COATED SOLAR REFLECTOR PANEL

Abstract

The present invention is in the field of solar energy collectors. In particular, the invention is directed to solar energy collectors that operate by concentrating solar radiation onto an absorber using a reflector. The invention may be embodied in the form of a unitary planar solar radiation reflector array having a plurality of upwardly facing reflective surfaces each of which is configured to reflect incident solar radiation, wherein each upwardly facing reflective surface is formed by coating a substrate with a coating material. The coating material may be a metallic coating of substantially even thickness formed by a metal deposition method such as a vapour deposition method or a thermal spray method.

Claims

1. A unitary planar solar radiation reflector array having a plurality of upwardly facing reflective surfaces each of which is configured to reflect incident solar radiation, wherein each upwardly facing reflective surface comprises a substrate coated with a coating material.

2. The unitary planar solar radiation reflector array of claim 1, wherein the coating material comprises a metal or a compound comprising a metal.

3. The unitary planar solar radiation reflector array of claim 2, wherein the coating formed by the coating material has a substantially even thickness.

4. The unitary planar solar radiation reflector array of claim 1, wherein the coating formed by the coating material is a film.

5. The unitary planar solar radiation reflector array of claim 1, wherein the coating formed by the coating material has a thickness of less than about 100 m.

6. The unitary planar solar radiation reflector array of claim 1, wherein the coating is formed by a metal deposition method.

7. The unitary planar solar radiation reflector array of claim 1, wherein the coating is formed by a vapour deposition method or a thermal spray method.

8. The unitary planar solar radiation reflector array of claim 1 having an axis and/or a plane, wherein the upwardly facing reflective surfaces of the reflector array are each disposed at an angle to the axis and/or plane.

9. The unitary planar solar radiation reflector array of claim 8, wherein the angle of each upwardly facing reflective surface is fixed.

10. The unitary planar solar radiation reflector array of claim 9, wherein the upwardly facing reflective surfaces of the reflector array are disposed at different angles, the angle increasing toward an edge of the reflector array.

11. The unitary planar solar radiation reflector array of claim 1, wherein the array is formed as a panel.

12. The unitary planar solar radiation reflector array of claim 11, wherein the substrate is an artificial polymeric material.

13. The unitary planar solar radiation reflector array of claim 1, wherein the substrate is formed by moulding, casting, extruding, slumping, 3-D printing, or stamping.

14. The unitary planar solar radiation reflector array of claim 1, wherein each of the upwardly facing reflective surfaces of the reflector array are elongate and extend in parallel rows.

15. The unitary planar solar radiation reflector array of claim 1, wherein each of the upwardly facing reflective surfaces of the reflector array are either planar or curvilinear, or a confocal parabolic facet, focal length of each confocal parabolic facet incrementally increasing with increasing distance from an absorber such that an aggregate of all the confocal parabolic facets provides a segment of a parabolic curve.

16. The unitary planar solar radiation reflector array of claim 1, comprising a protective layer disposed over the reflector array, the protective layer allowing transmission of incident solar radiation to the reflective surface.

17. A solar energy collector comprising: a unitary planar solar radiation reflector array having a plurality of upwardly facing reflective surfaces each of which is configured to reflect incident solar radiation, wherein each upwardly facing reflective surface is formed by coating a substrate with a coating material, and a common focal absorber located over the upwardly facing reflective surfaces of the unitary solar radiation reflector array and upon which incident solar radiation from the reflectors of the unitary planar reflector is reflected, the absorber configured to receive a heat absorbing medium adapted to absorb heat from the reflected radiation.

18. The solar energy collector of claim 17, comprising an elevated support structure for the unitary array of reflectors and the absorber.

