WO2010101644A1

WO2010101644A1 - 3-d non-imaging radiant energy concentrator

Info

Publication number: WO2010101644A1
Application number: PCT/US2010/000661
Authority: WO
Inventors: James Rosa
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-03-05
Filing date: 2010-03-03
Publication date: 2010-09-10
Anticipated expiration: 2011-09-05

Abstract

A radiant energy trap with at least one refractor, reflector and receiver. The angle of acceptance of radiant energy can be flat panel equivalent with a relatively high concentration ratio (CR) of diffuse light. The refractor can be a composite of layers, solid or nested fluid layers. The fluid can be a transparent refractive component and can flow through the refractor as a thermal transfer medium. High solar energy utilization is achieved as a hybrid electric/thermal conversion, diffuse light concentrating solar collector PV cells can be displaced, proportional to the CR, with inexpensive optics. Overall orientation and relative angles of refractor surfaces can be changed to selectively reject a portion of diffuse light to increase CR. Radiant energy can be selectively directed to active PV area from PV cell contact area without reducing the angle of acceptance of ambient radiant energy. The refractor assembly can be arrayed and thermally isolated.

Description

TITLE

3-D non-imaging radiant energy concentrator

TECHNICAL FIELD The invention is a radiant energy trap. It relates to the field of solar energy and more particularly to diffuse light concentrating solar collectors.

BACKGROUND ART

Problems associated with the use of fossil fuels, such as global warming, environmental degradation, rising energy costs, peak oil, and global conflicts, have created a need for a solar based economy. Competitively priced solar based energy production will probably be required before this goal can be reached. Flat panel solar electric collectors (PV) are relatively expensive. Installed system costs are too high. Installed system payback periods, even with large subsidies, are too long to be generally accepted. The energy utilization of a typical PV collector is only about 15 % of the radiant energy striking it, with the operating efficiency dropping as the PV cells are heated by the sun. Flat panel PV cell collectors can be stationary and hemi-spherically collect ambient radiant energy, but operate less efficiently without direct sun. Previous attempts to economize solar energy include concentrating parabolic reflectors. They only work in direct sunlight, with significant costs incurred for critical reflector shape, support structure and sun tracking capability. Generated electricity would suffer transmission losses to less sunny regions. Providing most of a building's thermal and electrical needs, in seasonal climates, would require unreasonably large solar collector panel areas and costs.

Attempts to combine the best of flat panels, and parabolic concentrators include compound parabolic concentrators (CPC). CPCs use reflectors to concentrate and collect ambient light over a limited angle of acceptance (AOA) according to the ideal 2-D relationship, where the concentration ratio, CR= l/sin(half AOA). CPC reflector's are usually truncated in height, with a reduced CR and collect some light outside the AOA. CPC variants sometimes use transparent refractors. These types of collectors are more generally called radiant energy traps. Designs include those by Eshelman, Knowles, Winston, Gill, Vasylyev, Isofoton S.A., and Sci Tech U.S.A., and European patents EP0070747 and DE 3233081. Refractors are used in designs by Kapany, Johnson, Winston, Lee, Cherney, Fereidooni, Chen and in Bowden's designs, from the University of New South Wales. The main problems with prior art is that they suffer from a relatively small AOA, or too low a diffuse light CR-AOA combination, or material and manufacturing costs are too high for the relative size of the aperture (A) to the refractor size, or reflector area, which is described as the length of the reflector curve (RL) or height (H), as the ratios; RL/A and H/A respectively. 3-D concentrators, such as those in Steigerwald's patent #DE10059555 Al, Puall's patent application #20050081909, Lichy's patent application #20060072222, Bowden's thesis, Murtha's patents #6021007 and #6619282 suffer from low CR for the AOA or unreasonably high optics costs, when compared to the current invention.

Hybrid solar collectors combine electric and thermal functions to deliver more of the available solar energy. They can also be combined with a radiant energy trap. Numerous hybrid systems have been attempted, as in Mlausky and Winston's patent #4045246, Damsker's patent #4395582, Goldman's patent #4427838, the "CHAPS" project at Australian National University, CPC designs, by Brogren at Uppsala University in Sweden, Puall's patent application #20050081909, Johnson's patent #6080927 or Nicoletti's patent #7173179. These designs have poor energy utilization, small AOA for the CR, require sun tracking and/or are cost prohibitive, compared to the current invention.

