WO2006039156A2

WO2006039156A2 - Method and apparatus for illuminating a solar cell with indirect sunrays

Info

Publication number: WO2006039156A2
Application number: PCT/US2005/033720
Authority: WO
Inventors: Rou Farhadieh
Original assignee: Rou Farhadieh
Priority date: 2004-09-29
Filing date: 2005-09-20
Publication date: 2006-04-13
Also published as: WO2006039156A3; WO2006039149A2; WO2006039149A3

Abstract

Embodiments of the present invention relate to a method and apparatus for illuminating the surface of a solar cell using indirect sunrays. This forms a basis for solar panels that may be installed in places other than southerly oriented rooftops or open fields for direct exposure to sun. Sunrays are concentrated by a spherical lens on to the surface of optical fiber located within light guide. The concentrated light travels through optical fibers to the surface of solar cells located in a confined space, where the sun does not shine. The emerging sunlight from the end of the optical fiber is expanded through a series of mirrors, which eventually is reflected onto the surface of the solar cell, installed a fixed distance from the focal point of one of the mirrors.

Description

METHOD AND APPARATUS FOR ILLUMINATING A SOLAR CELL WITH INDIRECT SUNRAYS

CLAIM FOR PRIORITY

This application claims the benefit of and priority from, U.S. Provisional Applications Serial No. 60/614,173 filed September 29, 2004, titled "Method and Apparatus for

Illuminating a Solar Cell with Indirect Sunrays to Generate Electric Power" and Serial

No. 60/614,289 filed September 29, 2004, titled "Compact Solar Apparatus for

Producing Electricity and Method of Producing Electricity Using a Compact Solar

Apparatus", the complete subject matter of each of which is incorporated herein by reference in its entirety.

CONTRACTUAL ORIGIN OF INVENTION Not Applicable. BACKGROUND OF THE INVENTION

1. Field of the Invention

This application is directed in general to the field of solar energy, but includes photovoltaic and fiber optics. This application is directed in particular to a method and apparatus for illuminating a solar cell with indirect sunrays to generate electric power.

2. Background of the Invention

Historically, solar panels and solar tiles are installed on rooftops and wired to invertors and batteries for storing generated electricity, converted from sun energy. These known arrangements have a number of limitations, including the availability of large southerly oriented roof area.

Other methods for transmitting sunbeams to solar cells are known. One known method is described in U.S. Patent No. 6,689,949 B2, incorporated herein by reference in its entirety. The '949 patent describes a concentrating photovoltaic module which provides concentration in the range of about 500 to over 1 ,000 suns and a power range of a few kW to 50 kW. A plurality of such modules may be combined to form a power plant capable of generating over several hundred megawatts. The concentrating photovoltaic module is based on a Photovoltaic Cavity Converter ("PVCC") as enabling technology for very high solar-to-electricity conversions. The use of a cavity containing a plurality of single junction solar cells of different energy bandgaps and simultaneous spectral splitting of the solar spectrum employs a lateral geometry in the spherical cavity (where the cell strings made of the single junction cells operate next to each other without mutual interference). The purpose of the cavity having a small aperture for the pre-focused solar radiation is to confine (trap) the photons so that they can be recycled effectively and used by the proper cells. Passive or active cooling mechanisms may be employed to cool the solar cells.

U.S. Patent No. 6,717,045 B2, which is incorporated herein by reference in its entirety, relates to a solar photovoltaic array module design, which constitutes three steps of optical concentration of photovoltaic electric power generation systems. A compound parabolic concentrator ("CPC") is mounted under a first optical concentrating fresnel lens that concentrates the intensity of sunlight to five times above normal level. The focused sunlight is further concentrated twenty times by the second optical concentrator CPC. The high mirror quality of the CPC allows 98% of the reflected rays to be focused at the bottom of the CPC. The intensified sunlight passes through a third optical concentrator glass lens, having an anti-reflection coating on the top of the glass lens' surface, incident on the multi-junction solar cell accomplishing the third optical concentration for the photovoltaic electric energy conversion.

