FIELD OF THE INVENTION The present invention relates to a system for concentration of solar energy to generate heat and/or power. More specifically, the present invention is concerned with a system of modular solar units.
OBJECT OF THE INVENTION An object of the invention is an assembly of units consisting of mirrors assembled along at least one parabolic arch, each mirror comprising two opposing lateral edges and opposing inner and outer longitudinal edges, each mirror being longitudinally secured to another mirror along their respective inner longitudinal edges by at least one securing device positioned at the centre of the parabolic arch, and secured at each lateral edge to wheels supports.
Other objects, advantages and functions of the resent invention will become apparent in the following description of possible embodiments, given as examples only, in relation to the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS In the appended drawings:
FIG. 1 is a top view of an assembly according to an embodiment of an aspect of the present invention;
FIG. 2A is a perspective view of the assembly of FIG. 1;
FIG. 2B is an exploded view of the assembly of FIG. 1;
FIG. 3A is a schematical exploded view of the internal structure of a mirror according to an embodiment of an aspect of the present invention;
FIG. 3B shows a detail of FIG. 3A;
FIG. 4A is a bottom view of a mirror according to an embodiment of an aspect of the present invention;
FIG. 4B is a side view of a mirror according to an embodiment of an aspect of the present invention;
FIG. 5A is an exploded view of a wheel, with cross plates, reinforcements and fixation holes according to an embodiment of an aspect of the present invention;
FIG. 5B is a perspective view of a wheel according to an embodiment of an aspect of the present invention;
FIG. 6 is a side view of a cross plate of the wheel of FIG. 5;
FIG. 7 is an exploded view of a wheel support according to an embodiment of an aspect of the present invention;
FIG. 8A is a top view of the wheel support of FIG. 7;
FIG. 8B is a perspective view of the wheel support of FIG. 7
FIG. 8C is a side view of the wheel support of FIG. 7;
FIG. 8D is an end view of the wheel support of FIG. 7;
FIG. 9A is a perspective view of a wheel support allowing anchoring of an assembly according to an embodiment of an aspect of the present invention;
FIG. 9B is a side view of the wheel support of FIG. 9A;
FIG. 10A is a perspective view of a wheel support with a motorised unit according to an embodiment of an aspect of the present invention;
FIG. 10B is an exploded view of the wheel support of FIG. 10A;
FIG. 11 schematically shows a unit of two mirror sections connected using a continuous central member according to an embodiment of an aspect of the present invention;
FIG. 12 is a side view of the unit of FIG. 11;
FIG. 13 schematically shows a unit of two mirror sections connected using connecting members according to an embodiment of an aspect of the present invention;
FIG. 14 shows an securing device between two mirror sections according to another embodiment of an aspect of the present invention; and
FIG. 15A-FIG. 15E are side views of an assembly in different angular orientation orientations according to an embodiment of an aspect of the present invention.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION FIG. 1 illustrates a collector according to an embodiment of an aspect of the present invention. The illustrated collector consists of a structural row of units each comprising two mirror sections 6a, 6b symmetrically positioned relative to a concentrator line 5, which extends at the center of the two mirror sections 6a, 6b and contains a heat-transfer fluid, along a parabolic arch (see FIG. 14 for example), and wheels 4 of a smaller size than the assembled mirror sections 6a, 6b, i.e. the radius D/2 of the wheels 4 is smaller than the width d of each section 6a, 6d (D<2d). The assembly of the two mirror sections 6a, 6b can pivot completely from a position in which the concave surface of the collector, formed by the two mirror sections 6a, 6b, is oriented upwards (see FIG. 15D) to a position in which the convex surface of the collector, formed by the two mirror sections 6a, 6b, is oriented upwards (see FIG. 15A).
Each mirror 6a, 6b comprise two opposing lateral edges 25, 27 and two opposing inner 21 and outer 23 longitudinal edges, each one of the two mirrors being longitudinally secured with the other one, i) along their respective inner longitudinal edges 23 by at least one securing device positioned at the centre of the parabolic arch they form and discussed hereinbelow in relation to FIGS. 11-14 for example; and ii) at each lateral edge 25, 27 by a wheel support 31 at at least two distinct support points 39, 33 (see FIG. 2).
FIG. 2B shows the assembly of mirror sections 6a, 6b, wheels 4 and the concentrator line 5. Supporting arms, or caloarms 13 support the concentrator line 5 between the wheels 4, at the center of the parabolic arch. Such supporting arms 13, located only at the center of the parabolic arch, as opposed to at its extremities, allow uniting the assembly on as many points and thus distributing the loads uniformly.