DISCLOSURE OF THE INVENTION

The invention is a radiant energy trap comprising at least one refractor, reflector and receiver. The refractor has a transparent surface area that accepts ambient radiant energy. Opposed to the refractor's transparent surface area is a facing, interfaced reflective refractor surface area and juxtaposed to both, an interfaced receiver refractor surface area. The receiver has opposing longitudinal edges forming the height of the receiver, with one edge adjacent to the transparent surface area and the opposite edge adjacent to the interfaced reflective surface area. The transparent and reflective surface areas extend from their respective receiver longitudinal edge, in a transverse direction until their longitudinal edges meet. The refractor's surface area has opposing transverse ends. The combination of the refractor's surface areas and longitudinal edges form a refractive space. The interfaced reflector surface is a grooved corrugation, with the groove length orthogonal to the receiver's opposing longitudinal edges. The refractor surface areas are primarily shaped and positioned, relative to one another, so that accepted radiant energy is directed and concentrated on to the smaller receiver, through refraction, reflection and total internal reflection. The receiver can have functions such as a thermal absorber, a detector or transducer. The receiver can have flat opposing faces and opposed refractor sections to support the use of bi-facial photoelectric (PV) cells, which can have contact lines shaped as diffuse light reflectors. The refractor can be a composite of layers, solid or nested fluid layers. The fluid can be a transparent refractive component of the invention. The fluid can flow through the refractor as a thermal transfer medium or be optically independent by flowing on the outer surface of the refractor. The refractor can have adjacent reflectors, which can be symmetrical or asymmetrical reflectors, with optically dependent or independent sections. The refractor assembly can be enclosed with the aperture a transparent glazing and can be thermally insulated. The reflector-refractor combination can be arrayed. An array can be framed to form a collector module. The invention can be used as a diffuse light concentrating, hybrid electric and thermal conversion collector with exceptionally high energy utilization. The invention can be made using conventional materials and manufacturing processes. The invention is relatively inexpensive from a material and manufacturing perspective with a relatively high concentration (CR) of diffuse light for the wide angle of acceptance (AOA) of ambient radiant energy. Additional embodiments are useful to reduce cost or improve thermal or electric conversion performance, so that solar energy production can be competitive with widely varying applications and costs of fossil fuel energy production.

BRIEF DESCRIPTION OF DRAWINGS

Fig. Ia and b are transverse cross-sections of this inventor's prior art.

Fig. 2a and b are a transverse cross-sections of embodiments of this inventor's prior art.

Fig. 3 is a perspective view of a refractor section from this inventor's prior art.

Fig. 4 is a perspective view of PV cell contact lines shaped as diffuse light concentrators. Fig. 5 is a perspective view of a refractor section.

Fig. 6a, b and c are transverse cross-sectional views of Fig. 5 in several embodiments.

BEST MODE FOR CARRYING OUT THE INVENTION

The invention is a radiant energy trap comprising at least one refractor, reflector and receiver. The refractor has a transparent surface area that accepts ambient radiant energy. Opposed to the transparent surface area is a facing, interfaced reflective-refractor surface area and juxtaposed to both, an interfaced receiver-refractor surface area. The receiver has opposing longitudinal edges forming the height of the receiver, with one edge adjacent to the transparent surface area and the opposite edge adjacent to the interfaced reflective surface area. The transparent and reflective surface areas extend from their respective receiver longitudinal edge, in a transverse direction until their longitudinal edges meet. The refractor's surface area has opposing transverse ends. The combination of the refractor's surface areas and longitudinal edges form a refractive space. The interfaced reflector surface can be a V grooved corrugation, with the groove length orthogonal to the adjacent opposing receiver edges. The refractor surface areas are primarily shaped and positioned, relative to one another, so that accepted radiant energy is directed and concentrated on to the smaller receiver, through refraction, reflection and total internal reflection. The refractor surfaces can have a longitudinally elongated prism like shape and a transverse triangular like cross-section with two sides and a base. The two sides can be a transparent surface accepting ambient radiant energy. The base of the prism like shape can be an interior facing reflective component. The height of the triangular cross-section can correspond to the receiver position, which is elongated similarly to the refractor's elongation. The receiver can have functions such as a thermal absorber, a detector or transducer. The receiver can have flat opposing faces and opposing refractor sections to support the use of bi-facial photoelectric (PV) cells, which can have contact lines shaped as diffuse light reflectors. The refractor can be a composite of layers that are solid or have nested fluid layers. An outer solid layer can be a transparent material such as glass or acrylic. The fluid can be a transparent refractive component with a similar refractive index, such as mineral oil or a water-glycol solution. The fluid can flow through the refractor as a thermal transfer medium, with fluid port and pump through means or be optically independent from the refractive function by flowing along the outside of the refractor. The invention can be a hybrid electric and thermal conversion collector. The refractor can be formed by suitable methods including thermo-forming or bonding of sheet materials, such as glass, plastic or metal. The refractor can be thermally isolated. The refractor can have adjacent reflectors, which can be symmetrical or asymmetrical reflectors, with optically dependent or independent sections. The reflector(s) can be made of materials such as rear or front silvered or aluminized glass or acrylic or sun rated clear plastic or front silvered or aluminized metal sheet. The refractor assembly can be enclosed with the aperture a transparent glazing and can be thermally insulated. The refractor or refractor-reflector combination can be arrayed. An array can be framed and form a collector module.