19. A method for collecting solar energy, the method comprising: providing a solar energy collector comprising: a unitary planar solar radiation reflector array having a plurality of upwardly facing reflective surfaces each of which is configured to reflect incident solar radiation, wherein each upwardly facing reflective surface is formed by coating a substrate with a coating material, and a common focal absorber located over the upwardly facing reflective surfaces of the unitary solar radiation reflector array and upon which incident solar radiation from the reflectors of the unitary planar reflector is reflected, the absorber configured to receive a heat absorbing medium adapted to absorb heat from the reflected radiation, disposing a heat absorbing medium into the absorber, and causing or allowing solar radiation to incide on the reflector array such that the heat absorbing medium is heated by the reflected solar radiation.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0120] With respect to the drawings:

[0121] FIG. 1 is a prior art installation of a parabolic trough reflector showing the scale and complexity of the support structures.

[0122] FIG. 2 is a cross-sectional diagrammatic representation of a reflector array and absorber of an exemplary solar energy collector of the present invention.

[0123] FIG. 3 is a magnification of a section of the cross-sectional diagrammatic representation of the reflector array shown in FIG. 2.

[0124] FIG. 4 is a perspective diagrammatic representation of the reflector array shown in FIG. 2.

[0125] FIG. 5 is a cross-sectional diagrammatic representation of the reflector array of FIG. 2, as fitted with a toughened glass layer.

[0126] FIGS. 6A, 6B and 6C are perspective diagrammatic representation of several reflector arrays, each of dimension 1800 mm900 mm although each configured for different applications.

[0127] FIG. 7 is a cross-sectional diagrammatic representation of a reflector array whereby a metallized reflective coating is applied to the underside of an optically transparent substrate.

[0128] Reference is made firstly to FIG. 2 which shows a portion of a solar energy collector of the present invention comprising a unitary planar reflector array 10, having an upper side 15 and a lower side 20. The upper side has a plurality of upwardly facing reflective surfaces (not readily visible in this drawing, but clearly shown in following drawings).

[0129] The closely spaced lines 25 represent beams of solar radiation reflected from the reflector array 10. The beams 27 of incoming solar radiation from the sun 40 are essentially parallel to each other and at 90 degrees to the plane of the reflector array 10. It will be noted that the reflected beams 25 are directed toward an absorber pipe 30 maintained by a support (not shown) over the reflector array 10. A heat transfer medium runs through the pipe absorber 30, and is heated by the radiation beams 25 impinging on the outside of the pipe absorber 30.

[0130] The upwardly facing reflective surfaces of the upper side 15 of the reflector array 10 are curvilinear in this embodiment, and angled to the plane of reflector array 10. Each of the upwardly facing reflective surfaces (which are shown in greater detail in FIG. 3) is a confocal parabolic facet, the focal length of each facet incrementally increasing with increasing distance from the absorber. The aggregate of all facets providing one half of a parabolic curve, wherein the absorber coincides with the common focus of all of the parabolic curve elements.

[0131] Curve 66 represents one of the plurality of curves which derive the virtual parabolic curve resulting from the aggregate of all reflective surfaces. The remaining curves which so define the remainder of the reflective surfaces are not shown for clarity.

[0132] In reality, a second reflector array (being a mirror image) would be disposed to the left (as drawn) of the absorber 30, with the second reflector array providing the second half of the precise parabolic curve.

[0133] The angles of the reflective upwardly facing reflective surfaces are shallow toward the end 10a of the reflector array 10, increasing incrementally toward the end 10b of the reflector array 10 as discussed further infra.

[0134] Turning now to FIG. 3, greater detail of the reflector array is shown. Three upwardly facing reflective surfaces 50a, 50b, 50c are shown, being the first three surfaces (from to left to right) starting from the point marked 10a of FIG. 2.

[0135] Although not obvious from the drawing, the upwardly facing reflective surfaces are at different angles: 50a<50b<50c. The actual angles are chosen such that solar radiation incident on the surface is directed to the absorber pipe 30 disposed in a fixed position over the reflector array 10. The angles are the product of the increasing slope of the virtual parabolic curve (resulting from the aggregate of all reflective surfaces) as it moves away from the axis of symmetry, according to the well known formula y=ax.sup.2.

