Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S20/00—Solar heat collectors specially adapted for particular uses or environments
  • F24S20/20—Solar heat collectors for receiving concentrated solar energy, e.g. receivers for solar power plants
• • 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
  • F24S10/40—Solar heat collectors using working fluids in absorbing elements surrounded by transparent enclosures, e.g. evacuated solar collectors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
  • F24S40/00—Safety or protection arrangements of solar heat collectors; Preventing malfunction of solar heat collectors
  • F24S40/40—Preventing corrosion; Protecting against dirt or contamination
  • F24S40/46—Maintaining vacuum, e.g. by using getters
• • 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
• • 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 refers to improvements for solar collector receiver tubes.
• the problem related to the presence of hydrogen and the consequential decay in the device characteristics is of particular relevance since at such higher temperatures there is a higher hydrogen outgassing from the metallic parts of the receiver.
• the purpose of the present invention is to reduce the intensity of this phenomenon, and in a first aspect thereof it consists in a solar collector receiver tube containing a getter system comprising a mechanical support and pills of compressed powders of a getter material, wherein said mechanical support comprises a holder consisting in a base and two lateral shoulders, characterized in that said getter powder pills have a diameter equal to or higher than 15 mm, a diameter/height ratio comprised between 2 and 5, and they are housed within said holder on said base in a single line.
• Figure 1A shows a side view and figure IB a view from above of a first embodiment of the getter system, to be used within the receiver tubes, according to the present invention
• Figure 2A shows a side view and figure 2B a view from above of an alternate embodiment of the getter system, to be used within the receiver tubes, according to the present invention
• Figure 4 shows a view from above of a getter system, to be used within the receiver tubes, incorporating one of the elastic elements depicted in figure 3,
• Figure 5 is a cross sectional representation of another embodiment of a getter system, to be used within the receiver tubes.
• the dimensions and the dimensional ratios of the elements are not correct but have been altered in order to improve the comprehensions of the graphical representation of the invention.
• some elements optionally present such as, for example, optional heat shields or fixing means for the hoi der/sl edge, have not been depicted since they are not essential for its comprehension.
• the pills surface increase, while keeping the same height, renders them more fragile and consequently more difficult to handle, but, on the other side, the height increase results in a negative effect on the pumping speed and in the difficulties that gaseous impurities encounter in reaching the inner pill regions. Therefore the detrimental effects to be expected in adopting pills with an enlarged diameter would have not prompted a person skilled in the art to adopt such a solution.
• the getter pills to be used in the present invention are obtained by a suitable compression of the powders of the getter materials and do not comprise binders, that would otherwise affect the capacity of the material intended as amount of hydrogen adsorbed by each pill. This is a fundamental aspect that affects the pill structure resistance and the associated constraints for its successful employ in the solar collector application.
• the optimal ratio between the pills diameter and their height is comprised between 2 and 5, and for the very same reasons problems start to manifest for pills with a diameter bigger than 35 mm.
• the pills diameter is comprised between 18 and 25 mm and the ratio between their diameter and their height is comprised between 3 and 4.
• the arrangements currently employed envision the use of two distinct holders for each receiver tube, with the associated positioning and fixing problems, in addition to the structural costs that include not only the holder but also the elements that complete the mechanical support, i.e. the confinement metallic mesh, spacers and suitable heat shields.
• the holder has a width that is 1-3 mm larger than the pills diameter, this solves a technical problem associated with the pill structure swelling as a consequence of the hydrogen sorption by the getter material, by allowing for some degree of accommodation of the pill within the holder.
• the height of the holder intended as height of the elements that constitute the lateral shoulders
• the height of the lateral shoulders is 0,5-1 mm less than the pills height. This assures that the net itself acts also a constraining element for the getter material pills, to limit their reciprocal movement and the possibility that as a consequence of hits they fragment with a consequent increase in the powder generation.
• the shoulder height is 1-3 mm more than the pills height for the very same reason and technical effect above described.
• the holder contains also one or more elastic elements in direct contact with one ore more getter materials pills.
• the pressure value exerted is a key parameter and its strictly dependent and specifically linked to the field of application, since an excessive pressure value would help in breaking the pills structure rather than preventing its breaking by restraining its movements within the holder.
• the determination of such value is rendered more difficult by the fact that it should take into account the pill swelling consequent to hydrogen sorption by the getter material, as well as an increased brittleness of the pill structure as a consequence of its hydrogen sorption.
• the inventors have found that the compression force exerted by the elastic means shall be comprised between 50N and 150N. This value is considered and measured in a newly installed getter systems, therefore when getter material pills may be considered "fresh", i.e. have adsorbed a minimal amount of hydrogen.
• the elastic elements shall be free of sharp corners in their contact region with the getter material pills, in order to avoid to have preferential powder generation spots, so they shall present flat or rounded surfaces in such contact points. Such characteristics will be referred hereinafter as “distributed contact”.
