Abstract:
A concentrating solar collector heat collecting element insulating shield has an elongated hemi-cylindrical body having an internal diameter approximately equivalent to (able to physically engage to) the outer diameter of the concentrating solar power (CSP) heat collecting element, either the evacuated outer tube, the fluid-carrying inner tube, or both. The device may have multiple layers of insulating/reflecting material, sheet metal, polymer, composite, may have flanges, fingers or other attachments to the CSP heat collecting element tube, or may be slightly greater than 180 degrees in arc so as to grip the CSP heat collecting element.

Description:
COPYRIGHT NOTICE 
       [0001]    A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 37 CFR 1.71(d). 
       CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0002]    N/A 
       FIELD OF THE INVENTION 
       [0003]    This invention relates generally to concentrating solar power devices, and specifically to heat collector elements of concentrating solar power devices. 
       STATEMENT REGARDING FEDERALLY FUNDED RESEARCH 
       [0004]    This invention was not made under contract with an agency of the US Government, nor by any agency of the US Government. 
       BACKGROUND OF THE INVENTION 
       [0005]    Concentrating solar power (CSP) collectors consist of a long trough of reflective material having a parabolic shape designed to focus the sun&#39;s rays upon a long tubular heat collecting element (HCE) running the length of the reflector. The HCE in turn consists of a metal tube through which fluid is pumped. Usually, the HCE is a two tube design having an inner (fluid carrying) tube and an outer tube as well. The outer tube is normally glass with the interior cavity holding the inner tube and being evacuated: the evacuated space between the two tubes serves to insulate the hot inner tube from the ambient environment, at least in terms of conductive heat transfer. When radiant sunlight hits the reflector, it is reflected and concentrated on the HCE, resulting in the HCE becoming hot.  FIG. 1  is a PRIOR ART perspective front elevational view of a single concentrating solar power collector with most ancillary equipment removed. Concentrating solar power collector (CSP)  100  has reflector trough  102  and heat collecting element (HCE)  104 : sunlight falling on the reflector  102  is concentrated on the HCE  104 . Of particular note is that the HCE becomes quite hot. Once hot, the HCE in turn becomes a source of heat loss, that it is, it rejects heat into the environment around it. This heat loss represents a loss of efficiency and energy from the solar power system. Heat may be rejected by several means, principally via radiation to the surroundings. (As noted previously, the evacuated outer tube insulates against conductive heat loss. However, since the outer tube must be transparent, it cannot stop all radiant heat loss.) Since the most effective color for absorbing light is black, the inner HCE tube may be a dark color. However, since the most effective color for radiating heat is also black, the HCE fluid tube may be an effective radiator, adding to the undesired heat loss. Additionally, the extent that the outer glass tube gets hot (or in a hypothetical system lacking an outer tube) convection of heat into air flowing around the HCE results in heating of the air and loss of energy as well. 
         [0006]      FIG. 2  is a PRIOR ART cross-sectional view of a heat collector element designed to alleviate some of these problems. Concentrating solar power heating element  200  shows a double tube system consisting of glass outer tube  202  having within it evacuated chamber  204 , meaning that fluid-carrying metallic inner tube  206  having therein fluid conduit  208  suffers a much reduced loss from convection of air past the HCE. However, inner tube  206  may still radiate heat outward to or through outer tube  202 . Since the outer surface of glass tube  202  also gets very hot, convective heat loss from that surface also occurs. 
         [0007]    Consideration of the structure of the device shows that sunlight concentrated by the reflector falls primarily on one face of the device. Unconcentrated sunlight directly from the sun is much weaker and is the a negligible source of energy input on the back side of the device. 
         [0008]    It would be preferable to take advantage of this asymmetrical energy flux to provide for more effective insulation of the HCE. 
       SUMMARY OF THE INVENTION 
       [0009]    General Summary 
         [0010]    A CSP heat collecting element insulating shield has an elongated hemi-cylindrical body having an internal diameter very slightly greater than (or approximately equivalent to, meaning able to physically engage to) the outer diameter of the CSP heat collecting element, either the evacuated outer tube, the fluid-carrying inner tube, or both. The device may have multiple layers of insulating/reflecting material, sheet metal, polymer, may have flanges, fingers or other attachments to the CSP heat collecting element tube, or may be slightly greater than 180 degrees in arc so as to grip the CSP heat collecting element. In diverse embodiments, a positive standoff (for example, 1/32 inch) between the interior diameter of the device and the outer diameter of the HCE tube it is affixed to can be assured by geometry of the fingers or other attachments, or by use of dimples, shims, ridges or other suitable means. 
         [0011]    Summary in Reference to Claims 
         [0012]    It is therefore a first aspect, advantage, objective and embodiment of the invention, in addition to those discussed previously, to provide a concentrating solar power (CSP) heat collecting element device for use on a CSP heat collecting element having an outside diameter and length, the CSP heat collecting element insulating device comprising:
       a body having a semi-circular cross section and an elongated length, the semi-circular cross section of the body having an inside diameter approximately equal to that of such CSP heat collecting element outside diameter.       
 
