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AU784427B2 - Reflector for solar collector tube array - Google Patents
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AU784427B2 - Reflector for solar collector tube array - Google Patents

Reflector for solar collector tube array Download PDF

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Publication number
AU784427B2
AU784427B2 AU97477/01A AU9747701A AU784427B2 AU 784427 B2 AU784427 B2 AU 784427B2 AU 97477/01 A AU97477/01 A AU 97477/01A AU 9747701 A AU9747701 A AU 9747701A AU 784427 B2 AU784427 B2 AU 784427B2
Authority
AU
Australia
Prior art keywords
reflector
side wall
collector tube
collector
reflected
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
AU97477/01A
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AU9747701A (en
Inventor
David Mills
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Solahart Industries Pty Ltd
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Solahart Industries Pty Ltd
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Filing date
Publication date
Application filed by Solahart Industries Pty Ltd filed Critical Solahart Industries Pty Ltd
Publication of AU9747701A publication Critical patent/AU9747701A/en
Assigned to SOLAHART INDUSTRIES PTY LTD reassignment SOLAHART INDUSTRIES PTY LTD Alteration of Name(s) of Applicant(s) under S113 Assignors: SOLSEARCH PTY LTD
Application granted granted Critical
Publication of AU784427B2 publication Critical patent/AU784427B2/en
Anticipated expiration legal-status Critical
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Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S23/00Arrangements for concentrating solar-rays for solar heat collectors
    • F24S23/70Arrangements for concentrating solar-rays for solar heat collectors with reflectors
    • F24S23/80Arrangements for concentrating solar-rays for solar heat collectors with reflectors having discontinuous faces
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24SSOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
    • F24S23/00Arrangements for concentrating solar-rays for solar heat collectors
    • F24S23/70Arrangements for concentrating solar-rays for solar heat collectors with reflectors
    • F24S2023/83Other shapes
    • F24S2023/838Other shapes involutes
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B10/00Integration of renewable energy sources in buildings
    • Y02B10/20Solar thermal
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/40Solar thermal energy, e.g. solar towers

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Optical Elements Other Than Lenses (AREA)
  • Photovoltaic Devices (AREA)

