. In an alternate embodiment, to ameliorate this
limitation the parabolic mirrors can be placed closer together,
thus decreasing somewhat the cross-section of the entry area for
each channel. This allows the base of the parabolic mirrors to be
raised, so as to increase the gap between the base of the parabolic
mirror and the top of the concentration chamber, while still
ensuring that all EM radiation that enters the channeling area
through the entry area impinges on the concave surface of the
parabolic mirror. The increased gap between the base of the
parabolic mirrors and the top of the concentration chamber allows
the mirrors to be rotated further in a counter-clockwise direction
(as drawn in FIGS. 5 and 6) such that a larger range of angles of
radiation incident on the entry to the channeling area can be
directed toward the exit of the channeling area.
[0041] FIG. 7 is a cross-section schematic which shows such a
variation of the example shown in FIG. 6. In this variation,
focusing mirror 310 that have a back side adjacent to a slot or
spot 320, have a rear reflecting surface 370 that reflects EM
radiation (an example of which is depicted by light ray 400) onto
one of the focusing mirrors 310. Reflecting surfaces 370 can
increase the amount of EM radiation that eventually gets directed
into slots or spots 320. Similarly, the upper outside surfaces of
concentration chamber 330 can be shaped to reflect EM radiation
onto reflecting surfaces 370 and/or focusing mirrors 310 in order
to capture even more EM radiation.
[0042] The invention is not limited to the above-described
exemplary embodiments. It will be apparent, based on this
disclosure, to one of ordinary skill in the art that many changes
and modifications can be made to the invention without departing
from the spirit and scope thereof.
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