POLYCARBONATE PARABOLIC TROUGH SOLAR CONCENTRATOR

Abstract

The parabolic trough solar concentrator described within is sized for shipping in containers and mounting on existing structures without requiring specialized labor or equipment. Besides achieving a proximity to the thermal load not previously achievable economically and preserving precious land, the concentrator array shelters the area below from the sun reducing its energy requirement for cooling and making it more inhabitable when cooling is not provided. As the troughs are generally mounted on an incline on roof structures, they can provide for rainwater collection.

Claims

1. A Polycarbonate Parabolic Trough Solar Concentrator comprising: a body comprised of a top surface, a bottom surface, two opposing ends, and two opposing longitudinal sides, wherein said body is further comprised of a top layer of an adhesive backed reflective film fixed to a flexible sheet, wherein said flexible sheet lays on top of a sheet of multi-walled polycarbonate, wherein said body is held in a shape of a parabolic curve by a frame.

2. The Polycarbonate Parabolic Trough Solar Concentrator of claim 1, wherein said flexible sheet is comprised of an aluminum sheet.

3. The Polycarbonate Parabolic Trough Solar Concentrator of claim 1, wherein said reflective layer is laminated to said flexible sheet.

4. The Polycarbonate Parabolic Trough Solar Concentrator of claim 2, wherein said reflective layer is laminated to said aluminum sheet.

5. The Polycarbonate Parabolic Trough Solar Concentrator of claim 3, wherein said reflective layer is laminated to said flexible sheet by a graphics roll laminator.

6. The Polycarbonate Parabolic Trough Solar Concentrator of claim 4, wherein said reflective layer is laminated to said aluminum sheet by a graphics roll laminator.

7. The Polycarbonate Parabolic Trough Solar Concentrator of claim 1, wherein said sheet of multi-walled polycarbonate is curved up to its rated minimum cold-bent radius to achieve said shape of said parabolic curve.

8. The Polycarbonate Parabolic Trough Solar Concentrator of claim 1, wherein said sheet of multi-walled polycarbonate is comprised of a 6mm twin wall polycarbonate sheet.

9. The Polycarbonate Parabolic Trough Solar Concentrator of claim 1, wherein said sheet of multi-walled polycarbonate is comprised of a 16mm triple wall polycarbonate sheet.

10. The Polycarbonate Parabolic Trough Solar Concentrator of claim 1, wherein said Polycarbonate Parabolic Trough Solar Concentrator comprises a focus of 20″, a functional aperture of approximately 62 inches, a f/D of approximately 0.32, and a length of approximately 60 inches.

11. The Polycarbonate Parabolic Trough Solar Concentrator of claim 1, wherein said Polycarbonate Parabolic Trough Solar Concentrator further comprises a CRg between 60 to 95, and an absorber comprising a diameter of 0.840″ OD.

12. The Polycarbonate Parabolic Trough Solar Concentrator of claim 1, wherein said frame is comprised of opposing longitudinal side chord rails, connected to two opposing end longitudinal rails.

13. The Polycarbonate Parabolic Trough Solar Concentrator of claim 12 wherein a bulkhead is connected to each of said opposing longitudinal side chord rails.

14. The Polycarbonate Parabolic Trough Solar Concentrator of claim 12 wherein said opposing end longitudinal rails are each further comprised of an internal rail tube.

15. The Polycarbonate Parabolic Trough Solar Concentrator of claim 14 wherein said opposing end longitudinal rails are connected to said opposing longitudinal side chord rails by a tube clamp connected to each end top surface of said chord rail, wherein said tube clamp engages an end of said rail tube.

16. The Polycarbonate Parabolic Trough Solar Concentrator of claim 12, wherein a bulkhead is connected to each of said opposing longitudinal side chord rails.

17. The Polycarbonate Parabolic Trough Solar Concentrator of claim 16, wherein said bulkhead is comprised of a plurality of spokes to allow sunlight to pass through said bulkhead.

18. A method of manufacturing a Polycarbonate Parabolic Trough Solar Concentrator comprising the steps of: a. creating a body of said Polycarbonate Parabolic Trough Solar Concentrator by; b. cutting a multi-wall polycarbonate sheet to a specified width and a specified length; c. cutting an aluminum sheet to a specified width less than said specified width of said multi-wall polycarbonate sheet, and a specified length less than said specified length of said multi-wall polycarbonate sheet; d. applying an adhesive backed reflective film to a top surface of said aluminum sheet; and e. fastening said body to a frame.

