Parabolic trough solar collector

Abstract

The invention relates to a parabolic trough solar collector (1), comprising: - a parabolic trough reflector (200) consisting of a matrix array of reflective tiles with a parabolic segment cross-section (210), said tiles arranged in rows and columns; - an absorber tube arranged along the linear focal point of the reflector and inside which a heat-transfer fluid circulates; - a frame (100) supporting the absorber tube as well as the reflector, the frame comprising an elongate central torsion body (110) oriented parallel to the linear focal point of the reflector as well as a plurality of curved support arms (120) extending symmetrically pairwise on either side of this elongate central body and to which the reflective tiles are attached; characterised in that each of the reflective tiles comprises a concrete base covered by a mirror on the concave upper face thereof.

Description

[0001] Cylindro-parabolic solar collector

[0002] [The present invention relates to the field of solar energy capture and more particularly relates to a solar collector of the cylindrical-parabolic type.

[0003] Due to its abundant availability, its renewable nature, its reduced environmental impact compared to fossil fuels and its ability to be used in remote locations or those not connected to the electricity grid, solar energy has many advantages.

[0004] Among the various technological solutions aimed at capturing part of this energy, solar collectors make it possible to capture solar radiation and transmit its thermal energy to a heat transfer fluid in the form of heat.

[0005] In particular, cylindro-parabolic collectors are known which comprise a cylindro-parabolic reflector and focus the captured light rays towards an absorber tube arranged along the linear focus of this reflector.

[0006] The tube contains a heat transfer fluid, usually oil or water, which circulates to absorb the heat generated by sunlight. The absorbed heat can then be used to produce steam, which can be used to generate electricity using a steam turbine or to provide heat for industrial processes or heating systems.

[0007] The main advantage of parabolic trough collectors is their ability to concentrate sunlight into a narrow linear area, resulting in higher temperatures and better solar energy conversion efficiency.

[0008] Furthermore, parabolic trough collectors can be used in a modular manner and combined to form large-scale solar collection systems capable of producing a significant amount of electricity or heat.

[0009] Such a cylindro-parabolic collector typically comprises a frame supporting the absorber tube as well as a matrix network of reflecting tiles with a section in the form of a portion of a parabolic dish, arranged in rows and columns so as to constitute the cylindro-parabolic reflector.

[0010] As disclosed for example by document WO 2013 / 084016 A1, the support frame generally comprises an elongated central torsion body oriented parallel to the linear focus of the cylindro-parabolic reflector and making it possible to limit the deformations of the reflector due to the torsional forces that it undergoes due to its own mass and external forces such as the wind.

[0011] Made of galvanized steel or aluminum, this elongated central body is usually in the form of a cylindrical tube or tubular frame.

[0012] Such a support frame also comprises a plurality of curved support arms extending symmetrically two by two on either side of this elongated central body in directions perpendicular to the linear focus of this reflector and on which the reflective slabs are fixed.

[0013] Made for example from welded metal tubes or a stamped sheet metal side, these arms allow the load and rigidity to be distributed evenly along the surface of the reflector.

[0014] The chassis is also generally mounted pivoting around a longitudinal axis parallel to the linear focus of the parabolic trough reflector by means of pylons rigidly anchored to the ground via concrete foundations.

[0015] Reflective tiles are conventionally formed by a mirror comprising a "thick" glass substrate (thickness of at least 4 millimeters) so as to present a certain resistance to deformation, as well as a reflective layer generally made of silver applied against the convex lower face of this substrate.

[0016] Generally fixed at four points to two adjacent support arms, these reflective slabs unfortunately tend to deform at their four corner areas in strong winds, which causes them to be defocused and a significant reduction in the solar energy absorbed by the heat transfer fluid circulating in the absorber tube, which can lead to the solar collector being shut down.

[0017] It is also known to produce these reflective tiles from an aluminium sheet onto which a reflective polymer film is glued, these sheets then being mounted to slide along curved guide rails provided on the support frame so as to give them a parabolic section profile.

