Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S10/00—Solar heat collectors using working fluids
  • F24S10/70—Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits
  • F24S10/75—Solar heat collectors using working fluids the working fluids being conveyed through tubular absorbing conduits with enlarged surfaces, e.g. with protrusions or corrugations
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
  • F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
  • F24S23/80—Arrangements for concentrating solar-rays for solar heat collectors with reflectors having discontinuous faces
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S23/00—Arrangements for concentrating solar-rays for solar heat collectors
  • F24S23/70—Arrangements for concentrating solar-rays for solar heat collectors with reflectors
  • F24S2023/83—Other shapes
  • F24S2023/838—Other shapes involutes
• • Y—GENERAL 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
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/40—Solar thermal energy, e.g. solar towers
  • Y02E10/44—Heat exchange systems

Definitions

• the present invention relates in general to a new configuration for a solar concentrator of the CPC type, with the elimination of thermal shorts and of optical losses.
• One recurring concern is to reduce or even eliminate the optical losses that result from the existence of a certain gap between absorber and the mirrors reflecting towards it the incoming solar radiation.
• This gap is a necessity in case the collector is of the atmospheric type (in opposition to those that use vacuum for all or for part of their configuration), since, if the absorber touches the mirrors or other surfaces that come close to it, there is thermal short circuit from which unwarranted thermal losses result, which may even create a survival problem for the whole collector.
• the absorber 1 (an inverted V defined by portions AC and CB) may be illuminated on its two faces 1' and 1", as can be seen by what happens to the two parallel rays 4 and 4' that are incident on the concentrator, one 4, on directly incident on face 1 ' of the absorber and the other 4 ' , after two reflections on the down face 1 " of the absorber
• This concentrator concentrates onto the absorber ACB with the shape of an inverted V the radiation incident on aperture EF and making angles ⁇ comprised between the values ⁇ , angles that the direction EF and FC make with the normal to the aperture EF which is also the symmetry axis of the ensemble.
• the concentrating optics is conceived for a virtual ACB absorber with a triangular shape.
• the face AB is virtual, and all radiation crossing it ends up, without losses, on the down surface of the inverted V absorber, allowing for the reflecting mirror to start on the virtual absorber segment AB, without touching its active surfaces and establishing the desired large gap, thus avoiding the thermal short between the absorber and the mirror 2.
• this solution is entirely equivalent to the one presented in Fig. 2, in which the absorber 1, still in the shape of an inverted V, extends itself to the points G and H (the same signaled in Fig. 1 and which result from the intersection AC and CB segments extensions with the reflector surface).
• the reflector extending from G to M and from this point H, and which is designated as involute is constituted by two arcs of circumference with the sane radius AB/2 and centered in A and B, respectively.
• absorber 1 is only active on its face 1 ' , directly exposed to the incident radiation.
• the same two parallel rays 4 and 4' as in Fig 1 are seen being absorbed, respectively, directly and after one reflection on reflector 2.
• fin also commonly named by the word fin, only active on one side 1', is available from a large number of manufacturers/suppliers, being a standard product of flat plate solar collector absorbing 1 fins industry. On the other hand, at present, there are practically no suppliers of fins 1 coated on both sides 1' and 1", as in the case of Fig. 1.
• a severe limitation of the configuration in Fig.2 is that it promotes the contact between reflector 2 and absorber 1, causing thermal short circuits and thus thermal losses.
• the solar collector of the present invention solves the optical and thermal losses problems without losing the advantages of the solar collectors of prior art.
• the present invention discloses a low concentration CPC type concentrating collector, comprising at least an absorber, at least an absorber tube and concentrating reflectors, the said concentrator being characterized in that further comprises a bottom set, in that said absorber, concentrating reflectors and bottom set are superimposed, without contacting each other, and in that having concentration values in the range of about 1 to 3, wherein said bottom set has at least two side walls and a bottom wall, with each side wall making an angle ( ⁇ ) of at least 90° with said bottom wall and said absorber has a surface selected from the group comprising an inverted V shape, any profile with the shape of a line or a similar polygonal and open curve and combinations thereof.