U.S. Patent No. 6,730,840 B2, incorporated herein by reference in its entirety, describes a concentrating photovoltaic module comprising a lightguide member having at least one exit face and a plurality of entrance faces; and at least one solar cell placed immediately after the exit face of the lightguide member; wherein the lightguide member is comprised of a light transmissive, solid medium having no refractive-index- discontinuity portion. A surface of the lightguide member is smooth and the lightguide member makes sunbeams incident on the plurality of entrance faces, totally reflected on side faces, and emergent from the exit face, whereby the sunbeams can be concentrated on the solar cell with high efficiency. The foregoing inventions are not considered economically feasible, as they require 1000's of light members to even illuminate a square inch of a solar cell.

U.S. Patent Publication No. 2005/0034752 published Feb. 17, 2005, No. 2005/0034751 published February 17, 2005 and an article titled "A Wall of Mirrors", Fortune Small Business, February 2005, pp. 40-41 disclose an apparatus for increasing or concentrating the amount of sunlight that strikes the solar cells. The disclosed apparatus uses a tracking heliostat array of optical elements (i.e., mirrors) to concentrate the light prior to its striking the cells.

U.S. Patent Application No.: filed , 2005 (Attorney Docket No. 070- 01744) which claims priority from U.S. Provisional Patent Application No.: 60/614,289 filed September 29, 2004, the complete subject matter of which is incorporated herein by reference in its entirety, relates to a compact solar apparatus (a Compact Solar Module ("CSM") and a method of producing electricity using such an apparatus in residential buildings for example. One embodiment of the module is made of two arrays of 2 x 4 solar cells for example, each having a predetermined surface area (36 square inches for example). Each array covers an area of 1 x 2 square ft, generating combined power of about 52.8 Watts for example. One exemplary embodiment of a Compact Solar Module consists of 2x8 sub-CSM assembled back-to-back for example, generating a total of 422.8 Watts for example, and having the assembled dimension of 27.5"x8'x7.6" for example. The compact feature of solar module relies on sunray transmission to the solar cells and their illumination through optical fibers and sets of concave and convex mirrors and lenses. To illuminate the entire surface of a photocell a 2x2 array of mirrors/fibers, arranged in square configuration for example, are utilized. This configuration optimizes material usage, cost effectiveness and provides greater sun energy for PV cells illumination.

SUMMARY OF INVENTION Embodiments of the present invention relate to a method and apparatus for illuminating at least a portion of the surface of a solar cell using indirect sunrays. This enables the solar panels to be installed in places other than southerly oriented rooftops or open fields for direct exposure to sun. In at least one embodiment, sunrays are concentrated by a spherical lens on to the surface of optical fiber located within a light guide. The concentrated light travels through one or more optical fibers to the surface of solar cells located in a confined space, where the sun does not shine. The emerging sunlight from the end of fiber is expanded through a series of mirrors, which eventually is reflected onto the surface of the solar cell, installed a fixed distance from the focal point of one of the mirrors.

Embodiments of the present invention use photovoltaic cells not directly exposed to sunrays. Sunrays emerging from one end of the optical fiber (sunlight guide) illuminate the surface of the PV cells. Embodiments of the invention are adapted to provide a basis for energizing photocells with indirect sunlight and provide for sun tracking during daylight hours and seasonal changes. Embodiments comprise illuminating a single PV cell with an array of 2x2 mirrors for example, arranged in square pattern to insure complete surface illumination of the solar cell.

