U.S. patent application number 11/124615 was filed with the patent office on 2006-11-09 for reflecting photonic concentrator.
Invention is credited to Christopher W. Straka.
Application Number | 20060249143 11/124615 |
Document ID | / |
Family ID | 37392988 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060249143 |
Kind Code |
A1 |
Straka; Christopher W. |
November 9, 2006 |
Reflecting photonic concentrator
Abstract
A linearly reflecting trough concentrator that receives spectral
energy, preferably visible and near-infrared solar energy spectra,
and linearly reflects that energy onto a smaller area on one side
of the device, thereby concentrating the energy. The linearly
reflecting trough concentrator has the geometry of a single
slope-relief interval in a Fresnel lens, and in preferred
embodiment comprises an array of heliostatic facets connected
continuously to form the base of the trough, a non-imaging focal
point where a photonic receiver is located, and a relief surface to
connect the heliostatic array to the receiver location. When
spectral energy enters the trough at an angle normal to the array's
horizontal reference, the concentrator linearly reflects energy to
one side of the device where an energy receiver is mounted. The
concentrator comprises an array of heliostats oriented according to
the negative profile of two interleaved linear Fresnel lens, where
the slope of one is the relief of the other. The concentrator
reflects energy above and to each side of the device. Optionally
using a reflecting projector on one side of the device, energy is
then doubly concentrated to the other side. The device offers
higher concentration ratios with an equivalent trough depth than
prior art reflective trough concentrators. The device requires less
depth and offers a lower-profile than prior art reflecting
concentrators with the same degree of concentration.
Inventors: |
Straka; Christopher W.;
(Owl's Head, ME) |
Correspondence
Address: |
CHRIS A. CASEIRO
VERRILL DANA, LLP
ONE PORTLAND SQUARE
PORTLAND
ME
04112-0586
US
|
Family ID: |
37392988 |
Appl. No.: |
11/124615 |
Filed: |
May 6, 2005 |
Current U.S.
Class: |
126/600 |
Current CPC
Class: |
F24S 23/80 20180501;
F24S 2023/874 20180501; G02B 19/0019 20130101; G02B 19/0033
20130101; Y02E 10/40 20130101; G02B 19/0042 20130101; Y02E 10/45
20130101; F24S 23/74 20180501 |
Class at
Publication: |
126/600 |
International
Class: |
F24J 2/38 20060101
F24J002/38 |
Claims
1. A reflective photonic concentrator having a plurality of
heliostats formed according to the concave side of two linear
Fresnel lens, such that the heliostats are interleaved so that an
arc that is the slope for one of the interleaved reflectors is a
relief to the other interleaved reflector.
2. The reflective photonic concentrator of claim 1 having two
symmetrical and opposed heliostats that reflect toward opposite
targets.
3. The reflective photonic concentrator of claim 1 further being
capable of mechanically alternating between a collapsed position
and an expanded, operation position.
4. The reflective photonic concentrator of claim 1 further focused
to concentrate photonic energy in infinite-infinite,
infinite-finite, finite-finite, and finite-infinite conjugates
toward vertical or near-vertical planes above and on each side of
the reflective concentrator.
5. The reflective photonic concentrator of claim 1 further having a
reflective, diffusing projector to redirect photonic energy
striking one vertical or near vertical plane across the reflective
concentrator to the opposite vertical or near vertical plane.
6. A reflective linear trough concentrator having an asymmetrical
geometry for reflectively concentrating spectral energy with the
invention comprising: a) a reflective surface area for linear
concentration of energy onto an energy receiver; b) a vertically
oriented sidewall with inward tilt where an energy receiver is
located to receive concentrated energy; and c) a relief plane that
connects the bottom of the reflective surface area to the bottom of
the sidewall where the energy receiver is located.
7. The reflective surface area of the reflective concentrator of
claim 6 where a single heliostat, formed from a plurality of
smaller non-imaging heliostatic facets, and a single relief are
arranged according to the geometry of the inside profile (the
concave side) of a single Fresnel slope-relief lens interval.
8. The reflective surface area of the reflective concentrator of
claim 6 using a single paraboloid and imaging heliostat in
infinite-infinite or infinite-finite conjugates, and having a
relief such that the profile appears as the geometry of a single
Fresnel slope-relief lens interval.
9. The vertical orientation of the reflective concentrator of the
sidewall of claim 6, the sidewall being between 30 degrees inward
to the trough and 90 degrees normal to the horizontal plane of the
invention.