• the low concentration CPC type concentrating collector has a surface with an open polygonal line shape with at least three straight segments.
• the low concentration CPC type concentrating collector of the present invention has a reflecting bottom set.
• the low concentration CPC type concentrating collector of the present invention has a bottom set comprising a thermal insulation.
• the low concentration CPC type concentrating collector of the present invention has thermal insulation having a reflector totally or partially covering its upper face.
• a preferred embodiment of the low concentration CPC type concentrating collector of the present invention shows an asymmetrical geometry.
• Another preferred embodiment of the low concentration CPC type concentrating collector of the present invention has a concentration value of 1.5.
• an absorber grid made of concentrators of the invention comprising at least two of said concentrating collectors, one box comprising at least with one cover, at least, one insulation and one back part, one fluid inlet and one fluid outlet one header tube, one collector tube and expansion guides, is characterized by said header, said fluid inlet and said fluid outlet being installed in a top of a same side of said box; said collector tube and said expansion guides being installed in a top at the opposite side of the box, and by said header tube being blocked in its middle point.
• said cover comprises a transparent material with a polygonal structure of the honeycomb type or the like, a single thin film, a double film or the like and combinations thereof.
• Fig. 1 shows in a schematic view a prior art solar collector of the CPC type.
• Fig.2 shows in a schematic view another prior art collector of the CPC type, equivalent to the one of Fig.1 but without involute.
• Fig. 3(a) shows, in a schematic view, CPC type collectors of the prior art, having an inverted V shape absorber 1, which absorber 1 is truncated, not extending up to reflector 2.
• Fig. 3(b) shows a schematic view of another prior art collector equivalent to the one of Fig. 3 (a) but in which the reflector 2 is truncated, not extending up to absorber 1.
• Fig. 4 shows in a schematic view, an embodiment of a absorbing cavity of the present invention, comprising reflectors 2, an inverted V shape absorber, a tubular section 10 and a bottom set 3, constituted by 5 walls.
• Fig. 5(a) shows another embodiment of the present invention comprising thermal insulation 6 and having an upper side that may be reflecting or not.
• Fig 5(b) shows another embodiment of the present invention, in which the absorber 1 is a surface with an open polygonal line shape with 4 straight segments.
• Fig 6(a) shows a perspective view of an embodiment of the present invention illustrating an absorber grid constituted by several concentrating collectors of the present invention, placed side by side and contained inside a box 7, with a transparent glass cover 8 and thermal insulation 14 on a back side 9.
• Fig. 6(b) shows a schematic detail of the absorbing grid of Fig. 6(a) which, for drawing clarity sake, only shows the header tube 11 and the collector tube 11'. It further shows a system of guides 13, fixed to a side wall of the box 7.
• Fig. 7 shows another embodiment of the present invention in which the geometry of the concentrating collector is not symmetrical.
• Fig. 8 further shows another embodiment of the present invention in which the concentrating collector is truncated and comprises a transparent insulation 15 placed in between reflectors 2 and cover 8.
• the present invention relates to a new configuration of a solar collector of the
• the CPC type enabling the development of an anidolic type optics (ideal or non imaging optics) preserving characteristics of the prior art which allowed for lossless optical performance, and simultaneously avoiding thermal shorts which would result in substantial efficiency losses.
• the configuration developed further shows features that allow it to preserve this behavior even at high temperatures, in spite of the expansion that results from them.
• the concentrating collector of the present inventions is susceptible of presenting larger concentration values and better control thermal losses.
• Fig. 4 shows an embodiment of the present invention in which the absorber used for the definition of anidolic reflectors EE' and FF' is the segment E'CF' in inverted V shape, having an opening angle 2 ⁇ represented in dashed line to underline its virtual nature.
• This figure further shows a real inverted V absorber 1 with slightly larger dimensions, with an angle 2 ⁇ slightly smaller (L e., ⁇ ⁇ ⁇ ), at least one absorber tube 10 and concentrating reflectors 2.
• On the base of this collector there is a bottom set 3, comprising at least two side walls 3' and one bottom wall 3" which correspond respectively to the straight segments IJ, LM and JL.
• the referred bottom set 3 may be reflecting totally or partially.
• the bottom set may also be formed in a non-reflecting and insulating material, like cardboard or the like.