FIG. 3A is an exploded schematic view of the sandwich composition of a mirror section. Each mirror section is structuring. Different layers form an internal structure that is non uniform in the body thereof. Details of reinforcing elements between the mirrors and the wheels are also shown. Structuring elements, comprising for example a mirror plate 12, a rear plate 14, an inner extrusion 9, i.e. along the inner longitudinal edge 23, an outer extrusion 10, i.e. along the outer longitudinal edge 21, and an intermediate longitudinal reinforcement 2, form an envelope and allow distributing the load on a large surface thus reducing the risks of tearing or breakage of the mirrors. Mirror anchoring rods 130 provide a mechanical link between the wheels and the mirror sections. A lower bow 1 allows rigidifying the structure at the position of the anchoring rods 130. The internal structure of the mirror thus comprises at least two inner layers, i. e. an upper layer 15, based on a triaxle glass fiber or carbon fiber for example, of a thickness forming preferably at most 5% of the thickness of the mirror, and a lower layer 16, based on rigid foam such as polystyrene for example. Out of the two outer layers forming the envelope, i.e. the mirror plate 12 and the rear plate 14, both in aluminum for example, the mirror plate 12 is treated to yield a reflecting power. The layers are glued together using epoxy glue for example.
FIG. 4B is a side view of the mirror showing the mirror anchoring rods 130. As shown in FIG. 4A, the lower layer 16 may comprise three panels 16a, 16b and 16c. The lateral edges 25, 27 of the mirror sections have two widths s and S, with s smaller tan S, forming a sufficient opening for clearance of the wheels (see FIG. 1 for example). This shape of the lateral edges 25, 27 of the mirror sections allows using wheels 4 all having a same diameter and smaller than the assembled mirror sections (s<S), so as to allow rotation of the assembled mirrors on up to 275° without interference with the supports of the wheels. Due to the position of the mirror anchoring rods 130 in relation to each mirror section, a mirror section, locally, i.e. at the positions of the mirror anchoring rods 130, needs be reinforced so as to ensure distribution of mechanical stresses, as illustrated in FIG. 3B: the outer extrusion 10, the mirror plate 12, the inner extrusion 9, and the rear plate 14 provide such reinforcement, by forming an envelope, i.e. a closed mirror structure, of a cell type, shown on FIG. 4B.
Each mirror has a sectional inertia at the gravity center of at least lx=1.34 E+008 and ly=2.11 E+009. Such sectional inertia in relation to axis x and y ensures structural rigidity to the assembly. This structural rigidity translates into torsional strength and bending strength, over large mirror sections.
The wheels 4, as shown on FIG. 5, 9 or 10 for example, may be formed out of a square tube for example. They transmit a controlled rotation movement to the mirrors and are used as uniting elements between longitudinally adjacent mirror sections s1, s2, s3, s4 (see for example FIGS. 1 and 2).
FIG. 5 show an assembly of a wheel 4 with cross plates 2 and reinforcements 300 allowing supporting and positioning of the wheels. The cross plates 2 allow securing the lateral edges 25, 27 of the mirrors to the wheels 4. Mirror fixation holes 7 receive the mirror anchoring rods 130 (see FIG. 3b), so as to precisely position the mirrors and yield the precise desired parabolic arch, thereby ensuring optical precision at the focus of the parabola and reduced assembly time. These cross plates 2 are very precisely laser cut with a predetermined positioning of the fixation holes 7. These cross plates 2 are then secured to the wheels 4 using bolts and provided with the structural reinforcements 300 in such a way as to yield mechanical strength between each cross plate. Indeed, the mirror sections may be submitted to lateral forces originating from a variety of sources. Simple thermal expansion of a 30 meter-long row of mirrors affects the assembly significantly between summer and winter for example. The reinforcements 300 of the cross plates 2 prevent the cross plates 2 from bending when submitted to such forces for example.
FIG. 6 is a side view of a cross plate 2 of a wheel. Precise location of the holes 7 is shown, as well as fixation holes 42 between the cross plates 2 and the wheels 4 and fixation holes 7 of the mirrors 6 to the cross plates 2.