         [0014]    It is therefore another aspect, advantage, objective and embodiment of the invention to provide a CSP heat collecting element device further comprising:
       an arc of the semi-circular cross section, the arc being greater than 180 degrees, whereby the device may maintain physical engagement with such CSP heat collecting element.       
 
         [0016]    It is therefore another aspect, advantage, objective and embodiment of the invention to provide a CSP heat collecting element device further comprising:
       an arc of the semi-circular cross section, the arc being less than 180 degrees;   at least one upper projection (“finger”) from the body and at least one lower projection (“finger”) from the body, the upper and lower projections (“fingers”) cooperating to maintain physical engagement with such CSP heat collecting element by clipping or gripping when the CSP heat collecting element device is placed on such CSP heat collecting element.       
 
         [0019]    It is therefore another aspect, advantage, objective and embodiment of the invention to provide a CSP heat collecting element device further comprising:
       an attachment to such CSP heat collecting element.       
 
         [0021]    It is therefore another aspect, advantage, objective and embodiment of the invention to provide a CSP heat collecting element device wherein the attachment further comprises one member selected from the group consisting of: a braze weld, a weld, solder, adhesive, bolts, tabs, detents, hooks, studs, rivets and combinations thereof. 
         [0022]    It is therefore another aspect, advantage, objective and embodiment of the invention to provide a CSP heat collecting element device wherein the elongated length is approximately the same as such CSP heat collecting element length. 
         [0023]    It is therefore another aspect, advantage, objective and embodiment of the invention to provide a CSP heat collecting element device wherein the body is sheet metal. 
         [0024]    It is therefore another aspect, advantage, objective and embodiment of the invention to provide a CSP heat collecting element device wherein the body is high temperature polymer or composite. 
         [0025]    It is therefore another aspect, advantage, objective and embodiment of the invention to provide a CSP heat collecting element device used on a CSP heat collecting element having an inner fluid-carrying tube and an outer evacuated tube, respectively having an inner fluid-carrying tube outer diameter and an outer evacuated tube outer diameter, wherein:
       the semi-circular cross section inner diameter is approximately equal to the inner fluid-carrying tube outer diameter.       
 
         [0027]    It is therefore another aspect, advantage, objective and embodiment of the invention to provide a CSP heat collecting element device used on a CSP heat collecting element having an inner fluid-carrying tube and an outer evacuated tube, respectively having an inner fluid-carrying tube outer diameter and an outer evacuated tube outer diameter, wherein:
       the semi-circular cross section inner diameter is approximately equal to the outer evacuated tube diameter.       
 
         [0029]    It is therefore another aspect, advantage, objective and embodiment of the invention to provide a CSP heat collecting element device used on a CSP heat collecting element having an inner fluid-carrying tube and an outer evacuated tube, respectively having an inner fluid-carrying tube outer diameter and an outer evacuated tube outer diameter, further comprising:
       a second body having a second semi-circular cross section and a second elongated length, the semi-circular cross section of the body having a diameter approximately equal to that of such CSP heat collecting element;   the first body semi-circular cross section inner diameter approximately equal to such CSP heat collecting element outer evacuated tube outer diameter; and   the second body semi-circular cross section inner diameter approximately equal to such CSP heat collecting element inner fluid-carrying tube outer diameter.       
 
