Abstract:
The invention relates to the field of solar radiation collectors intended to convert energy of solar radiation into thermal energy, specifically, to the solar radiation collectors constructed as the combination of a concentrated solar radiation receiver, a single-curvature or compound-curvature concentrator and a tracking mechanism. A thermal insulation of the concentrated solar radiation receiver and the concentrated solar radiation receiver itself play a role of details in the tracking mechanism.

Description:
FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0001]     Not Applicable.  
       BACKGROUND OF THE INVENTION  
       [0002]     This invention relates to the field of solar radiation collectors intended to convert energy of solar radiation into thermal energy, especially, to the solar collectors, which incorporate single-curvature or compound-curvature concentrators.  
         [0003]     In the case of application of single-curvature parabolic mirrors as the concentrators, the modular solar radiation collector is constructed as combination of an elongated receiver, the single-curvature concentrator and a tracking mechanism, which ensures steady positioning the elongated receiver in the focal zone of the single-curvature concentrator.  
         [0004]     It is known, that such solar collectors allow to achieve temperatures of a working fluid significantly higher than 100° C.; this in turn gives possibility to apply obtained thermal energy in different processes of industry or to convert this thermal energy into electricity with sufficiently high coefficient of performance.  
         [0005]     In the most cases, the single-curvature concentrator is constructed as a trough-wise parabolic mirror or a single-curvature Fresnel lens.  
         [0006]     The elongated receiver is constructed usually as a pipe with an outer coating intended to absorb concentrated and direct solar radiation, and a transparent (glass) elongated envelope positioned around the pipe. The transparent envelope is sealed with the pipe at its ends and the gap between the pipe and the elongated envelope is vacuum-insulated in order to suppress convective losses of thermal energy from the outer surface of the pipe.  
         [0007]     There are some drawbacks, which characterize this construction.  
         [0000]     1. Concentrated solar radiation illuminates only a part of the whole surface of the radiation receiving pipe; at the same time, heat loss by radiation occurs from the entire outer surface of this pipe.  
         [0000]     2. Sealing the metal pipe of the receiver with the glass envelope is very expensive and sophisticated from the technological point of view.  
         [0000]     3. It is impossible to insulate thermally the radiation receiving pipe in a modular manner.  
         [0000]     4. Low strength of the glass envelope does not give possibility to apply this glass envelope as a carrying element of the construction of a solar collector.  
         [0008]     Same drawbacks are true for the common solar collectors with application of compound-curvature dish-type concentrators.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009]     A first version of this invention proposes a solar radiation modular collector with a concentrating unit of the single-curvature type (one-axis sun tracking concentrator) and with a receiver of concentrated solar radiation in the form of a radiation receiving pipe.  
         [0010]     The radiation receiving pipe is provided with a thermal insulation layer in the form of a metal envelope, which can be vacuum-insulated or filled with material with low thermal conductivity. In addition, the internal cavity of this metal envelope can comprise some radiant shields from metal foil with high reflection coefficient in the infrared range. The single-curvature concentrator can be constructed as a parabolic trough-wise reflector, or as a single-curvature Fresnel lens or mirror.  
         [0011]     The metal envelope insulates most of the outer surface of the radiation receiving pipe with significant diminishment of heat losses caused by convection and radiation from this part of the outer surface.  
         [0012]     The metal envelope of the radiation receiving pipe is constructed from two elongated internal and external sections, which are joined by two elongated connection straps and sealed at their ends by face planes.  
         [0013]     The internal elongated section comprises a cylindrical sub-section, which encloses a significant part of the radiation receiving pipe; this cylindrical sub-section is transformed at its longitudinal margins to flat or single-curved strips with a certain angle of convergence with respect to the cylindrical sub-section. In such a way, the cross-section of the internal section is somewhat similar to the vertical cross-section of a jug. The external section encloses the internal one.  
         [0014]     The internal cavity between the internal and external sections of the metal envelope is evacuated in order to suppress convective loss of heat. In addition, this space can be filled with a porous material and/or layers of metal foil in order to diminish heat loss by radiation.  