Description

AUSTRALIA
Patents Act 1990 COMPLETE SPECIFICATION STAN4DARD PATENT Applicant SeLSEAReH PTY-B LT~ A.C.N. 067 407 309 Invention Title: REFLECTOR FOR SOLAR COLLECTOR TUBE ARRAY The following statement is a full description of this invention, including the best method of performing it known to me/us: REFLECTOR FOR SOLAR COLLECTOR TUBE ARRAY Field of the Invention This invention relates to a reflector for use in conjunction with an array of parallel solar collector tubes and to a collector system comprising the reflector and an array of the collector tubes mounted to receive back reflection from the reflector. The invention has application in a solar collector system that is mounted to the roof of a building and connected to a hot water supply within the building. However, it will be understood that the invention may have broader application.
Background of the Invention Reflectors currently are employed in conjunction with arrays of parallel solar collector tubes for back-reflecting incident radiation that passes between the tubes. The reflectors are employed for the purpose of maximising collection efficiency and, hence, for balancing the conflicting requirements for minimising the number of collector tubes in each installation and maximising the effective collection area.
Of the various known types of reflectors, that which is the most relevant to the present invention is the Compound Parabolic Concentrator ("CPC reflector").
The CPC reflector comprises a plurality of parallel, longitudinally-extending 25 major channels and a plurality of longitudinally-extending primary cusps. The primary cusps are positioned to locate behind respective ones of the collector tubes and they define the common edges margins) of adjacent ones of the major channels. Each of the major channels is defined by two parallel, longitudinally-extending minor channels, and a longitudinally-extending secondary cusp is located within each major channel between the two minor channels. The surface of each minor channel (as seen in cross-section) is generated as an involute of the contiguous collector tube and it extends between the adjacent primary and secondary cusps.
As a consequence of the CPC reflector geometry, light that falls incident on the surface of any one of the minor channels will be reflected into the contiguous collector tube, either directly or as a secondary reflection from the surface of the same minor H:%.zonmep \idc\RcdlecDr for Solar Collctor Tub Army COMPLETE Dec 2001 .doc 27112/01 3 channel. In the limiting condition, light which falls incident on the surface of any one of the minor channels and tangential to the contiguous collector tube will be reflected back along its own path. As a corollary, light which falls incident on the surface of any one of the minor channels will not be reflected to a distant collector tube or to the surface of the other minor channel within the same major channel.
The CPC reflectors offer the advantages of having low profiles, low tube requirements and low reflector area requirements. However, the CPC reflectors have certain inter-related disadvantages: They cannot conveniently be formed from glass (the ideal reflector material) because of the inherently tight curve of the reflecting surfaces of the minor channels resulting from the use of typically sized collector tubes.
15"(b) They must be formed from metal, typically from anodised aluminium sheeting.
15 They are prone to surface degradation.
Weather (water and dust) marking of the channel-defined reflector surface will occur.
Flowing from the above disadvantages, the CPC reflectors exhibit a lower overall 20 efficiency than that which is provided by the present invention and defined in the following passages of this specification.
Sinmary of the Present Invention 25 In accordance with a first aspect of the present invention, there is provided a 9*o* reflector for use with an array of parallel, elongate solar collector tubes, and for backreflecting radiation that passes in use between the collector tubes, the reflector including: a plurality of parallel, longitudinally-extending channels and a plurality of longitudinally-extending cusps; the cusps being positioned to locate in use behind respective ones of the collector tubes and each cusp being located between adjacent ones of the channels; each channel being defined by opposing side walls which converge from associated ones of the cusps to a common longitudinally-extending trough; and each side wall having a profile that curves between an associated cusp and an associated trough and being configured in a manner such that in use a significant H:\emilyw\keep\retype\P44521 pgs 3, 4, 9.doc 6/02/06 4 portion of radiation that falls incident on the side wall will be reflected to the opposing side wall and thence to a collector tube mounted in use above the cusp of the opposing side wall and a significant portion of radiation that falls incident on the side wall will be reflected directly to the collector tube mounted in use above the cusp of the opposing side wall.