[0018] Unfortunately, these reflective aluminum tiles also tend to warp, which also causes problems focusing the light rays on the absorber tube.

[0019] In addition, these reflective tiles are particularly difficult to install because they require the use of lifting cradles supporting the aluminum rolls.

[0020] We also know of reflective tiles developed by the German company ToughTrough® and made up of a reflective coating based on a "thin" glass substrate about one millimeter thick covering a polyurethane foam core on the back of which is affixed a composite back layer made of steel and glass fibers.

[0021] The German company Solarlite® offers reflective tiles made from a hollow base made from a resin / glass fiber composite material, this base being filled with a foam core and covered with a mirror based on a "thin" glass substrate.

[0022] These latter types of reflective slabs made from composite material are unfortunately particularly expensive to produce. Furthermore, due to their relatively low mass, the anchor pylons of collectors equipped with these slabs must be associated with more massive concrete foundations to ensure satisfactory anchoring to the ground.

[0023] Recently, a new type of parabolic trough solar collector was developed by an international consortium within the framework of the CONSOL® project. This collector comprises a support frame consisting of a concrete shell with a parabolic trough surface made from a single piece and on which rests a reflector made of several flexible aluminum sheets coated with a reflective coating and glued to the concave upper surface of this support shell. Similar to this solution, we can also cite the patent application published under number DE 31 33 906 A1.

[0024] Although these latter solutions seem attractive at first glance, the construction of such a concrete shell is particularly complex and expensive to implement. Furthermore, due to its size and mass, this shell cannot be transported and must therefore be built on site.

[0025] The present invention therefore aims to at least partially remedy the aforementioned drawbacks.

[0026] For this purpose, it offers a parabolic-cylindrical type solar collector comprising:

[0027] - a cylindro-parabolic reflector consisting of a matrix network of reflective tiles with a section in the form of a portion of a parabolic dish, arranged in rows and columns;

[0028] - an absorber tube arranged along the linear focus of said reflector and inside which a heat transfer fluid circulates;

[0029] - a frame supporting said absorber tube as well as said reflector, said frame comprising an elongated central torsion body oriented parallel to the linear focus of said reflector as well as a plurality of curved support arms extending symmetrically two by two on either side of this elongated central body and to which said reflective slabs are fixed.

[0030] According to the invention, each of said reflective slabs comprises a corresponding concrete base covered on its concave upper face by a mirror. Such a conformation of the reflective slabs forming the reflector ensures excellent mechanical rigidity, making it possible to avoid any risk of deformation and defocusing even in the event of strong wind.

[0031] Furthermore, the cost price of the parabolic trough collector according to the invention proves to be particularly reasonable in comparison in particular with parabolic trough collectors whose reflector is made up of slabs equipped with a base made of composite material.

[0032] Finally, due to the greater mass of its concrete base slabs, the parabolic trough collector naturally has better anchoring to the ground, which makes it possible to reduce the volume and mass of the buried foundations.

[0033] For reasons of cost and ease of manufacture, the base of each said reflective tile preferably has a flat lower face.

[0034] In order to limit the mass of the reflective tiles, their base advantageously has a thickness of less than or equal to 50 millimeters at the thinnest zone, this thickness preferably being between 30 and 40 millimeters.

[0035] In order for these reflective tiles to have excellent bending resistance, their base is preferably made of reinforced concrete.

[0036] In order to avoid any risk of corrosion, it is also possible to alternatively make these bases in fiber-reinforced concrete.

[0037] According to a first preferred embodiment, the mirror of each said reflective slab preferably comprises a transparent substrate covered on its convex lower face with a reflective layer.

[0038] This transparent substrate is preferably made of glass due to its excellent light transmission combined with controlled cost.

[0039] In order to provide it with a certain flexibility allowing it to be cold-bent, this transparent substrate advantageously has a thickness less than or equal to two millimeters. According to a second preferred embodiment, the mirror of each said reflective slab is constituted by a reflective coating directly affixed against the concave upper face of said base.