Collector components can be produced and secured by conventional means. Collector components can include; a transparent cover plate, end caps, a back plate, framing, plumbing, electrical connections, suitable thermal isolation and ancillary elements. The invention is a direct and diffuse radiant energy concentrator that can have a relatively high concentration (CR) of diffuse light, while maintaining an angle of acceptance (AOA), of ambient radiant energy, equivalent to a flat panel collector. It can replace PV collectors, flat or evacuated tube collectors, some parabolic collectors and be used as a secondary for other concentrating collectors. There are additional embodiments, than those described, within the scope of this invention.

Fig. Ia and b are transverse cross-sections from this inventor's prior invention. In Fig. Ia the bifacial receiver 1 is centered between an opposed, paired, prism shaped transparent refractor 2, which is nested within an overall half round specular reflector 3, to accept ambient radiant energy through aperture A. For comparison purposes in the drawings that follow simple overall half round adjacent reflectors and equivalent aperture size are used, except where noted. In Fig. Ib the bifacial receiver 1 is within the refractor 2b which is centered between adjacent specular reflector sections 3b. The refractor has a pair of adjacent interior facing half round specular reflectors 4 and two flat transparent sides 5.

Fig. 2a and b are a transverse cross-sections, from this inventor's prior invention, of additional embodiments. In Fig. 2a the bifacial receiver 1 is interfaced with the transparent refractor 22, which is half of the refractor area of Fig. Ia, based on a receiver 1 of the same size. The refractor 22 is nested within an overall half round specular reflector 23. This embodiment would simplify assembly and reduce refractor cost, however the aperture A2 to the receiver 1 proportion, lowers the CR. In Fig. 2b the bifacial receiver 1 is within the refractor 22b, which is centered between adjacent specular reflector sections 23b. The refractor 22b has a flat, interior facing specular reflector 24 and a pair of transparent sides 25. The refractor 22b has a smaller cross-sectional area than the one in

Fig. Ib, based on a receiver 1 of the same size. The flat interior reflector 24 is shorter than the pair of adjacent interior facing half round specular reflectors 4 in Fig. Ib.

Simple trough type solar collectors are two dimensional concentrators extended in the third, longitudinal, dimension. Fig. 3 is an embodiment of this inventor's prior invention, a perspective view of a refractor section. The opposed paired prism shaped refractor 31 with interior receiver assembly 32 comprises the refractive part of a 3-D concentrator. A magnified view 33 is required to see the smaller scale of the multiple sectioned receiver assembly 32. Transverse oriented adjacent strips of bifacial receiver sections 32a separated by opposing paired diffuse light concentrating specular reflecting sections 32b. This significantly increases total reflector area and receiver complexity but can avoid having contact lines in active cell areas. Replacing many reflectors and bifacial PV cells as small narrow strips, with a larger reflector and cell would simplify construction. Fig. 4a and b are schematic magnified cross-sectional edge views of PV cells and their contact lines, which normally block light from reaching the active part of the cell. Fig. 4a is a bifacial PV cell 41 with ribbon shaped contacts 42, 43, 44. Contacts typically take up about 6% to 9 % of the surface of a PV cell. Within a transparent refractor this light can be redirected to the PV cells active surface by shaping the contact lines as diffuse light concentrators. The bifacial PV cell 41 in Fig. 4b shows contact lines 42b, 43b, 44b shaped as diffuse light concentrators. Based on light entering a transparent refractor with a 1.48 refractive index and striking the PV cell 41, with the distance 45 between the contacts 42 and 44 in Fig. 4b, the V-groove concentrator shaped contact 42b redirects all the radiation to the active surface for a contact that takes up about 6.5% of the overall surface area, which provides an optical boost or CR of about 1.07. The truncated compound parabolic shaped contact 43b on the PV cells opposing face 46 is for a slightly wider contact. The truncated compound parabolic shaped contact 44b takes up about 8.5% of the surface area 45 and creates a CR of about 1.09. On an A4 page the PV cells and contacts in Fig. 4 would be magnified about 70 times that of an actual cell. The design of these V trough and truncated compound parabolic reflectors are known to those versed in the art. The contacts' shape could be, such as, extruded wire or laid down as solder with a guide to shape the solder appropriately.