         [0015]     It is possible to apply filling the internal cavity of the metal envelope with a gas with low thermal conductivity, for example, krypton.  
         [0016]     The gap between the elongated connection straps is glazed in order to diminish heat losses, which occur from the part of the radiation receiving pipe that is not enclosed by the cylindrical sub-section of the internal elongated section.  
         [0017]     It should be noted, that some metal envelopes, which are constructed as it has been described about, could be situated sequentially around one radiation receiving pipe.  
         [0018]     Thermal losses in the proposed construction of the thermal insulation occur mainly by three ways: 
        1. By thermal conductivity of the walls of the metal envelope.     2. By radiation from the illuminated surface of the radiation receiving pipe.     3. By convection via the internal cavity between the internal flat strips, the glazing and the radiation receiving pipe. The glazing of the internal cavity between the internal flat strips allows to diminish significantly thermal losses occuring by convection. In addition, the glazing may be provided with a transparent coating, which reflects back infrared radiation from the radiation receiving pipe.        
 
         [0022]     It is clear, that limited thermal conductivity of the walls of the metal envelope causes temperature gradient in it and in turn this can cause deformation of the metal envelope.  
         [0023]     In order to prevent this, the internal and external sections of the metal envelope can be provided with corrugations, which decrease to zero in the vicinity of the connection straps. These corrugations can be directed inwards or outwards with respect to the internal cavity of the metal envelope.  
         [0024]     The outer surface of the external section of the metal envelope can be painted with black or selective paint with very low emittance coefficient in the infrared range; it allows to elevate temperature of the external section of the metal envelope at the expense of the direct solar radiation falling on its surface. It in turn diminishes heat losses caused by thermal conductivity of the metal envelope and by radiation and thermal conductivity via the internal cavity of the metal envelope.  
         [0025]     The proposed receiver of the solar radiation can be rigidly joined by a set of truss struts with the single-curvature concentrator, which should be turned by a tracking mechanism in accordance with the sun motion. In this case, the receiver is turned and moved through turning the single-curvature concentrator.  
         [0026]     However, the mechanical strength of the metal envelope allows to construct the modular solar collector in such a way, that its metal radiation receiving pipe is stationary, and the metal envelope with the single-curvature concentrator, which is rigidly joined with the metal envelope by the set of the truss struts, is turning around the metal radiation receiving pipe by the tracking mechanism. In such a way, the radiation receiving pipe plays the role of a bearing element and an axle.  
         [0027]     The radiation receiving pipe can be provided in this case with a set of ribs in order to prevent contact of the internal surface of the metal envelope with the black or selective coating of the radiation receiving pipe. In addition, the cylindrical surface of these ribs can be provided with an antifriction coating.  
         [0028]     The proposed construction of the thermal insulation of the radiation receiving pipe allows to assemble the solar radiation collector in modular manner without expensive sealing between a glass cylindrical envelope and the radiation receiving pipe.  
         [0029]     Some solar radiation modular collectors can be situated in some rows and the solar radiation modular collectors, which are positioned in the parallel rows, can be provided with common tracking mechanisms.  
         [0030]     The second version of the proposed solar collector is based on application of same technical solutions in the case, when compound-curvature concentrators and, particularly, dish-type parabolic mirrors are used as the concentrators of solar radiation.  
         [0031]     In the case of application of the compound-curvature concentrators in the form of the dish-type mirrors, a module of the proposed system comprises a bearing pipe that is mounted on the vertical posts. A heat transfer medium (working fluid) flows in the bearing pipe.  
         [0032]     The bearing pipe is provided with a layer of thermal insulation.  
         [0033]     Some T-pieces are built into the bearing pipe. The lower branch of each T-piece is sealed by a metal convex spherical cap and a part of the outer surface of the T-piece is covered with a layer of thermal insulation.  
         [0034]     In addition, there is a solar radiation receiving member, which is constructed from a dish-type plate and a double-wall funnel.  
