Note: Descriptions are shown in the official language in which they were submitted.
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SUNLIGHT CONCENTRATING AND HARVESTING DEVICE
CROSS-REFERENCE
[01] The present application claims priority to United States Provisional
Patent Application
No. 61/798,205, filed March 15, 2013, entitled "Concentrated Photovoltaic
Panel" the entirety
of which is incorporated herein by reference for all purposes. The present
application also
claims priority to or the benefit of the following applications filed on March
4, 2014: United
States Patent Application Nos. 14/196,523; 14/196,291 and 14/196,618; United
States
Provisional Patent Application No. 61/948,020; and International Patent
Application Nos.
PCT/CA2014/050168 and PCT/CA2014/000167. The present application also claims
the
benefit of the following application filed on March 17, 2014: United States
Patent Application
No. 14/215,913.
FIELD
[02] The present technology relates to devices for concentrating and
harvesting sunlight.
BACKGROUND
[03] One way to harvest solar energy is to use concentrated solar power
systems such as
concentrated photovoltaic systems that employ optical components to
concentrate solar
energy (sometimes to great degrees) onto photovoltaic cells. Compact optical
systems and
components for concentrating solar energy have been developed over the years.
Some of
these designs comprise a two-stage solar concentrator or collector in which a
light focusing
layer is optically coupled to a light redirecting layer. The redirecting layer
includes a light-
guide that guides the sunlight laterally within the light-guide towards a
solar collector by total
internal reflections with almost no loss of energy. Several examples are shown
in United
States Patent Application Publication No. 2012/0019942, entitled "Light-Guide
Solar Panel
and Method of Fabrication Thereof' which is assigned to the applicant of the
present
application.
[04] One of the difficulties with concentrated photovoltaic systems is that a
relatively
significant amount of heat (thermal energy) is generated at the photovoltaic
cell, which can
reduce the efficiency of light-to-electricity conversion by the cell, and
should be removed
from the cell during operation of the device. In order to transfer this heat
away from the cell,
conventional concentrated photovoltaic systems typically have the photovoltaic
cell on an
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outer surface of the device, attached a large heat sink. While such designs
are adequate for
their intended purpose, improvements in this area may nonetheless be
desirable.
SUMMARY
[05] It is an object of the present technology to ameliorate at least one of
the
inconveniences present in conventional concentrated photovoltaic systems, be
it one of the
inconveniences described above or otherwise.
[06] In one aspect, embodiments of the present technology provide a device for
concentrating and harvesting sunlight comprising:
a panel having at least one rigid layer, the at least one rigid layer having
at least one
patterned electrical circuit thereon;
an array of sunlight concentrating and harvesting units, each unit being
formed by at least
one rigid element and a portion of the at least one rigid layer, each unit
including:
a rigid optical concentrating element secured to the at least one rigid layer
for
concentrating sunlight received by the unit,
a photovoltaic cell secured to the at least one rigid layer and sandwiched
within
the panel for converting concentrated sunlight into electrical energy, and
an electrical conductor in electrical communication with the photovoltaic cell
to
receive electrical energy therefrom, the electrical conductor being in
thermal communication with the photovoltaic cell to receive thermal
energy therefrom, the electrical conductor being the primary heat sink for
the photovoltaic cell, the photovoltaic cell being primarily cooled via
conduction;
the electrical conductor and the optical concentrating element of each unit
being
dimensioned and arranged within the unit such that the electrical conductor
does
not materially impede transmission of sunlight received by the unit within the
unit to the photovoltaic cell;
the electrical conductor being at least electrically and thermally
interconnected with the
patterned circuit to transmit electrical energy and thermal energy received
from
the photovoltaic cell away from the unit.
[07] In the context of the present specification, the term "rigid" should be
understood to
mean that a "rigid" structure is one that generally maintains its form under
normal operating
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conditions on its own, without requiring external forces (such as those
generated by a
pressured gas) to do so. "Rigid", however, in the present context does not
mean that the
structure in question is completely inflexible; as structures which are
slightly flexible or
expandable and return to their original size and shape after flexion (and/or
expansion) are
included within the definition of "rigid" in the present context.
[08] In the context of the present specification a "patterned" electrical
circuit should be
understood to be an electric circuit not of a random layout. In some
embodiments, the
patterned electrical circuit includes portions that are of a repeating design.
[09] In the context of the present specification two elements may be "secured"
together in
any number of various ways. For example, such elements may bonded to one
another (be it
permanently or releasably), by being formed together in a single physical
element, by being
held in place one with respect to another by other elements, etc.
[10] In the context of the present specification, an electrical conductor is
considered to be the
primary heat sink for the photovoltaic cell when under normal operating
conditions of the device,
a greater amount of thermal energy transferred away from the photovoltaic cell
via direct
conduction is transferred away via the electrical conductor than via any other
element of the
device.
[11] In the context of the present specification, a photovoltaic cell is
considered to be
primarily cooled via conduction when under normal operating conditions of the
device, more
thermal energy is transferred away from the photovoltaic cell via direct
conduction than via
direct convection or direct radiation.
[12] In the context of the present specification, two elements are
electrically interconnected
when electricity can pass between them, be it directly or indirectly. Thus,
two elements may, for
example, be electrically interconnected via their direct physical connection
to each other or via
their direct physical connection to a third element, etc.
[13] In the context of the present specification, two elements are thermally
interconnected
when thermal energy can transfer between them via conduction, either directly,
or indirectly
through a third element.
[14] In some embodiments the photovoltaic cell is sandwiched between the at
least one rigid
layer and the rigid optical concentrating element.
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[15] In some embodiments the optical concentrating element of each unit is a
series of optical
concentrating elements. In some such embodiments the optical concentrating
element of each
unit is a series of concentric annular optical concentrating elements.
[16] In some embodiments the rigid optical concentrating elements of multiple
units are all
part of a single rigid layer distinct from the at least one rigid layer having
the at least one
patterned electrical circuit thereon.
[17] In some embodiments the electrical conductor and the optical
concentrating element of
each unit being dimensioned and arranged within the unit such that the
electrical conductor
impedes transmission of no more than 20% of sunlight received by the unit
within the unit to the
photovoltaic cell.
[18] In some embodiments, each unit of the array further includes a rigid
optical redirecting
element secured to the at least one rigid layer for redirecting sunlight
received by the unit; and
the electrical conductor, the optical concentrating element, and the optical
redirecting element of
each unit are dimensioned and arranged within the unit such that the
electrical conductor does
not materially impede transmission of sunlight received by the unit within the
unit to the
photovoltaic cell.
[19] In some embodiments the photovoltaic cell is sandwiched between the at
least one rigid
layer and the rigid optical concentrating element.
[20] In some embodiments the photovoltaic cell is sandwiched between the at
least one rigid
layer and the rigid optical redirecting element.
[21] In some embodiments the optical redirecting element of each unit is a
series of optical
redirecting elements.
[22] In some embodiments, the optical concentrating element of each unit is a
series of optical
concentrating elements; and the optical redirecting element of each unit is a
series of optical
redirecting elements.
[23] In some embodiments, the optical concentrating element of each unit is a
series of
concentric annular optical concentrating elements; and the optical redirecting
element of each
unit is a series of concentric annular optical redirecting elements.
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[24] In some embodiments, the rigid optical concentrating elements of multiple
units are all
part of a first single rigid layer distinct from the at least one rigid layer
having the at least one
patterned electrical circuit thereon; and the rigid optical redirecting
elements of multiple units are
all part of a second single rigid layer distinct from the at least one rigid
layer having the at least
one patterned electrical circuit thereon and the first single rigid layer.
[25] In some embodiments, the rigid optical redirecting element redirects
light into a light
guide for transmission to the photovoltaic cell.
[26] In some embodiments the light guide has a secondary optical element for
redirecting light
in the light guide.