19. The method of manufacturing a Polycarbonate Parabolic Trough Solar Concentrator of claim 18 wherein said specified width of said multi-wall polycarbonate sheet is approximately 60 inches and said specified length of said multi-wall polycarbonate sheet is approximately 72 inches.

20. The method of manufacturing a Polycarbonate Parabolic Trough Solar Concentrator of claim 19 wherein said specified width said aluminum sheet is 59.5 inches and said specified length of said aluminum sheet is 71.5 inches.

21. The method of manufacturing a Polycarbonate Parabolic Trough Solar Concentrator of claim 18 further comprising the step of laying said aluminum sheet with applied adhesive backed reflective film onto said multi-wall polycarbonate sheet.

22. The method of manufacturing a Polycarbonate Parabolic Trough Solar Concentrator of claim 21 further comprising the step of clamping a first end of said multi-wall polycarbonate sheet to a first opposing longitudinal rail of said frame and clamping a second end of said multi-wall polycarbonate sheet to a second opposing longitudinal rail of said frame.

23. The method of manufacturing a Polycarbonate Parabolic Trough Solar Concentrator of claim 22 further comprising the step of arching said body into a parabolic curve, wherein said aluminum sheet moves freely upon said multi-wall polycarbonate sheet.

24. The method of manufacturing a Polycarbonate Parabolic Trough Solar Concentrator of claim 23 further comprising the step of applying a reflective edge tape to seal said adhesive backed reflective film and said aluminum sheet to the first and second ends of said multi-wall polycarbonate sheet.

25. The method of manufacturing a Polycarbonate Parabolic Trough Solar Concentrator of claim 24 further comprising the step of connecting a first bulkhead to a first opposing longitudinal side chord rail of said frame and connecting a second bulkhead to a second opposing longitudinal side chord rail of said frame.

26. The method of manufacturing a Polycarbonate Parabolic Trough Solar Concentrator of claim 18 wherein the step of applying said adhesive backed reflective film to said top surface of said aluminum sheet is further comprised of laminating said reflective film with a graphics roll laminator.

27. The method of manufacturing a Polycarbonate Parabolic Trough Solar Concentrator of claim 18 wherein said multi-wall polycarbonate sheet is pre-drilled to correspond with components of said frame for assembly.

28. The method of manufacturing a Polycarbonate Parabolic Trough Solar Concentrator of claim 18 wherein said body and said frame components can be disassembled and transported in compact, substantially flat containers.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0025] FIG. 1 Perspective view of an embodiment of the polycarbonate parabolic trough solar collector with struts and torque tube.

[0026] FIG. 2 Top view of an embodiment of the polycarbonate parabolic trough with struts and torque tube.

[0027] FIG. 3 End view of an embodiment of the polycarbonate parabolic trough with struts and torque tube.

[0028] FIG. 4 Bottom view of an embodiment of the polycarbonate parabolic trough with struts and torque tube.

[0029] FIG. 5 Longitudinal side view of the end of an embodiment of the polycarbonate parabolic trough with struts and torque tube.

[0030] FIG. 6 Perspective view of a preferred embodiment of the polycarbonate parabolic trough solar collector without struts and torque tube.

[0031] FIG. 7 Top view of a preferred embodiment of the polycarbonate parabolic trough without struts and torque tube.

[0032] FIG. 8 End view of a preferred embodiment of the polycarbonate parabolic trough without struts and torque tube.

[0033] FIG. 9 Bottom view of a preferred embodiment of the polycarbonate parabolic trough without struts and torque tube.

[0034] FIG. 10 Longitudinal side view of the end of a preferred embodiment of the polycarbonate parabolic trough without struts and torque tube.

[0035] FIG. 11 Blow up cross-section view of FIGS. 5 and 10 longitudinal side view of end.

[0036] FIG. 12 Blow up cross-section view of FIGS. 3 and 8 corner of end view.