         [0035]     The upper side of the dish-type plate has the concave surface in the form of a spherical segment with the radius almost identical to that of the metal convex spherical cap. In such a way, this pair: the spherical cap of the T-piece and the concave surface of the dish-type plate present a spherical joint. The lower surface of the dish-type plate is covered with a layer of a solar radiation absorption coating.  
         [0036]     The upper surface of the dish-type plate and the outer surface of the metal convex spherical cap can be provided with antifriction coatings.  
         [0037]     The upper edge of the internal wall of the double-wall funnel is joined with the edge of the dish-type plate and the edge of its outer wall is provided with a flange.  
         [0038]     The distal (lower) aperture of the double-wall funnel can be glazed in order to diminish heat losses via its internal cavity. In addition, this glazing can be provided with a transparent coating, which reflects back infrared radiation from the layer of the solar radiation absorption coating of the dish-type plate.  
         [0039]     The internal surface of the internal wall of the double-wall funnel can be provided with the property of high reflectivity for solar radiation; in such a way, this internal wall plays a role of an additional non-imaging concentrator of the solar radiation.  
         [0040]     There is a bearing housing with a split lower flange and two longitudinal slots; this housing is mounted on the thermal insulation of the T-piece.  
         [0041]     The open sections of the longitudinal slots are closed by a clamp.  
         [0042]     The flanges of the bearing housing and the outer wall of the double-wall funnel are joined by a flexible joint, which plays at the same time a role of a thermal insulator.  
         [0043]     The outer wall of the double-wall funnel serves at the same time for mounting truss struts, which serve in turn for installation of a dish-type concentrating mirror with its frame.  
         [0044]     The frame of the dish-type mirror is joined through cylindrical hinges with tracking rods.  
         [0045]     The internal cavity between the walls of the double-wall funnel and between the flexible joint and the lower branch of the T-piece can be filled with thermo-insulating material with low thermal conductivity.  
         [0046]     It should be noted that heat transfer from the internal surface of the spherical cap to the working medium is performed mainly by natural convection, conduction and boiling. In order to diminish temperature drop between this internal surface and the working medium, the internal surface of the spherical cap may be provided with fins and/or a porous coating from metal powder; this porous coating has open porosity.  
         [0047]     It is possible to apply a funnel with a single wall instead of the aforementioned double-wall funnel; in this case the lower edge of the funnel is joined with a connecting branch with a flange; this connecting branch is joined in turn with the lower flange of the flexible joint. The truss struts are joined in this case with the connecting branch.  
         [0048]     In addition, it is possible to obviate application of the dish-type plate. The outer surface of the metal convex spherical cap is provided in this case with a radiation absorption coating. This coating must be stable against friction with the upper edge of the aforementioned double- or single-wall funnel.  
         [0049]     A solar radiation collector can be assembled from some solar radiation modular collectors, which are described above; these some solar radiation modular collectors are placed in the form of parallel rows and bearing pipes are interconnected in series in each row.  
         [0050]     The solar radiation modular collectors, which are positioned in parallel and/or belong to one set of interconnected in series bearing pipes, have the common tracking units. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0051]      FIG. 1  is a transverse cross-section of a receiver of a concentrated solar radiation collector module with a concentrating single-curvature unit.  
         [0052]      FIG. 2  is an isometric view of an internal section of a metal envelope of the receiver, which is shown in  FIG. 1 , with corrugations directed inwards.  
         [0053]      FIG. 3  is an isometric view of an external section of the metal envelope of the receiver, which is shown in  FIG. 1 , with corrugations directed outwards.  
         [0054]      FIG. 4  is an axial cross-section of a radiation receiving pipe of the receiver, which is shown in  FIG. 1 .  
         [0055]      FIG. 5  is a transverse cross-section of the solar radiation collector modules with concentrating single-curvature units and with some elements of a tracking mechanism.  
         [0056]      FIG. 6  is a longitudinal cross-section of the solar radiation collector module with a concentrating compound-curvature unit and with some elements of a tracking mechanism.  