[27] In some embodiments, the electrical conductor, the optical concentrating
element, and the
optical redirecting element of each unit are dimensioned and arranged within
the unit such that
the electrical conductor impedes transmission of not more than 20% of sunlight
received by the
unit within the unit to the photovoltaic cell.
[28] In some embodiments the photovoltaic cell is at least partially encased
in a thermal
insulator.
[29] In some embodiments, the electrical conductor is a part of the patterned
circuit. In other
embodiments, the electrical conductor is a distinct element from the patterned
circuit.
[30] In another aspect, embodiments of the present technology provide a device
for
concentrating and harvesting sunlight comprising:
a panel having a plurality of rigid layers bonded together;
an array of sunlight concentrating and harvesting units formed by the
plurality of layers
of the panel, each one of the array of sunlight concentrating and harvesting
units including:
a series of optical concentrating elements associated with a first surface of
one of
the layers of the plurality of layers for concentrating sunlight received by
the unit;
a series of optical redirecting elements associated with a second surface of
one of
the layers of the plurality of layers for redirecting sunlight received by the
unit;
a photovoltaic cell sandwiched between two of the layers of the plurality of
layers
for converting concentrated and redirected sunlight into electrical energy;
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one of the layers of the plurality of layers having an electrical conductor in
electrical
communication with the photovoltaic cell to receive electrical energy
therefrom,
the electrical conductor being in thermal communication with the photovoltaic
cell to receive thermal energy therefrom, the electrical conductor being the
primary heat sink for the photovoltaic cell, the photovoltaic cell being
primarily
cooled via conduction;
the electrical conductor, the series of optical concentrating elements and the
series of
optical redirecting elements being dimensioned and arranged within the unit
such
that the electrical conductor does not materially impede transmission of
sunlight
received by the unit within the unit to the photovoltaic cell;
one of the layers of the plurality of layers having a patterned circuit
electrically and
thermally interconnected with photovoltaic cells of at least some of the units
to
receive electrical energy and thermal energy therefrom for transmission away
from the units.
[31] In some embodiments, the series of optical concentrating elements are
formed on the
first surface; and the series of optical redirecting elements are formed on
the second surface.
[32] In some embodiments, the electrical conductor, the optical concentrating
element, and the
optical redirecting element of each unit are dimensioned and arranged within
the unit such that
the electrical conductor impedes transmission of not more than 20% of sunlight
received by the
unit within the unit to the photovoltaic cell.
[33] In one aspect, embodiments of the present technology provide a
concentrated
photovoltaic panel comprising:
= a receiver substrate assembly including:
o a rigid sheet of light transmissive material having a first surface, a
second surface opposite the first surface, and a conductor pattern
attached to the first surface; and
o at least one receiver assembly affixed to the rigid sheet, each receiver
assembly including a photovoltaic cell in electrical communication
with the conductor pattern;
= at least
one light-guide optic attached to and supported by the receiver substrate
assembly, each light-guide optic in optical communication with the
photovoltaic cell of an associated one of the at least one receiver assembly
for
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guiding light received via the receiver substrate assembly toward said
photovoltaic cell.
[34] In some embodiments the at least one light-guide optic is attached to and
supported by
the first surface of the receiver substrate assembly.
[35] In some embodiments the concentrated photovoltaic panel of further
comprises at least
one focusing optic attached to and supported by the second surface of the
receiver substrate
assembly, each focusing optic being associated with and in optical
communication with one
of the at least one light-guide optic, each focusing optic comprising at least
one focusing
element for cooperative operation with the light-guide optic.
[36] In some embodiments each light-guide optic comprises at least one
reflective surface
for guiding light received via the receiver substrate assembly toward the
photovoltaic cell of
the associated receiver assembly.
[37] In some embodiments the at least one focusing element includes a lens.
[38] In some embodiments the metallization pattern includes two or more bus
bars.
[39] In some embodiments the light transmissive material of the rigid sheet is
a thermally
insulating material.
[40] In some embodiments the light transmissive material of the rigid sheet is
glass.
[41] In some embodiments the first and second surfaces of the rigid sheet are
flat and
parallel to each other.
[42] In some embodiments the light-guide optic is made of a different material
than the
rigid sheet.
[43] In some embodiments the light-guide optic is made of poly(methyl)
methacrylate.
[44] In some embodiments the focusing optic is made of a different material
than the rigid
sheet.
[45] In some embodiments the focusing optic is made of poly(methyl)
methacrylate.
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[46] In some embodiments at least one of the at least one light-guide optic
and the at least
one focusing optic is 3D printed onto the rigid sheet.
[47] In some embodiments the conductor pattern comprises at least two bus bars
and a
plurality of interconnection traces for electrical connection of the at least
one receiver
assembly to the bus bars.
[48] In some embodiments the conductor pattern comprises a heat spreader
portion.
[49] In some embodiments the heat spreader portions comprises a positive half
and a
negative half, each half comprising a plurality of arms in the shape of
circular arcs and a
terminus interconnected by an interconnection trace.
[50] In some embodiments the conductor pattern is metalized onto the first
surface.
[51] In some embodiments the conductor pattern is formed from a sheet of
conductive
material.
[52] In some embodiments the conductor pattern is disposed between the rigid
sheet and
one of the light guide optic and the focusing optic, and the heat spreader
portion is shaped and
positioned so as to avoid blocking light transmitted from the focusing optic
to the reflecting
surfaces of the light guide optic.
[53] In another aspect, embodiments of the present technology provide a solar
panel
comprising:
at least one sheet of glass having a top face and a bottom face; and
a plurality of optical units connected to the at least one sheet of glass,
each optical unit
including:
a first optical element attached to the top face of the at least one sheet of
glass,
a second optical element attached to the bottom face of the at least one sheet
of
glass,
a photovoltaic cell, and
electrical connectors connected to the photovoltaic cell,
the photovoltaic cell and the electrical connectors being sandwiched between
other
elements of the optical unit.
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[54] In another aspect, embodiments of the present technology provide a solar
concentrating optical unit comprising:
a transparent substrate having a top face and a bottom face;
a first optical element attached to the top face of the transparent substrate,
the first
optical element having a plurality of lenses for concentrating incoming
sunlight such that the
sunlight begins to focus as it is transmitted trough the transparent
substrate;
a second optical element attached to the bottom face of the transparent
substrate, the
second optical element having a plurality of first reflectors for reflecting
sunlight having been
concentrated by one of the lenses of the first optical element;
a second reflector for receiving light reflected from by the first reflectors,
the second
reflector reflecting light towards bottom face of the transparent substrate
towards a focus;
a photovoltaic cell adjacent the focus for receiving light from the second
reflector, the
photovoltaic cell facing away from the bottom face of the transparent
substrate.
[55] Embodiments of the present technology each have at least one of the above-
mentioned
object and/or aspects, but do not necessarily have all of them. It should be
understood that
some aspects of the present technology that have resulted from attempting to
attain the above-
mentioned object may not satisfy this object and/or may satisfy other objects
not specifically
recited herein.
[56] Additional and/or alternative features, aspects and advantages of
embodiments of the
present technology will become apparent from the following description, the
accompanying
drawings and the appended claims.