In at least one embodiment, the cell has a predefined surface area (6x6 sq. inches for example), which is assembled on a rigid flat surface. A front-surface concave mirror (convex mirror or some combination of concave and convex mirrors) expands the sunbeam transmitted by the optical fiber; it illuminates at least a portion of, if not all of, the solar cell located in the path of the expanded beam. The optical arrangement enables solar cell surface illuminating at greater than one sun power. One embodiment of the method of capturing, transmitting, expanding and illumination of photovoltaic cells includes, but is not limited to: A spherical mirror, located at the end of light-guide tube, which is oriented towards sun, focuses the sunrays to the polished surface of the optical fiber. This fiber is terminated in a ferrule installed at the end of the light guide. The focused beam of sunrays is transmitted by the optical fiber to a remote location. It emerges from the other polished end of the optical fiber, which is terminated inside a single fiber ferrule. Transmitted beam from this fiber couples with four smaller diameter fibers in a four-fiber ferrule. In at least one embodiment, the core diameter of the single fiber originating from the light guide tube is larger than the diameter of the combined fibers (four fibres for example) terminated in a ferrule. The fibers fan out and are terminated in another set of single-fiber ferrules that are integral part of a front-surface concave mirror (convex mirror or some combination of concave and convex mirrors).

The fiber-terminated ferrules are locked in the apex of the front-surface concave mirrors (convex mirrors or some combination of convex and concave mirrors).

When assembled, the axis of the ferrule/optical fiber is parallel and coincident with the mirror axis and perpendicular to the surface of the solar cell. The light from the ferrule is incident on a front surface of a small convex mirror (concave mirror or some combination of convex and concave mirrors) whose axis is coincident with that of the concave mirror (convex mirror or some combination thereof) and located a fixed distance from the end of the optical fiber, that is terminated in the ferrule, locked in the concave mirror (convex mirror or some combination of convex and concave mirrors). The emerging sunbeam from the fiber end, incident on the surface of the convex mirror expands and covers the entire surface of the concave mirror. The reflected light from the concave mirror (convex mirror or some combination of concave and convex mirrors) illuminates surface of the solar cell, which is located a fixed distance away from the front face of concave mirror. The emerging, expanding sunbeam from each of the mirrors covers a segment of the solar cells. A 2x2 array for example of concave mirrors (convex mirrors or some combination of convex and concave mirrors) arranged in square pattern illuminates the entire surface of a single solar cell.

At least one embodiment comprises an apparatus for producing electrical power using at least one solar cell located away from or remote to a solar source. In this embodiment, the apparatus comprises at least one collector, a concentrator, at least one reflector and at least one photocell. The at least one collector is directed towards the solar source and is adapted to collect light produced thereby. The concentrator is coupled to at least the collector and is adapted to concentrate the light collected by the collector. The at least one reflector is coupled to at least the concentrator and receives the concentrated light and produces reflected light. The at least one photocell is in spaced relationship to the at least one reflector, wherein the at least one photocell produces electrical power from the reflected light incident upon at least a portion thereof.

Still another embodiment comprises an apparatus for producing electrical power using at least one solar cell located away from a solar source. This embodiment of the apparatus comprises at least one light guide, at least one optical fiber, at least one set of primary and secondary reflective surfaces and at least one photocell. The at least one light guide is directed towards the solar source and is adapted to collect light produced thereby. The at least one optical fiber has a proximal end communicating with the light guide and a distal end coupled to a ferrule, where the optical fiber is adapted to concentrate the light collected by the light guide and transmit it to the ferrule. The at least one set of primary and secondary reflective surfaces receives the concentrated light and produces reflected light, wherein at least one of the reflective surfaces is coupled to the ferrule. The at least one photocell is in spaced relationship to at least one of the first and second reflective surfaces, wherein the photocell produces electrical power from the reflected light that is incident upon at least a portion thereof.

Still another embodiment comprises a method for producing electrical power using at least one solar cell located away from a solar source. In this embodiment the method comprises collecting light produced by the solar source and concentrating the collected light. The concentrated light is transmitted. The transmitted, concentrated light is received and reflected light is produced using at least one set of reflective surfaces. Electric power is produced using the reflected light.