[0040] In order to allow the reflector to follow the sun in its daily path, the frame is advantageously mounted to pivot around a longitudinal axis parallel to the linear focus of said reflector by means of two pylons arranged near the two longitudinal ends of this frame.

[0041] Furthermore, the height of said pylons defining the distance between the ground and said longitudinal pivot axis of said chassis is preferably defined so as to allow the latter to pivot through 360°.

[0042] Finally, this pivoting articulation of said chassis with respect to said pylons is ensured for example by means of two cylindrical pins projecting at the two longitudinal ends of said elongated torsion body and cooperating with two rotating joints arranged at the tops of said pylons.

[0043] The invention also relates, in a second aspect, to a solar collection assembly formed from at least one alignment of several such cylindrical-parabolic solar collectors.

[0044] The description of the invention will now be continued by the detailed description of an exemplary embodiment, given below for illustrative but non-limiting purposes, with reference to the appended drawings, in which:

[0045] - figure 1 is a perspective view of a cylindrical-parabolic solar collector according to the invention;

[0046] - Figure 2 represents an exploded perspective view from another angle of the cylindrical-parabolic solar collector according to the invention; and

[0047] - Figure 3 represents a sectional view of one of the reflective slabs forming the parabolic trough reflector.

[0048] Figures 1 and 2 represent a parabolic trough solar collector

[0049] 1 according to the invention. An orthogonal reference frame XYZ is defined with respect to this solar collector 1, comprising three axes perpendicular two by two, namely

[0050] - an X axis, defining a longitudinal, horizontal direction, parallel to the linear focus of this solar collector 1;

[0051] - a Y axis, defining a transverse, horizontal direction, which with the X axis defines a horizontal XY plane, and

[0052] - a Z axis, defining a vertical direction, perpendicular to the horizontal XY plane.

[0053] In the remainder of the description and with reference to the reference defined above, the terms “longitudinal” or “longitudinally” will refer to a direction parallel to the X axis, the terms “transverse” or “transversely” will refer to a direction parallel to the Y axis, and the terms “vertical” or “vertically” will refer to a direction parallel to the Z axis.

[0054] On the other hand, the terms "front" and "rear" will be used to specify the longitudinal positioning of certain elements relative to the orientation of the X axis. Similarly, the terms "upper" and "lower" will be used to specify the relative position of certain elements relative to the orientation of the Z axis.

[0055] The terms "external" and "internal" will be used to define the relative position of an element with reference to the median vertical longitudinal plane of the solar collector 1. The element closest to this plane will thus be called internal as opposed to the other element further from this same plane which will be called external.

[0056] Finally, the term "substantially" indicates that a slight deviation is allowed from a predetermined nominal orientation, while remaining included in the scope of the invention. For example, "substantially vertical" indicates that a deviation of the order of 10° to 20° from a strictly vertical orientation is allowed within the scope of the invention. With reference to these figures 1 and 2, the cylindrical-parabolic solar collector 1 comprises a frame 100 supporting a cylindrical-parabolic reflector 200 as well as an absorber tube 300 extending along the linear focus of this reflector 200 in order to receive the light rays captured and reflected by the latter.

[0057] Inside this absorber tube 300, a heat transfer fluid circulates, typically consisting of oil or water, and designed to absorb the heat generated by the light rays striking this tube.

[0058] The frame 100 conventionally comprises an elongated central torsion body in the form of a beam 110, oriented parallel to the linear focus of the cylindrical-parabolic reflector 200 and making it possible to limit the deformations of this reflector 200 due to the torsional forces which it undergoes due to its own mass and external forces such as the wind.

[0059] According to alternative embodiments not shown, the elongated central body 110 of the support frame 100 may be shaped differently, it being able, for example, to take the form of a cylindrical tube or a tube with a polygonal section (for example, square or hexagonal).

[0060] This frame 100 also comprises a plurality of curved lateral support arms 120 extending symmetrically two by two on either side of the elongated central torsion body 110 to which they are rigidly fixed and in directions perpendicular to the linear focus of the reflector 200.

[0061] In this case, these support arms 120 are sixteen in number (eight on each side of the elongated central torsion body 110) and are distributed at regular intervals along the latter.