• getter materials preferred are the ones that exhibit a good hydrogen sorption capacity even when used at high temperatures.
• getter materials useful for the present invention are the ones described in US patent 3203901 (Zr-Al alloys), US patent 4306887 (Zr-Fe alloys), GB patent 2077487 (Zr-V-Fe alloys), US patent 5961750 (Zr-Co-Rare earths alloy).
• yttrium alloys As described in the international patent applications WO 2007/148362, WO 2007/099575 and WO 2010/105945.
• the above-mentioned getter alloys are the ones preferably used with the present invention, but any hydrogen getter material may be employed with the inventive concept disclosed.
• FIGS 1A and IB a first embodiment for the getter system 10 for solar collectors receiver tubes is shown, wherein the pills of getter material 11, 1 , 11 " ... are aligned on the flat base 12 of the holder and a confinement metallic net 14 is present, fixed to the holder, for example by means of electric welding.
• FIG 1A there is also present an optional element 15 that acts as a stopper, mechanically operated, once the pills have been loaded into the holder.
• Figure 1A shows only one of such elements 15 close to one of the holderends, but there could be a second stopping elements 15', as shown in figure IB, at the secondend.
• the metallic net can be fixed on the holder in various ways, for example it may be fixed on the holder lateral shoulders 13, 13 ', or wrapped and fixed at the flat base 12, on its outer face.
• the preferred fixing arrangement provides for a slight overlapping of the edges of net 14, and afterwards performing a single electrical welding in order to fix the net 14 on the holder.
• the metallic net can be arranged not over the entire length of the holder, thus leaving the ends free, so as to avoid interferences with possible means required for anchoring the holder within the receiver tube.
• the getter system 20 comprises getter materials pills 21, 2 , 21 " ... placed on the base of the holder structure, that is closed by means of a cover 23 that comprises openings in which a metallic mesh 22 is arranged.
• Cover 23 is then fixed onto the holder base by suitable anchoring means, such as, for example, clews, not shown.
• FIG 2A there are also shown some tabs 24 folded in such a way as to act as stoppers for the getter material pills 21. 21 ', 21 " ... placed on the holder base.
• This arrangement has the advantage of allowing to manufacture the closed holder structure by means of a semifinished product, the holder cover with its metallic mesh fixed upon, and therefore simplify the assembly operations of the getter system used in the present invention.
• the holder is slightly wider with respect to the pills diameter and the lateral shoulders height is slightly lower with respect to the pills height.
• the preferred dimensions envision the usage of a holder with a width 1-3 mm larger with respect to the pills diameter, and a lateral shoulders height 0,5-lmm lower with respect to the pills height.
• the pills stoppers 24 also serve the purpose of exerting a slight longitudinal pressure on the pills line, therefore limiting their transversal movement.
• the net has holes, or more generically apertures, that have a size between 10 and 500 ⁇ .
• the metallic net openings are comprised between 20 e 50 ⁇ . In case the openings are not circular or roughly circular, the above size refers to their maximum width.
• FIG. 3 Examples of possible embodiments for elastic elements to be used within the holder are shown in figure 3.
• Each of the depicted elements, 31, 32, 33, 34, has the part that should be in contact with the getter pill, 311, 312, 321, 322, 331, 332, 341, 342 that is flat or rounded, therefore suitable to realize a distributed contact with the getter pill surface.
• Figure 4 shows a view from above of a holder 40, containing one of such elastic elements 41.
• the cover element of the holder has been represented with the getter material pills 42, 42' ... disposed on.
• the cover and base of the holder indentify the parts of the getter system that within the receiver tube are directed respectively toward the outside (the cover) or toward the inner part of the tube (the base). Cover and base therefore refer to the geometrical positioning not to the way the getter system is assembled, as for example in the embodiment depicted in figure 4 the getter pills are placed on the would-be cover.
• An alternate embodiment of the getter system envisions the use of a modified perforated cover, that instead of presenting a flat surface presents a series of one or more depressions in the net in correspondence to the getter pills, such depressions also presenting rounded or planar contact surfaces in order to achieve a distributed contact interface between the cover and the getter pills.
• a cross-section 50 of this arrangement is schematically represented in Fig. 5, where a pill of compressed getter material 51 is disposed over the flat holder base 52, and is vertically restrained by the depressions 53, 53' of the net 54 being part of the perforated cover 55.
• Such an arrangement has the advantage of restraining also the pills with regards to vertical displacements.
• the even more preferred embodiment envisions both the use of the depressed perforated cover and of elastic elements for restraining the pills displacement in all directions, but those may also be singly adopted.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Thermal Sciences (AREA)
• Physics & Mathematics (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Thermal Insulation (AREA)
• Photovoltaic Devices (AREA)
• Ultra Sonic Daignosis Equipment (AREA)

Applications Claiming Priority (2)

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• 2010
  • 2010-08-06 IT IT001519A patent/ITMI20101519A1/it unknown
• 2011
  • 2011-07-22 JP JP2013522193A patent/JP2013534303A/ja active Pending
  • 2011-07-22 US US13/813,902 patent/US20130125874A1/en not_active Abandoned
  • 2011-07-22 WO PCT/EP2011/062678 patent/WO2012016865A1/en not_active Ceased
  • 2011-07-22 CN CN2011800387131A patent/CN103080666A/zh active Pending
  • 2011-07-22 EP EP11735440.7A patent/EP2601453A1/en not_active Withdrawn

Non-Patent Citations (1)

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