BRIEF DESCRIPTION OF DRAWINGS The invention together with the above and other objects and advantages will be best understood from the following detailed description of the preferred embodiment of the invention shown in the accompanying drawing, wherein:

Fig. 1 depicts a partial cross-sectional view of a light guide in accordance with at least one embodiment; Fig. 2 depicts a cross-sectional view of an assembled solar cell/fiber/mirrors arrangement in accordance with one embodiment;

Fig. 3A depicts a schematic representation of an assembled solar cell/fiber/mirrors interconnect system in accordance with one embodiment;

Fig. 3B depicts a cross-sectional view of the assembled solar cell/fiber/mirrors of Fig. 3A taken along line B-B;

Fig. 4 depicts a schematic representation of a single to multi-fiber connector in accordance with one embodiment; and.

Fig. 5 depicts a high-level flow diagram illustrating one method for illuminating a solar cell using indirect sunrays to generate electrical power.

DETAILED DESCRIPTION OF THE INVENTION Exemplary embodiments of the invention are depicted in Figs. 1 and 2. Fig. 1 depicts a partial cross-sectional view of the light guide tube 110 (comprising in one embodiment, a collector 112 and concentrator 114). Fig. 1 illustrates the spherical condensing lens and the single-fiber ferrule in the guide. In at least one embodiment, the guide tube 110 may, in one embodiment, be attached to a tracking mechanism for sun tracking so that at least a portion of the light guide is moveable.

More specifically, Fig. 1 depicts light-guide tube 110, which holds or contains the spherical lens 111 that collects and focuses the sunrays onto the polished surface of the optical fiber 201. The spherical lens 111 is installed such that it may collect sunrays from any angle of orientation. Nevertheless, for maximum capture of sunrays, the light- guide 110 holding the lens is oriented southward such that the surface of the spherical lens 111 is generally perpendicular and the axis of light-guide 110 is parallel to the incoming sunrays. The light-guide 110 may be secured to a sun-tracking mechanism, which can follow the sun during daylight hours of different seasons. The focal length of the lens 111 is, in one embodiment, selected such that the sunbeam diameter is reduced to the outer diameter of optical fiber 201 , such that the beam is focused on the polished surface of the optical fiber terminated in the ferrule 202. The focused beam should substantially cover the entire core of the optical fiber. In this invention, ferrule 202 secures a single fiber 203, which extends to the solar module located a considerable distance away, in an enclosed space.

Fig. 2 depicts a cross sectional view of a quadrant assembly of a solar module and the manner in which a portion of the solar cell is illuminated. More specifically, Fig. 2 illustrates the connector 300 that couples the light from single fiber 203 to the optical fiber 401a. While only one optical fiber 401a is illustrated in the Figures, four optical fibers are contemplated. These fibers are terminated in ferrule 402a, which is locked in the apex of a concave (convex mirror or some combination of concave and convex mirrors) mirror 510a. While only one fiber 401a, ferrule 402a, and mirror 510a are illustrated in Fig. 2, more fibers; ferrules and mirrors (four fibers, four ferrules, and four mirrors for example) are contemplated. Alternatively, one ferrule is adapted to receive a plurality of optical fibers to facilitate compactness of design.

The cross-sectional are of the core of the single fiber 203 extending from the light-guide to ferrule 301 in connector 300 (better illustrated in Fig. 4) is generally large enough to cover the total core of the four fibers that are terminated in multi-fiber ferrule 302 in connector 300. The connector 300 enables the interface of the two joining fibers to touch and allow for the transmission of light for one to four optical fibers. The ferrules

301 and 302 in connector 300 (better illustrated in Fig. 4) are spring-loaded when interconnecting enabling physical contacts between the fiber ends. This enables transmission and coupling of all sunrays from 1 to 4 fibers. Each ferrule 302 contains a plurality of optical fibers (four optical fibers for example) of the same diameter. Figs. 3A and 3B depict one embodiment of an assembled solar cell/mirrors/fiber interconnect system. Figs. 3A and 3B depict an array of the concave mirrors (a 2x2 array for example) and the fiber from each that originates from a multi-fiber ferrule. Each fiber from the four mirror/fiber assembly is terminated in a single ferrule that is interconnected to a single fiber which is terminated in ferrule that is assembled in the light guide. Figs. 3A, 3B further depict that optical fibers 401a, 401 b, 401c and 401 d are terminated in ferrules 402a, 402b, 402c and 402d, which in turn are secured in mirrors

510a, 510b, 510c and 51Od. Fig. 2 provides detail of one such fiber and the adjoining optics.