[0062] The support frame 100 is further pivotally mounted around a longitudinal axis A parallel to the linear focus of the cylindrical-parabolic reflector 200 by means of two pylons 400 arranged near the two longitudinal ends of this frame 100.

[0063] As illustrated in Figure 2, the pivoting articulation of this support frame 100 with respect to these two pylons 400 is advantageously ensured by means of two cylindrical metal pins 111 projecting at the two longitudinal ends of the elongated central torsion body 110 and cooperating with two rotating joints 410 arranged at the tops of the pylons 400.

[0064] Each pin 111 extends in this case from a respective metal plate 112 fixedly attached by screwing onto a longitudinal end of the elongated central torsion body 110.

[0065] According to embodiment variants not shown, these transmission means may differ by being, for example, of the worm screw type.

[0066] The height of the pylons 400 defining the distance between the ground and the pivot axis A of the chassis 100 (and therefore of the reflector 200) will be advantageously defined so as to allow this reflector 200 to pivot through 360° in order to follow the sun in its daily path and thus capture solar radiation in optimal conditions.

[0067] As illustrated in Figure 2, the cylindro-parabolic reflector 200 consists of a matrix network of nxm reflecting tiles 210 with a section in the form of a portion of a parabola, arranged in n longitudinal lines parallel to the linear focus of this reflector 200 and m transverse columns.

[0068] Advantageously having a longitudinal dimension at least twice its transverse dimension, each reflective slab 210 is fixed to two adjacent support arms 120.

[0069] In the embodiment illustrated in the figures, the reflector 200 is made up of twenty-four reflective tiles 210 arranged in six longitudinal lines (n equal to 6) and four transverse columns (m equal to 4), these tiles 210 each having dimensions of approximately three meters long and 0.9 to 1.25 meters wide, such that this reflector 200 extends longitudinally over a dozen meters with a transverse opening of approximately six meters.

[0070] According to embodiment variants not shown, the dimensions of each reflective slab 210 as well as the number of lines n and / or columns m may differ depending in particular on the dimensions that one wishes to give to the reflector 200 in length and / or in opening. It will be noted with reference to FIG. 2 that the width of these slabs 210 advantageously increases with their transverse spacing relative to the elongated central torsion body 110.

[0071] According to the invention and as illustrated in the sectional view of Figure 3, each reflective slab 210 comprises a concrete base 211 covered on its concave upper face by a mirror 212.

[0072] For reasons of ease and cost of manufacture, the base 211 has a flat lower face so as to allow the pouring of concrete into a formwork open on top and the convex lower face of which has a profile in the form of a portion of a parabola corresponding to that which one wishes to give to the concave upper face of this base 311.

[0073] In order to limit the mass of the reflective tiles 210, this base 211 will advantageously have at its thinnest zone a thickness e less than or equal to 50 millimeters and preferably between 30 and 40 millimeters.

[0074] Furthermore, and so that these reflective tiles 210 have excellent resistance to bending, their base 211 will preferably be made of reinforced concrete, for example with stainless steel or galvanized steel reinforcement in order to protect it from corrosion.

[0075] In order to avoid any risk of corrosion, it is also possible to make these 211 bases in fiber-reinforced concrete, although this may have a negative impact on the cost price and bending strength.

[0076] Fixedly affixed by gluing to a corresponding base 211 by suitable means (for example epoxy or polyurethane glue or even double-sided adhesives), the mirror 212 of each reflective panel 210 advantageously comprises a transparent substrate covered on its convex lower face with a reflective layer, for example silver.

[0077] Preferably made of glass due to its excellent light transmission combined with controlled cost, this transparent substrate advantageously has a thickness less than or equal to two millimeters and even more advantageously less than or equal to one millimeter.

[0078] The use of such a transparent "thin" glass substrate with a certain flexibility thus allows it to be cold-bent by gravity, which proves to be particularly advantageous from an economic point of view.