         [0057]      FIG. 7  is a cross-section of a combined unit: a T-piece—solar radiation receiver with application of a double-wall funnel and a dish-type radiation absorption plate.  
         [0058]      FIG. 8  is a cross-section of a combined unit: a T-piece—solar radiation receiver with application of a single-wall funnel and a dish-type radiation absorption plate.  
         [0059]      FIG. 9  is a cross-section of a combined unit: a T-piece—solar radiation receiver with application of a metal convex spherical cap for absorption of concentrated solar radiation.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0060]      FIG. 1  shows the transverse cross-section of the receiver of concentrated solar radiation with a concentrating single-curvature unit.  
         [0061]     It comprises: a radiation receiving pipe  101  with a selective coating  102  of its outer surface and low circular ribs  103 , and a metal envelope  104 .  
         [0062]     This metal envelope includes an internal elongated section  105  and an external elongated section  106 , which are joined by two elongated connection straps  107  and sealed at their ends by face planes; the internal elongated section  105  comprises in turn a cylindrical sub-section  108 , which encloses a significant part of the radiation receiving pipe  101 ; this cylindrical sub-section  108  is transformed at its longitudinal margins to flat strips  109  with a certain angle of convergence with respect to the cylindrical sub-section  108 .  
         [0063]     The external elongated section  106  comprises a cylindrical sub-section  110 , which encloses the cylindrical sub-section  108 ; this cylindrical sub-section  110  is transformed at its longitudinal margins to flat strips  111  with the same angle of convergence as the flat strips  109 .  
         [0064]     Two elongated connection straps  112  join the flat strips  109  and  111 .  
         [0065]     The internal space between the internal and external sections is evacuated in order to suppress convective losses of heat. In addition, this space can be filled with a porous filler  113 .  
         [0066]     In addition, radiation shields in the form of metal foils  114  are situated in the internal cavity of the metal envelope  104 .  
         [0067]     The flat strips  109  are provided with longitudinal clamps  115 , which serve for fastening glazing  116 .  
         [0068]      FIG. 2  demonstrates the isometric view of the internal section of the metal envelope with corrugations directed inwards.  
         [0069]     It comprises a cylindrical sub-section  201 , which is transformed at its longitudinal margins to flat strips  202 .  
         [0070]     The cylindrical sub-section  201  and the flat strips  202  are provided with corrugations  203 , which decrease to zero at their lower margins, these corrugations  203  are directed inwards with respect to the cylindrical sub-section  201 .  
         [0071]      FIG. 3  is an isometric view of an external section of the metal envelope with corrugations directed outwards.  
         [0072]     It comprises a cylindrical sub-section  301 , which is transformed at its longitudinal margins to flat strips  302 .  
         [0073]     The cylindrical sub-section  301  and the flat strips  302  are provided with corrugations  303 , which decrease to zero at their lower margins, these corrugations  303  are directed outwards with respect to the cylindrical sub-section  301 .  
         [0074]      FIG. 4  demonstrates an axial cross-section of the radiation receiving pipe. It comprises a metal pipe  401  that is provided with two bellows  402  at its extreme sections, these bellows are intended to compensate thermal expansion of the metal pipe  401 . The outer surface of the metal pipe  401  is provided with a selective coating  403 . It should be noted, that this selective coating could cover only the part of the outer surface, which can be irradiated by the concentrated solar radiation. In addition, the metal pipe  401  is provided with low ribs  404 , which prevent immediate contact of the selective coating  403  with the surface of the internal section of the metal envelope in the process of its turning around the metal pipe  401 . The cylindrical surfaces of the low ribs are provided with antifriction coatings  405 .  
         [0075]     Flanges  406  are installed on the ends of the metal pipe  401 .  
         [0076]      FIG. 5  is a transverse cross-section of two solar radiation collectors positioned in parallel with a common tracking rod and with a concentrating single-curvature units.  