FIG. 7 is an exploded view of a wheel support 31, comprising lateral bows 30 and radial supports 10. Adjusting rods 20 connect the wheel support 31, via radial supports 10, to a head anchor 42 supported by a anchoring post 100 (see FIGS. 10, 14), allowing adjusting the radial supports 10 in relation to two axes, which permits the optical adjustment of the collector. Rollers 50 allow the wheels to rotate on the radial supports 10 with limited friction. The width of the radial supports 10 allows accommodating thermal expansion of a row of an assembled collector. The lateral bows 30 are all identical, which simplifies inventory.
FIG. 8 show the wheel support 31 of FIG. 7 once assembled. A width of about 200 mm between the lateral bows 30, in case of a typical assembly of a length of 100′ for example, allows absorbing variations in the position of the wheels due to thermal expansion of the materials, for example due to temperature variations between winter and summer times. As discussed hereinabove, the wheel support 31, secured by the adjusting rods 20, in oblong apertures in the head anchors 42 for example, to the head anchors 42, may be adjusted in translation and in rotation in such a way as to accommodate variations of the ground-anchoring elements, such as the posts 100 (FIG. 15), thus allowing the precision required for aligning and balancing a row as assembled shown in FIGS. 1 and 2 for example. FIG. 9 show a wheel support 110, typically at the end of a row of an assembly of units of the invention, which is used essentially for vertically securing the row to anchor heads 42, or beams for example (see FIG. 2). Indeed, during high winds, the parabolic shape of the collector is exposed to lift and drag forces. These forces tend to move the collector vertically, either upwards or downwards. The resulting force on the collector may vary depending on the inclination of the mirrors and of the trajectory of the wind. Supports 101 are thus used to keep the mirrors in place along the vertical axis with a limited friction opposed to the rotation of the wheels. The support 101 allows rotation of the system, thermal expansion of the rows, and securing the row to the anchor head 42. An external device 90, generally consisting of a metal plate or of a cable for example, is camber secured to the wheel 4, so as to keep the wheel on its support.
For the remaining supports in the row, FIG. 10A shows an assembled view and FIG. 10B shows an exploded view of a wheel support 50, of the type illustrated in FIGS. 7 and 8 and further provided with a motorised rotation unit. In order to allow rotation of one or more units of collectors, the mechanised unit is positioned at the center of the assembly for example (see FIG. 2B), or at an extremity thereof, so that the assembly can be made to completely pivot on wheel supports 31 into a so called closed or sheltered mode for example (FIG. 15A). The motorised wheel support 50, illustrated in FIG. 10, is easily assembled and compact. Such a motorised wheel, besides the same functions as the intermediate wheels, performs the mechanical driving of the row, thanks to a rack system or a toothed wheel for example.
The motorised unit provides driving the wheel, using a driving belt for example, or a chain, which plays the role of a retaining device 9, a motor able to operate in two directions and variable speed and powering the rotation of the row and resistant to bad weather, or gears and bearings, and in turn allows driving the whole assembly in an accurate tracking of the sun. It also allows pivoting the assembly to different positions, from 0 corresponding to the closed or sheltered mode of the collector, to about 275°, as schematically shown in FIG. 14.
At the position of the supports 50, at least one retaining device 9 is configured to prevent the wheel from detaching from the supporting structure on which the wheel support is set, while driving it. For the remaining, non-motorised, wheels, a fixation bow may be used, configured so as not to interfere with the rotation movement.
FIG. 11 illustrates an embodiment according to an aspect of the present invention, of a unit of two mirror sections 6a, 6b. The securing device between the mirror sections 6a, 6b is a continuous longitudinal member 110 having a Z cross section, positioned between the two mirror sections 6a, 6b. The member 110 comprises a first surface 111 connected to a second surface 113 by a body 115 forming the central part of the Z shape, the first surface 111 being secured along the inner longitudinal edge 23a of the first mirror section 6a and the second surface 113 being secured along the inner longitudinal edge 23b of the second mirror section 6b, thus forming a unit 1000. The unit 1000 thus formed has a Z cross section, and comprises two mirrors sections 6a, 6b offset one relative to the other by the body 115 of the continuous longitudinal member 110, i.e. the two mirrors are placed along two offset parabolic arches, hence two focal lengths. The offset between the two parabolic arches, each one with its mirror, allows obtaining two solar concentration zones, i.e. two distinct focal lines (See FIG. 13). Such an assembly of two mirrors by a continuous longitudinal member 110 having a Z section yields a unit 1000 that has bending strength, while allowing reducing the thickness of the mirrors 6a, 6b, i.e. the total cost of each mirror square meter. Moreover, such a unit 1000 allows using large sized mirrors 6a, 6b.