10. The relief plane of the reflective concentrator of claim 6 that
connects the bottom of the reflective surface area to the bottom of
the sidewall where the energy receiver is located such that the
shadow of the top edge of an inwardly tilted sidewall strikes the
angle where the relief plane meets the reflective surface area.
11. The asymmetrical geometry of the reflective concentrator of
claim 6 where the energy is redirected across the line of
symmetry.
12. The rotational axis of the reflective concentrator of claim 6
where the axis is orthogonal to the reflective plane and parallel
to the linear extension of the reflective surface.
13. The symmetrical assemblage of two asymmetrical reflective
concentrators of claim 6 where the back of one concentrator's
sidewall is oriented to the back of the other concentrator's
sidewall.
14. The rotational axis of the symmetrical assemblage of claim 8
where the axis is orthogonal to the reflective plane and parallel
to the linear extension of the reflective surface.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to solar energy
concentration, optics, and power systems, and more specifically to
a reflecting photonic concentrator system using a heliostatic
array.
BACKGROUND OF THE INVENTION
[0002] Capturing solar radiation energy for conversion to heat and
electricity has become a significant alternate energy source.
However, although safe and clean, such systems typically are not
very efficient and therefore often require significant time before
investment in such technologies is returned. Attempts have been
made to concentrate solar radiation energy to improve the
efficiency of solar energy systems. Prior art linear trough
concentrators that track the light source, especially the sun, are
mostly parabolic in cross-section and require significant depths to
realize higher degrees of concentration.
[0003] For solar thermal applications where a fluid is superheated
in a pipe, the width of the pipe does not require a significant
depth to achieve reasonable concentration levels. For photovoltaic
(PV) applications however, the width of a horizontally oriented
photovoltaic cell requires significant depth but still achieves
geometric concentration of less than three (3.times.), the
theoretical maximum for the aperture width of a parabolic trough
over the PV width, because the tangent of the reflectively incident
angle on the PV approaches infinity using this geometry.
[0004] One attempt to improve the efficiency of conventional PV
panels is described in U.S. Pat. No. 4,023,368 issued 17 May 1977
to Kelly, which relates to the use of side reflectors to reflect
incident sunlight onto conventional solar cells that have been
placed obliquely to the sun's normal rays. U.S. Pat. No. 5,899,199
issued 4 May 1999 and U.S. Pat. No. 6,131,565 issued 17 Oct. 2000,
both to Mills, relate to a solar energy collector system employing
at least one group of rotatable arrays of reflectors and at least
two spaced-apart target receiver systems associated with the or
each group of reflectors. These patents require rotation of the
arrayed reflectors and do not provide for the use of stationary
reflectors. U.S. Pat. No. 6,612,705 issued 2 Sep. 2003 to Davidson
et al. relates to a multiple reflecting optical system for
projecting reflected solar energy onto a conversion surface
perpendicular to the original rays's direction by means of
reflective balls. However, this reference does not provide for the
concentration of incident solar energy. U.S. Pat. Appl. 20010045212
filed 29 Nov. 2001 by Frazier relates to a solar collection system
that requires double reflection of incident light off two
reflective surfaces. None of these systems, however, create the
desired multiplier effect necessary to attain optimal device
efficiency.
[0005] What is needed is a system for solar radiation collection,
concentration, and conversion into thermal and electric energy that
is cost-competitive with conventional energy sources. The ideal
system should achieve concentration multiplier effects sufficient
to attain optimal device efficiency. The ideal system would present
a low architectural profile, yet be capable of tracking the sun
both as it proceeds across the sky throughout the day and
throughout the seasons. Finally, the ideal system would comprise a
static unit and not require the use of complicated internal
adjustments in order to maximize energy concentration.
SUMMARY OF THE INVENTION
[0006] Accordingly, it is an object of the present invention to
provide a reflecting concentrator assembly that is cost-competitive
with conventional energy sources. It is another object of the
present invention to provide a reflecting concentrator assembly
that achieves concentration multiplier effects sufficient to attain
optimal device efficiency.
[0007] It is a further object of the present invention to provide a
reflecting concentrator assembly that presents a low architectural
profile, yet be capable of tracking the sun both as it proceeds
across the sky throughout the day and throughout the seasons.
[0008] It is yet another object of the present invention to provide
a reflecting concentrator assembly that does not require the use of
complicated internal adjustments in order to maximize energy
concentration.