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BRIEF DESCRIPTION OF THE DRAWINGS
[57] For a better understanding of the present technology, as well as other
aspects and
further features thereof, reference is made to the following description which
is to be used in
conjunction with the accompanying drawings, where:
[58] FIG. 1 is a perspective view of a conventional (prior art) photovoltaic
panel;
[59] FIG. 2 is a rear perspective view of an embodiment of a concentrated
photovoltaic
panel including the present technology;
[60] FIG. 3 is an exploded perspective view of the concentrated photovoltaic
panel
apparatus of the concentrated photovoltaic panel of FIG. 2;
[61] FIG. 4 is a plan view of an embodiment of a receiver substrate assembly;
[62] FIG. 5 is a detail view of a portion of the receiver substrate assembly
of FIG. 4;
[63] FIG. 6 is a rear plan view of an alternate embodiment of a receiver
substrate assembly
having two arrays of receiver assemblies;
[64] FIG. 7A is a perspective view of an embodiment of a heat spreader portion
of a
receiver substrate assembly;
[65] FIG. 7B is a perspective view of another embodiment of a heat spreader
portion of a
receiver substrate assembly;
[66] FIG. 8A is a perspective view of another embodiment of a heat spreader
portion of a
receiver substrate assembly;
[67] FIG. 8b is a perspective view of a cell receiver assembly including the
heat spreader
portion of FIG. 8A;
[68] FIG. 8C is an exploded view of an embodiment of an optical unit including
the heat
spreader portion of FIG. 8A;
[69] FIG. 9 is a cross-sectional view of an embodiment of an optical unit that
has a curved
light guide optic;
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[70] FIG. 10 is a cross-sectional view of an embodiment of an optical unit
that has a
focusing optic and a light guide optic, and the focusing optic reflects light
directly to a
conditioning surface;
[71] FIG. 11 a cross-sectional view of an embodiment of an optical unit in
which the light
guide optic has reflecting surfaces that reflect light in three different
paths;
[72] FIG. 12 a cross-sectional view of another embodiment of an optical unit
in which the
light guide optic has reflecting surfaces that reflect light in three
different paths;
[73] FIG. 13 is a cross-sectional view of an embodiment of an optical unit
where the light
guide optic includes tertiary reflectors;
[74] FIG. 14 is a cross-sectional view of another embodiment of an optical
unit where the
light guide optic includes tertiary reflectors;
[75] FIG. 15 is a cross-sectional view of an embodiment of an optical unit
that has a
redirecting optic between the receiver substrate assembly and the light guide
optic;
[76] FIG. 16 is a cross-sectional view of another embodiment of an optical
unit in which
the light guide optic has tertiary reflectors;
[77] FIG. 17 is a cross-sectional view of an embodiment of an optical unit in
which the
light guide optic includes lenses;
[78] FIG. 18 is a cross-sectional view of an embodiment of an optical unit
that has the
receiver assembly on the second surface or the rigid sheet;
[79] FIG. 19 is a cross-sectional view of another embodiment of an optical
unit that has the
receiver assembly on the second surface or the rigid sheet;
[80] FIG. 20 is a cross-sectional view of another embodiment of an optical
unit that has a
redirecting optic between the receiver substrate assembly and the light guide
optic;
[81] FIG. 21 is a cross-sectional view of an embodiment of an optical unit in
which the
light guide optic has focussing portions and guiding portions;
[82] FIG. 22 is a cross-sectional view of an embodiment of an optical unit in
which the
light guide has three stages;
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[83] FIG. 23 is a cross-sectional view of an embodiment of an optical unit in
which the
focusing optic has lenses and redirecting surfaces;
[84] FIGS. 24A and 24B show cross-sectional views of an embodiment of an
optical unit
transmitting light through the gaps in a heat spreader portion, and where the
light guide optic
has a redirecting portion and a guiding portion;
[85] FIG. 24C is an exploded view of the light guide optic and envelope of
FIGS. 24A and
24B
[86] FIG. 25 is a cross-sectional view of another embodiment of an optical
unit transmitting
light through the gaps in a heat spreader portion, and where the light guide
optic has a
redirecting portion and a guiding portion;
[87] FIG. 26 is a cross-sectional view of another embodiment of an optical
unit transmitting
light through the gaps in a heat spreader portion, and where the light guide
optic has a
redirecting portion and a guiding portion; and
[88] FIG. 27 is a perspective view of another embodiment of an optical unit.
DETAILED DESCRIPTION OF SOME EMBODIMENTS
[89] FIG. 2 is a rear perspective view of an embodiment of a concentrated
photovoltaic
(CPV) panel 2 (a device for concentrating and harvesting sunlight) of the
present technology.
In this embodiment, the CPV panel 2 has a receiver substrate assembly 10,
light-guide optics
40 attached to the receiver substrate assembly 10, focusing optics 50 (shown
in FIG. 3)
attached to the receiver substrate assembly 10 (collectively referred to
herein as "CPV panel
apparatus" 6), a panel frame 4 and a junction box 38. (In other embodiments,
the structure of
a CPV panel may different. For example, in other embodiments the focusing
optics 50 may
not be present.) In this embodiment, the CPV panel 2 is made to have
dimensions similar to
those of a conventional non-concentrating photovoltaic panel 100, such as that
shown in FIG.
1, and thereby serve as a replacement product in suitable deployments (e.g.,
may replace
conventional photovoltaic panels mounted on a tracker). This is not required
to be the case,
and in other embodiments, CPV panels may be of different dimensions.
[90] In this embodiment, the receiver substrate assembly 10 includes a rigid
sheet 12 of
light transmissive material with a conductor pattern 30 (including a patterned
electrical
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circuit) and receiver assemblies 20 affixed thereto. The rigid sheet 12 has a
first surface 14
and a second surface 16 opposite the first surface 14. Each receiver assembly
20 is attached to
the first surface 14 of the rigid sheet 12 and electrically connected to the
conductor pattern 30.
For example, each receiver assembly 20 can be bonded to the rigid sheet 12 at
bond sites 26
with a conductive epoxy, which can allow attachment to the rigid sheet 12 and
electrical
connection to the conductor pattern 30 in a single step during assembly.
Alternatively,
positive and negative contacts of each receiver assembly 20 may be soldered to
the conductor
pattern 30. In yet other embodiments, one of the positive or negative contacts
of each receiver
assembly 20 may be soldered to or bonded with a conductive epoxy to the
conductor pattern
30 while the other contact is electrically connected to the conductor pattern
30 by wire
bonding, spring clipping or any other means known in the art.
[91] The conductor pattern 30 provides electrical paths between the receiver
assemblies 20
and the junction box 38. In the embodiment illustrated in FIGS. 3, 4 & 5, the
conductor
pattern 30 includes a positive bus bar 34, a negative bus bar 36 and a
plurality of
interconnection traces 32 which connect, directly or indirectly, each receiver
assembly 20 to
the bus bars 34, 36. In the embodiment of FIG. 4, the conductor pattern 30
electrically
connects 22 strings of 16 series-connected receiver assemblies 20 in parallel.
In other
embodiments, the conductor pattern 30 can be designed to provide electrical
paths for two or
more arrays 60 of receiver assemblies 20. As shown in FIG. 6, the conductor
pattern 30 can
comprise two halves 30a, 30b, each of which provide electrical paths for an
array 60 of
receiver assemblies 20 to a junction box 38. As will be appreciated by a
person skilled in the
art, patterns other than those shown and/or described herein may be used to
suit specific
applications.
[92] The conductor pattern 30 is formed of an electrically conductive metal
such as silver
or copper. The conductor pattern 30 can be applied onto the first surface 14
of the rigid sheet
12 by any suitable metalization process, which could, for example, include
sputtering,
galvanizing or screen printing a thick film. Alternatively, conductors, such
as wires, ribbons
and/or foils, can be attached to the rigid sheet 12 using a bonding agent such
as epoxy and/or
by soldering the conductors to metalizations on the rigid sheet 12 (e.g.,
metalized dots).
[93] Unlike conventional solar concentrators, the conductor pattern 30 is
sandwiched
within the panel 2 (for example, in some embodiments, between the rigid sheet
12 and either a
light guide optic 40 or a focusing optic 50).
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[94] The conductor pattern 30 may also serve as a heat spreader by spreading
the heat
generated at the photovoltaic cell 24 away from the photovoltaic cell 24 via
conduction, to be
dissipated through the rigid sheet 12 and the light guide optic 40. Where the
optical units 8
(comprising the light guide optic 40, the photovoltaic cell 24 and, where
present, the focusing
optic 50) are sufficiently small, the interconnection traces 32 of the
conductor pattern 30 may
be capable of dissipating heat from the photovoltaic cell 24 fast enough to
keep the
photovoltaic cell 24 cool enough to operate efficiently. However, for larger
optical units 8, the
interconnection traces 32 may be insufficient for cooling the photovoltaic
cell 24. More
elaborate conductor patterns 30 that have heat spreader portions 70
electrically and thermally
connected to the interconnection traces 32 may therefore be employed to cool
larger optical
units 8. The larger the optical unit 8, the greater the surface area of the
conductor pattern 30
required.