DETAILED DESCRIPTION OF THE INVENTION

[0037] Referring now to the drawings and more particularly FIGS. 1 and 6, preferred embodiments of a parabolic trough solar collector are shown. The parabolic trough solar collector is generally comprised of a body 1, frame 10, and bulkhead 70. The body 1 of the trough is comprised of a top surface 2, a bottom surface 4, opposing ends 6 and opposing longitudinal sides 8, wherein the shape of said body 1 is generally rectangular. The purpose of said body 1 is to provide a parabolic reflective surface to concentrate solar energy onto an absorber tube.

[0038] With reference more particularly to FIG. 12, the body 1 of the trough is preferably comprised of a sheet of flexible material, preferably an aluminum sheet 30 placed on top of a multi-wall polycarbonate sheet 20. The aluminum sheet 30 ends 31 short of the end 6 of said polycarbonate sheet 20. An adhesive-backed flexible silvered polymer mirror reflective film 26, such as Reflectech, is laminated to the aluminum sheet 30. The aluminum sheet 30 and multi-wall polycarbonate sheet 20 are flat sheets elastically bent into a parabolic curvature 100 (FIGS. 3 and 8) by applying a set of end moments 101 and forces to the longitudinal rails 15 to which polycarbonate sheet 20 and aluminum sheet 30 are held to by angle 16 in addition to fasteners or pins to form a channel-shaped, indexed fastening. Curving the multi-wall polycarbonate sheet 20 up to its rated minimum cold-bent radius induces internal stresses increasing its strength and rigidity, similar to pre-stressed concrete elements. Construction in this manner achieves capability for mass production, while surface slope errors can be held within tolerances required for most industrial heat processes including cogeneration. The aluminum sheet 30 ends 31 are cut sufficiently short of the longitudinal rails 15 and angle 16 such that end moments 101 and forces are not imposed upon the aluminum sheet 30. The aluminum sheet 30 is lightly clamped to the multi-wall polycarbonate sheet 20 by angle 16 and edge tape 28 is applied on the top surface 2 end 6, spanning over the top of the reflective layer 26 edge, aluminum sheet 30, end 31, and multi-wall sheet 20 end 6.

[0039] With reference more particularly to FIGS. 3 and 8, a longitudinal side 8 bulkhead 70 for a trough, is connected to the frame 10 by longitudinal side 8 chord rail 50, where the chord rail 50 passes below a focus with an f/D of .32 is shown. Said bulkhead is comprised of a plurality of spokes 71 to increase strength of the bulkhead 70, but still allow light to pass through the bulkhead 70 to the trough body 1 top surface 2. The chord rail 50 functions to provide frame 10 support to the body 1 longitudinal sides 8 and to act as a connection point for said bulkhead 70. The chord rail 50 also accommodates mounting hardware for an absorber tube, which is mounted within the specified focus. Those familiar in the art will recognize that many mounting means could be utilized for mounting an absorber tube to said chord rail 50, including but not limited to clamps, brackets, angles, pylons, etc. Forces which create torsion on the trough are resisted by the trough body 1 and frame 10. Once assembled, the trough frame 10 is fastened by rotational means to a framework which positions and secures the assembled trough. Those familiar with the art will recognize that any framework construction means could be used to secure and position the assembled trough. Preferably, means that utilize pre-cut materials with simple, easy to find fasteners, or quick-connect components would further the object of the invention of simple construction and deployment. The trough's pivot is located along the axis of symmetry above or below the chord rail 50 such that the mass above and below the pivot of the trough is fairly balanced as it tracks the sun, so torsion is normally low and the accuracy of the trough geometry sufficient for industrial heat requirements including cogeneration in normal environmental conditions with the minimum framework structure.

[0040] The bulkhead 70 is fastened to the chord rail 50. The function of the bulkhead 70 is to apply a light downward load on the top surface 2 which increases the conformance of the body 1 to a parabolic curvature 100, particularly when the axis of symmetry is not in-line with the center of gravity, such as when the trough is aligned with morning or afternoon sun.

[0041] With further reference to FIGS. 3 and 8, the bulkhead 70 attachment to the chord rail 50 and the chord rail 50 attachment to tube clamps 19 is accomplished with standard connection means such as nuts, bolts, and clamps to minimize the need for specialized tools and skilled labor. Those skilled in the art will appreciate that any connection means could be utilized to facilitate assembly of the various embodiments, including but not limited to snap lock means, cam-lock means, ties, etc. FIG. 3 demonstrates a preferred embodiment where said frame 10 is further comprised of a longitudinal torque tube 60 connected to said chord rail 50 by diagonal struts 55. Said torque tube 60 and diagonal struts 55 function to add increased rigidity to said frame 10 in locations where high winds are prevailing. In areas not prone to high winds, the embodiment shown in FIG.8 without said torque tube and struts is preferred due to the decreased weight, packaged size, and decreased assembly burden.