         [0033]    It is therefore another aspect, advantage, objective and embodiment of the invention to provide a CSP heat collecting element device used on a CSP heat collecting element having an inner fluid-carrying tube and an outer evacuated tube, respectively having an inner fluid-carrying tube outer diameter and an outer evacuated tube outer diameter, further comprising:
       at least one standoff device dimensioned and configured to maintain a standoff between the body inside diameter and the CSP heat collecting element outside diameter.       
 
         [0035]    It is therefore another aspect, advantage, objective and embodiment of the invention to provide a CSP heat collecting element device used on a CSP heat collecting element having an inner fluid-carrying tube and an outer evacuated tube, respectively having an inner fluid-carrying tube outer diameter and an outer evacuated tube outer diameter; wherein the standoff device further comprises:
       at least one dimple.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0037]      FIG. 1  is a PRIOR ART perspective front elevational view of a single concentrating solar power collector with most ancillary equipment removed. 
           [0038]      FIG. 2  is a PRIOR ART cross-sectional view of a heat collector element. 
           [0039]      FIG. 3  is a cross-sectional view of a first embodiment of the invention on the evacuated outer tube. 
           [0040]      FIG. 4  is a cross-sectional view of a second embodiment of the invention on the fluid-carrying inner tube. 
           [0041]      FIG. 5  is a cross-sectional view of a third embodiment of the invention on the fluid-carrying inner tube, showing attachment of the device to the tube. 
           [0042]      FIG. 6  is a perspective frontal view of a fourth embodiment of the invention. 
           [0043]      FIG. 7  is a perspective frontal view of a fifth embodiment of the invention. 
           [0044]      FIG. 8  is a cross-sectional view of a sixth embodiment of the invention. 
           [0045]      FIG. 9  is a cross-sectional view of a seventh embodiment of the invention on the evacuated outer tube. 
       
    
    
     INDEX TO REFERENCE NUMERALS 
       [0000]    
       
         Concentrating solar power collector (CSP)  100   
         Reflector trough  102   
         Heat collecting element (HCE)  104   
         Heat collecting element (HCE)  200   
         Evacuated outer tube  202   
         Evacuated chamber  204   
         Fluid-carrying inner tube  206   
         Fluid conduit  208   
         Evacuated outer tube  302   
         Shield device body  310   
         Fluid-carrying inner tube  406   
         Shield device  410   
         Shield device  510   
         Attachment  512   
         Shield device body  610   
         Shield device body  710   
         First type of finger  714   
         Second type of finger  716   
         Shield device body  800   
         First layer  820   
         Second layer  822   
         Third layer  824   
         Evacuated outer tube  902   
         Shield device body  910   
         Dimple  990   
       