In accordance with a second aspect of the present invention, there is provided a solar collector assembly including a plurality of elongate substantially parallel solar collector tubes, and a reflector in accordance with the first aspect of the present invention, each collector tube being mounted adjacent and above a cusp of the reflector.
Each of the side walls of the channels within the reflector has a profile that effectively is generated at least in part with respect to its distant collector tube, 15 rather than solely with respect to the contiguous tube as in the case of the above described CPC reflector. As a consequence, for a given collector tube size, the side walls of the channels in the reflector will have more shallow curves than those that define the surfaces of the minor channels within the CPC reflector. This in turn permits the reflector of the present invention to be formed from glass. Also, in having a single 20 trough located geometrically between the walls within each of the channels, the nadir of ~the trough may be apertured at intervals along its length, to permit draining of water that would otherwise settle and degrade the reflecting surface.
Preferred Features of the Invention The reflector of the present invention may be formed fabricated, moulded, pressed or rolled) from any reflective material, including polished sheet metal and anodised aluminium. However, it is preferred that the reflector be formed from glass having a reflective surface coating.
In one aspect of the invention, each side wall is profiled such that, in the limiting condition, light which falls incident on the side wall and travels along a path tangential to an associated collector tube remote from the side wall will be reflected back along the same path.
H:\emilyw\keep\retype\P44521 pgs 3, 4, 9.doc 6/02/06 Preferably, the reflector is substantially symmetrical when viewed in transverse cross-section.
In a second aspect of the invention, each side wall is profiled such that, in the limiting condition, light which falls incident on a side wall and travels along a path tangential to a collector tube contiguous with the side wall will be reflected to an opposing side wall and will be re-reflected tangentially to an associated collector tube remote from the side wall.
The invention will be more fully understood from the following description of the prior art CPC reflector and preferred embodiments of reflectors in accordance with the present invention. The description is provided with reference to the accompanying drawings.
Brief Description of the Drawings In the drawings: Figure 1 shows an end view of a portion of a (prior art) CPC reflector mounted behind an array of three parallel collector tubes.
Figure 2 shows an arrangement that is similar to that of Figure 1 but in respect of a reflector that has a profile that meets the requirements of a first aspect of the present invention.
Figure 3 shows an arrangement which is similar to that of Figure 2 but in 25 respect of a reflector that has a profile that meets the requirements of a second aspect of the present invention.
Figure 4 shows graphs of optical efficiency against radiation incidence angle for reflectors as illustrated in Figures 1 to 3.
Detailed description of Prior Art and the present Invention As illustrated in Figure 1, the CPC reflector comprises a plurality of parallel, longitudinally extending major channels 10 and a plurality of longitudinally extending primary cusps 11. The primary cusps are positioned to locate behind respective collector tubes 12 and they define common edges (or margins) of adjacent ones of the H:Sw XeppomRci ori for Solu Collector Tub Army COMPLETE Dec 2001.doc 27/1201 -6major channels Each of the major channels is defined by two parallel, longitudinally-extending minor channels 13, and a longitudinally-extending secondary cusp 14 is located centrally within each of the major channels 10 and separates the two minor channels 13 within each of the major channels.
The surface of each minor channel 13 (as seen in cross-section) is generated as an involute of the contiguous collector tube, and the surface extends between the adjacent primary and secondary cusps. Thus, each of the minor channels 13(a) as indicated at the left hand side of Figure 1 has a surface which is an involute of the contiguous collector tube 12(a) as also indicated at the left hand side of Figure 1.
As a consequence of the CPC reflector geometry, light of near-normal 15 incidence that impinges on the surface of any one of the minor channels will be reflected into the contiguous collector tube, as indicated in the case of light ray 15 as shown in Figure 1. Light which is displaced further from the normal and which falls incident on the surface of any one of the minor channels 13 will also be reflected into the contiguous collector tube, but in this case as a secondary reflection as indicated in the case of the light ray 16 which is shown in Figure 1.