[0042] Specific examples of the embodiments disclosed herein are set forth below.

[0043] Trough Structure.

[0044] The preferred embodiment of the parabolic trough solar concentrator is comprised of a focus of 20″, a functional aperture of approximately 62 inches, and f/D of approximately 0.32, and a length of approximately 60 inches. The top surface 2 of the trough body 1 accommodates a reflective layer 26 which is comprised of an adhesive backed reflective film, laminated to an aluminum sheet 30, where reflective film edge tape 28 or liquid edge sealer is used to seal said reflective layer 26 and aluminum sheet 30 to a multi-wall polycarbonate sheet 20.

[0045] The trough body 1 can be scaled-up from an approximately 5′ aperture using 6 mm twin wall polycarbonate sheet 20 to an approximately geometrically similar trough exceeding 20 ′ aperture using a 16 mm triple wall polycarbonate sheet 20 while still retaining the desired characteristics. Maintaining the CRg between 60 to 95, one can see that the preferred embodiment provides a CRg of approximately 70 with an absorber diameter of 0.840″ OD. This corresponds to common ½″ NPT black steel pipe, which is the smallest practical absorber tube size. Laser intercept testing shows that for a trough with an approximately square aperture of the described construction, the CRg at the middle of the reflector will degrade from a CRg of 76 to a CRg of 62, with gradual intercept losses from the rim inboard as the middle of the trough is approached. The minimum bend radius of 16 mm triple wall polycarbonate is approximately 138″ which would allow a parabolic trough with as small a focus as 69″, and approximately geometrically similar troughs to the preferred embodiment that will provide CRg's between 60 and 95 with commercially available utility grade 2.75″, 3.15″, and 3.54 receivers, commonly known as Heat Collector Elements (HCE's) such as the Rioglass PTR series. As the trough design is scaled-up, the reflector sheet thickness may be increased to approach 0.050″ in large designs which will aid in its resistance to damage from hail and other impacts.

[0046] Trough Construction

[0047] The preferred method of manufacture is to cut the frame 10 components to length and drill them for fasteners. Frame components are generally comprised of chord rails 50, bulkheads 70, longitudinal rails 15 with interior rail tubes 17, tube clamps 19, and angles 16 as shown in FIGS. 8 and 12. If the troughs are to be deployed in an area with high winds, said frame 10 is further comprised of struts 55 and longitudinal torque tubes 60 to increase rigidity of said frame 10 as shown in FIG. 3. Finished aluminum sheets 20 and polycarbonate sheets 30 are pre-cut for assembly on-site. All components are pre-drilled to achieve the desired shape, geometry, and pre-loading as specified herein. Furthermore, pre-drilling of all components greatly simplifies assembly in the field.

[0048] The multi-wall polycarbonate sheet 20 is cut to a width of approximately 60″ and a length of approximately 72″. The aluminum sheet 30 of 0.032″ thickness, is cut to a width of 59.5″ to match the width of the reflective film and a shorter length (such as 71.5″). The reflective layer 26 film is applied to a top surface of the aluminum sheet 30 by a graphics roll laminator prior to packaging and shipment, from one opposing end 6 to the other opposing end 6 according to the specifications of the film. Typical graphics roll laminators, such as those made by Royal Sovereign, can achieve very good results, however, industrial-grade laminators at dedicated facilities may improve quality and have a better long-term availability rate for producing large volumes of troughs.