• Tubular section 10, shown in Fig. 4 is an absorber tube 10 in which a fluid is circulated to extract the energy absorbed by the referred absorber 1 (or fin 1).
• FIG. 5(a) another embodiment of the present invention is shown.
• This figure shows that the volume between the bottom set 3 and the absorber 1 may be filled with thermal insulation 6, of the rock wool type or the like.
• the referred thermal insulation 6 may (or may not) present its upper horizontal face 5 as a reflecting one.
• Fig. 5(b) another embodiment of the present invention is shown in which the absorber 1 is an open polygonal line defined by 4 straight segments, i.e. , it presents itself slightly bent in points C and C", with the reflectors EE' and FF' configured to preserve the anidolic and ideal characteristics of the collector.
• This configuration of absorber 1, with four segments, generates more mechanical rigidity in the direction perpendicular to the one being represented.
• the new concentrating collector shows an asymmetrical geometry, in which the full acceptance angle is the sum of two angles, ⁇ i and ⁇ 2, (wherein ⁇ i is different from ⁇ 2).
• the concentration values are in the range of 1 to 3, usually less than 2 for totally stationary collectors as described in the document by Ari Rabl, 1985, entitled “Active Solar Collectors and Their Applications", New York: Oxford University Press, Inc.
• the concentrating collector has a concentration of 1.5.
• FIG. 6 (a) a perspective view is shown, of another embodiment of the present invention, in which several concentrating collectors of the invention, having absorbers 1 of inverted V shape, are placed side by side, so as to form an absorbing grid.
• the concentrating collectors of the invention are contained in a box 7 comprising a transparent glass, thermal insulation 14 and a back part 9.
• Fig. 6(b) there is shown a schematic detail of the embodiment of Fig. 6(a) which represents said absorbing grid.
• absorber tubes 10 are shown connected to two tubes 11 and 11', header and collector, with expansion guides 13 also being shown.
• said header tube 11, said fluid inlet R and said fluid outlet S are installed at one top of the same side of said box 7, said collector tube and said expansion guides being installed on the top of the opposite side of the box 7.
• This figure underlines in a schematic way the intake of fluid by the absorber grid from the outside, from the side of the header tube 11 which extends into the box 7 in the R point, and delivers heated fluid to the outside, on the side of the same header tube 11 which exits the box at S point.
• This header tube 11 is blocked in the middle in a way such that it forces the fluid to flow along the absorber tubes 10, which tubes extend before that point, between R and N, up to the collector tube 11 'and forced to return through the remaining absorber tubes 10, again up to the header tube 11.
• This configuration of the absorber grid of the present invention is different from the conventional ones, which usually use two or four grid inlets/outlets, in the former case in diagonal and in the latter one in four symmetrical points.
• the solution for the absorbing cavity of the present invention allows various types of design solutions that distance themselves from those above cited in the Portuguese Patent PT 102938, entitled “Colector solar de baixa concentracao, ideal, do tipo CPC", European Patent EP 0678714 Bl, entitled “Solar energy collector of the non-evacuated compound parabolic concentrator type” and Portuguese Patent PT 80405, 1987, entitled “1.2 X CPC with tubular receiver with headers ideally illuminated” and which used the injection of polyurethane foam to fill all of the volume between the reflector and the bottom of the collector box.
• the present invention allows for a larger flexibility in volume filling with thermal insulation; in particular with the possibility of discard, totally or partially, the use of expanded polyurethane foam.
• polyurethane foam is a material that has obvious life limitations with respect to temperatures above 100 0 C, the solutions of prior art were mainly directed to lower concentration values.
• the new configuration of the absorbing cavity is also compatible with truncated CPC optical configurations, L e. , wherein the reflector 2 does not reach the surface EF (Fig. 7) which would be the entrance aperture for the solar radiation of the non-truncated concentrator, as in patents PT 102938, EP 0678714 Bl and
• cover 8 may be designed to comprise a transparent material of a polygonal honeycomb type structure or a single or double thin film and combinations thereof.

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

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• 2008
  • 2008-07-17 PT PT104133A patent/PT104133A/pt not_active IP Right Cessation
• 2009
  • 2009-07-17 WO PCT/PT2009/000042 patent/WO2010008311A2/en active Application Filing
  • 2009-07-17 EP EP09788435A patent/EP2318774A2/de not_active Withdrawn

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