Figs. 2 and 4 depict at least one embodiment of the at least one reflector 510. The terminated fiber 401a in ferrule 402a is secured at the apex of the concave mirror 510a (convex mirror or some combination of convex or concave mirrors). A small

(approximately 3 mm) front-surface convex mirror 520a (concave mirror or some combination of concave and convex mirrors) secured in a clear glass plate 610, is placed slightly ahead of the focal distance of the concave mirror 510a such that the axis of both mirrors and optical fibers are coincident. This arrangement will expand the reflected light from the concave mirror 510a.

The Photovoltaic cell 710 installed on a flat surface 720 and is located a predetermined fixed distance away from the glass plate 610. Spacer 730 insures this distance is preserved at all time. The surface of the photovoltaic cell 710 is parallel with the glass plate 610, and perpendicular to the reflected sunrays from the concave mirror 510a. The distance between the solar cell surface 710 and the focal plane of the concave mirror 510a is such as to allow the expanded sunrays to cover the entire ^ΛA surface of the solar cell.

When the 2x2 array of concave mirrors are flooded with sunrays, the reflected light from these mirrors not only cover the entire surface of the mirrors, but the expanded sunray envelope will overlap, thus providing a light of greater intensity.

In at least one embodiment, the spherical mirror at the end of light guide 110 concentrates and focus the sunrays to a smaller diameter as it shines on the polished surface of the optical fibers, each of which is terminated in a ferrule within a interconnect device. Light source from single fiber couples with the cores of four fibers terminated in a single ferrule. Such fiber ferrule fans out, each terminated in a ferrule that is locked at the apex of a concave mirror (secondary reflective surface for example).

In at least one embodiment, a four fiber ferrule serves as a light source to the four concave mirrors 510 (the secondary reflector). The polished end of fiber is located between the focal point and the apex of the convex mirror 520 (concave mirror or some combination thereof) (the primary reflective surface for example). Light emerging from the optical fiber upon contact with the convex mirror reflects back to the concave mirror, which fills up the entire surface of the concave mirror 510. The primary reflector acts as a light source to the secondary reflective surface. The convex mirror 520 is located along the axis of the concave mirror 510, between the focal point and the center of the concave mirror 510. This allows the reflecting light from the concave mirror 510 to expand as it penetrates the clear plate 610.

The flat rigid surface on which the photovoltaic cells are installed is positioned proximate about the clear plate 610 or edge of the concave mirror (about 1.25 inch for example). This arrangement enables the incident light from the concave mirror to generally cover the entire VA surface of the solar cell. The beam diameter has the same size as the diameter of the VA cell. As a result, portions of this light fall on the adjacent surfaces of the VA cell. Similar light coverage will result from other adjacent concave mirrors 510. The incident light from each mirror onto the solar cell generally overlaps the light from other mirrors. The unions of these lights increase intensity of light on the surface of the solar cell. This translates to greater sun power intensity that illuminates the solar cell. The resulting output is generally greater than the existing solar panels that are installed on the roofs of homes. Additionally, the sun-tracking capability of at least one embodiment provides an increased source of solar input and electrical output. In at least one embodiment, one or both of the concave and convex mirrors 510 and

520 are front-surface nickel-plated. The optical fiber may be either glass with large core or made of polycarbonate or similar high transmitting, commercially available materials. The flat plate 610 is glass, clear Lexon or polycarbonate. Fiber ferrules and connector are made of known Hi Tech engineered materials. Fig. 5 depicts a high-level flow diagram illustrating one method, generally designated 800, for illuminating a solar cell using indirect sunrays to generate electrical power, using the apparatus, or any portion thereof, described previously. In at least one embodiment, method 800 comprises collecting light produced by a solar source, block 810 (using at least one moveable light guide directed towards the solar source for example). The collected light is concentrated and transmitted, blocks 812 and 814 respectively.