[0049] Following installation of a first end of the multi-wall polycarbonate sheet 20 and aluminum sheet 30, with laminated reflective layer 26 onto the top surface of a first longitudinal rail 15 and loosely clamping with angle 16 and locating the sheets with pins or fasteners, end tubes 17 are placed in tube clamps 19 of one opposing end 6, where the bottom portions 19a of said tube clamps 19 are attached to the top surface of said chord rail 50 and the top portions 19b of the tube clamps 19 are installed loose enough to allow the longitudinal rail 15 to rotate freely. The second end of the multi-wall polycarbonate sheet 20 and aluminum sheet 30 with laminated reflective layer 26 are placed on the second opposing end 6 longitudinal rail 15 and loosely clamped by its angle 16 and the sheets are located with pins or fasteners. The body 1, comprised of the multi-wall polycarbonate sheet 20 and aluminum sheet 30, with laminated reflective layer 26, is then arched manually, and the end rail tubes 17 are placed in the other opposing end 6 set of tube clamps 19 with the top portions 19b of the tube clamps 19 loosely installed. As the bending occurs, the monolithic aluminum sheet 30 slides on the multi-wall polycarbonate sheet 20 as the top surface of the multi-wall sheet shrinks due to compression. At this point, the induced axial load produces a nonconstant moment distribution along the multi-wall sheet approximating a parabolic curve 100. Once the body 1 has achieved a parabolic curve 100, the body 1 is ready to have edge tape 28 applied to the top surface 2 opposing ends 6 to span over the top of the reflective layer 26 and multi-wall polycarbonate sheet 20 which seals the reflective layer 26, aluminum sheet 30 and multi-wall polycarbonate sheet 20 at the opposing ends 6. The bulkhead 70 of the desired shape produces end moments 101 and downward force on the top surface 2 of the body 1 to further maintain the parabolic shape 100 of the body 1. A first bulkhead 70 is attached to a first chord rail 50. A second bulkhead 70 is attached to a second chord rail 50. Installation of said bulkheads 70 causes the longitudinal rails 15 to further rotate in relation to their respective tube clamps 19 creating bending moments at the opposing ends 6 of the body 1, which alters the moment distribution along the body 1 to better conform to a parabolic curve 100. The tube clamp 19 bolts are then torqued such that the angle of the longitudinal rails 15 becomes fixed. The angles 16 are then removed to apply edge tape 28 spanning over the top of the reflective layer 26 and multi-wall polycarbonate sheet 20 to seal the longitudinal sides of the aluminum sheet 30 to the multiwall sheet 20. The position of the aluminum sheet 30 to the multiwall sheet 20 will remain in place with the angles 16 removed due to the compression force applied by the bulkhead 70. Once edge tape 28 is installed, the angles 16 are secured with fasteners providing high sheer resistance but minimal compression to the sheets of the body 1.

[0050] Alternative Reflector.

[0051] In an alternative embodiment, the adhesive-backed polymer film reflective layer 26 laminated to the monolithic aluminum sheet 30 is replaced with an approximately 0.032″ aluminum reflector sheet such as Alanod's Mico-Sun. As the trough design is scaled-up, the aluminum sheet 30 thickness may be increased to approach 0.050″ in large designs.

[0052] Trough Use.

[0053] The preferred method of tough use is comprised of positioning said troughs in longitudinal strings of four troughs to form one module with the longitudinal sides 8 aligned North to South so that the troughs track the sun as it crosses East to West. It is a specific objective to provide a functional design of a trough that can be manually handled and used as a solar shelter and energy-generating canopy for a camp. A further specific objective is to provide a trough and associated parts where an array can be packed-in by people or animals to a remote region in a densely-packed, disassembled condition and then be assembled on site with minimal tools and technical experience not exceeding that required to assemble IKEA furniture.

[0054] In yet another embodiment, the troughs may be individually assembled into an array on existing or purpose-built structures such as a flat or trussed sloped roof. It is another specific objective to provide a parabolic trough solar concentrator that is as small as practically possible so as to have as low a profile to the wind as possible such that a building or structure may not have to be reinforced to accommodate the weight or environmental effects of an array of the parabolic trough solar concentrators described herein.

[0055] In yet another embodiment, an individual trough may be erected with an absorber tube to generate hot water or steam, or a tubular container for cooking or other processes as used in known solar cooking devices.

[0056] Actuation.

[0057] The preferred method of actuation of the preferred embodiments is by joining the longitudinal rails 15 together at the end tubes 17 by split clamps spanning the end tubes of adjacent troughs. A set of ¾″ tube clamps are mounted onto the two adjacent chord rails 50 in the center of the module and a pin spans between them to attach a linear actuator which is used to raise and lower that side of the chord rail.

[0058] It is understood that the foregoing examples are merely illustrative of the present invention. Certain modifications of the articles and/or methods may be made and still achieve the objectives of the invention. Such modifications are contemplated as within the scope of the claimed invention.