As also shown in Figure 1, light which falls incident on the surface of any one of the minor channels 13 and tangential to the contiguous collector tube 1 2 will be reflected back along its own path. This is indicated by the dotted lines 17 in the 25 drawing.
Figure 2 shows one form of reflector that meets the requirements of the present invention and, in contrast with the CPC reflector as above defined, it comprises a plurality of parallel, longitudinally extending channels 20 and a plurality of longitudinally extending cusps 21. The cusps are positioned to locate behind respective collector tubes 22 and they define common edges (or margins) of adjacent ones of the channels The collector tubes 22 are of a type that is known per se. Each collector tube typically has an inner glass tube, having one closed end, and an outer glass tube that envelopes the outer surface of the inner tube. The outer surface of the inner tube is H:ASurnKcp\lped'Rnlse for Solu Collecto Tube Amy COMPLETE Dec 2001 .doc 27/12/01 -7coated with a solar selective surface coating (for example, a reactively sputtered metal carbide on a non-reactively sputtered bright metal base) and the space between the two tubes is evacuated. Heat exchange fluid, typically water, is conveyed into and through a metal U-tube (not shown) that is located within the inner collector tube and arrangements are provided for conducting heat from the inner tube to the heat exchange fluid. A manifold arrangement is employed for channelling water into and from the Utube in an array of the collector tubes.
Each of the channels 20 as defined by opposing side walls 22 which converge toward a common a single) longitudinally extending trough 24. Although not shown in the drawings, the lowermost portion of each trough is apertured at intervals along its length to permit drainage of any water that might collect in the channel.
Each side wall 23 of each channel 20 has a profile that curves between its associated cusp 21 and the trough 24. Also, each side wall is configured in a manner such that radiation that falls incident on the side wall will be reflected either to the opposing side wall and thence to the distant collector tube that is mounted above the cusp of the opposing side wall or directly to the distant collector tube.
Also, the profile of each side wall 23 is generated such that light which falls incident on the side wall and tangential to the distant collector tube will be reflected back along its own path, as indicated in the case of the light ray 25 in Figure 2.
Radiation that is angularly displaced to a certain extent from normal incidence (as illustrated by numeral 26) and that impinges on the side wall 23 will be reflected 25 directly into the lower region of the distant collector tube 21. Radiation that is angularly displaced to a further extent from the normal (as indicated by numeral 27) will be reflected into the distant collector tube but, in this case, as a secondary reflection from the opposing side wall 23 of the channel.
Figure 3 of the drawings shows a second form of the reflector that meets the requirements of the present invention. This is similar to that which is shown in Figure 2 and like reference numerals are employed to identify like elements.
However, in the case of the Figure 3 embodiment of the invention, the profile of each side wall 23 is generated in a manner such that radiation that falls incident on the side wall and tangential to its contiguous collector tube will be reflected horizontally H:ASui'TmoKfeApec'Rfluctdor for Solar Collector Tube Amy COMPLETE Dec 200l.doc 27/12/01 -8to the opposing side wall and be re-reflected tangentially to the distant collector tube.
This is indicated by the ray lines 28 in Figure 3.
Radiation that falls incident inside of the ray lines 28 will be reflected to the distant collector tube 22, either by re-radiation as indicated in the case of ray line 29 or directly in the case indicated by ray line 30 in Figure 3.
Figure 4 shows comparative graphs of optical efficiency against radiation angle for: A CPC reflector having a reflectance of 0.95.
A reflector configuration as shown in Figure 2, with a reflectance of 0.95.
A reflector configuration as shown in Figure 3, with a reflectance of 0.95.
A CPC reflector having a reflectance of 0.82.
From the graphs it can be observed in general that the reflectors of the present invention exhibit optical efficiencies that are higher than that ofa CPC reflector having a reflectance of 82% but not so high as the CPC reflector having a reflectance of However, given that the CPC reflector cannot be formed conveniently with a reflectance as high as 95% (for reasons previously stated), it may be concluded that the reflectors of the present invention do offer measurable advantages over prior art reflectors.
Variations and modifications as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.
H:Eumi ovnpap=dAflm for Solar Collscr Tube Amy COMPB W Doc 2001.dc 27/12lIl