[0079] The mirrors 212 may also comprise at least one protective layer, including in particular a copper or tin layer applied against the reflective layer so as to prevent it from tarnishing and to allow the mirror 212 to be bonded against the base 211.

[0080] According to alternative embodiments, the mirrors 212 of the reflective panels 210 can be made differently.

[0081] Each mirror 212 may thus comprise an aluminum substrate covered on its concave upper face with a thin reflective layer deposited for example via a physical vapor deposition process (commonly referred to by the English acronym PVD for “Physical Vapor Deposition”). One or more protective layers may also be applied against this reflective layer.

[0082] This thin reflective layer can, for example, be made from a reflective polymer film such as the “Solar Mirror Film 1100” film produced by the American company 3M®.

[0083] According to another embodiment, the mirror 212 of each reflective panel 210 may consist of a reflective coating directly applied against the concave upper face of the base 211 of this panel 210.

[0084] Many variant embodiments are of course conceivable and it is recalled in this regard that the present invention is not limited to the embodiments described and shown, but also encompasses all variant embodiments within the reach of those skilled in the art.

Claims

CLAIMS 1. [Solar collector of the parabolic trough type (1) comprising; - a cylindro-parabolic reflector (200) consisting of a matrix network of reflective tiles with a section in the form of a portion of a parabolic element (210), arranged in rows and columns; - an absorber tube (300) arranged along the linear focus of said reflector (200) and inside which a heat transfer fluid circulates; - a frame (100) supporting said absorber tube (300) as well as said reflector (200), said frame (100) comprising an elongated central torsion body (110) oriented parallel to the linear focus of said reflector (200) as well as a plurality of curved support arms (120) extending symmetrically two by two on either side of this elongated central body (110) and to which said reflective slabs (210) are fixed; characterized in that each of said reflective slabs (210) comprises a corresponding concrete base (211) covered on its concave upper face by a mirror (212).

2. Solar collector (1) according to claim 1, characterized in that the base (211) of each said reflective slab (210) has a flat lower face.

3. Solar collector (1) according to one of claims 1 or 2, characterized in that the base (211) of each said reflective slab (210) has at its thinnest zone a thickness (e) less than or equal to 50 millimeters.

4. Solar collector (1) according to claim 3, characterized in that said thickness (e) is between 30 and 40 millimeters.

5. Solar collector (1) according to one of claims 1 to 4, characterized in that the base (211) of each said reflective slab (210) is made of reinforced concrete.

6. Solar collector (1) according to one of claims 1 to 4, characterized in that the base (211) of each said reflective slab (210) is made of fiber concrete.

7. Solar collector (1) according to one of claims 1 to 6, characterized in that the mirror (212) of each said reflective slab (212) comprises a transparent substrate covered on its convex lower face with a reflective layer.

8. Solar collector (1) according to claim 7, characterized in that said transparent substrate is made of glass.

9. Solar collector (1) according to one of claims 7 or 8, characterized in that said transparent substrate has a thickness less than or equal to two millimeters.

10. Solar collector (1) according to one of claims 1 to 6, characterized in that the mirror (212) of each said reflective slab (212) is constituted by a reflective coating directly affixed against the concave upper face of said base (211).

11. Solar collector (1) according to one of claims 1 to 10, characterized in that said frame (100) is pivotally mounted around a longitudinal axis. (A) parallel to the linear focus of said reflector (200) by means of two pylons (400) arranged near the two longitudinal ends of this frame (100).

12. Solar collector (1) according to claim 11, characterized in that the height of said pylons (400) defining the distance between the ground and said longitudinal pivot axis (A) of said frame (100) is defined so as to allow the latter to pivot through 360°.

13. Solar collector (1) according to one of claims 11 and 12, characterized in that the pivoting articulation of said frame (100) with respect to said pylons (400) is ensured by means of two cylindrical pins (111) projecting at the two longitudinal ends of said elongated torsion body (110) and cooperating with two rotating joints (410) arranged at the tops of said pylons (400).

14. Solar collection assembly formed from at least one alignment of several cylindrical-parabolic solar collectors according to one of claims 1 to 13.|

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