WO2013096824A1

WO2013096824A1 - Solar concentrator

Info

Publication number: WO2013096824A1
Application number: PCT/US2012/071347
Authority: WO
Inventors: Robert D. Battis; Wayne Armstrong; John Magno
Original assignee: Laser Energetics, Inc.
Priority date: 2011-12-22
Filing date: 2012-12-21
Publication date: 2013-06-27

Abstract

Provided is a solar radiation concentrator including a film that uses total internal reflection, the film including a total reflective transmitter and being added to a solar panel to improve optical absorption of solar radiation on the solar pane}. In an application, the film further includes a bottom surface having a first index of retraction upon which a plurality of spiked structures are arranged, each spiked structure having a second index of refraction, and the film also includes a top surface.

Description

SOLAR CONCENTRATOR

CROSS REFERENCE T€> RELATED APPLICATIONS

[0001 j This application is related to and claims priority from U.S. Provisional

Patent Application No. 61 /579,372 filed on December 22, 201 1, by Robert Battis, et ai. titled "TrT Solar Concentrator", which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

|0002j This invention generally relates to a total reflective transmitter coupler that significantly increases the photon coupling with a solar panel, and more particularly to- using an optical film incorporating the principle of total internal reflection on a solar panel.

BACKGROUND OF TOE INVENTION

[0003 J Most solar cel l panels, such as illustrated in Figure 1. are installed at a fixed orientation, which means their efficiency declines as the angle with respect to the sun changes during the day - i.e., when the sun is not orthogonal to the front surface of the panel. Light or photon coupling is reduced by reflection, which lends to increase at non-orthogonal angles. Attempts have been made to reduce this degradation or to improve the sun's photon coupling by adding an anti-reflection (AR) coating to the panel's top surface and/or by installing the panel in a rotating/orientating mechanism which tracks the sun across the sky, thereby maintaining the panel 's top surface orthogonal to the sun.

[0004] AR coatings provide only a limited improvement in photo coupling. One problem is that the AR coatings must be transparent so as not to block the incoming light, but they thus cannot stop most of the light reflected from the solar panel from escaping.

[0005| The use of a rotating and/or orientating mechanism also entails several drawbacks. For example, these mechanisms add to the initial and maintenance cost for solar panels so equipped. Also, they are prone to break down, and require electrical energy to operate - which reduces the overall energy-producing efficiency of the solar panel system. 10006] Optical films have been designed which optimize the throughput of incident light.

One such film and the method of producing the film is taught in U.S. Patent Application No. 1 1/417,132 to Jong M. Kim, filed May 4, 2006, available as U.S. Patent Application Publication Serial No. 2006/0268418, hereinafter, "the ' 132 application", which is also incorporated herein by reference.

[0007] It is thus desirable to provide for a total reflective transmitter coupler that significantly increases the sun's photon coupling with a solar panel and thereby improves solar panel efficiency without the need to rotate the panel or to add an AR coating to the solar panel.

SUMMARY OF THE INVENTION

[0008] An aspect of the present invention is to the use of a film incorporating total internal reflection to enhance the coupling of solar radiation to a solar panel solar cell, photo voltaic cell, or other device that couples solar radiation into a closed space such as windows or sky lights. This is achieved by the addition of a film which efficiently re-directs the solar radiation at less than nominal angles for non-rotating solar panels. Thi is achieved with little or no loss due to the principle of total internal reflection ("TIR") withi n the film. In one

embodiment of the invention. TRT (TM) film by Laser Energetics, inc. is employed.

[0009] In another aspect of the invention, a solar radiation concentrator including a film using TIR is provided. The film may be polymeric or non-polymeric. The film is added to a solar panel to improve optical absorptio of solar radiation on the solar panel. In one

embodiment, the film includes a bottom surface having a first index of refraction. Multiple spi ked structures are arranged on the bottom surface, each spiked structure having a second index of refraction . The film also includes a top surface.

[0010] In one aspect of the invention, the film is added to the solar panel by coupling. In another aspect, the film is added by gluing.

[00.11] in various embodiments of the invention, the first and second index of refraction may be the same or may differ from each other. Different index of refraction may be due to different characteristics between the elements or parts, including, but not limited to: various chemical additives, air and modification of basic part chemistry through manufacturing processes.