[0009] The present invention is a linearly reflecting trough
concentrator with asymmetrical geometry that realizes 7.times.
geometric concentration with trough depth comparable to prior art
parabolic trough concentrators. The concentrator assembly of the
present invention requires less depth to provide a lower profile
device that more readily integrates with building applications and
that is more compact for space applications, e.g. satellite solar
power. The concentrator assembly evenly distributes reflected
energy to avoid the creation of "hot spots" on the target
concentration areas that are oriented in a vertical or near
vertical plane. Also, the assembly may be scaled to allow greater
degrees of concentration by increasing the width of the
concentration area without significantly increasing the depth.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows the reflection path of light from a heliostatic
array of the present invention onto two opposing target areas.
[0011] FIG. 2 shows a reflection path of light from a heliostatic
array and reflecting projector of the present invention onto one
target area.
[0012] FIG. 3 shows a side view and ray-trace diagram of reflective
concentrator with faceted, non-imaging heliostat.
[0013] FIG. 4 shows a side view and ray-trace diagram for parabolic
imaging heliostat.
[0014] FIG. 5 shows an isometric projection of reflective
concentrator.
[0015] FIG. 6 shows a symmetrical assemblage of two reflective
concentrators.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] In a linearly reflecting trough concentrator of the present
invention and being formed from a heliostatic array, photonic
energy, especially in the form of light waves in the visible and
infrared spectra, strikes a set of reflective surfaces at an
incident angle of 90 degrees. Each of the individual reflective
surfaces describe a separate heliostat. The light is then reflected
to a target plane in such a way that it is evenly reflected to
avoid hot spots. A second set of reflective surfaces similarly
reflect light arriving at an incident angle of 90 degrees toward an
opposing target plane in the same manner.
[0017] When the individual heliostatic reflective surfaces are
joined together along their lateral edges, a parabolic curve is
formed, thereby creating a single heliostat. In the same manner,
when the second set of reflective surfaces are likewise joined
together, a separate parabolic curve is formed representing a
second heliostat. According to the principle of a Fresnel lens, the
depth required to maintain one larger curve may be reduced by
dividing the curve into segments and then flattening the curved
segments onto the same plane. The segment's curvature is the slope,
and the interval segment necessary to join each slope is the
relief.
[0018] In a first embodiment, the present invention provides a
reflective concentrator assembly that uses the Fresnel lens
principle to describe the negative, inside profile of two
refractive lenses that are superimposed, or interleaved, over one
another. Where the first set of reflective surfaces are slopes
having their own reflective target, the second set of reflective
surfaces are reliefs that allow the first three slopes to be formed
contiguously by a reflective material or substrate. Further, the
relief surfaces do not interfere with the reflective pathway of
photonic energy toward the target area when that photonic energy
strikes the heliostatic array at an incident angle of 90 degrees.
Because one embodiment of the concentrator assembly is symmetrical,
the inverse is true where the second set of reflective surfaces are
slopes having their own target, and the first set of reflective
surfaces are reliefs.
[0019] FIG. 1 shows the concentrator assembly of the present
invention and depicts the reflective pathway of energy striking the
heliostatic array at incident angle of 90 degrees and being
reflected toward the two target areas. It is contemplated that
these two target areas may comprise photonic transducers or
receiving devices. In a second embodiment, a reflective projector
may be used in conjunction with the heliostatic array. The
reflective surface of the projector is designed to receive photonic
energy arriving at a plurality of incident angles from the second
set of reflective surfaces of the concentrator, and to evenly
reflect and distribute that energy to the first target area
described above.
[0020] FIG. 2 represents the concentrator assembly with the
reflective projector attached to the right side of the heliostatic
array and depicts the path of photonic energy striking the
heliostatic array at incident angle of 90 degrees. While a first
set of light rays strike the first set of reflective surfaces and
are reflected toward the first target area directly, a second set
of light rays reflect from the second set of reflective surfaces
onto the projector surface, which in turn reflects these rays again
toward the first target area. The projector substitutes the second
target area described above so that photonic energy striking the
projector surface is redirected to the first target area. It is
contemplated that this target area may comprise a photonic
transducer or receiving device.
[0021] A heliostatic array may be formed from a single piece of
bright aluminum or from reflective material applied to a molded or
extruded plastic. Four times (4.times.) the energy concentration is
realized when the device reflects light striking a 12.8 inches wide
heliostatic array onto a 3.2 inch target using a reflecting
projector. In an embodiment with 6 heliostats, light striking three
of the heliostats reflects directly onto the target area, while
light striking the other three heliostats reflects toward the
projector and is reflected a second time toward the target area.
The number of heliostats, i.e. slopes and reliefs, may be increased
to allow a flatter profile while ensuring that any particular
slope/relief surface does not interfere with the reflective path of
another surface toward its target area.
