权利要求：
1. An illumination panel comprising:
a receiver substrate assembly including:
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
at least one receiver assembly affixed to the rigid sheet, each receiver assembly including a light source in electrical communication with the conductor pattern;
at least one reflecting optic attached to and supported by one of the first surface and the second surface of the receiver substrate assembly, each reflecting optic in optical communication with the light source of an associated one of the at least one receiver assembly, reflecting light received therefrom, at least a portion of the reflected light diverging from an optical axis of the reflecting optic; and
at least one refracting optic attached to and supported by an other one of the first surface and the second surface of the receiver substrate assembly, each refracting optic associated with and in optical communication with one of the at least one reflecting optic, each refracting optic comprising at least one curved refracting surface, the divergent reflected light being refracted and collimated by the at least one curved refracting surface.
2. The illumination panel of claim 1, wherein each reflecting optic comprises at least one reflective surface for guiding light received from the light source out through the receiver substrate assembly.
3. The illumination panel of claim 1, wherein the at least one refracting element includes a lens.
4. The illumination panel of claim 1, wherein the conductor pattern includes two or more bus bars.
5. The illumination panel of claim 1, wherein the light transmissive material of the rigid sheet is a thermally insulating material.
6. The illumination panel of claim 1, wherein the light transmissive material of the rigid sheet is glass.
7. The illumination panel of claim 1, wherein the first and second surfaces of the rigid sheet are flat and parallel to each other.
8. The illumination panel of claim 1, wherein the reflecting optic is made of a different material than the rigid sheet.
9. The illumination panel of claim 1, wherein the reflecting optic is made of poly(methyl) methacrylate.
10. The illumination panel of claim 1, wherein the refracting optic is made of a different material than the rigid sheet.
11. The illumination panel of claim 1, wherein the refracting optic is made of poly(methyl) methacrylate.
12. The illumination panel of claim 1, wherein at least one of the at least one reflecting optic and the at least one refracting optic is 3D printed onto the rigid sheet.
13. The illumination panel of claim 1, wherein 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.
14. The illumination panel of claim 1, wherein the conductor pattern comprises a heat spreader portion.
15. The illumination panel of claim 14, wherein the heat spreader portion 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.
16. The illumination panel of claim 1, wherein the conductor pattern is metalized onto the first surface.
17. The illumination panel of claim 1, wherein the conductor pattern is formed from a sheet of conductive material.
18. The illumination panel of claim 1, wherein the conductor pattern comprises a heat spreader portion.
19. The illumination panel of claim 18, wherein the conductor pattern is disposed between the rigid sheet and one of the reflecting optic and the at least one refracting optic, and the heat spreader portion is shaped and positioned so as to avoid blocking light transmitted from the reflecting surfaces of the reflecting optic to the at least one refracting optic.
20. A panel comprising:
a rigid sheet of light-transmissive material having a first surface and a second surface opposite the first surface, a light source being affixed to one of the first surface and the second surface;
at least one reflecting optic attached to and supported by one of the first surface and the second surface of the rigid sheet of light-transmissive material, the at least one reflecting optic being in optical communication with the light source and having at least one reflective surface, reflecting light received therefrom, at least a portion of the reflected light diverging from an optical axis of the reflecting optic;
at least one refractive optic attached to and supported by an other one of the first surface and the second surface of the rigid sheet of light-transmissive material, the least one refractive optic associated with and in optical communication with one of the at least one reflecting optic, each refractive optic having at least one refractive element for cooperative operation with the at least one reflecting optic, each refractive optic having at least one curved refracting surface, the divergent reflected light being refracted and collimated by the curved refracting surface; and
the light source being intermediate the at least one reflecting optic and the at least one refractive optic.
21. An illumination panel comprising:
a receiver substrate assembly including:
a rigid sheet of light transmissive material having a first surface, a second surface opposite the first surface; and
a light source affixed to the first surface of the rigid sheet and in electrical communication with a conductor;
a refracting optic attached to and supported by one of the first surface and the second surface of the receiver substrate assembly, the refracting optic having a plurality of concentric ring-shaped lenses and a light-transmissive body, each of the concentric ring-shaped lenses having a curved refractive surface;
a reflecting optic attached to and supported by an other of the first surface and the second surface of the receiver substrate assembly, the reflecting optic having a plurality of ring-shaped reflective surfaces and a light-transmissive body, each of the ring-shaped reflective surfaces associated with and in optical communication with one of the ring-shaped lenses;
each of the ring-shaped reflective surfaces being shaped and positioned to receive light from the light source and to reflect the received light through the light-transmissive body of the reflecting optic, at least a portion of the reflected light diverging from an optical axis of the reflecting optic, the rigid sheet and the light-transmissive body of the refracting optic towards one of the ring-shaped lenses associated with that one of the ring-shaped reflective surfaces, a ring-shaped focus of the one of the ring-shaped lenses associated with that one of the ring-shaped reflective surfaces being positioned near that ring-shaped reflective surface such that the divergent light from the ring-shaped reflective surfaces is refracted by the curved refracting surface of that lens and transmitted to the exterior of the illumination panel as a collimated beam of light.
22. The illumination panel of claim 21, wherein the reflecting optic further comprises a ring-shaped conditioning surface that receives light directly from the light source and reflects the received light towards the ring-shaped reflecting surfaces.
具体实施方式：
[0065]FIG. 2 is a rear perspective view of an embodiment of a concentrated photovoltaic (CPV) panel 2. The CPV panel 2 has a receiver substrate assembly 10, one or more light-guide optics 40 attached to the receiver substrate assembly 10, optionally, one or more 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. The CPV panel 2 may be 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).
[0066]The receiver substrate assembly 10 includes a rigid sheet 12 of light transmissive material with a conductor pattern 30 and at least one receiver assembly 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 sites26 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.
[0067]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.
[0068]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).
[0069]Unlike conventional solar concentrators, the conductor pattern 30 is sandwiched between the rigid sheet 12 and either a light guide optic 40 or a focusing optic 50.
[0070]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 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.
[0071]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 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.
[0072]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.
[0073]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.
[0074]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 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.
[0075]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.
[0076]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.
[0077]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.
[0078]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 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).
[0079]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.
[0080]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.
[0081]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.
[0082]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 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 assembly 10 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.
[0083]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.
[0084]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.
[0085]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 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.
[0086]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.
[0087]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.
[0088]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
[0089]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.
[0090]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.
[0091]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 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.
[0092]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.
[0093]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.
[0094]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 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.
[0095]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.
[0096]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.
[0097]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 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.
[0098]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.
[0099]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.
[0100]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.
[0101]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