Claims (9)

1. A reflector for use with an array of parallel, elongate solar collector tubes, and for back-reflecting radiation that passes in use between the collector tubes, the reflector including: a plurality of parallel, longitudinally-extending channels and a plurality of longitudinally-extending cusps; the cusps being positioned to locate in use behind respective ones of the collector tubes and each cusp being located between adjacent ones of the channels; each channel being defined by opposing side walls which converge from associated ones of the cusps to a common longitudinally-extending trough; and each side wall having a profile that curves between an associated cusp and an associated trough and being configured in a manner such that in use a i" significant portion of radiation that falls incident on the side wall will be reflected 15 to the opposing side wall and thence to a collector tube mounted in use above the cusp of the opposing side wall and a significant portion of radiation that falls incident on the side wall will be reflected directly to the collector tube mounted in use above the cusp of the opposing side wall. 20
2. A reflector as claimed in claim 1, wherein each side wall is profiled such that, in the limiting condition, light which falls incident on the side wall and travels along a path tangential to an associated collector tube remote from the side wall will be reflected back along the same path.
3. A reflector as claimed in claim 1, wherein each side wall is profiled such that, in the limiting condition, light which falls incident on a side wall and travels along a path tangential to a collector tube contiguous with the side wall will be reflected to an opposing side wall and will be re-reflected tangentially to an associated collector tube remote from the side wall. H:\emilyw\keep\retype\P44521 pgs 3, 4, 9.doc 6/02/06
4. A reflector as claimed in any one of claims 1 to 3, wherein the reflector is substantially symmetrical when viewed in transverse cross-section.
5. A reflector as claimed in any one of the proceeding claims, wherein the reflector is formed of glass having a reflective surface coating.
6. A reflector as claimed in any one of claims 1 to 4, wherein the reflector is formed of polished sheet metal.
7. A reflector as claimed in claim 6, wherein the sheet metal is anodised aluminium.
8. A solar collector assembly including a plurality of elongate substantially parallel solar collector tubes, and a reflector as claimed in any one of the proceeding claims, each collector tube being mounted adjacent and above a cusp of the reflector.
9. A reflector substantially as hereinbefore described with reference to, and as shown in, Figures 2 to 4 of the accompanying drawings. A solar collector substantially as hereinbefore described with reference to, and as :shown in, Figures 2 to 4 of the accompanying drawings. Dated this27th day of December 2001 SelseSEC By Its Patent Attorneys SECi3 4, GRIFFITH HACK QWo Fellows Institute of Patent and Trade Mark Attorneys of Australia H:%SuxAKup*=Apaector for Solar Collector Tube Arry -COMPLBTE Doe 2001.doc 27112/01
AU97477/01A 2001-01-03 2001-12-27 Reflector for solar collector tube array Ceased AU784427B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPR2381A AUPR238101A0 (en) 2001-01-03 2001-01-03 Reflector for solar collector tube array
AUPR2381 2001-01-03

Publications (2)

Publication Number Publication Date
AU9747701A AU9747701A (en) 2002-07-04
AU784427B2 true AU784427B2 (en) 2006-03-30

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AUPR2381A Abandoned AUPR238101A0 (en) 2001-01-03 2001-01-03 Reflector for solar collector tube array
AU97477/01A Ceased AU784427B2 (en) 2001-01-03 2001-12-27 Reflector for solar collector tube array

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AUPR2381A Abandoned AUPR238101A0 (en) 2001-01-03 2001-01-03 Reflector for solar collector tube array

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DE (1) DE10200042A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103335418A (en) * 2013-07-24 2013-10-02 中国科学院工程热物理研究所 Trough type solar thermal collector with variable lens area

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102006001566B3 (en) * 2006-01-12 2007-04-26 Paradigma Energie- Und Umwelttechnik Gmbh & Co. Kg Thermo-siphon-type solar store for heating water has outer storage tank with several round apertures having ring seals
CN100439630C (en) * 2007-02-05 2008-12-03 李先航 Heat preservation euphotic solar energy roof
KR20110127450A (en) * 2010-05-19 2011-11-25 세라믹뱅크 주식회사 Heat collector for solar water heater
DE102013014220A1 (en) * 2013-08-28 2015-03-19 Carcoustics Techconsult Gmbh solar panel
CN106482362A (en) * 2016-12-07 2017-03-08 福建工程学院 A kind of roof tile type solar collector

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5275150A (en) * 1992-08-26 1994-01-04 Herman Lai Solar collector

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5275150A (en) * 1992-08-26 1994-01-04 Herman Lai Solar collector

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103335418A (en) * 2013-07-24 2013-10-02 中国科学院工程热物理研究所 Trough type solar thermal collector with variable lens area
CN103335418B (en) * 2013-07-24 2014-12-03 中国科学院工程热物理研究所 Trough type solar thermal collector with variable lens area

Also Published As

Publication number Publication date
DE10200042A1 (en) 2005-04-14
AU9747701A (en) 2002-07-04
AUPR238101A0 (en) 2001-02-01

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Owner name: SOLAHART INDUSTRIES PTY LTD

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