     
       DETAILED DESCRIPTION 
       [0071]    For purposes of the present application, “approximately equal” or “slightly greater than” means a diameter or length able to make physical engagement with another diameter or length by means of being the same within a close tolerance, usually meaning a diameter at least one or two mils greater than the diameter of the HCE tube to be gripped or a length at least one or two mils less than the length of the HCE tube to be gripped. However, if the materials are flexible, even one or two mils difference may not be necessary, while if the material is not flexible or the configuration is not conducive to a tight grip, a diameter more than one or two mils greater may fit the applicant&#39;s chosen definition. This is important as the retrofit embodiments of the invention allows easy installation to the installed base of CSP systems, while the original equipment embodiments of the invention may be more easily manufactured. In addition, the slight gap shown in the diagrams in between the inner surface of the insulating shield and the outer surface of the HCE tube to which it is attached assures the insulating ability of the device. In diverse embodiments, a positive standoff (for example, 1/32 inch) between the interior diameter of the device and the outer diameter of the HCE tube it is affixed to can be assured by geometry of the fingers or other attachments, or by use of dimples, shims, ridges or other suitable means. 
         [0072]      FIG. 3  is a cross-sectional view of a first embodiment of the invention on the evacuated outer tube. Evacuated outer tube  302  may be seen to have shield device body  310 . While the shield device may be original equipment, it may also be a retrofit which simply slips onto the HCE. It will be appreciated from  FIG. 3  and  FIG. 1  that the HCE has a length and an outer diameter, and that the device may be made with a length and diameter which match the HCE, so as to allow easy installation. In alternative embodiments, the device may be made in a standardized length shorter than the HCE length, then short lengths may be installed as desired or practical onto the HCE. 
         [0073]    In use, the shield will act to insulate the side of the HCE which is facing away from the reflector trough, reducing heat losses by radiation, convection and/or conduction. 
         [0074]      FIG. 4  is a cross-sectional view of a second embodiment of the invention on the fluid-carrying inner tube. Fluid-carrying inner tube  406  rather than the outer tube is the carrier for the shield device  410 . In this case, the length and diameter of the HCE which are important are the length and diameter of the interior tube. 
         [0075]    Note that in CSP systems which may have only a single tube, this configuration is the default configuration, though such CSP systems are at best rare, due to the fact that the evacuation is usually necessary for economical operation. 
         [0076]    In general these configurations are held onto the tube simply be a physical engagement thereto, which may be clamping or clasping, for example. In a simple preferred embodiment, the device is held on by virtual of having an arc of a circle measuring slightly more than 180 degrees. The degree of arc in excess of 180 will depend on the ductility and nature of the materials used in the device and HCE, for example, with sheet metal or softer polymers an arc of 190 or 210 degrees is perfectly possible, as the material will allow itself to pass over the HCE easily. With harder polymers, metals or the like, this can be reduced, as the material will have less give and will thus hold itself on with a smaller angle, and will require a smaller angle in order to fit on. Angles of approximately 181 degrees can be envisioned. 
         [0077]      FIG. 5  is a cross-sectional view of a third embodiment of the invention on the fluid-carrying inner tube, showing attachment of the device to the tube. Assuming material thermal compatibility, shield device  510  may have attachment  512  used to secure it to the tube. The attachment  512  may be a braze weld, a weld, solder, adhesive, bolts, tabs, detents, hooks, studs, rivets, combinations thereof and so on. 
         [0078]      FIG. 6  is a perspective frontal view of a fourth embodiment of the invention. Shield device body  610  is shown in perspective, without the HCE, for clarity. This embodiment may correspond to any of the first three embodiments. 
         [0079]      FIG. 7 , however, is a perspective frontal view of a fifth embodiment of the invention, showing for example purposes two different types of projections or fingers. Shield device body  710  has fingers or projections which allow the device body to subtend an arc of less than 180 degrees yet still have simple physical engagement. First type of finger  714  and second type of finger  716  are exemplary only, any shape of finger may be used. Note that having two or more different types/shapes of fingers or attachments on a single device is perfectly acceptable, however in practice having only a single type of attachment is a bit more likely. 
         [0080]    Such embodiments may be used in “deep trough” designs in which the CSP reflector trough is deeper and radiates to a wider arc of the HCE. On the other hand “shallow trough” designs, in which the reflector trough is less than 180 degrees, would likely be more acceptable for use with the embodiments having a greater than 180 degree arc. 
         [0081]      FIG. 8  is a cross-sectional view of a sixth embodiment of the invention. Shield device body  800  may be composed of more than a single layer. For example, it might have a first layer  820 , a second layer  822  and a third layer  824 . These layers might be a combination of reflective and refractory materials such as a first layer of foil or reflective coating, a second layer of insulating material, and a third layer of structural material or the like. One, two, three or more layers may be used in any embodiment. 
         [0082]      FIG. 9  is a cross-sectional view of a seventh embodiment of the invention on the evacuated outer tube. In embodiments, a positive standoff may be desirable or necessary. The standoff may be 1/32 inch but it may be larger or smaller as necessary for installation, thermodynamic efficiency and other considerations. The standoff between the interior diameter of the device  910  and the outer diameter of the HCE tube  902  it is affixed to can be assured by geometry of the fingers or other attachments, or by use standoff devices  990 , such as dimples, shims, ridges or other suitable means. 
         [0083]    In the presently preferred embodiment and best mode presently contemplated for carrying out the invention, the device may be standardized to standard HCE sizes and provided in lengths shorter than the HCE, with multiple devices used to cover the length of the HCE. 
         [0084]    The disclosure is provided to render practicable the invention by those skilled in the art without undue experimentation, including the best mode presently contemplated and the presently preferred embodiment. Nothing in this disclosure is to be taken to limit the scope of the invention, which is susceptible to numerous alterations, equivalents and substitutions without departing from the scope and spirit of the invention. The scope of the invention is to be understood from the appended claims.