[0136] The upwardly facing reflective surfaces 50a, 50b, 50c are formed by a PVD process. In the PVD process the underlying substrate 35 is coated with a thin reflective aluminium film. For ease of manufacture, all surfaces 50a, 50b, 50c, 50d, 50e, 50f are coated with the aluminium film, however it is preferred that surfaces 50d, 50e and 50f are of reduced reflectance and/or reduced specular reflection. Reduction in the reflectance or specularity of the surfaces 50d, 50e and 50f may be achieved by roughening or removing the aluminium film (for example by laser ablation). Alternatively, the underlying substrate 35 may have dimpling in the areas 50d, 50e and 50f such that when the aluminium film is applied, light is scattered in an incoherent manner. Such dimpling or surface roughening may be most easily achieved during stamping or rollformingthis area of the mould is roughed and the reflective surface is polished.

[0137] It will be noted that solar radiation reflected from surfaces 50d, 50e and 50f would scatter and diffuse, and not be directed to the focus line. The reflectivity of these surface should therefore be eliminated or reduced to avoid reflection of sunlight to other than the absorber tube.

[0138] The substrate 35 may be formed by industrial 3-D printing (using LDPE) onto a 0.5 mm zincalume sheet 55. For high volume production, an accurate extrusion, stamping or similar thermoforming method will more likely be used to form the substrate. The extruded substrate may be sandwiched between a zincalume sheet, and protective glass sheet (as discussed more fully infra)

[0139] Turning now to FIG. 5, there is shown an embodiment of the invention having a protective toughened glass sheet 60 applied over the upper side 15 of the reflector array 10. The toughened glass 60 rests on support surfaces 65, of which there may be two or more for a given reflector array. The position of the support surfaces 65 in the context of a reflector array may be seen by reference to FIG. 2 and FIG. 4.

[0140] In this embodiment, the toughened glass 60 forms a seal such that the chambers (one marked as 70) may retain a non-reactive gas therein.

[0141] FIGS. 6A, 6B and 6C show the modular nature of certain embodiments of the present reflector array. FIG. 6A shows a 1800 mm900 mm half-reflector panel, two or which can be opposed (in a mirror image manner) to form a full reflector panel of dimension 3600 mm900 mm, with the absorber tube (not shown) running parallel to the short axis of symmetry of the full panel. FIG. 6B shows a full reflector panel of dimension 1800 mm900 mm, with the absorber tube (not shown) running parallel to the short axis of symmetry of the full panel. FIG. 6C shows a full reflector panel of dimension 1800 mm900 mm, with the absorber tube (not shown) running parallel to the long axis of symmetry of the full panel.

[0142] FIG. 7 shows a reflector array formed from a transparent substrate 100 moulded from an optically transparent UV stable polycarbonate of the type used in CompactDisc manufacture. The transparent substrate 100 is moulded so as to have a plurality of downwardly facing surfaces 105. A thin metallized film (not shown) is applied to the downwardly facing surface 105 in a manner similar to CompactDisc manufacture, so as to as to provide upwardly facing reflective surfaces 110. The underside of the metallized coating is protected by the addition of a liquid protective coating 115, which is subsequently hardened in a manner similar to that for CompactDisc manufacture. In use, incident solar radiation 27 is reflected 28 off the metallized coating toward the absorber 30.

[0143] It will be understood that the invention is not limited to any particular embodiment of the invention as disclosed herein. Equivalents, extensions, variations, deviations, etc., of the various exemplified embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. Such equivalents, extensions, variations, deviations, etc., are within the scope and spirit of the present invention.

[0144] It will be further appreciated that any of the features of any aspect of the invention disclosed herein are all combinable with each other in any number and in any combination without any limitation whatsoever. The ability to combine any features in any number to provide a range of combinations extends to features defined in the following claims.