Fig. 5 is a perspective view of a refractor section embodiment with magnified views. The longitudinal prism shaped transparent refractor section 51 encloses a central, longitudinal, vertically aligned, bifacial receiver section 52. A magnified view of a portion of the receiver section 53 shows one side of a bifacial PV cell 54 with a pair of V shaped contact lines 55. Similarly longitudinal but perpendicular to the bifacial receiver section 52 is a corrugated specular reflector section 56 interfaced with and facing into the refractor section 51. A magnified view of a portion of the corrugated reflector section 57 is shown with V shaped corrugation 58 transversely aligned 59. A groove depth that is small relative to the refractor height minimizes the gap between the bottoms of the receiver and grooves. The V angle 58a would typically subtend about 120°.

Fig. 6a, b and c are transverse cross-sectional views of Fig. 5 in several embodiments. In Fig. 6a aperture A6 accepts ambient light. The receiver 61, which receives at least a portion of the accepted ambient light, is centered within the refractor 62. The refractor 62 has two transparent sides 63. The refractor base 64 comprises the V corrugated reflector 56 of Fig. 5, unseen in this edge view. Adjacent to the refractor 62 are overall half round reflector sections 65 providing a 180° transverse angle of acceptance (AOA) of ambient light. The adjacent reflectors 65 can also be shaped for smaller transverse angles of acceptance, by those versed in the art, that reject some ambient light, but increases the concentration ratio (CR). CR is the aperture A6 to the receiver 61 proportion. Each refractor side 63 and the base 64 form a side to base angle (SBA) 66. This angle, can be sized for total internal reflection (TIR) of all the light entering the refractor 62, as dependant on the refractive index (RI), or for selective rejection of ambient light, substantially in the longitudinal direction. For TIR with a RI of about 1.5 and delivery of the accepted light to the receiver, the SBA is about 30°. Decreasing the SBA selectively rejects some diffuse light while increasing the CR.

In Fig. 6b the CR, the aperture A6 to receiver 61b proportion, is larger than in Fig. 6a, while having the same transverse AOA for the same RI. The receiver 61b as bifacial PV cells can be supported by a transparent material 61c, RI matched to the refractor 62bc, such as glass, EVA or silicone rubber as appropriate to the application. In Fig. 6b the refractor is a composite of materials. The outer solid refractive layer 62b, such as glass or acrylic, can contain an inner fluid, transparent refractive section 62c, such as water with anti-freeze or oil. The RI-SBA relationship of each refractive layer is described in the inventor's previous inventions. The inner refractive fluid can be used as a heat transfer medium and be pumped through the refractor 62b to remove heat from the receiver 61b as described previously. A hybrid solar collector is created with a receiver composed of bifacial PV cells. Adjacent to the refractor 62bc are overall half round reflector sections 65b. Note that the height H of the reflectors 65b and receiver 61b are equal, as the reflectors are designed for 180° transverse AOA, based on the receiver height H. The SBA 67, subtending an angle of about 23.5°, is reduced relative to that in Fig. 6a, which, for the same RPs as Fig. 6a, causes a small loss of radiant energy longitudinally. With the transverse cross-section of this collector embodiment aligned in the East- West direction and facing the plane of the sun, the radiant energy lost from the refractor would be diffuse light and only a few percent of the total annual radiant energy reaching the aperture. This is a suitable trade-off for a higher CR with essentially a flat panel equivalent AOA. The refractor base 64b and corrugated reflector 66 can be individuated or a single component.

Fig. 6c is an array of two of the refractor in Fig. 6b, side by side, with a top transparent cover plate 68, a base or bottom plate 64c, which would be the integrated corrugated reflector/base version and back insulation 69, which would improve the thermal performance. Higher thermal performance can be achieved with evacuated space 70 above and also below the refractors 62bc, without the use of the insolation 69. A double sided flat reflector 71 balances the bifacial output for E-W transverse orientation along with side reflectors 72. Note that the refractors' solid transparent outer surface 73 and the corrugated reflector/base 64c meet at transverse points 74, which allows the use of flat adjacent reflectors 71,72. In warmer climates or for PV cell only applications the collector can be simplified and less expensive to produce by eliminating the cover plate and insolation. Removing the adjacent flat reflectors leaves only internal, weather protected, V groove corrugated reflector sections. Without forced circulation of the transparent refractor heat transfer fluid, natural convection within the refractor would reduce the temperature of a receiver of bifacial PV cells and increase their output. A solid refractor on the scale of thickness of a pane of glass, extruded from acrylic is another cost effective possibility.