[95] FIGS. 7A & 7B show substantially flat heat spreader portions 70a, 70b of
conductor
pattern 30. The heat spreader portion 70a has a positive half and a negative
half. The positive
half includes a positive terminus 72, positive arms 76 and interconnection
traces 32
electrically and thermally connecting the positive terminus 72 and the
positive arms 76. The
negative half includes a negative terminus 74, negative arms 78 and
interconnection traces 32
electrically and thermally connecting the negative terminus 74 and the
negative arms 78. The
positive terminus 72 is disposed proximate to the negative terminus 74 to
allow their
connection (e.g., by soldering) with the positive and negative contacts of the
receiver
assembly 20. The interconnection traces 32 extending from the heat spreader
portion 70a
electrically connect the positive half of one heat spreader portion 70a to the
negative half of
the next heat spreader trace 70a of the string or a bus bar 34, 36. Gaps 80
are provided
between arms 76, 78 to facilitate heat dissipation and to allow light to be
focused therethrough
by the focusing optic 50 into the light guide optic 40. The heat spreader
portion 70a is
designed to allow light to be transmitted from the focusing optic 50 to the
light guide optic 40
with little shading. The heat spreader portion 70a illustrated in FIG. 7A
allows light from
concentric lenses (e.g., toroidal lenses) of a focusing optic 50 to pass
through gaps 80,
through the rigid sheet 12 and into the light guide optic 40, shaded only by
the
interconnection traces 32. The heat spreader portion 70b can be scaled to
accommodate larger
optical units 8 by increasing the number of positive and negative arms 76, 78,
as shown in
FIG. 7B. Such heat spreader portions 70a, 70b can be metalized onto the rigid
sheet 12 or
stamped from a sheet or foil of conductive material (commonly used in the
fabrication of
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circuit boards) such as conductive metals (e.g., copper, gold or aluminum) and
polymers
loaded with conductive materials and bonded to the rigid sheet 12.
[96] In another embodiment, the heat spreader portion 70 may have one or more
fins 82, 84
extending outwardly from the first surface 14 of the rigid sheet 12. FIGS. 8A-
8C show a heat
spreader portion 90a, 90b that has positive arms 76, negative arms 78, a
positive terminus 72
and a negative terminus 74, all of which lie flat against the rigid sheet.
These portions the lie
flat against the rigid sheet 12 can be metalized onto the rigid sheet 12 or
can be attached to the
rigid sheet 12 with an adhesive or soldered to metalizations on the rigid
sheet 12. The heat
spreader portion further has a positive fin 82 and a negative fin 84, which,
in the illustrated
embodiment, are attached to and extend perpendicularly from those portions
that lie flat
against the rigid sheet 12.
[97] The heat spreader portion 90a shown in FIG. 8A can be stamped for a
single sheet of
conductive material and bent or folded to form the functional heat spreader
portion 90a.
Alternatively, each of the positive half and the negative half of the heat
spreader portion 90a
can be integrally formed, for example, by 3D printing onto the rigid sheet 12
or molding each
half of the heat spreader portion 90a and attaching it to the rigid sheet 12
with an adhesive or
by soldering to metalizations on the rigid sheet 12.
[98] In the embodiment of FIG. 8B, the positive arms 76 and negative arms 78
of the heat
spreader portion 90b are more densely packed thereby increasing the surface
area over which
heat can be dissipated. FIG. 8B also illustrates how the positive arms 76,
negative arms 78,
positive terminus 72 and negative terminus 74 lie flat against the rigid sheet
12 and the
positive fin 82 and negative fin 84 extend perpendicularly from those portions
that lie flat
against the rigid sheet 12. This heat spreader portion 90b cannot be stamped
from a single
sheet of conductive material. Instead the parts that lie flat against the
rigid sheet 12 can be
metalized onto the rigid sheet 12 or stamped from a sheet of conductive
material or otherwise
formed and bonded to the rigid sheet 12, while the positive and negative fins
82, 84 must be
separately stamped from a sheet of conductive material or otherwise formed and
be soldered
or attached to those portions that lie flat against the rigid sheet 12 with an
electrically and
thermally conductive adhesive. Alternatively, each of the positive half and
the negative half
of the heat spreader portion 90b can be integrally formed, for example, by 3D
printing onto
the rigid sheet 12 or molding each half of the heat spreader portion 90b and
attaching it to the
rigid sheet 12. As shown in FIG. 8B the receiver assembly 20 can be mounted
across the
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positive terminus 72 and the negative terminus 74 for connection with the
positive terminus
72 and the negative terminus 74. The positive fin 82 and the negative fin 84
can have bent
portions 82p, 84n to accommodate the receiver assembly 20. The bent portions
82p, 82n
should have a height from the rigid sheet that is short enough not to impede
the transmission
of light from the light guide optic 40 to the photovoltaic cell 24. The
positive fin 82
electrically and thermally interconnect the positive arms 76 and the positive
terminus 72.
Similarly, the negative fin 84 electrically and thermally interconnect the
negative arms 78 and
the negative terminus 74. As shown in FIG. 8C, the light guide optic 40 can be
provided with
a groove 86 to accommodate the fins 82, 84. Use of such fins 82, 84 may reduce
shading
while increasing the surface area for dissipation of heat, and facilitate
alignment of the light
guide optic 40 with the receiver assembly 20 and thereby the photovoltaic cell
24.
[99] The conductor pattern 30 can additionally or alternatively serve as
and/or include
alignment markers to facilitate assembly of the CPV panel apparatus 6.
Alignment markers
could, for example, be metalized dots (not shown). Alignment markers could,
for example,
facilitate the location of bond sites 26 for dispensing of a bonding agent for
attachment of the
receiver assemblies 20 to the rigid sheet 12 and placement of the receiver
assemblies 20 on
the rigid sheet 12. Alignment markers could also facilitate alignment of the
light-guide optic
40 and the receiver assembly 20 (more particularly, the photovoltaic cell 24)
of each optical
unit 8. Where the optical unit 8 includes a focusing optic 50 for insertion of
light into the
light-guide optic 40 to be guided thereby toward the photovoltaic cell 24,
alignment markers
could facilitate alignment of the focusing optic 50 with the light guide optic
40.
[100] Each receiver assembly 20 includes a photovoltaic cell 24 for conversion
of
concentrated sunlight into electricity. Each photovoltaic cell 24 can be
mounted on a receiver
substrate 22 of the receiver assembly 20 and is in electrical communication
with the
conductor pattern 30.
[101] The photovoltaic cell 24 can be a high efficiency photovoltaic cell,
such as a multi-
junction solar cell. For example, the photovoltaic cell 24 can be a
GaInP/GaInAs/Ge III-V
triple-junction solar cell.
[102] The receiver assembly 20 can also include a bypass diode (not shown) to
prevent the
failure of a string of receiver assemblies 20 connected in series due to
failure, shading or any
other issues that would cause one of the series connected receiver assemblies
20 to enter an
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open circuit state. Alternatively, the bypass diode may be separate from the
receiver assembly
20 and may be electrically connected directly to the interconnection traces 32
(e.g., by
soldering the bypass diode to each end of a discontinuity in the
interconnection traces).
[103] The receiver substrate 22 provides a medium on which electrical
connections can be
made between the electrical components of the receiver assembly 20, including
the
photovoltaic cell 24 and, if present, the bypass diode, and the conductor
pattern 30. Electrical
components of the receiver assembly 20 may be soldered to conductors on the
receiver
substrate 22 to form electrical connections. The receiver substrate 22 can be
a surface mount
substrate with positive and negative contacts on the backside of the substrate
(i.e., the surface
of the substrate opposite that on which the photovoltaic cell 24 is mounted)
for electrical
connection to the conductor pattern 30.