[0022] Without the reflecting projector, 2.times. concentration is
realized when light striking the 12.8 wide heliostatic array is
reflected toward two 3.2 inch targets above and on each side of the
heliostatic array.
[0023] In a third embodiment of the present invention, shown in
FIG. 3, concentrating reflector 10 comprises reflective surface
area 20, relief plane 30, and vertically oriented sidewall 40 for
mounting solar receiver 50. In a preferred embodiment, wherein
reflective surface 20 is faceted and non-imaging, a parabolic shape
is described having a curve formed of large intervals to form the
single heliostat. When the profile of the single reflective surface
20 is joined to relief plane 30, the negative profile, i.e., the
concave inside edge, is described for a single convex slope-relief
Fresnel lens interval.
[0024] In a Fresnel lens, the convex thickness of a lens may be
reduced by dividing the arc of the lens into segments and then
flattening the top of each curved segments onto the same plane. The
segment's curvature is the slope, and the interval segment
necessary to eliminate thickness and join each slope is the relief.
The preferred embodiment of the disclosed invention is derived from
embodiments having multiple negative (concave) Fresnel slope-relief
intervals.
[0025] FIG. 3 also shows a ray-trace diagram that depicts the
reflection path of Spectral energy 60 that strikes reflective
surface area 20 to be concentrated onto solar receiver 50. Spectral
energy 60 enters the aperture of the concentrating reflector 10 at
an incident angle of ninety (90) degrees to the horizontal plane of
the invention. In a preferred embodiment, the horizontal plane is
depicted by transparent glazing surface 11 that bridges the left
and right top edges of the concentrating reflector's side view. In
a preferred embodiment of seven heliostatic facets 21 through 27
that are connected contiguously to form a non-imaging reflective
array, spectral energy 60 is redirected onto solar receiver 50.
This embodiment describes a geometric concentration ratio of seven
(7.times.) where seven facets 21 through 27 concentrate spectral
energy 60 entering an aperture area that is seven times wider than
the width of solar receiver 50. At each point where the heliostatic
facets join one another, two reflected rays 61 and 62 emerge from
one spectral ray 60 that enters the aperture of concentrating
reflector 10. Reflected ray 61 optimally strikes at or near the top
edge of solar receiver 50 as a result of reflection calculated from
the angle of each facet at its top most end. Reflected ray 62
optimally strikes at or near the bottom edge of solar receiver 50
as a result of reflection calculated from the angle of each facet
at its bottom-most end.
[0026] FIG. 4 shows a side view of imaging reflective concentrator
110 having an imaging focus of concentrated spectral energy. In
this embodiment different from that shown in FIG. 1, reflective
surface 120 is a continuous paraboloid with no discernable facets.
Incident spectral rays 160 enter aperture 111 to be concentrated
onto solar receiver 150. Relief plane 130 joins the reflective
surface area to sidewall 140, which may optionally be used to mount
solar receiver 150.
[0027] FIG. 5 shows an isometric projection of concentrating
reflector 10. Concentrating reflector end 13 is beveled inwardly
from the top aperture area where glazing 11 sits to the bottom of
reflector 12 where relief slope 30 joins reflective surface area
20. In one embodiment, lip 14 is provided to describe a seating
area for glazing 11. The dimension of rotational axis 80 runs
lengthwise through any point of concentrating reflector 10.
Rotation about this single axis enables linear concentration for an
energy source, ideally the sun, relative to a static orientation of
the concentrating reflector.
[0028] FIG. 6 shows an end view of an assemblage of two
asymmetrical concentrating reflectors 210 and 210' oriented
back-to-back to form a single symmetrical reflecting concentrator
200 that rotates linearly about a single axis 280. Rotation about
this single axis enables linear concentration for an energy source,
ideally the sun, relative to a stationary orientation of the
assemblage.
[0029] In yet another embodiment, each heliostat in the array may
be separate yet connected to adjacent heliostatic reflectors so
that the entire array is initially collapsed and is expanded in
place. This embodiment is particularly well suited for deployment
into outer space and other applications that may benefit from
transportation of a smaller, collapsed apparatus followed by
expanded deployment of the apparatus once disposed at the point of
use. It is further understood that concentrators of the present
invention may be mounted on means capable of tracking the motion of
the sun both as it proceeds across the sky throughout the day and
throughout the seasons in order to maximize the amount of spectral
energy captured.
[0030] It will now be apparent to those skilled in the art that
other embodiments, improvements, modifications, details,
variations, and uses can be made consistent with the letter and
spirit of the foregoing disclosure and within the scope of this
patent, which is limited only by the following claims, construed in
accordance with the patent law, including the doctrine of
equivalents.
* * * * *