Embodiments of this invention have a significantly higher CR-AOA combination than that claimed by prior art except for Murtha's, which has a much lower energy utilization capability, with a much higher optics cost. The embodiments in this description reduce material costs and manufacturing complexity. Less reflector area and more internal reflector results in less reflective loss, which improves performance. There are other possible embodiments of this invention, in addition to the ones described here, for illustrative purposes only, including additional elements and ancillary components, without departing from the scope of the invention.

Claims

1. 1 claim a radiant energy trap comprising; at least one refractor, reflector and receiver of said radiant energy; wherein said refractor comprises at least one transparent material, said refractor comprises a transparent surface area, said refractor's transparent surface area comprises an aperture to accept ambient said radiant energy, said refractor comprises an interfaced reflective surface area, said refractor's interfaced reflective surface substantially opposing said refractor's transparent surface area, said refractor's interfaced reflective surface area comprises a grooved corrugation, said grooved corrugation comprises transverse groove lengths, said refractor comprises a juxtaposed interfaced receiver surface area, said juxtaposed interfaced receiver surface area comprises opposed longitudinal edges, said opposed longitudinal edges comprise a spanned receiver height, wherein one of said opposed longitudinal edges adjacent said refractor's transparent surface, the opposite one of said opposed longitudinal edges adjacent said refractor's interfaced reflective surface area, said refractor's transparent surface area and interfaced reflective surface area comprise a common longitudinal edge locus, said common longitudinal edge locus and said opposed longitudinal edges generally coextensive, said refractor's surface area comprises opposing transverse ends, said refractor's surface areas, said common longitudinal edge locus and said opposed longitudinal edges comprise a refractive space, said interfaced receiver surface area orthogonal to said transverse groove lengths, said interfaced receiver surface area substantially smaller than both said refractor's transparent or interfaced reflective surface areas, said refractor's surface areas primarily comprise a conformal, positional and proportional relationship, said refractor surface areas' primary conformal, positional and proportional relationship comprises an optical relationship, said optical relationship comprises an alignment to direct said accepted ambient radiant energy to said refractor's interfaced receiver, said optical relationship comprises refraction, reflection and total internal reflection, said refractor comprises a fluid and a solid transparent material.

2. 1 claim the radiant energy trap of claim 1, wherein said refractor comprises a longitudinally elongated, transversely triangular prism type shape, said transversely triangular prism type shape comprises two sides, a base and corresponding side to base angles (SBA), said refractor's interfaced receiver area comprises a longitudinally elongated bifacial receiver, said bifacial receiver transversely bisecting said refractor, said interfaced reflector's grooved corrugation comprises V like grooves with flat sides, a V bottom angle, top width and depth, said width smaller than and said depth substantially smaller than said receiver height, said refractor's at least one transparent material comprises an outer solid transparent material nesting an inner fluid transparent material.

3. 1 claim the radiant energy trap of claim 2, wherein said refractor comprises fluid port means for flow through of said nested inner transparent fluid.

4. 1 claim the radiant energy trap of claim 2, wherein said bifacial receiver comprises bifacial PV elements.

5. 1 claim the radiant energy trap of claim 4, wherein each face of said bifacial PV elements comprise contact lines shaped as diffuse light concentrating reflectors.

6. 1 claim the radiant energy trap of claim 2, wherein said refractor's longitudinally elongated transverse triangular prism type shape comprises a pair of longitudinally elongated opposing transverse edges, said at least one reflector adjacent to said refractor, said at least one reflector adjacent to said refractor comprises longitudinal edges, wherein a said at least one reflector's longitudinal edge adjacent to a said refractor's longitudinally elongated opposing transverse edges.

7. 1 claim the radiant energy trap of claim 6, wherein said at least one adjacent reflector comprises a pair of facing, transversely opposed correspondingly adjacent reflectors.

8. 1 claim the radiant energy trap of claim 7, wherein said pair of facing transversely opposed reflectors and said refractor's transverse triangular prism type shape two sides correspondingly form an orthogonal junction, said pair of transversely opposing reflectors comprise an overall half-round symmetrical circular arc transverse cross-section.

9. 1 claim the radiant energy trap of claim 8, wherein said non-ambient RI is about 1.5, said V like groove angle subtends approximately 120°, said SBA subtends about 30° or less.

10. 1 claim the radiant energy trap of claim 2 as a combination of elements, such as, plumbing, electrical, structural, optical or thermal control, ancillary or arrayed related elements.