[104] The light guide optics 40 are made of a light transmissive material and
guide light
received via the rigid sheet 12 substantially laterally toward their
associated photovoltaic cells
24. Each light guide optic 40 has a central axis and rotational symmetry about
the central axis
44. Light is guided by the light-guide optics 40 by at least one reflection on
at least one
reflective surface 42. The at least one reflection on the at least one
reflective surface 42 can be
total internal reflections on surfaces that interface with materials having a
lower index of
refraction than the light-guide optics 40, reflections on mirror coated
surfaces of the light-
guide optics 40 or a combination thereof. The one or more reflective surfaces
42 can form
concentric rings about the central axis 44, an example of which is shown in
Fig. 3.
[105] Each focusing optic 50 is made of a light transmissive material and
directs light
towards one or more reflective surfaces 42 of an associated light-guide optic
40. Use of
focusing optics 50 may therefore allow for thinner CPV panel apparatus 6 than
would
otherwise be possible.
[106] Non-limiting examples of light transmissive materials that may be used
to form the
rigid sheet 12, the light guide optics 40 and/or the focusing optics 50
include glass, light
transmissive polymeric materials such as rigid, injection molded poly(methyl
methacrylate)
(PMMA), polymethyl methacrylimide (PMMI), polycarbonates, cyclo olefin
polymers (COP),
cyclo olefin copolymers (COC), polytetrafluoroethylene (PTFE), or a
combination of these
materials. For example, the rigid sheet 12 can be a sheet of glass, and the
light guide optics 40
and the focusing optics 50 can be made of PMMA. Alternatively, the light guide
optics 40
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and/or the focusing optics 50 can be made of a silicone rubber such as
silicone having
hardness, when cured, of at least 20 Shore A. Attachment of each light-guide
optic 40 and
focusing optic 50 to the receiver substrate assembly 10 can be achieved by
optically bonding
the optics 40, 50 to the receiver substrate assembly 10 with an optical
bonding agent, laser
welding (where the rigid sheet 12 and the light-guide optics 40 and focusing
optics are made
of polymers) or any other means known in the art. As an example, if the light
guide optics 40
and the focusing optics 50 are made of a polymeric material, they can be
optically bonded to
the glass rigid sheet 12 using an optical adhesive such as a silicone.
Alternatively, the light
guide optics 40 and the focusing optics 50 can be 3D printed directly on the
glass rigid sheet
12 or the surfaces of the receiver substrate assembly10 can be coated with a
polymer, such as
a silicone rubber, and the polymeric light guide optics 40 and focusing optics
50 can be 3D
printed thereon.
[107] Although FIGS. 2 and 3 show circular light guide optics 40 and circular
focusing
optics 50, the light guide optics 40 and/or the focusing optics 50 can be
cropped into a tileable
shape such as a square or a hexagon to eliminate dead space between optical
units 8.
[108] FIG. 9 is a cross sectional view of an optical unit 108 having a
parabolic light guide
optic 140 optically bonded to the first surface 14 of a receiver substrate
assembly 10. In this
embodiment, light 11, typically from the sun, impinges on the rigid sheet 12
at an angle
substantially normal to the second surface 16. The light 11 is transmitted
through the rigid
sheet 12, exiting through the first surface 14 into the light guide optic 140.
The reflective
surface 142 can be parabolic in shape and have a mirror coating 148 to reflect
the light
impinging thereon towards the focus of the parabola where a photovoltaic cell
24 can be
placed to convert the light 11 into electricity. Non-limiting examples of
materials that can be
used for the mirror coating 148 are metals such as aluminum or silver, or a
dielectric.
[109] In some embodiments a cell envelope 21 may surround the photovoltaic
cell 24, which
is typically the hottest portion of an optical unit 108, and serve as thermal
insulation to protect
the physical integrity of the materials of the light guide optic 40. Where the
receiver assembly
20 is attached to a rigid sheet 12 made of glass, and the light guide optic is
made of a polymer
such as PMMA, it may only be necessary to provide a cell envelope 21 about the
photovoltaic
cell 24 on the side facing the light guide optic 40. The cell envelope 21 can
be a dome (e.g., a
hemisphere) of thermally insulating material, e.g., a polymer such as silicone
or glass. The
light guide optic 40 can therefore include a cavity 45 complementary in shape
to the cell
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envelope 21 to house the cell envelope 21. Alternatively, the cell envelope 21
may be filled
with a gas such as air contained by the cavity 45. An example of a cell
envelope 21 and cavity
45, to thermally insulate the light guide optic 140 from heat generated at the
photovoltaic cell
24, is shown in FIG. 9.
[110] FIG. 10 is a cross sectional view of an optical unit 208 including a
focusing optic 250
optically bonded to the second surface 16 of a receiver substrate assembly 10,
and a light
guide optic 240 optically bonded to the first surface 14 of the receiver
substrate assembly 10.
In this embodiment, the focusing optic 250 is formed of a plurality of lenses
adjacent to one
another and has rotational symmetry about the central axis 44. The lenses 52
can therefore
form concentric rings about the central axis 44. Although FIG. 10 shows a
focusing optic 250
with three lenses 52 on either side of the central axis 44, greater or fewer
lenses may be used
depending on the dimensions of the optical unit 8 and the materials used.
[111] The light guide optic 240 is stepped and substantially wedge-shaped in
cross section,
having a plurality of reflective surfaces 242 separated by step surfaces 246.
A reflective
surface 242 is positioned near the focus of each lens 52, such that
substantially all of the
sunlight 11 impinging upon the surface 54 of a lens 52 is focused by the lens
52 toward the
reflective surface 242. The focused light 13 is transmitted through the light
transmissive body
251 of the focusing optic 250, through the rigid sheet 12 and through the
light transmissive
body 241 of the light guide optic 240 to the reflective surfaces 246. Where
the conductor
pattern 30 includes heat spreader portions (not shown) the lenses 52 focus the
light 13 through
the gaps 80 of the heat spreader portions 70a, 70b, 90a, 90b. The focused
light 13 may be
reflected by the reflective surfaces 242 by total internal reflection or,
where the reflective
surfaces 242 are mirror coated, by specular reflection. The reflected light 15
is transmitted in
the light transmissive body 241 of the light guide optic 240 towards a
conditioning surface
243, which may be a parabolic section in cross section and which reflects the
reflected light
15 towards the photovoltaic cell 24. The reflected light 15 may be reflected
by the
conditioning surface 243 by total internal reflection, or where the
conditioning surface 242 is
mirror coated, by specular reflection. The path of the concentrated light 17,
which has been
reflected by the conditioning surface 243, is focused towards the focus of the
parabola but
intercepted by the photovoltaic cell 24 which converts the concentrated light
17 into
electricity.
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[112] In embodiments having multiple reflective surfaces 242, each reflective
surface 242
may be identical to the others such that substantially all of the light in the
optical unit 208 is
generally transmitted in the same direction toward the conditioning surface
243, i.e., the light
may be collimated as shown in Fig. 10. Alternatively, the reflective surfaces
242 may be
different from one another, such that a reflective surface or a group of
reflective surfaces
reflect light in one direction, and another reflective surface or another
group of reflective
surfaces reflect light in another direction or directions
[113] As shown in FIGS. 11 and 12, an optical unit 308, 408 can include a
focusing optic
250, a receiver substrate assembly 10, a low index film 9 and a light guide
optic 340, 440. The
low index film 9 has a lower index of refraction than the light transmissive
body 341, 441. An
example of a low index film material is a layer of a low index polymer or
polytetrafluoroethylene (Teflon), which can be deposited onto the first
surface 14 of the rigid
sheet 12. The focused light 13 is transmitted through the light transmissive
body 251 of the
focusing optic 250, through the rigid sheet 12, through the low index film 9
and through the
light transmissive body 341, 441 and onto the reflective surfaces 342a, 342b,
342c.