         [0077]     It shows posts  501  with pipes  502  installed on their upper sections. A metal envelope  503 , which is provided with glazing  504 , is situated on pipe  502  and can rotate around this pipe. Truss struts  505  serve for fastening frames  506 , which in turn serve for installation of parabolic trough-wise mirrors  507 . A common tracking rod  508  is joined by hinged units  509  with frames  506 . This allows to perform tracking after the sun motion by a common tracking unit.  
         [0078]      FIG. 6  shows a longitudinal cross-section of the solar radiation collector module with a concentrating compound-curvature unit and with some elements of a tracking mechanism.  
         [0079]     It comprises bearing pipes  601  with expansion units  621 , which are mounted on vertical posts  602 . A working medium flows in the bearing pipes  601 . The bearing pipes  601  are provided with layers  603  of a thermal insulation.  
         [0080]     T-piece  604  is built into the bearing pipes  601 . The lower branch of T-piece  604  is sealed by a metal convex spherical cap  605 .  
         [0081]     T-piece  604  is covered with layer  606  of a thermal insulation.  
         [0082]     In addition, there is a solar radiation receiving member, which constructed from a dish-type plate  607  and a double-wall funnel  608 .  
         [0083]     The upper side of the dish-type plate  607  has the concave surface in the form of a spherical segment with the radius almost identical to that of the metal convex spherical cap  605 . In such a way, this pair: the metal convex spherical cap  605  and the concave surface of the dish-type plate  607  present a spherical joint.  
         [0084]     The lower surface of the dish-type plate  607  is covered with layer  608  of a solar radiation absorption coating.  
         [0085]     The upper edge of the internal wall of the double-wall funnel  608  is joined with the edge of the dish-type plate  607  and the edge of its outer wall is provided with flange  609 .  
         [0086]     The distal (lower) aperture of the double-wall funnel  608  is glazed by glazing  610  in order to diminish heat losses via its internal cavity.  
         [0087]     There is a bearing housing  611  with a split lower flange  612  and two longitudinal slots; this bearing housing  611  is mounted on the thermal insulation  606  of T-piece  604 .  
         [0088]     The open sections of the longitudinal slots of the bearing housing  611  are closed by a clamp. The flanges  612  and  609  of the bearing housing  611  and of the outer wall of the double-wall funnel  608  are joined by a flexible joint  613 , which plays at the same time a role of a thermal insulator.  
         [0089]     The outer wall of the double-wall funnel  608  serves at the same time for mounting truss struts  614 , which in turn serve for installation of a dish-type concentrating mirror  615  with its frame  616 .  
         [0090]     Frame  616  of the dish-type concentrating mirror  615  is joined through cylindrical hinges  619  and  620  with tracking rods  617  and  618 .  
         [0091]      FIG. 7  demonstrates a cross-section of a combined unit: a T-piece—solar radiation receiver with application of a double-wall funnel and a dish-type radiation absorption plate.  
         [0092]     It comprises: bearing pipes  701  and  702  with insulting layers  703  and  704 ; T-piece  705  with an insulating layer  706 , the lower branch of this T-piece  705  is sealed by a metal convex spherical cap  707 . In addition, there is a solar radiation receiving member, which is constructed from a dish-type plate  708  and a double-wall funnel  709 .  
         [0093]     The upper side of the dish-type plate  708  has the concave surface in the form of a spherical segment with the radius almost identical to that of the metal convex spherical cap  707 . In such a way, this pair: the metal convex spherical cap  707  of T-piece  705  and the concave surface of the dish-type plate  708  present a spherical joint.  
         [0094]     The lower surface of the dish-type plate  708  is covered with layer  710  of solar radiation absorption coating.  
         [0095]     The upper edge of the internal wall of the double-wall funnel  709  is joined with the edge of the dish-type plate  708  and the edge of its outer wall is provided with flange  711 .  
         [0096]     The distal (lower) aperture of the double-wall funnel  709  is glazed with glazing  712 .  