Method 800 further comprises receiving the concentrated light and producing reflected light, blocks 816 and 818 respectively. In at least one embodiment, the collected light is concentrated using a least one optical fiber and at least one set of reflective surfaces (primary and secondary reflective surfaces for example). Electrical power is produced using the reflected light, block 820 using at least one photocell for example, where the electrical power is produced from the reflected light that is incident upon at least a portion of the photocell.

While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

CLAIMSThe embodiment of the invention in which an exclusive property or privilege is claimed is defined as follows:

1. An apparatus for producing electrical power using at least one solar cell located away from a solar source, the apparatus comprising: a collector directed towards the solar source and adapted to collect light produced thereby; a concentrator coupled to at least said said collector, said concentrator adapted to concentrate said light collected by said collector; a reflector coupled to at least said concentrator, said reflector receiving said concentrated light and producing reflected light; and a photocell in spaced relationship to said reflector, wherein said photocell produces electrical power from said reflected light incident upon at least a portion thereof.

2. The apparatus of Claim 1 wherein said collector comprises at least one light guide.

3. The apparatus of Claim 1 wherein said concentrator comprises an optical fiber having a proximal end communicating with said collector and a distal end coupled to a ferrule, said optical fiber adapted to concentrate said light collected by said collector and transmit said collected light to said ferrule.

4. The apparatus of Claim 3 wherein said ferrule is coupled to said at least one reflector.

5. The apparatus of Claim 1 wherein said at least one reflector comprises at least one set of reflective surfaces receiving said concentrated light and producing said reflected light.

6. The apparatus of Claim 5 wherein said at least one set of reflective surfaces comprises a set of primary and secondary reflective surfaces.

7. The apparatus of Claim 6 wherein said primary reflective surface comprises at least one of a spherical convex mirror and a concave mirror.

8. The apparatus of Claim 7 wherein at least one of said spherical convex mirror and said concave mirror is nickel plated.

9. The apparatus of Claim 6 wherein said secondary reflective surface comprises at least one of a concave mirror and a spherical convex mirror.

10. The apparatus of Claim 1 wherein at least a portion of said collector is moveable.

11. An apparatus for producing electrical power using at least one solar cell positioned remote from a solar source, the apparatus comprising: at least one light guide directed towards the solar source and adapted to collect light produced thereby; a least one optical fiber having a proximal end communicating with said light guide and a distal end coupled to a ferrule, said optical fiber adapted to concentrate said light collected by said light guide and transmit said collected light to said ferrule; at least one set of primary and secondary reflective surfaces receiving said concentrated light and producing reflected light, wherein at least one of said reflective surfaces is coupled to said ferrule; and at least one photocell in spaced relationship to at least one of said first and second reflective surfaces, wherein said photocell produces electrical power from said reflected light that is incident upon at least a portion thereof.

12. The apparatus of Claim 11 wherein said primary reflective surface comprises a nickel-plated spherical convex mirror.

13. The apparatus of Claim 11 wherein said secondary reflective surface comprises a concave mirror.

14. The apparatus of Claim 11 wherein said ferrule is coupled to at least said secondary reflective surface.

15. The apparatus of Claim 11 wherein at least a portion of said light guide is moveable.

16. A method for producing electrical power using at least one solar cell located away from a solar source, the method comprising: collecting light produced by the solar source; concentrating said collected light; transmitting said concentrated light; receiving said concentrated light and producing reflected light using at least one set of reflective surfaces; and producing electric power using said reflected light.

17. The method of Claim 16 wherein said light is collected using at least one moveable light guide directed towards the solar source.

18. The method of Claim 16 wherein said collected light is concentrated using a least one optical fiber.

19. The method of Claim 16 wherein said at least one set of reflective surfaces comprises at least one set of primary and secondary reflective surfaces.

20. The method of Claim 16 wherein said electric power is produced using at least one photocell, wherein said photocell produces electrical power from said reflected light that is incident upon at least a portion thereof.