FIG. 12 is a side view of the assembly of FIG. 11. It shows the profile of the central rigidifying member 110. As occurs in steel I-beams for example, the Z section of this member 110 allows significantly rigidifying the assembly along the focal axis of the virtual parabola.
FIG. 13 illustrates another embodiment of a unit according to an aspect of the present invention, in which the securing device between the mirror sections 6a, 6b consists of connecting members 210. For example, two connecting members 210 are positioned between the mirror sections 6a, 6b. Each connecting member 210 has a Z cross section, with a first surface 211 connected to a second surface 213 by a body 215 forming the central part of the Z shape, the first surface 211 being secured along the inner longitudinal edge 23a of the first mirror section 6a and the second surface 213 being secured along the inner longitudinal edge 23b of the second mirror section 6b, thus forming a unit 200. The unit 200 thus formed has a Z cross section, and comprises two mirrors sections 6a, 6b positioned on two parabolic arches offset one relative to the other by the body 215 of the connecting members 210, hence two focal lengths. In comparison to the central continuous member 110 of FIG. 11, using discontinuous connecting members 210 allows a flow of air or liquid between the mirror sections 6a, 6b, i.e. in between the free spaces between the connecting members 210.
As schematically shown on FIG. 12, in the case of an attachment between the mirror sections 6a, 6b allowing an offset between two parabolic arches yielding two distinct focal zones, as discussed in reaction to FIGS. 11 and 13 for example, an hybrid application may be contemplated. Using a concentrator line comprising two zones of distinct circumferences A and B as diagrammatically shown in FIG. 12 for example, the mirror section 6a may be used to heat the fluid in the concentrator line by directing the solar rays onto the first zone, for thermal conversion, while solar rays reflected by the mirror 6b are directed to photovoltaic cells provided on zone B for example, for photoelectric conversion.
FIG. 14 illustrates a securing device between the mirror sections 6a, 6b in a symmetrical assembly, i.e. along a single parabolic arch, as opposed to two offset parabolic arches. In this configuration, the securing device between the mirror sections 6a, 6b comprises brackets 35 supported at an end of the supporting arms 13 opposing an end of the supporting arms 13 provided with tongs 37 that grip the concentrator line 5 and rigidify the elements forming the parabola. The brackets 35 attach to the outer extrusions 23a and 23b respectively of the mirror sections a shown on FIG. 14.
The securing members 110, 210 may be used as bearing points for the supporting arms 13 of the concentrator line 5 (See FIG. 13).
In all cases, at least a first one of the two mirrors comprises lateral edges 25, 27 resting on a wheel support and two inner 23 and outer 21 longitudinal edges, the inner longitudinal edge 23 being secured by a securing device to the second one of the mirrors, the outer longitudinal edge 21 being free (see FIG. 2). The inner longitudinal edge 23, together with the inner extrusion 9, ensures the structural strength required for supporting the supporting arms 13. The supporting arms 13 support the concentrator line 5, for example using tongs 37 at a first end thereof (see FIG. 14 for example). Leak tightness at the outer longitudinal edge 21 is ensured by the outer extrusion 10 of the mirror, which also reinforces the cohesion between the elements forming the mirror as discussed in relation to FIG. 3A for example. The lateral edges 25, 27 absorb loads applied to the mirrors and transfer these loads to the wheel supports.
The securing device between the two mirror sections 6a, 6b may thus be configured so as to optimize at least one of the following features: bending strength and dissipation of over-pressure in openings between consecutive securing elements (see for example FIGS. 13, 14).
The simplified concept and combination of supporting function to optical positioning function allows a significant reduction of the number of components required for assembly, hence time and assembly parts savings of about 50% compared to systems having a supporting structure coupled to a reflective element. Moreover, the mirrors according to the invention can be efficiently stored and transported into very small spaces such as a freight container.
The closed-cell structure of the mirror, as detailed in relation to FIG. 3 for example, i.e. comprising elements all over the perimeter of the mirror that cooperate together to yield a very rigid structure, has a high torsional strength as well as a high bending strength. Such a structure allows reducing the thickness of the plates 12 and 14, in aluminum for example, which can be 0.020″ for example (see FIG. 3). Such high torsional and bending strengths combine into a high resistance to environment challenges (rain, hail, snow, strong winds etc. . . . ), while securing the optical configuration required for concentration of solar rays.
The scope of the claims should not be limited by the embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.