[0012] Another alternate aspect of the invention provides that the structures comprising the film are aciuailv etched onto the substrate of the solar panel or by using laser ablation techniques, which substrate may be glass or a non-glass material.

[0013] In another aspect of the present invention, a light transmitting medium

incorporating a fi!rn that uses total internal reflection is provided. The film is added to a base medium to improve optical absorption of electromagnetic radiation, the film comprising a total reflective transmitter. Examples of light transmitting medium include but are not limited to a window, a skylight and a fluorescent light fixture cover.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Embodiments will be described with reference to the following drawing figures, in which like numerals represent like items throughout the figures, and in which:

[0015] FIG. 1 is a plan view of a typical prior art solar panel.

[0016] FIG. 2 is a perspective view illustrating the sun's track relative to a solar panel incorporating an embodiment of the present invention.

[0017] FIG. 3 is- a sectioned profile view of an exemplary total reflective transmitter film that is useful for understanding the present invention.

[0018] FIG. 4 Is a perspective view of an exemplary total reflective transmitter film that is useful for understanding the present invention.

[0019] FIG. 5 is a plan view of an exemplary installation of an exemplary total reflective transmitter on a solar panel that is useful for understanding the present invention.

[0020] FIG. 6 is a profile view of exemplary uses of an exempl ary total reflective transmit ter that is useful for understanding the present invention. DETAILED DESCRIPTION

[0021] In the following description, for purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the invention. It. will be apparent, however, to one having ordinary skill in the art, that the invention may be practiced without these specific details. In some instances, well-known features may be omitted or simplified so as not to obscure the present invention. Furthermore, reference in the specification to '"one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the in vention. The appearances, of the phrase "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

(0022] An embodiment of the present invention advantageousl provides for a total reflective transmitter coupler that significantly increases the sun's photon coupling and thereby improves solar panel efficiency without the need to rotate or otherwise actively orient the panel or add an AR coating to the solar panel.

[0023) In one embodiment, an optica! film, such as the film taught in the ¹132 application referred to above, hereinafter referred to as a "total reflective transmitter film", or simply as the "Solar Concentrator" in the form of an overlay sheet 1.00 in Fig. 2, applied to the top of a standard solar cell panel 300. The Solar Concentrator uses the principle of total internal reflection ("TIR") to increase the solar coupling to the solar cells by redirecting the light from the sun as the sun^'s angle varies during tire day, as illustrated in Figure 2. This enhanced coupiing improves solar cell efficiency without the need to rotate the solar cell to track the sun as it moves across the sky.

[0024] In an embodiment, the form of the Solar Concentrator is a film illustrated in a sectioned profile in Fig. 3 and as a 3 dimensional sheet in Fig. 4. The Solar Concentrator comprises a substrate, substantially parallel optical microstructure segments 150, 160 with different optical indices of refractions to couple the sun's photons from the top surface 120 to the solar panel located just below the bottom surface 130. [0025] A typical Soiar Concentrator structure consists of 3 important components or parts as visible in Fig. 3. The first is a substrate 160 which is a transporting platform to carry materials and a supporter of the main structures. The substrate may be a film or sheet which is transparent with a tailored index of refraction to a wavelength range optimal for soiar cells. The spikes 170 may be formed from this substrate with the same index of refraction or may be added separately with a different index of refraction.

[0026] The second component is the main structure or spikes 170 which act as light guiding pipes and light reflecting surfaces. This structure consists of plural light pipes which are tilted with a certain angle according to the light coming from the sun located top side of the film. The angles of these light pipes are by design and are set during the fabrication process. The side wall angles of the light pipes may be different based upon a design or processing techniques, in the illustrated embodiment of Figs. 3 and 4, the spikes 170 form a repetitive structure in the X direction with height in the Y direction and elongated extension in the Z direction. The spikes 170 may also form a repetitive structure in both X and Z directions, with height in the Y direction.

[0027] The third component is the surrounding medium 150 around the light pipes. This is a material or gas such as air which has a lower refractive index compared to the spikes.