         [0097]     There is a bearing housing  713  with a split lower flange  714  and two longitudinal slots; this bearing housing  713  is mounted on the thermal insulation  706  of T-piece  705 .  
         [0098]     Flanges  714  and  711  of the bearing housing  713  and of the outer wall of the double-wall funnel  709  are joined by a flexible joint  715 , which plays at the same time a role of a thermal insulator.  
         [0099]     The outer wall of the double-wall funnel  709  serves at the same time for mounting truss struts  716 , which in turn serve for installation of a dish-type concentrating mirror with its frame.  
         [0100]      FIG. 8  shows a cross-section of a combined unit: a T-piece—solar radiation receiver with application of a single-wall funnel and a dish-type radiation absorption plate.  
         [0101]     It comprises: bearing pipes  801  and  802  with insulting layers  803  and  804 ; T-piece  805  with an insulating layer  806 , the lower branch of T-piece  805  is sealed by a metal convex spherical cap  807 . In addition, there is a solar radiation receiving member, which constructed from a dish-type plate  808  and a single-wall funnel  809 .  
         [0102]     The upper side of the dish-type plate  808  has the concave surface in the form of a spherical segment with the radius almost identical to that of the metal convex spherical cap  807 . In such a way, this pair: the metal convex spherical cap  807  of the T-piece and the concave surface of the dish-type plate  808  present a spherical joint.  
         [0103]     The lower surface of the dish-type plate  808  is covered with layer  810  of a solar radiation absorption coating.  
         [0104]     The lower edge of the single-wall funnel  809  is joined with a connecting branch  811  with flange  812 , which is joined in turn with the lower flange of a flexible joint  813 . Truss struts  814  are joined in this case with the connecting branch  811 , these truss struts serve in turn for installation of a dish-type concentrating mirror with its frame.  
         [0105]     The distal (lower) aperture of the single-wall funnel  809  is glazed with glazing  815 .  
         [0106]     There is a bearing housing  816  with a split lower flange  817  and two longitudinal slots; this bearing housing  816  is mounted on the thermal insulation  806 . The split lower flange  817  of the bearing housing  816  is joined with the flexible joint  813 , which plays at the same time a role of a thermal insulator serving in turn for installation of a dish-type concentrating mirror with its frame.  
         [0107]      FIG. 9  is a cross-section of a combined unit: a T-piece—solar radiation receiver with application of a metal convex spherical cap for absorption of concentrated solar radiation.  
         [0108]     It comprises: bearing pipes  901  and  902  with insulting layers  903  and  904 ; T-piece  905  with an insulating layer  906 , the lower branch of T-piece  905  is sealed by a metal convex spherical cap  907 .  
         [0109]     The outer surface of the metal convex spherical cap  907  is provided with a radiation absorption coating  908 .  
         [0110]     There is a double-wall funnel  909 ; the upper edge of this double-wall funnel is in immediate contact with the radiation absorption coating  908  of the metal convex spherical cap  907 , and the double wall funnel  909  can be turned in two directions around this metal convex spherical cap  907 .  
         [0111]     In such a way, this pair: the metal convex spherical cap  907  of T-piece  905  and the double-wall funnel  909  present a spherical joint.  
         [0112]     The outer edge of the outer wall of the double-wall funnel  909  is provided with flange  910 .  
         [0113]     The distal (lower) aperture of the double-wall funnel  909  is glazed with glazing  911 .  
         [0114]     There is a bearing housing  912  with a split lower flange  913  and two longitudinal slots; this bearing housing  912  is mounted on the thermal insulation  906  of T-piece  905 .  
         [0115]     Flanges  913  and  910  of the bearing housing  912  and of the outer wall of the double-wall funnel  909  are joined by a flexible joint  914 , which plays at the same time a role of a thermal insulator. The outer wall of the double-wall funnel  909  serves at the same time for mounting truss struts  915 , which serve in turn for installation of a dish-type concentrating mirror with its frame.  
         [0116]     Other embodiments and configurations may be devised without departing from the spirit of the invention and the scope of appended claims.