[114] In this embodiment, the reflective surfaces 342a intercept the focused
light 13 and
reflect it, such that the reflected light 15a is transmitted through the light
transmissive body
341,441 of the light guide optic 340,440 towards the low index film 9. The
reflected light 15a
is then reflected a second time by the low index film 9 via total internal
reflection (TIR) and is
transmitted towards a conditioning surface 343, 443. Reflective surfaces 324b
intercept the
focused light 13 and reflect it directly towards the conditioning surface 343,
442. The
conditioning surface 343, 443 reflects the reflected light 15a, 15b towards
the photovoltaic
cell 24 for harvesting electricity. Reflective surfaces 342c reflect the
focused light 13 directly
towards the photovoltaic cell 24. In these embodiments, the reflective
surfaces 342a-342c are
separated by step surfaces 346. FIG. 11 shows an optical unit 308 wherein each
reflective
surface 342a, 342b, 342c has a different profile in cross section. FIG. 12
shows an optical unit
308 having a group of two reflective surfaces 342a, a group of two reflective
surfaces 342b
and a reflective surface 342c. In an alternative embodiment similar to that of
FIG. 12, any
number of reflective surfaces 342a, 342b, 342c and corresponding lenses 52 may
be included.
[115] Fig. 13 shows a cross section of an optical unit 508 in which the light
guide optic 540
includes a plurality of reflective surfaces 542a-542d, each reflective surface
542a-542d
having a different profile in cross section from the others, separated by a
plurality of step
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surfaces 546a-546c each step surface 546a-546c having a different profile in
cross section
from the others. The light guide optic 540 also includes tertiary reflector
547 with a secondary
reflective surface 549. The gap 527 between the low index film 9 and the
tertiary reflector 547
can be filled with a gas such as air or any suitable light transmissive
material having a lower
refractive index than the light transmissive body 541 of the light guide optic
540. The
secondary reflective surfaces 549 can be mirror coated or they can reflect
light by TIR.
[116] Reflective surfaces 542a and 542b intercept the focused light 13 and
reflect it towards
the low index film 9, which further reflects the reflected light 15 towards a
secondary
reflective surface 549. The secondary reflective surface 549 then reflects the
reflected light 15
towards a conditioning surface 543 which reflects the light towards the
photovoltaic cell 24.
Reflective surfaces 542c and 542d intercept the focused light 13 and reflect
if towards the
conditioning surface 543, which redirects the light towards the photovoltaic
cell 24. The
conditioning surface 543 may reflect the reflected light 15 one or more times.
The
conditioning optic 543 can include a parabolic section in cross section and
other curved or flat
portions in order to concentrate light towards the photovoltaic cell 24. The
focusing optic 550
may include dead space 53 in the vicinity of the central axis 44.
[117] FIG. 14 is a cross sectional view of an optical unit 608 generally
similar to that of FIG.
13. In this embodiment the light guide optic 640 includes a plurality of
reflective surfaces
642a-642d, each reflective surface 642a-642d having a different profile in
cross section from
the others, separated by a plurality of step surfaces 646a-646c each step
surface 646a-646c
having a different profile in cross section from the others. The step surfaces
646a-636c, unlike
those described in earlier embodiments, are also reflective. Additionally, the
light guide optic
640 includes a plurality of tertiary reflectors 647 with secondary reflective
surfaces 649,
opposite the step surfaces 646a-646c. For every reflective surface 642a-642c,
excluding the
reflective surfaces 643d nearest the central axis, there is a corresponding
secondary reflective
surface 649.
[118] In this embodiment, light 11 impinging on the lenses 52 is focused by
the lenses. The
focused light 13 is transmitted through the light transmissive body 551 of the
focusing optic
550, through the rigid sheet 12 and through the light transmissive body 641 of
the light guide
optic 640 onto a reflective surface 642a-642d. Although the reflective
surfaces 642a-642c and
the step surfaces 646a-646c need not be identical in shape, the trajectory of
the light between
them is similar: The focused light 13 is reflected by a reflective surface
642a-642c towards a
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corresponding step surface 646a-646c. The reflected light 15 is then reflected
a second time
by a step surface 646a-646c towards a corresponding secondary reflective
surface 649 which
reflects the light a third time towards a conditioning surface 643, which
further reflects the
light towards the photovoltaic cell 24.
[119] FIG. 15 shows a cross section of an optical unit 708 having a focusing
optic 250, a
receiver substrate assembly 10, a redirecting optic 755, a low index film 709,
and a light guide
optic 740. The redirecting optic 755 can be made of light transmissive
materials including
glass, polymeric materials such as injection molded poly(methyl methacrylate)
(PMMA),
polymethyl methacrylimide (PMMI), polycarbonates, cyclo olefin polymers (COP),
cyclo
olefin copolymers (COC), polytetrafluoroethylene (PTFE), or silicones. In this
embodiment,
the redirecting optic 755 is assembled onto the first surface 14 of the rigid
sheet 12, the planar
surface 759 of the redirecting optic 755 being optically bonded thereto. The
non-planar
surface 758 of the redirecting optic 755 includes a plurality of redirecting
elements 756 with
redirecting surfaces 757, and is coated by a low index film 709, such that the
focused light 13
is reflected by a redirecting surface 757 via TIR. Alternatively, the
redirecting surfaces 757
may be coated with a reflective material, which may be more economical than
coating the
entire non-planar surface 758 with a low index film 709.
[120] The light guide optic 740 includes a plurality of indentations 770
shaped to house the
redirecting elements 756. The light guide optic 740 can be assembled onto and
optically
bonded to the redirecting optic 755 using optical adhesive such as silicone.
The light guide
optic further includes a reflective surface 742 that is continuous with a
conditioning surface
743. Light 11 impinging on the surface 54 of the lenses 52 is focused and
transmitted through
the light transmissive body 251 of the focusing optic 250, through the rigid
sheet 12, and into
the redirecting optic 755, where the light is reflected by a redirecting
surface 757. The
reflected light 15 is transmitted out of the redirecting optic through output
faces 771 adjacent
to the redirecting surfaces 757, and into the light guide optic 740 through
input faces 772,
which are part of the indentations 770. In the light guide optic 740, the
reflected light can be
reflected by the reflective surface 742 directly to the photovoltaic cell, or
to the conditioning
surface 743. Light impinging on the conditioning surface 743 is concentrated
towards the
photovoltaic cell 24.
[121] FIG. 16 shows a cross section of an embodiment of an optical unit 808 in
which the
path of light is generally similar to that of FIG. 15. However, in this
embodiment, the light
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guide optic 840 is made with a plurality of tertiary reflectors 870 including
redirecting
surfaces 857. When the light guide optic 840 is assembled onto the first
surface 14, air fills
the gap 873 between the first surface 14 and the tertiary reflector 870. In an
alternative
embodiment, the gap 873 can be filled with any suitable material having a
refractive index
lower than that of the light transmissive body 841.
[122] In this embodiment the focused light 13 converges towards the focal
point of the lens
52, but before reaching the focal point, it is intercepted by a redirecting
surface 857 the
reflects the focused light 13 by TIR. The reflective surface 842 is continuous
with the
conditioning surface 843. As in FIG. 15 the reflected light can be reflected
by the reflective
surface 842 directly to the photovoltaic cell, or to the conditioning surface
843. Light
impinging on the conditioning surface 843 is concentrated towards the
photovoltaic cell 24.
[123] FIG. 17 shows a cross section of an optical unit 908 in which the light
guide optic 940
includes a plurality of lenses 952 and reflective surfaces 942, and is
attached to the rigid sheet
12 by means of optical attachment features 974. The optical attachment
features can be
optically and mechanically bonded, by means of an optical adhesive, to the
first surface 14 of
the rigid sheet 12. Likewise, the cell envelope 21, which in this embodiment
must be made of
a solid, optically transmissive material such as silicone, is mechanically and
optically bonded
to a cavity 945 in the light guide optic 940.