[0028] in an embodiment of the invention, the Soiar Concentxator film design is optimized for a solar cell panel application by controlling the refractive index difference between the microstructure 150, 160 as well as the spike profiles 170 angles and separation which are the transition structure separating the indexed elements 150. 160, and the height 1 0 of the microstructure.

[0029] An important design feature illustrated in Fig. 4 is that the Solar Concentrator [100] in one embodiment of the invention has all the spikes oriented along the same direction of the sheet. These spikes are preferably oriented perpendicular to the path of the sun when the Solar Concentrator 100 is installed on a solar- cell panel.

[0030] Applying the Solar Concentrator 100 to a solar panel for a particular application and location may take several forms, one of which is illustrated in Fig. 5. in Fig. 5 the solar cell area is divided into two zones 200. 210 and the Solar Concentrator in zone 2 210 is reversed 105 relative to the zone 1 200 concentrator 100. In another embodiment of the application, one Solar Concentrator 100 with uniform spikes is used over the complete solai- panel. In still another embodiment of the concept, a Solar Concentrator is created that has non uniform spikes 170. that is: spikes with differing angles, spacing' s and heights, and even spikes with non-straight or curved sides. These variations of the basic Solai- Concentrator concept would be implemented to enhance photon coupling under various solar panel sendee environments, but as otherwise limited by manufacturing considerations.

[0031] A first example of using the total reflective transmitter to attain TIR has been described herein - that is, increasing the solar coupling to the solar ceils without the need for AR coatings and/or rotation/orientation machinery in a solar panel. Fig. 6 shows how the total reflective transmitter can be generally used in several settings.

[0032] Generally, total reflective transmitter film 100 is useful in providing Till in other settings. For example, a window, skylight or fluorescent light fixture 310 equipped with a total reflectiv transmitter film would allow increased throughput of the incident light, regardless of the angle of the window pane, skylight or fluorescent light fixture 310 with the light source. A fluorescent light fixture thus may use the total reflective transmitter film to increase the brightness of fluorescent light emitting from the fixture without the need to increase fluorescent bulb wattage.

[0033] Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

CLAIMS:

1. A solar radiation concentrator comprising a film that uses total interna] reflection, the film being added to a solar panel to improve optica! absorption of solar radiation on the solar panel, the film comprising a total reflective transmitter.

2. The solar radiation concentrator according to claim 1. wherein the film further comprises a bottom surface having a first index of refraction upon which a. plurality of spiked structures are arranged, each spiked structure having a second index of refraction and further comprising a top surface.

3. The solar radiation concentrator according to claim 2. wherein the first and second index of refraction are the same.

4. The solar radiation concentrator according to claim 2, wherein the first and second indices of refraction are different.

5. The solar radiation concentrator according to claim 4, wherein the first and second indices of refraction are produced by chemical additives.

6. The solar radiation concentrator according to claim 1 , wherein the film is a polymeric film.

7. The solar radiation concentrator according to claim 1 , wherein the film is a non-polymeric film.

8. The solar radiation concentrator according to claim 1. wherein the film is added to the solar panel by coupling.

9. The solar radiation concentrator according to claim 8, wherein the film is coupled to the solar panel by gluing.

10. The solar radiation concentrator according to claim L wherein the film is formed by etching a solar panel substrate.

11. The. solar radiation concentrator according to claim 10, wherein the solar panel substrate is glass.

12. The solar radiation concentrator according to claim 1 , wherein the film is formed b laser ablation of the solar panel substrate.

13. The solar radiation concentrator according to claim 12, wherein the soiar panel substrate is glass.

14. The solar radiation concentrator according to claim 10, wherein the solar panel substrate is comprised of a non-glass material.

15. The solar radiation concentrator according to claim 12, wherein the solar panel substrate is comprised of a non-glass material.

16. A light transmitting medium comprising a film that uses total internal reflection, the film being added to a base medium to improve optical absorption of electromagnetic radiation, the film comprising a total reflective transmitter.

17. The light transmitting medium, according to claim 16, wherein the medium is a window.

18. The light transmitting medium according to claim 16, wherein the medium is a skylight.

19. The light transmitting medium according to claim 16. wherein the medium is a fluorescent light fixture cover.