[124] Light 11 impinging on the second surface 16 of the rigid sheet 12, is
transmitted to the
light guide optic 940 through the optical attachment features 974 or through
the lenses 952.
Light 11 entering the light guide optic through the lenses 952 is transmitted
from the first
surface 14 of the rigid sheet 12 to a layer 975, which in some embodiments may
be air or any
suitable light transmissive material. From the layer 975, the light 11 is
transmitted to the
lenses 952 which focus the light towards reflective surfaces 942, which
reflect the light
towards a conditioning surface 943. Light 11 entering the light guide optic
940 through the
optical attachment features 974 is transmitted directly from the first surface
14 of the rigid
sheet to the optical attachment features 974. These optical attachment
features 974 include
reflecting surfaces 976 which reflect the light impinging thereon towards the
conditioning
surface 943. Light impinging on the conditioning surface 943 is then reflected
towards the
photovoltaic cell 24. The lenses 952 are largest near the central axis 44 and
smallest near the
peripheral edge 980 of the optical unit 908. This is to adjust the focal
lengths of the lenses 952
so that the overall thickness of the light guide optic 940 may be reduced.
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[125] FIG. 18 shows a cross section of an optical unit 1008 having a parabolic
light guide
optic 1040 optically bonded to the second surface 16 of a receiver substrate
assembly 10. In
this embodiment, light 11 typically impinges on the rigid sheet 12 at an angle
normal to the
first surface 14. The light 11 is transmitted through the rigid sheet 12,
exiting through the first
surface 14 into the light guide optic 1040. The reflective surface 1042, which
is a parabolic
section in cross section, has a mirror coating 148 to reflect the light
impinging thereon
towards the focus of the parabola. The reflected light is transmitted through
the light
transmissive body 1041 of the light guide optic 1040 and back through the
rigid sheet into a
secondary optic 1077. The secondary optic includes a mirror coated hyperbolic
surface 1078,
which intercepts the light 15 before reaching the focus of the parabola. The
hyperbolic surface
1078 redirects the light towards the photovoltaic cell 24. In this embodiment,
the conductor
pattern 30 and cell receiver assemblies 20 are assembled onto the first
surface 14 of the rigid
sheet 12.
[126] FIG. 19 is a cross sectional view of an optical unit 1108 having the
light guide optic
1140 assembled onto the second surface 16 of the rigid sheet 12 and the
conductor pattern 30
and the receiver assembly 20 on the first surface 14 of the rigid sheet 12. In
this embodiment
the focusing optic 1150 includes a secondary reflector surface 1178 and a
cavity 1179 for
housing the cell envelope 21, which in this embodiment extends from the first
surface 14 of
the rigid sheet 12, covering the photovoltaic cell 24 and the receiver
assembly 20.
[127] Light 11 impinging on the surface 54 of the lenses 52, is focused and
transmitted
through the light transmissive body 1151 of the focusing optic 1150, through
the rigid sheet
12 and through the light transmissive body 1141 of the light guide optic 1140.
Before the
focused light 13 reaches the focus of the lens 52, it is intercepted by a
reflective surface 1142
which reflects the light towards a conditioning surface 1143. The conditioning
surface 1143
reflects the light back through the rigid sheet 12 and the light transmissive
body 1151 of the
focusing optic 1150 to the secondary reflector surface 1178 which focuses the
concentrated
light 17 onto the photovoltaic cell 24. Reflections on the secondary reflector
surface 1178
may be TIR or specular reflections off a mirror coating applied to the
secondary reflector
surface 1178.
[128] FIG. 20 shows a cross section of an optical unit 1208 generally similar
to the
embodiment of FIG. 15 in that it includes a focusing optic 250, a receiver
substrate assembly
10, a redirecting optic 755, and a light guide optic 1240.
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[129] The light guide optic 1240 includes a planar reflective surface 1242, a
plurality of step
reflector surfaces 1281 opposite to the planar reflective surface 1242 and a
conditioning
surface 1243. The step reflector surfaces 1281 are separated by input surfaces
1282 which are
generally perpendicular to the step reflector surfaces 1281.
[130] Light 11 is focused by the lenses 52 and then reflected by the
redirecting surfaces 757.
The light 15 reflected by the redirecting surface 757 exits the redirecting
elements 756
through the output surfaces 771, and enters the light guide optic 1240 through
the input
surfaces 1282. The reflected light is then transmitted in the light guide
optic 1240 by total
internal reflections on the planar reflective surface 1242 and on the
plurality of step reflector
surfaces 1281 until it reaches the conditioning surface 1243 which reflects
the light towards
the photovoltaic cell 24, There is an area 1275 between the redirecting optic
755 and the light
guide optic 1240 that can be filled with air or any suitable light
transmissive material such as
an optical adhesive.
[131] FIG. 21 is a cross section of an optical unit 1308 in which the light
guide optic 1340
includes focusing portions 1383 and guiding portions 1384. The focusing
portions 1383
include a plurality of reflecting surfaces 1342 to reflect the light 11 into
the guiding portions
1384. The light guide optic 1340 has a plurality of reflector elements 1385
that can be filled
with air or a light transmissive material having a lower index of refraction
than the light guide
optic 1340, to allow TIR on the reflective surfaces 1342 and on a plurality of
step reflector
surfaces 1381.
[132] In this embodiment, light 11 enters the optical unit 1308 through the
second surface 16
and is transmitted to the plurality of reflecting surfaces 1342 which reflect
the light through an
output area 1386 to a guiding portion 1384. The light in the guiding portions
1384 is
transmitted via total internal reflections on the step reflector surfaces 1381
and on planar
reflectors 1387 positioned opposite to the step reflector surfaces 1381. The
guiding portions
1384 guide the light towards a conditioning surface 1343 which focuses the
light onto the
photovoltaic cell 24. Although, FIG. 21 shows a light guide optic 1340 with
two guiding
portions 1384 and two focusing portions 1383, it is possible to manufacture an
optical unit
with any number of focusing portions and corresponding guiding portions.
[133] Turning to FIG. 22 there is provided an optical unit having a light
guide optic 1440
composed of three light guide stages 1440a, 1440b, 1440c. The first light
guide stage 1440a
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includes reflecting surfaces 1442a and a first conditioning surface 1443a; the
second light
guide stage 1440b includes reflecting surfaces 1442b; and the third light
guide stage 1440c
includes a reflecting surface 1442c and a second conditioning surface 1443c.
The three light
guide stages 1440a, 1440b, 1440c can manufactured separately, for example, by
injection
molding, 3D printing or embossing, and subsequently assembled together. The
first and
second light guide stages 1440a and 1440b are optically bonded, for example,
by means of an
optical bonding agent at the bonding interface surface 1489 denoted by the
dotted line.
Further, all three light guide stages 1440a, 1440b, 1440c can be bonded to the
first surface 14
of the rigid sheet 12 by means of an optical bonding agent 1488b, for example
a polymer such
as silicone rubber or gel. As shown in FIG. 22, when the light guide optic
1440 is assembled,
gaps 1490 remain between the light guide stages 1440a, 1440b, 1440c. These
gaps 1490 allow
for TIR on the reflecting surfaces 1442a, 1442b, 1442c and on the conditioning
surfaces
1443a, 1443c.
[134] A focusing optic 550 is optically and mechanically bonded to the second
surface 16 of
a rigid sheet 12 also by means of an optical bonding agent 1488a, for example
a polymer such
as silicone rubber or gel. Light 11 impinging on the lenses 52 are focused
towards the
reflecting surfaces the 1442a, 1442b and 1442c. The reflecting surfaces 1442a
and 1442b of
the first and second light guide stages 1440a, 1440b reflect the light towards
the first
conditioning surface 1443a. Light travels from the second light guide stage
1440b to the first
light guide stage 1440a through the bonding interface 1489. The first
conditioning surface
1443a reflects the light towards the photovoltaic cell 24. The reflecting
surface 1442c of the
third light guide stage 1440c reflects light towards the second conditioning
surface 1443c,
which reflects the light towards the photovoltaic cell 24.
[135] FIG. 23 shows a cross section of an optical unit 1508 in which the
focusing optic 1550
includes a plurality of lenses 1552 and a plurality of redirecting surfaces
1592. In this
embodiment the light guide optic 1540 has reflecting surface 1542 coated with
a mirror
coating 148. Light impinging on the lenses 1552 is focused towards the
redirecting surfaces
1592 which reflect the light through the rigid sheet 12 into the light guide
optic 1540. In the
light guide optic 1540, the light 1542 is transmitted towards the reflecting
surface 1542,
which reflects the light towards the photovoltaic cell 24.
[136] As described in FIGS. 7A and 7B, conductor patterns employing heat
spreader
portions 70 may be electrically and thermally connected to the interconnection
traces 32 of an
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optical unit 8 in order to cool larger optical units 8. FIG. 24A shows a cross
section of an
optical unit 1708 employing conductor patterns such as those described in
FIGS. 7A and 7B.
This figure illustrates how the path of the focused light 13 is not
interrupted by the positive
arms 76 or negative arms 78 of the heat spreader portion 70a, and instead, the
light 13 is
transmitted through the gaps 80, into the light guide optic 1740.
[137] The optical unit 1708 shown in FIG. 24A includes a focusing optic 1750,
two layers of
an optical bonding agent 1788a, 1788b, a receiver substrate assembly 1710, and
a light guide
optic 1740. The focusing optic 1750 is optically and mechanically bonded to
the second
surface 16 of the rigid sheet 12 by means of an optical bonding agent 1788a.
The light guide
optic 1740 includes a redirecting portion 1740a and a guiding portion 1740b
which can be
manufactured separately, for example by injection molding or embossing, and
then assembled
together by means of an optical adhesive or any suitable optical bonding
means. When
assembled together, gaps 1790 remain between the redirecting portion 1740a and
the guiding
portion 1740, to enable TIR at a plurality of reflective surfaces 1742 of the
redirecting portion
1740a.
[138] As will be appreciated by those skilled in the art, optics of any of the
optical units
described above can be employed as a illumination device by reversing the
direction of light
travelling therethrough and replacing the photovoltaic cell 24 with a light
source 25, such as a
light-emitting diode (LED) or an organic light-emitting diode (OLED), a plasma
light bulb,
fluorescent light bulbs, or any other type of suitable light-source. In some
embodiments the
light source 25 can be an optical fibre transferring light from source remote
originating source
(not shown). In order to illustrate this duality of the optical units, the
direction of light rays
11 of FIGS. 24A-26 are omitted in order to show that the light could be
entering the optical
unit through the lenses 1752, or it could be emerging therefrom. The heat
produced by the
photovoltaic cell 24 or light source 25 is transmitted away from the central
axis 44 towards
the edges by means of the positive arms 76 and the negative arms 78. The
direction of heat
transfer is shown in FIG. 24B by arrows 1794.
[139] In this embodiment, the receiver assembly 20 is coated with an optical
and dielectric
encapsulant 1793, which in some embodiments may be the same material as the
optical
bonding agent 1788b. The envelope 1721 thermally insulates the photovoltaic
cell 24 or the
light source 25 from the light guide optic 1740. The envelope 1221 can be a
separate molded
component. However, in one alternative embodiment, the optical bonding agents
1788b, the
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encapsulant 1793 and the envelope 1721 can all be made of the same material,
for example
silicone, and therefore they would be a single component.
[140] It is possible to assemble the light guide optic 1740 with the envelope
1721 into a
single solid piece by attaching the envelope 1721 to a cavity 1745 in the
light guide optic
1740. The redirecting portion 1740a, the guiding portion 1740b and the
envelope can be
manufactured separately, for example by injection molding, and subsequently
bonded
together by means of a suitable bonding agent before being assembled onto the
first surface
14 of the receiver substrate assembly 1710 by means of the optical bonding
agent 1855b. FIG.
24C shows how the redirecting portion 1740a, the guiding portion 1740b and the
envelope
1721 fit together.
[141] An optical unit 1708 such as the one shown in FIGS. 24A-24C can behave
as a solar
concentrator by focusing light 11 impinging on the surface 1754 of the lenses
1752. The
focussed light 13 is transmitted through the light transmissive body 1751 of
the focusing optic
1740, the optical bonding agents 1788a, 1788b, the rigid sheet 12 and through
the gaps 80 of
the heat spreader portion 70a of the conductor pattern 30 into the redirecting
portion 1740a of
the light guide optic 1740. The focussed light 13 is intercepted by a
reflective surface 1742,
which reflects the light through the bonding interface 1789 into the guiding
portion 1740b
where the light is reflected towards the photovoltaic cell 24 by a
conditioning surface 1743.
[142] The same optical unit 1708 of FIGS. 24A-24C can be used as an
illumination device in
the following manner. Light 17 diverging away from the light source 25 is
transmitted
through the encapsulant 1793 and the envelope 1721 into the guiding portion
1740b of the
light guide optic 1740. The conditioning surface 1743 then reflects the light
through the
bonding interfaces 1789 into the redirecting portion 1740a of the light guide
optic 1740 where
the reflective surfaces 1742 reflect the light such that it diverges away from
the reflective
surfaces 1742 towards the lenses 1752. The light 13 diverges away from the
reflective
surfaces 1742 to the lenses 52 through gaps 80 in the heat spreader 70a of the
portion of the
conductor pattern, thereby avoiding the positive and negative arms 76, 78 and
the positive and
negative termini 72, 74. The lenses 1752 collimate the output light 11.
[143] FIG. 25 show a cross section of an optical unit 1808 generally similar
to the
embodiment shown in FIGS. 24A-24C and any elements not described in relation
to this
embodiment below can be found in the description of the embodiment above. The
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embodiment of FIG. 25 differs from that of FIGS. 24A-24C only in that the
envelope 1821
includes a spherical optic 1895 and an encapsulating material 1896. The
spherical optic 1895
can be a bead made of a light transmissive material capable of withstanding a
high flux of
light, such as glass or silicone. The encapsulating material can be air or any
suitable light
transmissive material. In some embodiments the encapsulating material may be
the same
material as the bonding agent 1788b.
[144] It is also possible to use the rigid sheet 12 for the same purpose as an
envelope 21,
where the rigid sheet is made of a thermally insulating material such as
glass. This can be
achieved by positioning the photovoltaic cell 24 or the light source 25
against the second
surface 16 with an encapsulant 1993 between the glass and the receiver
assembly 20. This
encapsulant 1993 may extend to the edges of the optical unit 1908
encapsulating the positive
and negative arms 96,98 and forming an optical bond between the focusing optic
1750 and the
receiver substrate assembly 1910. In this embodiment, the positive terminus
1972 is raised
away from the positive and negative arms 76, 78, and therefore, the focusing
optic 1950 has a
groove 1994 to house the positive terminus 1972. The positive terminus 1972
has extensions
1995 that extend to the glass in order to transfer heat thereto.
[145] It will be appreciated by those skilled in the art that the photovoltaic
cells 24 described
above can be replaced by any suitable solar energy collector.
[146] FIG. 27 is an isometric view of an assembled optical unit 1608 including
a light guide
optic 1640, a receiver substrate assembly 10 and a focusing optic 1650. The
rigid sheet 12 is
cropped into a hexagonal shape for the purpose of illustrating a single
assembled optical unit,
however a CPV 2, as shown in FIG. 2, panel may include several optical units
on a single
rectangular receiver substrate assembly. Although this embodiment shows a
circular light
guide optic 1640 and a circular focusing optic 1650, these can be cropped into
a tillable shape
such as a square or a hexagon to eliminate dead space.
[147] Modifications and improvements to the above-described embodiments of the
present
technology may become apparent to those skilled in the art. The foregoing
description is
intended to be exemplary rather than limiting. The scope of the present
technology is
therefore intended to be limited solely by the scope of the appended claims.
